vol. 35 april 1991 no. 2 - johnson matthey technology ......vol. 35 april 1991 contents knitted...

UK ISSN 0032-1400

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their application in industry

VOL. 35 APRIL 1991

Contents

Knitted Gauze for Ammonia Oxidation

Platinum and Iridium Silicide Infrared Imagers

Palladium-Chromium Strain Gauges

Carbonylation Reactions in Aqueous or Mixed Solvent Systems

Palladium-Modified Aluminide Coatings

Solid State Amorphisation of the Platinum Metals

Palladium in a Thin-Film Hydrogen Sensor

Fluorophosphine Complexes of the Platinum Group Metals

Precious Metals Science and Technology

Controlling Automobile Emissions

Binary Coatings for DSA@ -type Electrodes

The Noril’sk-Talnakh Deposits

Abstracts

New Patents

NO. 2

58

64

65

70

82

83

85

86

93

94

95

96

101

114

Communications should be addressed to The Editor, Platinum Metals Review

Johnson Matthey Public Limited Company, Hatton Garden, London E C l N 8EE

Knitted Gauze for Ammonia Oxidation NEW INDUSTRIAL RHODIUM-PLATINUM FABRIC CATALYST

By B. T. Horner Johnson Matthey, Materials Technology Division, Royston

Nitric acid is used in the manufacture offer- tilisers, explosives, plastics and other chemicals, and its production has been the subject of substantial technical development since its incep- tion on an industrial scale at the turn of the century. Thus, a modem manufacturing plant is as different from its early predecessors as the com- puter is from the abacus. The exception to this is the catalyst, the design of which differs little from that used in the early years of this century. An early patent filed by Karl Kaiser in 1909 suggested the use of a platinum gauze (l) , and he settled on “a thickness of thread of 0.06 millimetres, and netting of about 1050 meshes per square centimetre.. .”. Today the vast majority of nitric acid plants use 1024 mesh gauze of 0.076 mm and/or 0.060 mm diameter wire.

Nitric acid production plants can be broadly classified into two types according to the reaction process: (i) A single pressure process carried out at either medium pressure (4 - 6 atmospheres) or high pressure (7 - 14 atmospheres) (ii) A dual pressure process where ammonia oxidation is carried out at medium pressure, and the absorption stage is completed at high pressure.

The overall chemical reaction sequence in both processes is described by the following equations:

4NH, + 5 0 , = 4 N 0 + 6H,O ammonia

2NO + 0, = 2N0, oxidation

3N0, + H,O = 2HN0, + NO absorption

The ammonia oxidation stage utilises a catalyst pack of up to 36 platinum group alloy gauzes, the number being dependent on the pressure in the plant, and the make-up of the pack is designed to maximise the efficiency of the reaction.

The process is fast, but during the reaction contact between the gas and the catalyst is

required for times of the order of seconds in order to maintain process efficiency. The catalysts employed have a typical service life of 50 - 300 days, depending upon the pressure of the system. Conventional woven rhodium- platinum catalyst gauzes fulfil the requirements of the plant quite successfully.

Initial work on catalyst development was performed using flat gauzes (2), and has progressed by the almost exclusive use of woven gauzes. Woven gauzes, however, restrict catalyst development, because only alloys with mechanical properties that satisfy the requirements of the weaving loom can be considered for use. Gauze and catalyst pack designs, therefore, have evolved together from the initial concept, rather than the concept driving the development.

Why Develop New Gauzes? Since very little has changed in the design of

catalysts from almost the start of the industrial ammonia oxidation process, it appears that this could be an area for potential improvement. There are numerous pressures on the fertiliser manufacturing industry, not least of which is concern for the environment which ha; increased in recent years. A reduction in the rate of application of nitrogen-based fertiliser seems inevitable, and this in turn could result in a decline in industrial output. There are many indications that the industry is already stream- lining itself for this eventuality.

One of the major costs of the nitric acid production process is the catalyst. In a typical plant, the catalyst could consist of 25 kg of 10 per cent rhodium-platinum, which at present metal price levels (platinum f;6860/kg and rhodium f;90,000/kg) would cost approximately E350,000. Fluctuations in metal prices and especially the

Platinum Metals Rev., 1991, 35, (2), 58-64 58

recent high cost of rhodium further increases the need for the nitric acid producers to make optimum use of this asset. With the widespread adoption of the “just in time” philosophy, pressure is being put upon the catalyst gauze manufacturers to improve hrther their response to the needs of the catalyst users. The process of weaving gauze is, however, inherently inflex- ible, since it ties up large amounts of metal for long periods of time, to the possible financial detriment of both the supplier and the user.

As previously stated the catalyst used for ammonia oxidation must fulfil several needs. Lower- ing the amount of rhodium in a catalyst will substantially reduce its cost, but then it will not be able to meet its full requirements. Changing the alloy composition and seeking to develop new alloys would be difficult also, under such con’- straints. A compromise is needed between cost and requirements, and an appreciation that any benefits from alternative alloys, such as higher conversion efficiencies and longer life, will be more difficult to instigate.

An alternative flexible catalyst manufacturing system was therefore believed to offer solutions, providing that the resultant catalyst was able to meet specification. Knitting was identified as a possible method of manufacture. No one, however, had been able to successfully knit the relatively low tensile strength platinum group alloys used for ammonia oxidation catalysts, beyond laboratory scale.

Gauze Manufacturing Trials Initial attempts to produce knitted gauzes on

a commercial knitting machine proved difficult, the wire breaking frequently. Sufficient material was produced, however, to enable basic catalyst proving trials to take place. This knitted material was found to be significantly lighter than the same area of conventionally woven catalyst gauze.

Trials were carried out in a high pressure ammonia oxidation development reactor built by Johnson Matthey (3). The initial trials were restricted due to the limited availability of material, the catalyst pack consisting of 16 knitted gauzes backed up with 4 woven catalyst gauzes. The results, however, were encouraging.

Fig. 1 Initially, gauze produced by knitting was significantly lighter than the same area of woven gauze, and this was allowed for by using four knitted gauzes as a substitute for one woven gauze. Dur- ing use knitted gauzes developed a faceted appearance, comparable to that of conventional woven material x 80 approx.

As the knitted catalyst, shown in Figure 1, was 75 per cent lighter than the conventional gauze, four knitted catalysts were used as a substitute for one woven gauze, thus maintaining the weight of the catalyst charge. The resulting ammonia conversion efficiency was recorded as being 3 per cent higher than normal, and the light-off characteristics were also improved. Subsequent examination of the surface of the knitted gauzes by scanning electron microscopy revealed a well-developed, faceted structure, comparable to that observed on used conventional gauzes. It was found that no reaction occurred on the surface of the woven gauze, indicating that any improvements could be attributed to the knitted material.

Additional fabrication work was undertaken, but this did not produce a knitted gauze having a 1:l weight ratio with the woven gauze. En- couraged by previous success, however, further pilot plant catalyst trials were carried out at both medium and high pressures using various industrial pack simulations. Every permutation gave improved plant performance, Table I. The make up of the packs and the test conditions are given in Table 11.

In view of the novelty of the concept and the lighter weight catalyst fabric, a continuous 4 day trial at medium pressure was undertaken to assess

Platinum Meialr Rev., 1991, 35, (2) 59

.m c

E I $ a

L W c n

2 5 C

m

t m

x PI

r-

Ln m r-

Ln (0 I\

t

m

t (D r-

0 m r-

0 (D r-

r- t r-

t Ln N co c o w

~ - m o r - N r - r - m c o a I- " N N N N

m m c o b N N

x N

t t t L? F ! " ! z z z

2 r D m w I h

Platinum Metals Rev., 1991, 35, (2) 60

Tabl

e I

Res

ults

of

Pilo

t Pl

ant

Tri

als

.Con

diti

ons

Med

ium

pr

essu

re

Hig

h pr

essu

re

Pac

k co

nstr

ucti

on

Sta

ndar

d

Sta

ndar

d

50%

kni

tted

100%

kni

tted

(a

100%

kni

tted

Red

uced

w

eig

ht*

(b

)

Sta

ndar

d

Sta

ndar

d

40

% k

nitt

ed

Run

nu

mbe

r

85

/34

85

/35

8711

6

8819

8811

10

8811

1A

8715

88

/22

88

/17

Cam

p a i

g n

hour

s

10.5

12.5

13.3

9.8

26

.5

9.8

10

.8

6.5

9.5

Am

mon

ia

rang

e,

per

cent

9.9-

10

.1

9.9-

10

.2

9.8-

1 0

.1

1 0.0

- 1 0

.2

9.5-

10

.3

10.2

-1 0

.4

1 0.5

- 1 0

.9

10.2

-10.

5

10.2

- 10

.9

Inle

t te

mpe

ratu

re,

OC

267-

272

269-

271

287-

298

273-

280

259-

267

2 59-

272

268-

270

2 7

5-28

3

2 72

- 2

73

Rea

ctor

te

mpe

ratu

re,

OC

741-

748

737-

743

733-

740

765-

79

5

730-

769

747-

760

825-

845

850-

863

8 24-

8

74

per

cent

90.4

89

.3

94.5

94.5

94.7

87.7

91.6

90.4

93.3

Ave

rage

co

nver

sion

ef

fici

ency

, -

Pre

ssur

e dr

op,

iwg

1 .o

1 .o

2.7

0.2

1.2

0.8

-

-

3.5

. 100

% k

nitt

ed p

ack

but

wit

h 2

8 1

7 w

eave

equ

ival

entl

rat

her

than

32

18 w

eave

equ

ival

entl

kni

tted

gau

zes

Table II

Test Conditions and Pack Construction for the Evaluation of Knitted 10 Per Cent Gauze Catalysts

Medium pressure trials

Pack construction Targeted operating conditions I Standard pack

8 x 1024iY10.076 mm

50% knitted pack 16 x 260#/0.076 mm knit 4 x 1024#/0.76 mm knit

100% knitted pack 32 x 260#/0.076 mm knit (a) 28 x 260#/0.076 mm knit (b)

Loading 12 tonneslday NH, Pressure 56 psi Percentage of ammonia 10.0 Inlet temperature 27OOC Reactor size 1.25" dia

High pressure trials

Standard pack 21 x 1024#/0.076mm

40% knitted pack 32 x 260#/0.076 mm knit 13 x 1024#/0.076 mm knit

Loading 78.9 tonneslday NH, Pressure 135 psi Percentage of ammonia 10.5 Inlet temperature 27OOC Reactor size 2.0" dia

the durability of the knitted catalyst. The results confirmed those of the short term trials.

Some possible explanations for the improved efficiency of the knitted catalyst could be its open weave, or a feature associated with it, coupled with the increased number of gauzes required to provide the equivalent weight. Scanning electron microscopy showed that the reactants had penetrated to greater depths than normal, presumably because the gas needed to travel further before finding a reaction site, thus increasing contact time. However, an important feature of the knitted material is that, unlike woven gauze, the crossover points of the wires are more accessible to gas impingement. The loss of catalytic area on a woven gauze due to masking at crossover points is 10 per cent of the total area theoretically available. Therefore, it was postulated, if equivalent weight knitted catalysts could be manufactured, then fewer gauzes would

be required to fulfil the same function. Alter- natively, lighter weight packs could be used to achieve the same result.

To ensure initial acceptance by the chemical industry, the production of a knitted gauze of equivalent weight to the conventional woven gauze was considered desirable, although not essential to ultimate performance. Using the experience gained, a knitting machine believed to be suitable for producing such a fabric was identified; this being a commercially available 6 inch diameter circular knitting machine with a single feed. The single feed system reduced the need to carry large stock levels of wire during the development stages, although multiple feed units were available for the knitting machine, and could be used to scale up the operation and increase the flow of knitted material from the machine. With such a feature it is possible to commence knitting as soon as wire of the

Platinum Metah Rev., 1991, 35, (2) 61

CLEARING r; LATCH

C L 0 S IN G LATCH ON HOOK CAST - OFF

LATCH OPENING

YARN FEEDING

Fig. 2 The knitting process imposes severe distortions on the metal feed wire, but co-knitting a polyester yam gives support to the wire and reduces friction at the needles

correct diameter and with the necessary mechanical properties, becomes available. It soon became apparent that, due to the relatively low tensile strength of the alloys being used, and to the surice friction generated, the wire could not withstand the severe deformation it was subjected to. Therefore changes to the basic design of the knitting machine were made and special features were developed to assist in the production of knitted noble metal gauzes.

The knitting process is shown in Figure 2. Here the degree of deformation, as well as the mechanical operations that produce it, are shown. To overcome the problems resulting from such severe distortions, a polyester yarn was added to the metal wire feed. This had the effect of wrapping the wire, giving i t mpport, and also reducing friction in the needles. After fabrication the co-knitted polyester is removed. Fur- thermore, the mechanical properties of the rhodium-platinum wire being knitted were optimised by varying the annealing conditions, so as to produce properties which were more amenable to the high degree of deformation ex- perienced by the wire during the knitting process. To reduce further the friction forces, several

lubricants were investigated and the optimum one identified. Using a knitting head with 370 needles (19 per inch), a fabric was produced with an effective weight of 590 g/m* , the same as for typical woven gauze. During trials it was found that by careful adjustment the machine could be made to produce ibr ic with a weight tolerance o f f 25 per cent. Thus, a flexible manufacturing technique was successfully developed enabl- ing fabrics of different cloth densities to be produced, using noble metals and alloy wires of various diameters, including rhodium-platinum and rhodium-palladium-platinum.

Commercial Trials An industrial plant operated under atmospheric

conditions with a production capacity of 160 tomes per day of nitric acid was used for the initial trials, the campaign lasting for 75 days. An examination of the catalyst pack by scanning electron microscopy again revealed excellent surface development, and also showed that activation had occurred in the areas of potential masking, see Figure 3. This may be compared with the woven gauze shown as Figure 4. The results of an EDXA (energy dispersive


Fig. 3 After commercial trials under atmospheric conditiona. excellent aurface development wm evident on a hutted gauze, and this extended to areas of potential maaking

x 100 approx.

X-ray analysis) of the gauze surface were most informative, and are given in Table 111. Only low levels of rhodium were detected on the surface of the knitted samples. These may be explained by a better gas distribution throughout the catalyst pack, which promotes a more consistent temperature profile and thus reduces the redistribution of rhodium, which usually occurs at low operating temperatures. This unexpected finding is still under investigation, and is supported by the results of further trials. Generally a pack becomes uneconomic to use when rhodium levels on the surface reach 50 per cent. Any lowering of this rate of rhodium redistribution would be expected to extend the life of the catalyst. A reduction in the redistribution of rhodium should also reduce rhodium losses

Fig. 4 Characteristic faceted development on the surface of a conventionally woven rhodium-platinum catalyst gauze, after use for the oxidation of ammonia

x 100 approx.

which, at the present time, could provide a significant financial saving. Total noble metal loss when using a knitted catalyst was, however, the same as when a woven catalyst gauze was employed.

Several industrial trials are at present being conducted at low, medium and high pressures, and initial results show that knitted catalysts give a performance superior to that of woven gauzes. These trials will be reported in a later issue of Platinum Metals Review.

Summary The development of knitted gauzes has many

potential benefits both for the catalyst supplier and the nitric acid producer, and thus the present project has met most of its initial aims. The

Platinum Metals Rev., 1991, 35, ( 2 ) 63

Fig. 4 Characteristic faceted development on the surface of a conventionally woven rhodium-platinum catalyst gauze, after use for the oxidation of ammonia

x 100 approx.

Tabla 111

Surface Rhodium Concentrations as Determined by EDXA per relit

Knitted pack Conventional woven pack I Gauze 1 knitted 8.9 Gauze 2 knitted 9.0 Gauze 3 woven 11.5 Gauze 4 woven 11.9 Gauze 5 woven 9.7

2.5 2.7 1.4 1.5 1.2

Starting rhodium content of knitted gauze 10.05 per cent

potential benefits can be summarised as follows: (a) Increased conversion efficiency (b) Reduced rhodium oxide formation (c) Higher surface area available for catalysis (d) Fabric flexibility providing greater resistance to damage by thermal shock (e) Stronger material, the ability to resist tear- ing being superior to that of woven gauze (f) Choice of alloy: any changes from the standard 10 per cent rhodium-platinum catalyst can be considered; indeed any combination of rhodium, platinum and palladium can be knitted into gauzes, and many have been. If a chosen alloy can be processed to wire of a suitable diameter, then the possibility of knitting it is extremely high

(g) Only minimal stock levels are required; this enables the supplier to respond more quickly to the needs of the consumer.

Johnson Matthey believe that this range of products and the associated technology, will have a major impact on the chemical industry and will encourage platinum metals catalyst development to take place in ways that, previously, have only been considered in theory.

References 1 K. Kaiser, German Paten? 271,517, 1909 2 S. L. Handforth and J. N. Tilley, Id. Eng. Ind.,

3 K. G. Gough and B. L. Wibberley, Platinum Metals 1934, 26, (12), 1287

Rev., 1986, 30, (4), 168

Platinum and Iridium Silicide Infrared Imagers INCREASING OPPORTUNITIES FOR DIVERSE APPLICATIONS

In a recent communication from the David Sarnoff Research Center, Princeton, New Jersey, the background to the continuing development of platinum silicide infrared imaging devices is discussed (J. R. Tower, Influred Technol., 1991, 25, (2), 103-106).

When the concept of Schottky-barrier infrared focal plane arrays was first put forward by researchers at the Rome Air Development Center, in 1973, it was proposed that detectors formed by the reaction of platinum, or palladium, with p-type silicon would be sensitive in the 1 to 5 pm band. Before the end of the decade the Sarnoff Laboratory had demonstrated a 25 x 50 platinum silicide imager

operating in the 3 to 5 pm band, and five years later they had developed a 160 x 244 array with a noise equivalent temperature difference of 0.1 K. Now they are developing cameras around three focal plane arrays, namely 64x 128 and 320 x 244 infrared charge-coupled devices and a 640 x 480 complementary metal-oxide silicon infhred imager. Applications include thermo- graphy, radiometry, industrial process control and scientific imaging.

In the future it is planned to produce iridium silicide complementary metal-oxide silicon infmred imagers with wavelength capability from 1 to 10 pm or 0.2 to 10 with back- or front-side illumination, respectively.


Palladium-Chromium Strain Gauges STATIC STRAIN MEASURABLE AT HIGH TEMPERATURES

By Jih-Fen Lei Sverdrup Technology Inc., NASA Lewis Research Center Group, Cleveland. Ohio, U.S.A.

In order to meet urgent needs in aerospace research, an electrical resistance strain gauge of palladium-13 weight per cent chromium alloy is being developed both infine wire and thinfilm forms at the NASA Lewis Research Center. The wire strain gauge has platinum wire wound around the gauge grid to serve as the temperature compensator, and is coated with a special alumina-based overcoat. This gauge has a susciently small apparent strain, with good reproducibility between thermal cycles to 80OOC. The apparent strain of the gauge can therefore be corrected within a reasonable error up to this temperature. The thinfilm gauge, which provides a means for non-intrusive strain measurements, demonstrates the possibility of extending the use of this palladium alloy to approximately ZOOO°C.

In the work to design and develop hypersonic aerospace vehicles or advanced gas turbine engines, there is an urgent requirement for a high temperature strain gauge that can be used to provide accurate static strain measurements on various hot structures, in order to validate the design codes. The temperatures on the leading edges of hypersonic vehicles or gas turbine blades may exceed 1000°C, but existing static strain gauges are not capable of satisfying the need for high accuracy at these temperatures.

An ideal resistance static strain gauge should have two basic properties: fwst, its resistance change must be due mainly to the strain. Any other effects which cause resistance changes, for example temperature or time, should be avoided or minimised. Secondly, it should have a stable and reproducible resistance at all temperatures up to the maximum operating temperature. Phenomena which affect the structural stability, and therefore the electrical stability, have to be avoided. Based on these requirements the material used for a static strain gauge must be structurally and chemically stable, and oxidation resistant. In addition, it should have a relatively low temperature coefficient of resistance. The use of presently available commercial resistance static strain gauges has

generally been limited to a maximum operating temperature of 400OC. At higher temperatures the materials currently used for gauges experience either oxidation or structural changes. As a result the characteristics of the gauges do not remain within acceptable limits over long periods of time, neither do they vary in a predictable way.

The work to develop a high temperature resistance strain gauge has recently centred on three groups of materials: the historically promising ironchromium-aluminium systems, platinum-tungsten alloys and the recently developed palladium-chromium solid solutions. The first of these has been used in gauges such as Kanthal A-1 (l), BCL3 (2), and Chinese gauges which operate at temperatures up to 70O0C and 800OC (3,4). These iron-chromium- aluminium alloys offer good self-protection against oxidation and low, but not constant, temperature coefficients of resistance. However, they exhibit microstructural instability in the temperature range 375 to 525OC. The apparent strain versus temperature characteristics of these iron-chromium-aluminium based gauges are therefore sensitive to any heat treatment process, as well as to the heating and cooling rates at which the gauges pass through this transition

Platinum Metals Rev., 1591, 35, (2) , 65-69 65

0.024

-n

T 7 1

L

- - I

-0 001 [ - -

I I I I 1 1 0 1 2 3 4 5 6

TIME, hours

Fig. 1 The resistance dritl at 8OOOC for a 25 pm diameter palladium-chromium wire, bare and after coating with various overcoats: 0 no coating 0 alumina

alumina-2 wt.%CeOz alumina-4 wt.%ZrO2

A alumina-1 wt.%YzO, A alumina-6 wt.%ZrOz

temperature range (5 , 6). This sensitivity to thermal processing limits the use of these gauges for static strain measurements.

Platinum alloys were extensively investigated for strain gauge application in the 1960s and 1970s. Of all the alloys studied, platinum- tungsten and platinum-palladium-molybdenum appeared to be the most promising (7). These platinum-based alloys have high melting points and are highly sensitive to strain. They are, however, also characterised by low resistivity, excessive sensitivity to trace impurities, and high temperature coefficients of electrical resistance. The performance of these platinum- based gauges for dynamic strain measurements has been shown to be satisfactory at temperatures up to 80OOC (8), but the use of these alloys for static strain measurement is generally limited to about 600OC. This is because of possible phase changes and the severe internal oxidation that the materials experience at,higher temperatures (9, 10, 11).

Although the use of palladium-chromium alloys as possible high temperature strain gauge materials had been suggested in the early 1960s (12), essentially no work was done until recently. In 1985 after an extensive search, palladium- chromium was identified as the best candidate material for static strain applications at temperatures up to at least 1000°C (1 1). In this NASA supported contract, a total of thirty-four

palladium-chromium alloys were studied and palladium-13 weight per cent chromium was chosen as the optimum composition. An alloy of this composition has a lower temperature coefficient of resistance than alloys containing less

Gauge wires Compensator wires

+\

2.6 mm

Lead wires

Fig. 2 The confiiration of a palladium- chromium temperature-compensated wire strain gauge, using 25 jtm diameter palladium-13 wt.% chromium wire for the strain gauge wires, 25 pm diameter platinum wire for the compensator wires and 76 pm diameter palladium-13 wt.% chromium for the lead wires

Platinum Metals Rev. , 1991, 35, ( 2 ) 66

than 13 weight per cent chromium, while alloys with more than 13 weight per cent chromium have poorer resistance to oxidation ( 13).

Work at NASA Lewis Research Center to develop a high temperature static strain gauge has therefore concentrated on palladium- 13 weight per cent chromium, with the objective of developing both a fine wire and a thin film high temperature static strain gauge system. As the self-protecting oxidised scale on palladium- 13 weight per cent chromium has been found to be insufficient to provide the required stability when this alloy is prepared as fine wire or as a thin f im (14), an additional overcoat system is needed to protect the gauge against oxidation. In addition, the temperature coefficient of resistance of this alloy is still higher than desired, approximately 175 pohm/ohm°C, so temperature compensation is necessary in order to minimise the temperature effect on the resistance change of the gauge.

Several overcoat systems have been studied, including alumina and alumina with an addition of zirconia, yttria, ceria or hafnia. Coatings consisting of mixtures of alumina and zirconia, or alumina and yttria, have been shown to provide a better diffusion barrier for oxygen, and result in a significant reduction in the drift rate of palladium-13 weight per cent chromium fine wires (14), as shown in Figure 1. As the amount of the zirconia or yttria increases the oxidation rate decreases, and therefore the electrical resistance drift rate of the wire also decreases. However, the amount of the zirconia and yttria additions should be less than 6 weight per cent and 1 weight per cent, respectively, in order to prevent any possible interaction between the palladium-chromium and the overcoat.

Temperature compensation of the gauge is achieved by the use of a Wheatstone bridge circuit, with a compensator element connected to the adjacent arm of the bridge. The configura- tion of a compensated palladium-chromium wire gauge is shown in Figure 2 . The gauge is fabricated from 25 gm diameter wire, and the compensating resistor is 25 pm diameter platinum wire. Platinum is used as the compensator element because it has a much higher temperature coefficient of resistance than

Fig. 3 After the application of an alumina precoat, the compensated wire gauge is taped down with high temperature adhesive strips. Here the substrate is an IN-718 test bar

palladium- 13 weight per cent chromium, and because it has good structural and chemical stability at high temperatures. Platinum is wound around the gauge grid to minimise the temperature gradient effect. The lead wires are also palladium- 13 weight per cent chromium, but of 76 pm diameter. The lead wires are spot welded to the gauge and to the compensator wires.

The compensated palladium-13 per cent chromium wire gauge has been tested on a Hastelloy-X coupon and an IN-718 cantilever beam. The gauges are mounted with either high temperature ceramic cements or flame-sprayed powders. A layer of alumina is first applied to the substrate as the precoat, and the gauge is then taped down on this precoat by means of high temperature adhesive strips, see Figure 3. A layer of alumina and zirconia, or alumina and yttria mixture is applied, to the open areas between the strips. The strips are then removed and the final alumina mixture overcoat is applied. The cemented gauge can be used satisfactorily up to approximately 6OOOC (15). At higher temperatures, the porous cement is insufficient to protect the gauge system from oxidation and prevent electrical leakage to ground. The flame-sprayed ,gauge has been demonstrated to work reasonably well at temperatures up to 8OO0C, since the flame-sprayed technique usually produces a denser film (16). The change in apparent strain of a prestabilised gauge from


I.

- 2 0 0 \ 1 I I I I I 1 0 1 0 0 200 300 400 500 600 700 f

TEMPERATURE, 'C

Fig. 4 For two thermal cycles to 8OOOC the plot of a p parent strain versus temperature for a palladium- chromium compensated wire strain gauge, after prestabilising at 78OoC for 50 h, shows reproducibility to be within 50 microstrain: with strain sensitivity (Gauge Factor, G F s (6RIR)&) = 1.3: 0 heating cycle 1 0 cooling cycle 1

heating cycle 2 cooling cycle 2

room temperature to 8OOOC is within 300 microstrain (p inchhnch), with a reproducibility to within 50 microstrain between thermal cycles to 8OO0C, see Figure 4. The apparent strain of the gauge can therefore be corrected at temperatures up to 8OO0C, due to its small value and its repeatibility. This is a significant advance on the previous techniques for existing static strain gauges, as demonstrated by the data in Figure 5 .

The strain sensitivity (gauge factor) of this compensated wire gauge, both in tension and in

compression, is approximately 1.3 at room temperature. The gauge responds linearly to the imposed strain to at least f 2000 microstrain. Furthermore, the strain sensitivity of the gauge does not vary significantly with temperature (16).

The development of a palladium-13 weight per cent chromium thin film gauge has commenced. Two sputtered thin film gauges, each with four lead pads on an alumina bar, are shown in Figure 6. Palladium-13 weight per cent chromium wire, 75 pm in diameter is used for the lead wires, which are parallel-gap welded to

W

z- c UI

I-

w K s <

6ooo]

4 000 -

2000-

0-

-2000-

-4000 I I 1 I I I I

Fig. 5 A comparison of a p parent strain versus temperature for four high temperature strain gauges demonstrates the value of the palladium-13 wt.% chromium, for temperatures up to 8OO0C, and strain sen- .e i t i vi t y (.): Gauge Factor = 2.0; (+): Gauge Factor = 1.3:

Pd-13 wt.96 Cr gauge (+) 0 Chinese gauge up to

Platinum Merak Rev., 1991, 35, (2) 68

Pd-13 wt.96 Cr gauge (+) 0 Chinese gauge up to

0 Kanthal A-1 gauge (.) 0 BCL3 gauge (.)

7OOOC (.)

the thin film lead pads. The apparent strain change versus temperature characteristics of these sputtered thin film gauges is linear and repeatable at temperatures up to 1000°C. The reproducibility of the apparent strain between repeated thermal cycles to 1000°C can be further improved by prestabilising the gauge before testing, and by coating the gauge with the

Fig. 6 These two sputtered thin fdm gauges, on an alumina test beam, were produced as part of a NASA development programme. The enlarge- ment below shows details of the palladium- chromium thin film gauges

alumina-based mixture overcoat. This indicates that the maximum temperature at which this thin film gauge can be used can be extended up to at least 1000°C.

Work is currently underway at NASA Lewis Research Center to fabricate palladium- chromium thin film gauges with a compensator element to minimise the apparent strain.

References

1 H. F. Hobart, NASA CP-24444, 1986, pp.91-96 2 M. M. Lemcoe, ISA CP-572, 1975, pp.1-10 3 T.-T. Wu, L.-C. Ma and L.-B. Zhao, 3. Exp.

Mech., 1981, 117-123 4 T.-T. Wu and L.-C. Ma, 4th SEM Annu. Hostile

Environments and High Temp Measurements C o d Proc., 1987, pp.30-37

5 H. F. Hobart, NASA TM-86973, 1985 6 J.-F. Lei, NASA CR-187056, 1991 7 R. Bertodo, Brit.3. Appl. Phys., Ser. 2,1%8,1,1743 8 K. E. Easterline, Brit. 3. Appl. Phys., 1963,14,79 9 S. P. Wnuk, Proc. of Technical Committee on

Strain Gauges, 1974, pp.5-9

10 D. P. Kershisnik, Society for Experimental Strain

11 C. 0. Hulse, R. S. Bailey and F. D. Lemkey,

12 R. Benodo, Platinum Metals Rm., 1964,8, (4), 128 13 C. 0. Hulse, R. S. Bailey, H. P. Grant and J. S.

Przybyszewski, NASA CR-180811, 1987 14 J.-F. Lei, J. Minter and H. J. Van Horn, Elec-

trochem. Soc. Extended Abstracts, 1990, Vo1.90-1, No.933

Analysis, Spring Meeting, 1973

NASA CR-174833, 1985

15 J.-F. Lei, NASA CR-185153, 1989 16 J.-F. Lei and W. D. Williams, AIAA-90-5236,1990


Carbonylation Reactions in Aqueous or Mixed Solvent Systems CATALYSIS BY RUTHENIUM CARBONYL COMPLEXES

By Professor M. M. Taqui Khan Central Salt and Marine Chemicals Research Institute, Bhavnagar, India

In recent years much interest has been focused on carbonylation reactions in aqueous or biphasic systems catalysed by platinum group metals complexes. This is due to the reactivity of platinum group metals ions as catalysts designed to activate small molecules. When used in C , chemistry a variety of reactions can be catalysed by these complexes, in particular by ruthenium complexes. Ruthenium has several oxidation states and co-ordination numbers, and is relatively cheap. Additionally, ruthenium catalysts are stable and their reaction conditions are usually mild, making them excellent for homogeneous catalysis. Various reactions of ruthenium carbonyl complexes and ruthenium saloph dichloride complexes with carbon monoxide have been investigated in this laboratory, and are considered here.

The importance of C, chemistry and its sources of natural gas or synthesis gas have increased considerably in recent years ( 1). This is due mainly to the reactivity of platinum group metals ions as catalysts which are designed to activate small molecules, such as carbon monoxide, hydrogen, olefm, oxygen and nitric oxide under mild conditions (2). The importance of homogeneous catalysis in the next decade will be mostly focused on low energy synthetic routes (3), with minimum or zero by- products. This approach needs careful planning of synthetic routes, with fewer steps to achieve product selectivity and specificity under milder conditions. The platinum group metals ions of the 4d series, namely ruthenium, rhodium, and palladium occupy a unique place in the Periodic Table, and offer a balance between the thermodynamic stability and kinetic lability of the complexes. Although rhodium (4) and palladium (5) complexes have been widely used in industry, the application of rhodium as a catalyst has been comparatively less well- known. Ruthenium offers the advantage of being available in several oxidation states varying

from 0 to 8 and co-ordination numbers from 4 to 7, and these factors together with its lower cost make it an excellent candidate for homogeneous catalysis.

The ruthenium complex ethylenediamine- tetraacetatoaquo-ruthenium(II1) [Ru(EDTA- H) (H,O)l (1) reacts with carbon monoxide to give [Ru"'(EDTA-H)(CO)] (2) which is ultimately reduced to [Ru"(EDTA-H)(CO)I - (3). In our laboratory we have been investigating the chemistry of [RulI1(EDTA- H)Cll- (6-8) and its reactivity for the activation of oxygen (9, lo), nitrogen (11, 12), hydrogen (13, 14) nitric oxide (15) and carbon monoxide (16-21). The [Ru"'(saloph)C1,1- (4) (where saloph = bis(salicy1aldehyde)-o- phenylenediimine) (22) is an excellent catalyst for oxygenation (23) and oxidative and reductive carbonylation (24,25). In the present paper the catalysis of complex [Ru"(EDTA-H) (C0)l- (3) in the water gas shift reaction (16), the hydroformylation of olefins (17), the carbonylation of cyclohexene (18), amines (19), ammonia (20), benzyl chloride (21) and the catalysis of [Rull(saloph)C1,l* - in oxidative

Platinum Metals Rev. , 1991, 35, (2), 70-82 70

..............

..... ...... I 0

II 0

0

2

1

3

Scheme I


and reductive carbonylations (24, 25) will be discussed. The reactions proceed under mild conditions of temperature and pressure, with a high degree of specificity in most cases.

Reactions of [Ru1"(EDTA-H)Cl1 - Interaction of Carbon Monoxide with [Ru"~(EDTA-H)(H, O)]

The interaction of carbon monoxide with [Ru"'(EDTALH) (H,O)l (1) gives an aquo- carbonyl species 2 which loses a proton to form the hydroxo species 2a (Scheme I). The equilibrium between 2 and 2a is pH dependent. Complex 2a forms the p-carbonyl-p-hydroxo dimer 2b at p'H 3.5. Heating complexes 2a or 2b to 60°C in an atmosphere of carbon monoxide at 10 to 15 atmospheres gives the stable ruthenium(I1) carbonyl 3, which is used as a catalyst in a number of reactions. The structure of the ruthenium(I1) carbonyl 3, see Figure 1, indicates that CO retains its nucleophilic

character in the complex, which is thus an excellent catalyst for CO insertion in M-0, M-C and M-N bonds. The Ru-C bond length of co- ordinated CO is larger than, and the C-0 distance shorter than, that of most other ruthenium(I1) carbonyls (26), indicating a weaker bonding of Ru-CO in this complex.

Catalysis of the Water Gas Shift Reaction The water gas shift reaction is essentially a

reaction between carbon monoxide and water to form hydrogen and carbon dioxide:

CO + H,O - CO, + H, The reaction is exothermic and acts as a

source of hydrogen in ammonia plants (27,28). The source of the carbon monoxide is the gasification of coal or natural gas. The conventional catalyst (27) chromium activated iron oxide (Fe, 0, /Cr2 0,) or cobalt-molybdenum catalyst (CoOIMoO,) are used for the reaction

Fig. 1 The stable ruthenium(l1) carbonyl complex [Ru"(EDTA-H)(CO)I - acts as a catalyst for a number of carbonylation reactions under mild conditions. Here, the bond lengths are given in bgstrom units

Platinum Metals Rev., 1 9 9 1 , 35, (2) 72

H L

k I I V I I V L R U " - C O + H ~ O - L R U - C O + H - R U - c o 3 I 3a I 3b

K1 i l ' O L R U " ( H ~ O ) + H * + C O ~

O H

fast c-

L = E D T A - H

Scheme 11

I OH

//O

If I '0

L RU"- c

,H HHjc

at a temperature of 400-460°C and at a pressure of 200 atmospheres of COY or CO+H,.

In view of the extreme importance of this reaction to industry as a source of hydrogen we have studied the catalysis of the water gas shift reaction by [Ru"(EDTA-H)(CO)I - (3) at 45-8OoC and 15-35 atm of CO (16). Since the reaction is exothermic, the optimum temperature of the reaction catalysed by 3 is about 50°C, at 15 atmospheres of CO. From the kinetic data the mechanism shown in Scheme I1 is proposed for the water gas shift reaction catalysed by 3.

It has been suggested that the rate determining step of the reaction is the oxidative addition of H,O to Ru"(EDTA-H)(CO) (3) to form the hydrido carbonyl species 3a and 3b. The formation of 3a and 3b as intermediates is supported by NMR of the hydrides in solution, which gives peaks at - 20.1 and 8.1 ppm, respectively, for hydrides cis and trans to CO, respectively. Insertion of CO into the RuIV-OH bond in a fast step gives the 11 -formato intermediate, 3c, which dissociates in a fast step to form CO, , H, and LRu~~(H,O), and this gives 3 on reaction with COY thus completing the catalytic cycle. The values of the equilibrium constant, K , , and the rate constant at 50°C and 15 atm of CO are 11/M and 80.0/minY respectively, with a

turnover of 350 moles of CO,/H, per mole of the catalyst per hour; the highest reported so far in the liquid phase. The activation energy of the reaction is 1.47 kcal/mole which amounts to a decrease of about 45 kcal/mole for the proposed dissociation of H , 0 into H and OH in the rate determining step. The entropy and enthalpy of activation are 2.45 e.u. (entropy units) and 0.83 kcal/mole.

Hydroformylation of 1-Hexene Recently much attention has been diverted to

water soluble catalyst in order to achieve a high conversion of end olefms to the linear aldehydes in the 0x0 reaction (29, 30). The use of the water soluble phosphine ligands, especially the sulphonated phosphines (29, 30), offers a simple biphasic system wherein the Rh(1) catalyst is maintained in the aqueous phase, whereas the organic phase contains the reactants and products with different ligands. The use of a soluble Rh(1) catalyst and 1-hexene as substrate gives a linear to branched chain aldehyde ratio ranging from 9: 1 to 18: 1 at 80°C and at a CO pressure of 8 atmospheres (30). The complex IRu~~(EDTA-H)COI - (3) catalyses the hydroformylation of 1-hexene to 98 per cent 1 -heptaldehyde in a homogeneous system at 130°C and 80 atmospheres of syngas in a contact time of 12 hours (17). The mechanism of


K1 [Ru"L(H20)]-+CO = [Ru" L(CO)]-

1 3 K2

[Ru"L(CO)]-+ H2 [Ru"L(CO)(H)]2-+ H+

3 4t K3 [Ru"L(CO)(H)]~-+ R d [Rdl L(CO)(H)(R)l2-

5t

[Ru" L(C0)(H)(R)l2- k_ [LRu"(CO)(HR)]~-

6t

[LRu" (C0)(HR)l2- fast_ [LRu" - CORH]*-

7 t H z K O - [Ru"L(CO)(H)]~-+ RCHO [LRu"-CORH]~- fas t

4t

L = E O T A - H R = I - hexene

Scheme III

the reaction is depicted in Scheme 111. The values of the equilibrium constants K , , K,, and K, and the rate constant, k, at 130°C (80 atm of CO) are 4.9/M, 190/M, 5.3IM and 0.32/min, respectively.

Allylic and Vinylic Carbonylation of Cyclohexene

The complex [Ru"(EDTA-H)(CO)I - (3) catalyses the carbonylation of cyclohexene in an alcohol : water mixture of ratio 80 : 20 to give the vinylic aldehyde cyclohexene- 1- carboxylaldehyde (20%), allylic aldehyde, cyclohexene-3-carboxylaldehyde (20%) and cyclohexane carboxylaldehyde (60%) (18). The optimum reaction conditions are 12OOC and 20 atmospheres of CO partial pressure. The

carbonylations of 1-, 3- and 4-methyl cyclohexenes conducted at 16OOC and 20 atmospheres of CO partial pressure gave the corresponding alcohols, 1-(2-methylcyclohexene)methanol, 1-(4-methylcyclohexene)- methanol and 1-(5-methykyclohexene)- methanol, respectively. The rate of carbonylation has first order dependence with respect to catalyst, CO pressure and substrate concentrations, respectively. The mechanism of the reaction is given in Scheme IV.

The substrate cyclohexene reacts with complex 3 in a pre-equilibrium step K , to form the mixed ligand q2-olefin complex 3c. The rate determining step of the reaction is considered to be the insertion of the ruthenium catalyst in the allylic C-H bond to form an allylic


insertion into allylic C - H bond

0

reductive elimination

reductive elimination with double bond migration

CHO CHO

+ c o 1 c o insertion

0

3e

CHO

- 4 water gas

shift reaction 6 and + H2

L = EDTA-H

Scheme IV

intermediate 3d. The next step, CO insertion (or alkyl migration) which is a well-known step in homogeneous catalysis, affords an acyl species 3e which, on reductive elimination and sixnultaneous double bond migration gives cyclohexene- 1-carboxyaldehyde and cyclohexene-3-carboxyaldehyde, regenerating species 3 by reaction with CO. Cyclohexane carboxyaldehyde is formed by hydrogenation

of cyclohexene- 1-carboxyaldehyde and of cyclohexene-3-carboxyaldehyde by hydrogen gas released by the water gas shift reaction. The Occurrence of the water gas shift reaction under the reaction conditions has been established in our earlier studies (16). The values of the constants K, and k at 120°C and 20 atmospheres of CO are 1.9/M and 1.43/min, respectively. The activation energy of the reaction was


[LRu"(HzO)]-+ C O

1

[L R ull (C O)]-+ R N E t

3 0

\ E t 3f 0

39

3 K2 - [ L Ru" (C O)(N R E t2) ]

3f

0

k I I II /R - LRu -C-N-Et \ E t 39

f a s t co - [ L R ull (C O)]- +

0

II / E t R-C-N

\ E t N,N-d ie thy l fo rmamide (R=H) N, N -diethylpropionamide (R= Et)

0

II / E+ / E t LRuIl-C-N-Et + RN

'R \ E t 39

f a s t co - H2 + [LRu"(CO)]-+

3 / E t

I N \ E t o=c

N, N- te t rae thy lu rea

R = H(diethylamine), R = Et(triethy1amine)

Scheme V


16 kcal/mole. The endothermicity of the reaction reflects on the energy needed to insert CO into the allylic C-H bond of cyclohexene.

Carbonylation of Primary and Secondary Amines

The complex [Ru"(EDTA-H)(CO)I- (3) catalyses the carbonylation of diethylamine and triethylamine (19) at a CO pressure of 5-26 atm and temperatures in the range 80-100°C in aqueous media. The products of the carbonylation of diethylamine are N,N-diethylformamide (80%) and also N,N- tetraethylurea (20°/0), whereas triethylamine gives 100 per cent N,N-diethylpropionamide. The observed rates for the carbonylation of diethylamine and triethylamine are 5.9 x lO-,/min and 12.5 x IO-'/min, respectively, at 100°C and 25 atm of CO. The rates are in accord with the higher basicity of triethylamine as compared to diethylamine. The mechanisms of the reaction are depicted in Scheme V.

Carbonylation of Ammonia The extension of the carbonylation of tertiary

and secondary amines is the carbonylation of ammonia (20) which was conducted over a range of CO pressures 50-80 atm and in the

temperature range 50-60°C. The main product of the reaction is urea, with small quantities of formaldehyde. The reaction gives a new route for urea synthesis from carbon monoxide and ammonia. The synthesis of urea through the established ammonium carbamate route re- quires temperatures of the order of 400-5OO0C and a high pressure of 200-300 atm. The catalysis of carbonylation of ammonia by 3 drastically reduces the input of energy required for the synthesis of urea, see Scheme VI.

The rate determining step of the reaction is the homolytic cleavage of NH, into H and NH, followed by the oxidative addition to [Ru"(EDTA-H)COI- (3) to form a Ru(1V) hydrido imide complex 3h. Insertion of CO into the Ru-N bond gives the 7'-formamide intermediate 3i which reacts with another molecule of NH, to give urea, H, and 3, thus completing the catalytic cycle. The proposed rate determining step of the reaction is the oxidative addition of NH, to LRu"-CO to give 3h (Scheme VI).

Carbonylation of Aryl Halides The carbonylation of benzyl chloride (21) is

catalysed by the complex [Ru"(EDTA- H)(CO)l- (3) at 8OoC and 20 atmospheres of

k LRU1' -CO+NH, - LRu'"-CO I 3h t 3 NH2

L = E D T A - H 3i Scheme VI


[L Ru"(H 2 O)]- + CO

1

[L Ru"(CO)]- + RCL

3

R

I [L- RuiV(CO)]

I

1 3J C l

- [LRu"(CO)]-+ H2

R 3

I - [L-Ru'"(CO)] 1

I 3J C l

R

co I I - [L- Ru'"-C~]

3K

R

co I

[L-Ru'~-CC] 3K ' L ILRu l ' (CO) ] - C2H50H

+RCOOC2H5 + HCl

L = H - EDTA (protonated ethylenediaminetetraacetic acld)

R = CbHsCH2

Scheme VII

CO in an 8:2 ethano1:water mixture. The products of the carbonylation of benzyl chloride are phenylacetic acid and ethylphenylacetate in a 4:6 molar ratio. The reaction proceeds with 100 per cent conversion of the substrates to products, with an overall turnover frequency of 44 moles of the products per hour.

The mechanism of the reaction as depicted in Scheme VII shows the equiIibrium formation of the carbonyl complex in step 1. The rate determining step of the reaction is the oxidative addition of RCI to [Ru"(EDTA-H)(CO)I- (3) to form the Ru(1V)-alkyl complex 3J. Fast inser-

tion of CO into the M-C bond of 35 forms the aroyl intermediate 3K. Nucleophilic attack of OH- or RO- on the carbonyl carbon of 3K gives the products RCOOH or ester RCOOC,H, and the catalyst (Scheme VII).

Reactions of [Ru(saloph)Cl, 1 - Reductive Carbonylation of Nitrobenzene

The reductive carbonylation of nitrobenzene to phenylurethane is a very important reaction from the view point of the production of polyurethane foam and fibres (31). Various transition metal ion catalyst have been used for


this reaction (32, 33). The ruthenium(II1) complex [Ru(saloph)Cl,]- (4) (saloph = bis- (salicy1aldehyde)-o-phenylenediimine) catalyses the reductive carbonylation of nitrobenzene in ethanol at 15 atmospheres of CO and at 160°C to phenylurethane, with a turnover rate of 80 moles of product per mole of the catalyst per hour (24). The mechanism of the reaction is depicted in Scheme VIII.

In the proposed mechanism (Scheme VIII)

complex 4 reacts with a molecule of CO to give [LRu~~~(CO)CII species 4a in a pre- equilibrium step. The solution spectrum of the carbonylation experiment, conducted in the absence of substrate nitrobenzene, showed a peak at 370 nm which is attributed to the LMCT band of the carbonyl complex 4a. In a second pre-equilibrium step, nitrobenzene forms a mixed ligand complex 4b which reacts with another CO molecule in a rate determining

4 4a K1

L R u " ' C L ~ + C O ---- L R U ~ ~ ~ ( C O ) U + ci-

L = bls(sa1icylaldehyde)-0- phenylenedii mine(saloph)

Scheme VIII

Platinum Metah Rev., 1991, 35, ( 2 ) 79

step to give Ru(II1) nitroso complex 4c by the deoxygenation of the -NO, group of nitrobenzene and the release of CO, . The solution spectrum of the reaction mixture withdrawn while the reaction was in progress showed the characteristic peak of a Ru-NO bond at 316 nm. The nitroso complex 4c quickly takes up one more molecule of CO in a fast step, to give a nitrido intermediate species 4d via the deoxygenation of the nitroso -NO

group. Migration of CO to the electrophilic nitrogen atom of the M=N+-R intermediate gives the co-ordinated phenylisocyanate complex 4e which reacts with ethanol in the presence of C1- in a fast step to give phenylurethane; simultaneously regenerating the active catalytic species 4a.

The activation energy, E,, calculated from the temperature dependence of the rate of carbonylation of nitrobenzene in the range

ii C

i C

K1 L R u " ' C l 2 + C O LRu"'(CO)CL + C l -

4 a

i C

K2 I LRu"'(CO)CL + RNH2 .[LRu"'] + C l -

R N H 2

RNH2 = cyclohexylamine L = saloph

Scheme IX

R


140-16OoC is 38 kcal/mole. The AH* and AS* values calculated at 160°C are 37.0 kcal/mole and + 86.0 e.u., respectively. The AH* value of 37.0 kcal/mole observed in this study indicates that the reductive carbonylation of nitrobenzene is highly endothermic in nature. This is expected because of the bond breaking reaction in the transition state. The high positive value of AS+ (+86.0 e.u.) reflects on the various dissociative steps involved in the formation of the active intermediate. The catalytic activity of a Schiff base complex depends on the presence of labile axial chloride groups to facilitate such dissociation and the formation of a nitroso complex species 4c. The driving force for the reaction is thus the high positive entropy of the reaction.

Oxidative Carbonylation of Cyclohexylamine

The oxidative carbonylation of different primary and secondary amines catalysed by Co(sa1en) (where salen = bis(salicyla1dehyde)- ethylenediimine) have been reported (34, 35). The turnover number based on the amount of amine converted was found to be 0.50-2.0. Palladium catalysts have been reported to catalyse the oxidative carbonylation of amines to urethanes (36).

The complex KLRu1I1(saIoph)ClL 1 4 selectively catalyses the oxidative carbonylation of

cyclohexylamine in ethanol medium to cyclohexylurethane at 16OOC and at CO+O? (1:O.S) pressure of 21 atm (25). A turnover number of 30 mole per mole catalyst per hour was observed in this reaction. The activation energy for the reaction was 2 1 .O kcal/mole.

The oxidative carbonylation of amines has certain advantages over the reductive carbonylation of nitro complexes (37). Compared to the reductive carbonylation of nitrobenzene by complex 4 (24), the oxidative carbonylation of cyclohexylamine proceeds at an activation energy which is 16 kcal/mole lower than that of the former. The mechanism of the oxidative carbonylation of cyclohexylamine is depicted in Scheme IX. It may be seen that the mechanisms of the reductive and oxidative carbonylations differ in the routes leading to the formation of the isocyanate species 4d. In the mechanism of oxidative carbonylation proposed in Scheme IX, species 4d is suggested to be formed by intramolecular oxygenation of the primary amine by the Ru(V)-0x0 species 4g, with the simultaneous elimination of a water molecule. In addition to the above differences, the reactions also differ in the stoichiometry of CO required for the reaction. In the case of oxidative carbonylation only one mole of CO is required for the entire reaction (Scheme IX), whereas for the reductive carbonylation three moles of CO are required for the reaction.

References

M. T. Gillies. “C, based chemicals from H , and CO,” Noyes Data Corporation, New Jersey, U.S.A., 1982 M. M. Taqui Khan and A. E. Martell, “Homogeneous Catalysis by Metal Complexes,” Vol. 1, Academic Press, N. Y., 1976 B. Cornils, “New Synthesis with CO,” ed. J. Falbe, Springer, Berlin, 1980, pp. 1-181 Yu. V. Gulerich, N. A. Bumagin, I. P. Beletskaya and J.Tsuji, “Organic Synthesis via Metal Car- bonyls,” Vol. 2, ed. I. Wender and P. Pino, Wiley, N. Y., 1977, p. 595; A. Spencer, “Com- prehensive Coordination Chemistry,” ed. G. Wilkinson, R. D. Gillard and J. A. McClevet, Pergamon, Oxford, 1987, Ch. 61.2, p. 230 and references therein I. Wender, Catal. Rev. Sci. Eng., 1976, 14, 97; D. Foster, Adv. Organomer. Chem., 1979,17,255

6 M. M. Taqui Khan, G. Ramachandraiah and A. Prakash Rao, fnorg. Chem., 1986, 25, 665

7 M. M. Taqui Khan, G. Ramachandraiah and R. S. Shukla, fnorg. Chem., 1988, 27, 3274

8 M. M. Taqui Khan, Amjad Hussain, K. Venkatasubramanian, G. Ramachandraiah and V. Oomen, 3. Mol. Catal., 1988, 44, 117

9 M. M. Taqui Khan, Pure Appl. Chem., 1983, 55, 159

10 M. M. Taqui Khan, Amjad Hussain, G. Ramachandraiah and M. A. Moiz, fnorg. Chem., 1986, 25, 3023

11 M. M. Taqui Khan, R. C. Bhardwaj and C. Bhardwaj, J. Chem. SOC., Chem. Commun., 1985, 1690

12 M. M. Taqui Khan, R. C. Bhardwaj and C. Bhardwaj, Angew. Chem., Int. Ed. Engl., 1988, 27, 923

Platinum Metals Rev. , 1991, 35, (2) 81

1 M. T. Gillies. “C, based chemicals from H , and CO,” Noyes Data Corporation, New Jersey, U.S.A., 1982

2 M. M. Taqui Khan and A. E. Martell, “Homogeneous Catalysis by Metal Complexes,” Vol. 1, Academic Press, N. Y., 1976

3 B. Cornils, “New Synthesis with CO,” ed. J. Falbe, Springer, Berlin, 1980, pp. 1-181

4 Yu. V. Gulerich, N. A. Bumagin, I. P. Beletskaya and J.Tsuji, “Organic Synthesis via Metal Car- bonyls,” Vol. 2, ed. I. Wender and P. Pino, Wiley, N. Y., 1977, p. 595; A. Spencer, “Com- prehensive Coordination Chemistry,” ed. G. Wilkinson, R. D. Gillard and J. A. McClevet, Pergamon, Oxford, 1987, Ch. 61.2, p. 230 and references therein

5 I. Wender, Catal. Rev. Sci. Eng., 1976, 14, 97; D. Foster, Adv. Organomer. Chem., 1979,17,255

13 M. M. Taqui Khan, S. A. Samad and M. R. H. Siddiqui, 3. Mol. Catal., 1989, 53, 23

14 M. M. Taqui Khan, S. A. Samad, Z. Shirin and M. R. H. Siddiqui, 3. Mol. Catal., 1989, 54, 81

15 M. M. Taqui Khan, Z. Shirin, M. R. H. Siddiqui and K. Venkatasubramanian Inorg. Chem. (Sub- mitted)

16 M. M. Taqui Khan, S . B. Halligudi and S . Shukla, A n g m . Chem., Int. Ed. Engl., 1988, 27, 734

17 M. M. Taqui Khan, S. B. Halligudi and S. H. R. Abdi, 3. Mol. Caral., 1988, 48, 313

18 M. M. Taqui Khan, S . B. Halligudi, S . H. R. Abdi and S. Shukla, 3. Mol. Catal., 1990,61, 275

19 M. M. Taqui Khan, S. B. Halligudi and S. H. R. Abdi, 3. Mol. Catal., 1988, 48, 325

20 M. M. Taqui Khan, S. B. Halligudi, S. H. R. Abdi and S. Shukla, 3. Mol. Catal., 1988, 48, 25

21 M. M. Taqui Khan, S. B. Halligudi and S. H. R. Abdi, 3. Mol. Catal., 1988, 44, 179

22 M. M. Taqui Khan, S. A. Mirza, A. Prakash Fbo and C. Sreelata, 3. Mol. Catal., 1988, 44, 107

23 M. M. Taqui Khan, C. Sreelata, S. A. Mirza, G . Ramachandraiah and S. H. R. Abdi, Inorg. Chem. Aria, 1988, 154, 103

24 M. M. Taqui Khan, S. B. Halligudi, S . Shukla and A. Shaikh, 3. Mol. Catal., 1990, 57, 307

25 M. M. Taqui Khan, S. B. Halligudi and N. Shukla, 3. Mol. Catal., 1990, 59, 303

26 J. S. Stainko and S . Chaipaymgpundu, 3. Am. Chem. Soc., 1970, 92, 5580; R. S . Sundberg, R. F. Bryan, I. F. Taylor and H. Taube, 3. Am. Chem. Sor., 1974, 96, 381

27 R. B. Anderson, “Catalysis”, Vol. 4, ed P. H. Emmett, Reinhold, N. Y., 1957, p. 1

28 P. J. Denny and D. A. Whan, “Catalysis”, Vol. 2, London, 1978, p. 46

29 A. Dedieu, P. Escaffre, J. M. Frances, P. Kalck and A. Thorez, Nouv. 3. Chim., 1986, 10, 631

30 B. Beson, P. Kalck and A. A. Thorez, European Appl. 179004; P. E. Scaffre, A. Thorez and P. Kalck,J. Chem. Soc., Chem. Connun., 1987, 146

31 R. G. Arnold, J. A. Nelson and J. J. Verbanc, Chem. Rev. , 1957, 57, 47

32 K. Univerferth, R. Hontsch and K. Schwetlick, 3. Prakr. Chem., 1974, 321, 86; S . Fukuoka, M. Chono, M. Kohno, Chemtech, 1984,14, ( l l ) , 670

33 V. I. M. Yuvenskii and B. K. Nefedov, Russ. Chem. Rev. , 1980, 56, 470

34 G. Mandinelli, M. Nali, B. Rindone and S. Tollari, 3. Mol. Catal., 1987, 39, 71

35 F. Benedini, M. Nali, B. Rindone, S . Tollari, S. Cenini, G. Lamonica and F. Posta, 3. Mol. Caral., 1986, 34, 155

36 S. Fukuoka, M. Chono and M. Kohno, 3. Chem. Soc., Chem. Commun., 1984, 399

37 S. Fukuoka, M. Chono and M. Kohno, Chemtech, 1984, 14, ( l l ) , 670

Palladium-Modified Aluminide Coatings Over the past decade progress in the develop-

ment of platinum-modified aluminide coatings suitable for the protection of gas turbine engine components against high temperature oxidation and hot corrosion has been recorded in this journal on a number of occasions (1-3). Such coatings may, however, include a brittle platinum-aluminium phase which could decrease the fatigue life of coated components. There is no brittle phase in the corresponding region of the palladium-aluminium phase diagram and, for this and other reasons, researchers at the Office National d’Etudes et de Recherches Aerospatiales and the Laboratoire de Chimie du Solide Mineral, CNRS, France, have recently reported on an investigation of palladium-modified aluminide coatings as potential low cost, high performance alter- natives to platinum-modified aluminides (4).

The diffusion of hydrogen into a palladium coating can result in embrittlement and blister- ing, but methods of preventing this have been developed. One involves predepositing and diffusion vacuum annealing a palladium-transition metal alloy onto the substrate prior to the aluminising treatment. If the second component is an element,in which the solubility of

hydrogen is much lower-than in palladium, such as nickel, cobalt or chromium, the predeposited layer produced prevents gas in- take during the ahminising process. Alter- natively, a duplex predeposit consisting of a 8 pm pure palladium underlayer is coated with 2-3 pm of a suitable transition metal which serves as a barrier to the diffusion of hydrogen. It is suggested that electroless deposition is a possible way of coating complex shaped components.

The results of cyclic oxidation tests at 1 100°C and hot corrosion tests at 85OoC, carried out on coated Inconel 100 coupons, show that palladium-containing coatings have far better resistance than conventional aluminide coated samples. Field trials are now taking place.

References 1 R. G. Wing and I. R. McGill, Platinum Metals

Rev., 1981, 25, (3), 94 2 J. L. Cocking, G. R. Johnson and P. G. Richards,

Platinum Metals Rev. , 1985, 29, (l) , 17 3 G. J. Tatlock, T. J. Hurd and J. S. Punni,

Platinum Metals Rev. , 1987, 31, (l), 26 4 S. Alp&ine, P. Steinmetz, A. Friant-Costantini

and P. Josso, Surf. Coat. Technol., 1990, 43/44, (1-3), 347

Platinurn Metals Rev., 1991, 35, (2) 82

Solid State Amorphisation of the Platinum Metals A REVIEW OF SOME RECENT PUBLICATIONS

The absence of crystal defects such as grain boundaries and dislocations in amorphous metals makes them interesting both for basic research and in many applications. The amorphous state tends to confer improved mechanical strength, high wear-, corrosion- and electrical-resistance, and soft magnetic behaviour. Amorphous materials can combine a range of these physical and magnetic properties which, due to the absence of specific intermetall; compounds, can be varied continuously by altering the composition of the alloy.

Until recently amorphous metallic materials were associated with rapid quenchuig of the melt, which is the usual method of preparation. Recently however, it has been demonstrated that it is possible to form amorphous alloys by reactions which occur in the solid state. An ap- preciable number of the solid state amorphisation reactions which have been studied to date, including some of the very earliest, have involved alloys of the platinum group metals.

The first solid state amorphisation reaction was reported in 1983, this being the reaction of hydrogen with crystalline Zr, Rh leading to the formation of an amorphous hydride compound (1). At around the same time another group of investigators succeeded in producing an amorphous rhodium-silicon material by annealing a polycrystalline rhodium and an amorphous silicon bilayer at a temperature of 3OOOC (2 ) . Following this it was shown that a similar process could occur in wholly polycrystalline metallic systems, when an amorphous alloy was formed by diffusion at the interface between thin layers (300A) of gold and lanthanum, at temperatures between 50 and 8OoC (3).

In melt spinning processes glass formation is expected to occur at compositions corresponding to deep eutectic points in the phase diagram. However, solid state amorphisation reactions

tend to take place at compositions which corres- pond to intermetallic compounds with high melting points.

A solid state amorphisation process depends critically on the fact that the amorphous phase has a free energy which is lower than the non- equilibrium state of the crystalline solid. Thus a thermodynamic driving force for the formation of the glassy phase exists. In solid state amorphisation by diffusion from thin layers, this driving force results from the large negative heat of mixing of the individual elements. The formation of the metastable amorphous phase, rather than more stable equilibrium crystalline phases, occurs as a result of kinetic considerations. For instance, solid state amorphisation between thin layers is more likely to occur where the diffusion of one element into the other is fast when compared with the self-diffusion of the elements. In this way the amorphous alloy forms long before the collective rearrangement of the two species, which is necessary for intermetallic nucleation, can occur.

Thin Film Diffusive Couples Incorporating Platinum Metals

Two recent papers from Cornell University, New York, deal with the formation, by solid state amorphisation, of glassy platinum-aluminium alloys by diffusion from thin films of the elemental metals.

In the first of these papers, platinum- aluminium thin film samples were prepared on sodium chloride substrates and oxidised silicon wafers by electron beam evaporation te,chniques, at a pressure of 5 x lo-’ Torr (4). Two types of sample were prepared: the first a co-evaporated platinum-aluminium amorphous alloy, 77 nm thick, overlaid with a 47 nm thick crystalline layer of pure aluminium, and the second a polycrystalline platinum-aluminium bilayer.


Heating the co-evaporated platinum- aluminium/aluminium sample rapidly to 22OOC caused a number of transformed regions to form and grow. These result from the formation of amorphous islands in the still largely crystalline aluminium overlayer. All the amorphous regions appear to form simultaneously and thereafter their number remains constant. Complete amorphisation was achieved at a temperature of 45OoC, at which point all the remaining aluminium was incorporated in the amorphous phase. The non-uniformity of the reaction was attributed to the presence of a non-uniform alumina layer at the aluminium/platinum- aluminium interface.

Observations of the platinum-aluminium bilayer showed that an amorphous layer was present between the tbo as-deposited polycrystalline fdms, indicating that transformation to the glassy phase can occur at temperatures around 70OC. As the temperature was raised, the amorphous region grew until limited by the crystallisation of the Al, Pt, intermetallic compound at 45OOC. The composition of the amorphous phase varied

between 60 and 75 atomic per cent aluminium. In the second paper concerning solid state

amorphisation of platinum-aluminium, multilayers comprising three aluminium layers (outside layers 15-25 nm thick and inside layer 20-35 nm thick) separated by two platinum layers (10 nm thick) were examined ( 5 ) .

Amorphisation was achieved by heating the sample at a rate of S°C/min and then holding it at 2OOOC for 15 minutes. Three samples were treated in this way, and subsequently heated to higher temperatures until crystallisation commenced. In the first sample, of measured composition 24k4 atomic per cent platinum, the crystallisation temperature was around 36OOC and the dominant phase was Pt Al I , . The second sample, containing 25k4 atomic per cent platinum, crystallised at around 27OOC to form, mainly, the PtAl intermetallic compound. The third sample, of composition 36k4 atomic per cent platinum, crystallised at the still lower temperature of 23OOC to form mostly Pt,Al,. Thus it was concluded that solid state amorphisation does occur in the platinum-aluminium

system at compositions between those of the equilibrium compounds Pt Al.', and Pt Al I .

In both of the above publications the authors comment that at least one of the essential criteria for solid state amorphisation, namely a negative enthalpy of mixing of the constituent elements, is met in the platinum-aluminium system. However the proposed kinetic criterion for solid state amorphisation predicts the anomalous diffusion of one element. The first of the two papers reported the low temperature dissolution of aluminium in a co-evaporated platinum- aluminium alloy, indicating its role as the faster diffusing species. However, the aluminium im- purity diffusion and platinum self-diffusion coefficients are within the same order of magnitude over a wide temperature range, showing that the proposed kinetic requirement for glassy phase formation at low temperatures is not satisfied.

Ball-Milled Alloys Containing Platinum Metals

Mechanical alloying was developed some years ago as a method of combining particular metals and non-metals, which were difficult to combine by more conventional methods. A typical mechanical alloying process involves the use of a high energy ball mill in which the metallic powder particles are repeatedly trapped by col- liding balls, causing major deformation and cold welding. The successive deformation and welding of grains leads to a progressively refined lamellar-type of grain structure.

Reports of the production of glass) materials by ball milling elemental powders together suggest that the mechanism is essentially solid state amorphisation occurring by interdiffusion within layered composite powders. In solid state amorphisation reactions caused by ball milling intermetallic powders, the situation is slightly different. In this case the ball milling process must introduce sufficient free energy to render the intermetallic unstable with respect to the glassy phase. Diffusion can then occur at an increased rate due to local temperature rises caused by the milling action.

A recent publication from the University of Amsterdam reported the amorphisation of

Platinum Metak Rev., 1991, 35 84

palladium-zirconium alloys by ball milling (6). In these experiments a range of palladium- zirconium alloys were prepared by arc melting the constituents together, then crushing and milling the ingot. Milling was carried out under argon to prevent oxidation. The products of the milling process were examined by X-ray diffraction which showed that single phase amorphous Pd,Zr alloys were obtained, for x>45. The upper limit for x was certainly greater than 60. For x<45 a two phase material consisting of an amorphous phase and PdZr, intermetallic was formed.

In a further publication the same group of investigators considered the amorphisation of platinum-zirconium alloys by a high-energy ball milling process. Using X-ray diffraction and dif- ferential thermal analysis, they established the feasibility of amorphising Pt,, 2rb7 and Pt,,Zr,, alloys by ball milling for about 270 hours, under an argon atmosphere (7).

Studies of the palladiudplatinum-zirconium system represent an extreme test of the current models describing solid state amorphisation by ball milling (8). Palladium and platinum display the largest heats of mixing, and therefore form with zirconium the most stable intermetallic compounds. Despite the stability of the crystalline phases the ball milling process is still able to produce the metastable glassy state.

Future Work The dimensions of amorphous materials which

can be produced by the melt spinning route are limited by the need for extremely rapid quen- ching. Solid state amorphisation by diffusion from thin layers is similarly constrained by the thickness of a single amorphous layer, but it is possible to use a composite structure to produce a bulk glassy material. In the same way, solid state amorphisation by ball milling offers the possibility of producing bulk glassy alloys by an industrial scale process. The unusually high exothermic alloying reactions of the platinum group metals, with a range of other elements, and their correspondingly stable intermetallic compounds, do not in any way preclude their participation in such amorphisation reactions. In fact, the high

negative heat of mixing of a variety of metals with the platinum group metals appears to favour solid state amorphisation reactions, and is likely to ensure the inclusion of the platinum group metals in future work in this area. M.L.D.

References 1 X. L. Yeh, K. Samwer and W. L. Johnson, Appl.

Phys. Lett., 1983, 42, (3), 242 2 S. R. Herd, K. N. Tu and K. Y. Ahn, Appl. Phys.

Lett., 1983, 42, (3, 597 3 R. B. Schwarz and W. L. Johnson, Phys. Rev. Lett.,

1983, 51, (5), 415 4 J. M. Legresy, B. Blanpain and J. W. Mayer, J .

Mater Res., 1988, 3, (9, 884 5 B. Blanpain, L. H. Allen, J. M. Legresy and J. W.

hlayer, Phys. Rev. B, 1989, 39, (18), 13067 6 F! I. Loeff, E H. M. Spit and H. Bakker, J. Less-

Common Met., 1988, 145, 271 7 F. H. M. Spit, I? I. Loeff and H. Bakker,J. Non-

Cyst. Solids, 1989, 108, (2), 233 8 A. W. Weeber and H. Bakker, Proc. Conf. on

Liquid and Amorphous Metals 6, Garmisch Partenkkhen, Federal Republic of Germany, 24-29 Aug., 1986; 2. Phys. Chem. (Fmnkfun am Main), 1988, 157, 221

Palladium in a Thin-Film Hydrogen Sensor

There is a growing interest in the development of solid state devices for use as chemical sensors, and following the significant progress made in hydrogenated amorphous silicon thinfilm transistor technology, the possibility of using devices based upon this as sensors has become very attractive.

A recent letter from the Istituto di Elettronica dello Stato Solido, CNR, Italy, describes the development of a palladium-gate thin-film transistor as a hydrogen sensor (L. Mariucci, A. Pecora, C. Puglia, C. Reita, G. Petrocco and G. Fortunato, Jpn. J. Appl. Phys., Part 2 Lett.,

Although the electrical characteristics of a top-gate device are inferior to those of a bottom-gate one, the former was selected to meet the requirement of a gate electrode in direct contact with the environment. A 100 nm thick layer of palladium was sputter deposited onto the 9 nm thick silicon nitride employed as the gate insulator. This enables the device to respond in a relatively fast time and in a relatively stable and reproducible manner to hydrogen, and the investigation has shown that such devices are good enough for application as hydrogen sensors.

1990, 29, (12), L2357-L2359).


Fluorophosphine Complexes of the Platinum Group Metals DEVELOPMENTS INVOLVING ORGANIC DERIVATIVES

By Lutz Heuer Institut fur Anorganische und Analytische Chemie, Braunschweig, Germany

Dedicated to Henri Moissan on the occasion of the one hundredth anniver- sary of his discovery of the first fluqrophosphine platinum complex, this review describes the recent interest, and developments influorophosphines as ligands for platinum group metals. The synthesis, structure, reactions, stability, and the potential of these compounds as homogeneous and heterogeneous catalysts are the main features of this article.

Looking for a way of preparing fluorine chemically, Moissan reacted phosphorus pen- tafluoride and platinum black (1). He was able to isolate a product of composition F,PPt.

2PF, + 2Pt - (F,P)?Pt?F, (i)

In 1891 he recognised the true structure of the first trifluorophosphine complex (2), see Equa- tion (i) and Figure l. This “failed” attempt at preparing fluorine had started the chemistry of fluorophosphines, won after the discovery of the first carbonyl complexes by Schiitzenberger, in 1868 (3). Interestingly both complexes, the first PF, complex as well as the first CO complex, involved a platinum(I1) atom, see in Figure 1.

Following the preparation by Chatt in 1949 of some further platinum(I1) complexes of PF, , and his postulation of the similarity between trifluorophosphine and carbonyl complexes with respect to their bonding situation (4), the interest of chemists was drawn to fluorophosphines and their co-ordination compounds. Nevertheless it

took some eight years before the first organo(difluoro)phosphine and di(organ0)- fluorophosphine compounds were successfully synthesised, and published by Burg (5).

With organofluorophosphines now available, their use as ligands in co-ordination chemistry has been studied intensively, and hundreds of mono-, di-, and triflucrophosphine complexes of different transition metals have been prepared (6), as indicated in Table I.

Why Examine Ligands of Formula C,P-F2-, Instead of PF,?

Organofluorophosphines are compounds involving a carbon-phosphorus-fluorine (C-P-F) moiety. In contrast to other fluorophosphines, for example Si-P-F, N-P-F, P-P-F, 0-P-F, S- P - 4 and X-P-F (where X = halogen), they show a stable element-phosphorus bond (here C-P). The physical and chemical properties of organofluorophosphines also resemble those of

1 pF3, / F \ / F

,Pt \ / p + \

F pF3 F

\ /“ 2 co

/pt \ c , co Fig. 1 The fwst platinum(I1) complexes of these particular ligande: (1) the PF, complex which was charaeterieed in 1891 by Moissan and (2) the CO complex whieh was prepared by Schiitzenberger in 1868


Table I

Fluorophosphine Complexes of Transition Metals

Me, N-PF , F-PF, C-PF, (Fig. 2)

F-P-F bond angles: 97.70 96.3O 91.5O

P-F bond lengths: 157 pm 157-1 58 pm 161 .O pm I

Ni cu Z n - c o - Fe - Mn - Cr - Ti v

Fig. 2 An X-ray diffraction study shows dimeric 9-difluorophosphino anthracene in the solid state (9). The complex, which can be obtained in a single step synthesis, has a PF, moiety unable to rotate at the C-P

I

I bond

Zr Nb Mo Tc Pd Ag C d Rh Ru - - - -

Hf Ta W Re 0 s Ir - Pt Au Hg - - ~~ ~~

Blue typeface indicates known complexes, blue and underlining indicates known organofluorophosphine complexes 16. 7)

Table II

Comparison of Bond Angles and Lengths of PF3 and RPF,

PF , very closely (8 - lo), see Table 11. This has been confirmed by X-ray diffraction studies on two organofluorophosphines: the dimeric anthracene difluorophosphine, shown in Figure 2 (9), and for comparison the dimethylamino difluorophosphine (10).

One can clearly see the similarities in the bond angles of PF, and RPF, (where R = carbon bonded groups), despite strong steric hindrance,

in contrast to N-PF, without this sterk factor. In the example, Figure 2, the PF, moiety is unable to rotate at the C-P bond because of strong F-H “through-space’’ interactions.

This property serves to combine the special electronic effects of PF, with other characteristics of co-ordination compounds that are important in catalytic reactions, for example: stability, solubility, volatility, chirality, the bulk,


the possibility of heterogenisation, and so on. Surprisingly, the highly sterically hindered and

air-stable compound shown in Figure 2 was obtained in a single step synthesis, see Equation($:

the photochemical dimerisation of difluorophosphino anthracene (9)

Methods of Preparation The known types of organofluorophosphine

complexes of platinum group metals are given in Table 111. For most of these compounds an appropriate PF, complex is also known.

Most of these compounds have been prepared by an exchange reaction between a labile ligand and an excess of the organofluorophosphine (7, 14, 15), that is:

PtCI,(COD) + 2L + PtQ,L, + COD (iii) Os,(CO),,(MeCN)I + 2L -

Os,(CO),,L, + 2MeCN (iv) where COD = 1,8-~yclooctadiene, L = RPF,, R,PF, and R = carbon bonded organic moiety,

In the case of platinum(0) complexes a very large excess of organodifluorophosphe m y be used to get complexes of the type PtL, (reduction of platinum(I1) under formation of some organofluorophosphorane (16, 17), see Quation (v)). These complexes are not as stable against oxygen and moisture as their C1 PtL , analogs (17) and they may be transformed to mixed phosphine substituted complexes using tertiary phosphines (16), for example triphenylphosphine, see Equation (vi):

K,PtCl, + 5L - PtL, + 2KCl + LCl, (v) PtL, + 2PRJ - PtL,(PR,), + 2L (vi)

Bulky organic substituents involved in the fluorophosphine ligand have only a minor effect in the given preparation methods. For example two ‘BuPF, or (o,p-(CF,)C,H,),PF can co- ordinate to one platinum(I1) atom (18). In the case of tungsten a hexaco-ordinated. species is known, that is W(‘BuPF,), (13). On the other hand it is impossible to co-ordinate two phosphines such as ‘Bu , PF or (Me, Si) PF, on- to one platinum(I1) atom (7), but each of these ligands can co-ordinate to one metal, for example osmium or ruthenium (14). In a cluster

Fig. 3 A BF , -bridge chelating fluorophosphine ligand bonded to platinum(I1) has been studied in the solid state. The preparation is given by Equations vii and viii; R = 2,5-&methylphenyl (1 7)


Table 111

Known Types of Organofluorophosphine Complexes Involving I Platinum Group Metals

Rhodium

RhCp*CI,L (12)

RhCI(PPh,),L

Iridium

compound, for example Os,(CO),,L,, two ligands are always bonded to two different metal atoms (14, 15). Only if there are more RPF, ligands than metal atoms in a cluster, as in 0 s (CO) L, , will two organodifluorophosphines be connected with one metal centre (14).

Reactions of Platinum(0) and Platinum(I1) Complexes

The reactions of complexes of the type PtL, with water and oxygen lead to the formation of partly hydrolysed and oxidised organofluorophosphines co-ordinated to

platinum(II), see Equation (vii) (17). These complexes may be reacted with boron trifluoride etherate to yield BF: -bridged, chelating

Palladium

(a)

Platinum

PtCI,L,

PtCI,(PR,--L)

PtCI,(PR,)L

PtCI(PR,), (RPFO)

PtCI(CH,--L)L

PtL,

WPR, ),L2

Pt(AsR,),L,

Pt(tP),L

(a1 Palladium complexes are claimed by Kruck but they are not yet published (13) L = RPF,. R,PF; R = carbon bonded organic moiety; Cp' = C.Me.; tp = CHICH,PPh,l,. In the case of platinum(ll1 complexes, some more complicated compounds are known (see below1 For a review see 171, for further details see 114. 151

organofluorophosphine complexes, as shown in Figure 3 on the previous page (17).

R(PF,R), + 3H,O + 0.50, - Pt(PF(OH)R),(PF(O)R), + BF, - Pt(PF(OH)R),(PF(O)R), + 4HF (vii)

PtL(PF(0)R)-BF, -(PF(O)R)l (viii) where R = a carbon bonded organic moiety.

Organofludrophosphine platinum(I1) complexes are very stable compounds which do not decompose under n o d conditions. These complexes are less stable only if the organic moiety is chosen from the group of multiple halogenated substituents, for example C6F, or CC1,H. This is in strong contrast to the stability of the corresponding organofluorophosphines themselves, which become more stable if they are either


Ruthenium

Osmium

Fig. 4 The PtCIZ(Cp*PFz), complex as observed in the solid etate by X-ray mraction (19)

halogenated in the organic part or if the organic moiety shows a reasonable steric bulk.

As a typical example of a platinum(I1) complex involving a bulky substituent, the X-ray structure of PtCl,(Cp*PF2)2 is shown in Figure 4 (19).

On the other hand bulky substituents involved in the phosphine ligand, such as 2,4,6-trimethylphenyl difluorophosphine, display a most interesting chemistry if

they are co-ordinated to platinum(I1). PtCl,(PF,C,H,Me,),, for example, splits off HCl if heated in vacuum (20) and gives a compound involving a Pt-C bond, see Figure 5.

The remaining chlorine atom in the compound shown in Figure 5 may be replaced by organic moieties using, for example, SnMe, or HgPh,, and yielding the methylated or phenylated complexes, respectively.

Another most interesting aspect of

Pt-C- bond


Fig. 5 An X-ray diffraction study of an organomotalfic organofluorophosphine platinum(l1) compound with bulky substituents attached to the pbosphine digand (20) and containing a Pt-C bond

Fig. 6 A study in the solid state of the hypervalent phosphorus atom in an organofluorophmphine moiety shows the RPF2 p u p in a trigonal bipyramidd coordination mode with one fluorine in the axial position and one fluorine in the equatorial position (21)

organofluorophosphines bonded to platinum(I1) has been found in the compound shown in Figure 6. In the solid state the ortho-subsututent of the aromatic ring system (-CH,NMe,) is found to co-ordinate into the PF, moiety, representing the first example of an hypervalent phosphorus in this type of compound (21).

Reactions of Ruthenium and Osmium Complexes

Complexes of type M,(CO),, +Ln (M = Os, Ru, n = 1-4; M = Os, n = 6) are stable compounds in the solid state, and in the case of osmium also in solution (14, 15), see Figure 7. Treatment of these complexes with trimethylamine oxide in the presence of free ligand leads to the formation of mixtures of compounds involving different numbers of ligands. Therefore one may start with M3(C0),, (M = Ru, 0 s ) and end up with all the possible com-

Fig. 7 A typical co-ordination mode in an osmium cluster compound, is shown for example in the solid state structure of 083(Co),o( 'BU~PWI (15)


Complexes of type M,(CO),, +Ln (M = Os, Ru, n = 1-4; M = Os, n = 6) are stable compounds in the solid state, and in the case of osmium also in solution (14, 15), see Figure 7. Treatment of these complexes with trimethylamine oxide in the presence of free ligand leads to the formation of mixtures of compounds involving different numbers of ligands. Therefore one may start with M3(C0)12 (M = Ru, 0 s ) and end up with all the possible complexes given above (n = 1-0 see TabJe(II1) of which n = 3 represents the main producr if an excess of amine oxide and ligand is usad (14) Numbers n > 3 are difficult to obtain by this method, indeed n = 5 has never been fully characterised. Using ultraviolet llght, Os3(C0) 12

and excess ligand n = 6 has been found to be the major product (14).

Rhodium, Palladium and Iridium Complexes

Even though rhodium is one of the few metals showing a strong nuclear magnetic spin of %, which suggests that any conceivable rhodium organofluorophosphine complexes would have an interesting NMR spectra, little is known about this class of compounds (7). In the opinion of the author, organofluorophosphine complexes of rhodium as well as of iridium represent a challenge for every preparative chemist, especially with respect to possible compounds analogous to Wilkinson’s and Vaska’s complexes.

Palladium organofluorophosphine complexes are known to undergo some of the reactions given for platinum; however, the appropriate platinum complexes are more stable and, for this reason, have been studied in greater detail. The identi- ty of some palladium compounds involving organofluorophosphine ligands are claimed by Kruck (1 3) but have not yet been published.

Properties of Complexes of Organofluorophosphines

In contrast to the more or less volatile PF, -complexes of transition metals, organofluorophosphine complexes are much less volatile, or non-volatile, solids; and due to the organic group they are more resistant to moisture and to air. Almost all of the known organofluorophosphine complexes of the platinum group metals may be stored for months in the solid state at room temperature, without using any protective methods, and without any changes occurring. Indeed, even in solution most of them are stable against moisture and oxygen.

The solubility of organofluorophosphine complexes of these metals is influenced by the organic group bonded to the phosphorus and by the general bonding state on the metal. Dichloromethane or other polar solvents are perfectly capable of dissolving reasonable amounts of most of these complexes. It is possible, however, to use hydrophobic or hydrophilic organic moieties to increase or decrease the

solubility of a given co-ordination state in a given solvent. For example, using dichloromethane as the solvent the solubility of complexes of the type C1,Pt(PF,lo,o-R,CbH,l), increases in the following order: R = Me0 < Me < PhO < H

In some dozens of X-ray determinations of organofluorophosphine complexes of transition metals a somewhat shorter metal-phosphorus bond length has always been observed, compared with that of the appropriate triorganophosphine co-ordination compound (7). In the case of platinum(I1) complexes, the Pt-P bond length correlates with the ” P- 195 Pt coupling constant in the NMR spectra of these compounds (7,21). Both indicate a strong metal-phosphorus interaction, which is reflected in strong chemical and physical bonding of the organofluorophosphine to the metal.

< CibH,,O (7).

Heterogenisation of Complexes of Organofluorophosphines

One main synthetic route to organofluorophosphines first developed by Lines and Centofanti (22) and then optimised by the author (7, 23) involves lithiation of an aromatic ring system, and treatment of this product with PF,Cl, which is a gas. (PF, may also be used but gives insufficient yields). It has been shown that this method is useful for transforming polystyrol to PF,-functionalised polystyrol, which readily yields platinum(I1) complexes on treatment with PtCl,(COD) (7).

PF, -functionalised polystyrol should also be a good starting material for other transition metal complexes, especially for the platinum metals.

Outlook The investigations on fluorophosphine com-

plexes started with the hope in finding some interesting new compounds which would become as relevant for catalytic processes as some particular CO complexes. The high sensitivity of compounds involving PF , to moisture and oxygen has destroyed the initial optimism. As organofluorophosphines are readily available and are much less sensitive to wet air this optimism may return. In addition, the possibility of


heterogenisation of active complexes by standard organic reactions may increase the interest of industrial chemists.

Heterogenisation may not only find application in catalytic reactions, one should also keep in mind the strong bonding of the platinum group metals to organofluorophosphines, a property which may be useful in the recovery of these expensive metals from solutions and mixtures in organic solvents, by absorption using polymeric organofluomphosphines.

Lastly, Pt(PF,), has been used for the preparation of special platinum metal catalysts by thermal decomposition (24). Because of the high toxicity and volatility of PF,, which is split off during this reaction, it may be better to use organofluorophosphine ligands instead.

Acknowledgements The author is indebted to Professors B. F. G.

Johnson, P. G. Jones, Dr. D. Schomburg and Dr. R. Schmutzler. Figures a* reprinted with permission of journals and/or authors.

References 1 H. Moissan, C . R . Hebd. Seances Acad. Sci.,

2 H. Moissan, Bull. Chem. SOC. Chim. Fr., 1891,

12 H. Werner, B. Klingert and A. L. Rheingold,

13 W. Krampe, T. Kruck and K. F. Tebbe, Chem. 1886, 102, 763

454 BeE, 1989, 122, 1477

Organometallics, 1988, 7 , 911

3 M. P. Schiitzenberger, Annales [Paris], 1868, 15, 100 and Bull. SOC. Chim. France, 1870, 14,97 and J. Prakt. Chem., 1871, 112, 159; see also, W. A. Herrmann, Chem. uns. Z i t , 1988, 22, 113

4 J. Chatt, J. Chem. Soc., 1949, 3340; J. Chatt and A. A. Williams, J. Chem. SOC., 1951, 3061

5 A. B. Burg et al., WADC-Report, 1956, 56-82, Part 111; A. Burg and G. Brendel (American Potash & Chemical Co.), U S . Patent 2,959,620; 1960

6 For reviews see, for example, J. F. Nixon, Adv. Inorg. Chem. Radiochem., 1970, 13, 363; J. F. Nixon and J. R. Swain, Platinum Metals Rev., 1975, 19, (I), 22 and J. F. Nixon, Adv. Inorg. Chem. Radiochem., 1985, 29, 41

7 L. Heuer, Dissertation, Technische Universitiit Braunschweig, W Germany, 1989 (German). A free copy of the thesis is available on request (from Dr. L. Heuer, Scheiblerstrape 83, D-4150 Krefeld, Germany)

8 IPF31: J. C. Marriott, J. A. Salthouse, M. J. Ware and J. M. Freeman, J. Chem. Soc., Chem. Commun., 1970, 595

9 LCPF21: L. Heuer, D. Schomburg and R. Schmutzler, Chem. Ber., 1989, 122, 1473

10 INPF21: E. D. Morris and C. E. Nordman, In- org. Chem., 1969, 8, 1673

1 1 L. Heuer, B. F. G. Johnson, J. Lewis and D. Schomburg, to be published

14 L. Heuer, I? Raithby, B. F. G. Johnson and J.

15 L. Heuer and D. Schomburg, to be published 16 J. F. Nixon and D. M. Sexton, Inorg. Nucl.

Chem. Lett., 1968,4, 275, andJ. Chem. SOC. (A), 1970, 321

17 L. Heuer, P. G. Jones, D. Schomburg and R: Schmutzler, New. J. Chem., 1990, 14, 891

18 L. Heuer, P. G. Jones and R. Schmutzler, J. Fluorine Chem., 1990,46, 243

19 L. Heuer, U. K. Bode, P. G. Jones and R. Schmutzler, Z . Naturfonch., 1989, 44b, 1082

20 L. Heuer, L. Ernst, R. Schmutzler and D. Schomburg, XI11 Int. Conf. Organomet. Chem., Book of Abstracts, Torino, 1988, 171; L. Heuer, L. Ernst, I! G. Jones, D. Schomburg, and R. Schmutzler, to be published

21 L. Heuer, D. Schomburg, P. G. Jones and R. Schmutzler, Phosphorus, Sulficr Silicon, 1990, 49/50, 421

22 E. L. Lines and L. F. Centofanti, Inorg. Chem., 1973, 12, 598

Lewis, to be published

23 L. Heuer and R. Schmutzler, J. Fluorine Chem., 1988, 39, 197

24 Laser Process. Diagn., ed. D. BWerle, Springer Ser. Chem. Phys. 39, Springer, Berlin, 1984, p.257; H. Schrijder, K. L. Kompa, D. Masci and I. Gianinoni, Appl. Phys. A , 1985, 38, (3), 227

Precious Metals Science and Technology In 1985, to commemorate the centenary of Edited by L. S. Benner, T. Suzuki, K. Meguro

the founding of Tanaka Kikinzoku Kogyo and S. Tanaka and consisting of some 800 pages K.K., a reference book entitled “Science of including 500 figures and tables, this transla- Precious Metals” was published in Japan (see tion will be a valuable addition to the literature. Platinum Metals Rev., 1986, 30, (2), 62). Further details, including price and

Now the English language version, “Precious availability, may be obtained from: Interna- Metals Science and Technology”, containing tional Precious Metals Institute, 4905 several additional chapters has been published Tilghman Street, Suite 160, Allentown, by the International Precious Metals Institute. Pennsylvania 18104, U.S.A.


Controlling Automobile Emissions Attendance at the 1991 Society of Automotive Engineers lnternational Congress and Exposition held in Detroit, Michigan, U.S.A. from 25th February to 1st March, 1991, was affected by the conflict in the Middle East; in particular representation from Europe and Japan was considerably less than usual. Nevertheless there was an extensive programme of technical papers covering many aspects of the motor car in a number of parallel sessions, several of which covered emissions technology.

A new impetus to developments in autocatalyst technology has resulted from the recently announced Clean Air Act in the U.S.A., which leads to substantially tighter limits for exhaust emissions, particularly in California, and also from the development of a major new market in Europe. Platinum group metals catalysts are, and for some years will continue to be, the accepted means of controlling automobile tailpipe emissions. In order to meet the increasingly more stringent regula- tions, however, factors such as the warm-up characteristics and the high temperature durability of catalysts are receiving attention.

One means of achieving better performance is to reduce the cold start emissions; in the U.S. Federal Test Procedure much of the total emissions arise from this part of the test. One solution is to get faster catalyst warm-up by moving the catalyst system closer to the engine so that maximum use is made of the heat generated by the engine just after it is started. Subsequently, a catalyst in this position may experience substantially higher temperatures than in the conventional underbody position.

A paper by R. J. Brisley, R. D. O’Sullivan and A. J. J. Wilkins of Johnson Matthey, described the changes in performance of both platinum-rhodium and palladium-rhodium catalysts over 100 hours of engine running, when the inlet temperature to the catalyst was varied between 780 and 960OC. It was concluded that platinum-rhodium catalysts had the better resistance to thermal degradation at higher temperatures, when compared at the same platinum group metals loadings and ratio. However, an improved palladium-rhodium

catalyst with a higher palladium loading gave a similar performance to the standard platinum- rhodium catalyst, even at the highest ageing temperature of 93OoC, except for the removal of nitrogen oxides which was still poorer. . In another paper M. J. Church, J. E. Thoss and L. D. Fizz of Johnson Matthey concluded that with platinum-rhodium catalysts, moving the catalyst to a hotter position did benefit performance, and that the gain in performance more than compensated for the increased deterioration caused by thermal ageing. Never- theless, the authors suggest that there is a limit to the benefits that can be gained by increasing the operating temperature; temperatures in excess of 95OOC should be avoided.

An alternative to mounting the catalyst close to the manifold is to heat the catalyst directly during a cold start. Several papers dealt with the use of heated metal substrates, in which the catalyst is heated by the application of electric power to the monolith upon which the catalyst is deposited. Papers by I. Gottberg, J. E. Ryd- quist, 0. Backlund and S. Wallman of Volvo Car Corporation, in collaboration with W. Maus, R. Briick and H. Swars of Emitec; by W. A. Whittenberger, Camet Co., and J. E. Kubsh, W. R. Grace; and by M. J. Heimrich of Southwest Research Institute and S. Albu and J. Osborn, C A m , all showed the benefits of this system, particularly for hydrocarbon emissions control. However, the electric power necessary to reach the required catalyst operating temperature quickly is high; typical values of 4 to 5 kW were indicated. The in-use durability of heated metal substrate based catalysts is still largely unknown.


While it is generally agreed that platinum- rhodium and palladium-rhodium three-way catalysts are the best means of achieving the control of pollutants from cars, discussions continue about the development of the monoliths used as the catalyst support medium, with the objective of maximising the contribution the monolith makes to the performance of the whole catalyst. J. P. Day and L. S. Sucha of Corning analysed the substrate parameters in- fluencing pressure drop and efficiency of the catalyst system, while M. Machida and J. Kitagawa of NGK Insulators, in collaboration with H. Yamamoto and F. Kato, Nissan, concentrated on the warm-up characteristics of thinner wall, low bulk density ceramic substrates. Metallic supports also received a lot of attention; F.-W. Kaiser and S. Pelters, of Porsche, compared the results obtained from a number of metal substrates with different cell densities, all coated with a similar platinum- rhodium catalyst formulation ( 5 : l), at a loading of 50 g/ft’.

Control of emissions from diesel engine vehicles, especially particulate emissions, achieved a new prominence this year, with a number of sessions devoted to this subject.

With catalysed systems, aimed at in-situ regeneration, the common problem considered in many papers was the formation of sulphates arising from fuel-derived sulphur.

Catalysts which give good reduction of car- bonaceous particulate matter are usually also good catalysts for further oxidation of the sulphur dioxide formed in the fuel combustion process. P. Zelenka of AVL, together with E. Lox and K. Ostgathe of Degussa offer the opinion that platinum-based catalysts provide the best guarantee of low tailpipe emissions and low rates of deterioration. This is due to their good performance at low temperatures (where the rate of sulphate formation is low), and their resistance to poisoning by oil additives. These authors conclude that, in addition to catalyst performance, careful optimisation of the engine combustion parameters is essential for success. Given the potential for better fuel economy, and hence reduced carbon dioxide emissions from diesel engines and their generally lower levels of gaseous pollutants compared with those for the corresponding petrol engines, interest in catalytic systems for the reduction of particulates and odours from diesel engines is likely to grow. D.E.W.

Binary Coatings for DSA@-type Electrodes Prior to the development of dimensionally

stable electrodes (DSA@) in the late 1 9 6 0 ~ ~ the production of chlorine and chlorate via the electrolysis of brine generally made use of graphite electrodes. Graphite electrodes required fre- quent maintenance, but DSA@ electrodes preserve both their shape and their voltage characteristics, and facilitate significant electrical power savings. They consist of a thin active coating, capable of catalysing the desired electrochemical reaction and of passing the electric current between a base metal support and the interface of the electrode with the electrolyte. The coating consists of a noble metal oxide mixed with a conducting or non conducting stabilising oxide, while the support is generally a valve metal such as niobium, tantalum, titanium or zirconium.

Such anodes have been considered for a variety of electrochemical processes, and a communication from the Swiss Federal Institute of

Technology, Lausanne, reports a systematic investigation of nine binary coatings made during the continuing search for a DSAO-type electrode suitable for oxygen evolution in concentrated. sulphuric acid solutions (Ch. Comninellis and G. P. Vercesi, J. Appl. Elec- rrockern., 1991, 21, (4), 335-345).

On the basis of cost and performance titanium, which is used in most conventional DSA@ applications, was selected as the base metal. The binary coatings consisted of a conducting oxide (RuO,, IrO, or PtOu.12fu.05) and a non conducting stabilising component (Ti0 , , ZrO, or Ta,O,), and compositions ranging from 10 to 100 per cent of conducting oxide were tested. The results are discussed.

It was concluded that the titanium electrode coated with IrO, and Ta,O,, 70 and 30 mol per cent, respectively, was the best tested. It also displayed the best catalyst dispersion and gave the longest service life.

Plutinum Metals Rev., 1991, 35, (2) 95

The Noril’sk-Talnakh Deposits THE LARGEST PLATINUM OCCURRENCES IN THE U.S.S.R. A s a general rule, this Journal does not aim to report on the occurrence or genesis of the platinum-group elements. None the less, the following account is published in the belief that it will interest many readers, and inform them of important platinL$erous deposits about which little has been written in Western literature. During August and September, 1990, Professor G. von Gruenewaldt, Director of the lnstitute for Geological Research on the Bushveld Complex at the University of Pretoria, spent four weeks visiting platinum producing areas in the U.S.S.R. as a guest of that country’s Academy of Sciences; his report follows.

The Noril’sk-Talnakh deposits are situated north of the Arctic Circle in northern Siberia, see Figure 1, in the Province of Krasnojarsk. The area is only accessible by boat from Murmansk, or by a four hour flight from Moscow. The deposit was discovered in about 1860, but serious mining operations did not commence until 1935. Today, the area supports a population of about 300,000, most of whom live in the towns of Noril’sk or Talnakh. Bulk supplies for the region, and ore, are shipped through the harbour town of Dudinka, 120 km due west of Noril’sk on the banks of the Yenisei River.

Geological Setting The platinum-group elements are a by-product

of massive and disseminated nickel-copper sulphide deposits associated with differentiated mafic (enriched in ferromagnesian silicates) intrusions. The deposits are situated on the northwestern edge of the Siberian platform, see Figure 1, which has been stable since the end of the Palaeozoic period. This platform is separated from the adjoining stable blocks, the Taimir Peninsula to the north and the Ural block to the west, by the Khatanga and Yenisei mughs, respectively. Within western Siberia, the base- ment rocks are overlain by dolomites and limestones dating from the Silurian period. These, in turn, are overlain by impure calcareous and dolomitic limestones (mark) and sulphate- rich evaporites of Devonian age, lower Car- boniferous limestones, and mid-Carboniferous to Permian continental sediments of the Tunguska

Group which include coal measures. Subsequent large scale rifting was heralded by the extrusion of large volumes of flood basalt, known as the Siberian Traps, of late Permian to Triassic age. Continued rifting resulted in the subsidence of the Khatanga and Yenisei troughs and the deposition of thick sedimentary sequences of early Triassic to mid-Tertiary age.

A variety of different intrusions were emplaced simultaneously with the extrusion of the basalt (1). These are mostly basaltic in composition (gabbros), undifferentiated and not mineralised, in contrast to the Noril’sk-type of intrusions which are well mineralised and well differentiated. The unmineralised intrusions are widely distributed, but the distribution of the mineralised intrusions is restricted, and two features seem to be important in their localisation. These are: first the development of a well differentiated sequence of basalts ranging from alkali-basalt, through magnesium-rich (picritic) basalt to silica- rich tholeiitic basalt at the base of the Traps, in the Noril’sk area. Secondly a structural control, in that all mineralised intrusions are emplaced on, or in the proximity of, the very prominent Noril’sk-Karealakh fault, see Figure 2. The most important are the Noril’sk I, Noril’sk I1 and Mount Chernaya intrusions, near the town of Noril’sk, and the larger Talnakh intrusion some 30 km further to the north. The ones near Noril’sk are intrusive into the continental sediments of the Tunguska Group and the overlying basalts, whereas the Talnakh intrusion was emplaced at a lower stratigraphic level and


Fig. 1 The Noril'sk-Talnakh nickel-copper- platinum- group metal deposits are situated well north of the Arctic Circle on the northwestern edge of the Siberian platform. The only other producer of platinum-group metals in the Soviet Union is Pechenga. Alluvial platinum was mined extensively in the past in the Nizhniy Tagil area of the Ural Mountains. Comparatively high concentrations of ruthenium, iridium and osminm in the chromite ores of Kempisay could constitute a future resource of these metals

Fig.% Generalised geological map of the Noril'sk area showing the location of the mineralised intrusions in relation to the Noril'sk-Karealakh fault


UMRED SERIES

up to 1OOm

Urmm DIBBAO SERIES

30-35m

is intrusive into limestones and evaporites. Exploration along the Nod’&-Karealakh fault

has also indicated some mineralisation in the South Noril’sk and Talminskaya areas, as well as in igneous rocks associated with a p a d e l fault in the Imangdinsky area. The differentiated, mineralised intrusions are generally between 50 and 150 m thick, and are subdivided on the basis of lithology into three zones, see Figure 3.

Mineralisation Massive nickel-copper-platinum-group ele-

ment sulphide ores are restricted to the basal portions, usually where the intrusions thicken. However, massive ore is frequently separated from the mafic intrusion by intervening sediments, and displays intrusive relations to the sediments and to the mafic intrusion. Breccia ore,

Fig.3 Generalised columnar section through a mineralised intrusion showing the distribution of the p l a t i n u m - g r o u p elements in the different ore types

I i i i 1 : I i I i 1 ; i i I i I ! I ’ I I I I I I I I I

usually copper-rich, suggests extensive mobilisa- tion of the ore, and consists of fragments of intrusive or sedimentary rocks, depending on the setting, in a matrix of massive ore. The fragments and surrounding rocks of the breccia ore are frequently heavily impregnated with sulphide. Skarn-type mineralisation is developed where mineralised portions of the intrusion are in contact with limestones.

A variety of different massive ore types are developed. The most common is termed pyrrhotite-chalcopyrite ore which grades about 3 per cent nickel, 4 per cent copper and 12 to 15 ppm platinum-group elements, with a p1atinum:palladium ratio of 0.3. Locally the massive ores are considerably enriched in copper (Figure 4) and consist almost entirely of the minemls cubanite and pentlandite. In these


copper-enriched ores, the platinum-group element content can increase to more than 60 ppm and numerous centimetre-sized platinum group minerals occur near the upper contact of this type of massive ore.

The Talnakh intrusion covers an area of about 80 sq km, and about 32 sq km is underlain by massive ore which attains a thickness of 40 m in the Oktyabrski Mine. Disseminated ore, on the other hand, has a much wider distribution and is developed over 60 sq km , that is 75 per cent of the intrusion (Figure 4). The thickness of the disseminated ore varies between 20 and 60 m, usually in accordance with the thickness of the intrusions.

Four different types of disseminated ore can be distinguished: (i) Heavy disseminations in the taxitic Lawer Gabbro Series, usually as large irregularly shaped

sulphide patches. The texture of the taxitic rock is very variable in that it contains coarse grained patches; plagioclase-rich segregations and fragments of gabbroic rocks, amongst others. (ii) The overlying picrite is characterised by the presence of numerous sulphide globules which are flattened parallel to the igneous layering. A notable texture is the distinct separation of pyrrhotite in the lower part of the spheres and chalcopyrite in the upper portion. Interstitial disseminated sulphides occur throughout this type of mineralisation. (iii) Upwards, these sulphides spheres decrease and make way for comparatively weak interstitial sulphide disseminations. (iv) Wkak sulphide disseminations in the upper taxitic gabbro, within the Upper Gabbro Series.

The disseminated ore has grades in the order

Fi g.4 The distribution of massive ore generally coincides with areau where the Talnakh intrusion eweeda 150 metres in thickness. In areas of no \iable mineralisation the intrusion is umally lem than 50 metres thick , I


of 0.3 per cent nickel, 0.4 per cent copper and 5 ppm platinum-group elements with a p1atinum:palladium ratio of about 0.25. It is of interest to note that the content of the platinum- group elements of the sulphides in the disseminated ore is higher than in the massive ore! Nickel and copper values in the upper tax- ite are, however, considerably lower, but what makes this layer of great interest is the recently recognised high platinum-group elements content with recorded values of up to 40 ppm with a p1atinum:palladium ratio as high as 0.7.

Mining Operations Although no production figures were made

available U.S.S.R. sales of platinum and palladium to the western world have amounted consistently to about 2,000,000 ounces annually over the past few years. If a local consumption of 1,000,000 ounces is assumed then the production of platinum-group elements from the Noril’sk area must amount to about 3,000,000 ounces, as the contribution made by other platinum-group element producing regions in the U.S.S.R., notably the Pechenga area, where grades are only 0.4 ppm and 0.04 ppm total platinum-group elements in massive and disseminated ores, respectively, is negligible in comparison.

At present nickel, copper and platinum-group elements are produced from six mines. Disseminated ore is being mined at an open cast operation on the Noril’sk I orebody, while the down dip extension is being mined underground in the Zapoljarni Mine. Four underground mines exploit the considerably larger Talnakh orebodies. These are the Oktyabrski, Taimirski, Komsomolski and Mayak Mines (Figure 4). In addition, the Gluboky and Skalesty Mines are presently being developed on the deeper parts of the orebody. Reserves of massive ores are estimated to last for another 50 years, and those of disseminated ores to last well beyond the twenty-first century at present production rates. Visits were arranged to the open cast mine at Noril’sk and the Oktyabrski Mine, while con- siderable time was also spent studying different ore types at mine dumps and in boreholes.

The refineries at Noril’sk produce nickel, copper and cobalt metal. Platinum-group metals concentrate is shipped to a platinum refinery in Krasnojarsk. All raw materials for the refining of the base metals, such as coal and pure silica sands, are obtained in the immediate surrounding of Noril’sk. The slags are used for concrete back-fill of the underground workings, the cement being produced locally from limestone and gypsum deposits. Electricity is generated in two power stations, one at Talnakh and the other at Noril’sk from gas which is piped to these plants. The gasfields are about 150 km due west, in the sedimentary succession of the Yenisei trough.

Petrogenesis The origin of the mineralisation is still being

hotly debated. One school of thought considers the mineralised intrusion to be shallow magma chambers in which basaltic magma of the Siberian Traps resided and became contaminated with sulphur from surrounding evaporite sequences prior to their extrusion as basalt (2). The immiscible sulphide liquid which formed in response to the contamination then extracted the nickel, copper and platinum-group elements from the fairly large volumes of magma as it passed through the chamber on its way to the surface. The other school of thought (1) postulates that a large volume of immiscible sulphide liquid formed at depth in a large magma chamber. This sulphide magma was emplaced, together with a comparatively small volume of silicate magma as a mixture of two immiscible liquids, into the sedimentary and lower basalt sequences.

Acknowledgements I am greatly indebted to my two hosts, Professor

Vadim Distler and Dr. Alexis Sokolov, as well as to their colleagues at the Academy of Sciences of the U.S.S.R., for their wonderful hospitality and for making the visit to Noril’sk possible. Thanks are also due to the many geologists at Noril’sk who shared their knowledge so readily with me.

References D. A. Dyuzhikov, V. V. Distler and B. M. Strunin, “Geology and Ore Deposits of the Noril’sk District”, Nauka, Moscow, 1988, p.279 (in Russian) A. J. Naldrett, “Magmatic Sulphide Deposits”, Oxford University Press, 1989, p.186


1 D. A. Dyuzhikov, V. V. Distler and B. M. Strunin, “Geology and Ore Deposits of the Noril’sk District”, Nauka, Moscow, 1988, p.279 (in Russian)

2 A. J. Naldrett, “Magmatic Sulphide Deposits”, Oxford University Press, 1989, p.186

ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES Growth and Characterization of Reactive- ly Sputtered Thin-Film Platinum Oxides J. R. MCBRIDE, G. w . GRAHAM, c. R. PETERS and w. H .

Thin-film oxides of Pt prepared by reactive sputtering were studied by XRD and Raman scattering. Dif- ferent phases of the Pt-0 system were obtained by adjusting sputtering parameters, such as gas composition, deposition rate and substrate temperature. The Raman spectra from PtO show two broad peaks at 438 and 657 cm-' and high resolution SEM and XRD line broadening in+cates mean aystallite sizes of the order of 300A IR reflectivity spectra yield two of the three IR-active phonons, and along with scanning tunneling microscopy measurements suggest that PtO is a semiconductor. Thermoelectric measurements show that the predominant carriers are p-type, and IR reflectivity data indicate a carrier concentration of - 4 x 1018/cm'.

The Equilibrium Shape and Surface Energy Anisotropy of Clean Platinum

WEBER, 3. Appl. Phys., 1991, 69, (3), 1596-1604

W. H. LEE, K. R. VANLOON, V. PETROVA, J . B. WOODHOUSE, C. M. LOXTON and R. I . MASEL, 3. Catal., 1990, 126, (2), 658-671 The equilibrium shape of clean Pt was measured by following changes in shape of micrometre-sized Pt droplets during annealing at 1200°C and 10- ' Torr in 0,. The Pt particles had a rounded shape with distinct (100) and (1 11) facets and stepped regions in between. At 12OO0C only 16% of their surfaces is covered by the facets; the majority of the surface is stepped. The surface energy of Pt only varies by about 92 ergkm? with crystal face: Pt(100) has the lowest surface energy, Pt(l11) has a slightly higher surface energy.

Oxidation of Clean and Pt-Covered Ni( 11 1)

and 1. W. GEUS, Appl. Surf. Sci., 1991, 45, 207-220 Clean and Pt-covered Ni( 1 1 1) surfaces have been exposed to 0, at various temperatures. On clean Ni a closed oxide layer is formed at room temperature, and at 250 and 4OO0C, O? penetrates into the bulk of the crystal. However, small amounts of Pt drastically decrease the extent of oxidation of Ni crystals at all temperatures. At room temperature, no oxidation occurs when the Pt coverage is > 1 monolayer. At 25OoC, a Ni oxide layer forms on top of the Pt overlayer, but no 0 penetrates through the Pt layer into the bulk. At 4OO0C, a Ni oxide layer forms on top of the Pt and a small fraction of the 0 diffuses through the Pt layer into the bulk crystal.

S. DECKERS, F. H. P. M. HABRAKEN, W. F. VAN DER WEG

Magnetic Phase Diagram of Ordered

M. KABURAGI, T. TONEGAWA and K . EBINA, 3. Magn. Magn. Muter., 1990, 908~91, 161-162 Magnetic properties of the pseudobinary ordered alloy Fe(Pd,Pt I -,), are calculated on the basis of the localised moment model by noting the local environment effect on the Fe atom. The alloy exhibits a wide range of magnetic structures depending on I'd concentration. At high temperatures the phase is paramagnetic. At low temperatures there are three magnetically ordered phases depending upon x: an antiferromagnetic phase for o(x<x, -0.53, intermediate magnetic phase for x , <x<x, - 0.67 and ferromagnetic phase for x,<x<l. The Nee1 temperature of 170 K is almost independent of x in the region of the antiferromagnetic phase. The Curie temperature of 530 K at x = 1, decreases monotonical- ly with decreasing x until it reaches a quadruple point' separating the above four phases.

Fe(Pd,PtI -,h

Magnetic Properties of Co/Pd Multilayers Determined by Brillouin Light Scattering and SQUID Magnetometry J. V. HARZER, B. HILLEBRANDS, R. L. STAMPS, G. GUN- THERODT, C. D. ENGLAND and C. M. FALCO, y. Appl. Phys., 1991, 69, (4), 2448-2454 The saturation magnetisation and volume and interface anisotropies of CoPd multilayerywith modula- tion wavelengths between 4 and 220 A, prepared by magnetically enhanced DC-triode sputtering on single-crystal sapphire substrates, were studied by using Brillouin light scattering from collective spin waves and by SQUID magnetometry. A Pd polarisation was found and the polarisation depth was eslimated. Samples with Co thickness of 2 atomic layers and Pd thickness of > 4 atomic layers exhibited a perpendicular magnetisation.

Structural and Electrical Properties of Granular Palladium Cluster Films A. CARL, G. DUMPICH and E. F. WASSERMAN, Thin Solid Films, 1990, 193/194, (1-2), 1065-1072 Thin granular Pd,C,-i films 10-70 nm thick were prepared by simultaneous co-deposition of pure Pd and high purity C on NaCl and quartz crystal substrates at room temperature under UHV. Dif- ferent evaporation rates for Pd and C enable Pd,c,-, films of metal volume fractions x = 0.1-1 to be made. TEM indicated networks of small Pd clusters embedded in amorphous C. Electrical resistance studies showed metallic resistance behaviour for fdms with 0.3<x<1 and variable range hopping conductivity for x<0.3. The metal insulator transition is at x = 0.3.


Crystal Nucleation and Glass Formation in Undercooled Pd-Ni-P Melts Y. xu and w . WANG, Muter. sci. Eng., 1990, A130,

Pd,, Ni,P, and Pd,,,, Ni,,,5 P ,, alloys were prepared and their undercooling was investigated in a 1.2 m drop tube filled with different inert gases at different pressures. As the cooling rates were reduced the crystal nucleation and growth processes wererevealed, and the interior heterogeneous nucleation was found to be responsible for the solidification of the undercooled melts. Time-temperature transformation curves allow predictions of the glass forming behaviour.

Magnetic Phase Diagram of Ge- Substituted CeRu,Si, in an Applied Field

HAEN and P. LEJAY, Solid State Commun., 1991, 77,

Long-range magnetic order can be induced in the heavy-fermion compound CeRu, Si, by slighly ex- panding its lattice by substituting a few percent of Ge for Si. For a concentration of lo%, the material ordered in the same collinear, incommensurate, modulated structure as that already reported for (Ce, La) Ru2 Si, . The (H, T ) phase diagram of this system was determined by elastic neutron scattering. The results were discussed in connection with the problem of magnetic correlations in pure CeRu > Si? .

(l), 93-100

J.-M. MIGNOT, P. BOUTROUILLE, L.-P. REGNAULT, P.

(5), 317-321

CHEMICAL COMPOUNDS Co-ordination of 3,3 LBipyridazine with Bivalent Copper, Palladium and Platinum

WHITE, Aust. 3. Chem., 1990, 43, ( l l ) , 1919-1928 Bis(ligand) complexes of the diimine 3,3’-bipyridazine (L) with bivalent Pt, Pd and Cu are described. Co-ordination of perchlorate in [PdL,I[CIO,I~ was indicated but not in [PtL,I[CIO,l,. Structure determination of the Pt complex showed a strictly planar PtN, moiety, and the whole complex cation was approximately planar. The structure of [PtL,l[CIO,l? was determined at 295 K by single-crystal X-ray diffraction methods, and was refined to a residual of 0.033 for 1942 “observed” independent reflections.

The Preparation of Novel Ruthenium Complexes for Use in Langmuir-Blodgett Films

RICHARDSON and G. G. ROBERTS, 3. Organomet. Chem., 1991, 401, (1-2), 181-186 A range of cationic cyclopentadienyl bisphosphine Ru nitrile complexes i(v’-CiHi)L,RuNC-ArylI +, where L = phosphine or phosphite, have been prepared and characterised for use with deposition for Langmuir-Blodgett films. The ready substitution of the phosphine ligands bound to Ru allows the complexes to be tailored for a wide range of properties.

H. A. GOODWIN, D. O N G M , B. W . SKELTON and A. H.

S. G. DAVIES, A. J . SMALLRIDCE, R. COLBROOK, T .

ELECTROCHEMISTRY The Stability of Hydrous Oxide Films on Platinum L. D. BURKE and J . F . O’SULLIVAN, 3. Appl. Elec- trochem., 1991, 21, (2), 151-157 The stability of hydrous oxide films grown on Pt in both acid and base was studied as a function of holding potential in solutions of different pH. The stability of the bulk of the hydrous oxide deposits on Pt was not very dependent on solution pH, due to a rather facile rearrangement of the initially anionic Pt oxide species to a virtually neutral state. Reduction of the bulk hydrous oxide in base showed a marked degree of inhibition in the region of 0 V(RHE); the effect appeared to be related to the presence of weakly bound H, on the Pt surface.

Effects of Adsorbed CO on the Electrode Reactions at a Platinum Electrode H. KITA, s. YE and K . S U G I M U R A , ~ . Electroanal. Chem. Interfacial Electrochem., 1991, 297, (l), 283-296 Studies of the behaviour and poisoning effects of the CO adsorbed at 50 and 500 mV (vs. RHE) on Pt performed in 1M HCIO, at room temperature showed that the CO addorbed on a Pt electrode stays im- mobile and does not migrate onto a bare surface. The adsorbed CO has a physical poisoning effect on the H evolution reaction. At a high CO coverage, the lack of a nearest pair of CO-free reaction sites causes a change in the reaction mechanism of H evolution.

Early Stages of Growth of Hydrous Platinum Oxide Films M. FAREBROTHER, M. GOLEDZINOWSKI, G. THOMAS and v . I. BIRSS, J . Electmanal. Chem. Interfacial Elec- trochem., 1991, 297, (2), 469-488 The growth of thin hydrous Pt oxide (&oxide) films by the rapid potential cycling method was studied. (3-Oxide formation began in only a few cycles of potential to an extent which was dependent on the sweep rate used during oxide growth. Its properties vary greatly after ca. 20-30 cycles of potential, and then become constant. The compact a-oxide, present along with the (3-oxide at all times, could be reduced and reformed in potential sweep studies, as well as thickened under potentiostatic conditions in the presence of the P-oxide, as at a bare Pt surface.

Study of the Characteristics of Elec- trochemical Cell PtlCaF, IPt in an At- mosphere of the Free Oxygen I. A . ZAKS and M . v. GLUMOV, Elektrokhimiya, 1990,

A study of the polarisation of a porous Pt electrode in contact with CaF, in partial oxygen pressure 10-10‘.‘ Pa was performed in a Pt/CaF,IPt electrochemical cell, in the solid electrolyte, at 1100-1200 K. The resistance of the electrolyte is directly proportional, and the polarisation of the electrolyte is reversibly proportional to the 0, pressure.

26, ( I l ) , 1473-1479


The Structure and Activity of Pt-Co Alloys as Oxygen Reduction Electro- catalysts 8. c. BEARD and P. N. ROSS, J. Electrochem. soc.,

Bimetallic C supported Pt-Co (3:l atom ratio) catalysts were prepared from a commercial 10% Pt/C catalyst with R particle sizes of 15-30& in both acid and alkaline aqueous media, followed by heat treatments to promote alloy formation. Greater alloying was observed in the catalyst prepared in the acid medium. X-ray diffraction studiesofthe acid-prepared catalyst showed lattice parameters tending away from Pt (3.927A) and toward that for Pt,Co (3.831&, greatly increased particle sizes and significant order- ing demonstrated by the presence of super-lattice reflections. Loss of Co in a fuel cell phosphoric acid environment was the lowest in catalysts which were the most alloyed, and where the Pt ,Co ordered phase was present.

Electrolytically Co-deposited Platinum- Palladium Electrodes and Their Electro- catalytic Activity for Ethylene Glycol Oxidation: A Synergistic Effect N. DALBAY and F. KADIRGAN, Electmchim. Acta, 1991,

The electrocatalytic oxidation of ethylene glycol has been investigated on Pt-Pd solid solution alloy electrodes of different compositions in alkaline aqueous

1990, 137, (1 I ) , 3368-3374

36, (2), 353-356

The Properties of Palladium Electrodes for Electrooxidation of Ethylene Glycol N. DALBAY and F. K A D ~ R G A N , ~ . Electroanal. Chem. In- terfacial Electrochem., 1990, 2%, (2), 559-569 Mechanistic studies were performed in alkaline medium, in order to interpret the electrocatalytic properties of Pd for the oxidation of ethylene glycol. The kinetic parameters, estimated from electrochemical data, suggest a one electron step to be rate determining and the rate of the reaction depends directly on the pH.

Cathodic Behaviour of Palladium in Elec- trolyte Solutions Containing Alkali Metal Ions V. E. KAZARINOV, I. I. ASTAKHOV, G . L. TEPLITSKAYA, I. G . KISELEVA, A. D. DAWWV, N. V. NEKRASOVA, D.

1991, 27, (l), 9-14 YU. KUDRYAVTSEV and T. B. ZHUKOVA, Elektmkhimiya,

Studies of the cathodic implantation of Li and also to a lesser degree of K, in Pd electrodes were performed during cathodic polarisation in aqueous or aprotonic electrolytes. In aprotonic electrolyte the formation of Li with Pd intermetals occurred during implantation; these can actively react with H,O and solid Pd based solutions. In aqueous electrolyte, on a Pd electrode of 0.5 mm thickness after 74 h polarisation, formation of solid electrolyte occurred with average concentration of 5'/0, while the electrode was gradually dissolving during the polarisation.

solution. Cyclic voltam-metry was used to find the surface characteristics and X-ray diffraction studies were used to verify homogeneity of electrolytically codeposited alloys.

Boundary Conditions in E1ectrochemica* Measurements of Diffusion Coefficients of Hydrogen in a-Palladium H. HAGI, Muter. Trans. JIM, 1990,31, (lo), 842-847 Studies of the boundary conditions in electrochemical H permeation through a-Pd showed that the varia- tions in electrode potential and current density at the cathode surface corresponded to those in the dissolved H concentration and H entry flux at the cathode

Electrocatalytic Hydrogenation Using precious ~~~~l ~~~~~~~~~~l~~ in ~ ~ d ~ ~ - Active Polymer Films L. CmHE, B . EHUL D. LIMOSIN and J.-C. MOUTE*, 3. Org. Chem., 1990, 55, (23), 5905-5910 Glassy C felt electrodes were modified by electrodeposition of poly(pyrro1e-viologen) fims followed by electroprecipitation of Pt, Pd, Rh or Ru micro- particles. The electrodes were active for the electrocatalytic hydrogenation of conjugated enones, styrene and benzonitrile in aqueous media of p H = l . Although the metal loadings were low, the electric and product yields were high, and the cathodes had long term stability.

A Complex Formation of Palladium with Tin(I1) in a Solution of Sulphuric Acid

Obshch. Khim., 1990, 60, (ll), 2421-2425 The interaction of K,PdCI, with SnSO, in H,SO, resulted in the formation of bimetallic Pd(I1) complexes, which convert into compounds according to the degree of oxidation of Pd, near to one. Chloride ions in Sn chloride Pd complexes totally mix with sulphate ions in the H,SO, solution without breaking the Pd-Sn bond. This effect is used for the preparation of new Pd-Sn complexes.

P. G. ANTONOV, I. A. AGAPOV and M.N. MAKSIMOV, Zh.

surface, respectively. The diffusion coefficients of H at 278-333 K and the temperature dependence of the diffusion of H free from the trapping effect and the surface effect in annealed a-Pd were given.

Electrochemical Behaviour of RuTi

Acta, 1991, 36, (l), 19-26 The electrochemical properties of RuTi alloy in acidic solution were investigated by cyclic voltammetry and steady-state polarisation measurements. The I-V pro- files for the formation/reduction of surface oxides and the deposition/dissolution of H at a RuTi electrode are similar to those at a Ru electrode. The 0 evolution and Ru corrosion reactions occur at nearly the same potential on Ru, but on RuTi the reactions are well resolved. RuTi does not catalyse MeOH oxidation; it forms a hydride on cycling negative of the normal H potential. Although hydride appears to suppress the H evolution reaction, H evolution activity remains relatively high. A model has been developed with two-step oxidation of the surface.

R. MANOHARAN and J. B. GOODENOUGH, Electrochim.


Effect of Composition on the Electro- catalytic Activity of the Ternary Oxide Ru o . Ti, o . 7 - .,Sn,O . I. Oxygen Evolution from HCIO, Solutions I . F. C. BOODTS and S. TRASATTI, 3. Electrochem. soc. ,

The electrocatalytic activity of ternary oxides of general formula Ru".,Ti(",, -xlSnxOl for 0, evolution from 1 mol/dm' HCIO, solution was studied as a function of x by current-potential curves and reaction order determination. The mechanism of 0, evolution was found not to depend on oxide composition, whereas the electrocatalytic activity was observed to increase with the increase in SnO, content. The surface charge drops dramatically after extensive 0, evolution thus indicating collapse of the surface morphology. The present results show that SnO, activates RuO, + T i 0 electrodes, decreasing their stability.

1990, 137, (12), 3784-3789

PHOTOCONVERSION Photochemical Reactivity of Diplatinum p-Alkenylidene Complexes: Evidence of Atom-Transfer Chemistry E. BARALT and c. M. LUKEHART, Inorg. Chem., 1991,

Complex [Pt , (p-C= CHPh)(C=CPh)(PEt,), IBF, (1) reacts under photolysis with Li halide or KSCN salts, I, and alkyl or aryl halides to give mono- or dihalide (or SCN) complexes of types IPt,(p- C=CHPh)(C =CPh)(PEt J ) XI or IPt ,(p- C=CHPh)(PEt ,) X,l. 2-Propanol is also catalytically oxidised to acetone and H, by (1) or selected derivatives upon irradiation. Thus (1) represents another type of system that exhibits photochemical atom-transfer reactivity.

Hydrogen Evolution at a Pt-Modified InP Photoelectrode: Improvement of Current-Voltage Characteristics by HCl Etching H. KOBAYASHI, F. MIZUNO, Y. NAKATO and H. TSUBOMURA, 3. Phys. Chem., 1991, 95, (2), 819-824 H photwvolution at pInP electrodes coated with Pt and I'd was studied before and after etching with concentrated HCI. Before etching electrodes with a continuous Pt layer have poor I-V behaviour, due to defect states in InP, and the photocurrent density decreases with illumination, due to increased defect density. After etching, stable efficient solar-to- chemical energy conversion was achieved. The barrier height increased to 1.0 V and the I-V characteristics improved remarkably with no degradation on illumination. The HCI dissolved the InP substrate in the InP/Pt interfacial region, simultaneously removing part of the Pt from the InP surface. A structural model of the etched electrode is proposed with the InP surface in direct contact with the solution due to minute Pt island formation. The cell characteristics of Pd deposited electrodes are poor and become worse on H , bubbling.

30, (2), 319-320

Supramolecular Photochemistry and Photophysics. Mutual Inhibition of Host and Guest Photochemistry and Luminescence in the Adduct of an Anthraceno-Crown Ether with Pt(bPY)(NH,), +

L. PRODI, R. BALLARDINI, M. T . GANDOLFI, V. BALZANI, 1. P. DESVERCNE and G. BOUAS-LAURENT, 3. Phys. Chem., 1991, 95, (5), 2080-2083 Pt(bpy)(NH,),?+ forms a 1:l adduct with the anthraceno-crown ether (1). The adduct formation causes strong changes in the absorption spectra, luminescence behaviour and photoreactivity. It is suggested that the adduct shows a sandwich-type conformation in which the Pt complex is inserted between the two aromatic moieties of (1). Such a structure allows the stabilisation of the adduct via both H bonds and T-T interactions and accounts for the mutual protection of the two components toward their luminescence and photoreactivity . Investigation of the Relation between the Photogenerated Intermediate Radicals and the Photocorrosion of CdS in Aqueous and Aqueous Ethanol Disper- sions of PtlCdS

Photochem. Photobiol. A: Chem., 1991, 56, ( l) ,

The spin-trapping technique showed that OH and CH CHOH radicals can be generated in the visible- light-illuminated dispersions of H , O/Pr/CdS/FOBN (or PBN) and C2H,0H-HfO/Pt/CdS/POBN (or PBN), where POBN = a-(4-pyridyl-N-oxide) N-tert- butyl nitrone and PBN = a-phenyl N-tert-butyl nitrone. OH radicals attack the surface of air-treated Pt/CdS to create photocorrosion, which destroys the surface composite layer, but this can be suppressed by addition of C2 H OH.

Stepwise Reduction of Coordinated Dinitrogen to Ammonia Via Diazinido and Hydrazido Intermediates on a Visible Light Irradiated Pt/CdS.Ag2 S/Ru02 Par- ticulate System Suspended in an Aqueous Solution of K[Ru(EDTA-H)C1]2H20 M. M'. TAQUI KHAN and N. NAGESWARA RAO, 3. Photochem. Photobiol. A: Chem., 1991, 56, (l), 101-111 The photocatalytic fmation of co-ordinated N, to NH, in aqueous solution at 3OoC and 1 atm N, is reported in the presence of modified semiconductor particulate system Pt/CdS.Ag, S/RuO, catalysed by KIRu(EDTA-H)CIl2H,O. Doping of CdS with Ag, S enhances the rate of NH, production at 505 nm. The quantum yields of the product were obtained at 5 monochromatic absorption lines between 450 and 550 nm. Illuminating the system with light of wavelength 505-525 nm gives the highest quantum yield of 0.35. A mechanism for NH, formation is proposed and the source of the N atom in NH is N, .

L. FENG, H. WANG, Z. ]IN, Q. LI and M. SHI, 3.

89-100


Photospillover of Hydrogen in the Semiconductor-Palladium Membrane System A. YU. GRAIFER, A. P. KOSHCHEEV and I. A . MYASNIKOV, Kiner. Katal., 1990, 31, (6), 1493-1501 Studies of H? photospillover in the dispersed ZnO/Pd membrane semiconductor system prepared by the deposition of ZnO onto a thin Pd membrane were performed during the photocatalytic decomposition of H,O, and also, directly during the reaction by thermodesorption mass-spectrometric method. The results showed the effect of spillover (mass-transfer) of H atoms with the surface of Pd membrane after stimulated UV light exposure of the semiconductor. The H atoms were either adsorbed from gaseous phase or formed during heterogeneous photo-gaseous decomposition of H ?O molecules.

Changes in the Redox State of Iridium Oxide Clusters and Their Relation to Catalytic Water Oxidation. Radiolytic and Electrochemical Studies

Phys. Chem., 1991, 95, (2), 616-621 Radiolytically prepared IrO,.nH, 0 clusters for the photochemical oxidation of H, 0 were oxidised and changes in optical absorptions and redox states were studied. The clusters contain 4 or 5 Ir atoms in Irl" and I$" states, formerly described as IrJ.?+. Pulse radiolytic studies revealed 3 processes in the subse- cond time scale: a short-lived intermediate such as an OH adduct, transforming to more stable oxidised species, and a rise in the 580nm absorption. The initial IrO, cluster is oxidised in 2 stages from Ir'.'+ to

and then to Ir' + . Further cluster oxidation ox- IrJ.x+ idises H,O to 0,. The Ir' + clusters decay to regenerate IrO, clusters of lower oxidation state.

Luminescent and Redox-Reactive Building Blocks for the Design of Photochemical Molecular Devices: Mono-, Di-, Tri-, and Tetranuclear Ruthenium(I1) Polypyridine Complexes

G. S. NAHOR, P. HAPIOT, P. NETA and A. HARRIMAN, 3.

G. DENTI, S. CAMPAGNA, L. SABATINO, S. SERRONI, M; CIANO and V. BALZANI, InOrg. Chem., 1990, 29, (23), 4750-4758 Mono-, di-, tri-, and tetrametallic complexes of general formulae RuL, (BL) , +, L, Ru(p- BL)RuL,", LRu[(p-BL)RuL,l, '+ and Rul(p BL)RuL,IJ8+ (L=bpyor biq, BL=2,3- or2,5-dpp) showed very intense absorption bands in the UV and visible regions, relatively long lived luminescence both in a rigid matrix at 77 K and in fluid solution at room temperature and a very rich electrochemical behaviour. The electrochemical, spectroscopic and photophysical properties of this family can be tuned by a suitable choice of L, BL and number of metal ions. These complexes are good candidates for light absorption and/or light emission sensitisers, for luminescent probes and photochemical cleavers of DNA.

The First Report of the Isolation and Characterisation of an Intermediate Formed upon Photolysis of a Ruthenium(I1) Diimine Compound, in which One of the Chelating Ligands is Bound in a Monodentate Fashion B. E. BUCHANAN, H . HUGHES, J. H . VAN DIEMEN, R. HAGE, J . G. HAASNOOT, J . REEDIJK and J . G . VOS, 3. Chem. SOC., Chem. Commun., 1991, ( 5 ) , 300-301 The isolation and characterisation of an intermediate produced upon photolysis of IRu(bipy), (L- L')l(PF,,): in MeCN (where bipy = 2,Zf-bipyridyl and L-L' = 4-rnethyl-3-(pyridin-2-yl)-1,2,4-triazole) in which L-Lf is co-ordinated to the metal centre in a monodentate fashion, via the N of the triazole ring, is reported. It is shown that the photochemically induced ligand dissociation can be reversed thermally. A mechanism for the photoinduced ligand exchange in these compounds in which monodentate intermediates are formed upon photolysis of Ru polypyridyl compounds, and thermal ring closure regenerates the starting compound, is confirmed.

ELECTRODEPOSITION AND SURFACE COATINGS Electroless Deposition of Pure Nickel, Palladium and Platinum

and P. JOSSO, Surf. Coat. Technol., 1990, 43144,

A new process for the electroless deposition of Pt, Pd and Ni was designed using hydrazine as the reducing agent. Electrochemical measurements for a wide range of bath compositions were performed and several were examined which gave high purity deposits of these metals. Bath composition and conditions leading to adherent and defect-free ductile coatings with purity higher than 99.9% were found. Long term stability of the baths was achieved as well as bath replenishment. For the Pd and Ni the level of contaminants was very small with no significant effect on the hardness of the coatings. Coatings of Pt, Pd and Ni were dense and regular.

Problems in DSAO Coating Deposition by Thermal Decomposition

zrochem., 1991, 21, (2), 136-142 Several dimensionally stable anodes, made up of an electrochemically active coating deposited on a base metal, were prepared by thermal decomposition of Ir, Ta, Sn, Ru and Pt chloride salts on Ti base. The initial coating composition does not necessarily cor- respond to the final coating. IrO], RuO, and Ta,O, compounds can be deposited with almost 100% yield, while SnO, and F't precursors give high material losses. The thermal deposition technique is sensitive to the geometry of the sample, the solvent that is used, and also the concentration and nature of the metal salts.

P. STEINMETZ, S. ALPERINE, A. FRIANT-COSTANTINI

(1-3), 500-510

C. COMNINELLIS and G. P. VERCESI, 3. Appl. Elec-

Plarinurn Metals Rev. , 1991, 35, (2) 105

Hydrogen Codeposition in Palladium Plating S. JAYAKRISHNAN and S. R. NATARAJAN, Met. Finish., 1991, 89, (l), 23-25 Hydrogen codeposition from ammonia complexed Pd plating solutions and the determination of the H:Pd ratio in the deposited metal were studied. The quanti- ty of codeposited H retained by electrodeposited Pd depends on the time lapsed after deposition. The stress and crack-free nature of electroplated Pd can be attributed to the Pd being in the thermodynamically stable alpha phase.

Electrodeposition of Ni-Transition Alloys for the Oxygen Evolution Reaction H. J . MIA0 and D. L. PIRON, J . Appl. Electrochem.,

Electrodes for the 0 evolution reaction (OER) were prepared by electrodeposition of Ni, Ni-Ru and Ni-Ir alloys in an attempt to fmd new electrocatalytic material for long-lasting, economic high performance electrodes. The electrodes were activated by anodic polarisation at 100 mA/cm’ to form an oxide layer. Ni-Ir alloys had better corrosion resistance and provide greater electrocatalytic activity for the OER than Ni-Ru alloys in alkaline solution.

1991, 21, ( I ) , 55-59

Conductance Response of PdlSnO, (1 10) Model Gas Sensors to H? and O2 T. B. FRYBERGER and s. SEMANCIK, Sens. Actuators B,

Surface analytical and tn situ conductance measurements showed that the H response of Pd/SnO, model sensors at moderate temperatures (400 K) was dominated by surface reactions. In the absence of 0, , H , increases the sensor conductance via chemisorption and dissociation on the Pd clusters followed by “spill-over’’ to the SnO, substrate. When 0, was available, the conductance was modulated by the reaction between chemisorbed H 2 and 0, to form volatile H , 0. The chemisorption and dissociation of 0 occurred on the Pd clusters.

Effects of Thickness and Additives on Thin-Film SnO? Gas Sensors J . KLOBER, M. LUDWIG and n. A. SCHNEIDER, Sens. Ac-

The effect of reducing gases on the electrical conductivity or gas sensitivity of thin-film Sn oxide sensors was studied as a function of the Sn oxide film thickness and the Pd concentration. The dependence on the film thickness showed a maximum at - 30-45 nm for H detection. It also depended on the Pd concentration. For CO a decrease of the sensitivity with increasing Pd thickness was observed at > 30 nm.

Electrocatalysis and Flow Detection of Alcohols at Ruthenium Dioxide-Modified Electrodes D. LEECH, 1. WANG and M. R. SMYTH, Electroanalysts,

A highly stable sensitive flow detection system for simple alcohols with a constant potential operation is described; it uses RuO, containing C paste electrodes. The optimisation of the system for Ru loading, pH, flow rate and operating potential is reported. The electrode response was stable over 2 weeks with a signal loss of 6%; repeated MeOH injections over a 2 h period gave a relative standard deviation of 3.4%. Detection limits for the alcohols depend on the number and position of the hydroxyl groups, with 30 ng for glycerol to 3 Fg for EtOH.

1990, 2, (4), 305- 309

tuators B, 1991, 3 , (l), 69-74

1991, 3, (I), 37-42

APPARATUS AND TECHNIQUE A New Hydrogen Sensor Based on a PtlGaAs Schottky Diode

and F. BRIONES, J . Electrochem. soc . , 1991, 138, ( I ) ,

H sensors based on a Pt/GaAs Schottky barrier have been fabricated with stable, sensitive and reproducible characteristics. Dark I-V and C-V measurements as a function of temperature have been used to characterise the devices. At 15OoC a minimum of 6 ppm of H , in N, , and 200 ppm of H, in synthetic air can be detected. In air, a linear response is found up to 3000 ppm H,. The sensitivity to H, is explained by Schottky barrier reduction. The sensor can operate over a wide temperature range and is sensitive even at room temperature. The diodes recover easily in air at 19OOC and show long-term stability.

Low-Level Moisture Generation

Chem., 1991, 63, (3), 198-202 Two complementary methods for generating moisture concentrations in the 0.02-50 ppm-v range in various gaseous media have been developed. The first method uses catalytic recombination of H , and 0, over a hot R/Rh catalyst using air as the balance gas, while the second is based on permeation of water

.through a membrane, using any gas compatible with the membrane material. This moisture generation system can be used to calibrate hygrometers and moisture generators, and study the behaviour of components used in high purity gas installations.

L. M. LECHUGA, A. CALLE, D. COLMAYO, P. TEJEDoR

159- 162

F. MERMOUD, M. D. BRANDT and 1. MCANDREW, Anal.

HETEROGENEOUS CATALYSIS Perfluorinated Membranes as Catalyst Supports

J. A. HEY and A. 1. SEEN, Appl. Organomet. Chem.,

Perfluorinated polymer Nafion and porous PTFE/Nafion composite membranes have been employed as supports for Pt and Pd metal particles and Ni complexes to be used as olefm conversion catalysts. For cyclohexene hydrogenation, the Pt and Pd supported systems had turnover numbers in excess of 6000, with no apparent poisoning, and could be easily regenerated.

A. M. HODGES, M. LINTON, A. W.-H. MAU, K. J . CAVELL,

1990, 4, (9, 465-473

Platinum Metals Rev . , 1991, 35, ( 2 ) 106

Stoichiometrie Composition of Platinum, Iridium and Platinum-Iridium Catalytic Precursors s. SUBRAMAN~AN and J. A. SCHWARZ, Appl. coral.,

The stoichiometry of Al , 0 , , TiO? , 1 1 .4%Ti02 - AI,O , and 0.87%Al ,O ,-TiO, supports for Pt, Ir and Pt-Ir precursors were assessed by temperature- programmed reduction and thermogravimetry . The H consumed and the observed weight change result from precursor reduction and support reduction. PtCI,, IrCI, and PtCI,-Ira, exist as supported en- tities after the catalysts, prepared from H,PtCI, and H, IrCI , , are dried at 423 K in air. The metal-support interactions for a given metal are stronger for Al, 0 , than for T i 0 *. Bimetal formation in the Pt-Ir system does not occur during drying.

1991, 68, (1-2), 131-147

Alumina-Supported Platinum-Rhenium Dehydrogenation Catalysts: Influence of Metal Ratio and Precursors on Catalytic Behavior

Chem. Res., 1991, 30, (3), 440-447 Two series of Pt-Re/Al, 0, dehydrogenation catalysts with 0.5 wt.% loading were prepared by incipient wetness from H,PtQ, and Re,O, with nominal &/Re atom ratios of 100/0, 75/25, 50150 and 25/75, and the second series was prepared from H?Pt(OH), and Re,O, with atom ratios of 100/0, 75/25, 50/50, 25/75 and 0/100. During dehydrogenation, nearly constant activity was observed on the 50/50, 75/25 and 100/0 Pt/Re fmt series catalysts for the conversion of cyclic C, hydrocarbons whereas for the dehydrogenation of cyclic C hydrocarbons activity

M. GARLAND, A. BAIKER and A. WOKAUN, Id. Eng.

con;inuily increased- with &easing Pt/Re ratio.

catalysts showed most promise for the highly selective dehydrogenation of methylcyclohexane.

‘Ompetition between‘Ethyne9 Ethene and UncHorinated 75/25 and 50/50 Pt-Re/M, 0 , Carbon Monoxide for the Active Sites during Hydrogenation at Transient Con- ditions over Supported Metal Catalysts

(1-2), 191-205 PlatinumlH-Mordenite Catalysts Pre- The effect of CO on the hvdrogenation of ethene over

L. CIDER and N.-H. SCHMN, Appl. coral., 1991, 68, Hydroconversion Of n-Heptane On

pared via Different Routes Pt/Al,O,, Pdh-Al,O, -and-Rh/Al,O, was tem- porarily eliminated after a short pulse of ethyne, propadiene or butadiene. The very slow thermal desorption of CO increased, an effect which is similar to the “cross-desorption” and “adsorption-assisted desorption”. The same phenomenon occurred for the reverse process; increased desorption of ethyne after a pulse of CO.

The Aromatisation of n-Heptane on Pt- Sn/AI, 0 and Pt-Ir/Al , 0 Catalysts M. WILDE. R. FELDHAUS. K. ANDERS and H.-D. NEUBAUER,’ Z . Phys. Chem.’ (L.eip.zig), 1990,271, ( S ) , 919-925 The aromatisation of n-heptane and methylcyclopen- tane was investigated at normal pressures over Pt-Ir and Pt-Sn catalysts supported on Al,O,. Pt- Sn/Al I 0 , had high activity and outstanding selectivity for dehydrogenation and dehydrocyclisation via 1,6 ring closure.

A Chemisorption and XPS Study of Bimetallic Pt-Sn/Al 0 Catalysts K. BALAKRISHNAN and J. SCHWANK, 3. caul . , 1990, 127, (I) , 287-306 Bimetallic 1 wt.%Pt-(0-3.25 wt.%)Sn/Al,O, catalysts, prepared by co-impregnation of non-porous Al, 0 ,, were studied by chemisorption of H,, 0, and CO at room temperature. Addition of Sn to Pt resulted in significant differences in the gas uptake characteristics of the three adsorbates. Both H, and CO showed an initial increase in gas uptake with addition of small amounts of Sn, and then the chemisorbed amount dropped off with further addition of Sn. XI’S of the reduced catalysts showed that in Al , 0 , supported samples most of the Sn was in a valence state of either Sn(I1) or Sn(1V).

A. K . ABOUL-GHEIT, M. F. MENOUN and A. K . EL- MORSI, 3. Chem. Technol. Bioiechnol., 1991, 50, (2),

Two Pt/H-mordenite catalysts were prepared by impregnating H,PtCI, in (a) H-mordenite (HM) and (b) NH, HM, followed by drying, calcination and reduction. Catalyst (a) was found to be more active for n- heptane hydroconversion, more selective for its isomerisation, and it encountered more diffusion limitation as it yielded a larger Thiele modulus. The catalyst also gave a lower effectiveness factor and lower activation energy, E,, values than catalyst (b). An increase in the catalytic activities was observed to a maximum at 3.0 MNIm’, followed by a decrease. High selectivities for central hydrocracking of heptane components and high iso-butane to n-butane ratios were obtained on both catalysts.

Characterization Study of Silica- Supported Platinized Tin Oxide Catalysts Used for Low-Temperature CO Oxida- tion: Effect of Pretreatment Temperature s. D. GARDNER, G. B. HOFLUND, D. R . SCHRYER and B. T. UPCHURCH,J. Phys. Chem., 1991,95, (2), 835-838 Pt/SnO, surfaces supported on SiO, used for low temperature CO oxidation in CO, lasers have been characterised before and after reduction in CO at 125 and 25OOC by various techniques. Pt was present initially as PtO and PtO,, small amounts of Pt(OH), and metallic Pt. Reduction at 125OC converts most of the Pt to Pt(OH), while reduction at 25OOC converts most of the Pt to metallic Pt. SnO, is partially reduced to SnO. At 25OOC the outermost Pt and Sn are covered by impurities from the SiO, substrate, while at 125OC the outermost atomic layers are enriched in Pt and Sn. IIS and XI’S data suggest that a Pt/Sn alloy may form during the reductions.

227-237


Microstructure and Reactivity of Pt-Ce and Rh-Ce Particles on Silica

Catal., 1991, 128, ( I ) , 161-185 The interactions of Ce with 20-200 A diameter particles of Pt and Rh on planar SiO, were studied using TEM and reactivity measurements following treatment in H 2 and O?. After heating Pt-Ce in H ? at 650°C, Ce formed a thin amorphous film on the SiO?, and the only crystalline phase observed was Pt metal for low Ce loadings. For high Ce loadings a phase was detected with a diffraction pattern of Ce hydride, and dark field imaging showed that this formed as cubes near the Pt particles. When Rh-(x was heated in H! , a Ce film formed on the SiO , . Non-Faradaic Electrochemical Modifica- tion of Catalytic Activity. 111. The Case of Methanol Oxidation on Pt c. G. VAYENAS and NEOPHYTIDES, 3. Catal., 1991,

The catalytic activity and selectivity of polycrystalline pt for the oxidation of methanol to formaldehyde and CO, can be dramatically and reversibly affected when O? - anions are electrochemically pumped to or from the Pt catalyst surface via the NEMCA effect. The studies were performed using stabilised ZrO, solid electrolyte at 600-900 K. The increases in the catalytic rate of H 2 C 0 and CO, formation were 10'-10' times higher than the rate of 0: - transport to or from the catalyst, and exceed the regular open- circuit catalytic rates by up to a factor of 15.

Mechanism of Sulfur Poisoning of Sup- ported Pd(Pt)/Al, 0 Catalysts for H -0 Reaction L.-D. AN and Y. Q. DENG, Appl. catal., 1990, 66, (2),

Spent commercial Pd(Pt)/Al,O, catalysts used in the elimination of H from CO? feed gas in the synthesis industry and deactivated by S poisoning were characterised by chemical analysis, XPS, IR, XRD and TPR. The negative charged S ions existed mainly as noble metal sulphides od in the surface of the catalysts. Under industrial reaction conditions, S b +

is the main state of S in the poisoned catalysts.

Catalytic Combustion of Methane over Supported Palladium Catalysts. I. Alumina Supported Catalysts. 11. Support and Possible Morphological Effects T. R. BALDWIN and R. BURCH, Appl. Catal., 1990,66,

A series of Pd/AI,O, catalyst were tested under continuous-flow conditions, for their activity towards CH, combustion in an 0, rich atmosphere and the effects of various precursor Pd salts and different supports in the preparation of Pd catalysts for CH, combustion were studied. Catalytic activities were found to increase dramatically after heating in a 1 YO CH, /air reaction mixture.

T. CHOJNACKI, K. KRAUSE and L. D. SCHMIDT, 3.

127, (2), 64-664

219-234

(2), 337-358; 359-381

Catalytic Oxidation of Methane over Palladium Supported on Alumina. Effect of Aging under Reactants P. BRIOT and M. PRIMET, Appl. Catal., 1991, 68,

After ageing a Pd/AI? 0, catalyst at 600% under a CH,-O,-N, mixture with a O,:CH, =4, it was found that the aged catalyst was more active than the fresh one, especially below 400°C. Ageing decreased metal dispersion and increased Pd particle size from 7-16 nm, and turnover was strongly enhanced. The reactivity of adsorbed 0 towards H increased with metal particle size. Pd may be in the form of bulk Pd oxide for reaction temperatures of >400°C and for CH,:O, mixtures rich in 02. The formation of bulk PdO appears to be metal particle size dependent.

Influence of Oxidation of Pd/AI,O, for the Reactions of CO with NH, and For- mamide Decomposition D. K. PAUL and s. D. WORLEY, 3. Phys. Chem., 1990,

The reaction of CO with NH, and the decomposition reactions for HNCO and formamide over Pd/AI,O, films were studied by IR spectroscopy. The formation of isocyanate species (NCO) was observed during all of these reactions over pre-oxidised W/AI 0 , , but not over pre-reduced surfaces. The NCO species were formed on Pd but spilled over to the AI,O, support. Pd became reduced during the course of the reaction of CO with NH , . Effect of Preparation Conditions on the Structure and Properties of Palladium- Aluminosilicate Catalysts

L. v . PAVLYUKEVICH and A. B. FASMAN, Kinet. Katal.,

Studies of the effect of preparation conditions of deposited Pd catalysts on the structure and activity during 2-ethylanthraquinone hydrogenation were performed on Pd catalysts supported on aluminosilicates containing 86.5% SiO,, 13% AI,O, and oxides of Na, Fe and Mn. The results showed that part of the metal interacts with the support, forming Pd,Si compounds in amount depending on preparation conditions. The effect of structural factors on the activity and selectivity of catalysts during the reaction was analysed.

Bulk Alloy Formation during Metal Ion Poisoning of Palladium

Catal., 1991, 69, (l), 85-95 Studies of the phase structure of Pd catalysts poisoned by metal ions, performed by XRD, electrochemical polarisation and AAS methods, showed bulk alloy formation during liquid phase hydrogenation at 295-350 K. Both ordered: Pd,Pb, Pd,Ge, PdGe, PdHg, Pd,Hg,, and disordered: Pd-Sn, Pd-Cd, Pd-Hg, alloys were identified.

(1-2), 301-314

94, (26), 8956-8959

E. M. MOROZ, S. D. MMHAILENKO, A. K. DZHUNUSOV,

1990, 31, (6), 1506-1510

T. MALLAT, Z . B O D N h , S. SZAB6 and J . PETR6, Appl.

Platinum Metak Rev., 1991, 35, (2) 108

CO Oxidation over Pd and Cu Catalysts. I. Unreduced PdC12 and CuC12 Dispersed on Alumina or Carbon. 11. Unreduced Bimetallic PdC12 -CuC12 Dispersed on A1203 or Carbon K. I. CHOI and M. A. VANNICE, 3. caul., 1991, 127, (2), 465-488; 489-511 CO can be oxidised at 300-400 K by 0, over dispersed, unreduced PdCl , or CuCl , , but specific activities for CO oxidation by 0 , over unreduced PdCl , -CuCI , catalysts were higher than on the reduced bimetallic catalysts. PdCI, was more active than CuClt and the addition of H,O vapour to the feed greatly enhanced the activity of the PdCl, catalysts. The activity of PdCl,-CuCI, catalysts can also be enhanced by 1-3 orders of magnitude by addition of H,O vapour to the feed, thus producing very active catalysts at 300 K. A reaction model that involves H,O as a reactant with the PdClCO species is proposed.

Hydroconversion of n-Nonane Catalyzed by PdHY Zeolites. I. Influence of Catalyst Pretreatment. 11. Effect of the Chromium Promoter

LEGLISE, J. . M. GoUPIL and D. CORNET, Appl. catal.,

Pd/EiY catalysts reduced at 573-873 K were studied during n-nonane hydroconversion at 473 K and 0.1 MPa. The catalyst reduced at 573 K had a stable activity and a high selectivity for isomerisation, but samples reduced at > 773 K initially favoured cracking at the expense of isomerisation. 3% Cr was added to Pd/SY zeolites to maintain a good dispersion of the noble metal upon reduction at elevated temperature. Catalysts reduced at 573 K showed a promoter effect limited to a change in reaction selectivity. However, if Cr was properly introduced in catalysts reduced at 773 K, it improved the dispersion of Pd and hence the hydrogenation function.

Catalysis with Palladium Deposited on Rare Earth Oxides: Influence of the Sup- port on Reforming and Syngas Activity and Selectivity

J. LEGLISE, A. CHAMBELLAN and D. CORNET; J.

1991, 69, (l), 15-31; 33-47

F. LE NORMAND. 1. BARRAULT. R. BREAULT. L. HILAIRE and A. K I E N N E ~ N N , 3. Phys. Chem., 19b1, 95, (I), 257-269 The effect of the support was tested on the reactivity of Pd/rare earth oxide catalysts (La,O,, GO,, Pr,O,,, Nd,O, andTb,O,) bymeasuringBETsur- face area, chemisorption, TPR and TPO, XRD and X P S . The catalysts were put into three classes according to their ability to create anion vacancies: (a) oxides of the type Re20J which are unreducible, (b) G O , where anion vacancies can be created extrin- sically by the reduction process, and (c) Pr,O,, and Tb,O, where anion vacancies exist due to the nonstoichiometric nature of these oxides. In syngas conversion the production of high alcohols at the metal-support interface is favoured by the presence of intrinsic anion vacancies on Pr,O,, and Tb.0,.

Preferential Site Displacement of Carbon Monoxide by Phosphine on Rh/A1203 Surfaces

Chem., 1990, 94, (21), 8326-8328 Transmission IR spectroscopic studies showed that specific bonding sites of CO are preferentially displaced upon exposure of a CO-saturated Rh/AI,O, surface to PH,. CO is bound in three primary adsorption states on Rh/AI,O,, with bridged, atop, and gem-dicarbonyl bonding. At all adsorption temperatures studied (90-300 K), exposure to PH, readily leads to removal of CO bound in gem-dicarbonyl sites. Production of Rh(C0)PH , was verified upon PH, exposure of a Rh/AI,O, surface containing only the gem-dicarbonyl species.

Protection of a Rh/A1203 Catalyst under Extreme Environmental Conditions D. K. PAUL and J. T. Y A T E S , ~ . Phys. Chem., 1991,95,

The removal of isolated AI-OH groups by the silation of Rh/AI,O, catalysts is effective in preventing catalyst degradation under conditions where CO adsorption occurs. The functionalisation of isolated AI-OH species by (CH ,) , SiCl led to the formation of very stable (CH,), Si-0-AI = (alumasiloxane) surface species. Silation by alkyl halosilanes may provide a practical route for the protection of Rh/AI,O, catalysts from oxidative degradation under the conditions encounteEd in automotive catalysts.

Membrane-Supported Rhodium Hydroformylation Catalysts

G. LU, J. E. DARWELL and J. E. CROWELL, 3. P'hyS.

(4), 1699-1703

J. FELDMAN and M. ORCHIN, 3. MOl. catal., 1990,63,

Films prepared from the THF solutions containing cellulose acetate, [HRh(CO)(PPh I ) I and PPh , were tested for catalytic activity in the vapour phase hydroformylation of C, H, and C, H, at 800 Torr and 8OoC, giving RCH,CH,CHO. Turnover rates were about 25 mol propanal/mol Rhh. No loss of Rh or PPh, was noted from the fdm. The turnover rates with the films were equal to or even slightly higher than when using homogeneous [HRh(CO)(PPh ,)I . Films prepared from poly(pheny1sulphone) were also active catalysts. The absence of 0, enabled the system to retain its activity for more than 13 days.

Carbon Monoxide Hydrogenation on Supported Rh-Mn Catalysts

Mol. Catal., 1990, 63, (2), 201-211 Rh/SiO, catalysts promoted with Mn show a higher specific activity for CO hydrogenation than unpromoted catalysts. This results in increased C,, product formation. Activation energy for chain growth is significantly higher on the Mn promoted catalysts, possibly because promoted catalysts provide more active sites and the insertion mechanism may be different to that for unpromoted catalysts.

(2), 213-221

A. S. LISITSYN, S. A. STEVENSON and €I. KNOZINGER, 3.

Ptatinum Metals Rev., 1991, 35, (2) 109

Catalytic Properties of Well Dispersed Supported Ruthenium Alloys B. COQ, A. BITTAR, R. DUTARTRE and F. FIGUERAS, J. Catal., 1991, 128, (l), 275-286 Small particles of Ru alloyed with Sn, Pb, Sb, Ge or Si were prepared by reacting a well dispersed Ru/Al,O, parent sample with an organometallic compound of the desired modifier, by the so-called controlled surface reaction method. The results showed that a topological segregation of Sn, and to a lesser extent Pb, takes place at the bimetallic surface, with the second metal occupying sites of lower co- ordination, displacing Ru onto the facets. Ge seems more randomly distributed at the surface.

Hydrogenation Pathway of Quinolines over Raney Nickel and RulC

TAMURA and I. MOCHIDA, Bull. Chem. SOC. Jpn.,

Quinoline, together with 2-methylquinoline and 8-methylquinoline were hydrogenated over Ru/C and Raney Ni catalysts, under 100 atm H, at 15OOC and 10 atm H, at 2OO0C, respectively. All the substrates were commonly hydrogenated into the initial products, 1,2,3,4-tetrahydroquinoIines. Ru/C promoted exclusively the direct hydrogenation of 1,2,3,4-tetrahydro derivatives to the final products. The effects of methyl substituent and different reac- tivities of quinoline and isoquinoline are discussed.

Catalysis of the Water-Gas Shift Reaction by Supported Ru,(CO),, with 2,2'- Bipyridine

KRAUSE, 3. Mol. Carol., 1991, 64, (2), 163-169 The water gas shift reaction was studied on Ru,(CO),, with 2,2'-bipyridine on silica gel, Mg silicate and X- and Y- mordenite zeolites in Na form supports, in a flow reactor at 100-15OoC and CO partial pressure of 7 bar. The highest activity of 8170 mol H,/mol Ru,(CO,,)/24 h was obtained with a Mg silicate support at 15OoC, and its activity was stable for long periods. The metal catalyst was well retained on the support during flow operation.

H. OKAZAKI, K. ONISHI, M. SOEDA, Y. IKEFUJI, R.

1990, 63, (ll), 3167-3174

U. KIISKI, T. VENALAINEN, T. A. PAKKANEN and 0.

HOMOGENEOUS CATALYSIS Homogeneous Hydroformylation of Olefins by cis-[PtCI, (PPh,), IlSnCI, G. MULLER, D. SAINZ and j. SALES, J. Mol. Catal.,

The catalytic activity of cis-IPtCI,(PPh,),l/SnCI, for the hydroformylation of various olefins was studied. For 1 -pentene and cyclohexene, conversions and hydroformylations are higher than for other Pt/Sn systems. The results obtained with cyclopentene (79% hydroformylation and TOF 180h) and allyl benzene (87% hydroformylation and TOF of 220h) were among the best yet reported.

1990, 63, (2), 173-180

Metal Colloid Morphology and Catalytic Activity: Further Proof of the In- termediacy of Colloids in the Platinum- Catalyzed Hydrosilylation Reaction L. N . LEWIS, R. J . URIARTE and N. LEWIS, J. Catd., 1991, 127, (l), 67-74 The Pt colloids formed during hydrosilylation reactions were studied by TEM and high-resolution electron microscopy (HREM). Reaction solutions were analysed for the addition of Et , SiH to either n-hexene or neohexene catalysed by bis(l,3-divinyl,l,l,3,3,- tetramethy1disiloxane)Pt" (Karstedt's catalyst) and showed dramatic differences between the morphology of the Pt colloid formed in each case. The neohexene reaction which gave 62% conversion to products in 1 h contained polycrystalline, 2.5 nm diameter Pt particles.

Tailored Cationic Palladium(I1) Com- pounds as Catalysts for Highly Selective Linear Dimerization of Styrene and Linear Polymerization of p- Divinylbenzene z . JIANG and A. SEN, 3. Am. Chem. SOC., 1990, 112,

The replacement of the weakly co-ordinating MeCN ligands in [Pd(MeCN),I(BF,) by more strongly ligating and bulkier pyridine and phosphine derivatives resulted in the formation of highly selective catalysts for selective linear dimerisation of styrene and linear polymerisation of pdivinyl- benzene. The new catalyst' systems differ from most existing systems in several important ways; specifically. (a) no indan derivative of higher oligomers are formed from styrene, (b) only styrene reacts when a mixture of styrene and a-methylstyrene is employed and (c) the ability to effect clean, linear dimerisation of styrene allowed the formation of a soluble, linear polymer from p-divinylbenzene.

Annulation via Alkylation-Alder Ene Cyclizations. Pd-Catalyzed Cyclo- isomerization of 1,6-Enynes

and T. MUELLER, J. Am. Chem. SOC., 1991, 113, (2),

A Pd(0)-catalysed alkylation of an ally1 substrate with a nucleophile containing a double or triple bond to allow subsequent thermal Alder ene reactions gives a novel annulation process. For a triple bond, a Pd(2 +) complex catalyses an equivalent of an Alder ene reaction. This new cyclisation was studied in terms of the effect of substitution on the olefin, the acetylene, and the tether connecting the two. The Pd(2+) catalysed reaction showed an ability to interact with remote non-reactive parts of substrates to affect conformation and selectivity. A novel cyclopentan- nulation of allyl alcohols and related derivative evolves in which Pd(0) catalyses formation of the first bond and a simple electronic switch to Pd(2+) catalyses formation of the second bond.

(26), 9655-9657

B. M. TROST, M. LAUTENS, C. CHAN, D. J. JEBARATNAM

636-644


Reactions of Cyclopalladated Compounds and Alkynes: New Pathways for Organic S ynthesis? M. PFEFFER, R e d . Trav. Chim. Pays-Bas, 1990, 109,

Cyclometallated compounds obtained by direct intramolecular C-H activation of a ligand by transition metals, and those derived from Pd(I1) were found to be fairly reactive towards insertion of internal alkynes into their metal-C bond. This reaction led to either new organometallic compounds by inclusion of one to three alkynes into the M-C bonds, or organic compounds, which were either carbocyclic or heterocyclic.

Chiral Rhodium(I1) Carboxamides. A New Class of Catalysts for Enantioselec- tive Cyclopropanation Reactions

(12), 567-576

M. P. DOYLE, B. D. BRANDES, A. P. KAZALA, R. J . PIETERS, M. B. JARSTFER, L. M. WATKINS and C. T. EAGLE, Tetrahedron Lett., 1990, 31, (46), 6613-6616 The preparation of an effective class of chiral catalysts, Rh,L, where L=Csubstituted ox- azolidinones and methyl 2-pymlidone-5-carboxylate7 based on the dirhodium(I1) framework with two N- Rh bonds in the cis geometry at each Rh face, are effective catalysts for enantioselective intermolecular cyclopropanation reactions, such as for styrene.

Efficient Activation of Acetals, Aldehydes, and Imines toward Silylated Nucleophiles by the Combined Use of Catalytic Amounts of [Rh(COD)CIl and TMS-CN under almost Neutral Con- ditions

MUKAIYAMA, Bu!l. Chem. SOC. Jpn., 1990, 63, (ll),

Studies of the reaction of trimethylsilyl cyanide (TMS-CN) with acetals in the presence of a catalytic amount of [Rh(COD)CII ?, Co(acac), or NiCl, showed the smooth formation of a-methoxy carbonitriles in good yields. The co-existence of catalytic amounts of IRh(COD)CII, and TMS-CN, allowed silyl enol ethers or ketene silyl acetals to react with acetals, aldehydes or imines to yield the corresponding coupling products in good yields under almost neutral conditions.

Homogeneous Catalysis. Catalytic Pro- duction of Simple Enols

T. SOGA, H. TAKENOSHITA, M. YAMADA and T.

3122-3131

S. H. BERGENS and B. BOSNICH, y. Am. Chem. SOC., 1991, 113, (3), 958-967 Complexes of the type [Rh(diphosphine)(solvent) , 1 +

in dry acetone or tetrahydrofuran solutions are effective catalysts for the production of synthetically useful quantities of simple enols from their corresponding allylic alcohols. A number of simple enols were produced, and the physical properties and stabilities were recorded. The mechanism of catalysis was inferred from specific isotopic labelling studies.

Poly-( 1 ,g-Naphthalene) as Support of Catalytically Active Osmium Clusters for Olefin Isomerisation H. P. FRITZ and T. TROBENBACH, 3. Mol. .catal., 1991,

The complex [H,0s,(CO)u-(FTh2)x-C,uH, with x=2-3 and n-55, was synthesised and shown to have significantly higher catalytic activity for the isomerisation of I-hexene than H,Os,(CO),- polystyryl chain, or than free H,Os,(CO),,. It may be considered as a model system for comparing its ‘linear’ or rather noncoiled structure with polymer- supported catalysts with alkane backbones.

Ruthenium-Catalyzed Allylation of Primary Alcohols by Allylic Acetates: A Novel Synthesis of a,P-Unsaturated Ketones

64, (2), 213-220

T. KONDO, T. MUKAI and Y. WATANABE,J. @. Chem., 1991, 56, (2), 487-489 A novel synthesis of a$-unsaturated ketones from primary alcohols and allylic acetates via T-

allylruthenium intermediates is described. The T-

allylruthenium intermediates act as nucleophiles rather than as electrophiles in reactions with aldehydes to give homoallylic alcohols. This behaviour contrasts with that of r-allylpalladium complexes which usually act as electrophiles.

Selectivity in Catalytic Diol Electrooxida- tion Using A Polypyridine Ru(IV) Complex

Tetrahedron, 1991, 47, (4/5), 851-857 The polypyridine [(bpy)(trpy)RUOl?+ complex, (bpy is 2,2’-bipyridine, trpy is 2,2’:6’,2‘’-terpyridine) was systematically studied to explore its oxidising ability. 1,2-, 1,3- and 174-butanediols and phthalic alcohol were oxidised electrocatalytically with different concentrations of the catalyst, pH and temperature. By controlling the number of coulombs passed through the electrolytic cell, it was possible to obtain selective reactions. Products obtained by controlled potential electrolysis were l-hydroxy-2-butanone, l-hydroxy-3-butanone, y-butyrolactone, phthalide, phthalic aldehyde and phthalic acid.

General Synthesis of Nova1 Chiral Ruthenium Catalysts and Their Use in Asymmetric Hydrogenation J. P. GENET, S. MALLART, C. PINEL, S. JUGE and 1. A. LAFFIT~E, Tetrahedron: Asymmetry, 1991, 2 , (l), 43-46 The fmt general synthesis of mononuclear hexaco- ordinate chiral Ru complexes is presented. Four chiral Ru(II)(2-methylallyl)~ complexes containing Diop, Chiraphos, Norphos and Binap were prepared in 50-71% yield under mild conditions, and were effective for asymmetric hydrogenation of unsaturated carboxylic acids to give the corresponding saturated derivatives attaining 90% optical purity.

M. NAVARRO, W. F. DE GIOVANI and J. R . ROMERO,


Homogeneous Catalysis in Water: A Remarkable Salt Effect in the Hydrogenation of Propionaldehyde with RuCl, (tppts) , and Related Complexes [tppts = (rn-NaSO,C, €I4) ,PI

Chem. SOC., Chem. Commun., 1990, (24), 1776-1778 New water soluble RU” complexes such as RuHI(tppts) >, exhibit an extremely high catalytic activity in the presence of various salts during hydrogenation of aldehydes. Mechanistic studies showed clearly that the salt effect occurred both via the cation and the anion in the catalytic cycle. The electrophilic cation favoured an unusual type of aldehyde co-ordination and reaction mechanism as the anion modified the co-ordination sphere around the Ru atom.

E. FACIE, F. SENOCQ, C. SANTINI and J.-M. BASSET, 3.

Dielectric Enhancement Layers for a PtlCo Multilayer Magneto-Optical Recor- ding Medium P. F. CARCIA, M. REILLY, w. B. ZEPER and H. w. VAN KESTEREN, Appl. Phys. Lett., 1991, 58, (2), 191-193 Studies showed that a transparent ZnO dielectric layer, with refractive index n - 2, not only enhanced the Kerr rotation of the Pt/Co recording layer, but also substantially increased its magnetic coercivity (Hc) . Coercivities of up to 3kOe were obtained in Pt/Co multilayers Kr sputtered on a ZnO layer, while maintaining square hysteresis loop shape for an applied magnetic field perpendicular to the thin film.

Thermal Stability of PtSi Contact to Ge,Si - x

Q. z . HONG, J . G . ZHU, c. B. CARTER and J. w. MAYER, Appl. Phys. Lett., 1991, 58, (9), 905-907 Studies of the thermal stability of PtSi contact to epitaxial Ge,,,Si,,,/(lOO)Si showed that the PtSi layer remained structurally and morphologically intact on the epitaxial Ge-Si alloy at -650OC. When annealed at higher temperatures, Pt Si penetrated locally into the alloy, although no chemical *action

CHEMICAL TECHNOLOGY

Low Severity coal Conversion by an Elm- troreduction Route M. FAROOQUE, A. KUSH, H. m u and J. MACWNALD, 3. Appl. Electrochem., 1991, 21, (2), 143-150 , was observed. Electrochemical conversion of coal to low molecular weight hydrocarbons through an electroreduction route involves reaction of H+ with the coal surface leading to hydrogenation of coal molecules at low severity operating conditions. The type of cell used is the same as that used in H,PO, fuel cells with the anode comprising a porous thin layer of supported Pt catalyst laminated on a porous, conductive graphite support layer. The matrix consisted of a thin porous layer of Sic soaked with H,PO, electrolyte. The liquid product compositions were dependent upon the parent coal and comprised a variety of aliphatic and aromatic compounds.

ELECTRICAL AND ELECTRONIC ENGINEERING Focused Ion Beam Induced Deposition of Platinum

KAESZ, 3. Vac. Sci. Technol. B, 1990, 8, (6),

Focused ion beam induced deposition of Pt fdm, using Ga+ ions, from a precursor gas of (methylcyclopentadieny1)trimethyl Pt, which is solid at room temperature, has been performed. The resulting film has a resistivity of 70-700 p 0 cm, depending on conditions. The resistivity and impuri- ty C content dropped as the ion current increased. The Pt fdm is amorphous and of composition 46%Pt, 24%C, 28%Ga and 2%0. Adding H, to the same area by a nozzle has little effect on the yield or resistivity. Pt formed in this way can fill trenches, while at near grazing incidence on a cleaved Si surface it forms discrete islands of size 0.25 pm. It may find applications in IC chip repair.

T. TAO, I .+. RO, J. MELNGAILIS, Z . XUE and H. D.

1826-1829

Barrier Layers for Realization of High Capacitance Density in SrTi03 Thin-Film Capacitor on Silicon

YAMAGuCHI and Y. MIYASAKA, Appl. Phys. Lett.,

High dielectric constant SrTiO, thin films were sputter deposited on barrier layers/Si substrate to produce a capacitor for dynamic random access memories. Dielectric constant (E) values of 140-210 were achieved for the 150 nm thick SrTiO, fdms using a Pt/Ti or Pt/Ta double-layer barrier. In the Pt(50 nm)/Ti(lO nm), Pt(50 nm)/Ti(SO nm) and Pt(50 nm)/Ta(lO nm) barrier, effective E decreased on annealing at 450-550OC. In the Pt(50 nm)/Ta barrier, increasing the Ta thickness from 10 to 50 nm remarkably improved the endurance to high-temperature annealing.

Preferential Reaction and Stability of the Au-SnlPt System: Metallization Structure for Flip-Chip Integration 0. WADA and T. KUMAI, Appl. Phys. Lett., 1991, 58,

Studies of thermal reactions of a metallisation system consisting of Au-Sn solder, Pt/Ti barrier, and Au/Zn/Au contact layers formed on an InP substrate were performed by AES, SEM and XRD. On heating to 4OOOC a moderate reaction was observed between Au-Sn and Pt, with a characteristic feature of preferential F’t-Sn interdiffusion to produce an intermediate layer involving the PtSn phase. The effective diffusion coefficient had an activation energy of 1.35 eV, and the lifetime of the Pt barrier was found to be in excess of lo8 h for 5OoC, which is suffcient for the application of this structure in devices.

T. SAKUMA, S. YAMAMICHI, S. MATSUBARA, H.

1990, 57, (23), 2431-2433

(9), 908-910


Stress Migration Resistance and Contact Characterization of Al-Pd-Si Intercon- nects for Very Large Scale Integrations

MORIBE and Y . TANICAKI, J. Vac. Sci. Technol. B,

Stress induced migration resistance and contacts to Si of Al-0.3%Pd-lohSi interconnections for submicron process integrated circuit devices were investigated and compared to those of Al-O.S%Cu-l%Si. From creep tests, Pd addition to Al reduced the grain boundary diffusion. Pd improved the stress-induced migration resistance and reduced void and hillock formation in Al-Si conductors. AlPd precipitates in Al-Pd-Si alloys formed at higher temperatures than AlCu compounds and may explain the improvements. Contact resistances were similar, but reliability and yield data from 1.2 pm ROM devices using Al-Pd-Si conductors were better than that from Al-Cu-Si conductors. Thus Al-Pd-Si metallisation is promising as an interconnection for submicron VLSIS.

Probe Beam Deflection Investigation of the Charge Storage Reaction in Anodic Iridium and Tungsten Oxide Films R. KOTZ, C. BARBERO and 0. IUAS, J. Elecmanal. Chem. Interfacial Elecmchem., 1990,296, (l), 37-49 The electrochromic charge storage reaction in anodic Ir oxide fdms (AIROF) was studied in aqueous electrolytes using the probe beam deflection (PBD) technique in combination with cyclic voltammetry. In acid electrolyte, of 1 M HCIO, for Ir and 1 M H,SO, for W, the sign of the PBD signal showed clearly that protons were ejected from the oxide fdm into the bulk electrolyte during oxidation. In basic electrolyte of 1 M LiOH, 1 M NaOH, OH- ions were consumed during the oxidation reaction in the AIROF. The change in sign of the beam deflection signal, indicative for one or the other reaction, occurred at -pH 4 (k0.5).

Structural and Electrical Evolution of the AllRuO, Interface upon Thermal An- nealing Q. T. w, E. KOLAWA and M.-A. NICOLET, Solid-state Electron., 1991, 34, (3), 271-278 The behaviour of the Al/RuO, interface was monitored by various techniques as a function of the annealing temperature: 450-550°C and the duration. An interfacial Al-0 compound layer grew with con- current reduction of a thin layer of RuOz. This result does not depend on the deposition conditions. Struc- tures of the type <Si>/SiO,/Al/RuO,/Al were annealed, and the specifx contact resistance between Al and RuO, was derived, and shown to decrease with annealing duration at 500OC. This evolution of the specific contact resistance indicated that the interfacial reaction does make an insulating interface, as expected if the interfacial growth were pure and dense Al 0 I . RuO, can be used as a diffusion barrier between Si and Al.

Y. KOUBUCHI, J . ONUKI, M. SUWA, S. FUKADA, S.

1990, 8, (6), 1232-1238

Reactively Sputtered RuO, Thin Film Resistor with Near Zero Temperature Coefficient of Resistance Q. X. JIA, 2. Q. SHI, K. L. JIAO, W. A. ANDERSON and F. M. COLLINS, Thin Solid Filmsj 1991, 196, (l), 29-34 Ru oxide thin film resistors with near zero temperature coefficients of resistance (TCR) were successfully deposited on SiO] /Si substrates by reactive DC magnetron sputtering. The TCR was a strong function of substrate temperature during sputtering. Around 8OoC a critical temperature was found where the TCR changed signs, between a temperature dependence of semiconductor-like behaviour and metal-like behaviour. Films with amorphous structure usually had a negative TCR, but fdms with a polycrystalline structure had a positive TCR. Resistors with near zero TCR may have a microcrystalline structure.

TEMPERATURE MEASUREMENT Temperature Measurement under Ex- treme Conditions R. MOBIUS, P.-E. NAU and R. WAHREN, Chem. Tech. (Leipzig), 1991, 43, (l), 26-29 The temperature of the reactors during the production of syngas from fuel oil was controlled by temperature measurement thermocouples (PtRh 3OiT'tRh 6), which were protected by sintered corun- dum conduits. At temperatures up to 1800 K and pressure up to 4 MPa the thermocouples and conduits were exposed to extreme conditions from the gas atmosphere and the oil ash. Accuracy of the measurements and the life of the thermocouples depend very much on the quality of the sintered corun- dum conduits and on stable plant operation.

Magneto-Resistance of a Highly Stable Industrial-Grade Platinum Resistance Thermometer between 20 and 240 K K. NARA, H. KATO and M. OKAJI, Cryogenics, 1991, 31,

The stability and magneto-resistance of a new Pt resistance thermometer made to the Japanese In- dustrial Standard were studied. The stability was estimated from the change in resistance at the triple point of water after thermal cycles between room temperature and liquid N, temperature. The varia- tion in the resistance values at 20, 50 and 100 cycles was < 1 mK. The magneto-resistance was measured between 20 and 240 K in a field of up to 8 T. The relative resistance increase, E , obeyed the equation t = D(T)B,/[l+E(T)BI. The fitting error in the field dependence was < 15 mK at >u) K and. - 0.1 % of the correction for a magnetic field of 8 T - which is a better fit than the previously reported equation. An extremely reliable screening procedure has been established to characterise long-term stability of small sensors for thermometry in magnetic fields.

(l), 16-20

Platinum Metah Rev. , 1991, 35, (2) 113

NEW PATENTS METALS AND ALLOYS Gold Coloured Alloy with Low Gold Content D. DAVIT2 U.S. Patent 4,948,557 A gold coloured alloy composition contains 24-27 wt.% Pd, 17-22 wt.% In, 5-30wt.% Cu, 1-20 wt.% Au and balance Ag, and may contain 0.25-1 wt.% Ru. The alloy is tarnish and corrosion resistant, and gives a rich gold colour at a reduced cost due to its reduced Au content. The novel alloy can be made in- to articles of jewellery, and is used in dentistry for crowns and bridges.

Oxidation Resistant Amorphous Alloy Thin Films MITSUI PETROCHEM. IND. K.K.

Japanese Appls. 21 107,748 -49 Amorphous alloy thin films contain Pt, Pd, at least one each of the light and heavy rare earth elements, and Fe and/or Co. The films have excellent oxidation resistance, with a direction of easy magnetisation ver- tical to the film surface.

ELECTROCHEMISTRY Oxygen Generating Electrode M. MUROYA Japanese Appl. 2177,394 An 0, generating electrode consists of a Ti base material with a coating of at least one oxide of IrO, or RuO,, on top of which is an Mn oxide layer. The IrO, andlor RuO, layer promotes the 0, generating reaction on the Mn oxide layer, prevents the Ti base material dissolving, and attaches the Mn oxide. The electrode gives good 0, generating efficiency, is used for electromagnetic propulsion vessels, and generates less chlorine.

Electrode for Electrolysis of Brine LIMES K.K. Japanese Appl. 2188,785 An electrode for electrolysis consists of a metal substrate -.&h a surface amorphous alloy layer having at least one Fe group element, at least one Pt group element, and at least one of Ti, Zr, Nb and Ta. The alloy layer is made by an ion-beam mixing method, and then treated with an acid. An electrode material having an irregular surface is produced.

Water-Repellant Electrode for Electrolytic Processes N. E. CHEMTECH K.K. Japanese Appl. 21145,788 An electrode consists of an electroconductive metal base coated with a f im of oxide of Pd, Rh, Ir or Ru, with metals Pd and Rh, and a water-repellant layer such as polytetrafluoroethylene. The electrode is used extensivelv for industrial electrolvsis. elec-

Durable Electrode for Electrolysis of Seawater ISHIFUKU METAL IND. K.K.

Japanese Appl. 21190,491 A Ti (alloy) based electrode has an intermediate layer with 0-20 mol% of at least one of the oxides of Ir, Mn, Co, Sn and Sb, and 80-100 mol% of oxides of Nb, Ta andlor Zr, dispersed in Pt; and an outer layer of mixed metal oxides including 5-95 mol% of Ir oxides. The electrode has low 0, overvoltage, excellent durability, and is used for electrolysis of seawater, surface treatment of metals, forming metal foils, and recovering metals.

Durable Electrode for Electrolysis Containing Platinum and Iridium

An electrode has a substrate, an intermediate layer consisting of a partial coating of dispersed Pt and a partial oxide coating which may contain Ir oxide, and an outer layer having 1-30 mol% Pt, 5-94 mol% Ir oxide, and 5-94 mol% of oxides of Nb, Ta and/or Zr. The electrode has low 0, overvoltage, low film resistance of the intermediate layer, good durability, and is used as an anode in electrolysis of sea water, and surface treatment of metals.

Activating a Titanium Anode for Electrochemical Processes

ISHIFUKU KINZOKU KO. Japanese Appl. 21200,790

VEB. CHEM. BIlTERFELD East German Patent 273,364

A Ti anode is activated by anodising in an electrolyte containing sealing components, fluoride, and 0.01-2.0 molA RuCl,. Oxidising is by spark discharge under a direct voltage of 10-200 V, followed by optional treatment with a solution of Pt group metal chlorides and tempering. Anodes with high electrical conductivity and stability are produced economically, for use in electrochemical processes, especially chloralkali electrolysis.

ELECTRODEPOSITION AND SURFACE COATINGS Palladium Electroplating Bathe AT. & T. BELL LAB. U.S. Patents 4,911,798-99 Electroplating of I'd or I'd alloys uses baths with conductivity >0.001 mhocm and pH >5, and containing (a) a Pd source, and alkyl ammonium chloride surfactant with 4-35C, and a specified brightener, or (b) Pd with alloying metals such as Pt, Rh, Ir, Ru, Au, Ag, Cu, Ni and Co, an alkylhydroxyamine, and a phosphate buffer system. The plated films thus obtained have (a) excellent adhesion and ductility, are crack-free, and are used for electrical contacts, or (b) corrosion resistance with high electrical conductivity, - ,

trolytic synthesis, and electroplating processes. with use for connector pin;.


Electroplating Non-Conductive Articles SHIPLEY CO. U.S. Patent 4,919,768 A non-conductive body is electroplated by treating the surface in sequence with (a) at least 0.01M Sn?' salt solution, (b) 0.00001-1.OM sulphide solution, and (c) 0.001-0.01M Pt or Pd salt solution, and electroplating the surface with Cu or solder. Deposition of a sulphide film allows direct electroplating without an electroless plating step. The plated article is a printed circuit board.

Coating Metallic Substrates to Increase Erosion Resistance AVCO CORP. U.S. Patent 4,931,152 Erosion resistance is imparted to a metallic substrate by coating with 0.1-1.5 mil Pt or Pd, 0.5-1.5 mil W, and 0.2-3 mil W C alloy or V matrix material having dispersed WC phases. The fmt layer retains substrate integrity and acts as a diffusion barrier. The method is used for (stainless) steels, and gives increased erosion resistance without loss of fatigue life.

Palladium-Nickel Film Formed by Jet- Plating FUJITSU LTD. Japanese Appl. 21133,595 A Pd fdm containing Ni is formed by jet-plating, using a plating solution containing 20-30 g/l Pd and 1-10 gA Ni. The method provides Pd fdms having good appearance for ornamental uses and also those having good electrical properties. In an example, a 0.75-lpm thick Pd film containing up to 20 wt.% Ni was formed on a substrate.

Palladium Plating Solution KURARAY K.K. Japanese Appl. 21153,077 An electric insulator is chemically plated using a solution of a Pd-urea complex salt and a reducing agent, followed by electroplating in the same solution. The method is used for Pd deposition on a specified portion of various shaped electric insulators, for example on a teeth restoration body.

Palladium Activating Solution for Electrolese Plating

A capacitor element is made by adding an activating solution of Pd chloride and Sn chloride to a resist, applying the resist to a ceramic substrate by screen printing, followed by electroless plating. The method is used for chip type multilayer ceramic capacitors, chip type electrolytic and other ceramic capacitors.

KANEHIRO METALLISIN. Appl. 21166,711

APPARATUS AND TECHNIQUE Preparation of Labelled Biologically Active Compounds AS. USSR MOL. GENETIC British Appl. 2,229,718A A biologically active compound labelled with a H isotope is prepared by interacting a starting compound, an inorganic vehicle and a Pt group metal catalyst with an isotope of H at 373-523 K, cooling, and isolating the product. The starting compound may be a complex of a Pt group meral with amines, sugars, or others. Increased incorporation of the isotope label can be,obtained, and the products can be used in medical and biological studies.

Thin Film Sensor with Platinum Layer HONEYWELL INC. Eumpean Appl. 375,3996 A thin fdm sensor consists of a layer of Si,N;, a 20-100 A thick metal oxide adhesion-promoter layer, and a Pt layer; where the Pt and metal oxide layers are formed by sputtering. The oxide layer provides an atomically smooth adhesive layer between the nitride and Pt layers. The sensor is used in the manufacture of microbridge mass air flow sensors.

Biosensor Module Including a Platinum Anode

A sensor module for determination of a substrate concentration, for example glucose concentration in a perfusion solution, has an amperometric enzyme electrode in a holder with a central Pt anode, contacted by an enzyme membrane with an outer membrane; and a reference electrode. The biosensor is a simple module of streamlined shape with a compact design.

Oxygen Sensing Device with Platinum Electrodes

A device for rapidly sensing the amount of molecular 0, in a combustion product gas contains a heated ceramic electrolyte disc coated with Pt electrodes. This serves as a shared wall between the product gas and reference air, generating a voltage output proportional to the partial pressure difference of 0,. The amount of 0, in the combustion gas is controlled to maximise efficiency and minimise pollution.

Iridium Crucible for Gallium Garnet Single Crystal Production

AVL. MEDI. INSTR. A.G. Eumpean Appl. 385,964A

NAT. AERO & SPACE ADMIN. U.S. POtt?nt 4,911,890

SHINETSU CHEM. IND. K.K. Japanese Appls. 6015,094 and 21175,685

Non-conductive objects are plated by coating with metallic Pd or Ag nuclei, immersing in a plating bath containing a Cu salt, a Ni salt and a reducing agent, electroplating at low current density to form a fdm with 280 wt.% Cu, and electroplating at high current density to obtain a fdm with > 3Owt.% Ni.

by heating in an Ir crucible, in an atmosphere with O 2 partial pressure of 20-100 mm Hg. A single crystal of Ga garnet at least 75 mm in diameter is pull- ed during or after the melting period, which has less defects and is useful for magnetic bubble memories or working substances for a magnetic refrigerator.


Plating Non-Eleetroconduetive Objects

Non-conductive objects are plated by coating with metallic Pd or Ag nuclei, immersing in a plating bath containing a Cu salt, a Ni salt and a reducing agent, electroplating at low current density to form a fdm with 280 wt.% Cu, and electroplating at high current density to obtain a fdm with > 3Owt.% Ni.

UEMURA KOGYO K.K. Japanese Appl. 21175,895

In the manufacture of a Ga garnet single crystal by the Czochralski method, the raw materials Ga,O, and rare earth metal oxides such as Gd 0 are melted by heating in an Ir crucible, in an atmosphere with O 2 partial pressure of 20-100 mm Hg. A single crystal of Ga garnet at least 75 mm in diameter is pull- ed during or after the melting period, which has less defects and is useful for magnetic bubble memories or working substances for a magnetic refrigerator.

Japanese Appl. 21166,711

Electrolytically Polished Platinum Probe for Microscopy AGENCY OF IND. SCI. TECH.

Japanese Appl. 21138,499 A Pt material containing 99.9% or more of Pt, 0.005% or less of Cu, and balance impurities such as Pd, Au, Ag, Mg, Mn, Fe and Zn, has a controlled crystdite grain size of 10-200pm diameter. The material is electrolytically polished to provide a Pt probe for the Scanning Tunnel Microscope (STM).

Oxygen Sensor with Improved Durability Against Sulphur Dioxide FUJIKURA CABLE WORKS K.K.

Japanese Appl. 21145,960 A ceramic 0, sensor consists of an ion conductive ceramic base plate, Pt electrodes, and porous thin film layers covering these electrodes. In an example Pt powder and stabilised ZrO, powder were mixed to prepare the porous thin film layers, which can also include Pd, Rh, Ir, 0 s or Ru in place of the Pt powder. The sensor has better durability against SO, thus allowing direct insertion into a combustion site.

Composite Electrode with Platinum Layers for Oxygen Sensor RIKEN CORP. Japanese Appl . 21210,254 A composite electrode consists of an element substrate made of a solid electrolyte with vapour coated Pt layers 0.01-lpm thick on both sides, and Pt paste layers having particle diameter 0.05-10 pm printed on the surface of the Pt layer. The composite electrode has improved adhesion to the solid electrolyte substrate, and it is used for a critical electric current-type 0, gas sensor.

JOINING Palladium Layer Used in Soldering Semiconductor Contacts IBM CORP. European Appl. 374,475A A 20-150 nm thick Pd layer in contact with a layer of Cu or solder is used in a fusion joining operation or as a dressing element for solder removal from a contact pad. The Pd operates in a reducing atmosphere to increase fusion at a low temperature in the total absence of flux. The method is used for repeated solder joining of devices without using a flux, in semiconductor contact technologies.

Alloy Solder for Bonding Precious Metal

A Sn-Cu-Zn base alloy for butt-welding precious metal in air consists of 15-20 wt.% Sn, 25-40 wt.% Zn, 2.5-10 wt.% Ag, 0.5-5 wt.% Au andlor 0.5-2 wt.% Pd, 0.1-2 wt% B andlor 0.1-1 wt.% P, and balance Cu. The solder is used for butt-welding chains and rings in air at a low temperature of 1100-1250°C, and the product is less amenable to crack generation when subjected to cold working.

HIRAI NECKLACE KOCY JUpaneSe Appl . 2192,491

HETEROGENEOUS CATALYSIS Three-Way Catalyst Containing Germanium Oxide

An exhaust gas purification catalyst consists of 0.1-10 gll Pt, 0.02-2 gA Rh, 30-200 gll active Al,O,, 10-150 gll Ceo,, and 1-50 gA GeO, on a monolithic support. The catalyst is useful for removing CO, hydrocarbons and NOx from exhaust gas, and also suppresses the formation of HIS.

Saccharose Tricarboxylic Acid Salt Production HOECHST A. G. European Appl . 378,127A Production of saccharose tricarboxylic acid salts is by reaction of saccharose with O I in aqueous medium in the presence of a 5-10 wt.% R on active C catalyst, with stepwise heating of the starting materials to 70-80°C. The saccharose tricarboxylic acid products are useful as builders in washing powders, for example as a replacement for phosphate builders; as additives to food products, and crosslinkers in lacquer compositions.

Platinum Catalyst for Aromatic Alcohol Production MITSUBISHI PETROCH. K.K. European Appl . 378,165A Aromatic alcohols are produced by reducing aromatic hydroperoxides with H, in a liquid phase, at 2O-12O0C, using a catalyst of Pt, or Pt and at least one of Pb, Sn, Cu, As, Sb, In, Se and Bi, supported on AI,O,, in a fLved bed reactor. The Pt catalyst has high and stable activity even during long periods of use. The products are useful as intermediates for various types of organic compounds, and as solvents.

Platinum Dehydrogenation Catalyst to Enhance Aromaticity SHELL INT. RES. Mii. B.V. European Appl . 383,395A A dehydrogenation catalyst containing a Group VIII noble metal, a Group IVA metal and a refractory oxide support-especially Pt, Sn and an AI?O, support-is used to enhance the aromaticity of a high viscosity index lubricating base oil feedstock. This can be followed by hydrotreating using a catalyst of Ni and/or Co and Mo and/or W. The aromaticity of the oil is increased, while maintaining the high viscosity index.

Spark Plug with Platinum-Containing High Voltage Electrode 1. A. MCDOUGAL European Appl. 386,941A A spark plug consists of high voltage and ground electrodes separated by an insulator, with a concentrically disposed electrically conducting winding. The high voltage electrode includes W based and Pt based layers of cermet ink, forming the elongated portion and exposed portions of the electrode; the Pt based layer being more resistant to corrosion. The spark plug has an increased spark size, which results in a larger flame kernel.

N. E. CHEMCAT. CORP. European Appl . 377,468A


Novel Isomerisation Catalyst Containing Platinum

An isomerisation catalyst consists of a crystalline aluminosilicate zeolite with an alkali metal cation in at least 50% of the cation sites, and a refractory inorganic oxide supporting Pt, and Sn and/or In. The novel catalyst can be used with another catalyst in the isomerisation of xylenes to give a specific product such as p-xylene, and can decompose the small amount of non-aromatic hydrocarbons normally present in the feedstock.

Fischer-Tropsch Catalyst with Increased Activity

A Fischer-Tropsch catalyst for converting syngas to hydrocarbons consists of CO on an Al,O, support, with the additional presence of Pt, Rh and/or Ir in an amount less than the Co. The added metals give a significant increase in syngas conversion activity, even in the absence of added metal promoters, and an increased liquid hydrocarbon yield is obtained with no increase in methane or oxygenate production.

Rhodium Hydrogenation Catalyst for Preparation of Tetracyclines HOUBA INC. World Appl. 90/7,492A a-6-Deoxytetracyclines are prepared by hydrogenation of a selected substrate such as a methylene tetracycline, an ethylene tetracycline or their salts, in the presence of a S i02 supported heterogeneous Rh catalyst. The products are useful in the production of the antibiotic deoxycycline (a-6-deoxy-5-oxytetra- cycline). The alpha epimers are stereospecifically produced at higher yields, using lower levels of Rh metal than prior methods.

TEIJIN PETROCH. IND. European Appl. 390,058A

DEN NORSKE STATS OL. World Appl. 90/7,377A

Palladium Catalyst for Preparation of Cinnamates MALLINCKRODT INC. World Appl. 90/10,617A Cinnamates such as 2-ethylhexyl-p-methoxycinnamate are prepared by reacting an iodobenzene compound with an acrylate ester, in the presence of a trialkylamine and a catalyst consisting of Pd on a C support. The process uses iodide compounds which can be recovered and recycled, and result in faster, cleaner reactions. The product cinnamates are used as sunblocking agents. '

Catalytic Purification of Isophthalic Acid AMOCO CORP. U.S. Patent 4,933,492 Crude isophthalic acid is purified by hydrogenation of the impurities at 100-3OO0C using a catalyst consisting of at least two of Pt, Pd, Rh, Ir, 0 s and Ru supported on active C particles at 0.01-2 wt.%. A uniform catalyst bpd or layers each having one metal component can be used. The method is useful for purification of isophthalic acid from liquid phase oxidation of m-xylene; the product is useful for manufacture of unsaturated polyesters.

Preparation of 3-Picoline by Catalytic Hydrogenation DU PONT DE NEMOURS co. U.S. Patent 4,935,521 A catalyst consisting of Pt or Pd metal on a solid support is used in the preparation of 3-picoline by reacting 2-methylglutaronitrile with H, , in the vapour phase at 225-325OC. The process involves recycling the separated by-products to increase the yield of 3-picoline, and makes the production more commercially viable. 3-Picoline is an intermediate for niacin, one of the B vitamins.

Palladium Catalyst for Preparation of Aldehydes from Cyanohydrins ALLIED-SIGNAL INC. U.S. Patent 4,939,304 Continuous and selective conversion of a cyanohydrin to the corresponding aldehyde involves contacting an acidic solution of the cyanohydrin with a catalyst of zero-valent Pd dispersed on a porous solid organic polymeric resin, in the presence of H, at 10-450 psig and 10-50OC. The catalyst shows higher activity and selectivity, has good physical and chemical stability, and is resistant to deactivation.

Platinum Catalyst for Carbon Monoxide Oxidation

An oxidation catalyst is prepared by impregnating a V 2 0 , or V,O, support with anaqueous acid solution containing Pt and Fe compounds, drying, calcining at ?00-7OO0C, and reducing under H , at 150-350OC. The catalyst can be coated on a porous ceramic monolith. It is used to catalyse the oxidation of CO with O l at 10-30°C, particularly in CO, lasers, exhaust gases, breathing masks, air or tobacco smoke.

Palladium Catalyst for Selective Hydrogenation of Impurities BEIJING RES. INST. CH. U.S. Patent 4,940,687 A catalyst for selective hydrogenation of acetylenic and/or dienic impurities consists of 0.1-1 wt.% Pd on an Al?O, support where the support is a-Al,O, calcined at 1150-1400°C, having specified pore properties. The catalyst can be used for selectively hydrogenating methylacetylene and propadiene impurities in a propylene stream obtained by hydrocarbon cracking, and can be used at high inlet temperatures in a single stage.

Fischer-Tropsch Synthesis Using Modified Ruthenium Catalyst UOP U.S. Patent 4,945,116 A catalyst used in the production of C,, hydrocarbons from CO and H, and/or H,O consists of an inorganic oxide support, 0.3-6 wt.% Ru present as 40-60 A particles, and 0.1-5 wt.% Al, Si, Pb, As or Bi as a modifier, particularly Si, which is in active contact with the Ru. The catalysts have improved stability and can be used for conversion of coal, peat or other heavy hydrocarbons into high quality liquid fuels such as gasoline or diesel fuel.

PHILLIPS PETROLEUM CO. u. s. Patent 4,940,686


Catalytic Conversion of ParaMins to Aromatic Hydrocarbons AMOCO CORP. U.S. Patents 4,946,812-13

and 4,950,828 Catalyst systems for converting light paraffins to aromatic hydrocarbons consist of (a) 0.01-10 wt.% of a Pt metal component, preferably Pt, (b) 0.1-10 wt.% of a c1 component, (c) optionally a Ga component, Cu or Au, and (d) a gallosilicate or borosilicate molecular seive, optionally dispersed in an inorganic oxide. The catalysts are used in the upgrading of 2-5C light paraffins to aromatics such as benzene, toluene, and xylenes which are used as high octane components for gasoline and chemical feedstocks; while production of methane, ethane and heavy aromatics are minimised.

Multi-Use Carbon Monoxide Oxidation Catalyst PHILLIPS PETROLEUM co. U.S. Patent 4,956,330 An oxidation catalyst consisting of a TiO, support impregnated with 0.1-10% Pt, 0.05-2.0% Fe, and 0.1-5Oh alkali metal, is activated by treating with a reducing gas. The catalyst oxidises CO to CO, in the presence of free 0, at 10-50°C, and is used in breathing masks, to eliminate CO from tobacco smoke, in C 0 2 lasers to recombine CO and O,, for engine exhaust gases.

Platinum Catalyst for Isomerisation of Alkyl Aromatic Compounds UOP U.S. Patent 4,957,891 An isomerisation catalyst consists of at least one Pt group metal, preferably 0.1-5 wt.% Pt, and a pen- tasil zeolite with 0.1-10 wt.% substituted Ga, in a Zr0,-Al,O, matrix containing 1-10 wt.% ZrO,, and may also contain 0.05-0.5 wt.% S. The catalyst is used for the isomerisation of a non-equilibrium C, aromatic mixture containing xylenes and ethyl benzene, and isomerisation takes place with minimal loss of alkyl aromatic hydrocarbons.

Hydrogenation Catalyst for Preparation of Alicyclic Diamines

Alicyclic diamines are prepared by catalytic hydrogenation of aromatic diamines at 100-230°C in the presence of a supported Pd-Ru catalyst having a Pd:Ru ratio of 0.001-2:l. Catalyst deterioration is avoided by inclusion of Pd, and the products are prepared more economically than by prior art.

Catalyst for Oxygen-Hydrogen Recombination HITACHI K.K. Japanese Appl. 21137,703 A catalyst for recombining 0, and H, consists of Pt or Pd supported by a metal or ceramic Al,O, base, and is laminated with each layer having a different mesh. The catalyst is positioned at the inlet or outlet nozzle of a heat exchanger with O,/H, gas flow. The recombiner is compact and has high efficiency.

NIPPON OXOCOHOL K.K. Japanese Appl. 21129,152

Particulates Collecting-Cleaning Filter for Diesel Engine Exhaust

A cleaning filter has a catalyst consisting of 0.5-5.0 gA of at least one of Pt, Pd and Rh, and 0.05-0.5 molfl of a Mo oxide supported on a ceramic filter base material. The filter is used for removing particulates contained in exhaust gas from diesel engines. Catalyst durability is improved by the Pt group element, and initiation and ignition properties are improved by the Mo oxide.

Production of Aromatic Carboxylic Acids OSAKA GAS K.K. Japanese Appl. 21 15 7,245 Aromatic carboxylic acids are produced by reacting an aromatic sulphonyl halide and a fatty acid metal salt or metal alkoxide with CO in the presence of a Pd catalyst such as PdlC, Pd black, (Ph P) , PdCI, , and so on. A carboxy or alkoxycarbonyl group can be introduced into an optional position of an aromatic ring in high yield. The products are useful as intermediates for plastic monomers, functional pigments, liquid crystals, drugs and agrochemicals.

Palladium Catalyst for Preparation of Indanones BABCOCK-HITACHI K . K . Japanese Appl. 2/164,838 Indanones are prepared by oxidation of indene or alkyl indene at 3O-8O0C in the presence of an oxidising agent, an organic solvent, water, and a.supported catalyst of formula M,PdX,, where M is Li, Na or K and X is C1, Br or I. The method enables 1- and 2-indanones, which are useful for pharmaceutical products to be prepared with high selectivity.

Preparation of Noble Metal Combustion Catalysts

TOYOTA J I W S H A K.K. Japanese Appl. 21149,308

TANAKA KIKINZOKU KOGYO Japanese Appls. 21169,029-30

Combustion catalysts are prepared by dipping carriers in aqueous nitric acid solutions of (a) dinitrodiamine complexes of at least one of Pt, Pd and Ru, or (b) Rh nitrate; mixed with aldehydes and surfactants, so that the noble metal is reduced and deposited on the carrier. High catalytic activity is obtained because noble metal particulates are uniformly dispersed on the carrier, and because a large surface area of the carrier is retained by using the cationic surfactant.

New Waste Gas Purification Catalyst TOYOTA JIWSHA K . K . Japanese Appl. 21191,548 A new catalyst to purify car exhaust has a support, a layer such as Al,O, with Ce oxide and Pd oxide particles, and catalyst metals loaded on the layer. An example catalyst has a monolithic support, 0.05 molfl Pd, 0.3 molA Ce, 120 gA Al,O,, 1.5 gA Pt and 0.3 gA Rh. Sulphate anions formed from All 0 , , G O , , SO, and 0, during lean combustion can be decom- posed to SO,, SO, and PdS by the Pd oxide, and the catalyst suppresses H , S generation.


Dehydrogenation Catalyst for Preparation of Alkylbenzenes IDEMITSU KOSAN K.K. Japanese Appl. 21196,731 Alkylbenzenes are prepared by dehydrogenation of alkenylcyclohexenes at 300-5OO0C in liquid or gaseous phase in the presence of a catalyst consisting of 0.05-20 wt.% of Pt group metal complex anions supported on fibrous clay minerals. The catalyst is especially Pt complex anions on sepiolite. The catalyst shows high activity, and gives alkylbenzenes in high yield and selectivity.

Curved Plate Shaped Exhaust Purification Catalyst MATSUSHITA ELEC. IND. K.K.

Japanese Appl. 21198,641 A catalyst used for purification of combustion engine exhaust consists of a honeycomb ceramic support with an activated AI,O, layer containing Pt group metals, and optionally Ba oxide and Ce oxide, coated on the curved surface of the support. A catalyst is produced which is shaped like a curved honeycomb structure plate.

Three-Way Catalysts with Two Different Layers on a Honeycomb Support MATSUSHITA ELEC. IND. K.K.

Japanese Appl. 21203,938 and 21218,438 Catalysts for purification of exhaust gas consist of a honeycomb structure coated with (a) activated Al?O, containing Pd, and then activated Al, 0 , containing Rh; or (b) an activated Al,O, layer containing Ce oxide and BaO or BaCO, , then with Pd supported on Al?O, containing Pt, mixed with Rh supported on Al,O, containing Ce. The catalysts are useful for treating hydrocarbons, CO and NO, exhausted from household appliances and automobiles.

Exhaust Purification Catalyst Containing Platinum and Rhodium

A waste gas purification catalyst is produced by loading an activated Al,O, coated support with Pt and Rh using a mixed gas of Pt and Rh compounds, for example a mixed gas of Pt flouride and Rh fluoride. An example catalyst contained 1.5 gfl Pt and 0.3 gfl Rh. Crystal growth of the Pt and Rh can be minimised, so that the catalyst has improved durability. The catalyst is used for removing hydrocarbons, CO and NO, from car exhaust.

Exhaust Purification Catalyst with Segregated Precious Metals

An exhaust gas purification catalyst is manufactured by adding zeolite - which has been ion exchanged with Pd - to an Al,O, slurry to form an activated Al,O, layer on the zeolite by a wash coat method, and then supporting Pt and Rh on the activated Al,O, layer. In an example the activated Al ,02 was also impregnated with Ce and La.

TOYOTA JIDOSHA K.K. Japanese Appl. 21207,842

TOYOTA JIDOSHA K.K. Japanese Appl. 21218,439

Catalytic Rebalance Cell for Chromium- Iron Redox Accumulator SIEMENS A.G. German Appl. 3,843,312 An FeJf ion reduction catalyst consists of hydrophobised active C loaded with a Pt group metal, Au or Ag, or hydrophobised WC, and is used for reduction of FeJ+ ions with H, in a rebalance cell for a Cr/Fe redox ion accumulator. The catalyst separates the H, gas space from the FeJf electrolyte liquid space. The reduction process is accelerated, making the rebalance cell practical.

Exhaust Purification Catalyst with Separated Catalytic Metals MAZDA MOTOR CORP. German Appl. 4,004,572 An engine exhaust gas purification catalyst consists of a catalyst support, a first coating of active All 0 , containing 1.0 gfl Pt and Rh, and a second coating of 0.5 gfl Pd (minimum) and a composite powder having Zr and La (]-lo%) on the surface of Ce (5-30%). The catalyst has excellent temperature resistance, and Pt and Rh in one layer prevents the Pt sintering, while Zr and La prevent thermal deterioration of Ce.

Methanol Synthesis Catalyst Production AKAD. WISSENSCHAFT DDR

East German Patent 276,429 A catalyst for CH , OH production is prepared by impregnating a highly porous mineral support with an aqueous solution containing 2-5 wt.% Pd as a Pd salt, 0.2-1 wt.% Co, Ni or preferably Fe as an ac- tivator, and 0.5-5 wt.% Na andlor 0.5-10 wt.% Mg as promoter, followed by drying, calcining, and reducing. The catalyst has high quality properties and is used for CH , OH production.

Palladium Catalyst for Hydrogen Purification AZERB. AZIZBEKOV. PETROCHE.

Russian Patent 1,528,542 Spent catalyst from hydrogenation of acetylenic hydrocarbons, which contains 1.2-1.4wt.% Pd is used in the purification of H,. The purification is in two stages: the fmt removes Hg by adsorption purification, reducing the Hg content to O%, and the second reduces 0, in the presence of the Pd catalyst at 25-1OO0C, to give 0.035% 0, in the purified H 2 product. The method gives increased purification and simultaneous removal of Hg.

Palladium Catalyst for Production of Succinic Anhydride AS. USSR BASHKIRSK Russian Patent 1,541,210 Succinic anhydride is prepared by hydrogenation of maleic anhydride at 15-5OoC, at a H, pressure of 1-30 atm, in an acetone medium, and in the presence of a PdlC catalyst modified with triethylamine at a Pd:(C,H,),N molar ratio of 1:(0.5-2). The method offers increased productivity; giving 100% yields of succinic anhydride, which is an intermediate for products used in the agriculture and printing industries.

Platinum Metals Rev . , 1991, 35, (2) 119

HOMOGENEOUS CATALYSIS

Isomerisation of Saturated Alkyl Carboxylic Acids DU PONT DE NEMOURS co. European Appl. 374,687A A process for isomerisation of 4-20C saturated alkyl carboxylic acids involves heating at 17O-25O0C and a CO pressure of 200-10,000 psi, in the presence of an iodide or bromide promoted Rh catalyst present at 1 part wt. Rh to 50-200 parts wt. saturated acid. This

Rhodium Carbonylation Catalyst for Preparation of Carboxylic Acids B.P. CHEMICALS LTD. European Appl. 391,680A Preparation of (n + l)C carboxylic acids is effected by reaction of CO with an nC alcohol in the presence of a Rh catalyst, in a liquid reaction medium containing water and a catalyst stabiliser from quaternary ammonium iodides. Using this process, precipitation of Rh containing complexes from the reaction medium is reduced.

gives an improved process for isomerisation of linear branched carboxylic acids, for example isomerisation of 2-methylglutaric acid to adipic acid.

Manufacture of ~ l ~by id^ Hy drocarbonylation HOECHST CELANESE U.S. Patent 4,935,554

Palladium Catalyst for Preparation of Nabumetone HOECHST CELANESE co. European Appl. 376,516A Nabumetone is prepared by reacting 2-bromo-6-methoxynaphthalene with 3-buten-2-01 at 50-2OO0C, for 0.25-10 hours, in an inert atmosphere, and in the presence of a Pd catalyst. The catalyst consists of a Pd compound combined with a trivalent P ligand, for example Pd(I1) acetate with

A single-step process for manufacture of 1,3-propanediol is by hydrocarbonylation of an epoxide at 50-200°Cand 200-10,000 psig pressure, using a reaction mixture containing: 0.01-30 wt.% ethylene oxide, 0.00001-0.2 M Rh as catalyst, tricyclohexylphosphine, H,O, CO, H, and an acid, in ether. The process gives increased yields of 1,3-glycols which are used as intermediates in the manufacture of esters and polyesters.

triphenyl phosphine, and is regenerated by using with a base. The product is a non-steroidal anti- inflammatory drug, and is produced in high yields. EASTMAN c''

~~~~l Preparation of Arylalkenes U.S. Patent 4,935,559

A novel oremration of an arvlalkene compound and Recovery of Homogeneous Rhodium Catalysts ELI LILLY & CO. European Appl. 376,610A A homogeneous catalyst containing a Pt group metal, especially Rh, can be recovered in high yield from a reaction mixture by (a) solvent removal, (b) addition of a lower alkanoic acid, and (c) recgvering the precipitated catalyst. The process can be used for recovery of Rh(I1) octanoate catalysts used in I-carbacephem carboxylate production, giving the catalyst in active form and ready for re-use.

Stereo Selective Ruthenium Catalysts for Asymmetric Hydrogenation TAKASAGO INT. CORP. European Appl. 385,733A Preparation of an optically active 6-t- butoxy-3,5-dihydroxyhexanoic ester from a 4-t- butoxyacetoacetic ester includes two asymmetric hydrogenation steps in the presence of different Ru- optically active phosphine complex catalysts. The product can be obtained in good yield, at high stereo selectivity.

Palladium Catalyst System for C arbony lation

A catalyst system for carbonylation consists of a Group VIII metal compound, specifically a Pd(I1) compound, a phosphine compound, and optionally a protonic acid. The catalyst is used for carbonylation of an acetylene or olefin compound using CO, and may be used to prepare a, P-olefmically unsaturated compounds or methyl methicrylate.

SHELL INT. RES. Mii. B.V. European Appl. 386,833A

- - an alkyliodide is by reaction of an iodoaromatic compound, an alkene and an alkanol at 15-200°C, in the presence of 0.05-5.0 wt.% of a I'd catalyst, preferably Pd acetate, and the absence of Bronsted bases. The method is used for preparation of styrene, 1 ,4-divinylbenzene, and 1,3-divinylbenzene, and enables easier separation of the iodoalkane species from the reaction products, and easy recovery of I.

Palladium Catalyst System for Preparation of Conjugated Dienes SHELL OIL CO. U.S. Patent 4,943,670 Butadiene derivatives are prepared by reacting propadiene or 1,2-butadiene with a formic acid salt in the presence of a catalyst system having a Pd salt and a P compound. The products are conjugated dienes which are used as monomers for elastomers and rub- bers, and as intermediates for catalysts, pharmaceuticals and agrochemicals. The products are obtained in high yields with good conversion, from readily available starting materials.

Pyrochlore Catalysts for Oxidation of Organic Compounds MONSANTO CO. U.S. Patent 4,959,494 Organic compounds are produced by oxidation of alcohols, olefm, alkynes, carbohydrates, aldehydes, ketones and vicinal diols with 0, , in the liquid phase at 20-1OO0C and 25-100 psi, using pyrochlore catalysts containing Pt, Rh, Ir, 0 s or especially Ru. The method is useful for production of polycarbox- ylates and carboxylic acids, and high conversion and selectivity are obtained for conversion of cyclohex- anediol to adipic acid.


Manufacture of Glycols by Epoxide Hy drocarbonylation HOECHST CELAN'ESE U.S. Patent 4,935,554 A single-step process for manufacture of 1,3-propanediol is by hydrocarbonylation of an epoxide at 50-200°Cand 200-10,000 psig pressure, using a reaction mixture containing: 0.01-30 wt.% ethylene oxide, 0.00001-0.2 M Rh as catalyst, tricyclohexylphosphine, H,O, CO, H, and an acid, in ether. The process gives increased yields of 1,3-glycols which are used as intermediates in the manufacture of esters and polyesters.

Novel Preparation of Arylalkenes EASTMAN KODAK CO. U.S. Patent 4,935,559 A novel preparation of an arylalkene compound and an alkyliodide is by reaction of an iodoaromatic compound, an alkene and an alkanol at 15-2OO0C, in the presence of 0.05-5.0 wt.% of a I’d catalyst, preferably I’d acetate, and the absence of Bronsted bases. The method is used for preparation of styrene, 1 ,4-divinylbenzene, and 1,3-divinylbenzene, and enables easier separation of the iodoalkane species from the reaction products, and easy recovery of I.

One-Step Preparation of Schiff’s Bases from Olefms AGENCY OF IND. SCI. TECH.JapaneSe Appl. 21157,253 Schiff s bases are produced efficiently in one step by reacting olefins and isonitriles at 50-200°C in the presence of a Ru complex and H, . Preferred Ru complexes are those of lower valent Ru, having CO, organic phosphines or unsaturated hydrocarbons as ligands, for example Ru(C0) J . The Schiffs bases are used as intermediates for N compounds, additives for polymers, and as functional materials for liquid crystals.

Preparation of Epoxy Compounds from Olefms SUMITOMO CHEM. IND. K.K.

Japanese Appl. 2/157,270 Epoxy compounds are prepared by reaction of lower olefins with organic hydroperoxides using a catalyst consisting of one or more compounds containing Ru andlor Os, and Mo compounds. The mol ratio of Ru and/or 0s:Mo is below 1. The products are useful materials for antifreeze, surfactants, polyesters, polyurethanes, perfumes or cosmetics.

Rhodium Hydroformylation Catalyst SAGAMI CHEM. RES. CENTRE

Japanese Appl. 21174,740 Aldehydes are prepared by reacting CO and H, with a terminal olefin, at 50-25OOC and 8-300 kg/cmz pressure, in the presence of a catalyst consisting of Rh and Re compounds. The catalyst is highly active, stable, and has high selectivity. This gives a high yield industrial method for manufacturing aldehydes by hydroformylation in the liquid or air phase; the products are useful as materials and intermediates in organic syntheses.

Ruthenium Hydrogenation Catalyst for Preparation of 1’4-Butanediol MITSUBISHI KASEI COW. Japanese Appl. 2/200,648 1 ,4-Butanediol and/or tetrahydrofuran are prepared by catalytic hydrogenation of succinic acid and/or succinic anhydride at 50-25OOC and 0.1-200 kg/cm! H,, using a catalyst consisting of a Ru compound, an organophosphine, and a hexafluorophosphate anion. The Ru can be present as metallic Ru, a Ru salt, Ru oxide, or a Ru complex. By using the catalyst, the products are prepared in higher yield and selectivity under mild conditions.

Ruthenium Catalyst System for y-Butyrolactone Preparation MITSUBISHI KASEI CORP. Japanese Appl. 2/200,680 y-Butyrolactone is prepared by catalytic hydrogenation of maleic acid and/or d e i c anhydride in the liquid phase in the presence of a catalyst consisting of Ru compound(s), organophosphine(s), conjugated base(s), and one or more chlorine-containing compounds. Using the catalyst, y-butyrolactone is prepared with higher yield and selectivity.

Oxidation of Monoolefms to Ketones ATOCHEM. French Appl. 2,638,739 A process for the oxidation of terminally unsaturated monoolefins is effected in a liquid medium containing a tertiary alcohol and >5 wt.% water, and a catalyst consisting of AgNO,, and Pd in the form of a salt, a complex and optionally an organophosphorus compound. The method is particularly useful for the preparation of ketones, especially methyl ketones, and results in higher selectivity and productivity.

Palladium Carbonylation Catalyst for Production of Ketenes RH~NE-POULENC CHIMI. French Appl. 2,639,940 Ketenes are prepared by reaction of a gem- dichloroalkane with CO in the presence of Pd and a phosphine, where the Pd is in the form of finely divided metallic Pd or complexes. The method is specially suited to the production of ketene from methylene chloride. This method does not need pyrolysis techniques, using acids or acid anhydrides, which call for extreme reaction conditions.

Synthesis of Symmetrically Substituted Ureas POUDRES & EXPLOSIFS French Appl. 2,643,078 A new synthesis of symmetrically substituted ureas is by reaction of a primary amine and CO, in the presence of an ethynylic derivative and a Ru, 0 s and/or Fe complex. The synthesis has a shorter reaction time, and high purity of the crude product avoids an extra purification stage and the difficult removal of contaminants. The products are intermediates in the synthesis of pharmaceuticals.

Enantio-Selective N-Acyl @)-Amino Acid Production AKAD. WISSENSCHAFT D.D.R.

E a s t German P a t e n t 275,671 Production of N-acyl (S)-amino acid derivatives is achieved by catalytic asymmetric hydrogenation of a solution or suspension of the corresponding acrylate, in the presence of a chiral Rh chelate catalyst of the carbohydrate-bis (phosphinous ester) type, having free OH groups in the sugar. The catalyst provides a more rapid reaction and a better optical field than known catalysts. The products are useful as pharmaceuticals or intermediates.

Rhodium Hydrogenation Catalyst for Preparation of Piperidine MOSCOW LOMONOSOV. UNIV.

Russian P a t e n t 1,327,493 Simplified production of piperidine or its derivatives is by hydrogenation of pyridine at pH 1-2.5, in isopropanol, in the presence of s mineral acid and a Rh catalyst of formula RhCI(CH, -CH(COOH)),; where n is 6 or 4. The catalyst is moisture-resistant and easily separable, and results in 100°/~ yields of piperidine and its derivatives, which are used in the synthesis of biologically active substances.

P l a t i n u m Meta l s Rev., 1991, 35, (2) 121

FUEL CELLS Platinum Alloy Electrocatalyst for Fuel Cell N.E. CHEMCAT. CORP. European Appl. 386,764A An electrocatalyst consists of a Pt-Fe-Co-Cu quaternary ordered alloy containing 40-70 at.% Pt, 9-27 at.% Fe, 9-27 at.% Co, and 9-27 at.% Cu dispersed in and on a conductive carrier, such as a C powder. The alloy preferably has an average crystallite size not above 100 A . The catalyst has high activity, a long life, and is used in an acid electrolyte fuel cell.

Fuel Cell Catalyst with Platinum and Platinum Alloy Crystallites INT. FUEL CELLS CORP. U. S. Patent 4,937,220 A high surface area Pt catalyst consists of approximately equal amounts of Pt and Pt alloy crystallites dispersed on a C support. The Pt alloy crystallites are Pt,Cr, PtV, PtMn, PtMo or RW, and are used with Pt to retard recrystallisation. The catalyst is used in the cathode and anode of fuel cells.

Magneto-Optical Recording Element EASTMAN KODAK co. European Appl. 367,685A A magneto-optical recording element includes a layer of magneto-optical medium on a substrate. This layer consists of alternating Co layers about one atom thick and Pd layers at least 6 A thick. An increased carrier to noise ratio is obtained, and less materials and manufacturing time are required than for conventional magneto-optical recording elements.

Palladium Plated Connection Leads for Plastic Packaged IC TEXAS INSTRUMENTS INC. Eumpean Appl. 384,586A A high reliability plastic package for a semiconductor IC includes leads for external connection which are Pd plated and solder dipped, where the Pd plating consists of 80% Pd-20% Ni. The device also includes a semiconductor support which is Pd plated, and Au wires for connecting the plated leads to the IC. The Pd plated leads provide high reliability wire and frame bonding, with high crack and corrosion resistance, and good economy.

High Current Density Cathode CHEMICAL TECHNOLOGY Containing Iridium - Regeneration of Metal Oxides after Oxidation of Waste

U.S. SEC. OF THE ARMY U.S. Patent 4,911,626 A long-life, high current density cathode consists of a sintered billet of W and Ir powders which is im-

B,.itish 2,226,331~ pregnated with a mixture of powdered emitter coated with Rh, Ir, 0 s or W, followed by Ir and Ba perox- ide. This is min above the melting point of the impregnent; and

impregnent, The cathode is used in microwave

U.K. ATOMIC ENERGY AUTH.

Oxides of Rh, Ir, 0 s or Ru are used in the oxidation of waste material, particularly waste containing

waste substance the metal oxide is regenerated to the

by firing in dry for about

polychlorinated biphenyls. After treatment of the cooling the billet and removing any pieces of loose higher valency State by an process. devices, and provides a higher energy density than

GLASS TECHNOLOGY Platinum Bushings for Spinning Glass Fibre TANAKA KIKitizoKu KOGYO Japanese Appl. 2197,433 Bushings for spinning glass fibre or continuous glass fdament are made of Pt or Pt alloy, with a bushing plate reinforcedly supported from the underside with a Si,N, support with a coating of Al,O, or ZrO?.

ELECTRICAL AND ELECTRONIC ENGINEERING Thin Film Amorphous Alloy with Good Magneto-Optical Properties MITSUI PETROCHEM. IND. K.K.

Eumpean Appl. 364,63 1A A thin amorphous alloy fdm contains Fe andlor Co, Pt and/or Pd, and at least one other element from specified groups, and has an easy axis of magnetisation perpendicular to the fdm face. The film has excellent magneto-optic properties, including high coercive force and large Kerr and Faraday angles, and has high oxidation resistance and reflectance.

currently available.

Manufacture of Electrochromic Planar Dimmer TOYODA GOSEI K.K. U. S. Patent 4,933,050 A planar dimmer is made by applying long stripes of a thermosetting resin paint mixed with Pd and Cu on a glass or resin base, heating to harden the paint, immersing in acid, and forming metal fdms on the stripes by electroless plating. An electrode layer is then formed on the base, and a colour forming layer formed on the electrode layer. The dimmer colours and discolours throughout, quickly and evenly.

Silver-Palladium Thick Film Conductor Compositions DELCO ELTRN. CORP. U. S. Patent 4,939,022 A first thick film conductor composition consists of

Al,O, and/or 0-15 wt.% SiO,. A second thick fdm conductor including Ag and Pd in wt. ratio of at least 0.25 makes a low electrical resistance contact with the first. Thick f h conductive films primarily of Ag compatible for use with those of Ag and Pd are used in “hybrid devices”; useful in situations where fdm discontinuities are a problem.

60-90 wt.% Ag, 0.5-5 wt.% Pd, and 0-25 wt.%


Electronic Coating Composition Containing a Platinum Catalyst GENERAL ELECTRIC CO. U.S. Patent 4,943,601 A latent curable electronic coating composition which is stabilised against premature gelation consists of an olefin organopolysiloxane, an organohydrogen polysiloxane, a Pt catalyst to cause co-reaction of these siloxanes, a combination of inhibiting agents, and a silanol-containing dimethylsiloxane hydrqlysate. The composition can be cured on a substrate at elevated temperature, and has improved adhesion to substrates.

Ground Coating Conductive Paint Composition SUMITOMO METAL MINI K.K.

Japanese Appl. 2186,665 A paint composition consists of 50-80 wt.% metallic powder comprising Ag powder or 90-99 wt.% Ag powder (average particle size 0.5-3.0pm) and 10-1 wt.% Pd powder (average particle size up to 0.3pm); acid-proof glass powder, glass powder containing PbO, and an organic vehicle. The composition is used prior to metal plating on the terminal electrodes of laminated Pb perovskite capacitors of the sintered type, to give high corrosion resistance.

Oxidation Resistant Rare Earth Permanent Magnet

A rare earth permanent magnet consists of a matrix mainly consisting of a Ru-rare earth element- transition metal phase, dispersed in which is a tetragonal magnetic compound containing rare earth elements, transition metals and B. The magnet is made by magnetic moulding a starting powder which is a mixture of the Ru and magnetic pha! The rare earth magnet has good oxidation resista..,..

TOHOKU METAL IND. LTD. Japanese Appl. 2187,502

Platinum-Manganese-Antimony Compound for Magneto-Optical Use

A PtMnSb compound for magneto-optical applications is prepared by polishing the surface of a PtMnSb compound raw material having a Clb-type crystalline structure, and then heat treating at 100-700OC. A material with a large magnetic (phonetic) rotation angle is obtained.

Rare Earth Permanent Magnet with Matrix Containing Palladium

A rare earth permanent magnet has a matrix containing Pd, a rare earth element, and a transition metal, with a dispersed phaseof an R,Tl, intermetallic compound (where R is a rare earth element and T is a transition metal). The permanent magnet is prepared by field pressing rare earth magnet alloy powder, and has good oxidation resistance.

KUREHA CHEM. IND. K.K. JapaneSe Appl. 2/92,900

TOHOKU METAL IND. LTD. Japanese Appl. 211 17,103

Screen Ink Compositions for Preparation of Thin Film Resistors MATSUSHITA ELEC. IND. K.K.

Japanese Appl. 2455,964 Screen ink compositions are formed by kneading mixtures containing a Ru compound, optionally a metal compound (not Ru), a carboxylic acid of a terpenoid, amine salts of abietic acid and of rosin, and a solvent. The screen inks are screen printed and baked to form thin fdm resistors, which are used as heads of heat sensitive printers and electrodes.

Superconducting Oxide Film with Platinum Base Material MITSUI MINING & SMELTING

Japanese Appl. 21162,616 A complex oxide fdm of Bi, Sr, Ca and Cu is formed on a base material which may consist of Pt, Au, Ag or Cu, or an alloy having one of these as the major component. The fdm is doped with Pb from a vapour atmosphere to produce a superconductive film. A c- axis oriented fdm is easily produced which has a critical temperature of 100K, and is useful as a low resistance substrate circuit or magnetic shield plate.

Ruthenium Oxide System Thin Film MATSUSHITA ELEC. IND. K.K.

Japanese Appl. 21177,502 A Ru oxide system thin film consists of Ru, one or more of Pt, Ti, Si, Mo and W, and oxygen. The thick fdm is etched by plasma etching, preferably by reactive ion etching using CF, . The method is used to obtain fine patterns of Ru oxide system thin film with good precision.

Electroconductive Paste for Aluminium Nitride Substrate Circuit Board

An electroconductive paste containing Cu, Pd, glass frit, resin,and solvent is used for IC boards which are capable of being electroplated without activation of the AlN substrate. The circuit board is made by forming the electroconductive circuitry on an AIN substrate by coating the paste thickly, firing the substrate, and plating without substrate activation. Using this method the plating processes are simplified.

Glaze for Platinum-Based Resistance Layers

DAIKEN KAGAKU KOGYO JapaneSe Appl. 21208,275

VEB. THERMO GERABERG East German Patent 275,311

A low cost glaze is used to passivate Pt-based resistance layers on ceramic substrates. The glaze is crystallising, hermetic, has a high melting point (95O-98O0C), and contains SO, , Al,O,, ZnO, B,O,, BaO, Na20 , and small amounts of other oxides. The glaze has a high insulation resistance, a resistance to voltages up to SO0 V, and a lower thermal coefficient of expansion. The Pt resistor degrades less due to reduced material transfer.


MEDICAL USES Conjugate Platinum Coordination Com- pound Monoclonal Antibody Complexes JOHNSON MATTHEY P.L.C.

U. S. Patents 4,952,676 and 4,956,454 New conjugate Pt co-ordination compound/monoclonal antibody complexes contain amine groups, and have a functional polymethylene moiety of ether, ester andlor peptide groups. The complexes can be prepared by linking the monoclonal antibody to the Pt co-ordination compound via a peptide linkage. The complexes are useful as site-specific or disease-specific chemotherapeutic agents for treatment of tumours.

Electrode for Use in 'a Living Body INA SEITO K.K. Japanese Appl. 21107,229 An electrode used for measurement of electric phenomena in a living body has a non-degradable electrically conductive material including Pt, Ti or C, homogeneously dispersed in a substrate material such as hydroxy apatite, or formed as a separate layer. The electrode can be strongly adhered to a living body because of its high affinity for the living body and surface activity, and electrode activity can be maintained for a long time.

Metal Composite Material for Dental Use

Japanese Appls. 2/147,175-78 A metal composite consists of a 0.05-0.5 mm thick alloy plate containing 10-25 wt.% Au, 15-35 wt.% Pd, 45-70 wt.% Ag, and optionally (a) 5-15 wt.% Cu, or (b) 0.1-5 wt.% Sn and/or In. The plate is superposed on one side of an expanded net or coated with alloy powder or granules, followed by hot bonding at 6OOOC or above.

a-Aryl Propionic Acid Preparation for Anti-Inflammatory

a-Aryl propionic acid is prepared by reaction of a- aryl ethyl alcohol with CO at 80-180°C, in the presence of a Rh catalyst and an I-containing compound in atomic ratio Rh:I 1:0.5-6; and additiondly a compound to form a complex with Rh, and an acid compound. The product is useful for analgesic anti- inflammatories.

Platinum Complexes as Low Toxicity Anti-Tumour Agents TANABE SEIYAKU K.K. Japanese Appl. 2/212,497 New Pt complexes are useful as anti-tumour agents with low toxicity and high water-solubility. The Pt complexes can be administered orally or parenterally in the form of tablets, capsules, powders, injections or suppositories at a daily dose of 10-500 rnglm*. The Pt complexes can be used for treatment of malignant lymphoma, leukaemia and tumours.

TOKURIKI HONTEN K.K.

DAICEL CHEM. IND. K.K. Japanese Appl. 2/164,841

Stable Aqueous Solution of Cisplatin for Parenteral Administration

A stable aqueous solution of cisplatin in a sealed con- tainer has a pH of 5-7.5 and contains up to 1 mg/ml cisplatin and a pharmaceutically acceptable source of chloride ion equivalent to 20-100 mg/ml of NaCl. The solution contains less aquated Pt species, is closer to physiological pH, and is used for parented administration of cisplatin.

New Platinum Complexes for Treating Malignant Tumours LAB. BELLON R. European Appl. 389,338A New Pt complexes such as cis (2-amin0, 2-aminomethyl bicyclo-(3,2,1)-octane) dichloro Pt are prepared by reacting K tetrachloroplatinate with a diamine at O-8O0C, in a N , atmosphere. The complexes are used for treating malignant tumours, particularly cancers of the digestive system, pulmonary systems, testicles, ovaries, as well as cancers of the head and neck. The dose is 250-1000 mg/m! for humans, either orally or intravenously.

New Diaminocyclohexane Platinum Complexes with Anti-Tumour Activity SHIONOGI SEIYAKU K.K. European Appl. 390,138A New anti-tumour diaminocyclohexane Pt(I1) complexes are effective against cisplatin-resistant ascitic murine leukaemia, murine leukaemia, and solid tumours with only ' slight haemotoxicity and nephrotoxicity. The Pt complexes can be administered parenterally to humans and animals, for example intravenously or by an intravenous drip.

Platinum Xerogels with Anti-Tumour Activity AS. UKR. PHYS. CHEM. World Appl. 90/8,768A New Pt-containing xerogels are prepared by reacting a Pt complex such as cisplatin with a polymethylsilox- ane hydrogel in aqueous NaCl solution. The products are 3-dimensionally crosslinked polymers with a globular structure, having globule diameter 4-7 nm and surface area 80-200 m'/g. The xerogels are used as anti-tumour agents.

Novel Boron-Free Palladium Dental Alloy PIERCE & STEVENS CO. U.S. Patent 4,917,861 A dental alloy of exceptional high temperature strength consists of 50-85 wt.9'0 Pd, 5-40 wt.% Co and/or Cu, 1-15 wt.% Ga, up to 5 wt.% Ru, Au, Ni, In, Sn and mixtures as modifier, 0.01-4.05 wt.% Ge, Li and mixtures as an 0, scavenger, and up to 0.5 wt.% Ir, Re and mixtures as a grain refiner. The alloy is used for dental restorations, and has high tarnish resistance, good bonding, and good casting characteristics and solderability.

BRISTOL-MYERS SQUIB. European Appl. 369,714A

The New Patents abstracts have been prepared from material published by Dement Publications Limited.


vol. 35 april 1991 no. 2 - johnson matthey technology ......vol. 35 april 1991 contents knitted...

Documents