ic5the ylide-metal complex. preparations and structures of palladium(i1) complexes with a stable...

8/13/2019 ic5The Ylide-Metal Complex. Preparations and Structures of Palladium(I1) Complexes with a Stable Sulfur or a Nitr…

http://slidepdf.com/reader/full/ic5the-ylide-metal-complex-preparations-and-structures-of-palladiumi1-complexes 1/4

Ylide-Metal Complex

existence of M n ( C 0 ) 6 2 + is not a consequence of reduced0-donating ability of carbonyl but rather is a result of the muchgreater HOMO stabilization in the carbonyl parent specieswith a resultant increased difficulty of oxidation.

A careful examination of our calculations indicates that theorigin of the HOMO stabilization lies in the electron dis-tributions within the ligand moieties. In the series, the electronpopulation on a carbonyl carbon ato m is less than t hat on th ecarbon ato m of the methyl isocyanide adjace nt to the metal.

Consequently, the carbonyl carbo n atom s carry greater positivecharge s than do their methyl isocyanide counterparts. Suchpositive charges in proximity to the transition m etal have astabilizing effect upon its 3d electrons and the resultantHOMO. Thus , the positive charge stabilization is not a d irectone in the sense of having a higher charge on the metal butis indirec t, throu gh its near-neighbor interactions. Identifi-cation of this phenomenon is particularly relevant since thereare computational methods in the literature which do notinclude such interactions in their calculational procedure.

Acknowledgment. The au thors wish to thank th e NationalScience Foundation (Grant GP-27636) and the WisconsinAlumni R esearch Foundation for support of this work.

Registry No. Mn(c0)6+, 21331-06-6 ; Mn(CO)s(CNCH3)+,

4 5 1 1 3 - 8 7 - 9 ; M n ( C 0 ) 4 ( C N C H 3 ) 2 + , 4 5 1 4 6 -1 7 - 6 ; M n ( C O ) 3 -(CNC H3)3+ , 45167-07-5 ; Mn(CQ)z(CN CH3)4+, 45186-22-9 ;

M n ( C O ) ( C N C H 3 ) 5 + , 4 5 21 1 - 8 2- 3 ; M n ( C O ) s B r , 1 4 51 6 -5 4 -2 ;M n ( C 0 ) 4 ( C N C H 3 ) B r , 3 9 0 4 8 - 7 9 - 8 ; M n ( C O ) 3 ( C N C H 3 ) z B r ,38833-18-0 ; Mn(C0)2(CNCH3)3Br , 39043-33-9; Mn(C O)(CN C-H3)4Br, 38 833- 19-1; Fe(CNCH3)6*+, 17455-63-9; Mn(CNCH3)6+,4 5 22 8 -3 9 -5 ; M n ( C 0 ) 5 C N , 1 56 0 2- 37 -6 ; M I I ( C N ) ~ ~ - , 9567-57-8;

References and Notes

CNCH3, 593-75-9.

(1) L. Malatesta and F. Bonati, “Isocyanide Complexes of Metals,”Wiley-Interscience, New York, N. Y., 1969.

Inorganic Chemistry, Vol. 14, No. 2, 1975 253

I. Ugi, Ed., “Isonitrile Chemistry,” Academic Press, New York, N. Y.,1971.F. A . Cotton and G . Wilkinson, “Advanced Inorganic Chemistry,” 2nded, Interscience, New York, N . Y., 1966, pp 744-745.A. C. Sarapu and R. F. Fenske, Inorg. Chem. , 11 3021 (1972).M. B. Hall and R. F. Fenske, Inorg. Chem., 11 768 (1972).M. B. Hall, Ph .D. Thesis, Universityof Wisconsin, Madison, Wis., 1971.E. Clementi, J . Chem. Phys., 40, 1944 (1964).E. Clementi in “Tables of Atomic Functions,” a supdement to E..Clementi, I B M J . Res. Develop., 9, 2 (1965).R. S. Mulliken, J . Chem. Phys. , 23, 1833 (1955).D. . Radtke, Ph.D. Thesis, University of Wisconsin, Madison, Wis.,

1966.E, Clementi and D. L. Raimondi, J . Chem. Phys. , 38, 2686 (1968).W . J. H ehre, R. F. Stewart, and J. A. Pople, J . Chem. Phys. , 51 2657(1969).J. W . Richardson, W . C. Nieuwpoort, R. R. Powell, and W. F. Edgell,J . Chem . Phys. , 36, 1057 (1962).R . F. Fenske and D. D. Radtke, Inorg. Chem., 7 , 479 (1968).A. C. Sarapu, Ph.D. Thesis, University of Wisconsin, Madison, Wis.,1972.C. C . Costain, J Chem. Phys., 29 864 (1958).G. Herzberg, “Spectra of Diatomic Molecules,” Van Nostrand, Princeton,N. J . , 1950, p 522.R. L. DeKock, A. C. Sarapu, and R . F. Fenske, Inorg. Chem., 10 38(1971).R. F. Fenske and R. L. DeKock, Inorg. Chem., 11 437 (1972).P. T. Manoharan and W. C . Hamilton, Inorg. Chem., 2 1043 (1963).A. Tullberg and N .-G. Vannerberg,Acta Chem. Scad. 21 1462 (1967).D. H. Liskow, C. F. Bender, and H. F. Schaefer, 111, J . Amer . Chem.SOC., 4, 5178 (1972).R. S. Mulliken, J . Chem. Phys. , 23, 1841 (1955).F. A . Cotton and C. S.Kraihanzel, J . Amer. Chem.SOC. 4,44 32 (1962).L. M. Bower and M. H. B. Stiddard, Inorg. Chim. Acta 1,2 31 (1967).L. H. Jones, Inorg. Chem., 7, 1681 (1968).F. A . Cotton. Ittorp. Chem.. I 1683 (1968).E. B. W ilson, Jr., J.-C. Decius, and P. C . Cross, “Molecular Vibrations,”McGraw-Hill, New York, N . Y., 1955, p 74.M. B. Hall and R. F. Fenske, Inor‘g. Chem., 11, 1619 (1972).W. . Horrocks, Jr., and R. H. Mann, Spectrochim. Acta, 19, 1375(1963).F. A. Cotton and R. V. Parish, J . Chem. Soc., 1440 (1960).F. A. Cotton and F. Zingales, J . Amer . Chem. SOC., 3, 351 (1961).T. L. Brown and M . Kubota, J . Amer . Chem.SOC. 3, 4175 (1961).P. M . Treichel, G. E. Dirreen, and H. J . Mueh, J . Organometal. Chem.,44, 339 (1972).

Contribution from the Department of Applied Chemistry,Faculty of Engineering, Osaka Universi ty, Yam ada-Kami, Suita, Osaka 565, Japan

The Ylide-Metal Com plex. Preparations and Structures of

Palladium(I1) Complexes with a Stable Sulfur or a Nitrogen Ylide

H I R O S H I K O E Z U K A , G E N - E T S U M A T S U B A Y A S H I, a nd T O S H I O T A N A K A ’

Received June 25, 1974 AIC404 12V

Palladium (I1) com plexes with a stable sulfur ylide, PdClzL(Scy ), PdzC14(PPhMez)z(Scy), and PdClz(Scy)z [L = PPh3,PPhzMe, AsPh3; Scy = (CH3)zSC(CN )z], and with a nitrogen ylide, PdClzL(Ncy) and Pd zCb(Ncy)z [L = PPh3, PPhzMe,PPhMez; Ncy = 3-CH 3C5 H4N C(C N)2], were prepared. Thr ee types of coordination sites were found in Scy; Scy actsas a monodentate ligand through one nitrile group and the dimethylsulfonium sulfur and as a bidentate one through twonitrile groups to give the Scy-bridged dimer. The configurations of the complexes are elucidated on the basis of the analogyof Scy to tricya nome thanide anion and dimethyl sulfoxide. The differenc e of nucleophilicity between Scy and Nc y is discussed

from their structures.

IntroductionT o date, several publications have reported th e reactions of

various ylides with transition metal compounds, especiallymetal carbonyls, which ar e of interest in organometallic andorganic reactions.1-8 These studies primarily concern the useof vlides as a s ubs trate in organometallic reactions. On the

withdrawing power than the carbonyl in the phenacylide, andtherefore they are expected to be less reactive at the ylidecarbon.

This paper reports the isolation of palladium(I1) co mplexeswith SCYnd NC Y nd their configurations. T he nucleophilicityof these Ylides is also discussed.

other h and, there have been %w reports on metal complexeswith ylides as ligand molecules.9-12 Recently , we preparedsome palladium(I1) a nd platinum(I1) halide complexes withstable sulfonium phenacylide C H ~ ( C ~ H S ) S C H C ( O ) C ~ H ~ C ~ - ~and discussed the bonding character of the metal-ylide carbonbond.13 Th e Scy and Ncy ylides used in the present study

Experimental Section

Dimethylsulfonium dicyanomethylide, (CH3)2SC(CN)2 (Scy), 14

a nd 3 -m et hy lp yr id in iu m d ic ya no me th yl id e, ~ - C H ~ C S H ~ N C ( C N ) ~(Ncy),ls were prepared according to the literature.

All man ipulations for preparing the ylide complexes were carriedout in air.

involve two cyano groups, which have more electron-- Preparation of p - Dimethylsulfonium dicyanomethy1ide)-bis(di-



54 Inorganic Chemistry, Vol 14, No. 2 975

Table I. Melting Poinl, Eleme ntal Analysis, and Molecular Weight of the Ylide Complexes

Koezuka, Matsubayashi, and Tanaka

% C % B N Mol wta

Complex MP c Calcd Found Calcd Foun d Calcd Found Calcd Found

SCYPdC1, (SCY),PdC1, (P Ph,)(Scy )PdCI, (PPh,Me)(Scy)Pd, Q, (PPhMe ,) §cy)PdCI, (AsPh )(§cy)CEICI

NCYPdzC L (NcY1 2

PdCl PPR 3 (Ncy )PdC1, (PPh, Me)(Ncy)FdC1, (PPhMe, )(N cy)

102-103b>1 4 5 d e c>169 dec>1 7 0 d e c> I 5 2 d e c>140 dec

211-212c>175 dec>207 .5 dec>168 dec>1 1 1 d e c

a In C ~ ~ O K O ~ O ~ I I I .it.14 100-101 . Lit.' j 214

47.5927.9548.8342 .9233.3239.5468 .7832.3254 .3449 .4243.20

~ n se th y l~ R n en yB p ~osp P n in e ) t eb h 36h lorcP lp ( I~ ) . 15-ml di-

chlorometh ane solution of Scy (0.16 g, 1.3 mmol) was added to a15-ml dich1orome:hane solution of bis(dimethylpheny1phosphine)-dichloro-~ ,~* ' -dichloro-pal ladium(1) (0.40 g, 0.64 mmol) , and the

mixture was st irred for 1.5 hr. The addit ion of petroleum ether tothe solution gave orange needles (0.34 g, yield 71%).

Dichloro(methyldiphenylphosphine)(dimethylsulfonium di-cyanornethylide)palladiuni(II) a n d dichloro(dimethylpheny1-phosphine)(3-methylpyridiniumdicyanomethylide)palladium( 11)weresynthesized by the same way.

Preparation o f Dichlorotriphenylphosphine(dimethy1sulfoniuaYldicyanonaethylide)pallwdinm(iiI). A suspension of bis(tripheny1-phosphine)dichloro-b,b -dichloro-palladium(I1) 0.29 g, 0.33 mm ol)and §cy (0.18 g, 1.4 mmol) in acetonitrile (10 0 ml) was refluxed for

4 hr to give an almost clear solution. Th e solution was concen tratedto about half-volume under reduced pressure and filtered. The addition

of diethyl ether to the f i l t rate gave reddish orange crystals (0.18 g,yield 48%).

Dichlorotriphenylarsine(dimethy1sulfonium dicyanomethy1ide)-palladium(l1) and dichlorotriphenylphosphine(3-methylpyridinium

dicyanomethylide)palladium(lI) were synthesized similarly, but theforme r wa.s obtained from a chloroform-benzene solution as browncrystals .

Preparation o f Dic Bor~bis(diimetly~sM~~oniumicyanomethy-~ ~ ~ ~ ~ p ~ ~ ~ a ~ ~ ~ ~ ~ ~o a suspension of bis(benzonitri1e)dichloro-palladiuni(T1) (0.30 g9 0.78 mmol) in acetonitrile (5 ml) a 10-in1

acetonitrile solution of Scy (0.40g, 3.2 mmol) was added. The mixturewas refluxed for 2.5 hr and evaporated to half-volume under reduced

pressure, and a 1:1 mixture of dichloromethane and petroleum etherwas added to the solution to give yellow crystals (0.1 1 g, yield 33% ).

~ ~ e ~ ~ r ~ ~ ~ ~ ~ ~f )ichloro(saseehyldiph~~y~~~osphine)(3-methyl-~~~i~~~~~~ diicyeaaaomethyside)paBladiurrn(IH). A 10-ml 1,2-dichloro-

ethane solution o f N c y (0.14 g 0.87 nirnol) was gradually dropped

into a suspension of bis(methyldiphenylphosphine)dichloro-k,,u -di-

chloro-palladium(H1) (0.30 g, 0.40 mmol) in 1,2-dichloroethane (IO

ml) to give an oran ge solution. A fter refluxing for 1 hr, the solventwas removed under reduced pressure to produce a n oil , which wasdissolved in dichloromethane. Th e addition of petroleum ether to thesolution gave an orange-yellow powder (0.20 g, yield 47%).

Preparation of Bis(3-a~lethylpyridinium dicyanomethy1ide)di-%~WoPo-ll,y'-aBichloro-pallladium(II). o a solution of bis(benzo-nitrile)dichloropalladium(II) (0.30 g, 0.78 mmol) in 10 ml of di-

chloromethanc was mixed N cy (0.26 g, 1. 6 mmol) in dichloromethane(20 ml) with st irr ing to give a brown precipitate. Th e mixture wasfurth er st irred for 4 hr . The product was separated by f i l t rat ion,washed with dichloromethane and then diethyl ether , and dried in

vucuo (0.11 g3yield 42%).The melt ing points and analytical data for the yl ides and their

complexes are l is ted in Table 1.

Physical Measurements. Ir (4000-200 cm-1) and pmr spectra weremeasured as described elsewhere.13

Molecular weights were determined in chloroform at 25 or 37'

irsing a Mechrolab v a p r pressure osmometer. The molecular weightsof the yl ide complexes are also l is ted in Ta ble I.

esullts and Discussion

The ylides used here are represented by the canonicalstriictnres 1-111. The ~(Cpd) ands of free ylides in thesolid-state spectrum appear around 2190 and 2155 cm-1, as

47.5328 .2048.9742 .8833.1639.4068 .7232.3454 .2349.0443.07

4.79 4.752.82 2.793.74 3.733.80 3.893.73 3.863.04 3.194.49 4.222.11 2.233.72 3.773.71 3.733.84 3.81

22.2013.04

4.955.563.703 ,84

26.7312.56

7.047.868.89

21.5713.06

5 .0 0 5 6 6 5 2 15 .64 504 4343.83 757 4914.03

26.6411.89

7.00 597 4787.99 535 4379 .05 473 405

Table 11 Ir Data of the Wide Complexes (cm-' )

4 C N ) v ( P a - c i )Dichloro- Wujolmethane mull

§ cy 2 1 8 8 ,2 1 5 5 2 1 8 8 ,2 1 6 1PdCl,(Scy), 2224,221 1, 344

.-_l_-_l__omple x Nujol mull

2 1 8 8 ,2 1 5 7PdCI,(PPh,)(Scy) 222 4,2 180 2211, 2182, 356

PdCl,(PPh,Me)(Scy) 2214,2176 2213,2180, 361

Pd,Cl,(PPhMe,) ,(Scy) 223 6,2 194 220 8,2 178 , 359

PdCl, (AsPh&Scy) 2221 ,217 8 2215 ,2180 , 362

N C Y 2 1 9 1 ,2 1 6 0 , 2 1 8 4 ,2 1 5 6 ,

Pdz Cl, ( N ~ Y ) , 2 2 4 5 ,2 2 0 5 , 3 6 2

PdCl, (PPh ,) (Ncy) 2210 ,218 4 , 2213 ,2188 , 360

PdC1,(PPh2Me)(Ncy) 220 7,2 177 , 220 9,2 184 , 345

PdCl, (PPhMe,) (Ncy) 2204 ,217 2 , 22 04 ,21 79 , 362

2164

2165

2164

2164

2136 2142

2181

2 1 6 2 2 1 6 3 ,2 1 4 2

2156 2159

2 1 5 3 2 1 7 5 ,2 1 5 4

C N

I I1 I11

X = (CH,) ,§ or 3 C H , C j H , N

shown in Tab le IT which indicates a significant contributionof II l l4 in which lone-pair electrons of the ylide delocalizeover the two cyano groups. §cy and Ncy have two coordinationsites to metal halides; the coordination through the ylide carbonwould lead to a high-frequency shift of v(CN) due to a nincreasing contribution of 11and that through a nitrile groupwould usually cause a high-frequency shift of v(CN) as wasshown in some nitrile complexes.16-19 In fact, v C W ) fre-

quencies of the complexes prepared are higher tha n those o fthe original ylides as found in Ta ble %I.Therefore, the CQ-

ordination site toward the palladium is not revealed from theshifts of v(CN) frequency.

The Sulfur Ylide Complexes. It is to be noted that thereis a close similarity in the structure between Scy2OJ1 andtricyanomethanide anion (TCM);22,23 both §cy and TCM havea trigonal-planar configuration around the central carbon atom.Mean bond lengths of the C-C (1.40A) and C-N (1.16 Abonds in §cy ar e essentially identical with those (1.40 and 1.15A) in TCM, respectively. The molecular orbital calculationson dicyanomethylene anion24 and TCM25 have indicated thata significant electron charge is placed on the nitrile nitrogenatoms . Further more , various first-row transition metalcomplexes of TCM ar e known to have a polymeric octahedral



Ylide-Metal Complex

Table III. Pmr Data of the Ylide Complexes inDichloromethane at 23

Inorganic Chemistry Vol 14 No. 2 1975 255

is known to involve the sulfur-bonded ligand and exhibits astrong v(Pd-S) band a t 415 cm-1.31 Th e ir spectrum ofPdClz(Scy)z shows a strong band at 378 cm-1, while nocorresponding absorption occurs in other Scy complexes. The378-cm-1 band m ay therefo re be assigned as the Pd-S vi-bration. Thus, the 6 3.01 signal in the pmr spectrum is at-tributed to the methyl protons of sulfur-bonded Scy. Th eoccurrence of four v(CN) bands in this complex also supportstwo kin ds of Scy with different coordination atoms (nitrogen

and sulfur) in the solid state, although there app ears only onev(Pd-C1) band.

The Nitrogen Ylide Complexes. PdChL(Ncy) (L = PPh3,PPhzMe, PPhMez) in the solid state shows only one v(Pd-C1)band, suggesting a trans configuration for these complexes.There is an analogy in the structure among TC M , Scy, andpyridinium dicyanom ethylide.223 This leads us to theconclusion that N cy coordinates to the palladium atom throughone nitrile group in these complexes. Molecular weight de-terminations confirm tha t all the Ncy complexes partly dis-sociate in solution. The pmr spectrum of PdCh (PPh3 )(Ncy)at room tem peratur e gives one methyl signal of Ncy a t 6 2.40,and a t -28O one more signal appears a t 6 2.48, which suggeststhe rate of dissociative exchange of Ncy is depressed at lowtemp erature. In PdClz(PPh 2Me)(N cy) and PdC12-(PPhMea)(Ncy), such separated signals have not been observedat low tem perature for the proximity in chem ical shift betweenthe coordinating and free Ncy.

There are two possible structures in the dinuclear complexof PdzC14(Ncy)2; one is a chl oride -bridg ed conf igura tion, andthe other a Ncy-bridged one analogous to Pd2C14-(PPhM e2)z(Scy). In the ir spectrum down to 200 cm-1, onlyone v(Pd-Cl) band is observed at 362 cm-1, which is assignedl o the palladium-terminal chlorine stretching vibration. Thisresult seems to indicate that the complex is a chloride-bridgeddimer, though no palladium-bridged chlorine vibration has beenfound. Th e highest v(CN) frequencies of this compoundamong the Ncy complexes obtained may be due to the factthat the Ncy is located trans to the bridged chloride. Th e

pmr spectru m was not mea sured be cause of its low solubilityin common organic solvents.

Conclusion

That both Scy and Ncy complexes involve the palladi-um-nitrogen or -sulfur bond is a striking contrast to the caseof methylphenylsulfonium p-chlorophenacylide, CH3-(C6H5)SCHC(O)C6H4Cl-p, which coordinates to Pd(I1) andPt(I1) th roug h the ylide carb on, as previously reported.13 Thisis attributed to a reduction of the net charge on the ylide carbonin Scy and N cy owing to a higher electronegativity of the cyanogroup than the carbonyl one. The present results clearlyindicate that Scy and Ncy do not show the so-called ylidecharac ter in spite of having formal ylide structures.

Ncy seems to be a poorer donor than Scy in that thecomplexes with Ncy dissociate to a greater extent than theScy complexes and tha t Ncy is less reactive than Scy. Indeed,Ncy does not react with bis(methyldipheny1phosphine)di-

chloro-p,p'-dichloro-palladium(1) in dichloromethane,but Scydoes. This may be due to th e difference in geometry betweenNcy and Scy; the latter has a planar-trigonal configurationaround the central carbon atom. On the other hand, pyri-dinium dicyanomethylide is nonplanar a round the ylide carbon,which causes a decrease of the negative charg e on the n itrilegroups32 and hence a small affinity of N cy toward Pd(I1 ) ion.Th e weaker nitrogen-palladium bond in the Ncy complexesis also shown by the smaller u(C N) shifts in Ncy than in Scyupon complex formation.

Registry No. PdClz(Scy)z, 53092-84-5; PdClz(PPh3)(Scy),5 3 1 1 1 - 2 9 -8 ; P d C l z ( P P h a M e ) ( S c y ) , 5 3 1 1 1 - 3 0 - 1 ; P dz C1 4-

(PPhMe2)2(Scy), 531 11-32-3; PdClz(AsPh3)(Scy), 531 11-31-2;

Chem shifts, 6

Complex Scy or Ncy CH,

SCYP ~ C ~ , ( S C ~ ) , ~PdC1, (PPh, )(Scy )PdCI, (PPh,Me)(S cy)Pd, CI,(PPhMe,), (Scy )

PdC1, (AsPh,)(Scy)NCYPdCl,(PPh,)(Ncy)PdC1, (PPh,Me)(Ncy)PdC1, (PPhMe )(Ncy)

In acetonitrile-d,.

2.163 .01 .2 .722.812.842.85

2.852.402.402.422.43

configuration, n which each nitrogen atom of TC M is attachedto a diff erent me tal ion.23125~26 n view of the se fac ts and th eelemental analysis, a Scy-bridged dimer configuration, A, may

H 3 C b S & H 3

A

be suggested for the Pd2Ch(PPhMe 2)2(Scy) complex. Thisconfiguration is in accordance with (i) the ir spectrum of thecomplex showing only one v(Pd-C1) band a t 359 cm-1 in thesolid state (Table 11) and (ii) the reaction of this compoundwith 2 mo lar equiv of p-toluidine in dichlorome thane yieldingthe original sulfur ylide and trans-PdCl2(PPhMez)(p-toluidine).That this compound in the solid state exhibits the highestv(CN) frequencies among the Scy complexes obtained (Table11) also confirms th e dinuclear configuration.

Molecular weight (T able I) and electrical conductivity27measurements indicate that Pd2Ch(PPhMez)2(Scy) partlydissociates into neu tral species in solution. N o isolation of themononuclear complex with PPhMez has, however, beensuccessful even when 4 molar equiv of Scy was allowed to reactwith bis(dimethylphenylphosphine)dichloro-p,~'-dichloro-palladium(I1) in 1 Zdichloroethane a t refluxing temperature.

Th e ir spectra of PdClzL (Scy) (L = PPh3, PPhzM e, AsPh3)show only one v(Pd-C1) band a round 360 cm-1 in the solidstate (Table 11), suggesting that they are in a trans config-uration around th e palladium atom. In view of the fact thatthe freque ncies of both v(CN) and v(P d-Cl) are close to thoseof PdzCh(PPhMez)z(Scy), these mononuclear complexeswould involve the coordination through one nitrile group of

Scy to the palladium atom.Th e isolation of the Pd(I1) complex with two molecules,PdClz(Scy)2, was established by elemen tal analysis. Thiscompound is practically insoluble in less polar organ ic solvents,while a little soluble in m ore polar ones, such as acetonitrile.The pmr spectrum of a saturated solution in acetonitrile-&shows two Scy CH3 signals at 6 3.01 and 2.72 (Ta ble 111) withan integra ted intensity ratio of 1:2. Th e ratio did not changedown to -45 . The latter peak is assigned to the methyl protonsof free S cy, which m ay be originally nitrogen bonded, becauseof its identical shift with Scy in acetonitrile. Th e formerchemical shift is lower by about 0.15 6 unit than those of otherScy com plexes, although solvents used are different (Table 111).

The analogy between the oxygen atom and the dicyano-meth ylene group28-30 mak es the S cy ligand analo gous to

dimethyl sulfoxide (DM SO) The PdC12(DMS0)2 complex



256 Inorganic Chemistry, Vole14, No. 2 1975 Wagner, Bates, and Poindexter

P d ~ @ l 4 ( N c y ) z ,53 1 1 1 - 3 3 - 4 ; P d C h ( P P h 3 ) ( W c y ) , 5 3 1 1 1 - 3 4 - 5;P d C l z ( P P h z M e ) ( N c y ) , 5 3 1 1 1 - 3 5 - 6 ; P d C l z ( P P h M e a ) ( N c y ) ,531 11-36-7; Scy, 5362-7 8-7; Ncy, 3189-5 6-8; bis(dirnethylpheny1-phosphine)dichloro-k,k -dichloropalladium(II), 15699-80-6; bis-(triphenylphosphine)dichloro-~,~'-dichloropalladiurn(II),5 134-30-2;

b i s ( me t hy l d i pheny l phosph i ne ) d i cA l or o~ ~ ,~ '~ d i ch l o r opa l ~ ad i u r n~ I I ) ~29884-90-9; bis(benzonitrile)dichloropalladium(II), 14220-64-5.

References and Notes

1 ) D. K. Mitchell, W . D. Korte, and W. C. Kaska, Chem. Commun., 1384(1970).

(2) J. C . Kotz and D. G. Pedrotty, J . Organometal. Chem., 22,425 (1970);D. Cashman and F. J. Lalor, ibid., 32, 351 (1971).

(3) S. 2. Goldberg, E. N. Duersler, and K. N . Raymond, Chem. Commun. ,826 (1971).

(4) K. A . 0 tarzewski, H. T. Dieck, K. D. Franz, and F. Hohmann, J .Organometal. Chem., 42, C35 (1972).

(5) A. Greco, J . Organometal. Chem., 43, 351 (1972).(6) H. Alper and R. A . Partis, J . Organometal. Chem. 44 371 (1972).(7) D. K. Mitchell and W. C. Kaska, J . Organometal. Chem., 49, C73

(1973).(8) H. Berke and E. Lindner, Angew. Chem., 85, 668 (1973).(9) R. H. rnup and M. C. Baird, Inorg. Nuc l . Chem. Lett., 5, 65 (1969).

(10) R. J. Sundberg, R. . Shepherd, and H. Taube, J . Amer . Chem. Soc.,94, 6558 (1972).

(1 1) H. Schmidbauer, J. Adlkofer, and W . Buchner, Angew. Chem., 85,448(1973); H . Schmidbauer and R. Franke, ibid., 89 49 (1973); H. H.Farsch and H. Schmidbauer, ibid., 85 910 (1973).

(12) W. C. Kaska, D. K. Mitchell, and R . F. Reichelderfer, J . Organometal.

Chem., 47 391 (1973).(13) H. Koezuka, G. Matsubayashi, and T. Tanaka, Inorg. Chem., 13, 443(1974).

(14) W. J. Middleton, E. L. Buhle, J. G . McNally, Jr. , and M . %anger,J.Org. Chem., 30, 2384 (1965).

(15) A . Rieche and P. Dietrich, Chem. Ber., 96 044 (1963).(16) W . Gerrard, M . F. Lappert, H . Pyszora, and J. 41. Wallis, J . Chem.

Soc., 2182 (1960).(17) M . W. Duckworth, G .W. A . Fowles, and R. A Hodless, J. Chem. Soc.,

5665 (1963).(18) S . C. Jain and K. ivest, Can. J . Chem., 41, 2130 (1963).

I 9 ) Not all increases in v(CN) epresent coordination in nitriles. For example,in the nitrile-coordinated pentaammineruthenium(l1) omplexes of severalsubstituted benzonitriles, acetonitrile, and cyanopyridines, v C N ) of acoordinated nitrile shows a decrease from the free-ligand value: R. E.

Clarke and P. C. Ford, Inorg. Cihem. 9: 727 (1970); R. E. Clarke andP. C. Ford, ibid., 9, 495 (1970).

(20) A . F. Cook and J. G Moffatt, J .Amer. Chem. Soc., 90, 740 (1968).(21) A. T. Christensen and W . G. Witmore, Acta Crystallogr.,Sect. B , 25,

73 (1969).(22) C. Bugg, R. Desiderato, and R. L. Sass, J . Amer. Chem. ,Sot., 86 3157

(1964).(23) C. Biondi, M . Bonamico, L. Torelli, and A. Vaciago, Chem. Commun.,

191 (1965).2 0 ) H. Goetz, B. Klabuhn, F. Marschner, 1%Hohberg, and W. Skuballa,

Telrahedron, 27, 999 (1971).(25) J . H. Enemark and R . H. Holm, Inorg. Chem., 3, 1516 (1964).(26) W. El. Baddley, Inorg. Chim. Acta , R e v . 2 7 (1968).(27) .A = 9.1 X 10-1 ohm-* cm2mol-l for 3.5 X 1 0 4 Msolution in acetonitrile

at 250.(28) M . J. Middleton and 1. A. Engelhardt, J. Amer . Chem. Sac. 2788

(1958).(29) H. Kohler, W. Eichler, and R . Salewski, Z . Anorg. Allg, Chem. , 379,

(30) R, El King and M . S. Saran, J . Amer . Chem. Soc. 95. 1811 (19'73).(31) B. F. Johnson and R. A Ealton, Spectrachim. Acra, 22, 1853 (1966).(32) C. Bugg and K. L. Sass, Acta Crystallogr., 8, 591 (1965).

183 (1970).

Contribution from the LJ S. Army Electronics Technology and Devices Laboratory (ECOM),Fort Monmouth, New Jersey 07703

ynarnic Nuclear

esidinag ow theBURKWARD E. W A G N E R . * R I C H A R D D. BATES, J r . , a n d E D W A R D H. POINDEXTER

Received Febmary 13, 1974 AIC40099X

The solvation of inert, low-spin Cr(1) complexes by nmr-activ e species in t.he second coordination sphere has been investigated

by dynamic nuclear polarizat ion (dnp), an nm -es r double-resonance technique. A t 75-G magnetic field, dipolar(through -space) and scala r (Fermi-con tact) interaction between a nuclear spin and an electron spin on different molecules

can be distinguished . Only dipolar coupling was observed for [Cr (CN )sNQ ]3- and the nuclear test probes octafluoro-naphthalene OFN),rimethyl phosphite, Li f, and BF4-. There is little unpaired spin density at the periphery of the nitrosyl

complex. Th e order of observed solvation interaction is BF4- < E l 2 0 < Li+, dem onstrat ing electrostat ic effects. WithCr(bipy)3+, moderate scalar coupling is observed for OFN and the phosphite, indicating the presence of unpaired spin

density in the plane of the bipyridyl ring, at the rim of the complex. W ith Cr(C6H6)2+ serving as radical probe, stro ngscalar coupling by transient bonding interaction is observed for trimethyl phosphite and for BFn--, The absence of scalarcoupling with OF N suggests a lack of unpaired spin density above the planes of the n-benzene rings. The da ta ar e consistentwith penetration of small ligands into the space between the benzene rings and transient bond formation directly with the

metal. Th e general applic ability of dnp to the study of second coordination sph ere molecular interactions having correlationtimes shorter than 10-8 sec is discussed.

IntroductionA metal complex in solution interacts with surrounding

solvent molecules, counterions, or other dissolved species. Th eimportance of this second coordination sphere (SCS) inligand-exchange reactions, and to catalysis in general, isbeginning to be realized.* N m r is one of the few techniquesthat can yield information at the molecular level about in-teractions occurring at the outer fringes of a complex.2+3Dipolar broadening of nmr lines sometim es allows the detectionof preferential orientation of rnoiecules near th e surfa ce of aparamagnetic complex.4~5Distances of closest approach and

solvation geometries can sometimes be deduced from dipolar

(pseudocontact) chemical shifts of solvent molecules positionedin the SCS of transition metal complexes exhibiting strongg-tensor anisotropy.2.6

Th e present work examines the applicability of dynamicnuclear polarization (dnp), a double-resonance nmr-esrtechnique, as a tool for studying S@S nteractions of par-amagnetic ions in solution. D np measure s the weak couplingbetween nuclear spins on One molecule and an electron spinon ano ther molecule during encoanters of the two species insolution. As the technique is only responsive to fast molecularinteractions (correlation times shisrler than 10-8 sec), it is

especialy suited for iravcsfigations o f diffusion-controlled

ic5the ylide-metal complex. preparations and structures of palladium(i1) complexes with a stable...

Documents