Polyhedron Vol. 12, No. 10, pp. 1123-1128, 1993 Printed in Great Britain

0277-5387193 $6.00+ .Nl 0 1993 Pergamon Press Ltd

REACTIONS OF AMINES WITH ARENE-RUTHENIUM COMPLEXES : CRYSTAL STRUCTURES OF [(1,3,5-Me&H,)

RuCI,(HNC,H,~)] AND [(1,3,5-Me,C6H,)RuC12,0J

LEE CARTER, DAVID L. DAVIES,* JOHN FAWCETT and DAVID R. RUSSELL

Chemistry Department, University of Leicester, Leicester LEl 7RH, U.K.

(Received 10 November 1992 ; accepted 10 February 1993)

Abstract-A range of primary and secondary amines have been reacted with the dimers [(arene)RuCl,], to give simple adducts [(arene)RuCl@JHRR’)]. We have structurally characterized the complexes [(1,3,5-Me,C6H3)RuC12(HNCSHlo)l and [(1,3,5-Me3C6H3) RuC12(NCsH,)]. Amine exchange reactions have been performed to assess the relative stabilities of these adducts. With certain ligands complex cations, [( 1,3,5-Me3C6H3)RUCl (NHRR’),]+, can form, although these are more easily prepared by reaction in the presence of AgBF,.

The reactions of the dimers [(arene)RuCl,], with tertiary phosphines, phosphites and nitrogen bases such as pyridine, hydrazines and ammonia have been well studied. ’ However, the reactions with simple amines are much less well investigated and are limited to complexes with primary amines.2,3 In particular, a previous study using ultrasound promoted reactions found no reactions with sec- ondary or tertiary amines. This is unlikely to be due to steric crowding since tertiary phosphines will coordinate easily.

The recent publication3 of the use of ultrasound to promote the reactions of the dimers [(arene) RuClJ2 with amines prompted us to report our work in this area. We have established that such reactions are just as easily performed thermally. Thus, heating a suspension of [(1,3,5-Me3C6H3) RuC~~]~ with a slight excess of amine in dichloro- methane or chloroform leads after a few hours to a red-orange solution from which the adducts [( 1,3,5- Me3C6H3)RuC12(NHRR-‘)] (la-e) can be isolated. An analogous product (If) can be isolated starting from a solution of [(p-cymene)RuCl,], (Scheme 1). Of particular note is the formation of secondary amine adducts lc-f.

The complexes were characterized by ‘H NMR, microanalysis and FAB mass spectroscopy. In most cases molecular ions were observed in the FAB

*Author to whom correspondence should he addressed.

mass spectra (see Experimental), although in a number of samples ions due to dimeric species were also observed. These may have been formed in the matrix, or possibly by reactions in the spectrometer. All the complexes show the expected signals due to coordinated arene and the amine in their ‘H NMR spectra. The coordinated mesitylene signals occur at cu 6 2.0-2.2 and 6 4.8-5.0. It is noticeable that for lc and Id the methylene groups attached to nitrogen contain inequivalent hydrogens, i.e. NCHH, ’ as expected for diastereotopic protons. This shows that dissociation of the amine is slow, at least on the NMR time-scale, since these hydrogens are equivalent in the free amines. However, complexes lc and Id are unstable in solution with some loss of amine occurring, thus free amine is always observed in the NMR spectra of these products. Complex lc also decomposes in the solid state over a period of several days and hence the analysis results are inaccurate.

In the reactions with benzylamine the products formed depend on the reaction time or the solvent used. The adduct lb can be made without con- tamination by the cationic product by reacting [(1,3,5-Me3C6H3)RuClJ2 with excess benzylamine in refluxing hexane or by using exactly 1 equivalent per ruthenium atom in dichloromethane. If excess benzylamine is used in chloroform then a mixture of the adduct [(1,3,5-Me,C6Hs)RuC12(NHRR’)] and the salt [(1,3,5-Me,C,H,)RuCl(NHRR’)&J] is formed, which cannot be separated easily. This sol-

1123

1124

la-f

axwlc R R’

i.3,.5-Mc$& H Ph a

1,3.5-Me&& H CHzPh b

1,3.5-Me&H3 Et Et , c

1,3,544e-$~3 Bu Bu d

p-v== Et Et f

le arenc = 1.3,5-MC&&~; RR’NH = pip&line

20

R R’

---t-l- H Ph a

H CH2Ph b

Scheme 1.

vent dependence has been observed previously in the reaction of pyrazoles

+

‘th [(benzene)RuC12]2.4 Although steric factors o not prevent the for-

mation of complexes of set ndary amines they may influence their relative sta

P

ility. In order to try and assess the degree of steric crowding in these com- plexes we determined the Icrystal structure of the piperidine adduct le. For omparison purposes we

1 also determined the structu e of the related pyridine complex [(1,3,5-Me&H, RuC12(NCSHS)],

? which

has been made previously4 ‘* The structures of the complexes are shown in F gs 1 and 2, respectively, and selected bond lengths and angles are listed in

I

Table 1. The most notable feature of the structures is the orientation of the pi eridine, with the N-H

and the sterically more demanding CH2 g pointing towards the arene. This may be d active forces between the alkyl groups on e and the piperidine ring and also the posse of hydrogen bonding between the N-H and chlorine atoms. The

to Cl(l) and 2.712 hydrogen bonding,

ered that this hydro- calculated position

and was not found in the difference-Fourier map. The Ru-N bond in the piperidine complex, 2.153(4) I&, is longer than in the pyridine complex, 2.127(7) A, as expected. The average Ru-Cl bond lengths and Cl-Ru-Cl bond angle are the same in the two complexes. The mesitylene ring is essentially planar in both structures and the distances from the ring to the metal are 1.673 and 1.676 8, for the piperidine and pyridine complex, respectively.

We thought it might also be possible to assess the role of steric factors in determining the relative stability of these amine complexes by attempting amine exchange reactions.

[(1,3,5-Me3C6H3)RuClZL]+L1e

[(1,3,5-Me3C6H3)RuC12L’]+L

This has resulted in the following series of stabi- lities : le > la > ld., Qualitatively we have observed that the primary amine complexes are more stable than the secondary amine ones, however, piperidine seems to be a special case. The use of this amine exchange reaction is limited by the occurrence of competing side reactions in certain cases. For exam- ple, the reaction of the piperidine complex le with

Reactions of amines with [(arene)RuCl,], 1125

Fig. 1. Molecular structure of [(1,3,5-MesCaH,)RuC12 (HNWJdl(W

Fig. 2. Molecular structure of [(1,3,5-Me3C6HJRuCIz (NW-LN

Table 1. Selected bond lengths (A) and angles (“) for the complexes [(1,3,5-Me3C6H3)RuClz (HNC,H,J and [(1,3,5-MejC6Hs)RuClI(NCSH5)]

Ru-Cl( 1) 2.409(2) Ru-Cl( 1) 2.419(2) Ru-Cl(2) 2.422( 1) Ru-Cl(2) 2.415(2) Ru-N( 1) 2.153(4) Ru-N( 1) 2.127(7)

Cl( I)-Ru-Cl(2) 88.4( 1) Cl( l)-Ru-Cl(2) 88.4(l) N( 1)-Ru-Cl( 1) 80.4( 1) N(l)-Ru---CI(l) 87.4(2) N( l)-Ru-Cl(2) 82.4( 1) N( I)-Ru-Cl(2) 85.4(2)

1 equivalent of benzylamine when monitored by ‘H NMR shows the presence of some starting complex le, some lb and some species, which judging by the chemical shift of the mesitylene protons are due to cationic species containing two amines. During the course of our work a report has been published on amine exchange reactions of the complex ‘cations [(dppe)PdMe(NRR’RR”)]+, which concluded that both steric and electronic factors were important in determining the relative stability of the various cations. ’

As mentioned above with benzylamine it is possible to form the cation [(1,3,5-Me3C6H3) RuCI(NHRR’),]+ by direct reaction of [(1,3,5- Me3C6H3)RuC1& with benzylamine. Similar be- haviour has been observed previously for aro- matic amines. An alternative is to react the amine adducts [(1,3,5-Me3C6H3)RuC12(NHRR1)] with 1 equivalent of amine and AgBF,. Using this method we have isolated the compounds 2a and 2b.

The ‘H NMR spectra of the cations showed peaks in the expected regions. However, the mesi- tylene signals for 2a are shifted to higher field than in la, while for 2b they are to lower field than in lb. Since complexes 2 contain cationic ruthenium

fragments one might expect a shift to lower field, as is observed with 2b. Thus, the upfield shift for 2a may be due to the ring current effects of the phenyl rings. It is noteworthy that for la the methyl groups of the mesitylene ring are ca 0.2 ppm upfield from the complexes We, which may also be a conse- quence of a ring current effect.

EXPERIMENTAL

Petroleum ether and diethyl ether were dried by refluxing over purple sodium/benzophenone under nitrogen, while dichloromethane was purified by refluxing over calcium hydride. The compounds [(p- cymene)RuC1&6 and [(1,3,5-Me3C6H3)RuCI&7 were prepared using literature procedures. The reactions described were performed in deoxy- genated solvents under nitrogen ; however, once iso- lated as pure solids the compounds are relatively air-stable and precautions for their storage are unnecessary,

‘H NMR spectra were recorded on a Bruker AM300 or a Varian EM390 spectrometer. Micro- analyses were performed by Butter-worth Labor-

1126 L. CARTER et al.

atories Ltd, Middlesex. FAB mass spectra were per- formed at the SERC Mass Spectroscopy service centre at University College Swansea.

Preparation of [(1,3,5-Me,CgH3)RuC12(NHzPh)]

(la)

Aniline (114 mg, 1.55 mol) was added to a suspension of [(1,3,5-Me3

T

6H3)R~C12]2 (301 mg, 0.52 mmol) in dichlorome hane (50 cm3) and the mixture was refluxed for 2.5 h. The solvent was removed and the solid was ashed with petroleum ether. Recrystallization : f om dichloromethane/ dietbyl ether gave [(1,3,5-Me,C,H,)RuCl,(NH, Ph)] as a yellow solid (338i mg, 85%). Found: C, 47.2; H, 4.8; N, 3.5. Calc. lfor CISHlgC12NRu: C, 46.8; H, 5.0; N, 3.6%. ‘I+ NMR (CDCl,): 2.00 (s, 9H, Me), 4.83 (s, 3H, C6H13), 7.25 (m, 5H, Ph).

Preparation of [(1,3,5-Me&H3)RuC1@H2CH2

WI (lb)

Benzylamine (90 mg, 0.8 suspension of [(1,3,5-Me3 I

mmol) was added to a gH3)R~C1Z]2 (245 mg,

0.42 mmol) in dichloromethane (50 cm’) and the mixture was refluxed for 2.5 h. The solvent was removed and the solid was ‘washed with petroleum ether. Recrystallization fi om dichloromethane/ diethyl ether gave [( 1 ,3,5-Me$&)RuC1+NHNH2 CH,Ph)] as orange crystalsi(287 mg, 86%). Found : C, 48.2; H, 5.6; N, 3.4. C&c. for C,6HZIC12NRu: C, 48.1; H, 5.3; N, 3.5%. ‘H NMR (CDCl,): 2.21 (s, 9H, Me), 3.22 ( r, 2H, CHJ, 4.92 (s, 3H, C H,), Mass spectrum: m/z 399 ( 1

2H, NH), 4.12 (m, 7.30 (m, 5H, Ph).

)+, 364 (M-Cl)+.

Preparation of [( 1 ,3,5-M&C6H3)RuC12(NHEt2)1

(W

Diethylamine (94 mg, 1.2 mmol) was added to a suspension of [(1,3,5-Me3

b:

GH3)R~C12]2 (251 mg, 0.43 mmol) in chloroform ,50 cm3) and the mixture was refluxed for 2 h. The s lvent was removed and the solid was washed with etroleum ether to leave [(1,3,5-Me&H3)RuC12(

i

Etz)] as a yellow solid (232 mg, 74%). Found : , 33.4 ; H, 4.3 ; N, 1.3. Calc. for C,,H,,Cl,NRu: ,42.7; H, 6.3; N, 3.8%. ‘H NMR (CDCl,) : 1.22 t, 6H, CHCHZ, J(7)], 2.26 (s, 9H, C6Me3), 3.13 ( 2H, CHH’), 4.91 (s, 3H, k

,2H, CHH’), 3.63 (m, 6H3). Mass spectrum:

m/z 378 (M+H)+.

Preparation of [(1,3,5-Me3CsH3)RuC12(NHBuJ]

(W

Dibutylamine (278 mg, 15 mmol) was added to a suspension of (252 mg,

0.43 mmol) in chloroform (75 cm’) and the mixture was refluxed for 1.5 h. The solvent was removed and the solid was washed with petroleum ether. Recrystallization from dichloromethane/petroleum ether gave [(1,3,5-Me3C6H3)RuC12(NHBuJ] as a yellow solid (363 mg, 100%). Found: C, 48.6 ; H, 7.6; N, 3.6. Calc. for C17H3,ClZNRu: C, 48.4; H, 7.4; N, 3.3%. ‘H NMR (CDC13) : 0.90 [t, 6H, CH3, J(7)], 1.28 (m, 4H, CHJ, 1.55 (m, 4H, CH2), 2.26 (s, 9H, C,Me,), 3.01 (m, 2H, NCHH’), 3.47 (m, 2H, NCHH’), 4.90 (s, 3H, C6H3). Mass spectrum m/z 422 (M+H)+.

Preparation of [(1,3,5-Me3CJ13)RuC12(HNC

Hdl W

Piperidine (183 mg, 2.15 mmol) was added to a suspension of [(1,3,5-Me3CsH3)RuC12]2 (252 mg, 0.43 mmol) in chloroform (50 cm3) and the mixture was refluxed for 3 h. The solvent was removed and the solid was washed with petroleum ether. Re- crystallization from dichloromethane/petroleum ether gave [(1,3,5-Me3CsH3)RuC1@NCSHlo>l as an orange solid (281 mg, 86%). Found : C, 44.5 ; H, 5.9; N, 3.7. Calc. for C14HZ3C12NRu: C, 44.5; H, 6.1 ; N, 3.7%. ‘H NMR (CDC13): 1.40-1.90 (m, 6H, various piperidine), 2.26 (s, 9H, C6Me3), 2.93 [dt, 2H, NCH, J(12,12)], 3.75 [d, 2H, NCHH’, 5(12)], 4.97 (s, 3H, C6H3). Mass spectrum : m/z 378 (M+H)+, 342 (M+H-Cl)+.

Preparation of [(p-cymene)RuC12(NHEtJ] (If)

Diethylamine (39 mg, 0.53 mmol) was added to a solution of [(p-cymene)RuClz]z (108 mg, 0.176 mmol) in chloroform (50 cm3). The mixture was refluxed for 3 h, during which time the solution became orange. The solvent was removed and the solid was washed with petroleum ether. Re- crystallization from dichloromethane/petroleum ether gave [(p-cymene)RuC12(NHEt2)] as a bright yellow solid (66 mg, 50%). Found : C, 43.6 ; H, 6.5 ; N, 3.5. Calc. for Cr,H,,Cl,NRu: C, 44.3; H, 6.6; N, 3.7%. ‘H NMR (CDC13): 1.22 [t, 6H, CH2CH3, J(7)], 1.31 [d, 6H, CHMe2, J(7)], 2.23 (s, 3H, &H,Me), 3.03 [sep, lH, CHMe,, J(7)], 3.16 (m, 2H, CHH’), 3.50 (m, 2H, CHH’), 5.33,5.38 [(AB),, 4H, CsH4, J(AB)6].

Amine exchange reactions

Complex Id (250 mg, 0.59 mmol) and aniline (166 mg, 1.78 mmol) were refluxed in chloroform (50 cm’) for 2.5 h. The solvent was removed and the oily solid was washed with petroleum ether to give

Reactions of amines with [(arene)RuCl j2 1127

a yellow solid, identified as complex la on the basis of its ‘H NMR spectrum (157 mg, 70%).

The same general procedure was used for the reaction of complex la with piperidine in equimolar amounts to give complex le in 71% yield. Using the same method refluxing of complex le with ani- line gave no reaction.

Preparation of [(1,3,5-Me,C,H,)RuCl(NHZPh)J

DWG4

Aniline (48 mg, 0.52 mmol) and AgBF, (101 mg, 0.52 mmol) were added to a solution of [(1,3,5- Me,CgHs)RuC12(NHzPh)] (20 mg, 0.52 mmol) in dichloromethane (50 cm3) and the mixture was stirred for 0.5 h. The AgCl was removed by filtra- tion through celite and the solvent was rotary evap- orated. Recrystallization from dichloromethane/ diethylether gave [(1,3,5-Me,C,H,)RuCl(NH, Ph)d[BF,] as an orange crystalline solid (259 mg, 94%). Found : C, 47.2; H, 4.9 ; N, 5.0. Calc. for C,,HZ6BC1F4N2Ru: C, 47.6; H, 4.9; N, 5.3%. ‘H NMR (CDCI,): 1.69 (s, 9H, &Me& 4.48 (br, 2H, NH), 4.76 (s, 3H, CJII,), 5.83 (br, 2H, NH), 7.35 (m, lOH, Ph).

Preparation of [(1,3,5-Me3CJ13)RuC1(NHZCHZ

Ph)dBF,I (W

Benzylamine (47 mg, 0.44 mmol) and AgBF4 (86 mg, 0.44 mmol) were added to a solution of [( 1, 3,5-Me3C6H3)RuC12(NH2CHzPh)] (177 mg, 0.44 mmol) in dichloromethane (60 cm3) and the mixture was stirred for 0.5 h. The AgCl was removed by filtration through celite and the solvent was rotary evaporated. Recrystallization from dichloro- methane/diethylether gave [(1,3,5-Me,C,J-I~)RuCl (NH,CH,Ph)J[BF,] as an orange crystalline solid (170 mg, 68%). Found: C, 49.7; H, 5.4; N, 4.9. Calc. for C23H30BClF4N2Ru: C, 49.5 ; H, 5.4; N, 5.0%. ‘H NMR (CD,&): 2.30 (s, 9H, &Me,), 2.50 (br, 2H, NH), 4.01 (m, 4H, CHJ, 4.42 (br, 2H, NH), 5.10 (s, 3H, CsH3), 7.34 (m, lOH, Ph). Mass spectrum: m/z 471 [Ml+, 364 [M-NH2CH2 Ph]+ (M refers to the complex cation).

X-ray structure determinations

Crystals of [( 1 ,3,5-Me3C6H3)RuC12(HNCSH l0)] were grown from dichloromethane/mesitylene, while those of [(1,3,5-Me3C6H3)RuC12(NCSHS)I were grown from dichloromethane/diethylether. The crystals used for data collection were mounted in air and the unit cell parameters were determined by least-squares refinement of o-measurements of

different layers.8 Data were collected on a Stoe

STADI-2 diffractometer with an o-scan technique in the range 7 < 28 < 54”. Scattering factors were taken from ref. 9.

Crystal data for [C14H23C12NR~] (le). A4 = 377.3; monoclinic, space group P2Jc, a = 11.573(g), b = 9.341(8), c = 15.100(14) A, jj = 107.3(l)“, U = 1558.3 A3, 2 = 4, p = 12.09 cm- I, I(Mo-K,) = 0.7107 A, P(OO0) = 768, D, = 1.61 g cn~-~. Crystal dimensions 0.48 x 0.28 x 0.155 mm.

The intensities of 3178 unique reflections were measured and these data were corrected for Lorentz and polarization effects to give 2098 unique reflec- tions with I > 30(I). The structure was solved using the PATT option of SHELXS-86 ; all subsequent calculations were performed with the computer pro- gramme SHELX-76. lo All hydrogen atoms were included in calculated positions (C-H = 1.08 A) and all non-hydrogen atoms were refined aniso- tropically. Final cycles of least-squares refinement used a weighting parameter w = l/(o’F+gF’), where g = 0.0007, and gave final residual indices of R = 0.038 and R,,, = 0.041.

Crystal data for [C14H1&12NR~]. M = 371.3; orthorhombic space group P212121, a = 13.623(14), b = 13.928(14), c = 7.633(2) A, U = 1448.27 A3, z=4, p = 13.01 cm-‘, I(Mo-K,) = 0.7107 A, F(OOO) = 744, D, = 1.70 g cm3. Crystal dimen- sions 0.38 x 0.12 x 0.06 mm.

The intensities of 1740 reflections were measured and these data were corrected for Lorentz and polar- ization effects to give 1411 unique reflections with 2 > 30(I). The structure was solved by direct methods using SHELXS-86 ; all subsequent calcu- lations were carried out with the computer pro- gram SHELX-76. ‘O All hydrogen atoms were put in calculated positions (C-H = 1.08 A) and all non-hydrogen atoms were refined anisotropically. Final cycles of least-squares refinement used a weighting parameter w = 1.1 827/(02F+gF2), where g = 0.0007, and gave final residual indices of R = 0.0416 and R, = 0.0422.

Acknowledgements-We thank the S.E.R.C. for a studentship (L.C) and for use of the Mass Spectroscopy Service Centre at University College Swansea and Leices- ter University Computer Centre who provided support and facilities for X-ray single-crystal calculations.

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