Inorg. Chem. zyxwvut 1984, 23, zyxwvu 4057-4064 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM 4057 angle (1 16O in la,b; 109.3’ in 9) accompanying Ir-Ir bond formation to force the N atoms somewhat toward tetrahedral geometry. Intramolecular contacts are significant (-3.2 A) in one region of molecule 9, between the chloropyrazolyl bridges and phenyl rings C(31)<(36) and C(61)<(66). This twists the bridging ligands with res ect to the Ir-Ir bond, planes with Ir(2) so displaced by 0.52 and 0.23 A. Reaction of complex 1 with methyl iodide (1 equiv or excess) afforded a 1:l adduct as a yellow powder (lo), which like 7 and 8 showed poor solubility in organic solvents. Two vco absorptions were found in the IR spectrum at 2013 and 1993 cm-’, and the 31P NMR spectrum consisted of two resonances having equal intensity (-140.5, -141.8 ppm) attributable to PPh3 ligands attached to distinguishable metal atoms. These data indicate a structure similar to C, with Me and I in apical positions at Ir as has been established crystallographicallyla for the Me1 adduct of complex 2. By contrast, a corresponding reaction with MeBr appeared to give several products, and a bromo analogue of 10 has not yet been isolated. These ob- servations will be consolidated as part of a more extensive examination of the reactivity of compound 1 toward func- tionalized organic molecules. There is a close stereochemical relationship between the structures of compounds 1 and 9. Both are enantiomeric (C, causing Ir(1) to deviate 0.16 and 0.61 zyxwvuts w from the two pyrazolyl molecular symmetry) and share the same (trans) orientation of terminal ligands in the equatorial plane at Ir, i.e. the oxi- dative addition step occurs with no net ligand reorganization at the metal center. The dimer (1) and related complexes are in principle resolvable, either by incorporation of a chiral phosphine or related ligand or via diastereomer formation involving successive oxidative addition/reductive elimination of an optically pure substrate. Access to such resolved com- plexes and their relevance to reactions involving asymmetric induction or chiral recognition is being investigated. Acknowledgment. We thank the NSERC (Canada) and the NSF (U.S.) for financial support of this research; S.R.S. gratefully acknowledges receipt of a University Research Grant from Imperial Oil Ltd. and a generous loan of iridium tri- chloride from Johnson-Matthey Inc. Registry No. la, 80461-91-2; lb, 92283-13-1; 2, 80462-13-1; 7, 80462-14-2; 8, 80462-15-3; 9, 80461-90-1; 10, 80471-11-0; trans- IrCl(C0) (PPh3)2, 15318-31-7; [Ir(C8H12)C1]2, 12 1 12-67-3; 12, 7553-56-2; Br2, 7726-95-6; C12, 7782-50-5; Ir, 7439-88-5; methyl iodide, 74-88-4; methyl bromide, 74-83-9; pyrazole, 288-13-1. Supplementary Material Available: Listings of thermal parameters, anisotropic and isotropic temperature factors, least-squares planes, bond lengths and bond angles, and observed and calculated structure factors for compounds la, lb, and 9 (51 pages). Ordering information is given on any current masthead page. Contribution from the Laboratoire de Chimie de Coordination, ERA 670 CNRS, UniversitE Louis Pasteur, F-67070 Strasbourg Cedex, France, Institut ftir Anorganische Chemie der Universitat Wiirzburg, D-8700 Wiirzburg, FRG, and Laboratoire de Chimie Mingrale, Ecole Nationale SupErieure de Chimie, F-67008 Strasbourg Cedex, France Synthesis and Spectroscopic Studies of Metal-Metal-Bonded Linear Heterotrimetallic Gold(1) Complexes. Crystal Structure of [n -Bu,N][Au[C~(CO)~-T~C~H~]~] PIERRE BRAUNSTEIN,*+ ULRICH SCHUBERT,* and MICHEL BURGARDt Received December 27, 1983 A series of heterotrimetallic Au(1) anionic complexes of the general formula [M’-Au-M’]- with M’ zyxw = Mn(CO)5 (l), CO(CO)~ (2), Cr(CO)$p (3), Mo(CO)~C~ (4), W(CO)$p (5), and Fe(CO)&p (6) have been prepared and characterized. The linear coordination about the gold atom is evidenced by infrared spectroscopy, particularly in the metal-metal stretching region where a strong absorption between 150 and 200 cm-I is typical for the v,,(Au-M’) vibration. The corresponding approximate force constants are compared with those of other related linear trimetallic complexes. It is found that metal-metal bond strength increases in the M’-M-M’ systems in the following sequence of M = Pd < Pt < Au < Hg. The same trend is observed for the covalency of these complexes as deduced from their u(C0) frequencies. The molecular structure of [n-Bu4N] [Au[Cr(CO),Cplz] (3) has been determined by X-ray diffraction: P2,/c with zyxwv a = 11 10.6 (6) pm, b = 1690.5 (14) pm, c = 2209.2 (8) pm, p = 122.46 (3)O, and zyxwvut Z = 4. The complex anion has approximate C, symmetry. The Cr(l)-Au-Cr(2) angle is 162.2 (3)’, and the Au-Cr distances are 264.1 (9) and 263.5 (8) pm. The coordination about the Cr atoms is of the “four-legged piano-stool” type. The 1 9 7 A ~ Mossbauer parameters of 1,4, and 6 have been measured and are compared with those obtained for AuC12- and Ad,. Considering the linearity of these molecules, the IS and QS values are consistent with complexes in which the Au(1) center has a sp, hybridization. They furthermore confirm the bonding scheme deduced from infrared spectroscopy, in which u bonding between the metals is predominant and zyx x effects will arise from x donation into the gold 6p, and 6py orbitals. Introduction Polymetallic complexes in which the metal atoms are con- nected to each other through metal-metal bonds only form now a well-known class in organometallic chemistry.lS2 Previously, we have shown that the reaction of carbonyl- metalates, [M’I- with cis or trans square-planar palladium or platinum halide complexes can be successfully applied to the synthesis of heterotrimetallic chain complexes (eq l).3-7 Such complexes are of interest for numerous reasons: (i) They contribute to a better knowledge of the role of metal-metal bonding in stabilizing polymetallic complexes + Universitt Louis Pasteur. * Universitit Wiirzburg. f Ecole Nationale Suptrieure de Chimie. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA L (1) 1 t MCIzLz 4- 2[M’l- - M-M-M’ 4- 2CI- L M=Pd.Pt; L=py3, RNC!,’ RCNf CO;6.7 M’=Mn(C0)5,Co(C0)4. Fe(C0)sNO. Cr(C0)3Cp. MO(CO)~C~. W(CO),Cp (Cp -?-CsHs) since, in these examples, their cohesion is achieved without the assistance of bridging ligands. This proved to be partic- (1) Cotton, F. A,; Wilkinson, zyxwv G. “Advanced Inorganic Chemistry”,4th ed.; Wiley-Interscience: New York, 1980. (2) Roberts, D. A.; Geoffroy, G. L. In “Comprehensive Organometallic Chemistry”; Wilkinson, G., Stone, F. G. A,, Abei, E. W., Eds.; Perga- mon Press: Oxford, 1982; Chapter 40. 0020-1669/84/1323-4057$01.50/0 0 1984 American Chemical Society