c4 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Journal of Organometallic Chemistry, 447 (1993) C4-C6 JOM 23405PC zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Preliminary Communication Synthesis of the heterodinuclear Fe-Pt complex [(OC),Fe{ p-CN(2,6_xylyl)}- (p-dppmMPPh,)l containing a bridging isonitrile ligand and electrophilic additions leading to p-aminocarbyne complexes Michael Knorr, Thierry Faure and Pierre Braunstein Laboratoire de Chimie de Coordination, lJR4 0416 CNRS, Universith Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg Cedex (France) (Received November 9, 1992) Abstract Reaction of [(OC),I(MeO),Si]Fe(c-dppm)PtH(PPh3)1 (1) (dppm = Ph,PCH,PPh,) with 2,6-xylyl isonitrile (GNR) affords the hetero- dinuclear complex [(OC),Fe&CNR&dppm)Pt(PPh,)l (2) which contains a rare example of an isonitrile bridging a metal-metal bond. In the presence of HBF, or (Me,O)BF,, the bridging isonitrile is protonated or alkylated, leading to aminocarbyne (or iminium) type complexes [(OC),Fe(F-CNRR’Q-dppm)Pt(PPh3)HBF4] (3? R’ = H, 4, R’ = Me). The synthesis of [(OC),Fe(?*-CL2-Si(BMe),(OMe)X~- dppm)Pt(CNR)IPF,] (5) is also reported. Homobinuclear complexes with bridging isonitrile of the type M&CNR)M (both with bent or linear CNR groups) are a class of compounds similar to their well documented CO-bridged counterparts [ 11. However, reports focussing on heterodinuclear complexes M(p- CNR)M’ containing bridging isonitrile(s) appear to be still very scarce [2] and concern systems without metal-metal bond. In the course of studies on dppm-bridged heterodi- nuclear silyl complexes of the type [(OC>,{(MeO>,Si}- Fe&dppm)ML,] (dppm = Ph,PCH,PPh,; M = Ni, Pd, Pt, Rh, Re, Ru,. . . ) [3] we added dropwise at 0°C a CH,Cl, solution of 2,6-xylyl isonitrile (0.132 g, 1 mmol) to a stirred suspension of [(OC),((MeO),Si}Fe(c- dppm)PtH(PPh,)] (1) (1.048 g, 0.95 mmol) in CH,Cl,. The solution was stirred for 1 day at room temperature and then layered with Et,O. After a few days at - lo” C, orange air-stable crystals were isolated as dichloromethane solvate in 58% yield. The elemental Correspondence to: Dr. P. Braunstein. 0022-328X/93/$6.00 analysis and spectroscopic data are consistent with the formulation [(OC),Fe&-CNRXP-dppm)Pt(PPh,)] (2). In addition to the v(C0) vibrations at 1994(m) and 1926&s, br), the IR spectrum of 2 contains a u(CN) vibration at 1667(m, br) cm-‘. This low stretching frequency is indicative of a bridging, bent CL-RCN ligand [lg, lkl. As a comparison, the complex [Pd,Cl,(CL-CNR>,(py),l which contains two linear p- RCN ligands has v(CN) vibrations at 2056 and 1976 cm-’ [lgl. In the 31P{1H) NMR spectrum three mutu- ally coupled phosphorus nuclei are observed, with a strong coupling of 152 Hz between the two P nuclei of the dppm and a weak cis coupling with the PPh, attached to Pt. The observation of a 2+3J(PFePt) of 75 Hz [4* I supports the presence of a metal-metal bond [51, as exists in the precursor complex 1 [3a]. Two isomeric forms are conceivable due to the bent nature of the CNR group [li]. The isomer with the bulkier xylyl group oriented toward the Fe centre would seem to be favoured on steric grounds, but we have no direct proof for this. The reaction may be initiated by insertion of the isonitrile in the Pt-H bond of 1, resulting in a formimidoyl intermediate [6] or, altema- tively, by insertion into the M-SiR, bond [7] (inter- mediate species are observed during IR-monitoring of the reaction). A reductive elimination reaction of HSi(OMe),, similar to that observed in the reaction of the dinuclear Fe-Rh complex [(OC),Fe{$+.+-Si- (OMe),(bMe))&-dppmXp-H)fihCl] with CO [3d], can be ruled out since we found no evidence for v(SiH) in the IR spectrum of the reaction mixture. It is known that dinuclear complexes in which an isonitrile ligand bridges between two iron or two plat- inum centres are susceptible to protonation or alkyla- tion at the nitrogen atom, due to its basic character, to give p-iminium- or aminocarbyne-type derivatives [ lk, In, 81. In an analogous manner, 2 reacts instantly in cold CH,Cl, with an excess of HBF, . Et 2O to give quantitative yields of [(OC),Fe{~-CNH(R)}(~- dppm)Pt(PPh,)][BF,l (3). Similarly, the nitrogen atom can be methylated by [Me,O][BF,] to give [(OC),- Fe{p-CNMe(R)}(p-dppm)Pt(PPh,)I[BF,] (4) [4*1. The much lower v[C=N(R)R’] frequencies in 3 (1527 cm-‘) * Reference number with asterisk indicates a note in the list of references. 0 1993 - Elsevier Sequoia S.A. All rights reserved