UNUSUAL, COORDINATIVELY UNSATURATED RHODIUM RHENIUM AND IRIDIUM RHENIUM ALKYL, ACYL, AND HYDRIDO COMPLEXES - STRUCTURE OF [RHRE(CH3)(CO)4(PH2PCH2PPH2)2][CF3SO3].3CH2CL2

The unusual alkyl complexes [MRe(CH3)(CO)4(dppm)2][CF3SO3] (M = Rh (3), Ir (7); dppm = Ph2PCH2PPh2) are prepared by the reaction of [RhRe(CO)4(dppm)2] (1) or [IrRe(CO)5(dppm)2] (2) with methyl triflate. Compound 3 reacts with H2 to yield methane and [RhRe(CO)4(mu-H)(dppm)2][CF3SO3] and with LiBEt3H to give methane and 1. Under carbon monoxide compound 3 yields the analogous acyl species [RhRe(C(O)CH3)(CO)4(dppm)2][CF3SO3] (4), and reaction of this with LiBEt3H gives 1 and acetaldehyde. Stepwise removal of two carbonyl groups from 3 can be effected with use of Me3NO in acetonitrile to give first [RhRe(CH3)(CO)3(CH3CN)(dppm)2][CF3SO3] (5) and then [RhRe(CH3)(CO)2(CH3CN)2(dppm)2][CF3SO3] (6). The iridium methyl species 7 also reacts with LiBEt3H to yield methane and [IrRe(CO)4(dppm)2]; however at -60-degrees-C the intermediate hydrido methyl species, [IrRe(CH3)(CO)4(mu-H)(dppm)2] (12) can be observed. Reaction of 7 with H2 gives methane together with [IrRe(CO)4(mu-H)(dppm)2][CF3SO3] (10). Under carbon monoxide 7 yields first [IrRe(CH3)(CO)5(dppm)2][CF3SO3] (8) then [IrRe(C(O)CH3)(CO)5(dppm)2][CF3SO3] (9). A series of hydride complexes [IrReH(CO)4(mu-H)(dppm)2][CF3SO3]2 (13), [IrRe(H)2(CO)4(mu-H)(dppm)2][CF3SO3] (14), and [IrRe(H)2(CO)4(dppm)2] (15), have also been prepared. The structure of 3 has been determined by X-ray techniques. This compound crystallizes with three molecules of CH2Cl2 in the triclinic space group P1BAR with a = 15.055 (1) angstrom, b = 21.239 (3) angstrom, c = 10.662 (1) angstrom, alpha = 97.83 (1)-degrees, beta = 105.647 (7)-degrees, gamma = 100.195 (9)-degrees, V = 3169.7 angstrom 3, and Z = 2. Refinement has converged to R = 0.039 and R(w) = 0.049 on the basis of 8106 observations and 494 parameters varied. The methyl group is coordinated to Rh opposite the Rh-Re bond. Of the four carbonyls bound to Re, two are also semibridging to the Rh center. The Rh-Re separation is 2.8510 (5) angstrom, and the Rh-CH3 distance is 2.097 (6) angstrom.