DINUCLEAR RHODIUM COMPLEXES WITH 3-BRIDGING AND 4-BRIDGING LIGANDS - PREPARATION AND CRYSTAL-STRUCTURE OF [RH2(PH2PCH2PPH2)2(MU-CL)(MU-CO)(CO)2][RH(CO)2CL2] . CH2CL2

The reaction of four moles of bis(diphenylphosphino)methane (dpm) or bis(diphenylarsino)methane (dam) with three moles of Rh2(CO)4Cl2 produces [Rh2(dpm)2(μ-Cl)(CO)2][Rh(CO)2Cl2] or [Rh2(dam)2(μ-Cl)(CO)2][Rh(CO)2Cl2]. Reaction of Rh2(dam)2(CO)2Cl2 with Rh2(CO)4Cl2 proceeds by halide ion abstraction to give [Rh2(dam)2(μ-Cl)(CO)2][Rh(CO)2Cl2]. Carbon monoxide adds to [Rh2(dpm)2(μ-Cl)(CO)2][Rh(CO)2Cl2] to give [Rh(dpm)2(μ-Cl)(μ-CO)(CO)2][Rh(CO)2Cl2]. The crystal structure of [Rh2(dpm)2(μ-CO)(μ-Cl)(CO)2] [Rh(CO)2Cl2] · CH2Cl2 has been determined by X-ray diffraction. The crystals are monoclinic, space group P21/c, with lattice constants: a 16.302(4) Å, b 18.370(3) Å, c 19.189(3) Å, β 91.11(2)°, Z = 4. Positional and isotropic thermal parameters of the non-hydrogen atoms were refined using a full-matrix least-squares method to a final R index of 0.085 for 6401 reflections with Inet > 3σ(Inet). Bond distances: RhRh, 2.838(1) Å; RhC (bridged), 2.094(11), 2.051(11) Å; RhC (terminal), 1.813(1), 1.839(1) Å; P⋯P(av.), 3.055(6) Å. Correlations between P⋯P or As⋯As distances and M⋯M distances are noted for dpm or dam as bridging ligands. © 1979.