Dinuclear rhodium complexes with three and four bridging ligands. The preparation and crystal structure of [Rh 2(Ph 2PCH 2PPh 2) 2(μ-Cl)(μ-CO)(CO) 2][Rh(CO) 2Cl 2] · CH 2Cl 2

Abstract

The reaction of four moles of bis(diphenylphosphino)methane (dpm) or bis(diphenylarsino)methane (dam) with three moles of Rh 2(CO) 4Cl 2 produces [Rh 2(dpm) 2(μ-Cl)(CO) 2][Rh(CO) 2Cl 2] or [Rh 2(dam) 2(μ-Cl)(CO) 2][Rh(CO) 2Cl 2]. Reaction of Rh 2(dam) 2(CO) 2Cl 2 with Rh 2(CO) 4Cl 2 proceeds by halide ion abstraction to give [Rh 2(dam) 2(μ-Cl)(CO) 2][Rh(CO) 2Cl 2]. Carbon monoxide adds to [Rh 2(dpm) 2(μ-Cl)(CO) 2][Rh(CO) 2Cl 2] to give [Rh(dpm) 2(μ-Cl)(μ-CO)(CO) 2][Rh(CO) 2Cl 2]. The crystal structure of [Rh 2(dpm) 2(μ-CO)(μ-Cl)(CO) 2] [Rh(CO) 2Cl 2] · CH 2Cl 2 has been determined by X-ray diffraction. The crystals are monoclinic, space group P2 1/ 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 I net > 3σ( I net). Bond distances: RhRh, 2.838(1) Å; RhC (bridged), 2.094(11), 2.051(11) Å; RhC (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.