CRYSTAL AND MOLECULAR STRUCTURE OF DI-MU-BIS(DIPHENYLARSINO)METHANE-BIS(TRANS-CHLOROCARBONYLRHODIUM(I)), RH(CO)CL((C6H5)2ASCH2AS(C6H5)2)2RH(CO)CL

The structure of diµ-bis(diphenylarsino)methane-bis(trans-chlorocarbonylrhodium(I)), Rh(CO)Cl((C6H5)2AsCH2As(C6H5)2)2Rh(CO)Cl has been determined from three-dimensional X-ray data collected by counter methods. The final R factor obtained from a block-diagonal least-squares refinement for 2544 reflections is 0.068. The material crystallizes in the triclinic system with space group PI and a unit cell of dimensions a - 11.371 (2), b = 10.413 (2), c = 12.753 (3) Å and α = 100.35 (3), β = 103.60 (2), γ = 118.42 (2)°. The calculated density for two empirical formula units, Rh(CO)Cl((C6H5)2AsCH2As(C6H5)2)2 is 1.747 g/cm3 which agrees with the experimental value of 1.71 g/cm3 determined by the flotation method. The crystal consists of discrete dimeric molecules of 1 symmetry held together by bridging diarsine molecules. The Rh-Rh distance within the dimer is 3.396 (1) Å and appears to be more the result of the steric requirements of the diarsine molecules than any significant metal-metal interaction. The approach is sufficiently close, however, that the coordination about each rhodium atom is best described as approximately square pyramidal. The centrosymmetrically related rhodium atom occupies the apical position while the “basal plane” consists of a terminal chlorine atom, a terminal carbonyl group, and two arsenic atoms, one from each of the two bridging diarsine molecules, in a trans configuration. © 1969, American Chemical Society. All rights reserved.