Crystal and molecular structure of di-µ-trimethylsilylmethyl-bis[(tri-methylphosphine)(trimethylsilylmethyl)chromium(II)](4 Cr–Cr)

Abstract

The crystal and molecular structure of the title compound has been determined by direct methods and refined by least squares to R 0.029 3 based on 4 345 diffractometer data. Crystals are triclinic with a= 16.975(7), b= 11.396(6), c= 10.678(6)Å, α= 114.87(7), β= 91.75(7), γ= 84.98(7)°, space group P, and Z= 2. The binuclear molecule possesses an approximate two-fold axis and contains two bridging alkyl groups arranged in a cis configuration. One H atom from each bridging CH₂ group makes a close contact (ca. 2.25Å) with one of the metal atoms, introducing a slight asymmetry in the Cr–C bridge bonds. The short Cr–Cr distance [2.1007(5)Å] is consistent with the presence of a quadruple metal–metal bond. However, in order to account for the overall coordination geometry, and in particular the accommodation of the two cis electron-deficient bridges, it is suggested that the M[graphic omitted]M system is bent. A simple description of this in terms of d-orbital overlap integrals is presented.