Preparation and properties of group VI metal carbonyls containing the ligand bis(di- o-tolyl)phosphinomethane. Crystal and molecular structure of dicarbonylbis(di- o-tolyl)phosphinomethanechromium

Abstract

Complexes of Group VI metal carbonyls with the ligand bis(di- o-tolyl)phosphinomethane have been prepared and characterised by NMR spectroscopy. The crystal structure of Cr(CO) 2(BDT oM) has been determined by conventional X-ray diffraction techniques. The orange tabular crystals are monoclinic, space group Cc, a 24.197(1), b 8.162(1), c 16.736(1) Å, β 124.14(1)°, V 2735.8 Å 3, Z = 4. Refinement by full-matrix least-squares methods employed anisotropic thermal parameters for the heavier atoms and the coordinated o-tolyl group. One carbonyl ligand was positioned from a ‘difference’ map. The final residual, R, is 0.078 for 1673 observed reflections. The complex is monomeric. The BDT oM ligand coordinates to chromium through one phenyl ring (three sites) and one phosphorus atom, with two carbonyl groups completing an octahedral ‘piano stool’-like arrangement. The coordinated arene ring is planar and is in a staggered arrangement relative to the other donors. The CrC(arene) bonds range from 2.166(10) to 2.260(9) Å (average 2.210 Å); the distance of Cr from the plane of the ring is 1.698 Å. The o-methyl carbon and the non-coordinated phosphorus atom are significantly displaced from the ring plane.