Synthesis and spectroscopic properties of Mo(VI) complexes with phosphine oxide ligands and the crystal structures of MoO2X2(OPMe3)(2) (X=Cl or Br) and MoO2Br2{0-C6H4(P(O)Ph-2)(2)}center dot 2CH(2)Cl(2)

The colourless neutral Mo(VI) complexes [MoO2Cl2(OPMe3)(2)], [MoO2Cl2(L-L)] (L-L = Ph2P(O)CH2P(O)Ph-2, Ph2P(O)CH2CH2P(O)Ph-2 and o-C6H4(P(O)Ph-2)(2)) have been obtained in good yield by reaction of MoO2Cl2 with the ligand in anhydrous CH2Cl2 solution. The corresponding light yellow bromo species were obtained from reaction of a CH2Cl2 solution of the phosphine oxide ligand with MoO3 and HBr. The complexes have been characterised by IR, H-1, P-31{H-1} and where possible by Mo-95 NMR spectroscopy and trends in the spectroscopic data are discussed. Crystal structures of [MoO2X2(OPMe3)(2)] (X = Cl or Br) and [MoO2Br2{o-C6H4(P(O)Ph-2)(2)}] (.) 2CH(2)Cl(2) are also described. Each of the compounds adopts a distorted octahedral geometry at Mo(VI) with trans halo ligands, a cis dioxo unit and with the O-bound phosphine oxide ligands completing the coordination environment