coordination studies of 1,2-bis(diphenylphosphino)ethane with di-μ-hydroxo dinuclear complexes of tungsten(iv) and molybdenum(iv)

The new trifluoroethoxo phosphine complexes [Cp2M(η1-dppe)(CF3CH2O)]+ and [Cp2(CF3CH2O)M(μ-dppe)MCp2(CF3CH2O)]2+ (M = Mo or W, Cp = η-C5H5 and dppe = Ph2PCH2CH2PPh2) have been prepared by reaction of cationic di-μ-hydroxo dinuclear complex of molybdenocene or tungstenocene [Cp2M(μ-OH)2MCp2]2+ with dppe. From the 1H and 31P NMR data, the configurations of the products could be assigned. Furtheremore, X-ray crystallography was used to definitively identify one of the product [Cp2(CF3CH2O)Mo(μ-dppe)MoCp2(CF3CH2O)]2+, which crystallizes in space group P21/c(#14) with a = 12.230(5) Å, b = 11.149(5) Å, c = 28.966(7) Å, β = 101.07(3)°, V = 3876(2) Å3, and Z = 2. It was ascertained that the amount of dppe added to the reaction mixture could influence the product distribution. A mechanism involving initial replacement of the hydroxo ligand by the alkoxo group followed by nucleophilic attack of the phosphine is proposed on the basis of the reaction profile.