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(eta(1)-dppe)-(CF3CH2O)](+) and [Cp-2(CF3CH2O)M(mu-dppe)MCp2(CF3CH2O)](2+) (M = Mo or W, Cp = eta-C5H5 and dppe = Ph2PCH2CH2PPh2) have been prepared by reaction of cationic di-mu-hydroxo dinuclear complex of molybdenocene or tungstenocene [Cp2M(mu-OH)2MCp(2)](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(mu-dppe)MoCp2(CF3CH2O)](2+), which crystallizes in space group P21/c(#14) with a = 12.230(5) A, b = 11.149(5) A, c = 28.966(7) A, beta = 101.07(3), V = 3876(2) A3, 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.