The new trifluoroethoxo phosphine complexes [Cp2M(?1-dppe)(CF3CH2O)]+ and
[Cp2(CF3CH2O)M(?-dppe)MCp2(CF3CH2O)]2+ (M = Mo or W, Cp = ?-C5H5 and dppe =
Ph2PCH2CH2PPh2) have been prepared by reaction of cationic di-?-hydroxo
dinuclear complex of molybdenocene or tungstenocene [Cp2M(?-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(?-dppe)MoCp2(CF3CH2O)]2+, which
crystallizes in space group P21/c(#14) with a = 12.230(5) ?, b = 11.149(5)
?, c = 28.966(7) ?, ? = 101.07(3)?, V = 3876(2) ?3, 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.
Coordination studies of 1,2-bis(diphenylphosphino)ethane with di-μ-hydroxo dinuclear complexes of tungsten(IV) and molybdenum(IV)