Synthesis and characterization of the triethylphosphine adduct of bis(2,4-dimethylpentadienyl)tungsten, [W(2,4-C7H11)(2)(PEt3)], a complex with one eta(5)-U and one eta(5)-S pentadienyl ligand

The reaction of [WCl4(PEt3)(2)] with 4 equiv. of the 2,4-dimethylpentadieny l anion leads to the spontaneous reduction of the w(IV) complex by two of t he dienyl anions, along with incorporation of the other two anions in, the resulting W(II) complex [W(2,4-C7H11)(2)(PEt3)] (2,4-C7H11 = 2,4-dimethylpe ntadienyl). Spectroscopic data reveal a low symmetry structure, presumed to be analogous to that found for the molybdenum analogue, in which one dieny l ligand was bound in the usual eta(5)-U conformation, the other in the unc ommon eta(5)-S (sickle) conformation,This has been confirmed through a sing le crystal X-ray diffraction study. (C) 1999 Elsevier Science S.A. All righ ts reserved.