SYNTHESIS OF 2 TANTALUM COMPLEXES BEARING CYCLOPENTADIENYL ANALOGS

Reaction of Li[C5H5B-NMe2] with (TBM)TaMe2Cl (TBM = tribenzylidenemeth ane) gives (TBM)[C5H5B-NMe2]TaMe2 (1). A single crystal diffraction st udy revealed a metallocene-like environment with the metal binding mor e strongly to the boratabenzene ring carbons furthest from the boron a tom. Cp [C4H4B-N(CHMe2)(2)]Ta(eta(4)-C4H6) (2) (Cp* = C5Me5) is obtai ned from the reaction of Cp[C4H4B-N(CHMe2)(2)]TaCl2, and (C4H6Mg)(THF )(2). The diene fragment binds in a trans configuration. The oxidation state of tantalum in 2 can be considered as I, III or V if all resona nce contributions are taken into account. (C) 1997 Elsevier Science B. V.