Reactions of a hydrido(hydrogermylene) tungsten complex with some heterocumulenes: hydrogermylation and thermal rearrangement

Reaction of a hydrido(hydrogermylene) tungsten complex Cp*(CO)(2)(H)W=Ge(H)[C(SiMe3)(3)] (1) with isocyanate PhNCO at room temperature resulted in stoichiometric hydrogermylation at the C=O bond to give a W-Ge-O-C-N five-membered chelate complex. In contrast, the reactions of 1 with isothiocyanates RNCS (R = Ph, Me) led to hydrogermylation at the C-N bond to yield W-Ge-N-C-S five-membered chelate complexes. In both cases, the most electronegative atom in the isocyanate or isothiocyanates attacks the germanium of 1. Gentle heating of the latter chelate complexes in hydrocarbon solvents caused rearrangement of the chelate ring to cleanly afford W-Ge-S-C-N chelate complexes. Molecular structures of these three different types of five-membered metallacycles have been determined by X-ray crystallography, and possible reaction mechanisms for the hydrogermylation and rearrangement reactions have been proposed.