Synthesis and reactivity of alkynyl niobocene complexes

The synthesis of alkynyl containing niobocene complexes with differing auxiliary ligands is described. The niobium(III) derivatives of the general formula [Nb(η5-C5H4SiMe3)2(CCR)(L)] where L is either carbonyl, phosphine, phosphite, or isocyanide, were prepared by the reaction of the bis(alkynyl)magnesium reagent with the corresponding cloro-niobocene precursor. In a similar manner the niobium(V) imido compounds, of the general formula, [Nb(NR′)(η5-C5H4R″)2(CCR)], were prepared. The characterization of these complexes is discussed. The reactivity of the alkynyl compounds towards oxidation and protonation has been studied.