The chemistry of niobium and tantalum dithiocarbamato-complexes. Part 3. Protonation of [Nb(NNMeR)(S2CNEt2)3](R = Me or Ph)

Abstract

The reactions of [Nb(NNMeR)(S₂CNEt₂)₃](R = Me or Ph) with an excess of anhydrous HBr have been studied in MeCN. The reactions, which yield [NbBr₂(S₂CNEt₂)₃] and the corresponding substituted hydrazine, occur in two stages: the first is the initial rapid formation of [Nb(NHNHMeR)(S₂CNEt₂)₃]²⁺, and the second the slow decomposition of this species to yield the products. The sites of protonation of the hydrazide residue have been established by comparison of the rates of protonation of the species with methyl or phenyl substituents. The introduction of methanol into these systems inhibits the rate of protonation due to specific solvation of the monoprotonated complex.