Dehydrocoupling Reactions of Dimethylamine-Borane by Pt(II) Complexes: A New Mechanism Involving Deprotonation of Boronium Cations

Coordinatively unsaturated Pt(II) complex [Pt((IBu)-Bu-t')((IBu)-Bu-t)](+) stabilized by N-heterocyclic carbene (NHC) ligands dehydrogenates N,N-dimethylamineborane through a mechanism that involves hydride abstraction, assisted by an amine, to yield a platinum-hydride complex [PtH((IBu)-Bu-t')((IBu)-Bu-t)] with concomitant formation of the boronium cation [(NHMe2)(2)BH2](+). This latter species is very likely in equilibrium with the THF stabilized borenium cation [(NHMe2)(THF)BH2](+), bearing an acidic NH group that is able to protonate the platinum hydride [PtH((IBu)-Bu-t')((IBu)-Bu-t)] releasing H-2, the amino borane H2B-NMe2 and regenerating the catalytic [Pt](+) species.