The Simplest Amino-borane H2B=NH2 Trapped on a Rhodium Dimer:Pre-Catalysts for Amine-Borane Dehydropolymerization

The μ-amino-borane complexes [Rh2(LR)2(μ-H)(μ-H2B=NHR′)][BArF4] (LR=R2P(CH2)3PR2; R=Ph, iPr; R′=H, Me) form by addition of H3BNMeR′H2 to [Rh(LR)(η6-C6H5F)][BArF4]. DFT calculations demonstrate that the amino-borane interacts with the Rh centers through strong Rh-H and Rh-B interactions. Mechanistic investigations show that these dimers can form by a boronium-mediated route, and are pre-catalysts for amine-borane dehydropolymerization, suggesting a possible role for bimetallic motifs in catalysis. Bridges of boron: Mechanistic investigations show that rhodium dimers bridged by amino-borane can form by a boronium-mediated route starting from amine-borane. These types of complexes are pre-catalysts for amine-borane dehydropolymerization, suggesting a possible role for bimetallic motifs in catalysis.