Catalytic Redistribution and Polymerization of Diborazanes: Unexpected Observation of Metal-Free Hydrogen Transfer between Aminoboranes and Amine-Boranes

Ir-catalyzed (20 degrees C) or thermal (70 degrees C) dehydrocoupling of the linear diborazane MeNH2-BH2-NHMe-BH3 led to the formation of poly- or oligoamino-boranes [MeNH-BH2](x) (x = 3 to > 1000) via an initial redistribution process that forms MeNH2 center dot BH3 and also transient MeNH=BH2, which exists in the predominantly metal-bound and free forms, respectively. Studies of analogous chemistry led to the discovery of metal-free hydrogenation of the B=N bond in the "model" aminoborane iPr(2)N=BH2 to give iPr(2)NH center dot BH3 upon treatment with the diborazane Me3N-BH2-NHMe-BH3 or amine-boranes RR'NH center dot BH3 (R, R' = H or Me).