Exploring the reactivity of iridium and rhodium bisphosphine complexes with amine-boranes

This thesis details the reactivity of amine-boranes with iridium and rhodium bis-phosphine complexes and offers mechanistic insights into the catalytic dehydrocoupling of amineboranes to produce polyamino-boranes [H2BNRH]n that are isoelectronic to the societally ubiquitous polyolefins [H2CCRH]n. The 18-electron cationic complexes [Ir(H)2(PCy3)(η2-H2)2][BArF 4] (II) and [Rh(PP)(η6- C6H5F)][BArF 4] (VI and VII) have been used to study the catalytic dehydrogenation of Nsubstituted amine-boranes (H3BâNRH2, Chapter 2 and 3), B,N-substituted amine-boranes (PhH2BâNRMe2, Chapter 4) and cyclic amine-boranes (Chapter 5). The stoichiometric (1 equivalent) reactions of metal-complexes (II, III and VI) with amineboranes result in the formation of metalâââamine-borane complexes which have either been isolated in the solid state or characterised in situ in the solution state by NMR spectroscopy and ESI-MS. Further addition of amine-boranes to these metalâââamineborane complexes results in the dehydrogenation/dehydrocoupling of the amine-boranes. Direct intermediates involved in the catalytic dehydrogenation/dehydrocoupling processes have either been isolated or characterised in situ to gain insight into the dehydrogenation mechanism. Dehydrogenation mechanisms have been postulated based upon the observed intermediates, kinetic studies, and DFT calculations performed by Prof. Stuart A Macgregor (Heriot-Watt University, Edinburgh). Overall, a detailed investigation into the coordination chemistry of metalâââamine-borane complexes and their subsequent dehydrogenation is reported.