Unexpected Chemistry of Molecular Precursors to Boron Arsenide Materials

Simple arsine-boranes were explored as precursors to the semiconductor ceramic cubic boron arsenide (BAs). In preparing Ph 2 AsHBH 3 , spontaneous hydrogen loss was observed to give cyclo -arsine boranes, (Ph 2 AsBH 2 ) n , and other products. At low temperature, Ph 2 AsHBH 3 could be isolated and observed to engage in spontaneous hydrogen to form (Ph 2 AsBH 2 ) n rings. These rings exhibit dynamic behavior through varying ratios of n = 3, 4, but n = 5 could be observed and promoted under non-equilibrium conditions. Interestingly, the arsine substrate appears catalyze the decomposition of THF-borane, and simple boranes are catalysts for the dehydrocoupling of Ph 2 AsH. However, the most chemically odd observation was the relative lability of As–C bonds under mild conditions. While (Ph 2 AsBH 2 ) n and Ph 3 AsBH 3 are competent substrates for the formation of boron arsenide products under pyrolysis conditions, particularly in air, ceramic yields suffer from volatility of the substate under pyrolysis conditions and competitive arsenic oxidation occurred unpredictably. Arsenic chemistry aside, this overall strategy is valid for the production bulk boron arsenide substrates, through further substrate development is needed.