Study of the Reaction of Pentaborane with Hydrazine and Substituted Hydrazines

摘要

Pentaborane and hydrazine were found to react in solution according to the following equation: B5H9 + 2 N2H4 yields B5N4H16 + 0.5 H2. The process includes an initial fast reaction followed by a slow reaction that evolves hydrogen and an insoluble solid product. The hydrogen evolution was found to be a first-order process with a rate constant of 1.74=0.1 x 0.0001/sec at 25C. The ratedetermining step was found to be dependent only on the hydrazine concentration. When monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine were used in place of normal hydrazine, the respective reactions were as follows: B5H9 + 4 CH3NHNH2 yields B5N8H20 (CH3)4 + 0.5 H2, and B5H9 + 2 H2NN(CH3)2 yields B5N4H13(CH3)4. The hydrogen from the reaction involving MMH also evolved by a first-order process, and the postulated mechanism is the same. The products of the pentaborane-hydrazine and pentaborane-MMH reactions are insoluble in nonpolar solvents. They thermally decompose, evolving hydrogen. It is believed that the products are polymeric substances. Attempts to obtain a definitive structure for the insoluble products by nuclear-magneticresonance techniques and high-resolution infrared analysis were unsuccessful. (Author)