Synthesis and energetic characterization of borane-amines on high-nitrogen heterocycles

Abstract. Over the last several decades, borane-amines have gathered attention in a variety of fields ranging from hydrogen storage materials to hypergolic fuels. Current approaches to hypergolic fuels center about hydrazine systems, which are exceptionally toxic in nature. Borane-amines have advantages over hydrazine fuels, as borane-amines are generally markedly less toxic than hydrazine in addition to retaining hypergolic functionality. In this work, new borane-amines were synthesized on high nitrogen content heterocycles by reacting the parent amine with two equivalents of borane dimethylsulfide (BMS) in anhydrous THF. Isolation of the relevant borane-amine is achieved by diluting the reaction with hexanes, which precipitates out the requisite borane-amine. Chemical identity of products was confirmed by x-ray crystallography, TGA, HRMS, 1H NMR, 13C NMR, and 11B NMR, while energetic impact and friction sensitivity testing were used to identify sensitivity to physical stimuli. Most isolated borane-amines decomposed in the presence of atmospheric moisture, save one. Additionally, some became sensitive to impact and friction stimuli. However, all novel borane-amines identified in this work retain the characteristic hypergolicity with white fuming nitric acid (WFNA) which is expected for borane-amines.