Solid-State Structures of Primary Long-Chain Alkylamine Borane Adducts - Synthesis, Properties and Computational Analysis

Two new members of the amine boranes family are hexadecylamine borane C16H33NH2BH3 (C16AB) and octadecylamine borane C18H35NH2BH3 (C18AB). They are easily synthesized by reaction of the corresponding amines with borane dimethyl sulfide. Both are white solids; they are crystalline and isostructural (monoclinic, s.g. P2(1)/a (No. 14)). Their successful synthesis has been verified by molecular (FTIR, Raman, NMR) and structural analyses as well as computational calculations (e. g. Mulliken charges). These analyses have also pointed out the existence of dihydrogen bonds between H delta+ of NH2 of one molecule and H delta- of BH3 of another molecule. The thermal stability of C16AB and C18AB was studied. Both solids melts at 70-80 degrees C; between 100 and ca. 210 degrees C they dehydrogenate while releasing 1.1-1.4 wt% of pure H-2; and, above 210 degrees C, they decompose in high extent. All of these findings may open the way to future works on molecular self-assembly, synthesis of advanced materials and hydrogen storage. This is discussed hereafter.