Borohydride-induced destabilization of hydrazine borane

We investigated the destabilization of 4 mol of hydrazine borane N₂H₄BH₃ in the presence of 1 mol of an alkaline borohydride (LiBH₄ or NaBH₄) and, in a second step, of 1 mol of NH₃BH₃ in addition. The destabilization was followed by TGA, DSC and μGC. The solid residues were analyzed by solid-state ¹¹B NMR, IR and XRD. The presence of the borohydride effectively destabilizes N₂H₄BH₃ which is thus able to liberate H₂ from 50 °C. Seeing the results from the other side, one could consider that the alkaline borohydrides are destabilized by N₂H₄BH₃. Such destabilization approach is attractive as it involves boron-based materials only. The best decomposition results were obtained with the sample containing 4 mol of N₂H₄BH₃ and 1 mol of LiBH₄ (containing 16 equiv. H₂). Upon heating up to 300 °C at 5 °C min⁻¹, this sample releases 12.1 mol of H₂ (dehydrogenation extent of 76%) and 1.1 mol of N₂H₄. A solid residue of empirical formulae LiB₅N_5.8H_3.4 is formed. It is composed of polyborazylene- and/or boron nitride-like materials. This is an attractive feature as it implies recyclability of the polymer and elaboration of inorganic ceramics at relatively low temperatures. Our main results are reported herein.