The decomposition of α-LiN ₂ H ₃ BH ₃ : an unexpected hydrogen release from a homopolar proton–proton pathway

The intermolecular interactions of N–H⋯B–H (proton–hydride) have been considered to mediate the release of hydrogen from B–N-based complexes. Mass spectroscopy studies on the thermal decomposition of isotopomer α-LiN2H3BD3, however, indicate that the initial dehydrogenation occurs through a homopolar N–H⋯H–N (proton–proton) pathway, followed by the N–H⋯B–H (proton–hydride) and B–H⋯B–H (hydride–hydride) pathways. The unexpected scission of the N–H bonds prior to B–H bonds can be attributed to the molecular structure of Li[NH2–NH–BH3], in which the detachment of the (N)H atoms results in a significant reduction of the N–N and N–B bond length, hence reducing the (N)H detachment energy. The scission of N–H bonds further facilitates the detachment of the (B)H atom, therefore, promoting the following proton–hydride and hydride–hydride dehydrogenation pathways.