The decomposition of α-LiN2H3BH3: an unexpected hydrogen release from a homopolar proton-proton pathway

The intermolecular interactions of N-H center dot center dot center dot 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 alpha-LiN2H3BD3, however, indicate that the initial dehydrogenation occurs through a homopolar N-H center dot center dot center dot H-N (proton-proton) pathway, followed by the N-H center dot center dot center dot B-H (proton-hydride) and B-H center dot center dot center dot 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.