Lithium Hydrazinidoborane Ammoniate LiN2H3BH3·0.25NH3, a Derivative of Hydrazine Borane

Boron- and nitrogen-based materials have shown to be attractive for solid-state chemical hydrogen storage owing to gravimetric hydrogen densities higher than 10 wt% H. Herein, we report a new derivative of hydrazine borane N₂H₄BH₃, namely lithium hydrazinidoborane ammoniate LiN₂H₃BH₃·0.25NH₃. It is easily obtained in ambient conditions by ball-milling N₂H₄BH₃ and lithium amide LiNH₂ taken in equimolar amounts. Both compounds react without loss of any H atoms. The molecular and crystallographic structures of our new compound have been confirmed by NMR/FTIR spectroscopy and powder X-ray diffraction. The complexation of the entity LiN₂H₃BH₃ by some NH₃ has been also established by thermogravimetric and calorimetric analyses. In our conditions, LiN₂H₃BH₃·0.25NH₃ has been shown to be able to release H₂ at temperatures lower than the parent N₂H₄BH₃ or the counterpart LiN₂H₃BH₃. It also liberates non-negligible amounts of NH₃ at temperatures lower than 100 °C. This is actually quite detrimental for chemical H storage, but alternatively LiN₂H₃BH₃·0.25NH₃ might be seen as a potential NH₃ carrier.