The assignment of 11 B and 1 H resonances in the post-reaction mixture from the dry synthesis of Li(BH3 NH2 BH2 NH2 BH3 )

We report a detailed 1 H NMR and 11 B NMR study of as synthesised Li ( BH 3 NH 2 BH 2 NH 2 BH 3 ) obtained in a novel dry-synthesis method. A combination of 1D and 2D single- and triple-quantum techniques was used for the assignment of all observed signals. Minor side-products and reactants were detected in the product: NH 3 BH 3 , Li ( NH 2 BH 3 ) , Li ( BH 4 ) , and two yet unknown salts containing 7-membered chain anions: ( BH 3 NH 2 BH 2 NH 2 BH 2 NH 2 BH 3 ) - and ( BH ( NH 2 BH 3 ) 3 ) - . We believe the assignment provided within this study might be helpful when analysing the mixtures containing numerous ammonia borane derivatives, which often give overlapping signals that are hard to distinguish.

In-Situ and Real-time Monitoring of Mechanochemical Preparation of Li2 Mg(NH2 BH3 )4 and Na2 Mg(NH2 BH3 )4 and Their Thermal Dehydrogenation

For the first time, in situ monitoring of uninterrupted mechanochemical synthesis of two bimetallic amidoboranes, M₂ Mg(NH₂ BH₃ )₄ (M=Li, Na), by means of Raman spectroscopy, has been applied. This approach allowed real-time observation of key intermediate phases, and a straightforward follow-up of the reaction course. Detailed analysis of time-dependent spectra revealed a two-step mechanism through MNH₂ BH₃ ⋅NH₃ BH₃ adducts as key intermediate phases which further reacted with MgH₂ , giving M₂ Mg(NH₂ BH₃ )₄ as final products. The intermediates partially take a competitive pathway toward the oligomeric M(BH₃ NH₂ BH₂ NH₂ BH₃ ) phases. The crystal structure of the novel bimetallic amidoborane Li₂ Mg(NH₂ BH₃ )₄ was solved from high-resolution powder diffraction data and showed an analogous metal coordination to Na₂ Mg(NH₂ BH₃ )₄ , but a significantly different crystal packing. Li₂ Mg(NH₂ BH₃ )₄ thermally dehydrogenates releasing highly pure H₂ in the amount of 7 wt.%, and at a lower temperature then its sodium analogue, making it significantly more viable for practical applications.