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 )

Abstract

We report a detailed ${}^{1}H$ NMR and ${}^{11}B$ NMR study of as synthesised $\text{Li}\left({\text{BH}}_3{\text{NH}}_2{\text{BH}}_2{\text{NH}}_2{\text{BH}}_3\right)$ 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: ${\text{NH}}_3{\text{BH}}_3$ , $\text{Li}\left({\text{NH}}_2{\text{BH}}_3\right)$ , $\text{Li}\left({\text{BH}}_4\right)$ , and two yet unknown salts containing 7-membered chain anions: ${\left({\text{BH}}_3{\text{NH}}_2{\text{BH}}_2{\text{NH}}_2{\text{BH}}_2{\text{NH}}_2{\text{BH}}_3\right)}^{-}$ and ${\left(\text{BH}{\left({\text{NH}}_2{\text{BH}}_3\right)}_3\right)}^{-}$ . 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.

Keywords: 1 H NMR; 11 B NMR; Li(B3N2); amidoboranes; ammonia borane.