Homopolar Dihydrogen Bonding in Alkali-Metal Amidoboranes and Its Implications for Hydrogen Storage

摘要

The solid-state structures of LiNH_2BH_3 and NaNH_2BH_3 have been shown recently to exhibit intricate M~δ+ • • • ~δ-H-B and N-H~δ+ • • • ~δ-H-B interactions. However, closer inspection of these structures reveals additional homopolar H • • • H interactions, viz., B-H~δ- • • •~δ-H-B and N-H~δ+• • • ~δ+H-N, which contribute to the relative stability of the extended structures of these crystalline materials. In addition, an NMR study of the isotopomer LiND_2BH_3 shows that a significant quantity of H_2 is desorbed thermally along with HD, which can only arise from hydride-hydride interactions, either directly from B-H~δ-• • • ~δ-H-B moieties or indirectly through the participation of Li-H intermediates.