Homopolar dihydrogen bonding in alkali metal amidoboranes: crystal engineering of low-dimensional molecular materials.

Hydrogen bonding is a predominant interaction in supramolecular chemistry. The absence of a conventional hydrogen bond donor in LiNMe(2)BH(3) and KNMe(2)BH(3) results in the formation of elaborate M···H-B polymeric arrays supported by heteropolar and homopolar H···H bonding, in a unique synergistic combination of unconventional intermolecular interactions.

Homopolar dihydrogen bonding in alkali-metal amidoboranes and its implications for hydrogen storage.

The solid-state structures of LiNH(2)BH(3) and NaNH(2)BH(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(2)BH(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.