New alkali metal primary amide ladder structures derived from tBuNH(2): building cisoid and transoid ring conformations into ladder frameworks

Two novel alkali metal amide ladder complexes have been synthesised and crystallographically characterised. Derived from the same primary amine precursor (tBuNH(2)), they represent important additions to the series of ladder arrangements previously established within secondary amide chemistry. Thus the sodium amide.amine complex [{[tBuN(H)Na](3) . H(2)NtBu}(x)] forms an infinite wavelike ladder structure. Covering three nitrogen-sodium rungs, its curved sections display a cisoid conformation of amide substituents; but where these curved sections fuse, a transoid conformation is found. Every third sodium cation along the ladder framework is ligated by a tert-butylamine solvent molecule. In contrast, the heterobimetallic derivative, [{[tBuN(H)](2)LiNa . tmeda}(2)], adopts a finite oligomeric ladder structure limited to only four nitrogen-metal rungs in length. The central rungs contain lithium, while the outer rungs contain sodium. As in the all-sodium structure, the ladder is curved; there is a mixture of cisoid and transoid ring conformations within its framework. TMEDA solvent molecules complete the structure by chelating the sodium cations at the ladder ends.