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 an d crystallographically characterised. Derived from the same primary am ine precursor (tBuNH(2)), they represent important additions to the se ries of ladder arrangements previously established within secondary am ide chemistry. Thus the sodium amide.amine complex [{[tBuN(H)Na](3) . H(2)NtBu}(x)] forms an infinite wavelike ladder structure. Covering th ree nitrogen-sodium rungs, its curved sections display a cisoid confor mation of amide substituents; but where these curved sections fuse, a transoid conformation is found. Every third sodium cation along the la dder framework is ligated by a tert-butylamine solvent molecule. In co ntrast, the heterobimetallic derivative, [{[tBuN(H)](2)LiNa . tmeda}(2 )], adopts a finite oligomeric ladder structure limited to only four n itrogen-metal rungs in length. The central rungs contain lithium, whil e the outer rungs contain sodium. As in the all-sodium structure, the ladder is curved; there is a mixture of cisoid and transoid ring confo rmations within its framework. TMEDA solvent molecules complete the st ructure by chelating the sodium cations at the ladder ends.