Syntheses and structural studies of [2-(6-methyl)pyridyl]- and (8-quinolyl)trimethylsilylamido-lithium complexes

Abstract

Reactions of 6-methyl-2-trimethylsilyaminopyridine (Hmtmsap) with LiBuⁿ in hexane–diethyl ether, [LiBuⁿ(tmen)](tmen =N,N,N′,N′-tetramethylethylenediamine), or LiBuⁿ in hexane, yield, respectively, [{Li(OEt₂)(mtmsap)}₂](1), [Li(tmen)(mtmsap)](2), and [{Li(mtmsap)}₂](3). Mixtures (5:2) of Hmtmsap and 2-amino-6-methylpyridine (Hamp) yield the complex molecule [Li₇(mtmsap)₅(amp)₂](4). Corresponding compounds, prepared via metallation of 8-trimethylsilyl-aminoquinoline (Htmsaq), are [{Li(OEt₂)(tmsaq)}₂](5), [Li(tmen)(tmsaq)](6), and [{Li(tmsaq)}₂](7). Compounds (1), (2), and (4)–(7) are crystalline and have been characterized by X-ray structure determination. Compounds (1) and (5) are dimeric with four-co-ordinate lithium centres, the amido-N bridging; (7) is based on the structure of (5), but with a gap in the metal co-ordination spheres where the ether ligands reside in (5). Compounds (2) and (6) are monomeric with four-co-ordinate metal centres, and (4) has seven different metal environments, each either three- or four-co-ordinate and with both bridging amido-N and pyridine-N centres.