Structural diversity in polyamine Lewis base stabilised lithium aryloxides

Five new lithium aryloxide complexes stabilised by polyamine ligands have been synthesised by simple deprotonation reactions of the parent aryl alcohols H-OAr [OAr = OC6H5, OC6H2-2,4,6-(Me)(3) and OC6H2-2,6-(Bu-t)(2)-4-(Me)] with LiN(SiMe3)(2) in the presence of the Lewis bases N,N,N',N'-tetramethylethylenediamine (TMEDA) and N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA). All the compounds have been characterised by multinuclear NMR and X-ray crystallographic studies. The PMDETA derivative of the phenol adopts a tetrameric ladder-like structural motif in the solid state, exhibiting an unusual bridging coordination mode of the N-donor ligand. The 2,4,6-trimethylphenol derivatives exhibit dimeric (TMEDA), and tetrameric (PMDETA) structural motifs in the solid state. Meanwhile, the TMEDA and PMDETA derivatives of the sterically hindered 2,6-di-tert-butyl-4-methylphenol exhibit a rare monomeric structural motifs, which appears to remain unaltered in C6D6 solution.