Structural diversity in polyamine Lewis base stabilised lithium aryloxides

Abstract

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-(^tBu)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.