Structural and catalytic studies of lithium complexes bearing pendant aminophenolate ligands

Abstract

Lithium complexes bearing mono-anionic aminophenolate ligands are described. Reactions of ligand precursors HON^MePh^OMe, HON^MePh^SMe, HON^MeC^OMe or HON^MeC^NMe2 [HON^MePh^OMe = (2-OMeC₆H₄CH₂)N(Me)(CH₂-2-HO-3,5-C₆H₂(^tBu)₂); HON^MePh^SMe= (2-SMe-C₆H₄CH₂)N(Me)(CH₂-2-HO-3,5-C₆H₂(^tBu)₂); HON^MeC^OMe = (MeOCH₂CH₂)N(Me)(CH₂-2-HO-3,5-C₆H₂(^tBu)₂); HON^MeC^NMe2 = (Me₂NCH₂CH₂)N(Me)(CH₂-2-HO-3,5-C₆H₂(^tBu)₂)] with 1.1–1.3 molar equivalents of ⁿBuLi in diethyl ether solution afford (LiON^MePh^OMe)₂ (3), (LiON^MePh^SMe)₂ (4), (LiON^MeC^OMe)₂ (5) and (LiON^MeC^NMe2)₂ (6) as dinuclear lithium complexes. The BnOH adduct of 5, (BnOH)(LiON^MeC^OMe) (7), was prepared from the reaction of 5 and BnOH in diethyl ether solution. The molecular structures are reported for ligand precursor HON^MePh^SMe and compounds 3–5 and 7. These dinuclear lithium complexes show excellent catalytic activities toward the ring-opening polymerization of L-lactide in the presence of benzyl alcohol.