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(Me)Ph(OMe), HON(Me)Ph(SMe), HON(Me)C(OMe) or HON(Me)C(NMe2) [HON(Me)Ph(OMe) = (2-OMeC(6)H(4)CH(2)) N(Me)(CH(2)-2-IIO-3,5-C(6)H(2)((t)Bu)(2)); IION(Me)Ph(SMe) = (2-SMe-C(6)H(4)CII(2)) N(Me)(CII(2)-2-IIO-3,5-C(6)H(2)(tBu) 2); HONMeCOMe = (MeOCH(2)CH(2)) N(Me)(CH(2)-2-IIO-3,5-C(6)H(2)((t)Bu)(2)); HON(Me)C(NMe2) = (Me(2)NCH(2)CH(2)) N(Me)(CH(2)-2-IIO-3,5-C(6)H(2)((t)Bu)(2))] with 1.1-1.3 molar equivalents of (n)BuLi in diethyl ether solution afford (LiON(Me)Ph(OMe)) 2 (3), (LiON(Me)Ph(SMe)) 2 (4), (LiON(Me)C(OMe)) 2 (5) and (LiON(Me)C(NMe2))(2) (6) as dinuclear lithium complexes. The BnOH adduct of 5, (BnOH)(LiON(Me)C(OMe)) (7), was prepared from the reaction of 5 and BnOH in diethyl ether solution. The molecular structures are reported for ligand precursor HONMePhSMe 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.