Structural and catalytic studies of zinc complexes containing amido-oxazolinate ligands

Abstract

Several zinc complexes bearing amido-oxazolinate ligands are described. Reactions of ligand precursors, HNC(2)(E)Oxa (HNC(2)(E)Oxa = HNC(2)(Me)Oxa, HNC(2)(OMe)Oxa, HNC(2)(StBu)Oxa and HNC(2)(NMe2)Oxa) or HNPh(SMe)Oxa, with half or one molar equivalent of ZnEt(2) afford bis(chelate) zinc complexes, (NC(2)(E)Oxa)(2)Zn [C(2)(E) = propyl, (1); C(2)(E) = 2-methoxyethyl, (2); C(2)(E) = 2-N,N'-dimethylethyl, (3)] or zinc ethyl complexes, (NC(2)(StBu)Oxa)ZnEt(4) and (NPh(SMe)Oxa)ZnEt(5), using tetrahydrofuran or hexane as solvents. The zinc benzyl oxide complexes, [(NC(2)(E)Oxa)Zn(μ-OBn)](2) [C(2)(E) = propyl, (6); C(2)(E) = 2-methoxyethyl, (7); C(2)(E) = 2-tert-butylthioethyl, (8)], are obtained from the reactions of ligand precursors, HNC(2)(E)Oxa, with one molar equivalent of ZnEt(OBn) (generated in situ on 1:1 ratio of ZnEt(2) and BnOH) in tetrahydrofuran. The molecular structures are reported for compounds 1, 3, 5, 6 and 7. All eight compounds were assessed as efficient catalyst precursors towards the ring-opening polymerization of L-lactide and ε-caprolactone.