Zinc complexes bearing tridentate O,N,O-type half-Salen ligands for ring-opening polymerization of lactide

•A number of half-Salen zinc Schiff-base complexes were synthesized.•These complexes were active in lactide polymerization.•The activity of these complexes was closely related to their structures.

A number of unreported zinc complexes based on tridentate O,N,O-type half-Salen ligands were prepared. All the complexes were characterized by 1H, 13C NMR and elemental analysis. These complexes were used as catalysts with 2-propanol for the ring-opening polymerization of l-lactide and rac-lactide. They were effective in lactide polymerization with good conversions. And polymerizations were living with the narrow molar mass distributions. The bulky substituents with relatively larger steric hindrance of the ligands coordinated to the central metal centers had relatively low polymerizing activity.

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