A number of unreported zinc complexes based on tridentate O, N, O-type half-Salen ligands were prepared. All the complexes were characterized by H-1, C-13 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. (C) 2015 Elsevier Ltd. All rights reserved.