A series of lithium complexes bearing NNO-tridentate Schiff base ligands were successfully synthesized, characterized by X-ray crystallography, and investigated as catalysts for the ring opening polymerization of L-lactide. The electronic effects and steric bulk of the ligands coordinated to Li atoms were determined to greatly influence its catalytic properties. Li complexes with electron-donating or bulky substituents of ligands both revealed higher catalytic activities than did the electron-withdrawing groups during polymerization. Among the Li complexes, [L-Bu-Li](2) with the two tert-butyl groups exhibited the highest catalytic activity and outstanding controllability. (C) 2018 Elsevier Ltd. All rights reserved.