Synthesis, characterization, and catalytic activity of lithium complexes bearing NNO-tridentate Schiff base ligands toward ring-opening polymerization of l-lactide

Abstract 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.