Cubane-Type Polynuclear Zinc Complexes Containing Tridentate Schiff Base Ligands: Synthesis, Characterization, and Ring-Opening Polymerization Studies of rac-Lactide and e-Caprolactone

摘要

New polynuclear zinc complexes containing tridentate Schiff base ligands were successfully synthesized and fully characterized. The solid-state structure of the complexes was determined using single crystal X-ray diffraction. The complexes display a tetranuclear cubane-like core structure [Zn_4O_4] and sowed good catalytic activity towards the ring-opening polymerization (ROP) of rac-lactide (rac-LA) and ε-caprolactone (ε-CL) under solvent-free conditions. The polylactic acid (PLA) obtained from rac-LA showed isotactic enrichment, as proved by homonuclear decoupled ~1H-NMR analysis. These complexes also showed good activity and superior control towards the ROP of rac-LA and ε-CL in the presence of benzyl alcohol as a co-initiator. Furthermore, kinetic studies demonstrated that the ROP of rac-LA and ε-CL has a first order dependence on both monomer (rac-LA and ε-CL) and catalyst concentration.