含O,O,O-及N,N,N-三牙配位基之金屬錯合物之合成、結構解析及其在左旋乳酸交酯與環己內酯開環聚合反應之應用

Abstract

A family of metal complexes of the type ([(L1-H)Li]2 (1), [(L1-H)Li(THF)]2 (2), [(L1-H)Li(BnOH)]2 (3), [L1Zn]2 (4), [L1AlOBn]2 (5), L2MgBu (6) and L2ZnEt (7)), where L1-H2 = O,O,O-tridentate bis(phenolate) ligand and L2-H = N,N,N-anilido-aldimine ligand, has been synthesized and characterized, including a structural determination of complexes 1, 2, 3, 5, 6 and 7. Their suitability for initiating the ring-opening polymerization (ROP) of L-lactide (LA) and e-caprolactone (CL) has been investigated in the presence or absence of benzyl alcohol (BnOH). All the metal complexes have shown efficient and controlled activity toward the ring-opening polymerization of cyclicesters as shown by the linear relationship between the percentage conversion and the number-average molecular weight in short period of time. In the anilido–aldimine system, the activity of magnesium complex is higher than that of zinc complex, which is probably due to the better Lewis acidity and more oxophilic nature of magnesium metal. And for bis(phenolate) system, the activity of lithium complex is investigated for ROP of lactide where as aluminium and zinc complexes used for ROP of caprolactone. The polymerization kinetics using complex 7 in the presence of BnOH as an initiator was also studied, and the experimental results reveal that the rate of reaction is first-order dependence on monomer and second-order dependency on catalyst 7 concentration. On the basis of literature report, polymerization results and crystal structure of 2 and 3, a mechanism for ROP of lactide has been proposed.