Preparation of Tridentate Pyrazolonate and Schiff base Calcium Complexes and Their Applications in Ring-Opening Polymerization of Lactides

• Main Authors: Mon-Wei Hsiao, 蕭孟維
• Other Authors: Chu-Chieh Lin
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/79948620820148986098

博士 === 國立中興大學 === 化學系所 === 102 === This thesis describes the synthesize and characterization of calcium complexes based on tridentate pyrazolonate and Schiff base ligands, all of the complexes are good catalysts in ring-opening polymerization of L-lactide. Detailed mechanism investigation was proceeded via time-dependent 1H NMR and kinetic studies. Part 1 A series of calcium complexes supported by NNO-tridentate pyrazolonate ligands have been synthesized and characterized. X-ray structural studies indicate that these complexes bear a mononuclear feature with hexa-coordinated calcium centers bonding to two pyrazolonate ligands. Polymerization of L-lactide catalyzed by these complexes proceeds rapidly and well controlled in the presence of a variety of alcohols. In addition, these complexes reveal good immortal feature with the addition of up to 80 equiv of benzyl alcohol as a transfer agent. Furthermore, kinetic studies show ROP of L-lactide is a first-order dependency on [LA] and a second-order dependency on [BnOH]. Part 2 Tridentate Schiff base calcium complexes have been prepared and characterized. These complexes have been employed as catalysts of ring-opening polymerization of lactides, and reveals good activities and control manner. Schiff base calcium complexes show better activities as compared to the calcium complexes with similar pyrazolonate ligands reported, and the donor groups at the arm of ligands have significant effect on the catalytic activities. Kinetic studies reveal a first order dependency on [LA] and a second order dependency on [BnOH]. The dissociation of ligand from the complex was observed during addition of alcohol, indicating forming another active species similar to that reported in the literature.