Synthesis of N,N,O-chelate zinc and aluminum complexes and their catalysis in the ring-opening polymerization of ε-caprolactone and rac-lactide
作者:Wei-Li Kong、Zuo-Yun Chai、Zhong-Xia Wang
DOI:10.1039/c4dt01364f
日期:——
Zinc and aluminum complexes supported by N,N,O-chelate ligands were synthesized and characterized. The zinc complexes [Zn(Et)2-OC(R1)CH}-6-(3,5-Me2C3HN2)C5H3N}]2 (R1 = Ph, 1a; R1 = But, 1b) were synthesized by reaction of ligand precursors 2-R1C(O)CH2}-6-(3,5-Me2C3HN2)C5H3N (R1 = Ph, HL1; R1 = But, HL2) with ZnEt2. The aluminum complexes [Al(R)22-OC(Ph)CH}-6-(3,5-Me2C3HN2)C5H3N}] (R = Me, 2a; R = Et, 2b) were synthesized by reaction of HL1 with AlMe3 or AlEt3. Similar treatment of the ligand precursor 2-Ph2C(OH)CH2}-6-(3,5-Me2C3HN2)C5H3N (HL3) with AlMe3 or AlEt3 afforded aluminum complexes [Al(R)22-OC(Ph)2CH2}-6-(3,5-Me2C3HN2)C5H3N}] (R = Me, 3a; R = Et, 3b). The complexes were characterized by 1H and 13C1H} NMR spectroscopy, elemental analyses and single crystal X-ray diffraction (for 1a, 1b, 2b and 3a). All the complexes are active to catalyze the ring-opening polymerization of ε-caprolactone in the presence of BnOH, leading to polycaprolactone with good molecular weight control and relatively narrow molecular weight distribution. The zinc complexes/BnOH showed good catalytic activity for the ring-opening polymerization of rac-lactide, displaying good molecular weight control and very narrow molecular weight distributions. The PLA catalyzed by complex 1a/BnOH showed somewhat hetero-stereoselectivity with Pr up to 0.73 when the polymerization was performed in THF at 0 °C. Complex 1a/BnOH also catalyzed block copolymerization of ε-CL and rac-LA with good molecular weight control of the polymer. Kinetic studies of the polymerization reactions were performed.
合成并表征了由 N,N,O-螯合物配体支持的锌和铝络合物。配体前体 2-R1C(O)CH2}-6-(3,5-Me2C3HN2)C5H3N(R1 = Ph,HL1;R1 = But,HL2)与 ZnEt2 反应合成了锌配合物 [Zn(Et)2-OC(R1)CH}-6-(3,5-Me2C3HN2)C5H3N}]2(R1 = Ph,1a;R1 = But,1b)。铝配合物 [Al(R)22-OC(Ph)CH}-6-(3,5-Me2C3HN2)C5H3N}] (R = Me,2a;R = Et,2b)是通过 HL1 与 AlMe3 或 AlEt3 反应合成的。将配体前体 2-Ph2C(OH)CH2}-6-(3,5-Me2C3HN2)C5H3N (HL3) 与 AlMe3 或 AlEt3 进行类似处理,可得到铝配合物 [Al(R)22-OC(Ph)2CH2}-6-(3,5-Me2C3HN2)C5H3N}] (R = Me,3a;R = Et,3b)。这些复合物通过 1H 和 13C1H}1a、1b、2b 和 3a 的)单晶 X 射线衍射。所有配合物在 BnOH 的存在下都能有效催化δ-己内酯的开环聚合反应,从而生成分子量控制良好且分子量分布相对较窄的聚己内酯。锌配合物/BnOH 对 rac-内酯的开环聚合具有良好的催化活性,显示出良好的分子量控制和非常窄的分子量分布。复合物 1a/BnOH 催化的聚乳酸具有一定的异质-立体选择性,在 0 °C 的 THF 中进行聚合时,Pr 可高达 0.73。复合物 1a/BnOH 还能催化 ε-CL 和 rac-LA 的嵌段共聚,并能很好地控制聚合物的分子量。对聚合反应进行了动力学研究。