Faculty of Chemistry, University of Duisburg-Essen and Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, S07 S03 C30, D-45141 Essen, Germany.
Dalton Trans. 2020 Oct 6;49(38):13475-13486. doi: 10.1039/d0dt02831b.
A series of gallium complexes L12Ga4Me8 (1), L22Ga4Me8 (2), and L32Ga4Me8 (3) was synthesized by reaction of GaMe3 with Schiff base ligands L1-3H2 (L1H2 = 2,4-di-tert-butyl-6-{[(3-hydroxypropyl)imino]methyl}phenol; L2H2 = 2,4-dichloro-6-{[(3-hydroxypropyl)imino]methyl}phenol; L3H2 = 4-tert-butyl-2-{[(3-hydroxypropyl)imino]methyl}phenol) and characterized by 1H, 13C NMR, IR spectroscopy, elemental analysis and single crystal X-ray analysis (1, 2), proving their tetranuclear structure in the solid state. Complexes 1-3 showed good catalytic activity in the ring opening homopolymerization (ROP) and ring opening copolymerization (ROcoP) of lactide (LA) and ε-caprolactone (ε-CL) in the presence of benzyl alcohol (BnOH) in toluene at 100 °C, yielding polymers with the expected average molecular weights (Mn) and narrow molecular weight distributions (MWD), as well as a high isoselectivity for the ROP of rac-lactide (rac-LA), yielding isotactic-enriched PLAs with Pm values up to 0.78. Kinetic studies with complex 1 proved the first order dependence on monomer concentration, while mechanistic studies confirmed the coordination insertion mechanistic (CIM) pathway. Sequential addition of monomers gave well defined diblock copolymers of PCL-b-PLLA and PLLA-b-PCL, proving the living character of the polymerization reactions. The catalysts also showed perfect selectivity for the copolymerization of cyclohexene oxide (CHO) with both succinic anhydride (SA) and maleic anhydride (MA) in the presence of BnOH and produced >99% alternating block copolymers.
一系列镓配合物 L12Ga4Me8（1）、L22Ga4Me8（2）和 L32Ga4Me8（3）是通过 GaMe3 与席夫碱配体 L1-3H2（L1H2=2,4-二叔丁基-6-[(3-羟丙基)亚氨基]甲基苯酚；L2H2=2,4-二氯-6-[(3-羟丙基)亚氨基]甲基苯酚；L3H2=4-叔丁基-2-[(3-羟丙基)亚氨基]甲基苯酚）反应合成的，并通过 1H、13C NMR、IR 光谱、元素分析和单晶 X 射线分析（1、2）进行了表征，证明了它们在固态下的四核结构。配合物 1-3 在 100°C 下，在苯甲醇（BnOH）存在下，在甲苯中对丙交酯（LA）和ε-己内酯（ε-CL）的开环均聚（ROP）和开环共聚（ROcoP）反应中表现出良好的催化活性，得到了预期平均分子量（Mn）和窄分子量分布（MWD）的聚合物，以及对 rac-丙交酯（rac-LA）的 ROP 具有高的等规选择性，得到 Pm 值高达 0.78 的等规富集 PLA。配合物 1 的动力学研究证明了单体浓度的一级依赖性，而机理研究证实了配位插入机理（CIM）途径。单体的顺序添加得到了具有明确定义的聚己内酯-b-聚丙交酯和聚丙交酯-b-聚己内酯嵌段共聚物，证明了聚合反应的活性。催化剂在苯甲醇存在下对环己烯氧化物（CHO）与丁二酸酐（SA）和马来酸酐（MA）的共聚反应也具有完美的选择性，生成了>99%的交替嵌段共聚物。
