Sumrit Pattarawut, Chuawong Pitak, Nanok Tanin, Duangthongyou Tanwawan, Hormnirun Pimpa
Laboratory of Catalysts and Advanced Polymer Materials, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand.
Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, and Special Research Unit for Advanced Magnetic Resonance (AMR), Kasetsart University, Bangkok 10900, Thailand.
Dalton Trans. 2016 May 31;45(22):9250-66. doi: 10.1039/c6dt00990e.
Two series of four-coordinate aluminum () and five-coordinate aluminum () complexes were successfully synthesized via the reactions between the corresponding salicylbenzoxazole ligands and 1 or 0.5 equivalents of AlMe3, respectively. The synthesized aluminum complexes were characterized by (1)H and (13)C NMR spectroscopy and elemental analysis. The solid-state structures of complexes and were determined using single crystal X-ray diffraction. Upon addition of 1 equivalent of benzyl alcohol, all complexes were efficient initiators for the ring-opening polymerization (ROP) of rac-lactide (rac-LA) and ε-caprolactone (ε-CL). The polymerizations were living with a good control over molecular weights and molecular weight distributions. Under immortal polymerization conditions, all four-coordinate aluminum complexes () exhibited a living polymerization with the obtained molecular weights proportional to the ratio of monomer/benzyl alcohol and the PDIs were narrow. Kinetic studies revealed that both rac-LA and ε-CL polymerizations mediated by all complexes were first-order in monomers. The effects of ligand structure and coordination geometry on the catalytic activity and stereoselectivity were discussed. A good isoselectivity control was achieved for the polymerizations mediated by complexes (Pm = 0.75), (Pm = 0.74), and (Pm = 0.74).
通过相应的水杨基苯并恶唑配体分别与1当量或0.5当量的AlMe₃反应，成功合成了两个系列的四配位铝（）和五配位铝（）配合物。合成的铝配合物通过¹H和¹³C NMR光谱以及元素分析进行表征。配合物和的固态结构通过单晶X射线衍射确定。加入1当量的苄醇后，所有配合物都是外消旋丙交酯（rac-LA）和ε-己内酯（ε-CL）开环聚合（ROP）的有效引发剂。聚合反应具有活性，对分子量和分子量分布有良好的控制。在不死聚合条件下，所有四配位铝配合物（）都表现出活性聚合，得到的分子量与单体/苄醇的比例成正比，且多分散指数较窄。动力学研究表明，所有配合物介导的rac-LA和ε-CL聚合反应对单体均为一级反应。讨论了配体结构和配位几何对催化活性和立体选择性的影响。对于由配合物（Pm = 0.75）、（Pm = 0.74）和（Pm = 0.74）介导的聚合反应，实现了良好的等规选择性控制。
