文献类型：期刊文献

英文题名：Exploring Steric Effects of Zinc Complexes Bearing Achiral Benzoxazolyl Aminophenolate Ligands in Isoselective Polymerization of rac-Lactide

作者：Hu, Jianwen;Kan, Chao;Ma, Haiyan[1]

机构：[1]East China Univ Sci & Technol, Sch Chem & Mol Engn, Shanghai Key Lab Funct Mat Chem, 130 Meilong Rd, Shanghai 200237, Peoples R China; East China Univ Sci & Technol, Sch Chem & Mol Engn, Lab Organometall Chem, 130 Meilong Rd, Shanghai 200237, Peoples R China

年份：2018

卷号：57

期号：17

起止页码：11240

外文期刊名：INORGANIC CHEMISTRY

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000443923700079)】；

基金：This work was subsidized by the National Natural Science Foundation of China (NNSFC, Grant 21474028) and the Fundamental Research Funds for the Central Universities (Grant WD1113011). All financial support is gratefully acknowledged. H.M. also thanks the very kind donation of a Braun glovebox by AvH foundation.

语种：英文

摘要：A series of tridentate achiral benzoxazolylbased aminophenolate zinc complexes, LZnN(SiMe3)(2) (L = 2-{[benzoxazoly-CH2N(R-3)-]CH2}-6-R-1-4-R-2-C6H2O, R-1 = R-2 = Cl, R-3 = Bn (1); R-1 = R-2 = Bu-t, R-3 = Bn (2); R-1 = trityl, R-2 = Me: R-3 = Bn (3); R-3 = phenethyl (4); R-3 = 3-methylbutyl (7); R-3 = n-hexyl (8); R-3 = cyclopentyl (9); R-3 = cyclooctyl (11); R-3 = 1-adamantyl (12)), was synthesized via the reactions of Zn[N(SiMe3)(2)](2) and 1 equiv of the corresponding aminophenol proligands. All of the complexes were obtained as racemates, and the X-ray diffraction studies confirmed the monomeric structures of typical complexes 11 and 12, where the metal center is tetra-coordinated by three donors of the aminophenolate ligand and one silylamido group. All of the complexes proved to be efficient initiators for the ring-opening polymerization of rac-lactide (rac-LA) at ambient temperature, and the polymerizations were better controlled in the presence of 2-propanol. The substituents on the ortho-position of the phenoxide unit of the ligand and the skeleton nitrogen atom show significant influences on the stereoselectivity of the corresponding complex toward the polymerization of rac-LA, leading to the production of heterotactic biased polylactide (PLA) by complexes 1 and 2 (P-m = 0.40-0.44) and moderately to highly isotactic PLA by complexes 3-12 (P-m = 0.74-0.89). Detailed mechanism studies and microstructure analysis of typical PLA samples revealed that these zinc initiators afforded isotactic stereoblock PLAs via a chain-end control mechanism, and there is no obvious polymer exchange process during the polymerization process.