Department of Chemistry, Indian Institute of Technology Madras, Chennai-600 036, Tamil Nadu, India.
Dalton Trans. 2013 Dec 14;42(46):16412-27. doi: 10.1039/c3dt52065j.
A series of Ti(IV), Zr(IV) and Hf(IV) benzotriazole phenoxide (BTP) complexes were synthesized and characterized by various spectroscopic techniques, elemental analysis and X-ray crystallography. The monosubstituted Zr(IV) BTP complexes [(μ-L)Zr(O(i)Pr)3]2 1-3 [L = (C1)BTP-H (1), (TCl)BTP-H (2), (pent)BTP-H (3)] and tetrasubstituted Zr(IV), Hf(IV) complexes ZrL4 4-6 [L = (C1)BTP-H (4), (TCl)BTP-H (5), (pent)BTP-H (6)] and HfL4 7-9 [L = (C1)BTP-H (7), (TCl)BTP-H (8), (pent)BTP-H (9)] were prepared by the reaction of Zr(O(i)Pr)4·((i)PrOH) and Hf(O(t)Bu)4 in toluene with the respective ligands in different stoichiometric proportions. The reaction between BTP and TiCl4 and ZrCl4 and HfCl4 in a 2 : 1 stoichiometric reaction resulted in the formation of disubstituted group IV chloride complexes L2MCl2 10-12 [L = (C1)BTP-H, M = Ti, Zr and Hf]. The molecular structures of complexes 1, 4, 7, 10, 11, and 12 were determined by single-crystal X-ray studies. The X-ray structure of 1 reveals a dimeric Zr(IV) complex containing a Zr2O2 core bridged through the oxygen atoms of the phenoxide groups. Each Zr atom is distorted from an octahedral symmetry. These complexes were found to be active towards the ring-opening polymerization (ROP) of L-lactide (L-LA) and rac-lactide (rac-LA). Complex 1 produced highly heterotactic poly(lactic acid) (PLA) from rac-LA under melt conditions with narrow molecular weight distributions (MWDs) and well controlled number average molecular weights (M(n)). Additionally, epoxide polymerizations using rac-cyclohexene oxide (CHO), rac-propylene oxide (PO), and rac-styrene oxide (SO) were also carried out with these complexes. The yield and molecular weight of the polymer was found to increase with the extension of reaction time. Compounds 1-12 were activated by methylaluminoxane (MAO) and show good activity for ethylene polymerization and produced high molecular weight polyethylene.
一系列 Ti(IV)、Zr(IV) 和 Hf(IV) 苯并三唑苯氧基（BTP）配合物通过各种光谱技术、元素分析和 X 射线晶体学进行了合成和表征。单取代的 Zr(IV) BTP 配合物 [(μ-L)Zr(O(i)Pr)3]2 1-3 [L = (C1)BTP-H (1)、(TCl)BTP-H (2)、(pent)BTP-H (3)] 和四取代的 Zr(IV)、Hf(IV) 配合物 ZrL4 4-6 [L = (C1)BTP-H (4)、(TCl)BTP-H (5)、(pent)BTP-H (6)] 和 HfL4 7-9 [L = (C1)BTP-H (7)、(TCl)BTP-H (8)、(pent)BTP-H (9)] 通过 Zr(O(i)Pr)4·((i)PrOH) 和 Hf(O(t)Bu)4 在甲苯中与相应配体以不同的化学计量比反应制备。BTP 与 TiCl4 和 ZrCl4 和 HfCl4 的反应以 2:1 的化学计量比形成二取代的 IV 族氯化物配合物 L2MCl2 10-12 [L = (C1)BTP-H，M = Ti、Zr 和 Hf]。配合物 1、4、7、10、11 和 12 的分子结构通过单晶 X 射线研究确定。1 的 X 射线结构揭示了一个二聚 Zr(IV) 配合物，其中包含一个通过苯氧基氧原子桥接的 Zr2O2 核。每个 Zr 原子都偏离八面体对称。这些配合物被发现对 L-丙交酯（L-LA）和 rac-丙交酯（rac-LA）的开环聚合（ROP）具有活性。配合物 1 在熔融条件下由 rac-LA 产生高度不等规的聚乳酸（PLA），具有窄分子量分布（MWD）和受控的数均分子量（M(n)）。此外，还使用这些配合物进行了 rac-环氧化物（CHO）、rac-环氧丙烷（PO）和 rac-苯乙烯氧化物（SO）的环氧化物聚合。聚合物的产率和分子量随着反应时间的延长而增加。化合物 1-12 被甲基铝氧烷（MAO）激活，对乙烯聚合表现出良好的活性，生成高分子量聚乙烯。
