Achiral lanthanide alkyl complexes bearing N,O multidentate ligands. Synthesis and catalysis of highly heteroselective ring-opening polymerization of rac-lactide

doi:10.1021/om0700359

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	Achiral lanthanide alkyl complexes bearing N,O multidentate ligands. Synthesis and catalysis of highly heteroselective ring-opening polymerization of rac-lactide
	Liu, Xinli ; Shang, Xiaomin ; Tang, Tao ; Hu, Ninghai ; Pei, Fengkui ; Cui, Dongmei ; Chen, Xuesi ; Jing, Xiabin
刊名	ORGANOMETALLICS
	2007-05-07
卷号	26 期号:10 页码:2747-2757
ISSN号	0276-7333
DOI	10.1021/om0700359
英文摘要	Alkane elimination reactions of amino-amino-bis(phenols) H2L1-4, Salan H2L5, and methoxy-beta-diimines HL6,7 with lanthanide tris(alkyl) s, Ln(CH2SiMe3)(3)(THF)(2) (Ln = Y, Lu), respectively, afforded a series of lanthanide alkyl complexes 1-8 with the release of tetramethylsilane. Complexes 1-6 are THF-solvated mono( alkyl) s stabilized by O, N, N, O-tetradentate ligands. Complexes 1-3 and 5 adopt twisted octahedral geometry, whereas 4 contains a tetragonal bipyramidal core. Bearing a monoanionic moiety L-6 (L-7), complex 7 ( 8) is a THF-free bis(alkyl). In complex 7, the O, N, N-tridentate ligand combined with two alkyl species forms a tetrahedral coordination core. Complexes 1, 2, and 3 displayed modest activity but high stereoselectivity for the polymerization of rac-lactide to give heterotactic polylactide with the racemic enchainment of monomer units P-r ranging from 0.95 to 0.99, the highest value reached to date. Complex 5 exhibited almost the same level of activity albeit with relatively low selectivity. In contrast, dramatic decreases in activity and stereoselectivity were found for complex 4. The Salan yttrium alkyl complex 6 was active but nonselective. Bis(alkyl) complexes 7 and 8 were more active than 1-3 toward polymerization of rac-LA, however, to afford atactic polylactides due to di-active sites. The ligand framework, especially the "bridge" between the two nitrogen atoms, played a significant role in governing the selectivity of the corresponding complexes via changing the geometry of the metal center. The NMR spectrum of the active species of the rac-lactide oligomer attached to complex 1 demonstrated a coordination-insertion mechanism. In addition it also confirmed that the geometry of the metal center of complex 1 in the solid state was retained in solution ( THF) during the polymerization, which contributed significantly to the high selectivity of the complex.
语种	英语
出版者	AMER CHEMICAL SOC
WOS记录号	WOS:000246027300038
内容类型	期刊论文
源URL	[http://ir.iccas.ac.cn/handle/121111/62675]
专题	中国科学院化学研究所
通讯作者	Cui, Dongmei
作者单位	1.Chinese Acad Sci, Changchun Inst Appl Chem, State Key Lab Polymer Phys & Chem, Changchun 130022, Peoples R China 2.Changchun Univ Technol, Dept Chem Engn, Changchun 130012, Peoples R China
推荐引用方式 GB/T 7714	Liu, Xinli,Shang, Xiaomin,Tang, Tao,et al. Achiral lanthanide alkyl complexes bearing N,O multidentate ligands. Synthesis and catalysis of highly heteroselective ring-opening polymerization of rac-lactide[J]. ORGANOMETALLICS,2007,26(10):2747-2757.
APA	Liu, Xinli.,Shang, Xiaomin.,Tang, Tao.,Hu, Ninghai.,Pei, Fengkui.,...&Jing, Xiabin.(2007).Achiral lanthanide alkyl complexes bearing N,O multidentate ligands. Synthesis and catalysis of highly heteroselective ring-opening polymerization of rac-lactide.ORGANOMETALLICS,26(10),2747-2757.
MLA	Liu, Xinli,et al."Achiral lanthanide alkyl complexes bearing N,O multidentate ligands. Synthesis and catalysis of highly heteroselective ring-opening polymerization of rac-lactide".ORGANOMETALLICS 26.10(2007):2747-2757.