Synthesis and Characterization of Lanthanide Amides Bearing Aminophenoxy Ligands and Their Catalytic Activity for the Polymerization of Lactides

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• 作者：Jie Zhang ; Jinshui Qiu ; Yingming Yao ; Yong Zhang ; Yaorong Wang ; Qi Shen
• 刊名：Organometallics
• 出版年：2012
• 出版时间：April 23, 2012
• 年：2012
• 卷：31
• 期：8
• 页码：3138-3148
• 全文大小：440K
• 年卷期：v.31,no.8(April 23, 2012)
• ISSN：1520-6041

文摘

A series of neutral lanthanide complexes supported by aminophenoxy ligands were synthesized, and their catalytic behavior in the polymerization of l-lactide and rac-lactide was explored. The amine elimination reactions of equimolar amounts of Ln[N(TMS)₂]₃(渭-Cl)Li(THF)₃ and aminophenol [HONH]¹ {[HONH]¹ = 2,6-Me₂-C₆H₄NHCH₂(3,5-^tBu₂-C₆H₂-2-OH)} in toluene gave the dimeric lanthanide complexes {[ON]¹Ln[ONH]¹}₂ (Ln = La (1), Nd (2)), whereas the similar reactions of La[N(TMS)₂]₃(THF)₂ or Ln[N(TMS)₂]₃(渭-Cl)Li(THF)₃ (Ln = Nd, Sm) with the aminophenols [HONH]² {[HONH]² = (慰-OCH₃-C₆H₄)NHCH₂(3,5-^tBu₂-C₆H₂-2-OH} and [HONH]³ {[HONH]³ = (NC₅H₄)NHCH₂(3,5-^tBu₂-C₆H₂-2-OH)} generated the neutral aminophenoxy lanthanide amides {[ON]²Ln[N(TMS)₂]}₂ [Ln = La (3), Nd (4), Sm (5)] and {[ON]³Ln[N(TMS)₂](THF)}₂ [Ln = La (6), Nd (7), Sm (8)], respectively, in high isolated yields. These complexes have been fully characterized. X-ray structural determination revealed that complexes 1 and 2 have unsolvated centrosymmetric dimeric structures, in which one hydrogen atom belonging to the amino group of the ligand is reserved. Complexes 3鈥?b>5 are isostructural and have an unsolvated dimeric structure. The coordination geometry around each of the lanthanide metal atoms can be described as a distorted trigonal bipyramid. Complexes 6 and 7 have a solvated dimeric structure, and the lanthanide metal centers have distorted capped trigonal-prismatic geometries. It was found that complexes 3鈥?b>8 are highly efficient initiators for the ring-opening polymerization of l-lactide and rac-lactide, affording polymers with high molecular weights.