Syntheses of lanthanide monochloride and monoborohydride complexes supported by bridged bis(guanidinate) ligand and the use of borohydride complexes in polymerization of cyclic esters

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• 作者：Xingmin Zhang ; Chuanyong Wang ; Mingqiang Xue ; Yong Zhang ; Yingming Yao ; Qi Shen
• 关键词：Lanthanide monochloride complex ; Monoborohydride complex ; Bridged bis(guanidinate) ligand ; Polymerization
• 刊名：Journal of Organometallic Chemistry
• 出版年：2012
• 出版时间：15 August, 2012
• 年：2012
• 卷：713
• 期：Complete
• 页码：182-188
• 全文大小：548 K

文摘

Reaction of LnCl₃ with bridged bis(guanidinate) lithium salt LLi₂ (1) (L?=?iPr(Me₃Si)NC(NiPr)N(CH₂)₃NC(NiPr)N(SiMe₃)iPr) afforded the monochlorides LLnCl(THF)₂ (Ln?=?Nd (2), Yb (3), Y (4)) and LYbCl(DME) (5) (DME?=?1,2-dimethoxyethane). Complexes 2-5 were structurally characterized. Treatment of the chlorides with NaBH₄ gave the monoborohydride complexes LLnBH₄(DME) (Ln?=?Nd (6), Yb (7), Y (8)). X-ray crystal structure analyses of 6-8 revealed each complex was monomer with the central metal ligated by one L, one ¦Ç³-BH₄ group and one DME. Complexes 6-8 initiate ring-opening polymerization (ROP) of ?-caprolactone (?-CL), l-lactide (l-LA) and rac-lactide (rac-LA) as single-site initiators. The highest activity and the best molecular mass control for all the three monomers were found for the Nd system 6. The ROP of ?-CL in toluene with 6 gave the polymers with the in good agreement with the (?=?the number averaged molar mass) at the molar ratio of monomer to 6 up to 600 and moderate molar mass distributions () (?=?the weight averaged molar mass). The ROP of l-LA with 6 in THF afforded the polymers with controlled molar mass and relatively narrow . Complexes 6-8 are active in the ROP of rac-LA affording poly(LA) with a slight heterotactic bias (Pr?=?0.62-0.72).