Synthesis and Reactivity of Rare-Earth-Metal Monoalkyl Complexes Supported by Bidentate Indolyl Ligands and Their High Performance in Isoprene 1,4-cis Polymerization

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• 作者：Guangchao Zhang ; Shaowu Wang ; Shuangliu Zhou ; Yun Wei ; Liping Guo ; Xiancui Zhu ; Lijun Zhang ; Xiaoxia Gu ; Xiaolong Mu
• 刊名：Organometallics
• 出版年：2015
• 出版时间：September 14, 2015
• 年：2015
• 卷：34
• 期：17
• 页码：4251-4261
• 全文大小：688K
• ISSN：1520-6041

文摘

A series of novel rare-earth-metal monoalkyl complexes incorporating partially rotation restricted [N,N]-bidentate indolyl ligands were synthesized and characterized, and their reactivities and catalytic activities were investigated. Treatment of [RE(CH₂SiMe₃)₃(thf)₂] with 1 equiv of 2-[(N-2,6-diisopropylphenyl)iminomethyl)]indole (2-(2,6-ⁱPr₂C₆H₃N鈺怌H)C₈H₅NH) in toluene at room temperature afforded the rare-earth-metal monoalkyl complexes [畏¹:畏¹-2-(2,6-ⁱPr₂C₆H₃N鈺怌H)Ind]₂RE(CH₂SiMe₃)(thf) (Ind = indolyl; RE = Yb (1), Er (2), Y (3), Dy (4), Gd (5)) and the samarium complex [畏¹:畏¹-2-(2,6-ⁱPr₂C₆H₃N鈺怌H)Ind]₃Sm (6) via alkane elimination in good yields. Treatment of complex 2 or 3 with 1 equiv of PhSiH₃ in toluene at 80 掳C for 12 h afforded the dinuclear complexes {[渭-畏⁶:畏¹:畏¹-2-(2,6-ⁱPr₂C₆H₃NCH₂)Ind]RE[2-(2,6-ⁱPr₂C₆H₃N鈺怌H)Ind]}₂ (Ind = indolyl, RE = Er (7), Y (8)) in good isolated yields. Treatment of complex 2 or 3 with 1 equiv of amidine (2,6-ⁱPr₂C₆H₃)N鈺怌HNH(2,6-ⁱPr₂C₆H₃) in toluene produced the corresponding complexes [畏¹:畏¹-2-(2,6-ⁱPr₂C₆H₃N鈺怌H)C₈H₅N]₂RE[(2,6-ⁱPr₂C₆H₃)N鈺怌HN(2,6-ⁱPr₂C₆H₃)] (RE = Er (9), Y (10)) possessing the amidinate ligand [(2,6-ⁱPr₂C₆H₃N)₂CH]^{鈭?/sup>. The molecular structures of all complexes were determined by X-ray crystallography. The monoalkyl complexes 1鈥?b>5 were tested as isoprene polymerization initiators. Among the complexes investigated, the optimum combination 5/AliBu₃/[Ph₃C][B(C₆F₅)₄] displayed a high catalytic activity in isoprene polymerization, producing polymers with an extremely high 1,4-cis selectivity (up to 99%), a high number-average molecular weight (M_n = 7.2 脳 105), and a narrow molecular weight distribution (PDI = 1.34) at an isoprene to initiator molar ratio of 6000:1.}