Controlled Benzylation of α-Diimine Ligands Bound to Zirconium and Hafnium: An Alternative Method for Preparing Mono- and Bis(amido)M(CH2Ph)n (n = 2, 3) Complexes as Catalyst Precursors for Isospecific Polymerization of α-Olefins
Controlled Benzylation of α-Diimine Ligands Bound to Zirconium and Hafnium: An Alternative Method for Preparing Mono- and Bis(amido)M(CH2Ph)n (n = 2, 3) Complexes as Catalyst Precursors for Isospecific Polymerization of α-Olefins
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DOI：
10.1021/om800880n
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发表时间：
2009-01
期刊：
影响因子：
2.8
通讯作者：
H. Tsurugi;R. Ohnishi;H. Kaneko;T. Panda;K. Mashima
中科院分区：
文献类型：
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作者：
H. Tsurugi;R. Ohnishi;H. Kaneko;T. Panda;K. Mashima
M(CH2Ph)4 (M = Zr, Hf) 与各种 α-二亚胺配体的反应通过配体 C=N 键的分子内苄基化提供酰胺-亚氨基或二酰胺复合物。 α-二亚胺配体的选择性苄基化，即单苄基化和双苄基化，是通过改变亚胺部分或配体主链的氮原子上的取代基来完成的。第二个苄基化步骤的动力学分析表明，苄基通过有序的四中心过渡态从金属中心迁移到 C=N 部分（对于 3a，ΔS⧧ = -3(4) eu；对于 5b，ΔS⧧ = -5(9) eu）。用B(C6F5)3或[Ph3C][B(C6F5)4]活化后，酰胺基亚氨基(3, 6)和二酰胺基(2, 4)配合物成为1-己烯聚合的活性催化剂，所得聚(1-己烯)具有中等的全同立构规整度([mmmm]，高达90%)。乙烯基环己烷的聚合也被以中等活性催化，通过链端控制机制得到高度全同立构的聚(乙烯基环己烷)([mmmm]>95%)。
Reactions of M(CH2Ph)4 (M = Zr, Hf) with various α-diimine ligands afforded amido-imino or diamido complexes through intramolecular benzylation of the C═N bonds of the ligands. Selective benzylation of α-diimine ligands, i.e., single- and double-benzylation, was accomplished by varying the substituent on the nitrogen atom of the imine moiety or the ligand backbone. Kinetic analysis of the second benzylation step indicated that the benzyl group migrated from the metal center to the C═N moiety via an ordered four-center transition state (ΔS⧧ = −3(4) eu for 3a; −5(9) eu for 5b). Upon activation with B(C6F5)3 or [Ph3C][B(C6F5)4], amido-imino (3, 6) and diamido (2, 4) complexes became active catalysts for 1-hexene polymerization, and the resulting poly(1-hexene)s had moderate isotacticity ([mmmm], up to 90%). Polymerization of vinylcyclohexane was also catalyzed with moderate activity to give highly isotactic poly(vinylcyclohexane) ([mmmm] > 95%) via a chain-end control mechanism.