2,4,6‐Triphenylpyridinium: A Bulky, Highly Electron‐Withdrawing Substituent That Enhances Properties of Nickel(II) Ethylene Polymerization Catalysts,Angewandte Chemie International Edition

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2,4,6‐Triphenylpyridinium: A Bulky, Highly Electron‐Withdrawing Substituent That Enhances Properties of Nickel(II) Ethylene Polymerization Catalysts
Angewandte Chemie International Edition ( IF 16.1 ) Pub Date : 2020-11-23 , DOI: 10.1002/anie.202013854
Mateusz Janeta _{1,

2} , Julius X. Heidlas ₁ , Olafs Daugulis ₁ , Maurice Brookhart ₁

Affiliation

The reactivity of Ni^II and Pd^II olefin polymerization catalysts can be enhanced by introduction of electron‐withdrawing substituents on the supporting ligands rendering the metal centers more electrophilic. Reported here is a comparison of ethylene polymerization activity of a classical salicyliminato nickel catalyst substituted with the powerful electron‐withdrawing 2,4,6‐triphenylpyridinium (trippy) group to the ‐CF₃ analogue. The trippy substituent is substantially more electron‐withdrawing (σ_meta=0.63) than the trifluoromethyl group (σ_meta=0.43) which results in a ca. 8‐fold increase in catalytic turnover frequency. An additional advantage of trippy is the high steric bulk relative to the trifluoromethyl group. This feature results in a four‐fold increase in polymer molecular weight owing to enhanced retardation of chain transfer. A significant increase in catalyst lifetime is observed as well.

中文翻译：

2,4,6-三苯基吡啶鎓：一种庞大的，高吸电子取代基，可增强镍（II）乙烯聚合催化剂的性能

Ni ^II和Pd ^II烯烃聚合催化剂的反应性可以通过在支持性配体上引入吸电子取代基来增强，使金属中心更具亲电性。此处报道的是将经典的水杨酸锂镍催化剂取代有强大的吸电子2,4,6-三苯基吡啶鎓（三联吡啶）基团与-CF ₃类似物的乙烯聚合活性。所述取代基的trippy基本上多种吸电子（σ_元= 0.63）比三氟甲基（σ_元= 0.43），结果约为催化周转频率提高了8倍。Trippy的另一个优点是相对于三氟甲基而言，空间体积大。由于增强了链转移的阻滞作用，该功能导致聚合物分子量增加了四倍。还观察到催化剂寿命的显着增加。

更新日期：2020-11-23

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