2,4,6‐Triphenylpyridinium: A Bulky, Highly Electron‐Withdrawing Substituent That Enhances Properties of Nickel(II) Ethylene Polymerization Catalysts
| Autor: | Olafs Daugulis, Maurice Brookhart, Julius X. Heidlas, Mateusz Janeta |
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| Rok vydání: | 2021 |
| Předmět: |
Steric effects
chemistry.chemical_classification Trifluoromethyl 010405 organic chemistry Substituent chemistry.chemical_element Chain transfer General Chemistry Polymer General Medicine 010402 general chemistry 01 natural sciences Catalysis 0104 chemical sciences Nickel chemistry.chemical_compound chemistry Polymer chemistry Polar effect |
| Zdroj: | Angewandte Chemie. 133:4616-4619 |
| ISSN: | 1521-3757 0044-8249 |
| DOI: | 10.1002/ange.202013854 |
| Popis: | The reactivity of NiII and PdII 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 (σmeta =0.63) than the trifluoromethyl group (σmeta =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. |
| Databáze: | OpenAIRE |
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