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Updated: Nov 29, 2025

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
2,4,6-Triphenylpyridinium: A Bulky, Highly Electron-Withdrawing Substituent That Enhances Properties of Nickel(II)
Mateusz Janeta1,2, Julius X Heidlas1, Olafs Daugulis1
1Department of Chemistry, University of Houston, Houston, TX, 77204-5003, USA.
Abstract:
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.
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