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Updated: Nov 24, 2025

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
First experimental evidence for a bis-ethene chromium(I) complex forming from an activated ethene oligomerization
S Chabbra1,2, D M Smith3, N L Bell1
1EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, Scotland, UK.
Abstract:
A bis-ethene chromium(I) species, which is the postulated key intermediate in the widely accepted metallacyclic mechanism for ethene oligomerization, is experimentally observed. This catalytic transformation is an important commercial route to linear α-olefins (primarily, 1-hexene and 1-octene), which act as comonomers for the production of polyethene. Here, electron paramagnetic resonance studies of a catalytic system based on [Cr(CO)4(PNP)][Al(OC(CF3)3)4] [PNP = Ph2PN(iPr)PPh2] activated with Et6Al2 provide the first unequivocal evidence for a chromium(I) bis-ethene complex. The concentration of this species is enhanced under ethene and isotope labeling studies that confirm its composition as containing [Cr(C2H4)2(CO)2(PNP)]+ These observations open a new route to mechanistic studies of selective ethene oligomerization.
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