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Single- and double-coordination mechanism in ethylene tri- and tetramerization with Cr/PNP catalysts
journal contributionposted on 2023-05-18, 16:13 authored by Britovsek, GJP, McGuinness, DS, Wierenga, TS, Young, CT
The mechanism of ethylene trimerization and tetramerization with a chromium–diphosphinoamine (Cr–PNP) catalyst system has been studied with combined experimental and theoretical methods. Of the total product output, 1-octene, cyclopentanes, n-alkanes, and higher (C10+) olefins are formed with a fractional (∼1.4) order response to ethylene concentration, whereas 1-hexene formation is approximately first-order in ethylene. Theoretical studies suggest a mechanism involving a cationic monometallic catalyst in Cr(I) and Cr(III) formal oxidation states. A key feature of the developed model is the occurrence of a double-coordination mechanism in which a bis(ethylene) chromacyclopentane intermediate is responsible for 1-octene formation as well as the other coproducts that have a greater than first-order response to ethylene. In contrast, 1-hexene is formed primarily from a mono(ethylene) chromacyclopentane intermediate. The selectivity of catalysis is governed by the competition between single- and double-coordination pathways. The mechanistic model developed displays excellent correlation with experimental observations and is able to fully explain the formation of all products generated with this catalyst.
Australian Research Council
Publication titleACS Catalysis
Department/SchoolSchool of Natural Sciences
PublisherAmerican Chemical Society
Place of publicationUnited States of America
Rights statementCopyright 2015 American Chemical Society.