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Single- and double-coordination mechanism in ethylene tri- and tetramerization with Cr/PNP catalysts
journal contribution
posted on 2023-05-18, 16:13 authored by Britovsek, GJP, McGuinness, DS, Wierenga, TS, Young, CTThe 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.
Funding
Australian Research Council
History
Publication title
ACS CatalysisVolume
5Issue
7Pagination
4152-4166ISSN
2155-5435Department/School
School of Natural SciencesPublisher
American Chemical SocietyPlace of publication
United States of AmericaRights statement
Copyright 2015 American Chemical Society.Repository Status
- Restricted