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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, 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.

Funding

Australian Research Council

History

Publication title

ACS Catalysis

Volume

5

Issue

7

Pagination

4152-4166

ISSN

2155-5435

Department/School

School of Natural Sciences

Publisher

American Chemical Society

Place of publication

United States of America

Rights statement

Copyright 2015 American Chemical Society.

Repository Status

  • Restricted

Socio-economic Objectives

Organic industrial chemicals (excl. resins, rubber and plastics)

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