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Alternating α-olefin distributions via single and double insertions in chromium-catalyzed ethylene oligomerization

journal contribution
posted on 2023-05-19, 00:40 authored by Tomov, AK, Nobbs, JD, Chirinos, JJ, Prabhjot, KS, Malinowski, R, Ho, SKY, Young, CT, McGuinness, DS, White, AJP, Elsegood, MRJ, Britovsek, GJP
The catalytic oligomerization of ethylene with chromium-based complexes containing bis(benzimidazolemethyl)amine (BIMA) ligands results in alternating distributions of linear α-olefins (LAOs). Extremely high activities are obtained (>100 000 g mmol–1 h–1 bar–1) with N-alkyl-substituted BIMA ligands, whereas bulky groups on the central nitrogen or alternative central donors result in much lower activities. Variations in the ligand backbone, as well as methylation of the benzimidazole units, lead to reduction in activity. The alternating LAO distributions have been mathematically analyzed using second-order recurrence relations. The shape of the distributions is affected by ethylene pressure (1–4 bar) and by the cocatalyst to some degree. On the basis of the results and analysis presented herein, we propose that the alternating behavior originates from the ability of these chromium BIMA catalysts to undergo single as well as double ethylene insertion reactions. A minor second distribution (<5 wt %) of 2-ethyl-1-alkenes is obtained under certain conditions, resulting from incorporation of 1-butene. DFT studies (M06L) and experimental observations regarding the reaction between AlMe3 and the N-methyl BIMA ligand 2 have shown that deprotonation of the benzimidazole N–H units can occur, which suggests a change in coordination of the BIMA ligand under oligomerization conditions.

Funding

Australian Research Council

History

Publication title

Organometallics

Volume

36

Pagination

510-522

ISSN

0276-7333

Department/School

School of Natural Sciences

Publisher

Amer Chemical Soc

Place of publication

1155 16Th St, Nw, Washington, USA, Dc, 20036

Rights statement

Copyright 2016 American Chemical Society

Repository Status

  • Restricted

Socio-economic Objectives

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

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