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

Tomov, AK, Nobbs, JD, Chirinos, JJ, Prabhjot, KS, Malinowski, R, Ho, SKY, Young, CT, McGuinness, DS ORCID: 0000-0002-6615-7807, White, AJP, Elsegood, MRJ and Britovsek, GJP 2017 , 'Alternating α-olefin distributions via single and double insertions in chromium-catalyzed ethylene oligomerization' , Organometallics, vol. 36, no. 3 , pp. 510-522 , doi: 10.1021/acs.organomet.6b00671.

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Abstract

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 (3 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.

Item Type: Article
Authors/Creators:Tomov, AK and Nobbs, JD and Chirinos, JJ and Prabhjot, KS and Malinowski, R and Ho, SKY and Young, CT and McGuinness, DS and White, AJP and Elsegood, MRJ and Britovsek, GJP
Keywords: oligomerisation, DFT
Journal or Publication Title: Organometallics
Publisher: Amer Chemical Soc
ISSN: 0276-7333
DOI / ID Number: 10.1021/acs.organomet.6b00671
Copyright Information:

Copyright 2016 American Chemical Society

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