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

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posted on 20.12.2016 by Atanas K. Tomov, James D. Nobbs, Juan J. Chirinos, Prabhjot K. Saini, Robert Malinowski, Sarah K.Y. Ho, Craig T. Young, David S. McGuinness, Andrew J.P. White, Mark Elsegood, George J.P. Britovsek
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.

History

School

  • Science

Department

  • Chemistry

Published in

Organometallics

Volume

36

Issue

3

Pages

510-522

Citation

TOMOV, A.K. ... et al, 2017. Alternating α-olefin distributions via single and double insertions in chromium-catalyzed ethylene oligomerization. Organometallics, 36 (3), pp. 510-522.

Publisher

ACS Publications (© 2016 American Chemical Society)

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

01/11/2016

Publication date

2016-11-16

Copyright date

2017

Notes

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Organometallics, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.organomet.6b00671.

ISSN

0276-7333

eISSN

1520-6041

Language

en

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