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

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Title: Alternating alpha-olefin distributions via single and double insertions in chromium-catalyzed ethylene oligomerization.
Authors: Tomov, AK
Nobbs, JD
Chirinos, JJ
Saini, PK
Malinowski, R
Ho, SKY
Young, CT
McGuinness, DS
White, AJP
Elsegood, MRJ
Britovsek, GJP
Item Type: Journal Article
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 (<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.
Issue Date: 16-Nov-2016
Date of Acceptance: 1-Nov-2016
URI: http://hdl.handle.net/10044/1/60063
DOI: https://dx.doi.org/10.1021/acs.organomet.6b00671
ISSN: 0276-7333
Publisher: American Chemical Society
Start Page: 510
End Page: 522
Journal / Book Title: Organometallics
Volume: 36
Issue: 3
Copyright Statement: © 2016 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Organometallics, after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acs.organomet.6b00671
Keywords: Science & Technology
Physical Sciences
Chemistry, Inorganic & Nuclear
Chemistry, Organic
Chemistry
METAL-COMPLEXES
CHAIN GROWTH
LIGANDS
TETRAMERIZATION
TRIMERIZATION
POLYMERIZATION
MECHANISM
REACTIVITY
DONOR
Science & Technology
Physical Sciences
Chemistry, Inorganic & Nuclear
Chemistry, Organic
Chemistry
METAL-COMPLEXES
CHAIN GROWTH
LIGANDS
TETRAMERIZATION
TRIMERIZATION
POLYMERIZATION
MECHANISM
REACTIVITY
DONOR
0302 Inorganic Chemistry
0305 Organic Chemistry
0399 Other Chemical Sciences
Organic Chemistry
Publication Status: Published
Appears in Collections:Chemistry
Catalysis and Advanced Materials
Faculty of Natural Sciences



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