Efficient 1-hexene trimerization with triazacyclohexane chromium catalysts and detailed product analysis by 13C NMR

Alexander G. N Coxon; Randolf D. Kohn

doi:10.1021/acscatal.6b00542

Efficient 1-hexene trimerization with triazacyclohexane chromium catalysts and detailed product analysis by ¹³C NMR

Alexander G. N Coxon, Randolf D. Kohn

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

17 Citations (SciVal)

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Abstract

Triazacyclohexane chromium precatalysts are described which catalyze the selective trimerization of 1-pentene, 1-hexene, and 1-octene with unprecedented activity, reaching nearly 5000 turnovers in 1 h. The isomer distribution of the trimers has been analyzed in detail by application of quantitative ¹³C NMR spectroscopy to ¹³C labeled samples. All endocyclic elimination products predicted by the metallacyclic mechanism have been characterized, and many have been confirmed by their independent syntheses. Significant variations in the isomer distribution are observed on variation of the ligand bulk. Quantification gave considerable insights into the relative abundance of metallacyclic intermediates, with 1,3-substituted chromacyclopentanes being by far the most abundant resting state. Ring expansion selectivity favors 1,2-insertion into the less hindered Cr–C bond, but some 2,1-insertion products have also been identified.

Original language	English
Pages (from-to)	3008-3016
Number of pages	9
Journal	ACS Catalysis
Volume	6
Issue number	5
Early online date	30 Mar 2016
DOIs	https://doi.org/10.1021/acscatal.6b00542
Publication status	Published - 6 May 2016

Keywords

selective olefin trimerization
catalysis
chromium
13C NMR characterization
metallacycle
oligomerization

Access to Document

10.1021/acscatal.6b00542

Supporting Information revised final2.PDF
This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysi, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acscatal.6b00542
Accepted author manuscript, 1.69 MB
Efficient 1-Hexene Trimerization.PDF
This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysi, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acscatal.6b00542
Accepted author manuscript, 975 KB
Copy of Labelled_13C_trimer_shifts_and_coupling_constants.PDF
This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Catalysi, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acscatal.6b00542
Accepted author manuscript, 935 KB
Copy of NMR_shift_calculator_for_C5_C6_C8_trimersAccepted author manuscript, 1.88 MB

http://dx.doi.org/10.1021/acscatal.6b00542

Randolf Kohn
- R.D.Kohnbath.acuk
- Department of Chemistry - Senior Lecturer
Person: Research & Teaching

Avance NEO 500 MHz Nuclear Magnetic Resonance (NMR) Spectrometer (1South)
Material and Chemical Characterisation (MC2)
Facility/equipment: Equipment
Electrospray Time-of-Flight Mass Spectrometer (Open-Access)
Material and Chemical Characterisation (MC2)
Facility/equipment: Equipment
MC2-Mass Spectrometry (MS)
Material and Chemical Characterisation (MC2)
Facility/equipment: Technology type

Cite this

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title = "Efficient 1-hexene trimerization with triazacyclohexane chromium catalysts and detailed product analysis by 13C NMR",

abstract = "Triazacyclohexane chromium precatalysts are described which catalyze the selective trimerization of 1-pentene, 1-hexene, and 1-octene with unprecedented activity, reaching nearly 5000 turnovers in 1 h. The isomer distribution of the trimers has been analyzed in detail by application of quantitative 13C NMR spectroscopy to 13C labeled samples. All endocyclic elimination products predicted by the metallacyclic mechanism have been characterized, and many have been confirmed by their independent syntheses. Significant variations in the isomer distribution are observed on variation of the ligand bulk. Quantification gave considerable insights into the relative abundance of metallacyclic intermediates, with 1,3-substituted chromacyclopentanes being by far the most abundant resting state. Ring expansion selectivity favors 1,2-insertion into the less hindered Cr–C bond, but some 2,1-insertion products have also been identified.",

keywords = "selective olefin trimerization, catalysis, chromium, 13C NMR characterization, metallacycle, oligomerization",

author = "Coxon, {Alexander G. N} and Kohn, {Randolf D.}",

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doi = "10.1021/acscatal.6b00542",

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TY - JOUR

T1 - Efficient 1-hexene trimerization with triazacyclohexane chromium catalysts and detailed product analysis by 13C NMR

AU - Coxon, Alexander G. N

AU - Kohn, Randolf D.

PY - 2016/5/6

Y1 - 2016/5/6

N2 - Triazacyclohexane chromium precatalysts are described which catalyze the selective trimerization of 1-pentene, 1-hexene, and 1-octene with unprecedented activity, reaching nearly 5000 turnovers in 1 h. The isomer distribution of the trimers has been analyzed in detail by application of quantitative 13C NMR spectroscopy to 13C labeled samples. All endocyclic elimination products predicted by the metallacyclic mechanism have been characterized, and many have been confirmed by their independent syntheses. Significant variations in the isomer distribution are observed on variation of the ligand bulk. Quantification gave considerable insights into the relative abundance of metallacyclic intermediates, with 1,3-substituted chromacyclopentanes being by far the most abundant resting state. Ring expansion selectivity favors 1,2-insertion into the less hindered Cr–C bond, but some 2,1-insertion products have also been identified.

AB - Triazacyclohexane chromium precatalysts are described which catalyze the selective trimerization of 1-pentene, 1-hexene, and 1-octene with unprecedented activity, reaching nearly 5000 turnovers in 1 h. The isomer distribution of the trimers has been analyzed in detail by application of quantitative 13C NMR spectroscopy to 13C labeled samples. All endocyclic elimination products predicted by the metallacyclic mechanism have been characterized, and many have been confirmed by their independent syntheses. Significant variations in the isomer distribution are observed on variation of the ligand bulk. Quantification gave considerable insights into the relative abundance of metallacyclic intermediates, with 1,3-substituted chromacyclopentanes being by far the most abundant resting state. Ring expansion selectivity favors 1,2-insertion into the less hindered Cr–C bond, but some 2,1-insertion products have also been identified.

KW - selective olefin trimerization

KW - catalysis

KW - chromium

KW - 13C NMR characterization

KW - metallacycle

KW - oligomerization

U2 - 10.1021/acscatal.6b00542

DO - 10.1021/acscatal.6b00542

M3 - Article

SN - 2155-5435

VL - 6

SP - 3008

EP - 3016

JO - ACS Catalysis

JF - ACS Catalysis

IS - 5

ER -

Efficient 1-hexene trimerization with triazacyclohexane chromium catalysts and detailed product analysis by 13C NMR

Abstract

Keywords

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Randolf Kohn

Equipment

Avance NEO 500 MHz Nuclear Magnetic Resonance (NMR) Spectrometer (1South)

Electrospray Time-of-Flight Mass Spectrometer (Open-Access)

MC2-Mass Spectrometry (MS)

Cite this

Efficient 1-hexene trimerization with triazacyclohexane chromium catalysts and detailed product analysis by ¹³C NMR