Insights in the mechanism of selective olefin oligomerisation catalysis using stopped-flow freeze-quench techniques: A Mo K-edge QEXAFS study
Insights in the mechanism of selective olefin oligomerisation catalysis using stopped-flow freeze-quench techniques: A Mo K-edge QEXAFS study
The activation of [MoX3(L)] (with X = Cl, Br; L = tridentate ligands with S3 and SNS donor sets) by AlMe3, analogous to the industrially important [CrCl3(L)] catalysts for selective oligomerisation of alkenes, has been investigated by Mo K-edge X-ray absorption (XAS) and UV–visible spectroscopies. Time-resolved stopped-flow XAS, in combination with a newly developed anaerobic freeze-quench approach, have established the complete alkylation of the Mo centres and a slower, stepwise sequence for [MoBr3(L)]. No evidence for directly bonded or bridged Mo–Mo dimers was observed at the high Mo:AlMe3 ratios used in this study. Decomposition of the complexes is in competition with the activation and resulted in precipitation of particulate Mo over time and explains the deactivation as observed in catalytic tests. The novel freeze-quench approach, which can trap reaction solutions within 1 s of mixing, opens up a large field of homogeneous catalysis and liquid chemistry to be studied, being able to quench this rapidly, whilst characterisation techniques with long data acquisition can be performed.
247-258
Bartlett, S.
42fc0f18-bc06-4377-854f-1c1afce58b0b
Wells, Peter P.
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Nachtegaal, Maarten
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Dent, Andrew J.
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Cibin, Giannantonio
61a833d3-097f-4817-bcd3-6b26cf42dbe5
Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Evans, John
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Tromp, Moniek
a5da2bdf-9f4e-452a-8aa8-032e0c9b6660
1 December 2011
Bartlett, S.
42fc0f18-bc06-4377-854f-1c1afce58b0b
Wells, Peter P.
bc4fdc2d-a490-41bf-86cc-400edecf2266
Nachtegaal, Maarten
37fbcbc5-08e8-4eda-9350-2b162693013f
Dent, Andrew J.
24c2a218-cb0e-4193-af0b-3ff1dc42b552
Cibin, Giannantonio
61a833d3-097f-4817-bcd3-6b26cf42dbe5
Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Evans, John
05890433-0155-49fe-a65d-38c90ea25c69
Tromp, Moniek
a5da2bdf-9f4e-452a-8aa8-032e0c9b6660
Bartlett, S., Wells, Peter P., Nachtegaal, Maarten, Dent, Andrew J., Cibin, Giannantonio, Reid, Gillian, Evans, John and Tromp, Moniek
(2011)
Insights in the mechanism of selective olefin oligomerisation catalysis using stopped-flow freeze-quench techniques: A Mo K-edge QEXAFS study.
Journal of Catalysis, 284 (2), .
(doi:10.1016/j.jcat.2011.10.015).
Abstract
The activation of [MoX3(L)] (with X = Cl, Br; L = tridentate ligands with S3 and SNS donor sets) by AlMe3, analogous to the industrially important [CrCl3(L)] catalysts for selective oligomerisation of alkenes, has been investigated by Mo K-edge X-ray absorption (XAS) and UV–visible spectroscopies. Time-resolved stopped-flow XAS, in combination with a newly developed anaerobic freeze-quench approach, have established the complete alkylation of the Mo centres and a slower, stepwise sequence for [MoBr3(L)]. No evidence for directly bonded or bridged Mo–Mo dimers was observed at the high Mo:AlMe3 ratios used in this study. Decomposition of the complexes is in competition with the activation and resulted in precipitation of particulate Mo over time and explains the deactivation as observed in catalytic tests. The novel freeze-quench approach, which can trap reaction solutions within 1 s of mixing, opens up a large field of homogeneous catalysis and liquid chemistry to be studied, being able to quench this rapidly, whilst characterisation techniques with long data acquisition can be performed.
Text
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Published date: 1 December 2011
Organisations:
Organic Chemistry: Synthesis, Catalysis and Flow, Chemistry, Faculty of Natural and Environmental Sciences
Identifiers
Local EPrints ID: 336551
URI: http://eprints.soton.ac.uk/id/eprint/336551
ISSN: 0021-9517
PURE UUID: 96c9a6cf-6778-4f01-aa3f-bc43e846ac71
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Date deposited: 29 Mar 2012 12:58
Last modified: 29 Oct 2024 02:32
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Contributors
Author:
S. Bartlett
Author:
Maarten Nachtegaal
Author:
Andrew J. Dent
Author:
Giannantonio Cibin
Author:
Moniek Tromp
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