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Insights in the mechanism of selective olefin oligomerisation catalysis using stopped-flow freeze-quench techniques: A Mo K-edge QEXAFS study

Bartlett, S. A., Wells, P. P., Nachtegaal, M., Dent, A. J., Cibin, G., Reid, G., Evans, J. & Tromp, M., 1-Dec-2011, In : Journal of Catalysis. 284, 2, p. 247-258 12 p.

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  • Insights in the mechanism of selective olefin oligomerisation catalysis using stopped-flow freeze-quench techniques

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DOI

  • Stuart A. Bartlett
  • Peter P. Wells
  • Maarten Nachtegaal
  • Andrew J. Dent
  • Giannantonio Cibin
  • Gillian Reid
  • John Evans
  • Moniek Tromp

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.

Original languageEnglish
Pages (from-to)247-258
Number of pages12
JournalJournal of Catalysis
Volume284
Issue number2
Publication statusPublished - 1-Dec-2011
Externally publishedYes

    Keywords

  • RAY-ABSORPTION-SPECTROSCOPY, METAL OXIDATION-STATE, ETHYLENE TRIMERIZATION, LIGAND STRUCTURE, CR-PNP, COMPLEXES, TETRAMERIZATION, COORDINATION

ID: 107577574