On the importance of decarbonylation as a side-reaction in the ruthenium-catalysed dehydrogenation of alcohols: a combined experimental and density functional study

Nicolas Sieffert*, Romain Reocreux, Patrizia Lorusso, David J. Cole-Hamilton, Michael Buehl

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)
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Abstract

We report a density functional study (B97-D2 level) of the mechanism(s) operating in the alcohol decarbonylation that occurs as an important side-reaction during dehydrogenation catalysed by [RuH2(H2)(PPh3)3]. By using MeOH as the substrate, three distinct pathways have been fully characterised involving either neutral tris- or bis-phosphines or anionic bis-phosphine complexes after deprotonation. α-Agostic formaldehyde and formyl complexes are key intermediates, and the computed rate-limiting barriers are similar between the various decarbonylation and dehydrogenation paths. The key steps have also been studied for reactions involving EtOH and iPrOH as substrates, rationalising the known resistance of the latter towards decarbonylation. Kinetic isotope effects (KIEs) were predicted computationally for all pathways and studied experimentally for one specific decarbonylation path designed to start from [RuH(OCH3)(PPh3)3]. From the good agreement between computed and experimental KIEs (observed kH/kD=4), the rate-limiting step for methanol decarbonylation has been ascribed to the formation of the first agostic intermediate from a transient formaldehyde complex.

Original languageEnglish
Pages (from-to)4141-4155
Number of pages15
JournalChemistry - A European Journal
Volume20
Issue number14
Early online date5 Mar 2014
DOIs
Publication statusPublished - 1 Apr 2014

Keywords

  • Decarbonylation
  • Density functional calculations
  • Isotope effects
  • Reaction mechanisms
  • Ruthenium
  • Formic-acid decomposition
  • Efficient hydrogen-production
  • Transition-metal compounds
  • Olefin metathesis
  • Highly efficient
  • Noncovalent interactions
  • Agostic interactions
  • Complexes
  • Generation
  • Hydride

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