N-Heterocyclic Carbene Non-Innocence in the Catalytic Hydrophosphination of Alkynes

William J. M. Blackaby, Samuel E. Neale, Connie J. Isaac, Sara Sabater, Stuart A. Macgregor, Michael K. Whittlesey

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Abstract

Studies on alkyne hydrophosphination employing nickel-NHC catalysts (NHC=N-heterocyclic carbene) revealed that the free N-alkyl substituted NHCs themselves were catalytically active. DFT calculations showed the mechanism involves the NHC acting as a Brønsted base to form an imidazolium phosphide species which then undergoes rate-limiting nucleophilic attack at the terminal alkyne carbon. This mechanism explains the preference seen experimentally for reactions with aryl substituted phosphines and alkynes, while the rearrangements of the alkenyl anion formed upon P−C bond formation account for the observation of both Z- and E-regioisomers of the products.

Original languageEnglish
Pages (from-to)1893-1897
Number of pages5
JournalChemCatChem
Volume11
Issue number7
Early online date20 Feb 2019
DOIs
Publication statusPublished - 4 Apr 2019

Keywords

  • density functional calculations
  • homogeneous catalysis
  • hydrophosphination
  • N-heterocyclic carbene
  • reaction mechanisms

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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  • Cite this

    Blackaby, W. J. M., Neale, S. E., Isaac, C. J., Sabater, S., Macgregor, S. A., & Whittlesey, M. K. (2019). N-Heterocyclic Carbene Non-Innocence in the Catalytic Hydrophosphination of Alkynes. ChemCatChem, 11(7), 1893-1897. https://doi.org/10.1002/cctc.201900220