Palladium(II) Complexes of New Bulky Bidentate Phosphanes: Active and Highly Regioselective Catalysts for the Hydroxycarbonylation of Styrene

Jamie J. R. Frew, Karen Damian, Hendrik Van Rensburg, Alexandra M. Z. Slawin, Robert. P. Tooze, Matt Clarke

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)

Abstract

The synthesis of four new bulky bidentate phosphines that possess both tert-butyl and trifluoromethylphenyl substituents is described. Symmetric ligands were readily obtained by alkylation of phosphidoboranes of the type Li[P(BH3)(tBu)(Ar)] with dihaloalkanes. Non-symmetric ligands were prepared from a new stable precursor, tBu(2)P(BH3)(CH2)(3)Br, that should prove useful for other ligand syntheses. Palladium(II) complexes of the four new ligands were prepared and were characterised by spectroscopic methods, microanalysis and X-ray crystallography. The new [PdCl2(L)] complexes were evaluated as catalysts for the hydroxycarbonylation of styrene and found to give unprecedented regioselectivity and yields for a diphosphine-based catalyst. A study on promoter effects reveals that the presence of acid and chloride is necessary to achieve such selectivities. It has been proposed in the literature that such conditions result in a new pathway in which styrene is converted into 2-phenethyl chloride, with the latter being the real substrate in the reaction. However, a deuterium labelling study seems to rule out this mechanism, at least under the conditions used herein.

Original languageEnglish
Pages (from-to)10504-10513
Number of pages10
JournalChemistry - A European Journal
Volume15
Issue number40
DOIs
Publication statusPublished - 12 Oct 2009

Keywords

  • carbonylation
  • diphosphanes
  • fluorinated phosphanes
  • palladium
  • reaction mechanisms
  • 2-ARYLPROPIONIC ACIDS
  • INTERNAL ALKENES
  • VINYL AROMATICS
  • LINEAR ESTERS
  • CARBONYLATION
  • HYDROFORMYLATION
  • METHOXYCARBONYLATION
  • HYDROESTERIFICATION
  • DIPHOSPHINES
  • LIGANDS

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