Behaviour of [PdH(dppe)2]X (X = CF3SO 3-, SbF6-, BF4 -) as proton or hydride donor: Relevance to catalysis

Michele Aresta, Angela Dibenedetto, Imre Pápai, Gábor Schubert, Alceo Macchioni, Daniele Zuccaccia

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The synthesis, characterization and properties of [PdH(dppe) 2]+ CF3SO3--·0.125 THF (1; dppe = l,2-bis-(diphenylphosphanyl)ethane) and its SbF6 - (1′) and BF4- (1″) analogues, the missing members of the [MH(dppe)2]+ X- (M = Ni, Pd, Pt) family, are described. The Pd hydrides are not stable in solution and can react as proton or hydride donors with formation of dihydrogen, [Pd(dppe)2]2+ and [Pd(dppe)2]. Complexes 1-1″ react with carbocations and carbanions by transferring a hydride and a proton, respectively. Such H- or H+ transfer occurs also towards unsaturated compounds, for example, hydrogenation of a C=C double bond. Accordingly, 1 can hydrogenate methyl acrylate to methyl propionate. Complex 1″ is an effective (hourly turnover frequency = 16) and very selective (100%) catalyst for the hydrogenation of cyclohexen-2-one to cyclohexanone with dihydrogen under mild conditions. Density functional calculations coupled with a dielectric continuum model were carried out to compute the energetics of the hydride/proton transfer reactions, which were used to rationalize some of the experimental findings. Theory provides strong support for the thermodynamic and kinetic viability of a tetracoordinate Pd complex as an intermediate in the reactions.

Original languageEnglish
Pages (from-to)3708-3716
Number of pages9
JournalChemistry - A European Journal
Volume10
Issue number15
DOIs
Publication statusPublished - Aug 6 2004

Keywords

  • Density functional calculations
  • Homogeneous catalysis
  • Hydride ligands
  • Hydrogenation
  • Palladium

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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