Molybdenum carbonyl complexes in the solvent-free catalytic hydrogenation of ketones

Barbara F.M. Kimmich, Paul J. Fagan, Elisabeth Hauptman, William J. Marshall, R. Morris Bullock

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Abstract

The heterodifunctional ligand Li[η 5-C 5H 4(CH 2) 2PR 2] (R = Ph, Cy, and Bu) reacts with Mo(CO) 3(diglyme) to give the molybdenum anion complex Li{Mo(CO) 35-C 5H 4(CH 2) 2PR 2]}. Protonation with HOAc gives the metal hydride complexes HMo(CO) 251- C 5H 4(CH 2) 2PR 2], in which the phosphine and cyclopentadienyl ligands are linked by a two-carbon bridge. Crystal structures of HMo(CO) 25:n 1-C 5H 4CH 2) 2PR 2] with all three R groups (R = Ph, Cy, and tBu) are reported. Syntheses of the C 3-bridged complex, HMo(CO) 25: η 1-C 4H 5(CH 2) 3- PPh 2], and a W analogue, HW(CO) 35-C 5H 4(CH 2) 2P tBu 2], were carried out by analogous routes. Hydride transfer to Ph 3C +BAr′ 4; [Ar′ = 3,5-bis(trifluoromethyl)phenyl] from the catalyst precursors HMo(CO) 251-C 5H 4(CH 2) 2PR 2] leads to homogeneous catalysts for hydrogenation of ketones, with the best performance being found for R = Cy. Protonation of HMo(CO) 25: η 1-C 5H 4(CH 2) 2PR 2] by HOTf leads to metal triflate complexes (TfO)Mo(CO) 251-C 5H 4(CH 2) 2PR 2], which are used in ketone hydrogenation. Compared to the previously prepared complexes that did not have the phosphine and Cp linked together, these new complexes provide catalysts that have much longer lifetimes (up to about 500 turnovers) and higher thermal stability. Solvent-free ketone hydrogenation can be carried out with these complexes at catalyst loadings as low as 0.1 mol%.

Original languageEnglish
Pages (from-to)6220-6229
Number of pages10
JournalOrganometallics
Volume24
Issue number25
DOIs
Publication statusPublished - Dec 5 2005

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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