Ruthenium substituted Keggin type polyoxomolybdates: Synthesis, characterization and use as bifunctional catalysts for the epoxidation of alkenes by molecular oxygen

Ronny Neumann, Mazal Dahan

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)

Abstract

The ruthenium substituted polyoxomolybdate of the Keggin structure, Q4PRuIII(H2O)Mo11O39 (Q=n-Bu4N), has been synthesized and characterized. The IR spectra show that this compound is isostructural with the known manganese and cobalt analogs. The cyclic voltammogram showed similar redox potentials and the UV-vis spectra showed similar energies for the d-d transitions compared to the corresponding tungstate, Q4PRuIII(H2O)W11O39. The catalytic activity of the molybdate versus tungstate in reactions with molecular oxygen was, however, significantly different. IR and 31P NMR evidence indicated that treatment of Q4PRuIII(H2O)Mo11O39 with oxygen showed no structural changes whereas, for Q4PRuIII(H2O)W11O39, a clear change was observed. This finding probably explains the lack of catalytic activity for the latter in the co-oxidation of cumene and 1-octene to cumyl alcohol and 1-octene oxide. For the molybdenum compound, this reaction took place by a kinetic balance of ruthenium metal-catalyzed autooxidation of cumene to cumene hydroperoxide and the molybdenum catalyzed oxygen transfer from cumene hydroperoxide to 1-octene to yield the products. High catalyst loading led to reaction inhibition whereas low loading and excess cumene led to increased autooxidation.

Original languageEnglish
Pages (from-to)3557-3564
Number of pages8
JournalPolyhedron
Volume17
Issue number20
Publication statusPublished - Sep 30 1998

Keywords

  • Alkenes
  • Bifunctional catalysts
  • Molecular oxygen
  • Polyoxomolybdates

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Ruthenium substituted Keggin type polyoxomolybdates: Synthesis, characterization and use as bifunctional catalysts for the epoxidation of alkenes by molecular oxygen'. Together they form a unique fingerprint.

Cite this