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 journalArticle

42 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

Fingerprint

epoxidation
Ruthenium
Epoxidation
Molecular oxygen
Alkenes
ruthenium
alkenes
Olefins
Catalyst activity
tungstates
Molybdenum
Molybdenum compounds
Oxygen
catalysts
Catalysts
catalytic activity
oxygen
synthesis
molybdenum compounds
Manganese

Keywords

  • Alkenes
  • Bifunctional catalysts
  • Molecular oxygen
  • Polyoxomolybdates

ASJC Scopus subject areas

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

Cite this

@article{514f50add62046f898d9e817a5d3228d,
title = "Ruthenium substituted Keggin type polyoxomolybdates: Synthesis, characterization and use as bifunctional catalysts for the epoxidation of alkenes by molecular oxygen",
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.",
keywords = "Alkenes, Bifunctional catalysts, Molecular oxygen, Polyoxomolybdates",
author = "Ronny Neumann and Mazal Dahan",
year = "1998",
month = "9",
day = "30",
language = "English",
volume = "17",
pages = "3557--3564",
journal = "Polyhedron",
issn = "0277-5387",
publisher = "Elsevier Limited",
number = "20",

}

TY - JOUR

T1 - Ruthenium substituted Keggin type polyoxomolybdates

T2 - Synthesis, characterization and use as bifunctional catalysts for the epoxidation of alkenes by molecular oxygen

AU - Neumann, Ronny

AU - Dahan, Mazal

PY - 1998/9/30

Y1 - 1998/9/30

N2 - 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.

AB - 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.

KW - Alkenes

KW - Bifunctional catalysts

KW - Molecular oxygen

KW - Polyoxomolybdates

UR - http://www.scopus.com/inward/record.url?scp=0000965944&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000965944&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0000965944

VL - 17

SP - 3557

EP - 3564

JO - Polyhedron

JF - Polyhedron

SN - 0277-5387

IS - 20

ER -