Manganese triazacyclononane oxidation catalysts grafted under reaction conditions on solid cocatalytic supports

Nicholas J. Schoenfeldt, Zhenjuan Ni, Andrew W. Korinda, Randall J. Meyer, Justin M Notestein

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) are highly active and selective alkene oxidation catalysts with aqueous H 2O2. Here, carboxylic acid-functionalized SiO2 simultaneously immobilizes and activates these complexes under oxidation reaction conditions. H2O2 and the functionalized support are both necessary to transform the inactive [(tmtacn)MnIV (μ-O)3MnIV (tmtacn)]2+ into the active, dicarboxylate-bridged [(tmtacn)MnIII (μ-O)(μ-RCOO) 2MnIII (tmtacn)]2+. This transformation is assigned on the basis of comparison of diffuse reflectance UV-visible spectra to known soluble models, assignment of oxidation state by Mn K-edge X-ray absorption near-edge spectroscopy, the dependence of rates on the acid/Mn ratios, and comparison of the surface structures derived from density functional theory with extended X-ray absorption fine structure. Productivity in cis-cyclooctene oxidation to epoxide and cis-diol with 2-10 equiv of solid cocatalytic supports is superior to that obtained with analogous soluble valeric acid cocatalysts, which require 1000-fold excess to reach similar levels at comparable times. Cyclooctene oxidation rates are near first order in H 2O2 and near zero order in all other species, including H2O. These observations are consistent with a mechanism of substrate oxidation following rate-limiting H2O2 activation on the hydrated, supported complex. This general mechanism and the observed alkene oxidation activation energy of 38 ± 6 kJ/mol are comparable to H 2O2 activation by related soluble catalysts. Undesired decomposition of H2O2 is not a limiting factor for these solid catalysts, and as such, productivity remains high up to 25 °C and initial H2O2 concentration of 0.5 M, increasing reactor throughput. These results show that immobilized carboxylic acids can be utilized and understood like traditional carboxylic acids to activate non-heme oxidation catalysts while enabling higher throughput and providing the separation and handling benefits of a solid catalyst.

Original languageEnglish
Pages (from-to)18684-18695
Number of pages12
JournalJournal of the American Chemical Society
Volume133
Issue number46
DOIs
Publication statusPublished - Nov 23 2011

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Manganese
Catalyst supports
Oxidation
Carboxylic Acids
Catalysts
Alkenes
Carboxylic acids
X-Rays
X ray absorption
Olefins
Epoxy Compounds
Productivity
Chemical activation
Throughput
Spectrum Analysis
Acids
triazacyclononane
1,4,7-trimethyl-1,4,7-triazacyclononane
Surface structure
Density functional theory

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Manganese triazacyclononane oxidation catalysts grafted under reaction conditions on solid cocatalytic supports. / Schoenfeldt, Nicholas J.; Ni, Zhenjuan; Korinda, Andrew W.; Meyer, Randall J.; Notestein, Justin M.

In: Journal of the American Chemical Society, Vol. 133, No. 46, 23.11.2011, p. 18684-18695.

Research output: Contribution to journalArticle

Schoenfeldt, Nicholas J. ; Ni, Zhenjuan ; Korinda, Andrew W. ; Meyer, Randall J. ; Notestein, Justin M. / Manganese triazacyclononane oxidation catalysts grafted under reaction conditions on solid cocatalytic supports. In: Journal of the American Chemical Society. 2011 ; Vol. 133, No. 46. pp. 18684-18695.
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