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Ebbe Nordlander. Portrait.

Ebbe Nordlander

Professor

Ebbe Nordlander. Portrait.

Relationship between Hydrogen-Atom Transfer Driving Force and Reaction Rates for an Oxomanganese(IV) Adduct

Author

  • Allyssa A. Massie
  • Arup Sinha
  • Joshua D. Parham
  • Ebbe Nordlander
  • Timothy A. Jackson

Summary, in English

Hydrogen atom transfer (HAT) reactions by high-valent metal-oxo intermediates are important in both biological and synthetic systems. While the HAT reactivity of FeIV-oxo adducts has been extensively investigated, studies of analogous MnIV-oxo systems are less common. There are several recent reports of MnIV-oxo complexes, supported by neutral pentadentate ligands, capable of cleaving strong C-H bonds at rates approaching those of analogous FeIV-oxo species. In this study, we provide a thorough analysis of the HAT reactivity of one of these MnIV-oxo complexes, [MnIV(O)(2pyN2Q)]2+, which is supported by an N5 ligand with equatorial pyridine and quinoline donors. This complex is able to oxidize the strong C-H bonds of cyclohexane with rates exceeding those of FeIV-oxo complexes with similar ligands. In the presence of excess oxidant (iodosobenzene), cyclohexane oxidation by [MnIV(O)(2pyN2Q)]2+ is catalytic, albeit with modest turnover numbers. Because the rate of cyclohexane oxidation by [MnIV(O)(2pyN2Q)]2+ was faster than that predicted by a previously published Bells-Evans-Polanyi correlation, we expanded the scope of this relationship by determining HAT reaction rates for substrates with bond dissociation energies spanning 20 kcal/mol. This extensive analysis showed the expected correlation between reaction rate and the strength of the substrate C-H bond, albeit with a shallow slope. The implications of this result with regard to MnIV-oxo and FeIV-oxo reactivity are discussed.

Department/s

  • Chemical Physics

Publishing year

2018-07-16

Language

English

Pages

8253-8263

Publication/Series

Inorganic Chemistry

Volume

57

Issue

14

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Organic Chemistry

Status

Published

ISBN/ISSN/Other

  • ISSN: 0020-1669