Equatorial Ligand Perturbations Influence the Reactivity of Manganese(IV)-Oxo Complexes

Allyssa A. Massie, Melissa C. Denler, Luísa Thiara Cardoso, Ashlie N. Walker, Kamal Hossain, Victor W. Day, Ebbe Nordlander, Timothy A. Jackson

Research output: Contribution to journalArticlepeer-review

Abstract

Manganese(IV)-oxo complexes are often invoked as intermediates in Mn-catalyzed C-H bond activation reactions. While many synthetic MnIV-oxo species are mild oxidants, other members of this class can attack strong C-H bonds. The basis for these reactivity differences is not well understood. Here we describe a series of MnIV-oxo complexes with N5 pentadentate ligands that modulate the equatorial ligand field of the MnIV center, as assessed by electronic absorption, electron paramagnetic resonance, and Mn K-edge X-ray absorption methods. Kinetic experiments show dramatic rate variations in hydrogen-atom and oxygen-atom transfer reactions, with faster rates corresponding to weaker equatorial ligand fields. For these MnIV-oxo complexes, the rate enhancements are correlated with both 1)the energy of a low-lying 4E excited state, which has been postulated to be involved in a two-state reactivity model, and 2)the MnIII/IV reduction potentials.

Original languageEnglish
Pages (from-to)4178–4182
JournalAngewandte Chemie (International edition)
Volume56
Issue number15
DOIs
Publication statusPublished - 2017

Subject classification (UKÄ)

  • Materials Chemistry
  • Physical Chemistry

Free keywords

  • C-H activation
  • Hydrogen atom transfer
  • Kinetics
  • Manganese
  • Metal-oxo compounds

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