title: Equatorial Ligand Perturbations Influence the Reactivity of Manganese(IV)-Oxo Complexes.
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 MnIVcenter, 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-lying4E excited state, which has been postulated to be involved in a two-state reactivity model, and 2) the MnIII/IVreduction potentials.
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence, KS, USA.
authors.forename: Allyssa A
authors.initials: AA
authors.lastname: Massie
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence, KS, USA.
authors.forename: Melissa C
authors.initials: MC
authors.lastname: Denler
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence, KS, USA.
authors.forename: Luísa Thiara
authors.initials: LT
authors.lastname: Cardoso
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence, KS, USA.
authors.forename: Ashlie N
authors.initials: AN
authors.lastname: Walker
authors.affiliation: Chemical Physics, Department of Chemistry, Lund University, Box 124, 22100, Lund, Sweden.
authors.forename: M Kamal
authors.initials: MK
authors.lastname: Hossain
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence, KS, USA.
authors.forename: Victor W
authors.initials: VW
authors.lastname: Day
authors.affiliation: Chemical Physics, Department of Chemistry, Lund University, Box 124, 22100, Lund, Sweden.
authors.forename: Ebbe
authors.initials: E
authors.lastname: Nordlander
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence, KS, USA.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Jackson
mesh_terms: D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D000077318:Density Functional Theory; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D008345:Manganese; D010100:Oxygen
keywords: C−H activation; hydrogen atom transfer; kinetics; manganese; metal-oxo compounds