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

Massie, Allyssa A.; Denler, Melissa C.; Cardoso, Luísa Thiara; Walker, Ashlie N.; Hossain, Kamal LU ; Day, Victor W.; Nordlander, Ebbe LU and Jackson, Timothy A. (2017) In Angewandte Chemie (International edition) 56(15). p.4178-4182
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.... (More)

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.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
C-H activation, Hydrogen atom transfer, Kinetics, Manganese, Metal-oxo compounds
in
Angewandte Chemie (International edition)
volume
56
issue
15
pages
4178 - 4182
publisher
John Wiley & Sons
external identifiers
  • scopus:85015179485
  • wos:000397599500014
ISSN
1433-7851
DOI
10.1002/anie.201612309
language
English
LU publication?
yes
id
45cc51d7-dd37-4dd5-8f7c-430330430cb9
date added to LUP
2017-03-30 09:53:29
date last changed
2018-03-18 05:11:12
@article{45cc51d7-dd37-4dd5-8f7c-430330430cb9,
  abstract     = {<p>Manganese(IV)-oxo complexes are often invoked as intermediates in Mn-catalyzed C-H bond activation reactions. While many synthetic Mn<sup>IV</sup>-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 Mn<sup>IV</sup>-oxo complexes with N5 pentadentate ligands that modulate the equatorial ligand field of the Mn<sup>IV</sup> 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 Mn<sup>IV</sup>-oxo complexes, the rate enhancements are correlated with both 1)the energy of a low-lying <sup>4</sup>E excited state, which has been postulated to be involved in a two-state reactivity model, and 2)the Mn<sup>III/IV</sup> reduction potentials.</p>},
  author       = {Massie, Allyssa A. and Denler, Melissa C. and Cardoso, Luísa Thiara and Walker, Ashlie N. and Hossain, Kamal and Day, Victor W. and Nordlander, Ebbe and Jackson, Timothy A.},
  issn         = {1433-7851},
  keyword      = {C-H activation,Hydrogen atom transfer,Kinetics,Manganese,Metal-oxo compounds},
  language     = {eng},
  number       = {15},
  pages        = {4178--4182},
  publisher    = {John Wiley & Sons},
  series       = {Angewandte Chemie (International edition)},
  title        = {Equatorial Ligand Perturbations Influence the Reactivity of Manganese(IV)-Oxo Complexes},
  url          = {http://dx.doi.org/10.1002/anie.201612309},
  volume       = {56},
  year         = {2017},
}