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

• 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.

Subject headings

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Keyword

C-H activation

Hydrogen atom transfer

Kinetics

Manganese

Metal-oxo compounds

Publication and Content Type

art (subject category)

ref (subject category)