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Issue 36, 2013
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Reaction landscape of a pentadentate N5-ligated MnII complex with O2˙ and H2O2 includes conversion of a peroxomanganese(III) adduct to a bis(μ-oxo)dimanganese(III,IV) species

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Abstract

Herein we describe the chemical reactivity of the mononuclear [MnII(N4py)(OTf)](OTf) (1) complex with hydrogen peroxide and superoxide. Treatment of 1 with one equivalent superoxide at −40 °C in MeCN formed the peroxomanganese(III) adduct, [MnIII(O2)(N4py)]+ (2) in ∼30% yield. Complex 2 decayed over time and the formation of the bis(μ-oxo)dimanganese(III,IV) complex, [MnIIIMnIV(μ-O)2(N4py)2]3+ (3) was observed. When 2 was formed in higher yields (∼60%) using excess superoxide, the [MnIII(O2)(N4py)]+ species thermally decayed to MnII species and 3 was formed in no greater than 10% yield. Treatment of [MnIII(O2)(N4py)]+ with 1 resulted in the formation of 3 in ∼90% yield, relative to the concentration of [MnIII(O2)(N4py)]+. This reaction mimics the observed chemistry of Mn-ribonucleotide reductase, as it features the conversion of two MnII species to an oxo-bridged MnIIIMnIV compound using O2 as oxidant. Complex 3 was independently prepared through treatment of 1 with H2O2 and base at −40 °C. The geometric and electronic structures of 3 were probed using electronic absorption, electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD), variable-temperature, variable-field MCD (VTVH-MCD), and X-ray absorption (XAS) spectroscopies. Complex 3 was structurally characterized by X-ray diffraction (XRD), which revealed the N4py ligand bound in an unusual tetradentate fashion.

Graphical abstract: Reaction landscape of a pentadentate N5-ligated MnII complex with O2˙− and H2O2 includes conversion of a peroxomanganese(iii) adduct to a bis(μ-oxo)dimanganese(iii,iv) species

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Publication details

The article was received on 15 May 2013, accepted on 09 Jul 2013 and first published on 12 Jul 2013


Article type: Paper
DOI: 10.1039/C3DT51277K
Citation: Dalton Trans., 2013,42, 13014-13025
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    Reaction landscape of a pentadentate N5-ligated MnII complex with O2˙ and H2O2 includes conversion of a peroxomanganese(III) adduct to a bis(μ-oxo)dimanganese(III,IV) species

    D. F. Leto, S. Chattopadhyay, V. W. Day and T. A. Jackson, Dalton Trans., 2013, 42, 13014
    DOI: 10.1039/C3DT51277K

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