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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
Leto, Domenick F. Chattopadhyay, Swarup Day, Victor W. Jackson, Timothy A.
Leto, Domenick F.
Chattopadhyay, Swarup
Day, Victor W.
Jackson, Timothy A.
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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.
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2013-07-19
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Royal Society of Chemistry
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Leto, Domenick F., Swarup Chattopadhyay, Victor W. Day, and Timothy A. Jackson. "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." Dalton Transactions 42.36 (2013): 13014.