A MnIIMnIII‐Peroxide Complex Capable of Aldehyde Deformylation

Ribonucleotide reductases (RNRs) are essential enzymes required for DNA synthesis. In class Ib Mn₂ RNRs superoxide (O₂^.?) was postulated to react with the Mn^II₂ core to yield a Mn^IIMn^III‐peroxide moiety. The reactivity of complex 1 ([Mn^II₂(O₂CCH₃)₂(BPMP)](ClO₄), where HBPMP=2,6‐bis{[(bis(2‐pyridylmethyl)amino]methyl}‐4‐methylphenol) towards O₂^.? was investigated at ?90 °C, generating a metastable species, 2 . The electronic absorption spectrum of 2 displayed features (λ_max=440, 590 nm) characteristic of a Mn^IIMn^III‐peroxide species, representing just the second example of such. Electron paramagnetic resonance and X‐ray absorption spectroscopies, and mass spectrometry supported the formulation of 2 as a Mn^IIMn^III‐peroxide complex. Unlike all other previously reported Mn₂‐peroxides, which were unreactive, 2 proved to be a capable oxidant in aldehyde deformylation. Our studies provide insight into the mechanism of O₂‐activation in Class Ib Mn₂ RNRs, and the highly reactive intermediates in their catalytic cycle.