A High-Valent Iron(IV) Peroxo Core Derived from O₂

Dioxygen-tolerant [NiFe] hydrogenases catalyze not only the conversion of H₂ into 2 H⁺ and 2 e^- but also the reduction of O₂ to H₂O. Chemists have sought to mimic such bifunctional catalysts with structurally simpler compounds to facilitate analysis and improvement. Herein, we report a new [NiFe]-based catalyst for O₂ reduction via an O₂ adduct. Structural investigations reveal the first example of a side-on iron(IV) peroxo complex. Dioxygen-tolerant [NiFe] hydrogenases catalyze not only the conversion of H₂ into 2 H⁺ and 2 e^- but also the reduction of O₂ to H₂O. A new [NiFe]-based complex is a synthetic mimic of such hydrogenases and catalyzes O₂ reduction via an O₂ adduct, which was shown to be the first example of a side-on iron(IV) peroxo complex.