Structure and reactivity of a mononuclear non-haem iron(III)–peroxo complex

Iron–oxygen intermediates identified The iron–oxygen species iron(III)-peroxo, iron(III)-hydroperoxo and iron(IV)-oxo are key intermediates often detected in the catalytic cycles of dioxygen activation by haem and non-haem iron enzymes. The high-resolution crystal structure of a mononuclear non-haem side-on iron(III)-peroxo complex has now been determined, and a series of chemical reactions in which the iron(III)-peroxo complex is cleanly converted to an iron(III)-hydroperoxo complex is described. All three of these iron species have been spectroscopically characterized, and relative reactivity studies demonstrate that iron(III)-hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes. This work shows how a series of biologically important iron–oxygen intermediates make use of a synthetic iron complex bearing a simple but versatile macrocyclic ligand.