An Fe IV=O group meets with H 2O 2! Reaction of high-valent iron with the reactive oxygen species (ROS) hydrogen peroxide (H 2O 2) is in general reserved for heme centers. Employing a biomimetic metal complex, the direct reaction of a mononuclear nonheme oxoiron(IV) species with H 2O 2 was observed and studied mechanistically, offering a new perspective for the chemistry between ROS and high-valent oxometal complexes