Crystallographic and Spectroscopic Characterization of a Nonheme Fe(IV)=O Complex

Following the heme paradigm, it is often proposed that dioxygen activation by nonheme monoiron enzymes involves an iron(IV)=oxo intermediate that is responsible for the substrate oxidation step. Such a transient species has now been obtained from a synthetic complex with a nonheme macrocyclic ligand and characterized spectroscopically. Its high-resolution crystal structure reveals an iron-oxygen bond length of 1.646(3) angstroms, demonstrating that a terminal iron(IV)=oxo unit can exist in a nonporphyrin ligand environment and lending credence to proposed mechanisms of nonheme iron catalysis.