A Stable “End‐On” Iron(III)–Hydroperoxo Complex in Water Derived from a Multi‐Iron(II)‐Substituted Polyoxometalate and Molecular Oxygen

Head over EELS: Reaction of O2 with a hexa-iron(II)-substituted polyoxometalate in water yields a polyoxometalate with “end-on” hydroperoxo groups, {FeIIIO2H}, at the terminal positions. The hydroperoxo moiety, stabilized by hydrogen bonding with water, is unusual for its long OO bond and nearly linear Fe-O-O bond angle. Electron energy-loss spectroscopy (EELS) is used to determine the oxidation state of iron.