Amavadin and Homologues as Mediators of Water Oxidation

The vanadium(IV) N‐hydroxyiminodicarboxylate complexes [V(HIDPA)2]2− and [V(HIDA)2]2−, close models of the amavadin (a natural product from Amanita fungi lacking the V=O group but exhibiting a rare NO‐bound oxyiminate moiety), are shown to be the first recognized complexes of the early transition metals (up to periodic Group 7) that mediate the oxidation of water. The reactions were analyzed by visible spectrophotometry, mass spectrometry, and measurement of evolved dioxygen using Ce4+ as sacrificial oxidant. A mechanism proposed on the basis of DFT calculations involves the reversible oxidation to the mononuclear VV‐{ON˙