Nickel and Copper Corroles: Well‐Known Complexes in a New Light

Until very recently the Ni and Cu corroles, already described in the sixties, were regarded as the MII complexes 1 (M = Ni, Cu). Some doubt arose about this interpretation after the existence of FeIV corroles demonstrated that corroles can stabilize metals in unusual oxidation states. Thorough physical studies have now shown that the metal atoms in the Ni and Cu corroles do in fact have the formal oxidation state +III (2).