Abstract
The new ligands N‐[2‐(arylazo)phenyl]salicylideneamine, H~2~L~sal~ [where H represents the dissociable protons upon complexation and aryl groups of H~2~L~sal~ are phenyl for H~2~L^1^~sal~, p‐methylphenyl for H~2~L^2^~sal~, and p‐chlorophenyl for H~2~L^3^~sal~], were prepared by the reaction of 2‐(arylazo)aniline, H~2~L, with salicylaldehyde. H~2~L~sal~ ligands afforded stable orthometalated complexes, (L~sal~)Ni, upon treatment with Ni(CH~3~COO)~2~·4H~2~O. The dianionic (L~sal~)^2–^ ligands bind Ni^II^ in tetradentate (C,N,N,O) fashion in distorted square‐planar geometry. Reaction of (L~sal~)Ni with meta‐chloroperbenzoic acid, tert‐butyl hydroperoxide, or hydrogen peroxide furnished the metalloazosalophens, (OL~sal~)Ni, as a result of oxygen insertion into the Ni–C bond. The X‐ray structures of (L^1^~sal~)Ni and (OL^1^~sal~)Ni were determined as representatives for unequivocal characterization. Treatment of (OL^1^~sal~)Ni with dilute HClO~4~ liberated 2‐(2‐aminophenylazo)phenol, H~2~L^1^OH, which is an ortho‐hydroxylated derivative of H~2~L^1^. The cyclic voltammograms of (OL~sal~)Ni complexes display a reversible reductive response near –1.06 V vs. SCE.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)