Stabilization of nickel(III)-1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane by axial binding of anions in neutral aqueous solutions

The title tervalent nickel complex, Ni^IIIL⁵aq, is stabilized in neutral and slightly alkaline aqueous solutions in the presence of stabilizing anionic ligands via the formation of Ni^IIIL⁵X₂ complexes, where X=F^-, SO₄^2-, HPO₄^2-, HCO₂^-, C₆H₅CO₂^-, CH₃CO₂^- and (CH₃)₃CCO₂^-. These complexes can be used as new powerful single electron oxidizing reagents in this medium. Some of the properties of the Ni^IIIL⁵X₂ complexes are described and discussed.