Ligand-based radicals

Electrochemical reduction of [Ni(bipy)3] + affords [Ni(bipy)3]+ and [Ni(bipy)3], which are formulated as Ni and Ni -bipy radical anion complexes, respectively. These species are highly reactive and illustrate the problems of assigning redox products as genuine metal-based or ligand-based radicals. 

Many derivatives of the Group VI metal carbonyls, [M(CO)6] (M = Cr, Mo, or W) undergo reversible one-electron oxidation or reduction, and stable, sometimes isolable, metal- or ligand-based radicals have been fully characterized. The redox potentials of representative complexes are listed in Table I. 

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