Cyclic voltammetric studies of dioxygenbridged dinuclear cobalt(III) complexes
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Cyclic voltammetric studies were carried out for dioxygen-bridged dinuclear cobalt(III) complexes using platinum electrodes at different values of pH and ionic strength. Reversible electrode reactions occur particularly for the dioxygen complexes [(phen)2Co(μ-O2,NH2)Co(phen)2] (ClO4)42H2O and [(bpy)2Co(μ-u-O2, NH2)Co(bpy)2] (ClO4)4H2O with 1,10-phenanthroline (phen) and 2,2-bipyridine (bpy) as the non-bridging ligands. For complexes with ammonia (NH3) ethylenediamine (en) as the terminal ligands, there is quasi-reversible electrode behaviour at pH < 3 due to protonation of the peroxo complexes which subsequently undergo equilibration with isomeric forms. Such behaviour is well-marked for the peroxo complex [(en)2Co(μ-O2 NH2)Co(en)2](NO3)3. The decaammine complex [(NH3 5Co(μ-O2Co(NH3)5](NO3)5 shows only a cathodic peak due to intramolecular charge transfer decomposition in solution after reduction at the electrode. Diffusion coefficients for all the dioxygen complexes were determined from the plots ofI p vs.v 1/2.
KeywordsCyclic voltammetric studies dioxygen-bridged dinuclear Co(III) complexes superoxo complexes peroxo complexes coordinated dioxygen systems
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