IMPACT OF CHROMIUM COORDINATION ON THE SINGLE-ELECTRON POTENTIALS FOR THE REDUCTION OF OXYGEN TO WATER

Chemical equilibration of CrOO2+ has allowed evaluation of the potential for the half-reaction CrOO2+ + H+ + e(-) --> CrOOH2+ as +0.82 V vs NHE. Kinetic data for the reaction of CrO2+ and H2O2 allow refinement of the potential for the CrO2+ + 2H(+) + e(-) --> Cr3+ + H2O reaction to lie within the range 1.71 V less than or equal to E degrees less than or equal to 1.85 V. With these values the potentials for each step of reduction of water to oxygen, as mediated by chromium complexation, are obtained. The chemical implications of these findings for the reactions and reactivity of the three chromium-containing species CrOO2+, CrOOH2+, and CrO2+ are presented.