The transition state of the charge separation Co(H2O)(4)(2+) --> CoOH(H2O)(2)(+) + H3O+ is located by density functional theory calculations. The H3O+ unit is already separated from the CoOH(H2O)(2)(+) moiety by more than 3 Angstrom, and the charge centers form a Co2+-OH--H3O+ salt bridge, lowering the barrier for the reaction. The transition state is calculated to lie 166 kJ/mol above the products, including zero-point corrections, which compares favorably with the 110 +/- 20 kJ/mol kinetic energy release measured in an earlier work (Faherty, K. P.; et al. J. Phys. Chem. A 2001, 105, 10054). The deviation is interpreted as fractions of the energy going into rotational and vibrational excitation of the products.