The reduction of LCoOOH(2+) (L = L(1) = [14]aneN(4) and L(2) = Me(6)[14]aneN(4)) by Cr2+, Fe2+, VO2+, V2+, Ti3+, and Co(tim)(2+) has been studied in acidic aqueous solution. The L(1)CoOOH(2+)/Fe2+ reaction takes place with a second-order rate constant 4.8 L mol(-1) s(-1) at 25 degrees C and 0.10 M H3O+. It is accompanied by a large negative entropy of activation, -122 J mol(-1) K-1. In the presence of a large excess of Fe2+, this reaction proceeds with a 1:2 stoichiometry and produces L(1)Co(3+) and Fe3+. A Fenton mechanism is proposed for this and other reduction reactions of LCoOOH(2+). The oxidation of LCoOOH(2+) by RU(bipy)(3)(3+), Fe(phen)(3)(3+), IrCl62-, VO2+, and Fe3+ has also been investigated. The outer-sphere electron transfer reactions with Ru(bipy)(3)(3+), Fe(phen)(3)(3+), and IrCl(6)(2-)proceed with a 1:2 stoichiometry. The reaction of L(1)CoOOH(2+) with Fe3+ produces O-2 With a second-order rate constant 2.74 L mol(-1) s(-1) at 25 degrees C and 0.10 M H3O+. Unlike the reduction reactions, the kinetics of the oxidation of L(1)CoOOH(2+) are acid-dependent.