The electrochemical behavior of [Rh2(dimen)4]2+ (dimen = 1,8-diisocyanomenthane) in the nonaqueous solvents CH3CN and CH2Cl2has been investigated by cyclic voltammetry, potential-step methods, and double-potential-step chronocoulometry. The appearance of the cyclic voltammogram is dramatically influenced by relatively weak ionic aggregation of the [Rh2(dimen)4]2+ species with the supporting anion and by the strong complexation of the 2e oxidized species [Rh2(dimen)4]4+ formed at the electrode. The formal 2e couple E°'4+/2+in CH2Cl2solutions in the presence of ClO4- is +0.46 V vs. Ag/AgCl. The relative stabilities of the 2e oxidized species [Rh2(dimen)4(X)2]2+ (X = PF6-, ClO4-, and Cl-) are estimated. The Cl- and ClO4- complexes are respectively 46.6 and 4.6 kcal/mol more stable than the corresponding PF6- complex. The differences in the behavior of the [Rh2(dimen)4]2+ system studied here are compared to the previously studied [Rh2(bridge)4]2+ system.