The oxidations of two fulvalenediyl (Fv) dirhodium complexes [(Fv)Rh-2(CO)(4), 1, and (Fv)Rh-2(CO)(2)(mu-dppm), 2] have been studied by voltammetry, coulometry, IR spectroelectrochemistry, UV-VIS spectroscopy, and X-ray crystallography. Both complexes undergo net two-electron oxidations to dications having a Rh-Rh bond. The M-M bond distances are 2.837(1) Angstrom in 2(2+) and 4.511(1) Angstrom in 2. Quasi-reversible cyclic voltammetric responses were exploited over a range of sweep rates to give CV curves successfully fit to an EE mechanism by digital simulations : for 1, E(o)’(1) = -0.10 V (vs Fc), k(s1) = 0.013 cm s(-1), (1 - alpha(1)) = 0.66, E(o)’(2) = -0.24(5) V, k(s2) = 0.044 cm s(-1), alpha(2) = 0.5; for 2, E(o)’(1) = -0.76 V, k(s1) = 0.035 V, (1 - alpha(1)) = 0.75, E(o)’(2) = -0.776 V, k(s2) > 0.2 cm s(-1), alpha(2) = 0.5. Complementary results were obtained for the reduction of the dications 1(2+) or 2(2+). The effect of the bridging fulvalenediyl ligand is to retard the oxidation process by an amount consistent with the calculated barrier to rotation around the C-C bond of the eta(5),eta(5)’-C10H8 ligand. In both complexes the 0/1+ redox process is slower than the 1+/2+ process. The electron transfer rates are consistent with a progressive increase in the Rh-Rh bond order in the 0/1+/2+ charged complexes rather than full M-M bond formation and cleavage in a single step.