The anodic electrochemical oxidations of ReCP(CO)(3) (1, Cp = eta(5)-C5H5), Re(eta(5)-C5H4NH2)(CO)(3) (2), and ReCp*(CO)(3) (3, Cp* = eta(5)-C5Me5), have been studied in CH2Cl2 containing [NBU4][TFAB] (TFAB = [B(C6F5)(4)](-)) as supporting electrolyte. One-electron oxidations were observed with E-1/2 = 1.16, 0.79, and 0.91 V vs ferrocene for 1-3, respectively. In each case, rapid dimerization of the radical cation gave the dimer dication, [Re2Cp2 gamma(CO)(6)](2+) (where Cp-gamma represents a generic cyclopentadienyl ligand), which may be itself reduced cathodically back to the original 18-electron neutral complex ReCp gamma(CO)(3). DFT calculations show that the SOMO of 1(+) is highly Re-based and hybridized to point away from the metal, thereby facilitating the dimerization process and other reactions of the Re(II) center. The dinners, isolated in all three cases, have long metal-metal bonds that are unsupported by bridging ligands, the bond lengths being calculated as 3.229 angstrom for [Re2Cp2(CO)(6)](2+) (1(2)(2+)) and measured as 3.1097 angstrom for [Re-2(C5H4NH2)(2)(CO)(6)](2+) (2(2)(2+)) by X-ray crystallography on [Re-2(C5H4NH2)(2)(CO)(6)][TFAB](2). The monomer/dimer equilibrium constants are between K-dim = 10(5) M-1 and 10(7) M-1 for these systems, so that partial dissociation of the dimers gives a modest amount of the corresponding monomer that is free to undergo radical cation reactions. The radical 1(+) slowly abstracts a chlorine atom from dichloromethane to give the 18-electron complex [ReCp(CO)(3)Cl](+) as a side product. The radical cation 1(+) acts as a powerful one-electron oxidant capable of effectively driving outer-sphere electron-transfer reactions with reagents having potentials of up to 0.9 V vs ferrocene.