The cyclic voltammograms in DMF or acetonitrile of[Cr(CN)(CO)(5)](-) (Ia) and [Cr(I)(CO)(5)](-) (IIa) show two anodic waves. Under an inert atmosphere, only the first one corresponding to a one-electron-transfer appears reversible for scan rates of 0.1 V s(-1). In DMF, in the presence of oxygen, the reversibility totally disappears. Macroscale electrolysis in a batch cell at a potential corresponding to the plateau of the first wave involves two moles of electrons per mole of starting material; during electrolysis, decomposition with CO evolution is observed for both complexes while in the case of IIa, additional formation of iodine takes place. In the presence of oxygen, CO2 is produced during electrolysis. The chemical transformations in MeCN of the two neutral species Cr(CN)(CO)(5) (Ib) and Cr(I)(CO)(5) (IIb) were studied by cyclic voltammetry immediately after their generation by one-electron oxidation in a flow cell of the parent complexes Ia and IIa. A comparative study of solutions in MeCN of Ia, IIa and Cr(CO)(6) which have been subject to uv irradiation for approximate to 15 min shows that in both cases the first step of the chemical transformation consists in a ligand exchange with formation of [Cr(CN)(NCMe)(CO)(4)] or [Cr(NCMe)(CO)(5)], respectively. Ib (Ia) and IIb (IIa) also proved to be efficient redox catalysts for the electrooxidation of the cyanide ion and of triphenylphosphine.