The syntheses of copper and bis(η-cyclopentadienyl)molybdenum complexes of a dithiolene ligand incorporating a trioxadithia-15-crown-5-unit [1,4,7-trioxa-10,13-dithiacyclopentadec-11-ene-11,12-dithiolate(2–)] are described. The electrochemistry of these complexes was investigated by cyclic voltammetry in acetonitrile. Upon addition of an excess of alkali-metal cations large shifts of the redox potentials of the compounds were observed.