Abstract[Rh(η5‐C5H5)(C8H4S8)] and [M(η5‐C5Me5)(C8H4S8)] [M = RhIII and IrIII. C8H4S82− = 2‐{(4,5‐ethylenedithio)‐1,3‐dithiole‐2‐ylidene}‐1,3‐dithiole‐4,5‐dithiolate(2−)] were prepared by reactions of [NMe4]2[C8H4S8] with [Rh(η5‐C5H5)Cl2]2 or [M(η5‐C5Me5)Cl2]2 (M = Rh and Ir). They exhibit oxidation potentials of between +0.16 and +0.24 V (versus Ag/Ag+) with oxidation of the dithiolate ligand. The geometries and electronic states of their one‐electron‐oxidized species [M(L)(C8H4S8)]+ and [RhX(L)(C8H4S8)] (M = Rh and Ir; X = Br and I; L = η5‐C5H5 and η5‐C5Me5), obtained by reactions of the above complexes with bromine, iodine, or the ferrocenium cation are discussed based on their ESR spectra. The oxidized η5‐C5Me5‐metal complexes exhibit electrical conductivities of between 10−6 and 10−4 S cm−1, while some oxidized η5‐C5H5‐Rh complexes show conductivities of between 10−3 and 10−2 S cm−1 measured for compacted pellets at room temperature. The X‐ray crystal structures of the two‐electron‐oxidized species [MI(η5‐C5Me5)(C8H4S8)](I3) (M = Rh and Ir) were also clarified. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)