Synthesis and Some Properties of Bis(ruthenocenyl)thiophene Derivatives – Possible Spin‐Coupling in the Two‐Electron Oxidized Species of Dinuclear Ruthenocenes Bridged by Thiophene Derivatives

The binuclear ruthenocene derivatives bridged by thiophene, 3,4‐ethylenedioxythiophene, 2,2′‐bithiophene, thieno[3,2‐ b ]thiophene, or 3,6‐dimethylthieno[3,2‐ b ]thiophene were prepared by the Suzuki coupling of 2‐ruthenocenyl‐4,5‐tetramethyl‐1,3‐dioxaborolane with the corresponding diiodo compounds. In addition, thiophene‐ and bithiophene‐bridged binuclear pentamethylruthenocenes were prepared by the reaction of bis(pentamethylruthenocenyl)diyne and‐tetrayne with NaSH, respectively. The cyclic voltammogramsof these complexes exhibit one‐step two‐electron redox waves in the lower potential region (0–0.3 V versus FcH/FcH + ). The two‐electron oxidized species of the thiophene‐bridged binuclear ruthenocene derivatives are comparatively stable and adopt the spin‐coupled and structurally isomerized fulvene complex‐type structure. The solid structure of the oxidized species of bis(pentamethylruthenocenyl)thiophene was determined by X‐ray diffraction analysis. The thieno[3,2‐ b ]thiophene‐bridged analog shows a temperature‐dependent 1 H NMR spectrum in CD 3 NO 2 . The dicationic species exist as a Ru II –Ru IV mixed‐valence species in CD 3 CN.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)