Study for the Novel Metal-metal Interaction in the Binuclear Ruthenocene Derivatives

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Previously, we have reported that some of the binuclear ruthenocene derivatives took an EEC type of redox process and gave a stable oxidized species as isolable crystals, although ruthenocene itself underwent an irreversible 2e-oxidation. As a recent result, it became clear that there is a resonance of the limited structures among Ru (II)-Ru (II), Ru (III)-Ru (III), and Ru (II)-Ru (IV), and various reactions take place from either of the limited structure according to the total structure of the molecule, the kind of the bridging ligand, and so on. For example, the previouslyreported (μ-η^6, η^6-fulvalene) diruthenium complex reacted with nitriles to give a Ru (II)-Ru (IV) mixed-valence complex and with bromine to give Ru (IV)-Ru (IV) complex through the Ru (II)-Ru (IV) state. In the oxidation of the thiophene-bridsing binuclear ruthenocene derivatives, no stable oxidizing species was obtained, but the reaction of the oxidizing species with nitriles gave a stable Ru (II)-Ru (IV) derivat … More ive (78th Annual Meeting of Chem. Soc. Jpn, 2000). However, in the oxidation of binuclear ruthenocene derivatives bridged by the thieno [3, 2-b] thiophene, a stable Ru (II)-Ru (II) type of complex was isolated and the reaction of it with nitrile afforded the Ru (II)-Ru (IV) complex (50th Symposium on Organometllic Complex, 2000).In connection with the binuclear ruthenocene derivatives bridged by an unsaturated compound, the synthesis of the homoannnularly bridged binuclear ruthenocene derivatives was examined. As the result, the (μ-η^5, η^5-indacene-4, 8-dione)-buridging binuclear Ru complexes could be prepared. In the protonation of the compouns, the carbonyl group was protonated but not be converted to a hydroxyl group and the positive charge is almost localized on the oxygen atom. Such protonation is rarely reported. The structure of the resulting dication complex was determined by X-ray diffraction. We think that the α-ruthenocenium cation part cannot take a stabe fulvene structure, because the μ-η^5, η^5-indacene-4, 8-dione ligand is forced to take the planar structure (78th Annual Meeting of Chem. Soc. Jpn, 2001). Less