Synthesis and structure of the first sulfur-donor adduct of a diruthenium tetracarboxylate

The first sulfur-donor adduct of a diruthenium tetracarboxylate, [Ru2(μ-O2CCH3)4(THT)2]PF6 (1), where THT=tetrahydrothiophene, has been synthesized and characterized by X-ray diffraction, IR and UV–Vis spectroscopy, magnetic susceptibility and electrochemistry. Complex 1 displays a typical RuRu bond length of 2.285(4) Å but a very long RuS axial bond of 2.627(13) Å. The redox potential for the [Ru2(μ-O2CCH3)4(THT)2]+/0 couple is −322 mV (vs. Fc/Fc+) which is comparable to other moderately strong Lewis base adducts. Axial ligand binding is driven by σ-donation with little π-backdonation from the metal centers.