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Mixed-Valent Ruthenocene–Vinylruthenium Conjugates: Valence Delocalization Despite Chemically Different Redox Sites

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journal contribution
posted on 07.02.2019 by Christopher Hassenrück, André Mang, Rainer F. Winter
Ruthenocene–vinylruthenium conjugates Rc/Rc*–CHCH–Ru­(CO)­(L)­(PiPr3)2 (Rc = (η5-C5H5)­Ru­(η5-C5H4); Rc* = (η5-C5Me5)­Ru­(η5-C5H4); L = Cl or κO,O-acetylacetonato) have been prepared and investigated in their neutral, mono-, and dioxidized states by cyclic voltammetry, IR and UV/vis/NIR spectroelectrochemistry, and EPR spectroscopy. Their corresponding radical cations are (almost) completely delocalized mixed-valent systems as indicated by the low half-widths, the absence of solvatochromism, and the low-energy cutoff of their IVCT bands in the near-infrared (NIR) and their IR and EPR spectroscopic signatures. The degree of electronic coupling even exceeds that of their ferrocene analogs despite comparable differences between the intrinsic half-wave potentials of the vinylruthenium and the metallocenyl entities and substantially smaller half-wave potential splittings, ΔE1/2, in the ruthenocene congeners. All experimental results are backed by quantum chemical calculations.