Synthesis, structure and redox chemistry of 1,2-bis(ruthenocenyl)ethylene derivatives: a novel structural rearrangement to a (µ-η6∶η6-pentafulvadiene)diruthenium complex upon two-electron oxidation
Abstract
Formylruthenocene, 1-formyl-1′,2′,3′,4′,5′-pentamethylruthenocene and 1-formyl-2,3,4,5-tetramethylruthenocene were treated with TiCl4–Zn in thf to afford the corresponding ethylene derivatives trans-1,2-bis(ruthenocenyl)ethylene, trans-1,2-bis(1′,2′,3′,4′,5′-pentamethylruthenocenyl)ethylene and trans-1,2-bis(2,3,4,5-tetramethylruthenocenyl)ethylene in excellent yields. Similarly, the dimethyl analogs were obtained from acetylruthenocene and 1-acetyl-1′,2′,3′,4′,5′-pentamethylruthenocene in good yields. Cyclic voltammograms of the ethylene complexes showed an irreversible two-electron oxidation wave at significantly lower potential than that of pentamethylruthenocene or ruthenocene. Two-electron chemical oxidation of these complexes with p-benzoquinone–BF3·OEt2 gave stable dicationic (µ-η6∶η6-pentafulvadiene)diruthenium complexes in moderate yields. The molecular structures of five complexes were determined by X-ray diffraction.
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