Metal-metal bond formation between [n]metallocenophanes: Synthesis and characterisation of a dicarba[2]ruthenocenophanium dimer

The redox properties of dicarba[2]ruthenocenophane were investigated using cyclic voltammetry (CV), and the results compared to those reported for ruthenocene. In the presence of the weakly-coordinating supporting electrolyte the latter exhibited a partially reversible oxidation wave corresponding to the formation of the ruthenocenium ion. This ruthenocenium ion exists in equilibrium with the metal metal-bonded dimer dication, as demonstrated in situ by voltammetry and NMR spectroscopy experiments. Under identical experimental conditions, CV scans of dicarba[2]ruthenocenophane show that it undergoes an irreversible one-electron oxidation. Bulk anodic electrolysis confirmed the one-electron oxidation of dicarba[2]ruthenocenophane , its exclusive conversion to the single product, and the subsequent quantitative reduction of that product back to dicarba[2]ruthenocenophane. Unlike the highly temperature and concentration-dependent voltammetry of ruthenocene, that of dicarba[2]ruthenocenophane varies little with changes in the medium.