ELECTRON-, ANION-, AND PROTON-TRANSFER PROCESSES ASSOCIATED WITH THE REDOXCHEMISTRY OF FE(ETA 5-C5PH5)((ETA 6-C6H5)C5PH4 AND ITS PROTONATED FORM FE(E TA 5-C5PH5)((ETA 6-C6H5)C5PH4H)BF4 AT MICROCRYSTAL-ELECTRODE-SOLVENT (ELECT ROLYTE) INTERFACES

Voltammograms of microcrystals of Fe(η5-C5Ph5)((η6-C6H5)C5Ph4) and [Fe(η5-C5Ph5)((η6-C6H5)C5Ph4H)]BF4 mechanically attached to graphite or gold electrodes are well-defined when the electrode is placed in (70:30) water/acetonitrile (0.1 M electrolyte) media. The simplest processes at the electrode−solvent (electrolyte) interface are the chemically reversible oxidation of Fe(η5-C5Ph5)((η6-C6H5)C5Ph4), Fe(η5-C5Ph5)((η6-C6H5)C5Ph4)(solid) + X-(solution) ⇌ [Fe(η5-C5Ph5)((η6-C6H5)C5Ph4)][X](solid) + e- when X- is the electrolyte anion (ClO4-, BF4-, Cl-, or F-), and the chemically reversible reduction of [Fe(η5-C5Ph5)((η6-C6H5)C5Ph4H)]BF4, [Fe(η5-C5Ph5)((η6-C6H5)C5Ph4H)][BF4](solid) + e- ⇌ Fe(η5-C5Ph5)((η6-C6H5)C5Ph4H)(solid) + BF4-(solution), when BF4- is the electrolyte anion. Anion exchange between BF4-(solid) in [Fe(η5-C5Ph5)((η6-C6H5)C5Ph4H)]BF4 and the electrolyte anion, X-(solution), is rapid so that the potentials of both processes are dependent on the electrolyte anion. Cyclic voltammograms scanned over...