Effect of solvent, electronic, and steric factors on the reactivity of 1,1'-diethylferrocene, 1,1'-diacetylferrocene, and 1,1'-bis(diphenylphosphino)ferrocene towards hydrogen peroxide

Abstract

The oxidation of Fc(C₂H₅)₂, Fc(COCH₃)₂, and Fc(PPh₂)₂, where Fc is a ferrocene, with hydrogen peroxide in aprotic (dioxane and acetonitrile) and hydroxyl-containing (ethanol, acetonitrile–water, and water) solvents is studied via electron spectroscopy. The reactivity of these metal complexes relative to an oxidant is due to the electron-donor or electron-acceptor properties of substituents, their sizes, and their capability for the specific solvation by a particular solvent. Possible mechanisms of the oxidation of metal complexes are discussed. When Fc(PPh₂)₂ is oxidized, the formation of ferrocenyl cation Fc⁺(PPh₂)₂ is due to the redox isomerism of ferrocenylphosphonium cation Fc(PPh₂)P⁺Ph₂, which can form during the reaction between protonated complex Fc(PPh₂)P(H⁺)Ph₂ and H₂O₂.