The Redox Behaviour of Ferrocene Derivatives. VIII. 1,1'-bis(diphenyl-phosphino)ferrocenes

A study has been made of the possibility of increasing the stability of the 1,1′-bis(diphenylphosphino)ferrocenium monocation by introduction of appropriate substituents into the cyclopentadienyl ligands. The electrochemical behaviour of a series of 1,1′-bis(diphenylphosphino)ferrocenes bearing substituents with a range of electronic properties has been examined. The results reveal that, the higher the electron-donating ability of the substituents, the longer is the lifetime of the corresponding 1,1′-bis(diphenylphosphino)ferrocenium monocation. However, no stable ferrocenium cation has been obtained; mass spectrometry shows that mixtures of mono- and di-bis(diphenylphosphine)oxides are ultimately formed as products resulting from decomposition of the initially electrogenerated 1,1′-bis(diphenylphosphino)ferrocenium species.