Redox behavior of boronato-functionalized 1,1′-bis(diphenylphosphino)ferrocenes

The one-electron oxidation of 1,1'-bis(diphenylphosphino)-2-[1-((boronato-functionalised)amino)ethyl)]ferrocenes leads to ferrocenium congeners which are generally more stable than the unsubstituted 1,1'-bis(diphenylphosphino)ferrocenium ion. 1,1'-bis(Diphenylphosphino)ferrocenes bearing in position 2 different bulky substituents also tend to improve the chemical stability of the respective ferrocenium congeners, without affecting the localization of the ferrocene/ferrocenium electrode potential. It is hence assumed that, independently from their inductive effects, sterically encumbering X substituents in 1,1'-bis(diphenylphosphino)-2-[1-((X)amino)ethyl]ferrocenes attenuate the well known instability of the 1,1'-bis(diphenylphosphino)ferrocenium cation. Mass spectrometric techniques have however proved that, as it happens for solutions of 1,1'-bis(diphenylphosphino)ferrocenium ion, the ultimate fate of the highly reactive 1,1'-bis(diphenylphosphino)-2-[1-((X)amino)ethyl]ferrocenium ions is the rearrangement to 1,1'-bis(oxodiphenylphosphoranyl)-2-[1-((X)amino)ethyl]ferrocenes, a reaction which is likely triggered by traces of water. (C) 2001 Published by Elsevier Science B.V.