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

• Published in: Journal of organometallic chemistry Vol. 637; pp. 800 - 804
• Main Authors: Zanello, Piero, Cinquantini, Arnaldo, Fontani, Marco, Giardiello, Marco, Giorgi, Gianluca, Landis, Clark R, Kimmich, Barbara F.M
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 03.12.2001
• Subjects: 1,1′-bis(Diphenylphosphino)-2-[1-((boronato-functionalised)amino)ethyl)]ferrocenes; Electrochemistry; Ferrocenium ion rearrangement; Mass spectrometry; 1,1′-bis(Diphenylphosphino)-2-[1-((boronato-functionalised)amino)ethyl)]ferrocenes; Electrochemistry; Ferrocenium ion rearrangement; Mass spectrometry
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(01)01132-9

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. The one-electron oxidation of 1,1′-bis(diphenylphosphino)-2-[1-((X)amino)ethyl]ferrocenes (X = sterically encumbering substituents) in nonaqueous solution affords the fairly stable ferrocenium congeners, which, because of traces of water, relatively slowly convert to the corresponding 1,1′-bis(oxodiphenylphosphoranyl)-2-[1-((X)amino)ethyl]ferrocenes.