Unlocking a Ferrocenium Superoxidizer with the Perfluorinated Cp* Ligand

Abstract

The photolytically induced arene displacement of [Fe(C5H5)(oDCB)][PF6] (oDCB = ortho-dichlorobenzene) in the presence of [NEt4][C5(CF3)5] afforded the highly fluorinated and benchstable ferrocene [Fe(C5H5)(C5(CF3)5)]. The perfluorinated Cp* ligand exerts an extreme electron withdrawing effect on the ferrocene with E1/2 = 1.35 V (vs. Fc/Fc+). This proved to be the highest value obtained for any ferrocene reported so far. The corresponding stable and storable ferrocenium complex [Fe(C5H5)(C5(CF3)5)][AsF6] was generated in quantitative yield and represents not only the most oxidizing ferrocenium species, but also the strongest known isolable organometallic oxidizer. Its strength was demonstrated by the twofold oxidation of [Fe(C5(CH3)5)2] to its dication and an oxidative C-H activation of ortho-terphenyl. This unprecedented redox chemistry combined with perfluorocarbon solubility allows for selective and quantitative recycling of the highly fluorinated ferrocene. Together with the low basicity and inertness of [Fe(C5H5)(C5(CF3)5)], the chemistry of strong oxidizers is herein expanded into organometallics.