Synthesis, chemical reactivity and electrochemical behaviour of mono- and difluoro metallocenes

• The synthesis of mono- and difluorometallocenes was reported.
• The mild fluorination agent NFSI is highly suitable for the redox-prone ferrocene.
• Subsequent reactions to 1,1′-asymmetrically disubstituted compounds are possible.
• Half-wave potentials of fluoro-ferrocenes were recorded for the first time.
• Electrochemical increments for all mono- and 1,1′-dihalogen substituted ferrocenes are tabulated.

We report the synthesis of mono- and 1,1′-difluoro-substituted metallocenes (ferrocene, ruthenocene) and of asymmetrical 1,1′-disubstituted ferrocenes with one substituent being fluorine. Lithiation of metallocenes and subsequent addition of the fluorinating agent NFSI gave the fluorinated metallocenes after optimization of the experimental conditions. All new compounds were comprehensively characterized and the cyclic voltammograms of fluoro- and 1,1′-difluoroferrocene were recorded and compared to other mono- and dihalogenated ferrocenes. Half-wave potentials of +106 mV and +220 mV vs. FcH0/+ were obtained for monofluorinated species and difluorinated ferrocene, respectively. Both values are remarkably low compared to the other halogenated ferrocenes (Cl, Br, and I). Finally, 1-bromo-1'-fluoro-ferrocene turns out to be an ideal starting material for further fluoro-substituted ferrocene derivatives.

Herein we present a facile and convenient one-pot synthesis of fluoro- and difluoro containing metallocenes. Lithiation of metallocenes and subsequent addition of the fluorinating agent NFSI gave fluorinated metallocenes in good yields. Electrochemical measurements were carried out with monofluoro- and 1,1′-difluoroferrocene and the obtained data were compared to other mono- and dihalogenated ferrocenes. 1-Bromo-1'-fluoro-ferrocene turns out to be an ideal starting material for further fluoro-substituted ferrocene derivatives.Figure optionsDownload as PowerPoint slide