Chemists Make Elusive Multifluorinated Ferrocene | Chemical & Engineering News
Volume 93 Issue 1 | p. 21 | Concentrates
Issue Date: January 5, 2015

Chemists Make Elusive Multifluorinated Ferrocene

Pentafluoroferrocene is only the second fluorinated ferrocene reported—and the most fluorinated reported
Department: Science & Technology
News Channels: Organic SCENE, JACS In C&EN
Keywords: organometallic chemistry, fluorine chemistry, ferrocene, crystallography, cyclic voltammetry
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X-ray crystal structure of pentafluoroferrocene.
Credit: Adapted from J. Am. Chem. Soc.
X-ray crystal structure of pentafluoroferrocene.
 
X-ray crystal structure of pentafluoroferrocene.
Credit: Adapted from J. Am. Chem. Soc.

Ferrocene, the iconic sandwich-shaped metal complex, is the compound that made researchers hungry to explore organometallic chemistry. Chemists have prepared countless derivatives by modifying ferrocene’s two cyclopentadiene rings. But fluorinated ferrocenes have proven elusive, a frustrating situation given the importance of fluorinated hydrocarbons in catalysis. Chemists in Germany have now made 1,2,3,4,5-pentafluoroferrocene, which is only the second fluorinated ferrocene reported, after monofluoroferrocene in 1971 (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja511588p). Karlheinz Sünkel of Ludwig Maximilian University of Munich and coworkers performed five sequential lithiation-fluorination reactions to obtain pentafluoroferrocene in 6.7% yield from ferrocene. Chemists in the 1960s predicted that polyfluorinated ferrocenes would have high oxidative stability. Surprisingly, cyclic voltammetry data suggest the new compound is easy to oxdize, particularly when compared with pentachloroferrocene or with similar ruthenium complexes. The researchers corroborated their experimental results with density functional theory calculations and verified pentafluoroferrocene’s structure with NMR and IR spectroscopy and X-ray crystallography.

 
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