Ferrocenium tetrafluoroborate
Ferrocenium tetrafluoroborate is an organometallic compound with the formula [Fe(CH)]BF. This salt is composed of the cation [Fe(CH)] and the tetrafluoroborate anion (). The related hexafluorophosphate is also a popular reagent with similar properties. The cation is often abbreviated Fc or CpFe. The salt is deep blue in color and paramagnetic. Ferrocenium salts are sometimes used as one-electron oxidizing agents, and the reduced product, ferrocene, is inert and readily separated from ionic products. The ferrocene–ferrocenium couple is often used as a reference in electrochemistry. The standard potential of ferrocene-ferrocenium is 0.400 V vs. the normal hydrogen  electrode (NHE) and is often assumed to be invariant between different solvents. Preparation. Commercially available, this compound may be prepared by oxidizing ferrocene typically with ferric salts followed by addition of fluoroboric acid. A variety of other oxidants work well also, such as nitrosyl tetrafluoroborate. Many analogous ferrocenium salts are known.