Ferrocenium tetrafluoroborate
Ferrocenium tetrafluoroborate is an organometallic compound with the formula [Fe(C5H5)2]BF4. This salt is composed of the cation [Fe(C5H5)2]+ and the tetrafluoroborate anion (BF4−). The related hexafluorophosphate is also a popular reagent with similar properties. The cation is often abbreviated Fc+ or (Cp2Fe)+. 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. In acetonitrile solution that is 0.1 M in NBu4PF6, the Fc+/0 couple is +0.641 V with respect to the normal hydrogen electrode.
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.
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