Tetrafluoroborate is the anion BF
4. This tetrahedral species is isoelectronic with tetrafluoroberyllate (BeF
4), tetrafluoromethane (CF4), and tetrafluoroammonium (NF
4) and is valence isoelectronic with many stable and important species including the perchlorate anion, ClO
4, which is used in similar ways in the laboratory. It arises by the reaction of fluoride salts with the Lewis acid BF3, treatment of tetrafluoroboric acid with base, or by treatment of boric acid with hydrofluoric acid.
⭐ Core Definition: Tetrafluoroborate
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Tetrafluoroborate in the context of Ferrocenium
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 (BF
4). The related hexafluorophosphate is also a popular reagent with similar properties. The ferrocenium cation is often abbreviated Fc or Cp2Fe. The salt is deep blue in color and paramagnetic.
Ferrocenium salts are one-electron oxidizing agents, and the reduced product, ferrocene, is inert and often readily separated from ionic products. The ferrocene–ferrocenium couple is used as a reference in electrochemistry. The standard potential of ferrocene-ferrocenium is dependent on specific electrochemical conditions.
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