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by | Mar 19, 2018 | Brahea

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Ferrocenium hexafluorophosphate is an organometallic compound with the formula [Fe(C5H5)2]PF6. This salt is composed of the cation [Fe(C5H5)2]+ and the hexafluorophosphate anion (PF−
6). The related tetrafluoroborate 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 relatively 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+/Fc couple is +0.641 V with respect to the normal hydrogen electrode.[3]

Preparation and structure

Commercially available, this compound may be prepared by oxidizing ferrocene with ferric salts followed by addition of hexafluorophosphoric acid.[3]

The compound is monoclinic with well-separated cation and anion; the PF−
6 may rotate freely. The average Fe-C bond length is 2.047 Å, which is virtually indistinguishable from the Fe-C distance in ferrocene.[2]

References

  1. ^ "Ferrocenium hexafluorophosphate 388297". Sigma-Aldrich.
  2. ^ a b R. Martinez; A. Tiripicchio (1990). "Structure of ferrocenium hexafluorophosphate". Acta Crystallogr. C46 (2): 202–205. doi:10.1107/S0108270189005883.
  3. ^ a b Connelly, N. G.; Geiger, W. E. (1996). "Chemical Redox Agents for Organometallic Chemistry". Chem. Rev. 96 (2): 877–910. doi:10.1021/cr940053x. PMID 11848774.
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