Ferrocenium tetrafluoroborate explained

Ferrocenium tetrafluoroborate is an organometallic compound with the formula [Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>]BF4. This salt is composed of the cation [Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>]+ and the tetrafluoroborate anion . 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 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 dependent on specific electrochemical conditions.

Preparation

Commercially available, this compound may be prepared by oxidizing ferrocene typically with ferric salts followed by addition of fluoroboric acid.[1] A variety of other oxidants work well also, such as nitrosyl tetrafluoroborate.[2] Many analogous ferrocenium salts are known.[3]

Structure

According to X-ray crystallography, the structures of the metallocene component of FcBF4 and the parent ferrocene are very similar. The Fe-C distances in the cation are 209.5 pm, about 2% longer than the Fe-C distances in ferrocene.[4]

Notes and References

  1. N. G.. Connelly. W. E.. Geiger. Chemical Redox Agents for Organometallic Chemistry. Chemical Reviews. 1996. 96. 2. 877–910. 10.1021/cr940053x. 11848774.
  2. Solvent and electrolyte effects on the kinetics of ferrocenium-ferrocene self-exchange. A reevaluation . Roger M.. Nielson. George E.. McManis. Lance K.. Safford. Michael J. . Weaver . . 10.1021/j100342a086 . 1989 . 93 . 5 . 2152.
  3. J.. Le Bras. H. . Jiao . W. E. . Meyer . F.. Hampel . J. A.. Gladysz . Synthesis, Crystal Structure, and Reactions of the 17-Valence-Electron Rhenium Methyl Complex [(''η''<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)Re(NO)(P(4-C<sub>6</sub>H<sub>4</sub>CH<sub>3</sub>)<sub>3</sub>)(CH<sub>3</sub>)]+ : Experimental and Computational Bonding Comparisons with 18-Electron Methyl and Methylidene Complexes . J. Organomet. Chem.. 2000 . 616 . 54–66 . 10.1016/S0022-328X(00)00531-3.
  4. 10.1016/j.ica.2007.03.049 . Difference in Reactivity of Triel Halides EX3 Towards Ferrocene . 2007 . Scholz . Stefan . Scheibitz . Matthias . Schödel . Frauke . Bolte . Michael . Wagner . Matthias . Lerner . Hans-Wolfram . Inorganica Chimica Acta . 360 . 10 . 3323–3329 .