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 tetrafluoroborateanion (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 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.[2]
Preparation
Commercially available, this compound may be prepared by oxidizing ferrocene typically with ferric salts followed by addition of fluoroboric acid.[2] A variety of other oxidants work well also, such as nitrosyl tetrafluoroborate.[3] Many analogous ferrocenium salts are known.[4]
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.
[5]
^ abConnelly, N. G.; Geiger, W. E. (1996). "Chemical Redox Agents for Organometallic Chemistry". Chemical Reviews. 96 (2): 877–910. doi:10.1021/cr940053x. PMID11848774.
^Nielson, Roger M.; McManis, George E.; Safford, Lance K.; Weaver, Michael J. (1989). "Solvent and electrolyte effects on the kinetics of ferrocenium-ferrocene self-exchange. A reevaluation". J. Phys. Chem.93 (5): 2152. doi:10.1021/j100342a086.
^Le Bras, J.; Jiao, H.; Meyer, W. E.; Hampel, F.; Gladysz, J. A. (2000). "Synthesis, Crystal Structure, and Reactions of the 17-Valence-Electron Rhenium Methyl Complex [(η5-C5Me5)Re(NO)(P(4-C6H4CH3)3)(CH3)]+B(3,5-C 6H 3(CF 3) 2)− 4: Experimental and Computational Bonding Comparisons with 18-Electron Methyl and Methylidene Complexes". J. Organomet. Chem.616: 54–66. doi:10.1016/S0022-328X(00)00531-3.
^Scholz, Stefan; Scheibitz, Matthias; Schödel, Frauke; Bolte, Michael; Wagner, Matthias; Lerner, Hans-Wolfram (2007). "Difference in Reactivity of Triel Halides EX3 Towards Ferrocene". Inorganica Chimica Acta. 360 (10): 3323–3329. doi:10.1016/j.ica.2007.03.049.
