This compound is a yellow crystalline solid that is used in chemical laboratories as a weak reductant. The iron(II) core is easily oxidized to iron(III), yielding the monovalent cation decamethylferrocenium, and even to higher oxidation states.[5]
Preparation
Decamethylferrocene is prepared in the same manner as ferrocene from pentamethylcyclopentadiene. This method can be used to produce other decamethylcyclopentadienyl sandwich compounds.[1]
2 Li(C5Me5) + FeCl2 → Fe(C5Me5)2 + 2 LiCl
The product can be purified by sublimation. FeCp*2 has staggered Cp* rings. The average distance between iron and each carbon is approximately 2.050 Å. This structure has been confirmed by X-ray crystallography.[6]
Redox reactions
Like ferrocene, decamethylferrocene forms a stable cation because Fe(II) is easily oxidized to Fe(III). Because of the electron donating methyl groups on the Cp* groups, decamethylferrocene is more reducing than is ferrocene. In a solution of acetonitrile the reduction potential for the [FeCp*2]+/0 couple is −0.59 V compared to a [FeCp2]0/+ reference (−0.48 V vs Fc/Fc+ in CH2Cl2).[2] Oxygen is reduced to hydrogen peroxide by decamethylferrocene in acidic solution.[7]
Using powerful oxidants (e.g. SbF5 or AsF5 in SO2, or XeF+/Sb2F−11 in HF/SbF5) decamethylferrocene is oxidized to a stable dication with an iron(IV) core. In the Sb2F−11 salt, the Cp* rings are parallel. In contrast, a tilt angle of 17° between the Cp* rings is observed in the crystal structure of the SbF−6 salt.[5]
References
^ abcKing, R. B.; Bisnette, M. B. (1967). "Organometallic Chemistry of the Transition Metals XXI. Some π-pentamethylcyclopentadienyl Derivatives of Various Transition Metals". J. Organomet. Chem.8 (2): 287–297. doi:10.1016/S0022-328X(00)91042-8.
^Torriero, Angel A. J. (2014). "Characterization of decamethylferrocene and ferrocene in ionic liquids: argon and vacuum effect on their electrochemical properties". Electrochimica Acta. 137: 235–244. doi:10.1016/j.electacta.2014.06.005.
^Noviandri, Indra; Brown, Kylie N.; Fleming, Douglas S.; Gulyas, Peter T.; Lay, Peter A.; Masters, Anthony F.; Phillips, Leonidas (1 August 1999). "The Decamethylferrocenium/Decamethylferrocene Redox Couple: A Superior Redox Standard to the Ferrocenium/Ferrocene Redox Couple for Studying Solvent Effects on the Thermodynamics of Electron Transfer". The Journal of Physical Chemistry B. 103 (32): 6713–6722. doi:10.1021/jp991381+. ISSN1520-6106.
^Freyberg, Derek P.; Robbins, John L.; Raymond, Kenneth N.; Smart, James C. (1979). "Crystal and molecular structures of decamethylmanganocene and decamethylferrocene. Static Jahn-Teller distortion in a metallocene". J. Am. Chem. Soc.101 (4): 892–897. doi:10.1021/ja00498a017.