Decamethylferrocene
Decamethylferrocene or bis(pentamethylcyclopentadienyl)iron(II) is a chemical compound with formula or . It is a sandwich compound, whose molecule has an iron(II) cation attached by coordination bonds between two pentamethylcyclopentadienyl anions (, ). It can also be viewed as a derivative of ferrocene, with a methyl group replacing each hydrogen atom of its cyclopentadienyl rings. The name and formula are often abbreviated to DmFc, or . 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. Preparation. Decamethylferrocene  is prepared in the same manner as ferrocene from pentamethylcyclopentadiene. This method can be used to produce other decamethylcyclopentadienyl sandwich compounds. The product can be purified by sublimation. has staggered rings. The average distance between iron and each carbon is approximately 2.050 Å. This structure has been confirmed by X-ray crystallography. 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 groups, decamethylferrocene is more reducing than is ferrocene. In a solution of acetonitrile the reduction potential for the couple is −0.59 V compared  to a reference (−0.48 V vs Fc/ in ). Oxygen is reduced to hydrogen peroxide by decamethylferrocene in acidic solution. Using powerful oxidants (e.g. or in , or in ) decamethylferrocene is oxidized to a stable dication with an iron(IV) core. In the salt, the rings are parallel. In contrast, a tilt angle of 17° between the rings is observed in the crystal structure of the salt.