Decamethylferrocene or bis(pentamethylcyclopentadienyl)iron(II) is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with formula or . It is a

sandwich compound In organometallic chemistry, a sandwich compound is a chemical compound featuring a metal bound by hapticity, haptic, covalent bonds to two arene compound, arene (ring) ligands. The arenes have the formula , substituted derivatives (for example ...

, whose molecule has an

iron(II) In chemistry, iron(II) refers to the element iron in its +2 oxidation state. The adjective ''ferrous'' or the prefix ''ferro-'' is often used to specify such compounds, as in ''ferrous chloride'' for iron(II) chloride (). The adjective ''ferr ...

cation attached by

coordination bond In coordination chemistry, a coordinate covalent bond, also known as a dative bond, dipolar bond, or coordinate bond is a kind of two-center, two-electron covalent bond in which the two electrons derive from the same atom. The bonding of metal io ...

s between two pentamethylcyclopentadienyl anions (, ). It can also be viewed as a derivative of

ferrocene Ferrocene is an organometallic chemistry, organometallic compound with the formula . The molecule is a Cyclopentadienyl complex, complex consisting of two Cyclopentadienyl anion, cyclopentadienyl rings sandwiching a central iron atom. It is an o ...

, with a

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated a ...

replacing each

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

atom of its

cyclopentadienyl Cyclopentadienyl can refer to * Cyclopentadienyl anion, or cyclopentadienide, ** Cyclopentadienyl ligand * Cyclopentadienyl radical, • * Cyclopentadienyl cation, See also * Pentadienyl {{Chemistry index ...

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 In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are common reducing agents include hydrogen, carbon ...

. The iron(II) core is easily

oxidized Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

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 1,2,3,4,5-Pentamethylcyclopentadiene is a cyclic compound, cyclic diene with the formula , often written , where Me is Methyl group, . It is a colorless liquid. 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ligand ''1,2,3,4,5-penta ...

. This method can be used to produce other decamethylcyclopentadienyl sandwich compounds. :2 Li(C₅Me₅) + FeCl₂ → Fe(C₅Me₅)₂ + 2 LiCl 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 X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

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 Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not class ...

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 Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

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 {{chem2, SbF6(-) salt.

References

Ferrocenes Pentamethylcyclopentadienyl complexes One-electron reducing agents Metallocenes