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 haptic, covalent bonds to two arene (ring) ligands. The arenes have the formula , substituted derivatives (for example ) and heterocyclic deriv ...

, whose molecule has an

iron(II) In chemistry, iron(II) refers to the element iron in its +2 oxidation state. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe2+. The adjective ferrous or the prefix ferro- is often used to s ...

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 1,2,3,4,5-Pentamethylcyclopentadiene is a cyclic diene with the formula C5Me5H (Me = CH3). 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ligand ''1,2,3,4,5-pentamethylcyclopentadienyl'', which is often denoted Cp* (C5Me5) and read ...

anions (, ). It can also be viewed as a derivative of

ferrocene Ferrocene is an organometallic compound with the formula . The molecule is a complex consisting of two cyclopentadienyl rings bound to a central iron atom. It is an orange solid with a camphor-like odor, that sublimes above room temperature, a ...

, 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 . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

replacing each

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

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 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 commonly reducing agents include the Earth meta ...

. The iron(II) core is easily

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

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 diene with the formula C5Me5H (Me = CH3). 1,2,3,4,5-Pentamethylcyclopentadiene is the precursor to the ligand ''1,2,3,4,5-pentamethylcyclopentadienyl'', which is often denoted Cp* (C5Me5) and read ...

. 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 determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

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 clas ...

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 viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

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