Decamethylferrocene

Decamethylferrocene or bis(pentamethylcyclopentadienyl)iron(II) is a chemical compound with formula Fe(C₅(CH₃)₅)₂ or C₂₀H₃₀Fe. It is a sandwich compound, whose molecule has an iron(II) cation Fe²⁺ attached by coordination bonds between two pentamethylcyclopentadienyl anions (Cp*⁻, (CH₃)₅C−5). 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,^[3] Me₁₀Fc ^[4] or FeCp*₂.^[5]

Decamethylferrocene

Names
Preferred IUPAC name Decamethylferrocene
Other names Bis(η5-pentamethylcyclopentadienyl)iron(II) Decamethyl-ferrocene 1,1′,2,2′,3,3′,4,4′,5,5′-Decamethyl-ferrocene Bis(pentamethylcyclopentadienyl)iron(II) Permethylferrocene
Identifiers
CAS Number	12126-50-0 Y
3D model (JSmol)	Interactive image
ChemSpider	4321548 N
ECHA InfoCard	100.116.086
PubChem CID	5148079
CompTox Dashboard (EPA)	DTXSID80923743
InChI InChI=1S/2C10H15.Fe/c2*1-6-7(2)9(4)10(5)8(6)3;/h2*1-5H3;/q2*-1;+2 N Key: SEYZDJPFVVXSRB-UHFFFAOYSA-N N InChI=1/2C10H15.Fe/c2*1-6-7(2)9(4)10(5)8(6)3;/h2*1-5H3;/q2*-1;+2 Key: SEYZDJPFVVXSRB-UHFFFAOYAP
SMILES C[c-]1c(c(c(c1C)C)C)C.C[c-]1c(c(c(c1C)C)C)C.[Fe+2]
Properties
Chemical formula	C20H30Fe
Molar mass	326.305 g·mol−1
Appearance	Yellow crystalline solid[1]
Melting point	291 to 295 °C (556 to 563 °F; 564 to 568 K)[1]
Sublimation conditions	413 K, 5.3 Pa[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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]