Advanced Topic 699 of 1102 Inorganic Chemistry
Ferrocene
An iron sandwich complex with two cyclopentadienyl rings, a landmark organometallic compound.
In-depth explanation of Ferrocene
Ferrocene, Fe(C5H5)2, is an orange, air-stable solid in which an iron(II) ion is sandwiched between two parallel cyclopentadienyl rings, so it is called a sandwich complex. Its discovery in 1951 was a landmark because its structure was unexpected and launched modern organometallic chemistry. The cyclopentadienyl rings are aromatic, so ferrocene undergoes electrophilic substitution similar to benzene. Bonding involves the pi electrons of each ring interacting with iron d orbitals. Ferrocene is stable to about 400 degrees C and is reversibly oxidized to the ferrocenium ion.
Going deeper: Ferrocene
Key ideas: Fe(C5H5)2, an orange, air-stable sandwich compound with iron(II) between two parallel cyclopentadienyl rings; discovered in 1951. Each Cp- is a 6-pi-electron aromatic anion giving 6 electrons, Fe2+ is d6, so 6 + 12 = 18 electrons. Prepared from FeCl2 plus cyclopentadienide. Undergoes electrophilic substitution (Friedel-Crafts acylation) like benzene, but more readily; is easily oxidized to ferrocenium, a reversible one-electron couple used as an electrochemical standard.
Common mistakes and connections: Students think the rings bond to Fe through one carbon; all five carbons bond (eta5) and bond lengths are equal. Rings rotate nearly freely. Eclipsed form is slightly favored in the solid. Links to aromaticity, 18-electron rule and electrochemistry reference electrodes.
Visualization of Ferrocene
Ferrocene is reversibly oxidized to ferrocenium in a one-electron step, which is why the Fc/Fc+ couple is a standard redox reference. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Ferrocene is oxidized reversibly to the ferrocenium ion and is used as a redox reference in electrochemistry.
Frequently asked questions about Ferrocene
What is Ferrocene?
An iron sandwich complex with two cyclopentadienyl rings, a landmark organometallic compound.
Is Ferrocene a beginner, intermediate or advanced topic?
Ferrocene is a advanced topic in Inorganic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Ferrocene?
Study these earlier topics in Inorganic Chemistry first: Organometallic Compounds, Metal Carbonyls, Eighteen Electron Rule.
What comes after Ferrocene?
The next topics in Inorganic Chemistry are Zeigler-Natta Catalysts and Wilkinson's Catalyst.
Can I practise Ferrocene with quizzes?
Yes. The interactive lesson includes a self-check question on Ferrocene, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Ferrocene fits in Inorganic Chemistry
Ferrocene is topic 84 of 113 in Inorganic Chemistry.