FeC5H52

FeC5H52 is the empirical formula often used to denote ferrocene, an organometallic compound with the formula Fe(C5H5)2. It is a stable, blue-orange to yellowish crystalline solid that plays a central role in the development of metallocene chemistry.

Ferrocene features a sandwich structure in which a central iron atom is coordinated to two parallel cyclopentadienyl rings. Each cyclopentadienyl ring acts as an η5 ligand, donating six electrons to the iron and giving the complex an overall 18-electron count with iron in the +2 oxidation state. This arrangement confers unusual stability and a characteristic planarity of the rings relative to the iron center.

The compound was discovered in 1951 by Paolo Pauson and Thomas Kealy at Imperial Chemical Industries (ICI) in England. Its crystal structure and bonding were confirmed soon after, establishing ferrocene as the prototypical metallocene and prompting the rapid growth of organometallic chemistry. Ferrocene’s chemistry is dominated by its reversible one-electron redox couple, cycling between Fe(C5H5)2 (ferrocene) and [Fe(C5H5)2]+ (ferrocenium), which underpins many electrochemical and synthetic applications.

Applications of ferrocene and its derivatives are broad. It serves as a versatile synthetic building block for introducing the ferrocenyl moiety into pharmaceuticals, catalysts, and materials. Its stable, well-behaved electrochemistry makes it a common reference standard in cyclic voltammetry, and substituted ferrocenes are widely used in ligand design, liquid-crystal research, and nanomaterials.

Safety considerations are similar to other organometallic compounds: ferrocene is relatively low in toxicity but should be handled with standard laboratory precautions to avoid inhalation, ingestion, or skin contact.