Ferrocene, an organometallic compound, is orange solid with a camphor-like odor that sublimes above room temperature. It is soluble in most organic solvents and has a boiling point of 249 degC.
Fe(C5H5)2 is a complex of two cyclopentadienyl rings bound to a central iron atom, and this configuration is very stable and resistant to oxidation. The cyclopentadienyl ring is surrounded by a central iron atom that is normally in the +2 oxidation state (this can be observed using Mossbauer spectroscopy).
One of the distinctive characteristics of the cyclopentadienyl arrangement is the fact that each ring is assigned an extra electron, giving it six p-electrons and thus making it aromatic. This additional charge is shared with the iron atom through covalent bonding, which results in an 18-electron, inert gas-like structure.
This is a very interesting and important molecule and was the first sandwich compound to be discovered. The original work done by Woodward and colleagues in 1952 characterised the redox behaviour of ferrocene: an orange solution of ferrocene (Fc) turns blue on treatment with a mild oxidising agent like aqueous Ag2SO4 or p-benzoquinone. This was the beginning of the use of ferrocene in electrochemical studies. It has since become a very important symbol of organometallic electrochemistry.