338Ferrocene is an extremely stable complex. The first sandwich compound, it contains an
iron (II) center with two cyclopentadienyl ligands bonded through all ten carbon atoms.
This arrangement was a shocking novelty when it was first discovered, but the discovery
of ferrocene has led to a new branch of organometallic chemistry.
Ferrocene itself can be used as the backbone of a ligand, e.g. dppf. Ferrocene can itself
be oxidized to the ferrocenium cation (Fc+); the ferrocene/ferrocenium couple is often used
as a reference in electrochemistry.