What does it look like?
Ferrocene was (like many things) discovered by accident. Two groups, working independently, were both looking for something else where they in fact made an orange powder that they didn’t expect. Both knew that it was made from an iron atom and two cyclopentadiene (five carbon and atoms joined together with hydrogen’s attached), but thought that they would sit aligneded in a solid together.
But x-ray crystallography showed that that was wrong, and the ferrocene molecule takes up a ‘sandwich’ structure with the two cyclopentadiene rings either side of the iron atom. This remarkable discoverey also revleaved the strange propoerties of this material, and paved the way for the subsequent rapid growth of organometallic chemistry .
Where did the structure come from?
You can read more about the history of the structure of ferrocene from an excellent C&EN article here. The structure we’ve plotted today is actually a high-temperature form of ferrocene, and is #210932 in the Crystallography Open Database.