A metallocene is a compound typically consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula 2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride, vanadocene dichloride. Wikipedia

Compounds typically consisting of two cyclopentadienyl anions bound to a metal center Wikidata

Any of a class of organic compounds containing two cyclopentadienyl anions and a transition metal whose bonding involves overlap of ns and np orbitals of the metal with molecular orbitals of appropriate symmetry of each cyclopentadienyl ring; the rings are parallel to each other, or sometimes canted. Wiktionary

Organic compound. Wiktionary (translation)