Editing Metallocene (section)

{{Short description|Type of compound having a metal center}}
[[File:Metallocene.svg|thumb|150px|General [[chemical structure]] of a '''metallocene''' compound, where '''M''' is a [[metallic element|metal]] cation]]
A '''metallocene''' is a compound typically consisting of two [[cyclopentadienyl anion]]s ({{chem|C|5|H|5|−}}, abbreviated Cp) bound to a [[metallic element|metal]] center (M) in the [[oxidation state]] II, with the resulting general formula {{nowrap|(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>M.}} Closely related to the metallocenes are the metallocene derivatives, e.g. [[titanocene dichloride]] or [[vanadocene dichloride]]. Certain metallocenes and their derivatives exhibit [[catalysis|catalytic]] properties, although metallocenes are rarely used industrially. Cationic group 4 metallocene derivatives related to [Cp<sub>2</sub>ZrCH<sub>3</sub>]<sup>+</sup> catalyze [[Ziegler–Natta catalyst|olefin polymerization]].

Some metallocenes consist of metal plus two [[cyclooctatetraenide anion]]s ({{chem|C|8|H|8|2−}}, abbreviated cot<sup>2&minus;</sup>), namely the lanthanocenes and the [[actinocene]]s ([[uranocene]] and others).

Metallocenes are a subset of a broader class of compounds called [[sandwich compound]]s.<ref name="Wilkinson_G." />
In the structure shown at right, the two pentagons are the cyclopentadienyl anions with circles inside them indicating they are [[aromaticity|aromatically]] stabilized. Here they are shown in a [[staggered conformation]].