Editing Cyclopentadiene (section)

===Metallocene derivatives===
{{main|Metallocene}}
Metallocenes and related [[Cyclopentadienyl complex|cyclopentadienyl derivatives]] have been heavily investigated and represent a cornerstone of [[organometallic chemistry]] owing to their high stability. The first metallocene characterised, [[ferrocene]], was prepared the way many other metallocenes are prepared by combining alkali metal derivatives of the form MC<sub>5</sub>H<sub>5</sub> with dihalides of the [[transition metal]]s:<ref>{{cite book |author1-link=Gregory S. Girolami |author3-link=Robert Angelici |last1=Girolami |first1=G. S. |last2=Rauchfuss |first2=T. B. |last3=Angelici |first3=R. J. |title=Synthesis and Technique in Inorganic Chemistry |year=1999 |publisher=University Science Books |location=Mill Valley, CA |isbn=0-935702-48-2}}</ref> As typical example, [[nickelocene]] forms upon treating [[nickel(II) chloride]] with sodium cyclopentadienide in [[tetrahydrofuran|THF]].<ref>{{cite book |last1=Jolly |first1=W. L. |title=The Synthesis and Characterization of Inorganic Compounds |url=https://archive.org/details/synthesischaract0000joll |url-access=registration |year=1970 |publisher=Prentice-Hall |location=Englewood Cliffs, NJ |isbn=0-13-879932-6}}</ref>

: NiCl<sub>2</sub> + 2&nbsp;NaC<sub>5</sub>H<sub>5</sub> → Ni(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> + 2&nbsp;NaCl

Organometallic complexes that include both the cyclopentadienyl anion and cyclopentadiene itself are known, one example of which is the [[rhodocene]] derivative produced from the rhodocene monomer in [[protic solvent]]s.<ref>{{cite journal |title = Permethylmetallocene: 5. Reactions of Decamethylruthenium Cations |year = 1985 |last1 = Kolle |first1 = U. |last2 = Grub |first2 = J. |journal = [[Journal of Organometallic Chemistry|J. Organomet. Chem.]] |volume = 289 |issue = 1 |pages = 133–139 |doi =10.1016/0022-328X(85)88034-7 }}</ref>