Editing Cyclopentadienyl complex (section)

==Bonding modes==
In the vast majority of M–Cp complexes, all 5 carbon atoms of a Cp ligand bind the metal ([[Hapticity|''η''<sup>5</sup>-coordination]]). The M–Cp bonding arises from overlap of the five molecular orbitals in the Cp [[conjugated system|π system]] with the metal ''s'', ''p'', and ''d'' orbitals; hence these complexes are referred to as π-complexes.<Ref name=Elsch/>  ''η''<sup>5</sup>-coordinated Cp is [[isolobal]] to three facial carbonyls,<ref>{{cite book|pp=387-388|year=1985|publisher=Wiley|lccn=84-15310|isbn=0-471-87393-4|last1=Albright|first1=T.&nbsp;A.|last2=Burdett|first2=J.&nbsp;K.|author3=Whangbo Myung-Hwan|title=Orbital Interactions In Chemistry}}</ref> as well as [[scorpionate ligand]]s and thia-[[crown ether]]s.{{Cn|date=May 2025}}  Almost all of the [[transition metal]]s employ this coordination mode.<ref name=Elsch/>

In relatively rare cases, Cp binds to metals via only one carbon center. These types of interactions are described as σ-complexes because they only have a [[σ bond]] between the metal and the cyclopentadienyl group. Typical examples of this type of complex are group 14 metal complexes such as CpSiMe<sub>3</sub>. An example of both is (Cp<sub>2</sub>Fe(CO)<sub>2</sub>).  It is probable that ''η''<sup>1</sup>-Cp complexes are intermediates in the formation of ''η''<sup>5</sup>-Cp complexes.

Still rarer, the Cp unit can bond to the metal via three carbons. In these ''η''<sup>3</sup>-Cp complexes, the bonding resembles that in [[allyl ligand]]s. Such complexes, sometimes called "slipped Cp complexes", are invoked as intermediates in [[indenyl effect|ring slipping reactions]].