cyclo­penta­dienide

Other names: cyclo­penta­dienyl anion, Cp^-

[C₅H₅]^-

4/50 common

The cyclopentadienyl anion is the conjugate base of the simple hydrocarbon cyclopentadiene. Unlike most hydrocarbons, cyclopentadiene is fairly acidic and may be readily deprotonated; this is because the resultant cyclopentadieniede ring has 6 electrons in a conjugated π system and, like benzene, satisfies the Hückel criterion for aromatic ring stabilization. Cyclopentadienyl further sees frequent usage as a ligand in organometallic chemistry, where it is acts as a pentahaptic ligand capable of bonding obliquely through its π electron system to form coordination complexes such as ferrocene.