|Molar mass||65.09 g·mol−1|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
In chemistry, cyclopentadienyl is commonly used for an anionic cyclic group of atoms with the formula C5H5. Cyclopentadienyl is closely related to cyclopentadiene, from which it can be formed by deprotonation. Cyclopentadienyl has five carbon atoms bonded together in a pentagonal planar ring, all five of which are bonded to individual hydrogen atoms. Cyclopentadienyl anion is chemically aromatic and shows equal bond lengths between carbon atoms in the ring.