cyclopentadienyl
/ˌsʌɪkləʊpɛntəˈdʌɪənʌɪl/ /ˌsʌɪkləʊˌpɛntəˈdʌɪənɪl/Chemistry
noun
A planar cyclic anion, C5H5 −, derived from cyclopentadiene, which has aromatic character and forms complexes with metal atoms, most notably sandwich compounds in which a metal atom is bonded between two parallel cyclopentadienyl rings. Abbreviated Cp.
Origin
Early 20th century; earliest use found in Journal of the American Chemical Society. From cyclopentadiene + -yl.