Aromatic ionic species
Cyclopentadienyl anion
Names
IUPAC name
Cyclopentadienide
Identifiers
ChemSpider
InChI=1S/C5H5/c1-2-4-5-3-1/h1-5H/q-1
Key: SINKOGOPEQSHQD-UHFFFAOYSA-N
InChI=1/C5H5/c1-2-4-5-3-1/h1-5H/q-1
Key: SINKOGOPEQSHQD-UHFFFAOYAD
Properties
[C5 5 − or Cp−
Molar mass
65.09 g/mol
Conjugate acid
Cyclopentadiene
Except where otherwise noted, data are given for materials in their
standard state (at 25 °C [77 °F], 100 kPa).
Chemical compound
In chemistry , the cyclopentadienyl anion or cyclopentadienide is an aromatic species with a formula of [C5 5 − and abbreviated as Cp− .[1] cyclopentadiene . The cyclopentadienyl anion is a ligand which binds to a metal in organometallic chemistry .[2]
Resonance and aromaticity
Resonance structures of the cyclopentadienyl anion
The cyclopentadienyl anion is a planar, cyclic , regular-pentagonal ion; it has 6 π-electrons (4n + 2, where n = 1), which fulfills Hückel's rule of aromaticity. Each double bond and lone pair provides 2 π-electrons, which are delocalized into the ring.[3] conjugated system because there are alternating π and 𝜎 bonds .[4]
Cyclopentadiene has a pKa of about 16. It is acidic relative to many carbon acids. The enhanced acidity is attributed to stabilization of the conjugate base , cyclopentadienyl anion.
Ligand
Cyclopentadienyl anions form a variety of cyclopentadienyl complexes .[5]
Metallocene structure where "M" is a metal
