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Names | |||
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IUPAC name
Cyclopentadienide
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Identifiers | |||
3D model (
JSmol)
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ChemSpider | |||
PubChem
CID
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Properties | |||
[C 5H 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).
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In
chemistry, the cyclopentadienyl anion or cyclopentadienide is an
aromatic species with a formula of [C
5H
5−
and abbreviated as Cp−.
[1] It is formed by the deprotonation of
cyclopentadiene. The cyclopentadienyl anion is a
ligand which
binds to a
metal in
organometallic chemistry.
[2]
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] The cyclopentadienyl anion is a 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.
Cyclopentadienyl anions form a variety of cyclopentadienyl complexes. [5]