The cyclopentadienyl cation is another textbook example of an antiaromatic compound. It is conventionally understood to be planar, cyclic, and have 4 π electrons (4n for n=1) in a conjugated system. However, it has long been questioned if the cyclopentadienyl cation is genuinely antiaromatic and recent discoveries have suggested that it may ...

2024年1月15日 · Coordination of the cyclopentadienyl cation by [Sb3F16]− or C6F6 stabilizes the antiaromatic singlet state in the solid state.

2017年3月27日 · The cyclopentadienyl cation can only be prepared with difficulty, as this paper describes. Once it is formed, it has a triplet electronic ground state (with 2 unpaired electrons), and can be characterized by EPR (electron paramagnetic resonance) spectroscopy.

Antiaromatic Ions. In a similar fashion, cyclically conjugated ions with 4n pi electrons can be predicted to be antiaromatic and therefore highly unstable. An excellent example is the cyclopentadienyl cation. Above, the cyclopentadienyl anion was shown to be aromatic, however, the formation of a carbocation produces a different result.

2017年5月17日 · There are two important configurations of energy levels for 3-membered cyclic pi systems, depending on the number of pi electrons. With two pi electrons, we’d expect an aromatic molecule. One example is the cyclopropenium cation (below left), which is indeed aromatic. With 4 pi electrons, an antiaromatic molecule is expected.

Antiaromatic Ions. In a similar fashion, cyclically conjugated ions with 4n pi electrons can be predicted to be antiaromatic and therefore highly unstable. An excellent example is the cyclopentadienyl cation. Above, the cyclopentadienyl anion was shown to be aromatic, however, the formation of a carbocation produces a different result.

When a hydride anion (H - ) is removed from the s p 3 hybridized ring carbon of cyclopentadiene, the cyclopentadienyl cation will be formed and the hybridization of the s p 3 hybridized ring carbon will be changed from s p 3 to s p 2.

2021年1月1日 · The planar cyclopentadienyl cation is antiaromatic, and while the Cl and phenyl per-substituted analogs have been characterized (as ground state triplets or singlets with low-lying triplet states) [41], [42], [43], the parent is unknown.

2023年1月23日 · Hence, cyclopentadiene (its conjugate base i.e. Cyclopentadienyl anion is aromatic in nature) is much more acidic than cycloheptatriene (its conjugate base i.e. Cycloheptatrienyl anion is anti-aromatic in nature).

The singlet states of cyclopentadienyl (Cp) cations are considered as true prototypes of an antiaromatic system. Unfortunately, their high intrinsic reactivity inhibited their isolation in the solid state as a salt, and controlled reactions are also scarce. …