Cycloheptatrienide (Tropenide) Anion

Antiaromaticity in Monocyclic Conjugated Carbon Rings

“…The 4n cycloheptatrienide anion was obtained by the treatment of 7-methoxycycloheptatriene with K-Na alloy in THF at -20 °C and has high reactivity. 83 NMR spectroscopy of some monosubstituted derivatives showed that they have nonplanar structures, in contrast to the cation. 84 The ∆H acid of cycloheptatriene is 375 ( 3 kcal/mol, 31 making it 34 ( 3 kcal/mol more acidic than ethylene.…”

The Stable Pentamethylcyclopentadienyl Cation This work was supported by the U.S. National Science Foundation (Grant No. CHE-0091162). We thank Charlotte L. Stern for performing the crystal-structure analysis, Yuyang Wu for assistance in obtaining solid-state NMR data, Min Zhao and Stoyan Smoukov for providing ESR data, Alice L. Rodriguez for molecular modeling graphics, and John A. Pople and Mark A. Ratner for important discussions.

“…In contrast, the cyclopentadienyl cation, C 5 H 5 + ( 4 , Cp + ) has languished experimentally as an elusive charge variant. It shares with cyclobutadiene5–7 ( 5 ) and the cycloheptatrienyl anion8 ( 6 ), among others, the characteristics of possessing 4 n π electrons and thus potentially being antiaromatic. …”

Topological resonance energies of conjugated ions, radicals, and ion radicals

“…The corresponding TRE values are +0.225, +0.181, -0.220, -0.242, and -0.665. Thus, while the cation was isolated as solid crystals,86 the anion was found to be stable in solution only, and at temperatures not higher than 260 K. 87 The other members of the series have properties which interpolate nicely between these two boundary examples.88…”