Gas-phase generation of trifluoromethyl cyclopentadienides

Tetramethyltrifluoromethylcyclopentadienide 1a is unstable in solution but it can be readily generated in the gas phase. The proton affinities and fluoride binding energies of 1a and several other trifluoromethyl substituted cyclopentadienides are measured. The data is found to fit an additivity scheme, which suggests that pentakis(trifluoromethyl)cyclopentadiene is an exceptionally strong gas-phase acid, and indicates that substituted trifluoromethylcyclopentadienides may be accessible in solution under the appropriate reaction conditions.