Rare-gas insertion compounds of perfluorobenzene: Aromaticity of some unstable species

Calculations on the novel argon insertion compounds C6 F6 Arn, n=1-6, where the argon atoms are inserted into the C-F bonds in perfluorobenzene, suggest that all possible species, with one to six inserted argon atoms, occupy minima on their respective potential energy surfaces. Ring-current plots using the ipsocentric model indicate that there is no disruption of the aromatic π system upon argon insertion, and consequently all insertion compounds are aromatic according to the magnetic criterion. The barrier height for decomposition of the single-insertion compound, C6 F6 Ar, into C6 F6 +Ar is 19.5 kcalmol at HF6-311 G** and 29.5 kcalmol at B3LYP6-311 G**, suggesting that, although clearly thermodynamically unstable, argon-perfluorobenzene insertion compounds may be stable kinetically. Preliminary calculations indicate that other rare gas-perfluorobenzene insertion compounds may also be metastable. Both C6 F6 Ne and C6 F6 He are predicted to occupy minima on their respective potential energy surfaces. © 2005 American Institute of Physics.