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

摘要

Calculations on the novel argon insertion compounds C_6F_6Ar_n,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 pi 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,C_6F_6Ar,into C_6F_6+Ar is 19.5 kcal/mol at HF/6-311G~(**) and 29.5 kcal/mol at B3LYP/6-311G~(**),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 C_6F_6Ne and C_6F_6He are predicted to occupy minima on their respective potential energy surfaces.