1-Chlorooctafluoro-3-methylene-1-indanyt, 3-(chlorofluoromethylene)heptafluoro-1-indanyl, and 2- and 3-(dichloromethylene)heptafluoro-1-indanyl cations were generated from the corresponding dihalomethyleneindans in the system SbF5-SO2ClF. Isomerization of these cations yields thermodynamically more stable polyfluoromethylindenyl cations with chlorine atoms in the five-membered ring.