Formation of dications bearing a S(OH) 2 + group from long-lived 9,9-dimethyl-10 R-phenanthrenium cations in FSO 3 H–SbF 5 /SO 2 ClF/SO 2 : a mechanistic study

1 H and 13 C NMR studies have shown that the long-lived 9,9-dimethyl-10-R-phenanthrenium cations (R = PhCC, Me, OH) generated in FSO 3 H–SbF 5 /SO 2 ClF/SO 2 /CD 2 Cl 2 transform into long-lived 7-dihydroxysulfonio-9,9-dimethyl-10-R-phenanthrenium dications. The effect of the 10-R substituents on the reaction rate suggests that a key step in the reaction mechanism is addition of SO 2 to protonated phenanthrenium cations.