Isolable fluorinated triphenylmethyl cation salts of [HCBCl]: demonstration of remarkable hydride affinity.

Significantly fluorinated triarylmethyl cations have long attracted attention as potentially accessible highly reactive carbocations, but their isolation in a convenient form has proved elusive. We show that abstraction of chloride with a cationic silylium reagent leads to the facile formation of di-, tetra-, and hexafluorinated trityl cations, which could be isolated as analytically pure salts with the [HCBCl] counterion and are compatible with (halo)arene solvents. The FTr cation carrying six -F substituents was computationally predicted to possess up to 20% higher hydride affinity than the parent triphenylmethyl cation Tr. We report that indeed FTr displays reactivity unmatched by Tr. FTr at ambient temperature abstracts hydrides from the C-H bonds in tetraethylsilane, mesitylene, methylcyclohexane, and catalyzes Friedel-Crafts alkylation of arenes with ethylene, while Tr does none of these.