Isolable fluorinated triphenylmethyl cation salts of [HCB(11)Cl(11)](−): 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 [HCB(11)Cl(11)](−) counterion and are compatible with (halo)arene solvents. The F(6)Tr(+) cation carrying six meta-F substituents was computationally predicted to possess up to 20% higher hydride affinity than the parent triphenylmethyl cation Tr(+). We report that indeed F(6)Tr(+) displays reactivity unmatched by Tr(+). F(6)Tr(+) 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.