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.
Competing Interests: There are no conflicts to declare.
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