Lewis acidity enhancement of triarylboranes via peripheral decoration with cationic groups

The cationic boranes [Ar(N+)BMes(2)](+), [Ar(N+)(2)BMes](2+), and [Ar(N+)(3)B](3+) (Ar(N+) = [4-(Me(3)N)-2,6-Me(2)-C(6)H(2)](+); Mes = mesityl) have been synthesized and studied by cyclic voltammetry. The results obtained in this study show that the reduction potential of these derivatives in THF is increased by 0.36 V upon each substitution of a mesityl by a cationic Ar(N+) anilium group. Remarkably, the trication [3](3+), whose triflate salt is water soluble, complexes cyanide anions in pure water at pH 7. These properties underscore the dramatic effects caused by the increased number of cationic groups.