Lewis Acidity Enhancement of Triarylboranes via Peripheral Decoration with Cationic Groups

The cationic boranes [ArN+BMeS2](+), [Ar2N+BMeS](2+), and [Ar3N+B](3+) (ArN+ = [4-(Me3N)-2,6-Me-2-C6H2](+); 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 ArN+ 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.