Lewis Superacidic Tellurenyl Cation‐Induced Electrophilic Activation of an Inert Carborane

Abstract

The aryltellurenyl cation [2-(tBuNCH)C6H4Te]+, a Lewis super acid, and the weakly coordinating carborane anion [CB11H12]–, an extremely weak Brønsted acid (pKa = 131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C6H4Te][CB11H12], in which the Brønsted acidity (pKa 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude. The electrophilic activation of B-H bonds in the carborane moiety gives rise to a proton transfer from boron to nitrogen at slightly elevated temperatures, as rationalized by the isolation of a mixture of the zwitterionic isomers 12- and 7-[2-(tBuN{H}CH)C6H4Te(CB11H11)] in ratios ranging from 62:38 to 80:20.