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

The aryltellurenyl cation [2‐(tBuNCH)C(6)H(4)Te](+), a Lewis super acid, and the weakly coordinating carborane anion [CB(11)H(12)](−), an extremely weak Brønsted acid (pK (a)=131.0 in MeCN), form an isolable ion pair complex [2‐(tBuNCH)C(6)H(4)Te][CB(11)H(12)], in which the Brønsted acidity (pK (a) 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)C(6)H(4)Te(CB(11)H(11))] in ratios ranging from 62 : 38 to 80 : 20.