Acid-Induced Opening of [closo-B(10)H(10)](2-) as a New Route to 6-Substituted nido-B(10)H(13) Decaboranes and Related Carboranes

Protonation of the polyhedral anion closo-B(10)H(10)](2-) under superacidic conditions apparently generates an electrophilic intermediate, B(10)H(13)](+), that forms 6-R-nido-B(10)H(13) (R = aryl, alkyl, triflate) derivatives by electrophilic aromatic substitution, C-H bond activation, or ion-pair collapse, respectively. The proposed mechanism of formation of the 6-R-nido-B(10)H(13) derivatives via the boranocation B(10)H(13)](+) is discussed. The synthesis of carboranes, starting from 6-R-nido-B(10)H(13) decaboranes, and single-crystal X-ray diffraction analyses of several 6-R-nido-B(10)H(13) decaboranes and carboranes are described.