Acid-Induced Opening of [<i>closo</i>-B₁₀H₁₀]^2– as a New Route to 6‑Substituted <i>nido</i>-B₁₀H₁₃ Decaboranes and Related Carboranes

Protonation of the polyhedral anion [closo-B10H10]2– under superacidic conditions apparently generates an electrophilic intermediate, [B10H13]+, that forms 6-R-nido-B10H13 (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-B10H13 derivatives via the boranocation [B10H13]+ is discussed. The synthesis of carboranes, starting from 6-R-nido-B10H13 decaboranes, and single-crystal X-ray diffraction analyses of several 6-R-nido-B10H13 decaboranes and carboranes are described.