Iridium-Induced Regioselective B-H and C-C Activations at Azo-Substituted o-Carboranes

p-Methoxybenzeneazo-substituted o-carboranes have been synthesized and their reactivity with half-sandwich iridium and rhodium complexes has been investigated in detail. A variety of solvent- and base-dependent, highly site-selective B-H and C-C sigma-bond activations at the C/B cage have been observed. While the use of CH3OH leads to the formation of metallacarboranes, o-carborane clusters undergo cyclometallation reactions involving B(6)-H, B(4)-H or a rare B(7)-H activation in CH2Cl2. The synthesis of a unique pseudo-closo-iridacarborane through a very unconventional metal-mediated C-cage-C-cage activation is described in this contribution.