Triazole vs. triazolium carbene ligands in the site-selective cyclometallation of o-carboranes by M(III) (M = Ir, Rh) complexes

Ir(III) and Rh(III)-mediated site-selective cage B–H and C–H bond activation in o-carboranylmethyl derivatives has been achieved. The selectivity of the reaction is related to the electron donating properties of the ligand. 1,2,3-Triazole-derivatives use the N2 position of the triazole ring to direct the selective o-carborane B–H bond activation, whereas the corresponding triazolylidene derivatives lead to the cage C–H bond activation with complete site-selectivity.