Reaction C leads, by hydride transfer from water and formation of hypoiodic acid, to the intermediate hydride complex which can undergo reductive elimination to [B12H12] 2- . We propose this pathway, as we can exclude that the proton comes from the solvent: reactions in deuterated solvents such as CD3CN and DMSO-d6 can still lead to hydrodehalogenation, without deuterium transfer. For aryl halides, hydrodehalogenation requires a solvent or an additional molecule capable of β-hydride transfer. The solvents or substrates used here do not have β-hydrogen atoms.