Electrochemical Oxidation of [1-X-12-I-CB11Me10–] Anions: Formation of Borenium Ylides [12-Dehydro-1-X-CB11Me10] and Iodonium Ylide Anions [{12-(1-X-CB11Me10–)}2I+]

Cyclic voltammograms of 12-iodinated icosahedral carborane anions [1-X-12-I-CB11Me10–] (X = H, CH3, C2H5, C3H7, C4H9, C6H13, and COOCH3) show two one-electron anodic oxidation peaks at the Pt electrode in liquid SO2. Oddly, the first is irreversible and the second partially reversible. Mass spectrometry of the principal anionic product of preparative anodic oxidation of [1-H-12-I-CB11Me11–], identical with the anionic product of its reaction with [Et3Si–H–SiEt3]+ and/or Et3Si+, allows it to be identified as the iodonium ylide anion [{12-(1-H-CB11Me10–)}2I+]. Its reversible oxidation to a neutral ylide radical [{12-(1-H-CB11Me10•)}{12-(1-H-CB11Me10–)}I+] is responsible for the second peak. A DFT geometry optimization suggests that both the ylide anion and the ylide radical are very crowded and have an unusually large C–I–C valence angle of ∼132°; they are the first compounds with two bulky highly methylated CB11 cages attached to the same atom. Molecular iodine is another product of the electrolysis. We pr...