New approaches to the selective synthesis of the [2-B10H9I]− anion have been reported based on careful control of the reaction medium acidity. The mechanism of the iodination was proposed and the regioselectivity of electrophilic substitution of the [B10H10]2− anion was explained based on B3LYP-calculations of the potential energy surface of the system using the mixed basis 6-31G∗/LanL2DZ. The obtained compounds were characterized by IR and NMR (1H and 11B) spectroscopy, together with ESI-MS-spectrometry. The crystal structures of (PPh4)2[2-B10H9I] and {(PPh4)2[2-B10H9I]·2C4H8O2} were determined by X-ray diffraction.