Blue solutions and blue solids obtained from the reactions between iodine and antimony pentafluoride, and between iodine, iodine pentafluoride, and antimony pentafluoride, have been studied by chemical, spectroscopic, and magnetic techniques. Similar solutions are formed by iodine in the presence of iodine pentafluoride and the pentafluorides of P, As, Nb, and Ta, but only in the case of Ta is a stable solid isolated. The results are discussed in terms of the iodine molecule cation, I2+.