The adduct between IF7 and AsF5 has been shown to be ionic and consist of IF6+ and AsF6− ions. The environment of these ions appears to be octahedral. Based on this symmetry, force constants have been determined. Some controversy regarding the frequency position of the ν4 (F1u) vibration, and the assignment for the ν1 (A1g), ν2 (Eg) vibrations in IF6+ has existed. However, the proper ν4 assignment was eventually made, and Raman studies of IF6+AsF6− in HF solutions clearly indicated that the lower frequency band at 711 cm−1 was polarized. Thus, the depolarized 732 cm−1 vibration was assigned as the ν2 (Eg) mode. Recently, IF6+SbF6− has been prepared and the vibration spectrum analyzed. The results support previous assignments of Christe and Sawodny and verify the ν4 assignment.
L. J. Basile, F. A. Hohorst, and J. R. Ferraro, "A Normal Coordinate Treatment of IF6SbF6," Appl. Spectrosc. 29, 260-261 (1975)