INFRARED MATRIX-ISOLATION STUDIES OF THE M+HF-2(-) AND M+XHF- ION-PAIRS FOR X = CL, BR, AND I

The triatomic anions HF2- , ClHF- , BrHF- , and IHF- have been synthesized in alkali metal ion pairs in argon matrices. Infrared spectra of the M+HF2- ion pairs indicated a strongly bound species with v3 near 1360 cm-1 and v2 near 1200 cm-1. Infrared spectra of the mixed XHF- anions were characterized by an intense band between 2500 and 3000 cm-1, a second intense band between 750 and 950 cm-1, and, in the case of ClHF- and BrHF-, a third band between 725 and 825 cm-1. These data are employed to suggest that two forms of the anion are present, a type I asymmetric form, and a type II symmmetric form, with the position of the alkali metal cation in the ion pair determining which type of anion is formed. © 1979 American Chemical Society.