INFRARED-SPECTRA OF THE M+HI-2(-), M+HCLI-, AND M+HBRI- ION-PAIRS IN ARGON MATRICES

The salt-molecule reaction technique has been used to synthesize the HI2-, HC1I-, and HBrI- anions in ion pairs in argon matrices. Infrared spectra of the HI2- anion are characterized by an intense band near 673 cm-1 due to the antisymmetric stretching mode v3 of the anion in a centrosymmetric D∞h geometry. Weaker bands near 803 and 929 cm-1 are assigned to the combination modes v1 + v3 and 2v1 + v3. These spectra resemble closely the literature spectra of the HI2 radical, and suggest reassignment of the radical to the anion. Infrared spectra of the HC1I and HBrI- anions contained four bands, two of which were characteristic of hydrogen stretching vibrations, and have been assigned to a symmetric and an asymmetric form of the anion in these ion pairs. © 1979 American Chemical Society.