Matrix reactions of alkali metal chloride salts and HCl and DCl: Infrared spectra of the M+HCl2− and M+DCl2− ion pairs

Abstract

The matrix reactions of alkali metal chloride salts and HCl and DCl have been investigated in argon matrices, as well as the reaction of lithium metal with HCl and DCl. From each reaction product a single intense band was observed which has been assigned to the antisymmetric stretch ν₃ of the HCl₂⁻ and DCl₂⁻ anions in the M⁺HCl₂⁻ and M⁺DCl₂⁻ ion pairs. Comparisons to literature spectra, in conjunction with quartic deuterium shifts, indicate that the anion has a linear, centrosymmetric geometry in the isolated ion pair. A rough estimate for the bond strength of the hydrogen bond in this anion is 18±2 kcal/mole. Further, comparison to the spectra of earlier workers indicates that bands previously asigned to the HCl₂ radical are best reassigned to the isolated HCl₂⁻ anion.