Matrix isolation vibrational spectra of alkyl chalcogenides complexed with HCl: Structure of alkyl sulfide and alkyl selenide complexes with hydrochloric acid in ar matrices from infrared spectra

The matrix isolation technique has been used to isolate the hydrogen-bonded complexes of hydrochloric acid with some methyl and ethyl sulfides and selenides. In the ir spectra the perturbed vibrational mode of the complexed acid was observed as a rather complicated, broad band which exhibits multiplet structure. Evidence was obtained for the coexistence of 1:1, 2:1 and 1:2 complexes. The shifts Δν_ClH… of the 1:1 complexes correlate with the proton affinity values of the chalcogenide bases. Isotopic dilution experiments using DCl allowed us to determine a bifide structure for the 1:2 R₂X · (HCl)₂ complexes.