Vibrational frequencies and intramolecular forces in anionic tin-halogen complexes and related species

Article abstract of DOI:10.1021/ic50074a042

Far-infrared and Raman spectra are reported for solids containing the SnX₆^2- (X = Cl, Br, I) and SnX₃^- (X = F, Cl, Br, I) ions in combination with large monopositive cations. These results include the first complete report of infrared- and Raman-active fundamentals for SnF₃^-, SnI₃^-, and SnI₆^2-. Normal-coordinate vibrational analysis was performed for these complexes and for SnX₄ (X = Cl, Br, I) under a uniform set of approximations. For a series of compounds containing the same halide it is found that the primary stretching force constants are approximately proportional to the metal oxidation state divided by the coordination number. Theoretical values for the force constants were calculated using an ionic model. These reproduce the reduction in force constant which is observed upon going from SnX₄ to SnX₆^2-.