Structural features of the congruently melting compounds MAg(NO3)(2) (M = K, Rb, Cs) inferred from their Raman spectra

The compounds KAg(NO3)(2) and RbAg(NO3)(2) exhibit similar Raman spectra wh ich are consistent with their crystal structures determined by X-ray diffra ction. Polymeric complexes are formed between silver and nitrate ions and t he nitrate ions act as both unidentate and bidentate ligands. The compound CsAg(NO3)(2) has a different Raman spectrum. The well separated band at 224 cm(-1) in the external vibrational region and the unique three-peak profil e in the v(3) region suggest that there may exist discrete complexes of sil ver and nitrate ions in the crystal CsAg(NO3)(2). The strong interaction wh ich accounts for the nonequivalent sets of nitrate ions in molten AgNO3 app ears to exist also in the compounds KAg(NO3)(2), RbAg(NO3)(2) and CsAg(NO3) (2).