Spectrochemistry of Solutions: Part 5.1—Raman Spectroscopic Study of the Coordination of Silver(i) Ions in Liquid Ammonia by Thiocyanate lons

Abstract

A detailed study of the Raman spectra of mixtures of AgNO3 and KSCN in liquid ammonia solution indicates the formation of a weak S-bonded 1: 1 complex between Ag ■ and SCN-. Formation constants (concentration quotients) arc 3.1±0.5 and 1.3 ±0.4 kg mob1 at 293 and 233 K respectively. The formation of AgSCN is entropy favoured (±5 ~ 37 J mol-1 K-1) but enthalpy hindered (A 7/ ~ 8.2 kJ mol-1); the equilibrium [Ag(NH3)4]++SCN- [Ag(NH3)3SCN] + NH3 is proposed on the basis of these results. The possible existence of species such as [Ag2SCN]+ and [Ag(SCN)2]~ is suggested by some minor spectral features.