Fluorine magnetic resonance studies of metal-hexafluorosilicate ion-pairs in solution

Abstract

The low field shifts observed in the ¹⁹F spectra of aqueous solutions of the hexafluorosilicates of transition metal ions have been interpreted in terms of ion pair formation. The exchange of free and ion-paired hexafluorosilicate ions is so rapid that the ¹⁹F spectrum gives an average signal. From the changes in chemical shift with the concentration of salt, the value of the equilibrium constant and the ¹⁹F chemical shift of isolated ion-pairs have been calculated. The ¹⁹F chemical shift changes of the ion-pairs arise due to contact as well as pseudo-contact interactions.