Fluorostannates(II): the aqueous and molten SnF2–MF2 systems (M = Fe, Co, and Ni)

Abstract

The aqueous and molten SnF₂–MF₂(M = Fe, Co, and Ni) systems have been studied. The preparation of the hydrated trifluorostannates(II) M(SnF₃)₂,6H₂O and pentafluorodistannates(II) M(Sn₂F₅)₂,2H₂O from the aqueous systems and of distinct phases corresponding to the SnF₂–MF₂ molar compositions 8 : 1, 4 : 1, 2 : 1, 3 : 2, and 1 : 1 from the molten systems is described. The ¹¹⁹Sn Mössbauer parameters of these materials are consistent with the tin being in a pyramidal three-co-ordinated environment in the M(SnF₃)₂,6H₂O, M(Sn₂F₅),2H₂O, 8SnF₂–MF₂, 4SnF₂–MF₂, and 2SnF₂–MF₂ systems, but with an increase in the number of fluorine atoms bonded to the tin in the 3SnF₂–2MF₂ and SnF₂–MF₂ phases. The variation in chemical shift in all of the series of fluorostannates(II) is explained in terms of the different polarising powers of the transition-metal ions and their hydrates.