Far-infrared, Raman, and Mössbauer spectra of trihalogenostannate(II) complexes, [SnX3]–, [SnX2Y]–, and [SnXYZ]–, with different cations

Abstract

All ten of the binary and mixed trihalogeno-complexes of tin(II), [SnXYZ]^–(X, Y, or Z = Cl, Br, or I), have been prepared as salts of one or more of the cations [Et₄N]⁺, [Buⁿ₄N]⁺, and [Ph₄As]⁺. Their far-i.r. (to 80 cm^–1) and Raman spectra show that discrete pyramidal trihalogeno-anions are present in solution. This structure is retained in the solid state for the [Buⁿ₄N]⁺ salts, but with [Ph₄As]⁺ and [Et₄N]⁺ cations there is increasing solid-state interaction resulting in a lowering of symmetry. This is shown also by the ¹¹⁹Sn Mössbauer data. For salts of a given cation, the isomer shifts show a regular variation with the sums of the electronegativities of the halide ligands. Quadrupole splitting was observed in each case, and showed an inverse relationship to the isomer shifts in each series; this is most readily interpreted as a consequence of a quadrupole splitting–electronegativity correlation.

The species absorbed by an anion-exchange resin in the halide (X^– or Y^–) form from SnX₂–HX solutions (X or Y = Cl, Br, or I) are shown to be [SnX₃]^– or [SnX₂Y]^–, and not [SnX₄]^2– as previously reported for X = Cl.