Mössbauer spectra of tin(IV) iodide complexes

Abstract

The first examples of compounds containing the [SnR₂I₃]^– anion, i.e. [Buⁿ₄N][SnR₂I₃] (R = Me or Ph), have been prepared and characterized by IR, Raman and ¹¹⁹Sn Mössbauer spectroscopies, and X-ray powder diffraction data. The experimental data are consistent with a trigonal bipyramidal structure, with the R groups in equatorial positions, for the [SnR₂I₃]^– anions. Octahedral [SnR₂I₄]^2– anions could not be isolated and it is shown that the previously reported [Buⁿ₄N]₂[SnMe₂I₄] is actually a 1∶1 mixture of Buⁿ₄NI and [Buⁿ₄N][SnMe₂I₃]. The X-ray powder structure of Cs₂SnI₆ has been refined by the Rietveld method. The compound crystallises in the cubic Fm3m space group with a = 11.6410(3) Å and a Sn–I distance of 2.864(1) Å. The Sn–I distances in Cs₂SnI₆, SnI₄(bipy), SnI₄(Ph₃PO)₂ and SnI₄(Ph₂SO)₂ are related to the Mössbauer quadrupole splitting, showing that ligands that are weaker donors than I^– (i.e. have a more positive partial quadrupole splitting) give rise to Sn–I distances that are shorter than for the [SnI₆]^2– anion.