Mössbauer study of the Sn resonance in rare-gas matrix-isolated Sn(IV)-and Sn(II)halide molecules

Mössbauer absorption spectra of rare-gas matrix-isolated SnX₄ and SnX₂ molecules (X = F, Cl, Br, I) have been measured at matrix temperatures of a bout 5 K. The hyperfine interaction (hfi) parameters of ¹¹⁹Sn in argon matrix-isolated SnX₄ (X = Cl, Br, 1) molecules are identical with those of the corresponding crystalline compounds. This fact reveals that the inter-molecular interactions are negligible in the crystalline compounds as far as concerning the electronic structure of Sn⁴⁺. The ¹¹⁹Sn hfi parameters of rare-gas matrix-isolated SnX₂ molecules differ from those measured in the crystallin compounds. This arise from the totally different coordination of tin in the two situations. The analysis of the hfi parameters using a simple bonding model yields information about the ionicity of the Sn-halogen bonds and the bonding angle in these molecules. The observed isomer shifts and quadrupole interactions can only be explained in this model with a bonding angle θ = 95° ± 2° for all SnX₂ molecules and a slight increase of θ from Sn1₂ to SnF₂.