Information from the mössbauer spectra of tin(IV) halide complexes with 1,3-diethylthiourea. A redetermination of the crystal structure of tetrachlorobis(1,3-diethylthiourea)tin(IV)

Abstract

The Mössbauer quadrupole splitting of octahedral tin(IV) chloride complexes can give information about the Sn–Cl bond lengths. As the value of d(Sn–Cl) reported previously for SnCl₄(detu)₂(detu = 1,3-diethylthiourea) was too long for a complex showing a single line in the Mössbauer spectrum, we have redetermined the X-ray crystal structure, and found Sn–Cl distances which are compatible with the Mössbauer data. The compound crystallises in the centrosymmetric space group Rc, and the structure is disordered about a crystallographic two-fold axis passing through Sn and two Cl atoms. The disorder does not allow the unambiguous distinction between a cis or trans structure by X-ray crystallography, but IR and Raman spectroscopies show that both SnCl₄(detu)₂, and the new compound SnF₄(detu)₂, have a cis geometry. The isomer shift values for SnX₄(detu)₂ are –0.04, 0.62, 0.96 and 1.21 mm s^–1 for X = F, Cl, Br and I, respectively. The values for X = Cl and Br are much higher than previous values, and fully consistent with S-co-ordination by the detu ligand. The information on the donor atom in SnX₄L₂ complexes, which can sometimes by obtained from the Mössbauer isomer shift, is discussed.