A systematic FT-Raman spectroscopic study of twelve bis-thiourea complexes, A(tu)2B2 (A = Zn, Cd, Hg; B=Cl, Br, I, SCN)

This work undertakes a systematic FT-Raman study of twelve thiourea complexes with stoichiometries A(tu)(2)B-2 (A = Zn, Cd, Hg; B = C1, Br, I, SCN). With the exception of Cd(tu)(2)Cl-2, the Raman spectra are reported here for the first time. The main modifications observed in the vibrational dynamics of the organic ligand are basically due to the coordination with the cation, with the influence of the anion less clear. These modifications show an increase with the softness of the metallic ion. The statistical analysis of the band wavenumber data shows that the ligand/cation interactions are stronger than the corresponding cation-anion bonds. This could explain the thermal behaviour of these complexes, which decompose easily at moderately high temperatures (600-700 K), producing the corresponding sulfides. The coordination of the thiocyanate anion in their complexes is accomplished via the sulfur atom (Hg2+ complex) or via the nitrogen atom (Zn2+ and Cd2+ complexes), although in both cases the association is largely ionic. (C) 1999 Elsevier Science B.V. All rights reserved.