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

This work undertakes a systematic FT-Raman study of twelve thiourea complex es with stoichiometries A(tu)(2)B-2 (A = Zn, Cd, Hg; B = C1, Br, I, SCN). W ith 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 dynamic s of the organic ligand are basically due to the coordination with the cati on, with the influence of the anion less clear. These modifications show an increase with the softness of the metallic ion. The statistical analysis o f the band wavenumber data shows that the ligand/cation interactions are st ronger than the corresponding cation-anion bonds. This could explain the th ermal behaviour of these complexes, which decompose easily at moderately hi gh temperatures (600-700 K), producing the corresponding sulfides. The coor dination of the thiocyanate anion in their complexes is accomplished via th e sulfur atom (Hg2+ complex) or via the nitrogen atom (Zn2+ and Cd2+ comple xes), although in both cases the association is largely ionic. (C) 1999 Els evier Science B.V. All rights reserved.