Bond valence sum analysis (BVS) of metal ligand bond lengths in some Zn(II), Cd(II) dithiocarbamate complexes and their adducts

Bond valence sums have been calculated for a series of Zn(II), Cd(II) dithi ocarbamate complexes and their adducts. Values calculated from crystallogra phic distances predict the correct oxidation state of the metal centre in a wide range of structural types. The BVS analysis for the bisdithiocarbamat es of zinc, cadmium and their adducts has confirmed the valency of the cent ral metal to be 2.0 as expected. In the case of zincdithiocarbamate complex es, the valence bond sums are in general greater than the sums for the addu cts. The lower BVS values in the case of adducts are due to the change in c oordination geometry from tetrahedral to octahedral. But in the case of Cad mium dithiocarbamate complexes and their adducts no observable changes are seen in VBS values. Relatively larger size of cadmium ion compared to zinc ion, alleviates the strain involved in the transformation from tetrahedral to octahedral geometry.