Thermochemical features of di-n-propyldithiocabamate chelates of zinc-group elements

Abstract

Solution-reaction calorimetry was used to determine the standard molar enthalpy of formation at 298.15 K of crystalline [M(S₂CNPrⁿ₂)₂](M = Zn, Cd or Hg): –440.68 ± 2.85, –396.71 ± 2.60 and –240.50 ± 2.40 kJ mol^–1, respectively. The enthalpies of sublimation, 147 ± 2, 199 ± 1 and 200 ± 2 kJ mol^–1, were estimated by means of differential scanning calorimetry. From the standard molar enthalpies of formation of the gaseous chelates, –294 ± 4, –198 ± 3 and –41 ± 3 kJ mol^–1, the homolytic 182 ± 3, 154 ± 3 and 102 ± 3 kJ mol^–1 and heterolytic 745 ± 3, 681 ± 3 and 709 ± 3 kJ mol^–1 mean metal-sulfur bond enthalpies were calculated. The homolytic enthalpies decrease from zinc to mercury and are dependent on the nature of the radical attached to the nitrogen of the ligand.