METAL-SULFUR BOND ENTHALPY DETERMINATION OF DI-NORMAL-BUTYLDITHIOCARBAMATE CHELATES OF ZINC, CADMIUM AND MERCURY

The standard molar enthalpies of formation of crystalline [M(S2CNBu(n)2)2] (M = Zn, Cd or Hg), determined through reaction-solution calorimetry at 298.15 K, were found to be -471.23 +/- 3.90, -440.74 +/- 3.79 and -319.29 +/- 3.38 kJ mol-1, respectively. The corresponding molar enthalpies of sublimation, 107 +/- 3, 123 +/- 3 and 195 +/- kJ mol-1, were estimated by means of differential scanning calorimetry. From the standard molar enthalpies of formation of the gaseous chelates, -364 +/- 5, 318 +/- 5 and -124 +/- 5 kJ mol-1, the homolytic and heterolytic mean metal-sulphur bond enthalpies were calculated. The homolytic enthalpies decrease from zinc to mercury, while the heterolytic values are almost constant.71751175