Solution-reaction calorimetry was used to determine the standard molar enthalpy of formation at 298.1 5 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.712351238