The standard molar enthalpies of formation of crystalline [M(S2CNBun2)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 ± 3 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.