Crystalline bis-(n-dodecylammonium) tetrachlorocuprate (n-C12H25NH3)(2)CuCl4(s) and bis-(n-dodecylammonium) tetrachlorocadmate (n-C12H25NH3)(2)CdCl4(s) were synthesized. Chemical analysis, elemental analysis and X-ray crystallography were applied to characterise the compositions and crystal structures of the two complexes. In accordance with Hess' law, two thermochemical cycles were designed, and the enthalpy changes of the reactions of n-dodecylammonium hydrochloride with CuCl2 center dot 2H(2)O(s) and CdCl2-center dot 2.5H(2)O(s) were determined as Delta H-r(m)degrees(,1) = (32.86 +/- 0.40) kJ . mol(-1) and Delta H-r(m)degrees(,2) = -(5.28 +/- 0.38) kJ . mol(-1) by an isoperibol solution-reaction calorimeter, respectively. Eventually, the standard molar enthalpies of formation of the title compounds were derived to be Delta H-f(m)degrees [(n-C12H25NH3)(2)CuCl4, s] = -(1630.4 +/- 8.0) kJ . mol(-1) and Delta H-f(m)degrees [(n-C12H25NH3)(2)CdCl4, s] = -(1836.2 +/- 8.0) kJ . mol(-1), respectively. (c) 2013 Elsevier Ltd. All rights reserved.