Thermochemistry of the solid-state coordination compounds (C 2H 10N 2)MCl 4(s) (M = Cd and Cu)

Abstract

Tetrachlorocuprate (II) ethylenediammonium (C 2H 10N 2)CuCl 4(s) and tetrachlorocadmate (II) ethylenediammonium (C 2H 10N 2)CdCl 4(s) were synthesized. Chemical analysis, elemental analysis, and X-ray crystallography were applied to characterize 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 ethylenediamine dihydrochloride with CuCl 2·2H 2O(s) and CdCl 2·2.5H 2O(s) were determined as Δ r H m, 1 ∘ = ( 5.89 ± 0.22 ) kJ · mol - 1 and Δ r H m, 2 ∘ = - ( 2.88 ± 0.26 ) kJ · mol - 1 by use of an isoperibol solution–reaction calorimeter, respectively. The standard molar enthalpies of formation of the title complexes (C 2H 10N 2)CuCl 4(s) and (C 2H 10N 2)CdCl 4(s) were derived to be Δ f H m ∘ [(C 2H 10N 2)CuCl 4, s] = −(784.51 ± 1.35) kJ · mol −1 and Δ f H m ∘ [(C 2H 10N 2)CdCl 4, s] = −(960.99 ± 1.36) kJ · mol −1, respectively.