Calorimetric study of ethyleneurea, ethylenethiourea and propyleneurea cadmium chloride adducts

Adducts of the general formula CdCl2·nL [n=1 and 2; L=ethyleneurea (eu), ethylenethiourea (etu) and propyleneurea (pu)] were synthesized by a solid state route and characterized by elemental analysis, infrared spectroscopy, and reaction solution calorimetry. The infrared results showed that eu and pu coordinate through carbonylic oxygen atoms, whereas etu uses the nitrogen as coordinating site. The standard molar reaction enthalpy in condensed phase: CdCl2(c)+nL(c)=CdCl2·nL(c); ΔrHmθ, were obtained from reaction–solution calorimetry, to give the following values for mono and bisadducts: −20.0±0.1; −19.9±0.1; −13.3±0.1 and −38.6±0.1; −56.9±0.1; −17.0±0.1 kJ mol−1 for eu, etu and pu, respectively. The values of decomposition (ΔDHmθ) and lattice enthalpy (ΔMHmθ) as well as the mean cadmiumligand bond dissociation enthalpy, D(CdL), were calculated for all adducts.