Thermochemical studies of two copper(II) complexes with N-benzoyl-N′,N′-dialkylurea derivatives

The standard (p0=0.1 MPa) molar enthalpies of formation of crystalline bis(N-benzoyl-N′,N′-diethylureato)copper(II), Cu(BETU)2, and bis(N-benzoyl-N′,N′-diisobutylureato)copper(II), Cu(BIBU)2, were measured, at T=298.15 K, by solution–reaction isoperibol calorimetry, respectively, as −(833.7±9.7) and −(1050.6±12.1) kJ mol−1. The standard molar enthalpy of sublimation, at T=298.15 K, of Cu(BETU)2 was determined by a Knudsen effusion technique as (180±37) kJ mol−1. These values were used to derive the standard molar enthalpy of formation of Cu(BETU)2 in gaseous phase, and to evaluate the mean metal–ligand dissociation enthalpy of the complex relative to that of the ligand with hydrogen.