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

The standard ( p 0=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.