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) U 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.