Abstract The standard enthalpy of formation of crystalline bis(benzoylacetonato)copper(II) has been determined at 298.15 K by solution calorimetry: ΔHf°[Cu(bzac)2] (c)=−143.6±2.2 kcal mol−1. Enthalpy changes at 298.15 K for the following hypothetical gaseous reactions have been subsequently derived: Cu(g)+2bzac·(g)=[Cu(bzac)2](g) ΔH=−165.9±14.3 kcal mol−1 Cu2+(g)+2bzac−(g)=[Cu(bzac)2](g) ΔH=−747.3±14.4 kcal mol−1 The corresponding homolytic(\barE) and heterolytic(\barE′) copper(II)-oxygen mean bond energy parameters were calculated as \barECu-o=41±3 kcal mol−1 and \barE′Cu-o=187±3 kcal mol−1 respectively.