The standard (p ∘ =0.1MPa) molar enthalpies of formation of the crystalline complexes of dibenzoylmethane (Hdbm), thenoyltrifluoroacetone (Httfa), monothiodibenzoylmethane (HdbmS), and monothiothenoyltrifluoroacetone (HttfaS) of copper(II) were determined, at T=298.15K, by high precision solution-reaction calorimetry. The standard molar enthalpies of sublimation of the copper(II) β-diketonate complexes were measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean molar dissociation enthalpies copper(II)–ligand, 〈D m 〉(Cu–L), were derived. ΔfHm∘(cr)ΔcrgHm∘kJ·mol −1 kJ·mol −1 Bis(dibenzoylmethanate)copper(II), Cu(dbm) 2 −364.0±3.9230.7±8.2Bis(thenoyltrifluoroacetonate)copper(II), Cu(ttfa) 2 −1824.3±8.3167.9±7.4Bis(monothiodibenzoylmethanate)copper(II), Cu(dbmS) 2 35.6±7.7[241±15]Bis(monothiothenoyltrifluoroacetonate)copper(II), Cu(ttfaS) 2 −1405.7±8.3[177±15]