Standard enthalpies of formation of 3-methylpentane-2,4-dione and of bis(3-methylpentane- 2,4-dionato)copper(II): the mean (CuO) bond-dissociation enthalpy

The standard ( p o = 0.1 MPa) molar enthalpy of combustion in oxygen at 298.15 K of liquid 3-methylpentane-2,4-dione (HMe acac ) was measured by static bomb calorimetry as −(3353.2±1.7) kJ · mol −1 . The standard molar enthalpy of formation of the crystalline copper(II) complex with 3-methylpentane-2,4-dione was determined, at the temperature 298.15 K, by solution-reaction calorimetry. The vapour pressures of the complex were measured as function of temperature by the Knudsen-effusion technique, and the standard molar enthalpy of sublimation Δ g cr H o m (396.70 K)/(kJ · mol −1 ) = 130.7 ± 1.0, was derived by the Clausius-Clapeyron equation. From this value, the standard molar enthalpy of sublimation was calculated as Δ g cr H o m (298.15 K)/(kJ · mol −1 ) = 135.6 ± 1.0. Measurement of the standard molar enthalpy of sublimation using a direct microcalorimetric method, confirmed the value from the Knudsen technique.