Maria Luísa C.C.H. Ferrão

Energetics of metal-oxygen bonds in metal complexes of β-diketones

The thermochemical data available for standard enthalpies of formation, both in the crystalline and gaseous phases, of metal B-diketonates is reviewed, and the calculation of enthalpies of gas-phase decomposition of these complexes is presented. The homolytic metal-oxygen bond-dissociation enthalpies for several complexes of &diketones with different metals are calculated, and the results discussed in terms of structure and bonding and, whenever appropriate, trends in the data are suggested and discussed.

Enthalpies of combustion of four methyl-substituted heptane-3,5-diones and benzoylacetone

Abstract The standard enthalpies of combustion in oxygen at 298.15 K of the following β-diketones were measured in a static-bomb calorimeter: The standard enthalpies of formation of these β-diketones were derived for the keto-enol equilibrium mixtures in the condensed state and for the liquid and gaseous enol forms.

Standard enthalpies of formation of tris(β-diketonate) iron(III) complexes: the mean (FeO) bond-dissociation enthalpies

Abstract The standard (po = 101.325 kPa) molar enthalpies of formation of the crystalline complexes of iron(III) with 1-phenylbutane-1,3-dione ( hbzac ), 2,2,6,6-tetramethylheptane-3,5-dione ( hdpm ), 1,1,1-trifluoropentane-2,4-dione ( htfac ), and 1,1,1,5,5,5-hexafluoropentane-2,4-dione ( hhfac ) were determined, at 298.15 K, by solution-reaction calorimetry. The enthalpies of sublimation of the crystalline complexes were determined by high-temperature microcalorimetry, and average molar bond-dissociation enthalpies 〈Dm〉(FeO) were derived, based on an estimated D m (OH,Hl,enol) (kJ·mol −1 ) = (418 ± 20) . Fe(III)complex Δ f H m o (cr) (kJ·mol −1 ) Δ sub H m o (kJ·mol −1 ) 〈D m 〉(FeO) (kJ·mol −1 ) Fe(bzac)3 −985.2 ± 8.5 200 ± 5 175 ± 10 Fe(dpm)3 −1813 ± 12 146 ± 5 183 ± 10 Fe(tfac)3 −3220 ± 15 138 ± 5 176 ± 11 Fe(hfac)3 −5115 ± 15 120 ± 10 180 ± 11

Standard enthalpies of formation of bis(trifluoroacetylacetonato)copper(II) and bis(hexafluoroacetylacetonato)copper(II): the mean (CuO) bond-dissociation enthalpies

Abstract The standard (po = 101.325 kPa) enthalpies of formation at 298.15 K of the following crystalline solids were determined by solution-reaction calorimetry, and the enthalpies of sublimation were measured by microcalorimetry. Cu(II) complex Δ f H m o (cr)/(kJ · mol −1 ) Δ cr g H m o /(kJ · mol −1 ) Cu( tfac )2 −2064 ± 10 112 ± 3 Cu( hfac )2 −3311 ± 10 108 ± 6 Values of {〈Dm〉(CuO) − 0.5Dm(OH, Hl, enol)} were derived, showing a negligible effect of CF3 substitution in the ligand upon 〈Dm〉(CuO). ( tfac , 1,1,1-trifluoropentane-2,4-dionato; hfac , 1,1,1,5,5,5-hexafluoropentane-2,4-dionato.)

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.

Standard enthalpies of formation of tetrakis(pentane-2,4-dionato) zirconium(IV) and tetrakis(1,1,1-trifluoropentane-2,4-dionato)zirconium(IV): the mean (Zr−O) bond dissociation enthalpies

The standard (po = 0.1 MPa) molar enthalpies of formation at the temperature T = 298.15 K of the following crystalline solids were determined by solution-reaction calorimetry, and the standard molar enthalpies of sublimation at T = 298.15 K were measured by microcalorimetry. From the standard molar enthalpies of formation of formation of the gaseous complexes, the average molar bond-dissociation enthalpies 〈D〉(Zr-O) were derived.

Standard molar enthalpy of formation of tris(3-methylpentane-2,4-dionato)iron(III): the mean (FeO) bond-dissociation enthalpy

The standard ( p o = 0.1 MPa) molar enthalpy of formation of the crystalline complex of iron(III) with 3-methylpentane-2,4-dione (HMe acac ) was determined at the temperature 298.15 K, by solution-reaction calorimetry as −(1360.3 ± 5.8) kJ · mol −1 . The enthalpy of sublimation at the temperature 298.15 K, determined by microcalorimetry, was found to be (164.5 ± 2.8) kJ · mol −1 . From the standard molar enthalpy of formation of the gaseous complex, the mean molar bond-dissociation enthalpy, 〈 D m 〉(Fe-O), was derived as (172 ± 11) kJ · mol −1 .