Vapour pressures and standard molar enthalpies of sublimation of beryllium(II) and aluminium(III) benzoylacetonates

Abstract

The simultaneous torsion and mass-loss effusion technique was used to measure the vapour pressure of crystalline bis(benzoylacetonato)beryllium(II) — Be(BZAC)2 — and tris(benzoylacetonato)aluminium(III) — Al(BZAC)3 — , as a function of temperature, from 415.7 K to 437.6 K and from 461.9 K to 478.2 K respectively. From the temperature dependence of the vapour pressure, the standard molar enthalpies of sublimation, at the mean temperature of the experimental temperature ranges, were derived for both complexes. The mean values obtained from both techniques are: Be(BZAC)2, ΔcrgHmo(426.6 K) = 151.6 ± 1.8 kJ mol−1; Al(BZAC)3, ΔcrgHmo(470.1 K) = 186.6 ± 2.1 kJ mol−1. Using the estimated value of ΔcrgCpo = −50 J K−1 mol−1, for both beryllium(II) and aluminium(III) complexes, the standard molar enthalpies of sublimation at 298.15 K, werecalculated as 158.0 ± 1.8 kJ mol−1 and 195.2 ± 2.1 kJ mol−1 respectively.