Solubilities of Palladium(II) β-Diketonates (β-Diketonate = Acetylacetonate, Trifluoroacetylacetonate, Thenoyltrifluoroacetonate) in Supercritical Carbon Dioxide

The solubilities of palladium(II) -diketonates (PdL2, L = acetylacetonate (acac), trifluoroacetylacetonate (tfa), and thenoyltrifluoroacetonate (tta)) in supercritical carbon dioxide (SC-CO2) from 318 – 338 K and 8 – 25 MPa were investigated by UV-vis spectrophotometer equipped with a high-pressure optical cell. The molar absorptivities for Pd(acac)2, Pd(tfa)2, and Pd(tta)2 in SC-CO2 were estimated as 1.14  104 M-1 cm-1 at 324 nm, 8.16  103 M-1 cm-1 at 336.5 nm, and 2.70  104 M-1 cm-1 at 322.5 nm, respectively. Solubilities in SC-CO2 increase in order of Pd(tta)2 < Pd(acac)2 < Pd(tfa)2, i.e., 6.5  10-6 < 5.2  10-5 < 1.3  10-4 M at 318 K and 11.5 MPa. The experimental solubilities were correlated using the equation proposed by Chrastil and the thermodynamic parameters for each PdL2 were estimated.