SOLUBILITIES OF COPPER(II) AND CHROMIUM(III) BETA-DIKETONATES IN SUPERCRITICAL CARBON-DIOXIDE

The mole fraction solubilities of ten copper(II) and five chromium(III) beta-diketonates were measured in supercritical carbon dioxide with a spectroscopic technique and found to vary over 4 orders of magnitude. Observed trends indicate that the solubility in supercritical carbon dioxide is strongly dictated by the character of the hydrocarbon or fluorocarbon shell surrounding the central metal atom. A group-contribution approach was used to calculate the solubility parameter of the anion of the uncomplexed beta-diketone that was correlated to the experimentally measured solubility. A regular solutions approach was used for Cr(acac)(3) to quantitatively attempt to predict the solubility in supercritical carbon dioxide. Solubility data, solubility parameter trends, and limitations of regular solutions theory applied to supercritical fluids are discussed.