The solubility of palladium hexafluoroacetylacetonate [Pd(hfac)(2)] and nickel hexafluoroacetylacetonate dihydrate [Ni(hfac)(2)center dot 2H(2)O] in supercritical CO2 (scCO(2)) has been measured using a high-pressure variable volume view cell. At 313.2K and 8.9 MPa, the solubility of Pd(hfac)(2) is above 3.6 wt% (3.15 x 10(-3) mole fraction). Solubility measurements of Ni(hfac)(2)center dot 2H(2)O were also carried out at 313.2, 323.2 and 333.2 K in the 9.4-25.1 MPa pressure range. Ni(hfac)(2)center dot 2H(2)O mole fraction solubility values vary from 2.95 x 10(-5) to 2.02 x 10(-4). For a given temperature, the solubility increases with pressure due to the higher density of the solvent. At constant pressure, however, a crossover has been observed. At mole fractions below ca. 1.2 x 10(-4), solubility decreases with temperature due to the decrease in density of the fluid. On the contrary, at higher concentrations, solubility increases with temperature due to the increase in the solute vapour pressure. Ni(hfac)(2)center dot 2H(2)O solubility data were satisfactorily correlated to semi-empirical equations. The solubility of Ni(hfac)(2)center dot 2H(2)O in scCO(2) was more than 2 orders of magnitude lower than the solubility of Pd(hfac)2 at similar conditions. This is related to the presence of water molecules bound to Ni in the precursor which allow the formation of intermolecular hydrogen bonds and may cause the formation of a molecules network. Adding a small amount of a polar modifier such as ethanol (2-6.5 mol%) to scCO(2) increased substantially the solubility of the precursor. At EtOH concentrations close to 5 mol%, the solubilisation pressures were rather independent of the Ni(hfac)(2)center dot 2H(2)O concentration in the 1-6 x 10(-3) mole fraction range. The large solubility increase observed in scCO(2) modified with EtOH may be related to the rupture of the hydrogen bonded Ni(hfac)(2)center dot 2H(2)O network due to the better solvation of the complex in the CO2/EtOH mixture possibly by hydrogen bonding between Ni(hfac)(2)center dot 2H(2)O and EtOH. (C) 2012 Elsevier B.V. All rights reserved.