sodium hydroxide in ethanol; water addn. of 3 equiv. NaOH to mixt. of 3 equiv. diketone and 1 equiv. N-ligand (in EtOH), dropwise addn. of 1 equiv. aq. EuCl3, stirring (60°C, 1 h); cooling, collection (filtration), washing (EtOH, water), recrystn., drying (vac.);