Studies on Adduct Formation of β-Diketone Chelates with Heterocyclic Bases

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Abstract
Stability constants of the 1:1-adducts with heterocyclic Lewis bases on copper chelates of six β-diketones and two ethylesters of β-ketoacids (Cu(ligand)2·base) were determined by spectrophotometric measurements in visible region and the effects of β-diketone substituents, Lewis bases and organic solvents on the stability constants were studied. Terminal alkyl groups of β-diketones hardly hindered the adduct formation, because the adducts of β-diketone chelates except acetylacetone chelate had similar stability constants. Solvent effect was due to the formation of the solvates of the chelates or the solvation of N-base with solvent. This is related to the abnormal position of chloroform in the order of the adduct stability compared with oxygencontaining solvents. Infrared spectra indicate that the metal-oxygen bonding, as well as the basicity of Lewis bases is considered as an essential factor in the adduct formation of metal β-diketone chelates.