Studies on Mixed Chelates. XIII. Formation and Electronic Spectra of 5-Coordinated Mixed Copper(II) Chelates Containing N-Alkylated Ethylenediamine, Acetylacetonate, and Halide Anions

The visible absorption spectra of three new mixed chelates of copper(II), Cu(acac)(tmen)X (acac=acetylacetonate ion, tmen=N,N,N′,N′-tetramethylethylenediamine, and X−=Cl−, Br−, or I−) were studied in various organic solvents. The \ ildeνmax values of their d-d bands depend strongly on the nature of the solvent, similarly to the pseudohalide complexes reported in the preceding paper. These data show the existence of the equilibrium: [Cu(acac)(tmen)X][Cu(acac)(tmen)]++X− (5-coordinated) (4-coordinated, with axial solvation) in such solutions, which is shifted to the right hand side with increase of the solvent polarity and with decrease of the coordination ability of the X− anion, i.e., in the order Cl−→Br−→I−.