Application of the angular overlap model to the interpretation of the electronic spectra of some copper(II) and nickel(II) acetylacetonate complexes

Abstract

The angular overlap model has been used to calculate σ- and π;-bonding parameters for three copper complexes and one nickel complex of the type M(acac)₂(acac = the acetylacetonate anion or a closely related ligand). The results suggest that the orbital energy sequence in the copper complexes is probably d_xyd_z² > d_x²–y² > d_xz∼d_yz, but that in the nickel complex the stronger metal-ligand interaction causes the sequence d_xyd_x²–y² > d_z² > d_xz∼d_yz. The parameters estimated for the diamagnetic nickel complex can successfully be used to predict the d-orbital splittings observed for three paramagnetic nickel acetylacetonate complexes.