Ligand-field splittings in noncubic complexes. Part VI. Comparison of the crystal field and angular overlap treatments for eight-co-ordinate D2d systems

Abstract

The angular overlap method is applied to the d-orbital splitting in eight-co-ordinate complexes of D_2d symmetry. The effects of varying bond angles and relative bond lengths are discussed, and the results compared with those obtained by other workers using the crystal-field model. The angular overlap model is shown to yield qualitatively similar results to the crystal-field treatment when proper account is taken of π-bonding. The two methods are compared critically, and it is concluded that the angular overlap model is preferable since it takes explicit account of σ- and π-covalence and gives apparently reasonable results without much additional labour. The choice of parameters in the angular overlap model is less arbitrary, and the crystal-field model may exaggerate the effects of relatively distant ligands on the d-orbitals.