Ligand-field splitting in eight-co-ordinate complexes of dodecahedral structure

The splitting and the order of 3d- and 4d-orbital energies for some complexes of the first- and second-transition series having dodecahedral geometry is calculated by the simple crystal-field model. The relative order of energy levels depends on the nature of the ligands and their distances from the metal. The energy behaviour is further examined as a function of the ratio G2 : G4 by assuming first all ligands equal and at the same distance from central metal, and then for cases when all ligands are equal but at different distances from the central metal. The discussion is extended to cases when different ligands are present in the complex. The results suggest that there is no representative energy diagram valid for all MX8 dodecahedral complexes. The calculations are applied to some complexes of Zr, Mo, Ti, Cr, and Co in order to illustrate the variations met in actual cases. It is found that dxy is the most stable for 4d and dz2 for 3d complexes examined.