IMPACT ON LIGAND-FIELD THEORY OF THE REAL GROUND-STATE FOR CUCL2

The recent prediction by coupled pair functional Hartree-Fock calculat ions of a degenerate 2PI(g) ground term for linear CuCl2 has been conf irmed by local density functional (LDF) Slater-type orbital calculatio ns. This has prompted a new cellular ligand field (CLF) analysis. Cont rary to previous results on higher-co-ordinate chlorocuprates(II) and other complexes, the relative sigma to pi Cu-Cl bonding ratios for CuC l2, as predicted by the CLF e(lambda) parameters on the one hand and b y the LDF overlap populations on the other, do not agree. However, the CLF data do correlate with the computed LDF bonding energies but only when the whole d manifold (i.e. the 2PI(g), 2SIGMA(g)+ and 2DELTA(g) states) is taken into account. The interpretation and implications of these results within the ligand-field formalism are discussed.