Impact on ligand-field theory of the real ground state for CuCl2

Abstract

The recent prediction by coupled pair functional Hartree–Fock calculations of a degenerate 2Πg ground term for linear CuCl2 has been confirmed by local density funtional (LDF) Slater-type orbital calculations. This has prompted a new cellular ligand field (CLF) analysis. Contrary to previous results on higher-co-ordinate chlorocuprates(II) and other complexes, the relative σ to π Cu–Cl bonding ratios for CuCl2, as predicted by the CLF eλ parameters on the one hand and by 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 2Πg, 2Σg+ and 2Δg states) is taken into account. The interpretation and implications of these results within the ligand-field formalism are discussed.