Ligand-field splittings in non-cubic complexes. Part III. Tetragonal copper(II)–oxygen systems

Abstract

The d–d spectra of tetragonal copper(II)–oxygen systems are discussed. The position of the transition d_z²→d_x²–y² in eight compounds can be accounted for in terms of σ-bonding and electrostatic effects. The other two transitions are less readily treated since they are affected by π-bonding. However, the d orbital splitting in Cu(HCO₂)₂,4H₂O can be satisfactorily deduced from parameters obtained empirically by fitting the spectrum of Egyptian Blue CaCuSi₄O₁₀, where the bonding situation is similar. In- and out-of-plane π bonding parameters are calculated empirically for each compound and the results are compared with the anisotropic orbital reduction factors k_∥ and k_⊥.