A SPECTROPHOTOMETRIC STUDY OF HEXA-, PENTA-, AND TETRA- COORDINATED HALOGENOCOPPER(II) COMPLEXES IN ACETONE – HYDROHALIC ACID MIXTURES

A spectrophotometric study of the Cu(II) – acetone – hydrochloric (hydrobromic) acid systems has revealed that at relatively high ratios of halide: copper there is a probable equilibrium between four-, five-, and six-coordinate halogenocopper(II) complexes. A distorted tetrahedral species is favored at the highest ratios. Ligand field bands of pseudo-octahedral monohalogenocopper(II) complexes and, in the visible region, a charge transfer band of the six-coordinate complex, [CuCl4(ac)2]2−, have been identified. The results of the present work point to the important role of the solvent in determining the geometries and absorption spectra of the complexes, a factor that seems to have been misinterpreted by some previous workers.