Copper–halogen stretching frequencies

Abstract

The far-infrared spectra of some halogenocuprates of the types [CuX₄]^2–(planar and tetrahedral), [Cu₂X₆]^2–, CsCuX₃, and M₂^ICuCl₄,2H₂O have been studied. Complexes of the type CuX₂L₂(X = Cl or Br; L = donor ligand) are also considered. v(Cu–Cl) lies in the range 368—222 cm.^–1 and v(Cu–Br) between 278 and 168 cm.^–1. The spectra admit of a consistent interpretation without the need to postulate the presence of v(Cu–X) modes in the normal region due to stretching of copper–halogen “long” bonds. Bridging v(Cu–X) frequencies have been assigned but the range is severely overlapped by that of terminal v(Cu–X).