IR SPECTRA IN THE REGION OF STRETCHING VIBRATIONS OF THE METAL-LIGAND BOND OF METAL CHELATES WITH SULFUR-CONTAINING LIGANDS IN CHLOROFORM SOLUTION

Abstract

The IR spectra of metal complexes in the region of essentially stretching vibrations of the metal–ligand bond ν(ML) (L is the donor atom of the ligand) provide information about the structure of the coordination sphere and the character of chemical bonding [1]. However, the low-frequency region of these vibrations is not readily interpreted [2], especially in the case of polyatomic ligands, where one can expect complex shape of vibrations. The IR spectra in the region ν(MS) of a great number of metal complexes with bidentate chalcogen-containing ligands were interpreted in [3-5]. As follows from Table 1, the frequencies ν(MS) of metals in different oxidation states and with different atomic masses lie in the region 200-400 cm−1. The investigations in the region of ν(ML) known from the literature were generally accomplished for the solid state. Meanwhile, structural studies on metal complexes in solution are of great interest for rationalization of complexation, since the state of complexes in solution may change due to different factors [6, 7]. The aim of the present work is to investigate the IR spectra of the chelates listed in Table 1 in chloroform solution. The spectra in the region 200-400 cm−1 were measured on a Perkin-Elmer 325 spectrometer using a cell with polyethylene windows and with a teflon gasket (layer thickness 0.5 mm). The chelates under study possess very low solubility in CHCl3. Because of this, IR spectra could not be recorded for all compounds listed in Table 1. Figure 1 shows the IR spectra of the complexes in CHCl3 (0.03-0.06 M) and in the solid state.