NIR-FT RAMAN-SPECTROSCOPIC STUDIES OF HEXAMINE AND PENTAMMINE CHROMIUM(III) COMPLEXES

The NIR-FT-Raman spectra are presented for the hexammine [Cr(NH3)6]X3 (where X = Br-, NO3-), pentamminechloro [Cr(NH3)5Cl]X2 (where X = Cl-, ClO4-), and pentammineaqua [Cr(NH3)5(H2O)]X3 (where X = ClO4-, CF3SO3 -) chromium(III) complexes. The NIR-FT-Raman spectra, with an excitati on wavelength of 1064 nm, were obtained at room temperature without pr oblems from the strongly colored samples, which often cause problems w ith excitation by lasers in the visible region. All the Raman frequenc ies observed from the complexes have been assigned to the skeleton vib rational region from 100 to 600 cm-1. The symmetry and the general val ence force constants for the bonds chromium(III)-nitrogen, chromium(II I)-oxygen and chromium(III)-chloro have been obtained. The nature of t he metal-ligand bond between chromium(III) ammine complexes has been c ompared with recent results obtained for similar cobalt(III) ammine co mplexes.