| Popis: |
Raman spectra of XeF 6 in its solid fluorometalate complexes, in which it appears as XeF 5 + or Xe 2 F 11 + ion, show appreciable variations and the observed two distributions of intensities were explained by the effects of deformation of the ions or by the coupling of their vibrations. However, there is a number of exceptions. It is demonstrated here that in addition to kinematic, electronic effects also influence the shape of spectra. Partial charge on the F ligand of the anion governs the geometry of XeF 5 + with the consequent shifts and changes in intensities of the Raman bands. In known spectra of XeF 5 + · MF x − salts, ν 1 (axial XeF stretch) shifts to lower frequencies and becomes more intensive than ν 2 (symmetric basal Xe-F stretch) when the negative partial charge on the F ligand of the anion exceeds ca. 0.33, estimated by the Sanderson method, and one type of spectra transforms into the other. For other compositions of examined XeF 5 + compounds the same is observed. The deformation of XeF 5 + in compounds with polymeric anions or different interactions in compounds with monomeric anions of various composition have, in the examples studied, minor influences. Xe 2 F 11 + compounds are a separate family. Effect of the partial charge of the F ligand is not observed and the reasons for frequency shifts of ν 1 are to be searched for elsewhere. |
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