Fluoro Complexes of Uranium(IV) Part IV The Far Infrared Spectra of Fluoro Complexes of Uranium(IV)

P.G. Department of Chemistry, Sambalpur University, Burls, Orissa Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal Manuscript received 4 September 1972; revised 25 January 1972; accepted 28 June 1973 The far i.r. spectra of several fluoro complexes of uranium(IV) have been studied in the metal halogen stretching frequency region (500-300 cm-1) and have been compared with the i.r. band for uranium tetrafluoride and the available i.r. data of the fluoro complexes of actinides(V). The complexes of the type, MIIMIVF6 such as, (enH2)(UF6) show the metal halogen vibrational band in the region 420--440 cm -1. as compared to 420 cm -1 in uranium tetrafluoride, and indicate that uranium(IV) ion in the hexafluoro complexes is 8-coordinated. On the other hand complexes of the type, MIMIVF5 such as (CH3NH3)UF6 show the metal-halogen vibrational band at a higher frequency region, which are located in the range 460-470 cm -1 indicating a lower coordination number about uranium(IV) ion than the hexafluoro complexes. Most probable coordination number about the uranium(IV) ion in these complexes is seven. The present study show that the complexes formed by the organic ammonium fluorides with uranium(IV) fluoride are significantly different from the alkali fluoride-actinide(IV) fluorides. The apparent differences are not, however, surprising but the effect of the large size of the organic ammonium groups.