Actinide chemistry; high oxidation-state uranium fluoride and fluoride halide complexes.

The preparation of UF5 has been re-investigated in detail and it has been shown that the most reliable synthetic route is a novel reaction in which UF6 is interacted with hexamethyldisiloxane at room temperature. The pure UF5 produced has been employed in an investigation of the reactions of UF5.nCH3CN and UF5.nTPPO with trimethylsilylchloride which have been claimed to yield compounds of the type UFxC15-x.nCH3CN (0?x?5 and n = 1,2) and UFxC15-x.nTPPO (TPPO = (C6H5)3PO, 0?x?5 and n = 1,2). In the process of these studies a large number of products were obtained as single crystals and the single-crystal X-ray structures of the novel compounds, [UF4.TPPO]2F, [(UF3.3TPPO)2]2+ 2[UF6]-, cis-UO2Cl2.2TPP0 and ?-trans- UO2Cl2.2TPPO have been obtained. Attempts have been made to elucidate the infrared and e.s.r. spectra of these compounds in order to try to understand the nature of the chemical reactions which give rise to them. Efforts to prepare a mixed bromide fluoride of uranium (VI) have yielded only uranium pentafluoride or uranium tetrafluoride. The preparations of UF5.SbF5.L (L = CH3CN and TPPO) and UF5.2SbF5.5CH3CN were repeated and single crystals were successfully grown for X-ray examination. An attempt to obtain the novel UF5.2SbF5.5TPP0, however, gave inconclusive results.