Infrared spectrum, uranium

Only An(III) and An(IV) ions have been inserted into macrocyclic crown-ethers, e.g., in [UCl3(18-crown-6)]2[U02Cl3(OH)H20]. Hydrogen bond interactions between etheric oxygen and coordinated water molecules were only observed in the corresponding U02+ complexes [282]. The infrared spectrum and isotope effect of uranium-crown-ether complexes were reported [435], as well as the crystal structures... 

Chlorotris(//-cyclopentadienyl)uranium(IV) is an oxygen-sensitive brown solid. It can be handled in air for brief periods of time with minimal oxidation, which is evidenced by darkening of the color. The compound is soluble in ethereal and aromatic solvents but only sparingly soluble in aliphatic hydrocarbons. Solutions are exceedingly air-sensitive. The nmr spectrum in benzene exhibits a sharp singlet 9.6 ppm to high field of the solvent (r 12.4). The infrared spectrum (Nujol mull) exhibits typical 7t-cyclopentadienyl bands at 1013 (m) and 784 (s) cm i. Oxidation is evidenced by the appearance of the antisymmetric v(OUO) stretch of the uranyl group at 930 cm-i. 

Chloro(/7-cyclopentadienyl)thorium(lV) is a white solid, less oxygen-sensitive than the uranium analog but considerably more moisture-sensitive. Exposure to air causes the appearance of an ocher color. The compound is less soluble in all organic solvents than the uranium analog solutions are extremely air-sensitive. The nmr spectrum in benzene-de exhibits a sharp singlet at t3.81. The infrared spectrum (Nujol mull) shows 7t-cyclopentadienyl bands at 1016 (m), 812 (sh), and 788 (s) cm i. 

Both solution and solid-state vibrational spectroscopy have been employed to characterize the reaction shown above. In addition. X-ray powder diffraction of the recovered solids from the uranium experiment shows the presence of both (HjO" ") (SbFg) and UF4 -2SbF5. Raman spectroscopy of the solid mixture after vacuum removal of the solvent features bands at 667,561, and 295 cm due to the Vj, V2, and Vj stretching and bending modes of SbF g, respectively. The infrared spectrum of the solid also shows a broad band at 3058 cm (vj) and a sharp band at 1623 cm" (V4) due to the (HjO ) moiety. Little difference between the spectra reported for pure (HjO" ") (SbFg) (Christe et al. 1984) and our heterogeneous mixtures was observed. Therefore,... 

The molecular structure of this compound was determined by x-ray diffraction and the result is illustrated in Fig. 23.19. Although the uranium-bound hydrogen atom could not be precisely located in the diffraction study, it is evident in the infrared spectrum (Vu h = 1219 cm Vu d = 870 cm ) and in low-temperature HNMR spectra, which indicate instantaneous structure (25) ... 

The hexafluorouranate products are all air-sensitive, pale blue-green powders. The reaction of [UFg] with water produces [UFs] and [U02F4] whose presence in the product may be determined by the visible-near-infrared spectrum in acetonitrile. The characteristic fundamental V3 mode of [UFe] is found at 525 cm" in the infrared spectrum of the salts. Reactions of tetra-alkylammonium fluorides with uranium pentafluoride in acetonitrile yield the corresponding [UF ]" salts, but these salts were found to be unstable under vacuum after removal of acetonitrile. They can be prepared less conveniently in HF, however. The uranium in NaUFe is six oordinate in solution and in the solid state, whereas in KUFj the uranium is six-coordinate in solution and eight-coordinate in the solid state. The exact geometry of the isolated... 

This complex, unlike the simple homoalkyls of uranium 133), is stable at room temperature but decomposes without melting at 85 °C. The NMR spectrum of the diamagnetic complex confirms the presence of a Th—C a bond coordinated through the methylene carbon [t, 8.90 ppm singlet (2) t, 3.60 ppm doublet (2) t, 3.15— 2.60 ppm multiplet (3)]. Both the NMR and infrared spectra are in accordance with those of the presumably isostructural tetrabenzylzirconium and hafnium complexes. Also reported was the thorium(III) complex (C6H5CH2)3Th-THF. 

Only v3 is directly observed in the infrared. All of the frequencies for NpF6 lie intermediate between UF6 and PuFa. The infrared data make it possible to deduce the value of the Raman active frequencies in the case of uranium hexafluoride, a discrepancy was revealed between the value for the Raman spectrum as deduced by the method of Gaunt (88) from infrared measurements and the experimentally determined Raman spectrum of Bigeleisen et al. (10). Consequently, Claassen et al. (17) have measured... 

Uranium pentafluoride prepared in the above maimer is the low-temperature, form, which can be identified by its characteristic X-ray powder pattern. The single<rystal structure has been determined tetragonal symmetry, space group I42d(Z = 8), with eight-coordination and a geometry intermediate between a dodecahedron and a square antiprism. Uranium pentafluoride is air sensitive and disproportionates in water to give a precipitate of uranium tetrafluoride and a solution of uranyl fluoride. Consequently, UFs must be handled in an inert atmosphere. The near-infrared-visible spectrum of uranium pentafluoride in acetonitrile has been determined and is perhaps the most convenient characterization. 

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