Barry J. Gellatly

The chemistry of uranium. Part 23. Isomorphous tetrachlorobis(hexamethylphosphoramide)uranium(IV) and tetrabromobis(hexamethylphosphoramide)uranium(IV)

The structures of UCl 4 ·2hmpa and UBr 4 ·2hmpa have been determined by Fourier methods from single-crystal X-ray diffraction data Full-matrix least-squares refinement yielded final conventional R factors of 0.062 and 0.059 respectively. The complexes are isomorphout and crystallise in the space group P2 1 /n with a = 14.141(5), b = 10.530(5), c = 9.076(5) A , β = 93.33° and a = 14.348(5), b = 10.698 (5), c = 9.304(5), β = 91.95 respectively. The hmpa moieties are in trans-octahedral arrangement about the uranium atom. The principal bond lengths are U—X (X = Cl, Br) = 2.615, 2.78; U—O = 2.23, 2.18; O—P = 1.50, 1.53 A respectively.

The crystal structures of hexahalouranates. I. Bis(triphenylethylphosphonium) hexachlorouranate(IV) and bis(triphenylethylphosphonium) hexabromouranate(IV)

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Pentahalogeno-oxouranates(VI)

Pentafluoro- and tetrabromochloro-oxouranate(VI) salts, [Ph4P][UOF5] ana [Ph4P][UOClBr4], have been prepared by reaction of [Ph4P][UOCl5] with hydrogen fluoride and bromide respectively. Hydrolysis of [Ph4P]-[UOCl5] leads to a uranium(VI) anion which may contain a cis-dioxouranium(VI) group. The electron-transfer and vibrational spectra of these salts are discussed and compared with those of the corresponding tungsten(VI) species. A simple method for the preparation of [Ph4P][WOF5] is also reported.

The chemistry of uranium. Part 18. Arsine oxide and phosphine oxide complexes of uranium tetrahalides

A comparative study has been made between various arsine oxide and phosphine oxide complexes of uranium tetrahalides both in acetone solution and in the solid state. Conductimetric. potentiometric, and spectrophotometric methods have been used in solution, spectroscopic and structural methods on solids. The significantly greater ionising power of arsine oxide ligands is indicated and is discussed together with the structural differences between arsine oxide and phosphine oxide complexes of the type UCl4·2L and UX4·6L [X = Cl and Br; L = AsR3O, PR3O, or P(NMe2)3O; R = Me, Et, or Ph].

Chemistry of the trivalent actinides. Part III. Some chemical and physical properties of hydrated uranium(III) fluoride and the anhydrous chloride, bromide, and iodide. The stability of uranium(III) in aqueous solution and in organic solvents

The halides UX3(X = Cl, Br, or I) have been prepared and their electronic spectra measured at room and liquid nitrogen temperatures. The interactions of the halides with a large number of organic solvents are given. Hydrated uranium(III) fluoride, UF3,H2O, and a carbonate and hydroxide of uncertain compositions have been recognised. The extreme reactivity of uranium(III) to most anions and organic solvents in which it is soluble severely limits the chemistry of this oxidation state even if oxygen is rigorously excluded.