Some chemical aspects of tervalent uranium.

Uranium(III) chemistry is reviewed and contrasted with relevant aspects of the chemistries of the tervalent transuranium elements, and tetravalent and pentavalent uranium. The preparation and chemical properties of a number of hydrated and anhydrous uranium(III) compounds , including a new hydrated uranium(III) fluoride, are reported, and the stability of the hydrated uranium(III) cation in the presence of a large number of inorganic anions is described. The complex chemistry of uranium(III) is shown to be very limited and only with the oxygen donor ligands phenazone and 4-dimethylaminophenazone have solid complexes been prepared. An uncharacterised uranium(III) hexamethylphosphoramide complex has also been isolated. The presence of uranium(III) is demonstrated in these compounds. The electronic spectrum of the uranium(III) ion has been studied in various compounds and the results are discussed in terms of the chemical environment, particularly the effects on the 5f[3]-5f[3] and 5f[3]-5f[2] 6d[1] transitions. The magnetic behaviour of the uranium(III) ion is interpreted in terms of crystal field effects rather than intramolecular antiferromagnetism. No available theoretical treatment satisfactorily accounts for the spectral and magnetic properties of uranium(III)