Uranyl

Complexes of the uranyl ion are important in the extraction of uranium from its ores and in nuclear fuel reprocessing.

The most common arrangement is for the so-called equatorial ligands to lie in a plane perpendicular to the O–U–O line and passing through the uranium atom.

[3] The colour of uranyl compounds is due to ligand-to-metal charge transfer transitions at ca.

The hydroxide dissolves in strongly alkaline solution to give hydroxo complexes of the uranyl ion.

In uranyl nitrate, [UO2(NO3)2]·2H2O, for example, there are six donor atoms in the equatorial plane, four from bidentate nitrato ligands and two from water molecules.

[12] As discovered by Christian Friedrich Bucholz already in 1805,[13] uranyl nitrate, UO2(NO3)2, can be extracted from relatively concentrated aqueous solutions into diethyl ether.

Replacing the water molecules that are bound to the uranyl ion in aqueous solution by a second, hydrophobic, ligand increases the solubility of the neutral complex in the organic solvent.

[14] The complexes formed by the uranyl ion in aqueous solution are of major importance both in the extraction of uranium from its ores and in nuclear fuel reprocessing.

Later in the process, uranium is stripped from the organic solvent by treating it with strong nitric acid, which forms complexes such as [UO2(NO3)4]2− which are more soluble in the aqueous phase.

Uranyl salts are used to stain samples for electron and electromagnetic microscopy studies of DNA.

[15] Uranyl salts are toxic and can cause severe chronic kidney disease and acute tubular necrosis.

Uranyl ion accumulation in tissues including gonocytes[16] produces congenital disorders, and in white blood cells causes immune system damage.

Even if the uranium contained 235U which decays with a similar half-life of about 7.038×108 years, both of them would still be regarded as weak alpha emitters and their radioactivity is only hazardous with direct contact or ingestion.