Uranyl Complex

The uranium(v) species UO2+ exists, but is less stable than possibly owing to 

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Figure 3. Distribution of uranyl complexes as a function of pH at 25°C in presence of typical ligands in surface and ground waters (PCO2 = 10 atm, E F = 0.3 ppm, E Cl = 10 ppm, E SO4 = 100 ppm, E PO4 = 0.1 ppm, E Si02 = 30 ppm). Below pH 4-5 uranyl (U02 ) ion and uranyl fluoride complexes predominate, at intermediaiy pHs (4.5 < pH < 7.5) U02(HP04)2 is the predominant species, whereas at higher pH uranyl is complexed with carbonates. [Used with permission of Elsevier Science, from Langmuir (1978) Geochim Cosmochim Acta, Vol. 42, Fig. 11, p. 558].

Djogic R, Branica M (1991) Dissolved uranyl complexed species in artificial seawater. Marine Chem 36 121-135... 

The previously proposed uptake models were mathematical assumptions and had no physical or chemical basis. Millard and Hedges, on the other hand, considered the chemistry of bone-uranium interactions. With the D-A model, they proposed that U was diffusing into bone as uranyl complexes, and adsorbing to the large surface area presented by the bone mineral hydroxyapatite (Millard and Hedges 1996). Laboratory experiments showed a partition coefficient between uranyl and hydroxyapatite under oxic conditions of 10" -10, demonstrating U uptake in the U state without the need for reduction by protein decay products as proposed by Rae and Ivanovich (1986). 

The uranyl complex with malic acid does not show changing rotation with changing rotation. 

L. R. Morss, K. L. Nash, D. D. Ensor. Thermodynamics of Lanthanide and Uranyl Complexes with Tetrahydrofuran-2,3,4,5-tetracarboxylicAcid (THFTCA). J. Chem. Soc., Dalton Trans. 2000, 285-291. 

Vidali, M. et al J. Inorg. Nucl. Chem., 1975, 37, 1715-1719 A series of uranyl complexes of macrocyclic azomethines were used as ligands for transition metal ions, with perchlorate anions. Raman spectra of the uranyl-metal complexes could not be recorded because the samples exploded during attempted measurements. 

A complex of 1102 with L-P-(3,4-dihydroxyphenyl)alanine (dopa), [UO2-(dopa)] , has been reported,and a series of acylhydrazone adducts (L) [U02L2(N03)2] (L = acetyl, benzoyl, salicoyl, diacetyl, or diformylhydra-zone) and [U02L3(N03)2] (L = acetylhydrazone) have been described. The X-ray photoelectron spectral information obtained from uranyl complexes of 8-hydroxyquinoline is given in Table 3. The U 4/, 2 levels in the two... 

Table 3 X-Ray photoelectron spectral data obtained from 8-hydroxyquinoline and its uranyl complexes...

Among the known structures, the hexagonal bipyramidal (Has) geometry seems to be less common than others and it has only been definitely established for a few uranyl complexes (94—97). Probably an axial colHnear grouping, as in 0—U—0, is necessary for obtaining a geometry for the complexes. None of the octa-coordinated lanthanide complexes has a Hea geometry. 

Compared to studies in acidic media, studies on the electrochemical behavior of 1102 " in basic media are more limited. The report from Morris [52] describing voltammetry results for hydroxo and carbonato uranyl complexes is a recent example. Previous studies have been performed mostly in carbonate and bicarbonate solutions. Wester and Sullivan have studied the reduction of 1102 in these solutions to find an electrochemically irreversible process but disproportionation of U(V)02" " was evidenced only in the bicarbonate solutions [67]. 

Andersen prepared the first U amide traHj-[UO2 N(SiMe3)2 2(thf)2] (60) in 1979, from UO2CI2 and 2Na[N(SiMe3)2] in f. The structure of the ciystalline material was confirmed by X-ray data, albeit of poor quality recently a high-quality structure was obtained. The amido groups in 60 were readily displaced by treatment with ArOH and pyridine, yielding [UO2(OAr)2(py)3] (Ar = C6H3P 2-2,6). Reaction of 60 with the macrocyclic compound H4(10) (R = H or Me) resulted in the exclusive formation of the mono-uranyl complex [UO2 H2(10) (thf)] (61). " The latter upon addition of... 

ESR spectra, 511 Uranium(VI) complexes dioxoneocupferron, 512 Uranium hexaalkoxides physical properties, 347 Uranyl complexes cupferron, 512 formamide, 491 glycolic acid, 472 hexafluoroacetylacetone, 373, 377 photochemistry, 385 rearrangement, 384 maleic acid conformation, 467 neutral 1,3-diketones, 402 poly ketones, 399 Urea... 

Z = 16 hydrogen bonded co-crystal between the neutral uranyl complex [U02(H20)3] and [15] crown-5. The asymmetric unit contains a total of 32 independent molecules.76 Up-to-date information and a database of high Z structures is maintained online at http //www.dur.ac.uk/zprime. 

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