Uranyl chelate complexes

Uranyl chelate complexes. L. Cattalini, U. Croatto. S. Degetto and E. Tondello, Inorg. Chim. Acta, Rev., 1971,5,19-43 (268). 

At pH 6.5-S.5 the enol form of dibenzoylmethane (formula 54.1), a reagent of the P-diketone group, forms a yellow uranyl chelate complex which has been used for determination of uranium [76,77]. It dissolves in aqueous ethanol medium containing pyridine, or may be extracted with ethyl acetate, butyl acetate, or CHCI3 [78]. 

Spectrophotometric methods may often be applied directly to the solvent extract utilising the absorption of the extracted species in the ultraviolet or visible region. A typical example is the extraction and determination of nickel as dimethylglyoximate in chloroform by measuring the absorption of the complex at 366 nm. Direct measurement of absorbance may also be made with appropriate ion association complexes, e.g. the ferroin anionic detergent system, but improved results can sometimes be obtained by developing a chelate complex after extraction. An example is the extraction of uranyl nitrate from nitric acid into tributyl phosphate and the subsequent addition of dibenzoylmethane to the solvent to form a soluble coloured chelate. 

Consistent with the original supposition that sapphyrins should be good ligands for large cations, Woodward predicted that sapphyrins might form particularly stable chelate complexes with uranyl cation (U02 ), a species that is known to favor pentagonal planar coordination environments. " Unfortunately,... 

Treatment of U02C12(THF)3 in THF with 1 equiv. of Na[CH(Ph2P=NSiMe3)2] led to formation of an unusual red uranyl chloro-bridged dimer (70% yield) containing a uranium(vi)-carbon bond as part of a tridentate bis(imino-phosphorano)methanide chelate complex (Scheme 9). This was the first example of a uranyl-methine carbon bond. The methine carbon is displaced significantly from the uranyl equatorial plane.33... 

TRLIF has a range of potential applications to other ScF investigations. The methods discussed in the chapter are not limited to uranyl chelates in ScF CO2 and are applicable to other ScFs and other compounds such as polyaromatic hydrocarbons, lanthanide complexes, and luminescent chemical probes. Future investigations with TRLIF in ScFs could involve work on analytical and industrial extraction processes, determination of physical parameters such as solubility, or fundamental studies of solvent-solute interactions in ScF systems. 

Coordination compounds of diphosphazane dioxides with uranyl or thorium ions were synthesized [475], The crystal structure of [U02(N03)2L1] [L, = Ph2P(0) N(Ph)P(0)Ph2] reveal the bidentate chelating mode of binding of the diphosphazane dioxide to these metals. The chemistry of other uranium organophosphorus and related compounds is described [476-479]. Some of the actinide complexes are presented in Table 5.16. 

Polyfunctional phosphinopyridine VV,P-dioxides, (phosphinomethyl)pyridine A,P-dioxides and bis(phosphinomethyl)pyridine VV,P,P-trioxides have been prepared, and selected coordination chemistry with actinide ions has been explored. The phosphinopyridine A,P-dioxides form bidentate chelates with uranyl and Th , and in the solid state these complexes display six-membered chelate rings that appear to be relatively sterically congested." " The solvent extraction properties of these ligands are not unique since they resemble the performance of trialkylphosphine oxides." ... 

A dinuclear mixed ligand uranyl complex with dioxime, carbonate, and oxalate ligands (C2N2Hio)2[(U02)2(C03)(C204)2(C3H4N202)] H20 has been reported and characterized by X-ray diffraction. The uranyl ions in the dimer are six-coordinate, characterized by the presence of one three membered, one four membered, and one five membered chelate ring in the equtorial plane. 

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