Oxygen donor complexes actinide

Hydroxamates, cupferron, and related ligands. As anionic oxygen donor ligands, hydroxamates have a strong affinity for the oxophilic tetravalent actinides, with solution complex formation constants generally greatest for Pu and decreasing as follows Pu > Np > > U. ... 

The actinides have a high degree of specificity for neutral and anionic oxygen-containing organic molecules. The actinide complexes with O -donor ligands that are most widely studied include alkoxides, aryloxides amide, carboxylates, and oxalates. Complexes with alcohols, ethers, esters, ketones, aldehydes, ketoenolates, and carbamates have also been reported. 

Actinide halides and oxyhalides are known to form numerous complexes with oxygen and nitrogen donor ligands and the preparation and properties of such compounds have recently been reviewed (12, 13). Relatively few protactinium halide complexes are known, but this situation reflects the lack of research rather than a tendency not to form complexes. However, there is sufficient information available for certain ligands to permit a comparison with the behavior of other actinide halides, and to illustrate the similarities and differences observed with the tetrahalides of thorium to plutonium inclusive and, to a lesser extent, with the protactinium and uranium pentahalides. 

Even fewer complexes with nitrogen donor ligands have been reported and all are methyl cyanide adducts (Tables X and XI). Protactinium pentabromide forms a soluble 1 3 complex in contrast to the 1 1 complexes formed by niobium and tantalum pentahalides (46). Other actinide pentahalide-methyl cyanide complexes are still unknown. Protactinium tetrachloride, tetrabromide, and tetraiodide react with anhydrous, oxygen-free methyl cyanide to form slightly soluble 1 4 complexes (44, 48) which are isostructural with their actinide tetrahalide analogs. 

The fact that dithiophosphinic acids show the greatest selectivity for An over Ln " as compared to phosphinic and monothiophosphic acids is due to an increased covalency in the An—S bonds but not necessarily a shorter An—S bond. In addition, trivalent actinides show a thermodynamic preference to form bonds with soft donor atoms. The structural differences observed in the complexes of An with the three ligands studied are due to differences in the hard and soft nature of the oxygen and sulfur atoms, respectively, and their hydrogen-bonding ability."" ... 

Cm(iii) is a class A or hard metal ion and thus complexes far more strongly to oxygen and fluoride donors than to more polarizable donors such as chloride or sulfur. Solution reactions of Cm resemble those of the trivalent lanthanides and actinides. The fluoride, oxalate, phosphate, iodate, and hydroxide are essentially water-insoluble and the chloride, iodide, perchlorate, nitrate, and sulfate are water-soluble. The first hydrolysis constant for Cm ", i.e. for the reaction ... 

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