Thorium, chelates

Many adduct compounds of thorium chelates were prepared and the composition and melting points of some of them117,213 are included in Table 24. Attempts were made213, ... 

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

Phosphorus Donors. Phosphine coordination complexes of thorium are rare because the hard Th(IV) cation favors harder ligand donor types. The only stable thorium—phosphine coordination complexes isolated as of the mid-1990s contain the chelating ligand,... 

Although not part of soil, lichens, by virtue of their solubilising action on rocks, contribute to the elemental enrichment of soil. Several studies have identified lichen acids as complexing agents for the iron and aluminium of rocks (95, 96). An examination of the various structures indicates that the basic structure responsible for the chelation is the carboxylic acid group with an orthophenolic group. Grodzinskii (97) has found lichens to be intense accumulators of elements in the uranium-radium, actinouranium and thorium orders. 

The removal of thorium from the body has been achieved by the use of chelating agents, primarily ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) (Fried and... 

The effects of tetracycline injection following injection of thorium-228 were not reported. Studies with a similar actinide element, plutonium, suggest that a thorium-tetracycline complex may be formed, which is excreted rapidly through the kidneys. Similarly, chelating agents such as EDTA... 

Tried JF, Schubert J. 1961. Effect of chelating agent administration on the removal of monomeric and polymeric thorium. Rad Res 15 227-235. 

Peter-Witt E, Wolf V. 1985. Comparison of diethylenetriaminepentaacetic acid calcium chelate and diethylenetriaminepentaacetic acid zinc chelate in removing thorium-234 from the rat. Health Phys 49 395-404. 

Premuzic ET, Francis AJ, Lin M, et al. 1985. Induced formation of chelating agents by Pseudomonas aeruginosa grown in presence of thorium and uranium. Arch Environ Contam Toxicol 14 759- 768. 

Young WN, Tebrock HA. 1958. The treatment of exposure to thorium and uranium with a chelating agent and supportive measures. Ind Med Surg (Annual Meeting) 27 229-232. 

The reactions of ligand exchange have frequently been applied to synthesize chelates with the coordination unit containing N,0-donor centers. The complexes of titanium [280], thorium, and uranium [281] tetrachlorides with fe(salicylidene)alkylene-amines, obtained in THF solution, are evidently formed through THF complexes of the type MX (THF). An example of such syntheses is the transformation (3.107) [280] ... 

Schiff base and related complexes of uranium and thorium are widely described in recent literature and covered in a review [463]. Those of U(VI) have a practical use as catalytic organic oxidants [460] or as part of a polystyrene-supported chelating resin [464,465]. Among other Schiff base precursors, salicylaldehyde [466] and triethylenetetramine [464], 3-formylsalicylic acid and o-hydroxybenzylamine [465], or salicylaldehyde and l-amino-2-naphthol-4-sulfonic acid [467] were used. In the example of Schiff base complexes, kinetics of formation of U(VI) complexes and their pK values were studied [468]. 

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. 

Fontaine, R., Santoni, B., Prommier, C., Guiochon, G. Preparation and gas chromatographic analysis of thorium and uranium chelates. Chromatographia 3, 532 (1970). 

Table 11. Equilibrium constant data for the extraction of thorium by chelating acid - neutral donor combinations...

Mixtures of HIPT and HTTA were shown201 to give synergism in the extraction of thorium. In addition to the mixed chelates, several HIPT adducts of the mixed chelates were suggested to be responsible for the synergism. 

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