Aqueous thorium fluoride complexes

1 Formation constants of thorium fluoride complexes, ThF  

VIII Thorium Group 17 (halogens) compounds and complexes 

The experimental equilibrium constants from the various studies and their source are listed in Table VIII-6. The calculated equilibrium constants at zero ionic strength based on these literature data are discussed below and are summarised in Table VIII-7. Table VIII-6 demonstrates that the agreement of the experimental values is excellent in the cases where the experimental conditions are the same, indicating both a high accuracy and the absence of systematic errors. The uncertainty in the calculated equilibrium constants at zero ionic strength is much larger than the experimental values but this is a result of the uncertainties in the interaction coefficients. 

The equilibrium constants logn, p° (Vtll.l) refer to the reaction  

By combining these values with the logj /i° (VIII.2) = (3.18 + 0.02) (Table IV-2) for the protonation of fluoride  

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It has to be emphasised that these equilibrium constants must not be combined with 8(ThAN03) = (0.31 +0.12) kg-mol used in the Sections VII.3 and VIII. 1.2 on aqueous thorium hydroxide and fluoride complexes this value refers to a strict ion interaction approach where the effect of nitrate complexation is included in the interaction coefficient. The equilibrium constants for the formation of nitrate complexes must be combined with s(ThA NOj) = e(ThA CIO ,) = (0.70 + 0.10) kg-mol, ... 

MoU H, Denecke M, Jalilehvand F, Sandstrdm M and Grenthe 11999 Structure of the aqua ions and fluoride complexes of uranium (iv) and thorium (iv) in aqueous solution an exafs study. Inorganic chemistry 38(8), 1795-1799. 

The donor action of [NOs]" as an anionic ligand towards thorium(iv) and uranium(iv) in the presence of trimethylphosphine and tris(dimethylamino)phosphine oxide in aqueous media has been found to be very similar. The larger nitrate ion was observed to form more stable species with thorium than the chloride ion whereas in the uranium(iv) case both complexes formed equally readily. A study of the sulphate complexes of uranium(iv), neptunium(vi) and plutonium(vi) in HCIO4-H2SO4 solution showed the stability constants to follow the order U[Pg.453]

Thorium(IV) halides are made by direct combination of the elements. White ThF4, ThC and ThBr4, and yellow Thl4 crystallize with lattices in which Th(IV) is 8-coordinate. Reaction of Thl4 with Th yields Thl2 and Thl3 (both polymorphic) which are metallic conductors and are formulated as Th (F)2(e )2 and Th" (I )3(e ) respectively. Thorium(IV) fluoride is insoluble in water and aqueous alkali metal fluoride solutions, but a large number of double or complex fluorides can be made by direct combination of their constituents. Their structures are complicated. 

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