Thorium ion

S. Ahrland and co-workers, eds., Gmelin Handbook of Inorganic Chemistg, Thorium, Suppl Hoi D1, Properties of Thorium Ions in Solutions, 8th ed., Springer-Vedag, Berlin, 1988. 

It has also been argued10,40 that the second mechanism (rapid, reversible interconversion of II and IV) cannot be general. The basis for this contention is the fact that electrophilic catalysis is rare in nucleophilic aromatic substitution of non-heterocyclic substrates, an exception being the 2000-fold acceleration by thorium ion of the rate of reaction of 2,4-dinitrofluorobenzene with thiocyanate... 

Solutions of this reagent are destabilised by the presence of thorium ions. If a working temperature of 10-15°C is much exceeded, the risk of decomposition, not slowed by cooling and accelerating to explosion, exists. Titanium and zirconium salts also cause slight destabilisation, but decomposition temperatures are then 35 and 40°C, respectively. 

In aqueous solution, thorium exists as Th(IV), and no definitive data have been presented for the presence of lower-valent thorium ions in this medium. The standard potential for the Th(IV)/Th(0) couple has not been determined from experimental electrochemical data. The values presented thus far for the standard reduction potential have been calculated from thermodynamic data or estimated from spectroscopic measurements. The standard potential for the four-electron reduction of Th(IV) ions has been estimated as —1.9 V in two separate references 12. The reduction of Th(OH)4 to Th metal was estimated at —2.48 V in the same two publications. Nugent et al. calculated the standard potential for the oxidation ofTh(III) to Th(IV) as +3.7 V versus SHE, while Miles provides a value of +2.4 V [13]. The standard potential measurements from studies in molten-salt media have been the subject of some controversy. The interested reader is encouraged to look at the summary from Martinot [10] and the original references for additional information [14]. 

Milkey, R. G. Stability of Dilute Solutions of Uranium, Lead and Thorium Ions. Anal. Chem. 26, 1800 (1954). 

Yoshizuka, K., Shinohara, T., Shigematsu, H., Kuroki, S., Inoue, K. 2006. Solvent extraction and molecular modeling of uranyl and thorium ions with organophosphorus extractants. Solvent Extr. Res. Dev. Jpn. 13 115-122. 

Later work by Lin et al. overcame this problem by bubbling SC-C02 through a vessel containing TBP upstream of the extraction vessel43 Using this approach, super-saturation of the fluid phase by the extractant was avoided and a supercritical phase containing ca. 11% (on a molar basis)44 of TBP was consistently obtained (at 60°C and 120 atm pressure). This TBP-saturated C02 was then employed to extract uranyl and thorium ions from nitric acid solutions of various concentrations. The extraction of both ions increased with rising aqueous acidity, consistent with the extraction reactions observed in conventional systems (e.g., TBP-dodecane), such as that shown here for uranium ... 

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. 

In the hexavalent state these elements are similar to uranium in the quadrivalent state however they have, like uranium and protactinium in this valency state, externally the inert gas configuration of the thorium ion in the trivalent state that of the trivalent actinium ion. The name 5f series may perhaps be the best in place of actinides, thorides or uranides. 

S20g2-, 348, 349 third-body, effect on CO+O, 121 thorium ions, and H2O2 + I-, 407 —, catalysis of H202 + S203 , 362 time-of-flight mass spectrometer, and CI2+O, 19... 

The small steric size and propensity of cyanide groups to bridge metal centers have limited their use as ligands in molecular coordination chemistry of the actinides, where they are prone to form amorphous polymeric products. Limited metathesis studies have been conducted. Reaction of tetravalent halides with alkali metal cyanides in liquid ammonia is reported to give rise to a product of the formula UX3(CN)-4NH3, whereas use of the larger thorium ion yields unidentified products. 

Ureas. Urea adducts (and those of the closely related A-alkylated derivatives) may be prepared from nonaqueous solvents alternatively, preparation in aqueous alcoholic solution leads to the formation of hydrates. In contrast to the carbamides discussed above, there is relatively little variability in the coordination number of reported urea adducts of tetravalent actinides. Most complexes are either six- or seven-coordinate higher coordination numbers are observed for the larger thorium ion (Table 15). 

Thoron I (formula 4.9) reacts with thorium ions in acid medium to yield a red, water-soluble complex, which forms the basis for the spectrophotometric determination [48,49]. Thoron I in acid solution is orange. 

The thorium ion, Th4+, is more resistant to hydrolysis than other 4+ ions but undergoes extensive hydrolysis in aqueous solution at pH higher than 3 the species formed are complex and dependent on the conditions of pH, nature of anions, concentration, etc. In perchlorate solutions the main ions appear to be Th(OH)3 +, Th(OH)2+, Th2(OH) +, Th4(OH) +, while the final product is the hexamer Th6(OH)95 of course, all these species carry additional water.19 Hexameric ions exist also for Nbv and for Ce1 v and Ulv [M604(0H)J12 + ions are found in crystals of the sulfates. The metal atoms are linked by hydroxo or oxo bridges. In crystals of the hydroxide, Th(OH)4, or the compound Th(0H)2Cr04 HzO, chain-like structures have been identified, the repeating unit being Th(OH)2+ in solution, the polymers may have similar form (28-1) or may additionally be cross-linked. 

The enthalpy of solution of ThCl4(cr) in ca. 16000 H2O was given at 288 K as -Till kJmol by Chauvenet [1911CHA]. As discussed in Appendix A, use of the constants for the hydrolysis of the thorium ion selected in this review (Table VIl-15) and of that for the formation of the first thorium chloride complex (Section Vlll.2.2) leads to a dissolution reaction that can be written as ... 

As discussed in Appendix A, use of the adopted constants for the hydrolysis of the thorium ion (Table VII-15) indicates that, in the resulting solution, the largest part of the thorium is found as polymeric hydroxide species, with appearance of a very small amount of precipitate of Th(OH)4(am). Under these circumstances, these results will not be considered further. 

Sergeev, G. M., Almazova, V. D., Reaction of thorium(IV) with organic acids in aqueous solutions. I. Hydrolysis of thorium ions, Tr. Khim. Khim. TekhnoL, 1, (1970), 31-35. Cited on pages 135, 527. 

Usherenko, L. N., Skorik, N. A., Hydrolysis of rare earth metal, yttrium, scandium, and thorium ions in water and in aqueous-ethanol mixtures, Russ. J. Inorg. Chem., 17, (1972), 1533-1535. Cited on pages 135, 137, 140, 156, 157, 158, 534, 537, 538. 

OKA/MOC] Okamoto, Y., Mochizuki, Y., Tsushima, S., Theoretical study of hydrolysis reactions of tetravalent thorium ion, Chem. Phys. Lett., 373, (2003), 213-217. Cited on pages 100, 679. 

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