Thorium oxyhalides

Thorium metal, 24 759-761 in alloys, 24 760-761 preparation of, 24 759-760 properties of, 24 760-761 reactions of, 24 761 Thorium nitrate, 24 757, 766 Thorium oxalates, 24 768-769 Thorium oxide, 21 491 Thorium oxides, 24 757, 761-762 Thorium oxyhalides, 24 762 Thorium perchlorate, 24 764 Thorium phosphates, 24 765-766 Thorium pnictides, 24 761 Thorium sulfate, 24 764 Thorium-uranium fuel cycle, 24 758-759 Thorocene, 24 772 Thorotrast, 24 775-776 3A zeolite. See Zeolite 3A Three-boiling beet sugar crystallization scheme, 23 463-465 Three-color photography, 19 233-234 3D models, advantages of, 19 520-521 3D physical design software, 19 519-521 3D QSAR models, 10 333. See also QSAR analysis... 

Table 6.11 Enthalpy and entropy changes in disproportionation of thorium oxyhalides 2ThOX2 II1O2 + TI1X4...

The selected value corresponds to an enthalpy of formation of -(48.6 + 2.9) kJ-moT from Th02(cr) and Thl4(cr), for one mole ThOl2(cr), the most negative value for the thorium oxyhalide compounds. 

Thorium forms one series of halides, another one of oxyhalides, and also a series of double or complex halides. In general, stability of these compounds toward heat decreases as die atomic weight of die halogen increases. These compounds are often isostructural with the corresponding compounds of other actinide elements in the (IV) oxidation state. 

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. 

In his early study covering a large number of halides and oxyhalides of thorium and their hydrates, Chauvenet [1911CHA] reported a value of -293.67 kJ moT for the enthalpy of solution of ThBr4(cr) in ca. 16000 H2O, probably at 288 K. Use, as discussed in Appendix A, of the values adopted by this review (Table VII-15) for the hydrolysis of the thorium ion and of that for the formation of the first thorium bromide complex (Section VIII.2.2) leads to a dissolution reaction that can be written as ... 

This early study is eoncemed with the preparation and the investigation of the properties of thorium metal and of a large number of eompounds oxide, hydroxide, various halides, oxyhalides, halogenocomplexes, their hydrates and adducts with ammonia. Elemental analyses were given for many of the compounds studied. Enthalpies of solution at 288 K of the metal in cQ. 3.6 hd OCl and of a number of compounds in cq. 16000 H2O were reported. Values were given without any detail. Although the concentration of thorium in the calorimetric solutions was not specified in every case, it was assumed by this review to be the same throughout. 

Bagnall, K. W., Brown, D., Easey, J. F., Preparation, crystallographic properties, and infrared spectra of quadrivalent oxyhalides of thorium, protactinium, uranium, and neptunium, J. Chem. Soc. A, (1968), 288-291. Cited on pages 235, 254. 

Corbett, J. D., Smith, J. D., Garcia, E., The selective removal of oxygen from rare earth and thorium metals through oxyhalide formation, J. Less-Common Met., 115, (1986), 343-355. Cited on page 238. 

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