Thorium tetraiodide

Compounds of divalent samarium, europium, and ytterbium are well-known. In recent years, lower halides of other lanthanides, such as neodymium 48), praseodymium 45, 49, 90), and thulium 4) have been obtained by reducing the trihalide with the metal. The corresponding reaction of thorium tetraiodide with thorium metal has led to the identification of two crystalline forms of Thl2 41, 91) it is unlikely that the Th ", or even Th ", ion is present in Thl2, but like Prl2, which is formulated as Pr " (r)2( ) (2), the compound is probably of the type Th " (r)2(2 ) 41). Certainly one crystal form is diamagnetic 41), suggesting the latter formulation. 

Thorium Iodide, Thorium tetraiodide. I4Th mol wt 739.69. I 68.63%, Th 31,37%. Thl4. Prepd hy passing iodine vapors in an inert gas over the metal at elevated temp Allen, Yost, J. Chem. Phys. 22, 855 (1954). See also Cuthbert, Thorium Production Technology (Addison-Wesley, Reading, Mass., 1958). 

Thl4 THORIUM TETRAIODIDE 1651 T1203 DITITANIUM TRIOXIDE 1694... 

Thl4[g] THORIUM TETRAIODIDE (GAS) 1652 Ti305 TRITITANIUM PENTOXIDE 1695... 

SIN/PRA2] Singh, Z., Prasad, R., Venugopal, V., and Sood, D. D., Vapour pressure of thorium tetraiodide, Bhabha Atomic Research Centre, Report B.A.R.C.-1005, (1979). Cited on pages 263, 264, 566, 570. 

Uranium and thorium tetraiodides both form complexes with DMA, of composition Ul (DMA) and ThI (IMA)g, both of which are close to 2 1 electrolytes in nitromethane, but in very dilute solution (< lO" M) the molar conductivity of both tends towards the value for a 4 1 electrolyte, presumably because of entry of the solvent into the coordination sphere and displacement of the iodide ion. The uranium compound can also be obtained in poor yield ftom the chloride complex and sodium iodide in methyl cyanide at 50° in an inert atmosphere, but the reproducibility of the preparation under these conditions is poor. 

Flesch RM, Knacke O, Mtinstermann E (1986) Sublimation and dissociation of thorium tetraiodide and thorium oxide diiodide ftxnn Knudsen cells. Z Anorg Allg Chem 585 123-134... 

The iodide complexes are somewhat less stable, and well-characterized examples exist only for thorium, protactinium, and uranium. The thorium and uranium derivatives can be coveniently prepared by the reaction of iodine and metal, while protactinium tetraiodide is generated by reduction of Pals. The molecular structure of Thl4 has been examined the metal lies within a distorted square antiprism of iodide ions. 

The tetrahalides are the thorium halides of greatest practical importance. The tetrafluoride ThF4 is the preferred starting material for large-scale production of thorium metal (Sec. 10.4). ThF4 has been proposed as fertile material in the fuel mixture of the molten-salt reactor. The tetraiodide has been used as feed material in the iodide process for making very pure thorium metal (Sec. 10.4). 

Fuger, J., Brown, D., Thermodynamics of the actinide elements Part IV. Heats and free energies of formation of the tetrachlorides, tetrab-romides, and tetraiodides of thorium, uranium and neptunium, J. Chem. Soc., Dalton Trans., (1973), 428-434. Cited on pages 96, 231, 232, 250, 260, 266, 415, 423, 523, 543. 

Tetraphenylarsonium salts of the hexaiodocomplexes (7) of thorium (IV) and uranium (IV), [Ph Asl MI, have also been obtained by crystallisation of the tetraiodide/methyl cyanide complexes with tetraphenylarsonium iodide in methyl cyanide solution in the absence of free iodine which, when present, precipitates as Ph4AsI. ... 

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