Uranium IV Compounds

In normal laboratory work, these are the most important uranium halides, especially UCI4. 

U3O8 -b C3CI6 3 UCI4 -b Cl2C=CClCOCl etc. (reflux) 

Description Air-stable green solid Deliquescent green solid Deliquescent brown solid Deliquescent black solid 

Bp (°C) Solubility Coordination geometry Square antiprism 789 H2O and most org.solvents Dodecahedron 761 H2O and most org.solvents Pentagonal bipyramid H2O and most org.solvents Octahedron 

The layer structure of PuBrs [after A.F. Wells, Structural Inorganic Chemistry, Clarendon Press, Oxford (3rd edn, 1962) and reproduced by permission of the Oxford University Press]. Note that 9-coordination is prevented by non-bonding Br... Br interaction. The notation y = 0 and y = indicates the relative height of atoms with respect to the plane of the paper. The planes of the layers are normal to the plane of the paper. 

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Uranium(VI) salts chemisorbed on zeolites have also been observed (12) to undergo photoreduction to uranium(IV) compounds. Mechanisms for photoreduction of CuO, for example, have been widely reported in the chemical research literature (13-17). 

Table 7 Some Amine Complexes of Thorium(IV) and Uranium(IV) Compounds...

All the known tetraalkoxides are very easily hydrolyzed by water vapour and the uranium(IV) compounds oxidize rapidly in air, so their preparation must be carried out under nitrogen. Molecular weight determinations (M = Th, U) indicate a considerable degree of polymerization, approximately tetrameric in the case of Th(OR)4 with R = Pr or MeEtCH, but the molecular complexity decreases to about 3.4 for R = Bu, and with R = CEt3 and CMeEtPr the alkoxides are monomers in boiling benzene.653 The plutonium compound Pu(OCMeEt2)4 is volatile at 150 °C/0.05 torr, suggesting a low molecular complexity. 

Th(PhCOCHCOPh)4 has been reported as being isomorphous with the corresponding protactinium(IV), uraniumflV) and cerium(IV) complexes the coordination geometry in the last is a triangular faced dodecahedron, but a more recent publication73 reports the coordination geometry of the uranium(IV) compound as square antiprismatic. 

In the structures of compounds of the type M3UF7 the seven F atoms are statistically distributed over fluorite lattice sites.153 The nine-coordinate thorium atom in (NH ThFg is surrounded by a distorted tricapped trigonal prismatic array of fluorine atoms, with the prisms sharing edges to form chains, whereas the uranium(IV) compound contains discrete dodeca-hedrally coordinated [UF8]4 ions. The protactinium(IV), neptunium(IV) and plutonium(IV) analogues are isostructural with the uranium compound.154... 

Since four of the same aryloxide ligands can bind to uranium in the uranium(iv) compound, a three coordinate U[0(2,6-Bu2C6H3)]3 is presumably coordinatively unsaturated, and so forms a uranium-ring bond coordinative saturation can also be achieved by forming an adduct with a Lewis base. 

The fiuorosulfate dihydrate, PaF2S04 2H2O, analogous to the known uranium(IV) compound (1S2), is precipitated on the addition of aqueous hydrofluoric acid to solutions of protactinium(IV) in dilute sulfuric acid (131). Others (71, 84) have reported the formation of a white, insoluble precipitate in hydrofluoric acid, believed to be a tetrafluoride hydrate, but the product has not been completely characterized. 

II). Manganese (II) once formed makes manganese carbonate (Kashefi and Lovley, 2000). The resulting compounds produce ores and the ores formed are deposited around the hydrothermal vents. From the vents, uranium (VI) compounds come forth which are water soluble, and are reduced by P. islandicum to uranium (IV) compounds which are in turn insoluble and are deposited around the vents to make uranium ores (e.g., uraninite). Furthermore, the bacterium is able to reduce gold... 

CgHg)Cp U(THF) reacts with cyclooctatetraene to form the cot-bridged uranium(IV) compound [(CgHg)Cp U]2(/u.-CgHg) in quantitative yield. The same compound can be prepared from the reaction of 2 mol of Cp gU and 3 mol of cyclooctatetraene (equation 42). " ... 

Figure 1. The molecular structure of the uranium(IV) compound U4(A 3-0)2(02CNEt2)i2 (ethyl groups not shown).

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