Lutetium hydration

In aqueous media lutetium occurs as tripositive Lu3+ ion. All its compounds are in +3 valence state. Aqueous solutions of all its salts are colorless, while in dry form they are white crystalline solids. The soluble salts such as chloride, bromide, iodide, nitrate, sulfate and acetate form hydrates upon crystallization. The oxide, hydroxide, fluoride, carbonate, phosphate, and oxalate of the metal are insoluble in water. The metal dissolves in acids forming the corresponding salts upon evaporation of the solution and crystallization. 

After filling the tank with water, 2 g of the trichloride of lutetium hexa-hydrate LuC13.6H20, mass 389.42 g/mol-1, is added. 

Structure Non-hydrated rare earth fluorides have two different crystal systems, a hexagonal system (lanthanum to terbium) and an orthorhombic system (dysprosium to lutetium, yttrium). In the crystal of LaFs, the central ion is nine coordinated by nine fluoride atoms. Each fluoride atom further connects with two lanthanum atoms through a [13-bridge to form an infinite polymer. 

Hydrates of rare earth chlorides also have two different crystal systems a triclinic system for lanthanum, cerium, and praseodymium, as well as a monoclinic system for neodymium to lutetium and yttrium. CeCl3-7H20, as an example of the former system, is different from the above infinite polymer as two cerium atoms are connected by two [i2-bridges to form a dimer. The formula for this dimer is [(H20)7Ce([i2-Cl)2Ce(H20)7]Cl4 as shown in Figure 1.18. Therefore, the coordination number of cerium is nine and the polyhedron takes on a destroyed mono-capped square antiprism configuration. 

The solubility of rare earth carbonates is fairly low and ranges from 10 to 10 mol L . Rare earth carbonates can be obtained by the addition of ammonium carbonate to a solution of a rare earth water-soluble salt. In this case, the precipitates will all be hydrates. Lanthanum to neodymium carbonates contain eight water molecules while neodymium to lutetium carbonates contain two water molecules only. Rare earth carbonates can be dissolved in alkali metal carbonate solutions and form a double salt of alkali metals. 

When rare earth oxides, hydroxides, or carbonates react with dilute sulfuric acid, rare earth sulfate hydrates are obtained and they have the formula RE2(S04)3 H20 where = 3,4,5, 6,8, and 9. The most common is = 9 for lanthanum and cerium and = 8 for praseodymium to lutetium and yttrium. Anhydrous compounds may be obtained by heating the respective rare earth sulfate hydrate at 155-260 °C, however, they easily absorb water to become hydrated again. 

A determination of the stability constants of aquo-complexes of Eu " in acetone showed that as the concentration of water in the solution of europium nitrate in acetone was increased, the first co-ordination sphere of europium(iii) became occupied by three water molecules which replaced three acetone molecules, and only then did the replacement of NO3 anions by water occur. An n.m.r. study of the hydration of lutetium(iii) nitrate in aqueous acetone showed the co-ordination number of lutetium to tend to six with increasing water concentration. The coexistence of several aquo(methyl sulphoxide)lutetium(iii) complexes were identified in the study of the complex formation between lutetium and dimethyl sulphoxide in acetone. 

Ion-exchange has been indispensable in the characterization of the transamericium elements and is also important for some of the preceding elements, particularly for tracer quantities of material. We have seen in the case of the lanthanides (Chapter 27) that the +3 ions can be eluted from a cation-exchange column by various complexing agents, such as buffered citrate, lactate or 2-hydroxybutyrate solutions, and that the elution order follows the order of the hydrated ionic radii so that the lutetium is eluted first and lanthanum last. 

Cs2N4 75OPtC4 XH20, Platinate, tetracyano, cesium azide (1 2 0.25), hydrate, 21 149 Cs3C1 Lu, Cesium lutetium chloride, 22 6 CSjCI,Lu2, Cesium lutetium chloride, 22 6 Cs3Cl9Sc2, Cesium scandium chloride, 22 25... 

The 5-nitro-2-anthranilates of lanthanum(III), samarium(III), terbium(III), erbium(III) and lutetium(III) were obtained as hydrates having 2.5 mol of water molecules per 1 mol of compound [167]. The compounds are isostructural. The processes of dehydration and rehydration were investigated. The first step of dehydration does not cause a change of crystal structure. The entire dehydration gives anhydrous compounds wifii different structures to the structures of hydrates. The dehydration of the La, Sm, Tb and Br compounds was reversible and rehydration gives complexes having the same crystal structures as the initial compounds. 

In contrast, the anhydrous trichlorides, tribromides and triiodides and the reduced halides are extremely air sensitive materials and are rapidly hydrated or hydrolyzed in air. The triiodides are especially moisture sensitive and deliquesce. Unlike the trifluorides, the other trihalides are very soluble in water at 25°C. Solubilities of the trichlorides vary from 3.89 moles/ for lanthanum, to a minimum of 3.57 moles/ at terbium and back up to 4.10moles/ at lutetium with pH values of the saturated solutions in the range 1.0-2.0 (Spedding et al., 1974a). At high temperatures, the trichlorides, tribromides and triiodides also... 

Dehydration of the dehydrated trihalides is a final method for oxide conversion. The hydrated trichlorides, tribromides and triiodides, RXj- H20, are obtained by dissolution of the oxides in aqueous hydrohalic acid and condensation by warming and desiccation (Ashcroft and Mortimer, 1968 Brown et al., 1968). The hydrated trifluorides are prepared by dissolution of the oxide in HNO3 or HCl and precipitation with aqueous HF. The filtered trifluoride may be dehydrated by heating slowly to 600°C in an inert gas stream or in vacuum (Strizhkov et al., 1972). Products obtained by heating in air are contaminated with oxide fluoride (Batsanova, 1971). Thermal decomposition studies of the hydrated trichlorides, cf. section 5.1, have shown that the oxide chlorides are readily formed, but careful dehydration under N2 flow has apparently been successful for the chlorides (Ashcroft and Mortimer, 1968). Tribromides have also been prepared by careful vacuum dehydration, but the lutetium products were contaminated with oxide bromide (Brown et al., 1968). In general simple dehydration becomes increasingly difficult with increasing atomic number of both the lanthanide and the halide. 

The NTA complexes of praseodymium and dysprosium serve as examples of the former problem. These two compounds which have the formulae PrNTA-3H20 and DyNTA-4H 0 contain nine-coordinate praseodymium with one water of hydration (Martin and Jacobson, 1972a) and eight-coordinate dysprosium with two water molecules of hydration (Martin and Jacobson, 1972b). It is clear that neither of these is predicted by the stoichiometry of the complexes. The second problem is illustrated by the complexes R(N03)3-mDMSO ( = 3 or 4). The complex Nd(N03)3 4DMSO (Aslanov et al., 1972b) has all the nitrate ions coordinated in a bidentate fashion which results in overall ten-coordination. The complex Lu(N03)3-3DMSO (Aslanov et al., 1973) also has all three nitrate ions coordinated and the lutetium is nine-coordinate. 

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