Anhydrous Rare-Earth Chlorides

Rare earth chlorides, anhydrous, 28 Rare earth metals, 18 amalgams, concentration of, 17 Rhenium, metallic, 175 by reduction of ammonium per-rhenate, 177... 

In a similar manner, treatment of anhydrous rare-earth chlorides with 3 equivalents of lithium 1,3-di-ferf-butylacetamidinate (prepared in situ from di-ferf-butylcarbodiimide and methyllithium) in THF at room temperature afforded LnlMeCfNBuOils (Ln = Y, La, Ce, Nd, Eu, Er, Lu) in 57-72% isolated yields. X-ray crystal structures of these complexes demonstrated monomeric formulations with distorted octahedral geometry about the lanthanide(III) ions (Figure 20, Ln = La). The new complexes are thermally stable at >300°C, and sublime... 

Enthalpies of solution of anhydrous rare-earth chlorides in nonhy-droxylic solvents are also scant. What values exist are collected together in Table XII (178, 183, 218, 220-222), which includes alcohol and water values for ease of comparison. The values in this table are direct calorimetric measurements, performed on anhydrous trichlorides. The value for gadolinium trichloride in dimethylformamide is... 

The metallothermic reduction of the oxides by La produces the metals Sm, Eu, Tm, Yb, all having high vapour pressures. The reaction goes to completion due to the removal of the rare earths by volatilization from the reaction chamber (lanthanum has a low vapour pressure). The remaining rare earth metals (Sc, La, Ce, Pr, Nd, Y, Gd, Tb, Dy, Ho, Er, Lu) can be obtained by quantitative conversion of the oxides in fluorides, followed by reduction with Ca. The metallothermic reduction of the anhydrous rare earth chlorides could be also used to obtain La, Ce, Pr and Nd. The molten electrolysis can be applied to obtain only the first four lanthanide metals, La, Ce, Pr and Nd, because of the high reactivity of the materials that limits the operating temperatures to 1100°C or lower. 

In the electrolytic process, a fused mixture of anhydrous rare earth chlorides (obtained above) and sodium or potassium chloride is electrolyzed in an electrolytic cell at 800 to 900°C using graphite rods as the anode. The cell is constructed of iron, carbon or refractory hnings. Molten metal settles to the bottom and is removed periodically. 

Borohydride.—By reacting anhydrous rare earth chlorides with lithium borohydride (LiBIL) in THF, their chloroborohydrides (eq. 21) can be isolated [264—266]. In the case of europium no borohydride was... 

Manipulation. A concentrated solution of the anhydrous rare earth chloride J in ethyl alcohol (20 to 30 g. chloroform per 100 ml. absolute ethanol) is electrolyzed using a 110-volt direct current with the cell in series with a variable resistance. The current density should not exceed 0.05 to Fig. i.—Ceil for 0.1 amp. per square centimeter in order to eaXamargam8.rare Prevent dispersion of the mercury. The solution is electrolyzed for 15 to 40 hours. Under these conditions, a liquid to pasty amalgam is obtained containing 1 to 3 per cent of rare earth metal by weight. Results of typical runs are given in the accompanying table. 

THE AMMONIUM CHLORIDE ROUTE TO ANHYDROUS RARE EARTH CHLORIDES—THE EXAMPLE OF YCI3... 

The Ammonium Chloride Route to Anhydrous Rare Earth Chlorides 147... 

In a similar manner, treatment of anhydrous rare earth chlorides with three equivalents of lithium 1,3-di-ferf-butylacetamidinate (prepared in situ from di-fert-butylcarbodiimide, Bu -N=C=N-Bu , and methyllithium) afforded Ln[MeC (NBu )2]3 (Ln = Y, La, Ce, Nd, Eu, Er, Lu) in 57-72% isolated yields [6,7,26]. X-ray crystal structures of these complexes demonstrated monomeric formulations with distorted octahedral geometry around the lanthanide(III) ions (Eig. 3, Ln = La). The new complexes are thermally stable at >300°C, and sublime without decomposition between 180-220°C/0.05Torr. Other series of homoleptic lanthanide tris(amidinates) include the -cyclohexyl-substituted derivatives [RC(NCy)2]3Ln(THF)n (R = Me, Ln = Nd, Gd, Yb, n = 0 R = Ph, Ln = Nd, Y, Yb, n = 2). A sterically hindered homoleptic samarium(III) tris(amidinate), Sm[HC(NC6H3Pr 2-2,6)2]3, was obtained by oxidation of the corresponding Sm(II) precursor (cf.. Scheme 8) [6,7]. 

The above methods are suitable for the preparation of all the anhydrous rare earth chlorides, including that of jdtrium. For the preparation of SCCI3, see W. Fischer, R. Gewehr and H. Wingchen, Z. anorg. allg. Chem. 2, 170 (1939). 

The anhydrous rare earth chloride (1-2 g.) is heated in a stream of HBr for about seven hours. The temperature is slowly raised from 400 °C to slightly below the melting point of the bromide. 

The anhydrous rare earth chloride is heated for 4-6 hours until 600 °C is reached it is then held at this temperature for 30-40 hours in a stream of HI-H3 containing as much HI as possible. The iodides are cooled and stored under N3. 

The anhydrous rare earth chloride, in tetrahydrofuran solution, is treated (stirring) with the stoichiometric quantity of cyclo-pentadienylsodlum. The solvent is then removed by distillation and the product is sublimed at 200-250°C in vacuum (10 mm.). 

The preparation of amalgams of lanthanum, neodymium, and cerium by electrolysis of the anhydrous chlorides in alcoholic solution has already been described. The electrolysis of a rare earth chloride in water solution proves unsatisfactory because of the production of a precipitate of hydrous oxide at the cathode and the liberation of chlorine at the anode. 

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