Preparation of rare earth metals

LaDuca and Wolczanski (1992) developed a low-temperature method for the preparation of rare-earth metal nitrides involving the ammonolysis of molten molecular... 

E. Morrice, J. E. Murphy and M. M. Wong, Preparation of Rare Earth and Yttrium Metals by... 

The synthesis of chalcogenides such as those of the rare earth elements has traditionally been performed through the reaction of rare earth metals or oxides with a molten or vaporous chalcogen source in a high-temperature environment. Soft synthetic methods utilizing lower temperature conditions, such as hydrothermal or flux syntheses, can allow access also to thermodynamically metastable phases. Flux syntheses of R chalcogenides via an alkali poly-chalcogenide flux have been shown to be extremely versatile for the preparation of many new structures, some of which cannot be obtained by direct synthesis from the elements. 

Gschneidner Jr., K.A. (1980) Preparation and purification of rare earth metals and effect of impurities on their properties. In Science and Technology of Rare Earth Materials, eds. Subbarao, E.C. and Wallace, W.E. (Academic Press, New York), p. 25. 

The rare-earth metals are of rapidly growing importance, and their availability at quite inexpensive prices facilitates their use in chemistry and other applications. Much recent progress has been achieved in the coordination chemistry of rare-earth metals, in the use of lanthanide-based reagents or catalysts, and in the preparation and study of new materials. Some of the important properties of rare-earth metals are summarized in Table 18.1.1. In this table, tm is the atomic radius in the metallic state and rM3+ is the radius of the lanthanide(III) ion in an eight-coordinate environment. 

For preparation of alloys nickel by cleanliness of 99.99 %, magnesium by cleanliness of 99.95 %, lanthanum by cleanliness of 99.79 %, and mishmetall (industrial mixture of rare-earth metals (REM) Ce - 50, La - 27, Nd - 16, Pr - 5, others REM - 2wt. %) were used. The melting of metal charge was carried out in the vacuum-induction furnace under fluxing agent from eutectic melt LiCl-KCl. The composition of alloys was supervised by the chemical analysis and the X-ray testing. 

Suspensions of HTSC for the electrophoretic deposition of bismuth [403-409] and thallium [403] HTSC, various cuprates of rare-earth metals and barium [204, 407,410-414], and also silver HTSC [415,416] and PbO-HTSC [417] compositions have been used. These are prepared in acetone, acetonitrile, toluene, butanol, methylethylketone, or mixed solvents. They contain chemically pure materials (silver is introduced as AgaO) dispersed thoroughly, first mechanically and then in liquid) by ultrasonic treatment (in which case the particles became charged). The choice of solvent is by and large determined by its effect on the stability of the deposited oxide [417]. 

Catalytic activity of rare earth elements (i.e., lanthanides, symbol Ln) in homogeneous catalysis was mentioned as early as 1922 when CeCls was tested as a true catalyst for the preparation of diethylacetal from ethanol and acetaldehyde [1]. Solutions of inorganic Ln salts were subsequently reported to catalyze the hydrolysis of carbon and phosphorous acid esters [2], the decarboxylation of acids [3], and the formation of 4-substituted 2,6-dimethylpyrimidines from acetonitrile and secondary amines [4]. In the meantime, the efficiency of rare earth metals in heterogeneous catalysis, e. g., as promoters in lanthanide (element mixtures)-... 

Use Anhydrous trichloride of rare-earth metal is often used to prepare the metal. 

In 2003, O Shaughnessy and Scott reported the first example of rare-earth metal complexes supported by biaryl diamide ligands as the catalysts for the hydroamination reactions [159]. A series of C2 symmetric secondary diamine proligands L37-L40 were prepared by arylations of (7 )-2,2 -diamino-6,6 -dimethybiphenyl under palladium catalysis. L37 reacted with complexes [Ln N(SiHMe2)2 3(THF)2] to form the biaryl diamide complexes [Ln(L37) N(SiHMe2)2 (THF)2] (Ln = Y (190), La (191), Sm (192)). Deprotonation... 

Wu and coworkers prepared a new diamide ligand LSI with a CH2SiMc2 bridging unit and a series of rare-earth metal complexes supported by LSI. Diamide complexes [Ln(LSl) N(SiMe3)2 (THF)] (Ln = Y (222), Nd (223), Sm (224), Dy (22S), Yb (226)) were obtained from the reaction of H2LSI with 1 equiv of corresponding rare-earth metal amide complexes [Ln N(SiMc3)2 3( J.-Cl)Li(THF)3] in toluene (Scheme 82) [167]. 

The chemistry of organometallic group 4 metal compounds is well developed, thanks to their importance in polyolefin synthesis. Hence, their application in catalytic asymmetric hydroamination reactions is highly desirable. Group 4 metal complexes are commonly less sensitive and easier to prepare than rare earth metal complexes. Most important of all, many potential precatalysts or catalyst precursors are com mercially available. 

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