Neodymium carbonates

The anhydrous oxide absorbs moisture from the air at ambient temperatures forming hydrated oxide. The oxide also absorbs carbon dioxide from air, forming neodymium carbonate. 

It is clear that in the case of barium titanate, the dielectric constant is not steady in the temperature range (—55 to +125°C). Addition of neodymium carbonate in a NPO ... 

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. 

Mercury(I) bromide Mercury(I) carbonate Mercury(I) chloride Mercury(I) fluoride Mercury(I) iodide Mercury(I) oxalate Mercury(I) sulfate Mercury(I) thiocyanate Mercury(II) bromide Mercury(II) iodide Neodymium carbonate Nickel(II) carbonate Nickel(II) hydroxide Nickel(II) iodate Nickel(II) phosphate Palladium(II) thiocyanate Potassium hexachloroplatinate Potassium perchlorate Potassium periodate Praseodymium hydroxide... 

Cocondensation of La, Ce, Nd, or Er metal atoms with cyclooctatetraene at — 196°C yielded dinuclear complexes of the formula [CgHgR(THF)2][R(CgHg)2] after extraction with tetrahydrofuran (De Kock et al., 1978). The structure of the neodymium complex (fig. 23, table 15) shows two cyclooctatetraene rings in the anion, which are neither equidistant from the neodymium atom, nor p allel. The neodymium atom in the cation is asymmetrically located with respect to the central cyclooctatetraene ring with neodymium-carbon distances between 2.68 and 4.63 A (Ely et al., 1976 De Kock et al., 1978). 

The infrared absorption spectra of different rare earth carbonates have been recorded by several authors. The spectra can be used to identify the various structure types although the assignment of the bonds is not unambiguous in all cases. As a summary of the results, values observed for some neodymium carbonates are presented in table 8. 

Infrared absorption frequencies (cm ) and their assignments for neodymium carbonates (Caro et al., 1972 Dexpert et al., 1982) ... 

A Study of the Decomposition of Neodymium Hydroxy Carbonate and Neodymium Carbonate Hydrate, H. Hinode, R. Sharma and L. Eyring, J. Solid State Chem., 84,102-117(1990). 

Sihca is reduced to siUcon at 1300—1400°C by hydrogen, carbon, and a variety of metallic elements. Gaseous siUcon monoxide is also formed. At pressures of >40 MPa (400 atm), in the presence of aluminum and aluminum haUdes, siUca can be converted to silane in high yields by reaction with hydrogen (15). SiUcon itself is not hydrogenated under these conditions. The formation of siUcon by reduction of siUca with carbon is important in the technical preparation of the element and its alloys and in the preparation of siUcon carbide in the electric furnace. Reduction with lithium and sodium occurs at 200—250°C, with the formation of metal oxide and siUcate. At 800—900°C, siUca is reduced by calcium, magnesium, and aluminum. Other metals reported to reduce siUca to the element include manganese, iron, niobium, uranium, lanthanum, cerium, and neodymium (16). 

Hydrogen transfer reactions are highly selective and usually no side products are formed. However, a major problem is that such reactions are in redox equilibrium and high TOFs can often only be reached when the equilibria involved are shifted towards the product side. As stated above, this can be achieved by adding an excess of the hydrogen donor. (For a comparison, see Table 20.2, entry 8 and Table 20.7, entry 3, in which a 10-fold increase in TOF, from 6 to 60, can be observed for the reaction catalyzed by neodymium isopropoxide upon changing the amount of hydrogen donor from an equimolar amount to a solvent. Removal of the oxidation product by distillation also increases the reaction rate. When formic acid (49) is employed, the reduction is a truly irreversible reaction [82]. This acid is mainly used for the reduction of C-C double bonds. As the proton and the hydride are removed from the acid, carbon dioxide is formed, which leaves the reaction mixture. Typically, the reaction is performed in an azeotropic mixture of formic acid and triethylamine in the molar ratio 5 2 [83],... 

The oxide also may be formed by thermal dissociation of neodymium oxalate, hydroxide or carbonate ... 

The oxide is reduced to neodymium metal when heated with hydrogen, carbon monoxide, or other reducing agents. 

Fig. 16 Neodymium glutarate, a coordination polymer containing chains of edge-sharing NdOj polyhedra.52 Gray spheres denote carbon, red oxygen, and white hydrogen, with NdOs polyhedra in blue. Reproduced with permission. Copyright 1998, Royal Society of Chemistry.

Simultaneously to the disclosure of 112-117 by Liddle, Le Floch reported that complex 88 could be converted to complex 121, which is analogous to 112-117, by reaction with potassium bis(trimethylsilyl)amide.48 The second deprotonation of one of the methanide ligands to give a methandiide-methanide complex is noteable because amides, especially silyl-amides, are not usually basic enough to effect a second deprotonation at a carbon centre (cf. synthesis of 1-8) and it was suggested that coordination to the electropositive neodymium polarised the C-H bond sufficiently to activate it. 

Butadiene has been converted into poly-l,4-(cis-butadiene) in greater than 98.3% by Ziegler-Natta catalysis comprising neodymium versatate, diethyl aluminum chloride, diisobutylaluminum hydride, and triisobutyMuminum. The polymer was then converted into a polybutadiene-polyurethane copolymer by reacting with a diisocyanate and diol. This copolymer exhibited low cold flow and high affinity for silica or carbon black, excellent elasticity, and abrasion resistance. 

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