Niobium complexes oxidized

Tantalum and niobium are added, in the form of carbides, to cemented carbide compositions used in the production of cutting tools. Pure oxides are widely used in the optical industiy as additives and deposits, and in organic synthesis processes as catalysts and promoters [12, 13]. Binary and more complex oxide compounds based on tantalum and niobium form a huge family of ferroelectric materials that have high Curie temperatures, high dielectric permittivity, and piezoelectric, pyroelectric and non-linear optical properties [14-17]. Compounds of this class are used in the production of energy transformers, quantum electronics, piezoelectrics, acoustics, and so on. Two of... 

The processing of tantalum and niobium begins with the fluorination of the raw material, which always consists of complex oxide compounds containing tantalum and niobium. The main types of tantalum- and niobium-containing minerals are discussed in Chapter 1, and typical compositions of such minerals are presented in Table 2. 

The process of separating the intermediate products from the purified solutions, in the form of solid complex fluoride salts or hydroxides, is also related to the behavior of tantalum and niobium complexes in solutions of different compositions. The precipitation of complex fluoride compounds must be performed under conditions that prevent hydrolysis, whereas the precipitation of hydroxides is intended to be performed along with hydrolysis in order to reduce contamination of the oxide material by fluorine. 

In both cases, the fluorination of the complex oxides of tantalum and niobium leads to the formation of the water-soluble compounds (NH4)2TaF7 and (NH4)3NbOF6, the insoluble lithium fluoride and die gaseous components H20, NH3 and HF. 

Since the fluorination enables to separate components of complex oxide compounds containing tantalum and niobium, it seems that it is applicable for... 

Oxidation-Reduction Titrations. The extent of reduction resulting from reaction of niobium (V) chloride and bromide with pyridine was determined by indirect titration of crude reaction mixtures with standard ammonium tetrasulfato-cerate(IV) solution. Samples were stirred overnight in a stoppered flask with an excess of iron (III) ammonium sulfate. Any iron (II) formed by reaction with the niobium complex mixture was then titrated with the standard tetrasulfato-cerate(IV) solution using ferroin as indicator. Results of these determinations are given in Table III. 

Acetyl ligands, in niobium complexes, C-H BDEs, 1, 298 Achiral phosphines, on polymer-supported peptides, 12, 698 Acid halides, indium compound reactions, 9, 683 Acidity, one-electron oxidized metal hydrides, 1, 294 Acid leaching, in organometallic stability studies, 12, 612 Acid-platinum rf-monoalkynes, interactions, 8, 641 Acrylate, polymerization with aluminum catalysts, 3, 280 Acrylic monomers, lanthanide-catalyzed polymerization,... 

A number of complex niobium(V) oxide fluoride derivatives, such as... 

Properties A complex oxide of sodium, calcium, and niobium. Tantalum, rare-earth metals, and other elements may be present. Color brown to black, light brown streak. Hardness 5-5.5, d 4.2-6.4. 

A more recent example involving a-elimination is shown in equation 10.12. Here, Ag(I) is used to induce alkylidene formation by first oxidizing Ti to a (f1 state, which is followed by a-elimination and then RE of alkane. Similar chemistry occurs with vanadium and niobium complexes.31... 

The radionuclide zirconium-95 ( Zr) can be found among direct products of nuclear fission. Its radioactive decay leads to the daughter niobium-95 ( Nb). In the determination of Zr and Nb in samples of seawater and sea plants, the samples are mixed with oxalic acid in order that zirconium and niobium complexes can be formed in the presence of nitric acid. The oxalic acid is destroyed with potassium chlorate, and zirconium and niobium are precipitated as zirconium phosphate and niobic acid, respectively. Activities of rare-earth elements are removed, and zirconium is separated as barium hexafluorozirconate and ashed to zirconium pentox-ide. The niobium fraction is ashed to niobium pent-oxide. Both radionuclides are finally determined by y-ray spectrometry. 

Class 4 structures with octahedral anionic groups - complex oxides containing octahedrally coordinated titanium, niobium, tantalum. 

Samarskite-(Y) is a complex oxide of rare earths, uranium, calcium, niobium, tantalum and other elements it always occurs in the metamict state. This characteristic has been an obstruction to the study of the chemistry and crystal structure of this mineral. Although many chemical formulae and crystallographic data for samar-skite-(Y) have been proposed, no complete chemical or structural understanding of samarskite-(Y) has been achieved. 

Lundberg, M. and Sundberg, M. (1993). New Complex Structures in the Cesium-Niobium-Tungsten-Oxide System Revealed by Hrem, Ultmmicroscopy, 52, pp. 429-435. 

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