Niobium complexes synthesis

Niobium, tris(diethyldilhiocarbamato)oxy-stereochemistry, 1,82 structure, 1, 83 Niobium, tris(oxa ato)oxy-stereochcmistry, 1, 82 Niobium, tris(phcnylcncdirhio)-structure, 1, 63 Niobium alanate, 3, 685 Niobium complexes alkyl alkoxy reactions, 2, 358 amides, 2,164 properties, 2, 168 synthesis, 2, 165 applications, 6,1014 carbamicacid, 2, 450 clusters, 3, 672,673,675 hexamethylbenzene ligands, 3, 669 cyanides synthesis, 2, 9 p-dinitrogen, 3, 418 fluoro... 

Using an electron-gun source, tungsten atoms were reacted with benzene, toluene, or mesitylene at 77 K, to form the expected (arene)2W complex (42) in a yield of 30%, compared with the —2% yield from the previously published, bis(benzene)W synthesis (32). These arene complexes are reversibly protonated, to give the appropriate [(T7-arene)2WH] species. By using the same technique, the analogous, niobium complexes were isolated (43). 

The corresponding chemistry of analogous niobium complexes was inhibited by the requirement of a more complicated synthetic approach for the isolation of the niobaziridine hydride. The use of the isopropyl substitued —N(Pr )Ar amido ligand proved unsuitable for the stabilization of [Nb(H) N(P )Ar 2(ri -Me2CNAr)] because of insertion into the Nb—H bond. °2 These difficulties were overcome with use of the N(CH2Bu )Ar substituent and a synthetic approach based upon [Nb(O) N(CH2Bu )Ar 3]3 which enabled the isolation of [Nb(H) N(CH2Bu )Ar 2( ri -CH(Bu )=NAr)] via reduction. The synthesis of this species has opened routes to some unusual chemistry as shown in Scheme 6.5. ... 

Bis(arene)hafnium complexes, characteristics, 4, 697 Bis(arene)iron dications, characteristics, 6, 173 Bis(arene)niobium complexes, characteristics, 5, 95 Bis(arene)titanium(0) complexes, characteristics, 4, 243-244 Bis(arene)tricarbonylchromium complex, synthesis, 5, 258... 

Hydroamination is an atom-economical process for the synthesis of industrially and pharmaceutically valuable amines. The hydroamination reaction has been studied intensively, including asymmetric reactions, and a variety of catalytic systems based on early and late transition metals as well as main-group metals have been developed." However, Group 5 metal-catalysed hydroaminations of alkenes had not been reported until Hultzsch s work in 2011. Hultzsch discovered that 3,3 -silylated binaphtho-late niobium complex 69 was an efficient catalyst for the enantioselective hydroaminoalkylation of iV-methyl amine derivatives 70 with simple alkenes 71, giving enantioselectivities up to 80% (Scheme 9.30). Enantiomerically pure (l )-binaphtholate niobium amido complex 69 was readily prepared at room temperature in 5 min via rapid amine elimination reactions between Nb(NMe2)5 and l,l-binaphthyl-2-ol possessing bullqr 3,3 -silyl substituents. Since the complex prepared in situ showed reactivity and selectivity identical... 

Yin EX, Takanabe K, Kubota J, Domen K (2010) Polymerized complex synthesis of niobium-and zirconium-based electrocatalysts for PEFC cathodes. J Electrochem Soc 157(2) B240-B244... 

Galajov M, Garcia C, Gomez M, Gomez-Sal P. Alkyl chlorido hydridotris(3,5-dimethylpyrazolyl)borate imido niobium and tantalum(V) complexes synthesis, conformational states of alkyl groups in soHd and solution. X-ray diffraction and multinuclear magnetic resonance spectroscopy studies. Dalton Trans. 2014 43 5747-5758. 

Fryzuk MD, Kozak CM, Bowdridge MR et al (2001) Macrocyclic complexes of niobium(III) synthesis, structure, and magnetic behavior of mononuclear and dinuclear species that incorporate the [P2N2] system. Organometallics 20 3752-3761... 

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... 

For a long period of time, molten salts containing niobium and tantalum were widely used for the production by electrolysis of metals and alloys. This situation initiated intensive investigations into the electrochemical processes that take place in molten fluorides containing dissolved tantalum and niobium in the form of complex fluoride compounds. Well-developed sodium reduction processes currently used are also based on molten salt media. In addition, molten salts are a suitable reagent media for the synthesis of various compounds, in the form of both single crystals and powdered material. The mechanisms of the chemical interactions and the compositions of the compounds depend on the structure of the melt. 

This monograph compiles the latest research on the chemistry of complex fluorides and oxyfluorides of tantalum and niobium, and covers synthesis and fluorination processes, crystal structure peculiarities and crystal chemical classification, as well as the behavior of complex ions in fluorine solutions and melts. 

Scheme 26 Synthesis of rhenium and niobium polysulfido complexes from the corresponding doubly bonded complexes...

Many carbonyl and carbonyl metallate complexes of the second and third row, in low oxidation states, are basic in nature and, for this reason, adequate intermediates for the formation of metal— metal bonds of a donor-acceptor nature. Furthermore, the structural similarity and isolobal relationship between the proton and group 11 cations has lead to the synthesis of a high number of cluster complexes with silver—metal bonds.1534"1535 Thus, silver(I) binds to ruthenium,15 1556 osmium,1557-1560 rhodium,1561,1562 iron,1563-1572 cobalt,1573 chromium, molybdenum, or tungsten,1574-1576 rhe-nium, niobium or tantalum, or nickel. Some examples are shown in Figure 17. 

Recently, we succeeded in the synthesis and structural characterization of first niobium-containing metallasilsesquioxane complex. In analogy to the corresponding reactions with titanium tetraalkoxides, niobium pentaethoxide cleanly reacts with 3 in a 1 1 molar ratio to give high yields of dimeric [Cy7Si70i2Nb0Et( U-OEt)]2 (149) as a colorless, crystalline solid (Scheme 49). 

Dithioalkoxo- and dithiophenoxo-niobium(V) trichlorides [MCl3(SR)2] were obtained from NbCl5 and thiols and benzenethiol respectively.240 The synthesis of tris(benzenedithiolato) complexes was accomplished by reaction of the appropriate metal amide with a mixture of the dithiol and its sodium salt in THF. The structures of (AsPh4)[M(S2C6H4)3]241""243 showed the... 

Niobium and titanium incorporation in a molecular sieve can be achieved either by hydrothermal synthesis (direct synthesis) or by post-synthesis modification (secondary synthesis). The grafting method has shown promise for developing active oxidation catalyst in a simple and convenient way. Recently, the grafting of metallocene complexes onto mesoporous silica has been reported as alternate route to the synthesis of an active epoxidation catalyst [21]. Further the control of active sites, the specific removal of organic material (template or surfactant) occluded within mesoporous molecular sieves during synthesis can also be important and useful to develop an active epoxidation catalyst. Thermal method is quite often used to eliminate organic species from porous materials. However, several techniques such as supercritical fluid extraction (SFE) and plasma [22], ozone treatment [23], ion exchange [24-26] are also reported. 

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