Tantalum complexes applications

Talspeak, 959 Talspeak process. 960 Tantalum complexes applications, 1014 Tartaric acid metal complexes geochemistry, 867 Tcchnatcs... 

Since niobates and tantalates belong to the octahedral ferroelectric family, fluorine-oxygen substitution has a particular importance in managing ferroelectric properties. Thus, the variation in the Curie temperature of such compounds with the fluorine-oxygen substitution rate depends strongly on the crystalline network, the ferroelectric type and the mutual orientation of the spontaneous polarization vector, metal displacement direction and covalent bond orientation [47]. Hence, complex tantalum and niobium fluoride compounds seem to have potential also as new materials for modem electronic and optical applications. 

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

Although the elements tantalum and niobium were discovered more than 200 years ago in the form of oxides, the true beginning of the chemistry of tantalum and niobium was the discovery and investigation of complex fluorotantalates and fluoroniobates of alkali metals. Application of complex fluoride compounds enabled the separation of tantalum and niobium and in fact initiated the development of the industrial production of the metals and their compounds. 

Applications of heteroligand complexes in the analytical chemistry of niobium and tantalum. S. V. Elinson, Russ. Chem. Rev. (Engl. Transl.), 1975,44, 707-717 (131). 

The chapters for niobium and tantalum in COMC (1982) and COMC (1995) provide an in-depth discussion concerning complexes of these metals as well as their applications to catalysis.172 173 Alkylcyclopentadienyl complexes of niobium and tantalum have also been reviewed.1 Similarly to vanadium (Section 10.09.4.1.2), the... 

Inter- and intramolecular (cyclometallation) reactions of this type have been ob-.served, for instance, with titanium [408,505,683-685], hafnium [411], tantalum [426,686,687], tungsten [418,542], and ruthenium complexes [688], Not only carbene complexes but also imido complexes L M=NR of, e.g., zirconium [689,690], vanadium [691], tantalum [692], or tungsten [693] undergo C-H insertion with unactivated alkanes and arenes. Some illustrative examples are sketched in Figure 3.37. No applications in organic synthesis have yet been found for these mechanistically interesting processes. 

Compounds of the early transition metals have been found to function in this way. Titanium, zirconium, tantalum and tungsten are among the most prominent metals in these complexes. The complexes of titanium form the basis for most of the reagents currently reported in synthesis applications. 

Among the pentavalent elements, the most important are niobium and tantalum. Niobium is an excellent material for surface treatment of steel materials for chemical industry due to its high hardness and corrosion-resistance in wet acidic conditions. Nowadays, niobium is also used for the preparation of superconductor tapes and it is used in other branches of industry, for instance in nuclear technology and metallurgy. Tantalum is also of similar importance. For these applications, it is necessary to prepare high purity metal. Molten salt electrolysis, as an alternative process to classical thermal reduction, provides niobium and tantalum with required quality. In order to optimize these processes, it is necessary to know details of both complex formation and redox chemistry of the species present in the melts. 

Doye s group [81] showed that a dinuclear titanium-sulfonamidate complex (Scheme 21), with a tetrahedral sulfur in the ligand backbone, can be used for intermo-lecular hydroaminoalkylation as well. This system gives mixtures of branched and linear products, although to date there has been no mechanistic rationale provided for the reduced regioselectivity of group 4 metal complexes in this transformation. There has been one report by Zi s group [44] that describes axially chiral bis(sulfonamidate) tantalum and niobium complexes for application as precatalysts for hydroamination and hydroaminoalkylation. Unfortunately, these complexes did not show any reactivity for either of these reactions. 

Niobium pentoxide, Nb20s, acts as a smoke retarder for poly(vinyl chloride) but is less effective than V2O5. Tantalum pentoxide is even more limited and is unlikely to find application. Phosphinate complexes of tantalum have been used as fillers for special purpose high temperature laminates. They are polymeric species of the stoichiometry [Ta(0PPh20)2(0H)3] . ... 

Rock, S.E., Crain, D.J., Pettit, C.M., et al., 2012. Surface-complex films of guanidine on tantalum nitride electrochemicaUy characterized for applications in chemical mechanical planarization. Thin Solid Films 520, 2892—2900. 

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