Vanadium complexes applications

Bis( )6-arene)vanadium complexes applications, 5, 47 physical properties, 5, 47 reactivity, 5, 46 synthesis, 5, 45... 

Bis(cyclopentadienyl)vanadium(II) complexes applications, 5, 39 coordination compounds, 5, 37 vanadocenes, 5, 36... 

Vanadium complexes, 157, 158 Vapor phase chromatography, see Gas-liquid chromatography Vaso-depressor, 149 Vasodilator, 150 Veterinary applications, 138 Vinylchloride, 438... 

V NMR spectroscopy is a particularly useful method for solution studies of vanadium(V) complexes. Several correlations of the shielding in vanadium(V) complexes have been reported and have been used as empirical guides to the coordination number of the vanadium.57-64 Application of these correlations should, however, be used cautiously. 170 NMR spectroscopy65 and extended X-ray absorption fine structure (EXAFS) spectroscopy have been used for the characterization of solution complexes.66 Methods including potentiometry, X-ray diffraction, and UV-visible and IR spectroscopic techniques are also widely used in the characterization of the properties of vanadium complexes. Other methods for the characterization of low-level (sub-microgram) vanadium complexes have been described 67,68... 

Scheme 9.3 Application of chiral vanadium complex 1 in the total synthesis of Manassantin A, reported by Hanessian. ...

The route shown in Fig. 9.12 is one which has been operated commercially in the U.K. on a fairly small scale, quite successfully. As in the case of niobium, it is convenient to use the crude ferro alloy as feed to the chlorination stage. The chloride purification stages lead to pure vanadium trichloride, which is reduced with magnesium in a manner similar to that employed for titanium, zirconium or hafnium. Some of the complexities, applicable in the latter processes owing to the volatile nature of the chlorides, are absent with vanadium. The vanadium metal sponge has some properties in common with the other metal sponges. 

Transition metals complexes of tartaric acid have been the subject of research in all the main areas of practical applications of chirality biochanistry and medicinal chan-istry [1], asymmetric catalysis [2-4], and chiral separations [5-9]. It is not surprising that the rapid development of the chemistry of vanadium in recent decades smoothly covered all of these areas by itself. The main attention has been devoted to the insulin-mimetic activity of vanadium complexes of tartaric acid [10,11]. Chirality of some insu-linomimetic dinuclear vanadyl(IV)-tartrate complexes has been considered as well, resulting in an interesting finding that both the complexes of naturally occurring L-tartaric acid and racemic tartaric acid are highly active [12]. 

At present, the density functional theory (DFT) prevails in calculations of the structural and spectral parameters of transition metal complexes [18]. For this reason, and thanks to our previous positive experience with simulation and interpretation of the UV-Vis, IR, electronic and vibrational circular dichroism (BCD and VCD) spectra of chiral vanadium complexes [19], we decided to use the DFT methods as the main tool in the present work as weU. We shall present the calculated molecular stractures, vibrational and electronic spectra, as well as the V chemical shifts of the chosen anions of the vanadium(V) tartrato complexes. Where applicable, results are confronted with the available experimental data, with the aim to assess the reliability of the individual methods for future calculations of a similar kind. 

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... 

Vanadium, as V0S04, has been found to interfere with siderophore-mediated iron transport in bacteria and plants. This seems to imply that vanadium can be transported by siderophores, and a number of studies focussing on applications of hydroxamate V-complexes in biology have been initiated. 

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. 

The constitution of many of the heteropoly-acids and of their salts may thus be explained, although direct proof of the correctness of some of these formulae is lacking. Some of the heteropoly-compounds of vanadium are, however, very complex, and cannot be represented by application of the foregoing scheme. To take an extreme instance, Rogers1 prepared a black, crystalline compound to which he ascribed the following formula —... 

One of the most important applications of vanadium alkoxides is connected with their catalytical action on the reactions of oxidation of hydrocarbons and, in particular, alkanes, cycloalkanes, and so on. [645, 172], Except for VO(OR)3 it was proposed that the complexes already containing the peroxide groups in their composition — such as VO(OBu )2(OOBu ) [1516], VO(OR)(OOH)2, V02(00R) [172], and VIY(OPri)3(OOBu ) [25] — be used. 

One of the most significant results from the advent of these surface science studies on oxides relevant for the present catalytic applications is the fact that oxides can be multiply terminated and that they are not terminated [154, 180, 186-190] in cuts through the bulk structure. This is not unexpected in general [98,156,179] but it is of great value to know this in attempts to understand the mechanisms that activate oxides for catalysis. These rigorous studies must be differentiated from more empirical studies carried out on termination issue with qualitative methods and without predictive power but with the still invaluable advantage that they can be applied [97,191-193] to complex MMO catalyst systems. Such studies can be used to probe the surface reactivity, to address the issue of segregation of, for example, vanadium out of an MMO system and to compare different qualities of the nominally same material with speculative assumptions about the influence of defects. 

Arasabenzene, with chromium, 5, 339 Arcyriacyanin A, via Heck couplings, 11, 320 Arduengo-type carbenes with titanium(IV), 4, 366 with vanadium, 5, 10 (Arene(chromium carbonyls analytical applications, 5, 261 benzyl cation stabilization, 5, 245 biomedical applications, 5, 260 chiral, as asymmetric catalysis ligands, 5, 241 chromatographic separation, 5, 239 cine and tele nucleophilic substitutions, 5, 236 kinetic and mechanistic studies, 5, 257 liquid crystalline behaviour, 5, 262 lithiations and electrophile reactions, 5, 236 as main polymer chain unit, 5, 251 mass spectroscopic studies, 5, 256 miscellaneous compounds, 5, 258 NMR studies, 5, 255 palladium coupling, 5, 239 polymer-bound complexes, 5, 250 spectroscopic studies, 5, 256 X-ray data analysis, 5, 257... 

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