Vanadium anions

Allylvanadium complexes (see Allyl Complexes) are synthesized by allylation with Grignard reagents as shown in Scheme 25. Another synthetic route lies in the allylation of a vanadium anionic species with allylic chloride. Codimerization of vanadium-coordinated diphenylacetylene (tolane) and 1,3-butadiene affords the allyl complex (49) (Scheme 26). ... 

Research carried out in recent years suggests that some metals and their compounds represent a novel class of compounds that interfere with oestrogenic activity (EDCs). So far, cadmium, copper, cobalt, nickel, lead, mercury, tin, chromium, and vanadium anions and arsenates have been identified as metalloestrogens, capable of binding to estrogen receptors. These metals are a part of a group of... 

Figure B 1.11.5 is an example of how relative integrals can detennine structure even if the peak positions are not adequately understood. The decavanadate anion has the structure shown, where oxygens lie at each vertex and vanadiums at the centre of each octaliedron. An aqueous solution of decavanadate was mixed with about 8 mol% of molybdate, and the tiiree peaks from the remaining decavanadate were then computer-subtracted...

Iseda M, Nishio T, Han S Y, Yoshida H, Terasaki A and Kondow T 1997 Electronic structure of vanadium cluster anions as studied by photoeieotron spectroscopy J. Chem. Phys. 106 2182... 

The chemistry of vanadium compounds is related to the oxidation state of the vanadium. Thus, V20 is acidic and weaMy basic, VO2 is basic and weaMy acidic, and V2O2 and VO are basic. Vanadium in an aqueous solution of vanadate salt occurs as the anion, eg, (VO ) or (V O ) , but in strongly acid solution, the cation (V02) prevails. Vanadium(IV) forms both oxyanions ((V O ) and oxycations (VCompounds of vanadium(III) and (II) in solution contain the hydrated ions [V(H20)g] and [V(H20)g], respectively. 

For solvent extraction of pentavalent vanadium as a decavanadate anion, the leach solution is acidified to ca pH 3 by addition of sulfuric acid. Vanadium is extracted in about four countercurrent mixer—settler stages by a 3—5 wt % solution of a tertiary alkyl amine in kerosene. The organic solvent is stripped by a soda-ash or ammonium hydroxide solution, and addition of ammoniacal salts to the rich vanadium strip Hquor yields ammonium metavanadate. A small part of the metavanadate is marketed in that form and some is decomposed at a carefully controlled low temperature to make air-dried or fine granular pentoxide, but most is converted to fused pentoxide by thermal decomposition at ca 450°C, melting at 900°C, then chilling and flaking. 

For example, in Ni(CO) nickel metal having 28 electrons coordinates four CO molecules to achieve a total of 36 electrons, the configuration of the inert gas krypton. Nearly every metal forming a carbonyl obeys the 18-electron rule. An exception is vanadium, forming a hexacarbonyl in which the number of electrons is 35. This carbonyl, which has a paramagnetism equivalent to one unpaired electron, however, readily adds one electron to form a closed valence shell complex containing the V(CO)(, anion. 

The reaction of bis(benzene)vanadium [12129-72-5] with TCNE affords an insoluble amorphous black soHd that exhibits field-dependent magnetization and hysteresis at room temperature, an organic-based magnet (12). The anion radical is quite stable in the soHd state. It is paramagnetic, and its intense electron paramagnetic resonance (epr) spectmm has nine principal lines with the intensity ratios expected for four equivalent N nuclei (13) and may be used as an internal reference in epr work (see Magnetic spin resonance). 

Eosin Flavonoids Morin Flavonol, fisetin, robinetin Quercetin Rutin condensation products of urea, formaldehyde and methanol [126], pesticide derivatives [127] sweetening agents [128, 129] anion-active and nonionogenic surface-active agents [130] steroids, pesticides [29,132, 133] pesticides [134—137] vanadium in various oxidation states [138] uracil derivatives [139]... 

A thin layer deposited between the electrode and the charge transport material can be used to modify the injection process. Some of these arc (relatively poor) conductors and should be viewed as electrode materials in their own right, for example the polymers polyaniline (PAni) [81-83] and polyethylenedioxythiophene (PEDT or PEDOT) [83, 841 heavily doped with anions to be intrinsically conducting. They have work functions of approximately 5.0 cV [75] and therefore are used as anode materials, typically on top of 1TO, which is present to provide lateral conductivity. Thin layers of transition metal oxide on ITO have also been shown [74J to have better injection properties than ITO itself. Again these materials (oxides of ruthenium, molybdenum or vanadium) have high work functions, but because of their low conductivity cannot be used alone as the electrode. 

The cobalt complex is usually formed in a hot acetate-acetic acid medium. After the formation of the cobalt colour, hydrochloric acid or nitric acid is added to decompose the complexes of most of the other heavy metals present. Iron, copper, cerium(IV), chromium(III and VI), nickel, vanadyl vanadium, and copper interfere when present in appreciable quantities. Excess of the reagent minimises the interference of iron(II) iron(III) can be removed by diethyl ether extraction from a hydrochloric acid solution. Most of the interferences can be eliminated by treatment with potassium bromate, followed by the addition of an alkali fluoride. Cobalt may also be isolated by dithizone extraction from a basic medium after copper has been removed (if necessary) from acidic solution. An alumina column may also be used to adsorb the cobalt nitroso-R-chelate anion in the presence of perchloric acid, the other elements are eluted with warm 1M nitric acid, and finally the cobalt complex with 1M sulphuric acid, and the absorbance measured at 500 nm. 

Fig. 27. In vanadium borate 106 the macrocyclic borate ring (left) is sandwiched by two smaller (VO)60i2 rings (right) of triangular form via six axial B-( 3-0)-V bonds to form a cage-like cluster anion...

Vanadium borophosphates 107-109 that contain cluster anions with different ring sizes can be synthesized by hydrothermal reactions of vanadium(III) oxide, boric acid and an appropriate phosphate salt [145,146]. The ring size of the cluster anion with the composition [(VO)2BP20iol 4-6 is determined by the size of the cation that is, however, included only in the interior of the cages with n = 5 and 6 (Fig. 28). 

Fig 28. Vanadium borophosphates with the composition [(VO)2BP20io] n form cage-like cluster anions, which may be empty (107, n = 4) or centered by a cation (109, n = 6). For clarity only half of the vanadium and phosphorus atoms of the cluster anions are shown... 

Birnboim, H.C. (1988). A superoxide anion induced DNA strand-break metabolic pathway in human leukocytes effect of vanadium. Biochem. Cell. Biol. 66, 374-381. 

C° total concentration of pyrosulfate and sulfate anions Cv concentration of biatomic vanadium complexes C3l concentration of S03 in the melt phase Cp specific heat (kcal/kg °C)... 

One-electron reduction or oxidation of organic compounds provides a useful method for the generation of anion radicals or cation radicals, respectively. These methods are used as key processes in radical reactions. Redox properties of transition metals can be utilized for the efficient one-electron reduction or oxidation (Scheme 1). In particular, the redox function of early transition metals including titanium, vanadium, and manganese has been of synthetic potential from this point of view [1-8]. The synthetic limitation exists in the use of a stoichiometric or excess amount of metallic reductants or oxidants to complete the reaction. Generally, the construction of a catalytic redox cycle for one-electron reduction is difficult to achieve. A catalytic system should be constructed to avoid the use of such amounts of expensive and/or toxic metallic reagents. 

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