Water vanadium complexes

In this work ion-exchange and gel-permeation chromatography coupled with membrane filtration, photochemical oxidation of organic metal complexes and CL detection were applied to the study of the speciation of cobalt, copper, iron and vanadium in water from the Dnieper reservoirs and some rivers of Ukraine. The role of various groups of organic matters in the complexation of metals is established. 

Reports have appeared claiming that triperoxo vanadates behave as nucleophilic oxidants. In particular, triperoxo vanadium complexes, A[V(02)3]3H20 (A=Na or K), are proposed as efficient oxidants of a,-unsaturated ketones to the corresponding epoxide, benzonitrile to benzamide and benzil to benzoic acid, reactions which are usually carried out with alkaline hydrogen peroxide. Subsequent studies concerning the oxidation of cyclobutanone to 4-hydroxybutanoic acid, carried out with the above-cited triperoxo vanadium compound, in alcohol/water mixtures, clearly indicated that such a complex does not act as nucleophilic oxidant, but only as a source of HOO anion. 

A vanadium complex can be precipitated from a concentrated acetonitrile solution of (HPS)VO(OEt)(EtOH) by the addition of a small amount of water. This complex has an elemental analysis consistent with the formulation [(HPS)V0]20 MeCN. Its 51V NMR spectrum shows only the three upheld resonances. Addition of ethanol results again in complete conversion to the —530 ppm form (HPS)VO(OEt) (35). 

HjO, Water, chromium and vanadium complexes, 27 307, 309 iridium complex, 26 123 ruthenium complex, 26 254-256 HjOioOSjCiii, Osmium, decacarbonyldihy-dridotri-, 26 367... 

So far as is known, there is no biological component in the processes which lead to the formation of deposits such as Yeelirrie in ceilcrete (Dall Ag-lio et al., 1974). In such deposits the uranium is present in uranyl compounds, the precipitation of which appears to depend on the solubility relationships of uranyl and other ions, including complexes containing vanadium, in waters of varying composition carbonate concentration appears to have been especially important. 

OHj, Water, chromium and vanadium complexes, 27 307, 309 iridium complex, 26 123, 28 58 ruthenium complex, 26 254-256 OlPjRhCjjHgg, Rhodium(I), carbonyliodo-bis(tricyclohexylphosphine)-, 27 292 OLiNC,jH22, Lithium, (diethyl ether)(8-(dimethylamino)-l-naphthyll-, 26 154 OLUC21H25, Lutetium, bis(ii -Cyclopenta-dienyl)(tetrahydrofuran)-p-tolyl-,... 

Asymmetric sulfoxidation with chiral vanadium complexes is much older than Ti and A1 because this metal provides more robust catalysts which are not deactivated by the presence of water. The first contribution to the field was made by Bolm and co-workers in the second half of 1990s. These authors developed chiral catalysts formed in situ by the reaction of VO(acac)2 with chiral enantiopure Schiff ligands bearing one stereocenter based on a t-leucinol scaffold." The maximum ee achieved was 85% using low catalyst loadings (<1% mol) and without any precautions to avoid moisture or oxygen, which was unusual at that time as hydroperoxides... 

One property of liquid-liquid interfaces in general, and of ITIES in particular, is their ability to adsorb nanoparticles and, in certain cases, to form metal-like films. Pioneering measurements were carried out by Guainazzi et al. [330] who demonstrated that a direct current applied across the interface between Cu ion in water and a vanadium complex in 1,2- DCE causes deposition of a copper layer at the liquid-liquid boundary. Another seminal work is that of Efrima et al. who showed in 1988 the formation of silver metal-like films at the HjO-DCE interface [331], Since then, many publications have addressed this fascinating topic, and the field was excellently reviewed recently by Boerker et al. [332]. 

Weigh out about 2.67 g of the cobalt complex and dissolve in 60 cm water. Weigh out about 4.77 g of the vanadium complex (Sec. 10.3.2) and dissolve it in 100 cm water and add the solution slowly with stirring to the cobalt complex solution. Allow to stand in an ice bath until precipitation seems complete. Filter under suction and wash on the filter with small volumes of ethanol. Dry by continued suction while pressing between filter paper. Analyse for (V+ oxalate) using standardised permanganate (Sec. 10.3.2) and for cobalt as above in trisoxalatocobaltate(Ill). Assign a formula to the product. 

Vanadium IlI) bromide, VBr3. Dark green or black (V plus Br2) gives green solution in water and green crystalline VBr3,6H20. Forms many complexes. 

The tert-huty hydroperoxide is then mixed with a catalyst solution to react with propylene. Some TBHP decomposes to TBA during this process step. The catalyst is typically an organometaHic that is soluble in the reaction mixture. The metal can be tungsten, vanadium, or molybdenum. Molybdenum complexes with naphthenates or carboxylates provide the best combination of selectivity and reactivity. Catalyst concentrations of 200—500 ppm in a solution of 55% TBHP and 45% TBA are typically used when water content is less than 0.5 wt %. The homogeneous metal catalyst must be removed from solution for disposal or recycle (137,157). Although heterogeneous catalysts can be employed, elution of some of the metal, particularly molybdenum, from the support surface occurs (158). References 159 and 160 discuss possible mechanisms for the catalytic epoxidation of olefins by hydroperoxides. 

The Lo-Cat process, Hcensed by US Filter Company, and Dow/Shell s SulFerox process are additional Hquid redox processes. These processes have replaced the vanadium oxidizing agents used in the Stretford process with iron. Organic chelating compounds are used to provide water-soluble organometaHic complexes in the solution. As in the case of Stretford units, the solution is regenerated by contact with air. 

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