Vanadium complexes acetates

Acetic acid is formed when methane reacts with CO or C02 in aqueous solution in the presence of 02 or H202 catalyzed by vanadium complexes.327 A Rh-based FeP04 catalyst applied in a fixed-bed reactor operating at atmospheric pressure at 300-400° C was effective in producing methyl acetate in the presence of nitrous oxide.328 The high dispersion of Rh at sites surrounded by iron sites was suggested to be a key factor for the carbonylation reaction. 

The drawback of this reaction is that trifluoroacetic acid for the solvent and excess K2S2O8 for the oxidant are required. Although a bimetallic system based on Pd and Cu was initially used as the catalyst, it was determined that the reaction can proceed using only the copper catalyst. A radical mechanism is proposed. Vanadium complexes such as VO(acac)2 also effectively catalyze acetic acid formation from methane and CO (57). The yield reached 93% based on methane. 

The black vanadium complex precipitates immediately. Heat the mixture briefly, filter, wash the complex with dilute acetic acid and dry it. Dissolve the blue-black solid in a mixture (1 1) of xylene and glacial acetic acid by warming, and dilute the solution with xylene— glacial acetic acid (1 1) until it has a convenient intensity of colour (about lO" M). Store the reagent solution in a dark bottle. 

Hydroxy-containing polymers such as poly(methyl-methacrylate-co-hydroxyethyl methacrylate) [65,66] or secondary cellulose acetate [67,68] were used for this purpose. Vanadium (V) 8-hydroxy quinoline-hydroxy-ethyl methacrylate adduct, prepared by condensation of the latter with a VOQ2OH complex, is polymerized to... 

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. 

Macrocyclic ligands 1,4,7-triazacyclonona-iV-acetate 221 and iV-(2-hydroxybenzyl)-l,4,7-cyclononane 225 have been prepared from l,4,7-triazacyclio[5.2.1.04 10]decane 40 and were subsequently used for the synthesis of a series of mono- and dinuclear complexes of vanadium(rv) and (v) (Scheme 35) <1995ICA(240)217>. 

Vanadium(n) Complexes.—Dehydration of VSO. THjO has been shown to proceed via the formation of VS04,mH20 (where n = 6, 4, or 1) and V(OH)-(SO4), which were characterized by X-ray studies. The polarographic behaviour and the oxidation potential of the V -l,2-cyclohexanediamine-tetra-acetic acid complex, at pH 6—12, have been determined.Formation constants and electronic spectra have been reported for the [Vlphen),] " and [V20(phen)] complexes. The absorption spectrum of V ions doped in cadmium telluride has been presented and interpreted on a crystal-field model. The unpaired spin density in fluorine 2pit-orbitals of [VF ] , arising from covalent transfer and overlap with vanadium orbitals, has been determined by ENDOR spectroscopy and interpreted using a covalent model. " ... 

The kinetics of the reaction between [V(salen)] in pyridine and oxygen have been determined and interpreted in terms of the formation of a [V(salen)] -oxygen adduct. This reinforces the view that vanadium(iii) complexes can act as oxygen carriers. The oxidation of the 1,2-cyclohexanediaminetetra-acetic acid complex of V " has been studied in solutions of pH 6—12. ... 

From equation (30), whether a tris chelate is formed depends on the donor ability of the ligand. Several vanadium(IV) complexes with 1,2-dihydroxybenzenes formed from solutions of the ligand, VOSO4 and thallium(I) acetate.498 The compounds are of two types (I) T12[V(RC6H302)3] (R = H, 3-Me, 4-Me, 3-MeO) and (II) T12[V0(RC6H302)2] (R = CHO). 

The vanadium(V) oxidation of the sulfide PhCH=CHSPh has been studied in aqueous acetic acid containing perchloric acid. The reaction is first order in vanadiiun(V) and fractional order in sulfide. An intermediate complex of vanadium and the sulfide forms and its decomposition is the slow step of the reaction.181 Two Indian groups have reported on the use of ruthenium(VI) and ruthenium(III).182 183 The kinetics and mechanism of the oxidation of diethylene glycol by aqueous alkaline potassium bromate in the presence of Ru(VI)182 and the Ru(III)-catalysed oxidation of aliphatic alcohols by trichloroisocyanuric acid183 have been examined. 

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