Reactivity Of Vanadium Research Articles

High-temperature corrosion behaviour of plasma sprayed Gd2SrAl2O7 coatings by V2O5 at 700–1200 ºC

V2O5 melt reaction in GSA coating are investigated at 700ºC-1200ºC. Under corrosion conditions, severe chemical reaction occurs and brings down the reactivity of vanadium. Sr2V2O7, Al2O3 and GdVO4 are the main reaction products at 700–900 °C, and form a planar reaction zone (PRZ). The thick PRZ can be divided into several sublayers. After thermal corrosion at 1200 °C, PRZ morphology becomes homogenous and its compositions change to Sr3V2O8, Al2O3 and GdVO4. Additionally, an infiltrated reaction zone (IRZ) of GdAlO3 is observed below PRZ. Based on experimental observations, chemical reaction mechanisms governing corrosion process are proposed and a simple reaction schematic is established.

Synthesis, characterization and reactivity of vanadium, chromium, and manganese PNP pincer complexes

The synthesis of a series of vanadium, chromium, and manganese PNP complexes of the types [M(PNP)Cl3] (M=V, Cr) and [M(PNP)Cl2] (M=Cr, Mn) is reported. Vanadium and manganese PNP pincer complexes are described for the first time. All complexes are characterized by their magnetic moments, elemental analysis, and ESI MS. In addition, some compounds are characterized by X-ray crystallography. In a preliminary study, these complexes catalyze the oxidative homo-coupling of aryl Grignard reagents in the presence of MeI as oxidizing agents to give symmetrical biaryls, but are inactive in Kumada cross-coupling reactions. The reactivity of V(III), Cr(III), Cr(II) and Mn(II) is compared with related Fe(II) and Co(II) complexes of the types [Fe(PNP-iPr)Cl2], and [Co(PNP-iPr)Cl2]. In all cases, good to excellent isolated yields are obtained. However, since the respective metal chlorides in the absence of PNP ligands exhibited comparable reactivities, the new PNP complexes offer no real advantage for this type of coupling reactions.

Structure and Reactivity of Vanadium and Molybdenum Oxide‐Based Catalysts Supported on MgO‐Coated SBA‐15

Structure and Reactivity of Vanadium and Molybdenum Oxide‐Based Catalysts Supported on MgO‐Coated SBA‐15

Multinuclear NMR study of the reactive intermediates in enantioselective epoxidations of allylic alcohols catalyzed by a vanadium complex derived from a planar-chiral hydroxamic acid

Structure and reactivity of vanadium(V) complexes formed in situ in the catalytic system VO(Oalkyl)3/hydroxamic acid/tert-butylhydroperoxide (TBHP) have been examined by means of 51V, 13C and 17O NMR spectroscopy. For the first time, reactive vanadium(V) alkylperoxo intermediates in vanadium/hydroxamic acid epoxidations were observed and spectroscopically characterized. With a planar-chiral [2.2]paracyclophane-derived hydroxamate as ligand two diastereomeric alkylperoxo vanadium(V) complexes were formed in a 3∶1 ratio. They differ in the relative positioning of the VO group and the planar-chiral aromatic part. Upon addition of geraniol as substrate, these complexes disappear in a parallel manner, and geraniol epoxide is formed. Probably, the existence of these two diastereomeric complexes and their comparable reactivity account for the observed enantioselectivity level (≤71% ee) and hence sets a fundamental limitation for the use of such ligands in this asymmetric catalysis.

ChemInform Abstract: Relative Influence of Structure and Reactivity of Vanadium‐ and Molybdenum‐Containing Catalysts in Mild Oxidation of Hydrocarbons

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Structure and reactivity of vanadium(V) complexes formed in the reaction between vanadyl acetylacetonate and alkyl hydroperoxides. To the mechanism of selective epoxidation of olefins

Vanadium(V) complexes formed in the reaction between vanadyl acetylacetonate and alkylhydroperoxides are characterized according to their1H and51V NMR spectra and the reactivity of these complexes towards cyclohexene is studied.

Solvent effects on the reactivity of vanadium(II)

Absorption spectra of V(II), covering a range wide enough to encompass the expected three absorption bands arising from d-d transitions, were registered in nine solvents. The source of V(II) in most cases was V(DME) 2 (O 3 SCF 3 ) 2 (DME is 1,2-dimethoxyethane), but in some cases V(II) was generated by reducing V(O 3 SCF 3 ) 3 with Zn/Hg. Only in the case of the weakly nucleophilic solvent CH 2 Cl 2 is there evidence that the DME introduced with the solid affects the spectrum. Striking changes are registered in passing from a solvent such as H 2 O to solvents, the molecules of which have π-acid character. In the case of acetone, pyridine, and acetonitrile, strong MLCT absorption sets in, accompanied by hypsochromic shifts of those d-d transitions that are not obscured by the charge-transfer bands

REACTION OF HYDROGEN PEROXIDE WITH METAL COMPLEX. I. The Kinetics of the Reaction of Hydrogen Peroxide with N-Methyliminodiacetatodioxovanadate

Abstract The kinetics of the reaction of N-methyliminodiacetatodioxovanadate with hydrogen peroxide has been studied spectrophotometrically by a stopped-flow technique. Over the pH range 3 to 4, the rate of the mixed-ligand complex formation is of the first-order with respect to N-methyliminodiacetatodioxovanadate and hydrogen peroxide: where k is 9.2 × 103 M−1 sec−1 at 25°C and μ = 1.0 (NaClO4), ΔH ≠ 6.3 Kcal/mole and ΔS ≠ −19 e.u. Some discussions are made on the reactivity of vanadium (V) complexes.

675. The reactivity of vanadium and some vanadium alloys with low-pressure oxygen and nitrogen: R C Svedberg, Proc Vac Metallurgy Conf, J Vac Sci Technol, 8 (6), Nov–Dec 1971, VM41–VM47

675. The reactivity of vanadium and some vanadium alloys with low-pressure oxygen and nitrogen: R C Svedberg, Proc Vac Metallurgy Conf, J Vac Sci Technol, 8 (6), Nov–Dec 1971, VM41–VM47

The Reactivity of Vanadium and Some Vanadium Alloys with Low-Pressure Oxygen and Nitrogen

The reactivity of pure vanadium (<350 ppm total impurity content) and the alloys vanadium–10.5-wt% chromium, vanadium–9.5-wt% molybdenum, and VANSTAR-7 (V–9 wt% Cr–3 wt% Fe–l.3 wt% Zr–0.05-wt%) with oxygen and nitrogen at low partial pressures in the temperature range of 600–800 °C was determined utilizing a hot-wall ultrahigh vacuum microbalance system. The rate of reactivity was determined from continuous weight-gain measurements as a function of both temperature and pressure, for oxygen partial pressures of 10−5 to 10−7 Torr and nitrogen partial pressures of 10−4 to 10−6 Torr. Linear kinetics were observed, indicative of a process controlled by gas transport to the metal surface. The sticking probability for oxygen of 0.185±0.040 was found to be independent of temperature, pressure, and alloying additions. The rate of reaction with nitrogen was a function of alloying additions, with VANSTAR-7 and V-10.5Cr exhibiting the lowest reactivity. The sticking probabilities were compared with those reported in the literature. These results indicate that the sticking probabilities of low-pressure gases on refractory metals are not well defined and seem to be a function of the particular experimental apparatus utilized.

Reactivity of vanadium(V) polymeric and monomeric forms in complex formation with p-phenetidine

The formation of charge-transfer complex (CTC) between p-phenetidine and vanadium(V) species existing in acid medium at low vanadium(V) concentrations was studied. It was found that while the CTC formation rate is very low VO 2 +, it is maximal when decavanadate species are used. The results were interpreted on the ground of the electrostatic interaction between the reagents. The rate of depolymerisation of decavanadate species to VO 2 + and H 2VO 4 − was also studied and the rate constants of these processes estimated.