Vanadium nuclear magnetic resonance

The surface structure and reactivity of vanadium oxide monolayer catalysts supported on tin oxide were investigated by various physico-chemical characterization techniques. In this study a series of tin oxide supported vanadium oxide catalysts with various vanadia loadings ranging from 0.5 to 6. wt.% have been prepared and were characterized by means of X-ray diffraction, oxygen chemisorption at -78°C, solid state and nuclear magnetic resonance... 

When 51V nuclear magnetic resonance (NMR) was used to follow the catalysis of trimethoxybenzene (tmb) bromination, the only vanadium species that were observed under conditions of 0.5 mM total vanadium(V) were oxodiper-oxovanadium(V) (V0(02)2 , -688 ppm), oxoperoxovanadium(V) (V0(02)+, -529 ppm), and cw-dioxovanadium(V) (-540 ppm). Within the experimental error of the integration, all of the vanadium was detected in the vanadium(V) oxidation state under turnover conditions, since the integrated signal intensity at various times throughout the reaction was equivalent to that of an equimolar solution of cis-V02+. 

Until recently, probably the best understood oxidation state of vanadium was V(IV). This situation changed with the advent of high field nuclear magnetic resonance (NMR) spectrometers, which provided the means to obtain a detailed understanding of the V(V) oxidation state. Indeed, the past 2 decades have seen the redrawing of the landscape of V(V) science, particularly where the aqueous phase is involved. 

Heath, E. and O.W. Howarth. 1981. Vanadium-51 and oxygen-17 nuclear magnetic resonance study of vanadate(V) equilibria and kinetics../. Chem. Soc., Dalton Trans. 1105-1110. 

Tracey, A.S. and K. Radley. 1985. A vanadium-51 nuclear magnetic resonance investigation of vanadate oxyanions in a lyotropic liquid crystalline bilayer system. Can. J. Chem. 63 2181-2184. 

Magnetic Resonance. Both electron spin resonance and nuclear magnetic resonance have been observed in the alkali vanadium bronzes. The details of these investigations have been published (11), but the principal findings can be indicated here. 

The structure elucidation was difficult because standard methods could not be utilized. The paramagnetism of amavadin caused extreme peak broadening of nuclear magnetic resonance spectra. Due to the low volatility of the vanadium complex no useful mass spectra in El, Cl or FAB mode could be obtained. ... 

The study of ethylene and propylene copolymerisation, on vanadium and titanium catalysts of various compositions [70], led to the conclusion that studied catalytic systems contain two or three types of AC. This conclusion has been made as a result of the analysis of the MWD curves, carbon nuclear magnetic resonance spectroscopy analysis, and copolymers composition fractionation data. The analysis of a large number of copolymer fractions, produced by their dissolution in several solvents at various temperatures, has indicated the existence of several types of AC different both in stereospecificity and in reactivity. According to the authors of [70], a combination of copolymer fractionation results with gel chromatography data indicates the presence of two or three types of AC. 

The preparation of natural rubber-gra/t-methyl methacrylic acid has been reported by Lenka and coworkers. The vanadium ion was used as an initiator, which initiated the creation of free radicals on the backbone of natural rubber and this increased the interaction between the natural rubber and the methyl methacrylate surfaces. The coordination complexes derived from the acetylacetonate of Mn(III) ions could also be used as an initiator to form the natural rubber-gra/t-methyl methacrylic acid. Under different conditions, silver ions could be used as a catalyst to produce natural rubber-gra/t-methyl methacrylic acid with different concentrations of methyl methacrylic acid monomers, and potassium peroxydisulfate as an initiator. Consequently, these methods were successful in the preparation of compatible blended natural rubber and methyl methacrylic acid by graft copolymerization. This compatibility was confirmed by nuclear magnetic resonance and infrared spectroscopy techniques. The interaction between natural rubber and methyl methacrylic acid was significantly increased and was useful for further blending with other polyacrylate molecules or different polymer types. 

Howarth OW (1990) Vanadium-51 NMR. Progress in Nuclear Magnetic Resonance Spectroscopy 22 453-485. 

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