Vanadium complexes hydrogenated

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. 

Vanadium complexes of the first class of ligands catalyze the oxidation of bromide by hydrogen peroxide. These ligands (Figure 4) in-... 

Another system is relevant to this discussion of the oxidation of bromide by hydrogen peroxide. It does not catalyze precisely the same chemistry instead, the vanadium complex of tetraethylene glycol (H2teg) catalyzes the aerobic oxidation of bromide (from HBr) in 1,2-dichloroethane (30). 

In 1995, Bolm and Bienewald introduced a new, very practical method for the asymmetric catalytic oxidation of sulfides [44]. In the presence of vanadium complex prepared in situ from VO(acac)2 and 23 reactions of various sulfides or dithianes fike 24 with aqueous hydrogen peroxide afforded the corresponding sulfoxides with enantiomeric excesses of up to 85% (Eq. 2). Only traces of the corresponding sulfones were observed. The transformation can easily be carried out in open vessels at room temperature using inexpensive H2O2 as oxidant. 

Titanium(IV) and vanadium(V) form colored complexes when treated with hydrogen peroxide in 1 M sulfuric acid. The titanium complex has an absorption maximum at 415 nm, and the vanadium complex has an absorption maximum at 455 nm. A 1.00 X 10 M solution of the titanium complex exhibits an absorbance of 0.805 at 415 nm and of 0.465 at 455 nm, while a... 

X 10 M solution of the vanadium complex exhibits absorbances of 0.400 and 0.600 at 415 and 455 nm, respectively. A 1.000-g sample of an alloy containing titanium and vanadium was dissolved, treated with excess hydrogen peroxide, and diluted to a final volume of 100 mL. The absorbance of the solution was 0.685 at 415 nm and 0.513 at 455 nm. What were the percentages of titanium and vanadium in the alloy ... 

The TOF diffraction pattern is superimposed on the neutron impulse, which has a complex form. For correct interpretation of the structural information, TOF experiments should include the following scattering measurements of 1) specimen + container 2) vanadium or hydrogen standard 3) container 4) background without container [15]. The Q resolution of a TOF spectrometer is,... 

The colour sequence already described, for the reduction of van-adium(V) to vanadium(II) by zinc and acid, gives a very characteristic test for vanadium. Addition of a few drops of hydrogen peroxide to a vanadate V) gives a red colour (formation of a peroxo-complex) (cf. titanium, which gives an orange-yellow colour). 

Catalysts. In industrial practice the composition of catalysts are usuaUy very complex. Tellurium is used in catalysts as a promoter or stmctural component (84). The catalysts are used to promote such diverse reactions as oxidation, ammoxidation, hydrogenation, dehydrogenation, halogenation, dehalogenation, and phenol condensation (85—87). Tellurium is added as a passivation promoter to nickel, iron, and vanadium catalysts. A cerium teUurium molybdate catalyst has successfliUy been used in a commercial operation for the ammoxidation of propylene to acrylonitrile (88). 

Vanadium(V) does not oxidise hydrogen peroxide but forms peroxy complexes VO(02) and VO(02)J. Kinetic data are available. ... 

---