Vanadium trifluoride

Vanadium trifluoride, VF3. Yellow green (VCI3 plus HF at 600 C). Forms (VFa) " ion and Vp3,6H20 from aqueous HF. 

The fluorination of vanadium sesquioxide (V203) to vanadium trifluoride (VF3) can be carried out by using fluorine ... 

A new synthesis of ( )-tylophorine (2) has been based on the discovery that vanadium trifluoride oxide (VOF3) can be used to convert 1,2-diarylethylene derivatives into phenanthrenes in high yields. In the synthesis of ( )-tylophorine, as shown in Scheme 1, ring closure by VOF3 is accompanied by dehydrogenation to give a phenanthrene. Other syntheses of the phenanthroindolizidine ring system have been accomplished. "... 

Method 8. The previous syntheses start with a ready-made heterocyclic nucleus for ring E by contrast, in this recent method 69), ring E is assanbkd during the synthesis. As in methods 4-7, ring C is formed by an oxidative coupling between rings A and B, in this case with vanadium trifluoride oxide. 

The known halides of vanadium, niobium and tantalum, are listed in Table 22.6. These are illustrative of the trends within this group which have already been alluded to. Vanadium(V) is only represented at present by the fluoride, and even vanadium(IV) does not form the iodide, though all the halides of vanadium(III) and vanadium(II) are known. Niobium and tantalum, on the other hand, form all the halides in the high oxidation state, and are in fact unique (apart only from protactinium) in forming pentaiodides. However in the -t-4 state, tantalum fails to form a fluoride and neither metal produces a trifluoride. In still lower oxidation states, niobium and tantalum give a number of (frequently nonstoichiometric) cluster compounds which can be considered to involve fragments of the metal lattice. 

Chlorine Trifluoride Tech. Bull. , Morristown, Baker Adamson, 1970 Incandescence is caused by contact with bromine, iodine, arsenic, antimony (even at -10°C) powdered molybdenum, niobium, tantalum, titanium, vanadium boron, carbon, phosphorus or sulfur [1], Carbon tetraiodide, chloromethane, benzene or ether ignite or explode on contact, as do organic materials generally. Silicon also ignites [2],... 

A novel route to ( )-0-methylthalisopavine (26) involves the oxidation of the properly substituted tetrahydro-3-isoquinolone of type 129 with vanadium oxy-trifluoride to furnish bridged lactam 130. Compound 130 was then reduced to the racemic isopavine alkaloid 26 in an overall yield of 4.4% (Scheme 26) 136). 

Pentafluorocthyl iodide is of practical interest, particularly as a precursor of higher perfluoroal-kyl iodides. There are several patents for the preparation of the key compound from tetra-fluoroethene, iodine pentafluoride and iodine at 75-80 C in the presence of catalysts anti-mony(III) fluoride, titanium(lV) chloride, boron trifluoride, vanadium(V) fluoride, niobium(V) fluoride, and molybdenum(Vl) fluoride.11-13 The agents iodine monofluoride" and bromine monofluoride" can add to branched pcrfluoroalkcnes, e.g. perfluoro-2-methylbut-2-ene gives perfluoro-2-iodo-2-methylbutane.1415... 

Vanadium Tetrafluoride, hypovanadic fluoride, VF4, is produced by the action of anhydrous hydrogen fluoride on the corresponding chlorine compound, VC14, at temperatures from —28° to 0° C. It is an extremely deliquescent brown powder which readily undergoes hydrolysis with water, so that it does not give rise to double salts as in the case of the trifluoride. Its density at 23° C. is 2 9749. It decomposes above 325° C., yielding a mixture of the pentafluoride and the trifluoride 1... 

Although attempts have been made to prepare other fluorides with this stoichiometry, for example, by the interaction of the di- and trifluorides of iron and cobalt (54), these have been unsuccessful. For vanadium, the compound VF2, presumably contains vanadium(III) but the structure remains that of rutile, with a maximum 8 value of 0.04 (18 ). 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

Of course, most reactive metal fluorides, such as cobalt trifluoride [268] and vanadium pentafluoride, will react with alkenes but the reactions can be very difficult to control, except for haloalkenes [269]. Much easier control is possible with xenon fluorides [137], the reactivity decreasing in the series XeFe > Xep4 > Xep2. Since the first report of the use of xenon difluoride for the addition of fluorine to double bonds, many studies have been published and reviewed [54, 135] (Figure 3.61). 

Vanadium can react violently with bromine trifluoride, chlorine, lithium, and oxidants for example, powdered vanadium can explode in contact with chlorine. 

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