Tungsten bromide oxide

A stoichiometric mixture of 2.758 g. (15 mg. atoms) of tungsten powder, 6.956 g. (30 mmoles) of tungsten(VI) oxide, and 7.192 g. (45 mmoles) of bromine is put into the reaction tube. A small excess of 2 mg. of bromine per milliliter of tube volume is added to prevent the formation of lower tungsten bromides or bromide oxides. 

In the case of molten salts, the functional electrolytes are generally oxides or halides. As examples of the use of oxides, mention may be made of the electrowinning processes for aluminum, tantalum, molybdenum, tungsten, and some of the rare earth metals. The appropriate oxides, dissolved in halide melts, act as the sources of the respective metals intended to be deposited cathodically. Halides are used as functional electrolytes for almost all other metals. In principle, all halides can be used, but in practice only fluorides and chlorides are used. Bromides and iodides are thermally unstable and are relatively expensive. Fluorides are ideally suited because of their stability and low volatility, their drawbacks pertain to the difficulty in obtaining them in forms free from oxygenated ions, and to their poor solubility in water. It is a truism that aqueous solubility makes the post-electrolysis separation of the electrodeposit from the electrolyte easy because the electrolyte can be leached away. The drawback associated with fluorides due to their poor solubility can, to a large extent, be overcome by using double fluorides instead of simple fluorides. Chlorides are widely used in electrodeposition because they are readily available in a pure form and... 

Tungsten oxide tetrabromide was prepared by condensing a little of the bromide onto the oxide at — 196°C, then allowing slow warming by immersion of the container in an ice bath. Omission of the ice bath or use of large amounts of bromide may lead to explosions. 

In the fall of 1934, Dr. Grosse reduced this pure oxide by two methods and obtained from it the metal protactinium, which is even rarer than radium, but much more permanent in air. In die first method, he bombarded the oxide on a copper target, in a high vacuum, with a stream of electrons. After a few hours, he obtained a shiny, partly sintered, metallic mass, stable in air. In his second method, he converted the oxide to the iodide (or chloride or bromide) and cracked it in a high vacuum on an electrically heated tungsten filament, according to the reaction ... 

The action of carbon tetrachloride or a mixture of chlorine with a hydrocarbon or carbon monoxide on the oxide.—H. N. Warren 9 obtained aluminium chloride by heating the oxide to redness with a mixture of petroleum vapour and hydrogen chloride or chlorine, naphthalene chloride or carbon tetrachloride was also used. The bromide was prepared in a similar manner. E. Demarpay used the vapour of carbon tetrachloride, the chlorides of chromium, titanium, niobium, tantalum, zirconium, cobalt, nickel, tungsten, and molybdenum H. Quantin, a mixture of carbon monoxide and chlorine and W. Heap and E. Newbery, carbonyl chloride. 

A copper(O) complex, electro-generated from Cu(acac)2, is able to undergo an oxidative addition with benzyl and allyl bromides. Further reduction leads to the coupling products bibenzyl and 1,5-hexadienes Methyl-3-hexene-l,6-dicarb-oxylate can be prepared from butadiene and CO by electroreduction if di-Fe dicyclopentadienyl tetracarbonyl is used as redox catalyst Electro-generated low-valent tungsten species are able to reductively dimerize benzaldehyde to stilbene according to Eq. 83. The reduction potential was controlled at the third wave of the WClg catalyst (V = -1900 mV/SCE)... 

Tungsten oxide tetrabromide was prepared by condensing a little of the bromide onto... 

Oxidation of the bipyridyl tetracarbonyl derivatives of molybdenum and tungsten affords seven-coordinate derivatives of the dipositive metals (662), e.g., the compound W(CO)3(bipy)(HgCl)2 contains tung-sten-to-mercury bonds (273). Compounds containingbidentateterpyridyl have been obtained from Cr(CO)e and Mo(CO)6 by reaction with terpyridyl in isopentane solution under the influence of UV light. Pentacarbonyl-manganese bromide affords the compound Mn(CO)3(terpy)Br (274) which has an infrared spectrum identical with that of Mn(CO)3(bipy)Br (1, 78, 242, 377). 

Hydrogen peroxide can be used with molybdenum and tungsten catalysts to provide a convenient source of bromine in situ from bromide ion.226 This mimics the action of haloperoxidase enzymes. It provides a less hazardous way to use bromine. Soybean peroxidase can be used with hydrogen peroxide to oxidize alcohols to aldehydes and ketones.227 The use of hydrogen peroxide with an immobilized lipase has allowed the oxidation of linoleic acid to a monoepoxide in 91% yield. The enzyme could be reused 15 times.228 Indole has been oxidized to oxindole in 95% yield using hydrogen peroxide with a chloroperoxi-dase (4.48a).229... 

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