III Fluoride

Cobalt(III) fluoride has been found to be a useful fluorinating agent in the production of fluorocarbons it can be used for a variety of fluorinating reactions as a substitute for elementary fluorine. While it is not possible to obtain elementary fluorine by heating cobalt(III) fluoride, it can be used to prepare higher-valent volatile fluorides that could not otherwise be obtained except by the use of elementary fluorine. The method of preparation described here is similar to that used by Ruff and his coworkers.  

A reactor set up exactly like the one used in the preparation of anhydrous nickel fluoride is needed. 

Fifty grams of hydrated cobalt(II) chloride is heated in a porcelain dish until the compound is completely dehydrated. Hydrolysis with attendant formation of black cobalt oxide will cause no diflSculty. The hot cobalt(II) chloride is transferred to a hot porcelain mortar and ground to a uniform powder as rapidly as possible. After grinding, the material is transferred to the nickel reactor tray, and the 

The flow of fluorine is started, and the furnace is heated to 250° and maintained at this temperature for 3 hours after a test for chlorine has shown the latter to be absent from the exit gas. The fluorine is then purged from the system with dry nitrogen in preparation for the removal of the product. A metal can with a tight-fitting snap lid is cleaned and dried air in the container is displaced completely by dry nitrogen. The container is then placed beside the reactor containing the cobalt(III) fluoride. The reactor closure is removed, the tray is withdrawn, and the product transferred to the can as rapidly as possible (1 to 3 seconds being adequate), after which the container is capped. 

The product is a light brown solid that fiunes and turns dark brown in moist air. It is easily handled in a dry box and may be analyzed either for the elements or, as is more common, for available fluorine using iodometric methods. The yield will vary from 22 to 23 g. (90 to 95 per cent of theory). 

Pure anhydrous vanadium(III) fluoride is more conveniently prepared by the thermal decomposition, in an inert atmosphere, of ammonium hexafluorovanadate(III), the latter being formed by the fusion of ammonium hydrogen fluoride with vanadium (III) oxide. Long and Wilhelm were unsuccessful in their efforts to prepare vanadium(III) fluoride by these reactions their product became oxidized since it was not protected by an inert atmosphere. Also, there is evidence that these investigators started with impure vanadium (III) oxide. The procedure described below employs an inert atmosphere for the decomposition of the hexafluorovanadate. 

Previously, ammonium hexafluorovanadate (III) has been obtained only from aqueous solution. Its preparation in molten ammonium hydrogen fluoride has the advantage that it yields a product which is anhydrous. Aqueous preparations of ammonium hexafluorovanadate (III) tend to have sorbed moisture, which, during the decomposition, could through hydrolysis contaminate the vanadium(III) fluoride with oxide. 

One hundred and fifty grams (1 mol) of vanadium(III) oxide, either the commercial powder or that prepared by hydrogen reduction of vanadium(V) oxide, is mixed with 684 g. (12 mols) of ammonium hydrogen fluoride. The excess ammonium hydrogen fluoride serves to ensure complete reaction of the vanadium(III) oxide. The mixture is heated in a graphite crucible of the approximate dimensions 5-in. o.d. X 6-in. height X i-in. thickness. After it 

When pure reactants are employed, the yield of vanadium-(III) fluoride is quantitative, as this procedure does not involve the formation of volatile vanadium compounds. 

The product is a fine gray-green powder which has the crystallographic properties reported for the trifluoride. Anal. Calcd. for VF3 V, 47.0 F, 53.0. Found V, 47.0 F, 52.1. Fluorine is determined by a pyrohydrolytic procedure.Vanadium is determined by permanganate titration of a sample dissolved in sulfuric acid. Contamination of the product by nickel from the container is less than 0.05%, the limit of detection by spectroscopy. 

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Complex siher III) fluorides containing AgF " orAgF " ions and also Cs2AgF containing Ag(IV) are formed with fluorine. They are also strong fluorinating agents. 

Also, in anhydrous conditions, silver reacts with fluorine and forms silver difluoride AgFj and cobalt gives cobalt(III) fluoride, C0F3, these metals showing higher oxidation states than is usual in their simple salts. 

Cobalt is a bluish silvery metal, exhibits ferromagnetism, and can exist in more than one crystal form it is used in alloys for special purposes. Chemically it is somewhat similar to iron when heated in air it gives the oxides C03O4 and CoO, but it is less readily attacked by dilute acids. With halogens, the cobalt(II) halides are formed, except that with fluorine the (III) fluoride, C0F3, is obtained. 

Cobaltilll) nitrate Co(N03)3 has been prepared by the reaction of dinitrogen pentoxide with cobalt(III) fluoride. 

It is dissolved by bromine trifluoride, to form finally gold(III) fluoride, AuFj. This is a notable compound, for in it gold exhibits a simple valency of three, whereas in all other gold(III) compounds, gold is 4-coordinate, usually by complex formation (see below). 

Iron(III) fluoride [7783-50-8] most widely known fluoride of iron. It is light greenish (lime green) in color and the crystals have a rhombic... 

Hydrated iron(III) fluoride [15469-38-2] is easily prepared from yeHow Fe202 and hydrofluoric acid. Dehydration of FeF 3H20 produces... 

The green hexagonal crystals sublime above 1000°C. Iron(III) fluoride is slightly soluble ia water, freely soluble ia dilute HF, and nearly iasoluble ia alcohol, ether, and benzene. It is used as a catalyst ia organic reactions. 

Iron(III) fluoride ttihydrate [15469-38-2] FeF3-3H2 0, crystallizes from 40% HF solution ia two possible crystalline forms. At low temperature the a-form, which is isostmctural with a-AlF 3H2O, is favored. High temperatures favor P-FeF 3H2O, the stmcture of which consists of fluoride-bridged octahedra with one water of hydration per unit cell. 

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