Molybdenum oxide fluorides

Tungsten(VI) fluoride (WF6) and molybdenum(VI) fluoride (MoF6) are available commercially, and can be made by reaction of the metals with fluorine.4 In the case of uranium(VI) fluoride (UF6), a preparation that is claimed5 to be feasible in the laboratory uses uranium metal and chlorine trifluoride uranium(VI) fluoride is prepared6 commercially by the fluorination of uranium(IV) fluoride, itself prepared from an oxide and hydrogen fluoride. 

In the reactions with carbonyl compounds9 and carboxylic acids,21 molybdenum(VI) fluoride is converted into molybdenum(VI) tetrafluoride oxide (MoOF4), and with the thiocarbonyl compounds24 into molybdenum(IV) sulfide, but with acid chlorides, its fate is not known. 

Molybdenum(VI) fluoride will insert into graphite to give8,29 nominal C5MoF6 and other compositions, and with fullerene C60 it forms30 an intercalation compound in which some oxidation process has occurred since the molybdenum exists as a molybdenum(V) fluoride species. 

Presumably because of its lower electronegativity, bromine can stabilize Mo(V) as MoOBr8 but not Mo (VI) as MoOBr4. There are no reported molybdenum oxide iodides and no lower-valent [molybdenum(V) or molybdenum(IV)] oxide fluorides. The combination of oxygen plus chlorine can stabilize Mo (VI) in both M0O2CI2 and MoOCU, but MoCl is apparently unstable at room temperature. 

Chromium Compounds and the Lower Oxide Fluorides of Molybdenum and Tungsten... 

The oxide tetrafluorides and dioxide difluorides of molybdenum and tungsten are the most studied transition-metal oxide fluorides, and their preparation and properties are discussed separately below. 

Anionic Clusters Incorporating Molybdenum and Tungsten Oxide Fluoride Species... 

Violent reactions with ammonium salts, chlorate salts, beryllium fluoride, boron diiodophosphide, carbon tetrachloride + methanol, 1,1,1-trichloroethane, 1,2-dibromoethane, halogens or interhalogens (e.g., fluorine, chlorine, bromine, iodine vapor, chlorine trifluoride, iodine heptafluoride), hydrogen iodide, metal oxides + heat (e.g., beryllium oxide, cadmium oxide, copper oxide, mercury oxide, molybdenum oxide, tin oxide, zinc oxide), nitrogen (when ignited), silicon dioxide powder + heat, polytetrafluoroethylene powder + heat. 

Comparing results of molybdenum electro-deposition from several types of electrolytes, it was confirmed that the process is most successful in electrolytes consisting of a mixture of alkali metal fluorides and boron oxide (or alkali metal borate), to which molybdenum oxide or alkali metal molybdate is added as the electrochemical active component. 

Molybdenum oxide (a potential recombination catalyst) has. shown a mild corrosion-inhil)iting action. Uranium inclusions in the thoria have not been found to increase corrosion rates. Certain impurities, i.e., carbonate and sulfate carried through the production process, have not been found to affect corro.sion rates except when added in large qutmtity, as described below. Chloride, which can cause stress-corrosion cracking of stainless steel, is undesirable in any quantity, as is fluoride. 

Fused salt solutions may be found in which the solubility of these oxides is appreciable at high temperatures and from which crystals grow as the solution is cooled. Some of the fluxes which have been used for growth of the oxides of concern here are (a) potassium nitrate-sodium nitrate, (b) lead fluoride-bismuth oxide, (c) lead oxide-bismuth oxide, and (d) lithium hydroxide-boric acid-molybdenum oxide. Temperatures frequently are in the range of 1300°C. 

SoHd lubricants ate added to help control high friction characteristics in high speed or heavy-duty appHcations where high temperatures are generated. Molybdenum disulfide [1317-33-5] M0S2, may be used alone or in a complex compound formed by grinding with fine natural graphite, and zinc sulfide [1314-98-3] ZnS. Other compounds include calcium fluoride, cryoHte [15096-52-3] Na AlF, rare-earth oxides, and metal sulfides, eg, iron, antimony, or zinc (see LUBRICATION AND LUBRICANTS). 

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... 

Sulphides. MoS2 was prepared by electrolysis at 1000°C of a melt consisting of sodium tetraborate, sodium fluoride, sodium carbonate in which molybdenum (VI) oxide and sulphur were dissolved. The electrolysis was carried out at 1000°C with the melt contained in a graphite crucible also acting as anode. After electrolysis, the excess electrolyte was dissolved in water to obtain crystalline MoS2, containing however up to 2% carbon. A similar method was used for WS2 carbon was the principal impurity in the sulphides. 

Manganese trichloride oxide, 4141 Manganese trifluoride, 4335 Mercury(II) bromide, 0269 Mercury(I) fluoride, 4312 Mercury(II) iodide, 4602 Molybdenum hexafluoride, 4365 Molybdenum pentachloride, 4180 Neptunium hexafluoride, 4366 Osmium hexafluoride, 4370 Palladium tetrafluoride, 4347 Palladium trifluoride, 4341... 

Magnesium nitrate, Tin(ll) fluoride, 4693 Manganese(lV) oxide, Calcium hydride, 4705 Molybdenum(VI) oxide, Graphite, 4717 Nitric acid, Formaldehyde, 4436 Nitric acid, Formic acid, 4436 Nitric acid, Formic acid. Urea, 4436 Nitric acid, Metal thiocyanate, 4436 Oxalic acid, Urea, 0725 Ozone, Acetylene, 4846... 

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