Preparation of Molybdenum VI Oxide

Preparation of Molybdenum(VI) Oxide, a. Preparation of Molybdenum(VI) Oxide by the Thermal Decomposition of Ammonium Molybdate. Put a boat with 0.5 g of ammonium molybdate into a porcelain tube in an electric furnace. Connect one end of the 

Why is the ammonium molybdate roasted in a stream of air and at two different temperatures  

After complete oxidation of the taken amount of molybdenite, switch off the furnace and cool the apparatus in a stream of air. Disconnect receiver 6 from the apparatus and extract the sublimed molyb-denum(VI) oxide crystals from the receiver, and also from the 

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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. 

Molybdenum(VI) oxide is used in catalyst compositions to carry out desulfurization of petroleum feedstocks and to remove nitrogen-containing compounds from petroleum fractions. Other uses of this oxide include preparation of various molybdate salts and as reagents for chemical analyses. 

Molybdenum(VI) dioxyacetylacetonate (molybdenyl acetylacetonate) was first prepared by Gach1 by the action of acetylacetone upon molybdenum(VI) oxide at room temperature. Since he also isolated a small quantity of the same compound by the reaction between molybdenum (II) hydroxide and acetylacetone, he believed the compound to be Mo(C5H702)2. Rosenheim and Bertheim2 later prepared the compound by refluxing an ethanolic solution of acetylacetone with molybdic acid. They correctly identified the product as molybdenyl acetylacetonate. Morgan and Castell3 later duplicated the preparation of Rosenheim and Bertheim and verified their formula. 

Molybdenum oxide trichloride has been prepared by heating molybdenum(VI) oxide or molybdenum dioxide dichloride with molybdenum(V) chloride. Molybdenum(VI) oxide tetrachloride is a by-product of the latter reaction.1 It was also prepared by the sealed-tube reaction of liquid sulfur dioxide with molybdenum (Y) chloride2 and by the thermal decomposition of molybdenum oxide tetrachloride in a stream of nitrogen. In the following procedure, it is prepared by reducing molybdenum oxide tetrachloride with refluxing chlorobenzene.4... 

Preparative Methods to 5mL aqueous hydrogen peroxide solution (30%) is added, in portions, 1 g molybdenum(VI) oxide at 20 °C. The mixture is stirred at 20 °C for 20 min and at 40 °C for 4 h. After most of the molybdenum oxide has dissolved the mixture is filtered. The yellow solution is treated at 10 °C with 1 equiv of ligand dissolved in approx. 4 mL methanol. The mixture is stirred for 30 min at 20 °C, concentrated and kept 12 h at 0 °C. When the complex does not crystallize after addition of dichloromethane or benzene, the mixture is diluted with ethanol and carefully (shield protection) concentrated on a rotary evaporator. The procedure is repeated five times. The mixture is then further concentrated. The complex is usually obtained as a yellow microcrystalline powder, but if it is obtained as an oil the addition of diethyl ether with stirring at 5 °C yields a yellow powder. 

Various methods for the preparation of potassium octacyano-molybdate(IV) 2-hydrate from molybdenum(VI) oxide, molyb-dic acid, or molybdates have been reported. These methods, although in general rehable, have one unfavorable aspect in common low efficiencies due to conversions of less than 50%. 

MoS2 can be prepared by direct combination of the elements, by heating molybdenum(vi) oxide in hydrogen sulfide, or by fusing molybdenum(vi) oxide with a mixture of sulfur and potassium carbonate. It is the most... 

If molybdenum(VI) is generated by treatment of a polymer-supported complex containing molybdenum(V) with a hydroperoxide, then this polymer-supported oxidant may also be used to prepare sulphones from sulphoxides. In this case the yield is not good unless the sulphoxide is repeatedly passed through a column containing the oxidant or the reaction is performed by stirring the polymer and the sulphoxide together at 56 °C for 16 hours . ... 

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 contrast to the situation a decade ago, many incomplete cubane-type clusters with Mo304 S cores have been prepared and the structures have been determined by X-ray structure analyses. The results obtained are summarized in Tables I—III. The formal oxidation state of molybdenum in the compounds cited here is in all cases IV. Unlike Mo(VI) and Mo(V) compounds, mononuclear oxo or dioxo compounds of the Mo(IV) state are relatively rare and all the incomplete cubane-type compounds cited here have no terminal oxo ligand. Three Mo atoms form an equilateral triangle, and three single bonds exist between each Mo. Except for the compounds 1, 8, and 31 (Table III), and excluding Mo—Mo bonds, each molybdenum is octahedrally coordinated. 

Although the series is incomplete, cubane-type clusters with Mo404- S (n = 0,3, or 4) cores have been prepared and structures have been determined by X-ray crystallography. The results are summarized in Tables IV (53-57) and V (58-71). Contrary to the case of incomplete cubane-type clusters, wherein only the IV oxidation state of molybdenum appears, the oxidation state of molybdenum varies from VI to III. The total oxidation number of each Mo4 cluster is indicated in the tables. 

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