Molybdenum pentafluoride

Three other binary compounds of molybdenum and fluorine are known to exist molybdenum trifluoride [20193-58-2] MoF, molybdenum tetrafluoride [23412-45-5] MoF, and molybdenum pentafluoride [13819-84-6] MoF. Also known are the two oxyfluorides, molybdenum dioxydifluoride [13824-57-2] M0O2F2, and molybdenum oxytetrafluoride [14459-59-7] MoOF. The use of these other compounds is limited to research appHcations. 

Tungsten hexachloride and molybdenum pentafluoride desulfurize 2-methylthiirane to propene (72DOK(207)899) and a ruthenium(II) complex desulfurizes thiirane (73JA4758). 

The reaction between molybdenum hexacarbonyl and elemental fluorine at —65° results in the formation of Mo2F9, which upon thermal degradation produces molybdenum pentafluoride as one of the products.1 Other syntheses of molybdenum pentafluoride include the reduction of molybdenum hexafluoride with phosphorus trifluoride,2 tungsten hexacarbonyl, or molybdenum metal at high temperatures3 and the oxidation of powdered molybdenum metal with elemental fluorine at 900°.3 The present method consists in the reaction of molybdenum hexafluoride with powdered molybdenum metal at 60° and results in the formation of pure molybdenum pentafluoride in yields of 80% and greater. 

Caution. Molybdenum hexafluoride is a toxic, highly hygroscopic material, which must be handled in a clean, dry, high-vacuum system. Molybdenum pentafluoride is also a very hygroscopic compound, which must be handled either in a vacuum line or in an anhydrous, oxygen-free atmosphere. 

The first portion of molybdenum pentafluoride removed from the reaction vessel will contain as impurities the excess hexafluoride and possibly a small quantity of molybdenum oxy-fluoride, MoOF4. The first portion of pentafluoride is separated from the impurities using the apparatus shown in Fig. 6, with all joints sealed using Kel-F wax or using Teflon stopcocks, f The glass collection vessel is carefully degassed as previously described, and then the lower 6 cm. of the reaction vessel is cooled to —196°. The molybdenum pentafluoride is removed... 

Molybdenum pentafluoride is a bright yellow solid with a melting point of 67° and an extrapolated boiling point of 211°.2 It is very susceptible to hydrolysis however, it appears quite stable in a dry, stainless-steel vessel and can be handled for short periods in a dry-box (P205). It is insoluble in most organic solvents but dissolves in dimethyl ether and acetonitrile, giving pale yellow solutions from which addition complexes are obtained.4 The solid contains a tetramer, Mo4F20. 

The following are some further examples. Acetomesitylene is obtained from mesitylene and glacial acetic acid in the presence of phosphoric oxide and kieselguhr, yields reaching 82.5%.525,566 (o-Nitrobenzoyl)mesitylene is obtained (75%) from mesitylene and a-nitrobenzoic acid in the presence of boron trifluoride and trifluoroacetic anhydride.567 Toluene and benzoic acid in the presence of molybdenum pentafluoride give a 70% yield of 4-methylbenzo-phenone, but with aluminum chloride give a mixture of the 2- and the 4-methyl derivative.568... 

Contact with boron, silicon, red phosphorus, sulfur, or arsenic, antimony or bismuth usually causes incandescence [1]. Solid potassium or molten sodium explode with the pentafluoride, and aluminium foil ignites on prolonged contact [2], Molybdenum and tungsten incandesce when warmed [3],... 

Dining the reduction of iridium hexafluoride, osmium hexafluoride or rhenium hexafluoride with silicon to the pentafluorides, the hexafluorides must not be condensed directly onto undiluted silicon powder, or explosions may result [1]. The same is true for molybdenum hexafluoride and uranium hexafluoride [2],... 

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... 

For molybdenum trifluoride, it has been established that the cubic material contains oxide impurity, and the pure compound has been prepared by the reduction of the pentafluoride (38, 39) or hexafluoride (37) with molybdenum metal and has a rhombohedral unit cell. 

Tris(2,4-pentanedionato)molybdenum(III), synthesis 39 Potassium tetraoxalatouranate(IV), synthesis 40 Sulfur chloride pentafluoride, synthesis 41 Trifluoromethyl hypofluorite, synthesis 42 Ammonium perrhcnate, synthesis 43... 

Trimethylsilylamino tellurium pentafluoride lost the trimethylsilyl group in reactions with hydrogen fluorideS cesium fluoride, chlorine fluoride, sulfur fluorides, selenium tetrafluo-ride, phosphorus pentafluoride, tungsten hexachloride, molybdenum hexafluoride, and tungsten hexafluoride. ... 

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