Phosphorus III Fluoride

Phosphorus(III) fluoride can be prepared by the reaction of antimony (III) fluoride with phosphorus (III) chloride, using antimony (V) chloride as a catalyst,1 or by heating copper phosphide with lead fluoride.2 The procedure described here involves the reaction of arsenic(III) fluoride with phosphorus (III) chloride, using antimony(Y) chloride as a catalyst.3,4 

The apparatus consists of a glass reaction flask fitted with a side arm and dropping funnel. The side arm is connected to two glass traps in series by means of standard ground-glass joints and stopcocks. 

After the apparatus is assembled and thoroughly dried, 13.7 g. of freshly distilled phosphorus(III) chloride (0.10 mol) is introduced into the reaction flask, and 13.2 g. of arsenic (III) fluoride (0.10 mol) (synthesis 50) containing a few drops of antimony (V) chloride J is placed in the dropping funnel. The phosphorus (III) fluoride is readily generated by allowing the arsenic (III) fluoride to drop slowly into the phosphorus(III) chloride the reaction proceeds smoothly at room temperature and becomes more rapid with time. The gases formed by the reaction are led from the reaction flask through a trap cooled by an acetone-Dry Ice bath, to 

I The checkers report that satisfactory results may be obtained without the antimony (V) chloride catalyst. 

Phosphorus (III) fluoride is a fairly stable, colorless gas which is decomposed slowly by water, forming phosphorous acid and hydrogen fluoride. At elevated temperatures, in the presence of silica, it quickly decomposes. It condenses ft —101.1° to form a colorless, mobile liquid and solidifies at — 151.5° to a white solid. 

1-trisubstituted hydrazonium chlorides are colorless, crystalline compounds which are very soluble in water, many being highly hygroscopic. They are also soluble in ethanol but are only slightly soluble in ethyl ether. 1,1,1-Trimethylhydrazonium chloride melts at about 245° in a sealed capillary with decomposition. 1,1,1-Triethylhydrazonium chloride melts at about 177 to 178° in a sealed capillary. 

Phosphorus(III) fluoride can be prepared by the reaction of phosphorus (III) chloride with arsenic(III) fluoride,1,2 

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Cyanate condensation products of carbohydrazide, synthesis 11 Thiosemicarbazide, synthesis 12 Dithiocarbamates of selenium(II) and tellurium (II), synthesis 32 Aluminum phosphide, synthesis 7 Phosphorus(III) fluoride, synthesis 49... 

When pure, phosphorus(III) fluoride is odorless in concentrations which are great enough to cause the substance to be toxic. It is readily absorbed by sodium hydroxide with evolution of heat. 

The portion of the distillate boiling at 63° comprises the product. The yield is 11.2 g. (85 %). Arsenic(III) fluoride obtained in this manner is of sufficient purity to be used for the preparation of phosphorus (III) fluoride (synthesis 49) however, if desired, it can be further purified by distillation at atmospheric pressure in an all-glass system using a column packed with glass helices.3... 

F3B Bromine(III) fluoride, 8 184 F3Co Cobalt (III) fluoride, 3 175 F3P Phosphorus (III) fluoride, 4 149 F3Sb Antimony (III) fluoride, 4 134... 

MoFj—Molybdenum(VI) fluoride can be reduced to MoF6 by PF3, Mo(CO) ,9 or molybdenum powder.9 The preferred reducing agent appears to be phosphorus(III) fluoride at room temperature because of the ease of removal of both the volatile by-product PF8 (b.p. — 85°C.) and the excess PF3 (b.p. — 102°C.). 

If rapid evolution of phosphorus(III) fluoride is not noted within 5 minutes, more phosphorus(III) chloride is added, and time is allowed for the induction period. 

PCh GaCls Phosphorus (V) chloride, compound with gallium-(III) chloride, 7 81 PFj Phosphorus (III) fluoride, 4 149 6 95... 

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