Phosphonitrile fluorides

The compound 1,1-NsPsF4(CsHc)i can be prepared by the reaction between (monophenyl)phosphonitrile fluoride trimer and benzene in the presence of anhydrous aluminum chloride and triethylamine.2 In the absence of triethylamine, the product is contaminated with difficultly separable biphenyl. Triethylamine also improves the conversion of phosphonitrile chloride trimer to the geminally substituted diphenyl derivative6 by the Friedel-Crafts procedure.7 The Friedel-Crafts reaction can be used also for the preparation of the geminally substituted... 

The (1,1-diphenyl) phosphonitrile fluoride trimer is a colorless crystalline solid that melts at 68.5-69.5°C. It can be recrystallized from n-pentane, n-heptane, petroleum ether, or absolute methanol. It is also soluble in diethyl ether, carbon disulfide, and chloroform, but it is insoluble in and not attacked by water. The infrared spectrum shows a strong phosphorus-nitrogen stretching mode at 1250-1265 cm."1. Strong bands at 914-920, 900-906 cm."1 and at 812-820 cm."1 are associated, respectively, with phosphorus-fluorine asymmetric and symmetric stretching modes. 

This operation must be conducted with proper care to avoid loss of the volatile phosphonitrile fluoride. 

Trimeric phosphonitrile fluoride is colorless, normally a liquid at room temperature. The boiling point is 50.9° at 760 mm. the triple point is 27.8° the solid density, d4° = 2.237. The vapor pressure is given by ... 

Trimeric phosphonitrile fluoride is much less susceptible to nucleophilic attack than the tetramer, as evidenced by the fact that the trimeric fluoride can be washed with water. It is believed that the P—N ring structure remains intact during aqueous hydrolysis, although a defined product has not been isolated. There is no indication of a reaction between (PNF2)s and anihne or piperidine, but while ammonia reacts, no well-defined product... 

Tetrameric phosphonitrile fluoride is a colorless liquid which crystallizes slightly above room temperature. The normal boiling point is 89.7° the triple point is 30.5°. The solid density at 20° is 2.239, an approximate value for the liquid densityis 1.7. The vapor pressure of liquid (PNF2) 4 is given by the equation ... 

Tetrakis(l,l,l-trifluoro-2,4-pentanedionato)zirconium and (hafnium), S3mthesis 14 Fluorophosphoranes, synthesis 18 Phenyldibromophosphine, synthesis 19 Phosphonitrile fluorides, synthesis 20... 

The phosphonitrilic fluorides do not result from the interaction of ammonium fluoride with phosphorus pentachloride ammonium hexa-fluorophosphate is formed instead (47). They may be prepared indi-j ectly by the reaction of potassium fluorosulfite with the chlorides at 100°-120° (75),... 

The phosphonitrilic fluorides (PNF2)3,4 may also be hydrolyzed to the corresponding acids (75), apparently more readily than the chlorides (D. R. Smith, 2), the trimer in each case being more resistant to attack. 

The shortness and equality of the P-N bonds in the trimeric and in the tetrameric chloride have been demonstrated in Section IV,B. The thermochemical evidence for a bond order greater than unity in the trimeric chloride is confirmed by the high value of the observed P-N stretching frequency, which is maintained or even increased as the series is ascended. The effect of mass on ring vibration frequencies is not large m, 25), so that the higher and lower infra-red absorption frequencies characteristic of the phosphonitrilic fluorides and bromides, respectively, are indications of their relative bond strengths, and are consistent with the aromatic theory. 

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