Trimeric phosphonitrile fluoride

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. 

Phosphorus pentafluoride forms addition complexes with pyridine, pyrazine and ammonia. The latter is best made from phosphonitrilic fluoride trimer which gives a 40% yield according to... 

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... 

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. 

Both phosphonitrilic fluorides are solid, colorless, volatile substances at room temperature. They are thermally stable up to 300°C. The trimer boils at 51.8°C and crystallizes in monoclinic prisms. Triple point 27.1°C. It polymerizes to a rubbery form Iqr heating for 15 hours at 350°C. The tetramer boils at 89.7°C and forms triclinic-pinacoidal crystals. Triple point 30.4°C. 

Pentafluorobenzalddiyde reacts with bistrifluoromethyl nitroxide (see also p. 414) to give the amino-oxy-compound C6Fs CX>2-N(CF3)s, with the monohydrazide of cyclic trimeric phosphonitrile fluoride to give the hydrazone (117), and with ethyl acetoacetate and ammonia to give the expected dihydropyridine derivative (118). (Pfcntajauorophenyl)acetaldehyde is obtained in excellent yield from 2-(pentafluoropheny])ethanol and sodium dichromate in dimethyl sulphoxide the solvent may prevent further oxidation of the aldehyde. ... 

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