Trimeric and Tetrameric Phosphonitrile Bromides

The phosphonitrile bromides were first obtained by the ammonolysis of phosphorus(V) bromide. Reported prepa- University of Illinois, Urbana, 111. 

The trimer and tetramer are best separated by fractional crystalhzation from anhydrous f n-heptane or petroleum ether (b.p., 90 to 100°). The mixture is dissolved in sufficient hot solvent to yield a nearly saturated solution. The solution is cooled slowly as long as the characteristic flat prismatic crystals of the trimer continue to form but not until the needle-like crystals of the tetramer form. The remaining mother liquor is then removed by decantation, and the procedure is repeated with the decantate until about 70 to 75% of the trimer is recovered. Further crystallization from more dilute solutions then yields the tetramer. Both trimer and tetramer are purified by recrystallization from the same solvent, using activated charcoal to remove traces of color. The total recovery of separated trimer and tetramer depends upon how far the fractionation is carried but should amount to 90 to 95% of the original trimer-tetramer mixture. Anal. Calcd. for (PNBr2)3 or (PNBr2)4 N, 6.84. Found N, 6.87. 

Pure trimeric and tetramericphosphonitrile bromides melt at 192° and 202°, respectively. Both compounds dissolve in a variety of organic solvents, but the trimer is the more soluble. Thus, solubilities in anhydrous n-heptane and petroleum ether (b.p., 90 to 110°) at 25° are, respectively, trimer, 1.45 g. and 2.30 g., and tetramer, 0.15 g. and 0.27 g., each per 100 g. of solvent. The pure compounds hydrolyze slowly in contact with water or moist air. The infrared spectra are characterized by P-N stretching frequencies of 1175 cm. for the trimer and 1272 cm. for the tetramer. 

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Barium iodate 1-hydrate, synthesis 4 Indium(I) bromide, synthesis 6 Hexachlorodisiloxane, synthesis 7 Trichlorosilanethiol, synthesis 8 Tris(acetylacetonato)silicon chloride, synthesis 9 Titanium(III)chloride, synthesis 11 Bis[tris(acetylacetonato)titanium(IV)] hexachloro-titanate(IV), synthesis 12 Zirconium(IV) iodide, synthesis 13 (Triphenyl) aminophosphonium chloride, synthesis 19 (Dimethylamido)phosphoryl dichloride, synthesis 20 Bis(dimethylamido)phosphoryl chloride, synthesis 21 Trimeric and tetrameric phosphonitrilic bromides, synthesis 23 Phosphorus(V) chloride-boron trichloride complex, synthesis 24... 

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