Phosphonitrilic bromides

A series of phosphonitrilic bromides, (PNBr2) , analogous with the phosphonitrilic chlorides, have been made by the action of ammonia on phosphorus penta-bromide. The phosphonitrilic bromide, (PNBr2)3, forms colourless rhombohedral crystals which melt at 188°-190°, and are insoluble in water. A. Besson obtained white crystals of the phosphorus dibromonitride, (PBr2N) , or triphosphonitrilic bromide, in a somewhat similar manner to that employed for the corresponding chloride. The crystals melt at 188°-190°, and sublime in vacuo at 150°. This compound is insoluble in water, fairly soluble in ether, and less soluble in carbon disulphide and chloroform. 

A comparable preparative method can be usea for the phosphonitrilic bromides and chlorobromides. The trimeric and tetrameric. bromides (PNBr2)3,i may be prepared by the action of ammonia 6) or of ammonium bromide 8) on phosphorus pentabromide, though the dissociation of the latter at any convenient reaction temperature reduces the yield considerably, and the two polymers are difficult to separate. The mono-bromo-compound PaNaCIgBr, from ammonium bromide and phosphorus pentachloride, is the first derivative in which the chlorine atoms are substituted other than in pairs (64)- The dibromo and tetrabromo derivatives were obtained in the same investigation, by the use of phosphorus chlorobromides. 

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

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... 

PNBr2-PBr Phosphonitrile bromide compound, with phosphorus (V) bromide, 7 77 (PNBr2)3 Phosphonitrile bromide, trimeric, 7 76... 

Phosphonitrilic bromides (n =3, 4), discovered by Besson, are obtained, according to Grlmme, from a solution of PBrg in tetrachloroethene by reaction with NH Br ... 

Bromophosphazenes (phosphonitrilic bromides) are made by an analogous reaction to Equation 7.320 using appropriate bromine compounds. The fluorides can be made by treating the chlorides with potassium fluorosulphite (7.323). Cyclic fluorides exist up to at least (PNFj) and other halides up to the decamer and beyond, can be isolated. 

Partial ammonolysis of phosphorus(V) chloride or bromide and of monoalkyl- or -aryl-substituted dichloro- or dibromophos-phines in the presence of chlorine or bromine is a general method for the synthesis, respectively, of the corresponding simple or substituted phosphonitrile halides. " This type of reaction may yield either cyclic or linear poljuners, depending upon the temperature, solvent, reaction time, and/or reagent ratio. 

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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