Phosphonitrile bromide, compound

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

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. 

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. 

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