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Nitrides

The PN molecule is considered unstable, but is a product of crystalline phosphorus nitride decomposition at 1100 K. Similarly, H PN is considered unstable, and phosphorus nitride halogens like F PN, Cl PN, Br PN, and I PN oligomerise into cyclic polyphosphazenes. For example, compounds of the formula (PNCl) exist mainly as rings such as the trimer hexachlorophosphazene. The phosphazenes arise by treatment of phosphorus pentachloride with ammonium chloride:

PCl + NH Cl → 1/ n (NPCl) + 4 HCl

When the chloride groups are replaced by alkoxide (RO), a family of polymers is produced with potentially useful properties.