Hexachlorophosphazene

Hexachlorophosphazene
IUPAC name

Hexachlorotriphosphazene
Other names

Triphosphonitrilic chloride
Phosphonitrilic chloride, Hexachlorocyclotriphosphazene
2,2,4,4,6,6-hexachloro-2,2,4,4,6,6-
hexahydro-1,3,5,2,4,6-Triazatriphosphorine
Identifiers
CAS number 940-71-6 Y
PubChem 220225
ChemSpider 190959 Y
Jmol-3D images Image 1
Properties
Molecular formula N3Cl6P3
Molar mass 347.66 g/mol
Appearance colorless crystals
Density 1.98 g/mL at 25 °C
Melting point

112–15 °C
Boiling point

decomp.
Solubility in water decomp.
Solubility in chlorocarbons soluble
Structure
Dipole moment 0 D
Hazards
EU Index Not listed
Main hazards mild irritant
Flash point Non-flammable
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Hexachlorophosphazene is an inorganic compound with the formula (NPCl2)3. The molecule has a cyclic backbone consisting of alternating phosphorus and nitrogen atoms. It can be viewed as a trimer of the hypothetical compound N≡PCl2. Hexachlorophosphazene together with the related (NPCl2)4 are precursors to inorganic polymers called polyphosphazenes.

Contents

Synthesis

The reaction of PCl5 and NH4Cl affords substances with the empirical formula PNCl2:[1] Purification by sublimation gives mainly the trimer (PNCl2)3 and tetramer (PNCl2)4. These rings were described by Liebig in 1832[2][3] in his study of the reaction of PCl5 and NH3:

PCl5 + NH4Cl → 1/n (NPCl2)n + 4 HCl

Typically reactions are conducted in chlorobenzene solution.

Inorganic rings

Chemists have long known of rings containing carbon, e.g. benzene, pyridine, and cyclohexane. Related cyclic compounds lacking in carbon have also been studied. Hexachlorophosphazene is one such inorganic ring. Other well known inorganic rings include borazine, S4N4, and the cyclic siloxanes.

"Inorganic rubber"

Hexachlorophosphazene is a precursor to poly(dichlorophosphazene) or "inorganic rubber", whose discovery is attributed to H. N. Stokes in 1896.[2][4][5] Upon heating to ca. 250 °C, the trimer undergoes ring-opening polymerization to give the linear polymer (PNCl2)n. Subsequent replacement of the chloride centers by other groups, especially alkoxides, yields many polyphosphazenes, some with commercial uses.

See also

References

  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ a b c H. N. Stokes (1895), On the chloronitrides of phosphorus. American Chemical Journal, vol. 17, p. 275.
  3. ^ Liebig-Wöhler, Briefwechsel vol. 1, 63; Ann. Chem. (Liebig), vol. 11 (1834), 146.
  4. ^ H. N. Stokes (1896), On Trimetaphosphimic acid and its decomposition products. American Chemical Journal, vol. 18 issue 8, p. 629.
  5. ^ Mark, J. E.; Allcock, H. R.; West, R. “Inorganic Polymers” Prentice Hall, Englewood, NJ: 1992. ISBN 0-13-465881-7.