Triphosphorus pentanitride

Source: Wikipedia, the free encyclopedia.
Triphosphorus pentanitride
Names
IUPAC name
Triphosphorus pentanitride
Other names
Phosphorus(V) nitride, Phosphorus nitride
Identifiers
3D model (
JSmol
)
ECHA InfoCard
 100.032.018 Edit this at Wikidata
EC Number
  • 235-233-9
  • [N].[N].[N].[N].[N].[P].[P].[P]
Properties
P3N5
Molar mass 162.955 g/mol
Appearance White solid
Density 2.77 g/cm3 (α-P3N5)
Melting point 850 °C (1,560 °F; 1,120 K) decomposes
insoluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Triphosphorus pentanitride is an

binary nitride
. While it has been investigated for various applications this has not led to any significant industrial uses. It is a white solid, although samples often appear colored owing to impurities.

Synthesis

Triphosphorus pentanitride can be produced by reactions between various phosphorus(V) and nitrogen anions (such as ammonia and sodium azide):[1]

3 PCl5 + 5 NH3 → P3N5 + 15 HCl
3 PCl5 + 15 NaN3 → P3N5 + 15 NaCl + 20 N2

The reaction of the elements is claimed to produce a related material.

amorphous.[1][3]

hexachlorocyclotriphosphazene[4] or phosphorus pentachloride.[1]

(NPCl2)3 + 2 [NH4]Cl → P3N5 + 8 HCl
3 PCl5 + 5 [NH4]Cl → P3N5 + 20 HCl

P3N5 has also been prepared at room temperature, by a reaction between phosphorus trichloride and sodium amide.[5]

3 PCl3 + 5 NaNH2 → P3N5 + 5 NaCl + 4 HCl + 3 H2

Reactions

P3N5 is thermally less stable than either

decomposition to the elements occurring at temperatures above 850 °C:[1]

P3N5 → 3 PN + N2
4 PN → P4 + 2 N2

It is resistant to weak acids and bases, and insoluble in water at room temperature, however it

[NH4]H2PO4
.

Triphosphorus pentanitride reacts with

solid electrolytes and pigments.[6]

Structure and properties

Several

polymorphs are known for triphosphorus pentanitride. The alpha‑form of triphosphorus pentanitride (α‑P3N5) is encountered at atmospheric pressure and exists at pressures up to 11 GPa, at which point it converts to the gamma‑variety (γ‑P3N5) of the compound.[7][8] Upon heating γ‑P3N5 to temperatures above 2000 K at pressures between 67 and 70 GPa, it transforms into δ-P3N5.[9] The release of pressure on the δ-P3N5 polymorph does not revert it back into γ‑P3N5 or α‑P3N5. Instead, at pressures below 7 GPa, δ-P3N5 converts into a fourth form of triphosphorus pentanitride, α′‑P3N5.[9]

Polymorph Density (g/cm3)
α‑P3N5 2.77
α′‑P3N5 3.11
γ‑P3N5 3.65
δ‑P3N5 5.27 (at 72 GPa)

The structure of all polymorphs of triphosphorus pentanitride was determined by

X-ray diffraction. α‑P3N5 and α′‑P3N5 are formed of a network structure of PN4 tetrahedra with 2- and 3-coordinated nitrides,[7][9] γ‑P3N5 is composed of both PN4 and PN5 polyhedra[8] while δ-P3N5 is composed exclusively of corner- and edge-sharing PN6 octahedra.[9] δ-P3N5 is the most incompressible triphosphorus pentanitride, having a bulk modulus of 313 GPa.[9]

Potential applications

Triphosphorus pentanitride has no commercial applications, although it found use as a

red phosphorus in the late 1960s. The lighting filaments are dipped into a suspension
of P3N5 prior to being sealed into the bulb. After bulb closure, but while still on the pump, the lamps are lit, causing the P3N5 to thermally decompose into its constituent elements. Much of this is removed by the pump but enough P4 vapor remains to react with any residual oxygen inside the bulb. Once the vapor pressure of P4 is low enough, either filler gas is admitted to the bulb prior to sealing off or, if a vacuum atmosphere is desired, the bulb is sealed off at that point. The high decomposition temperature of P3N5 allows sealing machines to run faster and hotter than was possible using red phosphorus.

Related halogen containing cyclic polymers, trimeric hexabromophosphazene (PNBr2)3 (melting point 192 °C) and tetrameric octabromophosphazene (PNBr2)4 (melting point 202 °C) find similar lamp gettering applications for tungsten halogen lamps, where they perform the dual processies of gettering and precise halogen dosing.[10]

Triphosphorus pentanitride has also been investigated as a

metal-insulator-semiconductor devices.[11][12]

As a fuel in pyrotechnic obscurant mixtures, it offers some benefits over the more commonly used red phosphorus, owing mainly to its higher chemical stability. Unlike red phosphorus, P3N5 can be safely mixed with strong oxidizers, even potassium chlorate. While these mixtures can burn up to 200 times faster than state-of-the-art red phosphorus mixtures, they are far less sensitive to shock and friction. Additionally, P3N5 is much more resistant to hydrolysis than red phosphorus, giving pyrotechnic mixtures based on it greater stability under long-term storage.[13]

Patents have been filed for the use of triphosphorus pentanitride in fire fighting measures.[14][15]

See also

References

  1. ^
    doi:10.1002/anie.199308061
    .
  2. doi:10.1080/01418638108222114
    .
  3. doi:10.1246/cl.2000.1252
    .
  4. doi:10.1021/cm950385y
    .
  5. doi:10.1016/j.inoche.2004.03.009
    .
  6. doi:10.1080/10426509308032389
    .
  7. ^
    doi:10.1002/anie.199718731
    .
  8. ^
    doi:10.1002/1521-3773(20010716)40:14<2643::AID-ANIE2643>3.0.CO;2-T
    .
  9. ^
    S2CID 251743071
    .
  10. ISBN 0 7131 3267 1
  11. doi:10.1063/1.331380
    .
  12. S2CID 67837168
    .
  13. PMID 27862760
  14. ^ Phosphorus nitride agents to protect against fires and explosions
  15. ^ Manufacture of flame-retardant regenerated cellulose fibres, December 20, 1977
Retrieved from "https://en.wikipedia.org/w/index.php?title=Triphosphorus_pentanitride&oldid=1218742904"