Sodium phosphide

Sodium phosphide is the inorganic compound with the formula Na3P. It is a black solid. It is often described as Na+ salt of the P3− anion.[2] Na3P is a source of the highly reactive phosphide anion. It should not be confused with sodium phosphate, Na3PO4.

Sodium phosphide
Other names
sodium phosphide, common
3D model (JSmol)
ECHA InfoCard 100.031.834 Edit this at Wikidata
EC Number
  • 235-031-0
  • InChI=1S/3Na.P/q3*+1;-3 checkY
  • InChI=1/3Na.P/q3*+1;-3
  • [Na+].[Na+].[Na+].[P-3]
Molar mass 99.943 g/mol
Appearance red crystals
Density 1.74 g/cm3
Melting point 650 °C (1,202 °F; 923 K)
Solubility insoluble in liquid CO2
a = 4.9512 Å
c = 8.7874 Å
around P 5 near neighbours, trigonal bipyramid [1]
Related compounds
Other anions
sodium chloride
sodium nitride
Other cations
aluminium phosphide
lithium phosphide
potassium phosphide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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In addition to Na3P, five other binary compositions of sodium and phosphorus are known: NaP, Na3P7, Na3P11, NaP7, and NaP15.[3]

Structure and PropertiesEdit

The compound crystallizes in a hexagonal motif, often called the sodium arsenide structure.[4] Like K3P, solid Na3P features pentacoordinate P centers.[1]


The first preparation of Na3P was first reported in the mid-19th century. French researcher, Alexandre Baudrimont prepared sodium phosphide by treating molten sodium with phosphorus pentachloride.[5]

8 Na(l) + PCl5 → 5 NaCl + Na3P

Many different routes to Na3P have been described. Due to its flammability and toxicity, Na3P (and related salts) is often prepared and used in situ. White phosphorus is reduced by sodium-potassium alloy:[6]

P4 + 12 Na → 4 Na3P

Phosphorus reacts with sodium in an autoclave at 150 °C for 5 hours to produce Na3P.[7]

Alternatively the reaction can be conducted at normal pressures but using a temperatures gradient to generate nonvolatile NaxP phases (x < 3) that then react further with sodium.[8] In some cases, an electron-transfer agent, such as naphthalene, is used. In such applications, the naphthalene forms the soluble sodium naphthalenide, which reduces the phosphorus.[9]


Sodium phosphide is a source of the highly reactive phosphide anion. The material is insoluble in all solvents but reacts as a slurry with acids and related electrophiles to give derivatives of the type PM3:[6]

Na3P + 3 E+ → E3P (E = H, Me3Si)

The trimethylsilyl derivative is volatile (b.p. 30-35 C @ 0.001 mm Hg) and soluble. It serves as a soluble equivalent to "P3−".

Indium phosphide, a semiconductor arises by treating in-situ generated "sodium phosphide" with indium(III) chloride in hot N,N’-dimethylformamide as solvent. In this process, the phosphide reagent is generated from sodium metal and white phosphorus, whereupon it immediately reacts with the indium salt:[10]

Na3P + InCl3 → InP + 3NaCl

Sodium phosphide is also employed commercially as a catalyst in conjunction with zinc phosphide and aluminium phosphide for polymer production. When Na3P is removed from the ternary catalyst polymerization of propylene and 4-methyl-1-pentene is not effective.[11][citation needed]

polymerization of propene


Sodium phosphide is highly dangerous releasing toxic phosphine upon hydrolysis, a process that is so exothermic that fires result. The USDOT has forbidden the transportation of Na3P on aircraft and trains due to the potential fire and toxic hazards.[12]


  1. ^ a b Dong, Y; Disalvo, F.J (2005). "Reinvestigation of Na3P based on single-crystal data". Acta Crystallographica Section E. 61 (11): i223–i224. doi:10.1107/S1600536805031168.
  2. ^ Yunle, G; Fan, G; Yiate, Q; Huagui, Z; Ziping, Y (2002). "A solvothermal synthesis of ultra-fine iron phosphide". Materials Research Bulletin. 37 (6): 1101–1106. doi:10.1016/S0025-5408(02)00749-3.
  3. ^ Inorganic Chemistry, Egon Wiberg, Arnold Frederick Holleman Elsevier 2001 ISBN 0-12-352651-5
  4. ^ Beister, H.J.; Syassen, K.; Klein, J."Phase transition of Na3As under pressure" Zeitschrift für Naturforschung B: Chemical Sciences 1990, volume 45, p1388-p1392. doi:10.1515/znb-1990-1007
  5. ^ Baudrimont (1864). Annales de chimie et de physique. 2: 13. {{cite journal}}: Missing or empty |title= (help)
  6. ^ a b Becker, Gerd; Schmidt, Helmut; Uhl, Gudrun (1990). Tris(trimethylsilyl)phosphine and Lithium Bis(Trimethylsilyl)Phosphide.Bis-(Tetrahydrofuran). Inorganic Syntheses. Vol. 27. pp. 243–249. doi:10.1002/9780470132586.ch48. ISBN 9780470132586.
  7. ^ Xie, Y; Su, H; Li, B; Qian, Y (2000). "Solvothermal preparation of tin phosphide nanorods". Materials Research Bulletin. 35 (5): 675–680. doi:10.1016/S0025-5408(00)00263-4.
  8. ^ Jarvis, R. F.; Jacubinas, R. M.; Kaner, R. B. (2000). "Self-Propagating Metathesis Routes to Metastable Group 4 Phosphides". Inorganic Chemistry. 39 (15): 3243–3246. doi:10.1021/ic000057m. PMID 11196860.
  9. ^ Peterson, D. J. 1967. US Patent No. 3,397,039.
  10. ^ Khanna, P.K; Eum, M.-S; Jun, K.-W; Baeg, J.-O; Seok, S. I (2003). "A novel synthesis of indium phosphide nanoparticles". Materials Letters. 57 (30): 4617–4621. doi:10.1016/S0167-577X(03)00371-9.
  11. ^ Atarashi, Y.; Fukumoto, O. Japanese Patent No. JP 42,006,269.
  12. ^ Kenneth L Barbalace. "Sodium phosphide". Chemical Database.