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Phosphorus sulfides comprise a family of inorganic compounds containing only phosphorus and sulfur. These compounds have the formula P₄S_n with n ≤ 10. Two are of commercial significance, phosphorus pentasulfide (P₄S₁₀), which is made on a kiloton scale for the production of other organosulfur compounds, and phosphorus sesquisulfide (P₄S₃), used in the production of "strike anywhere matches".

There are several other phosphorus sulfides in addition to P₄S₃ and P₄S₁₀. Six of these phosphorus sulfides exist as isomers: P₄S₄, P₄S₅, P₄S₆, P₄S₇, P₄S₈, and P₄S₉. These isomers are distinguished by Greek letter prefixes. The prefix is based on the order of the discovery of the isomers, not their structure. All known molecular phosphorus sulfides contain a tetrahedral array of four phosphorus atoms. P₄S₂ is also known but is unstable above −30 °C.

Phosphorus monosulfide monomer, PS, is highly unstable and only exists at elevated temperatures. Its bond, worth about 55 kcal/mol, is about 2.4 angstroms long.

Preparation

The main method for preparing these compounds is thermolysis of mixtures of phosphorus and sulfur. The product distributions can be analyzed by P-NMR spectroscopy. More selective syntheses entail:

• desulfurization, e.g. using triphenylphosphine and, complementarily,
• sulfidation using triphenylarsine sulfide.

P₄S₃

Phosphorus sesquisulfide is prepared by treating red phosphorus with sulfur above 450 K, followed by careful recrystallization with carbon disulfide and benzene. An alternative method involves the controlled fusion of white phosphorus with sulfur in an inert, non-flammable solvent.

P₄S₄

The α- and β- forms of P₄S₄ can be prepared by treating the corresponding isomers of P₄S₃I₂ with ((CH₃)₃Sn)₂S:

P₄S₃I₂ can be synthesized by the reaction of stoichiometric amounts of phosphorus, sulfur, and iodine.

P₄S₅

P₄S₅ can be prepared by treating stoichiometric amounts of P₄S₃ with sulfur in carbon disulfide solution, in the presence of light and a catalytic amount of iodine. The respective product distribution is then analyzed by using P-NMR spectroscopy.

In particular, α-P₄S₅ can be easily made by the photochemical reaction of P₄S₁₀ with red phosphorus. Note that P₄S₅ is unstable when heated, tending to disproportionate to P₄S₃ and P₄S₇ before reaching its melting point.

P₄S₆

P₄S₆ can be made by abstracting a sulfur atom from P₄S₇ using triphenylphosphine:

P₄S₇ + Ph₃P → P₄S₆ + Ph₃PS

Treating α-P₄S₅ with Ph₃AsS in CS₂ also yields α-P₄S₆. The two new polymorphs δ-P₄S₆ and ε-P₄S₆ can be made by treating α-P₄S₄ with Ph₃SbS in CS₂.

P₄S₇

P₄S₇ is most conveniently made by direct union of the corresponding elements, and is one of the most easily purified binary phosphorus sulfides.

P₄ + 7 S → P₄S₇

P₄S₈

β-P₄S₈ can be made by treating α-P₄S₇ with Ph₃AsS in CS₂, which yields a mixture between α-P₄S₇ and β-P₄S₈.

P₄S₉

P₄S₉ can be made by two methods. One method involves the heating of P₄S₃ in excess sulfur. Another method involves the heating of P₄S₇ and P₄S₁₀ in 1:2 mole ratio, where P₄S₉ is reversibly formed:

P₄S₇ + 2 P₄S₁₀ ⇌ 3 P₄S₉

P₄S₁₀

P₄S₁₀ is one of the most stable phosphorus sulfides. It is most easily made by heating white phosphorus with sulfur above 570 K in an evacuated tube.

P₄ + 10 S → P₄S₁₀

See also

• Diphosphorus trisulfide (P₂S₃)

References

1. Jason, M. E.; Ngo, T.; Rahman, S. (1997). "Products and Mechanisms in the Oxidation of Phosphorus by Sulfur at Low Temperature". Inorg. Chem. 36 (12): 2633–2640. doi:10.1021/ic9614879.
2. Holleman, A. F.; Wiberg, E. Inorganic Chemistry. Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
3. Heal, H. G. The Inorganic Heterocyclic Chemistry of Sulfur, Nitrogen, and Phosphorus Academic Press: London; 1980 ISBN 0-12-335680-6.
4. Almasi, Lucreţia (1971). "The Sulfur–Phosphorus Bond". In Senning, Alexander (ed.). Sulfur in Organic and Inorganic Chemistry. Vol. 1. New York: Marcel Dekker. p. 43. ISBN 0-8247-1615-9. LCCN 70-154612.
5. ^ Jason, M. E. (1997). "Transfer of Sulfur from Arsenic and Antimony Sulfides to Phosphorus Sulfides. Rational Syntheses of Several Less-Common P₄S_n Species". Inorg. Chem. 36 (12): 2641–2646. doi:10.1021/ic9614881.
6. Nowottnick, H.; Blachnik, R. (1999). "Zwei neue Phosphorsulfide (Two New Phosphorus Sulfides)". Zeitschrift für anorganische und allgemeine Chemie. 625 (12): 1966–1968. doi:10.1002/(SICI)1521-3749(199912)625:12<1966::AID-ZAAC1966>3.0.CO;2-B.
7. ^ Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 15: The group 15 elements". Inorganic Chemistry, 3rd Edition. Pearson. p. 484. ISBN 978-0-13-175553-6.
8. "Phosphorus trisulfide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 563.
9. "Phosphorus pentasulfide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 565.
10. A. Earnshaw; Norman Greenwood (2002). "Phosphorus". Chemistry of the elements, 2nd edition. Butterworth Heinemann. p. 508. ISBN 0750633654.
11. ^ R. Bruce King (2005). "Phosphorus". Encyclopedia of Inorganic Chemistry, 2nd edition. Wiley. p. 3711. ISBN 9780470862100.
12. "Phosphorus heptasulfide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 566.
13. "Diphosphorus pentasulfide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 567.

• Inorganic phosphorus compounds
• Sulfides