Phosphorus pentasulfide

Phosphorus decasulfide

Names
Other names phosphorus sulfide sulfur phosphide phosphorus persulfide diphosphorus pentasulfide tetraphosphorus decasulfide phosphorus decasulfide
Identifiers
CAS Number	1314-80-3 Y
PubChem	14817
RTECS number	TH4375000
Properties
Chemical formula	P4S10
Molar mass	444.555 g mol
Appearance	greenish-gray to yellow solid[1]
Odor	rotten eggs[1]
Density	2.09 g/cm3
Melting point	288 °C (550 °F; 561 K)
Boiling point	514 °C (957 °F; 787 K)
Solubility in water	hydrolyses
Solubility in other solvents	0.222 g / 100g CS2 (at 17 °C) Insoluble in C6H6 Insoluble in hot xylene Insoluble in hot anisole.
Vapor pressure	1 mmHg (300°C)[1]
Structure
Crystal structure	triclinic, aP28
Space group	P-1, No. 2
Point group	Td
Hazards
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	389 mg/kg (oral, rat)[2]
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 1 mg/m3[1]
REL (Recommended)	TWA 1 mg/m3 ST 3 mg/m3[1]
IDLH (Immediate danger	250 mg/m3[1]
Related compounds
Related compounds	P4S3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Phosphorus pentasulfide is the inorganic compound with the formula P₄S₁₀. This yellow solid is the one of two phosphorus sulfides of commercial value. Samples often appear greenish-gray due to impurities.

Structure and synthesis

Its tetrahedral molecular structure is similar to that of adamantane and is almost identical to the structure of phosphorus pentoxide.^[3]

Phosphorus pentasulfide is obtained by the reaction of liquid white phosphorus (P₄) with sulfur above 300 °C. The first synthesis of P₄S₁₀ by Berzelius in 1843 ^[4][5] was by this method. Alternatively, P₄S₁₀ can be formed by reacting elemental sulfur or pyrite, FeS₂, with ferrophosphorus, a crude form of Fe₂P (a byproduct of P₄ production from phosphate rock):

4 Fe₂P + 18 S → P₄S₁₀ + 8 FeS

4 Fe₂P + 18 FeS₂ + heat → P₄S₁₀ + 26 FeS

Applications

Approximately 150,000 tons of P₄S₁₀ are produced annually. The compound is mainly converted to other derivatives for use as lubrication additives such zinc dithiophosphates. It is also used in the production of pesticides such as Parathion and Malathion.^[6] It is also a component of some amorphous solid electrolytes (e.g. Li₂S-P₂S₅) for some types of lithium batteries.

Phosphorus pentasulfide is a dual-use material, for the production of early insecticides such as Amiton and also for the manufacture of the related VX nerve agents.

Reactivity

Due to hydrolysis by atmospheric moisture, P₄S₁₀ evolves H₂S, thus P₄S₁₀ is associated with a rotten egg odour. Aside from H₂S, hydrolysis of P₄S₁₀ gives phosphoric acid:

P₄S₁₀ + 16 H₂O → 4 H₃PO₄ + 10 H₂S

Other mild nucleophiles react with P₄S₁₀, including alcohols and amines. Aromatic compounds such as anisole, ferrocene and 1-methoxynaphthalene react to form 1,3,2,4-dithiadiphosphetane 2,4-disulfides such as Lawesson's reagent.

In organic chemistry P₄S₁₀ is used as a thionation reagent. Reactions of this type require refluxing solvents such as benzene, dioxane or acetonitrile with P₄S₁₀ dissociating into P₂S₅. P₂S₅ can be trapped for example as the pyridine complex. Ketones are converted to thioketones. In esters, imides and lactones the oxygen atom can also be replaced by sulfur. With amides the reaction product is a thioamide. With 1,4-diketones the reagent forms a thiophene. Compared to the better known Lawesson's reagent P₄S₁₀ suffers from reduced yields.^[7]

References