Sulfur dichloride

Sulfur dichloride
IUPAC name Sulpur dichloride Sulfur(II) chloride Dichlorosulfane
Other names Sulpur chloride
Identifiers
CAS number	10545-99-0 Y
EC number	234-129-0
UN number	1828
RTECS number	WS4500000
Jmol-3D images	Image 1
SMILES ClSCl
Properties
Molecular formula	SCl2
Molar mass	102.97 g mol−1
Appearance	red liquid with pungent odour
Density	1.621 g cm−3, liquid
Melting point	−121.0 °C, 152.2 K, -185.8 °F
Boiling point	59 °C, 332 K, 138 °F (decomp.)
Solubility in water	hydrolysis
Refractive index (nD)	1.5570
Structure
Coordination geometry	C2v
Molecular shape	Bent
Hazards
MSDS	ICSC 1661
EU Index	016-013-00-X
EU classification	Corrosive (C) Irritant (Xi) Dangerous for the environment (N)
R-phrases	R14, R34, R37, R50
S-phrases	(S1/2), S26, S45, S61
NFPA 704	1 3 2 W
Autoignition temperature	234 °C
Related compounds
Related	Disulfur dichloride Thionyl chloride Sulfuryl chloride
Related compounds	Sulfur tetrafluoride Sulfur hexafluoride Disulfur dibromide
Y dichloride (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sulfur dichloride is the chemical compound with the formula SCl₂. This cherry-red liquid is the simplest sulfur chloride and one of the most common. It is used as a precursor to organosulfur compounds.^[1]

Chlorination of sulfur

SCl₂ is produced by the chlorination of either elemental sulfur or disulfur dichloride. The process occurs in a series of steps, some of which are:

S₈ + 4 Cl₂ → 4 S₂Cl₂; ΔH = −58.2 kJ/mol

S₂Cl₂ + Cl₂ → 2 SCl₂; ΔH = −40.6 kJ/mol

The addition of Cl₂ to S₂Cl₂ has been proposed to proceed via a mixed valence intermediate Cl₃S-SCl. SCl₂ undergoes even further chlorination to give SCl₄, but this species is unstable at near room temperature. It is likely that several S_xCl₂ exist where x > 2.

Disulfur dichloride, S₂Cl₂, is the most common impurity in SCl₂. Separation of SCl₂ from S₂Cl₂ is possible via distillation with PCl₃ to form an azeotrope of 99% purity

Use of SCl₂ in chemical synthesis

• SCl₂ is used in organic synthesis. It adds to alkenes to give chloride-substituted thioethers. Illustrative applications are its addition to 1,5-cyclooctadiene to give a bicyclic thioether^[2] and ethylene to give sulfur mustard S(CH₂CH₂Cl)₂.^[3]

SCl₂ is also a precursor to several inorganic sulfur compounds. Treatment with fluoride salts gives SF₄. Reaction with ammonia affords sulfur nitrides related to S₄N₄. With H₂S, SCl₂ reacts to give "lower" sulfanes such as S₃H₂.

Safety considerations

SCl₂ hydrolyzes with release of HCl. Old samples contain Cl₂.

References

1. ^ Schmidt, M.; Siebert, W. "Sulphur" Comprehensive Inorganic Chemistry Vol. 2, ed. A.F. Trotman-Dickenson. 1973.
2. ^ Bishop, Roger (1992), "9-Thiabicyclo[3.3.1]nonane-2,6-dione", Org. Synth. 70: 120, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv9p0692 ; Coll. Vol. 9: 692 
3. ^ R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0 471 95512 4.