Sulfur dichloride

Sulfur dichloride
IUPAC name	Sulfur dichloride Sulfur(II) chloride Dichlorosulfane
Other names	Sulfur chloride
Identifiers
CAS number	[10545-99-0]
EC number	234-129-0
UN number	1828
RTECS number	WS4500000
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 (152.15 K)
Boiling point	59 °C (332.15 K) (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
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