- Selenium monochloride
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Selenium monochloride Selenium monochlorideOther namesDichlorodiselenide, Diselenium dichloride, Selenium chloride, 1,2-dichlorodiselaneIdentifiers CAS number 10025-68-0 
Properties Molecular formula Se2Cl2 Molar mass 228.83 g/mol Appearance Reddish-brown oily liquid Density 2.7741 g/cm3 Melting point -85 °C (223.15 K)
Boiling point 127 °C at 0.997 atm (400.15 K at 0.997 atm)
Solubility in water insoluble; sol in CHCl3, CS2, MeCN Solubility Soluble in dry chloroform and carbon disulfide Hazards R-phrases 23/24/25-34 S-phrases 22-26-36/37/39-45 
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)Infobox references Selenium monochloride is an inorganic compound with the formula Se2Cl2. Although it is called selenium monochloride, a more descriptive name might be diselenium dichloride. It is a reddish-brown, oily liquid that is hydrolyses slowly. It exists in chemical equilibrium with SeCl2, SeCl4, chlorine, and elemental selenium.[1] Selenium monochloride is mainly used as a reagent for the synthesis of Se-containing compounds.
Contents
Structure and properties
Selenium monochloride exhibits C2 molecular symmetry, similar to hydrogen peroxide. The bond length of the Se-Se bond is predicted to be 2.253 Å and the Se-Cl bonds are both 2.227 Å.[2]
In acetonitrile solutions, it exists in equilibrium with SeCl2 and SeCl4.[3]
Preparation
Selenium monochloride was originally produced by the chlorination of selenium.[4] An improved method involves the reaction of a mixture of selenium, selenium dioxide, and hydrochloric acid:[5]
- 3 Se + SeO2 + 4 HCl → 2 Se2Cl2 + H2O
A dense layer of selenium monochloride settles from the reaction mixture, which can be purified by dissolving it in fuming sulfuric acid and reprecipitating it with hydrochloric acid. A second method for the synthesis involves the reaction of selenium with oleum and hydrochloric acid:[5]
- 2 Se + 2 SO3 + 3 HCl → Se2Cl2 + H2SO3 + SO2(OH)Cl
The crude selenium monochloride product is collected via distillation.
Reactions
Selenium monochloride is an electrophilic selenizing agent, and thus it reacts with simple alkenes to give bis(β-chloroalkyl)selenide and bis(chloroalkyl)selenium dichloride.[6] It converts hydrazones of hindered ketones into the corresponding selones, the structural analogs of ketones whereby the oxygen atom is replaced with a selenium atom.[6] Finally, the compound has been used to introduce bridging selenium ligands between the metal atoms of some iron and chromium carbonyl complexes.[6]
References
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419.
- ^ Prascher, Brian P.; Wilson, Angela K. A Computational Study of Dihalogen-μ-Dichalcogenides: XAAX (X = F, Cl, Br; A = S, Se). Journal of Molecular Structure. 2007, 814, 1-10.doi:10.1016/j.theochem.2007.02.040
- ^ Marc Lamoureux and John Milne "Selenium chloride and bromide equilibria in aprotic solvents; a 77Se NMR study" Polyhedron 1990, Volume 9, pp. 589-595. doi:10.1016/S0277-5387(00)86238-5
- ^ J. J. Berzelius, Annales de chimie et de physique 1818, vol. 9, 225. See also Kao, C. H.; Lenher, V. The Preparation of Selenium Monochloride and Monobromide, J. Am. Chem. Soc., 1925, 48, 772-774. doi:10.1021/ja01680a025
- ^ a b Fehér, F. "Diselenium Dichloride". In Handbook of Preparative Inorganic Chemistry; Brauer, G., Ed.; Academic Press: New York, 1963; Vol. 1; p 422-433.
- ^ a b c Back, Thomas G.; Moussa, Ziad "Diselenium Dichloride" Encyclopedia of Reagents for Organic Synthesis 2003 doi:10.1002/047084289X.rn00201
Selenium compounds Categories:- Selenium compounds
- Inorganic chlorine compounds
- Chalcohalides
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