Chemistry:Selenium monochloride
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| IUPAC name
Diselenium dichloride
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Other names
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3D model (JSmol)
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| Properties | |
| Se 2Cl 2 | |
| Molar mass | 228.84 g·mol−1 |
| Appearance | Reddish-brown oily liquid |
| Density | 2.7741 g/cm3 |
| Melting point | −85 °C (−121 °F; 188 K) |
| Boiling point | 127 °C (261 °F; 400 K) at 0.997 atm |
| insoluble | |
| Solubility in other solvents | Soluble in chloroform, carbon disulfide, and acetonitrile |
| −94.8·10−6 cm3/mol | |
| Hazards | |
| GHS pictograms |    
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| GHS Signal word | Danger |
| H301, H311, H314, H331, H373, H410 | |
| P260, P261, P264, P270, P271, P273, P280, P301+310, P301+330+331, P302+352, P303+361+353, P304+340, P305+351+338, P310, P311, P312, P314, P321, P322, P330, P361, P363, P391, P403+233, P405 | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is   ?)
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| Infobox references | |
Selenium monochloride or diselenium dichloride is an inorganic compound with the formula Se
2Cl
2. Although a common name for the compound is selenium monochloride, reflecting its empirical formula, IUPAC does not recommend that name, instead preferring the more descriptive diselenium dichloride.
Diselenium dichloride is a reddish-brown, oily liquid that hydrolyses slowly. It exists in chemical equilibrium with SeCl
2, SeCl
4, chlorine, and elemental selenium.[1] Diselenium dichloride is mainly used as a reagent for the synthesis of Se-containing compounds.
Structure and properties
Dielenium dichloride has the connectivity Cl–Se–Se–Cl. With a nonplanar structure, it has C2 molecular symmetry, similar to hydrogen peroxide and disulfur dichloride, which is referred to as gauche. The Se-Se bond length is 223 pm, and the Se-Cl bond lengths are 220 pm. The dihedral angle between the Cla
–Se–Se and Se–Se–Clb
planes is 87°.[2]
Preparation
Early routes to diselenium dichloride involved chlorination of elemental selenium.[3] An improved method involves the reaction of a mixture of selenium, selenium dioxide, and hydrochloric acid:[4]
- 3 Se + SeO
2 + 4 HCl → 2 Se
2Cl
2 + 2 H
2O
A dense layer of diselenium dichloride 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:[4]
The crude diselenium dichloride is removed via separatory funnel. Diselenium dichloride cannot be distilled without decomposition, even at reduced pressure.[4]
In acetonitrile solutions, it exists in equilibrium with SeCl
2 and SeCl
4.[5] Selenium dichloride degrades to diselenium dichloride after a few minutes at room temperature:[6]
- 3 SeCl
2 → Se
2Cl
2 + SeCl
4
Reactions
Diselenium dichloride is an electrophilic selenizing agent, and thus it reacts with simple alkenes to give bis(β-chloroalkyl)selenide and bis(chloroalkyl)selenium dichloride. It converts hydrazones of hindered ketones into the corresponding selenoketones, the structural analogs of ketones whereby the oxygen atom is replaced with a selenium atom.[7] Finally, the compound has been used to introduce bridging selenium ligands between the metal atoms of some iron and chromium carbonyl complexes.[7]
References
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ↑ Kniep, Rüdiger; Körte, Lutz; Mootz, Dietrich (1 January 1983). "Kristallstrukturen von Verbindungen A2X2 (A = S, Se; X = Cl, Br)". Zeitschrift für Naturforschung B 38 (1): 1–6. doi:10.1515/znb-1983-0102.
- ↑ Lenher, Victor; Kao, C. H. (1925). "The Preparation of Selenium Monochloride and Monobromide". Journal of the American Chemical Society 47 (3): 772–774. doi:10.1021/ja01680a025.
- ↑ 4.0 4.1 4.2 Fehér, F. "Diselenium Dichloride". In Handbook of Preparative Inorganic Chemistry; Brauer, G., Ed.; Academic Press: New York, 1963; Vol. 1; p 422-433.
- ↑ Lamoureux, Marc; Milne, John (1990). "Selenium chloride and bromide equilibria in aprotic solvents; a Se77 NMR study". Polyhedron 9 (4): 589–595. doi:10.1016/S0277-5387(00)86238-5.
- ↑ Maaninen, Arto; Chivers, Tristram; Parvez, Masood; Pietikäinen, Jarkko; Laitinen, Risto S. (1999). "Syntheses of THF Solutions of SeX2(X = Cl, Br) and a New Route to Selenium Sulfides SenS8−n(n = 1−5): X-ray Crystal Structures of SeCl2(tht)2 and SeCl2·tmtu". Inorganic Chemistry 38 (18): 4093–4097. doi:10.1021/ic981430h.
- ↑ 7.0 7.1 Back, Thomas G.; Moussa, Ziad (2003). "Encyclopedia of Reagents for Organic Synthesis". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn00201. ISBN 0-471-93623-5.
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