Diselenium dichloride
Names
IUPAC name
Diselenium dichloride
Other names
  • 1,2-Dichlorodiselane
  • Dichlorodiselane
  • Dichlorodiselenide
  • Selenium chloride
  • Selenium monochloride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.022
EC Number
  • 233-037-8
UNII
  • InChI=1S/Cl2Se2/c1-3-4-2 ☒N
    Key: VIEXQFHKRAHTQS-UHFFFAOYSA-N ☒N
  • InChI=1/Cl2Se2/c1-3-4-2
    Key: VIEXQFHKRAHTQS-UHFFFAOYAC
  • Cl[Se][Se]Cl
Properties
Se2Cl2
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 labelling:
GHS05: CorrosiveGHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Danger
H301, H311, H314, H331, H373, H410
P260, P261, P264, P270, P271, P273, P280, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P311, P312, P314, P321, P322, P330, P361, P363, P391, P403+P233, P405, P501
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

Selenium monochloride or diselenium dichloride is an inorganic compound with the formula Se2Cl2. 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 SeCl2, SeCl4, 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 + SeO2 + 4 HCl → 2 Se2Cl2 + 2 H2O

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]

2 Se + 2 SO3 + 3 HCl → Se2Cl2 + SO2 + H2O + SO2(OH)Cl

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 SeCl2 and SeCl4.[5] Selenium dichloride degrades to diselenium dichloride after a few minutes at room temperature:[6]

3 SeCl2 → Se2Cl2 + SeCl4

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

  1. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  2. ↑ 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.
  3. ↑ 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. 1 2 3 Fehér, F. "Diselenium Dichloride". In Handbook of Preparative Inorganic Chemistry; Brauer, G., Ed.; Academic Press: New York, 1963; Vol. 1; p 422-433.
  5. ↑ 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.
  6. ↑ 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. 1 2 Back, Thomas G.; Moussa, Ziad (2003). "Diselenium Dichloride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn00201. ISBN 0-471-93623-5.
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