Selenium monochloride
Encyclopedia
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
. Selenium monochloride is mainly used as a reagent
for the synthesis of Se-containing compounds.
, 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.
In acetonitrile
solutions, it exists in equilibrium with SeCl2 and SeCl4.
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:
The crude selenium monochloride product is collected via distillation.
s to give bis(β-chloroalkyl)selenide and bis(chloroalkyl)selenium dichloride. It converts hydrazone
s of hindered ketones into the corresponding selones, the structural analogs of ketones whereby the oxygen atom is replaced with a selenium atom. Finally, the compound has been used to introduce bridging selenium ligands between the metal atoms of some iron and chromium carbonyl complexes.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
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
Chemical equilibrium
In a chemical reaction, chemical equilibrium is the state in which the concentrations of the reactants and products have not yet changed with time. It occurs only in reversible reactions, and not in irreversible reactions. Usually, this state results when the forward reaction proceeds at the same...
with SeCl2, SeCl4, chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, and elemental selenium
Selenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
. Selenium monochloride is mainly used as a reagent
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
for the synthesis of Se-containing compounds.
Structure and properties
Selenium monochloride exhibits C2 molecular symmetryMolecular symmetry
Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can predict or explain many of a molecule's chemical properties, such as its dipole moment...
, similar to hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
. The bond length
Bond length
- Explanation :Bond length is related to bond order, when more electrons participate in bond formation the bond will get shorter. Bond length is also inversely related to bond strength and the bond dissociation energy, as a stronger bond will be shorter...
of the Se-Se bond is predicted to be 2.253 Å and the Se-Cl bonds are both 2.227 Å.
In acetonitrile
Acetonitrile
Acetonitrile is the chemical compound with formula . This colourless liquid is the simplest organic nitrile. It is produced mainly as a byproduct of acrylonitrile manufacture...
solutions, it exists in equilibrium with SeCl2 and SeCl4.
Preparation
Selenium monochloride was originally produced by the chlorination of selenium. An improved method involves the reaction of a mixture of selenium, selenium dioxide, and hydrochloric acid:- 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
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
and reprecipitating it with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
. A second method for the synthesis involves the reaction of selenium with oleum
Oleum
Oleum , or fuming sulfuric acid refers to a solution of various compositions of sulfur trioxide in sulfuric acid or sometimes more specifically to disulfuric acid ....
and hydrochloric acid:
- 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 alkeneAlkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s to give bis(β-chloroalkyl)selenide and bis(chloroalkyl)selenium dichloride. It converts hydrazone
Hydrazone
Hydrazones are a class of organic compounds with the structure R1R2C=NNH2. They are related to ketones and aldehydes by the replacement of the oxygen with the NNH2 functional group...
s of hindered ketones into the corresponding selones, the structural analogs of ketones whereby the oxygen atom is replaced with a selenium atom. Finally, the compound has been used to introduce bridging selenium ligands between the metal atoms of some iron and chromium carbonyl complexes.