''cis''-Dichlorobis(ethylenediamine)cobalt(III) chloride is a salt with the formula oCl₂(en)₂l (en =

ethylenediamine Ethylenediamine (abbreviated as en when a ligand) is the organic compound with the formula C2H4(NH2)2. This colorless liquid with an ammonia-like odor is a basic amine. It is a widely used building block in chemical synthesis, with approximately ...

). The salt consists of a cationic

coordination complex A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...

and a chloride anion. It is a violet diamagnetic solid that is soluble in water. One chloride ion in this salt readily undergoes

ion exchange Ion exchange is a reversible interchange of one species of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid. Ion exchange is used in softening or demineralizing of water, purification of ch ...

, but the two other chlorides are less reactive, being bound to the metal center.

Synthesis and optical resolution

''Cis''-dichlorobis(ethylenediamine)cobalt(III) chloride is obtained by heating a solution of ''trans''-dichlorobis(ethylenediamine)cobalt(III) chloride, e.g. using a steam bath. The

racemate In chemistry, a racemic mixture or racemate () is a mixture that has equal amounts (50:50) of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as r ...

can be resolved into two

enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

s (Λ and Δ) by the formation of the ''d''-α-bromocamphor-π-sulfonate salt. The

diastereomer In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have di ...

ic salts are separated by recrystallization. After their purification, the individual diastereomers are converted back to the chloride salt by reaction with ice cold hydrochloric acid. File:Delta-cis-dichlorobis(ethylenediamine)cobalt(III).png, Λ-''cis''- oCl₂(en)₂sup>+ File:Lambda-cis-dichlorobis(ethylenediamine)cobalt(III).png, Δ-''cis''- oCl₂(en)₂sup>+

Related complexes

This salt is less soluble than its dull-green isomer ''trans''-dichlorobis(ethylenediamine)cobalt(III) chloride. This pair of isomers were significant in the development of the area of

coordination chemistry A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...

.Jörgensen, S.M. "Ueber Metalldiaminverbindungen" '' J. prakt. Chem.'' (in German), 1889, volume 39, page 8. The chiral cis isomer is obtained by heating the trans isomer. Both isomers of dichlorobis(ethylenediamine)cobalt(III) have often been used in stereochemical studies. Tris(ethylenediamine)cobalt(III) chloride in contrast to the bis(ethylenediamine) complexes does not undergo substitution.

References

{{DEFAULTSORT:Dichlorobis(ethylenediamine)cobalt(III) chloride, cis Cobalt complexes Cobalt(III) compounds Chlorides Ethylenediamine complexes Chloro complexes