Wikipedia

trans-Dichlorobis(ethylenediamine)cobalt(III) chloride

trans-Dichlorobis(ethylenediamine)cobalt(III) chloride is a salt with the formula [CoCl2(en)2]Cl (en = ethylenediamine). It is a green diamagnetic solid that is soluble in water. It is the monochloride salt of the cationic coordination complex [CoCl2(en)2]+. One chloride ion in this salt readily undergoes ion exchange but the two other chlorides are less reactive, being bound to the metal center. The more stable cis-dichlorobis(ethylenediamine)cobalt(III) chloride is also known.

trans-Dichlorobis(ethylene­diamine)cobalt(III) chloride
Skeletal formulas of cis-dichlorobis(ethylenediamine)cobalt(III) chloride
sample
Names
IUPAC name
(OC-6-12′)-Dichloridobis(ethane-1,2-diamine-κ2N,N′)cobalt(1+) chloride(1−)
Identifiers
3D model (JSmol)
  • InChI=1S/2C2H8N2.3ClH.Co/c2*3-1-2-4;;;;/h2*1-4H2;3*1H;/q;;;;;+3/p-3
    Key: GVMSQWCTZLHSQH-UHFFFAOYSA-K
  • C(CN)N.C(CN)N.Cl[Co](Cl)Cl
Properties
C4H16Cl3CoN4
Molar mass 285.48 g·mol−1
Appearance green solid
Melting point decomposes
good
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
P261, P305+P351+P338
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis

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The compound is synthesized by the reaction of cobalt(II) chloride and ethylenediamine in hydrochloric acid in the presence of oxygen:

4 CoCl2 + 8 en + 4 HCl + O2 → 4 trans-[CoCl2(en)2]Cl + 2 H2O

The initial product contains HCl, which is removed by heating. Alternatively, (carbonato)bis(ethylenediamine)cobalt(III) chloride reacts with hydrochloric acid at 10 °C to give the same species.[1]

[Co(CO3)(en)2]Cl + 2 HCl → trans-[CoCl2(en)2]Cl + CO2 + H2O
 
UV-vis spectra of various stages in the conversion of trans-[CoCl2(en)2]+ to the cis isomer.
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This salt is more soluble than cis-dichlorobis(ethylenediamine)cobalt(III) chloride. This pair of isomers were significant in the development of the area of coordination chemistry.[2] 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. The trans isomer cation has idealized D2h point group symmetry, whereas the cis isomer cation has C2 symmetry.

Tris(ethylenediamine)cobalt(III) chloride in contrast to the bis(ethylenediamine) complexes does not undergo substitution.

References

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  1. ^ Springbørg, J.; Schaffer, C. E. (1973). "Dianionobis(Ethylenediamine)Cobalt(III) Complexes". Inorganic Syntheses. Vol. 14. pp. 63–77. doi:10.1002/9780470132456.ch14. ISBN 978-0-470-13245-6.
  2. ^ Jörgensen, S.M. "Ueber Metalldiaminverbindungen" J. prakt. Chem. (in German), 1889, volume 39, page 8. doi:10.1002/prac.18890390101
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