trans-Dichlorobis(ethylenediamine)cobalt(III) chloride

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trans-Dichlorobis(ethylene­diamine)cobalt(III) chloride
Skeletal formulas of cis-dichlorobis(ethylenediamine)cobalt(III) chloride
IUPAC name
(OC-6-12′)-Dichloridobis(ethane-1,2-diamine-κ2N,N′)cobalt(1+) chloride(1−)
3D model (JSmol)
  • InChI=1S/2C2H8N2.3ClH.Co/c2*3-1-2-4;;;;/h2*1-4H2;3*1H;/q;;;;;+3/p-3
  • C(CN)N.C(CN)N.Cl[Co](Cl)Cl
Molar mass 285.48 g·mol−1
Appearance green solid
Melting point decomposes
GHS labelling:
GHS07: Exclamation mark
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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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 trans-dichlorobis(ethylenediamine)cobalt(III) chloride is also known.


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.

Comparison of cis and trans isomers[edit]

This salt is more soluble than the cis isomer. This pair of isomers was significant in the development of the area of coordination chemistry.[2]

The trans isomer cation has idealized D2h point group symmetry, whereas the cis isomer cation has C2 symmetry.


  1. ^ Springbørg, J.; Schaffer, C. E. (1973). "Dianionobis(Ethylenediamine)Cobalt(III) Complexes". Inorganic Syntheses. Inorganic Syntheses. Vol. 14. p. 63-77. doi:10.1002/9780470132456.ch14. ISBN 9780470132456.
  2. ^ Jörgensen, S.M. "Ueber Metalldiaminverbindungen" Journal für praktische Chemie (in German), 1889, volume 39, page 8. doi:10.1002/prac.18890390101