Synthesis of Tris(ethylenediamine)cobalt(III) Chloride

Synthesis of Tris(ethylenediamine)cobalt(III) Chloride

Objective:

To synthesize tris(ethylenediamine)cobalt(III) chloride [Co(en)₃]Cl₃ ​, an octahedral coordination compound of cobalt(III) that exhibits optical activity.

Theory:

Coordination compounds consist of a central metal atom or ion surrounded by ligands. Ligands are molecules or ions that donate electron pairs to the metal center through coordinate bonds. In this experiment, cobalt(III) (Co³⁺) acts as the central metal ion, and ethylenediamine (C₂​H₈​N₂​) serves as a bidentate ligand, donating two pairs of electrons through its two amine groups.

Chemical Required:

1. 2 g CoCl₂​⋅6H₂​O
2. 7 mL distilled water
3. 2.2 mL ethylenediamine
4. 5 mL distilled water (for ethylenediamine solution)
5. 24 mL30% H₂​O₂​
6. 12 mL 5M HCl
7. 25 mL HCl (dilute)

Chemical Reaction:

Procedure:

Dissolve 2g of CoCl₂​⋅6H₂​O in 7 ml H₂​O

Mix 2.2mL of ethylenediamine with 5mL of distilled water in a separate beaker.

Slowly add the cobalt chloride solution dropwise into the ethylenediamine solution while stirring continuously.

Add 4 ml of 30% H₂​O₂ dropwise to the reaction mixture.

Stir the solution until effervescence stops, indicating that oxidation of Co²⁺ to Co³⁺ is completed.

Heat the reaction mixture in a boiling water bath or heating mantle to reduce its volume by half.

Add 12 ml of 5M HCL, followed by 25 ml of NaOH.

Cool the solution in an ice bath. Orange crystals of tris(ethylenediamine)cobalt(III) chloride will form.

Filter the crystals using a filter funnel and separate them.

Observations:

The solution changes color from pink to purple and then to orange as the reactions progress.

Orange crystalline product forms after cooling.