Question

Which one of the correct formula for the coordination compound tris[ethane-1,2-diamine] cobalt (III) sulfate? 

Hint:

Ethylenediamine (\({en}\)) is a bidentate ligand, meaning it forms two bonds with the central metal ion. In tris(ethylenediamine) cobalt(III) sulfate, each Co(III) is coordinated with three en ligands, making the complex \([{Co(en)}_3]^{3+}\).

Answer 1

Step 1: Understanding the Coordination Compound 
- The given complex contains tris(ethane-1,2-diamine), which means three molecules of ethylenediamine (en) ligand are coordinated to the central metal cobalt(III).
- The oxidation state of cobalt is +3 in this complex. 
Step 2: Determining the Formula 
- Cobalt (III) sulfate implies that sulfate (\({SO}_4^{2-}\)) is the counter ion.
- Since cobalt is in the +3 oxidation state and the ethylenediamine ligand (en) is neutral, the charge on the complex ion must be +3.
- To balance the charge, two complex cations \([{Co(en)}_3]^{3+}\) are needed with three sulfate anions (\({SO}_4^{2-}\)). 
Step 3: Final Formula 
The correct chemical formula of the given coordination compound is: \[ {[Co(en)}_3]_2({SO}_4)_3 \] 
Step 4: Conclusion 
- Ethylenediamine (en) is a bidentate ligand, meaning it forms two bonds with cobalt.
- The correct formula is \({[Co(en)}_3]_2({SO}_4)_3\), ensuring charge neutrality.