Determine the total number of stereoisomers (including optical isomers) that can exist for the complex ion [Co(en)₂Cl₂]⁺, where en = ethylenediamine.
Answer
Three stereoisomers
The correct answer is Three stereoisomers — Add the single trans isomer and the two enantiomers of the cis form: 1 + 2 = 3 stereoisomers.
Step-by-step solution
- Identify that the complex is octahedral with two bidentate en ligands and two monodentate Cl⁻ ligands.
- Realise that there are two distinct geometrical arrangements: cis and trans.
- Determine that the trans arrangement is a single, non‑optically active isomer.
- Note that the cis arrangement is optically active, giving a pair of enantiomers.
- Add the single trans isomer and the two enantiomers of the cis form: 1 + 2 = 3 stereoisomers.
Common mistake: Counting only two geometrical isomers and ignoring optical pair
Concept tested: Stereochemistry of coordination compounds
Published · How this solution was prepared and checked
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