Q.In which of the following coordination entities the magnitude of Δ₀ will be maximum?

Step 1. The spectrochemical series ranks these four ligands (weakest to strongest): ox²⁻ < H₂O < NH₃ < CN⁻.

Step 2. [Co(C₂O₄)₃]³⁻ uses oxalate, a moderate ligand positioned even below water in the series -- relatively small Δ₀.

Step 3. [Co(H₂O)₆]³⁺ uses water, stronger than oxalate but weaker than ammonia -- moderate Δ₀.

Step 4. [Co(NH₃)₆]³⁺ uses ammonia, a strong-field ligand -- large Δ₀, but still weaker than cyanide. …

Rank the four ligands attached to Co(III) by their position in the spectrochemical series and pick the complex whose ligand s …

• Assuming a higher negative charge on the ligand automatically means a stronger field -- oxalate (2-) is actually WEAKER field than neutral water and ammonia in the real spectrochemical series, so charge alone is not the deciding factor. …