Question

The correct increasing order of stability of the complexes based on \( \Delta \) value is:

• A. \( {IV}<{III}<{II}<{I} \)
• B. \( {I}<{II}<{IV}<{III} \)
• C. \( {III}<{II}<{IV}<{I} \)
• D. \( {II}<{III}<{I}<{IV} \)

Hint:

When determining the stability of metal-ligand complexes, remember that the strength of the ligand field and the charge on the metal ion influence the value of \( \Delta \) and, hence, the stability of the complex.

Answer 1

The Correct Option is C

The stability of complexes is often related to the value of \( \Delta \), which is the energy difference between the d-orbitals in the ligand field. Higher \( \Delta \) values typically correspond to more stable complexes. 
Based on the \( \Delta \) values: 
- \( [{Fe(CN)}_6]^{3-} \) has the highest \( \Delta \) value due to the strong field ligand \( {CN}^- \), making it the most stable complex. 
- \( [{Co(CN)}_6]^{3-} \) is slightly less stable compared to \( [{Fe(CN)}_6]^{3-} \). 
- \( [{Mn(CN)}_6]^{3-} \) has the lowest \( \Delta \) value and is the least stable among these complexes. Thus, the correct increasing order of stability is \( {III}<{II}<{IV}<{I} \).