Question

What is the decreasing order of field strength of given ligands? (A) S\(^{2-}\)
(B) Ethylenediamine
(C) NCS\(^{-}\)
(D) CN\(^{-}\)

• A. (A), (C), (B), (D)
• B. (A), (B), (C), (D)
• C. (B), (C), (D), (A)
• D. (D), (C), (B), (A)

Hint:

Strong field ligands like CN\(^{-}\) and ethylene diamine can cause a significant splitting of d-orbital energies, whereas weaker field ligands like S\(^{2-}\) have lesser effect.

Answer 1

The Correct Option is D

Step 1: Ligand Field Strength Defined.
Ligand field strength quantifies a ligand's capacity to perturb the energy levels of a metal ion's d-orbitals. This strength correlates with the ligand's electron donation capability.
Step 2: Ligand Analysis.
- S\(^{2-}\): Characterized by high charge density, classifying it as a strong field ligand.
- Ethylene diamine: A moderate field ligand, functioning as a bidentate ligand.
- NCS\(^{-}\): Exhibits weaker field strength than ethylenediamine.
- CN\(^{-}\): Possesses a very high charge density and superior electron-donating ability, making it a very strong field ligand.
Step 3: Ranking.
The field strength, from strongest to weakest, is ordered as follows:
(1) CN\(^{-}\) (strongest)
(2) NCS\(^{-}\)
(3) Ethylenediamine
(4) S\(^{2-}\) (weakest)
Final Answer: \[\boxed{\text{The correct answer is (4) (D), (C), (B), (A).}}\]