Which of the following is correct order of ligand field strength?

Options

A. `S^(2-)ltNH_(3)lt en ltCOltC_(2)O_(4)^(2-)`
B. `NH_(3)ltenltCOltS^(2-)ltC_(2)O_(4)^(2-)`
C. `COltenltNH_(3)ltC_(2)O_(4)^(2-)ltS^(2-)`
D. `S^(2-)ltC_(2)O_(4)^(2-)ltNH_(3)lten ltCO`

Answer

To determine the correct order of ligand field strength among the given ligands, we need to understand the relative strength of the ligands based on their ability to split the d-orbitals in transition metal complexes. Ligands can be classified as strong or weak field ligands, and this classification is based on their ability to cause splitting of the d-orbitals.

### Step-by-Step Solution:

1. **Identify the Ligands**:
The ligands mentioned in the question are likely to include carbonyl (CO), ethylene diamine (en), ammonia (NH3), oxalate (C2O4^2-), and sulfide (S2-).

2. **Classify the Ligands**:
- **Strong Field Ligands**: CO, CN^-, en (ethylene diamine)
- **Moderate Field Ligands**: NH3, C2O4^2- (oxalate)
- **Weak Field Ligands**: H2O, halides (F^-, Cl^-, Br^-, I^-), S2-

3. **Order of Ligand Field Strength**:
Based on the classification, we can establish the following order:
- CO > CN^- > en > NH3 > C2O4^2- > S2-

4. **Conclusion**:
The correct order of ligand field strength from strongest to weakest is:
- CO > en > NH3 > C2O4^2- > S2-

5. **Select the Correct Option**:
If the options provided in the question include the order mentioned above, select the one that matches it. If option 4 corresponds to this order, then it is the correct answer.