Question

Identify a lowest field strength ligand from following.

• A. \( I^{-} \)
• B. \( S^{2-} \)
• C. en
• D. CO

Hint:

Halide ions are generally weak-field ligands, while ligands that coordinate through Carbon or Nitrogen (like CO, CN, en) are strong-field ligands.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks to identify the weakest ligand among the choices based on the spectrochemical series.
Step 2: Detailed Explanation:
Based on the experimental determination of crystal field splitting energy, ligands are arranged as:
\( I^{-}<Br^{-}<S^{2-}<Cl^{-}<\dots<NH_{3}<en<CN^{-}<CO \).
Iodide ion (\( I^{-} \)) is at the start of the series, meaning it causes the least splitting and is the weakest (lowest field strength) ligand.
Step 3: Final Answer:
The lowest field strength ligand is \( I^{-} \).