Question

Which among the following is NOT a neutral ligand?

• A. Thiocyanate
• B. Ammine
• C. Aqua
• D. Carbon monoxide

Hint:

The names of anionic ligands generally end in "-o" (like chloro, cyano, thiocyanato), while neutral ligands typically retain their standard molecular names (with a few special exceptions like aqua, ammine, and carbonyl).

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
In coordination chemistry, a ligand can be neutral or charged (anionic/cationic). We need to identify the ligand in the list that possesses a formal electrical charge.

Step 2: Key Formula or Approach:
Write down the chemical formula for each ligand provided in the options and check for an overall ionic charge. Neutral ligands have a net charge of zero.

Step 3: Detailed Explanation:
Let's examine each ligand:
(B)

Ammine: The chemical formula is $\text{NH}_3$. It is a stable, neutral molecule with no charge.
(C)

Aqua: The chemical formula is $\text{H}_2\text{O}$. It is a neutral solvent molecule with no charge.
(D)

Carbon monoxide: As a ligand, it is called carbonyl (CO). It is a neutral molecule with no net charge.
(A)

Thiocyanate: The chemical formula is $\text{SCN}^-$. It is a polyatomic anion carrying a formal charge of $-1$. Therefore, it is strictly classified as an anionic ligand, not a neutral one.

Step 4: Final Answer:
Thiocyanate is an anionic ligand, meaning it is NOT a neutral ligand, which matches option (A).