Question

Which coordination complex from following contains neutral ligand?

• A. Pentacarbonyl iron(0)
• B. Trioxalatocobaltate(III) ion
• C. Sodium hexanitrocobaltate(III)
• D. Tetracyanonickelate(II) ion

Hint:

Look for ligands that are common neutral molecules like CO, NH3, H2O.

Answer 1

The Correct Option is A

Concept:
A ligand is an ion or molecule that donates a lone pair of electrons to a central metal atom or ion. Ligands may be:

• Neutral ligands: $H_2O,\ NH_3,\ CO,\ NO$
• Anionic ligands: $Cl^-,\ CN^-,\ OH^-,\ C_2O_4^{2-},\ NO_2^-$

We need the complex containing a neutral ligand.
Step 1: Check Option A: Pentacarbonyl iron(0)
Formula: \[ Fe(CO)_5 \] Ligand present: \[ CO \ (\text{carbonyl}) \] Carbonyl is a neutral ligand. \[ \Rightarrow \text{Contains neutral ligand} \]
Step 2: Check Option B: Trioxalatocobaltate(III)
Ligand present: \[ C_2O_4^{2-} \] Oxalate is negatively charged. \[ \Rightarrow \text{Anionic ligand} \]
Step 3: Check Option C: Sodium hexanitrocobaltate(III)
Ligand present: \[ NO_2^- \] Nitro ligand is anionic. \[ \Rightarrow \text{Not neutral} \]
Step 4: Check Option D: Tetracyanonickelate(II)
Ligand present: \[ CN^- \] Cyanide is anionic. \[ \Rightarrow \text{Not neutral} \]
Step 5: Final Answer
The complex containing a neutral ligand is: \[ \boxed{\text{Pentacarbonyl iron(0) \] Quick Tip:
Remember common neutral ligands: \[ NH_3,\ H_2O,\ CO \]