Question

Identify the geometry and magnetic behavior of the complex \([\text{Ni}(\text{CO})_{4}]\).

• A. square planar geometry and diamagnetic
• B. tetrahedral geometry and diamagnetic
• C. square planar geometry and paramagnetic
• D. tetrahedral geometry and paramagnetic.

Hint:

CO is a strong field ligand, so nickel is in zero oxidation state with all electrons paired and sp3 hybridisation.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
In \([\text{Ni}(\text{CO})_4]\) nickel is in the zero oxidation state, with configuration \(3d^{8}4s^{2}\).

Step 2: Pairing and hybridisation
CO is a strong field ligand, so the 4s electrons pair up in 3d and the configuration becomes \(3d^{10}\) with no unpaired electrons.
The vacant 4s and three 4p orbitals mix to form four \(sp^{3}\) hybrid orbitals, which accept four lone pairs from CO.

Step 3: Result
\(sp^{3}\) gives a tetrahedral shape, and with all electrons paired the complex is diamagnetic.

Final Answer:
The complex is tetrahedral and diamagnetic. \[ \boxed{\text{(B) }\text{tetrahedral geometry and diamagnetic}} \]