Question

The $Cl - Co - Cl$ bond angle values in a fac- $\left[ Co \left( NH _3\right)_3 Cl _3\right]$ complex is/are:

• A. $180^{\circ}$
• B. $90^{\circ}$
• C. $90^{\circ} \& 180^{\circ}$
• D. $90^{\circ} \& 120^{\circ}$

Answer 1

The Correct Option is B

The problem is about determining the bond angle values in a fac-\(\left[ Co\left( NH _3\right)_3 Cl _3\right]\) complex. This is a coordination complex with cobalt as the central metal atom coordinated with three ammonia \((\text{NH}_3)\) and three chloride ions \((\text{Cl}^-)\).

In coordination chemistry, complexes can form different geometries based on their coordination number and the type of ligands. For a fac-\(\left[ Co\left( NH _3\right)_3 Cl _3\right]\), we focus on the geometry of the face isomer.

The fac (facial) isomer of a \(ML_3L'_3\) complex typically forms an octahedral geometry. In an octahedral complex:

• Each ligand is bonded at \(90^{\circ}\) to its adjacent ligands along the faces of the octahedron.
• The facial isomer means that the same type of ligands occupy adjacent positions on the same face of the octahedron.

In this context, the \(Cl - Co - Cl\) bond angles refer to angles between the chloride ion ligands and the central cobalt, which in a fac isomer are located on the same face. Therefore, the bond angles between these chloride ligands are indeed \(90^{\circ}\).

Thus, the correct answer for the \(Cl - Co - Cl\) bond angle in the fac-\(\left[ Co \left( NH _3\right)_3 Cl _3\right]\) complex is:

90°