Question

The number of geometrical isomers of the complex $[Co(NO_2)_3(NH_3)_3]$ is

• A. 4
• B. 0
• C. 2
• D. 3

Answer 1

The Correct Option is C

The complex compound in question is [Co(NO_2)_3(NH_3)_3], which is an octahedral complex. To determine the number of geometrical isomers for this complex, let's analyze its structure and ligand arrangement.

In an octahedral complex, if the ligands are identical, they can be arranged in different positions around the central metal atom, giving rise to different geometrical isomers.

This complex contains two types of ligands:

• Three NO_2 groups, which are monodentate ligands.
• Three NH_3 groups, which are also monodentate ligands.

In the octahedral arrangement, we can have different geometrical isomers depending on how the NO_2 and NH_3 ligands are positioned relative to one another. Specifically, the two main types of geometrical isomers for this kind of complex are:

1. Facial (fac) isomer: All three NO_2 ligands or all three NH_3 ligands occupy adjacent positions at the corners of one face of the octahedron.
2. Meridional (mer) isomer: The three identical ligands are positioned such that they form a meridian plane, that is, two are adjacent, and the third is opposite to these two.

Therefore, the complex [Co(NO_2)_3(NH_3)_3] can exist as two geometrical isomers:

• Facial isomer (fac)
• Meridional isomer (mer)

This confirms that the number of geometrical isomers for the complex [Co(NO_2)_3(NH_3)_3] is indeed 2. Thus, the correct answer is:

2