Question

The complex $[Cr(NH_3)_4Cl_2]^+$ shows how many geometrical isomers?

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

For octahedral complexes of the type $[MA_4B_2]$, only cis and trans forms are possible geometrical isomers.

Answer 1

The Correct Option is B

The complex [Cr(NH₃)₄Cl₂]⁺ is an octahedral complex which consists of four ammonia (NH₃) ligands and two chloride (Cl) ligands. For octahedral complexes, geometrical isomerism arises when there are at least two different types of ligands attached to the metal center. In this case, the complex has NH₃ and Cl ligands. The two possible isomers for this complex occur due to the spatial arrangement of the Cl ligands:

• Cis isomer: In this arrangement, the two Cl ligands are adjacent to each other, occupying positions next to each other in the octahedral geometry.
• Trans isomer: Here, the Cl ligands are opposite to each other, occupying positions on opposite ends of the octahedral geometry.

Therefore, the [Cr(NH₃)₄Cl₂]⁺ complex can exhibit 2 geometrical isomers: cis and trans.

Geometrical Isomers
Cis
Trans

Conclusively, among the given options, the complex exhibits 2 geometrical isomers.

Answer 2

The coordination number of chromium in $[Cr(NH_3)_4Cl_2]^+$ is 6, suggesting an octahedral geometry.
The ligands are:
- 4 ammonia ($NH_3$)
- 2 chloride ions ($Cl^-$)
In an octahedral complex of type $[MA_4B_2]$, there are two geometrical isomers:
- cis-isomer: Both $Cl^-$ ligands adjacent to each other
- trans-isomer: Both $Cl^-$ ligands opposite each other
Thus, only 2 geometrical isomers are possible. 
Answer: $\boxed{2}$