Which of the following complex does not show geometric isomerism?

Q: Which of the following complex does not show geometric isomerism?

Which of the following complex does not show geometric isomerism?

Question

Accepted Answer

Option 4, $[Ni(CO)_{4}]$, is the correct answer because it does not show geometric isomerism. Here's the detailed explanation:

1. **Explanation for Option 4: $[Ni(CO)_{4}]$**
   - $[Ni(CO)_{4}]$ is a tetrahedral complex. In tetrahedral complexes, all four positions around the central metal atom are equivalent. Therefore, there is no possibility of geometric isomerism because there are no different spatial arrangements of ligands that can lead to distinct isomers. All ligands are symmetrically arranged around the central metal, resulting in only one possible structure.

2. **Explanation for why other options show geometric isomerism:**

- **Option 1: $[Pt(NH_{3})_{2}Cl_{2}]$**
     - This is a square planar complex. In square planar complexes, geometric isomerism is possible because the ligands can be arranged differently around the central metal. For $[Pt(NH_{3})_{2}Cl_{2}]$, there are two possible arrangements: the cis isomer, where the two chloride ions are adjacent to each other, and the trans isomer, where the chloride ions are opposite each other.

- **Option 2: $[Co(NH_{3})_{3}(NO_{2})_{3}]$**
     - This is an octahedral complex. Octahedral complexes can exhibit geometric isomerism when there are different types of ligands. In this case, the three $NO_{2}$ groups can be arranged in different positions relative to the $NH_{3}$ groups, leading to the possibility of facial (fac) and meridional (mer) isomers.

- **Option 3: $[CoCl_{2}(en)_{2}]$**
     - This is also an octahedral complex. The presence of bidentate ethylenediamine (en) ligands allows for geometric isomerism. The two chloride ions can be positioned either adjacent to each other (cis) or opposite each other (trans), resulting in different geometric isomers.

In summary, $[Ni(CO)_{4}]$ does not show geometric isomerism due to its tetrahedral geometry, where all ligand positions are equivalent. In contrast, the other complexes have geometries that allow for different spatial arrangements of ligands, leading to geometric isomerism.