The type of isomerism present in nitro pentaamine-chromium`(III)`chloride is:

Options

A. Polymerization
B. Geometrical
C. Optical
D. Linkage

Answer

To determine the type of isomerism present in nitro pentaamine-chromium(III) chloride, we can follow these steps:

### Step 1: Identify the Components of the Complex
The complex is nitro pentaamine-chromium(III) chloride. This means:
- The central metal atom is chromium (Cr) in the +3 oxidation state.
- There are five ammonia (NH₃) ligands, which are neutral.
- There is one nitro (NO₂) ligand.
- There is one chloride (Cl⁻) ion outside the coordination sphere.

### Step 2: Write the Formula of the Complex
The formula can be represented as [Cr(NH₃)₅(NO₂)]Cl₂. The nitro group can act as a bidentate ligand, meaning it can attach to the metal through either nitrogen (N) or oxygen (O).

### Step 3: Determine the Type of Ligand
The nitro group (NO₂) is an ambidentate ligand, which means it can coordinate to the metal through two different atoms (N or O). This property is crucial for identifying the type of isomerism.

### Step 4: Analyze Possible Isomerism
1. **Linkage Isomerism**: Since the nitro group can attach through either nitrogen or oxygen, we can have two different isomers:
- One where the nitrogen is bonded to chromium (NO₂).
- Another where the oxygen is bonded to chromium (ONO).

These two forms represent linkage isomers because they have the same molecular formula but different connectivity.

2. **Geometrical Isomerism**: This type of isomerism typically involves different spatial arrangements of ligands. However, in this case, with five identical ammonia ligands and one nitro ligand, we cannot form cis/trans isomers.

3. **Optical Isomerism**: Optical isomerism requires the absence of a plane of symmetry. Given the symmetrical nature of this complex (due to the arrangement of the ligands), it does not exhibit optical isomerism.

4. **Polymerization Isomerism**: This type involves complexes that have the same empirical formula but different molecular formulas. This does not apply here.

### Conclusion
Based on the analysis, the only type of isomerism that can occur in nitro pentaamine-chromium(III) chloride is **linkage isomerism**.

### Final Answer
The type of isomerism present in nitro pentaamine-chromium(III) chloride is **linkage isomerism**.

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