Which of the following co-ordination compound has three stereoisomers /

Options

A. `[Cd(gly) (H_2O)(NH_3)]^(+)`
B. `[PtBr_2(H_2O)_(2)]`
C. `[Cr(en)_(3)]^(3+)`
D. `[CoBr(NO_2)(en)_(2)]^(+)`

Answer

To determine which coordination compound has three stereoisomers, we need to analyze the given options based on their geometrical and optical isomerism.

### Step-by-Step Solution:

1. **Understanding Stereoisomers**: Stereoisomers are compounds that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of atoms. They can be classified into geometrical (cis/trans) and optical isomers (enantiomers).

2. **Identifying the Coordination Compounds**: The compounds mentioned in the question are:
- [Cd(Gly)(H2O)(NH3)]^+
- [PtBr2(H2O)]^2+
- [Cr(en)3]^3+
- [CoBr(NO2)2]^3+

3. **Analyzing Each Compound**:
- **[Cd(Gly)(H2O)(NH3)]^+**: This compound has a tetrahedral geometry. Tetrahedral complexes can show optical isomerism but typically do not have geometrical isomers. Therefore, it would not have three stereoisomers.

- **[PtBr2(H2O)]^2+**: This compound has a square planar geometry. Square planar complexes can exhibit cis/trans isomerism, leading to a maximum of two stereoisomers (cis and trans). Thus, it does not have three stereoisomers.

- **[Cr(en)3]^3+**: This compound has an octahedral geometry. While it can show optical isomerism, it does not have geometrical isomers. Therefore, it would not have three stereoisomers.

- **[CoBr(NO2)2]^3+**: This compound also has an octahedral geometry. It can exhibit both geometrical (cis/trans) and optical isomerism. The presence of two different types of ligands (Br and NO2) allows for the possibility of three stereoisomers: one cis form and two optical isomers (enantiomers).

4. **Conclusion**: The compound that has three stereoisomers is **[CoBr(NO2)2]^3+**.

### Final Answer:
The coordination compound that has three stereoisomers is **[CoBr(NO2)2]^3+**.