Which of the following will give maximum number of isomer ?

Options

A. `[Co(NH_(3))_(4)Cl_(2)]`
B. `[Ni(en)(NH_(3))_(4)]^(2+)`
C. `[Ni(C_(2)O_(4))(en)_(2)]^(2-)`
D. `[Cr(SCN)_(2)(NH_(3))_(4)]^(+)`

Explanation

To determine which of the given coordination compounds will yield the maximum number of isomers, we need to analyze each compound based on its ligands and coordination number.

### Step-by-Step Solution:

1. **Identify the Coordination Compounds**:
- (i) [Co(NH3)6]
- (ii) [Co(NH3)4Cl2]
- (iii) [Ni(en)3] (where en = ethylenediamine)
- (iv) [Cr(HCN)4(SCN)]

2. **Analyze Each Compound for Isomerism**:
- **Compound (i): [Co(NH3)6]**
- This complex has an octahedral geometry.
- It can only exhibit geometrical isomerism (cis/trans) but no optical isomerism since all ligands are identical.
- **Total Isomers**: 1 (geometrical only).

- **Compound (ii): [Co(NH3)4Cl2]**
- This complex also has an octahedral geometry.
- It can exhibit geometrical isomerism (cis/trans) due to the presence of two different types of ligands.
- It does not exhibit optical isomerism.
- **Total Isomers**: 2 (cis and trans).

- **Compound (iii): [Ni(en)3]**
- This complex has an octahedral geometry with bidentate ligands (en).
- It can exhibit optical isomerism due to the non-superimposable mirror images of the en ligands.
- **Total Isomers**: 2 (one pair of enantiomers).

- **Compound (iv): [Cr(HCN)4(SCN)]**
- This complex can exhibit linkage isomerism (due to SCN being able to bond through S or N).
- It can also exhibit geometrical isomerism (cis/trans) and optical isomerism for the cis form.
- **Total Isomers**:
- Linkage isomers: 2 (SCN and NCS)
- Geometrical isomers: 2 (cis and trans)
- Optical isomers: 1 (only for the cis form)
- **Total**: 2 (linkage) + 2 (geometrical) + 1 (optical) = 5 isomers.

3. **Conclusion**:
- After analyzing all four compounds, the one that yields the maximum number of isomers is **Compound (iv): [Cr(HCN)4(SCN)]** with a total of 5 isomers.

### Final Answer:
The compound that gives the maximum number of isomers is **[Cr(HCN)4(SCN)]**.