Which of the following gives the maxium number of isomers?

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)]^(+)`

Answer

To determine which of the given coordination complexes gives the maximum number of isomers, we will analyze each complex step by step.

### Step 1: Analyze the first complex - [Co(NH3)4Cl2]
- This complex can show geometrical isomerism (cis and trans forms).
- Since it has a plane of symmetry, it does not exhibit optical isomerism.
- **Total Isomers = 2 (cis and trans)**

### Step 2: Analyze the second complex - [Ni(en)(NH3)4]²⁺
- This complex cannot show geometrical isomerism due to the nature of the ligands.
- However, it is optically active, meaning it can form two optical isomers (enantiomers).
- **Total Isomers = 2 (optical isomers)**

### Step 3: Analyze the third complex - [Ni(C2O4)(en)2]²⁺
- Similar to the second complex, this complex cannot show geometrical isomerism.
- It can also show optical isomerism, resulting in two optical isomers.
- **Total Isomers = 2 (optical isomers)**

### Step 4: Analyze the fourth complex - [Cr(SCN)2(NH3)4]⁺
- This complex can show geometrical isomerism (cis and trans forms).
- The thiocyanate (SCN) ligand is ambidentate, meaning it can bind through either sulfur or nitrogen, leading to linkage isomerism.
- Therefore, we can have:
- 2 linkage isomers (one for each binding site of SCN).
- Each linkage isomer can also exist in cis and trans forms.
- **Total Isomers = 2 (linkage isomers) x 2 (geometrical isomers) = 4**

### Conclusion
After analyzing all four complexes, we find:
- Complex 1: 2 isomers
- Complex 2: 2 isomers
- Complex 3: 2 isomers
- Complex 4: 4 isomers

Thus, the complex that gives the maximum number of isomers is **[Cr(SCN)2(NH3)4]⁺**, which has a total of 4 isomers.

### Final Answer
The complex that gives the maximum number of isomers is **[Cr(SCN)2(NH3)4]⁺**.