The number of possible isomers of an octahedral complex `[Co(C_2O_4)_2 (NH_3)_2]^-` is

Options

A. 1
B. 2
C. 3
D. 4

Explanation

To determine the number of possible isomers of the octahedral complex \([Co(C_2O_4)_2(NH_3)_2]^-\), we need to analyze the coordination geometry and the ligands involved.

### Step 1: Identify the ligands and their coordination
The complex consists of:
- Two bidentate oxalate ligands \((C_2O_4)^{2-}\)
- Two monodentate ammonia ligands \((NH_3)\)

### Step 2: Understand the geometry
The complex is octahedral, meaning that the central cobalt ion is surrounded by six coordination sites. The bidentate oxalate ligands will occupy two sites each, while the ammonia ligands will occupy one site each.

### Step 3: Determine the types of isomers
In octahedral complexes, we can have:
1. **Geometric isomers**: These arise from the different spatial arrangements of the ligands. For this complex, we can have:
- **Cis isomer**: Both oxalate ligands are adjacent to each other.
- **Trans isomer**: The oxalate ligands are opposite each other.

2. **Optical isomers**: These occur when a complex can exist in two non-superimposable mirror images (chiral forms). The cis isomer can potentially exhibit optical isomerism due to the arrangement of the bidentate ligands.

### Step 4: Count the isomers
1. **Cis isomer**: This can exist in two forms (optical isomers).
2. **Trans isomer**: This does not exhibit optical isomerism.

Thus, the total number of isomers is:
- 2 (from cis) + 1 (from trans) = 3 isomers.

### Final Answer
The total number of possible isomers of the octahedral complex \([Co(C_2O_4)_2(NH_3)_2]^-\) is **3**.

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