Which of the following complex will follow EAN rule ?

Options

A. `[Mn(CO)_(5)]`
B. `[Mn(CO)_(6)]`
C. `[Fe(CO)_(5)]`
D. `[Co(CO)_(4)]`

Explanation

To determine which of the given complexes follows the Effective Atomic Number (EAN) rule, we will calculate the EAN for each complex using the formula:

\[ \text{EAN} = Z - X + Y \]

Where:
- \( Z \) = Atomic number of the metal
- \( X \) = Oxidation state of the metal
- \( Y \) = Number of electrons donated by the ligands

Let's analyze each complex step by step.

### Step 1: Calculate EAN for MnCO5
1. **Identify the metal and its atomic number**: Manganese (Mn) has an atomic number \( Z = 25 \).
2. **Determine the oxidation state**: In MnCO5, CO is a neutral ligand, so the oxidation state \( X = 0 \).
3. **Calculate the number of electrons donated by the ligands**: Each CO donates 2 electrons. With 5 CO ligands:
\[ Y = 5 \times 2 = 10 \]
4. **Calculate EAN**:
\[ \text{EAN} = 25 - 0 + 10 = 35 \]

### Step 2: Calculate EAN for MnCO6
1. **Identify the metal and its atomic number**: Manganese (Mn) has an atomic number \( Z = 25 \).
2. **Determine the oxidation state**: In MnCO6, CO is a neutral ligand, so the oxidation state \( X = 0 \).
3. **Calculate the number of electrons donated by the ligands**: With 6 CO ligands:
\[ Y = 6 \times 2 = 12 \]
4. **Calculate EAN**:
\[ \text{EAN} = 25 - 0 + 12 = 37 \]

### Step 3: Calculate EAN for FeCO5
1. **Identify the metal and its atomic number**: Iron (Fe) has an atomic number \( Z = 26 \).
2. **Determine the oxidation state**: In FeCO5, CO is a neutral ligand, so the oxidation state \( X = 0 \).
3. **Calculate the number of electrons donated by the ligands**: With 5 CO ligands:
\[ Y = 5 \times 2 = 10 \]
4. **Calculate EAN**:
\[ \text{EAN} = 26 - 0 + 10 = 36 \]

### Step 4: Calculate EAN for COCO4
1. **Identify the metal and its atomic number**: Cobalt (Co) has an atomic number \( Z = 27 \).
2. **Determine the oxidation state**: In CoCO4, CO is a neutral ligand, so the oxidation state \( X = 0 \).
3. **Calculate the number of electrons donated by the ligands**: With 4 CO ligands:
\[ Y = 4 \times 2 = 8 \]
4. **Calculate EAN**:
\[ \text{EAN} = 27 - 0 + 8 = 35 \]

### Summary of EAN Calculations
- EAN for MnCO5 = 35
- EAN for MnCO6 = 37
- EAN for FeCO5 = 36
- EAN for CoCO4 = 35

### Conclusion
The complexes that follow the EAN rule (which should equal 36 for 3D transition metals) are:
- **FeCO5** (EAN = 36)