Which of the following complex acts as reducing agent based on Sidgwick EAN rule?

Options

A. `[Mn(CO)_(5)]`-
B. `[Mn_(2)(CO)_(10)]`
C. `[Mn(CO)_(6)]`
D. `[V(CO)_(6)]^(-)`

Explanation

To determine which complex acts as a reducing agent based on Sidgwick's Effective Atomic Number (EAN) rule, we will analyze the provided complexes step by step.

### Step 1: Understand the EAN Rule
According to Sidgwick's EAN rule, the effective atomic number (EAN) of the central metal atom in a coordination complex is calculated using the formula:

\[ \text{EAN} = Z - \text{oxidation state} + 2 \times \text{coordination number} \]

Where:
- \( Z \) is the atomic number of the metal.
- The oxidation state is the charge on the metal in the complex.
- The coordination number is the number of ligands bonded to the metal.

### Step 2: Analyze Each Complex
We will calculate the EAN for each complex provided in the options.

#### Option A: MnCO5^-
1. **Identify the oxidation state of Mn**:
- CO is a neutral ligand (oxidation state = 0).
- The overall charge of the complex is -1, so:
\[ \text{Oxidation state of Mn} = -1 \]

2. **Calculate EAN**:
- Atomic number of Mn (Z) = 25
- Coordination number = 5 (since there are 5 CO ligands)
\[ \text{EAN} = 25 - (-1) + 2 \times 5 = 25 + 1 + 10 = 36 \]
- Since EAN = 36, this complex is neither oxidizing nor reducing.

#### Option B: Mn2CO10
1. **Identify the oxidation state of Mn**:
- The overall charge of the complex is 0 (neutral).
- Therefore, the oxidation state of each Mn atom is 0.

2. **Calculate EAN for one Mn**:
- Atomic number of Mn (Z) = 25
- Coordination number = 5 (each Mn is coordinated to 5 CO ligands)
\[ \text{EAN} = 25 - 0 + 2 \times 5 = 25 + 0 + 10 = 35 \]
- Since EAN = 35, this complex acts as an oxidizing agent.

#### Option C: MnCO6
1. **Identify the oxidation state of Mn**:
- CO is a neutral ligand (oxidation state = 0).
- Therefore, the oxidation state of Mn is 0.

2. **Calculate EAN**:
- Atomic number of Mn (Z) = 25
- Coordination number = 6 (since there are 6 CO ligands)
\[ \text{EAN} = 25 - 0 + 2 \times 6 = 25 + 0 + 12 = 37 \]
- Since EAN = 37, which is greater than 36, this complex acts as a reducing agent.

#### Option D: VCO6^-
1. **Identify the oxidation state of V**:
- CO is a neutral ligand (oxidation state = 0).
- The overall charge of the complex is -1, so:
\[ \text{Oxidation state of V} = -1 \]

2. **Calculate EAN**:
- Atomic number of V (Z) = 23
- Coordination number = 6 (since there are 6 CO ligands)
\[ \text{EAN} = 23 - (-1) + 2 \times 6 = 23 + 1 + 12 = 36 \]
- Since EAN = 36, this complex is neither oxidizing nor reducing.

### Conclusion
Based on the calculations, the complex that acts as a reducing agent is **MnCO6** (Option C).