Which of the following compound contain zero oxidation state of Fe :

Options

A. `[Fe(CN)_6]^-4`
B. `[Fe(CN)_6]^-3`
C. `Fe(CO)_5`
D. All of the above

Answer

To determine which of the given compounds contains iron (Fe) in the zero oxidation state, we will analyze each compound step by step.

### Step 1: Identify the Compounds
The compounds mentioned in the question are:
1. \( \text{[Fe(CN)_6]^{4-}} \)
2. \( \text{[Fe(CN)_6]^{3-}} \)
3. \( \text{[Fe(CO)_5]} \)

### Step 2: Calculate the Oxidation State of Iron in Each Compound

#### Compound 1: \( \text{[Fe(CN)_6]^{4-}} \)
- Let the oxidation state of Fe be \( x \).
- The oxidation state of CN is -1, and there are 6 CN ligands.
- The overall charge of the complex is -4.

The equation can be set up as follows:
\[ x + 6(-1) = -4 \]
\[ x - 6 = -4 \]
\[ x = -4 + 6 = +2 \]

So, the oxidation state of Fe in \( \text{[Fe(CN)_6]^{4-}} \) is +2.

#### Compound 2: \( \text{[Fe(CN)_6]^{3-}} \)
- Let the oxidation state of Fe be \( x \).
- The oxidation state of CN is -1, and there are 6 CN ligands.
- The overall charge of the complex is -3.

The equation can be set up as follows:
\[ x + 6(-1) = -3 \]
\[ x - 6 = -3 \]
\[ x = -3 + 6 = +3 \]

So, the oxidation state of Fe in \( \text{[Fe(CN)_6]^{3-}} \) is +3.

#### Compound 3: \( \text{[Fe(CO)_5]} \)
- Let the oxidation state of Fe be \( x \).
- The oxidation state of CO is 0, and there are 5 CO ligands.
- The overall charge of the complex is 0.

The equation can be set up as follows:
\[ x + 5(0) = 0 \]
\[ x = 0 \]

So, the oxidation state of Fe in \( \text{[Fe(CO)_5]} \) is 0.

### Conclusion
Among the three compounds analyzed, only \( \text{[Fe(CO)_5]} \) has iron in the zero oxidation state.

### Final Answer
The compound that contains iron in the zero oxidation state is:
**\( \text{[Fe(CO)_5]} \)**