Give number of non-classical ligands which are negative ligands
`CN^(Θ), S_(2)O_(3)^(2-),C_(3)H_(5)^(Θ),C_(5)H_(5)^(Θ)` .

Explanation

To solve the problem of identifying the number of non-classical ligands that are negatively charged from the given list, we can follow these steps:

### Step 1: Understand the Definitions
- **Non-classical ligands**: These are ligands that can act as both sigma donors and pi acceptors due to the presence of empty orbitals that can interact with the metal's orbitals.
- **Negative ligands**: These are ligands that carry a negative charge.

### Step 2: Analyze the Given Ligands
We have the following ligands to consider:
1. \( CN^{\Theta} \) (Cyanide)
2. \( S_2O_3^{2-} \) (Thiosulfate)
3. \( C_3H_5^{\Theta} \) (Propyl)
4. \( C_5H_5^{\Theta} \) (Cyclopentadienyl)

### Step 3: Classify Each Ligand
1. **Cyanide (\( CN^{\Theta} \))**: This is a classical ligand. It primarily acts as a sigma donor and does not participate in pi bonding with metals. Therefore, it is not considered a non-classical ligand.

2. **Thiosulfate (\( S_2O_3^{2-} \))**: This ligand is negatively charged and can act as a non-classical ligand due to its ability to participate in pi bonding.

3. **Propyl (\( C_3H_5^{\Theta} \))**: This ligand is neutral and does not carry a negative charge, so it is not considered in our count.

4. **Cyclopentadienyl (\( C_5H_5^{\Theta} \))**: This ligand is also neutral and does not carry a negative charge, so it is not included in our count.

### Step 4: Count the Non-Classical Negative Ligands
From our analysis:
- The only non-classical ligand that is negatively charged is \( S_2O_3^{2-} \).

### Conclusion
Thus, the total number of non-classical ligands that are negatively charged is **1**.

### Final Answer
**1 non-classical ligand that is negatively charged.**

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