Ziegler-Natta catalyst is

Options

A. `V_2O_5`
B. `A IE t_3 + Ti Cl_4`
C. `Rh//Pd`
D. `[RhC (PPh_3)_3]`

Explanation

To determine which of the given options is a Ziegler-Natta catalyst, we need to analyze the options provided and identify the correct catalyst used in polymerization.

### Step-by-Step Solution:

1. **Understanding Ziegler-Natta Catalyst**:
- The Ziegler-Natta catalyst is primarily used for the polymerization of alkenes to produce polymers like polyethylene and polypropylene. It typically consists of a combination of a transition metal compound and an organoaluminum compound.

2. **Analyzing the Options**:
- **Option A: V2O5** (Vanadium pentoxide)
- This compound is known to be a catalyst used in the contact process for the production of sulfuric acid (H2SO4). It is not a Ziegler-Natta catalyst.

- **Option B: Triethyl aluminum + TiCl4**
- This combination is indeed known as the Ziegler-Natta catalyst. Triethyl aluminum (an organoaluminum compound) reacts with titanium tetrachloride (TiCl4, a transition metal compound) to form the catalyst used in the polymerization of alkenes.

- **Option C: Rhodium or Palladium**
- While these are transition metals and can act as catalysts, they are not specifically Ziegler-Natta catalysts. They are often used in other types of catalytic processes.

- **Option D: Rhodium with Chlorine and Triphenylphosphine (PPh3)**
- This combination is known as the Wilkinson catalyst, which is used for hydrogenation reactions, not for the polymerization of alkenes.

3. **Conclusion**:
- Based on the analysis, the correct Ziegler-Natta catalyst from the options provided is **Option B: Triethyl aluminum + TiCl4**.

### Final Answer:
**Option B** is the Ziegler-Natta catalyst.