Which of the following is a s-bonded organometallic?

Options

A. Ferrocene
B. Grignard reagent
C. Cis-platin
D. All of these

Answer

To determine which of the given compounds is a sigma-bonded organometallic compound, we will analyze each option based on the definition of organometallic compounds and the nature of bonding involved.

### Step-by-Step Solution:

1. **Understanding Organometallic Compounds**:
- An organometallic compound is defined as a compound that contains a direct bond between a carbon atom and a metal atom. The bond formed between the carbon and metal is typically a sigma (σ) bond.

2. **Analyzing Ferrocene**:
- Ferrocene consists of an iron (Fe) atom sandwiched between two cyclopentadienyl (C5H5) anions.
- The bonding in ferrocene involves π-bonding from the cyclopentadienyl ligands to the iron, rather than a direct σ-bond between carbon and iron.
- Therefore, ferrocene is not classified as a σ-bonded organometallic compound.

3. **Analyzing Grignard Reagent**:
- A Grignard reagent is represented as R-Mg-X, where R is an organic group, Mg is magnesium, and X is a halogen.
- In this case, there is a direct σ-bond between the carbon atom (from R) and the magnesium atom (Mg).
- Thus, Grignard reagents are indeed classified as σ-bonded organometallic compounds.

4. **Analyzing Cis-Platinum**:
- Cis-platinum (cis-Pt(NH3)2Cl2) contains platinum (Pt) bonded to ammonia (NH3) and chloride (Cl) ligands.
- There are no carbon atoms directly bonded to the platinum in this compound, which means it does not meet the criteria for an organometallic compound.

5. **Conclusion**:
- Based on the analysis, the only compound that qualifies as a σ-bonded organometallic compound is the Grignard reagent.

### Final Answer:
The σ-bonded organometallic compound is the **Grignard reagent (R-Mg-X)**.

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