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 options is a sigma-bonded organometallic compound, we will analyze each option step by step.

### Step 1: Understand Organometallic Compounds
Organometallic compounds are defined as compounds that contain a direct bond between a carbon atom and a metal atom. The type of bond can be either a sigma (σ) bond or a pi (π) bond. Sigma bonds are single bonds, while pi bonds are involved in double bonds.

### Step 2: Analyze Each Option
**Option A: Ferrocene**
- Ferrocene has the formula Fe(C5H5)2, where iron (Fe) is sandwiched between two cyclopentadienyl (C5H5) anions.
- In ferrocene, the bonding between the carbon atoms of the cyclopentadienyl rings and the iron involves pi bonds due to the delocalization of electrons in the rings.
- Therefore, ferrocene is a pi-bonded organometallic compound.

**Option B: Grignard Reagent**
- A Grignard reagent has the general formula R-MgX, where R is an organic group and X is a halogen.
- For example, CH3MgBr is a Grignard reagent.
- In this case, the carbon (C) is directly bonded to magnesium (Mg) through a sigma bond.
- Therefore, the Grignard reagent is a sigma-bonded organometallic compound.

**Option C: Cisplatin**
- Cisplatin is a coordination complex with the formula cis-[Pt(NH3)2Cl2].
- In this compound, platinum (Pt) is bonded to ammonia (NH3) and chloride (Cl) ligands, but there are no carbon atoms present.
- Since there is no carbon-metal bond, cisplatin cannot be classified as an organometallic compound.

**Option D: All of These**
- Since only the Grignard reagent qualifies as a sigma-bonded organometallic compound, this option is incorrect.

### Conclusion
After analyzing all the options, the correct answer is **Option B: Grignard Reagent**, as it is the only compound that features a sigma bond between carbon and metal.

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