Question

An example of a sigma bonded organometallic compound is :

• A. Grignard's reagent
• B. Ferrocene
• C. Cobaltocene
• D. Ruthenocene

Answer 1

The Correct Option is A

The question asks us to identify which option represents a sigma-bonded organometallic compound. Let's analyze each option to determine this:

1. Grignard's Reagent: Grignard's reagent is an organometallic compound with the general formula {\text{R-Mg-X}}, where R is an alkyl or aryl group, Mg is magnesium, and X is a halogen (usually bromine or chlorine). The bond between the carbon atom (C) of the alkyl/aryl group and the magnesium (Mg) is a sigma bond. Therefore, Grignard's reagent is indeed a sigma-bonded organometallic compound.
2. Ferrocene: Ferrocene is an organometallic compound with a sandwich structure, where a ferrous ion (\text{Fe}^{2+}) is located between two cyclopentadienyl anions (\text{C}_5\text{H}_5^{-}) forming pi-bonds rather than sigma-bonds.
3. Cobaltocene: Similar to ferrocene, cobaltocene is comprised of a cobalt ion sandwiched between two cyclopentadienyl rings, forming pi-bonds. Thus, it is not sigma-bonded.
4. Ruthenocene: This is also a metallocene with a ruthenium ion sandwiched between two cyclopentadienyl rings, forming pi-bonds.

Analyzing all the options, the only compound that is sigma-bonded among them is the Grignard's reagent. Hence, the correct answer is Grignard's Reagent.