Question

Ferrocene is:

• A. \( Fe(\eta^5 - C_5H_5)_2 \)
• B. \( Fe(\eta^2 - C_5H_5)_2 \)
• C. \( Cr(\eta^5 - C_5H_5)_5 \)
• D. \( Os(\eta^5 - C_5H_5)_2 \)

Hint:

Ferrocene exhibits aromatic stability and undergoes electrophilic substitution reactions like benzene.

Answer 1

The Correct Option is A

Step 1: Understanding Ferrocene
Ferrocene is an organometallic compound with an iron (Fe\(^2+\)) center.
It consists of two cyclopentadienyl (\( C_5H_5^- \)) rings bonded in a sandwich-like structure.
Step 2: Type of Bonding
The hapticity (\(\eta^5\)) indicates that all five carbon atoms of the ring interact with the metal center.
This forms a stable and symmetrical structure.
Final Answer: The correct formula of ferrocene is \( Fe(\eta^5 - C_5H_5)_2 \).

Answer 2

Ferrocene is:
\( Fe(\eta^5 - C_5H_5)_2 \)

Explanation:
Ferrocene is a classic example of a metallocene compound, where an iron (Fe) atom is sandwiched between two cyclopentadienyl (C₅H₅) rings.

The notation \( \eta^5 \) indicates that all five carbon atoms of each cyclopentadienyl ring coordinate with the iron atom, forming a stable, symmetric, and highly conjugated structure.

This “sandwich” structure gives ferrocene its unique stability and interesting chemical properties, making it a landmark compound in organometallic chemistry.

Ferrocene exhibits aromaticity in both the cyclopentadienyl rings and the overall complex, contributing to its chemical inertness and ease of substitution reactions.

Its discovery opened the door to a whole class of sandwich compounds and has important applications in catalysis, materials science, and organometallic synthesis.