Question

Arrange the following ligands as per increasing hepticity: A. Allyl, B. Butadiene, C. Phenyl, D. Tropillium, E. Cyclooctatriene.

• A. $C<A<B<E<D$
• B. $A<B<C<E<D$
• C. $A<B<C<D<E$
• D. $B<C<A<E<D$

Hint:

Hapticity is just a "carbon count" of the attachment!

Answer 1

The Correct Option is A

Step 1: Concept Hapticity ($\eta$) refers to the number of atoms of a ligand that are coordinated to a central metal.

Step 2: Meaning Count the carbons involved in the $\pi$ system for each ligand.

Step 3: Analysis C. Phenyl ($\eta^{1}$ or $\eta^{6}$, but as a simple ligand fragment usually $\eta^{1}$). A. Allyl ($\eta^{3}$). B. Butadiene ($\eta^{4}$). E. Cyclooctatriene ($\eta^{6}$ usually). D. Tropillium ($\eta^{7}$).

Step 4: Conclusion The sequence $1 < 3 < 4 < 6 < 7$ matches order (A). Final Answer: (A)