Question

The correct trend in the rate of substitution of Cl$^-$ by pyridine in the following complexes is 

• A. III \(<\) II \(<\) IV
• B. II \(<\) III \(<\) IV
• C. I \(<\) III \(<\) IV
• D. I \(<\) II \(<\) IV

Hint:

In substitution reactions, electron-donating ligands and lower steric hindrance lead to faster substitution rates.

Answer 1

The Correct Option is A

Step 1: Understanding the complexes.
In these complexes, pyridine substitutes chloride ions. The rate of substitution is influenced by the electron-donating ability of the ligands and the steric hindrance around the metal center.
Step 2: Analyzing the trend.
Complex (IV) has the least steric hindrance and the highest electron-donating ability, making it the fastest in substitution. Complex (I) has more steric hindrance and lower electron donation, making it the slowest in substitution.
Step 3: Conclusion.
The correct trend in the rate of substitution is \( I<II<IV \), corresponding to option (D).