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Use ethelenediamine to answer this: Use the above-named chelating ligand to explain in terms of the collision theory why complexes resulting from coordination with chelating ligands are much more thermodynamically favorable than those without.
Accepted Answer
Chelating ligands, like ethylenediamine, form more stable complexes than monodentate ligands due to the chelate effect. This effect arises from the entropic contribution to the overall stability of the complex.
Here's how it relates to collision theory:
Collision Frequency: When a chelating ligand approaches a metal ion, it has multiple points of attachment. This increases the chances of a successful collision leading to complex formation, compared to a monodentate ligand that has only one point of attachment.
Entropy: The chelate effect is primarily driven by entropy. When a chelating ligand binds, it displaces multiple water molecules from the coordination sphere of the metal ion. This results in an increase in the number of free particles in solution, leading to a positive entropy change (ΔS). The overall change in Gibbs free energy (ΔG) is favorable because the entropic contribution outweighs the enthalpic contribution.
In simpler terms, the chelating ligand wraps around the metal ion, effectively increasing the concentration of the metal ion in the immediate vicinity of the ligand, making it more likely to form a complex. This increased probability of successful collisions leads to a more favorable thermodynamic outcome compared to monodentate ligands.
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