Distinguishing Between Strong and Weak Ligands
In coordination chemistry, ligands are molecules or ions that donate a pair of electrons to a central metal ion, forming a coordination complex. Ligands are classified as strong field ligands (SFL) and weak field ligands (WFL) based on their ability to split the d-orbitals of the central metal ion.
Strong ligands cause a large splitting of d-orbitals and often lead to low-spin complexes. Examples include CN⁻, CO, and NO₂⁻.
Weak ligands, on the other hand, result in a small splitting of d-orbitals and generally form high-spin complexes. Examples include H₂O, Cl⁻, and F⁻.
Differences Between Strong and Weak Ligands
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FAQs on Strong Ligand Vs. Weak Ligand
1. Is H₂O a strong or weak field ligand?
H₂O is a weak field ligand because it causes a small crystal field splitting.
2. Is CN⁻ a strong or weak ligand?
CN⁻ is a strong field ligand due to its high crystal field splitting energy.
3. Which type of ligand is strong or weak?
Strong ligands cause large crystal field splitting and form low-spin complexes, while weak ligands cause small splitting and form high-spin complexes.
4. Is EDTA a strong or weak field ligand?
EDTA is considered a strong ligand due to its polydentate nature and ability to stabilize metal complexes.
5. Is NH₃ a strong or weak ligand?
NH₃ is a borderline strong ligand; it can behave as a strong or weak ligand depending on the metal ion.
6. How to calculate CFSE?
Crystal Field Stabilization Energy (CFSE) is calculated using the energy difference between split d-orbitals in an octahedral or tetrahedral field.
7. Which ligand forms the most stable complexes?
Chelating ligands like EDTA form highly stable complexes due to the chelate effect.
8. What is the chelate effect?
The chelate effect refers to the increased stability of metal complexes due to multidentate ligands forming rings with the metal ion.
9. Is pyridine a strong field ligand?
Pyridine is a moderate field ligand, stronger than halides but weaker than CN⁻.
10. Which complexes are diamagnetic?
Complexes with strong field ligands that cause paired electrons in d-orbitals are diamagnetic.
