What is the Difference Between Strong Ligand and Weak Ligand?
🆚 Go to Comparative Table 🆚The difference between strong ligands and weak ligands lies in their ability to split the d-orbital energy levels of a central transition metal atom in a coordination complex. Ligands are classified as strong or weak based on the spectrochemical series, which ranks ligands according to the energy difference ΔO between the t2g and eg orbitals.
Strong ligands:
- Produce a large energy splitting (ΔO) between the t2g and eg orbitals.
- Tend to have electronegative atoms that are strongly electron-withdrawing, leading to poor orbital overlap between the ligand and the metal.
- Examples include CO, NH3, NO2-, and CN-.
Weak ligands:
- Produce a small energy splitting (ΔO) between the t2g and eg orbitals.
- Tend to have less electronegative atoms, allowing better orbital overlap between the ligand and the metal.
- Examples include I-, Br-, Cl-, F-, OH-, H2O, and NH3.
The spectrochemical series can be abbreviated as I- < Br- < Cl- < F- < OH- < H2O < NH3 < NO2- < CN-.
In summary, strong ligands produce a larger energy splitting between the t2g and eg orbitals, while weak ligands produce a smaller energy splitting. This difference in energy splitting is due to the varying electronegativity of the atoms in the ligands and the resulting orbital overlap between the ligand and the central metal atom.
Comparative Table: Strong Ligand vs Weak Ligand
The main difference between strong ligands and weak ligands lies in the extent of the splitting of the d orbitals of a metal ion. Here is a table comparing the characteristics of strong ligands and weak ligands:
| Feature | Strong Ligands | Weak Ligands |
|---|---|---|
| Definition | Ligands that cause a greater splitting of the crystal field are called strong ligands or strong field ligands. | Ligands that cause a smaller splitting of the crystal field are called weak ligands or weak field ligands. |
| Ligand Strength | Strong ligands are typically stronger ligands. | Weak ligands are typically weaker ligands. |
| Complex Formation | Strong ligands usually form low spin complexes. | Weak ligands tend to form high spin complexes. |
| Spectrochemical Series | Strong ligands are found toward the top of the spectrochemical series, which ranks ligands according to their intensity of f-f or d-d transitions. | Weak ligands are found toward the bottom of the spectrochemical series. |
Strong ligands, such as CN-, bind through more electronegative atoms like C and N, which allow better orbital overlap and stronger interactions with the metal ion. In contrast, weak ligands like water bind through less electronegative atoms like O, resulting in poor orbital overlap and weaker interactions with the metal ion.
- Ligand vs Chelate
- Strong vs Weak Electrolytes
- Weak vs Strong Acid
- Bidentate vs Ambidentate Ligands
- Weak vs Week
- Crystal Field Theory vs Ligand Field Theory
- Strong vs Weak Acids vs Bases
- Chelate vs Macrocyclic Ligands
- Ionic vs Covalent Bonds
- Ligase vs Lyase
- Weak Acid vs Dilute Acid
- Electrovalent vs Covalent Bond
- Voltage Gated vs Ligand Gated Ion Channels
- Double Bond vs Single Bond
- Covalent vs Noncovalent Bonds
- Ionic Bonding vs Metallic Bonding
- Concentrated Acid vs Strong Acid
- Hydrogen Bond vs Ionic Bond
- Coordinate Covalent Bond vs Covalent Bond