Inner Sphere Complex
- Ligand is directly attached to the metal.
- They share electrons.
- Example: [Fe(CN)₆]³⁻ → cyanide is directly bonded to iron.
Outer Sphere Complex
- Ligand is not directly attached to the metal.
- They are held by weak forces like attraction or hydrogen bonding.
- Example: [Cr(H₂O)₆]³⁺ + Cl⁻ → chloride is outside, just attracted to the metal.
In short:
- Inner sphere = direct bond
- Outer sphere = no direct bond, just attraction