Hello , Difference between strong and weak field ligands are as follows :

Strong Field Ligands :

• These ligands have more field strength
• These ligands may cause rearrangement of d electrons in metal
• They generally form low spin or inner orbital complexes
• For these ligands splitting energy > pairing energy

Weak Field Ligands :

• Ligands of less field strength
• These do not cause rearrangement of d electrons in metal.
• They generally form high spin or outer orbital complexes.
• For these ligands splitting energy < pairing energy.