Which of the following is an ambidentate ligand?

SCN^-

The correct answer is OPTION 3 - SCN^-

An ambidentate ligand is a ligand that can coordinate to a metal ion through two different atoms, but only one at a time.

1. NH₃ –

   • Monodentate ligand

   • Can donate a lone pair only through nitrogen
       Not ambidentate

2. H₂O –

   • Monodentate

   • Donates lone pair through oxygen
       Not ambidentate

3. SCN⁻ (Thiocyanate ion) –

   • Ambidentate ligand

   • Can bind through either sulfur (S) or nitrogen (N)
     
     

4. H₂N–CH₂–CH₂–NH₂ (Ethylenediamine) –

   • Bidentate ligand

   • Coordinates through two nitrogen atoms simultaneously
       Not ambidentate