Identify the ligands in the complex

The complex is $[\mathrm{M}(\mathrm{en})(\mathrm{SCN})_4]$ where:

• $\mathrm{en}$ = ethylenediamine
• $\mathrm{SCN}^-$ = thiocyanate ligand

Recall what an ambidentate ligand is

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

Examples:

• $\mathrm{NO_2^-}$ : through N or O
• $\mathrm{SCN^-}$ : through S or N

Examine each ligand

• en (ethylenediamine) is a bidentate ligand, not ambidentate. It always coordinates through its two nitrogen atoms simultaneously.
• SCN$^-$ is ambidentate, because it can bind through:
  • sulfur: thiocyanato-S
  • nitrogen: isothiocyanato-N

Count the ambidentate ligands present

There are $4$ ligands of type $\mathrm{SCN}^-$ in the complex, and each is an ambidentate ligand.

Therefore, the number of ambidentate ligands is $4$

Final answer

$\boxed{4}$

Comparison with stored correct answer

Stored correct answer = $4$

This matches the derived answer.