Identify the ligand

Ethylenediaminetetraacetate, $EDTA^{4-}$, is a well-known multidentate ligand.

Count donor atoms in $EDTA^{4-}$

$EDTA^{4-}$ has:

• 2 nitrogen atoms from the two amine groups
• 4 oxygen atoms that can coordinate from the four carboxylate groups

Total coordination sites

Hence, the total number of donor atoms (coordination sites) is $2 + 4 = 6$

Conclusion

Therefore, $EDTA^{4-}$ is a hexadentate ligand and has 6 coordination sites.