Ligands and complexes?

Question

What properties of a molecule or ion make the species a good ligand for forming complexes with transition metal ions?

Answer 1

The ligand must be a good electron pair donor.

Note that the transition metal form complexes by using the d or d hybrid orbitals that are not fully filled. By, complexation, the transition metal is able to attain a stable configuration by having a full d^10, much like a fully filled octet of s^2p^6.