plz give the factors affecting the stability of complex ion.

Factors Affecting Stability of a Complex Ion

1) Charge on the central metal ion: Greater the charge more will be the polarization powers hence more the stability of complex.

2) Basic nature of ligand: Ligand which easy donates electron pairs forms stable complex.

3) Presence of chelate rings: Formation of chelate rings increases the stability.The stability increases with the increase in the number of rings in the molecule:

  M(en) <   M(trien)  <  M(EDTA).

  (one ring)  (two rings)   (five rings)

4) Electronegativity increases the polarizing power and the ions with higher electronegativity give stable complexes.

5) Steric Effect:

  Steric hindrance can influence stability in many ways, e.g.

(i) Metal-ligand bonds are weakened due to the presence of bulky group near the coordinating site.

(ii) The substituting group prevents the ligand from assuming the planar configuration and hence introduce strain in the metal-donor bond.

(iii)Steric hindrance is also due to strained structure of the chelated ring, since it breaks the usual linear configuration of the complexes.

5) Ionization Energies: The electro negativity, covalent nature and ionic radii can be related to the ionization energies of the atoms. It is found that the stability constants for the metal complexes with a ligand increases with the ionization energies of the metallic species.