What is meant by the stability of a coordination compound in solution? State the factors which govern the stability of complexes.
What is meant by the stability of a coordination compound in solution? State the factors which govern the stability of complexes.
The stability of a coordination compound (aq) means the degree of association between the two species involved in the state of equilibrium. The magnitude of (stability or formation ) equilibrium constant for the association; quantitative expresses the stability.
For a reaction, M + 4L → ML4
(Stability constant) K=[ ML4 ] [M ][ L ]4
The higher the value of the stability constant, the higher is the proportion of ML4′
that exists in the solution.
(a) Thermodynamic stability:
The extent to which the complex will be formed or will be transformed into another species at the point of equilibrium is determined by thermodynamic stability.
(b) Kinetic stability:
Kinetic stability helps in determining the speed with which the transformation will occur to attain the state of equilibrium.
Factors affecting the stability of complex
(i) Charge on the central metal ion: The higher the charge on the central metal ion, the greater the stability of the complex.
(ii) Nature of the metal ion: The stability constant of the complex of metallic ions having the same charge on them decreases with the increase in the size of the metal ions for the same ligands.
(iii) Basic nature of the ligands: The higher the basic strength of the ligand, the greater the stability of the complex because it can easily donate electron pairs to central metal.
(iv) Presence of chelate rings: Chelate rings increases the stability of the complex by chelate effect. The chelate effect is maximum for the 5 and 6- membered rings.
(v) Effect of multidentate cyclic ligands: if the ligands are multidentate and cyclic without any steric effect, the stability of the complex is further increased.
The stability of a coordination compound (aq) means the degree of association between the two species involved in the state of equilibrium. The magnitude of (stability or formation ) equilibrium constant for the association; quantitative expresses the stability.
For a reaction, M + 4L → ML4
(Stability constant) K=[ ML4 ] [M ][ L ]4
The higher the value of the stability constant, the higher is the proportion of ML4′
that exists in the solution.
(a) Thermodynamic stability:
The extent to which the complex will be formed or will be transformed into another species at the point of equilibrium is determined by thermodynamic stability.
(b) Kinetic stability:
Kinetic stability helps in determining the speed with which the transformation will occur to attain the state of equilibrium.
Factors affecting the stability of complex
(i) Charge on the central metal ion: The higher the charge on the central metal ion, the greater the stability of the complex.
(ii) Nature of the metal ion: The stability constant of the complex of metallic ions having the same charge on them decreases with the increase in the size of the metal ions for the same ligands.
(iii) Basic nature of the ligands: The higher the basic strength of the ligand, the greater the stability of the complex because it can easily donate electron pairs to central metal.
(iv) Presence of chelate rings: Chelate rings increases the stability of the complex by chelate effect. The chelate effect is maximum for the 5 and 6- membered rings.
(v) Effect of multidentate cyclic ligands: if the ligands are multidentate and cyclic without any steric effect, the stability of the complex is further increased.
