question_answer 35)

What is meant by stability of a coordination compound in solution? State the factors which govern stability of complexes.

Answer:

Stability of a complex in solution means the measure of resistance to the replacement of a ligand by some other ligand. This stability ran be expressed in terms of equilibrium constant of the following reaction: Mn+ + NLm? [MLN]z+ Stability constant, Factors affecting the stability of a complex ion: (i) Factors affecting the stability of a complex ion : (1) Nature of the metal ion: (a) Greater the charge and smaller the size of the ion, more is its charges density and greater will be the stability of the complex i.e., why [Fe(CN)6]?3 is more stable than [Fe(CN)6]?4. (b) For the same charged metal ions, stability of the complexes increases as the size decreases e.g., Cu2+ complexes are more stable than Mn2+ complexes.           (2) Nature of the ligand. (a) More the basicity of ligand, more is its tendency to donate electron pair and therefore more is the stability of the complex. (b) For anionic ligands and complexes are more stable if ligand has greater charge and smaller size. (c) Chelating ligands form more stable complexes.