What is meant by stability of a coordination compound in solution? State the factors which govern stability of complexes.
The stability of a complex in a solution refers to the degree of association between the two species involved in a state of equilibrium. Stability can be expressed quantitatively in terms of stability constant or formation constant.
For this reaction, the greater the value of the stability constant, the greater is the proportion of ML3 in the solution.
Stability can be of two types:
(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: This helps in determining the speed with which the transformation will occur to attain the state of equilibrium.
Factors that affect the stability of a complex are:
(a) Charge on the central metal ion: Thegreater the charge on the central metal ion, the greater is the stability of the complex.
1. Basic nature of the ligand: A more basic ligand will form a more stable complex.
2. Presence of chelate rings: Chelation increases the stability of complexes.