Question
What is meant by stability of a coordination compound in solution? State the factors which govern stability of complexes.
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Answer
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. $\text{M}+3\text{L}\leftarrow\rightarrow\text{ML}_{3}$ Stability constant, $\beta=\frac{[\text{ML}_{3}]}{[\text{M}][\text{L}]^{3}}$ 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:
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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.
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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:- Charge on the central metal ion: Thegreater the charge on the central metal ion, the greater is the stability of the complex.
- Basic nature of the ligand: A more basic ligand will form a more stable complex.
- Presence of chelate rings: Chelation increases the stability of complexes.
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Code:
| | Column I (Complex ion) | | Column II (Hybridisation, number of unpaired electrons) |
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| | | 5. | sp3d2, 2 |
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