5. Thermodynamic stability
Existence of a complex under equilibrium condition.
It is a measure of tendency of metal ion to form a particular complex ion.
It is given by formation constant.
6. If Kf value is higher, the product will be in higher amount, that is, ligand bind to the metal ion
more strongly than the water.
If Kf value is lower, the product will be in lower amount, that is, ligand will not bind metal more
strongly than water.
7. 𝛥G=-RTlnKf
Positive value of Kf will give negative value of 𝛥G.
Negative value of Kf will give positive value of 𝛥G.
12. K1 > K2 > K3 > K4……..Kn-1 > Kn
Increase in number of ligands in coordination sphere causes to decrease the number of replaceable water
molecule
Steric hinderance increases
Electrostatic factor (in charged ligand)
13.
14.
15. Factors affecting stability of complexes
Nature of the central metal ion
Nature of the ligand
The chelate effect
Macrocyclic effect
Resonance effect
Steric effcet
16. Nature of the central metal ion
a) Charge on metal cation : Higher oxidation state, more stable complex.
Exception: The ligand which has vacant π* orbital like CO (Carbonyl), PMe3 (Trimethyl phosphene), CN- (good σ donor).
17. b) Charge on the central metal ion
Stability of complex increase with decrease in size of metal (if oxidation state is the same).
Nature of the central metal ion
Ni
2+ Co2+
Mn2+
Mg2+ Ca2+
Sr2+
Ba2+
Irving - Williams series
18. Nature of Ligands
Higher the ability to donate lone pair of electron, the higher will be the stability
NH3 >H2O >F-
Covalent character higher, stability will be higher
AgI2
- > AgBr2
- > AgCl2
- > AgF2
-
Vacant 𝜋-orbital ligand will form stable complex