Stability constant, thermodynamics, lead-ligand

Of course, for complexes to be formed, not only must they be of sufficient stability, but their rate of formation must also be sufficiently fast. This leads to the concept of labile and inert complexes. The rate with which a given complex exchanges its ligands with other complexes present in the solution is a mark of the lability property. Those for which these reactions are fast are said to be labile. Those for which they are slow are said to be inert. The lability concept only concerns reaction rates. Hence, it only concerns the kinetic aspects of complexation reactions. It has nothing to do with their thermodynamic aspect, that is, with the stability of complexes. A good example of the distinction between these two aspects is provided by the hexamminecobalt (III) complex [Co(NH3)6] +. It can survive for several days in acidic aqueous solution although it is not stable. (The fact that a compound is not stable is purely and simply in the realm of thermodynamics.) This is because it is inert. Its instability is proved by the equilibrium constant value of the following reaction ... 

---