Question

Explain the bonding in coordination compounds in terms of Werner’s postulates.

What postulates did Werner use to explain the bonding in coordination compounds?

Answer 1

1. The core metal atom or ion in a complex has two sorts of valencies: the primary and the secondary.
   
   1. Primary valency: This sort of valency (linkage) is ionisable and represents the core metal ion’s oxidation state. It is always fulfilled by a negative ion. The fundamental valencies are represented by dotted lines. Ions connected to the central metal ions via primary valencies can ionise in solution.
   2. Secondary valency: This sort of valency (linkage) cannot be ionized and corresponds to the coordination number of the central metal atom or ion. Every core metal atom or ion has a set number of secondary valencies (this number is actually the coordination number of the central metal ion). Secondary valencies can be met by either negative ions or neutral molecules. They are shown by thick lines, and the groups connected to the core metal ion via them are unable to ionize in the solution.
2. The center metal atom or ion usually satisfies all of its main and secondary valencies. To achieve this need, the core metal atom or ion can attach one or more negative ions via both primary and secondary valencies. As a result, some negative ions may serve more than one function. These ions do not ionise in solution.
3. Secondary valencies are directional, meaning they point in specific directions in space. The main valencies are not directional.