Question

Write the structure of the following complex on the basis of Werner’s theory:

CoCl₃·5NH₃

Answer 1

The oxidation state of cobalt in the complex CoCl₃·5NH₃ is +3. This gives three primary valencies, with three Cl atoms bonded to cobalt by these valencies. The remaining five NH₃ molecules are attached by secondary valencies, making the coordination number of cobalt six. One Cl atom is linked by both primary and secondary valencies and does not ionize in solution. The complex ionizes as follows:

\[\ce{CoCl3.5NH3 -> [CoCl.5NH3]^2+ + 2Cl^-}\]