Question

In the complex ion [Co(NH₃)₃(H₂O)₂Cl]⁺:

Write the geometry of the complex ion.

Answer 1

In the complex ion [Co(NH₃)₃(H₂O)₂Cl]⁺:

The coordination number of a complex is the number of ligand donor atoms bonded directly to the central metal ion.

In this complex:

• 3 NH₃ (neutral, monodentate) = 3 donor atoms

• 2 H₂O (neutral, monodentate) = 2 donor atoms

• 1 Cl⁻ (anionic, monodentate) = 1 donor atom

So, total coordination number = 3 + 2 + 1 = 6

A coordination number of 6 almost always corresponds to octahedral geometry in transition metal complexes.