Question

Which one of the following octahedral complexes will not show geometrical isomerism? (A and B are monodentate ligands)

• A. $\left[\right.\text{M}\text{A}_{4}\text{B}_{2}\left]\right.$
• B. $\left[\right.\text{M}\text{A}_{5}\text{B}\left]\right.$
• C. $\left[\right.\text{M}\text{A}_{2}\text{B}_{4}\left]\right.$
• D. $\left[\right.\text{M}\text{A}_{3}\text{B}_{3}\left]\right.$

Answer 1

Answer: (B)

Metal complexes that differ only in which ligands are adjacent to one another (cis) or directly across from one another (trans) in the coordination sphere of the metal are called geometrical isomers. They are most important for square planar and octahedral complexes.
$\left[\right.\text{M}\text{A}_{5}\text{B}\left]\right.$ can be written only in single octahedral structure. Hence, it does not show geometrical isomerism.