Facial isomerism is associated with which type of complex?

Facial isomerism occurs in octahedral complexes where two types of ligands are present, and specifically, it is observed in complexes of the type MA3B3. In these complexes, the three identical ligands (A) can occupy one face of the octahedron, while the three other identical ligands (B) occupy the opposite face. This arrangement creates two distinct arrangements of ligands, allowing for the possibility of geometrical isomers, specifically facial and meridional isomers.

The facial isomer has all three identical ligands on one face of the octahedron, while the meridional isomer has the identical ligands arranged around the equator. The ability to form such distinct groups of ligands based on their spatial arrangement is what defines facial isomerism.

In contrast, the other options represent complex types that do not facilitate facial isomerism. For instance, MA2B2 and MA4B2 complexes arrange their ligands differently and do not have the same potential for isomerism as an MA3B3 complex. MA2B6 also does not showcase facial isomerism due to having more dominant ligand types that fill the octahedral coordination sphere. Therefore, MA3B