Which one of the following octahedral complexes will not show geometric isomerism ? (A and B are monodentate ligands)
A
$[MA_2B_4]$
B
$[MA_3B_3]$
C
$[MA_4B_2]$
D
$[MA_5B]$
The answer is D.
Solution
$[MA_4B_2]$ and $[MA_2B_4]$: the two identical minority ligands can be adjacent (cis) or opposite (trans), so they show cis–trans isomerism. $[MA_3B_3]$: the three A ligands can lie on one face of the octahedron (facial, fac) or along a meridian (mer), so it shows fac–mer isomerism. $[MA_5B]$: there is only one B ligand. Whichever of the six positions it occupies, all arrangements are identical, so there is only one form. So $[MA_5B]$ will not show geometric isomerism.
ConceptGeometrical isomerism in octahedral complexes
Coordination Compounds in past papers
104 questions from this chapter have appeared across 27 exam years.
