Question

Facial and meridional isomerism will be exhibited by
A ) \[\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_3}{\text{C}}{{\text{l}}_3}} \right]\]
B ) \[\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_4}{\text{C}}{{\text{l}}_2}} \right]{\text{Cl}}\]
C ) \[\left[ {{\text{Coe}}{{\text{n}}_3}} \right]{\text{C}}{{\text{l}}_3}\]
D ) \[\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_5}{\text{Cl}}} \right]{\text{C}}{{\text{l}}_2}\]

Answer 1

Hint: Facial and meridional isomerism is shown by the octahedral complexes of type \[\left[ {{\text{M}}{{\text{a}}_3}{{\text{b}}_3}} \right]\]. Here, M is the metal, a and b are monodentate ligands.

Complete step by step answer:
Facial isomer is also called fac isomer and meridional isomer is also called mer isomer. Facial and meridional isomers are geometrical isomers. These isomers are present in an octahedral ligand having two different types of monodentate ligands. Three ligands of one type and three ligands of other types are present.
\[\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_3}{\text{C}}{{\text{l}}_3}} \right]\] is an octahedral complex having two different types of ligands. Ammonia and chlorine are two different types of ligands. Three molecules of ammonia and three molecules of chlorine are present in this complex. In the facial isomer, three chlorine ligands are on one face of regualr octahedron. Three ammonia ligands are present on the opposite face of the octahedron. In the meridional isomer, the ammonia ligands are present on different faces of octahedrons. Similarly chloride ligands are present on different faces of octahedrons.
So the correct option is \[\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_3}{\text{C}}{{\text{l}}_3}} \right]\]

- The complex \[\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_4}{\text{C}}{{\text{l}}_2}} \right]{\text{Cl}}\] is of the type \[\left[ {{\text{M}}{{\text{a}}_4}{{\text{b}}_2}} \right]\]. It doesn't exhibit facial meridional isomerism.
- The complex \[\left[ {{\text{Coe}}{{\text{n}}_3}} \right]{\text{C}}{{\text{l}}_3}\]is of the type \[\left[ {{\text{M}}{{\left( {{\text{aa}}} \right)}_3}} \right]\]. It doesn't exhibit facial meridional isomers. Here, aa is bidentate ligand.
- The complex \[\left[ {{\text{Co}}{{\left( {{\text{N}}{{\text{H}}_3}} \right)}_5}{\text{Cl}}} \right]{\text{C}}{{\text{l}}_2}\]is of the type \[\left[ {{\text{M}}{{\text{a}}_5}{\text{b}}} \right]\]. It doesn't exhibit facial meridional isomerism.

So the correct answer is A).

Note: In facial isomer, three ligands of the same type are present on one face of regular octahedron. The remaining three ligands of other types are present on the opposite face of the octahedron. In the meridional isomer, the three ligands of the same type are present on different faces of regular octahedrons.