Question

The total number of possible isomers for square planar ${\left[ {{\text{Pt}}\left( {{\text{Cl}}} \right)\left( {{\text{N}}{{\text{O}}_{\text{2}}}} \right)\left( {{\text{N}}{{\text{O}}_{\text{3}}}} \right)\left( {{\text{SCN}}} \right)} \right]^{{\text{2 - }}}}$ is:
A.16
B.12
C.8
D.24

Answer 1

To answer this question, you must recall the concept of isomerism in coordination compounds. Coordination compounds exhibit broadly two types of isomerism, namely structural and stereoisomerism.

Complete step by step solution:
The given coordination complex is given to have a square planar structure. The central metal ion has been coordinated by four different ligands.
Since all the ligands are different, we can conclude that the compound can form 3 geometrical isomers.
However, we know that an ambidentate ligand shows linkage isomerism as well. In simpler terms if a ligand has more than one donor atoms, the complex will have additional structural isomers.
In the given compound, we have two ambidentate ligands, namely the nitro group and the thiocyanate group. Both the ligands are bidentate.
In the nitro group, the two donor atoms are the nitrogen atom and the oxygen atom.
In the thiocyanate group, the two donor atoms are the nitrogen atom and the sulphur atom.
Thus, it is evident that each bidentate ligand has two linkage isomers and each linkage isomer, in turn, forms three geometrical isomers.
Therefore, the total number of isomers of the given compound $= 2 \times 2 \times 3 = 12$.
The total number of possible isomers for the square planar coordination complex ${\left[ {{\text{Pt}}\left( {{\text{Cl}}} \right)\left( {{\text{N}}{{\text{O}}_{\text{2}}}} \right)\left( {{\text{N}}{{\text{O}}_{\text{3}}}} \right)\left( {{\text{SCN}}} \right)} \right]^{{\text{2 - }}}}$ is 12.

The correct option is B.

Note: Coordination compounds also show optical isomerism. These are a pair of molecules which are non-superimposable mirror images of each other. Optical isomers of a compound have identical physical and chemical properties. They only differ in terms of the direction in which they rotate plane-polarized light.