Question

Which of the following 2 compounds exhibit both Geometrical and Structural isomerism?
A = $[Co(NH_3)_4Cl_2]NO_2$
B = $[Co(NH_3)_4Br]SO_4$
C = $[Co(NH_3)_3(NO_2)_2]$
D = $[Cr(H_2O)_6]Cl_3$

• A. A & C
• B. C & B
• C. B & D
• D. A & B

Hint:

When studying isomerism in coordination compounds, check for the possibility of different ligand arrangements (geometrical isomerism) and variations in how the ligands are connected to the central metal (structural isomerism).

Answer 1

The Correct Option is A

In coordination chemistry, isomerism can be classified into two main types: geometrical isomerism and structural isomerism. - Geometrical isomerism arises due to the different spatial arrangements of ligands around a metal center. This occurs only in coordination complexes where ligands are not identical, such as square planar and octahedral coordination compounds. 

- Structural isomerism arises when the connectivity of ligands in the coordination complex is different, such as linkage isomerism (where a ligand can coordinate via different atoms) or coordination isomerism (where different combinations of ions coordinate to the central metal ion). For the given compounds: 

1. A = \([Co(NH_3)_4Cl_2]NO_2\): This compound can exhibit both geometrical isomerism (cis/trans) due to the two chloride ligands and structural isomerism because the nitrite can act as a nitrito ligand or a nitro ligand. 
2. C = \([Co(NH_3)_3(NO_2)_2]\): This compound can exhibit geometrical isomerism due to the two nitrite ligands (cis/trans arrangement), and structural isomerism due to the different ways the ligands can bind to the metal (linkage isomerism). 
3. B = \([Co(NH_3)_4Br]SO_4\): This compound shows no geometrical isomerism (only one possible arrangement of ligands) and does not exhibit structural isomerism because the ligand coordination does not change. 
4. D = \([Cr(H_2O)_6]Cl_3\): This is an octahedral complex where the ligands are identical (water molecules), and it does not show either geometrical or structural isomerism. Thus, the compounds that exhibit both geometrical and structural isomerism are A and C.