Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): The total number of geometrical isomers shown by [Co(en)$_2$Cl$_2$]$^+$ complex ion is three.
Reason (R): [Co(en)$_2$Cl$_2$]$^+$ complex ion has an octahedral geometry.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. (A) is correct but (R) is not correct.
• C. (A) is not correct but (R) is correct.
• D. Both (A) and (R) are correct but (R) is not the correct explanation of (A).

Answer 1

Answer: (C)

(A) is not correct but (R) is correct.

Answer 2

The complex ion $[Co(en)_2Cl_2]^+$ has an octahedral geometry. However, it shows only two geometrical isomers:

• Cis-isomer: Both chloride ligands are adjacent to each other.
• Trans-isomer: Chloride ligands are opposite to each other.

This refutes the assertion that it shows three geometrical isomers. Thus, (A) is incorrect. However, the reason (R) stating that the complex has an octahedral geometry is true.

Final Answer: (3) (A) is not correct but (R) is correct.