Question

Which of the following exhibit both geometrical and optical isomerism? \[ \begin{aligned} \text{I. }&[\mathrm{Pt(en)_2Cl_2}]^{2+} \text{II. }&[\mathrm{Co(NH_3)_3(NO_2)_3}] \text{III. }&[\mathrm{Cr(H_2O)_2(C_2O_4)_2}]^{-} \text{IV. }&[\mathrm{Co(en)_3}]Cl_3 \end{aligned} \] The correct answer is

• A. I, III, IV only
• B. I, II, III only
• C. II, III, IV only
• D. I, III only

Hint:

Remember: \[ \boxed{ \begin{aligned} &[\mathrm{Co(en)_3}]^{3+} &&\rightarrow \text{Only optical isomerism}, &[\mathrm{Pt(en)_2Cl_2}]^{2+}, [\mathrm{Cr(H_2O)_2(C_2O_4)_2}]^{-} &&\rightarrow \text{Both geometrical and optical isomerism}. \end{aligned} } \]

Answer 1

The Correct Option is D

Step 1: Examine each complex. \[ \mathrm{[Pt(en)_2Cl_2]^{2+}} \] shows cis--trans geometrical isomerism, and the cis-form is optically active. Hence, \[ \boxed{\text{Both geometrical and optical isomerism}.} \] \[ \mathrm{[Co(NH_3)_3(NO_2)_3]} \] shows only geometrical (fac--mer) isomerism and does not exhibit optical isomerism. \[ \mathrm{[Cr(H_2O)_2(C_2O_4)_2]^{-}} \] shows cis--trans geometrical isomerism, and the cis-form exists as optical isomers. Hence, \[ \boxed{\text{Both geometrical and optical isomerism}.} \] \[ \mathrm{[Co(en)_3]Cl_3} \] shows only optical isomerism (\(\Delta\) and \(\Lambda\) forms), but no geometrical isomerism.

Step 2: Choose the correct complexes. Therefore, \[ \boxed{\text{I and III only}} \] exhibit both geometrical and optical isomerism. Hence, the correct option is \[ \boxed{(D).} \]