Question

Which of the following complexes do not exhibit geometrical isomerism? \[ \begin{aligned} \text{I.} \quad & [\mathrm{CrF_2(H_2O)_4}]Cl_2 \\ \text{II.} \quad & [\mathrm{Co(en)_3}]^{3+} \\ \text{III.} \quad & [\mathrm{CoF(NH_3)_5}](\mathrm{NO_3})_2 \end{aligned} \] The correct answer is

• A. I, II only
• B. II, III only
• C. I, III only
• D. I, II, III \bigskip

Hint:

For octahedral complexes:

• \([\mathrm{MA_4B_2}]\) \(\rightarrow\) cis-trans isomerism.
• \([\mathrm{MA_5B}]\) \(\rightarrow\) No geometrical isomerism.
• \([\mathrm{M(AA)_3}]\) (three identical bidentate ligands) \(\rightarrow\) Optical isomerism only.

Answer 1

The Correct Option is B

Step 1: I: [CrF₂(H₂O)₄]²⁺ type MA₄B₂ → shows geometrical isomerism. II: [Co(en)₃]³⁺ → only optical, no geometrical. III: [CoF(NH₃)₅]²⁺ type MA₅B → no geometrical. II & III do not exhibit geometrical isomerism.

Step 2: Write the final answer. \(\boxed{\text{II and III only}.}\)