Paper: CSIR-NET December 2014 · Subject: Physical Chemistry · Chapter: Group Theory · Topic: Symmetry Elements Point Groups · Marks: 2 · Difficulty: Easy
The point group symmetries for trans- $\left[\mathrm{Cr}(\mathrm{en})_{2} \mathrm{F}_{2}\right]+$ and $[\mathrm{TiCl} 6]^{3-}$, respectively, are
(a)$\mathrm{D}_{4 \mathrm{d}}$ and $\mathrm{D}_{3 \mathrm{d}}$
(b)$\mathrm{D}_{3 \mathrm{d}}$ and $\mathrm{D}_{4 \mathrm{d}}$
(c)$\mathrm{D}_{4 \mathrm{h}}$ and $\mathrm{D}_{3 \mathrm{h}}$
(d)$\mathrm{D}_{3 \mathrm{h}}$ and $\mathrm{D}_{4 \mathrm{h}}$
Answer
Answer: C ✓ checked by 4AB · confidence low
The source book printed A; on checking, C is correct — see the explanation.
[TiCl6]3- is Oh; no option is fully correct.
Explanation
Treating the en rings as point ligands, trans-[Cr(en)₂F₂]⁺ is D₄h. [TiCl₆]³⁻ is a regular octahedron (O_h), which no option offers; (c) is the option with the correct D₄h. The printed question is defective.