Question

$\textbf{Number of complexes which show optical isomerism among the following is \_\_\_\_\_\_.}$
\[ \text{cis}-[\text{Cr(ox)}_2\text{Cl}_2]^{3-}, \quad [\text{Co(en)}_3]^{3+}, \] \[ \text{cis}-[\text{Pt(en)}_2\text{Cl}_2]^{2+}, \quad \text{cis}-[\text{Co(en)}_2\text{Cl}_2]^{+}, \] \[ \text{trans}-[\text{Pt(en)}_2\text{Cl}_2]^{2+}, \quad \text{trans}-[\text{Cr(ox)}_2\text{Cl}_2]^{3-} \]

Answer 1

Correct Answer: 4

To determine the number of complexes that exhibit optical isomerism, it is important to understand the structural features and symmetry elements that influence chirality in coordination compounds. Optical isomerism arises when a compound has non-superimposable mirror images, or enantiomers, typically due to the absence of a plane of symmetry (POS) or a center of symmetry (COS).

Analysis of the Given Complexes:

• cis−[Cr(ox)₂Cl₂]³⁻: This complex can exhibit optical isomerism due to its lack of both POS and COS. The cis configuration allows for chirality, as the two oxalate ligands and two chloride ligands create a structure capable of forming non-superimposable mirror images.
• [Co(en)₃]³⁺: Optical isomerism is possible because the complex contains three bidentate ethylenediamine (en) ligands, creating a chiral coordination environment without POS or COS.
• cis−[Pt(en)₂Cl₂]²⁺: The cis arrangement of the two ethylenediamine ligands and two chloride ions gives rise to optical isomerism due to the lack of POS and COS.
• cis−[Co(en)₂Cl₂]⁺: This complex also shows optical isomerism, as it does not have POS or COS and the cis configuration enables chirality.
• trans−[Pt(en)₂Cl₂]²⁺: Optical isomerism is not possible because the trans configuration introduces symmetry, including POS or COS, eliminating the possibility of forming enantiomers.
• trans−[Cr(ox)₂Cl₂]³⁻: This complex cannot show optical isomerism due to the presence of POS or COS, making it symmetric.

Conclusion: Based on the analysis, four complexes can exhibit optical isomerism: cis−[Cr(ox)₂Cl₂]³⁻, [Co(en)₃]³⁺, cis−[Pt(en)₂Cl₂]²⁺, and cis−[Co(en)₂Cl₂]⁺.
Final Answer: (4)