Question

The total number of stereoisomers for the complex [Cr(ox)₂Clbr]³- (where oxalate) is:

• A. 2
• B. 4
• C. 3
• D. 1

Answer 1

The Correct Option is C

The given complex is [Cr(ox)\(_2\)ClBr]\(^{3-}\), where: - \( \text{ox} \) (oxalate) is a bidentate ligand, forming chelate rings with the central metal atom. - \( \text{Cl} \) and \( \text{Br} \) are monodentate ligands. ### Types of Isomerism: 1. Geometrical Isomerism: - The \( \text{Cl} \) and \( \text{Br} \) ligands can be arranged either cis (adjacent) or trans (opposite) to each other. - This results in two geometrical isomers: cis and trans. 2. Optical Isomerism: - Among the geometrical isomers, only the cis-isomer can exhibit optical isomerism. - The cis-isomer does not have a plane of symmetry, so it can exist as two enantiomers: \( d \)-form and \( l \)-form. Thus, the total number of stereoisomers for this complex is: \[ \text{1 trans-isomer (no optical isomerism) + 2 cis-enantiomers (d and l forms)} = 3 \text{ isomers}. \] ### Explanation with Diagrams: 1. Trans-isomer: This structure has a plane of symmetry, so no optical isomerism is observed. \[ \text{Cl and Br are opposite to each other.} \] 2. Cis-isomer: This structure does not contain a plane of symmetry, so it exhibits optical isomerism. \[ \text{Cl and Br are adjacent to each other. Two forms (d and l) are possible.} \] ### Conclusion: The total number of stereoisomers is \( \boxed{3} \).