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Question #44560

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The Question

A bimetallic coordination compound has the molecular formula $\ce{CoCr(en)3(ox)3}$ (where en = ethylenediamine, ox = oxalate). It exists as multiple coordination isomers. Isomer $C_1$ is characterized by having both a heteroleptic cation and a heteroleptic anion. Furthermore, the cationic entity of $C_1$ is diamagnetic at $298\text{ K}$ .

An engineered enzyme with a highly specific chiral pocket acts as a biological 'chiral filter'. When an aqueous solution of $C_1$ is passed through a column containing this enzyme, the active site exclusively binds the $\Lambda$ -enantiomer of the cation via a strict lock-and-key mechanism.

Identify the exact complex cation retained in the enzyme's active site, its magnetic nature, and the total number of stereoisomers for the coordination isomer $C_1$ .

Options

A.
$\Lambda\text{-}[\ce{Co(en)2(ox)}]^+$ , Diamagnetic, 4
B.
$\Lambda\text{-}[\ce{Cr(en)2(ox)}]^+$ , Paramagnetic, 4
C.
$\Lambda\text{-}[\ce{Co(en)2(ox)}]^+$ , Diamagnetic, 9
D.
$\Lambda\text{-}[\ce{Co(en)2(ox)}]^+$ , Paramagnetic, 4

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Coordination Isomerism|Optical Isomerism Logic|Enzyme Specificity 'Lock and Key'

Why This Question Is Tricky

Common Mistakes

The question tests the intersection of Coordination Isomerism, Crystal Field Theory, and Stereochemistry.

The primary 'Hidden Variable' trap lies in the stereochemical analysis of complexes with three bidentate ligands (e.g., $[\ce{Co(en)2(ox)}]^+$ ).

Students often erroneously apply the isomerism rules of $M(AA)_2B_2$ complexes, assuming a trans (achiral) isomer exists, leading to 3 isomers per ion and a total of 9 stereoisomers.

However, because 'ox' is also bidentate, it cannot span the 180-degree trans positions due to severe ring strain.

Thus, only the chiral $\Delta$ and $\Lambda$ forms exist, resulting in exactly 4 stereoisomers.

The biological 'lock and key' mechanism serves as a rigorous proxy for chiral resolution, demanding precise identification of the retained enantiomer.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Coordination Compounds - Class 12
Concept	Coordination Isomerism
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free