Question

EDTA forms a stable complex with a metal ion \(M^{3+}\). The complex formed is octahedral and represented as \([M(EDTA)]^{-\). Which of the following statements is correct?}

• A. EDTA acts as a tetradentate ligand and the complex shows geometrical isomerism only
• B. EDTA acts as a hexadentate ligand and the complex can show optical isomerism
• C. EDTA acts as a bidentate ligand and the complex shows linkage isomerism
• D. EDTA acts as a monodentate ligand and the complex is tetrahedral

Hint:

Remember the denticity of common ligands: \[ NH_3,\ H_2O,\ Cl^- \rightarrow \text{Monodentate} \] \[ C_2O_4^{2-},\ en \rightarrow \text{Bidentate} \] \[ EDTA^{4-} \rightarrow \text{Hexadentate} \]

Answer 1

The Correct Option is B

Concept: This question combines three important CUET topics:
• Denticity of ligands
• Coordination number
• Isomerism in coordination compounds Questions based on EDTA are extremely common because EDTA is one of the most important ligands mentioned in NCERT.

Step 1: Recall the structure of EDTA. EDTA stands for: \[ \text{Ethylenediaminetetraacetate} \] It contains:
• Two nitrogen donor atoms
• Four oxygen donor atoms Therefore total donor atoms: \[ 2+4=6 \] Hence EDTA is a: \[ \boxed{\text{Hexadentate ligand}} \]

Step 2: Determine the coordination number. Since EDTA donates six lone pairs simultaneously: \[ \text{Coordination Number}=6 \] A coordination number of six generally produces: \[ \boxed{\text{Octahedral geometry}} \] which agrees with the information given in the question.

Step 3: Examine the possibility of isomerism. Complexes containing multidentate ligands often possess chirality. Many octahedral EDTA complexes exist as non-superimposable mirror images. Therefore they can show: \[ \boxed{\text{Optical isomerism}} \]

Step 4: Eliminate incorrect options. Option (A): EDTA is not tetradentate. Incorrect. Option (C): EDTA is not bidentate. Incorrect. Option (D): EDTA is not monodentate and the complex is not tetrahedral. Incorrect.

Step 5: Final conclusion. EDTA acts as: \[ \boxed{\text{Hexadentate ligand}} \] and the complex can exhibit: \[ \boxed{\text{Optical isomerism}} \] Hence: \[ \boxed{\text{Option (B)}} \]