Given two statements — Statement-I: [Fe(ox)₃]³⁻ is chiral. Statement-II: trans-[Cr(H₂O)₂(ox)₂]⁻ is chiral. (oxH₂ = HOOC–COOH). Choose the most appropriate answer:
- A.Both Statement-I and Statement-II are correct
- B.Both Statement-I and Statement-II are incorrect
- C.Statement-I is correct but Statement-II is incorrect✓
- D.Statement-I is incorrect but Statement-II is correct
Correct Answer
(C) Statement-I is correct but Statement-II is incorrect
Solution & Explanation
Concept — Optical chirality in octahedral complexes: a complex is chiral if it has no plane of symmetry, no centre of symmetry and no improper axis, so that it and its mirror image cannot be superimposed. Tris-bidentate (M(AA)₃) and cis-bis-bidentate (cis-M(AA)₂X₂) arrangements are the classic chiral cases; trans-M(AA)₂X₂ is usually achiral. Statement-I: [Fe(ox)₃]³⁻ has three symmetrical bidentate oxalate ligands arranged like a three-bladed propeller around Fe³⁺. This M(ox)₃ unit has only a C₃ axis and no mirror/centre of symmetry, so it exists as two non-superimposable enantiomers (Δ and Λ). It is chiral → Statement-I is CORRECT. Statement-II: In trans-[Cr(H₂O)₂(ox)₂]⁻ the two H₂O ligands sit on opposite vertices (trans, 180° apart) and the two oxalates lie in the equatorial plane. This trans arrangement possesses a plane of symmetry, so the molecule is superimposable on its mirror image — it is achiral. (Only the cis isomer of this complex is chiral.) → Statement-II is INCORRECT. Therefore Statement-I is correct but Statement-II is incorrect — option C.
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