JEE Main 2025 Apr 4 Shift 1, Chemistry Q9: Isomerism In Co-ordination Compounds

JEE Main2025Apr 4, Shift 1Chemistry

Number of stereoisomers possible for the complexes, $[C r C l_{3} (p y)_{3}]$ and $[C r C l_{2} (o x)_{2}]^{3 -}$ are respectively

(py = pyridine, ox = oxalate)

A
3 & 3
B
2 & 2
C
2 & 3
D
1 & 2

Solution

$[C r C l_{3} (p y)_{3}]$ is of type $[M a_{3} b_{3}]$ . Such octahedral complexes exhibit facial (fac) and meridional (mer) geometrical isomers. Both isomers possess a plane of symmetry and are therefore optically inactive. Total stereoisomers $= 2$ .

$[C r C l_{2} (o x)_{2}]^{3 -}$ is of type $[M (AA)_{2} b_{2}]$ , where oxalate is a symmetric bidentate ligand. This gives a cis form and a trans form. The trans isomer has a plane of symmetry (optically inactive). The cis isomer is chiral and exists as a pair of enantiomers ( $d$ and $l$ ). Total stereoisomers $= 1 (trans) + 2 (cis enantiomeric pair) = 3$ .

$∴$ The answer is 2 & 3, i.e. option (3).

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JEE Main 2025 Apr 4 Shift 1, Chemistry Q9: Isomerism In Co-ordination Compounds

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