Number of stereoisomers possible for the complexes, $\left[\mathrm{CrCl}_{3}(\mathrm{py})_{3}\right]$ and $\left[\mathrm{CrCl}_{2}(\mathrm{ox})_{2}\right]^{3-}$ are respectively (py = pyridine, ox = oxalate)

JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Coordination Compounds

Number of stereoisomers possible for the complexes,

[CrCl_{3} (py)_{3}]

and

[CrCl_{2} (ox)_{2}]^{3 -}

are respectively
(py = pyridine, ox = oxalate)

(A) $3&3$
(B) $2&2$
(C) $2&3$ ✓ Correct
(D) $1&2$

Answer: (C)

Solution

[CrCl_{3} (py)_{3}]

the octahedron is of the

Ma_{3} b_{3}

type: the three chlorides can occupy one triangular face (facial) or lie along a meridian (meridional), and both arrangements are achiral, giving two stereoisomers. In

[CrCl_{2} (ox)_{2}]^{3 -}

the two bidentate oxalates together with two chlorides give cis and trans forms; the trans form is achiral while the cis form is chiral and occurs as a pair of enantiomers, giving three stereoisomers. The numbers of stereoisomers are therefore two and three respectively.

JEE Main · 2025 · 04 Apr 2025 · Shift 1 · Single correct option

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