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Chemistry · Coordination Compounds

JEE Main 2025 — 22 January, Evening Shift — Question 40

Identify the homoleptic complex(es) that is/are low spin.

(A) [Fe(CN)5NO]2−\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NO}\right]^{2-}

(B) [CoF6]3−\left[\mathrm{CoF}_{6}\right]^{3-}

(C) [Fe(CN)6]4−\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}

(D) [Co(NH3)6]3+\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}

(E) [Cr(H2O)6]2+\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}

Choose the correct answer from the options given below :

  1. Option A:

    (B) and (E) only

  2. Option B:

    (A) and (C) only

  3. Option C:

    (C) and (D) only

    Correct
  4. Option D:

    (C) only

Answer: C

Step-by-step solution

(A) [Fe(CN)5NO]−2→\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NO}\right]^{-2} \rightarrow Heteroleptic, Fe+2,3 d6\mathrm{Fe}^{+2}, 3 \mathrm{~d}^{6},

t2 g6eg0, d2sp3\mathrm{t}_{2 \mathrm{~g}}{ }^{6} \mathrm{e}_{\mathrm{g}}{ }^{0}, \mathrm{~d}^{2} \mathrm{sp}^{3}, Low spin (3d series + SFL)

(B) [CoF6]−3→\left[\mathrm{CoF}_{6}\right]^{-3} \rightarrow Homoleptic, sp3 d2\mathrm{sp}^{3} \mathrm{~d}^{2}, High spin,

Co+3,3 d6(3 d\mathrm{Co}^{+3}, 3 \mathrm{~d}^{6}(3 \mathrm{~d} series +WFL))

(C) [Fe(CN)6]−4→\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{-4} \rightarrow Homoleptic

Fe+2,3 d6, d2sp3,t2 g6eg0\mathrm{Fe}^{+2}, 3 \mathrm{~d}^{6}, \mathrm{~d}^{2} \mathrm{sp}^{3}, \mathrm{t}_{2 \mathrm{~g}}{ }^{6} \mathrm{eg}^{0} Low spin (3d series +SFL )

(D) [Co(NH3)6]+3→\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{+3} \rightarrow Homoleptic, Co+33 d6, d2sp3\mathrm{Co}^{+3} 3 \mathrm{~d}^{6}, \mathrm{~d}^{2} \mathrm{sp}^{3},

t2 g6eg0\mathrm{t}_{2 \mathrm{~g}}{ }^{6} \mathrm{eg}^{0}, Low spin (3d series + SFL ))

(E) [Cr(H2O)6]+2→\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{+2} \rightarrow Homoleptic

Cr+23 d4, d2sp3\mathrm{Cr}^{+2} 3 \mathrm{~d}^{4}, \mathrm{~d}^{2} \mathrm{sp}^{3}, High spin t2 g3eg1\mathrm{t}_{2 \mathrm{~g}}{ }^{3} \mathrm{e}_{\mathrm{g}}{ }^{1}

(3d series + WFL)

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
22 January, Evening Shift
Subject
Chemistry
Chapter
Coordination Compounds
Topic
Properties and importance of Coordination Complexes

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