JEE MAIN - Chemistry (2025 - 29th January Evening Shift - No. 8)
Identify the homoleptic complexes with odd number of $d$ electrons in the central metal :
(A) $\left[\mathrm{FeO}_4\right]^{2-}$
(B) $\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}$
(C) $\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NO}\right]^{2-}$
(D) $\left[\mathrm{CoCl}_4\right]^{2-}$
(E) $\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_3 \mathrm{~F}_3\right]$
Choose the correct answer from the options given below :
Explanation
Homoleptic complexes are complexes with identical ligands attached to the central metal atom.
(A) $${[Fe{O_4}]^{2 - }}$$ - Homdeptic
Central metal : Fe
IN this complex, Fe is in +6 oxidation state.
{oxidation state : $$x + 4( - 2) = - 2$$
$$x - 8 = - 2$$
$$x = - 2 + 6 = + 6$$
Configuration of $$Fe - {d^6}{s^2}$$
Configuration of $$Fe( + 6) - c{l^2}$$
Iron has even number of d electrons. So, it is not correct.
(B) $${[Fe{(N)_6}]^{3 - }}$$ - Homoleptic
Central metal : Fe
In this complex, the oxidation state of Fe is +3
Oxidation state :
$$x + 6( - 1) - 3$$
$$x - 6 = - 3$$
$$x = - 3 + 6 = + 3$$
Configuration of $$Fe - {d^6}{s^2}$$
Configuration of $$Fe( + 3) - {d^5}$$
Iron has odd number of d electrons.
So, it is correct.
(C) $${[Fe{(CN)_5}NO]^{2 - }}$$ - Not homoleptic
This complex has different type of ligands.
$${[CoC{l_4}]^{2 - }}$$ - Homoleptic
Central metal - Co
In this complex, the oxidation state of Co is +2
Oxidation state:
$$x + 4( - 1) = - 2$$
$$x - 4 = - 2$$
$$x = - 2 + 4 = + 2$$
Configuration of $$Co - {d^7}{s^2}$$
Configuration of $$Co( + 2) - {d^7}$$
Cobalt has odd number of d electrons.
So, it is correct.
(E) $$[Co{({H_2}O)_3}{F_3}]$$ - Not homoleptic,
It has different type of ligands.
Complexes B and D are homoleptic complexes with odd number of d electrons in the central metal. So, correct answer is
(B) and (D) only.
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