Given below are two statements: Statement I : $\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{3-},\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}$ and $\left[\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3-}$ ared $^{2} \mathrm{sp}^{3}$ hybridised Statement II : $\left[\mathrm{MnCl}_{6}\right]^{3-}$ and $\left[\mathrm{FeF}_{6}\right]^{3-}$ are paramagnetic and have 4 and 5 unpaired electrons, respectively. In the light of the above statements, choose the correct answer from the options given below:

(A) Statement I is correct but Statement II is false

(B) Both Statement I and Statement II are false

(C) Statement I is incorrect but Statement II is true

JEE Main · 2021 · 27 Jul 2021 · Shift 2 · Coordination Compounds

Given below are two statements:
Statement I :

[Mn (CN)_{6}]^{3 -}, [Fe (CN)_{6}]^{3 -}

and

[Co (C_{2} O_{4})_{3}]^{3 -}

ared

^{2} sp^{3}

hybridised
Statement II :

[MnCl_{6}]^{3 -}

and

[FeF_{6}]^{3 -}

are paramagnetic and have 4 and 5 unpaired electrons, respectively.
In the light of the above statements, choose the correct answer from the options given below:

(A)Statement I is correct but Statement II is false
(B)Both Statement I and Statement II are false
(C)Statement I is incorrect but Statement II is true
(D)Both Statement I and Statement II are true✓ Correct

Answer: (D)

Solution

Cyanide is a strong field ligand, so in

[Mn (CN)_{6}]^{3 -}

the

d^{4}

M n^{3 +}

and in

[Fe (CN)_{6}]^{3 -}

the

d^{5}

F e^{3 +}

pair their electrons within the

t_{2 g}

set; oxalate does the same for the

d^{6}

C o^{3 +}

[Co (C_{2} O_{4})_{3}]^{3 -}

. Pairing empties two inner

3 d

orbitals in each case, which are then used for bonding, so all three are

d^{2} s p^{3}

hybridised and the first statement holds. Chloride and fluoride are weak field ligands and force no pairing, so

[MnC l_{6}]^{3 -}

keeps the four unpaired electrons of

d^{4}

M n^{3 +}

and

[Fe F_{6}]^{3 -}

the five unpaired electrons of

d^{5}

F e^{3 +}

, making both paramagnetic as described. Both Statement I and Statement II are true.

JEE Main · 2021 · 27 Jul 2021 · Shift 2 · Single correct option

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JEE Main · 2021 · 27 Jul 2021 · Shift 2 · Coordination Compounds

Solution

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