Chemistry Q73 – JEE-MAIN 2025

Home Chemistry Coordination CompoundsQuestion #350

The number of paramagnetic complexes among

[F e F_{6}]^{3 -}

[F e (C N)_{6}]^{3 -}

[M n (C N)_{6}]^{3 -}

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

[M n C l_{6}]^{3 -}

, and

[C o F_{6}]^{3 -}

, which involved

d^{2} s p^{3}

hybridization is _______

Enter Calculated Numerical Value:

Clue 1 of 3: Determine Oxidation State and d-electron Count

For each complex, first find the oxidation state of the central metal ion and its corresponding d-electron configuration.

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Step 1: Analyze each complex for oxidation state and d-electron count✦ Active

Determine the oxidation state of the central metal and its $d$ -electron configuration for each complex:

[F e F_{6}]^{3 -} : F e^{3 +} (3 d^{5})

[F e (C N)_{6}]^{3 -} : F e^{3 +} (3 d^{5})

[M n (C N)_{6}]^{3 -} : M n^{3 +} (3 d^{4})

[C o (C_{2} O_{4})_{3}]^{3 -} : C o^{3 +} (3 d^{6})

[M n C l_{6}]^{3 -} : M n^{3 +} (3 d^{4})

[C o F_{6}]^{3 -} : C o^{3 +} (3 d^{6})

Step 2: Determine hybridization and magnetic properties based on ligand field strength○ Expand

Classify ligands as strong field (SFL) or weak field (WFL) and determine hybridization and paramagnetism:

[F e F_{6}]^{3 -} (F e^{3 +}, 3 d^{5}, F^{-} WFL) : High spin, 5 {unpaired e}^{-}, s p^{3} d^{2} hybridization. (Paramagnetic, not d^{2} s p^{3})

[F e (C N)_{6}]^{3 -} (F e^{3 +}, 3 d^{5}, C N^{-} SFL) : Low spin, 1 {unpaired e}^{-}, d^{2} s p^{3} hybridization. (Paramagnetic, d^{2} s p^{3} - Count 1)

[M n (C N)_{6}]^{3 -} (M n^{3 +}, 3 d^{4}, C N^{-} SFL) : Low spin, 2 {unpaired e}^{-}, d^{2} s p^{3} hybridization. (Paramagnetic, d^{2} s p^{3} - Count 2)

[C o (C_{2} O_{4})_{3}]^{3 -} (C o^{3 +}, 3 d^{6}, C_{2} O_{4}^{2 -} SFL) : Low spin, 0 {unpaired e}^{-}, d^{2} s p^{3} hybridization. (Diamagnetic, but d^{2} s p^{3} - Not paramagnetic)

[M n C l_{6}]^{3 -} (M n^{3 +}, 3 d^{4}, C l^{-} WFL) : High spin, 4 {unpaired e}^{-}, s p^{3} d^{2} hybridization. (Paramagnetic, not d^{2} s p^{3})

[C o F_{6}]^{3 -} (C o^{3 +}, 3 d^{6}, F^{-} WFL) : High spin, 4 {unpaired e}^{-}, s p^{3} d^{2} hybridization. (Paramagnetic, not d^{2} s p^{3})

💡 Teacher's Secret Hint

Remember that $C_{2} O_{4}^{2 -}$ (oxalate) is a strong field ligand for $C o^{3 +}$ .

Step 3: Count complexes satisfying both conditions○ Expand

The complexes that are both paramagnetic and involve $d^{2} s p^{3}$ hybridization are $[F e (C N)_{6}]^{3 -}$ and $[M n (C N)_{6}]^{3 -}$ . Therefore, the total number of such complexes is 2.

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Chemistry Question 73 – JEE-MAIN 2025

Clue 1 of 3: Determine Oxidation State and d-electron Count

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