JEE Main 2025 — Coordination Compounds Question with Solution

To determine which metal complexes are paramagnetic and have the same number of unpaired electrons, let's analyze each one:

$[\mathrm{Co}({\mathrm{NH}}_3{)}_6{]}^{3+}$:

Cobalt ion: ${\mathrm{Co}}^{3+}$

Electron configuration: $3d^6$

Orbital occupancy: ${\mathrm{t}}_{2g}^{2,2,2}$ ${\mathrm{e}}_g^{0,0}$

Magnetic property: Diamagnetic (unpaired electrons = 0)

$[\mathrm{Co}({\mathrm{C}}_2{\mathrm{O}}_4{)}_3{]}^{3-}$:

Cobalt ion: ${\mathrm{Co}}^{3+}$

Electron configuration: $3d^6$

Orbital occupancy: ${\mathrm{t}}_{2g}^{2,2,2}$ ${\mathrm{e}}_g^{0,0}$

Magnetic property: Diamagnetic (unpaired electrons = 0)

$[{\mathrm{MnCl}}_6{]}^{3-}$:

Manganese ion: ${\mathrm{Mn}}^{3+}$

Electron configuration: $3d^4$

Orbital occupancy: ${\mathrm{t}}_{2g}^{1,1,1}$ ${\mathrm{e}}_g^{1,0}$

Magnetic property: Paramagnetic (unpaired electrons = 4)

$[\mathrm{Mn}(\mathrm{CN}{)}_6{]}^{3-}$:

Manganese ion: ${\mathrm{Mn}}^{3+}$

Electron configuration: $3d^4$

Orbital occupancy: ${\mathrm{t}}_{2g}^{2,1,1}$ ${\mathrm{e}}_g^{0,0}$

Magnetic property: Paramagnetic (unpaired electrons = 2)

$[{\mathrm{CoF}}_6{]}^{3-}$:

Cobalt ion: ${\mathrm{Co}}^{3+}$

Electron configuration: $3d^6$

Orbital occupancy: ${\mathrm{t}}_{2g}^{2,1,1}$ ${\mathrm{e}}_g^{1,1}$

Magnetic property: Paramagnetic (unpaired electrons = 4)

$[\mathrm{Fe}(\mathrm{CN}{)}_6{]}^{3-}$:

Iron ion: ${\mathrm{Fe}}^{3+}$

Electron configuration: $3d^5$

Orbital occupancy: ${\mathrm{t}}_{2g}^{2,2,1}$ ${\mathrm{e}}_g^{0,0}$

Magnetic property: Paramagnetic (unpaired electrons = 1)

$[{\mathrm{FeF}}_6{]}^{3-}$:

Iron ion: ${\mathrm{Fe}}^{3+}$

Electron configuration: $3d^5$

Orbital occupancy: ${\mathrm{t}}_{2g}^{1,1,1}$ ${\mathrm{e}}_g^{1,1}$

Magnetic property: Paramagnetic (unpaired electrons = 5)

From this analysis, the paramagnetic complexes having the same number of unpaired electrons (4 unpaired electrons) are:

$[{\mathrm{MnCl}}_6{]}^{3-}$

$[{\mathrm{CoF}}_6{]}^{3-}$

These two complexes show the same paramagnetic property, each with 4 unpaired electrons.