'X' is the number of electrons in $\mathrm{t}_{2g}$ orbitals of the most stable complex ion among $[\mathrm{Fe}(\mathrm{NH}_3)_6]^{3+}$, $[\mathrm{Fe}(\mathrm{Cl}_6)]^{3-}$, $[\mathrm{Fe}(\mathrm{C}_2\mathrm{O}_4)_3]^{3-}$ and $[\mathrm{Fe}(\mathrm{H}_2\mathrm{O})_6]^{3+}$. The nature of oxide of vanadium of the type $\mathrm{V}_2\mathrm{O}_x$ is:

JEE Main · 2025 · 04 Apr 2025 · Shift 2 · Coordination Compounds

'X' is the number of electrons in

t_{2 g}

orbitals of the most stable complex ion among

[Fe (NH_{3})_{6}]^{3 +}

[Fe (Cl_{6})]^{3 -}

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

and

[Fe (H_{2} O)_{6}]^{3 +}

. The nature of oxide of vanadium of the type

V_{2} O_{x}

is:

Answer: (C)

The most stable complex among [Fe(NH

_{3}

)

_{6}

]

^{3 +}

, [FeCl

_{6}

]

^{3 -}

, [Fe(C

_{2}

_{4}

)

_{3}

]

^{3 -}

and [Fe(H

_{2}

_{6}

]

^{3 +}

is the oxalato complex [Fe(C

_{2}

_{4}

)

_{3}

]

^{3 -}

, stabilised by the chelate effect of the bidentate oxalate ligand. Iron here is Fe

^{3 +}

^{5}

), and oxalate is a weak-to-moderate field ligand, so the complex is high spin with the configuration

t_{2 g}^{3} e_{g}^{2}

. The number of electrons in the

t_{2 g}

orbitals is therefore X

= 3

, making the oxide V

_{2}

_{3}

. Vanadium(III) oxide, V

_{2}

_{3}

, is a basic oxide.

JEE Main · 2025 · 04 Apr 2025 · Shift 2 · Single correct option