Number of complexes with even number of electrons in $\mathrm{t}_{2 \mathrm{~g}}$ orbitals is - $\left[\mathrm{Fe}\left(\mathrm{H}_{2}\mathrm{O}\right)_{6}\right]^{2+},\left[\mathrm{Co}\left(\mathrm{H}_{2}\mathrm{O}\right)_{6}\right]^{2+},\left[\mathrm{Co}\left(\mathrm{H}_{2}\mathrm{O}\right)_{6}\right]^{3+}$, $\left[\mathrm{Cu}\left(\mathrm{H}_{2}\mathrm{O}\right)_{6}\right]^{2+},\left[\mathrm{Cr}\left(\mathrm{H}_{2}\mathrm{O}\right)_{6}\right]^{2+}$

JEE Main · 2024 · 08 Apr 2024 · Shift 1 · Coordination Compounds

Number of complexes with even number of electrons in

t_{2 g}

orbitals is -

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

[Cu (H_{2} O)_{6}]^{2 +}, [Cr (H_{2} O)_{6}]^{2 +}

(A)1
(B)3✓ Correct
(C)2
(D)5

Answer: (B)

Solution

Count

t_{2 g}

electrons (all are weak-field aqua, high-spin):

[F e (H_{2} O)_{6}]^{2 +}

d^{6} \Rightarrow t_{2 g}^{4}

(even);

[C o (H_{2} O)_{6}]^{2 +}

d^{7} \Rightarrow t_{2 g}^{5}

(odd);

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

d^{6} \Rightarrow t_{2 g}^{6}

high-spin? here

t_{2 g}^{4}

^{6}

— even;

[C u (H_{2} O)_{6}]^{2 +}

d^{9} \Rightarrow t_{2 g}^{6}

(even);

[C r (H_{2} O)_{6}]^{2 +}

d^{4} \Rightarrow t_{2 g}^{3}

(odd). Three complexes have an even

t_{2 g}

count. Option (2), 3.

JEE Main · 2024 · 08 Apr 2024 · Shift 1 · Single correct option

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