JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Coordination Compounds

Which of the following complex is octahedral, diamagnetic and the most stable?

(A) $Na_{3} [CoCl_{6}]$
(B) $[Ni (NH_{3})_{6}] Cl_{2}$
(C) $K_{3} [Co (CN)_{6}]$ ✓ Correct
(D) $[Co (H_{2} O)_{6}] Cl_{2}$

Answer: (C)

Solution

K_{3} [Co (CN)_{6}]

contains

Co^{3 +}

with electronic configuration

t_{2 g}^{6} e_{g}^{0}

CN^{-}

is a strong field ligand that causes pairing of all d-electrons, making the complex diamagnetic. The strong field also makes it the most stable among the given options. It is octahedral with coordination number 6.

JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Single correct option

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