JEE Main · 2008 · 27 Apr 2008 · Offline · Coordination Compounds

In which of the following octahedral complexes of Co (at. no. 27), will the magnitude of

Δ_{\circ}

be the highest?

(A) $[Co (CN)_{6}]^{3 -}$ ✓ Correct
(B) $[Co (C_{2} O_{4})_{3}]^{3 -}$
(C) $[Co (H_{2} O)_{6}]^{3 +}$
(D) $[Co (NH_{3})_{6}]^{3 +}$

Answer: (A)

Solution

The size of the octahedral splitting

Δ_{o}

tracks the field strength of the ligand, as set out in the spectrochemical series. Among the ligands offered, cyanide is the strongest-field ligand, well above ammonia, oxalate and water, so the hexacyanido complex

[Co (CN)_{6}]^{3 -}

experiences the largest splitting and has the highest

Δ_{o}

JEE Main · 2008 · 27 Apr 2008 · Offline · Single correct option

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