In which of the following octahedral complexes of Co (at. no. 27), will the magnitude of $\Delta_{\circ}$ be…

In which of the following octahedral complexes of Co (at. no. 27), will the magnitude of $\Delta_{\circ}$ be the highest?
  1. $\left[\mathrm{Co}(\mathrm{CN})_6\right]^{3-}$
  2. $\left[\mathrm{Co}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]^{3-}$
  3. $\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}$
  4. $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}$

Solution

$\mathrm{CN}^{\Theta}$ is stronger ligand hence $\Delta_{\circ}$ is highest.

Asked in: JEE Main 2008

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