Question

Which of the following complexes has minimum magnitude of Ape?

• A. ${\left[Cr(CN{)}_6\right]}^{3-}$
• B. ${{\left[Co(NH{)}_3\right)}_6]}^{3+}$
• C. ${[CoCl{]}_6]}^{3-}$
• D. ${\left[Cr{\left(H_{2}O\right)}_6\right]}^{3+}$

Answer 1

Answer: (C)

[a] In ${\left[Cr(CN{)}_6\right]}^{3-}$ and ${\left[Cr{\left(H_{2}O\right)}_6\right]}^{3+}$ both, $Cr$ is present as $C{r}^{3+}$.
$CFSE=-0.4\times 3=-1.2$
[b]$\ln {\left[CO{\left(N{H}_3\right)}_6\right]}^{3+},Co$ is present as $C{O}^{3+}$
$CFSE=-0.4\times 6=-2.4$
[c] $\ln {\left[COC{l}_6\right]}^{3-},CO$ is again present as $C{O}^{2+}$
$CFSE=-0.4\times 4+0.6\times 2=-1.6+1.2=-0.4$
Thus, the magnitude of ${\Delta }_o$ is minimum for ${\left[COC{l}_6\right]}^{3-}-$