Question

Which of the following pairs of complex ions has higher value of Crystal Field Stabilization Energy (CFSE) and why?

$\left[Co\right(N{H}_3{)}_4{]}^{2+}$ and $\left[Co\right(N{H}_3{)}_6{]}^{2+}$

Answer 1

Octahedral complex has higher Crystal Field Stabilization Energy (CFSE) or ${\Delta }_0$ than tetrahedral complex since ${\Delta }_0$ depends upon the number of ligands, if ligand increases then splitting of d-orbital increases.

${\Delta }_0=\frac{9}{4}{\Delta }_{t}CFSE\Rightarrow \left[CO\right(N{H}_3{)}_6{]}^{2+}>\left[CO\right(N{H}_3{)}_4{]}^{2+}$