Among the following complexes the one which shows zero crystal field stabilization energy (CFSE) is

${\mathrm{H}}_2\mathrm{O}\text{ is a weak field ligand, hence }{\Delta }_o<\text{ pairing energy}$

$\mathrm{CFSE}=(-0.4x+0.6y){\Delta }_o$

where, x and y are no. of electrons occupying $t_{2_g}$and $e_g$ orbitals respectively.

$\text{ For }{\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}\text{ complex ion, }$

${\mathrm{Fe}}^{3+}\left(3d^5\right)=t_{2g}^3{e}_g^2=-0.4\times 3+0.6\times 2=0.0\text{ or }0\mathrm{Dq}$