# What is the oxidation state of the metal centre in [Fe(OH_2)_5(NCS)]SO_4?

We have $\text{ferric ion}$, i.e. $F e \left(+ I I I\right)$.
We have ${\left[F e {\left(O {H}_{2}\right)}_{5} \left(N C S\right)\right]}^{2 +} S {O}_{4}^{2 -}$.
And the actual complex ion is ${\left[F e {\left\{{\left(O H\right)}_{2}\right\}}_{5} \left(N C S\right)\right]}^{2 +}$ after we remove the $S {O}_{4}^{2 -}$ counterion. The water ligands are neutral, but the thiocyanate ion has a formal $- 1$ charge. And thus we have an $F {e}^{3 +}$ centre. Capisce?