Coordination Compounds

We are given the compound:$\mathrm{Fe}_x[\mathrm{Fe}_y(\mathrm{CN})_6]_3$and asked to find the values of $x$ and $y$.Step 1. Identify familiar Prussian blue-type compoundsPrussian blue and related compounds have the general formula:$\mathrm{Fe}_4[\mathrm{Fe}(\mathrm{CN})_6]_3$This often corresponds to a mixed-valence compound containing both $\mathrm{Fe}^{2+}$ and $\mathrm{Fe}^{3+}$ ions.Step 2. Match with the given general formGiven formula: $\mathrm{Fe}_x[\mathrm{Fe}_y(\mathrm{CN})_6]_3$If we compare:$\mathrm{Fe}_4[\mathrm{Fe}(\mathrm{CN})_6]_3$we identify:$x=4,\;\;y=1$