In both the complexes, Fe is in +3 oxidation state with the configuration 3d5. CN- is strong ligand. In its presence, 3d electrons pair up leaving only one electron unpaired.The hybridization is d2 sp3 and forms inner orbital octahedral complex. In contrary to this, H2O is a weak ligand and in its presence 3d electrons do not pair up. The hybridization is sp3 d2 and forms an outer orbital octahedral complex containing 5 unpaired electrons. Hence it is strongly paramagnetic.
