`[Fe(CN)_(6)]^(3-)` involves ` d^(2)sp^(3)` hybridisation
One 3d orbital is singly occupied , hence it is weakly paramagnetic in nature . `[Fe(CN)_(6)]^(4-)` involves also `d^(2)sp^(3)` hybridisation but it has `Fe^(2+)` ion as central ion.
It has no unpaired electron , hence it is diamagnetic in nature
