Two heterobimetallic 2-dimensional layer complexes, {[Fe(bpy)(CN)₄]₂M(4,4′-bipyridine)}·4H₂O [bpy = 2,2′-bipyridine, M = Mn (1), Cu (2)] have been prepared by diffusion and their structures determined by single crystal X-ray diffraction. 1 and 2 are isomorphous, made of neutral bimetallic [Fe(bpy)(CN)₄]₂M(4,4′-bipyridine)] layers and uncoordinated water molecules located between the layers. Interestingly, complex 2 shows the compression of the Jahn–Teller distortion around the copper(II) ion. Magnetic investigation shows antiferromagnetic coupling between the manganese(II) and iron(III) ions mediated by bridging CN⁻ in 1, while ferromagnetic coupling between the copper(II) and iron(III) ions is seen in 2. Both complexes 1 and 2 reveal a metamagnetic-like behaviour with different critical fields (H_c, at 1.8 K): 2.0 kOe (1) and 3.2 kOe (2). The weak interchain antiferromagnetic interaction can be illustrated by the spin-polarization mechanism.