The syntheses, structures and magnetic properties of the compounds of formulae [Mn((R)-salmen)(CH₃OH)(CH₃CN)][MnCr(ox)₃](CH₃OH)_0.5(CH₃CN)_1.25 ((R)-1), [Mn((S)-salmen)(CH₃OH)(CH₃CN)][MnCr(ox)₃](CH₃OH)_0.5(CH₃CN)_1.25 ((S)-1), [Mn((R)-salmen)(CH₃OH)₂][MnCr(ox)₃](CH₂Cl₂)_0.375(CH₃OH)_0.125(H₂O)_0.375 ((R)-2) and [Mn((S)-salmen)(CH₃OH)₂][MnCr(ox)₃](CH₂Cl₂)_0.375(CH₃OH)_0.375(H₂O)_0.125 ((S)-2) (ox = oxalate, salmen²⁻ = N,N′-(1-methylethylene)bis(salicylideneiminate)), [Mn(salpn)(CH₃OH)_1.5(CH₃CN)_0.5][MnCr(ox)₃](CH₃OH)_0.82(H₂O)_0.93 (3) (salpn²⁻ = N,N′-(propane)bis(salicylideneiminate)) and [Mn(saltmen)(CH₃OH)(CH₃CN)][MnCr(ox)₃](CH₃OH) (4) (saltmen²⁻ = N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneiminate)) are reported. These compounds are prepared by the insertion of Mn^III–Schiff base complexes into bimetallic oxalate networks. Different types of bimetallic oxalate networks are obtained for each templating cation. Thus, [Mn((R)-salmen)]⁺ and [Mn((S)-salmen)]⁺ chiral templating cations give rise to a 2D chiral bimetallic oxalate layer in acetonitrile in (R)-1 and (S)-1 compounds, whereas a new type of achiral 3D oxalate network is obtained with the same templating cation in dichloromethane in (S)-2 and (R)-2. On the other hand, [Mn(salpn)]⁺ and [Mn(saltmen)]⁺ give rise respectively to a 3D chiral network and a 2D achiral network in compounds 3 and 4. The magnetic properties of the four compounds indicate that they undergo a long-range ferromagnetic ordering at ca. 5 K.