The synthesis and magnetic properties of the oxalate-based molecular soluble magnets with general formula [K(18-crown-6)](3)[M-II(H2O)(4){M-III (ox)(3)}(3)](M-III = Cr, Fe; M-II = Mn, Fe, Ni, Co, Cu; ox = C2O42-) are here described. All the reported compounds are isostructural and built up by 2D bimetallic networks formed by alternating M-III and M-II ions connected through oxalate anions. Whereas the (CrMII)-M-III derivatives behave as ferromagnets with critical temperatures up to 8 K, the (FeMII)-M-III present ferri-or weak ferromagnetic ordering up to 26 K.