The "templating" K crown ether cation allows for the preparation of soluble layered oxalate-based bimetallic magnets, as in [K(18-crown-6](3){Mn-3(H2O)(4)[Cr(ox)(3)](3)}, with an unprecedented bidimensional polymeric anionic network that involves both oxalato bridges and H bonds. As in other 2D oxalate-bridged compounds, the compound behaves as a soft ferromagnet, with the onset of magnetic ordering occurring at 3.3 K.