Like other iron oxalates, ferrous oxalates feature octahedral Fe centers. The dihydrate FeCO(HO) is a coordination polymer, consisting of chains of oxalate-bridged ferrous centers, each with two aquo ligands.<br />
When heated to 120 °C, the dihydrate dehydrates, and the anhydrous ferrous oxalate decomposes near 190 °C.  The products of thermal decomposition is a mixture of iron oxides and pyrophoric iron metal, as well as released carbon dioxide, carbon monoxide, and water.
Ferrous oxalates are precursors to iron phosphates, which are of value in batteries.