Among the new family complex compounds M(HCOO)2·2(NH2)2CO (M = Cd, Mn, Mg, Zn, Co), the tetragonal structures of Mn, Cd and Co compounds with a screw axis (space group: P41212) have been determined at room temperature. The structures are characterized by a stacking of layers along the 41 axis; each layer consists of an infinite squared network of (-formate-M-formate-)4 units. The two-dimensional character of the exchange interaction in the Mn and Co compounds is consistent with a structure where Mn or Co ions in the neighboring layers are only bonded by hydrogen bonds through urea dimers.
