In alkaline medium, malonamide forms anionic planar complexes [ML(2)](2-). xH(2)O where M is Ni or Cu. Thermograms and vibrational spectra clearly indicate that three different nickel anion complexes could be isolated, with x being respectively 2, 1 and 0. Only the monohydrate has been observed for the copper anionic compound. Malonamide also forms neutral trans-octahedral M(LK(2))(2)X(2) complexes (where M is Mn, Fe, Co, Ni, Cu, Zn;X is Cl, Br, I;LH(2) is CH2(CONH2)(2)) and polymeric [Cu(LH(2))X(2)](n) compounds (X is Cl or Br), The neutral 1/2 complexes all decompose, forming free ligand and MX, by an endothermic reaction, except for Fe(II) where an exothermic reaction occurs at relatively low temperatures. The thermal breakdown of Cu(LH(2))(2)Cl-2 and [Cu(LH(2))Cl-2](n) results in new polymeric structures, exhibiting bridging chlorines. The structures proposed for these compounds are supported by infrared spectra. The thermal stability of the M(LH,),X, complexes can be related to the metal-ligand bond strength and obeys the crystal field stabilization theory.