The article describes the thermal behaviour of Cu(II) complexes formed with ligands R1R2NCXCOOK (R1R2=H or CH3, X=O or S). The oxamates form 2/1 complexes Cu(R1R2NCOCOO)(2) . xH(2)O and deprotonated ionic complexes K2Cu[R2NCOCOO](2) . yH(2)O. These compounds form polymers by thermal decomposition and deprotonation of the primary or secondary amide function. The ligands break at the C-C bond by forming mainly CO2 and oxamides (R1R2NCOCONR1R2), by recombination of the amide functional groups. The thiooxamates also form 2/1 complexes and decompose without forming any other stable compound.