A series of copper(II) complexes, i.e. Cu 2 LCl 4 , CuLCl 2 ·H 2 O and [Cu 2 L 2 Cl 4 ]·2MeCN (8), based on a new potentially polytopic ligand, 3,5-bis(4,6-dimethylpyrimidin-2-yl)-4H-1,2,4-triazol-4-amine (3b, L), have been synthesized. The crystal structures of L and [Cu 2 L 2 Cl 4 ]·2MeCN were studied by X-ray single crystal analysis. The dinuclear compound [Cu 2 L 2 Cl 4 ]·2MeCN represents the first example of structurally characterized metal complexes with 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amines. Both copper atoms have distorted tetragonal–pyramidal 3N+2Cl environment. Surprisingly, in contrast to the complexes based on 3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-amine (pyridinyl analog of L), the compound [Cu 2 L 2 Cl 4 ]·2MeCN adopts a dinuclear trans-(N′,N 1 ,N 2 ) 2 double bridging binding mode which is due to tridentate coordination of two L molecules linking two copper atoms through N 1 ,N 2 -triazole and N′-pyrimidine atoms. It seems to be reasonable that it is methyl groups in pyrimidinyl moiety that obstruct the expected dinuclear (N′,N 1 ,N 2 ,N″) 2 double bridging coordination being one of the most common for 4-substituted 3,5-di(pyridin-2-yl)-4H-1,2,4-triazoles and 3,5-di(pyridin-2-yl)-1,2,4-triazolates. Due to π–π stacking interactions, molecules of Cu 2 L 2 Cl 4 in the structure of [Cu 2 L 2 Cl 4 ]·2MeCN form 1D chains.