Piperazine (and derivatives) copper(II) compounds:: 1,4-dimethylpiperazin-1,4-ium tetrachlorocuprate(II) and Cu-N bond formation in trichloro(1-methylpiperazin-1-ium-N4)copper(II) and trichloro(1,4-dimethylpiperazin-1-ium-N4)copper(II).

The ionic salt (H(2)Me(2)ppz)(2+) [CuCl4](2-) (1), the pseudotetrahedral zwitterionic [CuCl3(HMe(2)ppz)] (2) and [CuCl3(HMe(2)ppz)] (3) complexes of copper(II) have been synthesized and characterized, [(H(2)Me(2)ppz)(2+) = 1,4-dimethyl-piperazin-1,4-ium; (HMe(2)ppz)(+) = 1,4-dimethylpiperazin-1-ium; (H(2)Meppz)(+) = 1-methylpiperazin-1-ium]. The X-ray diffraction analysis of compound (1) shows that the [CuCl4](2-) anion possesses a flattened tetrahedral geometry with the two largest Cl-Cu-Cl angles being 125.90(5) and 131.41(5)degrees. The Cu-Cl distances range from 2.215(1) to 2.267(1) A and all the chlorine atoms are involved in bifurcated hydrogen bonds. Physico-chemical measurements, UV-Vis, IR and especially X-ray analysis, prove that complex 2 is the first example of a Cu(II) ion bonded to one nitrogen atom of the piperazinium ring which is not constrained into a macrocyclic ligand. In fact, the -CuCl3 group is coordinated to the (HMe(2)ppz)(+) cation in the unusual axial position similar to the Co(II) derivative. The CuCl3N coordination polyhedron exhibits a pseudotetrahedral geometry with the two largest CI-Cu-CI angles being 132.17(12) and 135.38(7)degrees Complex 3 shows the same physico-chemical behaviour as complex 2 confirming that this complex also contains a Cu(II)-N bond in a pseudo-tetrahedral environment. (C) 2001 Elsevier Science B.V. All rights reserved.