Synthesis, crystal and molecular structure of pseudotetrahedral Zn(II) zwittenonic complexes: trichloro( i -methylpiperazin.- i -ium-N4)zinc(II) and trichloro( i , 4-dimethylpiperazin- i -ium-N4)zinc(II)

The synthesis and the X-ray structure of the two pseudotetrahedral Zn(II) zwitterionic complexes: trichloro(1-methylpiperazin-1-ium-N4)zinc(II). [ZnCl3(H,Meppz)], and trichloro(1,4-dimethylpiperazin-1-ium-N4)zinc (II). [ZnCl3(HMe2ppz)], are described [(H2Meppz)+ = 1-methylpiperazin-1- ium monocation and (HMe2ppz)+ 1,4-dimethylpiperazin-1-ium monocation], [ZnCl3(H2Meppz)] and [ZnCl3(HMe2ppz)] complexes ave isomorphous and isostructural, respectively, to the [CoCl3(H2Meppz)] and [C0Cl3(HMe2ppz)] complexes. already reported in Iiterature by us. Both complexes present a very uncommon and distorted tetrahedral aminotrichlorozinc(II), NZnCl3, group, where N is a nitrogen atom of an aliphatic amine. So far this group has been found only in the (1,3,5,7-tetraazaadamantane)trichloro-zincate (II) anion [{(CH2)6N4}ZnCI3]. The bulky ZnCI3 group present in [ZnCl3 (HMe2ppz)], is coordinated to the axial position of the piperazine ring instead of the less hindered equatorial position, as found in the analogous [C0Cl3(HMe2ppz)] complex. An extended hydrogen bond network is present in the crystals of both the complexes but, while the [ZnCl3 (H2Meppz)] complex shows nearly Iinear N+...Cl intermolecular hydrogen bonds, the [ZnCl3(HMe2ppz)] complex shows a perfectly symmetrical (imposed by space group symmetry) ZnNCl three-centre intermolecular hydrogen bond. The solid state infrared spectra of both the compounds are discussed in agreement with the hydrogen bond network present in the crystals.