UNEXPECTED PIPERAZINE DERIVATIVE LIGANDS FROM A MIXTURE OF CuCl₂.2H₂O, Na₂CO₃, AND TRIETHYLENETETRAMINE TETRAHYDRO- CHLORIDE

Norihiro Tamura,^a Masato Sakai,^b Katsuya Kudoh,^b Goro Hihara^b and Hiroshi Miyamae^b

^aSchool of Dentistry, Meikai University, Saitama 350-0283, Japan; ^bDepartment of Chemistry, Josai University, Saitama 350-0295, Japan (miya@josai.ac.jp)

We have already reported that PbCl₂ can remove contaminated 2,2’,2”- triaminotriethylamine (tren) from commercially available triethylenetetramine (trien) [1]. There are another stories of impurities in trien.

One of us mixed CuCl₂.2H₂O with trien in water, the mixture gave a complex cation as shown in Fig. 1(1) with [CuCl₃]^2- anion. There is a ligand, 1-(6,3-diaza- hexyl)piperazine, which act as a tridentate with the terminal N of the piperidine ring being protonated. The starting Cu compound contains Cu(II) ion, but in the anion the Cu atom should be oxidation state of +1. The result indicates that the reaction must contain a redox step which might has relation to form a new ligand. The other trial to produce compound 1 gave us two nuclear Cu complex as shown in Fig. 2(2), when we had used excess of Na₂CO₃. The ligand is 1,4-bis(2-aminoethyl)piperazine which act as bidentate to each Cu and make bridging. There is no indication for redox process, but the excess of CO₃^2- ion seems to compensate the positive charge of the Cu(II) ions.

It is uncertain whether the organics come originally from impurities or from reaction products of the complex formation. However it is one of the good procedures to get the ligands, which are not commercially available.

Fig. 1. The structure of 1. Fig. 2. The structure of 2.

References

1 Miyamae, H., Yoshinari, K., Hihara, G. and Nagata, M. (1988) Acta Cryst. C44, 1528-1530.