Trichlorido(1-ethylpiperazin-1-ium)cobalt(II)

In the title complex, [Co(C6H15N2)Cl3], the Co2+ ion is coordinated in a distorted tetrahedral fashion by three chloride ions and one N atom of the piperazine ring; the ring adopts a chair conformation with the N—Co and N—CEt bonds in equatorial orientations. In the crystal, molecules are connected by N—H⋯Cl hydrogen bonds, generating (10-1) sheets.

In the title complex, [Co(C 6 H 15 N 2 )Cl 3 ], the Co 2+ ion is coordinated in a distorted tetrahedral fashion by three chloride ions and one N atom of the piperazine ring; the ring adopts a chair conformation with the N-Co and N-C Et bonds in equatorial orientations. In the crystal, molecules are connected by N-HÁ Á ÁCl hydrogen bonds, generating (101) sheets.
We acknowledge the NSF-MRI grant No. 1125975 "MRI Consortium Acquisition of a Single Crystal X-ray Diffractometer for a Regional PUI Molecular Structure Facility". Supporting information for this paper is available from the IUCr electronic archives (Reference: HB7215).

Comment
Piperazine (H 2 ppz) and its derivatives, are cyclic diamines possessing a non-planar six-membered ring analogous to cyclohexane with two basic nitrogen atoms in the 1,4 positions. As these nitrogen atoms are basic, piperazine (H 2 ppz) and its derivatives may coordinate metal ions as monodentate, bidentate or bidentate-chelate ligands. Several 1-methylpiperazine and 1,4-di-methylpiperazine platinum(II) complexes have been synthesized and characterized through X-ray diffraction (Ciccarese et al., 1998). The cobalt complexes [CoCl 3 (HMe2ppz)] and [CoCl 3 (H 2 Meppz)] have shown interesting cytotoxic activity on human colon and carcinoma cells (Marzotto et al., 2000). In order to explore possible biological applications and to gather further chemical and structural information on metal complexes capable of interacting selectively with nitrogen donors of DNA nucleobases, we have extended to cobalt(II) the study on the behaviour and coordinating properties of piperazine derivatives. This study includes the synthesis and structural characterization of the new complex, (C 6 H 15 N 2 )CoCl 3 (I).
Complex I is present as a neutral zwitterionic (amphiionic) species. The negative charge of the -CoCl 3 group is is noteworthy that this Co(II)-Cl distance increases on increasing the number of chloride ions bonded to cobalt(II) atom, but also increases when the chloride ions are involved in strong hydrogen bonding. In the structure of I, the Co-Cl1, 2.2720 (8) Å, and Co-Cl3, 2.2691 (8) Å, distances are significantly longer than the Co-Cl2 distance, 2.2419 (10) Å , as the former are involved in strong hydrogen bonding while the latter is not. The Co(II)-N1 distance, 2.0686 (15) Å, is typical (Clemente et al., 1999).
The structure consists of a neutral Co(II) complex with a 4-Etppz ligand bonded through the secondary nitrogen atom and three chloride ligands. The tertiary nitrogen atom is protonated balancing the overall charge (Fig. 1). Each complex undergoes two hydrogen bonding interactions as donors (N1-H1 and N2-H2) and two interactions as accpetors (Cl1 and Cl3). Hydrogen bonding occurs in two-dimensional sheets (Fig. 2). Dimer donor-acceptor hydrogen-bonding interactions (related by inversion) dominate the hydrogen bonding motif (R 2 2 (8)) with additional single donor-acceptor hydrogen bonding interaction joining the dimer interactions. The same hydrogen-bonding pattern is found in the structure of the related [CoCl 3 (H 2 Meppz)] complex (Clemente et al., 1999).

Experimental
The complex was synthesized by adding dropwise under stirring a blue-violet solution, previously prepared at 40°C, of anhydrous CoCl 2 in 10 ml EtOH, to a 1-ethylpiperazine (HEtppz) solution dissolved in 5 ml EtOH in a molar ratio 1:1.
After mixing, an aqueous hydrochloric acid solution was added to the blue powder compound and was stirred for 2 h. After filtration, the filtrate was allowed to stand at room temperature. Blue crystals were obtained by slow evaporation.

Refinement
Many hydrogen atoms were treated in calculated positions and refined in the model as riding with distances of C-H = 0.98 and 0.99 Å for the methyl and methylene groups, respectively, and with U iso (H) = k×U eq (C), k = 1.2. Hydrogen atoms H1 and H2 were located in the electron density map, and their positions were refined with U iso (H) = k×U eq (C), k =1.2.

Figure 1
ORTEP-3 view of (C 6 H 15 N 2 )CoCl 3 with displacement ellipsoids for non-H atoms drawn at the 30% probability level.  Perspective view of the crystal packing of the title complex. Hydrogen bonds are shown as dashed lines.

Trichlorido(1-ethylpiperazin-1-ium)cobalt(II)
Crystal data [Co(C 6  Special details Geometry. ENTER SPECIAL DETAILS OF THE MOLECULAR GEOMETRY Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).