trans-Bis[2-(piperazin-1-yl)ethanamine]bis(saccharinato)cobalt(II)

In the centrosymmetric title complex, [Co(C7H4NO3S)2(C6H15N3)2], the CoII ion is coordinated by two saccharinate (sac) anions and two neutral 2-piperazin-1-ylethanamine (ppzea) ligands, showing a distorted octahedral coordination. Sac is O-bonded via the carbonyl group, while ppzea acts as an N,N′-bidentate chelating ligand. The molecules are connected by N—H⋯N and N—H⋯O hydrogen bonds, forming a linear chain running parallel to the crystallographic a axis. The compound is isostructural with the reported Ni, Zn, and Cd analogues.

In the centrosymmetric title complex, [Co(C 7 H 4 NO 3 S) 2 -(C 6 H 15 N 3 ) 2 ], the Co II ion is coordinated by two saccharinate (sac) anions and two neutral 2-piperazin-1-ylethanamine (ppzea) ligands, showing a distorted octahedral coordination. Sac is O-bonded via the carbonyl group, while ppzea acts as an N,N 0 -bidentate chelating ligand. The molecules are connected by N-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds, forming a linear chain running parallel to the crystallographic a axis. The compound is isostructural with the reported Ni, Zn, and Cd analogues.

Comment
The saccharinate (sac) anion is formed by the deprotonation of saccharin and coordinates to various metal ions rather easily (Baran & Yilmaz 2006). In the course of the synthesis and structural characterization of mixed ligand-metal complexes of sac, recently we reported nickel(II), zinc(II) and cadmium(II) complexes of sac with 2-piperazin-1-ylethanamine (ppzea) (Guney et al., 2005;Yilmaz et al., 2005). In this paper, the crystal and molecular structure of the isomorphous sac complex of cobalt(II) with ppzea (I) is reported.
The title complex (I) is isostructural with the nickel(II), zinc(II) and cadmium(II) complexes of the same ligands (Guney et al., 2005;Yilmaz et al., 2005) and shows similar structural characteristics. In these isostructural complexes, the M II ions show an elongated octahedral geometry, possibly due to a poor overlap of the sp 3 lone pair on the N atom of ppz with the valence orbitals of the metal ions. As shown in Fig. 1, (I) is a mononuclear Co II complex, in which the Co II ion lies on a centre of inversion and also exhibits an elongated distorted octahedral geometry with two neutral bidendate (N,N') ppzea ligands and two anionic sac ligands. In spite of the common N-coordination mode, sac coordinates to Co II through the carbonyl O atom. The puckering parameters of the ppz ring system in (I) are q = 0.538 (2)Å and Θ = 5.4 (2)°, suggesting that the ppz rings exhibit a typical (e.g., cyclohexane-like) chair conformation.
The amine hydrogen atoms of ppzea form intramolecular hydrogen bonds with the negatively charged N atom of sac. The individual molecules are linked by N-H···N and N-H···O hydrogen bonds, involving the amine H atoms of ppzea and the ring N atom of ppzea and the sulfonyl O atoms of sac, forming a linear chain running paralel to the crystallographic a axis.

Experimental
A 20 ml e thanol solution containing ppzea (0.26 g, 2 mmol) and sacH (0.36 g, 2 mmol) was mixed with a 20 ml e thanol solution of Co(OAc) 2 ·4H 2 O (0.25 g, 1 mmol). The reaction solution was stirred for 1 h at room temperature. Red-brown prisms were obtained after 5 days by slow evaporation of the solution at room temperature.

Refinement
All N-bonded H atoms were refined freely, while C-bonded H atoms were placed in idealized locations (C-H = 0.95 Å) and included as riding atoms with U iso (H) = 1.2*U eq (C). The instruction DFIX was applied to the N4-H4A bond to increase its length to a reasonable value. Fig. 1. The molecular structure of (I) showing 30% displacement ellipsoids (arbitrary spheres for the H atoms). Symmetry code: (i) −x + 1, −y + 1, −z + 1. The intramolecular N-H···N hydrogen bonds are indicated by dashed lines.

Special details
Geometry. All e.s. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.