Diaquabis(ethylenediamine-κ2 N,N′)copper(II) bis(sulfamerazinate)

The asymmetric unit of the title compound, [Cu(C2H8N2)2(H2O)2](C11H11N4O2S)2, contains one sulfamerazinate anion in a general position and one half-cation that is located on a center of inversion. The CuII cation shows a strong Jahn–Teller distortion. It is coordinated by four N atoms of two ethylenediamine ligands in the basal plane and two O atoms at much longer distances in the axial positions in a bipyramidal coordination. In the crystal, the building blocks are connected by N—H⋯N, O—H⋯N, N—H⋯O and O—H⋯O hydrogen bonding into a two-dimensional network parallel to (001).


Comment
It is well known that many sulfonamide derivatives possess antibacterial activity (Anand, 1980;Kratz et al., 2000;Grave et al., 2010) including sulfamerazine which is widely used to treat susceptible microbial infections Clark et al., 1943). Faster absorption, low overall excretion rate by the kidneys, and an equal therapeutic and toxic effect of sulfamerazine compared to other sulfonamide drugs, such as sulfadiazine and sulfathiazole, have been claimed for its wider usage (Earle, 1944;Forbes et al., 1946).
The first crystal structure of sulfamerazine have been reported by (Acharya et al., 1982). The presence of several potential donor sites, namely the amino, pyrimidine and sulfonamide N atoms and the sulfonyl O atoms, make this ligand a versatile complexing agent.
As part of our efforts to investigate metal(II) complexes based on sulfonamides, we report herein the crystal structure of the new copper(II) complex: Diaquabis(ethylenediamine-κ2 N,N′)copper(II) bis(sulfamerazinate).
The asymmetric unit of the title compound contains one sulfamerazinate counter-ion and a half [Cu(en) 2 (H 2 O) 2 ] 2+ cation (en = ethylenediamine) (Fig. 1). The metal ion is located in a ML6 environment and coordinated by four N atoms of two ethylenediamine ligands and two O atoms of two water molecules. The four N atoms of the ligands in the equatorial plane form a square-planar arrangement, while the 6-fold coordination is completed by the two water O atoms in the axial positions. The apical Cu-O bridging separation is 2.513 (2) Å while the equatorial Cu-N bridging bond lengths are 2.0168 (19) Å and 2.0016 (18) Å, which is typical for a Jahn-Teller distortion. A sulfamerazine anion that is deprotonated at the N11 N atom is present in the structure (Fig. 1). To the best of our knowledge, a search in the Cambridge Structural Database reveal, that this is the first crystal structure where a sulfamerazinate anion act as a counter ion. A similar situation is observed in [Cu(en) 2 (OH 2 ) 2 ](Stz) 2 ·2H 2 O (Anacona et al., 2002) where a sulfathiazole acts as a deprotonated counter ion too.
In the crystal strcuture of the title compound every complex cation is linked via O-H···N, N-H···O and O-H···O hydrogen bonding to the counter cations, while the cations are interconnected via the N-H···N interaction, which lead to the formation of a two dimensional network (Fig. 2).

Experimental
The single crystals of [Cu(C 2 H 8 N 2 ) 2 (H 2 O) 2 ](C 11 H 12 N 4 SO 2 ) 2 were formed in a methanolic solution (50 ml) of Cu(CH 3 CO 2 ) 2 (0.362 g, 2 mmol) and sulfamerazine (1.057 g, 4 mmol) by adding ethylenediamine (0.5 ml, 7.3 mmol). The precipitate obtained immediately was filtred out and the resulting filtrate was left to slowly evaporate at room temperature which lead to the formation of blue single crystals suitable for X-Ray diffraction.

Refinement
All C-H and all N-H H atoms of the ethylenediamine molecules were positioned with idealized geometry (methyl H atoms allowed to rotate but not to tip) and were refined isotropic with [U iso (H) = 1.2 U eq (C,N)] (1.5 for methyl H atoms) using a riding odel with C-H = 0.93, 0.96 and 0.97 Å (for aromatic, methyl and methylene H atoms and N-H = 0.97 Å for amino H atoms. The N-H and the O-H water H atoms were located in difference map and refined with varying coordinates and fixed isotropic displacement parameters.

Figure 1
Crystal structure of the title compound with labeling and displacement ellipsoids drawn at the 50% probability level.  Crystal packing of the title compound, shown through the a axis, with hydrogen bonding drawn as dashed lines.

Diaquabis(ethylenediamine-κ 2 N,N′)copper(II) bis[(4-aminophenylsulfonyl)(4-methylpyrimidin-2-yl)azanide]
Crystal data 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 > σ(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.