Bis[4-amino-N-(4-methylpyrimidin-2-yl-κN 3)benzenesulfonamidato-κN](2,2′-bipyridine-κ2 N,N′)mercury(II)

The complete molecule of the title complex, [Hg(C11H11N4O2S)2(C10H8N2)], is generated by crystallographic twofold symmetry, with the mercury cation lying on the rotation axis. The mercury coordination polyhedron can be described as tetrahedral (from the N,N′-bidenate bipyridine molecule and the sulfonamide N atoms of the sulfamerazine anions) or as squashed trigonal-prismatic, if two long (> 2.80 Å) Hg—N bonds to pyrimidine N atoms are included. The dihedral angle between the aromatic rings in the anion is 73.3 (2)°. In the crystal, N—H⋯(N,O) and N—H⋯N hydrogen bonds link the molecules into a three-dimensional network.

The complete molecule of the title complex, [Hg(C 11 H 11 N 4 O 2 S) 2 (C 10 H 8 N 2 )], is generated by crystallographic twofold symmetry, with the mercury cation lying on the rotation axis. The mercury coordination polyhedron can be described as tetrahedral (from the N,N 0 -bidenate bipyridine molecule and the sulfonamide N atoms of the sulfamerazine anions) or as squashed trigonal-prismatic, if two long (> 2.80 Å ) Hg-N bonds to pyrimidine N atoms are included. The dihedral angle between the aromatic rings in the anion is 73.3 (2) . In the crystal, N-HÁ Á Á(N,O) and N-HÁ Á ÁN hydrogen bonds link the molecules into a three-dimensional network.

Comment
The mercury complexes of some related ligands have been reported (Garcia-Raso et al., 1997;. In the title complex, sulfamerazine behaves as a bidentate anionic ligand and Hg(II) ion is coordinated via sulfonamidic N(11) and pyrimido N(12) atoms, the fifth and sixth coordination sites are occupied by bipyridine molecule. The geometry of the complex is trigonal prismatic with the Hg atom lying on a twofold axis as the bpy molecule lies on the one part and the two larger sulfamerazine molecules lie on the other part. The bond angles around the S atom correspond to a distorted tetrahedral geometry. The bond distance C(18)-N(14) (Terminal amino group) of 1.371 (5) Å and the torsion angle C(15)-S(11)-N(11)-C(11) of 74.4 (4)° are larger than those observed in the related structures Hossain & Amoroso, 2012). The dihedral angle between the aromatic rings of the sulfamerazinate anion of 73.27 (13)° is larger than the value of 71.10 (14)°  and smaller than the value of 76.60 (8)° (Hossain & Amoroso, 2012) in the sulfadiazinate anion.
The packing of the complex unit ( Fig. 2) is governed by weak (intermolecular N-H···N, and N-H···O) hydrogen bonds (Table 2) between the amino (-NH2) group of one complex unit and the sulfonyl oxygen and the pyrimido nitrogen atoms of the next units.

Experimental
The complex was obtained by dissolving (2.723 g, 2 mmol) sulfamerazine in 50 ml of methanol followed by drop-wise addition of Hg(CH 3 COO) 2 ·4H 2 O (1.245 g, 1 mmol) in water with constant stirring on hot plate for 1 h. A white precipitate was formed, filtered and washed with methanol and dried in a desiccator over silica gel. The precipitate was dissolved in DMF, bipyri dine (0.235 g, 1 mmol) was added to this solution and stirred for 30 minutes. The solution was filtered and left for crystallization. A week later, colourless blocks were obtained.

Refinement
The H atoms were positioned geometrically and refined using a riding model except that for terminal amino group N (14) which were located from the difference map and fixed to 0.900 (3)   The molecular structure of (I), with 50% probability displacement ellipsoids for non-H atoms.  The packing of (I), viewed down the a-axis, showing one layer of molecules connected by N-H···N and N-H···O hydrogen bonds (dashed lines).