Dibromidobis{1-[4-(pyridin-4-yl)phenyl]ethanone-κN}mercury(II)

In the title compound, [HgBr2(C13H11NO)2], the HgII atom adopts a four-coordinated HgN2Br2 geometry, formed by two pyridine N atoms from two ligands and two bromide anions. The complex is located on a twofold axis. The coordination geometry is close to forming a see-saw (SS-4) polyhedron, the symmetry-related organic ligands being almost perpendicular; the dihedral angles between the two pyridine rings and between the two benzene rings are 85.5 (4) and 87.7 (4)°, respectively. Within the organic ligand, the pyridine ring is nearly coplanar with the benzene ring [dihedral angle = 13.1 (8)°]. In the crystal, the molecular complexes are connected through weak intermolecular C—H⋯Br contacts.

In the title compound, [HgBr 2 (C 13 H 11 NO) 2 ], the Hg II atom adopts a four-coordinated HgN 2 Br 2 geometry, formed by two pyridine N atoms from two ligands and two bromide anions. The complex is located on a twofold axis. The coordination geometry is close to forming a see-saw (SS-4) polyhedron, the symmetry-related organic ligands being almost perpendicular; the dihedral angles between the two pyridine rings and between the two benzene rings are 85.5 (4) and 87.7 (4) , respectively. Within the organic ligand, the pyridine ring is nearly coplanar with the benzene ring [dihedral angle = 13.1 (8) ]. In the crystal, the molecular complexes are connected through weak intermolecular C-HÁ Á ÁBr contacts.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BH2387).

Comment
Research on supramolecular compounds from asymmetric organic ligands has become popular because of their potential applications in areas such as magnetic (He et al., 2006), luminescent property (Allendorf et al., 2009;Hou et al., 2010) and nonlinear optical materials (Evans & Lin, 2002). Among available strategies, the geometry of organic ligands is one of the most important factors in determining the structure of the framework. Pyridyl derivatives have been widely used in supramolecular chemistry and many coordination polymers with versatile structures and potential properties have been reported (Fujita et al., 2005;Song et al., 2010). We report herein a molecular complex, HgL 2 Br 2 , generated from an asymmetric organic ligand, 1-(4-(pyridin-4-yl)phenyl)ethanone (L) and HgBr 2 .
In the title compound, each Hg II center adopts a distorted HgN 2 Br 2 tetrahedral coordination geometry, formed by two pyridine N atoms from two ligands and two bromide anions. The N1-Hg1-N1 i and Br1-Hg1-Br1 i angles are 100.3 (4)°a nd 147.81 (9)°, respectively [Symmetry code: (i) -x + 2, y, -z + 1.5]. Within the organic ligand, the pyridine ring is nearly coplanar with the benzene ring [dihedral angle: 13.1 (8)°]. In this compound, two ligands L are bridged by one Hg II center to form a molecular complex with a see-saw SS-4 polyhedron geometry (Fig. 1). The dihedral angles between two pyridyl planes and between two benzene planes are 85.5 (4) and 87.7 (4)°, respectively, close to 90°. So, a feature characteristic of the complex structure is the almost orthogonal arrangement for the two symmetry-related organic ligands.

Experimental
A solution of HgBr 2 (4.7 mg, 0.013 mmol) in CH 3 OH (2 ml) was layered onto a solution of L (5.0 mg, 0.025 mmol) in CH 2 Cl 2 (2 ml). The system was left for about three weeks at room temperature, and colourless crystals were obtained. Yield, 54%.

Refinement
All non-H atoms were refined with anisotropic displacement parameters. All H atoms were placed in idealized positions and treated as riding to their parent atoms, with C-H = 0.93 (aromatic CH) or 0.96 Å (methyl CH 3 ), and U iso (H) = 1.2 U eq (carrier C atom), with exception of the methyl H atoms, for which U iso (H) = 1.5 U eq (C13). Restraints for anisotropic displacements parameters of C2, C4, C7, C12 and C13 were applied.
supplementary materials sup-2 Figures   Fig. 1. The Hg II coordination environment of the title compound, with displacement ellipsoids at the 20% probability level. Unlabeled atoms are generated by symmetry operation -x + 2, y, -z + 1.5.