catena-Poly[[dichloridomercury(II)]-μ-1,4-bis[(pyridin-2-yl)methoxy]benzene-κ2 N:N′]

In the title compound, [HgCl2(C18H16N2O2)]n, the HgII atom is four-coordinated in a distorted tetrahedral environment defined by two Cl atoms and two N atoms from two 1,4-bis(pyridin-2-ylmethoxy)benzene ligands. The ligand shows a non-coplanar conformation, in which the dihedral angles between the two terminal pyridine rings and the linking benzene ring are 7.275 (17) and 74.020 (14)°. The flexible ligands link the HgII atoms into a chain running along [010], with an Hg⋯Hg separation of 10.335 (5) Å, which is equal to the b axis. The chains are connected by C—H⋯O and C—H⋯Cl hydrogen bonds.

In the title compound, [HgCl 2 (C 18 H 16 N 2 O 2 )] n , the Hg II atom is four-coordinated in a distorted tetrahedral environment defined by two Cl atoms and two N atoms from two 1,4bis(pyridin-2-ylmethoxy)benzene ligands. The ligand shows a non-coplanar conformation, in which the dihedral angles between the two terminal pyridine rings and the linking benzene ring are 7.275 (17) and 74.020 (14) . The flexible ligands link the Hg II atoms into a chain running along [010], with an HgÁ Á ÁHg separation of 10.335 (5) Å , which is equal to the b axis. The chains are connected by C-HÁ Á ÁO and C-HÁ Á ÁCl hydrogen bonds.

Related literature
For the synthesis of the ligand and general background to flexible pyridyl-based ligands, see: Liu et al. (2010a,b); Wang et al. (2007).

Comment
The metal-organic frameworks are determined by many factors, in which the organic ligands as building blocks and the kinds of metal ions are most important. Many pyridyl-containing ligands with strong coordination ability and functional characteristics have been studied over the recent years (Wang et al., 2007). The flexible bipyridyl ligands can react with transition metals to construct helical-like structures. Recently, as a continuation of previous studies (Liu et al., 2010a, b), we report here the crystal structure of the title compound.
In the title compound, the Hg II atom is four-coordinated by two Cl atoms and two N atoms from two 1,4-bis(pyridin-2-ylmethoxy)benzene ligands, forming a tetrahedral geometry (Fig. 1). The Hg-Cl bond lengths are 2.398 (2) and 2.452 (2) Å, and Hg-N bond lengths are 2.282 (5) and 2.411 (5) Å. The angles around the Hg atom are in a range of 100.63 (13)-122.30 (12)°. The ligand shows a noncoplanar conformation, in which the dihedral angles between the two terminal pyridine rings and the linking benzene ring are 7.275 (17) and 74.020 (14)°. In the crystal, the flexible ligands link the Hg II atoms into a chain running along [0 1 0], with an Hg···Hg separation of 10.335 (5)Å, which is equal to the b axis of the unit cell (Fig. 2). The chains are connected by C-H···O and C-H···Cl hydrogen bonds (Table 1).
The filtate was maintained for about one week at room temperature to give colorless block-like crystals suitable for X-ray analysis.