A one-dimensional HgII coordination polymer based on bis(pyridin-3-ylmethyl)sulfane

The reaction of HgII with the bridging ligand bis(pyridin-3-ylmethyl)sulfane afforded a one-dimensional zigzag chain polymeric structure, with the charge balanced by two coordinated chloride anions. C—H⋯Cl hydrogen bonds and Hg—Cl⋯π interactions, together with C—H⋯π hydrogen bonds, stabilize the crystal structure.

The reaction of mercury(II) chloride with bis(pyridin-3-ylmethyl)sulfane (L, C 12 H 12 N 2 S) in methanol afforded the title crystalline coordination polymer catena-poly [[dichloridomercury(II)]--bis(pyridin-3-ylmethyl)sulfane-2 N:N 0 ], [HgCl 2 L] n . The asymmetric unit consists of one Hg II cation, one L ligand and two chloride anions. Each Hg II ion is coordinated by two pyridine N atoms from separate L ligands and two chloride anions. The metal adopts a highly distorted tetrahedral geometry, with bond angles about the central atom in the range 97.69 (12)-153.86 (7) . Each L ligand bridges two Hg II ions, forming an infinite -(Hg-L) n -zigzag chain along the b axis, with an HgÁ Á ÁHg separation of 10.3997 (8) Å . In the crystal, adjacent chains are connected by intermolecular C-HÁ Á ÁCl hydrogen bonds, together with Hg-ClÁ Á Á interactions [chloride-tocentroid distance = 3.902 (3) Å ], that form between a chloride anion and the one of the pyridine rings of L, generating a two-dimensional layer extending parallel to (101). These layers are further linked by intermolecular C-HÁ Á Á hydrogen bonds, forming a three-dimensional supramolecular network.

Chemical context
The structural topology of coordination polymers generated from the self-assembly of transition metal ions and organic molecules functioning as spacer ligands depends mainly on the structures of the spacer ligands and the coordination geometries adopted by the metal ions. The flexibility, length and coordinating ability of the spacer ligands exert strong influences on the formation of coordination polymers and their resulting diverse topologies (Zheng et al., 2009;Leong & Vittal, 2011;Liu et al. 2011). For this reason, both rigid and flexible dipyridyl-type spacer ligands with strong coordinating ability and functional characteristics have been widely used to construct a variety of coordination polymers with interesting structures and attractive potential applications in material science (Silva et al., 2015;Furukawa et al., 2014;Wang et al., 2012).
Our group has also synthesized the flexible dipyridyl-type ligand bis(pyridine-3-ylmethyl)sulfane (L), and has reported its Ag I and Co II coordination polymers (Moon et al., 2017a,b). Our continuing interest in the development of coordination polymers based on this ligand led us to investigate a coordination polymer with an Hg II cation. The reaction of mercury(II) chloride with L (synthesized according to a previously reported procedure: Park et al., 2010;Lee et al., 2012) afforded the title compound. Herein, we describe its structure, which involves a one-dimensional zigzag-chain. Fig. 1 shows the molecular structure of the title compound, [HgLCl 2 ] n , L = bis(pyridine-3-ylmethyl)sulfane, C 12 H 12 N 2 S. The asymmetric unit comprises one Hg II cation, one L ligand and two chloride anions. The Hg II ion is four-coordinated, binding to two Cl anions and two pyridine N atoms from two separate symmetry-related L ligands, forming a highly distorted tetrahedral geometry ( Fig. 1), with the tetrahedral angles falling in the range of 97.69 (12)-153.86 (7) ( Table 1). The S atoms of the L ligands are surprisingly not bound to the soft Hg II cations. Each L ligand bridges two Hg II cations, resulting in an infinite zigzag chain propagating along the baxis direction (Fig. 2). The separation between the Hg II ions in the chain is 10.3997 (8) Å . In the L ligand, the dihedral angle between the two terminal pyridine rings is 78.52 (18) , and the flexible thioether moiety [C4-C6-S1-C7-C8] shows a bent arrangement with a gauche--anti configuration [C4-C6-S1-C7 = 71.9 (5) ; C6-S1-C7-C8 = 172.1 (5) ]. The conformation of the L ligand, along with its N py -Hg-N py coordination angle [98.39 (16) ], may induce the zigzag topology of the chain.

Figure 2
The polymeric zigzag chain propagating along the b-axis direction. H atoms are omitted for clarity. Table 2 Hydrogen-bond geometry (Å , ).

Figure 1
View of the molecular structure of the title compound, showing the atomnumbering scheme [symmetry codes: (i) Àx + 1 2 , y À 1 2 , Àz + 1 2 ; (ii) Àx + 1 2 , y + 1 2 , Àz + 1 the L ligand adopts a bent arrangement that is similar to that of the Hg II polymer described here. However, the title compound displays a zigzag topology and is the first example of an Hg II coordination polymer with the ligand L.

Synthesis and crystallization
The L ligand was synthesized according to a literature method (Park et al., 2010;Lee et al., 2012). Crystals of the title compound were obtained by slow evaporation of a methanol solution of L with HgCl 2 in a 1:1 molar ratio.

Figure 3
The layer formed through intermolecular C-HÁ Á ÁCl hydrogen bonds (yellow dashed lines) and Hg-ClÁ Á Á interactions (black dashed lines) between the zigzag chains. H atoms not involved in intermolecular interactions are omitted for clarity.

catena-Poly[[dichloridomercury(II)]-µ-bis(pyridin-3-ylmethyl)sulfane-κ 2 N:N′]
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.