Poly[(μ2-2-aminopyrimidine-κ2 N 1:N 3)di-μ2-chlorido-mercury(II)]

The title compound, [HgCl2(C4H5N3)]n, features a two-dimensional network parallel to (001) that is based on an HgII atom octahedrally coordinated by four μ2-Cl atoms and two μ2-2-aminopyrimidine (apym) ligands in trans positions, yielding a distorted HgCl4N2 octahedron. The coordination network can be described as an uninodal 4-connected net with the sql topology. The HgII ion lies on a site of -1 symmetry and the apym ligand lies on sites of m symmetry with the mirror plane perpendicular to the pyrimidine plane and passing through the NH2 group N atom. This polymeric structure is stabilized by N—H⋯Cl hydrogen bonds and columnar π–π stacking of pyrimidine rings, with a centroid–centroid distance of 3.832 (2) Å.

The title compound, [HgCl 2 (C 4 H 5 N 3 )] n , features a twodimensional network parallel to (001) that is based on an Hg II atom octahedrally coordinated by four 2 -Cl atoms and two 2 -2-aminopyrimidine (apym) ligands in trans positions, yielding a distorted HgCl 4 N 2 octahedron. The coordination network can be described as an uninodal 4-connected net with the sql topology. The Hg II ion lies on a site of 1 symmetry and the apym ligand lies on sites of m symmetry with the mirror plane perpendicular to the pyrimidine plane and passing through the NH 2 group N atom. This polymeric structure is stabilized by N-HÁ Á ÁCl hydrogen bonds and columnarstacking of pyrimidine rings, with a centroid-centroid distance of 3.832 (2) Å .
In this contribution, we have synthesized and characterized a two-dimensional framework containing [Hg(apym)Cl 2 ] unit in which Hg II ion is six coordinated via four chloride anions and a two apym molecules ( Fig. 1). Hg II ion exhibits slightly distorted octahedral coordination geometry for which the maximum deviation of twelve octahedral angles from an ideal 90° for cis angles is 0.82 (7)°.
In the crystal structure, Hg II ion lies on an inversion centre and the apym molecule lies on a special position of m site symmetry with mirror plane passing through an amino nitrogen. Hg II ions are connected to each other by the bridging chloride ions in [100] direction; the seperation between the two bridged Hg II ions is 3.8317 (1) Å, and is shorter than that in [Hg(µ 2 -Cl) 2 (C 7 H 9 N) 2 (µ 2 HgCl) 3 ] ∞ [3.9960 (9) Å, Hu et al., 2007]. The four-membered Hg 2 Cl 2 ring is planar and contains pairs of long and short Hg-Cl bonds [Hg1-Cl1 2.9881 (9) Å & Hg1-Cl1 2.3987 (8) Å]. The apym molecule acts as a bidentate ligand that links two neighbouring Hg II ions in the crystallographic b direction with seperation Hg1···Hg1 distance of 7.0683 (3) Å, in consequence leading to formation of two-dimensional infinite framework with grid size of 7.068×3.832 Å 2 (Fig. 2). The topological type of this layer arrangement is sql {4 4 .6 2 } (Blatov, 2006). Similar two-dimensional neutral polymer consisting of mercury(II) ions bridged by both pyrazine and bromide ligands has been reported by Mahmoudi & Morsali (2009). The title compound is isostructural with its Cd analogoue, reported by Salinas-Castillo et al. (2011).
It is noteworthy that in our previous works, apym either played a role of a counter ion for an anionic network or acted as an uncharged monodentate ligand ( Eshtiagh-Hosseini et al., 2009, 2010, 2011. Another point of interest is the existance of N-H···Cl hydrogen bonds as well as columnar π-π interactions between pyrimidine rings of apym ligands which are arranged into stacks propagating in the a direction (see Fig. 2) with the perpendicular separation of 3.509 (2) Å and the centroid-to-centroid distance of 3.832 (2) Å.

Experimental
To a solution of HgCl 2 (0.050 g, 0.2 mmol) in 10 ml of MeOH was added dropwise a solution of pyridine-2,5-dicarboxylic acid (0.018 g, 0.1 mmol) in 10 ml of MeOH in the reflux condition. After 15 min, 2-aminopyrimidine (0.020 g, 0.2 mmol) was added as solid form, and the resultant solution stirred and refluxed for 12 h. After cooling the solution, a colourless needle-like crystals were obtained (yield: 70%).

Refinement
H atoms bound to C atoms were placed in their idealized positions and were refined as riding on their parent atoms with C-H distance of 0.93 Å. The symmetry independent amine H-atom was first found in a difference Fourier map and then refined using a riding model with U iso ═ 1.2U iso (N). The highest peak in the final electron density difference map is located 1.07 Å from Hg1 atom.

Poly[(µ 2 -2-aminopyrimidine-κ 2 N 1 :N 3 )di-µ 2 -chlorido-mercury(II)]
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.