Chemical context   {#sec1}
==================

A variety of coordination polymers have been explored extensively over the last two decades because of their fascinating architectures and their useful applications in materials chemistry (Silva *et al.*, 2015[@bb17]; Furukawa *et al.*, 2014[@bb4]; Robson, 2008[@bb14]; Leong & Vittal, 2011[@bb9]). In this area of research, symmetrical dipyridyl ligands composed of two terminal pyridines with same substituted nitro­gen positions have been used mainly for the design and construction of the coordination polymers. By contrast, investigations based on unsymmetrical dipyridyl ligands, with the nitro­gen atoms in different positions on each of the two terminal pyridines, are still rare (Uemura *et al.*, 2008[@bb18]; Khlobystov *et al.*, 2003[@bb6]). Recently, our group and that of Gao have already reported Ag^I^ coordination polymers with some unsymmetrical dipyridyl ligands such as *N*-(pyridine-3-ylmeth­yl)pyridine-2-amine (Lee *et al.*, 2013[@bb8]; Zhang *et al.*, 2013[@bb19]), *N*-(pyridine-2-ylmeth­yl)pyridine-3-amine (Ju *et al.*, 2014[@bb5]; Moon & Park, 2014[@bb13]; Moon *et al.*, 2014[@bb11]; Zhang *et al.*, 2013[@bb19]) and *N*-(pyridine-4-ylmeth­yl)pyridine-3-amine (Lee *et al.*, 2015[@bb7]; Moon *et al.*, 2015[@bb12]; Zhang *et al.*, 2013[@bb19]). As a part of our ongoing efforts to construct coordination polymers with such unsymmetrical dipyridyl ligands, we prepared the title compound obtained by the reaction of mercury(II) chloride with an unsymmetrical dipyridyl ligand, namely *N*-(pyridine-4-ylmeth­yl)pyridine-3-amine, synthesized according to a literature procedure (Lee *et al.*, 2013[@bb8]). Herein, we report the crystal structure of the title compound.

Structural commentary   {#sec2}
=======================

The asymmetric unit of the title compound, {\[Hg*L*Cl~2~\]·0.5CHCl~3~}~*n*~, *L* = *N*-(pyridine-4-ylmeth­yl)pyridine-3-amine, C~11~H~11~N~3~, comprises one Hg^II^ ion, one *L* ligand, two chloride anions and one half-mol­ecule of chloro­form. The solvent mol­ecule is disordered over two orientations of equal occupancy about the crystallographic twofold rotation axis. As shown in Fig. 1[▸](#fig1){ref-type="fig"}, the coordination geometry of each Hg^II^ ion is highly distorted tetra­hedral with two coordination sites being occupied by two pyridine N atoms from two symmetry-related *L* ligands. The geometry of the Hg^II^ ion is completed by the coordination of two chloride ions. The tetra­hedral angles around the Hg^II^ ion fall in the range of 99.05 (17)--142.96 (7)° (Table 1[▸](#table1){ref-type="table"}).

Each *L* ligand bridges two Hg^II^ ions into an infinite zigzag chain propagating along the *b* axis (Fig. 2[▸](#fig2){ref-type="fig"}). The separation between the Hg^II^ ions through a *L* ligand in the chain is 8.1033 (6) Å. In the *L* ligand, the C~py~---N---C---C~py~ torsion angle is −70.9 (7)° while the dihedral angle between two terminal pyridine ring planes is 85.0 (2)°. The conformation of the *L* ligand, along with the the N~py~---Hg---N~py~ coordination angle \[99.05 (17)°\], may induce the zigzag topology of the chain.

Supra­molecular features   {#sec3}
==========================

In the crystal, adjacent zigzag chains are linked by inter­molecular N---H⋯Cl hydrogen bonds and weak inter­molecular C---H⋯π inter­actions (Table 2[▸](#table2){ref-type="table"}), forming a layer extending parallel to the *bc* plane (Figs. 2[▸](#fig2){ref-type="fig"} and 3[▸](#fig3){ref-type="fig"}). Furthermore, neighboring layers are packed by C---H⋯Cl hydrogen bonds (Table 2[▸](#table2){ref-type="table"}), resulting in the formation of a three-dimensional supra­molecular network (Fig. 3[▸](#fig3){ref-type="fig"}). This three-dimensional network is further stabilized by C---Cl⋯π inter­actions (Chifotides & Dunbar, 2013[@bb3]; Matter *et al.*, 2009[@bb10]) between the solvent chloro­form mol­ecules and the pyridine rings of *L* with Cl4⋯*Cg*2 = 3.442 (11) Å, C12---Cl4⋯*Cg*2 = 170.7 (8)°, Cl5⋯*Cg*2^iv^ = 3.626 (13) Å and C12---Cl5⋯*Cg*2^iv^ 144.1 (8)° \[yellow dashed lines in Figs. 1[▸](#fig1){ref-type="fig"}, 2[▸](#fig2){ref-type="fig"} and 3[▸](#fig3){ref-type="fig"}; *Cg*2 is the centroid of the N2/C7--C11 ring; symmetry code: (iv) −*x*, *y*, −*z* + \]. In addition, weak inter­molecular Cl⋯Cl contacts between the solvent chloro­form mol­ecule and the coordinating chloride anion \[Cl1⋯Cl3^v^ = 3.320 (5) Å, Hg1---Cl1⋯Cl3^v^ = 126.70 (14) and Cl1⋯Cl3^v^---C12^v^ = 169.2 (8)°; symmetry code: (v) *x* + , *y* + , *z*\] are observed.

Synthesis and crystallization   {#sec4}
===============================

The *L* ligand was synthesized according to a literature method (Lee *et al.*, 2013[@bb8]). X-ray-quality single crystals of the title compound were obtained by slow diffusion of a methanol solution of HgCl~2~ into a chloro­form solution of the *L* ligand.

Refinement   {#sec5}
============

Crystal data, data collection and structure refinement details are summarized in Table 3[▸](#table3){ref-type="table"}. A reflection affected by the beamstop was omitted from the final refinement. The chloro­form mol­ecule is disordered over two sets of sites about a twofold rotation axis with equal occupancy. The C---Cl bond lengths were restrained using the DFIX instructions in *SHELXL2014/7* (Sheldrick, 2015[@bb16]). All H atoms were positioned geometrically with *d*(C---H) = 0.93 Å for C*sp* ^2^---H, 0.97 Å for methyl­ene C---H, 0.98 Å for methine C---H, and 0.86 Å for amine N---H, and were refined as riding with *U* ~iso~(H) = 1.2*U* ~eq~(C,N).

Supplementary Material
======================

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: [10.1107/S2056989016015310/sj5509sup1.cif](https://doi.org/10.1107/S2056989016015310/sj5509sup1.cif)

Structure factors: contains datablock(s) I. DOI: [10.1107/S2056989016015310/sj5509Isup2.hkl](https://doi.org/10.1107/S2056989016015310/sj5509Isup2.hkl)

CCDC reference: [1507232](http://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1507232)

Additional supporting information: [crystallographic information](http://scripts.iucr.org/cgi-bin/sendsupfiles?sj5509&file=sj5509sup0.html&mime=text/html); [3D view](http://scripts.iucr.org/cgi-bin/sendcif?sj5509sup1&Qmime=cif); [checkCIF report](http://scripts.iucr.org/cgi-bin/paper?sj5509&checkcif=yes)

This work was supported by the National Research Foundation of Korea (NRF) project (2015R1D1A3A01020410).

Crystal data {#tablewrapcrystaldatalong}
============

  ---------------------------------------- ---------------------------------------
  \[HgCl~2~(C~11~H~11~N~3~)\]·0.5CHCl~3~   *F*(000) = 1928
  *M~r~* = 516.40                          *D*~x~ = 2.137 Mg m^−3^
  Monoclinic, *C*2/*c*                     Mo *K*α radiation, λ = 0.71073 Å
  *a* = 16.6906 (14) Å                     Cell parameters from 3870 reflections
  *b* = 9.1942 (8) Å                       θ = 2.0--28.3°
  *c* = 21.0159 (17) Å                     µ = 10.16 mm^−1^
  β = 95.501 (2)°                          *T* = 298 K
  *V* = 3210.2 (5) Å^3^                    Block, colorless
  *Z* = 8                                  0.4 × 0.3 × 0.3 mm
  ---------------------------------------- ---------------------------------------

Data collection {#tablewrapdatacollectionlong}
===============

  ---------------------------------------------------------- --------------------------------------
  Bruker APEXII CCD area detector diffractometer             2189 reflections with *I* \> 2σ(*I*)
  phi and ω scans                                            *R*~int~ = 0.044
  Absorption correction: multi-scan (SADABS; Bruker, 2014)   θ~max~ = 26.0°, θ~min~ = 2.5°
  *T*~min~ = 0.521, *T*~max~ = 0.928                         *h* = −12→20
  8852 measured reflections                                  *k* = −11→10
  3151 independent reflections                               *l* = −24→25
  ---------------------------------------------------------- --------------------------------------

Refinement {#tablewraprefinementdatalong}
==========

  ------------------------------------- ------------------------------------------------------------------------------------
  Refinement on *F*^2^                  3 restraints
  Least-squares matrix: full            Hydrogen site location: inferred from neighbouring sites
  *R*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.033   H-atom parameters constrained
  *wR*(*F*^2^) = 0.074                  *w* = 1/\[σ^2^(*F*~o~^2^) + (0.034*P*)^2^\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  *S* = 0.99                            (Δ/σ)~max~ = 0.001
  3151 reflections                      Δρ~max~ = 0.58 e Å^−3^
  190 parameters                        Δρ~min~ = −0.83 e Å^−3^
  ------------------------------------- ------------------------------------------------------------------------------------

Special details {#specialdetails}
===============

  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  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.
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å^2^) {#tablewrapcoords}
==================================================================================================

  ----- -------------- -------------- ------------- -------------------- ------------
        *x*            *y*            *z*           *U*~iso~\*/*U*~eq~   Occ. (\<1)
  Hg1   0.32126 (2)    0.66479 (3)    0.10699 (2)   0.06180 (11)         
  Cl1   0.44104 (11)   0.8055 (2)     0.11123 (9)   0.0766 (5)           
  Cl2   0.18389 (11)   0.6629 (2)     0.06581 (9)   0.0839 (6)           
  N1    0.3676 (3)     0.4300 (6)     0.0825 (2)    0.0548 (13)          
  N2    0.1898 (3)     0.1323 (5)     0.2816 (2)    0.0568 (13)          
  N3    0.2853 (4)     0.0648 (6)     0.0611 (2)    0.0641 (15)          
  H3    0.3015         −0.0182        0.0486        0.077\*              
  C1    0.3176 (4)     0.3179 (7)     0.0811 (3)    0.0522 (15)          
  H1    0.2663         0.3330         0.0938        0.063\*              
  C2    0.4398 (4)     0.4134 (8)     0.0648 (3)    0.0693 (18)          
  H2    0.4749         0.4922         0.0662        0.083\*              
  C3    0.4649 (5)     0.2790 (10)    0.0439 (4)    0.080 (2)            
  H3A   0.5163         0.2687         0.0310        0.096\*              
  C4    0.4152 (5)     0.1641 (8)     0.0423 (3)    0.075 (2)            
  H4    0.4322         0.0742         0.0284        0.090\*              
  C5    0.3372 (4)     0.1798 (7)     0.0618 (3)    0.0562 (16)          
  C6    0.2052 (4)     0.0749 (7)     0.0800 (3)    0.0615 (17)          
  H6A   0.1761         −0.0130        0.0667        0.074\*              
  H6B   0.1780         0.1559         0.0576        0.074\*              
  C7    0.2007 (4)     0.0955 (7)     0.1513 (2)    0.0499 (15)          
  C8    0.1386 (4)     0.1686 (7)     0.1738 (3)    0.0636 (17)          
  H8    0.0986         0.2093         0.1454        0.076\*              
  C9    0.1348 (4)     0.1821 (7)     0.2375 (3)    0.0664 (18)          
  H9    0.0904         0.2298         0.2512        0.080\*              
  C10   0.2502 (4)     0.0629 (7)     0.2600 (3)    0.0677 (19)          
  H10   0.2895         0.0249         0.2897        0.081\*              
  C11   0.2594 (4)     0.0424 (7)     0.1953 (3)    0.0618 (18)          
  H11   0.3040         −0.0060        0.1825        0.074\*              
  C12   0.0095 (13)    −0.2965 (16)   0.2726 (7)    0.128 (8)            0.5
  H12   0.0355         −0.3356        0.3128        0.153\*              0.5
  Cl3   −0.0016 (4)    −0.4392 (6)    0.2177 (3)    0.1288 (19)          0.5
  Cl4   0.0705 (7)     −0.1706 (11)   0.2464 (6)    0.201 (5)            0.5
  Cl5   −0.0803 (8)    −0.2208 (14)   0.2885 (6)    0.230 (7)            0.5
  ----- -------------- -------------- ------------- -------------------- ------------

Atomic displacement parameters (Å^2^) {#tablewrapadps}
=====================================

  ----- -------------- -------------- -------------- -------------- -------------- ---------------
        *U*^11^        *U*^22^        *U*^33^        *U*^12^        *U*^13^        *U*^23^
  Hg1   0.06149 (17)   0.07271 (18)   0.05193 (16)   0.00720 (15)   0.00918 (12)   −0.00275 (14)
  Cl1   0.0576 (10)    0.0833 (12)    0.0887 (13)    0.0035 (9)     0.0056 (10)    0.0198 (10)
  Cl2   0.0639 (11)    0.1104 (15)    0.0748 (11)    0.0191 (11)    −0.0065 (9)    −0.0262 (11)
  N1    0.052 (3)      0.069 (3)      0.044 (3)      0.012 (3)      0.006 (3)      −0.001 (2)
  N2    0.053 (3)      0.078 (4)      0.040 (3)      0.007 (3)      0.009 (3)      0.006 (2)
  N3    0.096 (4)      0.052 (3)      0.047 (3)      0.018 (3)      0.019 (3)      −0.004 (2)
  C1    0.053 (4)      0.063 (4)      0.041 (3)      0.017 (3)      0.007 (3)      −0.001 (3)
  C2    0.056 (4)      0.083 (5)      0.070 (4)      0.019 (4)      0.011 (4)      0.008 (4)
  C3    0.065 (5)      0.097 (6)      0.083 (6)      0.030 (5)      0.026 (4)      0.020 (5)
  C4    0.099 (6)      0.072 (5)      0.057 (4)      0.032 (5)      0.027 (4)      0.010 (4)
  C5    0.070 (4)      0.066 (4)      0.034 (3)      0.023 (4)      0.010 (3)      0.007 (3)
  C6    0.074 (5)      0.061 (4)      0.047 (4)      0.002 (4)      −0.004 (4)     0.001 (3)
  C7    0.061 (4)      0.053 (3)      0.036 (3)      0.000 (3)      0.002 (3)      0.006 (3)
  C8    0.052 (4)      0.082 (4)      0.053 (4)      0.017 (4)      −0.011 (3)     0.007 (4)
  C9    0.052 (4)      0.089 (5)      0.059 (4)      0.015 (4)      0.005 (3)      −0.002 (4)
  C10   0.065 (4)      0.083 (5)      0.055 (4)      0.018 (4)      0.004 (4)      0.017 (3)
  C11   0.061 (4)      0.083 (5)      0.042 (3)      0.029 (4)      0.008 (3)      0.003 (3)
  C12   0.18 (2)       0.108 (14)     0.098 (18)     0.000 (18)     0.04 (2)       −0.024 (10)
  Cl3   0.147 (5)      0.100 (3)      0.135 (4)      −0.006 (4)     −0.011 (5)     −0.026 (3)
  Cl4   0.208 (10)     0.167 (7)      0.234 (11)     −0.120 (7)     0.051 (8)      −0.057 (7)
  Cl5   0.184 (9)      0.242 (12)     0.281 (15)     −0.077 (9)     0.110 (10)     −0.150 (11)
  ----- -------------- -------------- -------------- -------------- -------------- ---------------

Geometric parameters (Å, º) {#tablewrapgeomlong}
===========================

  -------------------- ------------- -------------------------- ------------
  Hg1---N1             2.367 (5)     C4---C5                    1.409 (10)
  Hg1---Cl2            2.3718 (19)   C4---H4                    0.9300
  Hg1---Cl1            2.3759 (18)   C6---C7                    1.519 (7)
  Hg1---N2^i^          2.385 (5)     C6---H6A                   0.9700
  N1---C2              1.303 (8)     C6---H6B                   0.9700
  N1---C1              1.326 (8)     C7---C8                    1.358 (8)
  N2---C10             1.310 (8)     C7---C11                   1.371 (8)
  N2---C9              1.323 (8)     C8---C9                    1.352 (9)
  N2---Hg1^ii^         2.386 (5)     C8---H8                    0.9300
  N3---C5              1.366 (8)     C9---H9                    0.9300
  N3---C6              1.434 (8)     C10---C11                  1.394 (8)
  N3---H3              0.8600        C10---H10                  0.9300
  C1---C5              1.382 (8)     C11---H11                  0.9300
  C1---H1              0.9300        C12---Cl4                  1.670 (15)
  C2---C3              1.389 (11)    C12---Cl5                  1.713 (17)
  C2---H2              0.9300        C12---Cl3                  1.746 (13)
  C3---C4              1.342 (10)    C12---H12                  0.9800
  C3---H3A             0.9300                                   
                                                                
  N1---Hg1---Cl2       103.82 (14)   C1---C5---C4               115.5 (7)
  N1---Hg1---Cl1       102.31 (14)   N3---C6---C7               114.6 (5)
  Cl2---Hg1---Cl1      142.96 (7)    N3---C6---H6A              108.6
  N1---Hg1---N2^i^     99.05 (17)    C7---C6---H6A              108.6
  Cl2---Hg1---N2^i^    101.20 (14)   N3---C6---H6B              108.6
  Cl1---Hg1---N2^i^    100.11 (13)   C7---C6---H6B              108.6
  C2---N1---C1         120.0 (6)     H6A---C6---H6B             107.6
  C2---N1---Hg1        120.0 (5)     C8---C7---C11              117.5 (5)
  C1---N1---Hg1        119.7 (4)     C8---C7---C6               121.0 (5)
  C10---N2---C9        115.6 (5)     C11---C7---C6              121.5 (6)
  C10---N2---Hg1^ii^   122.4 (4)     C9---C8---C7               119.9 (6)
  C9---N2---Hg1^ii^    122.0 (4)     C9---C8---H8               120.0
  C5---N3---C6         123.7 (5)     C7---C8---H8               120.0
  C5---N3---H3         118.2         N2---C9---C8               124.5 (6)
  C6---N3---H3         118.2         N2---C9---H9               117.7
  N1---C1---C5         123.7 (6)     C8---C9---H9               117.7
  N1---C1---H1         118.2         N2---C10---C11             124.3 (6)
  C5---C1---H1         118.2         N2---C10---H10             117.8
  N1---C2---C3         120.6 (7)     C11---C10---H10            117.8
  N1---C2---H2         119.7         C7---C11---C10             118.1 (6)
  C3---C2---H2         119.7         C7---C11---H11             120.9
  C4---C3---C2         120.3 (7)     C10---C11---H11            120.9
  C4---C3---H3A        119.8         Cl4---C12---Cl5            110.8 (10)
  C2---C3---H3A        119.8         Cl4---C12---Cl3            109.4 (9)
  C3---C4---C5         119.9 (7)     Cl5---C12---Cl3            113.3 (11)
  C3---C4---H4         120.1         Cl4---C12---H12            107.7
  C5---C4---H4         120.1         Cl5---C12---H12            107.7
  N3---C5---C1         123.1 (6)     Cl3---C12---H12            107.7
  N3---C5---C4         121.4 (6)                                
                                                                
  C2---N1---C1---C5    0.3 (9)       N3---C6---C7---C8          150.4 (6)
  Hg1---N1---C1---C5   174.1 (4)     N3---C6---C7---C11         −29.1 (9)
  C1---N1---C2---C3    0.6 (9)       C11---C7---C8---C9         −2.3 (10)
  Hg1---N1---C2---C3   −173.3 (5)    C6---C7---C8---C9          178.2 (6)
  N1---C2---C3---C4    −0.8 (11)     C10---N2---C9---C8         −1.6 (10)
  C2---C3---C4---C5    0.1 (11)      Hg1^ii^---N2---C9---C8     179.0 (5)
  C6---N3---C5---C1    0.1 (9)       C7---C8---C9---N2          2.3 (11)
  C6---N3---C5---C4    −179.6 (5)    C9---N2---C10---C11        1.1 (10)
  N1---C1---C5---N3    179.5 (5)     Hg1^ii^---N2---C10---C11   −179.5 (5)
  N1---C1---C5---C4    −0.8 (9)      C8---C7---C11---C10        1.9 (10)
  C3---C4---C5---N3    −179.7 (6)    C6---C7---C11---C10        −178.7 (6)
  C3---C4---C5---C1    0.6 (9)       N2---C10---C11---C7        −1.4 (11)
  C5---N3---C6---C7    −70.9 (7)                                
  -------------------- ------------- -------------------------- ------------

Symmetry codes: (i) −*x*+1/2, *y*+1/2, −*z*+1/2; (ii) −*x*+1/2, *y*−1/2, −*z*+1/2.

Hydrogen-bond geometry (Å, º) {#tablewraphbondslong}
=============================

*Cg*1 is the centroid of the N1/C1--C5 ring.

  ------------------------- --------- --------- ----------- ---------------
  *D*---H···*A*             *D*---H   H···*A*   *D*···*A*   *D*---H···*A*
  N3---H3···Cl2^iii^        0.86      2.78      3.467 (5)   138
  C8---H8···Cl1^iv^         0.93      2.80      3.654 (6)   153
  C6---H6*B*···*Cg*1^iii^   0.97      2.71      3.465 (7)   135
  ------------------------- --------- --------- ----------- ---------------

Symmetry codes: (iii) −*x*+1/2, −*y*+1/2, −*z*; (iv) *x*−1/2, *y*−1/2, *z*.

![A view of the mol­ecular structure of the title compound, showing the atom-numbering scheme \[symmetry code: (i) −*x* + , *y* + , −*z* + \]. Displacement ellipsoids are drawn at the 30% probability level. Only one component of the disordered chloro­form mol­ecule is shown. The dashed line represents the inter­molecular C---Cl⋯π inter­action \[Cl4⋯*Cg*2 = 3.442 (11) Å; *Cg*2 is the centroid of the N2/C7--C11 ring\].](e-72-01513-fig1){#fig1}

![The layer formed through inter­molecular N---H⋯Cl hydrogen bonds (black dashed lines) and weak C---H⋯π inter­actions (red dashed lines). Disordered chloro­form mol­ecules and inter­molecular C---Cl⋯π inter­actions are shown as two-colored dashed lines and yellow dashed lines, respectively. H atoms not involved in inter­molecular inter­actions have been omitted for clarity.](e-72-01513-fig2){#fig2}

![The three-dimensional supra­molecular network constructed through inter­molecular C---H⋯Cl hydrogen bonds (light-blue dashed lines) and C---Cl⋯π inter­actions (yellow dashed lines) between the layers formed through N---H⋯Cl (black dashed lines) and C---H⋯π (red dashed lines) inter­actions. Disordered chloro­form mol­ecules are shown as two-colored dashed lines. H atoms not involved in inter­molecular inter­actions have been omitted for clarity.](e-72-01513-fig3){#fig3}

###### Selected geometric parameters (Å, °)

  ----------------- ------------- ------------------- -------------
  Hg1---N1          2.367 (5)     Hg1---Cl1           2.3759 (18)
  Hg1---Cl2         2.3718 (19)   Hg1---N2^i^         2.385 (5)
                                                       
  N1---Hg1---Cl2    103.82 (14)   N1---Hg1---N2^i^    99.05 (17)
  N1---Hg1---Cl1    102.31 (14)   Cl2---Hg1---N2^i^   101.20 (14)
  Cl2---Hg1---Cl1   142.96 (7)    Cl1---Hg1---N2^i^   100.11 (13)
  ----------------- ------------- ------------------- -------------

Symmetry code: (i) .

###### Hydrogen-bond geometry (Å, °)

*Cg*1 is the centroid of the N1/C1--C5 ring.

  *D*---H⋯*A*            *D*---H   H⋯*A*   *D*⋯*A*     *D*---H⋯*A*
  ---------------------- --------- ------- ----------- -------------
  N3---H3⋯Cl2^ii^        0.86      2.78    3.467 (5)   138
  C8---H8⋯Cl1^iii^       0.93      2.80    3.654 (6)   153
  C6---H6*B*⋯*Cg*1^ii^   0.97      2.71    3.465 (7)   135

Symmetry codes: (ii) ; (iii) .

###### Experimental details

  -------------------------------------------------------------------------- -------------------------------------------
  Crystal data                                                               
  Chemical formula                                                           \[HgCl~2~(C~11~H~11~N~3~)\]·0.5CHCl~3~
  *M* ~r~                                                                    516.40
  Crystal system, space group                                                Monoclinic, *C*2/*c*
  Temperature (K)                                                            298
  *a*, *b*, *c* (Å)                                                          16.6906 (14), 9.1942 (8), 21.0159 (17)
  β (°)                                                                      95.501 (2)
  *V* (Å^3^)                                                                 3210.2 (5)
  *Z*                                                                        8
  Radiation type                                                             Mo *K*α
  μ (mm^−1^)                                                                 10.16
  Crystal size (mm)                                                          0.4 × 0.3 × 0.3
                                                                             
  Data collection                                                            
  Diffractometer                                                             Bruker APEXII CCD area detector
  Absorption correction                                                      Multi-scan (*SADABS*; Bruker, 2014[@bb2])
  *T* ~min~, *T* ~max~                                                       0.521, 0.928
  No. of measured, independent and observed \[*I* \> 2σ(*I*)\] reflections   8852, 3151, 2189
  *R* ~int~                                                                  0.044
  (sin θ/λ)~max~ (Å^−1^)                                                     0.617
                                                                             
  Refinement                                                                 
  *R*\[*F* ^2^ \> 2σ(*F* ^2^)\], *wR*(*F* ^2^), *S*                          0.033, 0.074, 0.99
  No. of reflections                                                         3151
  No. of parameters                                                          190
  No. of restraints                                                          3
  H-atom treatment                                                           H-atom parameters constrained
  Δρ~max~, Δρ~min~ (e Å^−3^)                                                 0.58, −0.83
  -------------------------------------------------------------------------- -------------------------------------------

Computer programs: *APEX2* and *SAINT* (Bruker, 2014[@bb2]), *SHELXS97* and *SHELXTL* (Sheldrick, 2008[@bb15]), *SHELXL2014* (Sheldrick, 2015[@bb16]) and *DIAMOND* (Brandenburg, 2010[@bb1]).
