Crystal structure and Hirshfeld surface analysis of di­chlorido­{2,2′-[oxybis(methyl­idene)]di­pyridine}­mercury(II)

Derringer, J.J.; Bebout, D.C.

doi:10.1107/S2056989022010878

research communications

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ISSN: 2056-9890

Volume 78| Part 12| December 2022| Pages 1233-1237

https://doi.org/10.1107/S2056989022010878

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Crystal structure and Hirshfeld surface analysis of dichlorido{2,2′-[oxybis(methylidene)]dipyridine}mercury(II)

Jesse J. Derringer ^a and Deborah C. Bebout ^a ^*

^aDepartment of Chemistry, William & Mary, Williamsburg, VA 23187-8795, USA
^*Correspondence e-mail: dcbebo@wm.edu

Edited by C. Schulzke, Universität Greifswald, Germany (Received 30 September 2022; accepted 12 November 2022; online 17 November 2022)

The series of divalent metal chloride complexes of 2,2′-[oxybis(methylidene)]dipyridine (L) was extended with the preparation of the title compound, [HgCl₂(C₁₂H₁₂N₂O)] or [HgLCl₂] (1). The Hg²⁺ complex crystallizes in P2₁/n, isomorphic with dichloride Co²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ complexes of L. Metal ions of the isotypic complexes are coordinated by two chlorine atoms, as well as the oxygen atom and both nitrogen atoms of L. The complexes have a square-pyramidal coordination geometry with a chlorine atom in the apical position. Supramolecular interactions in 1 include offset face-to-face interactions between inversion-related complexes, leading to the formation of sheets parallel to the ab plane. Weak intermolecular H⋯Cl contacts link the sheets. Hirshfeld surface analysis indicates that H⋯H (36.5%), Cl⋯H/H⋯Cl (36.5%) and C⋯H/H⋯C (11.6%) interactions are dominant.

Keywords: crystal structure; mercury complex; Hirshfeld surface analysis.

CCDC reference: 2219283

1. Chemical context

Structural comparisons of group 12 metal ions in similar environments can help improve understanding of the effects of metal-ion replacement on the biological properties of organic molecules. Ether-containing bioactive compounds with group 12 metal ion-dependent bioactivity include flavonoids (Sreenivasulu et al., 2010 ; Kim et al., 2011 ; Li et al., 2017 ), ionophores (Ivanova et al., 2011 ), and pharmaceuticals (Zhang et al., 2014 ). Recent studies of 2,2′-[oxybis(methylidene)]dipyridine (L) with group 12 perchlorate salts revealed bis-tridentate chelate [ML₂](ClO₄)₂ complexes with either meridional octahedral (M = Zn²⁺ or Cd²⁺) or trigonal–prismatic (M = Hg²⁺) metal-ion coordination (Sturner et al., 2022 ). Isotypic square-pyramidal [MLCl₂] complexes of Zn²⁺ (τ = 0.03) and Cd²⁺ (τ = 0.11) have been reported previously (Addison et al., 1984 ; Li, 2008a ,b ). Herein, the preparation, crystal structure and Hirshfeld surface analysis of dichlorido{2,2′-[oxybis(methylidene)]dipyridine}mercury(II) is reported.

2. Structural commentary

Complex 1 crystallizes in the monoclinic space group P2₁/n as a monomer (Fig. 1). The tridentate ligand and two chlorides provide a slightly distorted square-pyramidal geometry (τ = 0.07; Table 1) to the metal ion (Addison et al. 1984). In the complex, tridentate L has an asymmetrical, slightly bent conformation in the basal plane with an N1—Hg1—N2 angle of 129.28 (8)°. Both chelate rings have an envelope conformation with O1 in the flap position. The mercury atom is 0.8100 (9) Å above the basal plane. The apical Hg—Cl distance is 0.0083 Å longer than the basal Hg—Cl distance.

Table 1
Selected geometric parameters (Å, °)

Hg1—N2	2.323 (2)	Hg1—Cl2	2.4598 (7)
Hg1—N1	2.324 (2)	Hg1—O1	2.5831 (18)
Hg1—Cl1	2.4515 (6)

N2—Hg1—N1	129.28 (8)	Cl1—Hg1—Cl2	120.18 (2)
N2—Hg1—Cl1	102.65 (5)	N2—Hg1—O1	65.35 (6)
N1—Hg1—Cl1	101.29 (6)	N1—Hg1—O1	65.59 (7)
N2—Hg1—Cl2	101.97 (5)	Cl1—Hg1—O1	133.20 (4)
N1—Hg1—Cl2	103.41 (6)	Cl2—Hg1—O1	106.62 (4)

Figure 1
The molecular structure of 1 with the atom-numbering scheme generated with ORTEP-3 for Windows (Farrugia, 2012

). Displacement ellipsoids are drawn at the 50% probability level and H atoms are displayed as small spheres of arbitrary radii.

3. Supramolecular features

The packing of 1 is stabilized by π–π stacking interactions (Fig. 2) and van der Waals interactions (Fig. 3). On the apical side of 1, pyridyl rings (centroids Cg1: N1/C1–C5; Cg2: N2/C8–C12) are stacked against separate inversion-related equivalents with a small offset (Table 2). In contrast, the basal face features an extended ligand conformation placing the N2 pyridyl rings across from the chelate rings of an inversion-related molecule (Fig. 2) with large offsets between the pyridyl ring centroids of the opposing ligand (Table 2). Although the large centroid offsets preclude π–π stacking interactions on the basal face, the predominantly planar ligand allows the inner and outer edges of N2 pyridyl rings to nestle along the inner edges of opposing N2 and N1 pyridyl rings, respectively (Fig. 2).

Table 2
Overview of pyridyl–pyridyl ring geometry metrics (Å, °) for [HgLCl₂] (1)

Cg1 and Cg2 are the centroids of the N1/C1–C5 and N2/C8–C12 rings, respectively.

Centroids	Dihedral angle between rings	Centroid–centroid distance	Centroid–plane distance	Centroid offset
Cg1⋯Cg1ⁱ	0.00	3.718 (2)	3.573 (2)	1.028
Cg2⋯Cg2ⁱⁱ	0.00	4.002 (2)	3.563 (4)	1.822
Cg2⋯Cg2ⁱⁱⁱ	0.00	5.005 (2)	3.536 (4)	3.542
Cg1⋯Cg2ⁱⁱⁱ	18.38 (12)	4.2944 (15)	2.826 (4)	3.233
Cg2⋯Cg1ⁱⁱⁱ	18.38 (12)	4.2944 (15)	3.702 (3)	2.176
Symmetry codes: (i) −x + 1, −y + 2, −z + 1; (ii) −x, −y + 1, −z + 1; (iii) −x + 1, −y + 1, −z + 1.

Figure 2
Offset face-to-face pyridyl ring arrangement between inversion-related molecules of 1 illustrated using Mercury 2020.1 (Macrae et al., 2020

). Ring centroids are shown as red spheres. Blue dashed lines show centroid–centroid distances (for numerical data, see Table 2

Figure 3
Crystal packing of compound 1 illustrated using Mercury 2020.1 (Macrae et al., 2020

). Face-to-face aromatic interactions occur within sheets of molecules in the ab plane. Short interatomic contacts within and between the sheets of 1 are shown by blue dashed lines (for numerical data, see Table 4

Aromatic stacking interactions contribute to formation of sheets parallel to the ab plane. Adjacent sheets are related by a 2₁ screw axis. Intermolecular van der Waals interactions, some of which could be described as weak hydrogen bonds involving C—H donors and Cl acceptors (Table 3; Brammer et al., 2001 ), occur within and between the sheets.

Table 3
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯Cl1ⁱ	0.95	2.73	3.623 (3)	157
C6—H6B⋯Cl2ⁱⁱ	0.99	2.79	3.746 (3)	164
C6—H6A⋯Cl1ⁱⁱⁱ	0.99	2.94	3.711 (3)	135
C11—H11⋯Cl1^iv	0.95	2.86	3.722 (3)	151
Symmetry codes: (i) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[x+{\script{1\over 2}}, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (iii) $[x-{\script{1\over 2}}, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (iv) $[-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

4. Hirshfeld surface analysis

Intermolecular interactions were investigated by quantitative analysis of the Hirshfeld surface and visualized with CrystalExplorer 21.5 (Spackman et al., 2021 ). Five hourglass features appeared on the Hirshfeld surface of 1 plotted over shape index (Fig. 4). Both hourglass features on the apical side reflect self-complementary face-to-face bump and hollow alignments between inversion-related pyridyl rings involved in π–π stacking. The hourglass features associated with O1 and C12 on the basal face arise from the bend of the O atom in the flap position of the chelate rings towards the inversion-related molecule (Fig. 2), resulting in notably shorter interatomic distances than for adjacent atoms (Table 4). The last hourglass feature reflects surface complementarity near the interior edges of inversion-related N2 pyridyl rings with a centroid offset of 3.452 Å. Additional blue and red horseshoe-shaped regions on the basal face correlate with a bump along the C9—C10 outer edge of the N2 pyridyl ring nesting against a hollow looping around N1, respectively.

Table 4
Short interatomic contacts (Å) in [HgLCl₂] (1)

Atoms	Distance	Atoms	Distance
Cl1⋯H2ⁱ	2.732	Cl2⋯H6Bⁱⁱ	2.785
Cl2⋯H3ⁱⁱⁱ	2.808	Cl2⋯H10^iv	2.813
H11⋯Cl1^v	2.862	O1⋯C12^vi	3.201 (3)
Symmetry codes: (i) −x + $[{3\over 2}]$ , y − $[{1\over 2}]$ , −z + $[{1\over 2}]$ ; (ii) x − $[{1\over 2}]$ , −y + $[{3\over 2}]$ , z − $[{1\over 2}]$ ; (iii) −x + 1, −y + 2, −z + 1; (iv) −x, −y + 1, −z + 1; (v) −x + $[{1\over 2}]$ , y − $[{1\over 2}]$ , −z + $[{1\over 2}]$ ; (vi) −x + 1, −y + 1, −z + 1.

Figure 4
(a) Apical and (b) basal plane views of the Hirshfeld surface of 1 plotted over shape index generated with CrystalExplorer 21.5 (Spackman et al. 2021

). Blue and red areas represent bumps and hollow regions, respectively, on the shape-index surface.

The Hirshfeld surface of 1 mapped with the function d_norm, the sum of the distances from a surface point to the nearest interior (d_i) and exterior (d_e) atoms normalized by the van der Waals (vdW) radii of the corresponding atom (r_vdW), is shown in Fig. 5. Contacts shorter than the sums of vdW radii are shown in red, those longer in blue, and those approximately equal as white spots. The most intense red spots correspond to a series of intermolecular contacts between the peripheral chlorine atoms and hydrogen atoms with Cl⋯H distances of 2.7319–2.8616 Å (Table 4), some of which could be regarded as weak hydrogen bonds (Brammer et al. 2001). There are also very faint red spots on the basal planes associated with an O1⋯C12 contact.

Figure 5
Views of the (a) apical and (b) basal plane Hirshfeld surface of 1 plotted over normalized contact distance (d_norm) in the range from −0.1617 to 1.4660 a.u. generated with CrystalExplorer 21.5 (Spackman et al. 2021

). Intermolecular contacts closer than the sum of their van der Waals radii are highlighted in red on the d_norm surface. Contacts near and longer than the sum of van der Waals radii are shown in white and blue, respectively.

The overall 2D fingerprint plot for 1 is provided in Fig. 6a. Interactions delineated into Cl⋯H/H⋯Cl (36.5%), H⋯H (36.5%) and H⋯Cl/H⋯Cl (11.6%) contacts are shown in Fig. 6b–d. Other minor contributions to the Hirshfeld surface are from C⋯C (4.1%), N⋯H/H⋯N (3.1%), O⋯C/C⋯O (2.8%), N⋯C/C⋯N (2.7%), Hg⋯C/C⋯Hg (0.7%), Hg⋯H/H⋯Hg (0.7%), O⋯N/N⋯O (0.7%), and Cl⋯C/C⋯Cl (0.5%) interactions.

Figure 6
The full two-dimensional fingerprint plots for 1, showing (a) all interactions, and components delineated into (b) Cl⋯H/H⋯Cl, (c) H⋯H, and (d) C⋯H/H⋯C interactions generated with CrystalExplorer 21.5 (Spackman et al. 2021

). The d_i and d_e values are closest internal and external distances (in Å) from given points on the Hirshfeld surface.

5. Database survey

A search of the Cambridge Structural Database (CSD, Version 5.43, update of June 2022; Groom et al., 2016 ) for complexes of mercury bound to an ether oxygen, two nitrogen and two chloride atoms yielded seven hits. Unlike the bis-aliphatic ether component of 1, all reported structures involved derivatized anisole ligands.

A search of the Cambridge Structural Database (CSD, Version 5.43, update of June 2022; Groom et al., 2016) for L yielded fourteen hits. Four [MLCl₂] complexes isotypic with 1 have been reported with M = Co (refcode RAVMOU; Misawa-Suzuki et al., 2022 ), Cu (refcode UGANIA; Li, 2008a), Zn (refcode UGANOG; Li, 2008b) and Cd (refcode TIGJID; Li, 2007 ). The isotypic complexes have square-pyramidal coordination geometries (τ = 0.03–0.14) and extended ligand conformations with slightly smaller pyridyl ring dihedral angles (range 12.88–16.85°) compared to 1. An extended conformation of L has also been reported in meridional octahedral complexes [CrLCl₃]·H₂O (refcode ZAXBUX; Chen et al., 2012 ), [FeLCl₃] (refcode RAVXEV; Misawa-Suzuki et al., 2022), [CoL₂](PF₆)₂ (refcode RAVLAF; Misawa-Suzuki et al., 2022), [CdL₂](ClO₄)₂·CH₃CN (refcode VAXXOL; Sturner et al., 2022), and [ZnL₂](ClO₄)₂·CH₃CN (refcode VAYCEH; Sturner et al., 2022), as well as the discrete square-planar and square-pyramidal cations of [CuLCl][CuLCl(H₂O)](ClO₄)₂ (refcode FOWJAD: Li et al., 2009 ). In contrast, substantially bent conformations of L are observed in slightly distorted octahedral facial complexes [RhLCl₃]·CH₂Cl₂ (refcode AWOQIN; Ojwach et al., 2011 ), [MoL(CO)₃] (refcode GUGWAG; Nanty et al., 2000 ) and (2,2′-bipyridine)(2,2′-[oxybis(methylidene)]dipyridine)(perchlorato)copper(II) perchlorate (refcode IXUYEF; Cheng et al., 2004 ) and distorted trigonal–prismatic [HgL₂](ClO₄)₂ (refcode VAXXUR; Sturner et al., 2022). The published structures document the coordinative flexibility of L.

6. Synthesis and crystallization

A solution of L (41 mg, 205 µmol) in 3 mL methanol was added to one equivalent of HgCl₂ (55 mg, 203 µmol) in 12 mL of methanol with stirring. The resulting precipitate was dissolved with the addition of 35 mL of methanol. The solution was filtered through Celite and fractionated. Pale-pink needles were obtained through slow evaporation (52 mg, 110 µmol, 54% yield), m.p.: 423–426 K. ¹H NMR (CD₃CN, nominally 2 mM, 293 K) δ: 8.69 (d, 2H, J = 5.4 Hz), 7.95 (ddd, 2H, J = 8.0, 8.0, 1.9 Hz), 7.53 (m, 2H), 4.88 (s, 4H). IR (ATR) ν/cm⁻¹: 3080(w), 3069(w), 3028(w), 2864(w), 1602(s), 1574(m), 1487(m), 1465(m), 1449(s), 1406(m), 1385(w), 1364(m), 1301(m), 1288(s), 1250(m), 1231(w), 1221(m), 1163(m), 1155(m), 1130(s), 1109(m), 1099(s), 1051(m), 1030(m), 1016(s), 1003(m), 995(m), 972(w), 961(w), 889(w), 851(m), 826(w), 816(w), 810(w), 773(s), 762(s), 723(s), 667(w), 646(m), 640(s), 629(m). Elemental analysis calculated for C₁₂H₁₂HgN₂O: C, 30.55; H, 2.56; N, 5.94. Found: C, 30.54; H, 2.51; N, 5.90%.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 5. The hydrogen atoms were placed in calculated positions with C—H distances of 0.95 Å (aromatic) and 0.99 Å (methylene) and refined as riding atoms with U_iso(H) = 1.2U_eq(C).

Table 5
Experimental details

Crystal data
Chemical formula	[HgCl₂(C₁₂H₁₂N₂O)]
M_r	471.73
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	100
a, b, c (Å)	8.0202 (6), 12.587 (1), 13.7761 (11)
β (°)	91.290 (1)
V (Å³)	1390.35 (19)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	11.44
Crystal size (mm)	0.46 × 0.16 × 0.14

Data collection
Diffractometer	Bruker SMART APEXII CCD
Absorption correction	Numerical (SADABS; Krause et al., 2015 )
T_min, T_max	0.144, 0.486
No. of measured, independent and observed [I > 2σ(I)] reflections	20815, 2763, 2638
R_int	0.022
(sin θ/λ)_max (Å⁻¹)	0.619

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.014, 0.034, 1.09
No. of reflections	2763
No. of parameters	163
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.87, −0.32
Computer programs: APEX3 (Bruker, 2015 ), SAINT-Plus (Bruker, 2012 ), SHELXS2014/5 (Sheldrick, 2015a ), SHELXL2014/5 (Sheldrick, 2015b ), ShelXle (Hübschle, 2011 ), ORTEP-3 for Windows (Farrugia, 2012 ), Mercury (Macrae et al., 2020 ), CrystalExplorer21.5 (Spackman et al., 2021), OLEX2 (Dolomanov et al., 2009 ), and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2219283

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989022010878/yz2024sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989022010878/yz2024Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989022010878/yz2024Isup3.cdx

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2015); cell refinement: SAINT-Plus (Bruker, 2012); data reduction: SAINT-Plus (Bruker, 2012); program(s) used to solve structure: SHELXS2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/5 (Sheldrick, 2015b); molecular graphics: ShelXle (Hübschle, 2011); software used to prepare material for publication: ORTEP-3 for Windows (Farrugia, 2012), Mercury (Macrae et al., 2020), CrystalExplorer 21.5 (Spackman et al., 2021), OLEX2 (Dolomanov et al., 2009), and publCIF (Westrip, 2010).

Dichlorido{2,2'-[oxybis(methylidene)]dipyridine}mercury(II) top

Crystal data top

[HgCl₂(C₁₂H₁₂N₂O)]	F(000) = 880
M_r = 471.73	D_x = 2.254 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 8.0202 (6) Å	Cell parameters from 9936 reflections
b = 12.587 (1) Å	θ = 2.9–26.1°
c = 13.7761 (11) Å	µ = 11.44 mm⁻¹
β = 91.290 (1)°	T = 100 K
V = 1390.35 (19) Å³	Needle, pink
Z = 4	0.46 × 0.16 × 0.14 mm

Data collection top

Bruker SMART APEXII CCD diffractometer	2763 independent reflections
Radiation source: fine-focus sealed tube	2638 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.022
ω and ψ scans	θ_max = 26.1°, θ_min = 2.2°
Absorption correction: numerical (SADABS; Krause et al., 2015)	h = −9→9
T_min = 0.144, T_max = 0.486	k = −15→15
20815 measured reflections	l = −17→17

Refinement top

Refinement on F²	Primary atom site location: other
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.014	H-atom parameters constrained
wR(F²) = 0.034	w = 1/[σ²(F_o²) + (0.0174P)² + 1.5258P] where P = (F_o² + 2F_c²)/3
S = 1.09	(Δ/σ)_max = 0.001
2763 reflections	Δρ_max = 0.87 e Å⁻³
163 parameters	Δρ_min = −0.32 e Å⁻³
0 restraints

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
Hg1	0.38378 (2)	0.68896 (2)	0.36993 (2)	0.01728 (4)
Cl1	0.55569 (8)	0.63592 (5)	0.23324 (5)	0.02356 (14)
Cl2	0.12028 (8)	0.78490 (5)	0.34042 (5)	0.02342 (14)
O1	0.4165 (2)	0.66608 (14)	0.55572 (13)	0.0180 (4)
N1	0.5538 (3)	0.81512 (16)	0.44555 (17)	0.0188 (5)
N2	0.2909 (3)	0.52695 (17)	0.42871 (15)	0.0165 (4)
C1	0.6644 (3)	0.8701 (2)	0.3933 (2)	0.0244 (6)
H1	0.672585	0.855181	0.326020	0.029*
C2	0.7663 (3)	0.9472 (2)	0.4339 (2)	0.0294 (7)
H2	0.842884	0.985000	0.395143	0.035*
C3	0.7549 (4)	0.9686 (2)	0.5324 (2)	0.0309 (7)
H3	0.821863	1.022269	0.562062	0.037*
C4	0.6442 (3)	0.9103 (2)	0.5865 (2)	0.0257 (6)
H4	0.636434	0.922285	0.654331	0.031*
C5	0.5445 (3)	0.8344 (2)	0.54108 (19)	0.0182 (5)
C6	0.4211 (3)	0.7698 (2)	0.59698 (19)	0.0211 (5)
H6B	0.455937	0.765959	0.666302	0.025*
H6A	0.309279	0.802897	0.592423	0.025*
C7	0.2934 (3)	0.5986 (2)	0.59428 (18)	0.0197 (5)
H7A	0.191536	0.639976	0.607620	0.024*
H7B	0.334940	0.567189	0.656137	0.024*
C8	0.2531 (3)	0.5114 (2)	0.52223 (18)	0.0173 (5)
C9	0.1749 (3)	0.4187 (2)	0.55252 (19)	0.0203 (5)
H9	0.151175	0.408214	0.619088	0.024*
C10	0.1324 (3)	0.3420 (2)	0.4844 (2)	0.0229 (6)
H10	0.075338	0.279417	0.503154	0.027*
C11	0.1740 (3)	0.3577 (2)	0.3883 (2)	0.0215 (6)
H11	0.148269	0.305511	0.340459	0.026*
C12	0.2539 (3)	0.4508 (2)	0.36382 (19)	0.0204 (5)
H12	0.283764	0.461234	0.298171	0.024*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.01956 (6)	0.01822 (6)	0.01414 (6)	−0.00100 (4)	0.00190 (4)	0.00056 (3)
Cl1	0.0263 (3)	0.0269 (3)	0.0177 (3)	0.0048 (3)	0.0053 (3)	0.0001 (3)
Cl2	0.0203 (3)	0.0259 (3)	0.0241 (3)	0.0031 (3)	0.0017 (3)	0.0013 (3)
O1	0.0181 (9)	0.0178 (9)	0.0181 (9)	−0.0010 (7)	0.0033 (7)	−0.0015 (7)
N1	0.0179 (11)	0.0155 (11)	0.0229 (12)	0.0018 (8)	0.0003 (9)	0.0010 (8)
N2	0.0146 (10)	0.0185 (11)	0.0165 (10)	0.0019 (8)	−0.0002 (8)	0.0004 (8)
C1	0.0230 (14)	0.0212 (13)	0.0291 (15)	0.0012 (11)	0.0045 (11)	0.0046 (11)
C2	0.0193 (14)	0.0205 (14)	0.0485 (19)	−0.0029 (11)	0.0022 (13)	0.0095 (13)
C3	0.0234 (15)	0.0177 (14)	0.051 (2)	−0.0022 (11)	−0.0094 (14)	−0.0026 (13)
C4	0.0249 (14)	0.0213 (14)	0.0306 (15)	0.0027 (11)	−0.0059 (12)	−0.0049 (11)
C5	0.0176 (13)	0.0155 (12)	0.0212 (13)	0.0045 (10)	−0.0024 (11)	−0.0011 (10)
C6	0.0226 (14)	0.0216 (13)	0.0191 (13)	0.0004 (11)	0.0013 (11)	−0.0054 (11)
C7	0.0200 (13)	0.0233 (13)	0.0158 (12)	−0.0017 (10)	0.0036 (10)	0.0017 (10)
C8	0.0130 (12)	0.0201 (13)	0.0189 (13)	0.0036 (10)	−0.0005 (10)	0.0034 (10)
C9	0.0162 (12)	0.0231 (13)	0.0216 (13)	0.0023 (10)	0.0010 (10)	0.0064 (11)
C10	0.0148 (13)	0.0179 (13)	0.0360 (16)	−0.0006 (10)	−0.0011 (11)	0.0065 (11)
C11	0.0183 (13)	0.0195 (13)	0.0264 (14)	−0.0002 (11)	−0.0041 (11)	−0.0036 (11)
C12	0.0209 (13)	0.0211 (13)	0.0191 (13)	0.0032 (11)	−0.0010 (10)	0.0009 (10)

Geometric parameters (Å, º) top

Hg1—N2	2.323 (2)	C4—C5	1.386 (4)
Hg1—N1	2.324 (2)	C4—H4	0.9500
Hg1—Cl1	2.4515 (6)	C5—C6	1.506 (4)
Hg1—Cl2	2.4598 (7)	C6—H6B	0.9900
Hg1—O1	2.5831 (18)	C6—H6A	0.9900
O1—C7	1.415 (3)	C7—C8	1.510 (4)
O1—C6	1.424 (3)	C7—H7A	0.9900
N1—C5	1.342 (4)	C7—H7B	0.9900
N1—C1	1.346 (4)	C8—C9	1.393 (4)
N2—C12	1.340 (3)	C9—C10	1.384 (4)
N2—C8	1.344 (3)	C9—H9	0.9500
C1—C2	1.379 (4)	C10—C11	1.386 (4)
C1—H1	0.9500	C10—H10	0.9500
C2—C3	1.389 (5)	C11—C12	1.381 (4)
C2—H2	0.9500	C11—H11	0.9500
C3—C4	1.382 (4)	C12—H12	0.9500
C3—H3	0.9500

N2—Hg1—N1	129.28 (8)	N1—C5—C4	121.5 (3)
N2—Hg1—Cl1	102.65 (5)	N1—C5—C6	117.1 (2)
N1—Hg1—Cl1	101.29 (6)	C4—C5—C6	121.4 (2)
N2—Hg1—Cl2	101.97 (5)	O1—C6—C5	107.6 (2)
N1—Hg1—Cl2	103.41 (6)	O1—C6—H6B	110.2
Cl1—Hg1—Cl2	120.18 (2)	C5—C6—H6B	110.2
N2—Hg1—O1	65.35 (6)	O1—C6—H6A	110.2
N1—Hg1—O1	65.59 (7)	C5—C6—H6A	110.2
Cl1—Hg1—O1	133.20 (4)	H6B—C6—H6A	108.5
Cl2—Hg1—O1	106.62 (4)	O1—C7—C8	109.3 (2)
C7—O1—C6	114.40 (19)	O1—C7—H7A	109.8
C7—O1—Hg1	112.52 (14)	C8—C7—H7A	109.8
C6—O1—Hg1	107.13 (14)	O1—C7—H7B	109.8
C5—N1—C1	118.9 (2)	C8—C7—H7B	109.8
C5—N1—Hg1	121.20 (18)	H7A—C7—H7B	108.3
C1—N1—Hg1	119.92 (19)	N2—C8—C9	121.4 (2)
C12—N2—C8	118.9 (2)	N2—C8—C7	118.3 (2)
C12—N2—Hg1	117.63 (17)	C9—C8—C7	120.2 (2)
C8—N2—Hg1	122.88 (17)	C10—C9—C8	119.1 (2)
N1—C1—C2	122.5 (3)	C10—C9—H9	120.4
N1—C1—H1	118.7	C8—C9—H9	120.4
C2—C1—H1	118.7	C9—C10—C11	119.2 (2)
C1—C2—C3	118.7 (3)	C9—C10—H10	120.4
C1—C2—H2	120.6	C11—C10—H10	120.4
C3—C2—H2	120.6	C12—C11—C10	118.5 (2)
C4—C3—C2	118.8 (3)	C12—C11—H11	120.7
C4—C3—H3	120.6	C10—C11—H11	120.7
C2—C3—H3	120.6	N2—C12—C11	122.8 (2)
C3—C4—C5	119.5 (3)	N2—C12—H12	118.6
C3—C4—H4	120.2	C11—C12—H12	118.6
C5—C4—H4	120.2

C5—N1—C1—C2	−1.4 (4)	C6—O1—C7—C8	157.7 (2)
Hg1—N1—C1—C2	178.8 (2)	Hg1—O1—C7—C8	35.2 (2)
N1—C1—C2—C3	0.3 (4)	C12—N2—C8—C9	−0.7 (4)
C1—C2—C3—C4	1.3 (4)	Hg1—N2—C8—C9	170.47 (18)
C2—C3—C4—C5	−1.7 (4)	C12—N2—C8—C7	−179.2 (2)
C1—N1—C5—C4	1.0 (4)	Hg1—N2—C8—C7	−8.0 (3)
Hg1—N1—C5—C4	−179.25 (19)	O1—C7—C8—N2	−20.4 (3)
C1—N1—C5—C6	−179.0 (2)	O1—C7—C8—C9	161.1 (2)
Hg1—N1—C5—C6	0.8 (3)	N2—C8—C9—C10	−1.3 (4)
C3—C4—C5—N1	0.6 (4)	C7—C8—C9—C10	177.1 (2)
C3—C4—C5—C6	−179.4 (3)	C8—C9—C10—C11	2.3 (4)
C7—O1—C6—C5	−174.0 (2)	C9—C10—C11—C12	−1.3 (4)
Hg1—O1—C6—C5	−48.6 (2)	C8—N2—C12—C11	1.8 (4)
N1—C5—C6—O1	35.2 (3)	Hg1—N2—C12—C11	−169.8 (2)
C4—C5—C6—O1	−144.8 (2)	C10—C11—C12—N2	−0.8 (4)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···Cl1ⁱ	0.95	2.73	3.623 (3)	157
C6—H6B···Cl2ⁱⁱ	0.99	2.79	3.746 (3)	164
C6—H6A···Cl1ⁱⁱⁱ	0.99	2.94	3.711 (3)	135
C11—H11···Cl1^iv	0.95	2.86	3.722 (3)	151

Symmetry codes: (i) −x+3/2, y+1/2, −z+1/2; (ii) x+1/2, −y+3/2, z+1/2; (iii) x−1/2, −y+3/2, z+1/2; (iv) −x+1/2, y−1/2, −z+1/2.

Overview of pyridyl–pyridyl ring geometry metrics (Å, °) for [HgLCl₂] (1) top

Cg1 and Cg2 are the centroids of the N1/C1–C5 and N2/C8–C12 rings, respectively.

Centroids	Dihedral angle between rings	Centroid–centroid distance	Centroid–plane distance	Centroid offset
Cg1···Cg1ⁱ	0.00	3.718 (2)	3.573 (2)	1.028
Cg2···Cg2ⁱⁱ	0.00	4.002 (2)	3.563 (4)	1.822
Cg2···Cg2ⁱⁱⁱ	0.00	5.005 (2)	3.536 (4)	3.542
Cg1···Cg2ⁱⁱⁱ	18.38 (12)	4.2944 (15)	2.826 (4)	3.233
Cg2···Cg1ⁱⁱⁱ	18.38 (12)	4.2944 (15)	3.702 (3)	2.176

Symmetry codes: (i) -x + 1, -y + 2, -z + 1; (ii) -x, -y + 1, -z + 1; (iii) -x + 1, -y + 1, -z + 1.

Short interatomic contacts (Å) in [HgLCl₂] (1) top

Atoms	Distance	Atoms	Distance
Cl1···H2ⁱ	2.732	Cl2···H6Bⁱⁱ	2.785
Cl2···H3ⁱⁱⁱ	2.808	Cl2···H10^iv	2.813
H11···Cl1^v	2.862	O1···C12^vi	3.201 (3)

Symmetry codes: (i) -x + 3/2, y - 1/2, -z + 1/2; (ii) x - 1/2, -y + 3/2, z - 1/2 ; (iii) -x + 1, -y + 2, -z + 1; (iv) -x, -y + 1, -z + 1; (v) -x + 1/2, y - 1/2, -z + 1/2; (vi) -x + 1, -y + 1, -z + 1.

Acknowledgements

The authors thank Professor Robert Pike for consulting on this work and for the extraordinary patience he has demonstrated while providing training in X-ray crystallography over the past seventeen years.

Funding information

Funding for this research was provided by: William & Mary; National Science Foundation, Directorate for Mathematical and Physical Sciences (grant No. 0443345).

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