Effect of the size of halide ligands on the crystal structures of halide-bibridged polymers of HgX2 with 4-ethyl­pyridine

Beebeejaun-Boodoo, B.M.P.

doi:10.1107/S2053229625009702

research papers

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 81| Part 12| December 2025| Pages 680-686

https://doi.org/10.1107/S2053229625009702

Open

access

Effect of the size of halide ligands on the crystal structures of halide-bibridged polymers of HgX₂ with 4-ethylpyridine

B. M. Parveen Beebeejaun-Boodoo ^a ^*

^aDepartment of Chemistry, University of Pretoria, Private Bag X20, Hatfield, 0028, Pretoria, South Africa
^*Correspondence e-mail: [email protected]

Edited by E. Reinheimer, Rigaku Americas Corporation, USA (Received 10 April 2025; accepted 1 November 2025; online 10 November 2025)

Halide-bridged polymers are a type of coordination polymer whereby halide ligands act as bridging ligands between the metal centres. The crystal structures of three halide-bibridged polymers of the formula [Hg(μ-X)₂(4-Etpy)]_n, namely, catena-poly[[(4-ethylpyridine)mercury(II)]-di-μ-halido], obtained through the combination of the organic ligand 4-ethylpyridine (4-Etpy, C₇H₉N) and HgX₂ (X = Cl, Br or I), were determined. In these structures, abbreviated as 4epHgCl, 4epHgBr and 4epHgI, respectively, the Hg^II ion exhibits a coordination number of five. All three structures were found to display a similar one-dimensional scalloped polymeric chain with halide ligands bridging pairs of Hg^II ions in a bidentate fashion; however, 4epHgI differs from the other two structures in terms of the packing arrangement of the polymer. The change of the halide ligand to the larger iodide ligand disrupts the formation of the regular halide-bibridged polymeric chain observed in the chloride and bromide analogues, with 4epHgI displaying pseudo-bridging in the polymer chain.

Keywords: coordination polymers; crystal structure; halide-bibridged polymers; mercury; ethylpyridine; organic-inorganic hybrid.

CCDC references: 2442692; 2442693; 2442694

1. Introduction

Halide-bridged polymers are a subgroup of coordination compounds comprising metal ions that are linked via bridging halide ligands into a polymeric structure. The metal ions are typically also coordinated to additional organic ligands, resulting in a polymer of the formula [M(μ-X)_y(L)_z]_n, with M indicating the metal ion, X the bridging halide ligand and L the organic ligand. Additional terminal halide ligands may also be present in these polymers. The structural diversity displayed by halide-bridged polymers make them excellent candidates for use in crystal engineering studies.

Halide-bridged polymers display physical properties, such as magnetic exchange and electrical conductivity along the halide-bridged polymer, as well as luminescence, catalytic activity and non-linear optical properties (Givaja et al., 2012 ; Eckberg et al., 1975 ; Crawford et al., 1977 ; Estes et al., 1978 ; Zhang et al., 1997 ; Wei et al., 1996 ; Slabbert et al., 2015a ). Of specific interest in the current study are halide-bridged polymers containing the metal ion Hg^II and the organic ligand 4-ethylpyridine (4-Etpy).

The Hg^II ion shows a range of coordination configurations ranging from trigonal planar, square-planar and octahedral to the preferred tetrahedral environment due to its softness and fully filled orbitals, allowing it to bind with soft anions such as Cl⁻, Br⁻ and I⁻ (Slabbert et al., 2015b ; Englert et al., 2010 ; Hu et al., 2007 ). The coordination around the Hg^II cations allows for a wide range of bonding distances to potential donor atoms (Englert et al., 2010). Halide-bridged polymers of divalent d¹⁰ metal cations with N-donor ligands have been studied, focusing on the effect of electronically modified pyridine/pyrazine-derived N-donor ligands on the structure of the coordinated halide-bridged chain (Hu et al., 2001 , 2003 ; Wang et al., 2009 ; Mahmoudi et al., 2009 ; Morsali et al., 2009 ). The size of the N-donor organic ligand has an effect on the halide-bridged polymer and the extent to which the width of the coordinating N-donor organic ligand can be increased without disrupting the chain of the halide-bridged polymer has also been investigated (Slabbert et al., 2015b).

A one-dimensional polymeric structure with composition [Hg(μ-Cl)₂(pyridine)₂]_n was reported for the combination of pyridine with HgCl₂, and the structure obtained is a chloride-bridged polymeric lattice of HgCl₄ square-planar entities with pyridine ligands occupying the trans-octahedral sites around the Hg^II ion (Canty et al., 1982 ). However, when the halide was changed from Cl⁻ to Br⁻ and I⁻, no polymer was formed. The reactions of HgX₂ (X = Cl, Br or I) with the organic ligand 2-(2-hydroxyethyl)pyridine also formed one-dimensional polymeric chains of [(X)Hg(μ-X)₂{2-(2-hydroxyethyl)pyridine}]_n (Mobin et al., 2010 ). In these polymers, the organic ligand binds to the Hg^II ion in a monotopic fashion via only the pyridine N-atom donor, leaving the –(CH₂)₂OH group at the ortho position as a pendant ligand. The halide-bridged polymer can either adopt a planar or a zigzag motif due to the flexibility of the Hg^II metal centre. If the bridging halide ligands of adjacent Hg^II ions are not arranged in a coplanar fashion, then a zigzag structure is favoured (Englert et al., 2010).

A search of the Cambridge Structural Database (CSD, Version 5.46, February 2025 update; Groom et al., 2016 ) revealed that no crystal structure containing the organic ligand 4-ethylpyridine and Hg^II has been reported in the literature. This indicated a gap in the literature, prompting the current investigation. This present study focuses on the organic–inorganic hybrid compounds formed by the reaction of HgX₂ (X = Cl, Br or I) with the N-donor ligand 4-ethylpyridine (4-Etpy), as illustrated in Scheme 1. The structures of the compounds formed are abbreviated as 4epHgX, with 4ep representing the organic ligand and HgX referring to the halide-bridged portion of the polymer. These reactions resulted in the formation of three new one-dimensional halide-bibridged polymers, namely, catena-poly[[(4-ethylpyridine)mercury(II)]-di-μ-chlorido], 4epHgCl, catena-poly[[(4-ethylpyridine)mercury(II)]-di-μ-bromido], 4epHgBr, and catena-poly[[(4-ethylpyridine)mercury(II)]-di-μ-iodido], 4epHgI.

2. Experimental

2.1. Chemicals and reagents

All chemicals were used as purchased without further purification: HgCl₂ (98%, Fluka), HgBr₂ (98%, Sigma–Aldrich), HgI₂ (99%, Riedel de Haen), 4-ethylpyridine (98%, Sigma–Aldrich), ethanol (EtOH) (99.5%, Merck), methanol (MeOH) (99%, Merck) and tetrahydrofuran (THF) (99.9%, Sigma–Aldrich).

2.2. Synthesis and crystallization

2.2.1. Synthesis of 4epHgCl

A solution of HgCl₂ (0.954 mmol, 0.2589 g) dissolved in EtOH (5 ml) was added to a slightly heated and stirred solution of 4-ethylpyridine (0.961 mmol, 0.1030 g) dissolved in EtOH (10 ml). The resulting solution was heated for 15 min and left at room temperature, open to the atmosphere, to crystallize. A batch of colourless rod-like crystals of 4epHgCl were harvested (yield 57%) upon formation after two weeks.

2.2.2. Synthesis of 4epHgBr

A solution of HgBr₂ (0.933 mmol, 0.3363 g) dissolved in THF (7 ml) was added to a slightly heated and stirred solution of 4-ethylpyridine (0.944 mmol, 0.1012 g) dissolved in MeOH (10 ml). The resulting solution was heated for 15 min, covered with Parafilm and left to crystallize at room temperature. A batch of colourless rod-like crystals of 4epHgBr were harvested (yield 62%) upon formation after two weeks.

2.2.3. Synthesis of 4epHgI

A solution of HgI₂ (0.940 mmol, 0.4270 g) dissolved in THF (7 ml) was added to a slightly heated and stirred solution of 4-ethylpyridine (0.950 mmol, 0.1018 g) dissolved in MeOH (10 ml). The resulting solution was heated for 15 min, covered with Parafilm and left to crystallize at room temperature. A batch of colourless needle-like crystals of 4epHgI were harvested (yield 59%) upon formation after two weeks.

2.3. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. The structures of 4epHgCl and 4epHgI were refined as two-component inversion twins with the twin law ( $[\overline{1}]$ 00 0 $[\overline{1}]$ 0 00 $[\overline{1}]$ ) applied to both. The BASF was refined to 0.186 for 4epHgCl and 0.026 for 4epHgI. The inclusion of the twin refinement improved the quality of the models, as evidenced by a decrease in the R factor. The riding model was employed to position the H atoms in the three structures.

Table 1
Experimental details

Experiments were carried out at 150 K with Mo Kα radiation using a Bruker PHOTON 100 CMOS diffractometer. Absorption was corrected for by multi-scan methods (SADABS; Bruker, 2013 ). H-atom parameters were constrained.

	4epHgCl	4epHgBr	4epHgI
Crystal data
Chemical formula	[HgCl₂(C₇H₉N)]	[HgBr₂(C₇H₉N)]	[HgI₂(C₇H₉N)]
M_r	378.64	467.54	561.54
Crystal system, space group	Orthorhombic, P2₁2₁2₁	Monoclinic, P2₁/c	Orthorhombic, Fdd2
a, b, c (Å)	3.9382 (5), 10.3571 (15), 22.758 (3)	4.0679 (5), 22.583 (3), 10.9050 (14)	30.3836 (14), 34.6159 (16), 4.3247 (2)
α, β, γ (°)	90, 90, 90	90, 95.488 (4), 90	90, 90, 90
V (Å³)	928.3 (2)	997.2 (2)	4548.5 (4)
Z	4	4	16
μ (mm⁻¹)	17.09	23.39	18.91
Crystal size (mm)	0.51 × 0.23 × 0.12	0.42 × 0.18 × 0.10	0.23 × 0.06 × 0.06

Data collection
T_min, T_max	0.068, 0.260	0.244, 0.745	0.366, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections	16644, 1876, 1869	21065, 2024, 1908	30677, 2271, 2251
R_int	0.058	0.062	0.038
(sin θ/λ)_max (Å⁻¹)	0.625	0.625	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.020, 0.053, 1.11	0.033, 0.094, 1.08	0.018, 0.045, 1.15
No. of reflections	1876	2024	2271
No. of parameters	103	96	102
No. of restraints	0	0	1
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.29, −1.22	2.19, −1.85	1.17, −0.46
Absolute structure	Refined as an inversion twin	–	Refined as an inversion twin
Absolute structure parameter	0.186 (14)	–	0.026 (7)
Computer programs: APEX2 (Bruker, 2013), SAINT (Bruker, 2013), SHELXT2013 (Sheldrick, 2015a ) and SHELXL2013 (Sheldrick, 2015b ) in WinGX (Farrugia, 2012 ), Mercury (Macrae et al., 2020 ), PLATON (Spek, 2020 ) and OLEX2 (Dolomanov et al., 2009 ).

3. Results and discussion

3.1. Crystallographic discussion of the structures

Three new crystal structures containing 4-ethylpyridine (4-Etpy) with Hg^II halides as the inorganic portions were determined, all displaying one-dimensional halide-bibridged polymeric structures, in which the Hg^II cations are bridged by two halide ligands. The crystallographic parameters of these structures are listed in Table 1 and their asymmetric units are illustrated in Fig. 1. Selected bond lengths and bond angles are given in Table S1 and weak C—H⋯X hydrogen-bonding interactions in Table S2 in the supporting information.

Figure 1
The asymmetric units of 4epHgCl, 4epHgBr and 4epHgI, showing the atomic numbering schemes. Displacement ellipsoids are drawn at the 50% probability level for all the structures and H atoms are shown as small spheres of arbitrary radii.

3.2. Crystal structures of 4epHgCl, 4epHgBr and 4epHgI

Similar one-dimensional halide-bridged polymers were obtained for 4epHgCl, 4epHgBr and 4epHgI; however, they are not isostructural. 4epHgCl, 4epHgBr and 4epHgI crystallize in the space groups P2₁2₁2₁, P2₁/c and Fdd2, respectively. The asymmetric units of all three structures consist of a Hg^II ion coordinated to two halide ligands and one 4-ethylpyridine organic ligand coordinated via the N atom, as illustrated in Fig. 1.

Repetition of the asymmetric unit results in the formation of a one-dimensional halide-bibridged polymer in all three structures, in which pairs of Hg^II ions are bridged by two halide ligands, as illustrated in Figs. 2(a)–(c). The polymer adopts a scalloped ribbon conformation, with all the organic ligands coordinated to the same side of the polymer chain, as shown in Figs. 2(d)–(f). In these polymers, the Hg^II ion adopts a square-pyramidal geometry, with four equatorial halide ligands and the 4-ethylpyridine ligand as the axial ligand. It was found that the basal plane of the square pyramid is not coplanar with the Hg^II ion in all three structures, indicating a slight distortion in the geometry.

Figure 2
The halide-bibridged polymer chains in (a) 4epHgCl, (b) 4epHgBr and (c) 4epHgI. The pseudo-parallelogram inorganic portion and the organic ligand tilt in (d) 4epHgCl and (e) 4epHgBr, and (f) the inorganic portion and organic ligand tilt in 4epHgI. The dotted lines in parts (c) and (f) indicate longer and weaker Hg⋯I bonding interaction in the polymeric structure.

In all the structures, the metal halide portion displays a puckered pseudo-parallelogram geometry, consisting of four unequal Hg—X bonds, in which the two opposite Hg—X bond lengths are similar, with two Hg—X bonds being shorter and two longer. Shorter Hg—X bonds alternate with longer Hg—X bonds, with similar shorter Hg—X bond lengths of 2.3471 (18) and 2.3562 (18) Å in 4epHgCl, 2.4732 (8) and 2.4815 (8) Å in 4epHgBr, and 2.6269 (6) and 2.6576 (6) Å in 4epHgI. The polymer chain in 4epHgI adopts a similar pattern to that of 4epHgCl and 4epHgBr, but does not consist of the repeating pseudo-parallelogram motif, but rather features open pseudo-parallelogram units, as illustrated in Fig. 2(f). The longer Hg—X bonds may be viewed as semi-coordinated interactions, and have values of 3.086 (2) and 3.094 (2) Å in the chloride structure, 3.1704 (9) and 3.2694 (2) Å in the bromide structure, and 3.1949 (6) and 3.8988 (8) Å in the iodide structure. The presence of the very long semi-coordinated Hg—I bond of 3.8988 (8) Å in 4epHgI causes the iodide-bibridged polymer to have a distorted geometry compared to the polymers in 4epHgCl and 4epHgBr, as can be seen in Figs. 2(d)–(f) (Slabbert et al., 2015b). The puckered geometry of the halide-bridged polymers in related compounds has been reported previously and is a mechanism to shorten the Hg⋯Hg distance, and thus the distance between the aromatic planes of the organic ligands, to allow for the formation of aromatic interactions between the organic ligands (Slabbert et al., 2015b).

As the size of the halide ligand increases from chloride to bromide to iodide, the Hg—X bond lengths increase, resulting in an increase in the Hg⋯Hg distance in the halide-bibridged polymer. The Hg⋯Hg distance is 3.9382 (6) Å in 4epHgCl, 4.0679 (6) Å in 4epHgBr and 4.3247 (5) Å in 4epHgI, indicating very weak mercurophilic interactions (Kumar et al., 2013 ; Doerrer et al., 2010 ) in the polymer chain. The Hg—N bond lengths decrease with an increase in halide ligand size, with Hg—N bond lengths of 2.441 (6) Å in 4epHgCl, 2.436 (7) Å in 4epHgBr and 2.373 (7) Å in 4epHgI.

Along the halide-bibridged polymer, the two opposite angles X1—Hg—X1 and X2—Hg—X2 have larger values than the X1—Hg—X2 angles within the polymer, with values of 91.51 (6) and 91.88 (6)° for the larger angles, and 87.23 (6) and 87.25 (6)° for the smaller angles in 4epHgCl. In the bromide analogue, 4epHgBr, the two opposite angles X1—Hg—X1 and X2—Hg—X2 are 91.23 (2) and 89.09 (2)°, respectively, while the angles inside the polymer, X1—Hg—X2, are 89.34 (2) and 86.96 (2)°. The X2—Hg—X2 angle is 94.841 (18)° and the X1—Hg—X2 angle is 96.216 (19)° in 4epHgI, with a semi-coordinated Hg⋯I interaction of 3.8988 (8) Å. The Hg—X—Hg angles are 91.51 (6) and 91.88 (6)° in 4epHgCl, 91.23 (2) and 89.09 (2)° in 4epHgBr, and 94.841 (18)° in 4epHgI. As the size of the halide ligand increases, the inter-strand X⋯X distances also increase from 3.792 (3) Å in 4epHgCl to 3.998 (1) Å in 4epHgBr to 4.3503 (9) Å in 4epHgI. This difference might be the reason for the formation of a less-symmetric structure as the size of the bridging halide increases (Hu et al., 2007).

While the aromatic groups of the ligands are coplanar in all the structures, the one-dimensional polymers differ in terms of the relative orientation of their methyl substituents, as illustrated in Figs. Figs. 2(d)–(f). This difference in orientation is also evidenced by the C2—C3—C6—C7 and C4—C3—C6—C7 torsion angles of 170.2 (7) and −12.1 (12)° in 4epHgCl, −130.2 (9) and 50.0 (12)° in 4epHgBr and −147.0 (12) and 32.1 (19)° in 4epHgI. Furthermore, the perpendicular distance between the plane containing the aromatic ring and the terminal aliphatic C7 atom increases from 0.262 Å in 4epHgCl to 1.078 Å in 4epHgBr; however, this distance decreases to 0.766 Å in 4epHgI, indicating that the spatial orientation of the ethyl group of the organic ligand is influenced by the size of the halide ligand in the polymeric chain.

In order to compare the geometric features of the one-dimensional halide-bibridged polymers for systems with composition [Hg(μ-X)₂(L)₂]_n, the structural descriptor angles θ, ψ and ω, originally defined by Hu et al. (2003), are used in this study, with small modifications made to the descriptors, as explained below. The descriptors are shown in Fig. 3. The angle θ indicates the orientation of the organic N-donor ligand relative to the one-dimensional halide-bridged chain, while the angle ψ is defined as the angle between the N atom, the metal ion to which it is coordinated and the adjacent metal centre (N—M1⋯M2). The angle, ω, between the aromatic ring plane and the metal centre plane that passes through the Hg metal centres of equivalent halide-bridged polymers gives an indication of the degree of tilt of the aromatic group of the organic ligand relative to the halide-bridged polymer, as shown in Figs. 2(d) and 2(e). The schematic representation of the relative orientation of the aromatic ligand with respect to the halide-bridged polymer, represented by θ, ψ and ω, are shown in Fig. 3.

Figure 3
The descriptor angles θ, ψ and ω adapted from Hu et al. (2003

). The orange spheres represent the metal cations, the grey spheres represent the bridging halide ligands and the thick orange and green lines represent the plane that contains the aromatic ring.

The angle between the aromatic plane of the organic ligand and the plane through the halide ligands, θ, is 80.96° in 4epHgCl, 89.40° in 4epHgBr and 75.74° in 4epHgI. The structures of 4epHgCl, 4epHgBr and 4epHgI exhibit ω angles of 65.31, 60.01 and 66.67°, respectively. There is a slight decrease in the ω angle from 4epHgCl to 4epHgBr, indicating that there is a larger degree of organic ligand rotation with the increase in size of the halide ligand. When the halide ligand changes to iodide, this trend does not continue, since a different structure is formed, as shown in Fig. 2(f), indicating that the size of the halide ligand in the halide-bridged polymer affects the conformation and rigidity of the polymer chain and this influences the orientation of the organic ligand attached to the chain. As the size of the halide ligand increases from chloride to iodide, the angle between the two metal-centre planes, containing the Hg^II cation, X1 and X2 in adjacent pseudo-parallelogram units, increases significantly from 15.60° in 4epHgCl to 19.82° in 4epHgBr to 30.50° in 4epHgI, indicating increasing spatial distortion and flexibility of the Hg—X—Hg bridge.

The centroid-to-centroid distance between the pyridine moieties of the organic ligands is 3.938 Å in 4epHgCl, 4.068 Å in 4epHgBr and 4.325 Å in 4epHgI, indicating weak aromatic interactions between neighbouring pyridine rings (Janiak et al., 2000 ). It should be noted that the centroid-to-centroid distance depends on the halide-bridge lengths. As the size of the halide ligand increases from chloride to bromide to iodide, both the Hg—X and the Hg⋯Hg distances increase, causing an increase in the centroid-to-centroid distances between the pyridine moieties of the organic ligands. The ψ angle is 85.9 (1)° for 4epHgCl, 88.0 (2)° for 4epHgBr and 83.1 (2)° for 4epHgI. The observed values of the ψ and θ angles in these halide-bibridged polymers indicate that the organic ligands are not perpendicular to the inorganic plane. This orientation has been adopted to ensure stability of the polymer via weak C—H⋯X hydrogen-bonding interactions, as listed in Table S2 in the supporting information. As can be seen from Table S2, both the donor–acceptor (D⋯A) distances and D—H⋯A angles increase as the size of the halide ligand increases. This results in weaker hydrogen-bonding interactions as the size of the halide increases and hence looser molecular packing of the polymeric chains within the crystal lattice.

The packing diagrams are illustrated in Figs. 4(a)–(c). Pairs of the halide-bridged polymers pack in a head-to-tail fashion, forming a layered structure in 4epHgCl and 4epHgBr, and a checkerboard pattern in 4epHgI. The one-dimensional halide-bibridged polymers in the structures of 4epHgCl and 4epHgBr pack in such a way that the halide-bridged portions of two neighbouring polymeric chains approach each other, as shown in Figs. 4(d) and 4(e). This allows for the formation of long semi-coordinated Hg⋯X⋯Hg interactions to neighbouring polymer chains, as illustrated in Figs. 4(d) and 4(e), resulting in a pseudo-one-dimensional halide-bridged polymer that shows octahedral coordination of the Hg^II ions, which completes the coordination of the Hg^II ion. The Hg⋯X contact distances are 3.394 (2) Å in 4epHgCl and 3.5909 (9) Å in 4epHgBr, indicating that the Hg⋯X interactions between neighbouring polymer chains become weaker as the size of the halide ligand increases from chloride to bromide. This type of interchain interaction between polymers of this type is also seen in the structure comprised of HgBr₂ and phenazine organic ligands (Slabbert et al., 2015b). The packing arrangement in 4epHgI is different to that of 4epHgCl and 4epHgBr, with adjacent polymer chain pairs rotated 90° relative to each other and with no interchain Hg⋯I interactions between neighbouring polymer chains. This means that the change of the halide ligand from chloride to bromide, with the organic ligand and metal ion remaining constant, can be accommodated in the specific structural type; however, the change to the larger iodide ligand represents a tipping point that requires a change to a different structure type.

Figure 4
Packing diagrams of (a) 4epHgCl, (b) 4epHgBr and (c) 4epHgI. The long semi-coordinated interactions forming the pseudo-octahedral polymer in (d) 4epHgCl and (e) 4epHgBr. (f) The halide-bibridged polymer in 4epCuBr (CSD refcode CEPYCU; Laing et al., 1971

The CuBr₂ analogue of 4epCuBr has been reported (CSD refcode CEPYCU; Laing et al., 1971 ); however, this compound exhibits a halide-bibridged polymer with a flat metal–halide portion, in which the Cu^II ion displays a tetragonal geometry due to Jahn–Teller distortion, with the 4-Etpy organic ligand coordinating to both sides of the halide-bibridged polymer, as illustrated in Fig. 4(f).

4. Conclusions

4epHgCl, 4epHgBr and 4epHgI display similar one-dimensional scalloped halide-bridged polymeric structures involving two halide ligands bridging two metal centres, in which the Hg^II ion adopts a coordination number of five. The size of the halide ligand has a significant effect on the structure, geometry and packing arrangement of the polymer chains, with 4epHgI displaying a different packing motif compared to the chloride and bromide analogues. In the structures of 4epHgCl and 4epHgBr, the polymer chains further associate via long semi-coordinated Hg⋯X interactions to form a pseudo-octahedral polymer. As the size of the halide ligands increases, the Hg—X bond length within the polymer chain increases, causing structural distortion in the polymer chain. The change of the halide ligand to the larger iodide ligand disrupts the formation of the regular halide-bibridged polymeric chain observed in the chloride and bromide analogues, with 4epHgI displaying pseudo-bridging in the polymer chain.

Supporting information

CCDC references: 2442692; 2442693; 2442694

Crystal structure: contains datablocks 4epHgCl_updated, 4epHgBr_updated, 4epHgI_updated, global. DOI: https://doi.org/10.1107/S2053229625009702/eq3024sup1.cif

Structure factors: contains datablock 4epHgCl_updated. DOI: https://doi.org/10.1107/S2053229625009702/eq30244epHgCl_updatedsup2.hkl

Structure factors: contains datablock 4epHgBr_updated. DOI: https://doi.org/10.1107/S2053229625009702/eq30244epHgBr_updatedsup3.hkl

Structure factors: contains datablock 4epHgI_updated. DOI: https://doi.org/10.1107/S2053229625009702/eq30244epHgI_updatedsup4.hkl

Selected geometry. DOI: https://doi.org/10.1107/S2053229625009702/eq3024sup5.pdf

Computing details top

catena-Poly[[(4-ethylpyridine)mercury(II)]-di-µ-chlorido], (4epHgCl_updated) top

Crystal data top

[HgCl₂(C₇H₉N)]	D_x = 2.709 Mg m⁻³
M_r = 378.64	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P2₁2₁2₁	Cell parameters from 9940 reflections
a = 3.9382 (5) Å	θ = 2.7–26.4°
b = 10.3571 (15) Å	µ = 17.09 mm⁻¹
c = 22.758 (3) Å	T = 150 K
V = 928.3 (2) Å³	Rod, colourless
Z = 4	0.51 × 0.23 × 0.12 mm
F(000) = 688

Data collection top

Bruker PHOTON 100 CMOS diffractometer	1869 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.058
Absorption correction: multi-scan (SADABS; Bruker, 2013)	θ_max = 26.4°, θ_min = 2.2°
T_min = 0.068, T_max = 0.260	h = −4→4
16644 measured reflections	k = −12→12
1876 independent reflections	l = −28→28

Refinement top

Refinement on F²	H-atom parameters constrained
Least-squares matrix: full	w = 1/[σ²(F_o²) + (0.0173P)² + 3.720P] where P = (F_o² + 2F_c²)/3
R[F² > 2σ(F²)] = 0.020	(Δ/σ)_max = 0.003
wR(F²) = 0.053	Δρ_max = 1.29 e Å⁻³
S = 1.11	Δρ_min = −1.22 e Å⁻³
1876 reflections	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
103 parameters	Extinction coefficient: 0.0084 (5)
0 restraints	Absolute structure: Refined as an inversion twin.
Primary atom site location: iterative	Absolute structure parameter: 0.186 (14)
Hydrogen site location: inferred from neighbouring sites

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.

Refinement. Refined as a 2-component inversion twin.

All the single-crystal X-ray diffraction data were collected on a Bruker Venture diffractometer, with a Photon 100 CMOS detector, at 150 (2) K employing a combination of φ and ω scans. A monochromatic Mo Kα radiation of wavelength 0.71073 Å, from an Iµs source, was employed as the irradiation source. Cooling was achieved using an Oxford Cryogenics Cryostream 700 cryostat. Data reduction were performed using the software SAINT-Plus (Bruker, 2013) and absorption corrections were performed using SADABS (Bruker, 2013) as part of the APEX2 suite (Bruker, 2013). All the crystal structures were solved either by direct methods or intrinsic phasing using SHELXT (Sheldrick, 2015a), as part of the WinGX suite (Farrugia, 2012) and OLEX2 (Dolomanov et al., 2009). The structures were refined using SHELXL2013 (Sheldrick, 2015b) in WinGX (Farrugia, 2012) and OLEX2 (Dolomanov et al., 2009) as GUI. Graphics and publication material were generated using Mercury (Macrae et al., 2020) and PLATON (Spek, 2020).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Hg1	0.23073 (7)	1.11285 (2)	0.57199 (2)	0.01796 (13)
N1	0.2748 (16)	0.8857 (5)	0.5996 (3)	0.0175 (12)
C5	0.1627 (19)	0.8454 (8)	0.6511 (3)	0.0196 (16)
H5	0.0456	0.9053	0.6754	0.023*
Cl1	0.6011 (5)	1.09430 (18)	0.49111 (8)	0.0196 (4)
C4	0.206 (2)	0.7210 (7)	0.6717 (3)	0.0191 (15)
H4	0.1194	0.6967	0.7090	0.023*
Cl2	−0.1398 (5)	1.17977 (19)	0.64681 (8)	0.0221 (4)
C3	0.3772 (19)	0.6323 (7)	0.6374 (3)	0.0154 (14)
C2	0.489 (2)	0.6735 (7)	0.5824 (3)	0.0181 (15)
H2	0.5991	0.6147	0.5567	0.022*
C1	0.4394 (19)	0.8019 (7)	0.5654 (3)	0.0185 (15)
H1	0.5250	0.8301	0.5286	0.022*
C6	0.438 (2)	0.4932 (8)	0.6548 (3)	0.0202 (16)
H6A	0.6784	0.4719	0.6466	0.024*
H6B	0.2959	0.4374	0.6295	0.024*
C7	0.364 (2)	0.4598 (8)	0.7185 (4)	0.0285 (19)
H7A	0.4304	0.3701	0.7260	0.043*
H7B	0.1211	0.4703	0.7262	0.043*
H7C	0.4939	0.5173	0.7443	0.043*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.01893 (18)	0.01697 (18)	0.01797 (18)	0.00154 (13)	0.00375 (12)	−0.00102 (9)
N1	0.020 (3)	0.015 (3)	0.018 (3)	0.001 (4)	−0.002 (2)	−0.003 (2)
C5	0.023 (4)	0.021 (4)	0.016 (3)	0.002 (3)	0.001 (3)	−0.002 (3)
Cl1	0.0217 (9)	0.0194 (9)	0.0177 (8)	−0.0003 (7)	0.0046 (6)	−0.0005 (7)
C4	0.021 (4)	0.021 (3)	0.016 (3)	0.000 (3)	0.003 (3)	0.000 (3)
Cl2	0.0229 (10)	0.0223 (9)	0.0212 (9)	0.0024 (7)	0.0054 (7)	−0.0032 (7)
C3	0.018 (3)	0.016 (4)	0.013 (3)	−0.001 (3)	−0.004 (3)	0.005 (3)
C2	0.021 (4)	0.013 (4)	0.021 (4)	0.001 (3)	−0.002 (3)	−0.004 (3)
C1	0.023 (4)	0.019 (4)	0.013 (3)	−0.005 (3)	−0.004 (3)	−0.003 (3)
C6	0.027 (5)	0.018 (4)	0.015 (4)	0.002 (3)	0.000 (3)	0.001 (3)
C7	0.038 (5)	0.028 (4)	0.019 (4)	0.004 (4)	−0.003 (4)	0.010 (3)

Geometric parameters (Å, º) top

Hg1—N1	2.441 (6)	C3—C6	1.514 (10)
Hg1—Cl1	2.3562 (18)	C2—H2	0.9500
Hg1—Cl2	2.3471 (18)	C2—C1	1.399 (11)
N1—C5	1.320 (9)	C1—H1	0.9500
N1—C1	1.334 (9)	C6—H6A	0.9900
C5—H5	0.9500	C6—H6B	0.9900
C5—C4	1.382 (11)	C6—C7	1.517 (10)
C4—H4	0.9500	C7—H7A	0.9800
C4—C3	1.380 (10)	C7—H7B	0.9800
C3—C2	1.393 (10)	C7—H7C	0.9800

Cl1—Hg1—N1	94.51 (15)	C1—C2—H2	120.2
Cl2—Hg1—N1	98.16 (15)	N1—C1—C2	121.7 (7)
Cl2—Hg1—Cl1	167.32 (7)	N1—C1—H1	119.1
C5—N1—Hg1	120.6 (5)	C2—C1—H1	119.1
C5—N1—C1	118.3 (6)	C3—C6—H6A	108.3
C1—N1—Hg1	120.8 (5)	C3—C6—H6B	108.3
N1—C5—H5	118.2	C3—C6—C7	115.9 (7)
N1—C5—C4	123.7 (7)	H6A—C6—H6B	107.4
C4—C5—H5	118.2	C7—C6—H6A	108.3
C5—C4—H4	120.4	C7—C6—H6B	108.3
C3—C4—C5	119.3 (7)	C6—C7—H7A	109.5
C3—C4—H4	120.4	C6—C7—H7B	109.5
C4—C3—C2	117.3 (7)	C6—C7—H7C	109.5
C4—C3—C6	124.2 (7)	H7A—C7—H7B	109.5
C2—C3—C6	118.4 (7)	H7A—C7—H7C	109.5
C3—C2—H2	120.2	H7B—C7—H7C	109.5
C3—C2—C1	119.7 (7)

Hg1—N1—C5—C4	−174.1 (6)	C4—C3—C2—C1	2.8 (11)
Hg1—N1—C1—C2	175.2 (5)	C4—C3—C6—C7	−12.1 (12)
N1—C5—C4—C3	0.4 (12)	C3—C2—C1—N1	−2.6 (11)
C5—N1—C1—C2	1.1 (11)	C2—C3—C6—C7	170.2 (7)
C5—C4—C3—C2	−1.7 (11)	C1—N1—C5—C4	0.0 (11)
C5—C4—C3—C6	−179.4 (7)	C6—C3—C2—C1	−179.4 (7)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···Cl1	0.95	2.88	3.527 (8)	126

catena-Poly[[(4-ethylpyridine)mercury(II)]-di-µ-bromido] (4epHgBr_updated) top

Crystal data top

[HgBr₂(C₇H₉N)]	F(000) = 832
M_r = 467.54	D_x = 3.114 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 4.0679 (5) Å	Cell parameters from 9889 reflections
b = 22.583 (3) Å	θ = 2.6–26.4°
c = 10.9050 (14) Å	µ = 23.39 mm⁻¹
β = 95.488 (4)°	T = 150 K
V = 997.2 (2) Å³	Rod, colourless
Z = 4	0.42 × 0.18 × 0.10 mm

Data collection top

Bruker PHOTON 100 CMOS diffractometer	1908 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.062
Absorption correction: multi-scan (SADABS; Bruker, 2013)	θ_max = 26.4°, θ_min = 2.6°
T_min = 0.244, T_max = 0.745	h = −5→5
21065 measured reflections	k = −28→28
2024 independent reflections	l = −13→13

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.033	w = 1/[σ²(F_o²) + (0.054P)² + 11.1648P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.094	(Δ/σ)_max = 0.001
S = 1.08	Δρ_max = 2.19 e Å⁻³
2024 reflections	Δρ_min = −1.85 e Å⁻³
96 parameters	Extinction correction: SHELXL2013 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0037 (4)
Primary atom site location: iterative

Special details top

Refinement. All the single-crystal X-ray diffraction data were collected on a Bruker Venture diffractometer, with a Photon 100 CMOS detector, at 150 (2) K employing a combination of φ and ω scans. A monochromatic Mo Kα radiation of wavelength 0.71073 Å, from an Iµs source, was employed as the irradiation source. Cooling was achieved using an Oxford Cryogenics Cryostream 700 cryostat. Data reduction were performed using the software SAINT-Plus (Bruker, 2013) and absorption corrections were performed using SADABS (Bruker, 2013) as part of the APEX2 suite (Bruker, 2013). All the crystal structures were solved either by direct methods or intrinsic phasing using SHELXT (Sheldrick, 2015a), as part of the WinGX suite (Farrugia, 2012) and OLEX2 (Dolomanov et al., 2009). The structures were refined using SHELXL2013 (Sheldrick, 2015b) in WinGX (Farrugia, 2012) and OLEX2 (Dolomanov et al., 2009) as GUI. Graphics and publication material were generated using Mercury (Macrae et al., 2020) and PLATON (Spek, 2020).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Hg1	0.41038 (7)	0.42522 (2)	0.13824 (3)	0.01892 (16)
Br1	0.79830 (19)	0.51020 (3)	0.15997 (7)	0.0187 (2)
Br2	0.02711 (19)	0.34692 (3)	0.05465 (7)	0.0208 (2)
N1	0.4445 (17)	0.3968 (3)	0.3546 (6)	0.0194 (14)
C1	0.613 (2)	0.4299 (4)	0.4419 (8)	0.0224 (18)
H1	0.7134	0.4655	0.4179	0.027*
C2	0.645 (2)	0.4143 (4)	0.5656 (8)	0.0194 (16)
H2	0.7625	0.4393	0.6246	0.023*
C3	0.505 (2)	0.3618 (3)	0.6029 (7)	0.0179 (11)
C4	0.332 (2)	0.3280 (4)	0.5112 (7)	0.0221 (17)
H4	0.2344	0.2915	0.5316	0.027*
C5	0.303 (2)	0.3476 (3)	0.3901 (7)	0.0179 (11)
H5	0.1763	0.3247	0.3298	0.022*
C6	0.541 (2)	0.3436 (4)	0.7359 (7)	0.0251 (18)
H6A	0.3254	0.3483	0.7696	0.030*
H6B	0.6999	0.3707	0.7821	0.030*
C7	0.659 (2)	0.2804 (4)	0.7573 (8)	0.028 (2)
H7A	0.4999	0.2531	0.7144	0.042*
H7B	0.6791	0.2718	0.8458	0.042*
H7C	0.8749	0.2754	0.7255	0.042*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.0196 (2)	0.0170 (2)	0.0195 (2)	−0.00505 (11)	−0.00147 (13)	−0.00051 (10)
Br1	0.0194 (4)	0.0140 (4)	0.0225 (4)	−0.0036 (3)	0.0012 (3)	−0.0016 (3)
Br2	0.0220 (4)	0.0159 (4)	0.0234 (4)	−0.0042 (3)	−0.0036 (3)	−0.0022 (3)
N1	0.020 (3)	0.018 (4)	0.020 (3)	0.002 (3)	−0.002 (3)	−0.006 (3)
C1	0.029 (5)	0.017 (4)	0.021 (4)	−0.006 (3)	−0.001 (3)	0.001 (3)
C2	0.014 (4)	0.018 (4)	0.025 (4)	−0.002 (3)	−0.004 (3)	−0.001 (3)
C3	0.024 (3)	0.011 (3)	0.018 (3)	−0.003 (2)	−0.002 (2)	0.000 (2)
C4	0.030 (4)	0.018 (4)	0.018 (4)	−0.001 (3)	0.002 (3)	0.002 (3)
C5	0.024 (3)	0.011 (3)	0.018 (3)	−0.003 (2)	−0.002 (2)	0.000 (2)
C6	0.036 (5)	0.026 (5)	0.012 (4)	−0.002 (4)	−0.004 (3)	−0.001 (3)
C7	0.042 (5)	0.013 (4)	0.027 (5)	−0.003 (4)	−0.006 (4)	0.003 (3)

Geometric parameters (Å, º) top

Hg1—Br1	2.4815 (8)	C3—C6	1.501 (11)
Hg1—Br2	2.4732 (8)	C4—H4	0.9500
Hg1—N1	2.436 (7)	C4—C5	1.387 (11)
N1—C1	1.346 (10)	C5—H5	0.9500
N1—C5	1.325 (11)	C6—H6A	0.9900
C1—H1	0.9500	C6—H6B	0.9900
C1—C2	1.388 (12)	C6—C7	1.517 (12)
C2—H2	0.9500	C7—H7A	0.9800
C2—C3	1.393 (11)	C7—H7B	0.9800
C3—C4	1.395 (11)	C7—H7C	0.9800

Br2—Hg1—Br1	163.92 (3)	C5—C4—H4	120.0
N1—Hg1—Br1	97.73 (16)	N1—C5—C4	123.1 (7)
N1—Hg1—Br2	98.28 (16)	N1—C5—H5	118.4
C1—N1—Hg1	121.1 (6)	C4—C5—H5	118.4
C5—N1—Hg1	121.2 (5)	C3—C6—H6A	108.8
C5—N1—C1	117.7 (7)	C3—C6—H6B	108.8
N1—C1—H1	118.6	C3—C6—C7	114.0 (7)
N1—C1—C2	122.7 (8)	H6A—C6—H6B	107.7
C2—C1—H1	118.6	C7—C6—H6A	108.8
C1—C2—H2	120.1	C7—C6—H6B	108.8
C1—C2—C3	119.8 (8)	C6—C7—H7A	109.5
C3—C2—H2	120.1	C6—C7—H7B	109.5
C2—C3—C4	116.7 (7)	C6—C7—H7C	109.5
C2—C3—C6	120.7 (7)	H7A—C7—H7B	109.5
C4—C3—C6	122.6 (7)	H7A—C7—H7C	109.5
C3—C4—H4	120.0	H7B—C7—H7C	109.5
C5—C4—C3	119.9 (8)

Hg1—N1—C1—C2	−178.2 (6)	C2—C3—C4—C5	−0.8 (12)
Hg1—N1—C5—C4	176.2 (6)	C2—C3—C6—C7	−130.2 (9)
N1—C1—C2—C3	1.2 (13)	C3—C4—C5—N1	2.7 (13)
C1—N1—C5—C4	−2.6 (12)	C4—C3—C6—C7	50.0 (12)
C1—C2—C3—C4	−1.1 (12)	C5—N1—C1—C2	0.6 (13)
C1—C2—C3—C6	179.1 (8)	C6—C3—C4—C5	179.0 (8)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···Br1	0.95	3.04	3.708 (9)	129
C2—H2···Br1ⁱ	0.95	3.03	3.961 (8)	166
C5—H5···Br2	0.95	3.04	3.723 (8)	130

Symmetry code: (i) −x+2, −y+1, −z+1.

catena-Poly[[(4-ethylpyridine)mercury(II)]-di-µ-iodido] (4epHgI_updated) top

Crystal data top

[HgI₂(C₇H₉N)]	D_x = 3.280 Mg m⁻³
M_r = 561.54	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Fdd2	Cell parameters from 9539 reflections
a = 30.3836 (14) Å	θ = 2.4–35.2°
b = 34.6159 (16) Å	µ = 18.91 mm⁻¹
c = 4.3247 (2) Å	T = 150 K
V = 4548.5 (4) Å³	Needle, colourless
Z = 16	0.23 × 0.06 × 0.06 mm
F(000) = 3904

Data collection top

Bruker PHOTON 100 CMOS diffractometer	2251 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.038
Absorption correction: multi-scan (SADABS; Bruker, 2013)	θ_max = 26.4°, θ_min = 2.4°
T_min = 0.366, T_max = 0.747	h = −37→37
30677 measured reflections	k = −42→42
2271 independent reflections	l = −5→5

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.018	w = 1/[σ²(F_o²) + (0.0183P)² + 39.4372P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.045	(Δ/σ)_max = 0.001
S = 1.15	Δρ_max = 1.17 e Å⁻³
2271 reflections	Δρ_min = −0.46 e Å⁻³
102 parameters	Absolute structure: Refined as an inversion twin.
1 restraint	Absolute structure parameter: 0.026 (7)
Primary atom site location: iterative

Special details top

Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Hg1	0.23465 (2)	0.12095 (2)	0.53653 (8)	0.02757 (9)
I2	0.27181 (2)	0.16710 (2)	0.12059 (11)	0.02746 (13)
I1	0.16471 (2)	0.09297 (2)	0.81462 (14)	0.03344 (13)
N1	0.2905 (2)	0.07371 (19)	0.6022 (18)	0.0300 (15)
C5	0.3319 (3)	0.0819 (2)	0.525 (3)	0.039 (2)
H5	0.3379	0.1060	0.4280	0.047*
C4	0.3664 (3)	0.0569 (2)	0.580 (3)	0.041 (2)
H4	0.3953	0.0637	0.5165	0.049*
C3	0.3590 (3)	0.0219 (2)	0.726 (2)	0.035 (2)
C2	0.3160 (3)	0.0136 (2)	0.805 (3)	0.038 (2)
H2	0.3090	−0.0103	0.8999	0.046*
C1	0.2830 (3)	0.0402 (2)	0.746 (2)	0.036 (2)
H1	0.2538	0.0344	0.8101	0.044*
C6	0.3953 (3)	−0.0061 (3)	0.802 (4)	0.056 (3)
H6A	0.3858	−0.0219	0.9809	0.067*
H6B	0.3990	−0.0238	0.6243	0.067*
C7	0.4380 (3)	0.0106 (3)	0.875 (3)	0.058 (3)
H7A	0.4507	0.0222	0.6877	0.087*
H7B	0.4577	−0.0096	0.9516	0.087*
H7C	0.4345	0.0306	1.0335	0.087*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.02800 (14)	0.02640 (14)	0.02831 (16)	0.00299 (12)	0.00808 (12)	0.00549 (13)
I2	0.0359 (3)	0.0274 (3)	0.0191 (2)	−0.0078 (2)	0.0003 (2)	0.00268 (18)
I1	0.0311 (2)	0.0400 (3)	0.0292 (3)	−0.0081 (2)	0.0101 (2)	−0.0027 (2)
N1	0.032 (3)	0.025 (3)	0.033 (4)	0.001 (3)	0.003 (3)	0.004 (3)
C5	0.030 (4)	0.028 (4)	0.059 (6)	−0.001 (3)	0.017 (4)	0.007 (5)
C4	0.025 (4)	0.029 (4)	0.070 (7)	0.001 (3)	0.005 (5)	−0.001 (5)
C3	0.030 (4)	0.027 (4)	0.047 (6)	0.002 (3)	−0.009 (4)	−0.001 (4)
C2	0.032 (4)	0.024 (4)	0.058 (6)	−0.002 (3)	−0.010 (5)	0.010 (5)
C1	0.031 (4)	0.030 (4)	0.049 (5)	−0.001 (3)	0.004 (4)	0.010 (4)
C6	0.033 (4)	0.030 (5)	0.106 (10)	0.005 (4)	−0.017 (7)	0.004 (6)
C7	0.044 (5)	0.038 (5)	0.092 (10)	−0.004 (4)	−0.026 (6)	0.008 (6)

Geometric parameters (Å, º) top

Hg1—I2ⁱ	3.1949 (6)	C3—C2	1.381 (13)
Hg1—I2	2.6576 (6)	C3—C6	1.504 (13)
Hg1—I1	2.6269 (6)	C2—H2	0.9500
Hg1—N1	2.373 (7)	C2—C1	1.384 (12)
I2—Hg1ⁱⁱ	3.1949 (6)	C1—H1	0.9500
N1—C5	1.332 (10)	C6—H6A	0.9900
N1—C1	1.335 (11)	C6—H6B	0.9900
C5—H5	0.9500	C6—C7	1.455 (13)
C5—C4	1.381 (12)	C7—H7A	0.9800
C4—H4	0.9500	C7—H7B	0.9800
C4—C3	1.385 (13)	C7—H7C	0.9800

I2—Hg1—I2ⁱ	94.841 (18)	C3—C2—H2	119.9
I1—Hg1—I2ⁱ	96.216 (19)	C3—C2—C1	120.2 (8)
I1—Hg1—I2	151.07 (2)	C1—C2—H2	119.9
N1—Hg1—I2	101.05 (17)	N1—C1—C2	122.7 (8)
N1—Hg1—I2ⁱ	89.85 (18)	N1—C1—H1	118.7
N1—Hg1—I1	105.63 (17)	C2—C1—H1	118.7
Hg1—I2—Hg1ⁱⁱ	94.841 (18)	C3—C6—H6A	108.2
C5—N1—Hg1	119.8 (6)	C3—C6—H6B	108.2
C5—N1—C1	117.6 (7)	H6A—C6—H6B	107.3
C1—N1—Hg1	122.2 (5)	C7—C6—C3	116.5 (8)
N1—C5—H5	118.7	C7—C6—H6A	108.2
N1—C5—C4	122.6 (8)	C7—C6—H6B	108.2
C4—C5—H5	118.7	C6—C7—H7A	109.5
C5—C4—H4	119.8	C6—C7—H7B	109.5
C5—C4—C3	120.4 (8)	C6—C7—H7C	109.5
C3—C4—H4	119.8	H7A—C7—H7B	109.5
C4—C3—C6	123.0 (9)	H7A—C7—H7C	109.5
C2—C3—C4	116.5 (8)	H7B—C7—H7C	109.5
C2—C3—C6	120.5 (9)

Hg1—N1—C5—C4	174.8 (9)	C4—C3—C2—C1	−1.9 (15)
Hg1—N1—C1—C2	−175.3 (8)	C4—C3—C6—C7	32.1 (19)
N1—C5—C4—C3	−1.3 (18)	C3—C2—C1—N1	2.6 (16)
C5—N1—C1—C2	−2.5 (15)	C2—C3—C6—C7	−147.0 (12)
C5—C4—C3—C2	1.3 (16)	C1—N1—C5—C4	1.9 (16)
C5—C4—C3—C6	−177.8 (12)	C6—C3—C2—C1	177.2 (11)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···I2	0.95	3.21	3.883 (9)	130
C5—H5···I1ⁱⁱⁱ	0.95	3.32	4.130 (9)	144

Symmetry code: (iii) x+1/4, −y+1/4, z−3/4.

Acknowledgements

The author would like to thank Dr F. Malan for assistance with the collection of the crystallographic data. BMPB-B acknowledges funding from the University of Pretoria as part of the RDP programme.

Conflict of interest

There are no conflicts of interest.

References

Bruker (2013). APEX2, SAINT-Plus and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Canty, A. J., Raston, C. L., Skelton, B. W. & White, A. H. (1982). J. Chem. Soc. Dalton Trans. pp. 15–18. CSD CrossRef Web of Science Google Scholar
Crawford, V. H. & Hatfield, W. E. (1977). Inorg. Chem. 16, 1336–1341. CrossRef CAS Web of Science Google Scholar
Doerrer, L. H. (2010). Dalton Trans. 39, 3543–3553. Web of Science CrossRef CAS PubMed Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Eckberg, R. P. & Hatfield, W. E. (1975). J. Chem. Soc. Dalton Trans. pp. 616–620. CrossRef Web of Science Google Scholar
Englert, U. (2010). Coord. Chem. Rev. 254, 537–554. Web of Science CrossRef CAS Google Scholar
Estes, W. E., Gavel, D. P., Hatfield, W. E. & Hodgson, D. J. (1978). Inorg. Chem. 17, 1415–1421. CSD CrossRef CAS Web of Science Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Givaja, G., Amo-Ochoa, P., Gómez-García, C. J. & Zamora, F. (2012). Chem. Soc. Rev. 41, 115–147. Web of Science CrossRef CAS PubMed Google Scholar
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CrossRef IUCr Journals Google Scholar
Hu, C. & Englert, U. (2001). CrystEngComm 23, 1–5. Google Scholar
Hu, C., Kalf, I. & Englert, U. (2007). CrystEngComm 9, 603–610. Web of Science CSD CrossRef CAS Google Scholar
Hu, C., Li, Q. & Englert, U. (2003). CrystEngComm 5, 519–529. Web of Science CSD CrossRef CAS Google Scholar
Janiak, C. (2000). J. Chem. Soc. Dalton Trans. pp. 3885–3896. Web of Science CrossRef Google Scholar
Kumar, M., Dalela, S. & Dinesh, S. (2013). AIP Conf. Proc. pp. 771–772. CrossRef Google Scholar
Laing, M. & Carr, G. (1971). J. Chem. Soc. A pp. 1141–1144. CSD CrossRef Web of Science Google Scholar
Macrae, C. F., Sovago, I., Cottrell, S. J., Galek, P. T. A., McCabe, P., Pidcock, E., Platings, M., Shields, G. P., Stevens, J. S., Towler, M. & Wood, P. A. (2020). J. Appl. Cryst. 53, 226–235. Web of Science CrossRef CAS IUCr Journals Google Scholar
Mahmoudi, G. & Morsali, A. (2009). CrystEngComm 11, 1868–1879. Web of Science CSD CrossRef CAS Google Scholar
Mobin, S. M., Srivastava, A. K., Mathur, P. & Lahiri, G. K. (2010). Dalton Trans. 39, 8698–8705. Web of Science CSD CrossRef CAS PubMed Google Scholar
Morsali, A. & Masoomi, M. Y. (2009). Coord. Chem. Rev. 253, 1882–1905. Web of Science CrossRef CAS Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Slabbert, C. & Rademeyer, M. (2015a). Coord. Chem. Rev. 288, 18–49. Web of Science CrossRef CAS Google Scholar
Slabbert, C. & Rademeyer, M. (2015b). CrystEngComm 17, 9070–9096. Web of Science CSD CrossRef CAS Google Scholar
Spek, A. L. (2020). Acta Cryst. E76, 1–11. Web of Science CrossRef IUCr Journals Google Scholar
Wang, R., Lehmann, C. W. & Englert, U. (2009). Acta Cryst. B65, 600–611. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Wei, M., Willett, R. D., Teske, D., Subbaraman, K. & Drumheller, J. E. (1996). Inorg. Chem. 35, 5781–5785. CSD CrossRef CAS Web of Science Google Scholar
Zhang, W., Jeitler, J. R., Turnbull, M. M., Landee, C. P., Wei, M. & Willett, R. D. (1997). Inorg. Chim. Acta 256, 183–198. CSD CrossRef CAS Web of Science Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 81| Part 12| December 2025| Pages 680-686

https://doi.org/10.1107/S2053229625009702

Open

access

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text
		Text

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Plain Text
		Text

Search IUCr Journals		doi		Advanced search
Author		volume	page

research papers\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)