Crystal structure of catena-poly[[di-iodidomer-cury(II)]-μ-2,2'-di-thio-bis-(pyridine N-oxide)-κ2O:O'].

The title compound, [HgI2(C10H8N2O2S2)] n , a one-dimensional coordination polymer with HgI2 units and 2,2'-di-thio-bis-(pyridine N-oxide) spacer ligands in an alternating fashion, forms helical chains running along the b axis in the crystal. Within a single coordination polymer strand, the axially chiral 2,2'-di-thio-bis-(pyridine N-oxide) ligands are homochiral, but the enanti-omeric conformation is present in adjacent strands. Within a coordination polymer strand, the iodido ligands point towards the centroids of the aromatic rings of the pyridine N-oxide moieties in the coordination sphere of HgII. Moreover, intra-strand C-H⋯O and C-H⋯I inter-actions, and inter-strand short S⋯I and S⋯O contacts are observed.

Chemical context

Research into one-dimensional coordination polymers has been an active field of research, not only due to the usually easy and straightforward synthesis, but also due to inter­esting structural features and introduction of these compounds as new materials such as coordination polymeric gels, fibres and nanostructures (Leong & Vittal, 2011 ▸). In the context of our structural studies on coordination polymers and discrete metallo­supra­molecular assemblies containing di­sulfide-based bridging (spacer) ligands (Seidel et al., 2013 ▸), 2,2′-di­thio­bis­(pyridine N-oxide) has attracted our inter­est. Recently, we reported one-dimensional coordination polymers from 2,2′-di­thio­bis­(pyridine N-oxide), and ZnII and CdII halides (Seidel et al., 2017 ▸), which represented the first structurally characterised coordination polymers containing 2,2′-di­thio­bis­(pyridine N-oxide) as a spacer ligand (i.e. involving both pyridine N-oxide moieties as coordinating groups). As a continuation of this work, we herein report the crystal structure of a one-dimensional coordination polymer formed from 2,2′-di­thio­bis­(pyridine N-oxide) and HgI2.

Structural commentary

The title compound, (I), is a one-dimensional coordination polymer consisting of HgI2 units joined by 2,2′-di­thio­bis­(pyridine N-oxide) as bridging ligands in a μ-κ2 O:O′ coordination mode. Fig. 1 ▸ depicts the repeat unit of the coordination polymer and the coordination sphere of the HgII ion. The HgII ion is tetra­coordinated by two iodide ligands and two O atoms of the bridging ligands, with a coordination sphere that is best described as a severely distorted tetra­hedron or a seesaw form (Yang et al., 2007 ▸). The C2—S1—S2—C7 torsion angle is 77.2 (2)°, which corresponds to the P form of the axially chiral gauche conformation of the di­sulfide-based ligand in the chosen asymmetric unit. The dihedral angle between the planes of the aromatic N1/C2–C6 and N2/C7–C11 rings is 71.8 (2)°.

Figure 1

Displacement ellipsoid plot (50% probability level) of the title compound, showing the repeat unit of the coordination polymer and the coordination sphere of HgII. H atoms are represented by small spheres of arbitrary radii. [Symmetry code: (i) −x + , y − , −z + .]

The strand of the coordination polymer propagates along a 21-screw axis parallel to the b axis (Fig. 2 ▸). Within a single strand, 2,2′-di­thio­bis­(pyridine N-oxide) exhibits exclusively either the right-handed P or the left-handed M conformation, i.e. the bridging ligands in each coordination polymer chain are homochiral. The centrosymmetric crystal structure (space group P21/n) features, however, both enanti­omeric conformations in adjacent strands, as shown in Fig. 2 ▸.

Figure 2

Two adjacent coordination polymer strands of the title compound, viewed along the [101] direction. P and M denote the handedness of the 2,2′-di­thio­bis­(pyridine N-oxide) ligand in the chains. H atoms have been omitted for clarity.

Supra­molecular features

In a single strand, the iodide ligands point towards the centroids of the aromatic rings of the pyridine N-oxide moieties in the coordination sphere of HgII, but I⋯π inter­actions are not observed. The I⋯Cg distances are long [I1⋯Cg1 = 3.940 (2) Å and I2⋯Cg2ii = 4.205 (2) Å] and the Hg—I⋯Cg angles are acute [Hg1—I1⋯Cg1 = 77.94 (3)° and Hg1—I2⋯Cg2ii = 68.79 (3)°] [Cg1 and Cg2 are the centroids of the N1/C2–C6 and N2/C7–C11 rings, respectively; symmetry code: (ii) −x + , y − , −z + ]. In the chain, potentially structure-influencing C—H⋯O and C—H⋯I inter­actions can be identified (Table 1 ▸). The di­sulfide moiety is involved in two inter-strand contacts that are shorter than the sum of the van der Waals radii (Bondi, 1964 ▸); the short contacts [S1⋯I1iii = 3.5983 (13) Å and S2⋯O2iv = 3.263 (4) Å; symmetry codes: (iii) x + , −y + , z + ; (iv) −x + 2, −y + 1, −z + 2], connect adjacent chains into a layer structure parallel to (01).

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯I2i	0.95	3.00	3.776 (6)	140
C11—H11⋯O1i	0.95	2.59	3.268 (7)	129

Symmetry code: (i) .

Database survey

A search for structures containing 2,2′-di­thio­bis­(pyridine N-oxide) in the Cambridge Structural Database (CSD; Groom et al., 2016 ▸) via the WebCSD inter­face (Thomas et al., 2010 ▸) in February 2018 revealed the aforementioned one-dimensional coordination polymers containing ZnII and CdII halide units (Seidel et al., 2017 ▸). In addition, there is an NaI coordination polymer, wherein the NaI ions are bridged via only one pyridine N-oxide moiety of the ligand in a μ-κ2 O:O coordination mode (Ravindran Durai Nayagam, 2010 ▸). The crystal structures of the free, unsolvated 2,2′-di­thio­bis­(pyridine N-oxide) (CSD refcode RIRPEN; Bodige et al., 1997 ▸) and some cocrystals (Bodige et al., 1997 ▸; Bond & Jones, 2000a ▸,b ▸) have also been reported.

The isomorphous series of one-dimensional ZnII coordination polymers, [ZnX 2(C10H8N2O2S2)] [X = Cl, Br, I; C10H8N2O2S2 is 2,2′-di­thio­bis­(pyridine N-oxide)] (Seidel et al., 2017 ▸) and (I) are topologically related but not isostructural. The Hg—I and Hg—O bond lengths in (I) are longer by ca 0.09 and 0.48 Å, respectively, than the corresponding Zn—I and Zn—O bond lengths in [ZnI2(C10H8N2O2S2)] (CSD refcode XAMNUX; Seidel et al., 2017 ▸). The deviations of the I—Hg—I and O—Hg—O angles from the ideal tetra­hedral angle of 109.5° are considerably larger in (I) than those of the corresponding I—Zn—I and O—Zn—O angles in XAMNUX. In (2,2′-bi­pyridine N,N′-dioxide)di­iodido­mercury(II) (CSD refcode FAYKEW; Tedmann et al., 2005 ▸), so far the only HgII complex with two pyridine N-oxide and two iodide ligands in the CSD, the I—Hg—I angle is 158.54 (4)°, which is similar to that of 155.113 (16)° observed in (I). The C2—S1—S2—C7 torsion angle in (I) [77.2 (2)°] is markedly smaller than that in RIRPEN, which is very close to the preferred value of 90° [89.89 (9)°], indicating some torsional strain in (I).

Synthesis and crystallization

A solution of 20 mg (0.044 mmol) HgI2 in 2 ml of methanol was mixed with a solution of 12 mg (0.048 mmol) 2,2′-di­thio­bis­(pyridine N-oxide) (Acros Organics) in 8 ml of methanol. The reaction mixture was left at room temperature and the solvent was allowed to evaporate slowly. Colourless crystals of (I) suitable for single-crystal X-ray analysis were obtained after ca four weeks.

After prolonged standing, colourless crystals of a second product appeared in the crystallization vessel, which were identified as [Hg2I2(C5H4NOS)2] (C5H4NOS− is pyri­thio­nate) in a preliminary X-ray analysis.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. H-atom positions were calculated geometrically and refined using a riding model, with U iso(H) = 1.2U eq(C). The C—H bond lengths were set at 0.95 Å.

Table 2

Experimental details

Crystal data
Chemical formula	[HgI2(C10H8N2O2S2)]
M r	706.69
Crystal system, space group	Monoclinic, P21/n
Temperature (K)	108
a, b, c (Å)	7.4207 (3), 18.7599 (7), 11.6463 (4)
β (°)	100.887 (4)
V (Å3)	1592.13 (10)
Z	4
Radiation type	Mo Kα
μ (mm−1)	13.81
Crystal size (mm)	0.16 × 0.10 × 0.04
Data collection
Diffractometer	Oxford Diffraction Xcalibur2
Absorption correction	empirical (using intensity measurements) (ShxAbs; Spek, 2009 ▸)
T min, T max	0.614, 0.885
No. of measured, independent and observed [I > 2σ(I)] reflections	21770, 6430, 4209
R int	0.069
(sin θ/λ)max (Å−1)	0.842
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.047, 0.059, 1.02
No. of reflections	6430
No. of parameters	172
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	1.64, −1.39

Computer programs: CrysAlis PRO (Rigaku OD, 2015 ▸), SHELXT2014 (Sheldrick, 2015a ▸), SHELXL2018 (Sheldrick, 2015b ▸), DIAMOND (Brandenburg, 2016 ▸) and enCIFer (Allen et al., 2004 ▸).

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989018003055/is5492sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989018003055/is5492Isup2.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S2056989018003055/is5492Isup3.mol

CCDC reference: 1825194

Additional supporting information: crystallographic information; 3D view; checkCIF report

[HgI2(C10H8N2O2S2)]	F(000) = 1264
Mr = 706.69	Dx = 2.948 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 7.4207 (3) Å	Cell parameters from 4297 reflections
b = 18.7599 (7) Å	θ = 3.6–32.1°
c = 11.6463 (4) Å	µ = 13.81 mm−1
β = 100.887 (4)°	T = 108 K
V = 1592.13 (10) Å3	Plate, colourless
Z = 4	0.16 × 0.10 × 0.04 mm

Oxford Diffraction Xcalibur2 diffractometer	6430 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Mo) X-ray Source	4209 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.069
Detector resolution: 8.4171 pixels mm-1	θmax = 36.8°, θmin = 3.6°
ω scans	h = −11→10
Absorption correction: empirical (using intensity measurements) (ShxAbs; Spek, 2009)	k = −26→31
Tmin = 0.614, Tmax = 0.885	l = −15→18
21770 measured reflections

Refinement on F2	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.059	H-atom parameters constrained
S = 1.02	w = 1/[σ2(Fo2) + (0.0045P)2] where P = (Fo2 + 2Fc2)/3
6430 reflections	(Δ/σ)max = 0.001
172 parameters	Δρmax = 1.64 e Å−3
0 restraints	Δρmin = −1.39 e Å−3

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.

	x	y	z	Uiso*/Ueq
Hg1	0.64620 (3)	0.14596 (2)	0.76452 (2)	0.01829 (5)
I1	0.38759 (5)	0.22283 (2)	0.63732 (3)	0.01977 (9)
I2	0.80134 (6)	0.07571 (2)	0.95050 (3)	0.02410 (9)
S1	0.9109 (2)	0.33156 (8)	0.84420 (11)	0.0169 (3)
S2	0.89904 (19)	0.43914 (8)	0.87677 (12)	0.0182 (3)
O1	0.9177 (5)	0.2100 (2)	0.7332 (3)	0.0175 (8)
O2	0.7700 (5)	0.5690 (2)	0.8952 (3)	0.0183 (8)
N1	0.8795 (6)	0.2607 (3)	0.6515 (4)	0.0162 (10)
N2	0.6271 (6)	0.5263 (2)	0.8586 (4)	0.0178 (10)
C2	0.8761 (7)	0.3286 (3)	0.6896 (4)	0.0135 (11)
C3	0.8382 (8)	0.3838 (3)	0.6102 (4)	0.0199 (13)
H3	0.839772	0.431876	0.636054	0.024*
C4	0.7978 (7)	0.3676 (3)	0.4917 (5)	0.0218 (13)
H4	0.773405	0.404774	0.435526	0.026*
C5	0.7931 (8)	0.2981 (3)	0.4560 (5)	0.0233 (14)
H5	0.760912	0.287104	0.375152	0.028*
C6	0.8351 (8)	0.2437 (3)	0.5370 (5)	0.0204 (13)
H6	0.832653	0.195319	0.512429	0.024*
C7	0.6611 (7)	0.4561 (3)	0.8435 (4)	0.0156 (11)
C8	0.5189 (8)	0.4097 (3)	0.8070 (5)	0.0207 (13)
H8	0.542666	0.360651	0.796344	0.025*
C9	0.3408 (8)	0.4351 (3)	0.7860 (5)	0.0261 (14)
H9	0.240770	0.403667	0.760625	0.031*
C10	0.3099 (8)	0.5073 (3)	0.8024 (5)	0.0264 (14)
H10	0.188027	0.525256	0.788713	0.032*
C11	0.4533 (8)	0.5521 (3)	0.8379 (5)	0.0231 (13)
H11	0.431858	0.601379	0.848200	0.028*

	U11	U22	U33	U12	U13	U23
Hg1	0.01884 (11)	0.01544 (11)	0.02109 (11)	0.00085 (10)	0.00505 (8)	0.00204 (9)
I1	0.0205 (2)	0.0230 (2)	0.01644 (18)	0.00366 (16)	0.00510 (14)	0.00259 (15)
I2	0.0291 (2)	0.0186 (2)	0.02230 (19)	0.00029 (17)	−0.00105 (16)	0.00206 (16)
S1	0.0211 (8)	0.0141 (7)	0.0146 (7)	0.0020 (5)	0.0016 (5)	0.0001 (5)
S2	0.0179 (7)	0.0155 (7)	0.0204 (7)	−0.0002 (6)	0.0017 (6)	−0.0037 (6)
O1	0.020 (2)	0.014 (2)	0.019 (2)	0.0012 (16)	0.0052 (16)	0.0031 (16)
O2	0.019 (2)	0.014 (2)	0.021 (2)	−0.0039 (16)	0.0034 (16)	−0.0005 (16)
N1	0.019 (3)	0.017 (3)	0.014 (2)	0.001 (2)	0.0071 (18)	0.0011 (19)
N2	0.022 (3)	0.014 (3)	0.018 (2)	−0.003 (2)	0.0044 (19)	0.0054 (19)
C2	0.011 (3)	0.016 (3)	0.014 (3)	−0.001 (2)	0.003 (2)	−0.002 (2)
C3	0.025 (3)	0.020 (3)	0.015 (3)	0.000 (2)	0.005 (2)	0.000 (2)
C4	0.019 (3)	0.026 (4)	0.021 (3)	0.000 (3)	0.007 (2)	0.007 (2)
C5	0.020 (3)	0.036 (4)	0.014 (3)	−0.006 (3)	0.006 (2)	−0.003 (3)
C6	0.020 (3)	0.025 (3)	0.019 (3)	−0.002 (2)	0.010 (2)	−0.007 (2)
C7	0.016 (3)	0.013 (3)	0.017 (3)	0.001 (2)	0.003 (2)	0.002 (2)
C8	0.020 (3)	0.017 (3)	0.025 (3)	−0.004 (2)	0.005 (2)	−0.004 (2)
C9	0.018 (3)	0.024 (4)	0.038 (4)	−0.008 (3)	0.010 (3)	−0.004 (3)
C10	0.016 (3)	0.024 (4)	0.041 (4)	−0.001 (3)	0.009 (3)	0.006 (3)
C11	0.023 (3)	0.012 (3)	0.033 (3)	0.002 (2)	0.004 (3)	0.004 (2)

Hg1—O1	2.432 (4)	C3—H3	0.9500
Hg1—O2i	2.524 (4)	C4—C5	1.366 (8)
Hg1—I2	2.6100 (4)	C4—H4	0.9500
Hg1—I1	2.6236 (4)	C5—C6	1.385 (8)
S1—C2	1.771 (5)	C5—H5	0.9500
S1—S2	2.058 (2)	C6—H6	0.9500
S2—C7	1.764 (6)	C7—C8	1.372 (7)
O1—N1	1.336 (5)	C8—C9	1.383 (8)
O2—N2	1.333 (5)	C8—H8	0.9500
N1—C6	1.351 (6)	C9—C10	1.393 (8)
N1—C2	1.352 (7)	C9—H9	0.9500
N2—C11	1.356 (7)	C10—C11	1.357 (8)
N2—C7	1.358 (7)	C10—H10	0.9500
C2—C3	1.381 (7)	C11—H11	0.9500
C3—C4	1.389 (7)
O1—Hg1—O2i	81.13 (12)	C5—C4—H4	120.0
O1—Hg1—I2	97.24 (8)	C3—C4—H4	120.0
O2i—Hg1—I2	101.01 (8)	C4—C5—C6	120.5 (5)
O1—Hg1—I1	100.48 (8)	C4—C5—H5	119.8
O2i—Hg1—I1	98.87 (8)	C6—C5—H5	119.8
I2—Hg1—I1	155.113 (16)	N1—C6—C5	118.6 (5)
C2—S1—S2	102.39 (19)	N1—C6—H6	120.7
C7—S2—S1	102.3 (2)	C5—C6—H6	120.7
N1—O1—Hg1	112.8 (3)	N2—C7—C8	120.3 (5)
N2—O2—Hg1ii	113.6 (3)	N2—C7—S2	110.4 (4)
O1—N1—C6	120.9 (5)	C8—C7—S2	129.3 (5)
O1—N1—C2	116.9 (4)	C7—C8—C9	119.4 (6)
C6—N1—C2	122.1 (5)	C7—C8—H8	120.3
O2—N2—C11	121.0 (5)	C9—C8—H8	120.3
O2—N2—C7	117.9 (5)	C8—C9—C10	119.1 (6)
C11—N2—C7	121.1 (5)	C8—C9—H9	120.4
N1—C2—C3	120.1 (5)	C10—C9—H9	120.4
N1—C2—S1	110.8 (4)	C11—C10—C9	120.3 (6)
C3—C2—S1	129.0 (4)	C11—C10—H10	119.9
C2—C3—C4	118.6 (5)	C9—C10—H10	119.9
C2—C3—H3	120.7	N2—C11—C10	119.9 (6)
C4—C3—H3	120.7	N2—C11—H11	120.1
C5—C4—C3	119.9 (5)	C10—C11—H11	120.1
Hg1—O1—N1—C6	−73.6 (5)	C2—N1—C6—C5	3.1 (8)
Hg1—O1—N1—C2	102.2 (4)	C4—C5—C6—N1	0.4 (9)
Hg1ii—O2—N2—C11	−76.5 (5)	O2—N2—C7—C8	179.4 (5)
Hg1ii—O2—N2—C7	103.9 (4)	C11—N2—C7—C8	−0.2 (8)
O1—N1—C2—C3	179.8 (5)	O2—N2—C7—S2	−0.6 (6)
C6—N1—C2—C3	−4.4 (8)	C11—N2—C7—S2	179.8 (4)
O1—N1—C2—S1	−3.7 (6)	S1—S2—C7—N2	−179.1 (3)
C6—N1—C2—S1	172.1 (4)	S1—S2—C7—C8	0.9 (6)
S2—S1—C2—N1	−180.0 (3)	N2—C7—C8—C9	−0.1 (8)
S2—S1—C2—C3	−3.9 (6)	S2—C7—C8—C9	179.9 (4)
N1—C2—C3—C4	2.3 (8)	C7—C8—C9—C10	0.0 (9)
S1—C2—C3—C4	−173.6 (4)	C8—C9—C10—C11	0.4 (9)
C2—C3—C4—C5	1.1 (9)	O2—N2—C11—C10	−179.0 (5)
C3—C4—C5—C6	−2.4 (9)	C7—N2—C11—C10	0.6 (8)
O1—N1—C6—C5	178.7 (5)	C9—C10—C11—N2	−0.7 (9)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···I2ii	0.95	3.00	3.776 (6)	140
C11—H11···O1ii	0.95	2.59	3.268 (7)	129