Isotypic one-dimensional coordination polymers: catena-poly[[di­chlorido­cadmium]-μ-5,6-bis­(pyridin-2-yl)pyrazine-2,3-di­carboxyl­ato-κ2N5:N6] and catena-poly[[di­chlorido­mercury(II)]-μ-5,6-bis­(pyridin-2-yl)pyrazine-2,3-di­carboxyl­ato-κ2N5:N6]

Alfonso, M.; Stoeckli-Evans, H.

doi:10.1107/S2056989016012093

research communications

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ISSN: 2056-9890

Volume 72| Part 8| August 2016| Pages 1214-1218

https://doi.org/10.1107/S2056989016012093

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Isotypic one-dimensional coordination polymers: catena-poly[[dichloridocadmium]-μ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ²N⁵:N⁶] and catena-poly[[dichloridomercury(II)]-μ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ²N⁵:N⁶]

Montserrat Alfonso ^a and Helen Stoeckli-Evans ^b ^*

^aInstitute of Chemistry, University of Neuchâtel, Av. de Bellevaux 51, CH-2000 Neuchâtel, Switzerland, and ^bInsitute of Physics, University of Neuchâtel, rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland
^*Correspondence e-mail: helen.stoeckli-evans@unine.ch

Edited by M. Zeller, Purdue University, USA (Received 22 July 2016; accepted 25 July 2016; online 29 July 2016)

The isotypic title one-dimensional coordination polymers, [CdCl₂(C₁₈H₁₄N₄O₄)]_n, (I), and [HgCl₂(C₁₈H₁₄N₄O₄)]_n, (II), are, respectively, the cadmium(II) and mercury(II) complexes of the dimethyl ester of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic acid. In both compounds, the metal ions are located on a twofold rotation axis and a second such axis bisects the C_ar—C_ar bonds of the pyrazine ring. The metal ions are bridged by binding to the N atoms of the two pyridine rings and have an MN₂Cl₂ bisphenoidal coordination geometry. The metal–N_pyrazine distances are much longer than the metal–N_pyridine distances; the difference is 0.389 (2) Å for the Cd—N bonds but only 0.286 (5) Å for the Hg—N bond lengths. In the crystals of both compounds, the polymer chains are linked via pairs of C—H⋯Cl hydrogen bonds, forming corrugated slabs parallel to the ac plane.

Keywords: crystal structure; isotypic coordination polymer; one-dimensional; MN₂Cl₂ bisphenoidal coordination geometry; dimethyl ester; pyrazine; pyridine; C—H⋯Cl hydrogen bonding.

CCDC references: 1495931; 1495930

1. Chemical context

The crystal structures of the dimethyl and diethyl esters of 5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylic acid (L1H₂; Alfonso et al., 2001 ) have been reported on recently (Alfonso & Stoeckli-Evans, 2016 ). They were originally synthesized to study the hydrolysis of these esters with first row transition metals (Alfonso, 1999 ). Subsequent studies of their reaction with d¹⁰ or post-transition metals lead to the formation of the title compounds, and we report herein on the syntheses and crystal structures of the title isotypic cadmium(II) and mercury(II) coordination polymers.

2. Structural commentary

In compounds (I) and (II), the metal atom is located on a twofold rotation axis and a second such axis bisects the C_ar—C_ar bonds of the pyrazine ring; as illustrated in Fig. 1 for the cadmium complex (I), and in Fig. 2 for the mercury complex (II). Details of the bond lengths and bond angles involving the metal atoms are given in Table 1 for (I), and in Table 2 for (II). The metal atoms are bridged by binding to the N atoms of the two pyridine rings, N2 and N2ⁱ; Cd1—N2 = 2.3862 (17) Å in (I) and Hg1—N2 = 2.590 (5) Å in (II). The Cd1—Cl1 bonds [2.4137 (6) Å] are longer than the Hg1—Cl1 bonds [2.3464 (16) Å], while the reverse is true for the metal–N_pyridine bonds: Cd1—N2 [2.3862 (17) Å] is shorter than Hg1—N2 [2.590 (5) Å]. The link to the pyrazine N atoms, N2 and N2ⁱ, is much weaker: Cd1⋯N1 = 2.7757 (17) Å and Hg1⋯N1 = 2.876 (5) Å. The difference in the metal–N_pyrazine and metal–N_pyridine bond lengths is 0.389 (2) Å for the Cd—N bonds but only 0.286 (5) Å for the Hg—N bonds (see Tables 1 and 2).

Table 1
Selected geometric parameters (Å, °) for (I)

Cd1—Cl1	2.4137 (6)	Cd1—N1	2.7757 (17)
Cd1—N2	2.3862 (17)

Cl1ⁱ—Cd1—Cl1	142.43 (3)	N2—Cd1—Cl1ⁱ	110.87 (4)
N2—Cd1—N2ⁱ	85.02 (8)	N2—Cd1—Cl1	96.81 (4)
Symmetry code: (i) $[-x+{\script{3\over 2}}, y, -z+{\script{3\over 2}}]$ .

Table 2
Selected geometric parameters (Å, °) for (II)

Hg1—Cl1	2.3464 (16)	Hg1—N1	2.876 (5)
Hg1—N2	2.590 (5)

Cl1ⁱ—Hg1—Cl1	158.87 (12)	Cl1ⁱ—Hg1—N2	102.86 (12)
N2—Hg1—N2ⁱ	83.1 (2)	Cl1—Hg1—N2	92.97 (12)
Symmetry code: (i) $[-x+{\script{3\over 2}}, y, -z+{\script{3\over 2}}]$ .

Figure 1
A view of the molecular structure of compound (I)

, showing the atom labelling [symmetry codes: (a) −x + $[{1\over 2}]$ , y, −z + $[{3\over 2}]$ ; (b) −x + $[{3\over 2}]$ , y, −z + $[{3\over 2}]$ ]. Displacement ellipsoids are drawn at the 50% probability level

Figure 2
A view of the molecular structure of compound (II)

The fourfold coordination geometry of the metal atoms differ slightly, as illustrated in Fig. 3 a structural overlap of the two compounds. In (I) atom Cd1 has a τ₄ parameter of 0.53, while for the Hg1 atom in (II) the τ₄ parameter = 0.30 (extreme values: τ₄ = 0 for square-planar, 1 for tetrahedral and 0.85 for trigonal–pyramidal geometry; Yang et al., 2007 ). When also considering the values of the Cl—M—Cl and N—M—N bond angles in both compounds (see Tables 1 and 2), we conclude that both metal atoms (M) have a bisphenoidal MN₂Cl₂ coordination environment.

Figure 3
A view of the structural overlap of the cadmium complex (I)

in blue and the mercury complex (II)

in red; also illustrating the slight difference in the bisphenoidal coordination geometry of the two metal atoms (MN₂Cl₂).

In both compounds, the pyrazine rings (N1/C1/C2/N1ⁱ/C1ⁱ/C2ⁱ) are not ideally planar [r.m.s. deviations are 0.096 and 0.092 Å for (I) and (II), respectively] and have twist-boat-like conformations [puckering parameters: amplitude (Q) = 0.166 (2) Å, θ = 87.8 (7)°, φ = 270.0 (7)° for (I), and amplitude (Q) = 0.160 (6) Å, θ = 90 (2)°, φ = 270 (2)° for (II); symmetry code: (i) −x + $[{1\over 2}]$ , y, −z + $[{3\over 2}]$ ].

The pyridine rings (N2/C3–C7), are inclined to the pyrazine ring mean planes by 40.58 (10)° in (I) and 42.1 (3)° in (II), and to one another by 67.37 (10)° in (I) and 67.3 (3)° in (II). The methylcarboxylate groups (C9/O2/C8/O1) are planar to within 0.019 (2) Å for atom O2 in (I) and 0.20 (7) Å for atom C8 in (II). Their mean planes are inclined to the mean plane of the pyrazine ring and to one another by 44.44 (16) and 68.8 (2)°, respectively, in (I), and by 43.0 (3) and 75.7 (5)°, respectively, in (II).

It can be seen from Fig. 4, a structural overlap of the ligand itself (Alfonso & Stoeckli-Evans, 2016) with the coordinating ligand in compound (I), that both the pyridine ring involving atom N4, and the carboxylate group, involving atoms O1 and O2, have been rotated by ca 100 and 160°, respectively, on coordination to the metal atom. While the pyrazine ring is ideally planar in the ligand (r.m.s. deviation = 0.032 Å), on coordination it is less planar with r.m.s. deviations of 0.096 and 0.092 Å for (I) and (II), respectively.

Figure 4
A view of the structural overlap of the ligand (Me₂L, green; Alfonso & Stoeckli-Evans, 2016

) and the coordinating ligand (blue) in compound (I)

3. Supramolecular features

In the crystals of both compounds, the polymer chains are linked via a pair of C—H⋯Cl hydrogen bonds, forming corrugated slabs parallel to the ac plane, as illustrated in Fig. 5. Within the slabs, the hydrogen bonding forms R₂²(16) and R₂²(18) type loops, as shown in Fig. 6. Details of the hydrogen bonding are given in Table 3 for compound (I) and Table 4 for compound (II). There are no other significant intermolecular interactions present for either structure.

Table 3
Hydrogen-bond geometry (Å, °) for (I)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C9—H9A⋯Cl1ⁱⁱ	0.97	2.69	3.577 (3)	151
Symmetry code: (ii) $[x-{\script{1\over 2}}, -y+2, z-{\script{1\over 2}}]$ .

Table 4
Hydrogen-bond geometry (Å, °) for (II)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C9—H9A⋯Cl1ⁱⁱ	0.96	2.81	3.647 (9)	146
Symmetry code: (ii) $[x-{\script{1\over 2}}, -y+2, z-{\script{1\over 2}}]$ .

Figure 5
A view along the a axis of the crystal packing of compound (I)

. The hydrogen bonds are shown as dashed lines (see Table 3

; only H atom H9A has been included).

Figure 6
A projection along the b axis of the crystal packing of compound (II)

. The hydrogen bonds are shown as dashed lines (see Table 4

; only H atom H9A has been included).

4. Database survey

A search of the Cambridge Structural Database (Version 5.37, update May 2016; Groom et al., 2016 ) for MN₂Cl₂ (where M = Cd and Hg; N_pyridine) four-coordinate metal ions yielded eight hits for M = cadmium and 52 hits for M = mercury. For the cadmium complexes, the Cd—Cl bonds are consistently longer than the Cd—N_pyridine bonds, and the Cl—Cd—Cl bond angles are consistently larger than the N—Cd—N bond angle, as in compound (I). A good example is dichloridobis{2-[(triphenylmethyl)amino]pyridine-κN}cadmium (VIWKIW; Zhang, 2008 ), with approximate bond lengths and bond angles of Cd—Cl = 2.387, Cd—N = 2.285 Å, Cl—Cd—Cl = 121.2 and N—Cd—N = 95.2 °.

For the mercury complexes, the Hg—Cl bond lengths are either longer or shorter than the Hg—N_pyridine bond lengths. For example, in bis(2-amino-3-methylpyridine)dichloridomercury(II) (LEHMAO; Tadjarodi et al., 2012 ) the approximate bond lengths and angles are Hg—Cl = 2.452, Hg—N = 2.267 Å, Cl—Hg—Cl = 119.9 and N—Hg—N = 101.3°, while in dichloridobis(3,3,3′,3′-tetramethyl-2,2′,3,3′-tetrahydro-1,1′-spirobi[indene]6,6′-diyl diisonicotinato)mercury (HUKTAJ; Lin et al., 2010 ) the approximate bond lengths and angles are Hg—Cl = 2.345, Hg—N = 2.593 Å, Cl—Hg—Cl = 167.5 and N—Hg—N = 104.7°. This latter example is similar to the situation in compound (II).

5. Synthesis and crystallization

The synthesis of the ligand dimethyl-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylate (Me₂L) has been reported on recently (Alfonso & Stoeckli-Evans, 2016).

Synthesis of compound (I): CdCl₂·2H₂O (22 mg, 0.1 mmol) in 25 ml of dry MeOH was slowly added to a solution of Me₂L in 10 ml of dry MeOH. The colourless solution that formed was stirred at room temperature for 1 h, then filtered to remove any impurities. The filtrate was allowed to stand over several days until colourless square rod-like crystals were obtained (yield: 40 mg, 75%). Elemental analysis for C₁₈H₁₄N₄CdCl₂O₄ (Mw = 533.63); calculated C 40.51, H 2.64, N 10.50%; found C 40.49, H 2.53, N 10.59%. Selected IR bands (KBr pellet, cm⁻¹): ν = 3066(w), 2997(w), 1751(vs), 1593(m), 1568(w), 1549(w), 1479(m), 1450(m), 1403(m), 1339(s), 1297(m), 1273(m), 1261(m), 1228(s), 1193(m), 1177(m), 1162(m), 1120(m), 1109(w), 1088(s), 1009(m), 974(m), 918(w), 827(m), 803(m), 789(m), 770(w), 758(m), 554(m).

Synthesis of compound (II): Me₂L (35 mg, 0.1 mmol) was added in solid form to a solution of HgCl₂·2H₂O (30 mg, 0.1 mmol) in 25 ml of dry MeOH. The colourless solution immediately obtained was stirred at room temperature for 2 h, filtered to remove any impurity, and the filtrate allowed to evaporate slowly. After two days colourless needle-like crystals were obtained (yield: 47mg, 76%). Elemental analysis for C₁₈H₁₄N₄Cl₂HgO₄ (Mw = 621.82); calculated C 34.77, H 2.27, N 9.01%; found C 34.79, H 2.44, N 9.03%. Selected IR bands (KBr pellet, cm⁻¹): ν = 3065(w), 2997(w), 2951(w), 2882(w), 1747(vs), 1590(m), 1568(m), 1546(w), 1477(m), 1447(m), 1402(m), 1338(s), 1279(m), 1223(s), 1195(m), 1176(s), 1105(w), 1086(s), 1003(m), 973(w), 827(w), 802(m), 788(m), 769(m), 755(m), 553(m).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 5. For both compounds the C-bound H atoms were included in calculated positions and treated as riding atoms: C—H = 0.93–0.97 Å with U_iso(H) = 1.5U_eq(C-methyl) and 1.2U_eq(C) for other H-atoms. For the mercury complex (II), R_int = 0.000 as only one equivalent was measured.

Table 5
Experimental details

	(I)	(II)
Crystal data
Chemical formula	[CdCl₂(C₁₈H₁₄N₄O₄)]	[HgCl₂(C₁₈H₁₄N₄O₄)]
M_r	533.63	621.82
Crystal system, space group	Monoclinic, P2/n	Monoclinic, P2/n
Temperature (K)	223	293
a, b, c (Å)	7.8919 (7), 10.5898 (7), 12.0875 (12)	8.1042 (6), 10.6002 (16), 12.2063 (10)
β (°)	102.061 (11)	103.158 (7)
V (Å³)	987.90 (15)	1021.07 (19)
Z	2	2
Radiation type	Mo Kα	Mo Kα
μ (mm⁻¹)	1.41	7.83
Crystal size (mm)	0.40 × 0.20 × 0.10	0.49 × 0.23 × 0.04

Data collection
Diffractometer	Stoe IPDS 1 image-plate	Stoe–Siemens AED2 four-circle
Absorption correction	Multi-scan (MULABS; Spek, 2009 )	ψ scan (X-RED; Stoe & Cie, 1997 )
T_min, T_max	0.938, 1.000	0.319, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	7196, 1918, 1684	1855, 1855, 1723
R_int	0.037	0.000
(sin θ/λ)_max (Å⁻¹)	0.614	0.600

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.022, 0.050, 0.95	0.032, 0.074, 1.11
No. of reflections	1918	1855
No. of parameters	133	133
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.34, −0.64	1.23, −1.08
Computer programs: EXPOSE, CELL and INTEGRATE in IPDS-I (Stoe & Cie, 2004 ), STADI4 and X-RED (Stoe & Cie, 1997), SHELXS97 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ), Mercury (Macrae et al., 2008 ), PLATON (Spek, 2009) and publCIF (Westrip, 2010 ).

Supporting information

CCDC references: 1495931; 1495930

Crystal structure: contains datablocks I, II, Global. DOI: https://doi.org/10.1107/S2056989016012093/zl2672sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016012093/zl2672Isup2.hkl

Structure factors: contains datablock II. DOI: https://doi.org/10.1107/S2056989016012093/zl2672IIsup3.hkl

checkCIF report

Computing details top

Data collection: EXPOSE in IPDS-I (Stoe & Cie, 2004) for (I); STADI4 Software (Stoe & Cie, 1997) for (II). Cell refinement: CELL in IPDS-I (Stoe & Cie, 2004) for (I); STADI4 Software (Stoe & Cie, 1997) for (II). Data reduction: INTEGRATE in IPDS-I (Stoe & Cie, 2004) for (I); X-RED Software (Stoe & Cie, 1997) for (II). For both compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

(I) catena-Poly[[dichloridocadmium(II)]-µ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ²N⁵:N⁶] top

Crystal data top

[CdCl₂(C₁₈H₁₄N₄O₄)]	F(000) = 528
M_r = 533.63	D_x = 1.794 Mg m⁻³
Monoclinic, P2/n	Mo Kα radiation, λ = 0.71073 Å
a = 7.8919 (7) Å	Cell parameters from 5000 reflections
b = 10.5898 (7) Å	θ = 2.0–25.9°
c = 12.0875 (12) Å	µ = 1.41 mm⁻¹
β = 102.061 (11)°	T = 223 K
V = 987.90 (15) Å³	Plate, colourless
Z = 2	0.40 × 0.20 × 0.10 mm

Data collection top

Stoe IPDS 1 image-plate diffractometer	1918 independent reflections
Radiation source: fine-focus sealed tube	1684 reflections with I > 2σ(I)
Plane graphite monochromator	R_int = 0.037
φ rotation scans	θ_max = 25.9°, θ_min = 2.6°
Absorption correction: multi-scan (MULABS; Spek, 2009)	h = −9→8
T_min = 0.938, T_max = 1.000	k = −12→12
7196 measured reflections	l = −14→14

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.022	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.050	H-atom parameters constrained
S = 0.95	w = 1/[σ²(F_o²) + (0.0331P)²] where P = (F_o² + 2F_c²)/3
1918 reflections	(Δ/σ)_max < 0.001
133 parameters	Δρ_max = 0.34 e Å⁻³
0 restraints	Δρ_min = −0.64 e Å⁻³

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
Cd1	0.7500	0.62102 (2)	0.7500	0.02022 (8)
Cl1	0.91939 (8)	0.69442 (6)	0.92817 (4)	0.03420 (15)
O1	0.5767 (3)	0.92856 (19)	0.83392 (17)	0.0493 (5)
O2	0.3843 (2)	0.97480 (15)	0.67432 (14)	0.0320 (4)
N1	0.4264 (2)	0.68120 (17)	0.79108 (14)	0.0207 (4)
N2	0.6038 (2)	0.45491 (16)	0.82537 (14)	0.0200 (4)
C1	0.3400 (3)	0.7889 (2)	0.76437 (17)	0.0212 (4)
C2	0.3377 (3)	0.5727 (2)	0.77768 (16)	0.0186 (4)
C3	0.4350 (3)	0.45962 (19)	0.82904 (15)	0.0183 (4)
C4	0.3567 (3)	0.3710 (2)	0.88644 (17)	0.0235 (4)
H4	0.2384	0.3774	0.8878	0.028*
C5	0.4558 (3)	0.2725 (2)	0.94191 (18)	0.0280 (5)
H5	0.4058	0.2111	0.9813	0.034*
C6	0.6287 (3)	0.2667 (2)	0.93806 (19)	0.0292 (5)
H6	0.6987	0.2007	0.9742	0.035*
C7	0.6976 (3)	0.3592 (2)	0.88040 (18)	0.0254 (5)
H7	0.8163	0.3552	0.8794	0.030*
C8	0.4490 (3)	0.9051 (2)	0.7648 (2)	0.0277 (5)
C9	0.4881 (4)	1.0825 (3)	0.6553 (3)	0.0502 (8)
H9A	0.4411	1.1183	0.5814	0.075*
H9B	0.6065	1.0555	0.6587	0.075*
H9C	0.4861	1.1456	0.7131	0.075*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cd1	0.01561 (12)	0.02520 (13)	0.01861 (12)	0.000	0.00071 (8)	0.000
Cl1	0.0255 (3)	0.0559 (4)	0.0204 (3)	−0.0113 (3)	0.0031 (2)	−0.0094 (2)
O1	0.0389 (11)	0.0448 (11)	0.0538 (12)	−0.0200 (9)	−0.0140 (9)	0.0170 (9)
O2	0.0327 (9)	0.0284 (8)	0.0340 (9)	−0.0013 (7)	0.0045 (7)	0.0099 (7)
N1	0.0177 (9)	0.0279 (9)	0.0163 (8)	−0.0020 (8)	0.0032 (7)	0.0030 (7)
N2	0.0157 (9)	0.0263 (9)	0.0177 (8)	0.0006 (7)	0.0025 (7)	0.0027 (7)
C1	0.0200 (11)	0.0264 (11)	0.0165 (10)	−0.0007 (9)	0.0023 (8)	0.0011 (8)
C2	0.0152 (11)	0.0263 (10)	0.0151 (9)	0.0007 (9)	0.0052 (8)	0.0016 (8)
C3	0.0166 (11)	0.0243 (10)	0.0132 (9)	−0.0014 (8)	0.0010 (8)	−0.0014 (8)
C4	0.0172 (10)	0.0323 (11)	0.0204 (10)	−0.0041 (10)	0.0023 (8)	0.0027 (9)
C5	0.0304 (13)	0.0296 (12)	0.0232 (11)	−0.0044 (10)	0.0037 (9)	0.0076 (9)
C6	0.0297 (13)	0.0295 (12)	0.0258 (12)	0.0050 (10)	0.0000 (10)	0.0069 (9)
C7	0.0189 (11)	0.0331 (13)	0.0235 (11)	0.0046 (9)	0.0030 (9)	0.0033 (9)
C8	0.0253 (13)	0.0280 (12)	0.0295 (12)	−0.0001 (9)	0.0049 (10)	0.0069 (9)
C9	0.0538 (19)	0.0375 (15)	0.0599 (18)	−0.0097 (13)	0.0134 (15)	0.0201 (13)

Geometric parameters (Å, º) top

Cd1—Cl1ⁱ	2.4137 (6)	C2—C2ⁱⁱ	1.406 (4)
Cd1—Cl1	2.4137 (6)	C2—C3	1.486 (3)
Cd1—N2	2.3862 (17)	C3—C4	1.387 (3)
Cd1—N2ⁱ	2.3862 (17)	C4—C5	1.389 (3)
Cd1—N1	2.7757 (17)	C4—H4	0.9400
O1—C8	1.193 (3)	C5—C6	1.377 (4)
O2—C8	1.330 (3)	C5—H5	0.9400
O2—C9	1.450 (3)	C6—C7	1.378 (3)
N1—C1	1.333 (3)	C6—H6	0.9400
N1—C2	1.337 (3)	C7—H7	0.9400
N2—C3	1.343 (3)	C9—H9A	0.9700
N2—C7	1.346 (3)	C9—H9B	0.9700
C1—C1ⁱⁱ	1.390 (4)	C9—H9C	0.9700
C1—C8	1.501 (3)

Cl1ⁱ—Cd1—Cl1	142.43 (3)	C3—C4—H4	120.5
N2—Cd1—N2ⁱ	85.02 (8)	C5—C4—H4	120.5
N2—Cd1—Cl1ⁱ	110.87 (4)	C6—C5—C4	118.7 (2)
N2ⁱ—Cd1—Cl1ⁱ	96.81 (4)	C6—C5—H5	120.7
N2—Cd1—Cl1	96.81 (4)	C4—C5—H5	120.7
N2ⁱ—Cd1—Cl1	110.87 (4)	C5—C6—C7	118.9 (2)
C8—O2—C9	115.7 (2)	C5—C6—H6	120.5
C1—N1—C2	118.54 (18)	C7—C6—H6	120.5
C3—N2—C7	117.28 (18)	N2—C7—C6	123.4 (2)
C3—N2—Cd1	123.17 (13)	N2—C7—H7	118.3
C7—N2—Cd1	118.96 (14)	C6—C7—H7	118.3
N1—C1—C1ⁱⁱ	120.30 (13)	O1—C8—O2	125.7 (2)
N1—C1—C8	115.93 (19)	O1—C8—C1	124.9 (2)
C1ⁱⁱ—C1—C8	123.75 (12)	O2—C8—C1	109.33 (19)
N1—C2—C2ⁱⁱ	119.71 (12)	O2—C9—H9A	109.5
N1—C2—C3	115.48 (17)	O2—C9—H9B	109.5
C2ⁱⁱ—C2—C3	124.75 (12)	H9A—C9—H9B	109.5
N2—C3—C4	122.68 (18)	O2—C9—H9C	109.5
N2—C3—C2	116.45 (17)	H9A—C9—H9C	109.5
C4—C3—C2	120.60 (19)	H9B—C9—H9C	109.5
C3—C4—C5	119.0 (2)

C2—N1—C1—C1ⁱⁱ	7.2 (3)	C2—C3—C4—C5	−174.32 (19)
C2—N1—C1—C8	−171.29 (18)	C3—C4—C5—C6	0.1 (3)
C1—N1—C2—C2ⁱⁱ	8.5 (3)	C4—C5—C6—C7	0.6 (3)
C1—N1—C2—C3	−168.82 (18)	C3—N2—C7—C6	0.8 (3)
C7—N2—C3—C4	0.0 (3)	Cd1—N2—C7—C6	172.27 (17)
Cd1—N2—C3—C4	−171.05 (15)	C5—C6—C7—N2	−1.2 (3)
C7—N2—C3—C2	174.10 (18)	C9—O2—C8—O1	5.2 (4)
Cd1—N2—C3—C2	3.0 (2)	C9—O2—C8—C1	−172.5 (2)
N1—C2—C3—N2	−36.1 (2)	N1—C1—C8—O1	−41.0 (3)
C2ⁱⁱ—C2—C3—N2	146.7 (2)	C1ⁱⁱ—C1—C8—O1	140.6 (3)
N1—C2—C3—C4	138.1 (2)	N1—C1—C8—O2	136.7 (2)
C2ⁱⁱ—C2—C3—C4	−39.0 (3)	C1ⁱⁱ—C1—C8—O2	−41.7 (3)
N2—C3—C4—C5	−0.5 (3)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C9—H9A···Cl1ⁱⁱⁱ	0.97	2.69	3.577 (3)	151

Symmetry code: (iii) x−1/2, −y+2, z−1/2.

(II) catena-Poly[[dichloridomercury(II)]-µ-5,6-bis(pyridin-2-yl)pyrazine-2,3-dicarboxylato-κ²N⁵:N⁶] top

Crystal data top

[HgCl₂(C₁₈H₁₄N₄O₄)]	F(000) = 592
M_r = 621.82	D_x = 2.023 Mg m⁻³
Monoclinic, P2/n	Mo Kα radiation, λ = 0.71073 Å
a = 8.1042 (6) Å	Cell parameters from 31 reflections
b = 10.6002 (16) Å	θ = 12.5–15.9°
c = 12.2063 (10) Å	µ = 7.83 mm⁻¹
β = 103.158 (7)°	T = 293 K
V = 1021.07 (19) Å³	Plate, colourless
Z = 2	0.49 × 0.23 × 0.04 mm

Data collection top

Stoe–Siemens AED2 four-circle diffractometer	1723 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.000
Plane graphite monochromator	θ_max = 25.2°, θ_min = 2.6°
ω/\2q scans	h = −9→9
Absorption correction: ψ scan (X-RED software; Stoe & Cie, 1997)	k = 0→12
T_min = 0.319, T_max = 1.000	l = 0→14
1855 measured reflections	2 standard reflections every 60 min
1855 independent reflections	intensity decay: 2%

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.074	H-atom parameters constrained
S = 1.11	w = 1/[σ²(F_o²) + (0.028P)² + 4.815P] where P = (F_o² + 2F_c²)/3
1855 reflections	(Δ/σ)_max < 0.001
133 parameters	Δρ_max = 1.23 e Å⁻³
0 restraints	Δρ_min = −1.08 e Å⁻³

Special details top

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

	x	y	z	U_iso*/U_eq
Hg1	0.7500	0.64352 (4)	0.7500	0.03521 (13)
Cl1	0.9248 (2)	0.6841 (2)	0.92787 (14)	0.0574 (5)
O1	0.5742 (7)	0.9336 (6)	0.8357 (5)	0.0780 (19)
O2	0.3825 (7)	0.9822 (5)	0.6779 (4)	0.0557 (13)
N1	0.4215 (6)	0.6897 (5)	0.7942 (4)	0.0319 (11)
N2	0.5940 (6)	0.4607 (5)	0.8247 (4)	0.0341 (12)
C1	0.3392 (7)	0.7964 (6)	0.7663 (5)	0.0315 (13)
C2	0.3366 (7)	0.5809 (6)	0.7789 (4)	0.0279 (12)
C3	0.4304 (7)	0.4674 (6)	0.8294 (4)	0.0289 (12)
C4	0.3561 (7)	0.3796 (6)	0.8876 (5)	0.0365 (15)
H4	0.2428	0.3874	0.8903	0.044*
C5	0.4514 (9)	0.2810 (7)	0.9412 (5)	0.0467 (17)
H5	0.4030	0.2207	0.9795	0.056*
C6	0.6207 (9)	0.2725 (7)	0.9373 (6)	0.0463 (17)
H6	0.6886	0.2070	0.9729	0.056*
C7	0.6856 (8)	0.3655 (7)	0.8783 (5)	0.0419 (16)
H7	0.7995	0.3609	0.8761	0.050*
C8	0.4467 (9)	0.9113 (7)	0.7670 (6)	0.0432 (16)
C9	0.4826 (13)	1.0900 (9)	0.6588 (9)	0.084 (3)
H9A	0.4477	1.1161	0.5817	0.126*
H9B	0.6003	1.0671	0.6752	0.126*
H9C	0.4661	1.1581	0.7070	0.126*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.02386 (18)	0.0439 (2)	0.03582 (19)	0.000	0.00254 (12)	0.000
Cl1	0.0379 (9)	0.0962 (16)	0.0361 (8)	−0.0145 (10)	0.0041 (7)	−0.0109 (9)
O1	0.061 (4)	0.065 (4)	0.090 (4)	−0.029 (3)	−0.022 (3)	0.019 (3)
O2	0.053 (3)	0.045 (3)	0.067 (3)	−0.007 (3)	0.010 (3)	0.018 (3)
N1	0.023 (2)	0.036 (3)	0.037 (3)	−0.003 (2)	0.008 (2)	0.004 (2)
N2	0.025 (2)	0.040 (3)	0.036 (3)	0.000 (2)	0.006 (2)	0.003 (2)
C1	0.031 (3)	0.028 (3)	0.036 (3)	−0.001 (3)	0.008 (2)	0.003 (3)
C2	0.022 (3)	0.037 (3)	0.028 (3)	0.003 (3)	0.011 (2)	0.001 (3)
C3	0.027 (3)	0.031 (3)	0.027 (3)	−0.001 (2)	0.004 (2)	0.000 (2)
C4	0.024 (3)	0.046 (4)	0.039 (3)	−0.002 (3)	0.007 (2)	0.003 (3)
C5	0.048 (4)	0.053 (5)	0.036 (3)	−0.005 (4)	0.002 (3)	0.008 (3)
C6	0.044 (4)	0.044 (4)	0.045 (4)	0.011 (3)	−0.001 (3)	0.014 (3)
C7	0.028 (3)	0.054 (4)	0.042 (3)	0.009 (3)	0.005 (3)	0.010 (3)
C8	0.041 (4)	0.038 (4)	0.051 (4)	0.003 (3)	0.009 (3)	0.003 (3)
C9	0.092 (7)	0.055 (6)	0.105 (8)	−0.020 (5)	0.022 (6)	0.031 (5)

Geometric parameters (Å, º) top

Hg1—Cl1ⁱ	2.3464 (16)	C2—C2ⁱⁱ	1.420 (11)
Hg1—Cl1	2.3464 (16)	C2—C3	1.480 (8)
Hg1—N2	2.590 (5)	C3—C4	1.389 (8)
Hg1—N2ⁱ	2.590 (5)	C4—C5	1.373 (9)
Hg1—N1	2.876 (5)	C4—H4	0.9300
O1—C8	1.197 (8)	C5—C6	1.386 (10)
O2—C8	1.327 (8)	C5—H5	0.9300
O2—C9	1.450 (9)	C6—C7	1.393 (10)
N1—C1	1.317 (8)	C6—H6	0.9300
N1—C2	1.334 (8)	C7—H7	0.9300
N2—C7	1.333 (8)	C9—H9A	0.9600
N2—C3	1.342 (7)	C9—H9B	0.9600
C1—C1ⁱⁱ	1.409 (12)	C9—H9C	0.9600
C1—C8	1.497 (9)

Cl1ⁱ—Hg1—Cl1	158.87 (12)	C5—C4—H4	120.3
N2—Hg1—N2ⁱ	83.1 (2)	C3—C4—H4	120.3
Cl1ⁱ—Hg1—N2	102.86 (12)	C4—C5—C6	119.1 (7)
Cl1—Hg1—N2	92.97 (12)	C4—C5—H5	120.4
Cl1ⁱ—Hg1—N2ⁱ	92.97 (12)	C6—C5—H5	120.4
Cl1—Hg1—N2ⁱ	102.86 (12)	C5—C6—C7	117.7 (6)
C8—O2—C9	116.6 (6)	C5—C6—H6	121.1
C1—N1—C2	119.4 (5)	C7—C6—H6	121.1
C7—N2—C3	117.7 (5)	N2—C7—C6	123.8 (6)
C7—N2—Hg1	118.5 (4)	N2—C7—H7	118.1
C3—N2—Hg1	122.8 (4)	C6—C7—H7	118.1
N1—C1—C1ⁱⁱ	120.0 (3)	O1—C8—O2	125.3 (7)
N1—C1—C8	115.9 (5)	O1—C8—C1	125.0 (7)
C1ⁱⁱ—C1—C8	124.0 (4)	O2—C8—C1	109.7 (6)
N1—C2—C2ⁱⁱ	119.3 (3)	O2—C9—H9A	109.5
N1—C2—C3	116.4 (5)	O2—C9—H9B	109.5
C2ⁱⁱ—C2—C3	124.2 (3)	H9A—C9—H9B	109.5
N2—C3—C4	122.3 (5)	O2—C9—H9C	109.5
N2—C3—C2	116.4 (5)	H9A—C9—H9C	109.5
C4—C3—C2	121.1 (5)	H9B—C9—H9C	109.5
C5—C4—C3	119.4 (6)

C2—N1—C1—C1ⁱⁱ	7.6 (10)	C2—C3—C4—C5	−174.7 (6)
C2—N1—C1—C8	−169.7 (5)	C3—C4—C5—C6	1.0 (10)
C1—N1—C2—C2ⁱⁱ	7.3 (9)	C4—C5—C6—C7	−0.2 (11)
C1—N1—C2—C3	−170.0 (5)	C3—N2—C7—C6	0.8 (10)
C7—N2—C3—C4	0.1 (9)	Hg1—N2—C7—C6	169.5 (6)
Hg1—N2—C3—C4	−168.1 (4)	C5—C6—C7—N2	−0.7 (11)
C7—N2—C3—C2	174.1 (5)	C9—O2—C8—O1	4.7 (12)
Hg1—N2—C3—C2	5.9 (7)	C9—O2—C8—C1	−173.0 (7)
N1—C2—C3—N2	−38.4 (7)	N1—C1—C8—O1	−39.6 (10)
C2ⁱⁱ—C2—C3—N2	144.5 (7)	C1ⁱⁱ—C1—C8—O1	143.2 (9)
N1—C2—C3—C4	135.7 (6)	N1—C1—C8—O2	138.2 (6)
C2ⁱⁱ—C2—C3—C4	−41.5 (9)	C1ⁱⁱ—C1—C8—O2	−39.0 (10)
N2—C3—C4—C5	−1.0 (9)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C9—H9A···Cl1ⁱⁱⁱ	0.96	2.81	3.647 (9)	146

Symmetry code: (iii) x−1/2, −y+2, z−1/2.

Acknowledgements

We are grateful to the Swiss National Science Foundation and the University of Neuchâtel for financial support.

References

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Volume 72| Part 8| August 2016| Pages 1214-1218

https://doi.org/10.1107/S2056989016012093

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