Synthesis, crystal structure and thermal properties of poly[di-μ-bromido-(μ-2,5-di­methyl­pyrazine)cadmium(II)]

In the title compound, the cadmium cations are octa­hedrally coordinated by four bromide anions and two 2–5-di­methyl­pyrazine ligands and linked into chains via pairs of μ-1,1-bridging Br⁻ anions that are further connected into layers by the bridging 2,5-di­methyl­pyrazine coligands.

Abstract

The title compound, [CdBr₂(C₆H₈N₂)]_n, was prepared by the reaction of cadmium bromide with 2,5-di­methyl­pyrazine in water. Its asymmetric unit consists of one Cd cation and one 2,5-di­methyl­pyrazine ligand that are located on a crystallographic mirror plane as well as one bromide anion that occupies a general position. The Cd cations are sixfold coordinated by four bromide anions and two 2,5-di­methyl­pyrazine ligands within slightly distorted trans-CdBr₄N₂ octa­hedra. The cations are linked into [100] chains via pairs of bridging bromide anions that are further connected into (001) layers by the bridging 2,5-di­methyl­pyrazine ligands. Powder X-ray diffraction (PXRD) shows that a pure crystalline phase has been obtained. Thermogravimetry coupled to differential thermoanalysis (TG-TDA) reveal that the 2,5-di­methyl­pyrazine ligands are removed in two separate steps leading to the formation of a compound with the composition (CdBr₂)₂(2,5-di­methyl­pyrazine) that decomposes into CdBr₂ upon further heating. PXRD measurements of the residue obtained after the first mass loss show that a new crystalline phase has been formed.

1. Chemical context

For several years, we and others have been inter­ested in the synthesis and crystal structures of coordination compounds based on transition metal halides and neutral organic coligands. In the beginning, we focused on compounds based on Cu^I, because they show an extremely versatile structural behavior (Kromp & Sheldrick, 1999 ▸; Peng et al., 2010 ▸; Näther & Jess, 2002 ▸, 2004 ▸; Li et al., 2005 ▸). Such compounds usually consist of CuX subunits that can comprise monomeric and dimeric units but also different kinds of chains that are further linked into more condensed networks when bridging coligands are used in the synthesis. In the course of our systematic work we found that upon heating, such compounds frequently lose their coligands in a stepwise manner, which leads to the formation of new copper halide compounds as inter­mediates that consist of condensed CuX networks (Näther et al., 2001 ▸, 2002 ▸). More recently, we have shown that this synthetic route can also be expanded to coordination compounds with, e.g. ZnX₂ and CdX₂ (X = Cl, Br, I), even if they, with few exceptions (Näther et al., 2007 ▸), do not show the same structural variability as the Cu compounds.

In the course of our project we especially used bridging coligands such as pyrazine derivatives to prepare compounds with more condensed networks. Some compounds with CdX₂ (X = Cl, Br, I) and pyrazine (C₄H₄N₂) have already been reported, including CdX₂(pyrazine) [X = Cl, Br, I, Cambridge Structural Database refcodes TISSUJ (Pickardt & Staub, 1996 ▸), RINSIQ and RINSOW (Bailey & Pennington, 1997 ▸); RINSOW01 and RINSIQ01 (Pickardt & Staub, 1997 ▸)], in which the Cd cations are linked by pairs of bridging halide anions into chains, which are further connected into layers by the pyrazine coligands. In this context we have reported on CdX₂ compounds with 2-chloro and 2-methyl­pyrazine, for which a different thermal reactivity was observed (Näther et al., 2017 ▸). In the coligand-rich compounds CdX₂(L)₂ (X = Cl, Br, I, L = 2-chloro and methyl­pyrazine: QAWHOO, QAWGON, QAWGUT, QAWHAA, QAWHEE and QAWHII; Näther et al., 2017 ▸), the Cd cations are octa­hedrally coordinated and linked into chains by pairs of bridging halide anions. If the 2-methyl­pyrazine compounds are heated, a transformation into 2-methyl­pyrazine-deficient compounds with the composition CdX₂(2-methyl­pyrazine) (X = Cl, Br, I) is observed, in which the CdX₂ chains are further linked into layers as with the pyrazine compounds mentioned above. In contrast, for the 2-chloro­pyrazine compounds, no 2-chloro­pyrazine-deficient compounds can be obtained and they can also not be prepared from solution (Näther et al., 2017 ▸).

In a continuation of this work we became inter­ested in compounds with 2,5-di­methyl­pyrazine (C₆H₈N₂) in which the coordination to each of the N atoms is sterically hindered because of the bulky methyl groups. A compound with the composition CdI₂(2,5-di­methyl­pyrazine) is already reported in the CSD (EHEQUG; Rogers, 2020 ▸). Surprisingly, the structure of this compound is completely different from that of the 2-methyl and 2-chloro­pyrazine compounds mentioned above. In EHEQUG, the Cd cations are tetra­hedrally coordinated by two iodide anions and two 2,5-di­methyl­pyrazine coligands and linked into chains by the coligands. Compounds with CdCl₂ or CdBr₂ and 2,5-di­methyl­pyrazine have not been reported. In the course of our investigations, we obtained crystals of the title compound, (I), by the reaction of CdBr₂ and 2,5-di­methyl­pyrazine, which were characterized by single crystal X-ray diffraction.

2. Structural commentary

The asymmetric unit of (I) consists of one Cd cation and one 2,5-di­methyl­pyrazine ligand that are located on a crystallographic mirror plane as well as one bromide anion that occupies a general position (Fig. 1 ▸). The Cd cations are octa­hedrally coordinated by four bromide anions that are located in the basal plane and two N-bonded 2,5-di­methyl­pyrazine ligands in the axial positions. The N—Cd—N and N—Cd—Br angles are close to the ideal values,whereas the Br—Cd—Br angles are significantly different from 90°, which shows that the octa­hedra are significantly distorted (Table 1 ▸). The cadmium cations are linked into chains via pairs of μ-1,1-bridging bromide anions that propagate in the crystallographic a-axis direction, which means that neighboring octa­hedra share common edges (Fig. 2 ▸). These chains are further linked into layers lying parallel to (001) by the bridging 2,5-di­methyl­pyrazine ligands (Fig. 3 ▸). It is noted that this topology is well known from CdX₂ compounds with pyrazine derivatives such as CdX₂(pyrazine) (X = Cl, Br, I) (Bailey & Pennington, 1997 ▸; Pickardt & Staub, 1997 ▸). It is also noted that the crystal structure of the title compound is completely different from the iodide analogue CdI₂(2,5-di­methyl­pyrazine) already reported in the literature (EHEQUG; Rogers, 2020 ▸).

Figure 1.

The crystal structure of (I) with labeling and displacement ellipsoids drawn at the 50% probability level. Symmetry codes for the generation of equivalent atoms: (i) −x + 1, y, z; (ii) x, y + , −z + ; (iii) −x + , y, −z + ; (iv) x − , y, −z + ; (v) x + , y, −z + .

Table 1. Selected geometric parameters (Å, °).

Cd1—Br1	2.6869 (4)	Cd1—N1	2.482 (5)
Cd1—Br1i	2.7893 (4)	Cd1—N2ii	2.494 (5)
Br1—Cd1—Br1iii	106.18 (2)	N1—Cd1—Br1	91.20 (6)
Br1—Cd1—Br1iv	86.222 (11)	N1—Cd1—N2ii	178.93 (15)
Br1i—Cd1—Br1iv	81.37 (2)	N2ii—Cd1—Br1iii	89.45 (6)
Br1iii—Cd1—Br1iv	167.574 (18)	N2ii—Cd1—Br1iv	89.94 (8)
N1—Cd1—Br1iv	89.25 (8)	Cd1—Br1—Cd1v	93.774 (11)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .

Figure 2.

Crystal structure of (I) with view of part of one [100] chain.

Figure 3.

Crystal structure of (I) with view along the crystallographic c-axis direction.

3. Supra­molecular features

The layers in (I) are stacked in the crystallographic c-axis direction such that the methyl groups of neighboring layers point towards each along the a-axis direction or that they are shifted relative to each other along the b-axis direction so that the methyl groups are opposite to the bromide anions (Fig. 4 ▸). In the crystal structure of (I) a number of inter­molecular C—H⋯Br contacts are observed but for all of them the H⋯Br distances are very long and the C—H⋯Br angles are far from linear, indicating that these are only very weak inter­actions (Table 2 ▸).

Figure 4.

Crystal structure of (I) with view along the crystallographic a- (left) and b-axis (right) directions.

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯Br1vi	0.95	3.02	3.624 (5)	123
C2—H2⋯Br1vii	0.95	3.02	3.624 (5)	123
C4—H4⋯Br1i	0.95	3.04	3.622 (5)	121
C4—H4⋯Br1iv	0.95	3.04	3.622 (5)	121
C5—H5B⋯Br1	0.98	2.83	3.658 (5)	142
C5—H5C⋯Br1iii	0.98	2.83	3.658 (5)	142
C6—H6B⋯Br1viii	0.98	2.86	3.674 (5)	141
C6—H6C⋯Br1ix	0.98	2.86	3.674 (5)	141

Symmetry codes: (i) ; (iii) ; (iv) ; (vi) ; (vii) ; (viii) ; (ix) .

4. Database survey

As mentioned in the Chemical context section, only one cadmium halide compound with 2,5-di­methyl­pyrazine is reported as a private communication in the CCDC database [CSD Version 5.43, September 2024 (Groom et al., 2016 ▸), search with CONQUEST (Bruno et al., 2002 ▸)]. However, a number of compounds with other twofold positively charged transition-metal cations, halide anions and 2,5-di­methyl­pyrazine are known. This include the two isotypic compounds MBr₂(2,5-di­methyl­pyrazine), in which the metal cations are square-planar coordinated by two bromide anions and two 2,5-di­methyl­pyrazine ligands and linked into chains by the neutral coligands [M = Ni (BRMPYN; Ayres et al., 1964 ▸) and M = Cu (DOVNUY; Butcher et al., 2009 ▸)]. The same structure is also observed in CuCl₂(2,5-di­methyl­pyrazine) (RAZYEX; Awwadi et al., 2005 ▸), but this compound is not isotypic to the bromide compounds mentioned before.

Several compounds are reported with Zn^II in which the Zn^II cations are tetra­hedrally coordinated, including ZnX₂(2,5-di­methyl­pyrazine) in which the Zn^II cations are linked into chains by the 2,5-di­methyl­pyrazine ligands (X = Cl, DOPYAJ, X = Br, DOPYIR, X = I, DOPZAK; Wriedt et al., 2009 ▸). In (ZnX₂)₂(2,5-di­methyl­pyrazine)₃ dinuclear complexes are formed in which the 2,5-di­methyl­pyrazine acts as bridging and terminal ligands (X = Cl, DOPYEN, X = Br, DOPYOX; Wriedt et al., 2009 ▸). In ZnBr₂(2,5-di­methyl­pyrazine)₂-2,5-di­methyl­pyrazine solvate, discrete complexes are observed (DOPYUD; Wriedt et al., 2009 ▸). Discrete complexes are also observed in ZnI₂(2,5-di­methyl­pyrazine)₂ (DOPZEO; Wriedt et al., 2009 ▸). Additional compounds are reported with Cu^II cations, including CuBr₂(2,5-di­methyl­pyrazine)(aceto­nitrile), in which the Cu^II cations are fivefold coordinated by two chloride anions, one aceto­nitrile ligand and two bridging 2,5-di­methyl­pyrazine ligands that link the cations into chains (MEVRAG; Näther & Greve, 2001 ▸).

Finally, two compounds with the composition (HgX₂)₂(2,5-di­methyl­pyrazine) (X = Cl, QUMVIE, X = Br, QUMTUO; Mahmoudi & Morsali, 2009 ▸) are also reported, and show a topology similar to that of the title compound.

5. Additional investigations

Comparison of the the experimental X-ray powder pattern of the sample with that calculated for the title compound from single-crystal data shows that a pure crystalline phase has been obtained (Fig. 5 ▸).

Figure 5.

Experimental (top) and calculated X-ray powder pattern (bottom) for (I).

Thermogravimetry and differential thermoanalysis (TG-DTA) measurements reveal that (I) decomposes in two steps that are accompanied with endothermic events in the DTA curve at peak temperatures of 207 and 276°C (Fig. 6 ▸). The experimental mass losses of the first and second thermogravimetric step of 13.9 and 14.1% are in good agreement with those calculated for the removal of a half 2,5-di­methyl­pyrazine ligand in each step (Δm_calc. = 14.2%). Therefore, one can assume that after the first mass loss a compound with the composition (CdBr₂)₂(2,5-di­methyl­pyrazine) is formed, which decomposes into CdBr₂ upon further heating.

Figure 6.

DTG, TG and DTA curves for (I) measured with a heating rate of 4°C min⁻¹. The mass loss is given in % and the peak temperature in °C.

To prove that a new crystalline phase had formed, the residue obtained after the first mass loss was investigated by powder X-ray diffraction, which shows that a compound with very good crystallinity was obtained with a powder pattern completely different from that of the title compound (Fig. 7 ▸). Unfortunately, indexing of this powder pattern failed, so that no structural information is available. However, it can be assumed that a more condensed CdBr₂ network formed.

Figure 7.

Experimental X-ray powder pattern of the residue obtained after the first mass loss in a TG measurement for (I) (top) and calculated powder pattern for (I) (bottom).

6. Synthesis and crystallization

CdBr₂ and 2,5-di­methyl­pyrazine were purchased from Sigma-Aldrich. 136.1 mg (0.5 mmol) of CdBr₂ and 54.1 mg of (0.5 mmol) 2,5-di­methyl­pyrazine were reacted in 2 ml of water for 2 d at 353 K, which led to the formation of colorless crystals suitable for single crystal X-ray diffraction.

The PXRD measurements were performed with Cu Kα₁ radiation (λ = 1.540598 Å) using a Stoe Transmission Powder Diffraction System (STADI P) equipped with a MYTHEN 1K detector and a Johansson-type Ge(111) monochromator. Thermogravimetry and differential thermoanalysis (TG-DTA) experiments were performed in a dynamic nitro­gen atmosphere in Al₂O₃ crucibles with 8°C min⁻¹ using a STA-PT 1000 thermobalance from Linseis. The TG-DTA instrument was calibrated using standard reference materials.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. The C—H hydrogen atoms were positioned with idealized geometry (methyl H atoms allowed to rotate but not to tip) and were refined isotropically with U_iso(H) = 1.2U_eq(C) (1.5 for methyl H atoms).

Table 3. Experimental details.

Crystal data
Chemical formula	[CdBr2(C6H8N2)]
M r	380.36
Crystal system, space group	Orthorhombic, Cmce
Temperature (K)	170
a, b, c (Å)	7.9334 (2), 15.4735 (6), 15.4898 (6)
V (Å3)	1901.49 (11)
Z	8
Radiation type	Mo Kα
μ (mm−1)	10.64
Crystal size (mm)	0.14 × 0.11 × 0.07
Data collection
Diffractometer	Stoe IPDS2
Absorption correction	Numerical
Tmin, Tmax	0.193, 0.276
No. of measured, independent and observed [I > 2σ(I)] reflections	14714, 1238, 1082
R int	0.039
(sin θ/λ)max (Å−1)	0.661
Refinement
R[F2 > 2σ(F2)], wR(F2), S	0.033, 0.088, 1.13
No. of reflections	1238
No. of parameters	64
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	1.99, −0.84

Computer programs: X-AREA (Stoe, 2008 ▸), SHELXT2014/4 (Sheldrick, 2015a ▸), SHELXL2016/6 (Sheldrick, 2015b ▸), DIAMOND (Brandenburg, 1999 ▸), XP in SHELXTL-PC (Sheldrick, 2008 ▸) and publCIF (Westrip, 2010 ▸).

Supplementary Material

CCDC reference: 2407788

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

supplementary crystallographic information

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Crystal data

[CdBr2(C6H8N2)]	Dx = 2.657 Mg m−3
Mr = 380.36	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmce	Cell parameters from 15283 reflections
a = 7.9334 (2) Å	θ = 5.3–57.8°
b = 15.4735 (6) Å	µ = 10.64 mm−1
c = 15.4898 (6) Å	T = 170 K
V = 1901.49 (11) Å3	Block, colorless
Z = 8	0.14 × 0.11 × 0.07 mm
F(000) = 1408

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Data collection

Stoe IPDS-2 diffractometer	1082 reflections with I > 2σ(I)
ω scans	Rint = 0.039
Absorption correction: numerical	θmax = 28.0°, θmin = 2.6°
Tmin = 0.193, Tmax = 0.276	h = −10→10
14714 measured reflections	k = −20→20
1238 independent reflections	l = −20→20

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Refinement

Refinement on F2	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.033	H-atom parameters constrained
wR(F2) = 0.088	w = 1/[σ2(Fo2) + (0.0592P)2] where P = (Fo2 + 2Fc2)/3
S = 1.13	(Δ/σ)max = 0.001
1238 reflections	Δρmax = 1.99 e Å−3
64 parameters	Δρmin = −0.84 e Å−3

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Special details

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.

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cd1	0.500000	0.60333 (2)	0.76619 (2)	0.02282 (15)
Br1	0.77081 (5)	0.60437 (3)	0.87036 (2)	0.02692 (15)
N1	0.500000	0.4430 (3)	0.7622 (3)	0.0250 (9)
C1	0.500000	0.3874 (3)	0.8292 (4)	0.0275 (11)
C2	0.500000	0.2984 (4)	0.8119 (4)	0.0294 (12)
H2	0.500000	0.259776	0.859575	0.035*
N2	0.500000	0.2645 (3)	0.7328 (3)	0.0263 (10)
C3	0.500000	0.3214 (4)	0.6659 (3)	0.0267 (11)
C4	0.500000	0.4088 (4)	0.6818 (4)	0.0264 (11)
H4	0.500000	0.447104	0.633895	0.032*
C5	0.500000	0.4195 (4)	0.9195 (3)	0.0350 (14)
H5A	0.500000	0.370280	0.959327	0.052*
H5B	0.600860	0.454687	0.929396	0.052*	0.5
H5C	0.399140	0.454687	0.929396	0.052*	0.5
C6	0.500000	0.2890 (4)	0.5746 (4)	0.0350 (14)
H6A	0.500000	0.338159	0.534803	0.052*
H6B	0.600860	0.253755	0.564744	0.052*	0.5
H6C	0.399140	0.253755	0.564744	0.052*	0.5

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Cd1	0.0223 (2)	0.0213 (2)	0.0248 (2)	0.000	0.000	0.00021 (14)
Br1	0.0231 (2)	0.0340 (3)	0.0237 (2)	−0.00048 (15)	0.00010 (13)	−0.00062 (14)
N1	0.031 (2)	0.022 (2)	0.022 (2)	0.000	0.000	0.0015 (16)
C1	0.031 (3)	0.025 (3)	0.026 (3)	0.000	0.000	0.0040 (19)
C2	0.036 (3)	0.026 (3)	0.026 (2)	0.000	0.000	0.003 (2)
N2	0.030 (2)	0.021 (2)	0.028 (2)	0.000	0.000	−0.0030 (17)
C3	0.029 (3)	0.025 (3)	0.026 (2)	0.000	0.000	0.002 (2)
C4	0.028 (3)	0.028 (3)	0.023 (2)	0.000	0.000	0.0009 (19)
C5	0.057 (4)	0.026 (3)	0.022 (2)	0.000	0.000	−0.001 (2)
C6	0.056 (4)	0.023 (3)	0.026 (2)	0.000	0.000	−0.004 (2)

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Geometric parameters (Å, º)

Cd1—Br1	2.6869 (4)	C2—N2	1.332 (7)
Cd1—Br1i	2.7893 (4)	N2—C3	1.360 (7)
Cd1—Br1ii	2.6869 (4)	C3—C4	1.374 (8)
Cd1—Br1iii	2.7893 (4)	C3—C6	1.500 (7)
Cd1—N1	2.482 (5)	C4—H4	0.9500
Cd1—N2iv	2.494 (5)	C5—H5A	0.9800
N1—C1	1.347 (7)	C5—H5B	0.9800
N1—C4	1.353 (7)	C5—H5C	0.9800
C1—C2	1.404 (8)	C6—H6A	0.9800
C1—C5	1.484 (8)	C6—H6B	0.9800
C2—H2	0.9500	C6—H6C	0.9800
Br1—Cd1—Br1ii	106.18 (2)	N2—C2—C1	124.2 (5)
Br1—Cd1—Br1iii	86.222 (11)	N2—C2—H2	117.9
Br1ii—Cd1—Br1i	86.222 (11)	C2—N2—Cd1vi	112.8 (4)
Br1i—Cd1—Br1iii	81.37 (2)	C2—N2—C3	116.5 (5)
Br1ii—Cd1—Br1iii	167.574 (18)	C3—N2—Cd1vi	130.7 (3)
Br1—Cd1—Br1i	167.574 (18)	N2—C3—C4	120.0 (5)
N1—Cd1—Br1iii	89.25 (8)	N2—C3—C6	120.1 (5)
N1—Cd1—Br1ii	91.20 (6)	C4—C3—C6	119.9 (5)
N1—Cd1—Br1	91.20 (6)	N1—C4—C3	123.4 (5)
N1—Cd1—Br1i	89.25 (8)	N1—C4—H4	118.3
N1—Cd1—N2iv	178.93 (15)	C3—C4—H4	118.3
N2iv—Cd1—Br1ii	89.45 (6)	C1—C5—H5A	109.5
N2iv—Cd1—Br1	89.45 (6)	C1—C5—H5B	109.5
N2iv—Cd1—Br1i	89.94 (8)	C1—C5—H5C	109.5
N2iv—Cd1—Br1iii	89.94 (8)	H5A—C5—H5B	109.5
Cd1—Br1—Cd1v	93.774 (11)	H5A—C5—H5C	109.5
C1—N1—Cd1	128.2 (4)	H5B—C5—H5C	109.5
C1—N1—C4	117.3 (5)	C3—C6—H6A	109.5
C4—N1—Cd1	114.4 (4)	C3—C6—H6B	109.5
N1—C1—C2	118.6 (5)	C3—C6—H6C	109.5
N1—C1—C5	120.8 (5)	H6A—C6—H6B	109.5
C2—C1—C5	120.6 (5)	H6A—C6—H6C	109.5
C1—C2—H2	117.9	H6B—C6—H6C	109.5
Cd1—N1—C1—C2	180.0	C1—C2—N2—C3	0.0
Cd1—N1—C1—C5	0.0	C2—N2—C3—C4	0.0
Cd1—N1—C4—C3	180.0	C2—N2—C3—C6	180.0
Cd1vi—N2—C3—C4	180.0	N2—C3—C4—N1	0.0
Cd1vi—N2—C3—C6	0.0	C4—N1—C1—C2	0.0
N1—C1—C2—N2	0.0	C4—N1—C1—C5	180.0
C1—N1—C4—C3	0.0	C5—C1—C2—N2	180.0
C1—C2—N2—Cd1vi	180.0	C6—C3—C4—N1	180.0

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

Poly[di-µ-bromido-(µ-2,5-dimethylpyrazine)cadmium(II)]. Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···Br1vii	0.95	3.02	3.624 (5)	123
C2—H2···Br1viii	0.95	3.02	3.624 (5)	123
C4—H4···Br1i	0.95	3.04	3.622 (5)	121
C4—H4···Br1iii	0.95	3.04	3.622 (5)	121
C5—H5B···Br1	0.98	2.83	3.658 (5)	142
C5—H5C···Br1ii	0.98	2.83	3.658 (5)	142
C6—H6B···Br1vi	0.98	2.86	3.674 (5)	141
C6—H6C···Br1ix	0.98	2.86	3.674 (5)	141

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