Poly­[copper(I)-[mu]-bromo-[mu]-2,3-di­methyl­pyrazine-N:N']

In the structure of the title compound, [CuBr(C₆H₈N₂)]_n, each Cu²⁺ cation is surrounded by two 2,3-di­methyl­pyrazine ligands and two Br^- anions in a distorted tetrahedral arrangement. The Cu²⁺ cations and Br^- anions form (Cu₂Br₂)₂ rhomboid dimers located around a centre of inversion. The 2,3-di­methyl­pyrazine ligands connect the Cu²⁺ cations in the dimers into sheets parallel to (010).

Computing details

Data collection: DIF4 (Stoe & Cie, 1992); cell refinement: DIF4; data reduction: REDU4 (Stoe & Cie, 1992); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL/PC (Siemens, 1990); software used to prepare material for publication: CIFTAB in SHELXL97.

Poly[copper(I)-µ-bromo-µ-2,3-dimethylpyrazine-N:N']

Crystal data

[CuBr(C6H8N2)]	Dx = 2.231 Mg m^−3
Mr = 251.59	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 140 reflections
a = 11.459 (2) Å	θ = 12–18.5°
b = 9.7078 (11) Å	µ = 8.17 mm^−1
c = 13.468 (4) Å	T = 293 K
V = 1498.2 (6) Å^3	Irregular polyhedron, orange
Z = 8	0.12 × 0.1 × 0.08 mm
F(000) = 976

Data collection

Phillips PW-1100 four-circle diffractometer	1681 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.031
Graphite monochromator	θmax = 30.0°, θmin = 3.0°
ω–θ scans	h = −16→1
Absorption correction: numerical (X-SHAPE (Stoe & Cie, 1998)	k = −13→1
Tmin = 0.386, Tmax = 0.520	l = −1→18
2821 measured reflections	4 standard reflections every 120 min
2186 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.032	H-atom parameters constrained
wR(F^2) = 0.085	w = 1/[σ^2(Fo^2) + (0.0467P)^2 + 0.6968P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max = 0.001
2186 reflections	Δρmax = 0.72 e Å^−3
94 parameters	Δρmin = −0.87 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0036 (4)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cu1	0.46639 (3)	0.57377 (4)	0.60884 (3)	0.03019 (13)
Br1	0.50724 (3)	0.68412 (3)	0.44811 (2)	0.02844 (11)
N1	0.6050 (2)	0.5955 (2)	0.70725 (17)	0.0201 (5)
C1	0.6095 (2)	0.5307 (3)	0.7951 (2)	0.0192 (5)
C2	0.7088 (2)	0.5406 (3)	0.8561 (2)	0.0216 (5)
N2	0.8046 (2)	0.6080 (3)	0.82603 (18)	0.0222 (5)
C3	0.7977 (2)	0.6744 (3)	0.7382 (2)	0.0241 (6)
H3	0.8618	0.7242	0.7158	0.029*
C4	0.6988 (2)	0.6702 (3)	0.6812 (2)	0.0233 (6)
H4	0.6965	0.7208	0.6225	0.028*
C5	0.5068 (3)	0.4461 (3)	0.8250 (2)	0.0278 (6)
H5A	0.4592	0.4977	0.8704	0.042*
H5B	0.5333	0.3632	0.8568	0.042*
H5C	0.4619	0.4229	0.7672	0.042*
C6	0.7101 (3)	0.4799 (4)	0.9578 (2)	0.0367 (8)
H6A	0.7739	0.5181	0.9949	0.055*
H6B	0.7193	0.3818	0.9531	0.055*
H6C	0.6380	0.5007	0.9907	0.055*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0243 (2)	0.0399 (2)	0.0264 (2)	−0.00295 (16)	−0.00025 (14)	0.00090 (17)
Br1	0.0405 (2)	0.02242 (16)	0.02244 (16)	0.00252 (12)	−0.00023 (11)	0.00262 (11)
N1	0.0193 (10)	0.0217 (11)	0.0193 (10)	−0.0010 (9)	−0.0025 (8)	0.0012 (9)
C1	0.0190 (12)	0.0170 (12)	0.0217 (12)	0.0023 (10)	0.0027 (10)	0.0019 (10)
C2	0.0194 (13)	0.0246 (13)	0.0208 (12)	0.0025 (11)	0.0013 (9)	0.0010 (11)
N2	0.0163 (11)	0.0282 (12)	0.0221 (11)	−0.0002 (9)	0.0003 (8)	0.0009 (10)
C3	0.0219 (13)	0.0269 (14)	0.0235 (13)	−0.0052 (11)	0.0023 (10)	0.0037 (12)
C4	0.0257 (14)	0.0245 (13)	0.0197 (12)	−0.0022 (11)	−0.0001 (10)	0.0047 (11)
C5	0.0234 (13)	0.0291 (14)	0.0309 (14)	−0.0041 (11)	0.0028 (12)	0.0071 (13)
C6	0.0268 (15)	0.060 (2)	0.0234 (15)	−0.0011 (16)	0.0003 (11)	0.0159 (15)

Geometric parameters (Å, º)

Cu1—N2^i	2.077 (2)	N2—C3	1.349 (4)
Cu1—N1	2.080 (2)	N2—Cu1^iii	2.077 (2)
Cu1—Br1	2.4602 (7)	C3—C4	1.370 (4)
Cu1—Br1^ii	2.6358 (6)	C3—H3	0.93
Br1—Cu1^ii	2.6358 (6)	C4—H4	0.93
N1—C1	1.341 (3)	C5—H5A	0.96
N1—C4	1.343 (4)	C5—H5B	0.96
C1—C2	1.407 (4)	C5—H5C	0.96
C1—C5	1.491 (4)	C6—H6A	0.96
C2—N2	1.341 (4)	C6—H6B	0.96
C2—C6	1.491 (4)	C6—H6C	0.96
N2^i—Cu1—N1	113.34 (10)	N2—C3—C4	121.8 (3)
N2^i—Cu1—Br1	118.14 (7)	N2—C3—H3	119.1
N1—Cu1—Br1	111.79 (7)	C4—C3—H3	119.1
N2^i—Cu1—Br1^ii	112.15 (7)	N1—C4—C3	122.1 (3)
N1—Cu1—Br1^ii	101.21 (7)	N1—C4—H4	119
Br1—Cu1—Br1^ii	97.80 (2)	C3—C4—H4	119
Cu1—Br1—Cu1^ii	82.20 (2)	C1—C5—H5A	110
C1—N1—C4	117.0 (2)	C1—C5—H5B	110
C1—N1—Cu1	122.95 (18)	H5A—C5—H5B	110
C4—N1—Cu1	119.96 (19)	C1—C5—H5C	110
N1—C1—C2	121.0 (2)	H5A—C5—H5C	110
N1—C1—C5	117.8 (2)	H5B—C5—H5C	110
C2—C1—C5	121.2 (2)	C2—C6—H6A	110
N2—C2—C1	121.3 (3)	C2—C6—H6B	110
N2—C2—C6	117.5 (3)	H6A—C6—H6B	110
C1—C2—C6	121.2 (3)	C2—C6—H6C	110
C2—N2—C3	116.7 (2)	H6A—C6—H6C	110
C2—N2—Cu1^iii	121.68 (19)	H6B—C6—H6C	110
C3—N2—Cu1^iii	119.93 (19)

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