2,3-Dimethyl­quinoxalinium dibromide

The title compound, C₁₀H₁₂N₂²⁺·2Br⁻, crystallizes with both the cation and the two Br⁻ anions lying on a crystallographic mirror plane. In the crystal structure, the anions and cations are linked by N—H...Br and C—H...Br hydrogen bonds, forming a layer-like structure. The layers are stacked in an offset ABABA… repeat pattern, involving no π–π stacking, but Br...aryl inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 297 K
• Mean [sigma](C-C) = 0.019 Å
• R factor = 0.069
• wR factor = 0.191
• Data-to-parameter ratio = 18.3

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT341_ALERT_3_B Low Bond Precision on C-C bonds (x 1000) Ang ...         19

Alert level C
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.16
PLAT480_ALERT_4_C Long H...A H-Bond Reported H7     ..  BR1     ..       2.95 Ang.

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2006); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Bruker, 2004); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

2,3-Dimethylquinoxalinium dibromide

Crystal data

C10H12N2^2+·2Br^−	F(000) = 312
Mr = 320.02	Dx = 1.860 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 1126 reflections
a = 9.920 (4) Å	θ = 2.3–29.3°
b = 6.582 (3) Å	µ = 7.06 mm^−1
c = 9.998 (4) Å	T = 297 K
β = 118.929 (6)°	Needle, yellow
V = 571.4 (4) Å^3	0.34 × 0.13 × 0.09 mm
Z = 2

Data collection

Bruker/Siemens SMART APEX diffractometer	1126 independent reflections
Radiation source: fine-focus sealed tube	1126 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.033
Detector resolution: 8.3 pixels mm^-1	θmax = 25.3°, θmin = 2.3°
ω scans	h = −11→10
Absorption correction: multi-scan (TWINABS; Sheldrick, 2002)	k = 0→7
Tmin = 0.184, Tmax = 0.529	l = 0→11
1576 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.069	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.191	H-atom parameters constrained
S = 1.13	w = 1/[σ^2(Fo^2) + (0.1277P)^2] where P = (Fo^2 + 2Fc^2)/3
1560 reflections	(Δ/σ)max < 0.001
86 parameters	Δρmax = 2.28 e Å^−3
0 restraints	Δρmin = −1.06 e Å^−3

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	Occ. (<1)
Br1	0.75950 (12)	0.2500	0.63619 (14)	0.0413 (4)
Br2	0.73345 (14)	0.2500	0.07210 (15)	0.0440 (5)
C1	0.4376 (14)	0.2500	0.1991 (14)	0.032 (3)
H1C	0.3852	0.1757	0.1050	0.048*	0.50
H1A	0.5351	0.1869	0.2641	0.048*	0.50
H1B	0.4541	0.3874	0.1781	0.048*	0.50
C2	0.3410 (13)	0.2500	0.2782 (12)	0.023 (2)
C4	0.3170 (14)	0.2500	0.5079 (13)	0.032 (3)
C5	0.3936 (18)	0.2500	0.6655 (16)	0.052 (4)
H5	0.5005	0.2500	0.7227	0.062*
C6	0.3026 (15)	0.2500	0.7305 (16)	0.043 (3)
H6	0.3491	0.2500	0.8366	0.052*
C7	0.1405 (18)	0.2500	0.6464 (14)	0.042 (3)
H7	0.0815	0.2500	0.6958	0.051*
C8	0.0712 (19)	0.2500	0.4887 (14)	0.043 (3)
H8	−0.0357	0.2500	0.4314	0.051*
C9	0.1562 (13)	0.2500	0.4165 (13)	0.026 (2)
C11	0.1748 (14)	0.2500	0.1920 (14)	0.033 (3)
C12	0.0972 (15)	0.2500	0.0276 (13)	0.032 (3)
H12C	0.1420	0.1483	−0.0077	0.048*	0.50
H12A	0.1079	0.3810	−0.0084	0.048*	0.50
H12B	−0.0100	0.2207	−0.0107	0.048*	0.50
N3	0.4012 (11)	0.2500	0.4251 (10)	0.028 (2)
H3	0.5001	0.2500	0.4777	0.034*
N10	0.0930 (11)	0.2500	0.2619 (10)	0.031 (2)
H10	−0.0058	0.2500	0.2076	0.037*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0206 (6)	0.0319 (6)	0.0537 (8)	0.000	0.0041 (6)	0.000
Br2	0.0217 (6)	0.0572 (9)	0.0459 (8)	0.000	0.0106 (5)	0.000
C1	0.028 (7)	0.039 (7)	0.044 (7)	0.000	0.030 (6)	0.000
C2	0.016 (6)	0.031 (6)	0.019 (5)	0.000	0.005 (4)	0.000
C4	0.024 (6)	0.025 (6)	0.036 (6)	0.000	0.006 (5)	0.000
C5	0.023 (8)	0.053 (9)	0.045 (8)	0.000	−0.010 (6)	0.000
C6	0.032 (8)	0.047 (8)	0.042 (7)	0.000	0.012 (6)	0.000
C7	0.061 (10)	0.048 (8)	0.030 (6)	0.000	0.032 (7)	0.000
C8	0.055 (10)	0.044 (8)	0.025 (6)	0.000	0.016 (6)	0.000
C9	0.022 (6)	0.017 (5)	0.037 (6)	0.000	0.011 (5)	0.000
C11	0.023 (7)	0.029 (6)	0.046 (7)	0.000	0.016 (6)	0.000
C12	0.032 (8)	0.032 (7)	0.033 (6)	0.000	0.016 (6)	0.000
N3	0.022 (5)	0.027 (5)	0.037 (5)	0.000	0.015 (4)	0.000
N10	0.024 (5)	0.024 (5)	0.033 (5)	0.000	0.005 (4)	0.000

Geometric parameters (Å, º)

C1—C2	1.509 (14)	C7—C8	1.382 (17)
C1—H1C	0.9600	C7—H7	0.9300
C1—H1A	0.9600	C8—C9	1.349 (18)
C1—H1B	0.9600	C8—H8	0.9300
C2—N3	1.291 (13)	C9—N10	1.358 (14)
C2—C11	1.445 (15)	C11—N10	1.303 (16)
C4—C5	1.380 (18)	C11—C12	1.439 (17)
C4—C9	1.403 (15)	C12—H12C	0.9600
C4—N3	1.432 (15)	C12—H12A	0.9600
C5—C6	1.34 (2)	C12—H12B	0.9600
C5—H5	0.9300	N3—H3	0.8600
C6—C7	1.41 (2)	N10—H10	0.8600
C6—H6	0.9300
C2—C1—H1C	109.5	C9—C8—C7	121.1 (14)
C2—C1—H1A	109.5	C9—C8—H8	119.5
H1C—C1—H1A	109.5	C7—C8—H8	119.5
C2—C1—H1B	109.5	C8—C9—N10	123.0 (10)
H1C—C1—H1B	109.5	C8—C9—C4	117.4 (11)
H1A—C1—H1B	109.5	N10—C9—C4	119.7 (10)
N3—C2—C11	116.4 (9)	N10—C11—C2	120.5 (10)
N3—C2—C1	122.3 (10)	N10—C11—C12	119.0 (11)
C11—C2—C1	121.2 (9)	C2—C11—C12	120.5 (10)
C5—C4—C9	124.6 (12)	C11—C12—H12C	109.5
C5—C4—N3	120.5 (11)	C11—C12—H12A	109.5
C9—C4—N3	114.9 (9)	H12C—C12—H12A	109.5
C6—C5—C4	115.2 (14)	C11—C12—H12B	109.5
C6—C5—H5	122.4	H12C—C12—H12B	109.5
C4—C5—H5	122.4	H12A—C12—H12B	109.5
C5—C6—C7	123.5 (12)	C2—N3—C4	125.4 (8)
C5—C6—H6	118.3	C2—N3—H3	117.3
C7—C6—H6	118.3	C4—N3—H3	117.3
C8—C7—C6	118.3 (11)	C11—N10—C9	123.1 (9)
C8—C7—H7	120.8	C11—N10—H10	118.5
C6—C7—H7	120.8	C9—N10—H10	118.5
C9—C4—C5—C6	0.000 (5)	C1—C2—C11—N10	180.000 (2)
N3—C4—C5—C6	180.000 (5)	N3—C2—C11—C12	180.000 (2)
C4—C5—C6—C7	0.000 (7)	C1—C2—C11—C12	0.000 (1)
C5—C6—C7—C8	0.000 (5)	C11—C2—N3—C4	0.000 (2)
C6—C7—C8—C9	0.000 (5)	C1—C2—N3—C4	180.000 (3)
C7—C8—C9—N10	180.000 (5)	C5—C4—N3—C2	180.000 (4)
C7—C8—C9—C4	0.000 (6)	C9—C4—N3—C2	0.000 (3)
C5—C4—C9—C8	0.000 (4)	C2—C11—N10—C9	0.000 (3)
N3—C4—C9—C8	180.000 (4)	C12—C11—N10—C9	180.000 (3)
C5—C4—C9—N10	180.000 (4)	C8—C9—N10—C11	180.000 (3)
N3—C4—C9—N10	0.000 (2)	C4—C9—N10—C11	0.000 (2)
N3—C2—C11—N10	0.000 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···Br1	0.86	2.28	3.135 (9)	175
N10—H10···Br2^i	0.86	2.27	3.126 (10)	178
C7—H7···Br1^i	0.93	2.95	3.731 (15)	142

Symmetry code: (i) x−1, y, z.