Bis(2,6-di­methyl­pyridinium) di­bromo­iodate bromide

In the title salt, 2C₇H₁₀N⁺·IBr₂⁻·Br⁻, each of the anions, viz. [IBr₂]⁻ and Br⁻, lie on a twofold axis. The IBr₂⁻ anion is almost linear, with a Br—I—Br angle of 178.25 (3)°. The cation is essentially planar (r.m.s. deviation = 0.0067 Å). In the crystal, each Br⁻ anion links two cations via N—H⋯Br⋯H—N hydrogen-bonding inter­actions.

Related literature

For background to this study, see: Kochel (2006). For comparison bond lengths and angles, see: Gardberg et al. (2002); Ahmadi et al. (2008).

Experimental

Crystal data

• 2C₇H₁₀N⁺·Br₂I⁻·Br⁻

• M_r = 582.92

• Monoclinic, C 2/c

• a = 13.8627 (16) Å

• b = 11.3622 (9) Å

• c = 13.8957 (15) Å

• β = 108.885 (13)°

• V = 2070.9 (4) ų

• Z = 4

• Mo Kα radiation

• μ = 7.33 mm⁻¹

• T = 293 K

• 0.34 × 0.28 × 0.15 mm

Data collection

• Agilent Xcalibur Eos diffractometer

• Absorption correction: analytical (CrysAlis PRO; Agilent, 2011) T_min = 0.578, T_max = 0.733

• 4417 measured reflections

• 1834 independent reflections

• 1280 reflections with I > 2σ(I)

• R_int = 0.034

Refinement

• R[F² > 2σ(F²)] = 0.040

• wR(F²) = 0.104

• S = 1.05

• 1834 reflections

• 92 parameters

• H-atom parameters constrained

• Δρ_max = 0.52 e Å⁻³

• Δρ_min = −0.58 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯Br2	0.86	2.45	3.315 (5)	179

Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

S1. Comment

Polyhalides display a variety of structures. Various compounds with interesting structures were found when protonated aromatic nitrogen bases were combined with polyhalides (Kochel, 2006). Herein, we report the crystal structure of [(C₇H₁₀N)⁺]₂. [IBr₂] ^–. Br^-, (I). Few crystals of (I) were found as an unexpected product from reaction mixture of CdI₂, HBr, 2,6-dimethylpyridine and Br₂ upon attempting to formulate [(C₇H₁₀N)]₂ [CdBr₄] salt of 2,6-dimethylpyrinium.

The title salt is depicted in Fig. 1. The IBr₂^– anion is symmetrical and almost linear, Br1—I—Br1ⁱ angle of 178.25 (3) °; (i) –x + 1, y, -z + 1/2], with I—Br1 distance of 2.7117 (9) Å. These values are in agreement with the values reported in the literature (Gardberg et al., 2002). The molecular dimensions of the cation are as expected (Ahmadi et al., 2008).

The cations are arranged as zigzag stacks parallel to the c-axis (Fig. 2). Moreover, alternating Br^- and IBr₂^- anions form stacks that separate the cations. Each bromide anion is hydrogen bonded via N1—H1A···Br2 with two cations along the b-axis (Table 1). There are no significant Br···Br or aryl···aryl interactions in the crystal structure; the shortest Br···Br separation is just greater than 5.0 Å and the shortest distance between the ring centroids is over 4.8 Å.

Related literature

For background to this study, see: Kochel (2006). For comparison bond lengths and angles, see: Gardberg et al. (2002); Ahmadi et al. (2008).

S2. Experimental

A solution of CdI₂ (0.37 g, 1 mmol) dissolved in 95% EtOH (10 ml) and 2 ml 60% HBr solution was added to a mixture of 2,6-dimethylpyridine (0.11 g, 1 mmol) dissolved in 95% EtOH (10 ml), 60% HBr (2 ml) and molecular bromine (2 ml). The resulting mixture was refluxed for 2 hr. On cooling few reddish crystals of the title complex were found mixed in the bulk of the precipitate formed which proved to be mainly 2,6-dimethylpyridinium bromide.

S3. Refinement

All H atoms were positioned geometrically and refined using a riding model, with N—H = 0.86 Å and C—H = 0.93 and 0.96 Å, for aryl and methyl H-atoms, respectively. The U_iso(H) were allowed at 1.5U_eq(C methyl) or 1.2U_eq(N/C non-methyl).

Computing details

Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

Molecular configuration and atom naming scheme for I. Displacement ellipsoids are drawn at the 30% probability level. A stands for the symmetry operation: -x + 1, y, -z + 1/2

Packing diagram of I, down crystallographic c axis. Interspecies hydrogen bonds are shown as dashed lines.

Bis(2,6-dimethylpyridinium) dibromoiodate bromide

Crystal data

2C7H10N^+·Br2I^−·Br^−	F(000) = 1104
Mr = 582.92	Dx = 1.870 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1414 reflections
a = 13.8627 (16) Å	θ = 3.0–29.4°
b = 11.3622 (9) Å	µ = 7.33 mm^−1
c = 13.8957 (15) Å	T = 293 K
β = 108.885 (13)°	Block, orange
V = 2070.9 (4) Å^3	0.34 × 0.28 × 0.15 mm
Z = 4

Data collection

Agilent Xcalibur Eos diffractometer	1834 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1280 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
Detector resolution: 16.0534 pixels mm^-1	θmax = 25.0°, θmin = 3.1°
ω scans	h = −16→12
Absorption correction: analytical (CrysAlis PRO; Agilent, 2011)	k = −12→13
Tmin = 0.578, Tmax = 0.733	l = −16→16
4417 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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.104	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0423P)^2 + 1.4129P] where P = (Fo^2 + 2Fc^2)/3
1834 reflections	(Δ/σ)max = 0.001
92 parameters	Δρmax = 0.52 e Å^−3
0 restraints	Δρmin = −0.58 e Å^−3

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.

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
I1	0.5000	0.56444 (5)	0.2500	0.0633 (2)
Br1	0.31439 (6)	0.56808 (6)	0.10417 (6)	0.0846 (3)
Br2	0.0000	0.55587 (7)	0.2500	0.0665 (3)
N1	0.1116 (3)	0.3483 (4)	0.1556 (3)	0.0529 (11)
H1A	0.0824	0.4027	0.1793	0.064*
C6	0.2531 (5)	0.3799 (6)	0.3092 (5)	0.081 (2)
H6A	0.2058	0.4369	0.3186	0.122*
H6B	0.3145	0.4188	0.3090	0.122*
H6C	0.2688	0.3237	0.3637	0.122*
C1	0.2069 (5)	0.3183 (5)	0.2109 (5)	0.0614 (16)
C5	0.0574 (5)	0.2992 (5)	0.0649 (5)	0.0654 (17)
C2	0.2529 (6)	0.2305 (6)	0.1722 (6)	0.085 (2)
H2A	0.3183	0.2057	0.2091	0.101*
C7	−0.0487 (5)	0.3421 (7)	0.0149 (5)	0.093 (2)
H7A	−0.0643	0.4021	0.0563	0.140*
H7B	−0.0955	0.2778	0.0069	0.140*
H7C	−0.0544	0.3742	−0.0506	0.140*
C4	0.1058 (8)	0.2137 (6)	0.0278 (6)	0.090 (2)
H4A	0.0720	0.1780	−0.0341	0.108*
C3	0.2038 (8)	0.1805 (6)	0.0814 (7)	0.098 (3)
H3A	0.2363	0.1235	0.0550	0.117*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.0866 (5)	0.0525 (4)	0.0601 (4)	0.000	0.0366 (3)	0.000
Br1	0.0928 (6)	0.0837 (5)	0.0703 (5)	0.0069 (4)	0.0166 (4)	−0.0037 (4)
Br2	0.0573 (5)	0.0564 (5)	0.0949 (7)	0.000	0.0371 (5)	0.000
N1	0.059 (3)	0.046 (3)	0.059 (3)	0.006 (2)	0.026 (2)	0.005 (2)
C6	0.065 (4)	0.083 (5)	0.082 (5)	0.005 (4)	0.005 (4)	−0.001 (4)
C1	0.058 (4)	0.056 (4)	0.074 (4)	0.010 (3)	0.028 (3)	0.023 (3)
C5	0.088 (5)	0.058 (4)	0.058 (4)	−0.014 (4)	0.034 (4)	−0.002 (3)
C2	0.098 (6)	0.068 (5)	0.107 (6)	0.035 (4)	0.061 (5)	0.032 (4)
C7	0.076 (5)	0.116 (6)	0.078 (5)	−0.017 (5)	0.012 (4)	0.001 (4)
C4	0.152 (8)	0.063 (5)	0.068 (5)	−0.018 (5)	0.054 (5)	−0.014 (4)
C3	0.151 (8)	0.066 (5)	0.101 (6)	0.031 (5)	0.076 (6)	0.011 (5)

Geometric parameters (Å, º)

I1—Br1	2.7117 (9)	C1—C2	1.383 (9)
I1—Br1^i	2.7117 (9)	C5—C4	1.372 (9)
Br2—Br2^ii	0.0000	C5—C7	1.490 (9)
Br2—Br2	0.0000	C2—C3	1.350 (10)
N1—C1	1.340 (7)	C2—H2A	0.9300
N1—C5	1.361 (7)	C7—H7A	0.9600
N1—H1A	0.8600	C7—H7B	0.9600
C6—C1	1.483 (8)	C7—H7C	0.9600
C6—H6A	0.9600	C4—C3	1.373 (10)
C6—H6B	0.9600	C4—H4A	0.9300
C6—H6C	0.9600	C3—H3A	0.9300
Br1—I1—Br1^i	178.25 (3)	C4—C5—C7	125.8 (7)
Br2^ii—Br2—Br2	0 (10)	C3—C2—C1	120.7 (7)
C1—N1—C5	125.0 (5)	C3—C2—H2A	119.6
C1—N1—H1A	117.5	C1—C2—H2A	119.6
C5—N1—H1A	117.5	C5—C7—H7A	109.5
C1—C6—H6A	109.5	C5—C7—H7B	109.5
C1—C6—H6B	109.5	H7A—C7—H7B	109.5
H6A—C6—H6B	109.5	C5—C7—H7C	109.5
C1—C6—H6C	109.5	H7A—C7—H7C	109.5
H6A—C6—H6C	109.5	H7B—C7—H7C	109.5
H6B—C6—H6C	109.5	C5—C4—C3	120.6 (7)
N1—C1—C2	117.0 (6)	C5—C4—H4A	119.7
N1—C1—C6	117.4 (5)	C3—C4—H4A	119.7
C2—C1—C6	125.6 (6)	C2—C3—C4	120.1 (7)
N1—C5—C4	116.6 (6)	C2—C3—H3A	119.9
N1—C5—C7	117.6 (6)	C4—C3—H3A	119.9
C5—N1—C1—C2	−0.2 (9)	C6—C1—C2—C3	−179.9 (7)
C5—N1—C1—C6	−178.7 (5)	N1—C5—C4—C3	0.4 (9)
C1—N1—C5—C4	−0.9 (9)	C7—C5—C4—C3	−179.4 (7)
C1—N1—C5—C7	178.9 (5)	C1—C2—C3—C4	−2.2 (11)
N1—C1—C2—C3	1.8 (9)	C5—C4—C3—C2	1.1 (11)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···Br2	0.86	2.45	3.315 (5)	179

 

Footnotes

‡Cuurrent address: Qassim University, Faculty of Science, Chemistry Department, Qassim, Saudi Arabia.