2,6-Di­methyl­pyridinium nitrate

In the crystal structure of the title compound, C₇H₁₀N⁺·NO₃⁻, the cations and anions are linked by N—H...O and C—H...O hydrogen bonds to form a supramolecular structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.034
• wR factor = 0.077
• Data-to-parameter ratio = 18.0

checkCIF results

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S1. Comment

Crystal structures of a few 2,6-dimethylpyridinium complexes have been reported previously (Jin et al., 2000; Pan et al. 2001). We report here the structure of the title salt, (I), obtained from 2,6-dimethylpyridine and nitric acid.

The asymmetric unit of (I), consists of one 2,6-dimethylpyridinium cation and one nitrate anion linked by N1—H1···O3 hydrogen bond and C7—H7CO2 interaction (Fig.1 & Table 2). In the crystal, the cations and anions are linked by a number of C—H···O interactions to form a network structure. A part of the network around a nitrate anion is shown in Fig. 2. In the network, the nitrate anion is arranged nearly parallel to two symmetry related cations [dihedral angle 12.33 (6)°] but it is inclined to the other cation (N1/C1—C7) with a dihedral angle of 60.42 (3)°. The network is further stabilized by π–π-stacking interactions involving pyridinium rings at (x, y, z) and (1/2 − x, 3/2 − y, −z), respectively, with a centroid–centroid separation of 3.558 (1) Å.

The bond lengths in (I) have normal values. In comparison with pyridine, the C—N—C angle in the pyridinium ring is always widened. For example, the C—N—C angle in 2,6-dimethylpyridine (Bond et al., 2001) is 119.0 (3)°, and 120° in its 1:1 complex with urea (Lee & Wallwork, 1965). In the 1:1 complex of 4-methylpyridine and pentachlorophenol, which has been crystallized as a salt at 80 K and a neutral adduct at 295 K, the C—N—C angles are 119.9 (2) and 118.0 (4)°, respectively (Malarski et al., 1987, 1996). In the salts of 2,6-dimethylpyridinium hydrogen phthalate and 2,6-dimethylpyridinium fumarate (Jin et al. 2000; Pan et al., 2001), this angle is widened to 123.83 (2) and 123.92 (17)°, respectively. Similar feature is also observed in the title salt, with a C1—N1—C5 angle of 124.90 (13)°.

S2. Experimental

2,6-Dimethylpyridine and aqueous nitric acid in an equimolar ratio were mixed together. Crystals of (I) formed in the resulting solution by slow evaporation for a month at 293 K.

S3. Refinement

Atom H1 was located in a difference Fourier map and refined isotropically; all other H atoms were placed in calculated positions and allowed to ride on their parent atoms. A rotating group model was used for the methyl groups.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SMART; data reduction: SAINT-Plus (Bruker, 2000); program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The structure of the title compound showing 50% probability displacement ellipsoids and the atom-numbering scheme.
	Fig. 2. A view of the hydrogen bonding network around a nitrate anion. The symmetry code for atoms C2^* and C6^* is (1/2 + x, 3/2 − y, 1/2 + z) and that for C4^# is (x, 2 − y, 1/2 + z).

2,6-Dimethylpyridinium nitrate

Crystal data

C7H10N^+·NO3^−	F(000) = 720
Mr = 170.17	Dx = 1.294 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 782 reflections
a = 15.918 (3) Å	θ = 2.8–19.8°
b = 7.560 (1) Å	µ = 0.10 mm^−1
c = 15.924 (3) Å	T = 293 K
β = 114.26 (1)°	Prism, colourless
V = 1747.1 (5) Å^3	0.3 × 0.2 × 0.2 mm
Z = 8

Data collection

Bruker SMART Apex CCD area-detector diffractometer	1091 reflections with I > 2σ(I)
Radiation source: sealed tube	Rint = 0.032
Graphite monochromator	θmax = 28.1°, θmin = 2.8°
ϕ and ω scans	h = −13→20
5170 measured reflections	k = −9→9
2069 independent reflections	l = −20→20

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)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.077	H atoms treated by a mixture of independent and constrained refinement
S = 0.86	w = 1/[σ^2(Fo^2) + (0.0314P)^2] where P = (Fo^2 + 2Fc^2)/3
2069 reflections	(Δ/σ)max < 0.001
115 parameters	Δρmax = 0.13 e Å^−3
0 restraints	Δρmin = −0.07 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
C1	0.14054 (9)	0.86336 (16)	0.06222 (9)	0.0635 (4)
C2	0.10556 (10)	0.87640 (15)	−0.03100 (10)	0.0690 (4)
H2	0.0462	0.8369	−0.0668	0.083*
C3	0.15770 (11)	0.94718 (16)	−0.07153 (10)	0.0706 (4)
H3	0.1340	0.9546	−0.1354	0.085*
C4	0.24362 (10)	1.00723 (16)	−0.02044 (9)	0.0691 (4)
H4	0.2786	1.0567	−0.0490	0.083*
C5	0.27894 (10)	0.99510 (17)	0.07338 (9)	0.0656 (4)
C6	0.09119 (9)	0.78637 (16)	0.11475 (9)	0.0717 (4)
H6A	0.1232	0.6827	0.1469	0.108*
H6B	0.0297	0.7549	0.0731	0.108*
H6C	0.0887	0.8717	0.1583	0.108*
C7	0.37155 (9)	1.05641 (16)	0.13605 (9)	0.0749 (4)
H7A	0.3660	1.1502	0.1741	0.112*
H7B	0.4037	1.0990	0.1006	0.112*
H7C	0.4053	0.9600	0.1743	0.112*
N1	0.22590 (8)	0.92208 (13)	0.10996 (9)	0.0617 (3)
H1	0.2464 (8)	0.9080 (13)	0.1664 (9)	0.057 (4)*
N2	0.35705 (9)	0.79802 (14)	0.33269 (9)	0.0661 (3)
O1	0.39264 (6)	0.78106 (11)	0.41608 (7)	0.0760 (3)
O2	0.39045 (7)	0.72683 (11)	0.28549 (6)	0.0802 (3)
O3	0.28628 (7)	0.88737 (11)	0.29672 (6)	0.0729 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0610 (9)	0.0600 (8)	0.0612 (9)	0.0070 (7)	0.0166 (8)	0.0029 (7)
C2	0.0664 (9)	0.0640 (8)	0.0629 (9)	0.0079 (7)	0.0127 (8)	0.0023 (7)
C3	0.0786 (10)	0.0665 (9)	0.0571 (9)	0.0104 (8)	0.0182 (8)	0.0044 (7)
C4	0.0764 (10)	0.0665 (8)	0.0647 (9)	0.0078 (8)	0.0293 (8)	0.0062 (7)
C5	0.0663 (9)	0.0640 (8)	0.0624 (9)	0.0059 (7)	0.0223 (8)	0.0039 (7)
C6	0.0648 (9)	0.0687 (8)	0.0753 (9)	0.0028 (7)	0.0223 (8)	0.0064 (7)
C7	0.0674 (9)	0.0743 (8)	0.0780 (10)	−0.0011 (7)	0.0248 (8)	0.0022 (7)
N1	0.0641 (8)	0.0625 (7)	0.0519 (8)	0.0067 (6)	0.0173 (7)	0.0051 (6)
N2	0.0666 (8)	0.0660 (7)	0.0594 (8)	0.0063 (6)	0.0194 (7)	0.0019 (6)
O1	0.0736 (6)	0.0838 (6)	0.0596 (6)	0.0138 (5)	0.0163 (5)	0.0065 (5)
O2	0.0859 (7)	0.0813 (6)	0.0692 (6)	0.0182 (5)	0.0277 (6)	0.0012 (5)
O3	0.0694 (6)	0.0796 (6)	0.0611 (6)	0.0153 (5)	0.0181 (5)	0.0045 (4)

Geometric parameters (Å, º)

C1—N1	1.3313 (16)	C6—H6A	0.96
C1—C2	1.3581 (17)	C6—H6B	0.96
C1—C6	1.4817 (18)	C6—H6C	0.96
C2—C3	1.3534 (19)	C7—H7A	0.96
C2—H2	0.93	C7—H7B	0.96
C3—C4	1.3506 (18)	C7—H7C	0.96
C3—H3	0.93	N1—H1	0.827 (12)
C4—C5	1.3661 (17)	N2—O2	1.2107 (13)
C4—H4	0.93	N2—O1	1.2176 (12)
C5—N1	1.3271 (16)	N2—O3	1.2342 (13)
C5—C7	1.4747 (17)
N1—C1—C2	117.63 (14)	H6A—C6—H6B	109.5
N1—C1—C6	117.52 (12)	C1—C6—H6C	109.5
C2—C1—C6	124.84 (13)	H6A—C6—H6C	109.5
C3—C2—C1	119.58 (14)	H6B—C6—H6C	109.5
C3—C2—H2	120.2	C5—C7—H7A	109.5
C1—C2—H2	120.2	C5—C7—H7B	109.5
C4—C3—C2	120.88 (14)	H7A—C7—H7B	109.5
C4—C3—H3	119.6	C5—C7—H7C	109.5
C2—C3—H3	119.6	H7A—C7—H7C	109.5
C3—C4—C5	119.74 (15)	H7B—C7—H7C	109.5
C3—C4—H4	120.1	C5—N1—C1	124.90 (13)
C5—C4—H4	120.1	C5—N1—H1	119.5 (8)
N1—C5—C4	117.24 (14)	C1—N1—H1	115.6 (8)
N1—C5—C7	118.23 (12)	O2—N2—O1	120.26 (12)
C4—C5—C7	124.53 (14)	O2—N2—O3	120.34 (12)
C1—C6—H6A	109.5	O1—N2—O3	119.39 (12)
C1—C6—H6B	109.5
N1—C1—C2—C3	0.06 (18)	C3—C4—C5—C7	−179.86 (12)
C6—C1—C2—C3	−179.07 (11)	C4—C5—N1—C1	−1.42 (18)
C1—C2—C3—C4	−0.90 (19)	C7—C5—N1—C1	178.91 (11)
C2—C3—C4—C5	0.62 (19)	C2—C1—N1—C5	1.15 (19)
C3—C4—C5—N1	0.50 (18)	C6—C1—N1—C5	−179.66 (11)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O3	0.827 (12)	1.912 (13)	2.7364 (17)	175.5 (11)
C2—H2···O1^i	0.93	2.51	3.3567 (19)	152
C4—H4···O1^ii	0.93	2.44	3.3438 (18)	165
C4—H4···O3^ii	0.93	2.54	3.3463 (18)	145
C6—H6B···O1^i	0.96	2.57	3.4700 (17)	156
C7—H7C···O2	0.96	2.58	3.3723 (16)	140

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