4-Cyano-1-methyl­pyridinium iodide

In the crystal structure of the title compound, C₇H₇N₂⁺·I⁻, the cations form inversion-related dimers via weak pairwise C—H...N hydrogen bonds. In the dimers, the pyridinium rings are parallel to one another with their mean planes separated by a normal distance of ca 0.28 Å. Weak C—H...N inter­actions between adjacent dimers generate a layer lying parallel to (10-1). The remaining H atoms form C—H...I inter­actions, which link the layers into a three-dimensional structure.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.020
• wR factor = 0.048
• Data-to-parameter ratio = 19.5

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT480_ALERT_4_C Long H...A H-Bond Reported H1B    ..  N2      ..       2.71 Ang.

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT128_ALERT_4_G Alternate Setting of Space-group P21/c   .......      P21/n
PLAT371_ALERT_2_G Long   C(sp2)-C(sp1) Bond  C4     -   C7     ...       1.45 Ang.
PLAT710_ALERT_4_G Delete 1-2-3 or 2-3-4 Linear Torsion Angle ... #         11
            C3  -C4  -C7  -N2     76.00  5.00   1.555   1.555   1.555   1.555
PLAT710_ALERT_4_G Delete 1-2-3 or 2-3-4 Linear Torsion Angle ... #         12
            C5  -C4  -C7  -N2   -102.00  5.00   1.555   1.555   1.555   1.555
PLAT961_ALERT_5_G Dataset Contains no Negative Intensities .......          !

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   1 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   6 ALERT level G = General information/check it is not something unexpected

   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
   0 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

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S1. Comment

Previously reported structures of four other cyano-1-methylpyridinium salts (Koplitz et al., 2003; Mague et al., 2005; Koplitz et al., 2012) include three layered compounds with all atoms, except the methyl H atoms, lying on crystallographic mirror planes. Interestingly, none of the iodide salts of the 4-, 3- and 2-cyano-1-methylpyridinium cation adopt this layer structure, possibly because the larger size and weaker hydrogen-bonding ability of iodide as compared with the smaller chloride and bromide ions provides a less restrictive set of interionic interactions.

The molecular structure of the title compound is illustrated in Fig. 1. In the crystal, the cations form inversion dimers via weak pairwise C2—H2···N2 hydrogen bonds (Table 1). In the dimers the pyridinium rings are parallel to one another with their mean planes separated by a normal distance of ca 0.28 Å. Weak C1—H1B···N2 interactions between adjacent dimers generate a layer lying parallel to (101), with the remaining hydrogen atoms forming C—H···I interactions (Table 1). The latter reinforce the construction of the layers as well as tying them together into a three-dimensional structure (Fig. 2).

In contrast to 3-cyano-1-methylpyridinium iodide (Koplitz et al., 2003) where each iodide ion interacts with three C—H groups, in the title compound each anion is linked by five C—H groups which may reflect the more linear shape of the cation in the present structure.

Related literature

For the structure of 3-cyano-1-methylpyridinium iodide, see: Koplitz et al. (2003). For the structure of 1-methylpyridinium iodide, see: Lalancette et al. (1978). For related structures see: Mague et al. (2005); Koplitz et al. (2012).

S2. Experimental

4-Cyanopyridine (10.55 g) was dissolved in benzene (40 ml). Iodomethane (9.5 ml) was added to this solution slowly with stirring and the solution was refluxed for 75 minutes. A yellow solid was collected by vacuum filtration (M.p. 462 - 466 K). Addition of ethanol to the supernatant (ca 2:1 benzene:ethanol) resulted in the the growth overnight of thin plate-like yellow crystals of the title compound, suitable for X-ray diffraction.

S3. Refinement

The C-bound H-atoms were included in calculated positions and treated as riding atoms: C—H = 0.95 and 0.98 Å for CH and CH₃ H-atoms, respectively, with U_iso(H) = k × U_eq(C), where k = 1.5 for CH₃ H-atoms and 1.2 for other H-atoms.

Computing details

Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); 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

	Fig. 1. A perspective view of the asymmetric unit of the title compound with atom numbering. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A view of the crystal packing of the title compound, showing the interpenetrating sheets of cations [colour key: C = gray, H = orange, N = blue, I = purple; C—H···I interactions are depicted as dashed lines].

4-Cyano-1-methylpyridinium iodide

Crystal data

C7H7N2^+·I^−	F(000) = 464
Mr = 246.05	Dx = 1.893 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 8899 reflections
a = 5.0734 (3) Å	θ = 2.3–28.6°
b = 11.4528 (7) Å	µ = 3.64 mm^−1
c = 15.0751 (9) Å	T = 100 K
β = 99.679 (1)°	Plates, yellow
V = 863.46 (9) Å^3	0.14 × 0.07 × 0.05 mm
Z = 4

Data collection

Bruker SMART APEX CCD diffractometer	1792 independent reflections
Radiation source: fine-focus sealed tube	1572 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
φ and ω scans	θmax = 26.5°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −6→6
Tmin = 0.614, Tmax = 0.836	k = −14→14
12786 measured reflections	l = −18→18

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)] = 0.020	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.048	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0159P)^2 + 1.1195P] where P = (Fo^2 + 2Fc^2)/3
1792 reflections	(Δ/σ)max = 0.002
92 parameters	Δρmax = 0.88 e Å^−3
0 restraints	Δρmin = −0.47 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. H-atoms were placed in calculated positions (C—H = 0.95 - 0.98 Å) and included as riding contributions with isotropic displacement parameters 1.2 - 1.5 times those of the attached carbon atoms.

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

	x	y	z	Uiso*/Ueq
I1	0.95185 (3)	0.378404 (15)	0.854589 (12)	0.02114 (7)
N1	0.6792 (5)	0.3458 (2)	0.18850 (15)	0.0201 (5)
N2	0.7382 (5)	0.0466 (2)	−0.07663 (17)	0.0307 (6)
C1	0.6477 (6)	0.4209 (3)	0.26587 (19)	0.0233 (6)
H1A	0.5052	0.4779	0.2472	0.035*
H1B	0.8159	0.4621	0.2871	0.035*
H1C	0.6013	0.3726	0.3146	0.035*
C2	0.8704 (6)	0.2626 (3)	0.19989 (19)	0.0218 (6)
H2	0.9858	0.2554	0.2562	0.026*
C3	0.8996 (6)	0.1883 (3)	0.13096 (19)	0.0219 (6)
H3	1.0361	0.1306	0.1387	0.026*
C4	0.7265 (6)	0.1986 (2)	0.04961 (18)	0.0207 (6)
C5	0.5356 (6)	0.2869 (3)	0.03797 (19)	0.0243 (6)
H5	0.4201	0.2965	−0.0181	0.029*
C6	0.5167 (6)	0.3604 (3)	0.10929 (19)	0.0223 (6)
H6	0.3883	0.4215	0.1023	0.027*
C7	0.7369 (6)	0.1158 (3)	−0.0225 (2)	0.0244 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.01891 (11)	0.02214 (12)	0.02205 (11)	0.00126 (7)	0.00256 (7)	0.00040 (7)
N1	0.0211 (12)	0.0212 (12)	0.0191 (12)	0.0000 (9)	0.0065 (9)	0.0021 (9)
N2	0.0343 (15)	0.0328 (15)	0.0257 (14)	0.0058 (12)	0.0071 (11)	−0.0015 (12)
C1	0.0265 (15)	0.0239 (15)	0.0201 (14)	0.0037 (12)	0.0055 (12)	0.0008 (11)
C2	0.0190 (14)	0.0260 (15)	0.0204 (14)	0.0032 (11)	0.0035 (11)	0.0053 (11)
C3	0.0197 (14)	0.0238 (15)	0.0237 (15)	0.0060 (11)	0.0078 (11)	0.0048 (11)
C4	0.0250 (15)	0.0217 (14)	0.0171 (14)	0.0001 (11)	0.0082 (11)	0.0021 (11)
C5	0.0229 (15)	0.0301 (17)	0.0190 (14)	0.0041 (12)	0.0010 (11)	0.0021 (12)
C6	0.0219 (14)	0.0228 (15)	0.0219 (14)	0.0053 (11)	0.0029 (11)	0.0033 (11)
C7	0.0253 (15)	0.0256 (16)	0.0234 (15)	0.0017 (12)	0.0073 (12)	0.0027 (12)

Geometric parameters (Å, º)

N1—C6	1.343 (4)	C2—H2	0.9500
N1—C2	1.350 (4)	C3—C4	1.388 (4)
N1—C1	1.480 (4)	C3—H3	0.9500
N2—C7	1.139 (4)	C4—C5	1.390 (4)
C1—H1A	0.9800	C4—C7	1.451 (4)
C1—H1B	0.9800	C5—C6	1.381 (4)
C1—H1C	0.9800	C5—H5	0.9500
C2—C3	1.370 (4)	C6—H6	0.9500
C6—N1—C2	121.4 (2)	C2—C3—H3	120.5
C6—N1—C1	119.8 (2)	C4—C3—H3	120.5
C2—N1—C1	118.7 (2)	C3—C4—C5	119.8 (3)
N1—C1—H1A	109.5	C3—C4—C7	120.6 (3)
N1—C1—H1B	109.5	C5—C4—C7	119.5 (3)
H1A—C1—H1B	109.5	C6—C5—C4	118.8 (3)
N1—C1—H1C	109.5	C6—C5—H5	120.6
H1A—C1—H1C	109.5	C4—C5—H5	120.6
H1B—C1—H1C	109.5	N1—C6—C5	120.3 (3)
N1—C2—C3	120.6 (3)	N1—C6—H6	119.9
N1—C2—H2	119.7	C5—C6—H6	119.9
C3—C2—H2	119.7	N2—C7—C4	176.3 (3)
C2—C3—C4	119.0 (3)
C6—N1—C2—C3	−1.6 (4)	C7—C4—C5—C6	175.8 (3)
C1—N1—C2—C3	177.5 (3)	C2—N1—C6—C5	2.4 (4)
N1—C2—C3—C4	−1.1 (4)	C1—N1—C6—C5	−176.7 (3)
C2—C3—C4—C5	2.9 (4)	C4—C5—C6—N1	−0.5 (4)
C2—C3—C4—C7	−175.0 (3)	C3—C4—C7—N2	76 (5)
C3—C4—C5—C6	−2.2 (4)	C5—C4—C7—N2	−102 (5)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···N2^i	0.95	2.58	3.434 (4)	149
C1—H1B···N2^ii	0.98	2.71	3.513 (4)	140
C1—H1A···I1^iii	0.98	3.04	3.999 (3)	166
C1—H1C···I1^iv	0.98	3.06	3.870 (3)	141
C2—H2···I1^v	0.95	2.99	3.796 (3)	144
C5—H5···I1^vi	0.95	2.94	3.839 (3)	158
C6—H6···I1^iii	0.95	3.01	3.916 (3)	161

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