2-(4-Iodo-1-methyl-1H-pyrazol-3-yl)-pyridinium dichloro­iodide

In the title mol­ecular salt, C₉H₉IN₃⁺·ICl₂⁻, the dihedral angle between the aromatic rings in the cation is 14.9 (2)°. The I—Cl bond lengths of the anion are distinctly different, by 0.149 (2) Å. The most significant inter­action in the crystal structure is a bifurcated N—H...(N,Cl) hydrogen bond.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.027
• wR factor = 0.069
• Data-to-parameter ratio = 16.8

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.94
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         I2
PLAT431_ALERT_2_C Short Inter HL..A Contact  I1     ..  Cl1     ..       3.53 Ang.

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.942
            Tmax scaled      0.566 Tmin scaled      0.320
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 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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S1. Comment

The title compound, (I), is a molecular salt (Fig. 1), with normal geometrical parameters for the organic component (Allen et al., 1995). The dihedral angle betwen the N1/C1—C5 and N2/N3/C6—C8 rings in the cation is 14.9 (2)°. The C1—N1—C5 bond angle of 124.2 (4)° is typically expanded due to the protonation of N1 (Wang et al., 1999).

The two I—Cl bond lengths (Table 1) in the ICl₂^- anion in (I) are significantly different, by some 0.149 (2) Å. Sometimes (Wang et al., 1999) the two bond lengths in the ICl₂^- anion are constrained to be the same by symmetry. However, in C₄H₁₂N₂·(ICl₂)₂, the difference between the two bonds of 0.22 Å (Romming, 1958) is even greater than seen here. In all cases, the Cl—I—Cl bond angle is close to linear, in accordance with the predictions of VSEPR or qualitative MO theory (Greenwood & Earnshaw, 1997).

In the crystal, the components interact by way of an intra/intermolecular bifurcated N—H···(N,Cl) hydrogen bond (Table 2). A weak C—H···Cl contact also occurs. The separation of I1 and Cl1ⁱⁱ (ii = x, 1/2 - y, z - 1/2) of 3.5275 (13) Å is some 0.2 Å less than the van der Waals separation of I and Cl of 3.73 Å. If this is considered to be a bonding interaction, [001] chains of ion-pairs are the result (Fig. 2).

Related literature

For background, see: Romming (1958); Greenwood & Earnshaw (1997); Wang et al. (1999). For reference structural data, see: Allen et al. (1995).

S2. Experimental

The title compound arose from the attempted methylation (with MeI) of 3-(2-pyridine)-pyrazole hydrochloride. Orange blocks of (I) were recoverd from the reaction. Their composition could not be determined on the basis of spectroscopic measurements and the single-crystal study was performed to identify the title compound. The mechanism of formation of (I) requires further investigation.

S3. Refinement

The N-bound H atom was located in a difference map and its position were freely refined with U_iso(H) = 1.2U_eq(N).

The C-bound H atoms were placed geometrically (C—H = 0.93–0.96 Å) and refined as riding with U_iso(H) = 1.2U_eq(carrier) or 1.5U_eq(methyl C). The methyl group was allowed to rotate, but not to tip, to best fit the electron density.

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. The molecular structure of (I) (50% displacement ellipsoids, arbitrary spheres for the H atoms, hydrogen bonds indicated by double dashed lines).
	Fig. 2. An [001] chain in (I) arising from N—H···Cl hydrogen bonds and possible I···Cl interactions. Symmetry code: (ii) x, 1/2 - y, z - 1/2.

2-(4-Iodo-1-methyl-1H-pyrazol-3-yl)-pyridinium dichloroiodide

Crystal data

C9H9IN3^+·Cl2I^−	F(000) = 896
Mr = 483.89	Dx = 2.241 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 5028 reflections
a = 8.4261 (4) Å	θ = 2.5–25.0°
b = 8.0183 (4) Å	µ = 4.74 mm^−1
c = 21.4692 (10) Å	T = 293 K
β = 98.604 (1)°	Block, orange
V = 1434.20 (12) Å^3	0.29 × 0.19 × 0.12 mm
Z = 4

Data collection

Bruker SMART 1000 CCD diffractometer	2523 independent reflections
Radiation source: fine-focus sealed tube	2256 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
ω scans	θmax = 25.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 1999)	h = −10→9
Tmin = 0.340, Tmax = 0.601	k = −7→9
8399 measured reflections	l = −25→25

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difmap and geom
R[F^2 > 2σ(F^2)] = 0.027	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.069	w = 1/[σ^2(Fo^2) + (0.0376P)^2 + 1.477P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.002
2523 reflections	Δρmax = 1.35 e Å^−3
150 parameters	Δρmin = −1.15 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: 0.0015 (2)

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	0.3644 (5)	0.1154 (6)	0.6860 (2)	0.0506 (11)
H1A	0.3397	0.0788	0.7246	0.061*
C2	0.2569 (6)	0.0942 (7)	0.6326 (2)	0.0626 (13)
H2	0.1585	0.0429	0.6339	0.075*
C3	0.2985 (6)	0.1513 (8)	0.5760 (2)	0.0641 (14)
H3	0.2264	0.1396	0.5390	0.077*
C4	0.4438 (6)	0.2244 (6)	0.5744 (2)	0.0526 (11)
H4	0.4704	0.2620	0.5363	0.063*
C5	0.5527 (5)	0.2428 (5)	0.62949 (19)	0.0361 (8)
C6	0.7118 (5)	0.3184 (5)	0.63513 (18)	0.0362 (8)
C7	0.8107 (5)	0.3601 (5)	0.59068 (18)	0.0401 (9)
C8	0.9446 (5)	0.4287 (5)	0.6250 (2)	0.0444 (10)
H8	1.0336	0.4701	0.6091	0.053*
C9	1.0300 (6)	0.4922 (8)	0.7394 (2)	0.0732 (17)
H9A	1.0087	0.4379	0.7771	0.110*
H9B	1.0117	0.6099	0.7426	0.110*
H9C	1.1395	0.4730	0.7340	0.110*
N1	0.5052 (4)	0.1889 (4)	0.68311 (17)	0.0395 (8)
H1	0.570 (6)	0.193 (6)	0.713 (2)	0.047*
N2	0.7823 (4)	0.3587 (4)	0.69377 (15)	0.0396 (8)
N3	0.9241 (4)	0.4256 (5)	0.68572 (16)	0.0437 (8)
I1	0.77668 (4)	0.33639 (5)	0.493422 (14)	0.06943 (16)
I2	0.37423 (3)	0.26801 (3)	0.869408 (12)	0.04377 (12)
Cl1	0.62989 (15)	0.1392 (2)	0.83096 (6)	0.0648 (3)
Cl2	0.13126 (16)	0.3839 (2)	0.90614 (6)	0.0740 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.045 (2)	0.060 (3)	0.049 (3)	−0.008 (2)	0.017 (2)	−0.002 (2)
C2	0.041 (2)	0.082 (4)	0.065 (3)	−0.024 (2)	0.008 (2)	−0.010 (3)
C3	0.049 (3)	0.092 (4)	0.048 (3)	−0.012 (3)	−0.002 (2)	−0.006 (3)
C4	0.050 (3)	0.070 (3)	0.036 (2)	−0.012 (2)	0.002 (2)	0.002 (2)
C5	0.040 (2)	0.035 (2)	0.033 (2)	−0.0018 (16)	0.0070 (16)	−0.0017 (16)
C6	0.041 (2)	0.0326 (19)	0.035 (2)	−0.0001 (16)	0.0065 (17)	0.0037 (16)
C7	0.044 (2)	0.047 (2)	0.030 (2)	−0.0020 (18)	0.0090 (17)	0.0002 (17)
C8	0.042 (2)	0.050 (2)	0.044 (2)	−0.0015 (19)	0.0155 (18)	0.0034 (19)
C9	0.056 (3)	0.112 (5)	0.048 (3)	−0.034 (3)	−0.006 (2)	−0.004 (3)
N1	0.0387 (19)	0.0448 (19)	0.0348 (18)	−0.0024 (15)	0.0047 (14)	0.0016 (15)
N2	0.0344 (17)	0.051 (2)	0.0330 (17)	−0.0054 (15)	0.0022 (14)	0.0047 (15)
N3	0.0359 (17)	0.055 (2)	0.0395 (19)	−0.0069 (16)	0.0026 (14)	0.0007 (16)
I1	0.0779 (3)	0.0981 (3)	0.03559 (19)	−0.0296 (2)	0.01929 (16)	−0.00920 (16)
I2	0.04535 (18)	0.04520 (18)	0.03920 (18)	−0.00216 (12)	0.00128 (12)	0.00301 (11)
Cl1	0.0531 (6)	0.0988 (10)	0.0434 (6)	0.0133 (6)	0.0107 (5)	0.0076 (6)
Cl2	0.0652 (8)	0.0984 (10)	0.0581 (8)	0.0316 (8)	0.0079 (6)	−0.0003 (7)

Geometric parameters (Å, º)

C1—N1	1.334 (6)	C7—C8	1.367 (6)
C1—C2	1.361 (7)	C7—I1	2.073 (4)
C1—H1A	0.9300	C8—N3	1.341 (5)
C2—C3	1.391 (7)	C8—H8	0.9300
C2—H2	0.9300	C9—N3	1.449 (6)
C3—C4	1.363 (7)	C9—H9A	0.9600
C3—H3	0.9300	C9—H9B	0.9600
C4—C5	1.392 (6)	C9—H9C	0.9600
C4—H4	0.9300	N1—H1	0.78 (5)
C5—N1	1.346 (5)	N2—N3	1.345 (4)
C5—C6	1.460 (6)	I2—Cl2	2.4819 (13)
C6—N2	1.348 (5)	I2—Cl1	2.6308 (13)
C6—C7	1.398 (5)
N1—C1—C2	120.0 (4)	C8—C7—I1	123.9 (3)
N1—C1—H1A	120.0	C6—C7—I1	131.2 (3)
C2—C1—H1A	120.0	N3—C8—C7	107.5 (4)
C1—C2—C3	118.1 (4)	N3—C8—H8	126.2
C1—C2—H2	120.9	C7—C8—H8	126.2
C3—C2—H2	120.9	N3—C9—H9A	109.5
C4—C3—C2	120.6 (4)	N3—C9—H9B	109.5
C4—C3—H3	119.7	H9A—C9—H9B	109.5
C2—C3—H3	119.7	N3—C9—H9C	109.5
C3—C4—C5	120.3 (4)	H9A—C9—H9C	109.5
C3—C4—H4	119.9	H9B—C9—H9C	109.5
C5—C4—H4	119.9	C1—N1—C5	124.2 (4)
N1—C5—C4	116.8 (4)	C1—N1—H1	120 (4)
N1—C5—C6	116.7 (4)	C5—N1—H1	116 (4)
C4—C5—C6	126.5 (4)	N3—N2—C6	104.6 (3)
N2—C6—C7	110.8 (3)	C8—N3—N2	112.2 (3)
N2—C6—C5	116.6 (3)	C8—N3—C9	127.8 (4)
C7—C6—C5	132.6 (4)	N2—N3—C9	119.9 (4)
C8—C7—C6	104.8 (3)	Cl2—I2—Cl1	178.86 (5)
N1—C1—C2—C3	−0.2 (8)	C5—C6—C7—I1	0.9 (7)
C1—C2—C3—C4	0.9 (9)	C6—C7—C8—N3	0.4 (5)
C2—C3—C4—C5	−0.1 (8)	I1—C7—C8—N3	179.1 (3)
C3—C4—C5—N1	−1.4 (7)	C2—C1—N1—C5	−1.4 (7)
C3—C4—C5—C6	−179.8 (5)	C4—C5—N1—C1	2.1 (6)
N1—C5—C6—N2	−13.3 (5)	C6—C5—N1—C1	−179.3 (4)
C4—C5—C6—N2	165.1 (4)	C7—C6—N2—N3	0.2 (4)
N1—C5—C6—C7	166.8 (4)	C5—C6—N2—N3	−179.7 (3)
C4—C5—C6—C7	−14.7 (7)	C7—C8—N3—N2	−0.3 (5)
N2—C6—C7—C8	−0.4 (5)	C7—C8—N3—C9	−176.6 (5)
C5—C6—C7—C8	179.4 (4)	C6—N2—N3—C8	0.1 (5)
N2—C6—C7—I1	−179.0 (3)	C6—N2—N3—C9	176.7 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···N2	0.78 (5)	2.32 (5)	2.683 (5)	109 (4)
N1—H1···Cl1	0.78 (5)	2.54 (5)	3.216 (4)	146 (5)
C2—H2···Cl2^i	0.93	2.77	3.664 (5)	160

Symmetry code: (i) −x, y−1/2, −z+3/2.