Bis(2-chloro-N-methyl­pyridinium) iodide triiodide

The title compound, 2C₆H₇ClN⁺·I^-·I₃^-, crystallizes with undulating layers of chains containing alternate iodide and triiodide anions formed from iodine and the heterocyclic iodide salt.

S1. Comment

Pyridine–iodine compounds are often an interesting starting point for studies of donor–acceptor complexes and salts (Zingaro et al., 1951; Kleinberg et al., 1953; Reid & Mulliken, 1954). N-Alkyl-substituted pyridines lose the possibility to coordinate through the nitrogen centre and, therefore, the reaction of 2-chloro-N-methylpyridinium iodide with iodine leads to a new iodide salt of a pyridine. The resulting product is a mixed iodide triiodide, (I). \scheme

Many crystal structures of pyridinium as well as triiodide salts are registered in the Crystal Structural Database (Allen & Kennard, 1993), but only 24 structures containing iodide triiodide are known previously. The structure of (I) exhibits a nearly linear triiodide with similar distances I—I of 2.921 (1) and 2.945 (1) Å, and an angle I—I—I of 177.06 (1)°. The I4 atoms with distances I4···I3ⁱ = 4.260 (1) Å as well as I4···I2ⁱⁱ = 4.103 (1) Å and angles I4···I3ⁱ—I1ⁱ = 161.68 (2)° as well as I4···I2ⁱⁱ—I1ⁱⁱ = 162.56 (2)° are arranged in undulating chains of alternate iodide and triiodide anions along the b axis, which are generated by a 2₁ screw axis [symmetry codes: (i) 1 + x, 1/2 − y, −1/2 + z; (ii) −x, −y, −1 − z]. These parallel chains form layers separated by 2-chloro-N-methylpyridinium cations exhibiting bonds and angles similar to those in the salts N-methylpyridinium iodide (Lalancette et al., 1978) and N-ethylpyridinium triiodide (Christie et al., 1991). The chlorine substituent in (I) shows an additional weak coordination to the triiodide anion with distances Cl2···I1 = 3.889 (2) and Cl2···I2 = 3.637 (2) Å.

S2. Experimental

A solution of 2-chloro-N-methylpyridinium iodide (0.128 g, 0.5 mmol) in 50 ml trichloromethane was covered with a filter and a solution of iodide (0.5 mM) in n-pentane added from above. After 10 d, dark-red prisms had grown.

S3. Refinement

All H atom were located from the difference map and placed in idealized positions using a riding model with distances C—H_phenyl = 0.95 Å and C—H_methyl = 0.98 Å. The torsion of the methyl H atoms and the isotropic displacement parameters of all H atoms were refined.

Computing details

Data collection: XSCANS (Siemens, 1994); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

(I)

Crystal data

2C6H7ClN^+·I^−·I3^−	F(000) = 1384
Mr = 764.75	Dx = 2.556 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.2902 (7) Å	Cell parameters from 84 reflections
b = 23.644 (2) Å	θ = 10–15.5°
c = 12.0207 (9) Å	µ = 6.53 mm^−1
β = 106.448 (6)°	T = 150 K
V = 1987.2 (3) Å^3	Prism, red
Z = 4	0.35 × 0.20 × 0.15 mm

Data collection

Siemens P4 four-circle diffractometer	4004 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.030
Graphite monochromator	θmax = 28.0°, θmin = 2.0°
ω scans	h = −2→9
Absorption correction: numerical (SHELXTL/PC; Sheldrick, 1997)	k = −2→31
Tmin = 0.300, Tmax = 0.474	l = −15→15
7177 measured reflections	4 standard reflections every 100 reflections
4780 independent reflections	intensity decay: <5%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.036	H-atom parameters constrained
wR(F^2) = 0.085	w = 1/[σ^2(Fo^2) + (0.0342P)^2 + 9.6004P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max < 0.001
4780 reflections	Δρmax = 0.87 e Å^−3
184 parameters	Δρmin = −1.41 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: 0.00156 (11)

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
I1	−0.35210 (5)	0.066901 (16)	−0.22275 (3)	0.02481 (10)
I2	−0.16630 (6)	−0.037187 (17)	−0.26476 (3)	0.02855 (11)
I3	−0.52092 (6)	0.174936 (17)	−0.17959 (3)	0.02922 (11)
I4	0.07353 (5)	0.200539 (18)	−0.64954 (3)	0.02882 (11)
Cl1	−0.2811 (3)	0.04391 (7)	−0.57694 (16)	0.0424 (4)
N1	−0.0928 (7)	0.1221 (2)	−0.4354 (4)	0.0255 (10)
C1	−0.2611 (9)	0.1075 (2)	−0.5079 (5)	0.0246 (11)
C2	−0.4185 (8)	0.1420 (3)	−0.5281 (5)	0.0272 (12)
H2	−0.5370	0.1308	−0.5802	0.033*
C3	−0.4015 (9)	0.1929 (3)	−0.4717 (5)	0.0298 (13)
H3	−0.5084	0.2175	−0.4837	0.036*
C4	−0.2277 (9)	0.2078 (3)	−0.3976 (5)	0.0296 (13)
H4	−0.2140	0.2431	−0.3583	0.036*
C5	−0.0755 (9)	0.1726 (3)	−0.3800 (5)	0.0311 (13)
H5	0.0442	0.1834	−0.3286	0.037*
C7	0.0819 (9)	0.0855 (3)	−0.4150 (6)	0.0297 (13)
H7A	0.1851	0.1015	−0.3519	0.045*
H7B	0.1227	0.0838	−0.4859	0.045*
H7C	0.0521	0.0473	−0.3938	0.045*
Cl2	0.1897 (2)	0.04991 (7)	−0.06470 (14)	0.0337 (3)
N2	0.2448 (7)	0.1430 (2)	0.0586 (4)	0.0223 (9)
C11	0.3278 (8)	0.0956 (3)	0.0337 (5)	0.0253 (11)
C12	0.5177 (8)	0.0842 (3)	0.0852 (5)	0.0277 (12)
H12	0.5746	0.0506	0.0670	0.033*
C13	0.6240 (9)	0.1225 (3)	0.1637 (5)	0.0305 (13)
H13	0.7555	0.1155	0.2006	0.037*
C14	0.5388 (9)	0.1710 (3)	0.1883 (5)	0.0280 (12)
H14	0.6114	0.1980	0.2414	0.034*
C15	0.3496 (9)	0.1800 (2)	0.1361 (5)	0.0249 (11)
H15	0.2902	0.2131	0.1545	0.030*
C17	0.0397 (9)	0.1547 (3)	0.0053 (6)	0.0360 (14)
H17A	−0.0371	0.1256	0.0290	0.054*
H17B	0.0123	0.1545	−0.0794	0.054*
H17C	0.0079	0.1919	0.0308	0.054*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.02228 (18)	0.0283 (2)	0.02338 (17)	−0.00284 (14)	0.00572 (13)	0.00223 (14)
I2	0.0298 (2)	0.0279 (2)	0.03022 (19)	0.00124 (15)	0.01224 (15)	−0.00025 (15)
I3	0.0339 (2)	0.0247 (2)	0.0304 (2)	0.00222 (16)	0.01135 (16)	0.00251 (15)
I4	0.02156 (18)	0.0345 (2)	0.02962 (19)	0.00192 (16)	0.00597 (14)	0.00466 (16)
Cl1	0.0483 (10)	0.0292 (8)	0.0450 (9)	0.0060 (7)	0.0054 (8)	−0.0087 (7)
N1	0.026 (2)	0.027 (2)	0.025 (2)	0.000 (2)	0.0103 (19)	0.0027 (19)
C1	0.031 (3)	0.022 (3)	0.022 (2)	0.001 (2)	0.008 (2)	0.000 (2)
C2	0.025 (3)	0.031 (3)	0.024 (3)	0.003 (2)	0.003 (2)	0.001 (2)
C3	0.029 (3)	0.028 (3)	0.036 (3)	0.009 (2)	0.015 (2)	0.000 (2)
C4	0.033 (3)	0.025 (3)	0.033 (3)	0.001 (2)	0.012 (3)	−0.004 (2)
C5	0.027 (3)	0.036 (3)	0.029 (3)	−0.001 (3)	0.006 (2)	−0.003 (3)
C7	0.035 (3)	0.021 (3)	0.038 (3)	0.007 (2)	0.018 (3)	0.007 (2)
Cl2	0.0322 (7)	0.0300 (7)	0.0361 (8)	−0.0025 (6)	0.0049 (6)	−0.0097 (6)
N2	0.020 (2)	0.025 (2)	0.023 (2)	0.0005 (19)	0.0072 (18)	0.0047 (19)
C11	0.028 (3)	0.024 (3)	0.025 (3)	−0.004 (2)	0.009 (2)	−0.001 (2)
C12	0.024 (3)	0.024 (3)	0.037 (3)	0.000 (2)	0.012 (2)	0.003 (2)
C13	0.025 (3)	0.039 (3)	0.028 (3)	−0.004 (3)	0.008 (2)	0.007 (3)
C14	0.031 (3)	0.030 (3)	0.025 (3)	−0.011 (2)	0.010 (2)	−0.005 (2)
C15	0.031 (3)	0.017 (3)	0.030 (3)	−0.008 (2)	0.015 (2)	−0.001 (2)
C17	0.025 (3)	0.035 (3)	0.045 (4)	0.006 (3)	0.005 (3)	0.002 (3)

Geometric parameters (Å, º)

I1—I2	2.9213 (6)	C4—C5	1.355 (9)
I1—I3	2.9446 (6)	Cl2—C11	1.704 (6)
Cl1—C1	1.704 (6)	N2—C15	1.347 (7)
N1—C1	1.334 (8)	N2—C11	1.347 (8)
N1—C5	1.356 (8)	N2—C17	1.477 (7)
N1—C7	1.501 (7)	C11—C12	1.373 (8)
C1—C2	1.372 (8)	C12—C13	1.377 (9)
C2—C3	1.369 (9)	C13—C14	1.375 (9)
C3—C4	1.374 (9)	C14—C15	1.361 (9)
I2—I1—I3	177.055 (18)	C15—N2—C11	119.5 (5)
C1—N1—C5	119.3 (5)	C15—N2—C17	118.9 (5)
C1—N1—C7	122.6 (5)	C11—N2—C17	121.5 (5)
C5—N1—C7	118.1 (5)	N2—C11—C12	121.4 (5)
N1—C1—C2	122.1 (5)	N2—C11—Cl2	117.8 (4)
N1—C1—Cl1	118.8 (5)	C12—C11—Cl2	120.8 (5)
C2—C1—Cl1	119.1 (5)	C11—C12—C13	118.7 (6)
C3—C2—C1	118.7 (6)	C14—C13—C12	119.6 (6)
C2—C3—C4	119.0 (6)	C15—C14—C13	119.5 (6)
C5—C4—C3	120.5 (6)	N2—C15—C14	121.2 (6)
C4—C5—N1	120.4 (6)
C5—N1—C1—C2	−0.3 (9)	C15—N2—C11—C12	−0.4 (8)
C7—N1—C1—C2	−178.3 (5)	C17—N2—C11—C12	−178.7 (6)
C5—N1—C1—Cl1	−180.0 (4)	C15—N2—C11—Cl2	180.0 (4)
C7—N1—C1—Cl1	2.0 (7)	C17—N2—C11—Cl2	1.7 (7)
N1—C1—C2—C3	−0.1 (9)	N2—C11—C12—C13	−0.1 (9)
Cl1—C1—C2—C3	179.6 (5)	Cl2—C11—C12—C13	179.6 (4)
C1—C2—C3—C4	0.4 (9)	C11—C12—C13—C14	−0.2 (9)
C2—C3—C4—C5	−0.3 (9)	C12—C13—C14—C15	1.0 (9)
C3—C4—C5—N1	−0.1 (10)	C11—N2—C15—C14	1.1 (8)
C1—N1—C5—C4	0.4 (9)	C17—N2—C15—C14	179.5 (5)
C7—N1—C5—C4	178.4 (6)	C13—C14—C15—N2	−1.5 (9)