1,4-Dimethyl-1,4-diazo­nia­bicyclo­[2.2.2]octane diiodide acetonitrile solvate

In the crystal structure of the title compound, C₈H₁₈N₂²⁺·2I⁻·CH₃CN, the dication lies on a mirror plane containing the mol­ecular dication threefold axis. The structure displays C—H...I inter­actions between H atoms of the 1,4-dimethyl-1,4-diazo­nia­bicyclo­[2.2.2]octane dication and the iodide anions. The H...I distances are in the range 2.96–3.18 (4) Å. The dications pack forming channels along the b axis, which contain the iodide anions and acetonitrile solvent mol­ecules.

S1. Comment

The 1,4-dimethyl-1,4-diazaniabicyclo[2.2.2]octane dication has been used as a non-coordinating divalent cation in salts of mono- and polynuclear transition metal complexes, and as the counter-ion for organic charge transfer salts. Several structures have been determined that contain the 1,4-dimethyl-1,4-diazaniabicyclo[2.2.2]octane dication, including transition metal complex salts (Christoph & Goedken, 1973; Bond & Willett, 1991), silicate clusters (Breu et al., 2004; Wiebcke et al., 1994) and calixarenes (Mansikkamaki et al., 2002, 2004, 2005), but only one simple salt of any diquaternary alkyl diazabicyclooctane dication has been determined with octadecyl n-alkyl groups [Cambridge Structural Database (Allen, 2002) refcode QETLEG (Ishioka et al., 2000)]. We report here the structure of the title compound (I), an acetonitrile solvate of 1,4-dimethyl-1,4-diazaniabicyclo[2.2.2]octane diiodide.

The structure of (I) is presented in Fig. 1. The asymmetric unit consists of part of one 1,4-dimethyl-1,4-diazaniabicyclo[2.2.2]octane dication and two iodide counter-ions. Atoms C1, C2, C5, C6, N1 and N2 all lie on special positions with mirror symmetry. Atoms C3 and C4 are on general positions. The mirror plane generates the third ethylene strap of the dication moiety. Both of the two unique I atoms are located on special positions with mirror site symmetry and near the methyl groups of the dication. Additionally, a disordered solvent molecule of acetonitrile is present.

Molecules of (I) show intermolecular C—H···I interactions between the H atoms of the dication and the I atoms (Table 1). Fig. 2 shows a view of these interactions. Atoms I1 and I2 each participate in three unique C—H···I interactions with the dication. Atom I1 also participates in a C—H···I interaction with the acetonitrile solvent molecule. In the overall structure, I1 and I2 are each within van der Waals contact of six H atoms. The I atoms are not within van der Waals contact of H1A, H1B, H2A and H2B of the ethylene strap that lies on a mirror plane. Note that as the positions of the H atoms bonded to the disordered acetonitrile solvate molecule were constrained as riding atoms, the C8—H8B···I1 hydrogen-bonding interaction listed in Table 1 may be suspect.

These C—H···I interactions are considered non-classical hydrogen bonds, as they involve combinations of weak donors (C—H) with strong acceptors (I⁻). Comparison of the normalized C—H···I distances of the C—H···I interactions in the structure of I (R_HX = 0.94–1.01) with the mean normalized distances of C—H···I interactions in the hydrogen-bonding analysis of Brammer et al. (2001) (R_HX = 0.982) suggests these interactions are typical of C—H···I hydrogen bonding. The angular relation of the C—H···I interactions [C—H···I = 152.0–159 (3)°] are also reasonable for C—H···I hydrogen bonding. The proximity of the C-atom donors that form these C—H···I interactions to the positively charged N atoms perhaps enhance their ability to participate in hydrogen bonding (Palusiak et al., 2005).

A packing diagram of the structure (Fig. 3) reveals that the dication moieties as well as the iodide anions and acetonitrile solvate molecules are packed in layers perpendicular to the b axis at 0.25b and 0.75b. Perpendicular to the layers, the dication moieties form roughly hexagonal channels, though no crystallographic three- or sixfold symmetry is present. Iodide anions and acetonitrile solvent molecules fill these channels in the structure.

S2. Experimental

The sample of 1,4-dimethyl-1,4-diazaniabicyclo[2.2.2]octane diiodide was synthesized by the method used to make the analogous N-methylpyridinium iodide (Wiley et al., 1972). Crystals of (I) were grown by slow evaporation from a solution containing 1,4-dimethyl-1,4-diazaniabicyclo[2.2.2]octane diiodide, 3',4'-dibutyl-5,5"-bis(dicyanomethylene)-5,5"-dihydro- 2,2':5',2"-terthiophene, water and acetonitrile.

S3. Refinement

The coordinates of all H atoms were refined, except atom H8A, H8B and H8C. These H atoms were placed in idealized positions and constrained to ride on their parent atoms, with C—H distances of 0.98 Å and U_iso(H) values of 1.5U_eq(C). Attempts to refine the coordinates of the H atoms on the disordered acetonitrile molecule were unsuccessful. The acetonitrile solvent molecule is disordered over a mirror plane. Refinement of this disorder required restraint of the N3—C7 bond length at 1.136 (3) Å, restraint of the C7—C8 bond length at 1.470 (3) Å, and restraint of the total distance between N3 and C8 at 2.606 (3) Å.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. A view of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Fig. 2. A view of the structure of (I), showing the intermolecular C—H···I interactions. Only H atoms participating in C—H···I interactions are shown with labels. I atoms are labeled with symmetry codes identifying the location relative to the dication asymmetric unit. [Symmetry codes: (i) 1 − x, −1/2 + y, 1 − z; (ii) 1/2 − x, 1 − y, −1/2 + z; (iii) x, y − 1, z − 1; (iv) x, y, z − 1.]

(I)

Crystal data

C8H18N2^2+·2I^−·C2H3N	F(000) = 832
Mr = 437.10	Dx = 1.846 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2ac 2n	Cell parameters from 2300 reflections
a = 20.174 (3) Å	θ = 2.0–25.0°
b = 7.343 (1) Å	µ = 3.98 mm^−1
c = 10.6140 (14) Å	T = 173 K
V = 1572.3 (4) Å^3	Plate, yellow
Z = 4	0.25 × 0.04 × 0.04 mm

Data collection

Siemens SMART platform CCD diffractometer	1508 independent reflections
Radiation source: normal-focus sealed tube	1297 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
ω scans	θmax = 25.0°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Blessing, 1995)	h = −22→24
Tmin = 0.592, Tmax = 0.85	k = −8→8
11185 measured reflections	l = −12→12

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)] = 0.029	Hydrogen site location: difference Fourier map
wR(F^2) = 0.045	H atoms treated by a mixture of independent and constrained refinement
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0111P)^2 + 1.9299P] where P = (Fo^2 + 2Fc^2)/3
1508 reflections	(Δ/σ)max = 0.001
121 parameters	Δρmax = 0.50 e Å^−3
3 restraints	Δρmin = −0.59 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	Occ. (<1)
I1	0.446123 (18)	0.7500	0.77407 (3)	0.03368 (12)
I2	0.17904 (2)	0.7500	0.97122 (4)	0.03812 (12)
N1	0.27879 (19)	0.2500	0.0689 (4)	0.0269 (10)
N2	0.39204 (19)	0.2500	−0.0362 (4)	0.0232 (9)
C1	0.2711 (3)	0.2500	−0.0732 (5)	0.0298 (13)
H1A	0.2439 (17)	0.139 (5)	−0.096 (3)	0.041 (11)*
H2A	0.3443 (17)	0.139 (5)	−0.183 (3)	0.035 (11)*
C2	0.3391 (3)	0.2500	−0.1352 (5)	0.0361 (15)
C3	0.31703 (18)	0.4167 (5)	0.1081 (4)	0.0280 (9)
H3A	0.3235 (17)	0.413 (5)	0.201 (4)	0.045 (12)*
H3B	0.2924 (15)	0.524 (5)	0.086 (3)	0.022 (9)*
C4	0.3846 (2)	0.4163 (6)	0.0454 (4)	0.0312 (9)
H4A	0.4181 (17)	0.412 (5)	0.103 (3)	0.036 (11)*
H4B	0.3891 (18)	0.516 (6)	−0.012 (3)	0.045 (12)*
C5	0.2114 (3)	0.2500	0.1304 (7)	0.0374 (15)
H5A	0.1876 (16)	0.138 (5)	0.102 (3)	0.034 (10)*
H5B	0.220 (3)	0.2500	0.220 (5)	0.043 (17)*
C6	0.4589 (3)	0.2500	−0.0984 (6)	0.0309 (14)
H6A	0.4601 (17)	0.147 (5)	−0.151 (3)	0.038 (11)*
H6B	0.491 (3)	0.2500	−0.038 (5)	0.028 (15)*
N3	0.1149 (3)	0.243 (4)	0.7302 (4)	0.0453 (14)	0.50
C7	0.0797 (3)	0.265 (3)	0.8120 (5)	0.0453 (14)	0.50
C8	0.0325 (3)	0.3002 (10)	0.9146 (6)	0.0453 (14)	0.50
H8A	0.0157	0.4250	0.9076	0.068*	0.50
H8B	0.0549	0.2851	0.9959	0.068*	0.50
H8C	−0.0045	0.2142	0.9088	0.068*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.0330 (2)	0.0369 (2)	0.03105 (19)	0.000	−0.00545 (17)	0.000
I2	0.0429 (2)	0.0350 (2)	0.0365 (2)	0.000	−0.00193 (19)	0.000
N1	0.016 (2)	0.034 (3)	0.031 (3)	0.000	0.0019 (19)	0.000
N2	0.021 (2)	0.025 (2)	0.024 (2)	0.000	−0.0001 (19)	0.000
C1	0.027 (3)	0.035 (4)	0.028 (3)	0.000	−0.005 (3)	0.000
C2	0.036 (4)	0.046 (4)	0.026 (3)	0.000	−0.007 (3)	0.000
C3	0.027 (2)	0.021 (2)	0.036 (2)	0.0017 (18)	0.0003 (19)	−0.0055 (18)
C4	0.030 (2)	0.025 (2)	0.039 (2)	−0.0035 (18)	0.006 (2)	−0.0074 (19)
C5	0.023 (3)	0.034 (4)	0.056 (4)	0.000	0.010 (3)	0.000
C6	0.030 (4)	0.033 (4)	0.030 (3)	0.000	0.005 (3)	0.000
N3	0.052 (3)	0.039 (4)	0.044 (2)	0.004 (4)	−0.0048 (17)	0.009 (4)
C7	0.052 (3)	0.039 (4)	0.044 (2)	0.004 (4)	−0.0048 (17)	0.009 (4)
C8	0.052 (3)	0.039 (4)	0.044 (2)	0.004 (4)	−0.0048 (17)	0.009 (4)

Geometric parameters (Å, º)

N1—C3	1.505 (4)	C3—H3B	0.96 (3)
N1—C3^i	1.505 (4)	C4—H4A	0.91 (3)
N1—C5	1.507 (7)	C4—H4B	0.96 (4)
N1—C1	1.517 (7)	C5—H5A	1.00 (3)
N2—C2	1.499 (7)	C5—H5B	0.97 (5)
N2—C6	1.501 (7)	C6—H6A	0.94 (3)
N2—C4	1.505 (4)	C6—H6B	0.92 (5)
N2—C4^i	1.505 (4)	N3—C7	1.133 (3)
C1—C2	1.520 (8)	C7—C8	1.470 (3)
C1—H1A	1.01 (3)	C8—H8A	0.9800
C2—H2A	0.97 (3)	C8—H8B	0.9800
C3—C4	1.516 (5)	C8—H8C	0.9800
C3—H3A	0.99 (4)
C3—N1—C3^i	108.8 (4)	N1—C3—H3A	109 (2)
C3—N1—C5	110.0 (3)	C4—C3—H3A	108 (2)
C3^i—N1—C5	110.0 (3)	N1—C3—H3B	109.6 (19)
C3—N1—C1	109.1 (3)	C4—C3—H3B	111.1 (19)
C3^i—N1—C1	109.1 (3)	H3A—C3—H3B	109 (3)
C5—N1—C1	109.8 (4)	N2—C4—C3	110.1 (3)
C2—N2—C6	109.4 (4)	N2—C4—H4A	106 (2)
C2—N2—C4	109.4 (3)	C3—C4—H4A	112 (2)
C6—N2—C4	110.1 (3)	N2—C4—H4B	104 (2)
C2—N2—C4^i	109.4 (3)	C3—C4—H4B	111 (2)
C6—N2—C4^i	110.1 (3)	H4A—C4—H4B	113 (3)
C4—N2—C4^i	108.5 (4)	N1—C5—H5A	108 (2)
N1—C1—C2	109.8 (4)	N1—C5—H5B	106 (3)
N1—C1—H1A	107 (2)	H5A—C5—H5B	112 (3)
C2—C1—H1A	113 (2)	N2—C6—H6A	107 (2)
N2—C2—C1	109.8 (4)	N2—C6—H6B	109 (3)
N2—C2—H2A	107 (2)	H6A—C6—H6B	114 (3)
C1—C2—H2A	109 (2)	N3—C7—C8	177 (2)
N1—C3—C4	109.8 (3)
C3—N1—C1—C2	59.4 (2)	C3^i—N1—C3—C4	59.6 (5)
C3^i—N1—C1—C2	−59.4 (2)	C5—N1—C3—C4	−179.7 (4)
C5—N1—C1—C2	180.0	C1—N1—C3—C4	−59.2 (4)
C6—N2—C2—C1	180.0	C2—N2—C4—C3	59.6 (5)
C4—N2—C2—C1	−59.4 (3)	C6—N2—C4—C3	179.9 (4)
C4^i—N2—C2—C1	59.4 (3)	C4^i—N2—C4—C3	−59.6 (5)
N1—C1—C2—N2	0.0	N1—C3—C4—N2	0.1 (5)

Symmetry code: (i) x, −y+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3A···I2^ii	0.99 (4)	3.11 (4)	4.045 (4)	157 (3)
C4—H4B···I1^iii	0.96 (4)	3.07 (4)	3.980 (4)	159 (3)
C6—H6A···I1^iv	0.94 (3)	3.04 (4)	3.921 (2)	157 (3)
C6—H6B···I1^v	0.92 (5)	3.07 (5)	3.940 (7)	159 (4)
C8—H8B···I1^vi	0.98	2.96	3.857 (7)	152
C3—H3B···I2^iii	0.96 (3)	3.08 (3)	3.981 (4)	157 (2)
C5—H5A···I2^iv	1.00 (3)	3.18 (4)	4.094 (3)	154 (2)

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