3,3'-Dimethyl-1,1'-(butane-1,4-di-yl)diimidazolium bis-(tetra-fluoro-borate).

The title compound, C(12)H(20)N(4) (2+)·2BF(4) (-), was prepared by the anion exchange of a dibromide ionic liquid with sodium tetra-fluoro-borate. The asymmetric unit contains one half of the imidazolium cation, which lies about an inversion centre at the mid-point of the central C-C bond of the linking butyl chain. The two planar imidazole rings (r.m.s. deviation = 0.0013 Å) are strictly parallel and separated by 2.625 (7) Å [vertical distance between the centroids of two imidazole rings], giving the mol-ecule a stepped appearance. In the crystal structure, inter-molecular C-H⋯F hydrogen bonds link the cations and anions, generating a three-dimensional network.

Related literature

For properties and applications of ionic liquids, see: Welton (1999 ▶); Olivier & Magna (2002 ▶); Nicholas et al. (2004 ▶); Yu et al.(2007 ▶). For dicationic ionic liquids, see: Leclercq et al. (2007 ▶); Payagala et al. (2007 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C12H20N4 2+·2BF4 −

M = 393.94

Monoclinic,

a = 5.195 (1) Å

b = 14.836 (3) Å

c = 11.790 (2) Å

β = 99.53 (3)°

V = 896.2 (3) Å3

Z = 2

Mo Kα radiation

μ = 0.15 mm−1

T = 293 K

0.30 × 0.10 × 0.10 mm

Data collection

Enraf–Nonius CAD-4 diffractometer

Absorption correction: ψ scan (North et al., 1968 ▶) T min = 0.958, T max = 0.986

1960 measured reflections

1763 independent reflections

1125 reflections with I > 2σ(I)

R int = 0.019

3 standard reflections every 200 reflections intensity decay: 1%

Refinement

R[F 2 > 2σ(F 2)] = 0.046

wR(F 2) = 0.155

S = 1.01

1763 reflections

119 parameters

H-atom parameters constrained

Δρmax = 0.20 e Å−3

Δρmin = −0.19 e Å−3

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ▶); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); 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.

Crystal structure: contains datablocks global, I. DOI: 10.1107/S160053681001593X/sj2792sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S160053681001593X/sj2792Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C12H20N42+·2BF4−	F(000) = 404
Mr = 393.94	Dx = 1.460 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 5.195 (1) Å	θ = 9–13°
b = 14.836 (3) Å	µ = 0.15 mm−1
c = 11.790 (2) Å	T = 293 K
β = 99.53 (3)°	Block, colorless
V = 896.2 (3) Å3	0.30 × 0.10 × 0.10 mm
Z = 2

Enraf–Nonius CAD-4 diffractometer	1125 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.019
graphite	θmax = 26.0°, θmin = 2.2°
ω/2θ scans	h = 0→6
Absorption correction: ψ scan (North et al., 1968)	k = 0→18
Tmin = 0.958, Tmax = 0.986	l = −14→14
1960 measured reflections	3 standard reflections every 200 reflections
1763 independent reflections	intensity decay: 1%

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.046	H-atom parameters constrained
wR(F2) = 0.155	w = 1/[σ2(Fo2) + (0.085P)2] where P = (Fo2 + 2Fc2)/3
S = 1.00	(Δ/σ)max < 0.001
1763 reflections	Δρmax = 0.20 e Å−3
119 parameters	Δρmin = −0.19 e Å−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.105 (11)

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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.

	x	y	z	Uiso*/Ueq
N1	0.9683 (4)	0.16123 (13)	0.88401 (17)	0.0515 (6)
C1	0.9656 (7)	0.24171 (19)	0.9557 (2)	0.0741 (9)
H1A	1.0716	0.2877	0.9296	0.111*
H1B	1.0336	0.2269	1.0343	0.111*
H1C	0.7897	0.2632	0.9504	0.111*
N2	1.0555 (4)	0.07197 (13)	0.75168 (16)	0.0469 (5)
C2	0.8390 (5)	0.08211 (17)	0.8951 (2)	0.0569 (7)
H2A	0.7331	0.0695	0.9494	0.068*
C3	0.8937 (5)	0.02637 (17)	0.8132 (2)	0.0549 (7)
H3A	0.8334	−0.0324	0.8002	0.066*
C4	1.0970 (5)	0.15315 (16)	0.7964 (2)	0.0488 (6)
H4A	1.1997	0.1975	0.7706	0.059*
C5	1.1592 (5)	0.03798 (17)	0.6510 (2)	0.0544 (7)
H5A	1.2626	−0.0156	0.6726	0.065*
H5B	1.2728	0.0832	0.6261	0.065*
C6	0.9446 (5)	0.01564 (17)	0.55255 (19)	0.0529 (7)
H6A	0.8367	0.0685	0.5327	0.063*
H6B	0.8352	−0.0315	0.5761	0.063*
B	0.5724 (6)	0.3204 (2)	0.6816 (3)	0.0585 (8)
F1	0.4655 (4)	0.37487 (13)	0.59228 (16)	0.0888 (7)
F2	0.5357 (3)	0.23068 (11)	0.65187 (17)	0.0857 (6)
F3	0.4510 (3)	0.33750 (12)	0.77629 (15)	0.0795 (6)
F4	0.8355 (3)	0.33695 (11)	0.70959 (16)	0.0822 (6)

	U11	U22	U33	U12	U13	U23
N1	0.0566 (13)	0.0546 (13)	0.0433 (11)	0.0030 (10)	0.0081 (10)	−0.0032 (9)
C1	0.090 (2)	0.0667 (19)	0.0645 (17)	0.0065 (16)	0.0092 (16)	−0.0171 (15)
N2	0.0506 (12)	0.0452 (11)	0.0472 (10)	−0.0001 (9)	0.0144 (9)	0.0006 (9)
C2	0.0621 (17)	0.0584 (16)	0.0546 (14)	−0.0007 (13)	0.0224 (13)	0.0061 (12)
C3	0.0637 (17)	0.0472 (14)	0.0585 (15)	−0.0084 (12)	0.0233 (13)	0.0030 (12)
C4	0.0503 (14)	0.0465 (14)	0.0503 (13)	−0.0034 (11)	0.0103 (11)	0.0029 (11)
C5	0.0552 (15)	0.0531 (14)	0.0592 (15)	0.0022 (12)	0.0221 (12)	−0.0017 (12)
C6	0.0595 (16)	0.0468 (14)	0.0565 (15)	−0.0010 (11)	0.0216 (13)	−0.0020 (11)
B	0.0488 (17)	0.0561 (18)	0.075 (2)	−0.0012 (14)	0.0230 (15)	0.0105 (16)
F1	0.0884 (14)	0.0919 (13)	0.0900 (13)	0.0186 (10)	0.0262 (10)	0.0321 (11)
F2	0.0812 (12)	0.0622 (11)	0.1163 (15)	−0.0155 (9)	0.0239 (11)	−0.0018 (10)
F3	0.0691 (11)	0.0908 (13)	0.0856 (12)	0.0016 (9)	0.0330 (9)	0.0107 (9)
F4	0.0492 (10)	0.0840 (13)	0.1164 (15)	−0.0131 (9)	0.0228 (9)	0.0000 (10)

N1—C4	1.326 (3)	C4—H4A	0.9300
N1—C2	1.369 (3)	C5—C6	1.507 (3)
N1—C1	1.465 (3)	C5—H5A	0.9700
C1—H1A	0.9600	C5—H5B	0.9700
C1—H1B	0.9600	C6—C6i	1.522 (4)
C1—H1C	0.9600	C6—H6A	0.9700
N2—C4	1.318 (3)	C6—H6B	0.9700
N2—C3	1.375 (3)	B—F1	1.370 (4)
N2—C5	1.472 (3)	B—F4	1.374 (3)
C2—C3	1.337 (3)	B—F2	1.381 (4)
C2—H2A	0.9300	B—F3	1.394 (4)
C3—H3A	0.9300
C4—N1—C2	108.4 (2)	N1—C4—H4A	125.5
C4—N1—C1	125.3 (2)	N2—C5—C6	112.0 (2)
C2—N1—C1	126.3 (2)	N2—C5—H5A	109.2
N1—C1—H1A	109.5	C6—C5—H5A	109.2
N1—C1—H1B	109.5	N2—C5—H5B	109.2
H1A—C1—H1B	109.5	C6—C5—H5B	109.2
N1—C1—H1C	109.5	H5A—C5—H5B	107.9
H1A—C1—H1C	109.5	C5—C6—C6i	111.3 (3)
H1B—C1—H1C	109.5	C5—C6—H6A	109.4
C4—N2—C3	108.2 (2)	C6i—C6—H6A	109.4
C4—N2—C5	125.3 (2)	C5—C6—H6B	109.4
C3—N2—C5	126.4 (2)	C6i—C6—H6B	109.4
C3—C2—N1	107.2 (2)	H6A—C6—H6B	108.0
C3—C2—H2A	126.4	F1—B—F4	109.8 (2)
N1—C2—H2A	126.4	F1—B—F2	110.6 (3)
C2—C3—N2	107.3 (2)	F4—B—F2	108.9 (2)
C2—C3—H3A	126.3	F1—B—F3	109.2 (2)
N2—C3—H3A	126.3	F4—B—F3	109.8 (3)
N2—C4—N1	108.9 (2)	F2—B—F3	108.5 (2)
N2—C4—H4A	125.5
C4—N1—C2—C3	0.4 (3)	C5—N2—C4—N1	178.3 (2)
C1—N1—C2—C3	−179.9 (2)	C2—N1—C4—N2	−0.3 (3)
N1—C2—C3—N2	−0.3 (3)	C1—N1—C4—N2	−180.0 (2)
C4—N2—C3—C2	0.2 (3)	C4—N2—C5—C6	−117.0 (3)
C5—N2—C3—C2	−178.0 (2)	C3—N2—C5—C6	60.9 (3)
C3—N2—C4—N1	0.1 (3)	N2—C5—C6—C6i	177.6 (2)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2A···F1ii	0.93	2.50	3.328 (3)	149
C3—H3A···F3iii	0.93	2.51	3.398 (3)	161
C4—H4A···F2iv	0.93	2.46	3.272 (3)	146
C4—H4A···F3iv	0.93	2.45	3.326 (3)	158

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2A⋯F1i	0.93	2.50	3.328 (3)	149
C3—H3A⋯F3ii	0.93	2.51	3.398 (3)	161
C4—H4A⋯F2iii	0.93	2.46	3.272 (3)	146
C4—H4A⋯F3iii	0.93	2.45	3.326 (3)	158

Symmetry codes: (i) ; (ii) ; (iii) .