Bis(1,3-dimethyl-1H-imidazolium) hexa-fluoro-silicate: the second monoclinic polymorph.

The title compound, 2C5H9N2 (+)·SiF6 (2-), (I), crystallized as a new polymorph, different from the previously reported one (Ia) [Light et al. (2007 ▶) private communication (refcode: NIQFAV). CCDC, Cambridge, England]. The symmetry [space groups P21/n for (I) and C2/c for(Ia)] and crystal packing patterns are markedly different for this pair of polymorphs. In (I), all imidazolium cations in the lattice are nearly parallel to each other, whereas a herringbone arrangement can be found in (Ia). In (I), each SiF6 (2-) dianion forms four short C-H⋯F contacts with adjacent C5H9N2 (+) cations, resulting in the formation of layers parallel to the ac plane. In (Ia), the C-H⋯F contacts are generally longer and result in the formation of layers along the bc plane.

Related literature

For the structure of the previously reported polymorph of (I) and its solvatomorph 6C5H9N2 +·3SiF6 2−·CH3OH, see: Light et al. (2007 ▶) and Tian et al. (2013 ▶), respectively. For an overview of polymorphism, see: Bernstein (2002 ▶); Linden (2011 ▶). For the practical importance of sterically non-hindered 1,3-dialkyl-1H-imidazolium salts with perfluoro anions of the main-group elements in the preparation of Arduengo carbene adducts, see: Tian et al. (2012 ▶). For graph-set notation, see: Etter et al. (1990 ▶); Bernstein et al. (1995 ▶); Grell et al. (1999 ▶).

Experimental

Crystal data

2C5H9N2+·SiF6 2−

M = 336.38

Monoclinic,

a = 8.2240 (8) Å

b = 9.7901 (9) Å

c = 8.7753 (9) Å

β = 90.106 (1)°

V = 706.53 (12) Å3

Z = 2

Mo Kα radiation

μ = 0.23 mm−1

T = 296 K

0.40 × 0.39 × 0.05 mm

Data collection

Bruker SMART APEXII diffractometer

Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T min = 0.913, T max = 0.988

3670 measured reflections

1373 independent reflections

1228 reflections with I > 2σ(I)

R int = 0.020

Refinement

R[F 2 > 2σ(F 2)] = 0.028

wR(F 2) = 0.081

S = 1.09

1373 reflections

134 parameters

All H-atom parameters refined

Δρmax = 0.18 e Å−3

Δρmin = −0.22 e Å−3

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and OLEX2 (Dolomanov et al., 2009 ▶); software used to prepare material for publication: SHELXTL and OLEX2.

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S1600536813018242/ld2107sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813018242/ld2107Isup2.hkl

Click here for additional data file.

Supplementary material file. DOI: 10.1107/S1600536813018242/ld2107Isup3.cdx

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

2C5H9N2+·SiF62−	F(000) = 348
Mr = 336.38	Dx = 1.581 Mg m−3
Monoclinic, P21/n	Melting point: 550 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 8.2240 (8) Å	Cell parameters from 3479 reflections
b = 9.7901 (9) Å	θ = 2.3–28.3°
c = 8.7753 (9) Å	µ = 0.23 mm−1
β = 90.106 (1)°	T = 296 K
V = 706.53 (12) Å3	Plate, colourless
Z = 2	0.40 × 0.39 × 0.05 mm

Bruker SMART APEXII diffractometer	1373 independent reflections
Radiation source: fine-focus sealed tube	1228 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
Detector resolution: 8.333 pixels mm-1	θmax = 26.0°, θmin = 3.2°
phi and ω scans	h = −10→10
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −12→9
Tmin = 0.913, Tmax = 0.988	l = −10→8
3670 measured reflections

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028	All H-atom parameters refined
wR(F2) = 0.081	w = 1/[σ2(Fo2) + (0.0471P)2 + 0.1056P] where P = (Fo2 + 2Fc2)/3
S = 1.09	(Δ/σ)max < 0.001
1373 reflections	Δρmax = 0.18 e Å−3
134 parameters	Δρmin = −0.22 e Å−3
0 restraints	Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.065 (7)

Experimental. A very tight closeness of the β-angle to 90° presented a certain difficulty in determination of the actual crystal system and the space group for (I).

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.

	x	y	z	Uiso*/Ueq
Si1	0.5000	0.5000	0.5000	0.02918 (18)
F1	0.31022 (9)	0.53884 (9)	0.55758 (10)	0.0445 (3)
F2	0.51424 (12)	0.38309 (9)	0.63991 (10)	0.0563 (3)
F3	0.42533 (10)	0.38065 (9)	0.38175 (11)	0.0532 (3)
N1	0.22279 (13)	0.08942 (11)	0.52963 (12)	0.0362 (3)
N2	0.34964 (14)	−0.03111 (12)	0.36255 (13)	0.0373 (3)
C1	0.31135 (17)	0.09435 (15)	0.40423 (16)	0.0387 (3)
C2	0.20313 (19)	−0.04525 (15)	0.56970 (17)	0.0419 (3)
C3	0.28241 (18)	−0.12049 (16)	0.46592 (16)	0.0423 (3)
C4	0.1593 (2)	0.20729 (16)	0.61283 (19)	0.0462 (4)
C5	0.4404 (2)	−0.06783 (19)	0.22545 (18)	0.0482 (4)
H1	0.341 (2)	0.1721 (19)	0.3610 (19)	0.048 (4)*
H2	0.146 (2)	−0.0695 (18)	0.658 (2)	0.054 (5)*
H3	0.297 (2)	−0.2124 (19)	0.4561 (19)	0.050 (5)*
H4A	0.218 (3)	0.282 (2)	0.590 (2)	0.074 (6)*
H4B	0.048 (3)	0.227 (2)	0.580 (3)	0.080 (6)*
H4C	0.162 (3)	0.188 (2)	0.718 (3)	0.093 (7)*
H5A	0.538 (3)	−0.015 (2)	0.227 (3)	0.071 (6)*
H5B	0.377 (3)	−0.058 (2)	0.141 (3)	0.074 (6)*
H5C	0.479 (3)	−0.164 (3)	0.229 (3)	0.094 (7)*

	U11	U22	U33	U12	U13	U23
Si1	0.0312 (3)	0.0258 (3)	0.0306 (3)	−0.00187 (16)	0.00740 (19)	−0.00332 (17)
F1	0.0342 (4)	0.0494 (5)	0.0499 (5)	0.0012 (3)	0.0113 (4)	−0.0102 (4)
F2	0.0701 (6)	0.0494 (5)	0.0494 (5)	0.0135 (4)	0.0180 (4)	0.0160 (4)
F3	0.0480 (5)	0.0516 (5)	0.0599 (6)	−0.0113 (4)	0.0085 (4)	−0.0269 (4)
N1	0.0388 (6)	0.0355 (6)	0.0343 (6)	−0.0044 (4)	0.0013 (5)	0.0033 (4)
N2	0.0358 (6)	0.0419 (6)	0.0343 (6)	−0.0026 (5)	−0.0012 (5)	0.0007 (4)
C1	0.0409 (7)	0.0381 (7)	0.0371 (7)	−0.0041 (6)	0.0022 (6)	0.0054 (6)
C2	0.0483 (8)	0.0387 (7)	0.0386 (7)	−0.0075 (6)	0.0025 (6)	0.0060 (6)
C3	0.0488 (8)	0.0361 (7)	0.0419 (8)	−0.0048 (6)	−0.0018 (6)	0.0034 (6)
C4	0.0532 (9)	0.0391 (8)	0.0463 (9)	−0.0031 (7)	0.0107 (7)	−0.0017 (6)
C5	0.0454 (8)	0.0607 (10)	0.0384 (8)	0.0026 (7)	0.0036 (6)	−0.0050 (7)

Si1—F3i	1.6783 (8)	N2—C5	1.4619 (19)
Si1—F3	1.6783 (8)	C1—H1	0.884 (19)
Si1—F2	1.6824 (8)	C2—C3	1.341 (2)
Si1—F2i	1.6824 (8)	C2—H2	0.934 (19)
Si1—F1	1.6849 (8)	C3—H3	0.912 (18)
Si1—F1i	1.6849 (8)	C4—H4A	0.90 (2)
N1—C1	1.3216 (18)	C4—H4B	0.98 (2)
N1—C2	1.3742 (18)	C4—H4C	0.94 (3)
N1—C4	1.4625 (19)	C5—H5A	0.96 (3)
N2—C1	1.3199 (18)	C5—H5B	0.91 (2)
N2—C3	1.3770 (19)	C5—H5C	0.99 (3)
F3i—Si1—F3	180.0	N2—C1—N1	109.20 (12)
F3i—Si1—F2	89.86 (5)	N2—C1—H1	128.1 (11)
F3—Si1—F2	90.14 (5)	N1—C1—H1	122.7 (11)
F3i—Si1—F2i	90.14 (5)	C3—C2—N1	107.19 (13)
F3—Si1—F2i	89.86 (5)	C3—C2—H2	131.8 (11)
F2—Si1—F2i	180.0	N1—C2—H2	121.0 (11)
F3i—Si1—F1	89.75 (4)	C2—C3—N2	107.14 (13)
F3—Si1—F1	90.25 (4)	C2—C3—H3	132.2 (11)
F2—Si1—F1	89.88 (4)	N2—C3—H3	120.6 (11)
F2i—Si1—F1	90.12 (4)	N1—C4—H4A	109.4 (14)
F3i—Si1—F1i	90.25 (4)	N1—C4—H4B	110.0 (13)
F3—Si1—F1i	89.75 (4)	H4A—C4—H4B	106.4 (18)
F2—Si1—F1i	90.12 (4)	N1—C4—H4C	108.6 (15)
F2i—Si1—F1i	89.88 (4)	H4A—C4—H4C	112 (2)
F1—Si1—F1i	180.00 (6)	H4B—C4—H4C	110 (2)
C1—N1—C2	108.26 (12)	N2—C5—H5A	106.3 (14)
C1—N1—C4	125.78 (12)	N2—C5—H5B	110.8 (14)
C2—N1—C4	125.94 (12)	H5A—C5—H5B	115.6 (19)
C1—N2—C3	108.21 (12)	N2—C5—H5C	111.8 (14)
C1—N2—C5	125.41 (13)	H5A—C5—H5C	104.5 (19)
C3—N2—C5	126.31 (13)	H5B—C5—H5C	107.7 (19)
C3—N2—C1—N1	0.05 (16)	C4—N1—C2—C3	−178.71 (14)
C5—N2—C1—N1	177.05 (13)	N1—C2—C3—N2	−0.22 (17)
C2—N1—C1—N2	−0.19 (16)	C1—N2—C3—C2	0.11 (17)
C4—N1—C1—N2	178.78 (13)	C5—N2—C3—C2	−176.85 (14)
C1—N1—C2—C3	0.26 (16)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···F3	0.884 (18)	2.164 (19)	2.9622 (17)	149.8 (14)
C2ii—H2ii···F2	0.934 (19)	2.26 (2)	3.1935 (18)	174.0 (5)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1⋯F3	0.884 (18)	2.164 (19)	2.9622 (17)	149.8 (14)
C2i—H2i⋯F2	0.934 (19)	2.26 (2)	3.1935 (18)	174.0 (5)

Symmetry code: (i) .