2,3,5,6-Tetra­fluoro-1,4-bis­(trimethyl­sil­yl)benzene

Finze, M.; Reiss, G.J.; Frohn, H.-J.

doi:10.1107/S1600536812010677

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 68| Part 4| April 2012| Page o1082

doi:10.1107/S1600536812010677

Open

access

2,3,5,6-Tetrafluoro-1,4-bis(trimethylsilyl)benzene

Maik Finze,^a ^* Guido J. Reiss ^b and Hermann-Josef Frohn ^c

^aInstitut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany, ^bInstitut für Anorganische Chemie und Strukturchemie, Lehrstuhl II: Material- und Strukturforschung, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany, and ^cInstitut für Anorganische Chemie, Universität Duisburg-Essen, Lotharstrasse 1, D-47048 Duisburg, Germany
^*Correspondence e-mail: maik.finze@uni-wuerzburg.de

(Received 17 February 2012; accepted 10 March 2012; online 17 March 2012)

The asymmetric unit of the title compound, C₁₂H₁₈F₄Si₂, contains two independent molecules, both lying on inversion centers. The C_arene—Si distances are significantly longer than in the analogous non-fluorinated compound. The packing of the molecules results in a herringbone motif in the ac plane.

Related literature

For the synthesis and chemistry of 1,4-(Me₃Si)₂—C₆F₄, see: Fearon & Gilman (1967 ); Tamborski & Soloski (1969 ); Fields et al. (1970 ); Sartori & Frohn (1974 ); Bardin et al. (1991 ); Frohn et al. (1998 ); Kashiwabara & Tanaka (2006 ). For related structures see: Rehm et al. (1999 ); Sekiguchi et al. (2000 ); Haberecht et al. (2002 , 2004 ); Krumm et al. (2005 ); Hanamoto et al. (2006 ).

Experimental

Crystal data

C₁₂H₁₈F₄Si₂
M_r = 294.44
Monoclinic, P 2₁ /c
a = 19.8389 (4) Å
b = 6.35013 (10) Å
c = 12.3827 (2) Å
β = 107.407 (2)°
V = 1488.53 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.26 mm⁻¹
T = 199 K
0.25 × 0.22 × 0.20 mm

Data collection

Oxford Xcalibur Eos diffractometer
8888 measured reflections
2626 independent reflections
2496 reflections with I > 2σ(I)
R_int = 0.015

Refinement

R[F² > 2σ(F²)] = 0.027
wR(F²) = 0.068
S = 1.09
2626 reflections
187 parameters
H-atom parameters constrained
Δρ_max = 0.39 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

Si1—C2	1.9101 (15)
Si2—C8	1.9077 (15)

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 $[Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton, England.]$ ); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2011); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536812010677/mw2055sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812010677/mw2055Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536812010677/mw2055Isup3.cml

checkCIF report

Comment top

The first synthesis of the title compound 1,4-bis(trimethylsilyl)tetrafluorobenzene, 1,4-(Me₃Si)₂—C₆F₄, was reported in 1967 starting from 1,2,4,5-tetrafluorobenzene, n-butyl lithium, and trimethylsilyl chloride (Fearon & Gilman 1967). Later, the compound was observed as a by-product in related reactions, improved methods for its selective synthesis were published and some reactions of 1,4-(Me₃Si)₂—C₆F₄ were described (Tamborski & Soloski, 1969; Fields et al. 1970; Sartori & Frohn, 1974; Bardin et al. 1991; Frohn et al. 1998; Kashiwabara & Tanaka, 2006). The 1,4-(Me₃Si)₂—C₆F₄ employed in the present study was prepared by a different route using poly(cadmium-2,3,5,6-tetrafluorobenzene), [1,4-Cd—C₆F₄]_n, and trimethylsilyl chloride as starting materials.

The title compound 1,4-bis(trimethylsilyl)tetrafluorobenzene (Figure 1) crystallizes in the monoclinic space group P2₁/c with two independent molecules each of which is located on a center of symmetry. Both crystallographically independent molecules display very similar geometric parameters. The C–C, C_methyl–Si and C–F bond lengths are in the expected range. Both C_arene–Si distances are slightly longer than those found for the non-fluorinated analogue 1,4-(Me₃Si)₂—C₆H₄ [d(C_arene–Si) = 1.8817 (12) Å] (Haberecht et al. 2004) and other non-fluorinated Me₃Si–C_arene compounds (Haberecht et al. 2004; Rehm et al. 1999). In contrast, for related 1-trimethylsilyl-2,3,5,6-tetrafluoro benzene fragments similar values were reported (Sekiguchi et al. 2000, Krumm et al. 2005). In the closely related compound 1,2,4-(iPr₃Si)₃—C₆F₃ (Hanamoto et al. 2006) the d(C_arene–Si) of the iPr₃Si groups in ortho positions [d(C–Si) = 1.937 (2), 1.934 (2)] are significantly longer than those in the title compound whereas the third C_arene–Si distance [d(C–Si) = 1.914 (2) Å], which corresponds to the iPr₃Si group that has two F atoms in the ortho positions, is close to the values determined for 1,4-(Me₃Si)₂—C₆F₄.

The 1,4-bis(trimethylsilyl)tetrafluorobenzene molecules are arranged in the ac plane to form a herringbone structure (Figure 2). The trimethylsilyl groups are interlinked by van der Waals interactions with methyl groups of neighboring molecules.

Related literature top

For the synthesis and chemistry of 1,4-(Me₃Si)₂—C₆F₄, see: Fearon & Gilman (1967); Tamborski & Soloski (1969); Fields et al. (1970); Sartori & Frohn (1974); Bardin et al. (1991); Frohn et al. (1998); Kashiwabara & Tanaka (2006). For related structures see: Rehm et al. (1999); Sekiguchi et al. (2000); Haberecht et al. (2002, 2004); Krumm et al. (2005); Hanamoto et al. (2006).

Experimental top

The starting material poly(cadmium-2,3,5,6-tetrafluorobenzene), [1,4-Cd—C₆F₄]_n, was synthesized by thermolysis of Cd(1,4-O₂C—C₆F₄) at 270 °C under vacuum according to a literature procedure (Sartori & Frohn, 1974).

7.1 g (27.3 mmol) poly(cadmium-2,3,5,6-tetrafluorobenzene), [1,4-Cd—C₆F₄]_n, was charged into a Duran-glass Carius tube inside a glove box. 6.55 g (60.3 mmol) freshly distilled (CH₃)₃SiCl was added under protection of dry nitrogen. The tube was sealed and shaken and heated inside an oven. The temperature was increased stepwise over 30 h to 222°C without visual change of the reaction components. Further heating from 230 to 250°C over 26 h was accompanied by a reduction of the liquid phase and a change of the color to light grey. The Carius tube was cooled stepwise to -78°C before opening under nitrogen protection. CAUTION: Handling of the sealed Carius tube should proceed behind a large protection screen with long-sleeve leather gloves. At 0°C 3.4 g (31.3 mmol) of (CH₃)₃SiCl were recovered by condensation under high-vacuum. The dark grey solid residue, which contained the co-product CdCl₂, was extracted with boiling petrol ether (60–70°C fraction). After removing the solvent from the extract a slightly brownish oil remained which was sublimed under high vacuum. The colorless crystals were collected on a water cooled sublimation finger. Yield ca 80%; mp 46°C [31–32°C isomeric mixture (Fields et al., 1970)]; NMR (20% CCl₄ solution): ¹H -0.39 p.p.m., ¹⁹F -124.2 p.p.m.; MS (EI, 73 eV) M^+. 294, the fragment ions 81 (CH₃SiF₂), 77 ((CH₃)₂SiF), and 73 ((CH₃)₃Si) possessed higher intensities than the parent ion; IR (neat): 2946 (m), 2889 (m), 1575 (w), 1487 (w), 1400 (st, b), 1343 (w), 1334 (w), 1286 (w), 1240 (st), 1214 (st), 1183 (m), 1035 (w), 921 (st), 830 (st, b), 748 (st), 684 (m), 613 (m), 566 (w), 432 (w).

Structure description top

For the synthesis and chemistry of 1,4-(Me₃Si)₂—C₆F₄, see: Fearon & Gilman (1967); Tamborski & Soloski (1969); Fields et al. (1970); Sartori & Frohn (1974); Bardin et al. (1991); Frohn et al. (1998); Kashiwabara & Tanaka (2006). For related structures see: Rehm et al. (1999); Sekiguchi et al. (2000); Haberecht et al. (2002, 2004); Krumm et al. (2005); Hanamoto et al. (2006).

Computing details top

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2011); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. : The two crystallographically independent molecules of the title compound (H-atoms are drawn with arbitrary radii; ' = -x, 1 - y, -z; '' = 1 - x, 2 - y, 1 - z).
	Fig. 2. : Molecular packing of the title compound viewed parallel to the b axis, showing the herringbone type motif (ball and stick type model with arbitrary atom radii).

2,3,5,6-Tetrafluoro-1,4-bis(trimethylsilyl)benzene top

Crystal data top

C₁₂H₁₈F₄Si₂	F(000) = 616
M_r = 294.44	D_x = 1.314 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 8162 reflections
a = 19.8389 (4) Å	θ = 3.1–28.3°
b = 6.35013 (10) Å	µ = 0.26 mm⁻¹
c = 12.3827 (2) Å	T = 199 K
β = 107.407 (2)°	Block, colourless
V = 1488.53 (5) Å³	0.25 × 0.22 × 0.20 mm
Z = 4

Data collection top

Oxford Xcalibur Eos diffractometer	2496 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.015
Equatorial mounted graphite monochromator	θ_max = 25.0°, θ_min = 3.2°
Detector resolution: 16.2711 pixels mm^-1	h = −22→23
ω–scan	k = −7→7
8888 measured reflections	l = −14→12
2626 independent reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.068	H-atom parameters constrained
S = 1.09	w = 1/[σ²(F_o²) + (0.0284P)² + 1.0425P] where P = (F_o² + 2F_c²)/3
2626 reflections	(Δ/σ)_max < 0.001
187 parameters	Δρ_max = 0.39 e Å⁻³
0 restraints	Δρ_min = −0.22 e Å⁻³

Crystal data top

C₁₂H₁₈F₄Si₂	V = 1488.53 (5) Å³
M_r = 294.44	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 19.8389 (4) Å	µ = 0.26 mm⁻¹
b = 6.35013 (10) Å	T = 199 K
c = 12.3827 (2) Å	0.25 × 0.22 × 0.20 mm
β = 107.407 (2)°

Data collection top

Oxford Xcalibur Eos diffractometer	2496 reflections with I > 2σ(I)
8888 measured reflections	R_int = 0.015
2626 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.027	0 restraints
wR(F²) = 0.068	H-atom parameters constrained
S = 1.09	Δρ_max = 0.39 e Å⁻³
2626 reflections	Δρ_min = −0.22 e Å⁻³
187 parameters

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Si1	0.12486 (2)	0.23395 (7)	0.19607 (3)	0.01427 (11)
C1	−0.01679 (8)	0.3116 (2)	0.03692 (12)	0.0145 (3)
F1	−0.03838 (4)	0.12566 (13)	0.06873 (7)	0.0203 (2)
C2	0.05291 (8)	0.3765 (2)	0.08187 (12)	0.0139 (3)
C3	0.06680 (7)	0.5691 (2)	0.04012 (12)	0.0141 (3)
F3	0.13382 (4)	0.64624 (14)	0.07568 (7)	0.0199 (2)
C4	0.08544 (8)	0.0143 (3)	0.25580 (13)	0.0224 (3)
H4A	0.0484	0.0679	0.2834	0.034 (5)*
H4B	0.1212	−0.0499	0.3170	0.037 (5)*
H4C	0.0663	−0.0886	0.1979	0.037 (5)*
C5	0.19335 (8)	0.1412 (3)	0.13233 (13)	0.0190 (3)
H5A	0.2119	0.2592	0.1019	0.033 (5)*
H5B	0.1727	0.0427	0.0728	0.030 (5)*
H5C	0.2309	0.0738	0.1894	0.037 (5)*
C6	0.16406 (9)	0.4291 (3)	0.30949 (13)	0.0241 (4)
H6A	0.1858	0.5406	0.2794	0.044 (6)*
H6B	0.1990	0.3611	0.3703	0.045 (6)*
H6C	0.1276	0.4864	0.3373	0.042 (6)*
Si2	0.35988 (2)	0.79571 (7)	0.56124 (3)	0.01519 (11)
C7	0.50606 (8)	0.8812 (2)	0.59251 (12)	0.0156 (3)
F7	0.51552 (5)	0.76178 (15)	0.68697 (7)	0.0227 (2)
C8	0.43772 (8)	0.9180 (2)	0.52347 (12)	0.0147 (3)
C9	0.43451 (7)	1.0409 (2)	0.42942 (12)	0.0152 (3)
F9	0.37103 (4)	1.08933 (14)	0.35422 (7)	0.0203 (2)
C10	0.36292 (9)	0.8818 (3)	0.70638 (13)	0.0235 (4)
H10A	0.3604	1.0326	0.7086	0.038 (6)*
H10B	0.4063	0.8348	0.7594	0.032 (5)*
H10C	0.3237	0.8222	0.7259	0.039 (6)*
C11	0.27524 (8)	0.8855 (3)	0.46024 (13)	0.0214 (3)
H11A	0.2727	0.8394	0.3853	0.031 (5)*
H11B	0.2729	1.0364	0.4617	0.030 (5)*
H11C	0.2365	0.8269	0.4816	0.034 (5)*
C12	0.36891 (9)	0.5045 (3)	0.55206 (14)	0.0235 (4)
H12A	0.3661	0.4662	0.4758	0.042 (6)*
H12B	0.3316	0.4365	0.5734	0.049 (6)*
H12C	0.4137	0.4610	0.6022	0.036 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si1	0.0148 (2)	0.0168 (2)	0.0121 (2)	0.00203 (16)	0.00533 (16)	0.00124 (16)
C1	0.0186 (7)	0.0128 (7)	0.0152 (7)	−0.0018 (6)	0.0099 (6)	0.0001 (6)
F1	0.0192 (5)	0.0163 (5)	0.0258 (5)	−0.0034 (4)	0.0073 (4)	0.0062 (4)
C2	0.0158 (7)	0.0160 (7)	0.0121 (7)	0.0017 (6)	0.0074 (6)	−0.0015 (6)
C3	0.0114 (7)	0.0177 (7)	0.0144 (7)	−0.0023 (6)	0.0057 (6)	−0.0030 (6)
F3	0.0124 (4)	0.0215 (5)	0.0247 (5)	−0.0043 (4)	0.0041 (4)	0.0018 (4)
C4	0.0210 (8)	0.0264 (9)	0.0213 (8)	0.0043 (7)	0.0089 (6)	0.0093 (7)
C5	0.0189 (8)	0.0216 (8)	0.0186 (7)	0.0019 (6)	0.0085 (6)	0.0008 (6)
C6	0.0262 (9)	0.0271 (9)	0.0162 (8)	0.0050 (7)	0.0019 (7)	−0.0033 (7)
Si2	0.0138 (2)	0.0159 (2)	0.0169 (2)	−0.00165 (16)	0.00616 (16)	−0.00042 (16)
C7	0.0187 (8)	0.0144 (7)	0.0135 (7)	0.0006 (6)	0.0045 (6)	0.0025 (6)
F7	0.0190 (5)	0.0288 (5)	0.0191 (5)	−0.0001 (4)	0.0039 (4)	0.0117 (4)
C8	0.0156 (7)	0.0134 (7)	0.0156 (7)	−0.0005 (6)	0.0055 (6)	−0.0020 (6)
C9	0.0122 (7)	0.0159 (7)	0.0153 (7)	0.0020 (6)	0.0006 (6)	−0.0009 (6)
F9	0.0124 (4)	0.0260 (5)	0.0192 (4)	0.0008 (4)	0.0000 (3)	0.0064 (4)
C10	0.0260 (9)	0.0264 (9)	0.0209 (8)	−0.0044 (7)	0.0116 (7)	−0.0012 (7)
C11	0.0157 (8)	0.0254 (9)	0.0240 (8)	−0.0011 (6)	0.0075 (6)	−0.0006 (7)
C12	0.0237 (8)	0.0185 (8)	0.0299 (9)	−0.0019 (7)	0.0105 (7)	0.0003 (7)

Geometric parameters (Å, º) top

Si1—C4	1.8574 (16)	Si2—C11	1.8579 (16)
Si1—C5	1.8595 (15)	Si2—C10	1.8620 (16)
Si1—C6	1.8602 (16)	Si2—C12	1.8644 (17)
Si1—C2	1.9101 (15)	Si2—C8	1.9077 (15)
C1—F1	1.3539 (17)	C7—F7	1.3591 (17)
C1—C3ⁱ	1.379 (2)	C7—C9ⁱⁱ	1.378 (2)
C1—C2	1.390 (2)	C7—C8	1.389 (2)
C2—C3	1.387 (2)	C8—C9	1.387 (2)
C3—F3	1.3605 (16)	C9—F9	1.3587 (16)
C3—C1ⁱ	1.379 (2)	C9—C7ⁱⁱ	1.378 (2)
C4—H4A	0.9600	C10—H10A	0.9600
C4—H4B	0.9600	C10—H10B	0.9600
C4—H4C	0.9600	C10—H10C	0.9600
C5—H5A	0.9600	C11—H11A	0.9600
C5—H5B	0.9600	C11—H11B	0.9600
C5—H5C	0.9600	C11—H11C	0.9600
C6—H6A	0.9600	C12—H12A	0.9600
C6—H6B	0.9600	C12—H12B	0.9600
C6—H6C	0.9600	C12—H12C	0.9600

C4—Si1—C5	112.29 (7)	C11—Si2—C10	108.76 (7)
C4—Si1—C6	109.29 (8)	C11—Si2—C12	110.31 (8)
C5—Si1—C6	109.76 (7)	C10—Si2—C12	111.96 (8)
C4—Si1—C2	109.89 (7)	C11—Si2—C8	110.18 (7)
C5—Si1—C2	108.36 (7)	C10—Si2—C8	108.80 (7)
C6—Si1—C2	107.11 (7)	C12—Si2—C8	106.81 (7)
F1—C1—C3ⁱ	117.10 (13)	F7—C7—C9ⁱⁱ	117.62 (13)
F1—C1—C2	120.37 (13)	F7—C7—C8	118.79 (13)
C3ⁱ—C1—C2	122.53 (14)	C9ⁱⁱ—C7—C8	123.58 (14)
C3—C2—C1	113.39 (13)	C9—C8—C7	113.74 (13)
C3—C2—Si1	120.39 (11)	C9—C8—Si2	126.70 (11)
C1—C2—Si1	126.13 (11)	C7—C8—Si2	119.55 (11)
F3—C3—C1ⁱ	117.22 (13)	F9—C9—C7ⁱⁱ	117.13 (13)
F3—C3—C2	118.72 (13)	F9—C9—C8	120.19 (13)
C1ⁱ—C3—C2	124.06 (13)	C7ⁱⁱ—C9—C8	122.68 (13)
Si1—C4—H4A	109.5	Si2—C10—H10A	109.5
Si1—C4—H4B	109.5	Si2—C10—H10B	109.5
H4A—C4—H4B	109.5	H10A—C10—H10B	109.5
Si1—C4—H4C	109.5	Si2—C10—H10C	109.5
H4A—C4—H4C	109.5	H10A—C10—H10C	109.5
H4B—C4—H4C	109.5	H10B—C10—H10C	109.5
Si1—C5—H5A	109.5	Si2—C11—H11A	109.5
Si1—C5—H5B	109.5	Si2—C11—H11B	109.5
H5A—C5—H5B	109.5	H11A—C11—H11B	109.5
Si1—C5—H5C	109.5	Si2—C11—H11C	109.5
H5A—C5—H5C	109.5	H11A—C11—H11C	109.5
H5B—C5—H5C	109.5	H11B—C11—H11C	109.5
Si1—C6—H6A	109.5	Si2—C12—H12A	109.5
Si1—C6—H6B	109.5	Si2—C12—H12B	109.5
H6A—C6—H6B	109.5	H12A—C12—H12B	109.5
Si1—C6—H6C	109.5	Si2—C12—H12C	109.5
H6A—C6—H6C	109.5	H12A—C12—H12C	109.5
H6B—C6—H6C	109.5	H12B—C12—H12C	109.5

F1—C1—C2—C3	179.45 (12)	F7—C7—C8—C9	−179.74 (13)
C3ⁱ—C1—C2—C3	−1.0 (2)	C9ⁱⁱ—C7—C8—C9	0.1 (2)
F1—C1—C2—Si1	−3.9 (2)	F7—C7—C8—Si2	−1.36 (19)
C3ⁱ—C1—C2—Si1	175.56 (11)	C9ⁱⁱ—C7—C8—Si2	178.52 (12)
C4—Si1—C2—C3	167.71 (11)	C11—Si2—C8—C9	−5.61 (16)
C5—Si1—C2—C3	−69.26 (13)	C10—Si2—C8—C9	−124.75 (14)
C6—Si1—C2—C3	49.09 (13)	C12—Si2—C8—C9	114.22 (14)
C4—Si1—C2—C1	−8.68 (15)	C11—Si2—C8—C7	176.25 (12)
C5—Si1—C2—C1	114.36 (13)	C10—Si2—C8—C7	57.10 (14)
C6—Si1—C2—C1	−127.29 (13)	C12—Si2—C8—C7	−63.93 (13)
C1—C2—C3—F3	−178.22 (12)	C7—C8—C9—F9	179.85 (13)
Si1—C2—C3—F3	4.96 (18)	Si2—C8—C9—F9	1.6 (2)
C1—C2—C3—C1ⁱ	1.1 (2)	C7—C8—C9—C7ⁱⁱ	−0.1 (2)
Si1—C2—C3—C1ⁱ	−175.76 (11)	Si2—C8—C9—C7ⁱⁱ	−178.38 (11)

Symmetry codes: (i) −x, −y+1, −z; (ii) −x+1, −y+2, −z+1.

Experimental details

Crystal data
Chemical formula	C₁₂H₁₈F₄Si₂
M_r	294.44
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	199
a, b, c (Å)	19.8389 (4), 6.35013 (10), 12.3827 (2)
β (°)	107.407 (2)
V (Å³)	1488.53 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.26
Crystal size (mm)	0.25 × 0.22 × 0.20

Data collection
Diffractometer	Oxford Xcalibur Eos
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	8888, 2626, 2496
R_int	0.015
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.027, 0.068, 1.09
No. of reflections	2626
No. of parameters	187
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.39, −0.22

Computer programs: CrysAlis PRO (Oxford Diffraction, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2011), publCIF (Westrip, 2010).

Selected geometric parameters (Å, º) top

Si1—C2	1.9101 (15)	Si2—C8	1.9077 (15)

C3—C2—Si1	120.39 (11)	C9—C8—Si2	126.70 (11)
C1—C2—Si1	126.13 (11)	C7—C8—Si2	119.55 (11)

Acknowledgements

This publication was funded by the German Research Foundation (DFG) and the University of Würzburg under the funding programme Open Access Publishing.

References

Bardin, V. V., Pressman, L. S., Rogoza, L. N. & Furin, G. G. (1991). J. Fluorine Chem. 53, 213–231. CrossRef CAS Web of Science Google Scholar
Brandenburg, K. (2011). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Fearon, F. W. G. & Gilman, H. (1967). J. Organomet. Chem. 10, 535–537. CrossRef CAS Web of Science Google Scholar
Fields, R., Haszeldine, R. N. & Hubbard, A. F. (1970). J. Chem. Soc. C, pp. 2193–2195. Google Scholar
Frohn, H.-J., Lewin, A. & Bardin, V. V. (1998). J. Organomet. Chem. 570, 255–263. Web of Science CrossRef CAS Google Scholar
Haberecht, M., Lerner, H.-W. & Bolte, M. (2002). Acta Cryst. E58, o436–o437. Web of Science CSD CrossRef IUCr Journals Google Scholar
Haberecht, M. C., Vitze, H., Lerner, H.-W. & Bolte, M. (2004). Acta Cryst. E60, o329–o330. Web of Science CSD CrossRef IUCr Journals Google Scholar
Hanamoto, T., Koga, Y., Kawanami, T., Furuno, H. & Inanaga, J. (2006). Tetrahedron Lett. 47, 493–495. Web of Science CSD CrossRef CAS Google Scholar
Kashiwabara, T. & Tanaka, M. (2006). Organometallics, 25, 4648–4652. Web of Science CSD CrossRef CAS Google Scholar
Krumm, B., Klapötke, T. M. & Polborn, K. (2005). Private communication (refcode NAXDAS). CCDC, Cambridge, England. Google Scholar
Oxford Diffraction (2009). CrysAlis PRO. Oxford Diffraction Ltd, Yarnton, England. Google Scholar
Rehm, J. D. D., Ziemer, B. & Szeimies, G. (1999). Eur. J. Org. Chem. pp. 2079–2085. Google Scholar
Sartori, P. & Frohn, H.-J. (1974). Chem. Ber. 107, 1195–1206. CrossRef CAS Web of Science Google Scholar
Sekiguchi, A., Fukaya, N., Ichinohe, M. & Ishida, Y. (2000). Eur. J. Inorg. Chem. pp. 1155–1159. CrossRef Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Tamborski, C. & Soloski, E. J. (1969). J. Organomet. Chem. 17, 185–192. CrossRef CAS Web of Science Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar