anti-2,2,3,3,6,6,7,7,10,10,11,11,14,14,15,15-Hexadeca­methyl-2,3,6,7,10,11,14,15-octa­silapenta­cyclo­[10.4.2.24,9.05,8.013,16]icosa-1(17),4,8,12(18),13(16),19-hexa­ene

Toma, Y.; Otsuka, K.; Kyushin, S.

doi:10.1107/S1600536813002584

organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 69| Part 3| March 2013| Page o341

doi:10.1107/S1600536813002584

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anti-2,2,3,3,6,6,7,7,10,10,11,11,14,14,15,15-Hexadecamethyl-2,3,6,7,10,11,14,15-octasilapentacyclo[10.4.2.2^4,9.0^5,8.0^13,16]icosa-1(17),4,8,12(18),13(16),19-hexaene

Yuki Toma,^a Kyohei Otsuka ^a and Soichiro Kyushin ^a ^*

^aDepartment of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Gunma 376-8515, Japan
^*Correspondence e-mail: kyushin@gunma-u.ac.jp

(Received 5 December 2012; accepted 25 January 2013; online 6 February 2013)

The title compound, C₂₈H₅₂Si₈, was synthesized by condensation of two molecules of 1,2,3,4-tetrakis(chlorodimethylsilyl)benzene with lithium. The 3,4-disila-1,2-benzocyclobutene rings in the centrosymmetric molecule are bridged by 1,1,2,2-tetramethyldisilanylene chains with an anti conformation. The benzene rings are deformed by fusion with a 3,4-disilacyclobutene ring resulting in a slight boat conformation. Two Si—C bonds are bent to reduce the steric repulsion between the methyl groups on the two Si atoms and the methyl groups on another two Si atoms.

Related literature

For structures of cyclophanes bridged by tetramethyldisilanylene chains, see: Sakurai et al. (1986 ); Sekiguchi et al. (1989 ).

Experimental

Crystal data

C₂₈H₅₂Si₈
M_r = 613.42
Monoclinic, P 2₁ /n
a = 7.9801 (8) Å
b = 18.9087 (14) Å
c = 12.6222 (10) Å
β = 104.2788 (9)°
V = 1845.8 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.31 mm⁻¹
T = 203 K
0.25 × 0.25 × 0.25 mm

Data collection

Rigaku R-AXIS IV Imaging Plate diffractometer
Absorption correction: multi-scan (REQAB; Jacobson, 1998 ) T_min = 0.927, T_max = 0.927
9672 measured reflections
3096 independent reflections
3076 reflections with I > 2σ(I)
R_int = 0.016

Refinement

R[F² > 2σ(F²)] = 0.029
wR(F²) = 0.076
S = 1.11
3096 reflections
171 parameters
H-atom parameters constrained
Δρ_max = 0.25 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: CrystalClear (Rigaku, 2003 ); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012 ); software used to prepare material for publication: SHELXL97 and Yadokari-XG 2009 (Kabuto et al., 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536813002584/ds2224sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536813002584/ds2224Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536813002584/ds2224Isup3.cml

checkCIF report

Comment top

Cyclophanes have been studied from the viewpoints of unique structures and interaction among aromatic rings. Some examples of cyclophanes bridged by silicon chains have so far been reported. [2.2]paracyclophane bridged by two 1,1,2,2-tetramethyldisilanylene chains has been synthesized, and its electronic properties have been reported (Sakurai et al., 1986). Also, [2.2.2](1,3,5)cyclophane bridged by three 1,1,2,2-tetramethyldisilanylene chains has been synthesized (Sekiguchi et al., 1989). Although cyclophanes bridged by silicon chains are attractive compounds, their studies have not further developed because of difficulty of synthesis. We report herein synthesis of a silicon-bridged [2.2]paracyclophane, in which two benzene rings are fused with 3,4-disilacyclobutene rings, and discuss the structural features of this compound.

The condensation of two molecules of 1,2,3,4-tetrakis(chlorodimethylsilyl)benzene with lithium in THF gave 1 in 2% yield (Fig. 1). The structure of 1 was determined by X-ray crystallography (Fig. 2). The molecule lies on an inversion center, and one half of the molecule corresponds to the asymmetric unit. Two 3,4-disila-1,2-benzocyclobutene rings are bridged by 1,1,2,2-tetramethyldisilanylene chains with an anti structure. The anti structure is favorable to avoid the steric hindrance among methyl groups on the 3,4-disilacyclobutene rings.

The benzene rings have a deformed structure due to fusion with a 3,4-disilacyclobutene ring (Fig. 3). The C—C bond is elongated in the order of C5—C6ⁱ (1.390 (2) Å), C1—C5 (1.399 (2) Å) (or C2ⁱ—C6ⁱ (1.396 (2) Å)), C1—C4 (1.417 (2) Å) (or C2ⁱ—C3ⁱ (1.418 (2) Å)) and C4—C3ⁱ (1.431 (2) Å). The Si1—C1—C4 and Si2ⁱ—C2ⁱ—C3ⁱ bond angles are large (127.24 (11) and 127.03 (11)°, respectively), and the Si1—C1—C5 and Si2ⁱ—C2ⁱ—C6ⁱ bond angles are small (115.53 (11) and 115.79 (11)°, respectively). As a result, two benzene rings are partially overlapped as shown in Fig. 4. This deformation of the bond angles is caused by the steric repulsion between the methyl groups on the Si1 and Si2ⁱ atoms and the methyl groups on the Si3 and Si4 atoms. This steric repulsion also makes the Si3—Si4 bond short (2.3245 (7) Å) compared with the standard Si—Si bond (2.34 Å).

The benzene rings are also deformed by the cyclophane structure (Fig. 3). The benzene rings are not planar but have a slight boat conformation. The dihedral angle between the C4—C5—C6ⁱ—C3ⁱ plane and the C1—C4—C5 (or C2ⁱ—C3ⁱ—C6ⁱ) plane is 5.8° (or 5.2°). The Si1—C1 and Si2ⁱ—C2ⁱ bonds are further tilted from the C4—C5—C6ⁱ—C3ⁱ plane with the angles of 16.8 and 15.4°. The distance between the C4—C5—C6ⁱ—C3ⁱ and C3—C6—C5ⁱ—C4ⁱ planes is 3.473 Å, and the distance between the C1 and C2 atoms is 3.383 Å. These structural features are similar to those of 1,1,2,2,9,9,10,10-octamethyl-1,2,9,10-tetrasila[2.2]paracyclophane (2) (Sakurai et al., 1986) as shown in Fig. 3.

Related literature top

For structures of cyclophanes bridged by tetramethyldisilanylene chains, see: Sakurai et al. (1986); Sekiguchi et al. (1989).

Experimental top

All operations except for Kugelrohr distillation were carried out in a glovebox. A mixture of 1,2,3,4-tetrakis(chlorodimethylsilyl)benzene (0.200 g, 0.446 mmol) and lithium (13.0 mg, 1.87 mmol) in THF (25 ml) was stirred at room temperature for 14 h. After removal of the solvent, the residue was dissolved in toluene, and insoluble materials were filtered off. The solvent was removed under reduced pressure. Kugelrohr distillation (300 °C/0.9 mm Hg) of the residue gave a colorless solid. The solid was recrystallized from hexane to give 1 (3 mg, 2%) as colorless crystals. Single crystals were obtained from hexane by slow evaporation.

M.p.: 328–330 °C. ¹H NMR (600 MHz, C₆D₆): δ 0.42 (s, 12H), 0.51 (s, 12H), 0.60 (s, 12H), 0.67 (s, 12H), 6.66 (s, 4H). ¹³C NMR (151 MHz, C₆D₆): δ -2.6, -1.3, -0.9, 136.0, 143.2, 160.2. ²⁹Si NMR (119 MHz, C₆D₆): δ -18.1, -3.7. IR (KBr): 2960, 2930, 2900, 2850, 1260, 1250, 1100, 1080, 1020, 800, 750 cm^-1. MS (EI, 70 eV): m/z 612 (M⁺, 29), 539 (23), 465 (18), 291 (15), 73 (100).

Computing details top

Data collection: CrystalClear (Rigaku, 2003); cell refinement: CrystalClear (Rigaku, 2003); data reduction: CrystalClear (Rigaku, 2003); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and Yadokari-XG 2009 (Kabuto et al., 2009).

Figures top

Fig. 1. Synthesis of 1.

Fig. 2. The molecular structure of 1, showing 50% probability displacement ellipsoids. [Symmetry code: (i) –x + 1, –y, –z + 1.]

Fig. 3. Comparison of the structures of 1 and 2.

Fig. 4. Top view of 1, showing 50% probability displacement ellipsoids. [Symmetry code: (i) –x + 1, –y, –z + 1.]

anti-2,2,3,3,6,6,7,7,10,10,11,11,14,14,15,15-Hexadecamethyl-2,3,6,7,10,11,14,15-octasilapentacyclo[10.4.2.2^4,9.0^5,8.0^13,16]icosa-1(17),4,8,12 (18),13 (16),19-hexaene top

Crystal data top

C₂₈H₅₂Si₈	F(000) = 664
M_r = 613.42	D_x = 1.104 Mg m⁻³
Monoclinic, P2₁/n	Melting point = 328–330 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 7.9801 (8) Å	Cell parameters from 11187 reflections
b = 18.9087 (14) Å	θ = 1.7–28.3°
c = 12.6222 (10) Å	µ = 0.31 mm⁻¹
β = 104.2788 (9)°	T = 203 K
V = 1845.8 (3) Å³	Prism, colourless
Z = 2	0.25 × 0.25 × 0.25 mm

Data collection top

Rigaku R-AXIS IV imaging plate diffractometer	3096 independent reflections
Radiation source: rotating anode	3076 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.016
Detector resolution: 10.00 pixels mm^-1	θ_max = 25.0°, θ_min = 2.0°
ω scans	h = −9→9
Absorption correction: multi-scan (REQAB; Jacobson, 1998)	k = −22→19
T_min = 0.927, T_max = 0.927	l = −15→15
9672 measured 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)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.076	H-atom parameters constrained
S = 1.11	w = 1/[σ²(F_o²) + (0.0349P)² + 0.7873P] where P = (F_o² + 2F_c²)/3
3096 reflections	(Δ/σ)_max = 0.021
171 parameters	Δρ_max = 0.25 e Å⁻³
0 restraints	Δρ_min = −0.25 e Å⁻³

Crystal data top

C₂₈H₅₂Si₈	V = 1845.8 (3) Å³
M_r = 613.42	Z = 2
Monoclinic, P2₁/n	Mo Kα radiation
a = 7.9801 (8) Å	µ = 0.31 mm⁻¹
b = 18.9087 (14) Å	T = 203 K
c = 12.6222 (10) Å	0.25 × 0.25 × 0.25 mm
β = 104.2788 (9)°

Data collection top

Rigaku R-AXIS IV imaging plate diffractometer	3096 independent reflections
Absorption correction: multi-scan (REQAB; Jacobson, 1998)	3076 reflections with I > 2σ(I)
T_min = 0.927, T_max = 0.927	R_int = 0.016
9672 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.029	0 restraints
wR(F²) = 0.076	H-atom parameters constrained
S = 1.11	Δρ_max = 0.25 e Å⁻³
3096 reflections	Δρ_min = −0.25 e Å⁻³
171 parameters

Special details top

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 > 2σ(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	0.18531 (5)	0.13135 (2)	0.45683 (3)	0.02369 (12)
Si2	0.43507 (5)	0.17209 (2)	0.40399 (3)	0.02186 (12)
Si3	0.50467 (6)	−0.03139 (2)	0.81537 (3)	0.02614 (12)
Si4	0.36313 (6)	0.07548 (2)	0.76574 (3)	0.02856 (13)
C1	0.24730 (19)	0.04152 (8)	0.52049 (12)	0.0218 (3)
C2	0.58255 (18)	0.09258 (7)	0.41846 (11)	0.0202 (3)
C3	0.58234 (19)	0.03950 (7)	0.33902 (11)	0.0209 (3)
C4	0.33293 (19)	0.02681 (7)	0.63061 (12)	0.0212 (3)
C5	0.2347 (2)	−0.01465 (8)	0.44684 (12)	0.0245 (3)
C6	0.6830 (2)	0.07907 (8)	0.52380 (12)	0.0238 (3)
C7	0.1117 (3)	0.19586 (9)	0.54917 (15)	0.0412 (4)
C8	0.0026 (2)	0.12151 (10)	0.33167 (14)	0.0354 (4)
C9	0.5452 (2)	0.24491 (9)	0.49722 (15)	0.0384 (4)
C10	0.3789 (2)	0.21016 (9)	0.26238 (13)	0.0361 (4)
C11	0.4144 (3)	−0.09537 (10)	0.90036 (13)	0.0402 (4)
C12	0.7449 (2)	−0.02692 (11)	0.86886 (15)	0.0452 (5)
C13	0.1573 (3)	0.09331 (11)	0.80715 (16)	0.0498 (5)
C14	0.5025 (3)	0.15680 (10)	0.78452 (15)	0.0530 (6)
H1	0.1681	−0.0086	0.3748	0.029*
H2	0.6955	0.1149	0.5768	0.029*
H3	0.0801	0.2402	0.5107	0.062*
H4	0.2048	0.2041	0.6137	0.062*
H5	0.0124	0.1767	0.5707	0.062*
H6	−0.0946	0.0988	0.3512	0.053*
H7	0.0401	0.0928	0.2781	0.053*
H8	−0.0322	0.1678	0.3010	0.053*
H9	0.6534	0.2570	0.4796	0.058*
H10	0.5682	0.2291	0.5725	0.058*
H11	0.4709	0.2862	0.4876	0.058*
H12	0.3141	0.2536	0.2619	0.054*
H13	0.3093	0.1765	0.2123	0.054*
H14	0.4842	0.2201	0.2398	0.054*
H15	0.4727	−0.1406	0.9023	0.060*
H16	0.2916	−0.1016	0.8686	0.060*
H17	0.4323	−0.0771	0.9741	0.060*
H18	0.7727	−0.0130	0.9452	0.068*
H19	0.7919	0.0076	0.8271	0.068*
H20	0.7947	−0.0730	0.8620	0.068*
H21	0.1841	0.1104	0.8819	0.075*
H22	0.0906	0.0500	0.8019	0.075*
H23	0.0906	0.1287	0.7591	0.075*
H24	0.4378	0.1958	0.7440	0.079*
H25	0.6045	0.1478	0.7578	0.079*
H26	0.5373	0.1689	0.8615	0.079*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si1	0.0281 (2)	0.0210 (2)	0.0237 (2)	0.00390 (15)	0.00974 (17)	0.00293 (15)
Si2	0.0282 (2)	0.0175 (2)	0.0200 (2)	−0.00024 (15)	0.00618 (17)	0.00197 (14)
Si3	0.0354 (3)	0.0275 (2)	0.0153 (2)	−0.00299 (17)	0.00606 (18)	−0.00042 (15)
Si4	0.0461 (3)	0.0221 (2)	0.0199 (2)	−0.00391 (18)	0.01276 (19)	−0.00352 (16)
C1	0.0220 (8)	0.0228 (7)	0.0226 (7)	−0.0009 (5)	0.0093 (6)	0.0020 (6)
C2	0.0225 (8)	0.0200 (7)	0.0201 (7)	−0.0035 (5)	0.0088 (6)	0.0019 (5)
C3	0.0235 (8)	0.0218 (7)	0.0186 (7)	−0.0048 (5)	0.0075 (6)	0.0015 (5)
C4	0.0262 (8)	0.0200 (7)	0.0197 (7)	−0.0041 (5)	0.0100 (6)	−0.0012 (5)
C5	0.0278 (8)	0.0277 (8)	0.0170 (7)	0.0010 (6)	0.0036 (6)	0.0019 (6)
C6	0.0298 (9)	0.0226 (8)	0.0193 (7)	−0.0012 (6)	0.0067 (6)	−0.0031 (5)
C7	0.0567 (12)	0.0318 (9)	0.0415 (10)	0.0143 (8)	0.0239 (9)	0.0031 (8)
C8	0.0297 (9)	0.0378 (10)	0.0374 (9)	0.0032 (7)	0.0056 (7)	0.0081 (7)
C9	0.0510 (11)	0.0228 (8)	0.0390 (9)	−0.0052 (7)	0.0062 (8)	−0.0034 (7)
C10	0.0478 (11)	0.0330 (9)	0.0282 (9)	0.0084 (7)	0.0108 (8)	0.0100 (7)
C11	0.0630 (13)	0.0371 (10)	0.0242 (8)	−0.0023 (8)	0.0181 (8)	0.0047 (7)
C12	0.0414 (11)	0.0606 (13)	0.0306 (9)	−0.0043 (9)	0.0030 (8)	−0.0091 (8)
C13	0.0696 (14)	0.0514 (12)	0.0374 (10)	0.0154 (10)	0.0303 (10)	0.0010 (9)
C14	0.0894 (17)	0.0341 (10)	0.0328 (10)	−0.0244 (10)	0.0104 (10)	−0.0051 (8)

Geometric parameters (Å, º) top

Si1—Si2	2.3805 (6)	C7—H4	0.9700
Si1—C1	1.8919 (15)	C7—H5	0.9700
Si1—C7	1.8785 (17)	C8—H6	0.9700
Si1—C8	1.8762 (18)	C8—H7	0.9700
Si2—C2	1.8902 (15)	C8—H8	0.9700
Si2—C9	1.8824 (17)	C9—H9	0.9700
Si2—C10	1.8758 (16)	C9—H10	0.9700
Si3—Si4	2.3245 (7)	C9—H11	0.9700
Si3—C11	1.8746 (17)	C10—H12	0.9700
Si3—C12	1.871 (2)	C10—H13	0.9700
Si3—C3ⁱ	1.9067 (15)	C10—H14	0.9700
Si4—C4	1.9004 (15)	C11—H15	0.9700
Si4—C13	1.873 (2)	C11—H16	0.9700
Si4—C14	1.8781 (19)	C11—H17	0.9700
C1—C4	1.417 (2)	C12—H18	0.9700
C1—C5	1.399 (2)	C12—H19	0.9700
C2—C3	1.418 (2)	C12—H20	0.9700
C2—C6	1.396 (2)	C13—H21	0.9700
C3—C4ⁱ	1.431 (2)	C13—H22	0.9700
C5—C6ⁱ	1.390 (2)	C13—H23	0.9700
C5—H1	0.9400	C14—H24	0.9700
C6—H2	0.9400	C14—H25	0.9700
C7—H3	0.9700	C14—H26	0.9700

Si2—Si1—C1	105.08 (5)	H3—C7—H4	109.5
Si2—Si1—C7	112.03 (7)	H3—C7—H5	109.5
Si2—Si1—C8	109.07 (6)	H4—C7—H5	109.5
C1—Si1—C7	114.11 (7)	Si1—C8—H6	109.5
C1—Si1—C8	109.64 (7)	Si1—C8—H7	109.5
C7—Si1—C8	106.85 (9)	Si1—C8—H8	109.5
Si1—Si2—C2	105.07 (5)	H6—C8—H7	109.5
Si1—Si2—C9	110.84 (6)	H6—C8—H8	109.5
Si1—Si2—C10	111.80 (6)	H7—C8—H8	109.5
C2—Si2—C9	109.74 (8)	Si2—C9—H9	109.5
C2—Si2—C10	113.21 (7)	Si2—C9—H10	109.5
C9—Si2—C10	106.26 (8)	Si2—C9—H11	109.5
Si4—Si3—C11	119.05 (7)	H9—C9—H10	109.5
Si4—Si3—C12	116.39 (7)	H9—C9—H11	109.5
Si4—Si3—C3ⁱ	76.36 (5)	H10—C9—H11	109.5
C11—Si3—C12	109.08 (9)	Si2—C10—H12	109.5
C11—Si3—C3ⁱ	116.01 (7)	Si2—C10—H13	109.5
C12—Si3—C3ⁱ	117.06 (7)	Si2—C10—H14	109.5
Si3—Si4—C4	76.50 (5)	H12—C10—H13	109.5
Si3—Si4—C13	118.85 (7)	H12—C10—H14	109.5
Si3—Si4—C14	116.39 (8)	H13—C10—H14	109.5
C4—Si4—C13	114.32 (8)	Si3—C11—H15	109.5
C4—Si4—C14	116.73 (8)	Si3—C11—H16	109.5
C13—Si4—C14	110.50 (11)	Si3—C11—H17	109.5
Si1—C1—C4	127.24 (11)	H15—C11—H16	109.5
Si1—C1—C5	115.53 (11)	H15—C11—H17	109.5
C4—C1—C5	116.18 (13)	H16—C11—H17	109.5
Si2—C2—C3	127.03 (11)	Si3—C12—H18	109.5
Si2—C2—C6	115.79 (11)	Si3—C12—H19	109.5
C3—C2—C6	116.36 (13)	Si3—C12—H20	109.5
Si3ⁱ—C3—C2	135.73 (11)	H18—C12—H19	109.5
Si3ⁱ—C3—C4ⁱ	103.43 (10)	H18—C12—H20	109.5
C2—C3—C4ⁱ	120.82 (13)	H19—C12—H20	109.5
Si4—C4—C1	135.16 (11)	Si4—C13—H21	109.5
Si4—C4—C3ⁱ	103.70 (10)	Si4—C13—H22	109.5
C1—C4—C3ⁱ	121.09 (13)	Si4—C13—H23	109.5
C1—C5—C6ⁱ	122.44 (14)	H21—C13—H22	109.5
C1—C5—H1	118.8	H21—C13—H23	109.5
C6ⁱ—C5—H1	118.8	H22—C13—H23	109.5
C2—C6—C5ⁱ	122.46 (13)	Si4—C14—H24	109.5
C2—C6—H2	118.8	Si4—C14—H25	109.5
C5ⁱ—C6—H2	118.8	Si4—C14—H26	109.5
Si1—C7—H3	109.5	H24—C14—H25	109.5
Si1—C7—H4	109.5	H24—C14—H26	109.5
Si1—C7—H5	109.5	H25—C14—H26	109.5

C1—Si1—Si2—C2	11.34 (7)	C12—Si3—Si4—C4	113.08 (8)
C1—Si1—Si2—C9	−107.13 (8)	C12—Si3—Si4—C13	−136.36 (10)
C1—Si1—Si2—C10	134.52 (8)	C12—Si3—Si4—C14	−0.33 (10)
C7—Si1—Si2—C2	135.78 (8)	C3ⁱ—Si3—Si4—C4	−0.64 (6)
C7—Si1—Si2—C9	17.31 (9)	C3ⁱ—Si3—Si4—C13	109.93 (9)
C7—Si1—Si2—C10	−101.04 (9)	C3ⁱ—Si3—Si4—C14	−114.04 (8)
C8—Si1—Si2—C2	−106.14 (8)	Si3—Si4—C4—C1	178.26 (16)
C8—Si1—Si2—C9	135.39 (9)	Si3—Si4—C4—C3ⁱ	0.85 (8)
C8—Si1—Si2—C10	17.04 (9)	C13—Si4—C4—C1	62.41 (17)
Si2—Si1—C1—C4	85.99 (13)	C13—Si4—C4—C3ⁱ	−115.00 (11)
Si2—Si1—C1—C5	−81.76 (11)	C14—Si4—C4—C1	−68.73 (18)
C7—Si1—C1—C4	−37.12 (16)	C14—Si4—C4—C3ⁱ	113.86 (12)
C7—Si1—C1—C5	155.13 (12)	Si1—C1—C4—Si4	21.9 (2)
C8—Si1—C1—C4	−156.92 (13)	Si1—C1—C4—C3ⁱ	−160.99 (11)
C8—Si1—C1—C5	35.33 (13)	C5—C1—C4—Si4	−170.37 (12)
Si1—Si2—C2—C3	86.84 (12)	C5—C1—C4—C3ⁱ	6.7 (2)
Si1—Si2—C2—C6	−82.38 (11)	Si1—C1—C5—C6ⁱ	162.33 (12)
C9—Si2—C2—C3	−153.95 (13)	C4—C1—C5—C6ⁱ	−6.8 (2)
C9—Si2—C2—C6	36.83 (13)	Si2—C2—C3—Si3ⁱ	18.9 (2)
C10—Si2—C2—C3	−35.43 (15)	Si2—C2—C3—C4ⁱ	−163.08 (11)
C10—Si2—C2—C6	155.35 (11)	C6—C2—C3—Si3ⁱ	−171.94 (12)
C11—Si3—Si4—C4	−113.06 (8)	C6—C2—C3—C4ⁱ	6.1 (2)
C11—Si3—Si4—C13	−2.49 (11)	Si2—C2—C6—C5ⁱ	164.24 (12)
C11—Si3—Si4—C14	133.53 (10)	C3—C2—C6—C5ⁱ	−6.2 (2)

Symmetry code: (i) −x+1, −y, −z+1.

Experimental details

Crystal data
Chemical formula	C₂₈H₅₂Si₈
M_r	613.42
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	203
a, b, c (Å)	7.9801 (8), 18.9087 (14), 12.6222 (10)
β (°)	104.2788 (9)
V (Å³)	1845.8 (3)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.31
Crystal size (mm)	0.25 × 0.25 × 0.25

Data collection
Diffractometer	Rigaku R-AXIS IV imaging plate diffractometer
Absorption correction	Multi-scan (REQAB; Jacobson, 1998)
T_min, T_max	0.927, 0.927
No. of measured, independent and observed [I > 2σ(I)] reflections	9672, 3096, 3076
R_int	0.016
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.029, 0.076, 1.11
No. of reflections	3096
No. of parameters	171
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.25, −0.25

Computer programs: CrystalClear (Rigaku, 2003), SIR2004 (Burla et al., 2005), ORTEP-3 for Windows (Farrugia, 2012), SHELXL97 (Sheldrick, 2008) and Yadokari-XG 2009 (Kabuto et al., 2009).

Acknowledgements

This work was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan and the Japan Society for the Promotion of Science. This work was also supported by the Element Innovation Project of Gunma University.

References

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