Influence of the molecular structures on the high-pressure and low-temperature phase transitions of plastic crystals

Wunschel, M.; Dinnebier, R.E.; Carlson, S.; Bernatowicz, P.; van Smaalen, S.

doi:10.1107/S0108768102021791

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Influence of the molecular structures on the high-pressure and low-temperature phase transitions of plastic crystals

M. Wunschel, R. E. Dinnebier, S. Carlson, P. Bernatowicz and S. van Smaalen

The crystal structures of tert-butyl-tris(trimethylsilyl)silane, Si[C(CH

)

]

[Si(CH

)

]

(Bu1), and di-tert-butyl-bis(trimethylsilyl)silane, Si[C(CH

)

]

[Si(CH

)

]

(Bu2), at room temperature and at 105 K have been determined by X-ray powder diffraction; the high-pressure behavior for pressures between 0 and 5 GPa is reported. The room-temperature structures have cubic $Fm\bar{3}m$ symmetry (Z = 4) with a = 13.2645 (2) Å, V = 2333.87 (4) Å³ for Bu1 and a = 12.9673 (1) Å, V = 2180.46 (3) Å³ for Bu2. The molecules are arranged in a cubic close packing (c.c.p.) and exhibit at least 48-fold orientational disorder. Upon cooling both compounds undergo a first-order phase transition at temperatures

= 230 (5) K (Bu1) and

= 250 (5) K (Bu2) into monoclinic structures with space group

. The structures at 105 K have a = 17.317 (1), b = 15.598 (1), c = 16.385 (1) Å, $\gamma$ = 109.477 (4)°, V = 4172.7 (8) Å³ and Z = 8 for Bu1and a = 17.0089 (9), b = 15.3159 (8), c = 15.9325 (8) Å, $\gamma$ = 110.343 (3)°, V = 3891.7 (5) Å³ and Z = 8 for Bu2. The severe disorder of the room-temperature phase is significantly decreased and only a two- or threefold rotational disorder of the molecules remains at 105 K. First-order phase transitions have been observed at pressures of 0.13-0.28 GPa for Bu1 and 0.20-0.24 GPa for Bu2. The high-pressure structures are isostructural to the low-temperature structures. The pressure dependencies of the unit-cell volumes were fitted with Vinet equations of state and the bulk moduli were obtained. At still higher pressures further anomalies in the pressure dependencies of the lattice parameters were observed. These anomalies are explained as additional disorder-order phase transitions.

Keywords: X-ray powder diffraction; synchrotron radiation; temperature dependence; high-pressure behavior; plastic crystals.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768102021791/os0101sup1.cif Contains datablocks global, 1, 2at105, 2at295
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768102021791/os01011sup2.hkl Contains datablock 1
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768102021791/os01012at105sup3.hkl Contains datablock 2at105
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768102021791/os01012at295sup4.hkl Contains datablock 2at295

CCDC references: 205164; 205165

Computing details top

For all compounds, data collection: SPEC package ESRF; cell refinement: JANA2000. Program(s) used to solve structure: DASH for (1), 2at105. For all compounds, program(s) used to refine structure: JANA2000; software used to prepare material for publication: JANA2000.

(1) top

Crystal data top

C₁₃H₃₆Si₄	Z = 8
M_r = 304.8	F(000) = 1245
Monoclinic, P_1_1_2₁/n	D_x = 0.970 (1) Mg m⁻³
a = 17.317 (1) Å	Synchrotron radiation, λ = 0.399828(2) Å
b = 15.598 (1) Å	µ = 0.22 mm⁻¹
c = 16.385 (1) Å	T = 105 K
β = 90°	colourless
V = 4172.7 (5) Å³	cylinder, 0.5 × 0.5 mm

Data collection top

Two-circle diffractometer	Data collection mode: transmission
Radiation source: synchrotron, ESRF beamline BM16	Scan method: continuous
Si(111) monochromator	2θ_min = 1.4°, 2θ_max = 13.997°, 2θ_step = 0.003°
Specimen mounting: lithiumborate glass capillary 0.5 mm diameter

Refinement top

Refinement on I_net	60 parameters
R_p = 0.066	6 restraints
R_wp = 0.084	73 constraints
R_exp = 0.145	H-atom parameters not defined
R(F) = 0.068	Weighting scheme based on measured s.u.'s
4200 data points	Background function: Manual background combined with 5 terms Legendre polynomial
Profile function: Pseudo-Voigt	Preferred orientation correction: none

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Si0a	0.1553 (7)	0.2422 (9)	0.3867 (8)	0.073 (7)*
C11a	0.1151 (8)	0.2906 (10)	0.4739 (9)	0.037 (4)*	0.507
C111a	0.1881 (11)	0.3779 (12)	0.5095 (10)	0.041 (6)*	0.659
C111/1a	0.0395 (9)	0.3220 (10)	0.4423 (11)	0.041 (6)*	0.659
C111/2a	0.0833 (11)	0.2134 (12)	0.5444 (11)	0.041 (6)*	0.659
C11d	0.1776 (8)	0.1412 (11)	0.4259 (8)	0.037 (4)*	0.493
C111d	0.1259 (9)	0.0525 (13)	0.3729 (10)	0.041 (6)*	0.641
C111/1d	0.2752 (11)	0.1588 (12)	0.4169 (9)	0.041 (6)*	0.641
C111/2d	0.1509 (11)	0.1262 (13)	0.5214 (10)	0.041 (6)*	0.641
Si0e	0.3431 (9)	0.7714 (12)	0.6135 (9)	0.073 (7)*
C11e	0.2856 (10)	0.8454 (12)	0.5771 (9)	0.037 (4)*	0.506
C111e	0.2128 (11)	0.8399 (13)	0.6418 (11)	0.041 (6)*	0.6574
C111/1e	0.3480 (12)	0.9494 (14)	0.5705 (9)	0.041 (6)*	0.6574
C111/2e	0.2466 (12)	0.8100 (15)	0.4880 (11)	0.041 (6)*	0.6574
C11f	0.2720 (10)	0.6622 (13)	0.6534 (9)	0.037 (4)*	0.278
C111f	0.1929 (12)	0.6800 (14)	0.6938 (9)	0.041 (6)*	0.3614
C111/1f	0.2430 (10)	0.5902 (14)	0.5784 (12)	0.041 (6)*	0.3614
C111/2f	0.3193 (11)	0.6229 (14)	0.7220 (12)	0.041 (6)*	0.3614
C11g	0.4012 (10)	0.7291 (12)	0.5373 (9)	0.037 (4)*	0.216
C111g	0.4232 (10)	0.6443 (14)	0.5765 (11)	0.041 (6)*	0.2812
C111/1g	0.3450 (12)	0.6959 (12)	0.4562 (11)	0.041 (6)*	0.2812
C111/2g	0.4850 (12)	0.8110 (13)	0.5141 (12)	0.041 (6)*	0.2812
Si21a	0.1042 (8)	0.3038 (9)	0.4975 (9)	0.037 (4)*	0.493
C211a	0.1774 (8)	0.3186 (9)	0.5895 (9)	0.041 (6)*	0.641
C211/1a	0.0973 (8)	0.4205 (10)	0.4664 (9)	0.041 (6)*	0.641
C211/2a	−0.0034 (8)	0.2221 (10)	0.5264 (9)	0.041 (6)*	0.641
Si21b	0.0586 (8)	0.2008 (9)	0.2797 (8)	0.037 (4)*
C211b	0.0577 (8)	0.3091 (11)	0.2230 (9)	0.041 (6)*
C211/1b	0.0885 (8)	0.1213 (10)	0.2049 (9)	0.041 (6)*
C211/2b	−0.0487 (8)	0.1384 (10)	0.3247 (9)	0.041 (6)*
Si21c	0.2749 (8)	0.3427 (10)	0.3261 (8)	0.037 (4)*
C211c	0.2538 (8)	0.4507 (10)	0.2897 (8)	0.041 (6)*
C211/1c	0.3624 (8)	0.3754 (10)	0.4056 (9)	0.041 (6)*
C211/2c	0.3054 (9)	0.2834 (10)	0.2340 (9)	0.041 (6)*
Si21d	0.1837 (7)	0.1139 (10)	0.4365 (8)	0.037 (4)*	0.507
C211d	0.0825 (9)	0.0224 (10)	0.4697 (8)	0.041 (6)*	0.659
C211/1d	0.2349 (8)	0.0661 (10)	0.3513 (9)	0.041 (6)*	0.659
C211/2d	0.2567 (8)	0.1495 (10)	0.5290 (9)	0.041 (6)*	0.659
Si21e	0.2700 (9)	0.8654 (12)	0.5673 (9)	0.037 (4)*	0.494
C211e	0.2585 (9)	0.9420 (12)	0.6560 (10)	0.041 (6)*	0.6426
C211/1e	0.3293 (10)	0.9402 (12)	0.4784 (9)	0.041 (6)*	0.6426
C211/2e	0.1629 (10)	0.7903 (12)	0.5300 (10)	0.041 (6)*	0.6426
Si21f	0.2527 (9)	0.6326 (12)	0.6642 (9)	0.037 (4)*	0.722
C211f	0.2169 (9)	0.6517 (12)	0.7723 (10)	0.041 (6)*	0.9386
C211/1f	0.1591 (10)	0.5892 (12)	0.5924 (9)	0.041 (6)*	0.9386
C211/2f	0.3089 (10)	0.5444 (12)	0.6688 (10)	0.041 (6)*	0.9386
Si21g	0.4169 (9)	0.7177 (12)	0.5167 (9)	0.037 (4)*	0.784
C211g	0.4610 (9)	0.6328 (12)	0.5689 (10)	0.041 (6)*
C211/1g	0.3442 (10)	0.6574 (12)	0.4292 (9)	0.041 (6)*
C211/2g	0.5054 (10)	0.8192 (12)	0.4736 (10)	0.041 (6)*
Si21h	0.4368 (9)	0.8365 (12)	0.7193 (9)	0.037 (4)*
C211h	0.3770 (10)	0.8406 (12)	0.8180 (10)	0.041 (6)*
C211/1h	0.5060 (10)	0.7633 (12)	0.7371 (9)	0.041 (6)*
C211/2h	0.5034 (10)	0.9584 (12)	0.6884 (9)	0.041 (6)*

Geometric parameters (Å, º) top

Si0a—C11a	1.86 (2)	C11g—C111/1g	1.63 (2)
Si0a—C11d	1.86 (2)	C11g—C111/2g	1.63 (2)
Si0a—Si21a	2.36 (2)	Si21a—C211a	1.93 (2)
Si0a—Si21b	2.359 (18)	Si21a—C211/1a	1.93 (2)
Si0a—Si21c	2.359 (17)	Si21a—C211/2a	1.933 (17)
Si0a—Si21d	2.36 (2)	Si21b—C211b	1.93 (2)
C11a—C111a	1.63 (2)	Si21b—C211/1b	1.93 (2)
C11a—C111/1a	1.63 (2)	Si21b—C211/2b	1.933 (18)
C11a—C111/2a	1.63 (2)	Si21c—C211c	1.93 (2)
C11d—C111d	1.63 (2)	Si21c—C211/1c	1.93 (2)
C11d—C111/1d	1.63 (2)	Si21c—C211/2c	1.93 (2)
C11d—C111/2d	1.63 (2)	Si21d—C211d	1.933 (17)
Si0e—C11e	1.86 (3)	Si21d—C211/1d	1.93 (2)
Si0e—C11f	1.86 (2)	Si21d—C211/2d	1.933 (19)
Si0e—C11g	1.86 (2)	Si21e—C211e	1.93 (2)
Si0e—Si21e	2.36 (3)	Si21e—C211/1e	1.93 (2)
Si0e—Si21f	2.36 (2)	Si21e—C211/2e	1.93 (2)
Si0e—Si21g	2.36 (2)	Si21f—C211f	1.93 (2)
Si0e—Si21h	2.36 (2)	Si21f—C211/1f	1.93 (2)
C11e—C111e	1.63 (3)	Si21f—C211/2f	1.93 (3)
C11e—C111/1e	1.63 (2)	Si21g—C211g	1.93 (3)
C11e—C111/2e	1.63 (2)	Si21g—C211/1g	1.93 (2)
C11f—C111f	1.63 (3)	Si21g—C211/2g	1.93 (2)
C11f—C111/1f	1.63 (3)	Si21h—C211h	1.93 (2)
C11f—C111/2f	1.63 (3)	Si21h—C211/1h	1.93 (3)
C11g—C111g	1.63 (3)	Si21h—C211/2h	1.93 (2)

C11a—Si0a—C11d	106.9 (9)	Si21e—Si0e—Si21h	113.8 (9)
C11a—Si0a—Si21a	0	Si21f—Si0e—Si21g	100.5 (9)
C11a—Si0a—Si21b	110.8 (9)	Si21f—Si0e—Si21h	106.7 (8)
C11a—Si0a—Si21c	114.7 (8)	Si21g—Si0e—Si21h	105.7 (8)
C11a—Si0a—Si21d	106.9 (8)	C111e—C11e—C111/1e	110.0 (14)
C11d—Si0a—Si21a	106.9 (8)	C111e—C11e—C111/2e	110.0 (13)
C11d—Si0a—Si21b	110.8 (8)	C111/1e—C11e—C111/2e	110.0 (12)
C11d—Si0a—Si21c	108.9 (8)	C111f—C11f—C111/1f	110.0 (12)
C11d—Si0a—Si21d	0	C111f—C11f—C111/2f	110.0 (13)
Si21a—Si0a—Si21b	110.8 (8)	C111/1f—C11f—C111/2f	110.0 (16)
Si21a—Si0a—Si21c	114.7 (7)	C111g—C11g—C111/1g	110.0 (14)
Si21a—Si0a—Si21d	106.9 (7)	C111g—C11g—C111/2g	110.0 (14)
Si21b—Si0a—Si21c	104.8 (7)	C111/1g—C11g—C111/2g	110.0 (13)
Si21b—Si0a—Si21d	110.8 (7)	C211a—Si21a—C211/1a	109.7 (9)
Si21c—Si0a—Si21d	108.9 (8)	C211a—Si21a—C211/2a	109.7 (9)
C111a—C11a—C111/1a	110.0 (13)	C211/1a—Si21a—C211/2a	109.7 (10)
C111a—C11a—C111/2a	110.0 (12)	C211b—Si21b—C211/1b	109.7 (9)
C111/1a—C11a—C111/2a	110.0 (12)	C211b—Si21b—C211/2b	109.7 (10)
C111d—C11d—C111/1d	110.0 (13)	C211/1b—Si21b—C211/2b	109.7 (9)
C111d—C11d—C111/2d	110.0 (11)	C211c—Si21c—C211/1c	109.7 (9)
C111/1d—C11d—C111/2d	110.0 (12)	C211c—Si21c—C211/2c	109.7 (9)
C11e—Si0e—C11f	110.7 (11)	C211/1c—Si21c—C211/2c	109.7 (10)
C11e—Si0e—C11g	118.1 (10)	C211d—Si21d—C211/1d	109.7 (9)
C11e—Si0e—Si21e	0	C211d—Si21d—C211/2d	109.7 (9)
C11e—Si0e—Si21f	110.7 (9)	C211/1d—Si21d—C211/2d	109.7 (9)
C11e—Si0e—Si21g	118.1 (9)	C211e—Si21e—C211/1e	109.7 (11)
C11e—Si0e—Si21h	113.8 (10)	C211e—Si21e—C211/2e	109.7 (11)
C11f—Si0e—C11g	100.5 (11)	C211/1e—Si21e—C211/2e	109.7 (10)
C11f—Si0e—Si21e	110.7 (10)	C211f—Si21f—C211/1f	109.7 (10)
C11f—Si0e—Si21f	0	C211f—Si21f—C211/2f	109.7 (11)
C11f—Si0e—Si21g	100.5 (10)	C211/1f—Si21f—C211/2f	109.7 (11)
C11f—Si0e—Si21h	106.7 (9)	C211g—Si21g—C211/1g	109.7 (11)
C11g—Si0e—Si21e	118.1 (10)	C211g—Si21g—C211/2g	109.7 (11)
C11g—Si0e—Si21f	100.5 (10)	C211/1g—Si21g—C211/2g	109.7 (10)
C11g—Si0e—Si21g	0	C211h—Si21h—C211/1h	109.7 (11)
C11g—Si0e—Si21h	105.7 (10)	C211h—Si21h—C211/2h	109.7 (11)
Si21e—Si0e—Si21f	110.7 (8)	C211/1h—Si21h—C211/2h	109.7 (10)
Si21e—Si0e—Si21g	118.1 (8)

(2at105) top

Crystal data top

C₁₄H₃₆Si₃	Z = 8
M_r = 288.7	F(000) = 1181
Monoclinic, P_1_1_2₁/n	D_x = 0.986 (1) Mg m⁻³
a = 17.0089 (9) Å	Synchrotron radiation, λ = 0.399828(2) Å
b = 15.3159 (8) Å	µ = 0.18 mm⁻¹
c = 15.9325 (8) Å	T = 105 K
β = 90°	colourless
V = 3891.7 (5) Å³	cylinder, 0.5 × 0.5 mm

Data collection top

Two-circle diffractometer	Data collection mode: transmission
Radiation source: synchrotron, ESRF beamline BM16	Scan method: continuous
Si(111) monochromator	2θ_min = 0.5°, 2θ_max = 13.997°, 2θ_step = 0.003°
Specimen mounting: lithiumborate glass capillary 0.5 mm diameter

Refinement top

Refinement on I_net	6 restraints
R_p = 0.067	59 constraints
R_wp = 0.089	H-atom parameters not defined
R(F) = 0.078	Weighting scheme based on measured s.u.'s
4500 data points	Background function: Manual background combined with 5 terms Legendre polynomial
Profile function: Pseudo-Voigt	Preferred orientation correction: none
74 parameters

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Si0a	0.1469 (8)	0.2438 (8)	0.3627 (7)	0.061 (5)*
C11a	0.1218 (8)	0.3217 (8)	0.4500 (8)	0.064 (5)*	0.534
C111a	0.1408 (8)	0.4326 (10)	0.4139 (9)	0.019 (4)*	0.6945
C111/1a	0.0187 (9)	0.2763 (9)	0.4800 (8)	0.019 (4)*	0.6945
C111/2a	0.1826 (9)	0.3286 (10)	0.5373 (8)	0.019 (4)*	0.6945
C11b	0.0758 (8)	0.1970 (8)	0.2631 (8)	0.064 (5)*
C111b	0.0751 (8)	0.2872 (10)	0.1997 (8)	0.019 (4)*
C111/1b	0.1119 (9)	0.1244 (8)	0.2052 (8)	0.019 (4)*
C111/2b	−0.0256 (9)	0.1360 (9)	0.2918 (8)	0.019 (4)*
C11c	0.2382 (8)	0.3649 (9)	0.3496 (7)	0.064 (5)*	0.284
C111c	0.3073 (9)	0.3854 (9)	0.4318 (9)	0.019 (4)*	0.3687
C111/1c	0.2928 (9)	0.3679 (9)	0.2586 (8)	0.019 (4)*	0.3687
C111/2c	0.1991 (9)	0.4541 (9)	0.3463 (9)	0.019 (4)*	0.3687
C11d	0.1451 (8)	0.1578 (9)	0.4556 (8)	0.064 (5)*	0.182
C111d	0.2351 (9)	0.1315 (9)	0.4566 (8)	0.019 (4)*	0.2367
C111/1d	0.1367 (8)	0.2065 (9)	0.5506 (9)	0.019 (4)*	0.2367
C111/2d	0.0617 (9)	0.0557 (9)	0.4458 (9)	0.019 (4)*	0.2367
Si0e	0.3413 (7)	0.7739 (7)	0.6184 (7)	0.061 (5)*
C11e	0.3000 (7)	0.8669 (8)	0.5666 (7)	0.064 (5)*	0.796
C111e	0.3646 (8)	0.9241 (8)	0.4863 (8)	0.019 (4)*
C111/1e	0.2013 (8)	0.8146 (9)	0.5264 (7)	0.019 (4)*
C111/2e	0.2960 (9)	0.9481 (9)	0.6388 (8)	0.019 (4)*
C11f	0.2631 (8)	0.6743 (8)	0.6874 (7)	0.064 (5)*	0.770
C111f	0.3163 (9)	0.6189 (8)	0.7459 (7)	0.019 (4)*
C111/1f	0.2081 (8)	0.7187 (9)	0.7550 (8)	0.019 (4)*
C111/2f	0.1924 (8)	0.5927 (9)	0.6254 (8)	0.019 (4)*
C11g	0.3946 (7)	0.7416 (7)	0.5189 (7)	0.064 (5)*	0.434
C111g	0.4879 (8)	0.8280 (9)	0.4965 (8)	0.019 (4)*	0.5648
C111/1g	0.4143 (7)	0.6405 (8)	0.5353 (8)	0.019 (4)*	0.5648
C111/2g	0.3310 (8)	0.7261 (9)	0.4326 (8)	0.019 (4)*	0.5648
Si21a	0.0964 (8)	0.3025 (8)	0.4812 (8)	0.064 (5)*	0.466
C211a	0.0539 (8)	0.4008 (9)	0.4456 (9)	0.019 (4)*	0.6055
C211/1a	0.0052 (9)	0.2015 (10)	0.5349 (8)	0.019 (4)*	0.6055
C211/2a	0.1877 (9)	0.3546 (10)	0.5625 (9)	0.019 (4)*	0.6055
Si21c	0.2818 (8)	0.3597 (9)	0.3472 (7)	0.064 (5)*	0.716
C211c	0.3516 (9)	0.3579 (9)	0.4451 (9)	0.019 (4)*	0.9313
C211/1c	0.3358 (9)	0.3353 (10)	0.2452 (8)	0.019 (4)*	0.9313
C211/2c	0.2712 (9)	0.4831 (10)	0.3383 (9)	0.019 (4)*	0.9313
Si21d	0.1793 (8)	0.1107 (9)	0.4029 (7)	0.064 (5)*	0.818
C211d	0.2783 (9)	0.1081 (9)	0.3408 (8)	0.019 (4)*
C211/1d	0.2029 (8)	0.1154 (10)	0.5239 (9)	0.019 (4)*
C211/2d	0.0838 (9)	−0.0029 (10)	0.3777 (9)	0.019 (4)*
Si21e	0.2572 (7)	0.8682 (8)	0.6009 (7)	0.064 (5)*	0.204
C211e	0.3283 (9)	1.0004 (10)	0.6040 (7)	0.019 (4)*	0.2655
C211/1e	0.1987 (8)	0.8405 (8)	0.4925 (8)	0.019 (4)*	0.2655
C211/2e	0.1739 (9)	0.8428 (9)	0.6917 (8)	0.019 (4)*	0.2655
Si21f	0.2241 (8)	0.6414 (8)	0.6562 (7)	0.064 (5)*	0.230
C211f	0.2104 (8)	0.6363 (9)	0.7789 (9)	0.019 (4)*	0.2993
C211/1f	0.1220 (9)	0.6491 (9)	0.6040 (7)	0.019 (4)*	0.2993
C211/2f	0.2414 (9)	0.5276 (9)	0.6175 (8)	0.019 (4)*	0.2993
Si21g	0.4343 (7)	0.7217 (7)	0.5385 (7)	0.064 (5)*	0.566
C211g	0.5285 (8)	0.8293 (10)	0.4979 (7)	0.019 (4)*	0.7352
C211/1g	0.4779 (8)	0.6432 (8)	0.6086 (8)	0.019 (4)*	0.7352
C211/2g	0.3745 (8)	0.6488 (9)	0.4418 (8)	0.019 (4)*	0.7352
Si21h	0.4453 (8)	0.8344 (7)	0.7234 (7)	0.064 (5)*
C211h	0.3923 (9)	0.8525 (8)	0.8284 (8)	0.019 (4)*
C211/1h	0.5048 (8)	0.7470 (9)	0.7434 (8)	0.019 (4)*
C211/2h	0.5261 (9)	0.9546 (9)	0.6865 (8)	0.019 (4)*

Geometric parameters (Å, º) top

Si0a—C11a	1.973 (19)	C11e—C111/2e	1.714 (18)
Si0a—C11b	1.973 (17)	C11f—C111f	1.71 (2)
Si0a—C11c	1.973 (15)	C11f—C111/1f	1.71 (2)
Si0a—C11d	1.973 (18)	C11f—C111/2f	1.714 (16)
Si0a—Si21a	2.376 (19)	C11g—C111g	1.714 (15)
Si0a—Si21c	2.376 (16)	C11g—C111/1g	1.714 (19)
Si0a—Si21d	2.38 (2)	C11g—C111/2g	1.714 (18)
C11a—C111a	1.714 (19)	Si21a—C211a	1.97 (2)
C11a—C111/1a	1.714 (18)	Si21a—C211/1a	1.965 (17)
C11a—C111/2a	1.714 (19)	Si21a—C211/2a	1.965 (18)
C11b—C111b	1.71 (2)	Si21c—C211c	1.97 (2)
C11b—C111/1b	1.71 (2)	Si21c—C211/1c	1.97 (2)
C11b—C111/2b	1.714 (18)	Si21c—C211/2c	1.97 (2)
C11c—C111c	1.714 (19)	Si21d—C211d	1.97 (2)
C11c—C111/1c	1.714 (19)	Si21d—C211/1d	1.965 (18)
C11c—C111/2c	1.71 (2)	Si21d—C211/2d	1.965 (16)
C11d—C111d	1.71 (2)	Si21e—C211e	1.965 (16)
C11d—C111/1d	1.714 (19)	Si21e—C211/1e	1.965 (17)
C11d—C111/2d	1.714 (16)	Si21e—C211/2e	1.965 (18)
Si0e—C11e	1.973 (19)	Si21f—C211f	1.965 (18)
Si0e—C11f	1.973 (14)	Si21f—C211/1f	1.97 (2)
Si0e—C11g	1.973 (17)	Si21f—C211/2f	1.97 (2)
Si0e—Si21e	2.376 (19)	Si21g—C211g	1.965 (15)
Si0e—Si21f	2.376 (14)	Si21g—C211/1g	1.965 (19)
Si0e—Si21g	2.376 (18)	Si21g—C211/2g	1.965 (17)
Si0e—Si21h	2.376 (15)	Si21h—C211h	1.965 (19)
C11e—C111e	1.714 (16)	Si21h—C211/1h	1.97 (2)
C11e—C111/1e	1.714 (16)	Si21h—C211/2h	1.965 (15)

C11a—Si0a—C11b	123.6 (9)	Si21f—Si0e—Si21g	107.9 (6)
C11a—Si0a—C11c	76.8 (7)	Si21f—Si0e—Si21h	116.4 (6)
C11a—Si0a—C11d	85.3 (7)	Si21g—Si0e—Si21h	90.9 (6)
C11a—Si0a—Si21a	13.8 (4)	Si0e—C11e—C111e	110.9 (9)
C11a—Si0a—Si21c	88.7 (6)	Si0e—C11e—C111/1e	110.9 (8)
C11a—Si0a—Si21d	119.5 (7)	Si0e—C11e—C111/2e	110.9 (8)
C11b—Si0a—C11c	116.0 (7)	C111e—C11e—C111/1e	108.0 (8)
C11b—Si0a—C11d	119.7 (7)	C111e—C11e—C111/2e	108.0 (8)
C11b—Si0a—Si21a	121.4 (8)	C111/1e—C11e—C111/2e	108.0 (10)
C11b—Si0a—Si21c	119.9 (7)	Si0e—C11f—C111f	110.9 (8)
C11b—Si0a—Si21d	101.6 (7)	Si0e—C11f—C111/1f	110.9 (8)
C11c—Si0a—C11d	122.1 (8)	Si0e—C11f—C111/2f	110.9 (8)
C11c—Si0a—Si21a	89.9 (6)	C111f—C11f—C111/1f	108.0 (9)
C11c—Si0a—Si21c	17.6 (6)	C111f—C11f—C111/2f	108.0 (9)
C11c—Si0a—Si21d	119.6 (8)	C111/1f—C11f—C111/2f	108.0 (9)
C11d—Si0a—Si21a	74.5 (6)	Si0e—C11g—C111g	110.9 (8)
C11d—Si0a—Si21c	111.3 (7)	Si0e—C11g—C111/1g	110.9 (8)
C11d—Si0a—Si21d	35.0 (6)	Si0e—C11g—C111/2g	110.9 (9)
Si21a—Si0a—Si21c	100.5 (6)	C111g—C11g—C111/1g	108.0 (10)
Si21a—Si0a—Si21d	109.4 (6)	C111g—C11g—C111/2g	108.0 (8)
Si21c—Si0a—Si21d	102.5 (7)	C111/1g—C11g—C111/2g	108.0 (9)
Si0a—C11a—C111a	110.9 (9)	Si0a—Si21a—C211a	109.8 (8)
Si0a—C11a—C111/1a	110.9 (8)	Si0a—Si21a—C211/1a	109.8 (7)
Si0a—C11a—C111/2a	110.9 (10)	Si0a—Si21a—C211/2a	109.8 (8)
C111a—C11a—C111/1a	108.0 (11)	C211a—Si21a—C211/1a	109.2 (9)
C111a—C11a—C111/2a	108.0 (9)	C211a—Si21a—C211/2a	109.2 (8)
C111/1a—C11a—C111/2a	108.0 (9)	C211/1a—Si21a—C211/2a	109.2 (8)
Si0a—C11b—C111b	110.9 (8)	Si0a—Si21c—C211c	109.8 (7)
Si0a—C11b—C111/1b	110.9 (10)	Si0a—Si21c—C211/1c	109.8 (7)
Si0a—C11b—C111/2b	110.9 (9)	Si0a—Si21c—C211/2c	109.8 (9)
C111b—C11b—C111/1b	108.0 (10)	C211c—Si21c—C211/1c	109.2 (10)
C111b—C11b—C111/2b	108.0 (11)	C211c—Si21c—C211/2c	109.2 (8)
C111/1b—C11b—C111/2b	108.0 (9)	C211/1c—Si21c—C211/2c	109.2 (8)
Si0a—C11c—C111c	110.9 (9)	Si0a—Si21d—C211d	109.8 (7)
Si0a—C11c—C111/1c	110.9 (9)	Si0a—Si21d—C211/1d	109.8 (8)
Si0a—C11c—C111/2c	110.9 (9)	Si0a—Si21d—C211/2d	109.8 (8)
C111c—C11c—C111/1c	108.0 (10)	C211d—Si21d—C211/1d	109.2 (9)
C111c—C11c—C111/2c	108.0 (10)	C211d—Si21d—C211/2d	109.2 (9)
C111/1c—C11c—C111/2c	108.0 (10)	C211/1d—Si21d—C211/2d	109.2 (8)
Si0a—C11d—C111d	110.9 (8)	Si0e—Si21e—C211e	109.8 (8)
Si0a—C11d—C111/1d	110.9 (10)	Si0e—Si21e—C211/1e	109.8 (7)
Si0a—C11d—C111/2d	110.9 (9)	Si0e—Si21e—C211/2e	109.8 (7)
C111d—C11d—C111/1d	108.0 (9)	C211e—Si21e—C211/1e	109.2 (7)
C111d—C11d—C111/2d	108.0 (10)	C211e—Si21e—C211/2e	109.2 (8)
C111/1d—C11d—C111/2d	108.0 (9)	C211/1e—Si21e—C211/2e	109.2 (8)
C11e—Si0e—C11f	118.6 (8)	Si0e—Si21f—C211f	109.8 (6)
C11e—Si0e—C11g	98.9 (7)	Si0e—Si21f—C211/1f	109.8 (7)
C11e—Si0e—Si21e	22.0 (4)	Si0e—Si21f—C211/2f	109.8 (7)
C11e—Si0e—Si21f	108.6 (7)	C211f—Si21f—C211/1f	109.2 (8)
C11e—Si0e—Si21g	117.6 (6)	C211f—Si21f—C211/2f	109.2 (8)
C11e—Si0e—Si21h	114.6 (6)	C211/1f—Si21f—C211/2f	109.2 (8)
C11f—Si0e—C11g	119.9 (7)	Si0e—Si21g—C211g	109.8 (7)
C11f—Si0e—Si21e	98.6 (7)	Si0e—Si21g—C211/1g	109.8 (7)
C11f—Si0e—Si21f	19.7 (4)	Si0e—Si21g—C211/2g	109.8 (8)
C11f—Si0e—Si21g	112.7 (7)	C211g—Si21g—C211/1g	109.2 (8)
C11f—Si0e—Si21h	96.9 (6)	C211g—Si21g—C211/2g	109.2 (7)
C11g—Si0e—Si21e	119.0 (7)	C211/1g—Si21g—C211/2g	109.2 (8)
C11g—Si0e—Si21f	108.1 (6)	Si0e—Si21h—C211h	109.8 (7)
C11g—Si0e—Si21g	21.1 (5)	Si0e—Si21h—C211/1h	109.8 (7)
C11g—Si0e—Si21h	108.6 (7)	Si0e—Si21h—C211/2h	109.8 (7)
Si21e—Si0e—Si21f	92.6 (6)	C211h—Si21h—C211/1h	109.2 (8)
Si21e—Si0e—Si21g	138.9 (6)	C211h—Si21h—C211/2h	109.2 (7)
Si21e—Si0e—Si21h	111.7 (6)	C211/1h—Si21h—C211/2h	109.2 (8)

(2at295) top

Crystal data top

C₁₃H₃₆Si₄	D_x = 0.878 (1) Mg m⁻³
M_r = 304.8	Synchrotron radiation, λ = 0.399828(2) Å
Cubic, Fm3m	µ = 0.19 mm⁻¹
a = 13.2645 (2) Å	T = 295 K
V = 2333.9 (1) Å³	colourless
Z = 4	cylinder, 0.5 × 0.5 mm
F(000) = 680

Data collection top

Two-circle diffractometer	Data collection mode: transmission
Radiation source: synchrotron, ESRF beamline BM16	Scan method: continuous
Si(111) monochromator	2θ_min = 1.12°, 2θ_max = 21.52°, 2θ_step = 0.005°
Specimen mounting: lithiumborate glass capillary 0.5 mm diameter

Refinement top

Refinement on I_net	13 parameters
R_p = 0.197	0 restraints
R_wp = 0.268	Only H-atom displacement parameters refined
R_exp = 0.240	Weighting scheme based on measured s.u.'s
R(F) = 0.501	Background function: Manual background combined with 4 Legendre polynoms
4081 data points	Preferred orientation correction: none
Profile function: Lorentzian

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

	x	y	z	U_iso*/U_eq
Si0	0	0	0	0.230 (18)*
Si1	0	0	0	1.14 (14)*
C1	0	0	0	1.14 (14)*
Met1	0	0	0	0.98 (7)*
Met2	0	0	0	0.98 (7)*
H1	0	0	0	0.98 (7)*
H2	0	0	0	0.98 (7)*

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