The polyocta­hedral silsesquioxane (POSS) 1,3,5,7,9,11,13,15-octa­phenyl­penta­cyclo­[9.5.1.1^3,9.1^5,15.1^7,13]octa­siloxane (octa­phenyl-POSS)

Solvent-free single crystals of 1,3,5,7,9,11,13,15-octa­phenyl­penta­cyclo­[9.5.1.1^3,9.1^5,15.1^7,13]octa­siloxane (abbreviated as octa­phenyl-POSS), C₄₈H₄₀O₁₂Si₈, were obtained by dehydration/condensation of the tetrol Si₄O₄(Ph)₄(OH)₄. The powder pattern generated from the single-crystal data matches well with the experimentally measured powder pattern of commercial octa­phenyl-POSS. The geometry of the centrosymmetric molecule in the crystal was compared with that in the gas phase, and had shorter Si—O bond lengths and a broader range of Si—O—Si bond angles. The average Si—O bond length [1.621 (3) Å], and Si—O—Si and O—Si—O bond angles [149 (5) and 109 (1)°, respectively] were within the same range measured previously for octa­phenyl-POSS solvates.

S1. Introduction

Fully condensed polyo­cta­hedral silsesquioxanes (POSS) are used in a variety of materials applications that include reinforcement of composites, and as nanoscale building blocks for the assembly of two- and three-dimensional structures (Laine, 2005). The importance of POSS has generated numerous reviews of their synthesis (Voronkov & Lavrentyev, 1982), characterization (Baney et al., 1995; Lickiss & Rataboul, 2008; Cordes et al., 2010), and incorporation into polymers, copolymers and nano-composites (Bourbigot et al., 2006). Hydro­phobic T₈[alkyl]₈ are used as alternatives to silica nanoparticles in organic polymer matrices to provide increased thermal stability, reduced flammability, higher glass transition temperatures (T_gs), and improved mechanical properties (Lichtenhan, 1995; Provatas & Matisons, 1997; Pittman et al., 2003; Phillips et al., 2004; Joshi & Butola, 2004). The aryl­silsesquioxanes, of which the most common is o­cta­phenyl-POSS, are characterized by their high thermal stability, and have been reviewed separately (Laine & Roll, 2011). Octa­phenyl-POSS has poor solubility in common solvents, with slight solubility in pyridine and CH₂Cl₂ (Pakjamsai & Kawakami, 2005), but can be used in nanocomposites by melt blending with polycarbonate (Zhao & Schiraldi, 2005) and ep­oxy (Dodiuk et al., 2005) resins to improve tensile and dynamic mechanical moduli, strength and toughness.

Footnote: A polyhedral `T' unit is often used to denote an Si atom with three bridging siloxane O atoms (the core structure), and when there are phenyl units attached at the silicon vertices, can be labelled as T₈Ph₈, also referred to as phenyl-T8, o­cta­(phenyl­silasesquioxane), or o­cta­(phenyl polyhedral oligosilsesquioxanes), i.e. o­cta­phenyl-POSS (Registered trademark #2, 048 of Hybrid Plastics Inc. https://www.hybridplastics.com/) with the stoichiometry (RSiO_3/2)₈. The CAS number is [5256-79-1].

Single-crystal structures of several fully condensed symmetric T-8 cages (R₈Si₈O₁₂), with eight Si atoms arranged at the corners of a cube, 12 O atoms bridging the edges of the Si₈ cube forming an inter­stitial cubo­cta­hedron, and eight R groups at the corners of the tetra­hedral Si atoms, have been obtained. These include o­cta­(methyl­silsesquioxane) (R = CH₃; Larsson, 1960a), o­cta­silsesquioxane (R = H; Larsson, 1960c), o­cta­(vinyl­silsesquioxane) (R = C₂H₃; Baidina et al., 1979), o­cta­(meth­oxy­silsesquioxane) (R = OCH₃; Day et al., 1985), o­cta­(allyl­silsesquioxanes) [R = OSi(CH₃)₃; Podberezskaya et al., 1981], and o­cta­(tolyl­silsesquioxane) (R = tolyl; Zakharov et al., 2010). In the case of the o­cta­phenyl­silsesquioxane (C₆H₅SiO_1.5)₈(C₆H₅), there are older structure reports, with solvates of pyridine (Larsson, 1960b) and o-di­chloro­benzene (Shklover et al., 1978), hydrates of acetone (Hossain et al., 1979) or water (Liu et al., 2004), and for [Si₈O₁₂Ph₈F]^- in the salt [NBu₄][Si₈O₁₂Ph₈F] (Bassindale et al., 2003). The equilibrium molecular structure in the gas phase has also been determined by electron diffraction (Zakharov et al., 2010). The crystal structure of dodeca(phenyl­silasesquioxanes) have also been reported (Clegg et al., 1980). We report here the crystal structure of unsolvated o­cta­phenyl-POSS.

S2. Experimental

Si₄O₄(Ph)₄(OH)₄ was obtained as a gift from Hybrid Plastics Inc. The theoretical powder pattern of o­cta­phenyl–POSS was calculated using Mercury (Macrae et al., 2008).

S2.1. Synthesis and crystallization

Single crystals of o­cta­phenyl-POSS were obtained by the self-condensation of the tetrol Si₄O₄(Ph)₄(OH)₄ (15 mg) in an inner vial of methanol (1 ml), with an outer vial (3 ml) of ether. After 2 d at room temperature, crystals were observed. The tetrol is soluble in methanol and insoluble in ether, and o­cta­phenyl-POSS is insoluble in both methanol and ether. We were expecting crystals of tetrol, but instead obtained solvent-free crystals of o­cta­phenyl-POSS resulting from the dehydrative coupling of two molecules of the tetrol (see Scheme).

Octa­phenyl-POSS is more typically synthesized by hydrolysis of either PhSiCl₃ or PhSi(OEt)₃, first prepared in low yield (Olsson, 1958), but subsequently with improved yields (Voronkov & Lavrentyev, 1982; Lickiss & Rataboul, 2008). However, another route to the synthesis of R₈T₈ cages is through the condensation of R₄T₄-tetrols under pressurized hydrogen (Feher & Budzichowski, 1989) or using ammonium salts (Tateyama et al., 2010; Liu et al., 2004), where the R = phenyl-POSS was obtained (Kawakami et al., 2011).

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

S3. Results and discussion

The structure of o­cta­phenyl-POSS (Fig. 1) may be described as an approximately cuboidal arrangement of Si atoms with an inter­stitial approximate cubo­cta­hedron of bridging O atoms. The Si—O contacts are in the range 1.6166 (11)–1.6258 (11) Å. The Si atoms have nearly ideal tetra­hedral bond angles ranging from 108.04 (6) to 111.58 (6)°, but the Si—O—Si bond angles are strained by the cuboidal geometry imposed by the Si atoms, and are widened to between 142.28 (7) and 153.22 (8)°, significantly distorted from the ideal oxygen bond angle of 104°. Si—C bonds are in the range 1.8382 (16)–1.8429 (15) Å.

The title compound packs into a c-centered monoclinic arrangement with molecules occupying the corners of the unit cell, as well as the c-face. Additional symmetry-generated molecules appear on the c-edges and in the center of the unit cell (Fig. 2). The inter­molecular inter­actions between neighboring molecules are van der Waals inter­actions described best by inter­calation of phenyl rings rather than π-stacking inter­actions (Fig. 3).

There have been several reported crystal structures for o­cta­phenyl-POSS. Preliminary powder XRD suggested rhombahedral crystals (Larsson, 1960b; Brown et al., 1964). The powder patterns of o­cta­phenyl-POSS could be indexed on the basis of a rhombahedral cell where a = 11.0 Å and α = 95°, with major d-spacings of 10.9 (vs), 8.1, 7.3, 4.76, 4.63 and 3.59 Å. A higher temperature form had d-spacings of 12.0, 10.6 (vs), 10.1, 9.4, 8.4, 7.7 and 3.88 Å. However, single-crystal data (crystallized from pyridine) showed two polymorphs, a triclinic form with one molecule in the unit cell and a monoclinic form with two molecules in the unit cell (Larsson, 1960b).

The monoclinic solvate from pyridine (Larsson, 1960b), the triclinic form from pyridine (Larsson, 1960b), and the triclinic form from pyridine and o-di­chloro­benzene (M_r = 732.8, Si₈O₁₂C₄₈H₄₀; Shklover et al., 1978) were reported previously; see Table 2 for the crystal data. The triclinic form undergoes a phase transition at 443 K, decomposes without melting at 723 K and has higher density than the monoclinic form (Larsson, 1960b). In the triclinic form, the solvent molecules were disordered in the large volume of the solvent cavity (150 ų; Shklover et al., 1978). Single-crystal solvates have also been obtained with acetone (Table 2), or with water (Liu et al., 2004). In all of these structures, the Si—O core framework remains the same, with Si—O bond lengths of 1.61–1.62 Å. A comparison of the geometric data from previously reported polymorphs with the data for solvent-free crystal structure reported here is presented in Table 2.

The equilibrium molecular structure of o­cta­phenyl-POSS in the gas phase and from theoretical calculations can be compared with its structure in the solid state, to assess the effects of inter­molecular inter­actions from the crystalline lattice (Zakharov et al., 2010). In the gas phase, o­cta­phenyl-POSS has d₄ point-group symmetry (the o­cta­hedral point group symmetry is broken by the planar phenyl groups), with Si—O bond lengths of 1.634 (15)–1.645 (19) Å, and a narrow range of Si—O—Si angles [148 (5)–150 (2)°]. In the present structural report, o­cta­phenyl-POSS sits on an inversion operation, giving the molecule rigorous C_i symmetry, though the core similarly approximates o­cta­hedral symmetry, with Si—O bond lengths of 1.6166 (11)–1.6258 (11) Å and a narrow range of Si—O—Si bond angles [142.28 (7)– 153.22 (8)°]. The Si₈O₁₂ cages of Si₈O₁₂(p-tolyl)₈ and Si₈O₁₂(p-ClCH₂C₆H₄)₈ were found to be significantly distorted from the gas-phase geometry, with Si—O—Si angles in the range 144.2 (2)–151.64 (16)° for Si₈O₁₂(p-tolyl)₈ and 138.8 (2)–164.2 (2)° for Si₈O₁₂(p-ClCH₂C₆H₄)₈ (Zakharov et al., 2010).

The powder pattern generated from the single-crystal data we obtained matches well with the powder pattern measured from a commercial sample manufactured by Hybrid Plastics, Inc. (Fig. 4). The powder pattern of the starting material, (Si₄O₄(Ph)₄(OH)₄, is shown for comparison, and is not a match.

Related literature

For related literature, see: Baidina et al. (1979); Baney et al. (1995); Bassindale et al. (2003); Bourbigot et al. (2006); Brown et al. (1964); Clegg et al. (1980); Cordes et al. (2010); Day et al. (1985); Dodiuk et al. (2005); Feher & Budzichowski (1989); Hossain et al. (1979); Joshi & Butola (2004); Kawakami et al. (2011); Laine (2005); Laine & Roll (2011); Larsson (1960a, 1960b, 1960c); Lichtenhan (1995); Lickiss & Rataboul (2008); Liu et al. (2004); Macrae et al. (2008); Olsson (1958); Pakjamsai & Kawakami (2005); Phillips et al. (2004); Pittman et al. (2003); Podberezskaya et al. (1981); Provatas & Matisons (1997); Shklover et al. (1978); Tateyama et al. (2010); Voronkov & Lavrentyev (1982); Zakharov et al. (2010); Zhao & Schiraldi (2005).

Computing details

Data collection: COSMO (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SADABS (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2013); molecular graphics: XP in SHELXL2013 (Sheldrick, 2013); software used to prepare material for publication: APEX2 Report Generator (Bruker, 2006).

Figures

	Fig. 1. Displacement ellipsoid plot of octaphenyl-POSS, with ellipsoids at the 50% probability level. H atoms are shown as open circles. Atom labels with the suffix `A' are generated by crystallographic inversion symmetry.
	Fig. 2. The crystal packing of octaphenyl-POSS in the C2/c space group (phenyl groups are not shown for clarity).
	Fig. 3. The intermolecular arrangement of neighboring octaphenyl-POSS molecules. Four phenyl rings are labeled and highlighted with a ball-and-stick representation, showing the absence of direct π–π stacking interactions. The C11B–C16B phenyl ring is arranged parallel to the plane of the page, showing that the C41–C46 phenyl ring does not lie directly above it. This can be seen also with the second symmetry-equivalent pair of phenyl rings, viz. C11–C16 and C41B–C46B.
	Fig. 4. Comparison of the powder X-ray diffraction pattern generated from single-crystal data (Theory) and the measured powder patterns of commercial octaphenyl-POSS (Ph8T8) and the tetrol Si4O4(Ph)4(OH)4 (Ph4T4OH).

1,3,5,7,9,11,13,15-Octaphenylpentacyclo[9.5.1.1^3,9.1^5,15.1^7,13]octasiloxane

Crystal data

C48H40O12Si8	F(000) = 2144
Mr = 1033.52	Dx = 1.400 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 16.406 (2) Å	Cell parameters from 9926 reflections
b = 13.8849 (17) Å	θ = 2.2–28.0°
c = 21.570 (3) Å	µ = 0.28 mm^−1
β = 93.458 (2)°	T = 100 K
V = 4904.7 (10) Å^3	Plate, white
Z = 4	0.45 × 0.30 × 0.07 mm

Data collection

Bruker Kappa APEXII DUO diffractometer	5707 independent reflections
Radiation source: fine-focused sealed tube	5201 reflections with I > 2σ(I)
Detector resolution: 8.333 pixels mm^-1	Rint = 0.022
ω scans	θmax = 28.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 2006)	h = −21→21
Tmin = 0.653, Tmax = 0.746	k = −18→18
16438 measured reflections	l = −28→28

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.035	H-atom parameters constrained
wR(F^2) = 0.095	w = 1/[σ^2(Fo^2) + (0.0485P)^2 + 7.6053P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
5707 reflections	Δρmax = 0.63 e Å^−3
307 parameters	Δρmin = −0.38 e Å^−3

Special details

Experimental. Absorption correction: 16803 Corrected reflections written to file mo_1732_0m.hkl Estimated minimum and maximum transmission: 0.6528 0.7456 The ratio of these values is more reliable than their absolute values! Additional spherical absorption correction applied with mu*r = 0.2000 Lambda/2 correction factor = 0.0015

The crystal was selected and mounted on a MiTeGen loop with Paratone-N oil. during collection the crystal slipped, and so had to be reindexed. The crystal slippage resulted in an incomplete sphere of data (97.5%).

Data were acquired on a Kappa APEX II DUO diffractometer using Mo Kα radiation from a sealed tube, monochromatized with a TRIUMPH monochromator. The crystal was mounted on a MiTeGen loop using paratone-N oil. Data were collected in φ and ω scans, and integrated using SAINT (Bruker, 2006). Multi-scan absorption corrections and scaling were applied using SADABS (Bruker, 2006), and the structure was solved using direct methods, and refined using the SHELXL2013 suite.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C11	0.13847 (9)	−0.02387 (11)	0.18861 (7)	0.0146 (3)
C12	0.19925 (10)	−0.09321 (12)	0.20040 (8)	0.0203 (3)
H12	0.2141	−0.1346	0.1678	0.024*
C13	0.23838 (11)	−0.10246 (14)	0.25940 (9)	0.0265 (4)
H13	0.2793	−0.1502	0.2668	0.032*
C14	0.21785 (11)	−0.04245 (15)	0.30699 (8)	0.0292 (4)
H14	0.2450	−0.0485	0.3470	0.035*
C15	0.15775 (11)	0.02668 (16)	0.29648 (8)	0.0300 (4)
H15	0.1435	0.0678	0.3293	0.036*
C16	0.11809 (10)	0.03590 (14)	0.23763 (8)	0.0225 (3)
H16	0.0768	0.0833	0.2308	0.027*
C21	0.26280 (8)	−0.07409 (11)	−0.03537 (7)	0.0132 (3)
C22	0.28411 (9)	−0.16287 (12)	−0.06074 (8)	0.0181 (3)
H22	0.2440	−0.2119	−0.0667	0.022*
C23	0.36386 (10)	−0.18003 (13)	−0.07737 (8)	0.0222 (3)
H23	0.3779	−0.2407	−0.0941	0.027*
C24	0.42256 (10)	−0.10848 (13)	−0.06950 (8)	0.0234 (4)
H24	0.4767	−0.1203	−0.0808	0.028*
C25	0.40245 (9)	−0.01969 (13)	−0.04509 (8)	0.0208 (3)
H25	0.4426	0.0294	−0.0401	0.025*
C26	0.32329 (9)	−0.00284 (12)	−0.02794 (7)	0.0170 (3)
H26	0.3100	0.0579	−0.0109	0.020*
C31	0.01312 (9)	−0.28363 (11)	−0.10470 (7)	0.0138 (3)
C32	−0.04954 (10)	−0.31391 (13)	−0.14748 (8)	0.0218 (3)
H32	−0.0964	−0.2745	−0.1550	0.026*
C33	−0.04391 (11)	−0.40056 (14)	−0.17899 (9)	0.0275 (4)
H33	−0.0870	−0.4202	−0.2076	0.033*
C34	0.02451 (11)	−0.45875 (13)	−0.16882 (8)	0.0238 (4)
H34	0.0282	−0.5181	−0.1904	0.029*
C35	0.08740 (10)	−0.43004 (12)	−0.12702 (8)	0.0204 (3)
H35	0.1344	−0.4695	−0.1202	0.025*
C36	0.08174 (9)	−0.34350 (12)	−0.09507 (7)	0.0174 (3)
H36	0.1249	−0.3246	−0.0663	0.021*
C41	−0.11248 (9)	−0.22708 (11)	0.11826 (7)	0.0130 (3)
C42	−0.07873 (9)	−0.24465 (12)	0.17834 (7)	0.0169 (3)
H42	−0.0299	−0.2125	0.1924	0.020*
C43	−0.11561 (10)	−0.30857 (12)	0.21785 (8)	0.0207 (3)
H43	−0.0917	−0.3200	0.2584	0.025*
C44	−0.18726 (10)	−0.35550 (12)	0.19800 (8)	0.0228 (3)
H44	−0.2125	−0.3991	0.2249	0.027*
C45	−0.22184 (11)	−0.33838 (14)	0.13870 (9)	0.0272 (4)
H45	−0.2710	−0.3701	0.1251	0.033*
C46	−0.18486 (10)	−0.27519 (12)	0.09920 (8)	0.0216 (3)
H46	−0.2089	−0.2644	0.0586	0.026*
O1	0.01096 (6)	−0.08997 (8)	0.10406 (5)	0.0174 (2)
O2	−0.03730 (7)	−0.19140 (8)	0.00462 (5)	0.0161 (2)
O3	0.09575 (6)	−0.12755 (8)	−0.04478 (5)	0.0172 (2)
O4	0.14973 (6)	−0.03997 (8)	0.05878 (5)	0.0163 (2)
O5	0.05027 (7)	0.09389 (8)	0.10045 (5)	0.0167 (2)
O6	0.13307 (6)	0.05788 (8)	−0.04539 (5)	0.0165 (2)
Si1	0.08573 (2)	−0.01414 (3)	0.11101 (2)	0.01078 (10)
Si2	0.15755 (2)	−0.04615 (3)	−0.01590 (2)	0.01073 (10)
Si3	0.00515 (2)	−0.17142 (3)	−0.06025 (2)	0.01109 (10)
Si4	−0.06665 (2)	−0.13942 (3)	0.06676 (2)	0.01047 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C11	0.0101 (6)	0.0197 (8)	0.0136 (7)	−0.0047 (5)	−0.0026 (5)	0.0033 (5)
C12	0.0178 (7)	0.0192 (8)	0.0225 (8)	−0.0031 (6)	−0.0084 (6)	0.0033 (6)
C13	0.0216 (8)	0.0270 (9)	0.0289 (9)	−0.0062 (7)	−0.0140 (7)	0.0122 (7)
C14	0.0245 (9)	0.0470 (12)	0.0150 (8)	−0.0153 (8)	−0.0092 (7)	0.0109 (7)
C15	0.0231 (8)	0.0541 (13)	0.0126 (8)	−0.0081 (8)	0.0001 (7)	−0.0039 (7)
C16	0.0145 (7)	0.0363 (10)	0.0165 (8)	−0.0005 (7)	−0.0008 (6)	−0.0024 (7)
C21	0.0083 (6)	0.0173 (7)	0.0135 (7)	0.0018 (5)	−0.0020 (5)	0.0023 (5)
C22	0.0128 (7)	0.0191 (8)	0.0223 (8)	−0.0001 (6)	−0.0007 (6)	−0.0002 (6)
C23	0.0171 (7)	0.0213 (8)	0.0286 (9)	0.0059 (6)	0.0030 (6)	−0.0014 (7)
C24	0.0107 (7)	0.0309 (9)	0.0288 (9)	0.0045 (6)	0.0032 (6)	0.0027 (7)
C25	0.0105 (7)	0.0244 (9)	0.0274 (9)	−0.0020 (6)	−0.0014 (6)	0.0029 (7)
C26	0.0112 (7)	0.0194 (8)	0.0200 (7)	0.0004 (6)	−0.0022 (6)	−0.0003 (6)
C31	0.0129 (6)	0.0151 (7)	0.0133 (7)	−0.0006 (5)	−0.0005 (5)	−0.0010 (5)
C32	0.0153 (7)	0.0251 (9)	0.0242 (8)	0.0044 (6)	−0.0052 (6)	−0.0077 (7)
C33	0.0221 (8)	0.0313 (10)	0.0280 (9)	0.0008 (7)	−0.0066 (7)	−0.0137 (7)
C34	0.0273 (9)	0.0200 (8)	0.0241 (8)	0.0022 (7)	0.0012 (7)	−0.0087 (7)
C35	0.0194 (7)	0.0191 (8)	0.0228 (8)	0.0055 (6)	0.0008 (6)	−0.0004 (6)
C36	0.0143 (7)	0.0182 (8)	0.0193 (7)	0.0012 (6)	−0.0025 (6)	−0.0009 (6)
C41	0.0109 (6)	0.0129 (7)	0.0151 (7)	−0.0003 (5)	0.0008 (5)	0.0000 (5)
C42	0.0131 (7)	0.0187 (8)	0.0186 (7)	0.0003 (6)	−0.0022 (6)	0.0031 (6)
C43	0.0229 (8)	0.0202 (8)	0.0189 (8)	0.0025 (6)	0.0001 (6)	0.0059 (6)
C44	0.0232 (8)	0.0188 (8)	0.0270 (9)	−0.0029 (6)	0.0065 (7)	0.0061 (6)
C45	0.0226 (8)	0.0286 (10)	0.0300 (9)	−0.0130 (7)	−0.0014 (7)	0.0031 (7)
C46	0.0198 (8)	0.0239 (9)	0.0203 (8)	−0.0077 (6)	−0.0048 (6)	0.0022 (6)
O1	0.0129 (5)	0.0211 (6)	0.0174 (5)	−0.0056 (4)	−0.0047 (4)	0.0021 (4)
O2	0.0167 (5)	0.0161 (5)	0.0157 (5)	−0.0009 (4)	0.0028 (4)	−0.0007 (4)
O3	0.0097 (5)	0.0198 (6)	0.0219 (6)	−0.0023 (4)	−0.0018 (4)	−0.0047 (4)
O4	0.0104 (5)	0.0254 (6)	0.0128 (5)	0.0022 (4)	−0.0019 (4)	0.0009 (4)
O5	0.0177 (5)	0.0149 (5)	0.0166 (5)	0.0031 (4)	−0.0061 (4)	−0.0003 (4)
O6	0.0115 (5)	0.0167 (6)	0.0213 (6)	0.0036 (4)	0.0004 (4)	0.0049 (4)
Si1	0.00722 (17)	0.0140 (2)	0.01069 (19)	−0.00050 (14)	−0.00308 (14)	0.00083 (14)
Si2	0.00633 (17)	0.0136 (2)	0.01194 (19)	0.00056 (14)	−0.00195 (14)	0.00075 (14)
Si3	0.00833 (18)	0.0125 (2)	0.01214 (19)	−0.00006 (14)	−0.00200 (14)	−0.00085 (14)
Si4	0.00713 (17)	0.0120 (2)	0.01195 (19)	−0.00032 (14)	−0.00178 (14)	0.00098 (14)

Geometric parameters (Å, º)

C11—C12	1.398 (2)	C41—C42	1.400 (2)
C11—C16	1.400 (2)	C41—C46	1.402 (2)
C11—Si1	1.8423 (15)	C41—Si4	1.8390 (15)
C12—C13	1.396 (2)	C42—C43	1.394 (2)
C13—C14	1.380 (3)	C43—C44	1.389 (2)
C14—C15	1.385 (3)	C44—C45	1.388 (3)
C15—C16	1.397 (2)	C45—C46	1.388 (2)
C21—C22	1.402 (2)	O1—Si1	1.6166 (11)
C21—C26	1.404 (2)	O1—Si4	1.6175 (11)
C21—Si2	1.8429 (15)	O2—Si4	1.6209 (11)
C22—C23	1.398 (2)	O2—Si3	1.6241 (11)
C23—C24	1.387 (2)	O3—Si2	1.6177 (11)
C24—C25	1.388 (3)	O3—Si3	1.6223 (11)
C25—C26	1.391 (2)	O4—Si1	1.6258 (11)
C31—C32	1.404 (2)	O4—Si2	1.6258 (11)
C31—C36	1.405 (2)	O5—Si1	1.6200 (12)
C31—Si3	1.8382 (16)	O5—Si3^i	1.6255 (11)
C32—C33	1.388 (2)	O6—Si4^i	1.6189 (11)
C33—C34	1.390 (2)	O6—Si2	1.6192 (11)
C34—C35	1.387 (2)	Si3—O5^i	1.6255 (11)
C35—C36	1.391 (2)	Si4—O6^i	1.6189 (11)
C12—C11—C16	118.09 (14)	C45—C46—C41	120.99 (15)
C12—C11—Si1	120.42 (12)	Si1—O1—Si4	153.22 (8)
C16—C11—Si1	121.47 (12)	Si4—O2—Si3	143.19 (8)
C13—C12—C11	120.84 (17)	Si2—O3—Si3	152.45 (8)
C14—C13—C12	120.21 (17)	Si1—O4—Si2	142.28 (7)
C13—C14—C15	120.01 (16)	Si1—O5—Si3^i	150.78 (8)
C14—C15—C16	120.01 (18)	Si4^i—O6—Si2	151.94 (8)
C15—C16—C11	120.82 (17)	O1—Si1—O5	109.03 (6)
C22—C21—C26	118.24 (14)	O1—Si1—O4	108.07 (6)
C22—C21—Si2	122.23 (11)	O5—Si1—O4	110.38 (6)
C26—C21—Si2	119.43 (12)	O1—Si1—C11	110.41 (6)
C23—C22—C21	120.63 (15)	O5—Si1—C11	109.91 (7)
C24—C23—C22	120.02 (16)	O4—Si1—C11	109.02 (6)
C23—C24—C25	120.23 (15)	O3—Si2—O6	109.70 (6)
C24—C25—C26	119.81 (15)	O3—Si2—O4	109.47 (6)
C25—C26—C21	121.06 (15)	O6—Si2—O4	108.04 (6)
C32—C31—C36	117.93 (14)	O3—Si2—C21	109.83 (7)
C32—C31—Si3	121.63 (12)	O6—Si2—C21	108.17 (6)
C36—C31—Si3	120.40 (11)	O4—Si2—C21	111.58 (6)
C33—C32—C31	120.92 (15)	O3—Si3—O2	108.79 (6)
C32—C33—C34	120.25 (15)	O3—Si3—O5^i	109.71 (6)
C35—C34—C33	119.84 (15)	O2—Si3—O5^i	108.51 (6)
C34—C35—C36	120.06 (15)	O3—Si3—C31	109.42 (6)
C35—C36—C31	120.99 (14)	O2—Si3—C31	110.62 (6)
C42—C41—C46	117.98 (14)	O5^i—Si3—C31	109.77 (6)
C42—C41—Si4	121.42 (11)	O1—Si4—O6^i	109.93 (6)
C46—C41—Si4	120.53 (12)	O1—Si4—O2	109.64 (6)
C43—C42—C41	121.00 (14)	O6^i—Si4—O2	107.72 (6)
C44—C43—C42	120.06 (15)	O1—Si4—C41	108.59 (6)
C45—C44—C43	119.67 (15)	O6^i—Si4—C41	110.01 (6)
C46—C45—C44	120.30 (16)	O2—Si4—C41	110.95 (6)
C16—C11—C12—C13	0.0 (2)	C12—C11—Si1—O5	−155.32 (12)
Si1—C11—C12—C13	−178.66 (13)	C16—C11—Si1—O5	26.04 (15)
C11—C12—C13—C14	−0.5 (3)	C12—C11—Si1—O4	−34.21 (14)
C12—C13—C14—C15	0.6 (3)	C16—C11—Si1—O4	147.15 (13)
C13—C14—C15—C16	−0.2 (3)	Si3—O3—Si2—O6	−55.39 (19)
C14—C15—C16—C11	−0.2 (3)	Si3—O3—Si2—O4	63.00 (19)
C12—C11—C16—C15	0.3 (2)	Si3—O3—Si2—C21	−174.16 (16)
Si1—C11—C16—C15	179.01 (14)	Si4^i—O6—Si2—O3	44.86 (18)
C26—C21—C22—C23	0.8 (2)	Si4^i—O6—Si2—O4	−74.42 (18)
Si2—C21—C22—C23	177.28 (13)	Si4^i—O6—Si2—C21	164.65 (16)
C21—C22—C23—C24	−0.8 (3)	Si1—O4—Si2—O3	−63.36 (14)
C22—C23—C24—C25	0.0 (3)	Si1—O4—Si2—O6	56.06 (14)
C23—C24—C25—C26	0.6 (3)	Si1—O4—Si2—C21	174.85 (12)
C24—C25—C26—C21	−0.5 (3)	C22—C21—Si2—O3	−11.23 (15)
C22—C21—C26—C25	−0.2 (2)	C26—C21—Si2—O3	165.18 (12)
Si2—C21—C26—C25	−176.74 (12)	C22—C21—Si2—O6	−130.94 (13)
C36—C31—C32—C33	0.3 (3)	C26—C21—Si2—O6	45.47 (14)
Si3—C31—C32—C33	−177.60 (14)	C22—C21—Si2—O4	110.35 (13)
C31—C32—C33—C34	−0.4 (3)	C26—C21—Si2—O4	−73.24 (13)
C32—C33—C34—C35	0.0 (3)	Si2—O3—Si3—O2	−61.84 (19)
C33—C34—C35—C36	0.4 (3)	Si2—O3—Si3—O5^i	56.72 (19)
C34—C35—C36—C31	−0.4 (3)	Si2—O3—Si3—C31	177.20 (16)
C32—C31—C36—C35	0.1 (2)	Si4—O2—Si3—O3	60.29 (13)
Si3—C31—C36—C35	178.03 (13)	Si4—O2—Si3—O5^i	−59.02 (13)
C46—C41—C42—C43	0.5 (2)	Si4—O2—Si3—C31	−179.49 (11)
Si4—C41—C42—C43	177.59 (12)	C32—C31—Si3—O3	−150.49 (13)
C41—C42—C43—C44	−0.4 (2)	C36—C31—Si3—O3	31.63 (15)
C42—C43—C44—C45	0.0 (3)	C32—C31—Si3—O2	89.67 (14)
C43—C44—C45—C46	0.4 (3)	C36—C31—Si3—O2	−88.22 (13)
C44—C45—C46—C41	−0.4 (3)	C32—C31—Si3—O5^i	−30.05 (15)
C42—C41—C46—C45	−0.1 (3)	C36—C31—Si3—O5^i	152.07 (12)
Si4—C41—C46—C45	−177.21 (14)	Si1—O1—Si4—O6^i	−55.59 (19)
Si4—O1—Si1—O5	56.83 (19)	Si1—O1—Si4—O2	62.65 (19)
Si4—O1—Si1—O4	−63.17 (19)	Si1—O1—Si4—C41	−175.99 (17)
Si4—O1—Si1—C11	177.68 (17)	Si3—O2—Si4—O1	−60.39 (14)
Si3^i—O5—Si1—O1	−49.51 (18)	Si3—O2—Si4—O6^i	59.21 (13)
Si3^i—O5—Si1—O4	69.06 (17)	Si3—O2—Si4—C41	179.67 (11)
Si3^i—O5—Si1—C11	−170.66 (15)	C42—C41—Si4—O1	−2.00 (15)
Si2—O4—Si1—O1	62.68 (14)	C46—C41—Si4—O1	175.04 (13)
Si2—O4—Si1—O5	−56.47 (14)	C42—C41—Si4—O6^i	−122.34 (13)
Si2—O4—Si1—C11	−177.29 (12)	C46—C41—Si4—O6^i	54.70 (15)
C12—C11—Si1—O1	84.37 (13)	C42—C41—Si4—O2	118.57 (13)
C16—C11—Si1—O1	−94.27 (14)	C46—C41—Si4—O2	−64.39 (14)

Symmetry code: (i) −x, −y, −z.