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Acta Cryst. (2011). E67, o375    [ doi:10.1107/S1600536810054462 ]

7-(tert-Butyldiphenylsilyloxy)-2,2-dimethyl-1-benzofuran-3(2H)-one

C. O. Salas, R. A. Tapia and A. Macías

Abstract top

The title compound, C26H28O3Si, is an allylic oxidation product of the tert-butyl(2,2-dimethyl-2,3-dihydrobenzofuran-7-yloxy)diphenylsilane with N-bromosuccinimide and 2,2'-azobis-isobutyronitrile. The nine-atom bicyclic system is almost planar, with an r.m.s deviation of 0.0123 (2) Å and a maximum deviation of 0.031 (2) Å for the O atom. In the crystal, the molecules pile up along the b axis but the strongest intermolecular contacts are the [pi]-[pi] stacking interactions between the benzene rings along the c axis [centroid-centroid distance = 3.655 (3) Å].

Comment top

Benzofuranones are very important compounds because of their use in a wide range of natural and synthetic products with relevant properties such as spiroannulated benzofuranones (Braun et al., 2008), aromatics spiroketals compounds (Zhou et al., 2008), aurones (Schoepfer et al, 2002; Löser et al., 2004), pyranobenzofuranes (Foroumadi et al., 2009) and some benzofuranes derivatives (Venkatesan et al., 2010). The benzofuranone 3 is the product of the allylic oxidation of the tert-butyl-(2,2-dimethyl-2,3-dihydrobenzofuran-7-yloxy)diphenylsilane with N-bromosuccinimide (NBS) and 2,2'-azobis-isobutyronitrile (AIBN) (Fig. 2). The molecular structure of the title compound is represented in Fig. 1. Bond lengths and angles are within the expected values and confirm the bond orders giving in the Scheme. The 9-atom bicyclic system is, as expected, planar, with r.m.s deviation = 0.0123 (2) Å and a maximum deviation of 0.031 (2) Å. The molecules pile up along the b axis but the strongest intermolecular contacts are the π–π stacking interactions between the benzo rings along the c axis [centroid–centroid distances = 3.655 (5) Å].

Related literature top

Benzofuranones are precursors of a wide range of natural and synthetic products. For a related transformation of benzofuranones in aurones, see: Schoepfer et al. (2002); Löser et al. (2004); in spiroannulated and aromatic spiroketal compounds, see: Braun et al. (2008); Zhou et al. (2008); in benzofurane derivatives, see: Venkatesan et al.(2010); and in pyranobenzofuranes, see: Foroumadi et al. (2009).

Experimental top

tert-Butyl-(2,2-dimethyl-2,3-dihydrobenzofuran-7-yloxy)diphenylsilane (2)

tert-Butyldiphenylsilyl chloride (1.0 g, 3.64 mmol) and imidazole (1.52 g, 22.35 mmol) were added to a solution of 2,2-dimethyl-2,3-dihydrobenzofuran-7-ol (1) (0.59 g, 3.62 mmol) in dry THF (50 ml) and the mixture was stirred at room temperature for 12 h. under an nitrogen atmosphere. Petroleum ether (100 ml) was added and the solid was filtered off and the solvents were removed in vacuo to give an oil residue, which was purified by flash column chromatography (CH2Cl2/ petroleum ether, 9:1) to give tert-butyl-(2,2-dimethyl-2,3-dihydrobenzofuran-7-yloxy)diphenylsilane (2) (1.43 g, 98%) as a colorless oil.

7-(tert-Butyldiphenylsilyloxy)-2,2-dimethylbenzofuran-3(2H)-one (3).

NBS (1.54 g, 8.70 mmol) and AIBN (25 mg) were added to a solution of tert-butyl(2,2-dimethyl-2,3-dihydrobenzofuran-7-yloxy)diphenylsilane (2) (1.0 g, 2.39 mmol) in dry CCl4 (150 ml) and the resulting suspension was stirred at reflux for 2 h. The mixture was cooled and filtered. The filtrate was evaporated to dryness in vacuo to give a residue, which was purified by flash column chromatography (CH2Cl2) to give 7-(tert-butyldiphenylsilyloxy)-2,2-dimethylbenzofuran-3(2H)-one (3) (0.75 g, 75%) as a white solid. mp: 354.5–355.5 K. Crystals were grown by slow evaporation from CH2Cl2.

Refinement top

H atoms were placed in idealized positions with C—H distances 0.95 – 0.98 Å and thereafter treated as riding. A torsional parameter was refined for each methyl group. Uiso for H were assigned as 1.2 times Ueq of the attached C atom (1.5 for the methyl groups).

Computing details top

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. The structure of the title compound, with displacement ellipsoids drawn at the 50% probability level and H atoms with arbitrary radius.
[Figure 2] Fig. 2. Chemical reactions scheme for obtain molecule 3.
7-(tert-Butyldiphenylsilyloxy)-2,2-dimethyl-1-benzofuran-3(2H)-one top
Crystal data top
C26H28O3SiZ = 2
Mr = 416.57F(000) = 444
Triclinic, P1Dx = 1.205 Mg m−3
a = 9.8210 (18) ÅMo Kα radiation, λ = 0.71073 Å
b = 11.081 (2) ÅCell parameters from 3414 reflections
c = 12.025 (2) Åθ = 2.3–27.3°
α = 98.803 (2)°µ = 0.13 mm−1
β = 112.151 (2)°T = 100 K
γ = 101.791 (2)°Prism, colourless
V = 1147.7 (4) Å30.49 × 0.43 × 0.10 mm
Data collection top
Bruker SMART 1000 CCD
diffractometer		4197 independent reflections
Radiation source: fine-focus sealed tube3325 reflections with I > 2σ(I)
graphiteRint = 0.032
ω scansθmax = 25.4°, θmin = 1.9°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)		h = −11→10
Tmin = 0.941, Tmax = 0.988k = −13→13
14369 measured reflectionsl = 0→14
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.044Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.111H-atom parameters constrained
S = 1.05 w = 1/[σ2(Fo2) + (0.0422P)2 + 0.8404P]
where P = (Fo2 + 2Fc2)/3
4197 reflections(Δ/σ)max < 0.001
276 parametersΔρmax = 0.83 e Å−3
0 restraintsΔρmin = −0.29 e Å−3
Crystal data top
C26H28O3Siγ = 101.791 (2)°
Mr = 416.57V = 1147.7 (4) Å3
Triclinic, P1Z = 2
a = 9.8210 (18) ÅMo Kα radiation
b = 11.081 (2) ŵ = 0.13 mm−1
c = 12.025 (2) ÅT = 100 K
α = 98.803 (2)°0.49 × 0.43 × 0.10 mm
β = 112.151 (2)°
Data collection top
Bruker SMART 1000 CCD
diffractometer		4197 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)		3325 reflections with I > 2σ(I)
Tmin = 0.941, Tmax = 0.988Rint = 0.032
14369 measured reflectionsθmax = 25.4°
Refinement top
R[F2 > 2σ(F2)] = 0.044H-atom parameters constrained
wR(F2) = 0.111Δρmax = 0.83 e Å−3
S = 1.05Δρmin = −0.29 e Å−3
4197 reflectionsAbsolute structure: ?
276 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Experimental. tert-Butyl-(2,2-dimethyl-2,3-dihydrobenzofuran-7-yloxy)diphenylsilane (2)

1H RMN (CDCl3, 200 MHz) d 1.18 (s, 9H, 3xCH3); 1.34 (s, 6H, 2xCH3), 2.96 (s, 2H, H3); 6.53–6.56 (m, 2H, H5, H4); 6.70 (m, 1H, H6); 7.35–7.44 (m, 6H, H—Ar); 7.38–7.83 (m, 4H, H—Ar). 13C RMN (CDCl3, 50 MHz) d 19.7 (C(CH3)3); 26.8 (3xCH3); 28.1 (2xCH3); 43.4 (C3); 86.4 (C2); 117.9 (C6); 119.6 (C5); 119.8 (C4); 127.5 (Ar); 127.8 (C3a); 129.6 (Ar); 133.9 (Ar); 135.7 (Ar); 139.9 (C7); 149.4 (C7a).

7-(tert-Butyldiphenylsilyloxy)-2,2-dimethylbenzofuran-3(2H)-one (3).

IR (NaCl, cm-1): 1714 (CO). 1H-RMN (CDCl3, 200 MHz) d 1.18 (s, 9H, 3xCH3); 1.30 (s, 6H, 2xCH3); 6.74 (t, 1H, J =7.7 Hz, H5,); 6.97 (dd, 1H, J =1.1, J =7.8 Hz, H6); 7.21 (dd, 1H, J =1,1, J =7,6 Hz, H4); 7.32–7.48 (m, 6H, H—Ar); 7.72–7.77 (m, 4H, H—Ar). 13C-RMN (CDCl3, 50 MHz) d 19.7 (C(CH3)3); 22.8 (3xCH3); 26.6 (2xCH3); 87.9 (C2); 117.0 (C5); 121.0 (C7); 121.8 (C4); 127.7 (Ar); 130.0 (Ar); 133.0 (C6); 135.5 (Ar); 142.4 (C3a); 162.4 (C7a); 204.8 (C3). MS (CI) m/z 417 [(M+, 74]; 359 (66); 339 (100).

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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
xyzUiso*/Ueq
Si10.05281 (6)0.33072 (5)0.76624 (5)0.01833 (15)
O10.32466 (15)0.13402 (12)0.72764 (12)0.0227 (3)
C20.4315 (2)0.05650 (19)0.75715 (18)0.0223 (4)
C30.3300 (2)−0.07888 (19)0.73025 (18)0.0227 (4)
C40.1727 (2)−0.07133 (18)0.68675 (17)0.0202 (4)
C50.0325 (2)−0.16301 (19)0.64733 (18)0.0232 (4)
H50.0270−0.25010.64470.028*
C6−0.0980 (2)−0.1229 (2)0.61233 (18)0.0252 (5)
H6−0.1955−0.18330.58390.030*
C7−0.0885 (2)0.0057 (2)0.61825 (18)0.0236 (4)
H7−0.18000.03110.59530.028*
C80.0501 (2)0.09704 (18)0.65653 (17)0.0193 (4)
C90.1812 (2)0.05545 (18)0.68970 (16)0.0188 (4)
C100.5136 (2)0.0626 (2)0.6729 (2)0.0296 (5)
H10A0.43790.03270.58600.044*
H10B0.58240.00830.68940.044*
H10C0.57340.15080.68860.044*
C110.5402 (2)0.1070 (2)0.8933 (2)0.0316 (5)
H11A0.59880.19550.90860.047*
H11B0.61090.05480.91590.047*
H11C0.48130.10330.94340.047*
O120.37919 (16)−0.17058 (14)0.74359 (14)0.0320 (4)
O130.06209 (15)0.22261 (12)0.65909 (12)0.0217 (3)
C140.0978 (2)0.27196 (18)0.90971 (18)0.0212 (4)
C150.2433 (2)0.2591 (2)0.97519 (19)0.0270 (5)
H150.32200.28670.94930.032*
C160.2760 (3)0.2073 (2)1.0766 (2)0.0323 (5)
H160.37640.20071.12000.039*
C170.1623 (3)0.1654 (2)1.1145 (2)0.0358 (6)
H170.18400.12911.18370.043*
C180.0170 (3)0.1763 (2)1.0515 (2)0.0371 (6)
H18−0.06130.14761.07760.045*
C19−0.0147 (2)0.2288 (2)0.9508 (2)0.0285 (5)
H19−0.11510.23580.90840.034*
C20−0.1450 (2)0.34886 (18)0.70512 (18)0.0215 (4)
C21−0.2426 (2)0.3037 (2)0.57890 (19)0.0253 (5)
H21−0.21150.25580.52520.030*
C22−0.3847 (2)0.3276 (2)0.5300 (2)0.0337 (5)
H22−0.44980.29580.44380.040*
C23−0.4303 (3)0.3977 (2)0.6075 (2)0.0379 (6)
H23−0.52730.41390.57480.045*
C24−0.3351 (3)0.4442 (2)0.7324 (2)0.0365 (6)
H24−0.36650.49280.78540.044*
C25−0.1943 (2)0.4205 (2)0.7807 (2)0.0281 (5)
H25−0.12980.45340.86680.034*
C260.1895 (2)0.48211 (19)0.77629 (18)0.0220 (4)
C270.3543 (3)0.4743 (2)0.8183 (3)0.0462 (7)
H27A0.35580.39730.76690.069*
H27B0.39510.47110.90540.069*
H27C0.41790.54950.80940.069*
C280.1375 (3)0.5049 (2)0.6466 (2)0.0318 (5)
H28A0.20370.58580.64970.048*
H28B0.03120.50860.61700.048*
H28C0.14420.43510.58990.048*
C290.1862 (3)0.5957 (2)0.8649 (2)0.0428 (6)
H29A0.25540.67390.86630.064*
H29B0.21950.58230.94860.064*
H29C0.08160.60340.83630.064*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Si10.0189 (3)0.0199 (3)0.0175 (3)0.0066 (2)0.0087 (2)0.0046 (2)
O10.0195 (7)0.0194 (7)0.0283 (8)0.0056 (6)0.0088 (6)0.0070 (6)
C20.0201 (10)0.0210 (10)0.0256 (11)0.0085 (8)0.0076 (8)0.0069 (8)
C30.0243 (10)0.0234 (11)0.0208 (10)0.0083 (9)0.0085 (8)0.0074 (8)
C40.0240 (10)0.0208 (10)0.0156 (9)0.0069 (8)0.0079 (8)0.0050 (8)
C50.0268 (11)0.0190 (10)0.0223 (10)0.0033 (8)0.0104 (9)0.0050 (8)
C60.0222 (10)0.0266 (11)0.0236 (11)0.0009 (9)0.0100 (9)0.0052 (9)
C70.0205 (10)0.0326 (12)0.0201 (10)0.0096 (9)0.0101 (8)0.0069 (9)
C80.0259 (10)0.0199 (10)0.0158 (9)0.0094 (8)0.0112 (8)0.0047 (8)
C90.0204 (10)0.0206 (10)0.0143 (9)0.0031 (8)0.0080 (8)0.0034 (8)
C100.0266 (11)0.0322 (12)0.0336 (12)0.0105 (9)0.0142 (10)0.0112 (10)
C110.0284 (12)0.0297 (12)0.0289 (12)0.0059 (9)0.0057 (10)0.0058 (9)
O120.0287 (8)0.0236 (8)0.0416 (9)0.0108 (7)0.0098 (7)0.0110 (7)
O130.0280 (8)0.0216 (7)0.0207 (7)0.0119 (6)0.0128 (6)0.0069 (6)
C140.0268 (11)0.0175 (10)0.0200 (10)0.0074 (8)0.0104 (8)0.0037 (8)
C150.0280 (11)0.0293 (12)0.0264 (11)0.0100 (9)0.0122 (9)0.0095 (9)
C160.0369 (13)0.0359 (13)0.0252 (11)0.0173 (10)0.0097 (10)0.0105 (10)
C170.0558 (16)0.0353 (13)0.0273 (12)0.0228 (12)0.0210 (11)0.0163 (10)
C180.0502 (15)0.0418 (14)0.0389 (13)0.0194 (12)0.0320 (12)0.0210 (11)
C190.0288 (12)0.0326 (12)0.0320 (12)0.0124 (10)0.0176 (10)0.0124 (10)
C200.0228 (10)0.0199 (10)0.0260 (11)0.0077 (8)0.0126 (9)0.0096 (8)
C210.0257 (11)0.0277 (11)0.0259 (11)0.0085 (9)0.0122 (9)0.0117 (9)
C220.0250 (11)0.0424 (14)0.0337 (13)0.0103 (10)0.0083 (10)0.0196 (11)
C230.0256 (12)0.0436 (14)0.0563 (16)0.0199 (11)0.0193 (11)0.0265 (12)
C240.0360 (13)0.0348 (13)0.0538 (16)0.0188 (11)0.0286 (12)0.0160 (12)
C250.0295 (12)0.0258 (11)0.0336 (12)0.0089 (9)0.0175 (10)0.0079 (9)
C260.0208 (10)0.0221 (10)0.0208 (10)0.0026 (8)0.0087 (8)0.0043 (8)
C270.0239 (12)0.0448 (15)0.0687 (18)0.0044 (11)0.0147 (12)0.0314 (14)
C280.0398 (13)0.0257 (12)0.0271 (11)0.0042 (10)0.0131 (10)0.0091 (9)
C290.0602 (17)0.0235 (12)0.0409 (14)−0.0067 (11)0.0316 (13)−0.0038 (10)
Geometric parameters (Å, °) top
Si1—O131.6627 (14)C16—C171.381 (3)
Si1—C141.866 (2)C16—H160.9500
Si1—C201.866 (2)C17—C181.381 (3)
Si1—C261.878 (2)C17—H170.9500
O1—C91.358 (2)C18—C191.382 (3)
O1—C21.465 (2)C18—H180.9500
C2—C111.513 (3)C19—H190.9500
C2—C101.515 (3)C20—C211.396 (3)
C2—C31.532 (3)C20—C251.400 (3)
C3—O121.218 (2)C21—C221.394 (3)
C3—C41.457 (3)C21—H210.9500
C4—C91.384 (3)C22—C231.382 (3)
C4—C51.394 (3)C22—H220.9500
C5—C61.379 (3)C23—C241.379 (3)
C5—H50.9500C23—H230.9500
C6—C71.398 (3)C24—C251.381 (3)
C6—H60.9500C24—H240.9500
C7—C81.383 (3)C25—H250.9500
C7—H70.9500C26—C281.526 (3)
C8—O131.367 (2)C26—C271.529 (3)
C8—C91.393 (3)C26—C291.534 (3)
C10—H10A0.9800C27—H27A0.9800
C10—H10B0.9800C27—H27B0.9800
C10—H10C0.9800C27—H27C0.9800
C11—H11A0.9800C28—H28A0.9800
C11—H11B0.9800C28—H28B0.9800
C11—H11C0.9800C28—H28C0.9800
C14—C151.397 (3)C29—H29A0.9800
C14—C191.400 (3)C29—H29B0.9800
C15—C161.383 (3)C29—H29C0.9800
C15—H150.9500
O13—Si1—C14107.62 (8)C17—C16—H16120.1
O13—Si1—C20108.10 (8)C15—C16—H16120.1
C14—Si1—C20111.46 (9)C18—C17—C16119.8 (2)
O13—Si1—C26103.79 (8)C18—C17—H17120.1
C14—Si1—C26116.95 (9)C16—C17—H17120.1
C20—Si1—C26108.36 (9)C17—C18—C19120.2 (2)
C9—O1—C2107.46 (14)C17—C18—H18119.9
O1—C2—C11107.94 (16)C19—C18—H18119.9
O1—C2—C10108.69 (16)C18—C19—C14121.5 (2)
C11—C2—C10112.76 (17)C18—C19—H19119.3
O1—C2—C3104.86 (15)C14—C19—H19119.3
C11—C2—C3111.31 (17)C21—C20—C25117.43 (18)
C10—C2—C3110.89 (17)C21—C20—Si1120.75 (15)
O12—C3—C4129.89 (19)C25—C20—Si1121.41 (16)
O12—C3—C2123.83 (18)C22—C21—C20121.4 (2)
C4—C3—C2106.28 (16)C22—C21—H21119.3
C9—C4—C5121.40 (18)C20—C21—H21119.3
C9—C4—C3106.16 (17)C23—C22—C21119.6 (2)
C5—C4—C3132.44 (18)C23—C22—H22120.2
C6—C5—C4117.65 (19)C21—C22—H22120.2
C6—C5—H5121.2C24—C23—C22120.0 (2)
C4—C5—H5121.2C24—C23—H23120.0
C5—C6—C7120.71 (19)C22—C23—H23120.0
C5—C6—H6119.6C23—C24—C25120.3 (2)
C7—C6—H6119.6C23—C24—H24119.8
C8—C7—C6121.96 (18)C25—C24—H24119.8
C8—C7—H7119.0C24—C25—C20121.3 (2)
C6—C7—H7119.0C24—C25—H25119.4
O13—C8—C7123.14 (17)C20—C25—H25119.4
O13—C8—C9119.85 (17)C28—C26—C27107.98 (18)
C7—C8—C9116.99 (18)C28—C26—C29108.62 (18)
O1—C9—C4115.22 (17)C27—C26—C29109.12 (19)
O1—C9—C8123.50 (17)C28—C26—Si1107.54 (14)
C4—C9—C8121.27 (17)C27—C26—Si1112.54 (15)
C2—C10—H10A109.5C29—C26—Si1110.90 (14)
C2—C10—H10B109.5C26—C27—H27A109.5
H10A—C10—H10B109.5C26—C27—H27B109.5
C2—C10—H10C109.5H27A—C27—H27B109.5
H10A—C10—H10C109.5C26—C27—H27C109.5
H10B—C10—H10C109.5H27A—C27—H27C109.5
C2—C11—H11A109.5H27B—C27—H27C109.5
C2—C11—H11B109.5C26—C28—H28A109.5
H11A—C11—H11B109.5C26—C28—H28B109.5
C2—C11—H11C109.5H28A—C28—H28B109.5
H11A—C11—H11C109.5C26—C28—H28C109.5
H11B—C11—H11C109.5H28A—C28—H28C109.5
C8—O13—Si1126.65 (12)H28B—C28—H28C109.5
C15—C14—C19116.86 (18)C26—C29—H29A109.5
C15—C14—Si1120.96 (15)C26—C29—H29B109.5
C19—C14—Si1121.97 (15)H29A—C29—H29B109.5
C16—C15—C14121.9 (2)C26—C29—H29C109.5
C16—C15—H15119.0H29A—C29—H29C109.5
C14—C15—H15119.0H29B—C29—H29C109.5
C17—C16—C15119.7 (2)
C9—O1—C2—C11−118.39 (17)C26—Si1—C14—C15−50.63 (19)
C9—O1—C2—C10119.01 (17)O13—Si1—C14—C19−108.91 (17)
C9—O1—C2—C30.37 (19)C20—Si1—C14—C199.4 (2)
O1—C2—C3—O12179.64 (18)C26—Si1—C14—C19134.85 (17)
C11—C2—C3—O12−63.9 (3)C19—C14—C15—C16−0.6 (3)
C10—C2—C3—O1262.5 (3)Si1—C14—C15—C16−175.34 (17)
O1—C2—C3—C40.30 (19)C14—C15—C16—C170.8 (3)
C11—C2—C3—C4116.76 (18)C15—C16—C17—C18−0.5 (3)
C10—C2—C3—C4−116.84 (18)C16—C17—C18—C190.1 (4)
O12—C3—C4—C9179.9 (2)C17—C18—C19—C140.1 (4)
C2—C3—C4—C9−0.8 (2)C15—C14—C19—C180.1 (3)
O12—C3—C4—C5−0.2 (4)Si1—C14—C19—C18174.87 (17)
C2—C3—C4—C5179.0 (2)O13—Si1—C20—C21−16.23 (18)
C9—C4—C5—C6−0.6 (3)C14—Si1—C20—C21−134.30 (16)
C3—C4—C5—C6179.51 (19)C26—Si1—C20—C2195.65 (17)
C4—C5—C6—C7−0.9 (3)O13—Si1—C20—C25171.27 (15)
C5—C6—C7—C81.3 (3)C14—Si1—C20—C2553.20 (19)
C6—C7—C8—O13177.67 (17)C26—Si1—C20—C25−76.85 (18)
C6—C7—C8—C9−0.2 (3)C25—C20—C21—C22−0.8 (3)
C2—O1—C9—C4−1.0 (2)Si1—C20—C21—C22−173.60 (16)
C2—O1—C9—C8178.51 (17)C20—C21—C22—C230.3 (3)
C5—C4—C9—O1−178.72 (16)C21—C22—C23—C240.3 (3)
C3—C4—C9—O11.2 (2)C22—C23—C24—C25−0.3 (3)
C5—C4—C9—C81.8 (3)C23—C24—C25—C20−0.2 (3)
C3—C4—C9—C8−178.34 (17)C21—C20—C25—C240.8 (3)
O13—C8—C9—O11.3 (3)Si1—C20—C25—C24173.55 (16)
C7—C8—C9—O1179.22 (17)O13—Si1—C26—C2856.95 (15)
O13—C8—C9—C4−179.26 (16)C14—Si1—C26—C28175.28 (13)
C7—C8—C9—C4−1.3 (3)C20—Si1—C26—C28−57.78 (16)
C7—C8—O13—Si178.3 (2)O13—Si1—C26—C27−61.85 (17)
C9—C8—O13—Si1−103.83 (18)C14—Si1—C26—C2756.47 (19)
C14—Si1—O13—C821.23 (17)C20—Si1—C26—C27−176.58 (16)
C20—Si1—O13—C8−99.27 (16)O13—Si1—C26—C29175.59 (15)
C26—Si1—O13—C8145.81 (15)C14—Si1—C26—C29−66.09 (18)
O13—Si1—C14—C1565.61 (18)C20—Si1—C26—C2960.85 (17)
C20—Si1—C14—C15−176.04 (16)
Acknowledgements top

We gratefully acknowledge the Unidade de Raios X, RIAIDT, University of Santiago de Compostela, Spain.

references
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