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Acta Crystallogr Sect E Struct Rep Online. 2010 February 1; 66(Pt 2): o461–o462.
Published online 2010 January 27. doi:  10.1107/S1600536810002722
PMCID: PMC2979722

tert-Butoxy­triphenyl­silane

Abstract

The title compound, C22H24OSi or Ph3SiOtBu, shows a distorted tetra­hedral coordination sphere around the Si atom. The C—O—Si angle is 135.97 (12)° and the O—Si distance is 1.6244 (13) Å. The mol­ecules are held together by weak inter­actions only. An H(...)H distance of 2.2924 (7) Å is found between aryl H atoms and is the shortest inter­molecular distance in the structure. With regard to the broad applicability of R 3SiO structural motifs in all fields of chemistry, the mol­ecule demonstrates a common model system for silicon centers surrounded by sterically demanding substituents.

Related literature

For the synthesis of Ph3SiO-t-Bu, see: Gilman et al. (1953 [triangle]). For the synthesis and structure of Ph3SiO-i-Pr, see: Wojtczak et al. (1996 [triangle]). For selected transition-metal complexes containing Ph3SiO groups, see: Bindl et al. (2009 [triangle]); Johnson et al. (2000 [triangle]); Ruiz et al. (2004 [triangle]); Schweder et al. (1999 [triangle]); Schweder et al. (2006 [triangle]); Wolff von Gudenberg et al. (1994 [triangle]). For selected main-group compounds containing Ph3SiO units, see: Apblett & Barron (1993 [triangle]); Chen et al. (2008 [triangle]); Ferguson et al. (1996 [triangle], 2005 [triangle]). For applications of silyl ethers in protecting group chemistry, see: Scheidt et al. (2002 [triangle]); Vintonyak & Maier (2007 [triangle]). For comparative O—Si distances, see: Bowes et al. (2002 [triangle]); Wojtczak et al. (1996 [triangle]) and for C—Si distances, see: Dilman et al. (2004 [triangle]); Lee et al. (2001 [triangle]); Wojtczak et al. (1996 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-0o461-scheme1.jpg

Experimental

Crystal data

  • C22H24OSi
  • M r = 332.5
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-0o461-efi1.jpg
  • a = 9.8054 (12) Å
  • b = 20.201 (7) Å
  • c = 10.231 (2) Å
  • β = 111.311 (18)°
  • V = 1888.0 (8) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.13 mm−1
  • T = 173 K
  • 0.30 × 0.20 × 0.20 mm

Data collection

  • Oxford Diffraction Xcalibur S diffractometer
  • Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006 [triangle]) T min = 0.962, T max = 0.975
  • 23180 measured reflections
  • 4203 independent reflections
  • 2597 reflections with I > 2σ(I)
  • R int = 0.045

Refinement

  • R[F 2 > 2σ(F 2)] = 0.042
  • wR(F 2) = 0.100
  • S = 0.89
  • 4203 reflections
  • 220 parameters
  • H-atom parameters constrained
  • Δρmax = 0.37 e Å−3
  • Δρmin = −0.24 e Å−3

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 [triangle]); cell refinement: CrysAlis RED (Oxford Diffraction, 2006 [triangle]); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 (Farrugia, 1997 [triangle]); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810002722/fb2173sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810002722/fb2173Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors are grateful to the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie for financial support. JOB thanks the Studienstiftung des deutschen Volkes (Max Weber-Programm) for a scholarship.

supplementary crystallographic information

Comment

Siloxy groups are versatile structural subunits both in organic and inorganic chemistry, e.g. in the design of transition metal based catalysts (Bindl et al., 2009; Schweder et al., 1999) such as in the recently developed molybdenum triphenylsiloxide complex, which serves as a catalyst for alkyne metathesis (Bindl et al., 2009). In the light of the impressive attainment in natural product synthesis, silyl ethers in addition proved to be an essential structural element in their role as commonly used protecting groups as they are applied for alcohol functionalities (Scheidt et al., 2002; Vintonyak & Maier, 2007). Aside from several known x-ray structures of triphenylsiloxy substituted transition metal complexes (Bindl et al., 2009; Johnson et al., 2000; Ruiz et al., 2004; Schweder et al., 1999; Schweder et al., 2006; Wolff von Gudenberg et al., 1994), there have also been reported some corresponding main group compounds (Apblett & Barron, 1993; Ferguson et al., 1996; Ferguson et al., 2005; Wojtczak et al., 1996) as well as palladium allyl species that contain triphenylsilyl ether subunits (Chen et al., 2008).

The title compound, tert-butoxytriphenylsilane, was originally synthesized by Gilman et al. (1953) by refluxing chlorotriphenylsilane in tert-butyl alcohol in the presence of dimethylaniline. While the crystal structure of Ph3SiO-i-Pr was found to be already determined (Wojtczak et al., 1996), no structural data about the bulkier substituted Ph3SiO-t-Bu have been described yet.

The molecule of the title compound features a distorted tetrahedral coordination around the silicon center. Contrary to the virtually tetrahedral O—Si—C7 and O—Si—C1 bond angles of 111.34 (8)° and 112.63 (8)°, respectively, the O—Si—C13 angle with a value of 102.31 (8)° was found to be significantly smaller. The remarkable sterical hindrance between the bulky tert-butoxy substituent and the three phenyl groups is also reflected by the large C19—O—Si bond angle of 135.97 (12)° which is comparable to the C—O—Si angle in the structurally characterized silylenol ether isopropenyloxy[tris(pentafluorophenyl)]silane [138.9 (1)°] (Dilman et al., 2004). However, the value of this angle in both the latter and the title compound is noticeably larger than the respective angle in iso-propoxytriphenylsilane [124.8 (1)°] (Wojtczak et al., 1996). In the title structure, the three C—Si bond lengths have values of 1.8545 (19) Å (C7—Si), 1.8541 (18) Å (C13—Si) and 1.8623 (19) Å (C1—Si) and thus are comparable to the distances found in the related systems (Dilman et al., 2004; Lee et al., 2001; Wojtczak et al., 1996). It is also worth mentioning that the interatomic O—Si distance with 1.6244 (13) Å is slightly shorter than those in the reported tetrameric triphenylsilanol [values denoted from 1.6397 (19) Å to 1.646 (2) Å] (Bowes et al., 2002) and the aforementioned Ph3SiO-i-Pr [1.641 (2) Å] (Wojtczak et al., 1996). The distance between the aryl H4 atomes (H4—H4'; -x+1, -y, -z+2) equals to 2.2924 (7) Å and it was identified as the shortest intermolecular distance in the structure.

Experimental

Potassium-tert-butoxide (503 mg, 4.48 mmol), dissolved in absolute tetrahydrofuran (4 ml), was added dropwise at 0°C to a stirred solution of chlorotriphenylsilane (1.10 g, 3.73 mmol) in 7 ml of absolute tetrahydrofuran. The resulting reaction mixture was stirred for 4 h at room temperature. After saturated aqueous NH4Cl solution (10 ml) had been added, the organic layer was separated and the aqueous phase extracted with diethyl ether (2×10 ml and 2×5 ml). The combined ether extracts were washed with water (10 ml) and then dried over anhydrous Na2SO4. After filtration, all volatiles were removed under reduced pressure to yield 90% (1.11 g) of a white solid. The crude product was purified by Kugelrohr distillation (140°C, 0.8 mbar). Recrystallization of the title compound from diethyl ether resulted in the formation of small and transparent plates in the range of 0.30 × 0.20 × 0.20 mm, suitable for single-crystal x-ray studies.

1H-NMR (300.1 MHz, CDCl3): δ = 1.29 [s, 9H; C(CH3)3], 7.34–7.45 (m, 9H; Haromat.), 7.68–7.71 (m, 6H; Haromat.).

{1H}13C-NMR (75.5 MHz, CDCl3): δ = 32.1 (3 C) [C(CH3)3], 74.1 (1 C) [C(CH3)3], 127.6 (6 C) (Cmeta), 129.5 (3 C) (Cpara), 135.5 (6 C) (Cortho), 136.6 (3 C) (Cipso).

{1H}29Si-NMR (59.6 MHz, CDCl3): δ = -22.2 (1Si).

GC/EI—MS (70 eV): tR = 7.06 min; m/z (%) = 332 (11) [M+], 317 (62) [(M-Me)+], 259 (100) [(Ph3Si)+], 199 (79) [(Ph2SiHO)+], 105 (5) [(SiPh)+].

Analysis: C22H24OSi calculated: C 79.47%, H 7.28%; found: C 79.4%, H 7.3%.

Refinement

All the H atoms could have been discerned in the difference electron density map. However, the H atoms were refined in their idealized geometric positions using the riding model approximation with Uiso(H) = 1.5Ueq(C) for the methyl H atoms and of Uiso(H) = 1.2Ueq(C) for the aryl H atoms. The applied C—H distance constraints: methyl 0.98 Å; aryl 0.95 Å.

Figures

Fig. 1.
The title molecule tert-butoxytriphenylsilane with the displacement ellipsoids drawn at the 50% probability level.

Crystal data

C22H24OSiF(000) = 712
Mr = 332.5Dx = 1.170 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 6858 reflections
a = 9.8054 (12) Åθ = 2.2–29.1°
b = 20.201 (7) ŵ = 0.13 mm1
c = 10.231 (2) ÅT = 173 K
β = 111.311 (18)°Block, colourless
V = 1888.0 (8) Å30.30 × 0.20 × 0.20 mm
Z = 4

Data collection

Oxford Diffraction Xcalibur S diffractometer4203 independent reflections
Radiation source: Enhance (Mo) X-ray Source2597 reflections with I > 2σ(I)
graphiteRint = 0.045
ω scansθmax = 27.2°, θmin = 2.4°
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)h = −12→12
Tmin = 0.962, Tmax = 0.975k = −26→25
23180 measured reflectionsl = −13→13

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.042Hydrogen site location: difference Fourier map
wR(F2) = 0.100H-atom parameters constrained
S = 0.89w = 1/[σ2(Fo2) + (0.0535P)2] where P = (Fo2 + 2Fc2)/3
4203 reflections(Δ/σ)max < 0.001
220 parametersΔρmax = 0.37 e Å3
0 restraintsΔρmin = −0.24 e Å3

Special details

Experimental. empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm
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 > 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)

xyzUiso*/Ueq
C10.27284 (19)0.12279 (9)0.61661 (17)0.0278 (4)
C20.1958 (2)0.08722 (10)0.68339 (19)0.0403 (5)
H20.09350.08080.6370.048*
C30.2644 (3)0.06106 (11)0.8152 (2)0.0556 (6)
H30.20980.03630.85830.067*
C40.4122 (3)0.07079 (12)0.8846 (2)0.0615 (7)
H40.45930.05350.97640.074*
C50.4911 (3)0.10533 (11)0.8215 (2)0.0506 (6)
H50.59320.11190.86920.061*
C60.4227 (2)0.13062 (9)0.68881 (19)0.0358 (5)
H60.47890.1540.64540.043*
C70.27111 (17)0.23135 (8)0.41104 (17)0.0238 (4)
C80.27112 (18)0.24872 (9)0.27948 (18)0.0285 (4)
H80.2230.22070.20170.034*
C90.3389 (2)0.30526 (9)0.25882 (19)0.0331 (4)
H90.33680.31620.16780.04*
C100.40953 (19)0.34582 (9)0.3708 (2)0.0349 (4)
H100.45880.38430.35760.042*
C110.40926 (19)0.33105 (9)0.50166 (19)0.0337 (5)
H110.45620.35980.57840.04*
C120.34073 (19)0.27453 (9)0.52133 (18)0.0292 (4)
H120.34090.26470.61220.035*
C13−0.01766 (18)0.17492 (9)0.40683 (17)0.0262 (4)
C14−0.1271 (2)0.12846 (10)0.3473 (2)0.0400 (5)
H14−0.1010.08560.32610.048*
C15−0.2717 (2)0.14281 (12)0.3185 (2)0.0533 (6)
H15−0.34440.11010.27760.064*
C16−0.3119 (2)0.20462 (12)0.3486 (2)0.0504 (6)
H16−0.41210.21470.32880.061*
C17−0.2070 (2)0.25123 (10)0.4069 (2)0.0425 (5)
H17−0.23420.2940.42720.051*
C18−0.0612 (2)0.23652 (9)0.43663 (18)0.0315 (4)
H180.01080.26940.47840.038*
C190.2491 (2)0.04775 (9)0.29651 (19)0.0333 (4)
C200.2387 (2)−0.01047 (10)0.3858 (2)0.0500 (6)
H20A0.28890.00040.48520.075*
H20B0.285−0.04930.36210.075*
H20C0.1356−0.02010.36790.075*
C210.1796 (3)0.02943 (11)0.1418 (2)0.0527 (6)
H21A0.07640.0180.11960.079*
H21B0.2311−0.00860.12230.079*
H21C0.18640.06710.08420.079*
C220.4025 (2)0.06981 (12)0.3291 (3)0.0613 (7)
H22A0.4040.10620.26640.092*
H22B0.46070.03280.31590.092*
H22C0.44390.0850.42670.092*
O0.16116 (12)0.10112 (6)0.31536 (11)0.0266 (3)
Si0.17626 (5)0.15575 (2)0.43643 (5)0.02347 (13)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
C10.0329 (10)0.0245 (10)0.0250 (9)0.0035 (8)0.0092 (8)−0.0018 (8)
C20.0516 (13)0.0398 (12)0.0318 (11)0.0006 (10)0.0180 (10)0.0021 (9)
C30.094 (2)0.0419 (14)0.0394 (13)0.0094 (13)0.0348 (14)0.0088 (11)
C40.098 (2)0.0445 (15)0.0280 (12)0.0286 (14)0.0059 (13)0.0077 (11)
C50.0549 (14)0.0406 (13)0.0373 (12)0.0218 (11)−0.0060 (11)−0.0078 (10)
C60.0378 (11)0.0305 (11)0.0320 (11)0.0081 (9)0.0042 (9)−0.0047 (9)
C70.0190 (8)0.0253 (9)0.0261 (10)0.0020 (7)0.0069 (7)0.0019 (8)
C80.0297 (10)0.0275 (10)0.0268 (10)0.0004 (8)0.0088 (8)−0.0013 (8)
C90.0383 (11)0.0327 (11)0.0314 (11)0.0013 (9)0.0162 (9)0.0046 (9)
C100.0326 (10)0.0257 (10)0.0460 (12)−0.0034 (9)0.0140 (9)0.0053 (9)
C110.0322 (10)0.0297 (11)0.0319 (11)−0.0064 (8)0.0029 (8)−0.0030 (8)
C120.0299 (10)0.0293 (10)0.0250 (9)−0.0008 (8)0.0060 (8)0.0012 (8)
C130.0251 (9)0.0294 (10)0.0256 (9)0.0010 (8)0.0108 (7)0.0060 (8)
C140.0265 (10)0.0374 (12)0.0571 (13)−0.0021 (9)0.0164 (9)−0.0025 (10)
C150.0244 (10)0.0573 (16)0.0770 (16)−0.0071 (11)0.0170 (11)0.0003 (13)
C160.0267 (11)0.0609 (16)0.0673 (15)0.0102 (11)0.0214 (11)0.0186 (13)
C170.0437 (12)0.0417 (13)0.0516 (13)0.0170 (11)0.0285 (10)0.0152 (10)
C180.0341 (10)0.0313 (11)0.0331 (11)0.0008 (9)0.0169 (8)0.0034 (9)
C190.0318 (10)0.0343 (11)0.0334 (11)0.0086 (9)0.0113 (8)0.0021 (9)
C200.0624 (15)0.0318 (12)0.0506 (13)0.0106 (11)0.0142 (11)0.0014 (10)
C210.0675 (16)0.0492 (14)0.0397 (13)0.0188 (12)0.0176 (11)−0.0022 (11)
C220.0397 (13)0.0515 (15)0.0967 (19)0.0006 (12)0.0295 (13)−0.0100 (13)
O0.0239 (6)0.0260 (7)0.0280 (7)0.0030 (5)0.0070 (5)−0.0026 (5)
Si0.0205 (2)0.0252 (3)0.0237 (3)−0.0009 (2)0.00684 (18)−0.0001 (2)

Geometric parameters (Å, °)

C1—C21.389 (2)C13—C141.388 (3)
C1—C61.393 (2)C13—Si1.8544 (17)
C1—Si1.8626 (18)C14—C151.371 (3)
C2—C31.375 (3)C14—H140.95
C2—H20.95C15—C161.378 (3)
C3—C41.376 (3)C15—H150.95
C3—H30.95C16—C171.362 (3)
C4—C51.366 (3)C16—H160.95
C4—H40.95C17—C181.382 (2)
C5—C61.375 (3)C17—H170.95
C5—H50.95C18—H180.95
C6—H60.95C19—O1.437 (2)
C7—C81.391 (2)C19—C221.485 (3)
C7—C121.393 (2)C19—C201.516 (3)
C7—Si1.8549 (18)C19—C211.524 (3)
C8—C91.376 (2)C20—H20A0.98
C8—H80.95C20—H20B0.98
C9—C101.374 (2)C20—H20C0.98
C9—H90.95C21—H21A0.98
C10—C111.373 (3)C21—H21B0.98
C10—H100.95C21—H21C0.98
C11—C121.376 (2)C22—H22A0.98
C11—H110.95C22—H22B0.98
C12—H120.95C22—H22C0.98
C13—C181.385 (2)O—Si1.6251 (12)
C2—C1—C6117.08 (17)C14—C15—H15120
C2—C1—Si120.00 (14)C16—C15—H15120
C6—C1—Si122.90 (14)C17—C16—C15119.53 (19)
C3—C2—C1121.4 (2)C17—C16—H16120.2
C3—C2—H2119.3C15—C16—H16120.2
C1—C2—H2119.3C16—C17—C18120.27 (19)
C2—C3—C4119.9 (2)C16—C17—H17119.9
C2—C3—H3120C18—C17—H17119.9
C4—C3—H3120C17—C18—C13121.47 (18)
C5—C4—C3120.0 (2)C17—C18—H18119.3
C5—C4—H4120C13—C18—H18119.3
C3—C4—H4120O—C19—C22110.67 (16)
C4—C5—C6120.0 (2)O—C19—C20109.03 (15)
C4—C5—H5120C22—C19—C20112.45 (17)
C6—C5—H5120O—C19—C21104.93 (14)
C5—C6—C1121.6 (2)C22—C19—C21109.93 (17)
C5—C6—H6119.2C20—C19—C21109.56 (17)
C1—C6—H6119.2C19—C20—H20A109.5
C8—C7—C12116.97 (16)C19—C20—H20B109.5
C8—C7—Si121.30 (13)H20A—C20—H20B109.5
C12—C7—Si121.69 (13)C19—C20—H20C109.5
C9—C8—C7121.87 (17)H20A—C20—H20C109.5
C9—C8—H8119.1H20B—C20—H20C109.5
C7—C8—H8119.1C19—C21—H21A109.5
C10—C9—C8119.50 (17)C19—C21—H21B109.5
C10—C9—H9120.3H21A—C21—H21B109.5
C8—C9—H9120.3C19—C21—H21C109.5
C11—C10—C9120.31 (17)H21A—C21—H21C109.5
C11—C10—H10119.8H21B—C21—H21C109.5
C9—C10—H10119.8C19—C22—H22A109.5
C10—C11—C12119.81 (17)C19—C22—H22B109.5
C10—C11—H11120.1H22A—C22—H22B109.5
C12—C11—H11120.1C19—C22—H22C109.5
C11—C12—C7121.52 (17)H22A—C22—H22C109.5
C11—C12—H12119.2H22B—C22—H22C109.5
C7—C12—H12119.2C19—O—Si135.97 (11)
C18—C13—C14116.93 (16)O—Si—C13102.32 (7)
C18—C13—Si122.11 (13)O—Si—C7111.33 (7)
C14—C13—Si120.89 (14)C13—Si—C7109.98 (8)
C15—C14—C13121.72 (19)O—Si—C1112.61 (7)
C15—C14—H14119.1C13—Si—C1111.02 (8)
C13—C14—H14119.1C7—Si—C1109.42 (8)
C14—C15—C16120.1 (2)

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FB2173).

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