Tetra­kis(4-tert-butyl­benz­yl)silane

Burnham, L.E.; Kachlan, R.M.; Thomas, A.A.; Ogle, C.A.; Jones, D.S.

doi:10.1107/S1600536810034173

organic compounds

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ISSN: 2056-9890

Volume 66| Part 9| September 2010| Page o2442

https://doi.org/10.1107/S1600536810034173

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Tetrakis(4-tert-butylbenzyl)silane

Lauren E. Burnham,^a Rulla M. Kachlan,^a Andy A. Thomas,^a Craig A. Ogle ^a and Daniel S. Jones ^a ^*

^aDepartment of Chemistry, The University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223, USA
^*Correspondence e-mail: djones@uncc.edu

(Received 14 August 2010; accepted 24 August 2010; online 28 August 2010)

The title compound, C₄₄H₆₀Si, was prepared as an internal standard for diffusion-ordered NMR spectroscopy. The Si atom lies on a special position with $[\overline4]$ site symmetry.

Related literature

For applications of the title compound in NMR spectroscopy, see: Li et al. (2009 ). For similar structures in the same space group, see: Liao et al. (2002 ); Laliberté et al. (2004 ). For a previously reported NMR standard, see: Monroe et al. (2010 ). For a description of the Cambridge Structural Database, see: Allen (2002 ).

Experimental

Crystal data

C₄₄H₆₀Si
M_r = 617.01
Tetragonal, P 4₂ /n
a = 17.394 (2) Å
c = 6.3613 (6) Å
V = 1924.7 (4) Å³
Z = 2
Cu Kα radiation
μ = 0.72 mm⁻¹
T = 295 K
0.31 × 0.15 × 0.12 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
5204 measured reflections
1738 independent reflections
1056 reflections with I > 2σ(I)
R_int = 0.036
3 standard reflections every 113 reflections intensity decay: 2%

Refinement

R[F² > 2σ(F²)] = 0.041
wR(F²) = 0.135
S = 1.02
1738 reflections
106 parameters
H-atom parameters constrained
Δρ_max = 0.13 e Å⁻³
Δρ_min = −0.11 e Å⁻³

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994 ); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ) and Mercury (Macrae et al., 2006 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810034173/su2206sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810034173/su2206Isup2.hkl

checkCIF report

Comment top

The title compound was prepared as an internal standard for diffusion-ordered NMR spectroscopy. A recent paper on this subject (Li et al., 2009) suggests an internal standard method for correlating diffusion coefficients with formula weights. The title compound was chosen because its shape in solution both approximates that of a spheroid and is similar to that of the species being studied. In addition, it neither reacts with the species under study nor gives interfering NMR signals.

The molecular structure of the title molecule is illustrated in Fig. 1. The molecule sits on a fourfold rotoinversion axis, with the Si atom located at the point of inversion and the four ligands arranged tetrahedrally around the Si atom. The crystal packing of the title compound, viewed along the c axis, is illustrated in Fig. 2.

The space group, P4₂/n, is relatively rare, comprising fewer than 700 of the half-million-plus structures in the Cambridge Structural Database [Version 5.31; Allen, 2002]. Similar structures which crystallized in the same space group include tetrakis(4-N-t-Butyl-N-aminoxylphenyl)silane (Liao et al., 2002) and tetrakis(4-(Ethoxycarbonylamino)phenyl)silane bis(dioxane) clathrate (Laliberté et al., 2004).

We have previously reported on the crystal structure of another NMR standard of smaller molecular weight, bis(2-naphthylmethyl)diphenylsilane (Monroe et al., 2010).

Related literature top

For applications of the title compound in NMR spectroscopy, see: Li et al. (2009). For similar structures in the same space group, see: Liao et al. (2002); Laliberté et al. (2004). For a previously reported NMR standard, see: Monroe et al. (2010). For a description of the Cambridge Structural Database, see: Allen (2002).

Experimental top

The synthesis of the title compound is descibed in Fig. 3. A dry, 250 ml Schlenk flask, equipped with a magnetic stirbar, was charged with 4-tertbutyltoluene (I) (7.13 g, 50 mmol), potassium tert-butoxide (6.72 g, 55 mmol), then purged with nitrogen. 100 ml of freshly distilled dry THF was added and the reaction was cooled to 195 K. n-BuLi (23.91 ml, 2.3M, 55 mmol) was then added dropwise. The Schlenk flask was then capped and kept at 233 K overnight. The solution was again cooled to 195 K and 2.09 ml (1.68 g, 10 mmol) of tetrachlorosilane was added dropwise. The reaction mixture was allowed to warm to room temperature and stirred for two hours. The mixture was then quenched with deionized water and extracted three times with petroleum ether. The combined organic layers were dried with magnesium sulfate, filtered, and evaporated. Bulb-to-bulb distillation gave a tan solid, which was recrystallized from petroleum ether to yield pure colorless crystals of tetrakis(4-tert-butylbenzyl)silane (II) (3.45 g, 56% recovery).

mp 407–409 K; ¹H NMR (Toluene-d₈, 300 MHz): 1.27 (s)9H, 2.14 (s)2H, 6.85 (d)2H, 7.20 (d)2H. ¹³C NMR (Toluene-d₈, 300 MHz): 31.66, 34.20, 20.71, 124.96, 128.75, 129.52, 147.13. GC/MS (70ev) m/z: 469.4, 57.1

Structure description top

We have previously reported on the crystal structure of another NMR standard of smaller molecular weight, bis(2-naphthylmethyl)diphenylsilane (Monroe et al., 2010).

For applications of the title compound in NMR spectroscopy, see: Li et al. (2009). For similar structures in the same space group, see: Liao et al. (2002); Laliberté et al. (2004). For a previously reported NMR standard, see: Monroe et al. (2010). For a description of the Cambridge Structural Database, see: Allen (2002).

Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. View of title molecule with 50% probability displacement ellipsoids [Symmetry codes: (i) -x + 1/2, -y + 1/2, z (ii) y, -x + 1/2, -z + 1/2 (iii) -y + 1/2, x, -z + 1/2].
	Fig. 2. Crystal packing diagram of the title compound viewed along the c axis.
	Fig. 3. Synthesis scheme.

Tetrakis(4-tert-butylbenzyl)silane top

Crystal data top

C₄₄H₆₀Si	D_x = 1.065 Mg m⁻³
M_r = 617.01	Cu Kα radiation, λ = 1.54184 Å
Tetragonal, P4₂/n	Cell parameters from 25 reflections
Hall symbol: -P 4bc	θ = 7.8–35.3°
a = 17.394 (2) Å	µ = 0.72 mm⁻¹
c = 6.3613 (6) Å	T = 295 K
V = 1924.7 (4) Å³	Prism, colorless
Z = 2	0.31 × 0.15 × 0.12 mm
F(000) = 676

Data collection top

Enraf–Nonius CAD-4 diffractometer	θ_max = 67.4°, θ_min = 3.6°
non–profiled ω/2θ scans	h = −20→20
5204 measured reflections	k = −20→15
1738 independent reflections	l = −7→0
1056 reflections with I > 2σ(I)	3 standard reflections every 113 reflections
R_int = 0.036	intensity decay: 2%

Refinement top

Refinement on F²	H-atom parameters constrained
Least-squares matrix: full	w = 1/[σ²(F_o²) + (0.0761P)² + 0.1124P] where P = (F_o² + 2F_c²)/3
R[F² > 2σ(F²)] = 0.041	(Δ/σ)_max < 0.001
wR(F²) = 0.135	Δρ_max = 0.13 e Å⁻³
S = 1.02	Δρ_min = −0.11 e Å⁻³
1738 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
106 parameters	Extinction coefficient: 0.0033 (6)
0 restraints

Crystal data top

C₄₄H₆₀Si	Z = 2
M_r = 617.01	Cu Kα radiation
Tetragonal, P4₂/n	µ = 0.72 mm⁻¹
a = 17.394 (2) Å	T = 295 K
c = 6.3613 (6) Å	0.31 × 0.15 × 0.12 mm
V = 1924.7 (4) Å³

Data collection top

Enraf–Nonius CAD-4 diffractometer	R_int = 0.036
5204 measured reflections	3 standard reflections every 113 reflections
1738 independent reflections	intensity decay: 2%
1056 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.041	0 restraints
wR(F²) = 0.135	H-atom parameters constrained
S = 1.02	Δρ_max = 0.13 e Å⁻³
1738 reflections	Δρ_min = −0.11 e Å⁻³
106 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.

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

	x	y	z	U_iso*/U_eq
Si	0.25	0.25	0.25	0.0599 (4)
C4	0.50538 (12)	0.30509 (12)	0.4293 (4)	0.0780 (7)
H4	0.5263	0.2856	0.5529	0.094*
C1	0.33661 (10)	0.25820 (11)	0.0742 (4)	0.0674 (7)
H1A	0.3507	0.2069	0.0288	0.081*
H1B	0.3217	0.2868	−0.0502	0.081*
C5	0.54015 (10)	0.36783 (10)	0.3360 (3)	0.0535 (5)
C7	0.44050 (11)	0.35854 (12)	0.0714 (4)	0.0668 (6)
H7	0.4193	0.3779	−0.0519	0.08*
C8	0.61357 (11)	0.40291 (11)	0.4257 (4)	0.0624 (6)
C2	0.40700 (10)	0.29575 (10)	0.1652 (4)	0.0580 (5)
C6	0.50509 (12)	0.39375 (12)	0.1556 (4)	0.0674 (6)
H6	0.5255	0.4365	0.0876	0.081*
C3	0.44105 (12)	0.27021 (12)	0.3468 (4)	0.0837 (8)
H3	0.42	0.2281	0.4163	0.1*
C9	0.62982 (15)	0.48273 (14)	0.3328 (5)	0.0951 (9)
H9A	0.634	0.4789	0.1827	0.143*
H9B	0.6771	0.5023	0.3896	0.143*
H9C	0.5885	0.517	0.3682	0.143*
C10	0.68066 (12)	0.35026 (15)	0.3687 (5)	0.0992 (9)
H10A	0.672	0.3001	0.4269	0.149*
H10B	0.7275	0.3711	0.4249	0.149*
H10C	0.6848	0.3465	0.2186	0.149*
C11	0.60896 (17)	0.41111 (18)	0.6619 (5)	0.1047 (9)
H11A	0.5674	0.445	0.6977	0.157*
H11B	0.6564	0.432	0.714	0.157*
H11C	0.6002	0.3616	0.7241	0.157*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.0473 (4)	0.0473 (4)	0.0852 (9)	0	0	0
C4	0.0612 (12)	0.0722 (13)	0.101 (2)	−0.0089 (11)	−0.0143 (12)	0.0413 (13)
C1	0.0543 (11)	0.0616 (11)	0.0863 (18)	0.0010 (9)	0.0016 (11)	0.0004 (11)
C5	0.0496 (10)	0.0501 (10)	0.0609 (12)	0.0033 (8)	0.0116 (10)	0.0070 (9)
C7	0.0658 (12)	0.0750 (13)	0.0596 (15)	−0.0063 (10)	0.0042 (10)	0.0141 (11)
C8	0.0584 (11)	0.0644 (12)	0.0645 (15)	−0.0057 (9)	0.0067 (10)	0.0059 (10)
C2	0.0477 (10)	0.0504 (10)	0.0759 (14)	0.0042 (8)	0.0086 (10)	0.0056 (10)
C6	0.0688 (12)	0.0698 (13)	0.0638 (14)	−0.0169 (10)	0.0105 (12)	0.0169 (11)
C3	0.0617 (12)	0.0677 (13)	0.122 (2)	−0.0127 (10)	−0.0093 (14)	0.0472 (14)
C9	0.0946 (17)	0.0790 (15)	0.112 (2)	−0.0315 (13)	−0.0090 (16)	0.0155 (15)
C10	0.0538 (12)	0.111 (2)	0.133 (3)	0.0025 (13)	0.0030 (14)	−0.0136 (19)
C11	0.118 (2)	0.120 (2)	0.0760 (19)	−0.0328 (17)	0.0054 (17)	−0.0061 (17)

Geometric parameters (Å, º) top

Si—C1ⁱ	1.882 (2)	C8—C11	1.512 (3)
Si—C1ⁱⁱ	1.882 (2)	C8—C10	1.527 (3)
Si—C1ⁱⁱⁱ	1.882 (2)	C8—C9	1.535 (3)
Si—C1	1.882 (2)	C2—C3	1.372 (3)
C4—C3	1.377 (3)	C6—H6	0.93
C4—C5	1.382 (3)	C3—H3	0.93
C4—H4	0.93	C9—H9A	0.96
C1—C2	1.504 (3)	C9—H9B	0.96
C1—H1A	0.97	C9—H9C	0.96
C1—H1B	0.97	C10—H10A	0.96
C5—C6	1.375 (3)	C10—H10B	0.96
C5—C8	1.526 (3)	C10—H10C	0.96
C7—C2	1.374 (3)	C11—H11A	0.96
C7—C6	1.387 (3)	C11—H11B	0.96
C7—H7	0.93	C11—H11C	0.96

C1ⁱ—Si—C1ⁱⁱ	110.68 (7)	C3—C2—C7	116.09 (19)
C1ⁱ—Si—C1ⁱⁱⁱ	107.08 (14)	C3—C2—C1	122.34 (18)
C1ⁱⁱ—Si—C1ⁱⁱⁱ	110.68 (7)	C7—C2—C1	121.6 (2)
C1ⁱ—Si—C1	110.68 (7)	C5—C6—C7	122.44 (19)
C1ⁱⁱ—Si—C1	107.08 (14)	C5—C6—H6	118.8
C1ⁱⁱⁱ—Si—C1	110.68 (7)	C7—C6—H6	118.8
C3—C4—C5	122.7 (2)	C2—C3—C4	121.94 (19)
C3—C4—H4	118.7	C2—C3—H3	119
C5—C4—H4	118.7	C4—C3—H3	119
C2—C1—Si	117.14 (16)	C8—C9—H9A	109.5
C2—C1—H1A	108	C8—C9—H9B	109.5
Si—C1—H1A	108	H9A—C9—H9B	109.5
C2—C1—H1B	108	C8—C9—H9C	109.5
Si—C1—H1B	108	H9A—C9—H9C	109.5
H1A—C1—H1B	107.3	H9B—C9—H9C	109.5
C6—C5—C4	115.05 (19)	C8—C10—H10A	109.5
C6—C5—C8	123.50 (17)	C8—C10—H10B	109.5
C4—C5—C8	121.4 (2)	H10A—C10—H10B	109.5
C2—C7—C6	121.8 (2)	C8—C10—H10C	109.5
C2—C7—H7	119.1	H10A—C10—H10C	109.5
C6—C7—H7	119.1	H10B—C10—H10C	109.5
C11—C8—C5	111.41 (19)	C8—C11—H11A	109.5
C11—C8—C10	109.4 (2)	C8—C11—H11B	109.5
C5—C8—C10	108.13 (17)	H11A—C11—H11B	109.5
C11—C8—C9	107.9 (2)	C8—C11—H11C	109.5
C5—C8—C9	111.83 (18)	H11A—C11—H11C	109.5
C10—C8—C9	108.09 (19)	H11B—C11—H11C	109.5

Symmetry codes: (i) −y+1/2, x, −z+1/2; (ii) −x+1/2, −y+1/2, z; (iii) y, −x+1/2, −z+1/2.

Experimental details

Crystal data
Chemical formula	C₄₄H₆₀Si
M_r	617.01
Crystal system, space group	Tetragonal, P4₂/n
Temperature (K)	295
a, c (Å)	17.394 (2), 6.3613 (6)
V (Å³)	1924.7 (4)
Z	2
Radiation type	Cu Kα
µ (mm⁻¹)	0.72
Crystal size (mm)	0.31 × 0.15 × 0.12

Data collection
Diffractometer	Enraf–Nonius CAD-4
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	5204, 1738, 1056
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.599

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.041, 0.135, 1.02
No. of reflections	1738
No. of parameters	106
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.13, −0.11

Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2006), WinGX (Farrugia, 1999).

Acknowledgements

This work was supported in part by funds provided by the University of North Carolina at Charlotte. Support for REU participant RMK was provided by the National Science Foundation, award number CHE-0851797. Many helpful discussions with T. Blake Monroe are gratefully acknowledged.

References

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