Tetra­kis(2,3,5,5-tetra­methyl­hexen-2-yl)silane

In the title compound, C₄₀H₇₆Si, the Si atom is located on a special position of site symmetry -4. Thus, there is just a quarter of a mol­ecule in the asymmetric unit. The C=C double bonds exhibit a trans configuration. The Si atom and the tert-butyl group are located on the same side of the plane formed by the C=C double bond and its four substituents. The crystal packing shows no short contacts between the mol­ecules and despite the low crystal density (0.980 Mg m⁻³), there are no significant voids in the structure.

Related literature

For information on the chemical background, see: Meyer-Wegner et al. (2011, 2014).

Experimental

Crystal data

• C₄₀H₇₆Si

• M_r = 585.10

• Tetragonal, I 4₁ /a

• a = 12.5780 (11) Å

• c = 25.053 (3) Å

• V = 3963.5 (7) ų

• Z = 4

• Mo Kα radiation

• μ = 0.08 mm⁻¹

• T = 173 K

• 0.32 × 0.28 × 0.16 mm

Data collection

• Stoe IPDS-II two-circle diffractometer

• Absorption correction: multi-scan (MULABS; Spek, 2009; Blessing, 1995) T_min = 0.963, T_max = 0.988

• 5117 measured reflections

• 1742 independent reflections

• 1301 reflections with I > 2σ(I)

• R_int = 0.045

Refinement

• R[F² > 2σ(F²)] = 0.051

• wR(F²) = 0.136

• S = 1.08

• 1742 reflections

• 95 parameters

• H-atom parameters constrained

• Δρ_max = 0.25 e Å⁻³

• Δρ_min = −0.17 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-RED32 (Stoe & Cie, 2001); data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 and publCIF (Westrip, 2010).

Supporting information

S1. Comment

Very recently, we have investigated the reaction of Si₂Cl₆ with NR₃ (R = Me, Et) and we have been able to show that amine-complexed dichlorosilylenes represent the key intermediates in this disproportionation reaction (Meyer-Wegner et al., 2011). In the course of these studies we isolated along with SiCl₄ the [4 + 1] cycloadduct of dichlorosilylene SiCl₂ with 2,3-dimethyl-1,3-butadiene (DMB) in good yield upon treatment of Si₂Cl₆ with catalytic amounts of NMe₃ or NMe₂Et in neat DMB (Meyer-Wegner et al., 2014). In this study we report on the reaction of Si₂Cl₆ with catalytic amounts of NMe₂Et in the presence of DMB. Subsequent treatment of this reaction mixture with tBuLi yielded the title compound (I) which could be isolated (Fig. 1).

In the title compound (Fig. 2), the Si centre is located on a special position of site symmtry 4. Thus, there is just a quarter of a molecule in the asymmetric unit. The C=C double bonds show a trans configuration. It is interesting to note, that the Si centre and the t-butyl group are located on the same side of the plane formed by the C=C double bond and its four substituents. The crystal packing (Fig. 3) shows no short contacts between the molecules and despite the fact that the crystal density is rather low [0.980 g/cm³], there are no significant voids in the structure.

Related literature

For information on the chemical background, see: Meyer-Wegner et al. (2011, 2014).

S2. Experimental

To Si₂Cl₆ (0.3 ml, 0.47 g, 1.74 mmol) in DMB (1.2 ml, 0.86 g, 10 mmol) a catalytic amount of NMe₂Et (0.012 g, 0.2 mmol) was added. Subsequent treatment of this mixture with a solution of tBuLi (16 mmol) in 10 ml of pentane yielded a colorless precipitate. After filtration all volatiles were removed in vacuo. The obtained residue was dissolved in benzene. This solution was stored at ambient temperature for a period of two days yielding single crystals of the title compound.

S3. Refinement

H atoms were geometrically positioned and refined using a riding model with fixed individual displacement parameters [U(H) = 1.2 U_eq(C) or U(H) = 1.5 U_eq(C_methyl)] and with C_methyl—H = 0.98 Å and C_methylene—H = 0.99 Å. The methyl groups attached to the double bond were allowed to rotate but not to tip.

Computing details

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA (Stoe & Cie, 2001); data reduction: X-RED32 (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).

Figures

	Fig. 1. Reaction of SiCl4 with tBuLi in the presence of 2,3-dimethyl-1,3-butadiene.
	Fig. 2. Perspective view of the title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are omitted for clarity. Symmetry codes: (A) -x + 1, -y + 3/2, z; (B) y - 1/4, -x + 5/4, -z + 1/4; (C) -y + 5/4, x + 1/4, -z + 1/4.
	Fig. 3. Packing diagram of the title compound; hydrogen atoms are omitted for clarity. The view direction is approximately down the a axis.

Tetrakis(2,3,5,5-tetramethylhexen-2-yl)silane

Crystal data

C40H76Si	Dx = 0.980 Mg m^−3
Mr = 585.10	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I41/a	Cell parameters from 4399 reflections
Hall symbol: -I 4ad	θ = 3.7–25.9°
a = 12.5780 (11) Å	µ = 0.08 mm^−1
c = 25.053 (3) Å	T = 173 K
V = 3963.5 (7) Å^3	Block, colourless
Z = 4	0.32 × 0.28 × 0.16 mm
F(000) = 1320

Data collection

Stoe IPDS-II two-circle diffractometer	1742 independent reflections
Radiation source: fine-focus sealed tube	1301 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.045
ω scans	θmax = 25.0°, θmin = 3.6°
Absorption correction: multi-scan (MULABS; Spek, 2009; Blessing, 1995)	h = −8→14
Tmin = 0.963, Tmax = 0.988	k = −14→14
5117 measured reflections	l = −25→29

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.136	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0654P)^2 + 0.753P] where P = (Fo^2 + 2Fc^2)/3
1742 reflections	(Δ/σ)max = 0.001
95 parameters	Δρmax = 0.25 e Å^−3
0 restraints	Δρmin = −0.17 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Si1	0.5000	0.7500	0.1250	0.0457 (3)
C1	0.52419 (16)	0.62670 (16)	0.08358 (7)	0.0522 (5)
H1A	0.5766	0.6452	0.0556	0.063*
H1B	0.5581	0.5731	0.1070	0.063*
C2	0.43057 (17)	0.57385 (17)	0.05637 (8)	0.0564 (5)
C3	0.38412 (17)	0.48729 (17)	0.07519 (8)	0.0595 (6)
C4	0.29391 (17)	0.42817 (18)	0.04703 (8)	0.0588 (5)
H4A	0.3062	0.3510	0.0518	0.071*
H4B	0.2996	0.4432	0.0084	0.071*
C5	0.17836 (18)	0.45239 (19)	0.06442 (8)	0.0628 (6)
C21	0.3961 (2)	0.62822 (18)	0.00476 (8)	0.0652 (6)
H21A	0.4590	0.6459	−0.0165	0.098*
H21B	0.3570	0.6935	0.0133	0.098*
H21C	0.3500	0.5802	−0.0156	0.098*
C31	0.4258 (2)	0.43428 (18)	0.12553 (9)	0.0695 (6)
H31A	0.3791	0.3750	0.1353	0.104*
H31B	0.4274	0.4862	0.1547	0.104*
H31C	0.4979	0.4075	0.1191	0.104*
C51	0.1061 (2)	0.3674 (2)	0.03927 (11)	0.0833 (8)
H51A	0.1139	0.3691	0.0004	0.125*
H51B	0.0320	0.3818	0.0488	0.125*
H51C	0.1266	0.2970	0.0526	0.125*
C52	0.1662 (2)	0.4487 (3)	0.12469 (10)	0.0881 (8)
H52A	0.0924	0.4648	0.1343	0.132*
H52B	0.2136	0.5013	0.1410	0.132*
H52C	0.1848	0.3775	0.1376	0.132*
C53	0.1450 (2)	0.5620 (2)	0.04480 (11)	0.0825 (7)
H53A	0.1528	0.5654	0.0059	0.124*
H53B	0.1902	0.6162	0.0614	0.124*
H53C	0.0707	0.5749	0.0545	0.124*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si1	0.0476 (4)	0.0476 (4)	0.0418 (5)	0.000	0.000	0.000
C1	0.0517 (11)	0.0526 (11)	0.0524 (10)	0.0025 (9)	−0.0010 (8)	−0.0013 (8)
C2	0.0612 (12)	0.0571 (12)	0.0508 (11)	0.0073 (10)	0.0031 (9)	−0.0075 (9)
C3	0.0636 (13)	0.0606 (13)	0.0543 (11)	0.0055 (10)	−0.0024 (9)	−0.0053 (9)
C4	0.0644 (13)	0.0599 (12)	0.0520 (10)	−0.0025 (10)	−0.0035 (9)	−0.0116 (9)
C5	0.0613 (13)	0.0744 (15)	0.0528 (11)	−0.0074 (11)	−0.0035 (10)	−0.0120 (10)
C21	0.0841 (16)	0.0659 (14)	0.0457 (10)	0.0062 (12)	−0.0018 (10)	0.0016 (9)
C31	0.0832 (15)	0.0641 (13)	0.0613 (12)	−0.0020 (12)	−0.0165 (11)	0.0081 (11)
C51	0.0674 (15)	0.0991 (19)	0.0833 (16)	−0.0160 (14)	−0.0095 (12)	−0.0227 (14)
C52	0.0807 (17)	0.122 (2)	0.0618 (13)	−0.0206 (16)	0.0092 (12)	−0.0160 (14)
C53	0.0744 (16)	0.0910 (19)	0.0821 (16)	0.0154 (14)	−0.0009 (12)	−0.0141 (13)

Geometric parameters (Å, º)

Si1—C1^i	1.8906 (19)	C5—C51	1.538 (3)
Si1—C1^ii	1.8906 (19)	C21—H21A	0.9800
Si1—C1	1.8907 (19)	C21—H21B	0.9800
Si1—C1^iii	1.8907 (19)	C21—H21C	0.9800
C1—C2	1.514 (3)	C31—H31A	0.9800
C1—H1A	0.9900	C31—H31B	0.9800
C1—H1B	0.9900	C31—H31C	0.9800
C2—C3	1.323 (3)	C51—H51A	0.9800
C2—C21	1.526 (3)	C51—H51B	0.9800
C3—C31	1.520 (3)	C51—H51C	0.9800
C3—C4	1.529 (3)	C52—H52A	0.9800
C4—C5	1.548 (3)	C52—H52B	0.9800
C4—H4A	0.9900	C52—H52C	0.9800
C4—H4B	0.9900	C53—H53A	0.9800
C5—C52	1.518 (3)	C53—H53B	0.9800
C5—C53	1.522 (4)	C53—H53C	0.9800
C1^i—Si1—C1^ii	107.53 (6)	C2—C21—H21A	109.5
C1^i—Si1—C1	113.43 (12)	C2—C21—H21B	109.5
C1^ii—Si1—C1	107.53 (6)	H21A—C21—H21B	109.5
C1^i—Si1—C1^iii	107.53 (6)	C2—C21—H21C	109.5
C1^ii—Si1—C1^iii	113.43 (12)	H21A—C21—H21C	109.5
C1—Si1—C1^iii	107.53 (6)	H21B—C21—H21C	109.5
C2—C1—Si1	118.82 (14)	C3—C31—H31A	109.5
C2—C1—H1A	107.6	C3—C31—H31B	109.5
Si1—C1—H1A	107.6	H31A—C31—H31B	109.5
C2—C1—H1B	107.6	C3—C31—H31C	109.5
Si1—C1—H1B	107.6	H31A—C31—H31C	109.5
H1A—C1—H1B	107.0	H31B—C31—H31C	109.5
C3—C2—C1	122.99 (19)	C5—C51—H51A	109.5
C3—C2—C21	123.0 (2)	C5—C51—H51B	109.5
C1—C2—C21	113.95 (18)	H51A—C51—H51B	109.5
C2—C3—C31	120.3 (2)	C5—C51—H51C	109.5
C2—C3—C4	124.31 (19)	H51A—C51—H51C	109.5
C31—C3—C4	115.20 (19)	H51B—C51—H51C	109.5
C3—C4—C5	118.12 (16)	C5—C52—H52A	109.5
C3—C4—H4A	107.8	C5—C52—H52B	109.5
C5—C4—H4A	107.8	H52A—C52—H52B	109.5
C3—C4—H4B	107.8	C5—C52—H52C	109.5
C5—C4—H4B	107.8	H52A—C52—H52C	109.5
H4A—C4—H4B	107.1	H52B—C52—H52C	109.5
C52—C5—C53	108.7 (2)	C5—C53—H53A	109.5
C52—C5—C51	109.1 (2)	C5—C53—H53B	109.5
C53—C5—C51	109.6 (2)	H53A—C53—H53B	109.5
C52—C5—C4	111.62 (19)	C5—C53—H53C	109.5
C53—C5—C4	110.24 (19)	H53A—C53—H53C	109.5
C51—C5—C4	107.60 (18)	H53B—C53—H53C	109.5
C1^i—Si1—C1—C2	−75.32 (15)	C1—C2—C3—C4	−176.17 (18)
C1^ii—Si1—C1—C2	165.92 (18)	C21—C2—C3—C4	2.6 (3)
C1^iii—Si1—C1—C2	43.44 (12)	C2—C3—C4—C5	−96.9 (3)
Si1—C1—C2—C3	−101.5 (2)	C31—C3—C4—C5	88.3 (2)
Si1—C1—C2—C21	79.6 (2)	C3—C4—C5—C52	−48.5 (3)
C1—C2—C3—C31	−1.6 (3)	C3—C4—C5—C53	72.4 (2)
C21—C2—C3—C31	177.2 (2)	C3—C4—C5—C51	−168.2 (2)

Symmetry codes: (i) −x+1, −y+3/2, z; (ii) −y+5/4, x+1/4, −z+1/4; (iii) y−1/4, −x+5/4, −z+1/4.