p-Bis­(tri­methyl­silyl)­benzene: rerefinement against new intensity data

The redetermination of the structure of the title compound, C₁₂H₂₂Si₂, agrees with the results previously reported by Menczel & Kiss [Acta Cryst. (1975). B31, 1787-1789], but with improved precision. The mol­ecules are located on centres of inversion. As a result, there is just a half mol­ecule in the asymmetric unit.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.038
• wR factor = 0.092
• Data-to-parameter ratio = 30.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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Computing details

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 1991).

p-Bis(trimethylsilyl)benzene

Crystal data

C12H22Si2	F(000) = 244
Mr = 222.48	Dx = 1.036 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 6.5410 (7) Å	Cell parameters from 11837 reflections
b = 10.5452 (10) Å	θ = 3.6–29.6°
c = 10.3952 (12) Å	µ = 0.22 mm^−1
β = 96.029 (9)°	T = 173 K
V = 713.05 (13) Å^3	Block, colourless
Z = 2	0.39 × 0.19 × 0.17 mm

Data collection

Stoe IPDS II two-circle diffractometer	1955 independent reflections
Radiation source: fine-focus sealed tube	1739 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.044
ω scans	θmax = 29.4°, θmin = 3.7°
Absorption correction: empirical (using intensity measurements) (MULABS; Spek, 1990; Blessing, 1995)	h = −9→8
Tmin = 0.920, Tmax = 0.964	k = −14→14
9295 measured reflections	l = −14→14

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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.092	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0421P)^2 + 0.2264P] where P = (Fo^2 + 2Fc^2)/3
1955 reflections	(Δ/σ)max < 0.001
64 parameters	Δρmax = 0.34 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

Experimental. ;

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	0.61753 (5)	0.71754 (3)	0.72548 (3)	0.02454 (11)
C1	0.55416 (18)	0.59355 (11)	0.59730 (11)	0.0218 (2)
C2	0.69981 (19)	0.54436 (12)	0.52133 (12)	0.0243 (2)
H2	0.8377	0.5737	0.5346	0.029*
C3	0.64670 (19)	0.45318 (12)	0.42652 (12)	0.0249 (2)
H3	0.7496	0.4219	0.3767	0.030*
C4	0.4851 (3)	0.86872 (16)	0.67299 (19)	0.0470 (4)
H4A	0.5349	0.8981	0.5924	0.071*
H4B	0.5145	0.9332	0.7403	0.071*
H4C	0.3365	0.8542	0.6587	0.071*
C5	0.9003 (2)	0.74497 (16)	0.75101 (15)	0.0361 (3)
H5A	0.9488	0.7745	0.6702	0.054*
H5B	0.9700	0.6656	0.7779	0.054*
H5C	0.9307	0.8093	0.8184	0.054*
C6	0.5229 (3)	0.6619 (2)	0.87860 (15)	0.0453 (4)
H6A	0.3742	0.6479	0.8645	0.068*
H6B	0.5531	0.7261	0.9460	0.068*
H6C	0.5918	0.5823	0.9059	0.068*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si1	0.02515 (18)	0.02445 (18)	0.02354 (17)	−0.00041 (13)	0.00030 (12)	−0.00650 (13)
C1	0.0243 (5)	0.0202 (5)	0.0204 (5)	−0.0003 (4)	0.0002 (4)	−0.0015 (4)
C2	0.0207 (5)	0.0259 (6)	0.0259 (6)	−0.0026 (4)	0.0009 (4)	−0.0039 (4)
C3	0.0234 (6)	0.0268 (6)	0.0250 (6)	−0.0005 (4)	0.0047 (4)	−0.0050 (4)
C4	0.0524 (10)	0.0293 (7)	0.0562 (10)	0.0070 (7)	−0.0092 (8)	−0.0095 (7)
C5	0.0309 (7)	0.0389 (8)	0.0382 (7)	−0.0053 (5)	0.0013 (6)	−0.0151 (6)
C6	0.0476 (9)	0.0618 (11)	0.0273 (7)	−0.0096 (8)	0.0080 (6)	−0.0083 (7)

Geometric parameters (Å, º)

Si1—C6	1.8622 (17)	C4—H4A	0.9800
Si1—C5	1.8633 (15)	C4—H4B	0.9800
Si1—C4	1.8683 (17)	C4—H4C	0.9800
Si1—C1	1.8817 (12)	C5—H5A	0.9800
C1—C2	1.3994 (17)	C5—H5B	0.9800
C1—C3^i	1.4007 (17)	C5—H5C	0.9800
C2—C3	1.3946 (17)	C6—H6A	0.9800
C2—H2	0.9500	C6—H6B	0.9800
C3—C1^i	1.4007 (17)	C6—H6C	0.9800
C3—H3	0.9500
C6—Si1—C5	109.95 (8)	H4A—C4—H4B	109.5
C6—Si1—C4	109.47 (10)	Si1—C4—H4C	109.5
C5—Si1—C4	109.39 (8)	H4A—C4—H4C	109.5
C6—Si1—C1	108.53 (7)	H4B—C4—H4C	109.5
C5—Si1—C1	110.51 (6)	Si1—C5—H5A	109.5
C4—Si1—C1	108.98 (7)	Si1—C5—H5B	109.5
C2—C1—C3^i	116.83 (11)	H5A—C5—H5B	109.5
C2—C1—Si1	123.01 (9)	Si1—C5—H5C	109.5
C3^i—C1—Si1	120.16 (9)	H5A—C5—H5C	109.5
C3—C2—C1	121.37 (11)	H5B—C5—H5C	109.5
C3—C2—H2	119.3	Si1—C6—H6A	109.5
C1—C2—H2	119.3	Si1—C6—H6B	109.5
C2—C3—C1^i	121.80 (11)	H6A—C6—H6B	109.5
C2—C3—H3	119.1	Si1—C6—H6C	109.5
C1^i—C3—H3	119.1	H6A—C6—H6C	109.5
Si1—C4—H4A	109.5	H6B—C6—H6C	109.5
Si1—C4—H4B	109.5
C6—Si1—C1—C2	−128.90 (12)	C4—Si1—C1—C3^i	−67.55 (13)
C5—Si1—C1—C2	−8.26 (13)	C3^i—C1—C2—C3	0.0 (2)
C4—Si1—C1—C2	111.96 (12)	Si1—C1—C2—C3	−179.51 (10)
C6—Si1—C1—C3^i	51.60 (13)	C1—C2—C3—C1^i	0.0 (2)
C5—Si1—C1—C3^i	172.23 (11)

Symmetry code: (i) −x+1, −y+1, −z+1.