4-Nitro-1-[(trimethyl­sil­yl)ethyn­yl]benzene: low-temperature polymorph at 100 K

The title compound, C₁₁H₁₃NO₂Si, is a low-temperature form of the previously reported room-temperature structure [Garcia et al. (1998). Acta Cryst. C54, 489-491]. At 298 K, the material crystallizes in the space group Pnma and occupies a crystallographic mirror plane, but at 100 K the space group changes to P2₁2₁2₁, the volume decreases by 5% and the mol­ecule distorts. The greatest mol­ecular distortions from C_s symmetry are rotations of the trimethyl­silyl and nitro groups by 10.56 (8) and 11.47 (9)°, respectively, to the benzene mean plane. At low temperature, the crystal also becomes an inversion twin, the refined ratio of the twin components being 0.35 (15):0.65 (15).

Key indicators

• Single-crystal X-ray study
• T = 100 K, P = 0.0 kPa
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.051
• wR factor = 0.123
• Data-to-parameter ratio = 33.7

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT230_ALERT_2_B Hirshfeld Test Diff for    Si1    --  C1      ..        7.4 su

Alert level C
STRVA01_ALERT_4_C           Flack test results are ambiguous.
           From the CIF: _refine_ls_abs_structure_Flack    0.350
           From the CIF: _refine_ls_abs_structure_Flack_su    0.150
PLAT033_ALERT_4_C Flack x Parameter Value Deviates from Zero .....      0.350
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          2

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           33.75
           From the CIF: _reflns_number_total               4690
           Count of symmetry unique reflns         2738
           Completeness (_total/calc)            171.29%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      1952
           Fraction of Friedel pairs measured     0.713
           Are heavy atom types Z>Si present        yes
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT115_ALERT_5_G ADDSYM Detects Noncrystallographic Inversion ...        100 Perc.
PLAT158_ALERT_4_G The Input Unitcell is NOT Standard/Reduced .....          ?
PLAT371_ALERT_2_G Long   C(sp2)-C(sp1) Bond  C2     -   C3     ...       1.44 Ang.
PLAT917_ALERT_2_G The FCF is likely NOT based on a BASF/TWIN Flack          !

   0 ALERT level A = Most likely a serious problem - resolve or explain
   1 ALERT level B = A potentially serious problem, consider carefully
   3 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   6 ALERT level G = General information/check it is not something unexpected

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

---

S1. Comment

At 298 K title molecule has C_s symmetry (Garcia et al., 1998; CSD refcode NILWIO; Allen, 2002), with all but two methyl groups lying in the mirror plane. When the temperature is reduced to 100 K, the inversion center vanishes and the space group changes from Pnma to P2₁2₁2₁, the unit cell volume is reduced from 1261.8 (3) to 1204.9 (5) ų, and the molecular symmetry is reduced to C₁. The mean plane of the six benzene C atoms, (mean deviation δ_r.m.s. = 0.004 Å), is normal to the b axis at 298 K but inclines +4.51 (8)° from normal at 100 K, while the C1—Si1—C9 plane is rotated off-normal by -6.05 (8)° and the NO₂ group is rotated off-normal by +15.78 (9)°.

Other geometrical parameters in the two polymorphs are similar, for example [those at 298 K are in parentheses] : C1≡C2 = 1.209 (2) [1.199 (4)] Å, Si1—C1 = 1.845 (2) [1.839 (3)] Å, Si1—C9 = 1.856 (2) [1.831 (4)] Å, Si1—C10 = 1.853 (2) [1.838 (3)] Å, Si1—C10B = 1.856 (2)[1.838 (3)] Å, N1—O1 = 1.219 (2) [1.201 (4)] Å, N1—O2 = 1.221 (2) [1.175 (4)] Å, Si1—C1≡C2 = 176.1 (2) [177.9 (3)]°, C1≡C2—C3 = 175.9 (2) [178.0 (3)]°, O1—N1—O2 = 123.5 (2) [122.9 (3)]°.

Related literature

For the synthesis of the title compound, see: Takahashi et al. (1980). For the crystal structure of the room temperature form of the title compound, see: Garcia et al. (1998). For a description of the Cambridge Structural Database, see: Allen (2002). For Hooft analysis of Bijvoet pairs, see: Hooft et al. (2008).

S2. Experimental

The compound was prepared by palladium(II) coupling of trimethylsilylacetylene with 4-nitroiodobenzene as described by (Takahashi et al., 1980).

S3. Refinement

Analysis of 1953 Bijvoet pairs yields a Hooft (Hooft et al., 2008) parameter y = 0.42 (6) and P3(rac-twin) = 1.000. The model was therefore refined as an inversion twin (SHELXL commands TWIN and BASF) giving the refined ratio 0.35 (15):0.65 (15) for the twin components. The C-bound H atoms were placed in calculated positions, guided by difference maps, and treated as riding atoms: C—H = 0.95 and 0.98 Å for CH(aromatic) and CH₃ H atoms, respectively, with U_iso = k × U_eq(C), where k = 1.5 for CH₃ H atoms and = 1.2 for other H atoms. A torsional parameter was refined for each methyl group.

Computing details

Data collection: COLLECT (Nonius, 2000); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR2002 (Burla et al., 2003); 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

Fig. 1. View of the molecular structure of the title compound, with atom numbering. The displacement ellipsoids are drawn at the 50% probability level.

4-Nitro-1-[(trimethylsilyl)ethynyl]benzene

Crystal data

C11H13NO2Si	F(000) = 464
Mr = 219.31	Dx = 1.209 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 2709 reflections
a = 10.222 (2) Å	θ = 2.5–34.3°
b = 7.128 (2) Å	µ = 0.18 mm^−1
c = 16.537 (4) Å	T = 100 K
V = 1204.9 (5) Å^3	Needle fragment, yellow
Z = 4	0.20 × 0.15 × 0.12 mm

Data collection

Nonius KappaCCD diffractometer	4690 independent reflections
Radiation source: sealed tube	3538 reflections with I > 2σ(I)
Horizonally mounted graphite crystal monochromator	Rint = 0.032
Detector resolution: 9 pixels mm^-1	θmax = 33.8°, θmin = 3.1°
ω and ϕ scans	h = −15→15
Absorption correction: multi-scan (SCALEPACK; Otwinowski & Minor, 1997)	k = −11→11
Tmin = 0.966, Tmax = 0.979	l = −25→25
17805 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.051	H-atom parameters constrained
wR(F^2) = 0.123	w = 1/[σ^2(Fo^2) + (0.046P)^2 + 0.4973P] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max < 0.001
4690 reflections	Δρmax = 0.36 e Å^−3
139 parameters	Δρmin = −0.32 e Å^−3
0 restraints	Absolute structure: Flack (1983), 1953 Bijvoet pairs
0 constraints	Absolute structure parameter: 0.35 (15)
Primary atom site location: structure-invariant direct methods

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.67962 (16)	0.2773 (3)	0.66604 (9)	0.0270 (3)
C2	0.77829 (16)	0.2789 (3)	0.70632 (9)	0.0252 (3)
C3	0.89002 (14)	0.2769 (3)	0.75911 (9)	0.0218 (3)
C4	1.01780 (16)	0.2851 (3)	0.72849 (9)	0.0262 (3)
H4	1.0316	0.2956	0.6719	0.031*
C5	1.12430 (15)	0.2779 (3)	0.78050 (10)	0.0265 (3)
H5	1.2111	0.2842	0.7602	0.032*
C6	1.10107 (14)	0.2614 (3)	0.86239 (9)	0.0234 (3)
C7	0.97590 (14)	0.2541 (3)	0.89480 (9)	0.0242 (3)
H7	0.9629	0.2433	0.9515	0.029*
C8	0.87080 (14)	0.2629 (3)	0.84253 (9)	0.0225 (3)
H8	0.7843	0.2594	0.8635	0.027*
C9	0.5612 (2)	0.2384 (5)	0.50094 (10)	0.0415 (5)
H9A	0.6112	0.1226	0.4926	0.062*
H9B	0.6129	0.3459	0.4825	0.062*
H9C	0.4794	0.2322	0.4702	0.062*
C10	0.4263 (2)	0.0658 (3)	0.64911 (14)	0.0376 (5)
H10A	0.4097	0.0836	0.707	0.056*
H10B	0.475	−0.0512	0.6409	0.056*
H10C	0.3429	0.0593	0.6201	0.056*
C10B	0.4280 (2)	0.4829 (3)	0.62787 (15)	0.0394 (5)
H10D	0.477	0.5912	0.6075	0.059*
H10E	0.4124	0.4982	0.686	0.059*
H10F	0.3439	0.4742	0.5996	0.059*
N1	1.21298 (13)	0.2499 (3)	0.91772 (9)	0.0345 (3)
O1	1.32160 (13)	0.2830 (3)	0.89090 (11)	0.0531 (4)
O2	1.19270 (16)	0.2043 (4)	0.98780 (9)	0.0670 (7)
Si1	0.52365 (4)	0.26554 (7)	0.61012 (3)	0.02349 (11)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0248 (7)	0.0341 (10)	0.0221 (7)	0.0007 (8)	−0.0007 (6)	−0.0014 (7)
C2	0.0248 (7)	0.0291 (9)	0.0219 (6)	0.0008 (7)	−0.0009 (5)	−0.0006 (7)
C3	0.0208 (6)	0.0240 (8)	0.0207 (6)	0.0008 (7)	−0.0020 (5)	0.0005 (6)
C4	0.0247 (7)	0.0345 (9)	0.0194 (6)	0.0007 (8)	0.0022 (6)	0.0026 (6)
C5	0.0189 (6)	0.0334 (10)	0.0270 (7)	−0.0001 (7)	0.0027 (5)	0.0008 (8)
C6	0.0183 (6)	0.0274 (9)	0.0245 (6)	0.0001 (8)	−0.0048 (5)	−0.0022 (8)
C7	0.0223 (6)	0.0311 (8)	0.0192 (5)	0.0013 (8)	−0.0001 (5)	−0.0013 (7)
C8	0.0177 (6)	0.0285 (9)	0.0212 (6)	−0.0005 (7)	0.0001 (5)	−0.0016 (7)
C9	0.0392 (9)	0.0626 (15)	0.0228 (7)	−0.0031 (12)	−0.0018 (7)	−0.0023 (10)
C10	0.0296 (10)	0.0364 (12)	0.0467 (12)	0.0002 (8)	0.0011 (9)	0.0090 (9)
C10B	0.0310 (10)	0.0343 (11)	0.0530 (13)	0.0074 (8)	−0.0112 (10)	−0.0091 (9)
N1	0.0235 (6)	0.0442 (10)	0.0357 (7)	0.0034 (8)	−0.0094 (6)	−0.0075 (9)
O1	0.0217 (6)	0.0733 (12)	0.0641 (10)	−0.0078 (7)	−0.0111 (7)	0.0065 (11)
O2	0.0388 (8)	0.136 (2)	0.0264 (7)	0.0166 (12)	−0.0122 (6)	−0.0023 (10)
Si1	0.02129 (18)	0.0293 (2)	0.01984 (18)	0.00030 (19)	−0.00383 (15)	−0.00043 (19)

Geometric parameters (Å, º)

C1—C2	1.209 (2)	C9—Si1	1.8560 (18)
C1—Si1	1.8450 (17)	C9—H9A	0.98
C2—C3	1.438 (2)	C9—H9B	0.98
C3—C8	1.397 (2)	C9—H9C	0.98
C3—C4	1.402 (2)	C10—Si1	1.853 (2)
C4—C5	1.388 (2)	C10—H10A	0.98
C4—H4	0.95	C10—H10B	0.98
C5—C6	1.380 (2)	C10—H10C	0.98
C5—H5	0.95	C10B—Si1	1.856 (2)
C6—C7	1.388 (2)	C10B—H10D	0.98
C6—N1	1.4671 (19)	C10B—H10E	0.98
C7—C8	1.380 (2)	C10B—H10F	0.98
C7—H7	0.95	N1—O1	1.219 (2)
C8—H8	0.95	N1—O2	1.221 (2)
C2—C1—Si1	176.09 (16)	H9A—C9—H9C	109.5
C1—C2—C3	175.90 (18)	H9B—C9—H9C	109.5
C8—C3—C4	119.38 (13)	Si1—C10—H10A	109.5
C8—C3—C2	119.25 (14)	Si1—C10—H10B	109.5
C4—C3—C2	121.36 (14)	H10A—C10—H10B	109.5
C5—C4—C3	120.35 (14)	Si1—C10—H10C	109.5
C5—C4—H4	119.8	H10A—C10—H10C	109.5
C3—C4—H4	119.8	H10B—C10—H10C	109.5
C6—C5—C4	118.44 (14)	Si1—C10B—H10D	109.5
C6—C5—H5	120.8	Si1—C10B—H10E	109.5
C4—C5—H5	120.8	H10D—C10B—H10E	109.5
C5—C6—C7	122.73 (14)	Si1—C10B—H10F	109.5
C5—C6—N1	118.86 (13)	H10D—C10B—H10F	109.5
C7—C6—N1	118.42 (14)	H10E—C10B—H10F	109.5
C8—C7—C6	118.29 (13)	O1—N1—O2	123.47 (16)
C8—C7—H7	120.9	O1—N1—C6	118.21 (16)
C6—C7—H7	120.9	O2—N1—C6	118.31 (15)
C7—C8—C3	120.81 (13)	C1—Si1—C10	108.92 (10)
C7—C8—H8	119.6	C1—Si1—C10B	109.77 (10)
C3—C8—H8	119.6	C10—Si1—C10B	107.68 (10)
Si1—C9—H9A	109.5	C1—Si1—C9	108.27 (8)
Si1—C9—H9B	109.5	C10—Si1—C9	111.68 (12)
H9A—C9—H9B	109.5	C10B—Si1—C9	110.51 (12)
Si1—C9—H9C	109.5
C8—C3—C4—C5	0.5 (3)	C6—C7—C8—C3	0.6 (3)
C2—C3—C4—C5	−178.28 (19)	C4—C3—C8—C7	−1.0 (3)
C3—C4—C5—C6	0.4 (3)	C2—C3—C8—C7	177.76 (18)
C4—C5—C6—C7	−0.9 (3)	C5—C6—N1—O1	10.6 (3)
C4—C5—C6—N1	178.80 (18)	C7—C6—N1—O1	−169.7 (2)
C5—C6—C7—C8	0.3 (3)	C5—C6—N1—O2	−168.0 (2)
N1—C6—C7—C8	−179.33 (18)	C7—C6—N1—O2	11.7 (3)