2,6 Lutidine

organic papers

o1242

Structure Reports Online

ISSN 1600-5368

2,6-Lutidine

Andrew D. Bond,* John E. Davies and Anthony J. Kirby

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, England

Correspondence e-mail: adb29@cam.ac.uk

Key indicators Single-crystal X-ray study

T= 120 K

Mean(C±C) = 0.004 AÊ

Rfactor = 0.057

wRfactor = 0.140 Data-to-parameter ratio = 8.4

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

#2001 International Union of Crystallography Printed in Great Britain ± all rights reserved

The crystal structure of 2,6-lutidine (2,6-dimethylpyridine, C7H9N), has been determined at 120 (2) K followingin situ

crystal growth from the liquid. In the non-centrosymmetric space group Fdd2, the asymmetric unit comprises half a molecule, each molecule being sited on a crystallographic diad axis. Molecules are linked via linear CÐH N interactions into one-dimensional chains that align in a parallel manner, giving rise to macroscopically polar crystals.

Comment

2,6-Lutidine (2,6-dimethylpyridine, C7H9N), (I), is present in

many complexes, coordinated to a metal centre (see, for example, Engelhardtet al., 1985). The free base (unprotonated and not coordinated to any metal centre) has also been observed in the crystal structures of three solvates, usually hydrogen bonded to the principal component of the structure (Bowmakeret al., 1997; Lintiet al., 1996; Cairaet al., 1999). The crystal structure of (I) itself, however, has not been reported to date, probably as a result of the dif®culties asso-ciated with obtaining suitable single crystals of (I), which is liquid at room temperature. We report here the crystal structure of (I), determined at 120 (2) K, following in situ

crystal growth from the liquid. This work forms part of a continuing study devoted to improving the techniques for determining the crystal structures of substances that are liquids at room temperature (see, for example, Bond & Davies, 2001a,b).

In the non-centrosymmetric space groupFdd2, the asym-metric unit comprises half a molecule of (I), with a crystal-lographic diad axis passing through atoms N1 and C4 (Fig. 1). Molecules of (I) are linked into one-dimensional chains propagating along the diad axis (parallel to [001]) by linear CÐH N interactions (Fig. 2; H4 N1i _{= 2.63 AÊ and C4Ð}

H4 N1 = 180_{; symmetry code: (i) x, y, 1 +z). Adjacent}

chains are parallel such that the structure is macroscopically polar; this observation may be of interest to researchers seeking organic molecular materials for non-linear optic (NLO) applications, particularly frequency doubling through second harmonic generation (SHG) (Bosshard et al., 1995).

The presence of the methyl substituents in the 2- and 6-pos-itions prevents adoption of an edge-to-face geometry between molecules (that might otherwise be expected), and the planes through the pyridyl rings of molecules in adjacent chains remain essentially parallel (Fig. 3).

Experimental

A sample (99%) of the title compound was obtained from the Aldrich Company and was used without further puri®cation. The crystal was grown in a 0.3 mm glass capillary tube atca260 K (a temperature only slightly less than the melting point of the solid in the capillary tube) using a technique described previously (Davies & Bond, 2001). Once grown, the crystal was cooled to 120 (2) K for data collection. The length of the cylindrical crystal was not estimated but it exceeded the diameter of the collimator (0.35 mm).

Crystal data

C7H9N Mr= 107.15

Orthorhombic,Fdd2 a= 13.782 (3) AÊ b= 14.805 (3) AÊ c= 6.317 (1) AÊ V= 1288.9 (4) AÊ3 Z= 8

Dx= 1.104 Mg mÿ3

MoKradiation Cell parameters from 1553

re¯ections

= 1.0±27.5

= 0.07 mmÿ1 T= 120 (2) K Cylinder, colourless 0.15 mm (radius)

Data collection

Nonius KappaCCD diffractometer Thin-slice!and'scans 1429 measured re¯ections 387 independent re¯ections 351 re¯ections withI> 2(I)

Rint= 0.034 max= 27.4 h=ÿ17!13 k=ÿ19!15 l=ÿ7!8

Acta Cryst.(2001). E57, o1242±o1244 Bond, Davies and Kirby C₇H₉N

o1243

organic papers

Figure 1

The molecular structure and atom-labelling scheme for (I) showing displacement ellipsoids at the 50% probability for non-H atoms. Atoms related by the diad axis are denoted by the suf®xA(XP; Sheldrick, 1993).

Figure 2

Chains of (I) running parallel to thecdirection, projected onto (100). CÐH N interactions are indicated by dotted lines (CAMERON; Watkinet al., 1996).

Figure 3

organic papers

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Re®nement

Re®nement onF2 R[F2_{> 2(F}2_{)] = 0.057} wR(F2_{) = 0.140} S= 1.11 387 re¯ections 46 parameters

H-atom parameters constrained

w= 1/[2_(F

o2) + (0.0788P)2

+ 0.8716P]

whereP= (Fo2+ 2Fc2)/3

(/)max= 0.007

max= 0.22 e AÊÿ3

min=ÿ0.18 e AÊÿ3

All H atoms were placed geometrically and allowed to re®ne with independent isotropic displacement parameters (one common displacement parameter for the methyl H atoms). The absolute structure could not be determined and Friedel pairs (288) were averaged prior to merging of data inFdd2; the reported value ofRint

corresponds to subsequent merging of equivalent re¯ections in this space group.

Data collection:COLLECT(Nonius, 1998); cell re®nement:HKL SCALEPACK(Otwinowski & Minor, 1997); data reduction:HKL DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure:SIR92 (Altomare et al., 1994); program(s) used to re®ne structure:SHELXL97 (Sheldrick, 1997); software used to prepare material for publication:SHELXL97.

We thank the EPSRC for ®nancial assistance towards the purchase of the Nonius CCD diffractometer.

References

Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994).J. Appl. Cryst.27, 435.

Bond, A. D. & Davies, J. E. (2001a).Acta Cryst.E57, o1087±o1088. Bond, A. D. & Davies, J. E. (2001b).Acta Cryst.E57, o1089±o1090. Bosshard, C., Sutter, K., Pretre, P., Hulliger, J., Florsheimer, M., Kaatz, P. &

Gunter, P. (1995).Organic Nonlinear Optical Materials. Basel: Gordon and Breach.

Bowmaker, G. A., Effendy, Kildea, J. D. & White, A. H. (1997).Aust. J. Chem. 50, 577±586.

Caira, M. R., Nassimbeni, L. R., Toda, F. & Vujovic, D. (1999).J. Chem. Soc. Perkin Trans.2, pp. 2681±2684.

Davies, J. E. & Bond, A. D. (2001).Acta Cryst.E57, o947±o949.

Engelhardt, L. M., Pakawatchai, C., White, A. H. & Healy, P. C. (1985).J. Chem. Soc. Dalton Trans.pp. 117±123.

Linti, G., Frey, R., KoÈstler, W. & Urban, H. (1996).Chem. Ber.129, 561±569. Nonius (1998).COLLECT. Nonius BV, Delft, The Netherlands.

Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter & R. M. Sweet, pp. 307±326. London: Academic Press.

Sheldrick, G. M. (1993).XP. University of GoÈttingen, Germany. Sheldrick, G. M. (1997).SHELXL97. University of GoÈttingen, Germany. Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996).CAMERON. Chemical

supporting information

sup-1 Acta Cryst. (2001). E57, o1242–o1244

supporting information

Acta Cryst. (2001). E57, o1242–o1244 [https://doi.org/10.1107/S1600536801019869]

2,6-Lutidine

Andrew D. Bond, John E. Davies and Anthony J. Kirby

2,6-Dimethylpyridine

Crystal data C7H9N Mr = 107.15

Orthorhombic, Fdd2 a = 13.782 (3) Å b = 14.805 (3) Å c = 6.317 (1) Å V = 1288.9 (4) Å3 Z = 8

F(000) = 464

Dx = 1.104 Mg m−3 Melting point: 267 K

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 1553 reflections θ = 1.0–27.5°

µ = 0.07 mm−1 T = 120 K

Cylinder, colourless 0.15 mm (radius)

Data collection Nonius KappaCCD

diffractometer

Radiation source: fine-focus sealed tube Thin–slice ω and φ scans

1429 measured reflections 387 independent reflections

351 reflections with I > 2σ(I) Rint = 0.034

θmax = 27.4°, θmin = 3.8° h = −17→13

k = −19→15 l = −7→8

Refinement Refinement on F2 Least-squares matrix: full R[F2 _{> 2σ(F}2_{)] = 0.057} wR(F2_{) = 0.140} S = 1.11 387 reflections 46 parameters 1 restraint

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

Hydrogen site location: inferred from neighbouring sites

H-atom parameters constrained w = 1/[σ2_(F

o2) + (0.0788P)2 + 0.8716P] where P = (Fo2 + 2Fc2)/3

(Δ/σ)max = 0.007 Δρmax = 0.22 e Å−3 Δρmin = −0.18 e Å−3

Special details

Experimental. Crystal grown in situ in a 0.3 mm Lindemann tube at 260 K. Absolute structure could not be determined and Friedel pairs (288) were averaged for the refinement.

supporting information

sup-2 Acta Cryst. (2001). E57, o1242–o1244

Refinement. Refinement of F2 _{against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F}2_, conventional R-factors R are based on F, with F set to zero for negative F2_{. The threshold expression of F}2 _{> σ(F}2_{) 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₎

x y z Uiso*/Ueq

N1 0.0000 0.5000 0.0817 (4) 0.0299 (8)

C2 0.0155 (2) 0.57658 (18) 0.1892 (3) 0.0325 (8)

C3 0.0153 (2) 0.5788 (2) 0.4104 (4) 0.0359 (8)

H3 0.030 (3) 0.637 (2) 0.483 (6) 0.050 (11)*

C4 0.0000 0.5000 0.5226 (7) 0.0385 (11)

H4 0.0000 0.5000 0.665 (8) 0.026 (11)*

C7 0.0315 (2) 0.66065 (19) 0.0612 (6) 0.0459 (8)

H7A 0.0658 0.6453 −0.0698 0.078 (7)*

H7B 0.0704 0.7036 0.1432 0.078 (7)*

H7C −0.0313 0.6880 0.0265 0.078 (7)*

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

N1 0.0301 (14) 0.0398 (18) 0.0198 (19) −0.0056 (13) 0.000 0.000

C2 0.0310 (17) 0.038 (2) 0.0286 (19) −0.0029 (11) −0.0009 (11) 0.0026 (11)

C3 0.0373 (19) 0.042 (2) 0.0280 (15) 0.0042 (11) −0.0016 (12) −0.0053 (12)

C4 0.039 (2) 0.053 (3) 0.024 (2) 0.0097 (17) 0.000 0.000

C7 0.0536 (16) 0.0422 (16) 0.0420 (18) −0.0118 (12) −0.0056 (17) 0.0076 (16)

Geometric parameters (Å, º)

N1—C2 1.339 (3) C4—C3i _{1.381 (4)}

N1—C2i _{1.339 (3) C4—H4 0.90 (5)}

C2—C3 1.397 (3) C7—H7A 0.9800

C2—C7 1.500 (4) C7—H7B 0.9800

C3—C4 1.381 (4) C7—H7C 0.9800

C3—H3 1.00 (4)

C2—N1—C2i _{119.0 (3) C3}i_{—C4—H4 120.9 (2)}

N1—C2—C3 121.8 (3) C3—C4—H4 120.9 (2)

N1—C2—C7 116.90 (19) C2—C7—H7A 109.5

C3—C2—C7 121.3 (3) C2—C7—H7B 109.5

C4—C3—C2 119.6 (3) H7A—C7—H7B 109.5

C4—C3—H3 122 (2) C2—C7—H7C 109.5

C2—C3—H3 118 (2) H7A—C7—H7C 109.5

C3i_{—C4—C3 118.2 (4) H7B—C7—H7C 109.5}

supporting information

sup-3 Acta Cryst. (2001). E57, o1242–o1244

C2i_{—N1—C2—C7 −179.4 (3) C2—C3—C4—C3}i _{−0.4 (2)}

N1—C2—C3—C4 0.9 (5)