N,N′ Di­methyl N,N′ di­phenyl­ethyl­enedi­amine

organic papers

o2904

16H20N2 doi:10.1107/S1600536805025298 Acta Cryst.(2005). E61, o2904–o2906

Acta Crystallographica Section E

Structure Reports Online

ISSN 1600-5368

N

,

N

_-Dimethyl-

_N

_,

_N

_{-diphenylethylenediamine}

Anders Lennartson,* Theonitsa Kokoli and Mikael Ha˚kansson

Department of Chemistry, Go¨teborg University, SE-412 96 Go¨teborg, Sweden

Correspondence e-mail: anle@chem.gu.se

Key indicators

Single-crystal X-ray study

T= 291 K

Mean(C–C) = 0.003 A˚

Rfactor = 0.055

wRfactor = 0.155

Data-to-parameter ratio = 10.7

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

#2005 International Union of Crystallography Printed in Great Britain – all rights reserved

The centrosymmetric title compound, C16H20N2, was

synthe-sized by deprotonation ofN,N0_{-diphenylethylenediamine with}

n-BuLi in tetrahydrofuran. The coordination geometry

around the N atoms is trigonal planar and the conformation about the ethane bond is staggered. The crystal structure displays intermolecular C—H interactions which give rise

to infinite pleated layers extended in the bc plane. The

possibility of obtaining an amine that can undergo crystal-lization-induced asymmetric transformation is discussed. This would enable the preparation of the pure enantiomers by absolute asymmetric synthesis.

Comment

We recently reported the crystal structure of N,N0

-diphenyl-ethylenediamine (DPHEDA), which was found to crystallize in space group P21/c (Lennartson, Kokoli & Ha˚kansson,

2005). Furthermore, the compound was found to form a C—

H - and N—H -bonded network in the solid state. In

order to find an amine crystallizing in a Sohncke space group, we prepared theN,N0-dimethylated derivativeN,N0

-dimethyl-N,N0-diphenylethylenediamine, (I). This derivative was

prepared by deprotonation of DPHEDA with n-BuLi in

tetrahydrofuran (THF) solution at 195 K, followed by treat-ment with methyl iodide, yielding (I) as monoclinic crystals.

N atoms in amines having three different substituents are chirogenic, a fact that early gained considerable interest (van Ryn, 1897, and references therein), and the amine (I) displays two chirogenic N atoms in solution. Separation into pure enantiomers by common methods, such as enantioselective chromatography, is nevertheless virtually impossible due to the low inversion barrier of trivalent N atoms, resulting in a very high rate of enantiomerization in solution (Lambert, 1971). In principle, however, there will be one pair of enan-tiomers, and onemesoform. If (I) were chiral in the solid state and crystallized in one of the Sohncke space groups (Flack, 2003), it would theoretically be possible to separate the pure enantiomers by means of crystallization-induced asymmetric

transformation (Eliel et al., 1994). Although this possibility was realised early (Behrend, 1890), such a resolution of an amine has, to the best of our knowledge, never been achieved, and would also be an example of absolute asymmetric synthesis (Brediget al., 1923; Feringaet al., 1999; Lennartson, Vestergren & Ha˚kansson, 2005; Vestergren et al., 2003). Resolution of amines which have no other element of chirality than a chirogenic N atom is only known for some bulky tertiary ammonium salts, where the steric crowding around the N centre increases the inversion barrier dramatically (Popeet

al., 1899). Quaternary ammonium salts have also been

subjected to total spontaneous resolution (Havinga, 1954;

Kostyanovsky et al., 2001). However, as in the case of

DPHEDA, the coordination geometry around the N atoms in (I) was found to be approximately trigonal planar rather than pyramidal, atom N1 lying only 0.051 (2) A˚ out of the least-squares plane formed by atoms C1, C7 and C8, and thus the molecule is virtually achiral in the solid state, and the conformation about the ethane bond is perfectly staggered (Fig. 1). There is a crystallographic centre of symmetry at the

mid-point of the ethane bond, C8—C8isymmetry code as in

Table 1). In contrast to DPHEDA, which forms a three-dimensional network, (I) displays infinite pleated layers extended in thebcplane (Fig. 2). The layers are formed by C— H interactions, which are known to often play a vital role in the formation of crystal structures (Nishio, 2004; Cantrillet al., 2000; Braga et al., 1998; Viswamitra et al., 1993). These

interactions involve the phenyl ring and H7Aii [symmetry

code: (ii) x, 1 2+ y,

3

2z], which is directed approximately

towards the centre of the ring system, the shortest distance

being C4 H7Aii, which is 2.85 (2) A˚ . This means that each molecule interacts with four adjacent molecules in a layer (Fig. 3). There are no interactions within the sum of the van der Waals radii between adjacent layers.

Even though (I) was found to be achiral in the solid state, this does not necessarily mean that resolution is impossible. We are currently working on the preparation of complexes, using (I) as a chelating ligand, which may lead to a successful absolute asymmetric synthesis.

Experimental

The reaction was carried out under a nitrogen atmosphere using dry glassware. Commercial N,N0_{-diphenylethylenediamine (Merck),}

methyl iodide (Merck) andn-BuLi in hexane (Acros Organics) were used as received. THF was distilled from sodium/benzophenone shortly prior to use.1_{H NMR and}13_{C NMR spectra were recorded in} CDCl3 on a Varian Unity 400 MHz NMR spectrometer. N,N0 -Diphenylethylenediamine (2.0 g, 9.4 mmol) was dissolved in THF (30 ml) and cooled to 195 K. n-BuLi (1.6 M in hexane, 6.0 ml, 9.6 mmol) was added dropwise at 195 K, followed by dropwise addition of methyl iodide (0.58 ml, 9.3 mmol). The solution was stirred at 195 K for 30 min, and at ambient temperature for 1 h. This procedure was repeated by cooling to 195 K, adding a second equivalent of n-BuLi and subsequently a second equivalent of methyl iodide. After stirring (30 min at 195 K and 1 h at ambient tempera-ture), the reaction was quenched with saturated aqueous NH4Cl (3 ml). The reaction mixture was extracted with diethyl ether (3

10 ml), and the combined ethereal solutions were dried over Na2SO4 and evaporated to give an oil. Ethanol (10 ml) was added and the solution was cooled to 253 K overnight, whereupon needles were formed. The mother liquor was filtered off and the crystals washed with cold ethanol to give brown–white needles, which were

recrys-organic papers

Acta Cryst.(2005). E61, o2904–o2906 Lennartsonet al. _C

16H20N2

o2905

Figure 1

ORTEP3plot (Farrugia, 1997) of (I), with the atom-numbering scheme. Displacement ellipsoids have been drawn at the 50% probability level. All H atoms have been omitted. [Symmetry code: (i)x,y,z.]

Figure 2

The pleated form of the layers, viewed in the direction of propagation of the pleats.

Figure 3

tallized from hot hexane (yield: 1.2 g, 55%). 1H NMR (400 MHz, CDCl3):2.96 (s, 6H, CH3), 3.56 (s, 4H, CH2), 6.74 (m, 3H, Ph), 7.27 (m, 2H, Ph).13C NMR (100 MHz, CDCl3):30.4 (CH3), 39.0 (CH2), 112 (Ph), 116.6 (Ph), 129.6 (Ph). Single crystals suitable for X-ray analysis were obtained by dissolving the amine (0.2 g) inn-hexane (3 ml). Toluene (5 drops) was added and the solution was heated to reflux for a few s. Slow evaporation of the solvent over several days afforded crystals suitable for single-crystal X-ray diffraction analysis.

Crystal data

C16H20N2 Mr= 240.34

Monoclinic,P21=c a= 6.374 (2) A˚

b= 10.302 (4) A˚

c= 10.447 (4) A˚

= 91.428 (14) V= 685.8 (4) A˚3 Z= 2

Dm= ? Mg m

3

MoKradiation Cell parameters from 4655

reflections

= 2.8–26

= 0.07 mm1 T= 291 (2) K Block, light yellow 0.40.40.4 mm

Data collection

Rigaku R-AXIS IIC image-plate system diffractometer

’scans

Absorption correction: none 4655 measured reflections 1307 independent reflections

987 reflections withI> 2(I)

Rint= 0.073

max= 26.0

h=7!7

k=12!12

l=12!12

Refinement

Refinement onF2 R[F2> 2(F2)] = 0.055

wR(F2_{) = 0.155} S= 1.05 1307 reflections 122 parameters

All H-atom parameters refined

w= 1/[2

(Fo2) + (0.088P)2]

whereP= (Fo2+ 2Fc2)/3

(/)max< 0.001 max= 0.13 e A˚

3

min=0.12 e A˚ 3

Table 1

Selected geometric parameters (A˚ ,_).

C1—N1 1.3746 (19)

C1—C2 1.391 (2)

C1—C6 1.397 (2)

C2—C3 1.374 (2)

C3—C4 1.369 (3)

C4—C5 1.359 (3)

C5—C6 1.373 (3)

C7—N1 1.438 (2)

C8—N1 1.441 (2)

C8—C8i

1.514 (3)

C1—N1—C7 120.25 (14)

C1—N1—C8 121.89 (14)

C7—N1—C8 117.47 (15)

Symmetry code: (i)x;yþ2;zþ2.

Coordinates andUisovalues were refined for all H atoms without constraints in order to avoid a biased hydrogen-bonding scheme.

Data collection: CRYSTALCLEAR (Rigaku, 2000); cell refine-ment: CRYSTALCLEAR; data reduction: CRYSTALCLEAR; program(s) used to solve structure:SIR92 (Altomare et al., 1993); program(s) used to refine structure:SHELXL97(Sheldrick, 1997); molecular graphics:ORTEP3(Farrugia, 1997) andPLUTON(Spek, 2003); software used to prepare material for publication: SHELXL97.

Financial support from the Swedish Research Council (VR) is gratefully acknowledged.

References

Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993).J. Appl. Cryst.26, 343–350.

Behrend, R. (1890). Berichte, 23, 454-458.

Braga, D., Grepioni, F. & Tedesco, E. (1998).Organometallics,17, 2669–2672. Bredig, G., Mangold, P. & Williams, T. G. (1923).Z. Angew. Chem.36, 456–

458.

Cantrill, S. J., Preece, J. A., Stoddart, J. F., Wang, Z. H., White, A. J. P. & Williams, D. J. (2000).Tetrahedron,56, 6675–6681.

Eliel, E. L. & Wilen, S. H. (1994).Stereochemistry of Organic Compounds, p. 316. New York: Wiley Interscience.

Farrugia, L. J. (1997).J. Appl. Cryst.30, 565.

Feringa, B. L. & van Delden, R. A. (1999).Angew. Chem. Int. Ed.38, 3419– 3438.

Flack, H. D. (2003).Helv. Chim. Acta,86, 905–921. Havinga, E. (1954).Biochim. Biophys. Acta,13, 171–174.

Kostyanovsky, R. G., Kostyanovsky, V. R., Kadorkina, G. K. & Lyssenko, K. A. (2001).Mendeleev Commun.pp. 1–5.

Lambert, J. B. (1971).Top. Stereochem.6, 19–105.

Lennartson, A., Kokoli, T. & Ha˚kansson, M. (2005).Acta Cryst.E61, o1245– o1247.

Lennartson, A., Vestergren, M. & Ha˚kansson, M. (2005).Chem. Eur. J.11, 1757–1762.

Nishio, M. (2004).CrystEngComm,6, 130–158.

Pope, W. J. & Peachey, S. J. (1899).Trans. Chem. Soc.75, 1127–1131. Rigaku. (2000).CRYSTALCLEAR. Version 1.3. Rigaku Corporation, Tokyo,

Japan.

Ryn, W. van (1897).Die Stereochemie des Stickstoffs.Zu¨rich: E. Seidel. Sheldrick, G. M. (1997).SHELXL97. University of Go¨ttingen, Germany. Spek, A. L. (2003).J. Appl. Cryst.36, 7–13.

Vestergren, M., Eriksson, J. & Ha˚kansson, M. (2003).Chem. Eur. J.9, 4678– 4686.

Viswamitra, M. A., Radhakrishnan, R., Bandekar, J. & Desiraju, G. R. (1993).

J. Am. Chem. Soc.115, 4868–4869.

organic papers

o2906

supporting information

sup-1 Acta Cryst. (2005). E61, o2904–o2906

supporting information

Acta Cryst. (2005). E61, o2904–o2906 [https://doi.org/10.1107/S1600536805025298]

N

,

N

′

-Dimethyl-

N

,

N

′

-diphenylethylenediamine

Anders Lennartson, Theonitsa Kokoli and Mikael H

å

kansson

N,N′-dimetyl-N,N′-diphenylethylenediamine

Crystal data

C16H20N2

Mr = 240.34 Monoclinic, P21/c Hall symbol: -P 2ybc

a = 6.374 (2) Å

b = 10.302 (4) Å

c = 10.447 (4) Å

β = 91.428 (14)°

V = 685.8 (4) Å3

Z = 2

F(000) = 260

Dx = 1.164 Mg m−3

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 4655 reflections

θ = 2.8–26°

µ = 0.07 mm−1

T = 291 K

Needle, light yellow 0.4 × 0.4 × 0.4 mm

Data collection

Rigaku R-AXIS IIC image-plate system diffractometer

Radiation source: rotating-anode X-ray tube, Rigaku R3h

Graphite monochromator

Detector resolution: 105 pixels mm-1

φ scans

4655 measured reflections

1307 independent reflections 987 reflections with I > 2σ(I)

Rint = 0.073

θmax = 26.0°, θmin = 2.8°

h = −7→7

k = −12→12

l = −12→12

Refinement

Refinement on F2 Least-squares matrix: full

R[F2 _{> 2σ(F}2_{)] = 0.055}

wR(F2_{) = 0.155}

S = 1.05 1307 reflections 122 parameters 0 restraints

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

Hydrogen site location: inferred from neighbouring sites

All H-atom parameters refined

w = 1/[σ2_(F

o2) + (0.088P)2] where P = (Fo2 + 2Fc2)/3 (Δ/σ)max < 0.001

Δρmax = 0.13 e Å−3 Δρmin = −0.12 e Å−3

Special details

supporting information

sup-2 Acta Cryst. (2005). E61, o2904–o2906

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

C1 0.2290 (2) 1.03606 (13) 0.77772 (13) 0.0508 (4) C2 0.3740 (2) 1.10868 (15) 0.84902 (15) 0.0567 (5) C3 0.5211 (3) 1.18350 (18) 0.78957 (17) 0.0649 (5) C4 0.5295 (3) 1.18973 (18) 0.65889 (18) 0.0704 (5) C5 0.3877 (3) 1.12002 (18) 0.58800 (17) 0.0722 (6) C6 0.2389 (3) 1.04417 (16) 0.64449 (16) 0.0638 (5) C7 −0.0789 (4) 0.8964 (3) 0.7567 (2) 0.0815 (6) C8 0.0676 (3) 0.94785 (17) 0.97092 (16) 0.0612 (5) N1 0.0820 (2) 0.95833 (15) 0.83383 (12) 0.0661 (5) H2 0.371 (3) 1.1093 (16) 0.9417 (19) 0.065 (4)* H3 0.623 (3) 1.233 (2) 0.8452 (19) 0.083 (6)* H4 0.636 (4) 1.245 (2) 0.622 (2) 0.098 (6)* H5 0.391 (3) 1.116 (2) 0.491 (2) 0.098 (6)* H6 0.142 (3) 1.000 (2) 0.5924 (18) 0.075 (5)* H7A −0.173 (3) 0.854 (3) 0.811 (2) 0.110 (8)* H7B −0.019 (4) 0.836 (3) 0.695 (3) 0.117 (8)* H7C −0.174 (5) 0.963 (4) 0.707 (3) 0.157 (12)* H8A 0.005 (3) 0.8588 (19) 0.9907 (18) 0.073 (5)* H8B 0.208 (3) 0.9510 (15) 1.0140 (17) 0.063 (4)*

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

C1 0.0532 (8) 0.0497 (8) 0.0499 (8) 0.0042 (6) 0.0061 (7) −0.0010 (6) C2 0.0555 (9) 0.0638 (9) 0.0508 (8) −0.0011 (7) 0.0026 (7) −0.0005 (7) C3 0.0563 (9) 0.0636 (10) 0.0750 (11) −0.0024 (7) 0.0020 (8) 0.0033 (8) C4 0.0744 (11) 0.0626 (10) 0.0750 (11) −0.0013 (8) 0.0203 (9) 0.0111 (8) C5 0.0975 (13) 0.0665 (11) 0.0536 (9) 0.0010 (9) 0.0187 (9) 0.0037 (7) C6 0.0823 (11) 0.0588 (9) 0.0505 (9) −0.0037 (8) 0.0021 (8) −0.0047 (7) C7 0.0784 (13) 0.0886 (14) 0.0776 (13) −0.0273 (11) 0.0023 (11) −0.0090 (11) C8 0.0613 (10) 0.0626 (10) 0.0599 (10) 0.0018 (7) 0.0088 (8) 0.0123 (7) N1 0.0644 (9) 0.0787 (10) 0.0552 (8) −0.0172 (7) 0.0053 (7) −0.0023 (6)

Geometric parameters (Å, º)

supporting information

sup-3 Acta Cryst. (2005). E61, o2904–o2906

C3—C4 1.369 (3) C7—H7C 1.05 (4) C3—H3 1.00 (2) C8—N1 1.441 (2) C4—C5 1.359 (3) C8—C8i _{1.514 (3)} C4—H4 0.98 (2) C8—H8A 1.023 (19) C5—C6 1.373 (3) C8—H8B 0.99 (2)

N1—C1—C2 122.41 (13) C1—C6—H6 120.4 (11) N1—C1—C6 120.52 (15) N1—C7—H7A 109.2 (15) C2—C1—C6 117.08 (15) N1—C7—H7B 111.7 (15) C3—C2—C1 120.77 (15) H7A—C7—H7B 111 (2) C3—C2—H2 118.7 (10) N1—C7—H7C 112.4 (19) C1—C2—H2 120.5 (10) H7A—C7—H7C 103 (2) C4—C3—C2 121.40 (18) H7B—C7—H7C 109 (2) C4—C3—H3 121.0 (11) N1—C8—C8i _{113.36 (18)} C2—C3—H3 117.6 (11) N1—C8—H8A 107.6 (10) C5—C4—C3 118.47 (17) C8i_{—C8—H8A 109.2 (10)} C5—C4—H4 123.6 (14) N1—C8—H8B 111.6 (10) C3—C4—H4 117.9 (14) C8i_{—C8—H8B 108.1 (10)} C4—C5—C6 121.56 (16) H8A—C8—H8B 106.7 (14) C4—C5—H5 122.3 (12) C1—N1—C7 120.25 (14) C6—C5—H5 116.1 (12) C1—N1—C8 121.89 (14) C5—C6—C1 120.72 (17) C7—N1—C8 117.47 (15) C5—C6—H6 118.9 (11)