Acta Cryst. (2009). C65, o160–o162.pdf

organic compounds

Acta Crystallographica Section C

Crystal Structure

Communications

ISSN 0108-2701

parallel to each other. Connecting pairs of adjacent N—HO

hydrogen-bonded chains separated by a one-half unit-cell

translation in the crystallographic b direction are BrO

interactions [Kubicki, 2004, and references therein;

Br2O1( x + 2 , y + 2 , z + 2) = 3.100 (3) A ˚ ] between mol-

ecules related by a 2 1 screw axis along the a axis, and in the

crystallographic c direction, intermolecular BrBr inter-

actions [Br2Br1( x + 2 , y +1, z 2 ) = 3.5268 (7) A ˚ ]

(Fig. 2), also between molecules related by a 2 1 screw axis,

along the c axis. Two BrO intermolecular interactions and

the N—HO hydrogen bond form a ring between adjacent

hydrogen-bonded chains described by graph-set motif R 3 (12)

(Etter, 1990; Bernstein et al. , 1995).

Atom Br2 is involved in two intermolecular interactions

(Fig. 3). It has been reported that the Br atom is frequently

involved in such contacts as a result of its nonspherical shape

(Lieberman et al. , 2000; Lommerse et al. , 1996; Beyer et al. ,

2001). Atom Br2 of (I) interacts with atom O1 in the molecule

at ( x + 2 , y + 2 , z + 2) head-on and with atom Br1 in the

molecule at ( x + 2 , y +1, z 2 ) side-on (O being a

nucleophile and Br an electrophile). Similar interactions were

N -(2,6-Dibromophenyl)formamide

Bernard Omondi,* Demetrius C. Levendis, Marcus Layh

and Manuel A. Fernandes

Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand,

PO Wits, 2050 Johannesburg, South Africa

Correspondence e-mail: bernardowaga@gmail.com

Received 11 February 2009

Accepted 3 March 2009

Online 18 March 2009

In the crystal structure of the title compound, C 7 H 5 Br 2 NO,

molecules related by translation are linked through N—HO

hydrogen bonds to form chains in the crystallographic a

direction, with the aryl rings stacked parallel to each other

along the chain. Besides the N—HO hydrogen bonds,

BrO and BrBr intermolecular interactions complete the

packing of molecules in the crystal structure.

Comment

The title compound, (I) (Fig. 1), is of interest as part of a study

on polymorphism and phase transformations in 2,6-disub-

stituted N -phenylformamides. Previous reports showed the

effect of different interactions (N—HO hydrogen bonds

and C—HO, ClCl and – intermolecular interactions)

on the phase transitions of 2-chloro-6-methyl- N -phenyl-

formamide (Omondi et al. , 2005). 2,6-Dibromo- N -phenyl-

formamide is only the second among the 2,6-disubstituted

N -phenylformamides that has a chiral crystal structure.

Another example of an N -phenylformamide which is chiral in

the crystalline state is 4-bromo-2,6-diﬂuoro- N -phenylform-

amide [Cambridge Structural Database (Allen, 2002) refcode

SEDGAJ; Ferguson et al. , 1998]. In this paper, N—HO,

BrBr and BrO intermolecular interactions are discussed.

Figure 1

A view of (I), showing the atom-numbering scheme. Displacement

ellipsoids are drawn at the 50% probability level and H atoms are shown

as small spheres of abitrary radii.

Molecules of compound (I) are linked through N—HO

hydrogen bonds, forming chains that run along the crystal-

lographic a direction. The molecules in the chains are related

by translation, with the aryl rings along the chain stacked

Figure 2

N1—H1O1 hydrogen-bonded chains (short-dashed lines) in (I),

showing the stacking relationship in each chain. Molecules along the

chain are related by a unit-cell translation. Long-dashed lines show

intermolecular Br1Br2 interactions that link up the hydrogen-bonded

chains. [Symmetry codes: (i) 1+ x , y , z ; (ii)

2 x ,1 y , 2 + z .]

o160 # 2009 International Union of Crystallography

doi:10.1107/S010827010900780X

Acta Cryst. (2009). C65, o160–o162

organic compounds

phenylaniline (5 g, 0.02 mol; Aldrich, purity >95%) was heated in a

tenfold excess of formic acid for a period of 15 h at 363 K. The excess

formic acid was then removed under reduced pressure to give a white

solid, which was treated with dilute hydrochloric acid (0.1 M HCl,

10 ml) and ethyl acetate (60 ml). The organic layer was separated

from the aqueous layer, dried over magnesium sulfate and ﬁltered.

Colourless needle-shaped crystals of (I) were grown from the ﬁltrate.

The purity of the compound was conﬁrmed by NMR analysis. It was

found to exist in solution (C 6 D 6 ) as a mixture of cis and trans isomers

in a 2:1 ratio.

Crystal data

C 7 H 5 Br 2 NO

M r = 278.94

Orthorhombic, P 2 1 2 1 2 1

a = 4.2946 (5) A ˚

b = 13.8755 (16) A ˚

c = 14.2541 (19) A ˚

V = 849.40 (18) A ˚ 3

Z =4

Mo K radiation

= 9.48 mm 1

T = 173 K

0.56 0.08 0.08 mm

Figure 3

A perspective view of compound (I), showing intermolecular Br1O

interactions as short-dashed lines and intermolecular Br1Br2 inter-

actions as long-dashed lines. The BrO interactions, together with N—

HO interactions, form an R 3

Data collection

Bruker SMART CCD area-detector

diffractometer

Absorption correction: multi-scan

( SADABS ; Bruker, 2004)

T min = 0.069, T max = 0.466

5541 measured reﬂections

2100 independent reﬂections

1841 reﬂections with I >2( I )

R int = 0.030

ring. [Symmetry codes: (i)

2 + x ,

2 y ,

2 z ; (ii) 2 + x ,

2 y ,2 z ; (iii)

2 x ,1 y , 2 + z .]

Reﬁnement

R [ F 2 >2( F 2 )] = 0.027

wR ( F 2 ) = 0.060

S = 1.03

2100 reﬂections

100 parameters

H-atom parameters constrained

observed in the crystal structures of 2,3,6,7-tetrabromo-

naphthalene (space group P 2 1 / c ) and the cocrystal of 2,3,6,7-

tetrabromonaphthalene and bromobenzene (Navon et al. ,

1997).

Although compound (I) has the same hydrogen-bonded

chains as the high-temperature forms of 2,6-dichloro- N -

phenylformamide and 2-chloro-6-methyl- N -phenylformam-

ide, and of 2,6-dimethyl- N -phenylformamide (Omondi et al. ,

2005), in which they all have one short axis of about 4 A ˚ along

which the formamide molecules are stacked along the N—

HO hydrogen-bonded chain (Fig. 2), the packing in (I) is

similar only to that in 2,6-dichloro- N -phenylformamide, where

the N—HO hydrogen-bonded chains in the high-tempera-

ture form are connected through ClCl contacts forming

(010) sheets.

Using the OPIX suite of programs (Gavezzotti, 2003), the

lattice energy of (I) was calculated to be 90.5 kJ mol 1 .

These calculations permitted estimation of the contributions

to this energy of the intermolecular N—HO, BrO and

BrBr interactions as 40, 9.5 and 8.1 kJ mol 1 ,

respectively. This energy pattern resembles that for the high-

temperature forms of 2,6-dichloro- N -phenylformamide and

2-chloro-6-methyl- N -phenylformamide, and that of 2,6-di-

methyl- N -phenylformamide (Omondi et al. , 2005), in which

there is one strong stabilizing interaction (along the N—

HO hydrogen-bonded chain), while the second and third

stabilizing interactions are signiﬁcantly weaker.

max = 0.63 e A ˚ 3

min = 0.34 e A ˚ 3

Absolute structure: Flack (1983),

with 840 Friedel pairs

Flack parameter: 0.055 (18)

Table 1

Hydrogen-bond geometry (A ˚ , ).

D —H A

D —H

H A D A

D —H A

N1—H1O1 i

0.88

2.08

2.793 (4)

138

Symmetry code: (i) x þ 1; y ; z .

H atoms were located in difference maps and then treated as

riding, with C—H = 0.95 ˚

and N—H = 0.88 ˚ , and with U iso (H) =

1.2 U eq (C,N).

Data collection: SMART (Bruker, 2004); cell reﬁnement: SAINT

(Bruker, 2004); data reduction: SAINT ; program(s) used to solve

structure: SHELXS97 (Sheldrick, 2008); program(s) used to reﬁne

structure: SHELXL97 (Sheldrick, 2008); molecular graphics:

ORTEP-3 (Farrugia, 1997), PLATON (Spek, 2009) and DIAMOND

(Brandenburg, 2006); software used to prepare material for publi-

cation: WinGX (Farrugia, 1999).

The authors thank the University of the Witwatersrand and

the National Research Foundation (GUN 2067413) for

funding and for providing the infrastructure to carry out this

work. BO thanks the International Union of Crystallography

for a PhD grant.

Experimental

2,6-Dibromo- N -phenylformamide was synthesized following a known

procedure (Ugi et al. , 1965). Commercially available 2,6-dibromo- N -

Supplementary data for this paper are available from the IUCr electronic

archives (Reference: GD3278). Services for accessing these data are

described at the back of the journal.

Acta Cryst. (2009). C65, o160–o162

Omondi et al. C 7 H 5 Br 2 NO o161

organic compounds

References

Flack, H. D. (1983). Acta Cryst. A39, 876–881.

Gavezzotti, A. (2003). OPIX . University of Milan, Italy.

Kubicki, M. (2004). Acta Cryst. B60, 333–342.

Lieberman, H. F., Davey, R. J. & Newsham, D. M. T. (2000). Chem. Mater. 12,

490–494.

Lommerse, J. P. M., Stone, A. J., Taylor, R. & Allen, F. H. (1996). J. Am. Chem.

Soc. 118, 3108–3116.

Navon, O., Bernstein, J. & Khodorkovsky, V. (1997). Angew. Chem. Int. Ed. 36,

601–603.

Omondi, B., Fernandes, A. M., Layh, M., Levendis, D. C., Look, J. & Mkwizu,

T. S. P. (2005). CrystEngComm , 7, 690–700.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Spek, A. L. (2009). Acta Cryst. D65, 148–155.

Ugi, I., Fetzer, U., Eholzer, U., Knupfer, H. & Offerman, K. (1965). Angew.

Chem. Int. Ed. 4, 472–484.

Allen, F. H. (2002). Acta Cryst. B58, 380–388.

Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem.

Int. Ed. Engl. 34, 1555–1573.

Beyer, T., Day, G. M. & Price, S. L. (2001). J. Am. Chem. Soc. 123, 5086–5094.

Brandenburg, K. (2006). DIAMOND . Crystal Impact GbR, Bonn, Germany.

Bruker (2004). SMART , SADABS and SAINT . Bruker AXS Inc., Madison,

Wisconsin, USA.

Etter, M. C. (1990). Acc. Chem. Res. 23, 120–126.

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

Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.

Ferguson, G., Low, J. N., Penner, G. H. & Wardell, J. L. (1998). Acta Cryst. C54,

1974–1977.

o162 Omondi et al. C 7 H 5 Br 2 NO

Acta Cryst. (2009). C65, o160–o162

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: