X-Ray structure determinations of bromo and/or bromomethylsubstituted benzenes: C-H···Br, C-Br···Br, and C-Br···p interactions

Article abstract of DOI:10.5560/ZNB.2012-0249

The structures of seven benzene derivatives [1,2,3-tri(bromomethyl)benzene, (1); 3,5-di(bromomethyl)bromobenzene, (2); 2,5-di(bromomethyl)bromobenzene, (3); 4-(bromomethyl)-2,5-dibromotoluene, (4); 4-(bromomethyl)bromobenzene, (5); 2,3-di(bromomethyl)bromobenzene, (6) and (bromomethyl)-p-dibromobenzene, (7)] with bromo and bromomethyl (and in one case methyl) substituents are presented and analysed in terms of Br···Br interactions up to 4.0 A , supported by hydrogen bonds H···Br. Some interactions of the type Br···π and π·· · π are encountered and play a subordinate role in the packing. Despite the close chemical similarity of the compounds, some of which are isomers with permuted substituent positions, the packing motifs are highly variable. Compounds 2-5 are based on layer structures with Brn (n=3, 4) and/or mixed Br/C rings. Compounds 1, 6 and 7 display three-dimensional packings of differing complexity, but with interpretable substructures; 1 can be analysed in terms of ribbons of linked Br3 and Br4 rings; 6 displays chains of linked B_r3 triangles; 7 consists of ribbons of linked Br4 quadrilaterals.

Full text of DOI:10.5560/ZNB.2012-0249

X-Ray Structure Determinations of Bromo- and/or Bromomethyl-
substituted Benzenes: C–H···Br, C–Br···Br, and C–Br···π Interactions
a
b
c
Peter G. Jones , Piotr Ku s´ and Ina Dix
a
Institut f u¨ r Anorganische und Analytische Chemie, Technische Universit a¨ t Braunschweig,
Postfach 3329, 38023 Braunschweig, Germany
Department of Chemistry, University of Silesia, 9, Szkolna Street, 40-006 Katowice, Poland
Institut f u¨ r Anorganische Chemie, Universit a¨ t G o¨ ttingen, Tammannstrasse 4, 37077 G o¨ ttingen,
Germany. Current address: Novartis Pharma AG, CH-4056 Basel, Switzerland
b
c
Reprint requests to Prof. Dr. P. G. Jones. Fax: +49-531-391-5387. E-mail: p.jones@tu-bs.de.
Z. Naturforsch. 2012, 67b, 1273 – 1281 / DOI: 10.5560/ZNB.2012-0249
Received September 18, 2012
Belatedly dedicated to Professor Joachim Heinicke on the occasion of his 65th birthday
The structures of seven benzene derivatives [1,2,3-tri(bromomethyl)benzene, (1); 3,5-
di(bromomethyl)bromobenzene, (2); 2,5-di(bromomethyl)bromobenzene, (3); 4-(bromomethyl)-2,5-
dibromotoluene, (4); 4-(bromomethyl)bromobenzene, (5); 2,3-di(bromomethyl)bromobenzene, (6)
and (bromomethyl)-p-dibromobenzene, (7)] with bromo and bromomethyl (and in one case methyl)
substituents are presented and analysed in terms of Br···Br interactions up to 4.0 A˚ , supported by
hydrogen bonds H···Br. Some interactions of the type Br···π and π···π are encountered and play
a subordinate role in the packing. Despite the close chemical similarity of the compounds, some of
which are isomers with permuted substituent positions, the packing motifs are highly variable. Com-
pounds 2–5 are based on layer structures with Brn (n = 3, 4) and/or mixed Br/C rings. Compounds 1,
6
and 7 display three-dimensional packings of differing complexity, but with interpretable substruc-
tures; 1 can be analysed in terms of ribbons of linked Br and Br rings; 6 displays chains of linked
3
4
Br triangles; 7 consists of ribbons of linked Br quadrilaterals.
3
4
Key words: Halogen Bonds, “Weak” Hydrogen Bonds, Secondary Interactions
Introduction
In general we have found that the packing diagrams
are dominated by Br···Br contacts and “weak” C–
We are interested in intermolecular secondary in- H···Br hydrogen bonds. To a lesser extent, H···π, π···π
teractions between bromine atoms in organic com- and Br···π contacts may also be observed. The Br···Br
pounds. One previous report concerned five doubly contacts tend to provide a more easily assimilated view
or quadruply bromomethyl-substituted benzene deriva- of the packing, because they often form clearly recog-
tives based on o-, m- and p-xylene, durene and iso- nisable, simple aggregates of bromine atoms (such as
durene [1]. Other papers have discussed the struc- chains or simple polygons).
tures of all di(bromomethyl)naphthalene isomers [2],
Halogen···halogen contacts are seen as a special
,6,7-tris(bromomethyl)naphthalene [3], 1,5-dibromo- case of “halogen bonding” [11 – 13]. The model in-
,6-dimethylnaphthalene [4], 2,5-bis(bromomethyl)- volves a positive area in the extension of the C–Hal
1
2
0
0
δ−
biphenyl [5], 2,2 -bis(bromomethyl)-p-terphenyl [6], bond, with which a second C–Hal
group may
mesitylene and dimesitylene compounds bearing bro- then interact via its negative region cylindrically sur-
momethyl units [7], a new polymorph of 1,4-dibromo- rounding the halogen atom. Correspondingly, one
◦
2
,5-dimethylbenzene [8] and two polymorphs of 1,4- C–Hal···Hal angle should be ca. 180 and the other
◦
bis(tribromomethyl)benzene [9]. Other authors have ca. 90 , corresponding to a “type II interaction” as de-
reported the structure of 1,3,5-tris(bromomethyl)- scribed by Desiraju and coworkers [14]; “type I” con-
benzene [10].
tacts, thought to represent less significant “packing ef-
©
2012 Verlag der Zeitschrift f u¨ r Naturforschung, T u¨ bingen · http://znaturforsch.com

1
274
P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
fects” with at best a weak interaction, have approxi- derivatives [2], the absolute torsion angles C–C–C–Br
◦
mately equal angles and are often formed across sym- all lie in the range 77 – 94 , so that the planes of the
metry elements.
C–C–Br units are approximately perpendicular to the
In this report we continue the theme of ring planes; in compounds with more than one bro-
bromomethyl-substituted benzenes [1], but have momethyl group, the Br atoms may in principle lie on
extended the scope of our studies to include some the same or on opposite sides of the ring plane. For
structures with additional bromine and (in one case) compounds 2, 3 and 6, the “trans” form (bromines on
methyl substituents directly bonded to the ring. Struc- opposite sides of the ring) is observed; for compound
tures of the following seven benzene derivatives are 1, Br2 is “trans” to Br1 and Br3. For substituents at
presented: 1,2,3-tri(bromomethyl)benzene, (1); 3,5- neighbouring ring positions, such contacts necessarily
di(bromomethyl)bromobenzene, (2); 2,5-di(bromo- lead to short intramolecular C–H···Br contacts (typi-
˚
methyl)bromobenzene, (3); 4-(bromomethyl)-2,5-di- cally with distances H···Br around 3 A and C–H···Br
◦
bromotoluene, (4); 4-(bromomethyl)bromobenzene, angles of ca. 135 ), which however will neither be tab-
(
(
5); 2,3-di(bromomethyl)bromobenzene, (6) and ulated nor discussed.
bromomethyl)-p-dibromobenzene, (7) (Scheme 1).
˚
There are no short (H···π < 2.9 A) C–H···π con-
The structure of 2,6-di(bromomethyl)bromobenzene tacts. The C–H···Br contacts for all compounds are
was investigated but proved to be severely disordered. summarised in Table 2, with Br···Br contacts in Ta-
ble 3. Again as for the naphthalene derivatives [2], few
Discussion
of the intermolecular C–H···Br contacts are very short
˚
(
cf. sum of van der Waals’ radii for H···Br 3.05 A). The
The molecular structures of compounds 1–7 are nominal limit for Br···Br distances based on van der
˚
presented in Figs. 1a–7a. All compounds crystallize Waals’ radii would be ca. 3.7 A, and we tend to call
with no imposed symmetry and with one molecule contacts below this value “short”, but some slightly
˚
in the asymmetric unit. All the aromatic ring systems longer contacts up to a limit of ca. 4.0 A have been
˚
are planar (max. mean deviation 0.005 A) and no di- included because of apparent structural relevance. We
rectly bonded substituent atom lies markedly out of have previously noted for systems involving I···I inter-
the ring plane. Bond lengths and angles may be re- actions that the sum of several borderline interactions,
garded as normal (Table 1). The ring angles at car- which we have loosely termed “tertiary interactions”,
bon atoms directly bonded to bromine are consistently may represent a significant contribution to a stable
◦
slightly larger than 120 . Similarly to the naphthalene packing pattern [15]; a more generalised form of this
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
CH3
Br
1
2
3
4
Br
Br
Br
Br
Br
Br
Br
Br
5
6
7
Scheme 1.

P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
1275
C–Brb
C–CH2–Brb C–C–CH2–Brb,c
Table 1. Selected details of molecular ge-
Comp.
Angle at
ipso-C
Disposition of
bromomethyl
groupsc
a
ometry ( A˚ and deg) .
1
2
3
4
1.978(2)
110.12(12)
112.12(12)
112.16(12)
89.8(2)
−92.3(2)
82.5(2)
C2 trans to C1
1
1
.979(2)
.981(2)
and C3
1.898(2)
122.3(2)
123.2(5)
trans
trans
1
1
.975(3)
.977(3)
111.2(2)
110.3(2)
77.4(3)
−74.8(3)
1.906(5)
1
1
.981(5)
.971(5)
110.6(4)
110.7(4)
−84.3(6)
86.3(5)
1.900(3)
122.0(3)
121.0(3)
1
1
.895(3)
.969(3)
110.2(2)
110.9(3)
89.9(3)
93.5(4)
5
6
1.902(4)
.968(4)
1.901(2)
121.7(3)
122.5(2)
1
trans
1
1
.981(2)
.969(2)
109.59(14)
112.43(15)
−93.9(2)
82.0(2)
7
1.894(2)
121.5(2)
121.6(2)
1
1
.895(2)
.977(2)
111.08(13)
−88.1(2)
a
Involving all bromine atoms (ring substituents and methyl substituents); b beginning
with the lowest-numbered bromine; c cis/trans = both bromine atoms on same/different
sides of ring system. The first two carbon atoms are chosen clockwise in the ring system,
starting from C1 at top right. Does not apply if only one bromomethyl group is present.
Table 2. Intermolecular C–H···Br hydro-
Comp. D–H···A
C–H
H···Br CH···Br Operator
gen bonds ( A˚ and deg).
1
C9–H9A···Br1
0.99
0.99
0.99
0.99
0.99
0.95
0.99
0.95
0.95
0.99
0.95
0.99
0.95
0.95
0.95
0.95
0.95
0.95
0.99
0.95
0.95
3.10
2.90
3.09
2.99
2.96
3.01
3.02
2.93
3.06
3.13
3.07
3.00
3.14
3.13
3.05
3.00
3.04
3.14
3.04
3.15
2.97
136
168
138
148
147
175
149
128
131
159
155
146
135
131
135
140
138
138
159
154
161
x−1/2, −y+3/2, z−1/2
−x+1/2, y−1/2, −z+1/2
x+1/2, −y+3/2, z+1/2
−x+3/2, y+1/2, −z+1/2
−x+1, −y+1, −z+1
−x+1, −y, −z+1
x, y, z−1
C9–H9B···Br2
C7–H7A···Br3
C8–H8B···Br3
C8–H8B···Br1
C4–H4···Br2
C7–H7A···Br3
C3–H3···Br1
C3–H3···Br3
C8–H8B···Br1
C3–H3···Br3
C8–H8A···Br3
C2–H2···Br1
C6–H6···Br1
C5–H5···Br1
C5–H5···Br2
C4–H4···Br3
C4–H4···Br3
C8–H8B···Br3
C5–H5···Br1
C3–H3···Br3
2
3
−x+1, −y+2, z+1/2
x+1/2, −y+1, z
x−1/2, −y+1, z
4
5
6
−x, −y+1, −z+1
−x, −y+1, −z+1
−x, −y+2, z+1/2
x−1/2, −y+3/2, z
−x+2, y−1/2, −z+1/2
−x+2, y−1/2, −z+1/2
x+1, y, z
x+1/2, −y+1/2, −z+1
x+1, y, z
7
−x+3/2, y+1/2, −z+1/2
−x, −y+1, −z
principle had already been presented by Dance [16]. It
Compound 1 displays a complex three-dimensional
is also appropriate to repeat our caveat from the naph- packing pattern, but the main features (Fig. 1b) can be
thalene systems [2]: in view of the large number of po- recognised in terms of ribbons of molecules parallel
tential interactions, the choice of a hierarchy of interac- to the b axis (which are then linked in the third di-
tions (in our case: the preference for basing discussion mension). The ribbons consist of linked triangles and
on Br···Br contacts) may to some extent be subjective. quadrilaterals and are built up from of a total of five

1
276
P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
Table 3. Br···Br contacts (
A˚
Comp. C–Br···Br–C
Br···Br
C–Br···Br
Br···Br–C Operator
1
C7–Br1···Br3–C9
3.7593(4)
3.8322(3)
3.9102(3)
3.9355(3)
3.9720(3)
3.5291(5)
3.5360(5)
3.8359(7)
3.6111(7)
3.7204(8)
3.9211(7)
4.0374(8)
4.0511(8)
3.9784(6)
3.7119(6)
3.8562(6)
3.6065(5)
3.8989(5)
3.7487(3)
3.9662(3)
3.9760(3)
3.5717(3)
3.7924(3)
3.8345(3)
3.7743(3)
84.53(6)
154.28(5)
133.98(6)
103.99(5)
72.93(5)
167.03(8)
149.84(7)
75.58(9)
113.5(2)
162.8(2)
139.1(2)
88.5(2)
139.56(5) −x+3/2, y+1/2, −z+1/2
and deg).
C8–Br2···Br3–C9
C7–Br1···Br2–C8
C7–Br1···Br2–C8
C7–Br1···Br3–C9
C1–Br1···Br3–C8
C7–Br2···Br3–C8
C8–Br3···Br3–C8
C1–Br1···Br3–C8
C7–Br2···Br3–C8
C1–Br1···Br3–C8
C1–Br1···Br2–C7
C7–Br2···Br3–C8
C2–Br1···Br2–C5
C2–Br1···Br2–C5
C2–Br1···Br3–C8
C1–Br1···Br2–C7
C1–Br1···Br2–C7
C8–Br3···Br3–C8
C1–Br1···Br3–C8
C1–Br1···Br3–C8
C1–Br1···Br2–C4
C1–Br1···Br2–C4
C1–Br1···Br2–C4
C4–Br2···Br3–C7
157.71(5) x, y+1, z
87.49(5) x+1/2, −y+3/2, z+1/2
147.30(5) −x+3/2, y−1/2, −z+1/2
72.76(5) x+1/2, −y+3/2, z+1/2
114.52(8) x, y+1, z−1
2
3
161.86(7) x+1, y, z−1
75.58(9)a −x, −y+1, −z+2
178.7(2) −x+1/2, y, z−1/2
82.4(2) −x+1, −y+1, z−1/2
110.5(2) −x+1/2, y+1, z−1/2
132.8(2) x−1/2, −y+2, z
109.5(2)
104.32(9)
168.37(9)
77.97(9)
164.53(9)
115.5(2) −x+1, −y+2, z−1/2
153.74(9) −x+1/2, y−1/2, −z+1/2
84.74(9) x+1/2, −y+1/2, z+1/2
163.21(8) −x+1, −y+1, −z+1
110.79(12) x−1, y, z−1
4
5
6
106.19(11) 158.48(12) x−1, y, z
b
81.48(7)
137.58(6)
143.39(7)
108.71(5)
156.44(6)
133.73(6)
84.99(6)
157.71(7) x+1/2, −y+1/2, −z+1
140.32(7) −x+1/2, −y+1, z−1/2
90.40(7) −x+1, y+1/2, −z+1/2
167.31(6) x−1/2, −y+3/2, z+1/2
82.57(6) −x+1/2, y−1/2, −z+1/2
97.34(6) −x+3/2, y−1/2, −z+1/2
157.40(6) −x+1, −y+1, −z
7
a
Angles equal by symmetry; b a symmetry-equivalent interaction is observed at x − 1/2, −y + 1/2,
−
z+1.
independent Br···Br contacts ranging in length from label these rings as R(20,7) and other rings accord-
˚
3
.76 to 3.97 A; there are no other such contacts shorter ingly. The layers, parallel to (111), are linked in pairs
˚
than 4.2 A. Two of the contacts are clearly type I; the (Fig. 2c) by the third and longest Br···Br contact; the
others have an intermediate form, with one angle ap- rings form an infinite stack parallel to the a axis via
◦
◦
proximately 90 and the other ca. 130 – 140 . It may symmetry operators −x, 1 − y, 1 − z and 1 − x, 1 − y,
be that the geometric constraints of forming a con- 1−z (referred to the molecule of the asymmetric unit)
˚
densed system of contact triangles does not allow type with two independent π···π distances of 3.7 A. Only
◦
II contacts with ideal 180 angles. The hydrogen bonds the shortest hydrogen bond H8B···Br1 is observed
H7A···Br3 and H8B···Br3, not shown explicitly in the within a given double layer; it supports the stacking
Figure, support the two interactions from Br1 to the interaction.
Br3 atoms (they are formed between the same pairs of
˚
Compound 3 is an isomer of 2, whereby the sub-
molecules). The shortest π···π contact is 4.03 A (op- stituents are permuted; its packing is, at least in two
erator 1 − x, 1 − y, 1 − z) and is probably of marginal dimensions, closely related to that of 2. Again, the two
significance.
shortest Br···Br contacts are Br1···Br3 and Br2···Br3
The packing of compound 2 is in marked contrast (both in this case corresponding reasonably well to
to that of 1; it involves only three Br···Br contacts, type II); they again combine to form highly corru-
but they are appreciably shorter (although only one gated layers parallel to the ac plane, consisting of
of them approximates to a type II contact and the R(20,7) rings (Fig. 3b). The equivalent molecules are
others are clearly type I). The two shortest, both ca. generated by a c glide plane and a 2 screw axis.
1
˚
3
.53 A, involve only translational symmetry; they com- The other three, appreciably longer, Br···Br contacts
bine to form highly corrugated layers consisting of 20- are formed to neighbouring layers but the correspond-
membered rings, seven atoms of which are bromine ing diagrams are highly complex. The main hydrogen
atoms (Fig. 2b). As an ad hoc notation related to the bond is a symmetric three-centre interaction, one com-
familiar graph sets for hydrogen bonds [17], we shall ponent of which, H3···Br1, lies within the layer.

P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
1277
Fig. 1. (a) Molecular structure of compound 1 in the crystal.
b) Packing diagram of compound 1 viewed parallel to the a
(
axis in the region x ≈ 0. Br···Br contacts are shown as dashed
bonds (the thicker bonds correspond to the central ribbon,
thinner bonds form parts of neighbouring, linked ribbons).
Approximate distances are given in A˚ ; Table 3 should be con-
sulted for exact values and symmetry operators. The “miss-
0
0
0
ing” contacts Br2 ···Br3 (intramolecular) and Br1···Br1 are
too long (at 4.90 and 4.27 A˚ respectively) to be considered as
structurally relevant.
Compound 4 again forms a layer structure, this time
parallel to (101). All three Br···Br contacts, which are
all quite long but correspond satisfactorily to type II,
combine to form Br rhombuses and two types of mixed
rings, R(12,4) in the centre of the cell surrounded by (b) Packing diagram of compound 2 viewed perpendicular
R(12,5) (Fig. 4b). All three contacts involve Br1; the to (111). The atoms Br1, 2, 3 correspond to the asymmetric
4
Fig. 2. (a) Molecular structure of compound 2 in the crystal.
unit. Br···Br contacts are shown as dashed bonds. (c) Packing
equivalent molecules are here generated by an n glide
of compound 2; depth-cued double layers (thinner bonds at
plane, a 2 screw axis and an inversion centre. The two
0
1
rear of diagram) showing the interconnecting Br3···Br3 con-
hydrogen bonds form a bifurcated system across an in-
version centre, and link neighbouring layers.
tacts (thin dashed bonds) and the incipient stacking in the a
direction. The origin is at the rear of the diagram.

1
278
P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
Fig. 3. (a) Molecular structure of compound 3 in the crystal. Fig. 4. (a) Molecular structure of compound 4 in the crystal.
b) Packing diagram of compound 3 viewed along the short (b) Packing diagram of compound 4 viewed perpendicular
b axis.
to (101).
(
Compound 5 also forms a layer structure, parallel to
Compound 6 is another isomer of 2 and 3 and might
the ac plane. The two Br1···Br2 contacts, which cor- therefore be expected to show a similarly simple layer
respond adequately to type II, combine to form zigzag pattern. In fact the opposite is the case; the packing
chains parallel to the short and polar c axis. The opera- (in space group P2 2 2 , which seldom leads to sim-
1
1 1
tors are purely translational. The molecular frames of 5 ple packing diagrams) is three-dimensional and in-
link the bromine chains to form R(16,6) rings (Fig. 5b). volves a variety of interactions. The simplest substruc-
Contacts of the form C1–Br1···π are observed within ture (Fig. 6b) is a chain of linked Br triangles parallel
3
◦
˚
the layer, with Br1···π 3.79 A and an angle of 77 , and to the short a axis; the main linear chain involves the
might be considered as part of stacking interactions be- shortest interactions Br3···Br3 (type II). The chain is
tween ring systems extended by the bromine atom. The supported by all five H···Br hydrogen bonds (including
two hydrogen bonds connect neighbouring layers (and two three-centre systems) and a contact C1–Br1···π,
◦
˚
indeed form layers in their own right parallel to the ab with Br1···π 3.70 A and an angle of 136 . It is surpris-
plane).
ing that the atom Br2 is involved in just one hydro-

P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
1279
Fig. 5. (a) Molecular structure of compound 5 in the crystal.
b) Packing diagram of compound 5 viewed parallel to the b
(
axis in the region y ≈ 7/8.
gen bond, whereas Br3 participates in three hydrogen
bonds and all three Br···Br contacts.
The packing of compound 7 is also three-
dimensional, but can be easily analysed in terms of
a double chain or “staircase” pattern of three indepen-
dent Br1···Br2 interactions, one of which is especially
short, parallel to the short a axis (Fig. 7b). The chain
is propagated via the 2 screw axis and the “rungs” via
1
the n glide plane. The interplanar angle between suc-
◦
◦
Fig. 6. (a) Molecular structure of compound 6 in the crystal.
cessive Br planes is 63.5 (or 116.5 ). A fourth in-
4
(
b) Packing diagram of compound 6 viewed parallel to the b
teraction Br2···Br3, formed over an inversion centre,
axis in the region y ≈ 1/4. For reasons of clarity, symmetry-
connects the chains in the third dimension, supported equivalent Br atoms are not labelled. Thin dashed lines in-
by the two H···Br hydrogen bonds (Fig. 7c). Three of dicate either hydrogen bonds or the Br···π interaction; only
one each of these interactions is shown. The hydrogen bond
the four contacts are a good (and the fourth a reason-
H8B···Br3 is omitted because it eclipses a Br···Br contact.
able) approximation to type II geometry.
Experimental Section
(for 4), 4-bromotoluene (for 5), 2,3-dimethylbromobenzene
All compounds were obtained from commercially (for 6), and 2,5-dibromotoluene (for 7) by radical bromina-
available hydrocarbons and bromohydrocarbons: 1,2,3- tion with N-bromosuccinimide in carbon tetrachloride. Spec-
trimethylbenzene (for 1), 3,5-dimethylbromobenzene (for 2), troscopic data for compounds 1 [18], 2 [19], 3 [20], 4 [21],
2
,5-dimethylbromobenzene (for 3), 2,5-dibromo-p-xylene 5 [22, 23], 6 [24, 25], and 7 [26] agree with those reported in

1
280
P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
Fig. 7. (a) Molecular structure of compound 7 in
the crystal. (b) Packing diagram of compound
7
in the crystal; view direction approximately
perpendicular to (011). For reasons of clarity,
symmetry-equivalent Br atoms are not labelled.
(
c) Packing diagram of compound 7 in the crys-
tal; view direction parallel to the short a axis;
one of the Br···Br contacts that connect the dou-
ble chains (seen here end-on as rhombuses) is la-
belled explicitly. Two representative H···Br hy-
drogen bonds are shown in the upper left corner
of the cell.
Table 4. Crystallographic data for compounds 1–7.
Compound
1
2
3
4
5
6
7
Formula
C9H9Br3
356.89
C8H7Br3
342.87
C8H7Br3
342.87
C8H7Br3
342.87
C7H6Br2
249.94
C8H7Br3
342.87
C7H5Br3
328.84
Mr
Crystal size, mm3 0.20×0.08×0.08 0.22×0.13×0.08 0.24×0.14×0.08 0.25×0.05×0.05 0.18×0.18×0.06 0.15×0.12×0.08 0.22×0.10×0.08
Crystal system
monoclinic
P21/n
8.7466(6)
8.3835(6)
14.1337(11)
90
94.420(4)
90
1033.30(13)
4
2.29
11.7
672
100(2)
66.7
triclinic
¯
P1
orthorhombic
Pca21
15.2421(6)
4.3633(3)
14.2695(6)
90
90
90
949.01(9)
4
2.40
monoclinic
P21/n
4.5278(6)
15.6051(18)
13.6899(16)
90
93.185(8)
90
965.8(2)
4
2.36
12.5
640
100(2)
60
orthorhombic
Pna21
9.6283(8)
18.1165(15)
4.4279(4)
90
orthorhombic
P212121
5.2694(3)
10.5073(3)
17.1833(6)
90
90
90
951.39(7)
4
2.39
monoclinic
P21/n
4.2600(2)
13.2354(3)
15.1444(4)
90
95.506(2)
90
849.94(5)
4
2.57
14.2
608
100(2)
64
Space group
a, A˚
b, A˚
c, A˚
7.3062(7)
8.8368(9)
8.9401(10)
66.972(6)
69.440(6)
71.419(6)
486.24(9)
2
2.34
12.4
320
100(2)
65.5
α, deg
β, deg
90
90
γ, deg
V, A˚ 3
772.36(11)
4
2.15
10.4
472
133(2)
57.4
13 198/1974/
0.047
82
Z
−
3
Dx, Mg m
−
1
µ, mm
12.7
640
12.7
640
F(000), e
T, K
100(2)
57.4
13 993/2429/
0.061
100
103(2)
62
29 282/302/
0.042
100
2
θmax, deg
Measured/indep. 4086/4086/
4431/4431/
−
25 218/2829/
0.065
101
19 601/2880/
0.032
91
refl./Rint
Ref. parameters
Restraints
−
110
0
101
18
1
18
58
0
0
Flack parameter x
wR (F , all refl.) 0.042
R [F > 4 σ (F)]
–
–
−0.01(2)
0.067
0.035
1.07
–
0.02(2)
0.057
0.026
1.07
0.003(10)
0.030
0.018
0.95
–
2
0.070
0.028
1.05
0.86
0.067
0.028
1.03
0.041
0.020
0.99
0.020
1.04
0.62
S
Max. ∆ρ, e A˚
−
3
0.92
0.92
0.69
0.51
0.75

P. G. Jones et al. · Bromo- and/or Bromomethyl-substituted Benzenes
1281
the literature. Single crystals used in crystallographic studies ning routines merge all equivalent reflections, so that no Rint
were obtained by slow evaporation of solutions: from ethanol value can be given, and the number of reflections is not well-
(
1, 3 and 7), hexanes (2 and 6), CCl4 (5), and CH Cl - defined because of overlap.
2 2
hexanes-ethanol (4).
Molecular structures are presented in the figures with ther-
mal ellipsoids at the 50% level. The following comments ap-
ply to all packing diagrams unless otherwise stated: Hydro-
X-Ray structure determinations
Crystal data are summarised in Table 4. Data were regis- gen atoms are omitted. The atoms labelled Br1, 2, 3 (without
tered on various diffractometers (Bruker SMART 1000 CCD, primes) correspond to the asymmetric unit. Br···Br contacts
Bruker APEX-2, Oxford Diffraction Xcalibur) using MoKα
are shown as dashed bonds, usually drawn thick (less impor-
radiation at low temperature. Absorption corrections were tant or significantly longer contacts may be drawn with thin
applied using the multi-scan method. Structures were refined lines). Primes indicate symmetry-equivalent atoms; the cor-
using the program SHELXL-97 [27, 28]. Hydrogen atoms responding operators are given explicitly in the tables.
were included using a riding model (for 4 the methyl group
CCDC 896170–896176 contain the supplementary crys-
was included as an idealized rigid group allowed to rotate but tallographic data for this paper. These data can be obtained
not tip). Compounds 1 and 2 were non-merohedrally twinned free of charge from The Cambridge Crystallographic Data
◦
by 180 rotation about c and b*, respectively; the untwin- Centre via www.ccdc.cam.ac.uk/data request/cif.
[
[
[
[
[
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4