One-dimensional hydrogen-bonded structures in the 1:1 proton-transfer salts of 4,5-dichlorophthalic acid with the aliphatic lewis bases diisopropylamine and hexamethylenetetramine

Article abstract of DOI:10.1007/s10870-009-9636-7

The crystal structures of the 1:1 proton-transfer compounds of 4,5-dichlorophthalic acid with the aliphatic Lewis bases diisopropylamine and hexamethylenetetramine, viz. diisopropylaminium 2-carboxy-4,5-dichlorobenzoate (1) and hexamethylenetetraminium 2-carboxy-4,5-dichlorobenzoate hemihydrate (2), have been determined. Crystals of both 1 and 2 are triclinic, space group P - 1, with Z = 2 in cells with a = 7.0299(5), b = 9.4712(7), c = 12.790(1) A, α = 99.476(6), β = 100.843(6), γ = 97.578(6)° (1) and a = 7.5624(8), b = 9.8918(8), c = 11.5881(16) A, α = 65.660(6), β = 86.583(4), γ = 86.987(8)° (2). In each, one-dimensional hydrogen-bonded chain structures are found: in 1 formed through aminium N ⁺-H...O_carboxyl cation-anion interactions. In 2, the chains are formed through anion carboxyl O???H-O _{bridging water} interactions with the cations peripherally bound. In both structures, the hydrogen phthalate anions are essentially planar with short intra-species carboxylic acid O-H...O_carboxyl hydrogen bonds [O...O, 2.381(3) A (1) and 2.381(8) A (2)].

Full text of DOI:10.1007/s10870-009-9636-7

J Chem Crystallogr (2010) 40:207–212
DOI 10.1007/s10870-009-9636-7
ORIGINAL PAPER
One-Dimensional Hydrogen-Bonded Structures in the 1:1
Proton-Transfer Salts of 4,5-Dichlorophthalic Acid
with the Aliphatic Lewis Bases Diisopropylamine and
Hexamethylenetetramine
•
Graham Smith Urs D. Wermuth
Received: 7 May 2009 / Accepted: 12 September 2009 / Published online: 2 October 2009
ꢀ Springer Science+Business Media, LLC 2009
Abstract The crystal structures of the 1:1 proton-transfer
compounds of 4,5-dichlorophthalic acid with the aliphatic
Lewis bases diisopropylamine and hexamethylenetetramine,
viz. diisopropylaminium 2-carboxy-4,5-dichlorobenzoate (1)
and hexamethylenetetraminium 2-carboxy-4,5-dichlorobenzo-
ate hemihydrate (2), have been determined. Crystals of both
1 and 2 are triclinic, space group P - 1, with Z = 2 in cells
acid: DCPA) has potential for the formation of stable
crystalline salts with nitrogen Lewis bases, stabilized by
hydrogen-bonding interactions. The pKa values, similar to
those of phthalic acid (2.95, 5.41) also allow for selective
formation of both 1:1 and 1:2 compounds through pH and
stoichiometric control, but to date, only a limited number
of structures of DCPA compounds have been reported and
the large majority of these have been 1:1 acid phthalate
salts (Scheme 1).
˚
with a = 7.0299(5), b = 9.4712(7), c = 12.790(1) A,
a = 99.476(6), b = 100.843(6), c = 97.578(6)ꢁ (1) and
˚
a = 7.5624(8), b = 9.8918(8), c = 11.5881(16) A, a =
The first reported examples were the 1:1 ammonium and
tetra(n-butyl)ammonium salts [1] and more recently the
tetramethylammonium salt [2]. Of interest also is the 1:1
salt with the proton sponge compound 1,8-bis(dimethyl-
amino)naphthalene (DMAN) which has steric strain
induced by the close proximity of the amine substituent
groups [3]. A 1:2 non-transfer adduct compound with
trans-cinnamamide is also known [4]. Our group therefore
began an investigation of the structural chemistry of the 1:1
salts of DCPA with a series of aliphatic and aromatic
nitrogen Lewis bases. The overall result, although not
outstanding has given a number of crystalline salts for
which the crystal structures have been determined [5–11]:
(a) with brucine [5]; (b) with the bicyclic bifunctional
heteroaromatic bases 8-hydroxyquinoline, 8-aminoquino-
line and quinoline-2-carboxylic acid (quinaldic acid) [6],
(the last being an unusual 1:1:1:1 salt-quinaldic acid adduct
monohydrate compound); (c) with the isomeric monoami-
nobenzoic acids [7]; with the substituted monocyclic het-
eroaromatic bases 2-aminopyrimidine, nicotinic acid and
isonicotinic acid [8], (the last being a 1:1:1 salt-methyl
DCPA monoester which was self-generated in the metha-
nol solvent used); (d) with the drug quinacrine [9]; (e) with
4-chloroaniline [10], and (f) with 1,10-phenanthroline [11].
Among the total set of these 1:1 hydrogen-bonded
DCPA compounds, structurally there is generally
65.660(6), b = 86.583(4), c = 86.987(8)ꢁ (2). In each, one-
dimensional hydrogen-bonded chain structures are found: in
1 formed through aminium N?–H…Ocarboxyl cation–anion
interactions. In 2, the chains are formed through anion car-
boxyl OÁÁÁH–Obridging
interactions with the cations
water
peripherally bound. In both structures, the hydrogen
phthalate anions are essentially planar with short intra-
species carboxylic acid O–H…Ocarboxyl hydrogen bonds
˚
˚
[O…O, 2.381(3) A (1) and 2.381(8) A (2)].
Keywords 4,5-Dichlorophthalic acid Á Proton-transfer
compounds Á Aliphatic Lewis bases Á Hydrogen bonding
Introduction, Results and Discussion
Introduction
The halo-substituted aromatic dicarboxylic acid 4,5-di-
chlorophthalic acid (4,5-dichlorobenzene-1,2-dicarboxylic
G. Smith (&) Á U. D. Wermuth
School of Physical and Chemical Sciences,
Queensland University of Technology, G.P.O. Box 2434,
Brisbane, QLD 4001, Australia
e-mail: g.smith@qut.edu.au
123

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J Chem Crystallogr (2010) 40:207–212
2-carboxy-4,5-dichlorobenzoate hemihydrate [HMT?
-
Cl
Cl
CO2
Cl
Cl
CO2H
CO2H
CO2H
Cl
Cl
DCPA-]Á0.5H2O (Scheme 2) (2).
-
-
CO2
CO2
General Structure Comparison
-
DCPA2-
DCPA
DCPA
The structure determinations of compounds [(DIPA)?
(DCPA)-] (1) and [(HMT)? (DCPA)-]Á0.5H2O (2) show
one-dimensional hydrogen-bonded chain structures. As
expected in each compound, single proton transfer to the
Scheme 1 Schematic of DCPA, DCPA- and DCPA2- anion species
low-dimensionality with the occurrence of three-dimensional
structures in only two examples, the salts with the 3- and
4-aminobenzoic acids [7]. This is due to the structure
extensions provided by the secondary carboxylic acid
substituent groups in these compounds. The other examples
are more commonly one- or two-dimensional but
zero-dimensional examples having no secondary hydrogen-
bonding extension include the salts with brucine [5], 1,
10-phenanthroline [11] and 2-aminopyrimidine [8] (a dis-
crete cation–anion ‘heterotetramer’ [12]). In the majority
of these examples the hydrogen DCPA anions are essen-
tially planar with the planarity achieved through short
intramolecular carboxylic acid O–H…Ocarboxyl hydrogen
Table 1 Crystal data for compounds 1 and 2
Compound
1
2
CCDC reference
Melting point (ꢁC)
Molecular formula
Mr
719976
190
719977
168
C14H19Cl2NO4
C14H7Cl2N4O4.5
384.22
336.20
Temperature (K)
Wavelength (k)
Crystal system
Space group
297(2)
170(2)
0.71073
Triclinic
P-1
0.71073
Triclinic
P-1
˚
bonds, e.g. 2.441(3) A in the brucinium DCPA compound
[5]. In the much less common structures having the non-
planar monoanion, e.g. salts with 3- and 4-aminobenzoic
acids [7] and with 4-chloroaniline [10], these anions form
homomeric hydrogen-bonded chains into which the cat-
ionic species are incorporated. Another observation with
these structures has been that water molecules of solvation
are uncommon despite the fact that the usual solvent systems
employed in the syntheses were ethanol–water or methanol–
water.
˚
a (A)
7.0299(5)
9.4712(7)
12.790(1)
99.476(6)
100.843(6)
97.578(6)
813.22(11)
2
7.5624(8)
9.8918(8)
11.5881(16)
65.660(6)
86.583(4)
86.987(8)
788.03(16)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dc (g cm-3
)
1.369
1.619
However, apart from the brucinium compound [5] we
have had lesser success in obtaining crystalline 1:1 aliphatic
Lewis base compounds with DCPA, being limited to those
salts reported here, with diisopropylamine (DIPA) and
hexamethylenetetramine (HMT), namely anhydrous diiso-
propylaminium 2-carboxy-4,5-dichlorobenzoate [DIPA?
DCPA-] (1) and the hydrated hexamethylenetetraminium
l (mm-1
)
0.413
0.445
F(000)
350
398
Instrument
Oxford diffraction Oxford diffraction
Gemini S CCD
Diffractometer
Gemini S CCD
Diffractometer
4,107, 25.0
Reflections total, hmax (ꢁ) 5,320, 25.0
Crystal size (mm)
0.45 9 0.20 9 0.08 0.45 9 0.35 9 0.18
Collection range
h
k
l
-8 to 8
-8 to 8
-11 to 11
-13 to 11
2,697
Cl
Cl
CO2H
-11 to 11
-14 to 15
H
H
+
N
(1)
Reflections (independent) 2,823
Reflections [F2 [ 2r(F2)] 2,263
-
CO2
2,106
Rint
R1 [F2 [ 2r(F2)]*
wR2 (all data)*
0.020
0.024
0.043
0.083
0.109
0.230
Cl
Cl
CO2H
N
N
S*
1.05
1.10
(2)
. 0.5H2O
+
N
N
H
np
202
242
-
CO2
Residuals: Dmax./min
0.240/-0.250
0.691/-0.544
-3
)
˚
(eA
Scheme 2 Schematic of [DIPA? DCPA-] (1) and [HMT?
DCPA-]Á0.5H2O (2)
‘
* R1 = (R|Fo| - |Fc|)/R |Fo|); wR2 = {R[w(F2o - Fc2)2]/R [w(Fo2)2]} ;
‘
S = {R[w(F2o - F2c)2]/(n - p)}
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J Chem Crystallogr (2010) 40:207–212
209
Fig. 1 Molecular configuration
and atom numbering scheme for
the diisopropylaminium cation
and the DCPA monoanion
species in 1. The inter-species
hydrogen bond is shown as a
dashed line. Non-hydrogen
atoms are shown as 40%
probability displacement
ellipsoids [18]
Fig. 2 Molecular configuration
and atom numbering scheme for
the hexamethylenetetraminium
cation, the DCPA monoanion
and the hemihydrate water
species in 2. The inter-species
hydrogen bonds are shown as
dashed lines. Non-hydrogen
atoms are shown as 40%
probability displacement
ellipsoids
amino-N of the Lewis base occurs, with a subsequent
formation of a primary hydrogen bond between this group
and a carboxyl oxygen acceptor of the DCPA anion.
Figures 1 and 2 show the molecular configuration and atom
naming schemes used for the DCPA anion species and the
protonated cation species in 1 and 2.
(Fig. 4). The HMT cations are peripherally attached to one
of the carboxyl oxygen atoms (O22).
The DCPA anions in both 1 and 2 have the essential
planarity common among its 1:1 salts, together with the
associated short intramolecular O–H…Ocarboxyl hydrogen
˚
bonds [2.381(3), 2.381(7) A, respectively]. Torsion angles
The chain structures formed in 1 and 2 are different in
their makeup. In 1, the cation–anion ‘heterodimer’ is
extended along the b axial direction of the unit cell through
the second aminium proton to a DCPA carboxyl-O
acceptor (Table 2; Fig. 3). With 2, the hydrogen-bonding
extension is also along the b axial direction in the cell but
the primary chain comprises anion carboxyl OÁÁÁH-Owater
associations (Table 1) through both water hydrogen donors
associated with these groups (C2–C1–C11–O11 and C1–
C2–C21–O22) are -170.8(2) and -176.0(2)ꢁ for 1 and
-173.7(6) and 173.6(5)ꢁ for 2. The planarity also means
that there are short intramolecular aromatic ring
C–H…O*carboxyl*interactions, typically for 1,
C3…O22, 2.659(3) A and C6…O12, 2.657(3) A (Table 2).
There is an absence in 1 or 2 of short intermolecular
ClÁÁÁCl interactions such as has been found in the DCPA
˚
˚
123

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J Chem Crystallogr (2010) 40:207–212
Fig. 3 The one-dimensional
hydrogen-bonded chain
structures of 1 in a perspective
view down the approximate a
direction of the unit cell.
Hydrogen bonds are shown as
dashed lines [symmetry code
ii
:
x, y - 1, z]. Hydrogen-bonding
associations are shown as
dashed lines
Fig. 4 The one-dimensional
hydrogen-bonded chain
structures in 2, viewed down the
a cell direction of the unit cell
[symmetry code ii: x, y ? 1, z]
123

J Chem Crystallogr (2010) 40:207–212
211
˚
Table 2 Hydrogen-bonding interactions (A/deg.) for 1 and 2
temperature evaporation of the hot-filtered solutions gave
in the case of 1, a white powder and with 2, a small
quantity of colourless crystal prisms. The powder from 1
was subsequently redissolved in a small quantity of water
and on evaporation provided prismatic crystals.
D–H…A
D–H
H…A
D…A
\DH…A
Compound 1a
O12–H12…O21
N1A–H1A…O22
N1A–H2A…O11i
C3–H3…O22
C6–H6…O11
Compound 2b
1.01(5) 1.37(5) 2.381(3)
0.91(3) 1.88(3) 2.788(3)
0.90(3) 1.90(3) 2.799(3)
180(7)
178(3)
174(2)
104
Crystallography
0.93
0.93
2.28
2.29
2.659(3)
2.657(3)
103
X-ray diffraction data for 1 and 2 were obtained either at
ambient temperature [297(2) K] (compound 1) or at 173(2)
K (2) on an Oxford Diffraction Gemini S CCD-detector
diffractometer by using crystal monochromatized Mo Ka
radiation. Data were corrected for absorption [14]. The
structures were solved by direct methods using either SIR
92 [15] (1) or SHELXS 97 [16] (2) and refined with
anisotropic thermal parameters for all non-hydrogen atoms
using SHELXL 97 [16] operating within WinGX [17].
Aminium and water protons were located by difference
methods and their positional and isotropic thermal dis-
placement parameters were refined. Others were included
in the refinements at calculated positions and treated as
O12–H12…O21
N3A–H3A…O22
O1W–H11W…O22
0.99(6) 1.39(6) 2.381(8)
0.86(8) 1.90(8) 2.736(7)
180(7)
162(8)
0.94(7) 1.98(7) 2.920(13) 177(7)
O1W–H12W…O11i 0.97(7) 1.84(7) 2.806(14) 174(6)
C3–H3…O22
C6–H6…O11
0.93
2.29
2.666(7)
104
0.93
2.28
2.662(9)
104
a
i
Symmetry code: x, y ? 1, z
b
i
Symmetry code: x, y - 1, z
compounds with the isomeric 3- and 4-aminobenzoic acids
˚
˚
˚
riding models with C–H = 0.93 A (aromatic) or 0.97
˚
- 0.98 A (aliphatic) and Uiso = 1.2Ueq(attached C). Gen-
[10] [3.2295(6), 3.3243(6) A and 3.2488(7) A, respectively].
This phenomenon has previously been described [13]
particularly in the structures of the dichloro-substituted
aromatic compounds. Absent as well are the short
Cl…Ocarboxyl associations found also in the 3- and
eral crystallographic details are given in Table 1.
CCDC 719976 and 719977 contain supplementary
crystallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data
request/cif by e-mailing datarequest@ccdc.cam.ac.uk, or
contacting The Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ.
˚
˚
4-aminobenzoates [3.2279(14) A and 3.2213(15) A,
respectively] [3].
Conclusion
Acknowledgments The authors acknowledge support from the
Australian Research Council and the School of Physical and Chem-
ical Sciences, Queensland University of Technology.
The hydrogen 4,5-dichlorophthalate anions have been
shown to promote the formation of one-dimensional
structure extension in 1:1 proton-transfer compounds with
the secondary and tertiary aliphatic amines considered in
this work. These provide further examples demonstrating
the preference for the retention of the planar internally
hydrogen-bonded DCPA monoanion species in the low-
dimensional hydrogen-bonded 1:1 salts with both the ali-
phatic and aromatic Lewis bases.
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