Two anilinium salts: Anilinium hydrogenphosphite and anilinium hydrogenoxalate hemihydrate

Article abstract of DOI:10.1107/S0108270100008015

In the title compounds, C₆H₅NH₃⁺·H₂PO₃^- and C₆H₅NH₃⁺·-C₂HO₄^-·0.5H₂0, the NH₃

Full text of DOI:10.1107/S0108270100008015

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Two anilinium salts: anilinium hydro-
genphosphite and anilinium hydrogen-
oxalate hemihydrate
J. A. PaixÄao,a* A. Matos Beja,a M. Ramos Silvaa and
J. Martin-Gilb
Figure 1
ORTEPII (Johnson, 1976) plot of compound (I). Displacement ellipsoids
are drawn at the 50% probability level.
a
Ã
Â
Departamento de Fõsica, Faculdade de Ciencias e Tecnologia, Universidade de
Coimbra, P-3004-516 Coimbra, Portugal, and bETSII, Tecnologias del Medio
Ambiente, Universidad de Valladolid, SP-47011 Valladolid, Spain
Correspondence e-mail: jap@pollux.fis.uc.pt
tions and that it becomes ordered in the low-temperature
phase. The structural phase transition appears to be explained
in terms of the coupling between the shear strain and ordering
Received 1 March 2000
Accepted 30 May 2000
+
+
+
In the title compounds, C6H5NH3 ÁH2PO3 and C6H5NH3 Á-
of the NH3 group via an acoustic soft phonon mode.
Quasielastic neutron scattering data (Brierley et al., 1982;
Schweiss et al., 1983a,b) con®rm that in the high-temperature
+
C2HO4 Á0.5H2O, the NH3 groups of the anilinium ion are
ordered at room temperature. The rotation of these groups
along the NÐCaryl bond, which is often observed at room
temperature in other anilinium compounds, is prevented by
+
phase the NH3 group has a hindered rotation by jumps of 60ꢁ
around the Caryl±N axis, a model which had been previously
suggested based on indirect evidence of NMR and NQR data.
We have decided to investigate other anilinium compounds
searching for possible occurrence of low-temperature phase
transitions associated with a quenching of the molecular
+
hydrogen bonds between the NH3 group and the anions. In
both compounds, the geometry of the cation is signi®cantly
distorted from D6h to a symmetry close to C2v. The angle ipso
to the substituent is signi®cantly larger than 120ꢁ, as expected
from the ꢀ-electron-withdrawing character of the NH3+ group.
+
rotation of the NH3 group. We have so far found one new
compound, anilinium perchlorate, which possibly falls into this
category. The low-temperature behaviour of this compound
has been studied recently in our laboratory, and an anomalous
behaviour of the dilatation parameters was observed at ca
200 K. This anomaly is probably related to a quenching of the
rotation of the NH3+ group which was shown to be disordered
and possibly rotating at room temperature (PaixaÄo et al.,
1999).
Comment
A number of anilinium compounds exhibit structural phase
transformations induced by order/disorder transitions of the
NH3+ groups. The potential energy barrier for rotation of the
+
NH3 group is small provided the H atoms interact weakly
+
with neighbouring molecules. In this case, the NH3 group
behaves as a molecular rotor at room temperature, but the
rotation is eventually inhibited at a lower temperature. Phase
transitions have been observed most notably on anilinium
halides and in a number of ortho- and para-substituted anili-
nium compounds (Hartmann & Weiss, 1991; Krishnan &
Weiss, 1983). Anilinium bromide is probably the most thor-
oughly studied of these compounds, for which X-ray, neutron
and several spectroscopic studies have been reported
(Schweiss et al., 1983a; Kanesaka & Fujii, 1996; Fecher et al.,
1981). The structure is orthorhombic above Tc = 296.7 K and
becomes monoclinic below this temperature. X-ray, neutron
and NMR studies have shown that in the high-temperature
Figure 2
The packing diagram of compound (I) projected along the a axis showing
the hydrogen-bonding scheme as dashed lines.
+
phase the NH3 group is disordered over two alternate posi-
ꢀ
1132 # 2000 International Union of Crystallography Printed in Great Britain ± all rights reserved
Acta Cryst. (2000). C56, 1132±1135

organic compounds
The OÐPÐO bond angles are in the range 107.4 (9)±
115.70 (8)ꢁ, which are typical values for this ion. The re®ned
Ê
PÐH bond length [1.29 (2) A] is in good agreement with other
X-ray studies of phosphite and hydrogenphosphite salts
(Pecaut & Bagieu-Beucher, 1993; Averbuch-Pouchot, 1993).
The main remarkable feature of the hydrogenoxalate ion is
the twist by 5.15 (3)ꢁ around the central C7ÐC8 bond. Each of
Ê
the two carboxy groups is planar within 0.004 (1) A and the H
atom is also practically planar with the carboxylic group. The
2
2
longer than usual Csp ÐCsp bond [1.5457 (15) A] is char-
Ê
acteristic of the hydrogenoxalate ion [average value
Ê
1.549 (9) A; Allen et al., 1987]. There is a clear asymmetry
between the CÐO bond lengths of the unionized carboxylic
group, which shows that the H atom is not disordered. The
C1ÐO1 and C1ÐO2 bonds are intermediate between the
values of a C O and a CÐO bond and are typical of a
Figure 3
ORTEPII (Johnson, 1976) plot of compound (II). Displacement
ellipsoids are drawn at the 50% probability level.
. . .
Pursuing these studies, we have synthesized and determined
the crystal structure at room temperature of two new anili-
nium salts, anilinium hydrogenphosphite, (I), and anilinium
hydrogenoxalate hemihydrate, (II). The X-ray study reported
delocalized C O bond of a carboxylate group. Most likely,
the small difference between these two bond lengths is due to
a distinct participation of atoms O1 and O2 in hydrogen
bonding. Compound (II) contains a solvent water molecule
sitting on a twofold axis at the special position 4e.
+
here shows that the NH3 group is well ordered at room
temperature in both compounds. Also, powder X-ray diffrac-
tion data collected in our laboratory between 100 K and room
temperature did not show evidence for any phase transition
occurring in this temperature range.
In each salt, full capability for hydrogen bonding of the
anions and amino group is achieved. In compound (I), the
strongest hydrogen bond links directly the hydrogenphosphite
Ê
ions along the 21 screw axis [O3Á Á ÁO2 2.550 (7) A], forming
Similar to other anilinium compounds, the symmetry of the
benzene ring is closer to C2v (mm) than to D6h (6/mmm)
(Colapietro et al., 1981). The distortion of the ring is highly
signi®cant in the two compounds, involving bond distances as
well as angles. The endocyclic angle ipso to the substituent is
larger than 120ꢁ, as expected from the ꢀ-electron withdrawing
zigzag chains running along b. Atom O1 is an acceptor of two
+
protons from the NH3 group [NÐH7BÁ Á ÁO1 2.804 (2); NÐ
Ê
H7CÁ Á ÁO1 2.693 (2) A], the third proton being donated to the
Ê
O2 atom [NÁ Á ÁO2 2.799 (2) A]. In compound (II), the
carboxylic H atom links two hydrogenoxalate ions head-to-tail
forming chains parallel to the b axis. The carboxy O1 and O2
+
+
character of the NH3 group (Domenicano & Murray-Rust,
atoms are acceptors from two distinct H atoms of the NH3
Ê
1979). In both compounds, the two aromatic CÐC bonds
involving the C atom ipso to the substituent, C1ÐC2 and C1Ð
C6, are somewhat shorter than the central CÐC bonds of the
ring, C2ÐC3 and C5ÐC6. The C1ÐN distance is close to the
lower band of the range reported for anilinium salts [average
group [N1Á Á ÁO1 2.7955 (15); N1Á Á ÁO2 2.8067 (14) A], the third
H atom being donated to a water molecule [N1Á Á ÁO5
Ê
2.8163 (15) A], forming an in®nite two-dimensional network
of hydrogen bonds extending in the (100) plane. Atom O3
does not appear to be involved in hydrogen bonding.
Ê
bond distance: 1.465 (7) A; Allen et al., 1987].
In both compounds, the N1 atom deviates from the least-
Ê
squares plane of the ring [(I) 0.032 (3); (II) 0.053 (2) A]. These
deviations correspond to a small out-of-plane bending of the
+
NH3 group by 1.31 (11) and 1.75 (9)ꢁ, respectively, for
compounds (I) and (II). In compound (I), the substituent is
also slightly bent in the plane of the ring towards the atom C6.
+
No sign was found of static or dynamic disorder of the NH3
groups in both compounds, in contrast with other anilinium
salts where the ammonium group is disordered at room
+
temperature (PaixaÄo et al., 1999). In compound (I), the NH3
group is staggered with respect to the ring while in (II), the
+
conformation of the NH3 group is such that one of the H
atoms is almost eclipsed with the ring. This eclipsed confor-
mation was found in a number of anilinium salts and it appears
to be preferred over the staggered conformation.
The geometry of the anions is unexceptional. Inspection of
the PÐO bond of the hydrogenphosphite ion clearly shows
that the acidic H atom is bonded to O3 as there is a signi®cant
lengthening of the PÐO3 bond compared with the other two.
Figure 4
The packing diagram of compound (II) projected along the a axis showing
the hydrogen-bonding scheme as dashed lines. Benzene rings have been
omitted for clarity.
J. A. Paixao et al. C6H8N+ÁH2PO3 and C6H8N+ÁC2HO4 Á0.5H2O 1133
ꢀ
Acta Cryst. (2000). C56, 1132±1135
Ä

organic compounds
Table 3
Selected geometric parameters (A, ) for (II).
Experimental
ꢁ
Ê
Compounds (I) and (II) were synthesized by reacting an aqueous
solution of diphenylformamidine (Aldrich, 99%) with phosphoric
acid (Aldrich, 85%) and oxalic acid, respectively. Single crystals of
prismatic form grew from the solution, by slow evaporation, over a
period of a few months from which one small specimen was selected
and used for X-ray analysis.
O1ÐC7
O2ÐC7
O3ÐC8
1.2453 (14)
1.2365 (14)
1.1963 (14)
O4ÐC8
C7ÐC8
1.3057 (14)
1.5475 (15)
N1ÐC1ÐC2ÐC3
O1ÐC7ÐC8ÐO3
178.38 (13)
5.00 (17)
O2ÐC7ÐC8ÐO4
5.16 (15)
Table 4
Hydrogen-bonding geometry (A, ) for (II).
Compound (I)
ꢁ
Ê
Crystal data
C6H8N+ÁH2PO3
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
3
Dx = 1.409 Mg m
Mo Kꢂ radiation
Cell parameters from 25
re¯ections
N1ÐH1AÁ Á ÁO5i
N1ÐH1BÁ Á ÁO1ii
N1ÐH1CÁ Á ÁO2
O4ÐH4AÁ Á ÁO1i
O5ÐH5AÁ Á ÁO2
0.939 (19)
0.886 (17)
0.926 (19)
0.85 (2)
1.915 (19)
1.949 (17)
1.89 (2)
1.77 (2)
1.898 (19)
2.8163 (15)
2.7955 (15)
2.8067 (14)
2.6177 (14)
2.7516 (13)
160.1 (16)
159.3 (15)
171.2 (17)
173 (2)
Mr = 175.12
Monoclinic, P21=a
Ê
a = 6.216 (2) A
ꢃ = 9.74±15.21ꢁ
ꢄ = 0.292 mm
T = 293 (2) K
Ê
b = 14.219 (6) A
0.877 (18)
163.8 (17)
1
Ê
c = 9.342 (3) A
ꢁ = 90.91 (3)ꢁ
V = 825.6 (5) A
Z = 4
1
2
Symmetry codes: (i) x; y 1; z; (ii) x; 1 y; z
.
3
Ê
Prism, colourless
0.34 Â 0.34 Â 0.34 mm
Compound (II)
Data collection
Crystal data
C6H8N+ÁC2HO4 Á0.5H2O
Enraf±Nonius CAD-4 diffract-
ometer
ꢃ
max = 25.98ꢁ
3
Dx = 1.418 Mg m
Mo Kꢂ radiation
Cell parameters from 25
re¯ections
h = 7 ! 7
Mr = 192.17
Monoclinic, C2=c
Pro®le data from !±2ꢃ scans
3607 measured re¯ections
1612 independent re¯ections
1221 re¯ections with I > 2ꢀ(I)
Rint = 0.023
k = 0 ! 17
l = 11 ! 11
Ê
a = 23.9825 (19) A
3 standard re¯ections
frequency: 180 min
intensity decay: 1%
ꢃ = 11.43±16.26ꢁ
Ê
b = 5.7253 (14) A
1
Ê
c = 13.891 (2) A
ꢄ = 0.117 mm
T = 293 (2) K
ꢁ = 109.340 (11)ꢁ
3
Ê
V = 1799.7 (5) A
Z = 8
Prism, white
0.49 Â 0.48 Â 0.29 mm
Re®nement
Re®nement on F2
R[F2 > 2ꢀ(F2)] = 0.028
wR(F2) = 0.084
S = 1.048
1612 re¯ections
140 parameters
All H-atom parameters re®ned
w = 1/[ꢀ2(Fo2) + (0.0380P)2
+ 0.3216P]
where P = (Fo2 + 2Fc2)/3
(Á/ꢀ)max < 0.001
Data collection
3
Ê
Áꢅmax = 0.25 e A
Enraf±Nonius CAD-4 diffract-
ometer
ꢃmax = 27.47ꢁ
3
Ê
0.25 e A
Áꢅmin
=
h = 0 ! 30
Extinction correction: SHELXL97
(Sheldrick, 1997)
Extinction coef®cient: 0.015 (2)
Pro®le data from !±2ꢃ scans
2189 measured re¯ections
2062 independent re¯ections
1735 re¯ections with I > 2ꢀ(I)
Rint = 0.005
k = 0 ! 7
l = 18 ! 17
3 standard re¯ections
frequency: 180 min
intensity decay: 1.7%
Re®nement
Re®nement on F2
R[F2 > 2ꢀ(F2)] = 0.034
wR(F2) = 0.101
S = 1.054
2062 re¯ections
164 parameters
(Á/ꢀ)max < 0.001
3
Ê
Áꢅmax = 0.31 e A
Table 1
Selected geometric parameters (A, ) for (I).
3
Ê
0.16 e A
Áꢅmin
=
ꢁ
Ê
Extinction correction: SHELXL97
(Sheldrick, 1997)
Extinction coef®cient: 0.0211 (14)
P1ÐO1
P1ÐO2
1.4919 (14)
1.4954 (15)
P1ÐO3
P1ÐH1
1.5538 (16)
1.29 (2)
All H-atom parameters re®ned
w = 1/[ꢀ2(Fo2) + (0.0529P)2
+ 0.8427P]
O1ÐP1ÐO2
O1ÐP1ÐO3
115.70 (8)
107.40 (9)
O2ÐP1ÐO3
111.75 (9)
178.3 (2)
2
2
where P = (Fo + 2Fc )/3
NÐC1ÐC2ÐC3
178.7 (2)
NÐC1ÐC6ÐC5
All H atoms could be clearly located in a difference Fourier
synthesis and have been re®ned isotropically. Examination of the
crystal structures with PLATON (Spek, 1995) showed that there are
no solvent-accessible voids in the crystal lattice for compound (I) and
that no further solvent molecules could be accommodated in
compound (II). All calculations were performed on a Pentium-II
350 MHz PC running LINUX.
Table 2
Hydrogen-bonding geometry (A, ) for (I).
ꢁ
Ê
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
For both compounds, data collection: CAD-4 Software (Enraf±
Nonius, 1989); cell re®nement: CAD-4 Software; data reduction:
HELENA (Spek, 1997); program(s) used to solve structure:
SHELXS97 (Sheldrick, 1997); program(s) used to re®ne structure:
SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII
O3ÐH8Á Á ÁO2i
NÐH7AÁ Á ÁO2ii
NÐH7BÁ Á ÁO1iii
NÐH7CÁ Á ÁO1
0.82 (3)
0.94 (3)
0.87 (3)
0.93 (3)
1.74 (3)
1.88 (3)
2.00 (3)
1.77 (3)
2.550 (2)
2.799 (2)
2.804 (2)
2.693 (2)
173 (3)
165 (2)
154 (2)
174 (2)
Symmetry codes: (i) x; 1 y; 1 z; (ii) ‡ x; 12 y; z; (iii) x
;
2 2
y; z.
1
2
1 1
1134 J. A. Paixao et al. C6H8N+ÁH2PO3 and C6H8N+ÁC2HO4 Á0.5H2O
Acta Cryst. (2000). C56, 1132±1135
ꢀ
Ä

organic compounds
Colapietro, M., Domenicano, A., Marciante, C. & Portalone, G. (1981). Acta
Cryst. B37, 387±394.
Domenicano, A. & Murray-Rust, P. (1979). Tetrahedron Lett. 24, 2283±2286.
Enraf±Nonius (1989). CAD-4 Software. Version 5.0. Enraf±Nonius, Delft, The
Netherlands.
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Johnson, C. K. (1976). ORTEPII. Report ORNL-5138. Oak Ridge National
Laboratory, Tennessee, USA.
(Johnson, 1976); software used to prepare material for publication:
SHELXL97.
The authors are indebted to Dr J. C. Prata Pina for his
invaluable assistance in the maintenance of the CAD-4
diffractometer. This work was supported by FundacËaÄo para a
Ã
Ciencia e para a Tecnologia (FCT).
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È
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Gott-
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Supplementary data for this paper are available from the IUCr electronic
archives (Reference: SK1377). Services for accessing these data are
described at the back of the journal.
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J. A. Paixao et al. C6H8N+ÁH2PO3 and C6H8N+ÁC2HO4 Á0.5H2O 1135
ꢀ
Acta Cryst. (2000). C56, 1132±1135
Ä