Syntheses, crystal structures and thermal behavior of five new complexes containing 2, 4, 6-trifluorobenzoate as ligand

Article abstract of DOI:10.1002/zaac.201200222

Five new complexes containing 2, 4, 6-trifluorobenzoateas ligand have been synthesized and structurally characterized, namely Li(C₆F ₃H₂COO)(H₂O) (P2₁, Z = 2, 1),Cs(C₆F₃H₂COO)(C₆F ₃H₂COOH) (P2₁/c, Z = 4, 2),Cu(C ₆F₃H₂COO)₂(H₂O) ₂ (P1, Z = 1, 3), Cu(C₆F₃H₂COO) ₂(MeOH) (P2₁/c. Z = 4, 4) and Ag(C₆F ₃H₂COO)(H₂O) (C2/c, Z = 8, 5). 1-3 and 5 are coordination polymers forming strands (1, 3, 5) or corrugated layers (2). In 1 and 2 the benzoate ligand acts as a bridging ligand, whereas in 3 and 5 the benzoate ligand is not bridging and the molecular units are interconnected by bridging water molecules. In 4 and 5, dimeric Cu₂ and Ag₂ units, respectively, are formed with short M...M contacts. The dimeric units in 4 resemble the well-known paddlewheel structural motif. In 5 these dimeric units are further connected by bridging water molecules, whereas in 4 only very weak F...H interactions connect the dimeric units. DTA/TG experiments on 1, 3 and 4 reveal that in a first step solvent molecules (H ₂O, MeOH) are unquestionably released. In 1-5 the torsion angles of the carboxylate group with respect to the aromatic ring deviate significantly from zero. These results are in very good agreement with the results of quantum chemical calculations of free 2, 4, 6-trifluorobenzoic acid and its dimer at the DFT and RI-MP2 level of theory. Copyright

Full text of DOI:10.1002/zaac.201200222

ARTICLE
DOI: 10.1002/zaac.201200222
Syntheses, Crystal Structures and Thermal Behavior of Five New Complexes
Containing 2,4,6-Trifluorobenzoate as Ligand
Rainer Lamann,[a] Michael Hülsen,[b] Michael Dolg,[b] and Uwe Ruschewitz*[a]
In Memory of Professor Welf Bronger
Keywords: Carboxylates; Coordination polymers; Crystal structure; Density functional calculations; Fluorinated ligands
Abstract. Five new complexes containing 2,4,6-trifluorobenzoate contacts. The dimeric units in 4 resemble the well-known paddlewheel
as ligand have been synthesized and structurally characterized, structural motif. In 5 these dimeric units are further connected by
namely
Li(C6F3H2COO)(H2O)
(P21,
(P21/c,
Z
Z
=
=
2,
4,
1), bridging water molecules, whereas in 4 only very weak F···H interac-
2), tions connect the dimeric units. DTA/TG experiments on 1, 3 and 4
Cs(C6F3H2COO)(C6F3H2COOH)
¯
Cu(C6F3H2COO)2(H2O)2 (P1, Z = 1, 3), Cu(C6F3H2COO)2(MeOH) reveal that in a first step solvent molecules (H2O, MeOH) are unques-
(P21/c. Z = 4, 4) and Ag(C6F3H2COO)(H2O) (C2/c, Z = 8, 5). 1–3 and tionably released. In 1–5 the torsion angles of the carboxylate group
5 are coordination polymers forming strands (1, 3, 5) or corrugated with respect to the aromatic ring deviate significantly from zero. These
layers (2). In 1 and 2 the benzoate ligand acts as a bridging ligand, results are in very good agreement with the results of quantum chemi-
whereas in 3 and 5 the benzoate ligand is not bridging and the molecu-
lar units are interconnected by bridging water molecules. In 4 and 5,
dimeric Cu2 and Ag2 units, respectively, are formed with short M···M
cal calculations of free 2,4,6-trifluorobenzoic acid and its dimer at the
DFT and RI-MP2 level of theory.
ported for a reliable experimental comparison of their adsorp-
tion properties. But very recently Banerjee et al. reported some
isostructural porous coordination polymers and found that the
H2 uptake is “system-specific”.[5] In a different approach fo-
cusing on the optical properties it was reported that CPs with
perfluorinated ligands show a significantly enhanced lumines-
cence.[6] In this context, we have started to investigate CPs
with fluorinated and perfluorinated aromatic carboxylates as
bridging ligands.[7–9] Indeed, we observed a bright lumines-
cence in CPs of 4f-elements with tetrafluoroterephthalate as
bridging ligand.[9] In this contribution we will report our in-
vestigations on compounds with 2,4,6-trifluorobenzoate as li-
gand. Although an efficient synthesis of 2,4,6-trifluorobenzoic
acid[10,11] is known since 1970,[12] its crystal structure has only
been reported very recently.[13] Even more surprisingly only
two crystal structures of metal 2,4,6-trifluorobenzoates have
been published up to now.[14,15] Both contain dimeric Ru2 units
with a paddlewheel-like arrangement of the trifluorobenzoate
ligands. So the focus of this investigation is on the synthesis
and structural characterization of 2,4,6-trifluorobenzoates with
different metal ions and their thermal behavior. In the follow-
ing, five new complexes will be presented.
Introduction
The replacement of C–H by C–F entities in organic com-
pounds leads to dramatic changes of their properties and reac-
tivities. This aspect is well-known and well-established. But
only recently, it was found that also in the field of coordination
polymers (CPs) and metal-organic frameworks (MOFs) the use
of fluorinated and perfluorinated bridging ligands may lead to
materials with new or at least improved properties. So it was
found that FMOF-1 shows a very high H2 adsorption ca-
pacity.[1] This finding was corroborated by a theoretical inves-
tigation.[2] But in another work only a slightly enhanced H2
adsorption capacity was reported[3] and Klopper et al. calcu-
lated an even lower H2 adsorption enthalpy for fluorobenzene
compared to unsubstituted benzene.[4] These discrepancies can
simply be explained by the fact that for a long time no iso-
structural fluorous and non-fluorous compounds have been re-
* Prof. Dr. U. Ruschewitz
Fax: +49-221-470-3933
E-Mail: Uwe.Ruschewitz@uni-koeln.de
[a] Department für Chemie
Universität zu Köln
Institut für Anorganische Chemie
Greinstraße 6
50939 Köln, Germany
[b] Department für Chemie
Universität zu Köln
Results and Discussion
Institut für Theoretische Chemie
Greinstraße 4
50939 Köln, Germany
Li(C6F3H2COO)(H2O) (1)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201200222 or from the au-
thor.
Lithium-2,4,6-trifluorobenzoate·H2O crystallizes in the
acentric monoclinic space group P21 (Z = 2). The unit cell
Z. Anorg. Allg. Chem. 2012, 638, (᭿), 1–9
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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R. Lamann, M. Hülsen, M. Dolg, U. Ruschewitz
ARTICLE
Figure 1. Left: ORTEP plot (asymmetric unit) of Li(C6F3H2COO)(H2O) (1) with labeling of atoms. Thermal ellipsoids are drawn at the 50%
probability level. Right: Tetrahedral coordination sphere of the lithium ion (O1i: 2–x, 1/2+y, 1–z; O2ii: x, 1+y, z).
parameters are a = 5.411(1) Å, b = 4.9795(9) Å, c = temperature range 270–310 °C a weight loss of approx. 40%
14.775(3) Å, and β = 90.51(2)°. The asymmetric unit is shown is observed, which points to a decomposition of the ligand.
in Figure 1 (left). Li+ occupies the general position 2a and
is coordinated by four oxygen atoms in a slightly distorted
tetrahedral arrangement (Li–O: 1.927(4)–2.022(3) Å; O–Li–O:
Cs(C6F3H2COO)(C6F3H2COOH) (2)
94.64(13)–116.68(15)°, Figure 1 (right)). These oxygen atoms
stem from the carboxylate groups of three trifluorobenzoate
ligands (O1, O2) and one water molecule (O3). The carboxyl-
ate group of the 2,4,6-trifluorobenzoate ligand is μ3-bridging
with O1 coordinating to two Li+ cations. The bridging nature
of the carboxylate groups leads to strands of LiO4 tetrahedra
along [010] (Figure 2).
Cesium-2,4,6-trifluorobenzoate·C6F3H2COOH crystallizes
in the monoclinic space group P21/c (Z = 4) with a =
14.479(2) Å, b = 7.223(1) Å, c = 14.103(4) Å, and β =
90.07(2)°. The asymmetric unit is shown in Figure 3. It con-
sists of one cesium cation, one trifluorobenzoate anion and one
trifluorobenzoic acid molecule.
Figure 3. ORTEP plot (asymmetric unit) of Cs(C6F3H2COO)-
(C6F3H2COOH) (2) with labeling of atoms. Thermal ellipsoids are
drawn at the 50% probability level.
Cs+ occupies the general position 4e and is surrounded by
five oxygen atoms (O1i, O1ii, O2, O3ii and O4). O1 and O2(H)
stem from the acid molecule, whereas O3 and O4 constitute
the carboxylate group of the anion. The bond lengths range
from 3.077(4) Å (Cs1–O1ii) to 3.174(3) Å (Cs1–O2). The
-COOH group of the acid coordinates in a μ3-bridging mode
Figure 2. Strands of bridged LiO4 tetrahedra along [010] in the crystal
structure of Li(C6F3H2COO)(H2O) (1). Hydrogen atoms of water mo-
lecules are omitted.
Weak O–H···O bonds (2.016(2) and 2.125(1) Å) connect with O1 coordinating to two Cs+ cations, whereas the benzoate
these strands to layers in the (001) plane. These layers are anion coordinates in a μ2-bidentate bridging mode. The coordi-
further connected to a 3D structure by weak C–H···F nation sphere of the Cs+ cation with an unusual small coordi-
(2.514(1)–2.535(2) Å) and O–H···F (2.723(1) Å) interac- nation number (CN = 5) is completed by short Cs···F contacts.
tions.[16]
Four such contacts in the range 3.329(4) Å (Cs1–F1) to
The DTA/TG diagram of 1 (Figure S2, Supporting Infor- 3.636(3) Å (Cs1–F5iv) are found as shown in Figure 4. Taking
mation) shows a broad endothermic weight loss of 9.0% in the only Cs–O bonds into account, complex corrugated double-
temperature range 110–150 °C, which corresponds to the re- layers perpendicular to [100] are formed. These layers are ob-
lease of one water molecule (calc.: 9.3%). A sharp endother- viously held together by weaker Cs···F interactions. Within the
mic signal without any weight loss is observed at 250 °C. The layers strong hydrogen bonds are found (O3···H5–O2:
nature of this signal is unclear, but it might be possible that a 1.65(9) Å),[16] which connect the anion and the acid molecule
melting or a phase transition of anhydrous 1 occurs. In the (Figure 3).
2
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Five New Complexes with the Ligand 2,4,6-Trifluorobenzoate
Figure 4. Coordination sphere of the cesium cation in
Cs(C6F3H2COO)(C6F3H2COOH) (2); i: 1–x, –1/2+y, 1/2–z; ii: x,
3/2–y, –1/2+z; iii: 1–x, 1/2+y, 1/2–z; iv: –x, –1/2+y, 1/2–z.
Figure 6. Strands of edge-sharing CuO6 octahedra along [100] in the
crystal structure of Cu(C6F3H2COO)2(H2O)2 (3).
Cu(C6F3H2COO)2(H2O)2 (3)
Within these strands strong hydrogen bonds are found:
O1···H4–O3 = 1.68(9) Å. Weaker hydrogen bonds connect the
strands to layers in the (001) plane: O1···H3–O3 = 2.01(6) Å.
These layers are held together by weak interactions including
H···F interactions starting at 2.521(3) Å.
The DTA/TG curve of 3 (Figure S5, Supporting Infor-
mation) shows a continuous weight loss of approx. 13% start-
ing at 90 °C up to ca. 200 °C. This is much larger than the
weight loss calculated for the release of two water molecules
(8%). Therefore it must be assumed that compound 3 already
starts decomposing at these low temperatures. A further large
weight loss is observed in the temperature range 220–260 °C
(Ͼ 40%). The remaining mass of approx. 30% is larger than
the calculated value for CuO (17.7%).
Copper(II)-2,4,6-trifluorobenzoate·2H2O crystallizes in the
¯
triclinic space group P1 (Z = 1) with a = 3.649(2) Å, b =
6.421(3) Å, c = 16.107(9) Å, α = 80.65(6)°, β = 84.50(6)°, and
γ = 87.40(5)°. The asymmetric unit is shown in Figure 5 (left).
Cu2+ occupies the special position 1e and is coordinated octa-
hedrally by six oxygen atoms (Figure 5, right), which belong
to four water molecules (O3) and the carboxylate groups of
two different benzoate ligands (O2). The second oxygen atom
of the carboxylate group (O1) is non-coordinating, which leads
to a significantly shorter C–O bond (C1–O1 = 1.235(5) Å vs.
C1–O2 = 1.261(4) Å). The bond lengths within the CuO6 octa-
hedron range from 1.931(3) Å (Cu1–O2) to 2.667(3) Å (Cu1–
O3). As expected for Cu2+ (3d9) a strong Jahn–Teller distortion
is observed. Additionally, O–Cu–O angles close to 90°
(89.2(1) and 90.8(1)°) are observed in the square planar CuO4
plane, but the apices of the octahedron are significantly tilted
(O3–Cu1–O3: 77.6(1) and 102.4(1)°, respectively).
Cu(C6F3H2COO)2(MeOH) (4)
Copper(II)-2,4,6-trifluorobenzoate·MeOH crystallizes in the
Compared to 1 and 2, the benzoate ligand in 3 is only uni- monoclinic space group P21/c (Z = 2) with a = 7.665(1) Å, b
dentately bonded to copper and is thus not bridging the copper = 12.596(2) Å, c = 17.206(3) Å, and β = 84.50(6)°. Cu2+ occu-
cations, which are interconnected via water molecules to form pies the general position 4e. For Cu(C6F3H2COO)2 MeOH (4)
strands of edge sharing octahedra along [100] (Figure 6).
the well-known paddlewheel structural motif is found
Figure 5. Left: ORTEP plot (asymmetric unit) of Cu(C6F3H2COO)2(H2O)2 (3) with labeling of atoms. Thermal ellipsoids are drawn at the 50%
i
ii
probability level. Right: Coordination sphere of the Cu2+ cation in 3; : 1–x, 1–y, –z; : 2–x, 1–y, –z; iii: –1+x, y, z.
Z. Anorg. Allg. Chem. 2012, 1–9
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R. Lamann, M. Hülsen, M. Dolg, U. Ruschewitz
ARTICLE
(Figure 7), which was also reported for some RuII-2,4,6-tri- Ag(C6F3H2COO)(H2O) (5)
fluorobenzoates[15] and CuII acetate monohydrate.[17] Each
Silver-2,4,6-trifluorobenzoate·H2O crystallizes in the mono-
copper dimer is bridged by four 2,4,6-trifluorobenzoate ligands
(Cu–O: 1.941(4)–1.988(3) Å). The axial position is coordi-
nated by the MeOH oxygen atom (Cu1–O5: 2.150(6) Å) and
the Cu1–Cu1 distance within the dimer is 2.657(1) Å. All these
distances are very close to those found in CuII acetate monohy-
drate: Cu–Obridging = 1.945–1.994 Å, Cu–Oaxial = 2.156 Å and
Cu–Cu = 2.616 Å. The paddlewheel units in 4 are held to-
gether by weak F···H interactions starting at 2.451(4) Å
(F2···H4).
clinic space group C2/c (Z = 8) with a = 32.405(7) Å, b =
3.6553(6) Å, c = 13.705(3) Å, and β = 90.67(2)°. The asym-
metric unit is shown in Figure 8.
Figure 8. ORTEP plot (asymmetric unit) of Ag(C6F3H2COO)(H2O)
(5) with labeling of atoms. Thermal ellipsoids are drawn at the 50%
probability level.
Ag+ occupies the general position 8f and forms a dimeric
Ag2 unit (Ag–Ag: 2.819(1) Å). Each Ag+ atom is coordinated
by four oxygen atoms: two of them belong to bridging carb-
oxylate groups (Ag1–O2: 2.196(3) Å; Ag1–O1: 2.212(3) Å)
and two to water molecules (Ag1–O3: 2.455(4) Å; Ag1–O3:
2.803(4) Å). The O–Ag–O angles within the AgO4 polyhedron
deviate strongly from the ideal angle in a tetrahedron (109.5°
vs. 70.2(1)–165.1(1)°). The dimeric unit is shown in Figure 9.
Figure 7. Paddlewheel structural motif in Cu(C6F3H2COO)2·MeOH
(4). The labeling of the atoms of the asymmetric unit is given. Thermal
ellipsoids in the ORTEP plot are drawn at the 50% probability level.
It should be emphasized that one of the most famous MOFs
(HKUST-1)[18] also contains a Cu2 paddlewheel as characteris-
tic structural building unit. Here the Cu2 dimers are bridged
by the carboxylate groups of trimesate anions (BTC3–), the
axial positions are occupied by water molecules. As trimesate
is a trifunctional ligand these paddlewheels are connected to
form an open framework structure. The search for an analo-
gous perfluorinated copper trimesate was unsuccessful up to
now. So it is interesting to note that at least with monofunc-
tional 2,4,6- trifluorobenzoate such a Cu2 paddlewheel struc-
tural motif can be obtained.
Figure 9. Dimeric unit in Ag(C6F3H2COO)(H2O) (5).
These dimers are bridged through water molecules to form
strands along [010]. These strands are held together by weak
H···F interactions starting at 2.625(3) Å (H1···F2).
The DTA/TG diagram (Figure S7, Supporting Information)
shows a small endothermic weight loss of 2.5% at about
80 °C, which could not be assigned to any reasonable effect in
Theoretical Investigations
In most coordination compounds containing the benzoate
4. So it might be interpreted as a hint for an impurity in the anion as ligand an almost planar arrangement of the carboxyl-
investigated sample (see: Experimental Section). In the tem- ate group and the phenyl moiety is found (Figure 11). A survey
perature range 120–140 °C another endothermic weight loss of of the Cambridge Structural Database (CSD)[19] shows that in
approx. 7.5% is observed. This agrees well with the calculated more than 40% of the crystal structures containing benzencar-
value for the loss of one coordinating methanol molecule boxylate anions a torsion angle between the carboxylate group
(7.2%). A large weight loss of approx. 50% at 270 °C points and the phenyl ring in the range 0–10° is found. In contrast,
to a decomposition of 4. The remaining mass of approx. 40% for all compounds in this publication containing 2,4,6-trifluo-
is significantly larger than the calculated value for CuO (18%). robenzoate as ligand, a significant twist out of the plane of the
4
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Five New Complexes with the Ligand 2,4,6-Trifluorobenzoate
phenyl ring is observed (Table 1). This effect can be attributed
The results of the calculations on benzoic acid are outlined
to an electrostatic repulsion between the fluorine atoms on the in Table 2. The optimizations of conformer I show that the
ring and the oxygen atoms of the carboxylate groups as well molecule is almost planar for the density functional methods
as a decrease in aromatic character of the carboxylate group as well as for the RI-MP2 method. This is in accordance with
due to the electron-withdrawing nature of the fluorine structural data of benzoates, where mainly planar anions are
atoms.[20,21]
found (Figure 11). The optimized molecular structure of con-
former II of benzoic acid yields a slightly out-of-plane tilted
carboxylate group. The values for the dihedral angles range
from –18.6° to –25.0°. But the relative energies of the com-
pounds show that conformer I is the more stable one (5.5–
6.3 kcal·mol–1, Table S3 in the Supporting Information). The
calculations of the dimers (Table S1, Supporting Information)
yield planar molecular structures for the optimized DFT and
RI-MP2 structures as well. The next step was to find the opti-
mized geometries of 2,4,6-trifluorobenzoic acid. Here, the cal-
culations on conformer I show a different picture: DFT calcu-
lations yield dihedral angles from ca. –39.0° to –43.1°. The
optimizations within the RI-MP2 framework result in even
higher dihedral torsion angles of ca. –46.4° to –49.1°. These
values are similar to the dihedral angles calculated from the
optimization of the dimers (Table S2, Supporting Information).
For conformer II smaller torsion angles are calculated (Table
Table 1. Torsion angles of the carboxylate group with respect to the
phenyl moiety as found in the crystal structures of compounds 1–5
containing 2,4,6-trifluorobenzoate as ligand.
Li(C6F3H2COO)(H2O) (1)
C3–C2–C1–O2
C7–C2–C1–O2
C3–C2–C1–O1
C7–C2–C1–O1
41.5(2)°
–137.7(2)°
–137.8(2)°
43.0(2)°
Cs(C6F3H2COO)(C6F3H2COOH) (2)
O1–C1–C2–C3
O2–C1–C2–C3
O1–C1–C2–C7
O2–C1–C2–C7
O4–C8–C9–C10
O3–C8–C9–C10
O4–C8–C9–C14
O3–C8–C9–C14
–129.3(5)°
50.4(6)°
46.3(6)°
–134.0(4)°
134.8(5)°
–46.8(6)°
–46.4(6)°
132.0(4)°
Cu(C6F3H2COO)2(H2O)2 (3)
O1–C1–C2–C3
O2–C1–C2–C3
O1–C1–C2–C7
O2–C1–C2–C7
–133.0(4)°
46.7(5)°
47.5(6)°
–132.8(3)°
Cu(C6F3H2COO)2(MeOH) (4)
C7–C2–C1–O2
C3–C2–C1–O2
C7–C2–C1–O1
C3–C2–C1–O1
C14–C9–C8–O4
C10–C9–C8–O4
C14–C9–C8–O3
C10–C9–C8–O3
–121.3(6)°
53.0(7)°
58.2(7)°
–127.5(5)°
–88.2(7)°
89.8(7)°
Figure 10. The two possible conformers of benzoic acid (R = H) and
2,4,6-trifluorobenzoic acid (R = F). For I the carboxylate-proton is
orientated away from the phenyl moiety, for II the carboxylate-proton
is pointing towards the substituent at the phenyl moiety.
92.9(7)°
–89.0(6)°
Ag(C6F3H2COO)(H2O) (5)
O1–C1–C2–C3
O2–C1–C2–C3
O1–C1–C2–C7
O2–C1–C2–C7
137.0(4)°
–43.4(6)°
–41.9(6)°
137.7(4)°
In order to investigate the dihedral torsion of the carboxylate
group with respect to the benzene plane in more detail, quan-
tum chemical calculations were carried out on the respective
acids. So the scope of the calculations was on both 2,4,6-tri-
fluorobenzoic acid and benzoic acid; the investigation of the
latter was done for benchmarking purposes. There are two pos-
sible orientations of the hydrogen atom of the carboxylate
group in space. Those rotational conformations are illustrated
in Figure 10. The computational investigation is based on ge-
ometry optimizations of both possible conformers of benzoic
acid and 2,4,6-trifluorobenzoic acid in order to compare the
dihedral angles of the optimized molecular structures. The di-
hedral angles are defined in terms of the atom labels as shown
in Figure 10: α = Є(C4–C2–C1–O6), β = Є(C4–C2–C1–O5),
γ = Є(C3–C2–C1–O6), and δ = Є(C3–C2–C1–O5).
Figure 11. Torsion angles of the carboxylate group vs. the phenyl
moiety of benzoates (dark grey) and 2,6-difluorobenzoates (light grey)
as found in the Cambridge Structural Database (CSD).[19]
.
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R. Lamann, M. Hülsen, M. Dolg, U. Ruschewitz
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Table 2. Calculated dihedral angles for benzoic acid and its 2,4,6-fluorinated derivative.
benzoic acid
Conf.
Method
Basis set
α
β
γ
δ
I
I
I
II
II
II
B3LYP
TZVP
QZVP
QZVP
TZVP
QZVP
QZVP
0.3
0.4
0.0
–20.5
–18.6
–23.8
–179.7
–179.6
–180.0
159.4
161.1
156.0
–179.7
–179.6
–180.0
158.1
160.3
155.2
0.3
0.4
0.0
–22.0
–20.0
–25.0
RI-BP86
RI-MP2
B3LYP
RI-BP86
RI-MP2
2,4,6-trifluorobenzoic acid
Conf.
Method
Basis set
α
β
γ
δ
I
I
I
II
II
II
B3LYP
TZVP
QZVP
QZVP
TZVP
QZVP
QZVP
–40.3
–39.0
131.6
–23.4
–18.4
150.5
139.2
140.5
–49.1
155.9
161.0
–30.4
137.4
138.5
–46.4
154.0
159.7
–27.3
–43.1
–42.0
132.9
–26.7
–20.9
151.8
RI-BP86
RI-MP2
B3LYP
RI-BP86
RI-MP2
2), but it was found that conformer II is less stable than con- dlewheel motif is still formed. So we think that the search for
former I (Table S3, Supporting Information).
isostructural perfluorinated MOFs is still worth the effort.
Despite this nice agreement between computational and ex-
perimental results it should be noted that the calculations were
performed on the acids as optimized gas-phase structures. So-
lid state geometries of the anions should differ to these values.
But nevertheless, the trend is clear: for unsubstituted benzoates
and benzoic acid a planar conformation is preferred, whereas
for fluorinated benzoates and benzoic acid a significant twist
out of the plane of the phenyl moiety is found. Experimentally,
results very similar to our observations in this contribution
were found for 2,6-difluorobenzoates, as shown in Figure 11,
as well as for tetrafluoroterephthalates.[8]
Experimental Section
Li(C6F3H2COO)(H2O) (1): 2,4,6-trifluorobenzoic acid (100 mg,
0.57 mmol) and lithium acetate dihydrate (58 mg, 0.57 mmol) were
dissolved in deionized water (20 mL). After slow evaporation of the
solvent a precipitate was formed, from which single crystals of 1 were
isolated. X-ray powder diffraction patterns (Figure S1 in the Support-
ing Information) confirm that the sample is single phase. Elemental
analysis for Li(C6F3H2COO)(H2O) (200.03 g·mol–1): calcd. C 42.03%,
H 2.02%; found C 42.93%, H 1.92%.
Cs(C6F3H2COO)(C6F3H2COOH) (2): 2,4,6-trifluorobenzoic acid
(100 mg, 0.57 mmol) and cesium acetate (54.7 mg, 0.28 mmol) were
dissolved in deionized water (20 mL). After slow evaporation of the
solvent a precipitate was formed, from which a single crystal of 2 was
isolated. Due to the fact that few single crystals were formed, only an
X-ray powder diffraction pattern of 2 was recorded (Figure S3 in the
Supporting Information) confirming the purity of the sample.
Conclusion
We have synthesized and structurally characterized five
new complexes containing 2,4,6-trifluorobenzoate as ligand.
In two compounds (Li(C6F3H2COO)(H2O) (1) and
Cs(C6F3H2COO)(C6F3H2COOH) (2)) the benzoate ligand acts
as a bridging ligand so that coordination polymers with a 1D
Cu(C6F3H2COO)2(H2O)2 (3): 2,4,6-trifluorobenzoic acid (100 mg,
0.57 mmol) and copper acetate monohydrate (57 mg, 0.28 mmol) were
dissolved in deionized water (20 mL). After slow evaporation of the
solvent a precipitate was formed, from which blue single crystals of
3 were isolated. X-ray powder diffraction patterns (Figure S4 in the
Supporting Information) confirm that the sample is single phase. Ele-
mental analysis for Cu(C6F3H2COO)2(H2O)2 (449.74 g·mol–1): calcd.
C, 37.39%, H, 1.79%, found C, 38.58%, H, 2.38%.
(1) and
a 2D (2) structural motif are formed. In
Cu(C6F3H2COO)2(H2O)2 (3) and Ag(C6F3H2COO)(H2O) (5)
the benzoate ligand is not bridging and the molecular units
are interconnected by bridging water molecules to form 1D
structural motifs. Furthermore, in Cu(C6F3H2COO)2MeOH (4)
and 5, dimeric Cu2 and Ag2 units with short M···M contacts
are found. The dimeric units in 4 resemble the well-known
paddlewheel structural motif that was also found in some
RuII-2,4,6-trifluorbenzoates[15], CuII acetate monohydrate[17]
and the MOF HKUST-1 with 1,3,5-benzenetricarboxylate as
bridging ligand.[18] This seems to be quite remarkable, as a
perfluorinated analogue of this MOF is still unknown. For
comparable MOFs with 1,4-benzenedicarboxylate and its per-
fluorinated congeners as linkers it was argued that a twist of
the carboxylate group out of the plane of the aromatic ring
found in substituted systems is the reason that no isostructural
perfluorinated MOFs can be found.[20] Actually, torsion angles
Cu(C6F3H2COO)2(MeOH) (4): 2,4,6-trifluorobenzoic acid (100 mg,
0.57 mmol) and copper acetate monohydrate (57 mg, 0.28 mmol) were
dissolved in methanol (20 mL). After slow evaporation of the solvent
a precipitate was formed, from which turquoise single crystals of 4
were isolated. In the X-ray powder diffraction pattern (Figure S6 in
the Supporting Information) a small amount of an unidentified impu-
rity was observed. Elemental analysis for Cu(C6F3H2COO)2(CH3OH)
(445.76 g·mol–1): calcd. C, 40.42%, H, 1.81%, found C, 37.17%, H,
1.71%.
Ag(C6F3H2COO)(H2O) (5): 2,4,6-trifluorobenzoic acid (100 mg,
in the range 53.0(7)–58.7(6)° are found in 4, but the pad- 0.57 mmol) and silver acetate (95 mg, 0.57 mmol) were dissolved in
6
www.zaac.wiley-vch.de © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Z. Anorg. Allg. Chem. 2012, 1–9

Five New Complexes with the Ligand 2,4,6-Trifluorobenzoate
methanol (20 mL). After slow evaporation of the solvent a precipitate Crystallographic data (excluding structure factors) for the structures
was formed, from which single crystals of 5 were isolated. In the X-ray
reported in this paper have been deposited with the Cambridge
powder diffraction pattern (Figure S8 in the Supporting Information) a Crystallographic Data Centre as supplementary publications no.
large amount of an unidentified impurity was observed so that no fur-
ther analytical investigations were performed.
CCDC-884743
(Cs(C6F3H2COO)(C6F3H2COOH),
(Li(C6F3H2COO)(H2O),
1),
CCDC-884744
CCDC-884745
2),
(Cu(C6F3H2COO)2(H2O)2, 3), CCDC-884746 (Cu(C6F3H2COO)2-
(MeOH), 4), and CCDC-884747 (Ag(C6F3H2COO)(H2O), 5). Copies
of the data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK [Fax: +44 1223-336-033;
http://www.ccdc.cam.ac.uk/products/csd/request/].
Single Crystal Diffraction
Single crystals of 1–5 were isolated from the precipitates described
above and measured with a Stoe IPDS I single crystal diffractometer
(T ≈ 293 K). The data collection and reduction was performed with
the Stoe program package[22]. The crystal structures were solved by
direct methods using SIR-92[23] or SIR-2004[24]. The structural models
were completed using difference Fourier maps calculated with
SHELXL-97,[25] which was also used for the refinements. All pro-
grams are part of the WINGX program suite.[26] For the refinements
also SHELXLE[27], a frontend for SHELXL-97, was used. A numerical
absorption correction was calculated and applied using X-Red[28] and
X-Shape.[29] All non-hydrogen atoms were refined anisotropically. All
hydrogen atoms belonging to the 2,4,6-trifluorobenzoate ligand were
refined “riding” with fixed C–H distances (0.93 Å). More details of
the crystal structure solution and refinement are given in Table 3.
Elemental Analysis
Elemental analyses were carried out with a CHNS Euro EA 3000 Ana-
lyzer (HEKAtech GmbH).
DTA/TG Measurements
DTA/TG measurements were performed with a NETZSCH STA 409
C using alumina crucibles in a constant argon stream (50 mL·min–1).
The heating rate was 15 K·min–1. Sample masses were in the range
15–20 mg.
X-ray Powder Diffraction (XRPD)
Quantum Chemical Calculations
XRPD patterns were recorded with a Huber G670 Guinier dif-
fractometer with Cu-Kα1 radiation (λ = 1.54051 Å) with a Ge mono-
chromator and an image plate detector. The patterns were measured as
flat samples and are given in the Supporting Information.
The optimizations were carried out with the TURBOMOLE 6.3 pro-
gram package[30] at different levels of theory. At first, standard density
functional theory (DFT) was used for the geometry optimizations. The
Table 3. Crystal and structure refinement data for Li(C6F3H2COO)(H2O) (1), Cs(C6F3H2COO)(C6F3H2COOH) (2), Cu(C6F3H2COO)2(H2O)2
(3), Cu(C6F3H2COO)2(MeOH) (4), and Ag(C6F3H2COO)(H2O) (5).
1
2
3
4
5
Molecular formula
C7H4F3LiO3
200.03
C14H5CsF6O4
484.09
monoclinic
P21/c
C14H8CuF6O6
448.95
C15H8CuF6O5
445.76
monoclinic
P21/c
C7H4AgF3O3
300.97
monoclinic
C2/c
Formula weight /g·mol–1
Crystal system
Space group
T /K
monoclinic
triclinic
a)
¯
P21
P1
293
293
293
293
293
a /Å
b /Å
c /Å
α /°
5.411(1)
4.9795(9)
14.775(3)
90
90.51(2)
90
398.1(1)
2
1.67
14.479(2)
7.223(1)
14.104(2)
90
90.07(2)
90
1475.0(4)
4
2.18
3.649(2)
6.421(3)
16.107(9)
80.65(6)
84.50(6)
87.40(5)
370.5(3)
1
7.665(1)
12.596(2)
17.206(3)
90
101.68(2)
90
1626.9(4)
4
1.82
32.405(7)
3.6553(6)
13.705(3)
90
90.67(2)
90
1623.3(6)
8
2.46
β /°
γ /°
V /Å3
Z
D /g·cm–3
Crystal size /mm
μ /mm-1
2.00
0.1 ϫ 0.1 ϫ 0.1
1.578
0.3 ϫ 0.3 ϫ 0.1
0.1 ϫ 0.1 ϫ 0.1
2.599
0.1 ϫ 0.1 ϫ 0.1
1.433
0.1 ϫ 0.1 ϫ 0.1
b)
b)
–
–
Θmax /°
28.2
28.2
28.2
28.2
28.1
Number of reflections
measured
independent
Number of parameters
R-factors
Io Ͼ 2σ(Io)
3804
1804
127
13278
3312
231
4453
1645
132
15515
3696
248
5497
1938
135
R1 = 0.030
wR2 = 0.062
R1 = 0.048
wR2 = 0.066
0.050
R1 = 0.047
wR2 = 0.130
R1 = 0.054
wR2 = 0.135
0.078
R1 = 0.051
wR2 = 0.124
R1 = 0.072
wR2 = 0.135
0.084
R1 = 0.045
wR2 = 0.074
R1 = 0.147
wR2 = 0.094
0.164
R1 = 0.039
wR2 = 0.096
R1 = 0.058
wR2 = 0.104
0.038
all data
Rint
GooF
0.942
–0.148 / 0.158
1.045
–1.531 / 1.402
1.022
0.736
–0.872 / 0.591
1.042
–1.150 / 0.995
Δρmin/max /e·Å–3
–0.518 / 1.686c)
a) The absolute structure could not be determined, as 1 does not contain any heavy atoms. b) No absorption correction was applied. c) The high
positive electron density is located on the special position 1a (000), 1.845 Å and 1.983 Å apart from the oxygen atoms O1 and O3.
Z. Anorg. Allg. Chem. 2012, 1–9
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
7

R. Lamann, M. Hülsen, M. Dolg, U. Ruschewitz
ARTICLE
[13] R. Betz, T. Gerber, Acta Crystallogr., Sect. E 2011, 67, o539.
[14] Y. Sevryugina, B. Weaver, J. Hansen, J. Thompson, H. M. L. Dav-
ies, M. A. Petrukhina, Organometallics 2008, 27, 1750.
[15] H. Miyasaka, N. Motokawa, R. Atsuumi, H. Kamo, Y. Asai, M.
Yamashita, Dalton Trans. 2011, 40, 673.
[16] G. Jeffrey, An Introduction to Hydrogen Bonding, Oxford Univer-
sity Press New York, 1997.
chosen exchange-correlation functionals are the B3LYP hybrid func-
tional[31–36] and the BP86 generalized-gradient approximation func-
tional.[31,33,36,37] Besides density functional theory, second-order
Møller–Plesset perturbation theory (RI-MP2)[38] was also used for the
optimizations of the molecular structures. It was made use of the fro-
zen-core approximation in the RI-MP2 method i.e. that the 1s orbitals
of carbon, oxygen and fluorine were not correlated. Basis sets of dif-
ferent zeta qualities were used for the different methods. Among these
[17] P. de Meester, S. R. Fletcher, A. C. Skapski, J. Chem. Soc., Dalton
Trans. 1973, 2575.
are the def2-TZVP[39], def2-TZVPP[39] and def2-QZVP[40] basis sets. [18] S. S.-Y. Chui, S. M.-F. Lo, J. P. H. Charmant, A. G. Orpen, I. D.
Williams, Science 1999, 283, 1148.
[19] CSD Database, CCDC Cambridge (UK), Version: 5.33, Feb.
2012.
[20] Z. Hulvey, J. D. Furman, S. A. Turner, M. Tang, A. K. Cheetham,
Cryst. Growth Des. 2010, 10, 2041.
[21] Z. Wang, V. C. Kravtsov, R. B. Walsh, M. J. Zaworotko, Cryst.
Growth Des. 2007, 7, 1154.
[22] Stoe, IPDS Manual; Stoe & Cie GmbH: Darmstadt, 2001.
[23] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M. C.
Burla, G. Polidori, M. Camalli, J. Appl. Crystallogr. 1994, 27,
435.
If the abbreviation of a method is preceded by the flag RI, the usage
of the resolution of identity approximation[41] is implied. In these
cases, the adequate auxiliary basis sets were employed.[42, 43]
Supporting Information (see footnote on the first page of this article):
Experimental and simulated X-ray powder diffraction patterns of com-
pounds 1Ϫ5, DTA/TG diagrams of compounds 1, 3, 4 as well as tables
containing dihedral angles of optimized geometries and relative ener-
gies (kcal·mol–1) of both conformers of benzoic acid and 2,4,6-trifluoro
benzoic acid.
[24] M. C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G. L. Cas-
carano, L. De Caro, C. Giacovazzo, G. Polidori, R. Spagna, J.
Appl. Crystallogr. 2005, 38, 381.
[25] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
[26] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837.
[27] C. B. Hübschle, G. M. Sheldrick, B. Dittrich, J. Appl. Crystallogr.
2011, 44, 1281.
Acknowledgment
The help of Dr. Ingo Pantenburg for X-ray single crystal data collec-
tion, Peter Kliesen for DTA/TG measurements and Silke Kremer for
elemental analysis are acknowledged.
[28] X-Red, Stoe & Cie GmbH: Darmstadt, 2001.
[29] X-Shape, 1.06; Stoe & Cie GmbH: Darmstadt, 1999.
[30] Turbomole, V6.3 2011,
a development of University of
References
Karlsruhe and Forschungszentrum Karlsruhe GmbH, 1989–2007,
TURBOMOLE GmbH, since 2007; available from http://
www.turbomole.com.
[1] C. Yang, X. Wang, M. A. Omary, J. Am. Chem. Soc. 2007, 129,
15454.
[2] L. Zhang, Q. Wang, Y.-C. Liu, J. Phys. Chem. B 2007, 111, 4291.
[3] Z. Hulvey, D. A. Sava, J. Eckert, A. K. Cheetham, Inorg. Chem.
2011, 50, 403.
[4] O. Hübner, A. Glöss, M. Fichtner, W. J. Klopper, J. Phys. Chem.
A 2004, 108, 3019.
[5] P. Pachfule, Y. Chen, J. Jiang, R. Banerjee, Chem. Eur. J. 2012,
18, 688.
[6] B. Chen, Y. Yang, F. Zapata, G. Qian, Y. Luo, J. Zhang, E. B.
Lobkovsky, Inorg. Chem. 2006, 45, 8882.
[7] A. Orthaber, C. Seidel, F. Belaj, R. Pietschnig, U. Ruschewitz,
Inorg. Chem. 2010, 49, 9350.
[8] C. Seidel, R. Ahlers, U. Ruschewitz, Cryst. Growth Des. 2011,
11, 5053.
[9] C. Seidel, C. Lorbeer, J. Cybin´ska, A.-V. Mudring, U. Rusche-
witz, Inorg. Chem. 2012, 51, 4679.
[10] R. J. Harper, E. J. Soloski, C. Tamborski, J. Org. Chem. 1964, 29,
[31] J. C. Slater, Phys. Rev. 1951, 82, 538.
[32] A. D. Becke, J. Chem. Phys. 1993, 98, 5648.
[33] S. H. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 1980, 58, 1200.
[34] C. Lee, W. Yang, R. G. Parr, Phys. Rev. B: Condens. Matter 1988,
37, 785.
[35] P. J. Stephens, F. J. Devlin, C. F. Chabalowski, M. J. Frisch, J.
Phys. Chem. 1994, 98, 11623.
[36] A. D. Becke, Phys. Rev. A 1988, 38, 3098.
[37] J. P. Perdew, Phys. Rev. B 1986, 33, 8822.
[38] F. Weigend, M. Häser, Theor. Chem. Acc. 1997, 97, 331.
[39] F. Weigend, R. Ahlrichs, Phys. Chem. Chem. Phys. 2005, 7, 3297.
[40] F. Weigend, F. Furche, R. Ahlrichs, J. Chem. Phys. 2003, 119,
12753.
[41] K. Eichkorn, O. Treutler, H. Öhm, M. Häser, R. Ahlrichs, Chem.
Phys. Lett. 1995, 240, 283.
[42] F. Weigend, Phys. Chem. Chem. Phys. 2006, 8, 1057.
[43] A. Hellweg, C. Hättig, S. Höfener, W. Klopper, Theor. Chem. Acc.
2007, 117, 587.
2385.
[11] R. J. de Pasquale, C. Tamborski, J. Organomet. Chem. 1968, 13,
273.
Received: May 15, 2012
[12] S. Sugawara, N. Ishikawa, Kogyo Kagaku Zasshi 1970, 73, 972.
Published Online: ᭿
8
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 1–9

Five New Complexes with the Ligand 2,4,6-Trifluorobenzoate
R. Lamann, M. Hülsen, M. Dolg, U. Ruschewitz* .......... 1–9
Syntheses, Crystal Structures and Thermal Behavior of Five
New Complexes Containing 2,4,6-Trifluorobenzoate as Ligand
Z. Anorg. Allg. Chem. 2012, 1–9
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
9