Synthesis and characterization of two bifunctional pyrazole-phosphonic acid ligands

Article abstract of DOI:10.1515/znb-2019-0170

The bifunctional compounds 3,5-dimethyl-4-(4-phosphonophenyl)-1H-pyrazole 1 and 4-(4-phosphonophenyl)-1H-pyrazole 2 were synthesized via Suzuki-Miyaura coupling, starting from a Boc-protected pyrazolylboronic acid ester and the iodoarylphosphonate. The ta

Full text of DOI:10.1515/znb-2019-0170

Z. Naturforsch. 2019; 74(11–12)b: 891–899
BSayhanrethhNaetesghiisanad nChdristcophhaJarniaakc*terization of two bifunctional
pyrazole-phosphonic acid ligands
https://doi.org/10.1515/znb-2019-0170
as carboxylate, pyridyl, sulfonate, amine, etc., have been
used for the synthesis of MOFs, with the most important
and numerous class being the carboxylate compounds
[5]. The far less numerous, but very promising azolate,
especially pyrazolate, as well as phosphonate MOFs are
the main competitors in terms of thermal and chemical,
particularly hydrolytic stability [6, 7]. ZIF-8 [Zn(2-meth-
ylimidazolate)2] [8–10] is one of the most hydrolytically
stable azolate-based MOFs, and has been demonstrated
to be extremely stable in boiling water over a broad pH
range. Pyrazolate-based metal units often possess unsat-
urated metal centres and feature heterogeneous catalytic
properties, like MFU-1 [Co4O(3,5-dimethylpyrazolate)6],
and MFU-2 [Co4O(bdpb)3] (H2-bdpbꢀ=ꢀ1,4-bis[3,5-dimethyl)-
pyrazol-4-yl]benzene) [11] both of which contain redox-
active Co2+ centres. Moreover, coordination polymers and
MOFs based on pyrazolate are interesting for potential
applications such as heat transformation, magnetism, gas
separation, etc. [12–16]. Phosphonate MOFs with proven
porosity are still an emerging area with a relatively limited
Received October 24, 2019; accepted November 4, 2019
Abstract: The bifunctional compounds 3,5-dimethyl-
4-(4-phosphonophenyl)-1H-pyrazole 1 and 4-(4-phosp-
honophenyl)-1H-pyrazole
2
were synthesized via
Suzuki-Miyaura coupling, starting from a Boc-protected
pyrazolylboronic acid ester and the iodoarylphospho-
nate. The target compounds were isolated after acidic
hydrolysis in the form of the hydrochloride salts 1ꢀ·ꢀHCl
and 2ꢀ·ꢀHClꢀ·ꢀH2O with a yield of 81% and 86%, respectively.
Pd(dppf)Cl2 was found to be superior to Pd(PPh3)4 as a cat-
alyst; dry 1,4-dioxane as a solvent, Cs2CO3 as a base, and
no co-ligands were the best found conditions. The alterna-
tive routes through iodoarylphosphonate of iodoarylpyra-
zole, with the crucial steps based on the copper-catalyzed
coupling with acetylacetone or the Arbuzov reaction were
proven inefficient. The structures of the isolated hydro-
chloride salts 1ꢀ·ꢀHCl and 2ꢀ·ꢀHClꢀ·ꢀH2O feature hydrogen-
bonded networks involving the chloride anions.
Keywords: bifunctional ligands; hydrogen bond; phos- results, which are, though, very important, due to their
phonate; pyrazolate; Suzuki-Miyaura.
typically high stability. The scarcity of the results might be
explained by the propensity of the phosphonates to form
layered structures. The polymorphism, typical for multi-
dentate ligands, and low-reversibility of metal-ligand
bond formation, which hinders the isolation of good-
quality single-crystals, further complicate the synthesis
and investigation of porous metal-phosphonate networks
[17, 18]. Clearfieldetal. havedoneextensiveworktoprepare
a series of mesoporous metal phosphonate frameworks
with 1,4-phenylenediphosphonate and biphenyldiphos-
phonate as ligands and zirconium as the metal atom [19].
Wharmby et al. reported a series of isoreticular compounds
based on the linkers N,N′-piperazinediphosphonate
and N,N′-bispiperidinediphosphonate with Ni and Co
as metal atoms, which are porous to N2 with a pore
volume of up to 0.68 cm3 g−1 [20]. More recently, the sorp-
tion properties of M-CAU-29 (M=Ni, Mn, Co and Cd),
1 Introduction
The development of new ligand classes is crucial for the
progress of the field of coordination polymers (CPs) and,
in particular, its most important sub-field of metal-organic
frameworks (MOFs). The increase of the stability and
the tuning of structural characteristics of CPs/MOFs are
important for various potential applications, including
catalysis, gas storage and separation, sensing and heat
transformation [1–4]. In recent years, many types of poly-
topic organic ligands with different donor groups, such
having
a porphyrin-based tetraphosphonate linker,
*Corresponding author: Christoph Janiak, Institut für Anorganische
Chemie und Strukturchemie, Heinrich-Heine-Universität Düsseldorf,
Universitätsstraße 1, D-40225 Düsseldorf, Germany,
Tel.: +ꢀ49-211-81-12286, E-mail: janiak@uni-duesseldorf.de
Bahareh Nateghi: Institut für Anorganische Chemie und
Strukturchemie, Heinrich-Heine-Universität Düsseldorf,
Universitätsstraße 1, D-40225 Düsseldorf, Germany
were studied [21]. Ni-CAU-29 shows no uptake of N2 at
Tꢀ=ꢀ77 K, but a water uptake of 181 mg g−1 at 298 K. Mn-,
Co- and Cd-CAU-29 show N2 uptakes of 90, 145 and 180 m2
g−1 and H2O uptakes of 140, 166 and 116 mg g−1, respec-
tively. Further, Ni-metallated porphyrin-based tetraphos-
phonates with Zr and Hf atoms as metal nodes (Zr- and
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892ꢀ ꢀB. Nateghi and C. Janiak: Pyrazole-phosphonic acid ligands
Hf-CAU-30) demonstrated high specific surface areas of
1070 and 1030 m2 g−1, respectively [22].
2 Results and discussion
The use of the mixed-functional ligands is an Our strategy was to use the 1,4-diiodobenzene as a start-
approach to combine the advantages of different types ing compound and to substitute the iodine atoms sequen-
of coordination groups and to use them synergistically tially by pentane-2,4-dion-3-yl (i.e. acetylacetonyl, as a
in the structural context [23, 24]. The pyrazolate and 3,5-dimethylpyrazole synthon) and diethylphosphonyl
phosphonate pair is especially interesting, allowing to groups in either order. This route should potentially allow
target both single- and bimetal species. Indeed, both the preparation of the target compounds on a large scale
the pyrazolate and phosphonate ligands are effectively at low cost.
coordinated by divalent transition metal ions. However,
In the first attempted sequence, 3-(4-iodophenyl)-
the pyrazolate anion is more affine to ‘softer’ metal ions 2,4-pentadione was prepared according to a method
(e.g. Cu2+, Zn2+), while the oxygen-donating phospho- of Liu et al. [32], starting from 1,4-diiodobenzene and
nate group prefers ‘hard’ metal ions (e.g. Fe3+, Zr4+) in acetylacetone in the presence of CuI/l-proline as cata-
the HSAB [25] concept, which would allow for the tar- lyst (Scheme 1a). This intermediate and hydrazine mono-
geted bimetal approach. Mixed pyrazolate/phosphonate hydrate were dissolved in deionized water to afford the
MOFs are yet practically unknown. However, existing respective 3,5-dimethylpyrazole, following a known
mixed-ligand CPs with versatile architectures [26, 27], procedure by Spassow [33]. However, the next step to
with a combination of (organo)phosphonate groups synthesize the phosphonate ester through the nickel(II)
[28, 29] together with separate pyrazolate ligands, prove catalyzed conversion was not successful. The NH-pyrazole
the viability of the concept. Besides, high chemical is evidently not inert under the conditions of the Michae-
and thermal stabilities could also be expected as in the lis-Arbuzov reaction, which proceeds at high temperature
already more advanced CPs with mixed-functional car- (note, that under these conditions the acetylacetonyl pre-
boxylate-pyrazolate [13, 30] or carboxylate-phosphonate cursor is expected to be even less inert).
linkers [31].
In the reverse sequence (Scheme 1b), the diethyl
In this work, we have developed the synthesis of 4-iodophenylphosphonate was synthesized in the first
bi- or mixed-functional pyrazole-phosphonic acid mole- step, followed by a conversion attempt to diethyl-4-
cules based on a p-phenylene core, which should be (pentane-2,4-dion-3-yl)phenylphosphonate. A mixture of
primary targets as MOF ligands. To the best of our knowl- products was obtained and the purification trials, includ-
edge, 3,5-dimethyl-4-(4-phosphonophenyl)-1H-pyrazole ing column chromatography, were not successful.
and 4-(4-phosphonophenyl)-1H-pyrazole (Schemes
1
The failure of stepwise introduction of functionalities
and 2) are unknown so far, possibly because their low- prompted us to turn to the Suzuki-Miyaura cross-coupling
cost large-scale preparation is problematic, as is shown reaction between components already containing the
below.
necessary functionalization (Scheme 2). Commercially
Scheme 1:ꢁPotential, but unsuccessful routes towards 3,5-dimethyl-4-(4-phosphonophenyl)-1H-pyrazole, 1 starting from 1,4-diiodobenzene.
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B. Nateghi and C. Janiak: Pyrazole-phosphonic acid ligandsꢂ
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Scheme 2:ꢁReaction sequence for the successful synthesis of 1ꢀ·ꢀHCl and 2ꢀ·ꢀHClꢀ·ꢀH2O starting from 1,4-diiodobenzene.
+
available pinacol esters of the 1-Boc-3,5-dimethylpyra- pyrazolium-phosphonic acid or HAB molecules (Fig. 1b).
zole-4-boronic acid or 1-Boc-pyrazol-4-boronic acids Two pyrazolium moieties and two chloride ions are asso-
+
(Boc stands for N-tert-butyloxycarbonyl) were used as ciated in a 10-membered {-pzH ꢀ·ꢀ·ꢀ·ꢀCl−}2 hydrogen-bonded
the pyrazole containing reactants, and the synthesized ring motif, sustained by two strong charge-assisted
+
diethyl 4-iodophenylphosphonate as the phosphonate NH ꢀ·ꢀ·ꢀ·ꢀCl− hydrogen bonds. The two NHꢀ·ꢀ·ꢀ·ꢀCl distances
containing one. Our analysis of the literature indicated are slightly different with 3.060(2) and 3.169(2) Å, but
that while 1H-pyrazoles could participate in the Suzuki- are within the expected range of 3.05–3.2 Å for compara-
+
Miyaura coupling, both the number of steps and the yields ble NH ꢀ·ꢀ·ꢀ·ꢀCl− cases [35]. The observed ring motif has a
R2 (10)
are lower compared to the cases when N-protected pyra- graph set descriptor of
[36], which is typically seen
4
zoles are used. Pd(dppf)Cl2 as a catalyst demonstrated in structures of pyrazolium salts with halide anions [37].
higher efficiency compared to Pd(PPh3)4, and performed The phosphonic acid groups are also associated pairwise,
R2 (8)
well in dry 1,4-dioxane at Tꢀ=ꢀ100°C for 6 h, in the pres- forming simple {RPO(OH)2}2 rings with a
graph set
2
ence of Cs2CO3 as a base [34]. The bifunctional pyrazole- notation. This simple and symmetric association mode,
phosphonic acid was obtained through the hydrolysis of well-known for carboxylic acids, is common for com-
the obtained esters, thus liberating the phosphonic acid pounds containing a similar 1:1 donor/acceptor XO(OH)
and the 1H-pyrazole groups.
fragment (X=C, P, S) [38]. The {RPO(OH)2}2 ring is planar
Thus, 3,5-dimethyl-4-(4-phosphonophenyl)-1H-pyra- and built by strong O–Hꢀ·ꢀ·ꢀ·ꢀO bonds, with a typical Oꢀ·ꢀ·ꢀ·ꢀO
zole, 1, and 4-(4-phosphonophenyl)-1H-pyrazole, 2, were distance of 2.546(2) Å [39]. The additional P–OH donor of
synthesized via coupling and subsequent hydrolysis. The the phosphonic acid group, which is not involved in the
products were isolated in the form of the hydrochlorides formation of the ring pattern, forms a strong hydrogen
1ꢀ·ꢀHCl and 2ꢀ·ꢀHClꢀ·ꢀH2O in overall yields of 32% and 33%, bond with the chloride anion of a neighboring hydrogen-
+
respectively (Scheme 2).
bonded chain, d(Oꢀ·ꢀ·ꢀ·ꢀCl)ꢀ=ꢀ2.976(2) Å (Fig. 1c). The (···ꢀ H
Colorless needle-like crystals of 1ꢀ·ꢀHCl and ABꢀ·ꢀ·ꢀ·ꢀBAH ꢀ·ꢀ·ꢀ·ꢀ2Cl−)n chains are, thereby, associated into
2ꢀ·ꢀHClꢀ·ꢀH2O were obtained by slow evaporation of hydro- sheets, which in turn are held together by weaker inter-
chloric acid solutions of 1 and 2. The phase purities of the actions, among which very weak methyl-CHꢀ·ꢀ·ꢀ·ꢀO and
bulk samples were verified by comparison of the powder methyl-CHꢀ·ꢀ·ꢀ·ꢀCl− contacts are discernible.
+
X-ray diffraction patterns with the simulations from the
obtained single crystal X-ray data sets (Fig. S8 and Fig. are not packed tightly to have a possible additional sta-
S17; Supporting information available online). bilization from πꢀ·ꢀ·ꢀ·ꢀπ interactions. The latter would be
The chains within the stacks are not planar and hence
Compound 1ꢀ·ꢀHCl crystallizes in the monoclinic space typical for planar chains in bipyrazolium salts [37]. Two
group P21/c the co-crystallizing molecule hydrochlo- factors lead to the non-planarity: the {RPO(OH)2}2 ring
ric acid protonating the pyrazole group to a pyrazolium pattern is not co-planar to that of the phenyl group due to
cation (Fig. 1a). The structure of 1ꢀ·ꢀHCl can be dissected the tetrahedral environment of the phosphorus atom and
into hydrogen-bonded chains of centrosymmetric (···ꢀ the phenyl ring is not coplanar with the pyrazole ring. The
+
+
HABꢀ·ꢀ·ꢀ·ꢀBAH ꢀ·ꢀ·ꢀ·ꢀ2Cl−)n aggregates of the bifunctional latter deviation is due to repulsion of the methyl groups of
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894ꢀ ꢀB. Nateghi and C. Janiak: Pyrazole-phosphonic acid ligands
Fig. 1:ꢁ(a) Asymmetric unit (50% displacement ellipsoids), (b) chain sub-structure and (c) two-dimensional hydrogen-bonded network of
1ꢀ·ꢀHCl. Details of the hydrogen-bonding interactions (orange dashed lines) are given in Table 2.
the pyrazole ring and the hydrogen atoms on the phenyl an overall three-dimensional supramolecular struc-
group. The dihedral pyrazole-phenyl angle is ~3 7. 5 °.
ture, which consists of strong charge-assisted OHꢀ·ꢀ·ꢀ·ꢀCl−,
+
Compound 2ꢀ·ꢀHClꢀ·ꢀH2O crystallizes in the monoclinic NH ꢀ·ꢀ·ꢀ·ꢀCl−, plus OHꢀ·ꢀ·ꢀ·ꢀO and weak CHꢀ·ꢀ·ꢀ·ꢀCl− hydrogen
space group P21/c. The structure incorporates also a water bonds (Fig. 2b). The phenyl and pyrazolium rings are not
molecule of crystallization (Fig. 2a) to give the crystallo- coplanar but form a dihedral angle of 11.37(7)°.
graphic formula 2ꢀ·ꢀHClꢀ·ꢀH2O. Again, the hydrochloric acid
The thermogravimetric behavior of 1ꢀ·ꢀHCl shows a
molecule protonates the pyrazole group to a pyrazolium weight loss of 11.3% between Tꢀ=ꢀ150 and 250°C, which
cation. The water molecule perturbs the expected simple corresponds to the one molecule of hydrogen chloride
chain association which was seen in the structure of 1ꢀ·ꢀHCl (12.5% theoretically) (Fig. 3). The mass loss of ~5% in the
(Fig. 2b). The water molecule is held by hydrogen bonding range of 250 and 350°C is assigned to the dehydration (−1
from an N–H donor and to a Cl− and O(3)ꢀ=ꢀP acceptor. H2O, 7% theoretically) through the condensation of phos-
Each Cl− anion interacts with three H atoms (Fig. 2b), one phoric acid groups to give anhydrides [40].
+
from pzH , one from an H atom of {(RPO(OH)2)} and one
The themogravimetric behavior of 2ꢀ·ꢀHClꢀ·ꢀH2O in
from an H atom of the water molecule. The crystal struc- Fig. 4 shows a weight loss of 5.3% between Tꢀ=ꢀ60 and
ture shows a hydrogen-bonded network with head-to-tail 150°C corresponding to the one molecule of water (6.1%
+
linked pyrazolium-phosphonic acid or HAB molecules theoretically). The second step of 8.4% in the tempera-
+
via the N–Hꢀ·ꢀ·ꢀ·ꢀCl− hydrogen bonds between the –N2H2
ture range of 150–320°C is assigned to the one molecule of
and –PO3H2 moieties. Compound 2ꢀ·ꢀHClꢀ·ꢀH2O displays hydrogen chloride (14.2% theoretically).
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Fig. 2:ꢁ(a) Asymmetric unit (50% displacement ellipsoids) and (b) section of the three-dimensional hydrogen-bonded network of
2ꢀ·ꢀHClꢀ·ꢀH2O. Details of the hydrogen-bonding interactions (orange dashed lines) are given in Table 3.
Fig. 3:ꢁTGA diagram of 1ꢀ·ꢀHCl in the temperature range 27–600°C
Fig. 4:ꢁTGA diagram of 2ꢀ·ꢀHClꢀ·ꢀH2O in the temperature range
with a heating rate of 5 K min−1 under N2 atmosphere.
27–600°C with a heating rate of 5 K min−1 under N2 atmosphere.
3 Experimental section
absorbance bands are presented by using of the following
abbreviations: strong (s), medium (m), weak (w), broad
(br) and shoulder (sh). The powder X-ray diffraction pat-
terns (PXRD) were recorded using a Bruker AXS D2 Phaser
3.1 Materials and measurements
All reagents and starting materials were commercially with a flat silicon low background sample holder, using
available and used without further purification. Elemen- CuKα radiation with λꢀ=ꢀ1.5418 Å at 30 kV, 10 mA and a
tal analyses were performed on a Perkin Elmer CHN Lynxeye 1D detector. The measurement was performed at
1
13
31
2400 (Perkin Elmer, Waltham, MA, USA). H, C, P NMR room temperature with 2θ angles in the range 5–50° and a
spectra were collected with a Bruker Avance DRX-300 step size of 0.02° (in 2θ). Thermogravimetric analysis data
or Bruker Avance DRX-600 instrument. FT-IR spectra (TGA) was collected on a Netzsch TG 209 F3 Tarsus instru-
were recorded in ATR mode on a Bruker TENSOR 37 IR ment (Netzsch, Selb, Germany) equipped with an alu-
spectrometer (Bruker Optics, Ettlingen, Germany). The minum crucible and using a heating rate of 5 K min−1 in air.
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896ꢀ ꢀB. Nateghi and C. Janiak: Pyrazole-phosphonic acid ligands
3.2.3 Synthesis of 3,5-dimethyl-4-(4-phosphonophenyl)-
3.2 Synthesis of 3,5-dimethyl-4-(4-phosp-
1H-pyrazole, 1ꢁ·ꢁHCl
honophenyl)-1H-pyrazole, 1ꢁ·ꢁHCl
3.2.1 Synthesis of diethyl 4-iodophenylphosphonate
In a 15 mL Pyrex tube 0.76 g (0.002 mol) of 3,5-dimethyl-
4-(4-phosphonophenyl)-1-tert-butoxycarbonyl-pyrazole
In a two necked 50 mL flask 3.0 g (0.009 mol) of 1,4-dii- was dissolved in 3.0 mL of concentrated HCl and heated
odobenzene and 0.059 g (0.0004 mol) of anhydrous to 100°C for 24 h. A colourless crystalline product was
NiCl2 were suspended in 10 mL of mesitylene. The sus- obtained, which was dried in air (Fig. S7). Yield 0.61 g
pension was placed under nitrogen and heated to 160°C (81%). m.p. >350°C, decomp. >400°C. Elemental analysis
with refluxing. After 1 h 1.74 g (0.01 mol) of triethyl calcd. (%) for C11H14N2O3PCl: C 45.77, N 9.70, H 4.89; found C
phosphite was added dropwise over 2 h. After reflux- 44.25, N 9.75, H 3.43. – FT-IR ATR (neat): νmax (cm−1)ꢀꢀ=ꢀꢀ2708
ing for another 2 h for completion of the reaction, the (br), 1595 (w), 1203 (s), 1139 (s), 981 (s), 914 (s), 835 (s),
yellow suspension was allowed to cool to the room tem- 603 (s) (Fig. S9). – 1H NMR (300 MHz, NaOD, DMSO-d6): δ
perature. The yellow mixture was filtered to remove the (ppm)ꢀ=ꢀ2.24 (s, 6H), 7.23 (m, 2H), 7.68 (m, 2H) (Fig. S10). –
rest of nickel salt, washed with hexane and heated to 13C NMR (300 MHz, NaOD, DMSO-d6): δ (ppm)ꢀ=ꢀ12.91 (CH3),
130°C to remove mesitylene. The excess of solvent was 115.45 (C–N), 127–144.60 (aromatic C atoms) (Fig. S11). –
removed under reduce pressure. The yellow residue was 31P{H} NMR (300 MHz, NaOD, DMSO-d6): δ (ppm)ꢀ=ꢀ12.48
subjected to column chromatography (silica gel, 1:1 ethyl (Fig. S12).
acetate:hexane). The resulting liquid was dried under
reduce pressure to afford 1.83 g (61%) of pure product.
1
– H NMR (300 MHz, CDCl3): δ (ppm)ꢀ=ꢀ1.31 (t, 6H), 4.11 3.3 Synthesis of 4-(4-phosphonophenyl)-
(q, 4 H), 7.51 (d, 2H), 7.82 (d, 2H) (Fig. S1). – 13C NMR
1H-pyrazole, 2ꢁ·ꢁHClꢁ·ꢁH2O
(300 MHz, DMSO-d6): δ (ppm)ꢀ=ꢀ16.94 (CH3), 62.88 (CH2),
127.38 (O–CH3), 129.9 (O–CH3), 133.80–138.39 (aromatic 3.3.1 Synthesis of 4-(4-phosphonophenyl)-1-tert-
31
C atoms) (Fig. S2). – P{H} NMR (300 MHz, DMSO-d6): δ
(ppm)ꢀ=ꢀ18.05 (Fig. S3).
butoxycarbonyl-pyrazole
In a two necked 250 mL flask 1.0 g (0.003 mol) of diethyl
4-iodophenylphosphonate, 1.04 g (0.004 mol) of 1-Boc-
pyrazol-4-boronic acid pinacol ester and 3.8 g (0.012 mol)
3.2.2 Synthesis of 3,5-dimethyl-4-(4-phosphonophenyl)- of Cs2CO3 were placed under nitrogen and suspended in
1-tert-butoxycarbonyl-pyrazole
100 mL of 1,4-dioxane. Finally, 0.12 mg (0.15 mmol) of
Pd(dppt)Cl2 was added under constant stirring. The sus-
According to the Suzuki-Miyaura cross-coupling reaction pension was heated to 100°C for 6 h. After the reaction
[41], 1.0 g (0.003 mol) of diethyl 4-iodophenylphospho- was completed as monitored by TLC, the cooled dark
nate, 1.1 g (0.004 mol) of 3,5-dimethylpyrazole-4-boronic beige suspension was filtered and subjected to column
acid pinacol ester, and 3.9 g (0.012 mol) of Cs2CO3 were chromatography (silica gel, 97: 3% ethyl acetate-metha-
1
placed in a two necked 250 mL flask under nitrogen and nol) to yield 0.79 g (79%) of pure oily product. – H NMR
suspended in 100 mL of 1,4-dioxane. Finally, 0.122 mg (300 MHz, CDCl3): δ (ppm)ꢀ=ꢀ1.33 (t, 3H), 1.68 (s, 9H), 4.15
(0.15 mmol) of Pd(dppt)Cl2 was added under constant stir- (m, 4H), 7.61 (m, 2H), 7.80 (m, 2H), 8.03 (s, 1H), 8.38 (s,
ring. The suspension was heated to 100°C for 6 h. After 1H) (Fig. S13). – 13C NMR (300 MHz, CDCl3): δ (ppm)ꢀ=ꢀ16.34
the reaction was completed as monitored by TLC, the (CH3), 24.54 (CH3), 62.27 (CH3), 86.0 (CH2), 125.75 (s, C–N),
cooled dark beige suspension was filtered and subjected 127.21 (C–O), 141.65 (aromatic C atoms) (Fig. S14). – 31P{H}
to column chromatography (silica gel, 97: 3% ethyl ace- NMR (300 MHz, CDCl3): δ (ppm)ꢀ=ꢀ13.03 (Fig. S15).
tate-methanol) to yield 0.76 g (76%) of pure oily product.
1
– H NMR (600 MHz, CDCl3): δ (ppm)ꢀ=ꢀ1.35 (t, 6H), 1.66
(m, 9H), 2.26 (s, 3H), 2.46 (s, 3H), 4.19 (q, 4H), 7.32 (d, 3.3.2 Synthesis of 4-(4-phosphonophenyl)-1H-pyrazole,
13
2H), 7.84 (d, 2H) (Fig. S4). – C NMR (600 MHz, CDCl3):
δ (ppm)ꢀ=ꢀ16.75 (CH3), 28.42 (CH3), 62.59 (CH3), 85.74 (CH2)
136.83 (s, C–N), 140.70 (C–O), 148.89–150.69 (aromatic In
2ꢁ·ꢁHClꢁ·ꢁH2O
a
15 mL Pyrex tube 0.79 g (0.002 mol) of
C atoms) (Fig. S5). – 31P{H} NMR (600 MHz, CDCl3): δ 4-(4-phosphonophenyl)-1-tert-butoxycarbonyl-pyrazole
(ppm)ꢀ=ꢀ18.61 (Fig. S6).
was dissolved in 3.0 mL of concentrated HCl and heated
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Table 1:ꢁCrystal data and structure refinement for 1ꢀ·ꢀHCl and
2ꢀ·ꢀHClꢀ·ꢀH2O.
analysis calcd. (%) for C9H12N2O4PCl: C 38.80, N 10.05, H
4.34; found C 38.88, N 10.96, H 4.10. – FT-IR ATR (neat):
νmax (cm−1): 3120 (v), 1682 (w), 1607 (w), 1139 (s), 1050 (s),
992 (s), 926 (s), 827 (s), 741 (s), 572 (s) (Fig. S18). – 1H NMR
(600 MHz, NaOD, DMSO-d6): δ (ppm)ꢀ=ꢀ7.65 (m, 2H), 7.70
(m, 2H), 8.17 (s, 1H) (Fig. S19). – 13C NMR (600 MHz, NaOD,
DMSO-d6): δ (ppm)ꢀ=ꢀ123.76 (C–N), 130–136 (aromatic C
atoms) (Fig. S20). – 31P{H} NMR (600 MHz, NaOD, DMSO–
d6): δ (ppm)ꢀ=ꢀ12.96 (Fig. S21).
1ꢁ·ꢁHCl
2ꢁ·ꢁHClꢁ·ꢁH2O
Empirical formula
Mr/g mol−1
T/K
C11H14N2O3PCl
288.66
100(2)
C9H12N2O4PCl
278.63
100(2)
Wavelength/Å
Crystal system
Space group
a/Å
1.54178
Monoclinic
P21/c
1.54178
Monoclinic
P21/c
9.5963(19)
7.7811(16)
17.424(4)
95.52(3)
1295.0(5)
4
7.8070(5)
12.6042(8)
12.3523(8)
90.595(2)
1215.41(13)
4
b/Å
c/Å
β/deg
3.4 Single crystal X-ray diffraction
V/Å3
Z
Selected needle-like single crystals of suitable optical
quality of 1ꢀ·ꢀHCl and 2ꢀ·ꢀHClꢀ·ꢀH2O selected under a polar-
izing microscope and coated in perfluorinated oil were
mounted on a 0.2 mm cryo loop and transferred to the
diffractometer, a Bruker Kappa APEX2 CCD X-ray dif-
fractometer system (Bruker AXS Inc., Madison, WI, USA)
with microfocus tube, CuKα radiation (λꢀ=ꢀ1.54178 Å),
100ꢀ ꢀ2 K; multilayer mirror system, ω scans; data col-
lection with Apex2 [42], cell refinement with Smart and
Calcd. density/g cm−3
μ/mm−1
1.48
1.52
3.8
4.1
F(000)/e
600
576
Crystal size/mm3
θ range/deg
Reflections collected
Independent reflections; Rint
Completeness to θmax/%
Data; ref. parameters
Goodness-of-fit
R1; wR2 (all data)
Δρfin (max; min), e Å−3
0.4ꢀ×ꢀ0.2ꢀ×ꢀ0.1
4.629–68.021
14 605
2327; 0.0477
99.0
2327; 219
1.003
0.0379; 0.1075
0.595; −0.537
0.4ꢀ×ꢀ0.1ꢀ×ꢀ0.05
5.013–66.653
16 599
1241; 0.0371
99.7
2141; 202
1.059
0.0310; 0.0869 data reduction with Saint [43], experimental absorption
0.536; −0.312
correction with Sadabs [44]. The information regarding
data collection and structure refinement is summarized
in Table 1. The structures were solved by Direct Methods
to 100°C for 24 h. A colourless crystalline product was using Shelxl2016 [45, 46] and refined by full-matrix least-
obtained, which was dried in air (Fig. S16). Yield 0.68 squares on F2 using Shelx-97. Graphics were drawn with
g (86%). m.p. >300°C, decomp. >350°C. – Elemental Diamond [47].
Table 2:ꢁDetails of the hydrogen-bonding interactions in 1ꢀ·ꢀHCl.
a
D–Hꢁ·ꢁ·ꢁ·ꢁA
D–H/Å
Hꢁ·ꢁ·ꢁ·ꢁA/Å
Dꢁ·ꢁ·ꢁ·ꢁA/Å
D–Hꢁ·ꢁ·ꢁ·ꢁA/deg
Symmetry transformations
N1–H1ꢀ·ꢀ·ꢀ·ꢀCl1
O1–H1ꢀ·ꢀ·ꢀ·ꢀCl1i
N2–H2ꢀ·ꢀ·ꢀ·ꢀCl1ii
O2–H2ꢀ·ꢀ·ꢀ·ꢀO3iii
C1–H1Bꢀ·ꢀ·ꢀ·ꢀO1iv
C5–H5Aꢀ·ꢀ·ꢀ·ꢀCl1v
0.83(3)
0.85(4)
0.82(3)
0.81(3)
0.95(3)
1.01(3)
2.24(3)
2.13(4)
2.40(3)
1.74(3)
2.60(3)
2.86(3)
3.060(2)
2.976(2)
3.169(2)
2.546(2)
3.388(3)
3.692(2)
170(2)
170(3)
157(3)
172(3)
140(2)
141(2)
iꢀ=ꢀxꢀ−ꢀ1, −yꢀ+ꢀ1/2, zꢀ−ꢀ1/2
iiꢀ=ꢀ−ꢀxꢀ+ꢀ2, −yꢀ+ꢀ1, −zꢀ+ꢀ2
iiiꢀ=ꢀ−ꢀx, −yꢀ+ꢀ1, −zꢀ+ꢀ1
ivꢀ=ꢀ−ꢀxꢀ+ꢀ1, −yꢀ+ꢀ1, −zꢀ+ꢀ1
vꢀ=ꢀxꢀ−ꢀ1, y, z
aD, Donor; A, acceptor.
Table 3:ꢁDetails of the hydrogen-bonding interactions in 2ꢀ·ꢀHClꢀ·ꢀH2O.
a
D–Hꢁ·ꢁ·ꢁ·ꢁA
D–H/Å
Hꢁ·ꢁ·ꢁ·ꢁA/Å
Dꢁ·ꢁ·ꢁ·ꢁA/Å
D–Hꢁ·ꢁ·ꢁ·ꢁA/deg
Symmetry transformations
N1–H1ꢀ·ꢀ·ꢀ·ꢀCl1
N2–H2ꢀ·ꢀ·ꢀ·ꢀO4
O1–H1ꢀ·ꢀ·ꢀ·ꢀO3i
O2–H2ꢀ·ꢀ·ꢀ·ꢀCl1ii
O4–H4ꢀ·ꢀ·ꢀ·ꢀCl1iii
O4–H3ꢀ·ꢀ·ꢀ·ꢀO3iv
0.89(3)
0.98(2)
0.65(3)
0.75(3)
0.81(3)
0.89(3)
2.23(3)
1.61(2)
1.88(3)
2.31(3)
2.31(3)
1.82(3)
3.1092(16)
2.5871(18)
2.5324(17)
3.0491(14)
3.0881(13)
2.6786(16)
169(2)
176(2)
176(3)
171(2)
163(2)
161(3)
iꢀ=ꢀ−ꢀxꢀ+ꢀ1, −yꢀ+ꢀ1, −z
iiꢀ=ꢀxꢀ−ꢀ1, y, zꢀ−ꢀ1
iiiꢀ=ꢀ−ꢀxꢀ+ꢀ2, −yꢀ+ꢀ1, −zꢀ+ꢀ2
ivꢀ=ꢀ−ꢀxꢀ+ꢀ2, −yꢀ+ꢀ1, −zꢀ+ꢀ1
aD, Donor; A, acceptor.
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898ꢀ ꢀB. Nateghi and C. Janiak: Pyrazole-phosphonic acid ligands
[9] K. S. Park, Z. Ni, A. P. Cote, J. Y. Choi, R. Huang, F. J. Uribe-
Romo, H. K. Chae, M. O’Keeffe, O. M. Yaghi, Proc. Natl. Acad.
Sci. USA 2006, 103, 10186–10191.
[10] J. J. Low, A. I. Benin, P. Jakubczak, J. F. Abrahamian, S. A.
Faheem, R. R. Willis, J. Am. Chem. Soc. 2009, 131, 15834–15842.
[11] M. Tonigold, Y. Lu, A. Mavrandonakis, A. Puls, R. Staudt, J.
Möllmer. J. Sauer, D. Volkmer, Chem. Eur. J. 2011, 17, 8671–8695.
[12] J. Y. Lee, O. K. Farha, J. Roberts, K. A. Scheidt, S. T. Nguyen, J. T.
Hupp, Chem. Soc. Rev. 2009, 38, 1450–1459.
[13] C. Heering, I. Boldog, V. Vasylyeva, J. Sanchiz, C. Janiak, Cryst-
EngComm 2013, 15, 9757–9768.
[14] B. J. Burnett, P. M. Barron, W. Choe, CrystEngComm 2012, 14,
3839–3846.
[15] M. Viciano-Chumillas, S. Tanase, L. J. de Jongh, J. Reedijk, Eur.
J. Inorg. Chem. 2010, 22, 3403–3418.
[16] C. W. Lu, Y. Wang, Y. Chi, Chem. Eur. J. 2016, 22, 17892–17908.
[17] K. J. Gagnon, H. P. Perry, A. Clearfield, Chem. Rev. 2012, 112,
1034–1054.
[18] S. J. I. Shearan, N. Stock, F. Emmerling, J. Demel, P. A. Wright,
K. D. Demadis, M. Vassaki, F. Costantino, R. Vivani, S. Sallard, I.
R. Salcedo, A. Cabeza, M. Taddei, Crystals 2019, 9, 270.
[19] R. Silbernagel, C. H. Martin, A. Clearfield, Inorg. Chem. 2016,
55, 1651–1656.
[20] M. T. Wharmby, J. P. S. Mowat, S. P. Thompson, P. A. Wright, J.
Am. Chem. Soc. 2011, 133, 1266–1269.
[21] T. Rhauderwiek, K. Wolkersdörfer, S. Øien-ꢀØꢀdegaard, K. P. Lil-
lerud, M. Wark, N. Stock, Chem. Commun. 2018, 54, 389–392.
[22] T. Rhauderwiek, H. Zhao, P. Hirschle, M. Doeblinger, B. Bueken,
H. Reinsch, D. D. Vos, S. Wuttke, U. Kolb, N. Stock, Chem. Sci.
2018, 9, 5467–5478.
CCDC 1961142 and 1961143 contain the supplementary
crystallographic data for 1ꢀ·ꢀHCl and 2ꢀ·ꢀHClꢀ·ꢀH2O, respec-
tively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif.
4 Conclusions
In summary, two novel bifunctional pyrazolate-phos-
phonate ligands 3,5-dimethyl-4-(4-phosphonophenyl)-
1H-pyrazole, 1 and 4-(4-phosphonophenyl)-1H-pyrazole, 2
have been prepared via a Suzuki-Miyaura cross-coupling
and their crystal structures determined. These multiden-
tate ligands with five potential coordination sites offer
the use as suitable organic spacers to provide new coor-
dination polymers or metal-organic frameworks (MOFs).
The high thermal stability of the synthesized compounds
aids in the hydrothermal synthesis of coordination poly-
mers or MOFs. We are confident that in continuation of
this work a large number of interesting supramolecular
complexes for a variety of applications will be reported
in the future.
[23] J. Jia, X. Lin, C. Wilson, A. J. Blake, N. R. Champness, P. Hub-
berstey, G. Walker, E. J. Cussen, M. Schroeder, Chem. Commun.
2007, 840–842.
5 Supporting information
[24] X. J. Gu, Z. H. Lu, Q. Xu, Chem. Commun. 2010, 46, 7400–7402.
[25] T.–L. Ho, Chem. Rev. 1975, 75, 1–20.
1
13
31
PXRD patterns, H, C, P NMR and IR spectra are given
as supplementary material available online (DOI: 10.1515/
znb-2019-0170).
[26] M. O’Keeffe, Chem. Soc. Rev. 2009, 38, 1215–1217.
[27] M. O’Keeffe, O. M. Yaghi, Chem. Rev. 2012, 112, 675–702.
[28] P. O. Adelani, L. J. Jouffret, J. E. S. Szymanowski, P. C. Burns,
Inorg. Chem. 2012, 51, 12032–12040.
[29] P. O. Adelani, G. E. Sigmon, P. C. Burns, Inorg. Chem. 2013, 52,
6245–6247.
Acknowledgements: The authors thank Dr. Ishtvan
Boldog for his kind support during this project.
[30] J. Dechnik, A. Nuhnen, C. Janiak, Cryst. Growth Des. 2017, 17,
4090–4099.
[31] C. Heering, B. Francis, B. Nateghi, G. Makhloufi, S. Luedeke, C.
Janiak, CrystEngComm 2016, 18, 5209–5223.
[32] J. Liu, R. Zeng, C. Zhou, J. Zou, Chin. J. Chem. 2011, 29, 309–313.
[33] A. Spassow, Organic Syntheses 1955, 3, 390.
[34] A. Sarkar, S. R. Roy, N. Parikh, A. K. Chakraborti, J. Org. Chem.
2011, 76, 7132–7140.
References
[1] C. Janiak, Dalton Trans. 2003, 2781–2804.
[2] S. Kitagawa, R. Kitaura, S. I. Noro, Angew. Chem. Int. Ed. 2004,
43, 2334–2375.
[3] A. H. Chughtai, N. Ahmad, H. A. Younus, A. Laypkovc, F. Ver-
poort, Chem. Soc. Rev. 2015, 44, 6804–6849.
[4] J. R. Li, R. J. Kuppler, H. C. Zhou, Chem. Soc. Rev. 2009, 38,
1477–1504.
[5] S. Natarajan, P. Mahata, Curr. Opin. Solid State Mater. Sci. 2009,
13, 46–53.
[6] G. Alberti, M. Casciola, U. Costantino, R. Vivani, Adv. Mater.
1996, 8, 291–303.
[7] A. Clearfield, Dalton Trans. 2008, 6089–6102.
[8] X. C. Huang, Y. Y. Lin, J. P. Zhang, X. M. Chen, Angew. Chem. Int.
Ed. 2006, 45, 1557–1559.
[35] T. Steiner, Acta Crystallogr. B 1998, 54, 456–463.
[36] J. Grell, J. Bernstein, G. Tinhofer, Crystallogr. Rev. 2002, 8, 1–56.
[37] I. Boldog, J. C. Daran, A. N. Chernega, E. B. Rusanov, H.
Krautscheid, K. V. Domasevitch, Cryst. Growth Des. 2009, 9,
2895–2905.
[38] F. H. Allen, W. D. Samuel Motherwell, P. R. Raithby, G. P.
Shields, R. Taylor, New J. Chem. 1999, 23, 25–34.
[39] T. Steiner, Angew. Chem. Int. Ed. 2002, 41, 48–76.
[40] S. Vairam, S. Govindarajan, Thermochim. Acta 2004, 414,
263–270.
[41] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457–2483.
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B. Nateghi and C. Janiak: Pyrazole-phosphonic acid ligandsꢂ
ꢂ899
[42] Apex2, Data Reduction and Frame Integration Program for the
CCD Area-Detector System, Bruker AXS Inc., Madison, Wiscon-
sin (USA) 1997–2006.
[43] Smart, Saint, Area Detector Control and Integration Software,
Bruker AXS Inc., Madison, Wisconsin (USA) 2003.
[46] G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112–122.
[47] K. Brandenburg, Diamond (version 4.4), Crystal and Molecular
Structure Visualization, Crystal Impact – K. Brandenburg & H.
Putz Gbr, Bonn (Germany) 2009–2017.
[44] G. M. Sheldrick, Sadabs, Area-Detector Absorption Correction,
University of Göttingen, Göttingen (Germany) 1996.
[45] G. M. Sheldrick, Acta Crystallogr. 2015, A71, 3–8.
Supplementary Material: The online version of this article offers
supplementary material (https://doi.org/10.1515/znb-2019-0170).
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