Synthesis of tetraarylborates via tetralithio intermediates and the effect of polar functional groups and cations on their crystal structures

Article abstract of DOI:10.1039/C8DT04068K

A novel general protocol for the preparation of functionalized (COOH, CHO, C(O)NHtBu, B(OH)₂) tetraphenyl- and tetrakis(4′-biphenylyl)borates is reported. It involves four-fold halogen-lithium exchange in potassium tetrakis(iodophenyl)borates and tetrakis(4′-bromobiphenylyl)borate) using t-BuLi in THF at ?78 °C followed by treatment of the resulting tetralithio intermediates with electrophiles (CO₂, DMF, t-BuNCO, B(OMe)₃). X-ray crystal structures of ammonium tetrakis[4-(dihydroxyboryl)phenyl]borate, lithium tetrakis(3-carboxyphenyl)borate, and lithium tetrakis[4-(tert-butylcarbamoyl)phenyl]borate were determined showing a strong effect of the cation and polar functional group on supramolecular architecture.

Full text of DOI:10.1039/C8DT04068K

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Synthesis of tetraarylborates via tetralithio
intermediates and the effect of polar functional
groups and cations on their crystal structures†
Cite this: Dalton Trans., 2018, 47,
16627
a
Patryk Tomaszewski,a Marcin Wiszniewski, a Janusz Serwatowski,
a
Krzysztof Woźniak, b Krzysztof Durka a and Sergiusz Luliński
*
A novel general protocol for the preparation of functionalized (COOH, CHO, C(O)NHtBu, B(OH)2) tetra-
phenyl- and tetrakis(4’-biphenylyl)borates is reported. It involves four-fold halogen–lithium exchange in
potassium tetrakis(iodophenyl)borates and tetrakis(4’-bromobiphenylyl)borate) using t-BuLi in THF at
−78 °C followed by treatment of the resulting tetralithio intermediates with electrophiles (CO2, DMF,
t-BuNCO, B(OMe)3). X-ray crystal structures of ammonium tetrakis[4-(dihydroxyboryl)phenyl]borate,
lithium tetrakis(3-carboxyphenyl)borate, and lithium tetrakis[4-(tert-butylcarbamoyl)phenyl]borate were
determined showing a strong effect of the cation and polar functional group on supramolecular
architecture.
Received 10th October 2018,
Accepted 30th October 2018
DOI: 10.1039/c8dt04068k
rsc.li/dalton
Sonogashira coupling16 of tetra(4-iodophenyl)borate (3) should
be noted as examples of this approach. In this contribution,
Introduction
Tetraarylborates constitute an important class of compounds we present a method based on the conversion of halogenated
due to their widespread use in various fields including analyti- tetraarylborates into respective lithiated intermediates using
cal chemistry (as components of ion-selective electrodes),1–3 halogen–lithium exchange. The synthesis and reactivity of
organic synthesis (as donors of the nucleophilic aryl group)4–7 related lithiated arylboronates as convenient intermediates for
and homogeneous catalysis (as weakly coordinating anions for the preparation of functionalized arylboronic acids and boron
stabilization of active cationic metal centres).8–10 Due to their heterocycles were already reported.22–24 This methodology was
high tetrahedral symmetry and strong tendency to form dia- extended by our group in order to obtain selected heteroleptic
mondoid-type structures, they have also found applications in diarylborinic 8-oxyquinolinates.25 Now we demonstrate that
crystal engineering,11–13 supramolecular chemistry14,15 and tetralithiated tetraarylborates can be easily generated in good
materials science. For instance, interesting polymer networks yields and subsequently converted into respective derivatives
based on tetraarylborates were developed recently as single-ion bearing pendant carboxyl, formyl, amido, and boronic groups.
conducting solid electrolytes.16 Hence, the development of It should be noted that these compounds can be regarded as
new simple general synthetic routes to functionalized tetraaryl- anionic analogues of tetraphenylmethane and tetraphenylsi-
borates is an important task. Classical synthetic routes to tetra- lane derivatives which were already explored as important
arylborates involve transmetalation of aryllithium or arylmag- starting materials for various applications with a special
nesium compounds with boron compounds (such as boron emphasis on crystal engineering26 and for the preparation of
halides, trialkylborates or NaBF4).17–20 However, this approach three-dimensional covalent organic frameworks (COFs).27,28
significantly limits access to derivatives bearing many popular Thus, we discuss herein the crystal structures of the
functional groups attached to the aryl ring. Alternative strat- three obtained compounds with a special emphasis on the
egies relying on post-synthetic modifications of tetraarylborate effect of cation-framework interactions on the supramolecular
cores are scarce.
A
palladium-catalyzed cyanation21 and assembly.
aWarsaw University of Technology, Faculty of Chemistry, Noakowskiego 3, 00-664
Warsaw, Poland. E-mail: serek@ch.pw.edu.pl
bUniversity of Warsaw, Biological and Chemical Research Centre, Żwirki i Wigury
101, 02-089 Warsaw, Poland
Results and discussion
The synthesis of halogenated potassium tetraarylborates 1–4
was initially performed according to reported procedures.7
Thus, respective halogenated phenyllithiums were treated with
†Electronic supplementary information (ESI) available. CCDC 1840090, 1868753
and 1868754. For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c8dt04068k
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BF3·Et2O in Et2O at −78 °C in a ratio of ca. 5 : 1 followed by pound 6 bearing longer 4-biphenylyl arms was successfully
slow warming of the solution to room temperature and sub- prepared (Scheme 1).
sequent workup. This approach failed in the case of 5 as the
In the next step, halogenated potassium tetraarylborates
reaction of 3-bromo-5-fluorophenyllithium with BF3·Et2O pro- were subjected to halogen–lithium exchange reactions leading
ceeds in two steps. At lower temperatures (up to ca. 0 °C), an to respective lithiated intermediates. It is critical to use rigor-
initially formed aryltrifluoroborate anion is relatively inert. ously dried salts to avoid undesired in situ protonation of Ar–Li
Thus, nucleophilic substitution of fluorine ligands occurs slug- bonds. Thus, prior this step the compounds 1–6 were heated
gishly so that formation of the desired product is preceded by at 150 °C under high vacuum (10−4 Torr) for 1 hour and then
extensive degradation of the aryllithium species upon warming dissolved in dry THF. A solution of a halogenated tetraarylbo-
the reaction mixture. Compound 5 was successfully prepared rate was then added to a solution of tBuLi/THF (10 equiv.) at
using BCl3 as the boron source.29 According to our obser- −78 °C. In general, an immediate reaction was observed as
vation, the reaction occurs in two steps, too. The first one indicated by the formation of a coloured slurry (yellow, green
involves the rapid formation of lithium (3-bromo-5-fluorophe- or grey-violet, depending on the starting material). A mixture
nyl)trichloroborate upon addition of a solution of BCl3 in containing the lithiated intermediate 1-Li–6-Li was stirred for
hexane to the solution of aryllithium at −78 °C. The substi- 2 h at −78 °C to complete the reaction. Then, addition of the
tution of chlorine atoms starts at ca. −30 °C as indicated by a electrophile (CO2, DMF, tBuNCO or B(OMe)3) followed by
strong exothermic effect. When a suspension of the latter hydrolysis gave rise to a respective tetraarylborate bearing the
lithium salt (obtained from the reaction of aryllithium with carboxyl, formyl, amido or boronic functional group. In some
BCl3 in the molar ratio 1 : 1) was allowed to warm above cases, the exchange of the cation was performed in order to
−30 °C, a similar exothermic process was observed. 1H and 11
B
facilitate product isolation. It should be noted that the syn-
NMR analyses of the isolated solid revealed the formation of 5. thesis of 3b from the reaction of 1-bromo-4-(dimethoxymethyl)
This indicates that the intermediate aryltrichloroborate anion benzene with nBuLi in THF/Et2O followed by addition of BCl3
undergoes ligand redistribution processes under mild con- (0.2 equiv.) was attempted. However, acid hydrolysis and
ditions which kinetically favours the formation of 5. The use of workup resulted in 4-formylphenylboronic acid as a sole isol-
BCl3 instead of BF3·Et2O has also an additional advantage as able product. The substituted tetraarylborates were isolated in
the byproduct LiCl is easily removed during aqueous workup, the form of lithium, potassium or ammonium salts as white
whereas LiF forms a gelatinous phase which poses significant solids. Unfortunately, the analysis of products obtained from
problems during filtration. Thus, the syntheses of 1–4 were halogenated tetraarylborates 1, 2 and 5 showed that they are
repeated using BCl3 resulting in improved yields in compari- not sufficiently pure, presumably due to an incomplete
son with protocols based on BF3·Et2O. In addition, a new com- exchange of bromine atoms. Thus, one can recommend the
Scheme 1 Synthesis of halogenated tetrarylborates 1–6.
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use of more reactive tetra(iodophenyl)borates 3 and 4 for suc- coordination modes of respective cations. Since the binding in
cessful preparation of respective functionalized derivatives. On lithium coordination compounds is predominately electro-
the other hand, bromine–lithium exchange occurred effectively static in nature and the Li+ radius is of only 0.6 Å, its tetra-
in the case of tetrakis(4′-bromobiphenylyl)borate 6 as evi- hedral complexation with hard bases is strongly preferred.31 In
denced by high yield formation of compounds 6a–f. The the case of ammonium salts, the charge-supported hydrogen
higher reactivity of 6 when compared to 1–2 can be explained bonds with boronic groups could be expected but structural
+
in terms of a more effective separation of the negative charge analysis of 3d revealed preference for interaction of the NH4
in 6-Li gradually increasing within the entire tetraarylborate cation with the aromatic π-cloud.32,33 Consequently, such
scaffold upon consecutive formation of carbanionic centres.
interactions symmetrically connect four aromatic rings from
All the obtained compounds were fully characterized by two neighbouring anions of 3d (Fig. 1a). Due to these inter-
multinuclear NMR spectroscopy. 1H and 13C NMR spectra con- actions, the anion is significantly distorted from the general Td
firmed their structural formulation. 11B NMR spectra showed a symmetry with the rather small (102.6(8)°) C–B–C angle
signal of the tetra-coordinate boron atom in the range of −6 to between the aromatic rings sharing the same cation. The
−7 ppm. In addition, we would like to raise the stability issue propagation of this motif along the [010] direction results in
of the majority of obtained products under relatively strong the formation of a one-dimensional cation–anion string,
acidic conditions. For example, derivatives bearing carboxyl which resembles the structural motif found in unsubstituted
groups survive at a pH of ca. 1 (simply estimated by the litmus ammonium and alkaline metal tetraphenylborates.13 The dis-
paper test) for at least several hours at room temperature tance of the nitrogen atom to the aromatic ring centroid
without any significant degradation. This allows for a con- equals to 3.12(2) Å and is slightly longer than that in NH4BPh4
venient isolation of fully protonated forms of 3a, 4a and 6a in (3.048 Å).32 Boronic groups are linked via pairs of O–H⋯O
good yields. It is well known that many tetraarylborates hydrogen-bond interactions forming centrosymmetric dimers
undergo degradation at pH < 2–3 due to the protonolysis of a commonly encountered in crystal structures of boronic
B–C bond.30 The increased protonolytic stability of the acids.34,35 However, in 3d the p-(HO)2BC6H4 groups from adja-
obtained compounds is beneficial from the point of view of cent anions are not aligned in the same plane (the average dis-
applications which would involve the use of acidic reagents or tance between mean planes of corresponding aromatic rings is
catalysts (Schemes 2 and 3).
2.05(2) Å) (Fig. 1b). It is also noticeable that the entire group is
significantly bent out of its mean plane which is the result of
NH4 ⋯C(π) and boronic group hydrogen-bond interactions.
+
Structural analysis
Since each anion forms four hydrogen-bond connections to
the neighbours, the structure extends to the three-dimensional
diamondoid-type network. It is significantly elongated in the
[010] direction reflecting the distortion of molecular geometry
(Fig. 2a and b). Furthermore, the structure shows a six-fold
interpenetration level (Fig. 2c). Compared to related structures
of neutral tetraboronic acids based on tetraphenylmethane
and tetraphenylsilane backbones,26 where five-fold interpene-
Single crystals of 3c, 3d and 4a were grown by slow evaporation
of their wet acetone solutions. The ammonium salt 3d crystal-
lizes as a tetrahydrate in the non-centrosymmetric Pnn2 space
group. In turn, compounds 3c and 4a adopt the centro-
symmetric P21/c space group (4a described in the P21/n
setting) and incorporate lithium counterions into their struc-
tures. Thus, it is expected that structures of lithium and
ammonium salts would vary significantly due to different
Scheme 2 Synthesis of functionalized tetraphenylborates.
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Scheme 3 Synthesis of functionalized tetrakis(4’-biphenylyl)borates.
Fig. 1 Two main structural motifs governing the molecular organization in 3d: (a) NH4+⋯C(π) cation–anion chains, (b) hydrogen bonds formed
between boronic groups and water molecules, (c) hydrogen bond network formed with boronic groups and water molecules. Thermal motions are
shown as atomic displacement parameters (ADPs) at the 50% probability level. (d) The visualization of crystal voids (water molecules were excluded
from the structure).
tration was observed, the packing of 3d has a higher interpene- comprises only 14% of the total unit cell volume, whereas in
tration level due to significant structure elongation which neutral tetraboronic acids nearly 60% of the total crystal
allows for the insertion of one additional network. The inter- volume are available for guest molecules. Furthermore, the
penetrating networks are not independent of each other as channels in 3d are aligned in the [010] direction and are not
+
they are held by the NH4 ⋯C(π) interactions. Another impor- connected one with another (Fig. 1d). Since the structure was
tant difference is the increased compacity of the ionic tetra- obtained by crystallization from wet acetone solution, the
boronic structure. Both types of structures possess the volume channels are filled with water molecules which form well-
available for inclusion of guest molecules. However, in 3d it defined O–H⋯O interactions with boronic groups (Fig. 1c). In
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Fig. 2 Distorted diamondoid-type hydrogen-bonded network viewed parallel to (a) [010] and (b) [100] directions. (c) Graphical representation of
the six-fold network interpenetration in 3d.
Fig. 3 (a) Molecular structure of 3c. Thermal motions given as ADPs at the 50% probability level. (b) Fragment of the crystal structure of 3c showing
the formation of the (100) molecular layer. (c) The visualization of crystal voids (solvent molecules were excluded from the structure).
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summary, the supramolecular structure of 3d can be described of the van der Waals nature. The structure possesses nearly
as the 6-fold interpenetrated distorted diamondoid-type 17% of crystal voids (Fig. 3c). They are enclosed in the form of
network formed by two different structural motifs originating bubbles connected in a waved surface parallel to the (100)
from hydrogen-bonds between boronic groups as well as plane, thus partially separating the molecular planes and
+
NH4 ⋯C(π) interactions.
weakening their mutual interactions. The cavities are filled
In contrast to 3d, the crystal structure analysis of 3c and 4a with disordered acetone molecules. Despite the presence of
shows that coordination of lithium cations by oxygen atoms free N–H hydrogen bond donors, the solvent molecules are not
(either from the acetone or amide group) is preferred for involved in any interactions with these groups.
Li+⋯C(π) interactions. Thus, the molecular geometries are not
Unfortunately, we did not manage to obtain a single crystal
strongly affected by intermolecular interactions and adopt of the para-substituted tetracarboxylic derivative 3a; however,
well-defined tetrahedral symmetry. In the case of 3c, the Li+ its meta analogue 4a was successfully characterized (Fig. 4a).
cation is coordinated by oxygen atoms from two amide groups This is somewhat in contrast to our expectations, as crystal
and two acetone molecules (Fig. 3a). The oxygen atoms from structures of related neutral compounds tetrakis(4-carboxyphe-
two remaining amide groups play a role of acceptors in N– nyl)methane
and
tetrakis(4-carboxyphenyl)silane
were
H⋯O hydrogen bond interactions. It means that there are an reported and widely discussed,36–38 while their meta isomers
insufficient number of hydrogen-bond acceptors and thus two have not been published, so far. The crystal structure of 4a
N–H groups remain free. Despite the tetrahedral symmetry of seems not to be affected by ionic nature of this compound, as
the anion, structural propagation through N–H⋯O hydrogen (1) the lithium cation was found to be disordered over four
bonds and Li+-centred tetrahedra is restricted to (100) planes positions residing in the crystal cavity, (2) it is weakly solvated
(Fig. 3b), whereas interactions between such layers are mainly by the inserted solvent molecules, (3) it is not involved in any
Fig. 4 (a) Molecular structure of 4a with ADPs defined at 30% probability level. Solvent molecules are presented in capped stick style for clarity. (b)
Hydrogen-bonded (100) layer resulted from mutual COOH⋯HOOC interactions. (c) Disposition of two hydrogen-bonded tetrameric motifs from
neighbored layers (drawn in yellow and blue colors, respectively) defining the crystal cavity. (d, e) Void surface generated for hydrogen-bonded
anionic framework (solvent molecules and Li+ cations were extruded from the structure).
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interaction with the hydrogen-bonded framework, and (4) between the carboxylic groups, while lithium cations reside in
molecular aggregation mostly results from the H-bonding the structural cavities solvated by the included guest molecules
interactions of carboxylic groups. The mutual COOH⋯HOOC and do not participate in supramolecular assembly of the
hydrogen-bonds lead to the formation of a cyclic tetrameric anionic framework.
motif. It adopts a rectangular shape and boat conformation
Finally, we would like to stress that the obtained com-
(Fig. 4b and c). Each anion shares four such structural motifs; pounds are potentially interesting for a variety of applications.
however, their propagation is restricted to b and c directions. The work on the preparation of ionic covalent organic frame-
Consequently, herring-bone arrangement in the (100) layer is works, coordination polymers and other microporous
observed. The layers are mostly held by π-stacking and the materials using the obtained compounds as key substrates is
C–H⋯π(CvO) interactions operating along the [100] direction. currently in progress by our group. In addition, the use of
In contrast to 3d, the structure 4a is not affected by the inter- selected functionalized tetraarylborates in the construction of
penetration. Two hydrogen-bonded tetramers from neigh- electrochemical sensors can also be envisioned.
boured layers enclose the spherical cavity (Fig. 4c). They are
interconnected through the narrow necks of approximately 5 Å
diameter and comprise 51% of the unit cell volume (Fig. 4d
Experimental section
and e). They are filled with Li+ cations coordinated with
General comments
oxygen atoms of 4-hydroxy-4-methylpentan-2-one, and presum-
All reactions involving air and moisture sensitive reagents were
carried out under an argon atmosphere. Et2O and THF were
purified by refluxing with benzophenone ketyl and freshly dis-
tilled prior to use. Starting materials: dihalobenzenes, 4,4′-
dibromobiphenyl, nBuLi (2 M solution in hexanes), tBuLi (1.7
M in pentane), BF3·Et2O, and BCl3 (1 M solution in hexane)
and other important reagents including N,N-dimethyl-
formamide, tert-butyl isocyanate, and trimethoxyborane were
received from Aldrich. The NMR chemical shifts are given rela-
tive to TMS using known chemical shifts of residual proton
(1H) or carbon (13C) solvent resonances. 11B chemical shifts
were given relative to BF3·Et2O. The synthesis of lithium salts
with tetrakis(halophenyl)borate anions of 1–4 was reported
previously.20,21
ably 4-methylpent-3-en-2-one along with acetone (the exact
composition is not clear as solvent molecules are disordered
and can share the same position). The appearance of higher
molecular weight compounds apparently results from the
aldol-type self-condensation reaction of acetone.
Conclusions
In conclusion, optimization of the synthesis of halogenated
tetraarylborates 1–6 revealed that using BCl3 is more advan-
tageous than using BF3·Et2O as the substitution of chlorine
atoms occurs quantitatively under milder conditions com-
pared to the substitution of fluorines. Regarding subsequent
halogen–lithium exchange, the use of more reactive iodinated
tetraphenylborates proved to give optimal results. The gener-
ated tetralithiated tetraarylborates were successfully treated
Synthesis
Potassium tetrakis(4-bromophenyl)borate (1). 1,4-Dibromo-
with electrophiles such as CO2, DMF, tBuNCO, and B(OMe)3 to benzene (23.6 g 100 mmol) was dissolved in Et2O (150 mL).
furnish a series of novel tetraarylborates. We expect that deri- The solution was cooled to −40 °C and 2 M n-BuLi (50 mL,
vatization of the described tetrakis(lithioaryl)borate reagents 100 mmol) was added dropwise while maintaining the temp-
with other electrophiles may provide a wide and convenient erature below −30 °C. The resulting slurry was stirred for 1 h
access to various functionalized tetraarylborates, otherwise not at −40 °C and then cooled to −78 °C. Then a 1 M solution of
easily accessible.
BCl3 in hexane (20 mL, 20 mmol) was added dropwise.
The structural analyses show the ambivalent influence of A cooling bath was removed and the mixture was allowed to
cations on the topology of the obtained hydrogen-bonded warm to room temperature and left overnight. Solvents were
anionic frameworks. This is represented by the three studied evaporated under reduced pressure and the solid residue was
examples where such an effect is revealed at three different treated with a solution of aqueous KCl (5 g in 50 mL of water).
levels of supramolecular organization. In the case of 3c, the The crude product was filtered, washed with water (3 × 50 mL)
lithium cations are coordinated by amido groups and thus and DCM (2 × 25 mL) and dried under reduced pressure. The
directly participate in the formation of molecular layers. The dried product was dissolved in THF (100 mL). The resulting
network of ammonium salt 3d is based on the hydrogen-bond solution was filtered and evaporated. The pure anhydrous
interactions between the boronic groups resulting in diamond- product was obtained by heating for 2 h at 150 °C under high
oid topology. However, due to NH4⋯C(π) interactions the vacuum (10−4 Torr). White powder, dec. >356 °C, yield: 14.0 g
anions of 3d deviate from the tetrahedral geometry, which, in (84%). 1H NMR (400 MHz, acetone-d6) δ 7.14–7.12 (m, 16H)
turn, leads to a significant elongation of the network. This ppm; 13C NMR (101 MHz, acetone-d6) δ 161.2 (q, JBC
=
results in a higher level of network interpenetration and more 49.6 Hz), 137.7 (q, JBC = 1.6 Hz), 128.4 (q, JBC = 3.0 Hz),
compact character of the structure in comparison with neutral 116.2 ppm.11B NMR (96 MHz, acetone-d6) δ −7.5 ppm.
tetraboronic analogs. In the extreme example of 4a, the struc-
Potassium tetrakis(3-bromophenyl)borate (2). This com-
ture is dominated by the hydrogen-bond interactions formed pound was obtained as described for 1 starting with 1,3-dibro-
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mobenzene (13.3 g, 56.3 mmol). White powder, dec. >332 °C, 49.3 Hz), 141.0, 136.1, 132.4, 131.5, 128.2, 123.9 (q, JBC = 2.8
1
−
yield: 7.4 g (92%). H NMR (400 MHz, acetone-d6) δ 7.42–7.38 Hz), 119.3, 67.0, 25.2 ppm. HRMS (ESI): calcd for C48H32BBr4
(m, 4H), 7.23–7.18 (m, 4H), 7.09–7.05 (m, 4H), 7.01–6.98 (m, [M − K]− 938.9284; found 938.9313.
4H) ppm; 11B NMR (96 MHz, acetone-d6) δ −6.97 ppm; 13C
Ammonium tetrakis(4-carboxyphenyl)borate (3a). A solution
NMR (100 MHz, acetone-d6), δ 165.5 (q, JBC = 49 Hz), 137.7 (q, of 3 (9.0 g, 10.5 mmol) in THF (50 mL) was added to a stirred
JBC = 1.7 Hz), 134.3 (q, JBC = 1.2 Hz), 127.9 (q, JBC = 3.0 Hz), solution of tBuLi (1.7 M solution in pentane, 50 mL, 85 mmol)
125.5, 121.4 (q, JBC = 3.7 Hz) ppm.
in THF (150 mL) at −78 °C. The resulting dark-green mixture
Potassium tetrakis(4-iodophenyl)borate (3). This compound containing the tetralithio intermediate 3-Li was stirred for 1 h
was obtained as described for 1 starting with 1,4-diiodo- and cooled to −100 °C. Then it was saturated with dry gaseous
benzene (33.0 g, 100 mmol). White powder, dec. >355 °C, CO2 while maintaining the temperature below −80 °C. The
1
yield: 20.5 g (90%). H NMR (400 MHz, acetone-d6) δ 7.31 (dd, resulting white suspension was allowed to reach room temp-
J = 8 Hz, 8H), 6.93–6.88 (m, 8H) ppm; 13C NMR (101 MHz, erature and filtered. The solid was washed with Et2O (2 ×
acetone-d6) δ 161.7 (q, JBC = 49.5 Hz), 138.3 (q, JBC = 1.5 Hz), 50 mL) and treated with 20 wt% aq. NH4Cl (20 mL). The
134.5 (q, JBC = 2.9 Hz), 87.6 ppm. 11B NMR (96 MHz, acetone- mixture was concentrated under reduced pressure to remove
d6) δ −7.5 ppm.
THF and then acidified with aq. HCl (to reach pH of ca. 1)
Potassium tetrakis(3-iodophenyl)borate (4). This compound resulting in the formation of a viscous material at the bottom
was obtained as described for 1 starting with 1,3-diiodoben- of the flask. The supernatant was decanted, whereas the crude
zene (16.5 g, 50 mmol). White powder, dec. >350 °C, yield: product was washed several times with a small portion of cold
9.5 g (88%). 1H NMR (300 MHz, acetone-d6) δ 7.67–7.61 (m, water (acidified with a few drops of aq. HCl, pH = 3). Then it
4H), 7.28 (ddd, J = 5.4, 2.7, 1.2 Hz, 4H), 7.23 (dddd, J = 8.7, 3.8, was mixed with dichloromethane (20 mL) which led to the for-
2.5, 1.2 Hz, 4H), 6.90–6.82 (m, 4H) ppm; 13C NMR (101 MHz, mation of a white precipitate. The suspension was filtered and
acetone-d6) δ 165.9 (q, JBC = 49.2 Hz), 144.0 (q, JBC = 1.6 Hz), the solid was stirred with a mixture of acetone (10 mL) and di-
134.8 (q, JBC = 1.3 Hz), 131.3, 128.3 (q, JBC = 2.9 Hz), 94.8 chloromethane (20 mL) for 1 h at 0 °C and filtered. The
(q, JBC = 3.8 Hz) ppm. 11B NMR (96 MHz, acetone-d6) δ −7.27 – product was dried under reduced pressure to give 3a as a white
1
−7.33 (m) ppm.
powder, dec. >205 °C, yield: 4.8 g (87%). H NMR (400 MHz,
Potassium tetrakis(3-bromo-5-fluorophenyl)borate (5). This acetone-d6) δ 7.68 (d, J = 8.0 Hz, 2H), 7.38–7.33 (m, 2H) ppm;
compound was obtained as described for 1 starting with 11B NMR (96 MHz, acetone-d6) δ −6.5 ppm; 13C NMR
1,3-dibromo-5-fluorobenzene (25.5 g, 100 mmol). During the (100 MHz, acetone-d6) δ 170.9, 169.3 (q, JBC = 49 Hz), 135.4 (d,
addition of BCl3 (1 M solution in hexane, 25 mL, 25 mmol) the JBC = 2.0 Hz), 127.1 (q, JBC = 2.7 Hz), 126.3 ppm. HRMS (ESI):
temperature was kept below −70 °C. Then, the cooling bath calcd for C28H20BO8− [M − NH4]− 495.1245; found 495.1261.
was removed and the mixture was allowed to warm slowly.
Potassium tetrakis(4-formylphenyl)borate (3b). This com-
When the temperature increased to ca. −30 °C, the exothermic pound was obtained from 3 (2.15 g, 2.5 mmol). The lithiate
process started and the flask was placed again in the cooling 3-Li was generated as described for 3a. It was quenched with
bath. The temperature was kept below −20 °C for 30 min. DMF (1.8 g, 24.6 mmol). The resulting white suspension was
Then the temperature was kept below −10 °C for 40 min. stirred at −78 °C for 30 min and then allowed to warm to room
Further workup was carried out as described for 1. White temperature and evaporated under reduced pressure to leave a
1
powder, dec. >360 °C, yield: 14.5 g (78%). H NMR (400 MHz, white solid. It was mixed with Et2O (50 mL) and the suspen-
acetone-d6) δ 7.18–7.14 (m, 4H), 6.98–6.93 (m, 4H), 6.90–6.84 sion was filtered and the solid was washed with hexane
(m, 4H) ppm; 11B NMR (96 MHz, acetone-d6) δ −7.1 ppm; 13C (10 mL) and resuspended in hexane (10 mL). Then the mixture
NMR (100 MHz, acetone-d6) δ 165.8 (qd, J = 49.0 Hz, 3.0 Hz), was hydrolyzed aq. KCl (10 wt%, 10 mL) and aq. HCl (4 M, ca.
162.1 (dq, J = 259 Hz, 4 Hz), 133.4 (m), 120.7 (m), 119.7 (m), 5 mL) was added to reach the pH of ca. 3. The obtained yellow
113.3 (J
δ −114.88 ppm. HRMS (ESI): calcd for C24H12BBr4F4− [M − K]− water (2 × 10 mL) and DCM (4 × 5 mL), and dried to give 3b as
706.7655; found 706.7674.
a cream-white powder, dec. >220 °C, yield: 0.91 g (77%). 1H
=
25 Hz); 19F NMR (376 MHz, acetone-d6) slurry was filtered to give a crude product. It was washed with
Potassium tetrakis(4-bromobiphenylyl)borate, THF solvate NMR (400 MHz, acetone-d6) δ 9.89 (s, 4H), 7.59 (d, J = 7.9 Hz,
(6·THF). A slurry of 4,4′-dibromobiphenyl (50.5 g, 160 mmol) 8H), 7.53–7.48 (m, 8H) ppm. 13C NMR (101 MHz, acetone-d6)
in Et2O (500 mL) was cooled to −20 °C and 2 M n-BuLi (80 mL, δ 192.3, 171.9 (q, JBC = 48.9 Hz), 135.9 (q, JBC = 1.4 Hz), 132.6,
160 mmol) was added dropwise while maintaining the temp- 127.3 (q, JBC = 2.8 Hz) ppm. 11B NMR (96 MHz, acetone-d6)
−
erature below −10 °C. The resulting mixture was stirred for 1 h δ −6.00 to −6.20 (m). HRMS (ESI): calcd for C28H20BO4
at −5 °C and then cooled to −78 °C. Then a 1 M solution of [M − K]− 431.1449; found 431.1464.
BCl3 in hexane (35 mL, 35 mmol) was added dropwise. Further
Lithium tetrakis[4-(N-tert-butylcarbamoyl)phenyl]borate (3c).
workup was performed as described for 1. White powder, dec. This compound was obtained from 3 (2.15 g, 2.5 mmol). The
>345 °C, yield: 29.5 g (82%). 1H NMR (300 MHz, DMSO-d6) lithiate 3-Li was generated as described for 3a. It was
1H NMR (400 MHz, DMSO-d6) δ 7.62–7.56 (m, 16H), 7.44–7.38 quenched with t-BuNCO (1.98 g, 20.0 mmol). The mixture was
(m, 8H), 7.33 (d, J = 8.1 Hz, 8H), 3.62–3.58 (m, 1H), 1.75–1.71 stirred at −78 °C for 30 min and then allowed to warm to room
(m, 1H). 13C NMR (101 MHz, DMSO-d6) δ 163.2 (d, JBC
=
temperature. Then it was evaporated to leave a solid residue
16634 | Dalton Trans., 2018, 47, 16627–16637
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which was hydrolyzed with aq. HCl (3 M, ca. 10 mL) to reach 36H) ppm. 13C NMR (101 MHz, DMSO-d6) δ 206.9, 167.0, 162.7
the pH of ca. 3. The viscous residue was washed with water (q, JBC = 49.5 Hz), 138.8, 134.4, 133.7 (q, JBC = 2.8 Hz), 125.4,
(2 × 10 mL) and triturated with Et2O (10 mL). The resulting 121.6, 50.7, 31.1, 29.1 ppm. 11B NMR (96 MHz, DMSO-d6)
−
suspension was filtered to give a white solid. It was dissolved δ −6.7 ppm. HRMS (ESI): calcd for C44H56BN4O4 [M − Li]−
in acetone (3 mL) and a mixed solvent (DCM/hexane, 20 mL, 715.4389; found 715.4413.
1 : 1) was added. The resulting suspension was concentrated
Ammonium tetrakis(4-carboxybiphenylyl)borate (6a). A solu-
and filtered. The product was washed with DCM (3 mL) and tion of 6 (4.8 g, 5.0 mmol) in THF (25 mL) was added to a
dried to give 3c as a white powder, dec. >280 °C, yield: 1.45 g stirred solution of tBuLi (1.7 M solution in pentane, 25 mL,
(81%). 1H NMR (300 MHz, DMSO-d6) δ 7.39 (d, J = 8.1 Hz, 8H), 42 mmol) in THF (70 mL) at −78 °C. The resulting dark-blue
7.34 (s, 4H), 7.25–7.18 (m, 8H), 1.36 (s, 36H) ppm. 13C NMR mixture containing the tetralithio intermediate 6-Li was stirred
(101 MHz, DMSO-d6) δ 168.2, 167.0 (q, JBC = 49.1 Hz), 135.1, for 1 h. Carboxylation with gaseous CO2 and further workup
130.5, 125.1, 50.7, 29.2. 11B NMR (96 MHz, DMSO-d6) was carried out as described for analogous compound 3a.
−
δ −6.8 ppm. HRMS (ESI): calcd for C44H56BN4O4 [M − Li]− White powder, dec. >202 °C, yield: 2.9 g (73%). 1H NMR
715.4389; found 715.4417.
(400 MHz, DMSO-d6) δ 12.78 (broad, 4H), 7.94 (d, J = 8.5 Hz,
Ammonium tetrakis[4-(dihydroxyboryl)phenyl]borate (3d). 8H), 7.76–7.70 (m, 8H), 7.41 (s, 16H) ppm. 13C NMR (101 MHz,
This compound was obtained from 3 (4.3 g, 5.0 mmol). The DMSO-d6) δ 167.8, 164.3 (q, JBC = 49 Hz), 146.4, 136.5, 132.9,
lithiate 3-Li was generated as described for 3a. It was 130.3, 128.7, 126.4, 124.8 ppm. 11B (96 MHz, DMSO-d6)
quenched with B(OMe)3 (5.6 g, 6 mL, 55 mmol). The mixture −7.0 ppm. HRMS (ESI): calcd for C52H36BO8 [M − NH4]−
−
was stirred at −78 °C for 30 min and then allowed to warm to 799.2498; found 799.2522.
room temperature. Then it was evaporated to leave a white
Potassium tetrakis(4-formylbiphenylyl)borate (6b). This
solid residue. It was treated with aq. Na2S2O5 (10 wt%, 2 mL), compound was obtained as described for 3b starting with 6
aq. NH4Cl (20 wt%, 10 mL) and the pH was adjusted to the (4.8 g, 5.0 mmol). Yellow powder, dec. >205 °C, yield: 2.5 g
value of ca. 3–4 by the addition of aq. HCl. The mixture was (68%). 1H NMR (400 MHz, DMSO-d6) δ 9.98 (s, 4H), 7.91 (d, J =
evaporated to dryness and the obtained solid was triturated 8.2 Hz, 8H), 7.85 (d, J = 8.2 Hz, 8H), 7.48–7.44 (m, 16H) ppm.
with methanol (20 mL). The suspension was filtered and the 13C NMR (101 MHz, DMSO-d6) δ 193.0, 164.7 (q, JBC = 49.0 Hz),
filtrate was evaporated. The crude solid product was washed 148.1, 136.6, 134.5, 132.8, 130.6, 127.0, 125.0 ppm. 11B NMR
with cold water (5 mL) and dichloromethane (5 mL) and dried (96 MHz, DMSO-d6) δ −6.8 ppm. HRMS (ESI): calcd for
to give 3c as a white powder, dec. >340 °C, yield: 1.4 g (53%). C52H32BO8− [M − K]− 735.2701; found 735.2724.
1H NMR (400 MHz, acetone-d6) δ 7.47 (d, J = 9.0 Hz, 8H),
7.35–7.31 (m, 8H) ppm; 13C NMR (100 MHz, acetone-d6) (6c). This compound was obtained as described for 3c starting
Lithium tetrakis[4-(N-tert-butylcarbamoyl)biphenylyl]borate
δ 167.5 (q, JBC = 49 Hz), 135.4 (q, JBC = 2.0 Hz), 131.4 (q, JBC
=
with 6 (2.4 g, 2.5 mmol). The product was isolated as a white
1
2.7 Hz), 125.0 ppm; 11B NMR (96 MHz, acetone-d6) δ 28.4, powder, dec. >255 °C, yield: 0.91 g (78%). H NMR (300 MHz,
−6.6 ppm. HRMS (ESI): calcd for C24H24B5O8 [M − NH4]− DMSO-d6) δ 7.83 (d, J = 8.4 Hz, 8H), 7.71 (d, J = 8.8 Hz, 8H),
−
494.1967; found 494.1985.
7.67 (s, 4H), 7.46–7.36 (m, 16H), 1.40 (s, 36H) ppm. 13C NMR
Lithium tetrakis(3-carboxyphenyl)borate (4a). This com- (101 MHz, DMSO-d6) δ 166.7, 163.9 (q, JBC = 47.5 Hz), 144.5,
pound was obtained as described for 3a starting with 4 (2.15 g, 136.5, 133.8, 133.2, 128.3, 125.9, 124.6, 51.1, 29.1 ppm. 11B
2.5 mmol). Due to a significant solubility of 4a in water, the NMR (96 MHz, DMSO-d6) δ −6.8 ppm. HRMS (ESI): calcd for
reaction mixture obtained after addition of 4 M aq. HCl was C68H72BN4O4− [M − Li]− 1019.5652; found 1019.5674.
evaporated to dryness and the solid residue was extracted with
Potassium tetrakis(4-(dihydroxyboryl)biphenylyl)borate (6d).
acetone (30 mL). The extract was concentrated and then di- This compound was obtained as described for 3c starting with
chloromethane was added to precipitate the product as a white 6 (2.4 g, 2.5 mmol). However, the mixture obtained after
powder. Elemental analysis revealed that the product was addition with B(OMe)3 was warmed to room temperature and
obtained as a lithium salt contaminated with some amount of quenched with Me3SiCl (3 mL). The resultant solution was
potassium (ca. 10%). White powder, dec. >190 °C, yield: 0.9 g stirred for 1 h and evaporated under reduced pressure to leave
1
(68%). H NMR (400 MHz, acetone-d6) δ 8.07 (s, 1H), 7.55 (d, a pale yellow waxy residue. DCM (50 mL) was added and the
J = 7.6 Hz, 1H), 7.48 (s, 1H), 7.05 (td, J = 7.5, 3.9 Hz, 1H) ppm; obtained suspension was stirred for 30 min and filtered under
13C NMR (101 MHz, acetone-d6) δ 171.8, 162.7 (q, JBC = 49.5 argon. The filtrate was evaporated to dryness and the resulting
Hz), 140.1, 136.8, 129.6, 125.6, 124.0. 11B NMR (96 MHz, solid was treated with aq. KCl (10 wt%, 20 mL). Acetone
−
acetone-d6) δ −6.7 ppm; HRMS (ESI): calcd for C28H20BO8
(20 mL) was added to dissolve any remaining solid and the
mixture was concentrated to remove organic solvents. The
[M − Li]− 495.1245; found 495.1263.
Lithium tetrakis[3-(N-tert-butylcarbamoyl)phenyl]borate (4b). aqueous phase was decanted from over the precipitated waxy
This compound was obtained as described for 3c starting with material. It was washed with water (3 × 5 mL) and DCM
4 (1.08 g, 1.25 mmol). The product was isolated as the acetone (20 mL) was added. The obtained slurry was stirred for 2 h and
solvate. White powder, dec. >222 °C, yield: 0.75 g (78%). the product was filtered, washed with DCM (3 × 5 mL) and
1H NMR (300 MHz, DMSO-d6) δ 7.62 (s, 4H), 7.26 (d, J = 7.0 Hz, dried to give white powder, dec. >370 °C, yield: 1.55 g (77%).
4H), 7.09 (s, 4H), 7.01 (t, J = 7.4 Hz, 4H), 2.09 (s, 6H), 1.32 (s, 1H NMR (400 MHz, DMSO-d6) δ 8.06 (s, B(OH)2, 8H), 7.85
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Dalton Transactions
(d, J = 7.2 Hz, 8H), 7.62 (d, J = 7.1 Hz, 8H), 7.46–7.36 (m, 16H) For the better description of the position of disordered atoms,
ppm. 13C NMR (101 MHz, DMSO-d6) δ 163.5 (q, JBC = 49.4 Hz), the same anisotropic displacement parameters were used
143.7, 136.5, 135.1, 134.0, 129.1, 126.6, 125.5, 124.5 ppm. 11B (EADP instruction). Furthermore, the O1A and O1B atoms were
NMR (MHz, DMSO-d6) δ 28.0, −7.5 ppm. HRMS (ESI): calcd for restrained so that their Uij components approximate to isotropic
C48H40BO8− [M − K]− 798.3219; found 799.3239. Note: The stan- behavior (ISOR instruction). In the case of the model with fully
dard workup involving hydrolysis with an aqueous HCl product refined solvent molecules, several reflections were omitted as
was not effective and the formation of the 4-biphenylboronic their observed and calculated F2 values disagree significantly.
acid by-product was observed to a varying extent. Presumably 6d
In the case of 3c, the diffraction was not observed at a
is quite unstable at the lower pH (below 2–3) due to the cleavage higher theta (θ > 50°) angle even after prolonged data acqui-
of B–C bonds at the quaternary boron centre.
sition (180 s per frame). Furthermore, the structure contains
disordered solvent molecules located inside the crystal pores.
According to the SQUEEZE procedure, these correspond to
X-ray structural measurement and refinement details
The single crystals of 3c, 3d and 4a were obtained by slow 2 molecules of acetone. The disordered solvent molecules were
evaporation of the corresponding mixed acetone–water solu- masked using OLEX software.42
tions. They were measured at 100 K on a SuperNova diffracto-
The compound 3d crystallizes in the form of very tiny crys-
meter equipped with an Atlas detector (Cu-Kα radiation, λ = tals. Thus the diffraction was not observed at higher theta
1.54184 Å). Data reduction and analysis were carried out with angle (θ > 50°) and it was not measured.
the CrysAlisPro program.39 All structures were solved by direct
Crystallographic Information Files (CIFs) have been de-
methods
using
SHELXS-97 40
and
refined
using posited with the Cambridge Crystallographic Data Centre as
SHELXL-2014.41
supplementary publications no. 1840090 (3d),† 1841321 (3c)
Despite the fact that the measured diffraction data of 4a is and 1840091 (4a).
of good quality (Rint < 3.0%), the final R ad wR2 refinement
Crystal data for 3c. C44H52BN4O4Li·2C3H6O, Mr = 838.83 a.u.;
factors for this structure are of 13.81% and 38.5% (I ≥ 3σ(I)). monoclinic; P21/c; a = 17.560(3) Å, b = 22.0645(18) Å, c =
This is because of the poor description of the solvent mole- 16.8909(18) Å, β = 114.517(15)°, V = 5954.4(13) Å3; dcalc
=
cules located in the crystal cavities. We have found that at least 0.933 g cm−3; μ = 0.474 mm−1; Z = 4; F(000) = 1803; number of
three different solvent molecules may be presented in the collected/unique reflection (Rint = 9.19%) = 16 879/6449, R[F]/
ðmin=maxÞ
network voids including (a) acetone (not included in the wR[F] (I ≥ 3σ(I)) = 8.01%/18.63%, Δϱ
= −0.226/+0.270 e
res
refinement), (b) the product of its aldol condensation – Å−3
.
4-hydroxy-4-methylpentan-2-one, and (c) 4-methylpent-3-en-2-
Crystal data for 3d. C24H24B5O8NH4·4(H2O), Mr = 583.58 a.u.;
one – the dehydration product of the latter compound. Due to orthorhombic; Pnn2; a = 14.1966(9) Å, b = 8.5378(8) Å, c =
the geometrical similarity of all solvent molecules, their posi- 11.9968(16) Å, V = 1454.1(3) Å3; dcalc = 1.335 g cm−3; μ =
tions in the structure may overlap. This is especially noticeable 0.854 mm−1; Z = 2; F(000) = 990; number of collected/unique
for 4-methylpent-3-en-2-one, in which CvC sp2 carbon atom is reflection (Rint = 5.54%) = 2573/1009, R[F]/wR[F] (I ≥ 3σ(I)) =
ðmin=maxÞ
slightly pyramidilized, and some residual electron density was 6.84%/19.75%, Δϱ
= −0.26/+0.26 e Å−3
.
res
found in the direction perpendicular to the molecular plane
Crystal data for 4a. C28H20BO8LiC6H12O2·0.5C6H10O, Mr =
(1.03 e Å−3) suggesting the presence of other atoms close to 667.41 a.u.; monoclinic; P21/n; a = 15.1982(11) Å, b = 17.4686
the CvC sp2 carbon atom (probably oxygen atom with partial (5) Å, c = 17.705(2) Å, β = 101.258(14)°, V = 4610.0(7) Å3; dcalc
=
occupation). However, the 4-hydroxy-4-methylpentan-2-one 0.962 g cm−3; μ = 0.572 mm−1; Z = 4; F(000) = 1404; number of
does not fit as well and we were unable to find a more reliable collected/unique reflection (Rint = 2.75%) = 33 268/7059, R[F]/
ðmin=maxÞ
model to describe the solvent disorder. All atoms of disordered wR[F] (I
≥
3σ(I))
=
13.81%/38.47%, Δϱ
=
res
solvent molecules were refined isotropically with the site occu- −0.364/+1.220 e Å−3. Squeeze: R[F]/wR[F] (I ≥ 3σ(I)) = 4.48%/
ðmin=maxÞ
pancy factors fixed at the exact values of 0.5. Furthermore, we 12.0%, Δϱ
have found that the lithium cations are disordered over
4 different positions (see Fig. S31 SI†). The presence of lithium
cations was confirmed by atomic absorption spectroscopy ana-
= −0.217/+0.263 e Å−3
.
res
Conflicts of interest
lysis (AAS). The removal of all solvent molecules and lithium
cations followed by the SQUEEZE procedure resulted in the There are no conflicts to declare.
decrease of the R ad wR2 refinement factors to 4.48% and
12.0%, respectively, showing that, indeed, most of the refine-
ment problems are related to the improper description of
molecular species located in crystal cavities. Both crystallo-
Acknowledgements
graphic models (4a and 4a_squeeze) are provided in the ESI.† This work was supported by National Science Centre (Poland)
Besides the solvent disorder, two carboxylic groups from within the framework of the project DEC-UMO-2016/21/B/ST5/
COOH⋯HOOC dimers were also found to be disordered over 00118. X-ray measurements were performed in the
two positions each, probably being the result of the rotation of Crystallographic Unit of the Physical Chemistry Laboratory at
the 3-carboxyphenyl group along the B–C bond by small angle. the Chemistry Department of the University of Warsaw.
16636 | Dalton Trans., 2018, 47, 16627–16637
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21 N. Malek, T. Maris, M. Simard and J. D. Wuest, J. Am.
Chem. Soc., 2005, 127, 5910–5916.
References
1 E. Bakker, P. Bühlmann and E. Pretsch, Chem. Rev., 1997, 22 Y. Yamamoto, T. Seko and H. Nemoto, J. Org. Chem., 1989,
97, 3083–3132. 54, 4734–4736.
2 J. Bobacka, T. Alaviuhkola, V. Hietapelto, H. Koskinen, 23 P. Vedsø, P. H. Olesen and T. Hoeg-Jensen, Synlett, 2004,
A. Lewenstam, M. Lämsä, J. Pursiainen and A. Ivaska,
Talanta, 2002, 58, 341–349.
3 J. Bobacka, V. Väänänen, A. Lewenstam and A. Ivaska,
Talanta, 2004, 63, 135–138.
4 G. Lu, R. Franzén, Q. Zhang and Y. Xu, Tetrahedron Lett.,
2005, 46, 4255–4259.
892–894.
24 P. Kurach, S. Luliński and J. Serwatowski, Eur. J. Org.
Chem., 2008, 3171–3178.
25 G. Wesela-Bauman, L. Jastrzębski, P. Kurach, S. Luliński,
J. Serwatowski and K. Woźniak, J. Organomet. Chem., 2012,
711, 1–9.
5 R. Shintani, Y. Tsutsumi, M. Nagaosa, T. Nishimura and 26 J.-H. Fournier, T. Maris, J. D. Wuest, W. Guo and
T. Hayashi, J. Am. Chem. Soc., 2009, 131, 13588–13589. E. Galoppini, J. Am. Chem. Soc., 2003, 125, 1002–1006.
6 G.-R. Qu, P.-Y. Xin, H.-Y. Niu, X. Jin, X.-T. Guo, X.-N. Yang 27 A. P. Coté, A. I. Benin, N. W. Ockwig, M. O’Keeffe,
and H.-M. Guo, Tetrahedron, 2011, 67, 9099–9103. J. Matzger and O. Yaghi, Science, 2005, 310, 1166–1170.
7 T. Matsuda, K. Mizuno and S. Watanuki, J. Organomet. 28 H. M. El-Kaderi, J. R. Hunt, J. L. Mendoza-Cortes,
Chem., 2014, 765, 64–67.
8 J. Broeke, Arylborate Anions; Versatile Counterions, in
A. P. Coté, R. E. Taylor, M. O’Keeffe and O. M. Yaghi,
Science, 2007, 316, 268–272.
Homogeneous Catalysis with Potential for Use in Novel 29 E. Ihara, V. G. Young and R. F. Jordan, J. Am. Chem. Soc.,
Reaction Media, Utrecht, Netherlands, 2000. 1998, 120, 8277–8278.
9 E. Y.-X. Chen and T. J. Marks, Chem. Rev., 2000, 100, 1391– 30 T. Li, A. J. Lough, C. Zuccaccia, A. Macchioni and
1434. R. H. Morris, Can. J. Chem., 2006, 84, 164–175.
10 T. J. Herrington, A. J. W. Thom, A. J. P. White and 31 U. Olsher, R. M. Izatt, J. S. Bradshaw and N. K. Dalley,
A. E. Ashley, Dalton Trans., 2012, 41, 9019–9022. Chem. Rev., 1991, 91, 137–164.
11 P. K. Bakshi, A. Linden, B. R. Vincent, S. P. Roe, 32 T. Steiner and S. A. Mason, Acta Crystallogr., Sect. B: Struct.
D. Adhikesavalu, T. S. Cameron and O. Knop,
Can. J. Chem., 1994, 72, 1273–1293.
12 P. K. Bakshi, T. S. Cameron and O. Knop, Can. J. Chem.,
1996, 74, 201–220.
Sci., 2000, 56, 254–260.
33 M. Dąbrowski, K. Durka, S. Luliński, J. Serwatowski and
J. Warkocka, Acta Crystallogr., Sect. E: Struct. Rep. Online,
2011, 67, o3098.
13 U. Behrens, F. Hoffmann and F. Olbrich, Organometallics, 34 K. Durka, K. N. Jarzembska, R. Kamiński, S. Luliński,
2012, 31, 905–913.
14 S. Kiviniemi, M. Nissinen, T. Alaviuhkola, K. Rissanen and
J. Serwatowski and K. Woźniak, Cryst. Growth Des., 2012,
12, 3720–3734.
J. Pursiainen, J. Chem. Soc., Perkin Trans. 2, 2001, 12, 2364– 35 I. D. Madura, K. Czerwińska and D. Sołdańska, Cryst.
2369. Growth Des., 2014, 14, 5912–5921.
15 T. Alaviuhkola, J. Bobacka, M. Nissinen, K. Rissanen, 36 N. Malek, T. Maris, M. Simard and J. D. Wuest, Acta
A. Ivaska and J. Pursiainen, Chem. – Eur. J., 2005, 11, 2071–
Crystallogr., Sect. E: Struct. Rep. Online, 2005, 61, o518–
2080.
o520.
16 J. F. van Humbeck, M. L. Aubrey, A. Alsbaiee, R. Ameloot, 37 Y.-B. Men, J. Sun, Z.-T. Huang and Q.-Y. Zheng,
G. W. Coates, W. R. Dichte and J. R. Long, Chem. Sci., 2015,
6, 5499–5505.
17 F. P. Cassaretto, J. J. McLafferty and C. E. Moore, Anal.
Chim. Acta, 1965, 32, 376–380.
CrystEngComm, 2009, 11, 978–979.
38 J. B. Lambert, Y. Zhao and C. L. Stern, J. Phys. Org. Chem.,
1997, 10, 229–232.
39 CrysAlis Pro Software, Oxford Diffraction Ltd., Oxford, U.K.,
2010.
18 R. Anulewicz-Ostrowska, T. Kliś,
D. Krajewski,
B. Lewandowski and J. Serwatowski, Tetrahedron Lett., 2003, 40 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found.
44, 7329–7331. Crystallogr., 2008, 64, 112–122.
19 N. A. Yakelis and R. G. Bergman, Organometallics, 2005, 24, 41 G. M. Sheldrick, Acta Crystallogr., Sect. C: Struct. Chem.,
3579–3581. 2015, 71, 3–8.
20 N. Malek, M. Saied and J. D. Wuest, J. Soc. Chim. Tunis., 42 O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard
2006, 8, 55–61.
and H. Puschmann, J. Appl. Crystallogr., 2009, 42, 339–341.
This journal is © The Royal Society of Chemistry 2018
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