Polymetallated 4-tert-butylcalix[4]arene complexes of sodium and potassium stabilized by crown ethers: Syntheses, structures and activation of carbon dioxide

Article abstract of DOI:10.1002/ejic.200300550

4-tert-Butylcalix[4]arene and 18-crown-6 react with NaH in THF to form the complex [(18-crown-6)(THF)Na₄(4-tert-butylcalix[4]arene-4H)] ₂·3THF (1). Analogously, the reaction with 4-tert-butyltetrathiacalix[4]arene in DMF results in the formation of [(18-crown-6)Na(dmf)_1.5]₂[(4-tert-butyltetrathiacalix[4] arene-4H)₂Na₆(dmf)₂] (2) The X-ray analysis of 1 shows an Na₆O₆ skeleton consisting of two fused open heterocubanes. Two Na⁺ ions are encapsulated in the cavities of the calix[4]arene units. Additionally, two peripheral Na⁺ ions, each surrounded by a crown ether and one THF ligand, are connected to the central Na₆O₆ skeleton by one bridging oxygen of the calix[4]arene. In contrast, 2 contains the highly symmetrical anion [(4-tert-butyltetrathiacalix[4]arene-4H)₂Na₆(dmf) ₂]^2- and crown-ether-stabilized cations. While 1 shows a dynamic process in solution above 40 °C, the structure of the highly symmetrical compound 2 remains stable at higher temperatures. The solid-state structure of the potassium complex [(dibenzo-18-crown-6)K₄(4-tert- butylcalix[4]arene-4H)(THF)₃]₂·4THF (4) is similar to 1; however, the calix[4]arene units in the open heterocubane structure of 4 are shifted less than half a diameter to one another than in the sodium complex 1. According to the ¹H NMR spectra complex 3a, containing 18-crown-6, has a very similar structure to the related complex 4. Both 1 and 4 absorb carbon dioxide in THF and are active CO₂-transfer reagents towards 2-fluoropropiophenone; complex 2 is much less active. This clearly demonstrates the subtle influence of the structure of the alkali metal complexes on the CO₂ reactivity in these types of compounds. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300550

FULL PAPER
Polymetallated 4-tert-Butylcalix[4]arene Complexes of Sodium and Potassium
Stabilized by Crown Ethers: Syntheses, Structures and Activation of Carbon
Dioxide
Reinald Fischer,[a] Helmar Görls,[a] and Dirk Walther*[a]
Keywords: Alkali metals / Calixarenes / Carbon dioxide fixation / Carboxylation / Crown compounds
4-tert-Butylcalix[4]arene and 18-crown-6 react with NaH in
THF to form the complex [(18-crown-6)(THF)Na4(4-tert-bu-
tylcalix[4]arene-4H)]2·3THF (1). Analogously, the reaction
higher temperatures. The solid-state structure of the potas-
sium complex [(dibenzo-18-crown-6)K4(4-tert-butylca-
lix[4]arene-4H)(THF)3]2·4THF (4) is similar to 1; however, the
with 4-tert-butyltetrathiacalix[4]arene in DMF results in the calix[4]arene units in the open heterocubane structure of 4
formation of [(18-crown-6)Na(dmf)1.5]2[(4-tert-butyltetrathia-
calix[4]arene-4H)2Na6(dmf)2] (2) The X-ray analysis of 1
shows an Na6O6 skeleton consisting of two fused open heter-
ocubanes. Two Na+ ions are encapsulated in the cavities of
the calix[4]arene units. Additionally, two peripheral Na+ ions,
each surrounded by a crown ether and one THF ligand, are
connected to the central Na6O6 skeleton by one bridging
are shifted less than half a diameter to one another than in
the sodium complex 1. According to the 1H NMR spectra
complex 3a, containing 18-crown-6, has a very similar struc-
ture to the related complex 4. Both 1 and 4 absorb carbon
dioxide in THF and are active CO2-transfer reagents towards
2-fluoropropiophenone; complex 2 is much less active. This
clearly demonstrates the subtle influence of the structure of
oxygen of the calix[4]arene. In contrast, 2 contains the highly the alkali metal complexes on the CO2 reactivity in these
symmetrical
anion
[(4-tert-butyltetrathiacalix[4]arene-
types of compounds.
4H)2Na6(dmf)2]2− and crown-ether-stabilized cations. While 1
shows a dynamic process in solution above 40 °C, the struc-
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
ture of the highly symmetrical compound 2 remains stable at Germany, 2004)
Introduction
deprotonated thiacalixarene complexes of the LiϪCs
series,[14] and in 1995 Bock et al. published the molecular
structure of [Li3(calix[4]arene-3H)(NH3)]2 the first alkali
metal complex of a multiply deprotonated calix[4]arene.[15]
Calixarenes and their metal complexes have attracted
great interest during the last 20 years due to a number of
attractive aspects in different areas. A great number of de-
rivatives have been synthesized, structurally characterized
Surprisingly little is known about alkali metal complexes
and used for application in supramolecular chemistry (es- with fully deprotonated calix[4]arenes of the type [M4(4-
pecially host-guest complexes), for selective metal coordi- tert-butylcalix[4]arene-4H)(solv)x]2, which are useful build-
nation, as models for simulating catalytic oxide surfaces, ing blocks for the preparation of transition metal com-
and as catalysts and sensors.[1Ϫ7]
plexes. The first complex of this type with Li as the metal
Interactions with alkali metal ions have been intensively center was described by Davidson.[16] Recently, Floriani,[17]
investigated mainly due to their importance for the separ- and Fromm[18] prepared and structurally elucidated poly-
ation of the alkali metals and as models for metal-ion trans- metallated alkali metal complexes with Li, Na and K using
port.[8] The first complex of the monoanion of 4-tert-butyl- different synthetic procedures. Partial hydrolysis of the lith-
calix[4]arene with Csϩ was described 1991 by Har- ium derivative resulted in the formation of the doubly pro-
rowfield.[9] In 1993 Atwood isolated a monometallated so- tonated Li complex.[18] Furthermore, the syntheses and
dium complex in which two oxygens of the calixarene unit structures of dialkylated alkali metal calix[4]arene com-
chelate to the metal.[10] A number of other alkali metal plexes were recently described, and their reaction with
complexes with monoanionic and dianionic calixarenes are crown ethers in solution investigated by NMR spec-
also known.[11Ϫ13] Recently, Harrowfield described partially troscopy.[19]
It is well-known that alkali-metal phenolates react with
[a]
carbon dioxide to form complexes of hitherto unknown
structures which can undergo self-carboxylation to form
salicylic acid or the para-hydroxybenzoic acid. Additionally,
some alkali-metal phenolates are also able to carboxylate
Institut für Anorganische und Analytische Chemie of the
Friedrich-Schiller-Universität Jena,
August-Bebel-Str. 2, 07743 Jena, Germany
Fax: (internat.) ϩ49-3641-948-102
E-mail: cdw@uni-jena.de
Eur. J. Inorg. Chem. 2004, 1243Ϫ1252
DOI: 10.1002/ejic.200300550
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1243

R. Fischer, H. Görls, D. Walther
FULL PAPER
activated aliphatic CϪH bonds in dipolar aprotic solvents crown-6)(THF)Na4(4-tert-butylcalix[4]arene-4H)]2. THF is
to form aliphatic carboxylic acids upon hydrolysis.[20Ϫ24]
very easily eliminated from this complex at 0 °C or by bub-
Generally, calixarene alkali metal complexes containing bling a stream of inert gas through the solution. Complex
phenolate groups linked in the two ortho positions by meth- 1 is formed in a very selective reaction in high yields. Even
ylene groups should be of great interest in CO2 chemistry, if an excess of 18-crown-6 was used as a competitor ligand
especially for the design of metal complexes which could be for the calix[4]arene, only complex 1 was formed. This
active in both the fixation and the activation of carbon di- shows that the sodium strongly prefers the charged ligand
oxide. To the best of our knowledge, this aspect of calixar- to the neutral one. Single crystals were grown from THF
ene metal chemistry has been completely ignored so far.
solution and the structure of 1 was confirmed crystallo-
Here we report on the synthesis and molecular structures graphically with the molecular structure illustrated in Fig-
of new polymetallated sodium and potassium calix[4]arene ure 1.
complexes in combination with crown ethers, which act as
competitive ligands. Our aim was to construct soluble sys-
tems which would be active in both CO2 fixation and in
carboxylation reactions of activated aliphatic CϪH bonds.
Results and Discussion
Scheme 1 displays the starting calix[4]arene A and its sul-
fur-bridged analogue B, as well as the three crown ethers
used as co-ligands.
Figure 1. Molecular structure of [(18-crown-6)(THF)Na4(4-tert-bu-
tylcalix[4]arene-4 H)]2·3THF (1); non-coordinated THF and hydro-
˚
gen atoms have been omitted for clarity; selected bond lengths (A):
Na(1)ϪO(1) 2.275(3), Na(1)ϪO(3) 2.281(3), Na(1)ϪO(4) 2.292(3),
Na(2)ϪO(1) 2.383(3), Na(2)ϪO(2) 2.199(3), Na(2)ϪO(3) 2.359(3),
Na(2)ϪO(4A) 2.232(3), Na(3)ϪO(1) 2.327(3), Na(3)ϪO(3)
2.356(3), Na(4)ϪO(2) 2.216(3), Na(4)ϪO(5) 2.802(4), Na(4)ϪO(6)
2.805(4), Na(4)ϪO(7) 2.661(4), Na(4)ϪO(8) 2.714(4), Na(4)ϪO(9)
2.672(4), Na(4)ϪO(10) 2.820(4), Na(4)ϪO(11) 2.381(4),
Na(1)···Na(1A) 2.931(3), Na(1)···Na(2) 3.152(2); selected bond
angles (°): O(11)ϪNa(4)ϪO(5) 99.60(14), O(11)ϪNa(4)ϪO(6)
84.2(2), O(11)- Na(4)ϪO(7) 86.9(2), O(11)ϪNa(4)ϪO(8) 83.13(13),
O(11)ϪNa(4)ϪO(9)
86.1(2), O(11)ϪNa(4)ϪO(10)
81.6(2),
(11)ϪNa(4)ϪO(2) 177.7(2), O(1)ϪNa(1)ϪO(3A) 171.68(12),
O(1)ϪNa(1)ϪO(4A) 93.73(11), O(1)ϪNa(1)ϪO(4) 90.77(10),
O(2)ϪNa(2)ϪO(4A) 153.33(12), O(2)ϪNa(2)ϪO(1) 101.50(11),
O(2)ϪNa(2)ϪO(3) 102.82(11), O(1)ϪNa(2)ϪO(3) 86.91(10),
Na(1)ϪO(1)ϪNa(3) 118.7(3), Na(1A)ϪO(3)ϪNa(3) 117.3(3)
Scheme 1. The calix[4]arenes A and B and the crown ethers CϪE
used as ligands
Sodium Complexes with 4-tert-Butylcalix[4]arene (1 and 2)
In the absence of traces of water sodium hydride readily
reacts with the calix[4]arene A in THF to form completely
Figure 2 shows the Na6O6 skeleton of 1, with the
deprotonated products. In the presence of 15-crown-5 (C), Na(1)ϪO(4)ϪNa(1A)ϪO(4A)Ϫplane fusing two heterocu-
which is tailor-made for Naϩ, the resulting reaction product bane units. Since there are no bonding interactions between
is insoluble even in polar solvents such as THF, DMF or Na(3) and O(4) or Na(3A) and O(4A), two ‘‘open’’ hetero-
DMSO. We assume, therefore, that the fully deprotonated cubane units result.
calixarene-containing sodium complex consists either of
separated ions, which cannot be solvated effectively in or- tween the fully lithiated compound (with the coordination
ganic solvents, or forms a polymeric structure.
number 4 for Li)[18] and the potassium compound (open
Compound 1 can be considered as an intermediate be-
However, with 18-crown-6 (D) as co-ligand, a crown heterocubane structure), reflecting also the intermediate
ether which does not ‘‘fit’’ effectively to Naϩ,[25] complex 1 size of the Na cation between Li and K.
was obtained as a THF-soluble product. From this solution
Furthermore, in 1 the two calix[4]arene units are shifted
we isolated well-shaped single crystals containing three by half a diameter with respect to one another. This is dif-
non-coordinated molecules of THF per dimeric unit [18- ferent to the reported pyridine-stabilized sodium complex
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Calix[4]arene Complexes of Sodium and Potassium Stabilized by Crown Ethers
FULL PAPER
the above type of asymmetric compounds. As expected, the
˚
NaϪO(phenolate) distance [2.216(3) A] is the shortest
NaϪO bond due to the anionic nature of the Na6O6 skel-
eton containing the calixarene units.
The 1H NMR spectrum in [D8]THF at room temperature
suggests that the structure found in the solid state is also
maintained in solution at ambient temperature (Figure 3).
As expected for this structure three signals of tert-butyl
groups in a 2:1:1 ratio (at δ ϭ 0.76, 0.95 and 1.29 ppm),
and four signals for the meta-protons of the phenolates at
δ ϭ 6.27, 6.54, 6.84 and 6.90 ppm are observed at 20 °C.
Furthermore, four doublets belonging to the bridging meth-
ylene groups at δ ϭ 2.71, 2.82, 3.77 and 4.73 ppm appear.
Figure 2. Na8O8 cluster core of 1 with the central Na6O6 skeleton
[(pyridine)4Na4(4-tert-butylcalix[4]arene-4H)]2·THF
in
which this shift is very small.[10] Consequently, the sodium
atoms in the plane fusing the two heterocubanes exhibit co-
ordination numbers of four in 1, in contrast to the above
pyridine complex where these Naϩ ions have a coordination
number of five.
In the central Na6O6 skeleton the oxygen atoms of the
calix[4]arene are situated at the corners of a deformed
rhomb, in contrast to their positions in the free calix[4] ar- Figure 3. Temperature-dependent 1H NMR spectra of 1 in
ene where these oxygens occupy the corners of a square.[26]
[D8]THF
Na(3) and Na(3A) are encapsulated in the cavities of the
calix[4]arenes and are in contact with the aromatic π-sys-
tems of two calix[4]arene phenyl rings. These rings are al-
Increasing the temperature results in a significant change
most parallel to each other and the NaϪC bond lengths of the NMR spectra. At 42.5 °C the two signals at higher
˚
(between 2.931 and 3.500 A) are similar to previously re- field coalesce and at higher temperatures only two signals
ported values.[18,19]
for the tert-butyl protons in a ratio of 2:2 (at δ ϭ 0.82 and
The peripheral Na(4) and Na(4A) atoms, with a coordi- 1.25 ppm) appear. The signals of the meta-protons of the
nation number of eight, each surrounded by the six oxygens phenolates (at δ ϭ 6.40 and 6.84 ppm) and of the bridging
of 18-crown-6 and one THF oxygen, are linked to the cen- CH2 (at δ ϭ 2.74 and 4.19 ppm) show the same behavior,
tral Na6O6 skeleton by only one bridging calixarene phenol- indicating that at higher temperature two pairs of equiva-
ate. The six crown ether oxygens adopt almost coplanar po- lent phenolates exist in the molecule.
1
sitions with the sodium ion out of this plane (deviation
The reversible nature of the temperature-dependent H
˚
from the least-squares plane: 0.15 A, shifted in the direction NMR spectra implies a dynamic process, the activation en-
of the coordinated phenolate). Furthermore, the coordi- ergy of which (∆H ϭ 65.0 Ϯ 0.5 kJ·molϪ1) can be calcu-
nated THF and the oxygen of the phenolate group lie trans lated from the temperature of coalescence and the separ-
1
to each other, perpendicular to the plane formed by the ation of the signals in the H NMR spectra.
crown ether. This type of coordination is, in principle, well-
One possibility to explain this dynamic behavior would
known for symmetric 18-crown-6 sodium complexes of the be the dissociation of 1 into the ions [Na(18-crown-6)]ϩ and
type [(18-crown-6)NaL2]X (L ϭ THF,[27Ϫ30] H2O[31,32] with [(4-tert-calix[4]arene-4H)Na3]2Ϫ. However, this process can
different anions; for a review see ref.[33]). Moreover, asym- be excluded because in this case three different species
metric types of the composition [(18-crown-6)Na(X)] (L ϭ would exist in solution above 40 °C: the starting compound
THF or 1,3-dioxolane; X ϭ anionic ligand) have recently 1 and the ionic compounds [Na(18-crown-6)]ϩ and [(4-tert-
been found as well.[34Ϫ36]
butylcalix[4]arene)Na3]2Ϫ. This is not in agreement with the
1
The NaϪO(crown) distances in 1 [between 2.661(4) and simple H NMR pattern at high temperatures. However, a
˚
2.805(4) A] are considerably longer than the NaϪO(THF) translation process involving the translation of one calix[4]-
˚
distance [2.381(4) A]. These values lie in a typical range for arene unit in the direction defined by the Na(2)ϪNa(2A)
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R. Fischer, H. Görls, D. Walther
FULL PAPER
axis, and the translation of the other calix[4]arene in the pyramids, with the Na ions at the apex and four oxygens in
opposite direction, could explain the NMR spectroscopic the base. In addition, the oxygen atoms of the calix[4]arene
data. Simultaneously, the sodium ions Na(4) and Na(4A) phenolates are located at the corners of a cube and the 4-
would undergo a 1,3-shift. An alternative process would be tert-butyltetrathiacalix[4]arene moieties are in an eclipsed
the synchronized rotation of both calix[4]arene units in arrangement. There is no interaction of the Naϩ ions with
1
around their central axis. The rhomb of the free electron-pairs of the sulfur atoms. In contrast to
Na(1)ϪNa(2)ϪNa(1A)ϪNa(2A) may be fixed during this the sodium-calixarene complex 1, where a sodium atom is
process in which 1 would act in solution as a ‘‘temperature- found inside the cavities, the cavities of 2 contain a DMF
dependent molecular slide clutch’’. A similar process, with molecule, which coordinates to Na(1) and Na(4).
an activation enthalpy, ∆HΘ, of 45 kJ·molϪ1 was recently
The two counterions [(dmf)Naϩ(18-crown-6)] and
found for a mononuclear Zn calixarene complex.[37] Al- [(dmf)2Naϩ(18-crown-6)] have different coordination en-
though the NMR spectroscopic data do not allow us to vironments. In [(dmf)Naϩ(18-crown-6)] the crown ether
distinguish between the translation and the rotation process oxygens are arranged in a ‘‘boat form’’ with the sodium ion
in 1, it is reasonable to favor the translation process, since a below the plane. The coordination of six oxygens of the
rotation would require more activation energy than a simple crown ether and one DMF molecule results in a coordi-
transition process.
nation number of seven for the sodium ion. This arrange-
The reaction of the sulfur-bridged calix[4]arene B with ment is similar to that in compound 5 and will be discussed
NaN(SiMe3)2 in the presence of 18-crown-6 in a molecular in more detail below.
ratio of 1:4:1 in THF results in an insoluble product.
The structural motif of the other cation [(dmf)2Naϩ(18-
Recrystallization from DMF gives well-shaped single crys- crown-6)] is typical of the above-mentioned group of sym-
tals of the composition [(18-crown-6)Na(dmf)1.5]2[(4-tert- metrical [(18-crown-6)NaL2]ϩ complexes,[27Ϫ33] with a hex-
butyltetrathiacalix[4]arene-4H)2Na6(dmf)2] (2). Complex 2 agonal-bipyramidal arrangement of the eight oxygen li-
contains the same molecular ratio between calix[4]arene, so- gands surrounding the sodium ion. The sodium ion is situ-
dium and 18-crown-6 as 1; however the 1H NMR spectrum ated in the center of the plane formed by the six oxygens of
of 2 exhibits only a simple pattern indicating a high sym- the crown ether compound. In addition, the two DMF li-
metry of the molecule.
Unfortunately, due to the poor crystal quality only the
gands lie trans to each other.
The 1H NMR spectrum in [D8]THF is in agreement with
structural motif could be determined by X-ray analysis. this highly symmetrical structure found in the solid state:
However, the complex is undoubtedly an ionic compound besides the DMF protons only one singlet for the protons
consisting of two [(dmf)nNaϩ(18-crown-6)]ϩ (n ϭ 1, 2) of the tert-butyl groups (at δ ϭ 1.14 ppm), one singlet for
cations and the anion [(dmf)2Na6(4-tert-butyltetra- the meta CH groups of the aromatic rings (at δ ϭ 7.42 ppm)
thiacalix[4]arene2]2Ϫ. Figure 4 displays the structure motif and one singlet for the OCH2 groups of the crown ether (at
of the anionic part.
δ ϭ 3.59 ppm), with the expected intensities, were observed.
According to the 1H NMR spectrum, this structure is main-
tained even at higher temperatures.
Potassium Complexes with 4-tert-Butylcalix[4]arene and
Crown Ethers
The reaction of A with KN(SiMe3)2 and 18-crown-6 (D)
in a molar ratio of 1:4:1 in THF afforded a mixture of the
two compounds 3a and 3b even if the molecular ratio of A/
18-crown-6 was varied from 1:1 to 1:2. Complex 3a crys-
tallized as large, colorless crystals of the composition [(18-
crown-6)K4(4-tert-butylcalix[4]arene-4H)(THF)n], and 3b
crystallized as fine needles. Separation of 3a from the reac-
tion mixture was possible by repeated decanting of 3a from
the suspension followed by washing the crystals with THF
Figure 4. Structural motif of the [(4-tert-butyltetrathiacalix[4]arene-
4H)2Na6(dmf)2]2Ϫ anion of 2; the counterions [(dmf)2Na(18-crown-
6)]ϩ, [(dmf)Na(18-crown-6)]ϩ and the hydrogen atoms have been
omitted for clarity
1
at Ϫ78 °C. According to the H NMR spectrum the purity
of 3a was greater than 95%. However, since 3a could not
be isolated as single crystals suitable for X-ray crystallogra-
phy, we performed a similar reaction with the closely related
Complex 2 contains two perpendicular mirror planes, one dibenzo-18-crown-6 instead of 18-crown-6 to get better
of which consists of Na(2), Na(3), Na(5) and Na(6), and crystals of this type of compound.
the other S(1), S(2), S(6) and S(8). The central unit of the
Reaction of ligand A with KN(SiMe3)2 and dibenzo-18-
structure is an octahedron with Na(1), Na(2), Na(3), Na(4), crown-6 (E) in a molar ratio of 1:4:1 in THF did indeed
Na(5) and Na(6) at the corners. Every plane of the octa- yield the complex [(dibenzo-18-crown-6)K4(4-tert-butylca-
hedron is capped by an oxygen of the phenolate rings. The lix[4]arene-4H)(THF)3]2·4THF (4) in a mixture with a se-
sodium atoms Na(3), Na(2) Na(5), and Na(6) form square cond product of the composition [(dibenzo-18-crown-
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Calix[4]arene Complexes of Sodium and Potassium Stabilized by Crown Ethers
FULL PAPER
6)2K4(4-tert-butylcalix[4]arene-4H)] (according to the 1H
The calixarene oxygens coordinate to the central potass-
NMR spectrum of the reaction mixture). Single crystals of ium rhomb containing K(2), K(3), K(2A) and K(3A). K(2)
compound 4 grown from THF were suitable for X-ray and K(2A) have coordination numbers of five, with a dis-
analysis. Figure 5 shows the molecular structure and con- torted square-pyramidal arrangement of the phenolate oxy-
tains selected bond lengths and bond angles in the figure gen atoms. K(3) and K(3A) also have a coordination num-
caption; Figure 6 shows the K8O8 core.
ber of five due to three phenolate oxygen atoms and two
coordinated THF molecules.
The two calix[4]arene units are shifted less than half a
diameter with respect to one another, therefore the
[(THF)K(dibenzo-18-crown-6)]ϩ moieties are much closer
to the central K6O6 skeleton.
The structure of 4 is very similar to the reported struc-
tures of the complexes [(THF)5K4(4-tert-butylcalix[4]arene-
4 H)]2·4THF[17] and [(THF)5K4(4-tert-butylcalix[4]arene-4
H)]2·THF.[18] The most remarkable difference consists in the
different coordination of the peripheral ions K(4) and
K(4A), indicating the influence of the crown ether ligand:
as they are surrounded by the crown ether oxygens and one
THF, both K(4) and K(4A) are only coordinated to one
calix[4]arene oxygen bridge, in contrast to the previously
described THF-stabilized complexes, where two oxygen
bridges link these Kϩ ions.
K(1) and K(1A) inside the calix[4]arene cores are bonded
to only two oxygen atoms of the phenolates, although they
also interact with the π-electron systems of the two nearly
parallel phenolates. The K(1)ϪCaromat distances lie within
Figure 5. Molecular structure of 4; non-coordinated THF and hy-
drogen atoms have been omitted for clarity; selected bond lengths
˚
(A): K(1)ϪO(2) 2.704(4), K(1)ϪO(4) 2.842(4), K(2)ϪO(2)
reported ranges[18] [2.931(3)Ϫ3.435(4) A for the first ring
˚
2.619(4), K(2)ϪO(3) 2.599(4), K(2)ϪO(4) 2.574(4), K(3)ϪO(1A)
2.702(4), K(2)ϪK(2A) 3.477(2), K(3)ϪO(1) 2.744(4), K(3)ϪO(2)
2.678(4), K(3)ϪO(12) 2.776(7), K(3)ϪO(13) 2.833(6), K(3)ϪK(2A)
˚
and 3.058(4)Ϫ3.152(3) A for the second ring]. However,
˚
there are also contacts to the ipso carbon atoms of the other
2.6391(18A, K(4)ϪO(3) 2.681(4), K(4)ϪO(5) 2.827(5), K(4)ϪO(6)
˚
˚
2.779(4), K(4)ϪO(7) 2.797(5) A, K(4)ϪO(8) 2.848(5), K(4)ϪO(9)
2.812(5), K(4)ϪO(10) 2.841(5), K(4)ϪO(11) 2.758(8)
two phenyl rings [K(1)ϪCipso ϭ 2.977(3) and 2.964(5) A].
The structure of the crown ether part is very similar to
that in the sodium compound 1. The coordination number
of the potassium ion is eight, and the crown ether oxygens
are arranged in an almost coplanar arrangement. The pot-
˚
assium ion lies above this plane, with a deviation of 0.53 A.
This structural motif is known for 18-crown-6 complexes of
both sodium and potassium.[38] The KϪO(crown) distances
˚
in 4 vary between 2.779(4) and 2.848(5) A. As expected for
the coordination of an anionic oxygen ligand, the KϪO dis-
tance to the bridging calix[4]arene moiety [K(1)ϪO(3)
˚
2.681(4) A] is significantly shorter than the other KϪO dis-
tances.
1
The H NMR spectrum of 4 is in agreement with the
structure found in the solid state and is very similar to that
of 3a, which contains 18-crown-6 instead of dibenzo-18-
crown-6. Therefore, we assume that 3a has a similar non-
ionic cluster-like structure to that of complex 4.
Figure 6. The K8O8 core in 4 with the central K6O6 skeleton and
the two peripheral Kϩ ions (each surrounded by the crown ether
oxygens and one oxygen of THF) bridged by O(3) and O(3A),
respectively
The molecular structure of 4 shows some similarities to
The temperature-dependent 1H NMR spectra of complex
the sodium compound 1. In both complexes the central 3a give evidence for an interesting reversible reaction. At
M6O6 moiety consists of two fused open heterocubanes ambient temperature three chemically different tert-butyl
where the corners are occupied alternately by alkali metal protons in a molecular ratio 2:1:1 are observed at δ ϭ 1.15,
cations and oxygens of the calix[4]arenes. However, there 1.11 and 1.08 ppm. Upon warming, the signals of the tert-
are remarkable differences in the details of the structure. In butyl protons and the meta protons of the phenolate groups
contrast to 1, the central heterocubane units in 4 are ar- become more and more equal and, in a simultaneous pro-
ranged nearly perpendicularly, and the peripheral cess, the intensity of the original signals of 3a disappears,
[(THF)K(4)(dibenzo-18-crown-6)]ϩ unit interacts with the while new signals of a highly symmetric compound appear
1
phenolate oxygen bridge O(3) of the central skeleton and without coalescence. At 55 °C the H NMR spectrum con-
not with O(2) as found in 1.
tains only signals for chemically equivalent phenolate
Eur. J. Inorg. Chem. 2004, 1243Ϫ1252
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1247

R. Fischer, H. Görls, D. Walther
FULL PAPER
groups. Therefore, we assume that a reversible, temperature- chelating ligands, in contrast to 5, where only one oxygen
dependent dissociation of compound 3a may proceed of the calixarene is coordinated. This reflects again the
according to Equation (1):
stronger ligand-effect of the crown ether compared with the
other ligands in the above complexes. The coordinated 18-
crown-6 is folded away from the calix[4]arene moiety, so
there is no space for another THF molecule to coordinate
to the sodium cation, which has a coordination number of
seven. The structure of the crown ether part in 5 is very
different from that in complex 1, where the oxygens form a
coplanar arrangement: the crown ether oxygens in 5 form
a ‘‘distorted boat’’ with the plane formed by O(6), O(7),
O(9), and O(10). The sodium ion lies below this plane,
whereas the other two oxygens [O(5) and O(8)] are above
the plane, with very different deviations from the least-
square plane [1.86 A for O(5) and 0.80 A for O(8)]. Accord-
ing to a search of the Cambridge Crystallographic Database
a few other 18-crown-6 complexes of sodium exist in which
an analogous arrangement has been found.[39,44] It is, how-
ever, noteworthy that the six calixarene oxygens in similar
sodium complexes can assume a chair form as well.[41,42]
3a ǟǞ 2 [K(18-crown-6)(THF)2]ϩ ϩ [K3(calix[4]arene-4H)]22Ϫ
(1)
1
Due to the similarities with the H NMR spectrum of
the anion of 2 we suggest that the anion [K3(calix[4]arene-
4H)]22Ϫ could have a similar molecular structure.
One of the reasons for the different behavior between the
sodium complex 1 and the potassium complex 3a in solu-
tion at increasing temperatures may be the different coordi-
nating ability of 18-crown-6 to Naϩ and Kϩ, which favors
the formation of an ionic product for Kϩ.
˚
˚
Fixation of CO2 by 1, 2 and 4 and CO2-Transfer Reaction
with 2-Fluoropropiophenone
Sodium phenolate reacts with carbon dioxide to give a
product of unknown structure which is able to carboxylate
activated aliphatic CϪH bonds in dipolar aprotic
solvents.[13Ϫ17] Therefore it may be expected that some of
the above alkali metal calix[4]arene complexes containing
four linked phenolate rings should, in principle, be capable
of carboxylating activated CϪH bonds.
Compound 1 reacts rapidly with CO2 in THF. If water is
not excluded very carefully the resulting products are
NaHCO3 and compound 5 [Equation (2)], which could be
obtained as single crystals from THF.
The X-ray structure of 5 (Figure 7) shows that the com-
pound contains a single deprotonated [calix[4]arene-3H]Ϫ
anion that is connected to the counterion [Na(18-crown-
6)]ϩ by a phenolate bridge of the calix[4]arene monoanion
˚
[NaϪO(3) ϭ 2.454(5) A]. The other three oxygens of the
calixarene unit do not coordinate [NaϪO distances:
Na···O(1) 4.869(5), Na···O(2) 3.507(6), Na···O(4) 3.984(4)
A]. The O···O distances between the calixarene oxygens of
Figure 7. [Na(18-crown-6)(4-tert-butylcalix[4]arene-H)]·OEt2 (5);
˚
the non-coordinated ether and the hydrogen atoms have been omit-
˚
ted for clarity; selected bond lengths (A): NaϪO(3) 2.454(4),
˚
˚
O(1)···O(2)
[2.932(6) A],
O(1)···O(4)
[2.669(6) A],
NaϪO(5) 2.522(5), NaϪO(6) 2.612(6), NaϪO(7) 2.532(5),
NaϪO(8) 2.574(5), NaϪO(9) 2.586(5), NaϪO(10) 2.703(6); selec-
ted bond angles (°): O(3)ϪNaϪO(5) 148.2(2), O(3)ϪNaϪO(6)
94.8(2), O(3)ϪNaϪO(7) 89.2(2), O(3)ϪNaϪO(8) 113.4(2),
˚
˚
O(2)···O(3) [2.597(6) A], and O(3)···O(4) [2.528(6) A] are
typical for intramolecular hydrogen bonds. The much
shorter separations between the phenolate oxygen atom
O(3) and its neighboring atoms O(2) and O(4) suggests
rather strong intramolecular hydrogen bonds between these
atoms. In contrast, the other O···O distances are signifi-
cantly longer, although they are also in the range of hydro-
O(3)ϪNaϪO(9)
101.6(2),
O(3)ϪNaϪO(10)
97.4(2),
Na(1)ϪO(1)ϪNa(3) 118.7(3)
Compound 5 displays a simple NMR spectrum. In the
gen bonds. A more detailed discussion about the nature of 1H NMR spectrum only one singlet is observed for the tert-
the hydrogen-bond system is, however, not possible, because butyl groups (at δ ϭ 1.17 ppm) and for the meta protons of
the hydrogen atoms were not found in the Fourier map. In the calix[4]arene unit (at δ ϭ 6.87 ppm). The OH protons
this connection it is interesting to note that, in the known appear at δ ϭ 13.39 ppm. Furthermore, two doublets of the
monometallated sodium compound of A,[10] containing calix[4]arene CH2 protons were observed at δ ϭ 3.07 and
methanol as co-ligand, and the tetrathia analogue B,[14] 5.52 ppm. The crown ether CH2 protons give a signal at
with water and THF as co-ligands, the calixarene units also δ ϭ 3.62 ppm. From these data we can conclude that, in
form an intramolecular hydrogen-bond system. However, in solution, the (18-crown-6)Naϩ moiety jumps from one phe-
these complexes the two calixarene oxygens act as bidentate nol oxygen to another.
1248
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Eur. J. Inorg. Chem. 2004, 1243Ϫ1252

Calix[4]arene Complexes of Sodium and Potassium Stabilized by Crown Ethers
FULL PAPER
In contrast to these results, the reaction of 1 with carbon sume that dipolar aprotic solvents (such as DMF, DMSO
dioxide, with strict exclusion of moisture, proceeds differ- or N-methyl-ε-caprolactam) are stronger ligands than THF
ently. When a solution of 1 in hot THF under an atmos- and can additionally split the NaϪO bonds of the NaOPh
phere of CO2 is quickly cooled down in a dry ice bath, a oligomer in solution. This could result in more-reactive
clear solution is obtained, although the starting compound species which carboxylate activated CϪH bonds much bet-
is only sparingly soluble in cold THF. This is the first evi- ter than the ‘‘closed’’ heterocubane system found in com-
dence for the formation of a reaction product with CO2. In plexes of the type (LNaOPh)[23,24] or polymeric NaOPh.[24]
1
the H NMR spectrum the signals of 1 disappear upon up- In contrast, 1 and 4 are complexes with ‘‘open’’ heterocub-
take of carbon dioxide and a set of new signals appear at ane structures in which the NaϪO bonds should be more
δ ϭ 1.17 (s), 3.07 (d), 3.62 (s), 5.52 (d) and 6.87 ppm (br). reactive in carboxylation reactions of activated aliphatic
The CO2-containing complex could not be isolated because CϪH bonds. The different structure of 2, which exhibits a
the weakly coordinated CO2 is easily eliminated during highly symmetrical anionic structure, could then explain
work up. The final product is again the complex 1. This why 2 is less active.
clearly demonstrates that the CO2 fixation is a reversible
reaction. The same behavior was observed for 2, meaning
Conclusions
that both 1 and 2 are able to act as reversible CO2 carriers.
To prove that the CO2 products are capable of transfer-
ring their CO2 to activated aliphatic CϪH bonds we investi-
gated the reactions of 1, 2 and 4 in THF with 2-fluoropro-
piophenone under an atmosphere of carbon dioxide. After
24 h the reaction mixture was treated with dimethyl sulfate
to yield the methyl ester of the unstable 3-ketocarboxylic
acid. For comparison, the same reaction was carried out
with sodium phenolate, which is known to act as a CO2-
transfer reagent.
Sodium and potassium complexes of calix[4]arenes and
crown ethers yield different types of stable molecular struc-
tures depending on the diameter of the alkali metal cations,
the different size of the cavities of the calix[4]arenes and the
different efficiency of the coordination by additional crown
ether ligands. Even a relatively small difference of the size
˚
in the cavities of A (CϪCH2 ϭ 1.516Ϫ1.581 A) and B
(CϪS ϭ 1.777 A) results in a completely different structure
˚
type for complexes 1 and 2, even though the ratio between
18-crown-6, Naϩ ions and calix[4] arene is the same. While
1 shows a dynamic process in solution above 40 °C, the
structure of the highly symmetrical compound 2 remains
stable at higher temperatures.
Figure 8 shows that in all four reactions 2-benzoyl(2-
fluoro)methylpropionate was formed, although in veryy dif-
ferent yields. Whereas sodium phenolate/CO2 and 2/CO2
show very little activity (9% and 8% yield, respectively), the
systems 1/CO2 and 4/CO2 are very efficient CO2-transfer
reagents that form the carboxylation product in a highly
selective reaction (about 90%).
The structure of the potassium compound 4 is also differ-
ent from the related sodium complex 1. In 4 the calix[4]ar-
ene units are less shifted with respect to the plane fusing
the two heterocubane units, and the coordination of the
peripheral [(THF)K(dibenzo-18-crown-6)]ϩ is also differ-
1
ent. Temperature-dependent H NMR spectra suggest, in
this case, that a dissociation process proceeds resulting in
the formation of ionic species.
Compounds 1 and 4, containing the calix[4]arene A, are
active CO2-transfer reagents towards 2-fluoropropio-
phenone, in contrast to 2, which contains the calix[4]arene
B. This clearly demonstrates the subtle influence of the
structure of the alkali-metal complexes on the CO2 reactiv-
ity in these types of compounds.
Figure 8. Carboxylation of 2-fluoropropiophenone by the com-
plexes 1/CO2, 2/CO2, 4/CO2 and PhONa/CO2 (for comparison) in
THF at ambient temperature; reaction time: 24 h, molar ratio: 2-
fluoropropiophenone/complex ϭ 1:4; the yield was determined by
19F NMR spectroscopy
Experimental Section
Due to the sensitivity of the substances to moisture and partly to
air all manipulations were carried out under an atmosphere of ar-
gon. The solvents DMF and DMSO were dried with molecular
sieves and THF with benzophenone/sodium, and freshly distilled
before use.
Although the reasons for the remarkable difference in the
carboxylation reactivity are hitherto unknown, the follow-
ing points attract attention. Generally, CO2-transfer reac-
tions between NaOPh/CO2 and substrates containing ali-
phatic activated CϪH bonds such as acetone or aceto-
phenone only proceed efficiently if dipolar aprotic solvents
are used as solvent; the activity in THF is very low.[23] The
reaction with 2-fluoropropiophenone confirms this (Fig-
4-tert-Butyltetrathiacalix[4]arene was prepared from 4-tert-bu-
tylphenol and sulfur in a solution of tetraethylene glycol dimethyl
ether.[20] 4-tert-Butylcalix[4]arene, sodium hydride, NaN(SiMe3)2,
KN(SiMe3)2, 4-tert-butylphenol, dibenzo-18-crown-6, 15-crown-5
and 18-crown-6 were purchased from Aldrich and tetraethylene gly-
ure 8). To explain this solvent-dependent activity, we as- col dimethyl ether from Merck-Schuchardt.
Eur. J. Inorg. Chem. 2004, 1243Ϫ1252
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1249

R. Fischer, H. Görls, D. Walther
FULL PAPER
Most of the synthesized complexes contain extremely weakly
product 3a approximately 3% based on the composition [(18-
bound THF in the crystals which is extremely easily released when crown-6)K4(4-tert-butylcalix[4]arene-4H)]. According to the 1H
not in contact with the mother liquor. In addition, THF is very
easily eliminated from complex 1 even at Ϫ78 °C in a stream of
NMR spectrum the purity of the product was greater than 95%.
3a: H NMR (200 MHz, [D8]THF, 10 °C): δ ϭ 1.08 (s, 9 H, tBu),
1
inert gas. The other complexes (except 2 and 5) eliminate solvent 1.11 (s, 9 H, tBu), 1.15 (s, 18 H, tBu), 2.67 (br., CH2), 3.45 (s, 24
when handled at 0 °C. This resulted in problems in obtaining mic-
roanalyses for 1, 3a, and 4 from the bulk material. Furthermore,
only approximate yields (%) could be calculated on the basis of
complex compositions due to loss of non-coordinated volatile sol-
vents. These problems are well-known for alkali metal compounds
of calixarenes containing volatile ligands.[12,14,18]
H, CH2O), 4.44 (br., CH2), 6.63 (s, 4 H, m-CH), 6.91 (s, 4 H, m-
CH) ppm. H NMR (200 MHz, [D8]THF, 55 °C): δ ϭ 1.12 (s, 36
1
H, tBu), 2.67 (br., CH2), 3.46 (s, 24 H, CH2O), 4.44 (br., CH2),
6.82 (s, 8 H, m-CH) ppm.
3b: 1H NMR (200 MHz, [D8]THF, 10 °C): δ ϭ 1.11 (s, 36 H, tBu),
2.70 (br., 4 H, CH2), 3.46 (s, 48 H, CH2O), 4.50 (br., 4 H, CH2),
6.66 (s, 8 H, m-CH) ppm.
1H and 13C NMR spectra were recorded on a Bruker AC 200 F
spectrometer. Mass spectra were recorded on
MAT SSQ 710.
a
Finnigan [(Dibenzo-18-crown-6)K4(4-tert-butylcalix[4]arene-4 H)(THF)3]2·
4THF (4): Dibenzo-18-crown-6 (0.45 g, 1.25 mmol) and
KN(SiMe3)2 (1.07 g, 5.38 mmol) were added to a suspension of 1
[(18-Crown-6)(THF)Na4(4-tert-butylcalix[4]arene-4H)]2·3THF (1):
18-Crown-6 (0.33 g, 1.25 mmol) and sodium hydride (0.13 g,
5.42 mmol) were added to a suspension of A (0.81 g, 1.25 mmol)
in THF (50 mL). The reaction mixture was stirred and heated in a
water bath to reflux. Hydrogen gas was liberated while the starting
materials gradually dissolved. The hot solution was filtered through
a Schlenk frit. Complex 1 crystallized from the filtrate. The color-
less crystals lost non-coordinated THF and formed an amorphous
powder. Yield: 1.3 g (ca. 95% based on the composition [(18-crown-
6)(THF)Na4(4-tert-butylcalix[4]arene-4H)]2. 1H NMR (200 MHz,
[D8]THF, 20 °C): δ ϭ 0.76 (s, 9 H, tBu), 0.95 (s, 9 H, tBu), 1.29 (s,
(0.81 g, 1.25 mmol) in THF (50 mL). The reaction mixture was
stirred and heated in a water bath to reflux while the starting mate-
rials gradually dissolved. The hot solution was filtered through a
Schlenk frit. Compound 4 crystallized from the filtrate as a mixture
with ‘‘K4(4-tert-butylcalix[4]aren-4H)(dibenzo-18-crown-6)2(THF)n’’.
The large colorless crystals of 4 were separated from the fine
needles of the by-product by pouring off the suspension. The color-
less crystals lost non-coordinated THF and formed an amorphous
powder. Yield: 0.44 g of a white amorphous crude product. (ca.
25% based on the composition [(dibenzo-18-crown-6)K4(4-tert-
butylcalix[4]arene-4H)(THF)3]2. 1H NMR (200 MHz, [D8]THF,
10 °C): δ ϭ 1.09 (s, 9 H, tBu), 1.10 (s, 9 H, tBu), 1.15 (s, 18 H,
tBu), 3.00 (d, 2JH,H ϭ 11.7 Hz, 2 H, CH2), 3.92 (br., 8 H, O-CH2),
3.99 (br., 8 H, O-CH2), 4.46 (br., 2 H, CH2), 6.73 (br., 8 H, m-CH),
6.82 (br., 8 H, o-C6H4) ppm.
2
2
18 H, tBu), 2.71 (d, JH,H ϭ 13.1 Hz, 2 H, CH2), 2.82 (d, JH,H
ϭ
13.6 Hz, 2 H, CH2), 3.45 (s, 24 H, CH2O), 3.77 (d, 2JH,H ϭ 13.6 Hz,
2
2 H, CH2), 4.73 (d, JH,H ϭ 13.3 Hz, 2 H, CH2) 6.27 (s, 2 H, m-
CH), 6.54 (s, 2 H, m-CH), 6.84 (s, 2 H, m-CH), 6.90 (s, 2 H, m-
1
CH) ppm. H NMR (200 MHz, [D8]THF, 60 °C): δ ϭ 0.86 (s, 18
2
H, tBu), 1.25 (s, 18 H, tBu), 2.74 (d, JH,H ϭ 13.3 Hz, 4 H, CH2), [(18-Crown-6)Na](4-tert-butylcalix[4]arene-H)·OEt2 (5): Carbon di-
3.38 (s, 24 H, OCH2), 4.19 (br., 4 H, CH2), 6.40 (s, 4 H, m-CH),
oxide gas and water (54 µL, 3.0 mmol) were added to a suspension
6.84 (s, 4 H, m-CH) ppm. 13C{1H} NMR (50.3 MHz, [D8]THF, 60 of crude product of 1 (1.07 g, 1.0 mmol) in THF (50 mL). The
°C): δ ϭ 32.1, 32.6 (CH3, tBu), 33.9 (CH2), 34.8 (C, tBu), 70.5 reaction mixture was then stirred and heated in a water bath to
(CH2O), 123.6, 134.3 (br., o-C), 125.7, 132.1 (m-CH), 129.3, 163.7
(ipso-C). Well-shaped crystals suitable for the X-ray analysis crys-
tallized from a solution in THF.
reflux. The hot solution was filtered through a Schlenk frit. The
complex 5·THF crystallized from the clear filtrate. Single crystals
of 5·OEt2 suitable for X-ray analysis were obtained by recrystalliza-
tion of 5·THF from diethyl ether. Yield: 0.54 g (58%) of colorless
5·THF. C56H79NaO10: calcd. C 71.92, H 8.52; found C 71.46,
[(18-Crown-6)Na(dmf)1.5]2[(4-tert-butyltetrathiacalix[4]arene-
4H)2Na6(dmf)2] (2): 18-Crown-6 (0.33 g, 1.25 mmol) and sodium
hydride (0.13 g, 5.42 mmol) were added to a suspension of B
(0.90 g, 1.25 mmol) in THF (50 mL). The reaction mixture was
stirred and heated in a water bath to reflux. Hydrogen gas was
liberated during the reaction. The resulting white precipitate was
separated from the reaction mixture by filtration through a Schlenk
frit. Single crystals for X-ray analysis of 2 were obtained by recrys-
1
H 8.98. H NMR (200 MHz, [D8]THF, 25 °C): δ ϭ 1.17 (s, 36 H,
2
tBu), 3.07 (d, JH,H ϭ 12.1 Hz, 4 H, CH2), 3.62 (s, 24 H, O-CH2),
2
5.52 (d, JH,H ϭ 12.1 Hz, 4 H, CH2), 6.87 (br., 8 H, m-CH), 13.39
(s, 3 H, OH) ppm. 13C{1H} NMR (50.3 MHz, [D8]THF, 25 °C):
δ ϭ 32.1 (CH3, tBu), 34.1, 35.1, 70.8 (O-CH2), 124.8, 131.2, 139.4,
154.2 (ipso-C) ppm.
tallization of the precipitate from a solution in DMF. Yield: 2.85 g Reaction of 1 with CO2: A suspension of 1 (1.0 mmol) in THF (50
(91%) of colorless needles of 2. C119H171N5Na8O25S8: calcd. C mL) under a carbon dioxide atmosphere was refluxed, resulting in
56.90, H 6.86, N 2.79, S 10.21; found C 56.07, H 6.81, N 3.21, a clear solution which was quickly cooled down in a dry ice bath.
1
1
S 9.44. H NMR (200 MHz, [D7]DMF, 30 °C): δ ϭ 1.14 (s, 36 H, No precipitation was observed. H NMR (200 MHz, [D8]THF, 25
tBu), 3.59 (s, 24 H, OCH2), 7.43 (s, 8 H, m-CH) ppm. 13C{1H}
NMR (50.3 MHz, [D7]DMF, 30 °C): δ ϭ 32.0 (CH3, tBu), 33.6 (C,
tBu), 70.5 (CH2O), 126.3, 134.3, 132.3, 135.9, 171.1 (ipso-C) ppm.
°C): δ ϭ 1.17 (s, 36 H, tBu), 3.07 (d, JH,H ϭ 12.0 Hz, 4 H, CH2),
2
2
3.62 (s, 24 H, O-CH2), 5.52 (d, JH,H ϭ 12.0 Hz, 4 H, CH2), 6.87
(s, 8 H, m-CH) ppm. Carbon dioxide was liberated from this prod-
uct during warming of the solution to reflux under an atmosphere
of argon. The NMR spectroscopic data of the resulting precipitate
were identical to those of the starting compound 1.
[(18-Crown-6)K4(4-tert-butylcalix[4]arene-4H)(THF)n] (3a): A sus-
pension of 1 (0.81 g, 1.25 mmol) in THF (50 mL) was reacted with
18-crown-6 (0.33 g, 1.25 mmol) and KN(SiMe3)2 (1.07 g,
5.38 mmol). Large colorless crystals of 3a were decanted from a
suspension of fine needles of 3b. The crystals of 3a were washed
with THF at Ϫ78 °C in order to remove impurities of 3b from the
surface of the crystals. The colorless crystals very easily lost non-
coordinated THF when not in contact with the mother liquor and
formed an amorphous powder. Yield: 0.04 g of the amorphous
Carboxylation of 2-Fluoropropiophenone:
A suspension of 1
(1.0 mmol), 2 (1.0 mmol) or 4 (1.0 mmol) in THF (30 mL) was
warmed to reflux under an atmosphere of carbon dioxide. The
solution was then quickly put in a dry ice cooling bath. 2-Fluoro-
propiophenone (0.152 g, 1.0 mmol) was then added from a syringe.
The reaction mixture was shaken for 24 h followed by addition of
1250
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Eur. J. Inorg. Chem. 2004, 1243Ϫ1252

Calix[4]arene Complexes of Sodium and Potassium Stabilized by Crown Ethers
FULL PAPER
dimethyl sulfate (0.69 g, 5.5 mmol) and Na2CO3 (0.5 g). The mix-
ture was then shaken for 24 h. Yield of 2-fluoro-2-benzoyl-methyl-
propionate (as determined by 19F NMR spectroscopy): 92% for 1/
1.22° Յ Θ Յ 27.41°, completeness Θmax ϭ 87.3%, 27449 indepen-
dent reflections.
Crystal Data for 4:[49] C168H232K8O30, Mr ϭ 3044.34 g·molϪ1, col-
orless prism, size 0.32 ϫ 0.28 ϫ 0.20 mm3, monoclinic, space group
1
CO2; 8% for 2/CO2; 89% for 4/CO2. H NMR (200 MHz, CDCl3,
3
25 °C): δ ϭ 1.86 (d, JH,F ϭ 22.6 Hz, 3 H, CH3), 3.76 (s, 3 H,
˚
P21/n, a ϭ 16.7197(2), b ϭ 18.9198(5), c ϭ 27.1965(6) A, β ϭ
COOCH3), 7.42Ϫ8.04 (m,
5
H, Ph) ppm. 13C{1H} NMR
3
˚
97.489(1)°, V ϭ 8529.8(3) A , T ϭ Ϫ90 °C, Z ϭ 2, ρcalcd. ϭ
1.185 g·cmϪ3, µ(Mo-Kα) ϭ 2.69 cmϪ1, F(000) ϭ 3264, 62897 reflec-
tions in h(Ϫ21/18), k(Ϫ24/19), l(Ϫ34/35), measured in the range
1.31° Յ Θ Յ 27.45°, completeness Θmax ϭ 97.5%, 19016 indepen-
dent reflections, Rint ϭ 0.096, 10537 reflections with Fo Ͼ 4σ(Fo),
803 parameters, 4 restraints, R1obs ϭ 0.132, wR2obs ϭ 0.347, R1all ϭ
0.214, wR2all ϭ 0.395, GOOF ϭ 1.280, largest difference peak and
(50.3 MHz CDCl3, 25 °C): δ ϭ 20.9 (d, 2JF,C ϭ 23.3 Hz, CH3), 53.1
1
2
(COOCH3), 97.0 (d, JF,C ϭ 195.1 Hz, CF), 20.9 (d, JF,C
ϭ
23.3 Hz, CH3), 128.5 (CH), 129.6 (d, 4JF,C ϭ 5.6 Hz, m-CH), 130.0
(d, 3JF,C ϭ 20.4 Hz, ipso-C), 133.8 (CH), 168.7 (d, 2JF,C ϭ 25.6 Hz,
2
COOCH3), 191.6 (d, JF,C ϭ 25.2 Hz, CϭO) ppm. 19F NMR
3
(188.3 MHz, CDCl3, CFCl3, 25 °C): δ ϭ Ϫ151.9 (q, JH,F
ϭ
22.6 Hz) ppm. MS (EI): m/z ϭ 210 [Mϩ], 179 [Mϩ Ϫ OCH3], 151
[Mϩ Ϫ COOCH3], 105 [PhCO]. GC-IR: ν(CϭO) ϭ 1777 cmϪ1
ν(COOCH3) ϭ 1712 cmϪ1
Ϫ3
˚
hole: 3.123/Ϫ1.179 e·A
.
,
.
Crystal
Data
for
5:[49]
C56H79NaO10·C4H10O,
Mr ϭ
1009.30 g·molϪ1, colorless prism, size 0.32 ϫ 0.30 ϫ 0.28 mm3,
monoclinic, space group P21, a ϭ 12.6427(5), b ϭ 12.7316(3), c ϭ
Carboxylation with 2/CO2 yielded the product in very low yield.
Upon reaction with dimethyl sulfate, white crystals of 4-tert-butyl-
tetrathiacalix[4]arene tetramethyl ether[44] crystallized as the first
product from the reaction mixture. 1H NMR (200 MHz, CDCl3,
25 °C): δ ϭ 1.28 (s, 36 H, tBu), 3.42 (s, 12 H, OCH3), 7.42 (s, 8 H,
m-CH) ppm.
˚
18.4929(6) A, α ϭ 90.00°, β ϭ 94.233(1)°, γ ϭ 90.00°, V ϭ
2968.5(2) A , T ϭ Ϫ90 °C, Z ϭ 2, ρcalcd. ϭ 1.129 g·cmϪ3, µ(Mo-
3
˚
Kα) ϭ 0.82 cmϪ1, F(000) ϭ 1096, 4475 reflections in h(0/14), k(0/
14), l(Ϫ20/20), measured in the range 2.21° Յ Θ Յ 23.26°, com-
pleteness Θmax ϭ 99.4%, 4475 independent reflections, 3732 reflec-
tions with Fo Ͼ 4σ(Fo), 648 parameters, 7 restraints, R1obs ϭ 0.068,
wR2obs ϭ 0.171, R1all ϭ 0.100, wR2all ϭ 0.201, GOOF ϭ 1.129,
Flack-parameter Ϫ0.1(9), largest difference peak and hole: 0.544/
Crystal Structure Determination: The intensity data for the com-
pounds were collected on a Nonius KappaCCD diffractometer,
using graphite-monochromated Mo-Kα radiation. Data were cor-
rected for Lorentz and polarization effects, but not for absorption
effects.[45,46] The structures were solved by direct methods
(SHELXS[47]) and refined by full-matrix least-squares techniques
against F2o (SHELXL-97[48]). All hydrogen atoms were included at
calculated positions with fixed thermal parameters. All non-hydro-
gen atoms were refined anisotropically.[48] The R1 values are rela-
tively high, since the compounds are large systems that contain
both slightly disordered coordinated and non-coordinated solvent
molecules. In addition, tert-butyl groups cause high anisotropic dis-
placement parameters. This is typical for a number of similar com-
pounds.[14,18] Very recently the general reasons for the difficulties
in obtaining low R1 values have been discussed in detail.[14]
Ϫ3
˚
Ϫ0.319 e·A
.
Acknowledgments
Financial support for this work from the Deutsche Forschungsge-
meinschaft (SFB 436), and the Fonds der Chemischen Industrie is
gratefully acknowledged.
[1]
A. F. D. de Namor, R. M. Cleverley, L. Z. Zapata-Ormachea,
Chem. Rev. 1998, 98, 2495Ϫ2525.
[2]
A. Ikeda, S. Shinkai, Chem. Rev. 1997, 97, 1713Ϫ1734.
[3]
A. F. D. de Narmor, R. M. Cleverley, L. Z. Ormachea, Chem.
Rev. 1998, 98, 2495Ϫ2525.
Since the quality of the data of both modifications of compound
2 is too low, we will only publish the conformation of the molecule
and the crystallographic data. We have not deposited the data with
the Cambridge Crystallographic Data Center. Although the R1
value for 4 is also high, the estimated standard derivations (e.s.d.)
for the bond lengths and angles are small (see Figure 5), therefore
the structural data have been deposited. XP (SIEMENS Analytical
X-ray Instruments, Inc.) was used for structure representations
[4]
D. Roundhill, Prog. Inorg. Chem. 1995, 43, 533Ϫ592.
[5]
C. Wieser, C. B. Dielemann, D. Matt, Coord. Chem. Rev. 1997,
165, 93Ϫ161.
C. D. Gutsche, in Calixarenes Revisited. Monographs in Supra-
molecular Chemistry, No 1 (Ed.: J. F. Stoddart), RSC, Cam-
bridge 1998.
C. Floriani, R. Floriani-Moro, Adv. Organomet. Chem. 2001,
47, 167Ϫ233.
[6]
[7]
[8]
V. B öhmer, Angew. Chem. 1995, 107, 785 Ϫ818.; Angew. Chem.
[49]
Crystal Data for 1:
C
H224Na8O29, Mr ϭ 1325.60 g·molϪ1, col-
148
Int. Ed. Engl. 1995, 34, 713Ϫ1734.
orless prism, size 0.40 ϫ 0.35 ϫ 0.32 mm3, triclinic, space group
P1, a ϭ 16.6116(6), b ϭ 17.3483(9), c ϭ 17.9319(9) A, α ϭ
[9]
J. M. Harrowfield, M. I. Ogden, W. R. Richmond, A. H. White,
˚
¯
J. Chem. Soc., Chem. Commun. 1991, 1159Ϫ1161.
F. Hamada, K. D. Robinson, G. W. Orr, J. L. Atwood, Supra-
mol. Chem. 1993, 2, 19.
P. Thuery, Z. Asfari, J. Vicens, V. Lamare, J.-F. Dozol, Poly-
hedron 2002, 21, 2497Ϫ2503 and references cited therein.
S. R. Dubberley, A. J. Blake, P. Mountford, Chem. Commun.
1997, 1603 Ϫ1604.
T. A. Hanna, L. Liu, L. N. Zakharov, A. L. Rheingold, W. H.
3
˚
[10]
97.769(2)°, β ϭ 105.557(2)°, γ ϭ 115.616(2)°, V ϭ 4297.3(3) A ,
T ϭ Ϫ90 °C,
Z ϭ 2, ρ , µ(Mo-Kα) ϭ
calcd. ϭ 1.024 g·cmϪ3
[11]
0.86 cmϪ1, F(000) ϭ 1432, 11345 reflections in h(0/17), k(Ϫ19/17),
l(Ϫ19/18), measured in the range 4.93° Յ Θ Յ 23.31°, completeness
[12]
Θ
max ϭ 91.3%, 11345 independent reflections, 8317 reflections with
Fo Ͼ 4σ(Fo), 946 parameters, 0 restraints, R1obs ϭ 0.087, wR2obs ϭ
0.246, R1all ϭ 0.118, wR2all ϭ 0.2704, GOOF ϭ 1.092, largest differ-
[13]
Watson, C. D. Gutsche, Tetrahedron 2002, 58, 9751Ϫ9757.
A. Bilyk, A. K. Hall, J. M. Harrowfield, M. W. Hosseini, B.
Ϫ3
˚
[14]
ence peak and hole: 0.523/Ϫ0.426 e·A
.
W. Skeleton, A. H. White, Inorg. Chem. 2001, 40, 672Ϫ686.
Crystal Data for 2: C108H136N20Na8O5S8, Mr ϭ 2234.77 g·molϪ1
,
[15]
H. Bock, A. John, C. Näther, Z. Havlas, J. Am. Chem. Soc.
colorless prism, size 0.04 ϫ 0.03 ϫ 0.03 mm3, monoclinic, space
1995, 117, 9367Ϫ9368.
M. G. Davidson, J. A. K. Howard, S. Lamb, C. W. Lehmann,
Chem. Commun. 1997, 1607Ϫ1608.
G. Guillemot, E. Solari, C. Rizzoli, C. Floriani, Chem. Eur. J.
˚
group P21/n, a ϭ 12.8900(1), b ϭ 32.1789(5), c ϭ 33.4040(4) A,
[16]
3
˚
β ϭ 94.988(8)°, V ϭ 13803.0(3) A , T ϭ 20 °C, Z ϭ 4, ρcalcd. ϭ
1.075 g·cmϪ3, µ(Mo-Kα) ϭ 2.05 cmϪ1, F(000) ϭ 4720, 77462 reflec-
tions in h(Ϫ15/12), k(Ϫ38/41), l(Ϫ32/43), measured in the range
[17]
2002, 8, 2072 Ϫ2080.
Eur. J. Inorg. Chem. 2004, 1243Ϫ1252
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1251

R. Fischer, H. Görls, D. Walther
FULL PAPER
[18]
[37]
[38]
E. D. Gueneau, K. M. Fromm, H. Goesmann, Chem. Eur. J.
T. Kajiwara, S. Yokozawa, T. Ito, N. Iki, N. Morohashi, Angew.
Chem. 2002, 114, 2180Ϫ2182; Angew. Chem. Int. Ed. 2002,
41, 2076Ϫ2078.
G. G. Tanalova, N. S. A. Elkarim, V. S. Talanov, R. E. Hanes
Jr., H.-S. Hwang, R. A. Bartsch, R. D. Rogers, J. Am. Chem.
Soc. 1999, 121, 11281Ϫ11290.
W. Uhl, F. Hannemann, J. Organomet. Chem. 1999, 579,
18Ϫ23.
P. Doppelt, J. Fischer, L. Richard, R. Weiss, New. J. Chem.
1987, 11, 357Ϫ360.
M. Tahiri, P. Doppelt, J. Fischer, R. Weiss, Inorg. Chem. 1988,
27, 2897Ϫ2899.
M. Dobler, J. D. Dunitz, P. Seiler, Acta Crystallogr., Sect. B
1974, 30, 2741Ϫ2743.
H. Kumagai, M. Hasegawa, S. Miyanari, Y. Sugawa, Y. Sato,
T. Hori, S. Udea, H. Kamiyama, S. Miyano, Tetrahedron Lett.
1997, 38, 3971Ϫ3972.
P. Lhotak, M. Himl, S. Pakhoverova, I. Stibor, Tetrahedron
Lett. 1998, 39, 8915Ϫ8918.
COLLECT, Data Collection Software, Nonius B. V., The Ne-
therlands, 1998.
Z. Otwinowski, W. Minor, ‘‘Processing of X-ray Diffraction
Data Collected in Oscillation Mode’’, in Methods in Enzy-
mology, Vol. 276, Macromolecular Crystallography, Part A
(Eds.: C. W. Carter, R. M. Sweet), Academic Press, 1997, pp.
307Ϫ326.
G. M. Sheldrick, Acta Crystallogr., Sect. A 1990, 46, 467Ϫ473.
G. M. Sheldrick, SHELXL-97 (Release 97-2), University of
Göttingen, Germany, 1997.
CCDC-216538 (1), -216539 (4), and -216540 (5) contain the
supplementary crystallographic data for this paper. These data
can be obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: (in-
ternat.) ϩ 44-1223-336-033; or deposit@ccdc.cam.ac.uk).
Received August 8, 2003
2003, 9, 509Ϫ514.
S. R. Dubberley, A. J. Blake, P. Mountford, Dalton Trans. 2003,
2418Ϫ2427 and references cited therein.
[19]
[20]
G. Bottachio, G. P. Chiosoli, J. Chem. Soc., Chem. Commun.
1966, 618.
[39]
[40]
[41]
[42]
[43]
[21]
G. Bottachio, G. P. Chiosoli, M. Felicioli, Gazz. Chim. Ital.
1973, 103, 105Ϫ116.
G. Bottachio, M. Marchi, G. P. Chiosoli, Gazz. Chim. Ital.
[22]
1976, 106, 499Ϫ500.
D. Walther, U. Ritter, S. Geßler, J. Sieler, M. Kunert, Z. Anorg.
[23]
Allg. Chem. 1994, 620, 101Ϫ106 and references cited therein.
M. Kunert, M. Nauck, J. Sieler, E. Dinjus, Chem. Ber./Recueil
[24]
1997, 130, 1461Ϫ1465 and references cited therein.
R. M. Izatt, J. S. Bradshaw, S. A. Nielsen, J. D. Lamp, J. J.
[25]
Christensen, D. Sen, Chem. Rev. 1985, 85, 271Ϫ339.
G. D. Andreetti, R. Ungaro, A. Pochini, J. Chem. Soc., Chem.
[26]
[44]
[45]
[46]
Commun. 1979, 1005Ϫ1007.
D. J. Darensbourg, C. G. Bauch, A. L. Rheingold, Inorg. Chem.
[27]
1987, 26, 977Ϫ980.
W. Liaw, D. Ou, Y. Li, W. Lee, C. Chuang, Y. Lee, G. Lee, S.
[28]
Peng, Inorg. Chem. 1995, 34, 3747Ϫ 3754.
E. S. Schmidt, A. Jokisch, H. Schmidbauer, J. Am. Chem. Soc.
[29]
1999, 121, 9758Ϫ9759.
S. Anfang, M. Karl, N. Faza, W. Massa, J. Magull, K.
[30]
Dehnicke, Z. Anorg. Allg. Chem. 1997, 623, 1425Ϫ1432.
H. Zhang, X. Wang, B. K. Teo, J. Am. Chem. Soc. 1996, 118,
11813Ϫ11821.
M. A. Bush, M. R. Truter, J. Chem. Soc. B 1971, 1440Ϫ1446.
J. W. Steed, Coord. Chem. Rev. 2001, 215, 171Ϫ221.
K. M. Fromm, E. D. Gueneau, J.-P. Rivera, G. Bernadelli, Z.
[47]
[48]
[31]
[32]
[49]
[33]
[34]
Anorg. Allg. Chem. 2002, 628, 171Ϫ178.
J. W. Steed, P. C. Punkt, J. Chem. Soc., Dalton Trans. 1999,
2141Ϫ2146.
[35]
[36]
T. Akutagawa, T. Hasegawa, T. Nakamura, S. Takeda, T. Inabe,
K. Sugiura, Y. Sakata, A. E. Underhill, Chem. Eur. J. 2001,
4902Ϫ4912.
Early View Article
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1252
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Eur. J. Inorg. Chem. 2004, 1243Ϫ1252