Dendritic zirconium-peroxotungstosilicate hybrids: Synthesis, characterization, and use as recoverable and reusable sulfide oxidation catalysts

Article abstract of DOI:10.1002/ejic.200901141

A series of dondrimer-confaining polyoxomotalalos (DENDRIPOMs) was synthesized by coupling zirconium-peroxotungstosilicate [Zr₂(O ₂)₂ (SiW₁₁O₃₉)₂] ¹² with ammonium dendrons by electrostatic bonding. These DENDRIPOMs were successfully characterized by standard physicochemical techniques (e.g. IR and NMR spectroscopy and MS), and they represent the first examples of dendritic POMs based on zirconium-substituted polytungstates. The data obtained arc consistent with structures in which the anionic POM is surrounded by cationic ammonium dondrons. In contrast to the potassium salt of [Zr₂(O ₂)₂(SiW₁₁O₃₉)₂] ^12-, the dendritic counterparts are soluble in common organic solvents, an important feature for the use of DENDRIPOMs in homogeneous catalysis. Our DENDRIPOMs are stable, efficient, recoverable, and reusable catalysts for the oxidation of sulfides in aqueous/CDCl₃ biphasic media, with hydrogen peroxide as the oxidant, in contrast to their nondendritic n-butyl ammonium counterpart. Two cycles of catalytic reactions were performed without any appreciable loss of activity. We also discovered that the reaction kinetics and selectivity of the DENDRIPOMs arcs influenced by the structure of the countercation used.

Full text of DOI:10.1002/ejic.200901141

FULL PAPER
DOI: 10.1002/ejic.200901141
Dendritic Zirconium-Peroxotungstosilicate Hybrids:
Synthesis, Characterization, and Use as Recoverable and Reusable Sulfide
Oxidation Catalysts
Claire Jahier,[a] Sib Sankar Mal,[b] Ulrich Kortz,*[b] and Sylvain Nlate*[a]
Keywords: Dendrimers / Polyoxometalates / Homogeneous catalysis / Oxidation / Catalyst recovery / Zirconium
A
series of dendrimer-containing polyoxometalates
counterparts are soluble in common organic solvents, an im-
(DENDRIPOMs) was synthesized by coupling zirconium-per- portant feature for the use of DENDRIPOMs in homogeneous
oxotungstosilicate [Zr2(O2)2(SiW11O39)2]12– with ammonium
dendrons by electrostatic bonding. These DENDRIPOMs
were successfully characterized by standard physicochemi-
cal techniques (e.g. IR and NMR spectroscopy and MS), and
they represent the first examples of dendritic POMs based
on zirconium-substituted polytungstates. The data obtained
are consistent with structures in which the anionic POM is
surrounded by cationic ammonium dendrons. In contrast to
the potassium salt of [Zr2(O2)2(SiW11O39)2]12–, the dendritic
catalysis. Our DENDRIPOMs are stable, efficient, recovera-
ble, and reusable catalysts for the oxidation of sulfides in
aqueous/CDCl3 biphasic media, with hydrogen peroxide as
the oxidant, in contrast to their nondendritic n-butyl ammo-
nium counterpart. Two cycles of catalytic reactions were per-
formed without any appreciable loss of activity. We also dis-
covered that the reaction kinetics and selectivity of the
DENDRIPOMs are influenced by the structure of the
countercation used.
tion of POMs with appropriate organic molecules has re-
sulted in a variety of inorganic–organic hybrids with spe-
cific properties.
Introduction
Research on dendritic catalysts has been developing dur-
ing the last decade, because of the potential applications of
such compounds in various areas.[1] The use of dendrimers
in catalysis, pioneered by van Leeuwen,[2b,2d] has received
considerable attention, because the large size of these com-
pounds may allow for easy recovery of the catalyst, an es-
sential feature for reaction efficiency, economy, and envi-
ronmental compatibility.[2] In addition, by virtue of chemi-
cal and structural modifications, it is possible to design a
variety of dendritic compounds with specific properties.
Numerous dendrimers have been used in different domains
such as supramolecular chemistry,[1d] nanoscience,[1c] drug
delivery,[3] and catalysis.[2] Among them, a few examples
based on polyoxometalates (POMs) have been reported.[4]
POMs[5] are a large class of inorganic cage complexes with
highly interesting properties that render them attractive for
potential applications in a variety of fields such as catalysis,
biology, magnetism, optics, and medicine.[6] The combina-
An area of particular interest to us has been studying
how the dendritic structures may alter the properties of the
incorporated POMs. In this context, we designed and pre-
pared various dendritic POM hybrids (DENDRIPOMs)
based on electrostatic bonding between the triply charged
Venturello ion [PO4{WO(O2)2}4]3– and dendritic cations,
and then we used these materials as recoverable catalysts in
the oxidation of organic substrates such as alkenes,
alcohols, and sulfides.[4d–4j] The investigation of these DEN-
DRIPOMs clearly indicated that the dendritic structure
modulates the properties of the anionic POMs. For exam-
ple, we have shown that the nature of the dendritic wedge
is closely related to the catalytic efficiency, the stability, the
solubility, and the recyclability of the POM clusters. More
recently, we reported the first examples of optically active
DENDRIPOMs, prepared by electrostatic interaction be-
tween an achiral POM and enantiopure dendritic cations,
and by selecting an enantioselective reaction we demon-
strated chirality transfer from dendritic wedges to a catalyti-
cally active POM unit.[4j] Thus, exploring the chemistry of
DENDRIPOMs remains an interesting and challenging
topic in POM chemistry and material science alike. Almost
all DENDRIPOMs reported to date are based on the Ven-
turello ion.
[a] ISM, UMR CNRS N° 5255, Université Bordeaux 1,
351 Cours de la liberation, 33405 Talence Cedex, France
Fax: +33-5-40006994
E-mail: s.nlate@ism.u-bordeaux1.fr
[b] Jacobs University, School of Engineering and Science,
P. O. Box 750 561, 28725 Bremen, Germany
E-mail: u.kortz@jacobs-university.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200901141.
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C. Jahier, S. S. Mal, U. Kortz, S. Nlate
FULL PAPER
In this paper, we demonstrate that dendritic zirconium- troscopy by following the complete disappearance of the
peroxotungstosilicate hybrids can also be prepared, and we triplet at δ = 3.24 ppm, assigned to the CH2I groups, and
show their potential as efficient and recoverable sulfide oxi- the appearance of a new triplet attributed to the CH2O
dation catalysts.
groups. Tri(4-tert-butylphenyl) dendron 4b was prepared by
the coupling reaction of protected dendron P[9] with 4-tert-
butylphenol (4c) in the presence of K2CO3, as summarized
in Scheme 2.
Results and Discussion
Synthesis and Characterization of Zirconium-Peroxo-Based
DENDRIPOMs
The synthetic strategy used to incorporate the zirconium-
peroxo-containing tungstosilicate[7] [Zr2(O2)2(SiW11O39)2]12–
into dendrimers involves the electrostatic coupling of de-
signed dendritic cations with the anionic zirconium-per-
oxotungstosilicate in a biphasic mixture of water and meth-
ylene dichloride.
Scheme 2. Synthesis of tri(4-tert-butylphenyl) dendron 4b.
Dendron 4b was characterized by NMR spectroscopy,
Synthesis of Dendritic Quaternary Ammonium Bromide
Salts
Dendritic quaternary ammonium salts 7a,b and their mass spectrometry, and elemental analysis before use. Its
nondendritic counterpart 7c were prepared by the reaction mass spectrum shows a prominent peak at m/z = 701.45
of alcohol 3 with AB3 phenol dendrons 4a,[8] 4b and 4-tert- (calcd. 701.98) [M + Na]+. The bromination of compounds
butylphenol (4c), respectively (Scheme 1). The reaction of 5a–c with PBr3 affords their bromobenzyl counterparts
1-chloro-4-iodobutane (in excess) with 4-hydroxybenzyl 6a,[4i] 6b, and 6c in good to excellent yields. The reaction of
alcohol (1) led to alcohol 2 in 90% yield. The latter, in the trihexylamine with bromobenzyl compounds 6a, 6b, and 6c
presence of NaI in butanone, gave alcohol 3 in 96% yield. leads to the corresponding ammonium salts 7a, 7b, and 7c
The reaction of iodo compound 3 with triallyl dendron 4a, in 94, 98, and 97% yield, respectively. Ammonium salts 7b
tri(4-tert-butylphenyl) dendron 4b, and 4-tert-butylphenol and 7c have been characterized by mass spectrometry, and
(4c) led to the corresponding triallyl dendron 5a,[4i] tri(4- their mass spectra show molecular peaks at m/z = 1109.59
tert-butylphenyl) dendron 5b, and alcohol 5c, respectively. [M – Br]+ (calcd. 1109.73) and m/z = 580.51 [M – Br]+
The reaction was easily monitored by 1H NMR spec- (calcd. 580.95), respectively.
Scheme 1. Synthesis of ammonium bromide salts 7a–c.
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Dendritic Zirconium-Peroxotungstosilicate Hybrids
Synthesis of DENDRIPOMs 8a–c
troscopic data would be a good line of evidence for the
presence of the polyanion in these systems. Unfortunately,
all attempts to perform 29Si and 183W NMR spectroscopy
were futile. We have not been able to observe any signal in
the 29Si and 183W NMR spectra yet, probably because of
the low receptivity of Si and W in dilute systems. In certain
POM systems we have observed 29Si and 183W NMR spec-
tra, but this has become increasingly difficult with dendritic
POM frameworks. However, efforts have been devoted to
the characterization of these hybrids by NMR (1H and 13C)
and IR spectroscopy and especially by elemental analysis
(see the Experimental Section and the Supporting Infor-
mation). The data reported in this manuscript agree with
the proposed structures for these DENDRIPOMs. To the
best of our knowledge, DENDRIPOMs 8a–c represent the
first examples of dendritic POM salts based on a zirco-
nium-containing polytungstate.
The potassium salt of the anionic zirconium-peroxo-con-
taining tungstosilicate [Zr2(O2)2(SiW11O39)2]12– reacts with
ammonium compounds 7a, 7b, and 7c in a biphasic mixture
of water and methylene dichloride to give the corresponding
DENDRIPOMs 8a, 8b, and 8c, which contain the poly-
anion at the core. These compounds were obtained in 98,
95, and 95% yield, respectively. The syntheses of 36-allyl
DENDRIPOM 8a and 12-(4-tert-butylphenyl) DENDRI-
POM 8c are summarized in Scheme 3, whereas that of 36-
(4-tert-butylphenyl) DENDRIPOM 8b is shown in
Scheme 4. The NMR and IR spectroscopic and elemental
analysis data reported for DENDRIPOMs 8a–c were in
agreement with the structures shown in Schemes 3 and 4
(see the Experimental Section and the Supporting Infor-
mation for the spectra). Furthermore, in contrast to the po-
tassium salt of polyanion [Zr2(O2)2(SiW11O39)2]12–
,
DENDRIPOMs 8a–c are soluble in common organic sol-
vents, indicating transfer of the polyanion into the organic
phase. In addition, the 1H NMR signals of DENDRIPOMs
Catalytic Oxidation Tests with DENDRIPOMs 8a and 8c
1
8a–c are broad compared to the H NMR signals of the
To evaluate the catalytic efficiency of our DENDRIPOMs
ammonium bromide salts of dendrons 7a–c, probably due 8a and 8c in oxidation reactions, we tested the oxidation
to substitution of the bromide ions by the polyanion. We of thioanisole (9a), 4-bromothioanisole (9b), and diphenyl
have tried very hard to crystallize our DENDRIPOMs, but sulfide (9c), as well as cyclooctene (10) and cyclohexanol
up to now all attempts to obtain single crystals suitable for (11), with H2O2 (35%) in a biphasic mixture of water and
XRD studies have failed. Some 29Si and 183W NMR spec- CDCl3 (0.4%, Scheme 5). The properties of 8a and 8c were
Scheme 3. Synthesis of 36-allyl DENDRIPOM 8a and 12-(4-tert-butylphenyl) DENDRIPOM 8c.
Eur. J. Inorg. Chem. 2010, 1559–1566
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C. Jahier, S. S. Mal, U. Kortz, S. Nlate
FULL PAPER
Scheme 4. Synthesis of 36-(4-tert-butylphenyl) DENDRIPOM 8b.
compared to those of their nondendritic n-butyl ammonium and DENDRIPOM catalysts 8a and 8c indicated that
counterpart 8d (see Supporting Information for IR and DENDRIPOMs were more active. Within the DENDRI-
NMR spectra of 8d). The results reported in Table 1 clearly POM series, 8a was more active than 8c (87 vs. 76% conver-
show that DENDRIPOMs 8a and 8c oxidize thioanisole sion, Table 1, entries 1 and 6) and slightly more selective for
(9a) to the corresponding sulfoxide 12a and sulfone 13a, sulfone 13a (78 vs. 73%).
with 87% conversion for 8a and 76% conversion for 8c,
after 15 min reaction time, whereas only 6% of 12a was
Table 1. Catalytic oxidation of sulfides with DENDRIPOMs 8a
obtained with nondendritic POM 8d. In addition, 8a and
8c do not react with diphenyl sulfide (9c). The comparison
between the catalytic activity of the nondendritic POM 8d
and 8c and nondendritic n-butyl ammonium salt 8d, as well as the
oxidation of cyclooctene (10) and cyclohexanol (11) with 8a and
8c, by using H2O2.[a]
Entry Catalyst Substrate Time[b] % Conversion[c] Product[c] (% yield)
1
2
3
4
5
6
7
8
8a
8c
8d
9a
9b
9c
10
11
9a
9b
9c
10
11
9a
15 min 87
15 min 100
12a (22) 13a (78)
13b (100)
12c (32) 13c (68)
14 (0)
15 (0)
12a (27) 13a (73)
13b (100)
12c (39) 13c (61)
14 (0)
15 (0)
12a (6) 13a (0)
12a (10) 13a (0)
12c (0) 13c (0)
24 h
48 h
48 h
100
–
–
15 min 76
15 min 100
24 h
48 h
100
–
9
10
11
12
13
48 h
–
15 min
6
30 min 10
24 h
9c
–
[a] Catalytic conditions: in CDCl3 at 35 °C under vigorous stirring;
reactants were added as follows: catalyst (0.4 mol-%), H2O2 (35%
in H2O, 800 equiv.), CDCl3, and substrate (250 equiv.). [b] Nonop-
timized reaction times. [c] Conversion determined from the relative
intensities of the 1H NMR signals of the substrate and the product.
After the first 15 min, the reaction became extremely
slow, without any appreciable activity (2 to 5% conversion),
even upon lengthening the reaction time up to 6 h or raising
Scheme 5. Catalytic oxidation of 9a–c, 10, and 11 with 8a and 8c.
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Dendritic Zirconium-Peroxotungstosilicate Hybrids
1
just before use. All other chemicals were used as received. The H
the temperature up to 50 °C. In contrast to thioanisole (9a),
DENDRIPOMs 8a and 8c selectively oxidize 4-bromo-
thioanisole (9b) to the corresponding sulfone 13b with
100% conversion after 15 min (Table 1, entries 2 and 7).
Under analogous reaction conditions, no trace of sulfoxide
was observed. In the case of the diphenyl sulfide (9c), the
reaction kinetics was low with DENDRIPOMs and gave
quantitatively sulfoxide 12c in 32 to 39% conversion
(Table 1, entries 3 and 8) and sulfone 13c in 68 to 61%
and 13C NMR spectra were recorded at 25 °C with a Bruker AC,
250 FT spectrometer (250.13 MHz for H and 62.91 MHz for 13C)
1
and a Bruker AC 200 FT spectrometer (200.16 MHz for 1H and
50.33 MHz for 13C) at the CESAMO (Bordeaux, France). All
chemical shifts are referenced to Me4Si (TMS). Mass spectrometry
was performed by the CESAMO with a QStar Elite mass spectrom-
eter (Applied Biosystems) equipped with an ESI source, and spec-
tra were recorded in the positive mode. The electrospray needle was
maintained at 4500 V and operated at room temperature. Samples
conversion. No trace of sulfoxide 12c or sulfone 13c was were introduced by injection through a 10 µL sample loop into a
200 µL/min flow of methanol from the LC pump. Elemental analy-
ses were carried out at the Vernaison CNRS center. The infrared
spectra were recorded in KBr pellets with a FTIR Paragon 1000
Perkin–Elmer spectrometer, unless otherwise indicated. Organic
oxidation products were identified by correlation to authentic sam-
ples.
observed when using n-butyl salt 8d. It is interesting to note
that these reactions did not proceed in the absence of DEN-
DRIPOMs 8a and 8c, when carried out under similar con-
ditions. The catalyst was easily recovered by precipitation
1
with diethyl ether and checked by H NMR and IR spec-
troscopy before a new catalytic cycle was conducted. Two
reaction cycles were performed in order to test the stability
of 8a, 8c, and 8d under catalytic reaction conditions.
Dendritic Zirconium-Peroxotungstosilicate Hybrids
Alcohol 2: To a solution of 4-hydroxybenzyl alcohol (1) (5.00 g,
Thioanisole (9a) was used as a model substrate and was 40.27 mmol) in dmf (20 mL) were added 1-chloro-4-iodobutane
(6.4 mL, 11.44 g, 52.36 mmol) and K2CO3 (14.09 g, 100.67 mmol).
The mixture was stirred overnight at room temperature and ex-
tracted with diethyl ether (3ϫ30 mL). The resulting solution was
washed with water and dried with sodium sulfate. After removal of
the solvent under vacuum, the product was purified by chromatog-
raphy on a silica gel column with a 9:1 petroleum ether/diethyl
ether mixture to provide 7.78 g (90%) of 2 as a white solid. 1H
NMR (CDCl3, 250.13 MHz): δ = 7.27 (d, 2 H, Ar), 6.88 (d, 2 H,
Ar), 4.62 (d, 2 H, CH2OH), 3.99 (t, 2 H, OCH2), 3.60 (t, 2 H,
ClCH2), 1.96 (broad, 2 H, CH2), 1.55 (broad, 2 H, CH2) ppm. 13C
NMR (CDCl3, 62.91 MHz): δ = 158.4 (Cq, ArO), 133.2 (Cq, Ar),
128.7 (CH, Ar), 114.4 (CH, Ar), 66.7 (OCH2), 64.8 (OCH2), 44.7
(ClCH2), 31.5 (CH2), 30.2 (CH2) ppm. C11H15ClO2 (214.69): calcd.
C 61.54, H 7.04; found C 61.69, H 6.98.
oxidized with DENDRIPOMs without any appreciable loss
in activity and selectivity, whereas the activity decreased sig-
nificantly after the first cycle with n-butyl salt 8d: only 3%
of 12a was obtained after 4 h reaction time. In the case of
cyclooctene (10) and cyclohexanol (11), DENDRIPOMs do
not display any appreciable reactivity, and epoxide 14 and
ketone 15 were not observed (Scheme 4 and Table 1, entries
9, 10).
Conclusions
We have synthesized and characterized dendritic zirco-
nium-peroxo-containing tungstosilicate salts (DENDRI-
POMs) and used them as recoverable catalysts in the oxi-
dation of sulfides to the corresponding sulfoxides and sul-
fones, with hydrogen peroxide as the oxidant, with good to
excellent conversion. These compounds represent the first
examples of DENDRIPOMs based on a zirconium-con-
taining polytungstate. A study of the countercation effects
revealed that the dendritic structure modifies the solubility,
reactivity, and selectivity of the polyanion. These results
highlight that some key parameters important in catalysis
can be tuned by modifying the local environment of the
polyanion. We believe that an appropriate design of den-
dritic structures will enable the use of a large variety of
POM species in catalysis. Hence DENDRIPOMs represent
a promising and elegant approach with respect to catalytic
activity, selectivity (including enantioselectivity), and cata-
lyst recovery. We are currently working in this area.
Alcohol 3: A mixture of alcohol 2 (3.00 g, 13.97 mmol) and NaI
(4.20 g, 28.00 mmol) in 2-butanone (20 mL) was stirred for 24 h at
80 °C. After removal of the solvent under vacuum, the residue was
extracted with dichloromethane (3ϫ30 mL). Then the organic
layer was washed with a saturated aqueous solution of Na2S2O3.
The solvent was removed under vacuum to provide 4.10 g (96%)
1
of 3 as a white solid. H NMR (CDCl3, 250.13 MHz): δ = 7.25 (d,
2 H, Ar), 6.85 (d, 2 H, Ar), 4.55 (broad, 2 H, CH2OH), 3.96 (t, 2
H, OCH2), 3.24 (t, 2 H, ICH2), 2.07–1.82 (m, 4 H, CH2) ppm. 13C
NMR (CDCl3, 62.91 MHz): δ = 158.4 (Cq, ArO), 133.3 (Cq, Ar),
128.7 (CH, Ar), 114.3 (CH, Ar), 66.7 (OCH2), 64.9 (OCH2), 31.5
(CH2), 30.2 (CH2), 6.7 (ICH2) ppm. C11H15IO2 (306.13): calcd. C
43.16, H 4.94; found C 42.77, H 4.64.
Dendron 4b: In a Schlenk tube, a mixture of protected triiodo-
phenol dendron P[9] (2.00 g, 2.99 mmol), 4-tert-butyl phenol (4c),
(2.03 g, 13.51 mmol), and K2CO3 (3.80 g, 27.14 mmol) in dmf
(20 mL) was stirred for 48 h at room temperature. K2CO3 (2.14 g,
15.28 mmol) and water (4 mL) were added, and the reaction mix-
ture was stirred at 40 °C for 48 h. The mixture was then extracted
with CH2Cl2 (3ϫ30 mL), and the resulting solution was washed
with water and dried with sodium sulfate. After removal of the
solvent under vacuum, the product was purified by chromatog-
raphy on a silica gel column with a 9:1 pentane/diethyl ether mix-
ture to provide 1.62 g (80%) of 4b as a white solid. 1H NMR
(CDCl3, 250.13 MHz): δ = 7.27 (d, 8 H, Ar), 6.79 (d, 8 H, Ar),
4.66 (broad, 1 H, OH), 3.87 (t, 6 H, OCH2), 1.82 (broad, 6 H,
CH2), 1.60 (broad, 6 H, CH2), 1.30 (s, 27 H, CH3) ppm. 13C NMR
(CDCl3, 62.91 MHz): δ = 156.7 (Cq, ArO), 153.3 (Cq, ArO), 143.2
Experimental Section
General Remarks: Reagent-grade tetrahydrofuran (thf) and diethyl
ether were predried with Na foil and distilled from sodium benzo-
phenone under argon immediately prior to use. Acetonitrile
(CH3CN) was stirred under argon overnight over phosphorus pent-
oxide, distilled from sodium carbonate, and stored under argon.
Methylene chloride (CH2Cl2) was distilled from calcium hydride
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C. Jahier, S. S. Mal, U. Kortz, S. Nlate
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(Cq, Ar), 138.7 (Cq, Ar), 127.7 (CH, Ar), 126.2 (CH, Ar), 115.0
(CH, Ar), 113.9 (CH, Ar), 68.3 (OCH2), 42.1 (Cq-CH2), 34.07 (Cq-
CH3), 33.7 (CH2), 31.6 (CH3), 23.7 (CH2) ppm. ESI-MS: calcd. for
[M + Na]+ 701.98; found 701.45. C46H62O4 (678.99): calcd. C
81.37, H 9.20; found C 81.28, H 9.08.
113.9 (CH, Ar), 67.6 (CH2-O), 67.3 (CH2-O), 34.1 (BrCH2), 34.1
(Cq-CH3), 33.7 (CH2), 31.5 (CH3), 26.0 (CH2) ppm. C21H27BrO2
(391.34): calcd. C 64.45, H 6.95; found C 64.62, H 7.17.
Ammonium Bromide Dendron 7a: A mixture of triallylphenyl bro-
mobenzyl compound 6a[4i] (0.76 g, 1.66 mmol) and tri-n-hex-
ylamine (1.6 mL, 4.98 mmol) in CH3CN (3 mL) was stirred for 16 h
Dendron 5b: A mixture of tri(4-tert-butylphenyl) dendron 4b
(1.00 g, 1.47 mmol), alcohol 3 (0.408 g, 1.33 mmol), and K2CO3 at 80 °C. After removal of the solvent under vacuum, the residue
(0.617 g, 4.41 mmol) in dmf (10 mL) was stirred for 48 h at room was washed with petroleum ether (3ϫ30 mL) and dried under vac-
temperature. The reaction mixture was then extracted with CH2Cl2
(3ϫ20 mL), and the resulting solution was washed with water and NMR (CDCl3, 200.16 MHz): δ = 7.40 (d, 2 H, Ar), 7.17 (d, 2 H,
uum to provide ammonium salt 7a with 94% yield (1.10 g). 1H
dried with sodium sulfate. The solvent was removed under vacuum,
and the product was purified by chromatography on a silica gel
column with a 6:4 petroleum ether/diethyl ether mixture to provide
0.855 g (75%) of 5b as a yellow solid. 1H NMR (CDCl3, 250 MHz):
Ar), 6.90 (d, 2 H, Ar), 6.82 (d, 2 H, Ar), 5.49 (m, 3 H, CH=CH2),
4.96 (m, 6 H, CH=CH2), 4.59 (s, 2 H, NCH2), 4.09 (m, 4 H, CH2-
O), 3.20 (m, 6 H, NCH2), 2.37 (d, 6 H, CH2CH=CH2), 2.01 (broad,
4 H, CH2), 1.74 (m, 18 H, CH2), 0.88 (m, 9 H, CH3) ppm. 13C
δ = 7.27–7.25 (m, 10 H, Ar), 6.90–6.76 (m, 10 H, Ar), 4.61 (d, 2 NMR (CDCl3, 62.91 MHz): δ = 160.4 (Cq, ArO), 156.6 (Cq, ArO),
H, CH2-OH), 4.01 (m, 4 H, CH2-O), 3.86 (t, 6 H, CH2-O), 1.98
(broad, 4 H, CH2-CH2), 1.80 (broad, 6 H, CH2-CH2), 1.57 (broad,
143.3 (Cq, Ar), 133.9 (Cq, Ar), 132.7 (CH=CH2), 126.2 (CH, Ar),
118.9 (CH, Ar), 117.59 (CH=CH2), 115.0 (CH, Ar), 113.8 (CH,
6 H, CH2-CH2), 1.28 (s, 27 H, CH3) ppm. 13C NMR (CDCl3, Ar), 67.7 (CH2O), 67.2 (CH2O), 58.4 (CH2N), 41.2 (CH2), 31.5
63 MHz): δ = 156.7 (Cq, Ar-O), 143.1 (Cq, Ar), 138.2 (Cq, Ar),
(CH2), 31.2 (CH2), 26.6 (CH2), 26.1 (CH2), 25.9 (CH2), 22.6 (CH2),
129.4 (CH, Ar), 127.5 (CH, Ar), 126.2 (CH, Ar), 114.4 (CH, Ar), 22.5 (CH2), 13.9 (CH3) ppm. C45H72BrNO2 (738.97): calcd. C
113.9 (CH, Ar), 68.3 (CH2-O), 64.9 (CH2-OH), 42.1 (Cq-CH2), 34.1 73.14, H 9.82; found C 74.15, H 9.89.
(Cq-CH3), 33.8 (CH2), 31.2 (CH3), 23.8 (CH2) ppm. C57H76O6
Ammonium Bromide Dendron 7b: This compound was synthesized
(857.22): calcd. C 79.87, H 8.94; found C 79.00, H 8.68.
according to the same procedure as described above for 7a, but
Alcohol 5c: This compound was synthesized according to the same
procedure as described above for 5b, but with 4-tert-butylphenol
(4c) instead of tri(4-tert-butylphenyl) dendron 4b. Alcohol 5c was
obtained in 95% yield as a white solid, after chromatography on a
silica gel column with a 7:3 petroleum ether/diethyl ether mixture.
1H NMR (CDCl3, 250 MHz): δ = 7.30 (m, 4 H, Ar), 6.86 (m, 4 H,
Ar), 4.61 (s, 2 H, CH2-OH), 4.02 (broad, 4 H, CH2-O), 1.97 (broad,
with tri(4-tert-butylphenyl)bromobenzyl compound 6b instead of
triallylphenyl bromobenzyl compound 6a. Ammonium salt 7b was
obtained as a yellow solid in 98% (0.46 g) yield. 1H NMR (CDCl3,
200.16 MHz): δ = 7.42 (d, 2 H, Ar), 7.25 (m, 6 H, Ar), 6.94 (d, 2
H, Ar), 6.79 (m, 6 H, Ar), 4.81 (s, 2 H, NCH2), 4.01 (m, 4 H, CH2-
O), 3.84 (broad, 6 H, CH2-O), 3.24 (broad, 6 H, NCH2), 1.97
(broad, 4 H, CH2), 1.78 (broad, CH2), 1.56 (broad, CH2), 1.32
4 H, CH2-CH2), 1.30 (s, 9 H, CH3) ppm. 13C NMR (CDCl3, (broad, CH2), 1.27 (broad, CH2), 0.88 (broad, 9 H, CH3) ppm. 13
63 MHz): δ = 158.9 (Cq, Ar-O), 156.8 (Cq, Ar-O), 138.8 (Cq, Ar), NMR (CDCl3, 62.91 MHz): δ = 160.8 (Cq, ArO), 156.7 (Cq, ArO),
132.9 (Cq, Ar), 129.4 (CH, Ar), 127.5 (CH, Ar), 114.4 (CH, Ar), 143.1 (Cq, Ar), 133.9 (CH, Ar), 127.5 (Cq, Ar), 126.2 (CH, Ar),
114.0 (CH, Ar), 67.9 (CH2-O), 67.6 (CH2-O), 64.9 (CH2-OH), 34.1 118.8 (Cq, Ar), 115.2 (CH, Ar), 113.9 (CH, Ar), 68.3 (CH2O), 67.8
(Cq-CH3), 31.5 (CH3), 26.0 (CH2) ppm. C21H28O3 (328.45): calcd. (CH2O), 67.2 (CH2O), 58.5 (CH2N), 42.0 (CH2), 34.0 (CH2), 33.7
C
C 76.79, H 8.59; found C 76.29, H 8.52.
(CH2), 31.5 (Cq-CH3), 31.2 (CH2), 26.1 (CH2), 26.0 (CH2), 23.7
(CH2), 22.7 (CH2), 22.5 (CH2), 13.9 (CH3) ppm. MALDI-TOF:
calcd. for [M – Br]+ 1109.73; found 1109.59. C75H114BrNO5
(1189.63): calcd. C 75.72, H 9.66; found C 75.89, H 9.22.
Dendron 6b: PBr3 (0.05 mL, 0.53 mmol) was added to a cooled mix-
ture (0 °C) of dendron 5b (1.00 g, 1.16 mmol) in toluene (5 mL).
The resulting solution was stirred at room temperature for 4 h. Af-
ter removal of the solvent, the residue was extracted with Et2O,
washed with water, and dried with sodium sulfate. The solvent was
removed under vacuum to provide 1.05 g (99%) of 6b as a yellow
oil. 1H NMR (CDCl3, 250 MHz): δ = 7.33–7.26 (m, 8 H, Ar), 6.88–
6.77 (m, 8 H, Ar), 4.50 (s, 2 H, Br-CH2), 4.04 (broad, 4 H, CH2-
O), 3.87 (broad, 6 H, CH2-O), 1.98 (m, 4 H, CH2-CH2), 1.82 (m,
6 H, CH2-CH2), 1.58 (m, 6 H, CH2-CH2), 1.34 (s, 27 H, CH3) ppm.
13C NMR (CDCl3, 63 MHz): δ = 159.1 (Cq, Ar-O), 156.7 (Cq, Ar-
Ammonium Bromide Salt 7c: This compound was synthesized ac-
cording to the same procedure as described above for 7a, but with
bromobenzyl compound 6c instead of triallylphenyl bromobenzyl
compound 6a. Ammonium salt 7c was obtained as a light orange
1
oil in 97% (2.9 g) yield. H NMR (CDCl3, 200.16 MHz): δ = 7.43
(d, 2 H, Ar), 7.28 (d, 2 H, Ar), 6.87 (d, 2 H, Ar), 6.83 (d, 2 H, Ar),
4.84 (s, 2 H, NCH2), 4.02 (broad, 4 H, CH2-O), 3.28 (broad, 6 H,
NCH2), 1.97 (broad, 4 H, CH2), 1.76 (broad, 6 H, CH2), 1.33
O), 143.1 (Cq, Ar), 138. 8 (Cq, Ar), 134.1 (Cq, Ar), 130.5 (Cq, Ar), (broad, CH2) 1.29 (s, 9 H, CH3), 0.89 (broad, CH3) ppm. 13C NMR
127.5 (CH, Ar), 126.2 (CH, Ar), 114.7 (CH-CH2), 114.0 (CH, Ar),
(CDCl3, 62.91 MHz): δ = 160.7 (Cq, ArO), 156.6 (Cq, ArO), 143.3
113.9 (CH, Ar), 68.3 (CH2-O), 67.6 (CH2-O), 67.3 (CH2-O), 42.1 (Cq, Ar), 133.9 (Cq, Ar), 126.2 (CH, Ar), 119.0 (CH, Ar), 115.1
(Cq-CH2), 34.1 (CH2-Br), 34.0 (Cq-CH3), 33.7 (CH2), 31.6 (CH3),
26.1 (CH2), 23.7 (CH2) ppm. C57H75BrO5 (920.12): calcd. C 74.41,
H 8.22; found C 74.41, H 7.50.
(CH, Ar), 113.8 (CH, Ar), 67.7 (CH2O), 67.2 (CH2O), 58.4
(CH2N), 41.2 (Cq-CH3), 34.0 (CH2), 31.5 (CH2), 31.2 (CH2), 26.1
(CH2), 26.0 (CH2), 22.6 (CH2), 22.5 (CH2), 13.9 (CH3) ppm. ESI-
MS: calcd. for [M – Br]+ 580.95; found 580.51. C39H66BrNO2
(660.86): calcd. C 70.88, H 10.07; found C 71.34, H 10.24.
Bromobenzyl Compound 6c: This compound was synthesized ac-
cording to the same procedure as described above for 6b, but with
alcohol 5c instead of tri(4-tert-butylphenyl) dendron 5b. Bro-
36-Allyl Dendritic Zirconium-Peroxotungstosilicate Hybrid 8a: To a
water solution (0.5 mL) of POM K12[Zr2(O2)2(SiW11O39)2]·28H2O
mobenzyl compound 6c was obtained in 93% yield (2.0 g) as a
1
white solid. H NMR (CDCl3, 250 MHz): δ = 7.33–7.26 (m, 4 H, (189 mg, 0.029 mmol) was added a solution of ammonium bromide
Ar), 6.87–6.82 (m, 4 H, Ar), 4.51 (s, 2 H, BrCH2), 4.02 (broad, 4
dendron 7a (300 mg, 0.406 mmol) in CH2Cl2 (3 mL). The mixture
H, CH2-O), 1.97 (broad, 4 H, CH2-CH2), 1.30 (s, 9 H, CH3) ppm.
was vigorously stirred at room temperature for 24 h. The CH2Cl2
13C NMR (CDCl3, 63 MHz): δ = 156.7 (Cq, Ar-O), 143.3 (Cq, Ar), layer was with dried with sodium sulfate. After evaporation under
130.5 (CH, Ar), 129.9 (Cq, Ar), 126.3 (CH, Ar), 114.8 (CH, Ar), vacuum, the residue was washed with diethyl ether to provide den-
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Eur. J. Inorg. Chem. 2010, 1559–1566

Dendritic Zirconium-Peroxotungstosilicate Hybrids
1
dritic POM 8a as a yellow solid (398 mg, 98%). H NMR (CDCl3, NMR (CDCl3, 200.16 MHz): δ = 3.26 (broad, 96 H, CH2-N), 1.60
200.16 MHz): δ = 7.43 (broad, 24 H, Ar), 7.19 (broad, 24 H, Ar),
(broad, 96 H, CH2), 1.37 (broad, 96 H, CH2), 0.90 (broad, 144 H,
6.83 (broad, 48 H, Ar), 5.52 (m, 36 H, CH=CH2), 5.01–4.94 (m, CH3) ppm. 13C NMR (CDCl3, 62.91 MHz): δ = 58.8 (CH2-N), 24.0
96 H, CH=CH2 and NCH2), 4.12 (broad, 48 H, CH2-O), 3.19 (CH ), 19.5 (CH ), 13.5 (CH ) ppm. FTIR (KBr pellets): ν = 1473
˜
2
2
3
(broad, 72 H, NCH2), 2.40 (d, 72 H, CH2CH=CH2), 2.24 (broad,
48 H, CH2), 1.81 (broad, 72 H, CH2), 1.29 (broad, 216 H, CH2),
0.86 (broad, 108 H, CH3) ppm. 13C NMR (CDCl3, 62.91 MHz): δ
= 160.1 (Cq, ArO), 156.7 (Cq, ArO), 137.7 (Cq, Ar), 134.6
(CH=CH2), 134.3 (Cq, Ar), 127.6 (CH, Ar), 119.9 (CH, Ar), 117.6
(CH=CH2), 114.8 (CH, Ar), 113.8 (CH, Ar), 64.5 (CH2O), 64.1
(CH2O), 58.1 (CH2N), 42.7 (Cq-CH2), 41.9 (CH2), 31.2 (CH2), 29.3
(CH2), 26.0 (CH2), 22.5 (CH2), 22.3 (CH2), 14.0 (CH3) ppm. FTIR
(s), 1382 (w), 955 (s), 914 (s), 877 (m), 805 (m), 741 (s) cm–1.
Supporting Information (see footnote on the first page of this arti-
cle): IR spectra of K12[Zr2(O2)2(SiW11O39)2]12–·28H2O, 7a, 7c, 8a–
d, and n-butylammonium iodide salt; NMR spectra of 8a, 8b, and
8d.
Acknowledgments
(KBr pellets): ν = 1469 (s), 1378 (w), 957 (s), 909 (vs), 879 (m), 825
˜
(m), 793 (vs) cm–1. C540H920N12O134Si2W22Zr2 (14008.52): calcd. C
46.30, H 6.62, N 1.20, W 28.87; found C 46.52, H 6.42, N 1.23, W
29.15.
S. N. and C. J. thank the Agence National de la Recherche (grant
ANR-06-BLAN-0215), the University Bordeaux 1, and the Centre
national de la recherche scientifique (CNRS) for financial support.
C. J. thanks the European Science Foundation (ESF) European
Cooperation in Science and Technology (COST) D40 action for a
Short Term Scientific Missions (STSM) grant, allowing for a re-
search visit at Jacobs University Bremen. U. K. and S. S. M. thank
Jacobs University Bremen and the Fonds der Chemischen Industrie
for research support. We also thank Dr. Bassem Bassil and Dr.
Nadeen Nsouli for assistance in the lab.
36-(4-tert-Butylphenyl) Dendritic Zirconium-Peroxotungstosilicate
Hybrid 8b: This compound was synthesized according to the same
procedure as described above for 8a, but with tri(4-tert-bu-
tylphenyl) ammonium bromide dendron 7b instead of triallylphenyl
ammonium bromide dendron 7a. Dendritic POM salt 8b was ob-
tained as a light yellow solid in 95% (0.416 g) yield. 1H NMR
(CDCl3, 300 MHz): δ = 7.37 (dbroad, 24 H, Ar), 7.18 (mbroad, 96 H,
Ar), 6.84–6.69 (mbroad, 120 H, Ar), 6.79 (m, 6 H, Ar), 4.81 (sbroad
,
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and Dendrons, Concepts, Synthesis and Applications, VCH-
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science”, special triple issue of C. R. Chimie, Vol. 6, Issues 8–10,
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24 H, NCH2), 3.93 (broad, 48 H, CH2-O), 3.78 (tbroad, 72 H, CH2-
O), 3.14 (broad, 72 H, NCH2), 1.90 (broad, 48 H, CH2), 1.74
(broad, CH2), 1.50 (broad, 72 H, CH2), 1.36 (broad, CH2), 1.20
(broad, 324 H, CH3), 0.80 (broad, 108 H, CH3) ppm. 13C NMR
(CDCl3, 62.91 MHz): δ = 160.5 (Cq, ArO), 156.9 (Cq, ArO), 156.7
(Cq, ArO), 143.2 (Cq, Ar), 143.1 (CH, Ar), 138.5 (Cq, Ar), 134.2
(Cq, Ar), 127.5 (CH, Ar), 126.2 (CH, Ar), 119.6 (Cq, Ar), 115.2
(CH, Ar), 114.0 (CH, Ar), 113.9 (CH, Ar), 68.3 (CH2O), 67.6
(CH2O), 67.4 (CH2O), 58.3 (CH2N), 42.0 (Cq-CH2), 34.0 (Cq-CH3),
33.7 (CH2), 33.5 (CH2), 31.5 (CH3), 31.2 (CH2), 27.5 (CH2), 26.0
(CH2), 23.7 (CH2), 22.4 (CH2), 13.9 (CH3) ppm. FTIR (KBr pel-
lets): ν = 1469 (s), 1378 (w), 957 (s), 909 (vs), 879 (m), 825 (m),
˜
793 (vs) cm–1. C900H1424N12O170Si2W22Zr2 (19416.44): calcd. C
55.67, H 7.39, W 20.83; found C 55.04, H 7.48, W 20.07.
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8708.
12-(4-tert-Butylphenyl) Dendritic Zirconium-Peroxotungstosilicate
Hybrid 8c: This compound was synthesized according to the same
procedure as described above for 8a, but with 4-tert-butylphenyl
ammonium dendron 7c instead of triallylphenyl ammonium bro-
mide dendron 7a. Dendritic POM salt 8c was obtained as a light
1
yellow solid in 95% (0.374 g). H NMR (CDCl3, 250.13 MHz): δ
= 7.44 (broad, 24 H, Ar), 7.28 (d, 24 H, Ar), 6.88–6.81 (m, 48 H,
Ar), 4.92 (broad, 24 H, CH2N), 4.00 (broad, 48 H, CH2-O), 3.20
(broad, 72 H, CH2N), 1.94 (broad, 48 H, CH2), 1.79 (broad, CH2),
1.40 (broad, CH2), 1.28 (s, 108 H, CH3), 0.86 (broad, 108 H, CH3)
ppm. 13C NMR (CDCl3, 62.91 MHz): δ = 160.1 (Cq, ArO), 156.7
(Cq, ArO), 143.2 (Cq, Ar), 134.2 (CH, Ar), 126.1 (CH, Ar), 119.9
(Cq, Ar), 114.6 (CH, Ar), 113.8 (CH, Ar), 67.4 (CH2O), 62.8
(CH2O), 58.1 (CH2N), 33.9 (Cq-CH2), 31.5 (CH3), 31.2 (CH2), 26.0
(CH2), 25.9 (CH2), 22.4 (CH2), 22.2 (CH2), 13.9 (CH3) ppm. FTIR
(KBr pellets): ν = 1469 (s), 1378 (w), 957 (s), 909 (vs), 880 (m), 827
˜
(m), 793 (vs) cm–1. C468H848N12O134Si2W22Zr2 (13071.16): calcd. C
43.00, H 6.54, N 1.29, W 30.94; found C 42.24, H 6.30, N 1.29, W
29.92.
[5] a) M. T. Pope, A. Müller, Angew. Chem. Int. Ed. Engl. 1991,
30, 34–48; b) J. T. Rhule, C. L. Hill, D. A. Rud, R. F. Schinazi,
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1998, 98, 359–388; d) M. T. Pope, A. Müller, Polyoxometalate
Chemistry: From Topology via Self-Assembly to Applications,
Kluwer Academic, Dordrecht, 2001.
n-Butyl Zirconium-Peroxotungstosilicate Hybrid 8d: This com-
pound was synthesized according to the same procedure as de-
scribed above for 8a, but with n-butylammonium iodide instead of
triallylphenyl ammonium bromide dendron 7a. Dendritic POM salt
1
8d was obtained as a light yellow solid in 96% (0.125 g) yield. H
Eur. J. Inorg. Chem. 2010, 1559–1566
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1565

C. Jahier, S. S. Mal, U. Kortz, S. Nlate
FULL PAPER
[6] For the multiple facets of POM chemistry, see ref.[5] and the
special issue dedicated to POMs: Chem. Rev. 1998, 98, 1–390.
[7] a) S. S. Mal, N. H. Nsouli, M. Carraro, A. Sartorel, G. Scor-
rano, H. Oelrich, L. Walder, M. Bonchio, U. Kortz, Inorg.
Chem. 2010, 49, 7–9; b) B. S. Bassil, S. S. Mal, M. H. Dickman,
U. Kortz, H. Oelrich, L. Walder, J. Am. Chem. Soc. 2008, 130,
6696–6697.
[8] S. Nlate, L. Plault, F.-X. Felpin, D. Astruc, Adv. Synth. Catal.
2008, 350, 1419–1424.
[9] V. Sartor, S. Nlate, J. L. Fillaut, L. Djakovitch, F. Moulines, V.
Marvaud, F. Neveu, J. C. Blais, J. F. Létard, D. Astruc, New J.
Chem. 2000, 24, 351–370.
Received: November 24, 2009
Published Online: February 23, 2010
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Eur. J. Inorg. Chem. 2010, 1559–1566