Tethered ansa-bridged titanium complexes immobilized on 3-mercaptopropyl-functionalized silica gel and their application for the hydrosilylation of imines

Article abstract of DOI:10.1039/c2dt31207g

Four tethered titanocene complexes were covalently immobilized onto 3-mercaptopropyl-functionalized silica gel. We have investigated the influence of the length of the tether and of the ansa-bridge on the activity in the heterogeneous hydrosilylation of the cyclic imine 2-phenylpyrroline, taken as an illustrative example. Possible metal leaching during the reaction was investigated using ICP/OES, recycling studies and the three-phase test. The novel immobilized catalysts exhibit an activity similar to their homogeneous analogues in the tested hydrosilylation reactions with a TOF of ～20 h ^-1. Furthermore, our results indicate that metal leaching is negligible under the applied reaction conditions.

Full text of DOI:10.1039/c2dt31207g

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PAPER
Tethered ansa-bridged titanium complexes immobilized on 3-mercaptopropyl-
functionalized silica gel and their application for the hydrosilylation of imines
a
a
a
b
Heidrun Gruber-Woelfler, Georg J. Lichtenegger, Christoph Neubauer, Eleonora Polo* and
Johannes G. Khinast
a
Received 5th June 2012, Accepted 16th August 2012
DOI: 10.1039/c2dt31207g
Four tethered titanocene complexes were covalently immobilized onto 3-mercaptopropyl-functionalized
silica gel. We have investigated the influence of the length of the tether and of the ansa-bridge on the
activity in the heterogeneous hydrosilylation of the cyclic imine 2-phenylpyrroline, taken as an illustrative
example. Possible metal leaching during the reaction was investigated using ICP/OES, recycling studies
and the three-phase test. The novel immobilized catalysts exhibit an activity similar to their homogeneous
analogues in the tested hydrosilylation reactions with a TOF of ∼20 h− . Furthermore, our results indicate
that metal leaching is negligible under the applied reaction conditions.
1
3
2
33,34
35
silica, polymeric supports
immobilization inside a polymeric matrix.
using covalent tethering techniques is currently the most promis-
and hybrid silica, or (iv) self-
Introduction
36–38
Immobilization
Hydrosilylation of unsaturated compounds has gained consider-
able importance during the last few years due to its simplicity
and the mild reaction conditions.
39
ing approach for designing stable heterogeneous catalysts.
1
–4
Although hydrogenation is
However it is not a painless procedure, because, besides the
extra steps required for chemical derivatization, in a lot of cases
the immobilization can bring about a more or less drastic
decrease of the activity and/or stereocontrol, likely due to the
reduced accessibility of the metal center and to the interference
of the solid matrix surface.
We have previously reported the covalent immobilization of
an ω-alkenyl tethered ethylenebis(indenyl)zirconium complex on
H-terminated Si(111) surfaces using UV-mediated alkene hydro-
silylation, thus making possible the development of structured
catalytic surfaces with highly controlled properties. Although flat
functionalized surfaces can be used as sensors or can find appli-
cation in microreactors, for detailed characterization and bulk
syntheses high-surface-area supports are required.
widely practiced in industrial plants and gives, after work-up, the
same products as some hydrosilylation reactions, this methodo-
logy is affected by several disadvantages, such as high operating
pressure, increased safety requirements, metal leaching, and
difficult, if not impossible, catalyst recycling. The latter two
drawbacks also affect the catalysts used for hydrosilylation reac-
tions in the homogeneous phase. In general, the immobilization
of homogeneous catalysts on solid supports can circumvent
these problems and improve the resource management. However,
only few studies have been reported in the area of hydrosilyl-
ation with supported catalysts, including the hydrosilylation of
ketones with Rh-based catalysts supported either on organic
polymeric matrices or silica, and the heterogeneous hydro-
silylation of alkenes with Rh-
40
5
,6
6
7,8
9
,10
11–13
and Pt-based catalysts.
Therefore, we adopted an immobilization approach that com-
bines a high-surface-area with the catalytic efficiency of Group
metallocenes. The target of this research was the test of the
In addition, titanocene complexes are known to be highly active
and selective catalysts for hydrosilylations.
supported Ti-based catalysts have been mainly used for
polymerizations,
4
,14–17
However,
4
feasibility and efficiency of the immobilization process, the
characterization of the supported catalysts, the study of their
activity in a model reaction, and, finally, the investigation of
their recycling and the detection of possible leaches during
hydrosilylation.
We have synthesized four new ansa-bridged bis(indenyl) tita-
nium complexes (Fig. 1) bearing ω-alkenyl tethers of different
lengths on either an ethylene (1 and 2) or a methylene bridge
18–22
23–26
24,27
epoxidations,
oxidations,
and
28
29
hydrogenations, as well as anticancer drugs. Heterogeneous
Group 4 metallocene catalysts can be prepared by a number of
30,31
methods:
(i) direct adsorption of the catalyst onto the
support, (ii) grafting on carriers previously modified with MAO,
alkylaluminum, organosilanes or borates, (iii) direct synthesis on
(
3a,b and 4). Complexes 1 and 2 are related to the zirconium
a
complex successfully immobilized on H-terminated Si(111)
Institute for Process and Particle Engineering, Graz University of
40
Technology, Inffeldgasse 21A/II, A-8010 Graz, Austria.
E-mail: khinast@tugraz.at; Fax: +43 316 873 7963
surfaces, while 3a,b and 4 are particularly interesting, because
the shorter bridge keeps the rings closer to the catalytic center,
thus exerting a stronger influence on its activity, that could be
tuned in future studies through a rational choice of the indenyl
b
C.N.R. (ISOF, U.O.S. Ferrara), c/o Dip. di Chimica, Via L. Borsari 46,
I-44121 Ferrara, Italy. E-mail: eleonora.polo@isof.cnr.it;
Fax: +39 0532240709; Tel: +39 0532455159
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and also one main point of this work. The heterogeneity of the
immobilized titanocene 4 was tested using ICP/OES, recycling
studies and a three-phase test.
Our results indicate that: (i) the novel immobilized catalysts
are highly active for the tested heterogeneous hydrosilylation
reactions; (ii) under the applied hydrosilylation conditions metal
leaching is negligible.
Results and discussion
Synthesis of the titanium complexes
The synthesis of the functional ethylene-bridged ligands was
carried out according to the synthetic pathway reported by
49
Panarello et al., and the metalation was performed by reaction
of their potassium salts with TiCl ·2THF to give OctEBITiCl 1
4
2
and ButEBITiCl 2. This synthetic sequence gave the best results
2
compared with other possible approaches, because the presence
of the tether, combined with the reactivity of the metal, restricts
the range of possible reagents in order to avoid either the
polymerization of the double bond or the reduction of the metal.
The NMR data of complexes 1 and 2 are consistent with the
presence of mixtures of rac/meso isomers as was reported for the
40
corresponding zirconium complex of 1.
4
3
Fig. 1 Tethered titanocene complexes immobilized on MPSG.
Separation of the meso isomer by selective precipitation did
not work in both cases, because the hydrocarbon chain of the
ω-alkenyl tether greatly increases the solubility of the complexes
in most organic solvents, including pentane.
substituents. Methylene-bridged bis(indenyl) complexes have
been extensively studied in polymerization, but far less in cataly-
sis for fine chemicals synthesis.
Therefore, isomer mixtures were used to test the feasibility of
the immobilization procedure, to optimize it, and to investigate
the activity and the actual heterogeneity of the immobilized cata-
lysts. Methylene bridged complexes, 3a,b and 4, bearing a
saturated/unsaturated tether were prepared starting from indene
and the corresponding ketones via benzofulvenes 5a,b/5*a,b
We report here the covalent immobilization of complexes 1–4
on 3-mercaptopropyl-functionalized silica gel (MPSG). Silica
gel is a well established support that offers remarkable advan-
tages over other organic/inorganic solid matrices, because it is a
commercially available high-surface-area substrate with a known
constant composition, enabling easy analysis and interpretation
of the results. Silica shows great resistance to organic solvents,
no swelling, very high thermal resistance, and good mechanical
stability. MPSG has already been used with success in pharma-
ceutical processes up to the pilot plant scale.
50
(Scheme 1) according to the Stone and Little procedure.
Metallocene 3b can be used as a reference for the reactivity in
solution without possible interference from the terminal double
bond. Reaction of the benzofulvene mixtures 5/5*a,b with indenyl
lithium, followed by treatment with n-butyllithium (n-BuLi),
gave the corresponding dilithium salts 6a,b, that yielded the
desired metallocenes 3a,b after metallation with TiCl ·2THF
Scheme 1). Also in this case, chiral separation of the methyl-
ene-bridged metallocenes was found to be quite impossible.
Therefore, we tested another approach in order to prevent at
least the formation of the undesired meso isomer. The bisdi-
lithium salt 5a was reacted with a dichlorotitaniumbinaphtholate
tetrahydrofurane complex prepared according to Brintzinger’s
procedure. The particular spatial array of binaphthol rings
makes the coordination of the ligand to the metal center with
indenyl moieties on the same side (i.e., the meso isomer)
impossible. Furthermore, the binaphthol σ-ligand makes the
complex less sensitive towards air and humidity in comparison
with the corresponding dichloride. The NMR spectra of com-
pound 4 confirmed that only the rac-mixture was present.
The activity of the titanium catalysts was tested for the hetero-
geneous hydrosilylation of 2-phenylpyrroline, an imine often
4
(
4
1–43
used as a model compound for asymmetric syntheses,
because it is very stable and easily synthesized. The reduction
product, 2-phenylpyrrolidine, is a valuable intermediate for the
3
9
synthesis of pharmaceuticals and agrochemicals, e.g., it is a
key intermediate in the preparation of tricyclic systems, such as
pyrrolo[2,1-a]isoquinolines, which exhibit significant activities
51
4
4,45
as antidepressant drugs.
Particular care was paid to the characterization of the sup-
ported catalysts and the detection of possible leaches during
hydrosilylation. Indeed, metal contamination of the products is a
serious issue in the synthesis of active pharmaceutical intermedi-
4
6,47
ates.
Leaching of the catalyst into the product would involve
4
8
time-consuming and costly purification steps. Furthermore,
leaching of the active metal leads to a decreased turnover fre-
quency (TOF) of the catalyst.
Immobilization of the complexes
The determination of the true catalytically active species (i.e.,
homogeneous or heterogeneous) is therefore an important issue
The immobilization of the complexes onto MPSG (Scheme 2)
was performed using AIBN [(2,2′-azobis(2-methylpropionitrile)]
12712 | Dalton Trans., 2012, 41, 12711–12719
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Table 1 ICP/OES and elemental analyses of the solid support (MPSG)
and the immobilized titanium complexes
b/c
b/c
d/e
Compound
C
S
Ti
MPSG
OctEBITiCl
ButEBITiCl
ButMBITiCl 3a
ButMBITibin 4
7.2/6.1
14.8/12.3
12.1/10.0
11.1/9.3
17.3/14.4
4.2/1.4
3.8/1.2
4.2/1.3
4.5/1.4
3.9/1.2
—
a
a
2
1
2
0.5/0.10
0.6/0.12
0.6/0.10
0.5/0.10
2
a
2
a
a
Immobilized on MPSG. wt%. mmol g−1, by elemental analysis.
b
c
d
e
−1
wt%. mmol g determined by ICP/OES.
2
Fig. 2 ATR-IR spectrum of OctEBITiCl on MPSG.
hydrosilylation, we used the mixtures of the rac/meso isomers of
the titanium complexes 1, 2, 3a, and the rac isomers of its
binaphtholate derivative 4. The synthesis, immobilization and
testing of enantiomerically pure titanocene complexes will be
the topic of future studies.
In all cases, sonication of the immobilized complexes in a
coordinating solvent (THF), followed by filtration and washing
was repeated three times. Only the first washing contained just a
very tiny amount of adsorbed catalyst, but the following two
were clean.
Scheme 1 Synthesis of 1-carbon-bridged metallocenes.
The heterogeneous catalysts were further characterized using
SEM/EDX, elemental analysis, and ICP/OES. The results
(
Table 1) indicate that the molar ratio of S : Ti is about 12 : 1,
−1
and about 0.1 mmol g (= 0.5 wt%) of titanium could be
detected on the solid support. Catalytic materials with similar
amounts of Ti have been also reported by other groups.
23,24,29
Another evidence of the covalent immobilization was given
by the ATR-IR spectra of the immobilized titanocene complexes.
The signal of the terminal double bond of the original complexes
was not detectable, while the specific modes of the indene func-
tionalities, such as the vC–H stretching of the benzene ring at
−
1
∼
3000–3100 cm , the signals of the indene ring between 1400
−1
and 1700 cm
, and the CH2 signals at ∼2920 and
40,56,57
∼
2850,
were still present. As a typical example, the spec-
trum of OctEBITiCl on MPSG is shown in Fig. 2.
2
Scheme 2 Immobilization of the tethered titanium complexes on
MPSG.
Hydrosilylation of 2-phenylpyrroline
In order to test the activity of the novel titanocene complexes,
hydrosilylation of 2-phenylpyrroline (Scheme 3) was used as a
model reaction. The complexes were activated with n-BuLi and
or ACHN [(1,1′-azobis(cyclohexanecarbonitrile)] as radical
initiators.
52–55
In order to get a preliminary proof of the successful immobil-
ization of the tethered complexes and their activity in
PhSiH (both 5 mol equiv. referring to Ti) in anhydrous THF.
The catalytic loading was ∼2 mol% referring to the imine. After
3
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Scheme 3 Hydrosilylation of 2-phenylpyrroline with titanocene
complexes.
Table 2 Yields of the hydrosilylation of 2-phenylpyrroline using
a
homogeneous and immobilized titanium complexes
Scheme 4 Model of the interaction of the terminal double bond of 1
with titanium (R = butyl).
c
Entry
Compound
Yield [%] after 3 h
1
2
3
4
5
6
ButMBITiCl
2
3b
95
8
93
27
90
91
OctEBITiCl
ButMBITiCl
2
1
3a
1
b
2
b
OctEBITiCl
2
b
ButEBITiCl
2
2
b
ButMBITibin 4
a
Hydrosilylations were carried out at 60 °C with 2 mol% catalyst
(
referring to imine in THF); catalysts were activated with n-BuLi and
b
c
3
PhSiH . Immobilized on MPSG. Yields determined by GC.
addition of the activating chemicals, 2-phenylpyrroline was
added, and the reaction mixtures were heated to 60 °C. The reac-
tion progress was monitored by GC analysis. The results of these
experiments are shown in Table 2.
All immobilized catalysts proved to be very active for the
hydrosilylation of the model imine, with the exception of
complex 1. In the other cases more than 90% yield could be
Fig. 3 FTIR spectra of functional and activated complex 1.
achieved within 3 h, that corresponds to a turnover frequency
1
(
TOF) of 20 h− . The catalysts 1–3 are rac/meso mixtures and
compound 4 is a rac mixture, therefore the hydrosilylations were
not enantioselective, and in all reactions equal parts of the two
enantiomers of 2-phenylpyrrolidine were produced, as confirmed
by polarimetry and chiral GC.
terminal double bond at 1710 cm− (Fig. 3), after treatment of 1
1
with 2 equiv. of n-BuLi, while the spectrum does not change
after addition of PhSiH . Accordingly, the H NMR spectrum of
1
3
The low yield of immobilized OctEBITiCl 1 (Table 2, entry
1 treated with 2 equiv. of n-BuLi showed a shift of the two term-
2
4
), compared with the other complexes, can be attributed to a
inal double bond signals from 5.00 ppm to 5.50 ppm, and from
13
possible backfolding of the Ti active center onto the surface due
to the longer and non-rigid tether. This backfolding can lead to
undesired interactions of the Ti centers with the still freely avail-
able SH groups, and, thus, to a lower activity of this immobilized
metallocene. In order to get an indirect support to the possibility
of such backfolding, we tested the reactivity of pure 1 in the
same reaction in solution. The yield was even lower than with
the immobilized catalyst, and this result can be attributed to a
possible interference of the terminal double bond with the metal
centre reactivity (Scheme 4). Similar interactions have been
reported in the literature for tethered Group 4 metallocenes.
In our case the interaction should be weaker, because the
Ti(IV) center does not change its oxidation state, and does not
shift to a 14-electron cationic titanium species that coordinates
more strongly to a double bond.
5.70 ppm to 6.10 ppm, respectively. The C NMR signals at
114.1 and 139.1 ppm were also shifted to 119.5 and 145.9 ppm,
respectively.
On the basis of these results we can conclude that the terminal
double bond of 1 persists as a vinyl group and interacts with the
metal, thus reducing its activity. When the complex is covalently
attached to functionalized silica gel, the double bond disappears
and this kind of interference does not occur. Therefore, the
immobilized compound shows a higher activity than the homo-
geneous analogue.
58
The butenyl tether of the other immobilized complexes 2, 3a,
and 4 is shorter and less flexible. Backfolding is therefore mini-
mized, and the yields obtained with these heterogenized com-
plexes are accordingly higher (entries 3, 5 and 6 in Table 2).
5
9
Comparison of the results of immobilized ButMBITiCl 3a
2
The proposed interaction of the terminal double bond with the
metal was investigated by IR and NMR spectroscopies. In prin-
ciple, if such interaction does exist, the addition of a reagent like
n-BuLi, that reacts directly on the metal centre, should induce a
change also in the spectroscopic properties of the double bond.
Indeed, the FTIR spectra showed a shift of the signal of the
(Table 2, entry 3) with the results obtained with the corres-
ponding catalyst without the double bond in the tether, 3b, in a
homogeneous solution (Table 2, entry 1) indicates that the
immobilization of the metallocenes with butenyl tethers has
apparently only minor influences on the activity of these
complexes.
12714 | Dalton Trans., 2012, 41, 12711–12719
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Scheme 5 Reaction scheme of the three-phase test.
Fig. 4 Effect of catalyst recycling on the yield. Hydrosilylations of
2
4
-phenylpyrroline were carried out with immobilized ButMBITibin
(15 mol% referring to imine) in THF at 60 °C.
Heterogeneity of the reaction
Several methods are available to discriminate between soluble
and insoluble catalysts, including the hot filtration or split test,
the three-phase test, and the addition of catalyst poisons that
Scheme 6 Synthesis and immobilization of 5-allyl-4-dihydro-2H-
pyrrole.
4
7,60–62
deactivate soluble reactive metal species.
In our case the
last approach was not applicable, because the immobilized com-
plexes are also sensitive to air, humidity and many chemicals.
The first method we used to detect the presence of Ti leached
into the reaction mixture was ICP/OES analysis. During standard
heterogeneous hydrosilylation reactions at 60 °C, samples were
taken through a syringe filter (Whatman Puradisc 4, 4 mm dia-
meter, 0.45 μm, PTFE), the solvent was evaporated and the
residue dissolved in HNO . The samples were taken at different
3
Scheme 7 Treatment of the immobilized compounds to release the
products of the three-phase test.
stages and times: after addition of n-BuLi, PhSiH , the imine,
3
and after 1, 3 and 5 h of reaction.
The analyses of all samples with ICP/OES found a Ti concen-
tration in the reaction solution of ∼1.6 ppm, which corresponds
to less than 0.01% of the initial amount of Ti.
The second method used to detect potential Ti leaching was
recycling studies. After reaction the catalytic particles were sep-
arated from the reaction mixture by filtration, washed with THF,
and reused under the same reaction conditions, including the
activation steps. The results using immobilized ButMBITibin are
shown in Fig. 4.
perform the test, we synthesized 5-allyl-3,4-dihydro-2H-pyrrole,
an imine that can be immobilized on 3-mercaptopropyl-silica gel
using the same approach used for the titanocene complexes, i.e.,
by reaction of the imine with MPSG in toluene using ACHN as
a radical initiator (Scheme 6). To ensure that an active catalyst
was present, a soluble imine, i.e., 2-phenylpyrroline, was also
added. The conversion of the soluble imine was monitored using
GC analysis.
The data indicate that the activity remains practically the same
even after the third recycle (Fig. 4). In accordance with the ICP/
OES analyses, this result confirms that the Ti leaching is negli-
gible and the immobilized catalyst is still active.
After reaction, the soluble portion was separated by filtration
and the immobilized compounds (i.e., the immobilized imine
and the corresponding amine, in the case of delivery in solution
of an active catalyst) were released from the support using an
67
Finally, we carried out the so-called “three-phase test”, which
is considered a strong indicator for the presence of catalytically
approach similar to the one published by Crosby and Kato,
i.e., the filtrate was treated with an excess of CH I/NaI in DMF
3
6
0,63,64
active homogeneous metal species.
oped by Rebek et al.,
The test, first devel-
at 75 °C for 20 h (Scheme 7).
6
5,66
1
13
is based on the covalent immobiliz-
H and C NMR data of the products showed the presence of
ation of one of the reaction partners and the study of its reaction
with a soluble reagent. The supported catalyst, ButMBITibin 4
immobilized on MPSG, represents the third phase (Scheme 5). If
the catalyst remains immobilized, it will be incapable of acces-
sing the supported reagent. On the contrary, if a homogeneous
active catalyst is released, the covalently immobilized substrate
will be converted into the corresponding amine. In order to
5-(3-iodopropyl)-3,4-dihydro-2H-pyrrole only, but not of 2-(3-
iodopropyl)pyrrolidine. However, when the same reaction was
carried out in the presence of the soluble ethylenebis(tetrahy-
droindenyl) titanium dichloride, the NMR spectra showed both,
the iodated imine and the iodated amine. In both experiments the
soluble imine, 2-phenylpyrroline, was converted in the usual
amount.
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1
All in all, the three-phase test indicates that, under the applied
reaction conditions, no homogeneous catalyst active for the
reduction of the immobilized imine is present. This test cannot
exclude leaches of any other Ti-compound from the solid
support, but together with the ICP/OES analyses, we can con-
clude that the Ti leaching for ButMBITibin 4 immobilized on
MPSG is only minimal. Currently, we assume that this is also
true for the other complexes.
drying operations of organic intermediates. H (200.13 MHz)
13
and C (50.32 MHz) NMR spectra of fulvenes, ligands and
metallocenes were recorded at room temperature with a Bruker
AC200 spectrometer. NMR spectra of imines and amines were
recorded on a Varian Inova 500 MHz spectrometer at
499.82 MHz and 125.69 MHz, respectively. Spectra were refer-
1
enced internally using the residual protio (δ = 7.24 ppm in H
spectra and 77.0 ppm in C spectra for CHCl ) solvent reso-
13
3
nance relative to tetramethylsilane (δ = 0). GC analysis was
carried out on a Perkin Elmer Clarus 500 using an Optima-5 MS
capillary column (Machery-Nagel, 30.0 m × 320 μm × 0.25 μm
nominal) with a flame ionization detector and nitrogen as a
carrier gas. 2-Phenylpyrrolidine enantiomer separation and
excess were determined by GC on a Megadex 5 column (25 m ×
Conclusions
The synthesis of four new tethered titanocene complexes and
their immobilization onto 3-mercaptopropyl-functionalized silica
gel (MPSG) is reported. We have investigated the influence of
the length of the tether and of the ansa-bridge on the activity in
the heterogeneous hydrosilylation of the cyclic imine 2-phenyl-
pyrroline. All immobilized complexes proved to be active and
our results indicate that the immobilization of the compounds
has apparently only minor influences on the activity of the tested
titanocene complexes, except in the case of excessive tether
lengths. The synthesis, immobilization and testing of enantio-
merically pure titanocene complexes will be the topic of future
studies. ICP/OES analyses, recycling studies and a three-phase
test indicate that leaching of Ti into the reaction solution is only
minimal under the applied reaction conditions. Such stable,
highly active, and leaching free heterogeneous catalysts could
play a major role in the preparation of pharmaceutical and fine
chemical intermediates, and to implement continuous processes
in these areas.
0
.25 pentyl-β-cyclodextrine in OV 1701) from Mega s.n.c.;
carrier gas: helium (0.8 atm). Polarimeter: Perkin Elmer Polari-
meter 341. GC/MS analysis: CI mass spectra were recorded with
an Agilent 5973 N mass selective detector on an Agilent Tech-
nologies 6890 N gas chromatograph, column: HP-5MS (Agilent
1
9091S-433); capillary: 30.0 m × 250 μm × 0.25 μm nominal;
carrier gas: helium. SEM/EDX was carried out with a FEI
Quanta 600 FEG-ESEM system and a NORAN Vantage system
2
with a Si(Li)-detector (10 mm , PlexUs 0.65 μm window,
energy resolution 132 eV). FTIR spectra were recorded on a
Bruker VERTEX 70 using a DLaTGS detector and an ATR unit:
−1
MVP Pro Star, Diamond crystal, resolution: 4 cm , 16 scans,
1
4
000–600 cm− . IR spectra of the functionalized silica particles
were recorded using a DRIFT unit (EasyDiff, spectral resolution:
−1
4
cm ; time: 3 min). ICP-OES: Varian Vista-MPX CCD Simul-
taneous ICP-OES Pd-Standard: 10 000 ppm Pd in 5% HNO3.
Elemental analysis (C, H, N, S) determined with an Elementar
Vario El III device (carrier gas: helium).
Experimental section
General remarks
All manipulations of air- and/or moisture sensitive materials
were carried out under an inert atmosphere using dual vacuum/
argon lines and standard Schlenk techniques, or in a dry box
under a nitrogen atmosphere (<10 ppm oxygen, <20 ppm water).
Solvents for synthesis and NMR characterization of air/moisture
sensitive reagents were thoroughly deoxygenated and distilled
under nitrogen from a suitable drying agent (pentane, petroleum
ether, diethyl ether, and THF from K; toluene from sodium;
CH Cl2 and CDCl3 from CaH ), and stored under argon in
Young’s ampoules. Solvents and solutions were transferred,
using a positive pressure of argon, through stainless steel cannu-
lae (diameter 0.5–2.0 mm) and mixtures were filtered in a
similar way using modified cannulae which could be fitted with
glass fiber filter disks (Whatman GFC).
Benzofulvenes (5/5*a,b). Pyrrolidine (3.0 mmol) was added
dropwise to a solution of the appropriate ketone (2.0 mmol) and
freshly distilled indene (5.0 mmol) in methanol (2 mL), under
nitrogen and cooled to 0 °C. The mixture became immediately
bright yellow. The cooling bath was removed, and the solution
stirred at room temperature until the TLC (cyclohexane) showed
traces of the starting ketone (about 30 min). Glacial acetic acid
(3.2 mmol) was carefully added, then diethyl ether and water
(20 mL each). The aqueous fraction was extracted with
petroleum ether (3 × 25 mL), and the combined organics washed
with water and brine (5 mL each), then dried, filtered and con-
centrated in vacuo at 30 °C. Indene in excess was removed by
distillation under high vacuum. The mixture of benzofulvene
isomers was clean enough to be used directly for the following
reaction.
2
2
Unless otherwise specified, all reagents were purchased from
commercial suppliers (Aldrich and Fluka) and used without
further purification. Indenyllithium was prepared by reaction of
freshly distilled indene in petroleum ether with n-BuLi at
1-(Hex-5-en-2-ylidene)-1H-indenes (5/5*a); yield 70%
38
(approx.). NMR as reported in the literature.
1-(Hexan-2-ylidene)-1H-indenes (5/5*b); yield 75%
−
15 °C, followed by filtration and storage under an inert
atmosphere.
(approx.). Two isomers (ratio 5/5* = 3 : 2 from methyl integrals).
1
H NMR (CDCl ): δ 7.79–7.63 (m, 2H, –ArH), 7.38–7.30 (m,
3
Reaction courses and product mixtures were routinely moni-
tored by thin layer chromatography (TLC) on silica gel 60 pre-
coated F254 plates (Fluka). Preparative flash chromatography
was performed with silica gel 60 Å (Lancaster, ASTM
2H, –ArH), 7.25–7.14 (m, 4H, –ArH), 6.74 (m, 4H, –CHvInd),
2.80–2.68 (m, 2H, –CH –*), 2.64–2.53 (m, 2H, –CH –), 2.43
2
2
(s, 3H,vC–CH *), 2.29 (s, 3H,vC–CH ), 2.10–1.90 (m, 4H,
3
3
–CH –), 1.85–1.51 (m, 4H, –CH –), 1.11 (t, 3H, J = 7.46 Hz,
2
2
2
30–400 mesh). Anhydrous magnesium sulphate was used in
–CH *), 1.00 (t, 3H, J = 7.59 Hz, –CH ).
3
3
12716 | Dalton Trans., 2012, 41, 12711–12719
This journal is © The Royal Society of Chemistry 2012

View Article Online
Methylene bridged dilithium salts (6a,b). The benzofulvene
mixture 5/5*a or 5/5*b (2 mmol) was dissolved in THF and
added to a solution of lithium indenyl (2 mmol) dissolved in
THF and cooled to −40 °C. The cooling bath was removed, the
mixture allowed to reach r.t. and stirred overnight, then cooled to
(m, 8H, –ArH), 6.70–6.20 (m, 4H, CpH), 2.70–2.30 (m, 2H,
–CH –), 2.20–1.75 (m, 2H, –CH –), 2.35 (s, 3H, bridge –CH
3
2
2
one isomer), 2.25 (s, 3H, bridge –CH one isomer), 1.55–1.40
3
13
(m, 2H, –CH –), 1.10 (t, 3H, J = 7.59 Hz, –CH ); C NMR
2
3
(CDCl ): δ 135.4, 131.9, 131.7, 130.9, 129.4, 128.3, 127.2,
3
0
°C and treated with n-BuLi (1.2 mmol). The reaction was
125.3, 116.4, 32.4, 29.7, 29.2, 27.3, 14.2. Anal. Calcd for
C H Cl Ti (431.22): C, 66.85; H, 5.61; Cl, 16.44. Found: C,
66.88; H, 5.62; Cl, 16.48.
allowed to reach r.t. and stirred for 6 h. The solvent was removed
under high vacuum, petroleum ether was added, and the lithium
salt was filtered via a cannula and washed twice with petroleum
ether to remove both unreacted ligand and n-BuLi in excess. The
residual solvent was pumped off leaving the lithium salt as a
purple pyrophoric powder (the color is due to the presence of
coordinated THF molecules).
24
24
2
1
,1′-Bi-2-naphtholateTiCl
binaphthol in diethyl ether (3 mL), degassed and cooled to
40 °C, 2.27 mmol of TiCl were added dropwise. The solution
2
·2THF. To 2.27 mmol of 1,1′-
−
4
became immediately dark red. The cooling bath was slowly left
to reach r.t., and the mixture stirred overnight. The solvent was
removed under vacuum and the resulting brown powder was
washed with pentane, and dried under reduced pressure. THF
2
,2′-Bis[(1H-inden-3′-yl)-hex-5-enyl]dilithium salt; yield
8% (two steps) from fulvenes 5a.
,2′-Bis[(1H-inden-3′-yl)-hexanyl]dilithium salt; yield 62%
5
2
(10 mL) was added and the solution was kept at room tempera-
(two steps) from fulvenes 5b.
ture for 2 days. The final reaction mixture was composed
of a dark red precipitate and a similarly dark red solution.
Pentane was added to increase the amount of precipitate, the sus-
pension was cooled to −40 °C and filtered cold. The solution,
concentrated and layered with pentane, produced another crop
of precipitate after several days at −15 °C. The collected
solids were dried under high vacuum giving a dark red solid
A small sample of compound 6a was treated with sat. NH Cl,
extracted with petroleum ether, dried, filtered, and evaporated
4
in vacuo to give an amount of raw diene enough for NMR
1
characterization. H NMR (CDCl ): δ 7.50–6.80 (m, 8H, –ArH),
3
6
.55 (m, 2H, CpH), 5.70 (m, 1H, –CHv), 4.95 (d, 1H, J = 17.1 Hz,
CH v), 4.90 (d, 1H, J = 10.25 Hz, CH v), 3.45 (m, 4H, CH
2
2
2
Cp), 2.50–2.20 (m, 2H, –CH –), 2.00–1.70 (m, 2H, –CH –),
2
2
1
3
(
yield: 88%).
1
.65 (s, 3H, –CH3); C NMR (CDCl ): δ 148.4 [C ], 144.9
3 q
[
1
3
C ], 144.1 [C ], 139.3 [C ], 128.3 [CH Ar], 125.3 [CH Ar],
q q q
rac 2,2′-Bis[(1H-inden-3′-yl)-hex-5-enyl]titanium binaphtho-
24.1 [CH Ar], 123.2 [CH Ar], 121.4 [–CH], 114.1 [CH v],
2
late (4). 1.50 mmol of 6a were dissolved in anhydrous THF
and cooled to −20 °C. Once cool, the solution of the ligand
was added slowly via a cannula to a solution of 0.80 mmol of
7.4 [–CH –], 36.5 [C–CH –Ar], 28.6 [–CH –], 24.8 [–CH ].
2
2
2
3
The same treatment was done on 6b.
1
H NMR (CDCl ): δ 7.45–6.80 (m, 8H, –ArH), 6.60 (m, 2H,
3
(
1,1′-binaphtholate)TiCl ·2THF in anhydrous THF at −20 °C.
2
CpH), 3.45 (m, 4H, CH2 Cp), 2.50–2.10 (m, 4H, –CH –),
2
After the addition, the reaction mixture was allowed to warm
to r.t. and stirred overnight. The following day the reaction
mixture was refluxed, then cooled to r.t., and the solvent
removed under vacuum. A red solid was obtained. Diethyl ether
was added and the solution was filtered. The solid residue was
washed three times with diethyl ether and dried to yield 4 as a
2
.0–1.70 (m, 2H, –CH –), 1.75 (s, 3H, bridge –CH ), 1.55–1.40
2 3
(m, 2H, –CH –), 1.00 (t, 3H, J = 7.59 Hz, –CH ).
2
3
rac and meso Titanocene dichlorides (3a,b). Bisdilithium salt
a,b (1.2 mmol) was dissolved in diethyl ether (15 mL, brown
6
solution) and added to a suspension of TiCl ·2THF dissolved in
4
diethyl ether (10 mL) and cooled to −78 °C. The reaction
mixture turned dark after a few minutes. The cooling bath was
removed, the mixture was allowed to reach r.t. and stirred over-
night. The solvent was pumped off under vacuum, leaving a
brown sticky solid, that was dissolved in dichloromethane
red solid.
Yield: 35%. H NMR (CDCl
1
): δ 8.05–7.76 (m, 4H, –ArH
3
binaphthol), 7.55–7.10 (m, 20H, –ArH, binaphthol + indenyl),
6.10–5.90 (m, 1H, –CHv), 5.10–4.95 (m, 2H, CH v),
3.25–3.05 (m, 2H, –CH –), 2.95–2.40 (m, 3H, –CH –), 2.36 (s,
3H, –CH ). Anal. Calcd for C44 Ti (642.61): C, 82.24; H,
5.33. Found: C, 82.25; H, 5.31.
2
2
2
(5 mL), precipitated with pentane (100 mL) and left at −15 °C
3
H O
34 2
overnight. A reddish-brown solid was obtained after filtration,
washing with cold pentane, and drying under high vacuum.
rac and meso 2,2′-Bis[(1H-inden-3′-yl)-hex-5-enyl]titanium
Immobilization of the titanium complexes on MPSG
-Mercaptopropyl functionalized silica gel and catalytic amounts
1
dichlorides (3a). Yield 45%. H NMR (CDCl ): δ 7.60–6.90 (m,
3
3
8
–
2
H, –ArH), 6.70–6.20 (m, 4H, CpH), 5.90–5.50 (m, 1H,
of AIBN [(2,2′-azobis(2-methylpropionitrile)] or ACHN [(1,1′-
azobis(cyclohexanecarbonitrile)] were added to a solution of the
titanium complex (1 mol equiv. referring to 1.2 mmol thiol
groups per gram silica gel in MPSG, according to Sigma) in
degassed anhydrous CH Cl (for AIBN) or toluene (for ACHN)
CHv), 5.20–4.60 (m, 2H, CH v), 3.50–2.70 (m, 2H, –CH –),
2
2
.40 (s, 3H, bridge –CH one isomer), 2.35 (s, 3H, bridge –CH
3
3
1
3
one isomer), 2.20–1.65 (m, 2H, –CH –); C NMR (CDCl ): δ
2
3
1
1
1
39.6 [–CH], 136.7 [C ], 132.8 [C ], 131.8 [C ], 129.9 [C ],
q q q q
2
2
26.4 [CH Ar], 125.3 [CH Ar], 124.6 [CH Ar], 121.4 [CH Ar],
14.5 [CH v], 39.4 [–CH –], 37.9 [–CH –], 29.4 [–CH –].
under argon. The suspension was continuously stirred and heated
under reflux for 18 h. To remove the non-immobilized com-
pounds, the particles were filtered, washed, sonicated 5 times for
2
2
2
3
Anal. Calcd for C H Cl Ti (429.20): C, 67.16; H, 5.17; Cl,
24
22
2
1
6.52. Found: C, 67.15; H, 5.15; Cl, 16.58.
1
min in CH Cl –toluene, and finally in THF, and dried in vacuo
2 2
rac and meso 2,2′-Bis[(1H-inden-3′-yl)-hexanyl]titanium
at r.t. The amount of immobilized metallocene was determined
by elemental analysis and ICP/OES.
1
dichlorides (3b). Yield 50%. H NMR (CDCl ): δ 7.62–6.95
3
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 12711–12719 | 12717

View Article Online
1
Preparation of 2-phenylpyrroline
-Phenylpyrroline was prepared following a synthesis by
H NMR (CDCl ): δ 5.77 (m, 1H, CH vCH–), 5.09 (m, 2H,
3
2
CH vCH–), 3.33 (m, 2H,vN–CH –), 3.14 (m, 2H, –CH –),
.25 (m, 2H, –CH –), 1.78 (m, 2H, –CH –); C NMR (CDCl3):
2 2
δ 168.9 (–CvN–), 132.9 (CH vCH–), 119.5 (CH vCH–),
1.9 (–NH–CH –), 42.0 (–CH –NH–), 30.1 (–CH –), 21.1
2 2 2
2
2
2
2
13
2
45
Coindet et al. Yield: 85.5%. GC/MS: R = 18.857 MS (m/z):
t
1
2
2
1
86, 174, 146 (M+), 117, 104, 91, 57; H NMR (CDCl ): δ 7.87
3
6
(
(dd, J = 1.47, 2H, 7.81 Hz, –ArH), 7.44 (m, 3H, –ArH), 4.06 (tt,
–CH –).
2
2
H, J = 1.96, 7.32 Hz,vN–CH –), 2.98 (m, 2H, –CH –), 2.04
2
2
13
(m, 2H, –CH –); C NMR δ (CDCl ) 174.25 (–CvN–), 134.1,
2 3
1
2
31.0, 128.7, 128.1 (all ArC), 61.2 (vN–CH –), 35.2 (–CH –),
2 2
Recycling studies
2.7 (–CH –).
2
At the end of the hydrosilylation reactions the catalytic particles
were separated from the reaction mixture by filtration, washed
three times with THF, and reused under the same reaction con-
ditions. To ensure complete activation of the catalyst, a higher
amount of n-BuLi, i.e., ∼20 mol equiv., and 5 mol equiv.
Hydrosilylation of 2-phenylpyrroline
The chosen metallocene (2 mol% referring to the imine) was dis-
solved in anh. THF (2 mL) in a dry Schlenk flask under an
argon atmosphere. In the order, n-BuLi (5 mol equiv. to catalyst),
phenylsilane (5 mol equiv. to catalyst) and the imine were added,
and the mixture was heated to 60 °C. The reaction progress was
monitored via GC until no further reaction progress could be
determined. Then the mixture was allowed to cool to r.t., opened
to air, and quenched with diethyl ether and HCl (1 M) until pH 2
was reached. The biphasic mixture was stirred for 20 min, the
layers were separated, and the organic phase washed with HCl.
The combined aqueous fractions were neutralized with NaOH
and extracted three times with diethyl ether. The combined
organic layers were dried over Na SO , filtered and reduced
PhSiH , was added before every use.
3
Immobilization of 5-allyl-3,4-dihydro-2H-pyrrole on MPSG
The procedure was the same used for the immobilization of tita-
nocenes using ACHN as a radical initiator. After drying in vacuo
the immobilized imine was analyzed by CHNS analysis:
−1
−1
0
.8% (0.6 mmol g ) N, 11.1% (9.2 mmol g ) C, 3.7%
−1
(1.2 mmol g ) S.
2
4
in vacuo to give the corresponding amine as a yellowish oil.
Three-phase test
2
-Phenylpyrrolidine. GC/MS R = 19.2 MS 146 (M+), 118,
t
The supported catalyst, ButMBITibin immobilized on MPSG
1
1
7
3
04, 91, 57; H NMR (CDCl ): δ 7.35–7.31 (m, 4H, –ArH),
.22–7.21 (m, 1H, –ArH), 4.07 (t, J = 7.5 Hz, 1H, –CH–NH–),
.13–3.09 (m, 2H, –NH–CH –), 2.2–2.1 (m, 2H, –CH –), 1.98
bs, 1H, –NH–), 1.77–1.60 (m, 2H, –CH –); C NMR (CDCl3):
δ 143.9, 130.6. 128.7, 127.8, 127.3, 126.9 (all ArC), 62.9
–NH–CH –), 47.0 (–CH –NH–), 34.3 (–CH –), 25.6 (–CH –).
3
(10 mol% referring to 2-phenylpyrrolidine), was suspended in
anh. THF and activated with n-BuLi (5 mol equiv. to catalyst)
and phenylsilane (5 mol equiv. to catalyst). The immobilized
imine (1 mol equiv. referring to 2-phenylpyrroline) and
2
2
1
3
(
2
2
-phenylpyrroline were added. The conversion of the soluble
(
2
2
2
2
imine was monitored using GC.
After 24 h the particles were removed by filtration, washed
with THF and dried under vacuum. To release the imine from
the solid support the particles were suspended in DMF, and an
Investigation of the interaction of the terminal double with
1
13
titanium by H and C NMR on complex 1. The titanium
complex was dissolved in diethyl ether and cooled to −78 °C,
equiv. of n-BuLi were added, the reaction mixture was allowed
to reach room temperature, and stirred overnight. The solvent
was evaporated under high vacuum, the residue was washed with
hot hexane, carefully dried under high vacuum, and dissolved in
excess of CH I and NaI was added. The mixture was heated to
3
2
7
5 °C for 20 h, then cooled to r.t. and the particles were removed
by filtration. The filtrate was reduced in vacuo, diluted with
diethyl ether, and extracted with water. The organic phase was
dried over Na SO , filtered, and the solvent evaporated under
2
4
C D to record NMR spectra.
6
6
1
13
reduced pressure. Control H and C NMR were carried out in
CDCl
Synthesis of 5-allyl-3,4-dihydro-2H-pyrrole. 2-Pyrrolidone
.
3
(
13 mmol) was dissolved in diethyl ether (20 mL) under argon,
1
and the solution was cooled to 0 °C. Trimethylsilylchloride
14 mmol) was added to give a white cloudy suspension, that
5-(3-Iodopropyl)-3,4-dihydro-2H-pyrrole. H NMR (CDCl
3
):
(
δ 3.45 (m, 2H,vN–CH
2H, –CH –), 2.28 (m, 2H, –CH
(m, 2H, –CH
(–NH–CH –), 42.0 (–CH
29.1 (–CH –), 24.3 (–CH
2
–), 2.94 (m, 2H, –CH
2
–I–), 2.35 (m,
was heated to 50 °C and refluxed for 30 min. After cooling to
r.t., the solids were removed by filtration and the filtrate (clear,
colorless solution) was cooled to 0 °C. Allylbromide (11 mmol,
2
2
–), 2.25 (m, 2H, –CH –), 1.78
2
13
–); C NMR (CDCl
–NH–), 36.1 (–CH
–), 11.1 (–CH –I).
): δ 177.5 (–CvN–), 65.9
2
3
–), 33.1 (–CH –),
2
2
2
2
1
M in diethyl ether) was added and the purple solution was
2
2
2
refluxed at 50 °C for 4 h, allowed to reach r.t., and stirred over-
night. The orange solution with suspended solids was cooled to
1
2-(3-Iodopropyl)pyrrolidine. H NMR (CDCl ): δ 3.14–3.05
3
0
°C and 1 M HCl was added. After extraction with diethyl
(m, 2H, –CH –I–), 2.85–2.80 (m, 2H, –NH–CH –), 2.75 (m,
2
2
ether, 1 M NaOH was added to the aqueous phase. After a
second extraction with diethyl ether the combined organic
phases were dried over Na SO and reduced in vacuo to give a
1H, –NH–CH –), 2.2–2.1 (m, 2H, –CH –), 1.98 (bs, 1H,
2 2
13
–NH–), 1.77–1.60 (m, 4H, –CH –); C NMR (CDCl ): δ 60.9
2
3
(–NH–CH –), 42.0 (–CH –NH–), 36.1 (–CH –), 30.1 (–CH –),
2
4
2
2
2
2
light brown oil.
28.3 (–CH –), 24.2 (–CH –), 10.1 (–CH –I).
2 2 2
12718 | Dalton Trans., 2012, 41, 12711–12719
This journal is © The Royal Society of Chemistry 2012

View Article Online
3
3
3
3 J. G. Lee and C. H. Brubaker, J. Organomet. Chem., 1977, 135,
Acknowledgements
1
15–124.
4 B. H. Chang, R. H. Grubbs and C. H. Brubaker, J. Organomet. Chem.,
985, 280, 365–376.
We kindly acknowledge the financial support of the Austrian
Science Fund (Elise-Richter Project No. V171-N19), the C.N.R.
Short Term Fellowship Program (years 2008 and 2009) for
supporting Dr E. Polo’s stay in Graz.
1
5 J. H. Z. dos Santos, H. T. Ban, T. Teranishi, T. Uozumi, T. Sano and
K. Soga, J. Mol. Catal. A: Chem., 2000, 158, 541–557.
6 H. G. Alt, J. Chem. Soc., Dalton Trans., 2005, 3271–3276.
7 B. Peifer, W. Milius and H. G. Alt, J. Organomet. Chem., 1998, 553,
3
3
205–220.
3
3
4
8 G. Tang, G. X. Jin and L. Weng, J. Organomet. Chem., 2004, 689, 678–684.
9 P. McMorn and G. J. Hutchings, Chem. Soc. Rev., 2004, 33, 108–122.
0 H. Gruber-Woelfler, S. Rivillon Amy, Y. J. Chabal, G. Schitter, E. Polo,
M. Ringwald and J. G. Khinast, Chem. Commun., 2008, 1329–1331.
Notes and references
1
2
3
4
5
J. F. Carpentier and V. Bette, Curr. Org. Chem., 2002, 6, 913–936.
H. Dong and H. Berke, Adv. Synth. Catal., 2009, 351, 1783–1788.
W. J. Li and S. X. Qiu, Adv. Synth. Catal., 2010, 352, 1119–1122.
O. Riant, N. Mostefaï and J. Courmarcel, Synthesis, 2004, 2943–2958.
C. E. Song, J. W. Yang, E. J. Roh, S. Lee, J. H. Ahn and H. Han, Angew.
Chem., Int. Ed., 2002, 41, 3852–3854.
41 C. A. Willoughby and S. L. Buchwald, J. Org. Chem., 1993, 58,
7627–7629.
42 C. A. Willoughby and S. L. Buchwald, J. Am. Chem. Soc., 1994, 116,
11703–11714.
43 C. A. Willoughby and S. L. Buchwald, J. Am. Chem. Soc., 1994, 116,
8952–8965.
44 B. E. Maryanoff, D. F. McComsey, J. F. Gardocki, R. P. Shank,
M. J. Costanzo, S. O. Nortey, C. R. Schneider and P. E. Setler, J. Med.
Chem., 1987, 30, 1433–1454.
6
7
M. Tan, Y. Zhang and J. Ying, Adv. Synth. Catal., 2009, 351, 1390–1394.
M. Capka, M. Czakoova, J. Hjortkjaer and U. Schubert, React. Kinet.
Catal. Lett., 1993, 50, 71–74.
8
9
I. Kolb, M. Cerny and J. Hetflej, React. Kinet. Catal. Lett., 1977, 7,
1
99–204.
45 C. Coindet, A. Comel and G. Kirsch, Tetrahedron Lett., 2001, 42,
6101–6104.
B. Marciniec, K. Szubert, M. J. Potrzebowski, I. Kownacki and
K. Leszczak, Angew. Chem., Int. Ed., 2008, 47, 541–544.
46 C. E. Garret and K. Prasad, Adv. Synth. Catal., 2004, 346, 889–900.
47 M. Lamblin, L. Nassan-Hardy, J.-C. Hierso, E. Fouquet and F. Felpin,
Adv. Synth. Catal., 2010, 352, 33–79.
1
0 G. Liu and M. Cai, J. Mol. Catal. A: Chem., 2006, 258, 257–260.
1 J. Alauzun, A. Mehdi, C. Reye and R. Corriu, Chem. Mater., 2007, 19,
373–6375.
1
1
1
1
6
48 M. Weck and C. W. Jones, Inorg. Chem., 2007, 46, 1865–1875.
49 A. Panarello, O. Vassylyev and J. Khinast, Synlett, 2005, 797–800.
50 K. J. Stone and R. D. Little, J. Org. Chem., 1984, 49, 1849–1853.
51 K. P. Bryliakov, D. E. Babushkin, E. P. Talsi, A. Z. Voskoboynikov,
H. Gritzo, L. Schroder, H. R. H. Damrau, U. Wieser, F. Schaper and
H. H. Brintzinger, Organometallics, 2005, 24, 894–904.
52 C. Baleizao, A. Corma, H. Garcia and A. Leyva, J. Org. Chem., 2004,
69, 439–446.
2 Z. M. Michalska, L. Rogalski, K. Rozga-Wijas, J. Chojnowski, W. Fortuniak
and M. Scibiorek, J. Mol. Catal. A: Chem., 2004, 208, 187–194.
3 J. Z. Yao, Y. Y. Chen and B. S. Tian, J. Organomet. Chem., 1997, 534,
5
1–56.
4 X. Verdaguer, U. E. W. Lange and S. L. Buchwald, Angew. Chem., Int.
Ed., 1998, 37, 1103–1107.
5 J. Yun and S. L. Buchwald, J. Am. Chem. Soc., 1999, 121, 5640–5644.
6 X. Verdaguer, U. E. W. Lange, M. T. Reding and S. L. Buchwald, J. Am.
Chem. Soc., 1996, 118, 6784–6785.
1
1
53 C. Baleizao, B. Gigante, D. Das, M. Alvaro, H. Garcia and A. Corma,
J. Catal., 2004, 223, 106–113.
1
7 M. B. Carter, B. Schiott, A. Gutierrez and S. L. Buchwald, J. Am. Chem.
Soc., 1994, 116, 11667–11670.
54 C. Baleizao, A. Corma, H. Garcia and A. Leyva, Chem. Commun., 2003,
606–607.
1
8 J. R. Severn, J. C. Chadwick, R. Duchateau and N. Friederichs, Chem.
Rev., 2005, 105, 4073–4147.
55 W. J. Sommer, K. Yu, J. S. Sears, Y. Ji, X. Zheng, R. J. Davis,
C. D. Sherrill, C. W. Jones and M. Week, Organometallics, 2005, 24,
4351–4361.
56 A. M. Noskov, Zh. Prikl. Spektrosk., 1968, 10, 403–406.
57 G. Socrates, Infrared and Raman Characteristic Group Frequencies,
Wiley, New York, 1980.
58 (a) M. Horáček, P. Štěpnička, J. Kubišta, I. Císařová, L. Petrusová and
K. Mach, J. Organomet. Chem., 2003, 666, 154–166; (b) M. V. Galakhov,
G. Heinz and P. Royo, Chem. Commun., 1998, 17–18; (c) Z. Wu,
R. F. Jordan and J. L. Petersen, J. Am. Chem. Soc., 1995, 117, 5867–5868;
S. B. Amin and T. J. Marks, Organometallics, 2007, 26, 2960–2963.
59 H. Gruber-Woelfler, M. Flock, R. C. Fischer, J. Sassmannshausen,
T. Stanoeva, G. Gescheidt and J. G. Khinast, Organometallics, 2009, 28,
2546–2553.
60 N. T. S. Phan, D. S. Van and C. W. Jones, Adv. Synth. Catal., 2006, 348,
609–679.
61 J. M. Richardson and C. W. Jones, in Catalysis of Organic Reactions,
ed. M. L. Prunier, CRC Press, 2009, pp. 193–202.
62 J. J. A. Widegren and R. G. Finke, J. Mol. Catal. A: Chem., 2003, 198,
317–341.
63 C. M. Crudden, M. Sateesh and R. Lewis, J. Am. Chem. Soc., 2005, 127,
10045–10050.
1
2
2
2
9 J. H. Yim and S. K. Ihm, J. Appl. Polym. Sci., 2006, 102, 2293–2298.
0 A. Koppl and H. G. Alt, J. Appl. Polym. Sci., 2001, 80, 454–466.
1 A. Koppl and H. G. Alt, J. Mol. Catal. A: Chem., 2001, 165, 23–32.
2 K. Weiss, C. Wirth-Pfeifer, M. Hofmann, S. Botzenhardt, H. Lang,
K. Brüning and E. Meichel, J. Mol. Catal. A: Chem., 2002, 182–183,
1
43–149.
3 J. Jarupatrakorn and T. D. Tilley, J. Am. Chem. Soc., 2002, 124,
380–8388.
2
2
2
2
2
8
4 E. Gianotti, C. Bisio, L. Marchese, M. Guidotti, N. Ravasio, R. Psaro and
S. Coluccia, J. Phys. Chem. C, 2007, 111, 5083–5089.
5 Y. Pérez, R. Ballesteros, M. Fajardo, I. Sierra and I. del Hierro, J. Orga-
nomet. Chem., 2011, 696, 1708–1715.
6 F. Carniato, C. Bisio, L. Sordelli, E. Gavrilova and M. Guidotti, Inorg.
Chim. Acta, 2012, 380, 244–251.
7 O. A. Kholdeeva, M. S. Mel’gunov, A. N. Shmakov, N. N. Trukhan,
V. V. Kriventsov, V. I. Zaikovskii, M. E. Malyshev and V. N. Romannikov,
Catal. Today, 2004, 91–92, 205–209.
2
2
8 R. Jackson, J. Ruddlesden, D. J. Thompson and R. Whelan, J. Organo-
met. Chem., 1977, 125, 57–62.
9 D. Perez-Quintanilla, S. Gomez-Ruiz, Z. Zizak, I. Sierra, S. Prashar,
I. del Hierro, M. Fajardo, D. Z. Juraniç and G. N. Kaluderovic,
Chem.–Eur. J., 2009, 15, 5588–5597.
64 I. W. Davies, L. Matty, D. L. Hughes and P. J. Reider, J. Am. Chem. Soc.,
2001, 123, 10139–10140.
3
0 F. Ciardelli, A. Altomare and M. Michelotti, Catal. Today, 1998, 41,
65 J. Rebek, D. Brown and S. Zimmerman, J. Am. Chem. Soc., 1975, 97,
454–455.
1
49–157.
3
3
1 G. G. Hlatky, Chem. Rev., 2000, 100, 1347–1376.
2 C. J. Miller and D. O’Hare, Chem. Commun., 2004, 1710–1711.
66 J. Rebek and F. Gavina, J. Am. Chem. Soc., 1974, 96, 7112–7114.
67 G. A. Crosby and M. Kato, J. Am. Chem. Soc., 1977, 99, 278–280.
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