Improved palladium and nickel catalysts heterogenised on oxidic supports (Silica, MCM-41, ITQ-2, ITQ-6)

Article abstract of DOI:10.1002/adsc.200404029

Two series of solid catalysts in which a chiral palladium or nickel complex with Schiff bases as ligands have been immobilized on ordered mesoporous silica supports (MCM-41), delaminated ITQ-2, ITQ-6 zeolites and amorphous silica have been prepared. Hydrogenation of alkenes and imines was studied with the homogeneous as well as with the counterpart heterogenized catalysts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs of 1,000,000 h ^-1. A moderate acidity in the support increases the catalytic activity considerably, and the easy recoverable immobilized catalysts can duplicate the activity of the homogeneous analogues. No deactivation of the catalysts was observed after repeated recycling.

Full text of DOI:10.1002/adsc.200404029

FULL PAPERS
Improved Palladium and Nickel Catalysts Heterogenised on
Oxidic Supports (Silica, MCM-41, ITQ-2, ITQ-6)
a, c
b
c,
a,
´
´
C. Gonzalez-Arellano, A. Corma M. Iglesias, * F. Sanchez *
a
´
Instituto de Química Organica General, CSIC, C/ Juan de la Cierva 3, 28006 Madrid, Spain
Fax: (þ34)-91-564-4872, e-mail: felix-iqo@iqog.csic.es
b
c
Instituto de Tecnología Química, UPV-CSIC, Avda. de los Naranjos s/n, 46022 Valencia, Spain
Instituto de Ciencia de Materiales de Madrid, CSIC , Cantoblanco, 28049 Madrid, Spain
Fax: (þ34)-91-372-0623, e-mail: marta.iglesias@icmm.csic.es
Received: January 28, 2004; Accepted: July 2, 2004
Abstract: Two series of solid catalysts in which a chiral with TOFs of 1,000,000 hÀ1. A moderate acidity in
palladium or nickel complex with Schiff bases as li- the support increases the catalytic activity considera-
gands have been immobilized on ordered mesoporous bly, and the easy recoverable immobilized catalysts
silica supports (MCM-41), delaminated ITQ-2, ITQ-6 can duplicate the activity of the homogeneous ana-
zeolites and amorphous silica have been prepared. logues. No deactivation of the catalysts was observed
Hydrogenation of alkenes and imines was studied after repeated recycling.
with the homogeneous as well as with the counterpart
heterogenized catalysts. The high accessibility intro-
duced by the structure of the supports allows the Keywords: chiral Schiff bases; hydrogenation; immo-
preparation of highly efficient immobilized catalysts bilized; nickel; palladium
Introduction
could be varied in order to improve the activities of
the complexes in catalytic hydrogenation reactions of al-
The development of efficient catalytic asymmetric reac- kenes and imines.
tions is one of the most challenging tasks in current syn-
Remarkable developments in homogeneous catalysis
thetic chemistry, much effort having been devoted to the have taken place over the past two decades.[5] Unfortu-
creation of new chiral N-ligands and their metal com- nately the recovery of the precious metals and expensive
plexes for evaluation in advanced asymmetric cataly- ligands from the reaction medium is often not feasible.
sis.[1] Condensation between an amine and an aldehyde, For this reason, there have been many approaches to
forming what is called a Schiff base, was one of the ear- “heterogenising” homogeneous catalysts by attaching
liest reported reactions in chemistry.[2] Schiff bases are well defined molecular species to polymeric supports.[6]
an important class of ligands in coordination chemistry Despite the development of some very effective sup-
and have studied extensively[3] as they are selective ported systems,[7] a general strategy for mimicking solu-
and sensitive toward various metal ions. Jacobsen and tion behaviour is yet to be developed. Reactions on sup-
Katsuki developed tetradentate salen ligands, now one ports are generally slower and less predictable than their
of the most intensely studied classes of chiral Schiff bas- solution counterparts, commonly requiring excesses of
es, able to coordinate easily to a wide variety of metals. reagents, higher temperatures and longer reaction
Chiral salen-containing complexes are now used as cat- times.[8]
alysts for a variety of enantioselective reactions such as
oxidation, aziridination, cyclopropanation, Diels–Alder provided new possibilities in catalysis.[9] These mesopo-
cyclisation, hydrogenation, etc.[4]
rous materials have unique structures characterised by
The discovery of mesoporous molecular sieves has
We are focusing on new chiral Schiff base ligands con- high surface areas, large pores, and high long-range or-
taining pyrrolidinamino functionalities in place of one der; properties that make them ideal catalyst supports.
phenolic group on salen ligands. The syntheses of the MCM-41 type silicates have been used as supports for
palladium and nickel(II) complexes are reported. The a variety of metals and metal complexes.[10] Recently a
method we have developed should allow the easy syn- new type of high surface area materials called delami-
thesis of a wide variety of chiral Shiff base ligands. The nated zeolites has been proposed as an alternative to
iminophenoxy ligands were designed to coordinate the known material.[11] Delaminated zeolites possess a
with Pd(II) and Ni(II), and the additional amino group high thermal/hydrothermal stability and acidity as in
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DOI: 10.1002/adsc.200404029
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Pd and Ni Catalysts Heterogenised on Oxidic Supports
FULL PAPERS
zeolites, and a very high external/internal surface area
ratio as in amorphous materials. The characteristics
named above make these delaminated zeolites a very
promising material as catalysts, fillers, and supports for
any type of active species. Our approach to the prepara-
tion of Pd and Ni complexes – both homogeneous and
supported on mesoporous solids – involves the use of
chiral Schiff base ligands as shown in Schemes 1 and 2.
The selective hydrogenation of imines is a reaction of in-
terest in the production of fine chemicals, and the cata-
lysts of choice have traditionally been Ir and Rh com-
plexes,[12] even if they require relatively high H2 pres-
sures (ꢀ80 bar) for carrying out the reaction. There is
incentive to design highly active catalysts that can
work under much milder reaction pressure and, if possi-
ble, to use less expensive metals such as palladium and
nickel. We show here that [N,N,O]-Pd and -Ni com-
plexes are active catalysts for hydrogenation of alkenes
and imines at 4 bar H2 pressure. Moreover by properly
Scheme 1. Synthesis of soluble ligands and homogeneous
complexes.
choosing the support it is possible to achieve a two- in which the silanol groups act as grafting centres. How-
fold increase in activity with respect to the homogene- ever, there are structural differences between the two
ous counterpart, by means of a cooperative effect of delaminated zeolites. Indeed, in the case of the ITQ-2
the support that may stabilise the charged reaction tran- there are “cup-like” apertures to the external surface
sition state.
with ꢀ0.8Â0.8 nm dimensions, while in the case of
the ITQ-6 these “cups” are less deep (ꢀ0.3 nm). In a
previous work and by a molecular dynamics study, we
have shown that there is a minimum of potential energy
in the void space of the “cups” in the ITQ-2, in which the
molecules that can fit have a high tendency to adsorb.
Taking this into account and the fact that the structured
silanols are located at the borders of those “cups”, one
can envisage a structural model analogous to that pre-
Results and Discussion
Synthesis of Homogeneous Catalysts (Reference
Systems)
All soluble ligands relevant for this work have been ob- sented by Breslow et al.[15] for cyclodextrins, in which
tained in high yields as described previously.[13] The syn- the grafted complex site is located at the border of the
thesis is shown in Scheme 1.
cyclodextrin “cup”. In our case, the metal complex will
be located at the border of the inorganic silicate cups.
Then, one may expect that the reactant is adsorbed in
the cavity of the delaminated zeolite and reacts there
with the catalyst located at the border. If this model is
Preparation of Immobilized Ligands and Complexes
In the last years we have developed a modular system correct, we should expect an increase in the concentra-
combining functionalised ligands with different sup- tion of reactants close to the catalytic active site, and
ports and linkers in order to have a systematic access consequently an increase in the rate of the reaction
to a variety of immobilised chiral catalysts.[7f–h,14] We should occur.
have applied here this methodology (Scheme 2) to im-
All solids were functionalised in the same manner ac-
mobilise Schiff base ligands on a mesoporous silica sup- cording to the procedure shown in Scheme 2. Supported
port, selected to encompass a wide range of topologies, precursors, 2-(support), were obtained by refluxing a
such as MCM-41, ITQ-2, and ITQ-6 delaminated zeo- mixture of the precursor 2 and the respective support,
lites, and amorphous silica (see characteristics in Ta- in toluene, for 16 hours. These anchored aldehydes re-
ble 1). With respect to the supports, both silica and acted with an equimolar amount of (S)-(N-benzyl-2-pyr-
MCM-41 are short range amorphous materials contain- rolidinyl)methylamine, (S)-[1-(1-naphthylmethyl)-2-
ing a large number of silanol groups available for graft- pyrrolidinyl]methylamine or (S)-[1-(2-naphthylmeth-
ing. In the case of MCM-41, however, the material pres- yl)-2-pyrrolidinyl]methylamine to afford the supported
ents a long-range ordering with hexagonal symmetry chiral Schiff ligands, 3–5-(support), as fine powdered
with regular monodirectional channels of 3.5 nm in di- solids. These materials were characterised by microanal-
ameter. On the other hand, ITQ-6 and ITQ-2 delaminat- ysis, FT IR and 13C NMR. In the 13C NMR spectra, the
À
ed zeolites present both short- and long-range order, to- C OH carbon signal appears at d¼ ꢀ153 ppm, and
gether with a very large, well structured external surface the imine carbon signals appear at d¼165–166 ppm.
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Table 1. Textural characteristics of the solid supports.
Support
(Pure Silica)
BET Surface Area
Micropore Surface
External (or Mesoporous)
Surface Area
(m2 ·gÀ1
)
(t-plot m2 ·gÀ1
)
(m2 ·gÀ1
)
Silica
750
1030
830
MCM-41
ITQ-2
ITQ-6
0
130
10
1030
700
608
618
Figure 1. Diffuse reflectance spectra of soluble and heteroge-
nised complexes.
Some of the bands characteristic of the complexes could,
however, could be distinguished. Major zeolite frame-
work bands appeared around 1140, 1040, 960, 785 and
740 cmÀ1. FTIR spectra are characteristic for the bind-
ing of imine nitrogen. The 1600 cmÀ1 frequencies may
Scheme 2. Synthesis of heterogenised ligands and complexes.
¼
¼
be assigned to C C and azomethine C N vibrations,
shifted to lower wavenumbers (relative to the free li-
gands) due to N-coordination of the imine.[16] The IR
spectra also shows strong bands at 1290 and ꢀ
Synthesis and Characterisation of Heterogenised
Complexes
The heterogenised ligands reacted with palladium(II) or 1500 cmÀ1 assigned to the symmetric and asymmetric
nickel(II) acetate to furnish the corresponding anchored n(COO) vibrations, respectively, in agreement with
Pd and Ni complexes that were used for catalytic hydro- those expected for monocoordinate acetate ligands.[17]
genation. The catalytic activities of the anchored com- New bands in the 500–600 cmÀ1 region are ascribed to
À
plexes were also compared to those of the homogeneous n(M O).
ones (3–5Pd and 3-5Ni) that were synthesised starting
from 3–5 as shown in Scheme 1.
The chiral Schiff base MII(OAc) complexes immobi-
lised on supports have been characterised by diffuse re-
The catalysts prepared in this way presented metal load- flectance UV spectroscopy and the typical UV-VIS
ings of 0.1–0.30 mmol metal/g support as determined by spectra are given in Figure 1. The DFTR spectra for all
atomic absorption analysis. The solids were characterised complexes were obtained in the 200–800 nm range.
by FTIR, DFTR and 13C NMR spectroscopy.
The complexes show several band maxima in the UV re-
gion agreeing with the assignment of the bands as intra-
ligand p!p*, n!p* transitions in the aromatic ring,
azomethine group and charge-transfer transition.[18]
The bands in the 400–450 nm region correspond to
Infrared and Electronic Spectra
Peaks due to the support dominate the spectra. These in- d-d transitions expected for planar complexes[19] and
À1
À
clude the O H vibration in the range 3700–3300 cm
.
MLCT bands. The diffuse reflectance spectra of M(li-
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Pd and Ni Catalysts Heterogenised on Oxidic Supports
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gand) complexes are almost identical before and after
heterogenisation process, indicating that the complexes
maintain their geometry and their electronic surround-
ings even after heterogenisation without significant dis-
tortion.
NMR Spectra
Diamagnetic palladium and nickel complexes have been
characterised by 13C NMR spectroscopy. In all cases, the
spectra show the simultaneous occurrence of two set of
signals which are attributable on the one hand to the
substituted benzaldimine entity and on the other hand
to the aliphatic part of the ligand. The 13C NMR spectra
Figure 2. Tested models for the hydrogenation reactions.
¼
showed the signals assigned to the C N carbon shifted to
high field and C1 at d ~162 shifted downfield confirming
that metallation had occurred.
The results show that the homogeneous Pd and Ni sys-
tems lead to quantitative conversion of olefins under the
hydrogenation conditions. In the present study, the or-
der of reactivity may be explained on the basis of the
Catalytic Hydrogenation
The availability of the structurally well defined Ni(II) steric factors. There were no significant differences in
and Pd(II) complexes enables us to explore the possibil- the electronic natures of the complexes.
ities of these complexes in hydrogenation reactions. The
As Tables 2 and 3 show, the heterogenised catalysts
hydrogenation of simple alkenes (cyclohexene, cyclooc- had, in general, higher activities than the homogeneous
tene), diethyl itaconate, diethyl 2-benzylidenesuccinate, counterpart (Figure 3). If we compare the heteroge-
diethyl 2-naphthylidenesuccinate and imines such as
anti-N-benzyl-(1-phenylethylidene)imine or 5-phenyl-
Table 3. Turnover rates for the catalytic hydrogenation of II
with catalysts derived from ligands 4,5.
3,4-dihydro-2H-pyrrole (Figure 2) with Pd and Ni com-
plexes were carried out under standard conditions
(EtOH as the solvent, 4 atm hydrogen pressure, 408C).
The hydrogenation was carried out to explore the possi-
bilities of recovering the catalysts, the influence of the
nature of the support, and for a comparison of the activ-
ity and stability of supported catalysts with their homo-
geneous counterpart. Tables 2–6 summarise the catalyt-
ic results obtained when homogeneous Schiff base com-
plexes were immobilised on different supports.
4Pd
4Ni
5Pd
5Ni
Homo
MCM-41
ITQ-2
ITQ-6
Silica
842760
901080
930480
947280
882960
964320
684000
846720
907440
947400
758880
961920
1013640
1033200
1075800
986400
999120
1033680
1047960
945960
TOF: hÀ1; conditions: 4 atm, 408C; S/C ratio 100000: 1.
Table 2. Turnover rates for the catalytic hydrogenation of alkenes with catalysts derived from ligand 3.
Pd
I
Ni
Pd
Ni
Pd
III
Ni
Pd
IV
Ni
Pd
V
Ni
II[a]
Homo
MCM-41
ITQ-2
ITQ-6
Silica
4040
4200
5700
5220
4260
4020
4620
6000
5340
3120
20500
18600
22500
15000
13500
21800
19500
22805
25500[b]
12300
3360
4980
5220
4860
4680
2400
4650
6000
5520
3360
640
900
943
810
809
220
670
630
530
450
153
187
280
207
200
117
307
420
226
149
TOF: hÀ1; conditions: 4 atm, 408C, S/C ratio 1000: 1.
[a]
S/C ratio 10000: 1.
[b]
S/C ratio 100000: 1; TOF: 128500 hÀ1
.
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planation for the higher rate, since the complex is in a
molecularly dispersed form and because of this, is not
subject to self-degradation. After prolonged storage
(3–6 months) at room temperature our heterogenised
catalysts showed the same features as the freshly pre-
pared catalysts in the standard hydrogenation reaction.
It was recently reported that Ir-xyliphos complexes
are very active and enantioselective catalysts for the hy-
drogenation of imines.[20] However, when they were sup-
ported on silica the authors found that the activity of the
heterogenised analogues was lower by a factor of 2 to 5.
Moreover, they observed that the polystyrene-bound
complexes were much less active, and in contrast with
the homogeneous complexes, the immobilised systems
were susceptible to deactivation. In their excellent
work, Pugin et al.[20] show that the decrease in activity
and catalyst life of their imine hydrogenation homoge-
neous catalyst upon heterogenisation was probably
due to limited mass transport in the pores and to the
proximity of the Ir complexes. In any case and by work-
ing at 80 bars and 25–308C in the presence of acetic
Figure 3. Comparison of the catalytic activities of homogene-
ous and heterogenised 3Pd on the hydrogenation reaction of
olefins.
nised catalysts we can observe that the activity of the acid, Pugin et al. obtained an unprecedented high activ-
ITQ-2 complex is higher. Depending on the studied sub- ity (TOF up to 20,000 hÀ1) and productivity (TON up to
strate the TOFs are about 2 to 3 times higher than those 195,000) of the silica bound catalyst; these values are
observed on the silica supported or homogeneous cata- much higher than previously reported on diphosphine
lyst. These results indicate that either the support or the Rh (2000 hÀ1) or Ru (400 hÀ1).[7,21]
metal complexes have a considerable effect on the cata-
From the above work it appeared to us that mesostruc-
lytic process, because of the stability of the active metal- tured solids and – well structured – all accessible delami-
lic species formed. The fact that the heterogenised cata- nated zeolites could be suitable supports for immobilis-
lysts have higher reaction rates is one of the expected ad- ing homogeneous imine hydrogenation catalysts, since
vantages of using heterogenised catalysts and is in good they could avoid the mass transfer limitations of the pre-
agreement with our former results.[4b] In different sys- viously reported support. Moreover, the fact that we
tems we have observed higher reaction rates on hetero- could control, up to a certain point, the polarity (acidity)
genised samples. The explanation could be that in the of the catalyst surface, could introduce an additional
homogeneous condition the reaction rate is decreased benefit from the point of view of increasing reactant
by the poor solubility of these complexes in most organic concentration at the surface, and/or stabilising reaction
solvents and by self-degradation. If we eliminate these transition states. Thus, for investigating these factors,
factors by heterogenising the complex we can expect a we have selected two model imines [anti-N-benzyl-(1-
higher reaction rate. The site isolation effect which phenylethylidene)imine, VI, 5-phenyl-3,4-dihydro-2H-
works on the heterogenised condition may also be an ex- pyrrole, VII].
Table 4. Turnover rates for the catalytic hydrogenation of imines.
3Pd
3Ni
3Pd
3Ni
4Pd
4Ni
5Pd
5Ni
VI[a]
VII[a]
VI[b]
VI[b]
Homo
MCM-41
ITQ-2
ITQ-6
Silica
3240
5520
5640
4860
3900
4800
4860
5700
5640
4440
167
500
560
517
160
93
440
533
513
153
337500
603240
402840
676320
294000
410940
623520
447720
600480
416640
309240
322560
375000
428520
285660
461520
476160
620960
620000
361440
[a]
TOF: hÀ1; conditions: 4 atm, 408C, S/C ratio 1000: 1.
S/C ratio 100000: 1
[b]
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Pd and Ni Catalysts Heterogenised on Oxidic Supports
FULL PAPERS
Table 5. Influence of the acidity of the supports on the activ-
For carrying out the hydrogenation reaction, we have
used our less conventional imine hydrogenation cata-
lysts based on Ni and Pd Schiff bases that can be eco-
nomically attractive with respect to those based on Rh,
Ru or Ir. The reaction conditions chosen were also mild-
er (Pꢁ10 bar) than those reported before.
ity in hydrogenation.[a]
Catalyst
Si/Al
III
IV
900
4285
1896
943
V
3Pd-(MCM-41)
3Pd-(MCM-41)
3Pd-(MCM-41)
3Pd-(ITQ-2)
1
15
50
1
20
4980
9091
6000
5220
9450
187
300
290
280
291
The results presented in Table 4 show that the Pd and
Ni complexes described here are very active in the ho-
mogeneous phase with TOF of ꢀ106 hÀ1. This value is
much higher than those reported before for Ir, Rh and
Ru complexes. We have checked that the catalytic activ-
ity observed is due to the complex and not to any metal
formed by decomposition of the complex in the reaction
media. In order to do this, the methodology used was as
described in the literature.[22] The presence of bulk metal
was eliminated as follows: the reaction mixtures were
passed through a micropore filter, the reactor was wash-
ed with ethanol and the washings filtered. The filter did
not show traces of bulk metal (microscope, 100Âmagni-
fication). Another problem that can mask the results
may come from the unperceived presence of colloidal
metal in “homogeneous” catalysts. Such colloidal parti-
cles can be catalytically active, and may be responsible
for all of the observed catalytic activity, since they may
3Pd-(ITQ-2)
4850
[a]
TOF: hÀ1; conditions: 4 atm, 408C; S/C ratio: 1000: 1.
Table 6. Influence of the Sn on the activity in hydrogena-
tion.[a]
Catalyst
Sn[b]
III
IV
900
1182
618
V
3Pd-(MCM-41)
3Pd-(MCM-41)
3Pd-(MCM-41)
–
4980
4912
4236
187
188
193
grafted
synthesis
[a]
TOF: hÀ1; conditions: 4 atm, 408C; S/C ratio: 1000: 1.
10–12% SnO2.
[b]
or may not be subsequently precipitated. It is not suffi- was claimed to be caused by the stabilisation of the tran-
cient, therefore, to verify merely that the solutions are sition state by the Hþ in the reaction media. If this is
clear, or to show that any bulk metal that is precipitated true, and since we have claimed an important role of
is catalytically inactive. Then, we have made a test using the adsorption characteristics of the mesoporous and
colloidal nickel as catalyst for the hydrogenation of delaminated zeolite supports on the reaction rate, we
imine VI and no reaction was observed after 3 h. Anoth- should increase still further the rate of the reaction by in-
erconsideration that supports the view that thesolutions troducing some acidity on the support. To do this, we
are homogeneous is the reproducibility of the reactions. have prepared MCM-41 and ITQ-2 containing a tetra-
It appears from the experiments described above that hedrally coordinated framework of Al. By doing this,
Ni- and Pd-salen complexes are stable under the reac- Brönsted acidity has developed on the catalyst as can
tion conditions and are very active for imine hydrogena- be seen by IR spectroscopy of adsorbed pyridine. In-
tion. When they were supported on amorphous silica, deed, after pyridine adsorption and desorption at
the TOF did not decrease but remained practically the 1508C in vacuum, an IR band at 1545 cmÀ1 develops
same as that in the homogeneous phase. Interestingly, that is due to pyridinium ions formed by pyridine proto-
the activity of the catalyst increased when supported nation on the surface Brönsted acid sites of the carrier.
on the mesoporous molecular sieve MCM-41. The in-
When the hydrogenation was performed with Pd- and
crease in activity is even higher in the case of the delami- Ni-salen complexes grafted on the acidic MCM-41 (Si/
nated zeolitic ITQ-2 material whose surface is formed Al¼15, 50) and ITQ-2 (Si/Al¼20) an increase in the re-
by cups in which the reactant will be concentrated by ad- action rate is observed (Table 5) with respect to the cat-
sorption.[11] In this case, the activity when grafted on alysts with non-acidic supports. At this point, it is worth
ITQ-2 is almost double that for the unsupported homo- noting that by grafting on an acidic delaminated zeolite
geneous catalyst.
with well structured “cups” at the surface in which the
In order to check for the presence of metal clusters substrate is adsorbed and concentrated, TOF as high
supported on the solid matrix, we have characterised as 9·103 hÀ1 can be obtained for the hydrogenation of di-
the solid before and after reaction. As can be deduced ethyl succinates.
from IR, 13C NMR and UV-VIS spectra, the nature of
On the other hand, Sn has been widely investigated as
¼
supported species is the same and the most important a selectivity promoter for the hydrogenation of C C
signals appear in the same position after reaction. double bonds, C Oaldehydic or ketonic groups; [23] for
¼
Also, high resolution TEM does not show changes be- this reason, we aimed to investigate the effect of Lewis
fore and after reaction.
acidic Sn(IV) centres on the catalytic behaviour of Pd
In a previous paper, Pugin et al. have shown that ace- in the hydrogenation of III, IV and V (Table 6). We
tic acid increases the reaction rate for the hydrogenation have prepared two series of Sn-MCM-41 supports, one
reaction in the homogeneous phase. The reason for this of then with the tin centres introduced during the
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Figure 4. Comparison of the catalytic activities of 3Pd and salen-Pd on the hydrogenation of imine VII.
MCM-41 synthesis (Snsynth-MCM-41), and other in
which the Sn has been incorporated to MCM-41 in a
post-synthesis treatment by a grafting procedure
(Sngraft-MCM-41). Table 6 shows that these Sn systems
do not improve the catalytic performance of 3Pd-
(MCM-41) catalyst and produce a lower activity.
There is, however, one aspect that we have not ach-
ieved with these catalysts and that is high enantioselec-
tivity. Indeed, the Pd and Ni catalysts, despite their very
high activity, give enantioselectivities in the order of 10–
15%. We believe that the low enantioselectivity of the
complexes for hydrogenation of prochiral substrates
can be due to the planarity of the metal complex. The in-
termediate species also presents a square-planar struc-
ture and the approximation of the substrate to the cata-
lytic centre by only one face is not sufficiently favoured
in this case.
Scheme 3. Proposed reaction pathway for the hydrogenation
reactions with Pd and Ni(II) complexes.
Comparison of Title Catalysts with Salen Complexes
olytic hydrogen cleavage. In the case of these Pd and Ni
The performance of catalysts described in the present complexes, heterolytic cleavage is preferred to give a hy-
work has been compared with that showed by soluble dride intermediate which involves charge separation
and heterogenised Pd and Ni complexes derived from without any oxidation of the metal. Heterolytic cleavage
the related salen ligand {salen¼(R,R)-N’,N’-bis-(3,5- of hydrogen by Pd complexes has been proposed be-
di-tert-butylsalicylidene)-1,2-cyclohexanediamine}.[24]
The result is displayed in Figure 4.
fore[25] and is supported from our experiments using
more polar and protonic acid media which produce a sig-
Under the conditions described in the experimental nificant increase of reaction rate, probably favouring
section, the Pd catalysts derived from ligand 3 display charge separation in the step of formation of the inter-
higher activity than those derived from salen ligand. mediate (Table 5).
One has to conclude that the our simpler chiral Schiff
On the basis of the experimental results a reaction
base ligands containing pyrrolidinylamino functionali- pathway based on heterolytic hydrogen cleavage (differ-
ties in place of one phenolic group on salen ligands im- ent from the oxidative addition of H2, generally accept-
prove the catalytic properties of salen-derived catalysts. ed for Rh and Ir complexes) is proposed in Scheme 3.
The accumulated evidence concerning the mecha- The catalyst adds hydrogen to give Complex-I which is
nisms of homogeneously catalysed hydrogenation indi- formed between the catalyst and hydrogen, involving
cates that three principal modes of hydrogen activation hydride ion transfer to the palladium replacing acetate
are suitable: oxidative addition, and homolytic or heter- ion, leaving acetic acid. In the second equilibrium step
1322
ꢀ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
Adv. Synth. Catal. 2004, 346, 1316–1328

Pd and Ni Catalysts Heterogenised on Oxidic Supports
FULL PAPERS
An additional boost in activity is achieved with these
supported salen complexes by changing the polarity
(acidity) of the catalyst, as a consequence of the stabili-
sation of the reaction transition state. The stability of the
catalysts was excellent and no deactivation was ob-
served. With the Pd and Ni salen catalysts the enantiose-
lectivity was low, but the possibility of using these sup-
ports for other more enantioselective transition metal
complexes is opened.
Experimental Section
General Remarks
All preparations of metal complexes were carried out under di-
nitrogen by conventional Schlenk tube techniques. Solvents
were carefully degassed before use. The silylating agent
OCN(CH2)Si(OEt3), was obtained from ABCR. C, H and N
analysis were carried out by the analytical department of the
Institute of Materials Science (C.S.I.C.) with a Perkin-Elmer
240C apparatus. Metal contents were analysed by atomic ab-
sorption using a Perkin Elmer Analyst 300 atomic absorption
apparatus and plasma ICP Perkin Elmer 40. IR spectra were
recorded with a Nicolet XR60 spectrophotometer (range
Figure 5. Recycling of 3Pd-(MCM-41) in the hydrogenation
of diethyl 2-benzylidenesuccinate.
the alkene forms a p-complex, i.e., Complex-II with the
palladium and simultaneous hydride ion transfer taking
place from palladium to alkene. The last step involves
transfer of a proton to the substrate, leading to the sep-
aration of the hydrogenated product from the catalyst,
thus a stable catalyst is regenerated.
1
4000–200 cmÀ1) in KBr pellets; H NMR, 13C NMR spectra
were taken on Varian XR300 and Bruker 200 spectrometers.
Chemical shifts are referred to tetramethylsilane (internal
standard). High resolution 13C MAS or CP/MAS NMR spectra
of powdered samples, in some cases also with a Toss sequence
in order to eliminate the spinning side bands, were recorded at
100.63 MHz, 6 ms, 900 pulse width, 2 ms contact time and 5–10
recycle delay, using a Bruker MSL 400 spectrometer equipped
with an FT unit. The spinning frequency at the magic angle
(54044’) was 4 KHz.[26] Optical rotation values were measured
at the sodium D line (589 nm) with a Perkin Elmer 241 MC po-
larimeter. Gas chromatographic analysis was performed using
a Hewlett-Packard 5890 II with a flame ionisation detector in a
cross-linked methylsilicone column.
Recycling of Heterogenised Catalysts
The major advantage of the use of heterogenised metal
complexes as catalysts for this reaction is the ease with
which they can be recovered as stable species from the
reaction mixture by simple filtration and reused. We
have carried out the heterogeneous asymmetric hydro-
genation of olefins until completion, filtered and washed
the heterogenised catalyst, then added fresh substrate,
and solvent without further addition of catalyst, for sev-
eral consecutive experiments and have found that both
The inorganic supports for anchoring were silica gel [Merck
silica, average pore diameter 40 ꢁ], purely siliceous MCM-
yield and activity are retained (Figure 5). After each ex- 41,[9] and delaminatedzeolitesITQ-2and ITQ-6.[11] In addition,
Al-containing MCM-41 (Si/Al: 15, 50), Al-containing ITQ-2
(Si/Al: 20) and Sn-containing MCM-41 (ꢀ10–12% Sn) were
used as supports for loading the complex.
periment a portion of supported catalyst was analysed to
determine the concentration of metal still present in the
support. Filtrate has been used in a new reaction and was
not found to catalyse hydrogenation.
Synthesis of Ligands
Conclusion
The soluble ligands 3–5 have been synthesised in high yields as
described previously,[13] and the heterogenised ligands were
obtained as described below.
In conclusion, we have shown that it is possible to boost
theactivityofatransitionmetalcomplexcatalystbyusing
an adequate support. We have seen that by using meso-
structured silicates and delaminated zeolites as carriers,
both with very high surface areas and accessibility to re-
actants, together with high adsorption capacity, the activ-
ity of the grafted Pd and Ni salen complex for the hydro-
genation reaction is higher than with the homogeneous
counterpart or when grafted on amorphous silica.
General Heterogenisation of Hydroxyaldehyde
Typically, to a suspension of silica or the corresponding meso-
porous solids MCM-41, ITQ-2 or ITQ-6 (2 g) in toluene
(25 mL), stirred at room temperature for 30 minutes, a solution
of 2 mmol of the aldehyde 2 in toluene (5 mL) and 400 mL of
water were added. The slurry was heated at 1008C for 16 h
Adv. Synth. Catal. 2004, 346, 1316–1328
asc.wiley-vch.de
ꢀ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1323

´
C. Gonzalez-Arellano et al.
FULL PAPERS
À
À
and the yellow solid was filtered off and washed successively
with toluene, petroleum ether, ethanol and ether. The solid
was dried under vacuum for 24 hours to afford the anchored
precursors precursor-(support) [2-Sil, 2-MCM-41, 2-ITQ-2, 2-
ITQ-6]. The loadings are based on the percent of nitrogen ob-
tained from the elemental analysis data.
(CH3CH2O ), 54.32 (NHCH2Ph), 41.86 (NHCH2CH2 ),
27.22 [C(CH3)3], 19.05 (CH3CH2O ), 9.21 (CH2Si ).
À
À
Synthesis of Heterogenised Terdentate Ligands
2-(Sil): anal. found: C 12.3, H 2.17, N 1.8%; (0.63 mmol/g);
Typically, a stirred slurry of 1 mmol of the corresponding anch-
ored hydroxyaldehyde 2-(Sil, MCM-41, ITQ-2, ITQ-6) was
prepared in ethanol (10 mL) under argon atroom temperature.
After 10 min, 125 mg (1.1 mmol) of the amine were added and
stirred for 16 hours. Then, the mixture was allowed to cool and
the deep yellow solid was filtered off and washed thoroughly
with ethanol and then with ether. The solid was dried under
vacuum to afford the corresponding anchored ligands: li-
gand-(support).
IR (KBr): n¼3478 (NH), 1642, 1564 cmÀ1 (C O , C C); UV-
VIS: l¼243, 298, 410 nm; 13C NMR (solid): d¼196.35
(CHO), 159.0 (NHCONH), 130.18 [C-C(CH3)3], 120.15 (C-
CHO), 42.83 (NHCH2Ph), 27.54 [C(CH3)3], 20.50
À
¼
À
À
À
(CH2CH2CH2 ), 17.53 (CH3CH2O ), 5.04 (CH2Si ).
2-(MCM-41): anal. found:
C 13.4, H 2.8, N 1.5%;
(0.55 mmol/g); IR (KBr): n¼3421 (NH), 1642, 1564 cmÀ1
(CO, C C); UV-VIS: l¼360, 425 nm. 13C NMR (solid): d¼
¼
199.29 (CHO), 160.58 (NHCONH), 147.84 (COH), 138.13
(C-CHNH-), 130.98 (CHarom), 120.18 (C-CHO), 57.45
3-(Sil): anal. found: C 17.1, H 2.7, N 2.8%; (0.60 mmol/g); IR
(KBr): n¼1628, 1564 cmÀ1 (C N, C O , C C); UV-VIS: l¼
¼
¼
¼
À
À
(CH3CH2O ), 54.29 (NHCH2Ph), 42.04 (NHCH2CH2 ),
13
¼
227, 268, 350, 430 nm; C NMR (solid): d¼165.39 (CH N),
À
À
27.60 [C(CH3)3], 18.99 (CH3CH2O ), 9.64 (CH2Si ).
159.81 (NHCONH), 156.04 (C-OH), 137.60 (C6, Carom, C4,
2-(ITQ-2): anal. found: C 12.9, H 2.2, N 1.4%; (0.50 mmol/g);
¼
C2), 128.26 (Carom, C3, C5), 64.80 (C2’, CH NCH2), 60.19
IR (KBr): n¼3414 (NH), 1640, 1557 cmÀ1 (CO, C C); UV-
¼
(CH2Ph), 56.79 (C5’), 43.33 (CH2CH2CH2Si, CCH2NH),
34.35 [C(CH3)3], 26.70 [C(CH3)3, C3’], 21.97 (CH2CH2Si,
C4’), 10.20 (CH2Si).
VIS: l 0 223, 260, 340 nm. 13C NMR (solid): d¼198.53
(CHO), 158.74 (NHCONH), 150.00 (COH), 138.35
À
(C-CHNH ), 132.53 (CHarom), 120.39 (C-CHO), 58.03
3-(MCM-41): anal. found:
C 16.3, H 3.0, N 2.5%;
À
À
(CH3CH2O ), 53.90 (NHCH2Ph), 41.53 (NHCH2CH2 ),
(0.44 mmol/g); IR (KBr): n¼1630, 1557 cmÀ1 (C N, C O,
¼
¼
À
À
28.42 [C(CH3)3], 17.02 (CH3CH2O ), 9.74 (CH2Si ).
C C); UV-VIS: l¼224, 264, 347, 419 nm; 13C NMR (solid):
¼
2-(ITQ-6): anal. found: C 8.7, H 1.4, N 1.1%; (0.38 mmol/g);
¼
d¼166.60 (CH N), 160.53 (NHCONH), 153.62 (C-OH),
IR (KBr): n¼3415 (NH), 1640, 1555 cmÀ1 (CO, C C); UV-
¼
136.99 (C6, Carom, C4, C2), 128.74 (Carom, C3, C5), 66.50 (C2’,
VIS: l¼215, 258, 334 nm; 13C NMR (solid): d¼197.56
(CHO), 159.95 (NHCONH), 146.84 (COH), 138.84 (C-
¼
CH NCH2), 58.98 (CH2Ph), 53.64 (C5’), 42.48 (CH2CH2CH2
Si, CCH2NH), 28.40 [C(CH3)3, C3’], 22.09 (CH2CH2Si, C4’),
8.02 (CH2Si).
À
CHNH ), 132.04 (CHarom), 119.91 (C-CHO), 57.79
À
(CH3CH2O), 52.45 (NHCH2Ph), 41.77 (NHCH2CH2 ), 27.70
3-(ITQ-2): anal. found: C 15.4, H 2.4, N 2.2%; (0.41 mmol/g);
À
IR (KBr): n¼1628, 1557 cmÀ1 (C N, C O , C C); UV-VIS: l¼
[C(CH3)3], 15.81 (CH3CH2O), 10.22 (CH2Si ).
¼
¼
¼
226 262, 332, 423; 13C NMR (solid): d¼166.96 (CH N), 160.41
2-(MCM-41, Si/Al ꢂ15): anal. found: C 36.2, H 3.3, N 1.4%;
(0.47 mmol/g); IR (KBr): n¼3407 (NH), 1639, 1512 cmÀ1 (CO,
¼
(NHCONH), 152.28 (C-OH), 137.72 (C6, Carom, C4, C2), 128.62
C C); UV-VIS: l¼349, 264, 223 nm; 13C NMR (solid): d¼
¼
¼
(Carom, C3, C5), 65.04 (C2’, CH NCH2), 58.86 (CH2Ph), 54.12
199.00 (CHO), 161.02 (NHCONH), 147.41 (COH), 137.83
(C5’), 43.20 (CH2CH2CH2Si, CCH2NH), 36.29 [C(CH3)3],
25.74 [C(CH3)3, C3’], 23.06 (CH2CH2CH2Si, C4’), 11.54
(CH2Si).
À
(C-CHNH ), 131.26 (CHarom), 120.03 (C-CHO), 57.31
À
À
(CH3CH2O ), 54.05 (NHCH2Ph), 42.00 (NHCH2CH2 ),
À
À
27.43 [C(CH3)3], 19.12 (CH3CH2O ), 9.58 (CH2Si ).
3-(ITQ-6): anal. found: C 11.6, H 1.8, N 1.7%; (0.31 mmol/g);
IR (KBr): n¼1628, 1564 cmÀ1 (C N, C O , C C); UV-VIS: l¼
2-(MCM-41, Si/Al ꢂ50): anal. found: C 28.1, H 5.3, N 2.7%;
(0.96 mmol/g); IR (KBr): n¼3408 (NH), 1642, 1563 cmÀ1 (CO,
¼
¼
¼
13
¼
219, 262, 329, 414 nm; C NMR (solid): d¼166.24 (CH N),
C C); UV-VIS: l¼353, 266, 226, 203 nm; 13C NMR (solid):
¼
159.20 (NHCONH, COH), 136.87 (C6, Carom, C4, C2), 128.02
d¼198.95 (CHO), 160.13 (NHCONH), 148.23 (COH),
¼
(Carom, C3, C5), 63.71 (C2’, CH NCH2), 53.88 (C5’), 43.69
(CH2CH2CH2Si, CCH2NH), 35.08 [C(CH3)3], 29.98 [C(CH3)3,
C3’], 23.06 (CH2CH2CH2Si, C4’), 12.26 (CH2Si).
À
137.95 (C-CHNH ), 131.00 (CHarom), 120.12 (C-CHO), 57.33
À
À
(CH3CH2O ), 54.00 (NHCH2Ph), 42.00 (NHCH2CH2 ),
À
À
27.20 [C(CH3)3], 19.00 (CH3CH2O ), 9.10 (CH2Si ).
3-(MCM-41, Si/Al ꢂ 15): anal. found: C 17.4, H 2.4, N 2.7%;
(0.5 mmol/g); IR (KBr): n¼1630 cmÀ1 (C N); UV-VIS: l¼
2-(ITQ-2, Si/Al ꢂ20): anal. found: C 13.7, H 2.5, N 1.6%;
(0.56 mmol/g); IR (KBr): n¼3422 (NH), 1642, 1565 cmÀ1
¼
420, 337, 264, 223 nm.
(CO, C C); UV-VIS: l¼346, 265, 223 nm; 13C NMR (solid):
¼
3-(MCM-41, Si/Al ꢂ 50): anal. found: C 25.9, H 2.9, N 5.1%;
(0.9 mmol/g); IR (KBr): n¼1634 cmÀ1 (C N); UV-VIS: l¼
d¼198.23 (CHO), 158.60 (NHCONH), 150.75 (COH),
¼
À
138.54 (C-CHNH ), 132.50 (CHarom), 120.08 (C-CHO), 58.00
404, 332, 262, 226 nm.
À
À
(CH3CH2O ), 53.92 (NHCH2Ph), 41.50 (NHCH2CH2 ),
3-(ITQ-2, Si/Al ꢂ 20): anal. found: C 17.8, H 2.6, N 2.9%;
(0.5 mmol/g); IR (KBr): n¼1631 cmÀ1 (C N); UV-VIS: l¼
À
À
28.43 [C(CH3)3], 17.00 (CH3CH2O ), 9.24 (CH2Si ).
¼
2-(MCM-41, Snsynth): anal. found: C 20.3, H 3.1, N 3.3%;
411, 332, 265, 227 nm.
(1.2 mmol/g); IR (KBr): n¼3394 (NH), 1644, 1565 cmÀ1
3-(MCM-41, Snsynth): anal. found: C 21.4, H 3.0, N: 3.5%;
(0.6 mmol/g); IR (KBr): n¼1638 cmÀ1 (C N); UV-VIS: l¼
¼
¼
(CO, C C); UV-VIS: l¼432, 343, 265, 224 nm.
2-(MCM-41, Sngraft): anal. found: C 17.6, H 2.6, N 2.5%;
(0.9 mmol/g); IR (KBr): n¼3428 (NH), 1640, 1566 cmÀ1
429, 338, 266, 228 nm.
3-(MCM-41, Sngraft): anal. found: C 19.0, H 3.1, N 3.1%;
(CO, C C); UV-VIS: l¼426, 347, 267, 227 nm. 13C NMR (sol-
(0.5 mmol/g); IR (KBr): n¼1634 cmÀ1 (C N); UV-VIS: l¼
¼
¼
13
¼
id): d¼198.65 (CHO), 160.32 (NHCONH), 147.75 (COH),
431, 335, 264, 228 nm; C NMR (solid): d¼165.70 (CH N),
À
138.00 (C-CHNH ), 131.04 (CHarom), 120.43 (C-CHO), 57.00
160.21 (NHCONH), 154.04 (C-OH), 137.32 (C6, Carom, C4,
1324
ꢀ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
Adv. Synth. Catal. 2004, 346, 1316–1328

Pd and Ni Catalysts Heterogenised on Oxidic Supports
FULL PAPERS
¼
C2), 128.50 (Carom, C3, C5), 66.65 (C2’, CH NCH2), 59.14 (CH2
[C(CH3)3], 25.31 (C3’), 23.58 (CH3), 20.35 (C4’, CH2CH2CH2Si),
9.41 (CH2Si).
Ph), 53.75 (C5’), 42.52 (CH2CH2CH2Si, CCH2NH), 28.35
[C(CH3)3, C3’], 22.00 (CH2CH2Si, C4’), 8.00 (CH2Si).
4-(Sil): anal. found: C 20.5, H 3.1, N 3.1%; (0.55 mmol/g); IR
(KBr): n¼1640–1600 cmÀ1 (C N, C O , C C); UV-VIS: l¼
¼
¼
¼
415, 327, 266 nm; 13C NMR (solid): d¼169.45 (NHCONH),
Synthesis of Metal Complexes
¼
156.21 (CH N), 129.76–120.00 (Carom), 62.43–61.00 (C2’,
The homogeneous chiral complexes[13] were also synthesised
and used as catalysts to compare the catalytic activities and
to evaluate the relations between the structural features of li-
gands and activity. Heterogenised complexes were synthesised
following the general method. To a suspension of heteroge-
nised ligand in toluene (20 mL) at room temperature was add-
ed an ethanolic solution of Pd(OAc)2 or Ni(OAc)2 (0.5 mmol/
15 mL). The resulting mixture was stirred under reflux for 12 h,
cooled to room temperature and filtered. The solid was washed
several times with ethanol, dried and filtered to afford the re-
spective heterogenised complexes, complex-(support), in al-
most quantitative yields.
¼
CH NCH2), 59.11 (C5’), 58.87 (CH2-naphthyl), 43.04 (CH2CH2
CH2Si, CCH2NH), 30.23 [C(CH3)3], 27.83 (C3’), 25.07 (C4’,
CH2CH2CH2Si), 22.32 (CH3), 10.84 (CH2Si).
4-(MCM-41): anal. found:
C 20.3, H 2.9, N 3.1%;
(0.56 mmol/g); IR (KBr, cmÀ1): n¼1634–1599 (C N, C O,
¼
¼
C C); UV-VIS: l¼423, 337, 266, 222; 13C NMR (solid): d¼
¼
¼
169.65 (NHCONH), 156.32 (CH N), 129.80–120.00 (Carom),
¼
62.50–61.00 (C2’, CH NCH2), 59.00 (C5’), 58.75 (CH2-naphthyl),
43.00 (CH2CH2CH2Si, CCH2NH), 30.20 [C(CH3)3], 27.80
(C3’), 25.00 (C4’, CH2CH2CH2Si), 22.06 (CH3), 10.45 (CH2Si).
4-(ITQ-2): anal. found: C 19.4, H 3.0, N 2.6%; (0.45 mmol/g);
IR (KBr): n¼1638–1602 cmÀ1 (C N, C O , C C); UV-VIS:
¼
¼
¼
3Pd-(Sil): anal. found: C 15.3, H 1.8, N 2.2, Pd 5.8%;
l¼427, 336, 265, 221 nm; 13C NMR (solid): d¼170.23
¼
¼
¼
(0.54 mmol/g); IR (KBr): n¼1627–1564 (C N, C O , C C),
558 cmÀ1 (Pd-O); UV-VIS: l¼411 nm; 13C NMR (solid): d¼
180.74 (OOCCH3), 169.09 (NHCONH), 161.69 (C-O-Pd),
¼
(NHCONH), 157.01 (CH N), 130.00–120.00 (Carom), 62.50–
¼
60.80 (C2’, CH NCH2), 59.00 (C5’), 58.56 (CH2-naphthyl), 43.00
¼
(CH2CH2CH2Si, CCH2NH), 30.00 [C(CH3)3], 28.03 (C3’),
25.00 (C4’, CH2CH2CH2Si), 22.72 (CH3), 10.65 (CH2Si).
4-(ITQ-6): anal. found: C 20.2, H 2.7, N 2.9%; (0.51 mmol/g);
156.35 (CH N), 128.68 (Carom, C5, C3), 121.16 (C6), 65.71
¼
(CH NCH2, C2’), 61.34 (CH2Ph), 56.49 (C5’), 42.05
(CH2CH2CH2Si, CCH2NH), 33.68 [C(CH3)3], 28.22 [C(CH3)3,
C3’], 20.33 (OOCCH3, C4’, CH2CH2CH2Si), 7.84 (CH2Si).
3Pd-(MCM-41): anal. found: C 15.0, H 2.0, N 2.2, Pd 2.9%;
IR (KBr): n¼1636–1600 cmÀ1 (C N, C O , C C); UV-VIS:
¼
¼
¼
l¼432, 336, 264, 221 nm; 13C NMR (solid): d¼169.67
¼
¼
¼
¼
(0.27 mmol/g); IR (KBr: n¼1632–1558 (C N, C O , CC),
562 cmÀ1 (Pd-O); UV-VIS: l¼225, 352, 410 nm; 13C NMR
(solid): d¼180.40 (OOCCH3), 160.07 (NHCONH, C-O-Pd),
(NHCONH), 156.02 (CH N), 130.00–120.00 (Carom), 63.00–
¼
61.00 (C2’, CH NCH2), 59.04 (C5’), 58.93 (CH2-naphthyl),
43.00–42.87 (CH2CH2CH2Si, CCH2NH), 30.41 [C(CH3)3],
27.92 (C3’), 25.00 (C4’, CH2CH2CH2Si), 22.30 (CH3), 10.92
(CH2Si).
¼
155.30 (CH N), 137.61 (C2), 128.70 (Carom, C5, C3), 120.00
¼
(C6), 70.60 (CH NCH2, C2’), 63.21 (CH2Ph), 58.64 (C5’),
42.97 (CH2CH2CH2Si, CCH2NH), 34.50 [C(CH3)3], 28.20
[C(CH3)3, C3’], 23.34 (C4’, CH2CH2CH2Si), 16.66 (OOCCH3),
11.23 (CH2Si).
5-(Sil): anal. found: C 20.8, H 3.1, N 3.1%; (0.56 mmol/g); IR
(KBr): n¼1638–1590 cmÀ1 (C N, C O , C C); UV-VIS: l¼
¼
¼
¼
13
¼
426 nm; C NMR (solid): d¼160.01 (CH N), 141.0–118.50
3Pd-(ITQ-2): anal. found: C 13.4, H 1.4, N 1.9, Pd 3.3%;
¼
(Carom), 62.85 (C2’), 60.13 (CH NCH2), 59.52 (CH2-naphthyl),
¼
¼
¼
(0.31 mmol/g); IR (KBr): n¼1630–1562 (C N, C O , C C),
560 cmÀ1 (Pd-O); UV-VIS: l¼225, 258, 289, 335, 412 nm;
13C NMR (solid): d¼186.92 (OOCCH3), 169.09 (NHCONH,
54.15 (C5’), 43.63–42.07 (CH2CH2CH2Si, CCH2NH), 33.14
[C(CH3)3], 29.97 [C(CH3)3], 25.45 (C3’); 23.54 (CH3), 20.36
(C4’, CH2CH2CH2Si), 9.63 (CH2Si).
¼
C-O-Pd), 158.65 (CH N), 137.78 (C2), 126.14 (Carom, C5, C3),
119.22 (C6), 65.23 (CH NCH2, C2’), 62.56 (CH2Ph), 57.83
(C5’), 46.66 (CH2CH2CH2Si, CCH2NH), 34.04 [C(CH3)3],
28.95 [C(CH3)3, C3’], 24.09 (C4’, CH2CH2CH2Si), 17.30
(OOCCH3), 12.45 (CH2Si).
5-(MCM-41): anal. found:
C 27.2, H 5.2, N 3.3%;
¼
(0.59 mmol/g); IR (KBr): n¼1638–1600 cmÀ1 (C N, C O,
¼
¼
C C); UV-VIS: l¼415, 334, 270 nm; 13C NMR (solid): d¼
¼
¼
159.81 (CH N), 140.70–118.41 (Carom), 62.72 (C2’), 60.23
¼
(CH NCH2), 59.42 (CH2-naphthyl), 54.25 (C5’); 43.51–42.19
3Pd-(ITQ-6): anal. found: C 9.8, H 0.9, N 1.4, Pd 2.7%;
(CH2CH2CH2Si, CCH2NH), 33.00 [C(CH3)3], 29.88
[C(CH3)3], 25.38 (C3’), 23.50 (CH3), 20.32 (C4’, CH2CH2CH2Si),
9.44 (CH2Si).
¼
¼
¼
(0.25 mmol/g); IR (KBr): n¼1630–1564 (C N, C O , C C),
534 cmÀ1 (Pd-O); UV-VIS: l¼229, 257, 285, 338, 410 nm;
13C NMR (solid): d¼185.23 (OOCCH3), 164.23 (NHCONH),
¼
5-(ITQ-2): anal. found: C 33.7, H 5.5, N 4.7%; (0.83 mmol/g);
160.23 (C-O-Pd), 156.23 (CH N), 137.90 (C2), 127.83 (Carom
,
IR (KBr): n¼1638–1598 cmÀ1 (C N, C O , C C); UV-VIS:
l¼427, 336, 265, 221 nm; 13C NMR (solid): d¼159.86
¼
¼
¼
¼
C5, C3), 120.07 (C6), 65.35 (CH NCH2, C2’), 62.31 (CH2Ph),
56.98 (C5’), 48.97 (CH2CH2CH2Si, CCH2NH), 34.65
[C(CH3)3], 29.55 [C(CH3)3, C3’], 23.61 (C4’, CH2CH2CH2Si),
19.12 (OOCCH3), 9.41 (CH2Si).
¼
(CH N), 140.90–118.20 (Carom), 62.81 (C2’), 60.03
¼
(CH NCH2), 59.22 (CH2-naphthyl), 54.15 (C5’), 43.50–42.20
(CH2CH2CH2Si, CCH2NH), 33.00 [C(CH3)3], 29.85
[C(CH3)3], 25.33 (C3’), 23.61 (CH3), 20.26 (C4’, CH2CH2CH2Si),
9.53 (CH2Si).
3Pd-(MCM-41, Si/Al ꢂ 15):anal. found: C 15.7, H 2.0, N 2.5,
¼
Pd: 4.3%; (0.4 mmol/g); IR (KBr): n¼1630 (CO), 1564(C N),
454 cmÀ1 (Pd-O); UV-VIS: l¼408, 343, 289, 255, 229 nm.
5-(ITQ-6): anal. found: C 23.1, H 3.6, N 3.2%; (0.56 mmol/g);
3Pd-(MCM-41, Si/Al ꢂ 50): anal. found: C: 18.9; H: 3.6; N:
IR (KBr): n¼1636–1595 cmÀ1 (C N, C O , C C); UV-VIS:
l¼432, 336, 264, 221 nm; 13C NMR (solid): d¼159.85
¼
¼
¼
2.5; Pd: 4.4%; (0.4 mmol/g); IR (KBr): n¼1626 (CO), 1555
À1
¼
(C N), 442 cm (Pd-O); UV-VIS: l¼405, 344, 289, 254,
¼
(CH N), 141.00–118.40 (Carom), 62.77 (C2’), 60.19
230 nm.
¼
(CH NCH2), 59.46 (CH2-naphthyl), 54.15 (C5’), 43.50–42.00
(CH2CH2CH2Si, CCH2NH), 33.08 [C(CH3)3], 29.90
3Pd-(ITQ-2, Si/Al ꢂ 20): anal. found: C 16.6, H 2.4, N 2.7,
Pd 5.1%; (0.5 mmol/g); IR (KBr): n¼1621 (CO), 1557
Adv. Synth. Catal. 2004, 346, 1316–1328
asc.wiley-vch.de
ꢀ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1325

´
C. Gonzalez-Arellano et al.
FULL PAPERS
À1
¼
¼
(C N), 450 cm (Pd-O); UV-VIS: l¼407, 350, 285, 237;
(C-O-Pd), 159.33 (CH N), 128.80–120.00 (Carom), 65.50–
13C NMR (solid): d¼187.00 (OOCCH3), 169.00 (NHCONH,
63.00 (C2’, CH NCH2), 60.15 (C5’), 59.00 (CH2-naphthyl), 44.08
¼
¼
C-O-Pd), 158.76 (CH N), 137.82 (C2), 126.04 (Carom, C5, C3),
(CH2CH2CH2Si, CCH2NH), 30.63 [C(CH3)3], 28.69 (C3’),
25.18 (C4’, CH2CH2CH2Si), 22.06 (CH3), 20.79 (OCOCH3),
7.76 (CH2Si).
¼
119.19 (C6), 65.27 (CH NCH2, C2’), 62.59 (CH2Ph), 57.80
(C5’), 46.70 (CH2CH2CH2Si, CCH2NH), 34.00 [C(CH3)3],
29.00 [C(CH3)3, C3’], 24.05 (C4’, CH2CH2CH2Si), 17.26
(OOCCH3), 12.41 (CH2Si).
4Pd-(ITQ-2): anal. found: C 18.0, H 2.9, N, 2.6, Pd 3.4%;
¼
¼
¼
(0.32 mmol/g); IR (KBr): n¼1638–1566 (C N, C O , C C),
594 cmÀ1 (Pd-O); UV-VIS: l¼221, 264, 287, 341, 419 nm;
13C NMR (solid): d¼179.12 (OOCCH3), 169.29–160.09
3Pd-(MCM-41, Snsynth): anal. found: C 22.7, H 2.7, N 2.7, Pd
¼
6.9%; (0.6 mmol/g); IR (KBr): n¼1628 (CO), 1560 (C N),
450 cmÀ1 (Pd-O); UV-VIS: l¼417, 343, 261, 225 nm.
(NHCONH, C-O-Pd), 159.67 (CH N), 130.00–120.0 (Carom),
¼
¼
3Pd-(MCM-41, Sngraft): anal. found: C 31.9, H 5.9, N 5.5, Pd
62.25, 61.90 (C2’, CH NCH2), 59.81, 58.60 (C5’; (CH2-naphthyl),
¼
1.3%; (0.1 mmol/g); IR (KBr): n¼1636 (CO), 1564 (C N),
44.00 (CH2CH2CH2Si, CCH2NH), 30.86 [C(CH3)3], 29.17,
23.14, 22.06, 20.04 (C3’, C4’, CH3, CH2CH2CH2Si, OCOCH3),
7.76 (CH2Si).
450 cmÀ1 (Pd-O); UV-VIS: l¼422, 342, 264, 220 nm.
3Ni-(Sil): anal. found: C 15.6, H 2.2, N 2.5, Ni 10.1%;
¼
¼
¼
(0.45 mmol/g); IR (KBr): n¼1618–1564 (C N, C O , C C),
571 cmÀ1 (Ni-O);UV-VIS: l¼265, 330, 412 nm; 13C NMR (sol-
id): d¼182.40 (OOCCH3), 174.14 (NHCONH, C-O-Pd),
4Pd-(ITQ-6): anal. found: C 19.6, H 2.8, N 2.9, Pd 4.7%;
¼
¼
¼
(0.44 mmol/g); IR (KBr): n¼1637–1564 (C N, C O , C C),
592 cmÀ1 (Pd-O); UV-VIS: l¼224, 260, 291, 342, 417 nm;
13C NMR (solid): d¼180.00 (OOCCH3), 169.00 (NHCONH),
¼
158.61 (CH N), 140.66 (C2), 128.04 (Carom, C5, C3), 79.02
¼
¼
(CH NCH2, C2’), 60.09 (CH2Ph, C5’), 42.86 (CH2CH2CH2Si,
CCH2NH), 28.06 [C(CH3)3), C3’], 23.21 (C4’, CH2CH2CH2Si,
OOCCH3), 11.97 (CH2Si).
160.74 (C-O-Pd), 159.41 (CH N), 128.70–120.00 (Carom),
¼
65.50–63.00 (C2’, CH NCH2), 60.09 (C5’), 59.00 (CH2-naphthyl);
44.13–44.01 (CH2CH2CH2Si, CCH2NH), 30.70 [C(CH3)3],
28.65 (C3’), 25.12 (C4’, CH2CH2CH2Si), 22.19 (CH3), 20.71
(OCOCH3), 7.79 (CH2Si).
3Ni-(MCM-41): anal. found: C 16.4, H 2.1, N 2.6, Ni 6.4%;
¼
¼
¼
(0.36 mmol/g); IR (KBr): n¼1630–1567 (C N, C O , C C),
568 cmÀ1 (Ni-O); UV-VIS: l¼234, 268, 338, 414 nm;
13C NMR (solid): d¼198.94 (OOCCH3), 160.23 (NHCONH,
4Ni-(Sil): anal. found: C 19.8, H 3.6, N 3.0, Ni 1.3%;
¼
¼
¼
(0.22 mmol/g); IR (KBr): n¼1642–1572 (C N, C O , C C),
557 cmÀ1 (Ni-O); UV-VIS: l¼214, 261, 359, 421 nm;
13C NMR (solid): d¼179.16 (OCOCH3), 162.60 (C-O-Ni),
¼
C-O-Pd), 152.47 (CH N), 136.69 (C2), 128.56 (Carom, C5, C3),
¼
120.31 (C6), 73.60 (CH NCH2, C2’), 63.53 (CH2Ph), 58.67
¼
(C5’), 40.47 (CH2CH2CH2Si, CCH2NH), 34.29 [C(CH3)3],
27.73 [C(CH3)3, C3’], 22.27 (C4’, CH2CH2CH2Si, OOCCH3),
15.36 (CH2Si).
162.24 (CH N), 141.50–120.00 (Carom), 62.39 (C2’), 61.81
¼
(CH NCH2), 57.00 (CH2-naphthyl), 54.20 (C5’), 44.00 (CH2CH2
CH2Si, CCH2NH)), 35.36 [C(CH3)3], 30.00 [C(CH3)3], 29.63
(C3’), 28.19 (CH3), 25.00 (C4’), 20.82 (CH2CH2CH2Si,
OCOCH3), 7.73 (CH2Si).
3Ni-(MCM-41, Si/Al ꢂ 15): anal. found: C 14.7, H 1.1, N 2.0,
¼
Ni 3.2%; (0.18 mmol/g); IR (KBr): n¼1632 (CO), 1568 (C N),
457 cmÀ1 (Ni-O); UV-VIS: l¼495, 412, 339, 266 nm.
4Ni-(MCM-41): anal. found: C 16.5, H 2.8, N 2.5, Ni 1.0%;
¼
¼
¼
3Ni-(ITQ-2): anal. found: C 14.0, H 1.1, N 2.0, Ni 1.4%;
(0.16 mmol/g); IR (KBr): n¼1643–1570 (C N, C O , C C),
557 cmÀ1 (Ni-O); UV-VIS: l¼219, 266, 338, 414 nm;
13C NMR (solid): d¼178.75 (OCOCH3), 162.61 (C-O-Ni),
¼
¼
¼
(0.20 mmol/g); IR (KBr): n¼1628–1557 (C N, C O , C C),
557 cmÀ1 (Ni-O);UV-VIS: l¼236, 263, 390 nm: 13C NMR (sol-
id): d¼184.82 (OOCCH3), 174.14 (NHCONH, C-O-Pd),
¼
162.20 (CH N), 141.50–120.13 (Carom), 62.37 (C2’), 61.70
¼
¼
158.86 (CH N), 128.56 (Carom, C5, C3), 118.58 (C6), 59.61
(CH NCH2), 57.06 (CH2-naphthyl), 54.18 (C5’), 44.00 (CH2CH2
(CH2Ph, C5’), 42.86 (CH2CH2CH2Si, CCH2NH), 34.61
[C(CH3)3], 29.03 [C(CH3)3, C3’], 23.45 (C4’, CH2CH2CH2Si,
OOCCH3), 10.83 (CH2Si).
CH2Si, CCH2NH), 35.32 [C(CH3)3], 30.09 [C(CH3)3], 29.60
(C3’), 28.11 (CH3), 24.85 (C4’), 20.79 (CH2CH2CH2Si,
OCOCH3), 7.76 (CH2Si).
3Ni-(ITQ-6): anal. found: C 9.1, H 1.1, N 1.3, Ni 0.9%;
4Ni-(ITQ-2): anal. found: C 18.3, H 2.8, N 2.5, Ni 0.9%;
¼
¼
¼
¼
¼
¼
(0.13 mmol/g); IR (KBr): n¼1621–1554 (C N, C O , C C),
592 cmÀ1 (Ni-O);UV-VIS: l¼260, 328, 415 nm; 13C NMR (sol-
id): d¼190.89 (OOCCH3), 165.34 (NHCONH, C-O-Pd),
(0.16 mmol/g); IR (KBr): n¼1638–1562 (C N, C O , C C),
554 cmÀ1 (Ni-O); UV-VIS: l¼209, 223,266, 340, 418 nm.
4Ni-(ITQ-6): found: C 20.1, H 2.5, N 2.7, Ni 1.7%;
¼
¼
¼
¼
159.60 (CH N), 127.31 (Carom, C5, C3), 118.34 (C6), 76.59
(0.29 mmol/g); IR (KBr): n¼1636–1566 (C N, C O , C C),
(CH NCH2, C2’), 62.28 (CH2Ph), 44.08 (CH2CH2CH2Si,
592 cmÀ1 (Pd-O); UV-VIS: l¼224 264, 341, 421 nm.
¼
CCH2NH), 24.42 (C4’, CH2CH2CH2Si, OOCCH3), 8.41
(CH2Si).
5Pd-(Sil): anal. found: C 17.6, H 3.0, N 2.7, Pd 5.9%;
¼
¼
¼
(0.56 mmol/g); IR (KBr): n¼1646–1572 (C N, C O , C C),
4Pd-(Sil): anal. found: C 19.5, H 3.0, N 3.0, Pd 4.9%;
571 cmÀ1 (Pd-O); UV-VIS: l¼218, 270, 360 nm.
¼
¼
¼
(0.46 mmol/g), IR (KBr): n¼1638–1572 (C N, C O , C C),
557 cmÀ1 (Pd-O); UV-VIS: l¼206, 221, 424 nm; 13C NMR
(solid): d¼180.03 (OOCCH3), 169.09 (NHCONH), 160.69
5Pd-(MCM-41): anal. found: C 19.7, H 3.0, N 2.9, Pd 5.4%;
¼
¼
¼
(0.51 mmol/g); IR (KBr): n¼1630–1566 (C N, C O , C C),
564 cmÀ1 (Pd-O); UV-VIS: l¼205, 222, 314, 412 nm.
5Pd-(ITQ-2): anal. found: C 18.1, H 2.5, N 2.6, Pd 7.7%;
¼
(C-O-Pd), 159.35 (CH N), 128.68–120.16 (Carom), 65.45–
63.00 (C2’, CH NCH2), 60.11 (C5’), 59.05 (CH2-naphthyl), 44.05
(CH2CH2CH2Si, CCH2NH), 30.68 [C(CH3)3], 28.67 (C3’),
25.14 (C4’, CH2CH2CH2Si), 22.16 (CH3), 20.76 (OCOCH3),
7.84 (CH2Si).
¼
¼
¼
¼
(0.72 mmol/g); IR (KBr): n¼1636–1560 (C N, C O , C C),
557 cmÀ1 (Pd-O); UV-VIS: l¼223, 262, 343, 408 nm;
13C NMR (solid): d¼176.23 (OCOCH3), 160.92 (C-O-Pd),
¼
157.81 (CH N), 138.70–117.91 (Carom), 63.62 (C2’), 61.23
¼
4Pd-(MCM-41): anal. found: C 13.2, H 1.6, N 1.5, Pd 4.2%;
(CH NCH2), 59.98 (CH2-naphthyl), 56.85 (C5’), 44.21–43.89
¼
¼
¼
(0.39 mmol/g); IR (KBr): n¼1634–1564 (C N, C O , C C),
571 cmÀ1 (Pd-O); UV-VIS: l¼223, 268, 410 nm; 13C NMR
(solid): d¼180.00 (OOCCH3), 169.14 (NHCONH), 160.64
(CH2CH2CH2Si, CCH2NH), 33.39 [C(CH3)3], 28.88
[C(CH3)3], 27.38 (C3’), 25.50 (CH3), 21.78 (C4’, CH2CH2CH2Si),
18.34 (OCOCH3), 7.64 (CH2Si).
1326
ꢀ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
Adv. Synth. Catal. 2004, 346, 1316–1328

Pd and Ni Catalysts Heterogenised on Oxidic Supports
FULL PAPERS
5Pd-(ITQ-6): anal. found: C 18.0, H 2.3, N 2.8, Pd 11.0%;
[4] a) Y. N. Ito, T. Katsuki, Bull. Chem. Soc. Jpn. 1999, 72,
¼
¼
¼
(0.80 mmol/g); IR (KBr): n¼1628–1564 (C N, C O , C C),
603–619; b) V. Ayala, A. Corma, M. Iglesias, J. A. Rin-
571 cmÀ1 (Pd-O); UV-VIS: l¼218, 270, 360 nm.
´
´
con, F. Sanchez, J. Catal. 2004, 224, 170–177.
5Ni-(Sil): anal. found: C 20.5, H 3.0, N 3.0, Ni 2.0%;
[5] a) H.-U. Blaser, Tetrahedron: Asymmetry, 1991, 3, 843–
866; b) R. Noyori, in: Asymmetric Catalysis in Organic
Synthesis, Wiley, New York, 1994; c) I. Ojima, in: Catalyt-
ic Asymmetric Synthesis, 2nd edn., Wiley-VCH, New
York, 2000; d) . E. N. Jacobsen, A. Pfaltz, H. Yamamoto
(Eds.), Comprehensive Asymmetric Catalysis, Springer,
Berlin, 1999.
[6] a) C. U. Pittman, Jr., in: Comprehensive Organometallic
Chemistry, (Ed.: G. Wilkinson), Pergamon, Oxford, 199
2, vol. 8, p. 553; b) S. C. Bourque, H. Alper, L. E. Man-
zer, P. Arya, J. Am. Chem. Soc. 2000, 122, 956–957.
[7] a) D. E. De Vos, I. F. K. Vankelecom, P. A. Jacobs, in:
Chiral Catalyst Immobilization and Recycling, Wiley-
VCH, Weinheim, 2000; b) C. Bianchini, D. G. Burnaby,
J. Evans, P. Frediani, A. Meli, W. Oberhauser, R. Psaro,
L. Sordelli, F. Vizza, J. Am. Chem. Soc. 1999, 121, 59
61–5971; c) H.-B. Yu, Q.-S. G. Hu, L. Pu, Tetrahedron
Lett. 2000, 41,1681–1685; d) H. Gao, R. Angelici, J.
Mol. Catal. 1999, 149, 63–74; e) K. Nozaki, Y. Itoi, F. Shi-
bahara, E. Shirakawa, T. Ohta, H. Takaya, T. Hiyama, J.
Am. Chem. Soc. 1998, 120, 4051–4052; f) A. Corma, C.
¼
¼
¼
(0.34 mmol/g); IR (KBr): n¼1622–1574 (C N, C O , C C),
550 cmÀ1 (Ni-O); UV-VIS: l¼212, 264, 341, 422 nm.
5Ni-(MCM-41): anal. found: C 21.8, H 3.9, N 3.0, Ni 1.8%;
¼
¼
¼
(0.30 mmol/g); IR (KBr): n¼1620–1568 (C N, C O , C C),
557 cmÀ1 (Ni-O); UV-VIS: l¼216, 265, 336, 414 nm.
5Ni-(ITQ-2): anal. found: C 18.9, H 2.8, N 2.5, Ni 1.2%;
¼
¼
¼
(0.19 mmol/g); IR (KBr): n¼1634–1564 (C N, C O , C C),
552 cmÀ1 (Ni-O); UV-VIS: l¼221, 267, 337, 418 nm.
5Ni-(ITQ-6): anal. found: C 22.7, H 2.50, N 2.9, Ni 1.9%;
¼
¼
¼
(0.32 mmol/g); IR (KBr): n¼1620–1566 (C N, C O , C C),
592 cmÀ1 (Ni-O); UV-VIS: l¼224, 266, 340, 424 nm;
13C NMR (solid): d¼163.50 (C-O-Ni), 163.25 (CH N),
¼
¼
142.63–121.14 (Carom), 64.10 (C2’), 63.07 (CHN CH2), 61.23
(CH2-naphthyl), 58.56 (C5’); 44.43–42.89 (CH2CH2CH2Si,
CCH2NH), 32.32 [C(CH3)3], 30.63 [C(CH3)3], 29.39 (C3’),
25.97 (CH3), 24.45 (C4’), 21.79 (CH2CH2CH2Si, OCOCH3),
7.65 (CH2Si).
Catalytic Experiments
The catalytic properties, in hydrogenation reactions, of the Pd
and Ni complexes were examined under conventional condi-
tions for batch reactions in a reactor (Autoclave Engineers)
of 100 mL capacity at 408C temperature, 4 atm dihydrogen
pressure and 1/1000, 1/10000 or 1/1000000 metal/substrate mo-
lar ratio. The evolutionof the reaction and optical purity (ee) of
hydrogenated product were monitored by gas chromatography
with a chiral glass capillary column {mixture of methyl silicone
(OV-1701) and methylsilicone-heptakis-[2,3-dipentyl-6-(tert-
butyldimethylsilyl)]-b-cyclodextrin as stationary phase}.[27]
´
del Pino, M. Iglesias, F. Sanchez, J. Chem. Soc. Chem.
Commun. 1991, 1253–1255; g) A. Corma, M. Iglesias,
´
M. V. Martín, J. Rubio, F. Sanchez, Tetrahedron: Asym-
metry 1992, 3, 845–848; h) A. Corma, A. Fuerte, M. Igle-
´
sias, F. Sanchez; J. Mol. Catal. A: Chemical 1996, 107,
225–234eferences cited therein.
[8] D. J. Gravert, K. D. Janda, Chem. Rev. 1997, 97, 489–510
references cited therein.
[9] a) C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartu-
li, J. S. Beck, Nature 1992, 359, 710; b) J. S. Beck, W. J.
Roth, M. E. Leonowicz, C. T. Kresge, K. D. Schmitt,
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[10] a) P. Sutra, D. Brunel, J. Chem. Soc. Chem. Commun. 199
6, 2485–2487; b) Y. V. S. Rao, D. E. De Vos, T. Bein,
P. A. Jacobs, J. Chem. Soc. Chem. Commun. 1997, 355–
357; c) C.-J. Liu, S.-G. Li, W.-Q. Pang, C. Che, J. Chem.
Soc. Chem. Commun. 1997, 65–67; d) for a review of cat-
alytic applications in general, see: J. Y. Ying, C. P. Meh-
nert, M. S. Wong, Angew. Chem. Int. Ed. 1999, 38, 56–
77; R. A. Sheldon, H. van Bekkum (Eds.), Fine Chemi-
calsthrough HeterogeneousCatalysis , Wiley-VCH, Wein-
heim, 2001
Recovery and Recycling of Catalysts
At the end of the hydrogenation process, the mixture of reac-
tion was filtered; the residue of zeolite-containing catalyst
was washed with CH2Cl2 to completely remove the remains
of products and/or reactants and used again.
Acknowledgements
´
´
Financial support by the Direccion General de Investigacion
´
Científica y Tecnica of Spain (Project MAT2000-1768-C02-02,
MAT2003-07945-C02-02) isgratefully acknowledged.
´
[11] a) A. Corma, V. Fornes, S. B. Pergher, Nature 1998, 396,
´
353; b) A. Corma, V. Fornes, J. Martínez-Triguero, S. B.
Pergher, J. Catal. 1999, 186, 57–63; c) A. Corma, U.
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Diaz, M. E. Domine, V. Fornes, Angew. Chem. Int. Ed.
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