Development of homogeneous and heterogenized rhodium(i) and palladium(ii) complexes with ligands based on a chiral proton sponge building block and their application as catalysts

Article abstract of DOI:10.1039/c1dt10597c

Chiral compounds prepared from proton sponge building block 8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-amine were found to be effective chiral ligands for obtaining complexes of rhodium(i) and palladium(ii) by reaction with [RhCl(cod)]₂, PdCl₂(cod) or Pd(OAc) ₂. The complexes bearing triethoxysilane groups were immobilized on mesoporous MCM-41 in order to obtain new heterogeneous catalysts. Both materials are active in the hydrogenation of alkenes and could be recycled without loss of activity or enantioselectivity.

Full text of DOI:10.1039/c1dt10597c

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2011, 40, 9589
www.rsc.org/dalton
PAPER
Development of homogeneous and heterogenized rhodium(I) and palladium(II)
complexes with ligands based on a chiral proton sponge building block and
their application as catalysts†
Gonzalo Villaverde,a,b Avelina Arnanz,a Marta Iglesias,*a Angeles Monge,a Fe´lix Sa´nchez*b and Natalia Snejkoa
Received 7th April 2011, Accepted 9th June 2011
DOI: 10.1039/c1dt10597c
Chiral compounds prepared from proton sponge building block
8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-amine were found to be effective chiral ligands for
obtaining complexes of rhodium(I) and palladium(II) by reaction with [RhCl(cod)]2, PdCl2(cod) or
Pd(OAc)2. The complexes bearing triethoxysilane groups were immobilized on mesoporous MCM-41
in order to obtain new heterogeneous catalysts. Both materials are active in the hydrogenation of
alkenes and could be recycled without loss of activity or enantioselectivity.
forward to derivatise. While 1 has a high affinity towards H+, it
is indifferent to other electrophiles, which is in contrast to usual
nitrogen bases. Some examples of reactivity of 1 apart from routine
protonation include, somewhat surprisingly, its role as a hydride
Introduction
Heterogenization of homogeneous single-site catalysts on solid
support materials allows combination of the superior activity
and selectivity of homogeneous with the simple recovery of
heterogeneous catalyst. Heterogenized catalysts can also be used
in fixed- or flow-bed reactors, which additionally simplify process
development. Therefore, such systems have been extensively
studied during the past two decades.1
donor in its reaction with mer-RhCl3(dmso)3 or [RuCl(dppb)]2(l-
Cl)3,6 with fluoroalkyl complexes of iridium,7 or with B(C6F5)38 to
form the 1,1,3-trimethyl-2,3-dihydroperimidinium cation (TMP+).
There is also a single example of a metal complex coordinating
(directly) to 1, (via the amino groups); the reaction with Pd(hfac)2
(hfac: hexafluoroacetylacetonate) immediately generates a poorly-
characterized charge-transfer product, which after standing for
a week forms the cationic complex [Pd(hfac)(1)]+.9 The hfac
ligand may be substituted for b-diketones and one of these
complexes was structurally characterized; coordination causes
severe distortion of the proton sponge, the N· · ·N distance
Active centers may be immobilized in several ways, depending
on the binding between active center and support. The family of
the silicon based porous MCM materials,2 led to new paths for
the reaction between suitable precursors with the Si–OH groups
in the internal walls of the large surface of the hexagonally ordered
parallel channels. The applications of the resulting inorganic
materials containing active sites are important in different fields,
ranging from catalysis to optoelectronics.1,3 Typical approaches
for such reactions include direct grafting, where a functionalized
complex reacts with the OH groups, or tethering where a step by
step route is followed, starting by reaction between the walls and
a functionalized organic molecule (ligand) which then binds the
metal center.4
˚
˚
opening to 2.94 A from 2.51 A. The proton sponge ligand is
easily displaced in this complex, even by water. 1 can also act as a
weak carbon nucleophile, but only in the presence of exceptionally
reactive electrophiles.10 Other examples for proton sponges in-
clude 4,9-dichloroquino[7,8-h]quinoline (2),11 1,8- bis(N,N,N,N-
tetramethylguanidino)naphthalene (3)12 and chiral, atropiso-
meric, binaphthyl substituted 1,8-bis(dimethylamino)naphthalene
derivatives (4) in the racemic as well as enantiopure states.13
Recently, the transition metal complexes of the proton sponge
2 14 and 3 15 were reported.
1,8-bis(dimethylamino)naphthalene (1) introduced by Alder5
R
and sold by Aldrich as “Proton Spongeꢀ” it is not only the
best-known compound of its type but is inexpensive and straight-
aInstituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ine´s
de la Cruz 3, Cantoblanco, 28049, Madrid, Spain. E-mail: marta.iglesias@
icmm.csic.es; Fax: (+)34(91)3720623; Tel: (+)34(91)3349000
bInstituto de Qu´ımica Orga´nica General, CSIC, C/Juan de la
Cierva, 3, 28006, Madrid, Spain. E-mail: felix-iqo@iqog.csic.es;
Fax: (+)34(91)5644853; Tel: 34(91)2587590
† Electronic supplementary information (ESI) available: Compound char-
acterization data, including images of 13C NMR spectra, kinetic curves,
HPLC traces and crystallographic data (CIF). CCDC reference numbers
805292–805293. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c1dt10597c
Chart 1
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9589–9600 | 9589
©

View Article Online
Several years ago, the formation of a diaminoacetal was
reported by condensation of 1,8-diaminonaphthalene with the
chromium tricarbonyl complex of benzaldehyde16 and the syn-
thesis of a Pd complex with a pincer ligand obtained via a
condensation of isopthalic dicarboxaldehyde and 2 equiv. of 1,8-
diaminonaphthalene.17 The aim of this study is to gain insight into
the effects of the ligand properties such as the rigidity or flexibility
of chiral chelating ligands and the influence of donor atoms in
determining the asymmetric induction in the catalytic process.
Specifically, to establish the relation between regioselectivity,
induced by chiral chelate ligands in the catalytic process to involve
each conformational isomer in the solution, and the enantiomeric
excess of the product. We believe that the potential of this chiral
building block to influence asymmetric transformations should
be investigated. As part of an ongoing project on the design
and synthesis of ligands for asymmetric catalytic reactions, we
developed a modular synthetic strategy for preparing new ligands
based on 8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-
amine (type (R,R)-A or type (R,R)-B in Fig. 1). Nitrogen atoms
from pyridine, amine or imine moieties are different electronically
and are assumed to provide different binding properties to
transition metals. Although pyridine is a strong electron-donating
ligand, the delocalized p-system provides a tool for tuning the
electronic nature of this moiety with substituents. While the
different donor abilities of the pyridine, phenol, amine or imine
groups can serve as an electronic differentiator for transition
metal-catalyzed asymmetric reactions, the trans-2,5-disubstituted
pyrrolidine moiety can provide a chiral influence for asymmetric
discrimination on prochiral substrates.
Recently, we have shown that complexes with anionic linear
Schiff ligands (Chart 2, (a)) have excellent catalytic activity in
several reactions.18 On the other hand, we have also developed
a series of novel conformationally restricted ONN-Pincer-type
ligands (Chart 2, (b)) resembling coordination environments
present in Schiff-base ligands.19 To study the scope and efficiency of
these systems, we modified the substituents on the pyridine ring or
on the imine group to create different electronic properties. Herein
we report the syntheses, characterization and reactivity of rhodium
and palladium complexes with chiral perimidino (R,R)-5, (R,R)-
6 (Fig. 1, type A), and imino derivatives (R,R)-7, and (R,R)-8
(Fig. 1, type B). These compounds were obtained via condensation
of an aldehyde and the chiral building block (proton sponge pre-
cursor) 8-((R,R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-amine
that exhibit unusual structures and interesting reactivity. These
complexes and their respective heterogenized complexes on MCM-
41 were shown to be effective catalysts for enantioselective
hydrogenation.
Chart 2
Results and discussion
Synthesis of ligands from 8-((2R,5R)-2,5-dimethylpyrrolidin-
1-yl)naphthalen-1-amine
Several groups20 including those of Alder,21 Staab,22 Pozharskii23
and Lloyd-Jones24 have investigated and derivatized the pro-
ton sponge 1,8-bis(dimethylamino)naphthalene. We have used
8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-amine as a
precursor to obtain new chiral ligands. This precursor has been
derivatized by reaction with different aldehydes in order to obtain
pincer-type ligands containing such functionality. Treatment of
different aldehydes (depicted in Scheme 1) with 8-((2R,5R)-2,5-
dimethylpyrrolidin-1-yl)naphthalen-1-amine, in ethanol at room
˚
temperature in the presence of molecular sieves (4 A), gave
compounds of type (R,R)-A or (R,R)-B (Scheme 1) in moderate to
good yield (40–70%). All new compounds have been characterized
by 1H NMR, 13C NMR, FTIR spectroscopy and ESI mass
spectrometry (see experimental).
Initially, we expected an imino compound as a product in
1
all cases. However, the H-NMR spectra of type (R,R)-A com-
pounds obtained from pyridine-2-carbaldehyde and 6-(2-hydroxy-
phenyl)pyridine-2-carbaldehyde did not match with the NMR
spectra of the expected imino compounds, as we could see the
signals of diastereotopic CH2-N groups as ABXY system at d 4.82,
4.57 ((R,R)-5), and 4.70, 4.45 ((R,R)-6) ppm. Thus, we suspected
that the products type (R,R)-A were not imino compounds.
Fig. 1 Chiral perimidine and imine ligands.
9590 | Dalton Trans., 2011, 40, 9589–9600
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Scheme 1 Condensation products of 8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-amine with different aldehydes.
˚
˚
Single crystal X-ray diffraction studies have been performed
on (R,R)-6. Fig. 2 shows the molecular structure with the atomic
numbering. Crystal data and structure refinement details of (R,R)-
6) are given in Table S1.† Each structure consists of a central
pyridine ring that is substituted at its 2-position by a phenol group
and at its 6-position by an amine-containing CH2(7aR,10R)-7a,10-
dimethyl-7a,8,9,10-tetrahydro-7H-pyrrolo[1,2-a]perimidine) unit.
The amine group is inclined essentially orthogonal to the plane
of the adjacent pyridyl unit. The phenol moieties are almost
co-planar with respect to the pyridine unit [tors.: C(17)–C(16)–
C(15)–N(3) -4.7 (3)] and are disposed mutually cis as a result
of a hydrogen bonding interaction between the phenol hydrogen
atom and the neighboring pyridine nitrogen [N(3)–H(1) 1.852(2)
A; O(1)–N(3) 2.576(2) A]. The ipso carbons, C(1) and C(7), deviate
˚
slightly from the naphthalene plane 0.032(6) and 0.081(6) A,
respectively. The torsion angle between C(7)–N(2) and C(1)–N(4)
is 7.0 (2) . The N(1)–N(2) distance (2.378(3) A) is shorter than an
idealized value, 2.51 A. This distortion of N::N could come from
the stress caused by the cyclisation. When we use 5 and 6 as chiral
chelate ligands, the nitrogen atom N(1) is not in the direction of
metal atom and the metal is far away. Thus, 5 and 6 act as chiral
N,N or N,N,O ligands, not as N,N,N- or N,N,N,O ligand. The
mass spectra of 6 reveal protonated molecular ion peak.
Treatment of 3-tert-butyl-2-hydroxy-5-methylbenzaldehyde
or N-(3-tert-butyl-5-formyl-4-hydroxyphenylcarbamoyl)-4-(tri-
ethoxysilyl)butanamide and 8-[(2R,5R)-2,5-dimethylpyrrolidin-
1-yl]naphthalen-1-amine in ethanol gave (R,R)-7 and, (R,R)-8,
imino ligands (type (R,R)-B), as yellow oils in good yields. Mass
spectrum of (R,R)-7 reveals protonated molecular ion peak while
in their IR spectra absorption bands characteristic for their imino
functionalities (ca. 1618 cm-1) are evident. In their 1H NMR
spectra, the imine compounds gave a singlet at d 8.26 ((R,R)-7),
8.32 ((R,R)-8) consistent with the presence of CH N protons,
phenol hydrogen atom appears at low field, as a broad singlet at
d 13.86 ppm ((R,R)-7), 14.11 ppm ((R,R)-8), these values suggest
that the proton is coordinate between the two nitrogen atoms
and the oxygen atom is inside the structure, stabilizing the imino
compounds and prevent the cyclization.
◦
˚
˚
To support the spectroscopic data, crystals of (R,R)-7 have been
the subject of single crystal X-ray diffraction studies. A perspective
view is depicted in Fig. 3; crystal data and structure refinement
Fig. 2 Molecular structure of (R,R)-6.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9589–9600 | 9591
©

View Article Online
Scheme 2 Synthesis of perimidine-complexes.
details of (R,R)-7 are given in Table S2.† The di amine group is Synthesis of rhodium and palladium complexes
inclined essentially orthogonal to the plane of the phenol unit
(46.80◦). There is a hydrogen bonding interaction between the
phenol hydrogen atom, the neighboring imine nitrogen [N(2)–
Several complexes incorporating (R,R)-5, (R,R)-6, (R,R)-7, and
(R,R)-8 as ligands were prepared by standard methods (Schemes 2,
3).
˚
˚
H(1) 1.850(3) A; O(1)–N(2) 2.591(3) A)] and the amine group
˚
˚
The reactions of (R,R)-5 and (R,R)-6 with [Pd(cod)Cl2] or
Pd(AcO)2 were carried out at room temperature in CH2Cl2 or
EtOH solution in a 1 : 1 complex : ligand ratio. The products,
[Pd(L*)X], 5Pd, 6Pd (L* = (R,R)-5, X = Cl2; (R,R)-6, X = OAc),
were obtained in almost quantitative yields as stable brown solids
by careful precipitation from pentane; which later underwent
elemental analysis, ESI-MS and 1H- 13C NMR spectroscopy. Thus,
the ESI-MS spectra of 5Pd and 6Pd show the peaks from the
fragments due to elimination of the ion chloride [M+ - Cl] (471.3
for 5Pd) or acetate [M+-OAc] (585.5 for 6Pd). All assignments
were confirmed by good agreement between the observed and
calculated isotopic distributions. The absence of the n(OH) band
[N(1)–N(2) 2.756 A; N(1)–H(1) 2.940(3) A]. The ipso carbons,
C(1) and C(3), deviate slightly from the naphthalene plane 0.110
˚
and 0.021 A, respectively. The torsion angle between C(1)–N(1)
and C(3)–N(2) is -13.4 (2)◦. In this case the N(1)–N(2) distance
˚
˚
(2.756(4) A) is larger than an idealized value, 2.51 A. The
stereochemistry of (R,R)-7 is the same as that of 8-((2R,5R)-2,5-
dimethylpyrrolidin-1-yl)naphthalen-1-amine, as expected, (R,R)-
7 and (R,R)-8 act as tridentate ligands when coordinated to
metals.
In both families, the absolute configuration of asymmetric
carbons is maintained throughout the process; starting from a
configuration R we obtain a configuration R.
9592 | Dalton Trans., 2011, 40, 9589–9600
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
after 1 h the corresponding L*-chiral ligand, in THF solution.
Filtration through Celite and evaporation of the solvent yielded
a solid product, which was recrystallized by careful addition
of diethyl ether. The experimental data allowed us to establish
that both (R,R)-5 and (R,R)-6 ligand act, in the formation
of complexes, as chelating ligands. In the 1H NMR spectra
the cyclooctadiene resonances are observed as four broad lines
between 1.8 and 4.8 ppm due to fluxionality in the conformation
of the cyclooctadiene chelate. Complexes exhibit four signals in
their 13C spectra attributable to the carbon atoms of the cod
ligand. Elemental analysis and the ESI-MS spectra (540.3 for 5Rh
and 632.3 for 6Rh corresponding to [M+ - PF6]) are consistent
with the proposed formulation shown in Scheme 2, but a single
crystal structure has not yet to be obtained. The –OH group
deprotonation was not observed for rhodium complex with ligand
6, the infrared spectrum presents a signal corresponding to n(OH)
at 3443 cm-1.
Fig. 3 Molecular structure of (R,R)-7.
The reactions between the imino compounds (R,R)-7 or (R,R)-
8 with Pd(OAc)2 were carried out at room temperature in
EtOH solution, respectively, in a 1 : 1 complex : ligand ratio.
The products, [Pd(L*)(OAc)], 7Pd, 8Pd (L* = (R,R)-7, (R,R)-
8) were obtained in almost quantitative yields as stable solids
(Scheme 3). These complexes were characterized by electro-spray
mass spectrometry. Thus, the ESI-MS spectrum of 7Pd shows
the peak from the fragment due to elimination of the acetate
at m/z 519.3 [M+-OAc]. All assignments were confirmed by
good agreement between the observed and calculated isotopic
distributions. In 7Pd, the absence of the n(OH) band (present
in the IR spectrum of the free ligand (R,R)-7 at ~3430 cm-1) is in
accordance with loss of the –OH proton. The IR spectrum showed
a band at 1585 cm-1 assigned to coordinated C N, about 30 cm-1
less than the free ligand, as expected for coordination of the imine.
The IR spectrum also shows strong bands at 1320 and 1650 cm-1
assigned to the symmetric and asymmetric n(COO) vibrations,
respectively, in agreement with those expected for monocoordinate
acetate ligands.25 A new band at 541 cm-1 is ascribed to n(Pd–O)
for 7Pd.
Scheme 3 Synthesis of imino-complexes.
(present in the spectra of the free ligand 6 at ~3430 cm-1) is in
accordance with loss of the -OH proton. The IR spectrum of
6Pd also shows strong bands at 1290 and ~1600 cm-1 assigned to
the symmetric and asymmetric n(COO) vibrations, respectively,
in agreement with those expected for monocoordinate acetate
ligands.25 New bands at 555 cm-1 are ascribed to n(Pd–O) (6Pd).
Diamagnetic palladium complexes have been characterized by
1H and 13C NMR spectroscopies. All assignments are based on
several correlations in the 2D spectra. They are fully consistent
with the structures depicted in Scheme 2. In all cases, the spectra
show the simultaneous occurrence of two sets of signals which
are attributable on the one hand to the substituted pyridine entity
and on the other hand to the amine sponge derivative part of the
ligand. In the 1H NMR spectra all the resonances were high field
shifted as compared to the uncoordinated ligand and they were
in agreement with metallation of the ligand with coordination of
the metal atom via the pyridine nitrogen atom. Deprotonation of
the –OH group was confirmed by the absence of OH resonance in
the 1H spectrum. The 1H NMR spectrum shows the signal of the
MeCOO protons as a singlet at d = 1.88 ppm (6Pd). The 13C NMR
spectrum of 6Pd showed the signals assigned to the OAc group.
The cationic complexes, [Rh(cod)(L*)]PF6, (5Rh,6Rh) (L* =
(R,R)-5, (R,R)-6), were synthesized by the reaction of [RhCl(cod)]2
with a stoichiometric amount of solid AgPF6 and, subsequently
Diamagnetic palladium complexes have been characterized by
1H and 13C NMR spectroscopy. All assignments are based on
several correlations in the 2D spectra. They are fully consistent
with the structures depicted in Scheme 3. In all cases, the spectra
show the simultaneous occurrence of two sets of signals which
are attributable on the one hand to the substituted pyridine entity
and on the other hand to the amine sponge derivative part of the
ligand. In the 1H NMR spectra all the resonances were high field
shifted as compared to the uncoordinated ligand and they were
in agreement with metallation of the ligand with coordination of
1
the metal atom via the pyridine nitrogen atom. In the H NMR
of both 7Pd and 8Pd, the absence of the OH resonance indicates
the deprotonation of the –OH group. The 1H NMR spectrum of
7Pd showed a singlet at 7.99 due to imine proton shifted upfield
0.27 ppm compared with the free ligand. Also, the acetate group
was observed as a singlet at 1.34 ppm. The 13C NMR spectrum of
7Pd showed the imine carbon at d 153.7 ppm (160.4 ppm for 8Pd)
and two signals for acetate at d 29.7 and 197.1.
Cationic complexes, [Rh(cod)(L*)]PF6, (7Rh, 8Rh) (L* = (R,R)-
7 and (R,R)-8), were synthesized by the reaction of [RhCl(cod)]2
with a stoichiometric amount of solid AgPF6 and, subsequently
after 30 min the corresponding L*-chiral ligand, in THF solution.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9589–9600 | 9593
©

View Article Online
Scheme 4 Heterogenization of imino complexes.
Filtration through Celite and evaporation of the solvent yielded a
solid product, which was recrystallized using Et2O. The 1H NMR
spectrum of the isolated product 7Rh showed four broad lines
between 1.8 and 4.8 ppm, due to fluxionality in the conformation
of the cod chelate, a singlet at d 5.96 due to the imine (5.93
8Rh), and a broad singlet at d 12.41 (9.82 for 8Rh) assigned
to the uncoordinated OH group. Complexes exhibit four signals
in the 13C spectrum attributable to the carbon atoms of the cod
ligand. ESI-MS spectrum show the mass for the molecular peak
at 625.5 for 7Rh [M+ - PF6]), but a single crystal structure has yet
to be obtained. IR spectra show the corresponding to n(OH) at
3408 cm-1. The n(C N) stretch was observed at 1619 cm-1.
When the chiral ligands are coordinated to the metal, this
introduces a new chiral centre in the complex at the coordinated
N atom and metal centre. We can deduce from NMR data, the
coordination of the metal ion is completely stereospecific and gives
rise to a single diastereoisomer.
Supported complexes were obtained by refluxing a mixture of
the precursor 8Pd or 8Rh and the support, in toluene, with metal
loadings of approximately 0.20–0.30 mmol-metal g-1 support.
These materials were characterized by elemental content analysis,
FT IR, DFTR and CP-MAS solid state, 13C NMR spectroscopy.
Complexation reactions yielded materials with the expected ratios
of metal to nitrogen loadings. In general these results showed us
that little other than the expected reactions are occurring on the
functionalized silica surface.
The presence of functional groups characteristic of 8Pd or
8Rh in the materials was checked by FTIR spectroscopy. The
stretching vibrations modes of the mesoporous framework (Si–
O–Si) of the grafted material 8Pd- or 8Rh-MCM are observed
at around 1240, 1070, and 810 cm-1, as in the parent MCM,
while new bands appear at ca. 2950 and 2850 cm-1, assigned to
the n(C–H) stretching of the aliphatic linear chain in MCM-
Pr and pyrrolidine ring. The presence of ligands leads to the
appearance of the n(C N, C O, C C) stretching modes at
1640–1570 cm-1. A new band at ca. 550 cm-1 is ascribed to n(Pd–O).
The complexes immobilized on supports have been characterized
by diffuse reflectance spectroscopy. The complexes show several
band maxima in the UV region agreeing with the assignment of the
bands as intraligand transitions in the aromatic ring, and charge-
transfer transition. The diffuse reflectance spectra of complexes
are almost identical before and after the heterogenization pro-
cess, indicating that the complexes maintain their geometry and
their electronic surrounding even after heterogenization without
significant distortion.
Heterogenization of complexes containing pendant alkoxy silane
groups to MCM-41
In the last years we have developed a modular system combin-
ing functionalized ligands with different supports and linkers
in order to have a systematic access to a variety of immo-
bilized chiral catalysts.4 The pure siliceous MCM-41 (MCM)
parent material was derivatized following the strategy depicted
in Scheme 4. This consisted of the grafting of a spacer,
CH2NHCONH(CH2)3Si(OEt)3, on the walls of the MCM mate-
rial. MCM-41 is short range materials containing a large number
of silanol groups available for grafting. MCM-41 however, presents
a long range ordering with hexagonal symmetry with regular
monodirectional channels of 3.5 nm diameter.
The materials were also characterized by cross-polarization
magic-angle spinning 13C CP MAS solid state NMR. The solid
state 13C CP MAS NMR spectra (Supporting Information) of
9594 | Dalton Trans., 2011, 40, 9589–9600
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Table 1 Catalytic hydrogenation of prochiral olefins with palladium and
Table 2 Recycling experiments of 8Rh-MCM in the catalytic hydrogena-
tion of (E)-diethyl 2-benzylidenesuccinate
rhodium-complexesa
Diethyl
itaconate
(E)-Diethyl 2-
benzylidenesuccinate
Cycle
TOF (h-1)a
ee (%)b
1
2
3
300
285
290
90
88
85
Entry Cat.
ee (%)c TOFb ee (%)d
TOFb
1
5Pd
£ 5
£ 5
£ 5
£ 5
£ 5
£ 5
£ 5
£ 5
6
588
600
582
590
600
1176 80
602 95
1164 90
3368 12
4980 £ 10
2800 15
50
97
10
60
85
118
36
109
92
158
210
108
300
640
900
565
78
a TOF: mmol subs./mmol cat.h. b Measured by HPLC (l: 254 nm,
hexane/iPrOH: 95 : 5, column chiralcel OD), (S) isomer.
2
5Rh
3
6Pd
4
6Rh
5
7Pd
6
8Pd-MCM
7Rh
Table 1 shows the effect of ligand substituents have on activ-
ity and enantioselectivity, if we compare the catalytic activity
of complex 6Pd, in this work, with that of previously re-
ported for [(S)-N-(tert-butyl)-1-((6-(2-hydroxyphenyl)pyridine-2-
yl)methyl)pyrrolidine-2-carboxamide]Pd (ligand type (a) in Chart
1, complex 6bPd in reference 19a) and with 13Pd-MCM-41
(described in reference 19b), which have the prolinamide as
chiral group, it appears that although the latter has a better
catalytic activity (TOF: 565 h-1 entry 11 vs. 109 h-1, entry 3),
the enantiomeric excess is comparable in both cases (15% vs.
10%).19a Similarly in this case the enantioselectivity increases
considerably when the catalyst is heterogenized (entry 12).19b If we
now compare the results obtained with the complexes derived from
(R,R)-7 (this work) with those previously reported for catalysts
with the phenol-imino-amino ligand, 2-(((1-benzylpyrrolidin-2-
yl)methylene)amino)-6-(tert-butyl)-4-methylphenol as ligand, (lig-
and type (b) in Chart 1, complexes 3Pd, 3Pd-MCM-41 in reference
18a) we found that the most active catalysts are those with
the Schiff base system derived with a proline derivative group
(entries 9, 10 in Table 1). However, the highest enantioselectivity
is obtained with the catalyst reported in this paper (entries 5, 7).
7
8
8Rh-MCM
3Pd (ref. 14a)
3Pd-MCM (ref. 14a)
6bPd (ref. 15a)
9
10
11
12
£ 10
£ 5
13Pd-MCM (ref. 15b) 10
234
30
a Conditions: 4 atm, 40 ◦C, S/C ratio 1000 : 1, diethyl itaconate; S/C
ratio 100 : 1, (E)-diethyl 2-benzylidenesuccinate. b TOF: h-1. c Measured
by HPLC (l: 230 nm, hexane/iPrOH: 98 : 2, column chiralcel AD-H), (S)
isomer. d Measured by HPLC (l: 254 nm, hexane/iPrOH: 95 : 5, column
chiralcel OD), (S) isomer.
8Pd-MCM, 8Rh-MCM materials are quite similar, since the
spectra are dominated by the resonances of the aliphatic and
aromatic groups. These signals appear at 8.6 and 8.3 ppm (Si–
CH2), 28.6 (CH2–CH2–CH2), 44.0–43.6 ppm (N–CH2); aromatic
region d = 130.3–156.4 ppm, d = 160.5, 160.1 ppm (N CH) and
d = 198 ppm (OAc). The majority of peaks corresponding to the
13C NMR spectrum of homogeneous complexes were present in
the 13C spectrum of their heterogenized counterparts.
Catalytic activity
Catalyst recycling
In order to evaluate the catalytic performances of these new
Rh(I), Pd(II) complexes we have tested them in hydrogenation
reactions. The following paragraphs show the results obtained in
experimental conditions that allow us to make a comparative study
of different catalysts and substrates. Obviously for preparative
application a tuning of conditions has to be done for each case.
Certainly for preparative applications it is necessary to adjust the
experimental conditions for each case.
We chose two substrates with different steric hindrance, as a
model, to make a comparative study between the soluble and
systems to check the recyclability heterogenised and later we will
study the full catalytic activity by varying the substrates and
reactions.
The structurally well defined supported rhodium and palladium
catalytic materials were tested in the asymmetric hydrogena-
tion of several substrates. The hydrogenation of (E)-diethyl 2-
benzylidenesuccinate or diethyl itaconate with Rh- and Pd-
complexes were carried out under standard conditions (EtOH
as the solvent, 4 atm hydrogen pressure, 40 ◦C). In all cases,
with all catalysts, complete conversion of substrate was observed.
Results were summarized in Table 1. Heterogenized catalysts show
higher enantioselectivity than the homogeneous catalysts. High
enantiomeric excess (98% ee) was observed in the asymmetric
hydrogenation of diethyl (E)-diethyl 2-benzylidenesuccinate.
From an environmental point of view, it is desirable to minimize the
amount of waste for each organic transformation. Reusability is an
important feature to be monitored for application of heterogenized
single-site catalysts. Before reuse, the catalyst was separated from
the reaction mixture by filtration and washed with ethanol. After
the first run, the reaction reached >99% after 3 h and this remained
steady up to the 4th run, proving that the catalyst is highly
stable and simple to recycle. Because the homogeneous catalyst
shows lower activity than the heterogenized, we confirmed that
the presence of site-isolated metal complexes grafted onto MCM-
41 was responsible for enhanced conversion and that the reaction
is truly heterogeneous.
The catalytic materials were easily separated from the sub-
strate/product solution by simple filtration subsequent washing,
and then added fresh substrate, and solvent without further
addition of catalyst. The recycling process could be repeated
four times with no significant loss in selectivity, and minimal losses
in activity (Table 2 and Fig. 4). Furthermore, the filtrate, which
was colorless, was placed in a catalyst free autoclave and fresh
substrate was added. Dihydrogen pressure was applied, however
no further conversion was observed. This demonstrates that no
metal leaching from the silica surface is occurring. The metal
content (loading) of the recycled catalytic material was the same
as the starting catalytic material suggesting little, if any, metal
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9589–9600 | 9595
©

View Article Online
Synthesis of ligands
(7aR,10R)-7a,10-dimethyl-7-(pyridin-2-ylmethyl)-7a,8,9,10-
tetrahydro-7H-pyrrolo[1,2-a]perimi dine ((R,R)-5). To a so-
lution of 8-[(2R,5R)-2,5-dimethylpyrrolidin-1-yl]naphthalen-1-
amine (300 mg, 1.25 mmol) in absolute ethanol (20 mL) and
˚
in the presence of molecular sieves (2 g, 4 A) was added a
ethanolic solution (10 mL) of 3 pyridine-2-carbaldehyde (133 mg,
1.25 mmol). The reaction mixture was stirred overnight at room
temperature and filtered. The residue was dried under reduced
pressure and purified by flash chromatography, Rf 0.25 (5 : 1
heptane/ethyl acetate) to obtain a pale pink solid Yield = 290 mg,
71%. M.p.: 58–60 ◦C. IR (KBr, cm-1): nCHarom 3048 (w); nCHalip 2970
Fig. 4 Recycling of 8Rh-MCM.
leaching. Hot filtration experiments and ICP measurements were
independently carried out to rule out the possibility of leaching.
In order to check the stability of metal complexes supported
on the solid matrix, we have characterized the solid before and
after reaction. As can be deduced from IR, 13C NMR and UV-
vis spectra the nature of supported species is very similar and the
most important signals for ligands appear in the same position
after reaction.
(m), 2922 (m); nC C, nC 1582 (s), 1435 (s), 1418 (s); dCH 1374
N
(m), 1337 (s); dCHout plane 810 (s), 756 (s); rCH 639 (m), 607 (w), 517
1
(m). H NMR (300 MHz, CDCl3): d 8.75 (ddd, 1H, H21, JHH
=
0.9, 1.6, 4.8 Hz); 7.70 (dt, 1H, H19, JHH = 1.7, 7.5 Hz); 7.58 (d,
1H, H18, JHH = 7.3 Hz); 7.45 (t, 1H, H13, JHH = 7.7 Hz); 7.33–7.22
(m, 4H, H8, H9, H12, H20); 6.56 (d, 1H, H14, JHH = 7.3 Hz); 6.25
(dd, 1H, H7, JHH = 3.0, 5.2 Hz); 4.82 (d, 1H, H16, -CH2-, ABXY,
JHH = 17.6 Hz); 4.57 (d, 1H, H16, -CH2-, ABXY, JHH = 17.6 Hz);
4.29 (m, 1H, H1, -CHpyrr); 2.55–2.47 (m, 2H, 2 -CH2pyrr); 2.34 (m,
Conclusions
1H, -CH2pyrr); 1.95 (m, 1H, -CH2pyrr); 1.49 (d, 3H, H0, -CH3, JHH
=
6.6 Hz); 1.37 (s, 3H, H5, -CH3). 13C NMR (125 MHz, CDCl3): d
159.6 (C17); 149.1 (C21); 141.9 (C15); 138.9 (C6); 137.0 (C19); 134.8
(C10); 127.0 (C13); 126.8 (C9); 121.8 (C20); 120.8 (C18); 117.1 (C8);
115.3 (C12); 114.9 (C11); 104.5 (C7); 103.9 (C14); 78.5 (C4); 53.8 (C16,
-CH2-); 52.6 (C1); 36.8 (C3); 29.5 (C2); 20.0 (C0, -CH3); 18.5 (C5,
-CH3). Anal. Calc. for C22H23N3 (329.4): C, 80.2; H, 7.0; N, 12.8.
Found: C, 80.2; H, 7.2; N, 12.5%. ESI-MS m/z (%): 329.0 [M+],
314.0 [M+-CH3], 252.0 [M+-Py].
In this work we report the synthesis of the first pincer type
complexes derived from a chiral proton sponge precursor, as well
as a surprising cyclisation transformation that takes place under
mild conditions to afford perimidine derivatives from several alde-
hydes and 8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-
amine with good yields. The complexes derived from both
types of ligands present high activity and enantioselectivity in
hydrogenation of prochiral olefins. The supported complexes in
MCM-41 show better activity than the homogeneous counterpart,
and they could be recycled for subsequent cycles without loss of
any material’s features.
Experimental section
General remarks
2-(6-{[(7aR,10R)-7a,10-dimethyl-7a,8,9,10-tetrahydro-7H-
pyrrolo[1,2-a]perimidin-7-yl]methyl} pyridin-2-yl)phenol ((R,R)-
All manipulations were carried out by using standard Schlenk
vacuum-line techniques under an atmosphere of oxygen-free
argon. All solvents for synthetic use were dried and distilled,
under an argon atmosphere, by standard procedures.26 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 90◦ 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 (54◦44¢) was 4 KHz. The reaction was monitored
by gas chromatography with helium as carrier gas, 10 psi; injector
temperature: 230 ◦C; detector temperature: 250 ◦C.
6). To
a solution of 8-[(2R,5R)-2,5-dimethylpyrrolidin-1-
yl]naphthalen-1-amine (50 mg, 0.208 mmol) in absolute ethanol
˚
(2 mL) and in the presence of molecular sieves (2 g, 4 A) was
added a ethanolic solution (4 mL) of 6-(2-hydroxyphenyl)pyridine-
2-carbaldehyde (41.4 mg, 0.208 mmol). The reaction mixture
was stirred overnight at room temperature and filtered. The
residue was dried under reduced pressure and purified by flash
chromatography (15 : 1 heptane/ethyl acetate) to afford a pale pink
◦
solid. Yield = 33 mg, 38%. M.p.: 90–93 C. IR (KBr, cm-1): nOH
3435 (m); nCHarom 3194 (w), 3051 (w); nCHalip 2963 (m), 2925 (m),
2867 (m); nC C, nC 1596 (s), 1578 (vs), 1458 (s), 1430 (s); dCH
N
9596 | Dalton Trans., 2011, 40, 9589–9600
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
1374 (m), 1335 (m), 1299 (s); dCHout plane 818 (s), 756 (s); rCH 633 (w).
1H NMR (300 MHz, CDCl3): d 13.60 (s br, 1H, OH); 7.84 (dd, 1H,
126.5 (C9); 125.7 (C12); 125.4 (C8); 122.4 (C11); 119.1 (C17); 118.5
(C13); 118.0 (C7); 58.8 (C1s); 51.4 (C1o); 34.7 (C23); 31.6 (C2o); 29.4
(3C, C25,26,27); 29.2 (C2s); 20.7 (C20, CH3-Ph); 18.3 (Co, CH3pyrr); 17.5
(Cs, CH3pyrr). Anal. Calc. for C28H34N2O (414.6): C, 81.1; H, 8.3;
N, 6.8. Found: C, 81.0; H, 8.5; N, 6.5%. ESI-MS m/z (%): 414.0
H27, JHH = 1.5, 8.0 Hz); 7.79 (s br, 1H, H20); 7.71 (t, 1H, H19, JHH
=
7.7 Hz); 7.39–7.31 (m, 3H, H9, H13, H25); 7.15 (s br, 1H, H18); 7.13
(d, 1H, H8, JHH = 4.4 Hz); 7.08 (d, 1H, JHH = 3.7 Hz) and 7.04 (d,
1H, JHH = 4.4 Hz) (H12 and H24); 6.95 (dt, 1H, H26, JHH = 1.5, 7.3
Hz); 6.44 (d, 1H, H14, JHH = 7.3 Hz); 6.11 (t, 1H, H7, JHH = 4.4 Hz);
4.70 (d, 1H, H16, -CH2-, ABXY, JHH = 17.6 Hz); 4.45 (d, 1H, H16,
-CH2-, ABXY, JHH = 17.6 Hz); 4.16 (m, 1H, H1, -CHpyrr); 2.42–2.32
(m, 2H, -CH2pyrr); 2.25–2.18 (m, 1H, -CH2pyrr); 1.84–1.81 (m, 1H,
-CH2pyrr); 1.37 (d, 3H, H0, -CH3, JHH = 5.9 Hz); 1.25 (s, 3H, H5,
-CH3). 13C NMR (125 MHz, CDCl3): d 159.9 (C22); 157.5 (C23);
156.7 (C17); 141.7 (C15); 138.8 (C6), 138.7 (C19); 134.9 (C10); 131.5
(C9); 127.1 (C13); 126.4 (C27); 126.3 (C18); 124.7 (C21); 119.2 (C24);
118.9 (C25); 118.6 (C26); 117.5 (C8); 117.4 (C20); 115.4 (C12); 114.9
(C11); 104.5 (C7); 104.1 (C14); 78.5 (C4); 53.2 (C16, -CH2-); 52.7 (C1);
36.9 (C3); 29.5 (C2); 20.0 (C0, -CH3); 18.6 (C5, -CH3). Anal. Calc.
for C28H27N3O (421.5): C, 79.8; H, 6.5; N, 10.0. Found: C, 79.6;
H, 6.8; N, 10.2%. ESI-MS m/z (%): 421.0 [M+], 406.0 [M+-CH3].
Crystal data for RR-6: C28H27N3O, M = 421.53, orthorho◦mbic,
t
[M+], 399.0 [M+-CH3], 223.0 [M+-CH3- Bu-Ar-OH-imine].
Crystal data for RR-7: C28H34N2O, M = 414.57, monoclinic,
◦
˚
˚
˚
a = 9.8047(8◦) A, b = 8.8134(8) A, c = 14.0070(12) A, a = 90.00 , b =
◦
˚
91.3630(10) , g = 90.00 , V = 1210.04(18) A3, T = 296(2)K, space
group P21, Z = 2, 8037 reflections measured, 4000 independent
reflections (Rint = 0.0324). The final R1 values were 0.0636 (I >
2s(I)). The final wR(F2) values were 0.1125 (I > 2s(I)). The final
R1 values were 0.1082 (all data). The final wR(F2) values were
0.1281 (all data). CCDC 805293.
˚
˚
˚
a = 10.414(3) A, b = 13.565(3) A, c = 15.401(4) A, a = 90.00 , b =
◦
◦
3
˚
90.00 , g = 90.00 , V = 2175.6(9) A , T = 296(2)K, space group
P212121, Z = 4, 15489 reflections measured, 2280 independent
reflections (Rint = 0.0750). The final R1 values were 0.0376 (I >
2s(I)). The final wR(F2) values were 0.0812 (I > 2s(I)). The final
R1 values were 0.0475 (all data). The final wR(F2) values were
0.0846 (all data). CCDC 805292.
N -(3-tert-butyl-5-((E)-(8-((2R,5R)-2,5-dimethylpyrrolidin-1-
yl)naphthalen-1-ylimino)methyl)-4-hydroxybenzylcarbamoyl)-4-
(triethoxysilyl)butanamide (R,R)-8. Using a similar procedure
to that described for (R,R)-7, from N-(3-tert-butyl-5-
formyl-4-hydroxyphenylcarbamoyl)-4-(triethoxysilyl)butanamide
(0.378 g, 0.832 mmol) and 8-[(2R,5R)-2,5-dimethylpyrrolidin-
1-yl]naphthalen-1-amine (200 mg, 0.832 mmol) in absolute
ethanol (3 mL). After purification by flash chromatography
(4 : 1 heptane/ethyl acetate) an orange oil was obtained. Yield =
1
405 mg, 72%. H NMR (300 MHz, CDCl3): d 14.11 (s br, 1H,
2-tert-butyl-6-((E)-(8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)-
naphthalen-1-ylimino)methyl)-4-methylphenol ((R,R)-7). To a so-
lution of 3-tert-butyl-2-hydroxy-5-methylbenzaldehyde (176 mg,
0.915 mmol) in absolute ethanol (20 mL) was added 8-[(2R,5R)-
2,5-dimethylpyrrolidin-1-yl]naphthalen-1-amine (200 mg, 0.915
mmol). After stirring at room temperature for 24 h, the reaction
mixture was filtered and washed with ethanol. The residue was
dried under reduced pressure and purified by flash chromatog-
raphy (10 : 1 heptane/ethyl acetate) to obtain◦a microcrystalline
orange solid. Yield = 199 mg, 58%. M.p.: 73–75 C. IR (KBr, cm-1):
OH); 8.32 (s, 1H, H16, N CH); 7.65 (dd, 1H, H9, JHH = 1.1, 7.9
Hz); 7.50 (d, 1H, H11, JHH = 7.9 Hz); 7.44–7.37 (m, 2H, H8, H12);
7.27 (d, 1H, H18, JHH = 2.7 Hz); 7.16 (d, 1H, H21, JHH = 2.7 Hz);
7.05 (d, 1H, H13, JHH = 7.7 Hz); 6.93 (dd, 1H, H7, JHH = 1.0, 7.2
Hz); 4.34 (s, 2H, H23, -CH2-); 3.80 (q, 6H, H28,29,30, JHH = 7.0 Hz);
3.75–3.69 (m, 1H, H1o, -CHpyrr); 3.54–3.48 (m, 1H, H1s, -CHpyrr);
3.23–3.16 (m, 2H, H25, -CH2-); 1.98–1.87 (m, 1H, H2o, -CH2pyrr);
1.75–1.70 (m, 1H, H2s, -CH2pyrr); 1.69–1.61 (m, 2H, H26, -CH2-);
1.46 (s, 9H, H34,35,36); 1.42–1.30 (m, 1H, H2o, -CH2pyrr); 1.26 (d,
3H, Ho, -CH3, JHH = 5.6 Hz); 1.20 (t, 9H, H31,32,33, JHH = 7.0 Hz);
1.13–1.10 (m, 1H, H2s, -CH2pyrr); 0.65 (m, 2H, H27, -CH2-Si); 0.39
(d, 3H, Hs, -CH3, JHH = 5.6 Hz). 13C NMR (125 MHz, CDCl3): d
160.5 (C16, N CH); 159.9 (C37, C O); 158.0 (C24); 146.9 (C14);
143.7 (C6); 138.0 (C22); 136.9 (C10); 130.5 (C19); 129.4 (C18); 129.2
(C21); 128.1 (C15); 126.9 (C9); 125.8 (2C, C12, C8); 122.5 (C11);
119.2 (C17); 118.7 (C13); 118.0 (C7); 58.9 (C1s); 58.5 (3C, C28,29,30);
51.5 (C1o); 44.6 (C23, -HN-CH2-Ph); 43.0 (C25, -CH2-); 34.9 (C20);
31.6 (C2o); 29.4 (3C, C34,35,36); 29.2 (C2s); 23.6 (C26, -CH2-); 18.4
(Co, CH3); 18.3 (3C, C31,32,33); 17.5 (Cs, CH3); 7.6 (C27, -CH2-Si).
n
OH 3445 (m); nCHarom 3049 (w); nCHalip 2961 (m), 2920 (m), 2870 (m);
nC N, nC 1618 (s), 1564 (vs), 1439 (s); dCHout plane 1370 (m), 1330
C
(s). UV-Vis: lmax = 302 nm, 343 nm. 1H NMR (300 MHz, CDCl3):
d 13.86 (s br, 1H, OH); 8.26 (s, 1H, H16, N CH); 7.67 (dd, 1H,
H9, JHH = 1.3, 8.4 Hz); 7.50 (d, 1H, H11, JHH = 8.0 Hz); 7.43–7.37
(m, 2H, H8, H12); 7.18 (d, 1H, JHH = 1.8 Hz) and 6.99 (d, 1H,
JHH = 1.8 Hz) (H18 and H21); 7.05 (d, 1H, H13, JHH = 7.5 Hz); 6.94
(dd, 1H, H7, JHH = 1.3, 7.1 Hz); 3.75–3.66 (m, 1H) and 3.51–3.46
(m, 1H) (H1s and H1o, -CHpyrr); 2.30 (s, 3H, H20, -CH3); 1.96–1.86
(m, 1H) and 1.80–1.70 (m, 1H) (H2s and H2o, -CH2pyrr); 1.46 (s,
9H, H25,26,27); 1.39–1.33 (m, 1H) and 1.18–1.09 (m, 1H) (H2s and
H2o, -CH2pyrr); 1.25 (d, 3H, -CH3, JHH = 6.2 Hz) and 0.36 (d, 3H,
-CH3, JHH = 6.2 Hz) (Ho and Hs). 13C NMR (125 MHz, CDCl3):
d 161.0 (C16, N CH); 158.2 (C24); 147.2 (C14); 143.7 (C6); 137.2
(C22); 136.9 (C10); 131.0 (C19); 130.8 (C18); 130.1 (C21); 128.1 (C15);
Synthesis of complexes
(R,R)-5Pd. Pd(cod)Cl2 (43 mg, 0.152 mmol) in CH2Cl2
(10 mL) was added to a solution of (R,R)-5 (50 mg, 0.152 mmol) in
the same solvent and the mixture was stirred at room temperature
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9589–9600 | 9597
©

View Article Online
1
for 6 h. After the solvent had been removed under vacuum
to 0.5 mL, the product was precipitated by careful addition of
pentane and collected by filtration, to afford a stable light brown
solid. Yield = 73 mg, 94%. IR (KBr, cm-1): nCHarom 3049 (w); nCHalip
dCHout of the plane 821 (m), 755 (m); dOCO 686 (w); nPd–O 555 (vw). H
NMR (300 MHz, CDCl3): d 9.35 (dd, 1HPy, JHH = 1.1, 7.5 Hz);
7.80 (m, 1HNph); 7.79 (m, 1HNph); 7.73 (d, 1HPy, JHH = 7.8 Hz);
7.61 (dd, 1HPy, JHH = 1.0, 7.9 Hz); 7.55 (d, 1HPh, JHH = 8.1 Hz);
7.40 (dd, 1HNph, JHH = 1.0, 7.9 Hz); 7.30 (d, 1HNph, JHH = 7.9 Hz);
7.20 (m, 1HPh); 7.19 (m, 1HPh); 6.85 (m, 1HNph); 6.68 (m, 1HPh);
2965 (m), 2925 (m) 2875 (m); nC C, nC 1609 (s) 1587 (vs), 1420
N
(s); dCH 1373 (m), 1338 (m); dCHout plane 811 (s), 758 (s); rCH 638 (w),
603 (w), 514 (w). 1H NMR (300 MHz, CDCl3): d 9.04 (m, 1HPy);
6.57 (d, 1HNph, JHH = 7.5 Hz); 4.57 (d, 1H, -CH2-, ABXY, JHH
=
7.63 (m, 1HPy); 7.56 (m, 1HPy); 7.28 (m, 1HPy); 7.13 (d, 2HNph
JHH = 8.0 Hz); 7.05 (d, 2HNph, JHH = 7.3 Hz); 6.38 (dd, 2HNph, JHH
,
=
17.2 Hz); 4.22 (d, 1H, -CH2-, ABXY, JHH = 17.1 Hz); 4.05 (m,
1H, -CHpyrr); 2.68 (dd, 1H, -CH2pyrr, JHH = 6.8, 12.1 Hz); 2.37 (m,
1H, -CH2pyrr); 1.91 (m, 1H, -CH2pyrr); 1.88 (s, 3H, CH3CO2-); 1.65
1.0, 6.4 Hz); 5.97 (d, 1H, -CH2-, ABXY, JHH = 18.1 Hz); 5.61 (d,
1H, -CH2-, ABXY, JHH = 18.1 Hz); 4.03 (m, 1H, -CHpyrr); 2.89–
2.56 (m, 2H, -CH2pyrr); 2.37–2.17 (m, 2H, -CH2pyrr); 1.25 (d, 3H,
-CH3, JHH = 10.2 Hz); 0.89 (s, 3H, -CH3). 13C NMR (125 MHz,
CDCl3): d 161.7 (CPy); 152.1 (CPy); 141.2 (CNph); 139.0 (CPy); 134.8
(CNph); 127.1 (CPy); 124.0 (2CNph); 123.7 (CPy); 118.0 (2CNph); 116.7
(2CNph); 105.1 (2CNph); 79.2 (-CN-CH3pyrr); 55.6 (-CH2-); 52.7 (-CH-
CH3pyrr); 36.6 (-CH2pyrr); 31.0 (-CH2pyrr); 20.0 (-CH3); 18.1 (-CH3).
Anal. Calc. for C22H23Cl2N3Pd (506.8): C, 52.1; H, 4.6; N, 8.3.
Found: C, 52.4; H, 4.8; N, 7.8%. ESI-MS m/z (%): 471.3 [M+-Cl],
435.3 [M+-2Cl], 329.3 [M+-2Cl-Pd].
(s, 3H, -CH3); 1.62 (m, 1H, -CH2pyrr); 1.35 (d, 3H, -CH3, JHH
=
6.2 Hz). 13C NMR (125 MHz, CDCl3): d 197.0 (CH3CO2-); 164.4
(C-O, CPh); 161.0 (CNph); 153.2 (CNph); 142.4 (CPy); 138.8 (CNph);
136.5 (CNph); 134.3 (CPy); 132.1 (CPh); 128.5 (CPh); 127.6 (CPy);
127.1 (CNph); 126.9 (CPy); 123.6 (CPy); 122.6 (CPh); 121.8 (CPh);
120.1 (CNph); 117.0 (CNph); 116.2 (CNph); 116.0 (CPh); 113.7 (CNph);
105.4 (CNph); 86.2 (-CN-CH3pyrr); 66.5 (-CH2-); 51.7 (-CH-CH3pyrr);
34.9 (-CH2pyrr); 28.7 (-CH2pyrr); 24.3 (CH3CO2-); 22.2 (-CH3); 20.0
(-CH3). Anal. Calcd. for C30H29N3O3Pd (586.0): C, 61.5; H, 5.0;
N, 7.2. Found C, 61.8; H, 4.9; N, 7.7%. ESI-MS m/z (%): 585.5
[M+], 526.5 [M-CH3CO2], 421.5 [M+-CH3CO2-Pd].
(R,R)-5Rh. AgPF6 (38.5 mg, 0.152 mmol) in THF (10 mL)
was added to a solution of [Rh(cod)Cl]2 (37 mg, 0.076 mmol) in
THF (10 mL) and the mixture was stirred vigorously at room
temperature for 30 min. The resulting AgCl was filtered off and
the yellow solution was treated with (R,R)-5 (50 mg, 0.152 mmol)
in the same solvent. The mixture was stirred at room temperature
for 2 h. After the solvent had been removed under vacuum to
0.5 mL, the product was precipitated by careful addition of Et2O
and collected by filtration, to afford a stable dark green solid.
Yield = 95 mg, 91%. IR (KBr, cm-1): nCHalip 2962 (m), 2924 (m)
(R,R)-6Rh. AgPF6 (48 mg, 0.190 mmol) in THF (10 mL) was
added to a solution of [Rh(cod)Cl]2 (46.4 mg, 0.095 mmol) in
THF (10 mL) and the mixture was stirred vigorously at room
temperature for 30 min. The resulting AgCl was filtered off and
the yellow solution was treated with (R,R)-6 (80 mg, 0.190 mmol)
in the same solvent. The mixture was stirred at room temperature
for 2 h. After the solvent had been removed under vacuum to
0.5 mL, the product was precipitated by careful addition of Et2O
and collected by filtration, to afford a stable (in solid state) dark
yellow solid. Yield = 133 mg, 90%. This compound decomposes in
solution (the compound turns red) and the NMR spectrum cannot
be collected in common solvents, only 13C MAS solid was used for
characterization; 1H NMR solid proton spectrum does not provide
information because the signals are broad. IR (KBr, cm-1): nOH
3443 (m); nCHarom 3101 (vw), 3058 (vw); nCHalip 2964 (m), 2926 (m),
2880 (m), 2837 (m); nC C, nC N 1596 (s), 1578 (s), 1537 (s), 1461 (s);
dCH 1378 (m), 1335 (m), 1299 (m); nPF 843 (vs); dCHout of the plane 760
(m); rCH 557 (s). 13C NMR (300 MHz, solid): d 158.3 (CPh); 154.5
(CPh); 152.0 (CPy); 140.2 (CNph); 138.5 (2C, CNph, CPy); 135.4 (CNph);
133.5 (CNph); 127.6 (2C, CNph, CPh); 126.3 (2CPy); 119.1 (5C, 3CPh,
CNph, CPy); 115.3 (2CNph); 104.6 (2CNph); 80.9 (5C, 2 -CH CH-cod, -
CN-CH3pyrr); 53.4 (-CH2-); 53.3 (-CH-CH3pyrr); 39.0 (-CH2pyrr); 30.6
(5C, 4 -CH2cod, -CH2pyrr); 19.7 (-CH3); 19.5 (-CH3). Anal. Calcd. for
C36H39F6N3OPRh (777.6): C, 55.6; H, 5.1; N, 5.4; found C, 50.8;
H, 4.5; N, 4.4%. (R,R)-6Rh + 3/2 CH2Cl2: C, 50.2; H, 4.5; N, 4.6).
ESI-MS m/z (%): 632.3 [M+], 523.3 [M+-H+-cod].
2886 (m), 2839 (m); nC C, nC 1614 (s), 1587 (s), 1413 (m); dCH
N
1378 (m), 1335 (m); nPF 842 (vs); dCHout plane 762 (m); rCH 558 (s). 1H
NMR (300 MHz, CDCl3): d 8.00 (m, 1HPy); 7.85 (m, 1HPy); 7.73
(m, 1HPy); 7.50 (m, 1HPy); 7.40 (dd, 2HNph, JHH = 1.0, 7.9 Hz); 7.24
(d, 2HNph, JHH = 7.9 Hz); 6.53 (d, 2HNph, JHH = 7.4 Hz); 5.82 (d, 1H,
-CH2-, ABXY, JHH = 16.2 Hz); 4.41 (d, 1H, -CH2-, ABXY, JHH
=
16.0 Hz); 4.05 (m, 2H, -CH Ccod); 3.87 (m, 1H, -CHpyrr); 3.58 (m,
2H, -CH Ccod); 2.58 (m, 2H, -CH2cod); 2.33 (m, 2H, -CH2cod); 2.21
(m, 2H, -CH2cod); 1.87 (m, 2H, -CH2cod); 1.68 (d, 3H, -CH3, JHH
=
6.0 Hz); 1.58 (m, 2H, -CH2pyrr); 1.32 (m, 2H, -CH2pyrr); 1.15 (s, 3H,
-CH3). 13C NMR (125 MHz, CDCl3): d 160.7 (CPy); 146.2 (CPy);
141.0 (CPy); 138.5 (CNph); 134.5 (CNph); 128.0 (2CNph); 126.4 (CPy);
123.7 (CPy); 117.5 (2CNph); 115.8 (2CNph); 105.7 (2CNph); 87.0 (2C,
-CH CHcod); 83.0 (2C, -CH CHcod); 77.2 (-CN-CH3pyrr); 57.9
(-CH2-); 51.6 (-CH-CH3pyrr); 39.6 (-CH2pyrr); 30.3 (2C, 2 -CH2cod);
29.9 (2C, 2 -CH2cod); 29.4 (-CH2pyrr); 20.3 (-CH3); 15.6 (-CH3). Anal
calcd. for C30H35F6N3PRh (685.5): C, 52.6; H, 5.1; N, 6.1. Found:
C, 52.3; H, 5.0; N, 5.8%. ESI-MS m/z (%): 540.3 [M+-PF6], 432.3
[M+-PF6-cod], 330.3 [M+-cod-Rh].
(R,R)-7Pd. Pd(AcO)2 (21.6 mg, 0.096 mmol) in EtOH (10 mL)
was added to a solution of (R,R)-8 (40 mg, 0.096 mmol) in the same
solvent and the mixture was stirred at room temperature overnight.
After the solvent had been removed under vacuum to 0.5 mL,
the product was precipitated by careful addition of pentane and
collected by filtration, to afford a stable light brown solid. Yield =
48 mg, 85%. IR (KBr, cm-1): nCHarom 3053 (w); nCHalip 2960 (vs),
2921 (vs), 2867 (s); nC 1650 (s); nC C, nC 1585 (vs), 1572 (vs),
(R,R)-6Pd. Pd(AcO)2 (26.7 mg, 0.119 mmol) in CH2Cl2
(10 mL) was added to a solution of (R,R)-6 (50.1 mg, 0.152 mmol)
in the same solvent and the mixture was stirred at room tempera-
ture overnight. After the solvent had been removed under vacuum
to 0.5 mL, the product was precipitated by careful addition of
pentane and collected by filtration, to afford a stable brown solid.
Yield = 65 mg, 85%. IR (KBr, cm-1): nCHarom 3055 (w); nCHalip 2964
(m), 2924 (w), 2891 (vw); nC 1624 (s); nC C, nC 1596 (vs),
O
N
1529 (s); dCH 1457 (s), 1426 (s), 1373 (s), nC–O 1320 (s); dCHout plane 819
1
(m), 765 (m); dOCO 710 (w); nPd–O 541 (vw). H NMR (300 MHz,
O
N
1573 (s), 1467 (s); dCH 1406 (s), 1378 (m), 1360 (m); nC–O 1317 (s);
CDCl3): d 7.99 (s, 1H, N CH); 7.30 (d, 1HNph, JHH = 6.4 Hz); 7.28
9598 | Dalton Trans., 2011, 40, 9589–9600
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
1
(m, 1HNph); 7.27 (d, 1HNph, JHH = 6.4 Hz); 7.26 (d, 1HNph, JHH
=
296. H NMR (300 MHz, CDCl3): d 8.32 (s, 1H, N CH); 7.68
(d, 1HNph, JHH = 8.0 Hz); 7.50 (t, 1HNph, JHH = 7.3 Hz); 7.44–7.40
(m, 2HNph); 7.36 (d, 1HPh, JHH = 2.2 Hz); 7.17 (d, 1HPh, JHH = 2.2
Hz); 7.06 (d, 1HNph, JHH = 6.6 Hz); 6.94 (d, 1HNph, JHH = 7.3 Hz);
4.34 (d, 2H, -CH2-Ph, JHH = 4.4 Hz); 3.78 (c, 6H, -O-CH2-CH3,
JHH = 7.3 Hz); 3.53–3.42 (m, 1H, -CHpyrr); 3.24–3.15 (m, 3H, 1H,
-CHpyrr, 2H, -CH2-); 1.97–1.85 (m, 2H, -CH2pyrr); 1.71–1.58 (m, 1H,
-CH2pyrr); 1.67–1.60 (m, 2H, -CH2-); 1.47 (s, 9H, -CH3t-Bu); 1.30–
1.28 (m, 4H) (1H, -CH2pyrr) (3H, CH3CO2-); 1.25–1.23 (m, 6H,
-CH3pyrr); 1.21 (t, 9H, -O-CH2-CH3, JHH = 7.3 Hz); 0.68–0.60 (m,
2H, -CH2-Si). 13C NMR (125 MHz, CDCl3): d 197.2 (CH3CO2-);
160.4 (N CH); 159.8 (C O); 158.2 (CPh); 146.9 (CNph); 138.5
(CNph); 137.9 (CPh); 133.7 (CNph); 130.1 (CPh); 129.4 (CPh); 129.1
(CPh); 128.1 (CNph); 126.8 (CNph); 125.4 (2CNph); 122.4 (CNph); 119.1
(CPh); 118.6 (CNph); 117.9 (CNph); 58.9 (-CH-CH3pyrr); 58.4 (3C, 3 -
O-CH2-CH3); 51.3 (-CH-CH3pyrr); 44.5 (-CH2-); 42.9 (-CH2-); 34.8
(Ct-Bu); 31.5 (-CH2pyrr); 29.7 (CH3CO2-); 29.3 (3C, 3 -CH3t-Bu); 29.1
(-CH2pyrr); 25.6 (-CH3pyrr); 23.5 (-CH2-); 18.2 (3C, 3 -O-CH2-CH3);
17.4 (-CH3pyrr); 7.5 (-CH2-Si).
5.9 Hz); 7.10 (d, 1HPh, JHH = 2.2 Hz); 7.05 (d, 1HPh, JHH = 2.2 Hz);
6.41 (d, 1HNph, JHH = 7.5 Hz); 6.31 (d, 1HNph, JHH = 7.5 Hz); 4.00
(dc, 1H, -CHpyrr, JHH = 1.3, 6.4 Hz); 2.37–2.30 (m, 1H, -CH2pyrr);
2.15–2.11 (m, 1H, -CH2pyrr); 2.10–2.00 (m, 1H, -CH2pyrr); 1.82–1.76
(m, 1H, -CH2pyrr); 1.40 (s, 3H, -CH3Ph); 1.34 (d, 3H, -CH3pyrr, JHH
=
7.0 Hz); 1.34 (s, 3H, CH3CO2-); 1.32 (d, 3H, -CH3pyrr, JHH = 6.0
H3); 1.29–1.27 (m, 1H, -CHpyrr); 1.09 (s, 9H, 3 -CH3t-Bu). 13C NMR
(125 MHz, CDCl3): d 197.1 (CH3CO2-); 153.7 (N CH); 142.0
(CNph); 141.1 (CPh); 139.2 (CNph); 136.9 (CPh); 136.4 (CPh); 135.1
(CPh); 134.3 (CNph); 130.2 (CNph); 130.3 (CNph); 127.8 (CNph); 126.9
(CNph); 116.1 (CPh); 115.2 (CPh); 114.9 (CNph); 103.3 (CNph); 102.7
(CNph); 52.2 (-CH-CH3pyrr); 36.4 (-CH2pyrr); 29.7 (CH3CO2-); 29.7
(-CH-CH3pyrr); 29.6 (-CH3Ph); 29.4 (-CH2pyrr); 22.7 (Ct-Bu); 20.1
(-CH3pyrr); 18.1 (3C, 3 -CH3t-Bu); 14.9 (-CH3pyrr). Anal. Calcd. for
C30H36N2O3Pd (579.0): C, 62.2; H, 6.3; N, 4.8; found: C, 62.6; H,
6.3; N, 4.7%. ESI-MS m/z (%): 519.3 [M+-OAc], 415.5 [L].
(R,R)-7Rh. AgPF6 (24.4 mg, 0.096 mmol) in THF (10 mL)
was added to a solution of [Rh(cod)Cl]2 (23.5 mg, 0.048 mmol) in
THF (10 mL) and the mixture was stirred vigorously at room
temperature for 30 min. The resulting AgCl precipitated was
filtered off and the yellow solution was treated with (R,R)-8 (40 mg,
0.096 mmol) in the same solvent. The mixture was stirred at
room temperature for 2 h. After the solvent had been removed
under vacuum to 0.5 mL, the product was precipitated by careful
addition of Et2O and collected by filtration, to afford a stable dark
beige solid. Yield = 67 mg, 90%. IR (KBr, cm-1): nOH 3408 (m);
nCHarom 3054 (vw); nCHalip 2962 (m), 2921 (m), 2882 (m), 2838 (m);
(R,R)-8Rh. AgPF6 (8.21 mg, 0.0325 mmol) in dry THF
(10 mL) was added to a solution of [Rh(cod)Cl]2 (7.93 mg, 0.0162
mmol) in the same solvent and the mixture was stirred vigorously
at room temperature for 30 min. The resulting AgCl precipitated
was filtered off and the yellow solution was treated with (R,R)-9
(22 mg, 0.0325 mmol) in dry THF. The mixture was stirred at room
temperature overnight. After the solution was purified through
celite and subsequent the solvent was removed under vacuum to
0.5 mL, the product was precipitated by careful addition of Et2O :
pentane (1 : 1) and collected by filtration, to afford a stable dark
green solid. Yield = 27.5 mg, 82%. UV-Vis: lmax (nm) = 512, 356,
287. 1H NMR (300 MHz, CDCl3): d 9.82 (s br, OH); 7.37–7.18 (m,
3HNph); 7.12–6.98 (m, 3H, 2HPh, 1HNph); 6.65 (d, 1HNph, JHH = 6.6
Hz); 6.43 (d, 1HNph, JHH = 6.6 Hz); 5.93 (s, 1H, N CH); 4.73–4.65
(m, 1H, -CH2pyrr); 4.44–4.37 (m, 2H, -CH Ccod); 4.31–4.05 (m, 5H)
(1H, -CH2pyrr, 2H, -CH C-cod, 2H, -CH2Ph); 3.76 (m, 6H, -O-CH2-
CH3); 3.25 (m, 3H) (1H, -CHpyrr, 2H, -CH2-); 2.66–2.54 (m, 2H,
-CH2cod); 2.45–2.31 (m, 2H, -CH2cod); 2.28–2.24 (m, 1H, -CH2pyrr);
2.24–2.04 (m, 4H, -CH2cod); 1.89–1.83 (m, 2H, -CH2-); 1.51–1.49
(m, 3H, -CH3pyrr); 1.37 (m, 9H, 3 -CH3t-Bu); 1.25–1.22 (m, 12H,
CH3pyrr, -O-CH2-CH3); 1.12–1.00 (m, 1H, -CH2pyrr); 0.89–0.74 (m,
2H, -CH2-Si). 13C NMR (125 MHz, CDCl3): d 166.4 (N CH);
155.8 (br, 2C, CPh, C37, C O); 148.9 (CNph); 141.6 (CNph); 138.5
(CPh); 136.6 (CNph); 134.7 (CPh); 128.9 (CPh); 127.0 (CPh); 126.7
(CNph); 125.5 (CNph); 124.9 (CNph); 124.4 (CNph); 122.0 (CNph); 120.3
(CPh); 115.9 (CNph); 115.4 (CNph); 80.4 (2C, -CH CHcod); 79.6 (2C,
-CH CHcod); 65.8 (3C, -O-CH2-CH3); 53.4 (-CH-CH3pyrr); 52.4
(-CH-CH3pyrr); 43.0 (-CH2-); 42.5 (-CH2-); 34.7 (Ct-Bu); 30.3 (2C,
-CH2cod); 30.0 (-CH2pyrr); 29.7 (2C, -CH2cod); 29.4 (3C, -CH3t-Bu);
29.1 (-CH2pyrr); 22.7 (-CH2-Si); 19.9 (3C, 3 -O-CH2-CH3); 16.2
(-CH3pyrr); 7.9 (2C, -CH3pyrr, -CH2-Si).
nC C, nC 1619 (m), 1591 (s), 1467 (m), 1432 (m); dCH 1375 (m),
N
1300 (s), 1231 (m); nPF 843 (vs); dCHout plane 755 (w), 731 (w); rCH 558
1
(m), 500 (m). H NMR (300 MHz, CDCl3): d 12.41 (s br, OH);
7.44–7.34 (m, 3HNph); 7.26–7.16 (m, 3HNph); 6.53 (m, 1HPh); 6.51
(m, 1HPh); 5.96 (s, 1H, N CH); 4.79–4.69 (m, 1H, -CH2pyrr); 4.41–
4.39 (m, 2H, -CH Ccod); 4.24–4.19 (m, 1H, -CH2pyrr); 4.11–4.07
(m, 2H, -CH Ccod); 3.29–3.20 (m, 1H, -CHpyrr); 2.66–2.55 (m, 2H,
-CH2cod); 2.52 –2.38 (m, 2H, -CH2cod); 2.31–2.28 (m, 1H, -CH2pyrr);
2.22 (s, 3H, -CH3Ph); 2.08–1.96 (m, 2H, -CH2cod); 1.95–1.84 (m, 2H,
-CH2cod); 1.46 (d, 3H, -CH3pyrr, JHH = 8.8 Hz); 1.40 (s, 9H, -CH3t-Bu);
1.28 (d, 3H, -CH3pyrr, JHH = 11.5 Hz); 0.91–0.86 (m, 1H, -CH2pyrr).
13C NMR (125 MHz, CDCl3): d 171.2 (N CH); 158.3 (CPh);
148.4 (CNph); 143.6 (CNph); 138.0 (CPh); 134.6 (CNph); 131.7 (CPh);
130.9 (CPh); 127.8 (CPh); 127.6 (CNph); 126.3 (CNph); 126.3 (2CNph);
122.7 (CNph); 120.1 (CPh); 116.1 (CNph); 115.3 (CNph); 83.0 (2C,
-CH CHcod); 80.8 (2C, -CH CHcod); 52.5 (-CH-CH3pyrr); 52.3
(-CH-CH3pyrr); 35.1 (Ct-Bu); 32.7 (-CH2pyrr); 30.3 (2C, 2 -CH2cod); 29.8
(3C, 3 -CH3t-Bu); 29.7 (2C, 2 -CH2cod); 29.5 (-CH2pyrr); 20.0 (-CH3Ph);
18.5 (-CH3pyrr); 8.8 (-CH3pyrr). Anal. Calcd. for C36H46F6N2OPRh
(770.6): C, 56.1; H, 6.0; N, 3.6; found: C, 51.8; H, 6.0; N, 3.1%.
7Rh·CH2Cl2: C, 51.9; H, 5.6; N, 3.3%. ESI-MS m/z (%): 625.5
[M+ - PF6], 415.5 [L].
(R,R)-8Pd. Pd(AcO)2 (10.11 mg, 0.045 mmol) in dry CH2Cl2
(10 mL) was added to a solution of (R,R)-8 (30.5 mg, 0.045
mmol) in the same solvent and the mixture was stirred at room
temperature overnight. After the solution was purified through
celite and subsequent the solvent was removed under vacuum
to 0.5 mL, the product was precipitated by careful addition of
pentane and collected by filtration, to afford a stable dark red
solid. Yield = 33 mg, 87%. UV-Vis: lmax (nm) = 531, 434, 376,
Synthesis of heterogenized complexes
A solution of metal complex (R,R)-8Pd or (R,R)-8Rh (0.022
mmol), bearing a triethoxysilyl group, in CH2Cl2 (5 mL) was added
to a well-stirred toluene suspension (25 mL) of the mesoporous
solid (MCM-41, 150 mg). The slurry was heated at 110 ◦C for
16 h. After the mixture was cooled, the solid was filtered off,
washed thoroughly with ethanol and diethyl ether and dried
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9589–9600 | 9599
©

View Article Online
under vacuum, to afford the respective heterogenized complexes
in almost quantitative yields.
2 (a) C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli and J. S.
Beck, Nature, 1992, 359, 710–712; (b) J. S. Beck, J. C. Vartuli, W. J.
Roth, M. E. Leonowicz, C. T. Kresge, K. D. Schmitt, C. T. W. Chu,
D. H. Olson, E. W. Sheppard, S. B. McCullen, J. B. Higgins and J. L.
Schlenker, J. Am. Chem. Soc., 1992, 114, 10834–10843.
3 (a) D. M. Ford, E. E. Simanek and D. F. Shantz, Nanotechnology,
2005, 16, S458–S475; (b) C. D. Nunes, M. Pillinger, A. A. Valente, I. S.
Gonc¸alves, J. Rocha, P. Ferreira and F. E. Ku¨hn, Eur. J. Inorg. Chem.,
2002, 5, 1100–1107.
4 (a) A. Corma, C. del Pino, M. Iglesias and F. Sa´nchez, Chem. Commun.,
1991, 18, 1253–1255; (b) A. Corma, M. Iglesias, M. V. Mart´ın, J. Rubio
and F. Sa´nchez, Tetrahedron: Asymmetry, 1992, 3, 845–848; (c) A.
Corma, A. Fuerte, M. Iglesias and F. Sa´nchez, J. Mol. Catal. A: Chem.,
1996, 107, 225–234 and references therein; (d) M. J. Alco´n, A. Corma,
M. Iglesias and F. Sa´nchez, J. Mol. Catal. A: Chem., 2003, 194, 137–
152.
(R,R)-8Pd–MCM. Stable dark brown-reddish solid. Elemen-
tal analysis indicated 1.4 mass% Pd. Found C,5.4; H, 1.4; N,
0.73%. IR (KBr, cm-1): nC
,
1641 (s), 1575 (s), nSi–O 1085,
O
C
N, C
C
nPd–O 544 (vw). DFTR: lmax (nm) = 675, 619, 488, 363, 329, 287,
263, 231. 13C NMR (300 MHz, Solid): d 198.0 (CH3CO2-); 160.5
(N CH); 158.0 (C O); 140.4–121.0 (15C, 5CPh and 10CNph);
120.7 (CPh); 59.5 (-O-CH2-CH3); 59.0 (-CHpyrr); 51.3 (-CHpyrr); 44.0
(-CH2-); 43.00 (-CH2-); 34.6 (Ct-Bu); 28.0 (6C, 3 -CH3t-Bu, 2 -CH2pyrr
,
CH3CO2-); 23.6 (-CH2-); 16.0 (4C, 3 -O-CH2-CH3, -CH3pyrr); 13.3
(-CH3pyrr); 8.6 (-CH2-Si).
5 R. W. Alder, P. S. Bowman, W. R. S. Steele and D. R. Winterman,
Chem. Commun., 1968, 13, 723–724.
6 S. N. Gamage, R. H. Morris, S. J. Rettig, D. C. Thackeray, I. S. Thorburn
and B. R. J. James, J. Chem. Soc., Chem. Commun., 1987, 12(12), 894–
895.
7 R. P. Hughes, I. Kovacik, D. C. Lindner, J. M. Smith, S. Willemsen,
D. Zhang, I. A. Guzei and L. R. Arnold, Organometallics, 2001, 20,
3190–3197.
8 A. Di Saverio, F. Focante, I. Camurati, L. Resconi, T. Beringhelli, G.
D’Alfonso, D. Donghi, D. Maggioni, P. Mercandelli and A. Sironi,
Inorg. Chem., 2005, 44, 5030–5041.
(R,R)-8Rh–MCM. Stable dark green solid. Elemental analysis
indicated 1.4 mass% Rh. Found C, 5.1; H, 1.4; N, 0.6%. IR
(KBr, cm-1): nC 1638 (s), nC
1580; nSi–O 1085, nP-F 803
O
N, C
C
(vs). DFTR: lmax (nm) = 666, 561, 362, 331, 287, 255, 226. 13C
NMR (300 MHz, Solid): d 160.1 (N CH); 152.0 (C O); 140.4–
115.0 (16Carom, 6CPh and 10CNph); 80.0 (4C, 2-CH CHcod); 59.5
(-O-CH2-CH3); 53.00 (2C, 2-CHpyrr); 43.6 (2C, 2 -CH2-); 34.3
(Ct-Bu); 28.6 (9C, 4-CH2cod, 3-CH3t-Bu, 2-CH2pyrr); 21.5 (-O-CH2-CH3,
-CH2-); 15.6 (-CH3pyrr); 8.3 (2C, -CH3pyrr, -CH2-Si).
9 T. Yamasaki, N. Ozaki, Y. Saika, K. Ohta, K. Goboh, F. Nakamura,
M. Hashimoto and S. Okeya, Chem. Lett., 2004, 33, 928–929.
10 F. Terrier, J. C. Halle, M. J. Pouet and M. P. J. Simonnin, J. Org. Chem.,
1986, 51, 409–411.
Catalytic activity
11 M. A. Zirnstein and H. A. Staab, Angew. Chem., 1987, 99, 460–461;
M. A. Zirnstein and H. A. Staab, Angew. Chem., Int. Ed. Engl., 1987,
26, 460–461.
12 V. Raab, J. Kipke, R. M. Gschwind and J. Sundermeyer, Chem. Eur. J.,
2002, 8, 1682–1693.
13 (a) J. P. Mazaleyrat and K. Wright, Tetrahedron Lett., 2008, 49, 4537–
4541; (b) G. Brancatelli, D. Drommi, G. Femino, M. Saporita, G.
Bottari and F. Faraone, New J. Chem., 2010, 34, 2853–2860.
14 H. U. Wu¨stefeld, W. C. Kaska, F. Schu¨th, G. D. Stucky, X. Bu and B.
Krebs, Angew. Chem., 2001, 113, 3280–3282; H. U. Wu¨stefeld, W. C.
Kaska, F. Schu¨th, G. D. Stucky, X. Bu and B. Krebs, Angew. Chem.,
Int. Ed., 2001, 40, 3182–3184.
15 U. Wild, O. Hu¨bner, A. Maronna, M. Enders, E. Kaifer, H. Wadepohl
and H. J. Himmel, Eur. J. Inorg. Chem., 2008, 4440–4447.
16 S. U. Son, H. Y. Jang, I. S. Lee and Y. K. Chung, Organometallics, 1998,
17, 3236–3239.
Hydrogenation of alkenes. The catalytic properties, in the
hydrogenation of (E)-diethyl 2-benzylidenesuccinate and diethyl
itaconate, of rhodium and palladium complexes were examined
under conventional conditions for batch reactions in a reactor
◦
(Autoclave Engineers) of 100 mL capacity at 40 C temperature,
4 atm dihydrogen pressure and 1/100 or 1/1000 metal/substrate
molar ratio. The evolution of the hydrogenated reaction product
was monitored by gas chromatography.
Specifically: To a suspension of the catalyst, 8Rh-MCM (15 mg,
2.0 10-3 mmol of Rh) in ethanol (40 mL), was added a solution of
52.4 mg (0.2 mmol) of (E)-diethyl 2-benzylidene succinate and the
mixture stirred at 40 ◦C, 1000 rpm. The evolution of the reaction
was monitored by gas chromatography.
17 I. G. Jung, S. U. Son, K. H. Park, K. C. Chung, J. W. Lee and Y. K.
Chung, Organometallics, 2003, 22, 4715–4720.
Recycling experiments. At the end of the process the reaction
mixture was centrifuged, and the catalyst residue washed to
completely remove any remaining products and/or reactants. The
solid was used again and any change in the catalytic activity was
observed. In each of the four runs, up to 95% conversion was
reached after 220 min and ee (%) was maintained after 4 cycles.
18 (a) C. Gonza´lez-Arellano, A. Corma, M. Iglesias and F. Sa´nchez,
Adv. Synth. Catal., 2004, 346, 1316–1328; (b) C Gonza´lez-Arellano,
E. Gutie´rrez-Puebla, M. Iglesias and F. Sa´nchez, Eur. J. Inorg. Chem.,
2004, 9, 1955–1962.
19 (a) N. Debono, M. Iglesias and F. Sa´nchez, Adv. Synth. Catal., 2007,
349, 2470–2476; (b) C. del Pozo, N. Debono, A. Corma, M. Iglesias
and F. Sa´nchez, ChemSusChem, 2009, 2, 650–657.
20 N. J. Farrer, R. McDonald and J. S. McIndoe,, Dalton Trans., 2006, 38,
4570–4579.
Acknowledgements
21 R. W. Alder, M. R. Bryce, N. C. Goode, N. Miller and J. Owen, J. Chem.
Soc., Perkin Trans., 1981, 1, 2840–2847.
The authors thank the Direccio´n General de Investigacio´n
Cient´ıfica y Te´cnica of Spain (Project MAT2006-14274-C02-02),
and Consolider Ingenio 2010-MULTICAT. G.V. thanks MCIINN
for financial support.
22 H. A. Staab, C. Krieger, G. Hieber and K. Oberdorf, Angew. Chem.,
Int. Ed. Engl., 1997, 36, 1884–1884.
23 (a) A. F. Pozharskii, O. V. Ryabtsova, V. A. Ozeryanskii, A. V.
Degtyarev, O. N. Kazheva, G. G. Alexandrov and O. A. Dyachenko,
J. Org. Chem., 2003, 68, 10109–10122; (b) A. V. Degtyarev and A. F.
Pozharskii, Chem. Heterocycl. Compd., 2008, 44, 1138–1145; (c) V. A.
Ozeryanskii, D. A. Shevchuk, A. F. Pozharskii, O. N. Kazheva, A. N.
Chekhlov and O. A. Dyachenko, J. Mol. Struct., 2008, 892, 63–67.
24 J. P. H. Charmant, G. C. Lloyd-Jones, T. M. Peakman and R. L.
Woodward, Eur. J. Org. Chem., 1999, 10, 2501–2510.
Notes and references
1 (a) M. H. Valkenberg and W. F. Ho¨lderich, Catal. Rev., 2002, 44, 321–
374; (b) A. Taguchi and F. Schu¨th, Microporous Mesoporous Mater.,
2005, 77, 1–45; (c) D. De Vos, M. Dams, B. Sels and P. Jacobs,
Chem. Rev., 2002, 102, 3615–3640; (d) F. Hoffmann, M. Cornelius
and J. Morell, Angew. Chem., 2006, 118, 3290–3328; F. Hoffmann, M.
Cornelius, J. Morell and M. Froba, Angew. Chem., Int. Ed., 2006, 45,
3216–3251.
25 K. Nakamoto, in IR and Raman Spectra of Inorganic and Co-
ordination Compounds, 5th; ed., WILEY & SONS, New York,
1997.
26 D. D. Perrin, S. L. F. Armarego, D. R. Perrin, in Purification of
Laboratory Chemicals, PERGAMON PRESS, New York, 1980.
9600 | Dalton Trans., 2011, 40, 9589–9600
This journal is
The Royal Society of Chemistry 2011
©