A cyclodextrin dimer as a supramolecular reaction platform for aqueous organometallic catalysis

Article abstract of DOI:10.1039/c3cc43647k

A reaction platform based on a cyclodextrin dimer, which is able to simultaneously include a substrate in one cavity and an organometallic catalyst into the other, proved to be highly efficient for aqueous hydroformylation reaction of higher olefins.

Full text of DOI:10.1039/c3cc43647k

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A cyclodextrin dimer as a supramolecular reaction
platform for aqueous organometallic catalysis†‡
Cite this: DOI: 10.1039/c3cc43647k
a
c
c
Claire Blaszkiewicz,ab Herve Bricout, Estelle Leonard, Christophe Len,
´
´
´
Received 15th May 2013,
Accepted 10th June 2013
d
b
b
a
David Landy, Christine Cezard, Florence Djedaıni-Pilard, Eric Monflier and
¨
a
´
Sebastien Tilloy*
DOI: 10.1039/c3cc43647k
www.rsc.org/chemcomm
A reaction platform based on a cyclodextrin dimer, which is able to
simultaneously include a substrate in one cavity and an organo-
metallic catalyst into the other, proved to be highly efficient for
aqueous hydroformylation reaction of higher olefins.
In organometallic catalysis processes, the most important goals are
to reach high levels of activity and selectivity. Traditionally, the
tuning of the ligands is the most widespread solution to increase
the catalytic performances of an organometallic complex. Unfortu-
nately, the syntheses of elaborated ligands are often complicated
and time consuming. An alternative approach was found in the field
of supramolecular catalysis which seeks to produce efficient and
selective organometallic complexes by using supramolecular inter-
actions such as hydrogen bonding, coordinative bonding, ion
pairing, p–p interactions and the formation of inclusion com-
pounds.1,2 While numerous supramolecular catalysis processes
are described in apolar solvents,3 the use of aqueous medium is
largely less widespread.4 Indeed, water competes very effectively for
Fig. 1 Cyclodextrin dimer as a supramolecular reaction platform for aqueous
organometallic catalysis (M = a transition metal; PHOS = a phosphane).
binding sites and particularly for hydrogen bonds.5 However in which is able to simultaneously include a substrate in one cavity
water, in contrast to organic solvents, the hydrophobic effect can be and an organometallic catalyst into the other (Fig. 1). So, the
an advantage when non-covalent substrate binding in a hydropho- interaction between the two included entities will be facilitated
bic cavity is combined with catalysis. Breslow, one of the pioneers in and thus will lead to a faster substrate transformation. Our
this field, attached a metal bonding group to b-cyclodextrin (b-CD) approach relies on the self-assembly of a b-CD dimer (CD-dim;
to generate an artificial enzyme.6 In this context, we propose a new Scheme 1) and a water-soluble rhodium phosphane complex pro-
concept based on a cyclodextrin dimer acting as a reaction platform, duced from a water-soluble phosphane bearing a well-recognized
biphenyl moiety7 (phosphane 1; Scheme 1). The catalytic perfor-
a
mances of this supramolecular catalytic platform were evaluated in
aqueous rhodium-catalyzed hydroformylation reaction.
´
Unite de Catalyse et de Chimie du Solide (UCCS), CNRS, UMR 8181,
´
Universite d’Artois, Rue Jean Souvraz, SP 18, F-62307 Lens, France.
Treatment of [Rh(COD)2+, BF4À] with two equivalents of 1 in D2O
E-mail: sebastien.tilloy@univ-artois.fr; Fax: +33321791755; Tel: 33321791754
b
c
´
produced a limpid yellow solution of [Rh(COD)(1)2 , BF4À] and its
Laboratoire des Glucides, CNRS FRE 3517, Universite de Picardie Jules Verne,
+
80039 Amiens, France
31P{1H} NMR spectrum exhibited a sharp doublet (d = 25 ppm; 1JRh,P
148 Hz). The interaction between CD-dim and [Rh(COD)(1)2 , BF4
=
]
´
´
`
Transformations Integrees de la Matiere Renouvelable - EA 4297 UTC/ESCOM,
+
À
Centre de Recherches de Royallieu, BP 20529, rue Personne de Roberval,
`
F-60205 Compiegne cedex, France
was studied using NMR spectroscopy measurements (all the data
relative to the studies of inclusion complexes are gathered in the
ESI‡). In the presence of one equivalent of CD-dim, the 31P{1H} NMR
signal was not shifted or modified but only a broadening was
observed. In parallel, the modifications of the aromatic and CD-
dim proton signals observed in the 1H NMR spectrum indicated that
d
´
Unite de Chimie Environnementale et Interactions sur le Vivant (UCEIV) – EA 4492,
´
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ˆ
Universite du Littoral Cote d’Opale 145, Avenue Maurice Schumann,
MREI 1, F-59140 Dunkerque, France
´
† Dedicated to Professor Andre Mortreux on the occasion of his 70th birthday.
‡ Electronic supplementary information (ESI) available: Synthesis, analytical data
and NMR or MALDI spectra. See DOI: 10.1039/c3cc43647k
c
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Fig. 3 Schematic representation of the inclusion complexes deducted from NMR
+
experiments: (a) CD-dim : [Rh(COD)(1)2+, BF4À] (1: 1) and (b) b-CD : [Rh(COD)(1)2
BF4À] (2 : 1).
,
Scheme 1 Chemical and schematic representation of CD-dim, phosphane
1 and b-CD.
the phosphane 1 was included in the CD-dim cavity. All these data
+
unambiguously showed that [Rh(COD)(1)2 , BF4À] formed an inclu-
sion complex with CD-dim. For comparison, the same kind of
experiments were performed with b-CD showing that [Rh(COD)-
(1)2 , BF4À] also formed an inclusion complex with this CD. The
+
Fig. 4 Molecular dynamic simulation of CD-dim : [Rh(COD)(1)2+, BF4À].
+
stoichiometry of the supramolecular species between [Rh(COD)(1)2 ,
BF4À] and b-CD or CD-dim was determined by a Job plot analysis of
titration experiments (Fig. 2).8 CD-dim formed a 1 : 1 inclusion
a reaction platform. The catalytic behaviour of the Rh–1 combi-
nation was investigated by a hydroformylation reaction in the
absence or presence of CD (b-CD or CD-dim) (see Table 1).
1-Decene was chosen as a highly hydrophobic substrate in order
to observe the potential role of the different combinations in the
mass transfer.10 As comparative data, another set of experiments
were realized with TPPTS (tris(m-sulfonatophenyl)phosphane
trisodium salt) as the ligand instead of 1.11,12 Indeed, this ligand
is very widespread in aqueous organometallic catalytic processes
and often used as a reference. The two first experiments were
performed without CD and, as expected, gave poor conversions
due to the low water-solubility of 1-decene in water (entries 1 and 2).
The addition of b-CD or CD-dim modified the chemoselectivity,
the regioselectivity and the conversion (entries 3–6). The
selectivity in aldehydes was increased in each case with the
higher value for the [Rh–1–CD-dim] combination (entry 6).
For the four combinations, the linear to branched aldehyde ratio
+
complex with [Rh(COD)(1)2 , BF4À] whereas b-CD formed a 2 : 1
inclusion complex with this rhodium species. Concerning the geo-
metry of these inclusion complexes, 2D T-ROESY NMR experiments
showed that the sulfophenyl moiety of the biphenyl group was
included by the secondary face for CD-dim whereas it was included
by the primary face for b-CD. Fig. 3a and b show a schematic
representation of these two inclusion complexes. This inversion of
+
the inclusion face observed for the b-CD : [Rh(COD)(1)2 , BF4À] (2: 1)
structure probably occurred to reduce the steric hindrances
around the metallic center. Molecular dynamics simulations of
+
CD-dim: [Rh(COD)(1)2 , BF4À] were performed in explicit water
(see ESI‡). The structure presented in Fig. 4 corresponds to the
most observed inclusion complex during the simulation.9 The
+
organometallic complex [Rh(COD)(1)2 , BF4À] is included in one
of the two CD-dim cavities and the free cavity is well oriented and
available to include a substrate. So, CD-dim will be able to act as
Fig. 2 Job-plot analysis of 1H NMR titration in D2O of [Rh(COD)(1)2+,BF4À] with (a) CD-dim and (b) b-CD.
c
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Table 1 Rhodium-catalyzed hydroformylation of 1-decene in the presence of
various ligand–CD couplesa
2 For selected reviews, see: (a) M. J. Wilkinson, P. W. N. M. van Leeuwen
and J. N. H. Reek, Org. Biomol. Chem., 2005, 3, 2371; (b) B. Breit, Angew.
`
Chem., Int. Ed., 2005, 44, 6816; (c) D. M. Vriezema, M. C. Aragones,
J. A. A. W. Elemans, J. J. L. M. Cornelissen, A. E. Rowan and R. J. M. Nolte,
Chem. Rev., 2005, 105, 1445; (d) A. Lu¨tzen, Angew. Chem., Int. Ed., 2005,
44, 1000; (e) D. Fiedler, D. H. Leung, R. G. Bergman and K. N. Raymond,
Acc. Chem. Res., 2005, 38, 351; ( f ) T. S. Koblenz, J. Wassenaar and
J. N. H. Reek, Chem. Soc. Rev., 2008, 37, 247; (g) M. Yoshizawa,
J. K. Klosterman and M. Fujita, Angew. Chem., Int. Ed., 2009, 48, 3418;
(h) J. Meeuwissen and J. N. H. Reek, Nat. Chem., 2010, 2, 615;
(i) S. Carboni, C. Gennari, L. Pignataro and U. Piarulli, Dalton Trans.,
2011, 40, 4355; ( j) T. R. Ward, Acc. Chem. Res., 2011, 44, 47.
Entry
Ligand
CD
Cb (%)
Sc (%)
l/b
1
2
3
4
5
6
TPPTS
1
TPPTS
1
TPPTS
1
(-)
(-)
b-CD
b-CD
CD-dim
CD-dim
5
2
45
40
49
99
65
69
89
77
78
94
2.7
3.1
1.9
2.2
2.0
2.1
3 For selected examples in organic medium, see: (a) M. L. Merlau,
M. Del Pilar Mejia, S. T. Nguyen and J. T. Hupp, Angew. Chem., Int.
Ed., 2001, 40, 4239; (b) B. Breit and W. Seiche, J. Am. Chem. Soc., 2003,
¨
125, 6608; (c) V. F. Slagt, M. Roder, P. C. J. Kamer, P. W. N. M. van
a
Experimental conditions: Rh(acac)(CO)2 = 21 mmol (1 eq.), ligand =
105 mmol (5 eq.), CD cavity = 210 mmol (10 eq.), substrate = 10.5 mmol
(500 eq.), 6 mL water, 80 1C, 50 bar CO/H2 (1/1), 1500 rpm, reaction time =
Leeuwen and J. N. H. Reek, J. Am. Chem. Soc., 2004, 126, 4056;
(d) X. B. Jiang, L. Lefort, P. E. Goudriaan, A. H. M. de Vries, P. W. N. M.
van Leeuwen, J. G. de Vries and J. N. H. Reek, Angew. Chem., Int. Ed.,
2006, 45, 1223; (e) S. Das, C. D. Incarvito, R. H. Crabtree and G. W.
Brudvig, Science, 2006, 312, 1941; ( f ) M. Yoshizawa, M. Tamura and
M. Fujita, Science, 2006, 312, 251; (g) H. Gulys, J. Benet-Buchholz,
E. C. Escudero-Adan, Z. Freixa and P. W. N. M. van Leeuwen, Chem.–
Eur. J., 2007, 13, 3424; (h) T. Smejkal and B. Breit, Angew. Chem., Int.
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X. P. Zhang, J. Am. Chem. Soc., 2008, 130, 5042; ( j) L. Diab, T. Smejkal,
b
c
9 h. C = 1-decene conversion. S = aldehyde selectivity.
(l/b) was around 2. This value is classical for hydroformylation
experiments performed in the presence of b-CD derivatives.13
Interestingly, the catalytic activity depended on the ligand–CD
combinations. Indeed, the [Rh–TPPTS–b-CD], [Rh–1–b-CD] and
[Rh–TPPTS–CD-dim] combinations nearly gave the same conver-
sions whereas the conversion was more than two times higher
for [Rh–1–CD-dim] (compare entries 3, 4 and 5 with entry 6).
More precisely, extra-conversions observed with the [Rh–1–CD-
dim] system were equal to 148%, 120% and 102% compared to
the [Rh–1–b-CD], [Rh–TPPTS–b-CD] and [Rh–TPPTS–CD-dim]
systems, respectively. Actually, the role played by the CD cavity
is different in the case of [Rh–1–CD-dim] compared to the three
other combinations. For the system [Rh–1–b-CD], [Rh–TPPTS–b-
CD] and [Rh–TPPTS–CD-dim], the three values of conversion
were similar and the CD moiety simply acted as a mass transfer
agent by forming an inclusion complex with 1-decene.12 The
extra-conversions observed in the case of [Rh–1–CD-dim] can be
easily explained by the anchoring of both the catalytic species
and the substrate on the CD-dim platform by supramolecular
interactions. So, 1-decene is in close proximity to the rhodium
species facilitating the catalytic act and leading to an extra-
conversion. The same experiments were performed with 1-hexa-
decene as a substrate and the same positive effect was observed.
Indeed, extra-conversions with the [Rh–1–CD-dim] system com-
pared to the other [Rh–1–b-CD], [Rh–TPPTS–b-CD] and [Rh–
TPPTS–CD-dim] systems were equal to 96%, 120% and 165%,
respectively (see ESI‡).
ˇ
ˇ
J. Geier and B. Breit, Angew. Chem., Int. Ed., 2009, 48, 8022;
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4 For selected examples in aqueous medium, see: (a) H. Yamaguchi,
T. Hirano, H. Kiminami, D. Taura and A. Harada, Org. Biomol. Chem.,
2006, 4, 3571; (b) C. Machut, J. Patrigeon, S. Tilloy, H. Bricout, F. Hapiot
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2000.
6 (a) R. Breslow and L. E. Overman, J. Am. Chem. Soc., 1970, 92, 1075;
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8 K. A. Connors, Binding Constants, Wiley, New York, 1987.
9 Note that [Rh(COD)(1)2+, BF4À] could also formed a 1 : 1 inclusion
complex with CD-dim by including each of its both phosphanes 1 in
each CD-dim cavity. This possibility was fully excluded by molecular
dynamics simulations which showed that this double inclusion
phenomenon is a very unlikely event (see ESI‡).
10 Although the ratio 1-decene/catalyst [Rh–1] is high and equal to 500,
1-decene is not a competitor for the catalyst into CD-dim cavities
since its water-solubility is only equal to 10 mM at 80 1C against
3.5 mM for the catalyst concentration (see ESI‡ for data).
To summarise, we have elaborated a supramolecular reac-
tion platform based on a CD dimer able to simultaneously host
the substrate and the catalyst. Schematically, the catalyst was
included inside one cavity while the substrate was included in
the other. The proximity between the catalyst and the substrate
allowed reaching higher catalytic activities than those reported
for classical systems based on CD. We are currently further
exploring the scope of this new class of catalyst.
ˆ
11 (a) E. G. Kuntz, CHEMTECH, 1987, 570; (b) E. G. Kuntz, Rhone–
The program ANR CP2D 2009 is acknowledged for financial
support.
¨
Poulenc, French Patent, 2366237, 1976; (c) R. Gartner, B. Cornils,
H. Springer and P. Lappe, DE Pat, 3235030, 1982.
12 Note that NMR experiments clearly demonstrated that b-CD or CD-dim
+
was unable to form an inclusion complex with [Rh(COD)(TPPTS)2
,
Notes and references
BF4À] (see ESI‡).
1 P. W. N. M. van Leeuwen, Supramolecular Catalysis, Wiley-VCH, 13 F. Hapiot, L. Leclercq, N. Azaroual, S. Fourmentin, S. Tilloy and
Weinheim, 2008.
E. Monflier, Curr. Org. Synth., 2008, 5, 162.
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun.