Poly(ruthenium carbonyl spirobifluorenylporphyrin): A new polymer used as a catalytic device for carbene transfer

Article abstract of DOI:10.1039/b306021g

Oxidative electropolymerization of tetraspirobifluorenyl porphyrin ruthenium(II) carbonyl complexes can be used to coat Pt electrodes with polymeric films; after being removed from the electrode, these polymeric materials are able to catalyze the heteroge

Full text of DOI:10.1039/b306021g

Poly(ruthenium carbonyl spirobifluorenylporphyrin): a new polymer
used as a catalytic device for carbene transfer†
a
a
a
a
b
Cyril Poriel, Yann Ferrand, Paul le Maux, Christine Paul, Joëlle Rault-Berthelot* and Gerard
a
Simonneaux*
a
Laboratoire de Chimie Organométallique et Biologique, UMR CNRS 6509, Université de Rennes I, 35042
Rennes cedex, France. E-mail: gerard.simonneaux@univ-rennes1.fr; Fax: 02 23 23 56 37; Tel: 02 23 23
62 85:
b
Laboratoire d’Electrochimie Moléculaire et Macromoléculaire, UMR CNRS 6510, Université de Rennes I,
3
4
5042 Rennes cedex, France. E-mail: joelle.rault@univ-rennes1.fr; Fax: 02 23 23 67 32; Tel: 02 23 23 59
0
Received (in Cambridge, UK) 30th May 2003, Accepted 1st August 2003
First published as an Advance Article on the web 19th August 2003
Oxidative electropolymerization of tetraspirobifluorenyl
porphyrin ruthenium(II) carbonyl complexes can be used to
coat Pt electrodes with polymeric films; after being removed
from the electrode, these polymeric materials are able to
catalyze the heterogeneous cyclopropanations and 2,3 sig-
matropic rearrangements with ethyl diazoacetate.
solvents and the solid film polymer was removed from the
anode, dried under vacuum and scratched in order to obtain a
fine totally insoluble powder.
Fig. 2A–B presents the cyclic voltammograms (CVs) re-
2
3
corded during the anodic oxidation of 1 (2.2 3 10 M) in
CH Cl + Bu NPF (0.2 M) using a Pt working electrode. The
2
2
4
6
CV recorded during the first anodic sweep exhibits the expected
well-known two reversible one-electron Ru porphyrin oxidation
Solid-state reactions constitute an important area of selective
1
+
organic reactions. Thus there are many examples of electro-
waves at 0.46 and 0.89 V (ref. Fc/Fc ), respectively (Fig.
2A).1
0,11
These two waves are followed by the irreversible
polymers, in which the deposit is directly used as a catalyst,
taking advantage of the electrode.2 To the best of our
knowledge, however, electropolymers have seldom been used
as catalysts after being removed from the electrodes. In fact,
electropolymerized metalloporphyrin films have so far been
mainly used as a catalytic electrode material for olefin
,3
spirobifluorene oxidation wave with a maximum at 1.37 V.
When scanning in a potential range including the three waves,
the CVs show the appearance and the regular growth of two new
reversible waves centered at 0.65 and 1.08 V and the continuous
increase in amplitude of the other peaks (Fig. 2B). This
indicates that a film is formed on the electrode as a consequence
of electropolymerization through the spirobifluorene groups.
Indeed, the electrode taken out of the electrochemical cell after
the tenth sweep, rinsed in dichloromethane and then studied in
a new electrolytic solution free of any electroactive species,
presents the CV shown in Fig. 2C. This CV shows four
reversible waves with maxima at 0.42, 0.68, 0.81 and 1.08 V,
corresponding to the oxidation of the metalloporphyrin unit
(0.42 and 0.81 V) and the p-doping process of the spirobi-
fluorene polymer (0.68 and 1.08 V).
2
epoxidation, biosensors and solar energy conversion. We are
particularly interested in the preparation of metalloporphyrin
network materials as a new generation of catalysts. In an ideal
case, the supported complexes can be recovered from reaction
mixtures by simple filtration, they can be recycled and they can
help selectivity. Metalloporphyrin molecules show a remark-
4,5
able diversity not only in oxidation but also in carbene
transfer catalysis.6 We have recently shown that poly-
,7
(
tetraspirobifluoreneporphyrin) complexed by manganese
showed potential applications as heterogeneous catalysts for
oxidation of olefins with iodobenzene diacetate and iodo-
sylbenzene. The present work will focus on carbene transfer to
8
olefins and sulfides using ruthenium spirobifluorenylporphyrin
polymers (Fig. 1). The ruthenium porphyrin monomers are
prepared by treatment of tetraspirobifluorene porphyrin with
3
Ru (CO)12 in o-dichlorobenzene at 160 °C (2 h) as previously
9
reported. After preparative macroelectrosyntheses at fixed
potential (1.4 V), the working electrodes were rinsed with
Fig. 2 Cyclic voltammograms (CVs) recorded during the anodic oxidation
2
3
2 2 4 6
of a 2.2 3 10 M solution of (TSP)RuCO in CH Cl + 0.2 M Bu NPF
Fig. 1 Electropolymerization of 1.
using a Pt working electrode. 2A: first anodic sweep of (TSP)Ru(CO)
between 0 and 1 V. 2B: Ten anodic sweeps of (TSP)Ru(CO) between 0 and
1.4 V. 2C: Three anodic sweeps of poly(1) film formed on the electrode
between 0 and 1.2 V.
†
Electronic supplementary information (ESI) available: experimental
details. See http://www.rsc.org/suppdata/cc/b3/b306021g/
2
308
CHEM. COMMUN., 2003, 2308–2309
This journal is © The Royal Society of Chemistry 2003

In order to study the behaviour of poly(1), spectroelec-
trochemical experiments were performed. UV-vis spectral
changes monitored during anodic oxidation of poly(1) in
2 2 4 6
CH Cl + Bu NPF (0.2 M) are shown in Fig. 3. The electronic
spectrum of neutral poly(1) obtained as a thin film on an ITO
glass electrode showed two main bands at 350 and 426 nm, due
to the neutral spirobifluorene chains and ruthenium porphyrins,
respectively (Fig. 3, 0 V). We can also observe bands at 534 and
Fig. 4 Competitive reactions of carbene transfer (cyclopropanation/
sigmatropic rearrangement) with 1 or poly(1).
576 nm (Q bands) similar to those of the monomer (533 and 569
nm). After progressive oxidation to 0.54 V, all bands decrease
in intensity as a new well-defined band starts to grow in at 650
nm. These data suggest the formation of a transient species, the
ruthenium carbon monoxide porphyrin radical cation.11 This
band disappears rapidly which indicates a transformation of the
radical inside the polymer. The final oxidation product (1.24 V)
has a UV-vis spectrum with a broad peak at 524 nm and a
relatively low molar absorptivity compared to the neutral
polymer, which is characteristic of a polyspirobifluorene in its
p-doped state.12 As expected, the IR spectrum of poly(1)
rearrangement of the sulfur ylide.14 Poly(1) also15,16 catalysed
decomposition of ethyl diazoacetate in the presence of styrene
resulting in the formation of the corresponding cyclopropane in
85% yield with a large excess of the trans isomer (trans : cis
ratio: 9 : 1). Similar results were obtained with the monomer
(see supplementary material† for details). The recovery and
recyclability of poly(1) have also been examined, leading to 7
recycling steps without decrease of activity.
To test a possible regioselectivity of the polymer vs.
monomer, competitive catalytic carbene transfer was performed
with a 1 : 1 mixture of styrene and allyl methyl sulfide. With
complex 1, the sigmatropic : cyclopropanation reaction ratio
was about 65 : 35 whereas we detected an increase of the
sigmatropic rearangement with the poly(1) (78 : 22). In these
external competition experiments, a 10 : 1 substrate to diazo
ratio was used in order to avoid the formation of over-addition
products. A plausible explanation for this different regiose-
lectivity is the presence of a crowded environment in the
polymer which would restrict the approach of the aromatic
olefin. Electropolymerization of metalloporphyrins bearing
only one spirobifluorene group will open a new route to less
crowded active sites. Future studies will focus on developing
stereoselective versions of these reactions using chiral ruthe-
nium polymers.
2
1
showed a CO vibration at 1949 cm in KBr very close to the
2
1 11
value observed in the monomer (1939 cm ). Analysis of the
material using scanning electron microscopy and electronic
microanalysis gives a ratio C : Ru of about 120 : 1 in agreement
with a conserved structure of monomers in poly(1).
Following the successful synthesis of the Ru porphyrin
polymers, their catalytic activity was initially tested in carbene
transfer catalysis. The catalytic studies involved the use of
diazoethyl acetate as a possible carbene precursor with styrene
or methyl allyl sulfide as substrates. The activity of the polymer
catalyst was first focused on methyl allyl sulfide which has not
been frequently used in metalloporphyrin-catalyzed carbene
transfer reactions13 and the results were compared to those for
the corresponding soluble monomer 1. The reaction was
monitored by gas chromatography and carbene insertion was
found to be the major reaction in all cases. Treatment of methyl
allyl sulfide with ethyl diazoacetate at 25 °C in the presence of
the ruthenium polymer results in the formation of ethyl
Notes and references
1
C. A. McNamara, M. J. Dixon and M. Bradley, Chem. Rev., 2002, 102,
275.
F. Bedioui, J. Devynck and C. Bied-Charreton, Acc. Chem. Res., 1995,
8, 30.
2
-(methylthio)pent-4-enoate with 87% yield (Fig. 4). The
3
formation of this compound derives from the [2,3]-sigmatropic
2
2
3
4
A. Deronzier and J. C. Moutet, Coord. Chem. Rev., 1996, 147, 339.
C. Crestini and P. Tagliatesta, The Porphyrin Handbook, K. M. Kadish,
K. M. Smith, R. Guilard (Eds.), Academic Press, San Diego, 2000, Vol.
1
1, p. 161.
5
E. Rose, M. Quelquejeu, R. P. Pandian, A. Lecas-Nawrocka, A. Vilar,
G. Ricart, J. P. Collman, Z. Wang and A. Straumanis, Polyhedron, 2000,
1
9, 581.
6
7
8
G. Simonneaux and P. Le Maux, Coord. Chem. Rev., 2002, 228, 43.
C. M. Che and J. S. Huang, Coord. Chem. Rev., 2002, 231, 151.
C. Poriel, Y. Ferrand, P. Le Maux, J. Rault-Berthelot and G.
Simonneaux, Chem. Commun., 2003, 1104.
9
C. Poriel, Y. Ferrand, P. Le Maux and G. Simonneaux, Synlett, 2003,
7
1.
1
0 D. P. Rillema, J. K. Nagle, L. F. Barringer and T. J. Meyer, J. Am. Chem.
Soc., 1981, 103, 56.
1
1
1 X. H. Mu and K. M. Kadish, Langmuir, 1990, 6, 51.
2 J. Rault-Berthelot, M. M. Granger and L. Mattiello, Synth. Met., 1998,
9
7, 211.
1
1
1
3 G. Simonneaux, E. Galardon, C. Paul-Roth, M. Gulea and S. Masson, J.
Organomet. Chem., 2001, 617–618, 360.
4 R. W. C. Cose, A. M. Davies, D. W. D. Ollis, C. Smith and I. O.
Sutherland, J. Chem. Soc., Chem. Commun., 1969, 293.
5 G. Du, B. Andrioletti, E. Rose and L. K. Woo, Organometallics, 2002,
21, 4490.
Fig. 3 Spectroelectrochemical experiments on poly(1) recorded from 0 V to
+
1
.7 V (reference Fc/Fc ).
16 M. Frauenkron and A. Berkessel, Tetrahedron Lett., 1997, 38, 7175.
CHEM. COMMUN., 2003, 2308–2309
2309