bands at 381, 407, 525, 578 and 615 nm and a main absorption
band at 480 nm. The electronic spectrum of neutral poly (1)
obtained as a thin film on a platinum surface by anodic
oxidation of a solution of 1 at 1.55 V and then undoped at 0.0V
is presented in Figure 3C. Two main bands are observed at 480
and 615 nm, with an additional absorption band which
maximum is at 360 nm and fits with the main aborption of the
poly(spirobifluorene) (Fig. 3B). This relatively large band hides
the bands observed at 381 and 407 nm in monomer 1. After
preparative electrosyntheses, the working electrodes were
rinsed with solvents and the solid film polymers removed from
the anode and dried under vacuum. The oxidatively formed
films of the metalloporphyrins are insoluble in a variety of
common solvents, such as acetone, dichloromethane, methanol,
acetonitrile and dimethyl sulfoxide.
Following, the successful synthesis of the Mn porphyrin
polymers, their catalytic activity was initially tested in the
epoxidation of styrene. After scratching the film out of the
electrode, the polymer was crushed to obtain a fine powder. The
catalytic essay involved the use of iodobenzene diacetate (Table
1, conditions A) and iodosylbenzene (Table 1, conditions B) as
possible oxidants and imidazole as the axial ligand for the
metalloporphyrin. The activity of the polymer catalyst was first
tested with iodobenzene diacetate which has not been frequently
used in metalloporphyrin-catalyzed oxidation reactions16 and
the results compared to the corresponding soluble monomer 1.
The styrene epoxidation reaction was monitored by gas
chromatography and styrene oxide was found to be the major
product in all cases (Table 1). Thus it should be noted that poly
(1) catalysts have efficiencies similar (or very close) to those of
the corresponding metalloporphyrin complexes in solution,
even with PhIO, which is almost insoluble in dichloromethane.
Thus this reaction, which is actually a triphasic system solid/
solid/liquid (polymeric PhIO/poly (1)/styrene) yielded 70%
epoxide after 3 h.
To test a possible regioselectivity of the polymer vs
monomer, competitive catalytic oxidation was performed with a
1+1 mixture of styrene and cyclooctene. With complex 1, the
styrene oxide/cyclooctene oxide ratio was about unity whereas
we detected a twofold excess of styrene oxide with the poly (1).
In these external competition experiments, a 10+1 alkene to
oxidant ratio was used in order to avoid the formation of over-
oxidized products. Plausible explanation for this moderate
regioselectivity is the presence of crowded environment in the
polymer which would restrict the approach of the internal
olefin.
The recovery and recyclability of the manganese spirobi-
fluorene polymers have been also examined. The catalysts were
first tested for activity in the epoxidation of styrene with
iodobenzene diacetate leading to 8 recycling steps without
decrease of activity (yield for each turn between 58 and 68%,
catalyst: 3 mg). Furthermore the resistance of the catalyst
towards oxidative degradation was also tested in the epoxida-
tion of styrene in stoichiometric experiment (oxidant/olefin
ratio = 1); progressive addition of iodobenzene diacetate to
olefin leads to 60% conversion. This reaction can be re-
produced: after several washes, the manganese polymer was
still efficient in olefin epoxidation without any loading of
metalloporphyrins in solution.
Notes and references
1 K. M. Kadish, K. M. Smith and R. E. Guilard, The Porphyrin Handbook
Academic Press: Boston, 2000, (Vols. 1–10).
2 J. A. Gladysz, Pure Appl. Chem., 2001, 73, 1319.
3 N. E. Leadbeater and M. Marco, Chem. Rev., 2002, 102, 3217.
4 P. Jego-Evanno, C. Moinet and G. Simonneaux, C. R. Acad. Sci. Paris,
IIc, 2000, 3, 711.
5 A. Bettelheim, B. A. White, S. A. Raybuck and R. W. Murray, Inorg.
Chem., 1987, 26, 1009.
Fig. 3 UV-Vis spectra of (TSP)Mn 1,poly(SBF), poly(TSP)Mn (poly (1))
Table 1 Epoxidation of alkenes by 1 and poly (1) using iodosylbenzene or
iodobenzene diacetate as oxidant.
6 G. Cauquis, S. Cosnier, A. Deronzier, B. Galland, D. Limousin, J. C.
Moutet, J. Bizot, D. Deprez and J. P. Pulicani, J. Electroanal. Chem.,
1993, 352, 181.
Yield
(%)a
Epoxide
aldehyde
7 S. E. Creager, S. A. Raybuck and R. W. Murray, J. Am. Chem. Soc.,
1986, 108, 4225.
Catalyst
Oxidant
Alkene
8 F. Bedioui, J. Devynck and C. Bied-Charreton, Acc. Chem. Res., 1995,
28, 30.
9 A. Deronzier and J. C. Moutet, Coord. Chem. Rev., 1996, 147, 339.
10 C. Poriel, Y. Ferrand, P. Le Maux and G. Simonneaux, Synlett., 2003,
71.
11 A. Osuka, K. Ida and K. Maruyama, Chem. Lett., 1989, 741.
12 C. L. Chiang and C. F. Shu, Chem. Mater., 2002, 14, 682.
13 A. Aviram, J. Am. Chem. Soc., 1988, 110, 5687.
14 J. Rault-Berthelot, M. M. Granger and L. Mattiello, Synth. Met., 1998,
97, 211.
15 K. M. Kadish, G. Royal, E. Van Caemelbecke and L. Gueletti, The
Porphyrin Handbook, K. M. Kadish, K. M. Smith, and R. Guilard,
Academic Press, San Diego, 2000, 9, , 1.
Styrene
4-Chlorostyrene
Styrene
4-Chlorostyrene
Styrene
4-Chlorostyrene
Styrene
65
60
70
50
71
71
75
73
2
3
b
b
Poly (1)
PhI(OAc)2
1.7
3.8
1.7
4
1.9
4
PhIOc
1
PhI(OAc)2
PhIOc
4-Chlorostyrene
a Yield based on starting olefin at room temperature. b Conditons A: Time
reaction: 90 min. (P)MnCl/iodobenzenediacetate/imidazole/alkene
(1/100/10/1000) in dichloromethane/acetonitrile (2+1). c Conditions B:
Time reaction: 90 min for 1 and 180 min for poly (1). (P)MnCl/
iodosylbenzene/imidazole/alkene(1/100/10/1000)in dichloromethane.
16 J. P. Collman, A. S. Chien, T. A. Eberspacher and J. I. Brauman, J. Am.
Chem. Soc., 2000, 122, 11098.
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