Influence of manganese tetraarylporphyrins substituents on the selectivity of cycloalkanes oxidation with magnesium monoperoxyphthalate

Article abstract of DOI:10.1016/j.molcata.2006.04.070

The catalytic properties of manganese porphyrins of the second and third generation and magnesium monoperoxyphthalate (MMPP) as oxidant have been studied in oxidation of cyclohexane or cyclooctane under mild conditions. We have found that the structure of

Full text of DOI:10.1016/j.molcata.2006.04.070

Journal of Molecular Catalysis A: Chemical 257 (2006) 154–157
Influence of manganese tetraarylporphyrins substituents on the selectivity
of cycloalkanes oxidation with magnesium monoperoxyphthalate
J. Połtowicz, K. Pamin, J. Haber∗
Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krako´w, Poland
Received 18 March 2006; received in revised form 27 April 2006; accepted 28 April 2006
Available online 12 June 2006
Abstract
The catalytic properties of manganese porphyrins of the second and third generation and magnesium monoperoxyphthalate (MMPP) as oxidant
have been studied in oxidation of cyclohexane or cyclooctane under mild conditions. We have found that the structure of manganese porphyrin has
an influence on selectivity of the investigated reaction. Apart from main cycloalkanes oxidation products (alcohol and ketone), olefins and epoxides
resulting from oxidative dehydrogenation of substrates in the course of reaction, were surprisingly found. This represents the first example of the
oxidative dehydrogenation of cycloalkanes with MMPP as oxygen donor. The reaction mechanism is discussed and proposed.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Metalloporphyrins; Cycloalkanes oxidation; Oxidative dehydrogenation
1. Introduction
which is commercially available, inexpensive and relatively new
oxygen donor [11]. MMPP displays low toxicity and is safe to
use in larger scale reaction. This versatile oxygen donor is capa-
ble of effecting many types of oxidation reactions. It has been
used with metalloporphyrins for alkene epoxidation [12–16],
benzene and alkylbenzene oxidation [17], hydroxylation of alka-
nes [18,19] and variety of organic molecules [20].
In our previous papers [14,15], we have shown that metallo-
porphyrins of the third generation with several nitro groups in
␤-position were active in epoxidation of linear and cyclic olefins
without requiring the addition of any nitrogen base. We have
found surprisingly that the activity of catalysts increases with
the electronegativity of the axial ligand, although the presence
of these ligands decreases the half-wave reduction potential of
metalloporphyrins.
Metalloporphyrins with electron-withdrawing substituents in
macrocyclic rings have been extensively used as precursors of
stable catalysts for epoxidation of olefins and hydroxylation of
alkanes in a liquid phase under mild conditions [1–5]. These
investigations allow to understand the factors that influence the
yields and selectivity of metalloporphyrins catalyzed oxidations
and should inspire the development of more active and selec-
tive hydrocarbon oxidation catalysts. The most efficient systems
involvemanganeseorironporphyrinsbearinghalogengroupson
the phenyl or pyrrole rings. Electron-withdrawing substituents
bring about an increase of the half-wave potential of the met-
alloporphyrins and thus protect the macrocyclic ligand from
oxidative self-destruction. This strategy can prevent also ␮-oxo
dimer formation and improve catalytic efficiency of metallopor-
phyrins. Most of the studies have been focused on the application
of these compounds as catalysts with different oxygen donors
like iodosylbenzene [6], hydrogen peroxide [7], hypochlorites
[8], monopersulphates[9], andmolecularoxygenwithsacrificial
co-reductant [10]. There are only a few papers concerning the
application of the magnesium monoperoxyphthalate (MMPP),
In this paper, we will continue our study on the application
of metalloporphyrins with different electron-withdrawing sub-
stituents on the macrocycle ring in the oxidation of cycloalkanes
using MMPP as oxygen donor. We have found that the presence
of different groups in porphyrin rings modifies the yield and
selectivity of the investigated reactions.
2. Experimental
∗
Oxidation of cycloalkanes was carried out in a glass reac-
tor of 10 mL volume. In a typical experiment, organic phase
Corresponding author.
E-mail address: nchaber@cyf-kr.edu.pl (J. Haber).
1381-1169/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2006.04.070

J. Połtowicz et al. / Journal of Molecular Catalysis A: Chemical 257 (2006) 154–157
155
Fig. 1. Structures of the third generation polynitrated manganese porphyrins Mn(TPFP␤(NO2)4P) and Mn(TDCP␤(NO2)5P).
consisting of 1 mL ethyl acetate as a solvent, 3.45 × 10−4 m
of hydrocarbon to be oxidized and 2.5 × 10−6 m of metallo-
porphyrin catalyst were mixed with 2 mL of aqueous solution
containing 7.0 × 10−4 m of oxidant MMPP and 1.0 × 10−5 m
of tetrabutylammonium chloride as phase transfer agent. The
reaction mixture was stirred with a magnetic bar and the temper-
ature was maintained constant. After 1 h of the reaction at room
temperature the products were analyzed by gas chromatogra-
phy. In a blank experiment no reaction was observed when the
manganese porphyrin catalyst was not present in the reaction
mixture.
Porphyrin ligands, TDCPP and TPFPP (with substituents
on phenyl rings, called sometimes the second generation por-
phyrins) were prepared according to a Lindsay method [21]
and nitrated by fuming acid to obtain TPCP␤(NO2)5P and
TPFP␤(NO2)4P (called sometimes third generation porphyrins
with substituents on phenyl and pyrrolic rings) [22] (Fig. 1).
Careful purification on Al2O3 and SiO2 permitted to obtain the
ligand substituted with five nitro groups. Ligand of the third
generation porphyrin TDCP␤Cl8P was obtained as described
by Lyons et al. [23]. Manganese complexes were prepared by
DMF metalation procedure with Mn(OAc)2 [24].
3. Results and discussion
A series of manganese porphyrins of the second and third
generation were applied as catalysts in the oxidation of two
model unreactive cycloalkanes (cyclohexane and cyclooctane)
with MMPP as oxygen donor at room temperature. All these
complexes turned out to be active catalysts for oxidation of
cycloalkanes. Table 1 shows the results of the oxidation of cyclo-
hexane. For the manganese porphyrins of second generation:
Mn(TPFPP) and Mn(TDCPP) with electron-withdrawing sub-
stituents on phenyl rings, the main products are cyclohexanone
and cyclohexanol. It is interesting to notice that in biological sys-
tems alcohol is always the main product. No other products were
detected in the organic phase, although the ketone and alcohol
were found at selectivies of about 50–60%. This suggests that
some other products were formed which were soluble in water.
These were probably polyhydroxylation compounds. Formation
of such products was postulated by Querci and Ricci [18] for the
same reaction with MMPP. Halogenation of pyrollic ring per-
formed for the Mn(TDCP␤Cl8P), increases its catalytic activity.
For this porphyrin with electron-withdrawing substituents on
phenyl and pyrrole rings the conversion of cyclohexane and the
yield to cyclohexanone increase while the yield to cyclohexanol
decreases. In contrast to chlorinated and perchlorinated metal-
loporphyrins, ring-polinitrated metalloporphyrins have received
little attention [14,15,22]. Polinitration of pyrollic rings also
causes an increase of the catalytic activity of manganese por-
phyrin similarly to halogenation but we observed the formation
Metalloporphyrins and ligands were purified by successive
chromatography on silica gel or alumina columns. The purity
of final products was checked by UV–vis and NMR spectro-
scopy.
Magnesium monoperoxyphthalate was purchased from
Aldrich and titrated iodometrically prior to use.
Table 1
Oxidation of cyclohexane catalyzed by manganese porphyrins with MMPP as oxygen donora
Catalyst
Cyclohexane
conversion (%)
Cyclohexanone
yield (%)
Cyclohexanol
yield (%)
Cyclohexene
yield (%)
Epoxide yield (%)
Mn(TDCPP)
Mn(TPFPP)
Mn(TDCP␤Cl8P)
Mn(TPCP␤(NO2)5P)
Mn(TPFP␤(NO2)4P)
84.3
95.5
100
100
97.2
30.7
32.5
38.8
39.4
40.3
26.9
21.3
20.8
18.1
15.2
–
–
–
2.2
1.4
–
–
–
7.1
5.9
a
See conditions in the text.

156
J. Połtowicz et al. / Journal of Molecular Catalysis A: Chemical 257 (2006) 154–157
Table 2
Oxidation of cyclooctane catalyzed by manganese porphyrins with MMPP as oxygen donora
Catalyst
Cyclooctane
conversion (%)
Cyclooctanone
yield (%)
Cyclooctanol
yield (%)
Cyclooctene
yield (%)
Epoxide yield (%)
Mn(TDCPP)
Mn(TPFPP)
Mn(TDCP␤Cl8P)
Mn(TPCP␤(NO2)5P)
Mn(TPFP␤(NO2)4P)
89.6
92.3
100
100
100
32.2
35.1
39.8
41.6
45.4
26.3
25.8
22.9
20.2
18.2
–
–
–
5.5
3.1
–
–
–
9.7
8.4
a
See conditions in the text.
of two new products: olefin and epoxide in small yields. Olefin
is the product of the oxidative dehydrogenation of cycloalka-
nes. It becomes then oxidized to the epoxide. The oxidation of
the olefins to epoxides by single oxygen donors was discussed
in our earlier study [14,15] It is worth noting that the charac-
ter of the substituents has significant influence on the activity
and selectivity of catalysts. Thus, by varying the structure of the
porphyrin ligand we are able to change the selectivity of the reac-
tion and its mechanism. The use of Mn(TDCP␤Cl8P) bearing
chloro substituents, moderately electron-withdrawing groups,
results in ketone and alcohol while the pernitro manganese
porphyrinsMn(TPCP␤(NO2)5P)andMn(TPFP␤(NO2)4P)with
bulky and strongly electron-withdrawing substituents produce
additionally olefin and epoxide. The most active among stud-
ied catalysts were two polynitrated manganese complexes:
Mn(TPCP␤(NO2)5P) and Mn(TPFP␤(NO2)4P) showing the
highest yields and the highest selectivity.
ing electron-withdrawing substituents on the phenyl and nitro
groups on pyrrole rings.
The mechanism of hydroxylation of the alkanes with metal-
loporphyrins as catalysts and oxygen donors was postulated by
Groves as a “rebound mechanism” [28]. The first step involves
reaction between metalloporphyrin and oxygen donor yielding
oxo-complex. The oxo-species is strongly electrophilic in nature
and may react with any electron rich region of a substrate. In the
case of alkanes, reaction of substrate with oxo-complex leads
to free radical and hydroxy metalloporphyrins in the solvent
cage. Recombination of this intimate pair: radical with man-
ganese intermediate would produce hydroxylated product and
the starting metalloporphyrin. Alcohol is obtained by this path-
way. Alternatively, theradicalmaydiffuseoutofthesolventcage
to produce a free radical and hydroxy manganese porphyrin. In
the next step free radical may react with substrate or metallo-
porphyrin giving other products.
The formation of products of the oxidative dehydrogenation
of cycloalkanes was also observed by Nappa and Tolman [25] in
oxidation of cyclohexane with iron porphyrins and iodosoben-
zeneasoxygendonor. Moreover, oxidativedehydrogenationwas
also present in oxidation of terpene derivative with metallopor-
phyrins and sodium hypochlorite or potassium monopersulfate
as oxygen donors [26], but this reaction pathway was sug-
gested to be rather unusual when using metalloporphyrins as
catalysts [26]. Oxidative dehydrogenation was also observed in
oxidation of cyclohexane with iodosobenzene and manganese
porphyrins [27]. The addition of tin Lewis acids, Ph3SnO2C8F15
and Ph3SnO3SC6F13 as axial ligands increase the yield of prod-
ucts in this reaction by reducing the electron density on metallic
center.
Fig. 2 presents our proposal of the modification of the reac-
tion mechanism. While, the oxidation of hydrocarbons with
iodosylbenzene as oxygen donor mainly leads to the formation
ofalcoholasthemainproductwithtracesofketone, inthecaseof
MMPP the main products are the ketone and alcohol with little
amounts of epoxide and olefin. Certain details of this mecha-
nism like formation of an oxocomplex from metalloporphyrin
and oxygen donor and its further reaction with alkane to radi-
The catalytic results of the oxidation of cyclooctane in the
presence of the same manganese porphyrins as catalysts are
shown in Table 2. The nature and location of the substituents
in porphyrin rings have a major influence on the yields and
products distribution in the oxidation of cyclooctane. Compari-
son of the results obtained for cyclohexane (Table 1) with those
observed in case of cyclooctane quoted in Table 2 indicates that
the latter is more reactive and gives higher yields of products. In
the case of cyclooctane oxidation with polynitrated manganese
porphyrins, the yields of olefin and epoxide increases in com-
parison with cyclohexane oxidation. The most efficient catalytic
system in this reaction, similarly to the cyclohexane oxidation,
involves polynitrated manganese porphyrins of the third gen-
eration: Mn(TPCP␤(NO2)5P) and Mn(TPFP␤(NO2)4P) bear-
Fig. 2. Scheme of the oxidation of cycloalkanes with metalloporphyrin and
MMPP.

J. Połtowicz et al. / Journal of Molecular Catalysis A: Chemical 257 (2006) 154–157
157
cal and hydroxy metalloporphyrins are generally agreed upon.
However, we suggest, on the grounds of our results, that in the
case of polynitrated metalloporphyrin with bulky and strongly
electron-withdrawing substituents the reaction may proceed by
different mechanism because electron transfer is faster than a
radical pair collapse. In other words, electron transfer mecha-
nism is the predominant pathway with the subsequent ion pair
collapse for alcohol formation. The same point of view was pre-
sented by Smegal and Hill [29]. Oxidation of alcohol usually
occurs in our system, resulting in the formation of the corre-
sponding ketone, the main product of our reaction [7,18,30]. A
competing pathway produced olefin via the proton transfer. The
result of the oxidation of olefin by oxo species is the epoxide
formation.
Concluding, in the case of the oxidation of cycloalkanes
with MMPP as oxygen donor the reaction may occur either
via the mechanism proposed by us for polynitrated metallopor-
phyrins or via the rebound mechanism for other second and
third generation metalloporphyrins depending on the nature of
the metalloporphyrins and the type of oxygen donor.
[2] F. Montanari, L. Casella (Eds.), Metalloporphyrin Catalyzed Oxidation,
Kluwer Academic Publishers, 1994.
[3] J. Haber, L. Matachowski, K. Pamin, J. Połtowicz, J. Mol. Catal. A: Chem.
198 (2003) 215.
[4] J. Haber, L. Matachowski, K. Pamin, J. Połtowicz, J. Mol. Catal. A: Chem.
91/92 (2004) 195.
[5] J. Połtowicz, J. Haber, J. Mol. Catal. A: Chem. 220 (2004) 43.
[6] J.T. Groves, W.J. Kruper, T.E. Nemo, R.S. Myers, J. Mol. Catal. 7 (1980)
169.
[7] P. Battioni, J.P. Renaud, J.F. Bartoli, M. Reina-Artiles, M. Fort, D. Mansuy,
J. Am. Chem. Soc. 110 (1988) 8462.
[8] E. Guilmet, B. Meunier, J. Mol. Catal. 23 (1984) 115.
[9] B. De Poorter, B. Meunier, J. Chem. Soc., Perkin Trans. II (1985) 1735.
[10] I. Tabushi, N. Koga, J. Am. Chem. Soc. 101 (1979) 6456.
[11] H. Heaney, Aldrichimica Acta 26 (1993) 35.
[12] C. Querci, M. Ricci, J. Chem. Soc., Chem. Commun. 14 (1989) 889.
[13] R. Iwanejko, P. Battioni, D. Mansuy, T. Młodnicka, J. Mol. Catal. 111
(1996) 7.
[14] J. Haber, R. Iwanejko, J. Połtowicz, P. Battioni, D. Mansuy, J. Mol. Catal.
152 (2000) 111.
[15] J. Haber, R. Iwanejko, J. Połtowicz, P. Battioni, D. Mansuy, J. Mol. Catal.
152 (2000) 117.
[16] P. Hoffmann, A. Robert, B. Meunier, CR Acad. Sci. Paris 314 (1992)
51.
[17] E. Baciocchi, O. Lanzalunga, A. Lapi, Tetrahedron Lett. 36 (1995)
3547.
[18] C. Querci, M. Ricci, J. Chem. Soc., Chem. Commun. 31 (1990) 1779.
[19] P. Hoffmann, A. Robert, B. Meunier, Bull. Soc. Chim. Fr. 129 (1992)
85.
[20] T. Cai Zheng, D.E. Richardson, Tetrahedron Lett. 36 (1995) 837.
[21] J.S. Lindsay, H.C. Hsu, I.C. Schreiman, Tetrahedron Lett. 27 (1986) 4969.
[22] J.F. Bartoli, P. Battioni, W.R. De Foor, D. Mansuy, J. Chem. Soc., Chem.
Commun. (1994) 23.
[23] J.E. Lyons, P.E. Ellis Jr., H.K. Myers Jr., J. Catal. 155 (1995) 59.
[24] A.D. Adler, F.R. Longo, J.D. Finarelli, J. Goldmacher, J. Assour, L.
Korssakow, J. Org. Chem. 32 (1967) 476.
[25] M.J. Nappa, C.A. Tolman, Inorg. Chem. 24 (1985) 4711.
[26] V. Maraval, J.E. Ancel, B. Meunier, J. Catal. 206 (2002) 349.
[27] M.J. Nappa, R.J. McKinney, Inorg. Chem. 27 (1988) 3740.
[28] T.J. McMurry, J.T. Groves, in: P.R. Ortiz de Montellano (Ed.), Cytochrome
P-450; Structure, Mechanism, and Biochemistry, Plenum Press, New York,
1985 (Chapter 1).
4. Conclusions
Magnesium monoperoxophthalate (MMPP) is a very effi-
cient oxygen donor in the oxidation of cycloalkanes catalyzed
by manganese porphyrins with multiple electron-withdrawing
peripheral substituents at room temperature and under phase-
transfer conditions. We have found that the presence of different
groups in porphyrin rings is capable of modifying the yield and
selectivity of the investigated reaction. The system with polyni-
trated metalloporphyrins as catalysts, besides alcohol and ketone
as the main oxidation products, gives olefin and epoxide which
are the products of oxidative dehydrogenation of cycloalkanes.
References
[29] J.A. Smegal, C.L. Hill, J. Am. Chem. Soc. 105 (1983) 3511.
[30] P. Battioni, J.P. Renaud, J.F. Bartoli, D. Mansuy, J. Chem. Soc., Chem.
Commun. (1986) 341.
[1] R.A. Sheldon (Ed.), Metalloporphyrins in Catalytic Oxidation, Marcel
Dekker Inc., Basel, 1994.