Chlorinated phthalocyanine iron(II) complex catalyzed oxidation of alkanes and alkenes with molecular oxygen in the presence of acetaldehyde

Article abstract of DOI:10.1055/s-2003-37128

Chlorinated phthalocyanine iron(II) complex is an excellent catalyst for the oxidation of alkanes and alkenes with molecular oxygen in the presence of acetaldehyde under O₂ (1 atm) at room temperature. The catalyst can be easily separated and reused for the next reaction.

Full text of DOI:10.1055/s-2003-37128

LETTER
321
Chlorinated Phthalocyanine Iron(II) Complex Catalyzed Oxidation of
Alkanes and Alkenes with Molecular Oxygen in the Presence of Acetaldehyde
C
hlorinatedPh
h
thalocyanin
u
Iron(II)
C
o
n
mplex -Ichi Murahashi,*a,b Xiang-Ge Zhou,a Naruyoshi Komiyaa
a
Department of Chemistry, Graduate School of Engineering Science, Osaka University 1-3, Machikaneyama, Toyonaka, Osaka 560-8531,
Japan
E-mail: mura@chem.es.osaka-u.ac.jp
b
Department of Applied Chemistry, Okayama University of Science 1-1, Ridai-cho, Okayama, Okayama 700-0005, Japan
Received 3 December 2002
R1
C
R3
R1
C
R3
Pc-M Complex cat.
R1
Abstract: Chlorinated phthalocyanine iron(II) complex is an excel-
lent catalyst for the oxidation of alkanes and alkenes with molecular
oxygen in the presence of acetaldehyde under O2 (1 atm) at room
temperature. The catalyst can be easily separated and reused for the
next reaction.
R2
H
R2
OH
+
CH3CHO
O2 (1 atm)
CH2Cl2, r.t.
C O
R2
R2 R1
R
R
R
R
Key words: oxidations, molecular oxygen, alkanes, iron phthalo-
cyanine catalyst
R
R
N
N
N
N
R
R
N
N
N
N
R1
R2
R
R
R2
R1
N
M
N
N
M
N
N
M
N
R
R
N
N
N
N
N
N
N
N
R
N
N
R
R
The catalytic oxidation of alkanes using molecular oxy-
gen is of importance in synthetic, industrial, and biologi-
cal points of view.1,2 Development of new strategies for
selective and efficient aerobic oxidation of alkanes under
mild conditions still continues to be an important goal.
Previously, we disclosed that the ruthenium-catalyzed ox-
idation of alkanes with peracetic acid and tert-butylhydro-
peroxide proceeds highly efficiently.3 Further, we
developed catalytic oxidation of hydrocarbons with mo-
lecular oxygen in the presence of ruthenium, iron, and
copper salt catalysts via in situ formation of peracetic acid
from acetaldehyde and molecular oxygen.4,5 Furthermore,
to get high turnover numbers, we developed an effective
ruthenium porphyrin complex catalyst Ru(TPFPP)(CO),
and found that the aerobic oxidation of alkanes with mo-
lecular oxygen can be carried out with high turnover num-
ber (TON) (~10000).6,7 We wish to report here that
chlorinated phthalocyanine iron(II) is a highly efficient
catalyst for aerobic oxidation of alkanes and alkenes in the
presence of acetaldehyde under under O2 (1 atm) at room
temperature. (Scheme 1).
R
R1 R2
5: R1 = H or t-Bu
2 = t-Bu or H
R = H
R = F
R = Cl
1:
2:
3:
4
R
Scheme 1
ed metal phthalocyanines,9,10 zeolite-engaged iron com-
plex embedded in a polymer membrane,11 MCM-41
supported metalphthalocyanines,12 and activated carbon
black supported metalphthalocyanines.13 The homoge-
neous catalytic oxidation of alkanes with KHSO5 was re-
cently reported in the presence of water soluble metal
phthalocyanines.14
We examined the catalytic activity of 21 phthalocyanine
complexes including five different Pc ligands 1–515 for
the aerobic oxidation of cyclohexane. The catalytic activ-
ity of Pc complexes is strongly dependent upon both cen-
tral metal and ligand (Table 1). In general, the Fe, Co, Mn,
and Ni complexes with substituted Pc ligands show better
catalytic activity. The corresponding Mg(II), Zn(II),
Sn(II), and Al(III)Cl complexes show no catalytic activi-
ty. The complex 3-Fe(II) (16Cl-Pc-Fe(II)) was found to be
the most effective catalyst. Haloganated Pc ligands bene-
fited the reaction due to enhancement of robustness of the
ligands during reaction. The catalytic activity is in the or-
der of 3-Fe(II) > 2-Fe(II) > 1-Fe(II).
Metal phthalocyanine complexes have been much less
studied as a catalyst for the catalytic oxidation of alkanes,
comparing to metalloporphyrins.8 Phthlocyanines have
extremely high stability and can be readily prepared;
therefore metal phthalocyanines can be used for the cata-
lytic oxidation of alkanes with molecular oxygen. The ox-
idations with phthalocyanine catalysts are limited to the
reactions with peroxides in the presence of heterogeneous,
immobilized metal phthalocyanine catalysts. tert-Butyl-
hydroperoxide and iodosylbenzene have been used for the
oxidation of alkanes in the presence of zeolite-encapsulat-
Low temperature decreases the reaction rate, while yields
remain almost the same, when the temperature increases
from 20 °C to 40 °C or higher. The catalytic activity is af-
fected by a solvent. Aprotic solvents such as dichloro-
methane are superior to others, and no product was
obtained in ethanol. It is noteworthy that the reaction in
benzotrifluoride (BTF), which is an alternative solvent to
dichloromethane, gives moderate and comparable yields.
Synlett 2003, No. 3, Print: 19 02 2003.
Art Id.1437-2096,E;2003,0,02,0321,0324,ftx,en;U12502ST.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214

322
S.-I. Murahashi et al.
LETTER
thermore, the TON 11000 was obtained under 10% oxy-
gen in nitrogen (1 atm O2 + 9 atm N2), which is a practical
condition fallen outside the explosion limits. The catalyst
3-Fe(II) could be reused after simple recovery,17 giving
the similar result. The oxidation of cyclohexene with 3-
Fe(II) catalyst gave allylic oxidation products predomi-
nantly along with cyclohexene oxide.18
Table 1 Aerobic Oxidation of Cyclohexane Catalyzed by Pc
Complexesa
Catalyst
Yield (%) (-ol:-one)b
15 (53:47)
11 (45:55)
16 (50:50)
22 (50:50)
16 (50:50)
13 (54:46)
16 (44:56)
15 (47:53)
16 (50:50)
16 (56:44)
14 (50:50)
11 (18:82)
TON
59
45
62
88
62
53
64
58
62
64
55
46
1-Fe(II)
1-Fe(III)Cl
2-Fe(II)
To clarify the reaction mechanism, we carried out compe-
tition experiments for the oxidation of para-substituted
ethylbenzenes (p-X-C6H4CH2CH3, X = MeO, Me, H, Br)
in the presence of 3-Fe(II) catalyst and acetaldehyde. The
rate data correlate well (r2 = 0.995) with Hammett linear
free-energy relationship with use of σ+ values. The ob-
served ρ value (–1.34) is close to that reported for oxo-
iron porphyrin species (–1.69),19 and quite different from
those for alkoxyl radical (–0.4).20 To get further evidence,
the competitive oxidations of cyclohexane/cyclohexane-
d12 and ethylbenzene/ethylbenzene-d10 were carried out,
and the deuterium isotope effects (kH/kD values) were de-
termined to be 6.2 and 6.7, respectively, which are consis-
tent with those of hydrogen abstraction process of oxo-
metalloporphyrin species.6,21 The mechanistic study sug-
gests that oxo-iron species would be generated from the
iron phthalocyanine complex under the present reaction
conditions. The present reaction can be rationalized by as-
suming cytochrome P-450 type mechanism. Oxo-metal
species (3-Fe(IV) = O) would be formed from the reaction
of 3-Fe(II) and peracetic acid, which is formed from the
reaction of acetaldehyde with molecular oxygen in the
presence of 3-Fe(II) catalyst (Scheme 2).22 The reaction
of alkane with oxo-metal species would give alcohol and
3-Fe(II)
5-Fe(II)
1-Co(II)
2-Co(II)
4-Co(II)
1-Mn(II)
1-Ni(II)
1-Cu(II)
1-Ru(III)(DCB)2Clc
a In a typical experiment, a mixture of cyclohexane (40 mmol), a cat-
alyst (0.010 mmol), acetaldehyde (4.0 mmol), and dry dichloro-
methane (10 mL) was vigorously stirred at room temperature under
oxygen atmosphere (1 atm). After the usual work up, the reaction
mixture was analyzed by GC and GC-MS. Yields were determined by
GC analyses based on acetaldehyde used.
b Cyclohexanol:cyclohexanone.
c With an axial ligand of 1,2-dicyanobenzene.
Addition of pyridine or imidazole as an axial ligand 3-Fe(II) complex to complete the catalytic cycle. Alcohols
showed little effect.
can be further converted to the corresponding ketones un-
der the reaction conditions. In the oxidation of alkenes,
the product yields were dependent on the steric hindrance
of the substrates. For example, the reaction of styrene
gave styrene oxide in 37% yield, while the oxidation of
more bulky cis-stilbene gave 9% of the trans-epoxide, and
no epoxide was obtained from trans-stilbene.
Induction period (IP) was observed in these reactions. The
IPs range from several minutes to 3 hours, and the reac-
tions were almost completed within the following 3 hours.
A notable effect on the IP is dependent on either ligands
or valency of central metals. For example, for the oxida-
tion with 1-Fe(II) 2 hours of IP was needed, while very
short IP was required for those with 1-Fe(III)Cl and 3-
Fe(II). Because of the robustness of 3-Fe(II), the catalytic
activity remained even after 15 hours, and the yields of the
products are increasing gradually. On the other hand, the
oxidation with 1-Fe(II) stopped after 6 hours because of
the decomposition of the catalyst.
Pc-Fe(II) (cat.)
O2
+
CH3CHO
CH3CO3H
H
CO2
+ CH3
Pc-Fe(IV)=O
H
CO3
CH3
Pc-Fe(II) +
+
R-H
+
Pc-Fe(II)
R-OH
Pc-Fe(IV)=O
The catalyst 3-Fe(II) is effective for the oxidation of both
alkanes and alkenes. Representative results for the oxida-
tion of hydrocarbons are shown in Table 2. Excess
amount of substrate is used to retard the over-oxida-
tion.3a,16 Tertiary C-H bonds can be oxidized easier than
those of secondary or primary C-H bonds. In case of the
oxidation of adamantane, the tertiary C-H bond was oxi-
dized predominantly, and the 1-substituted products were
obtained 15 times more than that of 2- position. From the
oxidation of indan, 1-indanone and 1-indanol were ob-
tained in 95% yield (44:56) based on acetaldehyde. The
catalytic oxidation of indan without a solvent gave high
TON 8500 with low catalyst loading (0.01%mmol). Fur-
Scheme 2
In summary, aerobic oxidation of alkanes and alkenes
with chlorinated phthalocyanine iron(II) catalyst in the
presence of acetaldehyde occurs under O2 (1 atm) at room
temperature with high TON (up to 11000). Because of
easy preparation of the catalyst and its stability, commer-
cially available chlorinated phthalocyanine iron(II) cata-
lyst is more attractive than Ru(TPFPP)(CO), which gives
similar high TON. The mechanism was disclosed for the
first time, to involve oxo-iron species likewise cyto-
chrome P-450.
Synlett 2003, No. 3, 321–324 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Chlorinated Phthalocyanine Iron(II) Complex
323
Table 2 Oxidation of Hydrocarbons with O2 with 3-Fe(II) Catalysta
Substrates
Yield (%)b
Product (Selectivity /%)
TON
88
22
(50)
(50)
(50)c
OH
O
21c
80c
(50)c
47
188
OH
OH
O
(83)
(8)
(8)
6
22
(33)
(33)
(16)
OH
OH
O
O
(16)
OH
95
76
377
320
O
(56)
(44)
OH
(70)
O
(30)
O
a In a typical experiment, a mixture of substrate (40 mmol), 3-Fe(II) (0.010 mmol), acetaldehyde (4.0 mmol), and dry dichloromethane (10 mL)
was vigorously stirred at room temperature under oxygen atmosphere (1 atm). After the usual work up, the reaction mixture was analyzed by
GC and GC-MS.
b Yields were determined by GC analyses based on acetaldehyde used.
c The values were obtained by the reaction using the recycled catalyst.
(6) Murahashi, S.-I.; Naota, T.; Komiya, N. Tetrahedron Lett.
Acknowledgment
1995, 36, 8059.
This work was supported by the Research for the Future Program,
the Japan Society for the Promotion of Science.
(7) Groves, J. T.; Bonchio, M.; Carofiglio, T.; Shalyaev, K. J.
Am. Chem. Soc. 1996, 118, 8961.
(8) (a) Berezin, B. D. In Coordination Compounds of
Porphyrins and Phthalocyanies; John Wiley & Sons:
Chichester, 1981, 11–22. (b) In MetalloporphyrinCatalyzed
References
Oxidations; Montanari F., Casella L., Kluwer Academic:
Dordrecht, 1994.
(1) Murahashi, S.-I. Angew. Chem., Int. Ed. Engl. 1995, 34,
2443.
(9) (a) Bulkus, K. J. Jr.; Eissa, M.; Levado, R. J. Am. Chem. Soc.
1995, 117, 10753. (b) Parton, R. F.; Peere, G. J.; Neys, P. E.;
Jacobs, P. A.; Claessens, R.; Baron, G. V. J. Mol. Catal A:
Chem. 1996, 113, 445. (c) Raja, R.; Ratnasamy, P. Catal.
Lett. 1997, 48, 1.
(2) (a) Sheldon, R. A.; Kochi, J. K. In Metal-Catalyzed
Oxidations of Organic Compounds; Academic Press: New
York, 1981. (b) Barton, D. H. R.; Doller, D. Acc. Chem. Res.
1992, 25, 504. (c) Shilov, A. E.; Shul’pin, G. Chem Rev.
1997, 97, 2879.
(10) (a) Herron, N.; Stucky, G. D.; Tolman, C. A. J. Chem. Soc.,
Chem. Commun. 1986, 1521. (b) Ichikawa, M.; Kimura, T.;
Fukuoka, A. Stud. Surf. Sci. Catal. 1991, 60, 335.
(11) Parton, R. F.; Vankelecom, I. F. J.; Casselman, M. J. A.;
Bezoukhanova, C. P.; Uytterhoeven, J. B.; Jacobs, P. A.
Nature (London) 1994, 370, 541.
(12) (a) Armengol, E.; Corma, A.; Forne’s, V.; Garci’a, H.;
Primo, J. Appl. Catal. A.: General 1999, 181, 305.
(b) Ernst, S.; Selle, M. Micropor. Mesopor. Mater. 1999, 27,
355.
(3) (a) Murahashi, S.-I.; Komiya, N.; Oda, Y.; Kuwabara, T.;
Naota, T. J. Org. Chem. 2000, 65, 9186. (b) Murahashi,
S.-I.; Oda, Y.; Naota, T.; Kuwabara, T. Tetrahedron Lett.
1993, 34, 1299. (c) Murahashi, S.-I.; Oda, Y.; Komiya, N.;
Naota, T. Tetrahedron Lett. 1994, 35, 7953.
(4) (a) Murahashi, S.-I.; Oda, Y.; Naota, T. J. Am. Chem. Soc.
1992, 114, 7913. (b) Murahashi, S.-I.; Oda, Y.; Naota, T.;
Komiya, N. J. Chem, Soc., Chem. Commun. 1993, 139.
(c) Komiya, N.; Naota, T.; Oda, Y.; Murahashi, S.-I. J. Mol.
Catal. A: Chem. 1997, 117, 21.
(13) Parton, R. F.; Neys, P. E.; Jacobs, P. A.; Sosa, R. C.;
Rouxhet, P. G. J. Catal. 1996, 164, 341.
(14) d’Alessandro, N.; Liberatore, L.; Tonucci, L.; Morvillo, A.;
Bressan, M. New J. Chem. 2001, 25, 1319.
(5) Murahashi, S.-I.; Saito, T.; Naota, T.; Kumobayashi, H.;
Akutagawa, S. Tetrahedron Lett. 1991, 32, 5991.
Synlett 2003, No. 3, 321–324 ISSN 0936-5214 © Thieme Stuttgart · New York

324
S.-I. Murahashi et al.
LETTER
(18) (a) Kasuga, K.; Tsuboi, K.; Handa, M.; Sugimori, T.;
(15) The complexes are commercially available except 1-Ru(III),
2-Fe(II), and 5-Fe(II) complexes. (a) 1-Ru(III), see: Keen, I.
M.; Malerbi, B. W. J. Inorg. Nucl. Chem. 1965, 27, 1311.
(b) 2-Fe(II), see: Jones, J. G.; Twigg, M. V. Inorg. Chem.
1969, 8, 2018. (c) 5-Fe(II), see: Metz, J.; Schneider, O.;
Hanack, M. Inorg. Chem. 1984, 23, 1065.
Sugebe, K. Inorg. Chem. Commun. 1999, 2, 507. (b) Nino,
M. E.; Giraldo, S. A.; Pez-Mozo, E. A. J. Mol. Catal. A:
Chem. 2001, 175, 139.
(19) Khanna, R. K.; Pauling, T. M.; Vajpayee, D. Tetrahedron
Lett. 1991, 32, 3759.
(16) If the amount of acetaldehyde was increased, the conversion
of cyclohexane went up; however, the selectivity was
decreased due to the formation of undesirable over-
oxidation products such as adipic acid, glutaric acid, and
succinic acid.3a
(20) Sakurai, H.; Hosomi, A. J. Am. Chem. Soc. 1967, 89, 458.
(21) Sorokin, A.; Robert, A.; Meunier, B. J. Am. Chem. Soc.
1993, 115, 7293.
(22) Ohkatsu, Y.; Hara, T.; Osa, T. Bull. Chem. Soc. Jpn. 1977,
50, 692.
(17) Evaporation of dichloromethane under vacuum (to ca. 2
mL), addition of diethyl ether (30 mL), and filtration gave 3-
Fe(II) complex.
Synlett 2003, No. 3, 321–324 ISSN 0936-5214 © Thieme Stuttgart · New York