Mild oxidative alkane functionalization with peroxides in the presence of ferrocene

Article abstract of DOI:10.1016/j.catcom.2012.11.003

Ferrocene in an unexpected emploi: alkanes can be efficiently oxygenated by H₂O₂ in the presence of catalytic amounts of this well-known organometallic compound in combination with pyrazine-2-carboxylic acid or 2,2′-bipyridine. Saturated hydrocarbons, RH, are also transformed into carboxylic acids, RCOOH, when reacted with the ferrocene/CO/S ₂O₈^{2 -}/H₂O system in acetonitrile solution.

Full text of DOI:10.1016/j.catcom.2012.11.003

Mild oxidative alkane functionalization with peroxides in the presence of
ferrocene
Georgiy B. Shul’pin, Marina V. Kirillova, Lidia S. Shul’pina, Armando
J.L. Pombeiro, Eduard E. Karslyan, Yuriy N. Kozlov
PII:
DOI:
Reference:
S1566-7367(12)00413-X
doi: 10.1016/j.catcom.2012.11.003
CATCOM 3324
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
8 September 2012
31 October 2012
1 November 2012
Please cite this article as: Georgiy B. Shul’pin, Marina V. Kirillova, Lidia S. Shul’pina,
Armando J.L. Pombeiro, Eduard E. Karslyan, Yuriy N. Kozlov, Mild oxidative alkane
functionalization with peroxides in the presence of ferrocene, Catalysis Communications
(2012), doi: 10.1016/j.catcom.2012.11.003
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ACCEPTED MANUSCRIPT
Ref. CATCOM-D-12-00836, Revised in accord with the suggestions of Reviewers and Editor
Catalysis Communications
Mild oxidative alkane functionalization with peroxides in the presence of ferrocene
Georgiy B. Shul’pin a,*, Marina V. Kirillova b,*, Lidia S. Shul’pina c, Armando J.L. Pombeiro*,b,
Eduard E. Karslyan b,c, Yuriy N. Kozlov a
a Semenov Institute of Chemical Physics, Russian Academy of Sciences, ulitsa Kosygina, dom 4, Moscow
119991, Russia
b Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Technical University of Lisbon,
Av. Rovisco Pais, 1049–001, Lisbon, Portugal
c Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsa Vavilova,
dom 28, Moscow 119991, Russia
__________________________________________________________________
FOOTNOTE:
* Corresponding authors. Fax: (+7499) 1376130 (G.B. Shul’pin); 351 21 846 4455 (M.V. Kirillova,
A.J.L. Pombeiro).
E-mail addresses: Shulpin@chph.ras.ru (G.B. Shul’pin); kirillova@ist.utl.pt (M.V. Kirillova);
pombeiro@ist.utl.pt (A.J.L. Pombeiro)
__________________________________________________________________
ARTICLE INFO
Keywords:
Alkanes
Homogeneous catalysis
Hydrogen peroxide
Hydrocarboxylation
Hydroperoxidation
Iron complexes
ABSTRACT
Ferrocene in an unexpected emploi: alkanes can be efficiently oxygenated by H2O2 in the presence of
catalytic amounts of this well-known organometallic compound in combination with pyrazine-2-
carboxylic acid or 2,2’-bipyridine. Saturated hydrocarbons, RH, are also transformed into carboxylic
2–
acids, RCOOH, when reacted with the ferrocene/CO/S2O8 /H2O system in acetonitrile solution.
_____________________________________________________________________________________
1

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1. Introduction
Soluble iron compounds are known to catalyze various processes (see reviews [1–11]) including
oxidation of C–H compounds with peroxides (see selected papers [11–23]). However, organometallic
complexes are very rarely used as (pre)catalysts in oxidations of aromatic and saturated hydrocarbons
[24–30]. In particular, it is surprising that ferrocene has never been applied in oxidation catalysis in spite
of being one of the most common organometallic compounds.
In the present work we have discovered, for the first time, that catalytic amounts of ferrocene
(compound 1) very efficiently induce several types of oxidative transformations of alkanes, namely (i) the
2–
oxidation by H2O2 or tert-butyl hydroperoxide and (ii) the hydrocarboxylation with the CO/S2O8 /H2O
system.
2. Results and discussion
The oxidation of gaseous (Tables 1 and 2) and liquid alkanes to the corresponding alkyl
hydroperoxides by H2O2 in the presence of catalytic amounts of ferrocene proceeds in MeCN at 50 ºC. An
obligatory component of the catalytic system is pyrazine-2-carboxylic acid (PCA). In the cyclohexane
oxidation the yield and turnover number (TON) after 1.5 h (Fig. 1) attained 32% and 1200, respectively.
In the ethane oxidation TON reached 970. Maximum yield (58% based on the alkane) was obtained for
the n-butane oxidation after 4 h (Table 1). These values can be considered as very high taking into
account the known inertness of alkanes.
Table. 1 here
Table 2 here
Fig. 1 here
Parameters of regio- and bond selectivity (1:7:7:6 for n-heptane, 1:10:33 for methylcyclohexane)
indicate that the reaction occurs with the participation of hydroxyl radicals. In accordance with this
assumption, the oxidation of cis- and trans-isomers of 1,2-dimethylcyclohexane is not stereospecific
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(Appendix A. Supplementary data, Table S1). In the alkane oxidation, samples of the reaction solutions
were analyzed by GC by applying a simple method developed earlier by some of us [8,27,28] which uses
PPh3 (see Experimental). Fig. 1 and Tables 1 and 2 demonstrate that the ferrocene-catalyzed oxidation of
alkanes, RH, affords predominantly the alkyl hydroperoxides, ROOH, whereas the ketones and alcohols
are formed in lower concentrations.
The rate dependence of cyclohexane oxygenation in the presence of the ferrocene/PCA combination is
first-order in hydrogen peroxide and second-order in the initial ferrocene (Fig. 2). The dependence of the
initial oxidation rate W0 is second-order in PCA at its low (< 2 × 10–3 M) concentrations. This dependence
has maximum (Fig. 3), thus suggesting the possible formation of adducts with PCA. The mode of
dependence of the initial cyclohexane oxidation rate on the initial cyclohexane concentration (W0 is
approaching to a plateau at high concentrations of cyclohexane, see Fig. 4) indicates that hydroxyl
radicals as oxidizing species competitively interact both with cyclohexane (CyH) and acetonitrile [13,
23]. Indeed, it follows from Fig. 4 that the ratio of constants kMeCN and kCyH for the interaction of
oxidizing species with MeCN and CyH, respectively, is equal to kMeCN[MeCN]/kCyH = 0.011 M which is
the typical for hydroxyl radicals value [13, 23].
The simplest kinetic scheme of the alkane oxygenation which is in agreement with obtained in our
work kinetic data (see Figs. 2–4) is shown below. In the first stage ferrocene is oxidized to ferricenium
cation (FeCp2)+ which in turn is transformed into species Fe, where Fe is a fragment containing one iron
ion. The formation of (FeCp2)+ is supported by the visible spectra obtained for the reaction mixture in the
initial period of the reaction: a growing with time peak at = 625 nm corresponds to the absorption of
ferricenium cation (see Fig. S1).
H+
FeCp2 + H2O2
(FeCp2)+
(FeCp2)+ → Fe
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Two reactions written above are the fast stages of the generation from FeCp2 and H2O2 the main species
active in the catalytic process. Fragment Fe produced in these two consecutive reactions interacts with a
PCA molecule to form complex Fe(PCA):
Fe + PCA
Fe(PCA)
(K1)
Here (PCA) is a PCA fragment (possibly pyrazinecarboxylate). The formed complex can react with the
second PCA molecule giving in this case an adduct containing two PCA fragments per one Fe ion:
Fe(PCA) + PCA
Fe(PCA)2
(K2)
Two adducts Fe(PCA) can dimerize to afford the dinuclear complex Fe2(PCA)2:
Fe(PCA) + Fe(PCA)
Fe2(PCA)2
(K3)
Dinuclear iron complexes are known to take part in alkane oxygenations with hydrogen peroxide [12,13].
We assume that complex Fe2(PCA)2 is a catalytically active species which produces hydroxyl radicals
from H2O2:
Fe2(PCA)2 + H2O2 → HO•
(k4)
Hydroxyl radicals react in parallel routes with solvent (acetonitrile) and substrate (cyclohexane, RH):
HO• + MeCN → products
(k5)
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HO• + RH → ... → ROOH
(k6)
The last reaction is the rate limiting step in the sequence of alkane transformations into cyclohexyl
hydroperoxide. Assuming that concentration of HO• is steady-state and concentrations of iron all
complexes are in quasi-equilibrium and taking into account conditions [Fe(PCA)] << [FeCp2]0 and
[Fe2(PCA)2] << [FeCp2]0 (that is K1 and K2 are low values) we come to the equation for the initial
reaction rate:
k4[Fe2(PCA)2][H2O2]0
W0 =
1 + k5[MeCN]/k6[RH]0
where [Fe2(PCA)2] = K3[Fe(PCA)]2
K1[FeCp2]0[PCA]0
and [Fe(PCA)] =
2
1 + K1K2[PCA]0
We can rewrite the equation for the initial reaction rate in the following form:
2
PCA]0
W0 =
2 2
(1 + [PCA]0 )
k4[H2O2]0(K1[FeCp2]0)2
here
=
1 + k5[MeCN]/k6[RH]0
and = K1K2
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For conditions of our experiments values = 30 M–1 s–1 and = 1.1 × 105 M–2. Using these values of
parameters and the initial reaction rates (presented by a dotted curve) have been calculated at
different concentrations of PCA under conditions described in the caption to Fig. 3. It can be seen that the
simulated curve coincides closely with the experimental curve. This testifies that our kinetic scheme
adequately reflects the real reaction.
tert-Butyl hydroperoxide (0.58 M; 70% aqueous) oxidizes cyclohexane (0.92 M) in MeCN at 50
ºC in the presence of ferrocene (1 × 10–3 M) and PCA (25 × 10–3 M) affording (after reduction with PPh3)
cyclohexanol (0.02 M) and cyclohexanone (0.001 M) after 4.5 h.
It is noteworthy that pyridine-2,3-dicarboxylic acid is substantially less efficient whereas picolinic acid
is almost inactive as co-catalysts in the oxidation induced by ferrocene. In the presence of 2,2’-bipyridine
(3 × 10–3 M) instead of PCA and ferrocene (5 × 10–4 M) the oxidation of cyclohexane (0.37 M) with H2O2
(1.2 M) occurs with a long induction period affording the oxygenates (0.028 M) after 200 min.
2–
We have also found the first example of alkane hydrocarboxylation with the CO/S2O8 /H2O system
promoted by an iron complex, i.e., ferrocene. In contrast to the alkane oxidation, this transformation does
not require the presence of PCA. Thus, the reaction of an alkane (RH) with CO and H2O in the presence
of K2S2O8 in neutral H2O–CH3CN medium at 60 ºC affords the corresponding carboxylic acid (RCOOH).
Linear alkanes (propane, n-butane, n-pentane, n-hexane and n-heptane) containing primary and secondary
carbon atoms lead to the formation of two to four isomeric acids (Table 3, Fig. S2). The carboxylation
reactions at secondary carbon atoms give branched acids which are formed in higher concentrations than
linear acids. This is reflected by the C(1) : C(2) : C(3) : C(n) regioselectivity parameters (normalized for
the relative number of hydrogen atoms) of 1 : 15: 14 (for n-C5H12), 1 : 15: 15 (for n-C6H14) and 1 : 18 : 18
: 18 (for n-C7H16). Only one carboxylic acid product is detected in the hydrocarboxylation of alkanes
bearing a single type of carbon atom, e.g., ethane and cyclohexane (Table 3). In the latter case, a small
amount of cyclohexanone and cyclohexanol (total yield of 1.1% after reduction of the reaction solution
6

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with PPh3) is also obtained due to the partial oxidation of alkane. In the hydrocarboxylation reactions
promoted by ferrocene, the maximum total yield of carboxylic acid products attains 60% (based on
alkane) for propane, followed by the 21% yield for n-butane. Other tested alkanes result in inferior yields
of carboxylic acids, namely 18.3% (for cyclohexane), 15% (for ethane), 12.6% (for n-pentane), 9.2% (for
n-heptane) and 8.3% (for n-hexane). Taking into consideration the previous background [31–35] and the
obtained herein experimental data (i.e., selectivity parameters typical for free-radical transformations with
the participation of a sulfate radical derived from K2S2O8), the present hydrocarboxylation reactions are
believed to proceed via a free-radical mechanism.
Table 3 here
3. Conclusions
We have discovered that alkanes can be easily oxidized with H2O2 or tert-BuOOH under mild
homogeneous conditions to the corresponding alkyl hydroperoxides in the presence of catalytic amounts
of ferrocene and pyrazine-2-carboxylic acid (PCA). Ferrocene has been also found to be a promoter of the
2–
alkane hydrocarboxylation with the CO/S2O8 /H2O system in aqueous acetonitrile. This work opens new
horizons in applications of organometallic compounds in oxidation catalysis.
4. Experimental
Ferrocene and co-catalyst were used in the form of stock solutions in MeCN. Aliquots of these
solutions were added to the reaction mixtures in alkane oxidations. The reactions of alkanes with H2O2
(50% aqueous) were typically carried out in air in thermostated (50 ºC) Pyrex cylindrical vessels with
vigorous stirring (CAUTION: the combination of air or molecular oxygen and H2O2 with organic
compounds at elevated temperatures may be explosive!). The reactions were stopped by cooling, and
typically analyzed twice, i.e., before and after the addition of an excess of solid PPh3. This method was
developed previously by some of us [8,27,28] for the analysis of reaction mixtures obtained from various
7

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alkane oxidations. In the case of the formation of the corresponding alkyl hydroperoxides as the main
products, if an excess of solid PPh3 is added to a sample of the reaction solution, ca. 10 min before GC
analysis, the alkyl hydroperoxide present is completely reduced to the corresponding alcohol. As a result,
the chromatogram differs from that of a sample not subjected to the reduction: the alcohol peak rises,
while the intensity of the ketone peak decreases. A Fisons Instruments GC 8000 series gas chromatograph
with a capillary column 30 m × 0.22 mm × 25 m, BP20 (SGE) (helium was the carrier gas; the internal
standard was nitromethane) was used.
The oxidations of gaseous alkanes with H2O2 were carried out in a 13 mL stainless steel autoclave,
equipped with a Teflon-coated magnetic stirring bar. In a typical experiment, after additions of all liquid
reagents in the form of stock solutions in acetonitrile, the autoclave was closed and pressurized with
gaseous alkane (typically 20.0, 6.0 or 0.7 atm of CH4 and C2H6, C3H8 or n-C4H10, respectively). The
reaction mixture was stirred for 4 h at 50 °C using a magnetic stirrer and an oil bath, whereupon it was
cooled in an ice bath, degassed, opened and transferred to a flask for GC analysis.
The hydrocarboxylation experiments were performed following the previously developed protocol
[31–35]. The reaction mixtures were placed into a 13.0-mL stainless steel autoclave, equipped with a
Teflon-coated magnetic stirring bar. Then the autoclave was closed and flushed with CO three times for
removing the air and finally pressurized with CO (CAUTION: Due to the toxicity of CO, the heating
oven should be located in a well-ventilated hood!) The reaction mixture was stirred using a magnetic
stirrer and an oil bath, whereupon it was cooled in an ice bath, degassed, opened and the contents
transferred to a flask. Diethyl ether and cycloheptanone (GC internal standard) were added. The obtained
mixture was vigorously stirred for 10 min, and the organic layer was analyzed typically by GC [a Fisons
Instruments GC 8000 series gas chromatograph equipped with 30 m × 0.22 mm × 25 m, BP20 (SGE)
capillary column (helium was the carrier gas) and the Jasco-Borwin v.1.50 software] (see Fig. S2).
Acknowledgements
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The authors thank the Russian Foundation for Basic Research (12-03-00084-a) and the Fundação
para a Ciência e a Tecnologia, FCT (PTDC/QUI-QUI/102150/2008; PEst-OE/QUI/UI0100/2011;
SFRH/BPD/34926/2007) for support.
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://xxxxxxxx
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Tables
Table 1. Oxygenation of light alkanes by the 1/PCA/H2O2 system a
___________________________________________________________
Alkane
(mmol)
___________________________________________________________
Products
before PPh3 after PPh3 Total yield Total
(M) (M) (%) TON
n-Butane MeCOEt
(0.22) EtCH(OH)Me
EtCH2CHO
0.015
0.0097
0.0064
0.0015
0.0019
0.0005
58
253
0.0034
0.0026
0.0009
0.0005
EtCH2CH2OH
EtCH2COOH
Propane MeCOMe
(1.9)
0.0097
0.0022
0.0046
0.001
0.0029
0.0145
0.000
7
8
267
970
MeCH(OH)Me
MeCH2CHO
MeCH2CH2OH
0.0081
Ethane
(6.5)
MeCHO
EtOH
MeCOOH
0.0585
0.0273
0.014
0.0169
0.065
0.015
a Conditions. Concentrations: ferrocene, 1 × 10–4 M; H2O2, 1.28 M; PCA,
25 × 10–4 M. Solvent was acetonitrile, 50 °C, 4 h. Total volume of the
reaction solution was 5 mL. Volume of the autoclave was 13 mL.
Concentrations of the products were measured before and after reduction
with PPh3. Yield is based on the alkane.
________________________________________
Table 2. Oxygenation of ethane by the 1/PCA/H2O2 system a
___________________________________________________________
Time (h) Products
___________________________________________________________
before PPh3 (M)
after PPh3 (M)
1
2
MeCHO
EtOH
MeCOOH
0.0012
0.000
0.0024
0.000
0.0015
0.002
MeCHO
EtOH
MeCOOH
0.018
0.0046
0.0016
0.002
0.015
0.002
4
MeCHO
EtOH
MeCOOH
0.0585
0.0273
0.014
0.0169
0.065
0.015
20
46
MeCHO
EtOH
MeCOOH
0.067
0.0146
0.008
0.053
0.0246
0.009
MeCHO
EtOH
MeCOOH
0.022
0.012
0.055
0.021
0.009
0.046
a Conditions. Concentrations: ferrocene, 1 × 10–4 M; H2O2, 1.28 M; PCA,
25 × 10–4 M. Solvent was acetonitrile, 50 °C. Total volume of the reaction
solution was 5 mL. Volume of the autoclave was 13 mL. In the absence of
ethane (blank experiment) concentration of MeCOOH (formed from
MeCN) was 0.002 M after 4 h.
___________________________________________________________
12

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Table 3. Hydrocarboxylation of alkanes by the 1/PCA/CO/K2S2O8 system a
___________________________________________________________
Alkane b
(atm; mmol)
CO
(atm)
Products
Yield Total
(%) yield (%)
___________________________________________________________
Ethane
10
1 c
20
10
EtCOOH
EtCOOH
9
15
9
15
Propane
6
20
10
Me2CHCOOH
Me(CH2)2COOH
Me2CHCOOH
Me(CH2)2COOH
17
2
51
9
19
60
1 c
n-Butane
0.75 c
10
20
EtCH(Me)COOH
Me(CH2)3COOH
19
2
21
n-Pentane d
1.0
Me(CH2)4COOH
MeCH(COOH)(CH2)2Me
EtCH(COOH)Et
0.8 12.6
8.2
3.6
n-Hexane d
1.0
20
20
Me(CH2)5COOH
MeCH(COOH)(CH2)3Me
EtCH(COOH)(CH2)2Me
0.4
4.0
3.9
8.3
9.2
n-Heptane d
1.0
Me(CH2)6COOH
MeCH(COOH)(CH2)4Me
EtCH(COOH)(CH2)3Me
0.3
3.6
3.5
Me(CH2)2CH(COOH)(CH2)2Me 1.8
Cyclohexane e
1.0
20
cyclo-C6H11COOH
cyclo-C6H11OH
cyclo-C6H10O
18.3 19.4
0.8
0.3
a Conditions. Amounts: ferrocene, 4 × 10–3 mmol; K2S2O8, 1.5 mmol;
Solvent was MeCN, 4 mL; H2O, 2 mL; 60 °C, 4 h. Volume of the autoclave
was 13 mL. Yield is based on the alkane. b Amounts as pressure for
gaseous ethane, propane and n-butane and as mmol for other alkanes are
given. c K2S2O8, 1.0 mmol. d Regioselectivity parameters
C(1):C(2):C(3):C(4) for pentane, hexane and heptane are 1:15:14; 1:15:15
and 1:18:18:18, respectively. e At 50 °C; CH3CN, 3 mL; H2O, 3 mL.
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Figures
0.08
0.06
OOH
OH
O
0.04
0.02
0.00
0
1
2
3
0.05
0.04
0.03
0.02
OOH
OH
O
0.01
0.00
0
10
20
Time (h)
Fig. 1. Oxidation of cyclohexane (0.37 M) with H2O2 (0.64 M; 50% aqueous) in the presence of ferrocene
(1 × 10–4 M) and PCA (25 × 10–4 M) in MeCN at 50 ºC (top) and 20 ºC (bottom). Concentrations of the
three products (cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone) were calculated from the
concentrations of cyclohexanol and cyclohexanone measured before and after reduction with PPh3 (for
this method, see [8,27,28]).
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20
16
12
8
1
16
12
2
8
4
4
0
0
0
2
4
6
8
104 [FeCp2]0 (M)
Fig. 2. Dependence of the initial rate W0 of oxygenates accumulation in the cyclohexane oxidation with
H2O2 in the presence of ferrocene in MeCN on the initial concentration of ferrocene (curve 1).
Conditions: [PCA]0 = 3 × 10−3 M, [H2O2]0 = 0.32 M, [cyclohexane]0 = 0.37 M, 50 °C. Curve 2:
½
linearization of curve 1 in coordinates [FeCp2]0–W0 .
Fig. 3 Dependence of the initial rate W0 of oxygenates accumulation in the cyclohexane oxidation with
H2O2 in the presence of ferrocene in MeCN on the initial concentration of PCA in the intervals 0–10 ×
10–3 M (curves 1 and 1a) and 0–2 × 10–3 M (curves 2 and 2a). Conditions: [FeCp2]0 = 5.0 × 10−4 M,
[H2O2]0 = 0.32 M, [cyclohexane]0 = 0.37 M, 50 °C. Dotted curves 1a and 2a present the simulated
dependence.
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Fig. 4. Curve 1: dependence of the initial rate W0 of oxygenates accumulation in the cyclohexane
oxidation with H2O2 in the presence of ferrocene in MeCN on the initial concentration of cyclohexane.
Conditions: [FeCp2]0 = 5.0 × 10−4 M, [PCA]0 = 3.0 × 10−3 M, [H2O2]0 = 0.32 M, 50 °C. Straight line 2:
linearization of the dependence presented by curve 1 in coordinates (1/W0)–(1/[PCA]0).
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Captions to Figures:
Fig. 1. Oxidation of cyclohexane (0.37 M) with H2O2 (0.64 M; 50% aqueous) in the presence of ferrocene
(1 × 10–4 M) and PCA (25 × 10–4 M) in MeCN at 50 ºC (top) and 20 ºC (bottom). Concentrations of the
three products (cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone) were calculated from the
concentrations of cyclohexanol and cyclohexanone measured before and after reduction with PPh3 (for
this method, see [8,27,28]).
Fig. 2. Dependence of the initial rate W0 of oxygenates accumulation in the cyclohexane oxidation with
H2O2 in the presence of ferrocene in MeCN on the initial concentration of ferrocene (curve 1).
Conditions: [PCA]0 = 3 × 10−3 M, [H2O2]0 = 0.32 M, [cyclohexane]0 = 0.37 M, 50 °C. Curve 2:
½
linearization of curve 1 in coordinates [FeCp2]0–W0 .
Fig. 3 Dependence of the initial rate W0 of oxygenates accumulation in the cyclohexane oxidation with
H2O2 in the presence of ferrocene in MeCN on the initial concentration of PCA (in the intervals 0–10 ×
10–3 M and 0–2 × 10–3 M). Conditions: [FeCp2]0 = 5.0 × 10−4 M, [H2O2]0 = 0.32 M, [cyclohexane]0 = 0.37
M, 50 °C. Dotted curves present the simulated dependence.
Fig. 4. Curve 1: dependence of the initial rate W0 of oxygenates accumulation in the cyclohexane
oxidation with H2O2 in the presence of ferrocene in MeCN on the initial concentration of cyclohexane.
Conditions: [FeCp2]0 = 5.0 × 10−4 M, [PCA]0 = 3.0 × 10−3 M, [H2O2]0 = 0.32 M, 50 °C. Straight line 2:
linearization of the dependence presented by curve 1 in coordinates (1/W0)–(1/[PCA]0).
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Graphical Abstract:
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Ref. CATCOM-D-12-00836, Revised in accord with the suggestions of Reviewers and Editor
Catalysis Communications
Mild oxidative alkane functionalization with peroxides in the presence of ferrocene
Georgiy B. Shul’pin a,*, Marina V. Kirillova b,*, Lidia S. Shul’pina c, Armando J.L. Pombeiro*,b,
Eduard E. Karslyan b,c, Yuriy N. Kozlov a
Highlights
Combination H2O2/ferrocene/pyrazinic acid oxygenates alkanes.
Turnover numbers were up to 1200.
2–
The ferrocene/CO/S2O8 /H2O system transforms RH into RCOOH.
The oxidation proceeds with the participation of free radicals.
24