Oxidations catalyzed by osmium compounds. Part 1: Efficient alkane oxidation with peroxides catalyzed by an olefin carbonyl osmium(0) complex

Article abstract of DOI:10.1016/j.jorganchem.2005.10.028

A carbonyl osmium(0) complex with π-coordinated olefin, (2,3-η-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium (1), efficiently catalyzes oxygenation of alkanes (cyclohexane, cyclooctane, n-heptane, isooctane, etc.) with hydrogen peroxide, as well as with tert-butyl hydroperoxide and meta-chloroperoxybenzoic acid in acetonitrile solution. Alkanes are oxidized to corresponding alcohols, ketones (aldehydes) and alkyl hydroperoxides. Thus, heating cyclooctane with the 1-H₂O₂ combination at 70 °C gave products with turnover number as high as 2400 after 6 h. The maximum obtained yield of all products was equal to 20% based on cyclohexane and 30% based on H₂O₂. The oxidation of linear and branched alkanes exhibits very low regio- and bond-selectivity parameters and this testifies that the reaction proceeds via attack of hydroxyl radicals on C-H bonds of the alkane. The oxygenation products were not formed when the reaction was carried out under argon atmosphere and it can be thus concluded that the oxygenation occurs via the reaction between alkyl radicals and atmospheric oxygen. In summary, the Os(0) complex is much more powerful generator of hydroxyl radicals than any soluble derivative of iron (which is an analogue of osmium in the Periodic System).

Full text of DOI:10.1016/j.jorganchem.2005.10.028

Journal of Organometallic Chemistry 691 (2006) 837–845
www.elsevier.com/locate/jorganchem
Oxidations catalyzed by osmium compounds. Part 1: Efficient
alkane oxidation with peroxides catalyzed by an olefin
carbonyl osmium(0) complex
a,
b
b
b
Georgiy B. Shul’pin *, Aleksandr R. Kudinov , Lidia S. ShulÕpina , Elena A. Petrovskaya
a
Kinetics and Catalysis, Semenov Institute of Chemical Physics, Russian Academy of Sciences, ulitsa Kosygina, dom 4, Moscow 119991, Russia
b
Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ulitsa Vavilova, dom 28, Moscow 119991, Russia
Received 16 July 2005; accepted 25 October 2005
Available online 1 December 2005
Abstract
A carbonyl osmium(0) complex with p-coordinated olefin, (2,3-g-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium
(1), efficiently catalyzes oxygenation of alkanes (cyclohexane, cyclooctane, n-heptane, isooctane, etc.) with hydrogen peroxide, as well as
with tert-butyl hydroperoxide and meta-chloroperoxybenzoic acid in acetonitrile solution. Alkanes are oxidized to corresponding alco-
hols, ketones (aldehydes) and alkyl hydroperoxides. Thus, heating cyclooctane with the 1–H2O2 combination at 70 ꢀC gave products with
turnover number as high as 2400 after 6 h. The maximum obtained yield of all products was equal to 20% based on cyclohexane and 30%
based on H2O2. The oxidation of linear and branched alkanes exhibits very low regio- and bond-selectivity parameters and this testifies
that the reaction proceeds via attack of hydroxyl radicals on C–H bonds of the alkane. The oxygenation products were not formed when
the reaction was carried out under argon atmosphere and it can be thus concluded that the oxygenation occurs via the reaction between
alkyl radicals and atmospheric oxygen. In summary, the Os(0) complex is much more powerful generator of hydroxyl radicals than any
soluble derivative of iron (which is an analogue of osmium in the Periodic System).
ꢁ 2005 Elsevier B.V. All rights reserved.
Keywords: Alkanes; Homogeneous catalysis; Hydrogen peroxide; Organometallic compounds; Osmium complexes; Oxidation
1. Introduction
presence of pyrazin-2-carboxylic acid [33]. Metal-catalyzed
alkane oxidations in solutions give directly valuable prod-
ucts such as alkyl hydroperoxides, alcohols, ketones, and
carboxylic acids under mild conditions (see, for example,
recent reviews [34,35]). It is interesting to note that
although iron plays an extremely important role in oxida-
tions occurring in living cells (e.g., cytochrome P450
[1,2,36] and methanemonooxygenase, MMO [1,2,37–39])
iron complexes and especially simple salts of this metal
do not usually exhibit high activity in oxidations in vitro.
Turnover numbers (TONs) in alkane oxidations are typi-
cally attain values only of 20–100 [34,35,40–45]. Thus,
TONs in FeCl3-catalyzed ‘‘Gif oxidations’’ (i.e., in the
presence of pyridine) have been reported to equal values
not higher than 1–20 [46]. Iron complexes (especially poly-
nuclear derivatives) containing N-ligands are more power-
ful catalysts [40–45,47]. As for the classical Fenton reagent
Saturated hydrocarbons, alkanes, are known to exhibit
only very low reactivity in reactions with variety of normal
reagents and in many cases the yields of the products are
negligible. In last decades, new methods of alkane func-
tionalization with participation of various transition metal
complexes in solutions have been discovered and developed
(see recent books and reviews [1–10]) and original publica-
tions [11–28]. Organometallic derivatives of transition met-
als very seldom exhibit high activity in alkane oxygenations
[29,30]. A remarkable example is methyltrioxorhenium
(MTO) [31,32] which efficiently oxidizes alkanes in the
*
Corresponding author.
E-mail address: shulpin@chph.ras.ru (G.B. Shul’pin).
URL: http://members.fortunecity.com/shulpin (G.B. Shul’pin).
0022-328X/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.10.028

838
G.B. Shul’pin et al. / Journal of Organometallic Chemistry 691 (2006) 837–845
[48–55], i.e., the Fe(II)–H2O2 combination, is concerned,
the efficiency of oxidation by this stoichiometric system is
very low and usually the reaction proceeds non-selectively
giving a variety of products (see also [47]). Catalytic system
FeCl3–H2O2 is also not efficient in alkane oxidation in ace-
tonitrile [42]. All these processes proceed with formation of
free hydroxyl radicals [48–62]. It should be also noted that
oxidations of alkanes, RH, with participation of cyto-
chrome P450 and MMO are believed to include in the cru-
cial step an abstraction of a hydrogen atom to produce an
alkyl radical, RÅ, which is involved into subsequent trans-
formations. One cannot exclude that this radical adds (at
least partly) molecular oxygen affording hydroperoxyl rad-
ical, ROOÅ.
It was interesting to compare catalytic activity of deriva-
tives of ruthenium and osmium which are analogues of iron
in the Periodic System. Surprisingly, although osmium-cat-
alyzed oxidation reactions of olefins [63–73] and alcohols
[74–78] have been reported and are used in organic synthe-
sis, much less is known about catalysis of alkane transfor-
mations by soluble osmium compounds [79–82]. Oxide of
high-valent osmium, OsO4 [79], and osmium chlorides [80]
have been used in alkane oxidations with hydrogen perox-
ide in organic solvents. Very recently, Mayer and co-work-
ers described [81] stoichiometric and catalytic oxidations of
alkanes with OsO4. This osmium derivative has been used as
a catalyst in oxidation of isobutane with NaIO4 in aqueous
solution (pH ꢀ 4.3; 168 h at 85 ꢀC), TON being only ca. 4.
Cyclohexene was oxidized by molecular oxygen or tert-
butyl hydroperoxide (TBHP) in the presence of osmium
carbonyl clusters supported on polymer matrices [82].
Acetonitrile was used as a solvent and reactions were car-
ried out in air at 50–70 ꢀC. The oxygenation of cyclic, linear
and branched alkanes, RH, gives rise to the formation of
the corresponding alkyl hydroperoxides, ROOH, as the
main primary products which further gradually decompose
to yield more stable products, the ketones (aldehydes) and
alcohols. The formation of alkyl hydroperoxides in addition
to the corresponding alcohols and ketones was demon-
strated employing a method previously used by us and
which is based on the GC analysis [2,34,84–87]. Usually
alkyl hydroperoxides are decomposed in the chromato-
graph to produce corresponding alcohol and ketone. If tri-
phenylphosphine is added to the reaction solution ca.
10 min before the 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). Comparing the
intensities of peaks attributed to the alcohol and ketone
before and after the reduction, it is possible to estimate
the real concentrations of the three products (i.e., alcohol,
ketone and alkyl hydroperoxide) present in the reaction
solution. In our kinetic studies presented below, we mea-
sured the concentrations of the cyclohexanone and cyclo-
hexanol only after the reduction with PPh3 because in this
case we obtained more precise values of the initial rates.
Kinetics of the cyclohexane, CyH, oxidation in homoge-
neous solution in acetonitrile are presented in Fig. 1. It can
be seen that the corresponding alcohol, ketone and alkyl
hydroperoxide are formed in comparable amounts. Turn-
over number under these conditions attains 550 (Table 1,
entry 1). When catalyst 1 was used in higher concentration
the TON became lower (entry 2) but in this case the max-
imum yield of all products was obtained: the concentration
of oxygenates attained 0.175 mol dmꢁ3 which corresponds
to yield of 20% based on cyclohexane and of 30% based on
H2O2 (assuming that two molecules of H2O2 are required
to produce one molecule of CyOOH). The highest TON
2. Results and discussion
In this work, we have found that p-olefin osmium(0)
complex, (2,3-g-1,4-diphenylbut-2-en-1,4-dione)undeca-
carbonyl triangulotriosmium (1), efficiently catalyses oxy-
genation of alkanes with hydrogen peroxide, as well as
with tert-butyl hydroperoxide (TBHP) and meta-chlorop-
eroxybenzoic acid (MCPBA). Complex 1 was synthesized
as described previously [83] starting from Os3(CO)11-
(MeCN) and trans-1,4-diphenylbut-2-ene-1,4-dione. The
structure of 1 was determined by the X-ray method [83].
2
x
6
x
4
2
0
3
CO
CO
OC
OC
c
x
Os
OC
CO
x
1
Os
OC
Os
OC
OC
O
CO
CO
0
1
2
3
4
time (h)
O
Fig. 1. Accumulation of oxygenates (concentrations, c, of cyclohexanone,
curve 1; cyclohexanol, curve 2; cyclohexyl hydroperoxide, curve 3, are
given) in the cyclohexane (initial concentration 1.38 mol dmꢁ3) oxidation
with H2O2 (1.4 mol dmꢁ3) catalyzed by 1 (2 · 10ꢁ4 mol dmꢁ3). Condi-
tions: solvent MeCN; homogeneous solution at 60 ꢀC.
Complex 1

G.B. Shul’pin et al. / Journal of Organometallic Chemistry 691 (2006) 837–845
839
Table 1
Efficiency of cycloalkane oxidation with H2O2 catalyzed by 1
Entry
Alkane
Media
1
Temperature (ꢀC)
Time (h)
TONa
1
2
3
4
5
a
Cyclohexane
Cyclohexane
Cyclohexane
Cyclooctane
Cyclooctane
MeCN
MeCN
MeCN
MeCN–H2Ob
H2Oc
2 · 10ꢁ4 mol dmꢁ3
5 · 10ꢁ4 mol dmꢁ3
5 · 10ꢁ5 mol dmꢁ3
5 · 10ꢁ5 mol dmꢁ3
2 · 10ꢁ5 mmol
60
60
60
70
70
4
14
2
6
6
550
350
900
2400
420
TON, turnover number, i.e., total moles of products produced per one mole of a catalyst.
Cyclooctane (0.5 mL) was partly insoluble in the reaction solution containing 0.4 mL 35% H2O2 and 0.8 mL MeCN.
The reaction was carried out in a two-phase system, volume of aqueous solution was 1 mL, volume of cyclooctane was 1 mL.
b
c
(2400) was attained when low concentration of 1 and large
amount of cyclooctane was used (entry 4). We have also
found that the efficient oxidation occurs in a biphasic sys-
tem in the absence of any organic solvent (entry 5).
We have studied dependences of the initial rates in the
cyclooctane oxidation on the concentrations of reactants.
The initial rate is proportional to the concentration of 1
(Fig. 2) and first order has been also found for hydrogen
peroxide (Fig. 3). The dependence of the initial hydrocar-
bon oxidation rate on the initial cyclooctane concentra-
tion (Fig. 4) exhibits a plateau when [cyclooctane]0 >
0.1 mol dmꢁ3. Such behaviour has been earlier explained
[42] by competition between cycloalkane and acetonitrile
for the interaction with an active oxidizing species (which
is most probably hydroxyl radical; see below). Generally
speaking, acetonitrile is not completely inert solvent in
this reaction and can be transformed into certain products
with low yields [88,89].
In order to get a mechanistic understanding of this oxi-
dation process, we studied the oxidation of some linear and
branched alkanes. The results are summarized in Tables 2
and 3. Table 2 demonstrates concentrations of all products
formed in the oxidation of normal heptane and gives also
the regioselectivity parameters C(1):C(2):C(3):C(4) for dif-
ferent times of the reaction. In addition to these parameters
for n-hexane and n-heptane, bond selectivity parameters,
1ꢀ:2ꢀ:3ꢀ, are given in Table 3 for the oxidation of some
branched alkanes (3-methylhexane, methylcyclohexane
and 2,2,4-trimethylpentane). Normalized parameters in
Table 3 have been calculated based only on concentrations
of isomeric alcohols obtained after reduction of the reac-
tion mixture with triphenylphosphine. This table contains
also stereoselectivity parameters trans/cis obtained for the
oxidation of disubstituted cyclohexanes (cis-1,2-dimethyl-
cyclohexane and cis-decalin).
5
4
3
2
W
1
0
2
4
6
8
10
0
[catalyst 1] × 104 (mol dm−3
)
Fig. 2. Dependence of the initial rate of cyclooctane oxidation on the
initial concentration of 1. Conditions: cyclooctane, 0.35 mol dmꢁ3; H2O2,
0.6 mol dmꢁ3; solvent MeCN; 70 ꢀC.
To compare selectivity parameters, the corresponding
data for some other systems are also given in Table 3.
Thus, it is believed that the alkane oxidation by reagent
6
4
6
4
(
2
W
2
W
0
0
0
0.1 0.2 0.3 0.4 0.5 0.6
[H2O2]0 (mol dm−3
0
0.1
0.2
0.3
0.4
)
[cyclooctane]0 (mol dm−3
)
Fig. 3. Dependence of the initial rate of cyclooctane oxidation on the
initial concentration of hydrogen peroxide. Conditions: cyclooctane,
0.35 mol dmꢁ3; 1, 2 · 10ꢁ4 mol dmꢁ3; solvent MeCN; 70 ꢀC.
Fig. 4. Dependence of the initial rate of cyclooctane oxidation on the
initial concentration of cyclooctane. Conditions: H2O2, 0.6 mol dmꢁ3; 1,
2 · 10ꢁ4 mol dmꢁ3; solvent MeCN; 70 ꢀC.

840
G.B. Shul’pin et al. / Journal of Organometallic Chemistry 691 (2006) 837–845
Table 2
Oxidation of n-heptane with H2O2 catalyzed by 1a
Time (h)
Concentration (mmol dmꢁ3
)
Regioselectivityb
al
one-2
one-3
one-4
ol-1
ol-2
ol-3
ol-4
Heptanoic acid
0.5
1.0
3.0
8.0
a
0.04
0.15
0.70
0.65
0.22
0.25
0.50
2.60
0.17
0.22
0.44
2.50
0.09
0.11
0.20
1.10
0.10
0.20
0.23
0.40
0.15
0.20
0.20
1.80
0.16
0.20
0.17
1.60
0.06
0.08
0.10
0.74
0.05
0.05
0.10
0.16
1.0:3.0:2.6:2.4
1.0:1.7:1.6:1.4
1.0:1.0:0.9:0.9
1.0:5.5:5.0:4.6
Reaction conditions: n-heptane, 0.9 mol dmꢁ3; H2O2, 1.2 mol dmꢁ3; 1, 1 · 10ꢁ4 mol dmꢁ3; solvent MeCN; homogeneous solution at 60 ꢀC.
Relative reactivities of hydrogen atoms at carbons 1, 2, 3 and 4, C(1):C(2):C(3):C(4), of the n-heptane chain. The parameters were normalized, i.e.,
b
calculated taking into account the number of hydrogen atoms at each carbon.
‘‘H2O2–VOꢁ–pyrazine-2-carboxylic acid’’ (see [1,2,10,34,
Os(III) + H2O2 ! Os(II) + HOOÅ + Hþ
3
35,90–93]) proceeds via the formation of hydroxyl radicals
which attack C–H bonds of the alkane. Oxidations with
H2O2 induced by irons salts Fe(ClO4)3 and FeSO4 as well
as the reaction stimulated by UV irradiation also occur
with the formation of HOÅ radicals. On the contrary,
alkane oxygenation by the ‘‘H2O2–[(TMTACN)MnIV(O3)-
MnIV(TMTACN)]2+–CH3COOH’’ system (see [2,10,34,35,
94–98]) apparently involves the interaction of the C–H
bonds with MnV@O species. It follows from Tables 2 and
3 that the oxidations by the ‘‘H2O2–1’’ system exhibit very
low selectivities for linear and branched alkanes and the
reaction with cis-decalin is not stereoselective. For exam-
ple, regioselectivity in the n-heptane oxygenation by this
system in MeCN (ca. 1:5:5:5; compare with the value for
the photoinduced reaction, 1:7:6:7) is noticeably lower than
the corresponding parameter (1:46:35:35) for the ‘‘H2O2–
[(TMTACN)MnIV(O3)MnIV(TMTACN)]2+–CH3COOH’’
system. These data testify clearly that 1-catalyzed alkane
oxygenation proceeds mainly with participation of free
hydroxyl radicals.
The ‘‘1–H2O2’’ system oxidizes also benzene in acetoni-
trile solution at 60 ꢀC. Phenol (TON = 500) and quinone
(TON = 300) were detected in the reaction mixture after
3 h. Ethylbenzene was oxidized under similar conditions
mainly to a mixture of ethylbenzene hydroperoxide, 1-
phenylethanol and acetophenone. It is important to note
that experiments on ethylbenzene oxidations at 70 ꢀC in
atmosphere of either argon or air gave absolutely different
results. Only traces of oxygenates have been found in the
reaction mixture after heating in an argon atmosphere.
On the contrary, when a slow stream of air was passed
through the reaction solution ethylbenzene reacted with
high conversion. As the reaction does not proceed in an
argon atmosphere it can be concluded that catalyst 1 does
not induce a substantial decomposition of hydrogen perox-
ide to yield dioxygen.
Other Os(n)–Os(n+1) pairs can also operate in such type
cycles, for example, the Os(III)–Os(IV) pair. Hydroxyl rad-
icals attack C–H bonds in accordance with equation:
RH + HOÅ = RÅ + H2O
Alkyl radicals add rapidly molecular oxygen from
atmosphere:
RÅ + O2 = ROOÅ
Peroxyl radicals can be reduced with a Ôlow-valentÕ osmium
species, for example:
ROOÅ + Os(II) = ROOꢁ + Os(III)
and after addition of a proton are transformed into the pri-
mary reaction product, alkyl hydroperoxide:
ROOꢁ + Hþ = ROOH
Aqueous solution of TBHP can be also used as an oxidant
instead of hydrogen peroxide. The reaction withcyclohexane
affords mainly cyclohexanol and less amounts of cyclohexa-
none and cyclohexyl hydroperoxide (Fig. 5). TON attains in
this case 20. The initial reaction rate does not depend on con-
centration of 1 when [1] > 1 · 10ꢁ3 mol dmꢁ3 (Fig. 6). Selec-
tivity parameters in the TBHP oxidations have been found to
be higher than those for the H2O2 oxidations. For example,
bond selectivity for the oxidation of methylcyclohexane was
1ꢀ:2ꢀ:3ꢀ = 1:5.4:66. This value is less than the corres-
ponding parameter for the oxidation with the ‘‘H2O2–
[(TMTACN)MnIV(O3)MnIV(TMTACN)]2+–CH3COOH’’
system (1:26:200). It is known that the radical tert-Me3COÅ
abstracts a hydrogen atom from branched alkanes to give
the 1ꢀ:2ꢀ:3ꢀ = 1:10:40 ratio [99]. The 1ꢀ:3ꢀ ratio in the oxida-
tion of isooctane with participation of this radical was found
to equal 1:41 [100]. The oxidation by the TBHP–1 system
exhibits low stereoselectivity. Thus, for oxidations of cis-
and trans-1,2-dimethylcyclohexanes trans/cis parameters
were 0.85 and 0.6, respectively. All these data allow us to
propose that in the TBHP oxidations the key step is the
attack of relatively weak voluminous tert-butoxyl radical,
tert-Me3COÅ, on C–H bonds of hydrocarbon substrates.
Complex 1 catalyzes also alkane oxidation with MCPBA
in acetonitrile at room temperature (for iron-catalyzed
alkane oxidations with MCPBA, see our recent paper
[44]). Total yield of oxygenates (ketone, alcohol and alkyl
One can assume that a key step of the oxidation is gen-
eration of hydroxyl radicals in the reaction between hydro-
gen peroxide and a Ôlow-valentÕ osmium derivative, similar
with formation of hydroxyl radicals in the Fenton reagent:
Os(II) + H2O2 ! Os(III) + HOÅ + HOꢁ
A Ôhigh-valentÕ derivative thus formed can be reduced with
a new molecule of H2O2 back to Os(II):

Table 3
Selectivity parameters in oxidation of alkanesa
Entry
System
C(1):C(2):C(3):C(4)b
1ꢀ:2ꢀ:3ꢀc
trans/cisd
n-Hexane
n-Heptane
3-Methylhexane
Methylcyclohexane
1:4: 10
2,2,4-Trimethylpentane
cis-DMCHe
cis-Decalin
1
2
3
1–H2O2 (MeCN, 60 ꢀC)
1–H2O2 (H2O, 70 ꢀC)
1–MCPBA (MeCN, 25 ꢀC)
1.0:6.2:7.1
1.0:5.5:5.0:4.6
1:9.5:9:9
1:6:19
1:4:11
1:5:8.5
1:2:14
0.9
0.7
0.5
0.65
2.9
1.3
0.55
1:34:29
1:36:36.5
1:11:260
1:20:520
4
5
6
7
8
9
10
11
a
MCPBA (MeCN, 25 ꢀC)
1:89:750
1:3:58
OsCl3–H2O2 (MeCN, 80 ꢀC)f
FeCl3–H2O2 (MeCN, 20 ꢀC)
Fe(ClO4)3–H2O2 (MeCN, 20 ꢀC)
FeSO4–H2O2 (MeCN, 20 ꢀC)
hm–H2O2 (MeCN, 20 ꢀC)
1:12:10:3.5
1:2:9
1.2
1.0
1:7:57
1:5:13
1:3:6
1:2:6
1:4:9
1:9:9
1:4:30
1:7:43
1:5:5:4.5
1:7:6:7
1:9:7:7
1.3
0.9
0.75
0.34
3.5
1.3
2.1
0.12
1:10:7
1:8:7
1:4:12
1:6:22
1:22:200
n-Bu4NVO3–PCA–H2O2 (MeCN, 40 ꢀC)g
[L2Mn2O3]2+–MeCO2H–H2O2 (MeCN, 20 ꢀC)h
1:6:18
1:26:200
1:46:35:35
1:5:50
All parameters were measured after reduction of the reaction mixtures with triphenylphosphine before GC analysis and calculated based on the ratios of isomeric alcohols. Reaction conditions for
the oxidations catalyzed by 1 are similar to those described in Table. 1.
b
Parameters C(1):C(2):C(3):C(4) are relative normalized (i.e., calculated taking into account the number of hydrogen atoms at each carbon) reactivities of hydrogen atoms at carbons 1, 2, 3 and 4, of
the chain of unbranched alkanes.
c
Parameters 1ꢀ:2ꢀ:3ꢀ are relative normalized reactivities of hydrogen atoms at primary, secondary and tertiary carbons of branched alkanes.
Parameter trans/cis is the ratio of trans-and cis-isomers of tert-alcohols formed in the oxidation of cis-disubstituted cyclohexanes.
cis-DMCH is cis-1,2-dimethylcyclohexane.
See [80].
PCA is pyrazine-2-carboxylic acid; for this system, which is believed to oxidize substrates via formation of hydroxyl radicals, see [1,2,10,34,35,90–93].
L is 1,4,7-trimethyl-1,4,7-triazacyclononane; for this system which is believed to oxidize substrates without participation of free radicals (though the formation of radicals in the course of the
d
e
f
g
h
reaction is assumed), see [2,10,34,35,94–98].

842
G.B. Shul’pin et al. / Journal of Organometallic Chemistry 691 (2006) 837–845
2
x
2.0
x
1.0
0.8
0.6
0.4
0.2
0
1
1.5
x
x
1.0
W
c
x
0.5
0
0.4
[catalyst 1] × 103 (mol dm−3
1.0
)
0
0.2
0.6
0.8
3
Fig. 7. Dependence of the initial rate of cyclohexane oxidation with
MCPBA on the initial concentration of 1. Conditions: cyclohexane,
0.46 mol dmꢁ3; MCPBA, 1.74 mol dmꢁ3; solvent MeCN; 25 ꢀC.
10
20
0
5
15
time (h)
Fig. 5. Accumulation of oxygenates (concentrations, c, of cyclohexanone,
curve 1; cyclohexanol, curve 2; cyclohexyl hydroperoxide, curve 3, are
given) in the cyclohexane (initial concentration 0.92 mol dmꢁ3) oxidation
with TBHP (0.78 mol dmꢁ3) catalyzed by 1 (1 · 10ꢁ3 mol dmꢁ3). Condi-
tions: solvent MeCN; homogeneous solution at 60 ꢀC.
2.0
1.5
1.0
2.0
1.5
1.0
W
0.5
A
0
0.8
[MCPBA]0 (mol dm−3
2.0
0
0.4
1.2
1.6
W
)
0.5
Fig. 8. Dependence of the initial rate of cyclohexane oxidation with
MCPBA on the initial concentration of MCPBA. Conditions: cyclohex-
ane, 0.46 mol dmꢁ3; 1, 1 · 10ꢁ3 mol dmꢁ3; solvent MeCN; 25 ꢀC. A: an
experiment without 1.
0
0
1
3
4
2
5
[catalyst 1] × 103 (mol dm−3
)
Fig. 6. Dependence of the initial rate of cyclohexane oxidation with
TBHP on the initial concentration of 1. Conditions: cyclohexane,
0.925 mol dmꢁ3; TBHP, 0.78 mol dmꢁ3; solvent MeCN; 60 ꢀC.
2.0
1.5
hydroperoxide) in the cyclohexane (0.46 mol dmꢁ3) oxida-
tion (MCPBA, 1.16 mol dmꢁ3
, ;
1, 1 · 10ꢁ3 mol dmꢁ3
1.0
MeCN; 25 ꢀC) attained 0.037 mol dmꢁ3 after 72 h which
corresponds to TON = 37. The oxidation under the same
conditions in the absence of 1 gave only 0.0017 mol dmꢁ3
products. The TON can be enhanced (up to 80 after 48 h)
using lower concentration of 1 (1 · 10ꢁ4 mol dmꢁ3). The
initial rate of oxygenate accumulation is proportional to
the concentration of catalyst 1 (Fig. 7). It is interesting that
order of the reaction in respect to MCPBA is higher than
unity (Fig. 8). First order has been found for substrate at
[cyclohexane]0 < 0.5 mol dmꢁ3, whereas the initial reaction
rate does not depend on the hydrocarbon concentration
at its higher concentration (Fig. 9).
W
0.5
0
0.4
[cyclohexane]0 (mol dm−3
1.0
0
0.2
0.6
0.8
)
Fig. 9. Dependence of the initial rate of cyclohexane oxidation with
MCPBA on the initial concentration of cyclohexane. Conditions:
MCPBA, 1.74 mol dmꢁ3; 1, 10ꢁ3 mol dmꢁ3; solvent MeCN; 25 ꢀC.
for the oxidations with H2O2 and TBHP. These parameters
are very close to the parameters obtained (Table 3, entry 4)
for much less efficient (see Fig. 8) non-catalyzed oxidation
Selectivity parameters in the Os-catalyzed oxidation
with MCPBA are much higher (Table 3, entry 3) than those

G.B. Shul’pin et al. / Journal of Organometallic Chemistry 691 (2006) 837–845
843
with MCPBA. The catalyzed oxidation of disubstituted
cyclohexanes occurs with partial retention of configuration
(the trans/cis parameter was found to equal 0.5; see Table
3). It is clear that in the case of MCPBA the oxidation does
not include free radicals as reactive intermediates.
acetonitrile ligand, Os3(CO)11(MeCN) (2) was synthesized
[102] starting from Os3(CO)12 (0.407 g, 0.45 mmol). A solu-
tion of 2 and trans-1,4-diphenylbut-2-en-1,4-dione (0.953 g,
0.40 mmol) in hexane (150 mL) was heated under reflux
during 22 h. After evaporation of the solvent in vacuum
and chromatography (silica gel, eluent hexane–chloroform
1:1), complex 1 was isolated (yield 0.374 g, 81%) as a yellow
solid, m.p. 160 ꢀC (with decomposition). The compound
was characterized by elemental analysis, 1H and 13C
NMR, IR spectra and X-ray analysis [83].
3. Conclusions
In this work, we describe for the first time that a low-
valent organometallic osmium complex is a very powerful
generator of hydroxyl radicals from hydrogen peroxide
and can be used as a catalyst in H2O2-oxygenations of sat-
urated and aromatic hydrocarbons. This catalyst is much
more efficient than any derivative of iron (an analogue of
osmium in the Periodic System).
Acknowledgements
This work was supported by the grant from the Section
of Chemistry and Material Science of the Russian Acad-
emy of Sciences (Program ‘‘A theoretical and experimental
study of chemical bonds and mechanisms of main chemical
processes’’). The authors thank also the Russian Basic
Research Foundation.
4. Experimental
The oxidations of hydrocarbons were carried out in
MeCN in air in thermostated Pyrex cylindrical vessels with
vigorous stirring. The total volume of the reaction solution
was 2 mL. Initially, a portion of H2O2 (35% aqueous),
TBHP (70% aqueous) or MCPBA (‘‘Fluka’’) was added
to the solution of the catalyst and substrate. After certain
time intervals samples (about 0.2 mL) were taken. In order
to determine concentrations of all cycloalkane (cyclohexane
or cyclooctane) oxidation products the samples of reaction
solutions were analyzed twice (before and after their treat-
ment with PPh3) by GC (Chromatograph-3700, fused
silica capillary column FFAP/OV-101 20/80 w/w, 30 m ·
0.2 mm · 0.3 lm; helium as a carrier gas) measuring con-
centrations of cycloalkanol and cycloalkanone. Oxidations
of other hydrocarbons were carried out analogously.
Authentic samples of all oxygenated products were used
to attribute the peaks in chromatograms (comparison of
retention times was carried out for different regimes of
GC-analysis). The reaction of MeCN with water in the pres-
ence of osmium derivatives can give some amount of acet-
amide [101]. Concentrations of products obtained in the
oxidation of benzene and ethylbenzene were measured
References
[1] A.E. Shilov, G.B. ShulÕpin, Chem. Rev. 97 (1997) 2879–2932.
[2] A.E. Shilov, G.B. ShulÕpin, Activation and Catalytic Reactions of
Saturated Hydrocarbons in the Presence of Metal Complexes,
Kluwer Academic Publishers, Boston, 2000.
[3] R.H. Crabtree, J. Chem. Soc., Dalton Trans. (2001) 2437–2450.
[4] Y. Ishii, S. Sakaguchi, T. Iwahama, Adv. Synth. Catal. 343 (2001)
393–427.
[5] J.A. Labinger, J.E. Bercaw, Nature 417 (2002) 507–514.
[6] A.A. Fokin, P.R. Schreiner, Chem. Rev. 102 (2002) 1551–1593.
[7] A.A. Fokin, P.R. Schreiner, Adv. Synth. Catal. 345 (2003) 1035–
1052.
[8] R.A. Periana, G. Bhalla, W.J. Tenn III, K.J.H. Young, X.Y. Liu,
O. Mironov, C.J. Jones, V.R. Ziatdinov, J. Mol. Catal., A: Chem.
220 (2004) 7–25.
[9] J.A. Labinger, J. Mol. Catal., A: Chem. 220 (2004) 27–35.
[10] G.B. ShulÕpin, Oxidations of C–H compounds catalyzed by metal
complexes, in: M. Beller, C. Bolm (Eds.), second ed., Transition
Metals for Organic Synthesis, vol. 2, Wiley–VCH, Weinheim/New
York, 2004, pp. 215–242.
[11] M. Muehlofer, T. Strassner, W.A. Herrmann, Angew. Chem., Int.
Ed. 41 (2002) 1745–1747.
[12] J. Le Bras, J. Muzart, Tetrahedron Lett. 43 (2002) 431–433.
[13] P.M. Reis, J.A.L. Silva, A.F. Palavra, J.J.R. Frau´sto da Silva, T.
Kitamura, Y. Fujiwara, A.J.L. Pombeiro, Angew. Chem., Int. Ed.
42 (2003) 821–823.
1
using H NMR method (solutions in acetone-d6; ‘‘Bruker
AMX-400’’ instrument, 400 MHz). To demonstrate the role
of atmospheric oxygen in the process, two experiments on
the oxidation of ethylbenzene were carried out under iden-
tical conditions but in different atmospheres. In the first
experiment, a slow stream of argon was passed through
the reaction solution during 1 h prior addition of hydrogen
peroxide and heating the solution at 70 ꢀC. In the parallel
experiment, a stream of air was used instead of argon. In
both cases, the reaction mixtures were treated with sodium
[14] M.N. Kopylovich, A.M. Kirillov, A.K. Baev, A.J.L. Pombeiro, J.
Mol. Catal., A: Chem. 206 (2003) 163–178.
[15] R.A. Periana, O. Mironov, D. Taube, G. Bhalla, C.J. Jones, Science
30 (2003) 814–818.
[16] M. Zerella, S. Mukhopadhyay, A.T. Bell, Org. Lett. 5 (2003) 3193–
3196.
[17] J.E. Remias, T.A. Pavlovsky, A. Sen, J. Mol. Catal., A: Chem. 203
(2003) 179–192.
[18] I. Go¨ttker-Schnetmann, M. Brookhart, J. Am. Chem. Soc. 126
(2004) 9330–9338.
1
boron hydride and the products were determined by H
NMR method. It turned out that in the experiment under
air ethylbenzene was converted mainly into 1-phenyletha-
nol with conversion ca. 40%. Only traces of 1-phenyl alco-
hol were found in the experiment under argon atmosphere.
Complex 1 was prepared in accordance with the method
described previously [83]. Carbonyl cluster containing
[19] K. Zhu, P.D. Achord, X. Zhang, K. Krogh-Jespersen, A.S.
Goldman, J. Am. Chem. Soc. 126 (2004) 13044–13053.
[20] A.N. Vedernikov, K.G. Caulton, Chem. Commun. (2004) 162–163.
[21] M. Yamaguchi, T. Kumano, D. Masui, T. Yamagishi, Chem.
Commun. (2004) 798–799.
[22] C. Thieuleux, E.A. Quadrelli, J.-M. Basset, J. Do¨bler, J. Sauer,
Chem. Commun. (2004) 1729–1731.

844
G.B. Shul’pin et al. / Journal of Organometallic Chemistry 691 (2006) 837–845
[23] S. Mukhopadhyay, A.T. Bell, Adv. Synth. Catal. 346 (2004) 913–
916.
[59] J. Peller, O. Wiest, P.V. Kamat, J. Phys. Chem. A. 108 (2004)
10925–10933.
[24] I. Bar-Nahum, A.M. Khenkin, R. Neumann, J. Am. Chem. Soc. 126
(2004) 10236–10237.
[25] C. Bolm, J.-C. Frison, J. Le Paih, C. Moessner, Tetrahedron Lett.
45 (2004) 5019–5021.
[26] T. Joseph, M. Hartmann, S. Ernst, S.B. Halligudi, J. Mol. Catal., A:
Chem. 207 (2004) 131–137.
[27] C. Pavan, J. Legros, C. Bolm, Adv. Synth. Catal. 347 (2005) 703–
705.
[60] M.G. Bryukov, V.D. Knyazev, S.M. Lomnicki, C.A. McFerrin, B.
Dellinger, J. Phys. Chem. A. 108 (2004) 10464–10472.
[61] C. Bohne, K. Faulhaber, B. Giese, A. Ha¨fner, A. Hofmann, H.
Ihmels, A.-K. Ko¨hler, S. Pera¨, F. Schneider, M.A.L. Sheepwash, J.
Am. Chem. Soc. 127 (2005) 76–85.
[62] C. Bae, J.F. Hartwig, N.K. Boaen Harris, R.O. Long, K.S.
Anderson, M.A. Hillmyer, J. Am. Chem. Soc. 127 (2005) 767–
776.
[28] A.M. Kirillov, M.N. Kopylovich, M.V. Kirillova, M. Haukka,
M.F.C. Guedes da Silva, A.J.L. Pombeiro, Angew. Chem., Int. Ed.
44 (2005) 4345–4349.
[29] B. Cornils, W.A. Herrman (Eds.), Applied Homogeneous Catalysis
with Organometallic Compounds, VCH, Weinheim, 1996.
[30] B. Cornils, W.A. Herrman (Eds.), Aqueous-Phase Organometallic
Catalysis, Wiley-VCH, Weinheim, 2004.
[63] R.A. Sanchez-Delgado, M. Rosales, M.A. Esteruelas, L.A. Oro, J.
Mol. Catal., A: Chem. 96 (1995) 231–243.
[64] O.A. Kholdeeva, V.P. Kirin, V.A. Maksakov, V.A. GrigorÕev,
Kinetics and Catalysis 36 (1995) 293–296.
[65] W.A. Herrmann, R.M. Kratzer, J. Blu¨mel, H.B. Friedrich, R.W.
Fischer, D.C. Apperley, J. Mink, O. Berkesi, J. Mol. Catal. A:
Chem. 120 (1997) 197–205.
[31] F.E. Kuehn, A. Scherbaum, W.A. Herrmann, J. Organometal.
Chem. 689 (2004) 4149–4164.
[66] A. Severeyns, D.E. De Vos, P.A. Jacobs, Topics Catal. 19 (2002)
125–131.
[32] F.E. Kuehn, W.A. Herrmann, in Ref. [30], pp. 488–500.
[33] U. Schuchardt, D. Mandelli, G.B. ShulÕpin, Tetrahedron Lett. 37
(1996) 6487–6490.
[34] G.B. ShulÕpin, J. Mol. Catal., A: Chem. 189 (2002) 39–66.
[35] G.B. ShulÕpin, Comptes Rendus, Chimie 6 (2003) 163–178 (in
English).
[67] A. Severeyns, D.E. De Vos, P.A. Jacobs, Green Chem. 4 (2002) 380–
384.
[68] V. Caps, S.C. Tsang, Appl. Catal., A: General 248 (2003) 19–31.
[69] V. Caps, I. Paraskevas, S.C. Tsang, Appl. Catal. A: General 252
(2003) 37–49.
[70] K. Lee, Y.-H. Kim, S.B. Han, H. Kang, S. Park, W.S. Seo, J.T.
Park, B. Kim, S. Chang, J. Am. Chem. Soc. 125 (2003) 6844–
6845.
[36] B. Meunier, S.P. de Visser, S. Shaik, Chem. Rev. 104 (2004) 3947–
3980.
[37] M.-H. Baik, M. Newcomb, R.A. Friesner, S.J. Lippard, Chem.
Rev. 103 (2003) 2385–2420.
[38] P.-P.H.J.M. Knopps-Gerrits, W.A. Goddard III, Catal. Today 81
(2003) 263–286.
[39] E.Y. Tshuva, S.J. Lippard, Chem. Rev. 104 (2004) 987–1012.
[40] J.-F. Bartoli, F. Lambert, I. Morgenstern-Badarau, P. Battioni, D.
Mansuy, Comptes Rendus, Chimie 5 (2002) 263–266 (in English).
[41] V. Balland, D. Mathieu, N. Pons-Y-Moll, J.-F. Bartoli, F. Banse,
P. Battioni, J.-J. Girerd, D. Mansuy, J. Mol. Catal., A: Chem. 215
(2004) 81–87.
[71] K. Khanbabaee, Nachr. Chemie 51 (2003) 442–446 (in German).
[72] P.P. Pescarmona, A.F. Masters, J.C. van der Waal, T. Maschmeyer,
J. Mol. Catal., A: Chem. 220 (2004) 37–42.
[73] K.J. Kim, H.Y. Choi, S.H. Hwang, Y.S. Park, E.K. Kwueon, D.S.
Choi, C.E. Song, Chem. Commun. (2005) 3337–3339.
[74] K.S. Coleman, M. Coppe, C. Thomas, J.A. Osborn, Tetrahedron
Lett. 40 (1999) 3723–3726.
[75] P.A. Shapley, N. Zhang, J.L. Allen, D.H. Pool, H.-C. Liang, J. Am.
Chem. Soc. 122 (2000) 1079–1091.
[76] W.P. Griffith, M. Suriaatmaja, Can. J. Chem. 79 (2001) 598–606.
[77] C. Do¨bler, G.M. Mehltretter, U. Sundermeier, M. Eckert, H.-C.
Militzer, M. Beller, Tetrahedron Lett. 42 (2001) 8447–8449.
[78] A.M. Khenkin, L.J.W. Shimon, R. Neumann, Inorg. Chem. 42
(2003) 3331–3339.
[42] G.B. ShulÕpin, G.V. Nizova, Y.N. Kozlov, L. Gonzalez Cuervo, G.
Suss-Fink, Adv. Synth. Catal. 346 (2004) 317–332, and references
¨
therein.
[43] G.V. Nizova, B. Krebs, G. Su¨ss-Fink, S. Schindler, L. Westerheide,
L. Gonzalez Cuervo, G.B. ShulÕpin, Tetrahedron 58 (2002) 9231–
9237.
[79] J.P. Lecomte, J.P. Costantini, D. Laucher, Fr. Pat. 2649097.
[80] G.B. ShulÕpin, G. Suss-Fink, L.S. ShulÕpina, Chem. Commun.
¨
[44] G.B. ShulÕpin, H. Stoeckli-Evans, D. Mandelli, Y.N. Kozlov, A.
Tesouro Vallina, C.B. Woitiski, R.S. Jimenez, W.A. Carvalho, J.
Mol. Catal., A: Chem. 219 (2004) 255–264.
(2000) 1131–1132.
[81] B.C. Bales, P. Brown, A. Dehestani, J.M. Mayer, J. Am. Chem.
Soc. 127 (2005) 2832–2833.
[45] G.B. ShulÕpin, C.C. Golfeto, G. Suss-Fink, L.S. ShulÕpina, D.
[82] S.N. Kholuiskaya, A.D. Pomogailo, N.M. Bravaya, S.I. Pomogailo,
V.A. Maksakov, Kinetika i Kataliz 44 (2003) 831–835 (in Russian).
[83] L.V. Rybin, E.A. Petrovskaya, M.I. Rybinskaya, M.K. Dzhafarov,
A.S. Batsanov, Y.T. Struchkov, N.A. ShtelÕtser, Metalloorg. Khim.
5 (1992) 684–689 (in Russian).
¨
Mandelli, Tetrahedron Lett. 46 (2005) 4563–4567.
[46] D.H.R. Barton, T. Li, Tetrahedron 54 (1998) 1735–1744.
[47] D. Bianchi, M. Bertoli, R. Tassinari, M. Ricci, R. Vignola, J. Mol.
Catal., A: Chem. 204–205 (2003) 419–424.
[48] A.Y. Sychev, V.G. Isak, Uspekhi Khimii 64 (1995) 1183–1208 (in
Russian).
[84] G.B. ShulÕpin, A.N. Druzhinina, React. Kinet. Catal. Lett. 47 (1992)
207–211.
[49] F. Gozzo, J. Mol. Catal., A: Chem. 171 (2001) 1–22.
[50] K. Otsuka, Y. Wang, Appl. Catal. A: General 222 (2001) 145–161.
[51] H.B. Dunford, Coord. Chem. Rev. 233–234 (2002) 311–318.
[52] M.L. Kremer, J. Phys. Chem. A 107 (2003) 1734–1741.
[53] C. Bolm, J. Legros, J. Le Paih, L. Zani, Chem. Rev. 104 (2004)
6217–6254.
[85] G.B. ShulÕpin, G.V. Nizova, React. Kinet. Catal. Lett. 48 (1992)
333–338.
[86] G.B. ShulÕpin, M.M. Bochkova, G.V. Nizova, J. Chem. Soc., Perkin
Trans. 2 (1995) 1465–1469.
[87] G.B. ShulÕpin, G.V. Nizova, Y.N. Kozlov, New J. Chem. 20 (1996)
1243–1256.
[54] J.F. Perez-Benito, J. Phys. Chem. A 108 (2004) 4853–4858.
[55] C. Crestini, A. Pastorini, P. Tagliatesta, Eur. J. Inorg. Chem. (2004)
4477–4483.
[56] I.M. Wasser, H.C. Fry, P.G. Hoertz, G.J. Meyer, K.D. Karlin,
Inorg. Chem. 43 (2004) 8272–8281.
[88] V.Y. Kukushkin, A.J.L. Pombeiro, Inorg. Chim. Acta 358 (2005) 1–
21.
[89] Y.N. Kozlov, G.V. Nizova, G.B. ShulÕpin, J. Mol. Catal. A: Chem.
227 (2005) 247–253.
[90] G.B. ShulÕpin, D. Attanasio, L. Suber, J. Catal. 142 (1993) 147–152.
[91] G.B. ShulÕpin, R.S. Drago, M. Gonzalez, Russ. Chem. Bull. 45
(1996) 2386–2388.
[57] M. Sam, J.H. Hwang, G. Chanfreau, M.M. Abu-Omar, Inorg.
Chem. 43 (2004) 8447–8455.
[58] M. Roeselova, J. Vieceli, L.X. Dang, B.C. Garrett, D.J. Tobias, J.
Am. Chem. Soc. 126 (2004) 16308–16309.
[92] G.B. ShulÕpin, Y. Ishii, S. Sakaguchi, T. Iwahama, Russ. Chem.
Bull. 48 (1999) 887–890.

G.B. Shul’pin et al. / Journal of Organometallic Chemistry 691 (2006) 837–845
845
[93] G.B. ShulÕpin, Y.N. Kozlov, G.V. Nizova, G. Suss-Fink, S.
[98] G.B. ShulÕpin, G.V. Nizova, Y.N. Kozlov, V.S. Arutyunov, A.C.M.
dos Santos, A.C.T. Ferreira, D. Mandelli, J. Organomet. Chem. 690
(2005) 4498–4504.
¨
Stanislas, A. Kitaygorodskiy, V.S. Kulikova, J. Chem. Soc., Perkin
Trans. 2 (2001) 1351–1371.
[94] J.R. Lindsay Smith, G.B. ShulÕpin, Tetrahedron Lett. 39 (1998)
4909–4912.
[99] C. Nguyen, R.J. Guajardo, P.K. Mascharak, Inorg. Chem. 35
(1996) 6273–6281.
[95] G.B. ShulÕpin, G. Suss-Fink, L.S. ShulÕpina, J. Mol. Catal., A:
[100] G.B. ShulÕpin, J. Gradinaru, Y.N. Kozlov, Org. Biomol. Chem. 1
(2003) 3611–3616.
¨
Chem. 170 (2001) 17–34.
[96] G.B. ShulÕpin, G.V. Nizova, Y.N. Kozlov, I.G. Pechenkina, New J.
Chem. 26 (2002) 1238–1245.
[97] C.B. Woitiski, Y.N. Kozlov, D. Mandelli, G.V. Nizova, U. Schuc-
hardt, G.B. ShulÕpin, J. Mol. Catal. A: Chem. 222 (2004) 103–119.
[101] E. Cariati, C. Dragonetti, L. Manassero, D. Roberto, F. Tessore,
E. Lucenti, Mol. Catal. A: Chem. 204–205 (2003) 279–285.
[102] B.F.G. Johnson, J. Lewis, D.A. Pippard, J. Chem. Soc., Dalton
Trans. (1981) 407–412.