A carboxylate-bridged Mn(II) compound with 6-methylanthranilate/bipy: oxidation of alcohols/alkenes and catalase-like activity

Article abstract of DOI:10.1080/00958972.2018.1469750

A novel manganese compound, [Mn₂(μ_1,3-6-CH₃-2-NH₂C₆H₄COO)₂(bipy)₄](ClO₄)₂ (bipy?=?2,2′-bipyridine), was synthesized and used as a catalyst precursor in the oxidation of alkenes and primary alcohols to corresponding aldehydes, ketones, and acids. The six-coordinate compound has a binuclear structure in which two Mn(II) ions adopt a syn-anti μ_1,3-bridging mode with two carboxylate groups and two chelated bipy ligands. The compound exhibits good activity in the oxidation of cyclohexene to 2-cyclohexene-1-one as the major product (93% conv. in 3?h, 79.3% selectivity) and of cinnamyl alcohol to cinnamaldehyde as the major product with 46% selectivity (100% conv. in 1.5?h) with tert-butyl hydroperoxide (TBHP) in acetonitrile at 70?°C. Furthermore, the catalase-like activity of the compound was studied in different solvents (acetonitrile, methanol, Tris-HCl buffer; TOF?=?29,910?h^?1 in Tris-HCl buffer).

Full text of DOI:10.1080/00958972.2018.1469750

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
A carboxylate-bridged Mn(II) compound with 6-
methylanthranilate/bipy: Oxidation of alcohols/
alkenes and catalase-like activity
Yalcin Kilic, Serkan Bolat & Ibrahim Kani
To cite this article: Yalcin Kilic, Serkan Bolat & Ibrahim Kani (2018): A carboxylate-bridged Mn(II)
compound with 6-methylanthranilate/bipy: Oxidation of alcohols/alkenes and catalase-like activity,
Journal of Coordination Chemistry, DOI: 10.1080/00958972.2018.1469750
To link to this article: https://doi.org/10.1080/00958972.2018.1469750
Accepted author version posted online: 27
Apr 2018.
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Publisher: Taylor & Francis
Journal: Journal of Coordination Chemistry
DOI: http://doi.org/10.1080/00958972.2018.1469750
A carboxylate-bridged Mn(II) compound with 6-methylanthranilate/bipy:
Oxidation of alcohols/alkenes and catalase-like activity
YALCIN KILIC†‡, SERKAN BOLAT†‡ and IBRAHIM KANI*†
†Department of Chemistry, Faculty of Science, Anadolu University, Eskisehir, Turkey
‡Department of Laboratory Technology, Vocational School, Izmir University of Economics, Izmir, Turkey
A novel manganese compound, [Mn2(µ1,3-6-CH3-2-NH2C6H4COO)2(bipy)4](ClO4)2 (bipy = 2,2'-
bipyridine), was synthesized and used as a catalyst precursor in the oxidation of alkenes and
primary alcohols to corresponding aldehydes, ketones, and acids. The six-coordinate compound
has a binuclear structure in which two Mn(II) ions adopt a syn-anti µ1,3-bridging mode with two
carboxylate groups and two chelated bipy ligands. The compound exhibits good activity in the
oxidation of cyclohexene to 2-cyclohexene-1-one as the major product (93% conv. in 3 h, 79.3%
selectivity) and of cinnamyl alcohol to cinnamaldehyde as the major product with 46%
selectivity (100% conv. in 1.5 h) with tert-butyl hydroperoxide (TBHP) in acetonitrile at 70 °C.
Furthermore, the catalase-like activity of the compound was studied in different solvents
(acetonitrile, methanol, Tris-HCl buffer; TOF = 29910 h–1 in Tris-HCl buffer).
Keywords: Manganese; Complex; Catalase; Oxidation; Catalysis
1. Introduction
Reactive oxygen species (ROS), such as superoxide anion, hydroxyl radical, and hydrogen
peroxide, are generated during aerobic respiration. These ROS are associated with numerous
pathological conditions, including atherosclerosis, ischemia, cancer, and Alzheimer’s disease as
*Corresponding author. Email: ibrahimkani@anadolu.edu.tr
1

well as aging [1]. All living cells, therefore, control ROS levels by using metalloenzymes such as
the superoxide dismutases (SODs) and catalases (CATs) [2]. During the past two decades, a wide
variety of binuclear manganese complexes has been synthesized to mimic structural features
[3-9]. Mn(II) is one of the most interesting metals because of the biomimetic functional model of
the catalase enzyme, which has a binuclear manganese compound. In addition, the use of
inorganic-organic hybrid compounds as catalysts for the oxidation of alcohols and alkenes is of
current interest, and the use of some efficient metal organic frameworks as catalysts has been
reported [10-18]. One of the main purposes of catalytic chemistry is to develop new
environmentally-friendly catalytic systems that show high atom efficiency without side-products
and also replace low-cost first-row transition metal complexes instead of high-cost active
platinum-group metal complexes. The coordination chemistry of manganese compound derivatives,
especially with chelating neutral N-based and/or O-containing ligands, has been used as a catalyst in
hydrocarbon oxidations because of the remarkably versatile redox chemistry of manganese [19-
26]. Therefore, the multinuclear μ-oxido- and μ-carboxylato-bridged manganese complexes have
attracted extensive interest in recent decades for selective catalytic oxidations and in bulk
oxidation chemistry [27-31].
One of the challenges in this area, particularly from a green chemistry perspective, is the
use of molecular oxygen (O2), t-BuOOH (tert-butylhydro-peroxide), and hydrogen peroxide
(H2O2), the most attractive oxidants because of their high active oxygen species content and
coproduction of only water. Published examples of the TBHP and H2O2 oxidation of alkenes and
alcohols catalyzed with Mn[10] compounds have attracted much interest, but the search for a
highly selective environmentally benign alkene oxidation with TBHP remains a challenge
[32-36].
As a continuation of our catalytic research, the purpose of this work was to synthesize a
new manganese compound with carboxylate and nitrogenous base ligands as oxidation catalysts.
Here, we report the synthesis, crystallographic structure, and physical properties of the
carboxylate-bridged homobinuclear compound of Mn(II), [Mn2(µ1,3-6-CH3-2-
NH2C6H4COO)2(bipy)4](ClO4)2, and its successful application as a catalyst precursor toward the
disproportionation of H2O2 in different solvents and in the oxidation of alkenes (ethylbenzene,
cyclohexene, 1-hexene, 1-octene) and primary alcohols (benzyl alcohols, 1-heptanol,
cyclohexanol, 1-octanol, cinnamyl alcohol) with TBHP as an oxidant in acetonitrile.
2

2. Experimental
2.1. Synthesis of compound
A solution of manganese(II) perchlorate hydrate (Mn(ClO4)2·xH2O) (347.0 mg, 0.96 mmol) in
methanol (10 mL) was added to a neutralized solution of 2-amino-6-methylbenzoic acid
(145.0 mg, 0.96 mmol) with NaOH (3.0 mL, 0.306 M). After a 1-hour mixing of the solution at
50 C, bipy (150.0 mg, 0.96 mmol) in methanol (2 mL) was added to the reaction mixture. The
final solution was refluxed for five hours, and then the solution was filtered over celite. After
solvent evaporation, the product was washed with diethyl ether and then dried under vacuum.
The single crystals of the yellow compound were obtained by diethylether diffusion to methanol.
The compound is soluble in polar solvents and slightly soluble in CH2Cl2 and CHCl3. Yield
182.0 mg, 61.5%; m.p. 252 °C. Anal. Found (%): C, 54.48; H, 3.46; N, 11.56. Calcd. for
C32H27ClMnN4O8 (%): C, 54.51; H, 3.92; N, 11.35. IR bands (KBr pellet, cm-1): 3384 (s), 3071
(s), 1588 (vs), 1468 (vs), 1439 (vs), 1161 (vs), 1079(vs). ΛM = 318.1 S cm2 mol-1.
2.2. Materials and measurements
All chemicals were purchased from commercial sources and used as received. IR spectra were
measured with a Jasco FT/IR-300 E spectrometer from 4000-400 cm-1. UV-vis spectra of
compound were recorded on a Shimadzu UV-2450 spectrophotometer. Crystallographic data
were collected at room temperature with a Bruker APEX II CCD using Mo-Kα radiation and
corrected for absorption with SADABS. The structure was solved by direct methods. All non-
hydrogen atoms were refined anisotropically by full-matrix least squares on F2.
2.3. Crystallographic analyses
Diffraction data for the compound were collected with a Bruker AXS APEX CCD diffractometer
equipped with a rotation anode at 296(2) K, by using graphite monochromated Mo K radiation
at λ = 0.71073 Å. The data reduction was performed with the Bruker SMART program package
[37]. The structure was solved by direct methods and the non-hydrogen atoms were located
through subsequent difference Fourier syntheses. The SHELXS-97 package was used for
structure solution and was refined with SHELXL-97 against F2 using first isotropic and later
anisotropic thermal parameters for all non-hydrogen atoms [38]. Hydrogens were added to the
3

structure model at calculated positions. The molecular drawing was obtained using MERCURY
[39]. PLATON program was used for geometric calculations [40].
2.4. Catalase activity
The catalase activity studies were performed by volumetric determination of the oxygen evolved
with a gas-volumetric burette (with a precision of 0.1 mL). The H2O2/catalyst ratio was used as
2.500. The catalyst concentration in the reaction mixture is 6.47×10-4 M. In a typical experiment,
a 30% H2O2 aqueous solution (9.7×10-3 mol, 1 mL) was added to closed vessels through the
rubber septum using a syringe containing acetonitrile (5.0 mL) solutions of the compound
(3.88×10-6 mol). After 10 min of stirring to get a stable temperature, 1 mL of H2O2 solution was
injected and the volume of evolved dioxygen was measured at time intervals of 1 min. The
volume of oxygen gas was calculated using the ideal-gas equation.
2.5. General procedure of the catalytic oxidation experiments
The study of catalytic reactions was performed in 50-mL flasks with a temperature controller
unit. An oxidant solution of 2 mL was added dropwise to a solution of catalyst and substrate at
70 C. The substrate-catalyst ratio was kept constant at 265. The reaction mixture was analyzed
at certain time intervals with a GC (HP-5) quartz capillary column (30 m × 0.32 mm × 0.25 μm)
and a FID detector.
3. Results and discussion
3.1. Spectral characterization
The FT-IR spectrum of the compound was recorded by preparing KBr pellets. The bands
observed at 1439 and 1588 cm–1 indicate symmetric and asymmetric vibrations of the
carboxylate group. The value of Δ (= νas(COO) - νs(COO)) = 150 cm-1 indicates that the
carboxylate ligand is coordinated in a bidentate bridging mode [41]. The bipy ligand generates
characteristic bands at 1500, 1474 and 1439 cm-1. A weak band at 3071 cm-1 indicates the
aromatic C-H stretch vibrations of the bipy ligand. The N-H stretching vibration of the
6-methylanthranilate ligand is observed around 3384 cm-1. In the compound spectrum, the
observed bands at 1120 cm-1 and 623 cm-1 are assigned to the perchlorate anion.
The UV-vis spectrum of the compound was recorded in acetonitrile solution. No
4

absorption bands exist in the visible region of the spectrum because of the d5 configuration of the
Mn(II) ion. The observed bands at 230 and 294 nm are related to the ligand-centered ππ* or
nπ* transitions in the bipy ligands.
Molar conductivity measurements allowed the verification of the compound’s stability
and the dissociation degree of the compounds in studied solutions. The compound has an M
value of 318.1 S cm2 mol–1, close to the expected value for 1:2 electrolyte in acetonitrile. Thus,
in solution, the compound retained its binuclear structure, and the perchlorate anions are not
coordinated to the manganese ions.
3.2. Crystal structure
The crystallographic data and corresponding selected bond lengths and angles of the compound
are given in tables 1 and 2. The crystal structure of the compound consists of a binuclear cation,
[Mn2(µ1,3-6-CH3-2-NH2C6H4COO)2(bipy)4]2+, as shown in figure 1. Two perchlorate anions are
outside the complex cation as counterions. Two chemically equivalent units crystallize in a unit
structure. Each structure has a center of symmetry. The carboxylate group of the
6-methylanthranilate ligand acts as the µ1,3-bidentate bridging mode in a syn-anti fashion. Each
Mn(II) ion is coordinated by four nitrogen atoms of two bipy ligands and two oxygen atoms of
two carboxylate groups. The geometry around the Mn(II) centers is distorted octahedral with
coordination angles within the range of 71.5(1)° to 105.6(9)° deviating from 90° and 159.9(1)° to
167.7(1)° deviating from 180°. The bite angles of bipy ligands are 71.5(1)° and 72.0(1)°. The
bipy ligand is closer to planarity, as indicated by the C7-C1-C2-C6 torsion angle at 0.51° and the
C12-C11-C16-C20 torsion angle at 8.63°.
The Mn-O bond length is similar (2.121(2) Å) and comparable to that of analogous
compounds [42-44]. The Mn-N bond lengths are within the range of 2.229(3) to 2.283(3) Å, with
an average value of 2.271 Å. The Mn...Mn distance (= 4.825 Å) is significantly longer than those
of analogous compounds found in [Mn2(OAc)2(4-aba)2(2,2′-bipy)2] (4.081 Å) and [Mn3(4-aba)6]n
(3.452(2) Å). The intermolecular weak hydrogen bonds are observed among the oxygen atoms of
the perchlorate ion, the carboxylate group, and the hydrogen atom of the amine group.
3.3. Alcohol and alkene oxidation
The Mn(II) compound has been tested for the oxidation of primary alcohols and alkenes to the
5

corresponding aldehyde, ketones, and carboxylic acids as a homogeneous catalyst precursor. The
catalytic reactions were performed under mild conditions (70 °C) in acetonitrile with TBHP as an
oxidant. The subs./cat. ratio (265) was kept constant in all catalytic reactions (tables 3 and 4).
In the Mn(II)/TBHP/olefin/CH3CN catalytic system, we observed that the most effective
among the studied alcohols is cinnamyl alcohol, while cyclohexene is the most reactive among
the studied alkenes. The compound has the highest activity for the oxidation of cyclohexene,
which is an electron-rich alkene; on the other hand, the catalyst has relatively low activity for the
electron-deficient alkene, ethylbenzene. The compound oxidized cyclohexene to cyclohexanone
(79.3%) (total conv. 92.8% in 3 h) and other products - 2-cyclohexen-1-ol (1.7%), cyclohexene
oxide (4.9%), and 1,2-cyclohexanediol (6.9%) - based on the total yield of products (total conv.
92.8% in 3 h, table 3). The rapid reaction reached a total conversion of 22.2% at 1 minute (TOF:
3556 h-1) and a total conversion of 92.8% within 3 h (TOF = 243 h-1) (figure 2). Ethyl benzene
oxidation shows the slowest kinetic profile among the other olefins (figure 2). Acetophenone was
detected in the oxidation of ethylbenzene (18.9% total conv. in 6 h).
In contrast to reported Mn(II) compounds, good results have been obtained for terminal
olefins 1-hexene (79.7%) and 1-octene (31.4%). Although 1-hexene is a substrate that is rather
hard to oxidize, the compound exhibits very high activity for the oxidation of 1-hexene,
affording 35.8% 2,5-hexenedione as a major product with the formation of other products; 15.2%
1-hexene-3-one and 28.7% 2-hexanal. The oxidation of 1-octene was catalyzed by the compound
to yield hexanoic acid (19.9%) and 1-octen-3-one (11.5%) after 24 h. The TOF value of the
compound is 212 h-1 for 1-hexene oxidation and 83 h-1 for 1-octene oxidation after a 24-h
reaction time (table 3).
The Mn(II)/TBHP/alcohol/CH3CN catalytic system exhibits very high activity for the
oxidation of cinnamyl alcohol, moderate activity for benzyl alcohol and cyclohexanol, and very
low activity for 1-octanol and 1-heptanol. The time-dependent catalytic activity results are
shown in figure 3 and table 4. Among the studied alcohols, the catalytic oxidation of cinnamyl
alcohol resulted in ~100% conversion in 90 min (TON ~ 266 h-1). The catalytic rate of cinnamyl
alcohol oxidation is extremely high: TOF = 11057 h–1 in the first minute of the reaction. Other
reaction products of cinnamyl alcohol are benzaldehyde (46.3%), cinnamyl aldehyde (15.9%),
styrene (14.2%), benzoic acid (14.0%), and 3-phenylglycidol (5.9%). Primary aliphatic alcohols
(1-heptanol and 1-octanol) were oxidized to carboxylic acids as their secondary oxidation
6

products, whereas secondary alcohol (cyclohexanol) was oxidized to cyclohexanone (43.6% in
6 h) without a carbon-carbon chain cleavage (table 4). These results support the reports that the
compound is more reactive in the oxidation of benzylic alcohols than that of aliphatic alcohols
[45]. Benzaldehyde and benzoic acid were detected during the catalytic oxidation of benzyl
alcohol. After a 24-h reaction, the total conversion was recorded at 80.2% for benzyl alcohol
oxidation with an aldehyde selectivity of 46.6% (table 4).
3.4. Catalase activity
The disproportionation of hydrogen peroxide to water and oxygen (catalase activity) was studied
with a Mn(II) compound at 25 C (table 5). The catalase activity was studied in a solvent (5 mL)
with the compound (3.88×10-6 mol) and 9.7×10-3 mol of H2O2. The same procedure was repeated
in different solvents. The blank experiment, performed without the catalyst, showed a negligible
decomposition of H2O2. The initial solution of the compound was colorless, and after H2O2 was
added, it became yellow, and an immediate evolution of oxygen was observed. The catalytic
activity of Mn(ClO4)2 toward H2O2 disproportion was tested under similar conditions used for
compound synthesis; ~1% of the H2O2 decomposition was observed. Observed initial rates were
expressed as mL s-1, taking the volume of the evolved oxygen into account and calculated from
the maximum curve slope describing the evolution of O2 vs. the time graph (table 5). The initial
rates are strongly dependent on the solvent. The induction period was not observed in any of the
studied solvents.
The catalytic activities of the compound toward H2O2 disproportionation were
investigated in acetonitrile, methanol, and a Tris-HCl buffer (table 5 and figure 4). The highest
activity was observed with 87.5% disproportionation (23×10-4 mL s-1 and TOF = 29910 h-1) in
the Tris-HCl buffer, which corresponds to the physiological conditions of the cell environment.
This result suggests that the compound would also be an active catalyst in vitro. The rate of
decomposition is almost 16 times and 49 times faster in the Tris-HCl buffer than in the
acetonitrile and methanol solutions, respectively.
We observed the systematic correlation between compound activity and the relative
dielectric constants of solvents; the activity increases in the order of the relative dielectric
constants: Tris-HCl buffer (TOF = 29910 h-1, υi = 383×10-3 mL s-1) > acetonitrile (TOF =
773 h-1, υi = 23.5×10-3 mL s-1 > methanol (TOF = 577 h-1, υi = 4.3×10-3 mL s-1). The observed
7

activity in different solvents indicates that Mn(II) solvent coordination is necessary for the
catalytic cycle.
4. Conclusion
A novel Mn(II) compound, [Mn2(µ1,3-6-CH3-2-NH2C6H4COO)2(bipy)4](ClO4)2, with
6-methylanthranilate and bipy has been synthesized, and the solid-state structure was
characterized through X-ray crystallography. The Mn(II) compound exhibited catalytic activity
as a homogeneous catalyst precursor for the oxidation of various alkenes and primary alcohols,
with a low-to-good yield under mild reaction conditions (70 C) in acetonitrile and with TBHP
as an oxygen source. All studied primary alcohols were selectively oxidized to corresponding
aldehydes and overoxidized product carboxylic acids. Linear secondary alcohols were converted
into corresponding ketones in a very low yield, whereas the complex showed higher activity in
the oxidation of benzylic alcohol (1-phenylethanol) to acetophenone in a very good yield (73%
in 6 h). Moreover, the homobinuclear Mn(II) compound exhibited remarkable activity
(383×10-3 mL s-1 and TOF up to 29910 h-1) in the Tris-HCl buffer at room temperature.
Acknowledgements
This work has been supported by The Scientific and Technological Research Council of Turkey
(TUBITAK) (Grant No. 113Z303) and the authors gratefully acknowledge the Medicinal Plants
and Medicine Research Centre of Anadolu University, Eskisehir, Turkey for the use of X-ray
Diffractometer. EU COST Action CM1402 “Crystallize” is acknowledged for discussion.
CCDC 993362 contains the supplementary crystallographic data for compound. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: (+44)
1223-336-033; or E-mail: deposit@ccdc.cam.ac.uk.
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Figure 1. Molecular structure of compound ((i) 1-x, -y, -z).
Figure 2. Alkene oxidation of Mn(II) compound with TBHP at 70 C in acetonitrile.
11

Figure 3. Primary alcohol oxidation of Mn(II) compound with TBHP at 70 C in acetonitrile.
Figure 4. Time dependence of O2 evolution upon reaction of the compound with H2O2 in
different solvents.
12

Table 1. Crystal data and structure refinement parameters of compound.
Empirical formula
MW
C56H48Cl2Mn2N10O12
1233.82
Refinement method
Temperature (K)
Wavelength (Å)
Color
Full-matrix least-squares on F2
296(2)
0.71073
Yellow
Crystal system
Space group
Triclinic
P-1
a (Å)
12.840(5)
b (Å)
14.794(5)
c (Å)
15.839(6)
α (°)
87.245(6)
β (°)
70.002(5)
γ (°)
87.716(6)
Volume, V (Å3)
2823.3(18)
2
Z
Density (mg m-3)
Absorption coefficient (mm-1)
θ range for data collection (°)
Goodness-of-fit on F2
R indices (all data)
Largest diff. peak and hole
Final R indices [I > 2σ(I)]
1.456
0.613
1.69 to 28.21
0.982
R1 = 0.0928, wR2 = 0.0619
1.093 and -0.550 e A-3
R1 = 0.0619, wR2 = 0.1798
13

Table 2. Selected bond lengths (Å) and angles (°) of compound 1.
Compound part 1A
Compound part 1B*
Mn(1)-O(1)
2.121(2)
2.154(2)
2.241(3)
2.302(3)
2.305(3)
2.271(3)
95.67(10)
160.13(10)
97.79(9)
167.74(10)
93.19(10)
85.58(10)
71.54(10)
90.82(9)
105.63(9)
97.28(10)
89.15(9)
72.03(10)
159.85(9)
94.49(10)
89.21(10)
Mn(2)-O(4)
2.113(2)
Mn(1)-O(2)
Mn(2)-O(3)
2.145(2)
Mn(1)-N(2)
Mn(2)-N(7)
2.229(3)
Mn(1)-N(1)
Mn(2)-N(6)
2.280(3)
Mn(1)-N(4)
Mn(2)-N(9)
2.261(3)
Mn(1)-N(3)
Mn(2)-N(8)
2.283(3)
O(2)-Mn(1)-N(3)
N(2)-Mn(1)-N(3)
O(1)-Mn(1)-N(1)
O(2)-Mn(1)-N(1)
N(3)-Mn(1)-N(1)
O(2)-Mn(1)-N(4)
N(3)-Mn(1)-N(4)
O(1)-Mn(1)-O(2)
O(1)-Mn(1)-N(2)
O(2)-Mn(1)-N(2)
O(1)-Mn(1)-N(3)
N(2)-Mn(1)-N(1)
O(1)-Mn(1)-N(4)
N(2)-Mn(1)-N(4)
N(1)-Mn(1)-N(4)
O(4)-Mn(2)-N(7)
O(4)-Mn(2)-N(9)
N(7)-Mn(2)-N(9)
O(3)-Mn(2)-N(6)
N(9)-Mn(2)-N(6)
O(3)-Mn(2)-N(8)
N(9)-Mn(2)-N(8)
O(4)-Mn(2)-O(3)
O(3)-Mn(2)-N(7)
O(3)-Mn(2)-N(9)
O(4)-Mn(2)-N(6)
N(7)-Mn(2)-N(6)
O(4)-Mn(2)-N(8)
N(7)-Mn(2)-N(8)
N(6)-Mn(2)-N(8)
100.57(10)
91.67(10)
163.13(11)
167.36(11)
94.84(11)
80.91(10)
71.86(10)
95.57(9)
98.56(10)
91.70(10)
95.04(10)
72.71(10)
162.94(9)
96.46(10)
90.85(11)
*The second unit parameters
14

Table 3. Oxidation of alkenes with Mn(II)/TBHP/acetonitrile system.
Conv.
(%)
Time
(h)
Total conv.
(%)
TON
(h-1)
Substrate
Product distribution
Cyclohexene oxide
2-Cyclohexene-1-one
2-Cyclohexene-1-ol
1,2-Cyclohexanediol
Acetophenone
4.9
79.3
1.7
Cyclohexene
3
92.8
246
6.9
Ethylbenzene
1-Hexene
18.9
15.2
28.7
35.8
19.9
11.5
6
18.9
79.7
50
1-Hexen-3-one
2-Hexenal
24
212
2,5-Hexanedione
Hexanoic acid
1-Octene
24
31.4
83
1-Octen-3-one
Reaction conditions: 1.46×10-2 mol of oxidant, 4.3×10-3 mmol of catalyst, subst./cat. =
266, T = 70 C, TON = number of moles of product per mole of catalyst.
15

Table 4. Oxidation of alcohols with Mn(II)/TBHP/acetonitrile system.
Conv.
(%)
Time
(h)
Total conv.
(%)
TON
(h-1)
Substrate
Products
Cinnamyl aldehyde
Benzaldehyde
Styrene
15.9
46.3
14.2
14
Cinnamyl alcohol
1.5
100
266
Benzoic acid
3-Phenylglycidol
Cyclohexanone
Heptanal
5.9
Cyclohexanol
Heptanol
43.6
12.4
3.1
6
6
43.6
15.5
116
41
Heptanoic acid
Octanal
2.0
Octanoic acid
Heptanal
2.5
1-Octanol
6
14.5
39
7.2
Heptanoic acid
Benzaldehyde
Benzoic acid
2.8
37.4
42.8
Benzyl alcohol
24
80.2
213
Reaction conditions: 1.46×10-2 mol of oxidant, 4.3×10-3 mmol of catalyst, subst./cat. = 266,
T = 70 C, solvent = acetonitrile
16

Table 5. H2O2 disproportionation with 1 in different solvents.
Solvent
Total O2 (mL)
υi×10-3 (mL s-1)
TON (h-1)
346
TOF (h-1)
577
Methanol
34
76
98
4.3
Acetonitrile
Tris-HCl Buffer
23.5
383
773
3092
997
29910
Reaction conditions: T = 25 C, H2O2 = 9.7×10-3 mol, catalyst = 3.88×10-6 mol, solvent
= 5 mL
Graphical abstract
17