Selective catalytic oxidation of benzyl alcohol to benzaldehyde by a mononuclear oxovanadium(V) complex of a bis(phenolate) ligand containing bulky tert-butyl substituents

Article abstract of DOI:10.1007/s11243-013-9769-6

A new mononuclear complex of vanadium(V), [V(O)(bp)(OCH₃)] (1) has been synthesized, where H₂bp is N,N′-bis(2-hydroxy-3,5-di- tert-butylbenzyl)-N′,N′-dimethylethylene-1,2-diamine. The complex was characterized by elemental analyses,

Full text of DOI:10.1007/s11243-013-9769-6

Transition Met Chem (2014) 39:33–39
DOI 10.1007/s11243-013-9769-6
Selective catalytic oxidation of benzyl alcohol to benzaldehyde
by a mononuclear oxovanadium(V) complex of a bis(phenolate)
ligand containing bulky tert-butyl substituents
Nader Noshiranzadeh
•
•
Mina Mayeli
Katarzyna Slepokura •
´
•
Rahman Bikas
Tadeusz Lis
Received: 19 August 2013 / Accepted: 4 October 2013 / Published online: 20 October 2013
Ó Springer Science+Business Media Dordrecht 2013
Abstract A new mononuclear complex of vanadium(V),
V(O)(bp)(OCH )] (1) has been synthesized, where H bp is
coordination chemistry of vanadium is the catalytic oxi-
[
dation of organic compounds such as olefins, sulfides,
alcohols, etc. [8–10].
3
2
0
0
0
N,N -bis(2-hydroxy-3,5-di-tert-butylbenzyl)-N ,N -dimeth-
ylethylene-1,2-diamine. The complex was characterized by
elemental analyses, spectroscopic methods and X-ray dif-
fraction measurement. Single-crystal X-ray diffraction
structure analysis of the complex revealed that the vana-
dium atom is octahedrally coordinated and that the
The oxidation of alcohols to their corresponding car-
bonyl compounds is one of the most important and fun-
damental reactions in organic synthesis [11, 12]. A number
of methods are known for alcohol oxidations, but oxidation
over metal catalysts using hydrogen peroxide are preferred
now for their economic benefits and environmental
acceptability, which depends mainly on the nature of the
by-product, i.e. water [13]. Recently, catalytic oxidation of
alcohols employing transition metal complexes, such as Fe
[14], Cu [15], Co [16], Mo [17], Pd [18], Mn [19], V [20],
etc., using H O has been developed. Oxovanadium com-
2
-
bis(phenolate) ligand (bp ) is N O -bonded to the vana-
2
2
dium(V) center in a tetradentate dinegative fashion.
Introduction
2
2
Vanadium is an important element in biology, inorganic
chemistry and organic syntheses [1–3]. The interest in
coordination chemistry of vanadium has increased in the
last decades because the active sites of some enzymes such
as haloperoxidases consist of vanadate moieties which are
able to catalyze oxidation reactions [4, 5]. Many vanadium
complexes show activity in oxidation and oxo transfer
reactions [6, 7]. Another important impetus to the
plexes are active catalysts in oxidation reactions using
H O , and some of them have been used for enantiose-
2
2
lective oxidation of prochiral substrates [21]. They can
catalyze oxidation of benzyl alcohol to benzaldehyde with
high selectivity in the presence of H O [22].
2
2
On the other hand, the bis(phenolate)-based ligands
obtained in the reaction of amines with phenols in the
presence of formaldehyde are interesting N-, O-donor
systems. Their metal complexes are good candidates for
catalytic oxidation studies because of their resistance to
oxidation in oxo transfer reactions [23]. Also, bis(pheno-
late)-based ligands are able to stabilize vanadium in high
oxidation state of 5? [24, 25]. Bis(phenolate) ligands
bearing bulky tert-butyl groups may be useful in the
selective oxidation reactions, because the incorporation of
bulky substituents at the ortho-positions with respect to the
phenolic O-donor atom directs the substrate toward the
metal center, giving rise to improved selectivity [26–28].
In this work, we report the synthesis, characterization,
crystal structure and catalytic reactivity of a new vana-
dium(V) complex of a tetradentate ligand including two
Electronic supplementary material The online version of this
article (doi:10.1007/s11243-013-9769-6) contains supplementary
material, which is available to authorized users.
N. Noshiranzadeh (&) ꢀ M. Mayeli ꢀ R. Bikas
Department of Chemistry, Faculty of Science, University of
Zanjan, 45195-313 Zanjan, Iran
e-mail: nadernoshiranzadeh@yahoo.com;
nadernoshiranzadeh@znu.ac.ir
´
R. Bikas ꢀ K. Slepokura ꢀ T. Lis
Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14,
5
0-383 Wroclaw, Poland
123

3
4
Transition Met Chem (2014) 39:33–39
phenolic rings bearing bulky tert-butyl substitutents in
ortho- and para- positions with respect to the phenolic
oxygen. The catalytic reactivity of this complex has been
investigated in the selective oxidation of primary alcohols
in the presence of H O .
1,043(s), 1,024(m), 987(s), 948(m), 938(m), 923(s),
910(w), 891(w), 879(s), 824(m), 813(m), 800(w), 782(m),
1
756(m), 725(m), 681(m), 665(w), 649(m), 540(m).
H
NMR (250.13 MHz, CDCl , 25 °C, TMS, ppm): d = 1.27
3
(m, 18 H, CH of t-Bu), 1.38 (m, 18 H, CH of t-Bu), 2.30
2
2
3
3
(
s, 6H, CH of N(CH ) ), 2.57 (m, 4 H, N–CH ), 3.65 (m,
3 3 2 2
4
2
H, Ar–CH ), 6.93 (d, 2H, J = 2.0 Hz, aryl), 7.20 (d,
4
2 HH
13
Experimental
2H, J = 2.0 Hz, aryl). C NMR (62.19 MHz, CDCl3,
HH
2
5 °C, TMS, ppm): d = 29.50 (CH of t-Bu), 31.7 (CH of
3
3
Materials and instrumentation
t-Bu), 34.0 (C of t-Bu), 35.0 (C of t-Bu), 44.8 (CH of
3
N(CH ) ), 49.0 (CH –N), 56.6 (Ar–CH ), 56.9 (CH –
3
2
2
2
2
All starting chemicals were commercially available
reagents and were used without further purification. IR
spectra were recorded in KBr disks with a Bruker FT-IR
spectrophotometer. UV–Vis solution spectra were recorded
N(CH ) ), 123.3, 124.8 (4CH of arom), 121.6, 136.0,
3 2
-
5
140.1, 153.3(8C of arom). UV–Vis (5 9 10
-1
M,
-
1
CH OH): k
(e, M cm ) = 216 (33 000), 279 nm (9
3
max
100).
1
using a thermo-spectronic Helios Alpha spectrometer. H
1
3
and C NMR spectra were measured with a Bruker
Spectrospin spectrometer at 250 and 62.5 MHz, respec-
tively. The reaction products of oxidation were determined
and analyzed by HP Agilent 6890 gas chromatograph
equipped with an HP-5 capillary column (phenyl methyl
siloxane 30 lm 9 320 lm 9 0.25 lm) and gas chro-
matograph–mass spectrometry (Hewlett-Packard 5973
Series MS-HP gas chromatograph with a mass-selective
detector). The elemental analyses (carbon, hydrogen and
nitrogen) were obtained using a Carlo ERBA Model EA
Synthesis of [V(O)(bp)(OCH )]
3
The appropriate amount of ligand H bp (0.524 g,
2
1.0 mmol) was dissolved in CH OH (30 mL containing
3
3 % (v/v) H O) in association with VO(acac) (0.265 g,
2
2
1.0 mmol). The solution was gently refluxed for 6 h. After
cooling, the resulting solid was filtered off, washed with
cooled absolute ethanol and dried at 100 °C. Single crystals
of [V(O)(bp)(OCH )] were obtained by thermal gradient
3
method. Yield 87 % (0.54 g). Anal. Calc. for
1
108 analyzer. Vanadium percentage of the complex was
C H N O V (MW = 620.77): C, 67.7; H, 9.2; N, 4.5; V,
35 57 2 4
measured by a Varian spectrometer AA 220 instrument.
8.2. Found: C, 67.8; H, 9.4; N, 4.5; V, 8.2 %. FT-IR (KBr,
-
1
cm ): 3,413(OH, w, br), 2,953(CH alif, s), 2,904(s),
2,867(m), 2,835(w), 2,810(w), 1,603(w), 1,467(s),
1,440(s), 1,411(m), 1,389(m), 1,359(s), 1,256(s), 1,241(s),
1,204(m), 1,070(s), 1,025(w), 958 (vs), 912(s), 871(w),
0
Synthesis of N,N -bis(2-hydroxy-3,5-di-tert-
0
0
butylbenzyl)-N ,N -dimethylethylene-1,2-diamine
H bp)
(
2
7
71(m), 761(m), 747(w), 648(w), 641(w), 589(m), 552(m).
-
5
-1
For synthesis of the amine-bis(phenolate) ligand, H bp,
2
UV–Vis (5 9 10
-
cm ) = 221 (32 000), 282 (15 500), 360 nm (2 600).
M, CH OH): kmax (e,
M
3
1
methanol (35 mL) was added to N,N-dimethylethane-1,2-
diamine (4.40 mL, 0.05 mol) and the rapidly stirred solu-
tion was cooled to 0 °C after which aqueous formaldehyde
X-ray crystallography
solution (37 wt% in H O, containing 10 % methanol as
2
stabilizer) (8 mL, 0.1 mol) was added dropwise. The
mixture was stirred for 15 min, then 2,4-di-tert-butylphe-
nol (20.63 g, 0.1 mol) was added, and the mixture was
refluxed for 48 h. At the end, the solution was evaporated
on a steam bath to 5 mL and cooled to room temperature.
The resulting white precipitate was separated and filtered
off, washed with 20 mL of cooled methanol and re-crys-
tallized. Yield 80 % (20.99 g). M.p. 131–133 °C. Anal.
Calc. for C H N O (MW = 524.82): C, 77.8; H, 10.7;
Data collection for X-ray structure determination was
performed on an Xcalibur R four-circle diffractometer with
a Ruby CCD detector with graphite monochromatized
MoKa radiation. The data were collected at 100(2) K using
an Oxford Cryosystems cooler. Data collection, cell
refinement, data reduction and analysis and absorption
correction were carried out with the Xcalibur R software,
Pro
CrysAlis
[29]. The structure was solved by direct
methods with SHELXS [30] and refined by full-matrix
2
least-squares techniques on F using SHELXL-2013 [30]
3
4 56 2 2
N, 5.3. Found: C, 77.8; H, 10.8; N, 5.3. FT-IR (KBr,
-
cm ): 3,188 (s, br), 2,950 (m,br), 2,865(m, br), 1,768(s),
1
with anisotropic thermal parameters for the non-H atoms
(except for the atoms of low-occupied positions of disor-
dered ligand). The H atoms were included from geom-
etry and were refined using a riding model, with
1
1
1
1
,605(m), 1,592(w), 1,571(s), 1,506(m), 1,483(s),
,467(m), 1,417(m), 1,388(m), 1,374(m), 1,360(m),
,303(m), 1,285(m), 1,256(m), 1,224(w), 1,202(w),
,160(m), 1,121(m), 1,105(s), 1,086(w), 1,057(w),
˚
C–H = 0.95–0.99 A, and with U (H) = 1.2U (CH, CH )
iso
eq
2
1
23

Transition Met Chem (2014) 39:33–39
35
Table 1 Crystallographic data of 1
structure plots were prepared with DIAMOND [31]. The
crystal data and refinement parameters are presented in
Table 1. CCDC 946551 contains the supplementary crys-
tallographic data for complex 1. This data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Complex 1
CCDC No.
Formula
946551
35 57 2 4
C H N O V
-
1
Mr/g mol
620.76
Crystal size/mm
Crystal shape, color
T/K
0.20 9 0.08 9 0.02
Plate, dark yellow
100(2)
Experimental setup for catalytic oxidation
˚
Radiation
MoKa (k = 0.71073 A)
Liquid phase catalytic oxidations of benzyl alcohol were
carried out under air (atmospheric pressure) in a 25-mL
round-bottom flask equipped with a magnetic stirrer. In a
typical experiment, H O was added to a flask containing
Crystal system, space group
Monoclinic, P2
15.268(6)
21.931(8)
21.810(8)
107.68(3)
6,958(5)
8
1
/n
˚
a/A
˚
b/A
2 2
-
3
˚
c/A
the catalyst (1.6 9 10 mmol) and benzyl alcohol
1 mmol) in a solvent (3 mL). The course of the reaction
(
b/°
˚
V/A
3
was monitored using a gas chromatograph equipped with a
capillary column and a flame ionization detector. The
oxidation products were identified by comparing their
retention times with those of authentic samples or alter-
Z
-
3
Calc. density/g cm
1.185
F(000)
2,688
1
-
1
natively by TLC, H NMR and GC–Mass analyses.
l/mm
Absorption correction
0.32
Empirical (multi-scan)
Tmin, Tmax
0.984, 1.000
Results and discussion
Measured reflections
41,364
R
int
0.187
Synthesis of ligand and V-complex
h, k, l
-18 ? 18, -26 ? 24, -26 ? 23
H range
2.33–25.50
12,957
0
The reaction of N,N -dimethylethane-1,2-diamine with 2,4-
Independent reflections
Observed reflections
Data/parameters/restraints
di-tert-butylphenol in the presence of formaldehyde (37 %)
5,826
gave the desired tetradentate bis(phenolate) ligand, H bp,
2
1,2957/912/451
0.096
in excellent yield and purity (Scheme 1). Complex
R1(Fobs
)
[
V(O)(bp)(OCH )] (1) was synthesized by the reaction of
3
2
wR2(F )
0.203
H bp/VO(acac) in 1:1 molar ratio in methanol
2
2
GooF = S
Shift/errormax
1.09
(
Scheme 1). The formation of the ligand, H bp, has been
2
0.000
confirmed by NMR and infrared spectroscopy. In the IR
spectrum of the ligand, the bands at 3,188, 1,592 and
-1
-
3
˚
Dqmax/Dqmin/e A
0.81/-0.72
P
P
the weighting scheme (w) is given in the crystallographic information
a
R1 ¼
jjFoj ꢁ jFcjj= jFoj;
1,256 cm are due to O–H, C=C and C–Ophenolic stret-
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
P Â À
Á ÃꢀP Â
Ã
2
2
c
2
2
o
2
wR2 ¼
w F ꢁ F
wðF Þ ; Detailed information on
ches, respectively [32, 33]. The elemental analysis is in
good accordance with the proposed structure. The complex
1 is slowly formed by the reaction of H bp with VO(acac)
o
file (CIF)
2
2
in methanol as solvent. During the reaction, vanadium(IV)
is oxidized to vanadium(V) by air. On complexation, the
shift of C–Ophenolic and C–N bands shows coordination of
or 1.5U (CH ). Since the crystals of 1 were small and the
eq
3
quality of the diffraction pattern was low, the presented
structure should be treated only as a model. The asym-
metric unit of 1 contains two crystallographically inde-
pendent complex molecules denoted as 1A and 1B. The bp
ligand in molecule 1B is disordered and refined in two sites
with s.o.f. = 0.830(5) and 0.170(5). In the refinement
procedure of the disordered region, some geometrical
restrains and constraints/restrains on the fractional coordi-
nates and anisotropic displacement parameters (SAME,
FLAT, EXYZ, EADP, SIMU instructions in SHELXL-
H bp as a tetradentate dianionic ligand. In the IR spectrum
2
-
1
of complex 1, the band at 958 cm is assigned to m(V=O)
[34, 35], and this band is observed as a new peak for the
complex that is not present in the spectrum of the free
ligand.
The electronic spectra of complex 1 (brown) and H bp
2
(colorless) in MeOH solutions are shown in Fig. 1. The
bis(phenolate) ligand displays two absorption bands at 216
and 278 nm. Based on their extinction coefficients, they are
assigned to p ? p* and n ? p* transitions, respectively.
The electronic spectrum of the complex is very similar to
2
013) were applied, for details see the CIF file. The
123

3
6
Transition Met Chem (2014) 39:33–39
Scheme 1 The synthesis
pathway of ligand H bp and
2
complex 1
O
Table 2 Selected bond lengths ( A˚ ) and angles (°) in complex 1
CH OH
˚
A
2
Bond
Angle
°
H
H O /Catalyst
2
2
V1A–O3A
1.585(4)
1.767(4)
1.886(4)
1.895(4)
2.242(5)
2.396(5)
O1M–V1A–O1A
O2A–V1A–O1A
O3A–V1A–N1A
O1 M–V1A–N1A
O2A–V1A–N1A
O1A–V1A–N1A
O3A–V1A–N2A
O1 M–V1A–N2A
O2A–V1A–N2A
O1A–V1A–N2A
N1A–V1A–N2A
97.46(17)
V1A–O1 M
V1A–O2A
159.23(16)
94.23(18)
160.27(19)
79.04(16)
83.09(16)
170.72(19)
83.97(18)
82.39(17)
83.21(17)
76.49(16)
Scheme 2 Catalytic oxidation of benzyl alcohol in the presence of
V(V) complex
V1A–O1A
V1A–N1A
V1A–N2A
Angle
O3A–V1A–O1M
O3A–V1A–O2A
O1 M–V1A–O2A
O3A–V1A–O1A
105.3(2)
95.9(2)
95.84(18)
95.9(2)
The asymmetric unit of 1 contains two crystallographically
independent complex molecules denoted as 1A and
1
B (Fig. 2, Fig. S1). The bp ligand in molecule 1B is dis-
ordered and refined in two sites: 1B with s.o.f. = 0.830(5)
and 1C with s.o.f. = 0.170(5). The two independent mol-
ecules 1A and 1B are very similar (Fig. S1), and in the
following description, only molecule 1A will be discussed.
In particular, the conformation of the organic ligand in the
high-occupied position of 1B is almost identical with that of
2
Fig. 1 The electronic spectra of H bp (blue), complex 1 (red) in the
methanol. (Color figure online)
1A, while the other position of 1B is slightly different in the
orientation of three N1-bonded methylene groups.
that of the free ligand, but is red shift in both absorption
peaks. These peaks are attributed to intraligand p ? p*
and n ? p* transitions, and the shifts indicate the coor-
dination of the ligand to the V(V) ion. For the complex, the
broad band at higher energy of *360 nm is due to the
ligand to metal charge transfer (LMCT) transition.
X-ray analysis reveals that the complex 1 is a neutral
mononuclear complex of oxovanadium(V). The coordina-
tion environment around the vanadium centers is best
described as a distorted octahedral [VO
N ] with nitrogen
4 2
atoms from the –NMe moiety, tertiary nitrogen, two oxygen
2
atoms provided by the bis(phenolate) ligand and two oxygen
atoms from methoxy and oxido ligands. In complex 1, two
phenolate donor atoms provided by the bis(phenolate)
ligand are located in a trans mode toward each other. The
tertiary nitrogen and two phenolate oxygen atoms together
with oxygen atom of methanol form the basal plane (with
X-ray structure of complex 1
The molecular structure of the complex [V(O)(bp)(OCH )]
3
(1) was determined by X-ray diffraction analysis. The
selected bond lengths and angles are tabulated in Table 2.
˚
r.m.s. deviation of fitted atoms = 0.060 A). Relative to this
1
23

Transition Met Chem (2014) 39:33–39
37
alcohol (scheme 2) as a representative substrate with
hydrogen peroxide was studied in the presence of complex
1
. Aqueous hydrogen peroxide (30 %) was selected as
oxidant by considering its high selectivity, atom economy
and environmentally benign properties. The results of
control experiments revealed that the presence of catalyst
and oxidant (H O ) is essential for the oxidation. To
2
2
achieve the maximum oxidation of alcohols, the effective
parameters for suitable reaction conditions such as the
oxidant concentration (moles of oxidant per moles of
substrate), solvent and temperature of the reaction were
investigated. The results of these studies are summarized in
Table 3. In all these reactions, benzyl alcohol gave the
benzaldehyde with 100 % selectivity by catalyst and there
was no other product. The effect of oxidant concentration
on the oxidation of benzyl alcohol by complex 1 is illus-
trated in Fig. 3. Different oxidant/substrate molar ratios
(1:1, 2:1, 3:1 and 4:1) were considered, while the ratio of
benzyl alcohol (1.0 mmol) to catalyst (1.6 lmol, 0.001 g)
in 3 mL of acetonitrile was constant. The conversion of
benzyl alcohol increased with increasing the amount of
Fig. 2 The molecular structure of one of two crystallographically
independent complex molecules (1A) present in 1. Displacement
ellipsoids are drawn at the 40 % probability level
plane, the vanadium atom is displaced toward the apical
˚
oxygen atom O3 by 0.27 A. The terminal V=O-type oxygen
atom O3A occupies an axial position at a distance of
˚
.585(4) A. The remaining axial position in the complex is
1
0
occupied by the nitrogen of the N,N -dimethyl moiety with
˚
the V–N bond length of 2.396(5) A. This bond is longer
2
than the others, which can be attributed to the trans influence
of the oxido group. The V–O and V–N bond lengths are
similar with other vanadium complexes with bis(phenolate)
ligands reported in CSD databases [36].
hydrogen peroxide in the reaction mixture. When H O /
2 2
substrate mole ratio was 3:1, the maximum conversion of
59 % was obtained at 60 ± 1 °C.
The intermolecular interactions in the crystal of 1 are
provided by weak C–HꢀꢀꢀO and C–Hꢀꢀꢀp contacts, in which
the methylene groups from molecule 1A and O3 atoms and
phenyl rings from 1B are involved (Table S1, Fig. S2).
In order to get the best reaction temperature, oxidation
of alcohols was studied at 25 (room temperature), 40, 60
and 70 °C and the results are shown in Fig. 4. At room
temperature, the oxidation of benzyl alcohol was low.
Increasing the reaction temperature from 25 to 70 °C
increased the conversion of benzyl alcohol, and 62 %
conversion was obtained at 70 °C. The influence of the
solvent nature in the catalytic oxidation of benzyl alcohol
was investigated (Table 3, entries 7–14). Methanol, ace-
tone, dichloromethane, chloroform, toluene, DMSO, THF
and acetonitrile were used as solvents. Of the various
Catalytic activity studies
Oxidation of benzyl alcohol
The catalytic activity of the complex 1 was tested in the
oxidation of alcohols. The catalytic oxidation of benzyl
Table 3 Comparison of the
A
-1
)
Entry Catalyst
H
O
2 2
(mmol) Solvent
Temp. (°C) Yield Selectivity (%) TON TOF (h
catalytic activities of catalyst 1
in the oxidation of benzyl
alcohol with hydrogen peroxide
in different conditions
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
3
4
3
3
3
3
3
3
3
3
3
3
CH
CH
CH
CH
CH
CH
CH
3
CN
3
CN
3
CN
3
CN
3
CN
3
CN
3
CN
60
60
60
60
25
40
70
30
57
59
55
13
31
62
49
51
25
14
29
45
2
100
100
100
100
100
100
100
100
100
100
100
100
100
100
188
356
368
344
81
47
89
92
86
20
48
97
77
204
39
22
45
70
3
194
388
306
816
156
88
(CH
Toluene
CHCl
CH Cl
THF
CH OH
DMSO
3 2
) CO 70
70
70
70
70
70
70
0
1
3
Reaction conditions: catalyst,
1
1
4
.6 lmol; benzyl alcohol,
mmol; solvent, 3 mL; time,
h
2
2
12
181
281
12
1
3
4
3
A
Yields are based on the
starting benzyl alcohol
1
123

3
8
Transition Met Chem (2014) 39:33–39
conversion in DMSO is due to the highest coordinating
ability of this solvent. High reactivity in toluene is due to
high solubility of the catalyst in this solvent.
Conclusion
A new vanadium(V) complex of a tetradentate bis(pheno-
late) ligand was synthesized and characterized by spectro-
scopic and single-crystal X-ray analyses. The catalytic
ability of this complex was investigated by using the envi-
ronmentally benign and clean oxidant H O for oxidation of
2
2
benzyl alcohol. The effects of various parameters including
the molar ratio of oxidant to substrate, the temperature and
the solvent have been studied, and the optimized conditions
were obtained. This complex is a selective catalyst for oxi-
dation of benzyl alcohol to benzaldehyde.
Fig. 3 Effect of H
alcohol by 1. Reaction conditions: catalyst, complex 1, 1.6 lmol
0.001 g); CH CN, 3 mL; benzyl alcohol, 1 mmol; temperature,
0 ± 2 °C
2 2
O concentration on the oxidation of benzyl
(
6
3
Acknowledgments We acknowledge the University of Zanjan for
funding this research work. R. Bikas thanks to the Ministry of Sci-
ence, Research and Technology of the I.R. Iran for scholarship No.
2
13631.
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