Homogeneous catalytic oxidation of alkenes employing mononuclear vanadium complex with hydrogen peroxide

Article abstract of DOI:10.1007/s13738-020-01988-x

Abstract: Homogeneous liquid-phase oxidation of alkenes (allylbenzene, cis-cyclooctene, 4-chlorostyrene, styrene, 2-norbornene, 1-methyl cyclohexene, indene, lemonine, and 1-hexene) were catalyzed by using vanadium complex [VO(hyap)(acac)₂] in existence of H₂O₂. The complex [VO(hyap)(acac)₂] was formed as a crystal by the reaction of [VO(acac)₂] and 2-hydroxyacetophenone (hyap) in the presence of methanol by refluxing the reaction mixture. Various analytical and spectroscopic techniques, namely FTIR, ESI–MS, UV–Vis, single-crystal XRD, and EPR, were used to analyze and optimize the structure of the complexes. Graphic abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s13738-020-01988-x

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-020-01988-x
ORIGINAL PAPER
Homogeneous catalytic oxidation of alkenes employing mononuclear
vanadium complex with hydrogen peroxide
Abhishek Maurya1
Received: 24 April 2020 / Accepted: 26 June 2020
©
Iranian Chemical Society 2020
Abstract
Homogeneous liquid-phase oxidation of alkenes (allylbenzene, cis-cyclooctene, 4-chlorostyrene, styrene, 2-norbornene,
1
-methyl cyclohexene, indene, lemonine, and 1-hexene) were catalyzed by using vanadium complex [VO(hyap)(acac) ] in
2
existence of H O . The complex [VO(hyap)(acac) ] was formed as a crystal by the reaction of [VO(acac) ] and 2-hydroxy-
2
2
2
2
acetophenone (hyap) in the presence of methanol by reꢀuxing the reaction mixture. Various analytical and spectroscopic
techniques, namely FTIR, ESI–MS, UV–Vis, single-crystal XRD, and EPR, were used to analyze and optimize the structure
of the complexes.
Graphic abstract
Keywords Vanadium(IV) complex · Homogeneous catalysis · Alkenes oxidation
Introduction
oxyfunctionalization of the organic substrates [1–3]. Gener-
ally, H O and TBHP are the environmentally genial, clean,
2
2
The most frequent catalytic oxidation is accommo-
dated by transition metals that operate hydrogen perox-
ide (H O ) or tert-butyl hydroperoxide (TBHP) for the
and comparatively low priced, commercially available and
good looking oxidizing agent [1–5]. The oxidation reaction
performed by metal catalysts depends on the metal center as
well as the nature of the ligands [6–9]. Nitrogen or oxygen-
carrying ligands of vanadium complexes have been widely
used as representative compounds for imitating the catalytic
properties of mono-oxygenases [9, 10]. Vanadium ion attrib-
utes diꢁerent oxidation states, such as oxovanadium (IV) and
2
2
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s13738-020-01988-x) contains
supplementary material, which is available to authorized users.
*
Abhishek Maurya
abhishekmauryaism@gmail.com
(
(
V) [11, 12], with the common coordination numbers of 6
octahedral), 5 (square pyramidal or trigonal bipyramidal),
1
Department of Chemistry, Indian Institute of Technology
and 4 (tetrahedral) [13–15]. Vanadium can perform liquid-
phase oxidation reactions of alkanes, alcohols, alkenes,
(
Indian School of Mines), Dhanbad, Jharkhand 826004,
India
Vol.:(0
1
123456789)
3

Journal of the Iranian Chemical Society
halides, aromatics through the heterogeneous or homog-
enous procedure [9, 14–26].
single-crystal XRD. The catalytic eꢃciency of complex was
explored by the homogenous oxidation of various alkenes in
the presence of hydrogen peroxide. During the catalytic pro-
cess, some of the products was formed by the oxidation of
alkenes which are the main implements for pharmacophore.
Thus, homogeneous liquid-phase oxidation reaction of
C–H, C–C, and C=C bonds by applying vanadium com-
plexes in the presence of peroxide is of basic signiꢂcance in
numerous ꢂeld such as organic synthesis, pharmaceutical,
laboratory, and industry [9, 16, 17, 20, 27, 28]. The fabrica-
tion of oxygen-containing products forming, oxidation of
alkenes is very demanding for the industrial point as well
as in practical organic synthesis. Epoxidation and oxidative
cleavage are the key operations involved in the oxidation of
alkenes [29–32]. The epoxidation products are very essen-
tial for industrial and synthetic purpose because most of the
epoxide products are used in the synthesis of plasticizers,
fragrance, epoxy resins, organic chemicals, anticorrosives,
and surfactants [33]. On the other hand, various carbonyl
compounds such as aldehydes and acids have been synthe-
sized from oxidative cleavage of alkenes, which are very
supreme intermediate for synthesis or stock chemicals. Ben-
zaldehyde is frequently used in foods and scented products
while occasionally used in cosmetics products [34], manu-
facturing of polymers and organic compounds. The carbox-
ylic acid is a very useful chemical for organic molecules
including drugs, ꢂne chemicals, and industrial interest. The
carboxylic acid functional species are frequently used in
the pharmacophore of miscellaneous variety of therapeu-
tic agents, which have a cardinal role in the biochemistry
of living organisms as well as in drug modeling [35, 36].
A huge amount (>450) of carboxylic acid-accommodated
drugs have been advertised in all over the world, such as
nonsteroidal anti-inꢀammatory drugs (NSAIDs), anticoagu-
lants, antibiotics, and cholesterol-lowering statins [35, 36].
Here, the author reports a vanadium complex that was
Results and discussion
Description of molecular structure
The solid-state structure of the complex [VO(hyap)(acac) ]
2
was conꢂrmed by a single-crystal analysis shown in Fig. 1.
However, the molecule was very similar to the [VO(acac) ],
2
except 2-hydroxyacetophenone which is coordinated to the
vanadium atom in the reported molecule. The molecular
structure of complex is uncomplicated octahedral geometry
with C H O V empirical formula and 403.31 molecu-
1
8
24
7
lar weight. The complex has a monoclinic system and P
2 /c space group with four Z value. The vanadium atom is
1
coordinated with six oxygen atoms which are octahedrally
arranged with the range of 1.574–2.403 Å bond length. The
intramolecular H-bond is represented by hydrogen of O1 and
O2. The selected bond lengths and bond angles of all atoms
are tabulated in Table S1.
FTIR studied
The partial FTIR spectral data of compound [VO(hyap)
(acac) ] are presented in the experimental section, and the
2
IR spectra for the given compound is shown in Figure S1,
−
1
which was recorded in the range 400–4000 cm . The com-
−
1
plex [VO(hyap)(acac) ] has one band at of 984 cm for
2
−
1
synthesized by the reaction of [VO(acac) ] and 2-hydroxy-
ν
[37], one band 1516 cm for ν
and one band at
C=C
2
VO
−
1
acetophenone (hyap). The synthesized complex was sepa-
rated as crystals and characterized by IR, UV, EPR, and
1555 cm for ν ; however, all these bands are comparable
CO
with the starting material [VO(acac) ]. But two additional
2
Fig. 1 ORTEP diagram of the complex [VO(hyap)(acac) ] with their packing
2
1
3

Journal of the Iranian Chemical Society
−
1,
−1
bands: 1621 cm and 3238 cm for ν and ν , were
by the addition of a 2-drop portion of 0.1 M 30% H O ,
CO
OH
2
2
appeared due to the presence of 2-hydroxyacetophenone,
which primarily indicates that 2-hydroxyacetophenone was
successfully coordinated with [VO(acac) ]. The ν band
which indicates the conversion of V(IV) to V(V) species.
EPR studies
2
OH
−
1
appeared slightly lowered at 3238 cm due to the existence
of H-bonding. The ν stretching frequency is less in the
Room-temperature X-band EPR experimental along with
computer-simulated spectra of the metal complex [VO(hyap)
VO
complex as compared to starting material [VO(acac) ], due
2
to the coordination of O-atom of 2-hydroxyacetophenone to
(acac) ] are represented in Fig. 3, whereas the recorded EPR
2
the V-metal [13].
spectra of complex [VO(hyap)(acac) ] are very close to
2
[
VO(acac) ]. Thus, it gives only idea that synthesized com-
2
UV–Vis spectra
plex is in V(IV) oxidation state, which shows axially sym-
(IV)
metrical signal of V =O [41–45]. A competently resolved
hyperꢂne splitting design was remarked for vanadium(IV)
oxido complex in parallel and perpendicular regions. The
hyperfine splitting is represented eight-line due to the
The spectra of the complex [VO(hyap)(acac) ] were recorded
2
in methanol by utilizing UV–Vis spectrophotometer at room
temperature (Figure S2), and the spectral data (maximum
absorbance with their extension coeꢃcient) of complex
are noted in the experimental section. The molar extinction
coeꢃcient (ε) across with the λ values of the complex is
max
3
3
3
(
4.11×10 )211 nm, (2.43×10 )253 nm, (1.70×10 )306 nm,
Expermental
Simulated
and (12.54)777 nm. The most achievable engagement for
these bands is n–σ*, π–π*, and n–π* electronic transitions,
*
respectively. The band 211 nm was assigned as n–σ tran-
*
sition, while band 253 nm was assigned as π–π and band
*
3
06 nm assigned as n–π transitions [15, 32, 38], while band
77 nm is due to d–d transition.
7
The effect of H O on the solution of the complex
2
2
[
VO(hyap)(acac) ] is shown in Fig. 2a. In this regard, the
2
spectral change observed by introducing a methanolic solu-
tion of the 2-drop section of 0.1 M solution of 30% H O
2
2
4
−
into the methanolic solution of complexes (3.87 × 10
3
000
3300
3600
3900
M) displays the disappearance of band 306 nm [39] and
increases other bands. Possibly, these spectral observations
in the complex have been indicated the formation of peroxo
species in the solution [39, 40]. Figure 2b displays spectral
Field (G)
Fig. 3 X-band EPR spectra of the metal complex [VO(hyap)(acac) ]
2
−
2
disappearance of bands 777 nm of complex (6.49×10 M)
at room temperature along with their computer-simulated spectra
a
b
7
77 nm
1
1
0
0
0
.6
.2
.8
.4
.0
0.9
0
0
.6
.3
0.0
2
40
320
400
480
650
780
910
1040
Wavelength (nm)
Wavelength (nm)
4
Fig. 2 Eꢁect of H O solution on the UV–Vis spectra of a complex
solution of 3.87×10− M complex. b Spectral change recorded with
2
2
solution. a Spectral change recorded by the introduction of a metha-
the introduction of a methanolic solution of a 2-drop portion of 0.1 M
−2
nolic solution of a 2-drop portion of 0.1 M H O in the methanolic
H O in the methanolic solution of 6.49×10 M complex
2 2
2
2
1
3

Journal of the Iranian Chemical Society
coupling of one unpaired electron (S=1/2) of V4+ (3d ) with
its own nucleus (S=7/2). Computer simulation of experi-
mental spectra was obtained with the spine Hamilton param-
eter g=(1.989, 1.981, 1.979) and hyperꢂne spacing A=(80,
1
presumably occurs as dilution of the catalyst obtains the
minimal volume to react at target site which may further
aꢁect the electronic and steric properties of the inter-
mediate species. Thus on decreasing the solvent amount
from 10 to 2.5 ml, the space of larger molecular interac-
tion between catalyst and reactant is provided. So, 2.5 ml
AcCN solvent is the best for the optimization of reaction
conditions to ꢂnd the highest % conversion (entry no. 8
of Table 1).
1
04, 112) G,‬ which represents that complex is isotropic.
Catalytic eꢀciency
Considering the importance of products of oxidation reac-
tion of alkenes, the vanadium complex [VO(hyap)(acac) ]
The temperature of the reaction mixture also aꢁects the
oxidation of alkenes. Among four diꢁerent temperatures:
60 °C, 70 °C, 80 °C, and 90 °C, under optimized condition
(i.e., catalyst amount 5 mg, 30% H O amount (2.834 g,
2
as a catalyst was synthesized. By using complex [VO(hyap)
(
acac) ] as a catalyst for the study of oxidation of allylben-
2
zene as a model substrate to optimization the reaction condi-
tion for maximum % conversion of alkenes (such as catalyst
amount variation, oxidant amount (H O ) variation, solvent
2
2
25 mmol), solvent amount (2.5 ml AcCN), allylbenzene
(0.602 g, 5 mmol)), reaction was performed for 6 h. Fig-
ure 4d represents that temperature 60 °C, 70 °C, 80 °C,
and 90 °C shows 53.5%, 63.7%, 92.4%, and 80.1% conver-
sion of allylbenzene. Thus on increasing the temperature
from 60 °C to 80 °C, the % conversion increases, but at
boiling temperature (90 °C), the % conversion declines,
because the maximum amount of solvents are in vapor
form. So, the 80 °C temperature is best for optimization
of the reaction (entry no. 8 of Table 1).
2
2
amount variation, temperature variation, solvent nature vari-
ation, and nature of oxidant (H O or TBHP) variation).
2
2
The outcome of catalyst amount on the oxidation of
allylbenzene on taking four diꢁerent sequential reactions
was examined using diꢁerent amounts of catalyst, i.e., 1 mg,
3
mg, 5 mg, 7 mg, whereas other variables were kept con-
stant, i.e., allylbenzene (0.602 g, 5 mol), 30% H O (2.267 g,
2
2
2
0 mmol) in 5 ml of acetonitrile at 80 °C. The samples were
analyzed by extracting the substrate and products from the
reaction mixture by n-hexane (0.5 ml) at 1 h time interval
for 6 h. It is clear from Fig. 4a that 1 mg catalyst shows
The nature of solvents also plays an important role in
the oxidation of alkenes. So, four diꢁerent solvents MeOH,
AcCN, DMF, and DMSO were taken under the optimized
condition, i.e., catalyst amount 5 mg, 30% H O amount
1
9.7%, 3 mg shows 45.3%, 5 mg shows 72.8% and 7 mg
2
2
shows 72.0% conversions of allylbenzene. On increasing the
catalyst amount from 1 to 5 mg, the % conversion increases
from 19.7 to 72.8%, but further increment of catalyst amount
does not aꢁect the % conversion. Thus, 5 mg catalyst was
best for the optimization of reactions condition (entry no. 3
of Table 1).
(2.834 g, 25 mmol), solvent amount (2.5 ml), allylbenzene
(0.602 g, 5 mmol), and 80 °C temperature. It is clear from
Fig. 4e MeOH, AcCN, DMF, and DMSO show 90.5%,
92.4%, 5.1%, and 17.3% conversion of allylbenzene in 6 h.
The % conversion of allylbenzene in higher polar solvents
(MeOH and AcCN) is higher (90.5 and 92.4%), but in the
lower polar solvent (DMF and DMSO), it is low (5.1 and
17.3%). As compared to the polarity, methanol is more
polar than acetonitrile, but reduces the % conversion,
because in case of methanol, most of solvents are in vapor
form at 80 °C temperature. So, the reaction condition with
AcCN as a solvent is optimized. (entry no. 8 of Table 1).
In the same optimization reaction condition (i.e.,
allylbenzene (0.602 g, 5 mmol), 5 mg catalyst, 1:5
substrate:oxidant ratio, 2.5 ml AcCN, and 80 °C tempera-
ture), 70% tert-butyl hydroperoxide (TBHP) (3.218 g,
25 mmol) oxidant was used in place of 30% H O as a oxi-
In succession to ꢂnd out the supreme reaction condition,
the oxidant amount has been varied with the substrate, i.e.,
molar ratios of substrate:oxidant, viz. 1:2, 1:3, 1:4, and 1:5
were examined while keeping the constant amount of cata-
lyst (5 mg) and allylbenzene (0.602 g, 5 mmol) in 5 ml of
acetonitrile at 80 °C for 6 h. It is clear from Fig. 4b that the
%
conversion increases (41.6%, 61.7%, 72.8% and 86.2%)
with increase in substrate:oxidant ratio (1:2, 1:3, 1:4, and
1
:5). So, 1:5 ratios give the best result for optimizing the
reaction condition (entry no. 7 of Table 1).
The eꢁect of solvent amount (i.e., 2.5 ml, 5 ml, 7.5 ml,
and 10 ml) on the oxidation of allylbenzene was playing
a valuable contribution while keeping the ꢂxed catalyst
amount (5 mg), allylbenzene (0.602 g, 5 mmol), and oxi-
dant 30% H O (2.834 g, 25 mmol) at 80 °C tempera-
2
2
dant nature variation. The TBHP is a weak oxidant, so it
shows only 76.8% conversion which is small as compared
to H O (92.4%) (Fig. 4f). So, H O is the best oxidant and
2
2
2
2
co-reactant for the oxidation reaction.
2
2
ture for 6 h. It is clear from Fig. 4c that 2.5 ml, 5 ml,
Table 1 entry no. 8 is the best reaction condition for the
highest % conversion of allylbenzene. The optimized con-
dition is allylbenzene (0.6029 g, 5 mmol), catalyst amount
5 mg, 30% H O amount (2.834 g, 25 mmol), solvent
7
7
.5 ml, and 10 ml solvent amounts shows 92.4%, 86.2%,
8.2%, and 65.6% conversion in 6 h. On extending the
solvent amount, the % conversion decreases because this
2
2
amount (2.5 ml AcCN), and 80 °C temperature for 6 h.
1
3

Journal of the Iranian Chemical Society
Fig. 4 Optimization of oxidation of allylbenzene with catalyst [VO(hyap)(acac) ]. a Catalyst amount variation. b H O amount variation. c Sol-
2
2
2
vent amount variation. d Temperature variation. e Solvent nature variation. f Oxidant nature variation
Substrate scope
98% for 4-chlorostyrene, 98 for 2-norbornene, and 70% for
lemonine. The aromatic alkenes such as allylbenzene, sty-
rene, and 4-chlorostyrene were given carbonyl compound
during oxidation process, basically benzaldehyde as major
product and benzoic acid as minor product. Whereas ali-
phatic alkenes such as cis-cyclooctene, 1-methyl cyclohex-
ene, 2-norbornene, and lemonine were given epoxide as
major products, while alcohol and carbonyl compounds as
minor products (Table 2). However Indene gives carbonyl
compounds as major products along with epoxide as minor
product, and 1-octene gives only aldehyde (pentanal and
hexanal).
By using the same optimized reaction condition, the dif-
ferent types of alkenes were oxidized such as styrene,
cis-cyclooctene, 1-octene, 1-methyl cyclohexene, indene,
4
-chlorostyrene, norbornene, and lemonine. Table 2 repre-
sents the % conversion along with the TON/TOF value and
product selectivity.
Thus, the % conversion of oxidation of various alkenes
by using catalyst [VO(hyap)(acac) ] is 92% for allylben-
2
zene, 99% for styrene, 83% for cis-cyclooctene, 31% for
1
-octene, 67% for 1-methyl cyclohexene, 99% for indene,
1
3

Journal of the Iranian Chemical Society
Table 1 Data of all the reaction parameters used for the optimization of oxidation of allylbenzene for 6 h
S. No.
Amount
mg)
Temp. (in °C)
Substrate:oxidant
Oxidant
Sol.
Sol.am. (in ml)
% Conv.
TON
TOF (h−1
)
(
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
3
5
7
5
5
5
5
5
5
5
5
5
5
5
5
5
80
80
80
80
80
80
80
80
80
80
60
70
90
80
80
80
80
1:4
1:4
1:4
1:4
1:2
1:3
1:5
1:5
1:5
1:5
1:5
1:5
1:5
1:5
1:5
1:5
1:5
H O
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
AcCN
MeOH
DMF
5
5
5
5
5
5
5
2.5
7.5
10
2.5
2.5
2.5
2.5
2.5
2.5
2.5
19.7
45.3
72.8
72.0
41.6
61.7
86.2
92.4
78.2
65.6
53.5
63.7
80.1
90.5
5.1
398
304
293
207
167
249
347
372
315
264
216
256
323
365
20
66
50
48
34
27
41
57
62
52
44
36
42
53
60
3
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
H O
2
H O
2
H O
2
H O
2
H O
2
H O
2
H O
2
H O
2
0
1
2
3
4
5
6
7
H O
2
H O
2
H O
2
H O
2
H O
2
H O
2
H O
DMSO
AcCN
17.3
76.8
70
309
11
51
2
TBHP
The comparison plot of % conversion of the catalyst
Physical measurements
[
VO(hyap)(acac) ], VO(acac), and blank is shown in
2
Fig. 5. For the model substrate (allylbenzene), blank reac-
The structure of vanadium metal complexes was charac-
terized by the various physicochemical method. FTIR of
complexes was taken from an Agilent Cary 600 Series
tion shows 2.8%, [VO(acac) ] shows 71.3% and catalyst
2
shows 92.4% conversion in optimized condition. It is clear
from Fig. 5 that the synthesized catalyst is an eꢁective
catalyst for the oxidation of alkenes. This is presumed that
the 2-hydroxyacetophenone in catalyst provides path for
the stabilization of intermediate species during catalytic
process, which enhances the oxidation of alkenes.
−
1
through ATR mode in the range 4000–400 cm . The elec-
tronic spectra metal complex was taken in a “SHIMADZU”
UV-1800 spectrophotometer series by dissolving in metha-
nol. The single-crystal XRD was analyzed by the CCD Eos
S2 detector of the Rigaku Oxford Diꢁraction system at room
temperature. The X-band EPR spectra of the metal complex
were recorded at 100 kHz ꢂeld modulation in Bruker EMX
spectrometer at room temperature. Catalytic oxidation of
various alkenes was monitored by an HP-5 capillary column
Experimental
(
30 m×0.25 mm×0.25 μm) and an FID detector of Agilent
Materials
gas chromatograph (7890B), and products of the oxidation
reaction were identiꢂed by GC–MS (Trace 1300 ISQ QD).
Initial reagents 2-hydroxyacetophenone (SRL, India),
V O (Merk, India), acetylacetone (Merck, India), sulfuric
Synthesis of [VO(hyap)(acac)2]
2
5
acid (Merk, India), potassium carbonate (Merck, India),
H O (Merck, India), TBHP (Merck, India), styrene (Alfa-
The complex [VO(hyap)(acac) ] was prepared by the reac-
2
2
2
Aesar, India), allylbenzene (Alfa-Aesar, India), 1-methyl
cyclohexene (Alfa-Aesar, India), cis-cyclooctene (Alfa-
Aesar, India), 1-octene (Alfa-Aesar, India), 4-chlorosty-
rene (TCI, Japan), indene (TCI, Japan), 2-norbornene(TCI,
Japan), lemonine(TCI, Japan), AR grade solvent (Merck
tion of 1.325 g [VO(acac) ] and 0.680 g 2-hydroxyacetophe-
2
none (hyap) in the methanol by reꢀuxing for 2–4 h (Scheme
S1). After completion of the reaction, the reaction mixture
was kept for slow evaporation to form greenish colored crys-
tals of the metal complex [VO(hyap)(acac) ].
2
&
Rankem, India), and HPLC grade solvent were used.
Yield: 33.43%; Anal. Calcd. For C H O V (MW
1
8
24
7
[
VO(acac) ] was used as a metal precursor, which synthe-
403.32) C, 53.60%; H, 6.00%; O, 27.77%;Found: C, 53.87%;
2
−
1
sized from reported literature [60].
H, 5.53%; FTIR (ATR, cm ): 3238(ν ), 1621(υ
),
CO(hyap)
O–H
1
3

Journal of the Iranian Chemical Society
Table 2 Table represents the % conversion and % selectivity of products of various alkenes catalysed by [VO(hyap)(acac) ] in the presence of
2
hydrogen peroxide
Substrate % Time TON
conversion (in h)
TOF
62
% Selectivity of products
References
[43, 46, 47]
6
372
–
–
6
7
2.76
1.52
3
2
7.23
8.47
9
9
2
9
4
6
400
335
100
55
[48–50]
–
–
[5, 51, 52]
8
4
5.06
1.25
14.93
58.74
8
3
3
1
6
6
126
271
21
45
[5, 51, 53]
[54, 55]
5
0.26
2
0.78
28.95
6
9
7
9
6
1
399
402
66
[40, 56]
[57, 58]
31.93
9.60
5
8.46
402
7
7.63
8.64
9
9
7
9
8
0
1
0.85
11.51
22.57
6
h
398
285
66
47
[54, 63]
[55, 59]
5
18.78
6
18.48
34.25
47.25
1
555(υ
), 1516(ν
), 984(ν
); UV–Vis[ε (L
S2 detector in the Rigaku Oxford Diꢁraction system by
using Mo K/radiation (λ=0.71073 Å). The crystal data of
complex were solved by a straight process (SIR92) [61] and
CO(acac)
−1
C=C
V=O
−
1
3
3
mol cm ), λ
(nm)]; (4.11˟10 ) 211, (2.43˟10 ) 253,
max
3
3
+
(
1.68˟10 ) 274, (1.70˟10 ) 306, (12.54) 777. ESI -MS: m/z
+
2
4
26.31 (Na[VO(hyap)(acac) ]) .
reꢂned through full-matrix least-squares versus F by retain-
2
ing SHELXS-2017 and SHELXL-2017 programs [62, 63].
The crystal data and structure reꢂnement parameters are
represented in Table 3. C, O, and V atoms were anisotropi-
cally reꢂned, and all H-atoms were placed in a deliberated
position, which reꢂned as controlled with C–H distances
from 0.93 to 0.96 Å and O–H is 0.82 Å.
Single‑crystal X‑ray analysis and structure
reꢁnement
The single-crystal X-ray analysis of complex [VO(hyap)
(
acac) ] was recorded at room temperature with CCD Eos
2
1
3

Journal of the Iranian Chemical Society
Fig. 5 Comparative plot of
conversion of oxidation of
various alkenes catalysed by
VO(hyap)(acac) ], [VO(acac) ],
99.2
99.1
99.8
98.7
Blank
1
00
%
92.4
8
7.6
VO(acac)2
9
0
84.3
8
3
[
2
2
[VO(hyap)(acac)2]
and without a catalyst
80
74.5
7
1.3
70.9
7
0.3
6
6.9
67.4
67.6
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
5
3.5
54.1
45.5
4
3.5
3
1.4
2
0.2
7
.8
6
.2
3
.9
2
.8
1
.6
1.4
Allylbenzene
Styrene
Cis-cyclooctene
1-octene
1-methyl
cyclohexene
Indene
4-chlorostyrene
Non borane
Lemonine
Table 3 Crystal data and structure reꢂnement parameters of the com-
conventional oxidation reaction, an aqueous solution of 30%
H O , alkene, and catalyst were mixed in acetonitrile and the
plex [VO(hyap)(acac) ]
2
2
2
solution was heated at 80 °C with constant stirring in an oil
bath. With the help of GC, the % conversion of the substrate
was monitored by using calibration plot of substrate. Before
the injection of samples in the GC, the reaction mixture was
extracted out from the catalyst’s solution through a biphasic
process (n-hexane). The products of oxidation reaction were
identiꢂed by GC–MS. To ꢂnd out the highest % conversion,
the reaction condition of alkene oxidation was optimized by
using diꢁerent parameters such as (1) catalysts amount, (2)
oxidant amount, (3) solvent amount, (4) temperature variation,
CCDC No.
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
1985769
C H O V
1
8
24
7
403.31
Monoclinic
P 2 /c
1
7.556
27.347
9.535
90.000
91.587
90.000
1969.5
4
(
5) nature of the solvent, and (6) nature of oxidant.
γ (°)
V (Å )
3
Conclusions
Z
ρcalc (g cm−3)
1.360
0.538
844
µ (Cu Ka or Mo Ka) (mm−1)
F(000)
The vanadium complex [VO(hyap)(acac) ] was synthesized
2
by the reaction of [VO(acac) ] and 2-hydroxyacetophenone.
2
The synthesis was uncomplicated and economical. The com-
plex was isolated as crystal form and analyzed by single-
crystal XRD analysis (CCDC No. 1985769). The functional
group was analyzed by FTIR, and the solution phase study
was done by UV–Vis, ESI mass, and EPR spectroscopy. The
eꢃciency of catalyst was checked by the oxidation of vari-
ous alkenes with the help of hydrogen peroxide which shows
high % conversion up to 99% along with high TON and TOF
value. In most of the cases, aldehyde, acid, and epoxide are
major products.
2
θ range (°)
5.60–55.66
10,210
4566
0.0563
2426
Reꢀections measured
Independent reꢀections
Rint
Index reꢀections (I>2σ(I))
Parameters
R1(I>2σ(I))
wR (all data)
235
0.1007
0.3044
1.075
2
GooF (all data)
Maximum peak and hole (e Å−3)
1.070/−0.445
Oxidation of alkenes
Supporting
The homogeneous catalytic oxidation of alkenes was carried
Spectra of FTIR, UV–Vis, ESI mass, synthetic scheme of
complex [VO(hyap)(acac)2], table of bond angle, and bond
length.
out by using complex [VO(hyap)(acac) ] in a 50-ml round-
2
bottom ꢀask equipped with water ꢀowed condenser. In a
1
3

Journal of the Iranian Chemical Society
Acknowledgements A. M. thanks Dr. C. Haldar, department of chem-
istry, IIT (ISM), Dhanbad, for providing instrumental facility. The
author acknowledges IIT (ISM), Dhanbad, Jharkhand, for fellowship.
The author acknowledges the central research facility, IIT (ISM), Dhan-
bad, for providing single-crystal XRD analysis.
32. A. Maurya, N. Kesharwani, P. Kachhap, V.K. Mishra, N. Chaud-
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Compliance with ethical standards
6. C. Ballatore, D.M. Huryn, A.B. Smith, ChemMedChem 8, 385
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2013)
Conflict of interest There are no conꢀicts of interest to declare.
7. S. Takizawa, T. Katayama, H. Somei, Y. Asano, T. Yoshida, C.
Kameyama, D. Rajesh, K. Onitsuka, T. Suzuki, M. Mikami, H.
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