Dioxotungsten(VI) complexes with isoniazid-related hydrazones as (pre)catalysts for olefin epoxidation: Solvent and ligand substituent effects

Article abstract of DOI:10.1039/c6ra05067k

The mononuclear dioxotungsten(vi) complexes [WO₂(L^3OMe)(D)] (1a and 1b), [WO₂(L^4OMe)(D)] (2a and 2b) and [WO₂(L^H)(D)] (3a and 3b) (D = EtOH (1a-3a) or MeOH (1b-3b); L^3OMe = 3-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L^4OMe = 4-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L^H = 2-oxybenzaldehyde isonicotinoyl hydrazonato) were synthesized by the reaction of [WO₂(acac)₂]·0.5C₆H₅Me with the respective isoniazid-related hydrazone. The compounds were characterized by microanalysis, FT-IR and NMR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction method. The crystal and molecular structures of 1a, 1b, 3a and [WO₂(acac)₂]·0.5C₆H₅Me were determined by single crystal X-ray diffraction. The structures of 1a, 1b, 3a are mononuclear and form hydrogen bonded centrosymmetric dimers. In all three complexes, the dimers are also held together by π?π interactions between aromatic rings. The catalytic performances (activity and selectivity) of 1a-3a and 1b-3b towards alkene epoxidation by tert-butyl hydroperoxide (TBHP) were investigated under different conditions.

Full text of DOI:10.1039/c6ra05067k

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: V. Vrdoljak, J.
Pisk, B. Prugoveki, D. Agustin, P. Novak and D. Matkovi-alogovi, RSC Adv., 2016, DOI:
10.1039/C6RA05067K.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Please do not adjust margins
RSC Advances
Page 1 of 11
View Article Online
DOI: 10.1039/C6RA05067K
Journal Name
ARTICLE
Dioxotungsten(VI) complexes with isoniazid-related hydrazones
as (pre)catalysts for olefin epoxidation: solvent and ligand
substituent effects
Received 00th January 20xx,
Višnja Vrdoljak,*a Jana Pisk, a,b,c Biserka Prugovečki, a Dominique Agustin,*b,c,d Predrag Novaka and
Dubravka Matković-Čalogovića
The mononuclear dioxotungsten(VI) complexes [WO2(L3OMe)(D)] (1a and 1b), [WO2(L4OMe)(D)] (2a and 2b) and [WO2(LH)(D)]
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
(3a and 3b) (D = EtOH (1a−3a) or MeOH (1b−3b); L3OMe = 3-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L4OMe
4-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, LH
2-oxybenzaldehyde isonicotinoyl hydrazonato) were
=
=
synthesized by the reaction of [WO2(acac)2]∙0.5C6H5Me with the respective isoniazid-related hydrazone. The compounds
were characterized by microanalysis, FT-IR and NMR spectroscopy, thermogravimetric analysis, and powder X-ray
diffraction method. The crystal and molecular structures of 1a, 1b, 3a and [WO2(acac)2]∙0.5C6H5Me were determined by
single crystal X-ray diffraction. The structures of 1a, 1b, 3a are mononuclear and form hydrogen bonded centrosymmetric
dimers. In all three complexes, the dimers are also held together by π∙∙∙π interactions between aromatic rings. The
catalytic performances (activity and selectivity) of 1a−3a and 1b−3b towards alkene epoxidation by tert-butyl
hydroperoxide (TBHP) were investigated under different conditions.
structurally characterized by the powder X-ray diffraction
method (PXRD).2a
Introduction
Compounds with active metal centres play an important role
The chemistry of hydrazones receives an ongoing attention in
various fields. Thus, isoniazid-related aroylhydrazones and
their coordination compounds are of particular interest
because of their biological activities1 and their structural
as functional materials in diverse fields.4 In this context, metal
complexes with coordinatively unsaturated metal ions as well
as those ligated by weakly coordinating ligands are of
particular interest. In addition to having other functions, they
also act as catalysts for the epoxidation of alkenes, an
important process of wide chemical and biochemical
significance. A variety of complexes has been used in this way
and those containing the {MO2}2+ unit are known as highly
selective catalysts.5-7
diversity.2
Although
various
metallosupramolecular
assemblies2 as well as mononuclear3 dioxomolybdenum(VI)
complexes with isoniazid-based aroylhydrazone derivatives are
known, related dioxotungsten(VI) complexes are rare. To the
best of our knowledge, only the dioxotungsten(VI) compounds
[WO2(NIH)]n and [WO2(VIH)]4 (where NIH2–
= 2-oxy-1-
The catalytic conversion of olefins to epoxides may involve
oxidants such as tert-butylhydroperoxide (TBHP),3b,5a-5c,7 O2,8
or H2O2,5d,5e usually in organic solvents. In accordance with the
requirements of "green" chemistry, these reactions have also
been performed under organic solvent-free conditions.
However, contrary to dioxomolybdenum(VI),3b,5a,5c,6,7b−7d
investigations of solvent-free epoxidations involving
dioxotungsten(VI) complexes are quite scarce. Examples are
[WO2(L’)(solv)] (solv = alcohol, L’= Schiff base)3b,9 [WO2L] (L =
naphthaldehyde isonicotinoyl hydrazonato and VIH2– = 3-
methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato) were
aUniversity of Zagreb, Faculty of Science, Department of Chemistry, Horvatovac, 102a,
10000 Zagreb, Croatia, Fax: ++ 385-1-4606341; Tel: ++385-1-4606353; E-mail:
visnja.vrdoljak@chem.pmf.hr
b Université de Toulouse, Institut Universitaire de Technologie Paul Sabatier,
Département de Chimie, Av. Georges Pompidou, CS 20258, F-81104 Castres Cedex,
France: Fax: 00335 63 351 910, Tel: 00335 63 621 172. E-mail: dominique.agustin@iut-
tlse3.fr
aminobisphenolato ligand)10 and [WO2(salen)] (salen
=
bis(salicylidenediamine)) complexes.11 We have previously
compared the catalytic activity of dioxomolybdenum(VI) and
dioxotungsten(VI) complexes with ligands derived from 4-
hydroxy-benzhydrazone.12 It was shown that the MoVI
complexes are more efficient catalysts for cyclooctene
epoxidation by tert-butyl hydroperoxide (TBHP) under organic
solvent-free conditions.
c CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP 44099,
F-31077 Toulouse Cedex 4, France
d Université de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, France
† Electronic Supplementary Information (ESI) available: (1) spectral data, (2) XRPD
patterns, (3) tables and (4) figures for compounds. Crystallographic data sets for the
structures 1a, 1b, 3a, and [WO2(acac)2]⋅0.5C6H5Me are available through the
Cambridge Structural Data base with deposition numbers 1454679-1454682. See
DOI: 10.1039/b000000x/
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 2 of 11
View Article Online
DOI: 10.1039/C6RA05067K
ARTICLE
Journal Name
Scheme
substituent is shown in red colour in Scheme 1.
2 = MeOH or EtOH). The R’
Mononuclear [WO2(LR)(D)] complexes (D
Synthesis of dioxotungsten(VI) complexes chelated by ONO
tridentate ligands
Compound [WO2(acac)2]∙0.5C6H5Me was used as a precursor
for the synthesis of dioxotungsten(VI) complexes of the type
[WO2(LR)(D)], Scheme 2, with isoniazid-related hydrazone
ligands. The products were obtained by the ligand exchange
strategy using the corresponding aroylhydrazone ligand in
Scheme
substituent is shown in red colour.
1 ,
The isoniazid-based hydrazones H2LR (H2L3OMe H2L4OMe and H2LH). The
ethanol (1a−3a) or methanol (1b−3b). The reactions were
performed under a dry argon atmosphere.
Considering these features, we have decided to investigate the
influence of the coordinated ligands (solvent (D) and isoniazid-
related hydrazones (LR)) on the solid-state structure and
catalytic activity of the [WO2(LR)(D)] complexes. To achieve this
aim, the investigation included a systematic variation of: (i) the
tridentate ligand (2-hydroxybenzaldehyde isonicotinoyl
hydrazone, H2LH, and two methoxy-substituted derivatives, i.e.
3-methoxy-2-hydroxybenzaldehyde isonicotinoyl hydrazone,
H2L3OMe, and 4-methoxy-2-hydroxybenzaldehyde isonicotinoyl
hydrazone, H2L4OMe, see Scheme 1), and (ii) the solvent D
(MeOH and EtOH). The mononuclear WVI complexes
Synthesis in the presence of a small amount of DMF proved to
be effective for producing products in crystalline form. Good
quality single crystals of 1a, 1b and 3a suitable for X-ray
diffraction analysis were obtained in this way. Otherwise, in
the absence of DMF, yellow powdered solids were obtained.
Thermal analysis
The thermal stability of the complexes was investigated under
an oxygen atmosphere. The mass loss corresponding to the
first step in the TG curves of 1a–3a, 1b–3b was related to the
− −3b), where
[WO2(LR)(EtOH)] (1a 3a) and [WO2(LR)(MeOH)] (1b
loss of the coordinated ethanol or methanol molecule. This
process occurred in the range 135−186 °C (1a), 159−210 °C
1b), 141−197 °C (2a), 154−193 °C (2b), 190−234 °C (3a) and
R
=
3OMe, 4OMe or H, have been investigated as
(
(pre)catalysts for the epoxidation of cyclooctene in the
presence of organic solvent as well as in its absence, using
TBHP (in decane or in water) as an oxidant.
175−237 °C (2b). These temperatures are generally much
higher than those required for alcohol removal from similar
dioxomolybdenum(VI) complexes, for instance 110–120 °C for
EtOH loss from a salicylidene-2-aminophenolato derivative,14
indicating that the alcohol donor forms a stronger bond with
W relative to Mo. The same trend was observed in a previous
report.12 All remaining unsolvated products started to
decompose at 298 °C for 1a and 1b, 308 °C for 2a and 2b, and
295 °C for 3a and 3b. The final residue was identified as WO3.
The first step in the thermogravimetric curve of
[WO2(acac)2]∙0.5C6H5Me was related to the loss of toluene
(65–104 °C) and was followed, upon further heating, by
significant weight loss in the range 128−449 °C due to ligand
decomposition.
Results and discussion
Synthesis of bis(acetylacetonato)dioxotungsten(VI) toluene
solvate (2/1), [WO2(acac)2]∙0.5C6H5Me
The synthesis of the starting tungsten precursor
[WO2(acac)2]∙0.5C6H5Me was performed from freshly prepared
WO2Cl2 and an excess of dry acetylacetone in toluene. Crystals
suitable for X-ray structure analysis were obtained directly
from the reaction mixture. The product can be recrystallized
from
a toluene/acetylacetone mixture. The previously
reported pseudopolymorph was identified as [WO2(acac)2].13
Surprisingly, the crystal and molecular structure of this
compound has not been reported previously.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 3 of 11
View Article Online
DOI: 10.1039/C6RA05067K
Journal Name
ARTICLE
H2L3OMe H2O).16 The N2−C1 bond length is shortened in the
⋅
complexes 1a and 1b (1.290(5) Å in 1a and 1.270(5) Å in 1b) in
Crystal and molecular structure of [WO2(acac)2]∙0.5C6H5Me
comparison to the free ligands (1.3552(18) Å and 1.339(2) Å in
H2L3OMe and H2L3OMe
⋅H2O, respectively), while the N1−N2 bond
is lengthened (1.401(4) Å in 1a and 1.395(3) Å in 1b) in
comparison to the free ligands (1.3791(19) Å and 1.3724(15) Å
in H2L3OMe and H2L3OMe
delocalization.
⋅H2O, respectively), due to electron
The C7−N1 bond length in 3a is 1.282(4) Å and is not
significantly different than in the free H2LH ligand, 1.2756(16)
Å.17 The N2-C1 bond is shortened in 3a (1.291(4) Å) in
comparison to the free H2LH ligand (1.3558(17) Å), whereas the
N1−N2 bond is lengthened in the complexes (1.399(4) Å) in
comparison to the free H2LH ligand (1.3699(15) Å) due to the
electron delocalization.
Fig.
1 ORTEP drawings of [WO2(acac)2]⋅0.5C6H5Me with the atom-labelling In 1a, 1b and 3a the ligand is not planar with the largest
scheme (displacement ellipsoids of non-hydrogen atoms are drawn at the 50%
probability level). Toluene molecule is omitted for clarity.
deviation from planarity being that of the phenyl and the
pyridyl moieties in 3a (φ = 8.94(12) , Table S2, see ESI†). The
largest dihedral angle between the planes of the five- and six-
°
membered chelate rings is also observed in 3a (ψ = 16.87(16)°,
Table S2).
In [WO2(acac)2]∙0.5C6H5Me the tungsten atom exhibits the
distorted octahedral coordination sphere. It is coordinated by
two cis oxo oxygen atoms and by four oxygen atoms from the
two acetylacetonate ligands (Fig. 1). The asymmetric unit
consists of the complex molecule and one half of the toluene
molecule of crystallization (Fig. S1, see ESI†).
The Cambridge Structural Database15 was searched for
structures with the XO2 unit (X was any element with the
coordination number of 6: two oxygen atoms from two dioxo
groups and four oxygen atoms from two acac ligands, including
substituted acac ligands). The search gave only 9 hits (6 Mo
complexes, 2 U compounds and a W complex). Since the data
A common feature of 1a, 1b and 3a is the association of the
molecules by hydrogen bonds (O5−H50∙∙∙N3) into
centrosymmetric dimers, graph set R22 (18), Fig. 2. The
shortest hydrogen bond distance is in complex 1b
d(O5∙∙∙N3[−x, y,1 ) = 2.692(4) Å (Table S3, see ESI†).
,
−
−z ]
Table 1 Selected bond lengths (Å) and angles (°) for compounds 1a, 1b and 3a
1a
1b
3a
W−O1
W−O2
2.001(2)
1.922(2)
1.706(2)
1.718(2)
2.292(2)
2.249(2)
1.275(4)
1.401(4)
1.290(5)
149.17(9)
97.60(10)
97.71(10)
78.35(9)
71.81(9)
98.56(10)
103.40(10)
80.73(9)
81.42(9)
104.48(11)
168.71(10)
92.41(10)
86.59(9)
161.35(10)
76.32(8)
2.000(3)
1.997(2)
1.927(3)
1.704(2)
1.719(2)
2.306(3)
2.248(3)
1.282(4)
1.399(4)
1.291(4)
148.58(9)
97.96(11)
98.93(11)
79.48(9)
71.91(9)
99.16(11)
102.06(11)
78.98(10)
81.17(9)
104.37(12)
169.69(11)
92.58(10)
85.92(10)
161.87(10)
77.13(9)
for the
W
complex (having 1,3-phenyl substituted
1.927(3)
acacetylacetonate) include only the unit cell and lack the
atomic coordinates, a comparison of bonds and angles with
the present structure is not possible. The bond distances and
angles around the W atom and within the chelate rings are
given in Table S1, see ESI†.) There are no classical hydrogen
bonds in the crystal structure, only a weak C−H∙∙∙O interacꢀon
between the toluene molecule and an oxo oxygen atom
W−O3
1.704(3)
W−O4
1.721(3)
W−O5
2.327(3)
W−N1
2.217(3)
C7−N1
1.284(5)
N1−N2
1.395(4)
N2−C1
1.270(5)
O1−W−O2
O1−W−O3
O1−W−O4
O1−W−O5
O1−W−N1
150.99(11)
96.44(14)
98.32(13)
80.63(11)
72.09(11)
98.56(14)
101.59(13)
80.73(12)
81.72(11)
104.90(14)
171.06(12)
96.10(12)
83.92(12)
157.88(13)
74.97(11)
(d(C15∙∙∙O5[-1/2-x,1/2+y,1/2-z]) = 3.337(12) Å).
Crystal and molecular structure of [WO2(LR)(D)]
In all compounds, the tungsten atoms exhibit the distorted
octahedral coordination sphere. The ligand is coordinated in O2−W−O3
the dianionic form to the cis-{WO2}2+ core via the ONO donor
O2−W−O4
O2−W−O5
atoms. The remaining sixth coordination site is occupied by the
O2−W−N1
oxygen atom from the solvent molecule (ethanol in 1a and 3a
methanol in 1b). The ORTEP plots of the molecular structures
of 1a 1b and 3a are given in the Supporting Information (Fig.
,
O3−W−O4
O3−W−O5
O3−W−N1
O4−W−O5
O4−W−N1
O5−W−N1
,
S2, see ESI†).
The distance from the W atom to the O donor atom of the
solvent molecule in 1a, 1b and 3a represents the longest bond
within the distorted octahedron (Table 1). The C7−N1 bond of
the L3OMe ligand in complexes 1a and 1b is 1.275(4) and
1.284(5) Å, respectively and is not significantly different than
in the free ligands (1.2791(18) Å in H2L3OMe and 1.276(2) Å in
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 4 of 11
View Article Online
DOI: 10.1039/C6RA05067K
ARTICLE
Journal Name
Fig. 2 Discrete dimer formed through intermolecular O5−H50∙∙∙N3[-x,-y,1-z] hydrogen bonds in 1b. Hydrogen bonds are shown by dotted lines.
and pyridyl rings in 1b, and between the two phenyl rings in 3a
(Fig. 3, Table S4, see ESI†).
Complex 1b is isostructural with the dioxomolybdenum(VI)
complex [MoO2(L3OMe)(MeOH)] (CSD code KANYIJ18 and
KANYIJ01).19 The powder X-ray diffraction patterns of 2a and
2b indicate that they are isostructural (Fig. S3). The
dioxotungsten(VI) complex 3a is isostructural with the
corresponding
[MoO2(LH)(EtOH)]
dioxomolybdenum(VI)
complexes,
UVAQOY)2b
and
(CSD code
[MoO2(LH)(MeOH)] (CSD code PAGCEF,20 PAGCEF01).21 PXRD
of 3a and 3b indicate that they are also isostructural (Fig. S3).
1a
IR spectroscopy
The IR spectroscopic analysis confirms the doubly
deprotonated state of the ONO ligands for all [WO2(LR)(D)]
complexes (Scheme 2). The bands found in the IR spectra of
H2LR, characteristic for the N−H and C=O groups (at ca. 3150
cm−1 and 1645 cm−1, respectively) are absent in the IR spectra
of the tungsten complexes, suggesting tautomerism
(=N−NH−(C=O)−
ꢀ
=N−N=(C−OH)−), deprotonaꢀon and
coordination through the oxygen atom. This is additionally
supported by the presence of a new band at ca. 1315 cm−1
assigned to the stretching vibrations of the C−O bond.22 Two
stretching vibration bands belonging to the C=Nimine and
C−Ophenolic bonds appeared in the spectra of the complexes at
ca. 1600 cm−1 and 1340 cm−1.22 They indicate that coordination
of the ligand L2− to the cis-{WO2}2+ core occurs through the
ONO donor atoms (Scheme 2). A band around 1050 cm–1, seen
1b
in the IR spectra of 1a
stretching vibration of the coordinated alcohol molecule.23
The presence of the {WO2}2+ core in 1a
3a and 1b 3b was
–3a and 1b–3b, is assigned to the C–O
−
–
identified by the appearance of the strong absorption bands
found in the range 959−949 cm−1 and 920−896 cm−1,
characteristic for νasym(WO2) and for the antisymmetric
combination of W=O and W−OEtOH (or W−OMeOH) stretchings,
respectively.24 The corresponding symmetric stretching bands
νsym(WO2) having significantly lower intensities appeared in the
same region but they either overlap with the asymmetric ones
or appear as shoulders.
3a
Fig. 3 Partial structural motif of endless chains in 1a, 1b and 3a. Hydrogen-bonds are
shown by blue dotted lines. Green dashed lines indicate π∙∙∙π interactions (values are
given in Å). The centroids of the five-membered chelate rings are shown as yellow
spheres, the centroids of pyridyl rings as green spheres and the centroids of the phenyl
rings as orange spheres.
UV-Vis spectroscopy
In all three complexes (1a, 1b and 3a), the dimers are also held
The electronic absorption spectrum of the ligands exhibit
several absorption bands with distinct maxima at 310 and 225
nm (H2L3OMe), at 338 and 219 nm (H2L4OMe), and at 294 and 325
nm (H2LH). These transitions are assigned to the intra-ligand
charge transfer transitions.25,26 Electronic spectra of the
together by π∙∙∙π interactions between the two pyridyl rings.
Neighboring dimer molecules are further connected by π···π
interactions between: the five-membered chelate rings and
phenyl rings in 1a, between the five-membered chelate rings
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 5 of 11
View Article Online
DOI: 10.1039/C6RA05067K
Journal Name
ARTICLE
dioxotungsten(VI) complexes 1a−3a and 1b−3b recorded in the reaction, but dissolved completely as the reactions
methanol exhibited N(pπ)–W(dπ) LMCT and O(pπ)–W(dπ) progressed. Under these conditions, it is known that TBHP is
LMCT bands in the 410–404 nm and 337–309 nm regions.27 mostly transferred to the organic phase.6b The substrate
Each complex displays additional bands in the higher energy conversion and the desired epoxide formation were monitored
region characteristic for intraligand transitions.
by analyzing only the organic layer. The analyses of the
aqueous layer were not carried out because the desired
epoxide is confined in the organic layer and only diol by-
NMR spectroscopy
The structures of all compounds in solution have been product may be partially lost in the aqueous layer. The
confirmed by one- and two-dimensional NMR techniques. The obtained results are compiled in Table 2 and the kinetic
proton and carbon resonances were unambiguously assigned profiles are presented in Fig. 4. The complexes with
1
by using H, APT, COSY, HSQC and HMBC experiments and are coordinated ethanol (1a
−
3a) are slightly more active than
3b). The profiles show similar
displayed in the supplementary material (Tables S5 and S6, those with methanol (1b
−
Scheme S1, see ESI†). In the 1H NMR spectra of the ligand evolution, with good activity in the first 20 minutes followed
molecules the most deshielded protons were those belonging by a slowdown. The two (pre)catalysts 3a and 2a, however,
to the NH and OH groups resonating at around 12 and 11 ppm, seemed to regain activity after 150 min.
respectively (Fig. S3–S5, see ESI†). The signals were somewhat
broadened indicating their involvement in hydrogen bonding
Table 2 Relevant catalytic results for the cyclooctene epoxidation by aqueous TBHP.a
Cat.
1a
Conversionb / %
Selectivityc / %
TOF20mind / h–1
TONe
63
interactions. In the complexes 1a, 2a and 3a those signals
20
17
28
23
31
22
3
12
33
8
73
171
81
disappeared reflecting their deprotonation upon coordination
of the ligands to tungsten.
1b
2a
70
117
93
Deprotonation was accompanied by shielding and deshielding
of the neighbouring hydrogen and carbon atoms (see Tables S1
and S2), as a result of the electron redistribution upon
complexation. Most of the neighbouring carbon atoms were
deshielded, i.e. they underwent upfield shifts upon
complexation up to 10.34 ppm as observed for carbon C-1 in
1a. The atoms C-4, C-12, C-14 and C-15 were also deshielded
but to a smaller extent, while C-5 experienced a shielding
effect up to 3.15 ppm as observed in 1a. These findings are in
accordance with the crystal structures obtained for these
compounds.
2b
3a
111
204
168
11
6
129
90
3b
a
Reaction conditions: time, 5 h; temperature, 80 °C; [W]/cyclooctene/TBHP
molar ratio: 0.25/100/200.
b
c
Calculated after
5
h.
Formed epoxide per
d
converted olefin after 5 h. n(cyclooctene transformed)/n(catalyst)/time at 20
minutes.e n(cyclooctene transformed)/
(catalyst at 5 h).
n
The cyclooctene conversion for all tested compounds after 5 h
is between 17 and 31%, following the order 3a 2a 2b 3b
1a 1b. The cycloctene oxide selectivity is rather poor, varying
>
>
≈
>
>
from 8 to 33%, certainly implying that the organic solvent-free
conditions and water from TBHP promote the cyclooctene
epoxide ring opening into the corresponding cyclooctanediol.6
The highest selectivity was observed for 2a and the lowest one
for 1a. The OMe substituent position has a marked influence
on the reaction selectivity. Poor results in terms of selectivity
and conversion could also be caused by the inhibition of the
tungsten catalyst in water, as stated elsewhere with other
tungsten-containing complexes.29–31 The highest turnover
Catalytic studies
The catalytic reactions were performed under different
experimental conditions in order to better understand the role
of solvent that delivers TBHP, water (procedure A) and decane
(procedure C) as well as the role of added organic solvent
(herein MeCN) with aqueous TBHP (procedure B) (Scheme 3).
As seen previously,6a TBHP in water without catalyst does
react poorly with cyclooctene under organic solvent free
conditions, as well as in the presence of organic solvent.28
frequency (TOF) is observed for 3a
.
Scheme 3 The different conditions used for the epoxidation.
Organic solvent-free epoxidation (catalytic procedure A)
All prepared mononuclear tungsten complexes [WO2(LR)(D)]
were employed as (pre)catalysts using aqueous TBHP as
oxidant, no additional organic solvent, and a 0.25 mol %
catalyst charge. After the TBHP addition at 80 °C, the tungsten
complexes remained partially undissolved at the beginning of
Fig. 4 Kinetic monitoring of cis-cyclooctene epoxidation with TBHP–H2O in the presence
of tungsten complexes: 1a – black circle, 1b – white circle, 2a – black triangle, 2b –
white triangle, 3a – black square, 3b – white square. Experimental conditions are in
Table 1.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 6 of 11
View Article Online
DOI: 10.1039/C6RA05067K
ARTICLE
Journal Name
linked to the protective hydrophobic effect of decane towards
We previously reported results of epoxidation catalysis with the epoxide opening with water.34
[WO2(LR*)(EtOH)] complexes (where LR* are the corresponding
4-hydroxy-benzhydrazide-related ligands).12 When comparing
with the isoniazide performance, it can be concluded that the
ligand hydrazone moiety does not influence the activity
whereas the aldehyde moiety does, the 4OMe derivative
always giving higher conversion than the corresponding 3OMe
derivative (Tables S7, Scheme S2, see ESI†). This could be
related to a steric impediment of the 3OMe substituent
toward the approach and coordination of TBHP to the metal
centre. As discussed earlier for the catalysts with molybdenum
complexes having a similar coordination sphere, the catalytic
cycle probably starts from the pentacoordinated mononuclear
compound [WO2(LR)]. The sixth coordination site is available
for the TBHP coordination and activation through the
assistance of an O−H∙∙∙O hydrogen bond.6b
One blank reaction was performed using TBHP in decane and
no solvent. After 5 h cyclooctene conversion of 17 % was
observed with selectivity of 49 % towards epoxide. The
catalysts have a very low conversion when using 0.25 mol %
catalyst charge. However, when adding the W complexes, the
lower selectivity showed that another transformation occurred
in addition to the epoxidation, but the nature of the other
compounds was not determined.
Table 3 Comparison of the catalytic parameters (conversion and selectivity) for the
cyclooctene epoxidation by TBHP (procedures A, B and C)a
Procedure:
Solvent:
TBHP in:
Catalyst
A
-
B
MeCN
water
Conv. (Selec.)
%
C
-
water
Conv. (Selec.)
%
decane
Conv. (Selec.)
%
1a
1b
2a
2b
3a
3b
20 (3)
17 (12)
28 (33)
23 (8)
31 (11)
22 (6)
66 (1)
51 (2)
78 (3)
63 (2)
47 (2)
35 (1)
20 (31)
22 (12)
20 (27)
25 (19)
29 (31)
23 (13)
Epoxidation of cyclooctene by aqueous TBHP in MeCN (catalytic
procedure B)
Acetonitrile is a commonly used solvent for metal-catalyzed
epoxidation.30 Addition of MeCN to the reaction mixture
positively affected the 1−3 catalyst activity, see Table 3. In all
cases, significant improvement of cyclooctene conversion was
observed (35−63%) aꢁer only 20 min of the reacꢀon progress.
Like under organic solvent-free conditions, the ethanol-
stabilized complexes were more active than those containing
methanol. The higher conversion for the complexes containing
a
Reaction conditions: time, 5 h; temperature, 80 °C; [W]/cyclooctene/TBHP
molar ratio: 0.25/100/200 for all compounds.
Conclusions
(L4OMe 2– and (L3OMe 2– ligands than for those having the (LH)2–
)
)
Replacement of the acetylacetonate ligands in [WO2(acac)2] by
the corresponding aroylhydrazone ligand H2LR in ethanol or
methanol results in mononuclear complexes [WO2(LR)(EtOH)]
ligand is more pronounced in MeCN. After 20 min, the
conversion reached again a plateau, implying possible catalyst
deactivation. All catalysts were poorly selective towards the
corresponding epoxide, which clearly indicates that the
addition of organic solvent does not promote epoxide
formation. The acetonitrile effect seems complex, since many
parameters affect the catalyst action: polarity, reactant and
product solubility, diffusion effects, solvent coordination to the
metal center, side reactions, etc.32,33 It has been suggested
that MeCN addition to alcohol-stabilized mononuclear
tungsten complexes leads to oligomerization.12 Certain
polynuclear complexes were found more active than the
corresponding alcohol-stabilized mononuclear ones,5a,5c
possibly explaining the better conversion in presence of MeCN
with the tested catalysts.
(
1a− −3b), respectively. Reactions
3a) and [WO2(LR)(MeOH)] (1b
in the presence of a small amount of DMF are effective in
producing crystals suitable for single crystal X-ray diffraction
experiment.
The association of the molecules by hydrogen bonds into
centrosymmetric dimers is a common feature of 1a, 1b and 3a.
Furthermore, the dimers are held together by π∙∙∙π
interactions involving the pyridyl rings.
All the dioxotungsten(VI) complexes led to greater cyclooctene
conversion by oxidation with TBHP in an acetonitrile solution
than in an organic solvent-free process but with very poor
selectivity towards the desired epoxide. Under organic solvent-
free conditions, use of TBHP in water or decane has no impact
to the cyclooctene conversion. Nevertheless, the use of TBHP
Epoxidation of cyclooctene by TBHP/decane under organic
solvent-free conditions (catalytic procedure C)
in decane has
a positive impact on the selectivity in
comparison to the use of aqueous TBHP.
The use of TBHP in decane did not result in any dramatic
change of the conversion parameters compared to procedure
A, yielding very similar results for all catalysts. This contrasts
with the positive contribution of decane observed with other
complexes.30 The solvent that delivers TBHP to the cyclooctene
solution (water or decane) has no influence on the conversion
rate. On the other hand, the epoxide selectivity was the same
or better than using aqueous TBHP. This has certainly to be
In general, the catalytic behaviour of the complexes depends
on the aroylhydrazone ligand, more precisely on the presence
and position of the substituent present in the salicylaldehyde
moiety. Compounds [WO2(L4OMe)(D)] achieved higher
conversions than the corresponding [WO2(L3OMe)(D)],
indicating the importance of the ring substituent position. The
complexes coordinated with ethanol showed higher
conversions than those with methanol.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 7 of 11
View Article Online
DOI: 10.1039/C6RA05067K
Journal Name
ARTICLE
(C=N), 1334 (C−Ophenolate), 1315 (C−Oenolate), 1199 (C−OEtOH),
949, 943 (WO2), 896 (O=W−OEtOH). UV-Vis (methanol): /nm
/dm3 mol–1 cm–1): 217, (38300), 337 (24800) and 407 (6414).
Experimental section
λ
Preparative part
(
ε
Ligands H2L3OMe, H2L4OMe and H2LH were prepared by Schiff base
condensation according to the procedure described in the
literature.35 The tungsten complex WO2Cl2 was prepared
according to literature procedure.36 Toluene and acetylacetone
were dried by refluxing over P2O5 and then distilled. Diethyl-
ether was dried over sodium wire and distilled. Methanol and
ethanol were dried using magnesium turnings and iodine and
then distilled. For the catalytic investigations cis-cyclooctene
(98% Aldrich), cyclooctene oxide (Aldrich), cis-1,2-
cyclooctanediol (99% Aldrich), TBHP (70% in water, Aldrich),
H2O2 (35% in water, Aldrich) and organic solvents (acetonitrile,
diethyl ether from ACROS) were commercially available and
used as received.
[WO2(LH)(EtOH)] (3a). Yield: 0.06 g, 55%. Calc. for
C15H15N3O5W (501.14): C, 35.95; H, 3.0; N, 8.4. Found: C, 35.65;
H, 2.8; N, 8.2%. TG: calc. for EtOH 9.2%, found 8.9%, calc. for
WO3 46.3%, found 45.95%. Selected IR data (cm−1): 1621
(C=N)py, 1600 (C=N), 1339 (C−Ophenolate), 1317 (C−O), 954
(WO2), 913, 905 (O=W−OEtOH). UV-Vis (methanol): λ/nm (ε
/dm3
mol–1 cm–1): 216, (27500), 294 (15650), 333 (12950) and 404
(1507).
[WO2(L3OMe)(MeOH)] (1b). Yield: 0.07 g; 62%. Anal. Calcd. for
C15H17N3O6W (517.142): C, 34.8; H, 2.9; N, 8.1. Found: C, 35.9;
H, 3.2; N, 7.6%. TG: calc. for MeOH 6.2%, found 6.2%, calc. for
WO3 44.8%, found 43.45%. Selected IR data (cm−1): 1621
(C=N)py, 1600 (C=N), 1345 (C−Ophenolate), 1315 (C−O), 1194
(C−OEtOH), 949 (WO2), 920, 910 (O=W−OEtOH). UV-Vis
Synthesis of [WO2(acac)2]∙0.5C6H5Me
A suspension of WO2Cl2 (2 g, 7 mmol) and 20 mL of
acetylacetone in 120 mL of toluene was refluxed under a dry
argon atmosphere for 9 h and left overnight. The obtained
mixture was refluxed additionally for 2 hours and filtered in a
glove box while still hot to remove insoluble impurities. The
solvent was evaporated by vacuum distillation to
approximately 5−10 mL and the resulꢀng soluꢀon was then
kept overnight at 10 °C to give a white solid. The obtained
precipitate was filtered and washed with dry diethyl-ether.
Yield: 1.9 g; 59%. Anal. Calcd. for C13.5H18O6W (460.12): C, 35.2;
H, 3.9. Found: C, 35.4; H, 3.8%. TG: calc. for C6H5CH3 10.01%,
found 9.85% calc. for WO3 50.4%, found 50.35%. Selected IR
data (cm−1): 1558, 1515, 954, 937, 909 cm−1.
(methanol):
λ/nm (ε
/dm3 mol–1 cm–1): 225, (42500), 309
(27350) and 410 (16314).
[WO2(L4OMe)(MeOH)] (2b). Yield: 0.06 g, 53%. Calc. for
C15H15N3O6W (517.14): C, 34.8; H, 2.9; N, 8.1. Found: C, 38.5;
H, 3.1; N, 7.9%. TG: calc. for MeOH 6.2%, found 6.4%, calc. for
WO3 44.8%, found 44.4 %. IR data (cm−1): 1615 (C=N)py, 1600
(C=N), 1334 (C−Ophenolate), 1314 (C−O), 1199 (C−OEtOH), 949, 943
(WO2), 896 (O=W−OEtOH). UV-Vis (methanol):
mol–1 cm–1): 217, (38300), 337 (24800) and 407 (6414).
λ/nm (ε
/dm3
[WO2(LH)(MeOH)] (3b). Yield: 0.08 g, 75%. Calc. for
C14H13N3O5W (487.1): C, 34.5; H, 2.7; N, 8.6. Found: C, 34.7; H,
2.8; N, 8.7%. TG: calc. for MeOH 6.6%, found 6.3%, calc. for
WO3 47.6%, found 47.4%. Selected IR data (cm−1): 1622
(C=N)py, 1602 (C=N), 1340 (C−Ophenolate), 1317 (C−O), 955
Synthesis of dioxotungsten(VI) complexes with hydrazone ligands
A mixture of [WO2(acac)2]∙0.5C6H5Me (0.22 mmol) and H2LR
(0.22 mmol) and 20 μL DMF in dry methanol or ethanol (35
mL) was refluxed for five hours under a dry argon atmosphere.
The obtained solution was cooled down to room temperature
and then concentrated under vacuum to one third of its
volume. The resulting solution was left at room temperature
for a few days. The obtained yellow precipitate was filtered,
rinsed with cold alcohol and dried in a desiccator up to the
constant weight.
(WO2_asym), 914, 906 (WO2_sym). UV-Vis (methanol):
/dm3 mol–1 cm–1): 216, (27500), 294 (15650), 333 (12950)
and 404 (1507).
λ/nm
(
ε
General procedure for the epoxidation of cyclooctene by aqueous
TBHP
Procedure A. A mixture of cyclooctene (2.76 mL, 20 mmol),
acetophenone (as an internal reference) and W (pre)catalyst
1a−3a and 1b−3b (0.05 mmol) was stirred and heated up to 80
[WO2(L3OMe)(EtOH)] (1a). Yield: 0.05 g; 43%. Anal. Calcd. for
C16H17N3O6W (531.17): C, 36.2; H, 3.2; N, 7.9. Found: C, 35.9;
H, 3.2; N, 7.6%. TG: calc. for EtOH 8.7%, found 8.35% calc. for
WO3 43.6%, found 43.9%. Selected IR data (cm−1): 1622
(C=N)py, 1600 (C=N), 1341 (C−Ophenolate), 1315 (C−O), 1194
(C−OEtOH), 959, 948 (WO2), 920, 910 (O=W−OEtOH). UV-Vis
°C before addition of aqueous TBHP (70% w/w, 5.48 mL, 40
mmol). The mixture is initially an emulsion, but two phases
become clearly visible as the reaction progresses, a colourless
aqueous one and a yellowish organic one. The reaction was
monitored for 5 h with withdrawal and analysis of organic
phase aliquots (0.1 mL) at required times. Each withdrawn
sample was mixed with 2 mL of Et2O, treated with a small
quantity of MnO2 and then filtered through silica and analyzed
by GC.
(methanol):
λ/nm (ε
/dm3 mol–1 cm–1): 225, (42500), 309
(27350) and 410 (16314).
[WO2(L4OMe)(EtOH)] (2a). Yield: 0.05 g, 43%. Calc. for
C16H17N3O6W (531.14): C, 36.2; H, 3.2; N, 7.9. Found: C, 36.0;
H, 3.0; N, 7.6%. TG: calc. for EtOH 8.7%, found 8.4%, calc. for
WO3 43.65%, found 43.1%. IR data (cm−1): 1616 (C=N)py, 1600
Procedure B. The procedure was performed in the same
manner as procedure A with addition of 2 mL of MeCN before
the addition of aqueous TBHP.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 8 of 11
View Article Online
DOI: 10.1039/C6RA05067K
ARTICLE
Journal Name
CuKα radiation. The sample was contained on a Si sample
Procedure C. The same as procedure A with using TBHP in holder. Patterns were collected in the range of 2 = 5 − 40°
θ
with the step size of 0.03° and at 1.5 s per step. The data were
collected and visualized using the X'Pert programs Suite. 37
decane (40 mmol, 6.5 mL) as oxidizing agent.
Physical methods. Elemental analyses were provided by the
Analytical Services Laboratory of the Ruđer Bošković Institute,
Zagreb. Thermogravimetric (TG) analysis was carried out with a
X-Ray Crystallography. Single crystal diffraction. The X-ray single-
crystal structure data obtained for [WO2(acac)2]
1a 1b and 3a are tabulated in Table 4. The single crystal X-ray
diffraction data were collected by ω-scans on an Oxford
Diffraction Xcalibur CCD diffractometer with graphite-
⋅0.5C6H5Me,
,
Mettler-Toledo
TGA/SDTA851e
thermobalance
using
aluminum crucibles. All experiments were recorded in a
dynamic atmosphere with a flow rate of 200 cm3 min−1.
Heating rates of 5 K min−1 were used for all investigations.
Fourier Transform Infrared spectra (FT-IR) were recorded in
3
monochromated Mo Kα radiation (λ = 0.71073 Å). Each single
crystal was glued onto a glass fibber and the data were
collected at room temperature. The data reduction was
performed using the CrysAlis software package.38 Solution,
refinement and analysis of the structures were done using the
programs integrated in the WinGX system.39
KBr pellets with
a Perkin-Elmer 502 spectrophotometer.
Spectra were recorded in the spectral range between
4500−450 cm−1. Electronic absorption spectra were recorded
at 25 °C on a Cary 100 UV-Vis Spectrophotometer.
All NMR spectra were recoded on Bruker Avance III HD 400 The structures were solved by using the SHELXS program and
spectrometer operating at 400 MHz equipped with
a
the Patterson method. The refinement procedure was
broadband observed (BBO) Prodigy cryoprobe and z-gradient performed by the full-matrix least-squares method based on F2
accessory. Compounds were dissolved in DMSO-d6 and against all reflections using SHELXL.40
measured in 5 mm NMR tubes at 298 K with TMS as an In [WO2(acac)2]∙0.5C6H5Me the non-hydrogen atoms were
internal standard. The sample concentration was 10 mg/ml.
refined anisotropically with exception of the toluene solvent
Proton spectra with spectral width of 6002 Hz and a digital molecule atoms which were refined isotropically. The toluene
resolution of 0.36 Hz per point were measured with 64 and solvent molecule is situated near the centre of symmetry and
128 scans. In the gCOSY experiment, 2048 points in the f2 is disordered over the two centrosymmetrically related
dimension and 128 increments in the f1 dimension were used. positions. Restraints on the C−C distances and angles, and
For each increment, 16 scans and the spectral width of 6010 planarity (FLAT) were used for the toluene molecule. The
Hz were applied. Digital resolution was 5.87 and 93.78 Hz per centre of symmetry is within the toluene molecule and is
point in f2 and f1 dimensions, respectively. The gHSQC and located between atoms C12 and its centrosymmetrically
gHMBC spectra were acquired with 16 and 32 scans, related pair C12[-x, -y, -z] so placement of H-atoms at C12[-x, -
respectively. Spectral width was 6009 Hz in f2 and 20124 Hz in y, -z and the neighbouring C15 was difficult and their
]
f1 dimension for both experiments. 1K data points were positions had to be fixed (Fig S1). All other hydrogen atoms
applied in the time domains and for each data set 256 were placed in calculated positions and refined using the riding
increments were collected. The resulting digital resolution was model.
5.86 Hz per point in f2 dimension and 314.4 Hz per point in f1 The non-hydrogen atoms in 1a
,
1b and 3a were refined
1b and 3a were
dimension. anisotropically. The hydrogen atoms in 1a
,
Catalytic reactions were followed by gas chromatography on placed in calculated positions and refined using the riding
an Agilent 6890A chromatograph equipped with FID detector, model, exceptions were hydrogen atoms of the coordinated
a HP5-MS capillary column (30m×0. 25m m×0. 25μ ) and solvent molecule hydroxyl group.
automatic sampling, or on a Fisons GC 8000 chromatograph
equipped with FID detector and with a SPB-5 capillary column
Acknowledgements
(30m ×0. 32mm ×0. 25μ ). The GC parameters were
quantified with authentic samples of the reactants and
products. The conversion of cis-cyclooctene and the formation
of cyclooctene oxide were calculated from calibration curves
(r2 = 0.999) relatively to an internal standard.
Financial support for this research was provided by Ministry of
Science and Technology of the Republic of Croatia. We
acknowledge the Centre National de la Recherche Scientifique
(CNRS) for financial support, the Université Paul Sabatier and
its Institut Universitaire Technologique for the facilities. All
authors want to thank Prof. R. Poli for suggestions and advices.
X-Ray Crystallography. Powder diffraction. The powder X-ray
diffraction data were collected by the Panalytical X’Change
powder diffractometer in the Bragg-Brentano geometry using
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 9 of 11
Journal Name
View Article Online
DOI: 10.1039/C6RA05067K
ARTICLE
Table 4 Crystallographic data for compounds [WO2(C5H7O2)2]
⋅
0.5 C6H5Me
,
1a
,
1b and 3a
[WO2(acac)2] ⋅ 0.5C6H5Me
C13.5H18O6W
1a
1b
3a
empirical formula
Mr
C16H17N3O6W
531.17
C15H15N3O6W
517.14
C15H15N3O5W
501.14
460.12
crystal colour, habit
crystal size (mm3)
crystal system
space group
unit cell parameters
a (Å)
colourless, plate
0.56×0.36×0.18
monoclinic
yellow, plate
yellow, plate
0.48×0.34×0.18
monoclinic
P21/n
yellow, plate
0.56×0.20×0.12
monoclinic
P21/n
0.56×0.38×0.18
triclinic
P21/n
P -1
7.3569(4)
16.2269(7)
13.5020(11)
7.2563(4)
10.4696(5)
12.6154(5)
6.7820(3)
30.3344(16)
7.9111(5)
8.1744(2)
12.5034(2)
15.3736(3)
b (Å)
c (Å)
α
β
γ
(°)
(°)
(°)
90
95.619(6)
90
113.702(4)
96.023(4)
97.909(4)
90
93.335(5)
90
90
97.032(2)
90
V (Å3)
1604.12(17)
4
855.54(8)
2
1624.78(15)
4
1559.48(6)
4
Z
Dcalc (g cm–3
)
1.905
295
2.062
295
2.114
295
2.135
295
temperature (K)
ꢀ
(mm–1
F(000)
)
7.220
884
6.791
512
7.148
992
7.439
960
number of unique data
number of data [Fo ≥ 4σ(Fo)]
number of parameters
R1a, [Fo ≥ 4σ(Fo)]
3639
5682
3835
3735
2646
5228
3053
2805
172
236
227
221
0.0327
0.0841
1.00
0.0269
0.0585
1.00
0.0251
0.0579
1.10
0.0235
0.0438
0.94
b
wR2
Goodness of fit on F2, S c
Min. and max. electron density (e Å–3
)
-2.47, 0.76
-1.35, 1.67
-1.80, 1.33
-0.61, 0.86
a R = ΣFo – Fc/ΣFo, b wR = [Σ(Fo2 – Fc2)2/Σw(Fo2)2]1/2 c S = Σ[w(Fo2 – Fc2)2/(Nobs – Nparam)]1/2
,
3 (a) V. Vrdoljak, B. Prugovečki, I. Pulić, M. Cigler, D. Sviben, J.
Parlov Vuković, P. Novak, D. Matković-Čalogović and M. Cindrić,
New J. Chem. 2015, 39, 7322; (b) J. Pisk, B. Prugovečki, D.
Matković-Čalogović, T. Jednačak, P. Novak, D. Agustin and V.
Vrdoljak, RSC Adv. 2014, 4, 39000; (c) S.-B. Ding and W.-H. Li, J.
Coord. Chem. 2013, 66, 2023; (d) M. Nandy, S. Shit, C. Razzoli, G.
Pilet and S. Mitra, Polyhedron, 2015, 88, 63.
Notes and references
1 (a) M. C. Rodríguez-Argüelles, S. Mosquera-Vázquez, P. Tourón-
Touceda, J. Sanmartín-Matalobos, A. M. García-Deibe, M.
Belicchi Ferrari, G. Pelosi, C. Pelizzi and F. Zani, J. Inorg.
Biochem., 2007, 101, 138; (b) D. S. Kalinowski, P. C. Sharpe, P.
V. Bernhardt and D. R. Richardson, J. Med. Chem., 2008, 51,
331.
4 A. Dolbecq, P. Mialane, L. Lisnard, J. Marrot and F. Sécheresse,
Chem. Eur. J., 2003, 9, 2914.
5 (a) J. Pisk, D. Agustin, V. Vrdoljak and R. Poli, Adv. Synth. Catal.,
2011, 353, 2910; (b) M. E. Judmaier, C. Holzer, M. Volpe and N.
C. Mösch-Zanetti, Inorg. Chem., 2012, 51, 9956; (c) J. Pisk, B.
Prugovečki, D. Matković-Čalogović, R. Poli, D. Agustin, and V.
Vrdoljak, V. Polyhedron, 2012, 33, 441; (d) M. Bagherzadeh, M.
Amini, H. Parastar, M. Jalali-Heravi, A. Ellern and L. K. Woo,
Inorg. Chem. Comm., 2012, 20, 86; (e) M. Bagherzadeh, M. Zare,
V. Amani, A. Ellern and L. K. Woo, Polyhedron, 2013, 55, 223;
6 (a) B. Guérin, D. Mesquita-Fernandes, J.-C. Daran, D. Agustin and
R. Poli, New J. Chem., 2013, 37, 3466; (b) J. Morlot, N.
2 (a) V. Vrdoljak, B. Prugovečki, D. Matković-Čalogović, R. Dreos, P.
Siega and C. Tavagnacco, Cryst. Growth Des., 2010, 10, 1373; (b)
V. Vrdoljak, B. Prugovečki, D. Matković-Čalogović, J. Pisk, R.
Dreos and P. Siega, Cryst. Growth Des., 2011, 11, 1244; (c) V.
Vrdoljak, B. Prugovečki, D. Matković-Čalogović, T. Hrenar, R.
Dreos and P. Siega, Cryst. Growth Des., 2013, 13, 3773; (d) W.-X.
Xu, Y.-M. Yuan and W. H. Li, J. Coord. Chem., 2013, 66, 2726; (e)
M. R. Maurya, L. Rana and F. Avecilla, Inorg. Chim. Acta, 2015,
429, 138.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 10 of 11
View Article Online
DOI: 10.1039/C6RA05067K
ARTICLE
Journal Name
D. Carvalho, L. P. Ferreira, C. D. Nunes and P. D. Vaz, J.
Organomet. Chem. 2014, 760, 2.
Uyttebroeck, D. Agustin and R. Poli, Chem. Cat. Chem., 2013, 5,
601.
7 (a) A. Rezaeifard, I. Sheikhshoaie, N. Monadi and M. Alipour,
Polyhedron, 2010, 29, 2703; (b) M. Loubidi, D. Agustin, A. C. R.
Chim. 2014, 17, 549. (c) W. Wang, T. Vanderbeeken, D. Agustin,
R. Poli, Catal. Commun. 2015, 63, 26. (d) W. Wang, T. Guerrero,
S. R. Merecias, H. García-Ortega, R. Santillan, J.-C. Daran, N.
Farfán, D. Agustin, R. Poli, Inorg. Chim. Acta, 2015, 431, 176.
8 M. A. Katkar, S. N. Rao and H. D. Juneja, RSC Advances, 2012, 2,
8071.
29 M. Ciclosi, C. Dinoi, L. Gonsalvi, M. Peruzzini, E. Manoury and R.
Poli, Organometallics 2008, 27, 2281.
30 C. Dinoi, M. Ciclosi, E. Manoury, L. Maron, L. Perrin and R. Poli,
Chem. Eur. J,. 2010, 16, 9572.
31 P. Sőzen-Aktas, E. Manoury, F. Demirhan and R. Poli, Eur. J.
Inorg. Chem., 2013, 2728.
32 A. Corma, P. Esteve and A. Martínez, J. Catal., 1996, 161, 11.
33 Z. Opre, T. Mallat and A. Baiker, J. Catal., 2007, 245, 482.
34 S. Bonollo, D. Lanari, L. Vaccaro, Eur. J. Org. Chem., 2011, 2587.
35 (a) J.-F. Lu, Acta Cryst, 2008, E64, o2032; (b) H. H. Rassem, A.
Salhin, B. Bin Salleh, M. M. Rosli and H.-K. Fun, Acta Cryst.,
2012, E68, o2279; (c) A. Salhin, A. A.Tameem, B. Saad, S.-L. Ng
and H.-K. Fun, Acta Cryst., 2007, E63, o2880.
9 X. Zhou, J. Zhao, A. M. Santos and F. E. Kühn, Z. Naturforsch, 2004,
59b, 1223.
10 A. Dupé, M. K. Hossain, J. A. Schachner, F. Belaj, A. Lehtonen, E.
Nordlander, and N. C. Mösch-Zanetti, Eur. J. Inorg. Chem., 2015,
3572.
11 D. D. Agarwal, R. Rastogi, V. K. Gupta and S. Singh, Indian J.
Chem., 99, 38A, 369.
36 W. C. Gibson, T. P. Kee and A. Shaw, Polyhedron, 1988, 7, 579.
37 X'Pert Software Suite, Version 1.3e; Panalytical B. V., Almelo, The
Netherlands, 2001.
12 V. Vrdoljak, J. Pisk, D. Agustin, P. Novak, J. Parlov Vuković and D.
Matković-Čalogović, New J. Chem., 2014, 38, 6176.
13 (a) S-B. Yu, and R. H. Holm, Inorg. Chem, 1989, 28, 4385; (b) W.
A. Herrmann, J. Fridgen, G. M. Lobmaier and M. Spiegler, New J.
Chem. 1999, 23, 5.
38 CrysAlisPro, Agilent Technologies, Version 1.171.37.33 (release
27-03-2014 CrysAlis171 .NET)
39 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
40 G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112.
14 D. Agustin, C. Bibal, B. Neveux, J.-C. Daran and R. Poli, Z. Anorg.
Allg. Chem. 2009, 635, 2120.
15 Cambridge Structural Database V5.37, Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge,
England, 2015)
16 (a) F. Zhi and R. Wang, Acta Crystallogr., 2010, E66, o892. (b) S.-J.
Peng and H.-Y. Hou, Acta Crystallogr., 2008, E64, o1996.
17 Y.-J. Xu, S.Zhao and S. Bi, Acta Crystallogr., 2007, E63, o4633.
18 Y. Lei and C. Fu, Synth. React. Inorg., Met.-Org., Nano-Met.
Chem., 2011, 41, 704.
19 S. Alghool and C. Slebodnick, Polyhedron, 2014, 67, 11.
20 Y.-L. Zhai, X.-X. Xu. and Y. Wang, Polyhedron, 1992, 11, 415.
21 V. S. Sergienko, V. L. Abramenko, L. Kh. Minacheva, M. A. Porai-
Koshits and V. G. Sakharova, Koord. Khim.. (Russ.)(Coord.
Chem.), 1993, 19, 28.
22 M. R. Maurya, S. Agarwal, C. Bader and D. Rehder, Eur. J. Inorg.
Chem., 2005, 147.
23 M. R. Maurya, S. Gopinathan, C. Gopinathan and R. C. Maurya
Polyhedron, 1993, 12, 159.
24 (a) Y.-L. Wong, J.-F. Ma, W.-F. Law, Y. Yan, W.-T. Wong, Z.-Y.
Zhang, T. C. W. Mak and D. K. P. Ng, Eur. J. Inorg. Chem. 1999,
313; (b) Y. –L. Wong, Y. Yan, E. S. H. Chan, Q. Yang, T. C. W. Mak
and D. K. P. Ng, J. Chem. Soc., Dalton Trans. 1998, 3057.
25 K. Chichak, U. Jacquenard and N.R. Branda, Eur. J. Inorg. Chem.
2002, 357.
26 P. Krishnamoorthy, P. Satyadevi, P. T. Mutiah and N. Dharmaraj,
RSC Advances, 2012, 2, 12190.
27 S. Gupta, A. Kumar Barik, S. Pal, A. Hazra, S. Roy, R. J. Butcher
and S. Kumar Kar, Polyhedron, 2007, 26, 133.
28 a) M. Lashanizadegan, S. Shayegan and M. Sarkheil, J. Serb.
Chem. Soc. 2016, 81, 153. (b) M. Ghorbanloo, R. Bikas and G.
Małecki, Inorg. Chim. Acta 2016, 445, 8. (c) C. I. Fernandes, M.
10 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 11 of 11
RSC Advances
View Article Online
DOI: 10.1039/C6RA05067K
Table of contents entry
The catalytic performances (activity and selectivity) of the
mononuclear dioxotungsten(VI) complexes [WO2(LR)(D)] towards
alkene epoxidation by tert-butyl hydroperoxide (TBHP) were
investigated under different conditions.