Ionic ammonium and anilinium based polymolybdate hybrid catalysts for olefin epoxidation

Article abstract of DOI:10.1016/j.apcata.2018.07.001

Ionic polymolybdate hybrids (IPH) are interesting catalysts for liquid phase olefin epoxidation with tert-butylhydroperoxide; (tbhp), e.g. conversion of terpenic and fatty acid methyl ester (FAME) components of biomass to useful bio-products. IPHs may be easily prepared, under clean, mild, aqueous phase conditions. The type of organic precursor and the synthesis conditions influence the structural features of the IPHs. In this work, IPH epoxidation catalysts possessing one- (1-D) or two-dimensional (2-D) structures were investigated, which included the new materials 1-D methylammonium ammonium trimolybdate [Mo₃O₁₀?CH₃NH₃·NH₄] (1) and 2-D bis(2,5-dimethylanilinium) pentamolybdate [Mo₅O₁₆?2(NH₃C₆H₃(CH₃)₂)] (4) with solved structures, and 1-D bis(3,5-dimethylanilinium) trimolybdate [Mo₃O₁₀·2(NH₃C₆H₃(CH₃)₂)] (2), bis(4-methylanilinium) trimolybdate [Mo₃O₁₀·2(NH₃C₆H₄CH₃)] (3), 2-D bis(anilinium) pentamolybdate [Mo₅O₁₆?2(NH₃C₆H₅)] (5), bis(4-methylanilinium) pentamolybdate [Mo₅O₁₆?2(NH₃C₆H₄CH₃)] (6) and bis(4-ethylanilinium) pentamolybdate [Mo₅O₁₆?2(NH₃C₆H₄C₂H₅)] (7). Systematic characterisation and catalytic studies helped gain insights into structure-activity relationships. The best-performing catalyst (2) was effective for the epoxidation of the FAMEs such as, methyl oleate which gave 92% methyl 9,10-epoxyoctadecanoate yield, at 99% conversion, at 70 °C. The reaction conditions (temperature, type of cosolvent and oxidant) influenced the catalytic reaction. Catalytic performance in consecutive batch runs was steady, and the structural features were essentially preserved.

Full text of DOI:10.1016/j.apcata.2018.07.001

Accepted Manuscript
Title: Ionic ammonium and anilinium based polymolybdate
hybrid catalysts for olefin epoxidation
˙
´
Authors: Barbara Bozek, Patrıcia Neves, Wiesław Łasocha,
Anabela A. Valente
PII:
S0926-860X(18)30324-7
DOI:
Reference:
https://doi.org/10.1016/j.apcata.2018.07.001
APCATA 16727
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
18-3-2018
17-5-2018
1-7-2018
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Please cite this article as: Bozek B, Neves P, Łasocha W, Valente AA, Ionic ammonium
and anilinium based polymolybdate hybrid catalysts for olefin epoxidation, Applied
Catalysis A, General (2018), https://doi.org/10.1016/j.apcata.2018.07.001
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Ionic ammonium and anilinium based polymolybdate hybrid
catalysts for olefin epoxidation
Barbara Bożeka,†, Patrícia Nevesb,†, Wiesław Łasochaa,c,*, Anabela
A.Valenteb,*
aJerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences,
Niezapominajek 8, 30-239 Krakow, Poland
bDepartment of Chemistry, CICECO – Aveiro Institute of Materials, University of Aveiro,
3810-193 Aveiro, Portugal
cFaculty of Chemistry, Jagiellonian University, ul. Gronostajowa 2, 30-387 Krakow,
Poland
†These authors contributed equally to this work.
*Corresponding authors. Fax: +351 234 401470.
E-mail addresses: atav@ua.pt (A.A. Valente), nclasoch@cyf-kr.edu.pl (W. Łasocha).
Graphical abstract
1

Highlights
 Ionic organo-polymolybdate hybrids (IPHs) easily synthesised under mild,
aqueous phase conditions
 Type of synthetic organic precursor and synthesis conditions influence structural
features of IPHs, influencing catalytic performance
 The best-performing catalyst possessed one-dimensional structure and selectively
converted biomass-derived olefins to the respective epoxides
 The best-performing catalyst possessed steady activity in consecutive batch runs,
with preservation of structural features
Abstract
Ionic polymolybdate hybrids (IPH) are interesting catalysts for liquid phase olefin
epoxidation with tert-butylhydroperoxide (tbhp), e.g. conversion of terpenic and fatty
acid methyl ester (FAME) components of biomass to useful bio-products. IPHs may be
easily prepared, under clean, mild, aqueous phase conditions. The type of organic
precursor and the synthesis conditions infleunce the structural features of the IPHs. In this
work, IPH epoxidation catalysts possessing one- (1-D) or two-dimensional (2-D)
structures were investigated, which included the new materials 1-D methylammonium
2

ammonium trimolybdate [CH3NH3·NH4·Mo3O10] (1) and 2-D bis(2,5-
dimethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H3(CH3)2)] (4) with solved
structures,
and
1-D
bis(3,5-dimethylanilinium)
bis(4-methylanilinium)
trimolybdate
trimolybdate
[Mo3O10·2(NH3C6H3(CH3)2)]
[Mo3O10·2(NH3C6H4CH3)]
(2),
(3),
2-D
bis(anilinium)
pentamolybdate
pentamolybdate
pentamolybdate
[Mo5O16·2(NH3C6H5)]
(5),
(6)
bis(4-methylanilinium)
and bis(4-ethylanilinium)
[Mo5O16·2(NH3C6H4CH3)]
[Mo5O16·2(NH3C6H4C2H5)] (7). Systematic characterisation and catalytic studies helped
gain insights into structure-activity relationships. The best-performing catalyst (2) was
effective for the epoxidation of the FAMEs such as, methyl oleate which gave 92 %
methyl 9,10-epoxyoctadecanoate yield, at 99 % conversion, at 70 C. The reaction
conditions (temperature, type of cosolvent and oxidant) influenced the catalytic reaction.
Catalytic performance in consecutive batch runs was steady, and the structural features
were essentially preserved.
Keywords: polymolybdates; hybrids; crystal structure; catalytic epoxidation; bio-derived
olefins
1. Introduction
The development of catalysts for chemical processes with reduced carbon footprint,
following green chemistry principles, is important. Catalytic epoxidation is a valuable
tool to convert unsaturated fatty acid methyl esters (FAMEs) and terpenic components of
(renewable) vegetable biomass to bio-products with wide application profiles. Interesting
FAMEs include methyl oleate (Ole) and methyl linoleate (LinOle), which are readily
3

available in nature; e.g. canola, soybean, sunflower and corn oils (Scheme 1). Epoxidised
FAMEs can act as alternative plasticizers/stabilizers for PVC production, solvents [1],
surface coatings [2,3] surfactants [4], biodegradable lubricants [5], fuel additives [6] and
as intermediates for producing resins[2] and polyols used for polyurethane foams
production [7]. On the other hand, terpenes are natural, abundant, inedible and relatively
inexpensive building blocks, useful for different industrial sectors. In particular, limonene
(Lim), a terpene which is extracted from citrus oil and pine wood [8], may be converted
to interesting bio-products such as, 1,2-epoxy-p-menth-8-ene (LimOx), 1,2:8,9-diepoxy-
p-menthane (LimDiOx) and 1-methyl-4-(1-methylethenyl)-1,2-cyclohexanediol
(LimDiOH) (Scheme 1). LimOx may be used as fragrance, solvent, and for producing
metal coatings, varnishes, and printing inks [9,10]; the reaction of LimOx with succinic
anhydride affords value-added polyesters [11]. LimDiOx is industrially used as a diluent
for epoxy resin and as a solvent [12,13]. Mono- or diepoxides of limonene are interesting
monomers for producing biodegradable non-isocyanate polyurethanes (an attractive
green alternative to traditional isocyanate polyurethanes, avoiding toxic monomers and
phosgene), and thermosetting polymers via copolymerization with CO2 [10,12-15].
Some industrial processes of FAMEs epoxidation involve the use of peracids as oxidising
agents, and strong mineral acids as catalysts, which may present several drawbacks
including low product selectivity, corrosion of equipment, and considerable waste
production [9]. On the other hand, it is desirable to substitute commercial Lim/peracid
stoichiometric epoxidation processes for alterative eco-friendly catalytic routes [16]. In
this sense, the use of versatile transition metal catalysts and hydroperoxide oxidants may
be advantageous.
In particular, polyoxometalates are versatile inorganic compounds, which have made part
of innovative research themes related to crystal engineering, molecular magnets, novel
4

surfactants, medicine, catalysis, etc. [17-31]. In general, polyoxometalates consist of
transition metal oxide polyhedra, may be prepared with different sizes, compositions,
nuclearity, structures/architectures, physicochemical properties, and exhibit counterion-
and pH-dependent extraordinary self-assembly behavior. Some of the earliest discovered
polyoxometalates include the molybdenum-based compound (NH4)3[PMo12O40], by
Berzelius, in 1826 [17]. Transition metal-oxo moieties exist in a variety of catalytic
systems, and, in particular, those based on molybdenum – readily available, relatively low
cost metal - may be promising for catalytic oxidation processes [32,33]. In the last couple
of decades, polyoxomolybdates possessing zero-, one-, two- and three-dimensional (n-D,
n=0,1,2,3) structures were developed for catalytic oxidation of different types of
substrates, e.g. alcohols, cycloalkanes and olefins [23-25,27-29,34]. Ionic
oxomolybdenum polynuclear compounds possessing charge-balancing organic cations
were effective epoxidation catalysts for the valorisation of biomass-derived olefins, under
mild reaction conditions [28,29,35,36].
In this work, one- (1-D) and two dimensional (2-D) ionic polymolybdate hybrid materials
(IPH) were explored as catalysts for the liquid phase epoxidation of olefins, such as
biomass-derived terpenic and fatty acid methyl ester compounds, at 70 ºC (Scheme 1).
The
[CH3NH3·NH4·Mo3O10]
[Mo3O10·2(NH3C6H3(CH3)2)]
IPHs
included:
1-D
methylammonium
ammonium
trimolybdate
trimolybdate
trimolybdate
1
and
bis(3,5-dimethylanilinium)
bis(4-methylanilinium)
2,
[Mo3O10·2(NH3C6H4CH3)] 3, and 2-D bis(2,5-dimethylanilinium) pentamolybdate
[Mo5O16·2(NH3C6H3(CH3)2)] 4, bis(anilinium) pentamolybdate [Mo5O16·2(NH3C6H5)] 5,
bis(4-methylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4CH3)] 6, and bis(4-
ethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4CH2CH3)] 7. The structures of the
new IPHs 1 and 3 were solved. Systematic characterisation and catalytic studies were
5

carried out to help understand structure-activity relationships, and investigate the catalyst
stability in recycling runs.
((Scheme 1 here))
2. Experimental
2.1. Materials and methods
For the syntheses of the molybdenum catalysts, molybdic acid (p.a. > 98%, POCh), acetic
acid (99 %, POCh), 2-propanol (> 99.5 %, Chempur), methylamine ( 98 %, BASF), 2,5-
dimethylaniline (99 %, Aldrich), were obtained from commercial suppliers and used as
received. For the catalytic tests, cis-cyclooctene (Cy, 95 %, Aldrich), methyl oleate (Ole,
99 %, Aldrich), methyl linoleate (LinOle, 95 %, Alfa Aesar), methyl decanoate (99 %,
Aldrich), undecane (> 99 %, Aldrich), tert-butylhydroperoxide (tbhp, 5.5 M in decane,
Sigma–Aldrich), H2O2 (30 % aq., Sigma–Aldrich), acetonitrile (99.9 %, Panreac),
anhydrous α,α,α-trifluorotoluene (tft, 99.8 %, Aldrich), toluene ((≥99.9 %, Aldrich),
1,2.dichloroethane (≥99 %, Aldrich), diethyl ether (puriss p.≥a., Sigma–Aldrich), pentane
( 95 %, Carlo Erba) and MoO3 (≥99.9 %, Analar) were acquired from commercial sources
and used as received.
Routine X-ray powder diffraction (XRPD) data were collected at ambient temperature on
a Philips Analytical Empyrean diffractometer equipped with a PIXcel 1D detector, with
automatic data acquisition (X’Pert Data Collector software v. 4.2) using
monochromatized Cu Kα radiation (λ = 1.54178 Å). Intensity data were collected by the
step-counting method (step 0.02), in continuous mode, in the 2θ range 5 - 60.
Attenuated total reflectance (ATR) FT-IR spectra were measured using a Specac Golden
Gate Mk II ATR accessory having a diamond top plate and KRS-5 focusing lenses.
6

Scanning electron microscopy (SEM) images were collected using a Hitachi S4100
microscope operating at 25 kV. Samples were prepared by deposition on aluminium
sample holders followed by carbon coating using an Emitech K 950 carbon evaporator.
2.2. Synthesis of the hybrid catalysts
The new hybrids methylammonium ammonium trimolybdate [CH3NH3·NH4·Mo3O10] 1
and bis(2,5-dimethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H3(CH3)2)] 4 were
synthesized as described in this section. Compounds bis(3,5-dimethylanilinium)
trimolybdate [Mo3O10·2(NH3C6H3(CH3)2)] 2, bis(4-methylanilinium) trimolybdate
[Mo3O10·2(NH3C6H4CH3)] 3, 2-D bis(anilinium) pentamolybdate [Mo5O16·2(NH3C6H5)]
5, bis(4-methylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4CH3)] 6, bis(4-
ethylanilinium) pentamolybdate [Mo5O16·2(NH3C6H4C2H5)] 7. were synthesised and
characterised as in ref. [27]. For the seven compounds, the syntheses were carried out
under acidic aqueous phase conditions, using molybdic acid and an organic compound
(of the type amine or aniline) as precursors of molybdenum and the constituent cations,
respectively.
2.2.1. Methylammonium ammonium trimolybdate 1
A mixture of molybdic acid (0.01 mol), methylamine (0.0005 mol) and H2O (10 mL)
were thoroughly mixed, placed in thermo-block and kept at 75 ºC for 7 days. The
synthesis afforded a white precipitate, which was filtered, washed with 2-propanol and
dried in air, at room temperature. Molybdic acid contains ca. 85 % MoO3 and sufficient
ammonium molybdate for synthesizing 1. Material 1 was obtained with 95 % yield. Anal.
Calcd for CH3NH3·NH4·Mo3O10 (497.92 g/mol): C, 2.41; N, 5.63; H, 2.02 %. Found: C,
2.37; N, 5.52; H, 1.96 %. Selected FT-IR ATR bands (cm–1) with assignments based on
7

comparisons to literature data for different compounds [37]:  = 3095m (ʋO-H,ʋC-H),
3022m (ʋO-H,ʋC-H), 2833vw (ʋO-H,ʋC-H), 2758vw, 2462vw, 1662vw, 1624vw,
1589vw, 1520w, 1436sh, 1421s, 1405 sh, 997vw, 895s (ʋMo-O-Mo), 872s (ʋMo-O),
864s, 773vw , 648vs (ʋMo-O), 462-505, 430vw, 390 vw.
2.2.2. Bis(2,5-dimethylanilinium) pentamolybdate 4
Molybdic acid (0.01 mol) was dissolved in 150 mL water, under reflux. Subsequently,
0.01 mol 2,5-dimethylammonium dissolved in 50 mL acetic acid was added, and the
resultant mixture was refluxed for 24 h. A white precipitate was filtered from the hot
mixture, washed with 2-propanol and dried in air, at room temperature. Material 4 was
obtained with 92 % yield. Anal. Calcd for Mo5O16 ·2(C8H12 N) (692.16 g/mol): C, 19.61;
N, 2.86; H, 2.47 %. Found: C, 19.54; N, 2.91; H, 2.58 %. Selected FT-IR ATR bands
(cm–1) with assignments based on comparisons to literature data for different compounds
[37]:  = 3047vw (ʋC-H, ʋO-H), 2918vw (ʋC-H, ʋO-H), 1598vw (δN-H, ʋC=C), 1562vw
(δN-H, ʋC=C), 1533vw, 1512vw, 1454vw (ʋC=C), 1301vw (ʋC-N), 1242vw, 1222vw,
1159vw, 1124vw (δC-H), 945m (ʋMo-O), 931w, 905m (ʋMo-O-Mo), 887vw, 852vs
(ʋMo-O), 812s, 757vs (δN-H,γC-H), 671vs (ʋMo-O), 546vs (δMo-O-Mo), 520sh,
482vw, 463vw, 443m, 428sh, 380s, 363s.
2.3. Thermal stability and structural studies by X-ray powder diffraction
The thermal stability and phase transformations of the IPHs were studied by variable
temperature X-ray powder diffraction (XRPD) measurements, under air atmosphere,
using a X‘Pert Pro MPD powder diffractometer equipped with a high-temperature
chamber (XRK chamber produced by Anton Paar). X-ray data were collected in the
temperature range 25-800 °C, and the 2θ range 5-60°.
8

The crystal structures were determined using a PANalytical X’Pert PRO MPD
diffractometer working in Bragg-Brentano geometry; radiation CuK 1.54187 Å; 2 in
the range 3 - 80°; interpolated step size of 0.02° 2. For 4, in order to avoid possible
texture effects, for final refinement measurements the sample was loaded into a glass
capillary (2r = 0.5 mm) and measured in Debye-Scherrer-Hull geometry. The second
derivative method and the Sonneveld-Visser program were used to determine the peak
positions in diffraction patterns. The unit cell parameters were obtained using the
PROSZKI package [38]. Structure solution for 1 was performed using EXPO-2014
program [39] working in direct methods mode; and program FOX [40] applying direct
space methods (global optimization, variant: parallel tempering) was used for 4.
Restrained Rietveld refinement was carried out using the Jana2006 program [41]. The
shape of the diffraction lines in both cases was described by pseudo-Voigt function, the
background was described by the Legendre polynomials (no. terms 15). Rietveld
refinement plots are given in the Supplementary Information section (SI): SI-Fig. 1 and
SI-Fig. 2.
2.4. Catalytic tests
The IPH catalysts were tested for the epoxidation the olefins methyl oleate (Ole), methyl
linoleate (LinOle), R-(+)-limonene (Lim), and cis-cyclooctene (Cy), using tert-
butylhydroperoxide (tbhp) as oxidant, and α,α,α-trifluorotoluene (tft) as solvent.
Hydrogen peroxide was used (for selected catalytic system) as oxidant instead of tbhp,
with acn as cosolvent allowing the miscibility of the substrate and oxidant. For the
reaction of Ole with tbhp, different cosolvents were tested, namely, 1.2-dichloroethane
(dce), toluene (tol), and acetonitrile (acn), besides tft. The catalytic reactions were carried
out in 10 mL borosilicate reactors equipped with a Teflon valve (for sampling) and a
9

magnetic stirrer. The reactor was loaded with catalyst (18 mol Mo), co-solvent (1 mL)
and olefin (1.8 mmol), and then immersed in a temperature-controlled oil bath at 55 or 70
C, under stirring (1000 rpm), for 10 min. The oxidant (2.75 mmol for Cy, Lim and Ole,
and 2.75 mmol or 4.80 mmol for MeOle reactions) was pre-heated in a separate flask for
10 min at the same temperature, and then added to the reactor. The instant that the pre-
heated oxidant was added to the reactor was taken as the initial instant of the catalytic
reaction. The reaction mixtures were analyzed using a Varian 3900 GC equipped with a
DB-5 capillary column (30 m × 0.25 mm × 0.25 μm) and a FID detector, with H2 as the
carrier gas, and quantifications were based on calibrations. The internal standards used
were undecane for the Cy and Lim reactions, and methyl decanoate for the Ole and LinOle
reactions. The experimental range of error was less than 6 %, based on replicates carried
out for selected experimental conditions. The material balance considering all reaction
products quantified by GC closed in: 100 % for Cy at 24 h reaction, 100 % for Ole at 6 h,
98 % for Lime and 98 % LinOle at 24 h reaction, 70 ºC. The reaction products were
identified by GC–MS (Trace GC 000 Series Thermo Quest CE Instruments GC; Thermo
Scientific DSQ II), using He as the carrier gas. The product identifications were based on
commercial mass spectrometry databases (Wiley6, NIST2.0, NIST Chemistry WebBook,
MAINLIB), and mass spectral matching data.
After each 24 h batch run (Cy reaction), the IPHs were separated from the reaction
mixtures by centrifugation (3500 rpm), thoroughly washed with diethyl ether/pentane,
dried overnight under atmospheric conditions, and finally vacuum-dried (ca. 4 bar) at 60
°C for 1 h. The initial mass ratios of olefin/oxidant/metal compound were the same for
all batch runs. The solids recovered from the first and second batch runs are denoted as
(i)-run1 and (i)-run2, respectively, where i = 1-7. The recovered molybdenum compounds
were characterized by ATR FT-IR spectroscopy, XRPD and SEM.
10

The homogeneous or heterogeneous nature of the catalytic reaction was studied by
carrying out a contact test (ct). Specifically, 2 and the benchmark catalysts MoO3 and
molybdic acid were mixed with the oxidant and solvent, under similar conditions to those
used for a normal catalytic test, but without substrate, for 24 h, at 70 C, with stirring.
The obtained mixture was heterogeneous (biphasic solid-liquid, containing oxidant,
solvent, and solid molybdenum compound), and was cooled to ambient temperature. The
solid compound was separated from the liquid phase by passing the heterogeneous
mixture through a filter equipped with a 0.2 µm PTFE membrane, giving the solution 2-
L-ct. Then, the substrate Cy (preheated to 70 C) was added to the solution 2-L-ct in an
amount to give an initial Cy concentration of 1.2 M (similar to that used for a normal
catalytic test); the resultant solution (a homogeneous liquid) was stirred for 24 h, at 70
C, and analysed by GC to check if the epoxidation reaction occurred in homogeneous
phase.
The oxidant efficiency was determined by iodometric titration for 2. After a 24 h catalytic
batch run at 70 ºC, the reaction mixture was cooled to ambient temperature, and liquid
samples were withdrawn for titration. The experimental range of error was 5-10 %, based
on replicates.
The structure-activity relationships were based on initial catalytic activity (or initial
turnover frequency) calculated for 1 h reaction, for which catalyst deactivation may be
neglected.
3. Results and Discussion
3.1. Crystal structures
11

Material 1 belongs to the group of trimolybdate type IPHs, their characteristic feature
being an infinite polymeric 1-dimensional (1-D) chain of Mo3O102- anions (Tables 1 and
2, SI-Fig. 1). The crystal structure of 1 is reflected in its morphological features, i.e. the
crystallites of 1 are thin needles (ca. 300-400 nm thick) (SI-Fig. 3.a). The anions are
surrounded by methylammonium and ammonium cations; the latter are connected with
anions by ionic interactions and a system of H-bonds (Figure 1). The chains are built of
edges and vertices shared by deformed MoO6 octahedra (Figure 1). Two MoO6 octahedra,
by sharing one edge, form dimers Mo2O10. Such dimers, in turn, by sharing two upper
and two lower vertices with identical dimers form infinite ribbons with the formula
Mo2O8. To the ribbons, alternately from both sides, are attached MoO6 octahedra. In this
way, infinite zigzag chains are obtained with the general formula Mo3O102-. Polymeric
anions are aligned parallel to the b axis. In each MoO6 octahedron there are two terminal
oxygen atoms in cis position to each other and four 3-O atoms. In a similar fashion,
several trimolybdate type IPHs are built, including methylammonium trimolybdate,
potassium, ammonium, silver, anilinium or 3,5-dimethylanilinium trimolybdate [27]. The
longer distance between the chains of 1 is 9.569 Å, and for the 1-D materials 2 and 3 it is
16.79 and 15.15 Å, respectively (SI-Fig. 5).
((Figure 1 and Tables 1 and 2 here))
The IPH 4 crystallises as very fine, thin plates (SI-Fig. 3.b) and is built in similar fashion
to the remaining layered pentamolybdate type IPHs (Figure 2, Tables 1 and 3, SI-Fig. 6).
Material 4 possesses parallel layers overlapping with crystallographic planes (200). The
interplanar d-spacing d(200) for 4 is 17.22 Å (SI-Fig. 6.a), and for the 2-D materials 5, 6
and 7 it is 13.60, 14.36 and 15.15 Å, respectively (SI-Fig. 6.b,c,d). Infinite, staggered
12

layers built of distorted MoO6 octahedra sharing edges and corners, form an open-
framework (Figure 2, Tables 1 and 3). In each asymmetric unit there are three Mo atoms,
8 oxygen atoms and one 2,5-dimethylanilinium cation. Due to the relative spatial
arrangement of the methyl substituents, in order to compensate the negative charge of the
anionic layers, the 2,5-dimethylanilinium cations form double layers of cations between
anionic layers. As a result, the interplanar d-spacing d(200) is greater for 4 than the
anilinium 5, 4-methylanilinium 6, or 4-ethylanilinium 7 pentamolybdates [27].
((Figure 2 and Table 3 here))
3.2. Thermal stability
The variable temperature XRPD studies indicated that the 1-D IPH 1 is stable up to 225
°C, and further increase of the temperature led to the formation of a 3-D material with a
system of infinite, parallel, hexagonal channels (SI-Fig. 4.a). The obtained non-
stoichiometric compound, the so-called hexagonal molybdenum oxide (PDF-4+: 048-
0399), consists of channels intercalated by small cations (e.g. Na+, K+), which, for 4, are
ammonium or methylammonium cations. The amount of cations may depend on the
temperature or synthesis conditions. Further heating to ca. 300 °C led to the formation of
stoichiometric, layered MoO3 (PDF-4+: 35-609). Similar behaviour was reported in the
literature for ammonium heptamolybdate tetrahydrate [42]. The IPH 3 is stable up to ca.
200 °C; in the range 225-300 °C it is transformed into an amorphous phase, and at ca.
350 C, layered MoO3 is formed (PDF-4+: 35-609) (SI-Fig. 4.b). Materials 1 and 4 are
thermally stable at the catalytic reaction temperature of 70 °C. The same applies for 2, 3,
5-7, based on thermal stability studies reported in the literature by some of us [27].
13

3.3. Catalytic studies
3.3.1. General considerations
The new IPHs methylammonium ammonium trimolybdate [CH3NH3·NH4·Mo3O10] 1 and
bis(2,5-dimethylanilinium) pentamolybdate [Mo5O16·2(C6H3NH3(CH3)2)] 4 possess the
same structure as 2/3 (1-D trimolybdate moities) or 5-7 (2-D pentamolybdate moieties),
respectively. Systematic catalytic and characterisation studies were carried out in order
to help gain insights into structure-activity relationships, and catalyst stability. For these
studies, cis-cyclooctene (Cy) was used as model substrate, tert-butyl hydroperoxide
(tbhp) as oxidant. α,α,α-Trifluorotoluene (tft) was chosen as solvent, since it is
hydrophobic, avoiding negative effects of moisture, for example, on epoxide selectivity
[29,35,43], and a non-coordinating solvent, avoiding competitive effects between the
solvent and reactant molecules for the coordination to the metal centres (based on
mechanistic considerations discussed ahead) [44]. For all catalysts investigated, 1,2-
cyclooctene epoxide (CyO) was formed in 100 % selectivity, and 97-100 % CyO yield,
at 70 C/24 h (Table 4). Without catalyst and/or oxidant, the reaction was very sluggish
(< 7 % CyO yield at 70 C/24 h) [43].
The highest catalytic activity was observed for 2 and 3, which led to 97 and 100 % CyO
-1
yield, respectively, at 1 h (turnover frequency (TOF) = 97 or 100 mol molMo h-1),
compared to 24-54 % yield (TOF in the range 24-54 mol molMo-1 h-1) for the remaining
compounds (Table 4). For 2 and 3, decreasing the reaction temperature from 70 to 55 C,
led to a decrease in initial activity from 97 to 71 mol molMo-1 h-1 for 2, and from 100 to
-1
91 mol molMo h-1 for 3 (Table 4). Nevertheless, quantitative CyO yield was reached
within 6 h reaction for these two catalysts, at 55 C. Clear, fair comparisons of the
catalytic results to literature data are not trivial due to the different reaction conditions
used between different works. A literature survey for polyoxomolybdates and the model
14

reaction Cy/tbhp, under similar reaction conditions (Table 5, [45-53]), indicated that 2
and 3 performed superiorly in relation to e.g. (H3biim)4[β-Mo8O26] where H2biim = 2,2’-
biimidazole [29], and [{MoO2(HC(3,5-Me2pz)3)}2(µ2-O)][Mo6O19] where HC(3,5-
Me2pz)3 = tris(3,5-dimethyl-1-pyrazolyl)methane [30].
((Tables 4 and 5 here))
3.3.2. Catalyst stability and benchmarking
The reaction mixtures were biphasic solid-liquid, for 1-7. After the catalytic reaction at
70 C, the used catalyst was characterised, and reused in consecutive catalytic batch runs
(details given in the experimental section). The used catalysts are denoted (i)-runx, where
i is referent to compounds 1-7, and x = 1 and 2 for the solids recovered from the batch
runs 1 and 2, respectively. For each IPH, excluding 3, the catalytic results were somewhat
comparable in consecutive batch runs (Figure 3). The characterisation studies for 1, 2, 4-
7 indicated somewhat comparable results for the original and respective used catalyst.
Hence, the chemical (based on FT-IR ATR spectroscopy, Figures 4 and 5), structural
(XRPD, Figures 4 and 6) and morphological (SEM, Figure 6) features were essentially
preserved during the catalytic process using 1, 2, 4-7. For 3, Cy conversion decreased
somewhat considerably from the first to the third run, suggesting that this catalyst was
less stable (Figure 3). The used catalyst exhibited a different FT-IR ATR spectrum, XRPD
pattern (amorphous material) and morphology (based on SEM) from the respective
original catalyst 3 (SI-Fig. 7). Overall, the best-performing catalyst in terms of activity
and stability was the IPH 2.
For the best-performing catalyst 2, a contact test (ct) was carried out in order to study the
homogeneous or heterogeneous nature of the catalytic reaction (details in the
15

experimental section). The solution obtained from the ct (2-L-ct) was tested for the
homogeneous catalytic reaction of Cy, and gave ca. 28 % conversion at 24 h. This result
is far poorer than that for the original catalyst 2 (97 % at 1 h), suggesting that the catalytic
contribution of the dissolved molybdenum species was relatively small, and thus the
activity is mainly attributed to the solid-state catalyst.
For comparison, commercial MoO3 and molybdic acid (denoted MoAc) were tested as
catalysts, under similar Cy reaction conditions to those used for 2 (Table 5). The
commercial catalysts led to much slower Cy reaction, at 70 ºC: for MoO3, 4 %/71 %
conversion, at 1 h/6 h (CyO yield was equal to conversion), and for MoAc, 4 %/96 %
conversion and 4 %/96 % CyO yield, at 1 h/6 h, whereas 2 led to 97 % conversion at 1 h.
On the other hand, MoO3 and MoAc presented considerable homogeneous catalytic
contributions, ascertained by the corresponding ct. Specifically, the liquid phase (MoO3-
L-ct) of the ct for MoO3 was tested for the reacion of Cy (in a similar fashion to that
described for 2), and gave 76 % conversion at 24 h, which is considerable in relation to
that for the normal catalytic test (without filtration of the solid) in the presence of MoO3
(96 % conversion at 24 h, Table 5). Likewise, the liquid phase (MoAc-L-ct) of the ct for
MoAc was tested for the reacion of Cy, and gave 100 % conversion at 24 h, which is
similar to that for the normal catalytic test using MoAc (100 % conversion at 24 h, Table
5).
((Figures 3, 4, 5 here))
3.3.3. Structure-activity relationships
The IPHs 1-7 possess an organic cationic component, and an inorganic anionic scaffold
consisting of corner and edge sharing Mo(VI)O6 octahedra, which are assembled to give
16

1-D structures (trimolybdate type IPHs 1-3) or 2-D structures (pentamolybdate type IPHs
4-7). Compounds 1-7 may be compared in two perspectives. One the one hand, a
comparison based on the nature of the organic part clearly shows that the anilinium-based
IPHs were more active than aliphatic amine-based IPH (Table 4). On the other hand, the
family of anilinium-based catalysts, which is more extensive, is interesting for more
detailed comparisons. A comparative study for the group of anilinium-based IPHs 2-7,
suggested that the type of substituents of the aniline ring may influence the crystalline
structure. For example, while the 3,5-dimethyl substitution led to the 1-D trimolybdate 2,
the 2,5-dimethyl substitution led to the 2-D pentamolybdate 4. On the other hand, the
synthesis conditions influence the structural features of the IPHs. For example, depending
on the temperature, time and acidic conditions, the syntheses using the same precursor of
bis(4-methylanilinium) gave the structurally different IPHs 3 and 6 [27]. In order to gain
insights into structure-activity relationships, the catalytic performances were compared
on the basis of initial activity. Figure 7.a compares the initial activity for the 1-D versus
2-D structures, and Figure 7.b shows the initial activity versus the distances between
chains/layers for the anilinium-based IPHs. The results suggest more significant influence
of the structure dimensionality (Figure 7.a) than the distance between chains/layers
(Figure 7.b) on the catalytic performances. The initial catalytic activity (mol molMo-1 h-1)
followed the order 6 (40) < 7 (44) < 5 (48) < 4 (54) << 2 (97) < 3 (100) (Table 4). The 1-
D IPHs 2 and 3 were far more active than the 2-D 4-7 ones. For example, the anilinium-
based IPHs 2 and 4, which possess 1-D and 2-D structures, respectively, and comparable
distances between chains/layers (16.79 and 17.22 Å, respectively), it was verified that the
1-D catalyst was far more active than the 2-D one. On the other hand, a comparitive study
of 2 and 3 (1-D structures) indicated that while the disubstituted anilinium possessed
longer distance between chains than the monosubstituted one, initial activity was
17

comparable for the two IPHs (Figure 7.b). The same applies when comparing 6 and 7 (2-
D structures) in that a substituent group with a longer carbon chain (4-methyl versus 4-
ethyl) led to enlarged interplanar distance of the IPH, but did not affect significantly the
initial activity. Moreover, the unsubstituted anilinium (5) possessed the smallest
interplanar distance of the 2-D catalysts, and its initial activity was comparable to those
of the remaining 2-D catalysts. These comparisons support the above hypothesis in that
the structure dimensionality of the anilinium-based IPHs is an important factor
influencing the catalytic activity.
Hence, the catalytic activity seems favoured by a lower structure dimensionality. Similar
effects were reported in the literature for (non-ionic) molybdenum-triazole hybrids
[54,55].
In order to help understand the influence of the structure on the catalytic activity, it is
important to take into consideration the reaction mechanism involved. The reaction
mechanism of olefin epoxidation with hydroperoxide oxidants, in the presence of
molybdenum catalysts, may involve the coordination of the hydroperoxide molecules to
the metal centre, giving an active oxidising species responsible for the O-atom transfer to
the olefin, which finally leads to the formation of epoxide product [56,57]. Since the
organic cations are in the acidic form (protonated), their influence on the Lewis acidity
of the metal centres (active sites) may be less important than the structural features. For
1-D structures, the active sites may be more accessible, and the interactions of the reactant
molecules with the metal centres may be less hindered, than for the 2-D structures,
favouring the reaction kinetics.
((Figures 6 and 7 here))
18

3.3.4. Catalytic conversion of biomass-derived olefins
The best-performing catalyst 2 was studied for the catalytic epoxidation of the bio-derived
FAMEs methyl oleate (Ole) and methyl linoleate (LinOle), which are, readily available
in nature (canola, soybean, sunflower and corn oils, for example), Scheme 1 [58]. The
system Ole/2/tbhp gave methyl 9,10-epoxyoctadecanoate (OleOx) as the main product
formed in 48/84/92 % yield, at 51/89/99 % conversion (0.5 h/6 h/24 h), 70 C (Figures 8
and 9.a). Methyl 9,10-dihydroxyoctadecanoate (OleOH) and methyl 9-oxooctadecanoate
were formed in yields of 4 and 3 %, respectively, at 24 h.
The fatty acid methyl ester LinOle possesses two double bonds C=C, and thus the LinOle
reaction was carried out using a molar ratios substrate:oxidant of 1.5 or 2.5, in the
presence of 2 (Figures 8 and 9.b). Monoepoxide products, namely methyl 9,10-epoxy-12-
octadecenoate and methyl 12,13-epoxy-9-octadecenoate (LinOleOx isomers) were
formed with 60 % total yield (at 72 % conversion, 2 h reaction). LinOleOx selectivity
decreased with reaction time greater than 2 h, which was accompanied by the formation
of (diepoxide) methyl 9,10-12,13-diepoxyoctadecanoate (LinOleDiox) and cyclization
products (e.g. methyl 10,13-epoxy-9,12-dihydroxyoctadecanoate). These results suggest
that LinOleOx is an intermediate of the conversion of LinOle to LinOleDiox and
cyclization products, in agreement with the literature [59]. For the molar ratios
LinOle:tbhp of 1.5 or 2.5, the LinOle reaction kinetics was similar (Figure 8), albeit the
higher amount of tbhp seems to favour the formation of LinOleDiox and cyclization
products (Figure 8.b); it was reached 36-39 % LinOleOx, 28-39 % LinOleDiox yield, and
16-28 % yield of cyclization products, at 94-95 % conversion.
((Figures 8 and 9 here))
19

Compound 2 was tested for the epoxidation of R-(+)-limonene (Lim), the most abundant
limonene isomer present in citrus oil, at 70 C (Scheme 1). The reaction was fast, and
gave mainly 1,2-epoxy-p-menth-8-ene (LimOx) formed in 71 %/76 % yield, at 83 %/96
% conversion (and 1 h/4 h) (Figures 8 and 10). Besides LimOx, it was formed 1,2:8,9-
diepoxy-p-menthane (LimDiOx) and 1-methyl-4-(1-methylethenyl)-1,2-cyclohexanediol
(LimDiOH) (5 %/10 % and 2 %/7 % yield, respectively, at 1 h/4 h).
To the best of our knowledge, 2 is the first IPH catalyst studied for (i) LinOle epoxidation
and (ii) Lim reaction with tbhp (also, no polyoxomolybdates were reported as catalysts
for the reaction system Lim/tbhp). Few studies were reported in the literature for
polyoxomolybdate-catalysed epoxidation of Ole. The compounds (C5H5NH)4[Mo8O26]
and [(CH3)3CC5H4NH]4[Mo8O26] led to ca. 99 % OleOx yield, at 6 h, 75 ºC (initial molar
ratio Mo:Ole:tbhp=1:100:152; dce as co-solvent) [28]; at lower reaction temperature (70
ºC), 2 led to 89 % OleOx yield, at 6 h. Under similar reaction conditions (time,
temperature) to those used for 2, the compound (H3biim)4[β-Mo8O26] (H2biim = 2,2’-
biimidazole) led to 64 % OleOx yield at 24 h, 70 C (initial molar ratio
Mo:Ole:tbhp=1:100:152; ionic liquid as co-solvent) [29]; in comparison to these results,
2 performed superiorly (92 % OleOx yield). Iodometric titration indicated approximately
100 % tbhp efficiency, i.e. the catalyst does not account for a measurable non-productive
decomposition of tbhp to molecular oxygen plus tert-butanol.
The influence of the temperature on the reaction of Ole with tbhp was studied in the range
55-85 ºC. Increasing the temperature led to faster reaction of Ole to OleOx; 19, 66 and 81
% OleOx yield at 1 h for the reaction temperature of 55, 70 and 85 ºC, respectively (Table
6). Approximately the same OleOx yield was reached at 6 h/85 ºC (89 %) and 24 h/70 ºC
(92 %).
20

The influence of the type of solvent (can, tft, dce, tol) on the Ole/tbhp reaction at 70 ºC
was studied (Table 6). The most significant difference in catalytic results was the much
slower initial reaction (based on conversion at 1 h, Table 6) for acn than the remaining
cosolvents. The cosolvent acn is more polar than the remaining ones, albeit no direct
relationship between the solvent polarity and the initial reaction rate could be established.
Based on the normalized spectroscopically derived empirical scale of solvent polarity
(adimensional EN , ranging from 0.000 for apolar tetramethylsilane to 1.000 for (most
T
polar) water [60]), the solvent polarity follows the order, tol (0.099) < tft (0.241) < dce
(0.327) < acn (0.460), whereas conversion at 1 h follows the order, acn (31 %) << tol (63
%) < tft (70 %) ≈ dce (71 %). An important characteristic that distinguishes acn from the
remaining cosolvents is its coordinating ability. While acn is an aprotic coordinating
cosolvent, the remaining cosolvents tft, dce and tol are non-coordinating. Thus, the slower
kinetics for acn may be partly due to competitive effects between the solvent and oxidant
molecules in the coordination to the molybdenum species, retarding the overall catalytic
reaction [61-65].
((Table 6 here))
The IPH catalyst 2 was further studied for Ole conversion using H2O2 as oxidant instead
of tbhp. Iodometric titration indicated 98 % H2O2 efficiency for the catalytic epoxidation
system. Hence, 2 enables very efficient use of the peroxide oxidants for catalytic
epoxidation. However, in relation to the reaction of Ole with tbhp, the catalyst was poorly
effective with H2O2 (13 % conversion at 24 h). According to the literature, the transition
state involved in the epoxidation reaction may differ for alkyl hydroperoxides versus
hydrogen peroxide as oxidant, affecting the reaction kinetics [66-72]. Nevertheless, tbhp
21

is an interesting oxidant, since its use for catalytic epoxidation presents as possible
advantages relatively safe transportation, storage, handling, and it is miscible with many
organic solvents [73], being the oxidant of choice for epoxidation processes by industries,
e.g. LyondellBasell [74] and Huntsman processes [75].
IPHs are versatile materials in that the type of transition metal and organic precursor may
be changed, which may lead to different performances. For example, it is possible that
tungsten-based IPHs may promote the one-pot epoxidation-hydrolysis of bio-olefins to
useful diols (e.g. intermediates to producing oleo-chemical based renewable polymers).
Kozhevnikov et al. [76] reported the reaction of oleic acid with H2O2 in the presence of a
peroxophosphotungstate homogeneous catalyst, which led to the corresponding diol
product in 61 % yield at 93 % conversion (80 ºC, 160 min); decreasing reaction
temperature and time (60 ºC, 50 min) led to the epoxide as the main product formed in 84
% yield at 95 % conversion. Later Poli et al. [77] reported the immobilisation of
peroxophosphotungstate on mesoporous silica SBA-15, as heterogeneous catalyst for the
reaction of Ole with H2O2, at 65 ºC; this catalyst was not effective in the first batch run,
but it was suggested that favourable changes in geometry of the polyanion occurred
during the first run, which led to superior results in the second run (4 % and 44 % epoxide
yield at 15 h. for runs 1 and 2, respectively). Very recently, it was reported that ionic
organic-inorganic polyoxotungstates are capable of promoting the oxidative cleavage of
fatty acids, at relatively high temperature (120 ºC); specifically, the reaction oleic
acid/H2O2 gave azelaic (C9 diacid) and pelargonic (C9 monoacid) acids, which are
industrially produced from oleic acid via ozonolysis (use of hazardous ozone) [78]. IPHs,
besides being versatile materials, may possess relatively high thermal stability (~200 ºC
[27]) for these catalytic applications.
22

((Figure 10 here))
Conclusions
Ionic polymolydate hybrids 1-7 were prepared in simple and relatively clean fashions,
and are effective olefin epoxidation catalysts. Catalyst stability and characterization
studies (FT-IR ATR spectroscopy, XRPD, SEM) of the used catalysts, indicated fairly
steady performances in consecutive batch runs, and the chemical, structural and
morphological features of the materials were essentially preserved. The type of synthetic
organic precursor and synthesis conditions influence the structural features of the IPHs,
with structure dimensionality (1-D, 2-D) impacting on the catalytic activity. The best-
performing catalyst 2 (in terms of activity and stability) possesses a 1-D structure. The
IPH 2 was effective for the conversion of biomass-derived olefins, specifically, fatty acid
methyl esters (methyl oleate (Ole), methyl linoleate (LinOle)) and terpene (limonene) to
bio-products; e.g. Ole was converted to the corresponding epoxide methyl 9,10-
epoxyoctadecanoate in 92 % yield, at 70 C/24 h (approximately atmospheric pressure).
The reaction kinetics seemed favoured by increasing the reaction temperature and using
non-ccordinating cosolvents. To the best of our knowledge, this is the first report of
LinOle epoxidation, and Lim/tbhp conversion in the presence of IPH catalysts.
Ionic polymetallate hybrids are versatile materials; by changing the type of transition
metal and organic precursor, their applications may be broadened to different types of
catalytic reactions, and different scientific fields.
Acknowledgments
23

This work was developed in the scope of the project CICECO – Aveiro Institute of
Materials [POCI-01-0145-FEDER-007679] financed by national funds through the
Fundação para a Ciência e a Tecnologia (FCT) [ref. UID/CTM/50011/2013] and
Ministério da Educação e Ciência (MEC) and when applicable, cofinanced by Fundo
Europeu de Desenvolvimento Regional (FEDER) under the PT2020 Partnership
Agreement. The FCT and the European Union are acknowledged for a post-doctoral grant
to P.N. [SFRH/BPD/110530/2015], cofunded by Ministério da Ciência, Tecnologia e
Ensino Superior (MCTES) and the European Social Fund through the program Programa
Operacional Potencial Humano (POPH) of Quadro de Referência Estratégica Nacional
(QREN). The European Union Erasmus+ programme [project number: 2016-1-PL01-
KA103-023786] is acknowledged for providing scholarship (financial support) for the
traineeship (B.B).
24

References
[1] P. Muturi, D. Q. Wang, S. Dirlikov, Prog. Org. Coat. 25 (1994) 85-94.
[2] N. O. Shaker, E. M. Kandeel, E. E. Badr, M. M. El-Sawy, J. Dispersion Sci.
Technol. 29 (2008) 421-425.
[3] S. F. Thames, H. Yu, Surf. Coat. Technol. 115 (1999) 208-214.
[4] K. M. Doll, S. Z. Erhan, J. Surfactants Deterg. 9 (2006) 377-383.
[5] A. Adhvaryu, S. Z. Erhan, Ind. Crops Prod. 15 (2002) 247-254.
[6] K. M. Doll, B. R. Moser, S. Z. Erhan, Energy Fuels 21 (2007) 3044-3048.
[7] E. Milchert, K. Malarczyk, M. Klos, Molecules, 20 (2015) 21481-21493.
[8] A. J. Bonon, Y. N. Kozlov, J. O. Bahu, R. Maciel Filho, D. Mandelli, G. B. Shul'pin,
J. Catal. 319 (2014) 71-86.
[9] A. Corma, S. Iborra, A. Velty, Chem. Rev. 107 (2007) 2411-2502.
[10] C. L. Li, S. van Berkel, R. J. Sablong, C. E. Koning, Eur. Polym. J. 85 (2016) 466-
477.
[11] R. C. Jeske, A. M. DiCiccio, G. W. Coates, J. Am. Chem. Soc. 129 (2007) 11330-
11331.
[12] P. A. Wilbon, F. Chu, C. Tang, Macromol. Rapid Commun. 34 (2013) 8-37.
[13] M. Baehr, A. Bitto, R. Muelhaupt, Green Chem. 14 (2012) 1447-1454.
[14] C. L. Li, R. J. Sablong, C. E. Koning, Angew. Chem. Int. Ed. 55 (2016) 11572-
11576.
[15] C. Martin, A. W. Kleij, Macromolecules, 49 (2016) 6285-6295.
[16] M. Guidotti, R. Psaro, I. Batonneau-Gener, E. Gavrilova, Chem. Eng. Technol. 34
(2011) 1924-1927.
[17] L. Cronin, A. Muller, Chem. Soc. Rev. 41 (2012) 7333-7334.
25

[18] J. M. Clemente-Juan, E. Coronado, A. Gaita-Arino, Chem. Soc. Rev. 41 (2012)
7464-7478.
[19] H. J. Lv, Y. V. Geletii, C. C. Zhao, J. W. Vickers, G. B. Zhu, Z. Luo, J. Song, T. Q.
Lian, D. G. Musaev, C. L. Hill, Chem. Soc. Rev. 41 (2012) 7572-7589.
[20] C. Streb, Dalton Trans. 41 (2012) 1651-1659.
[21] P. C. Yin, D. Li, T. B. Liu, Chem. Soc. Rev. 41 (2012) 7368-7383.
[22] B. Bujanovic, S. Ralph, R. Reiner, K. Hirth, R. Atalla, Materials 3 (2010) 1888-
1903.
[23] J. Du, J. Yu, J. Tang, J. Wang, W. Zhang, W. R. Thiel, M. Jia, Eur. J. Inorg. Chem.
(2011) 2361-2365.
[24] T. Okuhara, N. Mizuno, M. Misono, Appl. Catal. A-Gen. 222 (2001) 63-77.
[25] I. V. Kozhevnikov, Chem. Rev. 98 (1998) 171-198.
[26] H. Yanagie, A. Ogata, S. Mitsui, T. Hisa, T. Yamase, M. Eriguchi, Biomed.
Pharmacother. 60 (2006) 349-352.
[27] A. Szymanska, W. Nitek, M. Oszajca, W. Lasocha, K. Pamin, J. Poltowicz, Catal.
Lett. 146 (2016) 998-1010.
[28] C. A. Gamelas, P. Neves, A. C. Gomes, A. A. Valente, C. C. Romão, I. S.
Gonçalves, M. Pillinger, Catal. Lett. 142 (2012) 1218-1224.
[29] P. Neves, T. R. Amarante, A. A. Valente, M. Pillinger, I. S. Goncalves, Catal. Lett.
146 (2016) 841-850.
[30] A. C. Gomes, P. Neves, S. Figueiredo, J. A. Fernandes, A. A. Valente, F. A.
Almeida Paz, M. Pillinger, A. D. Lopes, I. S. Gonçalves, J. Mol. Catal. A: Chem.
370 (2013) 64-74.
[31] M. Najafi, A. Abbasi, M. Masteri-Farahani, V. H. Rodrigues, J. Sci., Islamic Repub.
Iran 25 (2014) 229-235.
26

[32] H. Arzoumanian, Coord. Chem. Rev. 178 (1998) 191-202.
[33] R. Sanz, M. R. Pedrosa, Curr. Org. Synth. 6 (2009) 239-263.
[34] A. Kumar, A. K. Gupta, M. Devi, K. E. Gonsalves, C. P. Pradeep, Inorg. Chem. 56
(2017) 10325-10336.
[35] T. R. Amarante, P. Neves, A. A. Valente, F. A. Almeida Paz, A. N. Fitch, M.
Pillinger, I. S. Gonçalves, Inorg. Chem. 52 (2013) 4618-4628.
[36] B. M. Trost, Y. Masuyama, Isr. J. Chem. 24 (1984) 134-143.
[37] M. Oszajca, N. Juszczyk, W. Lasocha, J. Mol. Struct. 965 (2010) 131-136.
[38] W. Lasocha, K. Lewiński, J. Appl. Cryst. 27 (1994) 437-438.
[39] A. Altomare, M. Camalli, C. Cuocci, C. Giacovazzo, A. Moliterni, R. Rizzi, J. Appl.
Cryst. 42 (2009) 1197-1202.
[40] V. Favre-Nicolin, R. Cerny, J. Appl. Cryst. (2002) 734-743.
[41] V. Petricek, M. Dusek, L. Palatinus, Jana 2006. The crystallographic computing
system, 2006, Institute of Physics, Czech Republic.
[42] J. Wienold, R. E. Jentoft, T. Ressler, Eur. J. Inorg. Chem. (2003) 1058-1071.
[43] P. Neves, L. S. Nogueira, A. C. Gomes, T. S. M. Oliveira, A. D. Lopes, A. A.
Valente, I. S. Goncalves, M. Pillinger, Eur. J. Inorg. Chem. (2017) 2617-2627.
[44] T. R. Amarante, P. Neves, C. Tomé, M. Abrantes, A. A. Valente, F. A. Almeida
Paz, M. Pillinger, I. S. Gonçalves, Inorg. Chem. 51 (2012) 3666-3676.
[45] H. C. Gao, J. H. Yu, J. Du, H. L. Niu, J. Wang, X. J. Song, W. X. Zhang, M. J. Jia,
J. Cluster Sci. 25 (2014) 1263-1272.
[46] M. Najafi, A. Abbasi, M. Masteri-Farahani, H. Shahbaazi, M. A. Motlagh, J.
Janczak, RSC Adv. 6 (2016) 29944-29949.
[47] S. Y. Li, C. W. Kee, K. W. Huang, T. S. A. Hor, J. Zhao, Organometallics 29 (2010)
1924-1933.
27

[48] J. Pisk, B. Prugovecki, D. Matkovic-Calogovic, T. Jednacak, P. Novak, D. Agustin,
V. Vrdoljak, RSC Adv. 4 (2014) 39000-39010.
[49] M. Ghorbanloo, R. Bikas, G. Malecki, Inorg. Chim. Acta 445 (2016) 8-16.
[50] C. Bhaumik, E. Manoury, J.-C. Daran, P. Soezen-Aktas, F. Demirhan, R. Poli, J.
Organomet. Chem. 760 (2014) 115-123.
[51] B. Zhang, S. Li, A. Pothig, M. Cokoja, S. L. Zang, W. A. Herrmann, F. E. Kühn,
Z. Naturforsch., B: Chem. Sci., 68 (2013) 587-597.
[52] M. Moghadam, V. Mirkhani, S. Tangestaninejad, I. M.-Baltork, M. M. Javadi,
Polyhedron 29 (2010) 648–654.
[53] M. Moghadam, V. Mirkhani, S. Tangestaninejad, I. M.-Baltork, M. M. Javadi,
Inorg. Chem. Commun. 13 (2010) 244–249.
[54] A. B. Lysenko, G. A. Senchyk, K. V. Domasevitch, J. r. Hauser, D. Fuhrmann, M.
Kobalz, H. Krautscheid, P. Neves, A. A. Valente, I. S. Gonꢀalves, Inorg. Chem. 54
(2015) 8327-8338.
[55] A. B. Lysenko, G. A. Senchyk, K. V. Domasevitch, M. Kobalz, H. Krautscheid, J.
Cichos, M. Karbowiak, P. Neves, A. A. Valente, I. S. Gonçalves, Inorg. Chem. 56
(2017) 4380-4394.
[56] L. F. Veiros, A. Prazeres, P. J. Costa, C. C. Romão, F. E. Kühn, M. J. Calhorda,
Dalton Trans. (2006) 1383-1389.
[57] F. E. Kühn, M. Groarke, E. Bencze, E. Herdtweck, A. Prazeres, A. M. Santos, M.
J. Calhorda, C. C. Romão, I. S. Gonçalves, A. D. Lopes, M. Pillinger, Chem. Eur.
J. 8 (2002) 2370-2383.
[58] Nikesh B. Samarth, P. A. Mahanwar, Open J. Org. Polym. Mater. 5 (2015) 1-22.
[59] G.J. Piazza, A. Nuñez, T. A. Foglia, J. Am. Oil Chem. Soc. 80 (2003) 901-904.
[60] C. Reichardt, Chem. Rev. 94 (1994) 2319-2358.
28

[61] W. R. Thiele, J. Mol. Catal. A: Chem. 117 (1997) 449-454.
[62] W. R. Thiele, Chem. Ber. 129 (1996) 575-580.
[63] S. M. Bruno, B. Monteiro, M. S. Balula, C. Lourenço, A. A. Valente, M. Pillinger,
P. Ribeiro-Claro, I. S. Gonçalves, Molecules 11 (2006) 298-308.
[64] S. Figueiredo, A. C. Gomes, J. A. Fernandes, F. A. A. Paz, A. D. Lopes, J. P.
Lourenço, M. Pillinger, I. S. Gonçalves, J. Organomet. Chem. 723 (2013) 56-64.
[65] M. Bagherzadeh,, H. Mohammadabadi, S. Abednatanzi, A. Abbasi, M. Amini,
Nanochem. Res. 2 (2017) 179-187.
[66] L. F. Veiros, A. Prazeres, P. J. Costa, C. C. Romão, F. E. Kühn, M. J. Calhorda,
Dalton Trans. (2006) 1383-1389.
[67] C. Dinoi, M. Ciclosi, E. Manoury, L. Maron, L. Perrin, R. Poli, Chem. Eur. J. 16
(2010) 9572-9584.
[68] P. J. Costa, M. J. Calhorda, F. E. Kühn, Organometallics 29 (2010) 303-311.
[69] A. Comas-Vives, A. Lledós, R. Poli, Chem. Eur. J. 16 (2010) 2147-2158.
[70] M. J. Calhorda, P. J. Costa, Curr. Org. Chem. 16 (2012) 65-72.
[71] C. Dinoi, R. Poli, L. Perrin, L. Maron, Dalton Trans. 41 (2012) 1131-1133.
[72] P. Sözen-Aktas, E. Manoury, F. Demirhan, R. Poli, Eur. J. Inorg. Chem. (2013)
2728-2735.
[73] https://www.lyondellbasell.com/globalassets/documents/chemicals-technical-
literature/t-hydro-product-safety-bulletin-3453.pdf. Consulted on the 3rd February
2018.
[74] https://www.lyondellbasell.com/en/about-us/company-investments/;
https://www.lyondellbasell.com/en/products-technology/chemicals/chemical-
type/peroxides/. Consulted on the 3rd February 2018.
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