Transit Met Chem (2017) 42:357–363
DOI 10.1007/s11243-017-0139-7
Enhanced reactivity in a heterogeneous oxido-peroxido
molybdenum(VI) complex of salicylidene 2-picoloyl hydrazone
in catalytic epoxidation of olefins
Zeinab Moradi-Shoeili1
Maryam Zare2 Serdar Akbayrak3 Saim Ozkar
4
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Received: 26 January 2017 / Accepted: 23 March 2017 / Published online: 3 April 2017
Ó Springer International Publishing Switzerland 2017
Abstract A molybdenum(VI) oxido-diperoxido complex
of salicylidene 2-picoloyl hydrazine (sal-phz) was synthe-
sized and successfully grafted onto chloro-functionalised
Fe3O4 nanoparticles. The resulting heterogeneous and
magnetically recoverable nanoscale catalyst MoO3(sal-
phz)/Fe3O4 was characterized by physicochemical and
spectroscopic techniques. The activity of this heteroge-
neous catalyst for the oxidation of olefins to corresponding
epoxides was efficiently increased by increasing the reac-
tion temperature up to 95 °C. The nanocatalyst proved to
be efficient for the selective epoxidation of a variety of
alkenes using t-BuOOH with high conversion and selec-
tivity. Leaching and recycling tests showed that the
nanocatalyst can be reused at least six times without sig-
nificant decrease in efficiency.
complexes of the type [MoO(O2)m(L)n] (n, m = 1, 2;
L = mono- or bidentate ligand) are an important class of
catalyst for the oxidation of olefins. Facile preparation, sta-
bility and low-cost synthesis make them attractive candidates
among a variety of complexes of various metals that are able to
catalyze olefin epoxidation [4]. Therefore, much effort has
gone into the design and fabrication of such complexes with
high reactivity and selectivity in olefin epoxidation reactions,
at either the stoichiometric or catalytic level [5, 6]. High valent
molybdenum oxido-peroxido species catalyze the epoxidation
ofavarietyofalkenesemployingH2O2 or t-BuOOH as oxidant
[7]. The catalytic activities of oxido-peroxido molybde-
num(VI) complexes are influenced by the number of peroxido
ligands attached to the metal, the nature of the remaining
ligands in the coordination sphere [8, 9] and the experimental
conditions [10]. Peroxidomolybdate complexes, especially
when the central metal is coordinated by an electron-with-
drawing ligand, are often observed to show low turnovers and
selectivity for the epoxide products under harsh reaction con-
ditions[11]. Moreover, previousexperimentalstudiesrevealed
that the peroxido derivatives of molybdenum(VI) complexes
usually show lower catalytic activities relative to the oxido
analogues [12]. More recently, we have demonstrated that the
catalytic activity of homogeneous and heterogeneous oxido-
peroxido molybdenum(VI) complexes in epoxidation reac-
tions can be improved at higher temperatures, and surprisingly
the conversion of olefins to epoxides increased in most cases
[13]. In continuation of our research into the catalytic activities
of heterogeneous molybdenum catalysts, in this work
MoO3(sal-phz)(CH3OH) (where sal-phz is salicylidene 2-pi-
coloyl hydrazine) has been immobilized on the surface of
Fe3O4 magnetic nanoparticles modified with 3-chloropropyl-
triethoxysilane (CPTES). Our aim was to prepare an efficient
and reusable catalytic system for epoxidation of olefins using
magnetic nanoparticles as a support. Scheme 1 shows the
Introduction
Catalytic epoxidation of olefins to their respective epoxides is
an important reaction in both laboratory synthesis and indus-
trial production [1–3]. Oxido-peroxido molybdenum(VI)
& Zeinab Moradi-Shoeili
1
Department of Chemistry, Faculty of Sciences, University of
Guilan, P.O. Box 41335–1914, Rasht, Iran
2
Materials Science and Engineering Department, Golpayegan
University of Technology,
P.O. Box 8771765651, Golpayegan, Iran
3
Department of Chemistry, Faculty of Arts and Science, Sinop
University, 57000 Sinop, Turkey
4
Chemistry Department, Middle East Technical University,
06800 Ankara, Turkey
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