2
C.I. Fernandes et al. / Journal of Organometallic Chemistry xxx (2014) 1e9
thiols to disulfides [16]. CO
2
sequestration, through a hydration
The SEM images and EDX analyses were obtained on a FEG-SEM
(Field Emission Gun Scanning Electron Microscope) from JEOL,
model JSM-7001F. The TEM images were obtained on a microscope
mechanism has also been studied by the development of a
magnetically supported Zn(II) complex with histidine that mimics
the bio-catalytic activity of Carbonic Anhydrase [17]. The catalyst
was found to maintain activity after 10 cycles. Immobilized Pd(II)
systems with catalytic activity in SuzukieMiyaura and high recy-
clability were also reported by the group of Thiel [18].
Olefin epoxidation is a major field of research in the preparation
of relevant building blocks for organic synthesis [19e21]. Among
other metal systems, Mo-catalyzed olefin epoxidation has received
interest from both academic and industrial research laboratories
6
Hitachi, model H-1800 with a LaB filament and an acceleration
tension of 200 kV.
The 57Fe Mössbauer spectra were recorded in transmission
mode at room temperature using
acceleration spectrometer and a 50 mCi Co source in a Rh ma-
trix. The velocity scale was calibrated using an -Fe foil. The spectra
were fitted to Lorentzian lines using the WinNormos software
a conventional constant-
57
a
program, and the isomer shifts reported are relative to metallic
at room temperature.
a-Fe
[22,23]. Since the first example of a molybdenum oxo complex
catalyzing the epoxidation of alkenes with peroxides such as
organic hydroperoxides and hydrogen peroxide [24], a variety of
different complexes have been developed [25e28]. Inclusively, in
recent times, many efficient epoxidation Mo-based catalysts are
2.2. Methods
2.2.1. Synthesis of ligand isonicotinoyl chloride (inicCl)
SOCl (5 mL) was added to isonicotinic acid (0.261 g, 2.12 mmol)
2
and the solution was refluxed under vigorous stirring during 3 h.
II
based on Mo organometallic complexes which work as pre-
II
catalysts [29]. Such pre-catalysts are simply organometallic Mo
VI
carbonyl complexes which can be oxidized to the dioxo Mo ho-
After that the solution was evaporated under vacuum [35,36].
ꢀ
1
mologues which are the active species [5].
IR (KBr
1395 (vs); 1242 (s); 753 (m); 677 (m).
n/cm ): 3421 (s); 3112 (s); 1734 (vs); 1639 (s); 1507 (s);
The use of complexes from the MoX
¼ mono or bidentate Lewis base ligands) heptacoordinate hal-
2
(CO)
3
L
n
(X ¼ Br, I;
1
L
n
H NMR(400.13 MHz, CDCl
3 2 1
, r.t, d ppm): 9.17 (d, H ), 8.55 (d, H ).
ocarbonyl family were reported to possess catalytic activity in
olefin epoxidation [30e33]. These complexes were developed in
pioneering work by Baker for catalytic applications other than
oxidation [34]. However, such systems were found to have quite
high performances, although it was found very recently that such
systems suffer from the ligand dependency which leads in some
cases to deactivation. This is true when ligands hold NH moieties as
already reported in the literature [31].
Continuing our research on olefin epoxidation [5,7,23,30e33],
we describe in the present work the preparation and subsequent
evaluation of the catalytic potential of a Mo complex anchored on
the surface of silica-coated magnetic iron oxide nanoparticles with
two different sizes. After preparation of the magnetic iron oxide
cores, these nanoparticles were subsequently coated with silica for
stabilization and to allow derivatization by grafting an organic
pyridine derivative. The latter allowed coordination of a Mo
organometallic complex. The resulting materials were used in
olefin epoxidation reactions. The advantage of these nanocatalysts
is that they are quite active in that transformation and can be easily
separated from the reaction medium by a magnet. This is a crucial
step in order to promote catalyst separation and recycling without
compromising product recovery which is usually an elaborate task
in homogeneous systems.
2.2.2. Synthesis of magnetic iron oxide nanoparticles (MNP)
The iron oxide magnetic nanoparticles were prepared according
to two different published procedures, allowing to obtain particles
with mean sizes of 30 nm (MNP30) [37] and 11 nm (MNP11
respectively [38]. Both materials were coated with oleic acid acting
as stabilizer.
)
In order to obtain the MNP30-Si and MNP11-Si materials, these
nanoparticles were coated with silica following a published pro-
cedure [37].
MNP30-Si: IR (KBr
MNP11-Si: IR (KBr
/cm 1): 1400 (vs); 1066 (s); 572 (vs).
ꢀ
n
ꢀ1
n
/cm ): 1400 (vs); 1088 (s); 588 (vs).
2.2.3. Preparation of MNP30-Si-inic and MNP11-Si-inic materials
0.150 g of inicCl ligand were dissolved in 5 mL of dry CH Cl and
2
2
added to 0.300 g of MNP30-Si or MNP11-Si in 30 mL of dry toluene.
The mixture was then stirred at 363 K under nitrogen atmosphere
for 3 h. The solid material obtained was magnetically separated,
washed repeatedly with toluene and CH
species and then dried under vacuum.
2 2
Cl to remove unanchored
2.2.3.1. MNP30-Si-inic. IR (KBr
(m); 1728 (w); 1638 (m); 1602 (m); 1408 (w); 1054 (m); 756 (w);
63 (m).
Elemental analysis (%): found C 12.29; H 1.38; N 1.69.
n
/cmꢀ1): 3377 (m), 3415 (m), 3115
5
2
. Materials and methods
2
.1. General
2.2.3.2. MNP11-Si-inic. IR (KBr
(
n
/cmꢀ1): 3407 (m), 3116 (m); 1732
w); 1639 (w); 1402 (w); 1090 (m); 756 (vw); 668 (m).
Elemental analysis (%): found C 11.12; H 1.26; N 2.28.
All reagents were obtained from Aldrich and used as received.
Commercial grade solvents were dried and deoxygenated by
ꢀ
standard procedures distilled under nitrogen, and kept over 4 A
2.2.4. Preparation of MNP30-Si-inic-Mo and MNP11-Si-inic-Mo
molecular sieves. The complex [MoI
according to a literature procedure [34].
FTIR spectra were obtained as KBr pellets on a Nicolet 6700 in
the 400e4000 cm range using 2 cm resolution. Powder XRD
measurements were taken on a Philips Analytical PW 3050/60
X’Pert PRO (theta/2 theta) equipped with an X’Celerator detector
and with automatic data acquisition (X’Pert Data Collector (v2.0b)
2
(CO)
3
(CH
3
CN)
2
] was prepared
materials
0.100 g of [MoI
2 3 2 2 2
(CO) (NCMe) ] dissolved in 5 mL of dry CH Cl
were added to a suspension of 0.600 g of MNP30-Si-inic or MNP11
-
ꢀ
1
ꢀ1
Si-inic in 30 mL of dry toluene. The mixture was then stirred at
363 K under nitrogen atmosphere for 3 h. The solid material ob-
tained was magnetically separated, washed repeatedly with
toluene and CH
2 2
Cl to remove the unanchored species and then
software), using a monochromatized CuK
beam. H and C solution NMR spectra were obtained with a
Bruker Avance 400 spectrometer.
a radiation as incident
dried under vacuum.
1
13
2.2.4.1. MNP30-Si-inic-Mo. IR (KBr n
/cmꢀ1): 3392 (m), 3152 (m);
Microanalyses (C, N, H, Mo) were performed at the University of
Vigo.
1734 (m); 1653 (m); 1636 (m); 1617 (m); 1399 (w); 1091 (m); 724
(w); 668 (m).
Please cite this article in press as: C.I. Fernandes, et al., Journal of Organometallic Chemistry (2014), http://dx.doi.org/10.1016/
j.jorganchem.2014.01.035