The rhodium complex of bis(diphenylphosphinomethyl)dopamine-coated magnetic nanoparticles as an efficient and reusable catalyst for hydroformylation of olefins

Article abstract of DOI:10.1039/c5nj01170a

A new bis(diphenylphosphinomethyl)dopamine (bpd) ligand has been prepared and anchored on the surface of magnetic nanoparticles (MNPs). The obtained ligand and the surface functionalized nanoparticles of type MNP@bpd have been characterized by various analytical techniques, such as NMR, IR, TEM, XRD, and VSM. TEM shows homogeneous distribution of the particles with the size ranging 5-7 nm. XRD Rietveld analysis confirms the formation of a pure and single Fe₃O₄ phase with high crystallinity. The ligands anchored on the magnetic nanoparticle surface have been confirmed by the shift of the characteristic Fe-O vibration band in the FT-IR spectrum, and have been supported by the stepwise weight loss in TGA as a function of temperature. The phosphorus content determined by ICP-MS is approximately 0.39 mmol of phosphine per gram of the nanoparticles. Magnetization-field curves recorded at room temperature reveal superparamagnetic behavior. MNP@bpd materials have proven to be excellent catalysts after in situ addition of the rhodium (Rh) metal precursor for the hydroformylation reaction of styrene and its derivatives. The extent of reusability of the catalyst has been tested and was found to be active even after seven consecutive cycles.

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Graphic Table of Contents
Rhodium complex of bis(diphenylphosphinomethyl) dopamine-coated
magnetic nanoparticles as efficient and reusable catalyst for hydroformylation of
olefins
Mohammed Nasiruzzaman Shaikh*,a, M. Bououdinab, Abiola Azeez Jimoha, Md. Abdul Aziza,
Aasif Helala, Abbas Saeed Hakeema, Zain H. Yamania, Tae-Jeong Kimc
Magnetic nanoparticles(MNP) functionalized by a new bis(diphenylphosphinomethyl)dopamine
(bpd) of type MNP@bpd were prepared, characterized and their reusability as catalysts were
assessed by hydroformylation reaction.

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Rhodium complex of bis(diphenylphosphinomethyl) dopamine-
coated magnetic nanoparticles as efficient and reusable catalyst
for hydroformylation of olefins
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Mohammed Nasiruzzaman Shaikh*,a, Mohamed Bououdinab, Abiola Azeez
Jimoha, Md. Abdul Aziza, Aasif Helala, Abbas Saeed Hakeema, Zain H. Yamania, Tae-
Jeong Kimc
www.rsc.org/
A new bis(diphenylphosphinomethyl) dopamine (bpd) ligand has been prepared and anchored on
the surface of magnetic nanoparticles (MNPs). The obtained ligand and the surface functionalized
nanoparticles of type MNP@bpd have been characterized by various analytical techniques, such
as NMR, IR, TEM, XRD, and VSM. TEM shows homogeneous distribution of the particles with the
size ranging 5-7 nm. XRD Rietveld analysis confirm the formation of pure and single Fe3O4 phase
with high crystallinity. The ligands anchoring on the magnetic nanoparticles surface have been
confirmed by the shift of the characteristic Fe-O vibration band in the FT-IR spectrum, and has
been supported by the stepwise weight loss in TGA as a function of temperature. The phosphorus
content determined by ICP-MS is approximately 0.39 mmol of phosphine per gram of the
nanoparticles. Magnetization-field curves recorded at room temperature reveal
superparamagnetic behavior. The materials MNP@bpd have proven to be an excellent catalyst
after in-situ addition of rhodium (Rh) metal precursor for the hydroformylation reaction of
styrene and its derivatives. The extent of reusability of the catalyst has been tested and was found
to be active even after seven consecutive cycles.
reports on homogeneous catalysis to produce oxo- chemicals are
available in the literature [9-13]. Homogeneous catalysts are
dominant because they react in the same phase as the reactant. By
nature, homogeneous catalysts are soluble in organic solvents, so
Introduction
In recent years, catalyzed hydroformylation has drawn much
attention as a commercially important reaction in the production of
aldehydes from aliphatic and substituted aromatic olefins with
syngas [1-8]. The aldehyde products can be converted into
numerous useful chemicals via condensation, hydrogenation,
amination and other processes. Consequently, a large number of
that all catalytic sites are accessible and easy to tune by organic
functional group inter-conversion. However, the solubility poses the
main challenge in homogeneous catalysis; that is, to separate the
catalyst from the desired product after the reaction. This limits the
scope of homogeneous catalysis for some applications, and is
occasionally considered as crucial drawback for product
commercialization.
During the last two decades, great efforts have been devoted to
develop alternatives to homogeneous catalysis in order to minimize
separation costs and maximize product purity. Heterogeneous
catalysis is the most obvious alternative, as it uses catalysts that are
easy to separate and reuse. In addition, it can minimize the use of
large quantities of environmentally toxic organic solvents that are
needed for separation of the homogeneous catalysts and
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purification of the reaction products. Most heterogeneous catalysts Chemicals procured from Sigma-Aldrich were used as-received
are based on solid supports such as silica [14-16]. Silica is highly unless otherwise stated. All reactions were carried out under
stable, robust and easy to functionalize; thereby organic functional argon atmosphere using standard Schlenk techniques. Solvents
groups can be easily anchored by either covalent binding or surface were dried using standard procedures. Deionized (DI) water
1
adsorption in order to provide catalytic centers. However, majority was used wherever needed. The H signatures were collected
fraction of the catalytic sites can dip inside the solid support, on a JEOL JNM-LA 500 Spectrometer, and the respective
becoming inaccessible and decreasing the overall catalytic activity. chemical shifts (δ) were defined using tetramethylsilane (TMS)
In addition, the bonds holding the catalyst to the solid support can as an internal standard. 31P NMR spectra were recorded on
break, causing the catalyst to leach out of the solid support and the same machine using 85% H3PO4 as an internal reference.
hence results in increasing the possibility of separation The FT-IR spectra of the functionalized MNPs were obtained
complications.
from a Nicolet 720 in the range of 400 to 4000 cm-1
, using KBr.
Thermal analysis was performed on the Mettler-Toledo with
model TGA1 STARe System on around 10 mg of dry samples
under argon atmosphere with a heating rate of 10 oC/min with
the temperature ranges 0-800 oC. X-ray diffraction patterns
were recorded using high resolution Rigaku Ultima IV
diffractometer equipped with Cu-Kα radiation. The data were
As an alternative support to silica, nanoparticles have attracted
much attention owing to their robustness and high surface area.
Because of the high surface area of nanoparticles supports, catalyst
centers anchored to nanoparticles are more exposed to the
reactant and therefore have increased catalytic activity. If
homogeneous units are anchored onto nanoparticle supports, they
can often still behave as if they were dissolved in solution, which
improves the overall catalytic activity. The choice of nanoparticles
can also be strategically made so that additional functionality is
introduced into the catalytic system. For example, super-
paramagnetic iron oxide nanoparticles (SPIONs) opened up a
promising research strategy for developing surface-coated
recyclable catalysts because they can easily be separated from
solution using a magnetic field [17-23].
acquired over the 2θ range between 15 and 85°. Rietveld
refinements were performed using PDXL program.The
phosphorous content in the sample was determined by
inductively coupled mass spectrometry (ICP-MS) method
(Thermo Scientific, model XSERIES 2), by dissolving it in
concentrated HNO3. The surface morphology of the NPs was
discerned by field emission scanning electron microscopy
(FESEM, LYRA 3 Dual Beam, Tescan) operated at 30 kV. FESEM
samples were prepared either from suspension or dry powder
and coated with gold in an automatic gold coater for 90 s. The
Energy Dispersive X-ray spectra (EDX) for the chemical and
elemental analysis of NPs were collected from X-Max detector
by Oxford Inc. TEM micrograph were obtained from an high-
resolution transmission electron microscopy (HRTEM) (JEOL
JEM-2100F) equipped with an energy dispersive X-ray
spectrometer (EDX) operated at 200 kV. 300 mesh copper
grids coated with carbon films were used for the imaging. The
transmission electron microscopy (TEM) samples were
prepared by dropping on a copper grid from an ethanolic
suspension and drying at room temperature. Magnetic
measurements were carried out at room temperature using
PMC Micromag 3900 model Vibrating Sample Magnetometer
(VSM) equipped with 1 tesla magnet and a sensitivity of 0.5
µemu. The conversion of the catalytic product were calculated
by Gas chromatography (GC) (Shimadzu) and products were
identified by the Gas chromatography integrated with mass-
spectrometry (GC-MS) with model GCMS-QP2010 Ultra from
Shimadzu.
Because iron oxide nanoparticles can be prepared from low cost-
materials via simple synthetic approaches, and since suitable
ligands can easily be anchored on their surface [24-27], they offer
excellent potential as
a catalyst support. Furthermore, their
insolubility in organic solvents and magnetic nature render them
easily separable from the heterogeneous reaction system; this
greatly reduces the efforts required to isolate the catalyst and
products. In addition, it is easy to tune the physical and chemical
properties, including the shape, size, and morphology, of these
magnetic particles [28-30]. In line with this effort, Alper et al.
recently reported magnetic particle-supported heterogeneous
catalytic systems using polyaminoamido (PAMAM) dendrons, and
the catalytic results obtained were encouraging [31]. They reported
up to 100% conversion with excellent regio-selectivity towards
branched to linear aldehyde ratio. In addition, Chouansong et al.
reported the triphenylphosphine ligand coated magnetic
nanoparticles with moderately high conversion of olefins [32].
Encouraged by this research, we synthesized new homogeneous
species, bis(diphenylphosphinomethylated)dopamine ligands, and
anchored them on magnetic nanoparticle surfaces followed by
detail characterization. These particles were exploited for the
conversion of a series of olefins into aldehydes, using Rh(I) as the
metal centre.
General procedure
Synthesis of magnetic nanoparticles (MNPs). Magnetite (Fe3O4)
nanoparticles in the range of 5-7 nm were synthesized (Scheme 1)
according to the procedure reported in the literature [33-35].
Hydrated FeCl2 (2 g, 10 mmol) and FeCl3 (8.08 g, 20 mmol) were
dissolved in 200 mL of DI water under argon at 90°C with vigorous
stirring. Concentrated NH4OH was slowly added until the solution
attained a pH of 9, attended by precipitation. The mixture was
Experimental
Materials and analysis
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allowed to stand for 4 h. The precipitate (black color) was washed temperature, the catalyst was magnetically separated, washed
several times with DI water and dried.
five times with dichloromethane (5 X 4 mL) and preserved for
use in subsequent cycles. The products were passed through
short silica gel column and injected into GC and GC-MS for
identification.
Synthesis of bis(diphenylphosphinomethyl) dopamine (bpd).
Dopamine was functionalized by a double phosphinomethylation
step on the primary amine via the reaction of dopamine
hydrochloride and diphenylphosphinomethanol, as per Scheme 1.
Diphenylphosphine (1.75 mL, 10 mmol) was added to a suspension
of 2.9 g paraformaldehyde (9.5 mmol) in 10 mL of anhydrous
Results and discussion
Synthesis: The magnetic nanoparticles were prepared by
coprecipitation using Fe(II) and Fe(III) precursors in a 1:2 molar
ratio. The medium of the reaction was made alkaline using
concentrated ammonium hydroxide, and the pH was kept
constant at 9 for 4 hours [33]. The black solid material was
collected using a strong magnet after repeated washing with
water to remove unreacted iron precursors. The surface of the
MNPs was decorated with functionalized dopamine bound via
its hydroxyl groups. The dopamine was phosphinomethylated
using a straightforward reaction with a quantitative yield [35,
36]. The first step of this reaction was to prepare the
phosphinoalcohol from the reaction of diphenylphosphine and
paraformaldehyde in dry toluene under heating at 120°C for 4
h, until the turbid solution became clear (Scheme 1). In this
reaction, equimolar amounts of dopamine hydrochloride were
added in situ into the reaction system, which was boiled at
120°C for another 24 h. A sticky solid was precipitated and
toluene under argon. The mixture was stirred for 4 h at 120
obtain a clear solution to which 0.76 g of dopamine hydrochloride
(4 mmol) was added and refluxed for 24 h at 120 C. The resulted
°C to
°
creamy suspension was filtered and subsequently washed first with
toluene and then with chloroform and DI water to give bpd as solid
with 90% yield. 31P NMR (200 MHz, in DMSO-d6): δ -28.71 (s, PPh2)
ppm. 1H NMR (500 MHz, DMSO-d6): δ 2.79 (t, 2H, NCH2CH2), 3.12 (t,
after drying under vacuum,
a cream-colored solid was
obtained with 90% yield. The obtained bpd ligand in
anhydrous methanol was sonicated with the suspended
solution of MNPs in chloroform for 6 h and produced a light
black powder after repeated washing with methanol.
Scheme 1. Preparation of ligand (bpd) and MNP@bpd
2H, NCH2CH2), 4.14 (br d, 4H, CH2P), 6.47 (d, 1H, C6H3), 6.55(s, 1H,
C6H3), 6.72 (d, 1H, C6H3), 7.43 (br s, 12H, CH), 7.56 (br s, 8H, CH),
9.03, 9.11 (2H, OH). FT-IR in KBr (in cm-1): 3124, 2926, 2571, 1628,
1436. Anal. Calcd for C34H33NO2P2●CHCl3: C, 62.84; H, 5.12; N,
2.09. Found: C, 62.68; H, 4.85; N, 2.32.
Fig. 1 TEM images of a) Fe3O4 and b) Fe3O4@bpd in same
Synthesis of MNP@bpd. The magnetite nanoparticles (MNPs) were
functionalized (Scheme 1) by modifying a reported procedure [34]
as follows: 200 mg of MNPs were suspended in 10 mL anhydrous
magnification c) particle size distribution curve
Characterization. The bis(diphenylphosphinomethylated)
ligand was characterized by nuclear magnetic resonance
(NMR) spectroscopy in deuterated dimethyl sulfoxide (DMSO-
CHCl3 to which
a
solution containing 200 mg of
bis(diphenylphosphinomethyl) dopamine in anhydrous methanol
was added under argon. The mixture was sonicated for 6 h. The
MNPs@bpd were collected with the help of a strong magnet after
washing repeatedly with methanol.
Catalytic hydroformylation reaction. MNP@bpd. 30 mg of
MNP@bpd with 1 mmol of the appropriate substrate were
placed in anhydrous tetrahydrofuran (THF) in a 45 mL Teflon-
lined autoclave.
[Rh(NBD)Cl]2 (0.003 mmol, 1.3 mg) was
added to this solution under argon. The sealed autoclave was
purged 3 times with syngas (1:1 CO and H2), pressurized at 200
psi and kept at 90°C for 16 h. After cooling to room
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d6).
Fig. 2 HRTEM images of a) Fe3O4@bpd b) selected area
diffraction (SAED) in set c) interplaner distances are 0.306 and
0.214 nm corresponding to (220) and (400) planes.
In the 1H NMR spectrum, the shift (δ) of the CH2-P proton
occurred at 4.14 ppm, and the presence of the ethylene side
chain was confirmed by the alkyl proton shifts at 2.79 and 3.12
ppm. The 31P NMR spectrum exhibited a shift at -28.71 ppm,
which was consistent with the data in the literature [10, 37-38]
(Supporting information). TEM images reveal spherical-shaped
and uniformly distributed particles (Figs 1a and 1b) with
average diameters between 5-7 nm. High-resolution TEM
(HRTEM) images are shown in figure 2.
Fig. 3 XRD pattern of the a) Fe3O4 and b) Fe3O4@bpd
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The higher order of crystallinity in the synthesized energy levels (keV). The presence of bpd on the surface of the
nanoparticles containing the ligand was evidenced from the MNPs was further characterized by Fourier transform infrared
Selected Area Diffraction Pattern (SADP) (Fig 2b) and the high
resolution fringes (Fig 2c). The crystalline nature of the
Sample name
Fe3O4
Hc (Oe)
3.97
Mr (emu/g)
0.802
Ms (emu/g)
60.17
Fe3O4@bpd
2.98
0.658
55.58
spectroscopy
transmittance
(FT-IR).
spectra
The
of
MNPs, bpd, and MNPs@bpd
are shown in Fig 5. All of the
characteristic peaks of the
dopamine compound were
observed; including the strong
appearance of the Fe-O
vibration shift at 593 cm-1 from
the parent’s MNPsat 587 cm-1.
The presence of 2933 cm-1
(aromatic C-H stretching), as
well as the 1630 cm-1 and 1431
cm-1 bands (Fig.5c) clearly
demonstrated the anchoring of
the phosphinylated dopamine
on the surface of MNPs.
Fig. 4 Elemental mapping of a) iron b) phosphorous of and c)rhodium and d) EDX spectra of
Fe O @bpd after the catalytic reaction and e) solid Fe3O4 f) solid Fe O @bpd in presence of
Thermal gravimetric analysis
(TGA) study was conducted to
investigate the thermal stability
3
4
3
4
magnet
MNP@bpd was further ascertained from their XRD signature
(Fig. 3) The XRD peaks at 2θ=30.20°, 35.70°, 43.10°, 53.40°,
57.10° and 63.20° and the corresponding indices are marked
against the peaks. All observed peaks can be indexed within
cubic spinel structure, in agreement with JCPDS card No. 19-
629. No additional peaks were detected thus confirming the
high purity of the formed MNPs, without the presence of any
other oxide or hydroxide phase(s). The broad diffraction peaks
confirmed the nanocrystalline nature of the material [39-40].
Rietveld refinements of XRD patterns confirm the purity of the
formed spinel cubic structure. The refined parameters are in
table 1 and it can be noticed that the value of crystallite size is
around 7-8 nm, in excellent agreement with the value (5-7 nm)
determined from TEM observations (Supporting information)
and this data is further supported by the particle size
and the strong attachment of the organic ligand on the MNPs
surface (Supporting information). The data showed that the
weight loss at temperatures < 100°C can be associated with
the loss of water molecules [34]. The largest weight loss (~9%)
occurred between 200 and ~450°C and could be attributed to
the elimination of ligands from the surface, in few steps. The
amount of bpd ligand on the surface was measured by
correlation with the phosphorus content.
distribution data (Fig. 1
c). However, the value of microstrain
increases from 0.160% for Fe3O4 to 0.421% for MNP@bpd
,
which is due to the ligand surrounding Fe3O4. The uniform
anchoring of the bpd ligand on the surface of nanoparticles
were demonstrated by the Energy Dispersive x-ray
Spectroscopy (EDX) elemental mapping shown in Fig. 4. It was
revealed that the phosphorous containing ligand and their
subsequent rhodium complexes obtained after the catalytic
reaction were distributed homogeneously on the surface of
the MNPs. However, figure 4d exhibited the EDX spectrum
from the same area and marked the Rh at its designated
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Fig. 5 FT-IR spectrum of a) bpd b) Fe3O4 c) Fe3O4@bpd with hydroformylation catalytic cycles. Significant changes were
KBr pallet
observed when dimeric Rh(NBD) in freshly distilled THF was used;
the latter is considered as a good solvent for hydroformylation over
hydrogenation because it has been reported to have led to
The ICP data yielded approximately 0.39 mmol phosphine/g of
the functionalized nanoagents. This amount of phosphine
loading on the surface of magnetite was very high compared
to the literature data [31, 32]. This can be attributed to the
smaller size and less sterically hindered ligand and thereby
occupying less area on the surface; thus, a larger number of
ligands were able to bind through the phenolic oxygen to the
Fe3O4. The possibility of leaching out of P and Rh was
examined via ICP-MS measurements, the amount of bpd ligand
remained unchanged and no Rh in the solution was traceable
in early stages. This was corroborated by their ability to
convert styrene completely into the corresponding formylated
product in the 1st cycle. However, there was a significant
(~35%) loss of from the MNP@bpd at the end of 7th cycle, due
likely to successive leaching.
formulation of desired products at 90°C [32].
Magnetization-field (M-H) curves recorded at room temperature
are illustrated in Fig 6. It can be clearly observed
a
superparamagnetic behavior for both samples. However, the
presence of very small paramagnetic component (saturation cannot
be reached) which was deduced using MicroMag software was
observed. The magnetic parameters determined from M-H after
removal of paramagnetic phase are reported in Table 1. It can
noticed that the value of corecivity (Hc) is very small within the
range 3.97-2.98 Oe, while the remanence (Mr) decreases slightly
from 0.802 emu/g for Fe3O4 to 0.658 emu/g for MNP@bpd.
Similarly to the remanence, the saturation magnetization (Ms)
reduces slightly by 5 emu/g for Fe3O4 and MNP@bpd. The above
changes are attributed to the attached bpd ligand on the surface of
MNPs.
Fig. 6 Magnetic hysteresis loops of the Fe3O4 and Fe3O4@bpd at
room temperature with 1 tesla magnet
The catalyst amount was optimized for the 1 mmol of substrate. In
lower amount of catalyst ( ca 15 mg) the 10-20 % hydrogenated
product was resulted from the hydroformylation product. As the
catalyst amount was increased to 30 mg, exclusively
hydroformylated product was observed; these conditions (30 mg of
catalyst loading and 200 psi applied pressure) are lower and hence,
more benign than those reported in the literature for a similar
system [31]. A series of substituted styrene were studied for the
activity of the catalyst toward electron-withdrawing and electron-
donating groups in different positions of the aromatic ring.
However, no significant differences were observed and [26] and the
Table 1. Magnetic properties obtained from magnetisation-field (M-
H) curves
Catalysis: The catalytic hydroformylation reaction was carried out
on a series of olefins (table 2) in the presence of the syngas at
different temperatures in a sealed autoclave pressured to 200 psi.
From Table 2, it is clear that the catalyst was very active and
selective toward linear aldehydes in the low temperature regime. A
reversal of the selectivity was observed at high temperatures for
styrene, reaching ~1.5. For example, when the catalytic reaction
was run at room temperature (RT) and 50 °C for 24 hours using
RhCl3 as the metal precursor with styrene as the substrate in dry
toluene, 35% and 100% conversion were observed with selectivities
of 0.20 and 0.47 for linear and branched aldehyde, respectively.
Table 2. Hydroformylationa of olefins using MNP@bpd with the
pressure of 200 psi using [Rh(NBD)Cl]2 as metal precursor
result was in conformity with entries 5 and 7 in Table 2. In addition,
the reactivity of 3-nitro styrene, entry 8, was found be
comparatively higher in selectivity among the series at the same
temperature.
O
O
MNP@bpd@Rh
CO:H2 (1:1)
Solvent
H
+
When the reaction was carried out at 120°C, the linear aldehyde (a
Linear (L)
Branched (B)
desired product was the major product. In this reaction, a moderate
amount (about 20%) of hydrogenated product was also observed,
Ent
Substrate
Time Solv.
(h)
Temp Convb
L
B
Ratioc
(L:B)
which could be attributed to the lower solubility of RhCl3 in toluene.
ry
(oC)
(%)
This effect can mitigate the entrance of olefins into the
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1d
2d
3d
4
Styrene
Styrene
Styrene
Styrene
24
24
20
22
19
Tol
Tol
RT
50
35
6
29
68
40
52
42
0.2
persistently active. The material was thermally stable even at high
temperatures. We believe that this new material is therefore
applicable for industrial catalytic hydroformylation process, and
that it may find many more applications in catalysis, a few of which
are currently under study in our lab.
100
100
100
100
32
60
48
50
0.47
1.50
0.92
1.19
THF
THF
THF
120
90
5
4-
90
Methylstyrene
4-Vinylanisole
Acknowledgments
6
7
18
18
THF
THF
90
90
100
100
46
56
54
44
0.85
1.27
4-
MNS gratefully acknowledge the National Plan for Science,
Technology and Innovation (MAARIFAH)-King Abdulaziz City for
Science and Technology though the Science and Technology Unit at
King Fahd University of Petroleum and Minerals (KFUPM), the
Kingdom of Saudi Arabia, award number 12-NAN2389-04. The
authors also gratefully acknowledge the Center of Research
Excellence in Nanotechnology (CENT) for providing all facilities for
analysis.
Chlorosyrene
3-Nitrostyrene
8
9
16
24
THF
THF
90
90
100
8
57
--
43
--
1.32
--
2-
Bromostyrene
1-Octene
10
24
24
THF
THF
90
90
100
27
49
14
15
13
3.26
1.07
11e
Styrene
a1 mmol of styrene in 10 mL anhydrous solvent under 200 psi pressure in
presence of syn gas (CO:H2 1:1) using 30 mg of catalyst
bdetermined by GC
cdetermined by GC-MS
d with RhCl3
ein presence of MNP@bpd but without Rh metal
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same condition. This was may be due to the bigger size of the
bromide adjacent to the alkene reaction site hinder olefin to
coordinate with the metal to form saturated 18e- species in the
reaction cycle. The nanocatalysts were recycled after washing
several times to remove all of the materials present after the first
round of catalysis, by keeping a magnet at the bottom. The
nanocatalyst was very active, even after the seven round at the
same temperature, pressure and duration and it was demonstrated
that with the use of 30 mg of catalyst, MNP@bpd, and the
corresponding amount of [Rh(NBD)Cl]2, the selectivity ratio was
0.92, and this trend existed until the second round of the reaction.
However, after the 3rd rounds, the selectivity was reversed for
unknown reasons. The catalyst activity was investigated towards
linear olefin as well; for example, the conversion of 1-Octene, was
complete (Table 2, entry #10), the linear to branched ratio, reaching
a value of about 3.26. Moreover, ca. 36% of the product contained
isoalkene and its hydrogenated analogue (n-alkane), comparable
with the data reported by Sharma and Jasra [41]. For comparison,
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Conclusion
In conclusion, we demonstrated the synthesis of
a new
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syngas pressure. The recyclability was tested with the catalyst on
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