Magnetic nanoparticle supported ionic liquid phase catalyst for oxidation of alcohols

Article abstract of DOI:10.1071/CH19627

Anew magnetic nanoparticle supported ionic liquid phase (SILP) catalyst containing perruthenate anions was prepared by a multistep procedure. The various analytical techniques such as FT-IR spectroscopy, X-ray photoelectron spectroscopy, transmission elec

Full text of DOI:10.1071/CH19627

CSIRO PUBLISHING
Aust. J. Chem.
Full Paper
https://doi.org/10.1071/CH19627
Magnetic Nanoparticle Supported Ionic Liquid
Phase Catalyst for Oxidation of Alcohols
A
A
A
Altafhusen Naikwade, Megha Jagadale, Dolly Kale, and
,
A B
Gajanan Rashinkar
A
Department of Chemistry, Shivaji University, Kolhapur, 416004, Maharashtra, India.
Corresponding author. Email: gsr_chem@unishivaji.ac.in
B
A new magnetic nanoparticle supported ionic liquid phase (SILP) catalyst containing perruthenate anions was prepared by
a multistep procedure. The various analytical techniques such as FT-IR spectroscopy, X-ray photoelectron spectroscopy,
transmission electron microscopy, thermogravimetric analysis, energy dispersive X-ray analysis, and vibrating sample
magnetometer analysis ascertained the successful formation of catalyst. The performance of a magnetically retrievable
SILP catalyst was evaluated in the selective oxidation of alcohols. The split test and leaching studies of the SILP catalyst
confirmed its heterogeneous nature. In addition, the reusability potential of SILP catalyst was also investigated which
revealed its robust activity up to six consecutive cycles.
Manuscript received: 4 December 2019.
Manuscript accepted: 26 February 2020.
Published online: 25 June 2020.
Introduction
[21]
and food analysis.
The applicability of Fe O MNP-based
3 4
The redesigning of chemical processes to avoid generation of
toxic waste and utilisation of hazardous substances has attracted
a great deal of attention, as green chemistry is becoming a pivotal
SILP nanocatalysts have witnessed an enormous growth to
organic transformations due to continuous increasing emphasis
[
22–30]
on developing greener pathways.
However, despite
[1,2]
issue.
In this context, supported ionic liquid phase (SILP)
the substantial progress, there is still room for development
especially towards designing green procedures using
magnetically retrievable supported ionic liquid-like phase
catalysts.
catalysis has originated as a subject of interest among the
scientific community. The concept of SILP catalysis involves
immobilization of ionic liquid (IL)-mimicking units onto a high
[
3–6]
surface area support material.
The various drawbacks
The selective oxidation of primary alcohols to aldehydes has
been a reaction of immense importance in synthetic chemistry.
Aldehydes are considered as privileged motifs due to their
extensive applications such as intermediates in the manufactur-
ing of agrochemicals, dyes, pharmaceuticals, and fine chemicals
associated with ILs could be circumvented by employing these
advanced materials in catalysis as powerful green tools. The
interest in SILP catalysts emanate from their fascinating
properties such as ease of product separation, selectivity, high
catalytic activity, efficient reusability, and ecologically benign
nature. Moreover, SILP catalysis may facilitate the application
of fixed bed reactors for chemical transformations in continuous
[
31,32]
particularly for the perfume industry.
plethora of synthetic strategies for the oxidation of alcohols
Consequently, a
have been unceasingly reported employing catalytic systems
[33–38]
[
7]
mode. SILP catalysis has achieved tremendous advances over
the past few years providing facile access to a large number of
privileged scaffolds under environmentally benign conditions.
Magnetic nanoparticles (MNPs) have been widely exploited in
various domains. The application of MNPs in the catalysis arena
has been a subject of intense research. MNPs have recently
emerged as a viable alternative to conventional catalytic supports
for the design of heterogeneous catalytic systems. The magneti-
cally retrievable nano-catalytic systems have been explored for
their potential in addressing various environmental and economic
with perruthenate anions.
to using different oxidants,
and SILP catalysts.
Efforts have also been devoted
39–43]
[
[44–52]
transition metals,
However, despite the impressive
[53–55]
progress, various challenges still exist that are associated with
difficulty in the separation and disposal of expensive or toxic
stoichiometric reagents. Moreover, the utilisation of excess
catalysts leads to generation of significant amounts of unwanted
by-products affording poor atom economy and high E-factors.
The cautious handling of sensitive reagents and removal
[56,57]
of unwanted by-products has become a tedious task.
[8]
issues. Surface functionalized MNPs are an elegant pathway
to bridge the gap between heterogeneous and homogeneous
Consequently, there is an urgent need to design robust
heterogeneous catalytic systems especially for oxidation of
primary alcohols.
[
catalysis. Amongst several MNPs, Fe O MNPs have attrac-
9]
3
4
tive properties like low toxicity, unique magnetic properties,
high surface area, good dispersivity, and magnetic retrievabil-
In continuance of our prior work regarding green chemis-
[58–60]
try,
of a Fe O MNP SILP catalyst containing perruthenate anions
we disclose herein a new approach for the preparation
[
ity. These properties are of use for a myriad of applications in
10]
3
4
[
11–16]
[17]
magnetically retrievable catalysis,
[
medical and bioengineering,
bioseparation,
environmental treatment,
bio-
[20]
and evaluated its potential as a heterogeneous catalyst for the
oxidation of primary alcohols.
18,19]
Journal compilation � CSIRO 2020
www.publish.csiro.au/journals/ajc

B
A. Naikwade et al.
795 589
1
057 959
a)
TEOS
b)
MNP
c)
MNP
d)
NMag 1
Sil@NMag 2
2942
1591
466
1059
OEt
Si
1549
e)
1437
EtO
Cl
OEt
1439
2937 f) 1636
887 865
3
-Chloropropyl triethoxysilane 3
O
1
438
MNP
Si
OEt
Cl
2939
2500
1637
2000
8
86 865
O
4000
3500
3000
1500
1000 500
3.Cl.Pr.Sil@NMag 4
Wavenumber [cm–1
]
Ph
P
Fig. 1. FT-IR spectra of (a) NMag 1, (b) Sil@NMag 2, (c) 3.Cl.Pr.Sil@NMag
4, (d) [Dppf@Sil@NMag]Cl 6, (e) [Dppf@Sil@NMag](RuO4)2 8 before
Ph
P
Fe
Ph
4 2
reaction, and (f) [Dppf@Sil@NMag](RuO ) 8 after six consecutive runs.
Ph
Bis(diphenylphosphino)ferrocene 5
2
6°C
1
00
90
80
OEt
Ph
Cl
5.757 % (0.3643 mg)
O
O
Si
P
115°C
3.949 % (0.2499 mg)
250°C
MNP
Ph
Ph
Fe
Cl
O
16.03 % (1.014 mg)
Si
P
O
Ph
425°C
OEt
7
0
[
Dppf@Sil@NMag]Cl 6
17.21 % (1.089 mg)
Residue: 55.83 %
KRuO 7
4
60
(
3.532 mg)
78°C
800 1000
H O, rt
2
5
10°C
9
OEt
50
Ph
O
Si
O
RuO
4
0
200
400
600
P
Temperature [°C]
Ph
Ph
MNP
Fe
O
4 2
Fig. 2. TGA curve of [Dppf@Sil@NMag](RuO ) 8.
Si
P
O
RuO
4
Ph
by FT-IR spectroscopy. In the FT-IR spectrum of NMag 1, a
ꢀ
OEt
1
characteristic band appeared at 589 cm and was assigned to
Fe–O stretching vibrations of the Fe O MNPs. The coating of a
silica shell on 1 was evidenced by FT-IR peaks at 959 (Si–O)
[
Dppf@Sil@NMag](RuO4)2
8
3
4
4 2
Scheme 1. Preparation of [Dppf@Sil@NMag](RuO ) 8.
ꢀ
1
symmetric, 1057 (Si–O–Si) siloxane asymmetric, and 795 cm
[
61]
(Si–O–Si) siloxane symmetric stretching modes (Fig. 1a).
The FT-IR spectrum of 3.Cl.Pr.Sil@NMag 4 showed a distinct
Results and Discussion
The preparative route for the MNP SILP catalyst containing
perruthenate anions is shown in Scheme 1. First, a chemical co-
precipitation approach was used to prepare Fe O MNPs
peak for the stretching vibration of C–H of the propyl group
[62]
ꢀ
1
at 2942 cm
(Fig. 1b).
The covalent grafting of bis-
3
4
(diphenylphosphino)ferrocene 5 onto 4 was evident from the
FT-IR spectrum of [Dppf@Sil@NMag]Cl 6, which displayed
(
NMag, 1). The surface of 1 was then coated by a sol–gel
approach with a silica shell to furnish Sil@NMag 2. The orga-
nofunctionalization of was achieved with 3-
chloropropyltriethoxysilane 3 to yield Fe O MNPs with a
ꢀ
1
bands in the region 1600–1450 cm for the C=C stretching of
ꢀ
the aromatic ring, and 1437 and 466 cm for P–CH and Fe–Cp
2
1
2
[
63]
3
4
stretching, respectively (Fig. 1c). In the FT-IR spectrum of 8
(Fig. 1d), the characteristic peaks observed at 887 and 865 cm
ꢀ1
chlorofunctionalized surface abbreviated as 3.Cl.Pr.Sil@NMag
. The unique ability of surface active silanol moieties of 2
4
are attributed to symmetric and asymmetric stretching vibra-
tions of Ru=O. The presence of these peaks strongly suggest
facilitates the generation of strong siloxane bonds (Si–O–Si)
with the silyl ether group of 3. The IL-mimic unit was then
grafted on 4 by reacting with bis(diphenylphosphino)ferrocene
[
64]
the successful immobilization of perruthenate anions on 8.
The quantification of the perruthenate anion content
5
6
7
to furnish the precursor abbreviated as [Dppf@Sil@NMag]Cl
. Lastly, 6 underwent an anion metathesis reaction with KRuO4
to afford the desired Fe O MNP SILP catalyst containing
in [Dppf@Sil@NMag](RuO ) 8 was carried out by energy-
4
2
dispersive X-ray (EDX) spectroscopy. The EDX elemental
mapping revealed the presence of 0.11 mmol of perruthenate
anion per gram of 8.
3
4
perruthenate anions, namely [Dppf@Sil@NMag](RuO ) 8.
4
2
The surface modifications of the Fe O nanocore during the
3
The thermogravimetric analysis (TGA) of [Dppf@Sil@NMag]-
(RuO ) 8 is depicted in Fig. 2. The thermal profile of 8 displayed
4
preparation of [Dppf@Sil@NMag](RuO ) 8 were monitored
2
4
4 2

SILP Catalyst for Oxidation of Alcohols
C
(a)
(b)
(c)
(d)
(e)
Fig. 3. TEM images of [Dppf@Sil@NMag](RuO
4
)
2
8 with SAED pattern (a–c) before reaction and [Dppf@Sil@NMag](RuO
4
)
2
8 after sixth
run (d–e).
The transmission electron microscopy (TEM) images of
Dppf@Sil@NMag](RuO ) 8 before and after catalysis (after
[
sixth run) are shown in Fig. 3a–d. TEM images showed the
4
2
[
30]
a)
b)
c)
d)
e)
quasispherical particles with a core–shell structure.
Fe O
3 4
MNPs have an average diameter of 2–11 nm. The selected area
electron diffraction (SAED) pattern demonstrates the white dots
and bright diffraction rings which designates the crystallinity of
the Fe O nanocore (Fig. 3c). Gratifyingly, qualitative alteration
in morphologies of fresh and reused catalysts was not observed
even after six consecutive runs.
The X-ray diffraction (XRD) patterns of Sil@NMag 2,
3
4
3.Cl.Pr.Sil@NMag
4,
[Dppf@Sil@NMag]Cl
6,
and
Dppf@Sil@NMag](RuO ) 8 before and after catalysis (after
[
sixth run) are depicted in Fig. 4a–e. The diffraction peaks were
4
2
20
30
40
50
60
70
80
well coordinated to the cubic inverse spinel structure of Fe O4
3
2
q [deg.]
and are consistent with JCPDS card no. 86-1339. All five
materials display characteristic diffraction peaks at 2y values
of 30.178, 35.498, 43.128, 57.128, 62.648, 66.838, and 75.098
being assigned to the (2 2 0), (3 1 1), (4 0 0), (5 1 1), (4 4 0),
Fig. 4. XRD pattern of (a) Sil@NMag 2, (b) 3.Cl.Pr.Sil@NMag 4,
c) [Dppf@Sil@NMag]Cl 6, (d) [Dppf@Sil@NMag](RuO 8 before
reaction, and (e) [Dppf@Sil@NMag](RuO 8 after six consecutive runs.
(
4 2
)
4 2
)
(4 4 2), and (6 2 2) crystal indices of a Fe O cubic lattice
respectively. The nearly identical reflections were displayed by
3 4
an initial weight loss of 5.75 % due to evaporation of physi-
sorbed water at 1158C. Furthermore, a minor mass loss of 3.94 %
centred around 2508C followed by two major mass losses of
all the materials, which revealed the behaviour of the Fe
nanocore in a very stable mode.
O
3 4
1
6.03 and 17.21 % at 425 and 5108C are observed by related
X-Ray photoelectron spectroscopy (XPS) was employed to
elucidate structural features of [Dppf@Sil@NMag](RuO 8.
The presence of Ru, O, C, Fe, Si, and P elements in 8 was
confirmed by a survey spectrum obtained from XPS results
(Fig. 5a). In the Fe 2p region the shift of the photoelectron peak
thermal collapse of organic layers on the surface of core–shell
MNPs and the perruthenate anion. Lastly, the generation
of thermostable metallic oxides and silica contributes large
residual weight.
)
4 2

D
A. Naikwade et al.
(a)
(b)
C 1s + Ru 3d
Ru 3d + C 1s
O 1s
Fe 2p
P 2p
Si 2p
800
600
400
200
0
280
285
290
Binding energy [eV]
Binding energy [eV]
(c)
(d)
Si 2p
P 2p
96
98
100
102
104
106
130
132
134
136
Binding energy [eV]
Binding energy [eV]
(e)
O 1s
(f)
Fe 2p
526
528
530
532
534
710
720
730
Binding energy [eV]
Binding energy [eV]
4 2
Fig. 5. XPS spectra of [Dppf@Sil@NMag](RuO ) (8): (a) survey spectrum, (b) Ru 3d and C 1s, (c) Si 2p, (d) P 2p, (e) O 1s, and (f) Fe 2p.
to higher binding energy is observed due to anchoring of
ferrocene onto the material in comparison with free ferrocene.
This fact was demonstrated by Dong and co-workers. In this
work, the successful grafting of the ferrocene unit was con-
firmed by photoelectron peaks in the Fe 2p region positioned
core level spectrum the signal at 101.2 eV also confirms the
66]
[
same fact (Fig. 5c).
Moreover, the contribution of the
perruthenate anion is designated by Ru 3d peaks at 280.0
(3d5/2) and 283.9 eV (3d3/2). The photoelectron peaks positioned
at 290.5 and 284.5 eV are indicative of carbons of benzene rings
[
65]
[67,68]
at 710.9 and 724.4 eV (Fig. 5f).
The C 1s and Ru 3d core
and ferrocenyl carbons respectively.
þ
The presence of
phosphonium cations (P ) bonded with sp hybridized carbons
3
level spectrum splits into six photoelectron peaks centred
at 280.0, 282.6, 283.9, 284.5, 285.9, and 290.5 eV (Fig. 5b).
The photoelectron peak located at 282.6 eV corresponds to
bonding between silicon and carbon. In addition, in the Si 2p
[
69]
is corroborated by the photoelectron peak at 285.9 eV.
The peak at 133.1 eV observed in the P 2p region also specify
[
70]
the phosphonium ion (Fig. 5d).
The peaks at 530.5 and

SILP Catalyst for Oxidation of Alcohols
E
30
20
10
0
Table 2. Screening of solvents for the [Dppf@Sil@NMag](RuO
promoted selective oxidation of benzyl alcohol
4
)
2
8
(
a)
b)
CH OH
CHO
2
(
[Dppf@Sil@NMag](RuO )2
8
4
Solvent, reflux
9a
10a
A
B
Yield [%]
Entry
Solvent
Toluene
Time [h]
–10
–20
–30
1
2
3
4
5
6
7
8
9
17
19
16
24
2.5
28
24
21
20
69
68
Acetonitrile
1,4-Dioxane
Dichloromethane
THF
at temperature T = 25°C
70
44
97
–15000 –10000 –5000
0
5000
10000 15000
DMF
Trace
Trace
41
DMSO
Applied magnetic field [T]
Ethanol
Methanol
43
Fig. 6. Magnetization curves obtained by vibrating sample magnetometer
analysis at room temperature: (a) bare MNPs and (b) [Dppf@Sil@NMag]-
A
Reaction conditions: 9a (1mmol), solvent (5mL), and [Dppf@Sil@NMag]-
8 (50 mg).
4 2
(RuO ) 8.
(
RuO
)
4 2
B
Isolated yield after column chromatography.
Table 1. Optimization of catalyst loading in the [Dppf@Sil@NMag]-
RuO 8 promoted selective oxidation of benzyl alcohol
(
4 2
)
Afterwards, our efforts were directed to evaluate the catalytic
CH2OH
CHO
[
Dppf@Sil@NMag](RuO4)2
THF
8
potential of [Dppf@Sil@NMag](RuO4)2 8 in the selective
oxidation of primary alcohols. The optimization of reaction
conditions was performed employing benzyl alcohol (9a) as a
model substrate. The optimization of catalyst loading was our
initial task. Different quantities of 8 were employed to perform a
model reaction in THF at ambient temperature (Table 1, entries
9
a
10a
A
B
Yield [%]
Entry
Catalyst loading
Temperature
Time [h]
[
mg (mol-%)]
[8C]
1
–5). The influence of temperature was found to be the crucial
1
2
3
4
5
6
7
8
9
15 (0.17)
25 (0.29)
50 (0.59)
75 (0.89)
100 (1.18)
50 (0.59)
50 (0.59)
15 (0.17)
25 (0.29)
50 (0.59)
75 (0.89)
100 (1.18)
No catalyst
Rt
Rt
22
20
19
18
18
9
10
25
parameter. The reactions could not proceed to a synthetically
useful degree at ambient temperature even after prolonged
reaction time. An enhancement in the yield of product was
observed with an increase in the reaction temperature (Table 1,
entries 6–12). The increase in quantity of 8 from 15 to 50 mg was
proven to be favourable, affording the corresponding product
Rt
37
Rt
38
Rt
38
40
45
50
6
67
1
0a up to 97 % yield (Table 1, entries 8–10). However, a rise in
Reflux
Reflux
Reflux
Reflux
Reflux
Rt
10
9
37
catalyst quantity (Table 1, entries 11–12) had no impact on yield
of product. Therefore, 50 mg of catalyst under reflux reaction
conditions was sufficient to drive the model reaction efficiently
to furnish the anticipated product in excellent yield within 2.5 h
(Table 1, entry 10). The reaction did not proceed even after an
extended period in the absence of 8 (Table 1, entry 13) suggest-
ing the crucial role of 8.
Next, the model reaction was carried out for the screening
array of solvents (Table 2). The solvents such as toluene,
acetonitrile, and 1, 4-dioxane (Table 2, entries 1–3) furnished
good yields. On the contrary, dichloromethane, methanol, and
ethanol afforded lower yields of anticipated products (Table 2,
entries 4, 8–9). The reaction progressed slowly in DMF and
DMSO resulting in the formation of trace amounts of 10a
(Table 2, entries 6–7). THF was found to be the suitable choice
for this protocol (Table 2, entry 5).
58
1
1
1
1
0
1
2
3
2.5
97
2.5
2.5
98
98
24
None
A
Reaction conditions: 9a (1mmol), THF (5mL), and [Dppf@Sil@NMag]-
RuO 8.
Isolated yield after column chromatography.
(
B
4 2
)
5
28.4 eV in the O 1s region are attributed to oxygen bonded with
[
71]
Si and lattice oxygen (Fig. 5e). Conclusively, the successful
formation of 8 was confirmed by these structural features.
Vibrating sample magnetometry (VSM) was used to explore
the magnetic behaviour of bare Fe O MNPs 1 and [Dppf@Sil@-
3
4
NMag](RuO ) 8 at room temperature. The magnetic hysteresis
2
With the optimized reaction conditions, the substrate scope
of the protocol was probed by performing oxidation of diversely
substituted alcohols 9a–o (Table 3). The electronic substitution
in aromatic alcohols displayed a strong influence on the yield
of reaction. Aromatic alcohols with electron-donating groups
9b–d, 9j, and 9o afforded good yields (Table 3, entries 2–4,
10, and 15) as compared with that of aromatic alcohols bearing
electron-withdrawing groups 9g,h and 9k (Table 3, entries 7, 8,
and 11). Gratifyingly, it is worth mentioning that heteroaromatic
4
curves in Fig. 6 illustrate lowering in the saturation magnetiza-
ꢀ
1
tion (M ) values from bare Fe O MNPs (22 emu g ) to
s
3 4
ꢀ
1
the final catalyst (11 emu g ). This decrease upon surface
modification of the bare Fe O MNPs 1 could be attributed
3
4
to a shielding effect of the non-magnetic silica and organic
[
72]
moieties.
In spite of this reduction in M values, 8 can be
s
effortlessly isolated from the reaction medium with a permanent
magnet.

F
A. Naikwade et al.
Table 3. (Continued)
4 2
Table 3. [Dppf@Sil@NMag](RuO ) 8 promoted selective oxidation
of alcohols
A
B
Entry
Alcohol
Product
Time
Yield
[%]
CH OH
CHO
2
[
h]
[
Dppf@Sil@NMag](RuO4)2
THF, reflux
8
1
4
5
9n
OH
10n
H
4
92
S
S
R
R
O
9a–o
10a–o
1
CH OH
CHO
4
87
2
A
B
Entry
Alcohol
Product
Time
h]
Yield
[%]
9
o
10o
OCH3
[
OCH3
OCH3
1
CH OH
CHO
2.5
97
OCH3
2
9
9
a
10a
10b
A
Reaction conditions: 9 (1 mmol), THF (5 mL), and [Dppf@Sil@NMag]-
RuO 8 (50 mg).
Isolated yield after column chromatography.
(
B
4 2
)
2
CH OH
CHO
3
89
2
b
alcohols such as (pyridine-2-yl)methanol, (furan-2-yl)-
methanol, and (thiophen-2-yl)methanol (9l–n) showed the high-
est reactivity furnishing excellent yields of anticipated products
(Table 3, entries 12–14). Despite steric congestion, sterically
hindered alcohols such as o-methoxy, o-methyl, and o-nitro
benzyl alcohols (9c,f,i) (Table 3, entries 3, 6 and 9) also afforded
a good yield of corresponding products.
OCH3
OCH3
CHO
3
4
CH OH
9c
10c
4
3
92
96
2
OCH3
OCH3
CH OH
CHO
2
The formation of anticipated products was ascertained by
1
9d
10d
13
spectroscopic techniques such as H NMR, C NMR, and
FT-IR spectroscopy and mass spectrometry (MS).
CH3
CH3
A plausible mechanism for the [Dppf@Sil@NMag](RuO4)2
5
CH OH
CHO
3
85
2
8
mediated oxidation of aromatic alcohols is depicted in
9
e
10e
Scheme 2. Initially, the alcohol attacks the perruthenate anion
to afford a metal alcoholate complex following a free radical-
[
73–75]
OEt
OEt
CHO
like transition state.
Subsequently, b-hydride elimination
6
7
CH OH 9f
10f
4
5
89
88
2
of the metal alcoholate complex with release of hydrogen leads
to formation of corresponding aldehydes. The cation in 8 has
profound influence on the performance of the catalyst. The
presence of a bulky, cylindrical ferrocenyl moiety causes
significant enhancement in the accessibility of reactants to the
active site which has a strong influence on the catalytic perfor-
CH3
CH3
CH OH
CHO
2
9g
10g
[
76–81]
mance of 8.
removal of the catalyst with a permanent magnet.
In addition, F O nanocores assist the facile
3 4
NO2
NO2
8
9
CH OH
CHO
4
89
A split test was performed to confirm the heterogeneity of
Dppf@Sil@NMag](RuO ) 8 using the model reaction. The
2
[
4 2
9
h
10h
catalyst was isolated magnetically after the completion of 50%
of reaction (determine by gas chromatography, GC). Further-
more, the reaction was allowed to continue for 8 h. Consequently,
the reaction failed to proceed which was revealed from GC-MS
analysis. In addition, no leaching of the metallic moiety in the
reaction mixture was suggested by inductively coupled plasma–
optical emissionspectroscopy(ICP-OES) analysis. Conclusively,
the course of reaction was operated in heterogeneous mode.
By virtue of industrial and green chemistry standpoints, the
recycling of the catalyst is very significant in commercial
operations. The model reaction was performed with optimized
parameters in order to test the reusability of [Dppf@Sil@NMag]-
NO2
NO2
NO2
O
CH OH 9i
CHO
10i
5
5
4
86
84
92
2
NO2
1
0
1
9j
10j
OH
H
1
CH OH
CHO
10k
2
9
k
(RuO ) 8. Subsequently, 8was isolated magnetically, washed with
4 2
Cl
Cl
THF, and dried under vacuum after each consecutive run. As
illustrated in Fig. 7, the product yield was well maintained
between 97–90 % from the 1st to 6th run during recycling
studies. FT-IR spectroscopy, TEM, and XRD analyses of
recycled [Dppf@Sil@NMag](RuO ) 8 after six consecutive
runs was undertaken to confirm its stability. Gratifyingly,
similar peak patterns in the FT-IR spectra of both fresh and
reused 8 (Fig. 1e, f), suggested retention of functional groups
1
2
3
9l
10l
4
5
89
86
OH
H
N
N
O
9m
10m
1
4
2
OH
H
O
O
O
(
continued)

SILP Catalyst for Oxidation of Alcohols
G
RuO4
Ph
P
P
Ph
Fe
Ph
O
2
R
H
RuO
4
Ph
[
Dppf@Sil@NMag](RuO ) 8
4 2
–
2H2
HO
O
O
O
O
O
H
H
O
Ru
O
Ru
R
H
O
O
R
H
H
Alcohol
Alcohol
Ph
Ph
P
P
Ph
Fe
Ph
Fe
Ph
Ph
P
P
Ph
Ph HO
H
O
O
O
H
H
H
O
O
H
Ru
O
Ru
R
O
O
O
R
Alcohol
Metal alcoholate complex
OEt
RuO
4
RuO4
Fe
Ph
Ph
Ph
O
O
Si
P
P
P
P
Fe
=
Ph
MNP
O
Ph
Ph
Si
O
RuO4
RuO4
OEt
Ph
Ph
[
Dppf@Sil@NMag](RuO ) 8
4 2
4 2
Scheme 2. Plausible mechanism for the [Dppf@Sil@NMag](RuO ) 8 promoted oxidation of alcohols.
9
7 %
96 %
Consequently, the stability of 8 was confirmed as no chemical or
physical deformations were observed after reusability studies.
9
4 %
93 %
1
00
92 %
9
0 %
9
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
Conclusion
In conclusion, we have prepared a new magnetic nanoparticle
supported ionic liquid phase catalyst containing perruthenate
anions. The catalyst displayed excellent catalytic activity in
the selective oxidation of primary alcohols to aldehydes. The
catalyst can be expediently isolated and recovered from the
reaction mixture with aid of an external magnet and can be
reused six times without considerable loss in catalytic activity.
The excellent yields, hassle free magnetic retrievability, and
recyclability are some prominent features of this protocol.
1
2
3
4
5
6
No. of cycles
Fig. 7. Reusability of [Dppf@Sil@NMag](RuO
4
)
2
8 in the selective
Experimental
oxidation of benzyl alcohol.
General Remarks
Dried glassware was used to perform all reactions in an air
atmosphere. KBr discs of samples (,5 % w/w) were used to
record FT-IR spectra on a Perkin–Elmer FTIR spectrophotom-
eter. A Bruker-AX8 X-ray diffractometer was employed for
XRD analysis. The elemental compositions of samples were
investigated by an energy-dispersive X-ray spectrometer, which
after recycling. TEM images of fresh and reused 8 (Fig. 3a–e)
indicated no alteration in morphology even after six consecutive
runs. In the X-ray diffractograms of fresh and reused 8 (Fig. 4d–
e), diffraction peaks coincide with the cubic inverse spinel
structure of the Fe O nanocore (JCPDS card no. 86-1339).
3
4

H
A. Naikwade et al.
was attached to a field emission scanning electron microscope
(OXFORD, Instruments). The INCA energy software was
isolated via magnetic separation, washed three times with
CH Cl (50 mL), DMF (50 mL), and methanol (50 mL), and
dried under vacuum to yield [Dppf@Sil@NMag]Cl 6. FT-IR
2
2
1
13
employed for ZAF correction of EDX data. H and C NMR
spectra were recorded on a Bruker AC spectrometer (75 MHz for
ꢀ1
nmax (KBr, thin film)/cm 3314, 1691, 1549, 1437, 1341, 1059,
961, 692, 466. Anal. Calc. for 0.2 mmol of Dppf units g of 6:
Found: C 33.59, O 51.53, Cl 0.57, Fe 4.56, P 0.60, Si 9.15 %.
1
3
1
C NMR and 300 MHz for H NMR) using CDCl as solvent
ꢀ1
3
and tetramethylsilane (TMS) as an internal standard. The values
of chemical shifts d and coupling constants are expressed in
parts per million (ppm) and hertz (Hz) respectively. A Shimadzu
QP2010 GCMS was employed to record mass spectra. A
transmission electron microscope (JEOL JEM 2100 (200 kV))
was used to investigate the morphology of the materials. A
MEL-TEMP capillary melting point apparatus was used to
determine melting points and are uncorrected. XPS spectra were
recorded on a PHI 5000 Versa Prob II, FEI Inc. X-ray photo-
electron spectrometer. Magnetic behaviour of material was
scrutinized using a USA, Model 7407 Lake Shore Magnetom-
eter. All other chemicals were used without further purification,
which were received from local suppliers.
Preparation of [Dppf@Sil@NMag](RuO ) 8
4 2
Potassium perruthenate 7 (0.4 mmol, 0.211 g) was added to a
suspension of 6 (1 g) in distilled water (20 mL). The mixture was
stirred for 24 h. Afterwards, the isolation of insoluble product
was achieved using an external bar magnet. Washing with
distilled water furnished [Dppf@Sil@NMag](RuO ) 8. FT-IR
4
2
ꢀ1
nmax (KBr, thin film)/cm 3393, 2937, 1636, 1439, 1063, 887,
865, 569, 470. Anal. Calc. for 0.11 mmol Ru g of 8: Found:
C 36.10, O 43.74, Fe 9.24, P 0.53, Ru 1.2, Si 9.19 %.
ꢀ
1
General Procedure for Oxidation of Alcohol
A primary alcohol (1 mmol) was added to a suspension of 50 mg
of [Dppf@Sil@NMag](RuO ) 8 in 5 mL of THF and refluxed.
Preparation of Fe O MNPs (NMag 1)
3
4
4
2
The chemical co-precipitation method was employed to prepare
Fe O MNPs according to the procedure reported in the litera-
TLC was used to monitor the reaction progress. Compound 8
was isolated magnetically after completion of the reaction.
Column chromatography (ethyl acetate/petroleum ether) was
used to purify the reaction mixture to afford pure products.
3
4
82]
[
ture.
A stock solution was prepared by dissolving
1
ꢀ
FeCl ꢁ4H O (2.0 g), FeCl ꢁ6H O (5.2 g), and HCl (12 mol L
,
.85 mL) in 25 mL of distilled water. A beaker containing
2
2
3
2
0
ꢀ1
aqueous NaOH (1.5 mol L , 250 mL) was heated maintaining a
temperature of 808C and the dropwise addition of stock solution
was carried out under a nitrogen atmosphere with vigorous
stirring. The magnetic separation of Fe O MNPs was achieved
Supplementary Material
Spectroscopic data of the synthesized aldehydes are available on
the Journal’s website.
3
4
and they were subsequently washed with distilled water. FT-IR
1
ꢀ
Conflicts of Interest
nmax (KBr, thin film)/cm 1690, 1417, 882, 720, 647, 589.
The authors declare no conflicts of interest.
Preparation of Sil@NMag 2
Acknowledgements
The coating of a silica layer on Fe O MNPs was achieved by a
4
3
[
83]
This work was financially supported by the Science and Engineering
Research Board (SERB), New Delhi, under Start-Up Research Grant
sol–gel approach by following the literature procedure.
Fe O MNPs 1 (1.0 g) were homogeneously dispersed in a
3
4
(
Young Scientists) – Chemical Sciences (NO. SB/FT/CS-060/2014).
mixture of deionized water (20 mL), ethanol (60 mL), and
concentrated aqueous ammonia solution (1.5 mL, 28 wt-%) and
ultrasonicated for 0.5 h. Subsequently, dropwise addition of a
tetraethylorthosilicate (TEOS) solution (0.45 mL of TEOS in
References
[
1] H. C. Erythropel, J. B. Zimmerman, T. M. de Winter, L. Petitjean, F.
Melnikov, C. H. Lam, A. W. Lounsbury, K. E. Mellor, N. Z. Jankovi c´ ,
Q. Tu, L. N. Pincus, M. M. Falinski, W. Shi, P. Coish, D. L. Plata, P. T.
Anastas, Green Chem. 2018, 20, 1929. doi:10.1039/C8GC00482J
2] P. T. Anastas, J. C. Warner, Green Chemistry: Theory and Practice
1
mechanical stirring. The resultant silica coated Fe O MNPs 2
0 mL of ethanol) was carried out in suspension under vigorous
3
4
were isolated by an external magnetic field, washed three times
with ethanol, and dried under vacuum. FT-IR n (KBr, thin
film)/cm 1222, 1057, 959, 795, 555.
[
[
max
1
998 (Oxford University Press: New York, NY).
ꢀ1
3] C. Van Doorslaer, J. Wahlen, P. Mertens, K. Binnemans, D. De Vos,
Dalton Trans. 2010, 39, 8377. doi:10.1039/C001285H
Preparation of 3.Cl.Pr.Sil@NMag 4
[4] V. Campisciano, F. Giacalone, M. Gruttadauria, Chem. Rec. 2017, 17,
18. doi:10.1002/TCR.201700005
[5] F. Giacalone, M. Gruttadauria, ChemCatChem 2016, 8, 664. doi:10.
002/CCTC.201501086
9
The 3-chloropropyl modified Fe O MNPs 4 were prepared on
3
4
[84]
the basis of the method reported in the literature. Fe O MNPs
4
coated with silica shell 2 (1 g) were suspended in 50 mL of dry
xylene. To the above suspension, 3-chloropropyltriethoxysilane
3
1
[
6] X. Zheng, S. Luo, L. Zhang, J.-P. Cheng, Green Chem. 2009, 11, 455.
doi:10.1039/B823123K
3
(5 mmol, 1 mL) was added slowly. The reaction mixture
was refluxed for 24 h and subsequently cooled to afford the
-chloropropyl modified Fe O MNPs 4. The product was
[
7] A. Riisager, R. Fehrmann, M. Haumann, P. Wasserscheid, Eur. J.
Inorg. Chem. 2006, 695. doi:10.1002/EJIC.200500872
3
[8] G. Molteni, A. M. Ferretti, S. Mondini, A. Ponti, J. Nanopart. Res.
2018, 20, 79. doi:10.1007/S11051-018-4184-8
[9] S. Shylesh, V. Sch u¨ nemann, W. R. Thiel, Angew. Chem. Int. Ed. 2010,
3
4
washed three times with deionized water (25 mL), methanol
25 mL), and xylene (25 mL) and dried under vacuum at 508C.
(
ꢀ
1
4
9, 3428. doi:10.1002/ANIE.200905684
10] H.-Y. L u¨ , S.-H. Yang, J. Deng, Z.-H. Zhang, Aust. J. Chem. 2010, 63,
290. doi:10.1071/CH09532
11] H. Dadhania, D. Raval, A. Dadhania, Polycyclic Aromat. Compd.
019, doi:10.1080/10406638.2019.1595057
FT-IR nmax (KBr, thin film)/cm 2942, 1890, 1643, 1062, 795.
[
[
1
Preparation of [Dppf@Sil@NMag]Cl 6
Bis(diphenylphosphino)ferrocene 5 (0.731 g, 1 mmol) was
added to a suspension of 4 (1 g) in 25 mL of DMF. The reaction
mixture was heated at 808C for 72 h. The insoluble product was
2
[12] J. S. Ghomi, S. Zahedi, Ultrason. Sonochem. 2017, 34, 916. doi:10.
1016/J.ULTSONCH.2016.08.003

SILP Catalyst for Oxidation of Alcohols
I
[
[
[
13] H. T. Nguyen, N.-P. T. Le, D.-K. N. Chau, P. H. Tran, RSC Adv. 2018,
, 35681. doi:10.1039/C8RA04893B
14] R.-Q. Yang, N. Zhang, X.-G. Meng, X.-H. Liao, L. Li, H.-J. Song,
Aust. J. Chem. 2018, 71, 559. doi:10.1071/CH18138
15] A. L. Cappelletti, P. M. Uberman, S. E. Mart ´ı n, M. E. Saleta, H. E.
Troiani, R. D. S a´ nchez, R. E. Carbonio, M. C. Strumia, Aust. J. Chem.
[42] T. M. A. Shaikh, L. Emmanuvel, A. Sudalai, J. Org. Chem. 2006, 71,
5043. doi:10.1021/JO0606305
[43] M. Uyanik, K. Ishihara, Chem. Commun. 2009, 2086. doi:10.1039/
B823399C
[44] M. F. Pinto, M. Olivares, A. Vivancos, G. Guisado-Barrios,
M. Albrecht, B. Royo, Catal. Sci. Technol. 2019, 9, 2421. doi:10.1039/
C9CY00685K
[45] A. Akbari, M. Amini, A. Tarassoli, B. Eftekhari-Sis, N. Ghasemian,
E. Jabbari, Nano-Struct. Nano-Objects 2018, 14, 19. doi:10.1016/
J.NANOSO.2018.01.006
[46] Y. Sun, H. Ma, Y. Luo, S. Zhang, J. Gao, J. Xu, Chem. – Eur. J. 2018,
24, 4653. doi:10.1002/CHEM.201705824
[47] F. Mao, Z. Qi, H. Fan, D. Sui, R. Chen, J. Huang, RSC Adv. 2017,
7, 1498. doi:10.1039/C6RA27073E
[48] M. A. Nasseri, K. Hemmat, A. Allahresani, E. Hamidi-Hajiabadi,
Appl. Organomet. Chem. 2019, 33, e4809. doi:10.1002/AOC.4809
[49] J. M. Hoover, J. E. Steves, S. S. Stahl, Nat. Protoc. 2012, 7, 1161.
doi:10.1038/NPROT.2012.057
8
2
015, 68, 1492. doi:10.1071/CH14722
16] H.-Y. L u¨ , S.-H. Yang, J. Deng, Z.-H. Zhang, Aust. J. Chem. 2010, 63,
290. doi:10.1071/CH09532
[
[
[
[
[
[
1
17] Y.-R. Cui, C. Hong, Y.-L. Zhou, Y. Li, X.-M. Gao, X.-X. Zhang,
Talanta 2011, 85, 1246. doi:10.1016/J.TALANTA.2011.05.010
18] P. B. Shete, R. M. Patil, B. M. Tiwale, S. H. Pawar, J. Magn. Magn.
Mater. 2015, 377, 406. doi:10.1016/J.JMMM.2014.10.137
19] S. Kumari, R. P. Singh, Int. J. Biol. Macromol. 2012, 51, 76. doi:10.
1
016/J.IJBIOMAC.2012.01.040
20] J. Mao, W. Jiang, J. Gu, S. Zhou, Y. Lu, T. Xie, Appl. Surf. Sci. 2014,
17, 787. doi:10.1016/J.APSUSC.2014.08.191
3
21] M. H. Mashhadizadeh, M. Amoli-Diva, M. R. Shapouri, H. Afruzi,
Food Chem. 2014, 151, 300. doi:10.1016/J.FOODCHEM.2013.
[50] X. Yan, X. Yue, K. Liu, Z. Hao, Z. Han, J. Lin, Front Chem. 2019,
11.082
7, 394. doi:10.3389/FCHEM.2019.00394
[
[
22] S. Rengshausen, F. Etscheidt, J. Großkurth, K. L. Luska, A. Bordet,
[51] R. Ray, S. Chandra, D. Maiti, G. K. Lahiri, Chem. – Eur. J. 2016,
22, 8814. doi:10.1002/CHEM.201601800
[52] X.-T. Zhou, H.-B. Ji, S.-G. Liu, Tetrahedron Lett. 2013, 54, 3882.
doi:10.1016/J.TETLET.2013.05.055
W. Leitner, Synlett 2019, 30, 405. doi:10.1055/S-0037-1611678
23] L. Offner-Marko, A. Bordet, G. Moos, S. Tricard, S. Rengshausen,
B. Chaudret, K. L. Luska, W. Leitner, Angew. Chem. Int. Ed. 2018,
5
7, 12721. doi:10.1002/ANIE.201806638
24] M. Nasrollahzadeh, Z. Issaabadi, S. Mohammad Sajadi, RSC Adv. 2018,
, 27631. doi:10.1039/C8RA04368J
[53] H. A. Beejapur, F. Giacalone, R. Noto, P. Franchi, M. Lucarini,
M. Gruttadauria, ChemCatChem 2013, 5, 2991. doi:10.1002/CCTC.
201300234
[
[
[
[
8
25] C. Garkoti, J. Shabir, S. Mozumdar, New J. Chem. 2017, 41, 9291.
doi:10.1039/C6NJ03985E
[54] H. A. Beejapur, V. Campisciano, F. Giacalone, M. Gruttadauria,
Adv. Synth. Catal. 2015, 357, 51. doi:10.1002/ADSC.201400641
[55] J. Fan, F. Pu, M. Sun, Z.-W. Liu, X.-Y. Han, J.-F. Wei, X.-Y. Shi,
New J. Chem. 2016, 40, 10498. doi:10.1039/C6NJ01476C
[56] F. Shi, M. K. Tse, M. Beller, Chem. Asian J. 2007, 2, 411. doi:10.1002/
ASIA.200600383
26] R. Teimuri-Mofrad, S. Esmati, M. Rabiei, M. Gholamhosseini-Nazari,
Heterocycl. Commun. 2017, 23, 439. doi:10.1515/HC-2017-0140
27] S.-Q. Bai, L. Jiang, S.-L. Huang, M. Lin, S.-Y. Zhang, M.-Y. Han,
J. Xu, Y. Lu, G.-X. Jin, T. S. Andy Hor, Aust. J. Chem. 2014, 67, 1387.
doi:10.1071/CH14148
[57] A. V. Biradar, M. K. Dongare, S. B. Umbarkar, Tetrahedron Lett.
[
[
[
28] M. B. Gawande, P. S. Branco, R. S. Varma, Chem. Soc. Rev. 2013, 42,
2009, 50, 2885. doi:10.1016/J.TETLET.2009.03.178
3371. doi:10.1039/C3CS35480F
[58] R. Kurane, J. Jadhav, S. Khanapure, R. Salunkhe, G. Rashinkar,
Green Chem. 2013, 15, 1849. doi:10.1039/C3GC40592C
[59] A. Naikwade, M. Jagadale, D. Kale, S. Gajare, G. Rashinkar,
Catal. Lett. 2018, 148, 3178. doi:10.1007/S10562-018-2514-1
[60] S. Khanapure, M. Jagadale, D. Kale, S. Gajare, G. Rashinkar, Aust. J.
Chem. 2019, 72, 513. doi:10.1071/CH18576
29] Z. Zarnegar, J. Safari, J. Nanopart. Res. 2014, 16, 2509. doi:10.1007/
S11051-014-2509-9
30] Y. Qiao, H. Li, L. Hua, L. Orzechowski, K. Yan, B. Feng, Z. Pan,
N. Theyssen, W. Leitner, Z. Hou, ChemPlusChem 2012, 77, 1128.
doi:10.1002/CPLU.201200246
[
31] D. I. Enache, J. K. Edwards, P. Landon, B. Solsona-Espriu, A. F.
Carley, A. A. Herzing, M. Watanabe, C. J. Kiely, D. W. Knight, G. J.
Hutchings, Science 2006, 311, 362. doi:10.1126/SCIENCE.1120560
32] M. Beller, C. Bolm, Transition Metals for Organic Synthesis, 2nd edn
[61] M. Kooti, M. Afshari, Mater. Res. Bull. 2012, 47, 3473. doi:10.1016/
J.MATERRESBULL.2012.07.001
[62] M. A. Zolfigol, R. Ayazi-Nasrabadi, RSC Adv. 2016, 6, 69595.
doi:10.1039/C6RA11620E
[63] C. Tang, Z. Zou, Y. Fu, K. Song, ChemistrySelect 2018, 3, 5987.
doi:10.1002/SLCT.201800610
[64] H. B. Friedrich, N. Singh, Catal. Lett. 2006, 110, 61. doi:10.1007/
S10562-006-0099-6
[65] Q. Dong, X. Zhuang, Z. Li, B. Li, B. Fang, C. Yang, H. Xie, F. Zhang,
X. Feng, J. Mater. Chem. A 2015, 3, 7767. doi:10.1039/C5TA00556F
[66] M. K. Kolel-Veetil, R. M. Gamache, N. Bernstein, R. Goswami, S. B.
Qadri, K. P. Fears, J. B. Miller, E. R. Glaser, T. M. Keller, J. Mater.
Chem. C 2015, 3, 11705. doi:10.1039/C5TC02956B
[
[
2004 (Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim).
33] T. J. Zerk, P. W. Moore, J. S. Harbort, S. Chow, L. Byrne, G. A.
Koutsantonis, J. R. Harmer, M. Mart ´ı nez, C. M. Williams, P. V.
Bernhardt, Chem. Sci. 2017, 8, 8435. doi:10.1039/C7SC04260D
34] P. W. Moore, C. D. G. Read, P. V. Bernhardt, C. M. Williams, Chem. –
Eur. J. 2018, 24, 4556. doi:10.1002/CHEM.201800531
[
[
35] B. Karimi, D. Elhamifar, O. Yari, M. Khorasani, H. Vali, J. H. Clark,
A. J. Hunt, Chem. – Eur. J. 2012, 18, 13520. doi:10.1002/CHEM.
201200380
[
36] R. Ciriminna, P. Hesemann, J. J. E. Moreau, M. Carraro, S. Campestrini,
[67] C. M. Woodbridge, D. L. Pugmire, R. C. Johnson, N. M. Boag, M. A.
Langell, J. Phys. Chem. B 2000, 104, 3085. doi:10.1021/JP993235þ
[68] F. Rondino, D. Catone, G. Mattioli, A. A. Bonapasta, P. Bolognesi,
A. R. Casavola, M. Coreno, P. O’Keeffe, L. Avaldi, RSC Adv. 2014,
4, 5272. doi:10.1039/C3RA45705B
M. Pagliaro, Chem. – Eur. J. 2006, 12, 5220. doi:10.1002/CHEM.
2
00501556
37] Y. Xie, Z. Zhang, S. Hu, J. Song, W. Li, B. Han, Green Chem. 2008,
0, 278. doi:10.1039/B715067A
[
[
1
38] J. Lybaert, B. U. W. Maes, K. Abbaspour Tehrani, K. De Wael,
[69] R. K. Blundell, P. Licence, Phys. Chem. Chem. Phys. 2014, 16, 15278.
doi:10.1039/C4CP01901F
Electrochim. Acta 2015, 182, 693. doi:10.1016/J.ELECTACTA.2015.
0
9.107
39] N. Ghalavand, M. M. Heravi, M. R. Nabid, R. Sedghi, J. Alloys Compd.
019, 799, 279. doi:10.1016/J.JALLCOM.2019.05.209
[70] Y. Nonoguchi, Y. Iihara, K. Ohashi, T. Murayama, T. Kawai, Chem.
Asian J. 2016, 11, 2423. doi:10.1002/ASIA.201600810
[71] L. Ji, L. Zhou, X. Bai, Y. Shao, G. Zhao, Y. Qu, C. Wang, Y. Li,
J. Mater. Chem. 2012, 22, 15853. doi:10.1039/C2JM32896H
[72] S. Ghosh, A. Z. M. Badruddoza, M. S. Uddin, K. Hidajat, J. Colloid
Interface Sci. 2011, 354, 483. doi:10.1016/J.JCIS.2010.11.060
[73] S. Kanemoto, S. Matsubara, K. Takai, K. Oshima, K. Utimato, H.
Nozaki, Bull. Chem. Soc. Jpn 1988, 61, 3607. doi:10.1002/AOC.3510
[
[
2
40] M. Mohammadi, A. Khazaei, A. Rezaei, Z. Huajun, S. Xuwei,
ACS Sustain. Chem. & Eng. 2019, 7, 5283. doi:10.1021/ACS
SUSCHEMENG.8B06279
[
41] V. Panwar, P. Kumar, S. S. Ray, S. L. Jain, Tetrahedron Lett. 2015, 56,
3948. doi:10.1016/J.TETLET.2015.05.003

J
A. Naikwade et al.
[
74] K. B.Sharpless, K. Akashi, K. Oshima,Tetrahedron Lett. 1976, 17, 2503.
75] D. G. Lee, L. N. Congson, Can. J. Chem. 1990, 68, 1774. doi:10.1002/
AOC.3477
76] U. Siemeling, T.-C. Auch, Chem. Soc. Rev. 2005, 34, 584. doi:10.1039/
B315486F
77] R. C. J. Atkinson, V. C. Gibson, N. J. Long, Chem. Soc. Rev. 2004, 33,
[80] P. Barbaro, C. Bianchini, G. Giambastiani, S. L. Parisel, Coord. Chem.
Rev. 2004, 248, 2131. doi:10.1016/J.CCR.2004.03.022
[81] Metallocenes (Eds A. Togni, R. L. Halterman) 1998 (Wiley-VCH:
Weinheim).
[
[
[
[
[
[82] X. Zhao, Y. Shi, T. Wang, Y. Cai, G. Jiang, J. Chromatogr. A 2008,
1188, 140. doi:10.1016/J.CHROMA.2008.02.069
[83] D. Yang, J. Hu, S. Fu, J. Phys. Chem. C 2009, 113, 7646. doi:10.1021/
JP900868D
[84] A. Naikwade, M. Jagadale, D. Kale, S. Gajare, P. Bansode, G. Rashinkar,
Appl. Organometal. Chem. 2019, 33, e5066
313. doi:10.1039/B316819K
78] Ferrocenes: Homogeneous Catalysis, Organic Synthesis, Material
Science (Eds A. Togni, T. Hayashi) 1995 (Wiley-VCH: Weinheim).
79] T. J. Colacot, Platin. Met. Rev. 2001, 45, 22.