Tuning the chemoselective hydrogenation of aromatic ketones, aromatic aldehydes and quinolines catalyzed by phosphine functionalized ionic liquid stabilized ruthenium nanoparticles

Article abstract of DOI:10.1039/c5cy00293a

Ruthenium nanoparticles (Ru NPs) stabilized by phosphine-functionalized ionic liquids (PFILs) were synthesized in an imidazolium-based ionic liquid using H₂ as a reductant. Characterization showed well-dispersed particles of about 2.2 nm (TEM) and confirmed the PFIL stabilization of the Ru NPs (NMR). The Ru NPs stabilized by PFILs exhibited excellent activity and switchable chemoselectivity in the heterogeneous selective hydrogenation of aromatic ketones, aromatic aldehydes and quinolines under mild conditions.

Full text of DOI:10.1039/c5cy00293a

Catalysis
Science &
Technology
View Article Online
View Journal | View Issue
PAPER
Tuning the chemoselective hydrogenation of
aromatic ketones, aromatic aldehydes and
quinolines catalyzed by phosphine functionalized
ionic liquid stabilized ruthenium nanoparticles†
Cite this: Catal. Sci. Technol., 2015,
5, 3728
He-yan Jiang* and Xu-xu Zheng
Received 28th February 2015,
Accepted 15th May 2015
Ruthenium nanoparticles (Ru NPs) stabilized by phosphine-functionalized ionic liquids (PFILs) were synthe-
2
sized in an imidazolium-based ionic liquid using H as a reductant. Characterization showed well-dispersed
particles of about 2.2 nm (TEM) and confirmed the PFIL stabilization of the Ru NPs (NMR). The Ru NPs sta-
bilized by PFILs exhibited excellent activity and switchable chemoselectivity in the heterogeneous selective
hydrogenation of aromatic ketones, aromatic aldehydes and quinolines under mild conditions.
DOI: 10.1039/c5cy00293a
www.rsc.org/catalysis
aromatic compounds, an important organic transformation,
since the resulting products are versatile precursors to many
Introduction
Metal nanoparticles are fascinating because of their applica-
tions in areas such as optoelectronics, sensing, medicine and
natural products and drug molecules. As part of our ongoing
3
2–34
research,
we herein disclose a practical, general, and effi-
1
–5
catalysis. The investigation of metal nanoparticles in cataly-
sis has been receiving increasing interest because nanometal
particles present an efficient combination of the advantages
of heterogeneous and homogeneous catalysts. Additional sta-
bilization, generally provided by phosphines, amines or poly-
mers, of nanoparticles influences the catalytic activity, selec-
cient method by which aromatic compounds can be hydroge-
nated with switchable excellent chemoselectivity under mild
conditions catalyzed by ruthenium nanoparticles (Ru NPs)
stabilized by phosphine-functionalized ionic liquids (PFILs).
To the best of our knowledge, the approach used here has
not been explored before.
6–12
tivity and recyclability.
Ionic liquid-stabilized metal
nanoparticles are interesting new catalytic materials for
hydrogenation and other applications. Furthermore, with
Results and discussion
Synthesis and characterization of ruthenium nanoparticles
3
both covalent and electrostatic stabilization, functionalized
ionic liquids containing metal-binding moieties have been
gradually employed in the synthesis of transition metal nano-
particles to improve the catalytic system stability and/or cata-
The synthesis of Ru NPs was achieved through the reduction of
RuO ·xH O or RuIJCOD)IJ2-methylallyl) (COD = cycloocta-1,5-diene)
2 2 2
1
3–17
lytic performance.
However, up to now, ionic liquid-
stabilized metal nanoparticles have been tested as catalysts
3
,18–21
mainly in the hydrogenation of alkenes or arenes.
The chemoselective reduction of aromatic compounds
(aromatic ketones, aromatic aldehydes, quinolines, etc.) by
means of heterogeneous catalysis is an important field in the
2
2–31
industrial hydrogenation process.
Furthermore, tuning
the hydrogenation chemoselectivity of aromatic compounds
in heterogeneous catalysis remains a formidable scientific
challenge. We focus on the selective hydrogenation of
Key Laboratory of Catalysis Science and Technology of Chongqing Education
Commission, Chongqing Key Laboratory of Catalysis and Functional Organic
Molecules, Chongqing Technology and Business University, Chongqing 400067, PR
China. E-mail: orgjiang@163.com; Fax: +86 23 6276 9652; Tel: +86 23 6276 9652
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/
c5cy00293a
4
Fig. 1 Synthesis of Ru NPs in [BMIM]BF .
3728 | Catal. Sci. Technol., 2015, 5, 3728–3734
This journal is © The Royal Society of Chemistry 2015

View Article Online
Catalysis Science & Technology
Paper
in [BMIM]BF (BMIM = 1-butyl-2,3-dimethylimidazolium) under
particles. XPS analysis of Ru NPs stabilized by ijBMIM]ijtppm]
showed the presence of ruthenium, phosphorus, nitrogen
and carbon, which signified the presence of ijBMIM]ijtppm] in
the ligand sphere of the Ru NPs. The X-ray diffraction pattern
of the isolated Ru NPs 1 (Fig. 3) generally showed the pre-
dicted lines of the Ru hcp structure in the wide-angle range.
4
H atmosphere (1 MPa) in the presence of 1.0 equivalent of
2
PFILs ijBMIM]ijtppm] or ijBMIM]ijtppt] (Fig. 1), which afforded a
dark suspension. For comparison, Ru NPs were also synthe-
sized in [BMIM]BF in the absence of any additional stabilizer.
4
A black powder could be isolated from the black suspension by
adding acetone and then centrifuging (8000 rpm for 10 min).
After being washed three times with acetone and dried under
reduced pressure, the isolated powder was analyzed by trans-
mission electron microscopy (TEM), X-ray photoelectron
spectroscopy (XPS), X-ray diffraction (XRD), nuclear magnetic
resonance (NMR) and infrared spectroscopy (IR).
3
1
P NMR studies of ijBMIM]ijtppm] and ijBMIM]ijtppm]
stabilized Ru NPs 1 in [BMIM]BF were conducted. The
4
3
1
P NMR spectrum of ijBMIM]ijtppm] showed a peak at δ = −5.4
3
1
ppm. However, no signal was detected in the P NMR spec-
trum of Ru NPs 1. After the mixture of isolated Ru NPs 1 and
hydrogen peroxide was further stirred at 50 °C for 10 h, an
oxide signal of ijBMIM]ijtppm] appeared at δ = 30.0 ppm. The
TEM analysis was conducted to characterize the isolated
Ru NPs and determine their mean diameter (Fig. 2). In gen-
31
P NMR observations may be explained by the fact that
eral, Ru NPs prepared from the precursor RuO
better dispersion than those from ijRuIJCOD)IJ2-methylallyl)2]
Fig. 2, images 1 and 2 versus 3 and 4), and the TEM image
2
·xH
2
O showed
majority of the ijBMIM]ijtppm] were attached to the Ru NP
surface, and free phosphine and attached phosphine
3
1
(
exchange very fast, affording no P NMR signal.
showed a trend toward agglomeration of the Ru NPs in the
absence of a functionalized ionic liquid (Fig. 2, image 5). The
TEM image of isolated Ru NPs 1, derived from RuO ·xH O,
2 2
showed the formation of nearly monodispersed Ru nano-
particles with an average diameter of 2.2 nm.
IR is effective for the investigation of the mutual ligand–
metal interactions of nanometal catalysts. Information on the
interaction between the nanometal and the phosphine in Ru
NPs 1 was confirmed by FTIR methods in which the red shift
−
1
of the P–C H deformation around 1469 cm in Ru NPs 1 is
6
5
XPS analysis of the isolated Ru NPs 1 was carried out to
elucidate the nature of the stabilizing layer of the nanometal
an indication of the coordination of ijBMIM]ijtppm] to the
metal Ru(0).
The effect of ijBMIM]ijtppm] in the catalyst is noteworthy.
Due to the strong coordination capacity of the anion of
ijBMIM]ijtppm], Ru NPs were well dispersed and highly stable
in catalytic hydrogenation. On the basis of these results, it
−
was deduced that the ijPIJC
6
H
5
)
2
IJC
6
H
4
-m-SO
3
) ] ions formed a
layer around the surface of the Ru NPs, leading to a sphere
of negative charge, and then the cation of ijBMIM]ijtppm] was
arranged into an outer layer for charge conservation (Fig. 4).
Recently, several groups have demonstrated that ionic liquids
possess self-organized structures, which can create an exter-
nal layer around the surface of the metal NPs to protect them
5
,20,35
from aggregation.
Catalytic hydrogenation
Initially, we chose styrene as a model substrate to explore the
catalytic performance of Ru NPs 1 under very mild conditions
(
2
30 °C, H at 1 MPa). Fig. 5 shows the effect of the conversion
Fig. 2 TEM images of Ru nanoparticles 1, 2, 3, 4 and 5.
Fig. 3 X-Ray diffraction pattern of isolated Ru NPs 1.
This journal is © The Royal Society of Chemistry 2015
Catal. Sci. Technol., 2015, 5, 3728–3734 | 3729

View Article Online
Paper
Catalysis Science & Technology
Fig. 6 Recyclability of Ru NPs 1 for the hydrogenation of styrene.
−3
Reaction conditions: styrene (8.9 × 10 mol; styrene/Ru = 500), 30 °C,
at 1 MPa.
H
2
Fig. 4 The PFIL IJ[BMIM]ijtppm]) stabilized/modified Ru nanoparticles.
recycles of styrene hydrogenation was 2.13 nm (S2 and S3 in
the ESI†). All the results above strongly supported the pro-
posal that the reaction progressed under heterogeneous catal-
ysis rather than homogeneous catalysis.
versus time. The hydrogenation of styrene produced only eth-
ylbenzene in the test. It was found that the conversion
increased linearly with time, showing no induction period,
proving that this catalyst did not convert into other catalyti-
cally active species. Furthermore, mercury-poisoning experi-
ments were run as they can selectively poison metal nano-
particles, by forming an amalgam with mercury, to help
distinguish between homogeneous and heterogeneous cata-
lysts. In such an experiment, the conversion was 61.6%
after the initial 1 hour; mercury was then added under argon
atmosphere and the reaction was completely terminated as
evidenced by the absence of change in the conversion after
an additional reaction time of 3 hours. In addition, it was
found that the amount of leaching from Ru NPs 1 was about
The chemoselective reduction of carbonyl compounds by
means of heterogeneous catalysis is of considerable impor-
tance in the synthesis of fine chemicals, particularly interme-
22–25
diates in the fragrance and pharmaceutical industries.
Baiker and coworkers found that Pd-ijBMIm]ijPF ] exhibited
good activity and selectivity in the hydrogenation of
6
36
23
acetophenone.
However, tuning the hydrogenation
chemoselectivity of aromatic carbonyl compounds in hetero-
geneous catalysis remains rather difficult. The effect of differ-
ent reaction factors on the chemoselective hydrogenation of
acetophenone is listed in Table 1. The importance of a basic
additive in a catalyst system for the selective hydrogenation
37,38
0
.9 ppm by ICP-AES analysis of the organic phase in styrene
of aromatic ketones has been well-established.
The Ru NPs
catalytic hydrogenation. The catalyst could be reused by sim-
ple liquid–liquid extraction after the reaction. The procedure
was repeated ten times and the results indicated that Ru NPs
had no catalytic activity at ambient temperature in [BMIM]BF
4
in the absence of a basic additive (Table 1, entry 1). Similar to
previous reports, a basic additive was helpful to improve the
catalytic performance; acetophenone could be hydrogenated
with 77.0% conversion and 99.0% chemoselectivity to
1
could be recycled without any loss of catalytic activity
(Fig. 6). The average diameter of the spent Ru NPs 1 after ten
1-phenylethanol in the presence of [BMIM]OH IJ1-butyl-2,3-
dimethylimidazolium hydroxide) (Table 1, entry 2). The PFIL
stabilizers showed an important influence on the catalytic
process; without the stabilizer, the hydrogenation resulted
in a conversion of 94% and a chemoselectivity as low as
76.6% to 1-phenylethanol (Table 1, entry 4). Ru NPs stabi-
lized by ijBMIM]ijtppm] showed lower activity but higher
chemoselectivity to 1-phenylethanol than Ru NPs stabilized
by ijBMIM]ijtppt] (Table 1, entries 2–3). These results indicated
that PFILs not only stabilized the metal particles in the prep-
aration of the catalyst, but also served to additionally modify
the Ru NPs in the chemoselective hydrogenation.
Since the properties of the metal precursors greatly
influence the particle size and dispersion of nanometal
3
,4
0
catalysts,
2 2
metal precursors, including RuO ·xH O and
Fig.
5 Reaction profiles for hydrogenation of styrene and Hg
−3
ijRuIJCOD)IJ2-methylallyl) ], were tested. Generally, Ru NPs 1
and 2, prepared from RuO ·xH O, showed higher activity
2 2
poisoning of Ru NPs 1. Reaction conditions: styrene (8.9 × 10 mol;
styrene/Ru = 500), 30 °C, H at 1 MPa.
2
2
3730 | Catal. Sci. Technol., 2015, 5, 3728–3734
This journal is © The Royal Society of Chemistry 2015

View Article Online
Catalysis Science & Technology
Paper
Table 1 Optimization of reaction conditions for the chemoselective
Table 2 Chemoselective hydrogenation of aromatic ketones catalyzed
a
a
hydrogenation of acetophenone by Ru NPs
by Ru NPs 1
Selectivity (%)
Selectivity (%)
Entry Catalyst Solvent
t (h) Conversion (%) Aa
Ab
Ac
Entry A–G Solvent
t (h) Conversion (%) A–G a A–G b A–G c
1
2
3
4
5
6
7
8
9
1
1
1
2
5
3
4
BMIMBF
BMIMBF
BMIMBF
BMIMBF
BMIMBF
BMIMBF
BMIMBF
4
4
4
4
4
4
4
15
15
15
15
15
15
15
1
0.0
77.0
92.0
94.0
48.0
69.0
0.0
100.0
26.1
99.0
—
—
—
1
2
3
4
5
6
7
8
9
1
A
A
B
B
C
C
D
D
E
E
F
BMIMBF
H O
2
BMIMBF
4
4
4
4
4
4
4
15
1
15
2
15
2
15
2
15
2
15
2
15
2
77.0
100.0
21.0
100.0
10.4
72.5
2.0
99.0
100.0
100.0
72.0
59.3
26.4
99.0
0.0
86.0 14.0
0.0 4.5
80.0 20.0
21.0 38.0
100.0
0.0
100.0
92.1
85.0
93.3
96.7
0.0
0.4
0.4
0.6
99.6
0.0
95.5
0.0
41.0
0.0
100.0
0.0
4.6
5.3
6.4
3.3
b
b
b
b
b
99.0 0.4 0.6
84.0 6.2 9.8
76.6 3.4 20.0
94.2 2.9 2.9
92.6 2.7 4.7
b
b
b
b
2
H O
BMIMBF
2
H O
b
Ru/C
1
5
—
—
—
BMIMBF
0.0
0.0
0.0
3.3
9.7
0.3
0.0
0.0
c
2
H O
2
H O
2
H O
0.0 0.4 99.6
55.9 18.4 25.7
34.6 1.2 64.2
2
H O
c
1
1
BMIMBF
0
Ru/C
b
b
b
0
2
H O
a
11
BMIMBF
Reaction was carried out at 30 °C. Substrate: in a 1 ml solution at
.8 M, PH2: 5.0 MPa. Substrate/Ru = 100 : 1, Ru/C (5 wt%, 36 mg).
1
1
2
3
F
G
G
2
H O
1
BMIMBF
Products were analyzed by using a GC instrument with an FID
detector and a β-DEX120 capillary column. [BMIM]OH = 0.20 mol
L
b
14
2
H O
100.0
100.0
−1
c
was added. Ru nanoparticles were isolated and redispersed in
a
The reaction conditions are the same as in Table 1. When
water.
−1
b
4
BMIMBF was the solvent, [BMIM]OH = 0.20 mol L was added. Ru
nanoparticles 1 were isolated and redispersed in water.
than 3 and 4, which were prepared from ijRuIJCOD)IJ2-
methylallyl) ] (Table 1, entries 2–3 versus 5–6). The best
2
chemoselectivity of 99.0% was achieved in the hydrogenation
of acetophenone to 1-phenylethanol using Ru NPs 1 as the
catalyst.
chemoselectivity appears to be delicately influenced by the
substituent in the substrate. In general, the activity and
chemoselectivity decreased by increasing the bulkiness of the
alkyl group from methyl or primary alkyl to isopropyl (Table 2,
entries 1–6). It was found that when the substituent is in the
para position, the substrate with an electron-donating group
showed poor reaction activity with excellent chemoselectivity
The best condition is when there is no solvent, and if a
3
9
solvent is needed then water is preferred. Indeed, water is
an attractive alternative to traditional organic solvents because
it is cheap, readily available, nontoxic, non-flammable and
safe to the environment. Ru NPs 1 isolated from centrifuga-
tion were redispersed in water to test the catalytic perfor-
mance (Table 1, entry 8). To our surprise, when water was
used as the solvent in the hydrogenation of acetophenone,
the reaction progressed very fast with a high chemoselectivity
to cyclohexylethanol. In comparison with the catalytic hydro-
to the CO hydrogenation product in [BMIM]BF or the full
4
hydrogenation product in water (Table 2, entries 7–8), and
substrates with electron-withdrawing groups showed good
reaction activity with the major chemoselectivity to CO
hydrogenation products in both [BMIM]BF4 and water
(Table 2, entries 9–12). Furthermore, 2-acetothiophene,
2-acetopyridine, and 2-acetopyrrole were also tested; 2-aceto-
thiophene and 2-acetopyrrole showed no reaction activity
during the test. The chemoselectivity of 2-acetopyridine to
CO and full hydrogenation products could reach 96.7%
and 100%, respectively (Table 2, entries 13–14). The effect of
the steric bulk and the electronic nature of the substrates
influence the activity and chemoselectivity of the reaction.
The chemoselective hydrogenation of aromatic aldehydes
was also tested (Table 3). In comparison with the chemoselective
hydrogenation of aromatic ketones, aromatic aldehydes could
be hydrogenated to the corresponding CO and full hydro-
genation products easily. Without the basic additive, benzal-
dehyde could be hydrogenated to the corresponding benzyl
alcohol in [BMIM]BF4 (Table 3, entry 1). The complete
genation in the ionic liquid BMIMBF , the high catalytic
4
activity in water may be attributed to the increased substrate
solubility in water as well as the interactions between water
4
0
and the substrate via hydrogen bonding. However, Ru NPs
isolated from centrifugation and redispersed in water
5
showed poor activity and chemoselectivity (Table 1, entry 9).
A commercially available Ru/C catalyst was also tested
under similar reaction conditions in the hydrogenation of
acetophenone (Table 1, entries 7 and 10). Overall, the Ru/C
catalyst showed poor activity and chemoselectivity towards
either 1-phenylethanol or cyclohexylethanol.
Some representative examples are listed in Table 2 for the
chemoselective hydrogenation of aromatic ketones catalyzed
4
by Ru NPs 1 in both [BMIM]BF and water. The extent of the
This journal is © The Royal Society of Chemistry 2015
Catal. Sci. Technol., 2015, 5, 3728–3734 | 3731

View Article Online
Paper
Catalysis Science & Technology
Table 3 Chemoselective hydrogenation of aromatic aldehydes catalyzed
Table 4 Chemoselective hydrogenation of quinoline and derivatives cat-
a
a
by Ru NPs 1
alyzed by Ru NPs 1
Selectivity (%)
Selectivity (%)
Entry I–L Solvent
t (h) Conversion (%) I–L a I–L b I–L c
T
Conversion M–P M–P M–P
Entry Catalyst M–P Solvent
(°C) (%)
a
b
c
1
2
3
4
5
6
7
8
9
1
1
I
I
J
J
BMIMBF
4
15
1
15
1
3
15
1
3
15
1
100.0
100.0
30.5
94.7
100.0
0.0
99.8
100.0
97.2
97.8
100.0
100.0 0.0
0.0 0.0
100.0 0.0
0.0
100.0
0.0
3.4
99.5
—
3.0
12.1
0.0
99.9
100.0
b
2
H O
1
2
3
4
5
6
7
8
9
10
1
1
1
M
M
M
M
M
M
N
N
N
O
O
O
P
BMIMBF
4
4
4
4
4
50
50
60
50
50
60
50
50
60
50
50
95.0
98.0 2.0
99.0 0.3
1.8 0.0 98.2
0.0
0.7
b,c
c
BMIMBF
4
H
H
2
O
O
93.0
98.6
67.0
30.0
92.0
98.4
81.3
97.7
97.9
86.8
b
b
H
H
2
O
O
96.6
0.5
—
0.0
0.0
—
2
J
2
Ru/Cb
Ru/C
Ru/C
1
1
1
1
1
1
1
BMIMBF
98.0 2.0
98.6 0.0
75.9 22.5
96.0 4.0
55.5 44.5
1.3 30.4 68.3
87.7 0.0 12.3
24.4 0.0 75.6
0.0 0.0 100.0
0.0
1.4
1.6
0.0
0.0
K
K
K
L
L
L
BMIMBF
4
H
H
2
O
O
b
b
H
H
2
O
O
97.0
87.9
0.0
0.0
2
2
BMIMBF
b,c
BMIMBF
4
100.0 0.0
H
H
2
O
O
b
b
c
0
1
H
H
2
O
O
0.1
0.0
0.0
0.0
2
2
3
BMIMBF
b,c
1
1
1
2
H
H
2
O
O
a
c
Reaction was carried out at 30 °C. Substrate: in a 1 ml solution at
.8 M, PH2: 3.0 MPa. Substrate/Ru = 100 : 1. Products were analyzed by
2
60 100.0
1
13
BMIMBF
50
50
60
46.0
71.7
95.8
100.0 0.0
100.0 0.0
100.0 0.0
0.0
0.0
0.0
b,c
using a GC instrument with an FID detector and a β-DEX120 capillary
column. Ru nanoparticles 1 were isolated and redispersed in water.
14
5
1
P
H
H
2
O
O
b
c
1
1
P
2
a
Reaction conditions: substrate in a 1 ml solution at 1.8 M, PH2: 5.0
hydrogenation product of benzaldehyde could be achieved in
water (Table 3, entry 2). When the substituent is in the para
position of benzaldehyde, CO and full hydrogenation could
be achieved in weak electron-donating group and electron-
withdrawing group substituted substrates (Table 3, entries 3–5
and 9–11). With a strong electron-donating group in the para
position, p-anisaldehyde could be hydrogenated with the
major chemoselectivity to the CO hydrogenation product
during our test (Table 3, entries 6–8).
MPa. Substrate/Ru = 100 : 1, Ru/C (5 wt%, 36 mg). Products were
analyzed by using a GC instrument with an FID detector and an HP-5
b
c
column, reaction time: 15 h. Reaction time: 1 h. Ru nanoparticles
were isolated and redispersed in water.
1
2-position of quinoline would cause the decrease of the
hydrogenation chemoselectivity due to the steric hindrance.
Introducing a methyl group in the quinoline molecule, espe-
cially in the 3-position of quinoline, obviously promoted the
formation of decahydroquinoline (Table 4, entry 12).
8-Methylquinoline could be hydrogenated with absolute
chemoselectivity to 1,2,3,4-tetrahydroquinoline during the
test (Table 4, entries 13–15).
Hydrogenation of quinoline and its derivatives is of con-
siderable industrial interest for the production of petro-
26–28
chemicals, fine chemicals, and pharmaceuticals.
However,
tuning the hydrogenation chemoselectivity of quinolines
in heterogeneous catalysis under mild conditions remains a
formidable scientific challenge. We investigated the catalytic
performance of Ru NPs for the hydrogenation of quinoline
and its derivatives (Table 4). Quinoline could be easily hydro-
genated to 1,2,3,4-tetrahydroquinoline at 50 °C with 98.0%
chemoselectivity in [BMIM]BF4 and 99.0% chemoselectivity
in water (Table 4, entries 1–2). Unprecedentedly, complete
hydrogenation of quinoline could also be achieved with
Conclusions
The results of this study demonstrated that PFIL-stabilized
Ru NPs are effective catalysts for the challenging selective
hydrogenation of aromatic ketones, aromatic aldehydes and
quinolines with a distinct high and switchable selectivity
towards different functional groups of substrates. The cata-
lytic performance is complementary to both classical homo-
geneous and heterogeneous catalysis. Additional work is cur-
rently in progress in this and related areas.
9
8.2% chemoselectivity in water at a reaction temperature
as low as 60 °C (Table 4, entry 3). A commercially available
Ru/C catalyst was also tested under similar reaction condi-
tions in the hydrogenation of quinoline (Table 4, entries 4–6).
The Ru/C catalyst showed poor activity with the major
chemoselectivity to 1,2,3,4-tetrahydroquinoline during the
test. Quinoline analogues were also tested. Generally, the
hydrogenation activity of 2- or 3-methylquinoline was almost
the same as quinoline. The presence of a substituent in the
Experimental section
Materials
All manipulations involving air-sensitive materials were car-
ried out using standard Schlenk line techniques under an
3732 | Catal. Sci. Technol., 2015, 5, 3728–3734
This journal is © The Royal Society of Chemistry 2015

View Article Online
Catalysis Science & Technology
Paper
atmosphere of nitrogen. RuO ·xH O, RuIJCOD)IJ2-methylallyl)
2
General procedure for the heterogeneous chemoselective
2
2
and Ru/C (5%) were purchased from Acros. Various sub-
strates and other reagents were of analytical grade. The purity
of hydrogen was over 99.99%. Phosphine-functionalized ionic
hydrogenation
In [BMIM]BF . The stainless steel autoclave containing the
4
previously prepared PFIL-stabilized Ru(0) catalyst was
charged with the appropriate substrate, then the autoclave
was sealed and purged with pure hydrogen several times.
After the reactants were heated to predetermined tempera-
ture, the reaction timing began. After completion of the reac-
tion and cooling to ambient temperature, the products were
isolated by liquid–liquid extraction with diethyl ether and
analyzed by gas chromatography.
4
1,42
liquids were synthesized according to the literature.
Prod-
ucts were analyzed by using a GC instrument (cyclo-
hexylcyclohexane used as an internal standard) with an FID
detector and an HP-5 column (30 m × 0.25 mm)/β-DEX120
capillary column (25 m × 0.25 mm). Products were confirmed
by GC-MS and NMR. TEM analyses were performed using a
JEOL JEM 2010 transmission electron microscope operating
at 200 kV with a nominal resolution of 0.25 nm. X-ray photo-
electron spectroscopy (XPS) measurements were performed
on a Thermo ESCALAB 250 spectrometer. XRD analysis was
performed with a D/MAX 2550 VB/PC using a graphite crystal
as a monochromator. Ru and P contents were characterized
using a Perkin Elmer Optima 2100DV ICP-AES (S1 in the
ESI†).
In water. The isolated nanoparticles dispersed in water
(
1 ml) were placed in a stainless steel autoclave, and the sub-
strate was added. Then the autoclave was sealed and purged
with pure hydrogen several times. After the reactants were
heated to predetermined temperature, the reaction timing
began. After completion of the reaction and cooling to ambi-
ent temperature, the products were isolated by liquid–liquid
extraction with diethyl ether or centrifugation and analyzed
by gas chromatography.
Synthesis of ruthenium nanoparticles
Preparation of nanocatalysts 1, 2 or 5. In a typical experi-
ment, RuO ·xH O (0.018 mmol) and PFILs (0.018 mmol for 1
Acknowledgements
2
2
and 2, no ligand for 5) were dispersed in [BMIM]BF
4
(1 mL)
This work was financially supported by the National Natural
Science Foundation of China (no. 21201184), Natural Science
Foundation Project of CQ (no. cstc2014jcyjA10105), Ministry
of Education of Chongqing (no. KJ1400601), Chongqing Key
Laboratory of Catalysis and Functional Organic Molecules
(BMIM = 1-butyl-2,3-dimethylimidazolium) and the reaction
mixture was placed in a 20 mL stainless-steel high pressure
reactor. After stirring the mixture at room temperature under
an atmosphere of N for 30 min, a constant pressure of H
2
2
(1 MPa) was introduced to the system and the content was
(
no. 1456028) and 100 Leading Scientists Promotion Project
stirred for 4 h at 75 °C. The reactor was cooled to ambient
temperature and carefully vented. A dark solution was
obtained. The Ru NPs embedded in [BMIM]BF4 were
employed for hydrogenation studies (see below). Isolation of
the Ru NPs for TEM, XPS, XRD analysis and for catalytic
experiments (see below) was achieved by dissolving the mix-
ture in acetone (5 mL), centrifuging (8000 rpm for 10 min),
washing with acetone (2 × 5 mL) and drying under vacuum.
Furthermore, the supernatant of the ijBMIM]ijtppm]-stabilized
Ru NPs 1 was analyzed by ICP-AES methods and about 2.2%
Ru and 5.4% ijBMIM]ijtppm] were lost during the washing
and drying procedure.
of Chongqing.
Notes and references
1 K. J. Klabunde and R. M. Richards, Nanoscale Materials in
Chemistry, Wiley-Interscience, New York, 2001.
2 G. Schmid, Clusters and Colloids. From Theory to
Applications, Wiley VCH, Weinheim, 2004.
3 J. Dupont and J. D. Scholten, Chem. Soc. Rev., 2010, 39,
1780–1804.
4 Y. Yuan, N. Yan and P. J. Dyson, ACS Catal., 2012, 2,
1057–1069.
Preparation of nanocatalysts 3 or 4. In a typical experi-
ment, RuIJCOD)IJ2-methylallyl)2 (0.018 mmol) and PFILs
5 K. L. Luska and A. Moores, ChemCatChem, 2012, 4, 1534–1546.
6 Y. M. A. Yamada, T. Arakawa, H. Hocke and Y. Uozumi,
Angew. Chem., Int. Ed., 2007, 46, 704–706.
(
0.018 mmol) were dispersed in [BMIM]BF (1 mL) and the
4
reaction mixture was placed in a 20 mL stainless-steel high
pressure reactor. After stirring the mixture at room tempera-
7 D. Astruc, F. Lu and J. R. Aranzaes, Angew. Chem., Int. Ed.,
2005, 44, 7852–7872.
ture under an atmosphere of N for 30 min, a constant pres-
sure of H (1 MPa) was introduced to the system and the con-
2
8 S. Jansat, M. Gomez, K. Philippot, G. Muller, E. Guiu, C.
Claver, S. Castillon and B. Chaudret, J. Am. Chem. Soc.,
2004, 126, 1592–1593.
9 H. Mao, J. Ma, Y. Liao, S. Zhao and X. Liao, Catal. Sci.
Technol., 2013, 3, 1612–1617.
10 G. S. Fonseca, A. P. Umpierre, P. F. P. Fichtner, S. R. Teixeira
and J. Dupont, Chem. – Eur. J., 2003, 9, 3263–3269.
11 C. Vollmer, E. Redel, K. Abu-Shandi, R. Thomann, H.
Manyar, C. Hardacre and C. Janiak, Chem. – Eur. J., 2010, 16,
3849–3858.
2
tent was stirred for 4 h at 75 °C. The reactor was cooled to
ambient temperature and carefully vented. A dark brown
solution was obtained which was used for the hydrogenation
reaction (see below). Isolation of the Ru NPs for TEM analysis
and catalytic experiments (see below) was achieved by dis-
solving the mixture in acetone (5 mL), centrifuging (8000
rpm for 10 min), washing with acetone (2 × 5 mL) and drying
under vacuum.
This journal is © The Royal Society of Chemistry 2015
Catal. Sci. Technol., 2015, 5, 3728–3734 | 3733

View Article Online
Paper
Catalysis Science & Technology
1
2 P. S. Roy and S. K. Bhattacharya, Catal. Sci. Technol., 2013, 3,
314–1323.
3 R. R. Dykeman, N. Yan, R. Scopelliti and P. J. Dyson, Inorg.
Chem., 2011, 50, 717–719.
26 D. Zhu, H. Jiang, L. Zhang, X. Zheng, H. Fu, M. Yuan, H.
Chen and R. Li, ChemCatChem, 2014, 6, 2954–2960.
27 L. Zhang, X. Wang, Y. Xue, X. Zeng, H. Chen, R. Li and S.
Wang, Catal. Sci. Technol., 2014, 4, 1939–1948.
28 Y. Sun, H. Fu, D. Zhang, R. Li, H. Chen and X. Li, Catal.
Commun., 2010, 12, 188–192.
29 G. S. Fonseca, J. D. Scholten and J. Dupont, Synlett,
2004, 1525–1528.
30 V. Kogan, Z. Aizenshtat and R. Neumann, New J. Chem.,
2002, 26, 272–274.
1
1
1
1
4 H. Zhang and H. Cui, Langmuir, 2009, 25, 2604–2612.
5 D. B. Zhao, Z. F. Fei, T. J. Geldbach, R. Scopelliti and P. J.
Dyson, J. Am. Chem. Soc., 2004, 126, 15876–15882.
1
6 N. Kocharova, J. Leiro, J. Lukkari, M. Heinonen, T. Skala, F.
Sutara, M. Skoda and M. Vondracek, Langmuir, 2008, 24,
3
235–3242.
1
1
1
2
2
2
7 B. Zhang, Y. Yuan, K. Philippot and N. Yan, Catal. Sci.
Technol., 2015, 5, 1683–1692.
8 J. Dupont, G. S. Fonseca, A. P. Umpierre, P. F. P. Fichtner
and S. R. Teixeira, J. Am. Chem. Soc., 2002, 124, 4228–4229.
9 A. Denicourt-Nowicki, B. Leger and A. Roucoux, Phys. Chem.
Chem. Phys., 2011, 13, 13510–13517.
0 W. Zhu, Y. Yu, H. Yang, L. Hua, Y. Qiao, X. Zhao and Z.
Hou, Chem. – Eur. J., 2013, 19, 2059–2066.
1 E. Redel, J. Kramer, R. Thomann and C. Janiak,
J. Organomet. Chem., 2009, 694, 1069–1075.
31 C. Chen, H. Chen and W. Cheng, Appl. Catal., A, 2003, 248,
117–128.
32 H. Y. Jiang, C. F. Yang, C. Li, H. Y. Fu, H. Chen, R. X. Li and
X. J. Li, Angew. Chem., Int. Ed., 2008, 47, 9240–9244.
33 H. Y. Jiang, B. Sun, X. X. Zheng and H. Chen, Appl. Catal., A,
2012, 421–422, 86–90.
34 H. Y. Jiang and X. X. Zheng, Appl. Catal., A, 2015, 499, 118–123.
35 Z. F. Wu and H. Y. Jiang, RSC Adv., 2015, 5, 34622–34629.
36 R. A. Sheldon, M. Wallau, I. W. C. E. Arends and U.
Schuchardt, Acc. Chem. Res., 1998, 31, 485–493.
37 T. Ohkuma, H. Ooka, T. Ikariya and R. Noyori, J. Am. Chem.
Soc., 1995, 117, 2675–2676.
38 A. Perosa, P. Tundo and M. Selva, J. Mol. Catal. A: Chem.,
2002, 180, 169–175.
39 R. A. Sheldon, Green Chem., 2005, 7, 267–278.
40 L. Foppa and J. Dupont, Chem. Soc. Rev., 2015, 44, 1886–1897.
41 C. P. Mehnert, R. A. Cook, N. C. Dispenziere and E. J.
Mozeleski, Polyhedron, 2004, 23, 2679–2688.
2 E. T. Silveira, A. P. Umpierre, L. M. Rossi, G. Machado, J.
Morais, G. V. Soares, I. J. R. Baumvol, S. R. Teixeira, P. F. P.
Fichtner and J. Dupont, Chem. – Eur. J., 2004, 10, 3734–3740.
3 F. Jutz, J. M. Andanson and A. Baiker, J. Catal., 2009, 268,
2
2
2
3
56–366.
4 J. Julis, M. Hölscher and W. Leitner, Green Chem., 2010, 12,
634–1639.
1
5 D. Gonzalez-Galvez, P. Lara, O. Rivada-Wheelaghan, S.
Conejero, B. Chaudret, K. Philippot and P. W. N. M. van
Leeuwen, Catal. Sci. Technol., 2013, 3, 99–105.
42 S. Wesselbaum, U. Hintermair and W. Leitner, Angew.
Chem., Int. Ed., 2012, 51, 8585–8588.
3734 | Catal. Sci. Technol., 2015, 5, 3728–3734
This journal is © The Royal Society of Chemistry 2015