Selective Semihydrogenation of Alkynes with N-Graphitic-Modified Cobalt Nanoparticles Supported on Silica

Article abstract of DOI:10.1021/acscatal.6b03140

For the first time N-graphitic-modified cobalt nanoparticles (Co/phen@SiO₂-800) are shown to be active in the semihydrogenation of alkynes to alkenes. Key to success for efficient catalysis is both the modification of the metal nanoparticles by nitrogen-doped graphitic layers and the use of silica as support. Several internal alkynes are converted to the Z isomer in high yields with up to 93% selectivity. In addition, a variety of terminal alkynes, including sensitive functionalized compounds, are readily converted into terminal alkenes. Notably, this non-noble-metal catalyst allows for the purification of alkenes by selective hydrogenation of the corresponding alkyne in the presence of an excess of olefin.

Full text of DOI:10.1021/acscatal.6b03140

Subscriber access provided by Fudan University
Article
Selective Semi-Hydrogenation of Alkynes with N-Graphitic-
Modified Cobalt Nanoparticles Supported on Silica
Feng Chen, Carsten Robert Kreyenschulte, Jörg Radnik, Henrik
Lund, Annette#Enrica Surkus, Kathrin Junge, and Matthias Beller
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.6b03140 • Publication Date (Web): 11 Jan 2017
Downloaded from http://pubs.acs.org on January 12, 2017
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street
N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 9
ACS Catalysis
1
2
3
4
5
6
7
8
9
Selective Semi-Hydrogenation of Alkynes with N-Graphitic-Modified
Cobalt Nanoparticles Supported on Silica
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Feng Chen,† Carsten Kreyenschulte,† Jörg Radnik,† Henrik Lund,† Annette-Enrica Surkus,†
Kathrin Junge,† Matthias Beller*,†
†Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein Straße 29a, Rostock, 18059, Germany
Supporting Information Placeholder
ABSTRACT: For the first time N-graphitic-modified cobalt nanoparticles (Co/phen@SiO2-800) are shown to be active in the
semi-hydrogenation of alkynes to alkenes. Key to success for efficient catalysis is both the modification of the metal nanoparti-
cles by nitrogen-doped graphitic layers and the use of silica as support. Several internal alkynes are converted to the Z isomer in
high yields with up to 93% selectivity. In addition, a variety of terminal alkynes including sensitive functionalized compounds
are readily converted into terminal alkenes. Notably, this non-noble metal catalyst allows for the purification of alkenes by selec-
tive
hydrogenation
of
the
corresponding
alkyne
in
the
presence
of
an
excess
of
olefin.
KEYWORDS: Cobalt nanoparticles, Heterogeneous catalysis, Semi-hydrogenation, Nitrogen-doped material, Silica
alloy octahedral NCs with tunable shapes and compositions
for the selective semihydrogenation of alkynes.21 Apart from
INTRODUCTION
palladium, heterogeneous nickel22, rhodium23 and several
Compounds containing C−C double bonds are highly valua-
ble building blocks in organic synthesis due to their versatile
further functionalization. In fact, well-defined E- or Z-olefins
constitute an integral part of many biologically active mole-
cules.1 Hence, numerous methodologies such as Wittig reac-
24
gold-based
catalysts
(Au@CeO2
,
Au25(SR)18/TiO2,25
Au/TiO2-R26, Au/TiO227 and AuNPore28) were also investigat-
ed for Z-selective semi-hydrogenations. Complementary to
all these efforts, a few selective catalysts based on more
available first-row transition-metals such as Fe29 and metal-
lated porous organic polymers (e.g. V, Cr)30 have been re-
cently developed, demonstrating the actual interest in this
methodology.
tion,2
Horner−Emmons−Wadsworth
reaction,3
Julia−Kocienski reaction,4 Peterson reaction,5 Takai olefina-
tion,6 olefin metathesis,7 as well as cross-coupling reactions8
have been developed to create C−C double bonds. In addi-
tion, the reduction of alkynes is a perfect atom-economic and
useful route to alkenes.1,9 Although transfer hydrogenation
processes10,11 have been developed, the semi-hydrogenation of
alkynes to olefins using hydrogen gas (H2) is more attractive
because of its price and environmental benefits.
Most of the heterogeneous materials known for semi-
hydrogenation of alkynes make use of specific metal nano-
particles on a given inorganic support. In general, the activity
of these catalysts is controlled by the size and the shape of
the particles as well as their interaction with the support.
Hence, modification of the support surface allows one to
tune the selectivity and activity of such systems. In this re-
spect, nitrogen-containing carbon materials are known to
alter the individual physical and catalytic properties of metal
nanoparticles.31 More specifically, the development of N-
doped graphenes is of special interest because their redox
behavior can be easily controlled.32 Regarding the support,
silica-based materials are inexpensive, biocompatible and
show thermal and mechanical stability.33 For example, Taou-
fik and co-workers reported very recently silica-supported
frustrated Lewis pairs for the Z-selective reduction of 3-
hexyne.34 However, the property of N-doped cobalt nanopar-
ticles supported on silica and their activity for catalysis is still
unknown. Therefore, the exploration of easily preparation of
functionalized cobalt nanoparticles and their application in
organic synthesis is absorbing. Following our interest on the
development of novel base metal catalysts, herein the syn-
thesis of N-doped graphene catalysts supported on silica and
In particular, homogeneous palladium catalysts have been
investigated for the hydrogenation of alkynes in the last
decade.1 Moreover, other metal complexes of ruthenium,12
vanadium,13 chromium,11e niobium,14 and even iron15 as well
16
as cobalt
were described for this reaction. Especially in
industry, heterogeneous catalysts are applied for the semi-
hydrogenation of alkynes due to their potential reusability
and recyclability. The most prominent example is the so-
called Lindlar catalyst (Pd/CaCO3 poisoned with Pb(OAc)2
and quinoline), which is well known for the selective hydro-
genation of alkynes to Z-alkenes.1,17 In the last decade, palla-
dium nanoparticles became attractive catalyst materials for
the selective semi-hydrogenation of alkynes.18 For example,
in 2014 Lipshutz and co-workers developed an elegant system
consisting of Pd nanoparticles in nanomicelles.19 Most re-
cently, the group of Bäckvall reported supported Pd NP on
amino-functionalized mesoporous hollow silica nanospheres
(Pd0-AmP-HSN) for Z-selective hydrogenations of alkynes.20
In addition, Yan, Lu and their co-workers reported the Pd-Pb
ACS Paragon Plus Environment

ACS Catalysis
Page 2 of 9
c
1
2
3
their efficient application for alkyne semi-hydrogenations are
described.
yield using dodecane as internal standard. Reaction time is
10 h. d20 bar H2.
4
RESULTS AND DISCUSSION
5
Initially, several cobalt catalysts immobilized on SiO2, C, B4C,
α-Al2O3 were prepared by pyrolysis (600 to 900 °C) of
Co(OAc)2 in the presence of 1,10-phenanthroline (1,10-phen),
2,2’-bipyridine (bipy) and terpyridine (terpy) under inert
conditions (argon atmosphere). All the resulting materials
showed activity in the semi-hydrogenation of the benchmark
substrate 1,2-diphenylethyne (1a) in acetonitrile at 30 bar of
H2 and 120 °C. As shown in Table 1, the heterogeneous cobalt
system prepared at 800 °C on SiO2 (Co/phen@SiO2) provided
the highest activity and selectivity for the formation of Z-
stilbene (100% conversion and 90% selectivity; Table 1, entry
4). Interestingly, in most cases no further hydrogenation
towards 1,2-diphenylethane (4a) was observed. Notably, this
hydrogenation process is influenced by the support, the
pyrolysis temperature and the ligand. Hence, cobalt materi-
als supported on C, α-Al2O3 and B4C were significant less
regioselective. For instance, the α-Al2O3 supported cobalt
catalyst35 which show high activity for hydrogenation gave
low conversion for the alkyne hydrogenation. Catalytic mate-
rials formed at 700 oC showed less selectivity as well as which
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. Powder diffraction pattern of cobalt catalysts
Co/phen@SiO2 prepared at different conditions: Without
pyrolysis (a), (b) – (e) pyrolysis at 600, 700, 800, 900 °C,
respectively. Phases are indicated as circles (Co), triangles
(CoO), squares (Co3O4).
Next, detailed characterizations of selected catalysts were
done to better understand their behavior. Firstly, the
Co/phen@SiO2 catalysts prepared under different conditions
were characterized by powder diffraction. Before pyrolysis
the deposited catalysts precursor (Figure1, pattern a) can be
determined as [Co(1,10-phen)2(H2O)2]OAc2∙6H2O (see Figure
S4)36.
o
formed at 600 C was less active in this benchmark process
(Table 1, entries 6-7). Notably, in case of Co/terpy@SiO2 a
good catalytic performance was obtained which is compara-
ble to Co/phen@SiO2 (Table 1, entries 4, 5, 9). Due to eco-
nomic advantages, the catalyst prepared from Co(OAc)2 and
1,10-phenanthroline was chosen for further tests. Interesting-
ly, the heterogeneous catalyst prepared in the presence of the
ligand is much more active compared to cobalt acetate pyro-
lysed on SiO2 (Table 1, entry 10). As expected, the material
prepared without cobalt acetate as well as the homogeneous
cobalt acetate phenanthroline complex gave very low conver-
sion (Table 1, entries 11-12). Variation of the critical reaction
parameters (solvent, reaction time and pressure of H2) led to
the best conditions (30 bar of hydrogen gas at 120 oC for 15 h;
Table 1, entries 13-14 and Table S1).
(a)
(b)
Table 1. Cobalt-catalyzed semi-hydrogenation of 1,2-
diphenylethyne: Variation of catalysts.a
(c)
(d)
catalyst ( 1 mol%)
Ph
Ph
Ph
+
Ph
Ph
Ph
+
Ph
H2 (30 bar)
MeCN, 120 oC
Ph
1a
2a (Z)
3a (E)
4a
yield (%)b
entry
precursor
ligand
support
C
pyrolysis conv.
T (oC)
2a
3a
4a
Co(OAc)2
Co(OAc)2
Co(OAc)2
Co(OAc)2
Co(OAc)2
Co(OAc)2
Co(OAc)2
1
1,10-phen
800
68
58
9
trace
2
3
4
5
6
1,10-phen
1,10-phen
1,10-phen
1,10-phen
1,10-phen
α
800
800
800
900
700
16
100
100
99
3
13
26
9
trace
trace
trace
trace
1
-Al2O3
B4C
74
90
90
78
SiO2
SiO2
SiO2
SiO2
10
21
99
7
8
9
1,10-phen
bipyridine
terpyridine
600
800
800
76
62
99
70
58
88
6
4
trace
trace
1
Co(OAc)2
Co(OAc)2
SiO2
SiO2
10
10
11
Co(OAc)2
--
--
SiO2
SiO2
800
800
29
4
26
0
2
1
0
2
1,10-phen
Co(OAc)2
SiO2
SiO2
SiO2
12
13c
14d
1,10-phen
1,10-phen
1,10-phen
--
2
78
0
68
70
2
8
0
trace
4
Co(OAc)2
Co(OAc)2
800
800
100
26
b
a0.25 mmol 1,2-diphenylethyne in 2 mL MeCN for 15 h. GC
ACS Paragon Plus Environment

Page 3 of 9
ACS Catalysis
1
2
3
to them, metallic Co particles are sometimes covered by
graphitic shells or attached to tubular or even more complex
graphitic structures.
(e)
(f)
4
5
6
7
8
The surface composition and element analysis of the materi-
als are summarized in Table 2. Pyrolysis at 700 to 900 °C led
to active catalysts, which contain 23.47%-29.48% carbon by
XPS measurements (Table 2). Materials prepared without
ligand or using bipyridine as ligand showed low activity and
contained very low amounts of carbon (1.0% and 1.43%).
Moreover, no nitrogen was detected for these latter two
materials by XPS and element analysis. These results clearly
show that the nitrogen doped graphitic layers are crucial for
the activity in semi-hydrogenation of alkynes. The chemical
state of Co and N was also measured with XPS. The N 1s
spectrum of the materials (Co/Phen@SiO2-900;-800;-700)
disclosed graphitic, pyrrolic and pyridinic nitrogen or nitro-
gen species bound to Co32c,f,38 (Figure 3). The less active cata-
lyst prepared at 600 °C contained oxidized nitrogen and
mainly pyridinic nitrogen. Notably, the presence of N-doped
graphitic layers on the support promote the semi-
hydrogenation of alkynes and the material prepared without
1,10-phenanthroline showed only low activity (Table 1, entry
10). This beneficial effect of N-doped graphitic layers is ex-
plained by a more facile heterolytic activation of molecular
hydrogen.39 In addition, the formed N-doped carbon materi-
als might influence the cobalt nanoparticles also electronical-
ly.40
9
10
11
12
13
14
15
16
17
18
19
20
21
(g)
(h)
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2. STEM measurements of Co/phen@SiO2-800: a-b)
high angle annular dark field (HAADF) and annular bright
field (ABF) images showing a metallic Co particle surrounded
by graphitic carbon, c-d) HAADF and ABF images showing
the variety of Co-containing particles attached to the support
and the attached carbon, e-h) STEM-EDX mapping of the
previous catalyst region showing the carbon/cobalt structure
present in the fresh specimen: e) overlay of cobalt (red),
carbon (green) and silica (blue) maps, f) cobalt map, g) car-
bon map, h) silica map. The SiO2 particle in the upper left
corner moved during acquisition while the rest stayed stable.
The corresponding EDX spectrum of the area is shown in
Figure S2.
The Co 2p spectrum of Co/phen@SiO2-800 revealed 780.3 eV
for Co 2p3/2 and 796.8 eV for Co 2p1/2 (Figure S8). These re-
sults indicate that mixtures of cobalt (II/III) exist on the
surface. There is a slight shift observed in the Co 2p level to
higher binding energy for the materials prepared at other
temperatures or using bipyridine as ligand. Meanwhile, the
Co/terpy@SiO2-800 gave a slight shift to lower binding ener-
gy which could be attributed to metallic cobalt (see SI). This
assumption is supported by the XRD measurements.
While no crystalline Co-phases can be identified by diffrac-
tion methods after pyrolysis at 600 °C, metallic cobalt, CoO
and Co3O4 can be discussed at higher pyrolysis temperatures.
It should be noted that the differentiation of the cobalt oxide
phases is uncertain due to the similar position of the main
reflection peaks and the low catalyst loading. Anyway, it can
be stated clearly that the crystallite sizes of the metallic co-
balt phase does change remarkably if higher pyrolysis tem-
peratures are applied (cf. 8.0 nm at 700 °C, 2.7 nm at 800 and
900 °C).37 In contrast to the Co/phen@SiO2 catalysts the
formation of CoO and Co3O4 seems to be favored if only the
pure cobalt acetate was pyrolysed or bipy was used as N-
containing ligand. In these cases the resulting catalysts
showed significantly lower activity for the benchmark reac-
tion (Table 1, entries 8 and 10, cf. Figure S6).
The kinetic data for the selective hydrogenation of 1,2-
diphenylethyne (1a) using catalyst Co/Phen@SiO2-800 is
shown in Figure 4. Full conversion was obtained after 15 h
and 90 % Z-stilbene was obtained. Meanwhile, only trace
amounts of over-hydrogenated 1,2-diphenylethane (4a) were
detected. These results indicate that the Co/Phen@SiO2-800
catalyst operates highly chemo- and stereoselective under
these conditions. Control experiments showed that Z-
stilbene is slowly converted to the corresponding E-stilbene
and that this reaction even proceeds without any catalyst,
albeit extremely slowly. Regarding chemoselectivity, only
trace amounts of over-hydrogenated 1,2-diphenylethane were
detected with or without catalyst. Moreover, E-stilbene is not
transformed into 1,2-diphenylethane in the presence of this
catalytic system (Scheme 1, a-d).
The most active catalyst Co/phen@SiO2-800 was investigated
by scanning transmission electron microscopy (STEM) analy-
sis (Figure 2), showing different types of cobalt-containing
structures. In fact, a wide variety of Co-containing particles
was formed. There are metal Co particles, Co-oxide particles
and core-shell type particles, where a metal center is at least
partially covered by small Co-oxide crystallites. Most of the
particles are closely attached to the support SiO2. Particle
sizes range from a few nanometers to about 50 nm. While Co
oxide particles usually show no graphitic structures attached
ACS Paragon Plus Environment

ACS Catalysis
Page 4 of 9
1
2
3
4
5
6
7
8
9
1800
1600
1400
1200
1000
(a)
(b)
(c)
(d)
(e)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
408 406 404 402 400 398 396 394
Binding Energy / eV
Figure 3. XPS measurements (N 1s) of (a) Co/phen@SiO2-
900; (b) Co/phen@SiO2-800; (c) Co/phen@SiO2-700; (d)
Co/phen@SiO2-600 and (e) Co @SiO2-800.
Table 2. XPS measurements of cobalt, nitrogen and
carbon content for the catalysts prepared on SiO2.
Co
(%)
content
N content (%)
C content (%)
Catalyst
XPS
0.25
EA
XPS
1.67
EA
0.62
XPS
EA
Co/Phen@SiO2-
900
Co/Phen@SiO2-
800
Co/Phen@SiO2-
700
Co/Phen@SiO2-
600
3.21
29.48
14.57
0.56
0.61
1.29
3.16
3.17
1.90
2.61
4.70
0.95
1.41
23.47
28.73
31.73
14.13
13.59
12.61
2.98
2.69
Co@SiO2-800
0.46
0.52
0.21
2.91
3.42
3.00
--
--
--
--
1.00
1.43
0.03
0.03
13.20
Co/bipy@SiO2-800
Co/terpy@SiO2-
800
Co/Phen@SiO2
3.10
0.41
27.77
0.70
2.54
8.06
2.92
45.02
15.96
100
80
60
40
20
0
1a
2a
3a
4a
0
5
10
15
20
25
time / h
Figure 4. Concentration/time diagram for the hydro-
genation of 1a using Co/Phen@SiO2-800.
ACS Paragon Plus Environment

Page 5 of 9
ACS Catalysis
1
2
3
4
yn-1-ylbenzene was tested under standard conditions and
high yield was obtained. However, the selectivity of Z/E is
only 3 : 2. Furthermore, the internal aliphatic alkyne oct-3-
o
yn-1-ol was selectively hydrogenated (40 bar H2, 85 C , 10 h)
5
6
7
8
to give (Z)-oct-3-en-1-ol in 63% yield (Table 4, entry 12). As
shown for the benchmark reaction, the catalyst can be easily
recycled by centrifugation (Table 4, entries 1-3). The liquid
phase after centrifugation was collected and analyzed by ICP-
MS. The result disclosed that no leaching occurred during
the reaction.
9
10
11
12
Table 4. Cobalt-catalyzed semi-hydrogenation of
various internal alkynes.a
Scheme 1. Control experiments.
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
To elucidate in more detail the active sites, the prepared
catalyst was washed with different solutions of hydrochloride
acid (1M and 2 M) for 30 min or (0.1 M and 0.2 M) for 2 min.
This procedure allows to remove cobalt oxide particles from
the surface and some metallic cobalt particles. Both of the
obtained materials were then characterized by XPS. As ex-
pected, the cobalt composition (Co2+ and Co3+) on the sur-
face decreased after washing (see SI). XRD measurements
showed that the cobalt oxide phase almost disappeared after
washing while some metallic cobalt was left. As shown in
Table 3, the activity of the catalysts washed with 1 M and 2 M
HCl decreased significantly for the semi-hydrogenation of
diphenylacetylene under the standard reaction conditions.
Besides, the selectivity for Z-stilbene also declined to 1.2 : 1
(Table 3, entries 1-2). Catalysts washed with 0.1 M and 0.2 M
HCl gave similar results (Table 3, entries 5-6). Hence, we
conclude that the cobalt oxide phase (Co2+ or Co3+) is also
crucial to obtain high activity and selectivity in this semi-
hydrogenation reaction in addition to the metallic cobalt
aReaction conditions: 0.25 mmol alkyne with 5-20 mg cata-
lyst. b Isolated yield and the ratio of Z/E is determined by
NMR. cGC yield using dodecane as an internal standard.
e
f
o
dAfter 2 runs. After 3 runs. 85 C, some other isomers were
detected.
with N-doped graphitic layers32c
.
Table 5. Cobalt catalyzed semi-hydrogenation of var-
ious terminal alkynes. a
Table 3. Cobalt-catalyzed semi-hydrogenation of 1,2-
diphenylethyne: Catalytic activity of catalysts washed
with HCl.a
aReaction conditions: 0.25 mmol alkyne with 5-20 mg cata-
lyst.
To explore the general performance of the most active cobalt
catalyst, the semi-hydrogenation of several internal aryl and
aliphatic alkynes were investigated. Aromatic substrates with
electron-donating groups and electron-withdraw groups
were converted to the corresponding alkenes in excellent
yields. In general, high selectivity for the Z isomer formation
(up to 93%) was achieved for these substrates. Interestingly,
halogenated (Cl and Br) diaryl alkynes are also compatible
with this cobalt system (Table 4, entries 4-6). Besides, prop-1-
ACS Paragon Plus Environment

ACS Catalysis
Page 6 of 9
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 5. Showcase of alkene purification using
Co/phen@SiO2-800.
CONCLUSION
In conclusion, we have developed a novel heterogeneous
cobalt catalyst on silica (Co/phen@SiO2-800), which is modi-
fied with N-doped graphitic layers. It shows high activity and
selectivity for the semi-hydrogenation of both internal and
terminal alkynes. Detailed characterizations disclose that
both metallic cobalt and cobalt oxide nanoparticles are ob-
tained during the pyrolysis process at 800 oC. Moreover,
nitrogen-doped graphitic layers are also formed which are
crucial for the high activity and selectivity in this transfor-
mation. Notably, the high chemoselectivity of this novel
heterogeneous cobalt catalyst is illustrated in the hydrogena-
tion of phenylacetylene in the presence of an excess of sty-
rene. This catalyst supplies an easy route to prepare N-doped
cobalt nanoparticles and apply it in semi-hydrogenation
sucessfully.
b
a0.5 mmol scale. GC yield using dodecane as an internal
standard; the yields in parentheses belong to the correspond-
ing over-hydrogenated products. 40 bar H2. Isolated yield
and ratio was determined by NMR.
c
d
In addition to internal alkynes, next different terminal al-
kynes were tested for the synthesis of terminal alkenes.
Ethynylbenzene gave 73% yield of styrene with full conver-
sion at standard conditions. Notably, only traces of ethylben-
zene were obtained. Hence, we believe that poly- or oli-
gomerization of the substrate or product constitutes the
major side-reactions. To reduce such processes, the reaction
EXPERIMENTAL SECTION
Preparation of heterogeneous Co catalyst on silica :
Co(OAc)2•4H2O (126.8 mg, 0.5 mmol) and 1,10-
phenanthroline (182.0 mg, 1.0 mmol) (Co:phenanthroline =
1:2 molar ratio) were stirred in ethanol (20 mL) for approxi-
mately 15 minutes at room temperature. Then the whole
o
o
was conducted at lower temperature (90 C) and to our de-
reaction mixture was agitated at 60 C for 1 hour. The sup-
light the yield of styrene increased to 88% (Table 5, entries 1-
3). Next, several other aryl and aliphatic terminal alkynes
were hydrogenated in the presence of 1-4 mol% catalyst at
port SiO2 (691.2 mg, Aerosil, OX-50 from EVONIK) was then
added and the mixture was stirred at room temperature
overnight. Then the ethanol was removed in vacuum and
leaving behind a pale brown solid that was dried at the pump.
The sample was grinded to a fine powder which was then
transferred to a ceramic crucible and placed in the oven. The
latter was evacuated to ca. 5 mbar and then flushed with
argon three times. The furnace was heated to 800 °C at a rate
of 25 °C per minute and held at 800 °C for 2 hours under
argon atmosphere. After the heating was switched off the
oven was allowed to reach room temperature. During the
whole process argon was constantly passed through the oven.
o
90-120 C. The corresponding products were obtained selec-
tively in up to 85% yield (Table 5, entries 4-14). Even sensi-
tive propargylic alcohols can be reduced as shown in the
reaction of 17α-ethynylestradiol (Table 5, entries 15-16).
Apart from its synthetic value, the semi-hydrogenation of
alkynes to alkenes is of special importance in the chemical
industry. For example, the removal of alkyne impurities from
alkenes is essential for the valorization of bulk feedstocks, e.g.
for industrial polymerizations. In these processes the catalyst
has to selectively reduce the alkyne in the presence of a large
excess of olefin. To demonstrate the principle feasibility of
our novel system for such transformations, we hydrogenated
a mixture of styrene and ethynylbenzene with a large excess
of the olefin (50 mg, 93.8/6.2) at 40 bar H2 with 40 mg cata-
lyst. After 2.5 h ethynylbenzene was hydrogenated complete-
ly and styrene was obtained in 99% purity (Figure 5). This
result highlights the potential application of cobalt catalysts
for the industrial purification of alkenes.
Catalytic hydrogenation of alkynes: The catalytic activity
tests were performed in a 300 ml autoclave advanced with an
internal aluminum plate to include seven uniform reaction
glass vials (4 ml) with cap, septum and needle. (Figure S1)
The autoclave is placed into an aluminum block as heating
system to perform the reactions. 1,2-diphenylethyne 1a (0.25
mmol) and cobalt catalyst were mixed with 2 mL MeCN in a
reaction vial (4 mL). The autoclave was flushed with hydro-
gen gas twice and pressurized with hydrogen. After comple-
ACS Paragon Plus Environment

Page 7 of 9
ACS Catalysis
1
2
3
4
5
6
7
8
11. (a) Wang, G.-H.; Bin, H.-Y.; Sun, M.; Chen, S.-W.; Liu, J.-H.;
tion of the reaction time, the autoclave was cooled to room
Zhong, C.-M., Tetrahedron 2014, 70, 2175-2179; (b) Cao, H.; Chen,
T.; Zhou, Y.; Han, D.; Yin, S.-F.; Han, L.-B., Adv. Synth. Catal.
2014, 356, 765-769; (c) Whittaker, A. M.; Lalic, G., Org. Lett. 2013,
15, 1112-1115; (d) Semba, K.; Fujihara, T.; Xu, T.; Terao, J.; Tsuji, Y.,
Adv. Synth. Catal. 2012, 354, 1542-1550; (e) Reyes-Sánchez, A.;
Cañavera-Buelvas, F.; Barrios-Francisco, R.; Cifuentes-Vaca, O. L.;
Flores-Alamo, M.; García, J. J., Organometallics 2011, 30, 3340-
3345; (f) Sodeoka, M.; Shibasaki, M., J. Org. Chem. 1985, 50, 1147-
1149.
12. (a) Shvo, Y.; Goldberg, I.; Czerkie, D.; Reshef, D.; Stein, Z.,
Organometallics 1997, 16, 133-138; (b) Radkowski, K.; Sundararaju,
B.; Fürstner, A., Angew. Chem. Int. Ed. 2013, 52, 355-360; (c)
Karunananda, M. K.; Mankad, N. P., J. Am. Chem. Soc. 2015, 137,
14598-14601.
13. (a) La Pierre, H. S.; Arnold, J.; Toste, F. D., Angew. Chem. Int.
Ed. 2011, 50, 3900-3903.
14. Gianetti, T. L.; Tomson, N. C.; Arnold, J.; Bergman, R. G., J.
Am. Chem. Soc. 2011, 133, 14904-14907.
15. (a) Srimani, D.; Diskin-Posner, Y.; Ben-David, Y.; Milstein,
D., Angew. Chem. Int. Ed. 2013, 52, 14131-14134; (b) Wienhofer, G.;
Westerhaus, F. A.; Jagadeesh, R. V.; Junge, K.; Junge, H.; Beller,
M., Chem. Comm. 2012, 48, 4827-4829.
16. Fu, S.; Chen, N.-Y.; Liu, X.; Shao, Z.; Luo, S.-P.; Liu, Q., J.
Am. Chem. Soc. 2016, 138, 8588-8594.
temperature and hydrogen was released. Dodecane (50 µL)
was added to the crude reaction mixture as internal standard
and analyzed by GC-FID.
Procedure for the purification of alkene: The experiment
was performed in a 300 ml autoclave advanced with an inter-
nal aluminum plate to include seven uniform reaction glass
vials (4 ml) with cap, septum and needle. (Figure S1) The
autoclave is placed into an aluminum block as heating sys-
tem to perform the reactions. The mixture of styrene and
ethynylbenzene (50 mg, 93.8% of styrene) was treated with
40 mg catalyst in 2 mL MeCN under 40 bar H2 for 2.5 h. Then
the autoclave was cooled to room temperature and hydrogen
was released. Dodecane (50 µL) was added to the crude reac-
tion mixture as internal standard and analyzed by GC-FID.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
AUTHOR INFORMATION
Corresponding Author
Matthias.Beller@catalysis.de
Notes
The authors declare no competing financial interest.
17. Lindlar, H., Helv. Chim. Acta 1952, 35, 446-450.
18. Venkatesan, R.; Prechtl, M. H. G.; Scholten, J. D.; Pezzi, R.
P.; Machado, G.; Dupont, J., J. Mater. Chem. 2011, 21, 3030-3036.
19. (a) Slack, E. D.; Gabriel, C. M.; Lipshutz, B. H., Angew.
Chem. Int. Ed. 2014, 53, 14051-14054.
20. Verho, O.; Zheng, H.; Gustafson, K. P. J.; Nagendiran, A.;
Zou, X.; Bäckvall, J.-E., ChemCatChem 2016, 8, 773-778.
21. Niu, W.; Gao, Y.; Zhang, W.; Yan, N.; Lu, X., Angew. Chem.
Int. Ed. 2015, 54, 8271-8274.
22. (a) Konnerth, H.; Prechtl, M. H. G., Chem. Comm. 2016, 52,
9129-9132; (b) Schutte, K.; Doddi, A.; Kroll, C.; Meyer, H.;
Wiktor, C.; Gemel, C.; van Tendeloo, G.; Fischer, R. A.; Janiak, C.,
Nanoscale 2014, 6, 5532-5544; (c) Alonso, F.; Osante, I.; Yus, M.,
Adv. Synth. Catal. 2006, 348, 305-308; (d) Nitta, Y.; Imanaka, T.;
Teranishi, S., Bull. Chem. Soc. Jpn 1981, 54, 3579-3580; (e) Brunet,
J. J.; Gallois, P.; Caubere, P., J. Org. Chem. 1980, 45, 1937-1945; (f)
Brown, C. A.; Ahuja, V. K., J. Chem. Soc., Chem. Commun. 1973,
553-554.
23. (a) Furukawa, S.; Komatsu, T., ACS Catal. 2016, 6, 2121-2125;
(b) Köhler, D.; Heise, M.; Baranov, A. I.; Luo, Y.; Geiger, D.; Ruck,
M.; Armbrüster, M., Chem. Mater. 2012, 24, 1639-1644.
24. Mitsudome, T.; Yamamoto, M.; Maeno, Z.; Mizugaki, T.;
Jitsukawa, K.; Kaneda, K., J. Am. Chem. Soc. 2015, 137, 13452-13455.
25. Li, G.; Jin, R., J. Am. Chem. Soc. 2014, 136, 11347-11354.
26. Li, S.-S.; Tao, L.; Wang, F.-Z.-R.; Liu, Y.-M.; Cao, Y., Adv.
Synth. Catal. 2016, 358, 1410-1416.
27. Liang, S.; Hammond, G. B.; Xu, B., Chem. Comm. 2016, 52,
6013-6016.
28. (a) Wagh, Y. S.; Asao, N., J. Org. Chem. 2015, 80, 847-851; (b)
Yan, M.; Jin, T.; Ishikawa, Y.; Minato, T.; Fujita, T.; Chen, L.-Y.;
Bao, M.; Asao, N.; Chen, M.-W.; Yamamoto, Y., J. Am. Chem. Soc.
2012, 134, 17536-17542.
29. Gieshoff, T. N.; Welther, A.; Kessler, M. T.; Prechtl, M. H.;
Jacobi von Wangelin, A., Chem. Commun. 2014, 50, 2261-2264.
30. Tanabe, K. K.; Ferrandon, M. S.; Siladke, N. A.; Kraft, S. J.;
Zhang, G.; Niklas, J.; Poluektov, O. G.; Lopykinski, S. J.; Bunel, E.
E.; Krause, T. R.; Miller, J. T.; Hock, A. S.; Nguyen, S. T., Angew.
Chem. Int. Ed. 2014, 53, 12055-12058.
ASSOCIATED CONTENT
Supporting Information
Additional experimental results, procedures and characteri-
zation data. This material is available free of charge via the
Internet at http://pubs.acs.org.
ACKNOWLEDGMENT
The Federal Ministry of Education and Research (BMBF) and
the State of Mecklenburg-Vorpommern are gratefully
acknowledged for their general support. We thank the ana-
lytical department of the Leibniz-Institute for Catalysis,
Rostock for their excellent analytical service. We thank Dr.
Matthias Schneider and Dr. Marga-Martina Pohl for the
characterization of the catalysts.
REFERENCES
1. Oger, C.; Balas, L.; Durand, T.; Galano, J.-M., Chem. Rev. 2013,
113, 1313-1350.
2. (a) Maryanoff, B. E.; Reitz, A. B., Chem. Rev. 1989, 89, 863-
927; (b) Wittig, G.; Schöllkopf, U., Chem. Ber. 1954, 1318−1330.
3. (a) Boutagy, J.; Thomas, R., Chem. Rev. 1974, 74, 87-99; (b)
Wadsworth, W. S.; Emmons, W. D., J. Am. Chem. Soc. 1961, 83,
1733-1738; (c) Horne, L.; Hoffmann, H.; Wippel, H. G., Chem. Ber.
1958, 91, 61–63.
4. Blakemore, P. R., J. Chem. Soc., Perkin Trans. 1 2002, 2563-
2585.
5. Peterson, D. J., J. Org. Chem. 1968, 33, 780-784.
6. Takai, K.; Nitta, K.; Utimoto, K., J. Am. Chem. Soc. 1986, 108,
7408-7410.
7. Vougioukalakis, G. C.; Grubbs, R. H., Chem. Rev. 2010, 110,
1746-1787.
8. (a) Dounay, A. B.; Overman, L. E., Chem. Rev. 2003, 103,
2945-2964; (b) Beletskaya, I. P.; Cheprakov, A. V., Chem. Rev.
2000, 100, 3009-3066.
9. Siau, W. Y.; Zhang, Y.; Zhao, Y., Top. Curr. Chem. 2012, 327,
33-58.
10. Wang, D.; Astruc, D., Chem. Rev. 2015, 115, 6621-6686.
ACS Paragon Plus Environment

ACS Catalysis
Page 8 of 9
1
31. (a) Li, M.; Xu, F.; Li, H.; Wang, Y., Catal. Sci. Technol. 2016,
Boissiere, C.; Chaneac, C.; Grosso, D.; Vasseur, S.; Miraux, S.;
2
3
4
5
6
7
8
9
6, 3670-3693; (b) Wang, H.; Maiyalagan, T.; Wang, X., ACS Catal.
2012, 2, 781-794.
Duguet, E.; Sanchez, C. J. Mater. Chem. 2007, 17, 1563-1569. (f)
Min, B. K .; Santra1, A. K.; Goodman, D. W. Catal. Today 2003,
85, 113-124.
32. (a) Wei, Z.; Chen, Y.; Wang, J.; Su, D.; Tang, M.; Mao, S.;
Wang, Y. ACS Catal. 2016, 6, 5816-5822 (b) Maleki, A.; Aghaei, M.;
Ghamari, N. Appl. Organometal. Chem. 2016, 30, 939-942. (c)
Wei, Z.; Wang, J.; Mao, S.; Su, D.; Jin, H.; Wang, Y.; Xu, F.; Li, H.;
Wang, Y., ACS Catal. 2015, 5, 4783-4789; (d) Zhong, W.; Liu, H.;
Bai, C.; Liao, S.; Li, Y., ACS Catal. 2015, 5, 1850-1856; (e) Shen, K.;
Chen, L.; Long, J.; Zhong, W.; Li, Y., ACS Catal. 2015, 5, 5264-5271;
(f) Han, C.; Bo, X.; Zhang, Y.; Li, M.; Wang, A.; Guo, L., Chem.
Commun. 2015, 51, 15015-15018; (g) Wang, Y.; Nie, Y.; Ding, W.;
Chen, S. G.; Xiong, K.; Qi, X. Q.; Zhang, Y.; Wang, J.; Wei, Z. D.,
Chem. Commun. 2015, 51, 8942-8945; (h) Maleki, A.; Paydar, R.
RSC Adv. 2015, 5, 33177-33184; (i) Maleki, A.; Ghamari; N.;
Kamalzare, M. RSC Adv. 2014, 4, 9416-9423; (j) Westerhaus, F. A.;
Jagadeesh, R. V.; Wienhöfer, G.; Pohl, M.-M.; Radnik, J.; Surkus,
A.-E.; Rabeah, J.; Junge, K.; Junge, H.; Nielsen, M.; Brückner, A.;
Beller, M., Nat. Chem. 2013, 5, 537-543; (k) Jagadeesh, R. V.;
Surkus, A.-E.; Junge, H.; Pohl, M.-M.; Radnik, J.; Rabeah, J.; Huan,
H.; Schünemann, V.; Brückner, A.; Beller, M., Science 2013, 342,
1073-1076.
34. Szeto, K. C.; Sahyoun, W.; Merle, N.; Castelbou, J. L.; Popoff,
N.; Lefebvre, F.; Raynaud, J.; Godard, C.; Claver, C.; Delevoye, L.;
Gauvin, R. M.; Taoufik, M., Catal. Sci. Technol. 2016, 6, 882-889.
35. (a) Chen, F.; Topf, C.; Radnik, J.; Kreyenschulte, C.; Lund,
H.; Schneider, M.; Surkus, A.-E.; He, L.; Junge, K.; Beller, M. J.
Am. Chem. Soc. 2016, 138 , 8781-8788; (b) Chen, F.; Surkus, A.-E.;
He, L.; Pohl, M.-M.; Radnik, J.; Topf, C.; Junge, K.; Beller, M. J.
Am. Chem. Soc. 2015, 137, 11718-11724..
36. Carballo, R.; Covelo, B.; Vazques-Lopez, E.; Garcia-
Martinez, E., Z. Anorg. Allg. Chem. 2003, 629, 244-248.
37. Crystallite size was calculated by applying the Scherrer
equation using the integral breadth under the assumption of
sperical shaped crystallites. K is set to 1.0747. The crystallite size
value was calculated for all reflection peaks of the Co phase and
the mean value is presented here.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
38. Wood , K. N.; O'Hayre, R.; Pylypenko, S. Energy Environ.
Sci. 2014, 7, 1212-1249.
39. Cheng, T.; Yu, H.; Peng, F.; Wang, H.; Zhang, B.; Su, D.,
Catal. Sci. Technol. 2016, 6, 1007-1015.
40. He, L.; Weniger, F.; Neumann, H.; Beller, M., Angew. Chem.
Int. Ed. 2016, 55, 12582-12594.
33. For some selected examples using silica as support, see(a)
Maleki, A.; Rabbani, M.; Shahrokh, S. Appl. Organometal. Chem.
2015, 29, 809-814; (b) Maleki, A. Helv. Chim. Acta, 2014, 97, 587-
593; (c) Maleki, A. Tetrahedron Lett. 2013, 54, 2055-2059; (d)
Maleki, A. Tetrahedron, 2012, 68, 7827-7833; (e) Julian-Lopez, B.;
ACS Paragon Plus Environment

Page 9 of 9
ACS Catalysis
TOC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
9
ACS Paragon Plus Environment