Alkyne-Functionalized Ruthenium Nanoparticles: Impact of Metal-Ligand Interfacial Bonding Interactions on the Selective Hydrogenation of Styrene

Article abstract of DOI:10.1021/acscatal.8b04028

In the present study, ruthenium nanoparticles functionalized with terminal and internal alkynes were prepared, and it was found that internal alkynes formed a η² side-on configuration on the surface of ruthenium nanoparticles, in sharp contrast to the ruthenium-vinylidene interfacial bonds for terminal alkynes. For the nanoparticles capped with terminal alkyne, hydrogenation of both the vinyl moiety and phenyl ring occurred, whereas selective hydrogenation of the vinyl moiety was observed with internal alkyne-functionalized nanoparticles. This work highlights the importance of the metal-organic interface in the rational design and engineering of the nanoparticle catalyst for organic synthesis.

Full text of DOI:10.1021/acscatal.8b04028

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Letter
Alkyne-functionalized ruthenium nanoparticles: impact of metal-ligand
interfacial bonding interactions on the selective hydrogenation of styrene
Fengqi Zhang, Jingjing Fang, Lin Huang, Wenming Sun,
Zhang Lin, Zhenqing Shi, Xiongwu Kang, and Shaowei Chen
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b04028 • Publication Date (Web): 30 Nov 2018
Downloaded from http://pubs.acs.org on November 30, 2018
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Alkyne-Functionalized Ruthenium Nanoparticles: Impact of Metal-Ligand
Interfacial Bonding Interactions on the Selective Hydrogenation of Styrene
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Fengqi Zhang†,a Jingjing Fang†,a Lin Huang†,a Wenming Sun,b Zhang Lin,c Zhenqing Shi c,
Xiongwu Kang*a and Shaowei Chen*a,d
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a Guangzhou Key Laboratory for Surface Chemistry of Energy Materials, New Energy Research
Institute, School of Environment and Energy, South China University of Technology,
Guangzhou Higher Education Mega Centre, Guangzhou 510006, China
b State Key Laboratory of Green Building Materials, China Building Materials Academy, Beijing
100041, China
c Guangdong Engineering and Technology Research Center for Environmental Nanomaterials,
School of Environment and Energy, South China University of Technology, Guangzhou,
Guangdong 510006, China
d Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa
Cruz, California 95064, United States
* E-mails: esxkang@scut.edu.cn; shaowei@ucsc.edu
† equal contributing authors
ABSTRACT
In the present study, ruthenium nanoparticles functionalized with terminal and internal
alkynes were prepared and it was found that internal alkynes formed a η2 side-on configuration
on ruthenium nanoparticles surface, in sharp contrast to the ruthenium-vinylidene interfacial
bonds for terminal alkynes. For the nanoparticles capped with internal alkyne, hydrogenation of
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both the vinyl moiety and phenyl ring occurred, whereas selective hydrogenation of the vinyl
moiety was observed with terminal alkyne-functionalized nanoparticles. This work highlights the
importance of metal-organic interface in the rational design and engineering of nanoparticle
catalyst for organic synthesis.
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KEYWORDS: ruthenium nanoparticles, internal alkyne, η2 side-on configuration, σ-π covalent,
interfacial charge transfer, styrene hydrogenation
Introduction
Catalysis plays a critical role in the production and transformation of valuable chemicals,
where high selectivity towards desired molecules and compounds significantly reduces the
amount of chemical wastes generated and represents an important part in the quest for “green
chemistries”.1-4 Towards this end, a range of synthetic approaches based on nanotechnology have
been reported in recent literatures.5 Among them, surface functionalization of transition metal
nanoparticles by selecting organic capping ligands has been demonstrated to be a powerful tool
in the manipulation and enhancement of the nanoparticle catalytic performance.6-11 For instance,
as one of the capping ligands, terminal alkyne molecules have been demonstrated effective in
modulating the catalytic activity of the metal nanoparticles in heterogeneous catalysis. For
instance, rod-shaped [Au25(PPh3)10(C≡CPh)5X2]2+ (X = Br, Cl) nanoclusters exhibited selective
catalytic activity towards the semi-hydrogenation of terminal alkynes, due to bridging of Au
atoms by deprotonated alkynes, while the uncapped Au nanoclusters are active in the
hydrogenation of both terminal and internal alkynes.12 In another study,13 the formation of
surface staple motifs of PhC≡C−Au−C≡CPh in alkynyl-protected Au34Ag28(PhC ≡ C)34
nanoclusters led to enhanced catalytic performance towards the hydrolytic oxidation of
organosilanes to silanols, in comparison to those with the surface ligands partially or completely
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removed. Wang’s group compared the catalytic activity of alkyne- and thiolate-capped Au38
nanoclusters in the semi-hydrogenation of alkynes to alkenes and observed markedly higher
activity of the former (>97%) than that of the latter (<2%).14 However, studies of the
functionalization of transition metal nanoparticle by internal alkynes have been scarce. There are
at least two immediate differences of the interfacial bonding interactions, as compared to those
with terminal alkynes. One is the metal-ligand interfacial bonding configuration, and the other is
the packing of organic ligands on the nanoparticle surface, both of the two factors are likely to
impact the interactions of metal nanoparticles with reaction species and hence the catalytic
performance. In addition, ruthenium (Ru), as the most active catalyst for the Fischer-Tropsch
reaction15 and hydrogenation of olefin and aromatics16, has been widely studied. Most
importantly, ruthenium demonstrates unique chemistry when interacting with nonmetal elements,
such as the formation of Ru=carbene double bonds17 and the tautomerization through 1,3-
hydrogen shift/l,2- hydrogen shift and the formation of Ru=vinylidene bonds18 when terminal
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alkynes assemble on Ru metal surface. Ruthenium nanoparticles passivated with such unique
metal-ligand interfacial bonds may therefore demonstrate unique physical and chemical
properties.
Herein, ruthenium nanoparticles capped with terminal alkynes and internal alkynes were
prepared (Scheme 1), and the impacts of the ruthenium-ligand interfacial bonds on the
hydrogenation of styrene were also examined. It was found that internal alkynes most likely
adopted the η2 side-on mode through δ-π covalent bonds on the Ru nanoparticle surfaces, in
contrast to the end-on ruthenium-vinylidene bonds formed with terminal alkynes. Interestingly,
Ru nanoparticles capped with internal alkyne moieties exhibited markedly higher selectivity
towards vinyl hydrogenation of styrene than that of terminal counterparts.
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R
C
R
R
HC
H C
HC
R
R
C
C
C
H C
C
HC
C
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H C
R
C
Ru
C HC R
alkyne
Terminal
H C
C
C
HC
R
1,2-propanediol
165°C
C
H C
R
RuCl3
C
Ru
HC
Internal
alkyne
HC
R
R
R
R
R
R
R
R
C
C
C
C
R
R
R
R
R
Ru
C
C
R
C
C
R
R
Scheme 1. Preparation and interfacial bonding interactions of terminal and internal alkyne
capped ruthenium nanoparticles.
Results and Discussion
Ruthenium nanoparticles were capped with 1-ethynyl-4-hexylbenzene (EHB, a terminal
alkyne), 1,2-bis(4-hexylphenyl)ethyne (BEHB, an internal alkyne) 1,4-bis(4-hexylphenyl)buta-
1,3-diyne (DEHB, internal diyne), 1-dodecyne (HC12, a terminal alkyne) and phenylethanethiol
(PThiol) and denoted as Ru@EHB, Ru@BEHB, Ru@DEHB, Ru@HC12 and Ru@PThiol,
respectively (Figure S1-3). The diameters of Ru nanoparticles were derived from the TEM
images shown in Figure S4, which are very similar at 1.4±0.3, 1.7±0.3 and 1.7±0.3 nm for
Ru@EHB, Ru@BEHB and Ru@DEHB respectively.
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The TGA and ICP-MS measurements of both the capping ligands and the Ru nanoparticles
were shown in Figure S5, Table 1 and Table S1. The footprint of the corresponding ligand on the
ruthenium core surface was estimated to be 10.7 Å2 for Ru@EHB, 27.2 Å2 for Ru@BEHB and
64.4 Å2 for Ru@DEHB. Since the steric hindrance of capping ligands in the side-on mode was
much larger than that in the end-on mode, the footprint of the former capping ligands would be
larger than that of the latter. Here the footprint of each hexylbenzene moiety on Ru@BEHB was
larger than that of Ru@EHB, suggesting that the terminal alkynes take the end-on mode while
internal alkynes adopt the side-on mode on Ru nanoparticle surface (Scheme 1). Since DEHB
has two conjugated C≡C triple bonds and needs more space than single C≡C triple bond of
BEHB when adsorbed on Ru nanoparticles surface in the side-on mode, the footprint of DEHB
shall be more than two times that of BEHB. Again, this agrees with our observation. One may
argue that alkyne moieties may form oligomers and polymers when adsorbed on Ru
nanoparticles surface. However, TG-GC-MS measurements for Ru@EHB, Ru@BEHB and
Ru@DEHB do not show any molecular pieces larger than the ligands, excluding the oligomers
and polymers on Ru nanoparticles surface. In all, the TGA analysis indicates the terminal and
internal alkynes might take the binding modes at the metal-ligand interface shown in Scheme 1.
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1
The ligand structures on Ru nanoparticle surface were further examined by H NMR
measurements in CD2Cl2, as shown in Figure S1. One can see that all nanoparticle samples
exhibited two main, broad peaks at ca. 0.9 and 1.3 ppm, due to the terminal methyl and
methylene protons of the respective ligands. More significant broadening can be seen with the
peaks for phenyl protons at ca. 7.0 ppm. This is consistent with the binding of the ligands onto
the nanoparticle surface via the acetylene moiety, most likely adopting an end-on configuration
for Ru@EHB and side-on for Ru@BEHB and Ru@DEHB (Scheme 1). In addition, the fact that
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only broad NMR features were observed suggests that the nanoparticles were spectroscopically
clean without excess monomeric ligands.19-21
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Table 1. Summary of TGA and ICP-OES data of Ru@EHB, Ru@BEHB and Ru@DEHB
nanoparticles
Sample
Tg (°C)
Ru@EHB Ru@BHBE Ru@DEHB
271
264
277
61.1
68.4
82.7
Ru weight (%) By TGA
58.3
65.1
79.3
Ru weight (%) by ICP-OES
Organic weight (%)
Number of ligands
38.9
31.6
51.8
17.3
21.9
123.6
Footprint (Å2)
10.7
27.2
64.4
The metal-ligand interfacial bonding interactions are further characterized by FTIR
spectroscopy and shown in Figure S3. The C≡C bonds for alkyne monomers and related bonds
for Ru nanoparticles are listed in Table 2. The absence of ≡C–H stretch at 3299 cm–1 for the
free ligands of EHB was absent for the Ru@EHB nanoparticles, and the C≡C stretch shifted
from 2108 cm–1 for EHB ligands to 1944 cm–1 and 2051 cm–1 for Ru@EHB. This has been
ascribed to the adsorption of the EHB ligands onto the ruthenium nanoparticle surface in an end-
on configuration with a Ru=C=CH- interfacial bonds, as observed previously.21-24 Similarly, the
C≡C vibration red-shifted from 2141 cm–1 for free BEHB ligands to 1960 cm–1 for Ru@BEHB,
and the diacetylene C≡C–C≡C vibrations showed a red-shift from 2215 cm–1 and 2141 cm–1
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for the free DEHB ligands25 to 2046 and 1950 cm–1 for Ru@DEHB (Figure S2). This marked
discrepancy of wavenumber strongly suggests that the alkyne ligands were indeed chemically
bonded onto the Ru surface, and the decreasing bonding order (lower peak wavenumbers) might
be attributed to the bonding interactions between the acetylene moieties and the ruthenium metal
cores. For the Ru@EHB nanoparticles, this is due to the formation of conjugated metal-ligand
interfacial bonds that led to effective intraparticle charge delocalization between the particle-
bound acetylene moieties, whereas for the Ru@BEHB and Ru@DEHB nanoparticles, the
weakening of the acetylene vibrations can be ascribed to the σ-π bonds formed by the internal C
≡ C moiety with the metal nanoparticle surface in a side-on η2 configuration, as observed
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previously in surface-enhanced Raman scattering measurements of terminal alkyne self-
assembly on transition-metal surfaces.24 In such δ-π bonds, the C≡C moiety lies flat onto the
metal with the π orbitals directed toward the surface plane such that charge transfer occurs from
the Ru d orbital to the C≡C π* orbital (Scheme 1).
Table 2. C≡C vibration in monomeric ligands and ligand-capped Ru nanoparticles
Sample
EHB Ru@EHB BEHB Ru@BEHB DEHB Ru@DEHB
ν (cm–1) 2108
2051
1944
2141
1960
2212
2138
2046
1950
The interfacial bonding interactions of Ru nanoparticles with terminal and internal alkynes
were further examined by XPS measurements. Figure 1A-C show the high-resolution XPS
spectra of the C 1s and Ru 3d electrons of Ru@EHB, Ru@BEHB and Ru@DEHB nanoparticles,
respectively. Deconvolution yields a pair of peaks at 284.9 and 284.4 eV, due to sp3 and sp2 C 1s
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electrons, respectively,26 and the binding energy of Ru 3d5/2 for Ru@EHB, Ru@BEHB and
Ru@DEHB nanoparticles was observed at 281.0 eV, 280.75 eV and 280.6 eV, respectively,
showing a positive shift of 0.80 eV, 0.55 eV and 0.4 eV, respectively, as compared to that of
metallic ruthenium (280.2 eV).27-28 Such high binding energy of Ru 3d5/2 for Ru@EHB
nanoparticles might be due to the nanosized Ru cores and strong electron withdrawing groups of
phenyl ring through Ru=C=CH bonds, as demonstrated in earlier studies.15, 29-30
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Raw
Sum
Baseline
Ru 3d3/2
(D)
(E)
(F)
(A)
(B)
(C)
EHB
Ru@EHB
Ru@EHB
Ru 3d5/2
C1s sp2
C1s sp3
Ru@BEHB
BEHB
Ru@BEHB
DEHB
Ru@DEHB
Ru@DEHB
300 350 400 450 500 550 600
Wavelength (nm)
280
282
284
286
288
Binding Energy (eV)
Figure 1 High resolution XPS spectra of (A) Ru@EHB, (B) Ru@BEHB and (C) Ru@DEHB
nanoparticles. Excitation and emission spectra of (D) EHB and Ru@EHB, (E) BEHB and
Ru@BEHB, and (F) DEHB and Ru@DEHB in CHCl3.
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The discrepancy of the interfacial bonding between terminal and internal alkynes onto Ru
metal nanoparticles was found to lead to a marked difference of the nanoparticle
photoluminescence properties. Figure 1D-F displays the excitation and emission spectra of
Ru@EHB, Ru@BEHB, and Ru@DEHB nanoparticles, along with those of the respective
ligands. The wavelengths of the excitation and emission maxima derived from these spectra are
listed in Table 3. It can be seen that free EHB monomers exhibited an excitation maximum (ex)
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at 302 nm and a corresponding emission maximum (em) at 358 nm, whereas for Ru@EHB they
red-shifted markedly to 357 nm and 436 nm, respectively, close to those of the DEHB (377 nm
and 432 nm), consistent with the formation of Ru=C=CH- conjugated bonds that led to
intraparticle charge delocalization between the particle-bound acetylene moieties and hence
analogous behaviors to the dimeric counterparts, as observed previously.7, 31 By sharp contrast,
the ex and em for Ru@DEHB are almost identical to those of DEHB, suggesting that side-on
interactions of the DEHB ligands to the nanoparticle surface did not lead to an appreciable
change of the ligand electronic energy. For Ru@BEHB, whereas the ex was almost unchanged
as compared to that of BEHB, the em showed a moderate red-shift of ca. 26 nm, suggesting that
the Ru-BEHB interfacial bonding interactions were in the intermediate between those of Ru-
EHB and Ru-DEHB.
Table 3. Excitation and emission maxima of monomeric ligands and ligand-capped Ru
nanoparticles in CHCl3
Sample
EHB
Ru@EHB BEHB Ru@BEHB DEHB Ru@DEHB
λex (nm)
302
357
436
376
409
375
435
377
432
377
437
λem (nm)
Δλ (nm)
358
78
26
5
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Previously, Philippot et al. studied styrene hydrogenation catalyzed by PVP-capped
ruthenium (Ru@PVP) nanoparticles and found that the molecule adsorbed onto the Ru@PVP
surface through the vinyl groups rather than the phenyl end,32 and hydrogenation of the phenyl
rings requires π coordination of the phenyl groups.33-34 When the Ru nanoparticle surface was
coordinated with CO groups in a bridging mode (CO bridging sites), hydrogenation of the phenyl
ring was substantially impeded, while the activity towards hydrogenation of the vinyl group was
slowed down slightly, as compared to that of CO-free Ru nanoparticles. When completely
saturated with CO, Ru@PVP nanoparticles displayed no activity towards either vinyl or phenyl
group.35-36 The authors further concluded that the CO-bridging sites are responsible for the
hydrogenation of phenyl groups.32
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(B)
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Ru@EHB
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Ru@PThiol
Ru@HC12
0
2
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10 12 14 16 18 20
2
4
6
8
10 12 14 16 18 20
Time (h)
Figure. 2. Evolution of hydrogenation of styrene products, (A) ethylbenzene and (B)
ethylcyclohexane, catalyzed by Ru@EHB (●), Ru@BEHB (▲), Ru@DEHB (■) Ru@PThiol(
◆) and Ru@HC12(▼).
As shown in Figure 2 and Table S2, ruthenium nanoparticles capped with terminal and
internal alkynes showed markedly different behaviors to each other. In contrast to the sequential
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hydrogenation of the vinyl and phenyl groups of styrene by Ru@EHB nanoparticles, Ru@DEHB
and Ru@BEHB are active only towards hydrogenation of the vinyl group, while almost inert to
the hydrogenation of the phenyl group. Such discrepancy of the catalytic selectivity between
ruthenium nanoparticles capped with internal alkynes (i.e., Ru@BEHB and Ru@DEHB) and
those functionalized with terminal alkynes (i.e., Ru@EHB) can be explained with this scenario.
The C≡C moieties in BEHB and DEHB ligands take the bridging sites on Ru nanoparticles
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surface through η2 σ-π bonds of C≡C and behave analogously to the CO on the bridging sites,
thus preventing the hydrogenation of phenyl group. By contrast, EHB tautomerized to vinylidene
moieties and preferred to take the hollow site on Ru nanoparticle surface in the end-on mode. In
addition, the π-π staking among the phenyl groups of EBH ligands led to the formation of EHB
molecular bundles and makes the styrene more accessible to the Ru sites.37-38
Consistent results were obtained in DFT calculations where we examined the adsorption of
terminal and internal alkynes on Ru metal surface, as shown in supporting information (Figure
S6-10). Figure S6 shows the transition states, molecular configurations and the energy barriers
for the transformation of adsorbed 1-propyne on Ru(0001) to the vinylidene (#1 to #9).
Although the energy of (#3) is slightly lower than #9 and one argue that #9 is more preferred
than vinylidene (#9), it is possible that when many terminal alkyne molecules adsorbed on Ru
metal surfaces, H from any other molecules could be present at the Hc site for CH3CC* and
form #7, rendering the tautomerization of terminal alkyne to vinylidene exothermic and
spontaneous.
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(B)
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Figure 3. The adsorption configurations of terminal alkyne 4-ethynyltoluene (A) and internal
alkyne 1,2-di-p-tolylethyne (B) on Ru (0001). The Ru atoms bonding with carbon atoms are
highlighted with green color. The adsorption energy in (A) is –4.07eV and that in (B) is –4.40
eV. The adsorption energy is defined as: Eads=E(mol/sur)–E(sur) –E(mol), where E(mol/sur) is the
energy of the system of the adsorbate taking the optimized configuration on Ru metal surface.
E(mol) is the energy of the free molecule of the adsorbate. E(sur) is the energy of the metal surface
without any adsorbate.
Most importantly, the DFT calculation (Figure 3) indicates that internal alkyne moieties
adsorb on the Ru surface via the bridging site and thus block the active site for the hydrogenation
of phenyl group. Instead, terminal alkyne moieties adsorb on Ru surface in side-on mode, further
tautomerize to vinylidene and take the hollow site in end-on mode, thus leaving the bridging site
available for the hydrogenation of phenyl group. Thus, the DFT calculation results agree well
with our anticipation and support the catalytic performance of Ru@EHB, Ru@BEHB and
Ru@DEHB nanoparticles.
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Styrene
Ethylbenzene
Ru@EHB
Ru@DEHB
2100
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0
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Wavenumber (cm-1)
Time (h)
Figure. 4. (A) In-situ FTIR spectra of Ru@EHB and Ru@DEHB nanoparticles poisoned for 4 h
in 1 atm CO atmosphere; (B) Evolution of hydrogenation products of styrene by Ru@EHB
poisoned with CO.
Figure 4 (A) shows the in-situ FTIR spectra of Ru@EHB and Ru@DEHB nanoparticles
poisoned in 1 MPa CO atmosphere for 4 h. It can be observed that the ratio of the intensity of
CO-bridging (1980 cm-1) to CO-top (2050 cm-1)39 for Ru@EHB is much higher than that of
Ru@DEHB, suggesting that Ru@EHB nanoparticles contained more CO-bridging sites than that
the CO-top sites and thus show high selectivity towards styrene hydrogenation. In Figure 4 (B)
and Figure S11, catalysis test shows that the CO poisoned Ru@EHB nanoparticles lost the
ability of producing cyclohexane, and the reaction rate of producing ethylbenzene by Ru@EHB
and Ru@DEHB were much slower. To prevent the possible aggregation of Ru nanoparticles
during catalysis reaction and further on the selectivity of hydrogenation of styrene by Ru@EHB
and Ru@DEHB nanoparticles, we further did the TEM for Ru@DEHB after catalysis and also
repeated the catalysis reaction for both Ru@EHB and Ru@DEHB. The size of Ru@DEHB after
catalysis is 1.8±0.2 nm (Figure S4-D), which is consistent with that of the as-prepared
Ru@DEHB (1.7±0.3). As shown in Figure S12, the selectivity of hydrogenation by Ru@EHB
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and Ru@DEHB in the second run is quite similar to that in the first, thus excluding the
possibility of the aggregation of Ru nanoparticles on the selectivity of hydrogenation of styrene.
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In addition, as EHB moieties adsorbed on Ru@EHB nanoparticles in the end-on mode and
molecular bundles, more space was available for the accessibility of styrene and hydrogenation.
By contrast, BEHB and DEHB take the side-on mode on both Ru@BEHB and Ru@DEHB
nanoparticles surfaces. Whereas an increasing fraction of Ru nanoparticles surface is not directly
bonded with ligands, the accessibility of styrene to these unbonded Ru surfaces could was
impeded by the hexylbenzene fragments of the capping ligands that adopted the side-on mode
(scheme 1), thus preventing the hydrogenation of styrene.
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Ru@HC12, sharing the same Ru=CH=C interfacial bonds but different molecular structure
of capping ligands with Ru@EHB, are still highly active to both vinyl and phenyl hydrogenation
and behave similarly to that of Ru@EHB. However, the reaction dynamics of hydrogenation of
phenyl groups for Ru@HC12 is largely slowed as compared to that of Ru@EHB, which might
be caused by the steric effect of the long alkyl chain, preventing the effective access of the
phenyl ring of styrene to and formation of π coordination with the Ru metal surface. For
Ru@PThiol nanoparticles, although PThiol ligands took the upright position on Ru nanoparticles
surface, Ru nanoparticles behaved much like that of partially CO-poisoned ruthenium
nanoparticles, with much slowed hydrogenation of vinyl and completely suppressed activity
towards hydrogenation of phenyl group.35-36 This might suggest that the inactivity of ruthenium
nanoparticles capped with moieties of internal alkynes are mainly caused by the occupation of
the bridging sites of ruthenium nanoparticles surfaces by C≡C triples bonds of internal alkynes.
Conclusion
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In summary, ruthenium nanoparticles capped with terminal and internal alkyne ligands were
prepared and the Ru-acetylene interfacial bonding interactions were examined by TGA, 1H NMR,
FTIR, XPS, photoluminescence measurements and DFT calculation. The results suggest that
internal alkyne adopted an η2 side-on configuration, forming δ-π covalent bonds on Ru
nanoparticle surface. Such interfacial bonds were somewhat weaker than that with terminal
alkynes, where Ru=C=CH- interfacial bonds were formed and extensive charge delocalization
occurred among the particle-bound acetylene moieties. Interestingly, the Ru nanoparticles
capped with terminal alkynes exhibited apparent catalytic activity towards hydrogenation of both
the vinly and phenyl groups of styrene, while Ru nanoparticle capped with internal alkynes
exhibited activity towards the vinyl group only. This discrepancy of catalytic behavior caused by
the capping alkynes was accounted for by the combined FTIR and catalysis tests of CO-poisoned
Ru nanoparticles, which suggests that the bridging sites might be responsible for the
hydrogenation of phenyl group by Ru nanoparticles capped with terminal alkynes.
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Notes
The authors declare no competing financial interest.
Acknowledgments
This work was supported by the National Natural Science Foundation of China (No. 51602106),
the Fundamental Research Funds for Central Universities (SCUT Grant No. 2017MS066 and
2017MS006). Z. L. would like to thank the Guangdong Innovative and Entrepreneurial Research
Team Program (No. 2016ZT06N569).
Supporting Information Available Detailed description of synthesis of BEHB and DEHB
1
monomers, Ru nanoparticles; H, 13C NMR and FTIR spectra of the EHB, BEHB and DEHB
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monomers; H NMR, FTIR spectra, TGA, TEM images of Ru nanoparticles capped with EHB,
BEHB, DEHB; DFT calculation for the transition state of tautomerization of terminal alkyne to
vinylidene and the adsorption mode of terminal and internal alkyne on Ru (0001) surface. This
information is available free of charge on the internet at http://pubs.acs.org.
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Table of contents (TOC):
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R
C
R
R
H C
HC
R
R
R
R
C
C
C
C
H C
C
C
HC
C
C
C
C
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R
R
R
R
R
C
Ru
Ru
C
HC R
HC
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H C
C
C
C
C
R
C
C
H C
R
C
HC
R
R
HC
H2
R
H2
R
R
H2
H2
Scheme of the interfacial bonding interactions of terminal and internal alkynes on Ru
nanoparticles and their impact on the hydrogenation dynamics of styrene
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