Ni nanoparticles on RGO as reusable heterogeneous catalyst: Effect of Ni particle size and intermediate composite structures in C-S cross-coupling reaction

Article abstract of DOI:10.3762/bjoc.13.174

The present work demonstrates the C-S cross-coupling reaction between aryl halides and thiols using nickel nanoparticles (Ni NPs) supported on reduced graphene oxide (Ni/RGO) as a heterogeneous catalyst. It is observed that the uniformly dispersed Ni NPs supported on RGO could exhibit excellent catalytic activity in C-S cross-coupling reactions and the catalytic application is generalized with diverse coupling partners. Although the electron-rich planar RGO surface helps in stabilizing the agglomeration-free Ni NPs, the catalytic process is found to occur involving Ni(II) species and the recovered catalyst containing both Ni(0)/Ni(II) species is equally efficient in recycle runs. A correlation of loading of Ni species, size of NPs and the intermediate Ni-related heterostructures formed during the catalytic process has been established for the first time, and found to be best in the C-S cross-coupling reaction for Ni(0) and Ni(II) NPs of the average sizes 11-12 nm and 4 nm, respectively.

Full text of DOI:10.3762/bjoc.13.174

Ni nanoparticles on RGO as reusable heterogeneous catalyst:
effect of Ni particle size and intermediate composite
structures in C–S cross-coupling reaction
Debasish Sengupta‡1, Koushik Bhowmik‡2, Goutam De*2 and Basudeb Basu*1
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2017, 13, 1796–1806.
1Department of Chemistry, University of North Bengal, Darjeeling
734013, India. Fax: +91 353 2699001; Tel: +91 353 2776381 and
2Nano-Structured Materials Division, CSIR–Central Glass & Ceramic
Research Institute, 196, Raja S. C. Mullick Road, Jadavpur, Kolkata
700032, India. Fax: +91 33 24730957; Tel: +91 33 23223403
doi:10.3762/bjoc.13.174
Received: 29 May 2017
Accepted: 09 August 2017
Published: 28 August 2017
Email:
Associate Editor: M. Rueping
Goutam De* - gde@cgcri.res.in; Basudeb Basu* -
basu_nbu@hotmail.com
© 2017 Sengupta et al.; licensee Beilstein-Institut.
License and terms: see end of document.
* Corresponding author ‡ Equal contributors
Keywords:
C–S cross-coupling; heterogeneous catalyst; Ni nanoparticle; reduced
graphene oxide; thioether
Abstract
The present work demonstrates the C–S cross-coupling reaction between aryl halides and thiols using nickel nanoparticles (Ni NPs)
supported on reduced graphene oxide (Ni/RGO) as a heterogeneous catalyst. It is observed that the uniformly dispersed Ni NPs
supported on RGO could exhibit excellent catalytic activity in C–S cross-coupling reactions and the catalytic application is general-
ized with diverse coupling partners. Although the electron-rich planar RGO surface helps in stabilizing the agglomeration-free Ni
NPs, the catalytic process is found to occur involving Ni(II) species and the recovered catalyst containing both Ni(0)/Ni(II) species
is equally efficient in recycle runs. A correlation of loading of Ni species, size of NPs and the intermediate Ni-related heterostruc-
tures formed during the catalytic process has been established for the first time, and found to be best in the C–S cross-coupling
reaction for Ni(0) and Ni(II) NPs of the average sizes 11–12 nm and 4 nm, respectively.
Introduction
The formation of a carbon–sulfur bond is an imperative step for Parkinson’s diseases etc. [1-4]. The first palladium-catalyzed
the synthesis of many biologically active chemical entities that arylation of thiols was reported by Migita and co-workers in
have significant applications in different therapeutic areas such 1980 [5], and soon after Cristau and co-workers developed a
as HIV, cancer, diabetes, inflammation, Alzheimer’s and nickel-catalyzed route for C–S cross-coupling reactions [6].
1796

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
Other metals such as copper [7], cobalt [8], iron [9], rhodium Results and Discussion
[10], manganese [11], indium [12], and bismuth [13] have been We synthesized Ni/RGO nanocomposites following our re-
used with specific electron-rich ligands in the C–S coupling ported method [48,49]. These materials were well characterized
reactions. However, these are less common compared to other by powder XRD, TEM, TGA and XPS studies. The preparation
C–X (X = C, O, N, P) coupling reactions, presumably because and characterization of the nanocomposites were described in
sulfur might suppress the catalytic function through its coordi- detail in our previous publications [48,49]. Usually, bare Ni
nating and adsorptive properties [14]. The Ni-catalyzed C–S NPs are unstable and likely to undergo aerial oxidation [43].
cross-coupling reactions generally involved Ni salts [15-18], However, in the Ni/RGO composite, the electron-rich RGO sur-
Ni–phosphine complexes [19-21], or Ni–NHC complexes face helps in stabilizing the Ni in its zero-valent state. The high
[22,23], although the actual catalyst is believed to be a surface area and planar structure of RGO prevent the Ni NPs (to
Ni(0)/Ni(I) species [16-21]. NiO supported on zirconia an optimum loading of Ni) from agglomeration and provide
(NiO–ZrO2) is thus far known to act as the only heterogeneous enough adsorption sites to the reacting molecules. In this work
nanocatalyst for C–S cross-coupling with limited applications graphene oxide (GO) was used as a support for in situ growth of
and poor yields [24].
Ni nanoparticles. The synthetic protocol presumably allows
initial interaction between the metal and functional groups on to
In recent years, graphene-based composite materials have the basal plane of GO [48]. The interaction could take place
become popular because of their unique physical, mechanical effectively due to the planar structure and large contact area of
and chemical properties [25-27]. Graphene, a single atomic GO. As a result, when reduced, the Ni nanoparticles could sit on
layer of conjugated sp2 carbon atoms with a large contact area, the RGO surface without agglomeration.
can adopt several guest particles [28,29]. Reduced graphene
oxide (RGO) with a high surface area can be easily dispersed in We prepared three different Ni/RGO nanocomposites by
aqueous or non-aqueous media and can be mingled with other varying the loading of Ni NPs. The crystallite sizes of Ni NPs in
nanomaterials to produce stable nanocomposites [30]. There- these three Ni(0)/RGO samples were calculated with X-ray line
fore, RGO is considered an excellent candidate for catalyst broadening using the (111) and (200) peaks as reported [48,49]
support [31,32]. To date, various magnetic or semiconducting (see also Supporting Information File 1). The average crystal-
nanoparticles (NPs) have been incorporated in GO surfaces and lite sizes of Ni NPs are 10, 11 and 17 nm in Ni/RGO-20
thoroughly studied in terms of their photocatalytic and electro- (20 wt % Ni), Ni/RGO-40 (40 wt % Ni) and Ni/RGO-60
chemical properties [33-37]. However, only few graphene- (60 wt % Ni) samples, respectively. It was observed that an
based metal nanocomposites have been recognized for organic optimum loading of 40 wt % Ni in Ni/RGO could be loaded
cross-coupling reactions [38-42]. In general, bare Ni NPs are without any agglomeration with a restriction of average
very unstable and readily oxidized in air [43]. A few literature size ≈11 nm. However, if the loading is increased to 60 wt %,
reports are available where Ni species immobilized on a solid the average size of NPs becomes significantly higher (17 nm)
surface have been used in C−C or C−N cross-coupling reac- due to agglomeration. Therefore, we found Ni/RGO-40
tions [44-47]. We have recently shown that uniformly dispersed (40 wt % Ni) is very suitable for our catalytic reactions.
Ni NPs that are free of agglomeration can be embedded in RGO
sheets (Ni/RGO). This very stable Ni/RGO nanocomposite We began our studies on optimizing the reaction taking 3-iodo-
enhances the reduction rate of Cr(VI) species to Cr(III) in the anisole and benzenethiol as model coupling partners and
presence of formic acid at room temperature [48]. Also, it can Ni/RGO as the catalyst. In the process, we first examined the
serve as an excellent catalyst for the Kumada–Corriu C–C coupling reactions with Ni/RGO-40 at varying temperatures,
cross-coupling reaction [49]. Since heterogeneous Ni catalysts bases and solvents, though other nanocomposites (Ni/RGO-20
are rarely studied for the C–S cross-coupling reaction between and Ni/RGO-60) were also tested (Table 1). All reactions were
aryl halides and thiols, presumably because of the fact that the carried out under a N2 atmosphere to avoid oxidative dimeriza-
thiols (bearing -S–H) might poison the catalyst, we became tion of thiols to disulfide [50]. Solvent optimization was started
interested to examine this catalyst. Herein, we present our with water (Table 1, entry 1) followed by toluene (Table 1,
studies which revealed that both Ni(0) and Ni(II) species entry 2) and isolating diaryl sulfide only 6–8% after 10 h, while
formed during the reaction and remaining on RGO could act as in DMSO the yield significantly rises to 86% within 3 h
the active catalysts for the C–S cross-coupling reaction. More- (Table 1, entry 3). The conversion was even higher (92%) when
over, a correlation between the loading of metal, the effect of DMSO was replaced with DMF (Table 1, entry 4). However, a
average NP size of Ni(0)/Ni(II) species in the catalyst and the drop in the catalyst loading or a lowering of the temperature
intermediate composite heterostructures has been established affected the course of the reaction by suppressing the overall
for the first time.
yield of the thioether (Table 1, entries 5 and 6). Without using
1797

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
Table 1: Optimization of the C–S cross-coupling reaction conditions using Ni/RGO-40.a
Entry
Catalyst
Solvent
Base
Temperature (°C)
Time (h)
Yieldb (%)
Ni content (mol %)
1
2
15
15
water
toluene
DMSO
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
None
100
100
100
100
100
80
10
10
3
8
6
3
15
86
92
81
61
74
83
63
0
4
15
3
5
10
3
6
15
10
10
3
7
15
100
100
100
100
100
100
100
100
100
8
15
KOH
9c
10
11d
12e
13f
14g
15h
15
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
3
none
RGO
15
10
10
3
0
91
84
79
92
15
3
15
3
15
3
a3-Iodoanisole (1 mmol), benzenethiol (1.2 mmol), K2CO3 (1.2 mmol) and solvent (3 mL) heated at 100 °C under N2. bIsolated yield. cReaction was
performed without N2. cDiphenyl disulfide was isolated (15%). dRGO (13.2 mg). eNi/RGO-20 catalyst. fNi/RGO-60 catalyst. gNi NPs. h4-Iodoanisole
(1 g, 4.27 mmol), benzenethiol (5.12 mmol), K2CO3 (5.12 mmol), Ni/RGO-40 catalyst (94.0 mg; Ni content is 37.60 mg, 0.64 mmol) and solvent
(4 mL) heated at 100 °C under N2.
any base, the yield was 74%, while the use of KOH as a base ic efficiency in the C–S coupling reaction. The catalytic reac-
afforded the thioether in 83% yield (Table 1, entries 7 and 8). tion was found to be scalable with comparable conversions
Formation of the diphenyl disulfide via oxidative dimerization (Table 1, entry 15).
of benzenethiol was noticed (15%) when the reaction was
carried out under aerobic conditions (Table 1, entry 9). Control We then extended the optimized reaction conditions (as in
experiments without the catalyst (Ni/RGO-40) or only with Table 1, entry 4) using Ni/RGO-40 to diverse functionalized
RGO (Ni-free) did not produce any cross-coupled sulfane prod- aryl halide/thiol combinations. The results are indeed encour-
uct (Table 1, entries 10 and 11). The reaction was then per- aging and summarized in Table 2. Both coupling partners, i.e.,
formed in the presence of Ni/RGO-20 and Ni/RGO-60 under the iodoarenes and arylthiols bearing different groups like Me,
similar conditions affording the thioether in 91% and OMe, F, COCH3, NO2 are equally efficient to undergo cross-
84% yields, respectively (Table 1, entries 12 and 13). These ob- coupling reactions producing the corresponding unsymmetrical
servations suggest that both Ni/RGO-20 and Ni/RGO-40 with diaryl sulfides 3a–i in 88–93% isolated yields (Table 2, entries
average Ni NPs size (≈10–11 nm) have better catalytic effi- 1–9). No significant influence of electron-donating or electron-
ciency (yield 91–92%) than Ni/RGO-60 (≈17 nm), presumably withdrawing groups has been noticed, which is in agreement
attributable to the larger active surface areas in the former two with previously reported results in C–S coupling reactions [19].
cases. On the other hand, bare Ni NPs (of an average In the case of iodobromoarenes or iodochloroarenes, we ob-
size ≈10 nm) prepared following the reported procedure [51], tained only iodo-coupled products 3j and 3k in excellent yields
gave the corresponding cross-coupled product in 79% yield (Table 2, entries 10 and 11). Bromoarenes remain unchanged
(Table 1, entry 14). This could be due to the agglomeration of under the given conditions. However, the cross-coupling of
NPs or further oxidation of Ni NPs in the absence of the elec- bromoarenes could be performed efficiently in the presence of
tron-rich RGO surface.
zinc dust (1 equivalent to the substrate bromoarene) in addition
to a catalytic amount of Ni/RGO-40 (Table 2, entries 12 and
Thus, the average size of Ni NPs supported with electron-rich 13). Although the exact role of zinc is not clearly understood,
RGO surface seems to be important to obtain maximum catalyt- based on literature reports [7,16], we presume that the oxidized
1798

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
Table 2: Ni/RGO-40 catalyzed C–S cross-coupling between aryl halide and thiol.a
Entry
1
Aryl halide (1)
Thiol (2)
Time (h)
2
Product (3)
Yieldb (%)
93
3a
3b
2
3
3
5
92
90
3c
3d
3e
3f
4
5
6
4
3
4
91
93
90
7
8
88
3g
3h
8
9
8
8
90
89
3i
3j
10
11
6
6
90
88
3k
1799

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
Table 2: Ni/RGO-40 catalyzed C–S cross-coupling between aryl halide and thiol.a (continued)
12c
13c
10
10
85
3l
88
3e
14d
8
87
3m
15d
16
8
84
3n
10
10
80
3o
17
75
3p
aAryl halide (1 mmol), thiol (1.2 mmol), K2CO3 (1.2 mmol), Ni/RGO-40 (40 wt %, 22 mg) and DMF (3 mL) heated at 100 °C under nitrogen. bIsolated
yield. cZn dust (1 mmol) was added. dAryl halide (0.5 mmol), 4-methylphenylthiol (1.2 mmol), K2CO3 (1.2 mmol), Ni/RGO-40 (40 wt %, 22 mg).
organonickel intermediate Ar–Ni(II)–Br (derived from the oxi- nificant drop in catalytic activity. Figure 1 shows the results of
dative addition of Ni to the Ar–Br bond) might not be suffi- consecutive recycle runs.
ciently reactive to the thiolate anion (Ar–S−K+) before being
reduced to the organonickel species [Ar–Ni(I)] in the presence
of zinc. Diiodobenzenes, however, underwent smooth coupling
affording the bis-coupled products 3m and 3n as the single
products (Table 2, entries 14 and 15). Using aliphatic thiols has
also resulted in the formation of unsymmetrical aryl alkyl
thioether 3o and 3p in relatively lower yields (75–80%; Table 2,
entries 16 and 17). Aliphatic thiols are, however, known to be
less reactive as compared to aromatic thiols in coupling
chemistry, which might be the reason to obtain lower yields
[15].
Reusability of the catalyst (Ni/RGO-40)
After establishing the generality of RGO-supported Ni NPs
size-specific catalytic efficiency in the C–S coupling reaction,
we recovered the catalyst from the reaction mixture (see Experi-
mental section) and studied its reusability. Here, we used
4-iodoanisole and benzenethiol as the model coupling partners.
Figure 1: Recycling experiments of Ni/RGO-40 catalyst in C−S cross-
coupling reaction between 4-iodoanisole and benzenethiol.
It was found that the catalyst can be reused at least for six times
for the same reaction examined consecutively without any sig-
1800

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
Characterization of the recovered catalyst
To establish the reaction mechanism, we characterized the
recovered catalyst by Raman, XRD, XPS and TEM studies. The
Raman and XRD results of fresh Ni/RGO-40 were reported in
our previous publication [48]. However, for comparison, Raman
and XRD of a fresh Ni/RGO-40 sample were again recorded
and presented along with that of the recovered sample. The
Raman spectrum of the Ni/RGO-40 composite (Figure 2a) ex-
hibits a characteristic D band at 1344 cm−1 (A1g vibrations of
six-membered sp2 carbon rings) and the G band at 1580 cm−1
(first-order scattering of the E2g mode of sp2 domains). After
the first run, the Raman spectrum of the recovered Ni/RGO-40
catalyst (Figure 2b), however, did not reveal any peak related to
the nickel oxide (NiO). The intensity ratio of the D over the G
band was found to be 1.03, which is similar to that of
Ni/RGO-40 before used in the C−S coupling reaction
(Figure 2a). The powder XRD of Ni/RGO-40, recovered after
the first cycle, was also recorded and is shown in Figure 3. The
XRD pattern (Figure 3a) of the fresh sample shows peaks for
Ni(111) and Ni(200) for Ni(0) being supported with RGO. The
crystallite sizes of Ni(0) in the recovered catalyst were found to
be 12 nm, calculated by using the X-ray line broadening method
based on (111), (200) peaks in Figure 3b. The particle size
clearly indicates that the planar surface of RGO effectively
prevents the agglomeration of Ni NP during the catalysis. Apart
from the characteristic peaks of Ni(0), two additional peaks
were observed in the XRD of the recovered catalyst (Figure 3b).
These two peaks indicate the presence of Ni(OH)2. It was
further confirmed by performing X-ray photoelectron spectros-
copy (XPS) of the recovered catalyst (Figure 4). The XPS of
fresh catalyst shows only Ni(0) related peaks [48]. The HRXPS
of Ni in the recovered Ni/RGO-40 (Figure 4a) clearly shows the
Figure 3: (a) XRD of fresh Ni/RGO-40 and (b) the recovered catalyst
after the first cycle of C–S coupling.
Figure 2: (a) Raman spectrum of fresh Ni/RGO-40 and (b) recovered
Figure 4: HRXPS of Ni in (a) Ni/RGO-40 catalyst recovered after the
catalyst after the first cycle of C–S coupling.
first cycle of the reaction. (b) Deconvoluted 2p3/2 peak of Ni from (a).
1801

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
peak at 852.9 eV corresponds to the 2p3/2 of the Ni(0) NPs [52].
Similarly the peak at 856.2 eV represents the 2p3/2 of Ni(OH)2
[52]. The deconvoluted spectrum (Figure 4b) shows that the
recovered catalyst contain 17% Ni(0) and 83% Ni(II) species. It
was interesting to observe that in the recycle runs, which
proceeded with excellent conversion to the thioether, the cata-
lytic system contains a significant amount of Ni(II) species em-
bedded with RGO in addition to Ni(0) NPs. Therefore,
assuming that Ni(II) species having embedded with RGO can
also be used as the catalytic system, we prepared a new nano-
composite [Ni(OH)2/RGO (30 wt %)] [48], with average parti-
cle size of 13 nm (calculated on the basis of Figure 5) and ex-
amined its catalytic efficiency in the C–S cross-coupling reac-
tion. We could achieve the C–S coupled thioether product in
82% yield only, which is lower than Ni/RGO-40 (see Support-
ing Information File 1, Table S1, a Table showing comparative
catalytic efficiency and NP sizes).
Figure 5: XRD of Ni(OH)2/RGO, prepared separately.
hydroxide and interestingly that is also equally active in
Mechanistically, the transition-metal-catalyzed C–S cross-cou- catalyzing the C–S coupling reaction. Initial oxidative addition
pling reaction, using mainly Pd, Cu or Ni species, is believed to to an Ar–I bond gives Ar–NiII–I followed by Ar–NiII–SPh, and
proceed through three major steps; viz. the initial oxidative ad- then the reductive elimination could result in the formation of
dition, then substitution by thiolate anion and finally the reduc- Ar–SPh (Figure 6). The resulting Ni(II) species could be con-
tive elimination. A more detailed study describing Pd- or verted mostly to Ni(OH)2 NPs in the presence of water during
Cu-catalyzed C–S coupling reactions as compared to Ni-cata- washing and subsequent recovery, as examined from the
lyzed reaction has been published [7,53,54]. However, as pro- powder XRD and HRXPS of the recovered catalyst after the
posed in previous investigations on the Ni-catalyzed C–S cou- first run (Figure 3b and Figure 4b). In support of our proposed
pling reaction [15,22,23], the catalytic cycle here is likely to reaction mechanism, we analyzed the TEM images of the fresh
occur in analogy. Examination of the recovered catalyst by Ni/RGO-40 catalyst and the recovered one after the first cycle
HRXPS suggests that there is significant quantity of Ni(II) of catalysis. In Figure 7a, we show the TEM image of fresh
Figure 6: Proposed mechanism for the RGO-supported Ni-catalyzed C–S cross-coupling reaction.
1802

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
Ni/RGO-40 (figure reproduced from our earlier publication, ref
[48]) for comparison and that of the recovered Ni/RGO-40 is
shown in Figure 7b. Figure 7b clearly shows the presence of
metallic Ni NPs and Ni(OH)2 on the RGO surface. One can
observe the co-existence of crystalline fringes of Ni<111> and
Ni(OH)2<100> (inset A; Figure 7b) along with the interlayer
spacing of RGO (inset B; Figure 7b). The particle size of Ni
NPs observed from TEM image was almost similar in the
before and after catalysis sample, i.e., around 11 nm, indicating
the particle agglomeration did not occur during the catalysis.
Again, the crystallite size of the Ni(OH)2 was found to be
around 4 nm, which is corroborated from the X-ray line broad-
ening method on the <100> peak of Ni(OH)2 in Figure 3b. It is
likely that Ni(OH)2 could form during the recovery of the cata-
lyst. In the recycle run, the major catalytic constituent Ni(OH)2
is presumably reduced by thiolate anions to Ni(I) species, which
then undergoes oxidative addition to the aryl halide forming a
Ni(III) species, as proposed previously [19].
Conclusion
In conclusion, we have shown that a RGO-supported Ni(0)
nanocomposite (Ni/RGO-40) with average size (≈11–12 nm) Ni
NPs display high catalytic efficiency for C–S cross-coupling
reactions and are applicable to a diverse range of coupling part-
ners. The catalytic performance is primarily dependent on the
NP sizes of the Ni species. The electron-rich planar surface of
RGO helps in stabilizing the NPs and prevents agglomeration
making them recyclable with almost equal efficiency. However,
post-catalytic investigations of the heterogeneous catalyst reveal
that the Ni NPs are considerably converted to Ni(OH)2, (aver-
age particle size 4 nm) and remain closely associated with the
Ni NPs on the electron-rich RGO surface and exhibit similar
catalytic efficiency.
Experimental
Chemicals were used as received. For column chromatography,
silica (60–120 mm, SRL, India) was used. For thin-layer chro-
matography (TLC), plates (Merck) coated with silica gel 60,
F254 were used.
The progress of the reaction was monitored by HPLC (Agilent
Technologies, 1260 Infinity), Column: ZORBAX Rx–SIL
(4.6 × 150 mm, 5 mm), eluent: n-hexane (flow rate
2 mL min−1). 1H and 13C NMR spectra were taken in CDCl3
using a Bruker Avance AV-300 spectrometer operating at
300 MHz and 75 MHz, respectively. Chemical shifts are re-
ported relative to tetramethylsilane (TMS) served as the internal
standard (δ = 0 ppm). 13C NMR spectra were recorded with
complete proton decoupling and chemical shifts are reported in
ppm with the solvent resonance as the internal standard (CDCl3:
δ = 77.00 ppm). Raman spectra were obtained using Renishaw
Figure 7: TEM image of (a) Ni/RGO-40 before usage as a catalyst (for
comparison, reprinted with permission from [48], copyright 2014 Amer-
ican Chemical Society) and (b) recovered catalyst after the first cycle
of reaction showing the different domains (marked by yellow enclo-
sures). The enlarged views of the marked rectangular areas in (b) are
shown in A (Ni species) and B (RGO).
1803

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
InVia Reflex micro Raman spectrometer with excitation of with water, dried over anhydrous Na2SO4, and concentrated to
argon ion (514 nm) lasers. The laser power was kept suffi- afford a residue, which was purified by column chromatogra-
ciently low to avoid heating of the samples and spectra were phy over a short column of silica gel and eluting with light
collected with a resolution of 1 cm−1. X-ray diffraction (XRD) petroleum to obtain 0.85 g (92%) of pure (4-methoxy-
studies of the powder samples were performed with Rigaku phenyl)(phenyl)sulfane as a colourless liquid.
Smartlab X-ray diffractometer operating at 9 kW (200 mA;
45 kV) using Cu Kα radiation. X-ray photoelectron spectros-
Supporting Information
copic (XPS) measurements were done on a PHI 5000
Versaprobe II XPS system with Al Kα source and a charge
Supporting Information File 1
neutralizer at room temperature, maintaining a base pressure
Powder XRD patterns of Ni/RGO-20 and Ni/RGO-40;
Table showing comparative catalytic performance and
effect of NP sizes; 1H and 13C NMR spectral data for
compounds 3a–p.
about 6 × 10−10 mbar and energy resolution of 0.6 eV.
General procedure for C–S cross-coupling
using Ni/RGO-40
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-13-174-S1.pdf]
A mixture of aryl halide (1 mmol), thiol (1.2 mmol), potassium
carbonate (1.2 mmol), Ni/RGO-40 catalyst (22 mg; Ni content
is 8.8 mg, 0.15 mmol, 15 mol %) in DMF (3 mL) were taken in
a 15 mL sealed tube, flashed and filled with N2 gas and quickly
screw-capped. The reaction mixture was then heated to
100 °C with a gentle magnetic stirring for hours. After
completion of the reaction, the mixture was allowed to cool,
diluted with ethyl acetate (3 mL), stirred gently and then
Supporting Information File 2
1H and 13C NMR spectra (scanned) for compounds 3a–p.
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-13-174-S2.pdf]
allowed to stand for 15 min. The supernatant liquid was Acknowledgements
carefully pipetted out into another flask and this process was Financial support from the Science and Engineering Research
repeated three more times. The organic part was washed with Board, New Delhi (No EMR/2015/000549) is gratefully
water, dried over anhydrous Na2SO4, concentrated to afford a acknowledged. DS and KB thank CSIR, India for providing
residue, which was purified by column chromatography over a fellowships.
short column of silica gel and eluting with light petroleum to
References
1. Kaldor, S. W.; Kalish, V. J.; Davies, J. F.; Shetty, B. V.; Fritz, J. E.;
obtain pure sulfanes. All unsymmetrical sulfanes were charac-
terized by 1H and 13C NMR and compared with the reported
Appelt, K.; Burgess, J. A.; Campanale, K. M.; Chirgadze, N. Y.;
data (see Supporting Information File 1, pages S3–S6).
Clawson, D. K.; Dressman, B. A.; Hatch, S. D.; Khalil, D. A.;
Kosa, M. B.; Lubbehusen, P. P.; Muesing, M. A.; Patick, A. K.;
In order to recover the catalyst, the insoluble materials obtained
Reich, S. H.; Su, K. S.; Tatlock, J. H. J. Med. Chem. 1997, 40,
after washing with ethyl acetate were thoroughly washed with
3979–3985. doi:10.1021/jm9704098
water (3 × 3 mL) followed by acetone (3 × 3 mL) and then dried
under vacuum to obtain a free-flowing black powder. This ma-
terial was used for the next catalytic cycle.
2. De Martino, G.; Edler, M. C.; Regina, G. L.; Cosuccia, A.;
Barbera, M. C.; Barrow, D.; Nicholson, R. I.; Chiosis, G.; Brancale, A.;
Hamel, E.; Artico, M.; Silvestri, R. J. Med. Chem. 2006, 49, 947–954.
doi:10.1021/jm050809s
3. Liu, G.; Huth, J. R.; Olejniczak, E. T.; Mendoza, R.; DeVries, P.;
Leitza, S.; Reilly, E. B.; Okasinski, G. F.; Fesik, S. W.;
von Geldern, T. W. J. Med. Chem. 2001, 44, 1202–1210.
doi:10.1021/jm000503f
Gram-scale procedure for C–S cross-
coupling using Ni/RGO-40
A mixture of 4-iodoanisole (1 g, 4.27 mmol), thiophenol
(0.563 g, 5.12 mmol), potassium carbonate (0.706 g,
5.12 mmol), Ni/RGO-40 catalyst (94.0 mg; Ni content is
37.60 mg, 0.64 mmol) in DMF (4 mL) were taken in a 15 mL
sealed tube, flashed and filled with N2 gas and quickly screw-
capped. The reaction mixture was then heated to 100 °C with a
gentle magnetic stirring for 3 hours. After cooling the reaction
mixture was diluted with ethyl acetate (4 mL), stirred gently
and then allowed to stand for 15 min. The supernatant liquid
was carefully pipetted out into another flask and this process
was repeated three more times. The organic part was washed
4. Nielsen, S. F.; Nielsen, E. Ø.; Olsen, G. M.; Liljefors, T.; Peters, D.
J. Med. Chem. 2000, 43, 2217–2226. doi:10.1021/jm990973d
5. Toshihiko, M.; Tomiya, S.; Yoriyoshi, A.; Jun-ichi, S.; Yasuki, K.;
Masanori, K. Bull. Chem. Soc. Jpn. 1980, 53, 1385–1389.
doi:10.1246/bcsj.53.1385
6. Cristau, H. J.; Chabaud, B.; Chêne, A.; Christol, H. Synthesis 1981,
892–894. doi:10.1055/s-1981-29636
7. Eichman, C. C.; Stambuli, J. P. Molecules 2011, 16, 590–608.
doi:10.3390/molecules16010590
8. Wong, Y.-C.; Jayanth, T. T.; Cheng, C.-H. Org. Lett. 2006, 8,
5613–5616. doi:10.1021/ol062344l
1804

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
9. Correa, A.; Carril, M.; Bolm, C. Angew. Chem., Int. Ed. 2008, 47,
2880–2883. doi:10.1002/anie.200705668
36.Zhang, X.-Y.; Li, H.-P.; Cui, X.-L.; Lin, Y. J. Mater. Chem. 2010, 20,
2801–2806. doi:10.1039/B917240H
10.Lai, C.-S.; Kao, H.-L.; Wang, Y.-J.; Lee, C.-F. Tetrahedron Lett. 2012,
53, 4365–4367. doi:10.1016/j.tetlet.2012.06.054
37.Guo, S.; Wen, D.; Zhai, Y.; Dong, S.; Wang, E. ACS Nano 2010, 4,
3959–3968. doi:10.1021/nn100852h
11.Liu, T.-J.; Yi, C.-L.; Chan, C.-C.; Lee, C.-F. Chem. – Asian J. 2013, 8,
1029–1034. doi:10.1002/asia.201300045
38.Scheuermann, G. M.; Rumi, L.; Steurer, P.; Bannwarth, W.;
Mülhaupt, R. J. Am. Chem. Soc. 2009, 131, 8262–8270.
doi:10.1021/ja901105a
12.Reddy, V. P.; Kumar, A. V.; Swapna, K.; Rao, K. R. Org. Lett. 2009, 11,
1697–1700. doi:10.1021/ol900009a
39.Kamal, A.; Srinivasulu, V.; Murty, J. N. S. R. C.; Shankaraiah, N.;
Nagesh, N.; Srinivasa Reddy, T.; Subba Rao, A. V. Adv. Synth. Catal.
2013, 355, 2297–2307. doi:10.1002/adsc.201300416
40.Zhang, N.; Qiu, H.; Liu, Y.; Wang, W.; Li, Y.; Wang, X.; Gao, J.
J. Mater. Chem. 2011, 21, 11080–11083. doi:10.1039/C1JM12539G
41.Feng, Y.-S.; Lin, X.-Y.; Hao, J.; Xu, H.-J. Tetrahedron 2014, 70,
5249–5253. doi:10.1016/j.tet.2014.05.083
13.Malik, P.; Chakraborty, D. Appl. Organomet. Chem. 2012, 26,
557–561. doi:10.1002/aoc.2871
14.Hegedus, L. L.; McCabe, R. W. Catalyst poisoning; Marcel Dekker:
New York, 1984.
15.Jammi, S.; Barua, P.; Rout, L.; Saha, P.; Punniyamurthy, T.
Tetrahedron Lett. 2008, 49, 1484–1487.
doi:10.1016/j.tetlet.2007.12.118
42.Zhai, Z.; Guo, X.; Jiao, Z.; Jin, G.; Guo, X.-Y. Catal. Sci. Technol. 2014,
4, 4196–4199. doi:10.1039/C4CY01048E
16.Cao, Y.-Q.; Zhang, Z.; Guo, Y.-X.; Wu, G.-Q. Synth. Commun. 2008,
38, 1325–1332. doi:10.1080/00397910801914111
17.Percec, V.; Bae, J.-Y.; Hill, D. H. J. Org. Chem. 1995, 60, 6895–6903.
doi:10.1021/jo00126a047
43.Yan, J.-M.; Zhang, X.-B.; Han, S.; Shioyama, H.; Xu, Q. Inorg. Chem.
2009, 48, 7389–7393. doi:10.1021/ic900921m
44.Lipshutz, B. H.; Tasler, S. Adv. Synth. Catal. 2001, 343, 327–329.
doi:10.1002/1615-4169(20010430)343:4<327::AID-ADSC327>3.0.CO;
2-R
18.Xu, X.-B.; Liu, J.; Zhang, J.-J.; Wang, Y.-W.; Peng, Y. Org. Lett. 2013,
15, 550–553. doi:10.1021/ol303366u
19.Venkanna, G. T.; Arman, H. D.; Tonzetich, Z. J. ACS Catal. 2014, 4,
2941–2950. doi:10.1021/cs500874z
45.Lipshutz, B. H.; Frieman, B. A.; Lee, C.-T.; Lower, A.; Nihan, D. M.;
Taft, B. R. Chem. – Asian J. 2006, 1, 417–429.
20.Zhang, J.; Medley, C. M.; Krause, J. A.; Guan, H. Organometallics
2010, 29, 6393–6401. doi:10.1021/om100816d
doi:10.1002/asia.200600031
46.Soulé, J.-F.; Miyamura, H.; Kobayashi, S. J. Am. Chem. Soc. 2013,
135, 10602–10605. doi:10.1021/ja404006w
21.Yatsumonji, Y.; Okada, O.; Tsubouchi, A.; Takeda, T. Tetrahedron
2006, 62, 9981–9987. doi:10.1016/j.tet.2006.08.001
22.Zhang, Y.; Ngeow, K. C.; Ying, J. Y. Org. Lett. 2007, 9, 3495–3498.
doi:10.1021/ol071248x
47.Hussain, N.; Gogoi, P.; Khare, P.; Das, M. R. RSC Adv. 2015, 5,
103105–103115. doi:10.1039/C5RA22601E
48.Bhowmik, K.; Mukherjee, A.; Mishra, M. K.; De, G. Langmuir 2014, 30,
3209–3216. doi:10.1021/la500156e
23.Guan, P.; Cao, C.; Liu, Y.; Li, Y.; He, P.; Chen, Q.; Liu, G.; Shi, Y.
Tetrahedron Lett. 2012, 53, 5987–5992.
49.Bhowmik, K.; Sengupta, D.; Basu, B.; De, G. RSC Adv. 2014, 4,
35442–35448. doi:10.1039/C4RA04834B
doi:10.1016/j.tetlet.2012.08.055
24.Pal, N.; Bhaumik, A. Dalton Trans. 2012, 41, 9161–9169.
doi:10.1039/C2DT30343D
50.Mandal, B.; Basu, B. RSC Adv. 2014, 4, 13854–13881.
doi:10.1039/C3RA45997G
25.Stankovich, S.; Dikin, D. A.; Dommett, G. H. B.; Kohlhaas, K. M.;
Zimney, E. J.; Stach, E. A.; Piner, R. D.; Nguyen, S. T.; Ruoff, R. S.
Nature 2006, 442, 282–286. doi:10.1038/nature04969
26.Balandin, A. A.; Ghosh, S.; Bao, W.; Calizo, I.; Teweldebrhan, D.;
Miao, F.; Lau, C. N. Nano Lett. 2008, 8, 902–907.
doi:10.1021/nl0731872
51.Wu, S.-H.; Chen, D.-H. J. Colloid Interface Sci. 2003, 259, 282–286.
doi:10.1016/S0021-9797(02)00135-2
52.Husin, H.; Su, W.-N.; Chen, H.-M.; Pan, C.-J.; Chang, S.-H.; Rick, J.;
Chuang, W.-T.; Sheu, H.-S.; Hwang, B.-J. Green Chem. 2011, 13,
1745–1754. doi:10.1039/C1GC15070G
53.Rout, L.; Saha, P.; Jammi, S.; Punniyamurthy, T. Eur. J. Org. Chem.
2008, 640–643. doi:10.1002/ejoc.200700978
27.Loh, K. P.; Bao, Q.; Eda, G.; Chhowalla, M. Nat. Chem. 2010, 2,
1015–1024. doi:10.1038/nchem.907
54.Schwab, R. S.; Singh, D.; Alberto, E. E.; Piquini, P.;
Rodrigues, O. E. D.; Braga, A. L. Catal. Sci. Technol. 2011, 1,
569–573. doi:10.1039/C1CY00091H
28.Li, B.; Cao, H.; Yin, J.; Wu, Y. A.; Warner, J. H. J. Mater. Chem. 2012,
22, 1876–1883. doi:10.1039/C1JM13032C
29.Li, W.; Wang, F.; Liu, Y.; Wang, J.; Yang, J.; Zhang, L.;
Elzatahry, A. A.; Al-Dahyan, D.; Xia, Y.; Zhao, D. Nano Lett. 2015, 15,
2186–2193. doi:10.1021/acs.nanolett.5b00291
30.Bai, H.; Li, C.; Shi, G. Adv. Mater. 2011, 23, 1089–1115.
doi:10.1002/adma.201003753
31.Li, M.; Pan, Y.; Guo, X.; Liang, Y.; Wu, Y.; Wen, Y.; Yang, H.
J. Mater. Chem. A 2015, 3, 10353–10359. doi:10.1039/C5TA00891C
32.Sabater, S.; Mata, J. A.; Peris, E. Organometallics 2015, 34,
1186–1190. doi:10.1021/om501040x
33.Zhang, P.; Zhang, X.; Zhang, S.; Lu, X.; Li, Q.; Su, Z.; Wei, G.
J. Mater. Chem. B 2013, 1, 6525–6531. doi:10.1039/C3TB21270J
34.Balcioglu, M.; Rana, M.; Yigit, M. V. J. Mater. Chem. B 2013, 1,
6187–6193. doi:10.1039/C3TB20992J
35.Li, B.; Cao, H.; Shao, J.; Qu, M.; Warner, J. H. J. Mater. Chem. 2011,
21, 5069–5075. doi:10.1039/C0JM03717F
1805

Beilstein J. Org. Chem. 2017, 13, 1796–1806.
License and Terms
This is an Open Access article under the terms of the
Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0), which
permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
(http://www.beilstein-journals.org/bjoc)
The definitive version of this article is the electronic one
which can be found at:
doi:10.3762/bjoc.13.174
1806