Biomimetic catalytic oxidative coupling of thiols using thiolate-bridged dinuclear metal complexes containing iron in water under mild conditions

Article abstract of DOI:10.1039/c9cy01667h

A green and efficient approach to disulfides via oxidative coupling of thiols was developed by adopting a biomimetic thiolate-bridged iron-ruthenium complex as the catalyst. Using environmentally friendly oxygen as the oxidant, a wide range of thiols including biologically important molecules can be smoothly converted into corresponding disulfides in water. Notably, two potential intermediate species were successfully isolated and unambiguously characterized, which is essential to reveal the detailed mechanism of this transformation. This catalytic system represents a rare and desired heteronuclear bimetallic scaffold for understanding the biological process of S-S bond formation from the viewpoint of bioinspired catalysis.

Full text of DOI:10.1039/c9cy01667h

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Biomimetic catalytic oxidative coupling of thiols
using thiolate-bridged dinuclear metal complexes
containing iron in water under mild conditions†
Cite this: Catal. Sci. Technol., 2019,
9, 6492
a
a
a
a
Yahui Zhang, Dawei Yang, * Ying Li, Xiangyu Zhao,
a
ab
Baomin Wang
and Jingping Qu
*
A green and efficient approach to disulfides via oxidative coupling of thiols was developed by adopting a
biomimetic thiolate-bridged iron–ruthenium complex as the catalyst. Using environmentally friendly oxygen
as the oxidant, a wide range of thiols including biologically important molecules can be smoothly
converted into corresponding disulfides in water. Notably, two potential intermediate species were
successfully isolated and unambiguously characterized, which is essential to reveal the detailed mechanism
of this transformation. This catalytic system represents a rare and desired heteronuclear bimetallic scaffold
for understanding the biological process of S–S bond formation from the viewpoint of bioinspired catalysis.
Received 19th August 2019,
Accepted 30th September 2019
DOI: 10.1039/c9cy01667h
rsc.li/catalysis
of oxygen has attracted considerable attention from the
Introduction
1
3
7
synthetic community. Up to now, many homogeneous and
8
Construction of the S–S bond is of great importance in
numerous fields of chemistry and biology, because the
resulting disulfides as structural linkers can play multifaceted
heterogeneous catalytic systems containing transition-metal
species utilizing oxygen have been successfully developed for
the oxidative coupling of thiols. However, most of these cases
usually have some obvious disadvantages including toxic
solvents, high temperature, long reaction times, relatively low
yields, and extra additives or bases. Therefore, the
establishment of efficient, green, and sustainable methods
for the formation of S–S bonds remains challenging and
highly desirable.
1–4
roles.
In biological proteins, the S–S bonds between
1
a
cysteine residues can stabilize the native structure. In drug
development, disulfides as a vital component exhibit unique
2a
pharmacological activities such as anti-alcoholic and anti-
2
b
bacterial effects.
In addition, this crucial motif also
3
4
extensively exists in natural products and food additives. In
this context, great efforts had been made to develop efficient
methods for the access to disulfides. Among these synthetic
In the past two decades, although several new strategies
5
14
have been developed,
the transition-metal catalyzed
pathways, the oxidative coupling of thiols is the most effective
strategy, especially for symmetrical disulfides. In fact, in
recent decade, oxidative coupling between two nucleophiles
catalyzed by transition metals has developed into an efficient
approach for chemical bond formations, in which oxidants
oxidative coupling of thiols to disulfides is still a most
commonly used one. From the conventional view of metal
catalysts, metal thiolate complexes usually play as inactive
1
5
species in these catalytic cycles. However, the discovery of
the active centres of various significant metalloenzymes in
nature provides new understanding of the role of sulfur
6
are usually involved. For example, to realize the formation of
1
6
S–S bonds, various oxidants are generally required, such as
donors. Besides, the cooperative effect of bi- or multi-
metallic sites is also essential to promote corresponding
7
,8
9
10
oxygen or air, hydrogen peroxide, halogens, high-valent
1
1
12
17
sulfur compounds and other agents. As people gradually
become aware of environmental protection, the employment
enzymatic activity. Nonetheless, there are no biomimetic
systems for the catalytic oxidation of thiols to disulfides in
aqueous
mechanistic
medium
reported.
Furthermore,
trapping
detailed
potential
a
investigations
by
State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2
intermediates using structural determination methods are
less developed, despite these being helpful to obtain insights
into biological processes involving S–S bond formation.
In our preliminary work, inspired by versatile
metalloenzymes in biology, we were always devoted to
constructing thiolate-bridged di- or multinuclear metal
complexes for small molecule activation and transformation,
Linggong Road, Dalian, 116024, P. R. China. E-mail: yangdw@dlut.edu.cn,
qujp@dlut.edu.cn
b
Key Laboratory for Advanced Materials, East China University of Science and
Technology, Shanghai, 200237, P. R. China
†
Electronic supplementary information (ESI) available: Experimental and
crystallographic details and spectral data. CCDC 1837831, 1837832, 1837835,
843162, 1869211, 1869214 and 1869707. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c9cy01667h
1
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1
8–20
1
adopting different types of sulfur donors.
Notably,
elemental analysis. In the H NMR spectrum of 2[PF ], three
6
several homo- and heterometallic thiolate complexes exhibit
excellent catalytic properties by the cooperation effect. In
order to further extend the catalytic performance of our
remarkably broad proton resonances appear at −6.42, −0.64,
and 3.03 ppm, which suggest that this iron–ruthenium
2
1
complex should be
a paramagnetic species. A similar
II
III
reaction platforms, herein, we utilized the flexible thioether-
phenomenon was also observed in other formal Fe Ru
−
29
dithiolate tridentate ligand tpdt (tpdt = SIJCH
2
CH
2
S )
2
) to
complexes.
Furthermore, solid evidence for the
prepare several tpdt-bridged heteronuclear complexes, among
which an iron–ruthenium complex was proven to be an
outstanding catalyst for the oxidation of mercaptans to
disulfides in water employing oxygen as the oxidant at room
temperature. Importantly, two potential intermediates during
the catalytic cycle were fully characterized by X-ray
crystallography.
paramagnetism of 2[PF ] was provided by other spectroscopic
6
3
0
methods. Using Evans' method,
the effective magnetic
susceptibility (μeff) of 2[PF ] in solution was determined to be
6
1
1.77μB by H NMR spectroscopy. In addition, the EPR
spectrum of complex 2[PF ] in the solid state at room
6
temperature features a diagnostic signal at g = 2.07 (Fig. S2†).
The above data indicate that complex 2[PF ] is in an S = 1/2
6
spin state. Differently, iron–cobalt complexes 4a[BPh ] and
4
1
4
b[BPh
4
] are all diamagnetic species confirmed by their
H
Results and discussion
Synthesis of thiolate-bridged heterometallic complexes with
NMR spectra, in which several intense resonances assignable
to Cp*, Cp′ and tpdt ligands appear in a common region.
This result is attributed to the fact that cobalt has one more
d electron than iron. In addition, their C NMR spectra were
fully consistent with the aforementioned H NMR results.
Furthermore, electrospray ionization high resolution mass
spectrometry (ESI-HRMS) was adopted to confirm the
molecular compositions of these complexes. As expected, the
corresponding molecular ion peaks for the cationic parts of
complexes 2[PF ], 4a[BPh ] and 4b[BPh ] were detected.
iron
1
3
Our investigation was initiated by the construction of
thioether-dithiolate-bridged heteronuclear metal complexes
containing iron. As illustrated in Scheme 1, a tpdt-bridged
1
3
κ
2
κ
iron–ruthenium complex [Cp*RuIJμ-1 SSS′:2 SS-tpdt)FeCp*]-
5
ijPF ] (2[PF ], Cp* = η -C Me ) was synthesized through the
6
6
5
5
assembly of the two mononuclear precursors [Cp*
2
2
3
23
RuIJMeCN) ]ijPF ] and [Cp*FeIJη -tpdt)] (1) in high yield. In
3
6
6
4
4
view of mononuclear iron precursor 1 as a versatile building
To get more structural information, these complexes were
clearly determined by X-ray diffraction analysis, and the
molecular structures of 2[PF ] and 4b[BPh ] are shown in
2
4
25
block and reaction platform, the mononuclear cobalt
3
analogue [Cp*CoIJη -tpdt)] (3) was synthesized by the
6
4
2
6
interaction of [Cp*CoIJμ-Cl) IJt-Cl) CoCp*] with 2 equiv. of
Fig. 1 and 2, respectively. Their geometric arrangement is
2
2
2
3
Li
3
cobalt
2
IJtpdt). Similarly, by adopting mononuclear cobalt complex
similar to that of the diiron analogue. Interestingly, it is
observable that the thioether sulfur atom in the bridging tpdt
ligand flipped from the original metal center to the other
one. This unusual phenomenon should be attributed to the
flexibility of the tpdt ligand, because a similar situation is
2
7
and [Cp*FeIJMeCN) ]ijPF ] as precursors, a similar iron–
3 6
3
κ
2
κ
complex
[Cp*FeIJμ-1 SSS′:2 SS-tpdt)CoCp*]ijBPh ]
4
(
4a[BPh ]) was smoothly generated in good yield. To
4
distinguish between iron and cobalt which have similar
atomic radii, we also conducted a reaction employing [Cp′
not observed when using other rigid tridentate ligands to
construct heteronuclear complexes. In 2[PF ], the Fe–Ru
6
5
28
31
FeIJMeCN)
3
]ijPF
6
] (Cp′= η -C
5
Me
4
H) to facilely afford the
3
2
corresponding iron–cobalt complex [Cp′FeIJμ-1 SSS′:2 SS-
bond distance is 2.691(2) Å, which is very close to that of our
κ
κ
2
9
tpdt)CoCp*]ijBPh ] (4b[BPh ]).
other reported thiolate-bridged FeRu complex. Because the
thioether sulfur atom is coordinated to the ruthenium center,
the interaction between the ruthenium center and bridging
thiolate sulfur atoms is evidently weakened, which is
4
4
These heteronuclear complexes were fully characterized by
H NMR, C NMR, ESI-HRMS, and IR spectroscopy as well as
1
13
Scheme 1 Synthesis of heterometallic complexes 2[PF
b[BPh
]. Reagents and conditions: (i) MeCN, −45 °C to rt, 88%; (ii) 2
3 6
equiv. of Li ]ijPF ]
6 4
], 4a[BPh ] and
4
4
†
2
IJtpdt), THF, rt, 2 h, 55%; (iii) 1 equiv. of [Cp FeIJMeCN)
Cp = Cp* or Cp′), 1 equiv. of NaBPh
, THF, −78 °C to rt, 82% for
a[BPh ], 83% for 4b[BPh ].
†
(
4
Fig. 1 Molecular structure of 2[PF
6
] at 50% probability of ellipsoids.
4
4
4
The PF anion and hydrogen atoms are omitted for the sake of clarity.
6
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1
7,34
systems,
we constructed heterometallic complexes to
pursue the development of new systems for biomimetic
catalysis. During our investigations about biomimetic
oxidation using oxygen, we found that tpdt-bridged homo- or
heterometallic complexes can serve as effective catalysts for
the oxidative coupling of mercaptans. Based on this finding,
a series of experiments were designed and performed.
At the outset, the catalytic transformation of thiophenol
(
5a) to diphenyl disulfide (6a) was selected as the model
reaction to optimize the reaction conditions. For the sake of
manifesting the unique catalytic nature of bimetallic
complexes by the cooperation effect, several mononuclear
precursor complexes were chosen as catalysts. In addition, to
understand the differences of metal centres in catalytic
4
Fig. 2 Molecular structure of 4b[BPh ] at 50% probability of ellipsoids.
4
The BPh anion and hydrogen atoms except for the hydrogen atom on
the Cp′ ring are omitted for the sake of clarity.
6
activity, diiron and nickel–iron analogues of complex 2[PF ]
were also examined. All experimental results are summarized
in Table 1 (the detailed coordination modes of the bridging
tpdt ligand are simplified due to space constraints of the
table).
consistent with the fact that the Ru1–S1 bond length of
2
.305(2) Å is significantly longer than the Fe1–S1 bond length
of 2.197(2) Å and almost equal to the Ru1–S2 bond length of
.307(3) Å. In 4b[BPh ], to stabilize the coordinatively
In the presence of 1 mol% catalyst, the mononuclear iron,
ruthenium, and cobalt complexes show poor activity for the
oxidative coupling of thiols in THF-d8 at room temperature
under an oxygen atmosphere (entries 1–5). Notably, when the
three labile MeCN groups were replaced by the tridentate
tpdt ligand, the conversion and yield significantly increased,
especially with mononuclear iron and cobalt complexes 1
and 3 (entries 3 and 5). To our delight, when the tpdt-
2
4
unsaturated iron center, the thioether sulfur atom occupies
the remaining coordination site. A similar situation was also
observed in the bidentate thiolate-bridged iron–cobalt
2
4
complex [Cp*CoIJμ-η :η -bdt)FeCp′]ijPF ] (bdt = benzene-1,2-
6
3
2
dithiolate). The minor substituent difference on the Cp
rings of complexes 4a[BPh ] and 4b[BPh ] has a slight effect
on the structural data. For example, the dihedral angles of
two Cp rings in 4a[BPh ] is 66.78IJ21)°, which is smaller than
]. Besides, the Fe–Co bond distance of
.6772(8) Å in 4a[BPh ] is slightly longer than 2.587(1) Å in
4
4
3
κ
2
κ
bridged diiron complex [Cp*FeIJμ-1 SSS′:2 SS-pdt)FeCp*]-
4
ijPF
were obtained as shown in entry 6. Nonetheless, iron–nickel
complex [Cp*FeIJμ-tpdt)NiIJdppe)]ijPF6] and iron–cobalt
complex 4a[BPh ] with a similar core structure were proven
6
] was adopted as the catalyst, a high conversion and yield
7
2
4
3.18IJ19)° in 4b[BPh
4
4
b[BPh
4
]. These two bond lengths are located in a common
4
range from 2.398(14) Å to 3.153(1) Å in reported dithiolate-
bridged iron–cobalt complexes.
to be poor promoters for the conversion of thiophenol to
diphenyl sulfide (entries 7 and 9). In addition, iron–
3
3
6
ruthenium complex 2[PF ] can also serve as an excellent
catalyst with a high conversion and yield similar to its diiron
analogue (entry 8). Essentially, its binuclear reaction scaffold
still remains after catalytic transformation, which is different
Aerobic oxidation of thiols catalysed by bimetallic complexes
Inspired by versatile catalytic properties mediated by
heterometallic clusters in metalloenzymes and homogeneous
3
2
from the diiron complex. As observed, [Cp*FeIJμ-1
κ
SSS′:2 SS-
κ
Table 1 Aerobic oxidation of thiophenol to diphenyl disulfide catalyzed by various mono- and dinuclear metal complexesa
b
b
Entry
Catalyst
Conversion (%)
Yield (%)
1
2
3
4
5
6
7
8
9
[Cp*FeIJMeCN)
3
]ijPF
]ijPF
[Cp*FeIJη -tpdt)]
6
]
6
]
16
16
74
33
68
100
36
100
20
9
12
71
31
66
93
34
95
11
[Cp*RuIJMeCN)
3
3
3
[Cp*RuIJη -tpdt)]
3
[Cp*CoIJη -tpdt)]
[Cp*FeIJμ-tpdt)FeCp*]ijPF
[Cp*FeIJμ-tpdt)NiIJdppe)]ijPF
2[PF
4a[BPh
6
]
6
]
6
]
4
]
a
b
Reaction conditions: thiophenol (1.8 mmol), catalyst (0.018 mmol, 1 mol%), THF-d
8
(0.6 mL), under an O
2
atmosphere, rt, 15 min. The
1
yield and conversion were determined by H NMR spectroscopy with hexamethylbenzene as an internal standard.
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pdt)FeCp*]ijPF ] was almost completely decomposed into
Under the green and mild conditions, we next examined the
6
unidentified insoluble species after the catalytic reaction was
completed.
substrate scope of this oxidation reaction using 2[PF ] (1
mol%) as the catalyst. As shown in Table 2, complex 2[PF ]
6
6
Moreover, we also explored the solvent effects in the
conversion and yield of this reaction. The screening results
show that THF is the optimal solvent (Table S1†).
Furthermore, the loading of catalyst 2[PF6] was also
investigated from 1 mol% to 0.1 mol%. As a result, 1 mol%
catalyst was required for the accomplishment of this catalytic
process, which is evidenced by the fact that the obvious
decrease of the yield is accompanied with the reduction of
the amount of catalyst (Table S2†). Besides, control
experiments have also been implemented to demonstrate the
importance of the compatibility between catalyst and oxidant.
One step further, we have also tried the synthesis of
unsymmetrical disulfides through the oxidative cross
was proven to be an efficient catalyst with good functional
group compatibility for oxidative coupling of thiols to
corresponding
disulfides.
For
instance,
thiophenol
derivatives (5b and 5c) bearing electron-donating and
electron-withdrawing groups at the para positions on the
phenyl ring can facilely be oxidized to afford the
corresponding disulfides (6b and 6c) in high yields. In
addition, benzyl mercaptan (5d) as a representative aliphatic
thiol was also oxidized to generate disulfide 6d in good yield.
Furthermore, conversion of some biological relevant
organosulfur compounds such as cysteine (5e) and reduced
glutathione (5f) into cystine (6e) and oxidized glutathione
(6f), respectively, were also realized in high yields. The
achievement of these two cases provides a new biomimetic
reaction platform in aqueous medium for obtaining more
insights into peptide bond formation in cells.
coupling of different thiols catalyzed by complex 2[PF ] under
6
similar conditions. Formation of unsymmetrical disulfides
was observed, but the selectivity is moderate due to the
appearance of homo-coupling products.
From the viewpoints of environmental and sustainable
3
5
Mechanistic considerations
prospects, we sought to develop a greener catalytic system
for the synthesis of disulfides. To achieve this aim, we
attempted to utilize water as the solvent, replacing THF.
Delightedly, the oxidative coupling of thiophenol catalyzed by
[PF ] smoothly proceeded in water , although it is necessary
6
to extend the reaction time to 3 h for complete conversion.
To get a deep insight into plausible reaction pathways of the
catalytic oxidation of thiols using 2[PF ], a series of
6
experiments were conducted to corroborate potential
intermediate species. Also, thiophenol was selected as a
representative substrate for mechanistic studies. Firstly, we
2
a
6
Table 2 Oxidation of thiols catalyzed by 2[PF ]
b
Entry
1
Thiol
Disulfide
Yield (%)
90
5
a
6a
6b
6c
2
3
4
90
89
82
5
b
5
5
c
d
6d
5
6
97
94
5
5
e
f
6e
6f
a
b
Reaction conditions: thiol (1.8 mmol), 2[PF
6
] (0.018 mmol, 1 mol%), H
2
2
O (2 mL), under an O atmosphere, rt, 3 h. Isolated yields.
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Fig. 4 Molecular structure of 8[PF
6
] at 50% probability of ellipsoids.
6
The PF anion and hydrogen atoms are omitted for the sake of clarity.
1
The H NMR spectrum of 7ijPF ] shows four sets of proton
Scheme
2
Synthesis of complexes 7ijPF
6
]
2
,
8[PF
6
]
and 9[BPh
4
].
(1
atm), THF, rt, 15 min, 88%; (iii) ex. PhSH, THF, rt, 15 min; (iv) 1 equiv. of
CoCp , 1 equiv. of Lut·HBPh , 1 equiv. of NaBPh
, THF, −78 °C to rt,
5%.
6 2
Reagents and conditions: (i) air, MeCN, rt, 1 h, 42%; (ii) ex. PhSH, O
2
resonances for the four inequivalent methylene groups in the
tpdt ligand and two intense singlets for the methyl groups of
two inequivalent Cp* groups. All assignments of H NMR
data are fully consistent with the structural information
determined from the
2
4
4
1
8
1
3
C NMR spectrum of 7ijPF ] .
6 2
Crystallographic analysis shows that one MeCN molecule
occupies the open coordination site (see Fig. 3). The Fe–Ru
distance in 7ijPF ] is slightly lengthened from 2.691(2) Å in
explored the reactivity of complex 2[PF
atmosphere of oxygen in the absence of thiophenol. Complex
[PF ] was robust under an inert atmosphere whether in
6
] towards one
6
2
2
6
6
2[PF ] to 2.794(2) Å.
solution or the solid state. However, when a THF solution of
Subsequently, under aerobic conditions, the reaction of
complex 2[PF ] was exposed to oxygen for about 1 h, further
2[PF ] with a slight excess of thiophenol gave the only
6
6
3
2
oxidized product 2ijPF
]
6 2
was detected by ESI-MS analysis,
product
(8[PF ]) in good yield (Scheme 2). Oxidation of 2[PF
a dicationic species was not observed. Complex 8[PF ] was
[Cp*FeIJμ-1
κ
SSS′:2
κ
SS-tpdt){Cp*RuIJt-SPh)}]ijPF
6
]
accompanied with a great deal of precipitates. This result
6
6
] to form
indicates that a disproportionation process of 2[PF ] may
6
6
occur, promoted by oxygen. However, the reaction selectivity
is too poor to conduct further isolation and purification of
complex 2ijPF ] . With weakly coordinative MeCN as the
unambiguously
characterized
by
spectroscopy
and
crystallography. Interestingly, the crystal structure shown in
Fig. 4 reveals that the pendent thioether sulfur atom in the
tpdt ligand returned from the ruthenium center to the iron
center. Meanwhile, a phenylthiolate group was coordinated
to the ruthenium centre.
6
2
III
III
solvent, an expected dicationic Fe Ru complex [Cp*RuIJμ-
3
κ
2
κ
1
SSS′:2
successfully isolated in moderate yield (Scheme 2).
Independently, complex 7ijPF can also be obtained by the
reaction of 2[PF ] with one-electron oxidant Fc·PF in MeCN.
SS-tpdt){Cp*FeIJt-MeCN)}]ijPF
6
]
2
(7ijPF
6
]
2
)
can be
]
6 2
Interestingly, treatment of 2[PF
thiophenol in THF-d under anaerobic conditions gave a
mixture of complex 8[PF ] and terminal hydride complex
6
] with an excess of
6
6
8
6
3
κ
2
[Cp*FeIJμ-1
SSS′:2
κ
SS-tpdt){Cp*RuIJt-H)}]ijPF
6
]
6
(9[PF ]),
1
identified using the H NMR spectrum and ESI-HRMS data.
Fig. 3 Molecular structure of 7ijPF
6
]
2
at 50% probability of ellipsoids.
Fig. 5 Molecular structure of 9[BPh
The BPh anion and hydrogen atoms except the terminal hydride are
omitted for the sake of clarity.
4
] at 50% probability of ellipsoids.
The two PF
clarity.
6
anions and hydrogen atoms are omitted for the sake of
4
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Due to the restriction of coordination number, the
phenylthiolate and hydride groups derived from thiophenol
didn't bind to the same bimetallic scaffold through an
this oxidation process is shown in Scheme 3. Firstly, catalyst
2[PF6] interacts with thiols to simultaneously generate
complexes 8[PF ] and 9[PF ], which is strongly supported by
6 6
the above experimental results. Then, these two complexes
3
6
oxidative addition fashion as in other metallic systems. In
1
the H NMR spectrum, four sharp peaks appear at 1.60, 1.68,
can transform into initial species 2[PF6] through two
1
.71 and 1.93 ppm, assignable to two sets of inequivalent
6
different pathways. In the left semicircle, complex 8[PF ]
Cp* methyl proton signals of complexes 8[PF ] and 9[PF ],
converts into 2[PF ] in the presence of a thiol and oxygen
6
6
6
respectively (Fig. S18†). In addition, a diagnostic signal for
the terminal hydride appears at −16.81 ppm in the high field
region, which is close to −16.44 ppm of a phosphine-
accompanied with the release of the oxidation product
PhSSPh and side-product H O. Meanwhile, in the right
2
semicircle, the intermediate 9[PF ] reduces molecular oxygen
6
3
7
dithiolate-bridged diruthenium terminal hydride complex,
to give H O along with the regeneration of complex 2[PF ].
2
6
but is significantly located in a higher field than those of
The two sections combine together to accomplish a catalytic
cycle. Finally, the main residue containing metals in solution
3
6a,38
other thiolate-bridged diruthenium complexes.
In
addition, the terminal hydride complex 8[PF ] can also be
was complex 8[PF ], which cannot further release disulfides
6
6
independently generated through the reductive protonation
through the left semicircle due to exhaustion of thiophenol.
of 2[PF ] in excellent yield (Scheme 2).
6
Single-crystals suitable for X-ray diffraction analysis were Conclusions
obtained by further counter ion exchange. As shown in Fig. 5,
In summary, several thiolate-bridged heteronuclear complexes
the molecular structure of 9[BPh ] reveals a hydride ligand
4
containing iron were successfully synthesized by an assembly
reaction and fully characterized by spectroscopy and
terminally coordinated to the ruthenium center accompanied
with shifting of the pendant thioether sulfur atom to the iron
center. These structural variations cause the Fe–Ru distance
crystallography. Iron–ruthenium complex 2[PF ] can serve as an
6
excellent catalyst for oxidation of thiols to symmetrical disulfides
employing environmentally friendly oxygen in aqueous medium
at room temperature. Unexpectedly, this green method is not only
applicable to common organic thiols, but also to small molecules
with biological significance such as cysteine and reduced
glutathione. Achievement of this bio-inspired oxidation by the
bimetallic cooperative effect is conducive to gain new insights
into some important biological processes involving S–S bond
formation. Furthermore, two potential intermediates in the
catalytic cycle were unambiguously characterized by X-ray
diffraction analysis, which provides vital evidence for the detailed
elucidation of the reaction mechanism. Studies on other potential
catalytic oxidation processes and biological activities are now in
progress.
of 2.7411(4) Å in 9[BPh
with 2.691(2) Å in 2[PF
bridged bimetallic systems, the terminal hydride complex
[BPh ] is relatively insensitive to temperature and is stable
under an inert atmosphere at room temperature.
In order to test the identity of potential intermediates, we
carried out the catalytic oxidation of thiophenol with these
4
] to be slightly lengthened compared
6
]. Interestingly, different from bdt-
2
9
9
4
complexes. Due to its insolubility in THF, complex 7ijPF
was firstly excluded as a potential intermediate species.
However, complex 8[PF ] can serve as an excellent catalyst for
oxidative coupling of thiols to disulfides under an O
6 2
]
6
2
atmosphere (Table S4†). In addition, 9[BPh ] was also proven
4
to be an effective catalyst for oxidation of thiols under similar
conditions, in spite of its relatively low efficiency compared
with 8[PF ]. This result can be explained by the instability of
6
9
[BPh
4
] in the presence of excess substrates under an O
2
Experimental section
General procedures
atmosphere. Realization of this catalytic reaction promoted
by these two complexes suggests that they should function as
essential intermediates during this catalytic process.
All manipulations were carried out under a dry argon
atmosphere by using standard Schlenk techniques and a
Mikrouna argon-filled glove box. All solvents were dried and
distilled over an appropriate drying agent under argon.
Based on the above results and previous reports for the
8
d
pathways of this type of reaction, a proposed mechanism of
3
9
40
41
pentamethylcyclopentadiene (Cp*H), Lut·HBPh
4
,
Fc·PF
6
,
2
2
3
23
[
Cp*RuIJMeCN) ]ijPF ], [Cp*FeIJη -tpdt)] (1), [Cp*CoIJμ-Cl) IJt-
3
6
2
2
6
27
28
Cl)
2
CoCp*],
[Cp*FeIJMeCN)
3
]ijPF
6
],
3 6
[Cp′FeIJMeCN) ]ijPF ]
3
42
and [Cp*RuIJη -tpdt)] were prepared according to literature
procedures. RuCl3 (Aldrich), anhydrous FeCl2 (Aldrich),
2 2 2 4 2
SIJCH CH SH) (Aldrich), NaBPh (Energy Chemical), CoCp
(
Energy Chemical), and mercaptans (Energy Chemical) were
used as received without further purification.
Spectroscopic measurements
Infrared spectra were recorded on
a NEXVSTM FT-IR
6
Scheme 3 Plausible catalytic mechanism for the 2[PF ]-catalyzed
oxidation of thiols to disulfides with molecular oxygen as an oxidant.
spectrometer. Elemental analyses were performed using a
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1
13
Vario EL analyzer. The H and
C NMR spectra were
transferred via a cannula to a THF (30 mL) solution of [Cp*
CoIJμ-Cl) IJt-Cl) CoCp*] (1.00 g, 1.89 mmol) and the mixture
recorded on a Brüker 400 Ultra Shield spectrometer. The
2
2
chemical shifts (δ) are given in parts per million relative to
was stirred for 2 h, resulting in a violet solution. All volatiles
were removed in vacuo and the residue was extracted with
n-hexane (3 × 100 mL). After being cooled to −30 °C for one
1
13
CD CN (1.94 ppm for H; 118.26 ppm for C), CD Cl (5.32
3
2
2
1
13
1
ppm for H; 53.84 ppm for C), CDCl3 (7.26 ppm for H,
7.16 ppm for C), C
C), THF-d (1.72, 3.58 ppm for H), and D O (4.79 ppm for
H). ESI-HRMS data were recorded on an HPLC/Q-Tof mass
1
3
1
3
7
D
6 6
(7.16 ppm for H, 128.06 ppm for
day, black thin slice crystals of [Cp*CoIJη -tpdt)] (3, 720 mg,
1
3
1
1
2.08 mmol, 55%) were isolated. H NMR (400 MHz, C D ,
8
2
6 6
1
ppm): δ 1.40 (s, 15H, Cp*–CH ), 1.82 (m, 4H, tpdt-CH ), 2.13
3
2
1
3
spectrometer. The EPR spectra were recorded at room
temperature on a JEOL JES-FE3AX spectrometer.
(m, 4H, tpdt-CH
2
). C NMR (100 MHz, C
D
6 6
, ppm): δ 9.29
(Cp*–CH ), 30.70 (SCH ), 45.95 (SCH ), 93.17 (Cp*–C). IR
3
−
2
2
1
(
film, cm ): 2960, 2905, 1428, 1372, 1095, 1022, 832. Anal.
calcd. for C14 23CoS : C, 48.54; H, 6.69. Found: C, 48.26; H,
H
3
X-ray crystallography procedures
6
.64.
3
2
κ
The data were obtained on a Brüker SMART APEX CCD
diffractometer with graphite monochromated Mo Kα
radiation (λ = 0.71073 Å). Empirical absorption corrections
were performed using the SADABS program. Structures
were solved by direct methods and refined by the full-matrix
Synthesis of [Cp*FeIJμ-1 SSS′:2 SS-tpdt)CoCp*]ijBPh ]
κ
4
(4a[BPh
4
]). At −78 °C, a solution of [Cp*FeIJMeCN)
3
]ijPF
6
] (165
mg, 0.36 mmol) in THF (20 mL) was added to a THF (20 mL)
4
3
mixed solution of 3 (125 mg, 0.36 mmol) and NaBPh (123
4
mg, 0.36 mmol). Then, the resulting solution was stirred
vigorously as it warmed to room temperature, resulting in a
brown-red solution. Then, the supernatant solution was
filtered and evaporated to dryness in a vacuum. The resulting
2
least-squares method based on all data using F with
4
4
SHELX2014. All of the non-hydrogen atoms were refined
anisotropically. All of the hydrogen atoms were generated
and refined in ideal positions.
3
κ
2
κ
product, [Cp*FeIJμ-1 SSS′:2 SS-tpdt)CoCp*]ijBPh ] (4a[BPh ],
4
4
One CH group in the tpdt ligand of complex 2[PF ] and
one CH group in the tpdt ligand of complex 7ijPF ] were
2 6 2
disordered and restrained during structural refinement.
Disordered atomic positions were split and refined using one
occupancy parameter per disordered group. We used
SQUEEZE to help us solve the level B alert of solvent
257 mg, 0.30 mmol, 82%), was obtained as a brown powder.
Crystals suitable for X-ray diffraction were obtained from a
CH Cl solution layered with n-hexane at room temperature.
2
6
2
2
1
H NMR (400 MHz, CD
1.67 (m, 2H, tpdt-CH ), 2.04 (m, 2H, tpdt-CH
Cp*–CH ), 2.68 (m, 2H, tpdt-CH ), 4.26 (m, 2H, tpdt-CH ),
2
Cl
2
, ppm): δ 1.20 (s, 15H, Cp*–CH
3
),
2
2
), 2.53 (s, 15H,
3
2
2
accessible voids when checking the cif file of 9[BPh ] through
CheckCIF (http://checkcif.iucr.org). Crystal data and
6.87 (m, 4H, Ph-H), 7.02 (m, 8H, Ph-H), 7.31 (m, 8H, Ph-H).
4
1
3
2 2 3
C NMR (100 MHz, CD Cl , ppm): δ 9.10 (Cp*–CH ), 10.50
collection details for 2[PF ] and 3 are given in Table S6;†
(Cp*–CH ), 40.30 (SCH ), 44.69 (SCH ), 95.96 (Cp*–C), 99.56
6
3
2
2
crystal data and collection details for 4a[BPh ] and 4b[BPh ]
(Cp*–C), 122.13 (Ph-C), 126.02 (Ph-C), 136.31 (Ph-C). ESI-
4
4
+
are given in Table S7;† crystal data and collection details for
ijPF ] , 8[PF ], and 9[BPh ] are given in Table S8.†
HRMS (m/z): calcd. for 4a : 537.0817; found: 537.0803. IR
−
1
7
(film, cm ): 3052, 2962, 2851, 1579, 1478, 1090, 1201, 733,
6
2
6
4
3
2
Synthesis
2[PF ]). A solution of [Cp*FeIJη -tpdt)] (1, 161 mg, 0.47 mmol)
in MeCN (15 mL) was cooled to −45 °C. Then, a solution of
Cp*RuIJMeCN) ]ijPF ] (237 mg, 0.47 mmol) in MeCN (20 mL)
of
[Cp*RuIJμ-1 SSS′:2 SS-tpdt)FeCp*]ijPF ]
3
705, 607. Anal. calcd. for C48H58BCoFeS : C, 67.29; H, 6.82.
κ
κ
6
3
(
6
Found: C, 67.54; H, 6.90.
3
2
Synthesis of [Cp′FeIJμ-1 SSS′:2 SS-tpdt)CoCp*]ijBPh ]
κ
κ
4
[
(4b[BPh
4
]). At −78 °C, a solution of [Cp′FeIJMeCN)
3
]ijPF
6
] (142
3
6
at −45 °C was transferred via a cannula to the cooled solution
of 1. The mixture was stirred overnight as it warmed to room
temperature. The resulting yellow-green solution was
mg, 0.32 mmol) in THF (20 mL) was added to a THF (20 mL)
mixed solution of 3 (111 mg, 0.32 mmol) and NaBPh (109
4
mg, 0.32 mmol). Then, the resulting solution was stirred
vigorously as it warmed to room temperature, resulting in a
brown-red solution. Then, the supernatant solution was
filtered and evaporated to dryness in a vacuum. The resulting
evaporated and washed with Et
2
O (3 × 10 mL). The product,
3
2
[
Cp*RuIJμ-1 SSS′:2 SS-tpdt)FeCp*]ijPF ] (2[PF ], 300 mg, 0.41
κ
κ
6
6
mmol, 88%), was obtained as a yellow-green crystalline
powder. Crystals suitable for X-ray diffraction were obtained
3
κ
2
κ
product, [Cp′FeIJμ-1
4 4
SSS′:2 SS-tpdt)CoCp*]ijBPh ] (4b[BPh ],
from
a
THF solution layered with n-hexane at room
227 mg, 0.27 mmol, 83%), was obtained as a brown powder.
Crystals suitable for X-ray diffraction were obtained from a
1
temperature. H NMR (400 MHz, CD CN, ppm): δ −6.42 (br),
3
−
1
5
0.64 (s), 3.03 (s). μeff (CD
.77μ . ESI-HRMS (m/z): calcd. for 2 : 580.0535; found:
80.0549. IR (film, cm ): 2962, 2852, 1379, 1021, 558. EPR
38FeRuS PF : C, 39.78;
3
CN, Evans' method, 25 °C) =
CH
2
Cl
2
solution layered with n-hexane at room temperature.
+
1
H NMR (400 MHz, CD Cl , ppm): δ 1.21 (s, 6H, Cp′–CH ),
B
2
2
3
−
1
1.84 (s, 15H, Cp*–CH
3
), 1.87 (s, 6H, Cp′–CH
3
), 2.48 (m, 4H,
(298 K): g = 2.07. Anal. calcd. for C24
H
3
6
tpdt-CH
(m, 4H, Ph-H), 7.00 (m, 8H, Ph-H), 7.28 (m, 8H, Ph-H).
NMR (100 MHz, CD Cl , ppm): δ 10.41 (Cp′–CH ), 11.15
(Cp*–CH ), 11.31 (Cp′–CH ), 35.95 (SCH ), 47.54 (SCH ),
2 2
), 3.10 (m, 4H, tpdt-CH ), 3.92 (s, 1H, Cp′–H), 6.85
1
3
H, 5.29. Found: C, 39.56; H, 4.99.
Synthesis of [Cp*CoIJη -tpdt)] (3). At room temperature, a
suspension of Li
reaction of BuLi (3.02 mL, 2.5 M solution in n-hexane, 7.56
mmol) and SIJCH CH SH) (580 mg, 3.78 mmol) at 0 °C, was
C
3
2
2
3
2
IJtpdt) in THF (30 mL), prepared by the
3
3
2
2
n
72.62 (Cp′–C), 91.37 (Cp*–C), 97.95 (Cp′–C), 98.42 (Cp′–C),
122.53 (Ph-C), 126.59 (Ph-C), 136.65 (Ph-C). ESI-HRMS (m/z):
2
2
2
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+
−1
calcd. for 4b : 523.0661; found: 523.0658. IR (film, cm ):
mmol) in THF (10 mL) was added to a THF (20 mL) mixed
3
051, 2913, 2851, 1579, 1478, 1426, 1096, 1020, 804, 705, 607.
solution of 2[PF ] (123 mg, 0.17 mmol), Lut·HBPh (73 mg,
6
4
Anal. calcd. for C48 58BCoFeS : C, 66.99; H, 6.70. Found: C,
H
3
0.17 mmol) and NaBPh
4
(58 mg, 0.17 mmol). The reaction
6
6.92; H, 6.68.
Synthesis
mixture was warmed to room temperature, resulting in a
brown-yellow solution. The supernatant solution was filtered
and evaporated to dryness under reduced pressure. The
3
2
of
(7ijPF
[Cp*RuIJμ-1 SSS′:2 SS-tpdt){Cp*FeIJt-
κ
κ
MeCN)}]ijPF
6
]
2
6 2 6
] ). Method A: A solution of 2[PF ] (152
mg, 0.21 mmol) in MeCN (20 mL) was stirred at room
temperature, exposing to air for 1 h. During this time, the
colour gradually changed from yellow-green to brown-yellow.
After removal of the volatiles under reduced pressure, the
residue was washed with Et O (3 × 10 mL) and a yellow
2
3
2
powder of [Cp*FeIJμ-1 SSS′:2 SS-tpdt){Cp*RuIJt-H)}]ijBPh ]
κ
κ
4
4
(9[BPh ], 130 mg, 0.14 mmol, 85%) was obtained. Crystals
suitable for X-ray diffraction were obtained from a THF
1
yellow residue was washed with Et O (3 × 10 mL) to afford
solution layered with n-hexane at room temperature. H NMR
2
3
2
κ
crystalline solids of [Cp*RuIJμ-1
κ
SSS′:2
SS-tpdt){Cp*FeIJt-
(400 MHz, CD
3
CN, ppm): δ −16.95 (s, 1H, Ru–H), 1.56 (s,
MeCN)}]ijPF ] (7ijPF ] , 80 mg, 0.09 mmol, 42%). Method B:
15H, Cp*–CH ), 1.90 (s, 15H, Cp*–CH ), 2.13 (m, 2H, tpdt-
6
2
6 2
3
3
Fc·PF (70 mg, 0.21 mmol) was added to a yellow-green MeCN
CH ), 2.39 (m, 2H, tpdt-CH ), 2.63 (m, 2H, tpdt-CH ), 3.17 (m,
6
2
2
2
(
20 mL) solution of 2[PF
6
] (152 mg, 0.21 mmol) and the
2
2H, tpdt-CH ), 6.84 (m, 4H, Ph-H), 6.99 (m, 8H, Ph-H), 7.27
1
3
mixture was stirred at room temperature for 1 h. The
resulting brown-yellow solution was evaporated, and then the
(m, 8H, Ph-H). C NMR (100 MHz, CD CN, ppm): δ 10.38
3
(Cp*–CH ), 11.81 (Cp*–CH ), 41.46 (SCH ), 42.09 (SCH ),
3
3
2
2
residue was washed with Et
by-product. The resulting product, [Cp*RuIJμ-1 SSS′:2 SS-
2
O (3 × 10 mL) to remove the Fc
95.75 (Cp*–C), 102.94 (Cp*–C), 122.76 (Ph-C), 126.59 (Ph-C),
3
2
+
136.74 (Ph-C). ESI-HRMS (m/z): calcd. for 9 : 581.0613; found:
κ
κ
−
1
tpdt){Cp*FeIJt-MeCN)}]ijPF
0%), was obtained as a yellow powder after drying in vacuo.
Crystals suitable for X-ray diffraction were obtained from a
]
6 2
6 2
(7ijPF ] , 173 mg, 0.19 mmol,
581.0615. IR (film, cm ): 3054, 2981, 2914, 1770, 1479, 1377,
9
3
1067, 705, 613. Anal. calcd. for C48H59BFeRuS : C, 64.07; H,
6.61. Found: C, 63.93; H, 6.39.
1
MeCN solution layered with Et
2
O at room temperature.
H
NMR (400 MHz, CD CN, ppm): δ 1.51 (s, 15H, Cp*–CH
3
3
), 1.81
Reaction of 2[PF
An excess of thiophenol (5 μL, 0.048 mmol) was added to a
solution of 2[PF ] (5 mg, 0.007 mmol) in THF-d (0.6 mL) at
6
] and thiophenol
(
s, 15H, Cp*–CH ), 1.95 (s, 3H, CH CN), 2.18 (m, 2H, tpdt-
3
3
CH
2
), 2.74 (m, 2H, tpdt-CH
2
2
), 2.92 (m, 2H, tpdt-CH ), 3.40 (m,
1
3
6
8
2
H, tpdt-CH
2 3
). C NMR (100 MHz, CD CN, ppm): δ 10.49
room temperature for about 15 min to give a yellow solution,
(
Cp*–CH ), 10.89 (Cp*–CH ), 38.40 (SCH ), 40.28 (SCH ),
3
3
2
2
1
which was a mixture of complexes 8[PF ] and 9[PF ]. H NMR
6
6
1
7
1
C
3
03.17 (Cp*–C), 106.17 (Cp*–C). ESI-HRMS (m/z): calcd. for
(
1
400 MHz, THF-d
.93 (9[PF
8
, ppm): δ 1.68, 1.71 (8[PF
]). ESI-HRMS (m/z): found for 8 : 689.0648; found
6
]), −16.81, 1.60,
2
+
−1
: 290.0268; found: 290.0259. IR (film, cm ): 2972, 2922,
484, 1380, 1269, 1020, 837, 736, 558. Anal. calcd. for
41FeRuS NP 12: C, 34.29; H, 4.54; N, 1.54. Found: C,
4.48; H, 4.30; N, 1.42.
Synthesis of [Cp*FeIJμ-1 SSS′:2 SS-tpdt){Cp*RuIJt-SPh)}]-
+
6
+
for 9 : 581.0613.
26
H
3
2
F
3
κ
2
Conflicts of interest
κ
6 6 6
ijPF ] (8[PF ]). To a stirred suspension of 2[PF ] (123 mg, 0.17
mmol) in THF (10 mL), thiophenol (60 μL, 0.58 mmol) was
There are no conflicts to declare.
added at room temperature, and the mixture was stirred
Acknowledgements
under an O
evaporated to dryness under reduced pressure. The residue
was washed with Et O (3 × 10 mL) to give a yellow product
2
atmosphere for 15 min. Then, the solution was
This work was supported by the National Natural Science
Foundation of China (No. 21571026, 21690064, and
2
3
2
κ
[
Cp*FeIJμ-1
κ
6 6
SSS′:2 SS-tpdt){Cp*RuIJt-SPh)}]ijPF ] (8[PF ], 125
21231003), the Program for Changjiang Scholars and
mg, 0.15 mmol, 88%). Crystals suitable for X-ray diffraction
Innovative Research Team in University (No. IRT13008), and
were obtained from a THF solution layered with n-hexane at
the “111” project of the Ministry of Education of China.
1
room temperature. H NMR (400 MHz, CD
3
CN, ppm): δ 1.64
), 2.69 (m, 2H, tpdt-
CH ), 2.80 (m, 2H, tpdt-CH ), 3.12 (m, 4H, tpdt-CH ), 6.84 (m,
3 3
(s, 15H, Cp*–CH ), 1.66 (s, 15H, Cp*–CH
Notes and references
2
2
2
13
1
H, Ph-H), 7.00 (m, 2H, Ph-H), 7.05 (m, 2H, Ph-H). C NMR
100 MHz, CD CN, ppm): δ 10.49 (Cp*–CH ), 10.78 (Cp*–
CH ), 38.72 (SCH ), 38.80 (SCH ), 100.65 (Cp*–C), 104.18
1 (a) M. Narayan, E. Welker, W. J. Wedemeyer and H. A.
Scheraga, Acc. Chem. Res., 2000, 33, 805–812; (b) G. Bulaj,
Biotechnol. Adv., 2005, 23, 87–92; (c) C. W. Gruber, M.
Čemažar, B. Heras, J. L. Martin and D. J. Craik, Trends
Biochem. Sci., 2006, 31, 455–464; (d) Z. Cheng, J. Zhang,
D. P. Ballou and C. H. Williams Jr, Chem. Rev., 2011, 111,
5768–5783; (e) J. Alegre-Cebollada, P. Kosuri, J. A. Rivas-
Pardo and J. M. Fernández, Nat. Chem., 2011, 3, 882–887; ( f )
W. Chen, L. Li, Z. Du, J. Liu, J. N. Reitter, K. V. Mills, R. J.
Linhardt and C. Wang, J. Am. Chem. Soc., 2012, 134,
(
3
3
3
2
2
(
Cp*–C), 122.45 (Ph-C), 128.22 (Ph-C), 132.19 (Ph-C). ESI-
+
HRMS (m/z): calcd. for 8 : 689.0648; found: 689.0656. IR
(
−
1
film, cm ): 2964, 2858, 1576, 1471, 1377, 1067, 841, 558.
4 6
Anal. calcd. for C30H43FeRuS PF : C, 43.22; H, 5.20. Found: C,
4
3.48; H, 5.06.
3
2
Synthesis of [Cp*FeIJμ-1 SSS′:2 SS-tpdt){Cp*RuIJt-H)}]-
κ
κ
ijBPh
4
] (9[BPh
4
]). At −78 °C, a solution of CoCp
2
(32 mg, 0.17
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2
500–2503; (g) T. Ilani, A. Alon, I. Grossman, B. Horowitz, E.
Scherlach, B. Urbansky, G. Lackner, D. Kalb, H.-M. Dahse,
D. Hoffmeister and C. Hertweck, Angew. Chem., Int. Ed.,
2014, 53, 13409–13413; (h) M. Feng and X. Jiang, Chem.
Commun., 2014, 50, 9690–9692.
Kartvelishvily, S. R. Cohen and D. Fass, Science, 2013, 341,
7
Albericio, Chem. Rev., 2014, 114, 901–926; (i) A. J.
Wommack, J. J. Ziarek, J. Tomaras, H. R. Chileveru, Y.
Zhang, G. Wagner and E. M. Nolan, J. Am. Chem. Soc.,
4–76; (h) M. Góngora-Benítez, J. Tulla-Puche and F.
4 (a) K. Klesk, M. Qian and R. R. Martin, J. Agric. Food Chem.,
2004, 52, 5155–5161; (b) A. Shimoyama, S. Kido, Y.-I.
Kinekawa and Y. Doi, J. Agric. Food Chem., 2008, 56,
9200–9205; (c) F. S. Hanschen, E. Lamy, M. Schreiner and S.
Rohn, Angew. Chem., Int. Ed., 2014, 53, 11430–11450.
5 (a) D. Witt, Synthesis, 2008, 16, 2491–2509; (b) B. Mandal
and B. Basu, RSC Adv., 2014, 4, 13854–13881; (c) J. Yuan, C.
Liu and A. Lei, Org. Chem. Front., 2015, 2, 677–680; (d) M.
Wang and X. Jiang, Top. Curr. Chem., 2018, 376, 1–40.
6 (a) C. Liu, H. Zhang, W. Shi and A. Lei, Chem. Rev.,
2011, 111, 1780–1824; (b) C. Liu, J. Yuan, M. Gao, S. Tang,
W. Li, R. Shi and A. Lei, Chem. Rev., 2015, 115, 12138–12204.
7 (a) N. Iranpoor and B. Zeynizadeh, Synthesis, 1999, 1, 49–50;
(b) S. M. S. Chauhan, A. Kumar and K. A. Srinivas, Chem.
Commun., 2003, 2348–2349; (c) J. A. Fernández-Salas, S.
Manzini and S. P. Nolan, Chem. Commun., 2013, 49,
5829–5831; (d) M. Li and J. M. Hoover, Chem. Commun.,
2016, 52, 8733–8736; (e) Y. Dou, X. Huang, H. Wang, L.
Yang, H. Li, B. Yuan and G. Yang, Green Chem., 2017, 19,
2491–2495.
8 (a) A. Cervilla, A. Corma, V. Fornés, E. Llopis, P. Palanca, F.
Rey and A. Ribera, J. Am. Chem. Soc., 1994, 116, 1595–1596;
(b) A. Dhakshinamoorthy, M. Alvaro and H. Garcia, Chem.
Commun., 2010, 46, 6476–6478; (c) M. Oba, K. Tanaka, K.
Nishiyama and W. Ando, J. Org. Chem., 2011, 76, 4173–4177;
(d) A. Corma, T. Ródenas and M. J. Sabater, Chem. Sci.,
2012, 3, 398–404; (e) P. Das, S. Ray, A. Bhaumik, B. Banerjee
and C. Mukhopadhyay, RSC Adv., 2015, 5, 6323–6331.
9 (a) A. Hatano, S. Makita and M. Kirihara, Bioorg. Med. Chem.
Lett., 2004, 14, 2459–2462; (b) R. Dong, M. Pfeffermann, D.
Skidin, F. Wang, Y. Fu, A. Narita, M. Tommasini, F.
Moresco, G. Cuniberti, R. Berger, K. Müllen and X. Feng,
J. Am. Chem. Soc., 2017, 139, 2168–2171.
2
014, 136, 13494–13497; ( j) C. Landeta, J. L. Blazyk, F.
Hatahet, B. M. Meehan, M. Eser, A. Myrick, L. Bronstain, S.
Minami, H. Arnold, N. Ke, E. J. Rubin, B. C. Furie, B. Furie,
J. Beckwith, R. Dutton and D. Boyd, Nat. Chem. Biol.,
2
015, 11, 292–298; (k) S. Lu, S.-B. Fan, B. Yang, Y.-X. Li, J.-M.
Meng, L. Wu, P. Li, K. Zhang, M.-J. Zhang, Y. Fu, J. Luo,
R.-X. Sun, S.-M. He and M.-Q. Dong, Nat. Methods, 2015, 12,
3
29–331; (l) M. Song, J.-S. Kim, L. Liu, M. Husain and A.
Vázquez-Torres, Cell Rep., 2016, 14, 2901–2911.
(a) T. T. Conway, E. G. DeMaster, D. J. W. Goon, F. N.
Shirota and H. T. Nagasawa, J. Med. Chem., 1999, 42,
2
4
016–4020; (b) K. C. Nicolaou, R. Hughes, J. A. Pfefferkorn,
S. Barluenga and A. J. Roecker, Chem. – Eur. J., 2001, 7,
280–4295; (c) S. A. Caldarelli, M. Hamel, J.-F. Duckert, M.
4
Ouattara, M. Calas, M. Maynadier, S. Wein, C. Périgaud, A.
Pellet and H. J. Vial, J. Med. Chem., 2012, 55, 4619–4628; (d)
R. V. J. Chari, M. L. Miller and W. C. Widdison, Angew.
Chem., Int. Ed., 2014, 53, 3796–3827; (e) O. Boutureira and
G. J. L. Bernardes, Chem. Rev., 2015, 115, 2174–2195; ( f )
Q.-Y. Hu, F. Berti and R. Adamo, Chem. Soc. Rev., 2016, 45,
1
691–1719; (g) L. R. Staben, S. G. Koenig, S. M. Lehar, R.
Vandlen, D. Zhang, J. Chuh, S.-F. Yu, C. Ng, J. Guo, Y. Liu, A.
Fourie-O'Donohue, M. Go, X. Linghu, N. L. Segraves, T.
Wang, J. Chen, B. Wei, G. D. L. Phillips, K. Xu, K. R. Kozak,
S. Mariathasan, J. A. Flygare and T. H. Pillow, Nat. Chem.,
2
016, 8, 1112–1119; (h) M. Feng, B. Tang, S. H. Liang and X.
Jiang, Curr. Top. Med. Chem., 2016, 16, 1200–1216; (i) A.
Zorzi, K. Deyle and C. Heinis, Curr. Opin. Chem. Biol.,
2
017, 38, 24–29; ( j) A. Beck, L. Goetsch, C. Dumontet and N.
Corvaïa, Nat. Rev. Drug Discovery, 2017, 16, 315–337; (k) D. S.
Nielsen, N. E. Shepherd, W. Xu, A. J. Lucke, M. J. Stoermer
and D. P. Fairlie, Chem. Rev., 2017, 117, 8094–8128; (l) Y.
Liu, Z. Xie, D. Zhao, J. Zhu, F. Mao, S. Tang, H. Xu, C. Luo,
M. Geng, M. Huang and J. Li, J. Med. Chem., 2017, 60,
10 (a) R. Priefer, Y. J. Lee, F. Barrios, J. H. Wosnick, A.-M.
Lebuis, P. G. Farrell and D. N. Harpp, J. Am. Chem. Soc.,
2002, 124, 5626–5627; (b) M. H. Ali and M. McDermott,
Tetrahedron Lett., 2002, 43, 6271–6273; (c) E. Bourlès, R. A.
de Sousa, E. Galardon, M. Selkti, A. Tomas and I. Artaud,
Tetrahedron, 2007, 63, 2466–2471.
2
227–2244; (m) J. Mantaj, P. J. M. Jackson, K. M. Rahman
and D. E. Thurston, Angew. Chem., Int. Ed., 2017, 56,
62–488.
4
3
(a) Y. Kishi, T. Fukuyama and S. Nakatsuka, J. Am. Chem.
Soc., 1973, 95, 6492–6493; (b) J. Kim, J. A. Ashenhurst and
M. Movassaghi, Science, 2009, 324, 238–241; (c) E. Iwasa, Y.
Hamashima, S. Fujishiro, E. Higuchi, A. Ito, M. Yoshida and
M. Sodeoka, J. Am. Chem. Soc., 2010, 132, 4078–4079; (d) P.
Klausmeyer, S. M. Shipley, K. M. Zuck and T. G. McCloud,
J. Nat. Prod., 2011, 74, 2039–2044; (e) C.-S. Jiang, W. E. G.
Müller, H. C. Schröder and Y.-W. Guo, Chem. Rev.,
11 (a) A. R. Hajipour, S. E. Mallakpour and H. Adibi, J. Org.
Chem., 2002, 67, 8666–8668; (b) R. Leino and J.-E. Lönnqvist,
Tetrahedron Lett., 2004, 45, 8489–8491.
12 (a) H. Firouzabadi, N. Iranpoor, H. Parham, A. Sardarian
and J. Toofan, Synth. Commun., 1984, 14, 717–723; (b) L.
Delaude and P. Laszlo, J. Org. Chem., 1996, 61, 6360–6370;
(c) S. Patel and B. K. Mishra, Tetrahedron Lett., 2004, 45,
1371–1372.
2
012, 112, 2179–2207; ( f ) K. C. Nicolaou, M. Lu, S.
13 (a) C. L. Hill, Nature, 1999, 401, 436–437; (b) T.
Punniyamurthy, S. Velusamy and J. Iqbal, Chem. Rev.,
2005, 105, 2329–2363; (c) L. Que, Jr. and W. B. Tolman,
Nature, 2008, 455, 333–340; (d) Z. Shi, C. Zhang, C. Tang
and N. Jiao, Chem. Soc. Rev., 2012, 41, 3381–3430.
Totokotsopoulos, P. Heretsch, D. Giguère, Y.-P. Sun, D.
Sarlah, T. H. Nguyen, I. C. Wolf, D. F. Smee, C. W. Day, S.
Bopp and E. A. Winzeler, J. Am. Chem. Soc., 2012, 134,
1
7320–17332; (g) P. Chankhamjon, D. Boettger-Schmidt, K.
6500 | Catal. Sci. Technol., 2019, 9, 6492–6502
This journal is © The Royal Society of Chemistry 2019

View Article Online
Catalysis Science & Technology
Paper
1
4 (a) D. P. Gamblin, P. Garnier, S. van Kasteren, N. J. Oldham,
A. J. Fairbanks and B. G. Davis, Angew. Chem., Int. Ed.,
24 (a) P. Sun, D. Yang, Y. Li, Y. Zhang, L. Su, B. Wang and J.
Qu, Organometallics, 2016, 35, 751–757; (b) Y. Zhang, D.
Yang, Y. Li, B. Wang, X. Zhao and J. Qu, Dalton Trans.,
2017, 46, 7030–7038.
25 Y. Zhang, D. Yang, Y. Li, X. Zhao, B. Wang and J. Qu,
Organometallics, 2018, 37, 3165–3173.
2
004, 43, 828–833; (b) J. L. G. Ruano, A. Parra and J. Alemán,
Green Chem., 2008, 10, 706–711; (c) H. T. Abdel-Mohsen, K.
Sudheendran, J. Conrad and U. Beifuss, Green Chem.,
2
013, 15, 1490–1495; (d) X.-B. Li, Z.-J. Li, Y.-J. Gao, Q.-Y.
Meng, S. Yu, R. G. Weiss, C.-H. Tung and L.-Z. Wu, Angew.
Chem., Int. Ed., 2014, 53, 2085–2089; (e) X. Xiao, M. Feng
and X. Jiang, Chem. Commun., 2015, 51, 4208–4211; ( f ) A.
Talla, B. Driessen, N. J. W. Straathof, L.-G. Milroy, L.
Brunsveld, V. Hessel and T. Noël, Adv. Synth. Catal.,
26 U. Kölle, F. Khouzami and B. Fuss, Angew. Chem., Int. Ed.
Engl., 1982, 21, 131–132.
27 D. Catheline and D. Astruc, J. Organomet. Chem., 1983, 248,
C9–C12.
28 D. Catheline and D. Astruc, Organometallics, 1984, 3,
1094–1100.
2
015, 357, 2180–2186; (g) X. Xiao, M. Feng and X. Jiang,
Angew. Chem., Int. Ed., 2016, 55, 14121–14125; (h) P. Huang,
P. Wang, S. Tang, Z. Fu and A. Lei, Angew. Chem., Int. Ed.,
29 (a) D. Yang, Y. Li, B. Wang, X. Zhao, L. Su, P. Tong, Y. Luo
and J. Qu, Inorg. Chem., 2015, 54, 10243–10249; (b) Y. Zhang,
J. Zhao, D. Yang, Y. Zhang, B. Wang and J. Qu, Inorg. Chem.
Commun., 2017, 83, 66–69.
2
018, 57, 8115–8119; (i) X. Xiao, J. Xue and X. Jiang, Nat.
Commun., 2018, 9, 2191–2199.
1
5 (a) L. S. Liebeskind, J. Srogl, C. Savarin and C. Polanco, Pure
Appl. Chem., 2002, 74, 115–122; (b) S. Otsuka, H. Yorimitsu
and A. Osuka, Chem. – Eur. J., 2015, 21, 14703–14707.
6 (a) J. C. Fontecilla-Camps, P. Amara, C. Cavazza, Y. Nicolet
and A. Volbeda, Nature, 2009, 460, 814–822; (b) Bioinspired
Catalysis, ed. W. Weigand and P. Schollhammer, WileyVCH,
Weinheim, 2015.
30 S. Venkataramani, U. Jana, M. Dommaschk, F. D.
Sönnichsen, F. Tuczek and R. Herges, Science, 2011, 331,
445–448.
31 M. Yuki, Y. Miyake and Y. Nishibayashi, Organometallics,
2010, 29, 5994–6001.
1
32 P. Tong, W. Xie, D. Yang, B. Wang, X. Ji, J. Li and J. Qu,
Dalton Trans., 2016, 45, 18559–18565.
1
7 (a) B. M. Hoffman, D. Lukoyanov, Z.-Y. Yang, D. R. Dean
and L. C. Seefeldt, Chem. Rev., 2014, 114, 4041–4062; (b) W.
Lubitz, H. Ogata, O. Rüdiger and E. Reijerse, Chem. Rev.,
33 (a) S. Cai, X.-F. Hou, Y.-Q. Chen and G.-X. Jin, Dalton Trans.,
2006, 3736–3741; (b) M. Murata, S. Habe, S. Araki, K. Namiki,
T. Yamada, N. Nakagawa, T. Nankawa, M. Nihei, J. Mizutani,
M. Kurihara and H. Nishihara, Inorg. Chem., 2006, 45,
1108–1116; (c) H. Gao, J. Huang, L. Chen, R. Liu and J. Chen,
RSC Adv., 2013, 3, 3557–3565; (d) M. E. Carroll, J. Chen, D. E.
Gray, J. C. Lansing, T. B. Rauchfuss, D. Schilter, P. I. Volkers
and S. R. Wilson, Organometallics, 2014, 33, 858–867; (e) P.
Ghosh, M. Quiroz, N. Wang, N. Bhuvanesh and M. Y.
Darensbourg, Dalton Trans., 2017, 46, 5617–5624.
34 P. Buchwalter, J. Rosé and P. Braunstein, Chem. Rev.,
2015, 115, 28–126.
35 P. Anastas and N. Eghbali, Chem. Soc. Rev., 2010, 39,
301–312.
36 (a) A. K. Justice, R. C. Linck, T. B. Rauchfuss and S. R.
Wilson, J. Am. Chem. Soc., 2004, 126, 13214–13215; (b) M. A.
Alvarez, M. E. García, D. García-Vivó, E. Huergo and M. A.
Ruiz, Inorg. Chem., 2018, 57, 912–915.
37 M. Yuki, K. Sakata, Y. Hirao, N. Nonoyama, K. Nakajima and
Y. Nishibayashi, J. Am. Chem. Soc., 2015, 137, 4173–4182.
38 (a) T. Iwasa, H. Shimada, A. Takami, H. Matsuzaka, Y. Ishii
and M. Hidai, Inorg. Chem., 1999, 38, 2851–2859; (b) M.
Gargir, Y. Ben-David, G. Leitus, Y. Diskin-Posner, L. J. W.
Shimon and D. Milstein, Organometallics, 2012, 31,
6207–6214.
39 C. M. Fendrick, L. D. Schertz, E. A. Mintz, T. J. Marks, T. E.
Bitterwolf, P. A. Horine, T. L. Hubler, J. A. Sheldon and D. D.
Belin, Inorg. Synth., 1992, 29, 193–198.
2
014, 114, 4081–4148; (c) M. Can, F. A. Armstrong and S. W.
Ragsdale, Chem. Rev., 2014, 114, 4149–4174.
1
8 (a) Y. Chen, Y. Zhou, P. Chen, Y. Tao, Y. Li and J. Qu, J. Am.
Chem. Soc., 2008, 130, 15250–15251; (b) Y. Chen, L. Liu, Y.
Peng, P. Chen, Y. Luo and J. Qu, J. Am. Chem. Soc.,
2
011, 133, 1147–1149; (c) X. Dong, L. Liu, Y. Zhou, J. Liu, Y.
Zhang, Y. Chen and J. Qu, Dalton Trans., 2015, 44,
4952–14958.
1
1
2
9 (a) Y. Li, Y. Li, B. Wang, Y. Luo, D. Yang, P. Tong, J. Zhao, L.
Luo, Y. Zhou, S. Chen, F. Cheng and J. Qu, Nat. Chem.,
2
013, 5, 320–326; (b) X. Ji, P. Tong, D. Yang, B. Wang, J.
Zhao, Y. Li and J. Qu, Dalton Trans., 2017, 46, 3820–3824; (c)
Y. Zhang, T. Mei, D. Yang, Y. Zhang, B. Wang and J. Qu,
Dalton Trans., 2017, 46, 15888–15896.
0 (a) D. Yang, Y. Li, L. Su, B. Wang and J. Qu, Eur. J. Inorg.
Chem., 2015, 2015, 2965–2973; (b) X. Ji, D. Yang, P. Tong, J.
Li, B. Wang and J. Qu, Organometallics, 2017, 36, 1515–1521;
(
c) Y. Zhang, P. Tong, D. Yang, J. Li, B. Wang and J. Qu,
Chem. Commun., 2017, 53, 9854–9857; (d) X. Zhao, D. Yang,
Y. Zhang, B. Wang and J. Qu, Chem. Commun., 2018, 54,
1
1112–11115.
1 (a) Y. Tao, B. Wang, B. Wang, L. Qu and J. Qu, Org. Lett.,
010, 12, 2726–2729; (b) Y. Tao, B. Wang, J. Zhao, Y. Song, L.
2
2
Qu and J. Qu, J. Org. Chem., 2012, 77, 2942–2946; (c) X.
Zhao, D. Yang, Y. Zhang, B. Wang and J. Qu, Org. Lett.,
2
018, 20, 5357–5361.
2 B. Steinmetz and W. A. Schenk, Organometallics, 1999, 18,
43–946.
40 P. A. Ulmann, A. B. Braunschweig, O.-S. Lee, M. J. Wiester,
G. C. Schatz and C. A. Mirkin, Chem. Commun.,
2009, 5121–5123.
2
2
9
3 Y. Li, Y. Zhang, D. Yang, Y. Li, P. Sun, B. Wang and J. Qu,
41 U. Jahn, P. Hartmann, I. Dix and P. G. Jones, Eur. J. Org.
Chem., 2001, 2001, 3333–3335.
Organometallics, 2015, 34, 1661–1667.
This journal is © The Royal Society of Chemistry 2019
Catal. Sci. Technol., 2019, 9, 6492–6502 | 6501

View Article Online
Paper
Catalysis Science & Technology
4
2 L. Y. Goh, M. E. Teo, S. B. Khoo, W. K. Leong and J. J. Vittal,
J. Organomet. Chem., 2002, 664, 161–169.
3 G. M. Sheldrick, SADABS, Program for area detector
adsorption correction, Institute for Inorganic Chemistry,
University of Göttingen, Germany, 1996.
44 G. M. Sheldrick, SHELXL-2014, Program for refinement of
crystal structures, University of Göttingen, Germany, 2014;
G. M. Sheldrick, SHELXS-2014, Program for Solution of
Crystal Structures, University of Göttingen, Germany,
2014.
4
6502 | Catal. Sci. Technol., 2019, 9, 6492–6502
This journal is © The Royal Society of Chemistry 2019