The ionic mononuclear and trinuclear Au(I)-complexes ligated by phosphine-functionalized ionic liquids: Synthesis, characterization, and catalysis to hydration of phenylacetylene

Article abstract of DOI:10.1016/j.jorganchem.2014.04.005

A series of ionic Au(I)-complexes ligated by the phosphine-functionalized ionic liquids were synthesized and characterized, which are composed of the Au(I)-complex cation and the counteranion of OTf^-, AuCl ₄^-, or PF₆^-, respectively. The single crystal X-ray diffraction analyses show that the Au(I)-centered vector in 1A, 1B, 2A, 3A, and 4A all possess the slightly twisted linear geometry, and in each individual the Au(I)-center is coordinated by one chlorine and one imidazolium-based phosphine. The aggregation of 1B in acetone can lead to the formation of the trinuclear Au(I)-complex of 1C due to the aurophilic Au(I)-Au(I) interaction, the electrostatic attraction, and the steric preference. When these ionic Au-complexes were employed as precatalysts for hydration of phenylacetylene in aqueous-methanol media, the reaction proceeded selectively according to Markovnikov's rule with moderate to high yields of acetophenone. The highest activities were achieved over 2A with hydrophobic PF₆^- as the counteranion and the trinuclear 1C under mild conditions (75 °C, 2 h), in conjunction with the additive of proton acid H₂SO₄. The ion-pair effect on the catalytic performance of the corresponding Au(I)-complexes, coming from the phosphine-ligated cations and the counteranions, were investigated.

Full text of DOI:10.1016/j.jorganchem.2014.04.005

Journal of Organometallic Chemistry 762 (2014) 40e47
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The ionic mononuclear and trinuclear Au(I)-complexes ligated by
phosphine-functionalized ionic liquids: Synthesis, characterization,
and catalysis to hydration of phenylacetylene
*
Xuezhu Wang, Yongyong Wang, Jing Zhang, Xiaoli Zhao, Ye Liu
Shanghai Key Laboratory of Green Chemistry and Chemical Processes, East China Normal University, Shanghai 200062, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of ionic Au(I)-complexes ligated by the phosphine-functionalized ionic liquids were synthesized
and characterized, which are composed of the Au(I)-complex cation and the counteranion of OTfꢀ, AuCl4ꢀ,
or PFꢀ6 , respectively. The single crystal X-ray diffraction analyses show that the Au(I)-centered vector in
1A, 1B, 2A, 3A, and 4A all possess the slightly twisted linear geometry, and in each individual the Au(I)-
center is coordinated by one chlorine and one imidazolium-based phosphine. The aggregation of 1B in
acetone can lead to the formation of the trinuclear Au(I)-complex of 1C due to the aurophilic Au(I)eAu(I)
interaction, the electrostatic attraction, and the steric preference. When these ionic Au-complexes were
employed as precatalysts for hydration of phenylacetylene in aqueous-methanol media, the reaction
proceeded selectively according to Markovnikov’s rule with moderate to high yields of acetophenone.
The highest activities were achieved over 2A with hydrophobic PFꢀ6 as the counteranion and the trinu-
clear 1C under mild conditions (75 ꢁC, 2 h), in conjunction with the additive of proton acid H2SO4. The
ion-pair effect on the catalytic performance of the corresponding Au(I)-complexes, coming from the
phosphine-ligated cations and the counteranions, were investigated.
Received 22 January 2014
Received in revised form
17 March 2014
Accepted 3 April 2014
Keywords:
Gold complexes
Phosphine ligands
Hydration of phenylacetylene
Functionalized ionic liquids
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
(Kucherov catalyst) [6,7] and HgOeBF3 (HennioneNieuwland
catalyst) [8].
The application of Au-complexes has been undervalued for
many years due to the preconceived opinion that gold was an
expensive and extremely inert metal [1]. Only in recent decade,
homogeneous catalysis promoted by Au-complexes containing
phosphines or N-heterocyclic carbene (NHC) has emerged as a
powerful tool for organic synthesis [2,3]. The cationic Au(I)-
complexes are featured with the strong Lewis acidity due to the
relativistic effect coming from the extent of contraction of 6s orbital
and the expansion of 5d orbital [4], which is of great interest to
catalyze the nucleophilic addition of water to alkynes following
Markovnikov’s rule for the generation of the ketones [1,5].
Benefiting from the clean water as the nucleophile, the synthesis of
carbonyl compounds by Au-catalyzed hydration of alkynes was
extensively attractive and potentially interested in industrial pro-
cesses because of the replacement of the uses of highly toxic
mercury salts and strong Brönsted or Lewis acids, like HgOeH2SO4
In order to develop the efficient catalytic systems for hydration
of alkynes, much effort has been devoted to modulate the struc-
tures and compositions of the Au(I) complexes ligated by the
phosphines or NHCs [2f,9], the reaction condition (microwave
irradiation) [10], and the reaction media (such as ionic liquids)
[11,12]. More recently, Nolan and Corma respectively reported the
use of cationic [(IPr)Au]þ[X]ꢀ (Xꢀ ¼ BF4ꢀ, SbFꢀ6 , OTfꢀ, PF6ꢀ, NTfꢀ2 )
generated in situ to be a versatile and selective catalyst for hydra-
tion of alkynes [13,14]. Comparatively, the examples of using the
multi-nuclear Au(I)-complexes to catalyze hydration of alkynes
have not been exploited yet, although many of them have been
synthesized [15].
It has been known that ionic liquids (ILs) can be functionalized
flexibly by incorporating functional moieties into the IL structure to
develop different functionalized ILs (FILs), which dually possess the
characters of the incorporated functionalities as well as those of the
ILs [16]. The phosphine-FILs have long been investigated for the
design of the ionic organometallic compounds and application to
homogeneous catalysis [17e19]. It has been found in our previous
work that, while the coordinating P(III) atom is vicinal to the
* Corresponding author.
E-mail address: yliu@chem.ecnu.edu.cn (Y. Liu).
http://dx.doi.org/10.1016/j.jorganchem.2014.04.005
0022-328X/Ó 2014 Elsevier B.V. All rights reserved.

X. Wang et al. / Journal of Organometallic Chemistry 762 (2014) 40e47
41
positive charged imidazolium ring, the corresponding phosphine-
FILs are featured with -acceptor character as well as -donor [20].
Hence, the varied coordination behaviors of such phosphine-FILs
are in great concerns in the coordinating chemistry and homoge-
neous catalysis, leading to the significant changes of the complex
configurations and catalytic performance.
Continuous efforts to utilize the phosphine-FILs (which can be
defined as the phosphino-imidazolium salts due to their solid state
at room temperature) with the positive charge vicinal to the P(III)
atom evoked us to prepare the corresponding ionic gold(I) com-
plexes of the types of [AuI(L)Cl]þYꢀ (1A, 1B, 2A, 3A, and 4A)
(L ¼ imidazolium-based phosphine, Scheme 1). Unexpectedly, the
trinuclear complex of the type of [AuI(L)CleAuCl2eAu(L)
Cl]þ[AuCl4]ꢀ (1C) was formed in good yield due to the aggregation
of 1B with its derivative [4]. The obtained ionic complexes (1Ae1C
and 2Ae4A) were investigated comparatively herein as the ho-
mogeneous precatalysts for hydration of phenylacetylene in
conjunction with Brönsted acid of H2SO4. The ligand effect and the
ion-pair effect on the catalytic performance of these Au(I)-
complexes were discussed.
the counteranion, while the use of equivalent of HAuIIICl4$4H2O led
to the formation of 1B with AuClꢀ4 as the counteranion. It was found
that the high valence state AuIII ion was partially reduced to AuI by
1 before the coordination, subsequently leading to the formation of
the monovalent Au(I)-complex of 1B with the left AuClꢀ4 as the
counteranion.1B could also be obtained through the ion-exchange of
1A with equivalent of HAuIIICl4$4H2O. When the collected yellow
crystal solids of 1B was dissolved in acetone and stood-by up to 72 h
at ambient condition, the redeorange solids were obtained unex-
pectedly after the solvent removal and recrystallization in acetonee
hexane, which proved to be a trinuclear Au(I)-complex of 1C;
Whereas under the similar conditions, the transformation of 1A with
OTfꢀ as the counteranion, or the others (2Ae4A), to the trinuclear
Au(I)-complexes like 1C was unsuccessful.
p
s
Following the similar procedures for preparation of 1A, the ionic
complexes of 2Ae4A ligated by the phosphine-FILs of 2e4 were
obtained respectively.
All of the obtained ionic Au(I)-complexes, with insensitivity to
moisture and oxygen both in the solid state and in organic solvent
at room temperature, were characterized by 1H/31P NMR spec-
troscopy and single-crystal X-ray diffraction analysis. The molecu-
lar structures in Fig. 1 show that, except for 1C, the others are
composed of the mononuclear Au(I)-complex cations with struc-
tural similarity to that of the neutral complex of AuI(PPh3)Cl [21],
and the corresponding counteranions. 1A, 1B, and 2A possess the
same Au(I)-complex cation, but are counteracted by the different
anions of OTfꢀ, AuCl4ꢀ, and PFꢀ6 respectively; While 1A and 4A
possess the different phosphine-ligated Au(I)-complex cation along
with the same counteranion of OTfꢀ. The Au(I)-centered vectors in
1A, 1B, 2A, 3A, and 4A are all in a slightly distorted linear
Results and discussion
Synthesis and characterization of the ionic Au(I)-complexes
When the phosphine-FIL of 1 was coordinated to the different Au-
precursors under the applied reactions conditions, the ionic com-
plexes of 1Ae1C were obtained respectively with good to excellent
yields (78e98 wt%). The use of equivalent of tetrahydrothiophenee
gold(I) chloride [AuI(tht)Cl] led to the formation of 1A with OTfꢀ as
Ph
Ph
N+
P
AuI Cl
OTf -
N
Me
Me
Cl
A
u
S
1A
l
C 2
H2
C
PPh2
N
CH2Cl2
HAuCl4 (Ion-exchange)
Me
N
Me
Me
OTf-
Ph
P
N
Ph
H
A
Ph
Cl
u
Cl
C
l4
1
Ph
P
AuI Cl
N
C
Acetone
RT
Me
N
H
AuI AuI AuI
C
l2
2
-
-
AuCl4
AuCl4
Me
N+
N
Me
Me
Cl
Cl
Ph
P
N
1B
Ph
Me
1C
Ph
PPh2
N
AuI Cl
S
Au Cl
CH2Cl2
Ph
N+
P
Me
Me
-
N
PF6
Me
-
N
PF6
Me
2
2A
Ph
PPh2
N+
Ph
P
AuI Cl
S
Au Cl
-
n-Bu
Me
PF6
N
N
N+
N
Acetone
-
n-Bu
Me
PF6
3
3A
Ph
P
PPh2
N+
Ph
N+
AuI Cl
OTf -
n-Bu
OTf-
Me
S
Au Cl
N
n-Bu
Me
CH2Cl2
4
4A
Scheme 1. Synthesis of the ionic Au(I) complexes ligated by the phosphine-FILs of 1e4.

42
X. Wang et al. / Journal of Organometallic Chemistry 762 (2014) 40e47
Fig. 1. The single crystal structure of the ionic Au(I)-complexes of 1A, 1B, 1C, 2A, 3A, 4A, 1B0, and 1C0.
configuration, which is the typical character for the mononuclear
Au(I)-complexes. Au(I) center is diagonally coordinated by one Clꢀ
and one imidazolium-based phosphine. The bond angles of P(1)e
Au(1)eCl(1) are 175e178ꢁ. The bond distances of AueP are in the
Actually 1C was not the direct aggregation of [LeAueCl]þ cation
with AuClꢀ4 anion in 1B, but the aggregation of [LeAueCl]þ cation
with AuClꢀ2 , the later was derived from the reduction of AuClꢀ4 anion
by acetone solvent. The presence of AuClꢀ2 could be confirmed by
the concomitant formation of 1B0 and 1C0 analogs as the minor
products during the crystal generation of 1B and 1C (Fig. 1). As
shown in Scheme 2, the trinuclear Au(I)-complex of 1C is the exact
adduct of 1B with 1B0. And the self-aggregation of 1B0 leads to the
formation of 1C0 (Scheme 2).
The driving force for the aggregation of mononuclear Au(I)-
complexes into multiple-nuclear ones has been usually ascribed
to the strong aurophilic Au(I)eAu(I) bonding (d10ed10) interaction
in the literature [4]. However, the absence of such aggregation of
1A, 1B, 2A, 3A, or 4A themselves implied that the additional
I
ꢀ
range of 2.221e2.227 A, which are comparative to that of Au (PPh3)
ꢀ
Cl (2.235 A, Table 1). The structure of 1C shows that the trimetallic
Au(I)-nucleus is arranged in an ideal linear array. The central Au(I)
in an inversion center is coordinated by two chlorine atoms and
another two cationic phosphine-ligated Au(I)-complex moieties in
perpendicular direction. The bond angles of Au(1)eAu(2)eAu(1a)
of 180ꢁ and P(1)eAu(1)eCl(1) of 176ꢁ are observed. The AueAu
ꢀ
distance is 3.08 A which is in the range of AueAu metal bonding
[22]. The selected bond distances and bond angles for compound
1Ae1C and 2Ae4A are given in Table 1.

X. Wang et al. / Journal of Organometallic Chemistry 762 (2014) 40e47
43
Table 1
ꢁ
ꢀ
The selected bond distances (A) and bond angles ( ) for the ionic Au-complexes.
Bond angles (ꢁ)
Shortest distance between the ion-pair (A)
ꢀ
ꢀ
Au-complex
Bond distances (A)
Au1eP1
Au1eCl1
Au1eAu2
P1eAu1eCl1
Au1eAu2eAu1a
1A
1B
2.2213(14)
2.2214(14)
2.2784(15)
2.2720(15)
e
e
176.74(6)
175.01(6)
e
e
Au1/O3 3.4427(70)
Au1/Cl3 5.3514(22)
Au1/Au2 7.1304(3)
Au2/Cl3 7.3889(28)
Au1/F3 3.7012(41)
Au1/F5 4.9436(75)
Au1/O1 6.7506(33)
Au1/Cl3 3.5449(20)
Au1/Au2 3.2545(3)
Au1/Cl3 4.7494(14)
e
1C
2A
3A
4A
1B0
2.2199(13)
2.2209(7)
2.2261(11)
2.2268(9)
2.2218(15)
2.2816(14)
2.2838(7)
2.2819(12)
2.2761(10)
2.2826(17)
3.0831(2)
176.14(5)
175.98(3)
175.26(4)
177.99(4)
175.16(6)
180.000(5)
e
e
e
e
e
e
e
1C0
2.2244(11)
2.235(3)
2.2940(11)
2.279(3)
3.0069(2)
e
172.22(4)
179.68(8)
180.0
e
AuI(PPh3)Cl [21]
electrostatic interaction and steric preference are also crucial fac-
tors for the aggregation of the mononuclear Au(I)-complexes. As for
1Ae4A, the aggregation of [LeAueCl]þ cation itself is not favored
due to the repulsive electrostatic force; As for 1B, the steric hin-
drance of the square-planar AuClꢀ4 anion with [LeAueCl]þ cation
also inhibits their aggregation. Only the aggregation between [Le
AueCl]þ cation and AuCl2ꢀ anion (derived from reduction of AuCl4ꢀ
anion in 1B) can lead to the formation of 1C, due to the aurophilic
Au(I)eAu(I) interaction, the electrostatic attraction, and the steric
preference.
dramatically influenced by the counteranions (Table 1). The ion-
pair distance in 1B (the shortest distance, Au1/Cl3 5.35 A) is
much longer than those in 1A (the shortest distance, Au1/O3
ꢀ
0
ꢀ
ꢀ
3.44 A), 2A (the shortest distance, Au1/F3, 3.70 A), and 1B (the
ꢀ
shortest distance of Au1/Cl3, 3.54 A). However, when the coun-
teranion of AuIIICl4L in 1B is replaced by AuIClꢀ2 , the ion-pair rela-
tionship as shown in 1B0 becomes much closer (1B, Au1/Au2,
0
ꢀ
ꢀ
7.13 A; 1B , Au1/Au2 3.25 A). Reasonably, the closer ion-pair dis-
tance in 1B0 gives rise to Au(I)eAu(I) aurophilic interaction for the
aggregation to the trinuclear Au(I)-complexes of 1C and 1C0. The
similar phenomenon is observed in the cases of 1C vs 1C0 (1C,
Au1/Au3, 8.88 A; 1C , Au1/Au3 6.38 A). And the bulky steric
hindrance of the cation impels the counteranion far away such as in
the cases of 2A vs 3A and 1A vs 4A. It is supposed that not only the
weak crystal packing force, but also the strong chemical in-
teractions such as electrostatic force, aurophilic interaction, and
hydrogen bonding may affect the ion-pair distance dramatically.
ꢀ
The comparative AueP distances (2.221e2.227 A) in the ionic
Au(I)-complexes of 1Ae1C, 2Ae4A, 1B0 and 1C0 than that of
0
ꢀ
ꢀ
I
ꢀ
Au (PPh3)Cl (2.235 A, Table 1) indicate that the AueP interactions in
these ionic Au(I)-complexes are not weakened because of the
electron-deficient nature of the phosphine-FILs of 1e4. In com-
parison to PPh3 as an electron-rich s-donor, 1e4 in which the P(III)
atoms are vicinal to the positive charge imidazoliums can mimic
the behaviors of the electron-deficient ligands of phosphites,
exhibiting the electron-withdrawing effect as a result of both
donation and -back bonding. Resultantly, the linkages of AueP in
1Ae1C, 2Ae4A, 1B0 and 1C0 got strengthened due to the additional
-back bonding interaction. In addition, the phosphine-FILs of 1e4
s-
Catalytic performance of the ionic Au(I)-complexes for hydration of
phenylacetylene
p
p
For the hydration of alkynes catalyzed by Au(I)-complexes, the
involvement of the proton acid as co-catalyst has been found
effective to promote the reactions [23]. Hence the inorganic acid of
H2SO4 was used herein in considerations of the ionic compatibility
with the ionic Au-complexes and the good solubility in H2O. The
insensitivity to moisture and oxygen of the ionic Au-complexes of
1Ae1C and 2Ae4A is the basic criteria for the precatalysts used in
hydration of alkynes. In our experiments, the hydration of phe-
nylacetylene was selected as a model reaction. The reaction con-
ditions were optimized over 1A firstly (Table 2).
with the electron-deficient nature are more robust against oxida-
tive degradation due to the delocalization of the lone-pair electrons
in the P atom to the adjacent positive imidazolium ring, resulting in
insensitivity to moisture and oxygen under ambient conditions.
Hence, the corresponding ionic complexes of 1Ae1C, 2Ae4A, 1B0
and 1C0 ligated by 1e4 are also featured with moisture- and oxy-
gen-insensitivity.
On the other hand, it is found that, as for 1A,1B, 2A, and 1B0 with
the same Au(I)-complex cation, their ion-pair distances are
Cl
AuI
L
Cl
AuI
L
Reduction
1B
AuI
AuIIICl4
L
AuI Cl AuICl2
L
AuI Cl AuIIICl4
Aggregation
Acetone
Cl
Cl
1B
1B'
1C (major)
PPh2
Aggregation
1B'
Me
L=
Me
N
N
Cl
AuI
L
Cl
AuI
L
1-methyl-2-diphenylphosphino-
3-methylimidazolium
AuI
AuICl2
Cl
Cl
1C' (minor)
Scheme 2. The proposed pathway for the formation of 1C.

44
X. Wang et al. / Journal of Organometallic Chemistry 762 (2014) 40e47
Table 3
Since phenylacetylene and 1A were insoluble in water, the co-
Different Au(I,III)-complexes as the homogeneous precatalysts for hydration of
solvent of MeOH was added to admit the accessibility of the sub-
strates to the catalytic site. MeOH was also believed to promote
hydration of alkynes through the formation of diacetal intermedi-
ate since the attack of MeOH to metalated-alkyne intermediate was
faster in comparison to H2O [9a,14]. Undoubtedly, neither 1A nor
H2SO4 alone was active under the applied conditions (entries 1 and
2). The involvement of H2SO4 as the additive was significantly
important to spur the activity of 1A (entries 3 vs 1 and 2). The
indispensable role of H2SO4 to spur the activity of the Au(I)-
catalysts was believed to cooperatively cleave the AueCl bond for
the generation of the unsaturated [R3PeAu]þ species to accom-
modate phenylacetylene for transmetalation and inhibit the deac-
tivation of the Au-catalyst [23]. The increased concentration of
H2SO4 couldn’t improve the yield of acetophenone further (entries
3 vs 4), while the prolonged reaction time from 2 h to 5 h increased
the yield from 58% to 79% (entry 5). Unexceptionally, the hydration
of phenylacetylene proceeded selectively according to Markovni-
kov’s rule to afford acetophenone with 100% selectivity.
phenylacetylene in conjunction of H2SO4.a
Entry
Cat
Conv. (%)c
Sel. to acetophenone (%)c
1
2
3
4
1A
1B
2A
3A
4A
1C
1C
56
47
86
71
34
81
64
100
100
100
100
100
100
100
5
6
7b
a
Au-complex 1 mol% (0.01 mmol), phenylacetylene 1 mmol, solvent 5 mL [H2SO4
aqueous solution (1.0 mol/L) 0.5 mL, H2O 1 mL, MeOH 3.5 mL], temperature 75 ꢁC.
b
1C 0.5 mol% (0.005 mmol).
GC analysis.
c
phenylacetylene. Reasonably, the close ion-pair relationship of 2A
could further consolidate such shielding effect to expel water
molecules out of the surroundings of [LeAuIeCl]þ.
In comparison to 2A, the increased bulky hindrance in the pe-
ripheral position of the imidazolium ring in 3A and 4A, led to the
decreased reaction rate. Especially over 4A with bulky
benzimidazolium-substituted phosphine, the yield of acetophe-
none dropped to 34% (entry 5). The trinuclear Au(I)-complex of 1C
exhibited much better activity, in comparison to 1B with the same
AuClꢀ4 counteranion, giving 81% yield of acetophenone (entry 6). 1C
as a trinuclear Au(I)-complex was featured with the inherent cat-
alytic nature, but not the simple adduct of two 1B. Since when the
concentration of 1C was decreased to half (0.5 mol%), the much
higher yield of acetophenone was obtained with 1C than that with
1B (entries 7 vs 2: yield 64% vs 47%).
Under the selected reaction conditions (0.5 mmol H2SO4, 2 h,
and 75 ꢁC), the catalytic performance of 1Ae3C and 2Ae4A for
hydration of phenylacetylene was investigated at the same
benchmark (Table 3).
As for 1A, 1B, and 2A with the same phosphino-imidazolium
cations, it was found that the counteranion effect played signifi-
cantly important role in tailoring the catalytic performance
(Table 1). The obtained yields of acetophenone over 1A, 1B, and 2A
followed the order of PFꢀ6 > OTfꢀ > AuCl4ꢀ. 1B with AuClꢀ4 coun-
teranion exhibited the lowest activity with acetophenone yield of
47% (entry 2), which suggested that AuClꢀ4 as a gold(III)-center unit
exhibit no additional contribution to the activation of phenyl-
acetylene. Comparatively, the presence of counteranion OTfꢀ with
the amphilicity in 1A could accelerate the reaction rate to some
extent (entry 1); whereas the presence of counteranion PFꢀ6 with
absolute hydrophobicity in 2A dramatically spurred the activity of
the corresponding cation [LeAuIeCl]þ, giving the yield of aceto-
phenone up to 86% (entry 3). As for PFꢀ6 , OTfꢀ, and AuCl4ꢀ, the hy-
drophobicity is in the ranking of PFꢀ6 (hydrophobicity) > OTfꢀ
(amphilicity) > AuClꢀ4 (hydrophilicity), which is in the same order
for the observed activity of 2A > 1A > 1B. Based on these results, it
is supposed that the counteranions with hydrophobicity might act
as the shields to besiege the hydrophobic [LeAuIeCl]þ cation
through the hydrophobic pushing-force, and then protect [LeAuIe
Cl]þ cation (as the catalytic site) from deactivation before the co-
ordination of the nucleophilic alkyne to [LeAuIeCl]þ for trans-
metallation [14]. Consequently, 2A with the most hydrophobic PF6ꢀ
counteranion exhibited the best activity towards hydration of
Conclusions
A series of ionic Au(I)-complexes ligated by the phosphine-FILs
were obtained and prove to be composed of the Au(I)-complex
cation and the different counteranion of OTfꢀ, AuCl4ꢀ, or PF6ꢀ by
the single crystal X-ray diffraction analysis. The Au(I)-centered
vectors in 1A, 1B, 1B0, 2A, 3A, and 4A all possess the slightly
twisted linear geometry in which the Au-center is coordinated by
one chlorine atom and one imidazolium-based phosphine. The
aggregation of 1B with 1B0 leads to the formation of the trinuclear
Au(I)-complexe of 1C, in which the trimetalic-Au nucleus is arrayed
in an ideal linear pattern. When these ionic Au-complexes were
employed as precatalysts for hydration of phenylacetylene in
aqueous-methanol media, the reaction proceeded selectively ac-
cording to Markovnikov’s rule with the moderate to high yields of
acetophenone. The catalytic performance of these ionic Au(I)-
complexes can be affected by several factors including the coun-
teranion effect, the steric hindrance of the involved phosphine, and
the inherent nature of the Au-nucleus. 2A possessing the hydro-
phobic anion of PFꢀ6 exhibited the best activity towards the acti-
vation of phenylacetylene, probably due to the protection of [Le
AuIeCl]þ catalytic site by the peripheral hydrophobic PFꢀ6 through
the hydrophobic pushing-force against the attack of water mole-
cules. 1C exhibited better activity due to the inherent catalytic
nature of the trimetalic-Au nucleus, but not the result of the simple
adduct of 1B.
Table 2
a
Hydration of phenylacetylene catalyzed by 1A in conjunction of H2SO4
O
Catalyst: 1A
Me
+
H2O
H2SO4
Entry Catalyst H2SO4 (mmol) Time (h) Conv. (%)b Sel. to acetophenone (%)b
1
2
3
4
5
e
0.5
e
2
2
2
2
5
0
0
56
58
79
e
1A
1A
1A
1A
e
Experimental section
0.5
1.0
1.0
100
100
100
Reagents and analysis
a
1A 1 mol%, phenylacetylene 1 mmol, solvent 5 mL [H2SO4 aqueous solution
(1.0 mol/L) 0.5 mL, H2O 1 mL, MeOH 3.5 mL], temperature 75 ꢁC.
The chemical reagents were purchased from Shanghai Aladdin
Chemical Reagent Co. Ltd. And Alfa Aesar China, and used as
b
GC analysis.

X. Wang et al. / Journal of Organometallic Chemistry 762 (2014) 40e47
45
received. 1H NMR spectra and 31P NMR spectra (with 75% H3PO4
sealed in a capillary tube as internal standard) were recorded on a
Bruker Avance 500 spectrometer at 298 K. Gas chromatography
(GC) was performed on a SHIMADZU-2014 equipped with a RTx-
the mixture for 1 h, chlorodiphenylphosphine (13.0 g, 59.3 mmol)
was added dropwise subsequently. The resultant mixture was
stirred for another 1 h at ꢀ78 ꢁC and then warmed up to ambient.
After quenching excess n-BuLi with deionized water, the solvent of
oily mixture was removed in vacuo. The obtained residue was pu-
rified by silica gel column chromatography with eluent of
PE:EA ¼ 8:1 to give 1-butyl-2-(diphenylphosphino)-benzimidazole
Wax capillary column (30 m ꢂ 0.25 mm ꢂ 0.25
mm). GCemass
spectrometry (GCeMS) was recorded on an Agilent 6890 instru-
ment equipped with an Agilent 5973 mass selective detector.
as the white solids (10.27 g, yield 58 wt%). 1H NMR (
d, ppm,
Synthesis
acetone-d6): 7.62 (d,1H, J ¼ 8 Hz, HAr), 7.59e7.53 (m, 5H, HAr), 7.39e
7.36 (m, 6H, HAr), 7.27e7.18(m, 2H, HAr), 4.45e4.41 (t, 2H, J ¼ 7.5 Hz,
NCH2CH2CH2CH3), 1.66e1.60 (m, 2H, CH2CH2CH2CH3), 1.28e1.23
1-Methyl-2-diphenylphosphino-3-methylimidazolium triflate (1)
Under N2 atmosphere, to a solution of 1-methylimidazole
(2.055 g, 25 mmol) in 80 mL dry THF cooled to ꢀ78 ꢁC, n-BuLi
(1.6 M, in hexane, 16 mL, 25 mmol) was added dropwise. Chlor-
odiphenylphosphine (5.73 g, 25 mmol) was added dropwise after
the mixture stirred for 1 h. The suspension stirred for another 1 h
and then warmed to room temperature slowly, the mixture stirred
continuously for another 2 h. After quenching excess n-BuLi with a
small amount of deionized water, THF was removed on a rotary
evaporator to obtain yellow mixture, which was dissolved in 5 mL
diethyl ether. The obtained ether solution was repeatedly washed
with deionized water, and then purified through silica gel column
chromatography with eluent of petroleum ether/ethyl acetate
(PE:EA ¼ 1:3) to afford 1-methyl-2-diphenylphosphinoimidazole
as the white solids (5.3 g, yield 80 wt%). Then the obtained solids
(1.5 g, 5.7 mmol) dissolved in 35 mL dry CH2Cl2 were cooled down
under N2 atmosphere to ꢀ78 ꢁC, which was treated with methyl
triflate (1.0 g, 6.3 mmol). The reaction mixture was stirred vigor-
ously at ꢀ78 ꢁC for 1 h and then warmed up to ambient. After
removed the solvent under vacuum, the obtained residue was
recrystallized from CH3COOCH2CH3/Et2O to yield 1 as the white
(m, 2H CH2CH2CH2CH3), 0.81e0.78 (t, 3H,
CH2CH2CH2CH3).
J
¼
7.5 Hz,
Under N2 atmosphere, to a solution of 1-butyl-2-(diphenyl-
phosphino)-benzimidazole (1.29 g, 3.6 mmol) in dry CH2Cl2 (40 mL)
cooled to ꢀ78 ꢁC was added methyl triflate (0.62 g, 3.8 mmol). The
solution was stirred with the reaction temperature increasing
from ꢀ78 ꢁC to ambient, and then stirred continuously at room
temperature for another 2 h. After removal of the solvent under
vacuum, the residue was washed with diethyl ether (10 mL ꢂ 3) to
afford the white powder as the product of 2 (1.84 g, yield 98 wt%).
1H NMR (
d, ppm, acetone-d6): 8.17e8.14(m, 1H, HAr), 8.07e8.05 (m,
1H, HAr), 7.82e7.77 (m, 2H, HAr), 7.71e7.58 (m, 10H, HAr), 4.81e4.76
(t, 2H, J ¼ 8 Hz, NCH2CH2CH2CH3), 3.94 (s, 3H, NCH3), 1.69e1.62 (m,
2H, CH2CH2CH2CH3), 1.30e1.28 (m, 2H, CH2CH2CH2CH3), 0.81e0.77
(t, 3H, J ¼ 7.5 Hz, CH2CH2CH2CH3) ppm. 31P NMR (
d6): ꢀ20.4 (s, PPh2).
d, ppm, acetone-
(1-Methyl-2-diphenylphosphino-3-methylimidazolium)-
chlorogold(I) triflate (1A)
[AuI(tht)Cl] was prepared according to the published methods
[24]. 1-Methyl-2-diphenylphosphino-3-methylimidazolium triflate
(430.4 mg, 1 mmol) was slowly added to a stirring solution of
[AuI(tht)Cl] (320.6 mg 1 mmol) in 10 mL of distilled dichloro-
methane, which was stirred at room temperature for adding
15 min. The solution was still colorless and then concentrated to
1 mL and 10 mL ether was added resulting in white precipitate. The
solid was then filtrated, washed with ether (5 mL ꢂ 3), and dried
under vacuum. Yield: 656.1 mg (98 wt%). The crystals of 1A suitable
for the single crystal X-ray diffraction analysis were obtained by
recrystalization from an acetone-dichloromethane solution layered
solids (2.2 g, yield 90 wt%). 1H NMR (
2H, NCHCHN), 7.52e7.50 (m, 6H, PPh2), 7.36e7.33(m, 4H, PPh2), 3.70
(s, 6H, 2NCH3), 31P NMR (
, ppm, chloroform-d): ꢀ25.59 (s, PPh2).
d, ppm, chloroform-d): 7.81 (s,
d
1-Methyl-2-diphenylphosphino-3-methylimidazolium
hexafluorophosphate (2)
Under N2 atmosphere, iodomethane (3.9 g, 27.5 mmol) was
added dropwise to
a solution of 1-methylimidazole (2.1 g,
25 mmol) in 20 mL dry THF, there were a large amount of white
solid precipitated after the mixture stirred in 30 ꢁC oil bath for 2 h.
After removal of the solvent under vacuum, the obtained residue
dissolved in 20 mL deionized water with ammonium hexa-
fluorophosphate (6.1 g, 37.5 mmol) added. 1-Methyl-3-
methylimidazolium hexafluorophosphate was obtained after 2 h
with the mixture was extracted with dichloromethane (6 mL ꢂ 3)
and then stripped of dichloromethane under vacuum. The
with n-hexane. 1H NMR (
PPh2), 7.77e7.70(8H, m, PPh2, NCHCHN), 3.59 (6H, s, 2NCH3). 31P
NMR ( , ppm, chloroform-d): 20.32 (s, PPh2). CHN-elemental
d, ppm, chloroform-d): 8.01e7.96 (4H, m,
d
analysis found for 1A (%): C 32.64, H 2.71, N 3.96 (Calcd., C 32.62,
H 2.74, N 4.23).
phosphine-FIL
of
1-methyl-2-diphenylphosphino-3-
methylimidazolium trifluoromethanesulfonate (2) was prepared
according to the published methods [18] with some modifications.
(1-Methyl-2-diphenylphosphino-3-methylimidazolium)-
chlorogold(I) tetrachloroaurate (1B)
1H NMR (
d
, ppm, chloroform-d): 7.59 (s, 2H, NCHCHN), 7.50e7.48
1B was prepared by ion exchange for 1A (132.6 mg 0.2 mmol)
with chloroauric acid (82.4 mg 0.2 mmol) in 10 mL of dry
dichloromethane. The obtained salmon pink solution after being
concentrated to 1 mL was treated with 10 mL diethyl to precip-
itate the yellow solids. The yellow solids were collected with
yield of 93 wt% (158.6 mg), after washing with diethyl ether
(5 mL ꢂ 3) and drying under vacuum. The single crystals of 1B
suitable for the single crystal X-ray diffraction analysis were ob-
tained from an acetonitrile-dichloromethane solution layered
(m, 6H, PPh2), 7.36e7.32(m, 4H, PPh2), 3.64 (s, 6H, 2NCH3), 31P NMR
(d
, ppm, chloroform-d): ꢀ25.50 (s, PPh2), ꢀ144.23 (sept, PFꢀ6 ).
1-Butyl-2-diphenylphosphino-3-methylimidazolium
hexafluorophosphate (3)
The
phosphine-FIL
of
1-butyl-2-diphenylphosphino-3-
methylimidazolium hexafluorophosphate (3) was prepared ac-
cording to the published methods [18].
with dry diethyl ether. 1H NMR (
7.97e7.92 (4H, m, PPh2), 7.84e7.83 (2H, m, PPh2), 7.78e7.75 (4H,
m, PPh2), 7.65 (2H, s, NCHCHN), 3.61 (6H, s, 2NCH3), 31P NMR (
d, ppm, methylene chloride-d2):
1-Butyl-2-diphenylphosphino-3-methylbenzo[d]imidazolium
triflate (4)
d
,
Under N2 atmosphere, to a solution of 1-butyl-benzimidazole
(8.6 g, 49.4 mmol) in 50 mL dry THF cooled to ꢀ78 ꢁC was added n-
BuLi (1.6 M in hexane, 37.0 mL, 59.3 mmol) dropwise. After stirring
ppm, methylene chloride-d2): 21.49 (s, PPh2). CHN-elemental
analysis found for 1B (%): C 23.93, H 2.08, N 3.05 (Calcd., C
23.95, H 2.13, N 3.29).

46
X. Wang et al. / Journal of Organometallic Chemistry 762 (2014) 40e47
[AuI(L)CleAuCl2eAu(L)Cl]AuCl4 (L ¼ 1-methyl-2-
diphenylphosphino-3-methylimidazolium, 1C)
The yellow and clear solution of 1B (103.5 mg, 0.12 mmol) in
4 mL of acetone was stirred vigorously for 72 h at room temper-
ature and then concentrated to 1 mL. After addition of 15 mL dry
diethyl ether to the concentrated solution, the orange solids were
precipitated and then collected after washing with n-hexane and
dryness in vacuo, with the yield of 78 wt% (76.8 mg). The crystals
of 1C were obtained by recrystallization from acetone-hexane. 1H
NMR (
(4H, m, PPh2), 7.60 (2H, s, NCHCHN), 3.51 (6H, s, 2NCH3); 31P NMR
, ppm, acetonitrile-d3): 20.49 (s, PPh2). CHN-elemental analysis
d, ppm, acetonitrile-d3): 7.87e7.81 (6H, m, PPh2), 7.74e7.70
(d
found for 1C (%): C 24.26, H 2.08, N 2.96 (Calcd., C 24.99, H 2.22, N
3.43).
(1-Methyl-2-diphenylphosphino-3-methylimidazolium)-
chlorogold(I) hexafluorophosphate (2A)
To a solution of [AuI(tht)Cl] (320.6 mg, 1 mmol) in 10 mL dry
dichloromethane was added slowly the phosphine-FIL of 2
(426.4 mg, 1 mmol). The obtained mixture was stirred vigorously
at room temperature for another 15 min to afford the colorless
solution, which was concentrated under vacuum to 1 mL. Then
10 mL diethyl ether was added into the above concentrated so-
lution to precipitate the white solids, which was collected after
washing with diethyl ether (5 mL ꢂ 3) and dryness under vacuum
to give 2A with the yield of 95 wt% (625.3 mg). The crystals of 2A
suitable for the single crystal X-ray diffraction analysis were ob-
tained by recrystalization from an acetone-dichloromethane so-
lution layered with n-hexane. 1H NMR (
8.01e7.96 (4H, m, PPh2), 7.77e7.70 (8H, m, PPh2, NCHCHN), 3.59
d, ppm, chloroform-d):
(6H, s, 2NCH3). 31P NMR (
d, ppm, chloroform-d): 20.32 (s,
PPh2), ꢀ143.52 (sept, PFꢀ6 ). CHN-elemental analysis found for 2A
(%): C 30.90, H 2.74, N 3.89 (Calcd., C 31.00, H 2.75, N 4.25).
(1-Methyl-2-diphenylphosphino-3-butylimidazolium)-
chlorogold(I) hexafluorophosphate (3A)
To a solution of [AuI(tht)Cl] (320.6 mg, 1 mmol) in 10 mL dry
dichloromethane was added slowly the phosphine-FIL of 3
(468.4 mg, 1 mmol). The obtained mixture was stirred vigorously
at room temperature for another 15 min to afford the colorless
solution, which was concentrated under vacuum to 1 mL. Then
10 mL diethyl ether was added into the above concentrated so-
lution to precipitate the white solids, which was collected after
washing with diethyl ether (5 mL ꢂ 3) and dryness under vacuum
to give 3A with the yield of 93 wt% (651.8 mg). The crystals of 3A
suitable for the single crystal X-ray diffraction analysis were ob-
tained by recrystalization from an acetone solution layered with
n-hexane. 1H NMR (
d, ppm, acetonitrile-d3): 7.89e7.84 (6H, m,
PPh2), 7.76e7.73 (4H, m, PPh2), 7.74 (1H, s, NCHCHN), 7.64 (1H, s,
NCHCHN), 4.06e4.03 (2H, t, J ¼ 8.0 Hz, CH2CH2CH2CH3), 3.42 (3H,
s, NCH3), 1.71e1.65 (2H, m, CH2CH2CH2CH3), 1.15e1.10 (2H, m,
CH2CH2CH2CH3), 0.84e0.81 (3H, t, J ¼ 7.4 Hz, CH2CH2CH2CH3). 31
P
NMR (
d
, ppm, acetonitrile-d3): 20.00 (s, PPh2), ꢀ143.11 (sept, PFꢀ6 ).
CHN-elemental analysis found for 3A (%): C 34.35, H 3.39, N 3.69
(Calcd., C 34.28, H 3.45, N 4.00).
(1-Butyl-2-diphenylphosphino-3-methylbenzoimidazolium)-
chlorogold(I) triflate (4A)
To a solution of [AuI(tht)Cl] (320.6 mg, 1 mmol) in 10 mL dry
dichloromethane was added slowly the phosphine-FIL of 4
(522.5 mg, 1 mmol). The obtained mixture was stirred vigorously
at room temperature for another 15 min to afford the colorless
solution, which was concentrated under vacuum to 1 mL. Then
10 mL diethyl ether was added into the above concentrated so-
lution to precipitate the white solids, which was collected after

X. Wang et al. / Journal of Organometallic Chemistry 762 (2014) 40e47
47
8004;
washing with diethyl ether (5 mL ꢂ 3) and dryness under vacuum
to give 4A with the yield of 86 wt% (649.3 mg). The crystals of 4A
suitable for the single crystal X-ray diffraction analysis were ob-
tained by recrystalization from a saturated methanol solution. 1H
(e) M.A. Celik, C. Dash, V.A.K. Adiraju, A. Das, M. Yousufuddin, G. Frenking,
H.V.R. Dias, Inorg. Chem. 52 (2013) 729e742;
(f) A. Almassy, C.E. Nagy, A.C. Benyei, F. Joó, Organometallics 29 (2010) 2484e
2490.
[3] (a) L.P. Liu, G.B. Hammond, Chem. Soc. Rev. 41 (2012) 3129e3139;
(b) Z. Li, C. Brouwer, C. He, Chem. Rev. 108 (2008) 3239e3265;
(c) A. Arcadi, Chem. Rev. 108 (2008) 3266e3325;
(d) D.J. Gorin, B.D. Sherry, F.D. Toste, Chem. Rev. 108 (2008) 3351e3378.
[4] (a) L. Rodríguez, M. Ferrer, R. Crehuet, J. Anglada, J.C. Lima, Inorg. Chem. 51
(2012) 7636e7641;
NMR (
d
, ppm, chloroform-d): 8.27e8.25 (4H, d, J ¼ 8 Hz, benz-
imidazole), 7.80e7.76 (10H, m, PPh2), 3.76e3.71 (5H, m, NCH3,
NCH2), 1.68 (2H, br, NCH2CH2), 1.28e1.25 (5H, m, CH2CH3). 31P NMR
(d, ppm, acetone-d6): 93.13 (s, PPh2). CHN-elemental analysis found
for 4A (%): C 39.73, H 3.44, N 3.39 (Calcd., C 39.77, H 3.47, N 3.71).
(b) S.G. Wang, W.H.E. Schwarz, J. Am. Chem. Soc. 126 (2004) 1266e1276;
(c) D.J. Gorin, F.D. Toste, Nature 446 (2007) 395e403;
(d) M. Lein, M. Rudolph, S.K. Hashmi, P. Schwerdtfeger, Organometallics 29
(2010) 2206e2210.
General procedures for the hydration of phenylacetylene catalyzed
by the ionic Au(I) complexes
[5] (a) X. Yao, C.J. Li, Org. Lett. 8 (2006) 1953e1955;
(b) S. Sanz, L.A. Jones, F. Mohr, M. Laguna, Organometallics 26 (2007) 952e
957.
[6] M. Kutscheroff, Chem. Ber. 17 (1884) 13e29.
[7] M.G. Kutscheroff, Chem. Ber. 42 (1909) 2759e2762.
[8] J.A. Nieuwland, R.R. Vogt, W.L.J. Foohey, J. Am. Chem. Soc. 52 (1930) 1018e
1024.
In a typical procedure, phenylacetylene (1 mmol), H2SO4
aqueous solution (0.5 mL, 1.0 mol/L), MeOH (3.5 mL), the isolated
crystalline Au-complex precatalyst (0.01 mmol), and the distilled
water (1 mL) were added sequentially to a safe glass pressure
reactor. The mixture was heated in oil bath at 75 ꢁC for 2 h. Upon
completion, the reaction mixture was cooled to room temperature
and then filtered. The combined filtrate after washing the residue
with MeOH (2 mL ꢂ 3) was analyzed by GC to determine the yield
of the product (1-dodecane as the internal standard). The struc-
tures of obtained products were further confirmed by GCeMass.
[9] (a) J.H. Teles, S. Brode, M. Chabanas, Angew. Chem. Int. Ed. 37 (1998) 1415e
1418;
(b) R.O.C. Norman, W.J.E. Parr, C.B. Thomas, J. Chem. Soc. Perkin Trans. 1
(1976) 1983e1987;
(c) Y. Fukuda, K.J. Utimoto, Org. Chem. 56 (1991) 3729e3731;
(d) P. Roembke, H. Schmidbaur, S. Cronje, H. Raubenheimer, J. Mol. Catal. A:
Chem. 212 (2004) 35e42;
(e) X. Xu, S.H. Kim, X. Zhang, A.K. Das, H. Hirao, S.H. Hong, Organometallics 32
(2013) 164e171.
[10] G.A. Carriedo, S. Lopez, S. Suarez-Suarez, D. Presa-Soto, A. Presa-Soto, Eur. J.
Inorg. Chem. 2011 (2011) 1442e1447.
X-ray crystallography
[11] M. Deetlefs, H.G. Raubenheimer, M.W. Esterhuysen, Catal. Today 72 (2002)
29e41.
[12] D.M. Cui, Y.N. Ke, D.W. Zhuang, Q. Wang, C. Zhang, Tetrahedron Lett. 51 (2010)
980e982.
[13] P. Nun, R.S. Ramón, S. Gaillard, S.P.J. Nolan, J. Organomet. Chem. 696 (2011) 7e
11.
Intensity data were collected at 298 K on a Bruker SMARTAPEX II
diffractometer using graphite monochromated Mo-Ka radiation
ꢀ
(l
¼ 0.71073 A). Data reduction included absorption corrections by
the multi-scan method. The structures were solved by direct
methods and refined by fullmatrix least-squares using SHELXS-97
(Sheldrick, 1990), with all non-hydrogen atoms refined anisotrop-
ically. Hydrogen atoms were added at their geometrically ideal
positions and refined isotropically. The crystal data and refinement
details are given in Table 4.
[14] A. Leyva, A. Corma, J. Org. Chem. 74 (2009) 2067e2074.
[15] (a) C. Latouche, Y.C. Lee, J.H. Liao, E. Furet, J.Y. Saillard, C.W. Liu, A. Boucekkine,
Inorg. Chem. 51 (2012) 11851e11859;
(b) M.A. Bennett, S.K. Bhargava, N. Mirzadeh, S.H. Priv0er, J. Wagler, A.C. Willis,
Dalton Trans. (2009) 7537e7551;
(c) T.L. Stott, M.O. Wolf, B.O. Patrick, Inorg. Chem. 44 (2005) 620e627.
[16] (a) K.L. Luska, A. Moores, Adv. Synth. Catal. 353 (2011) 3167e3177;
ꢁ
ꢁ
(b) J.A. Vicente, A. Mlonka, H.Q.N. Gunaratne, M. Swadzba-Kwasny,
P. Nockemann, Chem. Commun. 48 (2012) 6115e6117;
(c) J. Andrieu, L. Harmand, M. Picquet, Polyhedron 29 (2010) 601e605.
[17] K.L. Luska, K.Z. Demmans, S.A. Stratton, A. Moores, Dalton Trans. 41 (2012)
13533e13540.
Acknowledgments
This work was financially supported by the National Natural
Science Foundation of China (NSFC, Nos. 21273077 and 21076083),
and 973 Program from Ministry of Science and Technology of China
(2011CB201403).
[18] D.J. Brauer, K.W. Kottsieper, C. Liek, O. Stelzer, H. Waffenschmidt,
P. Wasserscheid, J. Organomet. Chem. 630 (2001) 177e184.
[19] (a) C. Barthes, C. Lepetit, Y. Canac, C. Duhayon, D. Zargarian, R. Chauvin, Inorg.
Chem. 52 (2013) 48e58;
(b) Y. Canac, N. Debono, L. Vendier, R. Chauvin, Inorg. Chem. 48 (2009) 5562e
5568;
(c) Y. Canac, C. Maaliki, I. Abdellah, R. Chauvin, New. J. Chem. 36 (2012) 17e
27;
Appendix A. Supplementary material
(d) I. Abdellah, C. Lepetit, Y. Canac, C. Duhayon, R. Chauvin, Chem. Eur. J. 16
(2010) 13095e13108;
(e) R. Chauvin, Eur. J. Inorg. Chem. (2000) 577e591;
(f) M. Azouri, J. Andrieu, M. Picquet, H. Cattey, Inorg. Chem. 48 (2009) 1236e
1242;
CCDC 961119, 961120, 961121, 961122, 961123, 961124, 961125,
and 961126 contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
(g) Y. Canac, N. Debono, C. Lepetit, C. Duhayon, R. Chauvin, Inorg. Chem. 50
(2011) 10810e10819.
[20] (a) Y. You, Y. Wang, X. Zhao, S. Chen, Y. Liu, Organometallics 32 (2013) 2698e
2704;
References
ꢁ
ꢁ
(b) C. Zhou, J. Zhang, M. Ðakovic, Z. Popovic, X. Zhao, Y. Liu, Eur. J. Inorg. Chem.
(2012) 3435e3440;
(c) X. Wang, J. Zhang, Y. Wang, Y. Liu, Catal. Commun. 40 (2013) 23e26;
(d) S. Chen, Y. Wang, W. Yao, X. Zhao, Y. Liu, J. Mol. Catal. A: Chem. 378 (2013)
293e298.
[1] R. Casado, M. Contel, M. Laguna, P. Romero, S. Sanz, J. Am. Chem. Soc. 125
(2003) 11925e11935.
[2] (a) N. Marion, S.P. Nolan, Chem. Soc. Rev. 37 (2008) 1776e1782;
(b) A.S.K. Hashmi, C. Lothschütz, C. Böhling, T. Hengst, C. Hubbert, F. Rominger,
Adv. Synth. Catal. 352 (2010) 3001e3012;
[21] N.C. Baenziger, W.E. Bennett, D.M. Soborofe, Acta Crystallogr. 32 (1976) 962e
963.
[22] J. Zank, A. Schier, H.J. Schmidbaur, Chem. Soc. Dalton Trans. (1998) 323e324.
[23] A.S.K. Hashmi, Catal. Today 122 (2007) 211e214.
[24] R. Uson, A. Laguna, M. Laguna, Inorg. Synth. 26 (1989) 85e91.
(c) A.S.K. Hashmi, D. Riedel, M. Rudolph, F. Rominger, T. Oeser, Chem. Eur. J. 18
(2012) 3827e3830;
(d) S. Cauteruccio, A. Loos, A. Bossi, M.C.B. Jaimes, D. Dova, F. Rominger,
S. Prager, A. Dreuw, E. Licandro, A.S.K. Hashmi, Inorg. Chem. 52 (2013) 7995e