Palladium Complexes Bearing Mesoionic Carbene Ligands: Applications in α-Arylation, α-Methylation and Suzuki-Miyaura Coupling Reactions

Article abstract of DOI:10.1002/ejic.201501031

Complexes of mesoionic carbene (MIC) ligands are gaining immense popularity in organometallic chemistry and homogeneous catalysis. We present here a series of palladium(II) complexes that are comprised of MIC donor ligands, and we demonstrate their applic

Full text of DOI:10.1002/ejic.201501031

DOI: 10.1002/ejic.201501031
Full Paper
Mesoionic Carbenes
Palladium Complexes Bearing Mesoionic Carbene Ligands:
Applications in α-Arylation, α-Methylation and Suzuki–Miyaura
Coupling Reactions
[a]
[a]
[a]
[a]
Ramananda Maity, Amit Verma, Margarethe van der Meer, Stephan Hohloch, and
Biprajit Sarkar*[
a]
Abstract: Complexes of mesoionic carbene (MIC) ligands are used for chemoselective Suzuki–Miyaura coupling reaction. This
gaining immense popularity in organometallic chemistry and complex delivers lower yields in α-arylation reactions compared
homogeneous catalysis. We present here a series of palla- with PEPPSI-type complexes, however, it gives an α-methylated
dium(II) complexes that are comprised of MIC donor ligands, product when the reaction is conducted in N,N-dimethyl-
and we demonstrate their applications in α-arylation, α-methyl- formamide. Mercury poisoning experiments suggest that the
ation, and Suzuki–Miyaura coupling reactions. All the com- Suzuki–Miyaura coupling reaction likely proceeds via Pd nano-
plexes have been structurally characterized by X-ray crystallo- particles. However, the α-arylation reaction proceeds homoge-
graphic analysis. These palladium(II) complexes are potent pre- neously, as shown by the negative mercury poison test. The
catalysts and they deliver good to excellent yields for both α- present results thus open up new avenues for MIC ligands in
arylation and Suzuki–Miyaura coupling reactions. A palla- catalytic α-arylation and α-methylation reactions.
dium(II) complex bearing two MIC units in a trans fashion is
Introduction
recently been used in photophysical applications.[14] In addi-
tion, substituted 1,2,3-triazoles can easily be synthesized by the
N-Heterocyclic carbenes (NHCs) have made an impressive im-
pact in a number of fields such as organometallic chemistry,
homogeneous catalysis,
redox-active molecular material chemistry and, very recently,
in metallosupramolecular chemistry. Although the majority of
these ligands are based on classical NHC donors (imidazol-2-
1
,3-dipolar cycloaddition reaction of an azide to an alkyne (click
[
1]
[15]
reaction).
Alkylation of the triazoles results in the formation
[
2]
[3]
biologically active complexes,
of the corresponding 1,2,3-triazolium salts, which are the pre-
cursors for the 1,2,3-triazol-5-ylidenes.
[
4]
[
5]
We present here the synthesis of PEPPSI-type palladium(II)
1
,2,3-triazol-5-ylidene complexes and Pd(MIC)2X (X = halide)
[
6]
2
ylidenes or 1,2,4-triazol-5-ylidenes), their mesoionic carbene
MIC) counterparts 1,2,3-triazol-5-ylidenes have received a lot of
type complexes along with their applications in α-arylation, α-
methylation, and Suzuki–Miyaura cross coupling reactions. All
(
[
7]
attention in the last few years. 1,2,3-Triazol-5-ylidenes have
been postulated as being even better ligands in catalysis be-
cause of their superior donor ability compared with their classi-
cal N-heterocyclic carbene (NHC) counterparts of the imidazole-
1
13
1
the complexes have been characterized by H, C{ H}, 2D cor-
relation NMR spectroscopy, mass spectrometry, and also by X-
ray crystallography.
[
7a]
2-ylidene type.
A number of important reactions have been
catalyzed by transition-metal complexes bearing 1,2,3-triazol-5-
[
8]
ylidenes with the catalytic transfer hydrogenation, oxidation
[
9]
[10]
reactions, hydroarylation of alkynes,
tions,
cross-coupling reac-
[
11]
[12]
and cyclization reactions[13] consti-
Results and Discussion
click reactions,
tuting prominent examples. Furthermore, such complexes have
Synthesis and Characterization of Complexes
The triazolium salts (R)-1 and (S)-1 were prepared from the cor-
responding triazoles by using methyl iodide as methylating
[
a] Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität
Berlin,
Fabeckstrasse 34–36, 14195 Berlin, Germany
E-mail: biprajit.sarkar@fu-berlin.de
http://www.bcp.fu-berlin.de/en/chemie/chemie/forschung/InorgChem/
agsarkar/index.html
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejic.201501031.
agent under heating conditions by using a reported proce-
[16]
dure. The reaction of the triazolium salt (R)-1 with PdCl and
2
K CO in pyridine or with the corresponding chloro-substituted
2
3
pyridines resulted in the formation of PEPPSI-type palladium(II)
complexes (R)-[2], (R)-[3] and (R)-[4] (Scheme 1).
Eur. J. Inorg. Chem. 2016, 111–117
111
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
The formation of these complexes was confirmed by 1H,
1
3
1
C{ H} NMR spectroscopy, mass spectrometry and X-ray crystal-
1
lography. The H NMR spectra of both complexes (R,R)-[5], and
(
S,S)-[5] show the disappearance of the triazolium C–H proton
[
16]
signals, which was observed at δ = 9.20 ppm for the original
triazolium salts (R)-1 and (S)-1, respectively. Two sets of signals
1
13
1
appeared in both H and C{ H} NMR spectra of complex (R,R)-
5]. This might be due to the presence of two different geomet-
[
rical isomers, depending on the two different relative orienta-
tions of the carbene moieties around the palladium(II) center.
At room temperature, the ratio of the two isomers as measured
Scheme 1. Preparation of complexes (R)-[2], (R)-[3] and (R)-[4].
1
from the H NMR spectrum was 1:0.2. Heating of a sample of
The triazolium salts as well as the palladium(II) complexes
were isolated in pure enantiomeric forms. All the complexes
were obtained in reasonable yields of 52–63.5 %, they were well
soluble in chlorinated solvents such as dichloromethane and
chloroform and they were all stable towards both air and mois-
ture. The formation of these complexes was easily monitored
(R,R)-[5] changed this ratio to 1:0.4 (Figure S11). Additional heat-
ing for 2 hours did not have any further influence on the ratio
of the two isomers. Furthermore, the addition of excess KI to
the reaction mixture also did not have any influence on the
isomer ratio. The complex (S,S)-[5] shows the presence of mainly
one isomer in solution. The resonance for the characteristic
carbene carbon atoms appeared at δ = 128.3, 128.8 {(R,R)-[5]}
and 127.5 {(S,S)-[5]} ppm, which are not significantly shifted
from the original triazolium C5 resonance (δ = 129.3 ppm).
However, a downfield shifted resonance was observed at δ =
1
by H NMR spectroscopy, which showed the disappearance of
[
16]
the triazolium C–H proton signal (δ = 9.20 ppm)
for the tri-
1
azolium salt (R)-1 in the H NMR spectrum of each complex.
The resonance of the pyridine protons appeared at δ = 8.90–
1
8
.94, 7.64–7.68, and 7.23–7.26 ppm in the H NMR spectrum of
1
44.3 and 144.6 ppm for complex (R,R)-[5] and δ = 143.8 ppm
complex (R)-[2]. However, four (δ = 8.94, 8.85, 7.63–7.67, and
.20 ppm) and two resonances (δ = 8.87 and 7.25–7.26 ppm)
for complex (S,S)-[5], attributed to the CTrz atom connected to
7
1
the aryl ring. These resonances fall in the range reported for
attributed to the pyridine protons, appeared in the H NMR
spectra of complexes (R)-[3] and (R)-[4], respectively. Upon com-
plex formation, the resonance for the α-hydrogen atoms of the
pyridine ring {(R)-[2]: δ = 8.90–8.94 ppm} was observed to be
more downfield shifted compared with their corresponding res-
[
18]
the palladium complexes bearing MIC donor ligands. The for-
mation of these complexes was supported by the ESI mass
spectrometric analysis (positive ions), which showed peaks at
+
m/z 759.0943 (calcd. for [(R,R)-[5]-I] 759.0937), and 669.1575
+
onance in free pyridine (δ = 8.62 ppm).[
17]
13
1
(calcd. for [(S,S)-[5]-Cl] 669.1570) as strongest signals.
The C{ H} NMR
spectrum of all complexes (R)-[2], (R)-[3], and (R)-[4] showed the
characteristic resonance for the carbene carbon atoms at δ =
X-ray Crystal Structures of Complexes
133.6, 128.77, and 128.76 ppm, which are not significantly Single crystals that were suitable for X-ray diffraction study
shifted from the C5 resonance of the precursor triazolium salt were obtained for all the complexes by slow diffusion of
[
16]
(
R)-1 (δ = 129.3 ppm). The ESI mass spectra (positive ions) of pentane into a saturated dichloromethane/acetonitrile solution
these complexes show peaks at m/z 495.9510 (calcd. for [(R)- of each complex at ambient temperature. Molecular structure
+
+
[
4
2]-I-Py] 495.9509), 495.9508 (calcd. for [(R)-[3]-I-(3-Cl-Py)]
analysis with these crystals confirmed the formation of palla-
+
95.9509) and 495.9507 (calcd. for [(R)-[4]-I-(4-Cl-Py)] 495.9509) dium(II) PEPPSI-type complexes (R)-[2], (R)-[3], and (R)-[4] along
for complexes (R)-[2], (R)-[3] and (R)-[4], respectively.
with the complexes of Pd(MIC) -type {(R,R)-[5] and (S,S)-[5]; Fig-
2
The reaction of the triazolium salts (R)-1 or (S)-1 with Ag O, ure 1}, respectively.
2
followed by the addition of [PdCl (CH CN) ] in dichlorometh-
2
3
2
ane, resulted in the formation of the mononuclear palladium(II)
complexes (R,R)-[5] or (S,S)-[5] in good yields (49 and 60 %;
Scheme 2). Both complexes were isolated in enantiomeric pure
forms. The solubility and stability of these complexes are similar
to the others discussed above.
Figure 1. ORTEP plots of complexes (R)-[2], (R)-[3], (R)-[4], (R,R)-[5] and (S,S)-
5]. Ellipsoids are drawn at 50 % probability. Solvent molecules have been
omitted for clarity.
[
Scheme 2. Preparation of complexes (R,R)-[5] and (S,S)-[5].
Eur. J. Inorg. Chem. 2016, 111–117
www.eurjic.org
112
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
The coordination geometry around the palladium(II) center 76 %; 7c: 72 %) was observed for both aryl halides. The active
in all complexes was distorted square planar, and the MIC and palladium catalyst was unaffected by the addition of excess Hg0
pyridine or another MIC donors were coordinated to the palla- to the reaction mixture and led to similar yield for the α-aryl-
dium center in a trans-fashion with the remaining coordination ation product. The reaction thus likely proceeds through a ho-
sites around the palladium center occupied by either iodide or mogeneous pathway.
chloride donors. The CMIC–Pd–NPy bond angles are in the range
II
[a]
Table 1. α-Arylation reaction using Pd complexes.
of 176.23(18)–177.05(14)°. The CMIC–Pd–CMIC bond angles in
complexes (R,R)-[5] and (S,S)-[5] measure 174.4(3) and 174.5(2)°,
respectively. These values, like the Pd–CMIC bond lengths
[
1.949(8)–2.032(5) Å], fall in the range previously described for
[
11c,11e]
palladium(II) MIC complexes of similar type.
However, the
Pd–CMIC bond lengths for PEPPSI-type complexes is slightly
longer in chloro-substituted pyridine complexes (R)-[3]
[
1.957(3) Å] and (R)-[4] [1.979(5) Å] compared with the value
in complex (R)-[2] [1.949(8) Å]. The Pd–CMIC bond lengths in
Entry
ArBr
Catalyst
Isolated yield [%]
Pd(MIC) X -type complexes [2.007(6)–2.032(5) Å] are longer
2
2
1
2
3
4
5
6
4-bromotoluene
4-bromotoluene
4-bromotoluene
4-bromotoluene
4-bromobenzene
4-bromoanisole
(R)-[2]
(R)-[3]
(R)-[4]
(R,R)-[5]
(R)-[2]
(R)-[2]
85
70
52
16
76
72
than those in PEPPSI-type complexes [1.949(8)–1.979(5) Å].
Suzuki–Miyaura Cross-Coupling and α-Arylation Reactions
II
Using Pd Complexes
[
1
a] Reactions conditions: catalyst (5.0 mol-%), NaOtBu (2.5 equiv.), toluene,
20 °C, 16 h.
Organic transformations that are brought about through metal-
catalyzed C–C bond-formation reactions have been widely stud-
[
11,19]
ied as mild catalytic methods.
Consequently, a large num-
Surprisingly, an α-methylation product was observed with
ber of synthetic transformations have been successfully cata- precatalyst (R,R)-[5], when the same reaction was carried out
lyzed by complexes possessing monodentate NHCs with palla- in N,N-dimethylformamide (DMF)/dioxane mixture and in the
[
20]
[21]
dium-catalyzed Heck or Suzuki coupling reactions and the absence of an aryl halide (Scheme 3). The product 8 was ob-
[
22]
ruthenium-catalyzed olefin metathesis
constituting promi- tained in 50 % yield. Given that DMF was used as solvent sys-
nent examples. It has also been seen that the palladium-cata- tem for the reactions, DMF is likely acting as a methyl donor in
lyzed intermolecular coupling reactions offer a mild and easy these cases. Performing the reaction under identical conditions
[
23]
way to synthesize α-aryl ketones and α-aryl esters. However, but in the absence of the precatalyst (R,R)-[5] did not lead to
α-arylation of amides is comparatively difficult and requires a any product formation, thus establishing the vital role of the
stronger base than required for ketones and esters to generate precatalyst for this reaction. No α-methylation product was ob-
[
24,25]
the enolate.
intramolecular α-arylation of amides,
Although there are a handful of examples of served on performing this reaction in either dioxane or toluene
[
24]
the intermolecular α- under identical conditions but in the absence of DMF. The reac-
and has rarely been ex- tion in a DMF–toluene mixture did lead to the α-methylation
[
25]
arylation of amides is less common
plored with palladium(II) NHC complexes until recently.
[
18b]
product, albeit in a much lower yield compared with that ob-
All the PEPPSI-type complexes (R)-[2], (R)-[3], and (R)-[4], tained upon reaction in the DMF/dioxane mixture mentioned
along with the Pd(MIC) X -type palladium(II) complex (R,R)-[5] above. A similar observation was also reported for palladium-
2
2
I
have been tested as catalysts for both the α-arylation and catalyzed α-arylation reactions with Cu as co-catalyst in DMF/
Suzuki–Miyaura cross-coupling reactions. The α-arylation reac- dioxane.[25a] In addition, a trace amount of N-methylformamide
tions were typically carried out in toluene in the presence of (NMF) was also detected in the reaction mixture by HPLC analy-
[
25a]
I
NaOtBu (2.5 equiv.) as a base, and the reactions were performed sis.
In our case, no additional Cu source is required for this
with 5.0 mol-% catalyst loading at 120 °C for 16 h.
On performing the reactions with substrate 6 and 4-bromo-
toluene, the complex (R)-[2] delivered the highest isolated yield
reaction. Despite the use of enantiopure ligands, and their
metal complexes, we did not observe any enantiomeric excess
in the products formed through either α-arylation or α-alkyl-
ation of amides. These results show that the incorporation of
just one chiral center in the ligand with relatively sterically un-
hindered groups is not enough to transfer chirality in the types
of catalysis tested here.
(
85 %) of compound 7b among the complexes; the lowest iso-
lated yield (16 %) was shown by the Pd(MIC) X -type complex
2
2
(
R,R)-[5]. The complexes (R)-[3] and (R)-[4], under the same reac-
tion conditions and with the same substrates, delivered com-
pound 7b with 70 and 52 % yield, respectively (Table 1). The
PEPPSI-type complexes (R)-[2], (R)-[3], and (R)-[4] were more ac-
tive precatalysts for the α-arylation reaction compared with the
Pd(MIC) X -type of complex (R,R)-[5]. The most active precata-
2
2
lyst (R)-[2] has also been tested for α-arylation reaction using
other aryl halides such as 4-bromobenzene and 4-bromo-
anisole; however, similar conversion into α-arylated product (7a:
Scheme 3. α-Methylation reaction using complex (R,R)-[5].
Eur. J. Inorg. Chem. 2016, 111–117
www.eurjic.org
113
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Both the PEPPSI-type and Pd(MIC) X -type complexes were
We have also performed the mercury poison test for the
2
2
used as precatalysts for the Suzuki–Miyaura cross-coupling re- Suzuki–Miyaura cross-coupling reaction under the described
actions. All these complexes show good conversion (Table 2) conditions. For these reactions no further conversion into the
0
into the biaryl aldehyde products when the reaction was coupling biaryl aldehyde product was observed after Hg addi-
started with 4-Cl/Br-benzaldehyde and phenylboronic acid or tion. As an example, addition of mercury after 1 h (80 %) con-
substituted phenylboronic acid. The reaction with 4-bromo- version using catalyst (R)-[4] inhibited further catalytic coupling
benzaldehyde occurred at room temperature. However, the use and no biaryl aldehyde product (phenylboronic acid and 4-
of 4-chlorobenzaldehyde as substrate required elevated tem- bromobenzaldehyde as substrates) was formed during the sub-
0
perature and longer reaction times for completion (Table 2). sequent 3 h time. This observation suggests that Pd nanoparti-
The PEPPSI-type complexes were more active precatalysts (99 % cles (NP) are the active catalyst in Suzuki–Miyaura cross-cou-
[
11c]
conv. in 3 h) compared with the Pd(MIC) X -type complex (75 % pling reactions under the described reaction conditions.
It
2
2
conv. in 3 h) (R,R)-[5].
should, however, be noted that the presence of the MIC ligands
are necessary for the generation of such Pd NP; the catalysis
does not work in the presence of only palladium(II) salts.
0
Table 2. Suzuki–Miyaura cross-coupling reaction.[a,b]
Conclusions
II
Two different types of chiral Pd complexes [PEPPSI-type and
Pd(MIC) X -type] with MIC ligands have been synthesized start-
2
2
ing from the chiral triazolium ligand precursors (R)-1 or (S)-1.
All the complexes have been tested as active precatalysts for
both Suzuki–Miyaura cross-coupling reaction and α-arylation of
amides. The PEPPSI-type complexes (R)-[2], (R)-[3], and (R)-[4]
Entry
1[
Ar
X
Catalyst
Time (h)
Conv. [%]
a]
Ph
Ph
Ph
Ph
Ph
4-MeC
3,5-Me
4-MeC
4-MeC
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
Cl
Cl
(R)-[2]
(R)-[3]
(R)-[4]
3
3
3
3
6
6
6
6
10
6
99
99
99
75
99
99
99
78
99
90
99
[
[
[
[
[
[
[
[
a]
a]
a]
a]
a]
a]
b]
b]
2
3
4
5
6
7
8
9
1
1
are more active catalysts compared with the Pd(MIC) X -type
2 2
(R,R)-[5]
(R,R)-[5]
(R,R)-[5]
(R,R)-[5]
(R,R)-[5]
(R,R)-[5]
(R,R)-[5]
(R,R)-[5]
complex (R,R)-[5] in both catalytic transformations. In the α-aryl-
ation of amides, the complex (R)-[2] shows better catalytic activ-
ity compared with both complexes (R)-[3] and (R)-[4]. Complex
(R)-[3], with 3-chloropyridine, shows better activity compared
with complex (R)-[4], bearing 4-chloropyridine as co-ligand. In
addition, α-methylated benzazepinone product 8 was obtained
with moderate yield (50 % isolated yield) when the reaction was
carried out in DMF/dioxane mixture in the absence of aryl hal-
ide under similar reaction conditions. DMF is suspected to be
acting as methyl donor in this reaction. A chemoselective
Suzuki–Miyaura cross-coupling reaction has also been carried
out using complex (R,R)-[5] with 1-bromo-3,5-dichlorobenzene
and phenylboronic acid as substrates. At room temperature,
only the biphenyl product was formed through the C–Br bond
activation and no formation of other products was observed
under the described reaction conditions. The PEPPSI-type com-
plexes are active precatalysts for the Suzuki–Miyaura cross-
coupling reaction for both bromo-benzaldehyde and chloro-
benzaldehyde substrates. Mercury poison tests show the heter-
ogeneous nature of the Suzuki–Miyaura cross-coupling reac-
tion, and Pd-NPs are likely to be the real active catalyst. How-
ever, the palladium catalyst was unaffected by the addition of
mercury in case of α-arylation of amides, possibly showing the
homogeneous nature of these reactions. No enantioselective
catalysis was observed with the described chiral complexes,
which might be the due to insufficient steric protection and/or
a more flexible nature of the chiral site of the complexes. It will
be intriguing to use either a larger or a rigid steric platform on
the chiral site of the complex and hence make these complexes
effective for enantioselective catalysis. Although no enantiose-
lective catalysis could be realized with these complexes, they
are nevertheless potent precatalysts for cross-coupling reac-
tions under mild conditions, and for intermolecular α-arylation
6
H
4
2
C
6
4
4
H
3
6
H
H
6
0[
1
b]
b]
3,5-Me
3,5-Me
C
C
H
H
2
6
3
[
2
6
3
10
[
a] Reactions conditions: aldehyde (1.0 equiv.), catalyst (2.5 mol-%), boronic
acid (1.2 equiv.), K CO (2.5 equiv.), H O/dioxane (3:2 v/v), room temperature.
b] Temperature: 60 °C.
2
3
2
[
The complex (R,R)-[5] was also successfully used for the
chemoselective Suzuki–Miyaura cross-coupling reaction with 1-
bromo-3,5-dichlorobenzene as substrate. The reaction of 1-
bromo-3,5-dichlorobenzene with either phenylboronic acid or
(
4-methylphenyl)boronic acid at room temperature gave quan-
titative conversion into the biaryl aldehyde products (Table 3).
No other higher substituted aldehyde products were obtained
during the reaction under these reaction conditions (Table 3).
Table 3. Chemoselective Suzuki–Miyaura cross-coupling reaction.[a]
Entry
Ar
X
Catalyst
Conversion [%] after 6 h
1[
2
a]
Ph
4-MeC H
6 4
Br
Br
(R,R)-[5]
(R,R)-[5]
99
99
[a]
[
a] Reactions conditions: aldehyde (1.0 equiv.), catalyst (2.5 mol-%), boronic
acid (1.2 equiv.), K
2
CO
3
(2.5 equiv.), H
2
O/dioxane (3:2 v/v), room temperature.
Eur. J. Inorg. Chem. 2016, 111–117
www.eurjic.org
114
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
and α-methylation of amides. The precedence of such inter- Compound (R)-[4]: Prepared by using the synthetic procedure de-
scribed for (R)-[2]. 4-Chloropyridine hydrochloride and CH CN were
molecular α-arylation and α-methylation of amides is limited.
Further research in our laboratory will be directed towards mak-
ing these potent catalysts function in an enantioselective fash-
ion.
3
1
used instead of pyridine, yield 0.172 g (0.233 mmol, 52 %). H NMR
3
4
(
400 MHz, CDCl ): δ = 8.87 (dd, J = 5.0, J = 1.4 Hz, 2 H, H ), 7.89–
3
P
y
7
7
1
.86 (m, 2 H, H ), 7.82–7.81 (m, 2 H, H ), 7.57–7.49 (m, 3 H, H ),
Ar Ar Ar
3
.43–7.33 (m, 3 H, H ), 7.26–7.25 (m, 2 H, H ), 6.86 [q, J = 6.9 Hz,
Ar
Py
3
H, N-CH(CH )], 3.89 (s, 3 H, N-CH ), 2.13 (d, J = 6.9 Hz, 3 H, N-CH-
3
3
13
1
CH ) ppm. C{ H} NMR (100.6 MHz, CDCl ): δ = 154.7 (C ), 146.0
3
3
Py
(
CPy), 143.4 (Ctrz-Ar), 138.4 [C -CH(CH )], 132.6 (C -Ctrz), 130.6 (CAr-
Ar 3 Ar
Experimental Section
H), 130.0 (C -H), 128.81 (C -H), 128.77 (C -H), 128.76 (Ctrz-Pd),
Ar
Ar
Ar
General Procedures: All reactions were carried out under a nitro-
128.6 (C -H), 127.5 (C -H), 124.9 (C ), 65.3 [N-CH(CH )], 37.8 (N-
Ar Ar Py 3
gen atmosphere either by using standard Schlenk techniques or in
CH ), 20.9 (N-CH-CH ) ppm. HRMS (ESI, positive ions): m/z calcd. for
3 3
+
a glove box. Glassware was oven-dried at 100 °C. Solvents were [(R)-[4]-I-(4-Cl-Py)] 495.9509; found 495.9507.
1
13
1
distilled by standard procedures prior to use. H and C{ H} NMR
spectra were recorded with a Bruker AVANCE 500, a JEOL ECS 400,
or a JEOL ECP 500 spectrometer. Chemical shifts (δ) are expressed
in ppm downfield from tetramethylsilane using the residual proto-
nated solvent as an internal standard. All coupling constants are
Compound (R,R)-[5]: To a mixture of triazolium salt (R)-1 (0.126 g,
.322 mmol) and Ag O (0.080 g, 0.346 mmol) was added dichloro-
0
2
methane (10 mL), and the resulting suspension was stirred at ambi-
ent temperature for 18 h under the exclusion of light. To the reac-
tion mixture were then added [Pd(Cl) (CH CN) ] (0.042 g,
1
1
2
3
2
expressed in Hertz and only given for H, H couplings unless men-
tioned otherwise. Mass spectra were obtained with an Agilent 6210
ESI-TOF MS. The triazolium salts (R)-1 and (S)-1[ were synthesized
as described previously. K CO , Ag O, KI, NaCl, and Pd(OAc) were
0
2
.162 mmol) and KI (excess). The reaction mixture was stirred for
4 h at ambient temperature then filtered through a pad of Celite
16]
to obtain a clear solution. The solvent was removed and the solu-
tion was concentrated to 2 mL and diethyl ether was added to the
solution to produce a yellow precipitate. The solid was washed with
diethyl ether and dried in vacuo, yield 0.070 g (0.079 mmol, 49 %).
2
3
2
2
purchased from commercial sources and were used as received
without further purification.
General Procedure for the Synthesis of Chiral PEPPSI Com-
plexes: To a mixture of triazolium salt (R)-1 (1.0 equiv.), PdCl2
1
Major isomer: H NMR (400 MHz, CDCl ): δ = 7.98–7.95 (m, 4 H,
3
H ), 7.64–7.61 (m, 4 H, H ), 7.45–7.40 (m, 5 H, H ), 7.32–7.29 (m,
Ar
Ar
Ar
(
1.1 equiv.), K CO (2.0 equiv.), and KI (excess) was added pyridine/
2 3
3
7
2
H, H ), 6.59 [q, J = 7.5 Hz, 2 H, N-CH(CH )], 3.89 (s, 6 H, N-CH ),
Ar 3 3
3
-chloropyridine/4-chloropyridine hydrochloride (5 mL; in case of 4-
3
13
1
.01 (d, J = 7.5 Hz, 6 H, N-CH-CH ) ppm. C{ H} NMR (100.6 MHz,
CDCl ): δ = 144.3 (C -Ar), 138.8 [C -CH(CH )], 130.6 (C -H), 128.91
CAr-H), 128.8 (Ctrz-Pd), 128.6 (C -H), 128.4 (C -H), 128.4 (C -Ctrz),
3
chloropyridine hydrochloride CH CN was used as solvent and
3
3
trz
Ar
3
Ar
3
.0 equiv K CO was used). The mixture was stirred for 24 h at 84 °C.
2 3
(
Ar Ar Ar
After removal of pyridine in vacuo, the residue was extracted with
dichloromethane and passed through a short pad of Celite to ob-
tain a clear solution. The solvents were removed under reduced
pressure and the resulting solid was packed onto a silica gel col-
umn. Elution with dichloromethane gave the desired products.
1
28.38 (C -H), 64.5 [N-CH(CH )], 37.3 (N-CH ), 21.0 (N-CH-CH ) ppm.
Ar 3 3 3
1
Minor isomer: H NMR (400 MHz, CDCl ): δ = 7.77–7.75 (m, 3 H,
3
3
H ), 7.72–7.69 (m, 3 H, H ), 7.38–7.35 (m, 14 H, H ), 6.92 [q, J =
7.0 Hz, 2 H, N-CH(CH )], 3.85 (s, 6 H, N-CH ), 2.07 (d, J = 7.0 Hz, 6
H, N-CH-CH ) ppm. C{ H} NMR (100.6 MHz, CDCl ): δ = 144.6 (Ctrz-
Ar), 139.3 [C -CH(CH )], 130.4 (C -H), 129.3 (C -H), 128.9 (C -H),
Ar
Ar
Ar
3
3
3
3
1
1
3
3
Compound (R)-[2]: The general procedure was applied starting
from triazolium salt (R)-1 (0.174 g, 0.446 mmol), PdCl2 (0.080 g,
Ar
3
Ar
Ar
Ar
1
28.8 (C -H), 128.6 (C -H), 128.42 (C -H), 128.42 (C -Ctrz), 128.3
Ar Ar Ar Ar
0
0
8
7
.451 mmol), K CO (0.123 g, 0.890 mmol), and KI (excess), yield
2 3
(
Ctrz-Pd), 64.6 [N-CH(CH )], 37.4 (N-CH ), 20.9 (N-CH-CH ) ppm.
HRMS (ESI, positive ions): m/z calcd. for [(R,R)-[5]-I] 759.0937; found
59.0943.
1
3 3 3
.198 g (0.282 mmol, 63 %). H NMR (400 MHz, CDCl ): δ = 8.94–
3
+
.90 (m, 2 H, H ), 7.92–7.89 (m, 2 H, H ), 7.85–7.82 (m, 2 H, H ),
Py
Ar
Ar
7
.68–7.64 (m, 1 H, H ), 7.57–7.48 (m, 3 H, H ), 7.43–7.37 (m, 3 H,
Py
Ar
3
H ), 7.26–7.23 (m, 2 H, H ), 6.90 [q, J = 7.2 Hz, 1 H, N-CH(CH )], Compound (S,S)-[5]: Prepared by following the procedure de-
Ar
Py
3
3
1
13
3
.91 (s, 3 H, N-CH ), 2.14 (t, J = 7.2 Hz, 3 H, N-CH-CH ) ppm. C{ H}
scribed for (R,R)-[5] from triazolium salt (S)-1 (0.126 g, 0.322 mmol)
NMR (100.6 MHz, CDCl ): δ = 154.0 (C ), 143.4 (Ctrz-Ar), 138.2 (CAr- and Ag O (0.080 g, 0.346 mmol) for the first step and
3
3
3
Py
2
Ctrz), 137.4 (C ), 133.6 (C -Pd), 130.6 (C -H), 130.0 (C -H), 128.8 [Pd(Cl) (CH CN) ] (0.042 g, 0.162 mmol) and KCl (excess) for the
Py
trz
Ar
Ar
2
3
2
(
C -H), 128.73 (C -H), 128.71 [C -CH(CH )], 128.6 (C -H), 124.9
second step. Exclusively one isomeric complex of compound (S,S)-
[5] was obtained as a yellow solid, yield 0.068 g (0.097 mmol, 60 %).
Ar
Ar
Ar
3
Ar
(C -H), 124.4 (C ), 65.3 [N-CH(CH )], 37.8 (N-CH ), 20.9 (N-CH-
Ar
Py
3
3
+
1
CH ) ppm. HRMS (ESI, positive ions): m/z calcd. for [(R)-[2]-I-Py]
H NMR (400 MHz, CDCl ): δ = 7.90–7.88 (m, 4 H, H ), 7.59–7.54 (m,
3
3
Ar
4
95.9509; found 495.9510.
6 H, H ), 7.53–7.51 (m, 4 H, H ), 7.44–7.41 (m, 4 H, H ), 7.36–7.33
Ar Ar Ar
3
(
m, 2 H, H ), 6.71 [q, J = 6.4 Hz, 2 H, N-CH(CH )], 4.13 (s, 6 H, N-
A
r
3
Compound (R)-[3]: Prepared by using the same synthetic proce-
dure described for (R)-[2], yield 0.208 g (0.283 mmol, 63.5 %).
3
13
1
CH ), 2.0 (d, J = 6.4 Hz, 6 H, N-CH-CH ) ppm. C{ H} NMR
1
3
3
H
(
100.6 MHz, CDCl ): δ = 143.8 (C -Ar), 140.7 [C -CH(CH )], 130.58
4
3 trz Ar 3
NMR (400 MHz, CDCl ): δ = 8.94 (t, J = 1.8 Hz, 1 H, H ), 8.85 (dt,
3
Py
(
C -H), 130.57 (C -H), 129.3 (C -H), 129.2 (C -H), 128.6 (C -H),
3
4
Ar Ar Ar Ar Ar
J = 5.4, J = 1.8 Hz, 1 H, H ), 7.89–7.86 (m, 2 H, H ), 7.82–7.80 (m,
Py
Ar
1
27.5 (C -H), 127.5 (C -Pd), 126.5 (C -C ), 64.8 [N-CH(CH )], 37.9
Ar trz Ar trz 3
2
H, H ), 7.67–7.63 (m, 1 H, H ), 7.58–7.48 (m, 3 H, H ), 7.43–7.35
Ar Py Ar
(
N-CH ), 21.6 (N-CH-CH ) ppm. HRMS (ESI, positive ions): m/z calcd.
3
3
3 3
(
m, 3 H, H ), 7.20 (dd, J = 5.4 Hz, 1 H, H ), 6.85 [q, J = 7.1 Hz, 1
Ar Py
+
for [S,S-[5]-Cl] 669.1570; found 669.1575.
H, N-CH(CH )], 3.90 (m, 3 H, N-CH ), 2.12 (m, 3 H, N-CH-CH ) ppm.
3
3
3
13
1
C{ H} NMR (100.6 MHz, CDCl ): δ = 152.9 (C ), 151.9 (C ), 143.3 General Procedure for Suzuki–Miyaura Coupling Reactions: To
3
Py
Py
(
Ctrz-Ar), 138.4 [C -CH(CH )], 137.5 (C ), 132.2 (C -Ctrz), 130.6 (CAr- a mixture of aryl halide (0.1 mmol), boronic acid (0.15 mmol), palla-
Ar 3 Py Ar
H), 130.1 (C -H), 128.82 (C -H), 128.80 (C -H), 128.77 (Ctrz-Pd),
dium(II) complexes (R)-[2], (R)-[3], R-[4], or (R,R)-[5] (0.0025 mmol,
Ar
Ar
Ar
1
28.6 (C -H), 127.4 (C -H), 124.6 (C ), 65.4 [N-CH(CH )], 37.8 (N-
2.5 mol-%) and K CO (2.5 equiv., 0.25 mmol) was added 1,4-diox-
Ar
Ar
Py
3
2
3
CH ), 20.9 (N-CH-CH ) ppm. HRMS (ESI, positive ions): m/z calcd. for ane (2 mL) and water (3 mL). The resulting suspension was stirred
3
3
+
[
(R)-[3]-I-(3-Cl-Py)] 495.9509; found 495.9508.
at the mentioned temperature. Water was added to the reaction
115 © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2016, 111–117
www.eurjic.org

Full Paper
mixture (10 mL) and the biphasic solution was extracted with di-
N. Hadei, M. G. Organ, Eur. J. Org. Chem. 2010, 4343–4354; j) J. Nasielski,
N. Hadei, G. Achonduh, E. A. B. Kantchev, C. J. ƠBrien, A. Lough, M. G.
Organ, Chem. Eur. J. 2010, 16, 10844–10853; k) M. G. Organ, M. Abdel-
Hadi, S. Avola, I. Dubovyk, N. Hadei, E. A. B. Kantchev, C. J. ƠBrien, C.
Valente, Chem. Eur. J. 2008, 14, 2443–2452; l) C. Valente, S. Çalimsiz, K.
Hoi, D. Mallik, M. Sayah, M. G. Organ, Angew. Chem. Int. Ed. 2012, 51,
chloromethane (15 × 2 mL). The organic part was dried with Na SO4
2
and the solvent was removed under vacuum at room temperature
1
to give the crude mixture, yields were determined by H NMR spec-
troscopic analysis and were based on the integrals of the aldehyde
protons.
3
314–3332; Angew. Chem. 2012, 124, 3370; m) C. Valente, S. Baglione, D.
Candito, C. J. ƠBrien, M. G. Organ, Chem. Commun. 2008, 735–737; n)
M. G. Organ, S. Avola, I. Dubovyk, N. Hadei, E. A. B. Kantchev, C. J. ƠBrien,
C. Valente, Chem. Eur. J. 2006, 12, 4749–4755; o) N. Hadei, G. T. Achon-
duh, C. Valente, C. J. ƠBrien, M. G. Organ, Angew. Chem. Int. Ed. 2011,
General Procedure for α-Arylation of Amides: An oven-dried
sealed tube equipped with a stir bar was charged with 6
(0.57 mmol) and the corresponding aryl halide (0.637 mmol) under
a nitrogen atmosphere. This was followed by addition of Pd catalyst
5
0, 3896–3899; Angew. Chem. 2011, 123, 3982; p) J. R. Perkins, R. G.
(
(
5 mol-%), corresponding base (1.4 mmol) and anhydrous toluene
10.0 mL) by using a syringe. The reaction vessel was sealed and
Carter, J. Am. Chem. Soc. 2008, 130, 3290–3291; q) G. Manolikakes, P.
Knochel, Angew. Chem. 2009, 121, 211–215; r) R. Zhong, A. Pöthig, Y.
Feng, K. Riener, W. A. Herrmann, F. E. Kühn, Green Chem. 2014, 16, 4955–
4962; s) S. Yasar, C. Sahin, M. Arslan, I. Özdemir, J. Organomet. Chem.
the reaction mixture was stirred at 120 °C for 16 h then cooled to
room temperature. The reaction was quenched with H O (15 mL)
2
2015, 776, 107–112.
and extracted with ethyl acetate. The organic part was dried with
MgSO4 and the solvent was removed. The crude mixture was
loaded onto a silica gel column and eluted with hexane/ethyl
acetate (100:20 v:v).
[
3] a) K. M. Hindi, M. J. Panzner, C. A. Tessier, C. L. Cannon, W. J. Youngs,
Chem. Rev. 2009, 109, 3859–3884; b) H. Sivaram, J. Tan, H. V. Huynh,
Organometallics 2012, 31, 5875–5883.
[
4] a) A. G. Tennyson, J. W. Kamplain, C. W. Bielawski, Chem. Commun. 2009,
2124–2126; b) L. Mercs, A. Neels, H. Stoeckli-Evans, M. Albrecht, Dalton
Trans. 2009, 7168–7178; c) R. Lalrempuia, N. D. McDaniel, H. Müller-Bunz,
S. Bernhard, M. Albrecht, Angew. Chem. Int. Ed. 2010, 49, 9765–9768;
Angew. Chem. 2010, 122, 9959; d) U. Siemeling, C. Färber, M. Leibold, C.
Bruhn, P. Mücke, R. F. Winter, B. Sarkar, M. von Hopffgarten, G. Frenking,
Eur. J. Inorg. Chem. 2011, 4607–4612; e) U. Siemeling, C. Färber, C. Bruhn,
Chem. Commun. 2009, 98–100.
5] a) A. Rit, T. Pape, A. Hepp, F. E. Hahn, Organometallics 2011, 30, 334–347;
b) F. M. Conrady, R. Fröhlich, C. Schulte to Brinke, T. Pape, F. E. Hahn, J.
Am. Chem. Soc. 2011, 133, 11496–11499; c) M. Schmidtendorf, T. Pape,
F. E. Hahn, Angew. Chem. Int. Ed. 2012, 51, 2195–2198; Angew. Chem.
2012, 124, 2238; d) C. Schulte to Brinke, T. Pape, F. E. Hahn, Dalton Trans.
2013, 42, 7330–7327; e) N. Sinha, F. Roelfes, A. Hepp, C. Mejuto, E. Peris,
F. E. Hahn, Organometallics 2014, 33, 6898–6904; f) R. Maity, A. Rit, C.
Schulte to Brinke, C. G. Daniliuc, F. E. Hahn, Chem. Commun. 2013, 49,
X-ray Crystallography: Single crystals suitable for X-ray diffraction
studies were obtained for the complexes (R)-[2]·CH Cl , (R)-
2
2
[
3]·CH Cl , (R)-[4], (R,R)-[5]·CH Cl , and (S,S)-[5]·CH CN by slow diffu-
2 2 2 2 3
sion of pentane into a concentrated dichloromethane/acetonitrile
solution of the corresponding complexes at room temperature. X-
ray diffraction data were collected at T = 140 K with a Bruker Smart
AXS diffractometer equipped with a rotating anode using graphite-
monochromated Mo-Kα radiation (λ = 0.71073 Å). The data were
collected by using the standard “phi-omega scan techniques”. The
structures were solved by direct methods using SHELXS-97 and re-
[
2
[26]
fined by full-matrix least-squares with SHELXL-97, refining on F .
Crystallographic details are given in Table S1. CCDC 1412898 {for
(
R)-[2]·CH Cl }, 1412895 {for (R)-[3]·CH Cl }, 1412899 {for (R)-[4]},
2 2 2 2
1
412896 {for (R,R)-[5]·CH Cl }, and 1412897 {for (S,S)-[5]·CH CN}
2 2 3
1
011–1013.
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre.
[
[
6] a) M. C. Jahnke, F. E. Hahn, Top. Organomet. Chem. 2010, 30, 95–129; b)
W. A. Herrmann, Angew. Chem. Int. Ed. 2002, 41, 1290–1309; Angew.
Chem. 2002, 114, 1342; c) A. Zanardi, R. Corberán, J. A. Mata, E. Peris,
Organometallics 2008, 27, 3570–3576; d) H. Braband, O. Blatt, U. Abram,
Z. Anorg. Allg. Chem. 2006, 632, 2251–2255; e) D. Enders, T. Balensiefer,
Acc. Chem. Res. 2004, 37, 534–541.
Acknowledgments
7] a) P. Mathew, A. Neels, M. Albrecht, J. Am. Chem. Soc. 2008, 130, 13534–
The Fonds der Chemischen Industrie (FCI) and the Freie Univer-
sität Berlin are kindly acknowledged for financial support. The
ERASMUS-MUNDUS program is acknowledged for providing a
post-doctoral fellowship to A. V.
1
2
7
3535; b) K. F. Donnelly, A. Petronilho, M. Albrecht, Chem. Commun.
013, 49, 1145–1159; c) R. H. Crabtree, Coord. Chem. Rev. 2013, 257, 755–
66; d) J. M. Aizpurua, R. M. Fratila, Z. Monasterio, N. Perez-Esnaola, E.
Andreieff, A. Irastorza, M. Sagartzazu-Aizpurua, New J. Chem. 2014, 38,
74–480; e) G. Guisado-Barrios, J. Bouffard, B. Donnadieu, G. Bertrand,
Angew. Chem. Int. Ed. 2010, 49, 4759–4762; Angew. Chem. 2010, 122,
869; f) J. D. Crowley, A. Lee, K. J. Kilpin, Aust. J. Chem. 2011, 64, 1118–
1132; g) D. Schweinfurth, N. Deibel, F. Weisser, B. Sarkar, Nachr. Chem.
011, 59, 937–941.
4
Keywords: Carbene ligands · Palladium · Cross-coupling ·
Arylation · Methylation
4
2
[
8] a) S. Hohloch, L. Suntrup, B. Sarkar, Organometallics 2013, 32, 7376–7385;
b) R. Maity, S. Hohloch, M. van der Meer, B. Sarkar, Chem. Eur. J. 2014,
20, 9952–9961; c) R. Maity, M. van der Meer, S. Hohloch, B. Sarkar, Orga-
nometallics 2015, 34, 3090–3096; d) A. Bolje, S. Hohloch, M.
van der Meer, J. Košmrlj, B. Sarkar, Chem. Eur. J. 2015, 21, 6756–6764; e)
M. Delgado-Rebollo, D. Canseco-Gonzalez, M. Hollering, H. Mueller-Bunz,
M. Albrecht, Dalton Trans. 2014, 43, 4462–4473; f) S. Hohloch, F. L.
Duecker, M. van der Meer, B. Sarkar, Molecules 2015, 20, 7379–7395.
[
1] For selected examples, see: a) M. Melaimi, M. Soleilhavoup, G. Bertrand,
Angew. Chem. Int. Ed. 2010, 49, 8810–8849; Angew. Chem. 2010, 122,
8992; b) M. Poyatos, J. A. Mata, E. Peris, Chem. Rev. 2009, 109, 3677–
3707; c) F. E. Hahn, M. C. Jahnke, Angew. Chem. Int. Ed. 2008, 47, 3122–
3172; Angew. Chem. 2008, 120, 3166; d) O. Kaufhold, F. E. Hahn, Angew.
Chem. Int. Ed. 2008, 47, 4057–4061; Angew. Chem. 2008, 120, 4122.
[
2] For selected examples, see: a) C. C. J. Loh, D. Enders, Chem. Eur. J. 2012,
1
8, 10212–10225; b) N. Marion, S. Díez-González, S. P. Nolan, Angew.
[9] a) S. Hohloch, L. Hettmanczyk, B. Sarkar, Eur. J. Inorg. Chem. 2014, 3164–
3171; b) A. Bolje, S. Hohloch, D. Urankar, A. Pevec, M. Gazvoda, B. Sarkar,
J. Košmrlj, Organometallics 2014, 33, 2588–2598; c) S. Hohloch, S. Kaiser,
F. L. Duecker, A. Bolje, R. Maity, J. Košmrlj, B. Sarkar, Dalton Trans. 2015,
44, 686–693; d) B. Bagh, A. M. McKinty, A. J. Lough, D. W. Stephan, Dalton
Trans. 2014, 43, 12842–12850; e) A. Prades, E. Peris, M. Albrecht, Organo-
metallics 2011, 30, 1162–1167; f) A. Petronilho, M. Rahman, J. A. Woods,
H. Al-Sayyed, H. Müller-Bunz, J. M. Don MacElroy, S. Bernhard, M. Al-
brecht, Dalton Trans. 2012, 41, 13074–13080.
Chem. Int. Ed. 2007, 46, 2988–3000; Angew. Chem. 2007, 119, 3046; c) D.
Enders, O. Niemeier, A. Henseler, Chem. Rev. 2007, 107, 5606–5655; d) V.
Cesar, S. B. Laponnaz, L. H. Gade, Chem. Soc. Rev. 2004, 33, 619–636; e)
F. A. Glorius, Top. Organomet. Chem. 2007, 21, 1; f) J. D. Egbert, C. S. J.
Cazin, S. P. Nolan, Catal. Sci. Technol. 2013, 3, 912–926; For specific se-
lected examples on PEPPSI complexes, see: g) L. Benhamou, C. Besnard,
E. P. Kündig, Organometallics 2014, 33, 260–266; h) J. J. Dunsford, K. J.
Cavell, Organometallics 2014, 33, 2902–2905; i) C. Valente, M. E. Belowich,
Eur. J. Inorg. Chem. 2016, 111–117
www.eurjic.org
116
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
[
10] R. Saravanakumar, V. Ramkumar, S. Sankararaman, Organometallics 2011,
0, 1689–1694.
11] For selected examples, see: a) J. Huang, J.-T. Hong, S. H. Hong, Eur. J. Org.
Chem. 2012, 6630–6635; b) S. Hohloch, W. Frey, C.-Y. Su, B. Sarkar, Dalton
Trans. 2013, 42, 11355–11358; c) D. Canseco-Gonzalez, A. Gniewek, M.
Szulmanowicz, H. Müller-Bunz, A. M. Trzeciak, M. Albrecht, Chem. Eur. J.
Angew. Chem. Int. Ed. 2012, 51, 5062–5085; Angew. Chem. 2012, 124,
5150; c) F.-S. Han, Chem. Soc. Rev. 2013, 42, 527–5298; d) U. Böhme, J.
Organomet. Chem. 2003, 671, 75–90.
3
[20] a) G. C. Fortman, S. P. Nolan, Chem. Soc. Rev. 2011, 40, 5151–5169; b) M.
Weck, C. W. Jones, Inorg. Chem. 2007, 46, 186–1875; c) B. Karimi, D. End-
ers, Org. Lett. 2006, 8, 1237–1240; d) Q. Xu, W.-L. Duan, Z.-Y. Lei, Z.-B.
Zhua, M. Shi, Tetrahedron 2005, 61, 11225–11229.
2012, 18, 6055–6062; d) T. Terashima, S. Inomata, K. Ogata, S.-i. Fuku-
zawa, Eur. J. Inorg. Chem. 2012, 1387–1393; e) E. C. Keske, O. V. Zenkina,
R. Wang, C. M. Crudden, Organometallics 2012, 31, 6215–6221; f) T. Mit-
sui, M. Sugihara, Y. Tokoro, S.-i. Fukuzawa, Tetrahedron 2015, 71, 1509–
[21] a) W. A. Herrmann, Angew. Chem. Int. Ed. 2002, 41, 1290–1309; Angew.
Chem. 2002, 114, 1342; b) E. A. B. Kantchev, C. J. O'Brien, M. G. Organ,
Angew. Chem. Int. Ed. 2007, 46, 2768–2813; Angew. Chem. 2007, 119,
2824; c) S. Díez-González, N. Marion, S. P. Nolan, Chem. Rev. 2009, 109,
3612–3676.
1514; g) A. Mohan, V. Ramkumar, S. Sankararaman, J. Organomet. Chem.
2015, 799–800, 115–121.
[
12] For selected examples, see: a) S. Hohloch, C.-Y. Su, B. Sarkar, Eur. J. Inorg.
Chem. 2011, 3067–3075; b) S. Hohloch, D. Scheiffele, B. Sarkar, Eur. J.
Inorg. Chem. 2013, 3956–3965; c) S. Hohloch, B. Sarkar, L. Nauton, F.
Cisnetti, A. Gautier, Tetrahedron Lett. 2013, 54, 1808–1812; d) T. Naka-
mura, T. Terashima, K. Ogata, S.-i. Fukuzawa, Org. Lett. 2011, 13, 620–623.
13] a) L. Hettmanczyk, S. Manck, C. Hoyer, S. Hohloch, B. Sarkar, Chem. Com-
mun. 2015, 51, 10949–10952; b) J. R. Wright, P. C. Young, N. T. Lucas, A.-
L. Lee, J. D. Crowley, Organometallics 2013, 32, 7065–7076; c) K. J. Kilpin,
U. S. D. Paul, A.-L. Lee, J. D. Crowley, Chem. Commun. 2011, 47, 328–330;
d) D. Canesco-Gonzalez, A. Petronilho, H. Müller-Bunz, K. Ohmatsu, T.
Ooi, M. Albrecht, J. Am. Chem. Soc. 2013, 135, 13193–13203.
[22] a) T. M. Trnka, R. H. Grubbs, Acc. Chem. Res. 2001, 34, 18–29; b) S. J.
Connon, S. Blechert, Angew. Chem. Int. Ed. 2003, 42, 1900–1923; Angew.
Chem. 2003, 115, 1944; c) A. Fürstner, Angew. Chem. Int. Ed. 2000, 39,
3012–3043; Angew. Chem. 2000, 112, 3140.
[23] For selected examples, see: a) D. A. Culkin, J. F. Hartwig, Acc. Chem. Res.
2003, 36, 234–245; b) B. C. Hamann, J. F. Hartwig, J. Am. Chem. Soc. 1997,
119, 12382–12383; c) H. Muratake, M. Natsume, Tetrahedron Lett. 1997,
38, 7581–7582; d) M. Miura, M. Nomura, Top. Curr. Chem. 2002, 219, 211–
241.
[24] For selected examples, see: a) X. Luan, R. Mariz, C. Robert, M. Gatti, S.
Blumentritt, A. Linden, R. Dorta, Org. Lett. 2008, 10, 5569–5572; b) Y.-X.
Jia, D. Katayev, G. Bernardinelli, T. M. Seidel, E. P. Kündig, Chem. Eur. J.
2010, 16, 6300–6309; c) X. Luan, L. Wu, E. Drinkel, R. Mariz, M. Gatti, R.
Dorta, Org. Lett. 2010, 12, 1912–1915; d) S. Lee, J. F. Hartwig, J. Org.
Chem. 2001, 66, 3402–3415; e) E. J. Hennessy, S. L. Buchwald, J. Am.
Chem. Soc. 2003, 125, 12084–12085; f) D. Solé, O. Serrano, J. Org. Chem.
2008, 73, 2476–2479; g) L. Liu, N. Ishida, S. Ashida, M. Murakami, Org.
Lett. 2011, 13, 1666–1669.
[25] a) A. Verma, N. Prajapati, S. Salecha, R. Giridhar, M. R. Yadav, Tetrahedron
Lett. 2013, 54, 2029–2031; b) B. Zheng, T. Jia, P. J. Walsh, Adv. Synth. Catal.
2014, 356, 165–178; c) K. H. Shaughnessy, B. C. Hamann, J. F. Hartwig, J.
Org. Chem. 1998, 63, 6546–6553; d) A. M. Taylor, R. A. Altman, S. L. Buch-
wald, J. Am. Chem. Soc. 2009, 131, 9900–9901; e) B. Zheng, T. Jia, P. J.
Walsh, Org. Lett. 2013, 15, 4190–4193.
[
[
14] For selected examples, see: a) D. G. Brown, N. Sanguantrakun, B. Schulze,
U. S. Schubert, C. P. Berlinguette, J. Am. Chem. Soc. 2012, 134, 12354–
12357; b) B. Schulze, U. S. Schubert, Chem. Soc. Rev. 2014, 43, 2522–
2571.
[
15] a) V. V. Rostovtsev, L. G. Green, V. V. Fokin, K. B. Sharpless, Angew. Chem.
Int. Ed. 2002, 41, 2596–2599; Angew. Chem. 2002, 114, 2708; b) C. W.
Tornoe, C. Christensen, M. Meldal, J. Org. Chem. 2002, 67, 3057–3064.
16] L. B. O. Freitas, P. Eisenberger, C. M. Crudden, Organometallics 2013, 32,
[
[
6635–6638.
17] G. R. Fulmer, A. J. M. Miller, N. H. Sherden, H. E. Gottlieb, A. Nudelman,
B. M. Stoltz, J. E. Bercaw, K. I. Goldberg, Organometallics 2010, 29, 2176–
2179.
[
18] a) R. Maity, M. van der Meer, B. Sarkar, Dalton Trans. 2015, 44, 46–49; b)
R. Maity, A. Mekic, M. van der Meer, A. Verma, B. Sarkar, Chem. Commun.
[26] SHELXS-97, SHELXL-97: G. M. Sheldrick, Acta Crystallogr., Sect. A 2008,
64, 112.
2015, 51, 15106–15109.
[
19] a) W. A. Herrmann, M. Elison, J. Fischer, C. Kocher, G. R. J. Artus, Angew.
Chem. Int. Ed. Engl. 1995, 34, 2371–2374; Angew. Chem. 1995, 107, 2602;
b) C. C. C. Johansson Seechurn, M. O. Kitching, T. J. Colacot, V. Snieckus,
Received: September 9, 2015
Published Online: December 7, 2015
Eur. J. Inorg. Chem. 2016, 111–117
www.eurjic.org
117
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim