Gold(I) complexes with "normal" 1,2,3-triazolylidene ligands: Synthesis and catalytic properties

Article abstract of DOI:10.1021/om400318p

1,2,3-Triazolylidenes as versatile, strong donor ligands have currently experienced a boost in complex synthesis as well as catalytic applications. Although many examples of "abnormal" 1,2,3-triazolylidenes have been described, their "normal" congeners have been barely examined to date (for abnormal carbenes the resonance structures of the carbenes cannot be drawn without adding additional charges, but this is possible for normal carbenes). Furthermore, no instance of utilization of this new ligand class in homogeneous catalysis can be found. Therefore, this work presents a variety of potential precatalysts descending from "normal" 1,2,3-triazolylidene Au chloride complexes. Synthesis and thorough characterization of the new compounds are presented, together with special ligand features such as buried volume and suspected anagostic interactions. The activity of the isolated precatalysts is examined in the intramolecular hydroamination of alkynes and compared with that of a popular imidazolylidene system. It is found that the activity of the best-performing "normal" 1,2,3-triazolylidene systems is quite similar to that of the imidazolylidene systems. However, mercury drop poisoning experiments suggest that improvements in ligand design are required to enhance catalyst stability.

Full text of DOI:10.1021/om400318p

Article
pubs.acs.org/Organometallics
Gold(I) Complexes with “Normal” 1,2,3-Triazolylidene Ligands:
Synthesis and Catalytic Properties
̈
thig, Karl Ofele, Mirza Cokoja,
Lars-Arne Schaper, Xuhui Wei, Sebastian J. Hock, Alexander Po
Wolfgang A. Herrmann,* and Fritz E. Kuhn*
̈
̈
Chair of Inorganic Chemistry/Molecular Catalysis, Catalysis Research Center, Technische Universitat
̈
̈
Munchen,
Ernst-Otto-Fischer-Straße 1, 85747 Garching bei Munchen, Germany
̈
*
S Supporting Information
ABSTRACT: 1,2,3-Triazolylidenes as versatile, strong donor ligands have currently
experienced a boost in complex synthesis as well as catalytic applications. Although many
examples of “abnormal” 1,2,3-triazolylidenes have been described, their “normal” congeners
have been barely examined to date (for abnormal carbenes the resonance structures of the
carbenes cannot be drawn without adding additional charges, but this is possible for normal
carbenes). Furthermore, no instance of utilization of this new ligand class in homogeneous
catalysis can be found. Therefore, this work presents a variety of potential precatalysts descending from “normal” 1,2,3-
triazolylidene Au chloride complexes. Synthesis and thorough characterization of the new compounds are presented, together
with special ligand features such as buried volume and suspected anagostic interactions. The activity of the isolated precatalysts is
examined in the intramolecular hydroamination of alkynes and compared with that of a popular imidazolylidene system. It is
found that the activity of the best-performing “normal” 1,2,3-triazolylidene systems is quite similar to that of the imidazolylidene
systems. However, mercury drop poisoning experiments suggest that improvements in ligand design are required to enhance
catalyst stability.
INTRODUCTION
Since access to variously substituted 1,2,3-triazolium salts as
precursors for abnormal triazolylidenes is straightforward and
due to their elevated σ-donor strength, numerous reports of
varied ligand systems and their catalytic application have
emerged. Recently we have shown that access to “normal”
■
Ever since the potential of N-heterocyclic carbenes (NHCs) as
versatile, tailor-made ligands for organometallic catalysts was
10
11
1
discovered, this research area has experienced an enormous
2
boost. Due to their almost unparalleled versatility, NHCs are
1
,2,3-triazolylidene ligands is possible by changing the 1,3,4-
nearly ubiquitous in organometallic research and applications
3
substitution in abnormal 1,2,3-triazolylidenes to a 1,2,4-
substitution pattern.
today. In addition to “normal” imidazoleylidenes, an entire
12
range of different N-heterocyclic carbenes with varying
substitution patterns is available. Nevertheless, it took more
than 30 years since the early beginnings of NHCs until the first
abnormal coordinated carbenes were described. Soon after, the
strong σ-donor properties of abnormally bound imidazolyli7-
denes were discovered and interest rose in this research area.
With the isolation of the first 1,2,3-triazolylidene ligands
During the past decade, scientific interest in homogeneous
Au-catalyzed organic transformations (i.e., hydration, hydro-
alkoxylation, or hydroamination of alkenes or allenes, enyne
4
5
6
13
cyclizations) has experienced steep growth. After the first
reports of the synthesis and preliminary application of NHC Au
14
compounds, this field quickly widened for this ligand
15a−d
class.
Even Au complexes with abnormal saturated
8
coordinated to transition metals, the definition of abnormal
15e,f
imidazolylidenes have been synthesized.
Furthermore,
binding carbenes was widened (Figure 1): for a normal NHC,
the free carbene structure can be drawn without additional
charge, while a graphical representation of free abnormal
abnormal triazolylidene compounds were isolated and prelimi-
11c
narily tested in catalytic applications. In order to examine the
viability of the new ligand system of normal triazolylidenes and
inspired by the wide variety of potential applications available
for NHC Au compounds, in this paper we have synthesized a
series of Au complexes coordinated with normal 1,2,3-
triazolylidene ligands and examined their feasibility in catalysis.
9
carbenes requires the indication of charges.
RESULTS AND DISCUSSION
■
Complex Synthesis and Characterization. For metal
complex synthesis, methyl- and cyclohexyl-substituted normal
Figure 1. Graphical representation of free carbene structures for
normal and abnormal imidazolylidenes as well as normal and abnormal
triazolylidenes.
Received: April 15, 2013
Published: May 29, 2013
©
2013 American Chemical Society
3376
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Organometallics
Article
triazolium chlorides were selected as precursors. They were
prepared according to routes described earlier by Moderhack
16
and co-workers, providing access a large variety of these salts.
After the successful synthesis of Rh and Ir complexes by
12
applying an in situ silver carbene generation reaction protocol,
the corresponding Au compounds were prepared analogously
Scheme 1). Isolation of the methyl triazolylidene Au−Cl
(
Scheme 1. Synthesis of Triazolylidene Au−Cl Complexes
a
Starting from Triazolium Chlorides
a
Reaction conditions: (a) 1 0.50 equiv of Ag O, room temperature,
2
Figure 2. Molecular structure for 2a, obtained from X-ray crystallo-
graphic data (thermal ellipsoids are shown at a probability level of
50%). Selected bond distances (Å), angles (deg) and torsion angles
exclusion of light, 2 h, CH Cl , 2 0.90 equiv of [AuCl(SMe )], room
2
2
2
temperature, exclusion of light, 2 h, CH Cl ; (b) 1 1.50 equiv of Ag O,
2
2
2
molecular sieves, room temperature, exclusion of light, 18 h, MeCN/
(
deg): Au1−C1 = 1.989(3), Au1−Cl1 = 2.2898(6), H4···Au1 =
CH Cl 1/1, 2 0.90 equiv of [AuCl(SMe )], room temperature, 2 h,
2
2
2
2.6030(2), H21a···Au1 = 2.7302(2), H17b···Au1 = 2.9254(2); Cl1−
CH Cl .
2
2
Au1−C1 = 174.98(7), Au1−H4−C4 = 141.0(2), Au1−H21a−C21 =
1
34.1(1), Au1−H17b−C17 = 130.6(2); N3−N2−N1−C16 =
compound 1a was confirmed by comparing H and 13C NMR
1
169.1(2).
12
values with previously published data. Note that for the
synthesis of complex 2a with cyclohexyl-substituted triazolyli-
dene different reaction conditions had to be applied. A MeCN/
CH Cl 1/1 solvent mixture only proved adequate for in situ
Furthermore, elemental analysis additionally supports the
isolation of 2a.
The crystal structure of 2a can be compared to the earlier
2
2
12
silver carbene generation. However, yields were unsatisfying in
this case (35%) and could not be further improveddespite
numerous attemptsby applying diverging reaction condi-
tions. As soon as the cyclohexyl-substituted carbene is bound to
the Au metal center, however, high complex stability of 2a is
observed, as the compound can even be purified by column
chromatography under aerobic conditions. Formation of 2a was
published structure of 1a. The carbene−metal distance in 2a,
Au1−C1 = 1.989(3) Å, is similar to the bond distance observed
in 1a (1.997(6) Å); the same is true for the Au1−Cl1 distance
(2.290(1) Å), which is 2.290(2) Å in 1a. A somewhat larger
variation is detected when the Cl1−Au−C1 angles (2a,
174.98(7)°; 1a, 177.13(15)°) or the torsion angles are
compared (N3−N2−N1−C16: 176.4(5)° in 1a and
169.1(2)° in 2a). These slight differences might be attributed
to the increased steric demand of the cyclohexyl ligand.
Interestingly, the structure of 2a shows a weak interaction
between the Au center and one proton of the triazolylidene’s
tolyl group, evidenced by the short H4···Au1 distance of
2.6030(2) Å. This interaction might be responsible for the
unusual upright position of the tolyl group, which is positioned
parallel to the ligand’s plane. A similar interaction with the
metal center can be observed for one proton of the
triazolylidene’s cyclohexyl group (H21a···Au1 = 2.7302(2)
Å). Both interactions can be described as anagostic
1
first confirmed by means of H NMR, since the proton bound
to the ipso carbon atom of the cyclohexyl ligand proved to be a
viable indicator for metal complexation. A shift for this
characteristic triplet of triplets from the triazolium salt (4.52
ppm in CDCl ) to the Au compound (4.40 ppm in CDCl )
3
3
could be monitored. Furthermore, the vanishing of the
characteristic triazolium proton signal (11.84 ppm in CDCl )
3
1
3
suggests metal coordination. C NMR gives further evidence
for metal complexation, since a resonance for the carbene
carbon can be identified at 158.2 ppm, which is, however, a
surprisingly low value in comparison to those for similar
1
4b
17
imidazolylidene-based compounds.
Nevertheless, it corre-
interactions. This observation correlates well with the
11c
1
sponds well with observations made by Crowley et al. for
abnormal triazolylidene Au compounds.
downfield-shifted H NMR signal of the ortho proton of the
tolyl group (8.26 ppm in 1a and 8.33 ppm in 2a). However, the
integral of this signal corresponds to two protons, suggesting
that the proton−Au interaction is too weak to prevent rotation
In addition to the NMR data (vide supra), mass spectroscopy
was necessary to prove the generation of an Au compound
instead of an Ag complex. ESI-MS and FAB-MS prove useful
for this purpose and give several mass peaks suggesting Au
1
of the tolyl group. Even in variable-temperature (VT) H NMR
studies the assumed rotation cannot be stopped at −87 °C. In
order to gain further insight into the nature of the Au···H
interactions and possible energetic benefits associated with
these, the optimized structure of 1a without protonsto
exclude any influence of a proton−metal interactionhas been
calculated. Interestingly, the optimized structure shows a very
similar position of the tolyl group relative to the heterocycle’s
plane (torsion angle C1−C2−C3−C4 −8(1)° vs 16.02° in the
calculated structure; see the Supporting Information for further
+
+
carbene complexation (513.5 [M − Cl] , 1061.3 [2M − Cl] ,
+
+
4
13.5 [M − Cy − Cl] for ESI; 513.5 [M − Cl] for FAB). The
observed mass peaks, corresponding to a bis(triazolylidene)
compound, are probably created under ESI conditions, since
single-crystal X-ray spectroscopy of 2a (Figure 2)grown by
slow evaporation of the solvent from a saturated solution of 2a
in dichloromethaneimplies that the mono(triazolylidene)
Au−Cl complex is the preferred species at room temperature.
3
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Organometallics
Article
details). Accordingly, it is possible to consider the observed
anagostic interaction as negligible, while the position of the
tolyl group may simply be explained through a π interaction of
the aromatic systems of the tolyl group and triazolylidene.
For complete characterization the buried volumes of the two
new triazolylidene ligands were calculated by uploading the
modified CIF files of 1a and 2a in the SambVca web application
provided by Cavallo and co-workers. Nolan et al. provided a
series of buried volumes calculated for NHC ligands obtained
from the corresponding [AuCl(NHC)] complexes. The
parameters utilized by this group were also used for our
calculations to allow for better comparison (see the Supporting
Information for further details). For the carbene ligand derived
for X-ray diffraction were grown by slow diffusion of pentane
into a solution of 1b in chloroform. Unfortunately, data were
insufficient for full structural characterization and solely allowed
for structural confirmation (see the ball-and-stick representa-
tion in the Supporting Information).
Compound 1c was synthesized according to a procedure
14a
reported earlier, describing the synthesis of the first NHC Au
acetate complex. For the generation of complex 1c, silver
acetate is added to the reaction mixture at −78 °C. Although
immediate precipitation of silver chloride could be observed,
the reaction mixture was stirred overnight at room temperature
18
19
1
to ensure full conversion. H NMR spectroscopy gave rise to a
new distinctive signal for the acetate ligand’s methyl group at
1.96 ppm in CD
downfield-shifted carbene signal at 176.9 ppm in CD Cl . In
2 2
Cl
. Furthermore, 13C NMR revealed a
2 2
from 1, buried volumes of 29.0% (2.00 Å M−C
distance)
distance) were obtained,
carbene
and 25.3% (2.28 Å M−C
carbene
whereas the carbene ligand derived from 2 gave buried
addition to full characterization (see the Experimental Section
for details), single crystals of 1c were grown by recrystallization
in MeCN. Figure 3 provides an ORTEP-style representation of
volumes of 34.8% (2.00 Å M−C distance) and 30.6%
carbene
(
2.28 Å M−C
distance). Accordingly, the buried volume
carbene
of the carbene ligand derived from 1 is slightly higher than that
of ICy (27.4% (2.00 Å); 23.5% (2.28 Å)) and the Vbur value of
the carbene ligand derived from 2 is somewhat smaller than
19
that of IMes (36.5% (2.00 Å); 31.2% (2.28 Å)).
In the search for viable triazolylidene Au precatalysts, a series
of halide substitution reactions starting from the methyl-
substituted triazolylidene Au chloride complex 1a has been
tested. Different Au compounds with a variety of ligands were
synthesized in order to avoid the use of Ag salts for halide
dissociation during catalysis, as the catalytic results may be
2
0
influenced. First of all, the synthesis of a phenylacetylide
21
congener was attempted, reported earlier for an abnormal
triazolylidene-substituted Au compound by Lee and
1
1c
Crowley. The reaction was straightforward and led to the
formation of the phenylacetylide-substituted, air- and moisture-
stable Au compound 1b in good yields (Scheme 2).
a
Scheme 2. Syntheses of Various Au Precatalysts
Figure 3. Molecular structure for 1c, obtained from X-ray crystallo-
graphic data (thermal ellipsoids are shown at a probability level of
50%). Selected bond distances (Å) and angles (deg): Au1−C1 =
1.970(3), Au1−O1 = 2.046(2), O1−C17 = 1.285(4), O2−C17 =
1.230(4), H4···Au1 = 2.5850(1); O1−Au1−C1 = 176.5(1).
the solid-state structure of compound 1c. The crystal structure
confirms the linear coordination with an O1−Au1−C1 angle of
1
76.5(1)°, close to the observations made for the related
a
22
Reaction conditions: (a) solution (made from stirring 2.10 equiv of
compounds [Au(IPr)(OAc)] first presented by Nolan et al.
two molecules in the asymmetric unit: angles 171.6(6)° and
t
KO Bu and 2.10 equiv of phenylacetylene in MeOH for 20 min at
room temperature) added, room temperature, 12 h, MeOH; (b) 1.20
equiv of AgOAc, −78 °C to room temperature, 16 h, CH Cl ; (c) 1.05
equiv of AgN(Tf) , room temperature, 5 min, CH Cl .
(
1
79.3(6)°) and the NHC Au acetate compound synthesized by
14a
2
2
Herrmann and co-workers (179.3(2)°). The angle is very
2
2
2
close to the P−Au−O angle in [Au(OAc)(PPh )]
3
23
(
177.3(2)°). The carbene carbon−Au bond length in 1c
1
Isolation of 1b was confirmed via H (shift of NMe singlet
from 4.22 ppm of 1a in CD Cl to 4.27 ppm of 1b in CDCl ,
shift of tolyl doublet from 8.26 ppm in CD Cl to 8.33 ppm in
(1.970(3) Å) is similar (within the limits of triple standard
deviation) to that of the compound previously described by
2
2
3
14a
Herrmann et al.
lengths observed for the two molecules of the IPr congener
(1.961(5) Å) and is between the bond
2
2
13
CDCl , appearance of additional Ph signals) and C NMR
3
23
(
characteristic carbene signal shifted to 180.1 ppm in CDCl for
(1.98(1) and 1.95(2) Å). The double-bond character of O2−
C17 is evident from the shortened bond length of 1.230(4) Å
in comparison to O1−C17 (1.285(4) Å). Just as in the crystal
3
1
b from 163.4 ppm in CD Cl for 1a). Compound 1b was
2 2
further characterized by ESI-MS, FAB-MS, and elemental
analysis (see the Experimental Section). Single crystals suitable
12
structures of 1a and 2a, an anagostic interaction between H4
3
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Organometallics
Article
a
Scheme 3. Synthesis of Acetonitrile-Coordinated Au Precatalyst 1e and Observed Bis(triazolylidene) Compound Formation
a
Reaction conditions: (a) 1.05 equiv of AgSbF , room temperature, 1 min, MeCN; (b) room temperature, weeks, MeCN/Et O.
6
2
and the Au center can be observed in 1c (H4···Au1 =
2.5850(1) Å).
Since silver bis(trifluoromethanesulfonyl)imide (Ag(NTf ))
2
is commonly used in Au-catalyzed organic transformations, we
decided to synthesize a well-defined triazolylidene Au
−
precatalyst with NTf2 as the anion. For the synthesis of
compound 1d (Scheme 2), an procedure reported earlier for
[
Au(NHC)(NTf )] compounds, described by Gagosz and co-
2
24
workers, was applied. Also for the normal triazolylidene
congener, the reaction proceeds smoothly and is complete after
5
min. The carbene carbon resonance shows an upfield shift in
C NMR, namely from 163.4 ppm (CD Cl ) in 1a to 156.1
1
3
2
2
ppm (CD Cl ) in 1d, which is in accordance with the reported
2
2
2
4
shift of [Au(IPr)(NTf )] (168.3 ppm in CD Cl ) from
AuCl(IPr)] (175.1 ppm in CD Cl ).
characteristic quartet for the NTf trifluoromethyl group can
be found at 120.0 ppm ( J = 323.0 Hz).
2
2
2
14b
[
In addition, the
2
2
−
2
1
CF
The transformations presented above describe reactions to
−
substitute the Cl anion in 1a by other anions, more or less
strongly bound to the metal center. However, halide
Figure 4. Molecular structure for 1f, obtained from X-ray crystallo-
graphic data (thermal ellipsoids are shown at a probability level of
replacement by a weakly coordinating anion (WCA) seems
5
0%). Selected bond distances (Å), angles (deg), and torsion angles
25
even more promising for possible catalytic applications. For
this reason, a series of exchange experiments were executed,
(
1
deg): Au1−C1 = 2.031(2), Au1−C17 = 2.026(2), N1−N2 =
.365(3), H4···Au1 = 2.5300(2), H20···Au1 = 2.8487(2); C1−Au1−
−
−
−
applying Ag salts of WCAs such as PF , BF , and SbF . In
C17 = 177.05(9), N1−C1−C2 = 103.2(2); N3−N2−N1−C16 =
176.8(2), C4−C3−C2−C1 = −7.9(4), C20−C19−C18−C17 =
−33.3(3).
6
4
6
−
−
the case of PF and BF , no clean product formation could be
6
4
19
observed. F NMR revealed not only the multiplets typical for
these anions but also resonances of suspected P−F or B−F
bond activation products, as already observed by other
room temperature and leads to decomposition and partial
14c,26
−
groups.
The use of SbF6 helps to avoid such side
bis(carbene) formation. However, upon heating in CD CN or
3
products and allows for clean isolation of the acetonitrile-
CD Cl for days, we were not able to isolate this bis(carbene)
2
2
coordinated compound 1e (Scheme 3).
species without side products.
14c
As mentioned by Nolan et al., only very short reaction
times followed by immediate filtration and evaporation of the
reaction solution prevents partial formation of a presumed
bis(carbene) side product. Complex 1e could be isolated as a
white powder, displaying high stability in the solid state when
stored under argon and limited stability when kept in solution
for 24 h at room temperature. Despite its limited stability in
solution, complete characterization could be carried out
The crystal structure of this Au bis(triazolylidene) complex
f reveals an almost ideal linear coordination of two normal
1
triazolylidene ligands (C1−Au1−C17 = 177.05(9)°). In the
crystal structure of the complex [Au(NHC) ]PF , described by
2
6
27
Meyer and co-workers, this angle is almost the same (C1−
Au1−C31 = 177.07(13)°). Au−carbene bond lengths, however,
are slightly elongated in the bis(triazolylidene) complex (Au1−
C1 = 2.031(2) Å, Au1−C17 = 2.026(2) Å) in comparison with
Meyer’s bis(NHC) compound (Au1−C1 = 2.015(3) Å, Au1−
C31 = 2.018(3) Å). This observed bis(triazolylidene)
formation represents a possible resting state of any of the
synthesized Au precatalysts in any desired catalytic cycle and
may prove to be an impediment for catalyst performance due to
its presumed stability. As in the other structures, a slight
anagostic interaction can be observed between the ortho proton
of the tolyl ligand and the metal center (H4···Au1 = 2.5300(2)
Å). However, in this example one tolyl ring is further twisted
relative to the triazolylidene plane (C17−C18−C19−C20
−33.4(3)°), certainly due to steric restrictions.
1
successfully. H NMR spectroscopy measured in CD Cl
2
2
suggests acetonitrile coordination, due to an additional methyl
1
3
group observable at 2.49 ppm. In the C NMR, a typical
upfield-shifted carbene carbon resonance can be identified at
1
56.6 ppm. In ESI-MS the Au acetonitrile cation can be found
+
(
[M − SbF ] 487.1) and FAB-MS gives mass peaks for [M −
6
+
+
SbF ] and [M − SbF − MeCN] as well as for the
6
6
bis(triazolylidene) Au compound. The presence of coordinated
acetonitrile could be unequivocally proven by elemental
analysis. This finding is of particular importance, because an
analysis of crystals of 1e presumed to be suitable for X-ray
diffraction only gave the structure of the related bis-
Nevertheless, apart from the observed slow bis(carbene)
formation behavior in solution, compound 1e seems most
promising for applications, due to its rather labile acetonitrile
substituent. Hence, the cyclohexyl-substituted acetonitrile-
(
triazolylidene) complex 1f (Figure 4). In another set of
crystals, the same structural information was found. This allows
us to conclude that the complex stability is limited in solution at
3
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Article
coordinated complex 2b was synthesized by following the
reaction protocol applied above (Scheme 4). When performed
Table 1. Overview of Catalytic Examinations of Catalysts
1a−e and 2a,b in the Intramolecular Hydroamination of
Alkyne-Amine S1
Scheme 4. Synthesis of Acetonitrile-Coordinated Precatalyst
a
2
b
temp
(°C)
time
(h)
yield
b
a
entry
catalyst
solvent
(%)
c
e
1
2
3
CD Cl2
34
24
24
24
0
2
c
d
[AuCl(SMe )]
CD Cl2
34
97
2
2
c
d
[Au(IPr)(NCMe)]
BF4
CD Cl2
34
84
2
c
d
4
5
6
7
8
9
1a
1b
1c
1d
1e
2a
2b
1d
1d
1d
1d
1d
1d
1d
1d
1d
CD Cl2
34
24
24
24
24
24
24
24
24
24
24
24
24
2
39
2
c
d
CD Cl2
34
11
2
c
d
CD Cl2
34
24
2
a
c
d
Reaction conditions: (a) 1.05 equiv of AgSbF , room temperature, 5
CD Cl2
34
75
6
2
c
d
min, MeCN.
CD Cl2
34
77
2
c
d
CD Cl2
34
23
2
c
d
as an NMR experiment, quantitative formation of 2b can be
observed within minutes. Therefore, no prolonged reaction
1
1
0
1
CD Cl2
34
77
2
c
e
toluene
toluene
DMSO
THF
34
18
c
e
time is necessary. When it is measured in CD Cl , the typical
2
2
12
85
70
c
e
methyl group representing the coordinated acetonitrile can be
1
1
1
3
4
5
34
9
c
e
observed at 2.52 ppm. The downfield-shifted signal of the
34
27
1
3
c
e
carbene carbon at 157.3 ppm in C NMR gives further
evidence for successful halide replacement.
CD CN
34
53
3
c
e
16
17
18
19
20
CD CN
80
67
3
c
e
These syntheses prove that viable Au precatalysts coordi-
nated by normal 1,2,3-triazolylidenes can be easily prepared in
good yields using standard reagents. Compounds 1a,b and 2a
are air- and moisture-stable, as observed in water-containing
NMR solvents over several days. Compounds 1c−e are air- and
moisture-stable for hours in the solid form but have to be
stored under argon. Furthermore, the compounds were
observed to be temporarily stable in water-containing NMR
solvents. However, within 1 day formation of a deep red
solution is observable, which can be ascribed to complex
decomposition and formation of colloidal Au nanoparticles.
Complex 2b appears to be less stable, and partial decom-
position could be monitored within hours in NMR solvents
containing only traces of moisture.
CD CN
80
14
21
24
24
89
3
c
e
CD CN
80
96
3
c
e
CD Cl2
24
43
2
c
e
[Au(IPr)(NCMe)]
BF4
CD Cl2
24
63
2
a
Catalytic reactions were performed in J. Young NMR tubes, using
0.138 mmol of S1 and 1.38 μmol of catalyst (see the Experimental
Section), with 1,3,5-trimethoxybenzene as internal standard in 0.6 mL
of deuterated solvent. Determined by NMR. ±1 °C. Average of
three runs. Average of two runs.
b
c
d
e
complexes 1e and 2b, while no Au colloids are observable
under the tested reaction conditions when using 1d or
[Au(IPr)(NCMe)]BF . These two complexes were also tested
at room temperature (Table 1, entries 19 and 20) and showed
mediocre activity. In order to examine whether carbene ligands
were necessary or whether Au nanoparticles catalyze the
4
Catalytic Application in Hydroamination. All synthe-
sized compounds were applied as catalysts in the hydro-
amination of 4-pentyn-1-amine, yielding a ring-closing product
28
(
Table 1), as recently shown for NHC Cu complexes. For
reaction, the Au precursor [AuCl(SMe )] was applied as
2
comparison of catalysts 1a−e and 2a,b, very mild reaction
conditions (34 °C, 24 h) were applied. Although this reaction is
also catalyzed at room temperature by some of the Au
compounds, this slightly elevated reaction temperature was
used in order to maintain the exact same conditions for all
catalytic tests. Since in this transformation no side products are
catalyst. Immediately, a black precipitate immediately formed
even at room temperature, while higher yields were obtained
(97%).
Since the most stable 1,2,3-triazolylidene precatalyst seems to
−
be NTf -substituted 1d, this compound was examined under
2
varied reaction conditions (Table 1, entries 11−18). At 34 °C,
1d catalyzes the ring-closing hydroamination reaction of S1
best in CD Cl , followed by acetonitrile. At elevated temper-
1
observed, yields can be monitored via H NMR spectroscopy
using 1,3,5-trimethoxybenzene as internal standard.
2
2
When the catalyst screening was performed, phenylacetylide-
substituted precatalyst 1b turned out to be the least active
catalyst, followed by the chloride-substituted complex 2a,
acetate-substituted congener 1c and chloride-substituted
complex 1a. Better-performing precatalysts contained mor−e
labile substituents, such as acetonitrile (1e, 2b) and NTf2
atures, the reaction is best catalyzed in MeCN, leading to
satisfactory yields (89%) within 14 h: however, not without
slightly visible Au colloid formation. Under these conditions,
kinetic measurements of the reaction were undertaken (Figure
5).
From the kinetic examination, a turnover frequency of 76 h−1
can be deduced. However, conversion strongly drops after the
first few hours and reaction is not complete even after 27 h. In
view of the fact that high yields were readily obtained with 1d at
34 °C within 24 h (Table 1, entry 7), the yields obtained at 80
°C give reason to question the catalyst stability under these
conditions. Therefore, poisoning experiments were undertaken
by adding mercury to the reaction solution (refer to Supporting
(
1d). In order to further compare the new 1,2,3-triazolylidene
compounds with more established catalytic systems, [Au(IPr)-
NCMe)]BF was applied as a precatalyst under the same
(
4
reaction conditions. Yields were found to be only slightly higher
in comparison to the most active normal 1,2,3-triazolylidene
compounds (Table 1; entries 3, 7, 8, and 10). However, minor
formation of Au colloids can be observed in the case of
3
380
dx.doi.org/10.1021/om400318p | Organometallics 2013, 32, 3376−3384

Organometallics
Article
“
normal” 1,2,3-triazolylidene catalyst, 1d, shows good stability
under mild conditions but is less stable at higher reaction
temperatures in comparison to [Au(IPr)(NCMe)]BF . As
4
1
1g,30
shown for “abnormal” 1,2,3-triazolylidenes by others,
substitution of the alkyl substituent at the N1 position should
certainly improve stability in the systems described here.
Furthermore, all tested NHC-based systems show inferior
catalytic performance in comparison to (undefined) Au
nanoparticles. When focusing on defined molecular homoge-
neous catalysts, however, improved ligand design seems
necessary to leverage the viability of “normal” 1,2,3-
triazolylidenes as effective ligands in catalysis and is currently
under investigation in our laboratories.
EXPERIMENTAL SECTION
General Information. All described manipulations were carried
out under an argon atmosphere by applying standard Schlenk
techniques or in a glovebox. Prior to use, glassware was dried at 80
■
Figure 5. Kinetic examination of the intramolecular hydroamination of
S1 at 80 °C, catalyzed by 1d (please refer to the Supporting
Information for experimental details).
°
C overnight and flame-dried in vacuo. Wilmad NMR tubes with
Information). Indeed, at 80 °C reaction temperature,
conversion drops significantly to 34% of the original yield
obtained under the same conditions without addition of
Teflon seals were used for catalytic examinations. In order to ensure
that the NMR tubes utilized for catalytic examinations did not contain
any traces of metal, these were cleaned with aqua regia between
catalytic experiments. An MBraun MB SPS solvent purification system
was used to obtain dry solvents. These were further degassed by
freeze−pump−thaw cycles. Commercially available compounds were
mercury, whereas the activity of [Au(IPr)(NCMe)]BF remains
4
unchanged. At 34 °C in MeCN, however, the activity of 1d
drops only to 74% of the original yield in the presence of
mercury, suggesting higher catalyst stability under milder
conditions (refer to Supporting Information, Table S2).
In order to examine whether the new 1,2,3-triazolylidene
catalysts also catalyze substrates other than terminal alkynes, we
synthesized 2-(2-phenylethynyl)aniline (S2) as the starting
material for hydroamination of an internal alkyne (Scheme
1
6
used as received. Following literature procedures, 1-methyl-2-phenyl-
4-p-tolyl-1,2,3-triazolium chloride and 1-cyclohexyl-2-phenyl-4-p-tolyl-
31
1
,2,3-triazolium chloride were prepared, as well as substrates S1 and
32
1
13
S2. H and C NMR spectroscopy was performed on a 400 MHz
Bruker Avance DPX or a 400 MHz Bruker Avance III spectrometer at
2
98 K. Residual solvent shifts of the deuterated solvents were used as
internal standards for calibration of spectra. Chemical shifts were
referenced relative to TMS in parts per million (ppm). Abbreviations
used for signal multiplicities: singlet (s), doublet (d), triplet (t),
quartet (q), multiplet (m), broad (br). A Varian 670 FT-IR
spectrometer was used to conduct IR measurements. Elemental
analyses were performed by the microanalytical laboratory of the
TUM.
2
9
5
). The reaction was complete within 24 h under mild
Scheme 5. Au-Catalyzed Hydroamination of Internal Alkyne
Substrate S2
Single-Crystal X-ray Structure Determinations. 2a: yellow
fragment, C H AuClN , M = 549.84, orthorhombic, space group
21
23
3
r
Pbca (No. 61), a = 9.7218(6) Å, b = 17.9719(11) Å, c = 22.2856(13)
3
−1
Å, V = 3893.7(4) Å , Z = 8, λ(Mo Kα) = 0.71073 Å, μ = 7.703 mm ,
−3
ρcalcd = 1.876 g cm , T = 123(1) K, F(000) = 2128, θ = 25.36°, R1
max
=
1
0.0157 (2905 observed data), wR2 = 0.0272 (all 3460 data), GOF =
conditions (1 mol % of 1d, 34 °C) in acetonitrile (monitored
via NMR spectroscopy). Again, slight formation of Au colloids
was observed. Interestingly, the transformation was complete
−3
.02, 236 parameters, Δρ
plate, C H AuN O , M = 505.32, orthorhombic, space group Pbca
= 0.413/−0.457 e Å . 1c: colorless
max/min
18
18
3
2
r
(
No. 61), a = 7.3069(1) Å, b = 19.8442(3) Å, c = 23.0312(3) Å, V =
much more quickly in CD Cl at room temperature (about 5
3
−1
2
2
3339.52(8) Å , Z = 8, λ(Mo Kα) = 0.71073 Å, μ = 8.826 mm , ρ
= 2.010 g cm , T = 123(1) K, F(000) = 1936, θ = 25.36°, R1 =
0.0167 (2556 observed data), wR2 = 0.0322 (all 3064 data), GOF =
1.031, 220 parameters, Δρmax/min = 0.458/−0.401 e Å . 1f: pale
yellow fragment, C H AuN F Sb, M = 931.35, triclinic, space group
P1
=
Z = 2, λ(Mo Kα) = 0.71073 Å, μ = 5.581 mm , ρ
T = 123(1) K, F(000) = 896, θmax = 25.41°, R1 = 0.0139 (5719
observed data), wR2 = 0.0361 (all 5806 data), GOF = 1.123, 419
calcd
−3
min at room temperature). However, also immediately heavy
precipitation of elemental Au was observed, which indicated
that the reaction is also easily catalyzed by (undefined) Au
nanoparticles.
max
−3
32 30
6
6
r
̅
(No. 2), a = 11.6548(4) Å, b = 11.9418(4) Å, c = 13.7014(5) Å, α
3
97.381(2)°, β = 108.494(1)°, γ = 114.191(1)°, V = 1574.32(10) Å ,
CONCLUSION
■
−1
−3
= 1.965 g cm ,
calcd
With newly synthesized 1,2,3-triazolylidene Au−Cl complexes
as starting materials, a selection of Au precatalysts was isolated
and characterized. Most isolated compounds show good
stability in air or in wet organic solvents at room temperature
for at least 1 day. On the basis of the described observations in
hydroamination catalysis, it seems that the newly isolated
catalyst systems exhibit limited stability at higher reaction
temperatures in comparison to the more common imidazoly-
lidene systems. Under mild conditions, some of the synthesized
triazolylidene Au catalysts perform nearly as well as the
renowned IPr-based Au systems. As can be deduced from
mercury catalyst poisoning experiments, the most stable
−3
parameters, Δρ
= 0.610/−0.485 e Å .
max/min
Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication numbers
CCDC-923626 (2a), CCDC-923624 (1c), and CCDC-923625 (1f).
Copies of the data can be obtained free of charge on application to the
CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (fax, (+44)1223-
3
36-033; e-mail, deposit@ccdc.cam.ac.uk).
Preparation of (1-Methyl-2-phenyl-4-tolyl-1,2,3-triazol-5-
ylidenyl)gold(I) Chloride (1a). Under an argon atmosphere, 20
mL of anhydrous dichloromethane were added to a Schlenk tube
3
381
dx.doi.org/10.1021/om400318p | Organometallics 2013, 32, 3376−3384

Organometallics
Article
charged with 1-methyl-2-phenyl-4-p-tolyl-1,2,3-triazolium chloride
(C ), 135.37, 133.12, 131.13, 130.17, 127.46, 126.89, 126.70 (all C ),
trz
ar
1
(
0.500 g, 1.75 mmol, 1.00 equiv) and silver(I) oxide (0.203 g, 0.880
119.97 (q, J = 323.0 Hz, SCF ), 42.54 (NCH ), 21.70 (CCH ). MS
CF 3 3 3
+
+
mmol, 0.50 equiv). The reaction solution was stirred at room
temperature under exclusion of light for 2 h. Subsequently, the
reaction mixture was filtered through Celite. All volatiles of the filtrate
were removed under vacuum to give a white precipitate. Then, the
white solid was dissolved in 5 mL of anhydrous dichloromethane and
(FAB) m/z (%): 727.2 [M] (3), 695.4 [M − NTf + Trz] (100),
2
+
446.2 [M − NTf ] (66). MS (ESI) m/z (%): 695.2 [M − NTf +
2
2
+
+
+
Trz] (88), 487.1 [M − NTf + MeCN] (100), 279.2 [NTf ] (9).
2
2
Anal. Calcd for C H AuF N O S (726.01): C, 29.76; H, 2.08; N,
18
15
6
4
4 2
7.71; S, 8.83. Found: C, 29.93; H, 2.23; N, 7.70; S, 8.82.
[
(SMe )AuCl] (0.309 g, 0.105 mmol, 0.60 equiv) was added. The
Preparation of (1-Methyl-2-phenyl-4-tolyl-1,2,3-triazol-5-
ylidenyl)gold(I) Acetonitrile Hexafluoroantimonate (1e).
Under an argon atmosphere, 8 mL of anhydrous acetonitrile were
added to a Schlenk tube to dissolve silver hexafluoroantimonate (0.056
g, 0.166 mmol, 1.05 equiv). The solution was transferred through
cannula to another Schlenk tube charged with 1a (0.076 g, 0.158
mmol, 1.00 equiv) in 2 mL of anhydrous acetonitrile. After stirring for
1 min, the reaction mixture was filtered through Celite. Removal of all
the volatiles gave an off-white solid (62.1 mg, 62.1%).
2
reaction mixture was stirred for 2 h under exclusion of light at room
temperature. The obtained pale yellow solution was filtered through
Celite, and diethyl ether was added to the filtrate to give 1a as a white
solid (0.495 g, 58.7%).
12
The obtained data agree with literature values.
Preparation of (1-Methyl-2-phenyl-4-tolyl-1,2,3-triazol-5-
ylidenyl)gold(I) Phenylacetylide (1b). Under an argon atmos-
phere, 8 mL of anhydrous methanol were added to a Schlenk tube
charged with potassium tert-butoxide (0.049 g, 0.441 mmol, 2.10
equiv) and phenylacetylene (0.045 g, 0.441 mmol, 2.10 equiv). After
1
3
H NMR (400 MHz, CD Cl ): δ (ppm) 8.12 (d, J = 8.2 Hz, 2H,
2
2
HH
CH ), 7.82−7.67 (m, 3H, CH ), 7.62−7.54 (m, 2H, CH ), 7.34 (d,
ar
ar
ar
3
2
0 min of stirring, 1a (0.100 g, 0.207 mmol, 1.00 equiv) was added to
J
= 7.8 Hz, 2H, CH ), 4.26 (s, 3H, NCH ), 2.49 (s, 3H, CCH ),
HH ar 3 3
13
the clear solution. The reaction mixture was stirred for 16 h at room
temperature to afford a white precipitate. The white solid was filtered
and washed with water, methanol, and diethyl ether (15 mL each).
Thereafter the solid was dried under vacuum to give the product as a
white powder (0.951 g, 83.7%).
2.43 (s, 3H. C NMR (101 MHz, CD Cl ): δ (ppm) = 156.66 (Au-
2 2
C ), 155.24 (C ), 141.30, 135.13, 133.28, 131.15, 130.31, 127.61,
trz
trz
126.92, 126.77 (all C ), 120.74 (Au−NCC), 42.69 (NCH ), 21.72
ar
3
+
(CCH ), 3.46 (NCCH ). MS (FAB) m/z (%): 486.4 [M − SbF ]
3
3
6
+
+
(20), 445.5 [M − SbF − MeCN] (100). MS (ESI ) m/z (%): 487.1
6
1
3
+
−
−
H NMR (400 MHz, CDCl ): δ (ppm) 8.33 (d, J = 8.2 Hz, 2H,
[M − SbF ] (100). MS (ESI ) m/z (%): 235.2 [SbF ] (100). Anal.
3
HH
6
6
CH ), 7.72−7.61 (m, 3H, CH ), 7.59−7.47 (m, 4H, CH and
Calcd for C H AuF N Sb (722.01): C, 29.90; H, 2.51; N, 7.75.
ar
ar
ar
18 18 6 4
H
), 7.35−7.12 (m, 6H, CH and H
), 4.27 (s, 3H,
6
Found: C, 30.28; H, 2.75; N, 7.51.
phenylacetylide
ar
phenylacetylide
13
NCH ), 2.39 (s, 3H, CCH ). C NMR (101 MHz, THF-d ): δ (ppm)
Preparation of (1-Cyclohexyl-2-phenyl-4-tolyl-1,2,3-triazol-
5-ylidenyl)gold(I) Chloride (2a). Under an argon atmosphere, a
mixture of 10 mL of anhydrous dichloromethane and 10 mL of
anhydrous acetonitrile was added to a Schlenk tube charged with 1-
cyclohexyl-2-phenyl-4-p-tolyl-1,2,3-triazolium chloride (0.200 g, 0.628
mmol, 1.00 equiv), silver(I) oxide (0.218 g, 0.942 mmol, 1.50 equiv),
and 3 Å molecular sieves. The reaction solution was stirred at room
temperature under exclusion of light for 18 h. Subsequently, the
mixture was filtered through Celite to another Schlenk tube charged
3
3
=
(
1
2
180.11 (Au-C ), 157.23 (C ), 140.04 (C ), 137.03 (C ), 133.08
trz trz ar ar
Au-CCPh), 132.65, 132.46, 130.97, 130.20, 129.16, 129.14, 128.52,
27.88, 127.68, 125.89 (all C ), 103.77 (Au−CCPh), 42.00 (NCH ),
ar
3
+
1.56 (CCH ). MS (FAB) m/z (%): 547.4 [M] (47), 445.5 [M −
3
+
phenylacetylene] (34). MS (ESI) m/z (%): 993.2 [2M − phenyl-
acetylene] (100). Anal. Calcd for C H AuN (547.13): C, 52.66; H,
3
+
24
20
3
.68; N, 7.68; Au, 35.98. Found: C, 53.01; H, 3.86; N, 7.30; Au, 36.0.
Preparation of (1-Methyl-2-phenyl-4-tolyl-1,2,3-triazol-5-
ylidenyl)gold(I) Acetate (1c). Under an argon atmosphere, 10 mL
of anhydrous dichloromethane were added to a Schlenk tube charged
with 1a (0.100 g, 0.207 mmol, 1.00 equiv). At −78 °C, the solution
was transferred to another Schlenk tube containing silver acetate
with [(SMe )AuCl] (0.111 g, 0.377 mmol, 0.60 equiv). After 2 h of
2
stirring under exclusion of light at room temperature, the obtained
yellow solution was filtered through Celite and the filtrate was
concentrated. Diethyl ether was then added to precipitate the product
as an off-white solid. The solid was dried in vacuo (0.120 g, 34.8%).
(
0.042 g, 0.249 mmol, 1.20 equiv) in 3 mL of anhydrous
1
3
dichloromethane. The reaction solution was stirred under exclusion
of light and was slowly warmed from −78 °C to room temperature
within 2 h. Then the reaction mixture was filtered through Celite and
the filtrate was concentrated. 10 mL of anhydrous hexane were added
to give a product as a white solid (48.3 mg, 56.3%).
H NMR (400 MHz, CDCl ): δ (ppm) 8.33 (d, J = 8.2 Hz, 2H,
3 HH
3
CH ), 7.82−7.64 (m, 3H, CH ), 7.46 (dt, J = 6.9, 1.5 Hz, 2H,
CH ), 7.27 (d, J = 8.2 Hz, 2H, CH ), 4.40 (tt, J = 12.1, 3.8 Hz,
ar
ar
HH
3
3
ar
HH
ar
HH
1H, NCH), 3.23−2.93 (m, 2H, CCH ), 2.39 (s, 3H, CCH ), 2.11−
2
3
3
1.83 (m, 4H, CCH ), 1.66 (d, J = 13.5 Hz, 1H, CCH ), 1.50−1.31
2
HH
2
1
3
13
H NMR (400 MHz, CD Cl ): δ (ppm) 8.35 (d, J = 8.1 Hz, 2H,
(m, 1H, CCH ), 1.31−1.04 (m, 1H, CCH ). C NMR (101 MHz,
2
2
HH
2
2
CH ), 7.78−7.63 (m, 3H, CH ), 7.60−7.50 (m, 2H, CH ), 7.31 (d,
CD Cl ): δ (ppm) 158.19 (Au-C ), 156.64 (C ), 140.42, 135.43,
ar
ar
ar
2 2 trz trz
3
J
= 7.8 Hz, 2H, CH ), 4.24 (s, 3H, NCH ), 2.40 (s, 3H, CCH ),
132.90, 131.06, 129.99, 128.06, 127.77, 127.47 (all C ), 63.43 (NCH),
HH
ar
3
3
ar
13
1
1
1
.96 (s, 3H, C(O)CH3). C NMR (101 MHz, CD Cl ): δ (ppm)
76.89 (Au-C ), 157.38 (C(O)CH ), 156.16 (C ), 140.61, 135.72,
32.69, 130.95, 130.05, 127.64, 127.47, 126.91 (all C ), 42.31
34.54 (CCH ), 26.23 (CCH ), 25.10 (CCH ), 21.68 (CCH ). MS
2
2
2
2
2
3
+
(FAB) m/z (%): 513.5 [M − Cl] (100). MS (ESI) m/z (%): 513.5
trz
3
trz
+
[M − Cl] (100). Anal. Calcd for C H AuClN (549.12): C, 45.87;
ar
21 23
3
(
4
(
NCH ), 24.17 (C(O)CH ), 21.69 (CCH ). MS (FAB) m/z (%):
H, 4.22; N, 7.64. Found: C, 46.05; H, 4.24; N, 7.40.
3
3
3
+
+
45.5 [M − acetate] (48). MS (ESI) m/z (%): 446.2 [M − acetate]
Preparation of (1-Cyclohexyl-2-phenyl-4-tolyl-1,2,3-triazol-
5-ylidenyl)gold(I) Acetonitrile Hexafluoroantimonate (2b).
Under an argon atmosphere, 8 mL of anhydrous acetonitrile were
added to a Schlenk tube to dissolve silver hexafluoroantimonate (0.064
g, 0.190 mmol, 1.05 equiv). Then, the solution was transferred through
a cannula to another Schlenk tube charged with 2a (0.100 g, 0.181
mmol, 1.00 equiv) in 2 mL of anhydrous acetonitrile. After it was
stirred for 5 min, the reaction mixture was filtered through Celite.
Removal of all the volatiles gave an off-white solid (0.086 g, 60.0%).
5). Anal. Calcd for C H AuN O (505.11): C, 42.78; H, 3.59; N,
18 18 3 2
8
.32. Found: C, 42.65; H, 3.64; N, 8.20.
Preparation of (1-Methyl-2-phenyl-4-tolyl-1,2,3-triazol-5-
ylidenyl)gold(I) Bis(trifluoromethanesulfonyl)imidate (1d).
Under an argon atmosphere, 10 mL of anhydrous dichloromethane
were added to a Schlenk tube charged with 1a (0.105 g, 0.218 mmol,
1.00 equiv) and silver bis(trifluoromethanesulfonyl)imide (0.089 g,
0.229 mmol, 1.05 equiv). The reaction mixture was stirred at room
1
3
temperature under exclusion of light for 5 min. Then the reaction
mixture was filtered through Celite and all volatiles of the filtrate were
evaporated under vacuum. An off-white solid (0.094 g, 67.8%) was
obtained as product.
H NMR (400 MHz, CD Cl ): δ (ppm) 8.12 (d, J = 8.1 Hz, 2H,
2 2 HH
CH ), 7.88−7.70 (m, 3H, CH ), 7.56−7.47 (m, 2H, CH ), 7.35 (d,
ar
ar
ar
3
3
J
= 7.9 Hz, 2H, CH ), 4.52 (tt, J = 12.1, 3.8 Hz, 1H, NCH),
HH
ar HH
2
3
2.66 (pseudo-td, J = 12.3, J = 3.4 Hz, 2H, CCH ), 2.52 (s, 3H,
HH
HH
2
1
3
H NMR (400 MHz, CDCl ): δ (ppm) 8.28 (d, J = 8.2 Hz, 2H,
NCCH ), 2.43 (s, 3H, CCH ), 2.19−2.08 (m, 2H, CCH ), 2.04−1.91
3
HH
3
3
2
13
CH ), 7.81−7.65 (m, 3H, CH ), 7.58−7.48 (m, 2H, CH ), 7.30 (d,
(m, 2H, CCH ), 1.48−1.19 (m, 4H, CCH ). C NMR (101 MHz,
ar
ar
ar
2
2
3
1
J
= 7.9 Hz, 2H, CH ), 4.23 (s, 3H, NCH ), 2.42 (s, 3H, CCH ).
CD Cl ): δ (ppm) 157.33 (Au-C ), 149.33 (C ), 141.20, 134.79,
HH
ar
3
3
2 2 trz trz
3
C NMR (101 MHz, CD Cl ): δ (ppm) 156.12 (Au-C ), 141.20
133.55, 131.35, 130.32, 127.83, 127.41, 127.29 (all C ), 121.10 (Au−
2
2
trz
ar
3
382
dx.doi.org/10.1021/om400318p | Organometallics 2013, 32, 3376−3384

Organometallics
Article
NCC), 63.79 (NCH), 35.39 (CCH ), 26.12 (CCH ), 25.04 (CCH ),
(4) (a) Crabtree, R. H. Coord. Chem. Rev. 2013, 257, 755. (b) Martin,
D.; Melaimi, M.; Soleilhavoup, M.; Bertrand, G. Organometallics 2011,
30, 5304.
2
2
2
2
1.71 (CCH ), 3.52 (Au-NCCH ). MS (FAB) m/z (%): 555.3 [M −
3
3
+
+
+
SbF ] (7), 514.3 [M − SbF − MeCN] (16), 315.1 [Trz] (12). MS
6
6
+
(
ESI) m/z (%): 555.1 [M − SbF ] (34), 514.1 [M − SbF −
(5) (a) O
̈
fele, K. J. Organomet. Chem. 1968, 12, P42. (b) Wanzlick, H.
6
6
+
−
MeCN] (3), 235.2 [SbF ] (2).
W.; Schonherr, H. J. Angew. Chem. Int. Ed. 1968, 7, 141−142.
6
̈
Procedures for Catalytic Examinations. Typical Catalytic
Procedure for Hydroamination of 4-Pentyn-1-amine (S1). In a
glovebox, a solution of S1 (34.5 mg, 414 μmol) and 1,3,5-
trimethoxybenzene (20 mg, 119 μmol, used as standard) in 0.9 mL
̈
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of DCM-d was prepared in a scintillation vial. Furthermore, a catalyst
2
(7) (a) Chianese, A. R.; Kovacevic, A.; Zeglis, B. M.; Faller, J. W.;
solution of 3 mg of 1e (4.14 μmol) in 0.9 mL of DCM-d was
2
Crabtree, R. H. Organometallics 2004, 23, 2461. (b) Schuster, O.;
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prepared in another scintillation vial. Portions (0.3 mL) of each
solution were quickly added to a Wilmad NMR tube with a Teflon seal
3
(
1
445.
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3534.
(9) Albrecht, M. Chimia 2009, 63, 105.
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(
so that the tube contained 138 μmol of S1, 49.6 μmol of standard,
and 1.38 μmol of 1e). The NMR tube was quickly sealed and
transferred out of the glovebox, and the reaction solution was
1
immediately cooled to −78 °C until measurement of the starting H
(
NMR spectrum. After measurement, the NMR tube was quickly
G. Angew. Chem., Int. Ed. 2010, 49, 4759−4762. (b) Guisado-Barrios,
G.; Bouffard, J.; Donnadieu, B.; Bertrand, G. Organometallics 2011, 30,
heated to 34 °C in an oil bath and left there for 24 h. After 24 h of
1
heating, another H NMR spectrum was measured to allow evaluation
6
017. (c) Schuster, E. M.; Botoshansky, M.; Gandelman, M. Dalton
Trans. 2011, 40, 8764. (d) Poulain, A. l.; Canseco-Gonzalez, D.;
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of conversion of S1.
̈
ASSOCIATED CONTENT
■
Neels, A.; Albrecht, M. Organometallics 2011, 30, 1021. (e) Keske, E.
C.; Zenkina, O. V.; Wang, R.; Crudden, C. M. Organometallics 2011,
*
S
Supporting Information
3
1, 456. (f) Cai, J.; Yang, X.; Arumugam, K.; Bielawski, C. W.; Sessler,
Text, figures, tables, and CIF files giving spectra of all new
compounds as well as detailed descriptions of buried volume
calculations, computational details, and specific crystallographic
information. This material is available free of charge via the
Internet at http://pubs.acs.org.
J. L. Organometallics 2011, 30, 5033. (g) Kilpin, K. J.; Gavey, E. L.;
McAdam, C. J.; Anderson, C. B.; Lind, S. J.; Keep, C. C.; Gordon, K.
C.; Crowley, J. D. Inorg. Chem. 2011, 50, 6334. (h) Clough, M. C.;
Zeits, P. D.; Bhuvanesh, N.; Gladysz, J. A. Organometallics 2012, 31,
5
231.
11) (a) Canseco-Gonzalez, D.; Gniewek, A.; Szulmanowicz, M.;
Muller-Bunz, H.; Trzeciak, A. M.; Albrecht, M. Chem. Eur. J. 2012, 18,
055. (b) Lalrempuia, R.; McDaniel, N. D.; Muller-Bunz, H.;
Bernhard, S.; Albrecht, M. Angew. Chem., Int. Ed. 2010, 49, 9765−
768. (c) Kilpin, K. J.; Paul, U. S. D.; Lee, A.-L.; Crowley, J. D. Chem.
(
AUTHOR INFORMATION
̈
■
6
̈
Corresponding Author
*
E-mail: wolfgangherrmann@ch.tum.de (W.A.H.); fritz.
kuehn@ch.tum.de (F.E.K.).
9
Commun. 2011, 328. (d) Zanardi, A.; Mata, J. A.; Peris, E.
Organometallics 2009, 28, 4335. (e) Saravanakumar, R.; Ramkumar,
V.; Sankararaman, S. Organometallics 2011, 30, 1689. (f) Prades, A.;
Peris, E.; Albrecht, M. Organometallics 2011, 30, 1162. (g) Bouffard, J.;
Keitz, B. K.; Tonner, R.; Guisado-Barrios, G.; Frenking, G.; Grubbs, R.
H.; Bertrand, G. Organometallics 2011, 30, 2617. (h) Keitz, B. K.;
Bouffard, J.; Bertrand, G.; Grubbs, R. H. J. Am. Chem. Soc. 2011, 133,
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the TUM graduate school and the Bavarian Network
of Excellence (NANOCAT) for generous financial support.
8
498. (i) Crowley, J. D.; Lee, A.-L.; Kilpin, K. J. Aust. J. Chem. 2011,
6
4, 1118. (j) Nakamura, T.; Terashima, T.; Ogata, K.; Fukuzawa, S.-i.
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