Synthesis and Catalytic Benefits of Tetranuclear Gold(I) Complexes with a C4-Symmetric Tetratriazol-5-ylidene

Article abstract of DOI:10.1021/acs.organomet.7b00712

The facile preparation of a C₄-symmteric tetratriazolium salt and its subsequent metalation to generate a series of tetranuclear mesoionic carbene gold(I) complexes is presented. The complete structural characterization of the metallic carbenes

Full text of DOI:10.1021/acs.organomet.7b00712

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX-XXX
Synthesis and Catalytic Benefits of Tetranuclear Gold(I) Complexes
with a C4‑Symmetric Tetratriazol-5-ylidene
Mariana Flores-Jarillo,† Daniel Mendoza-Espinosa,*,‡ Veronica Salazar-Pereda,†
́
and Simplicio Gonzalez-Montiel†
́
†
́
́
Area Academ
́
ica de Quımica, Universidad Auton
́
oma del Estado de Hidalgo, Carretera Pachuca-Tulancingo Km 4.5, Mineral de la
Reforma, Hidalgo, Mex
́
ico 42090
‡
́
́
Area Academ
́
ica de Quımica, CONACYT, Universidad Auton
́
oma del Estado de Hidalgo, Carretera Pachuca-Tulancingo Km 4.5,
Mineral de la Reforma, Hidalgo, Mex
́
ico 42090
S
* Supporting Information
ABSTRACT: The facile preparation of a C4-symmteric tetratriazolium salt and its subsequent metalation to generate a series of
tetranuclear mesoionic carbene gold(I) complexes is presented. The complete structural characterization of the metallic carbenes
and the benefits of cooperative catalysis in the processes of hydroamination and hydrohydrazination of terminal alkynes are
discussed.
metal complexes based on MICs have been reported in the
literature (Figure 1).
INTRODUCTION
■
In the past decade, N-heterocyclic carbenes (NHCs) where the
carbene center is not flanked by heteroatoms (nitrogen, sulfur,
oxygen) on both sides of their structures have attracted a great
deal of attention, as they have shown stronger σ donation
toward the metal center in comparison to classical analogues.1
These ligands, often referred as abnormal carbenes (aNHCs) or
more recently entitled mesoionic carbenes (MICs), owe this
description due to the fact that their structures can only be
represented as zwitterions and not in the neutral canonical
form.2 In particular, a subclass of MICs, namely 1,2,3-triazol-5-
ylidenes, have emerged as a useful alternative for the
coordination of transition metals and main-group elements
owing to their easy synthetic design via click chemistry.3 To
date, a large variety of metal complexes containing 1,2,3-triazol-
5-ylidenes have been reported and used as homogeneous
catalysts in a wide variety of organic transformations, including
C−C and C−N bond formations,4 hydroformylation,5 olefin
polymerization,6 and hydroaminations,7 among others.8
Despite the easy access to ligand platforms with various levels
of substitution and modification of steric and electronic
properties, most of the chemistry of 1,2,3-triazol-5-ylidenes is
dominated by monometallic complexes.3 Only recently, few
ligand platforms allowing the generation of di-9 and trinuclear10
The current development of multinuclear catalysts has
attracted the interest of both academia and industry, as these
species have shown their superiority in terms of selectivity and
reactivity in comparison to mononuclear partners.11 In
particular, it has been demonstrated by Peris,4c,7 Sarkar,10d
and our laboratory10b that the use of trinuclear carbene based
AuI and PdII complexes enhance the catalytic performance in
processes such as Suzuki−Miyaura coupling, α arylation of
ketones, and hydroammination in comparison to their
mononuclear counterparts. The overall improvement in the
catalytic activity in multinuclear systems is attributed mainly to
cooperative interactions provided by intermetallic distances,
tridimensional structures, and the enhanced probability of
interaction with the organic substrates.12
On the basis of these previous findings, and targeting the
introduction of a new framework able to coordinate four metal
centers, we report herein the preparation of the tetratriazolium
salt 2, which is constructed from the readily accessible
pentaerythritol scaffold. The subsequent metalation of the
Received: September 18, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00712
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Figure 1. Ligand platforms featuring bis- and tris-mesoionic carbenes.
Scheme 1. Synthesis of Tetratriazolium Salt 2
multicationic salt 2 by means of silver transmetalation or the in
situ deprotonation with KHMDS in the presence of AuCl-
(SMe2) allows for the synthesis of a series of tetranuclear gold
mesoionic carbenes featuring C4 symmetry. The full character-
ization of all products and the catalytic cooperativity of the gold
complexes in the processes of hydroamination and hydro-
hydrazination of terminal alkynes are discussed.
Scheme 2. Synthesis of Tetra-Au(I)-MIC Complexes 3 and 4
RESULTS AND DISCUSSION
■
The preparation of the tetracationic precursor 2 was
accomplished according to Scheme 1. The first step involves
the copper-catalyzed cycloaddition of tetrakis(2-
propynyloxymethyl)methane with mesityl azide in a mixture
of ethanol/water, providing the triazole 1 in good yields.
Further treatment of the latter precursor with excess methyl
iodide in acetonitrile for 72 h delivers the expected
tetratriazolium salt 2 in 80% yield, obtained after purification
by column chromatography using a DCM/ethanol mixture (9/
1).
second methodology for the metalation of salt 2. Thus, the
treatment of 2 with excess of silver(I) oxide for 48 h, followed
by the addition of AuCl(SMe2), allows for the high-yield
synthesis of the tetragold(MIC) complex 4 (87%), now
containing chloride atoms.
Formation of the tetratriazolium salt 2 was easily confirmed
by the appearance of a new signal in the 1H NMR spectrum at
4.63 ppm indicating methylation of the triazolyl moiety (at N-
3).The C4-fold axis in solution of 2 was revealed by the single
set of signals displayed for the mesityl (δ 2.11, 2.34, and 7.00
ppm) and methylene groups (δ 4.14 and 5.42 ppm). Most of
the resonances in the 1H NMR spectrum shifted only slightly in
comparison to the former triazole 1, with the exception of the
now acidic triazolium proton, which moved to higher frequency
(δ 9.36 ppm). The 13C NMR spectrum is also consistent with
the high symmetry in solution of the salt 2, displaying only a
singlet for the CH+ (δ 131.3 ppm) and NCH3 (δ 41.4 ppm)
groups. The initial attempt at metalation of salt 2 was carried
out by its one-pot reaction with potassium hexamethyldisila-
zane, potassium iodide, and AuCl(SMe2) under strict exclusion
of light (Scheme 2). After workup and purification, the
expected tetranuclear MIC gold iodide complex 3 was obtained
in good yield (94%) as a white solid. In order to avoid the use
of the highly air sensitive KHMDS base, we then evaluated a
Complexes 3 and 4 are air stable and highly soluble in
benzene, toluene, and a variety of chlorinated solvents. NMR
spectroscopy studies confirmed the formation of the expected
tetragold complexes 3 and 4 by the disappearance of the acidic
CH+ proton in the 1H NMR and the observation of a low-field
signal in 13C NMR at 161.3 and 161.4 ppm, respectively. The 4-
fold symmetry in solution for 3 and 4 was also supported by the
1
single set of signals observed in both the H and 13C NMR
spectra.
To gain further insight into the structural features of complex
4, single crystals were grown by slow evaporation of a
concentrated tetrahydrofuran solution at room temperature.
The X-ray diffraction analysis confirmed the formation of a
tetranuclear MIC-AuCl species, as previously depicted in
Scheme 1. Complex 4 crystallizes in the tetragonal I41/a
B
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Figure 2. Molecular structures of complexes 3 (right) and 4 (left). Ellipsoids for complex 4 are shown at 50% probability. Hydrogen atoms are
omitted for clarity.
space group with the asymmetric unit containing a one-fourth
formula unit of 4.
The highly symmetric molecular structure emulates a helix-
type framework (Figure 1). In complex 4, each gold center is
strongly coordinated to a MIC donor and bound to a chlorine
atom with bond distances of 2.012(8) and 2.275(3) Å,
Figure 3. Mononuclear MIC-Au(I) complexes 5 and 6.
respectively; both values are similar to analogous gold(I)
chloride complexes supported by MIC ligands.10b,13 The
Table 1. Optimization of the Hydrohydrazination of
C(5)−Au(1)−Cl(1) angle of 177.9(2)° is close to the expected
a
Phenylacetylene
180° for a linear geometry. Remarkably, the central carbon
atom (C9) belonging to the initial pentaerythritol scaffold
resides in a slightly distorted tetrahedral geometry with angles
of 108.1(3)°.
b
Despite the various attempts to crystallize complex 3, we
were not able to obtain appropriate X-ray-quality samples. The
best set of single crystals was obtained by slow evaporation of a
chloroform/dichloromethane solution at room temperature,
yielding light yellow needles. Although full refinement could
not be obtained due to crystal quality,14 the molecular structure
and the atom connectivity of complex 3 are unambiguous and it
resembles closely the structure of complex 4 (Figure 2, right).
It has been previously demonstrated how the use of two
different metal complexes can provide a better catalytic system
than the constituent monometallic units.14 The synergistic
phenomena observed originate from reactions between the
different metal species, and the multimetallic systems generated
in situ are considered to be involved in such processes as key
intermediates. Motivated by the hitherto documented
enhanced performance of carbene-based multinuclear precata-
lysts, we decided to test the efficiency of complexes 3 and 4 in
two carbon−nitrogen bond forming processes. The first
involved the hydrohydrazination of terminal alkynes employing
hydrazine as a nitrogen source,13f,15 and the second refers to the
hydroamination of phenylacetylene, a process for which several
AuI-based catalysts have shown good activity.16,17 To evaluate
the possible cooperative effects of the tetrametallic species, we
decided to compare the catalytic activities of complexes 3 and 4
with the analogous monometallic MIC-AuI complexes 5 and 6
reported previously by our group (Figure 3).10b,13f
entry
cat.
[cat.] (mol %)
temp (°C)
yield (%)
1
3
4
5
6
3
4
5
6
3
4
5
6
3
4
3
4
3
80
80
80
80
80
80
80
80
80
80
80
80
70
70
60
60
99
99
95
87
99
97
80
71
98
96
67
55
98
96
97
96
2
3
3
3
4
3
5
1
6
1
7
1
8
1
9
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
10
11
12
13
14
15
16
a
Reaction conditions: phenylacetylene (1.0 mmol), hydrazine (1.2
mmol), toluene (3 mL). Isolated yields as the average of two runs.
b
yields under these catalytic conditions with the monometallic
complex 6 being the less active of the series (entries 1−4). In
order to challenge the performance of the gold precatalysts,
several reaction conditions were modified, including the catalyst
loading and reaction temperatures. It can be observed that the
gradual decrease of the catalyst loading until 0.5 mol % (based
on the metal) does not affect the conversion percentages for
complexes 3 and 4; however, the monometallic complexes 5
and 6 significantly decrease the catalytic performance,
rendering conversions of 67 and 55%, respectively (entries 11
and 12). Interestingly, the temperature of the process
As an initial screening test for the hydrohydrazination
process, we carried out the stoichiometric reaction of hydrazine
with phenylacetylene at 80 °C using toluene, a catalyst loading
of 3 mol % (based on the metal), and KB(C6F5)4 as a halogen
scavenger to render the AuI active species. As observed in Table
1, the MIC-based AuI complexes 3−5 provide similar isolated
C
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employing catalysts 3 and 4 can also be decreased to 60 °C
without significant loss in the conversions (entries 15 and 16).
In order to get more insight into the catalytic behavior of
complexes 3−6, the catalytic profiles for the reaction of
hydrazine with phenylacetylene were performed with the
reaction conditions presented in Table 1 (entries 9−12). As
illustrated in Figure 4, catalysts 3 and 4 reach conversions of
To further evaluate the cooperative catalyst effect, complexes
3−6 were tested for their activities in the hydroamination of
phenylacetylene with aniline. The reactions were performed in
CD3CN at 70 °C, with 5 mol % of the catalyst (based on the
metal) and AgBF4 (10% mol) as the cocatalyst and monitored
by NMR spectroscopy over 6 h. All catalysts tested exclusively
produced compound 7, the result of a Markovnikov addition to
aniline with subsequent tautomerization of the enamine.
According to Table 3, the tetrametallic complexes 3 and 4
Table 3. Scope of the Hydroamination of Phenylacetylene
a
with Aniline
b
entry
cat.
[cat.] (mol %)
conversn (%)
1
3
4
5
6
3
4
5
6
3
4
5
6
3
4
5
6
5
99
99
91
93
99
99
82
83
97
96
63
60
95
96
49
53
2
5
3
5
4
5
Figure 4. Hydrohydrazination of phenylacetylene with hydrazine
catalyzed by 3−6. Reactions were carried out with toluene-d8 at 80 °C
and 0.5 mol % catalyst (based on metal). Conversions were
5
3
6
3
1
7
3
determined by H NMR spectroscopy on the basis of the amount of
8
3
phenylacetylene remaining in solution.
9
1
10
11
12
13
14
15
16
1
higher than 55% after only 4 h of reaction and their maximum
conversions are observed in 10 h. In the case of monometallic 5
and 6, the generation of products is much slower, reaching their
maximum conversion after 14 h and remaining unchanged after
that time.
1
1
0.5
0.5
0.5
0.5
The overall profile results suggest that the local concen-
tration of active sites provided by the multinuclear complexes
(dendrimeric effect)18 has an effect on the efficiency and
stability of the catalytic species.
With the optimized conditions in hand, we next tested
complexes 3 and 4 in the hydrohydrazination of several
terminal alkynes with hydrazine. According to Table 2, the
corresponding hydrazones were obtained in good to excellent
yields, with catalyst 4 showing slightly better results.
a
Reaction conditions: phenylacetylene (0.5 mmol), aniline (0.55
b
1
mmol), CD3CN (1 mL). Percentage conversions determined by H
NMR spectroscopy based on the amount of phenylacetylene
remaining in solution.
display slightly better performances in comparison to
complexes 5 and 6 under these catalytic conditions (entries
1−4). Further exploration on the optimized parameters
demonstrates that the catalyst loading for 3 and 4 can be
decreased 10-fold (0.5 mol %) without significant loss of the
conversions (entries 13 and 14). Similar to the hydro-
hydrazination reaction, the decrease in the loading of
monometallic complexes 5 and 6 gradually diminishes the
conversion to 49 and 53%, respectively (entries 15 and 16).
The representation of the reaction profiles for the reaction of
phenylacetylene with aniline (Figure 5), also gives a good
illustration of the faster rate for conversion to products and the
improved catalytic performance provided by the tetranuclear
complexes. For instance, complexes 3 and 4 reach conversions
above 85% after 4 h, while complexes 5 and 6 appear to lose
catalytic activity after 5 h of reaction.
Considering the good conversions under low catalyst loading
of complexes 3 and 4, these systems were then used to test the
effect of electronics and sterics of the aniline on the catalytic
performance. Table 4 reviews the most relevant results.
Complexes 3 and 4 both provided conversions higher than
90%, which places them among the most active AuI catalysts to
date.7,19
Table 2. Scope of the Hydrohydrazination of Terminal
a
Alkynes with Hydrazine
b
entry
cat.
R
yield (%)
1
3
4
3
4
3
4
3
4
3
4
3
4
Ph
Ph
96
98
93
93
90
91
88
92
97
97
83
87
2
3
4-(OMe)Ph
4-(OMe)Ph
4-(Br)Ph
4
5
6
4-(Br)Ph
7
2-(NH2)Ph
2-(NH2)Ph
2(Me)Ph
2(Me)Ph
3-pyridyl
8
9
10
11
12
3-pyridyl
a
With the clearly improved catalytic performance of the
tetranuclear complexes in comparison to their mononuclear
Reaction conditions: alkyne (1.0 mmol), hydrazine (1.2 mmol),
b
toluene (3 mL). Isolated yields as the average of two runs.
D
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Figure 6. Bimetallic and trimetallic MIC-Au(I) complexes 8 and 9.
Table 5. Hydrohydrazination of Terminal Alkynes with
Hydrazine Catalyzed by Multinuclear MIC-Au(I)
Complexes
Figure 5. Time course for the hydroamination of phenylacetylene with
aniline catalyzed by 3−6. Reactions were carried out with acetonitrile-
d3 at 70 °C with 0.5 mol % catalyst (based on metal). Conversions
were determined by 1H NMR spectroscopy on the basis of the amount
of phenylacetylene remaining in solution.
a
Table 4. Optimization of the Hydroamination of
Phenylacetylene with Substituted Anilines
b
a
entry
cat.
R
yield (%)
1
3
4
8
9
3
4
8
9
3
4
8
9
Ph
Ph
Ph
Ph
96
98
69
82
93
93
63
80
90
91
64
77
2
3
4
b
c
5
4-(OMe)Ph
4-(OMe)Ph
4-(OMe)Ph
4-(OMe)Ph
4-(Br)Ph
entry
cat.
Ar
conversn (%)
yield (%)
6
1
3
4
3
4
3
4
3
4
3
4
3
4
3
4
3
4
Ph
99
99
99
99
94
95
90
92
90
88
95
94
94
93
91
92
96
98
95
93
89
92
87
89
86
83
93
92
90
91
88
90
7
2
Ph
8
3
2-(Me)Ph
2-(Me)Ph
4-(Me)Ph
4-(Me)Ph
4-(OMe)Ph
4-(OMe)Ph
4-(NO2)Ph
4-(NO2)Ph
2,6-(Me)2Ph
2, 6-(Me)2Ph
2,4,6(Me)3Ph
2,4,6(Me)3Ph
2,6-(iPr)2Ph
2,6-(iPr)2Ph
9
4
10
11
12
4-(Br)Ph
5
4-(Br)Ph
6
4-(Br)Ph
7
a
Reaction conditions: alkyne (1.0 mmol), hydrazine (1.2 mmol),
8
b
toluene (3 mL). Isolated yields as the average of two runs.
9
10
11
12
13
14
15
16
conditions reported in Table 3 (entries 13−16) and using 3−6.
Thus, the formation process of 7 was disturbed by the addition
of an excess of elemental mercury just after the preparation of
the active catalyst times (t = 0). After NMR monitoring of the
reaction process over 8 h, the conversion percentages for the
reaction with mercury addition involving catalysts 3 and 4 were
92 and 95%, respectively (Figure 7).
A more detailed poisoning study for the process of formation
of 7 was performed by the addition of mercury at different
reaction times (t = 1, 2, 4, 6 h) using catalysts 3 and 4. As
shown in Figure 8, regardless of the mercury addition time, the
conversion percentages and catalytic activities of both
a
Reaction conditions: phenylacetylene (0.5 mmol), substituted aniline
b
(0.55 mmol), CD3CN (1 mL). Percentage conversions were
determined by H NMR spectroscopy on the basis of the amount of
phenylacetylene remaining in solution. Isolated yields as the average
1
c
of two runs.
counterparts, we were curious to further explore the effect of
the multinuclearity in the catalytic outcome. Hence, we
compared the catalytic performance of complexes 3 and 4
with that of our previously reported bi- and trinuclear gold
complexes 8 and 910b (Figure 6) in the process of
hydrohydrazination of terminal alkynes with hydrazine.
According to the results depicted in Table 5, we can observe
a proportional yield increase as the number of gold centers
increases. For instance, the maximum conversions obtained
with the bimetallic complex 8 ranged from 63 to 69%, while the
trimetallic complex 9 reached a maximum of 77−82%. It is also
noticeable that the best conversions of the series are still
achieved by the tetranuclear species.
In order to explore the formation of colloidal gold particles as
the active catalyst, mercury-poisoning tests were carried out for
the process of hydroamination of phenylacetylene with aniline.
For this purpose, catalytic reactions were set up using the
Figure 7. Mercury poisoning tests (t = 0) for the hydroamination of
phenylacetylene with aniline catalyzed by 3−6.
E
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which indicates the robustness of the catalysts reported. Further
exploration of the catalytic potential of complexes 3 and 4 is
currently being explored in our laboratory.
EXPERIMENTAL SECTION
■
Comercially available reagents and solvents were used as received.
Mesityl azide,21 tetrakis(2-propynyloxymethyl)methane,22and gold(I)-
MIC complexes 510b and 613f were synthesized according to the
methods reported in the literature. All manipulations related to the
synthesis of triazole 1 and triazolium salt 2 were performed in air. The
synthesis of gold metal complexes was performed under an
atmosphere of dry nitrogen using standard Schlenk techniques.
Melting points were determined on a Fisher-Johns apparatus and are
uncorrected. Elemental analyses were obtained with a Thermo
Finnegan CHNSO-1112 apparatus and a PerkinElmer Series II
CHNS/O 2400 instrument. X-ray diffraction analyses were collected
in an Agilent Gemini diffractometer using Cu Kα radiation (λ =
1.54184 Å). Data were integrated, scaled, sorted, and averaged using
the CrysAlisPro software package. The structures were solved using
direct methods, with SHELX 2014, and refined by full-matrix least
squares against F2.23 All non-hydrogen atoms were refined anisotropi-
cally. The positions of the hydrogen atoms were kept fixed with
common isotropic display parameters. The crystallographic data and
some details of the data collection and refinement are given in Table 6.
Table 6. Crystallographic Data and Summary of Data
Collection and Structure Refinement for 4
formula
fw
C57H64Au4Cl4N12O4
1910.88
tetragonal
I41/a
Figure 8. Mercury poisoning tests at different reaction times for the
hydroamination of phenylacetylene with aniline catalyzed by
complexes 3 (top) and 4 (bottom).
cryst syst
space group
T, K
293(2)
18.2131(4)
18.2131(4)
27.6462(12)
90
a, Å
complexes are not significantly affected. For instance, the
formations of 7 after mercury addition to complex 3 at 1 and 6
h only differ by 4%, while in the case of complex 4 the
percentage difference is 6%.
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
Z
90
The negligible change in the conversion percentages suggest
that, at 70 °C, the catalytic conversions for the tetranuclear
complexes are performed essentially by molecular species.
However, in the case of monometallic complexes 5 and 6, the
conversion percentages diminish drastically in both cases to less
than 35%, demonstrating an important heterogeneous gold
catalysis. Thus, the mercury poisoning tests indicate a poor
thermal stability of the monometallic gold complexes and
suggest a well-known process of decay or deactivation of the
gold catalyst usually attributed to the reduction of cationic gold
to Au(0) species.20
90
9170.8(5)
4
d
calc, g cm−3
1.384
μ, mm−1
13.129
33503
no. of rflns collected
T
min/Tmax
0.815
Nmeasd
3652
Rint
0.1854
0.0767
0.0887
0.1954
0.2080
0.990
R(I > 2σ(I))
R(all data)
Rw(I > 2σ(I))
Rw (all data)
GOF
CONCLUSIONS
■
In summary, we have reported the convenient preparation of
the tetratriazolium salt 2 and its subsequent metalation to
generate the tetranuclear mesoionic carbene gold(I) complexes
1
3 and 4. H and 13C NMR spectroscopy shows that 3 and 4
Data for complex 3: C57H72Au4I4N12O4; fw 2284.7; space group I41/a;
a = 18.2710(11) Å, b = 18.2710(11) Å, c = 28.426(4) Å, α, β, γ = 90°;
V = 9489.6(15); Z = 4; d = 1.805 Mg/m3; μ = 12.617 mm−1. The final
refinement parameters were GOF = 1.023, R1(I > 2σ(I)) = 0.1502,
and wR2 = 0.3848.
Synthesis of Tetratriazole 1. Cu(OAc)2·H2O (36 mg, 0.2 mmol,
0.05 equiv), 1,10-phenanthroline monohydrate (36 mg, 0.2 mmol,
0.05 equiv), and 793 mg (4.0 mmol, 4.00 equiv) of sodium L-ascorbate
were charged into a 100 mL round-bottomed flask equipped with a
magnetic stirrer. After addition of 10 mL of an EtOH/H2O mixture
(8/2 v/v), the resulting suspension was stirred for 5 min at room
temperature. Subsequently, 288 mg (1 mmol, 1.00 equiv) of
tetrakis((2-propynyloxy)methyl)methane and 645 mg (4.0 mmol,
feature symmetrical patterns displaying a C4-fold axis, and no
presence of conformational isomers was observed. The crystal
structures of 3 and 4 complement well the solution
characterization and confirm the presence of C4 symmetry in
the solid state. The catalytic trials in comparison with two
monometallic MIC-AuI complexes established the enhanced
performance of the tetranuclear gold complexes 3 and 4 in the
processes of hydroamination and hydrohydrazination of
terminal alkynes at very low catalyst loadings. Mercury
poisoning tests indicate that, even at 70 °C, the catalytic
conversions are performed by homogeneous molecular species,
F
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4.00 equiv) of mesityl azide were added to the reaction mixture, which
was stirred over 20 h at room temperature. The crude product was
diluted with 20 mL of water, and the resulting precipitate was filtered,
washed with water, and dried under vacuum to obtain the tetratriazole
as a beige solid in 90% yield (0.9 mmol, 840 mg). Mp: 158−159 °C
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00712.
■
S
1
dec. H NMR (CDCl3, 400 MHz): δ 1.90 (s, 24H, ArCH3), 2.33 (s,
12H, ArCH3),3.58 (s, 8H, OCH2), 4.68 (s, 8H, OCH2), 6.94 (s, 8H,
CHar), 7.53 (s, 4H, CHtriazole). 13C NMR (CDCl3, 100 MHz): δ 17.3
(ArCH3), 21.1 (ArCH3), 45.4 (Cquat), 65.1 (OCH2), 69.3 (OCH2),
124.2 (Car), 129.0 (CHar), 133.5 (CHtz), 135.0 (Car), 139.9 (Car), 145.2
(Ctz). Anal. Calcd for C53H64N12O4 C, 68.22; H, 6.91; N, 18.01.
Found: C, 68.43; H, 7.02; N, 18.36.
General procedures for catalytic experiments and sample
1H and 13C NMR for new compounds (PDF)
Accession Codes
CCDC 1558630 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_
request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: +44 1223 336033.
Synthesis of Tetratriazolium salt 2. Methyl iodide (3.7 mL, 60.0
mmol) was added to a 15 mL acetonitrile solution of triazole A (933
mg, 1.0 mmol) in a pressure tube, and the resulting solution was
refluxed for 72 h. After the mixture reached room temperature, the
solvent was removed under vacuum and the residue was purified by
column chromatography on silica gel using a dichloromethane/ethanol
9/1 mixture as eluent. The corresponding fractions were collected, and
the solvent was evaporated under reduced pressure to obtain a yellow
oil that solidified upon standing (1.2 g, 0.8 mmol, 80%). Mp: 135−136
AUTHOR INFORMATION
Corresponding Author
*E-mail for D.M.-E.: Dmendozae@conacyt.mx.
ORCID
■
1
°C. H NMR (CDCl3, 400 MHz): δ 2.11 (S, 24H, ArCH3), 2.34 (s,
12H, ArCH3), 4.14 (s, 8H, OCH2), 4.63 (s, 12H, NCH3), 5.42 (s, 8H,
OCH2), 7.00 (s, 8H, CHar), 9.36 (s, 4H, CHtriazolium). 13C NMR
(CDCl3, 100 MHz): δ 18.4 (ArCH3), 21.3 (ArCH3), 41.4 (NCH3),
46.6 (Cquat), 62.7 (OCH2), 71.4 (OCH2), 130.0 (CHar), 131.3
(CHtriazolium), 132.5 (Car), 134.5 (Car), 142.0 (Ctz), 142.5 (Car). Anal.
Calcd for C57H76I4N12O4: C, 45.61; H, 5.10; N, 11.20. Found C, 45.85,
H, 4.98, N, 11.17.
Daniel Mendoza-Espinosa: 0000-0001-9170-588X
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Synthesis of Tetratriazol-5-ylidene Gold Complex 3. In the
strict absence of light, choloro(dimethyl sulfide)gold (80 mg, 0.271
mmol), potassium hexamethyldisilazide (59 mg, 0.293 mmol),
potassium iodide (45 mg, 0.271 mmol), and triazolium 2 (100 mg,
0.0667 mmol), were combined in a Schlenk flask and dissolved in
THF (7 mL) at −78 °C. The resulting mixture was stirred for 16 h.
The final clear suspension was dried under vacuum, and the residue
was dissolved in 1 mL of dichloromethane and precipitated with
hexane (10 mL). The solid was filtered and dried under vacuum, giving
the title product in 94% yield (143 mg, 0.627 mmol) as a white solid.
Single crystals were obtained by slow evaporation of a concentrated
We are grateful to CONACYT-Mex
CONACyT-2016-222) and CONACYT (project 0223800)
́
ico (Grant Cat
́
edra-
for financial support.
REFERENCES
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1
dichloromethane/chloroform solution. Mp: 201−203 °C. H NMR
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3.81 (bs, 8H, OCH2), 4.34 (s, 12H, NCH3), 4.88 (s, 8H, OCH2), 6.97
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1
°C. H NMR (CDCl3, 400 MHz): δ 1.90 (s, 24H, ArCH3), 2.38 (s,
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DOI: 10.1021/acs.organomet.7b00712
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(14) Data for complex 3: C57H72Au4I4N12O4; fw 2284.7; space group
I41/a; a = 18.2710(11) Å, b = 18.2710(11) Å, c = 28.426(4) Å, α, β, γ
= 90°; V = 9489.6(15) Å3; Z = 4; d = 1.805 Mg/m3; μ = 12.617 mm−1.
Data were collected with an Agilent Gemini Diffractometer using Cu
Kα radiation (λ = 1.54184 Å). Data were integrated, scaled, sorted, and
averaged using the CrysAlisPro software package. The structures were
solved using direct methods, using SHELX 2014, and refined by full-
H
DOI: 10.1021/acs.organomet.7b00712
Organometallics XXXX, XXX, XXX−XXX