Exploring the scope of pyridyl- and picolyl-functionalized 1,2,3-triazol-5-ylidenes in bidentate coordination to ruthenium(II) cymene chloride complexes

Article abstract of DOI:10.1021/om500287t

1-(2-Pyridyl)-, 4-(2-pyridyl)-, 1-(2-picolyl)-, and 4-(2-picolyl)- functionalized 1,3,4-trisubstituted 1,2,3-triazolium salts (1A-D, respectively) were investigated as N-heterocyclic carbene (trzNHC) precursors for bidentate coordination to ruthenium(II) through the C^NHC and N ^pyridyl donors. In addition to the pyridyl and picolyl pendant groups, a variety of para-substituted phenyl rings were attached to the 1,2,3-triazolylidene via carbon or nitrogen atoms. The ruthenation was accomplished by metalation with Ag₂O to form intermediate silver carbene complexes and subsequent transmetalation with [Ru(η⁶-p- cymene)Cl₂]₂. The cationic ruthenium complexes [Ru(η⁶-p-cymene)(trzNHC)Cl]⁺ (3A-C) were readily obtained with 1-(2-pyridyl)-, 4-(2-pyridyl)-, and 1-(2-picolyl)-1,2,3-triazolium salts (1A-C) but not with the 4-picolyl analogue (1D). The bidentate coordination of the ligand precursors 1 was followed by multinuclear NMR spectroscopy, revealing significant changes in chemical shifts for triazole C-5, pyridine nitrogen atoms, and the neighboring α-proton (H-6 ^pyridyl) in ¹³C, ¹⁵N, and ¹H NMR spectra. The molecular composition of complexes 3A-C was confirmed by elemental analysis and positive ion electrospray ionization (ESI+) mass spectra, the latter showing ions corresponding to [Ru(η⁶-p-cymene)(trzNHC)Cl] ⁺. The solid-state structures of the three representative complexes were confirmed by single-crystal X-ray analyses; all complexes displayed a typical piano-stool type configuration. Preliminary catalytic activity screening of 3A-C in the oxidation of selected primary and secondary alcohols with tert-butyl hydroperoxide (TBHP) to give carbonyl compounds is also discussed.

Full text of DOI:10.1021/om500287t

Article
pubs.acs.org/Organometallics
Exploring the Scope of Pyridyl- and Picolyl-Functionalized 1,2,3-
Triazol-5-ylidenes in Bidentate Coordination to Ruthenium(II)
Cymene Chloride Complexes
Aljosa Bolje,† Stephan Hohloch,‡ Damijana Urankar,† Andrej Pevec,† Martin Gazvoda,† Biprajit Sarkar,‡
̌
and Janez Kosmrlj*,†
̌
†Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ask
̌
erce
̌
va 5, SI-1000 Ljubljana, Slovenia
‡Institut fur Chemie und Biochemie, Anorganische Chemie, Freie Universitat Berlin, Fabeckstraße 34-36, D-14195 Berlin, Germany
̈
̈
S
* Supporting Information
ABSTRACT: 1-(2-Pyridyl)-, 4-(2-pyridyl)-, 1-(2-picolyl)-,
and 4-(2-picolyl)-functionalized 1,3,4-trisubstituted 1,2,3-tri-
azolium salts (1A−D, respectively) were investigated as N-
heterocyclic carbene (trzNHC) precursors for bidentate
coordination to ruthenium(II) through the CNHC and Npyridyl
donors. In addition to the pyridyl and picolyl pendant groups,
a variety of para-substituted phenyl rings were attached to the
1,2,3-triazolylidene via carbon or nitrogen atoms. The
ruthenation was accomplished by metalation with Ag2O to
form intermediate silver carbene complexes and subsequent
transmetalation with [Ru(η6-p-cymene)Cl2]2. The cationic
ruthenium complexes [Ru(η6-p-cymene)(trzNHC)Cl]+ (3A−C) were readily obtained with 1-(2-pyridyl)-, 4-(2-pyridyl)-, and
1-(2-picolyl)-1,2,3-triazolium salts (1A−C) but not with the 4-picolyl analogue (1D). The bidentate coordination of the ligand
precursors 1 was followed by multinuclear NMR spectroscopy, revealing significant changes in chemical shifts for triazole C-5,
pyridine nitrogen atoms, and the neighboring α-proton (H-6pyridyl) in 13C, 15N, and 1H NMR spectra. The molecular composition
of complexes 3A−C was confirmed by elemental analysis and positive ion electrospray ionization (ESI+) mass spectra, the latter
showing ions corresponding to [Ru(η6-p-cymene)(trzNHC)Cl]+. The solid-state structures of the three representative complexes
were confirmed by single-crystal X-ray analyses; all complexes displayed a typical piano-stool type configuration. Preliminary
catalytic activity screening of 3A−C in the oxidation of selected primary and secondary alcohols with tert-butyl hydroperoxide
(TBHP) to give carbonyl compounds is also discussed.
electrochemical properties. This is illustrated by ruthenium
coordination compound I (Figure 1), showing about 100 times
higher catalytic activity for water oxidation in comparison to the
analogous pyridine- and phthalazine-based ruthenium com-
plexes.14,15 Compounds II16 and III17 have been designed for
applications in dye-sensitized solar cells, with the latter showing
INTRODUCTION
■
1
2
̈
Owing to the seminal work by Ofele and Wanzlick in 1968 on
the first metal complexes containing an N-heterocyclic carbene
(NHC), followed by Arduengo’s report on the isolation and
stability of free NHCs in 1991,3 the organometallic chemistry of
these ligands has witnessed an explosive development.4−6 The
success can be attributed to the fact that the complexes of these
ligands are remarkably robust toward decomposition and
extremely active in catalysis.
1,2,3-Triazol-5-ylidenes have recently emerged as a new
subclass of abnormal/mesoionic carbenes (trzNHCs).7−13
These are of particular interest due to their combination of
very high donor strength and ease of synthetic access through the
initial triazole formed by the copper-catalyzed azide−alkyne
cycloaddition reaction (CuAAC) followed by N-methylation.
Specific structural and electronic features place the donor
abilities of these mesoionic carbene ligands between those of the
most donating normal imidazol-2-ylidenes and abnormal
imidazol-4-ylidenes.7
Figure 1. Selected coordination compounds I−III with pyridyl-
functionalized trzNHCs.
Coordination compounds with pyridyl-functionalized
trzNHCs possess remarkable catalytic, spectroscopic, and
Received: March 18, 2014
Published: May 14, 2014
© 2014 American Chemical Society
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the highest radiative lifetime in comparison to all structurally
related complexes.
Scheme 1
Aiming at increasing the functionality of the 1,2,3-triazol-5-
ylidene ligands, we recently developed a selective approach to the
isomeric and homologous pyridyl-functionalized triazolium salts
1A−D (Figure 2), which should readily offer the possibility of
trzNHC complexes have been isolated and characterized, their
tendency to decompose is also well documented.6,7
Next, the above reaction conditions were employed for the
series of ligand precursors 1Aa−g, differently substituted at the
phenyl ring. Upon reaction with Ag2O the formation of the silver
intermediate complexes 2Aa−g took 2−5 days (Table 1, Time
Figure 2. Structures of triazolium salts 1A−D along with the atom-
numbering scheme used for NMR spectral assignment. Numbers
without a prime are for the 1,2,3-triazole ring, numbers with a single
prime are for the pyridine ring, and numbers with two primes are for the
phenyl ring, with C-1″ attached to the triazole.
Table 1. Synthesis of Complexes 3A
C,N-bidentate coordination by binding to the metal through
both the triazole carbenic carbon and pyridyl nitrogen atoms.18
The synthesis of compounds 1 took advantage of the CuAAC
ligation of the appropriate pyridine-bearing “click” partners, i.e.,
organic azides and terminal alkynes, into the appropriate
pyridine-functionalized 1,2,3-triazoles. In a subsequent step
these were selectively monomethylated at the triazole N3 atom.
The selectivity was achieved through pyridine nitrogen atom
protection by N-oxidation.18
In coordination chemistry, for the ligand precursors 1A−D it
was anticipated that the pyridyl pendant group would modulate
the electronic properties of the trzNHC ligand as well as provide
an opportunity for metal chelation. As chelators, these
compounds should easily offer the formation of five- and six-
membered metallacycles, with or without the π overlap between
the pyridine and trzNHC rings, with specific ligand geometry,
including bite angle and fine-tuned electronic properties. Here
we report their use as C,N-bidentate ligands in (η6-p-cymene)-
ruthenium(II) complexes, along with some preliminary catalytic
activity screening.
a
1A
R
Time 1 (days)
Time 2 (h)
3A, yield (%)
1Aa
1Ab
1Ac
1Ad
1Ae
1Af
H
3
2
5
2
2
2
2
2
2
2
2
2
2
2
3Aa, 86
3Ab, 96
3Ac, 92
3Ad, 91
3Ae, 89
3Af, 97
3Ag, 85
CH3
OCH3
CN
CF3
Br
1Ag
NO2
a
Percent overall yield of the pure product.
1). The progress of the reactions was monitored by taking
aliquots of the reaction mixtures and subjecting them to instant
1H NMR analyses in DMSO-d6, monitoring the disappearance of
the triazolium H-5 proton, as mentioned above. Upon the
addition of [Ru(η6-p-cymene)Cl2]2 the subsequent carbene
transfer to the ruthenium was completed in just 2 h, as
determined by TLC analysis (Time 2). A simple three-step
filtration−solvent evaporation−crystallization workup afforded
pure 3Aa−g in excellent 85−97% overall yields.
Ligand precursors from the series 1Ba−f were allowed to react
by the same pathway outlined in Scheme 1, and the results are
summarized in Table 2. Here too the slow formation of the
intermediate silver carbene complexes 2B was followed by rapid
ruthenation with [Ru(η6-p-cymene)Cl2]2 to give 3Ba−f in 72−
91% overall yield after isolation.
In contrast to the pyridyl-triazolium cations 1A,B, the
activation of the picolyl-triazolium cations 1C with Ag2O turned
out to be sluggish and did not proceed to completion by using the
above reaction conditions. Initial attempts to accelerate the
formation of the intermediate silver complexes 2C were made by
employing equimolar amounts of a base additive such as Cs2CO3
and Et3N. In those cases the conversion of 1C into 2C was
RESULTS AND DISCUSSION
■
Synthesis and NMR Spectroscopy Data. The library
member 1Aa was selected as a model substrate for ruthenation,
which was obtained by employing the established trans-
metalation procedures shown in Scheme 1.5,7,9,10 When 1Aa
was reacted with Ag2O in dry acetonitrile at room temperature to
form the silver carbene complex 2Aa, the latter was subjected
without isolation to transmetalation into 3Aa by the addition of
[Ru(η6-p-cymene)Cl2]2. The formation of the silver carbene
1
complex 2Aa from 1Aa was deduced by H NMR spectral
analysis of the reaction mixture by disappearance of the
triazolium H-5 proton, resonating at δ 9.04 ppm, from the
spectra. We were not successful in obtaining more experimental
data for the structure of 2Aa by NMR, mass spectrometry, or
isolation due to its instability. Despite the fact that some silver
1
instant as indicated by H NMR analysis, but the subsequent
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of DMSO-d6 and D2O (6:1 volume ratio) at 296 K by time-
dependent NMR spectroscopy indicated a complete exchange of
H-5 at 1Aa (9.04 ppm) and 1Ba (10.18 ppm) within 5 h, whereas
under the same reaction conditions 1Ca and 1Da remained
intact. The hydrogen−deuterium exchange at the last two
triazolium cations only occurred after 13 h of heating to 80 °C
and was accompanied by deuterium exchange of the bridging
methylene protons. An increased acidity of H-5 in the series of
the pyridyl-triazolium cations 1Aa and 1Ba over the picolyl
analogues 1Ca and 1Da is expected due to the σ-electron-
withdrawing pyridine ring attached directly to the triazolium
manifold in the former, increasing the electron deficiency of the
cationic ring.
Table 2. Synthesis of Complexes 3B
a
1B
R
Time 1 (days)
Time 2 (h)
3B, yield (%)
1Ba
1Bb
1Bc
1Bd
1Be
1Bf
H
4
3
6
7
6
3
2
2
2
2
2
2
3Ba, 78
3Bb, 81
3Bc, 91
3Bd, 80
3Be, 72
3Bf, 87
CH3
OCH3
CN
CF3
Br
All Ru−trzNHC compounds 3 in this investigation were fully
characterized by multinuclear 1D and 2D NMR spectroscopy,
high-resolution mass spectrometry with electrospray ionization,
and elemental analysis. For the p-cymene ligand, a doublet for
each of the four ring protons and two doublets for the methyl
groups of the isopropyl group in the 1H NMR spectra suggested
the asymmetry of the coordinated p-cymene ring. This was
corroborated by the presence of six nonequivalent aromatic p-
a
Percent overall yield of the pure product.
ruthenation with [Ru(η6-p-cymene)Cl2]2 into 3C did not
proceed. An additional screening finally revealed that, rather
than the use of additives, the reaction of 1C with Ag2O
1
conducted with gentle heating to 60 °C proved beneficial. H
1
cymene carbon resonances in 13C NMR spectra. H NMR
NMR analysis showed that the formation of the intermediate
silver complexes 2Ca−e,h was complete in 2−10 h. In sharp
contrast to the ruthenation of 2A,B, however, the reaction of
2Ca−e,h with [Ru(η6-p-cymene)Cl2]2 to give the final Ru−
trzNHC compounds 3Ca−e,h required 2−4 days for com-
pletion. The 4-chlorophenyl triazolium cation 2Ch was
examined instead of the 4-bromo derivative, in comparison to
the 3A,B series. Unlike the 3A,B compound series, pure products
3Ca−e,h could only be obtained after flash chromatographic
purification, resulting in a substantial drop in the yields (Table 3).
spectroscopy revealed the absence of the low-field triazolium H-5
proton resonance (for the atom-numbering scheme, see Figure
2).
As expected for the bidentate C,N-coordination, the binding of
the triazolium cation 1 to give the ruthenium compounds 3
induced the largest changes in the chemical shifts for the triazole
C-5 carbon atom, pyridine nitrogen N-1′, and the neighboring α-
proton H-6′. The corresponding 1H, 13C, and 15N NMR
chemical shifts data along with the coordination shifts (Δ1H
,
coord
13C
15N
Δ
coord, Δ coord) are collected in Table 4. The latter are defined
Table 3. Synthesis of Complexes 3C
as the difference between the chemical shift of the triazolylidene
ligand in its complex and that of the triazolium cation: i.e., Δcoord
= δcomplex − δtriazolium cation
.
For a given R = H, in comparison to the triazolium cation C-5
carbon resonances in the ligand precursors 1Aa−1Ca, the
corresponding carbenic C-5 resonances in 3Aa−3Ca shifted
upfield for ΔC‑5
= 45.2, 46.0, and 29.9 ppm, respectively
coord
(Table 4). Whereas ΔC‑5coord parameters were similar for 3Aa and
3Ba, significantly smaller changes in the chemical shifts were
observed for the coordination of 1Ca. No obvious correlation
with the varying electronic nature of the substituents R within
each series of compounds A−C could be observed.
a
1C
R
Time 1 (h)
Time 2 (days)
3C, yield (%)
1Ca
1Cb
1Cc
1Cd
1Ce
1Ch
H
4
8
2
2
4
2
2
2
3Ca, 50
3Cb, 45
3Cc, 40
3Cd, 38
3Ce, 45
3Ch, 42
CH3
OCH3
CN
10
3
The pyridine ring protons H-6′ were deshielded with ΔH‑6
′
coord
CF3
Cl
2
parameters of 0.47, 0.42, and 0.92 ppm for 3Ad−3Cd,
respectively (Table 4). Here too the coordination shifts for
3Ad and 3Bd were similar yet much smaller in comparison to
that for 3Cd.
9
a
Percent overall yield of the pure product.
A deshielding of the neighboring α-proton is a good indication
of the pyridine nitrogen coordination to the metal.21 Addition-
ally, the coordination of the pyridine group was confirmed
through the 15N NMR data. The binding of the pyridine ring to
ruthenium resulted in a large upfield 15N coordination shift of
Unexpectedly, the complexation of the compound series 1D
(1Da (R = H), 1Dc (R = OCH3), and 1De (R = CF3); Figure 2)
under the reaction conditions described above, either those for
the preparation of 3A,B or those for 3C, failed and only the
triazolium ions could be isolated.
The above results revealed a significant difference in the
reactivity of the isomeric and homologous triazolium cations
1A−C toward Ag2O. The silver complexation occurs through a
triazolium ring deprotonation by the silver base.5 The idea that
the acidity19 difference between the variously substituted
triazoles in 1A−C is playing a role was qualitatively supported
by hydrogen−deuterium exchange NMR experiments.20 Mon-
itoring the aqueous solution chemistry of 1Aa−1Ca in a mixture
ΔN‑1
′
= 60−77 ppm (Table 4). The values are in good
coord
agreement with the data reported in the literature for pyridine−
ruthenium(II) coordination.22
Although the coordination shift parameters for 3A−C could
reflect the distinct coordination bond lengths and the complex
geometries, these should be taken with caution, because it has
been demonstrated that the interpretation of the coordination
shift in terms of coordination strength must consider the NMR
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Table 4. H-6′, C-5, and N-1′ Chemical and Coordination Shifts (δ and Δcoord = δcomplex − δtriazolium cation; ppm) for Ruthenium(II)
Complexes 3A−C with Triazolium Salts 1A−C
compd
R
solvent
δH‑6
′
ΔH‑6
′
δC‑5
ΔC‑5
δN‑1
′
ΔN‑1
′
coord
coord
coord
a
b
1Aa
H
H
CDCl3
8.60
9.35
8.60
9.40
8.60
9.36
8.81
9.28
8.81
9.31
8.80
9.30
8.82
9.26
8.91
9.39
8.90
9.41
8.90
9.38
8.91
9.33
8.92
9.35
8.90
9.34
8.60
9.53
8.59
9.51
8.59
9.52
8.60
9.52
8.60
9.53
8.60
9.49
124.4
169.5
124.2
169.5
123.9
169.3
126.8
170.1
126.7
169.8
126.1
169.5
126.9
170.2
128.0
174.0
127.8
173.8
127.7
173.8
126.1
174.4
128.5
174.2
128.2
174.0
129.7
159.6
129.4
159.6
129.1
159.6
130.5
160.3
130.4
160.1
129.9
159.9
288
226
3Aa
CDCl3
0.75
0.80
0.76
0.47
0.50
0.50
0.44
0.48
0.51
0.48
0.42
0.43
0.44
0.93
0.92
0.93
0.92
0.93
0.89
45.2
−62
−61
−60
−62
−61
−61
−62
−66
−67
−66
−66
−66
−66
−76
−76
−76
−77
−77
−77
a
b
1Ab
CH3
CH3
OCH3
OCH3
CN
CN
CF3
CF3
Br
CDCl3
287
226
3Ab
CDCl3
45.3
45.4
43.3
43.2
43.4
47.3
46.0
46.0
46.1
48.3
45.7
45.8
29.9
30.2
29.5
29.8
29.7
30.0
a
b
1Ac
CDCl3
286
226
3Ac
CDCl3
a
b
1Ad
DMSO-d6
CDCl3
287
225
3Ad
a
b
1Ae
DMSO-d6
CDCl3
287
226
3Ae
a
b
1Af
DMSO-d6
CDCl3
287
226
3Af
Br
a
b
1Ag
NO2
NO2
H
DMSO-d6
CDCl3
287
225
3Ag
a
b
1Ba
DMSO-d6
CDCl3
309
243
3Ba
H
a
b
1Bb
CH3
CH3
OCH3
OCH3
CN
CN
CF3
CF3
Br
DMSO-d6
CDCl3
309
242
3Bb
a
b
1Bc
DMSO-d6
CDCl3
309
243
3Bc
a
b
1Bd
DMSO-d6
CDCl3
308
242
3Bd
a
b
1Be
DMSO-d6
CDCl3
309
243
3Be
a
b
1Bf
DMSO-d6
CDCl3
309
243
3Bf
Br
a
b
1Ca
H
DMSO-d6
CDCl3
311
235
3Ca
H
a
b
1Cb
CH3
CH3
OCH3
OCH3
CN
CN
CF3
CF3
Cl
DMSO-d6
CDCl3
311
235
3Cb
a
b
1Cc
DMSO-d6
CDCl3
312
236
3Cc
a
b
1Cd
DMSO-d6
CDCl3
312
235
3Cd
a
b
1Ce
DMSO-d6
CDCl3
312
235
3Ce
a
b
1Ch
DMSO-d6
CDCl3
312
235
3Ch
Cl
a
b
Data collected from ref 18. This work.
solvent and the nature of the counterion, if present.23 In our case,
from the 1H−15N HMBC spectra and compared with those for
the ligand precursors 1Aa−1Ca (Table S1, Supporting
Information). As expected, significantly smaller coordination
shifts were observed for those atoms in comparison to those for
C-5 and N-1′.
−
−
the different counterions TfO−, BF4 , and PF6 surround the
cationic ruthenium complex in 3A−C. With few exceptions,
DMSO-d6 and CDCl3 were employed for measuring NMR
spectra of the ligand precursors 1 and the complexes 3,
respectively, as shown in Table 4. The selection of the NMR
solvent was based on solubility and stability considerations.
Whereas the triazolium salts are sparingly soluble in CDCl3,
complexes 3 slowly decompose upon several hours in DMSO-d6.
Nevertheless, NMR results strongly confirm the formation of the
bidentate Ru−trzNHC complex. Elemental analyses of the
complexes suggested their molecular compositions including the
The donor strength of the NHC carbenes has been evaluated
on the basis of experimental 13C NMR parameters.24 In Pd−
trzNHC compounds only a moderate influence of the electronic
properties of the substituents on δcarbene was observed.10,25 In
compounds 3 the 13C NMR chemical shifts for the C-5 atoms
vary significantly between complex series spanning from 159.6
ppm for 3Ca to 169.5 ppm for 3Aa and 174.0 ppm for 3Ba.
Electron-withdrawing groups such as CF3 slightly increase the
NMR shifts to 160.1, 169.8, and 174.2 ppm for compounds 3Ce,
3Ae, and 3Be, respectively. On the other hand, for electron-
donating groups such as OCH3 the opposite trend can be seen
with δC‑5 values of 159.6, 169.3, and 173.8 ppm for the complexes
3Cc, 3Ac, and 3Bc, respectively (Table 4). Chemical shifts for
complexes 3B are comparable with those for the previously
−
−
counterions OTf−, BF4 , and PF6 in 3A−C, respectively. The
presence of these anions was also confirmed by 19F, 11B, and 31P
NMR spectroscopy. Positive-ion electrospray ionization (ESI+)
mass spectra of complexes 3 showed ions corresponding to
[Ru(η6-p-cymene)(trzNHC)Cl]+.
The 15N NMR chemical shifts for the noncoordinated triazole
nitrogen atoms N-1, N-2, and N-3 in 3Aa−3Ca were extracted
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reported analogues, where also C,N-bidentate triazolylidenes
were used (δC‑5 ranges from 172.4 to 174.1 ppm).14 In
comparison, the carbene chemical shifts for similar ruthenium-
(II) complexes containing monodentate triazolylidenes that
involve coordination only through the carbon C-5 vary between
158.5 and 163.0 ppm.14,26,27 The difference in the C-5 NMR
chemical shifts in the complex series 3A,B versus 3C might be
due to the pyridine moiety directly attached to the triazolylidene
ring in the former, withdrawing some electron density and thus
deshielding the carbene resonances. The C-5 chemical shifts in
the series 3C, having a methylene bridge between the pyridine
ring and a triazole moiety, are more comparable to those of the
carbene monodentate triazoylidene complexes than to the C,N-
bidentate analogues.
Crystallographic Data. Overall we were able to crystallize
one complex from each series. Single crystals for both 3Aa and
3Ca were obtained by layering a concentrated solution of
dichloromethane with hexane at 8 °C. X-ray-quality crystals of
3Bf were obtained from the NMR tube upon slow evaporation
from CDCl3 at 8 °C. All complexes display a typical piano-stool
type structure, as expected for half-sandwich complexes of this
type. While 3Bf crystallizes in the orthorhombic space group
P212121 as a solvate with one molecule of CDCl3, the other two
molecules were found to crystallize in a triclinic system in the
Table 6. Selected Bond Angles (deg) in the Complexes 3Aa,
3Bf, and 3Ca
atoms
3Aa
3Bf
3Ca
C5A−Ru1−N4
C5A−Ru1−Cl1
N4−Ru1−Cl1
N1−C5A−C4A
77.4(2)
85.5(1)
82.4(1)
101.8(4)
76.3(1)
88.3(1)
85.2(1)
103.2(3)
87.8(1)
85.9(1)
80.8(1)
101.8(3)
In the case of 3Aa and 3Bf the coordinating atoms and the
ruthenium form a five-membered planar ring. The dihedral
angles of the triazolylidene ring and the pyridine ring are thereby
only 6.7(2) and 3.4(1)° for 3Aa and 3Bf, respectively. In contrast
to that, in 3Ca with an additional CH2 group the coordinating
atoms form a six-membered ring in a boat-shaped conformation,
similar to that found in the metal complex of an analogous
flexible click N,N-chelator with a picolyl-triazole motif (compare
structures in Figure 3).7,9,30 All distances of the coordinating sites
space group P1 with no additional solvent molecules. For
̅
additional crystallographic information, see Table S2 (Support-
ing Information). The distances of Ru1 to the centroids of the p-
cymene ligands are 1.690(1), 1.701(1), and 1.712(1) Å for 3Aa,
3Bf, and 3Ca, respectively, and are therefore in the range of those
for previously reported systems.14,28 In all three cases the
pyridyl/picolyl-triazolylidene ligand is bound, as expected, to the
ruthenium center via the pyridine nitrogen N4 and the
triazolylidene carbon C5A. All bond lengths and angles are
within the expected range: e.g., Ru1−C5A 2.050(4) Å and Ru1−
N4 2.133(3) Å for 3Ca (for more details see Tables 5 and 6). In
Table 5. Selected Bond Lengths (Å) in the Complexes 3Aa,
3Bf, and 3Ca
Figure 3. ORTEP plots of the isomers 3Aa (top left), 3Bf (top right),
and 3Ca (bottom left) and the boat-shaped configuration of the six-
membered ring in 3Ca (bottom right). The ellipsoids are shown at a
probability level of 50%. Hydrogen atoms, solvent molecules, and
counterions are omitted for clarity.
atoms
Ru1−Cl1
Ru1−C5A
Ru1−N4
C5A−C4A
C4A−N3
N1−N2
3Aa
3Bf
3Ca
2.394(1)
2.033(4)
2.118(4)
1.385(6)
1.375(5)
1.339(5)
1.309(5)
1.373(5)
1.469(5)
1.402(6)
1.338(6)
1.472(6)
2.400(1)
2.027(2)
2.124(3)
1.380(4)
1.366(4)
1.350(4)
1.314(4)
1.346(4)
1.454(4)
1.426(4)
2.429(2)
2.050(4)
2.133(3)
1.412(5)
1.364(5)
1.339(4)
1.335(4)
1.364(5)
1.461(5)
to the ruthenium (Ru1−Cl1, Ru1−C5A, Ru1−N4, and Ru1-
Cym(cent)) in 3Ca are slightly elongated in comparison to those
in 3Aa and 3Bf (Table 5). The additional sp3 carbon atom also
results in a large dihedral angle between the picolyl group and the
triazolylidene plane of 45.4(1)°. The (substituted) phenyl
residues are strongly shifted toward the triazolylidene plane by
65.0(2), 47.1(1), and 39.8(1)° for 3Aa, 3Bf, and 3Ca,
respectively. For all three structures the packing seemed to be
uneventful with no significant shorts contacts and stacking effects
being observed.
Catalytic Activity. With the compounds 3 in hand, we
carried out a preliminary investigation of their catalytic activity in
the oxidation of selected alcohols with tert-butyl hydroperoxide
(t-BuOOH, TBHP) in water as a solvent. Examples of arene−
ruthenium31,32 and imidazolium-based Ru−NHC complexes33
that work efficiently in these systems are well documented,
whereas triazolylidene−ruthenium complexes were recently
reported for the oxidation of alcohols.26,27 A good to excellent
conversion of the two tested secondary benzyl alcohols,34 1-
phenylethanol (4a) and 1-phenylpropanol (4b), into the
N2−N3
N1−C5A
N3−C6A
N1−C1B
C1B−N4
C4A−C1
C1−N4
1.350(5)
1.485(5)
1.450(4)
1.353(4)
N1−C6B
C6B−C1B
Ru1−Cym(cent)
1.468(4)
1.516(5)
1.712(1)
1.690(1)
1.701(1)
all three cases the triazolylidene ligands show a delocalized
electronic structure with a slightly decreased N1−C5A−C4A
angle in comparison to the free triazolium cations reported
previously (compare Table 6). The chloride ligand Cl1 is
terminally bound, and the Ru1−Cl1 bond lengths are all within
the expected range.9,14,28,29
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corresponding ketones, acetophenone (5a) and propiophenone
(5b), respectively, was observed by using the different Ru−
trzNHC complexes 3 (0.1 mol %) in water at room temperature
for 3 h (Table 7, entries 1−8). The fact that under the same
Table 8. Oxidation of Selected Benzyl Alcohols using Ru−
a
trzNHC Complexes 3
Table 7. Oxidation of Selected Secondary Alcohols using Ru−
a
trzNHC Complexes 3
bc
,
entry alcohol
R
catalyst time (h) products 6, 7 (ratio)
d
1
2
3
4
5
6
7
8
4d
4d
4d
4d
4d
4e
4f
H
H
H
H
H
3Aa
3Ba
3Ca
3Cc
3Ce
3Ca
3Ca
3Ca
3
3
6a, 7a (1.5:1)
6a, 7a (1.6:1)
6a, 7a (6.0:1)
6a, 7a (1.7:1)
6a, 7a (1.2:1)
6b, 7b (5.4:1)
6c, 7c (1.5:1)
6d, 7d (2.3:1)
3
b
entry alcohol
R1
R2
CH3
3
product conversion (%)
3
3
1
2
3
4
5
6
7
8
9
4a
4a
4a
4b
4b
4b
4b
4b
4c
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
3Aa
3Ca
3Cc
3Aa
3Ba
3Ca
3Cc
3Ce
3Ca
5a
5a
5a
5b
5b
5b
5b
5b
5c
100
86
100
90
88
94
94
93
5
2-MeO, 5-Br
4-Cl
24
24
24
CH3
CH3
4g
4-MeO
CH3CH2
CH3CH2
CH3CH2
CH3CH2
CH3CH2
a
General reaction conditions: a mixture of the alcohol 4d−g (1.0
mmol), TBHP (4.0 mmol), and Ru catalyst (0.001 mmol, 0.1 mol %)
in distilled water (5 mL) was stirred at room temperature for the time
indicated, and aliquots (see the Experimental Section) were analyzed
b
by 1H NMR spectroscopy. As determined by 1H NMR spectroscopy.
c
−(CH2)5−
A full conversion of the alcohol 4 into a mixture of benzoic acid, 6,
a
d
General reaction conditions: a mixture of the alcohol 4a−c (0.5
and tert-butyl esters of peroxybenzoic acids 7 was noted. Products
mmol), TBHP (2.0 mmol), and Ru catalyst (0.0005 mmol, 0.1 mol %)
in distilled water (5 mL) was stirred at room temperature for 3 h. The
progress of the reaction was monitored by analyzing aliquots (see the
Experimental Section) by 1H NMR spectroscopy, indicating the
presence of the product 5 and in some cases unreacted starting alcohol
were isolated from the reaction mixture by extraction into dichloro-
methane and separated by column chromatography (light petroleum/
ethyl acetate 5/1) to give 6a and 7a in 53% and 35% yields,
respectively, relative to the starting alcohol 4d.
b
1
4. Determined by H NMR spectroscopy.
than the others. It is reasonable to expect that the oxidation of the
primary benzyl alcohols 4 initially affords peroxybenzoic acids 7,
which then undergo decomposition to benzoic acids 6 to the
extent that is specific for each present ruthenium complex 3. An
independent experiment where an authentic sample of perester
7a was subjected to the same reaction conditions as described for
the alcohol oxidation (Table 8, footnote a) did not support this
idea, as unreacted 7a was completely recovered from the reaction
mixture, with benzoic acid 6a being undetected. In addition, an
alternative that under the applied reaction conditions peresters 7
are formed from benzoic acids 6 was also ruled out by an
analogous experiment with 6a in place of 7a.
reaction conditions only minute amounts of cyclohexanone (5c)
formed from cyclohexanol (4c) indicates the selectivity this
catalytic system could potentially offer (Table 7, entry 9). Mild
reaction conditions requiring the environmentally benign solvent
water as well as the above indicated selectivity make our catalytic
system superior to some previously known imidazol-2-ylidene-
based complexes.35
A potential catalyst recycling was probed with complex 3Aa
(0.0005 mmol, 0.1 mol %), TBHP (2.0 mmol, 4 equiv), and 1-
phenylethanol (4a, 0.5 mmol) as substrate. After the reaction
mixture was stirred for 3 h at room temperature (Table 7, entry
1), the product was isolated by extraction into diethyl ether. For
subsequent cycles new portions of 1-phenylethanol (0.5 mmol)
and TBHP (2.0 mmol) were added to the water layer and the
reaction continued as described above. The conversions were
assayed by 1H NMR analyses of the organic layers to reach 100%,
72%, 51%, 33%, and 28% after each consecutive cycle. Although
the loss of structural integrity of the catalysts can be attributed to
the drop in the 1-phenylethanol (4a) to acetophenone (5a)
conversion, a steady decrease in its concentration in the reaction
mixture caused by the extractive workup over the cycles cannot
be ruled out at this point.
CONCLUSIONS
■
The scope of the pyridine-functionalized 1,2,3-triazolium salts as
N-heterocyclic carbene (trzNHC) precursors for bidentate
coordination to ruthenium(II) through the CNHC and Npyridyl
donors was investigated. In two consecutive steps, in the
formation of the intermediate silver carbene complex and in the
transmetalation with [Ru(η6-p-cymene)Cl2]2 into cationic [Ru-
(η6-p-cymene)(trzNHC)Cl]+ complexes, both 1-(2-pyridyl)-
and 4-(2-pyridyl)-substituted triazolium salts reacted similarly.
In contrast, the reactivity of 1-(2-picolyl) and 4-(2-picolyl)
analogues turned out to be completely different, demonstrating
the large impact of the linker between the pyridine and trzNHC
donors in ruthenium(II) coordination. NMR spectroscopic data
indicate significant modulation of the electronic properties of the
carbene center, suggesting the potential of the ligand to fine tune
the properties of [Ru(η6-p-cymene)(trzNHC)Cl]+ complexes. A
preliminary catalytic activity screening of these compounds in
TBHP oxidation of the selected primary and secondary alcohols
into the carbonyl compounds was surveyed. Although in this
particular reaction no change in the catalytic activity between the
structurally different complexes could be observed, a consid-
Surprisingly, under the same reaction conditions, a primary
benzyl alcohol (4d) was oxidized into a mixture of benzoic acid
(6a) and tert-butyl esters of peroxybenzoic acids (7a) (Table 8,
entries 1−5). No other products could be detected in the crude
reaction mixtures. Analogous results afforded phenyl-substituted
benzyl alcohols (4e−g, entries 6−8). To our knowledge, no such
transformation to tert-butyl peresters has been reported in the
literature. Recently, Wan et al. communicated a new synthesis of
these compounds from aldehydes and TBHP via Bu4NI-
catalyzed aldehyde C−H oxidation.36
In Table 8 it is intriguing that there are different ratios between
the products 6 and 7, with those in entries 3 and 6 being higher
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Rf(CH2Cl2/MeOH 10/1) = 0.2. Mp: 69−71 °C. IR: 2966, 1615, 1474,
erably faster benzylic oxidation in comparison to nonbenzylic
alcohol oxidation was demonstrated.
1
1255, 1223, 1150, 1029, 779, 704, 636 cm−1. H NMR (500 MHz,
CDCl3): δ 0.97 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.05 (d, J = 6.9 Hz, 3H,
(CH3)2CH), 1.99 (s, 3H, CH3Cym), 2.53 (dsept, J = 6.9 Hz, 1H,
(CH3)2CH), 4.30 (s, 3H, CH3−N-3), 5.11 (d, J = 5.9 Hz, 1H, ArHCym),
5.46 (dd, J = 6.2, 0.7 Hz, 1H, ArHCym), 5.64 (d, J = 5.8 Hz, 1H, ArHCym),
5.67 (d, J = 5.9 Hz, 1H, ArHCym), 7.70−7.66 (m, 4H, H-5′, H-3″, H-4″,
H-5″), 7.93−7.91 (m, 2H, H-2″, H-6″), 8.18−8.14 (m, 2H, H-3′, H-4′),
9.35 (d, J = 5.6 Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.7
(CH3Cym), 21.7 ((CH3)2CH), 22.5 ((CH3)2CH), 31.1 ((CH3)2CH),
38.5 (CH3−N-3), 84.4 (ArCym), 85.8 (ArCym), 87.7 (ArCym), 90.2
(ArCym), 101.6 (ArCym), 108.7 (ArCym), 114.3 (C-3′), 126.3 (C-5′),
126.4 (C-1″), 129.5 (C-3″, C-5″), 130.7 (C-2″, C-6″), 131.2 (C-4″),
141.2 (C-4′), 147.6 (C-4), 150.3 (C-2′), 156.0 (C-6′), 169.5 (C-5). 15N
NMR (51 MHz, CDCl3): δ 226 (N-1′), 240 (N-3), 264 (N-1), 334 (N-
2). 19F NMR (471 MHz, CDCl3): δ −78.2 (s, 3F, TfO−). HRMS (ESI
+): calcd for C24H26ClN4Ru+ [M]+ 507.0890, found 507.0887. Anal.
Calcd for C25H26ClF3N4O3RuS·2H2O: C, 43.38; H, 4.37; N, 8.10.
Found: C, 43.12; H, 3.71; N, 8.08.
3Ab (R = Me). Triazolium salt 1Ab (40.0 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 2 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Ab, 64.0 mg, 96%).
Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 66−68 °C. IR: 2963, 2926, 1616,
1480, 1255, 1223, 1151, 1029, 832, 779, 754, 635 cm−1. 1H NMR (500
MHz, CDCl3): δ 0.95 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.04 (d, J = 6.9
Hz, 3H, (CH3)2CH), 2.01 (s, 3H, CH3Cym), 2.54−2.50 (m, 4H, CH3,
(CH3)2CH), 4.29 (s, 3H, CH3−N-3), 5.07 (d, J = 6.0 Hz, 1H, ArHCym),
5.50 (d, J = 6.1 Hz, 1H, ArHCym), 5.62 (d, J = 6.0 Hz, 1H, ArHCym), 5.71
(d, J = 6.1 Hz, 1H, ArHCym), 7.48 (d, J = 7.8 Hz, 2H, H-3″, H-5″), 7.68
(dt, J = 6.3, 1.6 Hz, H-5′), 7.77 (d, J = 8.0 Hz, 2H, H-2″, H-6″), 8.15−
8.12 (m, 2H, H-3′, H-4′), 9.40 (d, J = 5.5 Hz, 1H, H-6′). 13C NMR (126
MHz, CDCl3): δ 18.8 (CH3Cym), 21.7 (CH3-C-4″), 21.8 ((CH3)2CH),
22.5 ((CH3)2CH), 31.1 ((CH3)2CH), 38.4 (CH3-N-3), 83.6 (ArCym),
85.9 (ArCym), 87.6 (ArCym), 90.4 (ArCym), 102.7 (ArCym), 108.6 (ArCym),
114.1 (C-3′), 123.2 (C-1″), 126.6 (C-5′), 130.2 (C-3″, C-5″), 130.5 (C-
2″, C-6″), 141.2 (C-4′), 141.6 (C-4″), 147.7 (C-4), 150.1 (C-2′), 156.3
(C-6′), 169.5 (C-5). 15N NMR (51 MHz, CDCl3): δ 226 (N-1′), 240
(N-3), 334 (N-2). 19F NMR (471 MHz, CDCl3): δ −78.2 (s, 3F, TfO−).
HRMS (ESI+): calcd for C25H28ClN4Ru+ [M]+ 521.1046, found
521.1040. Anal. Calcd for C26H28ClF3N4O3RuS·2H2O: C, 44.22; H,
4.57; N, 7.93. Found: C, 43.96; H, 3.85; N, 7.61.
3Ac (R = OMe). Triazolium salt 1Ac (41.6 mg, 0.10 mmol), Ag2O
(34.5 mg, 0.15 mmol), MeCN (4 mL), Time 1 = 5 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Ac, 63.0 mg, 92%).
Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 76−78 °C. IR: 2963, 1614, 1478,
1253, 1223, 1150, 1029, 843, 779, 754, 636 cm−1. 1H NMR (500 MHz,
CDCl3): δ 0.97 (d, J = 7.0 Hz, 3H, (CH3)2CH), 1.05 (d, J = 6.9 Hz, 3H,
(CH3)2CH), 2.01 (s, 3H, CH3Cym), 2.54 (dsept, J = 6.9 Hz, 1H,
(CH3)2CH), 3.95 (s, 3H, OCH3), 4.28 (s, 3H, CH3−N-3), 5.09 (d, J =
6.0 Hz, 1H, ArHCym), 5.48 (dd, J = 6.2, 0.7 Hz, 1H, ArHCym), 5.65 (d, J =
6.0 Hz, 1H, ArHCym), 5.71 (d, J = 5.9 Hz, 1H, ArHCym), 7.19 (d, J = 8.9
Hz, 2H, H-3″, H-5″), 7.67 (ddd, J = 6.5, 5.8, 2.2 Hz, H-5′), 7.83 (d, J =
8.6 Hz, 2H, H-2″, H-6″), 8.17−8.12 (m, 2H, H-3′, H-4′), 9.36 (d, J = 5.5
Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.8 (CH3Cym), 21.8
((CH3)2CH), 22.5 ((CH3)2CH), 31.1 ((CH3)2CH), 38.4 (CH3-N-3),
55.6 (OCH3), 83.8 (ArCym), 85.9 (ArCym), 87.6 (ArCym), 90.4 (ArCym),
102.2 (ArCym), 108.6 (ArCym), 114.2 (C-3′), 114.9 (C-3″, C-5″), 118.1
(C-1″), 126.4 (C-5′), 132.2 (C-2″, C-6″), 141.2 (C-4′), 147.6 (C-4),
150.3 (C-2′), 156.1 (C-6′), 161.7 (C-4″), 169.3 (C-5). 15N NMR (51
MHz, CDCl3): δ 226 (N-1′), 240 (N-3), 264 (N-1), 334 (N-2). 19F
NMR (471 MHz, CDCl3): δ −78.2 (s, 3F, TfO−). HRMS (ESI+): calcd
for C25H28ClN4ORu+ [M]+ 537.0995, found 537.0987. Anal. Calcd for
C26H28ClF3N4O4RuS·H2O: C, 44.35; H, 4.29; N, 7.96. Found: C, 44.58;
H, 3.81; N, 7.56.
EXPERIMENTAL SECTION
■
The reagents and solvents were used as obtained from commercial
sources (Sigma-Aldrich). Acetonitrile was dried over 3 Å molecular
sieves. The compounds 118 and Ag2O37 were prepared as described in
the literature. The compounds 5a,32,26 5b,32 5c,32 6a,38 6b,39 6c,d,40 and
7a,c,d36 were (after extractive workup from the crude reaction mixtures
by using dichloromethane) identified by comparison of their 1H NMR
spectral data to the literature reports. The tert-butyl perester structure of
7b was assigned on the basis of NMR spectral data comparison with
7a,c,d and HRMS spectra.
NMR spectra were measured with a 300, 400, and 500 MHz
spectrometers, using Si(CH3)4 as internal standard. The nitrogen
chemical shifts were extracted from 1H−15N HMBC spectra. Proton and
carbon spectra were referenced to TMS as the internal standard. Some
13C chemical shifts were determined relative to the 13C signal of the
solvent: CDCl3 (77.0 ppm), DMSO-d6 (39.5 ppm). 19F NMR, 11B
NMR, and 31P NMR spectra were referenced to CCl3F, 15% BF3
etherate in CDCl3, and 85% phosphoric acid, respectively, as external
standards at δ 0. 15N chemical shifts were extracted from H−15N
1
HMBC spectra (with 20 Hz digital resolution in the indirect dimension)
with respect to external 90% CH3NO2 in CDCl3 and are corrected to
external ammonia by addition of 380.5 ppm. Chemical shifts are given
on the δ scale (ppm). Coupling constants (J) are given in Hz. The
multiplicities are indicated as follows: s (singlet), d (doublet), t (triplet),
q (quartet), sept (septet), and m (multiplet). Assignments of proton,
carbon, and nitrogen resonances were performed by standard 2D NMR
techniques (1H−1H COSY, 1H−13C HSQC, 1H−13C HMBC, 1H−15N
HMBC).
A time-of-flight (TOF) mass spectrometer equipped with a double
orthogonal electrospray source at atmospheric pressure ionization (ESI)
coupled to an HPLC instrument was used for recording HRMS spectra.
Elemental analyses were performed with a CHNS/O analyzer. IR
spectra were obtained with an ATR as a solid sample support. Melting
points were determined on a Kofler micro hot stage instrument. The
reactions were monitored by TLC on TLC-CARDS silica gel, 220−440
mesh.
Diffraction data for 3Bf were collected at 150 K with a dual source
using an Atlas detector and equipped with mirror-monochromated Cu
Kα radiation (λ = 1.54184 Å) (University of Ljubljana). Crystal
structures of 3Aa and 3Ca were measured at 140(2) K using a graphite-
monochromated Mo Kα (λ = 0.71073 Å) radiation source (Freie
Universitat Berlin). The data for 3Bf were processed by using CrysAlis
̈
PRO.41 The data collection strategy for 3Aa and 3Ca was evaluated by
using Smart software. Data were recorded using standard ω-scan
techniques, and the data were reduced and scaled using Saint+ software.
The structures were solved by direct methods42 and refined by a full-
matrix least-squares procedure based on F2 using SHELXL-97.43 All
hydrogen atoms were included in the model at geometrically calculated
positions and refined using a riding model. CCDC 978664, 969025, and
978665 contain CIF files for the 3Bf, 3Aa, and 3Ca, respectively. These
data can be obtained free of charge from www.ccdc.cam.ac.uk/data_
requests/cif. Due to refinement problems, the deuterium atom in 3Bf
was refined as a normal hydrogen atom.
General Procedure for the Preparation of 3Aa−g and 3Ba−f.
A mixture of the triazolium salt 1Aa−g or 1Ba−f and Ag2O in
acetonitrile was purged with argon gas and stirred in the dark at room
temperature for Time 1 (Table 1 or 2). After the addition of [Ru(η6-p-
cymene)Cl2]2 the stirring was continued for 2 h (Time 2) and filtered
through Celite. The solvent was removed in vacuo, and the residue was
crystallized from chloroform (1−2 mL) with slow addition of hexane to
give the pure 3Aa−g or 3Ba−f. For quantities used in the above
procedure and analytical and spectral data of 3Aa−g and 3Ba−f, see
below.
3Ad (R = CN). Triazolium salt 1Ad (41.1 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 2 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Ad, 62.0 mg, 91%).
Rf(CH2Cl2/MeOH 10/1) = 0.4. Mp: 112−114 °C. IR: 3128, 2966,
2320, 1723, 1615, 1417, 1324, 1258, 1147, 1029, 826, 784, 742, 636
cm−1. 1H NMR (500 MHz, CDCl3): δ 0.97 (d, J = 6.9 Hz, 3H,
3Aa (R = H). Triazolium salt 1Aa (38.6 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 3 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Aa, 56.0 mg, 86%).
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(CH3)2CH), 1.03 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.98 (s, 3H, CH3Cym),
2.52 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 4.34 (s, 3H, CH3−N-3), 5.08
(d, J = 6.3 Hz, 1H, ArHCym), 5.45 (d, J = 6.3 Hz, 1H, ArHCym), 5.70 (t, J =
5.6 Hz, 2H, ArHCym), 7.66 (dt, J = 5.5, 3.4 Hz, H-5′), 7.98 (d, J = 8.5 Hz,
2H, H-3″, H-5″), 8.22−8.17 (m, 4H, H-4′, H-3′, H-2″, H-6″), 9.28 (d, J
= 5.7 Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.6 (CH3Cym),
21.7 ((CH3)2CH), 22.5 ((CH3)2CH), 31.1 ((CH3)2CH), 38.9 (CH3-N-
3), 85.0 (ArCym), 86.4 (ArCym), 87.2 (ArCym), 90.7 (ArCym), 100.9
(ArCym), 108.7 (ArCym), 114.5 (C-3′), 114.9 (C-4″), 117.8 (CN), 126.3
(C-5′), 131.1 (C-1″), 131.9 (C-2″, C-6″), 133.0 (C-3″, C-5″), 141.5 (C-
4′), 146.1 (C-4), 150.3 (C-2′), 155.6 (C-6′), 170.1 (C-5). 15N NMR (51
MHz, CDCl3): δ 225 (N-1′), 241 (N-3), 264 (N-1), 336 (N-2). 19F
NMR (471 MHz, CDCl3): δ −78.3 (s, 3F, TfO−). HRMS (ESI+): calcd
for C25H25ClN5Ru+ [M]+ 532.0842, found 532.0835. Anal. Calcd for
C26H25ClF3N5O3RuS·1.5H2O: C, 44.10; H, 3.99; N, 9.89. Found: C,
43.56; H, 3.41; N, 9.53.
4.2, 2.0 Hz, 2H, H-4′, H-3′), 8.31 (d, J = 8.0 Hz, 2H, H-2″, H-6″), 8.53
(d, J = 8.9 Hz, 2H, H-3″, H-5″), 9.26 (d, J = 5.5 Hz, 1H, H-6′). 13C NMR
(126 MHz, CDCl3): δ 18.6 (CH3Cym), 21.7 ((CH3)2CH), 22.7
((CH3)2CH), 31.1 ((CH3)2CH), 39.0 (CH3-N-3), 85.1 (ArCym), 86.4
(ArCym), 87.2 (ArCym), 90.7 (ArCym), 100.7 (ArCym), 108.8 (ArCym),
114.6 (C-3′), 124.4 (C-3″, C-5″), 126.3 (C-5′), 132.4 (C-2″, C-6″),
132.9 (C-1″), 141.4 (C-4′), 145.8 (C-4), 149.3 (C-4″), 150.4 (C-2′),
155.5 (C-6′), 170.2 (C-5). 15N NMR (51 MHz, CDCl3): δ 225 (N-1′),
241 (N-3), 264 (N-1), 337 (N-2), 367 (NO2). 19F NMR (471 MHz,
CDCl3): δ −78.3 (s, 3F, TfO−). HRMS (ESI+): calcd for
C24H25ClN5O2Ru+ [M]+ 552.0740, found 552.0729. Anal. Calcd for
C25H25ClF3N5O5RuS·1.5H2O: C, 41.24; H, 3.88; N, 9.52. Found: C,
41.03; H, 3.46; N, 9.35.
3Ba (R = H). Triazolium salt 1Ba (32.4 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 4 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Orange-yellow solid (3Ba, 58.0
mg, 78%). Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 101−103 °C. IR: 2967,
1617, 1498, 1460, 1326, 1286, 1050, 1033, 772, 749, 697, 671 cm−1. 1H
NMR (400 MHz, CDCl3): δ 1.00 (d, J = 7.0 Hz, 3H, (CH3)2CH), 1.08
(d, J = 6.9 Hz, 3H, (CH3)2CH), 2.01 (s, 3H, CH3Cym), 2.51 (dsept, J =
6.9 Hz, 1H, (CH3)2CH), 4.36 (s, 3H, CH3-N-3), 4.86 (d, J = 5.8 Hz, 1H,
ArHCym), 5.29 (d, J = 6.1 Hz, 1H, ArHCym), 5.48 (dd, J = 12.8, 6.0 Hz,
2H, ArHCym), 7.46 (ddd, J = 7.2, 5.7, 1.5 Hz, 1H, H-5′), 7.74−7.69 (m,
3H, H-3″, H-4″, H-5″), 8.09−8.02 (m, 4H, H-3′, H-4′, H-2″, H-6″),
9.39 (d, J = 5.5 Hz, 1H, H-6′). 13C NMR (100 MHz, CDCl3): δ 18.8
(CH3Cym), 21.6 ((CH3)2CH), 22.7 ((CH3)2CH), 31.2 ((CH3)2CH),
39.1 (CH3-N-3), 82.9 (ArCym), 86.0 (ArCym), 86.7 (ArCym), 90.2 (ArCym),
103.0 (ArCym), 108.5 (ArCym), 112.9 (C-3′), 125.4 (C-5′), 125.6 (C-2″,
C-6″), 129.8 (C-3″, C-5″), 131.2 (C-4″), 138.2 (C-1″), 139.5 (C-4′),
143.8 (C-4), 148.6 (C-2′), 157.3 (C-6′), 174.0 (C-5). 15N NMR (51
MHz, CDCl3): δ 231 (N-3), 243 (N-1′), 262 (N-1), 353 (N-2). 19F
NMR (471 MHz, CDCl3): δ −152.6 (d, J = 25 Hz, 4F, BF4). 11B NMR
3Ae (R = CF3). Triazolium salt 1Ae (45.4 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 2 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Ae, 64.7 mg, 89%).
Rf(CH2Cl2/MeOH 10/1) = 0.4. Mp: 76−78 °C. IR: 2966, 1729, 1616,
1481, 1324, 1256, 1224, 1156, 1069, 1029, 1015, 855, 779, 694, 637
cm−1. 1H NMR (500 MHz, CDCl3): δ 0.96 (d, J = 6.9 Hz, 3H,
(CH3)2CH), 1.04 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.97 (s, 3H, CH3Cym),
2.53 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 4.33 (s, 3H, CH3-N-3), 5.11 (d,
J = 6.1 Hz, 1H, ArHCym), 5.44 (d, J = 6.3 Hz, 1H, ArHCym), 5.69 (d, J =
6.6 Hz, 2H, ArHCym), 7.66 (q, J = 4.9 Hz, H-5′), 7.95 (d, J = 8.2 Hz, 2H,
H-3″, H-5″), 8.18 (t, J = 4.2 Hz, 4H, H-4′, H-3′, H-2″, H-6″), 9.31 (d, J =
5.6 Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.6 (CH3Cym), 21.7
((CH3)2CH), 22.4 ((CH3)2CH), 31.1 ((CH3)2CH), 38.7 (CH3−N-3),
85.0 (ArCym), 86.0 (ArCym), 87.6 (ArCym), 90.3 (ArCym), 101.1 (ArCym),
108.7 (ArCym), 114.4 (C-3′), 123.6 (q, J = 273 Hz, CF3), 126.3 (C-5′),
126.4 (q, J = 4 Hz, C-3″, C-5″), 130.2 (C-1″), 131.6 (C-2″, C-6″), 133.1
(q, J = 33 Hz, C-4″), 141.4 (C-4′), 146.4 (C-4), 150.3 (C-2′), 155.8 (C-
6′), 169.8 (C-5). 15N NMR (51 MHz, CDCl3): δ 226 (N-1′), 241 (N-3),
264 (N-1), 336 (N-2). 19F NMR (471 MHz, CDCl3): δ −62.9 (s, 3F,
CF3), −78.3 (s, 3F, TfO−). HRMS (ESI+): calcd for C25H25ClF3N4Ru+
[M]+ 575.0763, found 575.0758. Anal. Calcd for C26H25ClF6N4O3RuS·
H2O: C, 42.08; H, 3.67; N, 7.55. Found: C, 41.89; H, 3.48; N, 7.15.
3Af (R = Br). Triazolium salt 1Af (46.5 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 2 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Af, 71.0 mg, 97%).
Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 69−71 °C. IR: 2965, 1614, 1471,
1255, 1223, 1150, 1069, 1028, 1009, 838, 778, 753, 635 cm−1. 1H NMR
(500 MHz, CDCl3): δ 0.99 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.06 (d, J =
6.9 Hz, 3H, (CH3)2CH), 1.99 (s, 3H, CH3Cym), 2.54 (dsept, J = 6.9 Hz,
1H, (CH3)2CH), 4.30 (s, 3H, CH3-N-3), 5.12 (d, J = 6.1 Hz, 1H,
ArHCym), 5.45 (d, J = 6.3 Hz, 1H, ArHCym), 5.70 (t, J = 4.7 Hz, 2H,
ArHCym), 7.65 (q, J = 5.0 Hz, H-5′), 7.83 (d, J = 8.6 Hz, 2H, H-3″, H-5″),
7.87 (d, J = 8.2 Hz, 2H, H-2″, H-6″), 8.16 (d, J = 4.0 Hz, 2H, H-4′, H-3′),
9.30 (d, J = 5.6 Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.7
(CH3Cym), 21.8 ((CH3)2CH), 22.5 ((CH3)2CH), 31.1 ((CH3)2CH),
38.6 (CH3−N-3), 84.7 (ArCym), 86.0 (ArCym), 87.6 (ArCym), 90.3
(ArCym), 101.2 (ArCym), 108.8 (ArCym), 114.4 (C-3′), 125.3 (C-1″),
125.9 (C-4″), 126.3 (C-5′), 132.5 (C-2″, C-6″), 132.8 (C-3″, C-5″),
141.3 (C-4′), 146.7 (C-4), 150.4 (C-2′), 155.7 (C-6′), 169.5 (C-5). 15N
NMR (51 MHz, CDCl3): δ 226 (N-1′), 241 (N-3), 335 (N-2). 19F NMR
(471 MHz, CDCl3): δ −78.3 (s, 3F, TfO−). HRMS (ESI+): calcd for
C24H25BrClN4Ru+ [M]+ 586.9995, found 586.9970. Anal. Calcd for
C25H25BrClF3N4O3RuS·2H2O: C, 38.94; H, 3.79; N, 7.27. Found: C,
38.50; H, 3.25; N, 6.95.
−
(160 MHz, CDCl3): δ −1.2 (s, 1B, BF4 ). HRMS (ESI+): calcd for
C24H26ClN4Ru+ [M]+ 507.0884, found 507.0883. Anal. Calcd for
C24H26BClF4N4Ru·2.5H2O: C, 45.12; H, 4.89; N, 8.77. Found: C,
45.09; H, 4.00; N, 8.64.
3Bb (R = CH3). Triazolium salt 1Bb (33.8 mg, 0.10 mmol), Ag2O
(34.5 mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 3 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Bb, 49.4 mg, 81%).
Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 112−114 °C. IR: 2965, 1616,
1515, 1459, 1325, 1049, 1033, 779, 750, 708 cm−1. 1H NMR (400 MHz,
CDCl3): δ 0.95 (d, J = 7.0 Hz, 3H, (CH3)2CH), 1.03 (d, J = 6.9 Hz, 3H,
(CH3)2CH), 2.03 (s, 3H, CH3Cym), 2.50 (dsept, J = 6.9 Hz, 1H,
(CH3)2CH), 2.54 (s, 3H, CH3), 4.58 (s, 3H, CH3-N-3), 4.81 (d, J = 5.8
Hz, 1H, ArHCym), 5.31 (d, J = 6.7 Hz, 1H, ArHCym), 5.42 (d, J = 5.9 Hz,
1H, ArHCym), 5.54 (d, J = 6.1 Hz, 1H, ArHCym), 7.47−7.43 (m, 3H, H-5′,
H-3″, H-5″), 7.90 (d, J = 8.9 Hz, 2H, H-2″, H-6″), 8.06−7.99 (m, 2H, H-
3′, H-4′), 9.41 (d, J = 5.5 Hz, 1H, H-6′). 13C NMR (100 MHz, CDCl3):
δ 18.9 (CH3Cym), 21.5 (CH3-C-4″), 21.6 ((CH3)2CH), 22.7
((CH3)2CH), 31.2 ((CH3)2CH), 39.3 (CH3-N-3), 82.5 (ArCym), 86.0
(ArCym), 86.8 (ArCym), 90.3 (ArCym), 103.6 (ArCym), 108.3 (ArCym),
121.9 (C-3′), 125.2 (C-2″, C-6″), 125.5 (C-5′), 130.3 (C-3″, C-5″),
135.7 (C-1″), 139.5 (C-4′), 141.7 (C-4″), 143.8 (C-4), 148.5 (C-2′),
157.4 (C-6′), 173.8 (C-5). 15N NMR (51 MHz, CDCl3): δ 230 (N-3),
242 (N-1′), 263 (N-1), 353 (N-2). 19F NMR (471 MHz, CDCl3): δ
−152.6 (d, J = 25 Hz, 4F, BF4).11B NMR (160 MHz, CDCl3): δ −1.0 (s,
−
1B, BF4 ). HRMS (ESI+): calcd for C25H28ClN4Ru+ [M]+ 521.1046,
found 521.1036. Anal. Calcd for C25H28BClF4N4Ru·1.5H2O: C, 47.30;
H, 4.92; N, 8.82. Found: C, 47.16; H, 4.51; N, 9.27.
3Bc (R = OCH3). Triazolium salt 1Bc (35.4 mg, 0.10 mmol), Ag2O
(34.5 mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 6 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Bc, 56.8 mg, 91%).
Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 111−113 °C. IR: 2965, 1616,
1514, 1461, 1324, 1050, 1029, 842, 779, 751, 604 cm−1. 1H NMR (500
MHz, CDCl3): δ 0.96 (d, J = 7.0 Hz, 3H, (CH3)2CH), 1.04 (d, J = 6.8
Hz, 3H, (CH3)2CH), 2.02 (s, 3H, CH3Cym), 2.46 (dsept, J = 7.0 Hz, 1H,
(CH3)2CH), 3.96 (s, 3H, OCH3), 4.57 (s, 3H, CH3-N-3), 4.83 (d, J = 5.8
Hz, 1H, ArHCym), 5.30 (dd, J = 6.1, 1.3 Hz, 1H, ArHCym), 5.45 (d, J = 5.2
Hz, 1H, ArHCym), 5.54 (d, J = 6.9 Hz, 1H, ArHCym), 7.15 (d, J = 8.9 Hz,
2H, H-3″, H-5″), 7.43 (ddd, d, J = 7.2, 5.6, 1.7 Hz, 1H, H-5′), 7.94 (d, J =
3Ag (R = NO2). Triazolium salt 1Ag (43.1 mg, 0.10 mmol), Ag2O
(34.5 mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 2 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow solid (3Ag, 59.5 mg, 85%).
Rf(CH2Cl2/MeOH 10/1) = 0.6. Mp: 107−109 °C. IR: 2967, 1605,
1571, 1522, 1475, 1345, 1257, 1223, 1151, 1029, 866, 854, 779, 636
cm−1. 1H NMR (500 MHz, CDCl3): δ 0.99 (d, J = 6.9 Hz, 3H,
(CH3)2CH), 1.04 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.99 (s, 3H, CH3Cym),
2.54 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 4.36 (s, 3H, CH3-N-3), 5.10 (d,
J = 6.0 Hz, 1H, ArHCym), 5.45 (d, J = 6.2 Hz, 1H, ArHCym), 5.72 (dd, J =
10.4, 6.2 Hz, 2H, ArHCym), 7.66 (td, J = 5.7, 3.1 Hz, H-5′), 8.20 (dd, J =
2595
dx.doi.org/10.1021/om500287t | Organometallics 2014, 33, 2588−2598

Organometallics
Article
8.9 Hz, 2H, H-2″, H-6″), 8.05−8.00 (m, 2H, H-3′, H-4′), 9.38 (d, J = 5.2
Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.8 (CH3Cym), 21.6
((CH3)2CH), 22.7 ((CH3)2CH), 31.2 ((CH3)2CH), 39.2 (CH3-N-3),
55.9 (OCH3), 82.5 (ArCym), 85.9 (ArCym), 86.8 (ArCym), 90.2 (ArCym),
103.2 (ArCym), 108.4 (ArCym), 114.8 (C-3″, C-5″), 121.9 (C-3′), 125.4
(C-5′), 126.9 (C-2″, C-6″), 131.0 (C-1″), 139.5 (C-4′), 143.6 (C-4),
148.6 (C-2′), 157.3 (C-6′), 161.5 (C-4″), 173.8 (C-5). 15N NMR (51
MHz, CDCl3): δ 230 (N-3), 243 (N-1′), 262 (N-1), 353 (N-2). 19F
NMR (471 MHz, CDCl3): δ −152.5 (d, J = 25 Hz, 4F, BF4). 11B NMR
Hz, 1H, ArHCym), 5.53 (dd, J = 6.1, 1.4 Hz, 1H, ArHCym), 7.44 (ddd, d, J
= 6.8, 5.8, 2.3 Hz, 1H, H-5′), 7.81 (d, J = 8.7 Hz, 2H, H-3″, H-5″), 8.00
(m, 4H, H-3′, H-4′, H-2″, H-6″), 9.34 (dd, J = 5.7, 1.3 Hz, 1H, H-6′).
13C NMR (126 MHz, CDCl3): δ 18.7 (CH3Cym), 21.5 ((CH3)2CH),
22.8 ((CH3)2CH), 31.2 ((CH3)2CH), 39.3 (CH3-N-3), 83.2 (ArCym),
86.0 (ArCym), 86.9 (ArCym), 89.9 (ArCym), 102.2 (ArCym), 109.4 (ArCym),
121.9 (C-3′), 125.2 (C-5′), 140.5 (C-1″), 127.2 (C-2″, C-6″), 133.0 (C-
3″, C-5″), 137.1 (C-4″), 139.4 (C-4′), 144.0 (C-4), 148.9 (C-2′), 156.9
(C-6′), 174.0 (C-5). 15N NMR (51 MHz, CDCl3): δ 231 (N-3), 243 (N-
1′), 260 (N-1), 354 (N-2). 19F NMR (471 MHz, CDCl3): δ −153.0 (d, J
−
(160 MHz, CDCl3): δ −1.1 (s, 1B, BF4 ). HRMS (ESI+): calcd for
C25H28ClN4ORu+ [M]+ 537.0995, found 537.0991. Anal. Calcd for
C25H28BClF4N4ORu·1.5H2O: C, 46.13; H, 4.80; N, 8.61. Found: C,
46.17; H, 4.55; N, 9.00.
−
= 25 Hz, 4F, BF4 ). 11B NMR (160 MHz, CDCl3): δ −1.2 (s, 1B, BF4).
HRMS (ESI+): calcd for C24H25BrClN4Ru+ [M]+ 584.9995, found
584.9971. Anal. Calcd for C24H25BBrClF4N4Ru·H2O: C, 41.73; H, 3.94;
N, 8.11. Found: C, 41.42; H, 3.46; N, 8.06.
3Bd (R = CN). Triazolium salt 1Bd (34.9 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 7 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Orange-yellow solid (3Bd, 49.0
mg, 80%). Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 135−137 °C. IR: 2966,
2232, 1672, 1608, 1508, 1477, 1326, 1285, 1050, 1002, 853, 778, 749
cm−1. 1H NMR (500 MHz, CDCl3): δ 1.05 (d, J = 7.0 Hz, 3H,
(CH3)2CH), 1.11 (d, J = 7.1 Hz, 3H, (CH3)2CH), 2.00 (s, 3H, CH3Cym),
2.56 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 4.63 (s, 3H, CH3-N-3), 4.93 (d,
J = 5.9 Hz, 1H, ArHCym), 5.27 (d, J = 6.2 Hz, 1H, ArHCym), 5.47 (d, J =
5.9 Hz, 1H, ArHCym), 5.60 (d, J = 5.9 Hz, 1H, ArHCym), 7.47 (ddd, d, J =
7.2, 5.7, 1.6 Hz, 1H, H-5′), 8.00 (d, J = 8.6 Hz, 2H, H-3″, H-5″), 8.07 (td,
J = 7.7, 1.4 Hz, 2H, H-3′, H-4′), 8.35 (d, J = 8.6 Hz, 2H, H-2″, H-6″),
9.33 (d, J = 5.6 Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.7
(CH3Cym), 21.6 ((CH3)2CH), 22.7 ((CH3)2CH), 31.2 ((CH3)2CH),
39.5 (CH3-N-3), 83.8 (ArCym), 86.3 (ArCym), 86.6 (ArCym), 90.1 (ArCym),
101.9 (ArCym), 109.3 (ArCym), 115.2 (C-1″), 117.0 (CN), 121.9 (C-3′),
125.4 (C-5′), 126.6 (C-2″, C-6″), 133.7 (C-3″, C-5″), 139.6 (C-4′),
141.4 (C-4″), 144.2 (C-4), 148.8 (C-2′), 157.0 (C-6′), 174.4 (C-5). 15N
NMR (51 MHz, CDCl3): δ 233 (N-3), 242 (N-1′), 259 (N-1), 353 (N-
General Procedure for the Preparation of 3Ca−e,h. A mixture
of the triazolium salt 1Ca−e,h and Ag2O in acetonitrile was purged with
argon gas and stirred in the dark at 60 °C for Time 1 (Table 3). The
reaction mixture was cooled to room temperature. [Ru(η6-p-cymene)-
Cl2]2 was added, and the reaction mixture was stirred for Time 2 (Table
3) and then filtered through Celite. The solvent was removed in vacuo,
and the residue was subjected to flash column chromatography on silica
using hexane and a mixture of acetone and dichloromethane (1/1) as
eluent. The products 3Ca−e,h were recrystallized from chloroform (1−
2 mL) with slow addition of hexane. For quantities used in the above
procedure and analytical and spectral data of 3Ca−e,h, see below.
3Ca (R = H). Triazolium salt 1Ca (39.6 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 4 h, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol), Time 2 = 2 days. Yellow solid
(3Ca, 33.0 mg, 50%). Rf(CH2Cl2/MeOH 10/1) = 0.4. Mp: 103−105
°C. IR: 2922, 2851, 1608, 1442, 1304, 1162, 1077, 1023, 830, 770, 702
cm−1. 1H NMR (500 MHz, CDCl3): δ 0.82 (d, J = 7.0 Hz, 3H,
(CH3)2CH), 1.13 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.64 (s, 3H, CH3Cym),
2.25−2.19 (m, 1H, (CH3)2CH), 3.95 (s, 3H, CH3-N-3), 5.25 (dd, J =
6.1, 0.6 Hz, 1H, ArHCym), 5.39 (dd, J = 6.1, 0.6 Hz, 1H, ArHCym), 5.50−
5.47 (m, 2H, ArHCym, CH2), 5.69 (dd, J = 6.1, 0.6 Hz, 1H, ArHCym), 5.82
(d, J = 16.0 Hz, 1H, CH2), 7.46−7.43 (m, 1H, H-5′), 7.58 (dt, J = 6.4, 3.1
Hz, 4H, H-3′, H-3″, H-4″, H-5″), 7.84 (dd, J = 6.6, 3.0 Hz, 2H, H-2″, H-
6″), 7.92 (dt, J = 7.7, 1.5 Hz, 1H, H-4′), 9.53 (dd, J = 5.7, 1.2 Hz, 1H, H-
6′). 13C NMR (126 MHz, CDCl3): δ 18.1 (CH3Cym), 21.9 ((CH3)2CH),
22.8 ((CH3)2CH), 31.2 ((CH3)2CH), 37.2 (CH3-N-3), 56.9 (CH2),
86.0 (ArCym), 86.3 (ArCym), 86.6 (ArCym), 89.1 (ArCym), 97.6 (ArCym),
107.3 (ArCym), 124.8 (C-5′), 125.4 (C-3′), 126.9 (C-1″), 128.8 (C-2″,
C-6″), 130.4 (C-4″), 131.5 (C-3″, C-5″), 139.5 (C-4′), 148.7 (C-4),
154.6 (C-2′), 159.2 (C-6′), 159.6 (C-5). 15N NMR (51 MHz, CDCl3): δ
235 (N-1′), 237 (N-3), 246 (N-1), 345 (N-2). 19F NMR (471 MHz,
CDCl3): δ −73.5 (d, J = 713 Hz, 6F, PF6). 31P NMR (202 MHz,
CDCl3): δ −144.6 (sept, J = 713 Hz, 1P, PF6). HRMS (ESI+): calcd for
C25H28ClN4Ru+ [M]+ 521.1046, found 521.1040. Anal. Calcd for
C25H28ClF6N4PRu·2H2O: C, 42.77; H, 4.59; N, 7.98. Found: C, 42.99;
H, 4.32; N, 7.50.
2). 19F NMR (471 MHz, CDCl3): δ −152.7 (d, J = 25 Hz, 4F, BF4). 11
B
−
NMR (160 MHz, CDCl3): δ −1.2 (s, 1B, BF4 ). HRMS (ESI+): calcd
for C25H25ClN5Ru+ [M]+ 532.0842, found 532.0834. Anal. Calcd for
C25H25BClF4N5Ru·H2O: C, 47.15; H, 4.27; N, 11.00. Found: C, 46.88;
H, 4.08; N, 10.69.
3Be (R = CF3). Triazolium salt 1Be (39.2 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 6 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yellow-brown solid (3Be, 47.3
mg, 72%). Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 103−105 °C. IR: 2965,
1663, 1615, 1322, 1169, 1051, 1002, 856, 779, 750 cm−1. 1H NMR (500
MHz, CDCl3): δ 1.00 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.07 (d, J = 7.0
Hz, 3H, (CH3)2CH), 1.99 (s, 3H, CH3Cym), 2.51 (dsept, J = 7.0 Hz, 1H,
(CH3)2CH), 4.61 (s, 3H, CH3-N-3), 4.89 (dd, J = 6.0, 1.3 Hz, 1H,
ArHCym), 5.26 (d, J = 6.2 Hz, 1H, ArHCym), 5.47 (d, J = 1.3 Hz, 1H,
ArHCym), 5.54 (d, J = 6.0 Hz, 1H, ArHCym), 7.46 (td, d, J = 5.7, 3.0 Hz,
1H, H-5′), 7.96 (d, J = 8.2 Hz, 2H, H-3″, H-5″), 8.04 (m, 2H, H-3′, H-
4′), 8.29 (d, J = 8.2 Hz, 2H, H-2″, H-6″), 9.35 (d, J = 5.6 Hz, 1H, H-6′).
13C NMR (126 MHz, CDCl3): δ 18.7 (CH3Cym), 21.5 ((CH3)2CH),
22.8 ((CH3)2CH), 31.2 ((CH3)2CH), 39.4 (CH3-N-3), 83.7 (ArCym),
86.1 (ArCym), 86.9 (ArCym), 89.8 (ArCym), 102.0 (ArCym), 109.4 (ArCym),
121.9 (C-3′), 123.3 (q, J = 273 Hz,CF3), 125.3 (C-5′), 126.2 (C-2″, C-
6″), 127.0 (q, J = 4 Hz,C-3″, C-5″), 133.2 (q, J = 34 Hz, C-4″), 139.5 (C-
4′), 140.9 (C-1″), 144.1 (C-4), 148.8 (C-2′), 157.0 (C-6′), 174.2 (C-5).
15N NMR (51 MHz, CDCl3): δ 232 (N-3), 243 (N-1′), 260 (N-1), 354
(N-2). 19F NMR (471 MHz, CDCl3): δ −62.7 (s, 3F, CF3), −152.9 (d, J
3Cb (R = Me). Triazolium salt 1Cb (40.9 mg, 0.10 mmol), Ag2O
(34.5 mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 8 h, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol), Time 2 = 2 days. Yellow solid
(3Cb, 30.6 mg, 45%). Rf(CH2Cl2/MeOH 10/1) = 0.6. Mp: 118−120
°C. IR: 2922, 2852, 1609, 1443, 1305, 1240, 1162, 1077, 1020, 833, 765,
1
692 cm−1. H NMR (500 MHz, CDCl3): δ 0.86 (d, J = 7.0 Hz, 3H,
(CH3)2CH), 1.13 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.68 (s, 3H, CH3Cym),
2.28 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 2.46 (s, 3H, CH3), 3.94 (s, 3H,
CH3-N-3), 5.25 (d, J = 6.0 Hz, 1H, ArHCym), 5.37 (dd, J = 6.1, 0.6 Hz,
1H, ArHCym), 5.49−5.45 (m, 2H, ArHCym, CH2), 5.66 (dd, J = 6.0, 0.7
Hz, 1H, ArHCym), 5.80 (d, J = 16.0 Hz, 1H, CH2), 7.38 (d, J = 7.9 Hz, 2H,
H-3″, H-5″), 7.45−7.42 (m, 1H, H-5′), 7.58 (d, J = 7.6 Hz, 1H, H-3′),
7.71 (d, J = 8.1 Hz, 2H, H-2″, H-6″), 7.92 (dt, J = 7.7, 1.5 Hz, 1H, H-4′),
9.51 (dd, J = 5.8, 1.2 Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ
18.2 (CH3Cym), 21.5 (CH3-C-4″), 22.0 ((CH3)2CH), 22.7
((CH3)2CH), 31.2 ((CH3)2CH), 37.2 (CH3-N-3), 56.9 (CH2), 85.9
(ArCym), 85.9 (ArCym), 86.7 (ArCym), 88.8 (ArCym), 97.9 (ArCym), 107.8
(ArCym), 123.9 (C-1″), 124.8 (C-5′), 125.4 (C-3′), 129.5 (C-3″, C-5″),
131.3 (C-2″, C-6″), 139.4 (C-4′), 140.6 (C-4″), 148.9 (C-4), 154.6 (C-
2′), 159.1 (C-6′), 159.6 (C-5). 15N NMR (51 MHz, CDCl3): δ 235 (N-
−
= 25 Hz, 4F, BF4). 11B NMR (160 MHz, CDCl3): δ −1.2 (s, 1B, BF4 ).
HRMS (ESI+): calcd for C25H25ClF3N4Ru+ [M]+ 575.0763, found
575.0758. Anal. Calcd for C25H25BClF7N4Ru·2H2O: C, 43.03; H, 4.19;
N, 8.03. Found: C, 42.59; H, 3.75; N, 8.48.
3Bf (R = Br). Triazolium salt 1Bf (40.2 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 3 days, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol). Yelow solid (3Bf, 58.3 mg, 87%).
Rf(CH2Cl2/MeOH 10/1) = 0.3. Mp: 117−119 °C. IR: 2964, 1616,
1
1492, 1480, 1326, 1050, 998, 839, 779, 750, 709, 695 cm−1. H NMR
(500 MHz, CDCl3): δ 1.01 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.08 (d, J =
6.8 Hz, 3H, (CH3)2CH), 2.00 (s, 3H, CH3Cym), 2.51 (dsept, J = 6.9 Hz,
1H, (CH3)2CH), 4.59 (s, 3H, CH3-N-3), 4.88 (dd, J = 6.0, 1.3 Hz, 1H,
ArHCym), 5.26 (dd, J = 6.3, 0.7 Hz, 1H, ArHCym), 5.47 (dd, J = 6.0, 1.3
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1′), 237 (N-3), 245 (N-1), 345 (N-2). 19F NMR (471 MHz, CDCl3): δ
−73.4 (d, J = 713 Hz, 6F, PF6). 31P NMR (202 MHz, CDCl3): δ −144.5
(sept, J = 713 Hz, 1P, PF6). HRMS (ESI+): calcd for C26H30ClN4Ru+
[M]+ 535.1203, found 535.1194. Anal. Calcd for C26H30ClF6N4PRu·
0.4C6H14: C, 47.74; H, 5.02; N, 7.84. Found: C, 47.93; H, 4.65; N, 7.46.
3Cc (R = OMe). Triazolium salt 1Cc (42.6 mg, 0.10 mmol), Ag2O
(34.5 mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 10 h, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol), Time 2 = 4 days. Yellow solid
(3Cc, 27.0 mg, 40%). Rf(CH2Cl2/MeOH 10/1) = 0.6. Mp: 117−119
°C. IR: 2921, 1611, 1541, 1487, 1441, 1303, 1253, 1181, 1078, 1024,
833, 767, 693 cm−1. 1H NMR (500 MHz, CDCl3): δ 0.88 (d, J = 7.0 Hz,
3H, (CH3)2CH), 1.14 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.71 (s, 3H,
CH3Cym), 2.31 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 3.89 (s, 3H, OCH3),
3.94 (s, 3H, CH3-N-3), 5.25 (d, J = 6.0 Hz, 1H, ArHCym), 5.38 (dd, J =
6.2, 0.8 Hz, 1H, ArHCym), 5.47−5.43 (m, 2H, ArHCym, CH2), 5.66 (dd, J
= 5.9, 0.8 Hz, 1H, ArHCym), 5.80 (d, J = 16.0 Hz, 1H, CH2), 7.09 (d, J =
8.1 Hz, 2H, H-3″, H-5″), 7.45−7.42 (m, 1H, H-5′), 7.58 (d, J = 7.5 Hz,
1H, H-3′), 7.77 (d, J = 8.1 Hz, 2H, H-2″, H-6″), 7.92 (dt, J = 7.7, 1.5 Hz,
1H, H-4′), 9.52 (dd, J = 5.7, 1.2 Hz, 1H, H-6′). 13C NMR (126 MHz,
CDCl3): δ 18.3 (CH3Cym), 22.0 ((CH3)2CH), 22.8 ((CH3)2CH), 31.2
((CH3)2CH), 37.1 (CH3-N-3), 55.5 (OCH3), 56.8 (CH2), 85.8
(ArCym), 85.8 (ArCym), 86.6 (ArCym), 89.0 (ArCym), 97.8 (ArCym), 107.9
(ArCym), 114.2 (C-2″, C-6″), 118.8 (C-1″), 124.8 (C-5′), 125.4 (C-3′),
132.9 (C-3″, C-5″), 139.4 (C-4′), 148.7 (C-4), 154.6 (C-2′), 159.1 (C-
6′), 159.6 (C-5), 161.1 (C-4″). 15N NMR (51 MHz, CDCl3): δ 236 (N-
1′), 237 (N-3), 246 (N-1), 345 (N-2). 19F NMR (471 MHz, CDCl3): δ
−73.2 (d, J = 713 Hz, 6F, PF6). 31P NMR (202 MHz, CDCl3): δ −144.5
(sept, J = 713 Hz, 1P, PF6). HRMS (ESI+): calcd for C26H30ClN4ORu+
[M]+ 551.1152, found 551.1143. Anal. Calcd for C26H30ClF6N4OPRu·
1.5H2O: C, 43.19; H, 4.60; N, 7.75. Found: C, 43.30; H, 4.47; N, 7.14.
3Cd (R = CN). Triazolium salt 1Cd (42.2 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 3 h, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol), Time 2 = 2 days. Yellow solid
(3Cd, 26.0 mg, 38%). Rf(CH2Cl2/MeOH 10/1) = 0.8. Mp: 132−134
°C. IR: 2964, 2230, 1610, 1440, 1401, 1305, 1278, 1240, 1161, 1076,
1019, 831, 764, 691 cm−1. 1H NMR (500 MHz, CDCl3): δ 0.83 (d, J =
6.9 Hz, 3H, (CH3)2CH), 1.14 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.66 (s,
3H, CH3Cym), 2.22 (dsept, J = 6.8 Hz, 1H, (CH3)2CH), 3.97 (s, 3H,
CH3-N-3), 5.25 (d, J = 6.0 Hz, 1H, ArHCym), 5.40 (d, J = 6.0 Hz, 1H,
ArHCym), 5.44 (d, J = 15.9 Hz, 1H, CH2), 5.56 (d, J = 6.1 Hz, 1H,
ArHCym), 5.72 (d, J = 5.9 Hz, 1H, ArHCym), 5.85 (d, J = 15.9 Hz, 1H,
CH2), 7.47 (t, J = 6.7 Hz, 1H, H-5′), 7.62 (d, J = 7.6 Hz, 1H, H-3′), 7.89
(d, J = 8.2 Hz, 2H, H-3″, H-5″), 7.95 (dt, J = 7.6, 0.8 Hz, 1H, H-4′), 8.10
(d, J = 8.2 Hz, 2H, H-2″, H-6″), 9.52 (d, J = 5.3 Hz, 1H, H-6′). 13C NMR
(126 MHz, CDCl3): δ 18.2 (CH3Cym), 21.6 ((CH3)2CH), 23.0
((CH3)2CH), 31.4 ((CH3)2CH), 37.5 (CH3-N-3), 56.9 (CH2), 85.9
(ArCym), 86.5 (ArCym), 86.6 (ArCym), 89.5 (ArCym), 97.4 (ArCym), 107.8
(ArCym), 114.3 (CN), 118.0 (C-1″), 125.0 (C-5′), 125.5 (C-3′), 131.7
(C-4″), 132.4 (C-3″, C-5″), 132.7 (C-2″, C-6″), 139.6 (C-4′), 147.0 (C-
4), 154.5 (C-2′), 159.2 (C-6′), 160.3 (C-5). 15N NMR (51 MHz,
CDCl3): δ 235 (N-1′), 237 (N-3), 247 (N-1), 347 (N-2). 19F NMR (471
MHz, (v): δ −73.4 (d, J = 713 Hz, 6F, PF6). 31P NMR (202 MHz,
CDCl3): δ δ −144.6 (sept, J = 713 Hz, 1P, PF6). HRMS (ESI+): calcd
for C26H27ClN5Ru+ [M]+ 546.0999, found 546.0989. Anal. Calcd for
C26H27ClF6N5PRu·H2O: C, 44.04; H, 4.12; N, 9.88. Found: C, 44.34; H,
3.80; N, 9.34.
NMR (126 MHz, CDCl3): δ 18.1 (CH3Cym), 21.9 ((CH3)2CH), 22.6
((CH3)2CH), 31.2 ((CH3)2CH), 37.4 (CH3-N-3), 56.9 (CH2), 85.7
(ArCym), 87.2 (ArCym), 87.5 (ArCym), 88.3 (ArCym), 97.3 (ArCym), 107.3
(ArCym), 123.7 (q, J = 273 Hz, CF3), 124.9 (C-5′), 125.5 (C-3′), 125.7
(q, J = 4 Hz, C-3″, C-5″), 130.7 (C-1″), 132.5 (q, J = 33 Hz, C-4″), 132.4
(C-2″, C-6″), 139.6 (C-4′), 147.4 (C-4), 154.5 (C-2′), 159.2 (C-6′),
160.1 (C-5). 15N NMR (51 MHz, CDCl3): δ 235 (N-1′), 237 (N-3),
247 (N-1), 347 (N-2). 19F NMR (471 MHz, CDCl3): δ −63.0 (s, 3F,
CF3), −73.4 (d, J = 713 Hz, 6F, PF6). 31P NMR (202 MHz, CDCl3): δ
−144.6 (sept, J = 712 Hz, 1P, PF6). HRMS (ESI+): calcd for
C26H27ClF3N4Ru+ [M]+ 589.0920, found 589.0911. Anal. Calcd for
C26H27ClF9N4PRu·0.2C6H14: C, 43.49; H, 4.00; N, 7.46. Found: C,
43.39; H, 3.73; N, 7.39.
3Ch (R = Cl). Triazolium salt 1Ch (44.0 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 9 h, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol), Time 2 = 2 days. Yellow solid
(3Ch, 32.0 mg, 42%). Rf(CH2Cl2/MeOH 10/1) = 0.7. Mp: 122−124
°C. IR: 2963, 2925, 2238, 1607, 1476, 1437, 1305, 1239, 1162, 1093,
1077, 1014, 831, 763, 691 cm−1. 1H NMR (500 MHz, CDCl3): δ 0.84 (d,
J = 7.0 Hz, 3H, (CH3)2CH), 1.12 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.70
(s, 3H, CH3Cym), 2.24 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 3.95 (s, 3H,
CH3-N-3), 5.24 (dd, J = 6.1, 1.3 Hz, 1H, ArHCym), 5.36 (dd, J = 6.2, 1.5
Hz, 1H, ArHCym), 5.41 (d, J = 15.9 Hz, 1H, CH2), 5.48 (dd, J = 6.2, 1.4
Hz, 1H, ArHCym), 5.67 (dd, J = 6.1, 1.4 Hz, 1H, ArHCym), 5.81 (d, J =
15.9 Hz, 1H, CH2), 7.43 (ddd, J = 7.4, 5.8, 1.4 Hz, 1H, H-5′), 7.54 (d, J =
8.6 Hz, 2H, H-3″, H-5″), 7.59 (d, J = 9.5 Hz, 1H, H-3′), 7.82 (d, J = 8.5
Hz, 2H, H-2″, H-6″), 7.91 (td, J = 7.7, 1.6 Hz, 1H, H-4′), 9.49 (dd, J =
5.8, 1.6 Hz, 1H, H-6′). 13C NMR (126 MHz, CDCl3): δ 18.2 (CH3Cym),
21.8 ((CH3)2CH), 22.8 ((CH3)2CH), 31.2 ((CH3)2CH), 37.2 (CH3-N-
3), 56.8 (CH2), 85.8 (ArCym), 86.3 (ArCym), 86.8 (ArCym), 88.9 (ArCym),
97.6 (ArCym), 107.9 (ArCym), 124.9 (C-1″), 125.4 (C-5′), 125.5 (C-3′),
129.1 (C-3″, C-5″), 133.1 (C-2″, C-6″), 136.8 (C-4″), 139.6 (C-4′),
147.6 (C-4), 154.5 (C-2′), 159.2 (C-6′), 159.9 (C-5). 15N NMR (51
MHz, CDCl3): δ 235 (N-1′), 237 (N-3), 246 (N-1), 346 (N-2). 19F
NMR (471 MHz, CDCl3): δ −73.3 (d, J = 713 Hz, 6F, PF6). 31P NMR
(202 MHz, CDCl3): δ −144.6 (sept, J = 713 Hz, 1P, PF6). HRMS (ESI
+): calcd for C25H27Cl2N4Ru+ [M]+ 555.0656, found 555.0651.
tert-Butyl 2-Methoxy-5-bromobenzoperoxoate (7b). Rf(light
1
petroleum/ethyl acetate 5/1) = 0.5. H NMR (300 MHz, CDCl3): δ
1.42 (s, 9H, t-Bu), 3.90 (s, 3H, OCH3), 6.88 (d, J = 8.9 Hz, ArH), 7.59
(dd, J = 8.9, 2.6 Hz, ArH), 7.81 (d, J = 2.6 Hz, ArH). HRMS (ESI+):
calcd for C12H16BrO4+ [M + H]+ 303.0226, found 303.0225.
ASSOCIATED CONTENT
* Supporting Information
■
S
Figures, tables, and CIF files giving N-1, N-2, and N-3 chemical
and coordination shifts, crystallographic data for complexes 3Aa,
3Bf, and 3Ca, and NMR spectra of compounds 3. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail for J.K.: janez.kosmrlj@fkkt.uni-lj.si.
Notes
3Ce (R = CF3). Triazolium salt 1Ce (46.4 mg, 0.10 mmol), Ag2O (34.5
mg, 0.15 mmol), acetonitrile (4 mL), Time 1 = 2 h, [Ru(η6-p-
cymene)Cl2]2 (30.6 mg, 0.05 mmol), Time 2 = 2 days. Yellow solid
(3Ce, 33.0 mg, 45%). Rf(CH2Cl2/MeOH 10/1) = 0.7. Mp: 116−118
°C. IR: 2960, 2922, 1609, 1439, 1406, 1325, 1239, 1167, 1126, 1070,
1017, 832, 766, 691 cm−1. 1H NMR (500 MHz, CDCl3): δ 0.79 (d, J =
7.0 Hz, 3H, (CH3)2CH), 1.12 (d, J = 6.9 Hz, 3H, (CH3)2CH), 1.63 (s,
3H, CH3Cym), 2.11 (dsept, J = 6.9 Hz, 1H, (CH3)2CH), 3.97 (s, 3H,
CH3-N-3), 5.30 (d, J = 6.0 Hz, 1H, ArHCym), 5.38 (d, J = 6.0 Hz, 1H,
ArHCym), 5.45 (d, J = 15.9 Hz, 1H, CH2), 5.54 (d, J = 6.1 Hz, 1H,
ArHCym), 5.74 (d, J = 6.0 Hz, 1H, ArHCym), 5.85 (d, J = 15.9 Hz, 1H,
CH2), 7.46 (t, J = 6.7 Hz, 1H, H-5′), 7.62 (d, J = 7.6 Hz, 1H, H-3′), 7.86
(d, J = 8.2 Hz, 2H, H-3″, H-5″), 7.95 (dt, J = 7.7, 1.4 Hz, 1H, H-4′), 8.07
(d, J = 8.1 Hz, 2H, H-2″, H-6″), 9.53 (dd, J = 5.6, 0.9 Hz, 1H, H-6′). 13C
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We acknowledge financial support from the Ministry of
Education, Science and Sport, Republic of Slovenia, the
Slovenian Research Agency (Grant P1-0230; Young Researcher
Grant to A.B., Postdoctoral Grant to M.G. (430-168/2013/114),
and Grant P1-0175), the Fonds der Chemischen Industrie
(FCI), and the Deutscher Akademischer Austauschdienst
(DAAD). This work was also partially supported through the
infrastructure of the EN-FIST Centre of Excellence, Ljubljana,
Slovenia.
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