Introducing potential hemilability into "click" triazoles and triazolylidenes: Synthesis and characterization of d6-metal complexes and oxidation catalysis

Article abstract of DOI:10.1002/ejic.201402178

Hemilabile ligands are known to impart remarkable properties to their metal complexes. Herein, we present arene half-sandwich complexes of Ru^II, Os^II, and Ir^III with "click"-derived 1,2,3-triazole (L¹) and 1,2,3

Full text of DOI:10.1002/ejic.201402178

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DOI:10.1002/ejic.201402178
Introducing Potential Hemilability into “Click” Triazoles
and Triazolylidenes: Synthesis and Characterization of
6
d -Metal Complexes and Oxidation Catalysis
[a]
[a]
[a]
Stephan Hohloch, Lara Hettmanczyk, and Biprajit Sarkar*
Keywords: Nitrogen heterocycles / Oxidation / Carbene ligands / Ruthenium / Osmium
Hemilabile ligands are known to impart remarkable proper-
ties to their metal complexes. Herein, we present arene half-
sandwich complexes of Ru , Os , and Ir with “click”-de-
nitrogen “N2” of the 1,2,3-triazole. All complexes were ap-
plied for the catalytic oxidation of benzyl alcohol to benzal-
dehyde using N-methylmorpholine N-oxide as sacrificial oxi-
dant. Furthermore, oxidation of diphenylmethanol to benzo-
phenone was also achieved by using low catalyst loadings in
II
II
III
1
2
rived 1,2,3-triazole (L ) and 1,2,3-triazol-5-ylidene (L ) li-
gands containing a potentially hemilabile thioether donor.
Structural elucidation of the complexes revealed localization
II
very good yields. These are rare examples of Os –triazole, as
1
II
of double bonds within the triazole in L and a delocalized
situation within the triazolylidene ring of L . For complexes
with L , unusual coordination occurs through the less basic
well as of Os –triazolylidene complexes with “click”-derived
2
ligands.
1
Introduction
Bis-chelating substituted 1,2,3-triazoles can be synthe-
sized through Cu -catalyzed “click reaction” with ad-
I
One of the most used [3+2] cycloaddition reactions in
modern chemistry is probably the Cu -catalyzed reaction
between alkynes and azides, resulting in 1,2,3-triazoles,
I
ditional heteroatom donors either on the N1 or C4 atoms
[
2]
(
Figure 1) of the triazole ring. The most widely used bis-
3
[
1]
chelating ligands of this type has been L (Figure 1), where
the metal atom coordinates through the more basic N3
atom of the triazole ring, and the additional donating group
on the C4 atom of the 1,2,3-triazole. Alternatively, one can
install the donating group on the N1 atom, and generate
which constitutes the best “click reaction” known. The
ease and the sustainability of this reaction have turned it
into a “work horse” for modern synthetic chemists. One of
the fields in which substituted 1,2,3-triazoles are extensively
used at the moment is coordination and organometallic
4
[
2]
ligands L . This strategy has been successfully applied to
chemistry. Metal complexes bearing 1,2,3-triazole-based
ligands have been investigated for electron-transfer sys-
force metal binding to the less basic N2 atom through a
[
11]
[
3]
[4]
[5]
preferential chelating effect.
Since triazolylidene ligands
tems, photochemistry, magnetic properties, and for
[
6]
are derived from 1,2,3-triazoles (see above), such donor
atoms on N1 or C4 can also be present in the triazolylidene
homogeneous catalysis. Another interesting characteristic
of these 1,2,3-triazoles is that they can be easily converted
into 1,2,3-triazolylidenes, which belong to the class of ab-
normal carbenes (aNHC), by simple alkylation of N3 and
subsequent deprotonation.[ These compounds have also
been classified as mesoionic carbenes (MIC) in recent litera-
5
[7,9a]
ligands. Ligands such as L have been reported.
How-
3
ever, compared with their 1,2,3-triazole counterparts L ,
7]
[
8]
ture. Such aNHC’s are believed to even surpass the donor
abilities of their normal NHC counterparts, and to act as
an electron reservoir in redox transformations (noninnocent
[
9]
behavior). Therefore, it is not surprising that complexes
bearing such triazolylidene ligands are extensively used in
modern organometallics chemistry and homogeneous catal-
[
10]
ysis.
[
a] Institut für Chemie und Biochemie, Anorganische Chemie,
Freie Universität Berlin,
Fabeckstraße 34-36, 14195 Berlin, Germany
E-mail: biprajit.sarkar@fu-berlin.de
Figure 1. Potentially chelating 1,2,3-triazoles and 1,2,3-triazol-5-
ylidene ligands (top), and the ligands used in this work (bottom).
D denotes substituents with a heteroatom donor.
www.bcp.fu-berlin.de/en/chemie/sarkar
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201402178.
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their numbers are rather limited. To the best of our knowl- 1H and 13C NMR spectroscopy and mass spectrometry (see
edge, triazolylidenes with an additional donating hetero- Exp. Sect. and Supporting Information). Whereas 5 shows
6
1
atom on N1 (L ) that binds to a metal center in a chelating a well-resolved H NMR spectrum at 298 K, for 1 and 3
fashion, have not been reported. we observed spectra with broad peaks indicating fast trans-
Hemilabile donating groups on ligands are often useful formation of rotamers within the NMR time-scale at 298 K.
for generating stable catalysts in the resting state.[12] Thio- Heating the samples to 60 °C in methanol did not lead to
ether groups have been one of the most widely used hemil- complete resolution of the signals, but it clearly indicated
abile donors in organometallic chemistry.[ Recently, we the formation of the complexes (Figure S13 and S14, Sup-
13]
have reported on thioether functionalized ligands 1-[2- porting Information). Unfortunately, we were not able to
1
(
methylthio)phenyl]-4-phenyl-1H-1,2,3-triazole (L ) and 3- record the NMR spectra in higher boiling solvents because
methyl-1-[2-(methylthio)phenyl]-4-phenyl-1H-1,2,3-triazol- in coordinating solvents such as CD CN or [D ]DMSO the
3
6
2
[14]
5
-ylidene (L , Figure 1),
in which the donor atoms are complexes decomposed, and the complexes were not solu-
placed on N1 of the triazole/triazolylidene ring. In these ble in [D ]toluene. Nevertheless, we were able to identify the
8
cases, we did not observe coordination of the thioether signal at δ = 9.29 ppm for 1 and 3 as the C–H proton of
group to the metal centers. In this work, we have used the the 1,2,3-triazole ring. In contrast to the free ligand, this
1
2
II
ligands L and L to synthesize their Ru complexes [(Cym)- signal is shifted by about 1 ppm to high field. Such a shift
1
2
II
Ru(L )Cl]PF (1), [(Cym)Ru(L )Cl]PF (2), their Os com- clearly indicates binding of the ligand to the metal centers,
plexes [(Cym)Os(L )Cl]PF (3), [(Cym)Os(L )Cl]PF (4) as has been shown previously.
Cym = p-cymene), and their Ir complexes [(Cp*)Ir(L )- all the signals were well-resolved at 298 K, and appeared at
Cl]PF (5) and [(Cp*)Ir(L )Cl]PF (Cp* = pentamethylcy- the expected positions with appropriate integrals (see the
6
6
1
2
[3h,3i]
III
For the Ir complex 5,
6
6
III
1
(
2
6
6
clopentadienyl) (6). In doing so, we have explored the pos- Supporting Information).
sibility of obtaining thioether coordination in the ligands
1
2
II
L and L , and also looked for rare examples of Os com-
[
2e]
plexes with “click”-derived substituted 1,2,3-triazole and
,2,3-triazol-5-ylidene ligands. Herein, we present the syn-
1
thesis, spectroscopic and structural characterization of the
metal complexes and their use as catalysts for the oxidation
of benzyl alcohol and diphenylmethanol using NMO as a
sacrificial oxidant.
Results and Discussion
Synthesis and Characterization of Complexes
We recently reported on the synthesis of a highly effective
copper(I) catalyst containing a triazolylidene ligand with an
Scheme 1. Synthesis of triazole complexes 1, 3 (top), and 5 (bot-
tom).
2
additional SMe-donor function (L ) for the Huisgen [3+2]
cycloaddition between alkynes and azides.[
14]
Unfortu-
nately, several attempts at coordinating the SMe donor
function to the copper center were unsuccessful. Thioether
Synthesis of triazolylidene complexes 2, 4, and 6 was
donors are known to coordinate to piano stool arene d6 achieved by following a standard transmetallation protocol
2
complexes when present as substituents on N-heterocyclic (Scheme 2). The triazolium salt [HL ][I] was first reacted
[
13a]
carbene ligands.
Hence, in pursuit of realizing a thio- with basic silver(I) oxide in the presence of a chloride
2
ether coordination in L , we wanted to synthesize half- source (KCl) in acetonitrile (dichloromethane in the case of
sandwich Ru , Os , and Ir complexes with this ligand. 2) under exclusion of light, yielding the dicarbene silver(I)
II
II
III
We were also interested in the coordination mode of the complex. Afterwards the solvent was changed to dichloro-
1
non-methylated form (L ) towards metal centers and in methane and the corresponding chloro-bridged dimeric
finding out how these two coordination modes would affect metal precursors [Ru(Cym)Cl ] , [Os(Cym)Cl2]2 or
2
2
the catalytic properties of the complexes in oxidation cataly- [Ir(Cp*)Cl ] , respectively, were added under the exclusion
2
2
sis.
of light. Precipitation of AgCl indicated successful transme-
Synthesis of the triazole complexes 1, 3 and 5 was tallation. Filtration of AgCl and subsequent salt metathesis
achieved by mixing the chloro-bridged dimeric metal pre- with aqueous KPF from a methanol solution afforded the
6
cursors [Ru(Cym)Cl ] , [Os(Cym)Cl ] or [Ir(Cp*)Cl2]2 clean complexes in good yields as yellow solids. All com-
2
2
2 2
1
1
13
respectively with L in methanol and subsequent stirring at plexes were characterized by using H and C NMR spec-
room temperature overnight. Aqueous salt metathesis with troscopy and mass spectrometry. Disappearance of the C–
1
KPF afforded the pure complexes in good yields as yellow H signal of the triazolium ring in the H NMR spectra was
6
powders (Scheme 1). The complexes were characterized by a first indication for successful synthesis of the triazolylid-
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ene complexes. Furthermore, the observation of signals at δ
159.9, 163.3 and 150.5 ppm for 2, 4 and 6, respectively,
=
1
3
in the C NMR spectra proved the existence of the carbene
complexes (see Exp. Sect. and Supporting Information).
The carbene C signal for the Cp*-IrIII complex 6 appears
II
at a much higher field compared with its Cym-Ru and
II
Cym-Os counterparts. Furthermore, the molecular peaks
for the cationic parts of all complexes (without PF ) were
6
observed in the ESI mass spectrum. Thus, NMR spec-
troscopy and mass spectrometry unambiguously demon-
strate the formation of the triazole and triazolylidene com-
plexes. These data also provide evidence for the successful
II
[2e]
synthesis of rare Os complexes
with substituted 1,2,3-
triazoles as well as 1,2,3-triazol-5-ylidene ligands.
Figure 2. ORTEP plot of 2 (top left), 5 (bottom left) and 6 (top
right). Ellipsoids are shown with a probability level of 50%. Hydro-
gen atoms and counterions have been omitted for clarity. The boat
conformation around the metal center is shnown, with the example
of 2 (bottom right).
Table 1. Selected bond lengths [Å].
2
5
6
M–S1
2.351(1)
2.413(1)
2.048(2)
–
1.343(2)
1.306(3)
1.367(3)
1.395(3)
1.382(3)
2.360(1)
2.395(1)
–
2.094(2)
1.363(3)
1.301(4)
1.369(4)
1.370(4)
1.354(4)
2.328(2)
2.422(2)
2.036(4)
–
1.338(5)
1.355(5)
1.355(5)
1.399(5)
1.377(5)
M–Cl1
M–C1
M–N2
N1–N2
N2–N3
N3–C2
C2–C1
C1–N1
Scheme 2. Synthesis of the triazolylidene complexes 2, 4 (top), and
6
(bottom).
Crystal Structures of Complexes
Single crystals of 2 were obtained by slow diffusion of n-
hexane into a concentrated solution of 2 in dichlorometh-
1
In 5, the ligand L acts as a chelate, with the coordinating
ane at room temperature. In the case of complexes 5 and 6, atoms being the N2 nitrogen atom of the triazole and the
slow diffusion of hexanes into a concentrated solution of sulfur atom S1 of the thioether function. The Ir–N2 dis-
the metal complex in dichloromethane at 8 °C produced X- tance of 2.094(2) Å, and the Ir–S1 distance of 2.360(1) Å
ray quality crystals (see the Exp. Sect.). The crystallo- confirm the bonding of both these donor atoms to the irid-
graphic data are given in Table 5. All complexes display ium center. Thus, chelation forces the iridium center to bind
three-legged piano stool type coordination around the to the less basic nitrogen atom of the 1,2,3-triazole ring, as
metal center, which is typical for half-sandwich complexes has been previously reported for metal complexes with re-
6
[11]
(
Figure 2). The Cym ligand is bound in a η mode to the lated ligands. In 5, the donor atoms form a six-membered
II
5
Ru center in 2, whereas the Cp* ligand binds in a η mode chelate ring at the metal center, which displays a boat-
to the Ir center in 5 and 6. The distance of the centroid shaped conformation (Figure 2). Even though this coordi-
III
of the Cym ligand to the ruthenium center is 1.724(1) Å in nation type of triazole has been observed before by others,
2
. The corresponding distance between the centroid of Cp* it is the first time that such coordination has been observed
1
and the Ir center are 1.792(1) and 1.826(1) Å for 5 and 6, for ligand L . The N1–N2 distance of 1.363(3) Å inside the
respectively. The elongation of this distance in 6 might be 1,2,3-triazole ring in 5 is longer than the central N2–N3
due to steric repulsion with the phenyl substituent on the distance of 1.301(4) Å, revealing a localized central double
C2 atom of the ligand, which points towards the Cp* li- bond flanked by longer bonds (Table 1). The dihedral angle
gand; for complex 5 the phenyl substituent on C2 points in between the triazole ring and the thioanisole ring is
the opposite direction (Figure 2). The metal chloride dis- 39.5(1)°, and that between the triazole ring and the phenyl
tance is within the expected regions for all three complexes ring is 41.8(1)°. Although we have not been successful in
[
15]
(Table 1).
obtaining suitable single crystals of 1 and 3, spectroscopic
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data and comparison to 5 points to a similar coordination be the most active catalysts for this transformation, whereas
1
of L in these complexes (see Exp. Sect. and the Supporting use of osmium complex 4 (Table 3, entry 4) and the iridium
Information).
complexes 5 and 6 only results in moderate conversions af-
In triazolylidene complexes 2 and 6, the metal–carbene ter 3 h. Furthermore, the conversion achieved by using the
C1) bond lengths are 2.048(2) and 2.036(4) Å, respectively, substituted triazole complexes 1, 3 and 5 were always higher
(
and are in the range of previously reported triazolylidene than those achieved by using the corresponding triazolylid-
[
15]
complexes.
.328(2) Å, respectively, for 2 and 6 clearly establish the obtained by using the triazolylidene complexes 2, 4 and 6
binding of the thioether function to the metal center were lower than their respective triazole counterparts 1, 3,
The M–S1 distance with 2.3512(7) and ene complexes 2, 4, and 6. Although the total conversion
2
(
Table 1) and is consistent with previously reported sys- and 6, the propensity for overoxidation to benzoic acid was
[
13]
tems.
Similar to 5, in both 2 and 6, the coordinating markedly less for the triazolylidene-containing complexes 2,
atoms form a six-membered ring at the metal center, which 4 and 6 (Table 3, entries 2, 4 and 6). On comparing the
displays a boat-shaped conformation (Figure 2). In the tri- three different metal centers, it is seen that with the same
azolylidene rings of 2 and 6, a shrinking of the respective ligand, the osmium complexes display the highest propen-
angles around C1 is observed in comparison to its triazole sity for overoxidation to benzoic acid (Table 3, entries 3 and
counterpart in 3 (Table 2). These data thus unambiguously 4). On the other hand, the iridium complexes are the most
establish the chelating nature of the triazolylidene ligand L2 selective towards oxidation to benzaldehyde (Table 3, en-
in complexes 2 and 6, in which the additional heteroatom tries 5 and 6). Running the reactions under identical condi-
donor is attached to the nitrogen atom of the triazolylidene tions with the same amount of NMO but without the cata-
ring. The dihedral angles between the thioanisole ring and lysts resulted in no conversion into the products.
the triazolylidene ring in 2 and 6 are 29.9(1)° and 30.1(1)°,
respectively, and those between the phenyl ring and the tri-
azolylidene ring are 75.3(1)° and 61.9(1)°, respectively. De-
spite the absence of an X-ray crystal structure for the corre-
sponding osmium complex 4, comparison of the spectro-
scopic data point to an identical structure for 4, as has been
observed for 2 and 6.
Scheme 3. Oxidation of benzyl alcohol to benzaldehyde and ben-
zoic acid.
Table 2. Selected bond angles [°].
Table 3. Catalytic oxidation of benzyl alcohol under different con-
ditions.[
a]
2
5
6
[
c]
Benzoic acid[c]
C1–M–S1
N2–M–S1
N1–C1–C2
N1–N2–N3
84.8(1)
–
101.8(2)
102.9(2)
–
87.0(1)
–
101.7(3)
103.0(3)
Entry Cat. Loading Time Conv. Benzaldehyde
[mol-%]
[h] [%][
b]
84.9(1)
106.0(3)
109.4(2)
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
1
2
3
1
1
1
1
1
3
3
3
3
3
3
1
1
1
Ͼ99
98
99
58
44
15
96
44
99
59
77
–
66
93
78
59
77
21
41
23
100
34
7
22
41
23
79
1
Catalytic Oxidation Reactions
0.1
0.1
0.1
Inexpensive and simple oxidation of small molecules is
one of the major goals in organometallic chemistry, and the
oxidation of alcohols is of particular interest. In recent [a] Reaction conditions: benzyl alcohol (0.2 mmol), NMO
(
0.6 mmol), catalyst (1 or 0.1 mol-%), dichloromethane (4 mL),
years, N-methylmorpholine N-oxide (NMO) has emerged as
1
heated at reflux for 3 h or 1 h. [b] Determined by H NMR spectro-
scopic analysis with hexadecane as internal standard. [c] Ratio of
products given in percent.
a useful sacrificial oxidant for such oxidation reac-
[
11m,11n]
tions.
Inspired by these findings, we were interested
in performing oxidation reactions with the complexes men-
tioned above as catalysts, and NMO as a sacrificial oxidant.
Having established the efficiency of the complexes as cat-
For the first screening, benzyl alcohol was chosen as sub- alyst at 1 mol-% loading, we next turned to the most active
strate and 1 mol-% catalyst was used with NMO in a three- catalysts 1–3, and decreased the catalyst loading. We low-
fold excess (see Scheme 3 and Exp. Sect.).
ered the catalyst loading to 0.1 mol-% and also reduced the
The conversions where investigated after 3 h reaction by reaction time to 1 h. As can be seen from Table 3 (entries
H NMR spectroscopy by using hexadecane as an internal 7–9) the trends remained similar at these catalyst loadings.
1
standard. This transformation proceeded with excellent The reaction with triazole complexes 1 and 3 showed nearly
yields for the ruthenium and osmium catalysts, and af- quantitative conversions of benzyl alcohol, whereas tri-
forded benzaldehyde together with its overoxidation prod- azolylidene complex 2 displayed less than half the amount
uct benzoic acid (Scheme 3 and Table 3). Looking at the of product conversion compared with the reaction with
conversion, certain trends can be observed for this transfor- 1 mol-% catalyst loading. Triazolylidene-containing com-
mation. The ruthenium complexes 1 and 2 (Table 3, entries plex 2 showed less overoxidation to benzoic acid (Table 3,
1
and 2) and osmium complex 3 (Table 3, entry 3) seem to entry 8). Moreover, on lowering the catalyst loading, the
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use of osmium–triazole complex 3 led to less overoxidation Conclusions
than with a higher catalyst loading (Table 3, entry 9).
6
We have presented here six new arene d complexes with
click”-derived 1,2,3-triazole and 1,2,3-triazol-5-ylidene li-
gands, both of which contain
After investigating the efficiency of the compounds re-
ported here as catalysts for the oxidation of benzyl alcohol,
which is a primary alcohol, we turned out attention to the
catalytic oxidation of a secondary alcohol under the condi-
tions detailed above. For this purpose, diphenylmethanol
was chosen as substrate. One advantage of this system is
the fact that overoxidation is not possible for secondary
alcohols (Scheme 4 and Table 4).
“
a potentially hemi-
labile thioether donor. In doing so, we have presented rare
II
[2e]
examples of arene–Os complexes with a “click”-derived
triazole ligand, as well as with a triazolylidene abnormal
carbene type of ligand. Structural characterization of se-
lected examples has revealed the coordination of the thio-
ether donors to the metal centers. This additional coordina-
tion, which results in chelation of the ligands to the metal
centers, forces the metal centers to bind to the less basic
N2 atom of the 1,2,3-triazole ring, as has been observed
[
11]
previously.
For the 1,2,3-triazol-5-ylidene ligands, these
Scheme 4. Oxidation of diphenylmethanol using NMO as a sacrifi- are the first examples of metal complexes in which an ad-
cial oxidant.
ditional coordinating heteroatom has been incorporated
into the substituents at the N1 atom of the triazolylidene
ring. All complexes were investigated as catalysts for oxi-
dations of alcohols, and most were found to be potent cata-
lysts. A strong dependency of the outcome of the catalysis
on the metal center and the ligand was observed. The os-
mium complexes have been shown to be superior to their
ruthenium or iridium counterparts. Using the primary
alcohol (benzyl alcohol), overoxidation to benzoic acid was
observed, but this can be controlled to an extent by the use
of an appropriate ligand or an appropriate metal center. For
secondary alcohols, the catalyst loading could be reduced to
only 0.01 mol-% in the case of the osmium complex 3 and
still achieve high conversion after 1 h reaction. Our results
thus represent a new kind of chelation for abnormal carb-
Table 4. Catalytic oxidation of diphenylmethanol under different
[
a]
conditions.
Entry
Catalyst Loading [mol-%]
Time [h]
Conv. [%][b]
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
1
2
3
3
3
1
1
1
1
1
3
3
3
3
3
3
3
3
3
3
1
97
63
100
41
38
24
80
29
100
94
82
1
0.2
0.2
0.2
0.01
0.01
1
1
0
1
[
a] Reaction conditions: diphenylmethanol (0.2 mmol), NMO enes of the triazolylidene form. Furthermore, we have
II
(
(
0.6 mmol), catalyst (1 or 0.2 or 0.01 mol-%), dichloromethane shown that Os complexes with “click”-derived ligands are
1
4 mL), heated to reflux for 3 h or 1 h. [b] Determined by H NMR
potent oxidation catalysts. Considering the modular syn-
thetic approach amenable to these classes of ligands, and
the hitherto less explored coordination/organometallic
spectroscopic analysis with hexadecane as internal standard.
Similar trends to those of the primary alcohol oxidations
were observed with the secondary alcohol. The osmium
complex 3, which contains a triazole ligand, had the highest
efficiency for this transformation when 1 mol-% catalyst
was used (Table 4, entry 3). For all the other complexes at
chemistry of such hemilabile triazole/triazolylidene ligands
II
(
particularly with Os ), these and related complexes are ex-
pected to find use in many catalytic processes. Current work
in our laboratories is focused on some of these directions.
1
mol-% catalyst loading, use of complexes containing a tri-
azole ligand resulted in higher catalytic activity than use of
their triazolylidene counterparts (compare entries 1 and 2, Experimental Section
and 4 or 5 and 6). We took the three most active com-
plexes 1, 2, and 3 and reduced the catalyst loading to
.2 mol-%. The catalysts retained their efficiency at this cat-
3
Materials and Physical Methods: [RuCymCl
2
]
2
and [IrCp*Cl
was synthesized ac-
All the reagents were used as
2 2
]
were purchased from ABCR, and [OsCymCl ]
2 2
0
[16]
cording to a reported procedure.
1
2
alyst loading, and the trends observed were the same as supplied. Ligands L and [HL ][I] were synthesized according pre-
those mentioned above (entries 7–9). Osmium complex 3 viously published methods.[14a] The solvents used for metal com-
shows the highest potential for this oxidation reaction (en- plex synthesis were dried and distilled under argon and degassed
try 9). We were then interested in how low we could set
the catalyst loading with 3 and still achieve good yields.
Gratifyingly, lowering the catalyst loading to 0.01 mol-%
and heating the reaction to reflux for 3 h in dichlorometh-
ane delivered 94% product conversion (entry 10). Heating
the reaction to reflux for only 1 h at this catalyst loading
still gave a conversion of 82% (entry 11). These results
1
13
by common techniques prior to use. H and C NMR spectra were
recorded with a Jeol ECS 400 spectrometer. Mass spectrometry was
performed with an Agilent 6210 ESI-TOF. GC–MS analysis was
performed with a Varian Saturn 2100C (column: Varian factory
four capillary column VF-5ms). The presence of fluorine in the
–
complexes (as PF
6
) precluded the elemental analysis of these com-
pounds. An enquiry with at least five companies supplying elemen-
tal analysis instruments forced us to conclude that no instruments
clearly demonstrate the high potency of osmium complex 3 are available that can be used to accurately measure compounds
as an oxidation catalyst.
containing fluorine, without destroying the column of the elemental
Eur. J. Inorg. Chem. 0000, 0–0
5 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42178
/KAP1
Date: 28-05-14 11:02:56
Pages: 9
www.eurjic.org
FULL PAPER
analyzer. To demonstrate the purity of these complexes, the data
of all NMR spectra are reported in the Exp. Sect.
to cause precipitation of the desired product. The products were
obtained as yellow solids.
∧
1
2
2
Synthesis of N S Complexes: L (53.4 g, 0.2 mmol) and the corre-
sponding metal dimer [(RuCymCl , (OsCymCl , or (IrCp*Cl
.1 mmol] were dissolved in methanol (15 mL) and the solution
6
[Ru(Cym)Cl(L )] PF (2): L (82 mg, 0.2 mmol) was mixed under
2
)
2
2
)
2
2
)
2
,
nitrogen atmosphere with silver oxide (163 mg, 0.7 mmol), dis-
solved in dichloromethane (15 mL), and stirred under exclusion of
light for 2 d. The mixture was then filtered through Celite and the
0
was stirred at room temperature overnight. The solution was then
concentrated to 1/3 of its volume and potassium hexafluorophos-
2 2
metal dimer [RuCymCl ] (0.1 mmol) was added. The rest of the
phate (148 mg, 0.8 mmol) was added. The mixture was stirred for reaction was performed according to the general route, yield 63 g
1
10 min, then water (80 mL) was slowly added to induce precipi-
2 2
(0.084 mmol, 42%). H NMR (400 MHz, CD Cl ; 25 °C, TMS): δ
tation of the desired product. The yellow precipitate was filtered
and washed with water, then with diethyl ether, to gain the desired
complexes as yellow powders in good yields.
= 8.26–8.13 (m, 1 H, Ar-H), 7.86–7.70 (m, 4 H, Ar-H), 7.62–7.53
(m, 4 H, Ar-H), 5.45 [d, J = 6.3 Hz, 1 H, CH (Cym)], 5.38 [d, J =
5.9 Hz, 1 H, CH (Cym)], 5.24–5.13 [m, 1 H, CH (Cym)], 5.05 [d,
J = 6.0 Hz, 1 H, CH (Cym)], 4.01 (s, 3 H, N-CH
3
), 2.21–1.98 [m,
(Cym)], 0.87 [d, J
(Cym)], 0.73 [d, J = 6.9 Hz, 3 H, CH
Cl ; 25 °C, TMS): δ =
1
(1): Yield 112 mg (0.164 mmol, 82%). 1
OD; 25 °C, TMS): δ = 9.29 (s, 1 H, Triazol-
H), 8.13–8.01 (m, 3 H, Ar-H), 7.94–7.88 (m, 1 H, Ar-H), 7.87–
.78 (m, 1 H, Ar-H), 7.75–7.66 (m, 1 H, Ar-H), 7.58–7.46 (m, 3 H,
[
Ru(Cym)Cl(L )] PF
6
H
4
H, S-CH
3 3
and CH (Cym)], 1.31 [s, 3 H, CH
NMR (400 MHz, CD
3
=
7.0 Hz, 3 H, CH
3
3
5
7
13
(Cym)] ppm. C NMR (100 MHz, CD
2
2
1
1
8
59.8 (Carbene-C), 150.0 (Ctrz-Ph), 133.2, 131.9, 130.7, 130.2,
28.6, 126.8, 126.3, 112.0 (all Aryl-C), 100.7 [2ϫC (Cym)], 93.5,
Ar-H), 5.99–5.91 [m, 2 H, 2ϫCH (Cym)], 5.74 [br. s, 1 H, CH
Cym)], 5.68–5.60 [m, 1 H, CH (Cym)], 2.89 [br. s, 1 H, CH (Cym)],
.23 [br. s, 3 H, CH (Cym)], 2.10 (s, 3 H, S-CH ), 1.34–1.26 [m, 6
H, CH (Cym)] ppm. C NMR (100 MHz, MeOD; 25 °C, TMS):
δ = 151.0, 137.0 (CHTrz), 133.2, 132.1, 130.8, 129.6, 129.0, 128.1,
25.8 (all Aryl-C), 109.3, 103.1 [C (Cym)], 87.9, 87.4, 86.4, 85.5
Ar-CH (Cym)], 31.0 [CH (Cym)], 21.3 [CH (Cym)], 20.7 (S-CH ),
(Cym)] ppm. MS (ESI): m/z calcd. for
(
2
8.8, 87.7, 85.8 [CH (Cym)], 39.1 (N-CH
(Cym)], 20.3 (S-CH ), 17.2 [2ϫCH
m/z calcd. [C26 SClRu ] 552.0814; found 552.0815.
3
), 22.6 [CH
3
(Cym)], 21.8
3
3
[CH
3
3
3
(Cym)] ppm. MS (ESI):
1
3
3
+
29 3
H N
2
(4): Yield 97 mg (0.124 mmol, 62%). 1
Cl ; 25 °C, TMS): δ = 8.22–8.17 (m, 1 H, Ar-
[
Os(Cym)Cl(L )] PF
6
H
1
[
1
NMR (400 MHz,CD
2
2
3
3
H), 7.78–7.69 (m, 4 H, Ar-h), 7.60–7.53 (m, 4 H, Ar-H), 5.45–5.42
[m, 2 H, 2ϫCH (Cym)], 5.21 [d, J = 5.6 Hz, 1 H, C (Cym)], 5.09
3 3
9.0 [CH (Cym)], 17.1 [CH
+
[C
26
H
29
N
3
SClRu ] 538.0658; found 538.0681.
[
d, J = 5.6 Hz, 1 H, CH (Cym)], 3.99 (s, 3 H, N-CH
H, S-CH ), 2.05 [hept, J = 6.8 Hz, 1 H, CH (Cym)], 1.45 [s, 3 H,
CH (Cym)], 0.89 [d, J = 6.8 Hz, 3 H, CH (Cym)], 0.74 [d, J =
(Cym)] ppm. 13C NMR (100 MHz, CD
.8 Hz, 3 H, CH Cl
3
), 2.19 (s, 3
1
(3): Yield 106 mg (0.136 mmol, 68%). 1
OD; 25 °C, TMS): δ = 9.29 (s, 1 H, Triazol-
H), 8.04–7.88 (m, 4 H, Ar-H), 7.83–7.75 (m, 1 H, Ar-H), 7.73–
[
Os(Cym)Cl(L )] PF
6
H
3
NMR (400 MHz, CD
3
3
3
5
7
2
6
2
1
1
3
2
2
;
.65 (m 1 H, Ar-H), 7.56–7.43 (m, 3 H, Ar-H), 6.16–6.07 [m, 2 H,
ϫCH (Cym)], 5.97–5.78 [m, 2 H, CH (Cym)], 2.78 [br. s, 1 H,
CH (Cym)], 2.32 [br. s, 3 H, CH
.32–1.21 [m, 6 H, CH
5 °C, TMS): δ = 151.7, 138.6 (CHTrz), 134.5, 132.9, 132.2, 131.0,
30.3, 129.2, 127.2 (all Aryl-C), 102.3 [C (Cym)], 81.3, 80.9, 79.5,
5 °C, TMS): δ = 163.3 (Carbene-C), 151.1, 144.9, 140.5, 133.8,
32.5, 132.0, 131.2, 130.5, 129.1, 127.1, 126.7, 125.1 (all Aryl-C),
04.6, 94.0, 85.2, 80.6, 79.5, 78.0 [all C (Cym)], 38.6 (N-C), 30.7
3
(Cym)], 2.14 (s, 3 H, S-CH
3
),
1
2
1
7
3
(Cym)] ppm. 13C NMR (100 MHz, MeOD;
[CH (Cym)], 23.4 [CH
3
3 3
(Cym)], 22.6 [CH (Cym)], 21.1 (S-CH ),
+
1
6
7.6 [CH
42.1386; found 642.1383.
3
(Cym)] ppm. MS (ESI): m/z calcd. [C26H N SClOs ]
29 3
8.5 [CH (Cym)], 32.2 [CH (Cym)], 22.7 [CH
), 18.3 [CH (Cym)] ppm. MS (ESI): m/z calcd.
SClOs ] 628.1229; found 628.1228.
3 3
(Cym)], 22.2 [CH
2
(6): Yield 127 mg (0.158 mmol, 79%). 1
Cl ; 25 °C, TMS): δ = 8.21–8.17 (m, 1 H,
Ar-H), 7.91–7.84 (m, 2 H, Ar-H), 7.80–7.72 (m, 2 H, Ar-H), 7.62–
[
Ir(Cp*)Cl(L )] PF
6
H
(
Cym)], 20.7 (S-CH
3
3
+
NMR (400 MHz, CD
2
2
27 3
for [C25H N
1
(5): Yield 113 mg (0.144 mmol, 72%). 1
CO; 25 °C, TMS]: δ = 9.62 (s, 1 H, Triazol-
[
Ir(Cp*)Cl(L )] PF
NMR [400 MHz,(CD )
H), 8.26–8.16 (m, 2 H, Ar-H), 8.05–8.00 (m, 2 H, Ar-H), 7.99–
.93 (m, 1 H, Ar-H), 7.89–7.83 (m, 1 H, Ar-H), 7.58–7.47 (m, 3 H,
Ar-H), 2.39 (s, 3 H, S-CH
NMR (100 MHz, [D
CHTrz), 134.7, 134.0, 131.8, 130.7, 130.1, 129.3, 127.3, 127.2,
26.9, 123.8, 93.7, 20.4, 8.5 ppm. MS (ESI): m/z calcd.
6
H
7
1
.50 (m, 4 H, Ar-H), 4.10 (s, 3 H, N-CH
3
), 2.39 (s, 3 H, S-CH
3
),
) ppm. 13C NMR (100 MHz, CD
3 2
.22 (s, 15 H, Cp-CH
2
Cl ; 25 °C,
3
2
5
7
TMS): δ = 150.5 (Carbene-C), 141.5, 139.7, 133.5, 132.3, 131.6,
1
3
30.8, 130.1, 128.6, 126.7, 125.5, 123.7 (all Aryl-C), 94.00 (Cp-C),
8.5 (N-CH ), 22.0 (S-CH ), 7.8 (Cp-CH ) ppm. MS (ESI): m/z
SIr ] 644.1478; found 644.1467.
1
3
3
), 1.58 (s, 15 H, Cp-CH
3
) ppm.
C
3
3
3
6
]acetone; 25 °C, TMS): δ = 151.6, 138.0
30 3
calcd. [C26H N
+
(
1
Catalysis
+
[C
25
H
28
N
3
SClIr ] 630.1322; found 630.1303.
General Procedure for the Oxidation Catalysis: Oxidation catalysis
[
11n]
was performed by slight modification of a reported procedure.
To benzyl alcohol or diphenylmethanol (0.2 mmol), NMO
0.6 mmol) and the catalyst (1 mol-% or lower) were added anhy-
∧
2
Synthesis of the C S Complexes: L (82 mg, 0.2 mmol) was mixed
under a nitrogen atmosphere with silver oxide (163 mg, 0.7 mmol)
and potassium chloride (146 g, 2 mmol) and the mixture was dis-
solved in acetonitrile (15 mL) and stirred under exclusion of light
for 2 d. The mixture was then filtered through Celite and the vola-
tilities were removed under high vacuum. The corresponding metal
(
drous dichloromethane (4 mL). The reaction mixture was heated
to reflux for 3 h or less. After cooling to room temperature, the
solvent was removed and the residue was extracted in diethyl ether.
After filtering this mixture over cotton, the solvent was removed
2 2 2 2 2 2
dimer [RuCymCl ] , [OsCymCl ] , or [IrCp*Cl ] (0.1 mmol) was
1
again. Conversions were detected by H NMR spectroscopic analy-
added and the mixture was dissolved in dichloromethane (15 mL)
and stirred for 2 d under the exclusion of light. The mixture was
once again filtered through Celite to remove the silver chloride,
which precipitated during the reaction, and all volatilities were re-
moved under high vacuum. The crude product was then dissolved
in methanol (5 mL) and the solution was stirred for 5 min before
potassium hexafluorophosphate (148 mg, 0.8 mmol) was added.
The mixture was stirred for 15 min and water was added slowly
sis with hexadecane as internal standard.
X-ray Structure Analysis: X-ray quality crystals of 1 were grown
by slow diffusion of n-hexane into a concentrated solution of 1 in
dichloromethane at room temperature. X-ray quality crystals of 5
and 6 were obtained by slow diffusion of hexane into a concen-
trated solution of the corresponding complex in dichloromethane
at 8 °C (Table 5). Data were collected with a Bruker Smart AXS
Eur. J. Inorg. Chem. 0000, 0–0
6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42178
/KAP1
Date: 28-05-14 11:02:56
Pages: 9
www.eurjic.org
FULL PAPER
Table 5. Structural parameters.
Empirical formula
2
5
6
C
26
H26ClF
6
N
3
PRuS
C
25
H
28ClF
775.18
monoclinic, P2
1
6
IrN
3
PS
C
26 6 3
H30ClF IrN PS
M
r
697.07
monoclinic, P2
10.604(2), 24.493(5), 10.801(2)
789.21
monoclinic, Pn
10.726(5), 8.133(5), 16.339(5)
Crystal system, Space group
a, b, c [Å]
1
/n
/n
8.605(1), 22.776(4), 13.620(2)
α, β, γ [°]
V [Å ]
Z
Densitiy [gcm ]
F(000)
90, 93.028(5), 90
2801(1)
4
1.653
1408
90, 92.848(4), 90
2666.8(8)
4
1.931
1512
90, 91.562(5), 90
1425(1)
2
1.840
772
3
–3
Radiation
μ [mm ]
Mo-K
0.849
α
Mo-K
5.310
α
Mo-K
α
4.970
–
1
Crystal size
0.50ϫ0.16ϫ0.14
41247
8556
0.37ϫ0.13ϫ0.11
43514
8117
0.26ϫ0.20ϫ0.10
28384
8090
Measured reflections
Independent reflections
Observed [IϾ2σ(I)] reflections
7840
6593
7068
R
int
0.0254
0.0379, 0.0921, 1.174
1.342, –0.963
0.0337
0.0255, 0.0576, 1.092
2.082, –0.619
0.0533
0.0295, 0.566, 0.981
2.247, –1.412
2
2
2
R [F Ͼ 2σ(F )], wR(F ), S
Δρmax, Δρmin [eÅ ]
–3
system or a Bruker Kappa ApexII duo system. Data were collected
at 100(2) or 110(2) K, respectively, using graphite-monochromated
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Mo-K radiation (λ = 0.71073 Å). The strategy for the data collec-
tion was evaluated by using the Smart software or the CrysAlisPro
CCD software. The data were collected by standard “omega scan”
or “omega+phi scan” techniques, and were scaled and reduced
using Saint+software or the CrysAlisPro RED program. The struc-
tures were solved by direct methods using SHELXS-97[ and re-
17]
2
fined by full-matrix least-squares with SHELXL-97, refining on F .
CCDC-952335 (for 6), -952336 (for 5), and -952337 (for 2) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
1
13
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42178
/KAP1
Date: 28-05-14 11:02:56
Pages: 9
www.eurjic.org
FULL PAPER
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Published Online: ᭿
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42178
/KAP1
Date: 28-05-14 11:02:56
Pages: 9
www.eurjic.org
FULL PAPER
Catalysis for Oxidation
II
II
III
S. Hohloch, L. Hettmanczyk,
B. Sarkar* ........................................ 1–9
Ru , Os , and Ir complexes with a tria-
zole and a triazolylidene ligand containing
potential hemilabile thioether donors on
the N1 atom are presented. These are rare
Introducing Potential Hemilability into
II
“Click” Triazoles and Triazolylidenes: Syn-
examples of Os complexes with “click”-
derived triazole and triazolylidene ligands.
The new complexes (particularly the Os
6
thesis and Characterization of d -Metal
Complexes and Oxidation Catalysis
II
complexes) are shown to be potent oxi-
dation catalysts.
Keywords: Nitrogen heterocycles / Oxi-
dation / Carbene ligands / Ruthenium / Os-
mium
Eur. J. Inorg. Chem. 0000, 0–0
9
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim