Synthesis and Characterization of N-Trifluoromethyl N-Heterocyclic Carbene Ligands and Their Complexes

Article abstract of DOI:10.1021/acs.organomet.5b00137

Starting from N-trifluoromethyl benzimidazole (1), a series of N-trifluoromethyl benzimidazolium salts 2a-f·HA have been prepared and fully characterized. These were engaged in the formation of [Ir(CO)₂(NHC)Cl], [Rh(COD)(NHC)Cl], [Se(NHC)], and

Full text of DOI:10.1021/acs.organomet.5b00137

Article
pubs.acs.org/Organometallics
Synthesis and Characterization of N‑Trifluoromethyl N‑Heterocyclic
Carbene Ligands and Their Complexes
Pascal S. Engl, Remo Senn, Elisabeth Otth, and Antonio Togni*
Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Zu
̈
rich, Vladimir-Prelog-Weg 2,
CH-8093 Zurich, Switzerland
̈
*
S Supporting Information
ABSTRACT: Starting from N-trifluoromethyl benzimidazole
(
1), a series of N-trifluoromethyl benzimidazolium salts 2a−f·
HA have been prepared and fully characterized. These were
engaged in the formation of [Ir(CO) (NHC)Cl], [Rh(COD)-
2
(
NHC)Cl], [Se(NHC)], and [Au(NHC)Cl] derivatives. IR
analysis of [Ir(CO) (NHC)Cl] complexes revealed that the
2
trifluoromethyl substituent on nitrogen significantly decreases
the σ-donating ability of the carbene carbon. On the other
hand, the π-acceptor property of these novel ligands is enhanced. Examination of the 77Se NMR resonance of [Se(NHC)]
adducts and the redox potentials of [Rh(NHC)(COD)Cl] complexes further supports this assumption. In addition, the efficiency
of these new N-trifluoromethyl NHC ligands was investigated in π-acidic Au(I)-catalyzed hydroalkoxylation of cyclohexene. The
gold complexes bearing NHCs 2a and 2c−e compete with [Au(PPh )Cl] in terms of catalytic activity.
3
INTRODUCTION
such as the N-bis(trifluoromethyl) NHC ImN(CF ) shown in
3 2
■
1
Figure 1. These calculations predict that ImN(CF ) is a
3 2
The discovery by Arduengo et al. that carbenes are not
invariably reactive, unstable reaction intermediates has led to
the preparation of a myriad of N-heterocyclic carbenes (NHCs)
and ignited the curiosity of researchers toward possible2
applications of NHCs as ligands in homogeneous catalysis,
3
as well as components for medicinal, luminescent, and
4
functional materials. This is reflected by the abundance of
publications on NHCs and the vast structural diversity of
5
commercially available NHC precursors nowadays. The
striking success of NHCs in transition metal catalysis was
initially ascribed to their excellent σ-electron-donating proper-
Figure 1. Calculated Tolman electronic parameters (TEP) of
6
Ni(CO) (NHC) complexes bearing the NHC ligands ImN(Me)
ties, which leads to very strong metal carbene bonds, hence
3
2
and ImN(CF3) and schematic representation of crucial orbital
preventing decomposition of the catalyst and giving rise to high
catalytic activity. However, recent reports on the electronic
nature of NHCs have also highlighted the significance of π-
2
interactions.
7
bonding in transition metal catalysis. With the introduction of
significantly weaker donor ligand compared to its methyl
electron-withdrawing groups in the backbone structure or on
the substituents at the nitrogen atoms of the NHCs, one can
significantly improve metal-to-carbene π-back-donation. As a
analogue ImN(Me) . The ability of the nitrogen lone pair to
2
hyperconjugate into the σ*C−F antibonding orbital is
considered to decrease the π-overlap of this nitrogen with the
vacant p-orbital of the carbene. This in turn leads to an
increased π-acidity, as reflected by the substantially higher TEP
8
consequence of this increased π-acidity of the ligand, the metal
center becomes more electron-deficient, which has been shown
to lead to an accelerated or increased reactivity for, for example,
12
values for ImN(CF ) as compared to ImN(CH ) .
3 2
3 2
9
The larger TEP value of ImN(CF ) compared to ImN(Me)
π-acid-catalyzed cyclizations. As an interesting example, by
3 2
2
is assumed to be a consequence of the negative hyper-
conjugation from the nitrogen lone pair of ImN(CF ) into the
tuning the π-acceptor properties of ancillary NHC ligands,
1
0
Alcarazo et al. could selectively modulate the outcome of
three mechanistically distinct gold(I)-catalyzed processes. In
3 2
σ*CF antibonding orbital of the CF group, which leads to a
3
11
depletion of the electron density at the vacant p-orbital of the
carbene carbon. These considerations clearly call for a synthetic
order to evaluate the electronic effects of NHCs, Gusev used
computational methods to calculate the Tolman electronic
parameter (TEP) of a diverse group of representative NHC
ligands in [Ni(CO) (NHC)] complexes. Interestingly, this
study also included NHCs that have not yet been synthesized,
Received: February 17, 2015
Published: April 2, 2015
3
©
2015 American Chemical Society
1384
DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395

Organometallics
Article
method to access N-trifluoromethyl NHCs, since a major
impact on the behavior of the NHC as a ligand in transition
metal catalysis is anticipated.
the standard model system for estimating the electronic
properties of NHC ligands by measuring their average carbonyl
15
stretching frequency, ν , using IR spectroscopy. Iridium
av
We report herein the synthesis of a series of N-
trifluoromethyl NHC ligand precursors and their complexes
starting from N-trifluoromethyl benzimidazole (1), which can
be synthesized on a multigram scale following the procedure for
direct N-trifluoromethylation of azoles recently reported by our
complexes 3a−e were obtained by reaction of the in situ
generated free carbenes with [Ir(COD)Cl] using an excess of
2
NaH in THF (Scheme 3). Unfortunately, this protocol could
Scheme 3. Synthesis of [IrCl(COD)(NHC)] 3a−e and
1
3
group. This study includes an evaluation of the electronic
properties of these new N-trifluoromethyl NHC ligands and a
comparison with well-established NHCs and phosphines.
[IrCl(CO) (NHC)] 4a−e
2
RESULTS AND DISCUSSION
■
Treatment of N-trifluoromethyl benzimidazole (1) with an
excess of methyl triflate in CH Cl afforded benzimidazolium
2
2
salt 2a·HOTf as a bench-stable white solid in 96% yield. In
addition, alkyl iodides could successfully be applied for the
direct alkylation of 1, however, under harsher reaction
conditions and giving lower yields (Scheme 1).
not be applied for 2b·HI, which instead gave the undesired
[
IrI(COD)(2b)] complex, containing an iodide ligand. To
−
−
obtain iridium complex 3b, an anion exchange of I with NTf
2
Scheme 1. Synthesis of N-Trifluoromethyl Benzimidazolium
Salts 2a·HOTf, 2a·HI, and 2b·HI
prior to the reaction of 2b·HI with [Ir(COD)Cl]2 was
necessary.
Interestingly, the synthesis of iridium complex 3d also
afforded minor quantities of the dihydrobenzimidazole 2d·red
(
Figure 2). The formation of this byproduct is not unusual,
Disappointingly, it was not possible to arylate benzimidazole
1
with aryl halides. However, using diaryliodonium salts under
Figure 2. ORTEP drawing of 2d·red. Hydrogen atoms are omitted for
clarity, and thermal ellipsoids are set to 50% probability. Selected bond
lengths [Å], bond angles [deg], and torsion angles [deg]: C1−N1
1.474(2), C1−N2 1.471(2), N1−C2 1.394(3), C2−F1 1.337(3), N2−
C1−N1 103.65(15), N2−C1−N1−C2−144.45(18).
14
copper(II) catalysis, as recently presented by Gao,
benzimidazolium salt 2c·HOTf was initially prepared in 83%
yield (Scheme 2). The synthesis of benzimidazolium salts 2d·
Scheme 2. Synthesis of N-Trifluoromethyl Benzimidazolium
a
Salts 2c·HOTf, 2c·HBF , 2d·HBF , 2e·HBF , and 2f·HBF
4
4
4
4
considering the ability of NaH to act both as a base and as a
16
reductant. However, treatment of benzimidazolium salt 2d·
BF with NaH in the absence of [Ir(COD)Cl] did not lead to
4
the formation of dihydrobenzimidazole 2d·red.
Subsequent exposure of a solution of iridium complexes 3a−
e in CH Cl to carbon monoxide afforded the respective
2
2
[
Ir(CO) (NHC)Cl] complexes 4a−e. The corresponding TEP
2
parameters of complexes 4a−e were determined by applying a
relation established by Nolan and Plenio, correlating the
17
a
average CO stretching frequencies of [IrCl(CO) (NHC)]
Use of [Cu(OAc) ·H O] instead of [Cu(OTf) ].
2
2
2
2
complexes to the traditionally used [Ni(CO) (L)] system
3
(
Table 2). Known TEP values of typical tertiary phosphines
−1
HBF , 2e·HBF , and 2f·HBF required the use of [Cu(OTf) ]
span over a relatively large range between 2056.1 cm (PCy3)
4
4
4
2
1
18
instead of [Cu(OAc) ·H O]. Presumably, deprotonation of the
and 2110.8 cm− (PF3), while the lower TEP values of
standard NHCs are distributed over a relatively small range of
ca. 10 cm− (Figure 3). N-Trifluoromethyl NHCs 2a−e, on the
other hand, are found at higher TEP values, thereby accounting
for their less electron-donating nature. Furthermore, a
significant difference between the TEP parameters of NHCs
2a−e and that of NHC 5 (1,3-bis(2-propyl)-1H-benzimidazo-
2
2
newly formed benzimidazolium salt by acetate and consecutive
complexation of the NHC to the copper catalyst inhibited the
reaction.
Determination of the π-Acceptor Properties of N-
Trifluoromethyl NHC Ligands via IR and NMR Analysis.
1
Iridium carbonyl complexes [IrCl(CO) (NHC)] have become
2
1
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Article
Table 1. Important Bond Lengths, Bond Angles, and Torsion Angles of Selenium Adducts 6a−f
6
a
6b
6c
6d
6e
6f
Bond Lengths [Å]
1.804(4)
Se1−C1
N1−C2
N2−C9
1.820(3)
1.418(4)
1.467(4)
1.820(2)
1.424(2)
1.482(2)
1.809(2)
1.431(2)
1.429(2)
1.814(5)
1.439(6)
1.435(6)
1.816(7)
1.436(9)
1.435(9)
1.418(5)
1.437(5)
Bond Angles [deg]
105.1(3)
N1−C1−N2
105.7(2)
2.5(2)
105.6(1)
2.5(2)
105.0(1)
1.7(2)
105.7(4)
0.7(7)
105.6(5)
Torsion Angles [deg]
1.3(5)
Se1−C1−N1−C2
−3.1(9)
lylidene) can be noted (Table 2). This finding suggests that the
presence of a trifluoromethyl substituent at the nitrogen atom
can lead to a higher d → π*(NHC) back-donation and hence a
reduced d → π*(CO) back-donation compared to standard
NHCs.
electron-donating isopropyl groups of NHC 5 lead to an
electronically more shielded selenium atom. Accordingly, the
77
Se NMR resonance of the selenium adduct of NHC 5 is
shifted to higher field. Moreover, the introduction of an
additional electron-withdrawing p-nitrophenyl (2d), p-trifluoro-
methyl (2e), or pyridinyl (2f) substituent at the second
nitrogen atom leads to a further increase of the π-acidity of the
In order to quantify the contribution of the d → π*
8
interactions for NHC−metal bonds, Ganter has established an
77
alternative model system to compare the π-acceptor strength of
respective NHCs. While the respective Se NMR resonance of
adducts 6a−f are gradually shifted to lower field with increasing
π-acidity, the TEP values of 2a−e are barely affected.
Interestingly, the TEP parameters of NHCs 2a−e do not
77
different types of NHCs. It has been demonstrated that the Se
NMR chemical shift of the corresponding NHC selenium
adducts correlates with the π-acceptor character of the
7
7
77
13
respective carbene. Furthermore, the Se NMR chemical
shift can be measured with far greater accuracy as compared to
IR data. The NHC selenium adducts 6a−f were obtained in
one synthetic step by deprotonation of the NHC precursors
correlate with the Se NMR and C NMR chemical shifts of
the carbene atoms in 6a−e. Hence, comparison of the TEP
values of imidazolylidenes with those of benzimidazolylidenes
might be biased by the different nature of the metal to ligand
bonding of these two NHC classes. This can best be illustrated
by correlating the TEP values of SIPr and NHC 2b to the
respective 77Se NMR chemical shifts. While the TEP values of
2
a−f·HA with NaHMDS in the presence of selenium black
(
Scheme 4). Interestingly, benzimidazolium salts having a
triflate counterion could not be converted to the corresponding
selenium adducts. Instead, decomposition of the benzimidazo-
lium salts was observed under the applied reaction conditions.
Single crystals suitable for X-ray diffraction analysis were
obtained by slow evaporation of a solution of the
7
7
SIPr and 2b deviate substantially, the corresponding Se NMR
chemical shifts of the selenium adduct of SIPr and 2b are only 6
ppm apart, implying a similar degree of π-accepting character.
This observation can however be accounted for by the fact that
saturated NHCs such as SIPr are slightly better σ-donors than
their unsaturated analogues, which results in stronger metal to
corresponding selenium adducts 6a−f in CDCl . ORTEP
3
representations, as well as selected bond lengths and angles of
selenium derivatives 6a−f, are shown in Table 1. The Se−C
bond lengths of compounds 6a−f are all very similar and do
not show any significant deviation from the value found for
22
NHC bonding.
Electrochemical Analysis of Complexes 7a−e. The
redox potential E1 of metal complexes is highly sensitive to
/2
1
9
[
Se(IPr)] (1.853(7) Å) and [Se(SIPr)] (1.820(8) Å). The
the electron density at the metal center, which is in turn
affected by the acceptor and donor properties of its ligands.
More electronegative ligands remove electron density from the
metal center, thereby increasing the energy barrier toward
7
7
Se NMR chemical shifts of derivatives 2a−f range from 196 to
76 ppm, as presented in Table 2. Thus, compared to the
selenium adduct of NHC 5, the Se resonance of, for example,
2
7
7
23
6b is shifted by 148 ppm to lower field.
oxidation of the complex. In order to gain further insight into
the electronic properties of the N-trifluoromethyl NHC ligands,
rhodium complexes 7a−e were synthesized and their redox
This is a consequence of the increased π-acidity induced by
the trifluoromethyl group in 6b. On the other hand, the
1
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Table 2. Tolman Electronic Parameters (TEP) and NMR
Data of Selected Carbenes
Scheme 4. Synthesis of Selenium Adducts 6a−f
[
IrCl(CO) (NHC)]
[Se(NHC)]
2
1
3
77
δ( C)
δ( Se)
ligand
R = Me
TEP [cm−1]a
[ppm]
b
[ppm]
b
2
2
2
2
2
2
5
a
b
c
2059.0
2058.6
2058.0
2060.8
2059.9
n.d.
166.3
165.2
167.4
167.5
167.4
168.2
164.9
162.3
184.3
215
196
249
276
264
275
67
Table 3. Redox Potentials E1/2 [V] of [RhCl(COD)(NHC)]
Complexes 7a−e and 8
R = iPr
R = Ph
d
e
R = 4-NO Ph
2
R = 4-CF Ph
3
f
c
R = 4-F-py
2053.3
2051.5
2052.2
2060.2
2069.0
2068.9
d
IPr
90
d
SIPr
190
e
IDNP
[RhCl(COD)(NHC)]
f
IDA
182.3
856
a
ligand
A
R
yield (%)
E1/2 (V)
g
PPh3
7
7
7
a
b
c
2a
2b
2c
2d
2e
OTf
I
Me
iPr
Ph
72
65
76
57
58
n.d.
a
TEP parameters were calculated from the symmetric and
antisymmetric carbonyl stretching frequencies of the corresponding
IrCl(CO) (NHC)] complexes, using the relation TEP = 0.847 ×
1.012
0.858
1.053
1.025
0.773
BF4
[
2
−
b
1
20
7d
7e
8
BF
BF4
4
p(NO C H )
2 6 5
ν (CO) + 336 cm . The IR spectra of complexes 4a−e were
av
77
13
p(CF C H )
3
6
5
measured in CH Cl . The Se NMR and C carbene NMR chemical
2
2
c
shifts of selenium adducts 6a−f were measured in CDCl . The
3
a
+
26
symmetric and antisymmetric carbonyl stretching frequencies, as well
Calibrated against Fc/Fc E1 = 0.46, 0.1 M Bu NPF in CH Cl .
/2 4 6 2 2
as the 13C and Se chemical shifts, have been reported in ref 21. The
77
d
13
77
TEP parameters, as well as the C and Se chemical shifts, have been
reported in ref 19. IDNP = 1,3-bis(2,4-dinitrophenyl)-1H-imidazoly-
lidene. The TEP parameter has been reported in ref 9c. IDA = 1,3-
dimesityl-4,5-dioxo-4,5-dihydro-1H-imidazolylidene. The TEP param-
eters, as well as the C and Se chemical shifts, have been reported in
ref 8. The TEP parameter has been reported in ref 18.
attributed to the increased electron-withdrawing property of
the trifluoromethyl substituent of NHC 2b. Interestingly, the
redox potential of rhodium complex 7c (Figure 4) is lowered
by 0.167−0.195 mV compared to complexes 7d and 7e.
e
f
1
3
77
g
Figure 4. ORTEP drawing of 7c. Hydrogen atoms are omitted for
clarity, and thermal ellipsoids are set to 50% probability. Selected bond
lengths [Å], bond angles [deg], and torsion angles [deg]: Rh1−C1
Figure 3. Correlation of the average carbonyl stretching frequency νco
2
.015(2), Rh1−C16 2.208(2), Rh1−C17 2.175(2), Rh1−C20
.125(2), Rh1−C21 2.107(2), C1−N1 1.380(3), C1−N2 1.350(3),
values of [IrCl(CO) (L)] complexes with the Tolman electronic
2
2
parameter (TEP): (▲) N-trifluoromethyl NHCs 2a−e; (◆) standard
N1−C2 1.425(3), N2−C9 1.437(3), N1−C1−N2 104.25(2), C1−
Rh1−C21 95.62(8), N1−C1−Rh1−Cl1−76.2(2), C1−N2−C9−
C14−56.9(3).
NHCs; (●) tertiary phosphines.
potentials were determined by cyclic voltammetry (Table 3).
Except for rhodium complex 7a, the Rh(I/II) redox process of
When trying to rationalize the observed reduction potentials,
π-conjugation could easily be ruled out: First of all, the metal
center and the electron-withdrawing group at the Cpara are
separated by 7 bonds. Second, the near orthogonality of the
two aromatic systems renders their conjugation quite unlikely.
Finally, when comparing the N2−C3 bond distances of the
selenium adducts 6a−f, no change in bond length can be
7b−e turned out to be reversible. Notably, the redox potential
changes by 0.239 mV when replacing the electron-donating
isopropyl group on the nitrogen of 5 with a trifluoromethyl
group in complex 7b. Due to the fact that the Cl and COD
ligands remain constant in the [RhCl(COD)(NHC)] com-
plexes examined, the shift to higher redox potentials can be
1
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Article
2
8
observed, likewise hinting at a negligible π-conjugation. Similar
1.998(4) Å and Au−Cl = 2.2718(11) Å). The catalytic
activity of the Au(I)-NHC complexes 9a−e was then evaluated
in the intermolecular hydroalkoxylation of cyclohexene as a
model reaction, using the same reaction conditions as reported
24
observations were made by Plenio, who proposed that the
interaction between the NHC ligand and the metal center
could occur through π-face donation from an electron-rich N-
aryl moiety, hence increasing the electron density at the metal
center and possibly stabilizing higher oxidation states during
29
by Sato et al. For comparison, the catalytic activities of the
Au(I) complexes bearing PPh , IDNP, IPr, and NHC 5 are also
3
25
catalysis. Recently, Cavallo further examined this mode of
interaction with the help of DFT calculations. His findings
suggest a π-face donation from the Cipso of the N-aryl moiety to
an empty d-orbital of the metal center, this phenomenon
increasing for more electron donating para substituents. This
assumption is supported by the observation that the redox
potential of complex 7b is higher by 0.154 mV compared to
that of complex 7c, although an isopropyl group is generally
considered to be a better σ-electron donor than a phenyl group.
Indeed, in contrast to the phenyl group (7c), Cipso of the
isopropyl group (7b) does not possess any π-orbital to donate
electron density to the metal center.
provided in Table 4.
Table 4. Au(I)-Catalyzed Intermolecular Hydroalkoxylation
a
of Cyclohexene
b
entry
[Au(L)Cl]
yield (%)
1
2
3
4
5
6
7
8
9
9a, L = 2a
9b, L = 2c
9c, L = 2d
9d, L = 2e
9e, L = 2f
L = 5
70
74
75
Au-Catalyzed Hydroxyalkoxylation of Alkenes. We
were interested in comparing the influence on reactivity of the
novel N-trifluoromethyl NHC ligands with that of known
NHCs in π-acid gold catalysis. Similarly to a recent report by
77
11
77
c
2
7
L = IPr
35 (lit: 7)
Sato et al., we expected that the significant extent of Au-NHC
d → π* back-bonding would enhance the π-acidity of the metal
center, giving superior catalysts. The Au(I)-NHC complexes
c
c
L = PPh3
76 (lit: 63)
64 (lit: 66)
0
d
L = IDNP
none
1
0
9
a−e were synthesized by in situ deprotonation of the
a
Reaction conditions: 10 (0.25 mmol), 11 (2.5 mmol), gold complex
0.0125 mmol), and AgNTf (0.0125 mol) in PhCl (0.25 mL) for 20
h. Yields were determined by GC analysis, using n-tetradecane as an
corresponding benzimidazolium salts with K CO in the
2
3
(
2
presence of [Au(DMS)Cl] (Scheme 5).
b
c
d
internal standard. See ref 29. IDNP = 1,3-bis(2,4-dinitrophenyl)-1H-
Scheme 5. Synthesis of Au-NHC Gold Complexes 9a−e
imidazolylidene.
From the corresponding results, we conclude that the N-
trifluoromethyl NHCs 2a and 2c−e induce an intermediate π-
acidity between that of standard NHCs and phosphines. If the
catalytic activity were solely dependent on the π-acidity of the
gold complexes, one would therefore expect a correlation
between the analytical data and the reaction outcome. The gold
complex bearing the weakest π-accepting NHC, IPr, indeed
shows the lowest catalytic efficiency (35% yield). Interestingly,
the catalytic activities of the gold complexes 9a−d (70−77%
yield) were found to surpass that of [Au(IDNP)Cl] (64%
Single crystals of 9a suitable for X-ray diffraction analysis
were obtained by sublimation. The ORTEP representation of
yield) and compete with that of [Au(PPh )Cl] (76% yield).
3
Au(I) complex 9e, bearing the pyridinyl N-substituent, on the
other hand, leads to a yield of only 11%. Furthermore, although
the analytical data suggest that NHC 5 is a weaker π-acceptor
compared to the N-trifluoromethyl NHCs, the catalytic activity
of [Au(5)Cl] (77% yield) is comparable to that of gold
complexes 9a−d. This result can be rationalized by an
9
(
a is shown in Figure 5. Both the C1−Au bond length
1.982(6) Å) and the Au−Cl bond length (2.2778(14) Å) in 9a
are comparable to those in [Au(IPr)Cl] (C −Au =
carbene
3
0
observation made by Hahn et al. in palladium- and
platinum-catalyzed cross-coupling reactions, suggesting that
benzimidazolylidene ligands generally show improved perform-
ance over imidazolylidene ligands in such transformations.
However, no clear trend can be inferred from these simple
experiments, suggesting that, besides π-acidity, other factors
such as stability and solubility of the active catalyst play an
additional significant role.
CONCLUSIONS
■
Figure 5. ORTEP drawing of 9a. Hydrogen atoms are omitted for
clarity, and thermal ellipsoids are set to 50% probability. Selected bond
lengths [Å] and bond angles [deg]: Au1−C1 1.982(6), Au1−Cl1
A series of N-trifluoromethyl NHC ligand precursors 2a−f·HA
have been synthesized and fully characterized starting from N-
trifluoromethyl benzimidazole 1. In order to explore the π-
accepting properties of the corresponding NHC ligands, they
2
.2778(14), C1−N1 1.360(8), C1−N2 1.346(7), N1−C2 1.417(7),
N2−C9 1.456(8), N1−C1−N2 106.4(5).
1
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have been engaged in the formation of several organometallic
charged with benzimidazole (6000 mg, 50.8 mmol, 1.1 equiv), silica
sulfuric acid (150 mg), and HMDS (50 mL, 157.2 mmol, 3.4 equiv).
The reaction mixture was heated to reflux for 6 h. Subsequently, the
reaction was cooled to room temperature and filtered through a
cannula with a filter into a 200 mL Schlenk flask. The 250 mL two-
necked round-bottom flask was washed with toluene (2 × 10 mL).
The solvent and the HMDS were removed under reduced pressure
complexes. The spectroscopic analysis of [IrCl(CO) (NHC)]
2
complexes revealed that NHCs bearing a trifluoromethyl
substituent are significantly weaker donor ligands compared
to standard NHCs, as reflected by their higher TEP values. The
decreased σ-donating ability of the carbene carbon is
considered to be a consequence of the diminished π-overlap
with the nitrogen lone pair, due to hyperconjugation of the
nitrogen lone pair into the σ*C−F antibonding orbital of the
trifluoromethyl group. Concurrently, the π-accepting property
of these novel ligands is enhanced, which was verified by
examining the 77Se NMR resonance of [Se(NHC)] adducts
and the redox potentials of [RhCl(COD)(NHC)] complexes.
To further evaluate and compare the electronic properties of
our N-trifluoromethyl NHCs to those of well-established
(
15 mbar) to give the trimethylsilylated benzimidazole, which was then
−2
dried for an additional 30 min under high vacuum (4.2 × 10 mbar).
In a glovebox, the trimethylsilylated benzimidazole was dissolved in
CH Cl (15 mL), and LiNTf (155 mg, 0.924 mmol, 0.02 equiv) was
2
2
2
added. After shaking, 3,3-dimethyl-1-(trifluoromethyl)-1,2-benziodox-
ole (15 200 mg, 46.2 mmol, 1 equiv) and HNTf (1560 mg, 15.54
2
mmol, 0.12 equiv) were added, and the neck of the Schlenk flask was
rinsed with CH Cl (5 mL). The resulting clear solution was then
2
2
stirred at 35 °C for 20 h. The reaction mixture was then cooled to rt
and concentrated on a rotatory evaporator (650 mbar). The residue
NHCs and PPh , the intermolecular hydroalkoxylation of
3
was purified by column chromatography (Pentane/Et O, 10:1 to 2:1)
2
cyclohexene with 2-methoxyethanol using Au(I) complexes was
−2
and subsequent bulb-to-bulb distillation (60 °C, 5 × 10 mbar) to
carried out. The gold complexes 9a−d were found to be
afford 1 (6128 mg, 46.2 mmol, 71.3% isolated yield) as a colorless
1
catalytically active and compete with [Au(PPh )Cl] and
liquid. H NMR (300.13 MHz, CDCl ): δ = 8.15 (s, 1H, NCHN),
3
3
[
Au(5)Cl] complexes on the basis of product formation.
7.86 (d, J = 9.2 Hz, 1H, ArH), 7.60 (d, J = 7.3 Hz, 1H, ArH), 7.42 (m,
2
H, ArH). 19F NMR (282.38 MHz, CDCl ): δ = −57.04. C{ H}
13
1
3
NMR (75.47 MHz, CDCl ): δ = 143.78 (C), 138.21 (NCHN), 130.32
3
EXPERIMENTAL SECTION
■
(C), 125.58 (CH), 124.73 (CH), 124.13(CH), 118.90 (q, J = 263.5
General Information. All experiments were performed under an
argon atmosphere using standard Schlenk techniques. Solvents were
distilled and dried prior to utilization (CH Cl from CaH ; Et O,
Hz, NCF ), 111.40 (q, J = 2.1 Hz, CH). IR (neat): 3090.3, 1376.9,
3
−1
1320.9, 1292.2, 1231.8, 1150.9, 1000.6, 739.5 cm . HRMS (ESI): [M
+ H ] calcd for C H F N 187.05; found 187.0490. Anal. Calcd (%)
+
2
2
2
2
8
6
3
2
THF, and toluene from Na/benzophenone; chlorobenzene from
P O ). Unless otherwise stated all commercially available chemicals
for C H F N : C, 51.62; H, 2.71; N, 15.05. Found: C, 51.79; H, 2.82;
N, 15.18.
8 5 3 2
2
5
were used without further purification. Cyclohexene and 2-
methoxyethanol were purified by atmospheric distillation prior to
use. The following reagents and metal complexes were synthesized
according to reported procedures: 3,3-dimethyl-1-(trifluoromethyl)-
3-Methyl-1-(trifluoromethyl)-1H-benzo[d]imidazol-3-ium
Triflate (2a·HOTf). A 50 mL Young Schlenk flask was charged with 1
(1021 mg, 5.48 mmol, 1 equiv) and CH Cl (10 mL). Subsequently,
2 2
the reaction mixture was cooled to 0 °C, and methyl trifluorometha-
nesulfonate (0.95 mL, 8.23 mmol, 1.5 equiv) was added dropwise over
10 min. The reaction mixture was stirred at room temperature for 3 h.
Subsequently, all volatiles were removed under reduced pressure (9 ×
3
1
32
33
1
,2-benziodoxole, diaryliodonium triflates, NaHMDS, [Ir-
34 35 36
(
COD)Cl] , [Rh(COD)Cl] , [Rh(5)(COD)Cl], [Au(IDNP)-
2 2
37 38
Cl], [Au(IPr)Cl]. Diaryliodonium trilfates were converted to the
−
3
corresponding diaryliodonium tetrafluoroborates following a proce-
10 mbar) to give 2a·HOTf (1836 mg, 5.24 mmol, 95.6%) as a white
39
1
dure reported by Olofsson. Neutral aluminum oxide activity I was
purchased from ICN Biomedicals GmbH. Silica gel 60 (230−400
mesh) was purchased from Fluka. TLC plates were obtained from
Merck (silica gel 60 F254). NMR spectra were recorded on Bruker
DPX-200, DPX-300, DPX-400, and DPX-500 instruments operating at
the denoted spectrometer frequency given in MHz for the specified
solid. H NMR (300.13 MHz, MeOD-d ): δ = 10.40 (s, 1H, NCHN),
4
8.15−8.12 (m, 1H, ArH), 8.07−8.05 (m, 1H, ArH), 7.95−7.86 (m,
1
9
2H, ArH), 4.27 (s, 3H, NCH ). F NMR (282.38 MHz, MeOD-d ): δ
3
4
13
1
= −59.54 (NCF ), −80.18 (SCF ). C{ H} NMR (75.48 MHz,
3
3
MeOD-d ): δ = 143.64−142.97 (apt m, NCHN), 133.69 (C), 130.62
4
(CH), 129.83 (CH), 128.80 (C), 121.12 (q, J = 318.56 Hz, CF ),
3
1
13
nucleus. The H and C chemical shifts are referred to TMS and
118.87 (q, J = 268.5 Hz, CF ), 115.65 (CH), 114.49 (CH), 34.99
3
19
calibrated with the residual solvent peak. For F NMR, CFCl was
(NCH ). IR (neat): 3177.9, 3116.9, 1260.0, 1210.1, 1150.4, 1025.9,
3
3
−1
+
used as an external standard. The chemical shifts are reported in parts
per million (ppm), and coupling constants J are given in hertz (Hz).
High-resolution mass spectra were measured by the MS-service of the
754.5, 635.4 cm . HRMS (ESI): [M − CF O S] calcd for C H F N
201.06; found 201.0642. Anal. Calcd (%) for C H N O F S: C,
3
3
9
8
3
2
10
8
2
3 6
34.29; H, 2.30; N, 8.00. Found: C, 34.29; H, 2.29; N, 8.05. Mp: 135.8
°C.
“
̈ ̈
Laboratorium fur Organische Chemie der ETH Zurich”. Values are
given as m/z and the intensity I% of the base peak. Elemental analysis
3-Methyl-1-(trifluoromethyl)-1H-benzo[d]imidazol-3-ium Io-
dide (2a·HI). A septum cap vial (5 mL) tube was charged with 1
(160.0 mg, 0.86 mmol, 1 equiv) and THF (2 mL). Subsequently,
methyl iodide (0.2 mL, 3.19 mmol, 3.7 equiv) and the reaction mixture
were stirred at 120 °C for 12 h. Subsequently, the precipitate was
collected, washed with acetone (3 × 10 mL), and dried in vacuo to
was performed by the microelemental anaylsis service of the
“
Laboratorium fu
Mikroelementalanalytisches Laboratorium der ETH Zu
points were determined on a Buchi melting point B-540 apparatus in
̈
r Organische Chemie der ETH Zu
̈
rich and the
̈
rich”. Melting
̈
open capillaries and are uncorrected. IR spectra were recorded on a
Thermo Fischer Scientific Nicolet 6700 FT-IR equipped with a PIKE
Technologies GladiATR or on a PerkinElmer BX II using ATR FT-IR
technology and are reported as absorption maxima in cm . X-ray
diffraction structural analysis was carried out on a Siemens CCD
diffractometer (Siemens SMART PLATFORM, with CCD detector,
graphite monochromator, Mo Kα radiation). Details of the data
collection and refinement can be found in the Supporting Information.
The GC yields of ether 12 were determined by addition of n-
tetradecane as an internal standard on a Thermo Fischer Trace GC
afford 2a·HI (184.1 mg, 0.56 mmol, 65.3%) as a white, crystalline
1
solid. H NMR (300.13 MHz, DMSO-d ): δ = 10.71 (s, 1H, NCHN),
6
−1
8.25−8.21 (m, 1H, ArH), 8.13−8.09 (m, 1H, ArH), 7.89−7.86 (m,
1
9
2H, ArH), 4.18 (s, 3H, NCH ). F NMR (282.38 MHz, DMSO-d ): δ
3
6
13
1
= −59.45 (NCF ). C{ H} NMR (75.48 MHz, DMSO-d ): δ 143.46
(apt d, J = 3.1 Hz, NCHN), 131.87 (C), 128.98 (CH), 128.08 (CH),
3
6
126.65 (C), 116.99 (apt d, J = 268.0 Hz, NCF ), 114.93 (CH), 113.16
3
(CH), 34.34 (NCH ). IR (neat): 3013.7, 2980.1, 2924.1, 1363.5,
3
−
1
+
1235.2, 1184.1, 1135.8, 1083.2, 762.2 cm . HRMS (ESI): [M − I]
calcd for C H F N 201.06; found 201.0634. Anal. Calcd (%) for
2000 equipped with a flame ionization detector, using a ZB-5 column
9
8
3
2
with guardian (L: 30 m × i.d.: 0.25 mm, DF = 0.25 μm) and helium as
the carrier gas with a constant flow of 1.1 mL/min.
C H N F I: C, 32.95; H, 2.46; N, 8.54. Found: C, 32.74; H, 2.34; N,
9 8 2 3
8.40. Mp: 239.6 °C.
3-Isopropyl-1-(trifluoromethyl)-1H-benzo[d]imidazol-3-ium
Iodide (2b·HI). A septum cap vial (5 mL) tube was charged with 1
1-(Trifluoromethyl)-1H-benzo[d]imidazole (1). A 250 mL two-
necked round-bottom flask equipped with a reflux condenser was
1
389
DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395

Organometallics
Article
(
700 mg, 3.76 mmol) and 2-iodopropane (2 mL, 19.84 mmol). The
3080.3, 3038.6, 1530.6, 1357.2, 1239.6, 1205.6, 1022.8, 460.4, 692.9
−
1
+
reaction mixture was then stirred at 120 °C for 18 h. Subsequently,
diethyl ether (3 mL) was added. The resulting precipitate was filtered
off and recrystallized from MeOH/Et O to afford 2b·HI (455.1 mg,
3
cm . HRMS (ESI): [M − BF ] calcd for C H F N O F 308.07;
4
14
9
3
3
2 3
found 308.0641. Mp: 243.8 °C.
1-(Trifluoromethyl)-3-(4-(trifluoromethyl)phenyl)-1H-benzo[d]-
imidazol-3-ium Tetrafluoroborate (2e·HBF ). Synthesized according
2
1
3.9%) as a white, crystalline solid. H NMR (300.13 MHz, DMSO-
4
d ): δ = 10.59 (s, 1H, NCHN), 8.36−8.32 (m, 1H, ArH), 8.12−8.0
to general procedure A from 1 (545.2 mg, 2.93 mmol) and mesityl(4-
(trifluoromethyl)phenyl)iodonium tetrafluoroborate (2100 mg, 4.39
6
(
m, 1H, ArH), 7.88−7.5 (m, 2H, ArH), 5.19 (hept, J = 6.7 Hz, NCH),
19
1
6
=
.69 (d, J = 6.7 Hz, 6H, C(CH ) ). F NMR (282.38 MHz, DMSO-
mmol). The product was obtained as a white solid (749.7 mg, 1.79
3
2
13
1
1
d ): δ = −57.19 (NCF ). C{ H} NMR (100.62 MHz, DMSO-d ): δ
141.72 (NCHN), 130.58 (C), 128.97 (CH), 128.01 (CH), 127.15
mmol, 61.2%). H NMR (400.13 MHz, DMSO-d
6
): δ = 11.23 (s, 1H,
3
6
NCHN), 8.26 (apt t, J = 8.7 Hz, 3H, ArH), 8.13 (apt d, J = 8.3 Hz, 2H,
ArH), 7.91 (m, 3H, ArH). 19F NMR (282.38 MHz, DMSO-d
): δ =
). C{ H} NMR
): δ = 144.15 (apt d, J = 2.9 Hz, NCHN),
(
(
2
C), 117.04 (q, J = 268.2 Hz, NCF ), 115.30 (CH), 113.40−113.36
6
3
13
1
m, CH), 52.51 (NCH), 21.06 (CH ). IR (neat): 3119.6, 3017.8,
−57.67 (NCF
3
), −61.34 (ArCF
3
), −148.40 (BF
4
3
−1
981.2, 1556.9, 1423.9, 1356.7, 1219.5, 1171.4, 1057.5, 754.1 cm .
(100.62 MHz, DMSO-d
6
+
HRMS (MALDI/ESI): [M − I] calcd for C H F N 229.09; found
135.34 (C), 131.70 (C), 131.34 (C), 129.50 (CH), 129.07 (CH),
127.71 (2C, q, J = 3.8 Hz, CH), 126.98 (2C, CH), 126.77 (C), 123.55
(apt d, J = 272.8 Hz, CF ), 117.08 (apt d, J = 269.1 Hz, CF ), 114.75
11
12
3
2
2
7
29.0942. Anal. Calcd (%) for C H N F I: C, 37.10; H, 3.40; N,
11 12 2 3
.87. Found: C, 36.97; H, 3.36; N, 7.74. Mp: 228.9 °C.
3
3
General Procedure A. Synthesis of Benzimidazolium Salts 2c−f.
(CH), 113.63 (CH). IR (neat): 3144.0, 3072.3, 3017.8, 1567.3,
−1
Benzimidazolium salts 2c−f were synthesized starting from 1 following
1326.7, 1212.2, 1127.6, 1068.8, 1023.7, 853.8, 753.1 cm . HRMS
40
+
a modified procedure previously reported by Gao. To a solution of
(ESI): [M − BF ] calcd for C H F N 331.07; found 331.0670. Mp:
4
15
9
6
2
the corresponding diaryl iodonium salt (1.5 equiv) in DMF (0.2 M)
224.5 °C.
were added 1 (1 equiv) and Cu(OTf) (5 mol %). The resulting
3-(6-Fluoropyridin-3-yl)-1-(trifluoromethyl)-1H-benzo[d]-
imidazol-3-ium Tetrafluoroborate (2f·HBF ). Synthesized according
2
reaction mixture was stirred at 100 °C for 6 h. Subsequently, Et O was
4
2
added to precipitate the product, which was filtered off and washed
to general procedure A from 1 (723.1 mg, 3.88 mmol) and (6-
fluoropyridin-3-yl)(mesityl)iodonium tetrafluoroborate (2500.0 mg,
thoroughly with CH Cl . Subsequent recrystallization from acetone/
2
2
Et O afforded the product as a white solid.
5.83 mmol). The product was obtained as a white solid (250.9 mg,
2
1
1
-(Trifluoromethyl)-3-(phenyl)-1H-benzo[d]imidazol-3-ium Tri-
0.68 mmol, 17.5%). H NMR(400.13 MHz, acetone-d
6
): δ = 10.77 (s,
flate (2c·HOTf). Synthesized according to general procedure A from
1H, NCN), 8.73 (s, 1H, ArH), 8.63 (ddd, J = 9.1, 6.6, 2.8 Hz, 1H,
ArH), 8.27 (d, J = 8.0 Hz, 1H, ArH), 8.04 (m, 2H, ArH), 7.59 (dd, J =
1
4
2
1
(500 mg, 2.69 mmol) and diphenyliodonium triflate (1733.4 mg,
.03 mmol). The product was obtained as a white solid (919.9 mg,
.23 mmol, 83%). H NMR (300.13 MHz, DMSO-d ): δ = 11.14 (s,
1
9
8.8, 3.1 Hz, 1H, ArH), 7.46 (dd, J = 8.8, 3.1 Hz, 1H, ArH). F NMR
(376.46 MHz, acetone-d ): δ = −59.02 (NCF ), −64.99 (ArF),
1
6
6
3
13
1
H, NCHN), 8.24 (dt, J = 9.1, 1.6 Hz, 1H, ArH), 7.97−7.80 (m, 8H,
−151.74 (BF ). C{ H} NMR (100.62 MHz, acetone-d ): δ = 165.37
4
6
19
ArH). F NMR (282.38 MHz, DMSO-d ): δ = −57.54 (NCF ),
(apt d, J = 242.8 Hz, CF), 146.63 (d, J = 17.9 Hz, CCHN), 143.80
(apt d, J = 3.3 Hz, NCHN), 141.20 (d, J = 9.9 Hz, CH), 133.67 (C),
130.86 (CH), 130.37 (CH), 128.68 (apt d, J = 4.7 Hz, C), 128.36 (C),
6
3
−
(
1
(
77.77 SCF3). 13C{ H} NMR (75.48 MHz, DMSO-d ): δ = 162.54
1
6
C), 143.62 (apt d, J = 3.2 Hz, NCHN), 132.01 (CH), 131.53 (C),
31.45 (CH), 130.40 (CH), 129.28 (CH), 128.87 (CH), 126.80
CH), 125.59 (CH), 120.63 (apt d, J = 322.5 Hz, CF ), 117.07 (apt d,
117.56 (apt d, J = 272.5 Hz, CF ), 114.83 (CH), 113.71 (q, J = 1.5 Hz,
3
3
CH), 111.61 (d, J = 40.3 Hz, CH). IR (neat): 3150.7, 3086.9, 3048.0,
J = 268.9 Hz, CF ), 115.29 (CH), 113.54 (CH). IR (neat): 3132.6,
1569.2, 1495.0, 1474.9, 1422.8, 1365.4, 1287.6, 1242.9, 1210.5, 1165.6,
3
−
1
+
3
7
064.6, 3010.6, 1566.9, 1475.8, 1286.7, 1240.4, 1202.5, 1156.6, 1031.3,
1064.9, 1012.3, 919.3, 832.8, 760.0 cm . HRMS (ESI): [M − BF ]
4
−
1
+
44.7, 637.9 cm . HRMS (ESI): [M − CF O S] calcd for
calcd for C H F N 282.07; found 282.0651. Mp: 251.6 °C with
3
3
13
8
4
3
C H F N 263.08; found 263.0791. Anal. Calcd (%) for
decomposition.
1
4
10
3
2
C H N F O S: C, 43.70; H, 2.44; N, 6.79. Found: C, 43.52; H,
General Procedure B. Synthesis of N-Trifluoromethyl Benzimida-
15
10
2
6
3
2
.29; N, 6.82. Mp: 181.8 °C
zolium Triflimides (2a·HNTf and 2b·HNTf ). N-Trifluoromethylated
2
2
1
-(Trifluoromethyl)-3-(phenyl)-1H-benzo[d]imidazol-3-ium Tet-
benzimidazolium triflimides 2a·HNTf and 2b·HNTf were synthe-
2 2
rafluoroborate (2c·HBF ). Synthesized according to general proce-
sized via anion exchange from their corresponding triflate and iodide
analogues following a modified procedure previously reported by
4
dure A from 1 (120.1 mg, 0.64 mmol) and diphenyliodonium
tetrafluoroborate (355.85 mg, 0.97 mmol). The product was obtained
4
1
Yagupolskii. To an aqueous solution (0.16 M) of the corresponding
1
as a white solid (157.5 mg, 0.45 mmol, 70.3%). H NMR (300.13
benzimidazolium salt (1 equiv) was added LiNTf (2 equiv). The
2
MHz, acetone-d ): δ = 10.76 (s, 1H, NCHN) 8.27 (d, J = 8.64 Hz, 1H,
6
mixture was then stirred at room temperature for 6 h. The white
precipitate formed during the reaction was filtered off and recrystal-
1
9
ArH), 8.06−7.94 (m, 5H, ArH), 7.84 (apt d, J = 3.1 Hz, 3H, ArH).
F
NMR (282.38 MHz, acetone-d ): δ = −58.87 (NCF ), −151.85 (BF ).
6
3
4
lized from acetone/Et O to afford the N-trifluoromethylated
2
1
3
1
C{ H} NMR (75.48 MHz, acetone-d ): δ = 142.91 (d, J = 3.3 Hz,
6
benzimidazolium triflimides as a white solid.
C), 133.29 (d, J = 5.7 Hz, NCHN), 132.69 (C), 131.50 (CH),
3-Methyl-1-(trifluoromethyl)-1H-benzo[d]imidazol-3-ium Trifli-
1
2
3
1
30.68(C), 130.16, (CH), 128.54, (C), 126.65 (CH), 118.52 (q, J =
mide (2a·HNTf ). Synthesized according to general procedure B
2
69.1 Hz, CF ), 115.80 (CH), 114.58 (q, J = 1.6 Hz, CH). IR (neat):
from 2a·HOTf (1200 mg, 3.43 mmol) and LiNTf (1969.4 mg, 6.86
3
2
148.5, 3089.0, 3044.7, 1565.2, 1409.7, 1364.3, 1239.0, 1211.5, 1059.1,
mmol). The product was obtained as a white solid (1393.9 mg, 2.89
−1
+
1
019.1, 753.9, 689.9 cm . HRMS (ESI): [M − BF ] calcd for
mmol, 84.5%). H NMR (300.13 MHz, DMSO-d ): δ = 10.66 (s, 1H,
4
6
C H F N 263.08; found 263.0788. Mp: 175.2 °C.
NCHN), 8.23−8.20 (m, 1H, ArH), 8.12−8.10 (m, 1H, ArH), 7.91−
14
10
3
2
1
9
3
-(4-Nitrophenyl)-1-(trifluoromethyl)-1H-benzo[d]imidazol-3-
7.84 (m, 2H, ArH), 4.17 (s, 3H, NCH ). F NMR (282.38 MHz,
3
13
1
ium Tetrafluoroborate (2d·HBF ). Synthesized according to general
DMSO-d ): δ = −57.53 (NCF ), −78.75 (SCF ). C{ H} NMR
(75.48 MHz, DMSO-d ): δ = 143.49 (app d, J = 2.9 Hz, NCHN),
4
6
3
3
procedure A from 1 (545.4 mg, 2.93 mmol) and mesityl(4-
nitrophenyl)iodonium tetrafluoroborate (2000.0 mg, 4.39 mmol).
The product was obtained as a white solid (818.2 mg, 2.07 mmol,
6
131.88 (C), 129.01(C), 128.11 (CH), 126.72 (C), 119.46 (q, J = 321.9
Hz, CF ), 117 (apt d, J = 267.7 Hz, CF ) 114.88 (CH), 113.17 (CH),
3
3
7
0.7%). 1H NMR (300.13 MHz, DMSO-d ): δ = 11.30 (s, 1H,
6
34.16 (CH ). IR (neat): 3122.2, 1582.6, 1464.4, 1341.1, 1186.7,
3
−1
+
NCHN), 8.67 (d, J = 8.6 Hz, 2H, ArH), 8.28 (d, J = 7.8 Hz, 1H, ArH),
1
133.1, 1081.8, 1057.9, 882.1, 757.2, 604.9 cm . HRMS (ESI): [M −
1
9
8
.18 (d, J = 8.6, 2H, ArH), 8.03−7.91 (m, 3H, ArH). F NMR
N(SO CF ) ] calcd for C H F N 201.06; found 201.0634. Anal.
2
3
2
9
8
3
2
(
282.38 MHz, DMSO-d ): δ = −57.69 (NCF ), −148.40 (BF ).
C{ H} NMR (75.48 MHz, DMSO-d ): δ = 148.94 (C), 144.31 (apt
6
3
4
Calcd (%) for C H N O F S : C, 27.45; H, 1.68; N, 8.73. Found: C,
11 8 3 4 9 2
1
3
1
6
27.55; H, 1.67; N, 8.68. Mp: 73.4 °C.
d, J = 3.2 Hz, NCHN), 136.76 (C), 131.21 (C), 129.56 (CH), 129.14
CH), 127.41 (2C, CH), 126.75 (C), 125.75 (2C, CH), 117.05 (apt d,
J = 269.3 Hz, CF ), 114.67 (CH), 113.68 (CH). IR (neat): 3140.6,
3-Isopropyl-1-(trifluoromethyl)-1H-benzo[d]imidazol-3-ium Trifli-
(
mide (2b·HNTf ). Synthesized according to general procedure B from
2
2b·HI (320.0 mg, 0.89 mmol) and LiNTf (511.1 mg, 1.78 mmol).
3
2
1
390
DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395

Organometallics
Article
The product was obtained as a white, crystalline solid (278.5 mg, 0.55
7.33−7.21 (br m, ArH), 4.83 (td, J = 7.5, 4.4, 1 Hz, 1H, CHCOD), 4.60
1
mmol, 60.9%). H NMR (300.13 MHz, DMSO-d ): δ = 10.58 (s, 1H,
(td, J = 7.9, 3.9 Hz, 1H, CH ), 3.27−3.15 (m, 1H, CHCOD), 2.43
6
COD
NCHN), 8.34−8.31 (m, 1H, ArH), 8.13−8.09 (m, 1H, ArH), 7.90−
(td, J = 7.3, 4.0 Hz, 1H, CHCOD), 2.34−2.09 (m, 2H, CH
), 1.75−
2 COD
). F NMR
19
7
6
.83 (m, 2H, ArH), 5.18 (p, J = 6.7 Hz, 1H, NCH), 1.69 (d, J = 6.7 H,
1.54 (m, 4H, CH2 COD), 1.38−1.14 (m, 2H, CH
2 COD
19
13
1
H, C(CH ) ). F NMR (282.38 MHz, DMSO-d ): δ = −57.25
(282.38 MHz, CDCl ): δ = −53.0 (NCF ). C{ H} NMR (100.6
3
2
6
3
3
13
1
NCF , −78.73 (SCF ). C{ H} NMR (75.48 MHz, DMSO-d ): δ =
1
MHz, CDCl ) δ = 194.51 (d, J = 4.1 Hz, Ir−C), 137.64 (C), 135.66
3
3
6
3
41.75 (d, J = 3.1 Hz, NCHN), 130.61 (C), 128.97 (CH), 128.01
(C), 131.86 (C), 129.36 (CH), 129.05 (br s, 4C, CH), 125.17 (CH),
(
CH), 127.18 (C), 119.46 (q, J = 321.9 Hz, CF ), 117.07 (app d, J =
124.83 (CH), 119.7 (q, J = 267 Hz, CF ), 112.45 (q, J = 3.4 Hz, CH),
3
3
2
68.3 Hz, CF ), 115.22 (CH), 113.06 (CH), 52.47 (NCH), 21.04
111.43 (CH), 88.16 (2C, CHCOD), 86.09 (2C, CHCOD), 34.21
(CH2 COD), 32.10 (CH2 COD), 29.57 (CH2 COD), 28.36 (CH2 COD). IR
3
(
1
CH ). IR (neat): 3143.1, 3086.2, 2990.3, 1565.9, 1347.7, 1188.9,
3
−1
+
−1
135.8, 1049.3, 757.2 cm . HRMS (ESI): [M − N(SO CF ) ] calcd
(neat): 2933.2, 2880.3, 2832.6, 1358.8, 1320.8, 1165.9, 750.2 cm .
2
3 2
+
for C H F N 229.09; found 229.0947. Anal. Calcd (%) for
1
1
12
3
2
HRMS (ESI): [M ] calcd m/z for C22
H
F
21
IrN
3
2
: 598.0961; found
C H N O F S : C, 30.65; H, 2.37; N, 8.25. Found: C, 30.67; H,
13
12
3
4
9
2
598.0968. Anal. Calcd (%) for C H F IrN : C, 44.18; H, 3.54; N,
22 21 3 2
2
.47; N, 8.21. Mp: 83.8 °C.
General Procedure C. Synthesis of [Ir(COD)(NHC)Cl] Complexes.
4
.68. Found: C, 44.46; H, 3.20; N, 5.01 (solvent impurities accounted
for deviation). Mp: 189.2 °C.
4
The corresponding N-trifluoromethylated benzimidazolium salt (1
Chloro(η -cycloocta-1,5-diene)[3-(4-nitrophenyl)-1-(trifluoro-
equiv), [Ir(COD)Cl] (0.5 equiv), NaH (1.5 equiv), and THF (0.2
methyl)-1H-benzo[d]imidazol-3-ylidene]iridium (3d). Synthesized
according to general procedure C from 2d·BF4 (150 mg, 0.36
2
M) were added to a Young Schlenk flask, and the resulting reaction
mixture was stirred at 50 °C for 16 h. Subsequently, all volatiles were
removed under vacuum, and the residue was purified by flash column
chromatography (EtOAc/hexane = 1:0−2:1 v/v), followed by
mmol) and [Ir(COD)Cl] (120.9 mg, 0.18 mmol). The product was
2
1
obtained as an orange solid (70.7 mg, 0.11 mmol, 30.5%). H NMR
(
400.13 MHz, CDCl ): δ = 8.48 (d, J = 8.8 Hz, 2H, ArH), 8.36 (br s,
3
subsequent recrystallization from CH Cl /pentane to afford the
2
2
2H, ArH), 7.68 (d, J = 8.2, 1H, ArH), 7.41 (dt, J = 23.1, 7.5 Hz, 2H,
ArH), 7.22 (d, J = 8.0 Hz, 2H, ArH), 4.89 (q, J = 5.9 Hz, 1H, CHCOD),
desired [Ir(COD)(NHC)Cl] complexes.
4
Chloro(η -cycloocta-1,5-diene)[3-methyl-1-(trifluoromethyl)-1H-
benzo[d]imidazol-3-ylidene]iridium (3a). Synthesized according to
general procedure C from 2a·OTf (208 mg, 0.59 mmol) and
4
2
1
.72−4.66 (m, 1H, CHCOD), 3.19 (t, J = 6.7 Hz, 1H, CHCOD), 2.29−
.19 (m, 4H, CH2 and CHCOD), 1.71−1.62 (m, 4H, CH ),
COD
2 COD
). F NMR
2 COD
19
.41−1.35 (m, 1H, CH2
), 1.28−1.18 (m, 1H, CH
COD
[
Ir(COD)Cl] (200 mg, 0.29 mmol). The product was obtained as
13
1
2
(
376.46 MHz, CDCl ): δ = −53.14 (NCF ). C{ H} NMR (100.62
1
3
3
a yellow solid (187.6 mg, 0.35 mmol, 59.3%). H NMR (300.13 MHz,
MHz, CDCl ): δ = 195.11 (Ir−C), 147.81 (C), 143.07 (C), 134.85
3
CDCl ): δ = 7.57−7.57 (m, 1H, ArH), 7.39−7.26 (m, 3H, ArH),
3
(C), 131.98 (C), 125.65 (2C, CH), 125.49 (CH), 124.24 (4C, CH),
4
.87−4.79 (m, 2H, CH ), 4.39 (s, 3H, NCH ), 3.19−3.14 (m, 1H,
COD
3
1
19.66 (d, J = 267.6 Hz, CF ), 112.82 (q, J = 3.4 Hz, CH), 110.91
3
CH ), 3.00−2.94 (m, 1H, CH ), 2.35−2.22 (m, 4H, CH ),
1
COD
COD
COD
(CH), 89.67 (CHCOD), 88.4 (CHCOD), 54.36 (d, J = 1.8 Hz, CHCOD),
19
.92−1.66 (m, 4H, CH
52.58 (NCF ). C{ H} NMR (75.48 MHz, CDCl ): δ = 194.26
). F NMR (282.38 MHz, CDCl ): δ =
2
COD 3
5
4.15 (CHCOD), 33.85 (CH2 COD), 32.52 (CH2 COD), 29.47
13
1
−
3
3
(
2
CH2 COD), 28.47 (CH2 COD). IR (neat): 2974.0, 2920.8, 2885.8,
(
(
dd, J = 4.1 Hz, Ir−C), 135.15 (C), 132.01 (C), 125.04 (CH), 124.50
−1
835.5, 1528.7, 1378.5, 1212.6, 1160.8, 1022.1, 750.4 cm . HRMS
CH), 119.68 (apt d, J = 265.7 Hz, CF ), 112.38 (q, J = 3.1 Hz, CH),
+
3
(MALDI/ESI): [M ] calcd for C H N F O ClIr 643.08; found
23 20 3 3 2
110.29 (CH), 87.71 (CHCOD), 87.53 (CHCOD), 53.61 (CHCOD), 53.30
6
43.0825. Anal. Calcd (%) for C H N F O ClIr: C, 41.09; H, 3.13;
23 20 3 3 2
(
(
apt d, J = 2.2 Hz, CHCOD), 33.72 (CH2 COD), 33.36 (CH2 COD), 29.63
CH2 COD), 29.17 (CH2 COD). IR (neat): 2960.7, 2912.7, 2884.8,
N, 6.53. Found: C, 41.03; H, 3.23; N, 6.54. Mp: 217.8 °C
decomposition.
2
837.5, 1462.9, 1425.4, 1322.5, 1216.7, 1163.8, 1090.6, 965.3, 762.0
4
−3
+
Chloro(η -cycloocta-1,5-diene)[1-(trifluoromethyl)-3-(4-
cm . HRMS (MALDI/ESI): [M ] calcd for C H N F ClIr 536.08;
17
19
2 3
(
(
trifluoromethyl)phenyl)-1H-benzo[d]imidazol-3-ylidene]iridium
found 536.0805. Anal. Calcd (%) for C H N F ClIr: C, 38.09; H,
17
19
2 3
3e). Synthesized according to general procedure C from 2e·BF (150
4
3.57; N, 5.23. Found: C, 37.81; H, 3.65; N, 5.22. Mp: 176.5 °C with
mg, 0.36 mmol) and [Ir(COD)Cl] (120.6 mg, 0.18 mmol). The
2
decomposition.
product was obtained as a yellow solid (167.3 mg, 0.26 mmol, 73.6%).
4
Chloro(η -cycloocta-1,5-diene)[3-isopropyl-1-(trifluoromethyl)-
H-benzo[d]imidazol-3-ylidene]iridium (3b). Synthesized according
1
H NMR (400.13 MHz, CDCl ): δ = 8.24 (br s, 3H, ArH), 7.89 (d, J =
3
1
8
.1 Hz, 1H, ArH), 7.66 (d, J = 8.1 Hz, 1H, ArH), 7.39 (dt, J = 22.2, 7.5
to general procedure C from 2b·HNTf (250 mg, 0.70 mmol) and
2
Hz, 2H, ArH), 7.23 (d, J = 8.0 Hz, 1H, ArH), 4.85 (q, J = 6.5, 6.1 Hz,
1H, CHCOD), 4.65−4.60 (m, 1H, CHCOD), 3.18 (t, J = 7.3 Hz, 1H,
[
Ir(COD)Cl] (235.9 mg, 0.35 mmol). The product was obtained as a
2
1
yellow solid (195.6 mg, 0.35 mmol, 49.6%). H NMR (300.13 MHz,
CHCOD), 2.30−2.11 (m, 3H, CH
and CH2 COD), 1.71−1.60 (m,
2 COD
COD
CDCl ): δ = 7.57 (dd, J = 6.7, 2.3 Hz, 2H, ArH), 7.36−7.29 (m, 2H,
3
4
H, CH2
) 1.35−1.27 (m, 1H, CH
), 1.24−1.14 (m, 1H,
COD
ArH), 6.72 (hept, J = 7.1 Hz, 1H, NCH), 4.86−4.72 (m, 2H, CH ),
COD
CH2 COD). 19F NMR (376.46 MHz, CDCl ): δ = −53.15 (NCF ),
13 1
3
3
3
.22−3.16 (m, 1H, CH ), 3.12−3.07 (m, 1H, CH ), 2.37−2.18
COD
COD
−
62.71 (ArCF3). C{ H} NMR (100.62 MHz, CDCl ): δ = 195.05
(Ir−C), 140.77 (C), 143.07 (C), 135.17 (C), 131.93 (CH), 131.78
3
(
m, 4H, CH2
), 1.94−1.58 (m, 4H, CH
), 1.83 (d, J = 7.1 Hz,
COD
2 COD
19
CH ), 1.72 (d, J = 7.0 Hz, CH ). F NMR (282.38 MHz, CDCl ): δ =
−
=
3
3
3
13
1
(CH), 131.46 (C), 126.14 (C, CH), 125.48 (CH), 125.23 (2C, CH),
52.57 (d, J = 1.9 Hz, NCF3). C{ H} NMR (75.48 MHz, CDCl ): δ
3
1
23.82 (q, J = 272.5 Hz, CF ), 119.73 (q, J = 267.2 Hz, CF ), 112.71
192.85 (app d, J = 4.1 Hz, Ir−C), 133.33 (C), 132.61(C), 124.51
3
3
(
(
CH), 111.08 (CH), 89.22 (CHCOD), 87.32 (CHCOD), 54.18
CHCOD), 53.85 (CHCOD), 34.15 (CH2 COD), 32.18 (CH2 COD),
(
CH), 124.10 (CH), 119.66 (app d, J = 266.2 Hz, CF ), 112.86 (CH),
3
8
5
2
7.13 (NCH), 86.31 (CHCOD), 57.09 (CHCOD), 53.22 (CHCOD),
3.07 (q, J = 2.4 Hz, CHCOD), 34.26 (CH2 COD), 32.90 (CH2 COD),
9.65 (CH2 COD), 29.06 (CH2 COD), 21.37 (CH ), 20.42 (CH ). IR
2
1
9.53 (CH2 COD), 28.28 (CH2 COD). IR (neat): 2950.3, 2927.5,
−1
882.5, 2834.2, 1321.5, 1156.8, 1123.9, 1066.3, 1023.9, 747.7 cm .
3
3
+
HRMS (MALDI/ESI): [M ] calcd for C H N F ClIr 666.08; found
(
1
neat): 2985.3, 2939.2, 2906.2, 2839.2, 1404.5, 1359.6, 1316.3, 1287.8,
162.8, 1098.8, 1053.8, 753.1 cm . HRMS (MALDI/ESI): [M ] calcd
23 20
2 6
−3
+
666.0844. Anal. Calcd (%) for C H N F ClIr: C, 41.47; H, 3.03; N,
23 20 2 6
4
.21. Found: C, 41.75; H, 3.18; N, 4.26 (solvent impurities accounted
for C H N F ClIr 564.11; found 564.1126. Anal. Calcd (%) for
19
23
2 3
for deviation). Mp: 203.1 °C with decomposition.
C H N F ClIr: C, 40.46; H, 4.11; N, 4.97. Found: C, 40.29; H, 4.16;
19
23
2 3
General Procedure D. Synthesis of [Ir(CO) (NHC)Cl] Complexes.
N, 4.87. Mp: 224.8 °C with decomposition.
2
4
The appropriate [Ir(COD)(NHC)Cl] complex (1 equiv) was
Chloro(η -cycloocta-1,5-diene)[1-(trifluoromethyl)-3-(phenyl)-
H-benzo[d]imidazol-3-ylidene]iridium (3c). Synthesized according
1
dissolved in CH Cl (0.03 M) in a Young Schlenk flask. The solution
2 2
to general procedure C from 2c·OTf (200 mg, 0.48 mmol) and
was cooled to −78 °C, and the atmosphere inside the Young Schlenk
was replaced with CO. The solution was then allowed to warm to
room temperature and stirred for 20 h. Subsequently, all volatiles were
removed under vacuum and the residue was washed with pentane.
[
Ir(COD)Cl] (148 mg, 0.22 mmol). The product was obtained as a
2
1
yellow solid (123 mg, 0.45 mmol, 94%). H NMR (300.13 MHz,
CDCl ): δ = 8.44−7.5 (br m, 5H, ArH), 7.44−7.31 (m, 2H, ArH),
3
1
391
DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395

Organometallics
Article
Subsequent recrystallization from CH Cl /pentane afforded the
according to general procedure D from 3e (85 mg, 0.13 mmol).
2
2
desired [Ir(CO) (NHC)Cl] complex.
The product was obtained as a green solid (55.2 mg, 0.09 mmol,
2
1
Chlorodicarbonyl[3-methyl-1-(trifluoromethyl)-1H-benzo[d]-
imidazol-3-ylidene]iridium (4a). Synthesized according to general
procedure D from 3a (80 mg, 0.15 mmol). The product was obtained
69.6%). H NMR (400.13 MHz, CDCl ): δ = 7.93 (d, J = 8.3 Hz, 2H,
3
ArH), 7.84 (d, J = 8.4 Hz, 2H, ArH), 7.60 (t, J = 8.2 Hz, 1H, ArH),
1
9
7.51 (t, J = 7.8 Hz, 1H, ArH), 7.24 (d, J = 8.3 Hz, 1H, ArH). F NMR
(376.46 MHz, CDCl ): δ = −51.84 (NCF ), −62.77 (ArCF ).
1
as a yellow solid (71.1 mg, 0.15 mmol, 98.3%). H NMR (300.13
3
3
3
13
1
MHz, CDCl ): δ = 7.76−7.72 (m, 1H, ArH), 7.57−7.52 (m, 3H,
C{ H} NMR (100.62 MHz, CDCl ): δ = 185.14 (Ir−C), 179.14
3
3
19
ArH), 4.31 (s, 3H, NCH ). F NMR (282.38 MHz, CDCl ): δ =
51.51 (NCF3). C{ H} NMR (75.48 MHz, CDCl ): δ = 184.63
Ir−C), 179.68 (CO), 167.56 (CO), 134.39 (C), 131.32 (C), 126.46
CH), 126.31 (CH), 119.12 (q, J = 309.3 Hz, CF ), 117.07 (CH),
3
3
(CO), 167.45 (CO), 139.45 (C), 135.02 (C), 132.92 (q, J = 33.2 Hz,
C), 131.07 (C), 127.23 (2C, CH), 127.02 (2C, CH), 126.87 (2C,
CH), 123.54 (q, J = 272.8 Hz, CF ), 119.34 (q, J = 269.3 Hz, CF ),
13
1
−
3
(
3
3
(
3
113.64 (q, J = 3.8 Hz, CH), 112.46 (CH). IR (neat): 2071.5 (CO),
1
11.67 (CH), 37.48 (NCH ). IR (neat): 2073.2 (CO), 1988.0 (C
1974.1 (CO), 1616.5, 1347.7, 1327.7, 1218.1, 1166.8, 1130.8,
3
−1
−1
O), 1352.5, 1186.8, 1093.4 cm . IR (CH Cl ): 2075.4 (CO),
1109.8, 1068.7, 1025.2, 859.7, 756.6, 617.0 cm . IR (CH Cl ): 2076.9
2
2
2
2
−1
+
−1
+
1
993.2 (CO) cm . HRMS (MALDI/ESI): [M + Na ] calcd for
(CO), 1993.9 (CO) cm . HRMS (MALDI/ESI): [M + Na ]
C H N NaF O ClIr 506.97; found 506.9661. Anal. Calcd (%) for
calcd for C H N NaF O ClIr 636.97; found 636.9692. Anal. Calcd
11
9
2
3
2
17
8
2
6
2
C H N F O ClIr: C, 27.31; H, 1.46; N, 5.79. Found: C, 27.12; H,
(%) for C H N F O ClIr: C, 33.26; H, 1.31; N, 4.56. Found: C,
11
9
2
3
2
17 8 2 6 2
1.56; N, 5.63.
44.43; H, 1.34; N, 4.53.
Chlorodicarbonyl[3-isopropyl-1-(trifluoromethyl)-1H-benzo[d]-
imidazol-3-ylidene]iridium (4b). Synthesized according to general
procedure D from 3b (70 mg, 0.12 mmol). The product was obtained
General Procedure E. Synthesis of Selenones. The selenium
complexes 5a−f were synthesized from the corresponding benzimi-
dazolium salts 2a−f according to a modified procedure previously
1
4
2
as a yellow solid (56.2 mg, 0.11 mmol, 88.5%). H NMR (400.13
reported by Ganter. A mixture of benzimidazolium salt 2a−f (1
MHz, CDCl ): δ = 7.75−7.73 (m, 2H, ArH), 7.50−7.48 (m, 2H,
3
equiv), selenium powder (5 equiv), and Et O (0.06 M) was cooled to
2
ArH), 6.28 (hept, J = 7.0 Hz, 1H, NCH), 1.76 (dd, J = 7.1, 5.0 Hz, 6H,
−
78 °C. Subsequently, a solution of NaHMDS (1.1 equiv, 0.2 M in
2
1
9
C(CH ) ). F NMR (376.46 MHz, CDCl ): δ = −51.36 (d, J = 1.9
3
2
3
Et O) was added dropwise to the reaction mixture. The resulting
1
3
1
Hz, NCF3). C{ H} NMR (100.62 MHz, CDCl ): δ = 182.82 (d, J =
3
solution was stirred for 20 min at −78 °C; then the cooling bath was
removed, and the suspension was stirred for 4 h and allowed to warm
to room temperature. All volatiles were then removed in vacuo and the
residue was purified by flash column chromatography (CH Cl /
3
1
.9 Hz, Ir−C), 179.57 (CO), 167.56 (CO), 132.66 (C), 131.85 (C),
26.06 (CH), 125.72 (CH), 119.37 (d, J = 268.1 Hz, CF ), 114.10
3
(
(
1
CH), 113.92 (q, J = 4.3 Hz, CH), 58.20 (NCH), 20.67 (CH ), 20.32
3
2
2
CH ). IR (neat): 2988.6, 2069.5, 1985.7, 1346.3, 1210.9, 1184.8,
3
pentane, 0:1−2:1 v/v), followed by subsequent recrystallization from
−1
100.5, 1058.3, 758.7 cm . IR (CH Cl ): 2075.0 (CO), 1992.6
2
2
CH Cl /pentane to afford the desired product.
2
2
−
1
+
(
CO) cm . HRMS (MALDI/ESI): [M + Na ] calcd for
1
-Methyl-3-(trifluoromethyl)-1H-benzo[d]imidazole-2(3H)-sele-
C H N NaF O ClIr 535.00; found 534.9974. Anal. Calcd (%) for
none (6a). Synthesized according to the general procedure E, starting
13
11
2
3
2
C H N F O ClIr: C, 30.50; H, 2.17; N, 5.47. Found: C, 30.46; H,
from 2a·HNTf (230 mg, 0.48 mmol). The product was obtained as a
13
11
2
3
2
2
1
2
.08; N, 5.35.
Chlorodicarbonyl[1-(trifluoromethyl)-3-(phenyl)-1H-benzo[d]-
white solid (116.3 mg, 0.2 mmol, 86.9%). H NMR (300.13 MHz,
CDCl ): δ = 7.52 (d, J = 7.93 Hz, 1H, ArH), 7.41−7.29 (m, 2H, ArH),
3
1
9
imidazol-3-ylidene]iridium (4c). Synthesized according to general
procedure D from 3c (50 mg, 0.08 mmol). The product was obtained
as a yellow solid (39 mg, 0.07 mmol, 92%). H NMR (400.13 MHz,
7.27 (d, J = 8.12 Hz, 1H, ArH), 3.87 (s, CH , 3H, NCH ). F NMR
3 3
13
1
(282.38 MHz, CDCl ): δ = −54.23 (NCF ). C{ H} NMR (75.48
3
3
1
MHz, CDCl ): δ = 166.26 (Se−C), 133.60 (C), 130.14 (C), 125.47
3
CDCl ): δ = 7.83 (ddq, J = 8.4, 1.9, 0.9 Hz, 1H, ArH), 7.9−7.5 (br m,
(CH), 124.91 (CH), 119.91 (q, J = 267.2 Hz, CF ), 112.53 (q, J = 5.6
3
3
Hz, CH), 110.08 (CH), 33.33 (CH3). 77Se NMR (76.36 MHz,
4H, ArH), 7.59 (ddd, J = 8.4, 7.4, 1.1 Hz, 1H, ArH), 7.50 (ddd, J =8.3,
1
9
+
7
.4, 1.0 Hz, 1H, ArH), 7.31−7.25 (m, 2H, ArH). F NMR (376.46
CDCl ): 214.62 (q, J = 15.5 Hz). HRMS (MALDI/ESI): [M ] calcd
3
13
1
MHz, CDCl ): δ = −51.8 (NCF ). C{ H} NMR (100.62, CDCl ): δ
=
for C H N F Se 279.97; found 279.9721. Anal. Calcd (%) for
3
3
3
9
7
2 3
184.80 (d, J = 3.9 Hz, Ir−C), 179.47 (CO), 167.59 (CO), 136.47
C H N F Se: C, 38.73; H, 2.53; N, 10.04. Found: C, 38.76; H,
9 7 2 3
(
C), 135.39 (C), 131.04 (C), 130.73 (CH), 130.15−129.65 (4C, CH),
2.42; N, 9.91. Mp: 181.9 °C.
1
3
1
26.64 (CH), 126.54 (CH), 119.4 (q, J = 268 Hz, CF ), 113.39 (q, J =
1-Isopropyl-3-(trifluoromethyl)-1H-benzo[d]imidazole-2(3H)-se-
lenone (6b). Synthesized according to the general procedure E,
starting from 2b·HI (50 mg, 0.14 mmol). The product was obtained as
3
.9 Hz, CH), 112.81 (CH). IR (neat): 2066.7 (CO) 1984.2 (CO),
363.0, 1166.5, 753.3 cm . IR (CH Cl ): 2074.35 (CO), 1991.84
−1
2
2
−1
+
1
(
CO) cm . HRMS (ESI): [M ] calcd m/z for C H F IrN O :
a white, crystalline solid (36.9 mg, 0.12 mmol, 85.6%). H NMR
1
6
9
3
2
2
5
3
45.9934; found 545.9930. Anal. Calcd (%) for C H F IrN O : C,
5.20; H, 1.66; N; 5.13. Found: C, 35.63; H, 1.71; N, 5.10.
Chlorodicarbonyl[3-(4-nitrophenyl)-1-(trifluoromethyl)-1H-
(400.13 MHz, CDCl ): δ = 7.55 (apt dd, J = 6.7, 2.1 Hz, 2H, ArH),
16
9
3
2
2
3
7.35−7.27 (m, 2H, ArH), 6.02 (dt, J = 14.6, 7.4 Hz, 1H, NCH), 1.62
1
9
(d, J = 7.2 Hz, 6H, C(CH ) ). F NMR (376.46 MHz, CDCl ): δ =
3
2
3
13
1
benzo[d]imidazol-3-ylidene]iridium (4d). Synthesized according to
general procedure D from 3d (60 mg, 0.09 mmol). The product was
obtained as a green solid (55.2 mg, 0.09 mmol, 99.9%). H NMR
−53.74 (NCF ). C{ H} NMR (100.62 MHz, CDCl ): δ = 165.21
3
3
(Se−C), 131.31 (C), 130.69 (C), 124.82 (CH), 124.44 (CH), 119.91
1
(q, J = 266.9 Hz, CF ), 112.75 (q, J = 6.1 Hz, CH), 111.54 (CH),
3
7
7
(
400.13 MHz, CDCl ): δ = 8.52 (d, J = 9.1 Hz, 1H, ArH), 7.93 (br s,
51.53 (NCH), 19.45 (2C, CH3). Se NMR (76.36 MHz, CDCl ): δ =
195.63. HRMS (MALDI/ESI): [M ] calcd for C H N F Se 308.00;
3
3
+
2
7
H, ArH) 7.86 (d, J = 8.3 Hz, 1H, ArH), 7.63 (t, J = 7.9 Hz, 1H, ArH),
.54 (t, J = 7.8 Hz, 1H, ArH), 7.25 (d, J = 6.4 Hz, 1H, ArH). F NMR
11
11
2 3
19
found 308.0034. Anal. Calcd (%) for C H N F Se: C, 43.01; H, 3.61;
9 7 2 3
13
1
(
282.38 MHz, CDCl ): δ = −51.82 (NCF ). C{ H} NMR (100.62
N, 9.12. Found: C, 42.98; H, 3.62; N, 9.12. Mp: 120.6 °C.
1-Phenyl-3-(trifluoromethyl)-1H-benzo[d]imidazole-2(3H)-sele-
none (6c). Synthesized according to the general procedure E, starting
3
3
MHz, CDCl ): δ = 185.17 (Ir−C), 178.86 (CO), 167.32 (CO),
1
1
3
48.96 (C), 141.53 (C), 134.73 (C), 131.11 (C), 127.24 (2C, CH),
27.08 (2C, CH), 125.30 (2C, CH), 119.30 (apt d, J = 267.6 Hz,
from 2a·HBF
off-white solid (26.5 mg, 0.08 mmol, 32.4%). H NMR (300.13 MHz,
CDCl ): δ = 7.66−7.56 (m, 4H, ArH), 7.48−7.45 (m, 2H, ArH),
7.36−7.24 (m, 2H, ArH), 6.92 (d, J = 7.7 Hz, 1H, ArH). F NMR
(84 mg, 0.24 mmol). The product was obtained as an
4
1
CF ), 113.82 (apt d, J = 3.4 Hz, CH), 112.26 (CH). IR (neat): 2071.5
3
(
7
CO), 1972.1 (CO), 1530.1, 1348.2, 1197.2, 1161.4, 1025.9,
3
−1
19
58.3, 734.2, 694.6 cm . IR (CH Cl ): 2077.9 (CO), 1994.8 (C
2
2
−
1
+
). 13C{ H}
): δ = 167.36 (Se−C), 135.70 (C), 134.88
1
O) cm . HRMS (MALDI/ESI): [M + K ] calcd for
C H N KF O ClIr 629.94; found 629.9407. Anal. Calcd (%) for
C H N F O ClIr: C, 32.52; H, 1.36; N, 7.11. Found: C, 33.81; H,
(282.38 MHz, CDCl
NMR (75.48 MHz, CDCl
(C), 130.48 (C), 130.21 (2C, CH), 130.17 (CH), 128.47 (2C, CH),
125.55 (CH), 125.06 (CH), 120.04 (app d, J = 267.4 Hz, CF ), 112.44
(q, J = 5.7 Hz, CH), 111.01 (CH). 77Se NMR (76.36 MHz, CDCl
): δ
3
): δ = −54.03 (d, J = 2.1 Hz, NCF
3
16
8
3
3
4
3
16
8
3
3
4
1
.92; N, 6.32 (solvent impurities accounted for deviation).
Chlorodicarbonyl[1-(trifluoromethyl)-3-(4-(trifluoromethyl)-
3
3
+
phenyl)-1H-benzo[d]imidazol-3-ylidene]iridium (4e). Synthesized
= 249.41 (q, J = 14.8 Hz). IR (neat): HRMS (MALDI/ESI): [M ]
1
392
DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395

Organometallics
Article
1
calcd for C H N F Se 341.99; found 341.9878. Anal. Calcd (%) for
yellow solid (91.2 mg, 0.21 mmol, 71.5%). H NMR (300.13 MHz,
14
9
2 3
C H N F Se: C, 49.28; H, 2.66; N, 8.21. Found: C, 49.02; H, 2.54; N,
CDCl ): δ = 7.54 (d, J = 7.08 Hz), 7.41−7.30 (m, 3H, ArH), 5.18 (s,
14
9
2
3
3
8
.02 (solvent impurities accounted for deviation). Mp: 132.9 °C.
-(4-Nitrophenyl)-3-(trifluoromethyl)-1H-benzo[d]imidazole-
(3H)-selenone (6d). Synthesized according to the general procedure
2H, CH ), 4.55 (s, 3H, NCH ), 3.55−3.51 (m, 1H, CH ), 3.46−
COD
3
COD
1
3.41 (m, 1H, CH ), 2.54−2.39 (m, 4H, CH
), 2.06−1.97 (m,
COD
2 COD
19
2
4H, CH COD). F NMR (282.38 MHz, CDCl ): δ = −53.60 (NCF ).
2
3
3
13 1
E, starting from 2d·HBF (100 mg, 0.25 mmol). The product was
C{ H} NMR (100.62 MHz, CDCl ): δ = 194.26 (d, J = 4.1 Hz, Rh−
4
3
1
obtained as a orange solid (60.8 mg, 0.16 mmol, 62.1%). H NMR
C), 135.15 (C), 132.01 (C), 125.04 (CH), 124.50 (CH), 119.68 (apt
(
300.13 MHz, CDCl ): δ = 8.50 (d, J = 8.9 Hz, 2H, ArH), 7.74 (d, J =
3
d, J = 266.1 Hz, CF ) 112.38 (q, J = 3.4 Hz, CH), 110.29 (CH), 70.18
3
8
7
.9 Hz, 2H, ArH), 7.61 (d, J = 8.1 Hz, 1H, ArH), 7.35 (dtd, J = 21.2,
(CHCOD), 69.99 (CHCOD), 69.25 (CHCOD), 69.11 (q, J = 2.1 Hz,
19
.6, 1.2 Hz, 2H, ArH), 6.92 (d, J = 7.3 Hz, 1H, ArH). F NMR
CHCOD), 36.79 (CH2 COD), 33.41 (CH2 COD), 33.32 (CH2 COD), 28.94
13
1
(
282.38 MHz, CDCl ): δ = −54.26 (NCF ). C{ H} NMR (75.48
3
3
(CH2 COD), 28.89 (CH ). IR (neat): 3052.8, 2913.3, 2882.4, 2836.9,
3
MHz, CDCl ): δ = 167.43 (Se−C), 148.41 (C), 141.04 (C), 133.99
3
1462.9, 1427.8, 1349.4, 1326.1, 1255.7, 1215.4, 1164.3, 1134.1, 1090.3,
−
1
+
(
C), 130.63 (C), 130.05 (2C, CH), 125.93 (CH), 125.67 (CH),
9
65.6, 764.4 cm . HRMS (MALDI/ESI): [M ] calcd for
1
5
2
1
9
25.56 (2C, CH), 119.93 (app d, J = 267.8 Hz, CF ), 112.80 (q, J =
3
C H N F ClRh 446.02; found 446.0238. Anal. Calcd (%) for
1
7
19
2 3
.7 Hz, CH), 110.46 (CH). 77Se NMR (76.36 MHz, CDCl ): δ =
3
C H N F ClRh: C, 45.71; H, 4.29; N, 6.27. Found: C, 45.21; H,
17 19 2 3
76.03 (q, J = 15.1 Hz). IR (neat): 3117.4, 1613.9, 1590.2, 1519.9,
4
.41; N, 6.32 (solvent impurities accounted for deviation). Mp: 162.8
493.7, 1478.1, 1351.2, 1323.6, 1277.3, 1188.3, 1164.6, 1108.2, 1015.1,
°C.
−1
4
44.2, 851.7, 752.9, 731.7, 695.9, 614.4 cm . HRMS (MALDI/ESI):
Chloro(η -cycloocta-1,5-diene)[3-isopropyl-1-(trifluoromethyl)-
1H-benzo[d]imidazol-3-ylidene]rhodium (7b). Synthesized according
+
[
M ] calcd for C H N F O Se 386.97; found 386.9729. Anal. Calcd
14 8 3 3 2
(
%) for C H N F O Se: C, 43.54; H, 2.09; N, 10.88. Found: C,
to general procedure F from 2b·HNTf (100 mg, 0.28 mmol) and
14
8
3
3
2
2
4
3.69; H, 1.98; N, 10.91. Mp: 226.5 °C.
[Rh(COD)Cl] (69.3 mg, 0.14 mmol). The product was obtained as a
2
1
1
-(Trifluoromethyl)-3-(4-(trifluoromethyl)phenyl)-1H-benzo[d]-
yellow solid (86.4 mg, 0.18 mmol, 64.9%). H NMR (300.13 MHz,
imidazole-2(3H)-selenone (6e). Synthesized according to the general
procedure E, starting from 2e·HBF4 (100 mg, 0.24 mmol). The
CDCl ): δ = 7.56 (apt d, J = 6.8 Hz, 2H, ArH), 7.31 (td, J = 6.9, 5.9,
3
3.8 Hz, 2H, ArH), 6.96 (dt, J = 13.9, 6.9 Hz, 1H, NCH), 5.13 (m, 2H,
CHCOD), 3.54 (br s, 2H, CHCOD), 2.45 (m, 4H, CH2 COD), 1.94−1.58
product was obtained as a white solid (54.1 mg, 0.13 mmol, 55.2%).
1
H NMR (400.20 MHz, CDCl ): δ = 7.91 (d, J = 8.3 Hz, 2H, ArH),
(m, 4H, CH
), 1.85 (d, J = 7.1 Hz, 3H, CH ), 1.78 (d, J = 6.9 Hz,
3
2 COD 3
19
7
2
.65 (d, J = 8.4 Hz, 2H, ArH), 7.60 (d, J = 7.2 Hz, ArH), 7.33 (dt, J =
3H, CH ). F NMR (282.38 MHz, CDCl ): δ = −53.57 (NCF ).
3
3
3
8.0, 7.6 Hz, ArH), 6.92 (d, J = 8.0 Hz, ArH). 19F NMR (282.38 MHz,
13 1
C{ H} NMR (75.48 MHz, CDCl ): δ = 198.11 (dd, J = 48.7, 5.0 Hz,
3
13
1
CDCl ): δ = −54.23 (NCF ), −62.81 (ArCF ). C{ H} NMR
Rh−C), 133.40 (C), 132.31 (C), 124.42 (CH), 124.07 (CH), 119.60
3
3
3
(
1
1
100.64 MHz, CDCl ): δ = 167.35 (Se−C), 138.75 (d, J = 1.7 Hz, C),
(apt d, J = 265.7 Hz, CF ), 112.58 (q, J = 3.2 Hz, CH), 99.55 (d, J =
3
3
34.33 (C), 132.20 (q, J = 33.1 Hz, C), 130.52 (C), 129.29 (2C, CH),
27.42 (q, J = 3.7 Hz, 2C, CH), 125.78 (CH), 125.44 (CH), 123.62
7.0 Hz, CH2 COD)), 98.98 (d, J = 7.4 Hz, CH2 COD), 69.39 (app dd, J =
24.2, 14.4 Hz, NCH), 57.27 (CHCOD), 33.71 (CH2 COD), 31.98
(
q, J = 272.7 Hz, CF ), 119.96 (q, J = 267.4 Hz, CF ) 112.64 (q, J =
(CH2 COD), 29.24 (CH2 COD), 28.49 (CH2 COD), 21.29 (CH ), 20.66
3
3
3
77
5
2
1
9
.7 Hz, CH), 110.66 (CH). Se NMR (76.36 MHz, CDCl ): δ =
(CH ). IR (neat): 3049.76, 2980.03, 2939.44, 2833.51, 1476.45,
3
3
63.71 (q, J = 14.8 Hz). IR (neat): 3044.8, 1738.5, 1613.9, 1477.9,
1402.49, 1350.17, 1320.14, 1286.67, 1258.28, 1165.31, 1140.72,
−1
372.8, 1316.6, 1281.1, 1217.0, 1153.8, 1125.0, 1103.5, 1064.4, 1019.3,
1098.10, 1051.92, 992.68, 960.28, 858.19, 751.70, 701.15 cm .
−1
+
+
44.4, 827.3, 743.8, 715.7, 622.2 cm . HRMS (MALDI/ESI): [M ]
HRMS (MALDI/ESI): [M − Cl] calcd for C H N F Rh 439.09;
19
23
2 3
calcd for C H N F Se 409.98; found 409.9752. Anal. Calcd (%) for
found 439.0863. Anal. Calcd (%) for C H N F ClRh: C, 48.07; H,
15
18
2
6
19 23 2 3
C H N F Se: C, 44.03; H, 1.97; N, 6.85. Found: C, 43.97; H, 1.90;
4.88; N, 5.90. Found: C, 47.81; H, 4.91; N, 5.70 (solvent impurities
15
18
2 6
N, 6.85. Mp: 218.7 °C.
accounted for deviation). Mp: 217.5 °C with decomposition.
4
1
-(6-Fluoropyridin-3-yl)-3-(trifluoromethyl)-1H-benzo[d]-
Chloro(η -cycloocta-1,5-diene)[1-(trifluoromethyl)-3-(phenyl)-
imidazole-2(3H)-selenone (6f). Synthesized according to the general
1H-benzo[d]imidazol-3-ylidene]rhodium (7c). Synthesized according
to general procedure F from 2c·BF4 (170 mg, 0.49 mmol) and
procedure E, starting from 2f·HBF (25 mg, 0.07 mmol). The product
4
1
was obtained as a white solid (12.6 mg, 0.03 mmol, 49.9%). H NMR
[Rh(COD)Cl] (119.7 mg, 0.24 mmol). The product was obtained as
2
1
(
400.20 MHz, CDCl ): δ = 8.37 (s, 1H, ArH), 8.01 (td, J = 8.0, 6.8,
a yellow solid (187.3 mg, 0.37 mmol, 76%). H NMR (300.13 MHz,
3
2.7 Hz, 1H, ArH), 7.60 (d, J = 8.2 Hz, 1H, ArH), 7.35 (dt, J = 22.3, 7.5
CDCl ): δ = 8.14 (br s, 2H, ArH), 7.63 (dt, J = 14.1, 6.0 Hz, 4H,
3
Hz, 2H, ArH), 7.22 (dd, J = 8.6, 3.2 Hz, 1H, ArH), 6.94 (d, J = 8.2 Hz,
ArH), 7.36−7.23 (m, 3H, ArH), 5.08 (apt q, J = 7.8 Hz, 1H, CHCOD),
1
9
1
−
(
1
1
H, ArH). F NMR (376.56 MHz, CDCl ): δ = −54.41 (NCF ),
4.96 (apt q, J = 7.7 Hz, 1H, CH ), 3.53 (apt t, J = 7.2 Hz, 1H,
3
3
COD
64.32 (ArF). 1 C{ H} NMR (100.63 MHz, CDCl ): δ = 168.21
Se−C), 163.46 (d, J = 244.4 Hz, CF), 147.80 (d, J = 16.3 Hz, CH),
41.99 (d, J = 9.2 Hz, CH), 134.32 (C), 130.49 (CH), 125.98 (CH),
25.60 (CH), 119.90 (d, J = 267.9 Hz CF ), 112.77 (q, J = 5.7 Hz
CH), 111.21 (d, J = 39.4 Hz CH), 110.41 (CH). Se NMR (76.31
3
1
3
CHCOD), 2.76 (apt dt, J = 7.5, 4.1 Hz, 1H, CHCOD), 2.46−2.21 (m,
2H, CH2 COD), 1.90−1.68 (m, 4H, CH
), 1.56−1.48 (m, 1H,
2 COD
19
CH2 COD), 1.32 (apt td, J = 14.4, 7.7 Hz, 1H, CH
). F NMR
2 COD
13
1
3
(282.38 MHz, CDCl ): δ = −53.86 (NCF ). C{ H} NMR (75.48
3
3
77
MHz, CDCl ): δ = 200.54 (dd, J = 51.0, 5.1 Hz, Rh−C), 137.93 (C),
3
MHz, CDCl ): δ = 275.18 (q, J = 14.5 Hz). HRMS (MALDI/ESI):
135.41 (C), 131.92 (C), 129.59 (2C, CH), 129.33 (CH), 125.13 (2C,
3
+
[
M ] calcd for C H N F Se 360.97; found 360.9736. Anal. Calcd (%)
CH), 124.79 (2C, CH), 119.71 (q, 266.3 Hz, CF ), 112.17 (q, J = 3.0
13
7
3
4
3
for C H N F Se: C, 43.35; H, 1.96; N, 11.67. Found: C, 43.18; H,
Hz, CH), 111.37 (CH), 99.79 (d, J = 7.3 Hz, CHCOD), 98.83 (d, J =
7.0 Hz, CHCOD), 70.00 (d, J = 14.4 Hz, CHCOD), 69.40 (apt dd, J =
14.3, 1.9 Hz, CHCOD), 33.16 (CH2 COD), 31.55 (CH2 COD), 28.95
(CH2 COD), 28.06 (CH2 COD). IR (neat): 2938.3, 2836.4, 1357.0,
13
7
3 4
1
.96; N, 11.51.
General Procedure F. Synthesis of [Rh(COD)(NHC)Cl] Complexes.
The corresponding N-trifluoromethylated benzimidazolium salt (1
−1
+
equiv), [Rh(COD)Cl] (0.5 equiv), NaH (1.5 equiv), and THF (0.2
1322.9, 1163.5, 1032.1, 754.1, 696.4 cm . HRMS (MALDI/ESI): [M
− Cl] calcd for C H N F ClRh 473.07; found 473.0704. Anal. Calcd
2
M) were added to a Young Schlenk flask, and the resulting reaction
mixture was stirred at room temperature for 4 h. Subsequently, all
volatiles were removed in vacuo and the residue was purified by flash
column chromatography (EtOAc/hexane, 1:0−2:1 v/v), followed by
subsequent recrystallization from CH Cl /pentane to afford the
22
21
2 3
(%) for C H N F ClRh: C, 51.94; H, 4.16; N, 5.51. Found: C, 51.77;
22
21
2 3
H, 4.10; N, 5.41. Mp: 196.7 °C.
4
Chloro(η -cycloocta-1,5-diene)[3-(4-nitrophenyl)-1-(trifluoro-
methyl)-1H-benzo[d]imidazol-3-ylidene]rhodium (7d). Synthesized
2
2
desired [Rh(COD)(NHC)Cl] complex.
according to general procedure F from 2d·HBF
4
(120 mg, 0.29 mmol)
4
Chloro(η -cycloocta-1,5-diene)[3-methyl-1-(trifluoromethyl)-1H-
benzo[d]imidazol-3-ylidene]rhodium (7a). Synthesized according to
general procedure F from 2a·HOTf (100 mg, 0.29 mmol) and
and [Rh(COD)Cl] (70.4 mg, 0.14 mmol). The product was obtained
2
1
as an orange solid (91.8 mg, 0.17 mmol, 58%). H NMR (300.13
MHz, CDCl ): δ = 8.56 (apt d, J = 6.6 Hz, 4H, ArH), 7.67 (d, J = 7.6
3
[
Rh(COD)Cl] (70.4 mg, 0.14 mmol). The product was obtained as a
Hz, 1H, ArH), 7.46−4.35 (m, 2H, ArH), 7.27−7.24 (m, 1H, ArH),
2
1
393
DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395

Organometallics
Article
5
(
.18−5.04 (m, 2H, CHCOD) 3.55 (apt t, J = 7.0 Hz, 1H, CHCOD), 2.69
dt, J = 7.4, 4.4 Hz 1H, CHCOD), 2.39 (apt tt, J = 16.9, 7.7 Hz, 2H,
CH2 COD), 1.95−1.78 (m, 4 H, CH ), 1.67−1.57 (m, 1H,
6.48. Found: C, 24.82; H, 1.63; N, 6.56. Mp: 324.2 °C with
decomposition.
Chloro[1-(trifluoromethyl)-3-(phenyl)-1H-benzo[d]imidazol-3-yli-
dene]gold (9b). Synthesized according to the general procedure G,
starting from 2c·HOTf (278.9 mg, 0.68 mmol) and [Au(DMS)Cl]
2 COD
1
9
CH2 COD), 1.42−1.23 (m, 1H, CH2 COD). F NMR (282.38 MHz,
13
1
CDCl ): δ = −53.94 (NCF ). C{ H} NMR (75.48 MHz, CDCl ): δ
3
3
3
(
(
°
200 mg, 0.68 mmol). The product was obtained as a white solid
=
201.77 (d, J = 51.2 Hz, Rh−C), 148.13 (C), 143.25 (C), 134.73 (C),
1
150.2 mg, 0.30 mmol, 44.7%). H NMR (500.26 MHz, DMSO-d , 60
1
1
32.03 (C), 129.13 (br s, 2C, CH), 125.66 (CH), 125.48 (CH),
24.55 (2C, CH), 119.58 (d, J = 267.4 Hz, CF ), 112.56 (q, J = 3.1
6
C): δ = 7.96 (d, J = 9.2 Hz, 1H, ArH), 7.84−7.82 (m, 2H, ArH)
3
7
1
.73−7.69 (m, 4H, ArH), 7.62 (t, J = 7.8, 1H, ArH), 7.39 (d, J = 8.3,
Hz, CH), 110.89 (CH), 100.82 (d, J = 7.2 Hz, CHCOD), 100.59 (d, J =
.8 Hz, CHCOD), 70.43 (d, J = 14.3 Hz, CHCOD), 69.99 (d, J = 14.2 Hz,
CHCOD), 32.78 (CH2 COD), 32.06 (CH2 COD), 28.89 (CH2 COD), 28.21
CH2 COD). IR (neat): 3062.79, 2987.08, 1694.84, 1591.60, 1530.09,
19
H, ArH). F NMR(470.67 MHz, acetone-d ): δ = −52.82 (NCF ).
6
6
3
13
1
C{ H} NMR (125.80 MHz, DMSO-d , 60 °C): δ = 177.44 (q, J =
6
6
.0 Hz, Au−C), 136.19 (C), 135.51 (C), 130.26 (2C, CH), 129.77
(
1
6
(2C, CH), 129.11 (C), 126.81 (2C, CH), 126.77 (CH), 126.73 (CH),
342.75, 1325.85, 1164.93, 1110.01, 1020.84, 853.20, 748.61, 731.70,
−
1
+
118.83 (q, J = 266.3, CF ), 113.01 (CH). HRMS (MALDI/ESI): [M
95.32 cm . HRMS (MALDI/ESI): [M − Cl] calcd for
3
−
Cl + C H F N ] calcd for C H AuF N 721.11; found 721.1095.
14 9 3 2 28 18 6 4
C H N F O ClRh 518.06; found 518.0557. Anal. Calcd (%) for
C H N O F ClRh: C, 47.72; H, 3.64; N, 6.40. Found: C, 48.46; H,
3
23
20
3
3
2
Anal. Calcd (%) for C H AuF ClN : C, 33.99; H, 1.63; N, 5.66.
14
9
3
2
23
20
3
2 3
Found: C, 33.76; H, 1.95; N, 5.60 (solvent impurities accounted for
deviation). Mp: 274.8 °C with decomposition.
Chloro[3-(4-nitrophenyl)-1-(trifluoromethyl)-1H-benzo[d]-
imidazol-3-ylidene]gold (9c). Synthesized according to the general
.68; N, 8.01 (solvent impurities accounted for deviation) Mp: 227.2
°C with decomposition.
4
Chloro(η -cycloocta-1,5-diene)[1-(trifluoromethyl)-3-(4-
(
trifluoromethyl)phenyl)-1H-benzo[d]imidazol-3-ylidene]rhodium
7e). Synthesized according to general procedure F from 2e·HBF4
procedure G, starting from 2d·HBF (282.9 mg, 0.45 mmol) and
(
4
[
Au(DMS)Cl] (176.9 mg, 0.45 mmol). The product was obtained as
(
120 mg, 0.29 mmol) and [Rh(COD)Cl] (70.4 mg, 0.14 mmol). The
2
1
1
an off-white solid (82.1 mg, 0.15 mmol, 33.9%). H NMR (400.13
product was obtained as a yellow solid (96.2 mg, 0.17 mmol, 57%). H
NMR (300.13 MHz, CDCl ): δ = 8.38 (br s, 2H, ArH), 7.93 (d, J =
MHz, DMSO-d , 60 °C): δ = 8.58−8.54 (m, 2H, ArH), 8.20−8.16 (m,
6
3
2
H, ArH), 8.00−7.97 (m, 1H, ArH), 7.73 (ddd, J = 8.4, 7.4, 1H, ArH),
.64 (ddd, J = 8.3, 7.4, 1H, ArH), 7.48 (dt, J = 8.3, 0.9 Hz, 1H, ArH).
F NMR (376.46 MHz, DMSO-d , 60 °C): δ = −53.01 (NCF ).
8
.3 Hz, 2H, ArH), 7.61 (d, J = 7.5 Hz, 1H, ArH), 7.39−7.30 (m, 2H,
ArH), 7.26−7.21 (m, 1H, ArH) 5.10 (q, J = 7.1, 6.5 Hz, 1H,
CH ), 4.99 (q, J = 7.6 Hz, 1H, CH ), 3.51 (app t, J = 7.2 Hz,
7
1
1
9
6
3
2
COD
2 COD
3
1
C{ H} NMR (100.62 MHz, DMSO-d , 60 °C): δ = 177.79 (d, J =
1
2
H, CH2 COD), 2.65 (dt, J = 7.5, 4.2 Hz, 1H, CH2 COD), 2.50−2.25 (m,
6
6
.0 Hz, Au−C), 148.33 (C), 141.25 (C), 133.27 (C), 129.19 (C),
H, CHCOD), 1.94−1.79 (m, 4H, CH ), 1.63−1.53 (m, 1H,
COD
19
128.74 (2C, CH), 126.98 (CH), 126.87 (CH), 125.06 (2C, CH),
CHCOD), 1.39−1.26 (m, 1H, CH ). F NMR (282.38 MHz,
COD
13
1
118.76 (q = 266.6 Hz, CF ), 113.07 (q, J = 3.9 Hz, CH), 112.96 (CH).
CDCl ): δ = −53.95 (NCF ), 62.63 (ArCF ). C{ H} NMR (75.48
3
3
3
3
HRMS (MALDI/ESI): [M − Cl + C H F N O ] calcd for
MHz, CDCl ): δ = 201.38 (d, J = 56.6 Hz, Rh−C), 141.02 (C), 134.98
14
8
3
3
2
3
C H AuF N O 811.12; found 811.1188. Anal. Calcd (%) for
(
C), 134.98 (C), 131.99 (C), 131.88 (q, J = 33.1 Hz, CH), 128.64 (br,
28 16
6
6
4
C H AuF ClN O : C, 36.16; H, 1.49; N, 7.79. Found: C, 36.30; H,
14
8
3
3
2
2
1
1
C, CH), 126.42 (apt d, J = 3.9 Hz, CH), 125.47 (CH), 125.21 (CH),
23.79 (d, J = 272.7 Hz, CF ), 119.63 (apt d, J = 266.8 Hz, CF ),
1
.66; N, 7.80. Mp: 316.5 °C with decomposition.
3
3
Chloro[1-(trifluoromethyl)-3-(4-(trifluoromethyl)phenyl)-1H-
12.43 (q, J = 3.2 Hz, CH), 111.03 (CH), 100.51 (d, J = 7.3 Hz,
benzo[d]imidazol-3-ylidene]gold (9d). Synthesized according to the
CH2 COD), 99.77 (d, J = 6.9 Hz, CH2 COD), 70.18 (d, J = 14.5 Hz,
CH2 COD), 69.82 (d, J = 14.0 Hz, CHCOD), 33.05 (CH2 COD), 31.69
general procedure G, starting from 2e·HBF (282.9 mg, 0.68 mmol)
4
and [Au(DMS)Cl] (200 mg, 0.68 mmol). The product was obtained
(
CH2 COD), 28.92 (CH2 COD), 28.04 (CH2 COD). IR (neat): 2933.5,
1
as a white solid (156.2 mg, 0.28 mmol, 41.1%). H NMR (500.26
2
1
881.7, 2836.2, 1617.3, 1476.6, 1358.3, 1318.9, 1185.7, 1170.7, 1107.0,
MHz, acetone-d ): δ = 8.18−8.12 (m, 4H, ArH), 8.01 (ddt, J = 8.4,
−1
+
6
024.1, 851.0, 752.1, 713.0 cm . HRMS (MALDI/ESI): [M ] calcd
1
.8, 0.8 Hz, ArH) 7.77 (ddd, J = 8.4, 7.4, 1.1 Hz, 1H, ArH), 7.69 (ddd,
for C H N F ClRh 576.03; found 576.0268. Anal. Calcd (%) for
C H N F ClRh: C, 47.90; H, 3.50; N, 4.86. Found: C, 47.82; H,
3
19
23
20
2 6
J = 8.3, 7.4, 1.0 Hz, 1H, ArH), 7.58 (dt, J = 8.3, 0.9 Hz, 1H, ArH).
F
23
20
2 6
NMR (470.67 MHz, acetone-d ): δ = −54.19 (NCF ), −63.22
6
3
.44; N, 4.72. Mp: 213.0 °C with decomposition.
General Procedure G. Synthesis of [Au(NHC)Cl] Complexes. The
13
1
(
6
1
ArCF ). C{ H} NMR (125.80 MHz, acetone-d ): δ = 180.01 (q, J =
3
6
.1 Hz, Au−C), 141.19 (C), 134.98 (C), 132.70 (q, J = 32.8 Hz, C),
30.90 (C), 129.36 (2C, CH), 128.29 (q, J = 3.8 Hz, 2C, CH), 128.07
gold complexes were synthesized from the corresponding benzimida-
zolium salts 2a and 2c−f according to a modified procedure previously
reported by Nolan. The corresponding benzimidazolium salt (1
equiv), [Au(DMS)Cl] (1 equiv), K CO (3 equiv), and acetone (0.05
M) were added to a Schlenk flask, and the resulting reaction mixture
was stirred at 60 °C for 4 h in the dark. Subsequently, all volatiles were
removed in vacuo. The residue was dissolved in CH Cl and filtered
through a small pad of neutral aluminum oxide. The clear solution was
then concentrated to dryness under reduced pressure. Subsequent
recrystallization of the residue from acetone/pentane afforded the
desired [Au(CNHC)Cl] complex.
(
CH), 127.90 (CH), 124.80 (apt d, J = 271.9 Hz, CF ), 120.45 (apt d,
43
3
J = 265.9 Hz, CF ), 114.30 (q, J = 4.1 Hz, CH), 114.15 (CH). HRMS
3
2
3
(MALDI/ESI): [M − Cl + C H F N ] calcd for C H AuF N
1
5
8
6
2
30 16
12
4
8
3
57.08; found 857.0819. Anal. Calcd (%) for C H AuF ClN : C,
15 8 6 2
2.02; H, 1.43; N, 4.98. Found: C, 31.99; H, 1.45; N, 4.87. Mp: 335.6
2
2
°C with decomposition.
Chloro[3-(6-fluoropyridin-3-yl)-1-(trifluoromethyl)-1H-benzo[d]-
imidazol-3-ylidene]gold (9e). Synthesized according to the general
procedure G, starting from 2f·HBF4 (84.9 mg, 0.23 mmol) and
[Au(DMS)Cl] (67.9 mg, 0.23 mmol). The product was obtained as an
1
Chloro[3-methyl-1-(trifluoromethyl)-1H-benzo[d]imidazol-3-yli-
dene]gold (9a). Synthesized according to the general procedure G,
starting from 2a·HOTf (160 mg, 0.68 mmol) and [Au(DMS)Cl] (200
off-white solid (51.5 mg, 0.10 mmol, 43.6%). H NMR (500.26 MHz,
DMSO-d , 60 °C): δ = 8.79 (s, 1H, ArH), 8.52 (m, 1H), 7.98 (d, J =
6
8.0, 1H, ArH), 7.73 (t, J = 8.0 Hz, 1H, ArH), 7.65 (t, J = 7.8 Hz, 1H,
19
mg, 0.68 mmol). The product was obtained as a white solid (112.8 mg,
ArH), 7.60−7.53 (m, 2H, ArH). F NMR (470.67 MHz, DMSO-d6,
1
0
7
2
.26 mmol, 38.4%). H NMR (400.13 MHz, DMSO-d , 60 °C): δ =
60 °C): δ = −53.09 (NCF ), −65.54 (dd, J = 7.4 Hz, 3.5 Hz, ArF).
6
3
13
1
.98−7.94 (m, 1H, ArH), 7.87−7.84 (m, 1H, ArH), 7.69−7.64 (m,
C{ H} NMR (125.80 MHz, DMSO-d , 60 °C): δ = 178.45 (d, J =
6
19
H, ArH), 4.17 (s, 3H, NCH ). F NMR (282.4 MHz, DMSO-d , 60
6.5 Hz, Au−C), 162.90 (d, J = 240.9 Hz, CF), 146.30 (d, J = 16.9 Hz,
C), 141.10 (d, J = 9.7 Hz, C), 133.69 (C), 131.73 (d, J = 4.6 Hz, CH),
129.07 (CH), 126.93 (d, J = 6.7 Hz, CH), 118.73 (q, J = 266.5 Hz,
3
6
13
1
°
C): δ = −52.53 (d, J = 1.8 Hz, NCF ). C{ H} NMR (100.62 MHz,
3
DMSO-d , 60 °C): δ = 177.04 (d, J = 5.8 Hz, Au−C), 132.86 (C),
1
6
29.19 (C), 126.56 (CH), 126.22 (CH), 118.75 (app d, J = 265.5 Hz,
CF ), 113.10 (CH), 112.97 (q, J = 4.0 Hz, CH), 111.02 (CH), 110.71
3
+
CF ), 113.25 (CH), 112.71 (q, J = 4.0 Hz, CH), 36.77 (CH ). HRMS
(CH). HRMS (MALDI/ESI): [M
+
Na ] calcd for
3
3
+
(
MALDI/ESI): [M + Na ] calcd for C H AuF ClNNa 454.99; found
C H AuF ClN Na 535.98; found 535.9822. Anal. Calcd (%) for
13 7 4 3
9
7
3
4
54.9809. Anal. Calcd (%) for C H AuF ClN: C, 24.99; H, 1.63; N,
C H AuF ClN : C, 30.40; H, 1.37; N, 8.18. Found: C, 28.32; H, 1.22;
13 7 4 3
9
7
3
1
394
DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395

Organometallics
Article
N, 7.37 (solvent impurities accounted for deviation). Mp: 335.3 °C
with decomposition.
General Procedure H. Au(I)-Catalyzed Intermolecular Hydro-
alkoxylation of Cyclohexene (10) with 2-Methoxyethanol (11). A
septum cap vial tube (2 mL) wrapped in aluminum foil was charged
(13) (a) Charpentier, J.; Fru
̈
h, N.; Togni, A. Chem. Rev. 2015, 115,
̈
650−682. (b) Niedermann, K.; Fruh, N.; Senn, R.; Czarniecki, B.;
Verel, R.; Togni, A. Angew. Chem., Int. Ed. 2011, 50, 1059−1063.
(14) Lv, T.; Wang, Z.; You, J.; Lan, J.; Gao, G. J. Org. Chem. 2013, 78,
5723−5730.
the corresponding Au(I) complex 9a−e (0.0125 mmol), AgNTf (4.9
(15) (a) Kelly, R. A.; Clavier, H.; Giudice, S.; Scott, N. M.; Stevens,
E. D.; Bordner, J.; Samardjiev, I.; Hoff, C. D.; Cavallo, L.; Nolan, S. P.
Organometallics 2008, 27, 202−210. (b) Tolman, C. A. Chem. Rev.
2
mg, 0.0125 mmol), and chlorobenzene (0.25 mL), and the mixture
was stirred for 5 min. Then cyclohexene (10, 205 mg, 2.50 mmol) and
2-methoxyethanol (11, 19.0 mg, 0.250 mmol) were added to the
1
(
977, 77, 313−348.
16) Hesek, D.; Lee, M.; Noll, B. C.; Fisher, J. F.; Mobashery, S. J.
Org. Chem. 2009, 74, 2567−2570.
17) The average CO stretching frequency of [IrCl(CO) (NHC)]
mixture. The vial tube was sealed and stirred at 100 °C for 20 h.
Subsequently, the mixture was cooled to room temperature. Then, n-
tetradecane was added to the mixture as an internal standard. The
yield of the resulting (2-methoxyethoxy)cyclohexane (12) was
determined by GC analysis.
(
2
complexes ν (CO) can be related to the TEP parameter by the
av
−1
following equation: TEP = 0.847 × ν (CO) + 336 cm . For the
av
derivation of this equation, see ref 15a.
ASSOCIATED CONTENT
Supporting Information
NMR spectra for new compounds; crystallographic data (CIF
files) for 2d·red, 6a−f, 7a, and 9a. This material is available free
of charge via the Internet at http://pubs.acs.org.
(18) Gusev, D. G. Organometallics 2009, 28, 763−770.
■
(19) Nelson, D. J.; Collado, A.; Manzini, S.; Meiries, S.; Slawin, A. M.
*
S
Z.; Cordes, D. B.; Nolan, S. P. Organometallics 2014, 33, 2048−2058.
(
(
20) For the derivation of the equation, see ref 15a.
21) Manjare, S. T.; Yadav, S.; Singh, H. B.; Butcher, R. J. Eur. J.
Inorg. Chem. 2013, 5344−5357.
(22) Fantasia, S.; Peterson, J. L.; Jacobsen, H.; Cavallo, L.; Nolan, S.
AUTHOR INFORMATION
Corresponding Author
E-mail: atogni@ethz.ch.
P. Organometallics 2007, 26, 5880−5889.
■
(
23) Wolf, S.; Plenio, H. J. Organomet. Chem. 2009, 694, 1487−1492.
24) Leuthau
(
̈
sser, S.; Schmidts, V.; Thiele, C. M.; Plenio, H. Chem.
*
Eur. J. 2008, 14, 5465−5481.
Notes
(25) Credendino, R.; Falivene, L.; Cavallo, L. J. Am. Chem. Soc. 2012,
134, 8127−8135.
The authors declare no competing financial interest.
(
(
(
26) Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877−910.
27) See refs 9b and 9c.
28) Linden, A.; de Haro, T.; Nevado, C. Acta Crystallogr. 2012, C68,
ACKNOWLEDGMENTS
■
The authors are grateful to ETH Zu
Science Foundation (grants 200020_137712 and
̈
rich and the Swiss National
m1.
(29) Reaction conditions: 10 (0.25 mmol), 11 (2.5 mmol), gold
200020_156989) for financial support.
complex (0.0125 mmol), and AgNTf (0.0125 mol) in PhCl (0.25
mL) for 20 h. Yields were determined by GC analysis, using n-
2
tetradecane as an internal standard. See ref 9b.
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1
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DOI: 10.1021/acs.organomet.5b00137
Organometallics 2015, 34, 1384−1395