Hydroxyl and ester functionalized N-heterocyclic carbene complexes of iridium(i): Efficient catalysts for transfer hydrogenation reactions

Article abstract of DOI:10.1039/c4ra02993c

Hydroxyl and ester-functionalized iridium(i) complexes of N-heterocyclic carbenes (3a-e) were obtained by transmetalation reactions from the in situ prepared silver(i)-NHC complexes and characterized by IR, NMR, mass spectroscopies, and elemental analysis

Full text of DOI:10.1039/c4ra02993c

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Hydroxyl and ester functionalized N-heterocyclic
carbene complexes of iridium(I): efficient catalysts
for transfer hydrogenation reactions†
Cite this: RSC Adv., 2014, 4, 26222
a
b
a
a
Derya Gulcemal, Aytaç Gurhan Gokçe, Suleyman Gulcemal* and Bekir Çetinkaya
¨
¨
¨
¨
¨
Hydroxyl and ester-functionalized iridium(I) complexes of N-heterocyclic carbenes (3a–e) were obtained
by transmetalation reactions from the in situ prepared silver(I)–NHC complexes and characterized by IR,
NMR, mass spectroscopies, and elemental analysis. X-ray diffraction studies on single crystals of 3a, 3c
and 3d verify the square planar geometry at the iridium center. Ester functionalized iridium(I)–NHC
complexes were found to be highly active and selective catalysts for the transfer hydrogenation
reactions of various aldehydes and ketones. The influence of different ester substituents on the reactivity
of the complexes was studied and the complex with a pivaloyl substituent (3d) showed the best activity
(TON up to 10 000).
Received 3rd April 2014
Accepted 8th June 2014
DOI: 10.1039/c4ra02993c
www.rsc.org/advances
Recently, Yus et al. reported the preparation of 1-(b-hydroxy-
alkyl) substituted imidazole (I) and benzimidazole (II) deriva-
Introduction
Transfer hydrogenation is a metal-catalyzed process that tives by an epoxide ring opening with the free heterocycles
7
consists of hydrogen transfer from a hydrogen donor, typically under solvent-free conditions. The method allows the synthesis
1
2
-propanol, to an acceptor molecule. The reduction of alde- of OH functionalized azole derivatives under very mild and
hydes, ketones and imines into the corresponding primary and simple reaction conditions. Furthermore, this methodology was
secondary alcohols and amines is one of the fundamental also successfully applied to prepare chiral imidazolyl alcohols
2
7
functional group transformations. This environmentally with high enantiomeric excess by using chiral epoxides or in
friendly protocol is preferred for large-scale industrial use in the the presence of prochiral epoxides via chemoenzymatic
8
hope of avoiding or reducing the amount of waste production resolution.
and developing a greener process by reducing energy use and
3
lowering toxicity. The transfer hydrogenation is a safer when
compared with the conventional hydrogenation reaction using
the potentially explosive H gas.
2
There have been many reports of the use of iridium-catalyzed
4
transfer hydrogenation of carbonyl compounds and imines. In
particular, iridium complexes bearing N-heterocyclic carbene
(
NHC) ligands have been successfully used as catalyst for
5
transfer hydrogenation reactions. NHCs have emerged as a
versatile class of ligands since they oen give stable organo-
In view of the above information here we investigated the
metallic complexes due to the strength of the metal–NHC synthesis of hydroxyl and ester functionalized iridium(I)–NHC
6
bond. Additionally, their tunable character allows for the complexes and their application in the transfer hydrogenation
control of the electronic and steric properties at the metal reactions of aldehydes and ketones. Initially, 1-(2-hydroxy-
center.
cyclohexyl)-5,6-dimethylbenzimidazole was prepared by cyclo-
hexene epoxide ring opening reaction with the 5,6-dime-
thylbenzimidazole under solvent-free conditions. 5,6-
Dimethylbenzimidazole was used as the heterocyclic compo-
nent since our previous studies showed that attachment of
a
Ege University, Department of Chemistry, TR-35100, Bornova, Izmir, Turkey. E-mail:
suleyman.gulcemal@ege.edu.tr
b
Dokuz Eylul University, Department of Physics, TR-35160, Buca, Izmir, Turkey
†
Electronic supplementary information (ESI) available: For further details as well methyl groups on the 5,6-position of the benzene ring of
as copies of NMR and mass spectra of ligands, iridium(I) complexes and
corresponding alcohols obtained from catalytic reactions. CIF les are giving
crystallographic information for 3a, 3c and 3d. CCDC 985402–985404. For ESI
and crystallographic data in CIF or other electronic format see DOI:
benzimidazole has played an important role in rhodium(I)–
9
5b
NHC and iridium(I)–NHC catalyzed reduction reactions. In
the second step, ester functionalization of the corresponding
alcohol is carried out by different anhydrides. Then, we
1
0.1039/c4ra02993c
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obtained the corresponding 5,6-dimethylbenzimidazolium salts silver(I)–NHC complexes. The catalytic activity of the related
by simple quaternization of these 1-alkyl(5,6-dimethylbenzimi- complexes in the transfer hydrogenation of aldehydes and
dazole) derivatives with 2,4,6-trimethylbenzyl bromide. Finally, ketones was studied comparatively, and we observed that ester
synthesized 5,6-dimethylbenzimidazolium salts were employed functionalization increased the catalytic activity considerably.
to generate the alcohol and ester functionalized iridium(I)–NHC
complexes by transmetalation reaction from in situ formed
Results and discussion
Synthesis and characterization of compounds
The reaction between 5,6-dimethylbenzimidazole and cyclo-
ꢀ
hexene oxide under solvent-free conditions at 70 C produced
the 1-(2-hydroxycyclohexyl)-5,6-dimethylbenzimidazole (1a) in
97% yield (Scheme 1). Then, anhydrides were subsequently
reacted with 1a through its OH function to give corresponding
ester functionalized 5,6-dimethylbenzimidazolyl ligands (1b–e)
(
Scheme 1). The IR spectra indicate that OH group was con-
ꢁ
1
verted into ester. The OH stretching band (3127 cm ) of 1a
disappeared and the corresponding C]O bands for 1b–e were
observed at 1739, 1732, 1727 and 1716 cm respectively.
The 5,6-dimethylbenzimidazolium salts (2a–e) were synthe-
sized by the reaction of 1a–e with 2,4,6-trimethylbenzyl bromide
ꢁ
1
ꢀ
in toluene at 80 C (Scheme 1). These salts are white powders
and were obtained in 94% to 98% yields. The spectral properties
are similar to those of other reported 5,6-dimethylbenzimida-
5a,b
1
+
zolium salts.
In the H NMR spectrum of 2a–e the NCHN
protons appear at 9.93, 10.67, 10.53, 10.59 and 10.77 ppm
respectively, and these downeld signals indicate the formation
of 5,6-dimethylbenzimidazolium salts.
The new OH and ester functionalized [IrCl(COD)(NHC)]
(
COD: 1,5-cyclooctadiene) complexes 3a–e were prepared by
10
transmetalation from the in situ formed silver–NHC deriva-
tives by employing a two-step process (Scheme 1). The silver–
NHC species were not isolated. In the second step, the addition
2
of [IrCl(COD)] to the mixture gave the yellow complexes in good
yields (84% 3a, 80% 3b, 76% 3c, 78% 3d and 82% 3e) as air and
moisture stable solids.
The structure and the purity of complexes 3a–e was clearly
conrmed by IR, NMR, mass spectroscopies and elemental
analysis. X-ray diffraction studies on single crystals of 3a, 3c and
3d were also been achieved. The characteristic downeld
Scheme 1 Synthetic pathway for the related compounds (1a–e, 2a–e
ꢀ
and 3a–e): (i) neat, 70 C, 12 h; (ii) anhydride, NEt
3
, DMAP, CH
2 2
Cl , rt,
+
ꢀ
signals for the NCHN protons of the 5,6-dimethylbenzimida-
2 2
24 h; (iii) MesCH Br, PhMe, 80 C, 4 h; (iv) Ag O, CH Cl , rt, 1 h; (v)
2
2
1
[
IrCl(COD)] , CH
2
2
Cl
2
, rt, 12 h.
zolium salts 2a–e disappeared in the H NMR spectra of
Fig. 1 The molecular structures of 3a, 3c and 3d with displacement ellipsoids drawn at the 30% probability level and hydrogen atoms have been
omitted for clarity.
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complexes 3a–e, which conrms the deprotonation of the ben-
zimidazolium fragment. The coordination of the NHC to the
1
3
iridium center becomes evident in the C spectra. The chem-
ical shis were observed at 190.3, 191.3, 191.3, 191.7 and 191.1
ppm for the complexes 3a–e, respectively, and are comparable
5
13
to those of other reported Ir(I)–NHC complexes. The
C
chemical shis showed that Ccarbene is substantially deshielded.
Molecular structures
The crystal structures of the iridium complexes 3a, 3c and 3d
(Fig. 1) were determined by single crystal X-ray diffraction
studies. The structural studies showed that iridium centers are
in slightly distorted square-planar coordination environments.
The signicant bond distances and angles are tabulated in
Table 1. The iridium–NHC distances of 2.030(6) (3a), 2.024(4)
˚
(
3c) and 2.032(3) A (3d) are consistent with previously charac-
5a,b,g,m,n
terized NHC-supported [Ir(COD)Cl] complexes.
The
ꢀ
planes of benzimidazole rings make dihedral angles of 85.9(3) ,
ꢀ ꢀ
8
0.9(2) and 79.9(1) with the least square planes of trimethyl-
phenyl rings for 3a, 3c and 3d, respectively. The six-membered
cyclohexane ring in all three structures adopts a chair confor-
mation. The details of intra- and intermolecular interactions are Fig.
2
Time course of the catalytic transfer hydrogenation of
given in ESI.†
acetophenone.
Catalytic studies
be the least active catalyst under the same conditions. Aer 90
min, only a 27% conversion was achieved and it required 10 h
for the total conversion. The activity for the tested complexes
decreases in order 3d > 3e > 3c > 3b > 3a indicating that
increasing the steric bulk of the carbonyl group on NHC ligand,
increase the catalytic activity considerably (Fig. 2). Another
important observation during the catalytic process was the color
change to black with catalysts 3a and 3b, which are resulted
with lover activities. This color change was not observed with
the other catalysts (3c–e) which have bulkier ester groups.
Next, we studied the effect of further catalyst loading (Table
Using the reduction of acetophenone to 1-phenylethanol as a
benchmark reaction, all the synthesized complexes (3a–e) were
screened as catalysts in 2-propanol as a hydrogen donor and in
ꢀ
the presence of base (KOH) at 85 C. Time depended conver-
sions were given in Fig. 2. The blank experiment was carried out
without catalyst and less than 5% conversion was observed even
aer 24 h.
Within the iridium(I)–NHC complexes (3a–e) examined in
this study, the complexes 3d and 3e were found to be more
active than the others for the model reaction (Fig. 2). The full
conversion to 1-phenylethanol required only 10 min with cata-
2) since this is important for improving the environmental
ꢁ1
lyst 3d (nal TOF 1200 h ) and 15 min with catalyst 3e (nal
impact and cost of the process and also removal of residual
ꢁ
1
TOF 800 h ). The OH-functionalized complex (3a) was found to
3a
iridium from the desired products. For this purpose, rst 0.1
mol% catalyst loading investigated with the most active cata-
lysts 3d and 3e. Complex 3d showed better activity, achieving
complete reduction of acetophenone to 1-phenylethanol in 1 h,
while complex 3e required 4 h with the same catalyst loading
ꢀ
a
Table 1 Selected bond lengths ( A˚ ) and angles ( ) for 3a, 3c and 3d
3a
3c
3d
2.032(3)
Ir1–C1
Ir1–Cl1
Ir1–M1
2.030(6)
2.359(16)
1.979
2.024(4)
2.363(13)
1.975
2.364(8) Table 2 The effect of the catalyst loadinga
1.978
2.054
b
c
Ir1–M2
2.078
2.058
Entry
Cat.
% Cat.
Time [h]
Conv. [%]
Yield [%]
C1–N1
C1–N2
1.371(7)
1.354(7)
91.65(15)
91.48
90.59
86.62
1.369(5)
1.354(5)
85.90(12)
96.71
90.96
86.63
1.353(4)
1.361(4)
85.82(8)
96.84
90.82
86.79
1
2
3
4
5
3d
3e
3d
3d
3d
3d
0.1
0.1
0.05
0.025
0.01
0.05
1
4
2.5
6
9
>99
>99
>99
>99
>99
>99
98
97
98
99
98
98
C1–Ir1–Cl1
M1–Ir1–C1
M2–Ir1–Cl1
M1–Ir1–M2
M1–Ir1–Cl1
M2–Ir1–C1
d
174.13
175.64
174.57
176.17
174.08
175.45
6
3
a
ꢀ
Substrate (0.5 mmol), KOH (5 mol%), IPA (2.5 mL), 85 C.
Determined by using GC from an average of at least two runs.
Isolated yield. Scaled up by the factor 40.
a
b
c
M1 and M2 represent the midpoints of the olenic bonds C11–C12
and C15–C16, respectively.
d
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a
Table 3 Lifetime/stability studies with catalyst 3d
Table 4 Transfer hydrogenation of carbonyl compounds to alcohols
with catalyst 3d
a
st
nd
rd
th
th
Run
1
2
3
4
5
Time [h]
Conv. [%]
1
>99
1
>99
1
>99
1
>99
1.25
>99
b
a
ꢁ3
5
mmol of acetophenone, added in ve separate stages; 1 ꢂ 10
ꢀ
b
mmol of 3d; 0.05 mmol of KOH; IPA (5 mL); 85 C. Determined by
using GC from an average of at least two runs.
b
c
Entry
1
Substrates
Time [h]
2.5
Conv. [%]
Yield [%]
(Table 2, entries 1 and 2). Encouraged from these results,
>99
>99
>99
98
97
99
catalyst loading decreased to 0.05%, 0.025% and 0.01% and
complete conversions was achieved with catalyst 3d in 2.5 h, 6 h
and 9 h respectively (Table 2, entries 3–5). The catalyst 3d
(0.05%) was also used for 20 mmol preparative scale synthesis
2
3
3
2
of 1-phenylethanol and the reaction required 3 h for the total
conversion (Table 2, entry 6).
The lifetime/stability of the catalyst 3d was also examined by
4i
employing Cavell's previous method. A catalytic run was
initiated using 1 mmol acetophenone, 0.1 mol% catalyst 3d,
0.05 mmol of KOH and 5 mL of 2-propanol. Aer 1 h operating
time 5 mL aliquot was taken for the analysis and an additional 1
mmol of substrate was added to the solution and the reaction
monitored for an additional 1 h. Finally, a third (1 mmol),
fourth (1 mmol) and h (1 mmol) aliquots of substrate was
added and the reaction was again monitored. These results are
shown in Table 3. In the rst four runs, total conversions were
observed aer 1 h operating time. The h run required an
additional 15 min (75 min in total) for the complete conversion.
It is clear that the catalyst maintained high activity during the
entire experiment despite the decrease of the catalyst concen-
tration (due to loss of small amounts of catalyst as aliquots were
taken for GC analysis). Cavell's lifetime/stability experiments
carried out in this study indicate that basic hydrolysis does not
occur. Otherwise we could not repeat the subsequent cycles in
high yields; though reaction time increases.
4
5
1.5
>99
96
1.5
2
>99
>99
98
99
d
6
7
8
9
1.5
1.5
1.5
>99
>99
>99
98
97
98
Encouraged by the results obtained with complexes 3d, the
study of catalyst substrate scope to different carbonyl
compounds was examined and the results are presented in
Table 4. The catalyst 3d shows very high activity in the transfer
hydrogenation of aromatic and aliphatic ketones (Table 4,
entries 1–8) and aromatic aldehydes (Table 4, entries 9–11) with
0.1 mol% catalyst loading. It is worth nothing that, the 3d is very
tolerant to substrate variations. Complete conversions were
obtained for transfer hydrogenation of aromatic and aliphatic
ketones within only 1–3 h. Among the substrates examined,
only the transformation of 2-methoxybenzaldehyde to 2- 10
methoxybenzylalcohol (Table 4, entry 12) was disappointing,
and in this case 6 h required for the complete conversion.
Finally, selectivity of the catalytic system to ketone or alde-
hyde was investigated. The catalytic experiment was carried
3
6
>99
>99
97
96
11
using 0.5 mmol of benzaldehyde, 0.5 mmol of acetophenone, 5
ꢁ
4
ꢁ2
ꢂ 10 mmol (0.05 mol% for each substrate) of 3d, 2.5 ꢂ 10
mmol of KOH and 2.5 mL of 2-propanol and the results are
presented in Table 5. In our initial study, benzaldehyde was
added rst and acetophenone was added right aer to the
solution including catalyst, base and 2-propanol. Under these
a
Substrate (0.5 mmol), KOH (5 mol%), 3d (0.1 mol%), IPA (2.5 mL),
ꢀ
5 C. Determined by using GC from an average of at least two runs.
d 1
b
8
c
Isolated yield. Conversion determined by H NMR.
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a
Table 5 Selectivity studies with catalyst 3d
benzaldehyde and acetophenone substrates towards transfer
hydrogenation showed a clear preference of the aldehyde
reduction. The applications of this methodology to the asym-
metric synthesis of chiral iridium(I)–NHC complexes by using
chiral epoxides such as (R)-(+)-styrene oxide or in the presence
of prochiral epoxides via chemoenzymatic resolution are
underway in our laboratory.
b
c
Entry
Time [h]
Conv. to A/B [%]
Conv. to A/B [%]
1
2
3
4
5
6
7
8
9
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
35/0
81/0
100/0
100/0
28/15
79/15
100/15
100/16
100/24
100/41
100/62
100/79
100/91
100/100
—
Experimental
General considerations
The reagents and solvents were purchased from Sigma-Aldrich,
Merck and Alfa Aesar and were used as received. [IrCl(COD)]
100/3
100/15
100/34
100/51
100/67
100/84
100/93
100/100
2
11
was prepared according to the published procedure. The
synthesis of metal complexes was carried out using standard
Schlenk techniques under an argon atmosphere. Column
chromatography was performed on silica gel 60 (230–400
1
1
1
0
1
2
1
13
mesh). H NMR (400 MHz) and C NMR (100 MHz) spectra
were acquired on a Varian AS 400 Mercury spectrometer with
—
a
Substrate; benzaldehyde (0.5 mmol) and acetophenone (0.5 mmol),
3
CDCl as solvent and tetramethylsilane (TMS) as internal stan-
KOH (2.5 mol% for each substrate), 3d (0.05 mol% for each
substrate), IPA (2.5 mL), 85 C. Acetophenone was added right aer dard. Chemical shis (d) were reported in units (ppm) by
benzaldehyde and determined by using GC from an average of at least
two runs. Benzaldehyde was added right aer acetophenone and
determined by using GC from an average of at least two runs.
ꢀ
b
1
assigning TMS resonance in the H spectrum as 0.00 ppm and
CDCl resonance in the C spectrum as 77.0 ppm. All coupling
3
c
13
constants (J values) were reported in Hertz (Hz). Melting points
were recorded with Gallenkamp electrothermal melting point
apparatus. Elemental analyses were performed on a Perkin-
Elmer PE 2400 elemental analyzer. FTIR spectra were recorded
on a Perkin Elmer Spectrum 100 series. Mass spectra were
acquired using a Bruker HCT Ultra Ion Trap Mass Spectrometer.
The chromatographic analyses (GC) were performed with an
Agilent 7820A instrument equipped with a ame ionization
detector and an Agilent 19091J-413 column (30 m ꢂ 320 mm ꢂ
conditions, benzaldehyde was completely reduced to benzyl
alcohol (A) within 1.5 h while there was no conversion of ace-
tophenone to 1-phenylethanol (B) (Table 5, entries 1–3).
Reduction of acetophenone was started aer 2.5 h 3% conver-
sion, and full conversion to 1-phenylethanol was achieved
within 6 h (Table 5, entries 5–12). In the next attempt, aceto-
phenone was added rst and benzaldehyde was added right
aer. In this case, rst analysis aer 0.5 h showed that the
conversion to A and B is 28% and 15% respectively (Table 5,
entry 1). There was no change for conversion to B until complete
conversion to A was achieved (Table 5, entries 2 and 3). Then,
0.5 mm).
Syntheses
1a. A mixture of 5,6-dimethylbenzimidazole (7.30 g, 50
reduction of acetophenone was continued aer benzaldehyde mmol) and cyclohexene oxide (4.90 g, 50 mmol) was placed in a
ꢀ
was fully reduced to benzyl alcohol (Table 5, entry 4–10). As a 100 mL round bottom ask and stirred at 70 C for 12 h. The
result, in both case reduction of benzaldehyde was found to be resulting mixture was puried by recrystallization with acetone–
ꢀ
more favorable to acetophenone.
hexane to give a white solid (11.80 g, 97%). Mp: 232–233 C. IR: n
ꢁ1
1
ꢀ
(
lm) 3127 cm (OH). H NMR (400 MHz, CDCl
ppm): d ¼ 1.46–1.58, 1.80–1.90, 2.00–2.03, 2.21–2.29 (8H, 4m, 4
), 2.23 (3H, s, Ar-CH -BI), 2.35 (3H, s, Ar-CH -BI), 3.94–
3
, TMS, 25 C,
Conclusions
ꢂ CH
2
3
3
3
.97 (2H, m, 4 ꢂ CH ring), 5.37 (1H, s, OH), 7.08 (1H, s, ArH-BI),
In this report, 1-(2-hydroxycyclohexyl)-5,6-dimethylbenzimida-
zole (1a), obtained by the ring opening reaction of cyclohexene
oxide with 5,6-dimethylbenzimidazole, was converted to the
NHC precursors (2a–e) by quaternization with 2,4,6-trime-
thylbenzyl bromide directly (1a) or aer esterication of OH
group by various anhydrides (1b–e) to see the inuence of
structural modularity. Iridium complexes of NHC ligands were
studied for transfer hydrogenation reactions. The efficiency of
NHC–ester ligands in transfer hydrogenation reaction is greater
in comparison to the NHC–alcohol ligands. Therefore, we may
13
7
.19 (1H, s, ArH-BI), 7.48 (1H, s, NCHN). C NMR (100.6 MHz,
ꢀ
CDCl
3
, TMS, 25 C, ppm): d ¼ 20.2, 20.6 (2 ꢂ Ar-CH
3
-BI), 24.6,
2
1
5.6, 32.2, 34.7 (4 ꢂ CH ), 62.8 (CHN ring), 72.5 (CHO ring),
2
10.7, 119.7, 130.8, 131.7, 132.6, 140.0, (ArC), 141.6 (NCHN).
O: C, 73.74; H, 8.25; N, 11.47. Found: C,
Anal. calc. for C15
7
20 2
H N
+
+
3.70; H, 8.28; N, 11.43. LC-MS (ESI ): m/z 245.0 [M + H] .
General procedure for the synthesis of ester functionalized
,6-dimethylbenzimidazoles (1b–e)
5
conclude that strong coordinative O atom in NHC–alcohol Corresponding anhydride (6.0 mmol) was added to a solution of
serves as chelating ligand. The reaction rate strongly depends 1a (1.22 g, 5.0 mmol), triethylamine (0.7 mL, 5.0 mmol) and 4-
on the bulk of the carbonyl entity. A 1 : 1 mixture of dimethylaminopyridine (61 mg, 0.5 mmol) in dichloromethane
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(20 mL), and the mixture was stirred at room temperature for 24 131.0, 131.9, 132.8, 140.3, (ArC), 141.8 (NCHN), 165.5
h. Water (30 mL) was added to the resulting mixture and (OC(C H )). Anal. calc. for C H N O : C, 75.83; H, 6.94; N,
6
5
22 24 2 2
+
extracted with dichloromethane (3 ꢂ 15 mL). Combined 8.04. Found: C, 75.77; H, 6.96; N, 7.99. LC-MS (ESI ): m/z 349.2
+
organic fractions were dried with MgSO and the solvent was [M + H] .
4
evaporated. The resulting crude product was puried by column
chromatography (silica gel, dichloromethane–methanol 95 : 5)
to yield the corresponding ester functionalized 5,6-dime-
General procedure for the synthesis of 5,6-
dimethylbenzimidazolium bromide salts (2a–e)
thylbenzimidazole derivatives.
ꢁ1
1
b. Beige oil. Yield: 1.37 g, 96%. IR: n (lm) 1739 cm
2,4,6-Trimethylbenzyl bromide (426 mg, 2.0 mmol) was added
1
ꢀ
(
C]O). H NMR (400 MHz, CDCl , TMS, 25 C, ppm): d ¼ 1.45– to a solution of 1a–e (2.0 mmol) in toluene (10 mL), and the
3
ꢀ
1
.57, 1.88–2.03, 2.16–2.23 (8H, 3m, 4 ꢂ CH ), 1.64 (3H, s, mixture was stirred at 80 C for 4 h. The solid that separated out
2
OCCH ), 2.35 (3H, s, Ar-CH -BI), 2.39 (3H, s, Ar-CH -BI), 4.16– aer cooling to room temperature was ltered off and washed
3
3
3
4
.24 (1H, m, NCH ring), 5.13–5.19 (1H, m, OCH ring), 7.23 with diethyl ether (20 mL). The product was recrystallized from
1
3
(1H, s, ArH-BI), 7.52 (1H, s, ArH-BI), 7.82 (1H, s, NCHN).
C
dichloromethane–diethyl ether to give the corresponding 5,6-
ꢀ
NMR (100.6 MHz, CDCl
Ar-CH
3
, TMS, 25 C, ppm): d ¼ 20.3, 20.7 (2 ꢂ dimethylbenzimidazolium salts (2a–e).
ꢀ
3
-BI), 20.8 (OCCH
3
), 24.2, 25.2, 31.8, 31.9 (4 ꢂ CH
2
), 58.8
2a. White solid, Mp: 241–242 C. Yield: 900 mg, 98%. IR: n
ꢁ1
1
ꢀ
(CHN ring), 74.3 (CHO ring), 110.7, 120.5, 131.0, 131.9, 132.5, (lm) 3302 cm (OH). H NMR (400 MHz, CDCl
3
, TMS, 25 C,
1
40.5, (ArC), 142.5 (NCHN), 169.9 (OCCH ). Anal. calc. for ppm): d ¼ 1.40–1.51, 1.60–1.69, 1.79–1.85, 2.10–2.43 (8H, 4m, 4
3
C H N O : C, 71.30; H, 7.74; N, 9.78. Found: C, 71.33; H, 7.69; ꢂ CH ), 2.26, 2.27, 2.35 (15H, 3s, CH -Mes + Ar-CH -BI), 4.20–
1
7
22
2
2
2
3
3
+
+
N, 9.74. LC-MS (ESI ): m/z 287.1 [M + H] .
c. Colorless oil. Yield: 1.52 g, 97%. IR: n (lm) 1732 cm
4.28 (1H, m, NCH ring), 4.45–4.50 (1H, m, OCH ring), 4.89 (1H,
ꢁ
1
1
d, J ¼ 5.6 Hz, OH), 5.79 (2H, dd, J ¼ 14.8, NCH -Mes), 6.89 (2H, s,
2
1
ꢀ
(
C]O). H NMR (400 MHz, CDCl
3H, d, J ¼ 7.2 Hz, CH(CH ), 0.83 (3H, d, J ¼ 7.2 Hz, CH(CH
.45–1.57, 1.89–2.06, 2.20–2.22 (8H, 3m, 4 ꢂ CH ), 2.10–2.17 20.3, 20.5 (CH
1H, m, CH(CH ), 2.34 (3H, s, Ar-CH -BI), 2.38 (3H, s, Ar-CH
34.5 (4 ꢂ CH
BI), 4.18–4.25 (1H, m, NCH ring), 5.13–5.21 (1H, m, OCH ring), ring), 113.0, 113.7, 125.3, 129.9, 130.0, 130.6, 136.8, 136.9, 138.1,
3
, TMS, 25 C, ppm): d ¼ 0.63 ArH-Mes), 6.99 (1H, s, ArH-BI), 7.55 (1H, s, ArH-BI), 9.93 (1H, s,
+ 13
ꢀ
(
1
(
3
)
2
3
)
2
), NCHN ). C NMR (100.6 MHz, CDCl , TMS, 25 C, ppm): d ¼
3
2
3
-Mes), 20.7, 21.0 (2 ꢂ Ar-CH
3
-BI), 24.1, 24.9, 31.9,
), 46.8 (NCH -Mes), 64.2 (CHN ring), 70.8 (CHO
3
)
2
3
3
-
2
2
1
3
+
7.22 (1H, s, ArH-BI), 7.51 (1H, s, ArH-BI), 7.81 (1H, s, NCHN).
C
25 33 2 2
139.5 (ArC), 139.7 (NCHN ). Anal. calc. for C H BrN O : C,
ꢀ
NMR (100.6 MHz, CDCl , TMS, 25 C, ppm): d ¼ 18.5, 18.7 (2 ꢂ 65.64; H, 7.27; N, 6.12. Found: C, 64.67; H, 7.26; N, 6.10. LC-MS
3
+
+
CH(CH
CH ), 33.9 (CH(CH
20.5, 130.9, 131.8, 132.5, 140.4, (ArC), 142.6 (NCHN), 176.1 (lm) 1738 cm (C]O). H NMR (400 MHz, CDCl , TMS, 25 C,
3
)
2
), 20.3, 20.7 (2 ꢂ Ar-CH
3
-BI), 24.2, 25.3, 31.8, 32.0 (4 ꢂ (ESI ): m/z 377.2 [M ꢁ Br] .
2b. White solid, Mp: 252–253 C. Yield: 950 mg, 95%. IR: n
ꢀ
2
3 2
)
), 58.7 (CHN ring), 74.0 (CHO ring), 110.7,
ꢁ1
1
ꢀ
1
3
(
8
OCCH(CH
3
)
2
). Anal. calc. for C19
H
26
N
2
O
2
: C, 72.58; H, 8.33; N, ppm): d ¼ 1.52–1.60, 1.81–1.85, 1.91–1.95, 2.02–2.08, 2.21–2.31,
+
.91. Found: C, 72.63; H, 8.30; N, 8.96. LC-MS (ESI ): m/z 315.1 2.38–2.44 (8H, 6m, 4 ꢂ CH
2
3
), 1.53 (3H, s, OCCH ), 2.21, 2.22,
+
[M + H] .
2.23, 2.36 (15H, 4s, CH -Mes + Ar-CH -BI), 4.67–4.74 (1H, m,
3
3
ꢀ
1d. White solid, Mp: 110–111 C. Yield: 1.50 g, 92%. IR: n NCH ring), 5.11–5.17 (1H, m, OCH ring), 5.79 (2H, s, NCH -Mes),
2
ꢁ1
1
ꢀ
lm) 1727 cm (C]O). H NMR (400 MHz, CDCl , TMS, 25 C, 6.84 (2H, s, ArH-Mes), 6.91 (1H, s, ArH-BI), 7.56 (1H, s, ArH-BI),
3
(
+
13
ꢀ
ppm): d ¼ 0.79 (9H, s, C(CH
3 3
) ), 1.46–1.55, 1.90–2.06, 2.18–2.24 10.67 (1H, s, NCHN ). C NMR (100.6 MHz, CDCl , TMS, 25 C,
3
(
8H, 3m, 4 ꢂ CH
2
), 2.35 (3H, s, Ar-CH
3
-BI), 2.39 (3H, s, Ar-CH
3
-
ppm): d ¼ 20.2, (OCCH ), 20.5, 20.6 (CH -Mes), 20.8, 21.1 (2 ꢂ
3
3
BI), 4.19–4.27 (1H, m, NCH ring), 5.11–5.15 (1H, m, OCH ring), Ar-CH -BI), 23.6, 24.5, 31.0, 31.3 (4 ꢂ CH ), 47.3 (NCH -Mes),
3
2
2
1
3
7
.21 (1H, s, ArH-BI), 7.53 (1H, s, ArH-BI), 7.87 (1H, s, NCHN).
C
61.2 (CHN ring), 74.7 (CHO ring), 113.5, 113.8, 125.3, 125.5,
ꢀ
NMR (100.6 MHz, CDCl
3
, TMS, 25 C, ppm): d ¼ 20.3, 20.7 (2 ꢂ 128.2, 129.0, 129.8, 130.1, 130.3, 137.3, 137.4, 138.0, 139.5 (ArC),
+
Ar-CH -BI), 24.2, 25.3 (2 ꢂ CH ), 26.8 (C(CH ) ), 31.8, 32.1 (2 ꢂ 140.3 (NCHN ), 169.5 (OCCH ). Anal. calc. for C H BrN O : C,
3
2
3 3
3
27 35
2 2
CH ), 38.6 (C(CH ) ), 58.8 (CHN ring), 74.2 (CHO ring), 110.8, 64.92; H, 7.06; N, 5.61. Found: C, 64.98; H, 7.04; N, 5.59. LC-MS
2
3 3
+
+
1
(
8
20.2, 131.3, 132.1, 132.3, 140.6, (ArC), 141.7 (NCHN), 177.6 (ESI ): m/z 419.2 [M ꢁ Br] .
OCC(CH ). Anal. calc. for C20 : C, 73.14; H, 8.59; N,
2c. White solid, Mp: 185–186 C. Yield: 990 mg, 94%. IR: n
ꢀ
3
)
3
28 2 2
H N O
+
ꢁ1
1
ꢀ
.53. Found: C, 73.08; H, 8.61; N, 8.55. LC-MS (ESI ): m/z 329.2 (lm) 1732 cm (C]O). H NMR (400 MHz, CDCl , TMS, 25 C,
3
+
[M + H] .
ppm): d ¼ 0.41 (3H, d, J ¼ 6.8 Hz, CH(CH ) ), 0.68 (3H, d, J ¼ 6.8
3
2
ꢀ
1
e. White solid, Mp: 95–96 C. Yield: 1.69 g, 97%. IR: n (lm) Hz, CH(CH
3
)
2
), 1.49–1.57, 1.75–1.77, 1.85–1.87, 2.00–2.04, 2.33–
ꢁ1
1
ꢀ
1
716 cm (C]O). H NMR (400 MHz, CDCl
3
, TMS, 25 C, 2.37, (8H, 5m, 4 ꢂ CH ), 1.88–1.94 (1H, m, CH(CH ), 2.15,
2
3 2
)
ppm): d ¼ 1.50–1.63, 1.93–2.00, 2.06–2.16, 2.29–2.43 (8H, 4m, 4 2.17, 2.28, (15H, 3s, CH -Mes + Ar-CH -BI), 4.65–4.71 (1H, m,
3
3
ꢂ CH ), 2.23 (3H, s, Ar-CH -BI), 2.29 (3H, s, Ar-CH -BI), 4.36– NCH ring), 5.01–5.08 (1H, m, OCH ring), 5.73 (2H, dd, J ¼ 14.8
2
3
3
4
.43 (1H, m, NCH ring), 5.32–5.39 (1H, m, OCH ring), 7.24 (2H, t, Hz, NCH -Mes), 6.78 (2H, s, ArH-Mes), 6.87 (1H, s, ArH-BI), 7.55
2
+
13
J ¼ 8.0 Hz, ArH), 7.30 (1H, s, ArH-BI), 7.38–7.45 (1H, m, ArH), (1H, s, ArH-BI), 10.53 (1H, s, NCHN ). C NMR (100.6 MHz,
ꢀ
7
.49 (1H, s, ArH-BI), 7.66 (2H, d, J ¼ 7.2 Hz, ArH), 7.98 (1H, s, CDCl , TMS, 25 C, ppm): d ¼ 18.2, 18.8 (2 ꢂ CH(CH ) ), 20.3,
3
3 2
1
3
ꢀ
NCHN). C NMR (100.6 MHz, CDCl
2
3
, TMS, 25 C, ppm): d ¼ 20.7 (CH -Mes), 20.9, 21.2 (2 ꢂ Ar-CH -BI), 23.6, 24.7, 31.3, 31.4
3
3
0.1, 20.5 (2 ꢂ Ar-CH -BI), 24.0, 25.1, 31.7, 31.8 (4 ꢂ CH
3
2
), 58.6 (4 ꢂ CH
2
), 33.7 (CH(CH
3
)
2
2
), 47.4 (NCH -Mes), 61.3 (CHN ring),
(CHN ring), 75.1 (CHO ring), 110.7, 120.1, 128.1, 129.4, 129.6, 74.8 (CHO ring), 113.5, 113.9, 125.4, 125.5, 128.3, 129.1, 129.8,
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+
1
1
7
4
30.1, 130.5, 137.3, 137.4, 137.9, 139.7 (ArC), 140.6 (NCHN ), NCH
2
-Mes), 5.87–5.94 (1H, m, OCH ring), 6.21 (1H, s, ArH-BI),
75.8 (OCCH(CH ) ). Anal. calc. for C H BrN O : C, 66.03; H, 6.41 (1H, d, J ¼ 14.8 Hz, NCH -Mes), 6.86 (2H, s, ArH-Mes), 7.23
3
2
29 39
2
2
2
+
13
ꢀ
.45; N, 5.31. Found: C, 65.97; H, 7.44; N, 5.29. LC-MS (ESI ): m/z (1H, s, ArH-BI). C NMR (100.6 MHz, CDCl , TMS, 25 C, ppm):
3
+
47.3 [M ꢁ Br] .
d ¼ 20.4, 20.5, 21.1, 21.2 (CH -Mes + Ar-CH -BI), 25.3, 26.3, 28.7,
3
3
ꢀ
2
d. White solid, Mp: 199–200 C. Yield: 1.02 g, 94%. IR: n 30.6, 32.0, 32.8, 35.0, 36.8 (8 ꢂ CH
2 2
), 49.1 (NCH -Mes), 51.8,
ꢁ1
1
ꢀ
(
lm) 1727 cm (C]O). H NMR (400 MHz, CDCl
ppm): d ¼ 0.74 (9H, s, C(CH ), 1.59–1.73, 1.85–1.89, 1.99–2.05, (2 ꢂ COD-CH), 112.2, 112.5, 128.3, 129.8, 131.2, 131.3, 132.2,
.14–2.42, (8H, 4m, 4 ꢂ CH ), 2.05, 2.14, 2.31, 2.42 (15H, 4s, 134.7, 138.2, 138.6 (ArC), 190.3 (Ir-Ccarbene). Anal. calc. for
CH -Mes + Ar-CH -BI), 4.80–4.89 (1H, m, NCH ring), 5.15–5.21
3
, TMS, 25 C, 53.0 (2 ꢂ COD-CH), 68.0 (CHN ring), 70.5 (CHO ring), 85.6, 86.6
3 3
)
2
2
3
3
C
33
H
2
44ClIrN O: C, 55.64; H, 6.23; N, 3.93. Found: C, 55.57; H,
+
191
193
(
(
(
1H, m, OCH ring), 5.86 (2H, dd, J ¼ 14.8 Hz, NCH -Mes), 6.92 6.18; N, 3.90. LC-MS (ESI ): m/z 675.0 ( Ir), 677.0 ( Ir)
2
+
2H, s, ArH-Mes), 7.05 (1H, s, ArH-BI), 7.71 (1H, s, ArH-BI), 10.59 [M ꢁ Cl] .
+
13
ꢀ
ꢁ1
1
1H, s, NCHN ). C NMR (100.6 MHz, CDCl , TMS, 25 C, ppm):
3b. Yield: 121 mg, 80%. IR: n (lm) 1739 cm (C]O). H
3
ꢀ
d ¼ 19.7, 20.0 (CH
), 26.1 (C(CH
-Mes), 60.4 (CHN ring), 74.5 (CHO ring), 112.8, 113.2, 2.22, 2.26, 2.31 (15H, 4s, CH
24.7, 129.0, 129.4, 129.8, 136.6, 136.8, 137.5, 139.0 (ArC), 139.8 m, COD-CH), 3.71–3.74 (1H, m, COD-CH), 4.64–4.71 (2H, m,
3
-Mes), 20.2, 20.5 (2 ꢂ Ar-CH
3
-BI), 22.9, 24.0 (2 NMR (400 MHz, CDCl
3
, TMS, 25 C, ppm): d ¼ 1.52–1.74, 1.85–
ꢂ CH
2
3
)
3
), 30.7, 30.8 (2 ꢂ CH ), 37.8 (C(CH
2
3
)
3
), 46.7 1.99, 2.35–2.42 (16H, 3m, 8 ꢂ CH
2
), 1.81 (3H, s, OCCH
3
), 2.04,
(NCH
2
3
-Mes + Ar-CH
3
-BI), 3.11–3.15 (1H,
1
+
(NCHN ), 176.4 (OCC(CH
3
)
3
). Anal. calc. for C30
H
41BrN
2
O
2
: C, COD-CH), 5.69–5.75 (1H, m, NCH ring), 5.90 (2H, dd, J ¼ 14.8
6
6.53; H, 7.63; N, 5.17. Found: C, 66.50; H, 7.66; N, 5.14. LC-MS Hz, NCH -Mes), 5.99–6.02 (1H, m, OCH ring), 6.18 (1H, s, ArH-
2
+
+
13
(ESI ): m/z 461.3 [M ꢁ Br] .
BI), 6.88 (2H, s, ArH-Mes), 7.25 (1H, s, ArH-BI). C NMR (100.6
ꢀ
ꢀ
2
e. White solid, Mp: 226–227 C. Yield: 1.06 g, 95%. IR: n MHz, CDCl , TMS, 25 C, ppm): d ¼ 20.3, 20.6, 20.7, 21.0 (CH -
3
3
ꢁ1
1
ꢀ
(lm) 1716 cm (C]O). H NMR (400 MHz, CDCl
3
, TMS, 25 C, Mes + Ar-CH
3
-BI), 21.1 (OCCH
), 49.0 (NCH
64.4 (CHN ring), 71.9 (CHO ring), 84.9, 85.0 (2 ꢂ COD-CH),
-BI), 5.02–5.08 (1H, 111.8, 112.1, 128.5, 129.6, 130.9, 131.0, 131.6, 134.6, 137.9 (ArC),
), 191.3 (Ir-Ccarbene). Anal. calc. for
4.8 Hz, NCH -Mes), 6.81 (2H, s, ArH-Mes), 6.88 (1H, s, ArH-BI), C H ClIrN O : C, 55.72; H, 6.15; N, 3.71. Found: C, 55.78;
3
), 24.4, 25.1, 28.9, 29.8, 30.2, 32.5,
ppm): d ¼ 1.67–1.69, 1.74–1.80, 1.95–1.98, 2.04–2.07, 2.53–2.56, 32.9, 34.1 (8 ꢂ CH
8H, 5m, 4 ꢂ CH ), 2.13, (6H, s, CH -Mes), 2.20 (3H, s, Ar-CH
BI), 2.27 (6H, s, CH -Mes), 2.29 (3H, s, Ar-CH
2
2
-Mes), 51.8, 53.2 (2 ꢂ COD-CH),
(
2
3
3
-
3
3
m, NCH ring), 5.50–5.56 (1H, m, OCH ring), 5.73 (2H, dd, J ¼ 169.8 (OCCH
3
1
7
2
35 46
2 2
+
191
193
.32 (2H, t, J ¼ 8.4 Hz, ArH), 7.48–7.52 (1H, m, ArH), 7.58 (1H, s, H, 6.17; N, 3.73. LC-MS (ESI ): m/z 717.2 ( Ir), 719.2 ( Ir)
+
13
+
ArH-BI), 7.72 (2H, d, J ¼ 7.2 Hz, ArH), 10.77 (1H, s, NCHN ).
C
[M ꢁ Cl] .
ꢀ
ꢁ1
1
NMR (100.6 MHz, CDCl
3
, TMS, 25 C, ppm): d ¼ 20.2, 20.8 (CH
3
-
3c. Yield: 118 mg, 76%. IR: n (lm) 1734 cm (C]O). H
ꢀ
Mes), 20.7, 21.2, (2 ꢂ Ar-CH
CH ), 47.2 (NCH -Mes), 62.2 (CHN ring), 74.5 (CHO ring), 113.4, 7.2 Hz, CH(CH
14.2, 125.4, 128.4, 129.1, 129.7, 129.9, 130.1, 130.2, 133.4, 1.74–1.86, 1.88–1.95, 2.08–2.17, 2.20–2.45 (17H, 5m, 8 ꢂ CH
3
-BI), 23.9, 24.7, 30.8, 31.6 (4 ꢂ NMR (400 MHz, CDCl
3
, TMS, 25 C, ppm): d ¼ 0.70 (3H, d, J ¼
2
2
3
)
2
), 0.91 (3H, d, J ¼ 7.2 Hz, CH(CH
3 2
) ), 1.52–1.64,
1
1
2
+
+
3 2 3 3
37.2, 137.3, 138.2, 139.6 (ArC), 141.3 (NCHN ), 165.3 CH(CH ) ), 2.02, 2.23, 2.24, 2.32 (15H, 4s, CH -Mes + Ar-CH -BI),
(
4
OC(C H )). Anal. calc. for C H BrN O : C, 68.44; H, 6.64; N, 3.13–3.17 (1H, m, COD-CH), 3.75–3.80 (1H, m, COD-CH), 4.66–
6 5 32 37 2 2
.99. Found: C, 68.39; H, 6.62; N, 5.02. LC-MS (ESI ): m/z 481.2 4.71 (2H, m, COD-CH), 5.65–5.71 (1H, m, NCH ring), 5.86 (2H,
+
+
[M ꢁ Br] .
dd, J ¼ 14.8 Hz, NCH -Mes), 6.00–6.07 (1H, m, OCH ring), 6.09
2
1
3
(
1H, s, ArH-BI), 6.89 (2H, s, ArH-Mes), 7.22 (1H, s, ArH-BI).
C
ꢀ
NMR (100.6 MHz, CDCl
3
, TMS, 25 C, ppm): d ¼ 18.4, 18.6
General procedure for the synthesis of iridium(I)–NHC
complexes (3a–e)
(
CH(CH
5.3, 29.0, 29.6 (4 ꢂ CH
), 49.0 (NCH
O (23 mg, 0.1 mmol) was suspended in degassed dichloro- (CHN ring), 71.6 (CHO ring), 84.8, 84.9 (2 ꢂ COD-CH), 111.6,
methane (5 mL) and stirred at ambient temperature for 1 h 111.8, 128.5, 129.5, 130.8, 13.9, 131.5, 134.6, 138.0 (ArC), 176.0
shielded from light. [IrCl(COD)]
(67 mg, 0.1 mmol) was then (OCH(CH ), 191.3 (Ir-Ccarbene). Anal. calc. for C37 50ClIrN
added to the suspension and the reaction mixture was stirred at C, 56.79; H, 6.44; N, 3.58. Found: C, 56.84; H, 6.47; N, 3.61. LC-
3
)
2
), 20.2, 20.3, 20.6, 20.9 (CH
), 30.3 (CH(CH
-Mes), 51.6, 53.0 (2 ꢂ COD-CH), 64.5
3
-Mes + Ar-CH
3
-BI), 24.4,
2
2
3 2
) ), 32.5, 33.1, 33.9, 34.0
Under an argon atmosphere, a mixture of 2a–e (0.2 mmol) and (4 ꢂ CH
2
2
Ag
2
)
H
O :
2 2
2
3
2
+
191
193
+
ambient temperature for more 12 h. The resulting suspension MS (ESI ): m/z 745.1 ( Ir), 747.1 ( Ir) [M ꢁ Cl] .
ꢁ
1
1
was ltered over Celite®. The remaining solid was washed with
3d. Yield: 124 mg, 78%. IR: n (lm) 1728 cm (C]O). H
ꢀ
dichloromethane (2 ꢂ 5 mL) and the solvent of the ltrate was NMR (400 MHz, CDCl
3
, TMS, 25 C, ppm): d ¼ 0.74 (9H, s,
3 3
evaporated. The residue was puried by column chromatog- C(CH ) ), 1.44–1.58, 1.66–1.73, 1.82–1.90, 1.99–2.09, 2.13–2.27,
raphy on silica gel (eluent: dichloromethane) to give pure 2.38–2.41, (16H, 6m, 8 ꢂ CH
), 1.94, 2.16, 2.17, 2.25 (15H, 4s,
CH -Mes + Ar-CH -BI), 3.05–3.10 (1H, m, COD-CH), 3.68–3.71
2
complex as a yellow solid.
3
3
ꢁ
1
1
3
a. Yield: 119 mg, 84%. IR: n (lm) 3418 cm (OH). H NMR (1H, m, COD-CH), 4.57–4.63 (2H, m, COD-CH), 5.57–5.64 (1H,
ꢀ
(
2
400 MHz, CDCl
3
, TMS, 25 C, ppm): d ¼ 1.47–1.79, 1.88–2.01, m, NCH ring), 5.73 (2H, dd, J ¼ 14.8 Hz, NCH
2
-Mes), 5.99 (1H, s,
.17–2.37 (16H, 3m, 8 ꢂ CH ), 2.04, 2.25, 2.26, 2.29 (15H, 4s, ArH-BI), 6.01–6.05 (1H, m, OCH ring), 6.83 (2H, s, ArH-Mes),
2
13
ꢀ
CH -Mes + Ar-CH -BI), 3.01–3.08 (2H, m, COD-CH), 3.56 (1H, d, J 7.19 (1H, s, ArH-BI). C NMR (100.6 MHz, CDCl
3
, TMS, 25 C,
-BI), 24.6, 25.7
3 3
) ), 29.4, 29.5, 30.8, 32.9, 33.5, 33.8
3
3
¼
10.4 Hz, OH), 4.11–4.14 (1H, m, NCH ring), 4.65–4.70 (1H, m, ppm): d ¼ 20.3, 20.4, 20.8, 21.1 (CH
3 3
-Mes + Ar-CH
COD-CH), 4.75–4.80 (1H, m, COD-CH), 5.55 (1H, d, J ¼ 14.8 Hz, (2 ꢂ CH ), 26.7 (C(CH
2
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(
6 ꢂ CH
2
), 38.6 (C(CH
3
)
3
), 49.1 (NCH
2
-Mes), 51.6, 52.9 (2 ꢂ were rened anisotropically. All hydrogen atoms were treated as
˚
COD-CH), 64.7 (CHN ring), 72.3 (CHO ring), 84.9, 85.2 (2 ꢂ riding atoms (C–H ¼ 0.95 to 0.99 A). Equal Uij constraints
COD-CH), 111.7, 111.8, 128.8, 129.6, 131.0, 131.1, 131.8, 135.0, (EADP) were used for C13/C14 and C17/C18 atom pairs in 3a.
1
38.2, 138.5 (ArC), 177.5 (OC(CH ) ), 191.7 (Ir-Ccarbene). Anal. Similar Uij (SIMU) restraint was also applied to C12/C13, C14/
3 3
2 2
calc. for C38H52ClIrN O : C, 57.30; H, 6.58; N, 3.52. Found: C, C15, C34/C35 and C35/C37 atoms in 3c. Thermal ellipsoid plots
+
191
15
5
(
7.25; H, 6.54; N, 3.53. LC-MS (ESI ): m/z 759.1 ( Ir), 761.1 were generated using the program ORTEP-3.
1
93
+
Ir) [M ꢁ Cl] .
ꢁ
1
1
3
e. Yield: 134 mg, 82%. IR: n (lm) 1727 cm (C]O). H
Acknowledgements
ꢀ
NMR (400 MHz, CDCl
1
3
, TMS, 25 C, ppm): d ¼ 0.84–0.94, 1.26–
.35, 1.50–1.57, 1.66–1.72, 2.03–2.23, 2.37–2.53 (16H, 6m, 8 ꢂ The nancial support from The Turkish Academy of Sciences
CH ), 2.01, 2.11, 2.26, 2.29 (15H, 4s, CH -Mes + Ar-CH -BI), 3.11– (TUBA) and Ege University are gratefully acknowledged. The
2
3
3
3
.16 (1H, m, COD-CH), 3.83–3.86 (1H, m, COD-CH), 4.68–4.72 authors also acknowledge Dokuz Eylul University for the use of
-Mes), 5.98– the Agilent Xcalibur Eos diffractometer (purchased under
.04 (1H, m, NCH ring), 6.13 (1H, s, ArH-BI), 6.16–6.19 (1H, m, University Research Grant no. 2010.KB.FEN.13).
(2H, m, COD-CH), 5.83 (2H, dd, J ¼ 14.8 Hz, NCH
2
6
OCH ring), 6.83 (2H, s, ArH-Mes), 7.29–7.33 (2H, m, ArH), 7.32
(
1H, s, ArH-BI), 7.48 (1H, t, J ¼ 7.6 Hz, ArH), 7.74 (2H, d, J ¼ 8.4
References
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3
ꢀ
Hz, ArH). C NMR (100.6 MHz, CDCl
3
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2
5
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