Synthesis of bimetallic complexes bridged by 2,6-bis(benzimidazol-2-yl) pyridine derivatives and their catalytic properties in transfer hydrogenation

Article abstract of DOI:10.1039/c8dt03178a

A series of binuclear rhodium(i) and iridium(i) complexes with 2,6-bis(benzimidazol-2-yl) pyridine (bzimpy) derivatives were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular and crystal structures of complex 3d were determined by the single crystal X-ray diffraction technique. Their monometallic analogues were prepared to compare the catalytic properties of the bimetallic complexes. To determine the catalyst properties that result in a cooperative, bimetallic enhancement of the reaction rate, the systematic variation of the intermetallic distance and the ligand donor properties of the bimetallic complexes were explored based on the transfer hydrogenation reactions of ketones.

Full text of DOI:10.1039/c8dt03178a

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Synthesis of bimetallic complexes bridged by
2,6-bis(benzimidazol-2-yl) pyridine derivatives
and their catalytic properties in transfer
Cite this: Dalton Trans., 2018, 47,
17317
hydrogenation†
a
Salih Günnaz, *a Aytaç Gürhan Gökçeb and Hayati Türkmen
*
A series of binuclear rhodium(I) and iridium(I) complexes with 2,6-bis(benzimidazol-2-yl) pyridine
(bzimpy) derivatives were synthesized and characterized by elemental analysis and spectroscopic
methods. The molecular and crystal structures of complex 3d were determined by the single crystal X-ray
diffraction technique. Their monometallic analogues were prepared to compare the catalytic properties
of the bimetallic complexes. To determine the catalyst properties that result in a cooperative, bimetallic
enhancement of the reaction rate, the systematic variation of the intermetallic distance and the ligand
donor properties of the bimetallic complexes were explored based on the transfer hydrogenation reac-
tions of ketones.
Received 3rd August 2018,
Accepted 8th November 2018
DOI: 10.1039/c8dt03178a
rsc.li/dalton
The reduction of carbonyl compounds (CvO) is an impor-
tant transformation in synthetic organic chemistry since it is a
Introduction
Recently, bimetallic catalysts have been used to enhance the general entry into alcohols.12 While homogeneous monometal-
rate and selectivity of catalyzed reactions.1 A bimetallic catalyst lic (ruthenium, rhodium, and iridium) complexes are usually
is often substantially more efficient than a monometallic cata- employed as catalysts,13 far less attention has been devoted to
lyst with a similar structure. The increase in catalyst perform- bimetallic transition-metal-based systems.14 Iridium com-
ance is attributed to “cooperative” interactions between the plexes are preferable over those of rhodium because of their
two metals and the substrate of the reaction.2 In the literature, high activities and lower costs. Monometallic complexes
it has been reported that a number of bimetallic complexes bearing N, P, O, S, and C element-based ligands with various
contain a ligand bridging the two metal fragments. Different forms are perhaps the most classic and popular catalysts for
examples of bridged ligands have also been employed in the TH.15 The resulting complexes are neutral, mono or dicationic
synthesis of bimetallic complexes.3
and form metal–donor atom bonds useful for catalytic transfer
In recent years, the coordination chemistry of transition hydrogenation (TH) reactions.15 Monometallic complexes of
metal ions containing multidentate bis-benzimidazole deriva- ruthenium with the bzimpy ligand are known to be catalytic
tives has been thoroughly investigated.4 They have drawn a toward TH.16 The catalytic activities of bimetallic complexes
great deal of attention in various areas, including medicine,5 with monometallic counterparts have been compared in TH.17
research on magnetic properties,6 photochemistry,7 materials However, to the best of our knowledge, development of a bi-
science,8 solution studies,9 and homogeneous catalysis10 metallic complex of the bzimpy ligand is yet to be explored.
owing to the versatility of their steric and electronic properties. Herein, we extend the use of the bzimpy ligand for the syn-
In particular, studies on the interaction of transition metal thesis of bimetallic rhodium(I) and iridium(I) complexes. New
complexes with DNA have gained prominence, because of bimetallic complexes were investigated in the TH of aromatic
their relevance in the development of new reagents for biotech- and aliphatic ketones. Their electronic and catalytic properties
nology and medicine.11
were compared with monometallic analogues.
aEge University, Department of Chemistry, 35100 Izmir, Turkey.
E-mail: hayatiturkmen@hotmail.com, salihgunnaz@gmail.com
bAdnan Menderes University Department of Physics, 09010 Aydın, Turkey
†Electronic supplementary information (ESI) available. CCDC 1865637. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c8dt03178a
Results and discussion
Synthesis and characterization of ligands (1a–d, 2a–d)
The bzimpy ligands were synthesized according to the steps
illustrated in Scheme 1. At the first step, 2,6-bis(benzimidazol-
This journal is © The Royal Society of Chemistry 2018
Dalton Trans., 2018, 47, 17317–17328 | 17317

View Article Online
Paper
Dalton Transactions
Scheme 1 Synthesis of ligands 1a–d and 2a–d.
2-yl) pyridine (1a) and 2,6-bis(5,6-dimethylbenzimimidazol-2- Synthesis and characterization of bimetallic Rh(I)/Ir(I) complexes
yl) pyridine (2a) were prepared by the reaction of pyridine-2,6-
dicarboxylic acid with o-phenylenediamine and 4,5-dimethyl- We aimed at creating a general and robust methodology that
benzene-1,2-diamine in polyphosphoric acid (PPA). Bzimpy could be selected for different coordination motifs with the
ligands (1b–d, 2b–d) were obtained via the alkylation of the bzimpy ligand. Bimetallic Rh(I)/Ir(I) complexes were syn-
compounds (1a, 2a) with benzyl chloride, 2,4,6-trimethylbenzyl thesized by the reaction of [M(COD)Cl]2 (M = Rh, Ir) with the
bromide, and pentamethyl benzyl bromide in the presence of ligands (1a–d, 2a–d) in CH2Cl2 (Scheme 2). The bimetallic
KOH in acetone at reflux (Scheme 1). The ligands (1b–d, 2b–d) complexes (3a–d, 4a–d, 5a–d, 6a–d) were characterized by one-
were soluble in chlorinated solvents, alcohols, and DMSO. and two-dimensional NMR spectroscopy and single-crystal
The NMR spectroscopic data of 1b–d, 2b–d agreed with the X-ray diffraction (for 3d). The NMR chemical shifts displayed
proposed structures.
good agreement with the experimental values. The 1H-NMR
Compounds 1a–d and 2a–d were characterized by one- and spectra of these complexes showed some differences from
two-dimensional NMR spectroscopy and elemental analysis. their respective ligands, especially the pyridine backbone.
NMR chemical shifts were found to be in good agreement with Py-Hm and -Hp protons for 3a–d, 4a–d, 5a–d, and 6a–d
the experimental values. In the 1H-NMR spectra, the Py-Hp and complexes were observed as doublets and triplets in a 2 : 1
Py-Hm protons were observed as doublets and triplets in a 2 : 1 ratio with a general shift toward lower fields compared to their
ratio at around δ 8.11–8.56 ppm. Signals at δ 45.8–48.1 ppm respective ligands.
corresponded to the benzylic methylene carbon resonances for
1b–d and 2b–d.
Monometallic Rh(I)/Ir(I) complexes (8, 9) were synthesized
through the reaction of [M(COD)Cl]2 with 7 in CH2Cl2
Scheme 2 Synthesis of bimetallic and monometallic complexes (3a–d, 4a–d, 5a–d, 6a–d, 8, 9).
17318 | Dalton Trans., 2018, 47, 17317–17328
This journal is © The Royal Society of Chemistry 2018

View Article Online
Dalton Transactions
Paper
(Scheme 2). The complexes (8, 9) were characterized by NMR for bimetallic complexes (4a–4d), respectively. An oxidation
spectroscopy. The NMR chemical shifts were consistent with peak for the monometallic complex (8) at −0.38 V was
the experimental values. The 1H-NMR spectra of the NCHN observed. The shift of oxidation potential to a more positive
protons of complexes (8, 9) revealed singlets at δ 8.16 and value for 8 can be explained by either slower electron-transfer
8.58 ppm respectively.
kinetics or chemical reaction of the complex or surface passi-
vation of the electrode, or any combination of these effects.
Comparing the first reduction potentials of 8 and 4d, a more
positive reduction peak potential was observed in complex 4d.
The reduction potential of a complex is related to the charge
density on the metal. The reduction potential will shift toward
more positive potential values in Rh complexes because of the
smaller positive charge density on the metal.19 Therefore, in
the current study, 4d had the smallest positive charge density
on the metal and had the highest catalytic activity. This CV
result was in good agreement with the catalytic experiments.
Electrochemistry
Recently, various methods have attempted to experimentally
determine and compare the density of electrons on a metal
atom in complexes. These methods involve studies on cyclic
voltammetry and determination of CO stretching frequencies
in the IR spectra of complexes. We compared the electro-
chemical properties of bimetallic complexes and their mono-
metallic analogues using two different methods.
The electrochemical behaviors of the monometallic
complex (8) and bimetallic complexes (4a–4d) were investi-
gated by CV. The CV of 5.0 × 10−3 M of Rh-complexes is pre-
sented in Fig. 1.
Electron density comparison of 6d′ and 9′
The ν(CO) measurement of the complexes is used to determine
the electron density on the metal atom in a complex. The
measure of the CuO frequency of complexes gives information
about the electron donor abilities of the ligands. In this study,
the monometallic (9) and bimetallic (6d) complexes were con-
verted straightforwardly to the corresponding carbonyl deriva-
tives 9′ and 6d′, which allowed the electronic nature of the com-
plexes to be inferred from IR (Scheme 3). The C–O stretching
frequencies of the carbonyl complexes (6d′, 9′) were recorded in
CH2Cl2 solution. As expected, monometallic complex 9′ bearing
the benzimidazole derivative exhibited CO vibrations that
shifted toward a higher wave number compared to the bi-
metallic complex 6d′. The complexes (6d′, 9′) were characterized
by IR, 1H and 13C-NMR. The data obtained from these methods
also showed that the symmetrical ν(CO) in the respective
(6d′, 9′) complexes did not correlate with the catalytic activity.
The electrochemical responses of the complexes were very
similar with both showing two-step reduction peaks and one
oxidation peak. This result is in good agreement with the lit-
erature.18 The reduction potentials of the bimetallic complexes
(4a–4d) and monometallic complex (8) were determined by
cyclic voltammetry (CV) in DMSO. The reduction potential of a
given complex is directly related to the charge density at the
metal center. When the monometallic complex (8) was com-
pared to the bimetallic complexes (4a–4d), the reduction
potential of 8 at −0.45 V for the rhodium center shifted to
−0.55 V, −0.53 V, −0.54 and −0.56 V for 4a, 4b, 4c and 4d
respectively. Similar results were obtained for bimetallic com-
plexes (4a–4d). On the other hand, the second quasi reduction
peak of the bimetallic complexes at −0.50, −0.48, −0.51 and
−0.51 V may be due to the reduction of Rh(II) to Rh(I) for the
(4a–4d) complexes, respectively. On the reverse scan, the oxi-
dation peaks for bimetallic complexes at −0.68 V, −0.54, −0.50 Transfer hydrogenation of acetophenone catalyzed by
and −0.45 V can be attributed to the oxidation of Rh(I) to Rh(II) bimetallic Rh(I)/Ir(I) complexes
TH reaction is attractive as it can avoid the use of molecular
hydrogen in organic synthesis.20 The optimum temperature
Fig. 1 Cyclic voltammogram of the blank, monometallic and bimetallic
Rh(I) complexes at a platinum electrode after dissolution of 5.0 × 10−3
M
of the complex in DMSO containing 0.1 M TBAB. Scan rate 100 mV s−1
.
Scheme 3 Synthesis of mono- and bimetallic complexes (6d’, 9’).
Dalton Trans., 2018, 47, 17317–17328 | 17319
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
Dalton Transactions
Table 2 Catalytic activity for the TH of various ketones catalyzed by bi-
metallic (4d, 6d) and monometallic complexes (8, 9)a
for catalysis is 82 °C in the presence of KOH, which is known
to be the best inorganic base for this reaction.21 Catalytic
studies with bimetallic Rh(I)/Ir(I) complexes were performed
for the TH of acetophenone in the presence of KOH using
2-propanol (Table 1).
Reactions were performed under identical conditions to
allow the comparison of results. To investigate the time depen-
dency of auxiliary ligands on the catalytic activity, the pro-
perties of complexes coordinated by benzyl, 2,4,6-trimethyl
benzyl and pentamethyl benzyl were also studied. It was
observed that the steric effect of the benzyl substituent was
crucial in the bzimpy ligand type for the TH of ketones. The
catalytic activity of the complexes with pentamethyl benzyl
substituents (3d, 4d, 5d, and 6d) was higher than those with a
simple benzyl substituent (3b, 4b, 5b, 6b). This result indicates
that steric effects are dominant factors in this reaction, which
has also been reported by other researchers.22 The complexes
(3a, 4a, 5a, 6a) with less hindered H substitution exhibit
greater reactivities compared with benzyl substituted com-
plexes (3b, 3c, 4b, 4c, 5b and 5c). Subtle differences in the
coordination of the ligand may produce important differences
in its electron donation, thus producing an important impact
on the catalytic properties. Under the same reaction con-
ditions, the tested methyl substituted complexes (4, 6) showed
greater donor strength than its non-substituted analogue in
complexes (3, 5). The efficiency difference between catalysts
(4, 6) and (3, 5) could be explained by the electronic effect of
benzimidazole ligands. As shown in Table 1, the bimetallic
Conversion (%)
Entry R1
R2
Cat. 10 min 15 min 30 min
1
C6H5
CH3
4d
6d
8
54
78
12
22
24
34
4
60
98
18
25
28
44
6
82
—
33
38
36
49
11
14
67
94
21
32
76
90
25
28
71
89
37
39
89
—
46
49
84
—
47
50
99
—
48
51
57
72
23
32
68
82
28
38
76
91
32
43
73
88
30
41
53
68
22
29
46
57
28
36
70
77
39
58
9
2
C6H5
C2H5 4d
6d
8
9
4d
6d
8
7
9
3
4-OCH3-C6H4
3,4-diCH3-C6H3
2-Br-C6H4
4-Br-C6H4
2-Cl-C6H4
4-Cl-C6H4
C2H5
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
42
62
13
17
37
53
14
16
55
70
21
23
69
88
26
29
62
81
28
35
78
98
28
32
36
49
15
19
43
59
18
23
48
66
20
26
46
64
19
25
33
44
11
19
29
36
09
13
43
54
22
31
50
89
17
24
41
75
19
22
64
79
26
30
80
99
32
38
68
96
39
43
89
—
37
45
43
59
18
24
51
70
21
28
57
79
24
31
56
76
22
24
38
56
17
21
38
47
16
25
61
57
30
46
9
4
4d
6d
8
9
5
4d
6d
8
9
6
4d
6d
8
9
7
4d
6d
8
9
8
4d
6d
8
Table 1 Catalytic activity for the TH of acetophenone catalyzed by bi-
metallic complexesa
9
9
4d
6d
8
9
10
11
12
13
14
15
C3H7
4d
6d
8
Conversion (%)
9
C4H9
4d
6d
8
Entry
Cat.
10 min
15 min
30 min
60 min
1
2
3
4
5
6
7
8
3a
3b
3c
3d
4a
4b
4c
4d
5a
5b
5c
5d
6a
6b
6c
6d
6d
25
23
26
29
39
33
38
54
39
33
37
41
59
47
56
78
—
30
25
29
32
45
36
43
60
63
44
48
52
77
61
73
56
47
53
58
51
45
52
82
85
77
80
90
90
86
86
—
—
88
82
86
94
90
84
89
98
99
94
96
98
99
96
98
—
—
9
CH3
4d
6d
8
9
2-OCH3-2-CH3-C3H5 CH3
4d
6d
8
9
9
10
11
12
13
14
15
16
17
C6H10
—
4d
6d
8
9
C6H5-CH2
C6H5 4d
98 (10b)(21c)
84d, 75e, 79f
6d
8
9
a Reaction conditions: Acetophenone (1 mmol), 2-PrOH (1 mL), KOH
(0.1 mmol), catalyst (0.25 mol% based on the metal), 82 °C. b Room
temperature. c 60 °C. Base. d NaOH. e K2CO3. f Cs2CO3.
a Reaction conditions: Ketone (1 mmol), 2-PrOH (1 mL), KOH
(0.1 mmol), catalyst (0.25 mol% based on the metal), 82 °C.
17320 | Dalton Trans., 2018, 47, 17317–17328
This journal is © The Royal Society of Chemistry 2018

View Article Online
Dalton Transactions
Paper
Rh(I)/Ir(I) complexes (4d, 6d) were found to be the best active increase in catalytic yield (entries 7 and 8). The reduction of
catalysts in the TH of acetophenone. aliphatic ketones by monometallic and bimetallic catalysts
The effect of other bases on TH reaction was also investi- resulted in the quantitative formation of aliphatic alcohols
gated. NaOH, K2CO3 and Cs2CO3 were less efficient giving (entries 9–12). We also found that the alkyl length of aliphatic
yields of 84, 75 and 79%, respectively, under the similar con- ketones greatly influenced the reactivity (entries 9–11). To gain
ditions (entry 17). After obtaining higher catalytic activities in insight into the effect of the basic N atom in the pyridine of
preliminary studies, we extended our investigation to include the ligand and the number of benzimidazolyl subunits on the
the TH of various aromatic and aliphatic ketones. TH reactions central phenyl scaffold, we synthesized 1,3-bis(benzimidazol-2-
using bimetallic complexes (4d, 6d) and monometallic com- yl)benzene (m-Bimbe) 10, 2-phenylbenzimidazole (Imbe) 11,
plexes (8, 9) were performed on a series of aromatic ketones, and their iridium complexes (12, 13) (Scheme 4). The signifi-
and the results are given in Table 2. The reactions were typi- cantly decreased activity of 12 was likely the consequence of
cally carried out with 0.25 mol% of catalyst in 2-PrOH at 82 °C. the loss of N-atom in the ligand. These results suggest that the
The aryl ketones were chosen to explore the effects of elec- pyridine-N atom in the ligand plays an essential role in the TH
tronic and variations on the substrate backbone. Among the of ketones. We also investigated the number of benzimidazolyl
aromatic substrates examined, only the transformation of pro- groups on the ligand scaffold. Complex 13 (having only one
piophenone to 1-phenylpropionol (Table 2, entry 2) required a benzimidazolyl) was much less active than 12 (having two ben-
longer reaction time for complete conversion. The position of zimidazolyl subunits) (Table 3, entries 2 and 3).
the substituents on the phenyl ring causes significant changes
Molecular structure
in the reduction rate. On the other hand, an ortho- or para-sub-
stituted acetophenone with an electron donor substituent, The crystal structure of 3d (Fig. 2) was determined by single
such as 4-methoxy or 3,4-dimethyl, is reduced more slowly crystal X-ray diffraction. The title compound {Rh(COD)Cl}2L,
than acetophenone. For example, electron-withdrawing substi- where L represents 2,6-bis(1-pentamethylbenzyl-1-H-benzimi-
tuents, such as Cl and Br (entries 5–8), at the para position of dazole-2-yl)pyridine,23 is a bimetallic complex that consists of
the aryl ring of the ketone decreased the electron density of one and a half molecule of dichloromethane solvent in the
the (CvO) double bond, which improved the activity. In asymmetric unit.
addition, due to steric reasons, the effect of changing the
The complete molecular structure is generated by the
location of the substituents from the 2- to 4-position of the implementation of the crystallographic two-fold rotation
bromoacetophenone (entries 5 and 6) influenced the reactivity. whose axis bisects the pyridine ring and crosses midway
Furthermore, this process was less efficient in the reduction of between the N3 and C4 atoms. Each benzimidazole ring con-
ethyl methyl ketone (entry 9) and diethyl ketone (entry 12) nects to the [Rh(COD)Cl] units through the nitrogen atoms (N1
compared to acetophenone derivatives (entries 5–8). These and N1); thus, the tridentate units act as bis-monodentate
differences in the catalytic activity of substituted ketones could ligands in the compound. The coordination geometry around
be explained by the effects of the different steric and electronic the Rh center, formed by the cyclooctadiene (COD) ligand, the
environments.15
N1 atom of the benzimidazole ring, and the Cl1 atom is a
As shown in Table 2, under the same reaction conditions, it slightly distorted square-planar. The pyridine ring connects
was found that the bimetallic Rh(I)/Ir(I) complexes (4d, 6d) the Rh(I) metal centers through a N1–C1 atom bridge. The pyri-
were more active catalysts than their monometallic counter- dine and benzimidazole rings were approximately coplanar as
parts (8, 9). Chloroacetophenone resulted in a significant expected. The Rh–N and Rh–Cl bond distances were within the
Scheme 4 Synthesis of ligands (10, 11) and their iridium complexes (12, 13).
This journal is © The Royal Society of Chemistry 2018
Dalton Trans., 2018, 47, 17317–17328 | 17321

View Article Online
Paper
Dalton Transactions
binding of the COD unit reveals the larger trans influence of
the benzimidazole ligand compared to chloride. The penta-
methyl benzyl ring was oriented almost perpendicular to the
benzimidazole ring with a dihedral angle of 89.09(12)°. The
non-coordinating central pyridine ring and the benzimidazole
side arms resulted in an interplanar angle of 48.75(13)°.25 The
details of the intramolecular and intermolecular interactions
are given in the ESI.†
Conclusion
We reported the preparation and characterization of a series of
bimetallic Rh(I)/Ir(I) complexes (3a–d, 4a–d, 5a–d, 6a–d)
bearing monodentate ligands. Their catalytic activities were
investigated for the TH reaction of ketones. The catalytic
activity increased generally with the amount of electron
density on the metal. Among the bimetallic complexes, catalyst
6d demonstrated good catalytic activity, and alcohols with up
to 98% conversion were obtained within 15 min. As a result, it
was determined that the bimetallic complexes showed higher
activity than monometallic complexes. Comparing the bi-
metallic complex 6d and monometallic derivative 9 under the
same reaction conditions, it is found that the former provided
a good conversion (99%) while the conversion of the latter was
only 25%. The CH3 group on the benzimidazole ring had a sig-
nificant effect on the catalytic activity of the complexes
whereas that of benzyl, 2,4,6-trimethyl benzyl and pentamethyl
benzyl at the benzimidazole ring appeared to play a less impor-
tant role.
Fig. 2 The molecular structure of 3d with displacement ellipsoids
drawn at the 30% probability level and hydrogen atoms have been
omitted for clarity. Symmetry code: (i) −x, y, 1/2 − z.
Table 3 Catalytic activity for the TH of acetophenone catalyzed by
complexes 6a, 11, and 13a
Conversion (%)
Entry
Cat.
10 min
15 min
30 min
60 min
1
2
3
6a
12
13
59
38
21
77
57
28
90
88
66
99
93
80
Experimental section
General consideration
a Reaction conditions: Acetophenone (1 mmol), 2-PrOH (1 mL), KOH
(0.1 mmol), catalyst (0.25 mol% based on the metal), 82 °C.
Reactions involving air-sensitive components were performed
using a Schlenk-type flask under an argon atmosphere with
high vacuum-line techniques. The glass equipment was heated
under vacuum in order to remove oxygen and moisture, and
then filled with argon. The solvents were of analytical grade
and distilled under an argon atmosphere from sodium
(ethanol, methanol, diethyl ether, and pentane) and P2O5 (di-
chloromethane). The synthesis of bzimpy26 and the preparation
of 2,4,6-bromide and 2,3,4,5,6-pentamethylbenzyl bromide were
undertaken according to the literature.27 PPA is generally freshly
prepared. Approximately 25 mL PPA was obtained by mixing
18 g P2O5 and 10 g 85% H3PO4. The reagents were stirred at
100 °C under a dry atmosphere until a homogeneous, clear
viscous liquid was formed. Typically, this process takes around
Table 4 Selected bond lengths (Å) and angles (°)a
Rh1⋯Rh1i
Rh1–M1
Rh1–M2
Rh1–N1
Rh1–Cl1
N1–C1
N1–C10
N2–C5
N1–Rh1–M1
M2–Rh1–N1
M1–Rh1–M2
C1–N1–Rh1
8.083
2.010
1.980
2.102(3)
2.3817(10)
1.320(4)
1.392(4)
1.393(4)
175.52
91.36
Rh1–C11
Rh1–C12
Rh1–C16
Rh1–C15
N3–C2
N2–C1
C2–C1
2.101(3)
2.090(4)
2.120(4)
2.127(4)
1.339(4)
1.357(4)
1.474(4)
1.390(4)
176.61
C5–C10
Cl1–Rh1–M2
M1–Rh1–Cl1
N1–Rh1–Cl1
C10–N1–Rh1
93.49
87.88(8)
128.0(2)
87.53
126.0(2)
a M1 and M2 represent the midpoints of the olefinic bonds C15–C16
and C11–C12, respectively.
1
24 h. The H and 13C NMR spectra were recorded on a Varian
AS400 Mercury at Ege University. As solvents, CDCl3 and
d6-DMSO were employed, and the J values were in Hz.
expected range and in agreement with the related complexes
reported previously.9,24 The significant bond angles and bond
General procedures for the synthesis of compounds 1a and 2a
distances are listed in Table 4. The Rh–COD bond trans to ben- Compounds 1a and 2a were prepared by modification of the
zimidazole was longer than that to chloride. This type of previously published procedure.26 Pyridine-2,6-dicarboxylic
17322 | Dalton Trans., 2018, 47, 17317–17328
This journal is © The Royal Society of Chemistry 2018

View Article Online
Dalton Transactions
Paper
acid (20 mmol) was stirred with o-phenylenediamine or 4,5-di- BI-H), 7.19 (t, 2H, J = 7.6 Hz, BI-H), 7.76 (d, 2H, J = 7.9 Hz,
methylbenzene-1,2-diamine (44 mmol) in PPA (50 mL) at ca. BI-H), 8.07 (t, 1H, J = 7.8 Hz, Py-Hp), 8.42 (d, 2H, J = 7.6 Hz,
230 °C for four hours. The colored melt was poured into 500 mL Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ: 19.8, 19.9
of vigorously stirred cold water. The bulky blue-green precipitate (Ar-CH3), 46.8 (N-CH2), 105.9, 115.0, 120.6 (3 × BI-C), 121.1
was collected by filtration and treated with hot 10% aqueous (Py-Cm), 134.0, 135.1 (2 × Ar-C), 135.2 (BI-C), 142.0 (Py-Cp),
Na2CO3 solution. It was then filtered off and dissolved in hot 142.3 (BI-C), 149.0 (Py-Co), 155.4 (NvC-NH).
MeOH (∼500 mL). Upon cooling, needle light-brown and pinkish
Compound 1d: Yield: 82%. Elemental analysis: calcd (%)
crystals were filtered off and recrystallized from hot MeOH using for C43H45N5 (631.37): C, 81.74; H, 7.18; N, 11.08%. Found: C,
1
decolorizing carbon to obtain white needle crystals.
80.08; H, 7.06; N, 11.24%. H NMR (400 MHz, 303 K, CDCl3)
Compound 1a: Yield: 80%. Elemental analysis: calcd (%) δ: 2.02 (s, 12H), 2.13 (s, 12H), 2.21 (s, 6H, Ar-CH3), 6.18 (s, 4H,
for C19H13N5 (311.12): C, 73.30; H, 4.21; N, 22.49%. Found: C, N-CH2), 6.59 (d, 2H, J = 7.6 Hz), 7.01 (t, 2H, J = 7.5 Hz), 7.22
73.18; H, 4.27; N, 22.43%. 1H NMR (400 MHz, 303 K DMSO-d6) (t, 2H, J = 7.6 Hz), 7.81 (d, 2H, J = 7.6 Hz, BI-H), 8.11 (t, 1H, J =
δ: 7.41 (m, 4H, BI-H), 7.76 (m, 4H, BI-H), 8.21 (t, 1H, J = 7.7 Hz, 7.8 Hz, Py-Hp), 8.72 (d, 2H, J = 7.8 Hz, Py-Hm). 13C NMR
Py-Hp), 8.41 (d, 2H, J = 8.0 Hz, Py-Hm), 13.05 (2H, N–H). 1H NMR (100 MHz, 303 K, CDCl3) δ: 15.9, 17.7, 19.9 (3 × Ar-CH3), 47.8
(400 MHz, 303 K, CDCl3) δ: 7.33 (m, 4H, BI-H), 7.50 (m, 2H, (N-CH2), 112.0, 120.0, 122.5, 123.4, 126.1 (5 × BI-C), 128.2,
BI-H), 7.88 (m, 2H, BI-H), 7.97 (t, 1H, J = 7.8 Hz, Py-Hp), 8.48 133.4, 134.9 (3 × Ar-C), 136.0 (BI-C), 137.8 (Py-Cp), 142.4 (BI-C),
(d, 2H, J = 7.6 Hz, Py-Hm), 10.60 (2H, N–H). 13C NMR (100 MHz, 149.7 (Py-Co), 150.7 (NvC-N).
303 K, DMSO-d6) δ: 115.8, 121.6 (2 × BI-C), 124.3 (Py-Cm), 136.4
(Py-Cp), 140.4 (BI-C), 146.1 (Py-Co), 150.5 (NvC-NH).
Compound 2b: Yield: 79%. Elemental analysis: calcd (%)
for C37H33N5 (547.27): C, 81.14; H, 6.07; N, 12.79%. Found: C,
1
Compound 2a: Yield: 84%. Elemental analysis: calcd (%) 80.69; H, 6.21; N, 11.98%. H NMR (400 MHz, 303 K, CDCl3)
for C23H21N5 (367.18): C, 75.18; H, 5.76; N, 19.06%. Found: C, δ: 2.32 (s, 6H), 2.38 (s, 6H, BI-CH3), 5.49 (s, 4H, N-CH2), 6.80
74.26; H, 5.39; N, 18.74%. 1H NMR (400 MHz, 303 K, DMSO-d6) (d, 4H, J = 7.3 Hz, Ar-H), 6.96 (s, 2H, BI-H), 7.19 (m, 6H, Ar-H),
δ: 2.37 (s, 12H, BI-CH3), 7.51 (s, 4H, BI-H), 8.11 (t, 1H, J = 7.62 (s, 2H, BI-H), 7.94 (t, 1H, J = 7.9 Hz, Py-Hp), 8.30 (d, 2H, J =
7.7 Hz, Py-Hp), 8.26 (d, 2H, J = 8.0 Hz, Py-Hm). 1H NMR 7.9 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ: 20.5, 20.9
(400 MHz, 303 K, CDCl3) δ: 2.28 (s, 12H, BI-CH3), 7.21(s, 2H, (2 × BI-CH3), 47.8 (N-CH2), 110.9, 120.4, 125.6, 126.4 (4 × BI-C),
BI-H), 7.48 (s, 2H, BI-H), 7.82 (t, 1H, J = 7.7 Hz, Py-Hp), 8.22 (d, 2H, 127.5 (Py-Cm), 128.9, 132.3, 133.5 (3 × Ar-C), 135.4 (BI-C),
J = 8.0 Hz, Py-Hm), 12.23 (2H, N–H). 13C NMR (100 MHz, 303 K, 137.7 (Ar-C), 138.3 (Py-Cp), 141.8 (BI-C), 149.7 (Py-Co), 150.1
DMSO-d6) δ: 22.0 (BI-CH3), 121.6 (BI-C), 124.9 (Py-Cm), 130.6 (NvC-N).
(BI-C), 132.8 (Py-Cp), 139.5 (BI-C), 148.6 (Py-Co), 151.1 (NvC-NH).
Compound 2c: Yield: 84%. Elemental analysis: calcd (%)
for C43H45N5 (631.37): C, 81.74; H, 7.18; N, 11.08%. Found: C,
81.33; H, 7.03; N, 10.97%. 1H NMR (400 MHz, 303 K, CDCl3) δ:
2.01 (s, 12H), 2.06 (s, 6H, Ar-CH3), 2.14 (s, 6H), 2.24 (s, 6H,
General procedures for the synthesis of compounds 1b–d and
2b–d
2,6-Bis(2-benzimimidazolyl)pyridine or 2,6-bis(5,6-dimethyl- BI-CH3), 6.02 (s, 4H, N-CH2), 6.48 (s, 2H, BI-H), 6.72 (s, 4H,
benzimimidazol-2-yl)pyridine (1,6 mmol) and KOH Ar-H), 7.55 (s, 2H, BI-H), 8.01 (t, 1H, J = 7.9 Hz, Py-Hp), 8.38 (d,
(3.36 mmol) were dissolved in acetone. The mixture was 2H, J = 7.9 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ:
stirred and heated under reflux for one hour. Then, aryl chlo- 20.2, 20.5 (2 × Ar-CH3), 21.0, 21.1 (2 × BI-CH3), 45.8 (N-CH2),
ride/bromide (3,2 mmol) was added and refluxed for six hours. 111.9, 120.2, 125.5, 129.2 (4 × BI-C), 129.8 (Py-Cm), 131.7, 132.8
The volatiles were removed under vacuum, and then the (2 × Ar-C), 134.9 (BI-C), 137.1 (Py-Cp), 137.6 (BI-C), 138.2, 141.7
residue was dissolved with DCM (10 mL) and filtered with a (2 × Ar-C), 149.9 (Py-Co), 150.5 (NvC-N).
cannula. Diethyl ether (20 mL) was added to the solution. The
crystals obtained were filtered and dried under vacuum.
Compound 2d: Yield: 86%. Elemental analysis: calcd (%)
for C47H53N5 (687.43): C, 82.05; H, 7.77; N, 10.18%. Found: C,
Compound 1b: Yield: 83%. Elemental analysis: calcd (%) 81.76; H, 7.51; N, 10.65%. 1H NMR (400 MHz, 303 K, CDCl3) δ:
for C33H25N5 (491.21): C, 80.63; H, 5.13; N, 14.25%. Found: C, 2.07 (s, 12H), 2.13 (s, 6H), 2.15 (s, 12H, Ar-CH3), 2.23 (s, 6H),
79.91; H, 5.64; N, 13.86%. 1H NMR (400 MHz, 303 K, CDCl3) δ: 2.31 (s, 6H, BI-CH3), 6.16 (s, 4H, N-CH2), 6.43 (s, 2H), 7.58 (s,
5.55 (s, 4H, N-CH2), 6.81 (dd, 4H, J1 = 8.4 Hz, J2 = 1.6 Hz, BI-H), 2H, BI-H), 8.04 (t, 1H, J = 7.9 Hz, Py-Hp), 8.39 (d, 2H, J = 7.9 Hz,
7.25 (m, 10H, Ar-H, 2H, BI-H), 7.88 (d, 2H, J = 8.0 Hz, BI-H), Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ: 16.9, 17.0, 17.3
8.01 (t, 1H, J = 7.8 Hz, Py-Hp), 8.38 (d, 2H, J = 8.0 Hz, Py-Hm). (3 × Ar-CH3), 20.4, 21.1 (2 × BI-CH3), 47.4 (N-CH2), 112.3, 120.0,
13C NMR (100 MHz, 303 K, CDCl3) δ: 48.1 (N-CH2), 111.1, 125.5, 129.3 (4 × BI-C), 131.6 (Py-Cm), 132.6, 133.0 (2 × Ar-C),
120.5, 123.2, 124.0 (4 × BI-C), 125.9 (Py-Cm), 126.4, 127.6, 133.2 (BI-C), 135.2 (Py-Cp), 138.1 (BI-C), 141.7 (Ar-C), 149.9
128.9, 136.7 (4 × Ar-C), 137.2 (BI-C), 138.5 (Py-Cp), 143.0 (BI-C), (Py-Co), 150.5 (NvC-N).
149.9 (Py-Co), 150.2 (NvC-NH).
Compound 1c: Yield: 85%. Elemental analysis: calcd (%)
for C39H37N5 (575.30): C, 81.36; H, 6.48; N, 12.16%. Found: C,
General procedures for the synthesis of complexes 3a–d, 4a–d,
5a–d, and 6a–d
80.79; H, 6.56; N, 11.49%. 1H NMR (400 MHz, 303 K, CDCl3) δ: [M(COD)Cl]2 (0.12 mmol) in a dry dichloromethane solution
1.93 (s, 12H), 2.19 (s, 6H, Ar-CH3), 6.26 (s, 4H, N-CH2), 6.67 (d, (30 mL) was added under nitrogen to a dichloromethane solu-
2H, J = 7.6 Hz, BI-H), 6.71 (s, 4H, Ar-H), 6.98 (t, 2H, J = 7.7 Hz, tion (10 mL) of the ligand (0.12 mmol). The resulting solution
This journal is © The Royal Society of Chemistry 2018
Dalton Trans., 2018, 47, 17317–17328 | 17323

View Article Online
Paper
Dalton Transactions
was stirred for 24 hours at room temperature, and the yellow 11.7 Hz, COD-CH), 112.5, 120.4, 123.9, 124.8 (4 × BI-C), 127.6
precipitate was filtered off, washed with diethyl ether (20 mL), (Ar-C), 130.0 (Py-Cm), 133.1, 133.4 (2 × Ar-C), 136.2 (BI-C), 138.0
and dried in a vacuum to obtain the final product.
(Py-Cp), 140.9 (BI-C), 148.4 (Py-Co), 148.8 (NvC-N).
Complex 3a: Yield: 86%. Elemental analysis: calcd (%) for
Complex 4a: Yield: 79%. Elemental analysis: calcd (%) for
C35H37Cl2N5Rh2 (803.05): C, 52.26; H, 4.64; N, 8.71%. Found: C39H45Cl2N5Rh2 (859.12): C, 54.43; H, 5.27; N, 8.14%. Found:
1
1
C, 51.88; H, 4.52; N, 8.58%. H NMR (400 MHz, 303 K, CDCl3) C, 54.11; H, 5.12; N, 8.03%. H NMR (400 MHz, 303 K, CDCl3)
δ: 1.33 (m, 2H), 1.45 (m, 2H), 1.76 (m, 8H), 2.24 (m, 2H, δ: 1.32 (m, 2H), 1.41 (m, 2H), 1.79 (m, 8H, COD-CH2),
COD-CH2), 2.58 (m, 2H, COD-CH2, 2H, COD-CH), 3.57 (br, 2H, 2.18–2.68 (m, 12H, BI-CH3, 6H, COD-CH2), 3.58 (br, 2H), 4.79
COD-CH), 4.81 (br, 2H, COD-CH), 4.88 (br, 2H, COD-CH), 7.02 (br, 2H), 4.86 (br, 2H, COD-CH), 7.04 (s, 2H), 8.51 (s, 2H, BI-H),
(d, 2H, J = 7.6 Hz), 7.34 (m, 4H), 8.62 (d, 2H, J = 7.2 Hz, BI-H), 8.76 (t, 1H, J1 = 7.6 Hz, J2 = 8.0 Hz, Py-Hp), 10.58 (d, 2H, J =
8.87 (t, 1H, J1 = 7.6 Hz, J2 = 8.0 Hz, Py-Hp), 10.71 (d, 2H, J = 7.9 Hz, Py-Hm).
8.0 Hz, Py-Hm).
Complex 4b: Yield: 81%. Elemental analysis: calcd (%) for
Complex 3b: Yield: 84%. Elemental analysis: calcd (%) for C53H57Cl2N5Rh2 (1039.21): C, 61.16; H, 5.52; N, 6.73%. Found:
1
C49H49Cl2N5Rh2 (983.15): C, 59.77; H, 5.02; N, 7.11%. Found: C, 60.05; H, 5.62; N, 6.78%. H NMR (400 MHz, 303 K, CDCl3)
1
C, 59.12; H, 5.36; N, 6.88%. H NMR (400 MHz, 303 K, CDCl3) δ: 1.31 (m, 2H), 1.43 (m, 2H), 1.77 (m, 8H, COD-CH2),
δ: 1.37 (m, 2H), 1.49 (m, 2H), 1.77 (m, 8H), 2.26 (m, 2H, 2.18–2.68 (m, 12H, BI-CH3, 4H, COD-CH2, 2H, COD-CH), 3.57
COD-CH2), 2.58 (m, 2H, COD-CH2, 2H, COD-CH), 3.57 (br, 2H), (br, 2H), 4.75 (br, 2H), 4.86 (br, 2H, COD-CH), 4.93 (d, 2H, J =
4.81 (br, 2H), 4.88 (br, 2H, COD-CH), 4.97 (d, 2H, J = 16.4), 5.37 16.4), 5.32 (d, 2H, J = 16.4, N-CH2), 6.65 (d, 4H, J = 6.8 Hz),7.02
(d, 2H, J = 15.6, N-CH2), 6.67 (d, 2H, J = 8.0 Hz, Ar-H), 7.02 (t, (t, 4H, J1 = 7.2 Hz, J2 = 6.8 Hz, Ar-H), 7.07 (s, 2H, BI-H), 7.12 (t,
4H, J1 = 7.2 Hz, J2 = 7.6 Hz), 7.13 (t, 4H, J1 = 7.2 Hz, J2 = 6.8 Hz, 4H, J1 = 7.6 Hz, J2 = 7.2 Hz, Ar-H), 8.46 (s, 2H, BI-H), 8.56 (t,
Ar-H), 7.34 (d, 2H, J = 8.2 Hz), 7.44 (t, 2H, J1 = 7.2 Hz, J2
=
1H, J1 = 7.6 Hz, J2 = 8.0 Hz, Py-Hp), 10.09 (d, 2H, J = 8.0 Hz,
6.8 Hz), 7.55 (t, 2H, J1 = 7.2 Hz, J2 = 6.8 Hz, BI-H), 8.63 (t, 1H, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ: 20.6, 20.8 (2 × BI-
J1 = 7.6 Hz, J2 = 8.0 Hz, Py-Hp), 8.77 (d, 2H, J = 8.0 Hz, BI-H), CH3), 29.9, 30.4, 30.8, 31.9 (4 × COD-CH2), 47.9 (N-CH2), 75.2 (d,
10.16 (d, 2H, J = 8.0 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, J = 13.1 Hz), 76.1 (d, J = 13.7 Hz), 84.4 (d, J = 10.7 Hz), 84.7 (d,
CDCl3) δ: 29.8, 30.1, 30.7, 31.9 (4 × COD-CH2), 48.2 (N-CH2), J = 11.4 Hz, COD-CH), 110.5, 120.4, 125.8, 127.5 (4 × BI-C), 128.6
75.3 (d, J = 13.2 Hz), 76.3 (d, J = 14.1 Hz), 83.8 (d, J = 10.7 Hz), (Py-Cm), 128.8, 133.8, 133.9 (3 × Ar-C), 135.2 (BI-C), 136.3 (Ar-C),
84.6 (d, J = 11.3 Hz, COD-CH), 110.8, 120.9, 124.5, 125.4 (4 × 137.6 (Py-Cp), 139.2 (BI-C), 147.4 (Py-Co), 147.7 (NvC-N).
BI-C), 125.9 (Py-Cm), 127.7 (Ar-C), 128.9 (Py-Cm), 135.2 (Ar-C),
Complex 4c: Yield: 85%. Elemental analysis: calcd (%) for
136.0 (BI-C), 137.9 (Py-Cp), 140.6 (Ar-C), 142.2 (BI-C), 147.6 C59H69Cl2N5Rh2 (1123.30): C, 62.99; H, 6.18; N, 6.23%. Found:
1
(Py-Co), 148.4 (NvC-N).
C, 61.43; H, 6.01; N, 6.08%. H NMR (400 MHz, 303 K, CDCl3)
Complex 3c: Yield: 87%. Elemental analysis: calcd (%) for δ: 1.35–2.55 (m, 18H, Ar-CH3, 12H,BI-CH3, 2H, COD-CH, 16H,
C55H61Cl2N5Rh2 (1067.24): C, 61.81; H, 5.75; N, 6.55%. Found: COD-CH2), 3.56 (br, 2H), 4.73 (br, 2H), 4.88 (br, 2H, COD-CH),
1
C, 62.29; H, 5.89; N, 6.40%. H NMR (400 MHz, 303 K, CDCl3) 5.52 (d, 2H, J = 14.8), 5.64 (d, 2H, J = 15.2, N-CH2), 6.50 (s, 2H,
δ: 1.40–2.62 (m, 18H, Ar-CH3, 2H, COD-CH, 16H, COD-CH2), BI-H), 6.75 (s, 4H, Ar-H), 8.34 (s, 2H, BI-H), 8.71 (t, 1H, J1 = 7.2
3.56 (br, 2H), 4.77 (br, 2H), 4.89 (br, 2H, COD-CH), 5.53 (d, 2H, Hz, J2 = 8.0 Hz, Py-Hp), 10.17 (d, 2H, J = 8.0 Hz, Py-Hm). 13C
J = 14.8), 5.74 (d, 2H, J = 15.2, N-CH2), 6.72 (d, 2H, J = 8.8 Hz, BI- NMR (100 MHz, 303 K, CDCl3) δ: 20.1, 20.5 (2 × Ar-CH3), 20.8,
H), 6.78 (s, 4H, Ar-H), 7.14 (t, 2H, J1 = 7.8 Hz, J2 = 8.0 Hz), 7.38 20.9 (2 × BI-CH3), 29.8, 30.6, 30.9, 31.9 (4 × COD-CH2), 45.6
(t, 2H, J1 = 7.6 Hz, J2 = 7.6 Hz), 8.64 (d, 2H, J = 7.6 Hz, BI-H), (N-CH2), 74.7 (d, J = 13.1 Hz), 75.9 (d, J = 13.7 Hz), 84.3 (d, J =
8.79 (t, 1H, J1 = 7.8 Hz, J2 = 8.0 Hz, Py-Hp), 10.23 (d, 2H, J = 10.7 Hz), 84.5 (d, J = 11.4 Hz, COD-CH), 111.8, 120.0, 127.8 (3 ×
8.0 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ: 20.2, 20.9 BI-C), 129.3 (Py-Cm), 129.8 (BI-C), 133.0, 133.4 (2 × Ar-C), 134.4,
(2 × Ar-CH3), 29.7, 30.1, 30.8, 31.8 (4 × COD-CH2), 45.9 (N-CH2), 137.0 (2 × BI-C), 137.6 (Py-Cp), 138.1 (Ar-C), 139.4 (Ar-C), 148.2
74.8, 76.0, 84.6, 84.8 (br, 4 × COD-CH), 112.0, 120.6, 124.1, 124.9 (Py-Co), 148.6 (NvC-N).
(4 × BI-C), 127.5 (Ar-C), 129.9 (Py-Cm), 134.3, 137.0 (2 × Ar-C), 137.9
(Py-Cp), 138.4, 140.8 (2 × BI-C), 148.6 (Py-Co), 149.1 (NvC-N).
Complex 4d: Yield: 86%. Elemental analysis: calcd (%) for
C63H77Cl2N5Rh2 (1179.37): C, 64.07; H, 6.57; N, 5.93%. Found:
1
Complex 3d: Yield: 89%. Elemental analysis: calcd (%) for C, 63.71; H, 6.38; N, 6.01%. H NMR (400 MHz, 303 K, CDCl3)
C59H69Cl2N5Rh2 (1123.30): C, 62.99; H, 6.18; N, 6.23%. Found: δ: 1.38–2.61 (m, 30H, Ar-CH3, 12H, BI-CH3, 2H, COD-CH, 16H,
1
C, 62.76; H, 6.02; H, 5.91%. H NMR (400 MHz, 303 K, CDCl3) COD-CH2), 3.54 (br, 2H), 4.72 (br, 2H), 4.89 (br, 2H), 5.49 (d,
δ: 1.37–2.65 (m, 30H, Ar-CH3, 2H, COD-CH, 16H, COD-CH2), 2H, J = 15.2), 5.88 (d, 2H, J = 15.2), 6.27 (s, 2 H), 8.28 (s, 2 H,
3.55 (br, 2H), 4.77 (br, 2H), 4.90 (br, 2H, COD-CH), 5.52 (d, 2H, BI-H), 8.79 (t, 1H, J1 = 7.2 Hz, J2 = 8.0 Hz, Py-Hp), 10.16 (d, 2H,
J = 15.2), 5.96 (d, 2H, J = 15.2, N-CH2), 6.51 (d, 2H, J = 8.8 Hz), J = 8.0 Hz, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ: 16.8,
7.06 (t, 2H, J1 = 7.2 Hz, J2 = 8.0 Hz), 7.36 (t, 2H, J1 = 7.6 Hz, J2 = 16.9, 17.2 (3 × Ar-CH3), 20.4, 20.5 (2 × BI-CH3), 29.8, 30.6, 30.8,
7.6 Hz), 8.59 (d, 2H, J = 8.4 Hz, BI-H), 8.85 (t, 1H, J1 = 7.6 Hz, 31.9 (4 × COD-CH2), 47.1 (N-CH2), 74.7 (d, J = 13.8 Hz), 75.9 (d,
J2 = 8.0 Hz, Py-Hp), 10.22 (d, 2H, J = 8.0 Hz, Py-Hm). 13C NMR J = 13.8 Hz), 84.3 (d, J = 11.4 Hz), 84.7 (d, J = 11.4 Hz, COD-
(100 MHz, 303 K, CDCl3) δ: 16.9, 17.3, 19.9 (3 × Ar-CH3), 29.9, CH), 112.4, 119.7, 127.9 (3 × BI-C), 129.7 (Py-Cm), 133.0 (BI-C),
30.1, 30.7, 31.8 (4 × COD-CH2), 47.4 (N-CH2), 74.7 (d, J = 133.2, 133.3 (2 × Ar-C), 134.1, 136.0 (2 × BI-C), 137.8 (Py-Cp),
12.8 Hz), 75.9 (d, J = 13.6 Hz), 84.6 (d, J = 11.3 Hz), 84.9 (d, J = 139.6 (Ar-C), 148.1 (Py-Co), 148.9 (NvC-N).
17324 | Dalton Trans., 2018, 47, 17317–17328
This journal is © The Royal Society of Chemistry 2018

View Article Online
Dalton Transactions
Paper
1
Complex 5a: Yield: 86%. Elemental analysis: calcd (%) for C, 45.11; H, 4.42; N, 6.83%. H NMR (400 MHz, 303 K, CDCl3)
C35H37Cl2N5Ir2 (983.04): C, 42.76; H, 3.79; N 7.12%. Found: C, δ: 1.32 (m, 2H), 1.41 (m, 2H), 1.79 (m, 8H, COD-CH2),
1
42.88; H, 4.01; N, 7.18%. H NMR (400 MHz, 303 K, CDCl3) δ: 2.18–2.68 (m, 12H, BI-CH3, 4H, COD-CH2, 2H, COD-CH), 3.41
1.72 (m, 2H), 1.78 (m, 2H), 1.81 (m, 8H), 2.30 (m, 2H, (br, 2H), 4.62 (br, 2H), 4.83 (br, 2H, COD-CH), 6.72 (s, 2H),
COD-CH2), 2.55 (m, 2H, COD-CH2, 2H, COD-CH), 3.61 (br, 2H), 8.32 (s, 2H, BI-H), 8.61 (t, 1H, J1 = 7.6 Hz, J2 = 8.0 Hz, Py-Hp),
4.66 (br, 2H), 4.74 (br, 2H, COD-CH), 7.43 (m, 6H), 7.87 (m, 9.91 (d, 2H, J = 7.9 Hz, Py-Hm).
2H, BI-H), 8.57 (t, 1H, J1 = 7.6 Hz, J2 = 8.0 Hz, Py-Hp), 10.95 (d,
2H, J = 8.0 Hz, Py-Hm).
Complex 6b: Yield: 81%. Elemental analysis: calcd (%) for
C53H57Cl2N5Ir2 (1219.39): C, 52.20; H, 4.71; N, 5.74%. Found:
1
Complex 5b: Yield: 84%. Elemental analysis: calcd (%) for C, 52.38; H, 4.92; N, 5.78%. H NMR (400 MHz, 303 K, CDCl3)
C49H49Cl2N5Ir2 (1163.29): C, 50.59; H, 4.25; N, 6.02%. Found: δ: 1.34 (m, 2H), 1.46 (m, 2H), 1.79 (m, 8H, COD-CH2),
1
C, 49.68; H, 4.38; N, 6.19%. H NMR (400 MHz, 303 K, CDCl3) 2.23–2.76 (m, 12H, BI-CH3, 4H, COD-CH2, 2H, COD-CH), 3.37
δ: 1.42 (m, 2H), 1.48 (m, 2H), 1.73 (m, 8H), 2.29 (m, 2H, (br, 2H), 4.45 (br, 2H), 4.66 (br, 2H, COD-CH), 4.94 (d, 2H, J =
COD-CH2), 2.58 (m, 2H, COD-CH2, 2H, COD-CH), 3.21 (br, 16.4), 5.32 (d, 2H, J = 16.4, N-CH2), 6.63 (d, 2H, J = 6.8 Hz), 7.04
2H), 4.42 (br, 2H), 4.62 (br, 2H), 5.48 (d, 2H, J = 15.2), 5.70 (d, (t, 4H, J1 = 7.2 Hz, J2 = 6.8 Hz, Ar-H), 7.09 (s, 2H, BI-H), 7.14 (t,
2H, J = 15.2, N-CH2), 6.55 (d, 2H, J = 8.0 Hz), 7.07 (t, 2H, J1 = 4H, J1 = 7.6 Hz, J2 = 7.2 Hz, Ar-H), 8.37 (s, 2H, BI-H), 8.46 (t,
7.2 Hz, J2 = 7.6 Hz, BI-H), 7.13 (m, 6H, Ar-H), 7.34 (t, 2H, J1 = 1H, J1 = 7.6 Hz, J2 = 8.0 Hz, Py-Hp), 9.79 (d, 2H, J = 8.0 Hz,
7.2 Hz, J2 = 7.6 Hz, BI-H), 7.44 (d, 2H, J = 7.2 Hz), 7.55 (d, 2H, Py-Hm). 13C NMR (100 MHz, 303 K, CDCl3) δ: 23.1, 23.4 (2 × BI-
J = 7.2 Hz, Ar-H), 8.38 (d, 2H, J = 8.0 Hz, BI-H), 8.53 (t, 1H, J1 = CH3), 33.7, 34.3, 34.4, 35.8 (4 × COD-CH2), 48.7 (N-CH2), 60.2,
7.6 Hz, J2 = 8.0 Hz, Py-Hp), 9.76 (d, 2H, J = 8.0 Hz, Py-Hm). 13C 61.6, 71.6, 72.7 (4 × COD-CH), 114.9, 122.8, 130.6 (3 × BI-C),
NMR (100 MHz, 303 K, CDCl3) δ: 29.6, 30.4, 31.9, 32.3 (4 × 135.7 (Py-Cm), 136.6, 137.7, 133.9 (3 × Ar-C), 139.4, 140.1 (2 ×
COD-CH2), 47.2 (N-CH2), 56.3 (d, J = 13.2 Hz), 58.1 (d, J = BI-C), 141.3 (Py-Cp), 142.1 (Ar-C), 150.8 (Py-Co), 150.9 (NvC-N).
14.1 Hz), 69.2 (d, J = 10.7 Hz), 70.3 (d, J = 11.3 Hz, COD-CH),
Complex 6c: Yield: 85%. Elemental analysis: calcd (%) for
102.3, 119.8, 126.7 (3 × BI-C), 129.6 (Py-Cm), 132.7 (BI-C), 133.2, C59H69Cl2N5Ir2 (1303.55): C, 54.36; H, 5.34; N, 5.37%. Found:
1
134.9 (2 × Ar-C), 138.1, 139.7 (2 × BI-C), 140.9 (Py-Cp), 141.8 C, 54.43; H, 5.42; N, 5.48%. H NMR (400 MHz, 303 K, CDCl3)
(Ar-C), 149.8 (Py-Co), 149.9 (NvC-N).
δ: 1.26–2.38 (m, 18H, Ar-CH3, 12H, BI-CH3, 2H, COD-CH, 16H,
Complex 5c: Yield: 87%. Elemental analysis: calcd (%) for COD-CH2), 3.21 (br, 2H), 4.42 (br, 2H), 4.62 (br, 2H, COD-CH),
C55H61Cl2N5Ir2 (1247.45): C, 52.96; H, 4.93; N, 5.61%. Found: 5.49 (d, 2H, J = 14.8), 5.70 (d, 2H, J = 15.2, N-CH2), 6.52 (s, 2H,
1
C, 53.18; H, 5.19; N 5.88%. H NMR (400 MHz, 303 K, CDCl3) BI-H), 6.80 (s, 4H, Ar-H), 8.19 (s, 2H, BI-H), 8.43 (t, 1H, J1
=
δ: 1.42–2.66 (m, 18H, Ar-CH3, 2H, COD-CH, 16H, COD-CH2), 7.2 Hz, J2 = 8.0 Hz, Py-Hp), 9.71 (d, 2H, J = 8.0 Hz, Py-Hm). 13C
3.52 (br, 2H), 4.44 (br, 2H), 4.68 (br, 2H), 5.50 (d, 2H, J = 14.8), NMR (100 MHz, 303 K, CDCl3) δ: 20.1, 20.4 (2 × Ar-CH3), 20.8,
5.69 (d, 2H, J = 15.2, N-CH2), 6.72 (d, 2H, J = 8.8 Hz, BI-H), 6.78 20.9 (2 × BI-CH3), 30.7, 31.3, 31.5, 32.8 (4 × COD-CH2), 45.7
(s, 4H, Ar-H), 7.14 (t, 2H, J1 = 7.8 Hz, J2 = 8.0 Hz), 7.38 (t, 2H, J1 (N-CH2), 57.2, 58.6, 68.6, 69.7 (4 × COD-CH), 111.9, 119.9,
= 7.6 Hz, J2 = 7.6 Hz), 8.44 (d, 2H, J = 7.6 Hz, BI-H), 8.79 (t, 1H, 127.6 (3 × BI-C), 129.8 (Py-Cm), 130.0 (BI-C), 132.7, 133.6 (2 ×
J1 = 7.8 Hz, J2 = 8.0 Hz, Py-Hp), 10.23 (d, 2H, J = 8.0 Hz, Py-Hm). Ar-C), 134.7, 137.1 (2 × BI-C), 138.3 (Py-Cp), 139.1 (Ar-C), 147.8
13C NMR (100 MHz, 303 K, CDCl3) δ: 21.3, 21.5 (2 × Ar-CH3), (Py-Co), 147.9 (NvC-N).
31.8, 32.5, 32.6, 34.0 (4 × COD-CH2), 46.9 (N-CH2), 58.3, 59.7,
Complex 6d: Yield: 86%. Elemental analysis: calcd (%) for
69.7, 70.9 (4 × COD-CH), 113.0, 121.0, 128.7 (3 × BI-C), 130.9 C63H77Cl2N5Ir2 (1359.48): C, 55.65; H, 5.71; N, 5.15%. Found:
(Py-Cm), 131.0 (BI-C), 133.8, 134.7 (2 × Ar-C), 135.8, 136.3 (2 × C, 54.21; H, 5.52; N, 5.03%. 1H NMR (400 MHz, CDCl3) δ:
BI-C), 138.2 (Py-Cp), 139.5 (Ar-C), 140.2 (Py-Co), 148.9 (NvC-N).
1.19–1.49 (m, 8H, COD-CH2), 1.91–2.35 (m, 30H, Ar-CH3, 12H,
Complex 5d: Yield: 89%. Elemental analysis: calcd (%) for BI-CH3, 2H, COD-CH, 8H, COD-CH2), 3.18 (br, 2H), 4.40 (br,
C59H69Cl2N5Ir2 (1303.55): C, 54.36; H, 5.34; N, 5.37%. Found: 2H), 4.64 (br, 2H, COD-CH), 5.49 (d, 2H, J = 15.2), 5.91 (d, 2H, J
1
C, 54.71; H, 5.48; N 5.57%. H NMR (400 MHz, 303 K, CDCl3) = 15.2, N-CH2), 6.29 (s, 2H), 8.07 (s, 2H, BI-H), 8.46 (t, 1H, J1 =
δ: 1.37–2.65 (m, 30H, Ar-CH3, 2H, COD-CH, 16H, COD-CH2), 7.6 Hz, J2 = 8.0 Hz, Py-Hp), 9.72 (d, 2H, J = 8.0 Hz, Py-Hm). 13C
3.55 (br, 2H), 4.77 (br, 2H), 4.90 (br, 2H, COD-CH), 5.52 (d, 2H, NMR (100 MHz, 303 K, CDCl3) δ: 16.8, 16.9, 17.2 (3 × Ar-CH3),
J = 15.2), 5.96 (d, 2H, J = 15.2, N-CH2), 6.55 (d, 2H, J = 8.8 Hz), 20.3, 20.8 (2 × BI-CH3), 30.7, 31.4, 32.8 (4 × COD-CH2), 47.2 (N-
7.06 (t, 2H, J1 = 7.2 Hz, J2 = 8.0 Hz), 7.32 (t, 2H, J1 = 7.6 Hz, J2 = CH2), 57.2, 58.6, 68.5, 69.8 (4 × COD-CH), 112.4, 119.6, 127.8
7.6 Hz), 8.38 (d, 2H, J = 8.4 Hz, BI-H), 8.52 (t, 1H, J1 = 7.6 Hz, (3 × BI-C), 130.2 (Py-Cm), 133.0 (BI-C), 133.2, 133.3 (2 × Ar-C),
J2 = 8.0 Hz, Py-Hp), 9.76 (d, 2H, J = 8.0 Hz, Py-Hm). 13C NMR 134.1, 136.0 (2 × BI-C), 136.7 (Py-Cp), 139.1 (Ar-C), 148.1
(100 MHz, 303 K, CDCl3) δ: 16.9, 17.1, 17.2 (3 × Ar-CH3), 30.8, (Py-Co), 148.9 (NvC-N).
31.2, 31.6, 32.6 (4 × COD-CH2), 47.4 (N-CH2), 57.3, 58.6, 69.1,
69.8 (4 × COD-CH), 112.5, 120.2 (2 × BI-C), 123.9, 125.0 (2 ×
Synthesis of compound 7
Ar-C), 127.5 (BI-C), 130.6 (Py-Cm), 133.1 (BI-C), 133.2, 133.5 (2 × This ligand was prepared in the same manner as 2d using 5,6-
Ar-C), 134.1, 136.3 (2 × BI-C), 136.6 (Py-Cp), 140.5 (Ar-C), 148.1 dimethyl-1H-benzimidazole (0.146 g; 1 mmol) and penta-
(Py-Co), 148.5 (NvC-N).
methylbenzyl bromide (0.241 g; 1 mmol). White crystals were
Complex 6a: Yield: 79%. Elemental analysis: calcd (%) for obtained. Yield: 86%. Elemental analysis: calcd (%) for
C39H45Cl2N5Ir2 (1039.15): C, 45.08; H, 4.36; N, 6.75%. Found: C21H26N2 (306.44): C, 82.31; H, 8.55, N, 9.14%. Found: C,
This journal is © The Royal Society of Chemistry 2018
Dalton Trans., 2018, 47, 17317–17328 | 17325

View Article Online
Paper
Dalton Transactions
1
82.18; H, 8.49; N, 9.07%. H NMR (400 MHz, CDCl3) δ: 2.21 (s, General procedures for the synthesis of compounds 10 and 11
6H), 2.26 (s, 6H), 2.32 (s, 3H, Ar-CH3), 2.45 (s, 3H), 2.47 (s, 3H,
These ligands were prepared in the same manner as used for
complex 2a with isophthalic acid (20 mmol) or benzoic acid
(40 mmol) and 4,5-dimethylbenzene-1,2-diamine (44 mmol).
BI-CH3), 5.26 (s, 4H, N-CH2), 7.29 (s, 1H), 7.33 (s, 1H, BI-H),
7.60 (s, 1H, NvCH-N). 13C NMR (100 MHz, CDCl3) δ: 16.5,
16.8, 17.1, 20.3, 20.6 (5 × BI-CH3), 44.2 (N-CH2), 109.7, 120.3,
127.4, 131.1, 131.2 (5 × BI-C), 132.8, 133.3, 133.5, 136.0 (4 ×
Ar-C), 141.1 (BI-C), 142.8 (NvCH-N).
Compound 10: Yield: 74%. Elemental analysis: calcd (%)
for C24H22N4 (366.46): C, 78.66; H, 6.05; N, 15.29%. Found: C,
78.43; H, 6.16; N, 15.18%. 1H NMR (400 MHz, 303 K,
DMSO-d6) δ: 2.33 (s, 12H, BI-CH3), 7.37 (s, 4H, BI-H), 7.65 (t,
1H, J = 7.2 Hz, Ar-H), 8.17 (d, 2H, J = 8.0 Hz, Ar-H), 8.96 (s, 1H,
General procedures for the synthesis of complexes 8 and 9
Ar-H). 1H NMR (400 MHz, 303 K, CDCl3) δ: 2.30 (s, 12H,
[M(COD)Cl]2 (0.12 mmol) in a dry dichloromethane solution
(30 mL) was added under nitrogen to a dichloromethane
solution (10 mL) of the ligand (0.24 mmol). The resulting solu-
tion was stirred for 24 hours at room temperature, and then,
BI-CH3), 6.99 (t, 1H, J = 8.0 Hz, Ar-H), 7.29 (brs, 4H, BI-H), 7.76
(d, 2H, J = 7.6 Hz, Ar-H), 8.22 (s, 1H, Ar-H). 13C NMR (100 MHz,
303 K, DMSO-d6) δ: 22.5 (BI-CH3), 115.7 (BI-C), 124.7, 127.4,
129.8 (Ar-C), 131.1 (BI-C), 131.7 (Ar-C), 138.7 (BI-C), 150.5
the yellow precipitate was filtered off, washed with diethyl
(NvC-NH).
ether (20 mL), and dried in a vacuum to obtain the final
product.
Compound 11: Yield: 78%. Elemental analysis: calcd (%)
for C15H14N2 (222.29): C, 81.05; H, 6.35; N, 12.60%. Found: C,
Complex 8: Yield: 81%. Elemental analysis: calcd (%) for
80.09; H, 6.21; N, 12.43%. 1H NMR (400 MHz, 303 K,
C29H38ClN2Rh (552.98): C, 62.99; H, 6.93; N, 5.07%. Found: C,
DMSO-d6) δ: 2.30 (s, 6H, BI-CH3), 7.35 (s, 2H, BI-H), 7.44 (m,
1
62.81; H, 6.82; N, 4.99%. H NMR (400 MHz, 303 K, CDCl3) δ:
1H, Ar-H), 7.52 (t, 2H, J = 7.4 Hz, Ar-H), 8.15 (d, 2H, J = 6.8 Hz,
1.76 (m, 4H, COD-CH2), 2.14 (s, 6H), 2.28 (s, 6H), 2.33 (s, 3H,
Ar-H). 1H NMR (400 MHz, 303 K, CDCl3) δ: 2.35 (s, 6H,
Ar-CH3), 2.42 (s, 3H, BI-CH3), 2.47 (br, 3H, BI-CH3, 4H,
BI-CH3), 7.21 (brs, 1H, BI-H), 7.41 (m, 3H, Ar-H), 7.52 (brs, 1H,
COD-CH2), 3.53 (br, 2H), 4.66 (br, 2H, COD-CH), 5.20 (s, 2H,
BI-H), 8.04 (m, 2H, Ar-H). 13C NMR (100 MHz, 303 K, DMSO-
N-CH2), 7.27 (s, 1H), 7.32 (s, 1H, BI-H), 8.16 (s, 1H, NvCH-N).
d6) δ: 20.4 (BI-CH3), 126.7, 129.3, 129.9 (Ar-C), 130.9 (BI-C),
13C NMR (100 MHz, CDCl3) δ: 16.5, 16.9, 17.2 (3 × Ar-CH3),
20.4, 20.6 (2 × BI-CH3), 30.5, 31.5 (2 × COD-CH2), 44.8 (N-CH2),
75.5 (d, J = 13.8 Hz), 83.9 (d, J = 11.4 Hz), 110.3, 120.3, 126.2,
131.0 (Ar-C), 150.8 (NvC-NH).
General procedures for the synthesis of complexes 12 and 13
131.8, 132.9 (5 × BI-C), 133.5, 133.6, 133.7 (3 × Ar-C), 136.6
(BI-C), 140.1 (NvC-N).
[M(COD)Cl]2 (0.12 mmol) in a dry dichloromethane solution
Complex 9: Yield: 79%. Elemental analysis: calcd (%) for (30 mL) was added under nitrogen to a dichloromethane solu-
C29H38ClN2Ir (642.30): C, 54.23; H, 5.96; N, 4.36%. Found: C, tion (10 mL) of the ligand (0.24 mmol or 0.12 mmol). The
1
54.12; H, 5.83; N, 4.17%. H NMR (400 MHz, 303 K, CDCl3) δ: resulting solution was stirred for 24 hours at room tempera-
1.59 (m, 4H), 1.92 (m, 4H, COD-CH2), 2.14–2.42 (s, 15H, Ar- ture; then, the yellow precipitate was filtered off, washed with
CH3, 6H, BI-CH3), 3.17 (br, 2H), 4.39 (br, 2H, COD-CH), 5.27 (s, diethyl ether (20 mL), and dried in a vacuum to obtain the
2H, N-CH2), 7.21 (s, 1H), 7.34 (s, 1H, BI-H), 8.77 (s, 1H, NvCH- product.
N). 13C NMR (100 MHz, 303 K, CDCl3) δ: 16.4, 16.5, 16.7 (3 ×
Complex 12: Yield: 73%. Elemental analysis: calcd (%) for
Ar-CH3), 20.4, 20.6 (2 × BI-CH3), 31.2, 32.4 (2 × COD-CH2), 44.9 C40H46Cl2Ir2N4 (1038.16): C, 46.28; H, 4.47; N, 5.40%. Found:
1
(N-CH2), 58.3, 69.0 (2 × COD-CH), 110.4, 120.0, 125.9, 131.7, C, 46.09; H, 4.56; N, 5.42%. H NMR (400 MHz, 303 K, CDCl3)
133.1 (5 × BI-C), 133.2, 133.4, 133.7 (3 × Ar-C), 136.7 (BI-C), δ: 0.88–1.03 (m, 2H, COD-CH2), 1.19–1.22 (m, 2H, COD-CH2),
139.6 (NvC-N).
1.39–1.48 (m, 2H, COD-CH2), 1.66–1.71 (m, 2H, COD-CH2),
Complex 6d′: 1H NMR (400 MHz, CDCl3) δ: 2.10–2.43 (m, 1.92–2.03 (m, 2H, COD-CH2), 2.18–2.51 (m, 6H, COD-CH2,
30H, Ar-CH3, 12H, BI-CH3), 5.58 (s, 4H, N-CH2), 6.39 (s, 2H), 12H, BI-CH3, 1H, COD-CH), 2.96–2.71 (m, 2H, COD-CH),
7.89 (s, 2H, BI-H), 8.21 (t, 1H, J1 = 7.6 Hz, J2 = 8.4 Hz, Py-Hp), 3.04–3.08 (m, 2H, COD-CH), 3.25–3.26 (m, 2H, COD-CH),
8.52 (d, 2H, J = 7.6 Hz, Py-Hm). 13C NMR (100 MHz, CDCl3) δ: 3.99–4.04 (m, 2H, COD-CH), 4.23–4.25 (m, 2H, COD-CH),
16.8, 16.9, 17.2 (3 × Ar-CH3), 20.2, 20.8 (2 × BI-CH3), 48.2 (N- 4.58–4.60 (m, 2H, COD-CH), 4.69–4.71 (m, 2H, COD-CH), 6.78
CH2), 112.9, 119.2, 127.2 (3 × BI-C), 128.6 (Py-Cm), 129.7 (BI-C), (s, 1H, BI-H), 7.05 (s, 1H, BI-H), 7.52 (t, 1H, J = 7.8, Ar-H), 7.52
132.5, 133.1 (2 × Ar-C), 133.4, 134.0 (2 × BI-C), 134.9 (Py-Cp), (d, 1H, J = 7.2, Ar-H), 7.85 (s, 1H, BI-H), 8.18 (s, 1H, BI-H), 9.22
138.9 (Ar-C), 148.2 (Py-Co), 150.6 (NvC-N), 167.0 (Ir-CO), 170.8 (d, 1H, J = 8.4, Ar-H), 9.68 (s, 1H, Ar-H), 11.30 (brs, 1H, NH),
(Ir-CO). IR (cm−1): 2026.24 (CvO).
12.83 (brs, 1H, NH).
Complex 9′: 1H NMR (400 MHz, CDCl3) δ: 2.19–2.46 (s, 15H,
Complex 13: Yield: 76%. Elemental analysis: calcd (%) for
Ar-CH3, 6H, BI-CH3), 5.31 (s, 2H, N-CH2), 7.41 (s, 1H), 7.67 (s, C23H26ClIrN2 (558.14): C, 49.49; H, 4.70; N, 5.02%. Found: C,
1H, BI-H), 7.76 (s, 1H, NvCH-N). 13C NMR (100 MHz, CDCl3) 49.09; H, 4.73; N, 5.11%. 1H NMR (400 MHz, CDCl3) δ:
δ: 16.6, 16.9, 17.2 (3 × Ar-CH3), 20.4, 20.6 (2 × BI-CH3), 45.3 (N- 1.13–1.17 (m, 1H, COD-CH2), 1.31–1.42 (m, 3H, COD-CH2),
CH2), 110.8, 119.1, 125.3, 131.3, 133.4 (5 × BI-C), 133.9, 134.4, 2.10 (s, 3H, BI-CH3), 2.18–2.29 (m, 2H, COD-CH2), 2.36–2.43
134.9 (3 × Ar-C), 137.2 (BI-C), 139.8 (NvC-N), 167.3 (Ir-CO), (m, 1H, COD-CH2, 3H, BI-CH3), 2.54–2.58 (m, 1H, COD-CH),
171.4 (Ir-CO). IR (cm−1): 2024.21 (CvO).
3.16–3.20 (m, 2H, COD-CH), 4.47–4.52 (m, 2H, COD-CH),
17326 | Dalton Trans., 2018, 47, 17317–17328
This journal is © The Royal Society of Chemistry 2018

View Article Online
Dalton Transactions
Paper
4.56–4.60 (m, 2H, COD-CH), 6.65 (s, 1H, BI-H), 7.20 (t, 2H, J =
7.8 Hz, Ar-H), 7.26–7.31 (m, 1H, Ar-H), 8.06 (s, 1H, BI-H), 8.43
(d, 2H, J = 7.6 Hz, Ar-H), 11.02 (brs, 1H, NH).
M. J. Page, M. R. D. Gatus, M. Bhadbhade and
B. A. Messerle, Organometallics, 2015, 34, 4543–4552;
(d) S. Langbein, H. Wadepohl and L. H. Gade,
Organometallics, 2016, 35, 809–815; (e) G. Türkmen, A. Atik,
Z. S. Şahin and H. Türkmen, Tetrahedron, 2015, 71, 4770–
4778; (f) S. W. S. Choy, M. J. Page, M. Bhadbhade and
B. A. Messerle, Organometallics, 2013, 32, 4726–4729;
(g) J. H. H. Ho, S. W. S. Choy, S. A. Macgregor and
B. A. Messerle, Organometallics, 2011, 30, 5978–
5984.
General procedure for the TH reactions
A mixture of acetophenone (1 mmol), the catalyst (0.25 mol%),
KOH (0.1 mmol), and propan-2-ol (1 mL) was stirred at 82 °C.
At the desired reaction times, aliquots were withdrawn from
the reaction vessel. The reaction was monitored by 1H-NMR.
The conversions were recorded for an average of three runs.
4 (a) K. Chan, C. Yik-Sham Chung and V. Wing-Wah Yam,
Chem. Sci., 2016, 7, 2842–2855; (b) A. K. W. Chan, D. Wu,
K. M. C. Wong and V. W. W. Yam, Inorg. Chem., 2016, 55,
3685–3691; (c) J. Y. Shao and Y. W. Zhong, Inorg. Chem.,
2013, 52, 6464–6472.
X-Ray crystallography
CCDC 1865637† contains the supplementary crystallographic
data for 3d. A suitable single crystal sample of 0.127 × 0.328 ×
0.409 mm3 was chosen for crystallographic studies, and then
placed on the goniometer head of an Agilent X Calibur X-ray
diffractometer with an EOS CCD detector. All diffraction
measurements were performed at room temperature (25 °C)
within the θ range of 3.0 ≤ θ ≤ 29.2, and Mo-Kα (graphite
crystal monochromator λ = 0.7107 Å) was used as the radiation
source. The absorption correction was based on multiple
scans.28 The crystal structure was solved by direct methods
(SHELXS-97).29 A total of 15 414 reflections were collected for
hmin = −36, hmax = 32, kmin = −12, kmax = 12, and lmin = −18,
lmax = 29. The refinement of the structure was carried out by
the full-matrix least-squares technique on 335 parameters
using SHELXL-97,29 and during this process, 6812 unique
reflections (Rint = 0.0268) were used. Hydrogen atoms were
placed in calculated positions and treated as riding atoms with
C–H distances in the range of 0.93–0.97 Å and with Uiso(H)
values of 1.2Ueq(C). ORTEP-3 was used to generate the thermal
ellipsoid plots.30 All geometric calculations and molecular
graphics were generated using PLATON software.31 Further
details about the data collection conditions and parameters of
the refinement process are presented in Table S1.† The intra-
molecular- and intermolecular hydrogen bonding geometries
of the title compound are listed in Table S2.†
5 K. Li, T. Zou, Y. Chen, X. Guan and C. M. Che, Chem. – Eur.
J., 2015, 21, 7441–7453.
6 J. Qian, J. Hu, H. Yoshikawa, J. Zhang, K. Awaga and
C. Zhang, Eur. J. Inorg. Chem., 2015, 12, 2110–2119.
7 A. Y. Y. Tam, W. H. Lam, K. M. C. Wong, N. Zhu and
V. W. W. Yam, Chem. – Eur. J., 2008, 14, 4562–4576.
8 J. Wang, B. Djukic, J. Cao, A. Alberola, F. S. Razavi and
M. Pilkington, Inorg. Chem., 2007, 46, 8560–8568.
9 J. M. Bénech, C. Piguet, G. Bernardinelli, J. C. G. Bünzlic
and G. Hopfgartnerd, J. Chem. Soc., Dalton Trans., 2001, 5,
684–689.
10 (a) X. Wang, S. Wang, L. Li, E. B. Sundberg and
G. P. Gacho, Inorg. Chem., 2003, 42, 7799–7808; (b) M. Kose
and V. McKee, Polyhedron, 2014, 75, 30–39.
11 (a) V. G. Vaidyanathan and B. U. Nair, J. Inorg. Biochem.,
2002, 91, 405–412; (b) J. Wang, L. Shuai, X. Xiao, Y. Zeng,
Z. Li and T. M. Inoue, J. Inorg. Biochem., 2005, 99, 883–885;
(c) V. G. Vaidyanathan and B. U. Nair, Eur. J. Inorg. Chem.,
2003, 19, 3633–3638; (d) V. G. Vaidyanathan and B. U. Nair,
Dalton Trans., 2005, 2842–2848; (e) P. Wang, C. H. Leung,
D. L. Ma, S. C. Yan and C. M. Che, Chem. – Eur. J., 2010, 16,
6900–6911.
12 Modern Reduction Methods, ed. P. G. Andersson and
I. J. Munslow, Wiley-VCH, Weinheim, Germany, 2008.
13 A. Aupoix, C. Bournaud and G. Vo-Thanh, Eur. J. Org.
Chem., 2011, 2772–2776.
Conflicts of interest
14 (a) T. Ohkuma, H. Ooka, S. Hashiguchi, T. Ikariya and
R. Noyori, J. Am. Chem. Soc., 1995, 117, 10417–10418;
(b) D. Wang and D. Astruc, Chem. Rev., 2015, 115, 6621–
6686.
15 T. Ikariya and A. J. Blacker, Acc. Chem. Res., 2007, 40, 1300–
1308.
There are no conflicts to declare.
References
1 (a) P. Buchwalter, J. Rosé and P. Braunstein, Chem. Rev.,
2015, 115, 28–126; (b) E. K. van den Beuken and 16 S. Günnaz, N. Özdemir, S. Dayan, O. Dayan and
B. L. Feringa, Tetrahedron, 1998, 54, 12985–13011. B. Çetinkaya, Organometallics, 2011, 30, 4165–4173.
2 (a) J. Park and S. Hong, Chem. Soc. Rev., 2012, 41, 6931– 17 (a) J. M. Ashley, J. H. Farnaby, N. Hazari, K. E. Kim,
6943; (b) M. Delferro and T. J. Marks, Chem. Rev., 2011,
111, 2450–2485.
3 (a) M. Orbach, S. Shankar, O. V. Zenkina, P. Milko,
Y. Diskin-Posner and M. E. van der Boom, Organometallics,
2015, 34, 1098–1106; (b) A. L. Gavrilova and B. Bosnich,
Chem. Rev., 2004, 104, 349–384; (c) V. Diachenko,
E. D. Luzik Jr., R. E. Meehan, E. B. Meyer, N. D. Schley,
T. J. Schmeier and A. N. Tailor, Inorg. Chim. Acta, 2012, 380,
399–410; (b) R. Maity, S. Hohloch, C.-Y. Su, M. van der
Meer and B. Sarkar, Chem. – Eur. J., 2014, 20, 9952–9961;
(c) A. Volpe, S. Baldino, C. Tubaro, W. Baratta, M. Basato
and C. Graiff, Eur. J. Inorg. Chem., 2016, 2, 247–251.
This journal is © The Royal Society of Chemistry 2018
Dalton Trans., 2018, 47, 17317–17328 | 17327

View Article Online
Paper
Dalton Transactions
18 F. Hildebrand, C. Kohlmann, A. Franz and S. Lütz, Adv. 23 E. İnkaya, S. Günnaz, N. Özdemir, O. Dayan, M. Dinçer and
Synth. Catal., 2008, 350, 909–918.
B. Çetinkaya, Spectrochim. Acta, Part A, 2013, 103, 255–
19 (a) H. Türkmen, L. Pelit and B. Çetinkaya, J. Mol. Catal. A:
263.
Chem., 2011, 348, 88–93; (b) L. Gök, S. Günnaz, Z. S. Şahin, 24 Y. Takenaka and K. Osakada, Bull. Chem. Soc. Jpn., 2000,
L. Pelit and H. Türkmen, J. Organomet. Chem., 2017, 827,
96–104.
20 M. J. Palmer and M. Wills, Tetrahedron: Asymmetry, 1999,
10, 2045–2061.
73, 129–130.
25 H. Wu, X. Huang, J. Yuan, J. Ding and R. Yun,
Z. Kristallogr. - New Cryst. Struct., 2009, 224, 419–420.
26 A. W. Addison and P. J. Burke, J. Heterocycl. Chem., 1981,
18, 803–805.
21 (a) H. Türkmen, T. Pape, F. E. Hahn and B. Çetinkaya,
Organometallics, 2008, 27, 571–575; (b) H. Türkmen, 27 A. W. Van der Made and R. H. Van der Made, J. Org. Chem.,
T. Pape, F. E. Hahn and B. Çetinkaya, Eur. J. Inorg. Chem.,
2008, 5418–5423.
22 (a) M. Ikhile, V. O. Nyamori and M. D. Bala, Tetrahedron
1993, 58, 1262–1263.
28 CrysAlisPro Software system (Version 1.171.35.11), Agilent
Technologies UK Ltd, 2011.
Lett., 2012, 53, 4925–4928; (b) D. Gülcemal, A. G. Gökçe, 29 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found.
S. Gülcemal and B. Çetinkaya, RSC Adv., 2014, 4, 26222– Crystallogr., 2008, 64, 112–122.
26230; (c) S. Gülcemal, A. G. Gökce and B. Çetinkaya, 30 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565–566.
Inorg. Chem., 2013, 52, 10601–10609. 31 A. L. Spek, J. Appl. Crystallogr., 2003, 36, 7–13.
17328 | Dalton Trans., 2018, 47, 17317–17328
This journal is © The Royal Society of Chemistry 2018