Manganese(I)-Catalyzed Transfer Hydrogenation and Acceptorless Dehydrogenative Condensation: Promotional Influence of the Uncoordinated N-Heterocycle

Article abstract of DOI:10.1021/acs.organomet.9b00475

The four bidentate manganese(I) complexes [(C₅H₄N-C₅H₃N-OH)Mn(CO)₃Br] (1), [(C₉H₆N-C₅H₃N-OH)Mn(CO)₃Br] (2), [(C₈H₅N₂-C₅H₃N-OH)Mn(CO)₃Br] (3), and [(C₈H₅N₂-C₅H₃N-OCH₃)Mn(CO)₃Br] (4) were synthesized. These complexes were tested as catalysts for the transfer hydrogenation of ketones, and 3 showed the highest activity. The reactions proceeded well with 0.5 mol % of catalyst loading and 20 mol % of t-BuOK at 85 °C for 24 h. Furthermore, 3 was also used as a catalyst for the synthesis of primary alcohols via transfer hydrogenation of aldehydes and the synthesis of 1,2-disubstituted benzimidazoles and quinolines via acceptorless dehydrogenative condensations.

Full text of DOI:10.1021/acs.organomet.9b00475

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Manganese(I)-Catalyzed Transfer Hydrogenation and Acceptorless
Dehydrogenative Condensation: Promotional Influence of the
Uncoordinated N‑Heterocycle
Chong Zhang,† Bowen Hu,† Dafa Chen,*,† and Haiping Xia‡
†MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemical Engineering
& Technology, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
‡Shenzhen Grubbs Institute, Department of Chemistry, Southern University of Science and Technology, Shenzhen, People’s
Republic of China
S
* Supporting Information
ABSTRACT: The four bidentate manganese(I) complexes
[(C5H4N-C5H3N-OH)Mn(CO)3Br] (1), [(C9H6N-C5H3N-
OH)Mn(CO)3Br] (2), [(C8H5N2-C5H3N-OH)Mn(CO)3Br]
(3), and [(C8H5N2-C5H3N-OCH3)Mn(CO)3Br] (4) were
synthesized. These complexes were tested as catalysts for the
transfer hydrogenation of ketones, and 3 showed the highest
activity. The reactions proceeded well with 0.5 mol % of
catalyst loading and 20 mol % of t-BuOK at 85 °C for 24 h.
Furthermore, 3 was also used as a catalyst for the synthesis of
primary alcohols via transfer hydrogenation of aldehydes and
the synthesis of 1,2-disubstituted benzimidazoles and quinolines via acceptorless dehydrogenative condensations.
reported a manganese(I) complex based on the 6,6′-dihydroxy-
2,2′-bipyridine ligand for transfer hydrogenation of ketones,
aldehydes, and imines, exhibiting activity superior to that of a
similar complex with 2,2′-bipyridine as the ligand, indicating
the important role of the hydroxypyridyl fragment.14g
In addition to transfer hydrogenation, Mn(I) catalysts have
also been reported for acceptorless dehydrogenative con-
densations,15 which are attributed to H2-related reactions, as
well. For instance, Srimani and co-workers developed a
tridentate NNS-Mn(I) complex for the synthesis of benzimi-
dazoles from aromatic diamines and alcohols.16 Some other
Mn(I) catalysts for the production of quinolones from 2-
aminobenzyl alcohols with secondary alcohols (or ketones)
have also been reported.17
In recent years, we developed a series of 2-hydroxypyridyl-
based Ru and Ir complexes for transfer hydrogenation18 and
borrowing hydrogen reactions,19 including acceptorless de-
hydrogenative coupling reactions.19a During the course of
investigation, we found that a pendant N-heterocycle some-
times increased the catalytic efficiency dramatically.19b,d As an
extension, herein we report the synthesis and catalytic activity
of three Mn complexes containing 2-hydroxypyridyl and one
containing 2-methoxypyridyl complexes, 1−4. As expected,
complex 3 with a 2-hydroxypyridyl moiety and an uncoordi-
nated N-heterocycle is the best catalyst for transfer hydro-
genation and acceptorless dehydrogenative condensations.
INTRODUCTION
■
Complexes containing the 2-hydroxypyridyl fragment are
significant metal−ligand synergistic catalysts, which have
been widely used in many kinds of H2-related reactions.1,2 In
the presence of a base, 2-hydroxypyridyl can be changed into
2-pyridonate, which directly affects the metal center.
Transfer hydrogenation (TH) using alcohol as the hydrogen
sourse is an important and attractive method for reducing
ketones and aldehydes to alcohols.3 In comparison to catalytic
hydrogenation, which has been extensively applied in organic
synthesis and the pharmaceutical industry,4 transfer hydro-
genation can be carried out in conventional equipment: that is
to say, there is no need to use autoclaves and other devices.
However, although there have been some examples catalyzed
by base-metal complexes,5−7 the transfer hydrogenation of
ketones and aldehydes still mainly relies on noble-metal
catalysts, such as Rh,8 Os,9 Ir,10 Pd,11 and especially Ru,12
which are expensive and raise toxicity concerns. In recent
years, since the pioneer work of Beller et al.,13 manganese(I)-
catalyzed transfer hydrogenation has developed rapidly.14 For
example, in 2017, Sortais and co-workers reported a
manganese(I) catalyst bearing 2-(aminomethyl)pyridine as
the ligand, showing a TOF of up to 3600 h−1.14a Later, The
groups of Leitner, Kundu, and Pidko independently developed
similar bidentate NN-Mn(I) complexes for such trans-
formation.14b−d Perekalin et al. found that Shvo-type catalysts
were also effective for transfer hydrogenation of ketones,14e
and Kirchner’s group developed an enantioselective Mn-based
catalyst.14f In addition, very recently, Khusnutdinova’s group
Received: July 12, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.9b00475
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RESULTS AND DISCUSSION
■
Synthesis and Characterization of Mn(I) Complexes.
When C5H4N-C5H3N-OH (L1) was treated with Mn(CO)5Br,
the tricarbonyl bidentate complex [(C5H4N-C5H3N-OH)Mn-
1
(CO)3Br] (1) was isolated in 88% yield (Scheme 1). The H
Scheme 1. Synthesis of Complex 1
Figure 1. Molecular structure of complex 3. Hydrogen atoms have
been omitted for clarity. Selected bond distances (Å): Mn(1)−N(1),
2.0642(18); Mn(1)−N(2), 2.0627(18); Mn(1)−Br(1), 2.5667(4);
Mn(1)−C(14), 1.806(2); Mn(1)−C(15), 1.787(2); Mn(1)−C(16),
1.813(2); C(1)−O(1), 1.330(3); C(1)−C(2), 1.401(3); C(2)−C(3),
1.363(4); C(3)−C(4), 1.383(4); C(4)−C(5), 1.378(3); C(5)−N(1),
1.367(3), C(1)−N(1), 1.342(3).
NMR spectrum of 1 in d6-DMSO exhibits two groups of
signals between 9.17 and 7.04 ppm for the pyridyl groups (7H)
and one singlet at 13.04 ppm for the −OH group (1H). The
IR spectrum displays three strong absorption peaks with nearly
identical intensities at 2032, 1946, and 1924 cm−1 for the three
terminal CO groups, suggesting their mutually cis config-
uration. The intense absorption band at 3094 cm−1 is
consistent with the existence of an −OH group. The results
indicate there are three CO groups, one bromide, and two
pyridyl rings of ligand L1 coordinating with Mn.
atom. The C(1)−O(1) distance is 1.330(3) Å, in the range of
a single bond.12h,19
Ketone Transfer Hydrogenation. Initially, we tested the
catalytic activity of complexes 1−4 in a model reaction of
transfer hydrogenation of acetophenone with 2-propanol
(Table 1). The reactions were conducted at 85 °C in the
Similarly, thermal treatment of C9H6N-C5H3N-OH (L2),
C8H5N2-C5H3N-OH (L3), and C8H5N2-C5H3N-OCH3 (L4)
with Mn(CO)5Br generated the products [(C9H6N-C5H3N-
OH)Mn(CO)3Br] (2), [(C8H5N2-C5H3N-OH)Mn(CO)3Br]
(3), and [(C8H5N2-C5H3N-OCH3)Mn(CO)3Br] (4), respec-
Table 1. Optimization of Conditions for the Transfer
Hydrogenation of Acetophenone
a
1
tively (Scheme 2). The −OH signals of 2 and 3 in their H
Scheme 2. Synthesis of Complexes 2−4
b
entry
complex (amt (mol %))
base (amt (equiv))
conversn (%)
1
2
3
4
5
1 (0.5)
2 (0.5)
3 (0.5)
4 (0.5)
none
3 (0.5)
3 (0.5)
3 (0.3)
3 (0.5)
3 (0.5)
3 (0.5)
3 (0.5)
t-BuOK (0.1)
t-BuOK (0.1)
t-BuOK (0.1)
t-BuOK (0.1)
t-BuOK (0.1)
t-BuOK (0.1)
t-BuOK (0.2)
t-BuOK (0.2)
t-BuOK (0.2)
t-BuOK (0.2)
KOH (0.2)
74
48
79
46
19
70
90
70
71
81
76
15
c
6
7
8
9
d
e
10
11
12
NMR spectra appear at 13.31 and 13.15 ppm, respectively, and
the −OCH3 signal is located at 4.22 ppm. Each of these three
complexes shows three CO bands, suggesting the similarity of
their structures with that of complex 1. The CO bands of 2 are
located at 2022, 1926, and 1912 cm−1, red-shifted in
comparison to those of 1, indicating the more electron rich
center.12h The CO bands of 3 (2020, 1949, and 1918 cm−1)
are comparable to those of 2, suggesting the quinolyl group in
complex 2 and the naphthyridyl group in complex 3 have a
similar effect on their metal centers. The CO absorptions of 4
(2014, 1922, and 1896 cm−1) demonstrate that L4 donates the
most electron density to the metal center among the four
ligands.
Complex 3 were further identified by X-ray crystallography
(Figure 1). The Mn ion is coordinated in an octahedral
geometry. The ligand L3 coordinates with the Mn atom via its
bipyridyl N atoms. As mentioned above, the three CO groups
are facial, with one trans to the naphthalidine ring, the second
trans to the pyridonate group, and the third trans to the Br
K2CO3 (0.2)
a
Reaction conditions unless noted otherwise: acetophenone (1.0
b
mmol), 2-propanol (2.5 mL), 24 h, N2 atmosphere. Determined by
GC analysis based on acetophenone using dodecane as the internal
standard. T = 75 °C. 12 h. 18 h.
c
d
e
presence of 0.5 mol % of catalyst for 24 h under a N2
atmosphere, and the results are shown in Table 1. When
complex 1 was selected as the catalyst and 10 mol % of t-BuOK
was added as the base, the conversion was 74% (entry 1).
Complex 2 was less active, giving a conversion of 48% (entry
2). As discussed above, the metal center of 2 is more electron
rich than 1; thus, in terms of electronic effects, 2 should have
exhibited higher activity. Thus, the lower conversion is
probably mainly due to steric hindrance. Interestingly, when
the quinolyl in 2 was replaced by a naphthyridyl group, the
resulting complex 3 gave a much better result (79%, entry 3),
indicating that the uncoordinated N-heterocycle plays an
B
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a
important role in the catalytic cycle, which is consistent with
the results reported by other groups and our group
previously.19b,d,20 Although the metal center of 4 is more
electron rich than 3 on the basis of the IR results, its efficiency
was much lower (46%, entry 4), demonstrating the significance
of the hydroxyl group. In the absence of any Mn complex, the
reaction also proceeded with t-BuOK (10 mol %), while the
conversion was only 19% (entry 5).14e 3 was then selected as
the catalyst for further analysis. When the temperature was
reduced to 75 °C, the conversion was also decreased to 70%
(entry 6). When the amount of t-BuOK was increased to 20
mol %, the conversion reached 90% (entry 7). A catalyst
loading of 0.3 mol % lowered the conversion to 70% (entry 8).
Shorter reaction times also decreased the conversion (entries 9
and 10). Other bases such as KOH and K2CO3 did not
perform as well as t-BuOK (entries 11 and 12).
Table 2. Transfer Hydrogenation of Ketones
With the optimal conditions in hand, a series of substrates
were investigated, and the results are shown in Table 2. The
electron-withdrawing and electron-donating groups, whether at
the ortho, meta, or para position of acetophenone, did not
obviously influence the isolated yields, which were in the range
of 80−90% (entries 1−10). When aliphatic ketones were used,
the yields were also satisfactory (77−81%, entries 11−15).
Sterically hindered aromatic ketones, such as benzophenone
and 1-(naphthalen-2-yl)ethan-1-one, gave isolated yields of
diphenylmethanol and 1-(naphthalen-2-yl)ethan-1-ol of 81%
and 83%, respectively (entries 16 and 17).
Aldehyde Transfer Hydrogenation. Complex 3 is also
suitable for the transfer hydrogenation of aldehydes (Table 3).
Six characteristic aromatic aldehydes, including benzaldehyde,
4-methoxybenzaldehyde, 3-methylbenzaldehyde, 4-fluoroben-
zaldehyde, 4-chlorobenzaldehyde, and 2-naphthaldehyde, were
converted into the corresponding primary alcohols in yields
between 70 and 85%, under conditions similar to those for
ketone transfer hydrogenation (entries 1−6). 1-Heptanol
could also be isolated in 60% yield under the conditions of
1.0 mol % catalyst with 10 mol % t-BuOK (entry 7). Although
complex 3 is active for the transfer hydrogenation of both
ketones and aldehydes, its efficiency still needs to be
improved.14 Especially, in comparison to the reported Ru
catalysts, which showed TOF values higher than 106 h−1, much
progress is needed.12i,m
Synthesis of 1,2-Disubstituted Benzimidazoles. Ac-
ceptorless dehydrogenation condensation, which is mechanis-
tically related to the borrowing hydrogen reaction, has now
become an elegant pathway for the synthesis of N-hetero-
cycles.15−17 Recently, the synthesis of benzimidazoles catalyzed
by an Mn(I) complex using 1,2-diaminobenzene and alcohol as
starting materials was reported by Srimani’s group for the first
time (10 mol % of catalyst, 2 equiv of of t-BuOK, 140 °C and
20 h).16 To our delight, complex 3 is also suitable for such
transformations, and six different products were obtained in
the presence of 2 mol % of catalyst and 1.5 equiv of t-BuOK at
130 °C for 20 h (Table 4). 1-Benzyl-2-phenyl-1H-benzo[d]-
imidazole was generated in 82% yield from 1,2-diaminoben-
zene with benzyl alcohol (entry 1). No noteworthy change in
the isolated yields was found when an electron-donating group
(methoxy or methyl) was introduced at the ortho or para
position of the benzyl alcohol (entries 2−4). However, an
electron-withdrawing group, such as chloro, at the para
position of benzyl alcohol decreased the activity dramatically
(entry 5). 2-(Naphthalen-2-yl)-1-(naphthalen-2-ylmethyl)-1H-
benzo[d]imidazole could also be isolated in a yield of 75%
a
Reaction condition: substrate (1.0 mmol), 2-propanol (2.5 mL), 24
b
h, N2 atmosphere. Isolated yield.
(entry 6). Although complex 3 is more effective than Srimani’s
Mn catalyst,16 it is still not as competitive as Singh’s Ir catalyst
(0.1 mol % catalyst, 2 equiv of t-BuOK, 80 °C, and 6 h).21
Synthesis of Quinolines. The first report of Mn(I)-
catalyzed quinoline synthesis from 2-aminobenzyl alcohol and
1-phenylethanol was presented by Kirchner and co-workers.
The reactions were carried out in the presence of 5 mol % of
C
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a
Table 3. Transfer Hydrogenation of Aldehydes
Table 4. Scope of the Reaction To Synthesize 1,2-
Disubstituted Benzimidazole
a
a
Reaction conditions: aldehyde (1.0 mmol), 2-propanol (2.5 mL), 24
b
c
h, N2 atmosphere. Isolated yield. When the catalyst loading was 0.3
mol %, the yield decreased to 70%. Complex 3 (1.0 mol %), t-BuOK
d
(10 mol %).
a
catalyst, 2.1 equiv of t-BuOK, and 1.0 equiv of KOH at 140 °C
for 24 h.17a Later on, Srimani’s group developed a tridentate
NNS complex for the same reaction, and still 5 mol % catalyst
was needed.17b Maji et al. recently used acetophenone to
replace 1-phenylethanol and found the process proceeded well
with Mn(CO)5Br (2 mol %) and a NNN-ligand (2 mol %)
under basic conditions.17c We found that complex 3 could also
catalyze the reaction of 2-aminobenzyl alcohol with acetophe-
none (Table 5). When 3 (2 mol %) and t-BuOK (1 equiv)
were added, 2-phenylquinoline was obtained in 72% yield in
toluene at 130 °C after 20 h (entry 1). When an electron-
donating group was introduced to the ortho, meta, or para
position of acetophenone, similar results were obtained
(entries 2−4). However, electron-withdrawing groups de-
creased the yields slightly (entries 5−7). Propiophenone was
also suitable for this reaction, giving 3-methyl-2-phenylquino-
line in 72% yield (entry 8). Interestingly, 2-(6-methoxypyridin-
2-yl)-1,8-naphthyridine (L4), which was synthesized by the
reaction of 2-aminonicotinaldehyde with 1-(6-methoxypyridin-
2-yl)ethan-1-one, could also be obtained catalytically from (2-
aminopyridin-3-yl)methanol and 1-(6-methoxypyridin-2-yl)-
ethan-1-one (entry 9). Although complex 3 is comparable
with Maji’s Mn system,17c it is not as active as Verpoort’s Ru
system (1 mol % of catalyst, 1 equiv of base, 80 °C, and 1 h).22
Reaction conditions: 1,2-diaminobenzene (0.5 mmol), alcohol (1.5
b
mmol), toluene (3 mL), 130 °C, 20 h, N2 atmosphere. Isolated yield.
c
When the catalyst loading was 1.0 mol %, the yield decreased to 50%.
the corresponding secondary alcohols were obtained in
satisfactory yields. The results indicate the importance of
both the 2-hydroxy group and the uncoordinated N-hetero-
cycle, which are important for the design of more effective
catalysts. Furthermore, complex 3 was also suitable for
aldehyde transfer hydrogenation, acceptorless dehydrogenation
condensation of 1,2-diaminobenzene with alcohol, and accept-
orless dehydrogenation condensation of 2-aminobenzyl alcohol
with acetophenone, and a series of primary alcohols, 1,2-
disubstituted benzimidazoles, and quinolines were isolated,
respectively.
EXPERIMENTAL SECTION
■
General Considerations. All manipulations were carried out
under an inert nitrogen atmosphere using a Schlenk line. Solvents
were distilled from the appropriate drying agents under N2 before use.
All reagents were purchased from commercial sources. Liquid
compounds were degassed by standard freeze−pump−thaw proce-
dures prior to use. [2,2′-Bipyridin]-6-ol (L1)23 and 6-(quinolin-2-
yl)pyridin-2-ol (L2)24 were prepared as previously described. The H
1
NMR spectra were recorded on a Bruker Avance 400 spectrometer.
1
The H NMR chemical shifts were referenced to residual solvent as
CONCLUSIONS
■
determined relative to Me4Si (δ 0 ppm). The 13C{1H} chemical shifts
were reported in ppm relative to the carbon resonance of CDCl3
(77.0 ppm). Elemental analyses were performed on a PerkinElmer
240C analyzer. High-resolution mass spectra (HR-MS) were recorded
on a Varian 7.0 T FTICR-MS instrument by the ESI technique. IR
spectra were recorded on a Nicolet iS5 FT-IR spectrometer. X-ray
diffraction studies were carried out in a SuperNova X-ray single-
In summary, four bidentate manganese complexes, including
three with a 2-hydroxypyridyl group (1−3) and one with a 2-
methoxypyridyl group (4), were synthesized. These complexes
were tested as catalysts for ketone transfer hydrogenation, and
complex 3 was the most active. With 0.5 mol % of catalyst
loading and 20 mol % of t-BuOK at 85 °C for 24 h, a series of
D
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a
154.0, 153.8, 149.8, 140.0, 139.0, 137.9, 135.9, 123.2, 122.0, 117.0,
104.1.
Table 5. Scope of the Reaction To Synthesize Quinoline
Synthesis of 1. A solution of L1 (0.10 g, 0.58 mmol) and
Mn(CO)5Br (0.18 g, 0.64 mmol) was heated in refluxing ether (10
mL) for 3 h. The yellow precipitate was collected, washed with ether,
and dried under vacuum to provide 1 (0.20 g, 88%). Anal. Calcd for
C13H8N2O4BrMn: C, 39.93; H, 2.06; N, 7.16. Found: C, 39.96; H,
2.09; N, 7.20. IR (νCO, KBr, cm−1): 2032, 1946, 1924. IR (νOH, KBr,
1
cm−1): 3094. H NMR (400 MHz, d6-DMSO, ppm): 13.04 (s, 1H),
9.17 (d, J = 5.6 Hz, 1H), 8.52 (d, J = 8.0 Hz, 1H), 8.15 (t, J = 7.6 Hz,
1H), 8.10−8.08 (m, 1H), 8.02−7.98 (m, 1H), 7.65 (t, J = 6.4 Hz,
1H), 7.04 (d, J = 8.4 Hz, 1H).
Synthesis of 2. A solution of L2 (0.10 g, 0.45 mmol) and
Mn(CO)5Br (0.14 g, 0.50 mmol) was heated in refluxing ether (10
mL) for 3 h. The orange precipitate was collected, washed with ether,
and dried under vacuum to provide 2 (0.35 g, 85%). Anal. Calcd for
C17H10N2O4BrMn: C, 46.29; H, 2.29; N, 6.35. Found: C, 46.51; H,
2.35; N, 6.30. IR (νCO, KBr, cm−1): 2022, 1926, 1912. IR (νOH, KBr,
1
cm−1): 3122. H NMR (400 MHz, d6-DMSO, ppm): 13.31 (s, 1H),
8.81−8.74 (m, 2H), 8.57 (d, J = 8.8 Hz, 1H), 8.24−8.18 (m, 2H),
8.06 (t, J = 7.2 Hz, 2H), 7.82 (t, J = 7.2 Hz, 1H), 7.09 (d, J = 8.8 Hz,
1H).
Synthesis of 3. A solution of L3 (0.10 g, 0.45 mmol) and
Mn(CO)5Br (0.14 g, 0.49 mmol) was heated in refluxing ether (10
mL) for 3 h. The red precipitate was collected, washed with ether, and
dried under vacuum to provide 3 (0.38 g, 86%). Single crystals
suitable for an X-ray crystallographic determination were grown with
CH3OH/ether at ambient temperature. Anal. Calcd for
C16H9N3O4BrMn: C, 43.47; H, 2.05; N, 9.50. Found: C, 43.28; H,
2.07; N, 9.52. IR (νCO, KBr, cm−1): 2020, 1949, 1918. IR (νOH, KBr,
a
Reaction conditions: 2-aminoaryl alcohol (1.2 mmol), ketones (1.0
mmol), toluene (3 mL), 130 °C, 20 h, N2 atmosphere, isolated yield.
b
When the catalyst loading was 1.0 mol %, the yield decreased to
1
42%.
cm−1): 3114. H NMR (400 MHz, d6-DMSO, ppm): 13.15 (s, 1H),
9.28 (d, J = 2.4 Hz, 1H), 8.84−8.82 (m, 1H), 8.73−8.68 (m, 2H),
8.35 (d, J = 7.2 Hz, 1H), 8.07 (t, J = 7.6 Hz, 1H), 7.91 (q, J = 4.0 Hz,
1H), 7.12 (d, J = 8.4 Hz, 1H).
Synthesis of 4. A solution of L4 (0.10 g, 0.42 mmol) and
Mn(CO)5Br (0.13 g, 0.46 mmol) was heated in refluxing ether (10
mL) for 3 h. The red precipitate was collected, washed with ether, and
dried under vacuum to provide 4 (0.39 g, 85%). Anal. Calcd for
C17H11N3O4BrMn: C, 44.76; H, 2.43; N, 9.21. Found: C, 44.88; H,
2.45; N, 9.15. IR (νCO, KBr, cm−1): 2014, 1922, 1896. 1H NMR (400
MHz, d6-DMSO, ppm): 9.31−9.29 (m, 1H), 8.89−8.87 (m, 1H),
8.81−8.79 (m, 1H), 8.71 (dd, J = 8.0, 1.6 Hz, 1H), 8.53 (d, J = 7.6
Hz, 1H), 8.30 (t, J = 8.0 Hz, 1H), 7.93 (q, J = 4.0 Hz, 1H), 7.46 (d, J
= 8.4 Hz, 1H), 4.22 (s, 3H).
General Procedure for Ketone and Aldehyde Transfer
Hydrogenation. Under a nitrogen atmosphere, in a 15 mL Schlenk
tube, a mixture of the ketone or aldehyde (1.0 mmol), 2-propanol
(2.5 mL), complex 3 (0.5 mol %), and t-BuOK (20 mol %) was
stirred at 85 °C for 24 h. The reaction mixture was cooled to room
temperature, and 0.1 mL was sampled and immediately diluted with 5
mL of ethyl acetate precooled to 0 °C for GC analysis to calculate the
conversion of the reaction. After the reaction was completed, the
reaction mixture was condensed under reduced pressure and
subjected to purification by flash silica gel column chromatography
to afford the target product, which was identified by NMR analyses.
All analytical data of the known compounds are consistent with those
reported in the literature.
General Procedure for Synthesis of 1,2-Disubstituted
Benzimidazoles. Under a nitrogen atmosphere, in a 15 mL Schlenk
tube, a mixture of o-phenylenediamine (0.5 mmol), alcohol (1.5
mmol), complex 3 (2.0 mol %), and t-BuOK (0.75 mmol) was stirred
at 130 °C in toluene for 20 h. After the reaction was completed, the
reaction mixture was condensed under reduced pressure and
subjected to purification by flash silica gel column chromatography
to afford the target product, which was identified by NMR analyses.
All analytical data of the known compounds are consistent with those
reported in the literature.
crystal diffractometer or a Bruker D8 Quest X-ray diffractometer. Data
collections were performed using four-circle kappa diffractometers
equipped with CCD detectors. Data were reduced and then corrected
for absorption. Solution, refinement, and geometrical calculations for
all crystal structures were performed by SHELXTL. All of the GC
measurements were performed on Agilent GC7890A equipment using
an Agilent 19091B-102 (25 m, 220 μm) column.
Synthesis of 2-(6-Methoxypyridin-2-yl)-1,8-naphthyridine
(L4). A solution of 1-(6-methoxypyridin-2-yl)ethan-1-one (0.15 g,
0.98 mmol), 2-aminonicotinaldehyde (0.10 g, 0.82 mmol),and KOH
(0.09 g, 1.64 mmol) was refluxed in ethanol (10 mL) with stirring for
4 h. The crude product was purified by column chromatography on
silica gel (petroleum ether/ethyl acetate, v/v 1/1) to give the product
as a pale yellow solid (0.19 g, 98%). Mp: 108 °C. Anal. Calcd for
C14H11N3O: C, 70.87; H, 4.67; N, 17.71. Found: C, 70.69; H, 4.61;
N, 17.65. HRMS: calcd for C14H11N3O + H, 238.0980; found,
1
238.0988. H NMR (400 MHz, CDCl3, ppm): 9.15 (q, J = 2.0 Hz,
1H), 8.73 (d, J = 8.8 Hz, 1H), 8.49 (dd, J = 7.2, 0.4 Hz, 1H), 8.29 (d,
J = 8.4 Hz, 1H), 8.23 (dd, J = 8.0, 1.6 Hz, 1H), 7.80−7.76 (m, 1H),
7.49 (q, J = 4.4 Hz, 1H), 6.86 (dd, J = 8.4, 0.8 Hz, 1H), 4.09 (s, 3H).
13C NMR (100 MHz, CDCl3): 163.5, 159.4, 155.7, 153.7, 152.6,
139.6, 137.6, 137.0, 122.8, 122.0, 120.2, 115.6, 112.2, 53.4.
Synthesis of 6-(1,8-Naphthyridin-2-yl)pyridin-2-ol (L3). A
solution of 2-(6-methoxypyridin-2-yl)-1,8-naphthyridine (0.20 g, 0.84
mmol) in 5 mL of HBr (40% in water) was heated at reflux for 3 h.
After it was cooled to room temperature, the solution was neutralized
by slow addition of a saturated aqueous solution of NaOH. The
aqueous solution was extracted with CH2Cl2. The combined organic
extracts were dried over Na2SO4, filtered, and concentrated to afford
the product as a yellow solid (0.18 g, 95%). Mp: 202 °C. Anal. Calcd
for C13H9N3O: C, 69.95; H, 4.06; N, 18.82. Found: C, 69.78; H, 4.01;
N, 18.71. HRMS: calcd for C13H9N3O + H, 224.0824; found,
1
224.0834. H NMR (400 MHz, CDCl3, ppm): 10.85 (s, 1H), 9.19−
9.17 (m, 1H), 8.34 (d, J = 8.8 Hz, 1H), 8.25 (dd, J = 8.4, 2.0 Hz, 1H),
8.00 (d, J = 8.4 Hz, 1H), 7.58−7.49 (m, 2H), 6.99 (d, J = 6.8 Hz,
1H), 6.71 (d, J = 9.2 Hz, 1H). 13C NMR (100 MHz, CDCl3): 161.5,
General Procedure for Synthesis of Quinolines. Under a
nitrogen atmosphere, in a 15 mL Schlenk tube, a mixture of 2-
aminoaryl alcohol (1.2 mmol), ketone (1.0 mmol), complex 3 (2.0
E
DOI: 10.1021/acs.organomet.9b00475
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
mol %), and t-BuOK (1.0 mmol) was stirred at 130 °C in toluene for
20 h. After the reaction was completed, the reaction mixture was
condensed under reduced pressure and subjected to purification by
flash silica gel column chromatography to afford the target product,
which was identified by NMR analyses. All analytical data of the
known compounds are consistent with those reported in the
literature.
Diphenylmethanol.14e 1H NMR (400 MHz, CDCl3, ppm): 7.38−
7.30 (m, 8H), 7.27−7.23 (m, 2H), 5.81 (s, 1H), 2.92 (s, 1H). 13C
NMR (100 MHz, CDCl3): 143.8, 128.5, 127.6, 126.6, 76.3.
1-(Naphthalen-2-yl)ethan-1-ol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.82−7.77 (m, 4H), 7.48−7.42 (m, 3H), 5.04−4.99 (m, 1H),
2.10 (s, 1H), 1.55 (d, J = 6.4 Hz, 3H). 13C NMR (100 MHz, CDCl3):
143.2, 133.4, 133.0, 128.3, 128.0, 127.7, 126.2, 125.8, 123.9, 123.8,
70.5, 25.2.
1-Phenylethan-1-ol.14c 1H NMR (400 MHz, CDCl3, ppm): 7.29−
7.18 (m, 5H), 4.79−4.74 (m, 1H), 2.79 (s, 1H), 1.40 (d, J = 6.4 Hz,
3H). 13C NMR (100 MHz, CDCl3): 146.0, 128.5, 127.4, 125.5, 70.3,
25.2.
Phenylmethanol.14g 1H NMR (400 MHz, CDCl3, ppm): 7.33−
7.20 (m, 5H), 4.55 (s, 2H), 2.85 (s, 1H). 13C NMR (100 MHz,
CDCl3): 140.9, 128.6, 127.6, 127.1, 65.1.
1-(2-Chlorophenyl)ethan-1-ol.14c 1H NMR (400 MHz, CDCl3,
ppm): 7.59 (dd, J = 7.6, 1.6 Hz, 1H), 7.33−7.27 (m, 2H), 7.22−7.18
(m, 1H), 5.31−5.26 (m, 1H), 2.02 (s, 1H), 1.49 (d, J = 8.0, 3H). 13C
NMR (100 MHz, CDCl3): 143.1, 131.7, 129.4, 128.4, 127.2, 126.4,
67.0, 23.5.
(4-Methoxyphenyl)methanol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.23 (d, J = 8.4 Hz, 2H), 6.85 (d, J = 8.8 Hz, 2H), 4.52 (s, 2H),
3.77 (s, 3H), 2.55 (s, 1H). 13C NMR (100 MHz, CDCl3): 159.1,
133.2, 128.7, 113.9, 64.7, 55.3.
m-Tolylmethanol.25 1H NMR (400 MHz, CDCl3, ppm): 7.23−
7.19 (m, 1H), 7.12−7.06 (m, 3H), 4.55 (s, 2H), 2.62 (s, 1H), 2.32 (s,
3H). 13C NMR (100 MHz, CDCl3): 140.9, 138.2, 128.5, 128.3, 127.8,
124.1, 65.1, 21.4.
1-(3-Chlorophenyl)ethan-1-ol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.36−7.35 (m, 1H), 7.28−7.20 (m, 3H), 4.87−4.82 (m, 1H),
2.16 (s, 1H), 1.46 (d, J = 6.4 Hz, 3H). 13C NMR (100 MHz, CDCl3):
147.9, 134.4, 129.8, 127.5, 125.7, 123.6, 69.8, 25.2.
(4-Fluorophenyl)methanol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.29−7.26 (m, 2H), 7.04−6.98 (m, 2H), 4.58 (s, 2H), 2.52
(s, 1H). 13C NMR (100 MHz, CDCl3): 163.5, 161.1, 136.6, 128.8,
128.7, 115.4, 115.2, 64.4.
1-(4-Chlorophenyl)ethan-1-ol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.32−7.26 (m, 4H), 4.88−4.83 (m, 1H), 2.08 (s, 1H), 1.45 (d,
J = 6.4 Hz, 3H). 13C NMR (100 MHz, CDCl3): 144.3, 133.1, 128.6,
126.8, 69.7, 25.3.
(4-Chlorophenyl)methanol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.32−7.25 (m, 4H), 4.62 (s, 2H), 2.19 (s, 1H). 13C NMR
(100 MHz, CDCl3): 139.3, 133.3, 128.7, 128.3, 64.5.
1-(2-Bromophenyl)ethan-1-ol.18a 1H NMR (400 MHz, CDCl3,
ppm): 7.59 (dd, J = 7.6, 1.6 Hz, 1H), 7.51 (dd, J = 7.6, 0.8 Hz, 1H),
7.36−7.32 (m, 1H), 7.15−7.10 (m, 1H), 5.26−5.21 (m, 1H), 2.00 (s,
1H), 1.48 (d, J = 6.4 Hz, 3H). 13C NMR (100 MHz, CDCl3): 144.3,
133.1, 128.6, 126.8, 69.7, 25.3.
Naphthalen-2-ylmethanol.26 1H NMR (400 MHz, CDCl3, ppm):
7.82−7.77 (m, 4H), 7.49−7.43 (m, 3H), 4.81 (s, 2H), 1.98 (s, 1H).
13C NMR (100 MHz, CDCl3): 138.3, 133.4, 133.0, 128.4, 127.9,
1-(4-Fluorophenyl)ethan-1-ol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.31−7.26 (m, 2H), 7.02−6.96 (m, 2H), 4.83−4.79 (m, 1H),
2.54 (s, 1H), 1.42 (d, J = 6.4 Hz, 3H). 13C NMR (100 MHz, CDCl3):
163.3, 160.9, 141.6, 127.1, 127.0, 115.3, 115.1, 69.7, 25.2.
1-(o-Tolyl)ethan-1-ol.14g 1H NMR (400 MHz, CDCl3, ppm): 7.50
(d, J = 7.6 Hz, 1H), 7.24−7.11 (m, 3H), 5.13−5.09 (m, 1H), 2.33 (s,
3H), 1.85 (s, 1H), 1.45 (d, J = 6.8 Hz, 3H). 13C NMR (100 MHz,
CDCl3): 143.9, 134.3, 130.4, 127.2, 126.4, 124.5, 66.8, 24.0, 18.9.
1-(m-Tolyl)ethan-1-ol.14g 1H NMR (400 MHz, CDCl3, ppm):
7.23−7.20 (m, 1H), 7.16−7.12 (m, 2H), 7.07−7.06 (m, 1H), 4.83−
4.78 (m, 1H), 2.34 (s, 3H), 2.22 (s, 1H), 1.45 (d, J = 6.4 Hz, 3H). 13C
NMR (100 MHz, CDCl3): 145.9, 138.1, 128.4, 128.2, 126.2, 122.5,
70.4, 25.1, 21.5.
127.8, 126.2, 125.9, 125.5, 125.2, 65.5.
Heptan-1-ol.27 1H NMR (400 MHz, CDCl3, ppm): 3.60 (t, J = 6.8
Hz, 2H), 2.00 (s, 1H), 1.57−1.50 (m, 2H), 1.36−1.18 (m, 8H),
0.88−0.84 (m, 3H). 13C NMR (100 MHz, CDCl3): 62.9, 32.8, 31.8,
29.1, 25.7, 22.6, 14.1.
1-Benzyl-2-phenyl-1H-benzo[d]imidazole.16 1H NMR (400 MHz,
CDCl3, ppm): 7.87 (d, J = 8.0 Hz, 1H), 7.71−7.67 (m, 2H), 7.48−
7.42 (m, 3H), 7.36−7.29 (m, 4H), 7.25−7.21 (m, 2H), 7.11 (d, J =
6.4 Hz, 2H), 5.47 (s, 2H). 13C NMR (100 MHz, CDCl3): 154.2,
143.1, 136.4, 136.0, 130.0, 129.9, 129.3, 129.1, 128.8, 127.8, 126.0,
123.1, 122.7, 120.0, 110.6, 48.4.
1-(2-Methoxybenzyl)-2-(2-methoxyphenyl)-1H-benzo[d]-
imidazole.28 1H NMR (400 MHz, CDCl3, ppm): 7.85 (d, J = 8.0 Hz,
1H), 7.53 (dd, J = 7.6, 1.6 Hz, 1H), 7.46−7.42 (m, 1H), 7.28−7.17
(m, 4H), 7.04 (t, J = 7.6 Hz, 1H), 6.95 (d, J = 8.0 Hz, 1H), 6.82 (d, J
= 8.4 Hz, 1H), 6.76 (t, J = 7.2 Hz, 1H), 6.70−6.68 (m, 1H), 5.23 (s,
2H), 3.77 (s, 3H), 3.58 (s, 3H). 13C NMR (100 MHz, CDCl3): 157.6,
156.5, 152.5, 143.3, 135.5, 132.4, 131.4, 128.4, 127.8, 124.6, 122.5,
122.0, 120.8, 120.4, 119.8, 110.8, 110.8, 109.9, 55.2, 55.2, 43.6.
1-(4-Methoxybenzyl)-2-(4-methoxyphenyl)-1H-benzo[d]-
imidazole.16 1H NMR (400 MHz, CDCl3, ppm): 7.84 (d, J = 8.0 Hz,
1H), 7.64 (d, J = 8.8 Hz, 2H), 7.32−7.27 (m, 1H), 7.24−7.20 (m,
2H), 7.04 (d, J = 8.8 Hz, 2H), 6.97 (d, J = 8.8 Hz, 2H), 6.86 (d, J =
8.8 Hz, 2H), 5.39 (s, 2H), 3.85 (s, 3H), 3.79 (s, 3H). 13C NMR (100
MHz, CDCl3): 160.9, 159.1, 154.1, 143.2, 136.1, 130.7, 128.5, 127.2,
122.8, 122.5, 122.5, 119.7, 114.4, 114.2, 110.4, 55.4, 55.3, 47.9.
1-(4-Methylbenzyl)-2-(p-tolyl)-1H-benzo[d]imidazole.16 1H
NMR (400 MHz, CDCl3, ppm): 7.86 (d, J = 8.0 Hz, 1H), 7.59 (d,
J = 8.0 Hz, 2H), 7.33−7.28 (m, 1H), 7.25−7.17 (m, 4H), 7.14 (d, J =
8.0 Hz, 2H), 7.00 (d, J = 7.6 Hz, 2H), 5.41 (s, 2H), 2.41 (s, 3H), 2.34
(s, 3H). 13C NMR (100 MHz, CDCl3): 154.4, 143.2, 140.0, 137.5,
136.1, 133.5, 129.7, 129.5, 129.2, 127.2, 125.9, 122.8, 122.6, 119.9,
110.5, 48.2, 21.5, 21.1.
1-(3-Methoxyphenyl)ethan-1-ol.18a 1H NMR (400 MHz, CDCl3,
ppm): 7.26 (t, J = 8.0 Hz, 1H), 6.95−6.93 (m, 2H), 6.82−6.79 (m,
1H), 4.89−4.84 (m, 1H), 3.81 (s, 3H), 1.97 (s, 1H), 1.48 (d, J = 6.8,
3H). 13C NMR (100 MHz, CDCl3): 159.8, 147.6, 129.6, 117.7, 112.9,
110.9, 70.4, 55.2, 25.2.
1-(4-Methoxyphenyl)ethan-1-ol.14g 1H NMR (400 MHz, CDCl3,
ppm): 7.29 (d, J = 8.4 Hz, 2H), 6.87 (d, J = 8.4 Hz, 2H), 4.86−4.81
(m, 1H), 3.79 (s, 3H), 1.96 (s, 1H), 1.46 (d, J = 6.4 Hz, 3H). 13C
NMR (100 MHz, CDCl3): 159.0, 138.1, 126.7, 113.9, 70.0, 55.3, 25.0.
Heptan-2-ol.14c 1H NMR (400 MHz, CDCl3, ppm): 3.83−3.75
(m, 1H), 1.60 (s, 1H), 1.50−1.24 (m, 8H), 1.19 (d, J = 6.4 Hz, 3H),
0.89 (t, J = 6.4 Hz, 3H). 13C NMR (100 MHz, CDCl3): 68.2, 39.3,
31.9, 25.5, 23.5, 22.6, 14.0.
Pentan-3-ol.18b 1H NMR (400 MHz, CDCl3, ppm): 3.49−3.43
(m, 1H), 1.58−1.37 (m, 5H), 0.95 (t, J = 7.2 Hz, 6H). 13C NMR
(100 MHz, CDCl3): 74.7, 29.6, 9.9.
Cyclopentanol.14b 1H NMR (400 MHz, CDCl3, ppm): 4.33−4.29
(m, 1H), 2.25 (s, 1H), 1.87−1.69 (m, 4H), 1.64−1.50 (m, 4H). 13C
NMR (100 MHz, CDCl3): 73.8, 35.4, 23.3.
Cyclohexanol.14b 1H NMR (400 MHz, CDCl3, ppm): 3.62−3.56
(m, 1H), 2.37 (s, 1H), 1.98−1.84 (m, 2H), 1.80−1.65 (m, 2H),
1.62−1.48 (m, 1H), 1.33−1.11 (m, 5H). 13C NMR (100 MHz,
CDCl3): 70.2, 35.5, 25.5, 24.2.
1-(4-Chlorobenzyl)-2-(4-chlorophenyl)-1H-benzo[d]imidazole.16
1H NMR (400 MHz, CDCl3, ppm): 7.87 (d, J = 8.0 Hz, 1H), 7.60 (d,
J = 8.0 Hz, 2H), 7.44 (d, J = 8.4 Hz, 2H), 7.37−7.28 (m, 4H), 7.20
(d, J = 7.6 Hz, 1H), 7.02 (d, J = 8.0 Hz, 2H), 5.41 (s, 2H). 13C NMR
(100 MHz, CDCl3): 152.9, 143.1, 136.4, 135.9, 134.7, 133.9, 130.5,
129.4, 129.2, 128.4, 127.3, 123.5, 123.1, 120.2, 110.3, 47.8.
4-Phenylbutan-2-ol.14g 1H NMR (400 MHz, CDCl3, ppm): 7.29−
7.25 (m, 2H), 7.21−7.15 (m, 3H), 3.84−3.76 (m, 1H), 2.78−2.61
(m, 2H), 2.09 (s, 1H), 1.82−1.68 (m, 2H), 1.21 (d, J = 6.0 Hz, 3H).
13C NMR (100 MHz, CDCl3): 142.2, 128.5, 125.9, 67.5, 40.9, 32.2,
23.6.
2-(Naphthalen-2-yl)-1-(naphthalen-2-ylmethyl)-1H-benzo[d]-
imidazole.16 1H NMR (400 MHz, CDCl3, ppm): 8.13 (s, 1H), 7.88−
F
DOI: 10.1021/acs.organomet.9b00475
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
7.76 (m, 6H), 7.67−7.64 (m, 2H), 7.50−7.39 (m, 5H), 7.30−7.20
(m, 4H), 5.61 (s, 2H). 13C NMR (100 MHz, CDCl3): 154.3, 143.3,
136.4, 134.0, 133.8, 133.5, 132.9, 132.9, 129.3, 129.1, 128.6, 128.6,
127.9, 127.8, 127.3, 126.7, 126.7, 126.3, 126.1, 124.8, 123.9, 123.3,
122.9, 120.1, 110.6, 48.9.
AUTHOR INFORMATION
Corresponding Author
*E-mail for D.C.: dafachen@hit.edu.cn.
ORCID
Bowen Hu: 0000-0001-9815-8938
Dafa Chen: 0000-0002-7650-4024
Haiping Xia: 0000-0002-2688-6634
■
2-Phenylquinoline.2j 1H NMR (400 MHz, CDCl3, ppm): 8.25 (d,
J = 8.4 Hz, 2H), 8.18 (d, J = 7.2 Hz, 2H), 7.89 (d, J = 8.4 Hz, 1H),
7.84 (d, J = 8.0 Hz, 1H), 7.75 (t, J = 8.0 Hz, 1H), 7.56−7.52 (m, 3H),
7.49−7.46 (m, 1H). 13C NMR (100 MHz, CDCl3): 157.4, 148.2,
139.6, 136.9, 129.7, 129.7, 129.4, 128.9, 127.6, 127.5, 127.2, 126.4,
119.0.
Notes
The authors declare no competing financial interest.
2-(o-Tolyl)quinoline.2j 1H NMR (400 MHz, CDCl3, ppm): 8.18 (t,
J = 8.4 Hz, 2H), 7.84 (dd, J = 8.0, 0.8 Hz, 1H), 7.75−7.70 (m, 1H),
7.56−7.49 (m, 3H), 7.36−7.29 (m, 3H), 2.41 (s, 3H). 13C NMR (100
MHz, CDCl3): 160.4, 148.0, 140.8, 136.1, 136.1, 131.0, 129.8, 129.7,
129.7, 128.6, 127.6, 126.8, 126.5, 126.1, 122.4, 20.5.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (Nos. 21871068 and 21672045), the
China Postdoctoral Science Foundation (2016M591519), the
Heilongjiang Postdoctoral Foundation (LBH-Z16069), and
the National Natural Science Foundation of Heilongjiang
(Nos. B2018005 and LC2018005).
2-(m-Tolyl)quinoline.29 1H NMR (400 MHz, CDCl3, ppm): 8.19
(t, J = 8.8 Hz, 2H), 8.01 (s, 1H), 7.92 (d, J = 7.6 Hz, 1H), 7.87 (d, J =
8.4 Hz, 1H), 7.82 (d, J = 8.0 Hz, 1H), 7.74−7.70 (m, 1H), 7.54−7.50
(m, 1H), 7.41 (t, J = 7.6 Hz, 1H), 7.28 (d, J = 7.6 Hz, 1H), 2.48 (s,
3H). 13C NMR (100 MHz, CDCl3): 157.6, 148.3, 139.7, 138.5, 136.7,
130.1, 129.7, 129.6, 128.8, 128.3, 127.5, 127.2, 126.2, 124.7, 119.2,
21.6.
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■
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1H), 7.47−7.43 (m, 1H), 7.13 (t, J = 8.4 Hz, 2H). 13C NMR (100
MHz, CDCl3): 164.0, 161.5, 155.2, 147.2, 135.8, 134.7, 128.7, 128.6,
128.4, 128.3, 126.4, 126.0, 125.3, 117.5, 114.8, 114.6.
3-Methyl-2-phenylquinoline.2j 1H NMR (400 MHz, CDCl3,
ppm): 8.19 (d, J = 8.0 Hz, 1H), 8.06 (br s, 1H), 7.82 (d, J = 8.0
Hz, 1H), 7.72−7.68 (m, 1H), 7.64−7.61 (m, 2H), 7.57−7.45 (m,
4H), 2.50 (s, 3H). 13C NMR (100 MHz, CDCl3): 160.3, 137.1, 129.3,
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ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.9b00475.
Crystallographic details for complex 3, synthetic route of
L3, NMR spectra, and IR spectra of the new compounds
(PDF)
Accession Codes
CCDC 1939902 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
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DOI: 10.1021/acs.organomet.9b00475
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