Substituent Effect on the Catalytic Activity of Ruthenium(II) Complexes Bearing a Pyridyl-Supported Pyrazolyl-Imidazolyl Ligand for Transfer Hydrogenation of Ketones

Article abstract of DOI:10.1021/acs.organomet.5b00727

Air- and moisture-stable ruthenium(II) complexes bearing a multisubstituted pyrazolyl-imidazolyl-pyridine ligand were synthesized and structurally characterized by NMR and X-ray single-crystal crystallographic analyses. The substituents on the imidazolyl moiety of the NNN ligand exhibited a remarkable impact on the catalytic activity of the corresponding Ru(II) complexes for transfer hydrogenation of ketones in refluxing 2-propanol, following the order NHTs > Me > H > NO₂, to tune the catalytic activity. The highest final TOF value of 345 600 h^-1 was reached by means of 0.05 mol % of the Ru(II)-NHTs-substituted NNN complex as the catalyst. The corresponding structurally confirmed RuH complexes are proposed as the catalytically active species.

Full text of DOI:10.1021/acs.organomet.5b00727

Article
pubs.acs.org/Organometallics
Substituent Effect on the Catalytic Activity of Ruthenium(II)
Complexes Bearing a Pyridyl-Supported Pyrazolyl-Imidazolyl Ligand
for Transfer Hydrogenation of Ketones
†
†
†
,†,‡
Huining Chai, Tingting Liu, Qingfu Wang, and Zhengkun Yu*
†Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning 116023, People’s
Republic of China
‡
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354
Fenglin Road, Shanghai 200032, People’s Republic of China
*
S Supporting Information
ABSTRACT: Air- and moisture-stable ruthenium(II) complexes bearing a
multisubstituted pyrazolyl-imidazolyl-pyridine ligand were synthesized and
structurally characterized by NMR and X-ray single-crystal crystallographic
analyses. The substituents on the imidazolyl moiety of the NNN ligand
exhibited a remarkable impact on the catalytic activity of the corresponding
Ru(II) complexes for transfer hydrogenation of ketones in refluxing 2-
propanol, following the order NHTs > Me > H > NO , to tune the catalytic
2
activity. The highest final TOF value of 345 600 h− was reached by means
1
of 0.05 mol % of the Ru(II)-NHTs-substituted NNN complex as the
catalyst. The corresponding structurally confirmed RuH complexes are proposed as the catalytically active species.
INTRODUCTION
reactive and air- and moisture-stable, suggesting that they might
be used as efficient homogeneous catalysts.
■
1
Transition-metal-catalyzed transfer hydrogenation (TH) of
unsaturated CO and CN bonds using 2-propanol or
formic acid as the hydrogen source has been well explored as a
During our ongoing study on Ru(II)-NNN complex catalysts
for transfer hydrogenation of ketones, we have found that
Ru(II) complex catalysts bearing an unsymmetrical pyridyl-
2
robust protocol. The Noyori Ru(II) complexes containing a
3
4
9e,f,10
monotosylated 1,2-diamine or amino alcohol ligand have
been used as the most powerful catalysts in the asymmetric
transfer hydrogenation of ketones and imines. Baratta et al.
reported the versatile ruthenium(II) 2-aminomethylpyridine
based NNN ligand can exhibit very high catalytic activity.
Ru(II) complexes bearing a symmetrical 2,6-bis(3,5-dimethyl-
11
pyrazol-1-yl)pyridine ligand (A) or a unsymmetrical bis-
10b
(
trifluoromethyl)pyrazolyl-pyridyl-based ligand (B)
were
(
ampy) complexes, which had demonstrated efficient catalytic5
synthesized and showed good catalytic activity in the transfer
hydrogenation of ketones in refluxing 2-propanol, and the latter
performed more efficiently than the former. Both cationic and
neutral Ru(II) complexes C and D demonstrated very good
catalytic activity for transfer hydrogenation of ketones under
activity in (asymmetric) transfer hydrogenation of ketones.
The complexes bearing a ligand with an NH functionality
usually exhibit high catalytic activity in the transfer hydro-
6
genation reactions. Although various types of ligands and their
transition-metal complexes featuring no NH functionality have
also been developed for the same purpose, development of
7
9f
the same conditions. Intrigued by the catalytic activity
highly active catalytic systems is still strongly desired. Recently,
polydentate nitrogen-containing ligands such as 2,6-bis-
difference between complexes A and B and the structural
features of complexes C and D, we reasonably envisioned that
tuning the electronic property of the ligand in complexes of
type C or D may alter the catalytic activity of the corresponding
complexes for transfer hydrogenation of ketones (Chart 1).
Herein, we report the synthesis of Ru(II) complexes 4−6
bearing a pyridyl-based NNN ligand containing a coordinative
disubstituted imidazolyl moiety and their catalytic behaviors in
the TH reactions of ketones.
8a−c
8d−f
(
2
immino)pyridines,
,6-bis(oxazolinyl)pyridines (pybox)
2,2′:6′,2″-terpyridines (terpy),
and
8g,h
have attracted more
and more attention for their tunable properties and potential
applications in homogeneous catalysis and organic synthesis.
These kinds of ligands usually feature two symmetrical
coordinating arms. However, unsymmetrical polydentate
ligands have also been applied due to the higher catalytic
activity of their transition-metal complexes attributed to the
9
hemilabile properties of the ligands. In general, NNN ligands
can be conveniently prepared and structurally modified, and
Received: August 24, 2015
their corresponding transition-metal complexes are usually
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.5b00727
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Organometallics
Article
Chart 1. Ruthenium(II)-NNN Complex Catalysts
Characterization of Ru(II) Complexes 4−6. The NMR
analyses of complexes 4−6 are consistent with their
1
compositions. In the H NMR spectra, the proton resonances
of the NH functionality in ligand 3a and its Ru(II) complex 4a
were shown as singlets at 12.31 and 15.20 ppm, respectively,
while these signals disappeared in those of neutral complexes
5
a and 6a, revealing formation of a Ru−N bond in the
31
complexes under basic conditions. The P NMR resonances of
complexes 4a−c and 5a appeared at 20.4, 23.5, 19.0, and 22.4
ppm, respectively, suggesting the presence of two equivalent
PPh ligands positioned trans to each other in the complexes.
3
3
1
Complex 5a showed a 2.0 ppm increment in its P NMR
spectrum as compared to that of 4a, which is in accordance
with our previous observation
9f,10
and suggests a change of the
RESULTS AND DISCUSSION
Synthesis of Ligands and Their Ru(II) Complexes.
■
coordination pattern of the benzimidazolyl nitrogen atom in 5a
1
31
through extrusion of HCl from 4a. The H and P NMR
spectra of 6a exhibited a triplet at −6.84 ppm for Ru−H and a
Condensation of 6-(3,5-dimethyl-1H-pyrazol-1-yl)-
10d
picolinimidate (1)
with 4,5-dimethylbenzene-1,2-diamine
doublet at 43.3 ppm for its two PPh ligands, respectively.
3
(
2a), N,N′-(4,5-diamino-1,2-phenylene)bis(4-methylbenzene-
The solid-state molecular structures of complexes 4b and 6a
were confirmed by X-ray crystallographic studies (Figures 1 and
1
2
sulfonamide) (2b), and 4,5-dinitrobenzene-1,2-diamine
1
2a,13
(
(
3
2c)
97%), 3b (86%), and 3c (32%), respectively. Ligands 3a and
b were efficiently prepared, but 3c was obtained in only a low
in the presence of glacial acetic acid afforded 3a
yield by extending the reaction time. Reacting equimolar
amounts of ligand 3 with RuCl (PPh ) in refluxing 2-propanol
2
3 3
gave Ru(II) complexes 4a−c in 88−90% yields. Ionic complex
a was further converted to the corresponding neutral complex,
that is, complex 5a, by means of K CO base to remove one
4
2
3
molecule of HCl from 4a (Scheme 1). Treatment of 4a with
a
Scheme 1. Synthesis of Ligands and Complexes 4 and 5a
Figure 1. Molecular structure of complex 4b. Thermal ellipsoids are
set at 30% probability. Two chloroform molecules are omitted for
clarity.
2
). In the solid state, the central ruthenium atom of complex 4b
is situated in a distorted octahedral environment surrounded by
tridentate NNN ligand 3b, two trans PPh , and a chloro ligand
3
a
Legend: (i) HOAc, 118 °C, 4−12 h, 0.1 MPa N ; (ii) Ru(PPh ) Cl ,
2
3
3
2
iPrOH, 82 °C, 4 h, 0.1 MPa N ; (iii) K CO , CH Cl , 40 °C, 4 h, 0.1
MPa N2.
2
2
3
2
2
K CO in 2-propanol afforded RuH complex 6a in 75% yield,
2
3
suggesting that consecutive dehydrochlorination/reduction
occurred (eq 1). It is noted that, starting from 5a under the
same conditions, complex 6a was also obtained in a similar
yield.
Figure 2. Molecular structure of complex 6a. Thermal ellipsoids are
set at 30% probability.
B
DOI: 10.1021/acs.organomet.5b00727
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Organometallics
Article
positioned trans to the pyridyl nitrogen atom, with another
dissociated chloride anion nearby (Figure 1). The P−Ru−P
Table 1. Catalytic Activity of Complexes 4 and D for
a
Transfer Hydrogenation of Ketones
angle in 4b is 177.3°, revealing that the two PPh ligands are
3
almost vertically situated at the two sides of the ligand plane.
The molecular structure of complex 6a is similar to that of 4b,
but with a discrete Ru−H bond (1.28 Å). Such a Ru−H bond is
9
e,10b
shorter than those reported (∼1.53 Å).
The P−Ru−N
(
85.65−102.68°), P(1)−Ru−P(2) (159.73°), and N(3)−Ru−
H (176.10°) angles, two Ru−P bonds (2.316 and 2.318 Å), and
three Ru−N bonds (2.067−2.109 Å) also reveal a distorted six-
coordinated metal center in complex 6a. It is noteworthy that
the average Ru−P bond length in complex 4b (2.399 Å) is a
9
f
little bit longer than that in complex D (2.391 Å), suggesting
that the Ru(II) center of complex 4b is in a more loose
environment than that in complex D, and complex 4b may be
more catalytically active than complex D.
Transfer Hydrogenation of Ketones. Under the typical
conditions for transfer hydrogenation of ketones (82 °C, 0.1 M
ketone in 2-propanol), the TH reactions of various ketones was
conducted by means of complexes 4a−c as the catalysts (Table
1
). Alcohols were produced as the sole products in the presence
of iPrOK base and 0.1 mol % of the complex catalyst in
refluxing 2-propanol under a nitrogen atmosphere. Due to the
substituent effect from the functional groups on the imidazolyl
moiety of the NNN ligand, complexes 4a−c demonstrated
various catalytic activity different from that of complex D.
Among all the explored complexes, that is, 4a−c and D,
complex 4b, bearing two NHT substituents on the imidazoly
moiety of its ligand, exhibited the highest catalytic activity, 4a,
containing an NNN ligand with a Me -imidazolyl functionality,
2
showed a catalytic activity lower than 4b, but higher than
complex D, bearing a unsubstituted imidazolyl-containing
NNN ligand, whereas complex 4c, bearing an (NO ) -
2
2
imidazoly pyridyl-pyrazolyl ligand, that is, ligand 3c, exhibited
the lowest catalytic activity (Table 1). A remarkable substituent
effect was thus observed. The stronger electron-donating
capability of NHT functionalities than that of methyl groups
14
renders complex 4b more catalytically active than complex 4a,
while introduction of electron-withdrawing NO groups to
2
ligand 3c deteriorates the catalytic activity of complex 4c. The
capability for these substituents to enhance the catalytic activity
of the Ru(II)-NNN complexes is consistent with the electron-
donating property of the substituents, following the order
a
Conditions: ketone, 2.0 mmol (0.1 M in 20 mL of iPrOH); catalyst,
.1 mol %; ketone/iPrOK/Ru(II) cat. = 1000:20:1; 0.1 MPa N , 82
0
NHTs > Me > H > NO . The catalytic activity order of the
2
2
b
c
d
°
C. Determined by GC analysis. Cited from ref 9f. Using 0.2 mol %
catalyst.
complexes is 4b > 4a > D > 4c, revealing that introduction of
electron-donating substituents onto the coordinative imidazolyl
arm of the NNN ligands of type 3 enhances the catalytic
activity of complexes 4.
Due to the highest catalytic activity of complex 4b, it was
applied as the catalyst to explore the substrate scope in the
transfer hydrogenation of ketones (Table 2). Under the stated
conditions, acetophenone was converted to the corresponding1
alcohol within 30 s, reaching a final TOF value of 116 400 h−
reactions of p-, m-, and o-chloroacetophenones to efficiently
form the target alcohol products, reaching the highest final
TOF value of 345 600 h− (Table 2, entries 2−4).
Coordinatively saturated complex 4b is a highly active Ru(II)
1
5
,9,10
complex catalyst for TH of ketones,
but it is noted that the
related unsaturated Ru(II) complex reached a final TOF value
of 720 000 h− under the same conditions.
1
10h
(Table 1, entry 1), while propiophenone exhibited a lower
reactivity (Table 2, entry 1). A variety of substituted
acetophenones, aryl alkyl ketones, and aliphatic ketones were
also reacted to give the alcohol products. In most of the cases,
the reactions reached ≥96% conversions for the ketones over a
period of 20 s to 15 min. Substituents such as chloro, bromo,
fluoro, trifluoromethyl, methyl, and methoxy were tolerated on
the aryl groups of the ketone substrates, and they demonstrated
various electronic and steric effects (Tables 1 and 2). Lowering
the catalyst loading to 0.05 mol % still rendered the TH
Reaction Mechanism. In order to investigate the reaction
mechanism, the catalytic behaviors of complexes 4a, 5a, and 6a
were comparatively tested in the TH reactions of acetophe-
none, 2′-chloroacetophenone, and 2′-methyl acetophenone
(Scheme 2), respectively. Under the standard conditions as
shown in Table 2, the three complexes almost exhibited the
same catalytic activity. On the basis of the present experimental
9e,f,10b
results and those previously observed,
RuH complexes of
15
type 6 are proposed as the catalytically active species for the
C
DOI: 10.1021/acs.organomet.5b00727
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Article
Table 2. Transfer Hydrogenation of Ketones Catalyzed by
potassium alkoxide reacts with complex 5 to give an R(II)-
alkoxide intermediate species of type I, which undergoes β-H
elimination to generate the RuH complex. Complex 6 acts as
the catalytically active species to catalyze the reduction of
ketone via an inner-sphere pathway.
a
4
b
Scheme 3. Proposed Mechanism
CONCLUSIONS
■
In summary, Ru(II) complexes bearing an unsymmetrical
pyrazolyl-substituted imidazolyl-pyridine ligand have exhibited
different catalytic activity in the TH reactions of ketones. The
substituent effect from the functional groups on the imidazolyl
moiety of the ligand follows the order NHTs > Me > H > NO2.
Introduction of electron-donating NHTs and Me groups onto
the coordinative imidazolyl arm of the ligand remarkably
enhances the catalytic activity of the corresponding Ru(II)
complex catalysts. The structurally characterized RuH complex
is proposed to be the catalytically active species.
a
Conditions: ketone, 2.0 mmol (0.1 M in 20 mL of iPrOH); cat. 4b,
EXPERIMENTAL SECTION
General Considerations. The solvents were dried and distilled
prior to use by the literature methods. H and C{ H} NMR spectra
0
.1 mol %; ketone/iPrOK/4b = 1000:20:1; 0.1 MPa N , 82 °C.
■
2
b
c
Determined by GC analysis. Using 0.05 mol % catalyst.
1
13
1
Scheme 2. Comparative Experiments
were recorded on a Bruker DRX-400 spectrometer, and all chemical
1
shift values refer to δ
= 0.00 ppm, CDCl (δ( H), 7.26 ppm;
TMS
3
13
1
13
δ( C), 77.16 ppm) and DMSO-d (δ( H), 2.50 ppm; δ( C), 39.52
6
ppm). Elemental and HRMS analysis were achieved by the Analysis
Center, Dalian University of Technology and Dalian Institute of
Chemical Physics, Chinese Academy of Sciences. All the melting
points were uncorrected. TLC analysis was performed by using glass-
backed plates coated with 0.2 mm silica gel. Flash column
chromatography was performed on silica gel. All chemical reagents
were purchased from commercial sources and used as received unless
otherwise indicated.
X-ray Crystallographic Studies. The X-ray single-crystal
structures of complexes 4b and 6a were carried out on a SMART
APEX diffractometer with graphite-monochromated Mo Kα radiation
(λ = 0.710 73 Å). Cell parameters were obtained by global refinement
1
6
TH reactions, involving a plausible inner-sphere pathway.
The TH reaction initially starts from the dehydrochlorination
of complex 4 by iPrOK base, forming complex 5. The
D
DOI: 10.1021/acs.organomet.5b00727
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Organometallics
Article
of the positions of all collected reflections. Intensities were corrected
for Lorentz and polarization effects and empirical absorption. The
structures were solved by direct methods and refined by full-matrix
as a red-brown crystalline solid (423 mg, 90% yield). Mp: >320 °C
1
dec. H NMR (CDCl , 400 MHz): δ 15.20 (s, 1 H, NH), 8.62 and
3
6.64 (d each, J = 7.8 and 8.3 Hz, 1:1 H, 3-H and 5-H), 8.08 and 7.39 (s
2
least-squares on F . All non-hydrogen atoms were refined anisotropi-
each, 1:1 H, 8″-H and 5″-H), 7.29 (m, 1 H, 4-H), 7.18, 7.10, and 6.93
cally. All hydrogen atoms were placed in calculated positions. Structure
solution and refinement were performed by using the SHELXL-97
package. The X-ray crystallographic files, in CIF format, are available
from the Cambridge Crystallographic Data Centre on quoting the
deposition numbers CCDC 1003352 for 4b and CCDC 1003351 for
(m each, 12:6:12 H, 2 × PPh ), 5.98 (s, 1 H, 4′-H), 2.47 and 2.44 (s
3
each, 3:3 H, C7″-CH and C6″-CH ) 2.39 (s, 3 H, C3′-CH ), 2.31 (s,
3
3
3
1
3
1
3 H, C5′-CH ). C{ H} NMR (CDCl , 100 MHz): δ 157.8 and 151.7
3
3
(Cq each, C2 and C6), 151.1 and 143.4 (Cq each, C3′ and C5′), 148.9
and 134.7 (Cq each, C4″ and C9″), 141.3 (C4), 133.6 and 132.5 (Cq
6
a. Copies of this information may be obtained free of charge from the
Director, CCDC, 12 Union Road, Cambridge CB2 IEZ, UK (fax: +
4-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
each, C7″ and C6″), 132.0 (Cq, 2 × PPh ), 133.3, 129.2, and 127.7
3
(CH of 2 × PPh ), 120.5 and 113.0 (C8″ and C5″), 120.0 and 113.6
3
4
(C3 and C5), 108.3 (C4′), 20.5 (C7″-CH ), 20.3 (C6″-CH ) 15.3
3
3
31
1
www.ccdc.cam.ac.uk).
(C3′-CH ), 15.2 (C5′-CH ). P{ H} NMR (CDCl , 162 MHz): δ
3
3
3
−1
General Procedure for the Synthesis of Ligands 3: Synthesis of
a. A solution of methyl 6-(3,5-dimethyl-1H-pyrazol-1-yl)-
20.4 (PPh ). IR (KBr pellets, cm ): ν 3418, 3052, 1609, 1556, 1481,
3
3
1466, 1414, 1385, 1326, 1282, 1188, 1159, 1091, 1029, 999, 855, 791,
picolinimidate (1) (230 mg, 1.0 mmol) and 4,5-dimethylbenzene-
,2-diamine (2a) (136 mg, 1.0 mmol) in 10 mL of glacial acetic acid
745, 619. Anal. Calcd for C H Cl N P Ru·2/3C H : C, 66.14; H,
5
5
49
2
5
2
6
14
1
5.48; N, 6.54. Found: C, 65.94; H, 5.38; N, 6.60.
was refluxed under a nitrogen atmosphere for 4 h. The cooled solution
was diluted with water and neutralized with concentrated aqueous
ammonia (25%, 5 mL). The precipitate was collected and dried under
Synthesis of 4b. In a fashion similar to the synthesis of 4a,
RuCl (PPh ) (288 mg, 0.3 mmol) reacted with 3b (188 mg, 0.3
2
3 3
mmol) to afford 4b as a brown crystalline solid (350 mg, 88% yield).
Single crystals suitable for X-ray crystallographic determination were
vacuum to afford 3a as a brown solid (310 mg, 97% yield). Mp: 199−
1
2
00 °C. H NMR (DMSO-d , 400 MHz): δ 12.31 (s, 1 H, NH), 8.19
grown from the recrystallization in CHCl /n-hexane (1:3, v/v) at 25
6
3
1
and 7.80 (d each, J = 7.2 and 7.6 Hz, 1:1 H, 3-H and 5-H), 8.05 (t, J =
°C. Mp: >300 °C dec. H NMR (CDCl /CD OD, 400 MHz): δ 8.37
3
3
7
.8 Hz, 1 H, 4-H), 7.49 and 7.39 (s each, 1:1 H, 8″-H and 5″-H), 6.14
(s, 1 H, 3-H), 8.22 and 7.50 (d each, J = 8.2 and 8.2 Hz, 2:2 H, 4‴-H),
(
(
s, 1 H, 4′-H), 2.73 (s, 3 H, C3′-CH ), 2.22 (s, 3 H, C5′-CH ), 2.33
8.02 (d, J = 7.8 Hz, 1 H, 5-H), 7.41 (t, J = 8.1 Hz, 1 H, 4-H), 7.16 (d, J
3
3
13
1
s, 6 H, C6″-CH and C7″-CH ). C{ H} NMR (DMSO-d , 100
= 8.1 Hz, 2 H, 5″′-H), 7.03 and 6.83 (m each, 20:12 H, 2 × PPh and
3
3
6
3
MHz): δ 152.5 and 149.1 (Cq each, C2 and C6), 147.1 and 141.2 (Cq
5‴-H), 6.64 (d, J = 8.4 Hz, 1 H, 5″-H), 6.58 (s, 1 H, 8″-H), 5.96 (s, 1
each, C3′ and C5′), 142.5 and 133.5 (Cq each, C4″ and C9″), 139.8
H, 4′-H), 2.60 (s, 3 H, C3′-CH ), 2.36 (s, 3 H, C6‴-CH ), 2.26 (s, 3
3
3
13
1
(
C4), 132.1 and 130.5 (Cq each, C7″ and C6″), 119.3 and 112.2 (C8″
H, C6‴-CH ), 1.88 (s, 3 H, C5′-CH ). C{ H} NMR (CDCl /
3
3
3
and C5″), 118.6 and 116.4 (C3 and C5), 108.8 (C4′), 20.1(C7″-
CD OD, 100 MHz): δ 161.5 and 156.1 (Cq each, C2 and C6), 154.9
3
CH ), 20.0 (C6″-CH ) 14.0 (C3′-CH ), 13.3 (C5′-CH ). HRMS:
and 148.3 (Cq each, C3′ and C5′), 153.5 and 148.0 (Cq each, C4″
and C9″), 148.2 (C4), 145.6 and 129.2 (Cq each, C7″ and C6″),
139.8, 138.9, 137.5, 134.6, 134.3, 133.7, 133.5, and 132.5 (phenyl C of
3
3
3
3
calcd for C H N 317.1640, found 317.1638.
19
19
5
Synthesis of 3b. In a fashion similar to the synthesis of 3a, 1 (377
mg, 1.6 mmol) reacted with N,N′-(4,5-diamino-1,2-phenylene)bis(4-
methylbenzenesulfonamide) (2b) (730 mg, 1.6 mmol) to form 3b as a
NHTs), 135.7 (Cq, 2 × PPh ), 137.0, 133.2, and 131.6 (CH of 2 ×
3
PPh ), 123.0 and 117.0 (C3 and C5), 115.1 and 114.2 (C8″ and C5″),
3
1
brown solid (890 mg, 86% yield). Mp: 168−169 °C. H NMR
114.8 (C4′), 25.3 and 25.0 (C6″′-CH ), 19.4 (C3′-CH ), 18.6 (C5′-
3
3
31
1
(
DMSO-d , 400 MHz): δ 12.48 (s, 1 H, NH), δ 9.21 (br, 2 H, 6″-NH
CH ). P{ H} NMR (CDCl /CD OD, 162 MHz): δ 23.5 (PPh ). IR
6
3 3 3 3
−
1
and 7″-NH), 8.11 and 7.81 (d each, J = 7.0 and 8.0 Hz, 1:1 H, 3-H and
-H), 8.04 (t, J = 7.9 Hz, 1 H, 4-H), 7.39 and 7.19 (s each, 1:1 H, 8″-H
(KBr pellets, cm ): ν 3355, 3054, 1607, 1555, 1482, 1435, 1332,
1281, 1185, 1161, 1091, 1031, 975, 936, 811, 747, 698, 665, 547, 517.
Anal. Calcd for C H Cl N O P S Ru·2/3C H : C, 61.72; H, 4.98;
5
and 5″-H), 7.62 (m, 4 H, 4‴-H), 7.34 (d, J = 8.2 Hz, 4 H, 5‴-H), 6.14
6
7
59
2
7
4
2
2
6
14
(
(
s, 1 H, 4′-H), 2.68 (s, 3 H, C3′-CH ), 2.21 (s, 3 H, C5′-CH ), 2.33
N, 7.10. Found: C, 61.46; H, 4.83; N, 7.15.
3
3
13
1
s, 6 H, C6″′-CH ). C{ H} NMR (DMSO-d , 100 MHz): δ 152.6
Synthesis of 4c. In a fashion similar to the synthesis of 4a,
3
6
and 151.4 (Cq each, C2 and C6), 149.3 and 141.2 (Cq each, C3′ and
C5′), 146.1 (Cq, C2″), 143.6 and 135.9 (Cq each, C4″ and C9″),
RuCl (PPh ) (192 mg, 0.2 mmol) reacted with 3c (76 mg, 0.2 mmol)
2
3 3
to afford 4c as a red-brown crystalline solid (199 mg, 90% yield). Mp:
1
1
40.0 (C4), 135.6 and 125.2 (Cq each, C7″ and C6″), 133.0 (Cq,
>300 °C dec. H NMR (CDCl , 400 MHz): δ 8.55 and 8.12 (s, 1:1 H,
3
C3″′), 127.7 (Cq, C6″′), 129.7 (C4″′), 127.1 (C5″′), 118.9 and 117.1
5″-H and 8″-H), 7.35 (m, 2 H, 3-H and 4-H), 7.15 and 6.97 (m each,
(
(
C3 and C5), 115.4 and 107.1 (C8″ and C5″), 109.0 (C4′), 20.1
18:12 H, 2 × PPh ), 6.63 (d, J = 8.3 Hz, 1 H, 5-H), 6.08 (s, 1 H, 4′-H),
3
13
1
C6″′-CH ), 14.0 (C3′-CH ), 13.3 (C5′-CH ). HRMS: calcd for
2.63 (s, 3 H, C3′-CH ), 2.44 (s, 3 H, C5′-CH ). C{ H} NMR
3
3
3
3
3
C H N O S 627.1722, found 627.1708.
(CDCl , 100 MHz): δ 157.8 and 152.3 (Cq each, C2 and C6), 143.8
31
29
7
4
2
3
Synthesis of 3c. In a fashion similar to the synthesis of 3a, 1 (285
and 138.4 (Cq each, C3′ and C5′), 139.2 and 139.2 (Cq each, C4″
mg, 1.2 mmol) reacted with 4,5-dinitrobenzene-1,2-diamine (2c) (245
mg, 1.2 mmol) to give a brown solid, which was subject to purification
by silica gel column chromatography (eluent petroleum ether (60−90
and C9″), 133.8 (C4), 132.2 (Cq, 2 × PPh ), 133.2, 129.5, and 128.0
3
(CH of 2 × PPh ), 129.3 and 129.3 (Cq each, C6″ and C7″), 117.5
3
and 117.5 (C5″ and C8″), 128.0 and 113.2 (C3 and C5), 109.8 (C4′),
3
1
1
°
C)/ethyl acetate: 1:20, v/v), affording 3c as a yellow solid (150 mg,
15.8 (C3′-CH ), 15.2 (C5′-CH ). P{ H} NMR (CDCl , 162 MHz):
3
3
3
1
−1
3
2% yield). Mp: 251−252 °C. H NMR (DMSO-d , 400 MHz): δ
δ 19.0 (PPh ). IR (KBr pellets, cm ): ν 3442, 3051, 2706, 1604, 1478,
6
3
1
3.60 (s, 1 H, NH), 8.48 (s, 1:1 H, 5″-H and 8″-H), 8.30 and 7.96 (d
each, J = 7.6 and 8.1 Hz, 1:1 H, 3-H and 5-H), 8.20 (t, J = 7.9 Hz, 1 H,
1435, 1406, 1358, 1186, 1089, 1030, 982, 910, 838, 828, 793, 746, 530,
515, 430. Anal. Calcd for C H Cl N O P Ru·2/3C H : C, 60.41; H,
53
43
2
7
4
2
6
14
4
-H), 6.20 (s, 1 H, 4′-H), 2.73 (s, 3 H, C3′-CH ), 2.24 (s, 3 H, C5′-
4.65; N, 8.65. Found: C, 60.12; H, 4.52; N, 8.78.
3
13
1
CH ). C{ H} NMR (DMSO-d , 100 MHz): δ 156.5 and 152.6 (Cq
Synthesis of 5a. Under a nitrogen atmosphere, a mixture of
3
6
each, C2 and C6), 149.3 and 141.1 (Cq each, C3′ and C5′), 144.7 and
complex 4a (51.0 mg, 0.05 mmol) and K CO (67.4 mg, 0.50 mmol)
2
3
1
44.7 (Cq each, C4″ and C9″), 140.1 (C4), 138.4 and 138.4 (Cq each,
in 10 mL of dichloromethane was refluxed for 5 h. After cooling to
ambient temperature the reaction mixture was passed through a short
pad of Celite, which was then rinsed with 5 mL of dichloromethane.
All the volatiles of the combined filtrate were evaporated under
C7″ and C6″), 118.3 and 118.3 (C8″ and C5″), 119.8 and 113.5 (C3
and C5), 108.8 (C4′), 13.5 (C3′-CH ), 13.0 (C5′-CH ). HRMS: calcd
3
3
for C H N O 379.1029, found 379.1020.
17
13
7
4
General Procedure for the Synthesis of 4: Synthesis of 4a. Under
reduced pressure to give 5a as a red solid (42.5 mg, 90% yield). Mp:
1
a nitrogen atmosphere, a mixture of RuCl (PPh ) (437 mg, 0.5
>300 °C dec. H NMR (CDCl , 400 MHz): δ 7.89 (s, 1 H, 3-H), 7.38
2
3
3
3
mmol) and 3a (145 mg, 0.5 mmol) in 2-propanol (10 mL) was
refluxed for 3 h, forming a red-brown microcrystalline solid. After
cooling to ambient temperature, the precipitate was filtered off, washed
with diethyl ether (3 × 10 mL), and dried under vacuum to afford 4a
(d, J = 7.8 Hz, 1 H, 4-H), 6.33 (d, J = 8.2 Hz, 1 H, 5-H), 7.32 and 6.96
(m each, 1:1 H, 8″-H and 5″-H), 7.20, 7.05, and 6.89 (m each, 12:6:12
H, 2 × PPh ), 5.91(s, 1 H, 4′-H), 2.48 and 2.39 (s each, 3:3 H, C3″-
3
CH and C5″-CH ), 2.31 and 2.31 (s each, 3:3 H, C7″-CH and C6″-
3
3
3
E
DOI: 10.1021/acs.organomet.5b00727
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
CH ). 13C{ H} NMR (CDCl , 100 MHz): δ 156.7 and 155.9 (Cq
1
3
3
Notes
each, C2 and C6), 155.3 and 144.4 (Cq each, C3′ and C5′), 150.5
The authors declare no competing financial interest.
(
(
1
C2″), 145.5 and 130.5 (Cq each, C4″ and C9″), 141.0 (C4), 131.8
Cq, 2 × PPh ), 132.7, 127.5, and 126.2 (CH of 2 × PPh ), 128.4 and
3
3
ACKNOWLEDGMENTS
28.0 (Cq each, C7″ and C6″), 118.2 and 111.3 (C8″ and C5″), 117.0
■
and 114.6 (C3 and C5), 103.8 (C4′), 19.8 (C7″-CH ), 19.5 (C6″-
We are grateful to the National Natural Science Foundation of
China (21272232).
3
31
1
CH ) 14.1 (C3′-CH ), 14.1 (C5′-CH ). P{ H} NMR (CDCl , 162
3
3
3
3
−1
MHz): δ 22.4 (PPh ). IR (KBr pellets, cm ): ν 3057, 2917, 1960,
3
1
1
607, 1574, 1554, 1503, 1435, 1349, 1323, 1285, 1188, 1158, 1093,
029, 996, 926, 879, 859, 819, 786, 743, 698, 660, 459, 442. Anal.
REFERENCES
■
(
1) (a) Zuo, W. W.; Morris, R. H. Nat. Protoc. 2015, 10, 241−257.
b) Li, X. H.; Cai, Y. Y.; Gong, L. H.; Fu, W.; Wang, K. X.; Bao, H. L.;
Calcd for C H ClN P Ru: C, 67.58; H, 4.95; N, 7.16. Found: C,
55
48
5 2
(
6
7.62; H, 4.99; N, 7.10.
Synthesis of 6a. Under a nitrogen atmosphere, a mixture of
complex 4a (470 mg, 0.45 mmol) and K CO (621 mg, 4.5 mmol) in
Wei, X.; Chen, J. S. Chem. - Eur. J. 2014, 20, 16732−16737.
(
6
2
(
(
(
c) Sabater, S.; Baya, M.; Mata, J. A. Organometallics 2014, 33, 6830−
2
3
839. (d) Zuo, W. W.; Lough, A. J.; Li, Y. F.; Morris, R. H. Science
013, 342, 1080−1083.
2
0 mL of 2-propanol was refluxed for 3 h. After cooling to ambient
temperature all the volatiles were removed under reduced pressure. A
mL amount of dichloromethane was then added to dissolve the
2) (a) Lee, S. H.; Nikonov, G. I. ChemCatChem 2015, 7, 107−113.
8
b) Corbett, M.; Johnson, J. J. Am. Chem. Soc. 2013, 135, 594−597.
crude product, and the solution filtered to remove the inorganic salts.
The filtrate was concentrated under reduced pressure and then layered
by n-hexane (1:3, v/v) for recrystallization at 25 °C to give 6a as red-
c) Depasquale, J.; Kumar, M.; Zeller, M.; Papish, E. T. Organo-
metallics 2013, 32, 966−979. (d) Moore, C. M.; Szymczak, N. K.
Chem. Commun. 2013, 49, 400−402. (e) Wu, Z.; Perez, M.; Scalone,
M.; Ayad, T.; Vidal, R. V. Angew. Chem., Int. Ed. 2013, 52, 4925−4928.
1
brown crystals (328 mg, 75% yield). Mp: >300 °C dec. H NMR
(
CDCl , 400 MHz): δ 7.85 (d, J = 8.0 Hz, 1 H, 3-H), 7.41 (t, J = 8.0
3
(
f) Simon, M.; Li, C. J. Chem. Soc. Rev. 2012, 41, 1415−1427.
Hz, 1 H, 4-H), 7.24 and 6.33 (s each, 1:1 H, 5-H and 5″-H), 7.07 and
(
3) Selected recent reports: (a) Zimbron, J. M.; Dauphinais, M.;
Charette, A. B. Green Chem. 2015, 17, 3255−3259. (b) Pechac k, J.;
k, J.;
r, P. Tetrahedron: Asymmetry 2013, 24, 233−239.
c) Touge, T.; Hakamata, T.; Nara, H.; Kobayashi, T.; Sayo, N.; Saito,
T.; Kayaki, Y.; Ikariya, T. J. Am. Chem. Soc. 2011, 133, 14960−14963.
6
.96 (m each, 6:1:24 H, 8″-H and 2 × PPh ), 5.71(s, 1 H, 4′-H), 2.64
3
́ ̌
e
and 1.03 (s each, 3:3 H, C3″-CH and C5″-CH ), 2.21 and 2.04 (s
3
3
̌
́ ̌ ̌ ̌ ́ ́ ̌
lavík, J.; Prech, J.; Sot, P.; Januscak, J.; Vilhanova, B.; Vavrí
each, 3:3 H, C7″-CH and C6″-CH ), −6.84 (t, J = 26.4 Hz, Ru−H).
Vac
Kuzma, M.; Kace
3
3
1
3
1
C{ H} NMR (CDCl , 100 MHz): δ 159.2 and 153.1 (Cq each, C2
̌
3
(
and C6), 152.9 and 144.4 (Cq each, C3′ and C5′), 148.7 (C2″), 145.8
and 132.0 (Cq each, C4″ and C9″), 140.7 (C4), 135.7 (Cq, 2 × PPh ),
3
(
d) Ikariya, T.; Blacker, A. J. Acc. Chem. Res. 2007, 40, 1300−1308.
1
33.2, 128.1, and 127.3 (CH of 2 × PPh ), 128.3 and 127.9 (Cq each,
3
(
4) (a) Coll, M.; Ahlford, K.; Pam
Adv. Synth. Catal. 2012, 354, 415−427. (b) Coll, M.; Pam
Adolfsson, H.; Dieg
̀
ies, O.; Adolfsson, H.; Dieg
́
uez, M.
ies, O.;
C7″ and C6″), 117.8 and 110.8 (C8″ and C5″), 117.6 and 115.8 (C3
̀
and C5), 104.6 (C4′), 20.6 (C7″-CH ), 20.2 (C6″-CH ) 15.7 (C3′-
3
3
3
1
1
́
uez, M. Chem. Commun. 2011, 47, 12188−12190.
CH ), 15.3 (C5′-CH ). P{ H} NMR (CDCl , 162 MHz): δ 43.3 (d,
3
3
3
−
1
́
c) Guijarro, D.; Pablo, O.; Yus, M. Tetrahedron Lett. 2011, 52, 789−
(
7
J(P, H) = 25.1 Hz, PPh ). IR (KBr pellets, cm ): ν 3646, 3049, 2916,
3
91. (d) Deshpande, S. H.; Kelkar, A. A.; Gonnade, R. G.; Shingote, S.
1
895, 1600, 1552, 1497, 1477, 1433, 1347, 1324, 1293, 1184, 1155,
1089, 1025, 999, 980, 857, 745, 619, 562, 443, 413. Anal. Calcd for
K.; Chaudhari, R. V. Catal. Lett. 2010, 138, 231−238.
C H N P Ru·2/3C H : C, 70.83; H, 5.87; N, 7.00. Found: C, 70.39;
(5) (a) Chelucci, G.; Baldino, S.; Baratta, W. Acc. Chem. Res. 2015,
48, 363−379. (b) Chelucci, G.; Baldino, S.; Baratta, W. Coord. Chem.
Rev. 2015, 300, 29−85. (c) Zhang, S. M.; Baratta, W. Organometallics
2013, 32, 3339−3342. (d) Putignano, E.; Bossi, G.; Rigo, P.; Baratta,
W. Organometallics 2012, 31, 1133−1142. (e) Baratta, W.; Barbato, C.;
Magnolia, S.; Siega, K.; Rigo, P. Chem. - Eur. J. 2010, 16, 3201−3206.
(f) Baratta, W.; Ballico, M.; Chelucci, G.; Siega, K.; Rigo, P. Angew.
Chem., Int. Ed. 2008, 47, 4362−4365. (g) Baratta, W.; Chelucci, G.;
Herdtweck, E.; Magnolia, S.; Siega, K.; Rigo, P. Angew. Chem., Int. Ed.
2007, 46, 7651−7654. (h) Baratta, W.; Chelucci, G.; Gladiali, S.; Siega,
K.; Toniutti, M.; Zanette, M.; Zangrando, E.; Rigo, P. Angew. Chem.,
Int. Ed. 2005, 44, 6214−6219.
5
5
49
5
2
6
14
H, 5.76; N, 7.15.
Typical Procedure for the Catalytic Transfer Hydrogenation
of Ketones. The catalyst solution was prepared by dissolving complex
4
b (13.2 mg, 0.01 mmol) in 2-propanol (50.0 mL). Under a nitrogen
atmosphere, a mixture of a ketone (2.0 mmol), 10.0 mL of the catalyst
solution (0.002 mmol), and 2-propanol (9.6 mL) was stirred at 82 °C
for 10 min. Then, 0.4 mL of an 0.1 M iPrOK (0.04 mmol) solution in
2
0
-propanol was introduced to initiate the reaction. At the stated time,
.1 mL of the reaction mixture was sampled by a syringe and
immediately diluted with 0.5 mL of 2-propanol precooled to 0 °C for
GC analysis. After the reaction was complete, the reaction mixture was
concentrated under reduced pressure and subject to purification by
silica gel column chromatography to afford the alcohol product, which
was identified by comparison with the authentic sample through NMR
and GC analyses.
(6) (a) Zhao, B. G.; Han, Z. B.; Ding, K. L. Angew. Chem., Int. Ed.
2013, 52, 4744−4788. (b) Bizet, V.; Pannecoucke, X.; Renaud, J.-L.;
Cahard, D. Angew. Chem. 2012, 124, 6573−6576; Angew. Chem., Int.
Ed. 2012, 51, 6467−6470. (c) Strotman, N. A.; Baxter, C. A.; Brands,
K. M. J.; Cleator, E.; Krska, S. W.; Reamer, R. A.; Wallace, D. J.;
Wright, T. J. J. Am. Chem. Soc. 2011, 133, 8362−8371.
ASSOCIATED CONTENT
Supporting Information
■
(
7) Selected recent reports: (a) Li, K.; Niu, J. L.; Yang, M. Z.; Li, Z.;
Wu, L. Y.; Hao, X. Q.; Song, M. P. Organometallics 2015, 34, 1170−
176. (b) Lundgren, R. J.; Rankin, M. A.; McDonald, R.; Schatte, G.;
*
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.5b00727.
1
Stradiotto, M. Angew. Chem., Int. Ed. 2007, 46, 4732−4735. (c) Reetz,
M. T.; Li, X. G. J. Am. Chem. Soc. 2006, 128, 1044−1045.
(
2
d) Leijondahl, K.; Fransson, A.-B. L.; Bac
006, 71, 8622−8625.
8) Selected recent reviews and examples: (a) Tondreau, A. M.;
Stieber, S. C. E.; Milsmann, C.; Lobkovsky, E.; Weyhermuller, T.;
Semproni, S. P.; Chirik, P. J. Inorg. Chem. 2013, 52, 635−646.
(b) Darmon, J. M.; Stieber, S. C. E.; Sylvester, K. T.; Fernandez, I.;
̈
kvall, J.-E. J. Org. Chem.
NMR spectra of the new compounds (PDF)
X-ray crystallographic data for 4b (CIF)
X-ray crystallographic data for 6a (CIF)
All computed molecule Cartesian coordinates in a format
for convenient visualization (XYZ)
(
̈
́
Lobkovsky, E.; Semproni, S. P.; Bill, E.; Wieghardt, K.; De Beer, S.;
Chirik, P. J. J. Am. Chem. Soc. 2012, 134, 17125−17137. (c) Caulton,
K. G. Eur. J. Inorg. Chem. 2012, 2012, 435−443. (d) Aribia, K. B.;
AUTHOR INFORMATION
Corresponding Author
E-mail (Z.-K. Yu): zkyu@dicp.ac.cn.
■
Moehl, T.; Zakeeruddin, S. M.; Gratzel, M. Chem. Sci. 2013, 4, 454−
̈
*
459. (e) Li, S. L.; Xiao, T.; Lin, C.; Wang, L. Chem. Soc. Rev. 2012, 41,
F
DOI: 10.1021/acs.organomet.5b00727
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Organometallics
Article
5
950−5968. (f) Kaveevivitchai, N.; Chitta, R.; Zong, R.; El Ojaimi, M.;
Thummel, R. P. J. Am. Chem. Soc. 2012, 134, 10721−10724.
g) Dudnik, A. S.; Fu, G. C. J. Am. Chem. Soc. 2012, 134, 10693−
0697. (h) Harada, T.; Tsumatori, H.; Nishiyama, K.; Yuasa, J.;
Hasegawa, Y.; Kawai, T. Inorg. Chem. 2012, 51, 6476−6485.
9) (a) Naziruddin, A. R.; Kuo, C. L.; Lin, W. J.; Lo, W. H.; Lee, C.
S.; Sun, B. J.; Chang, A. H. H.; Hwang, W. S. Organometallics 2014, 33,
(
1
(
2
2
575−2582. (b) Toda, T.; Kuwata, S.; Ikariya, T. Chem. - Eur. J. 2014,
0, 9539−9542. (c) Zhu, Z.; Zhang, J.; Fu, H. Y.; Yuan, M. L.; Zheng,
X. L.; Chen, H.; Li, R. X. RSC Adv. 2014, 4, 52734−52739. (d) Yang,
M. J.; Liu, Y. J.; Gong, J. F.; Song, M. P. Organometallics 2011, 30,
3
793−3803. (e) Ye, W. J.; Zhao, M.; Du, W. M.; Jiang, Q. B.; Wu, K.
K.; Wu, P.; Yu, Z. K. Chem. - Eur. J. 2011, 17, 4737−4741. (f) Zeng, F.
L.; Yu, Z. K. Organometallics 2009, 28, 1855−1862.
(
10) (a) Du, W. M.; Wang, Q. F.; Wang, L. D.; Yu, Z. K.
Organometallics 2014, 33, 974−982. (b) Du, W. M.; Wu, P.; Wang, Q.
F.; Yu, Z. K. Organometallics 2013, 32, 3083−3090. (c) Du, W. M.;
Wang, Q. F.; Yu, Z. K. Chin. J. Catal. 2013, 34, 1373−1377. (d) Jin, W.
W.; Wang, L. D.; Yu, Z. K. Organometallics 2012, 31, 5664−5667.
(
1
e) Ye, W. J.; Zhao, M.; Yu, Z. K. Chem. - Eur. J. 2012, 18, 10843−
0846. (f) Du, W. M.; Wang, L. D.; Wu, P.; Yu, Z. K. Chem. - Eur. J.
2
012, 18, 11550−11554. (g) Zhao, M.; Yu, Z. K.; Yan, S. G.; Li, Y.
Tetrahedron Lett. 2009, 50, 4624−4628. (h) Zeng, F. L.; Yu, Z. K.
Organometallics 2008, 27, 6025−6028. (i) Zeng, F. L.; Yu, Z. K.
Organometallics 2008, 27, 2898−2901.
(
11) (a) Deng, H. X.; Yu, Z. K.; Dong, J. H.; Wu, S. Z.
Organometallics 2005, 24, 4110−4112. (b) Sun, X. J.; Yu, Z. K.; Wu,
S. Z.; Xiao, W. J. Organometallics 2005, 24, 2959−2963.
(
12) (a) Cheeseman, G. W. H. J. Chem. Soc. 1962, 1170−1176.
(
b) Arnold, F. E. J. Polym. Sci., Part A-1: Polym. Chem. 1970, 8, 2079−
089.
13) Kleineweischede, A.; Mattay, J. Eur. J. Org. Chem. 2006, 2006,
2
(
9
(
(
47−957.
14) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165−195.
15) (a) Perry, R. H.; Brownell, K. R.; Chingin, K.; Cahill, T. J., III;
Waymouth, R. M.; Zare, R. N. Proc. Natl. Acad. Sci. U. S. A. 2012, 109,
dez, F. E.; Puerta, M. C.; Valerga, P.
2
246−2250. (b) Fernan
́
Organometallics 2012, 31, 6868−6879. (c) Casey, C. P.; Clark, T. B.;
Guzei, I. A. J. Am. Chem. Soc. 2007, 129, 11821−11827.
(
2
́
16) (a) Comas-Vives, A.; Ujaque, G.; Lledos, A. Organometallics
007, 26, 4135−4144. (b) Bosson, J.; Poater, A.; Cavallo, L.; Nolan, S.
́
P. J. Am. Chem. Soc. 2010, 132, 13146−13149. (c) Pablo, O.; Guijarro,
D.; Kovacs, G.; Lledos, A.; Ujaque, G.; Yus, M. Chem. - Eur. J. 2012,
8, 1969−1983. (d) Casey, C. P.; Clark, T. B.; Guzei, I. A. J. Am.
́
́
1
Chem. Soc. 2007, 129, 11821−11823. (e) Enthaler, S.; Hagemann, B.;
Bhor, S.; Anilkumar, G.; Tse, M. K.; Bitterlich, B.; Junge, K.; Erre, G.;
Beller, M. Adv. Synth. Catal. 2007, 349, 853−860.
G
DOI: 10.1021/acs.organomet.5b00727
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