Construction of pincer-type symmetrical ruthenium(II) complexes bearing pyridyl-2,6-pyrazolyl arms: Catalytic behavior in transfer hydrogenation of ketones

Article abstract of DOI:10.1039/c4ra07524b

Convenient synthesis of four new distorted octahedral ruthenium(II) complexes (1, 2, 3, 4) having general molecular formula [RuCl₂LPAr₃] (L = pyridine-based tridentate ligands not containing N-H bonds) is described. Their composition and structure were determined by elemental analysis and NMR spectra, and complexes 2 and 4 were also identified by X-ray single-crystal diffraction. All ruthenium(II) complexes exhibited good to excellent catalytic activity in the transfer hydrogenation of ketones. Among them, complex 4 achieved the highest final TOF value of 51600 h^-1 for a high molar ratio of substrate to catalyst (2000:1).

Full text of DOI:10.1039/c4ra07524b

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A graphical and textual abstract for the contents pages
Four new ruthenium(II) complexes (1, 2, 3, 4) exhibited good to excellent catalytic activity, under the high
substrate to catalyst ratio (2000:1).

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Journal Name
RSCPublishing
ARTICLE
Construction of Pincer-Type symmetrical
Ruthenium(II) complexes bearing a Pyridyl-2,6-
Pyrazolyl Arms: Catalytic Behavior in Transfer
Hydrogenation of Ketones
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012,
Accepted 00th January 2012
Zhu Zhu, Jie Zhang, Haiyan Fu, Maolin Yuan, Xueli Zheng, Hua Chen, and
Ruixiang Li*
DOI: 10.1039/x0xx00000x
www.rsc.org/
Convenient synthesis of four new distorted octahedral ruthenium(II) complexes (
having general molecular formula [RuCl2 PAr3] ( = pyridineꢀbased tridentate ligands not
containing NꢀH bond) has been described. Their composition and structure have been
determined by elemental analysis and NMR spectra, and complexes were also identified
by Xꢀray single crystal diffraction. All ruthenium(II) complexes exhibited good to excellent
1, 2, 3, 4)
L
L
2, 4
catalytic activity in the transfer hydrogenation of ketones. Among them, complex
4 achieved
the highest final TOF value of 51600 hꢀ1 under the high molar ration of substrate to catalyst
(2000:1).
There be recently reported highly active ruthenium(II) NNN
phosphine complex16 for transfer hydrogenation of ketones. An
Introduction
Catalytic transfer hydrogenation of unsaturated organic
compounds has become reliable synthetic protocols beyond
conventional reduction reactions,1 not only because it meets the
increasing demand for clean and environmentally benign
processes in chemistry, but it is also considered relatively low
cost and easy operation. More recently, there is rapid growth in
the various transition metal complexes like cobalt,2 nickel,3
palladium,4a iron,4bꢀ4c rhodium,5a iridium5bꢀ5d employed for the
transfer hydrogenation of ketones, and particular attention has
been devoted to rutheniumꢀbased6 complexes.
acceleration effect is shown by the NꢀH functionality in the
pyrazolyl arms. However, several symmetrical and
unsymmetrical Ru(II) catalysts featuring no NꢀH functionality
have also been documented for TH of ketones: complex (A),17a
(B),17b (C),17c (D)17d (Scheme 1). Among both of unsymmetrical
Ru(II) complexes, (C) exhibited poor catalytic activity in the
presence of 0.3 mol% catalyst with final TOF values of 1960 hꢀ
1 and (D) reached 5940 hꢀ1 at S:C/200:1. Symmetrical (A) (6000
hꢀ1) exhibited higher reactive activity than (B) (1080 hꢀ1) under
the substrate to catalyst ratio (200:1).
In the meanwhile, varying levels of catalytic efficiency were
observed for this transformation in the presence of ruthenium
complexes containing Schiff base,7 tripodal phosphine
[MeC(CH2PPh2)3],8 arene,9
N
ꢀheterocyclic carbene,10 amineꢀ
based ligands,11 and pincer ligands.12 In particular, pincer type
tridentate pyridineꢀbased framework (L1ꢀPyꢀL2) has recently
been proven to be the convenient and attractive ligands because
of their tunable properties and potential application. Thus,
much effort has been devoted to the preparation of tridentate
pyridineꢀbased analogues PNP,13 PNN14 and CNN.15
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NMR spectra of compound
and ꢀCH2 of pyrazolyl, due to the coordination of L1 with
ruthenium metal, have a slight shift compared to that of L1
: δ ( ꢀNCH3) = 4.17, 4.16, 4.19 ppm, δ(ꢀCH2) = 6.85, 6.84,
1, 2 and 3, the resonances of ꢀNCH3
Scheme 1. Ru(II) complexes (A), (B), (C), and (D)
Previously, our research group had reported the synthesis of
symmetrical pincer type tridentate pyridineꢀbridged framework
NNN ligands, not incorporating NH group (Scheme 2).18a
Based on this result, we intend to synthesize symmetrical
ruthenium(II) complexes featuring no NꢀH functionality which
can catalyze the hydrogenation of ketones in the low catalyst
loading (Scheme 3).
[ 1ꢀ
3
6.86 ppm; L1: δ ( ꢀNCH3) = 3.98 ppm, δ(ꢀCH2) = 7.14 ppm ].
Similarly, there is the same phenomenon in the 1H NMR
spectra of compound
By slow diffusion of diethyl ether into a CH2Cl2 solution of
complexes, single crystals of and were obtained (Figure 1,
2). Attempts to obtain the single crystals of and were not
successful. The crystal structures of and were consistent
4.
2
4
1
3
2
4
with the results of NMR and elemental analysis (See Electronic
Supplementary Information).
The perspective view of
2 is shown in Figure 1, a distorted
octahedral geometry around the ruthenium center was observed,
with the two cis Cl atoms and the phosphorus located in the
apical position. The bond angles of Cl(1)ꢀRuꢀCl(2), PꢀRuꢀCl(1),
PꢀRuꢀN(3) and N(3)ꢀRuꢀCl(2) are 87.55(3)o, 87.15(3)o,
94.31(9)o and 91.00(9)o and the bond lengths of RuꢀCl(1), Ruꢀ
Cl(2), RuꢀP, RuꢀN(2), RuꢀN(3), RuꢀN(4) are 2.4558 Å, 2.4681
Å, 2.2958 Å, 2.117 Å, 1.989 Å, 2.081 Å.
Scheme 2. Ligands L1 and L2
The structural assignment of
4 is similar to complex 2
(Figure 2): The bond angles of Cl(1)ꢀRuꢀCl(2), PꢀRuꢀCl(2), Pꢀ
RuꢀN(1) and N(1)ꢀRuꢀCl(1) are 87.72(6)o, 93.19(6)o, 93.88(16)o
and 85.18(16)o respectively. The bond angle of P1ꢀRu1ꢀCl1
[178.28(6)o] is obviously larger than that [171.77(4)o] of P1ꢀ
Ru1ꢀCl2 in compound 2. The RuꢀCl(1) (2.4646 Å) bond length
is longer than RuꢀCl(2) (2.4550 Å), maybe because the
phosphine ligand is in the transꢀposition of Cl(1). The average
bond length (2.063 Å) of RuꢀN is little longer than that (2.028
Å) [RuCl2(PPh3)(Me4BPPy)] (A)17a and (2.053 Å) as the
reported analogous complex [RuCl2(PPh3)(NNN)](NNN:
tridentate dipyrazolpyridines).19
Scheme 3. Ru(II) complexes 1, 2, 3 and 4
Results and discussion
Preparation and Characterization of Ru(II) complexes 1-4
Reacting L1 or L2 with an equivalent amount of RuCl3·3H2O,
PAr3 (1 equiv) and triethylamine (1 mL) in ethanol afforded the
ruthenium compound
1ꢀ4 in red solid state by the similar means
of literature procedure (Scheme 4)18b
.
Figure 1. The molecular structure of complex 2. Selected
bond lengths [Å]: Ru1ꢀCl1 = 2.4558(9), Ru1ꢀCl2 = 2.4681(10),
Ru1ꢀP1 = 2.2958(11), Ru1ꢀN2 = 2.117(3), Ru1ꢀN3 = 1.989(3),
Ru1ꢀN4 = 2.081(3); angles [o]: Cl1ꢀRu1ꢀCl2 = 87.55(3), P1ꢀ
Ru1ꢀCl1 = 87.15(3), P1ꢀRu1ꢀCl2 = 171.77(4), N3ꢀRu1ꢀCl1 =
178.53(10), N3ꢀRu1ꢀP1 = 94.31(9), N4ꢀRu1ꢀN2 = 153.96(12),
N3ꢀRu1ꢀCl2 = 91.00(9).
Scheme 4. Preparation of compound 1ꢀ4
These target ruthenium complexes
1H NMR, 13C NMR, 31P NMR or elemental analysis (see
Supporting Information). The 31P NMR of
showed a singlet
1ꢀ4 were characterized by
1ꢀ4
1
at δ = 39.9, 43.9, 45.8 and 44.1 ppm respectively. In the H
2 | J. Name., 2012, 00, 1-3
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was detected in the absence of base, indicating presence of a
base is essential for the reaction to proceed efficiently (Table 2,
entry 10). Strong bases showed a better promotional role than
the weak ones (Table 2, entries 1ꢀ9). KOH was selected as the
reaction promoter although
worked well in reaction.
iPrOK, iPrONa, iPrOLi also
Table 2. Optimizing condition of base for TH of ketonesa.
Conv. (%)b
Entry
Base
10 min
61
76
75
75
85
67
35
56
ꢀꢀ
60 min
87
88
89
89
90
83
50
76
ꢀꢀ
120 min
88
240 min
90
1
2
tBuOK
iPrOK
iPrONa
iPrOLi
KOH
Figure 2. The molecular structure of complex 4. Selected
90
91
bond lengths [Å]: Ru1ꢀCl1 = 2.4646(17), Ru1ꢀCl2 = 2.4550(17),
Ru1ꢀP1 = 2.2760(17), Ru1ꢀN1 = 1.999(5), Ru1ꢀN2 = 2.106(5),
Ru1ꢀN4 = 2.085(5); angles [o]: Cl1ꢀRu1ꢀCl2 = 87.72(6), P1ꢀ
Ru1ꢀCl1 = 178.28(6), P1ꢀRu1ꢀCl2 = 93.19(6), N1ꢀRu1ꢀCl2 =
172.87(16), N1ꢀRu1ꢀP1 = 93.88(16), N4ꢀRu1ꢀN2 = 154.9 (2),
N1ꢀRu1ꢀCl1 = 85.18(16).
3
90
90
4
90
91
Hydrogenation of ketones catalyzed by complexes 1-4
5
90
91
Complexes
1ꢀ4, were employed as the catalysts for transfer
hydrogenation of acetophenone in low catalyst loading of 0.1
mol%, full details of which are provided in Table 1. From the
6
K3PO4
K2CO3
NaHCO3
CH3COOK
ꢀꢀ
84
85
entries 1ꢀ3 in Table 1, it can be seen that the catalyst
containing triphenylphosphine is a judicious choice for this
transformation. Over period of h, conversion of
2
7
58
68
a
1
acetophenone was reached 64%, 82%, and 59% respectively,
revealing in an order of the catalytic activity for TH of ketones:
8
80
85
2
>
1
>
3
, under the precise control of tridentate NNN ligand’s
electronic and geometric properties. Compared with the L1
ligand, complex bearing L2 ligand was also applied in the
4
9
ꢀꢀ
ꢀꢀ
catalytic system for the TH reaction of ketones and it exhibited
the highest catalytic activity under the same conditions (Table 1,
10
ꢀꢀ
ꢀꢀ
ꢀꢀ
ꢀꢀ
entries 4 vs 2). So complex
following investigation.
4 was chosen as the catalyst in the
Table 1. Screening the catalytic activity of various complexesa
a Reaction conditions: acetophenone (3.2 mmol), catalyst 4 (0.1
mol%) and base (2 mol%) dissolved in
determined by GC.
iPrOH 4 mL. b Conversion
After attempts to scope optimizing control of reaction
condition, we found the transformation was smoothly
performed in the presence of KOH with the substrate to catalyst
Conv. (%)b
Catal
Entry
1
Base
ratio (2000:1), using
iPrOH as hydrogen source. Next, the
yst
10 min 60 min 120 min 240 min
complex catalytic behavior has been explored with arylꢀ
4
iPrOK
43
64
69
75
1
substituted acetophenone derivatives and additional ketones as
substrates (Table 3).
2
3
4
iPrOK
iPrOK
iPrOK
55
18
76
82
59
88
89
76
90
90
80
91
2
3
4
a
Table 3. Transfer hydrogenation of various ketonesa
Reaction conditions: acetophenone (3.2 mmol), catalysts 1-4 (0.1
b
mol%) and base (2 mol%) dissolved in
determined by GC.
iPrOH 4 mL. Conversion
After examining the effects of various bases in the presence
of catalyst , we found only a trace amount of desired product
4
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VJieowuArrtnicalelONnlainme e
DOI: 10.1039/C4RA07524B
21
Entry
1
Ketones
Time(min)
10
Conv.(%)b
97(73)
TOF(hꢀ1)c
60
90(30)
18000
43800
30000
49800
49200
a Reaction conditions: acetophenone (3.2 mmol), catalyst 4 (0.05 mol%) ,
KOH (2.0 mol%), iPrOH 4 mL.
b Conversion determined by GC. Data in parentheses are the GC yields
after 2 min.
c TOF in 2 min.
d 0.1 mol % 4 was used.
e 0.2 mol % 4 was used.
O
2
30
5
98(50)
98(83)
96(82)
Cl
3
4
As seen in Table 3, most of the substrates could be converted
in good to excellent yields (≥ 90 %) and TOF value of 12000ꢀ
51600 hꢀ1 as initial reaction. Favorable yields were expected for
the relatively weaker electronꢀdeficient substrates (Table 3,
entries 2ꢀ6, 14) as the strong electron withdrawing group CF3 in
the substrate reduced the electron density in the ketone group
and deteriorated the catalytic efficiency (Table 3, entry 15). It
should be noted that the electronꢀdonating substituents, that is,
methyl and methoxyl, made the ketone substrates more
electronꢀrich and thus reacted less efficiently than their
analogues bearing electronꢀdeficient moiety (Table 3, entries 3
vs 8, 11 and 4, 6 vs 9, 12 and 2, 5 vs 10) except 2’ꢀ
chloroacetophenone (Table 3, entry 7).
5
5
6
60
10
10
96(40)
94(76)
98(86)
24000
45600
51600
7
As anticipated, increasing the steric hindrance of substrates
retarded the reaction. But attempt to prolong reaction time or
enlarge catalyst loading, it provided satisfactory yields (Table 3,
entries 16ꢀ19). Surprisingly, although acetophenone bearing an
orthoꢀCl, Br substituent reacted slower than those bearing meta
or para substituents, a contradictory result was observed for the
orthoꢀmethyl, methoxyl substrates (Table 3, entries 2 vs 3, 4
and 5 vs 6 and 7 vs 8, 9 and 10 vs 11, 12).
8
900
30
93d(35)
91(76)
10500
45600
9
O
10
60
92(27)
93(28)
16200
16800
OCH3
According to the related reported literature16bꢀ16d, 20 , we were
encouraged to propose the plausible mechanism in Scheme 5,
11
12
120
even though the RuꢀH active species of complex
isolated successfully. Ru(II) species (E) forms Ru(II)ꢀalkoxide
(F) under the presence of KOH and PrOH, then the subsequent
ꢀH elimination from (F) generates Ru(II)ꢀH intermediate (G)
4 was not
i
β
900
71d(18)
5400
with release of acetone. Coordination to the metal center and
insertion to the RuꢀH bond in (G) by the carbonyl of a ketone
substrate yields Ru(II)ꢀalkoxide (I), which undergoes alcohol
metathesis to give the desired product and complete the
catalytic cycle.
13
14
60
30
92(38)
98(42)
22800
25200
KOH
OH
N
R1
R2
Cl
N
PAr3
N
N
N
N
R1
R2
N
N
Ru
15
N
N
(E)
Ru
Ar3P
Cl
120
97d(48)
14400
O
(F)
Cl
O
OH
R3
R4
16
17
iPrOH
30
93(61)
36600
4050
N
PAr3
N
R1
R2
R1
R2
PAr3
N
N
N
N
N
N
N
N
53e(27)
Ru
Ru
1200
(G)
(I)
Cl
Cl
H
O
R3
O
R4
18
R3
R4
120
90(26)
15600
N
PAr3
R1
R2
19
20
N
N
N
N
30
60
99(63)
92(46)
37800
27600
Ru
(H)
Cl
H
O
R4
R3
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MHz, CDCl3, 25 oC, ppm):
δ 39.9. Anal. Calcd for
Scheme 5. The plausible catalytic cycle
C46H42Cl2N5O3PRu (915.14): C, 60.33; H, 4.62; N, 7.65.
Found: C, 60.36; H, 4.58; N, 7.62. HRMS (ESI) m/z: Calcd for
C46H42Cl2N5O3PRuNa [M+Na]+: 938.1344. found: 938.1338.
C46H42Cl2N5O3PRu (915.1446).
Experimental Section
1
Complex 2: red solid (308 mg, 68%). H NMR (400 MHz,
General considerations
o
CD2Cl2, TMS, 25 C, ppm): δ 7.54 (d, 3J(H,H) = 6.6 Hz, 3H,
phenyl), 7.50 (d, 3J(H,H) = 3.9 Hz, 3H, 4ꢀpyridyl, phenyl), 7.48
(s, 1H, phenyl), 7.45–7.41 (m, 6H, phenyl), 7.30 (d, 3J(H,H) =
7.6 Hz, 4H, phenyl), 7.23 (d, 3J(H,H) = 7.3 Hz, 2H, 3,5ꢀ
pyridyl), 7.17 (dd, 3J(H,H) = 7.5, 3.3 Hz, 9H, phenyl), 6.84 (s,
2H, pyrazolyl), 4.16 (s, 6H, NCH3). 13C NMR (101 MHz,
CDCl3, TMS, 25 oC, ppm): δ 155.7 (pyridyl C), 152.1
(pyrazolyl C), 147.6 (pyridyl CH), 137.9 (phenyl C), 133.9
(pyrazolyl C), 133.3 (phenyl CH), 132.0 (phenyl CH), 129.3
(phenyl C), 128.9 (phenyl CH), 128.2 (phenyl CH), 127.5
(phenyl CH), 125.3 (pyridyl CH), 116.9(phenyl CH), 104.8
(pyrazolyl CH), 39.7 (s, NCH3). 31P NMR (162 MHz, CDCl3,
25 oC, ppm): δ 43.9. Anal. Calcd for C43H36Cl2N5PRu (825.11):
C, 62.55; H, 4.39; N, 8.48. found: C, 62.47; H, 4.35; N 8.41.
HRMS (ESI) m/z: Calcd for C43H36Cl2N5PRuNa [M+Na]+:
848.1027. found: 848.1021. C43H36Cl2N5PRu (825.1129).
Unless otherwise noted, all the starting materials were
purchased from commercial sources and used as received. The
solvents were dried with the standard procedures prior to use.
All the preparation and purification of airꢀ and/or moistureꢀ
sensitive compounds were carried out under a nitrogen
atmosphere using the standard Schlenk techniques. Ligands L1
and L2 were prepared by means of literature procedure.18a 1
H
NMR, 13C NMR and 31P NMR spectra were recorded using a
Bruker Advance IIꢀ400 MHz spectrometer. The chemical shifts
of 31P{1H} NMR were relative to 85% H3PO4 as external
1
standard, and H NMR relative to TMS as internal standard.
Elemental analysis was carried out on an Italy CARLO ERBA
1106 Elemental analyzer. Mass Spectra (MS) was performed on
an Agilent LCMSꢀITꢀTOF Premier mass spectrometer. Single
crystals of
2 and 4 were measured on a Xcalibur, Eos
diffractometer using graphite monochromated Mo Kα radiation
(λ = 0.7107 Å) at 142.95(10) K and 140.00(10) K, respectively.
Using Olex2, the structure was solved with the Superflip
structure solution program using Charge Flipping and refined
with the ShelXL-2012 refinement package using Least Squares
1
Complex 3: red solid (413 mg, 73%). H NMR (400 MHz,
o
CD2Cl2, TMS, 25 C, ppm): δ 7.54 (d, 3J(H,H) = 6.6 Hz, 2H,
minimisation. The chromatographic analyses (GC) were phenyl), 7.50 (dd, 3J(H,H) = 14.1, 8.7 Hz, 5H, 4ꢀpyridyl,
phenyl), 7.46 (d, 3J(H,H) = 7.3 Hz, 6H, phenyl), 7.43 (t,
3J(H,H) = 8.7 Hz, 6H, phenyl), 7.37 (d, 3J(H,H) = 6.7 Hz, 4H,
performed with an
GC Agilent 6890N instrument equipped with an FID detector
and ECꢀ WAX capillary column (30 m×0.25 mm, 0.25 ꢁm film)
phenyl), 7.32 (d, 3J(H,H) = 7.8 Hz, 2H, 3,5ꢀpyridyl), 6.86 (s,
was used to detect the reaction products.
2H, pyrazolyl), 4.19 (s, 6H, NCH3). 13C NMR (101 MHz,
CDCl3, TMS, 25 oC, ppm): δ 155.3 (pyridyl C), 151.9
Synthesis of Ru(II) complexes 1-4
(pyrazolyl C), 148.6 (pyridyl CH), 137.7 (pyrazoly C), 137.3
Under nitrogen atmosphere, a mixture of RuCl3·3H2O (143 mg,
(phenyl C), 133.4 (phenyl CH), 132.8 (phenyl CH), 131.7
0.55 mmol) and L1 or L2 (215/146 mg, 0.55 mmol) in EtOH
(phenyl C), 131.4 (phenyl C), 129.7 (phenyl CH), 129.1
(phenyl CH), 128.7 (phenyl CH), 124.7 (s, CF3), 117.3 (pyridy
(30 mL) was refluxed for 5 h. The color of the solution changed
from black brown to redꢀbrown slowly and further generated
the redꢀbrown precipitates. After being cooled to room CH), 105.1 (pyrazolyl CH), 39.9 (s, NCH3); 31P NMR (162
temperature, the precipitates were filtered, washed with EtOH
MHz, CDCl3, 25 oC, ppm):
δ 45.8. Anal. Calcd for
and Et2O, and dried under vacuum. Without purification, this
compound was slurried in the EtOH solution (15 mL) of
MOTPP/TPP/TFTPP (194/144/256 mg, 0.55 mmol) and was
treated with excess Et3N (1 mL). The solid substance slowly
dissolved and the colour of the solution changed to redꢀorange.
After refluxed 6 h, the redꢀorange solution was cooled to room
temperature and the solvent was removed under vacuum to give
a solid red substance.
C46H33Cl2N5F9PRu (1029.08): C, 53.65; H, 3.23; N, 6.80.
found: C, 53.89; H, 3.29; N 6.81. HRMS (ESI) m/z: Calcd for
C46H33Cl2N5F9PRuNa [M+Na]+: 1052.0648. found: 1052.0641.
C46H33Cl2N5F9PRu (1029.0750).
1
Complex 4: red solid (246 mg, 64%). H NMR (400 MHz,
o
CD2Cl2, TMS, 25 C, ppm): δ 7.36 (t, 3J(H,H) = 7.8 Hz, 1H, 4ꢀ
pyridyl), 7.26–7.22 (m, 3H, phenyl), 7.17 (d, 3J(H,H) = 7.8 Hz,
2H, 3,5ꢀpyridyl), 7.09 (dd, 3J(H,H) = 7.9, 2.8 Hz 12H, phenyl),
6.55 (s, 2H, pyrazolyl), 4.01 (s, 6H, NCH3), 2.33 (s, 6H, CCH3).
13C NMR (101 MHz, CDCl3, TMS, 25 oC, ppm): δ 155.9
(pyridyl C), 151.2 (pyrazolyl C), 142.4 (pyridyl CH), 134.2
(pyrazolyl C), 133.4 (phenyl C), 131.9 (phenyl CH), 128.8
(phenyl CH), 127.4 (phenyl CH), 116.3 (pyridy CH), 104.5
(pyrazolyl CH), 37.3 (s, NCH3), 12.3 (s, CH3). 31P NMR (162
1
Complex 1: red solid (306 mg, 61%). H NMR (400 MHz,
o
CD2Cl2, TMS, 25 C, ppm): δ 7.53 (t, 3J(H,H) = 7.2 Hz, 4H,
phenyl), 7.48 (dd, 3J(H,H) = 11.3, 7.4 Hz, 3H, 4ꢀpyridyl,
phenyl), 7.44 (d, 3J(H,H) = 7.1 Hz, 4H, phenyl), 7.33 (d,
3J(H,H) = 7.8 Hz, 2H, 3,5ꢀpyridyl), 7.07 (t, 3J(H,H) = 9.0 Hz,
6H, phenyl), 6.85 (s, 2H, pyrazolyl), 6.67 (d, 3J(H,H) = 8.0 Hz,
6H, phenyl), 4.17 (s, 6H, NCH3), 3.75 (s, 9H, OCH3). 13C NMR
o
MHz, CDCl3, 25 oC, ppm):
δ 44.1. Anal. Calcd for
(101 MHz, CDCl3, TMS, 25 C, ppm): δ 160.0 (phenyl C),
155.9 (pyridyl C), 152.1 (pyrazolyl C), 147.8 (pyridyl CH),
134.7 (phenyl C), 131.7 (pyrazolyl C), 129.3 (phenyl C), 129.2
(phenyl CH), 128.9 (phenyl CH), 125.7 (phenyl CH), 125.2
(pyridyl CH), 116.7 (phenyl CH), 113.1 (phenyl CH), 104.6
(pyrazolyl CH), 55.2 (s, OCH3), 39.7 (s, NCH3). 31P NMR (162
C33H32Cl2N5PRu (701.08): C, 56.49; H, 4.60; N, 9.98. found: C,
56.38; H, 4.67; N 9.69. HRMS (ESI) m/z: Calcd for
C33H32Cl2N5PRuNa [M+Na]+: 724.0714. found: 724.0709.
C33H32Cl2N5PRu (701.0816).
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 5

Page 7 of 8
ARTICLE
RSC Advances
VJieowuArrtnicalelONnlainme e
DOI: 10.1039/C4RA07524B
Typical procedure for the catalytic transfer hydrogenation
of ketones
Guo, T. W. Graham, M. A. Gullons, K. A. Rashid, Dalton Trans.,
2009, 1407ꢀ1410.
6
(a) O. Dayan, S. Dayan, I. Kani, B. Çetinkaya, Appl. Organometal.
Chem., 2012, 26, 663ꢀ670; (b) T. Marimuthu, H. B. Friedrich,
Under nitrogen atmosphere, ketone (3.2 mmol), catalyst (1.6
ꢁmol) and 2ꢀpropanol (3 mL) were introduced into a Schlenk
tube. The solution was stirred at 82 °C for 10 min. Then 1 mL
of 0.064 mmol KOH 2ꢀpropanol solution was introduced to
initiate the transfer hydrogenation. At the state time, 0.1 mL of
the reaction mixture was sampled and diluted with 1 mL of 2ꢀ
propanol preꢀcooled at ꢀ10oC for immediate for GC analysis.
The conversions are determined by average of two runs of each
catalytic reaction. After the reaction was finished, the mixture
was purified by flash silica gel column chromatography
[petroleum ether (60ꢀ90oC)/EtOAc = 50:1] to afford the
corresponding alcohol product, which was identified by
comparison with the authentic sample through NMR and GC
analysis.
ChemCatChem, 2012,
Wu, Z. K. Yu, Chem. Eur. J., 2012, 18, 11550ꢀ11554; (d) B. Yigit ,
M. Yigit, I. Ozdemir, E. C etinkaya, Transition Met. Chem., 2012,
4, 2090ꢀ2095; (c) W. M. Du, L. D. Wang, P.
¸
37, 297ꢀ302; (e) M. Yoshimura, R. Kamisue, S. Sakaguchi, J.
Organomet. Chem., 2013, 740, 26ꢀ32; (f) M. D. Rebollo, D. C.
Gonzalez, M. Hollering, H. M. Bunz, M. Albrecht, Dalton Trans.,
2014, 43 , 4462ꢀ4473; (g) A. O. Ogweno, S. O. Ojwach, M. P.
Akerman, Dalton Trans., 2014, 43, 1228ꢀ1237.
7
I. Karamé, M. Jahjah, A. Messaoudi, M. L. Tommasino, M. Lemaire,
Tetrahedron Asym., 2004, 15, 1569ꢀ1581.
8
9
B.J. Sarmah, D.K. Dutta, J. Organomet. Chem., 2010, 695, 781ꢀ785.
(a) P. Singh, A. K. Singh, Organometallics, 2010, 29, 6433ꢀ6442; (b)
X. F. Wu, J. L. Xiao, Chem. Commun., 2007, 24, 2449ꢀ2466; c) L.
Gok, H. Turkmen, Tetrahedron, 2013, 69, 10669ꢀ10674.
10 (a) S. Horn, C. Gandolfi, M. Albrecht, Eur. J. Inorg. Chem., 2011, 18
,
Conclusions
2863ꢀ2868; (b) Y. B. Lai, C. S. Lee, W. J. Lin, A. R. Naziruddin, W.
Versatile pincer type tridentate pyridineꢀbridged framework,
not incorporating NH group, and their Ru(II) complexes were
successfully synthesized and characterized. These ruthenium
complexes, featuring no NH functionality, still exhibited very
high catalytic activity in the TH reaction of ketones with a high
substrate to catalyst ratio (2000:1).
S. Hwang, Polyhedron., 2013, 53, 243ꢀ248; (c) M. E. Humphries, W.
H. Pecak, S. A. Hohenboken, S. R. Alvarado, D. C. Swenson, G. J.
Domski, Inorg. Chem. Commun., 2013, 37, 138ꢀ143; (d) F. E.
Fernández, M. C. Puerta, P. Valerga, Organometallics, 2012, 31
,
6868ꢀ6879; (e) J. Witt, A. Pöthig, F. E. Kühn, W. Baratta,
Organometallic, 2013, 32, 4042ꢀ4045; (f) N. Gurbuz, E. O. Ozcan, I.
Ozdemir, B. Cetinkaya, O. Sahin, O. Buyukgungor, Dalton Trans.,
Notes and references
Prof. Ruixiang Li
2012, 41, 2330
–2339.
Key Laboratory of Green Chemistry and Technology, Ministry of 11 (a) M. B. D
í
azꢀValenzuela, S. D. Phillips, M. B. France, M. E. Gunn,
Education, College of Chemistry, Sichuan University, Chengdu, Sichuan
610064, PR China
M. L. Clarke, Chem. Eur. J., 2009, 15, 1227ꢀ1232; (b) W. Baratta, P.
Rigo, Eur. J. Inorg. Chem., 2008, 26, 4041ꢀ4053.
Fax: (+) 86ꢀ28ꢀ85412904;
12 M. Gagliardo, P. A. Chase, S. Brouwer, G. P. M. van Klink, G. van
Koten, Organometallic, 2007, 26, 2219ꢀ2227.
Eꢀmail: liruixiang@scu.edu.cn.
Electronic supplementary information (ESI) available: Details of the
13 (a) L. P. He, T. Chen, D. X. Xue, M. Eddaoudi, K. W. Huang, J.
Xꢀray crystallographic data and refinement of complexes
CCDC reference numbers 999183 and 999184.
See DOI: 10.1039/b000000x/
2 and 4.
Organomet. Chem., 2012, 700
, 202ꢀ206; (b) J. Zhang, M.
Gandelman, L. J. W. Shimon, H. Rozenberg, D. Milstein,
Organometallics, 2004, 23, 4026ꢀ4032; (c) J. Zhang, G. Leitus, Y.
BenꢀDavid, D. Milstein, J. Am. Chem. Soc., 2005, 127, 10840ꢀ
10841.
14 A. D. Zotto, W. Baratta, M. Ballico, E. Herdtweck, P. Rigo,
、
Organometallics, 2007, 26, 5636ꢀ5642.
15 (a) W. Baratta, M. Ballico, G. Esposito, P. Rigo, Chem. Eur. J., 2008,
14, 5588ꢀ5595; (b) W. Baratta, G. Chelucci, S. Gladiali, K. Siega, M.
Toniutti, M. Zanette, E. Zangrando, P. Rigo, Angew. Chem. Int. Ed.,
2005, 44, 6214ꢀ6219.
1
2
3
4
G. E. Dobereiner, R. H. Crabtree, Chem. Rev., 2010, 110, 681ꢀ701.
G. Q. Zhang, S. K. Hanson, Chem. Commun., 2013, 49, 10151ꢀ10153.
K. Shimura, K. Shimizu, Green Chem., 2012, 14, 2983ꢀ2985.
(a) S. Yasar, S. Cekirdek, N. A. Tas, S. Yildirim, I. Ozdemir, Turk J.
Chem., 2013, 37, 292ꢀ298; (b) R. Langer, M. A. Iron, L. Konstantin
ovski, Y. DiskinꢀPosner, G. Leitus, Y. BenꢀDavid and D. Milstein,
Chem. Eur. J., 2012, 18, 7196ꢀ7209; (c) B. A. F. Le Bailly and S. P.
16 (a) W. W. Jin, L. D. Wang, Z. K. Yu, Organometallics, 2012, 31
,
5664ꢀ5667; (b) W. M. Du, P. Wu, Q. F. Wang, Z. K. Yu,
Organometallics, 2013, 32, 3083ꢀ3090; (c) Q. F. Wang, W. M. Du,
T. T. Liu, H. N, Chai, Z. K. Yu, Tetrahedron Lett., 2014, 55, 1585ꢀ
1588; (d) W. M. Du, Q. F.Wang, L. D. Wang, Z. K. Yu,
Organometallics, 2014, 33, 974ꢀ982.
Thomas, RSC Adv. , 2011,
1, 1435ꢀ1445.
5
(a) V. Gierz, A. Urbanaite, A. Seyboldt, D. Kunz, Organometallics
,
17 (a) H. X. Deng, Z. K. Yu, J. H. Dong, S. Z. Wu, Organometallics,
2005, 24, 4110ꢀ4112; (b) Z. K. Yu, F. L. Zeng, X. J. Sun, H. X.
Deng, J. H. Dong, J. Z. Chen, H. M. Wang, C. X. Pei, J. Organomet.
2012, 31, 7532ꢀ7538; (b) Q. Lei,Y.W. Wei, D. Talwar, C. Wang, D.
Xue, and J.L. Xiao, Chem. Eur. J., 2013, 19, 4021ꢀ4029; (c) S. C.
Zinner, C. F. Rentzsch, E. Herdtweck, W. A. Herrmann, F. E. Kuhn,
Dalton Trans., 2009, 7055–7062; (d) X. H. Chen, W. L. Jia, R. W.
Chem., 2007, 692, 2306ꢀ2313; (c) F. L. Zeng, Z. K. Yu,
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

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Journal Name
ARTICLE
DOI: 10.1039/C4RA07524B
Organometallics, 2009, 28, 1855ꢀ1862; (d) M. Zhao, Z. K. Yu, S. G.
Yan, Y. Li, J. Organomet. Chem., 2009, 694, 3068ꢀ3075.
18 (a) Q. Yang, L. Wang, L. Lei, X. L. Zheng, H. Y. Fu, M. L. Yuan, H.
Chen, R. X. Li, Catal. Commun., 2012, 29, 194ꢀ197. (b) W. J. Ye,
M. Zhao, Z. K. Yu, Chem. Eur. J. 2012, 18, 10843ꢀ10846.
19 L. T. Ghoochany, S. Farsadpour, Y. Sun, W. R. Thiel, Eur. J. Inorg.
Chem., 2011, 23, 3431ꢀ3437.
20 ComasꢀVives. A, Ujaque.G, Lledó s. A, Organometallics, 2007, 26
,
4135ꢀ4144.
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