Synthesis of a series of new ruthenium organometallic complexes derived from pyridine-imine ligands and their catalytic activity in oxidation of secondary alcohols

Article abstract of DOI:10.1002/aoc.4750

Reactions of pyridine imines [C₅H₄N-2-C(H)?=?N-C₆H₄-R] [R?=?H (1), CH₃ (2), OMe (3), CF₃ (4), Cl (5), Br (6)] with Ru₃(CO)₁₂ in refluxing toluene gave the corresponding dinuclear ruthenium carbonyl complexes of the type {μ-η²-CH[(2-C₅H₄N)(N-C₆H₄-R)]}₂Ru₂(CO)₄(μ-CO) [R?=?H (7); CH₃ (8); OMe (9); CF₃ (10); Cl (11); Br (12)]. All six novel complexes were separated by chromatography, and fully characterized by elemental analysis, IR, NMR spectroscopy. Molecular structures of 7, 10, 11, and 12 were determined by X-ray crystal diffraction. Further, the catalytic performance of these complexes was also tested. The combination of {μ-η²-CH[(2-C₅H₄N)(N-C₆H₄-R)]}₂Ru₂(CO)₄(μ-CO) and NMO afforded an efficient catalytic system for the oxidation of a variety secondary alcohols.

Full text of DOI:10.1002/aoc.4750

Received: 20 September 2018
DOI: 10.1002/aoc.4750
Revised: 12 November 2018
Accepted: 13 November 2018
F U L L P A P E R
Synthesis of a series of new ruthenium organometallic
complexes derived from pyridine‐imine ligands and their
catalytic activity in oxidation of secondary alcohols
1
1
1
1
2
3
Zhiqiang Hao * | Ying Li * | Chen Li | Ruitao Wu | Zhihong Ma | Suzhen Li |
1
1
1
Zhangang Han | Xuezhong Zheng | Jin Lin
1
National Demonstration Center for
Reactions of pyridine imines [C H N‐2‐C(H) = N‐C H ‐R] [R = H (1), CH (2),
Experimental Chemistry Education,
College of Chemistry & Material Science,
Hebei Normal University, Shijiazhuang
5
4
6
4
3
OMe (3), CF (4), Cl (5), Br (6)] with Ru (CO) in refluxing toluene gave the
3
3
12
2
corresponding dinuclear ruthenium carbonyl complexes of the type {μ‐η ‐
CH[(2‐C N)(N‐C ‐R)]} Ru (CO) (μ‐CO) [R = H (7); CH (8); OMe (9);
050024, China
2
5
H
4
6
H
4
2
2
4
3
School of Pharmacy, Hebei Medical
University, Shijiazhuang 050017, China
CF (10); Cl (11); Br (12)]. All six novel complexes were separated by chroma-
3
3
Hebei College of Industry and
tography, and fully characterized by elemental analysis, IR, NMR spectroscopy.
Molecular structures of 7, 10, 11, and 12 were determined by X‐ray crystal dif-
fraction. Further, the catalytic performance of these complexes was also tested.
Technology, Shijiazhuang 050091, China
Correspondence
2
Jin Lin, College of Chemistry and Material
Science, Hebei Normal University,
Shijiazhuang 050024, China.
Email: linjin64@126.com
The combination of {μ‐η ‐CH[(2‐C H N)(N‐C H ‐R)]} Ru (CO) (μ‐CO) and
5
4
6
4
2
2
4
NMO afforded an efficient catalytic system for the oxidation of a variety sec-
ondary alcohols.
Zhihong Ma, School of Pharmacy, Hebei
Medical University, Shijiazhuang 050017,
China.
KEYWORDS
alcohol oxidation, pyridine‐imine ligand, ruthenium complex, synthesis
Email: mazhihong‐1973@163.com
Funding information
Science Foundation of Hebei Normal Uni-
versity, Grant/Award Numbers: L2017Z02
and L2018B08; National Natural Science
Foundation of China, Grant/Award Num-
ber: 21372061; Education Department
Foundation of Hebei Province, Grant/
Award Number: ZD2018005; Hebei Natural
Science Foundation of China, Grant/Award
Number: B2017205006
1
| INTRODUCTION
and analytical applications, in addition to their important
[
5–12]
roles in catalysis and organic syntheses.
Synthesis of carbonyl compounds via alcohol oxidation is
Schiff bases are one of the most prevalent ancillary
ligands in organometallic chemistry. These materials
which have oxygen and nitrogen donor atoms operate
as good chelating agents for transition metals.
metal complexes have a variety of biological, medicinal
[13]
one of fundamental reactions in organic chemistry. Alco-
hol oxidation reaction is widely investigated in both labora-
tories and industrial applications due to the importance of
its valuable products such as aldehydes and ketones, which
[1–4]
Their
are widely used in dyestuff, polymer precursors, pharmaceu-
*
[14]
These authors contributed equally to this work.
tical and agrochemical industries.
Conventionally, most
Appl Organometal Chem. 2018;e4750.
wileyonlinelibrary.com/journal/aoc
© 2018 John Wiley & Sons, Ltd.
1 of 9
https://doi.org/10.1002/aoc.4750

2
of 9
HAO ET AL.
2
reactions require stoichiometric amounts oxidation reagents
corresponding complexes {μ‐η ‐CH[(2‐C H N)(N‐C H ‐
5
4
6
4
[15]
[16]
such as dichromate or permanganate used in the liq-
uid phase. These oxidations are often toxic and harmful to
the environment, removal of traces of these reagents from
the reaction mixture is costly and difficult. In recent years,
considerable efforts have been devoted to the development
R)]} Ru (CO) (μ‐CO) [R = H (7); CH (8); OMe (9); CF
(10); Cl (11); Br (12)] were obtained in 40–77% yields
(Scheme 1).
The IR spectra of 7~12 all exhibited two strong termi-
nal carbonyl absorption at 2000 cm and a bridging car-
2
2
4
3
3
−
1
[17–23]
−1
1
of alcohol oxidation.
For example, employing O2
bonyl absorption at 1900 cm . The H NMR spectra of
the diruthenium complexes 7~12 are similar, and they
all show four groups of peaks at 7.29~8.71 ppm for the
pyridyl protons and two doublets at 6.38~7.38 ppm for
phenyl protons, plus one singlet for the carbon bridge
protons at 4.54~4.87 ppm. The molecular structures of 7,
10, 11 and 12 are presented in Figures 1–4, respectively
with the selected bond lengths and angles in the captions.
The crystallographic data of these compounds in CIF or
other electronic format see Supporting Information.
Complexes 7, 10, 11 and 12 are carbon bridged
diruthenium complexes, in which the functional group
C=N of two ligands simultaneously coupled to form a
C‐C bridged ligand. These complexes all contain a Ru
(CO) (μ‐CO) Ru (CO) unit, coordinated with the ligand.
would be highly desirable to avoid toxic and hazardous stoi-
chiometric oxidants. For this reason, several studies have
focused on utilizing molecular oxygen as oxidant in aerobic
[24]
oxidation reactions But due to the poor oxidation perfor-
mance of O itself, the reaction time was more than 20 hr
2
(even up to 48 hr) and the strong base and TEMPO were also
needed as additives to achieve high conversion or yield.
Therefore, the development of more efficient alcohol oxida-
tion system is still an important research area.
Alternatively, stable nitroxyl radicals, expecially N‐
methylmorpholine‐N‐oxide (NMO), have been used as oxi-
dant for mild and selective oxidation of alcohols to alde-
[25]
hydes, ketones.
reported a series of Ru (II) complexes, [RuCl(L)(CO)
PPh ) ] {where L = N‐[di (alkyl/aryl)carbamothioyl]
In 2011, karvembu and co‐workers
2
2
(
The Ru(1) and Ru(2) are coordinated with two nitrogen
atoms in the chain bridge, an intramolecular nitrogen
atom of the pyridyl, two terminal CO and a bridging
CO. Bridged ligands are simultaneously coordinated to
3
2
benzamide derivatives}, which could oxidize a wide variety
of alcohols to corresponding aldehydes or ketones in high
[26]
yields in the presence of NMO.
Recently, Mondal et al.
showed cis‐(CO)‐trans‐(X)‐[Ru (CO) (HL)X ] (where
two ruthenium atoms with a μ ‐N atom behaving as a
2
2
2
X = Cl and I)‐NMO to be an efficient catalytic system in
three‐electron donor. The Ru‐Ru bond distances are
2.8558(11) Å for 7, 2.8580(5) Å for 10, 2.8676(5) Å for 11
and 2.8659(9) Å for 12, respectively. Disorder on the loca-
[27]
alcohol oxidation.
Inspired by these studies and based
our continuing efforts in creating novel ruthenium organo-
metallic complexes, herein, we report the synthesis, charac-
terization, and oxidation of secondary alcohols catalyzed by
ruthenium pyridine‐imine based complexes in the presence
of N‐methylmorpholine‐N‐oxide as oxidant.
tion of CF has been shown in Figure 2. These complexes
3
are unexpected products and the structures are unusual.
[28,29]
On the basis of our previous research results,
we
believe that the reaction pathway may undergo a process
of carbon radical generation and coupling. A proposed
mechanism for the formation of these complexes is pro-
posed in Scheme 2. First, the N atom on pyridine coordi-
nates to the Ru atom forming N‐Ru coordinate bond.
Then the single electron of Ru atom and N atom of Schiff
base generates N‐Ru covalent bond. At the same time, the
C=N double bond of Schiff base occurs homolytic reac-
tion, formation of a single electron on C atom and N
atom, while another ligand has the same reaction, the
final coupling of C atom and C atom to form C‐C cova-
lent bond, while the two N atom with another Ru atom
generates N‐Ru coordination bond respectively.
2
2
| RESULTS AND DISCUSSION
.1 | Reactions of pyridine‐imine ligands
[
C H N‐2‐C(H) = N‐C H ‐R] [R = H (1); CH
5
4
6
4
3
(
2); OMe (3); CF (4); Cl (5); Br (6)] with
3
Ru (CO) in toluene
3
12
When pyridine‐imines [C H N‐2‐C(H) = N‐C H ‐R]
5
4
6
4
[
R = H (1); CH (2); OMe (3); CF (4); Cl (5); Br (6)] were
3 3
reacted with Ru (CO) in refluxing toluene for 8 hr, the
3
12
SCHEME 1 Synthesis of the complexes
7–12

HAO ET AL.
3 of 9
FIGURE 1 ORTEP view of cluster 7 showing 10% ellipsoids.
Hydrogen atoms have been omitted for clarity. Selected bond
lengths (Å) and angles (°): Ru(1)‐Ru(2) 2.8558(11), Ru(1)‐N(1)
FIGURE 3 ORTEP view of cluster 11 showing 10% ellipsoids.
Hydrogen atoms have been omitted for clarity. Selected bond
lengths (Å) and angles (°): Ru(1)‐Ru(1i) 2.8676(5), Ru(1)‐N(1)
2.248(3), Ru(1)‐N(2) 2.171(3), Ru(1)‐C(15) 2.032(4), N(2)‐Ru(1)‐N(1)
79.01(10), N(2i)‐Ru(1)‐N(1) 87.07(10), N(2)‐Ru(1)‐N(2i) 69.36(12),
N(1)‐Ru(1)‐Ru(1i) 119.16(7), Ru(1i)‐C(15)‐Ru(1) 89.7(2)
2
.257(5), Ru(1)‐N(2) 2.186(5), N(2)‐Ru(1)‐N(1) 77.95(18), N(4)‐
Ru(1)‐N(1) 87.31(16), N(4)‐Ru(1)‐Ru(2) 49.26(12), Ru(1)‐C(25)‐
Ru(2) 89.8(2), N(4)‐Ru(2)‐N(3) 77.3(2), N(2)‐Ru(2)‐N(3) 87.32(17)
FIGURE 2 ORTEP view of cluster 10 showing 10% ellipsoids.
Hydrogen atoms have been omitted for clarity. Selected bond
lengths (Å) and angles (°): Ru(1)‐Ru(1i) 2.8580(5), Ru(1)‐N(1)
FIGURE 4 ORTEP view of cluster 12 showing 10% ellipsoids.
Hydrogen atoms have been omitted for clarity. Selected bond
lengths (Å) and angles (°): Ru(1)‐Ru(1i) 2.8659(9), Ru(1)‐N(1)
2.245(5), Ru(1)‐N(2) 2.165(5), Ru(1)‐C(13) 2.049(8). N(2)‐Ru(1)‐N(1)
78.61(19), N(2i)‐Ru(1)‐N(1) 86.97(18), N(1)‐Ru(1)‐Ru(1i) 118.81(13),
Ru(1)‐N(2)‐Ru(1i) 81.07(17), Ru(1i)‐C(13)‐Ru(1) 88.7(4)
2
.260(3), Ru(1)‐N(2) 2.181(2), Ru(1)‐C(14) 2.026(3), N(2)‐Ru(1)‐N(1)
7.98(10), N(1)‐Ru(1)‐Ru(1i) 119.11(7), O(1)‐C(14)‐Ru(1) 135.14(10),
7
Ru(1)‐N(2)‐Ru(1i) 80.67(8), Ru(1)‐C(14)‐Ru(i) 89.72(19)
2.2 | Catalytic oxidation
stirred with 3.0 mmol H O in 6 mL CH Cl at 40 °C
2 2 2 2
under argon. As shown in Table 1, the reaction only gave
the acetophenone product in 13% yield (entry 1). A search
for more oxidants and solvents was pursued. Subse-
quently, TEMPO as co‐oxidant has been examined, the
desired product was obtained in 32% yield by simply
replacing H O with TEMPO (entry 2). Eventually, the
To develop an optimal catalytic system, the oxidation of
‐phenylethanol was chosen as a model reaction
Scheme 3) and the results are summarized in Table 1.
Our investigation began with complex 7 as a precatalyst
under the condition that 1.0 mmol 1‐phenylethanol was
1
(
2
2

4
of 9
HAO ET AL.
are the optimal reaction conditions for the oxidation of
aromatic alcohols.
Under the optimal reaction conditions, all six of ruthe-
nium complexes proved to be capable of catalyzing oxida-
tion of alcohols. A variety of secondary alcohols smoothly
underwent the oxidation. The yields% was found to vary
with the different catalysts, the catalytic results of com-
plexes 7–12 are shown in Table 2. Generally, the present
reactions were compatible with various groups, e.g. alk-
oxy, bromo, chloro and trifluoromethyl groups (Table 2,
entries 2–5). The 1‐phenylethanol with methoxy substitu-
ent was excellent substrate (Table 2, entry 2). When the 1‐
phenylethanols with electron withdrawing substituents
were employed as the substrates, all the oxidation reac-
tions proceeded smoothly with excellent yields (Table 2,
entries 3–6). Cyclohexanol and 2‐hexanol were all excel-
lent substrates (Table 2, entries 7 and 8). The reaction of
cyclohexanol gave the targeted product in 82–97% yield,
while the reaction of 2‐hexanol gave the targeted product
in 85–98% yield. Aryl or alkyl secondary alcohols
underwent this transformation to give the ketone prod-
ucts in good to excellent yields. Thus, the ruthenium com-
plexes as catalyst could catalyze the oxidation of the
secondary alcohols with high activities.
SCHEME 2 A plausible mechanism for the formation of 7–12
targeted product with 81.0% yield was obtained when
using CH CN as the solvent and NMO (3 mmol) as the
3
oxidant (entry 12). Note that the reaction can proceed at
a shorter time (1 hr) with complex 7 as a precatalyst, thus
it is complementary to the conditions described in entry
1
4. The solvent screening indicated that CH CN was the
3
most suitable solvent for the oxidation reaction. It can
be concluded that complex 7 (0.01 mmol) as catalyst, in
combination with 3 mmol NMO as oxidant in acetonitrile
Based on our preliminary data and related Ru‐
catalyzed alcohol oxidation processes, a proposed mecha-
2
nism for the present {μ‐η ‐CH[(2‐C H N)(N‐C H ‐
5
4
6
4
R)]} Ru (CO) (μ‐CO)/NMO‐catalyzed alcohol oxidation
2
2
4
SCHEME 3 The oxidation of 1‐phenylethanol
was as shown in Scheme 4. First, the diruthenium
a
TABLE 1 Optimization of oxidation of 1‐phenylethanol using 7
b
c
Entry
Cat.7 [mmol]
Oxidant
C:O ratio
Temp [°C]
Solvent
Time [h]
Yield [%]
1
2
3
4
5
6
7
8
0.01
0.01
0.01
0.01
0.01
0.005
0.02
0.03
0.01
0.01
0.01
0.01
0.01
0.01
0.01
H
2
O
2
1:300
1:300
1:300
1:200
1:400
1:300
1:300
1:300
1:300
1:300
1:300
1:300
1:300
1:300
1:300
40
40
40
40
40
40
40
40
40
40
60
80
80
80
80
CH
CH
CH
CH
CH
CH
CH
CH
2
2
2
2
2
2
2
2
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
2
2
2
2
2
2
2
2
6
6
6
6
6
6
6
6
6
6
6
6
2
1
0.5
13
32
62
42
55
36
58
56
26
70
75
81
82
81
63
TEMPO
NMO
NMO
NMO
NMO
NMO
NMO
NMO
NMO
NMO
NMO
NMO
NMO
NMO
1
9
1
1
1
1
1
0
toluene
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
CN
CN
CN
CN
CN
CN
1
2
3
4
5
a
Reaction conditions: 1.0 mmol 1‐phenylethanol, 6 mL solvent.
b
Catalyst: Oxidant ratio.
c
Isolated yield was determined by column chromatography.

HAO ET AL.
5 of 9
a
TABLE 2 Oxidation of various substrates catalyzed by 7‐12
Yield (%)
7
Entry
Substrate
Product
8
9
10
11
12
b
1
81
85
75
84
73
77
b
2
92
95
95
98
89
94
92
96
86
94
97
96
87
90
86
91
82
93
98
95
86
b
3
81
89
80
b
4
b
5
b
6
81
93
93
84
91
95
c
7
82
85
97
94
91
92
91
96
89
98
90
96
c
8
a
Reaction conditions:1 mmol substrate, 0.01 mmol catalyst, 3.0 mmol NMO, 6 mL acetonitrile, 80 °C, 1 hr.
b
Yield was determined by column chromatography.
c
Yield was determined by GC.
SCHEME 4 A proposed mechanism for
secondary alcohol oxidation catalyzed by
diruthenium carbonyl complexes/NMO
system

6
of 9
HAO ET AL.
TABLE 3 Crystal data and structure refinement parameters for 7, 10, 11, and 12
Complex
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
7
10
11
12
C
29
H
20
N
4
O
5
Ru
2
·0.5THF
C
31
H
18
F
6
N
4
O
5
Ru
2
·3THF
C
29
H
18Cl
2
N
4
O
5
Ru
2
29 2 4 5 2
C H18Br N O Ru
742.68
298(2)
1058.95
298(2)
775.51
298(2)
864.43
298(2)
Orthorhombic
Pna2(1)
19.068(7)
14.112(5)
11.648(4)
90
Monoclinic
C2/c
Monoclinic
C2/c
Monoclinic
C2/c
25.641(2)
9.2062(9)
19.3391(18)
90
20.4589(18)
8.9525(8)
17.4122(15)
90
20.5609(18)
9.0240(9)
17.4441(15)
90
b (Å)
c (Å)
α (°)
β (°)
90
105.126(2)
90
115.739(3)
90
114.482(3)
90
γ (°)
90
3
V (Å )
3134.2(19)
4
4407.0(7)
4
2872.8(4)
4
2945.6(5)
4
Z
F (000)
1480
2136
1528
1672
3
Dcalc (g/cm )
1.574
1.596
1.793
1.949
Crystal dimensions (mm)
θ Range (°)
0.18 × 0.13 × 0.10
2.27–25.02
18044
0.45 × 0.43 × 0.40
2.36–25.02
10592
0.31 × 0.15 × 0.10
2.53–25.02
6863
0.17 × 0.12× 0.04
2.18–25.02
6876
Reflections collected
Independent reflections
5241
3887
2535
2593
R
int
0.0395
0.0247
0.0232
0.0869
Parameters
406
336
191
191
2
Goodness of fit on F
1.060
1.138
1.048
0.939
R
1
1
, wR
2
2
[I > 2σ (I)]
0.0353, 0.0755
0.0472, 0.0802
1478744
0.0310, 0.0727
0.0477, 0.0829
1463119
0.0253, 0.0567
0.0467, 0.0671
1478743
0.0478, 0.0651
0.0990, 0.0715
1478745
R
, wR
(all data)
CCDC deposition no.
complex reacted with two molecules of NMO to form the
Ru‐O free radical species A, which then reacted with an
alcohol to afford a five‐membered ring transition state
intermediate B. Subsequently, Ru‐O bond, C‐H and O‐H
bond of the alcohol in intermediate B was gradually bro-
two terminal carbonyls and the two Ru atoms is linked by
a bridging carbonyl. In addition, the catalytic perfor-
mance of these dinuclear ruthenium carbonyl complexes
2
has been tested. The combination of {μ‐η ‐CH[(2‐C H N)
5
4
(N‐C H ‐R)]} Ru (CO) (μ‐CO) and NMO afforded an effi-
6
4
2
2
4
ken to release two molecules of H O and the C=O bond
cient catalytic system for oxidation of a variety of second-
ary alcohols, giving the corresponding ketones in good to
excellent yields.
2
gradually formed accompanied by the generation of car-
bonyl product. Finally, intermediate B is reconverted to
diruthenium complex to complete entire cycle.
4
4
| EXPERIMENTAL
3
| CONCLUSION
.1 | General considerations
In summary, a series of novel ruthenium carbonyl com-
plexes have been synthesized by reaction of pyridine
imines [C H N‐2‐C(H) = N‐C H ‐R] [R = H (1), CH
4.1.1 | Materials
5
4
6
4
3
(
2), OMe (3), CF (4), Cl (5), Br (6)] with Ru (CO) in
Schlenk and vacuum line techniques were employed for
all manipulations of air‐ and moisture‐sensitive com-
plexes. All solvents were distilled from appropriate drying
agents under an atmosphere of nitrogen prior to use.
3
3
12
refluxing toluene. The results clearly show that these
complexes are dinuclear rhenium clusters, in which each
rhenium atom is coordinated by three nitrogen atoms and

HAO ET AL.
7 of 9
Ligand precursors [C H N‐2‐C(H) = N‐C H ‐R] [R = H
4.2.3 | Synthesis of 9
5
4
6
4
(
1); CH (2); OMe (3); CF (4); Cl (5); Br (6)] were pre-
3 3
[30–33]
pared according to the literature methods.
By using a procedure similar to that described above,
ligand precursor 3 reacted with Ru (CO) gave product
3
12
9
in 54.8% yield as red solid. Mp: 156.3 °C; Anal. Calcd
for C31 Ru : C, 48.56; H, 3.16; N, 7.31, Found
%): C, 48.31; H, 3.38; N, 7.53. H NMR (ppm in
DMSO‐d , 500 MHz): δ 3.65 (s, 6H, OCH ), 4.82 (s, 2H,
4.1.2 | Equipment and analyses
H
24
N
4
O
7
2
1
(
1
13
H NMR and C NMR spectra were recorded on a Bruker
AV III‐500 instrument, while IR spectra were recorded as
KBr disks on a Thermo Fisher is50 spectrometer. X‐ray
measurements were made on a Bruker AXS SMART
6
3
CH), 6.66 (d, 4H, J = 9.0 Hz, Ph‐H), 7.19 (d, 4H,
J = 9.0 Hz, Ph‐H), 7.50 (t, 2H, J = 7.0 Hz, Py‐H), 8.08–
8.12 (m, 2H, Py‐H), 8.24 (d, 2H, J = 8.0 Hz, Py‐H), 8.58
13
1
000 CCD diffractometer with graphite monochromated
(d, 2H, J = 5.0 Hz, Py‐H); C NMR (DMSO‐d6,
125 MHz): δ 55.5, 70.6, 113.8, 120.4, 123.6, 124.6, 139.5,
Mo Kα (λ = 0.71073 Å) radiation. Elemental analyses
were performed on a Vario EL III analyzer.
−
1
151.9, 152.7, 153.2, 162.4. IR (υCO, KBr, cm ): 2030(s),
996(s), 1963(s).
1
4
4
.2 | Syntheses of ruthenium complexes
.2.1 | Synthesis of 7
4
.2.4 | Synthesis of 10
By using a procedure similar to that described above,
ligand precursor 4 reacted with Ru (CO) gave product
3
12
A solution of ligand precursor 1 (0.171 g, 0.938 mmol)
10 in 69.1% yield as red crystals. Mp: 163.2 °C; Anal.
and Ru (CO) (0.300 g, 0.469 mmol) in 30 ml of toluene
3
12
Calcd for C H F N O Ru : C, 44.19; H, 2.15; N, 6.65,
3
1
18
6
4
5
2
was heated at reflux for 8 hr. The solvent was then
removed in vacuo, and the residue was placed in an
1
Found (%): C, 44.39; H, 2.40; N, 6.42. H NMR (ppm in
CDCl , 500 MHz): δ 4.55 (s, 2H, CH), 7.18 (d, 4H,
3
Al O3 column. Elution with ethyl acetate/petroleum
2
J = 8.5 Hz, Ph‐H), 7.30 (d, 4H, J = 9.0 Hz, Ph‐H), 7.35–
ether developed a yellow band, which afforded 0.172 g
7
.37 (m, 2H, Py‐H), 7.73 (d, 2H, J = 7.5 Hz, Py‐H), 7.90–
(77.6%) of 7 as red crystals. Mp: 140.3 °C. Anal. Calcd
1
3
7.93 (m, 2H, Py‐H), 8.44 (d, 2H, J = 5.0 Hz, Py‐H);
C
for C H N O Ru : C, 49.29; H, 2.85; N, 7.93, Found
2
9
20
4
5
2
1
NMR (DMSO‐d , 125 MHz): δ 67.5, 120.0, 123.8, 124.9,
6
(
%): C, 49.49; H, 2.99; N, 7.77. H NMR (ppm in
1
26.1, 140.0, 153.1, 161.2, 162.3, 199.9, 200.4. IR (υCO,
DMSO‐d , 500 MHz): δ 4.54 (s, 2H, CH), 6.70 (s, 2H,
6
−
1
KBr, cm ): 2040(s), 2008(s), 1954(s).
Ph‐H), 7.07 (t, 4H, J = 8.0 Hz, Ph‐H), 7.16 (d, 4H,
J = 7.5 Hz, Ph‐H), 7.29 (d, 2H, J = 5.5 Hz, Py‐H), 7.70
(
d, 2H, J = 6.5 Hz, Py‐H), 7.86 (t, 2H, J = 7.5 Hz, Py‐H),
.42 (d, 2H, J = 2.5 Hz, Py‐H); C NMR (DMSO‐d6,
4
.2.5 | Synthesis of 11
13
8
1
1
2
25 MHz): δ 70.1, 119.7, 120.4, 123.6, 124.7, 128.7, 139.7,
By using a procedure similar to that described above,
ligand precursor 5 reacted with Ru (CO) gave product
−
1
52.7, 158.6, 162.0, 193.1. IR (υCO, KBr, cm ): 2034(s),
3
12
001(s), 1946(s).
1
1 in 43.3% yield as red crystals. Mp: 157.5 °C; Anal.
Calcd for C H Cl N O Ru : C, 44.91; H, 2.34; N,
2
9
18
2
4
5
2
1
7
(
(
.22, Found (%): C, 44.79; H, 2.16; N, 7.38. H NMR
4
.2.2 | Synthesis of 8
ppm in CDCl , 500 MHz): δ 4.65 (s, 2H, CH), 7.22
3
d, 4H, J = 8.0 Hz, Ph‐H), 7.38 (t, 4H, J = 8.5 Hz,
By using a procedure similar to that described above,
Ph‐H), 7.82 (t, 2H, J = 8.5 Hz, Py‐H), 8.17 (d, 2H,
ligand precursor 2 reacted with Ru (CO) gave product 8
3
12
J = 7.5 Hz, Py‐H), 8.58 (s, 2H, Py‐H), 8.71 (d, 2H,
in 48.5% yield as red solid. Mp: 151.3 °C; Anal. Calcd for
C H N O Ru : C, 50.68; H, 3.29; N, 7.63, Found (%): C,
13
J = 4.5 Hz, Py‐H); C NMR (DMSO‐d , 125 MHz): δ
6
3
1
24
4
5
2
7
1
2
0.0, 111.4, 121.9, 123.7, 124.8, 129.1, 131.3, 139.8,
52.9, 158.0, 161.5. IR (υCO, KBr, cm ): 2033(s),
004(s), 1945(s).
1
5
5
4
7
2
0.50; H, 3.45; N, 7.82. H NMR (ppm in DMSO‐d6,
−1
00 MHz): δ 2.09 (s, 6H, CH ), 4.80 (s, 2H, CH), 6.81 (d,
3
H, J = 8.5 Hz, Ph‐H), 7.10 (d, 4H, J = 8.5 Hz, Ph‐H),
.42–7.44 (m, 2H, Py‐H), 8.02–8.06 (m, 2H, Py‐H), 8.19 (d,
13
H, J = 8.5 Hz, Py‐H), 8.50 (d, 2H, J = 5.0 Hz, Py‐H);
C
4.2.6 | Synthesis of 12
NMR (DMSO‐d , 125 MHz): δ 70.2, 119.6, 123.6, 124.6,
6
1
29.0, 129.1, 139.6, 152.7, 156.2, 162.3, 200.4. IR (υCO,
By using a procedure similar to that described above,
−1
KBr, cm ): 2030(s), 1998(s), 1940(s).
ligand precursor 6 reacted with Ru (CO) gave product
3
12

8
of 9
HAO ET AL.
1
2 in 44.4% yield as red crystals. Mp: 159.6 °C; Anal.
ACKNOWLEDGMENTS
Calcd for C H Br N O Ru : C, 40.29; H, 2.10; N,
29
18
2
4
5
2
The authors gratefully acknowledge the financial support
from the National Natural Science Foundation of China
1
6
.48, Found (%): C, 40.49; H, 2.35; N, 6.67. H NMR
(
ppm in DMSO‐d , 500 MHz): δ 4.86 (s, 2H, CH), 7.08
6
(
No. 21372061), the Hebei Natural Science Foundation
(d, 4H, J = 9.0 Hz, Ph‐H), 7.21 (d, 4H, J = 9.0 Hz,
of China (No. B2017205006), the Education Department
Foundation of Hebei Province (No. ZD2018005), and the
Science Foundation of Hebei Normal University (Nos.
L2017Z02, L2018B08).
Ph‐H), 7.47 (t, 2H, J = 6.5 Hz, Py‐H), 8.08 (t, 2H,
J = 8.0 Hz, Py‐H), 8.20 (d, 2H, J = 7.5 Hz, Py‐H),
1
3
8
1
1
2
.56 (d, 2H, J = 5.0 Hz, Py‐H); C NMR (DMSO‐d6,
25 MHz): δ 70.0, 121.3, 123.6, 123.7, 128.4, 132.0,
39.8, 152.9, 157.6, 161.5, 200.6. IR (υCO, KBr, cm ):
−
1
035 (s), 2006 (s), 1947 (s).
ORCID
Jin Lin https://orcid.org/0000-0002-0310-6463
4.3 | Crystal structure determination
REFERENCES
Crystals of complexes 7, 10, 11, and 12 suitable for X‐ray
[
[
[
[
[
[
[
[
1] B. K. Singh, H. K. Rajour, A. Prakash, Spectrochim. Acta, Part A
012, 94, 143.
2] Q. Wang, Z. Y. Yang, G. F. Qi, D. D. Qin, Eur. J. Med. Chem.
009, 44, 2425.
diffraction were investigated with a Bruker AXS SMART
2
1
000 CCD diffractometer, using graphite monochromated
Mo Kα radiation (φ/ω scan, λ = 0.71073 Å). Semiempiri-
cal absorption corrections were applied for all complexes.
The structures were solved by direct methods and refined
by full‐matrix least‐squares. All calculations were done
using the SHELXL‐97 program system. Crystallographic
data and experimental details of the structure determina-
tions are given in Table 3. The single‐crystal X‐ray deter-
minations are illustrated in Figures 1–3, 2–4, 4. CCDC
2
3] K. Mohanan, C. J. Athira, Y. Sindhu, M. S. Sujamol, J. Rare
Earths 2009, 29, 705.
4] B. Suraj, M. N. Deshpande, D. G. Kolhatkar, Int. J. ChemTech
Res. 2012, 4, 578.
5] Y. Wang, M. Wang, Y. Wang, X. Wang, L. Wang, L. Sun,
J. Catal. 2010, 273, 177.
6] O. Kocyigit, E. Guler, J. Inclu. Phenom. Macrocycl. Chem. 2009,
1
478744, 1463119, 1478743, 1478745 for 7, 10, 11, and
67, 29.
1
2, respectively. Copies of this information may be
7] V. Bereau, C. Duhayon, A. Sournia‐Saquet, J. P. Sutter, Inorg.
Chem. 2012, 51, 1309.
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK, fax: +44 1223
8] R. Cristiano, F. Ely, H. Gallardo, Liq. Cryst. 2005, 32, 15.
3
36 033, e‐mail: deposit@ccdc.cam.ac.uk of www:
http://www.ccdc.cam.ac.uk.
[9] Y. Xu, L. Lin, M. Kanai, S. Matsunaga, M. Shibasaki, J. Am.
Chem. Soc. 2011, 133, 5791.
[
[
[
[
10] M. D. Peterson, R. J. Holbrook, T. J. Meade, E. A. Weiss, J. Am.
4
.4 | Catalytic oxidation of various
Chem. Soc. 2013, 135, 13162.
substrates
11] J. W. Leeland, F. J. White, J. B. Love, J. Am. Chem. Soc. 2011,
133, 7320.
The catalytic activity of the prepared ruthenium com-
plexes for the oxidation of various substrates was tested
in the presence of NMO (N‐methylmorpholine‐N‐oxide)
as oxidant. A typical reaction using these complexes as
catalyst and NMO as oxidant at 1:300 molar ratio is
described as follows. The catalytic reaction was carried
out under the following conditions: 0.01 mmol ruthe-
nium complex catalyst, 3 mmol of NMO and 1.0 mmol
12] Y. Xu, K. Kaneco, M. Kanai, M. Shibasaki, S. Matsunaga, J. Am.
Chem. Soc. 2014, 136, 9190.
13] Q. Cao, L. M. Dornan, L. Rogan, N. L. Hughes, M. J. Muldoon,
Chem. Commun. 2014, 50, 4524.
[14] K. Liu, T. T. Chen, L. Y. Dai, Catal. Lett. 2014, 144, 314.
[
15] G. Tojo, M. Fernández, Oxidation of Primary Alcohols to Car-
boxylic Acids: A Guide to Current Common Practice, Springer,
New York 2010.
substrate were mixed in 6 mL of CH CN. The reaction
3
[16] F. M. Menger, C. Lee, Tetrahedron Lett. 1981, 22, 1655.
[17] C. Parmeggiani, F. Cardona, Green Chem. 2014, 14, 547.
[18] B. L. Ryland, S. S. Stahl, Angew. Chem. Int. Ed. 2014, 126, 8968.
was stirred at 80 °C for 1 hr under 1 atmosphere. Sol-
vent was evaporated from the mother liquor under
reduced pressure and the residue was purified by
Al O column chromatography. Elution with petroleum
ether/ethyl acetate (1:10, V/V) gave the desired
product. The target product was identified by NMR
and the NMR data are available in the supporting
information.
[19] X. L. Wang, R. H. Liu, Y. Jin, X. M. Liang, Chem. – Eur. J. 2008,
4, 2679.
2
3
1
[20] M. B. Lauber, S. S. Stahl, ACS Catal. 2013, 3, 2612.
[21] M. Shibuya, S. Nagasawa, Y. Osada, Y. Iwabuchi, J. Org. Chem.
2014, 79, 10256.

HAO ET AL.
9 of 9
[
[
22] Y. Kadoh, M. Tashiro, K. Oisaki, M. Kanai, Adv. Synth. Catal.
015, 357, 2193.
[32] S. A. Moya, J. C. Araya, J. Gajardo, V. Guerchais, H. L. Bozec,
2
L. Toupet, P. Aguirre, Inorg. Chem. Commun. 2013, 27, 108.
23] T. Hirashita, M. Nakanishi, T. Uchida, M. Yamamoto, S.
[33] G. Hilt, J. Janikowski, M. Schwarzer, O. Burghaus, D. Sakw, M.
Bröring, M. Drüschler, B. Huber, B. Roling, K. Harms, G.
Frenking, J. Organomet. Chem. 2014, 749, 219.
Araki, I. W. C. E. Arends, R. A. Sheldon, ChemCatChem
2
016, 8, 2704.
[
[
[
[
[
[
24] S. E. Allen, R. R. Walvoord, R. Padilla‐Salinas, M. C.
Kozlowski, Chem. Rev. 2013, 113, 6234.
SUPPORTING INFORMATION
25] M. S. El‐Shahawi, A. F. Shoair, Spectrochim. Acta, Part A 2004,
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
6
0, 121.
26] N. Gunasekaran, N. Remya, S. Radhakrishnan, R. Karvembu,
J. Coord. Chem. 2011, 64, 491.
27] S. Jana, M. S. Jana, D. Sarkar, M. K. Paira, T. K. Mondal, J. Mol.
Struct. 2013, 1054, 83.
28] Y. Liu, Z. Ma, C. Sheng, Z. Han, X. Zheng, J. Lin, Chin. J. Inorg.
Chem. 2015, 31, 774.
How to cite this article: Hao Z, Li Y, Li C, et al.
Synthesis of a series of new ruthenium
organometallic complexes derived from pyridine‐
imine ligands and their catalytic activity in
oxidation of secondary alcohols. Appl Organometal
Chem. 2018;e4750. https://doi.org/10.1002/aoc.4750
29] Z. Ma, D. Fan, S. Li, Z. Han, X. Li, X. Zheng, J. Lin, New J.
Chem. 2015, 39, 1075.
[
[
30] P. Datta, C. Sinha, Polyhedron 2007, 26, 2433.
31] C. H. Chien, S. Fujita, S. Yamoto, T. Hara, T. Yamagata, M.
Watanabe, K. Mashima, Dalton Trans. 2008, 916.