Ruthenium (II) complexes of NO ligands: Synthesis, characterization and application in transfer hydrogenation of carbonyl compounds

Article abstract of DOI:10.1016/j.jorganchem.2015.10.028

New Schiff base ligands including azo group such as (4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(phenylimino)methyl)phenol 2, 4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(naphthalen-1-ylimino)methyl)phenol 3, 2-((E)-(benzylimino)methyl)-4-((E)-(4-ethylphenyl)diazenyl)phenol 4 and azo group-free ligand (E)-2-((benzylimino)methyl)phenol 8 and their ruthenium complexes 5-7 and 9 with [RuCl₂(p-cymene)] were synthesized and characterized by spectroscopic techniques including ¹H and ¹³C NMR, FT-IR and UV-Vis. According to the UV-visible, IR and NMR data, the Ru (II) complexes 5-7 and 9 are formed by the coordination of N, O atoms of the ligands. Molecular structures of the complex 7 and complex 9 were determined by single crystal X-ray diffraction studies. These Ruthenium (II) complexes 5-7 and 9 were used as catalysts for the transfer hydrogenation of a series of ketones and benzaldehyde in 2-propanol. Following the comparison of complex 9 with the other three azo containing complexes 5-7, it was observed that azo group has got remarkable increasing effect on the catalytic activity. The results showed that the complex 5 is efficient than the other Ru (II) complexes.

Full text of DOI:10.1016/j.jorganchem.2015.10.028

Accepted Manuscript
Ruthenium (II) complexes of NO ligands: Synthesis, characterization and application
in transfer hydrogenation of carbonyl compounds
Hatice Selvi Çalık, Esin Ispir, Şemistan Karabuga, Mehmet Aslantaş
PII:
S0022-328X(15)30199-6
10.1016/j.jorganchem.2015.10.028
JOM 19285
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 2 July 2015
Revised Date: 16 October 2015
Accepted Date: 23 October 2015
Please cite this article as: H.S. Çalık, E. Ispir, Ş. Karabuga, M. Aslantaş, Ruthenium (II) complexes
of NO ligands: Synthesis, characterization and application in transfer hydrogenation of carbonyl
compounds, Journal of Organometallic Chemistry (2015), doi: 10.1016/j.jorganchem.2015.10.028.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Ruthenium (II) complexes of NO ligands: Synthesis,
characterization and application in transfer hydrogenation of
carbonyl compounds
Hatice Selvi Çalıka, Esin Ispira*, Şemistan Karabugaa, Mehmet Aslantaşb
*E-mail: esinispir@ksu.edu.tr; Tel: 0090 3442801451
aDepartment of Chemistry, Kahramanmaraş Sütçü Imam University, Kahramanmaraş,
46050–9, Turkey
bPhysics Department, Science and Arts Faculty, Kahramanmaraş Sütçü Imam University,
Kahramanmaraş, 46050–9, Turkey
Abstract:
New Schiff base ligands including azo group such as (4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-
(phenylimino)methyl)phenol
ylimino)methyl)phenol
2,
4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(naphthalen-1-
2-((E)-(benzylimino)methyl)-4-((E)-(4-
3,
ethylphenyl)diazenyl)phenol 4 and azo group-free ligand (E)-2-((benzylimino)methyl)phenol
8 and their ruthenium complexes 5-7 and 9 with [RuCl2(p-cymene)] were synthesized and
1
characterized by spectroscopic techniques including H and 13C NMR, FT-IR and UV-Vis.
According to the UV-visible, IR and NMR data, the Ru (II) complexes 5-7 and 9 are formed
by the coordination of N, O atoms of the ligands. Molecular structures of the complex 7 and
complex 9 were determined by single crystal X-ray diffraction studies. These Ruthenium (II)
complexes 5-7 and 9 were used as catalysts for the transfer hydrogenation of a series of
ketones and benzaldehyde in 2-propanol. Following the comparison of complex 9 with the
other three azo containing complexes 5-7, it was observed that azo group has got remarkable
increasing effect on the catalytic activity. The results showed that the complex 5 is efficient
than the other Ru (II) complexes.
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Keywords: Ruthenium, transfer hydrogenation, NO complex, azo compounds.
Corresponding author:
E-mail: esinispir@ksu.edu.tr. (E. Ispir).
Introduction
Transfer hydrogenation is one of the most important method for reduction of ketones
and aldehydes, due to it is a valuable and atom-efficient reaction, more cost effective and
simpler experimental procedure [1]. It is a useful method for the reduction of carbonyl
compounds to their corresponding alcohols [2-4]. In addition to its use at important synthesis
stages of products which have pharmaceutical, natural and industrial values, the
hydrogenation reaction provides opportunity for such kind of studies to proceed rapidly
because of high reaction yield [5-7].
Transition-metal catalyzed processes for transfer hydrogenation of a wide variety of
functional groups by different hydrogen donors are interesting alternatives to molecular
hydrogenation [1]. The studies to develop the new catalysts for transfer hydrogenation is still
of considerable importance, in order to find more efficient catalysts [8]. The most active and
selective catalysts for the transfer hydrogenation reactions are ruthenium [9], iridium [10] and
rhodium [11] complexes containing NN, NNN, CNN, NO and PNP etc. type of ligands [12]
(Scheme 1). Besides that the NN- and NO-donor attached ligands play important role in
catalytic reactions [13].
Among the various ligand systems, Schiff base analogues have attracted great interest
in recent years. Azo group show donor properties and play an important role in coordination
chemistry [14]. Steric and electronic effects of substituent’s in the coordination zone increases
the activity of the metal and the other groups on ligands that not attended to coordination also
may have an impact on this activity.
Complex formation studies of ruthenium with azo/azoimine ligands and their usage at
transfer hydrogenation reaction, metal-carbon bond formation and catalytic transformations
have been ongoing [15]. The ruthenium complexes formed by different types of ligands have
significant importance. To design the new types of ruthenium (II) Schiff base complexes
bearing oxygen and nitrogen donor atoms have importance due to their potential catalytic
activities [5]. During recent years, half-sandwich (η6-arene)ruthenium (II) complexes draw
attention very much and proceed to be the subject of intense research in the field of
organometallic chemistry emphatically [16-18].
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In this context, our research group has focused on synthesis, characterization, and
catalytic activity of ruthenium (II) NO-type complexes 5-7, 9 that formed from Schiff base
ligands bearing azo group on the ligand system. In addition to this, one of the aims of our
study is to demonstrate that the azo group has got increasing effect on the catalytic activity.
For this purpose the catalytic activities of the complexes 5-7 which have azo group have
compared to the complex 9 without azo group. Also these ruthenium (II) NO-type Schiff base
complexes were tested as catalysts for transfer hydrogenation reaction to reduce carbonyl
compounds to their corresponding alcohols.
Experimental
Materials and methods
Reagents and solvents were purchased from chemical suppliers and purified to match
the reported physical and spectroscopic data. The solvents were carefully dried using standard
methods. Melting points were determined with an Electrothermal 9200 apparatus. IR spectra
were obtained using KBr discs (4000–400 cm–1) on a Shimadzu 8300 FTIR
spectrophotometer. The electronic spectra in the 200–900 nm range were obtained using DMF
on a Hithachi U-3900 spectrophotometer. ESI mass spectra were recorded on a ESI/MS
1
Tandem mass spectrometry. H and 13C NMR spectra were recorded on a Varian AS-
400 MHz instrument and Bruker 600 Mhz Ultrashield TM in CDCl3.The conversions were
determined by GC analysis with YL6500 Instrument.
The diffraction data for complexes (7 and 9) were collected at room temperature on a
Bruker APEX-II CCD diffractometer using graphite monochromated radiation (MoKα,
λ=0.71073 Å). ω/2θ scan mode was employed for data collection. The structures were solved
by SHELXS-97[19] and refined with SHELXL-97 [20] software package. In complex 7 and
9, all H atoms were refined using a riding model with distances of 0.93 Å (aromatic), 0.96 Å
(CH3), 0.97 Å (CH2), 0.98 Å (CH), and Uiso(H)=1.2Ueq(C) for methylene and aromatic,
1.50Ueq(C) for methyl. A summary of the key crystallographic information for both
complexes are given in Table 1. Molecular drawings of the complexes indicating atom
numbering scheme with thermal ellipsoids at %30 probabilities were obtained using ORTEP-
III [21] The PLATON [22] program was used for geometrical calculation and conformational
features of the complexes. Further experimental details have been deposited as supplementary
material at the Cambridge Crystallographic Data Centre CCDC 1052112 and 1061609.
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General procedure for the synthesis of ligands 2-4
Methanolic
solutions
(25
ml)
of
(E)-5-((4-ethylphenyl)diazenyl)-2-
hydroxybenzaldehyde 1 (508.56 mg, 2.00 mmol) and aromatic amines (2 mmol) were stirred
at reflux temperature for 8 h. After the end of reaction time, the mixtures were allowed to cool
and resulting solids were collected. The crude products were recrystallised from hot methanol
to yield pure crystalline products (Fig. 1).
Data for the ligands 2-4
For 4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(phenylimino)methyl)phenol 2
1
Color: Red. Yield: 545 mg (83%). m.p.119-120 °C. H NMR (600 MHz, CDCl3,δ,
ppm): 13.85 (s, 1H), 8.77 (s, 1H), 8.06 (m, 2H), 7.86 (d, J = 8.3 Hz, 2H), 7.48 (t, J = 7.7 Hz,
2H), 7.36 (m,5H), 7.17 (d, J = 8.5 Hz, 1H), 2.76 (q, J = 7.6 Hz, 2H), 1.32 (t, J = 7.6 Hz, 3H).
13C NMR (151 MHz, CDCl3,δ, ppm): 163.8, 162.2, 150.9, 147.8, 147.4, 145.6, 129.5, 128.6,
127.7, 127.5, 127.3, 122.7, 121.2, 118.9, 118.1, 28.8, 15.5. ESI (MeOH): 330 [M+H]+. FT-IR
(KBr, cm-1): 3402, 3062, 1613 and 1567. UV-vis (λmax, nm): 250, 352 (in 10-4 M DMF).
For 4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(naphthalen-1-ylimino)methyl)phenol 3
OH
N
N
N
4

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1
Color: Orange. Yield: 713.4 mg (94%). m.p. 162-163oC. H NMR (600 MHz,
CDCl3,δ, ppm): 13.93 (s, 1H), 8.87 (s, 1H), 8.30 (m, 1H), 8.14 – 8.09 (m, 2H), 7.95 – 7.91 (m,
1H), 7.87 (d, J = 8.3 Hz, 2H), 7.85 (d, J = 8.3 Hz, 1H),7.63 – 7.58 (m, 2H), 7.55 (t, J = 8.0
Hz, 1H), 7.37 (d, J = 8.3 Hz, 2H), 7.26 (d, J = 7.2 Hz, 1H), 7.24 (d, J = 8.8 Hz, 1H), 2.77 (q, J
= 7.6 Hz, 2H), 1.32 (t, J = 7.6 Hz, 3H). 13C NMR (151 MHz, CDCl3,δ, ppm): 163.8, 163.2,
150.9, 147.5, 145.8, 145.6, 134.0, 128.6, 128.2, 128.2, 127.8, 127.7, 127.4, 126.8, 126.7,
126.0, 123.1, 122.7, 119.2, 118.1, 114.2, 28.8, 15.4. ESI (MeOH): 380 [M+H]+. FT-IR (KBr,
cm-1): 3420, 3049, 1626, and 1579. UV-vis (λmax, nm): 253, 353(in 10-4 M DMF).
For 2-((benzylimino)methyl)-4-((E)-(4-ethylphenyl)diazenyl)phenol 4
1
Color: Yellow. Yield: 612 mg (89 %). m.p.78-80oC. H NMR (600 MHz, CDCl3,δ,
ppm): 14.04 (s, 1H), 8.55 (s, 1H), 8.00 (dd, J = 8.8, 2.4 Hz, 1H), 7.94 (d, J = 2.4 Hz, 1H),
7.83 (d, J = 8.3 Hz, 2H), 7.41 (m, 2H), 7.38 – 7.32 (m, 5H), 7.09 (d, J = 8.8 Hz, 1H), 4.88 (s,
2H), 2.75 (q, J = 7.6 Hz, 2H), 1.31 (t, J = 7.6 Hz, 3H).13C NMR (75 MHz, CDCl3, δ, ppm):
165.4, 164.5, 150.9, 147.2,145.3, 137.6, 128.8, 128.6, 127.9, 127.6, 127.1, 127.0, 122.6,
118.4, 118.1, 62.7, 28.8, 15.5. ESI (MeOH): 344 [M+H]+. FT-IR (KBr, cm-1): 3417, 3047,
1614, 1568.UV-vis (λmax, nm): 255, 357(in 10-4 M DMF).
General procedure for the preparation of complexes 5-7
Dichloro(p-cymene)ruthenium(II) dimer (153 mg, 0. 25 mmol) and KOH (32 mg,
0.5mmol) were added to the solutions of ligands (0.50 mmol) in methanol (10 ml) in one
portion and heated at 50 °C for 6 h under nitrogen atmosphere in a Schlenk tube. The
precipitate was collected by filtration, washed with a large quantity of petroleum ether and
diethyl ether and dried in vacuum.
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Data for complexes 5-7
For complex 5
1
Color: Orange. Yield: 222 mg (74%). m.p.224-225 °C. H NMR (300 MHz, CDCl3, δ, ppm):
7.92 (dd, J = 9.3, 2.5 Hz, 1H), 7.90 (s, 1H), 7.71(d, J = 8.3 Hz, 2H), 7.65 (m, 3H), 7.47 (t, J =
7.6 Hz, 2H), 7.36 (t, J = 7.3 Hz, 1H), 7.27 (d, J = 8.2 Hz, 2H), 7.06 (d, J = 9.3 Hz, 1H), 5.39
(d, J = 6.1 Hz, 1H), 5.30 (d, J = 6.1 Hz, 1H), 5.03 (d, J = 5.7 Hz, 1H), 4.20 (d, J = 5.7 Hz,
1H), 2.77 – 2.57 (m, 3H), 2.14 (s, 3H), 1.26 (t, J = 7.6 Hz, 3H), 1.19 (d, J = 7.0 Hz, 3H), 1.14
(d, J = 6.9 Hz, 3H). 13C NMR (75 MHz, CDCl3, δ, ppm): 168.3, 164.3, 158.3, 151.2, 146.1,
142.5, 134.8, 129.0, 128.4, 127.4, 127.3, 123.6, 123.5, 122.2, 117.8, 101.9, 98.2, 86.6, 83.8,
83.4, 80.7, 30.4, 28.7, 22.79, 21.6, 18.5, 15.5. ESI (MeOH): 564 [M-Cl]+. FT-IR (KBr, cm-1):
3047, 1613, 1589.UV-vis (λmax, nm): 266, 408 (in 10-4 M DMF). Anal. Calcd. For:
[C31H32ClN3ORu], C: 62.15, H. 5.38, N: 7.01. Found: C:62.01, H: 5.14, N: 7.04.
For complex 6
1
Color: Brown. Yield: 250 mg (77%). m.p.229-230°C. H NMR (300 MHz, CDCl3, δ,
ppm): 8.12 (dd, J = 7.4, 1.1 Hz, 1H), 8.06 – 7.92 (m, 1H), 7.89 (dd, J = 9.4, 5.1 Hz, 1H), 7.74
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– 7.52 (m, 1H), 7.25 (d, J = 8.4 Hz, 1H), 7.11 (d, J = 9.3 Hz, 1H), 5.45 (d, J = 6.1 Hz, 1H),
5.12 (d, J = 6.2 Hz, 1H), 5.06 (d, J = 5.7 Hz, 1H), 3.89 (d, J = 5.7 Hz, 1H), 2.78 – 2.58 (m,
1H), 1.96 (s, 1H), 1.28 – 1.16 (m, 1H). 9.07 (d, J = 9.0 Hz, 1H, minor isomer), 7.06 (d, J = 9.3
Hz, 1H, minor isomer), 5.36 (d, J = 6.7 Hz, 1H, minor isomer), 5.22 (d, J = 6.3 Hz, 1H, minor
isomer), 4.81 (d, J = 5.6 Hz, 1H, minor isomer), 3.59 (d, J = 5.5 Hz, 1H, minor isomer), 1.79
(s, 1H, minor isomer). 13C NMR (75 MHz, CDCl3, δ, ppm) 168.6, 166.9, 154.0, 151.2, 146.1,
142.6, 134.9, 133.9, 129.0, 128.4, 127.7, 127.2, 127.1, 126.7, 125.9, 122.2, 121.9, 121.3,
117.5, 104.2, 94.5, 86.7, 85.8, 84.5, 30.4, 28.8, 22.9, 21.1, 17.9, 15.5. Minor isomer peaks:
170.0, 165.2, 154.1, 151.24, 146.0, 134.7, 134.1, 127.58, 127.56, 127.4, 127.17, 124.7, 123.2,
122.19, 119.6, 119.0, 102.6, 95.8, 85.5, 83.8, 80.4, 30.3, 21.2 and 18.0. ESI (MeOH): 614 [M-
Cl]+. FT-IR (KBr, cm-1): 3048, 1620 and 1600. UV-vis (λmax, nm): 266, 409 (in 10-4 M DMF).
Anal. Calcd. For: [C35H34ClN3ORu], C: 64.75, H. 5.28, N: 6.47. Found: C:64.61, H: 5.16, N:
6.27.
For complex 7
Color: Orange. The single crystal was collected from DCM-Ether (1:3) solution.
Yield: 245 mg (80%). m.p.200-201°C. 1H NMR (300 MHz, CDCl3,δ, ppm): 7.88 (dd, J = 9.2,
2.5 Hz, 1H), 7.77 (s, 1H), 7.71 (d, J = 8.4 Hz, 2H), 7.58 (d, J = 2.5 Hz, 1H), 7.54 – 7.38 (m,
5H), 7.27 (d, J = 8.5 Hz, 2H), 7.03 (d, J = 9.2 Hz, 1H), 5.38 (m, 3H), 5.30 (d, J = 6.1 Hz, 1H),
5.13 (d, J = 5.7 Hz, 1H), 4.94 (d, J = 5.7 Hz, 1H), 2.82 – 2.62 (m, 3H), 2.15 (s, 3H), 1.26 (t, J
= 7.6 Hz, 3H), 1.20 (d, J = 6.9 Hz, 3H), 1.10 (d, J = 6.9 Hz, 3H). 13C NMR (75 MHz, CDCl3)
δ 168.8, 165.6, 151.1, 146.2, 142.5, 137.0, 132.9, 129.3, 128.6, 128.4, 128.4, 127.5, 123.5,
122.2, 119.3, 102.8, 96.2, 84.49, 84.2, 81.8, 79.4, 71.9, 30.6, 28.8, 22.7, 21.6, 18.5, 15.5. ESI
(MeOH): 579 [M-Cl]+. FT-IR (KBr, cm-1): 3047, 1607 and 1525. UV-vis (λmax, nm): 268, 409
(in 10-4 M DMF). Anal. Calcd. For: [C32H34ClN3ORu], C: 62.68, H. 5.59, N: 6.85. Found:
C:62.54, H: 5.46, N: 6.75.
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Sythesis of (E)-2-((phenylimino)methyl)phenol 8
25 mL 2-hydroxybenzaldehyde (508.5 mg, 2.00mmol) solution in methanol was added
aniline (186.3 mg, 2 mmol) in methanol (5 mL) and refluxed for 8 hours. The solution was
concentrated on air by removing solvent for two days and crystallized to give (E)-2-
((phenylimino)methyl)phenol 8 as a yellow needle crystals. Yield: 545 mg (83 %).
Synthesis of Complex 9
Complex 9 was synthesized according to the general procedure for complexes.
Dichloro(p-cymene)ruthenium(II) dimer (153 mg, 0. 25 mmol) and KOH (32 mg, 0.5mmol)
were added to the solutions of (E)-2-((phenylimino)methyl)phenol 8 (99 mg, 0.50 mmol in
methanol (10 ml) in one portion and heated at 50 °C for 6 h at nitrogen atmosphere in a
Schlenk tube. The precipitate was collected by filtration, washed with a large quantity of
petroleum ether and diethyl ether and dried in vacuum.
1
The complex 9 was obtained as orange crystals. Yield: 183 mg (78%). H NMR (300 MHz,
CDCl3, δ, ppm): 7.75 (s, 1H), 7.64 (d, J = 7.9, 2H), 7.45 (d, J = 7.8 Hz, 2H), 7.33 (t, J = 7.3
Hz, 1H), 7.22 (ddd, J = 8.6, 6.8, 1.8 Hz, 1H), 7.00 (d, J = 8.6 Hz, 1H), 6.95 (dd, J = 7.9, 1.8
Hz, 1H), 6.43 (dt,, J = 7.8, 0.9 Hz, 1H), 5.34 (d, J = 6.1 Hz, 1H), 5.25 (d, J = 6.1 Hz, 1H),
5.00 (d, J = 5.7 Hz, 1H), 4.20 (d, J = 5.7 Hz, 1H), 2.63 (hept, , J = 6.9 Hz,1H), 2.11 (s, 3H),
1.17 (d, J = 6.9 Hz, 3H), 1.12 (d, J = 6.9 Hz, 3H). 13C NMR (75 MHz, CDCl3, δ, ppm): 165.2,
164.2, 158.5, 135.5, 135.4, 128.8, 126.9, 123.7, 122.7, 118.1, 114.2, 101.4, 97.9, 86.5, 83.6,
83.5, 80.3, 30.3, 22.8, 21.6, 18.5. ESI (MeOH): 433 [M-Cl]+. FT-IR (KBr, cm-1): 3047, 1607
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and 1525. UV-vis (λmax, nm): 265, 410 (in 10-4 M DMF). Anal. Calcd. For: [C23H24ClNORu],
C: 59.16, H. 5.18, N: 3.00. Found: C:59.01, H: 5.14, N: 2.97.
Typical procedure for the transfer hydrogen reaction
Under nitrogen atmosphere, aromatic ketone (4 mmol), NaOiPr (0.8 mL, 0.1 M) and complex
5 (1 mg, 0.0012 mmol) were dissolved in degassed 2-propanol (18 mL) with nitrogen and the
mixture was refluxed for 24 h. The hydrogenation of the ketone began instantly, and the
conversion and enantiomeric excess was determined by GC using HP-5 column.
Result and Discussion
Synthesis and Characterization of ligands (2-4, 8) and complexes (5-7, 9)
(E)-5-((4-ethylphenyl)diazenyl)-2-hydroxybenzaldehyde 1 was synthesized according
to literature [23]. Three azo containing Schiff base ligands 2-4 and their Ru(II) complexes 5-7
were prepared as shown in Fig.1. The Schiff base ligands, 2, 3 and 4 have been prepared by
the condensation between (E)-5-((4-ethylphenyl)diazenyl)-2-hydroxybenzaldehyde 1 with
aniline, 1-naphthylamine and 4-ethylaniline, respectively in MetOH. Also the ligand 8 and its
Ru (II) complex 9 were synthesized as seen in Fig.1. The ligands are stable at room
temperature and soluble in common organic solvents such as EtOH, MeOH, DMF and
CH2Cl2. The complexes are also stable at room temperature in air.
The azo containing ligands 2-4 were completely characterized by IR, mass analyse, 1H
13
and C NMR. The IR spectra of Schiff Base ligands 2-4 have similar signals. These ligands
exhibit bands at 3402-3420 cm-1 and 3045-3062 cm-1 that are assignable to ν(OH) and ν(Ar-
CH) [24]. Both of these three ligands 2-4 show characteristic bands at 1613-1626 range can
be assigned to the azomethine ν(C=N) stretching. The distinctive bands of N=N group were
observed at 1567-157 9 cm-1range in ligands [8]. In complex this stretching shifted to lower
frequency (1607-1620), thereby indicating coordination of azomethine nitrogen atoms [25].
Also disappearance of ν(OH) bands proves that coordination occurred with oxygen atoms as
the other donor atom beside nitrogen atoms.
The electronic spectra of ligands and their Ruthenium (II) complexes 5-7 were
recorded in DMF in the range 800-200 nm. The spectra of ligands 2-4 are very similar and
display a strong band at 352-357 nm range. By comparing the spectra of the ligands 2-4 and
the corresponding complexes 2-4, the absorptions above 409 nm are assigned to ligand to
9

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metal charge transfer transitions and the absorptions below 409 nm are attributed to ligand
centered transitions [26].
1
In order to better understand the structure of the ligands 2-4 and 8, H and 13C NMR
analyses were studied. Ligands and complexes NMR spectra were given in Fig. S6-8 at
1
supporting files. The H NMR spectra of the ligands shows singlets in the 13.85-14.04 ppm
1
range can be attributed to the proton of the –OH group [27]. The H NMR resonance of
azomethine proton (CH=N) in ligands are observed at 8.77, 8.55 and 8.87 ppm respectively.
The quarted signals at 2.75-2.77 ppm range and the triplet signals at 1.31-1.32 ppm range
corresponding to –CH2 and –CH3 protons. The multiplets of the aromatic protons were in the
region of 8.00–7.09 ppm for ligands. Unlike other ligands, the peak at 4.88 ppm in the spectra
of ligand 4 was attributed to CH2 group.
1
The H NMR spectra (CDCl3) recorded during the reaction revealed formation of the two
isomers in preparation of complex 6. The spectrum exhibited one doublet at 8.12 ppm for
major complex 6 and one doublet at 9.07 ppm for minor complex 6 at ratio 1:0.33. This ratio
was also measured 5.45, 5.12, 5.06 and 3.89 ppm for major isomer and 5.36, 5.22, 4.81, and
3.59 ppm for minor isomer as doublets of p-cymene aromatic protons. Interestingly, the ratio
of isomer which was recorded as 1:0.33 at room temperature was changed to 1:0.22 by
dropping the temperature to -40 °C (233K).
Besides, the signals belonging to minor isomer at the low temperature disappeared in
31C NMR spectrum (Fig. S10, 11).
The [M+H]+ molecular ion peak for the ligand 2 is observed at m/z:330. The most
intense peaks at 301 and 194 corresponds to [C19H14N3O]+ and [C13H9N2]+ fragments. Also
the [M+H]+ molecular ion peak for the ligand 3 is observed at m/z:380. The peak at 235 may
be attributed to [C15H13N3]+. In the mass spectrum of the ligand 4, the peak observed at m/z:
344 can be assigned to the molecular ions [M+H]+. In the mass spectra of the complexes 5-7,
9, the peaks at m/z: 564, m/z: 614, m/z: 579 and m/z: 433 can be assigned to the [M-Cl]+ ion
peaks respectively.
In the title complex 7, Ru atom has a typical half-sandwich coordination environment
with three-coordinated by O1, Cl1, N1 and six C atoms of the aromatic ring of the p-cymene
ligand. Geometric parameters around Ru involving ring centroids are listed in Table 2. In
complex 7, the bond lengths of the configuration around the Ru1 atom are 2.4297(10) Å,
2.062(3) Å, 2.099(3) Å and 1.667(2) Å for the Ru1-Cl1, Ru1-O1, Ru1-N1 and Ru1-Cg4 (Cg4
is the centroid of C23-C28 ring) bonds, respectively, which are in good agreement with the
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literature values. The bond angles of the geometry around Ru including ring centroid are
127.97(8)o, 123.30(12)o and 132.87(12)o for the Ru1-Cg4-Cl1, Ru1-Cg4-O1 and Ru1-Cg4-
N1, which are comparable with previously reported Ru complexes having similar
coordination environment in the crystallographic studies [28-32]. In the complex 5, Cl and O
atoms involving in two C-HꢀꢀꢀCl and a C-HꢀꢀꢀO inter-molecular hydrogen bonding
interactions are observed [C7ꢀꢀꢀCl1=3.648(4) Å, C7-H7ꢀꢀꢀCl1=165.00o; C24ꢀꢀꢀCl1=3.4965(5)
Å, C24-H24ꢀꢀꢀCl1=140.00o; C25ꢀꢀꢀO1=3.5600 Å, C25-H25ꢀꢀꢀO1=172.42o] which help for
stabilizing the molecular packing. In addition, three C-HꢀꢀꢀCg (π-ring) interactions involving
neighboring molecules in the unit cell (Table 3 and Fig.2) and a short aromatic π-π stacking
interaction [Cg2-Cg2 (3-x, -y, 1-z) distance = 3.760(3) Å; Cg2 is the centroid of the C9-C14
ring] is available for forming three dimensional network (Fig.2).
The crystal structure of complex 9, has also a half-sandwich geometry about the
central Ru atom and its coordination geometry is quite similar to the complex 7 (Fig.3). In the
asymmetric unit, the bond lengths and angles in complex 9 are comparable with complex 7
and those of the related structures reported in literature [28-32], except for shorter Ru1-O1,
Ru1-N1 and Ru1-Cg3 (Cg3 is the centroid of C15-C20 ring) bond lengths (Table 2). In 9, the
Cl atom plays a vital role in the formation of dimeric units as a result C-HꢀꢀꢀCl interactions (an
intra-molecular contact with C9ꢀꢀꢀCl1<3.56 Å and three inter-molecular contacts with
CꢀꢀꢀCl<3.89 Å) which contribute the stability of the overall molecular structure. Besides a
number of C-HꢀꢀꢀCg (π-ring) interactions and some π-π stacking interactions [Cg1-Cg1 (1/2-x,
1/2+y, -z) = 5.203(3) Å, Cg2-Cg3 (x, y, z) = 4.869(3) Å, Cg3-Cg2 (-1/2+x, 1/2-y, z) =
5.009(3) Å; Cg1, Cg2 and Cg3 are the centroids of the C1-C6, C8-C13 and C15-C20 benzene
rings, respectively] between the adjacent molecules may stabilize the molecular packing (Fig.
S5 and Table 4). A comparison of Ru geometries, hydrogen bonding and short ring-
interactions, complex 9 has grater hydrogen bonding effects and better stable geometry than
complex 7.
Catalytic Studies
All the ligands 2-4 and 8 were converted to ruthenium catalysts 5-7 and 9 with
dichloro(p-cymene)ruthenium (II) dimer and these complexes were used as catalysts in
transfer hydrogen reaction. Initially, to determine the catalytic performance of the ruthenium
complexes 5-7 and 9, they were examined in the reduction of acetophenone to 1-
11

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phenylethanol as a chosen model reaction which was carried out at reflux temperature with
1000:3 substrat complex ratios in the presence of 0.1 M NaOH as a base. Transfer
i
hydrogenation reaction was applied in PrOH as a solvent and hydrogen source. Complex 5
was selected the best catalyst according to conversion of acetophenone to 1-phenylethanol for
24 hours (Table 5, entries 1-4). Following the selection of complex 5 amongst the other
complexes, 12 test reactions have been performed with different base types, amounts and
substrate/catalyst ratios to optimize and find out the best catalytic reaction conditions.
For this purpose, first of all the influence of base type was investigated by using 0.03
mmol 0.1 M NaOH, KOH, NaOiPr, NaOtBu and KOtBu base solutions and conversation rate
occurred as, KOtBu ˂ KOH ˂ NaOiPr ˂ NaOtBu ˂ NaOH (Table 5, entries 1, 5-8). In the
circumstances NaOH was selected as base in this system. The amount of base was increased
from 0.03 mmol to 0.1 mmol but the catalytic activity in conversion did not change anymore
(entries 9, 10). Besides, the ratio of substrate and complex was raised to 200 and 125 and the
conversion ratio remained almost the same in 8 hours as well and these results showed a bit
increase from 95 to 98 % as a result of enlarging the reaction time for 24 hours (entries 11,
12)
After the best conditions had been established for the complex 5, a series of ketones
and benzaldehyde were screened in transfer hydrogenation reaction. In all cases, the reaction
was performed by transfer hydrogenation of carbonyl compounds to alcohols in iPrOH and in
the presence of NaOH under the standard conditions (reflux temp., 200 substrate complex
ratio and 24 h), which are displayed in Table 6. No significant changes in the yield were
observed when the methyl-substituents were located in the o-, m- and p-positions of the
acetophenone (entries 2-4). Although m-bromo acetophenone reduction was yielded to similar
acetophenone with 91 % conversion (entry 6), the conversions of o- and p- bromo
acetophenones were observed lower (entries 5-7). It was also found that the best conversion
was obtained (99 %) in spite of steric effect of the o-methoxy substituent of the aromatic ring
(entry 8). Nevertheless, that conversion was found to decrease from 99 to 85 % while
proceeding towards p- position (entries 9 and 10). Besides, 2-acetonapthone was realized to
have similar conversion when compared to acetophenone in transfer hydrogenation (entry 11).
The use of sterically hindered ketones on aliphatic position of acetophenone such as 2-methyl-
1-phenylpropan-1-one and propiophenone led to a dramatic decrease in conversion value (45
and 52 % respectively at 24 h.) and when a higher catalyst amount was used, higher
conversion was obtained in comparison with substrate ratio (98 and 93 %, entries 12, 13). We
12

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also tested this reaction on benzophenone and its derivatives. As a result of this reaction, p-
methoxy on benzophenone had lower conversion ratio in comparison to the compounds which
involved benzophenone and methyl group bearing p- position (entries 14-16). Furthermore,
cyclohexanone as an aliphatic ketone and benzaldehyde as a simple aromatic aldehyde was
performed in transfer hydrogenation with good conversions (entries 17, 18).
Conclusions
Azo containing Schiff base Ru (II) complexes were synthesized by the reaction of
[RuCl2(p-cymene)] with 4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(phenylimino)methyl)phenol
2, 4-((E)-(4-ethylphenyl)diazenyl)-2-((E)-(naphthalen-1-ylimino)methyl)phenol 3 and 2-
((benzylimino)methyl)-4-((E)-(4-ethylphenyl)diazenyl)phenol 4 at 50°C in methanol.
According to the analytical, UV-visible, IR and NMR data, the Ru (II) complexes 5-7 and 9
are formed by the coordination of N and O atoms of the ligands.
These three Ruthenium (II) complexes 5-7 were used as catalysts for the transfer
hydrogenation of a series of ketones and benzaldehyde in 2-propanol. Following the
comparison of complex 9 with the other three complexes 5-7, it was observed that azo group
has got noticeably increasing effect on the catalytic activity. The results showed that the
[RuCl(2)p-cymene] complex 5 is efficient than the other Ru (II) complexes. Investigation of
side group effect of relevant complexes in transfer hydrogenation is under way.
Acknowledgements
This work was financially supported by the Unit of Coordination of Scientific
Research Projects, Kahramanmaraş Sütçü Imam University, Kahramanmaraş, Turkey (Project
no: 2014/2-45YLS). The authors are grateful to TUBITAK (113Z294) for research funds.
Also we would like to thank to DUPTAM, Dicle University, Turkey, for the use of X-ray
diffractometer.
13

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References
[1] E.O. Ozcan, D. Mercan, N. Gurbuz, E. Cetinkaya, B. Cetinkaya, I. Ozdemir, In situ
catalytic activities of 1,3-dialkyltetrahydropyrimidinium salts/[RuCl2(p-cymene)](2) system
for transfer hydrogenation reactions, Turk J Chem, 35 (2011) 699-709.
[2] A. Del Zotto, W. Baratta, M. Ballico, E. Herdtweck, P. Rigo, [RuCl2(PPh3)(PNN ')]
complexes as efficient catalysts in transfer hydrogenation of ketones, Organometallics, 26
(2007) 5636-5642.
[3] D.S. Matharu, D.J. Morris, G.J. Clarkson, M. Wills, An outstanding catalyst for
asymmetric transfer hydrogenation in aqueous solution and formic acid/triethylamine, Chem
Commun, (2006) 3232-3234.
[4] X.-H. Zhu, L.-H. Cai, C.-X. Wang, Y.-N. Wang, X.-Q. Guo, X.-F. Hou, Efficient and
versatile transfer hydrogenation catalysts: Iridium (III) and ruthenium (II) complexes with 4-
acetylbenzyl-N-heterocyclic carbenes, Journal of Molecular Catalysis A: Chemical, 393
(2014) 134-141.
[5] R.N. Prabhu, R. Ramesh, Synthesis, structural characterization, electrochemistry and
catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes containing tridentate
benzoylhydrazone ligands, J Organomet Chem, 718 (2012) 43-51.
[6] R. Malacea, R. Poli, E. Manoury, Asymmetric hydrosilylation, transfer hydrogenation and
hydrogenation of ketones catalyzed by iridium complexes, Coordin Chem Rev, 254 (2010)
729-752.
[7] S. Gladiali, E. Alberico, Asymmetric transfer hydrogenation: chiral ligands and
applications, Chem Soc Rev, 35 (2006) 226-236.
[8] S. Dayan, N.K. Ozpozan, N. Ozdemir, O. Dayan, Synthesis of some ruthenium(II)-Schiff
base complexes bearing sulfonamide fragment: New catalysts for transfer hydrogenation of
ketones, J Organomet Chem, 770 (2014) 21-28.
[9] T. Wang, X.Q. Hao, X.X. Zhang, J.F. Gong, M.P. Song, Synthesis, structure and catalytic
properties of CNN pincer palladium(II) and ruthenium(II) complexes with N-substituted-2-
aminomethyl-6-phenylpyridines, Dalton T, 40 (2011) 8964-8976.
[10] E. de Julián, J. Díez, E. Lastra, M.P. Gamasa, Iridium(I) complexes bearing the (S,S)-iPr-
pybox ligand in the asymmetric transfer hydrogenation of acetophenone, Journal of Molecular
Catalysis A: Chemical, 394 (2014) 295-302.
[11] M. Aydemir, N. Meric, C. Kayan, F. Ok, A. Baysal, Rhodium-catalyzed transfer
hydrogenation with functionalized bis(phosphino)amine ligands, Inorganica Chimica Acta,
398 (2013) 1-10.
[12] G. Chelucci, S. Baldino, W. Baratta, Ruthenium and osmium complexes containing 2-
(aminomethyl)pyridine (Ampy)-based ligands in catalysis, Coordin Chem Rev, 300 (2015)
29-85.
[13] S. Karabuga, S. Bars, I. Karakaya, S. Gumus, Efficient transfer hydrogenation reactions
with quinazoline-based ruthenium complexes, Tetrahedron Letters, 56 (2015) 101-104.
[14] Z. Shaghaghi, Spectroscopic properties of some new azo-azomethine ligands in the
presence of Cu2+, Pb2+, He2+, Co2+, Ni2+, Cd2+ and Zn2+ and their antioxidant activity,
Spectrochim Acta A, 131 (2014) 67-71.
[15] J.L. Pratihar, S. Bhaduri, P. Pattanayak, D. Patra, S. Chattopadhyay, Reactions of 2-
(arylazo)aniline with ruthenium substrates: Isolation, characterizations and reactivities of
delocalized diazoketiminato and orthometallated Ru(II) chelates, J Organomet Chem, 694
(2009) 3401-3408.
[16] F. Ding, Y.G. Sun, F. Verpoort, O,N-Bidentate Ruthenium Azo Complexes as Catalysts
for Olefin Isomerization Reactions, Eur J Inorg Chem, (2010) 1536-1543.
14

ACCEPTED MANUSCRIPT
[17] R.K. Rath, M. Nethaji, A.R. Chakravarty, Synthesis, crystal structure and catalytic
properties of (p-cymene)ruthenium(II) azophenol complexes: azophenyl to azophenol
conversion by oxygen insertion to a rutheniumcarbon bond, J Organomet Chem, 633
(2001) 79-84.
[18] R.K. Rath, M. Nethaji, A.R. Chakravarty, Transfer hydrogenation of acetophenone
promoted by (arene)ruthenium(II) reduced Schiff base complexes: an X-ray structure of [(η6-
p-cymene)RuCl(OC6H4-2-CH2NHC6H4-p-Me)], Polyhedron, 20 (2001) 2735-2739.
[19] M. Wachhold, W.S. Sheldrick, Methanolothermal synthesis of Rb3AsSe4 center dot 2
Se-6 and Cs3AsSe4 center dot 2 Cs2As2Se4 center dot 6 Te4Se2. Two selenidoarsenates with
six-membered chalcogen rings, Zeitschrift Fur Naturforschung Section B-a Journal of
Chemical Sciences, 52 (1997) 169-175.
[20] M. Wachhold, W.S. Sheldrick, Methanolothermal design and structure of cesium
polyselenidotellurates Cs4TexSe16-x (x = 1, 4) and Cs4Te9.74Se13.26 with ordered Se/Te
rings and chains, Journal of Solid State Chemistry, 134 (1997) 364-375.
[21] L. Farrugia, ORTEP-3 for Windows - a version of ORTEP-III with a Graphical User
Interface (GUI), Journal of Applied Crystallography, 30 (1997) 565.
[22] A. Spek, Single-crystal structure validation with the program PLATON, Journal of
Applied Crystallography, 36 (2003) 7-13.
[23] M. Odabaşoğlu, Ç. Albayrak, R. Özkanca, F.Z. Aykan, P. Lonecke, Some polyhydroxy
azo–azomethine derivatives of salicylaldehyde: Synthesis, characterization, spectroscopic,
molecular structure and antimicrobial activity studies, Journal of Molecular Structure, 840
(2007) 71-89.
[24] E. Peker, S. Serin, Synthesis and characterization of some cobalt(II), copper(II), and
nickel(II) complexes with new Schiff bases from the reaction of p-aminoazobenzene with
salicylaldehyde, Syn React Inorg Met, 34 (2004) 859-872.
[25] G. Venkatachalam, R. Ramesh, Catalytic and biological activities of Ru(III) mixed
ligand complexes containing N,O donor of 2-hydroxy-1-naphthylideneimines, Spectrochimica
Acta Part A: Molecular and Biomolecular Spectroscopy, 61 (2005) 2081-2087.
[26] A. Kilic, M. Ulusoy, M. Durgun, Z. Tasci, I. Yilmaz, B. Cetinkaya, Hetero- and homo-
leptic Ru(II) catalyzed synthesis of cyclic carbonates from CO2; Synthesis, spectroscopic
characterization and electrochemical properties, Appl Organomet Chem, 24 (2010) 446-453.
[27] E. Ispir, The synthesis, characterization, electrochemical character, catalytic and
antimicrobial activity of novel, azo-containing Schiff bases and their metal complexes, Dyes
Pigments, 82 (2009) 13-19.
[28] S.H. Dale, M.R.J. Elsegood, Oxalate complexes of the ([eta]6-p-cymene)ruthenium(II)
fragment:
[mu]-oxalato-[kappa]2O1,O2:[kappa]2O1',O2'-bis[([eta]6-p-
cymene)(triphenylphosphine-[kappa]P)ruthenium(II)] bis(tetrafluoroborate) and ([eta]6-p-
cymene)(oxalato-[kappa]2O,O')(pyridine-3,5-dicarboxylic acid-[kappa]N)ruthenium(II), Acta
Crystallographica Section C, 62 (2006) m166-m170.
[29] N.M. Sanchez Ballester, M.R.J. Elsegood, M.B. Smith, [mu]-Pyrazine-2,5-
dicarboxylato-bis[chlorido([eta]6-p-cymene)ruthenium(II)] tert-butanol disolvate, Acta
Crystallographica Section E, 64 (2008) m309-m310.
[30] R.E. Sykora, A.G. Harris, J.W. Clements, N.W. Hoffman, Dichlorido([eta]6-p-
cymene)(4-fluoroaniline-[kappa]N)ruthenium(II), Acta Crystallographica Section E, 67
(2011) m99-m100.
[31]
S.M.M.
Knapp,
L.N.
Zakharov,
D.R.
Tyler,
Dichlorido([eta]6-p-
cymene)(ethoxydiphenylphosphane)ruthenium(II), Acta Crystallographica Section E, 68
(2012) m1465.
15

ACCEPTED MANUSCRIPT
[32] S. Dayan, N.K. Ozpozan, N. Özdemir, O. Dayan, Synthesis of some ruthenium(II)–
Schiff base complexes bearing sulfonamide fragment: New catalysts for transfer
hydrogenation of ketones, J Organomet Chem, 770 (2014) 21-28.
16

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Table 1.
Crystal data and structure refinement for complex 5 and complex 9.
Properties
Complex 5
Complex 9
C23H24ClNORu
Empirical Formula
Formula weight
C32H34 ClN3ORu
613.14
466.95
Temperature
296(2) K
296(2) K
Wavelength
0.71073 Å
0.71073 Å
Crystal system, space group
Unit cell dimensions
Triclinic, P-1
a = 10.7316(4) Å
b = 11.4017(4) Å
c = 14.4256(6) Å
α = 102.069(2) o
β = 108.783(2) o
γ = 106.907(2) o
1506.93(10) Å3
2, 1.351 Mg/m3
0.637 mm-1
Monoclinic, P21/c
a = 17.9196(3)
b = 8.2451(1)
c = 13.4869(2)
α = 90.00
β = 94.7610(10)
γ = 90.00
Volume
1985.80 Å3
Z, Calculated density
Absorption coefficient
F(000)
4, 1.562 Mg/m3
0.937 mm-1
952
632
Crystal size
0.40 x 0.35 x 0.10 mm
1.58 to 30.84
-15≤h≤15
-16≤k≤16
-20≤l≤ 9
0.40 x 0.30 x 0.15 mm
2.28-39.71
-32 ≤ h≤ 32
-14 ≤ k≤ 14
-24 ≤ l≤ 23
Theta range for data collection (o)
Limiting indices
Reflections collected / unique
28805 / 8992
[R(int) = 0.0545]
94.8 %
0.9391 and 0.7847
Full-matrix least-squares on
F2
45966 / 12032
[R(int)=0.0234]
99.5 %
Completeness to theta
Max. and min. Transmission
Refinement method
0.8723 and 0.7057
Data / restraints / parameters
Goodness-of-fit on F2
8992 / 0 / 346
1.051
12032 / 0 / 247
1.050
Final R indices [I>2σ(I)]
R indices (all data)
R1 = 0.0630, wR2 = 0.1209
R1 = 0.1150, wR2 = 0.1459
1.330 and -0.704
R1 = 0.0337, wR2 = 0.0773
R1 = 0.0555, wR2 = 0.0881
0.973 and -0.608
Largest diff. peak and hole (e.Å3)

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Table 2.
Geometric parameters around Ru involving ring centroids (Å, o).
Complex 5
Complex 9
Cg4-Ru1
O1-Ru1
Cl1-Ru1
N1-Ru1
1.667(2)
Cg3-Ru1
O1-Ru1
Cl1-Ru1
N1-Ru1
1.6643(12)
2.0517(17)
2.4357(13)
2.0874(17)
129.33(3)
85.20(4)
2.062(3)
2.4297(13)
2.099(3)
Cg4-Ru1-Cl1
Cl1-Ru1-O1
Cl1-Ru1-N1
Cg4-Ru1-O1
O1-Ru1-N1
Cg4-Ru1-N1
127.97(8)
86.59(11)
82.62(11)
123.30(12)
88.65(14)
132.87(12)
Cg3-Ru1-Cl1
Cl1-Ru1-O1
Cl1-Ru1-N1
Cg3-Ru1-O1
O1-Ru1-N1
Cg3-Ru1-N1
85.06(4)
124.11(4)
88.62(4)
130.02(4)
Cg4 is the centroid of the (C23-C28) ring for complex 5 and Cg3 is the centroid of the (C15-
20) ring for complex 9.

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Table 3.
Hydrogen-bond geometry (Å, o) for Ru complex 5.
D-H···A
D-H
D...A
H...A
D-H…A
165.00
140.00
172.42
141.79
135.19
154.28
C7-H7···Cl1i
0.9300
0.9300
0.9300
0.9300
0.9300
0.9300
3.648(4)
3.496(5)
3.5600
3.914(7)
3.748(5)
3.951(7)
2.7400
2.7300
2.636(4)
3.1409
3.0306
3.0643
C24-H24···Cl1ii
C25-H25···O1ii
C12-H12···Cg1
C28-H28···Cg2iii
C31-H31B···Cg3iv
Symmetry codes: (i) 2-x,-y,1-z; (ii) 2-x,1-y,1-z; (iii) 1+x, y, z; (iv) 1+x,1+y, z.
Cg1, Cg2 and Cg3 are the centroids of the (C1-C6), (C9-C14) and (C15-C20) rings,
respectively.

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Table 4.
Hydrogen-bond geometry (Å, o) for Ru complex 9.
D-H···A
D-H
0.93
D...A
3.558(1)
H...A
2.801
D-H…A
139.38
C9-H9···Cl1i
C20-H20···Cg2i
C22-H22A···Cl1ii
C11-H11···Cl1iii
C10-H10··· Cg2iv
C13-H13···Cg3v
C14-H14C···Cg2vi
C23-H23C···Cg1vii
0.93
0.96
0.93
0.93
0.93
0.96
0.96
3.8223(16)
3.810(2)
3.886(2)
4.065(2)
3.7363(17)
3.812(3)
3.788(3)
3.2845
2.903
118.96
157.84
163.66
138.59
144.40
142.50
120.26
2.985
3.3203
2.9409
3.0056
3.2124
Symmetry codes: (i) x, y, z; (ii) x, y-1, z; (iii) 1+x, y-1/2, -z+1/2; (iv) 1-x, 1/2+y, 1/2-z; (v) x,
3/2-y, 1/2+z; (vi) x, 5/2-y, -1/2+z; (vii) x, -1+y, z.
Cg1, Cg2 and Cg3 are the centroids of the (C1-C6), (C8-C13) and (C15-C20) rings.

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Table 5.
Reaction optimization for transfer hydrogenation of acetophenone
Entry
Acetophenone
S/C
Complex
Basea
Time (h)
Conversion %d
1
2
3
4
5
6
7
8
9
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
1 mmol
333
333
333
333
333
333
333
333
333
333
200
125
5
6
7
9
5
5
5
5
5
5
5
5
NaOH
NaOH
NaOH
NaOH
KOH
24
24
24
24
24
24
24
24
24
95
89
79
67
83
91
72
86
94
NaOtBu
KOtBu
NaOiPr
NaOHb
NaOHc
NaOHb
NaOHb
10
11
12
24
24 (8)
8
94
98 (95)
95
a: 00.3 mmol, 0.1 M, b: 00.5 mmol, 0.1 M, c:0. 1 mmol, 0.1 M, d: Determined by GC (Agilent HP-5 column).

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Table 6.
Catalytic transfer hydrogenation of ketones with ruthenium complex 5
Time
(h)
Entry
1
Substrate
S/C
200
Conversion (%)a
98
Entry
10
Substrate
S/C
Time (h) Conversion %a
200
24
24
24
85
95
200
2
3
4
5
200
200
24
24
24
24
89
95
91
47
11
12
13
14
200
(100)
24
24
51
98
200
200
200
(100)
24
24
51
93
200
200
200
200
24
24
24
24
24
99
95
66
95
99
200
200
200
6
7
8
9
24
24
24
24
91
73
99
95
15
16
17
18
200
200

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Fig. 1. Reagent and conditions: (i) NaNO2, NaOH, H2O, 0-5 °C; (ii) methanol, reflux, 8 h;
(iii) KOH, [RuCl2(p-cymene)]2, MeOH, 50 °C, 12 h;

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Fig.2. An ORTEP view of complex 7, showing 30% probability displacement ellipsoids.
Hydrogen atoms have been omitted for clarity.

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Fig.3. An ORTEP view of the complex 9, showing 30% probability displacement ellipsoids.

ACCEPTED MANUSCRIPT
HO
N
N
N
N
O
PiPr2
N
O
PiPr2
R
N
N
NH2
HC
NH2
R
R
NO
NNN
CNN
PNP
NN
Scheme 1

ACCEPTED MANUSCRIPT
►
Three new azo-containing Schiff Bases and their Ru (II) metal complexes were
synthesized. And single-crystal X-ray analyses were performed for complex 7 and 9.
► The synthesized metal complexes were performed as catalysts for the transfer
hydrogenation of a series of ketone and benzaldehyde in 2-propanol.
► Following the comparison of complex 9 with the other three complexes 5-7, it was
observed that azo group has got remarkably increasing effect on the catalytic activity.
► Best active catalyst has found to be complex 5.