Synthesis and characterization of a ruthenium complex with bis(diphenylphosphino)propane and thioether containing ONS donor ligand: Application in transfer hydrogenation of ketones

Article abstract of DOI:10.1016/j.poly.2017.04.019

The synthesis and characterization of a mixed ligand Ru(II) complex, [Ru(dppp)(L)Cl] (1) (where, dppp?=?bis(diphenylphosphino) propane) is reported. The distorted octahedral geometry of the complex is confirmed by X-ray diffraction method. Cyclic voltammogram in CH₃CN exhibits Ru(II)/Ru(III) quasireversible oxidation couple along with reversible azo-bond reductions peaks with reference to Ag/AgCl electrode. The efficiency of the complex towards the transfer hydrogenation of ketones in i-PrOH is examined and an excellent catalytic conversion (90–98%) is observed. The electronic structure and redox properties are well corroborated with the DFT calculations.

Full text of DOI:10.1016/j.poly.2017.04.019

Accepted Manuscript
Synthesis and characterization of a ruthenium complex with bis(diphenylphos-
phino)propane and thioether containing ONS donor ligand: Application in
transfer hydrogenation of ketones
Sujan Biswas, Deblina Sarkar, Puspendu Roy, Tapan Kumar Mondal
PII:
S0277-5387(17)30288-7
DOI:
http://dx.doi.org/10.1016/j.poly.2017.04.019
POLY 12597
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
2 February 2017
11 April 2017
18 April 2017
Please cite this article as: S. Biswas, D. Sarkar, P. Roy, T. Kumar Mondal, Synthesis and characterization of a
ruthenium complex with bis(diphenylphosphino)propane and thioether containing ONS donor ligand: Application
in transfer hydrogenation of ketones, Polyhedron (2017), doi: http://dx.doi.org/10.1016/j.poly.2017.04.019
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1
Synthesis and characterization of
a
ruthenium complex with
bis(diphenylphosphino)propane and thioether containing ONS donor ligand:
Application in transfer hydrogenation of ketones
*
Sujan Biswas, Deblina Sarkar, Puspendu Roy and Tapan Kumar Mondal
Inorganic Chemistry Section, Department of Chemistry, Jadavpur University, Kolkata-700032,
India.
Abstract
The synthesis and characterization of a mixed ligand Ru(II) complex, [Ru(dppp)(L)Cl] (1)
(
where, dppp = bis(diphenylphosphino) propane) is reported. The distorted octahedral geometry
of the complex is confirmed by X-ray diffraction method. Cyclic voltammogram in CH CN
3
exhibits Ru(II)/Ru(III) quasireversible oxidation couple along with reversible azo-bond
reductions peaks with reference to Ag/AgCl electrode. The efficiency of the complex towards the
transfer hydrogenation of ketones in i-PrOH is examined and an excellent catalytic conversion
(
90-98%) is observed. The electronic structure and redox properties are well corroborated with
the DFT calculations.
Key words: Ruthenium complex; Thioether ligand; X-ray structure; Electrochemistry; Transfer
hydrogenation of ketones; DFT calculation.
Corresponding author: Ph.: 91-033-24572970; Email: tkmondal@chemistry.jdvu.ac.in

2
1. Introduction
Transition metal complexes with phosphine ligands have important industrial applications
because of their efficient catalytic activities [1, 2]. The electron donating and accepting ability of
bis(dialkylphosphino)alkane ligands in metal complexes can be easily tuned with the variation of
alkyl groups bonded to the phosphorus atoms [1, 3-5]. Moreover, this change affects the activity,
basicity, selectivity and stability of catalytic processes [6, 7]. Tolman made a useful comparison
between the electronic and the steric effects of these ligands [3].
Transfer hydrogenation of ketones to corresponding alcohols is one of the most important
fundamental subjects in modern synthetic chemistry [8, 9] and is a convenient method to reduce
carbonyl compounds without the use of hazardous hydrogen gas or moisture-sensitive hydride
reagents [10-13]. Moreover, the transfer hydrogenation of ketones is widely accepted in industry
as a cost-effective way for the production of a number of hydroxylated organic products [14].
The studies to develop the new catalysts for the transfer hydrogenation is still of considerable
interest for the finding of more efficient catalyst. The most efficient and selective catalyst for
transfer hydrogenation reactions are ruthenium, iridium and rhodium complexes [15-19]. The
‘‘Ru(P–P)” core is recognized as an active catalytic species for the hydrogenation of unsaturated
carbonyl compounds [20-22]. Recently, mixed-ligand diamine-bis(diphosphine) ruthenium(II)
complexes have received much attention due to their remarkable performance in selective and
asymmetric hydrogenation of carbonyl compounds [23-26].
Azo group shows donor properties and play an important role in coordination chemistry
[
27-29]. Synthesis of ruthenium complexes with azo ligands and their usages in transfer
hydrogenation, oxidation of alcohols and metal-carbon bond formation reactions are widely
studied [29-31]. The ruthenium complexes with polydentate ligands also have significant

3
importance in catalytic reactions [32-34]. As a part of our ongoing research on synthesis,
characterization and catalytic applications of ruthenium complexes [35-38], in the present work
we have synthesized
bis(diphenylphosphino)propane (dppp) with ONS donor azo-thioether ligand, 3-(2-(2-
methylthio)phenyl)hydrazono)pentane-2,4-dione (HL) (scheme 1). An array of tools including
a
ruthenium(II) complex, [Ru(dppp)(L)Cl] (1) bearing
(
X-ray diffractometry, electrochemistry, and electronic absorption and emission spectroscopy
abetted with DFT calculations were used to characterize the complex. Further, the catalytic
activity of the complex towards transfer hydrogenation of ketones was investigated.
Scheme 1. Synthesis of ruthenium(II) complex, [Ru(dppp)(L)Cl] (1)
2. Experimental
2
.1. Materials and methods
All the reagents and solvents were purchased from commercial sources and used as received.
Acetylacetone and inorganic metal salts were obtained from E. Merck, India. 2-Aminothiophenol
was purchased from Sigma Aldrich. 3-(2-(2-(Methylthio)phenyl)hydrazono)pentane-2,4-dione
(
HL) was prepared by following the published procedure [39]. Microanalyses (C, H, N) data
were obtained using a PerkinElmer Series-II CHN-2400 CHNS/O elemental analyzer. Electronic

4
spectra were measured on a Lambda 750 PerkinElmer spectrophotometer in acetonitrile. IR
-1
spectra were recorded on a RX-1 PerkinElmer spectrometer in the range of 4000-400 cm with
the samples in the form of KBr pellets. HRMS mass spectra were obtained on a Waters (Xevo
G2 Q-TOF) mass spectrometer. NMR spectra were recorded in CDCl on a Bruker (AC) 300
3
MHz FT-NMR spectrometer in the presence of TMS as internal standard. Cyclic voltammetric
measurements were carried out using a CHI Electrochemical workstation. A platinum wire
working electrode, a platinum wire auxiliary electrode and Ag/AgCl reference electrode were
used in a standard three-electrode configuration. Bu
4
NPF
6
was used as the supporting electrolyte
in acetonitrile and the scan rate used was 50 mV s under nitrogen atmosphere.
.2. Synthesis of ruthenium(II) complex, [Ru(dppp)(L)Cl] (1)
RuCl .3H O (0.13 g, 0.5 mmol) and 3-(2-(2-(methylthio)phenyl)hydrazono)pentane-2,4-dione
HL) (0.13 g, 0.5 mmol) were dissolved in 25 mL acetonitrile and refluxed for 1 h. After that
−
1
2
3
2
(
bis(diphenylphosphino)propane (dppp) (0.20 g, 0.5 mmol) was added to the solution. The
reaction mixture was heated for an additional 5 h. The solvent was then removed under reduced
pressure. The crude product was dissolved in dichloromethane and purified by column
chromatography using a silica gel (mesh 60-120). The orange band of 1 was eluted by 50% (v/v)
ethyl acetate-petroleum ether mixture. On removal of the solvent under reduced pressure the pure
complex 1 was obtained as an orange solid which was further dried under vacuum. Yield, 0.27 g
(
68%).
Anal. Calc. for C39
H39ClN
2
2
O RuS (1): C, 58.68; H, 4.92; N, 3.51; S, 4.02%. Found: C,
-1
1
5
8.26; H, 4.78; N, 3.42; S, 3.92%. IR data (KBr, cm ): 1665 υ(C=O); 1369 υ(N=N). H NMR
data (CDCl
3
, ppm): 6.82-7.86 (24H, m, aromatic protons), 3.06 (4H, br, PCH
2
), 2.67 (3H, s,
SCH ), 2.61 (2H, br, P CH
3
2
CH ), 2.52 (3H, s, CH ), 2.39 (3H, s, CH ). HRMS m/z, 821.3632
2
3
3

5
+
II
III
•−
(
M-Na : 821.26). E1/2 (Ru /Ru ): 1.12 V (∆E = 95 mV); E1/2(L/L ): -0.89 V (∆E = 75 mV) and
•
−
2-
E
pc (L /L ): -1.75 V.
2
.3. Crystal structure determination and refinement
Single crystals of 1 were obtained by slow diffusion of n-hexane into dichloromethane solution
of the complex. The crystal evaluation and data collection were performed on an automated
Bruker AXS Kappa smart Apex-II diffractometer equipped with an Apex-II CCD area detector
using a fine focus sealed tube as the radiation source of graphite monochromated Mo Kα
radiation (λ = 0.71073 Å). The reflections were successfully indexed by an automated indexing
routinebuilt into the APEX II programme suite [40]. Reflection data were recorded using the ω
scan technique. The structure was solved and refined by full-matrix least-squares techniques on
2
F using the SHELX-97 [41]. The absorption corrections were done by multi-scan method and
all the data were corrected for Lorentz, polarization effect. Hydrogen atoms were included in the
refinement process as per the riding model. Details of crystal analyses, data collection and
structure refinement are summarized in Table 1.
2
.4. Computational method
Full geometry optimization of the complex was carried out by density functional theory (DFT)
method using B3LYP hybrid exchange correlation functional [42,43]. All elements except
ruthenium were assigned the 6-31G(d) basis set, whilst the LanL2DZ basis set with effective
core potential was employed for ruthenium atom [44-46]. Vibrational frequency calculation was
performed to ensure that the optimized geometry was in local minima on the potential energy
surface and only positive Eigen values were obtained. Vertical electronic excitations based on
B3LYP optimized geometry were computed using the time-dependent density functional theory
(
TDDFT) formalism [47-49] using conductor-like polarizable continuum model (CPCM) [50-52]

6
in acetonitrile to simulate the solvent. All calculations were performed with Gaussian09 program
package [53]. GaussSum [54] was used to calculate the fractional contributions of various groups
to each molecular orbital.
2
.5. Procedure of transfer hydrogenation of ketones
In a typical experiment the ketone (1 mmol), KOH (0.1 mmol), and ruthenium(II) complex
0.0025 mmol) were added to 10 mL of i-PrOH, and the mixture was stirred at 80 °C in an inert
(
atmosphere. The reaction was then monitored at various time intervals by the use of GC. After
the reaction was complete, i-PrOH was removed on a rotary evaporator, and the resulting
semisolid was extracted with diethyl ether (5 × 10 mL). The extract was passed through a short
column of silica gel. The column was washed with ∼100 mL of diethyl ether. All the eluates
from the column were mixed, and the solvent from the mixture was evaporated off on a rotary
evaporator. The resulting residue was dissolved in 2-3 mL of hexane. Conversions were
determined by GC instrument equipped with a flame ionization detector (FID) using a HP-5
column of 30 m length, 0.53 mm diameter and 5.00 µm film thickness. The column, injector and
0
detector temperatures were 200, 250 and 250 C respectively. The carrier gas was N
2
(UHP
grade) at a flow rate of 30 mL/min. The injection volume of sample was 2 µL. The alcohols were
identified by GC co-injection with authentic samples.
3
. Results and discussion
3
.1. Synthesis and formulation
The ligand, 3-(2-(2-(methylthio)phenyl)hydrazono)pentane-2,4-dione (HL) was prepared by
following the published procedure [39]. The ruthenium(II) complex, [Ru(dppp)(L)Cl] (1)
(
where, dppp = bis(diphenylphosphino)propane) was synthesized by the reaction of RuCl
3
.3H O,
2

7
dppp and HL under refluxing condition in acetonitrile (scheme 1). The complex was
characterized by various spectroscopic techniques. Mass spectrum and elemental analysis data
support the composition of the complex (see experimental section). In the IR spectrum the bands
-1
at 1665 and 1369 cm correspond to υ(C=O) and υ(N=N) respectively. The υ(N=N) appeared at
lower frequency region compare to free ligand value supporting the coordination of azo-N to
*
1
ruthenium(II) and extensive dπ(Ru) → π (N=N) back donation in the complex. H NMR
spectrum of the complex was taken in CDCl . The aromatic proton signals appeared at 6.82-7.86
ppm region, while the expected singlet peaks correspond to S-CH and CH protons appeared at
.67, 2.52 and 2.39 ppm. The P-CH signals appeared as broad peaks at 3.06 and 2.61 ppm in the
3
3
3
2
2
complex. The geometry of the complex was further confirmed by single crystal X-ray structure
analysis.
3
.2. X-ray structure of [Ru(dppp)(L)Cl] (1)
Single crystals suitable for structure determination were obtained by slow diffusion of n-hexane
into dichloromethane solution of the complex. The crystallographic data collection and
refinement parameters are given in Table 1; selected bond lengths and angles are given in Table
2
. ORTEP plot with atomic numbering scheme is shown in Fig. 1. The ruthenium atom adopts a
distorted octahedral geometry in the complex, as evidenced by P1-Ru1-P1 (92.00(4)º), O1-Ru1-
N2 (87.62(11)º) and S1-Ru1-N2 (84.33(9)º) bite angles. The thioether ligand binds to the
ruthenium atom by thioether-S, azo-N and O atom of acetyl acetonato moiety. The dppp ligand
binds via its two P-atoms trans to the azo-N and Cl atoms, with Ru1-P1 and Ru1-P2 bond
distances of 2.2802(11) and 2.3602(11) Å respectively. The Ru1-Cl1 (2.4680(10) Å), Ru1-N2
(
2.044(3) Å) and Ru1-S1 (2.3031(10) Å) are in the typical range reported in the literature [55-
7].
5

8
3
.3. DFT computation and electronic structure
The geometry of complex 1 was optimized by DFT method in singlet ground state using the
B3LYP correlation functional. The optimized bond parameters are given in Table 2. The
calculated bond distances and angles are well correlated with the X-ray crystal structure data.
The contour plots of selected molecular orbitals of the complex are shown in Fig. 2,
while the energy and compositions are summarized in Table 3. The HOMO to HOMO-3 are
composed of mixed dπ(Ru) (29-47%) and π(L) (21-50%) orbitals along with significant
*
contribution of pπ(Cl) (10-39%) orbitals. The LUMO has π (L) character (94%) with major
*
contribution of π (N=N) orbital (42%) and the HOMO-LUMO energy gap in the complex is 3.45
*
eV. LUMO+1 to LUMO+5 are composed of π (dppp) orbitals along with reduced contribution of
*
dπ(Ru) and π (L).
3
.4. TDDFT calculation and electronic spectra
The solution spectrum of complex 1 in acetonitrile exhibits moderately intense broad peak at 466
-1
-1
-1
-1
nm (ε = 3907 M cm ). In addition, peaks at 390 nm (ε = 5547 M cm ) and 337 nm (ε = 9347
-1
-1
-1
-1
M cm ) along with a sharp peak at 305 nm (ε = 14062 M cm ) are observed (Fig. 3). To
interpret the electronic spectrum of the complex singlet-singlet vertical electronic excitations
were calculated by TDDFT/CPCM method in acetonitrile. The low energy broad peak at 446 nm
corresponds to HOMO → LUMO transition (λcalc. = 477 nm, Osc. Strength (f) = 0.035) having
mixed metal to ligand charge transfer (MLCT) and intra-ligand charge transfer (ILCT) character. The
band at 390 nm corresponds to HOMO-2 → LUMO transition (λcalc. = 403 nm, Osc. Strength (f) =
0
.047) with mixed MLCT and XLCT (halogen to ligand charge transfer) character, while the bands at 337
nm and 305 nm have ILCT character (Table 4).
.5. Electrochemistry
3

9
The electrochemical behavior of the complex was investigated by cyclic voltammetry (CV) in
-1
presence of Bu
4
NPF in acetonitrile at scan rate 50 mV S . Cyclic voltammogram exhibits one
6
quasireversible oxidation couple at 1.12 V (∆E = 96 mV) along with one reversible reduction
couple at -0.89 V (∆E = 74 mV) and an irreversible cathodic reduction peak with Epc, -1.75 V,
positive and negative to reference electrode (Ag/AgCl) respectively in the potential range 2.0 to
−2.0 V (Fig. 4). The oxidation process may be assigned as Ru(II) to Ru(III) oxidation or the
oxidation of redox active ONS ligand as the HOMO has 36% dπ(Ru) and 50% π(L) character.
•−
The reversible reduction couple at -0.89 V corresponds to L/L reduction as the LUMO has 94%
*
*
π (L) character with major contribution of π (N=N) orbital (42%). The cathodic peak at -1.75 V
•−
2-
corresponds to further reduction of L to L in the complex.
3.6. Catalytic transfer hydrogenation
The transfer hydrogenation is an important and efficient reaction in organic synthesis. Many
ruthenium(II) complexes were used as effective catalysts for transfer hydrogenation reactions,
which encourage us to use our synthesized complex for this purpose.
Initially to determine the catalytic efficiency of complex 1 for the conversion of
i
acetophenone to 1-phenylethanol as a model reaction using PrOH as the solvent was carried out
in presence of different bases. The conversion was found to be effective in presence of KOH in
t
comparison to Na
2
CO
3
, CH
3
COONa or KO Bu. Again, to understand the catalytic efficiency of
the complex 1, different catalyst:substrate (C:S) ratios were tested in the transfer hydrogenation
of acetophenone in i-PrOH/KOH and the results are given in Table 5. It is found that the
conversion is excellent in C:S ratio of 1:200. With the variation of C:S ratio to 1:400, 1:600,
1
:800, 1:1000 or 1:1200, the reaction still proceeds but a sharp decrease in rate of conversion is
observed for C:S ratio 1:600 to 1:1200. The conversion is excellent with appreciable turnover

10
number (TON) when the C:S ratio is 1:400 and hence this C:S ratio is the best choice for
catalytic transfer hydrogenation reactions for complex 1. A series of ketones were screened in
transfer hydrogenation reaction using the optimum condition, C:S ratio of 1:400 and KOH as
base. The results are summarized in Table 6. The maximum conversion was observed for p-
nitroacetophenone (98.3%). The conversions of other acetophenones were found to be in the
range 88-98%. The results are comparable to the other reported ruthenium(II) complexes [58-
6
1].
4. Conclusion
Herein we have successfully synthesized and characterized ruthenium(II) mixed ligand complex,
Ru(dppp)(L)Cl] (1) (where, dppp = bis(diphenylphosphino)propane). The distorted octahedral
[
geometry is confirmed by X-ray diffraction method. Cyclic voltammetric study supports the
participation of both Ru(II) and redox active ONS ligand in the redox processes. The efficiency
of the complex towards transfer hydrogenation reaction of ketones is studied and 90-98%
conversions are observed. Theoretical results obtained by DFT/B3LYP method well interpreted
the electronic structure and redox properties of the complex.
Acknowledgement
Financial support received from the Department of Science and Technology, New Delhi, India is
gratefully acknowledged. S. Biswas and P. Roy thankful to UGC, New Delhi, India for
fellowships.
Supplementary materials

11
Crystallographic data for the structure 1 was deposited with the Cambridge Crystallographic
Data center with the CCDC No. 1056208. Copies of this information may be obtained free of
charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (e-mail:
deposit@ccdc.cam.ac.uk or www:htpp://www.ccdc.cam.ac.uk).
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16
Table 1. Crystallographic data and refinement parameters for [Ru(dppp)(L)Cl] (1)
Empirical formula
Formula weight
Crystal system
Space group
a / Å
C
39
H
39ClN
2
O
2
2
P RuS
798.24
Monoclinic
P21/n
13.1224(5)
8.4006(3)
b / Å
c / Å
33.1797(12)
100.255(2)
3599.2(2)
4
β (°)
3
V / Å
Z
−3
ρcalcd / g cm
1.473
−1
µ / mm
0.694
T / K
293(2)
hkl range
F(000)
-15 to16, -10 to 10, -40 to 40
1640
θ range (°)
1.59 to 25.76
51552
Reflns collected
Unique reflns (Rint
)
6846
Observed data (I>2σ(I))
Data/restraints/parameters
R1, wR2 (I>2σ(I))
GOF
4490
6846 / 0 / 433
0.0523, 0.0872
0.987
−3
Largest diff. peak/hole / e Å
0.826/ -0.795

17
Table 2. X-ray and calculated bond distances (Å) and angles (°) of 1
Bond (Å)
X-ray
Calc.
Ru1-Cl1
Ru1-S1
Ru1-P1
Ru1-P2
Ru1-O1
Ru1-N2
O1-C1
2.4680(10)
2.3031(10)
2.2802(11)
2.3602(11)
2.052(2)
2.494
2.367
2.351
2.420
2.078
2.077
1.264
1.227
1.280
2.044(3)
1.267(4)
O2-C4
1.218(4)
N1-N2
1.288(4)
Angles (°)
N2-Ru1-O1
N2-Ru1-P1
N2-Ru1-P2
N2-Ru1-S1
N2-Ru1-Cl1
O1-Ru1-P1
O1-Ru1-P2
O1-Ru1-S1
O1-Ru1-Cl1
P1-Ru1-S1
P1-Ru1-P2
P1-Ru1-Cl1
P2-Ru1-S1
P2-Ru1-Cl1
S1-Ru1-Cl1
87.62(11)
90.46(9)
176.80(9)
84.33(9)
81.83(9)
93.29(7)
90.19(8)
171.90(8)
83.95(7)
87.70(4)
92.00(4)
171.90(4)
97.81(4)
95.62(4)
93.98(4)
87.70
92.15
176.36
84.11
82.11
92.36
90.91
171.66
83.99
89.55
91.25
173.31
97.15
94.34
93.26

18
Table 3. Energy and composition of selected molecular orbitals of 1
MOs
Energy (eV)
% of composition
Ru
11
02
03
01
22
03
36
47
33
29
18
12
20
11
07
04
05
L
Cl
01
0
dppp
60
72
95
94
58
03
04
06
07
06
01
28
30
09
61
88
82
LUMO+5
LUMO+4
LUMO+3
LUMO+2
LUMO+1
LUMO
-0.41
-0.45
-0.61
-0.72
-0.88
-1.63
-5.08
-5.43
-5.45
-5.73
-6.00
-6.32
-6.48
-6.56
-6.59
-6.74
-6.80
28
26
02
05
15
94
50
24
21
41
78
33
18
63
21
06
09
0
0
05
0
HOMO
10
23
39
24
03
32
32
17
11
02
04
HOMO-1
HOMO-2
HOMO-3
HOMO-4
HOMO-5
HOMO-6
HOMO-7
HOMO-8
HOMO-9
HOMO-10

19
Table 4. Selected vertical electronic transitions calculated by TDDFT/CPCM method and
experimental λmax (nm)
E
excitation
λexcitation Osc.
λexpt. (nm)
-
1
-1
(
eV)
.6013 476.6
.7430 452.00 0.0140
(nm)
Strength (f) Key transitions
Character
(
ε, M cm )
*
2
2
3
3
4
0.0353
(85%) HOMO → LUMO
π(L)/dπ(Ru) → π (L)
466 (3907)
*
(75%) HOMO-1 → LUMO
(78%) HOMO-2 → LUMO
(69%) HOMO-4 → LUMO
π(L)/dπ(Ru) → π (L)
*
.0790 402.7
.5409 350.1
.1984 295.3
0.0476
0.1163
0.0401
pπ(Cl)/dπ(Ru) → π (L) 390 (5547)
*
π(L) → π (L)
337 (9347)
*
(67%) HOMO - 7 → LUMO π(L) → π (L)
305 (14062)

20
a
Table 5. Effect of S:C ratio on the transfer hydrogenation of acetophenone
O
OH
Complex 1
i-PrOH, KOH
b
c
Entry
S:C ratio
Conversion (%)
TON
193
381
530
601
595
422
1
2
3
4
5
6
1:200
1:400
1:600
1:800
1:1000
1:1200
96.4
95.2
88.4
75.1
59.5
35.2
a
Reaction condition: acetophenone (2 mmol), complex 1 (10-0.8 µmol), catalyst:KOH 1:4 in i-
b
c
PrOH (10 mL) at 80 °C for 5 h; Conversion was determined by GC analysis; Turnover
number (TON) = mole of product/mol of catalyst.

21
a
Table 6. Catalytic transfer hydrogenation of ketones using complex 1
Complex 1
C : S = 1: 400
O
OH
OH
R2
O
+
+
R1
R2
R1
KOH, Reflux for 5 h
b
c
b
c
Entry Ketones
1
Alcohols
Conv. (%) TON
Entry
7
Ketones
Alcohols
Conv. (%) TON
95.2
381
O
89.6
358
2
3
96.6
97.2
386
389
8
9
87.9
95.7
352
383
O
OH
4
5
97.4
98.3
98.1
390
393
392
10
11
12
94.3
91.2
87.6
377
365
350
6
a
Experimental condition: reactions were carried out at 80 °C, ketone (1.0 mmol), complex 1 (0.25 mol%), KOH (0.1 mmol), i-PrOH
b
c
(
10 mL); Conversion was determined by GC analysis; Turnover number (TON) = mole of product/mol of catalyst.

22
Figure captions
Fig. 1. ORTEP plot with 35% ellipsoidal probability of [Ru(dppp)(L)Cl] (1)
Fig. 2. Contour plots of selected molecular orbitals of 1
Fig. 3. UV-Vis spectrum of 1 in acetonitrile
Fig. 4. Cyclic voltammogram of 1 in acetonitrile

23
Fig. 1

24
HOMO
HOMO-1
HOMO-2
LUMO
LUMO+1
Fig. 2
LUMO+2

25
Fig. 3

26
Fig. 4

27
GRAPHICAL ABSTRACT
Synthesis and characterization of
a
ruthenium complex with
bis(diphenylphosphino)propane and thioether containing ONS donor ligand:
Application in transfer hydrogenation of ketones
Sujan Biswas, Deblina Sarkar, Puspendu Roy and Tapan Kumar Mondal
Ruthenium
mixed
ligand
complex,
[Ru(dppp)(L)Cl]
(1)
(where,
.3H
dppp
=
bis(diphenylphosphino)propane) has been synthesized by the reaction of RuCl
3
2
O, dppp and
HL under refluxing condition (HL = 3-(2-(2-(methylthio)phenyl)hydrazono)pentane-2,4-dione).
X-ray structure exhibits distorted octahedral geometry around ruthenium. Cyclic voltammetric
study supports the participation of both Ru(II) and redox active ONS ligand in the redox
processes. The complex efficiently catalyzed the transfer hydrogenation of ketones in i-PrOH.

28
PICTORIAL ABSTRACT
Synthesis and characterization of
a
ruthenium complex with
bis(diphenylphosphino)propane and thioether containing ONS donor ligand:
Application in transfer hydrogenation of ketones
Sujan Biswas, Deblina Sarkar, Puspendu Roy and Tapan Kumar Mondal