Asymmetric transfer hydrogenation of ketones using Ru(0) nanoparticles modified by Chiral Thiones

Article abstract of DOI:10.1002/aoc.4885

The catalytic asymmetric transfer hydrogenation (ATH) of acetophenone in isopropanol by Ru(0) nanoparticles (NPs) obtained by the in-situ reduction of Ru (II) half-sandwich complexes of chiral 2-oxazolidinethiones and 2-thiozolidinethiones was examined and compared with the catalytic activity of Ru(0) NPs formed in-situ by the reduction of [Ru(p-cymene)(Cl)₂]₂ in presence of optically active ligands such as (S)-4-isobutylthiazolidine-2-thione, (S)-4-Isopropyl-2(?2-pyridinyl)-2-oxazoline, (8S, 9R)-(?)-cinchonidine, (S)-leucinol, (S)-phenylalaninol, and (S)-leucine. Three of the best catalytic systems were then examined for ATH of thirteen aromatic ketones with different electronic and steric properties. A maximum of 24% ee was obtained using NPs generated from the Ru (II) half-sandwich complex with (S)-4-isobutylthiazolidine-2-thione in the TH of acetophenone. The NPs were characterized by TEM and DLS measurements. Kinetic studies and poisoning experiments confirmed that the reaction is catalyzed by the chiral NPs formed in-situ. Complete characterization of the complexes, including the X-ray crystallographic characterization of two complexes, was also carried out.

Full text of DOI:10.1002/aoc.4885

Received: 19 October 2018
DOI: 10.1002/aoc.4885
Revised: 26 November 2018
Accepted: 1 February 2019
F U L L P A P E R
Asymmetric transfer hydrogenation of ketones using Ru(0)
nanoparticles modified by Chiral Thiones
Noor U. Din Reshi | Dineshchakravarthy Senthurpandi | Ashoka G. Samuelson
Department of Inorganic and Physical
The catalytic asymmetric transfer hydrogenation (ATH) of acetophenone in
isopropanol by Ru(0) nanoparticles (NPs) obtained by the in‐situ reduction
of Ru (II) half‐sandwich complexes of chiral 2‐oxazolidinethiones and
2‐thiozolidinethiones was examined and compared with the catalytic activity
of Ru(0) NPs formed in‐situ by the reduction of [Ru(p‐cymene)(Cl)2]2 in
presence of optically active ligands such as (S)‐4‐isobutylthiazolidine‐2‐thione,
(S)‐4‐Isopropyl‐2(−2‐pyridinyl)‐2‐oxazoline, (8S, 9R)‐(−)‐cinchonidine, (S)‐
leucinol, (S)‐phenylalaninol, and (S)‐leucine. Three of the best catalytic
systems were then examined for ATH of thirteen aromatic ketones with dif-
ferent electronic and steric properties. A maximum of 24% ee was obtained
using NPs generated from the Ru (II) half‐sandwich complex with (S)‐4‐
isobutylthiazolidine‐2‐thione in the TH of acetophenone. The NPs were
characterized by TEM and DLS measurements. Kinetic studies and poisoning
experiments confirmed that the reaction is catalyzed by the chiral NPs
formed in‐situ. Complete characterization of the complexes, including
the X‐ray crystallographic characterization of two complexes, was also
carried out.
Chemistry, Indian Institute of Science,
Bangalore 560012 Karnataka, India
Correspondence
Ashoka G. Samuelson. Department of
Inorganic and Physical Chemistry, Indian
Institute of Science, Bangalore 560012,
Karnataka, India.
Email: ashoka@iisc.ac.in
Funding information
Science and Engineering Research Board,
Grant/Award Number: EMR/2015/001853
KEYWORDS
asymmetric transfer hydrogenation, chiral nanoparticles, Ru half‐sandwich complexes
[
13]
1
| INTRODUCTION
are stabilized by ionic liquids.
The presence of numer-
ous active sites on the surface, coupled with their ease of
[
2]
Metal nanoparticles (NPs) particularly those of Pt, Ru,
Rh, and Pd have been widely explored as catalysts for
olefin hydrogenation, arene hydrogenation, polymeriza-
tion, oxidation, and C–C coupling.
ligands, surfactants, polymers, dendrimers, cyclodextrins
and ionic liquids have been used to stabilize the NPs in
solution or on the surface of a support.
the stabilizing ligand binds to the metal atoms on the sur-
face via a donor atom providing electronic, electrostatic
and/or steric stabilization. These nanoparticle catalysts
provide an opportunity to realize the efficiency of homo-
geneous catalysts along with the ease of separation as in
preparing makes NPs attractive catalysts. A significant
value addition to the catalytic utility of NPs is achieved
using chiral stabilizers. The metal NPs modified by chiral
compounds, sometimes referred to as chiral NPs can cat-
alyze the reactions in an enantioselective manner.
Thus, NPs of Pt, Ir, and Pd modified by cinchona alka-
loids have been used for the hydrogenation of ethyl
and other prochiral substrates to
give chiral products with over 97% ee in some cases.
However, cinchona alkaloid ligands appear to be unique.
Platinum NPs modified by DIOP, aminoalcohols, and
oxazoline ligands have also been used for catalyzing the
hydrogenation of ethyl pyruvate but the ee of the product
[
1–3]
A variety of
[14–18]
[4–10]
In each case,
[
10,13,16,18–23]
pyruvate
[24]
[2]
[
11,12]
the case of magnetic nanoparticles
or when they
Appl Organometal Chem. 2019;e4885.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
1 of 14
https://doi.org/10.1002/aoc.4885

2
of 14
DIN RESHI ET AL.
is uniformly poor in comparison with cinchonidine mod-
ified Pt systems.
work, we explore the use of Ru half‐sandwich com-
plexes ligated to chiral thiones to generate NPs in‐situ
under transfer hydrogenation (TH) conditions and
the utility of these chiral NPs to transfer chirality
during TH of aromatic ketones. We have also compared
their activity with the activity of NPs generated under
similar conditions by the in‐situ reduction of achiral
[Ru(p‐cymene)(Cl)2]2 in the presence of a variety of
chiral ligands.
[25]
The most commonly used method for the preparation
of chiral NPs is the reaction of an appropriate metal pre-
6
4
3
cursor such as Ru(η ‐C H )(η ‐C H ), Rh(η ‐C H ) ,
8
10
8
12
3
5 3
Pt (dba) , or Pd (dba) with a reducing agent (H , carbon
2
3
2
3
2
monoxide, alcohols, hydrazine, metal‐borohydrides, cit-
[
13]
rate) in the presence of an optically pure ligand.
For
example, Chaudret and co‐workers prepared chiral
6
4
Ru(0) NPs using Ru(η ‐C H )(η ‐C H ) by hydrogena-
8
10
8
12
[
26,27]
tion in presence of optically active N‐donor ligands.
The catalytic activity of these Ru(0) NPs was examined
in the transfer hydrogenation (TH) of acetophenone
and in the hydrogenation of o‐methylanisole and
dimethyl itaconate but they gave low optical yields
2
| RESULTS AND DISCUSSION
.1 | Synthesis and characterization of
2
complexes
[26]
(10%).
Similarly, Nindakova et al. carried out ATH of
acetophenone and methyl benzoylformate using Rh NPs
formed in‐situ by the reduction of rhodium complexes
in the presence of diamines, and cinchonidine, and
A series of chiral 2‐thiozolidinethiones (L1a‐L1 g) and 2‐
oxazolidinethiones (L2a‐L2e) were prepared from amino
[28]
obtained modest enantioselectivity.
In‐situ reduction
of chiral transition metal complexes is another method
of obtaining catalytically active chiral NPs. Chelated
iron complexes of the type trans‐[Fe (NCMe)CO
(
PPh C H CH=NCHPh) ][BF ] were shown by Morris
2 6 4 2 4 2
and co‐workers to give catalytically active Fe(0)
[29]
chiral NPs under the TH conditions.
Thus there is
ample scope for making new chiral NPs and studying
their reactivity.
Recently, we discovered serendipitously that under
TH conditions (refluxing IPA in the presence of KOH),
the cyclometallated Ru‐half sandwich complexes
undergo reduction resulting in Ru(0) NPs which are
FIGURE 1 Complexes synthesized in this work
[30]
active catalysts for the TH of ketones.
Singh et al.
6
reported the in‐situ generation of Ru(0) NPs from [(η ‐
+
benzene)Ru (en)Cl] and HCOOH which efficiently cat-
[
31]
alyzed the hydrogenation of arenes and heteroarenes.
The reduction of these seemingly robust complexes led
to the suspicion that the reduction of Ru (II) half‐
sandwich complexes under TH conditions particularly
when a higher amount of base is used is probably more
[32–35]
general than is assumed in the literature.
In this
FIGURE 2 Conversion profiles for the TH of acetophenone
during a standard catalytic run (black) and a run where the
catalyst is pre‐formed (red) for 15 mins before addition of
acetophenone (inset 0–30 min). Acetophenone 0.423 mmol, [S]/
[
1b]/ [KOH] = 100/1/25, IPA 10 mL; conversions of acetophenone
1
SCHEME 1 Preparation of complexes
to 1‐phenylethanol calculated from H NMR spectra

DIN RESHI ET AL.
3 of 14
[36–38]
acids using known methods.
The corresponding
2.3 | Kinetic studies
ruthenium complexes (1a‐1 g, 2a‐2e) were synthesized
by the reaction of these thiones with the dimer of
dichloro(p‐cymene)ruthenium (II) (P) in dichlorometh-
ane (Scheme 1). Figure 1 shows the list of complexes
synthesized. The synthesis of these complexes followed
usual reaction conditions for making half‐sandwich
complexes and the complexes were characterized using
standard spectroscopic and analytical methods and in
two cases by X‐ray crystallography.
Kinetic studies give one the most insightful data regard-
ing the nature of the true catalyst if it is molecular in
[
35]
nature or if they are NPs.
TH of acetophenone to
1‐phenylethanol using catalyst 1b was investigated care-
fully at short reaction times. The reaction profile showed
an induction period of 15 mins during which the cata-
lytic activity was very slow. The induction period was
followed by rapid catalysis of TH. The rate of the
reaction again decreased, once the reaction was close to
completion (Figure 2). This sigmoidal reaction profile
in reduction reactions is often easy to miss if the induc-
tion period is relatively small compared to the total time
2.2 | Generation of NPs under TH
conditions
TH of a test substrate, acetophenone, was carried out
using these complexes in refluxing isopropanol (IPA)
in presence of KOH. Some key observations made us
suspect that the complexes were being converted to Ru
NPs. Thus, when complex 1b was reacted with KOH
in refluxing IPA (molar ratio, [1b]/ [KOH] = 1/25),
the reaction mixture changed its color from red to dark
brown within a few minutes of reflux. After 1 hr of
reflux and removal of the solvent under vacuum, the
1
H NMR of the reaction mixture did not contain peaks
corresponding to complex 1b or any other soluble metal
complex. Similar results were obtained when complex
1
2
e was reacted with KOH (molar ratio, [1e]/ [KOH] = 1/
5) in IPA. The absence of a Ru complex in the H
1
FIGURE 3 Conversion profile for the TH of acetophenone in the
presence various poisons. The amounts of poisons added are given
in terms of number of equivalents relative to the catalyst 1b; poison
added after 15 mins of refluxing the reaction mixture in each case
NMR spectrum and the change in the color of the
reaction mixture suggested the reduction of the
[35]
complexes to give NPs.
One plausible pathway for
the formation of Ru(0) NPs could be the reductive
elimination of an HCl molecule from the intermediate
[30]
hydride complex.
The catalysis by bulk metal could be ruled out as no
precipitate was obtained when the reaction mixture
was filtered hot and the reaction mixture appeared
homogeneous to the naked eye while refluxing. We car-
ried out further tests to confirm the nature of the true
catalyst. The most commonly used mercury poisoning
test carried out using the procedure suggested by Finke
et al. pointed to a homogeneous species as the active
[35]
catalyst (See supplementary information).
However,
as pointed out by Finke, a negative result could be due
to the reluctance of mercury to form an amalgam with
ruthenium NPs. Hence more tests, especially in operandi,
were necessary to determine whether the active catalyst
is homogeneous or heterogeneous in nature. The experi-
ments carried out in this direction are described in the
following sections.
FIGURE 4 Size distribution of particles measured by dynamic
light scattering

4
of 14
DIN RESHI ET AL.
responsible for rapid catalysis was generated from com-
plex 1b when heated with KOH in refluxing IPA during
the induction period.
2.4 | Poisoning experiments
The use of poisons such as phosphines and sulfides to dis-
tinguish a homogeneous catalyst from a heterogeneous
[
39]
catalyst is well known.
Poisoning experiments were
carried out with PMe , 1,10‐phenanthroline and CS
3
2
using 1b as a representative catalyst. The poison was
added after 15 minutes to a standard reaction mixture
containing 1b, KOH, acetophenone, and IPA (1b/KOH/
acetophenone = 1/25/100). The data is shown in a graph-
ical form in Figure 3.
FIGURE 5 Deconvoluted 3p core level spectrum of Ru; blue,
baseline; red, sum spectrum; pink, 3p3/2; green 3p1/2
Adding 0.5 equivalents of 1,10‐phenanthroline (rela-
tive to Ru) led to a drastic reduction in yield: only 11%
conversion of acetophenone to 1‐phenylethanol was
observed in 8 hr. The addition of 0.5 equivalent of CS2
(relative to Ru) also decreased the conversion of
acetophenone to 1‐phenylethanol to 13% in 8 hr.
Compared to 1,10‐phenanthroline and CS , PMe proved
taken for the reaction. Induction periods are sure indica-
[39]
tors of an active species generated in‐situ.
There was
no induction period observed when complex 1b was
pretreated with KOH (1b/KOH = 1/25) in refluxing
IPA for 15 minutes prior to the addition of
acetophenone. This indicated that the active species
2
3
a weaker poison for this system. When PMe3 (0.5
1
3
FIGURE 6
C CP‐MAS NMR spectrum of the solid obtained from 1e

DIN RESHI ET AL.
5 of 14
equivalent relative to Ru) was added, a significant conver-
sion (30% in 8 hr) of acetophenone to 1‐phenylethanol
was observed. When 1 equivalent of PMe3 (relative
to Ru) was added, 15% conversion of acetophenone to
2.5 | Transmission electron microscopy
(TEM) and dynamic light scattering (DLS)
studies
1
‐phenylethanol was observed in 8 hr. The drastic
Aliquots taken from the dark solution obtained by
refluxing complex 1b and KOH in IPA ([1b]/[B]) = 1/25
for 1 hr were evaporated on a copper grid and the NPS were
reduction in the catalytic activity by the addition of
substoichiometric amounts of a poison strongly suggested
that NPs were active catalysts.
[35,39]
[35]
examined by transmission electron microscopy (TEM).
TABLE 1 ATH of acetophenone with Ru(0) NPs generated
a
b
c
Entry
Catalyst
Conversion (%)
Isolated yield
ee
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
90
96
85
82
86
68
78
85
89
78
80
80
65
70
98
30
96
95
100
94
96
93
90
92
86
90
79
75
78
59
70
75
77
72
74
71
58
61
90
25
89
90
95
89
89
87
85
85
0
24
9
20
10
12
10
0
1g
2a
2b
2c
2d
2e
20
7
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
12
15
0
d
1a
e
1a
0
P
‐
f
1b + 5 L1b
P+ 2 L1b
P+ 1 L1b
23
18
15
9
P+ 0.5 L1b
P+ 2 3a
P+ 2 3b
P+ 2 3c
P+ 2 3d
P+ 2 3e
8
20
0
0
0
a
Acetophenone 0.423 mmol, [S]/[Ru]/[B] = 100/1/25, reflux, IPA 10 ml 8 hr
b
1
Conversions of acetophenone to 1‐phenylethanol calculated from H NMR spectra, conversions given are mean of two values from two experiments, the error
is less than (± 3).
c
[45]
ee determined using chiral HPLC, Chiralcel OD column.
(ee given are mean of two values from two experiments, the error is less than (± 2). In all cases
except for Entry 21 major enantiomer is S.
d
Using LR grade IPA.
e
Reaction done under ambient conditions;
f
5
equivalent of L1b relative to 1b added.

6
of 14
DIN RESHI ET AL.
High resolution (HR) TEM images showed the presence of
NPs of various morphologies and their size varied from 2–
aromatic region could be assigned to aromatic carbon
atoms of p‐cymene and or the thione bound to Ru(0)
NPs. The peaks in the aliphatic region could be assigned
to IPA, aliphatic C atoms of p‐cymene and thione. The IR
4
nm. Bright field (BF) images showed the formation of
agglomerated NPs and the size of agglomerates was nearly
00–400 nm. The elemental mapping by Scanning Electron
−
1
3
spectrum of the solid showed peaks at ν (cm ) = 456
(Ru‐S), 507 (Ru‐N), 1368 (C=C), 1050 (C=S), 1504 (N‐
Microscopy (SEM) with Energy Dispersive X‐ray spec-
trometry (EDS) confirmed the presence of Ru. The EDS
spectrum which showed the presence of sulfur and potas-
sium besides ruthenium. Selected‐area electron diffraction
[
41,42]
C=S).
All of these vibrations, especially those involv-
ing sulfur could arise from the thione ligand or a derivative
adsorbed on the NPs.
(
SAED) spectrum indicated the amorphous nature of the
The binding of the chiral ligands would affect the envi-
ronment of the active centre for catalysis, thus yielding
alcohols with some ee. This binding of the chiral ligands
can take place through coordination of the S to the surface
material (see supplementary information for HRTEM
images, BF images, EDS and SAED spectra).
The DLS and Zeta potential measurements were car-
ried out on aliquots of the reaction mixture after 1 hr of
reflux. DLS measurements showed the presence of parti-
cles with a size distribution of 300–400 nm (Figure 4).
Further aggregation of the NPs after the reaction mixture
was cooled down could not be ruled out in both DLS and
HRTEM measurements. Zeta potential of the particles
was estimated to be nearly 30 mV which indicated that
[43,44]
similar to the binding of cinchonidine on Pt(0) NPs
or
[
28]
binding of chiral PNNP ligands on Fe(0) NPs
and vari-
[
26,27]
ous N‐donor ligands on Ru(0) NPs.
Having confirmed that Ru(0) NPs were formed by the
reduction of the complexes in refluxing IPA in presence
TABLE 2 ATH of acetophenone with varying mol% of 1b
[40]
these particles could easily aggregate.
were obtained from NPs formed from complexes 1d, 1e,
and 2e under the reaction conditions.
Similar results
mol% of
catalyst
a
b
c
Entry
Time (h) Conversion (%)
ee
1
1
1
2
4
8
21
35
72
96
not det.
23
25
2
.6 | XPS study
24
A stoichiometric reaction between a representative com-
plex (1b) and acetophenone was carried out in refluxing
IPA in presence of KOH ([1b]/ [acetophenone]/
2
3
5
2
3
79
98
25
23
10
1.5
2
95
100
25
23
[
KOH] = 1/1/25) for 1 hr. Although the reaction mixture
appeared homogenous while refluxing, stopping the
heating leads to the precipitation of a black solid. The
X‐ray photoelectron spectrum (XPS) of this black solid
showed the presence of K, Cl, S, N, and Ru. Ru (3p) core
level spectrum showed that Ru was present in the zero‐
oxidation state (Figure 5).
a
Acetophenone 0.423 mmol, [S]/[B] = 100/25, reflux, IPA 10 ml.
b
1
Conversions of acetophenone to 1‐phenylethanol calculated from H NMR
spectra (conversions given are mean of two values from two experiments,
the error is less than (± 3).
c
ee determined using chiral HPLC, Chiralcel OD column (ee given are mean
of two values from two experiments, the error is less than (± 2). In all cases
major enantiomer is S.
2
NPs
.7 | Nature of stabilizers attached to Ru
TABLE 3 ATH of acetophenone with 1b at different
temperatures
Temperature
(°C)
Time
(h)
Conversion
(%)
Ru NPs can be stabilized by thione, cymene, and IPA pres-
a
b
c
[4]
1
Entry
ee
ent in the reaction mixture. The H NMR of the reaction
mixtures obtained by refluxing complexes 1b or 1e with
KOH ([complex]/ [KOH] = 1/25) did not contain peaks
corresponding to the free thione or free cymene. These
observations suggested that the thione and p‐cymene, if
still present, were tightly bound to Ru NPs. However, a
1
2
3
82
60
25
3
98
92
8
23
25
9
40
not det.
a
Acetophenone 0.423 mmol, [S]/[1b]/[B] = 100/5/25, IPA 10 mL.
b
1
13
Conversions of acetophenone to 1‐phenylethanol calculated from H NMR
spectra, (conversions given are mean of two values from two experiments,
the error is less than (± 3).
C CP‐MAS NMR spectrum of the solid obtained by
refluxing the complex 1e and KOH ([1e]/ [KOH] = 1/25)
in IPA for 1 hour, followed by evacuation to remove resid-
ual organic species showed peaks in the aromatic and ali-
phatic regions (Figure 6). The peaks observed in the
c
ee determined using chiral HPLC, Chiralcel OD column (ee given are mean
of two values from two experiments, the error is less than (± 2). In all cases
major enantiomer is S.

DIN RESHI ET AL.
7 of 14
TABLE 4 ATH of various ketones using with 1b, 1e, and 2e
b
Conversion (%)
Isolated
yield
a
c
Entry
Substrates
Catalysts
1b
4 hr
8 hr
12 hr
ee
1
76
75
74
96
92
91
‐
‐
‐
90
85
81
24 (S)
20 (S)
17 (S)
1e
e
2
2
3
4
1b
55
54
58
82
84
80
91
95
96
86
88
85
17 (R)
15 (R)
14 (R)
1
2
e
e
1b
45
50
52
75
76
78
88
89
85
81
78
76
15 (R)
10 (R)
13 (R)
1
2
e
e
1b
55
56
58
83
80
81
93
89
92
87
80
79
20 (R)
11 (R)
10 (R)
1
2
e
e
5
6
1b
56
51
57
72
76
71
88
85
86
81
79
78
12 (R)
10 (R)
7 (R)
1
2
e
e
1b
49
45
46
68
67
65
88
85
86
82
78
76
21 (S)
18 (S)
15 (S)
1
2
e
e
7
1b
41
43
39
59
57
61
70
72
69
60
63
61
17 (S)
14 (S)
12 (S)
1
2
e
e
8
9
1b
54
51
56
80
82
84
93
90
91
88
85
84
16 (S)
17 (S)
15 (S)
1
2
e
e
1b
51
54
56
85
87
83
95
92
94
84
85
82
10 (S)
8 (S)
11 (S)
1
2
e
e
1
1
1
1
0
1
2
3
1b
55
58
57
81
83
80
98
91
89
92
82
80
22 (S)
21 (S)
19 (S)
1
2
e
e
1b
56
54
51
79
78
80
90
94
91
84
83
80
7 (S)
6 (S)
8 (S)
1
2
e
e
e
1b
35
38
37
43
44
47
51
58
56
40
41
40
8 (R)
6 (R)
7 (R)
1
2
e
e
e,f
1b
20
21
18
35
38
34
45
43
41
31
35
34
6 (R)
7 (R)
8 (R)
1
2
e
e
(Continues)

8
of 14
DIN RESHI ET AL.
TABLE 4 (Continued)
b
Conversion (%)
Isolated
yield
a
c
Entry
Substrates
Catalysts
1b
4 hr
8 hr
12 hr
ee
1
4
60
55
63
77
73
75
89
90
81
80
78
72
12 (S)
8 (S)
9 (S)
1
2
e
e
a
Ketone 0.423 mmol, [Substrate]/[Ru]/[Base] = 100/1/25, reflux, IPA 10 ml.
b
1
Conversions of ketones to alcohols calculated from H NMR spectra (conversions given are mean of two values from two experiments, the error is less than (± 3).
[45]
c
Determined by HPLC using chiralcel OD column for all alcohols except those in entries 2, 3, 4 and 12 where chiralcel OJ‐H column was used,
(ee given are
mean of two values from two experiments, the error is less than (± 2).
d
Conversion and isolated yield (in the brackets) after 8 hrs.
e
[Substrate]/[Ru]/[Base] = 100/5/25.
f
4
‐aminoacetophenone (B) and 1‐(4‐nitrophenyl)ethan‐1‐ol (C) were also formed. After 12 hr Catalyst 1b, 10% B and 7% C; Catalyst 1e, 12% B and 8% C; Cat-
alyst 6, 9% B and 5% C. The ee given is only of the major product (A) after 12 hr.
of KOH, these NPs were examined for their catalytic
activity in the ATH of acetophenone.
25 mol% of base. Under the conditions used ([S]/[C]/
[B] = 100/1/25, in refluxing IPA, acetophenone gave
90% conversion to 1‐phenylethanol in 8 hr using 1a
(
Entry 1, Table 1). Ru(0) NPs generated from all the
2
2
.8 | Catalytic studies
complexes catalyzed the ATH of acetophenone to give
1‐phenylethanol in good yields (Table 1). The catalytic
.8.1 | ATH catalyzed by Ru(0) NPs
activity was essentially independent of the ligand in the
precursor complex. Hence neither the substitution of S
by O nor varying substituents on the chiral carbon atom
caused a significant change in the rate of the reaction.
The rate of the reaction decreased sharply when the reac-
tion of acetophenone was carried out using laboratory
grade IPA without drying and distilling (Entry 13,
Table 1) and without maintaining a dry nitrogen
The catalytic activity of Ru(0) NPs formed in‐situ by the
reduction of complexes 1a‐1 g and 2a‐2e in refluxing
IPA and KOH was examined for ATH of acetophenone.
Based on the results obtained from the optimization stud-
ies with respect to the amount of base (see supplementary
information), TH reactions were carried out using
FIGURE 7 ORTEP diagram of
complexes (a) 1b and (b) 1d drawn at 50%
probability
TABLE 5 Selected bond lengths and bond angles of complexes 1b and 1d
Bond lengths in (Å)
Bond angles in (°)
Complex
Ru‐S1
Ru‐Cl1
Ru‐Cl2
Cl1‐Ru1‐Cl2
Cl1‐Ru1‐S1
Cl2‐Ru‐S1
1
1
b
d
2.3891(18)
2.4209(19)
2.424(2)
2.418(2)
86.36(7)
86.55(6)
90.00(8)
94.27(6)
92.65(9)
89.27(7)
2.4239(19)
2.4241(16)

DIN RESHI ET AL.
9 of 14
TABLE 6 Crystallographic data for the complexes 1b and 1d
Crystal identification
Complex 1b
Complex 1d
CCDC No.
1823343
1823342
Empirical Formula
Molecular Weight
Crystal System
Space Group
C
17
H
27 Cl
2
N Ru S
2
20 2 2
C H25 Cl N Ru S
481.48
Orthorhombic
P 2
515.50
Triclinic
P 1
1
1 1
2 2
Unit Cell Parameters
a = 10.1844(5) Å
b = 12.4645(6) Åb
a = 10.3065(5) Å
b = 10.5097(5) Å
c = 11.6955(6) Å
α = 114.490(2)°
β = 102.552(2)°
γ = 99.485(2)°
c = 16.2601(8) Å
3
Volume(Å )
2064.11(17)
1077.99(9)
Z
4
2
−3
Calculated Density (mg m
)
1.549
984
1.588
524
F(000)
3
Crystal Size (mm )
0.340 x 0.160 x 0.068
Tabular/Red
0.123 x 0.068 x 0.035
Block/Red
Crystal Habit/Color
Theta range for data collection
Index ranges
2.991 to 26.437°.
3.044 to 30.610
−12 < =h < =12, −15 < =k < =15, −20
−14 < =h < =14, −15 < =k < =15,
−16 < =l < =16
<
=l < =20
Reflections collected/Unique
Completeness to theta = 25.242°
Refinement method
40493/4227 [R (int) = 0.0490]
99.8%
40028/12991 [R (int) = 0.0585]
99.8%
2
2
Full‐matrix least‐squares on F
4227/1/227
Full‐matrix least‐squares on F
Data/restraints/parameters
12991/3/475
2
Goodness‐of‐fit on F
1.202
1.038
Final R indices [I > 2sigma(I)]
R indices (all data)
R1 = 0.0492, wR2 = 0.0994
R1 = 0.0544, wR2 = 0.1011
0.911 and − 0.698
R1 = 0.0467, wR2 = 0.1258
R1 = 0.0531, wR2 = 0.1302
1.745 and − 2.204
Largest diff. Peak and hole
−
3
(
e.Å )
atmosphere (Entry 14, Table 1). A recyclability test for the
TH reaction of acetophenone carried out using 1b showed
nearly complete loss of catalytic activity after the third
cycle (see supplementary information). A plausible
reason for this deactivation could be the agglomeration
of NPs over time.
The enantiomeric excess unlike catalytic activity
varied among the NPs generated from complexes with
different ligands. 1a and 2a gave a racemic mixture of
the product alcohol (Entries 1 and 8, Table 1). The best
ee (24%) was obtained with 1b (Entry 2, Table 1). The
effect of the supplemental free ligand was studied for
the TH catalyzed by 1b. When 5 equivalents of (S)‐4‐
isobutylthiazolidine‐2‐thione, L1b (relative to 1b) were
added to the reaction mixture, a large decrease in the con-
version was observed (entry 16 Table 1). However, there
was no change in the ee. This suggested that the excess
ligand merely poisoned the catalyst by blocking the active
sites on the surface.
[1]
TABLE 7 Intramolecular hydrogen bond distances and angles in
X‐ray crystal structures of complexes 1b and 1d
The ATH of acetophenone was also carried out using
Donor Acceptor H … A D … A
D‐H‐A
( )
o
NPs generated by the in‐situ reduction of [RuCl (p‐
Complex (D)
(A)
(Å)
(Å)
2
cymene)] (P) in the presence of various optically active
2
1
1
b
d
N1
Cl1
2.39(5) 3.176(11) 150(9)
ligands. Solutions of P and enantiomerically pure ligands
were reacted with KOH in refluxing IPA for 15 minutes
prior to the addition of acetophenone. Although the
N1
N2
Cl1
Cl3
2.442
2.299
3.073
3.109
128.93
153.17

10 of 14
DIN RESHI ET AL.
conversions were unaffected using different ligands, ee
changed significantly. Using L1b, ee decreased slightly
as compared to the NPs generated using 1b (P/L1b/
KOH/acetophenone = 1/2/25/100) (Entry 17, Table 1).
There was only a little change in ee when the ATH of
acetophenone was carried out using NPs generated with
P and L1b in the ratio (P/L1b/KOH/acetophenone = 1/
obtained in most cases in 12 hr. The maximum value of
ee was observed with acetophenone using 1b as catalyst
(24%, Entry 2, Table 1). Lesser ee was obtained with all
other substrates.
2‐bromoacetophenone and 4‐amino acetophenone
were difficult to reduce and less than 10% conversion
was obtained under standard catalytic conditions used
with all the three catalysts. When the catalyst loading
was increased to 5 mol%, TH of 4‐nitroacetophenone led
to the formation of three products,1‐(4‐nitrophenyl)
ethan‐1‐ol (carbonyl group reduced product A), 4‐
aminoacetophenone (nitro group reduced product B)
and 1‐(4‐nitrophenyl)ethan‐1‐ol (both nitro and carbonyl
group reduced C) with all the 3 catalysts (Entry 13,
Table 4). The TH of 4‐nitroacetopheneone catalyzed by
1
/25/100) (Entry 18, Table 1). On decreasing the amount
of L1b further (P/L1b/KOH/acetophenone = 1/0.5/25/
00), ee decreased sharply to 9% (Entry 19, Table 1).
1
Hence, NPs with other ligands were obtained using the
ratio (P/ligand/KOH/acetophenone = 1/2/25/100). The
NPs generated from P in presence of (S)‐(−)‐4‐Isopro-
pyl‐2(−2‐pyridinyl)‐2‐oxazoline (3a) afforded the product
in 8% ee (Entry 20, Table 1). Similarly, NPs generated
from P in presence of (8S,9R)‐(−)‐cinchonidine (3b)
afforded 1‐phenylethanol in 20% ee (Entry 21, Table 1).
However, the NPs generated from P in the presence of
L‐leucine (3c), L‐leucinol (3d), and L‐phenylalaninol
[30,35]
Ru(0) NPs is known to give these three products.
3
| SUMMARY AND CONCLUSIONS
(
3e) (entries 22–24, Table 1) gave racemic 1‐
The catalytic activity of Ru‐half‐sandwich complexes of
chiral 2‐oxazolidinethiones and 2‐thiozolidinethiones
could be attributed to NPs formed in‐situ by the reduction
of complexes.
phenylethanol in the ATH of acetophenone.
2
.8.2 | Varying catalyst loading and
temperature
TEM and DLS measurements confirmed the presence
of nanoparticles. The XPS showed the presence of Ru(0)
in the solid that precipitated out from the reaction mix-
ture. The product formation profile with a definite induc-
tion time, a rapid change in the color of the reaction
mixture and poisoning experiments strongly pointed to
the fact that the actual catalysts are NPs.
Catalyst loading had a significant effect on the reaction
rate (Table 2). However, the ee did not improve with
the increase in catalyst loading. Interestingly, the ee did
not change with the progress of the reaction, which sug-
gested that the chirality induction was due to the catalysis
by chiral NPs and not by the intact complex present ini-
tially in the reaction mixture.
Although the mercury drop experiment gave no evi-
dence of heterogeneous catalysis, all other observations
pointed to the NPs being true catalysts. This also
explained why the TH catalytic activity was essentially
ligand independent. NPs generated from a variety of com-
plexes including the precursor complex [Ru(p‐cymene)
Cl ] gave rise to excellent yields. However, ee changed
It also implies that the product was not affecting the
catalytically active sites.
A greater ee would have been observed at the initial
stage of the reaction if the chirality induction was only
due to the product formed by catalysis carried out by
the intact complex. The effect of temperature was also
investigated. Surprisingly, in the limited range of temper-
atures that could be examined, the ee did not improve as
expected at lower temperatures (Table 3).
2
2
significantly with the nature of the stabilizing ligand.
Furthermore, there was only a little decrease in the enan-
tiomeric excess when NPs were generated using the pre-
cursor complex [Ru(p‐cymene)Cl ] in the presence of
2
2
thione. Hence this provides an easy method to generate
Ru(0) NPs modified by a variety of chiral ligands for cat-
alyzing the ATH of ketones.
2.8.3 | Substrate scope
Since NPs generated from all the complexes showed sim-
ilar catalytic activity in the TH of acetophenone, NPs
from three readily accessible complexes 1b, 1e, and 2e
were used as catalysts for the TH of aromatic ketones
with varying electronic and steric properties (Table 4).
Ru(0) NPs generated from these three complexes
reduced most of the substrates efficiently and nearly
4 | EXPERIMENTAL SECTION
4.1 | General remarks
Ketones and amino acids were obtained from commercial
sources and used without further purification. All reac-
tions and manipulations were carried under an
9
0% conversion of acetophenone to 1‐phenylethanol was

DIN RESHI ET AL.
11 of 14
atmosphere of pure nitrogen using standard Schlenk tech-
niques in oven‐dried glassware. The solvents were purified
by standard methods under dry nitrogen before use. IPA
was dried by refluxing over activated magnesium (Mg/I2)
and was freshly distilled before use. DCM was dried by
refluxing with P O and distilled freshly before use. Ana-
from dichloromethane and diethyl ether (1:1) to give the
pure complex.
4
4
.3 | Characterization of complexes
2
5
.3.1 | Complex 1a
lytical thin layer chromatography (TLC) was performed
using precoated silica gel plates supplied by Merck
1
Yield: 75%. H NMR (CDCl 400 MHz, ppm) – δ = 0.94
3,
(60 F254). After elution, the plates were visualized using
(
3H, d, J = 6.94 Hz, isopropyl), 1.03 (3H, d, J = 6.56 Hz,
UV radiation. Preparative TLC was done using ChemLabs
Silica gel GF 254. The NMR spectra were recorded on a
Bruker AMX 400 spectrometer that operates at 400 MHz
isopropyl), 1.31(6H, d, J = 6.83 Hz, isopropyl), 1.85 (1H,
m), 2.25 (3H, s, methyl), 2.96 (1H, m, isopropyl), 3.13
(
1H, m), 3.30 (1H, m), 3.96 (1H, m), 5.19 (2H, m,
1
13
1
for H and 100 MHz for C NMR. Chemical shifts for H
NMR spectra are reported in ppm relative to the chloro-
form signal at δ 7.26 as a singlet.
1
3
cymene), 5.32 (2H, m, cymene), 9.98 (1H, s, NH);
C
NMR (CDCl , 100 MHz, ppm) – δ = 18.7, 19.2, 19.3,
3
22.73, 22.77, 30.9, 32.5, 35.8, 72.5, 82.7, 83.0, 84.3, 84.4,
Elemental analysis was carried out on a vario MICRO
CUBE CHNS instrument. HPLC was carried out on
Waters 1525 Binary HPLC Pump attached with Waters
100.1, 103.8, 195.9. Elemental analysis for
C H Cl NRuS , calcd. (%) C, 41.11; H, 5.39; N, 3.00; S,
16
25
2
2
13.72; found: C, 40.94; H, 5.37; N, 3.05; S, 13.81.
2
487 Dual λ Absorbance Detector. The chiral columns
used were Chiralcel OD column and chiralcel OJ‐H col-
[
45]
umn.
The absolute configuration of the products was
4.3.2 | Complex 1b
determined using optical activity measurements. Powder
XRD experiments were performed using PANalytical
EMPYREAN diffractometer using Cu Kα radiation
1
Yield: 78%. H NMR (CDCl 400 MHz, ppm) – δ = 0.88
3
,
(6H, m), 1.31 (6H, d, J = 6.85 Hz), 1.67(3H, m), 2.25
(3H, s), 2.96 (2H, m), 3.38 (1H, m), 4.24 (1H, m), 5.19
(2H, t, J = 6.07 Hz), 5.39 (2H, m), 10.01 (1H, s, NH),
Elemental analysis for C H Cl NRuS , calcd. (%) C,
42.41; H, 5.65; N, 2.91; S, 13.32; found: C, 42.39; H, 5.68;
N, 2.98; S, 13.40.
(
λ = 1.54178 Å) as the source. Bright field (BF) imaging,
high resolution (HR) TEM imaging, and selected area
diffraction patterns were obtained using JEOL 2100F
TEM. Energy dispersive X‐ray spectroscopy (EDS) was
performed using OXFORD EDS spectrometer attached
to the TEM. The operating voltage of the field emission
gun (EFG) is 200 kV. FT‐IR spectra were recorded using
Bruker ALPHA FT‐IR spectrometer. X‐ray photoelectron
spectroscopy was carried out using a Kratos AXIS Ultra
XPS spectrometer. The DLS and Zeta potential measure-
ments were carried out using Zeta Phase Analysis Light
Scattering (Zeta PALS).
1
7
27
2
2
4.3.3 | Complex 1c
1
Yield: 75%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 0.86
3
,
(
6H, m, isopropyl), 1.18 (1H, m), 1.30 (6H, d,
J = 7.07 Hz, isopropyl), 1.48 (1H, m), 1.70 (1H, m), 2.24
3H, s, methyl), 2.95 (1H, m, isopropyl), 3.13 (1H, m),
(
3
5
1
3
1
.26 (1H, m), 4.05 (1H, m), 5.19 (2H, m, cymene),
13
.38(2H, m, cymene), 9.95(1H, s, NH), C NMR (CDCl ,
3
4
.2 | Synthesis
00 MHz, ppm) – δ = 11.3, 15.1, 18.7, 22.72, 22.76, 26.0,
0.9, 35.2, 38.4, 71.1, 82.7, 83.0, 84.3, 84.4, 100.0, 103.9,
All ligands in enantiomerically pure form were synthe-
sized according to the literature procedures
used for the synthesis of the complexes using the
established procedure.
95.7. Elemental analysis for C H Cl NRuS , calcd.
[
36–38,46]
17 27
2
2
and
(
%) C, 42.41; H, 5.65; N, 2.91; S, 13.32; found: C, 42.38;
H, 5.70; N, 2.96; S, 13.44.
[47]
Briefly, [Ru(p‐cymene)Cl2]2
(
P) (0.16 mmol) was taken in a two‐neck round bottom
flask with a side arm. Then freshly dried dichlorometh-
ane (20 mL) was added to this flask under nitrogen
atmosphere. To this solution, ligand (0.33 mmol) was
added. The reaction mixture was stirred for 1 hr at room
temperature. The reaction mixture was then concentrated
to 2 ml and petroleum ether (10 mL) was added. A
red colored precipitate was formed. The solid was
filtered, washed with diethyl ether and recrystallized
4.3.4 | Complex 1d
1
Yield: 71%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 1.33
3,
(6H, d, J = 6.87, isopropyl), 2.26 (3H, s), 2.82 (1H, m),
2.99 (3H, m), 3.23 (1H, m), 4.38 (1H, m), 5.20 (2H, m),
5.41 (2H, m), 7.13 (2H, m), 7.23 (3H, m), 10.13 (1H, s,
13
NH), C NMR (CDCl , 100 MHz, ppm) – δ = 18.7, 22.7,
3
30.9, 36.5, 38.2, 66.9, 82.7, 83.0, 84.4, 84.6, 99.6, 104.4,

12 of 14
DIN RESHI ET AL.
1
27.7, 129.3, 129.7, 136.0, 186.4. Elemental analysis for
84.2, 99.7, 103.8, 188.1. Elemental analysis for
C H Cl NORuS, calcd. (%) C, 42.57; H, 5.58; N, 3.10;
C H Cl NRuS , calcd. (%) C, 46.60; H, 4.89; N, 2.72; S,
20
25
2
2
16 25
2
1
2.44; found: C, 46.64; H, 4.93; N, 2.69; S, 12.51.
S, 7.11; found: C, 42.62; H, 5.65; N, 3.02; S, 6.95.
4
.3.9 | Complex 2b
4
.3.5 | Complex 1e
1
Yield: 80%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 0.85 (6H,
m, isopropyl), 1.25 (1H, m), 1.31 (6H, d, J = 6.87 Hz, isopro-
pyl), 1.59 (2H, m), 2.26 (3H, s), 2.97 (1H, m), 4.02 (1H, m),
3,
1
Yield: 73%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 1.32
3,
(6H, d, J = 6.85 Hz, isopropyl), 2.26 (3H, s), 2.29 (1H,
m), 3.26 (1H, m), 3.64 (1H, m), 5.21 (2H, m), 5.28 (1H,
m) 5.42 (2H, m), 7.33 (5H, m), 10.22 (1H, s, NH), C
NMR (CDCl , 100 MHz, ppm) – δ = 18.7, 22.7, 30.9,
4.15 (1H, m), 4.61 (1H, t, J = 8.83 Hz), 5.20 (2H, m), 5.40
13
(
2H, t, J = 5.88), 9.90 (1H, s, NH), − δ = 18.8, 22.1, 22.7,
3
2
1
3.2, 25.4, 30.9, 43.2, 56.6, 76.8, 82.4, 82.8, 83.9, 84.2, 99.7,
03.8, 188.0. Elemental analysis for C H Cl NORuS,
4
1.0, 69.6, 82.8, 83.1, 84.5, 84.6, 99.8, 104.4, 126.7,
17
27
2
1
29.3, 129.5, 137.0, 197.5. Elemental analysis for
calcd. (%) C, 43.87; H, 5.85; N, 3.01; S, 6.89; found: C,
3.82; H, 5.81; N, 3.09; S, 6.78.
C H Cl NRuS , calcd. (%) C, 45.51; H, 4.62; N, 2.79; S,
19
23
2
2
4
1
2.79; found: C, 45.47; H, 4.59; N, 2.71; S, 12.68.
4
.3.10 | Complex 2c
4
.3.6 | Complex 1f
1
Yield: 79%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 0.83 (6H,
3
,
1
Yield: 70%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 1.32
m, isopropyl), 1.10 (2H, m), 1.31 (6H, d, J = 6.87 Hz, isopro-
pyl), 1.42 (1H, m), 2.26 (3H, s, methyl), 2.97 (1H, m, isopro-
pyl), 3.83 (1H, m), 4.28 (1H, m), 4.54 (1H, t, J = 9.3), 5.20
(2H, m, cymene), 5.40 (2H, t, J = 6.36, cymene), 9.86 (1H,
3,
(6H, d, J = 6.88 Hz, isopropyl), 2.24 (3H, s), 2.98 (5H,
m), 4.47 (1H, m), 5.18 (2H, m), 5.40 (2H, m), 7.06 (3H,
m), 7.35 (2H, m), 8.23 (1H, s), 10.10 (1H, s, NH), C
NMR (CDCl , 100 MHz, ppm) – δ = 15.7, 18.7, 22.7,
13
13
s, NH), C NMR (CDCl , 100 MHz, ppm) – δ = 11.2,
3
3
2
1
1
8.3, 30.9, 37.0, 66.3, 82.7, 83.0, 84.0, 84.6, 99.8, 104.3,
09.7, 111.9, 118.5, 120.1, 122.6, 124.5, 127.7, 136.5,
96.4. Elemental analysis for C H Cl NRuS , calcd.
14.6, 18.8, 22.6, 22.7, 25.4, 30.9, 38.5, 62.7, 74.3, 82.4, 82.8,
84.0, 84.2, 99.7, 103.9, 188. Elemental analysis for
C
17
H
27Cl
NORuS, calcd. (%) C, 43.87; H, 5.85; N, 3.01; S,
19
23
2
2
2
(%) C, 47.65; H, 4.73; N, 5.05; S, 11.56; found: C, 47.68;
6.89; found: C, 43.89; H, 5.79; N, 3.06; S, 6.75.
H, 4.79; N, 4.99; S, 11.21.
4.3.11 | Complex 2d
4.3.7 | Complex 1 g
1
Yield: 71%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 1.33
3,
(
2
(
(
8
1
6H, d, J = 6.89, isopropyl), 2.26 (3H, s), 2.72 (1H, m),
.99 (3H, m), 4.21 (2H, m), 4.45 (1H, t, J = 8.41), 5.22
2H, m), 5.42 (2H, m), 7.13 (2H, m), 7.28 (3H, m), 9.9
1H, s, NH), − δ = 18.8, 22.7, 30.9, 39.8, 59.1, 75.3, 82.5,
1
Yield: 68%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 1.31 (9
3,
H, m), 2.25 (3H, s), 2.99 (1H, m), 3.61 (2H, m), 4.24 (2H,
m), 4.78 (1H, m), 5.22 (2H, m) 5.42 (2H, m), 10.39 (1H, s,
NH). C NMR (CDCl , 100 MHz, ppm) – δ = 14.62,
8.77, 22.69, 22.71, 30.93, 34.95, 63.44, 66.02, 82.68,
3.21, 84.51, 84.86, 100.17, 104.29, 167.73, 198.59.
Elemental analysis for C H Cl NO RuS , calcd. (%) C,
8.63; H, 4.66; N, 2.82; S, 12.89; found: C, 38.70; H, 4.61;
13
3
2.7, 84.1, 84.2, 99.5, 103.9, 127.7, 129.4, 129.7, 135.3,
88.5. Elemental analysis for C H Cl NORuS, calcd.
1
8
20
25
2
(
%) C, 48.10; H, 5.05; N, 2.80; S, 6.41; found: C, 48.15;
16
23
2
2
2
H, 5.10; N, 2.76; S, 6.31.
3
N, 2.78; S, 12.79.
4.3.12 | Complex 2e
1
4
.3.8 | Complex 2a
Yield: 72%. H NMR (CDCl3, 400 MHz, ppm) ‐ δ = 1.33
(
6H, d, J = 6.94 Hz, isopropyl), 2.27 (3H, s), 3.00 (1H,
m), 4.31 (1H, t, J = 8.3 Hz), 4.89 (1H, t, J = 9.4 Hz), 5.10
(1H, t, J = 8.78 Hz), 5.23 (2H, m), 5.43 (2H, d,
J = 5.8 Hz), 7.28 (5H, m), 10.09 (1H, s, NH), C NMR
(CDCl , 100 MHz, ppm) – δ = 18.7, 22.7, 30.9, 61.5, 78.6,
1
Yield: 72%. H NMR (CDCl 400 MHz, ppm) ‐ δ = 0.87
3,
(3H, d, J = 6.83 Hz, isopropyl), 0.95 (3H, d, J = 6.93 Hz,
13
isopropyl), 1.31(6H, d, J = 6.85 Hz, isopropyl), 1.72 (1H,
m), 2.26 (3H, s, methyl), 2.96 (1H, m, isopropyl), 3.76
3
(1H, m), 4.29 (1H, m), 4.56 (1H, t, J = 9.36), 5.21 (2H,
82.5, 82.9, 84.1, 84.3, 99.4, 104.3, 126.7, 129.4, 129.6,
m, cymene), 5.40 (2H, m, cymene), 9.92 (1H, s, NH),
137.1, 189.3. Elemental analysis for C H Cl NORuS,
calcd. (%) C, 47.01; H, 4.78; N, 2.89; S, 6.59; found: C,
47.08; H, 4.71; N, 2.81; S, 6.40.
19
23
2
13
C NMR (CDCl , 100 MHz, ppm) – δ = 18.41, 18.49,
3
1
8.8, 22.6, 22.7, 30.9, 32.5, 63.9, 74.7, 82.4, 82.9, 84.0,

DIN RESHI ET AL.
13 of 14
4.4 | Crystal structure determination
4.5 | General procedure for the catalytic
ATH reaction
The molecular structures of 1b and 1d were obtained
using single crystal X‐ray crystallography. Single crystals
suitable for X‐ray diffraction were obtained by diffusion
of a non‐solvent into a concentrated solution of the
complex in dichloromethane. Complexes adopt the
familiar “three‐legged piano‐stool” or pseudo‐octahedral
geometry. Ru is surrounded by a sulfur atom, two chlo-
ride ions, and the p‐cymene group which is the seat of
the piano stool. The molecular structures for the new
complexes 1b and 1d are shown in Figure 7 as ORTEP
representations and the important bond lengths and
bond angles are given in Table 5. Single crystals were
picked under a polarizing microscope and mounted on
a glass fiber using glue for single crystal diffraction
studies. Intensity data were collected with Bruker
SMART APEX‐II diffractometer (3‐axis system) with
graphite monochromated (sealed) MoKα radiation
The catalyst (0.00423 mmol) was dissolved in 10 ml of
IPA. To this solution was added 0.423 mmol of the
ketone, followed by the addition of KOH (0.105 mmol)
as a solution in IPA. Then the reaction mixture was
refluxed. Aliquots of the reaction mixture were with-
1
drawn at specified intervals, and HNMR spectra
recorded in CDCl3 after removal of the solvent. The
conversions of acetophenone to 1‐phenylethanol were
calculated from the intensity ratios of the peaks arising
from the reactant and product. The alcohols were purified
by preparative thin layer chromatography. In case of
catalysis by NPs generated from P in the presence of
chiral ligands, the solution of P and the ligand was
reacted with KOH in refluxing IPA for 15 minutes prior
to the addition of substrate.
(
λ
=
0.71073 Å). Intensities were corrected for
4
.6 | Mechanistic studies
Lorentz‐polarization effects and absorption corrections
were performed through the program SADABS.
structures have been solved through direct methods
using the program SHELXS‐97
matrix least squares refinement on F using the pro-
gram SHELXL.
[48]
The
1b (21 mg (0.04 mmol) was reacted with KOH (1b/
KOH = 1/25) in refluxing IPA (10 ml) for 1 hr. The volatiles
were removed under vacuum from the reaction mixture
and CDCl was added. H NMR spectrum was recorded.
To study the effect of substrate, 1b was reacted with KOH
[49]
and refined by full‐
2
1
[50]
3
All non‐hydrogen atoms were refined
anisotropically as independent atoms and hydrogen
atoms were constrained on geometrically calculated
positions and refined using a riding model using HFIX
command. Moreover, they have been treated
isotropically throughout the refinement cycles and their
thermal parameter assumes the value of 1.20 times the
Ueq value (1.50 for CH3 group) of the non‐hydrogen
atom to which it binds. All computations have been
performed using the WinGX package and structures
in refluxing IPA for 1 hr in presence of acetophenone
(1b/KOH/acetophenone =1/25/1). Similarly, experiments
were carried out using complexes 1d, 1e, and 2e.
4.7 | Transmission electron microscopy
Aliquots were withdrawn after 1 hr from the reaction
mixture (standard catalytic conditions). These aliquots
were deposited on TEM grids as soon as these reached
the room temperature. The grid was then dried in a
vacuum desiccator. Subsequently, TEM, SAED, EDX,
and STEM analysis were carried out.
[
51]
have been drawn by ORTEP‐3 for windows program.
Selected crystallographic data and the refinement
parameters for the samples are listed in Table 6. CCDC‐
1
823343 (for 1b) and ‐ 1823342 (for 1d) contain supple-
mentary crystallographic data for the structures reported
in this paper.
ACKNOWLEDGEMENTS
The configuration around the chiral carbon center is
as expected S, same as that of the ligands used for the
synthesis. Both complexes showed intramolecular hydro-
gen bonding of the type N‐H···Cl (D‐H···A) between the
NH hydrogen of the ligand and one of the Cl atom
bonded to ruthenium. The hydrogen bonding distances
vary from 2.29 Å to 2.442 Å and the D‐H···A angle varies
N.U.R thanks Council of Scientific and Industrial
Research (CSIR), New Delhi for senior research fellow-
ship. Authors acknowledge Department of Science and
Technology (DST) New Delhi for research grant (SERB‐
EMR/2015/001853), NRC Indian Institute of Science
(IISc) for CP‐MAS Spectra, and IISc for funding the
procurement of a 200 kV FETEM.
o
o
from 153.17 to 128.93 , which is indicative of very
strong interactions (Table 7). This type of NH···Cl
(
D‐H···A) intramolecular hydrogen bonding has been
CONFLICT OF INTEREST
reported to be important for the stability of similar
complexes.
[47]
There are no conflicts to declare.

14 of 14
DIN RESHI ET AL.
ORCID
[31] A. D. Dwivedi, R. K. Rai, K. Gupta, S. K. Singh, ChemCatChem
2017, 9, 1930.
Ashoka G. Samuelson
https://orcid.org/0000-0001-9416-
[
32] N. Guerbuez, S. Yasar, E. O. Oezcan, I. Oezdemir, B.
Cetinkaya, N. Gürbüz, S. Yaşar, E. Ö. Özcan, İ. Özdemir, B.
Çetinkaya, Eur. J. Inorg. Chem. 2010, 2010, 3051.
162X
[
[
33] G. Koten, P. Dani, T. Karlen, R. Gossage, Angew. Chem. Int. Ed.
Engl. 2000, 39, 743.
REFERENCES
[
1] A. Roucoux, J. Schulz, H. Patin, Chem. Rev. 2002, 102, 3757.
2] D. Astruc, Nanoparticles and Catalysis, Wiley‐VCH, Weinheim
34] S. Yaşar, S. Çekirdek, I. Özdemir, S. Yasar, S. Cekirdek, I.
Ozdemir, J. Coord. Chem. 2014, 67, 1236.
[
2
008.
[
[
35] J. A. Widegren, R. G. Finke, J. Mol. Catal. A Chem. 2003, 198, 317.
[
3] P. Lara, A. Suárez, V. Collière, K. Philippot, B. Chaudret,
ChemCatChem 2014, 6, 87.
36] C. M. Marson, C. J. Matthews, E. Yiannaki, S. J. Atkinson, P. E.
Soden, L. Shukla, N. Lamadema, N. S. B. Thomas, J. Med.
Chem. 2013, 56, 6156.
[
4] P. Lara, K. Philippot, B. Chaudret, ChemCatChem 2013, 5, 28.
[
5] D. L. Feldheim, C. A. Foss, Metal Nanoparticles: Synthesis,
Characterization, and Applications, Marcel Dekker, New York
and Basel 2002.
[
[
37] Y. Zhang, T. Sammakia, Org. Lett. 2004, 6, 3139.
38] D. Delaunay, L. Toupet, M. Le Corre, J. Org. Chem. 1995, 60,
6604.
[
6] H. Bönnemann, W. Brijoux, Act. Met. Prep. Charact. Appl.,
Wiley‐VCH Verlag GmbH, Weinheim, Germany 2007 339.
[
[
39] R. H. Crabtree, Chem. Rev. 2012, 112, 1536.
40] W. B. Russel, D. A. Saville, W. R. Schowalter, Colloidal
Dispersions, Cambridge University Press 1989.
[
[
[
7] J. D. Aiken, R. G. Finke, J. Mol. Catal. A Chem. 1999, 145, 1.
8] K. Philippot, B. Chaudret, Comptes Rendus Chim. 2003, 6, 1019.
[
41] H. A. El‐Asmy, I. S. Butler, Z. S. Mouhri, B. J. Jean‐Claude, M.
Emmam, S. I. Mostafa, Inorg. Chim. Acta 2016, 441, 20.
9] T. Yonezawa, N. Toshima, H. S. N (Eds), Polym. – Stab. Met.
Nanoparticles Prep. Charact. Appl., Adv. Funct. Mol. Polym,
Vol. 2, Gordon & Breach, UK 2001, 65.
[
42] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds; Part B: Applications in Coordination,
Organometallic, and Bioinorganic Chemistry, John Wiley &
Sons, Inc., New York 1978.
[
[
[
[
[
[
10] H. U. Blaser, M. Studer, Acc. Chem. Res. 2007, 40, 1348.
11] K. V. S. Ranganath, F. Glorius, Catal. Sci. Technol. 2011, 1, 13.
12] A. Hu, G. T. Yee, W. Lin, J. Am. Chem. Soc. 2005, 127, 12486.
13] P. Barbaro, V. D. Santo, F. Liguori, Dalt. Trans. 2010, 39, 8391.
14] C. A. Stowell, B. A. Korgel, Nano Lett. 2005, 5, 1203.
[43] B. Panella, A. Vargas, A. Baiker, J. Catal. 2009, 261, 88.
[44] A. Baiker, J. Mol. Catal. A Chem. 1997, 115, 473.
[45] A. K. Pandia Kumar, A. G. Samuelson, J. Chem. Sci. 2016, 128,
1405.
15] T. Yasukawa, H. Miyamura, S. Kobayashi, J. Am. Chem. Soc.
2
012, 134, 16963.
[46] H. Brunner, U. Obermann, Chem. Ber. 1989, 122, 499.
[
[
16] A. Baiker, Catal. Today 2005, 100, 159.
[47] R. Mitra, S. Das, S. V. Shinde, S. Sinha, K. Somasundaram, A.
G. Samuelson, Chem. ‐ A Eur. J. 2012, 18, 12278.
17] S. L. Scott, E. W. Deguns, Nanostructured Catalysts, Springer
US, Boston, MA 2003.
[48] G. M. Sheldrick, SADABS, University of Göttingen, Germany
1
996.
49] G. M. Sheldrick, SHELXS97, University of Göttingen, Germany
997.
[
[
[
[
18] P. B. Wells, A. G. Wilkinson, Top. Catal. 1998, 5, 39.
19] T. Bürgi, A. Baiker, Acc. Chem. Res. 2004, 37, 909.
20] J. Margitfalvi, E. Tálas, E. Tfirst, Top. Catal. 2006, 39, 77.
[
1
[
50] G. M. Sheldrick, Acta Cryst. C 2015, 71, 3.
21] H. U. Blaser, H. P. Jalett, W. Lottenbach, M. Studer, J. Am.
Chem. Soc. 2000, 122, 12675.
[
51] L. J. Farrugia, J. Appl. Crystallogr. 2012, 45, 849.
[
[
[
[
[
22] M. von Arx, T. Mallat, A. Baiker, Top. Catal. 2002, 19, 75.
23] A. Baiker, J. Mol, Catal. A Chem. 2000, 163, 205.
SUPPORTING INFORMATION
24] M. Studer, H. ‐U. Blaser, Chem. Commun. 1998, 0, 1053.
25] A. Kraynov, R. Richards, Phys. Chem. Chem. Phys. 2007, 9, 884.
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
26] S. Jansat, D. Picurelli, K. Pelzer, K. Philippot, M. Gómez, G.
Muller, P. Lecante, B. Chaudret, New J. Chem. 2006, 30, 115.
[
[
[
[
27] K. Philippot, P. Lignier, B. Chaudret, Top. Organomet. Chem.
2
014, 48, 319.
How to cite this article: Din Reshi NU,
Senthurpandi D, Samuelson AG. Asymmetric
transfer hydrogenation of ketones using Ru(0)
nanoparticles modified by Chiral Thiones. Appl
Organometal Chem. 2019;e4885. https://doi.org/
10.1002/aoc.4885
28] L. O. Nindakova, N. M. Badyrova, V. V. Smirnov, V. O.
Strakhov, S. S. Kolesnikov, Russ. J. Gen. Chem. 2016, 86, 1240.
29] J. F. Sonnenberg, N. Coombs, P. A. Dube, R. H. Morris, J. Am.
Chem. Soc. 2012, 134, 5893.
30] N. U. D. Reshi, D. Chakravarthy, A. G. Samuelson, D.
Senthurpandi, A. G. Samuelson, J. Organomet. Chem. 2018,
8
66, 189.