'Click' generated 1,2,3-triazole based organosulfur/selenium ligands and their Pd(II) and Ru(II) complexes: Their synthesis, structure and catalytic applications

Article abstract of DOI:10.1039/c6dt01406b

1-(2,6-Diisopropylphenyl)-4-(phenylthio/selenomethyl)-1H-1,2,3-triazole (L1/L2) was synthesized by a 'Click' reaction and treated with [Pd(CH₃CN)₂Cl₂] for 5 h or [(η⁶-C₆H₆)RuCl(μ-Cl)]₂ for 8 h (followed by reaction with NH₄PF₆) at room temperature, resulting in complexes [Pd(L)Cl₂] (1 and 2) or [(η⁶-C₆H₆)Ru(L)Cl]PF₆ (3 and 4) (L = L1 or L2), respectively. The four complexes (1-4) and ligands (L1 and L2) were characterized with ¹H, ¹³C{¹H} and ⁷⁷Se{¹H} NMR spectroscopy and high resolution mass spectrometry. The single crystal structures of 1-4 were solved. The geometry of Pd in 1 and 2 is distorted square planar. The Pd-S and Pd-Se bond distances in 1 and 2 are 2.277(3) and 2.384(6) ? respectively. In 3 and 4, there is a pseudo-octahedral "piano-stool" type disposition of donor atoms around Ru. The Ru-S and Ru-Se bond lengths in 3 and 4 are 2.3728(12) and 2.4741(6) ? respectively. The catalytic activity of complexes 1 and 2 was explored for Suzuki-Miyaura coupling (SMC) in water and the Sonogashira coupling reaction. For various aryl bromides, including deactivated ones, complexes 1 and 2 were found to be efficient catalysts for both couplings. The optimum loading of 1 and 2 required to catalyze both coupling reactions is of the order of 0.001-2 mol% of Pd. For SMC, no additive or phase transfer catalyst was added. For catalysis of the transfer hydrogenation (TH) of aldehydes and ketones, the half-sandwich Ru(ii) complexes 3 and 4 were explored. Their optimum catalytic loading was found to be 0.1-0.4 mol% of Ru. For TH, both the water solvent and the glycerol hydrogen source are environmentally friendly. The catalytic efficiencies of 3 and 4 are comparable with those reported for other catalysts for TH carried out with 2-propanol or glycerol as a H-source. 1, with a sulfur ligand, is more efficient than 2 (Se analog) for both SMC and the Sonogashira coupling. The activities of 3 and 4 for TH are in the order Se > S.

Full text of DOI:10.1039/c6dt01406b

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: A. K. Singh, S.
Kumar and F. Saleem, Dalton Trans., 2016, DOI: 10.1039/C6DT01406B.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/dalton

Page 1 of 13
Dalton Transactions
Dynamic Article Links►
Journal Name
View Article Online
DOI: 10.1039/C6DT01406B
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
“Click” generated 1,2,3ꢀtriazole based organosulfur/selenium ligands
and their Pd(II) and Ru(II) complexes: their synthesis, structure and
catalytic applications
Satyendra Kumar, Fariha Saleem and Ajai K. Singh*
5
Received (in XXX, XXX) XthXXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
1ꢀ(2,6ꢀDiisopropylphenyl)ꢀ4ꢀ(phenylthio/selenomethyl)ꢀ1Hꢀ1,2,3ꢀtriazole (L1/L2) synthesized by ‘Click’
reaction, on treatment for 5 h with [Pd(CH3CN)2Cl2] and 8 h with [(η6ꢀC6H6)RuCl(ꢀꢀCl)]2 (followed by
reaction with NH4PF6), at room temperature results in complexes [Pd(L)Cl2] (1 and 2) and [(η6ꢀ
10 C6H6)Ru(L)Cl]PF6 (3 and 4) (L = L1 or L2) respectively. The four complexes (1−4) and ligands (L1 and
L2) were authenticated with 1H, 13C{1H} and 77Se{1H} NMR and high resolution mass spectrometry.
Single crystal structures of 1−4 were solved. The geometry of Pd in 1 and 2 is distorted square planar.
The Pd–S and Pd–Se bond distances in 1 and 2 are 2.277(3) and 2.384(6) Å respectively. In 3 and 4 there
is a pseudo octahedral “pianoꢀstool” type disposition of donor atoms around Ru. The Ru−S and Ru−Se
15 bond lengths in 3 and 4 are 2.3728(12) and 2.4741(6) Å respectively. Catalytic activity of the complexes
1 and 2 was explored for Suzuki−Miyaura coupling (SMC) in water and Sonogashira coupling reactions.
For various aryl bromides including deactivated ones the complexes 1 and 2 were found efficient for both
the couplings. The optimum loading of 1 and 2 required as a catalyst for both the coupling reactions is of
the order of 0.001−2 mol% of Pd. For SMC no additive or phase transfer catalyst was added. For catalysis
20 of transfer hydrogenation (TH) of aldehydes and ketones both half sandwich Ru(II) complexes 3 and 4
were explored. Their optimum loading as catalyst was found to be 0.1−0.4 mol % of Ru. In TH both
water used as a solvent, and glycerol as a hydrogen source are environmentally friendly. The catalytic
efficiency of both 3 and 4 is comparable with those of other catalysts reported for TH carried out with 2ꢀ
propanol or glycerol as a Hꢀsource. The 1 having sulfur ligand is more efficient than 2 (Se analog) for
25 both SMC and Sonogashira coupling. The activity of 3 and 4 for TH is in the order Se > S.
promising catalytic efficiency for various organic reactions. 11a,b,12
Introduction
However, it may also be partially attributed to strong electron
50 donating ability of S/Se.11a,b,12 The incorporation of the bulky 2,6ꢀ
diisopropylphenyl (dipp) group as a substituent in 1,2,3ꢀtriazole
based ligand may provide kinetic stability to the free ligand13 and
more electron density to metal center14a in its complex. The
presence of electron rich donor site in the ligand strengthens its
55 coordination with metal and increases electron density on it. High
electron density on metal may reduce activation energy for
oxidative addition and in turn, gives high efficiency to complex
catalyst functioning through this step.14b It is known that
introduction of a dipp group in Nꢀheterocyclic carbenes (NHC’s)
60 leads to a catalyst of high activity for Suzuki coupling of
aryl/heteroaryl chlorides in water.15 Thus introduction of 2,6ꢀ
diisopropyl phenyl group in a triazole based ligand is worth
exploring and sulfated/selenated 1,2,3ꢀtriazole based ligands (L1
and L2) and their Pd(II) and Ru(II) complexes 1−4 have been
65 synthesized and explored for Suzuki−Miyaura and Sonogashira
coupling and transfer hydrogenation(TH).
Copper(I) catalyzed 1,3ꢀdipolar cycloaddition reaction of
terminal alkyne with organic azide to form 1,4ꢀdisubstituted
1,2,3ꢀtriazole called ‘Click’ reaction has facilitated synthesis of
30 various triazole compounds needed in modern chemistry and
biology,1ꢀ5 including ligands with triazole core.6ꢀ8 The advantages
viz. mild reaction conditions, excellent functional group
tolerance, selectivity and simple work up procedure which results
in quantitative yield, give ‘Click’ reaction an edge over other
35 protocols.1aꢀb,7bꢀc 1,2,3ꢀTriazole functionalized with donor atom
containing groups coordinates in conjunction with two nitrogen
atoms and one carbon atom of the heterocyclic ring. Thus
functionalized 1,2,3ꢀtriazoles constitute a class of versatile
ligands for a variety of metal ions.8a,b,c,e,i,k Their several metal
40 complexes including those of palladium(II) and ruthenium(II) are
known for promising activity as
a catalyst for organic
transformations.5,9ꢀ12 The ligand architecture is considered
important to design an efficient catalyst. Consequently
replacement of benzene framework with 1,2,3ꢀtriazole backbone
45 in ligands found rewarding is also envisaged as worth exploring
further.6,9,12 Thus 1,2,3ꢀtriazole based organochalcogen ligands
were designed and their metal complexes found to show
The known catalysts for the two coupling reactions include
palladium(II) complexes of several phosphorus, carbene, imine,
thiocarboxamide/semicarbazone, palladacyles and pincer
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 |1

Dalton Transactions
Page 2 of 13
View Article Online
DOI: 10.1039/C6DT01406B
ligands.16ꢀ22 They are also reported to function via in situ
formation of Pd(0) species (discrete or nanoꢀsized).23ꢀ25 On 1,2,3ꢀ
triazoleꢀbased organosulfur/selenium ligands and applications of
their metal complexes as catalysts there are limited
reports.11a,b,d,12 Lone report on SMC12 using such a complex is
from our group but for Sonogashira coupling none is in our
knowledge. Palladium(II) complexes (1 and 2) of sterically
encumbered 1,2,3ꢀtriazoleꢀbased organosulfur/selenium ligands
reported herein catalyze SMC in water with good yield in short
45 selenomethyl)ꢀ1Hꢀ1,2,3ꢀtriazole (L1/L2) at room temperature,
facilitated by anion exchange with NH4PF6. The complexes 1 and
2 moderately soluble in CHCl3, CH3OH and CH3CN show good
solubility in DMSO and DMF. Half sandwich Ru(II) complexes,
3 and 4 are soluble in CH3CN. Elemental analyses, multinuclear
50 NMR, IR and highꢀresolution mass spectrometry (HRꢀMS)
consistent with simulated HRꢀMS (see Figs. S1ꢀS20 in ESI) have
authenticated each compound. Single crystal structures of 1−4
have been established with Xꢀray crystallography. In TGA plots
of all complexes (see Figs. S22ꢀS25 in ESI) there is no
55 decomposition before 200 ºC, indicating their suitability for high
temperature catalytic reactions.
5
10 time.
Ruthenium(II) complex catalyzed transfer hydrogenation
(TH)26 using organic solvents as a Hꢀsource, avoids use of
hazardous H2 as a reducing agent.27 The organic solvents
generally used as a Hꢀsource cum solvent are, 2ꢀpropanol, formic
15 acid, glycerol and cyclopentanol. The BINAP, 1,2ꢀdiamines and
PR3, pyridyl/bipyridyl ligands, benzimidazoles, thioamide and
NHCs are among the ligands forming complexes with Ru(II),
suitable to catalyze TH.28ꢀ32 Few Ru(II) complexes of
organochalcogen ligands promising for catalytic TH have been
20 reported by our research group.33 2ꢀPropanol and in some cases
glycerol were used as a Hꢀsource and solvent in them.33 The
Ru(II) complexes of 1,2,3ꢀtriazole based organosulfur/selenium
ligands for TH11a,b are reported scantly and the present ones (3/4)
are probably the first examples of such complexes explored to
25 catalyze TH in water. The biodegradable glycerol is attractive due
its low cost, ready availability, renewability34,35 and its ability to
dissolve bases, transitionꢀmetal complexes and organic
compounds even when they are sparingly soluble in water.35 The
protocol based on 3/4 and a nontoxic Hꢀsource glycerol in
30 aqueous medium for TH is also partially green.
NMR spectra. NMR spectra of L1−L2 and 1−4 are consistent
with their molecular structures depicted in Scheme 1 and given in
60 ESI (Figs. S1−S15). The signal in the 77Se{1H} NMR spectrum
of L2 (366.3 ppm) is at lower frequency with respect to that of
selenated alkyne (375.8 ppm). The signals in 77Se{1H} NMR
spectra of 2 and 4 appear at higher frequency (100.2 and 85.2
ppm respectively) relative to corresponding signal of free L2
65 (ESI; Figs. S5, S10 and S15). These shifts probably imply
1
coordination of L2 with Pd or Ru center via Se. In H NMR of
free L1 and L2 signals of H2C(9) (i.e. ECH2, E=S/Se) appear as a
singlet. On complexation these signals in the spectra of
complexes 1 and 2 appear at a higher frequency (up to ~0.47
70 ppm) relative to those of corresponding free ligands, supporting
the coordination of ligands with metal centres through S or Se.
Signals of H2C(9) in 1H NMR spectra of 3 and 4 appear at a
lower frequency (up to ∼0.25 ppm) relative to those of free L1
and L2. Such observation has been made in case of half sandwich
75 complexes of Ru(II) with organochalcogen ligands earlier.11a,b It
may be due the effect of electron rich arene ligand. The signals of
C(9) in 13C{1H} NMR spectra of 3 and 4 observed at a higher
frequency (up to ∼8.5 ppm) with respect to those of free ligands,
support their coordination with Ru via S/Se.
Results and discussion
Syntheses of L1 and L2, and their complexes with Pd(II) and
Ru(II) (1−4) are summarized in Scheme 1. The possibility of
thermal cycloaddition reaction to give L1/L2 is ruled out as we
35 do not get 1,5ꢀdisubstitedꢀ1,2,3ꢀtriazole as an additional product.
Thus ligand formation is via ‘Click’ reaction carried out at 90 ºC,
as at room temperature yield was 25% only. The presence of
sterically demanding isopropyl groups probably make the
reaction temperature high. The complexes 3 and 4 are formed by
40 chloro bridge cleavage of [(η6ꢀbenzene)RuCl(ꢀꢀCl)]2 followed by
reaction with 1ꢀ(2,6ꢀdiisopropylphenyl)ꢀ4ꢀ(phenylthio/
80
Crystal structures. Single crystals of 1−4 suitable for Xꢀray
diffraction were grown by slow evaporation of their solutions
made in methanolꢀacetonitrile mixture (1:6). The crystallographic
data and refinement parameters are given in ESI (Table S1). The
85
Fig. 1 ORTEP diagram of 1. Bond lengths (Å): Pd(1)─N(3) 2.002(8);
Pd(1)─Cl(2) 2.297(3); Pd(1)─Cl(1) 2.295(3); Pd(1)─S(1) 2.277(3). Bond
angles (°): N(3)─Pd(1)─S(1) 84.7(2); S(1)─Pd(1)─Cl(1) 89.52(11);
90 N(3)─Pd(1)─Cl(2) 93.6(2); Cl(1)─Pd(1)─Cl(2) 92.07(11).
ORTEP diagrams of 1−4 with 30% probability ellipsoids are
shown in Figs. 1−2 and 5−6 with selected bond distances and
angles. Ligands L1 and L2 exhibit identical bonding mode in the
Scheme 1 Syntheses of ligands and their complexes
2
|Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 3 of 13
Dalton Transactions
View Article Online
DOI: 10.1039/C6DT01406B
(C−H···Cl) in 1 and 2 result in the formation of a sheet like
structure (Figs. 3 and 4).
In single crystal structures of complexes 3 and 4 ruthenium has
pseudoꢀoctahedral halfꢀsandwich “pianoꢀstool” geometry. η6ꢀ
35 Benzene ring, nitrogen of 1,2,3ꢀtriazole, S or Se and Cl complete
coordination sphere of Ru. The Ru–S bond length in cation of 3
(2.3728(12) Å) is consistent with the values reported for halfꢀ
Fig. 2 ORTEP diagram of 2. Bond lengths (Å): Pd(1)─N(3) 2.011(3);
Pd(1)─Cl(2) 2.2815(12); Pd(1)─Cl(1) 2.3188(12); Pd(1)─Se(1)
2.3840(6).
Cl(2)─Pd(1)─Cl(1)
Cl(2)─Pd(1)─Se(1) 90.23(4).
Bond
angles
91.57(4);
(°):
N(3)─Pd(1)─Cl(1)
N(3)─Pd(1)─Se(1)
93.13(11);
85.05(10);
5
complexes 1−4, i.e. a fiveꢀmembered chelate ring is formed by
their coordination with each metal centre. The palladium in
complexes 1 and 2 has a distorted squareꢀplanar geometry with
10 sulfur or selenium cis to N (two Cl cis to each other). The Pd−S
bond distance in 1, 2.277(3) Ǻ is consistent with that of
40 Fig. 5 ORTEP diagram of 3. PF6ꢀ anion has been omitted for clarity. Bond
lengths (Å): Ru(1)─N(3) 2.082(3); Ru(1)─S(1) 2.3728(12); Ru(1)─Cl(1)
2.3993(14); Ru(1)─C 1.675(1); Bond angles (°): N(3)─Ru(1)─S(1)
80.42(9); N(3)─Ru(1)─Cl(1) 84.93(10); S(1)─Ru(1)─Cl(1) 80.89(5).
palladacycle
formed
with
2,3ꢀbis[(phenylthio)methyl]
quinoxaline (2.259(2)Ǻ)36 and Pd(II) complex of sulfated Schiff
base of 1ꢀhydroxyꢀ2ꢀacetophenone (2.2704(16) Ǻ).37
15
Fig. 3 Nonꢀcovalent interactions in 1
45 Fig. 6 ORTEP diagram of 4. PF6ꢀ anion has been omitted for clarity. Bond
lengths (Å): Ru(1)─N(3) 2.081(3); Ru(1)─Cl(1) 2.3973(14); Ru(1)─Se(1)
2.4741(6); Ru(1)─C 1.438(0). Bond angles (°): Cl(1)─Ru(1)─Se(1)
80.15(4); N(3)─Ru(1)─Cl(1) 84.53(10); N(3)─Ru(1)─Se(1) 81.36(9).
In 2, Pd–Se bond distance (2.3840(6) Ǻ) is close to the values
reported for Pd(II) complex of bis[(phenylseleno)methyl]
20 quinoxaline [2.3924(15) and 2.3991(15)Ǻ],36 and somewhat
shorter than that of Pd(II) complex of (Se, N, Se) pincer ligand
(2.4104(5)/2.4222(6) Å).23c The Pd−N bond distances in both 1
50
Fig. 7 Nonꢀcovalent interactions in 3
25
Fig. 4 Nonꢀcovalent interactions in 2
sandwich complex of Ru(II) with 1ꢀbenzylꢀ4ꢀ[(phenylthio)ꢀ
methyl]ꢀ1Hꢁ1,2,3ꢀtriazole [2.3847(11) Å]11a The Ru–Se bond
distance (2.4741(6) Å) in 4 is similar to the values reported for
55 [(η6ꢀC6H6)RuCl(Nꢀ{2ꢀ(phenylseleno)ethyl}pyrrolidine)]+
and 2 are almost same [2.002(8) and 2.011(3) Ǻ] and comparable
to the value reported for Pd(II) complex of a (P, N) ligand
(2.015(19) Ǻ).38 The Pd(1)−Cl(1) and Pd(1)−Cl(2) bond lengths
in 1 [2.295(3) and 2.297(3) Ǻ] and 2 [2.3188(12) and 2.2815(12)
(2.480(11) Å)39 and [(η6ꢀC6H6)Ru(2ꢀMeSC6H4CH=NCH2CH2ꢀ
SeC6H5)]2+ (2.4848(8) Å).40 The Ru−N bond distances of cation
of 3 and 4 (2.082(3) Å and 2.081(3) Å respectively) are
30 Å] are normal.23c Nonꢀcovalent secondary interactions
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 |3

Dalton Transactions
Page 4 of 13
View Article Online
DOI: 10.1039/C6DT01406B
consistent
with
that
of
cation
[(η6ꢀC6H6)Ru(2ꢀ
phenylboronic acid at 100 °C in presence of K2CO3, resulting in
∼99% conversion (Table 1 Entry1) into crossꢀcoupled product in
30 min. The conversion to the same coupled product was 71%
−
MeSC6H4CH=N−CH2CH2SC6H5)]2+ (2.073(6) Å).40 The PF6
anion has been found to be involved in C−H···F secondary
interactions in the crystals of 3 and 4 resulting in chain type 40 when this SMC reaction was carried out for 15 h at 0.001 mol%
structures as shown in Figs. 7 and 8.
5
catalyst loading (Table 1: Entry 2). On using 2 (0.01 mol%) as a
catalyst for the same SMC under identical reaction conditions, the
conversion was 81% for reaction time of 3 h and 99% for 12h
(Table 1: Entries 1 and 2). Among other aryl bromides the
45 activated ones gave good conversion when SMC was carried out
for 1ꢀ2 h in the presence of 1, however the reaction time
increased with 2 for coupling of the same substrate (Table 1,
Entries 3ꢀ6). 4ꢀBromonitrobenzene, 4ꢀbromoacetophenone and 4ꢀ
bromobenzoic acid were converted into coupled product within
50 30 min when 0.01 mol% loading of 1 was used for the coupling.
When complex 2 was used as a catalyst for SMC of these
substrates, increase in the catalyst amount/reaction time was
necessary for good conversion (Table 1, Entries 4ꢀ6). The
conversion of deactivated aryl bromides viz. 4ꢀbromotoluene and
55 4ꢀbromoanisole into coupled product was 51ꢀ99% when long
reaction time and high catalyst loading (0.1ꢀ1 mol%) were used
for SMC. The conversion of 4ꢀbromoanisole into coupled product
is ∼99% in 6 h at 0.1 mol% loading of 1, whereas 1.0 mol%
loading of catalyst 2 results only 35% conversion under identical
60 reaction conditions (Table 1, Entry 8). The conversion of 4ꢀ
bromotoluene catalyzed with 1 and 2 at 0.1 mol% loading into
coupled product is 63 and 51% respectively (Table 1, Entry 7).
Fig. 8 Nonꢀcovalent interactions in 4
Catalysis of Suzuki–Miyaura coupling (SMC)
10
Palladium(II) complexes 1 and 2 catalyze SMC efficiently in
water used many times for it as a coꢀsolvent with DMF, EtOH,
dioxane and THF.23c,41 No significant gain in catalytic activity
was observed in mixtures of water with DMF and EtOH, using
15 SMC reaction conditions optimized in water or attempting fresh
optimization. The reports on the use of discrete Pd(II) complexes
as a catalyst for SMC in water are scanty.5,15,23c,41a,b,42,43 In the
present study, 4ꢀbromobenzaldehyde was reacted with
Catalysis of Sonogashira coupling
65
The catalytic performance of Pd(II) complexes 1−2 has been
explored for Sonogashira (Csp2−Csp) coupling. To the best of our
knowledge no Pd(II) complex of 1,2,3ꢀtriazole based
organochalcogen ligand has been used to catalyze this coupling
70 so far, and the present one is the first attempt. The base and
solvent were optimized by choosing 4ꢀbromobenzaldehyde as a
substrate and 1 as a catalyst. The conversions were monitored
with 1H NMR. Among bases the (Table 2) best results were
Table 1 SuzukiꢀMiyaura C−C coupling reactions catalyzed with 1–2a
20 Ar−Br
+
PhB(OH)2
→
Ar−Ph
Entry
No.
Aryl bromide
1
2
Mol% time Converꢀ Mol% time Converꢀ
sionb
sionb
/Yieldc
81/70
99/ꢀ
/Yieldc
1
2
3
4
5
6
7
8
4ꢀBromobenzaldehyde 0.01 30min 99/91 0.01
4ꢀBromobenzaldehyde 0.001 15 h 71 0.01 12 h
4ꢀBromobenzonitrile
3 h
0.01 90min 70/62 0.1 90min 65/52
Table 2 Optimization of reaction condition for Sonogashira coupling
75 reaction catalyzed with 1a
4ꢀBromonitrobenzene 0.01 30min 99/93 0.01
4ꢀBromoacetophenone 0.01 30min 99/90 0.1
3h
5h
99/89
99/86
4ꢀBromobenzoic acid
4ꢀBromotoluene
4ꢀBromoanisole
0.01 30min 99/88 0.01 30min 99/93
0.1 12h 63/52 0.1 12h 51/42
0.1 6h 99/93 12h 35/ꢀ
Br−C6H4−CHO
+
PhCCH
→
CHO−C6H4−CCPh
Conversionb (%)
Entry No.
Solvent
DMA
DMF
DMSO
DMA
DMF
DMSO
DMF
EtOH
Base
K2CO3
K2CO3
K2CO3
KOH
1
1
2
3
4
5
6
7
8
55
99/87c
27
40
ꢀꢀ
ꢀꢀ
<10
26
aReaction conditions: ArBr (1.0 mmol), phenylboronic acid (1.2 mmol),
K2CO3 (2.0 mmol), water (3 mL), temperature of bath 100 °C, bNMR
conversion in %, cIsolated yield in %.
KOH
NaOH
phenylboronic acid to optimize the reaction conditions
25 (monitoring conversion with 1H NMR). Among bases K2CO3 was
found most suitable. On completion of the coupling reaction the
coupled product was isolated. In Table 1 optimum mol% of
catalyst required, reaction time, % isolated yield and %
Cs2CO3
K2CO3
aReaction conditions: 1.0 mmol of 4ꢀbromobenzaldehyde, 1.1 mmol of
phenylacetylene, 2.0 mmol of base, 1 mol % complex 1, 2 mol% of CuI,
3 mL solvent, N2 atmosphere, temperature of bath, 120 °C and reaction
80 time 12 h, b % conversion by NMR, cIsolated yield in %.
1
conversion estimated at the end of reaction with H NMR are
30 reported. Isolated yields are lower than conversions, as expected,
but both show similar trends with substrates. These results
indicate that in SMC catalyzed with 1 and 2 the coupling of
several aryl bromides can be successfully achieved in a short time
without any additive or phase transfer catalyst such as
35 tetrabutylammonium bromide (TBAB). The complex 1 at 0.01
mol% loading catalyzes SMC of 4ꢀbromobenzaldehyde with
obtained with K2CO3 and DMF was found to be best solvent.
Presence of CuI (2−4 mol%) as a coꢀcatalyst and N2 atmosphere
were found necessary to get good conversion. The scope of
substrates was explored under optimized reaction conditions
85 monitoring conversion with 1H NMR. In case of 4ꢀ
bromobenzaldehyde conversion at 120 °C into the coupled
4
|Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 5 of 13
Dalton Transactions
View Article Online
DOI: 10.1039/C6DT01406B
product was ∼99% when loading of 1 as a catalyst was 1 mol%.
Table 3 Sonogashira coupling reaction catalyzed with complexes 1 and 2a
reactions. Thus Pd(0)/Pd(II) in solution is most likely pathway for
50 these coupling reaction.
R−C6H4−Br
+
PhCCH
→
R−C6H4−CCPh
Catalysis of transfer hydrogenation (TH)
Entry
No.
Aryl halide
1
2
Mol% t (h) Conveꢀ Mol% t (h) Conveꢀ
The Ru(II) complexes 3 and 4 (0.1−0.4 mol%) were explored for
55 catalytic transfer hydrogenation (TH) of carbonyl compounds in
water using millimole amount of glycerol as a hydrogenꢀsource.
Reaction conditions were optimized in water by choosing
benzaldehyde as a model substrate and 4 as a catalyst. At reaction
temperature of 110 °C, combination of glycerol/2ꢀpropanol and
60 KOH was found best, as conversion achieved was maximum
(Table 4: glycerol: 95%, Entry 1; 2ꢀpropanol: 93%, Entry 6). TH
reaction was ineffective in the presence of KOH when citric and
acetic acids were used as Hꢀsources (Table 4, Entries 7 and 8).
Ascorbic acid is somewhat better than these two acids (Table 4,
65 Entry 2). High amount of 2ꢀpropanol or HCOOH with weak base
HCOONa also gave somewhat good results (Table 4, Entries 3
and 4). In comparison to 2ꢀpropanol which gave results
comparable to glycerol, the later was preferred as it is considered
a green solvent.33a,35 The combination of glycerol with HCOONa
70
rsion b/
Yieldc
99/87
84
rsion b/
Yieldc
60/52
40
99/88
74/61
87/80
43/31
ꢀꢀ
1
2
3
4
5
4ꢀBromobenzaldehyde
4ꢀBromobenzaldehyde 0.1
4ꢀBromobenzonitrile
4ꢀBromoacetophenone 0.1
1
8
12
1
0.1
2
1
2
12
12
12
12
12
12
12
2
12 99/91
12 60/43
8
12 61/53
12 40/32
4ꢀBromonitrobenzene
2
2
2
98/85
6d 4ꢀBromotoluene
7d 4ꢀBromoanisole
2
2
aReaction conditions: 1.0 mmol of ArBr, 1.1 mmol of phenylacetylene,
d
5
2.0 mmol of base (K2CO3), CuI equiv. to 4 mol%, 3 mL DMF solvent,
temperature of bath 120 °C, % conversion by NMRb, cIsolated yield in %.
When Sonogashira coupling of 4ꢀbromobenzaldehyde was carried
out in the presence of 1 mol% of 1 in copper free condition, no
conversion of substrate was noticed. The catalytic role of Pd was
10 ascertained by performing the coupling reaction without
palladium catalyst. The possibility of palladium free catalysis was
ruled out as only homoꢀcoupled product of phenylacetylene
(PhCCCCPh) was obtained (Glaserꢀtype reaction),19b,21c,d in the
absence of Pd. Moreover, the present Sonogashira coupling
15 reactions being amineꢀfree (K2CO3 is the base in the present case)
may be labeled as more environmentally friendly, as the amines
are not considered environmentally benign.21b The % conversion
Table
4 Optimization of reaction conditions for catalytic transfer
hydrogenation of carbonyl compounds using 4a
1
(monitored with H NMR) and isolated yield(%) for the catalytic
Entry No. Base/amount(mmol) Hꢀsource/amount(mmol) Conversion b
coupling of various substrates are given in Table 3. The 0.1ꢀ2
20 mol% of Pd and 2 mol% of copper iodide were required to get
good conversion into couple product, of electronically activated
aryl bromides (Table 3, Entries 1−5). 4ꢀBromobenzaldehyde and
4ꢀbromoacetophenone were converted 84 and 60% respectively
into the coupled product at 0.1 mol% loading of 1 (Table 3,
25 Entries 2 and 4). For the same substrate activity of 2 was lower
than that of 1 e.g. 1 mol% of palladium was necessary to get 74%
of 4ꢀbromoacetophenone converted into the coupled product
(Table 3, Entry 4). The 2 mol% of 1/2 gave almost complete
conversion of 4ꢀbromobenzonitrile and 4ꢀbromonitrobenzene into
30 the coupled products (Table 3, Entries 3 and 4). In the case of
deactivated aryl bromides viz. 4ꢀbromotoluene and 4ꢀ
bromoanisole conversion/yield of the crossꢀcoupled product was
low even when 2 mol% loading of 1 was used. On increasing the
amount of coꢀcatalyst, CuI to 4 mol%, with 2 mol% of Pd
35 catalyst, conversion was achieved up to 61% for these substrates
(Table 3, Entries 6 and 7). In case of 4ꢀbromoanisole coupling
was negligible in the presence of 2.
The nature of catalyst in the two coupling processes was
investigated by mercury and triphenylphosphine poisoning tests43
40 The reaction of 4ꢀbromobenzaldehyde with phenylboronic acid
(SMC)/phenylacetylene (Sonogashira coupling) was carried out
in the presence of 1 as described in the ESI. The results given in
Table S7 and S8 (ESI) reveal that catalytic processes are not
quenched in the presence of Hg(0)/PPh3 but do not reach to
45 completion, indicating that they are partially poisoned by Hg /
PPh3 and small contribution of heterogeneous pathway may exist.
(%)
1
2
3
4
5
6
7
8
KOH/1
KOH/1
HCOONa/2
HCOONa/2
HCOONa/2
KOH/1
Glycerol/2
Ascorbic acid /5
HCOOH/10
2ꢀPropanol/10
Glycerol/2
2ꢀPropanol /2
Citric acid/2
Acetic acid /5
95/89c
50
55
90
<10
93
<10
25
KOH/1
KOH/1
75 aReaction conditions: 1.0 mmol of benzaldehyde, 0.4 mol % of Ru(II)
complex 4, 3 mL of water, temperature 110 °C, reaction time 6 h.
b
%
conversion by NMR, cIsolated yield in %.
base does not work in the present case (Table 4, Entry 5). The
reaction of benzaldehyde was carried out under optimized
80 conditions in the presence of catalyst 4 without any hydrogen
source, to check possibility of KOHꢀpromoted TH. After 8 h of
reaction, conversion was <10%, affirming the role of the Ru as a
catalyst. The conversions in catalytic reactions monitored with 1H
NMR spectra and isolated yields of coupled products are given in
85 Table 5. The scope of substrates for the catalytic TH with 3 and 4
was studied and results are given in Tables 5. Activity of both 3
and 4 is highest for benzaldehyde (isolated yield up to ~99%,
Table 5, Entry 1). The conversion of acetophenone is ~ 99% with
4 and 70% with 3 (Table 5, Entry 4). The complex 4 is efficient
90 for catalytic TH of furfuraldehyde, 4ꢀchlorobenzaldehyde and 4ꢀ
bromobenzaldehyde but activity of 3 is lower (Table 5, Entry 5ꢀ7)
than that of
4 under identical reaction conditions. The
combination of glycerolꢀwater was not effective for 4ꢀ
bromoacetophenone and benzophenone as no conversion to
95 reduced product was achieved. In 2ꢀpropanol, used as a solvent
The 1 and 2 can survive at reaction temperatures of coupling
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 |5

Dalton Transactions
Page 6 of 13
View Article Online
DOI: 10.1039/C6DT01406B
and Hꢀsource their conversions were good (Table 5, Entries 3 and 45 electron rich which probably promotes the formation of metalꢀ
9). The comparison of the performance of 3 and 4 as catalysts for
TH, made with other catalysts reported to work in water, is a
mixed bag. The loading for good conversion[in H2OꢀMeOH
mixture; base: HCOONa) required for catalyst, [Ru(η6ꢀ
hydride species during the catalysis. Thus in TH catalyzed with 3
and 4, the formation of Ru−H bond containing intermediate and
the absence of the NH group in the ligand together suggest that a
conventional mechanism via alkoxide formation51 is most
5
arene)(dhbp)Cl]+, (dhbp = 6,6′ꢀdihydroxyꢀ2,2′ꢀbipyridyl)44 is 1 50 plausible.
mol%, higher than those of present complexes. The reaction time
16 h, is also long. The TH activity of 3 and 4 in waterꢀglycerol is
better than those of [(η5ꢀCp*/η6ꢀbenzene)Ru(L)Cl]PF6 (L=2ꢀ
The possibility in the present catalytic TH reaction, of
heterogeneous pathway due to formation of Ru NPs from 3 or 4,
was explored using mercury and PPh3 poisoning test.35,43,52 The
poisoning reagents were added to three TH reactions when they
55 progressed simultaneously under optimal conditions for 1, 2 and
3 h respectively, and the reactions continued further for optimum
time (details in ESI). The results are given in ESI (Table S9). The
presence of Hg (Ru:Hg ; 1:500) in the TH of benzaldehyde
catalyzed with 4 (0.1 mol%) did not show significant inhibition of
60 conversion. In the presence of 5.0 equiv of PPh3, only slight
decrease in percent conversion was noticed. Thus, the present
catalytic TH proceeds homogeneously and formation of Ru NPs
is negligible.
10 (pyridineꢀ2ꢀylmethylsulfanyl)benzoic acid).33a
Table 5 Catalytic transfer hydrogenation of carbonyl compounds using
complexes 3 and 4a
15
Entry
No.
Aldehyde/Ketone
3
4
Mol% t(h) Conveꢀ Mol% t(h) Conveꢀ
rsion b/
rsion b/
Yieldc
95/89
ꢀꢀ
93/84
99/87
80/72
83/71
99/88
35/ꢀ
65 DFT calculations
Yieldc
1
2
Benzaldehyde
Benzophenone
0.4
0.4
0.1
0.4
6
8
3
6
99/93 0.4
ꢀꢀ
99/90 0.2
70/59 0.2
8
8
5
6
10
8
6
8
3
Density functional theory (DFT) calculations made for 1−4 are
consistent with their structures and support experimental results
on their catalytic activity. For Pd(II) complexes 1 and 2, the
70 HOMOs (highest occupied molecular orbitals), constituted by
interaction of a dꢀorbital of Pd(II) and pꢀorbital of chlorine, are
positioned primarily on Pd and Cl atoms. In HOMO−1 the metal
dꢀorbital, pꢀorbitals of S/Se, chlorine and nitrogen (coordinated
one) of triazole ring have contribution. The HOMOs of Ru(II)
75 complexes 3 and 4 are essentially similar and positioned
primarily over Ru(II) and the η6ꢀbenzene ring and to some extent
on S/Se, N, and Cl donor atoms. The dꢀorbitals of Ru(II)
0.4
3d Benzophenone
4
5
6
7
8
Acetophenone
Furfuraldehyde
0.4 15 71/61 0.4
0.2
4ꢀBromobenzaldehyde 0.4 12 62/48 0.4
4ꢀBromoacetophenone 0.4 12 ꢀꢀ 0.4
95/88 0.4
4ꢀChlorobenzaldehyde 0.4 18 <10
9d 4ꢀBromoacetophenone 0.1
6
99/85
aReaction conditions: 1.0 mmol of carbonyl compound, 1.0 mmol of
b
KOH, 3 mL of water, 2.0 mmol of glycerol, temperature 110 °C.
%
Conversion determined with NMR. cIsolated yield, dreaction was
performed in 2ꢀpropanol.
20 Using HCOONa as a hydrogen source at pH 4 in water, [Ru(η6ꢀ
arene)(dmobpy)Cl]+(dmobpy = 4,4′ꢀdimethoxyꢀ2,2′ꢀbipyridine)45
shows better catalytic efficiency than 3 and 4. The optimum
loading of [(pꢀcymene)Ru(NHC)]46 as a TH catalyst in 2ꢀ
propanol is reported higher than those of 3 and 4, but with a
25 short reaction time ≤1 h. The optimum loading of Ru(II)
complexes of 1,3,5ꢀtriazaꢀ7ꢀphosphaadamantane (PTA) for
biphasic TH in aqueous medium47 is reported higher than those of
3 and 4. The catalytic TH efficiency of RuCl2(TPPMS)2]
(TPPMS
=
4ꢀ(diphenylphosphino)benzenesulfonic acid)48 in
30 aqueous medium is comparable to those of 3 and 4. Thus Ru
complexes, 3 and 4 can be rated as efficient TH catalysts, as
yields/conversions are better in a short time and optimum catalyst
loading is low relative to several Ru species mentioned above.
The performance of 3 and 4 may be partly ascribed to overall
35 strong ligating characteristics of L1 and L2 and their steric
influence. During TH reaction in glycerol, its dehydrogenation
gives dihydroxyacetone (1H NMR: δ 4.4 and 3.5 ppm) in a very
low yield which is very difficult to isolate economically.35,49
However its recovery is not of great concern due to low cost of
80
Fig. 9 Frontier molecular orbital diagrams of complexes 1−4
interacting with πꢀorbitals of η6ꢀbenzene ring and pꢀorbitals of
chlorine, nitrogen, and sulfur/selenium atoms compose their
HOMOs (Fig. 9). In simplistic terms catalytic activity of the
complexes may be correlated to their HOMO−LUMO energy
85 gap. Its low value results in high activity.54,11a,b Therefore
between complex 1 and 2, lower HOMO−LUMO energy gap
(calculated by DFT) in 1 makes it more catalytically active than
2 (Fig. 9), as found experimentally in SMC and Sonogashira
coupling reactions. HOMO−LUMO energy gap for Ru(II)
1
40 glycerol. In H NMR spectrum of reaction mixture recorded after
1 h of setting of TH reaction a broad singlet appears between −8
to −11.0 ppm, indicating the presence of H‾. Thus present
catalytic TH probably proceeds via formation of Ru−H bond.50
High electron donating ability of Se and S makes metal center
6
|Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 7 of 13
Dalton Transactions
View Article Online
DOI: 10.1039/C6DT01406B
complexes is lower for 4 than that of 3. Therefore Se analog (Fig.
9) shows higher catalytic activity for TH in comparison to that of
dried under ambient conditions. Melting points were determined
by taking the sample in a glass capillary sealed at one end, with
S one. However, variation in catalytic activities of various 60 an apparatus equipped with electric heating and reported as such.
complexes observed experimentally is moderate only but
consistent with DFT calculations.
The experimentally observed and DFT calculated Pd−Cl,
Pd−N, Ru−Cl, Ru−N and Ru−S/Se bond distances and various
The commercial nitrogen gas was passed successively through
traps containing solutions of alkaline anthraquinoneꢀsodium
dithionite, alkaline pyrogallol, concentrated. H2SO4 and KOH
pellets, before use. Nitrogen atmosphere was created using
5
bond angles are reasonably consistent (ESI; Tables S2ꢀS5 and 65 Schlenk techniques.
S6). However, calculated and observed Pd− S/Se bond distances
10 differ.
Physical measurements
1H, 13C{1H} and77Se{1H} NMR spectra were recorded on a
Bruker Spectrospin DPX 300 NMR spectrometer at 300.13, 75.47
Conclusions
70 and 57.24 MHz respectively. In H and 13C{1H} NMR chemical
1
The complexes (1−4) have been synthesized by reacting
shifts (in ppm) are reported relative to the internal standard
tetramethylsilane (TMS). 13C DEPT NMR was used routinely to
determine the number of hydrogen atoms linked to a carbon
atom. IR spectra in the range 4000−400 cm−1 were recorded on a
75 Nicolet Protége 460 FTꢀIR spectrometer as KBr pellets.
Elemental analyses were carried out with a Perkin–Elmer 2400
Series II C, H, N analyzer. Thermogravimetric analyses (TGA)
up to 700 ºC were carried out on a PerkinꢀElmer Pyris Diamond
thermogravimetric analyzer (N 535ꢀ0010). The powder XRD data
80 of complexes (1ꢀ4) were collected on a Rigaku Ultima IV
diffractometer using CuꢀKα at room temperature over a 2θ range
of 5° to 70°. In Fig. S21 (ESI) the powder diffraction patterns are
shown.
Singleꢀcrystal data were collected with a Bruker AXS SMART
85 Apex CCD diffractometer using MoꢀKα (0.71073 Å) radiation.
The software SADABS57a was used for absorption correction and
SHELXTL for space group, structure determination, and
refinement.57b,c Hydrogen atoms have been included in idealized
positions with isotropic thermal parameters set at 1.2 times those
90 of the carbon atoms to which they were attached. The leastꢀ
squares refinement cycles on F2 were performed until the model
appropriate metal precursors with click generated ligands 1ꢀ(2,6ꢀ
diisopropylphenyl)ꢀ4ꢀ(phenylthio
/
selenomethyl)ꢀ1Hꢀ1,2,3ꢀ
15 triazole (L1 / L2). The complexes and their ligands have been
characterized with multinuclear NMR spectroscopy and HRꢀMS.
The single crystal structures of 1−4 reveal geometry around Pd in
1 and 2 as distorted square planar. In case of 3 and 4 there is a
pseudo octahedral “pianoꢀstool” disposition of donor atoms
20 around Ru. The complexes 1 and 2 efficiently catalyze SMC (in
aqueous medium) and Sonogashira coupling reactions. The
catalyst loading of 0.1−0.01 mol% is optimum for SMC, while
for Sonogashira coupling loading of 0.1−2 mol% of Pd is
essential. The ruthenium(II) complexes 3 and 4 have been
25 explored as catalysts for transfer hydrogenation (TH) of
aldehydes and ketones in aqueous media using glycerol as a
hydrogen source. The optimum loading of 3 and 4 required for
TH is 0.1−0.4 mol%. The poisoning experiments for TH show
that catalytic process is nearly homogenous. The coupling
30 reactions are also inferred overwhelmingly homogeneous on the
basis of poisoning experiments. The nature of the chalcogen
appears to affect the catalytic efficiency of complexes 1−4. In
view of literature reports15 the effect of steric bulkiness of dipp
group present on ligands on catalytic efficiency, can not be rule
35 out. The results of DFT calculations are consistent with the
experimental results on activity of these complexes for SMC and
Sonogashira coupling i.e. 1 in which palladium is coordinated
with sulfur is more efficient than 2. The catalytic activity of Ru
complexes 3 and 4 for TH is also consistent with DFT
40 calculations.
converged.
Highꢀresolution
mass
spectral
(HRꢀMS)
measurements were made with a Bruker Micro TOFꢀQ II
machine using electron spray ionization (10 eV, 180 °C source
95 temperature and sodium formate as a calibrant) and dissolving the
sample in CH3CN. HRꢀMS was simulated using program
developed by Scientific Instrument Services.58 All DFT
calculations were carried out at the Supercomputing Facility for
Bioinformatics and Computational Biology, IIT Delhi, with the
100 GAUSSIANꢀ0359 programs. The geometries of complexes 1−4
have been optimized at the B3LYP60 level using an SDD basis set
for metal atoms and chalcogen and 6ꢀ31G* basis sets for C, N,
and H. Geometry optimizations have been carried out without any
symmetry restriction with Xꢀray coordinates of the molecule.
105 Harmonic force constants have been computed at the optimized
geometries to characterize the stationary points as minima. The
molecular orbital plots are created using the Chemcraft program
package (http://www. chemcraftprog.com).
Experimental
Diphenyldiselenide,
NaBH4,
propargyl
bromide,
2,6ꢀ
45 diisopropylaniline, phenyl acetylene and NH4PF6 procured from
SigmaꢀAldrich (USA) were used as received. Phenylboronic acid,
thiophenol, aryl halides, aldehyde and ketones were procured
locally. Bis(acetonitrile)dichloropalladium(II) was prepared by
refluxing palladium chloride in acetonitrile. The reported
50 methods were used to synthesize [{(η6ꢀC6H6)RuCl(ꢀꢀCl)}2],55a
propargyl phenyl sulfide/selenide.55b Solvents were dried or
distilled before use by standard procedures.55c The reported
methods were used to synthesize 2ꢀazidoꢀ1,3ꢀdiisopropylꢀbenzene
from 2,6ꢀdiisoropylaniline.56 The ligand precursors were purified
55 by column chromatography using silica gel (60−120 mesh) and nꢀ
hexane and its mixtures with chloroform/ethyl acetate in variable
proportions as eluent. All reactions were carried out in glassware
110 Syntheses of L1 and L2: A roundꢀbottom reaction flask was
charged with 2ꢀazidoꢀ1,3ꢀdiisopropylbenzene (0.203 g, 1.0 mmol)
30 mL of CH3CN and propargyl phenyl sulfide (0.148 g, 1.1
mmol)/propargyl phenyl selenide (0.195 g, 1.1 mmol). In two
separate test tubes, each of CuSO4·5H2O (0.249 g, 1.0 mmol) and
115 sodium ascorbate (80 mol%, 0.158 g) was dissolved in 3 mL of
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 |7

Dalton Transactions
Page 8 of 13
View Article Online
DOI: 10.1039/C6DT01406B
distilled water separately. Both solutions were mixed, and the
(C5), 23.7 (C4), 27.8 (C9), 123.8, 124.1, 126.2, 128.9, 129.3,
resulting dark brown mixture was quickly added to the reaction 60 130.5, 131.8, 132.1, 134.8, 145.2. IR (KBr; cm−1): 474 (w), 574
flask and the reaction mixture stirred for 24 h at 90° C under
nitrogen atmosphere. After 24 h same amount of CuSO4·5H2O
and sodium ascorbate was added again to the reaction mixture,
and it was stirred further for next 24 h at 90° C. Thereafter,
(w), 748 [m; νC−H (aromatic)], 807 [m; νC−H (aromatic)], 1062
(m), 1255 (m), 1469 [s; C−C (aromatic)], 1573 [m; N=N], 2360
(m), 2361 (w), 2869 [m; νC−H (isopropyl)], 2963 [s; νC−H
(aliphatic)], 3076 [m; νC−H (aromatic)]. HRꢀMS [M+H−2Cl]
ν
ν
5
solvent of the reaction mixture was reduced to minimum level. 65 (m/z) = 458.0874; Calcd. value for C21H26N3PdS = 458.0884
The mixture was poured into water (30 mL) and extracted with
CHCl3 (3 × 25 mL). Organic layers were combined together and
10 washed with water (30 mL), 20% ammonia solution (30 mL) and
brine (30 mL) successively. The organic phase was dried over
(error δ: 2.1 ppm).
Complex 2; Yellow solid, Yield: (0.50 g, 87%); m.p. 272 °C(d).
Anal. Found: C, 43.17; H, 4.15; N, 6.39 %. Calcd. for
1
[C21H25Cl2N3PdSe]: C, 43.81; H, 4.38; N, 7.30 %. H NMR (300
anhydrous Na2SO4 and its solvent evaporated under reduced 70 MHz, DMSOꢀd6, 25 °C, TMS); δ (ppm): 1.0 (s, 12H, −H3C(5)),
pressure on a rotary evaporator to give L1 and L2 as yellow
solid. Their further purification was done by column
15 chromatography on silica gel using hexaneꢀethyl acetate mixture
(95:5) as an eluent.
1.56−2.0 (m, 2H, >HC(4)), 4.36−4.90 (m, 2H, −H2C(9)−),
7.40−7.69 (m, 6H, ArH), 7.77−7.90 (m, 2H, ArH), 8.70 (s, 1H,
HC(7)). 13C{1H} NMR (75 MHz, DMSOꢀd6, 25 °C, TMS):
δ(ppm): 23.4 (C5), 23.7 (C4), 28.0 (C9), 124.0, 129.1, 129.2,
L1; Yellow solid, Yield: (0.287 g, 82%); m.p. 119 °C. Anal. 75 129.9, 130.2, 130.3, 131.9, 132.7, 145.0, 145.2. 77Se{1H} NMR
Found: C, 71.14; H, 6.89; N, 11.31 %. Calcd. for [C21H25N3S]: C,
71.75; H, 7.17; N, 11.95 %.1H NMR (300 MHz, CDCl3, 25 °C,
20 TMS); δ (ppm): 0.98−1.25 (m, 12H, −H3C(5)), 2.03−2.08 (m, 2H,
>HC(4)), 4.32 (s, 2H, −H2C(9)−), 7.14−7.44 (m, 9H, ArH).
(57 MHz, DMSOꢀd6, 25 °C, Me2Se): δ (ppm) 466.5. IR (KBr;
cm−1): 469 (w), 576 (w), 742 [m;
C−H (aromatic)], 869 [m; νC−H
(aromatic)], 1062 (m), 1254 (m), 1470 [s; C−C (aromatic)], 1566
[m; N=N], 2360 (m), 2353 (w), 2867 [m; C−H (isopropyl)], 2962
C−H (aliphatic)], 3073 [m; C−H (aromatic)].
ν
ν
ν
ν
ν
13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS): δ (ppm): 80 [s;
23.7−23.8 (C5), 28.0 (C9), 28.6 (C4), 123.5, 124.9, 126.4, 128.6,
129.9, 130.7, 132.9, 134.6, 144.4, 145.7. IR (KBr; cm−1): 480 (w),
ν
Syntheses of ruthenium complexes 3 and 4: To a solution of
0.2 mmol of L1 (0.07 g,) or L2 (0.065 g) made in CH3OH (5 mL)
was added a solution of [{(η6ꢀC6H6)RuCl(ꢀꢀCl)}2] (0.05 g, 0.1
25 557 (w), 713 [m;
ν
C−H (aromatic)], 1116 (m), 1382 (w), 1452 [m;
νC−C (aromatic)], 1637 [m; νN=N], 2358 (w), 2831 [m; νC−H
(isopropyl)], 2925 [s; νC−H (aliphatic)], 3081 [m; νC−H 85 mmol) made in CH3OH (5 mL), and the mixture was stirred for 8
(aromatic)]. HRꢀMS [M+Na] (m/z) = 374.1659; Calcd. value for
C21H25N3SNa = 374.1661 (error δ: 0.6 ppm).
h at room temperature. The resulting orange solution was filtered,
and the volume of the filtrate reduced up to ~1 mL with rotary
evaporator. Solid NH4PF6 (0.032 g, 0.2 mmol) was added to the
concentrate with stirring and the resulting orange microcrystalline
30 L2; Light yellow solid, Yield: (0.338 g, 85%); m.p. 110 °C. Anal.
Found: C, 63.24; H, 6.19; N, 10.53 %. Calcd. for [C21H25N3Se]:
1
C, 63.31; H, 6.32; N, 10.55 %. H NMR (300 MHz, CDCl3, 25 90 solid filtered, washed with 5 mL of ice cold CH3OH, and dried in
°C, TMS); δ (ppm): 1.05−1.11 (m, 12H, −H3C(5)), 2.05−2.14 (m,
2H, >HC(4)), 4.29 (s, 2H, −H2C(9)−), 7.23−7.51 (m, 9H, ArH).
35 13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS): δ (ppm): 20.4
(C4), 23.9−24.0 (C5), 28.2 (C9), 123.6, 124.7, 127.4, 129.0,
vacuo.
Complex 3; Yield: (0.561 g, 79%); m.p. 234 °C(d). Anal. Found:
C, 45.50; H, 4.34; N, 5.97 %. Calcd. for [C27H31N3ClRuS][PF6]:
C, 45.60; H, 4.39; N, 5.91 %.1H NMR (300 MHz, CD3CN, 25 °C,
129.3, 130.6, 133.1, 133.3, 145.3, 146.0. 77Se{1H} NMR (57 95 TMS); δ (ppm): 1.18−1.34 (m, 12H, −H3C(5)), 2.32−2.41 (m, 2H,
MHz, CDCl3, 25 °C, Me2Se): δ (ppm) 366.3. IR (KBr; cm−1): 466
(w), 692 (m), 740 [m; C−H (aromatic)], 1050 (s), 11179 (s), 1361
40 [w], 1470 [s; νC−C (aromatic)], 1575 [m; νN=N], 2334 (w), 2870
[m;
C−H (isopropyl)], 2967 [s; νC−H (aliphatic)], 3119 [m; νC−H
>HC(4)), 4.07−4.32 (m, 2H, −H2C(9)−), 7.46−7.72 (m, 8H, ArH),
8.18 (s, 1H, HC(7)). 13C{1H} NMR (75 MHz, CD3CN, 25 °C,
TMS): δ (ppm): 22.7−22.8−23.4−23.6 (C5), 28.6−28.8 (C4), 36.5
(C9), 87.51 (C14) 124.4−124.5, 126.6, 129.6, 130.3, 131.6,
ν
ν
(aromatic)]. HRꢀMS [M + H] (m/z) = 400.1299; Calcd. value for 100 132.2, 132.3, 134.9, 145.6−145.8, 147.2. IR (KBr; cm−1): 483
C21H26N3Se = 290.1032 (error δ : ꢀ2.9 ppm).
(w), 558 (w), 757 [m;
ν
C−H (aromatic)], 842 [s; νP−F], 1094 (w),
1181 (w), 1471 [m; νC−C (aromatic)], 1574 [b;
νc=c], 1624 [w;
45 Synthesis of Pdꢀcomplexes 1 and 2: To a solution of 0.2 mmol
of L1 (0.070 g) or L2 (0.079 g) in CH3CN (5 mL) was added a
solution of [(CH3CN)2PdCl2] (0.052 g, 0.2 mmol) made in 5 mL 105 [M−PF6] (m/z) = 566.0970; Calcd. value for C27H31ClN3RuS =
ν
N=N], 2362 (w), 2873 [m; νC−H (isopropyl)], 2949 [s; νC−H
(aliphatic)], 3093 [m;
νC−H (aromatic)]. HRꢀMS (CH3CN; m/z):
of CH3CN. The reaction mixture was stirred for 5 h at room
temperature. The solvent was removed from the pale yellow
50 coloured solution under reduced pressure and the residue was
washed with diethyl ether (5 mL) and dried in vacuo.
566.0963 (error δ: ꢀ0.3 ppm).
Complex 4; Yield: (0.614 g, 81%); m.p. 230 °C(d). Anal. Found:
C, 42.80; H, 4.14; N, 5.47 %. Calcd. for [C27H31N3ClRuSe][PF6]:
C, 42.78; H, 4.12; N, 5.54 %.1H NMR (300 MHz, CD3CN, 25 °C,
Complex 1; Yellow solid, Yield: (0.485 g, 92%); m.p. 278 °C(d). 110 TMS); δ (ppm): 1.33−1.63 (m, 12H, −H3C(5)), 2.21−2.34 (m, 2H,
Anal. Found: C, 47.70; H, 4.69; N, 7.87 %. Calcd. for
[C21H25Cl2N3PdS]: C, 47.69; H, 4.76; N, 7.95 %. H NMR (300
55 MHz, DMSOꢀd6, 25 °C, TMS); δ (ppm): 0.98 (s, 12H, −H3C(5)),
>HC(4)), 3.91−4.15 (m, 2H, −H2C(9)−), 7.44−7.70 (m, 8H,
ArH,), 8.12 (s, 1H, −HC(7)). 13C{1H} NMR (75 MHz, CD3CN,
25 °C, TMS): δ (ppm): 22.7−22.8−23.7−23.72 (C5), 28.6 (C4),
28.8 (C9), 86.9 (C14) 124.4−124.5, 127.0, 130.0, 130.7, 130.9,
1
1.89 (s, 2H, >HC(4)), 4.37−4.78 (m, 2H, −H2C(9)−), 7.35−7.53
(m, 6H, ArH), 7.84−8.13 (m, 2H, ArH), 8.78 (s, 1H, HC(7)). 115 131.1, 132.1, 132.2, 145.6−145.8, 148.0. 77Se{1H} NMR (57
13C{1H} NMR (75 MHz, DMSOꢀd6, 25 °C, TMS): δ (ppm): 23.4
MHz, CD3CN, 25 °C, Me2Se): δ (ppm) 452.0. IR (KBr; cm−1):
8
|Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 9 of 13
Dalton Transactions
View Article Online
DOI: 10.1039/C6DT01406B
471 (w), 557 (w), 742 [m;
(m), 1241 (m), 1470 [m;
(w), 2874 [m; C−H (isopropyl)], 2968 [s;
[m; νC−H (aromatic)]. HRꢀMS (CH3CN; m/z): [M−PF6] (m/z) =
614.0410; Calcd. value for C27H31ClN3RuSe = 614.0417 (error δ:
1.0 ppm).
ν
C−H (aromatic)], 843 [s;
C−C (aromatic)], 1627 [w;
C−H (aliphatic)], 3099
ν
P−F], 1091
4ꢀMethoxybiphenyl: White solid. 1H NMR (300 MHz, CDCl3, 25
ν
ν
N=N], 2361 60 °C, TMS); δ (ppm): 3.81 (s, 3H), 6.96 (d, 2H, J = 8.4 Hz),
ν
ν
7.28−7.30 (m, 1H), 7.39 (t, 2H, J = 7.2 Hz), 7.50−7.55 (m, 4H).
13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS); δ (ppm): 55.2,
114.1, 126.6, 126.7, 128.1, 128.7, 133.7, 140.7, 159.1
5
65 General procedure for Sonogashira coupling reaction
catalyzed with 1 and 2
Procedure for SuzukiꢀMiyaura C−C coupling reaction
catalyzed with 1 and 2
Aryl bromide (1.0 mmol), phenylboronic acid (0.147 g, 1.2
The round bottom flask charged with aryl bromide (1.0 mmol),
phenyl acetylene (0.112 g, 1.1 mmol) and K2CO3 (0.276 g, 2.0
70 mmol) and 3 mL of DMF was degassed with N2 to protect
reaction mixture from moisture. Thereafter palladium complex 1
or 2 (0.1–2 mol%) and CuI (2–4 mol%) were added and the
mixture was heated at 120° C for 12 h under nitrogen atmosphere.
The progress of reaction was monitored by 1H NMR
75 spectroscopy to estimate conversions. When maximum
conversion of ArBr into coupled product occurred, the reaction
mixture was cooled to room temperature and extracted with
ethylacetate (2×15 mL). The extract was washed with brine (2×10
mL) and aqueous ammonia (10 mL). After drying over anhydrous
80 Na2SO4 its solvent was evaporated off with rotary evaporator.
The resulting residue was purified by column chromatography
using silica gel (60−120 mesh) and nꢀhexane and its mixtures
with chloroform/ethyl acetate in variable proportions as eluent.
The yield was calculated. The authentication by matching 1H and
85 13C{1H} NMR with literature data was carried out for each
coupled product.22a,d
10 mmol), K2CO3 (0.276 g, 2.0 mmol), water (3 mL) and a
palladium complex 1 or 2 (0.01ꢀ1 mol%) were charged in a round
bottom flask. It was placed on an oil bath maintained at 100 °C
under aerobic condition and its content stirred. The progress of
reaction was monitored by 1H NMR spectroscopy to estimate
15 conversions. When maximum conversion of ArBr into coupled
product occurred, the reaction mixture was cooled to room
temperature. It was mixed with water (20 mL) and extracted with
diethyl ether (3×10 mL). For benzoic acid derivatives the reaction
mixture was mixed with 20 mL of water acidified with 20% HCl
20 and extracted with ethyl acetate (3×10 mL). Organic phase was
dried over anhydrous Na2SO4. Its solvent was removed on rotary
evaporator to isolate coupled product and its yield was
determined. Further purification (if required) was done by
column chromatography on silica gel (60−120 mesh) using ethyl
25 acetateꢀhexane mixture as an eluent, before yield calculation. The
coupled products were authenticated by matching their NMR data
with the literature reports.23b,c
1
4ꢀ(Phenylethynyl)benzaldehyde: Light yellow solid. 1H NMR
(300 MHz, CDCl3, 25 °C, TMS); δ (ppm): 10.03 (s, 1H), 7.87 (d,
2H, J = 8.2 Hz), 7.67 (d, 2H, J = 8.2 Hz), 7.57ꢀ7.53 (m, 2H),
90 7.39ꢀ7.36 (m, 3H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C,
TMS); δ (ppm): 191.8, 135.8, 132.5, 132.2, 130.02, 130.0, 129.3,
128.9, 122.9, 93.8, 88.9
4−Phenylbenzaldehyde: Light yellow solid. H NMR (300 MHz,
CDCl3, 25 °C, TMS); δ (ppm): 7.39−7.50 (m, 3H), 7.62−7.65 (m,
30 2H), 7.75 (d, J = 8.4 Hz, 2H), 7.95 (d, J = 8.4 Hz, 2H), 10.05 (s,
1H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS); δ (ppm): δ
127.3, 127.6, 128.4, 128.9, 130.2, 135.1, 139.7, 147.1, 191.9
4ꢀPhenylbenzonitrile: Pale yellow solid. 1H NMR (300 MHz,
CDCl3, 25 °C, TMS); δ (ppm): δ 7.34−7.44 (m, 3H), 7.49−7.52
35 (m, 2H), 7.54−7.60 (m, 4H). 13C{1H} NMR (75 MHz, CDCl3, 25
°C, TMS); δ (ppm): 110.3, 118.5, 126.7, 127.2, 128.3, 128.7,
132.1, 138.5, 145.0
1
1ꢀNitroꢀ4ꢀ(phenylethynyl)benzene: Lightꢀyellow solid. H NMR
(300 MHz, CDCl3, 25 °C, TMS); δ (ppm): 7.36− 7.39 (m, 3H),
95 7.54−7.56 (m, 2H), 7.64−7.66 (m, 2H), 8.22 (d, 2H, J = 8.7 Hz);
13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS); δ (ppm): 86.5,
93.7, 121.1, 122.6, 127.5, 128.3, 129.3, 130.8, 131.2, 145.9
4ꢀ(Phenylethynyl)benzonitrile: Yellow solid. 1H NMR (300 MHz,
CDCl3, 25 °C, TMS); δ (ppm): 7.36−7.40 (m, 3H), 7.53−7.56 (m,
100 2H), 7.59−7.64 (m, 4H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C,
TMS); δ (ppm): 86.7, 92.7, 110.4, 117.5, 121.1, 127.2, 127.4,
128.1, 130.7, 131.03, 131.05
1
4ꢀNitrobiphenyl: Pale yellow solid. H NMR (300 MHz, CDCl3,
25 °C, TMS); δ (ppm): 7.40−7.51 (m, 3H), 7.61 (d, J = 8.4 Hz,
40 2H), 7.71 (d, 2H, J = 9.0 Hz), 8.26 (d, 2H, J = 9.0 Hz); 13C{1H}
NMR (75 MHz, CDCl3, 25 °C, TMS); δ (ppm): 123.1, 127.0,
127.2, 127.6, 128.8, 129.0, 138.6, 146.9, 147.5
1
4−Acetylbiphenyl: White solid. H NMR (300 MHz, CDCl3, 25
1ꢀMethoxyꢀ4ꢀ(phenylethynyl)benzene: Lightꢀyellow solid. 1H
NMR (300 MHz, CDCl3, 25 °C, TMS); δ (ppm): 3.82 (s, 3H),
105 6.85−6.89 (m, 2H), 7.29−7.35 (m, 3H), 7.45−7.52 (m, 4H);
13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS); δ (ppm): 54.2,
87.0, 88.3, 112.9, 114.3, 122.5, 126.9, 127.3, 130.4, 132.0, 158.6
°C, TMS); δ (ppm): 2.61 (s, 3H), 7.38−7.48 (m, 3H), 7.60−7.68
45 (m, 4H), 8.01 (d, 2H, J = 8.4 Hz). 13C{1H} NMR (75 MHz,
CDCl3, 25 °C, TMS); δ (ppm): 26.5, 127.1, 127.2, 128.1, 128.8,
128.8, 135.7, 139.7, 145.6, 197.6
1
4ꢀCarboxylicbiphenyl: White solid. H NMR (300 MHz, DMSO,
1
25 °C); δ (ppm): 7.39−7.52 (m, 3H), 7.72 (d, J = 6.9 Hz, 2H),
50 7.79 (d, J = 8.4 Hz, 2H), 8.02 (d, J = 8.4 Hz, 2H). 13C{1H} NMR
(75 MHz, DMSO, 25 °C, TMS); δ (ppm): δ 126.8, 127.0, 128.3,
129.1, 129.6, 130.0, 139.0, 144.3, 167.2
1ꢀMethylꢀ4ꢀ(phenylethynyl)benzene: White solid. H NMR (300
MHz, CDCl3, 25 °C, TMS); δ (ppm): 2.35 (s, 3H), 7.14 (d, J = 7.8
110 Hz, 2H), 7.30−7.35 (m, 3H), 7.42 (d, 2H, J = 7.2 Hz), 7.50−7.53
(m, 2H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS); δ (ppm):
21.2, 88.4, 89.3, 119.9, 123.2, 127.8, 128.0, 128.8, 131.2, 131.3,
138.1
1
4ꢀMethylbiphenyl: Colourless solid. H NMR (300 MHz, CDCl3,
25 °C, TMS); δ (ppm): 2.37 (s, 3H), 7.22 (d, 2H, J = 7.8 Hz),
55 7.27−7.32 (m, 1H), 7.37−7.42 (m, 2H), 7.48 (d, 2H, J = 8.1 Hz),
7.55−7.58 (m, 2H). 13C{1H} NMR (75 MHz, CDCl3, 25 °C,
TMS); δ (ppm): 21.0, 126.9, 126.9, 128.6, 129.4, 136.9, 138.3,
141.1
115 Procedure for catalytic transfer hydrogenation (TH)
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 |9

Dalton Transactions
Page 10 of 13
View Article Online
DOI: 10.1039/C6DT01406B
Bratsos, D. Urankar, E. Zangrando, P. GenovaꢀKalou, J. Košmrlj, E.
Alessio and I. Turel, Dalton Trans., 2011, 40, 5188–5199.
I. Stengel, A. Mishra, N. Pootrakulchote, S.ꢀJ. Moon, S. M.
Zakeeruddin, M. Grätzel and P. Bäuerle, J. Mater. Chem., 2011, 21,
3726–3734.
In a round bottom flask an aldehyde (or a ketone) (1.0 mmol),
KOH (0.056 g, 1.0 mmol), glycerol (0.184 g, 2.0 mmol) and a
complex 3/4 (0.1–0.4 mol %) were mixed in water (3 mL) and the
mixture heated at 110 °C for optimum time (Table 5). The
conversion into corresponding alcohol was monitored by 1H
NMR. After maximum conversion, the resulting product was
extracted with diethyl ether (2×5 mL) from the reaction mixture.
The organic phases were combined, dried over Na2SO4 and its
solvent was evaporated off with a rotary evaporator. The resulting
60
65
4
5
5
6
F. Kong, C. Zhou, J. Wang, Z. Yu and R. Wang, Chem Plus Chem,
2013, 78, 536–545.
(a) E. M. Schuster, M. Botoshansky and M. Gandelman, Angew.
Chem. Int. Ed., 2008, 47, 4555–4558; (b) V. D. Bock, H. Hiemstra
and J. H. van Maarseveen, Eur. J. Org. Chem., 2006, 51–68.
(a) S. Badèche, J.ꢀC. Daran, J. Ruiz and D. Astruc, Inorg. Chem.,
2008, 47, 4903–4908; (b) R. J. Detz, S. A. Heras, R. de Gelder, P. W.
N. M. van Leeuwen, H. Hiemstra, J. N. H. Reek and J. H. van
Maarseveen, Org. Lett., 2006, 8, 3227–3230; (c) S. Fukuzawa, H.
Oki, M. Hosaka, J. Sugasawa and S. Kikuchi, Org. Lett., 2007, 9,
5557–5560; (d) D. D. Díaz, K. Rajagopal, E. Strable, J. Schneider
and M. G. Finn, J. Am. Chem. Soc., 2006, 128, 6056–6057; (e) H.
Oki, I. Oura, T. Nakamura, K. Ogata, S.ꢀichi Fukuzawa,
Tetrahedron: Asymmetry, 2009, 20, 2185–2191.
(a) Y. Li, J. C. Huffman and A. H. Flood, Chem. Commun., 2007,
2692–2694. (b) M. Obata, A. Kitamura, A. Mori, C. Kameyama, J.
A. Czaplewska, R. Tanaka, I. Kinoshita, T. Kusumoto, H.
Hashimoto, M. Harada, Y. Mikata, T. Funabiki and S. Yano, Dalton
Trans., 2008, 3292–3300; (c) J. D. Crowley and P. H. Bandeen,
Dalton Trans., 2009, 39, 612–623. (d) T. L. Mindt, C. Müller, M.
Melis, M. de Jong and R. Schibli, Bioconjugate Chem., 2008, 19,
1689–1695; (e) B. M. J. M. Suijkerbuijk, B. N. H. Aerts, H. P.
Dijkstra, M. Lutz, A. L. Spek, G. van Koten and R. J. M. K. Gebbink,
DaltonTrans., 2007, 1273–1276; (f) H. Struthers, B. Spingler, T. L.
Mindt and R. Schibli, Chem. Eur. J., 2008, 14, 6173–6183; (g) S.ꢀQ.
Bai, L. Jiang, A. L. Tan, S. C. Yeo, D. J. Younga and T. S. A. Hor,
Inorg. Chem. Front., 2015, 2, 1011–1018; (h) S.ꢀQ. Bai, L. Jiang, J.ꢀ
L. Zuoc and T. S. A. Hor, Dalton Trans., 2013, 42, 11319–11326; (i)
D. Schweinfurth, R. Pattacini, S. Strobela and B. Sarkar, Dalton
Trans., 2009, 9291–9297; (j) R. Saravanakumar, V. Ramkumar and
S. Sankararaman, Organometallics, 2011, 30, 1689–1694; (k) S.
Hohloch, L. Hettmanczyk and B. Sarkar, Eur. J. Inorg. Chem., 2014,
3164–3171.
7
70
10 product was isolated and purified by column chromatography
using silica gel (60−120 mesh) and nꢀhexane and its mixtures
with chloroform/ethyl acetate in variable proportions as eluent.
1
The yield was calculated. The products were analyzed with H
and 13C{1H } NMR spectra to authenticate them.35
75
1
15 Phenylmethanol: Colourless liquid. H NMR (300 MHz, CDCl3,
25 °C, TMS); δ (ppm): 2.30 (br s, 1H, ꢀOH), 4.62 (s, 2H),
7.23−7.32 (m, 5H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C,
TMS); δ (ppm): 65.2, 127.0, 127.6, 128.5, 140.9
8
80
1
1ꢀPhenylethanol: Colourless liquid. H NMR (300 MHz, CDCl3,
20 25 °C, TMS); δ (ppm): 1.51 (d, 3H, J = 6.3), 4.87−4.93 (m, 1H),
7.28−7.39 (m, 5H); 13C{1H} (75 MHz, CDCl3) δ 25.1, 70.3,
124.4, 127.4, 128.4, 148.8
85
1
Diphenylmethanol: White solid. H NMR (300 MHz, CDCl3, 25
°C, TMS); δ (ppm): 2.29 (d, 1H), 5.81 (d, 1H), 7.23−7.60 (m,
25 10H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C, TMS); δ (ppm):
76.2, 126.5, 127.5, 128.5, 143.8
90
(4ꢀChlorophenyl)methanol: White solid. 1H NMR (300 MHz,
CDCl3, 25 °C, TMS); δ (ppm): 1.78(b, 1H, ꢀOH), 4.68 (d, 2H, J =
4.8), 7.28−7.36 (m, 4H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C,
30 TMS); δ (ppm): δ 64.5, 128.2, 128.6, 133.4, 139.2
95
1
Furanꢀ2ꢀylmethanol: Colorless oil. H NMR (300 MHz, CDCl3,
25 °C, TMS); δ (ppm): 2.39 (b, 1H, ꢀOH), 4.57 (s, 2H), 6.26−6.34
(m, 2H), 7.38 (s, 1H); 13C{1H} NMR (75 MHz, CDCl3, 25 °C,
TMS); δ (ppm): 57.3, 107.7, 110.3, 142.5, 154.0.
9
(a) D. Huang, P. Zhao and D. Astruc, Coord.Chem.Rev.,2014, 272,
145–165; (b) T. Terashima, S. Inomata, K. Ogata and S.ꢀi. Fukuzawa,
Eur. J. Inorg. Chem. 2012, 1387–1393; (c) T. Mitsui, M. Sugihara,
Y. Tokoro and S.ꢀi. Fukuzawa, Tetrahedron, 2015, 71, 1509ꢀ1514;
(d) T. Karthikeyan and S. Sankararaman, Tetrahedron Lett., 2009,
50, 5834–5837; (e) S. Hohloch, W. Frey, C.ꢀY. Suc and B. Sarkar,
Dalton Trans., 2013, 42, 11355–11358; (f) S. Inomata, H. Hiroki, T.
Terashima, K. Ogata and S.ꢀichi Fukuzawa, Tetrahedron, 2011, 67,
7263ꢀ7267; (g) D. C.ꢀGonzalez, A. Gniewek, Michal Szulmanowicz,
H. M.ꢀBunz, A. M. Trzeciak and Martin Albrecht, Chem. Eur. J.
2012, 18, 6055–6062; (h) R. Maity, A. Verma, M. van der Meer, S.
Hohloch and B. Sarkar, Eur. J. Inorg. Chem., 2016, 111–117.
100
105
110
115
120
125
35 Acknowledgements
Council of Scientific and Industrial Research, and Department of
Atomic Energy (BRNS), India supported the work through
projects. SK and FS thank to UGC (India) for fellowship.
Notes and References
40 aDepartment of Chemistry, Indian Institute of Technology Delhi, New
10 (a) K. F. Donnelly, A. Petronilho and M. Albrecht, Chem. Commun.,
2013, 49, 1145ꢀ1159; (b) D. Liu, W. Gao, Q. Dai and X. Zhang, Org.
Lett.,7, 2005, 4907ꢀ4910.
11 (a) F. Saleem, G. K. Rao, A. Kumar, G. Mukherjee and A. K. Singh,
Organometallics, 2013, 32, 3595−3603; (b) F. Saleem, G. K. Rao, S.
Kumar, M. P. Singh and A. K. Singh, Dalton Trans., 2015, 44,
19141–19152; (c) L. Bernet, R. Lalrempuia, W. Ghattas, H. Muellerꢀ
Bunz, L. Vigara, A. Llobet and M. Albrecht, Chem. Commun., 2011,
47, 8058–8060; (d) F. Saleem, G. K. Rao, A. Kumar, G. Mukherjee,
and A. K. Singh, Organometallics, 2014, 33, 2341−2351.
12 F. Saleem, G. K. Rao, A. Kumar, S. Kumar, M. P. Singh and A. K.
Singh, RSC Adv., 2014, 4, 56102–56111.
13 G. GuisadoꢀBarrios, J. Bouffard, B. Donnadieu and G. Bertrand,
Angew. Chem. Int. Ed., 2010, 49, 4759–4762.
14 (a) D. J. Tempel, L. K. Johnson, R. L. Huff, P. S. White and M.
Brookhart, J. Am. Chem. Soc., 2000, 122, 6686ꢀ6700; (b) B.ꢀT. Luo,
H. Liu, Z.ꢀJ. Lin, J. Jiang, D.ꢀS. Shen, R.ꢀZ. Liu, Z. Ke and F.ꢀS. Liu,
Organometallics, 2015, 34, 4881−4894;
15 (a) E. L. Kolychev, A. F. Asachenko, P. B. Dzhevakov, A. A. Bush,
V. V. Shuntikov, V. N. Khrustalevc and M. S. Nechaev, Dalton
Delhi–110016,
India.
E–mail:
aksingh@chemistry.iitd.ac.in,
ajai57@hotmail.com; FAX: +91 11 26581102; Tel: +91 11 26591379
† Electronic Supplementary Information (ESI) available: Spectral data of
L1 and L2 and 1–4; single crystal data of complexes 1–4 (CCDC
45 1472950ꢀ1472953), See DOI: 10.1039/b000000x/
1
(a) J. E. Moses and A. D. Moorhouse, Chem. Soc.Rev., 2007, 36,
1249–1262; (b) D. Fournier, R. Hoogenboom and U. S. Schubert,
Chem. Soc. Rev., 2007, 36, 1369–1380; (c) J.ꢀF. Lutz, Angew. Chem.
Int. Ed., 2007, 46, 1018–1025.
50
55
2
3
(a) C. J. Hawker, V. V. Fokin, M. G. Finn and K. B. Sharpless, Aust.
J. Chem., 2007, 60, 381–383; (b) H. C. Kolb, K. B. Sharpless, Drug
Discovery, Today, 2003, 8, 1128−1137.
(a) K. D. Bodine, D. Y. Gin, M. S. Gin, J. Am. Chem. Soc., 2004,
126, 1638−1639; (b) G. Lu, S. Lam and K. Burgess, Chem.
Commun., 2006, 1652–1654; (c) J.–F.Lutz, H. G. Börner and K.
Weichenhan, Macromolecules, 2006, 39, 6376ꢀ6383; (d) M. Whiting,
J. C. Tripp, Y.ꢀC. Lin, W. Lindstrom, A. J. Olson, J. H. Elder, K. B.
Sharpless and V. V. Fokin, J. Med. Chem. 2006, 49, 7697ꢀ7710; (e) I.
10|Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 11 of 13
Dalton Transactions
View Article Online
DOI: 10.1039/C6DT01406B
Trans., 2013, 42, 6859ꢀ6866; (b) C. Fleckenstein, S. Roy, S.
Leuthaußer and H. Plenio, Chem. Commun., 2007, 2870–2872.
Ohkuma, Pure Appl. Chem., 2001, 73, 227ꢀ232; (d) R. Noyori,
Angew. Chem. Int. Ed., 2002, 41, 2008–2022.
16 (a) A. F. Littke, C. Dai and G. C. Fu, J. Am. Chem. Soc., 2000, 122,
4020–4028; (b) J. P. Wolfe and S. L. Buchwald, Angew. Chem. Int.
Ed., 1999, 38, 2413–2415; (c) A. F. Littke and G.C. Fu, Angew.
Chem. Int. Ed., 2002, 41, 4176–4211; (d) X. Bei, H. W. Turner, W.
H. Weinberg and A. S. Guram, J. Org. Chem.,1999, 64, 6797–6803.
17 R. B. Bedford and C. S. J. Cazin, Chem. Commun., 2001, 1540–1541.
18 (a) C. Zhang and M. L. Trudell, Tetrahedron Lett., 2000, 41, 595–
598; (b) Z. Xiong, N. Wang, M. Dai, A. Li, J. Chen and Z. Yang,Org.
Lett.,2004, 6, 3337ꢀ3340; (c) E. Sindhuja, R. Ramesh and Y. Liub,
Dalton Trans., 2012, 41, 5351–5361; (d) D. Pandiarajan, R. Ramesh,
Y. Liu and R. Suresh, Inorg. Chem. Commun., 2013, 33, 33–37; (e)
M. S. Subhas, S. S. Racharlawar, B. Sridhar, P. K. Kennady, P. R.
Likhar, M. L. Kantama and S. K. Bhargavad, Org. Biomol. Chem.,
2010, 8, 3001–3006.
19 (a) Y. Ma, C. Song, W. Jiang, Q. Wu, Y. Wang, X. Liu and M. B.
Andrus, Org. Lett., 2003, 5, 3317–3319, (b) D. Méry, K. Heuzé and
D. Astruc, Chem. Commun., 2003, 1934–1935.
20 20 (a) R. Chinchilla and C. Nájera, Chem. Rev., 2007, 107, 874–922; (b)
B. de CarnéꢀCarnavalet, A. Archambeau, C. Meyer, J. Cossy, B.
Folléas, J.ꢀL. Brayer and J.ꢀP. Demoute, Org. Lett., 2011, 13, 956–
959.
30 (a) S. Günnaz, N. Özdemir, S. Dayan, O. Dayan and B. Çetinkaya,
Organometallics, 2011, 30, 4165–4173; (b) H. Türkmen, Đ. Kani and
B. Çetinkaya, Eur. J. Inorg. Chem., 2012, 4494–4499; (c) O. Dayan,
N. Özdemir, Z. ꢁerbetci, M. Dinçer, B. Çetinkaya and O.
Büyükgüngör, Inorg. Chim. Acta, 2012, 392, 246–253.
31 (a) N. Gürbüz, S. Yaꢂar, E. Ö. Özcan, Đ. Özdemir and B. Çetinkaya,
Eur. J. Inorg. Chem., 2010, 3051–3056; (b) A. Bolje, S. Hohloch, M.
van der Meer, J. Košmrlj and B. Sarkar, Chem. Eur. J., 2015, 21,
6756–6764; (c) M. DelgadoꢀRebollo, D. CansecoꢀGonzalez, M.
Hollering, H. MuellerꢀBunz and M. Albrecht, Dalton Trans., 2014,
43, 4462–4473.
32 (a) I. Ödemir, S. Yaꢂar and B. Çetinkaya, Transition Met Chem.,
2014, 30, 831–835; (b) A. Kanchanadevi, R. Ramesh and D. Semeril,
J. Organomet. Chem., 2016, 808, 68–77; (c) D. Pandiarajan and R.
Ramesh, J. Organomet. Chem., 2013, 723, 26–35; (d) D. Pandiarajan
and R. Ramesh, Inorg. Chem. Commun., 2011, 14, 686–689.
33 (a) O. Prakash, H. Joshi, K. N. Sharma, P. L. Gupta and A. K. Singh,
Organometallics, 2014, 33, 3804−3812; (b) A. K. Sharma, H. Joshi,
K. N. Sharma, P. L. Gupta, and A. K. Singh, Organometallics, 2014,
33, 3629−3639; (c) O. Prakash, K. N. Sharma, H. Joshi, P. L. Gupta
and A. K. Singh, Dalton Trans., 2013, 42, 8736–8747.
34 (a) T. P. Anastas, J. Warner, Green Chemistry: Theory and Practice;
Oxford University Press: Oxford, U.K., 1998; (b) M. Pagliaro, M.
Rossi, The Future of Glycerol; 2nd ed.; RSC Publishing: Cambridge,
U.K., 2010;(c) A. E. DíazꢀÁlvarez, J. Francos, B. LastraꢀBarreira, P.
Crochet and V. Cadierno, Chem. Commun., 2011, 47, 6208–6227; (d)
A. Wolfson, C. Dlugy and Y. Shotland, Environ. Chem. Lett., 2007,
5, 67ꢀ71; (e) R. A. Sheldon, Chem. Commun., 2008, 3352–3365; (b)
P. Gallezot, Green Chem., 2007, 9, 295ꢀ302.
5
10
15
75
80
85
90
95
21 (a) H. Hu, F. Yang and Y. Wu, J. Org. Chem., 2013, 78, 10506–
25
30
35
40
10511; (b) H. V. Huynh and C.ꢀS. Lee, Dalton Trans., 2013, 42,
6803–6809; (c) D. A. Alonso, C. Nájera and M. C. Pacheco,
Tetrahedron Lett., 2002, 43, 9365–9368; (d) H. Kima and P. H. Lee,
Adv. Synth. Catal., 2009, 351, 2827–2832.
22 (a) A. Scharf, I. Goldberg and A. Vigalok, J. Am. Chem. Soc., 2013,
135, 967–970; (b) M. Gazvoda, M. Virant, A. Pevec, D. Urankar, A. 100
Bolje, M. Kočevar and J. Košmrlj, Chem. Commun., 2016, 52, 1571–
1574.
35 O. Prakash, K. N. Sharma, H. Joshi, P. L. Gupta and A. K. Singh,
Organometallics, 2014, 33, 2535–2543.
36 F. Saleem, G. K. Rao, P. Singh and A. K. Singh, Organometallics,
2013, 32, 387–395.
37 A. Kumar, M. Agarwal and A. K. Singh, J. Org. Chem., 2008, 693,
3533–3545.
38 E. M. Schuster, M. Botoshansky and M. Gandelman,
Organometallics, 2009, 28, 7001–7005.
23 (a) Peter G. Gildner and Thomas J. Colacot, Organometallics, 2015,
34, 5497−5508; (b) G. M. Scheuermann, L. Rumi, P. Steurer, W.
Bannwarth and R. Mulhaupt, J. Am. Chem. Soc., 2009, 131, 8262– 105
8270; (c) G. K. Rao, A. Kumar, J. Ahmedz and A. K. Singh, Chem.
Commun., 2010, 46, 5954–5956; (d) S. Kumar, G. K. Rao, A. Kumar,
M. P. Singh and A. K. Singh, Dalton Trans., 2013, 42, 16939–16948.
24 (a) R. Ciriminna, V. Pandarus, G. Gingras, F. Béland, P. Demma
Carà and M. Pagliaro, ACS Sustainable Chem. Eng., 2013, 1, 57–61; 110 39 P. Singh, M. Singh and A. K. Singh, J. Org. Chem., 2009, 694, 3872–
(b) Henri Doucet and JeanꢀCyrille Hierso, Angew. Chem. Int. Ed.,
2007, 46, 834–871; (c) K. R. Reddy, N. S. Kumar, P. S. Reddy, B.
Sreedhar and M. L. Kantam, J. Mol. Catal. A: Chem., 2006, 252, 12–
16.
3880.
40 P. Singh and A. K. Singh, Organometallics, 2010, 29, 6433–6442.
41 (a) H. D. Velazquez and F. Verpoort, Chem. Soc. Rev., 2012, 41,
7032ꢀ7060; (b) M. Charbonneau, G. Addoumieh, P. Oguadinma and
A. R. Schmitzer, Organometallics, 2014, 33, 6544−6549; (c) M.
Mondal and U. Bora, Green Chem., 2012, 14, 1873ꢀ1876.
42 (a) T. Tu, X. Feng, Z. Wang and X. Liu, Dalton Trans., 2010, 39,
10598ꢀ10600; (b) B. Karimi and P. F. Akhavan, Chem. Commun.,
2009, 3750ꢀ3752; (c) Y. Zhang, M.ꢀT. Feng and J.ꢀM. Lu, Org.
Biomol. Chem., 2013, 11, 2266ꢀ2272.
43 J. A. Widegren and R. G. Finke, J. Mol. Catal. A: Chem., 2003, 198,
317–341.
44 I. Nieto, M. S. Livings, J. B. Sacci, L. E. Reuther, M. Zeller and E. T.
Papish, Organometallics, 2011, 30, 6339–6342.
45 25 (a) S. Urgaonkar and J. G. Verkade, J. Org. Chem., 2004, 69, 5752– 115
5755; (b) B. M. Choudary, S. Madhi, N. S. Chowdari, M. L. Kantam
and B. Sreedhar, J. Am. Chem. Soc., 2002, 124, 14127–14136.
26 (a) R. C. Larock, Organic Transformations; VCH: New York, 1989l
p 411; (b) G. W. Kabalka, R. S. Verma, In Comprehensive Organic
Synthesis; B. M. Trost, Ed.; Pergamon Press: Oxford, U.K., 1991; 120
Vol. 8, p 363.
27 (a) N. Uematsu, A. Fujii, S. Hashiguchi, T. Ikariya, R. Noyori, J. Am.
Chem. Soc., 1996, 118, 4916–4917; (b) M. J. Palmer, M. Wills,
Tetrahedron: Asymmetry, 1999, 10, 2045−2061.
50
55 28 (a) T. Ohkuma, H. Ooka, T. Ikariya and R. Noyori, J. Am. Chem. 125 45 C. Aliende, M. PérezꢀManrique, F. A. Jalón, B. R. Manzano, A. M.
Soc. 1995, 117, 10417ꢀ10418; (b) R. Noyori and T. Ohkuma, Angew.
Chem. Int. Ed., 2001, 40, 40ꢀ73. (c) T. Ohkuma,H. Doucet, T. Pham,
K. Mikami, T. Korenaga, M. Terada and R. Noyori, J. Am. Chem.
Soc. 1998, 120, 1086ꢀ1087; (d) T. Ohkuma, M. Koizumi, H. Doucet,
T. Pham, M. Kozawa, K. Murata, E. Katayama, T. Yokozawa, T. 130
Ikariya and R. Noyori, J. Am. Chem. Soc. 1998, 120, 13529ꢀ13530;
(e) S. Naskar and M. Bhattacharjee, J. Organomet. Chem., 2005, 690,
5006–5010; (f) A. Kanchanadevi, R. Ramesh and N. Bhuvanesh, J.
Organomet. Chem., 2015, 788, 49–57; (g) S. S. Bhosale and K. S.
Singh, Synth. Commun., 2015, 45, 1411–1420.
Rodrıguez and G. Espino, Organometallics, 2012, 31, 6106–6123.
46 N. Gürbüz, E. Ö. Özcan, Đ. Özdemir, B. Çetinkaya, O. ꢁahin and O.
Büyükgüngör, Dalton Trans., 2012, 41, 2330–2339.
47 (a) D. J. Darensbourg, F. Joo, M. Kannisto, A. Katho, J. H.
Reibenspies and D. J. Daigle, Inorg. Chem., 1994, 33, 200–208; (b)
D. J. Darensbourg, F. Joo, M. Kannisto, A. Katho and J. H.
Reibenspies, Organometallics, 1992, 11, 1990–1993.
48 (a) F. Joó and A. Bényei, J. Org. Chem., 1989, 363, C19–C21; (b) A.
Bényei and F. Joó, J. Mol. Catal., 1990, 58, 151–163.
́
60
65
70
135 49 (a) E. Farnetti, J. Kašpar and C. Crotti, Green Chem., 2009, 11, 704–
709; (b) A. E. DíazꢀÁlvarez, P. Crochet and V. Cadierno, Catal.
Commun., 2011, 13, 91–96; (c) A. Azua, J. A. Mata and E. Peris,
Organometallics, 2011, 30, 5532–5536.
29 (a) H. Doucet, T. Ohkuma, K. Murata, T. Yokozawa, M. Kozawa, E.
Katayama, A. F. England, T. Ikariya and R. Noyori, Angew. Chem.
Int. Ed., 1998, 37, 1703–1707; (b) K. Mikami, T. Korenaga, M.
Terada, T. Ohkuma, T. Pham and R. Noyori, Angew. Chem. Int. Ed.,
1999, 38, 495ꢀ497; (c) R. Noyori, M. Koizumi, D. Ishii and T. 140
50 B. Deb, P. P. Sarmah and D. K. Dutta, Eur. J. Inorg. Chem., 2010,
1710–1716.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 |11

Dalton Transactions
Page 12 of 13
View Article Online
DOI: 10.1039/C6DT01406B
51 R. Noyori, M. Yamakawa and S. Hashiguchi, J. Org. Chem., 2001,
66, 7931–7944.
52 M. R. Eberhard, Org. Lett., 2004, 6, 2125–2128.
53 (a) E. Bayram, J. C. Linehan, J. L. Fulton, J. A. S. Roberts, N. K.
Szymczak, T. D. Smurthwaite, S. Özkar, M. Balasubramanian and R.
G. Finke, J. Am. Chem. Soc., 2011, 133, 18889–18902; (b) E.
Bayram and R. G. Finke, ACS Catal., 2012, 2, 1967–1975.
54 (a) C. A. Mebi, J Chem Sci, 2011, 123, 727–731; (b) P. K. Chattaraj
and B. Maiti, J. Am. Chem. Soc., 2003, 125, 2705–2710.
5
10 55 (a) R. A. Zelonka and M. C. Baird, Can. J. Chem., 1972, 50,
3063−3072; (b) N. Arnau, M. MorenoꢀMañas and R. Pleixats,
Tetrahedron, 1993, 49, 11019–11028; (c) B. S. Furniss, A. J.
Hannaford, P. W. G. Smith, A. R. Tatchell, Vogel’s Textbook of
Practical Organic Chemistry, 5th ed.; ELBS/Longman Group U.K.
15
20
25
30
35
40
Ltd., 1989.
56 Q. Liu and Y. Tor, Org. Lett., 2003, 5, 2571ꢀ2572.
57 (a) G. M. Sheldrick, SADABS V2.10, University of Gottingen,
Germany, 2003; (b) G. M. Sheldrick, Acta Crystallogr., Sect. A:
Found. Crystallogr., 1990, 46, 467ꢀ473; (c) G. M. Sheldrick,
SHELXLNT Version 6.12, University of Gottingen, Germany, 2000.
58. (a) J. J. Manura and D. J. Manura, Isotope Distribution Calculator,
SIS, 1996 (http:/www.sisweb.com/mstools.htm); (b) P. E. Kruger, F.
Launay and V. McKee, Chem. Commun., 1999, 639–640.
59 M. A. Robb, J. A. Cheeseman, J. A. Montgomery, T. Vreven, K. N.
Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V.
Barone, M. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.Toyota, R. Fukuda, J.
Hasegawa, M. Ishida, M. Nakajima, Y. Honda, K. Kitao, H. Nakai,
M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken,
V. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K.
Morokuma, J. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D.
A. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J.
V.Ortiz, Q. Cui, A. G. Baboul, G. Clifford, J. Cioslowski, B. B.
Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. A.
Martin, D. J. Fox, T. Keith, M. A. AlꢀLaham, C. Y. Peng, A.
Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez and J. A. Pople, Gaussianꢁ03; Gaussian,
Inc.: Wallingford, CT, 2004.
60 (a) A. D. Becke, J. Chem. Phys.,1993, 98, 5648ꢀ5652; (b) C. Lee, W.
Yang and R. G. Parr, Phys. Rev., B1988, 37, 785ꢀ789.
12|Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 13 of 13
Dalton Transactions
View Article Online
DOI: 10.1039/C6DT01406B
“Click” generated 1,2,3-triazole based organosulfur/selenium
ligands and their Pd(II) and Ru(II) complexes: their synthesis,
structure and catalytic applications
Satyendra Kumar, Fariha Saleem and Ajai K. Singh*
Sonogashira and SuzukiꢀMiyaura coupling were catalyzed with Pd(II) complexes (0.001ꢀ2
mol%) and transfer hydrogenation (in waterꢀglycerol) with Ru(II) complexes (≤ 0.4 mol%)