Arene-ruthenium(II)-phosphine complexes: Green catalysts for hydration of nitriles under mild conditions

Article abstract of DOI:10.1016/j.inoche.2019.107698

Three new arene-ruthenium(II) complexes were prepared by treating [{RuCl(μ-Cl)(η⁶-arene)}₂] (η⁶-arene = p-cymene) dimer with tri(2-furyl)phosphine (PFu₃) and 1,3,5-triaza-7-phosphaadamantane (PTA), respectively to obtain [RuCl₂(η⁶-arene)PFu₃] [Ru]-1, [RuCl(η⁶-arene)(PFu₃)(PTA)]BF₄ [Ru]-2 and [RuCl(η⁶-arene)(PFu₃)₂]BF₄ [Ru]-3. All the complexes were structurally identified using analytical and spectroscopic methods including single-crystal X-ray studies. The effectiveness of resulting complexes as potential homogeneous catalysts for selective hydration of different nitriles into corresponding amides in aqueous medium and air atmosphere was explored. There was a remarkable difference in catalytic activity of the catalysts depending on the nature and number of phosphorus-donor ligands and sites available for catalysis. Experimental studies performed using structural analogues of efficient catalyst concluded a structural-activity relationship for the higher catalytic activity of [Ru]-1, being able to convert huge variety of aromatic, heteroaromatic and aliphatic nitriles. The use of eco-friendly water as a solvent, open atmosphere and avoidance of any organic solvent during the catalytic reactions prove the reported process to be truly green and sustainable.

Full text of DOI:10.1016/j.inoche.2019.107698

Journal Pre-proofs
Arene-Ruthenium(II)-Phosphine Complexes: Green Catalysts for Hydration
of Nitriles Under Mild Conditions
Komal M. Vyas, Poulami Mandal, Rinky Singh, Shaikh M. Mobin, Suman
Mukhopadhyay
PII:
S1387-7003(19)30963-3
DOI:
https://doi.org/10.1016/j.inoche.2019.107698
INOCHE 107698
Reference:
To appear in:
Inorganic Chemistry Communications
Received Date:
Revised Date:
Accepted Date:
20 September 2019
11 November 2019
21 November 2019
Please cite this article as: K.M. Vyas, P. Mandal, R. Singh, S.M. Mobin, S. Mukhopadhyay, Arene-
Ruthenium(II)-Phosphine Complexes: Green Catalysts for Hydration of Nitriles Under Mild Conditions,
Inorganic Chemistry Communications (2019), doi: https://doi.org/10.1016/j.inoche.2019.107698
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Arene-Ruthenium(II)-Phosphine Complexes: Green Catalysts for
Hydration of Nitriles Under Mild Conditions
a,b*
Komal M. Vyas, Poulami Mandal, Rinky Singh, Shaikh M. Mobin, Suman
a
a
a
a
Mukhopadhyay
a
Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road,
Simrol, Indore-453552, India
b
Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar-388120, India
*Corresponding author: komal_vyas@spuvvn.edu
Abstract
Three new arene-ruthenium(II) complexes were prepared by treating [{RuCl(µ-
6
6
Cl)(η -arene)}
2
] (η -arene=p-cymene) dimer with tri(2-furyl)phosphine (PFu
3
) and 1,3,5-
] [Ru]-1,
[Ru]-3. All the
6
triaza-7-phosphaadamantane (PTA), respectively to obtain [RuCl
2
(η -arene)PFu
3
6
6
[
RuCl(η -arene)(PFu
3
)(PTA)]BF
4
[Ru]-2 and [RuCl(η -arene)(PFu
3
)
2
]BF
4
complexes were structurally identified using analytical and spectroscopic methods including
single-crystal X-ray studies. The effectiveness of resulting complexes as potential
homogeneous catalysts for selective hydration of different nitriles into corresponding amides
in aqueous medium and air atmosphere was explored. There was a remarkable difference in
catalytic activity of the catalysts depending on the nature and number of phosphorus-donor
ligands and sites available for catalysis. Experimental studies performed using structural
analogues of efficient catalyst concluded a structural-activity relationship for the higher
catalytic activity of [Ru]-1, being able to convert huge variety of aromatic, heteroaromatic
and aliphatic nitriles. The use of eco-friendly water as a solvent, open atmosphere and
avoidance of any organic solvent during the catalytic reactions prove the reported process to
be truly green and sustainable.
Keywords: Green Chemistry, Homogeneous Catalysis, Organometallic Chemistry, Ru(II)-
Arene Complexes
Hydration of nitrile into amide is a key organic transformation, which is utilized
extensively to generate pharmaceuticals and other industrial products. Amides have been
found to be very essential as the amide linkage paves the way for generation of various
polymeric products with versatile industrial applications [1]. The conventional procedure to
obtain amides through acid or base catalysis is plagued by drawbacks like overreaction with
formation of carboxylic acids and harsh conditions which limits the application in presence of

other sensitive functional groups [2, 3]. The formation of amide has been identified as one of
the most challenging syntheses in industry and considered as a high-priority research field by
ACS GCIPR in 2005. Therefore, developing atom-efficient catalytic procedures for amide
formation that avoids the acid/base and/or stoichiometric reagents, is a key goal and highly
desirable methodology in modern chemistry [4]. Homogeneous or heterogeneous catalysis
involving metal appears to be more attractive and potent alternatives due to their superior
substrate scope and easy handling [5]. A huge variety of highly selective homogeneous metal
catalysts have been reported for the formation of amide [6-9].
Amongst all transition metal based catalysts, ruthenium is considered as one of the
highest explored metals for transformation of nitrile to amide because few of the highly
efficient catalysts containing ruthenium, are reported with high substrate acceptance toward
the nitrile hydration [5e, 10-16] especially, with phosphine containing ligands [8, 9, 10, 17-
22] Most of these catalysts work only in organic media with or without the presence of water
and operate in an inert atmosphere like nitrogen and argon [18]. Therefore, to develop safer
and more eco-friendly procedures, some groups are working since last few years to explore
the possibility of development of new homogeneous catalysts, which are able to perform the
selective hydration of nitriles to amides in aqueous medium [6,10,12,13,15,23]. It is
important to note that development of organic transformations in aqueous medium has
become one of the key requirements in contemporary chemistry in line with the increasing
interest of academia and industry in satisfying the principles of “Green Chemistry”, [24, 25]
being water the most suitable solvent that can be thought of in terms of safety, accessibility,
cost and environmental impact [26].
In view of this, we present the synthesis of three new ruthenium(II)-arene complexes
where tri(2-furyl) phophine (PFu
3
) has been utilized as co-ligand which has already shown
remarkable impact in various transition metal based organic transformation [27]. The three
6
6
new compounds [RuCl
2
(η -arene)PFu
3
,] [Ru]-1, [RuCl(η -arene)(PFu
3
4
)(PTA)]BF [Ru]-2
6
[
PTA = 1,3,5-triaza-7-phosphaadamantane] and [RuCl(η -arene)(PFu
3
)
2
]BF , [Ru]-3 have
4
shown excellent selective hydration of different nitrile derivatives to their corresponding
amides using these complexes in aqueous media and relatively mild condition in open
atmosphere with excellent yield.
Though ruthenium based organometallic complexes have been studied for organic
transformation of nitrile to amide, there are only few reports where water soluble complexes
act as homogeneous catalyst in aqueous medium. One such report has highlighted the use of
PTA based ruthenium compounds for efficient hydrolysis of nitriles in water medium [19a].

Our research has been initiated for alternative phosphine based ligands, which in conjunction
with ruthenium can be effective hydrolytic catalyst. Tris(2-furyl)phosphine (PFu ) with
3
additional electronegative heteroatoms is an automatic choice as it is reported to be poorer σ-
donor and relatively easily dissociable, which may be the prerequisite for improved catalytic
6
activity. The PFu
3
coordinated arene-ruthenium(II) complexes [RuCl
]BF
2
(η -arene)PFu
3
], [Ru]-1
6
and [RuCl(η -arene)(PFu
3
)
2
4
[Ru]-3 were achieved in excellent yield by the reaction of
], with PFu in methanol-dichloromethane solvent
6
arene-ruthenium dimer [{(η -arene)RuCl
2
}
2
3
mixture. Furthermore, substitution of ruthenium bonded chloride in [Ru]-1 with PTA
6
furnished [RuCl(η -arene)(PFu
3
)(PTA)BF ] [Ru]-2 in mild condition (Scheme S1 in ESI).
4
The orange-brown to red-brown coloured complexes [Ru]-1-3 were characterized by
1H, 13C and 31P NMR (Figs. S1-S9 in ESI) spectroscopy, elemental analysis and ESI-MS
1
1
techniques (Figs. S10-S12 in ESI). H NMR spectra of all the complexes, The H NMR
spectra of all the complexes showed the downfield shift of the protons of PFu in comparison
3
with the free uncoordinated ligand, which is consistent with the coordinated P-donor ligands
1
to Ru centre. The H NMR peaks for coordinated aromatic group upfield shift is also
observed as expected. Compound [Ru]-2 shows typical peaks for coordinated PTA ligand
within the range 5.81-4.17 ppm [19a]. All the complexes were further structurally confirmed
by single-crystal X-ray studies with the most suitable crystals of the synthesized complexes
(
Fig. 1, and Tables S1-S3 in ESI). The ruthenium centre exhibits pseudo-octahedral three
6
legged piano-stool geometry in which the η -arene ring occupies apical position and
remaining three positions are occupied by one phosphorus atom of ligand PFu
3
and two
chloride ligand in [Ru]-1, one phosphorus atom of ligand PFu3, one phosphorus atom of
ligand PTA and one chloride ligand in [Ru]-2 and two phosphorus atoms of two PFu
one chloride ligand in [Ru]-3. The Ru-P bond distances for the coordinated PFu
3
3
and
are
2
.3176(11) Å and 2.2998(9) Å in [Ru]-1 and [Ru]-2, respectively. Compound [Ru]-3
crystallizes in crystallographically two different units. The Ru-P bond distances in [Ru]-3 for
coordinated PFu ligands are 2.333(4) Å and 2.306(5) Å in one unit whereas 2.330(4) Å and
.302(4) Å in other. The Ru-P bond distance due to PTA coordination in [Ru]-2 is 2.313(11)
3
2
Å. The Ru-C bond distances are also comparable with other analogous complexes. The bond
angles Cl(1)-Ru-P(1) (82.90(5)), Cl(1)-Ru-P(2) (90.23(4)), and Cl(1)-Ru-Cl(2) (87.38(6)),
and those between the centre of the p-cymene ring and the legs, showed typical values for
6
[
RuCl
2
(η -arene)(PFu
3
)] species.

[Ru]-1
[Ru]-2
[Ru]-3
Fig. 1. ORTEP diagram of the ruthenium(II)-arene complexes (50% probability thermal
ellipsoids).
In the beginning, the hydration of nitriles into amides was investigated using
ruthenium catalysts, [Ru]-1-3, in water under moderate reaction conditions. Benzonitrile was
selected as a model substrate for its conversion into benzamide in the presence of synthesized
arene-ruthenium(II) catalysts. In classical experiment, the ruthenium catalyst (different
mol%) was added to the solution of benzonitrile (1 mmol) in water (3 mL) and the reaction
was heated in an oil bath at desired temperature. The progress of the reaction was examined
by taking regular samples and analysing by gas chromatography (GC). As depicted in Table
S4, all the synthesized complexes were able to catalyse the hydration of benzonitrile to
benzamide. Within the group of synthesized catalysts, the reaction of benzonitrile with [Ru]-
1
catalyst resulted in complete conversion with >99% selectivity for benzamide at 80°C in 4
3
1
h (Table S4, entries 6-10). The reaction mixture was analysed by P NMR after 4 hrs which
showed the presence of phosphorus of tri phenyl phosphine after the reaction (Fig. S13).
Some traces of triphenyl phosphine and triphenyl phosphine oxide were observed in case of
[
Ru]-3, lowering the selectivity of [Ru]-3 to amide. However, drastic decrease in the
catalytic conversion of benzonitrile was observed when the temperature was decreased to
0°C or lower (Table 1, entries 1-5). Remarkably, complete conversion of benzonitrile to
benzamide was attained at 80°C, which was able to produce benzamide quantitatively in only
h (Table S4, entry 8). However, with decrease in the amount of catalyst even after
6
4
increasing time resulted in lower catalytic conversion of benzonitrile to benzamide (Table S4,
entries 6, 7). As previously observed in case of certain Ruthenium(II)-arene complexes [12,
1
9a], in this case also no traces of benzoic acid were noticed by GC in the reaction mixtures
with any catalyst.
In comparison with [Ru]-1 catalyst, [Ru]-2 and [Ru]-3 catalysts appeared to be less
effective (Fig.2), as the complete catalytic conversion of benzonitrile to benzamide was not

attained with [Ru]-2 or [Ru]-3 catalysts even at 80°C for 12 h (Table S4, entries, 11-30).
However, lower conversion and selectivity were observed with decrease in temperature
(
60°C). The efficiency of [Ru]-1 was found to be much greater than other two catalysts under
analogous conditions. Moreover, the time for completion of reaction can be reduced by
increasing the temperature to 90°C or 100°C.
The Hg(0) is able to poison metal-particle heterogeneous catalysts and is extensively
used test [28]. This test is carried out by adding Hg(0) to the reaction mixture. The decrease
in catalytic activity by Hg(0) is an evidence for a heterogeneous catalyst and no significant
change in the catalytic activity suggests homogeneous catalysis. We have performed the
mercury poisoning test to understand whether the reaction is homogeneous or heterogeneous.
The test was performed with catalyst [Ru]-1 in the presence of excess Hg(0) (Table S4, entry
31). The results confirmed no significant decrease in the catalytic conversion of benzonitrile
to benzamide, confirming no involvement of heterogeneous ruthenium nanoparticles/colloids
and the hydration of nitrile was predominantly homogeneous in nature [28].
1
00
80
60
40
20
0
6
0°C
0°C
8
[Ru]-1
[Ru]-2
[Ru]-3
Catalyst
Fig. 2. Effect of temperature on the catalytic hydration of benzonitrile to benzamide by arene-
ruthenium(II) catalysts. Reaction Conditions: benzonitrile (1.0 mmol), catalyst (3 mol%), T =
60°C (blue)/80°C (red) and water (3 mL).
The coordination of the substrate onto ruthenium(II) arene complexes involves Cl
release from one Ru-Cl bond. In accordance with this, to explore the effect of unique
structural benefits with [Ru]-1 catalyst on its catalytic efficacy, catalytic activity of [Ru]-1
was compared by using structurally similar ruthenium catalysts with PTA ([Ru]-2) and with
another extra PFu
3
([Ru]-3) ligands, in place of one of the two chlorides, for the catalytic
hydration of benzonitrile using optimized reaction conditions. Interestingly, replacement of

one chloride with PTA and PFu in ruthenium catalysts [Ru]-2 and [Ru]-3, respectively,
3
resulted in noticeable decrease in the activity in the order of [Ru]-1 > [Ru]-2 > [Ru]-3 for the
catalytic hydration of benzonitrile to benzamide (as shown in Fig. 3 and Table S5 in ESI).
These results clearly illustrated that replacement of the labile chloro group using bulky PTA
in [Ru]-2 or PFu in [Ru]-3 demonstrated significant decrease in the catalytic hydration
3
suggesting dissociation of one of the attached chloro group during the reaction to deliver
vacant sites for the coordination of nitrile (Fig. 3).
40
30
20
10
0
[Ru]-1
[Ru]-2
[Ru]-3
Catalyst
Fig. 3. Effect of the structure of catalyst on the catalytic hydration of benzonitrile to
benzamide using different arene-ruthenium(II) catalysts. Reaction Conditions: benzonitrile
(
1.0 mmol), catalyst (3 mol%), T = 80°C and water (3 mL).
After getting encouraging results for [Ru]-1 with benzonitrile, variety of nitriles
having different substituents was subjected to the catalytic action of [Ru]-1 using optimized
reaction conditions. Selected results are depicted in Table 1. As detected for benzonitrile,
which was transformed into benzamide with 99% GC yield after 4 h of heating (Table 1,
entry 1), most of the other substituted nitriles could be converted to the corresponding
primary amides in excellent yields after 2−24 h irrespective of their substitution arrangement
and electronic nature.
A minor impact of the electronic property of the aromatic ring was observed, with
substrates having electron-donating groups resulting in comparatively a low reactivity (e.g.,
entry 12 vs 13). A lesser efficient hydration (entry 8 vs 18) was observed in ortho substituted
derivatives. Interestingly, no traces of the corresponding benzoic acid in any case were
noticed by GC in the reaction mixtures. However, probably due to steric hindrance, ortho-
substituted substrates displayed a lower reactivity compared to their meta- or para-substituted

derivatives (e.g., 2 vs 11; 3 vs 5, 23; 7 vs 26, 14 or 8 vs 6, 18). Remarkably, the presence of
common functional groups, like halide, hydroxyl, amino, nitro or ether was tolerated
confirming the high potential of [Ru]-1 for practical applications. It is worth to note about the
conversion of nitrile even having thiomethyl group, since sulfur species form strong metal-
sulfur bond which is a poison for homogeneous catalysts (entry 28 in Table 1) [29]. Thus, as
detected for benzonitrile, substituted benzonitriles (e.g., entries 6-9, 12, 14, 18 and 19) having
electron-withdrawing groups resulted in the corresponding amides in high yields and short
reaction times. Chromatographic workup using silica gel and solvent removal gave pure
samples of amides, which were identified by comparing their H and 13C NMR data with
previously reported in the literature.
1
Table 1. Catalytic hydration of nitrile derivatives into corresponding amides by [Ru]-1 in
aqueous medium.
[
a]
-1 [b]
Entry
Substrate
R=Ph
Time (h)
4
24
8
24
6
4
8
8
8
4
8
4
8
2
12
24
4
2
6
Yield /Sel. % TOF(h )
1
2
3
4
5
6
7
8
9
>99/>99
44/>99
>99/>99
44/>99
98/>99
>99/>99
90/>99
92/>99
95/>99
>99/>99
>99/>99
>99/>99
>99/>99
>99/>99
85/>99
45/87
8.3
0.6
4.2
0.6
5.4
8.3
3.7
3.8
3.9
8.3
4.2
8.3
4.2
16.6
2.4
0.6
8.3
16.6
5.5
1.2
3.7
16.6
16.6
16.6
8.3
R=2-C
R=2-C
6
6
H
H
4
NH
OH
2
4
R=2-Pyridyl
R=3-C
R=3-C
R=2-C
R=2-C
R=2-C
6
6
6
6
6
H
4
H
4
H
4
H
4
H
4
OH
Cl
Br
Cl
F
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
R=3-Pyridyl
R=4-C
R=4-C
R=4-C
R=4-C
R=2-C
R=4-C
R=3-C
R=4-C
R=3-C
R=4-C
R=4-C
R=4-C
R=4-C
6
6
6
6
6
6
6
6
6
6
6
6
6
H
4
H
4
H
4
H
4
H
4
H
4
H
4
H
4
H
4
H
4
H
4
H
4
H
4
NH
NO
2
2
OMe
Br
Me
BrMe
Me
Cl
>99/>99
>99/>99
>99/>99
86/98
F
CHO
COOH
Me
24
8
2
2
2
90/98
>99/>99
>99/>99
>99/>99
>99/>99
OH
R=4-Pyridyl
R=3-C NH
6
H
4
2
4

2
2
2
2
3
3
3
3
3
3
6
7
8
9
0
1
2
3
4
5
R=3-C
R=4-C
R=4-C
6
6
6
H
H
H
4
4
4
Br
F
SMe
4
>99/>99
90/>99
89/97
>99/>99
>99/>99
98/>99
>99/>99
>99/>99
>99/>99
>99/>99
8.3
2.5
1.2
4.2
16.6
8.2
16.6
16.6
16.6
16.6
12
24
8
2
4
2
2
2
2
R= -CH=CHPh
n
R= Propyl
R=Pyrazyl
R=Me
n
R= Pentyl
R=piperonyl
R= 2-Pyrimidyl
Conditions: nitrile (1.0 mmol), catalyst (3 mol%), T = 80°C and water (3 mL). [a] Yield was
determined by GC (uncorrected GC area). [b] Turnover frequency ((mol product/mol
Ru)/time) was calculated at the time indicated in each case.
The extensive scope of the reaction was also evaluated by using another types of
nitriles like heteroaromatic (entries 4, 10, 24, 31, 35), aliphatic (entries 30, 32, 33) and α, β-
unsaturated (entry 29), which were all easily and completely hydrated with higher reactivity
with respect to the previously reported examples [18, 19] Complex [Ru]-1 was particularly
found to be most effective in case of heteroaromatic nitriles. In addition, for this specific
class of substrates, noticeable difference in activity was observed, based on the position of the
heteroatom and the C=N unit. Notably, poor conversion of 2-cyanopyridine to picolinamide
was observed at even after heating for 24 h with [Ru]-1. However, 3-cyanopyridine and 4-
cyanopyridine were almost converted into nicotinamide and isonicotinamide, respectively,
after only 2−4 h of heating (entries 10 and 24). Steric hindrance could be the possible reason
for the difference in catalytic activity observed as in 2-cyanopyridine, 3-cyanopyridine and 4-
cyanopyridine. Extremely fast reactions were witnessed in case of 3-pyrimidinecarbonitrile
and pyrazinecarbonitrile (entries 31 and 35). In particular, hydration of pyrazinecarbonitrile
resulted in pure anti-tuberculosis drug pyrazinamide in excellent yield. The catalyst [Ru]-1
was also active for the hydration of aliphatic nitriles with good yields in 2 h only confirming
the extensive scope of the catalytic hydration (entries 30, 32, 33). It is important to note that
neither polymerization process nor hydration of C=C bond were observed in these reactions.
Studies on the conversion of nitrile derivatives into corresponding amides have been
2
carried out particularly in inert atmosphere using N or Ar gas. It should be noted that even
after avoiding the use of any inert gas, we attained complete conversion of many nitriles into
their corresponding amides with excellent yields in aqueous medium at 80°C using arene-
ruthenium(II) complexes containing Phosphorus-donor, which is so far one of the best results

obtained to the best of our knowledge [19]. A table comparing the data of similar results in
water are included in the supplementary information (Table S6 in ESI).
Though there are various advantages of homogeneous catalysis, the recovery of
catalyst from the reaction mixture has some limitations. However, due to good solubility of
[
Ru]-1 in water during the catalytic process on heating, we were able to recover the catalyst
easily from the reaction mixture and reuse in further hydration of nitrile without any
substantial loss in the catalytic activity. After each catalytic run, the extraction of amides
from the reaction mixture was carried out using suitable organic solvent, whereas catalyst
persisted in the aqueous phase. After adding appropriate amount of distilled water to aqueous
phase to make it 3 mL, it was further used for next catalytic run. In a typical run, 1 mmol of
benzonitrile was further added to the aqueous phase and the reaction was carried out at
optimized conditions. Fig. 4 shows an excellent recyclability of [Ru]-1 for the hydration of
nitrile to primary amide upto 4 catalytic runs without significant loss in the catalytic activity.
A slight decrease in catalytic activity observed after individual catalytic run was due to the
incompletion of catalyst recovery during the transfer of the aqueous phase, which was visible
to the naked eye from the light yellow colour of the product.
1
00
80
60
40
20
0
1
2
3
4
Catalytic runs
Fig. 4. Recyclability of [Ru]-1 catalyst for the catalytic hydration of benzonitrile to
benzamide. Reaction Conditions: benzonitrile (1.0 mmol), catalyst (3 mol%), T = 80°C and
water (3 mL).
In summary, we have successfully explored the catalytic efficiency of arene-
ruthenium(II) complexes bearing tri-(2-furyl)phosphine ligand, [Ru]-1-3, for the highly
selective hydration of nitriles to their corresponding amides under challenging reaction
conditions, i.e., in an aqueous medium and open air atmosphere. Among the three complexes
screened, [Ru]-1 with two chloride and one PFu ligands, was found to be the best for
3

catalytic systems with high selectivity and conversion. The reaction has been carried out for a
wide variety of substrates, including aromatic, heteroaromatic, aliphatic and α, β-unsaturated
ones. The varied scope and great acceptance toward functional groups exhibited by the
ruthenium catalyst [Ru]-1, make this catalytic process an attractive synthesis for the
formation of amides avoiding the use of classical organic solvent and inert atmosphere. To
the best of our knowledge, [Ru]-1 is so far one of the most efficient ruthenium catalysts for
the transformation of nitriles in aqueous medium and air atmosphere reported till date in the
literature. Exploration of the catalytic efficiency of structurally analogues of arene-
ruthenium(II) complex, highest efficiency of [Ru]-1 catalyst revealed a unique structure-
activity relationship. Due to the presence of two labile chloro groups, superior catalytic
activity of [Ru]-1 has been observed through dissociation of chloride ligand from
coordination sphere. Moreover, the catalytic studies of ruthenium catalyst revealed high
recyclability of the catalyst up to 4 runs. We anticipate that this study could offer insights
toward the synthesis of simple yet efficient catalyst for the hydration of nitrile to precious
amides and could be applicable to many other industrially important catalytic
transformations.
Supporting Information
The supporting information includes experimental details, all spectral data as well as
catalytic data and copies of NMR spectra of the synthesized amides. CCDC 1551675,
1840409 and 1840408 contain the supplementary crystallographic data for [Ru]-1, [Ru]-2
and [Ru]-3, respectively. The crystallographic data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Acknowledgements
The authors are thankful to DST SERB India and UGC-BSR Research Start-Up Grant
for financial assistance. Support of SIC, IIT Indore for analytical studies has been gratefully
acknowledged.

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ꢀ
ꢀ
ꢀ
Three new arene-ruthenium(II) complexes with phosphine ligands have been
prepared.
All the complexes have been structurally identified using analytical and spectroscopic
methods including single-crystal X-ray studies.
The effectiveness of resulting complexes for selective hydration of different nitriles in
aqueous medium and air atmosphere is explored.

Arene-Ruthenium(II)-Phosphine Complexes: Green Catalysts for
Hydration of Nitriles Under Mild Conditions
a,b*
Komal M. Vyas, Poulami Mandal, Rinky Singh, Shaikh M. Mobin, Suman
a
a
a
a
Mukhopadhyay
a
Discipline of Chemistry, School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road,
Simrol, Indore-453552, India
b
Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar-388120, India
*Corresponding author: komal_vyas@spuvvn.edu
Graphical abstract