Ruthenium(II) carbonyl complexes of P,P and P,O donor diphosphine ligands, Ph2P(CH2)nPPh2 and Ph2P(CH2)nP(O)Ph2, n = 2, 3 and their activities in catalytic transfer hy

Article abstract of DOI:10.1080/00958972.2018.1449947

The polymeric precursor [RuCl₂(CO)₂]_n reacts with the ligands, P∩P (a, b) and P∩O (c, d), in 1:1 M ratio to generate six-coordinate complexes [RuCl₂(CO)₂(?²-P∩P)] (1a, 1b) and [RuCl₂

Full text of DOI:10.1080/00958972.2018.1449947

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Ruthenium(II) carbonyl complexes of P,P and P,O
donor diphosphine ligands, Ph2P(CH2)nPPh2 and
Ph2P(CH2)nP(O)Ph2, n = 2, 3 and their activities in
catalytic transfer hydrogenation reactions
Biswajit Deb & Dipak Kumar Dutta
To cite this article: Biswajit Deb & Dipak Kumar Dutta (2018): Ruthenium(II) carbonyl complexes
of P,P and P,O donor diphosphine ligands, Ph2P(CH2)nPPh2 and Ph2P(CH2)nP(O)Ph2, n = 2, 3 and
their activities in catalytic transfer hydrogenation reactions, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2018.1449947
To link to this article: https://doi.org/10.1080/00958972.2018.1449947
Accepted author version posted online: 08
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Publisher: Taylor & Francis
Journal: Journal of Coordination Chemistry
DOI: http://doi.org/10.1080/00958972.2018.1449947
Ruthenium(II) carbonyl complexes of P,P and P,O donor diphosphine ligands,
Ph2P(CH2)nPPh2 and Ph2P(CH2)nP(O)Ph2, n = 2, 3 and their activities in
catalytic transfer hydrogenation reactions
BISWAJIT DEB*† and DIPAK KUMAR DUTTA‡
†Department of Chemistry, Karimganj College, Karimganj-788710, Assam, India
‡Materials Science Division, CSIR-North East Institute of Science and Technology, Jorhat-785 006, Assam, India
The polymeric precursor [RuCl2(CO)2]n reacts with the ligands, PP (a,b) and PO (c,d), in 1:1
molar ratio to generate six-coordinate complexes [RuCl2(CO)2(ƞ2-PP)] (1a, 1b) and
[RuCl2(CO)2(ƞ2-PO)] (1c, 1d), where PP: Ph2P(CH2)nPPh2, n = 2(a), 3(b); PO:
Ph2P(CH2)nP(O)Ph2, n = 2(c), 3(d). The complexes are characterized by elemental analyses,
mass spectrometry, thermal studies, IR and NMR spectroscopy. 1a-1d are active in catalyzed
transfer hydrogenation of acetophenone and its derivatives to corresponding alcohols with
turnover frequency (TOF) of 75-290 h-1. The complexes exhibit higher yield of hydrogenation
products than catalyzed by RuCl3 itself. Among 1a-1d, the Ru(II) complexes of bidentate
phosphine (1a, 1b) show higher efficiency than their monoxide analogues (1c, 1d). However, the
recycling experiments with the catalysts for hydrogenation of 4-nitroacetophenone exhibit a
different trend in which the catalytic activities of 1a, 1b and 1d decrease considerably, while 1c
shows similar activity during the second run.
Keywords: Ruthenium; Phosphine; Carbonyl; Transfer hydrogenation; Catalysis
1. Introduction
The coordination chemistry of symmetric and unsymmetric diphosphine ligands is of interest
because of their structural novelty, reactivity and catalytic activity [1-5]. However,
unsymmetrical P,X donor diphosphine ligands exhibit capability of coordinating either as
monodentate (ƞ1-P coordinated) or bidentate chelating (ƞ2-P,X coordinated) depending upon the
*Corresponding author. Email: b.deb@rediffmail.com
1

environment around the central metal [2a, 6]. Though metal complexes of P,O donor ligands
show interesting coordination chemistry as well as catalytic activity [2a, 2e, 6b], the use of metal
complexes containing P,S or P,Se donors in catalytic reactions is not encouraging because of
metal poisoning by sulfur [7a, 7b] and deselination of selenide under the reaction condition
[7a, 7c]. Ruthenium catalyzed reactions for organic synthesis receive much attention and a large
number of highly efficient synthetic approaches are documented [2a, 8, 9]. In general,
ruthenium(II) complexes are efficient hydrogenation catalysts for reduction of ketones
[2a, 9-12]. Noyori and Ohkuma discovered that ruthenium(II) complexes of diphosphine and
1,2-diamine ligands, in the presence of a base and 2-propanol, are excellent catalysts for
hydrogenation of ketones under mild conditions [10f]. Despite the large number of Ru(II)
carbonyl complexes reported [2a, 11-14], the use of ruthenium(II) carbonyl species as
hydrogenation catalysts (which are generally considered as sluggish catalysts for hydrogenation
reaction [13]) are scanty [2a, 10-12]. As part of our research activities [2, 11, 15], herein we
report the synthesis of four ruthenium(II) carbonyl complexes of P,P and P,O donor diphosphine
ligands viz. Ph2P(CH2)nPPh2 and Ph2P(CH2)nP(O)Ph2, n = 2, 3 and their activities towards
catalytic transfer hydrogenation. Recycling experiments of these catalysts have been investigated
under similar experimental conditions in order to evaluate the effect of ligands during the
catalytic cycle.
2. Experimental
2.1. General information
All operations were carried out under nitrogen. All solvents were distilled under N2 prior to use.
The metal salt RuCl3·xH2O and ligands Ph2P(CH2)2PPh2, Ph2P(CH2)3PPh2, Ph2P(CH2)2P(O)Ph2,
Ph2P(CH2)3P(O)Ph2 and substrates, acetophenone and its derivatives, were purchased from M/S
Aldrich, USA and used without purification. Elemental analyses were performed on a Perkin-
Elmer 2400 elemental analyzer. IR spectra (4000-400 cm-1) were recorded on KBr discs in a
Perkin–Elmer system 2000 FT-IR spectrophotometer. 1H, 13C and 31P NMR spectra were
recorded in CDCl3 solution on a Bruker DPX-300 Spectrometer and chemical shifts were
reported relative to SiMe4 and 85% H3PO4 as internal and external standards, respectively. Mass
spectra of the complexes were recorded on an ESQUIRE 3000 Mass Spectrometer. Thermal
2

analyses of the complexes were carried out using a thermal analyzer (TA instrument, Model STD
2960 simultaneous DTA-TGA) in N2 atmosphere with a heating rate of 10 C/min.
2.2. Synthesis of [RuCl2(CO)2]n
The starting [RuCl2(CO)2]n was prepared by passing CO through a refluxing solution of
RuCl3·3H2O in ethanol for 24 h [16].
2.3. Synthesis of [RuCl2(CO)2(ƞ2-PP)] (1a,1b) and [RuCl2(CO)2(ƞ2-PO)] (1c,1d), where
PP = Ph2P(CH2)2PPh2 (a), Ph2P(CH2)3PPh2 (b), Ph2P(CH2)2P(O)Ph2 (c),
Ph2P(CH2)3P(O)Ph2 (d)
[RuCl2(CO)2]n (0.439 mmol, 100 mg) in methanol (10 cm3) was stirred for 1 h with an equimolar
quantity of ligand [0.439 mmol, 175 mg (a), 181mg (b), 182 mg (c) and 188 mg (d)] in
dichloromethane to produce 1a-1d. The solvent was removed under vacuum and washed with
diethyl ether. The resulting yellow compound was recrystallized from dichloromethane/hexane
to give bright yellow powder.
2.4. Analytical data for 1a-1d
1a: IR (KBr, cm-1): 1988, 2053 [(CO)]. 1H NMR (CDCl3, ppm): δ 2.21, 2.91, (m, CH2), 7.36,
7.56, 7.93 (m, Ph). 13C NMR (CDCl3, ppm): δ 25.4, 33.4 (CH2), δ 128-133 (Ph), 191.8 (CO).
31P{1H} NMR (CDCl3, ppm): δ 42.4 [d, JP-P = 78 Hz, PIII]. Mass: 624.9 (M/Z+). Elemental
analyses: Found (Cald. for C28H24O2P2Cl2Ru), C 53.12 (53.67); H 3.71 (3.83).
1b: IR (KBr, cm-1): 1990, 2057 [(CO)]. 1H NMR (CDCl3, ppm): δ 2.13, 2.36, 2.96 (m, CH2),
7.38, 7.52, 7.76 (m, Ph). 13C NMR (CDCl3, ppm): δ 22.7, 27.6, 31.7 (CH2), δ 128-134 (Ph),
192.5 (CO). 31P{1H} NMR (CDCl3, ppm): δ 20.3, 29.1 [s, PIII]. Mass: 641.1 (M/Z+). Elemental
analyses: Found (Cald. for C29H26O2P2Cl2Ru), C 54.03 (54.39); H 3.96 (4.06).
1c: IR (KBr, cm-1): 1986, 2052 [(CO)], 1176 [(PO)]. 1H NMR (CDCl3, ppm): δ 2.23, 2.89, (m,
CH2), 7.35, 7.61, 7.92 (m, Ph). 13C NMR (CDCl3, ppm): δ 24.2, 31.6 (CH2), δ 128.2, 131, 135
(Ph), 189.6 (CO). 31P{1H} NMR (CDCl3, ppm): δ 18.6 [d, JP-P = 51.39 Hz, PIII], 53.9 [d, JP-P
=
51.39 Hz, PV]. Mass: 642.8 (M/Z+). Elemental analyses: Found (Cald. for C28H24O3P2Cl2Ru),
C 51.89 (52.33); H 3.62 (3.73).
3

1d: IR (KBr, cm-1): 1992, 2058 [(CO)], 1160 [(PO)]. 1H NMR (CDCl3, ppm): δ 2.18, 2.38,
2.89 (m, CH2), 7.35, 7.48, 7.87 (m, Ph). 13C NMR (CDCl3, ppm): δ 21.9, 28.2, 32.3 (CH2),
δ 128.7-134.6 (Ph), 190.8 (CO). 31P{1H} NMR (CDCl3, ppm): δ 18.9 [s, PIII], 54.0 [s, PV]. Mass:
655.9 (M/Z+). Elemental analyses: Found (Cald. for C29H26O3P2Cl2Ru), C 52.82 (53.04); H 3.84
(3.96).
2.5. General procedure for the catalytic transfer hydrogenation
In an inert atmosphere, substrate [Acetophenone/ derivatives of acetophenone (26.28 mmol)], the
ruthenium catalyst precursor (0.0438 mmol) and 25 ml of propan-2-ol were introduced into a two
necked round bottom flask fitted with a condenser and heated at 83 C for 10-20 minutes. NaOH
was then added to the reaction mixture (0.24 mmol in 5 ml propan-2-ol) and refluxed at 83 C.
The progress of the reaction was monitored by TLC and the product was isolated by column
chromatography using ethyl acetate and hexane as eluents. The products were characterized by
1H NMR, mass spectrometry and melting point determination followed by comparison with
literature data. In order to study the recycling experiments, the organometallic residues of 1a-1d
along with the silica gel were collected from the chromatographic column and refluxed in
propan-2-ol to dissolve the residue to get a solution. The silica gel was separated by filtration and
the residue was recovered by removing the solvent in vacuum. The residue was reused by
maintaining similar experimental conditions as described above.
3. Results and discussion
3.1. Synthesis and characterization of 1a-1d
The polymeric precursor [RuCl2(CO)2]n reacts with PP and PO type bidentate ligands in 1:1
molar ratio to afford six-coordinate complexes, [RuCl2(CO)2(ƞ2-PP)] (1a,1b) and
[RuCl2(CO)2(ƞ2-PO)] (1c,1d), respectively (scheme 1). Though [RuCl2(CO)2(dppe)] (1a) was
reported [14b], its synthetic route was quite complicated; the synthetic route of the title
complexes in the present manuscript is simpler than the reported one [14b].
4

Cl
Cl
O
P
Cl
Cl
(c,d)
DCM/stirr.
P O
(a,b)
DCM/stirr.
P
P
[RuCl2(CO)2]n
Ru
Ru
P
CO
P
CO
CO
CO
[1c,1d]
[1a,1b]
P
P:
Ph2P(CH2)2PPh2(a)
Ph2P(CH2)3PPh2(b)
:
Ph2P(CH2)2P(O)Ph2 (c)
P O
(d)
Ph2P(CH2)3P(O)Ph2
Scheme 1. Synthesis of 1a-1d.
Elemental analyses and mass spectrometric results are consistent with the proposed
formulas of 1a-1d. IR spectra of 1a-1d show two equally intense υ(CO) bands in the region
1986-2058 cm-1 confirming the presence of two terminal carbonyl groups cis to one another. The
υ(P–O) bands of 1c and 1d at 1176 and 1160 cm-1 are about 6 and 17 cm-1, respectively, lower
than that of the corresponding free ligands [υ(P–O) = 1182(c), 1177(d) cm-1], revealing
coordination to metal through an O donor. The 13C NMR spectra show only one signal for the
two non-equivalent carbonyl carbons as broad singlet in the region δ 189–193 ppm for 1a-1d.
31P{1H} NMR spectrum of 1a shows one doublet at δ = 42.4 ppm (JP-P = 78 Hz) and 1b shows
two sharp singlets at δ = 20.3 and 29.1 ppm for two P(III)-atoms, exhibiting a downfield shift
compared to the free ligands [a: δ = -11.5 ppm (d, JP-P = 84.2 Hz, PIII); b: δ = -16.9 ppm (s, PIII)]
which is in agreement with chelate formation in the complexes. 31P NMR spectra of 1c and 1d
exhibit two distinct doublet and singlet resonances, respectively, corresponding to two different
phosphorus atoms. The pentavalent phosphorus bonded to oxygen and the tertiary phosphorus
bonded to the metal resonate at δ 53.9 (d, JP-P = 51.39 Hz) [1c], 54.0 (s) [1d] and δ 18.6 (d, JP-P
51.39 Hz) [1c], 18.9 (s) [1d] ppm, respectively. The tertiary and pentavalent phosphorus in 1c
=
and 1d show a significant downfield shift compared to the free ligands c [δ -12.2, 7.8, (d, Jp-p
=
84 Hz) and d [δ -10.5, 18.3, s], respectively, which further corroborates chelation in complexes.
The thermal stability of the complexes has been measured under N2 showing all the complexes
stable to about 300 C. Attempt to substantiate the structures of 1a-1d by single crystal X-ray
diffraction were not possible as no suitable crystals could be developed despite several attempts.
5

3.2. Catalytic activities of 1a-1d
The reactivities of 1a-1d have been evaluated in catalytic transfer hydrogenation, exhibiting high
efficiency in the reduction of acetophenone and its derivatives to their corresponding alcohols
with isolated yields 62.3–98.5% over 2–5 h with TOF 75-290 h-1 (scheme 2, table 1), which are
higher than the activity of RuCl3 itself. As shown in table 1, that catalytic activity varies with
respect to substituent in the acetophenone fragment. The presence of electron-withdrawing
substituent (Cl / Br / NO2) in the substrates gives higher TOF than that containing electron-
donating group (-OMe). The introduction of electron-withdrawing substituents to the para
position of the aryl ring of the ketones decrease the electron density on the C-O bond and
facilitates hydrogenation reaction. However, the efficiency of 1a-1d depends on the nature of the
ligands and follows the order 1a > 1b > 1c > 1d > RuCl3. The recycling experiments of the
organometallic residues are performed by maintaining similar experimental conditions for
hydrogenation of 4-nitroacetophenone to its corresponding alcohol. In this case, the catalytic
efficiencies of 1a, 1b and 1d decrease considerably, while 1c shows similar activity during the
second run (figure 1). In order to explain the above facts one must understand the mechanistic
aspects of the transfer hydrogenation reactions. The detailed mechanistic studies of the reaction
have not been performed here, as it was well explained by Bäckvall [17]. Therefore, in the
present study, only the most crucial part of the catalytic reaction has been highlighted.
O
OH
Isopropanol, NaOH
Ru-Catalyst
83oC, 2-5h
Y
Y
[Y = H, OCH3, Cl, Br, NO2]
Scheme 2. Reduction of ketones.
In a typical hydrogenation reaction, the basic requirements are formation of metal
hydride species and a free coordination site for maintaining the catalytic cycle [17]. In our study,
the hydride formation is proposed to occur as usual from substitution of the chloride by
isopropoxide (generated from 2-propanol and base), followed by β-elimination [17]. These facts
were well explained in our previous study for similar complexes [11b].
6

The generation of a vacancy can be provided either by (i) dissociation of the CO group
[10c] or (ii) the partial dissociation of the chelate ligand [17] as proposed previously for similar
catalyst precursors. In the case of 1a-1d, the first proposition is applicable as the catalytic
activity is inhibited when the reactions are performed under CO atmosphere (1 atm). This is
consistent with the dissociation of CO, which provides the required vacant site on the metal for
substrate coordination. Such observation was also reported in our earlier studies [11b]. The
dissociation of a CO group in 1a-1d during the catalytic cycle was confirmed by IR
spectroscopy; the IR spectra exhibit intense υCO bands from 1983-1963 cm-1 (table 2), which
corresponds to monocarbonyl Ru(II) species.
The higher catalytic activities of 1a and 1b over 1c and 1d in the first run may be due to
easier CO dissociation caused by ‘soft’ phosphorus donors which stabilize metal ions in low
oxidation state by dπ-σ* back bonding. However, the Ru-CO bonds in 1c and 1d are partially
stabilized due to the presence of σ donor oxygen along with phosphorus donor and hence retard
the catalytic activity. Amongst 1a and 1b, 1a shows higher catalytic activity than 1b due to the
chelate effect of the diphosphine (PP) ligands. Similarly, 1d shows less activity than 1a-1c
because of formation of less stable seven-membered chelate ring by Ph2P(CH2)3P(O)Ph2.
However, during recycling experiments, the catalytic activities of 1a, 1b and 1d reduce
significantly due to partial decomposition of the catalyst to ruthenium black during catalysis and
hence become unfavorable to reuse for several runs. Such decomposition is not observed in the
case of 1c during catalytic cycle. This suggests that the ligand remains bound to the metal center
to stabilize the catalyst and hence catalysis with similar efficiency.
To establish the fate of the catalysts, the organometallic residues of 1a-1d (termed as
1a*-1d*, respectively) after completion of the reactions were collected and their spectroscopic
investigations (viz. IR, 1H NMR and 31P NMR) were carried out. The significant IR, 1H NMR
and 31P NMR data are summarized in table 2. The IR data of 1a*-1d* show υCO and υRu-H
stretching in the range 1963-1983 and 1910-1922 cm-1, respectively, substantiating the formation
of monocarbonyl hydrido species. The appearance of IR, 1H and 31P NMR data of 1a*-1c*
(table 2) suggests the probable formation of dihydrido Ru(II) catalytic precursors, whereas the
spectroscopic data of 1d* indicates the formation of a mixture of mono and dihydrido species. In
both 1c* and 1d*, the P=O group remains bonded to ruthenium as evidenced by υP=O stretching
and 31P NMR data of P=O ligands in the complexes. Attempts were made to establish the
7

structural features of the organometallic residues (1a*-1d*) by single crystal X-ray diffraction,
but failed as no suitable crystals could be developed despite several attempts.
4. Conclusion
Four Ru(II) complexes, [RuCl2(CO)2(ƞ2-PP)] (1a,1b) and [RuCl2(CO)2(ƞ2-PO)] (1c,1d) have
been synthesized and characterized. The complexes are active in catalyzed transfer
hydrogenation of acetophenone and its derivatives to corresponding alcohols with turnover
frequency (TOF) of 75-290 h-1, which are higher than the activity of RuCl3. Among 1a-1d, the
Ru(II) complexes of bidentate phosphine (1a, 1b) show higher efficiency than their monoxide
analogues (1c, 1d). However, the recycling experiments with the catalysts for a selected
hydrogenation of 4-nitroacetophenone exhibit a different trend in which the catalytic activities of
1a, 1b and 1d decrease considerably, while 1c shows similar activity during the second run.
Acknowledgement
The author B. Deb is grateful to UGC for financial supports vide fund No. F.5-208/2015-
16/MRP/NERO/1103, dated 29-03-2016. Thanks are also to CSIR-North East Institute of
Science and Technology, Jorhat, Assam, for the instrumental and literature support.
References
[1]
(a) M. Arisawa, T. Yamada, S. Tanii, Y. Kawada, H. Hashimoto M. Yamaguchi. Chem.
Commun., 52, 13580 (2016). (b) H. Fernandez-Perez, P. Etayo, A. Panossian, A. Vidal-
Ferran. Chem. Rev., 111, 2119 (2011). (c) A. Bader, E. Lindler. Coord. Chem. Rev., 108,
27 (1991). (d) R.W. Wegman, A.G. Abatjoglou, A.M. Harrison. J. Chem. Soc., Chem.
Commun., 1891 (1987).
[2]
(a) D.K. Dutta, B. Deb. Coord. Chem. Rev., 255, 1686 (2011). (b) D.K. Dutta, B. Deb,
B.J. Sarmah, J.D. Woollins, A.M.Z. Slawin, A.L. Fuller, R.A. Randall. Eur. J. Inorg.
Chem., 835 (2011). (c) D.K. Dutta, J.D. Woollins, A.M.Z. Slawin, D. Konwar, P. Das, M.
Sharma, P. Bhattacharya, S.M. Aucott. Dalton Trans., 2674 (2003). (d) P. Das, M.
Sharma, N. Kumari, D. Konwar, D.K. Dutta. Appl. Organomet. Chem., 16, 302 (2002).
(e) D.K. Dutta, B. Deb, G. Hua, J.D. Woollins. J. Mol. Catal. A, 353–354, 7 (2012).
T.C. Blagborough, R. Davis, P. Ivison. J. Organomet. Chem., 467, 85 (1994).
[3]
8

[4]
[5]
A.G. Abatjoglou, L.A. Kapicak, US Patent, 429161 (1984).
(a) S.A. Burgess, A.J. Kendall, D.R. Tyler, J.C. Linehan, A.M. Appel. ACS Catal., 7,
3089 (2017). (b) D. Bezier, O. Daugulis, M. Brookhart. Organometallics, 36, 443 (2017).
(c) A. Mukherjee, P. Paul, S. Bhattacharya. J. Organomet. Chem., 834, 47 (2017). (d) M.
Rosales, H. Perez, F. Arrieta, R. Izquierdo, C. Moratinos, P.J. Baricelli. J. Mol. Catal. A
Chem., 421, 122 (2016).
[6]
[7]
(a) A.R. Sanger. Can. J. Chem., 61, 2214 (1983). (b) K.Y. Monakhov, E.V. Grachova,
G.L. Starova, T. Zessin, G. Linti. J. Organomet. Chem., 714, 22 (2012).
(a) B. Deb, P.P. Sarmah, K. Saikia, A.L. Fuller, R.A.M. Randall, A.M.Z. Slawin, J.D.
Woollins, D.K. Dutta. J. Organomet. Chem., 696, 3279 (2011). (b) E. Hauptman, P.J.
Fagan, W. Marshall. Organometallics, 18, 2061 (1999). (c) J. Michalski, Z.
Skrzypzynski. J. Organomet. Chem., 97, C 31 (1975).
[8]
[9]
(a) V. Ritleng, C. Sirlin, M. Pfeffer. Chem. Rev., 102, 1731 (2002). (b) For books
covering this field, see: S.I. Murahashi (Ed.), Ruthenium in Organic Synthesis, Wiley-
VCH, Weinheim (2004). (c) C. Bruneau, P.H. Dixneuf (Eds.), Ruthenium Catalysts and
Fine Chemistry, Topics in Organometallic Chemistry, Vol. 11, Springer, Berlin (2004).
(d) B.M. Trost, M.U. Fredericksen, M.T. Rudd. Angew. Chem. Int. Ed., 44, 6630 (2005).
(a) T. Touge, H. Nara, M. Fujiwhara, Y. Kayaki, T. Ikariya. J. Am. Chem. Soc., 138,
10084 (2016). (b) X. Chen, Y. Jing, X. Yang. Chem. Eur. J., 22, 1950 (2016). (c) B.
Xiong, J. Jiang, S. Zhang, H. Jiang, Z. Ke, M. Zhang. Org. Lett., 19, 2730 (2017). (d) C.
Kerner, J. Lang, M. Gaffga, F.S. Menges, Y. Sun, G.N. Scaatteburg, W.R. Thiel.
ChemPlusChem, 82, 212 (2017). (e) M.D. Rebollo, D.C. Gonzalez, M. Hollering, H.M.
Bunz, M. Albrecht. Dalton Trans., 43, 4462 (2014).
[10] (a) A.H. Obaid, N.G. Stracey, C.D. Incarvito, B.Q. Mercado, J. Parr. J. Organomet.
Chem., 830, 74 (2017). (b) J.S.M. Samec, J.E. Backvall, P.G. Andersson, P. Brandt.
Chem. Soc. Rev., 35, 237 (2006). (c) J. Albers, V. Cadierno, P. Crochet, S.E. Garcia-
Garrido, J. Gimeno. J. Organomet. Chem., 692, 5234 (2007). (d) M.B. Diaz-Valenzuela,
S.D. Phillips, M.B. France, M.E. Gunn, M.L. Clarke. Chem. Eur. J., 15, 1227 (2009).
(e) R. Noyori, S. Hashiguchi. Acc. Chem. Res., 30, 97 (1997). (f) R. Noyori, T. Ohkuma.
Angew. Chem. Int. Ed., 40, 40 (2001). (g) N. Mohan, R. Ramesh. Appl. Organomet.
Chem., 31, e3648 (2017).
9

[11] (a) B. Deb, B.J. Borah, B.J. Sarmah, B. Das, D.K. Dutta. Inorg. Chem. Commun., 12, 868
(2009). (b) B. Deb, P.P. Sarmah, D.K. Dutta. Eur. J. Inorg. Chem., 1710 (2010).
[12] (a) V. Cadierno, P. Crochet, J. Diez, S.E. Garcia-Garrido, J. Gimeno. Organometallics,
22, 5226 (2003). (b) V. Cadierno, P. Crochet, J. Díez, J. García-Álvarez, S.E. García-
Garrido, S. García-Granda, J. Gimeno, M.A. Rodríguez. Dalton Trans., 3240 (2003).
(c) D. Pandiarajan, R. Ramesh. Inorg. Chem. Commun., 14, 686 (2011).
[13] S. Rajagopal. J. Mol. Cat., 81, 185 (1993).
[14] (a) M.F. Mahon, M.K. Whittlesey, P.T. Wood. Organometallics, 18, 4068 (1999). (b)
J.D. Gargulak, A.J. Berry, M.D. Noirot, W.L. Cladfelter. J. Am. Chem. Soc., 114, 8933
(1992). (c) C.F.J. Barnard, D. Phil. Thesis, The University of York, York, U.K., 197.
(d) C.F.J. Barnard, J.A. Daniels, R.J. Mawby. J.C.S. Dalton, 961 (1976). (e) L.D. Brown,
C.F.J. Barnard, J.A. Daniels, R.J. Mawby, J.A. Ibers. Inorg. Chem., 17, 2932 (1978) (f)
J.M. Bray, R.J. Mawby. J. Chem. Soc., Dalton Trans., 2989 (1987).
[15] (a) B. Deb, D. K. Dutta, Polyhedron, 28, 2258 (2009). (b) B. Deb, B. J. Sarmah, B. J.
Borah, D. K. Dutta, Spectrochim. Acta A, 72, 339 (2009). (c) K. Saikia, B. Deb, J. Mol.
Catal. A: Chem., 381, 188 (2014). (d) B. Deb, D.K. Dutta. Chem. J. Karimganj Coll., 1,
16 (2016).
[16] (a) M.L. Berch, A. Davison. J. Inorg. Nucl. Chem., 35, 3763 (1973). (b) R. Colton, R.H.
Farthing. Aust. J. Chem., 20, 1283 (1967). (c) R.J. Irving. J. Chem. Soc., 2879 (1956).
(d) M.J. Cleare, W.P. Griffith. J. Chem. Soc. A, 372 (1969).
[17] (a) J.S.M. Samec, J.E. Bäckvall, P.G. Andersson, P. Brandt. Chem. Soc. Rev., 35, 237
(2006). (b) J.E. Backvall. J. Organomet. Chem., 652, 105 (2002).
[18] C. Standfest-Hauser, C. Slugovc, K. Mereiter, R. Schmid, K. Kirchner, L. Xiao, W.
Weissensteiner. J. Chem. Soc., Dalton Trans., 2989 (2001).
10

%Yield
Figure 1. The catalytic activity of 1a-1d before and after recycling experiments during transfer
hydrogenation of 4-nitroacetophenone.
11

Table 1. Catalytic transfer hydrogenation of selected substrates by ruthenium
catalysts.
TOF
(h-1)c
Reaction Isolated
time (h) yieldb (%)
Entry Substrate
Catalysts
RuCl3
1a
43.3
98.5
51.9
O
1
118.2
106.1
104.8
79.0
CH3
5
5
1b
88.4
87.3
65.8
35.8
85.0
76.1
75.2
62.3
42.0
95.6
92.4
91.5
80.7
40.5
93.2
90.5
89.5
75.2
51.5
96.3
94.5
92.4
73.3
1c
1d
RuCl3
1a
42.9
O
2
3
4
5
102.0
91.3
CH3
1b
H3CO
1c
90.2
1d
74.8
RuCl3
1a
63.0
O
143.4
138.6
137.2
121.0
60.8
CH3
4
4
2
1b
Cl
1c
1d
RuCl3
1a
O
139.8
135.8
134.3
112.8
154.5
288.9
283.5
277.2
219.9
CH3
1b
Br
1c
1d
RuCl3
1a
O
CH3
1b
O2N
1c
1d
aYield: Calculated with respect to substrate only
bTOF = [amount of product (mol)/amount of catalyst (Ru mol)]/time (hour)].
12

Table 2. Important IR, 1H NMR and 31P NMR data of 1a*-1d*.
Recovered
catalysts
IR data (cm-1)
1H NMR (δ/ppm)
31P NMR (δ/ppm)
1a*
1963 (νCO)
-7.9 (dd, JP-H = 28.5 Hz,
JH-H = 5.8 Hz, Ru-H)
52.5 (d, JP-P = 68.3 Hz)
1920 (νRu-H
)
)
)
1b*
1c*
1974 (νCO)
1922 (νRu-H
-6.8 (d, JH-H = 5.8 Hz, Ru-H) 25.3, 33.5 (s, PIII)
-5.9 (d, JH-H = 5.8 Hz, Ru-H)
1977 (νCO)
1910 (νRu-H
-6.9 (d, JP-H = 32.5, Ru-H)
-7.5 (d, JP-H = 32.5, Ru-H)
20.5 (s, PIII)
58.3 (s, PV)
1172 (νP-O
)
1d*
1983, 1979 (νCO)
-7.6 (d, JP-H = 14.2, Ru-H)
21.4, 24.3 (s, PIII)
58.9, 62.3 (s, PV)
1918, 1912 (νRu-H) -6.8 (dd, JP-H = 43.2 Hz,
JH-H = 5.6 Hz, Ru-H)
1162 (νP-O
)
-8.3 (dd, JP-H = 36.4 Hz,
JH-H = 5.6 Hz, Ru-H)
13