Synthesis and characterization of ruthenium(II) complexes based on diphenyl-2-pyridylphosphine and their applications in transfer hydrogenation of ketones

Article abstract of DOI:10.1016/j.ica.2010.12.057

Synthesis and characterization of the ruthenium complexes [RuH(CO)Cl(κ¹-P-PPh₂Py)₂(PPh ₃)] (1) and [Ru(CO)Cl₂(κ¹-P-PPh ₂Py)(κ²-P-N-PPh₂Py)] (2) containing diphenyl-2-pyridylphosphine (PPh₂Py) are described. Spectral and structural data suggested linkage of the PPh₂Py in κ¹-P bonding mode in 1 and both the κ¹-P and κ²-P-N bonding modes in 2. The complex 1 reacted with N,N-donor bases viz., ethylenediamine (en), N,N′-dimethyl-(ethylenediamine) (dimen), 1,3-diaminopropane (diap), 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) and di-2-pyridylaminomethylbenzene (dpa) to afford cationic complexes of formulation [RuH(CO)(κ¹-P-PPh ₂Py)₂(N-N)]⁺ (3-8) [N-N = en, 3; dimen, 4; diap, 5; bipy, 6; phen, 7; and dpa, 8], which have been isolated as their tetrafluoroborate salts. The complexes under investigation have been characterized by elemental analyses, spectroscopic and electrochemical studies. Molecular structures of 2, 3, 6, and 8 have been determined by single crystal X-ray diffraction analyses. Further, the complexes 1-8 act as effective precursor catalyst in transfer hydrogenation of acetophenone/ketones in basic 2-propanol.

Full text of DOI:10.1016/j.ica.2010.12.057

Inorganica Chimica Acta 368 (2011) 124–131
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and characterization of ruthenium(II) complexes based
on diphenyl-2-pyridylphosphine and their applications in transfer
hydrogenation of ketones
Prashant Kumar a, Ashish Kumar Singh a, Mahendra Yadav a, Pei-zhou Li b, Sanjay Kumar Singh b, Qiang Xu b,
Daya Shankar Pandey a,
⇑
a Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, UP, India
b National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
a r t i c l e i n f o
a b s t r a c t
Synthesis and characterization of the ruthenium complexes [RuH(CO)Cl(j
1-P-PPh2Py)2(PPh3)] (1) and
Article history:
Received 24 May 2010
Received in revised form 18 December 2010
Accepted 21 December 2010
Available online 30 December 2010
[Ru(CO)Cl2(
j j
1-P-PPh2Py)( 2-P–N-PPh2Py)] (2) containing diphenyl-2-pyridylphosphine (PPh2Py) are
described. Spectral and structural data suggested linkage of the PPh2Py in
j
1-P bonding mode in 1 and
both the j j
1-P and 2-P–N bonding modes in 2. The complex 1 reacted with N,N-donor bases viz., ethy-
lenediamine (en), N,N0-dimethyl-(ethylenediamine) (dimen), 1,3-diaminopropane (diap), 2,20-bipyridine
(bipy), 1,10-phenanthroline (phen) and di-2-pyridylaminomethylbenzene (dpa) to afford cationic com-
Keywords:
Ruthenium
Diphenyl-2-pyridylphosphine
Diamine
Diimine
plexes of formulation [RuH(CO)(j
1-P-PPh2Py)2(N-N)]+ (3–8) [N-N = en, 3; dimen, 4; diap, 5; bipy, 6; phen,
7; and dpa, 8], which have been isolated as their tetrafluoroborate salts. The complexes under investiga-
tion have been characterized by elemental analyses, spectroscopic and electrochemical studies. Molecu-
lar structures of 2, 3, 6, and 8 have been determined by single crystal X-ray diffraction analyses. Further,
the complexes 1–8 act as effective precursor catalyst in transfer hydrogenation of acetophenone/ketones
in basic 2-propanol.
Acetophenone
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
Highly active catalyst precursors of the type [trans-RuCl2(diphos-
phine)(1,2-diamine)] for selective hydrogenation of ketones have
The phosphines are indispensable ligands in transition metal
catalyzed reactions. Their electronic and steric effects have a pro-
nounced influence on organic transformations that take place at
the transition metal centers [1–3]. In this context, hetero bifunc-
tional phosphines containing ‘‘soft’’ phosphorus and ‘‘hard’’ nitro-
gen/oxygen donor atoms have drawn special attention [4–11].
These phosphines display interesting properties such as selective
binding to various types of metal ions (hard and soft), dynamic
behavior via reversible dissociation of the weaker metal–ligand
bonds and stereo-electronic control about the metal centers [11].
It has been demonstrated that complexes containing ‘‘Ru–(P–N)’’
(P–N = pyridylphosphine) moieties serve as efficient catalysts in
homogeneous catalytic hydrogenation reactions. Therefore a large
number of ruthenium complexes containing hetero-bifunctional
phosphines have been synthesized and their properties studied
by spectroscopic and electrochemical techniques [12–19]. Further-
more, a number of homogeneous hydrogenation catalysts based on
ruthenium complexes have been reported in the literature [9–11].
been developed by Noyori et al. They have established that when
diphosphine is chiral and diamine (H2N–NH2) is achiral, it can gen-
erate alcohol as the product with high ee values [20–22]. It has
been proposed that such reactions follow metal–ligand bifunc-
tional catalysis or so called ionic hydrogenation wherein substrate
is not directly bonded to the metal center rather it involves an out-
er sphere H-bonding interaction between the ‘‘RuH–NH’’ unit and
ketone, with added H2 derived from metal hydride and an amine
proton [23–25]. Notably, hydrogenation of substrates via a mecha-
nism excluding direct bonding of substrate at the metal center has
been demonstrated in late 1960’s [26,27].
Hydrogen transfer (HT) catalysis is an attractive protocol in the
reduction of ketones to alcohol. Ru(II) complexes are generally em-
ployed as the most useful catalysts for such reactions [3,28–33]. To
develop and explore hydrogen transfer catalysts in the present
study, we choose PPh2Py as a versatile ligand which may bind
the metal center in a monodentate, chelating or bridging mode
depending upon requirements at the reaction center [34–39]. In
its chelating coordination mode it forms four membered rings
which are strained, relatively unstable and plays a vital role in
catalysis [40–44]. In this paper we reported the syntheses, charac-
terization and reactivity of hydrido carbonyl ruthenium(II)
⇑
Corresponding author. Tel.: +91 542 6702480; fax: +91 542 2368174.
E-mail address: dspbhu@bhu.ac.in (D.S. Pandey).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.12.057

P. Kumar et al. / Inorganica Chimica Acta 368 (2011) 124–131
125
complexes containing PPh2Py and various bidentate N,N-donor
2.2. X-ray crystallography
bases. Also, we describe herein crystal structures of 2, 3, 6 and 8
and application of 1–8 as catalyst precursors for hydrogen-transfer
activity in the reduction of ketones to alcohol in basic 2-propanol.
In search of new procedures for bleaching pulp some of the sub-
strates were chosen as a model for chromophore units present in
lignin, the aim of hydrogenation being to reduce the degree of
conjugation in lignin [45].
Molecular structures of 2, 3, 6, and 8 have been determined
crystallographically. ORTEP views at 30% thermal ellipsoid proba-
bility with atom numbering scheme is shown in Figs. 1–4. Details
about the data collection, solution and refinement are given in
the Section 3 and important geometrical parameters are summa-
rized below the Figs. 1–4. It should be noted that the ligand di-2-
pyridylaminomethylbenzene in 8 is disordered however overall data
strongly supported the proposed formulation. Further, the ligand di-
2-pyridyl-aminomethylbenzene coordinated to metal center
ruthenium in complex 8 in bidentate manner.
2. Results and discussion
2.1. Synthesis and characterization
Crystal structure of 2 exhibited that the ligand PPh2Py is coordi-
nated to ruthenium in a P,N-chelating mode forming a four
membered chelate ring with a bite angle of 68.10(12)°. Distorted
octahedral coordination geometry about the metal center in
this complex is evidenced by the angles P1–Ru–P2, P1–Ru–N1,
Cl1–Ru–Cl and C36–Ru1–Cl1 which are 104.16(5)°, 68.10(12)°,
89.73(4)° and 175.39(16)°, respectively. Ru1–P1 and Ru1–N1 bond
distances in this complex are 2.320(12) and 2.143(4) Å, respec-
tively which lies within the reported range [47,48]. The complexes
3, 5, and 8 (Figs. 2–4) displayed analogous structural features. In its
crystal structure, these exhibited distorted octahedral geometry
about the ruthenium center completed by nitrogen from bidentate
diamine/diimine ligands, PPh2Py phosphorus, hydride and car-
bonyl carbon. The angles N1–Ru–N2 in 3 and 6 are 77.3(3)° and
The ruthenium complex RuH(CO)Cl(PPh3)3 reacted with hetero-
bifunctional phosphine PPh2Py in benzene under refluxing condi-
tions to afford P-coordinated neutral complex [RuH(CO)Cl
(j
1-P-PPh2Py)2(PPh3)]. In presence of an excess of NH4Cl in meth-
anol the complex
PPh2Py)] (2), containing both the
1
yielded [Ru(CO)Cl2(
j
1-P-PPh2Py)(
j
2-P–N-
j
1-P and
j
2-P–N bonded PPh2Py
(Scheme 1). On the other hand, reactions of 1 with N,N-donor bases
viz., ethylenediamine (en), N,N0-dimethyl-(ethylenediamine) (di-
men), 1,3-diaminopropane (diap), 2,20-bipyridine (bipy), 1,10-
phenanthroline (phen), and di-2-pyridylaminomethylbenzene
(dpa) gave cationic complexes of the formulations [RuH(CO)
(j
1-P-PPh2Py)2(N–N)]+ (3–8) [N–N = en, 3; dimen, 4; diap, 5; bipy,
6; phen, 7; and dpa, 8], which were isolated as their tetrafluorobo-
rate salts.
The complexes 1–8 are air-stable, non-hygroscopic crystalline
solids, soluble in halogenated solvents viz., chloroform, dichloro-
methane, and insoluble in benzene, hexane, n-pentane, diethyl
ether and petroleum ether. Characterization of the complexes un-
der study has been achieved by means of standard spectroscopic
techniques (FAB-MS, IR, 1H and 31P{1H}NMR, electronic absorption
and electrochemical studies) as well as elemental analyses. FAB
mass spectral data supported formation of the respective com-
plexes. Resulting data along with their assignments are summa-
rized in Section 3 and representative spectra for 1–3, 6 and 7 are
depicted in Figs. S1–S5 (supporting information). The position
and overall fragmentation pattern of respective complexes con-
formed well to their formulations.
IR spectra of 1–8 displayed vibrations associated with
m(C@N)
and (C@C) along with the bands corresponding to coordinated
m
m
m
(CO) and
(C„O) and
m
(Ru–H) (Section 3). Interestingly, the position of
m(Ru–H) displayed shift towards higher and lower fre-
quency, respectively. It indicated a decrease in the metal to car-
bonyl carbon interaction and an increase in Ru–H bond order. In
the precursor complex RuH(CO)Cl(PPh3)3, band associated with
Fig. 1. Molecular structure of 2 and selected bond lengths (Å) and angles (°): Ru1–
Cl 2.4393(13), Ru1–Cl1 2.4315(13), Ru1–C36C„O 1.843(5), Ru1–P1 2.3207(12),
Ru1–P2 2.3224(13), N1–Ru1–P1 68.10(12), N1–Ru1–P2 171.86(12), P1–Ru1–P2
104.16(5), P1–Ru1–Cl1 93.77(4), P2–Ru1–Cl1 90.30(5), Cl1–Ru1–Cl 89.73(4),
N1–Ru1–Cl 91.31(12), N1–Ru1–Cl1 87.77(11), N1–Ru1–C36C„O 90.52(19), P1–
Ru1–C36C„O 89.55(15), P2–Ru1–C36 91.99(16), O1–Ru1–C36C„O 175.7(5),
Cl–Ru1–C36C„O 86.03(15), Cl1–Ru1–C36C„O 175.39(16).
m
(C„O) stretches at 1918 cmꢀ1 while in complex 1 it vibrated at
1938 cmꢀ1. It shows that the PPh2Py in 1 is relatively poor
electron donor in comparison to PPh3 in precursor complex
RuH(CO)Cl(PPh3)3 [46].
Scheme 1. Preparation of 1–8.

126
P. Kumar et al. / Inorganica Chimica Acta 368 (2011) 124–131
Fig. 2. Molecular structure of 3 and selected bond lengths (Å) and angles (°): Ru1–
P1 2.3446(18), Ru1–P2 2.3482(19), Ru1–H1 1.60(11), Ru1–N1 2.213(7), Ru1–N2
2.175(7), Ru1–C24C„O 1.761(9), N1–Ru1–N2 77.3(3), P1–Ru1–P2 165.78(6), N1–
Ru1–P1 98.35(19), N1–Ru1–P2 95.70(19), N2–Ru1–P1 92.05(18), N2–Ru1–P2
93.15(18), N1–Ru1–H1 169(4), N2–Ru1–H1 93(3), P1–Ru1–H1 88(4), P2–Ru1–H1
79(4), C24C„O–Ru1–N1 97.6(4), C24C„O–Ru1–N2 174.3(4), C24C„O–Ru1–P1
86.2(3), C24C„O–Ru1–P2 89.9(3), C24C„O–Ru1–H1 92(3), O1–Ru1–C24C„O
179.0(8).
Fig. 4. Molecular structure of 8 and selected bond lengths (Å) and angles (°): Ru1–
P1 2.373(3), Ru1–H1 1.00(2), Ru1–N1 2.177(9), Ru1–N3 2.234(9), Ru1–C33C„O
1.847(14), N1–Ru1–N3 83.7(4), P1–Ru1–P1 167.76(11), N1–Ru1–P1 90.65(6), N3–
Ru1–P1 96.12(5), N1–Ru1–H1 79(4), N3–Ru1–H1 162(4), P1–Ru1–H1 84.16(13),
C33C„O–Ru1–N1 176.0(5), C33C„O–Ru1–N3 100.3(4), C33C„O–Ru1–P1 88.93(7),
C33C„O–Ru1–H1 97(4), O1–Ru1–C33C„O 177.0(11). The unlabeled part is gener-
ated by symmetry. Symmetry code = x, ꢀy + 1/2, z.
bond lengths are comparable to the bond distances in other closely
related Ru(II) amine complexes [56].
Crystal structures of 2, 3, 6, and 8 revealed the presence of
extensive intermolecular C–HꢁꢁꢁX (X = N, Cl and F) and C–Hꢁꢁꢁ
p
interactions. These interactions play significant role in the building
of huge supramolecular moieties [57]. Some interesting motifs
resulting from weak bonding interactions (intermolecular C–Hꢁꢁꢁ
(2.74 Å) in 8 are shown in Figs. 5 and 6.
p
2.3. NMR spectral studies
The 1H and 31P NMR spectral data of the complexes is summa-
rized in Section 3. Shifts in the position of resonances associated
with various protons of the ligand and 31P nuclei in comparison
to the precursor complex RuH(CO)Cl(PPh3) have been taken as an
evidence for coordination of PPh2Py to the metal center ruthenium.
Metal bound hydride in 1 and 3–8, resonated in high field side at d
ꢀ7.62 (dt, 12 Hz), ꢀ10.34 (t, 21 Hz), ꢀ10.68 (t, 16 Hz), ꢀ10.86 (t,
18 Hz), ꢀ11.34 (t, 17 Hz), ꢀ11.68 (t, 18 Hz), and ꢀ11.78 (t, 23 Hz)
ppm, respectively. The presence of a triplet associated with metal
bound hydride in 1H NMR spectra of respective complexes sug-
gested coupling of the hydride with two 31P nuclei [58,59]. The
31P{1H}NMR spectra of respective complexes like 1H NMR revealed
Fig. 3. Molecular structure of 6 and selected bond length (Å) and angles (°): Ru1–P1
2.3421(13), Ru1–P2 2.3693(13), Ru1–H1 1.49(4), Ru1–N1 2.134(4), Ru1–N2
2.188(4), Ru1–C45C„O 1.847(6), N1–Ru1–N2 75.62(15), P1–Ru1–P2 171.54(4),
N1–Ru1–P1 92.73(11), N1–Ru1–P2 89.11(11), N2–Ru1–P1 98.30(10), N2–Ru1–P2
90.15(10), N1–Ru1–H1 94.1(18), N2–Ru1–H1 169.5(17), P1–Ru1–H1 84.1(16),
P2–Ru1–H1 87.6(16), C45C„O–Ru1–N1 176.9(2), C24C„O–Ru1–N2 107.4(2),
C45C„O–Ru1–P1 86.29(17), C45C„O–Ru1–P2 91.44(17), C24C„O–Ru1–H1
82.9(18), O1–Ru1–C45C„O 176.0(5).
75.62(15)°, respectively, while N1–Ru–N3 in 8 is 83.8(4)°. It sug-
gested inward bending of the diamine/diimine moiety towards
metal center. Further, its lower value in comparison to ideal angle
of 90° is probably the source of observed distortion from octahe-
dral geometry. Ru(1)–P(1) and Ru(1)–P(2) bond distances are
2.345(2) and 2.348(2) Å in 3, 2.342(1) and 2.369(1) Å in 6 and
2.374(3) and 2.374(3) Å in 8. These are essentially equivalent and
comparable to those in other related complexes [49–52]. The
PPh2Py ligands are trans-disposed as indicated by P1–Ru1–P2
angles of 167.76(6)°, 171.54(4)° and 167.90(13)° in 3, 6, and 8,
respectively. Carbonyl carbon bond distances are normal [Ru1–
C24, 1.768(9) Å, 3; Ru1–C45, 1.847(6) Å, 6; and Ru1–C33,
1.842(1) Å, 8] [53]. Ru(1)–H(1) bond distances in 3, 6 and 8 are
1.60(11), 1.49(4) and 1.38(8) Å, respectively. These are shorter in
comparison to those reported in other complexes [54,55]. Ru–N
Fig. 5. Counter anion (BF4ꢀ) encapsulated in self-assembled cavity of complex 8.

P. Kumar et al. / Inorganica Chimica Acta 368 (2011) 124–131
127
Fig. 6. C–Hꢁꢁꢁ
p
interactions in 8 generating zig-zag motif [C(19)–H19BꢁꢁꢁCg {C(7)–C(8)–C(9)–C(10)–C(11)–N(5)} = 3.341 Å (range 2.754–4.287 Å)].
the presence of a single species. 31P{1H}NMR spectrum of 1 exhib-
ited doublets at d 49.54 ppm and a triplet at 46.35 ppm assignable
to the 31P nuclei of coordinated PPh2Py and PPh3. On the other
hand, 2 displayed a singlet at d ꢀ11.10 ppm and doublet at d
30.80 ppm associated with the chelated and unchelated PPh2Py.
It is interesting to note that in complex 2, the 31P nuclei of PPh2Py
exhibited an up-field shift in comparison to the uncoordinated li-
gand (d ꢀ3.9 ppm). It may be attributed to involvement of the
phosphorus nuclei in the formation of a strained four membered
ring about the metal center. In an analogous manner, 31P{1H}NMR
spectra of 3–8 displayed singlets in the region d 40.40–8.02 ppm,
consistent with the octahedral structure containing a C2 axis,
essentially that of the solid state structure with minor distortions.
2.5. Electrochemistry
Electrochemical properties of 3, 6, and 7 have been studied by
cyclic voltammetry using 0.1 M tertabutylammonium perchlorate
(TBAP) as supporting electrolyte. Potential of the Fc/Fc+ couple un-
der experimental conditions was 0.10 V (80 mV) versus Ag/Ag+.
Resulting data is summarized in Table 1 and selected voltammo-
grams are depicted in Fig. S6 (supporting information). In the ano-
dic potential window, 3 displayed an irreversible peak at 0.83 V,
which has been assigned to RuII/III oxidation. On the other hand,
three irreversible peaks at ꢀ0.48, ꢀ0.96 and ꢀ1.31 V in cathodic
potential window have been assigned to stepwise reduction of
the N,N-donor ligands ‘en’. The complexes 6 and 7 in its cyclic vol-
tammogram exhibited oxidative responses at 0.78 (63) and 0.72
(75) V, respectively assignable to RuII/III oxidations. The oxidations
in 6 and 7 are reversible and characterized by a peak-to-peak sep-
aration (dEp) of ꢂ100 mV and the anodic peak current (ipa) is al-
most equal to cathodic peak current (ipc), which is expected for a
reversible one electron-transfer process. The higher potential re-
quired for oxidation of the metal center in 6 as compared to that
2.4. Electronic absorption spectral studies
The electronic absorption spectra of 1–8 were acquired in ace-
tonitrile (10ꢀ4 M) at room temperature. Resulting data is summa-
rized in the Section 3 and spectra of 3 and 5–8 are depicted in
Fig. 7. Ruthenium(II) hydrido complexes usually exhibit intense
peaks in the UV region corresponding to ligand based p–
p⁄ transi-
in 7, may be attributed to coordination of a
p-acceptor ligand. As
phen is better -acceptor in comparison to bipy, the oxidation in
p
tions with overlapping metal-to-ligand charge transfer (MLCT)
transitions in the visible region [60,61]. An analogous general pat-
tern has been observed in the electronic absorption spectra of com-
plexes under study. The complexes 1–8 displayed intense
transitions in the UV–Vis region. On the basis of its intensity and
position, the lowest energy transitions in the visible region at
ꢂ488–411 and 393–335 nm have been tentatively assigned to
7 takes place at lower potential in comparison to 6. In the cathodic
potential window, 6 and 7 displayed three irreversible peaks at
ꢀ1.32, ꢀ1.41, ꢀ1.92 V (6) and ꢀ1.22, ꢀ1.33, ꢀ1.87 V (7), which
may be assigned to the stepwise reduction of diimine ligands.
2.6. Transfer hydrogenation of ketones
Md ? L metal to ligand charge transfer transitions (MLCT).
p⁄
p
Bands in the high-energy side at ꢂ243–288 nm have been assigned
Ruthenium complexes with the formulations [RuCl2(P–P)(N–N)]
have been utilized as hydrogenation precursor catalysts using 2-
propanol as the source of hydrogen [20,23–25,62–65]. To examine
applicability of the complexes under study as catalysts, these were
tested for hydrogenation of acetophenone in basic 2-propanol
solution at 80 °C, (Eq. (1), Table 2), using the complex (0.01 mmol),
added KOH (0.2 mmol), and ketone (1.2 g, 10.0 mmol) at a catalyst/
base/substrate (Cat/Base/S) ratio of 1:20:1000. Resulting data indi-
cated that 1–8 are reasonably good hydrogen-transfer catalysts in
an inert atmosphere.
to intra-ligand
p
?
p⁄/n ? p⁄ transitions [60]. Absorption bands at
ꢂ251, 257 and 249 nm in the spectra of 6, 7, and 8, respectively
have been assigned to
imine ligands [61].
p ?
p⁄ transitions associated with aromatic
PhCOCH3 þ ðCH3Þ CHðOHÞ catalyst;KOH
PhCHðOHÞCH3 þ ðCH3Þ2CO
!
2
80ꢃ
C
ð1Þ
A ‘‘blank’’ experiment was performed in the absence of ruthe-
nium complexes (using 0.02 M KOH and 1.0 M acetophenone in
Table 1
Cyclic voltammetric data of the complexes.
Complex
E1/2 (V)
E1/2 (V)
Ru II/III
Ligand centered
3
6
7
0.83*
0.78(63)
0.72(75)
ꢀ0.48, ꢀ0.96, ꢀ1.31
ꢀ1.32, ꢀ1.41, ꢀ1.92
ꢀ1.22, ꢀ1.33, ꢀ1.87
*
Irreversible peak.
Fig. 7. UV–Vis spectra of 3 and 6–8.

128
P. Kumar et al. / Inorganica Chimica Acta 368 (2011) 124–131
Table 2
Table 3
Catalyzed hydrogen-transfer hydrogenation of acetophenone.a
Transfer-hydrogenation of substrates catalyzed by 3.
Precursor catalysts
Conversion (%)
Substrate
Structure
Conversiona (%)
94
[Ru(CO)ClH(
j
1-P-PPh2Py)2(PPh3)] (1)
2-P-N-PPh2Py)( 1-P- PPh2Py)] (2)
86
81
94
88
84
80
92
90
42
Acetophenone
O
[Ru(CO)Cl2(
j
j
[Ru(CO)H(
[Ru(CO)H(
[Ru(CO)H(
[Ru(CO)H(
[Ru(CO)H(
[Ru(CO)H(
j
j
j
j
j
j
1-P-PPh2Py)2(en)]BF4 (3)
1-P-PPh2Py)2(dimen)]BF4 (4)
1-P-PPh2Py)2(diap)]BF4 (5)
1-P-PPh2Py)2(bipy)]BF4 (6)
1-P-PPh2Py)2(phen)]BF4.(7)
1-P-PPh2Py)2(dpa)]BF4 (8)
4-Methylacetophenone
96
O
[RuCl(p-cymene)]2(l-Cl)2
a
Experimental conditions (see Section 3): Reactions were carried out at 80 °C for
24 h, catalyst:base:substrate being 1:20:1000.
4-Phenyl-2-butanone
86
76
O
2-propanol, S/base = 50). It showed ꢂ15% conversion of acetophe-
none after 24 h, however higher concentration of KOH (0.66 M
KOH, S/base = 1.5), exhibited 86% conversion. Such metal free base
catalysed conversions are well documented in literature [66,67].
Complexes 1–8 gave ꢂ65% conversion after 5 h and relative activ-
ity sequence was en ꢂphen > dpa > bipy ꢂ dimen (up to ꢂ12 h).
Conversion versus time plots for PPh2Py containing precursor cat-
alysts 3, and 5–8 is depicted in Fig. 8. Activities of the imine con-
taining complexes were found to be comparable to those of
amine based complexes. It suggested that active hydrogen on
nitrogen are not essential for hydrogenation and mechanisms
other than ionic such as more classical ‘‘hydride’’ or ‘‘unsaturated’’
mechanisms may be operative [20,23–25,63,68–70]. Such findings
for ‘‘NH-free’’ active Ru(II) systems are not novel and have been de-
scribed in literature [32]. Hydrogenation catalysed by 3 followed
bifunctional mechanism in which ‘‘RuH–NH’’ unit plays a signifi-
cant role. For example in first 3 h at 80 °C, conversion achieved
using 3 was almost twice in comparison to that observed in pres-
ence of 4, a factor consistent with the fact that 3 statistically has
twice as many H atoms available compared to 4 for forming the re-
quired H-bonded reaction intermediates.
4-Methoxypropiophenone
O
OMe
O
Acetovanillone
16
OMe
OH
a
Isolated yield after column chromatography.
Data for the reduction of respective ketones to alcohol is
illustrated in Table 2. Reduction of C@C bond in styrene was
not observed when lignin model compound 3,4-dimethoxystyrene
was tested as the substrate under analogous hydrogen-
transfer conditions, further demonstrating general selectivity of
hydrogenation of acetophenone (Table 3). This catalyst system was
tested for several alkyl-aryl ketones selected as model substrate for
carbonyl components of the lignin (see Table 3). It was observed
that the substituents like p-Me and p-OMe on aryl moiety do not
seriously inhibit hydrogenation process however, introduction of
a p-OH group influences the course of reaction, as evidenced by
ineffective reduction of acetovanillone. The phenyl substituted dial-
kyl ketone 4-phenyl-2-butanone gets readily reduced. Reetz and Li
have recently reported the use of p-cymene containing precursor
[RuH(CO)Cl((j
1-P-PPh2Py)2(N–N)]+ systems in the reduction of
polar C@O bond [8,23–25,65–67]. Among the complexes under
study, 3 and 7 exhibited highest activity towards hydrogen-transfer
[{(g l-Cl)}2] in presence of BINOL-derived diphosph-
6-C10H14)RuCl (
onites for extremely effective asymmetric hydrogen-transfer
hydrogenation (from 2-propanol) of ketones, it is notable that these
systems do not require ancillary diamine ligands [71]. In addition,
Deng’s and Noyori’s group have earlier used the same precursor
in presence of a chiral diamine for hydrogenation of ketones in
either aqueous media using sodium formate or basic 2-propanol
[72,73].
3. Experimental
3.1. Reagents
The solvents were purified by standard procedures prior to its
use [74]. Hydrated ruthenium(III) chloride, diphenyl-2-pyridyl-
phosphine, triphenylphosphine, ethylenediamine, N,N0-dimethyl
(ethylenediamine), 1,3-diaminopropane, 2,20-bipyridine, 1,10-phe-
nanthroline, dipyridylbenzylamine, ammonium tetrafluoroborate,
acetophenone, 4-methylacetophenone, 4-phenyl-2-butanone,
Fig. 8. Conversion of acetophenone vs. reaction time plots for 3 and 5–8.

P. Kumar et al. / Inorganica Chimica Acta 368 (2011) 124–131
129
4-methoxypropiophenone and acetovanillone, (all Sigma–
Aldrich) were used as received without further purifications. The
ligand di-2-pyridylbenzylamine and precursor complex RuH(CO)
Cl(PPh3)3 were synthesized and purified following the literature
procedures [75,76].
25H, Ph (PPh2Py) and (PPh3)]. 31P{1H} NMR (d, ppm): ꢀ10.65 (s),
30.80 (d, J = 16.1 Hz,
j
1-P-N-PPh2Py). IR (KBr pellets, cmꢀ1): 1938
m(CO), 1618, 1584, 1483, 1432, 1354, 1088, 1026, 948, 736, 698.
UV–Vis, kmax, nm (
e
): 482 (6850), 380 (27 070), 288 (26 270).
3.5. Synthesis of [Ru(CO)H(
j
1-P-PPh2Py)2(en)]BF4
3
3.2. General considerations
To a suspension of 1 (87 mg, 0.091 mmol) in methanol (25 mL)
ethylenediamine (en) (0.1 mmol) was added and refluxed for 8 h,
whereupon orange suspension turned yellowish-green. After cool-
ing to room temperature it was concentrated under reduced pres-
sure to about 5 mL and a saturated solution of ammonium
tetrafluoroborate dissolved in methanol was added to it. It gave a
yellow product which was filtered, washed twice with diethyl
ether (2 ꢄ 5 mL) and dried under vacuum. Yield: 74 mg (94%).
Microanalytical data C37H37BN4OF4P2Ru requires: C, 55.31; H,
4.64; N, 6.97. Found: C, 55.34; H, 4.62; N, 6.87%. FAB-MS [m/z,
Elemental analyses for C, H and N were performed on an Exeter
Analytical Inc. Model CE-440 Elemental analyser. IR and electronic
absorption spectra were acquired on a Varian 3300 FT-IR and
Shimadzu UV-1700 series spectrometers, respectively. 1H and 31P
NMR spectra were obtained on a JEOL AL 300 FT-NMR spectrome-
ter at room temperature in CDCl3. Residual protonated species in
the deuterated solvents were used as internal references, all the
1H shifts (s = singlet, d = doublet, t = triplet, sept = septet, m = mul-
tiplet, br = broad) are reported relative to external TMS, while
31P{1H} NMR shifts relative to external aqueous H3PO4 (85%) and
J values are given in Hz. FAB mass spectra were obtained on a JEOL
SX 102/Da-600 Mass Spectrometer. Cyclic voltammetric measure-
ments were performed on a CHI 620c Electrochemical Analyzer.
A platinum working electrode, platinum wire auxiliary electrode
and Ag/Ag+ reference electrode were used in a standard three-
electrode configuration. Tetrabutylammonium perchlorate (TBAP)
was used as supporting electrolyte and solution concentration
was ca. 10ꢀ3. The potential of Fc/Fc+ couple under experimental
conditions was 0.10 V (80 mV) versus Ag/Ag+.
obs. (calcd.) assignments]: 716.7 (716) [RuH(CO)(
j
1-P-PPh2Py)2
(en)]+; 453.5 (453) [RuH(CO)( 1-P-PPh2Py)(en)]+. 1H NMR (d
j
ppm): 1.55 (br s, 4H, NH2), 2.70 (br s, 4H, CH2), 8.42 [d, 1H, H6
py (PPh2Py)], 7.90 [m, 1H, H3 py(PPh2Py)], 7.80–7.66 [m, 4H, H2
Ph (PPh2Py)], 7.24 (m, 1H, H5 py (PPh2Py), 6.68–7.55 [m, 20H, Ph
(PPh2Py)], ꢀ10.34 (t, Ru–H, 21 Hz). 31P{1H} NMR (d ppm): 40.40
(s, PPh2Py). IR (KBr pellets, cmꢀ1): 3329, 3252, 3055, 2938, 2005
m(Ru–H), 1933
m(CO), 1562, 1482, 1434, 1161, 1094, 1028, 750,
694. UV–Vis, kmax, nm (e): 453 (110), 362 (5242), 259 (9160).
The complexes 4–8 were synthesized following exactly the
same procedure as described for 3 using respective bases. Charac-
terization data of these complexes are summarized below.
3.3. Synthesis of [RuH(CO)Cl(j
1-P-PPh2Py)2(PPh3)] 1
3.6. Characterization data of [RuH(CO)(j 4
1-P-PPh2Py)2(dimen)]BF4
To a suspension of RuH(CO)Cl(PPh3)3 (95 mg, 0.1 mmol) in ben-
zene (25 ml), PPh2Py (52 mg, 0.2 mmol) was added and contents of
the flask were refluxed for 6 h whereupon it turned orange. After
cooling to room temperature, benzene was removed under re-
duced pressure and diethyl ether (5 mL) added to it. The orange
product thus obtained was filtered, washed twice with diethyl
ether and dried under vacuum. Yield: 89 mg (94%). Microanalytical
data C53H44N2OP3RuCl requires: C, 66.70; H, 4.65; N, 2.94. Found:
C, 66.64; H, 4.62; N, 2.90%. FAB-MS [m/z, obs. (calcd.) assignments]:
Yield: 75 mg (86%). Microanalytical data C39H39BN4OF4P2Ru re-
quires: C, 56.46; H, 4.74; N, 6.75. Found: C, 56.42; H, 4.68; N, 6.77%.
1H NMR (d ppm): 1.58 (br s, 2H, NH), 2.01 (d, 6H, CH3), 2.92 (br, s,
4H, CH2), 8.38 [d, 1H, H6 py (PPh2Py)], 7.94 [m, 1H, H3 py
(PPh2Py)], 7.88–7.82 [m, 4H, H2 Ph (PPh2Py)], 7.18 [m, 1H, H5 py
(PPh2Py)], 6.72–7.58 (m, 20H, Ph (PPh2Py)], ꢀ10.68 (t, Ru–H,
16 Hz). 31P{1H} NMR (d ppm): 48.06 (s, PPh2Py). IR (KBr pellets,
cmꢀ1): 3292, 3269, 3058, 2919, 2018
1593, 1482, 1434, 1397, 1183, 1180, 1054
820, 696. UV–Vis, kmax, nm ( ): 435 (370), 355 (5420), 243 (5500).
m
(Ru–H), 1936
m(CO), 1625,
954.3 (954) [RuH(CO)Cl(
j
1-P-PPh2Py)2(PPh3)]; 692.1 (692) [RuH
(CO)Cl(
j
1-P-PPh2Py)2]; 428.9 (429) [RuH(CO)Cl(
j
1-P-PPh2Py)]. 1H
m
(BF4ꢀ), 1038, 937,
e
NMR (d ppm): 8.26 [d, 1H, H6 py (PPh2Py)], 7.99 [m, 1H, H3 py
(PPh2Py)], 7.92–7.85 [m, 4H, H2 Ph (PPh2Py)], 7.10 [m, 1H, H5 py
(PPh2Py)], 6.68–7.55 [m, 25H, Ph (PPh2Py) and (PPh3)], ꢀ7.62 (t,
Ru–H, 12 Hz, 1H). 31P{1H} NMR (d ppm): 49.54 (d, PPh2Py) and
3.7. Characterization data of [RuH(CO)(j 5
1-P-PPh2Py)2(diap)]BF4
46.35 (t, PPh3). IR (KBr pellets, cmꢀ1): 2008
m
(Ru–H), 1938
1625, 1593, 1475, 1434, 1394, 1087, 1055, 950, 746, 696. UV–Vis,
kmax, nm ( ): 468 (2680), 371 (6360), 246 (39 300).
m(CO),
Yield: 74 mg (85%). Microanalytical data C38H39BN4OF4P2Ru re-
quires: C, 55.83; H, 4.81; N, 6.85. Found: C, 55.84; H, 4.78; N, 6.88%.
1H NMR (d ppm): 1.59 (s, 4H, NH2), 2.82 (s, 6H, CH2), 9.28 (d, 1H, H6
py (PPh2Py)], 8.64 (m, 1H, H3 py (PPh2Py)], 7.98–7.82 [m, 4H, H2
Ph (PPh2Py)], 7.28 [m, 1H, H5 py (PPh2Py)], 6.82–7.48 (m, 20H,
Ph (PPh2Py), ꢀ10.68 (t, Ru–H, 16 Hz). 31P{1H} NMR (d ppm):
46.36 (s, PPh2Py). IR (KBr pellets, cmꢀ1): 3329, 3313, 3243, 3054,
e
3.4. Synthesis of [Ru(CO)Cl2(j j
2-P-N-PPh2Py)( 1-P-PPh2Py)] 2
To a suspension of 1 (95 mg, 0.1 mmol) in methanol (25 mL) an
excess of NH4Cl was added and contents of the flask were refluxed
for 4 h. Slowly it dissolved and gave a yellow solution which was
filtered to remove any solid residue, concentrated to ꢂ10 mL under
reduced pressure and kept in a refrigerator for slow crystallization.
After 24 h, microcrystalline product separated, which was filtered
washed with diethyl ether and dried under vacuo. Yield: 0.30 g
(72%). Microanalytical data C35H28Cl2N2OP2Ru requires: C, 57.86;
H, 3.88; N, 3.86. Found: C, 57.88; H, 3.84; N, 3.88%. FAB-MS [m/z,
2927, 2014
1092,1046
m
(Ru–H), 1938
m
(CO), 1638, 1560, 1482, 1434,
m
(BF4ꢀ), 1038, 958, 750, 695. UV–Vis., kmax, nm (
e
):
411 (315), 335 (5260), 253 (8745).
3.8. Characterization data of [Ru(CO)H(
6
j
1-P-PPh2Py)2(bipy)]BF4ꢁH2O
Yield: 83 mg (95%). Microanalytical data C45H39BF4N4O2P2Ru
requires: C, 58.90; H, 4.28; N, 6.11. Found: C, 58.88; H, 4.30; N,
6.09%. FAB-MS [m/z, obs. (calcd.) assignments]: 812.8 (812) [RuH
obs. (calcd.) assignments]: 726.5 (726) [Ru(CO)Cl2(
2-P-N-PPh2Py)]; 463.3 (463) [Ru(CO)Cl2( 2-P-N-PPh2Py)]; 427.8
(428) [Ru(CO)Cl(
2-P-N-PPh2Py)]+. 1H NMR (d ppm): 8.45 [d, 1H,
j
1-P-PPh2Py)
(j
j
j
(CO)(j j
1-P-PPh2Py)2(bipy)]+; 784.7 (784) [RuH( 1-P-PPh2Py)2(bi-
H6 py (PPh2Py)], 8.01 [m, 1H, H3 py (PPh2Py)], 7.94–7.88 [m, 4H,
H2 Ph (PPh2Py)], 7.22 (m, 1H, H5 py (PPh2Py)], 6.72–7.58 [m,
py)]+; 521.5 (521) [RuH( 1-P-PPh2Py)(bipy)]+. 1H NMR (d ppm):
j
6.80–8.50 (m, 36H, Ph), ꢀ11.34 (t, Ru–H, 17 Hz). 31P{1H}NMR (d

130
P. Kumar et al. / Inorganica Chimica Acta 368 (2011) 124–131
ppm): 44.20 (s, PPh2Py). IR (KBr pellets, cmꢀ1): 3099, 3076, 3050,
2010 (Ru–H), 1948 (CO), 1482, 1443, 1432, 1164, 1091, 1056
(BF4ꢀ), 1039, 751, 696. UV–Vis, kmax, nm (
): 447 (700), 393
(6160), 251 (8890).
3.12. General procedure for the catalytic studies
m
m
m
e
Standard literature procedures were followed for hydrogen-
transfer catalysis experiments [23–25,65]. All the catalytic reac-
tions were carried out under inert atmosphere (N2) using 10ꢀ5
M
3.9. Characterization data of [Ru(CO)H(j 7
1-P-PPh2Py)2(phen)]BF4
catalyst in 2-propanol (10 ml) and the catalyst/KOH/substrate in
a molar ratio of 1:20:1000. The reaction mixture was magnetically
stirred and heated at 80 °C for 24 h. The reactions were quenched
at 0 °C and samples were collected and diluted with 1 mL of ethyl
acetate and acetone (4:1 v/v). The products were isolated and iden-
tified by 1H NMR in CDCl3 and the yield of respective processes was
calculated considering relative integrals of the ketones and alcohol.
Yield: 84 mg (96%). Microanalytical data C47H37BN4OF4P2Ru re-
quires: C, 61.12; H, 4.04; N, 6.07. Found: C, 61.10; H, 4.08; N, 6.03%.
FAB-MS [m/z, obs. (calcd.) assignments]: 923.6 (923) [RuH(CO)-
(
j
1-P-PPh2Py)2(phen)]BF4; 836.8 (836) [RuH(CO)(
j
1-P-PPh2Py)2-
(phen)]+; 573.6 (573) [RuH(CO)(
j
1-P-PPh2Py)(phen)]+; 545.5
(546) [RuH(j
1-P-PPh2Py)(phen)]+. 1HNMR (d ppm): 6.70–8.30 (m,
36H, Ph), ꢀ11.68 (t, Ru–H, 18 Hz). 31P{1H} NMR (d ppm): 46.80
4. Conclusions
(s, PPh2Py). IR (KBr pellets, cmꢀ1): 3099, 3046, 3017,
v
(Ru–H)
(BF4ꢀ) 1055,
e): 433 (338), 387 (1730), 257
In summary, through this work we have developed a range of
new cationic hydrido-carbonyl Ru(II) complexes incorporating het-
ero-difunctional P,N-phosphine, diphenyl-2-pyridylphosphine and
diamine (en, dimen and diap) or diimine (bipy, phen and dpa) li-
gands. From spectral and structural studies it has been established
that the coordinated PPh2Py acts both as monodentate and chelat-
ing ligand. Furthermore, it has been shown that 1–8 act as precur-
sor catalysts for transfer hydrogenation of acetophenone and some
other related ketones under inert atmosphere.
2001,
m(CO) 1953, 1585, 1482, 1431, 1152, 1091, m
1038, 846, 694. UV–Vis, kmax, nm (
(9240).
3.10. Characterization data of [Ru(CO)H(j 8
1-P-PPh2Py)2(dpa)]BF4
Yield: 76 mg (86%). Microanalytical data C56H48BF4N6OP2Ru re-
quires: C, 62.73; H, 4.52; N, 7.84. Found: 62.70; H, 4.53; N, 7.82%.
1H NMR (d ppm): 8.77 (d, 6H, PPh2Py), 8.36 (2H, d, py), 7.54 (2H,
t, py), 7.38 (2H, d, py), 7.27 (2H, d, Ph), 7.20 (1H, t, Ph), 7.18 (2H,
d, Ph), 6.92 (2H, t, py), 5.58 (2H, s, CH2), ꢀ11.78 (t, Ru–H, 23 Hz).
31P{1H} NMR (d ppm): 36.48 (s, PPh2Py). IR (KBr pellet, cmꢀ1):
Acknowledgements
We gratefully acknowledge financial support from the Depart-
ment of Science and Technology, Ministry of Science and Technol-
ogy, New Delhi, India (Grant No. SR/SI/IC-15/2007). We are also
thankful to the Head, Department of Chemistry, Banaras Hindu
University, Varanasi (UP) India and National Institute of Advanced
Industrial Science and Technology (AIST), Osaka, Japan for extend-
ing facilities.
2023
(BF4ꢀ), 846, 694. UV–Vis, kmax, nm (
249 (8930).
m
(Ru–H), 1950
m
(CO), 1599, 1477, 1434, 1185, 1093, 1053
m
e
): 417 (500), 377 (4420),
3.11. X-ray structure determinations
Suitable crystals of 2, 3, 5 and 8 for single X-ray diffraction anal-
yses were obtained from CH2Cl2/petroleum ether (40–60 °C) at
room temperature by slow diffusion method. Preliminary data on
the space group and unit cell dimensions as well as intensity data
were collected on an R-AXIS RAPID II diffractometer using graph-
Appendix A. Supplementary material
CCDC 755241, 755242, 755243 and 755244 contain the supple-
mentary crystallographic data for 2, 3, 6 and 8, respectively. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. FAB
spectra (S1–S5), cyclic voltammograms of 1, 6 and 7 (S6), figures of
weak interactions of 2, 6, and 8 (S7-S11), respectively. Supplemen-
tary data associated with this article can be found, in the online
version, at doi:10.1016/j.ica.2010.12.057.
ite-monochromatized Mo Ka radiation. Structures were solved by
direct methods (SHELXS 97) and refined with full-matrix least
squares on F2 (SHELX 97) [77–79]. Non-hydrogen atoms were refined
with anisotropic thermal parameters. All the hydrogen atoms were
geometrically fixed and allowed to refine using a riding model. The
computer program PLATON was used for analyzing the interactions
and stacking distances [77–79].
Complex 2: Formula = C35H28Cl2N2OP2Ru, Mr = 726.54, mono-
clinic, P 21/n, a = 11.5092(11), b = 10.8017(10), c = 25.399(2), b =
References
93.662, V = 3151.2(5), Z = 6, Dcalc = 2.294,
k = 0.71073, R(all) = 0.0850, R(I > 2 (I)) = 0.0589, wR2 = 0.2356,
wR2 [I > 2 (I)] = 0.1600, GOF = 1.072.
Complex 3: Formula = C37H37BF4N4OP2Ru, Mr = 803.55, ortho-
rhombic, P 21 21 21, a = 12.594(3), b = 15.155(3), c = 19.534(4),
l = 1.200, T(K) = 293(2),
[1] C.A. Tolman, Chem. Rev. 77 (1977) 313.
[2] P.W.N.M. van Leeuwen, P.C.J. Kamer, J.N.H. Reek, P. Dierkes, Chem. Rev. 100
(2000) 2741.
r
r
[3] M.T. Reetz, X.-G. Li, J. Am. Chem. Soc. 128 (2006) 1044.
[4] C.S. Slone, D.A. Weinberger, C.A. Mirkin, Prog. Inorg. Chem. 48 (1999) 233.
[5] A. Bader, E. Lindner, Coord. Chem. Rev. 108 (1991) 27.
[6] G.R. Newkome, Chem. Rev. 93 (1993) 2067.
[7] P. Espinet, K. Soulantica, Coord. Chem. Rev. 193–195 (1999) 499.
[8] P. Braunstein, F. Naud, Angew. Chem., Int. Ed. 40 (2001) 680.
[9] Evans, J.A. Osborn, F.H. Jardine, G. Wilkinson, Nature 208 (1965) 1203.
[10] J. Halpern, J.F. Harrod, B.R. James, J. Am. Chem. Soc. 88 (1966) 5150.
[11] G. Francio, R. Scopelliti, C. Grazia Arena, G. Bruno, D. Drommi, F. Faraone,
Organometallics 17 (1998) 338.
[12] S.L. Queiroz, A.A. Batista, G. Oliva, M.T.P. Gambardella, R.H.A. Santos, K.S.
MacFarlane, S.J. Rettig, B.R. James, Inorg. Chim. Acta 267 (1998) 209.
[13] S.L. Queiroz, A.A. Batista, M.P. de Araujo, R.C. Bianchini, J. Ellena, B.R. James,
Can. J. Chem. 81 (2003) 1263.
[14] A.A. Batista, E.A. Polato, S.L. Queiroz, O.L. Nascimento, B.R. James, S.J. Rettig,
Inorg. Chim. Acta 230 (1995) 111.
a
= b =
T(K) = 293(2), k = 0.71073, R(all) = 0.0910, R(I > 2
wR2 = 0.1515, wR2 [I > 2 (I)] = 0.1260, GOF = 1.002.
Complex 6: Formula = C45H39BF4N4O2P2Ru, Mr = 917.62, mono-
clinic, P 21/c, a = 11.198(2), b = 22.121(4), c = 19.365(6), = 90.00,
b = 116.682, = 90.00, V = 4286.2(17), Z = 4, Dcalc = 1.422,
0.500, T(K) = 293(2), k = 0.71073, R(all) = 0.1171, R(I > 2
0.0538, wR2 = 0.1545, wR2 [I > 2 (I)] = 0.1169, GOF = 1.035.
Complex 8: Formula = C56H48BF4N6OP2Ru, Mr = 1070.86, ortho-
rhombic, P n m a, a = 19.375(4), b = 16.930(3), c = 15.385(3),
b = = 90.00, V = 5046.6(17), Z = 1, Dcalc = 0.331, = 0.108, T(K) =
293(2), k = 0.71073, R(all) = 0.1827, R(I > 2 (I)) = 0.1091, wR2 =
0.3301, wR2 [I > 2 (I)] = 0.2946, GOF = 1.059.
c
= 90.00, V = 3728.1(13), Z = 4, Dcalc = 1.542,
l = 0.574,
r(I)) = 0.0726,
r
a
c
l =
r(I)) =
r
a
=
[15] M.P. de Araujo, E.M. Valle, J. Ellena, E.E. Castellano, E.N. dos Santos, A.A. Batista,
Polyhedron 23 (2004) 3163.
[16] S.E. Clapham, A. Hadyovic, R.H. Morris, Coord. Chem. Rev. 248 (2004) 2201.
[17] R. Noyori, T. Ohkuma, Angew. Chem., Int. Ed. 40 (2001) 40.
c
l
r
r

P. Kumar et al. / Inorganica Chimica Acta 368 (2011) 124–131
131
[18] K. Abdur-Rashid, A.J. Lough, R.H. Morris, Organometallics 20 (2001) 1047.
[19] K. Abdur-Rashid, S.E. Clapham, A. Hadzovic, J.N. Harvey, A.J. Lough, R.H. Morris,
J. Am. Chem. Soc. 124 (2002) 15104.
[20] H. Doucet, T. Ohkuma, K. Murata, T. Yokozawa, M. Kozawa, E. Katayama, A.F.
England, T. Ikariya, R. Noyori, Angew. Chem., Int. Ed. 37 (1998) 1703.
[21] T. Ohkuma, M. Koizumi, H. Doucet, T. Pham, M. Kozawa, K. Murata, E.
Katayama, T. Yokozawa, T. Ikariya, R. Noyori, J. Am. Chem. Soc. 120 (1998)
13529.
[53] M. Chandra, A.N. Sahay, D.S. Pandey, M.C. Puerta, P. Valerga, J. Organomet.
Chem. 648 (2002) 39.
[54] K. Osakada, T. Yamamoto, A. Yamamoto, A. Takenaka, Y. Sasada, Inorg. Chim.
Acta 9 (1979) 105.
[55] M.R. Churchill, K.M. Keil, F.V. Bright, S. Pandey, G.A. Baker, J.B. Keister, Inorg.
Chem. 39 (2000) 5807.
[56] B.K. Panda, S. Chattopadhyaya, K. Ghosh, A. Chakravorty, Organometallics 21
(2002) 2773.
[22] K. Mikami, T. Korenaga, M. Terada, T. Ohkuma, T. Pham, R. Noyori, Angew.
Chem., Int. Ed. 38 (1999) 495.
[57] A. Singh, A.K. Singh, M. Trivedi, D.S. Pandey, J. Organomet. Chem. 690 (2005)
4243.
[23] M.P. Magee, J.R. Norton, J. Am. Chem. Soc. 123 (2001) 1778.
[24] R.M. Bullock, Chem. Eur. J. 10 (2004) 2366.
[58] D.K. Gupta, O.S. Sisodia, A.N. Sahay, D.S. Pandey, Synth. React. Inorg. Metal –
Org. Chem. 28 (1998) 355.
[25] T. Ikariya, K. Murata, R. Noyori, Org. Biomol. Chem. 4 (2006) 393.
[26] J. Halpern, L.-Y. Wong, J. Am. Chem. Soc. 90 (1968) 6665.
[27] B.R. James, Chem. Eng. News 11 (2002) 8.
[28] T. Ikariya, A.J. Blacker, Acc. Chem. Res. 40 (2007) 1300.
[29] X. Wu, J.L. Xiao, Chem. Commun. (2007) 2449.
[30] S. Gladiali, E. Alberico, Chem. Soc. Rev. 35 (2006) 226.
[31] J.S.M. Samec, J.-E. Bajckvall, P.G. Andersson, P. Brandt, Chem. Soc. Rev. 35
(2006) 237.
[32] M.J. Palmer, M. Wills, Tetrahedron: Asymmetry 10 (1999) 2045.
[33] R. Noyori, S. Hashiguchi, Acc. Chem. Res. 30 (1997) 97.
[34] K. Wajda, F. Pruchnik, T. Lis, Inorg. Chim. Acta 40 (1980) 207.
[35] K. Wajda-Hermanowicz, F.P. Pruchnik, Transition Met. Chem. 13 (1988) 101.
[36] V.K. Jain, V.S. Jakkal, R. Ohra, J. Organomet. Chem. 389 (1990) 417.
[37] C.G. Arena, E. Rotondo, F. Araone, Organometallics 10 (1991) 3877.
[38] P. Braunstein, D.G. Kelly, A. Tiripicchio, F. Ugozzoli, Bull. Soc. Chim. Fr. 132
(1995) 1083.
[39] P. Kumar, A.K. Singh, D.S. Pandey, J. Organomet. Chem. 694 (2009) 3643.
[40] K. Nishide, S. Ito, M. Yoshifuji, J. Organomet. Chem. 682 (2003) 79.
[41] P. Govindaswamy, Y.A. Mozharivskyj, M. Kollipara, Polyhedron 23 (2004)
3115.
[59] M. Trivedi, M. Chandra, D.S. Pandey, M.C. Puerta, P. Valerga, J. Organomet.
Chem. 689 (2004) 879.
[60] S. Kar, T.A. Millar, S. Chakraborty, B. Sarkar, B. Pradhan, R.K. Singh, T. Kunda,
M.D. Ward, G.K. Lahiri, Dalton Trans. (2003) 2591.
[61] H.A.S. Silva, R.M. Carlos, A.J. Camargo, C.M.C. Picchi, R.H. de Almeida Santos,
B.R. McGarvey, D.W. Franco, Inorg. Chim. Acta 357 (2004) 3147.
[62] J.-X. Gao, T. Ikariya, R. Noyori, Organometallics 15 (1996) 1087.
[63] O.M. Akotsi, K. Metera, R.D. Reid, R. McDonald, S.H. Bergens, Chirality 12
(2000) 514.
[64] E. Lindner, H.A. Mayer, I. Warad, K. Eichele, J. Organomet. Chem. 665 (2003)
176.
[65] E. Lindner, I. Warad, K. Eichele, H.A. Mayer, Inorg. Chim. Acta 350 (2003) 49.
[66] M.D. Le Page, B.R. James, Chem. Commun. (2000) 1647.
[67] C. Thoumazet, M. Melaimi, L. Ricard, F. Mathey, P.L. Floch, Organometallics 22
(2003) 1580.
[68] C. Standfest-Hauser, C. Slugovc, K. Mereiter, R. Schmid, K. Kirchner, L. Xiao, W.
Weissensteiner, J. Chem. Soc., Dalton Trans. (2001) 2989.
[69] B.R. James, Adv. Organomet. Chem. 17 (1979) 319.
[70] R.A.W. Johnstone, A.H. Wilby, I.D. Entwistle, Chem. Rev. 85 (1985) 129.
[71] M.P. de Araujo, A.T. de Figueiredo, A.L. Bogado, G.V. Poelhsitz, J. Ellena, E.E.
Castellano, C.L. Donnici, J.V. Comasseto, A.A. Batista, Organometallics 24
(2005) 6159.
[42] I. Moldes, E. De la Encarnacion, J. Ros, A. Alvarez-Larena, J.F. Piniella, J.
Organomet. Chem. 566 (1998) 165.
[43] E. Drent, P. Arnoldy, P.H.M. Budzelaar, J. Organomet. Chem. 455 (1993) 247.
[44] C.S. Consorti, G. Ebeling, J. Dupont, Tetrahedron Lett. 43 (2002) 753.
[45] T.Q. Hu, B.R. James, in: T.Q. Hu (Ed.), Chemical Modification, Properties and
Usage of Lignin, Kluwer Publishers, Dordrecht, The Netherlands, 2002, p. 247.
[46] G.A. Olalere, L. Ling-Kang, Inorg. Chim. Acta 360 (2007) 2464.
[47] T. Hayashida, H. Nagashima, Organometallics 21 (2002) 3884.
[48] H. Aneetha, P.S. Zacharias, B. Srinivas, G.H. Lee, Y. Wang, Polyhedron 18 (1999)
299.
[49] J.C. McConway, A.C. Skapski, L. Phillips, R.J. Young, G. Wilkinson, J. Chem. Soc.,
Chem. Commun. (1974) 327.
[50] I. de Los Rios, M.J. Tenorio, M.A.J. Tenorio, M.C. Puerta, P. Valerga, J. Organomet.
Chem. 57 (1996) 525.
[72] Y. Ma, H. Liu, L. Chen, X. Cui, J. Zhu, Deng, J. Org. Lett. 5 (2003) 2103.
[73] M. Yamakawa, I. Yamada, R. Noyori, Angew. Chem., Int. Ed. 40 (2001) 2818.
[74] D.D. Perrin, W.L.F. Armango, D.R. Perrin, Purification of Laboratory Chemicals,
Pergamon, Oxford, UK, 1986.
[75] N. Ahmad, J.J. Levison, S.D. Robinson, M.F. Uttley, Inorg. Synth. 15 (1974)
45.
[76] B. Antonioli, J.B. David, K.C. Jack, G. Kerstin, G. Karsten, K. Olga, F.L. Leonard,
C.M. John, J.S. Peter, J.S. Christopher, W. Marco, Dalton Trans. (2006) 4783.
[77] S. Mackay, W. Dong, C. Edwards, A. Henderson, C. Gilmox, N. Stewart, K.
Shankland, A. Donald, University of Glasgow, Scotland, 1999.
[78] G.M. Sheldrick, SHELXS-97-A Program for Automatic Solution of Crystal
Structures, University of Goettingen, Germany, 1997. Release 97-2; G.M.
Sheldrick, Acta Cryst. A46 (1990) 467.
[51] P. Ghosh, A. Chakravorty, Inorg. Chem. 36 (1997) 64.
[52] O.S. Sisodia, A.N. Sahay, D.S. Pandey, U.C. Agrawala, N.K. Jha, P. Sharma, A.
Toscano, A. Cabrera, J. Organomet. Chem. 560 (1998) 35.
[79] PLATON A.L. Spek, Acta Crystallogr., Sect. A 46 (1990) C31.