The dual role of cis-[RuCl2(dmso)4] in the synthesis of new water-soluble Ru(II)-phosphane complexes and in the catalysis of redox isomerization of allylic alcohols in aqueous-organic biphasic systems

Article abstract of DOI:10.1016/j.jorganchem.2012.07.042

New air-stable, water-soluble Ru(II)-phosphane complexes were synthesized in high purity by the reaction of cis-[RuCl₂(dmso)₄] with 2 equivalents of 1,3,5-triaza-7-phosphaadamantane (pta) and its N-methyl and N-benzyl derivatives (pta-Me and pta-Bn, respectively). All new complexes were characterized by elementary analysis and spectroscopic methods (NMR, ESI-MS) and the molecular structures of cis-cis-trans-[RuCl₂(dmso) ₂(pta)₂], cis-cis-trans-[RuCl₂(dmso) ₂(pta-H)₂]Cl₂ (obtained in acidic solutions) and that of cis-cis-trans-[RuCl₂(dmso)₂(pta-Me) ₂](CF₃SO₃)₂ were determined by single crystal X-ray diffraction. Under mild conditions, cis-[RuCl ₂(dmso)₄] actively catalyzed the transformation of allylic alcohols into the corresponding ketones with 100% selectivity while in the same reaction the new Ru(II)-pta complexes showed moderate activity and selectivity.

Full text of DOI:10.1016/j.jorganchem.2012.07.042

Journal of Organometallic Chemistry 717 (2012) 116e122
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The dual role of cis-[RuCl2(dmso)4] in the synthesis of new water-soluble
Ru(II)ephosphane complexes and in the catalysis of redox isomerization
of allylic alcohols in aqueouseorganic biphasic systems
*
Antal Udvardy, Attila Csaba Bényei, Ágnes Kathó
Department of Physical Chemistry, University of Debrecen, P.O. Box 7, H-4010 Debrecen, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
New air-stable, water-soluble Ru(II)ephosphane complexes were synthesized in high purity by the
reaction of cis-[RuCl2(dmso)4] with 2 equivalents of 1,3,5-triaza-7-phosphaadamantane (pta) and its
N-methyl and N-benzyl derivatives (pta-Me and pta-Bn, respectively). All new complexes were charac-
terized by elementary analysis and spectroscopic methods (NMR, ESI-MS) and the molecular structures
of cis-cis-trans-[RuCl2(dmso)2(pta)2], cis-cis-trans-[RuCl2(dmso)2(pta-H)2]Cl2 (obtained in acidic solu-
tions) and that of cis-cis-trans-[RuCl2(dmso)2(pta-Me)2](CF3SO3)2 were determined by single crystal
X-ray diffraction.
Under mild conditions, cis-[RuCl2(dmso)4] actively catalyzed the transformation of allylic alcohols into
the corresponding ketones with 100% selectivity while in the same reaction the new Ru(II)epta
complexes showed moderate activity and selectivity.
Received 25 June 2012
Received in revised form
24 July 2012
Accepted 26 July 2012
Keywords:
Water-soluble phosphanes
Ruthenium
Allylic alcohols
Isomerization
Ó 2012 Elsevier B.V. All rights reserved.
Biphasic catalysis
1. Introduction
sulfonated aryl, and cyclohexyl phosphanes, both in aqueous and
in non-aqueous media [8,10e14]. In addition, several ligands with
Water is widely considered useful for elimination of hazardous
organic solvents in organic synthesis and catalysis. An additional
green feature of applying water-soluble catalysts is that the use of
aqueouseorganic biphasic systems allows recycling of the catalyst
under mild conditions by easy phase separation [1e4].
The chemistry of Ru(II) catalysts containing water-soluble
phosphanes as ligands have received considerable attention in
recent years [4]. In many cases, Ru(II)-complexes of tertiary phos-
phanes applied in homogeneous catalysis are synthesized from
RuCl3$aq as starting material. However, ligand exchange reactions
of water-soluble Ru(II)-complexes containing sufficiently labile
ligands allow more precise control of the composition and struc-
ture of the products [5]. For example, [Ru(H2O)6](tos)2 (tos ¼ p-
toluene-sulfonate) can be efficiently used for this purpose.
However, this compound is tedious to synthesize, highly sensitive
to oxygen and is stable only in acidic solutions [6,7].
N- and O-donor atoms were studied in substitution reactions of
both isomers of [RuCl2(dmso)4] [15]. This was ein parte motivated
by the expected biological effects of the products [16e19]. While 1
itself also shows antitumor and remarkable antimetastatic activity,
certain of its substituted derivatives are even more effective [20].
1,3,5-Triaza-7-phosphadamantane (1,3,5-triaza-7-phosphatricyclo
[3.3.1.1]decane, pta) is a small, aliphatic tertiaryphosphane with
a cage structure, well soluble in water. Ru(II)epta complexes such as
[RuCl2(pta)4] have already been applied in biphasic catalysis [21] and
the field is well reviewed [5,22,23]. In contrast to other tertiary
aminoalkylphosphanes where alkylation takes place on phosphorus,
pta is alkylated smoothly on one of its nitrogen atoms [24]. The charge
and steric bulk of such ligands are changed by quaternarization and
this is reflected also in their water-solubility [25]. Coordination
properties of alkyl-pta derivatives and catalytic applications of their
complexes received less attention than those of pta. Rare examples
include the use of (pta-Bn)Cl (Scheme 1) in Rh-catalyzed hydro-
The ruthenium(II) dimethylsulfoxide complexes, cis- and trans-
[RuCl2(dmso)4] are conveniently prepared and easy-to-handle
formylation of higher olefins [26,27] and that of [(h-arene)RuCl2(pta-
compounds [8,9]. Earlier cis-[RuCl2(dmso)4],
precursor for the synthesis of Ru(II)-complexes with aryl,
1
was used as
Bn)]Cl in hydration of nitriles [28]. [CpRuCl(pta-Me)2](OSO2CF3)2
and [CpRu(pta-Me)2(H2O)](OSO2CF3)3 were found effective catalysts
of the redox isomerization of allylic alcohols [29]. In addition, pta
has been successfully used for synthesis of anticancer Ru(II)earene
complexes [30]. It is interesting, therefore, that reactions of pta and
* Corresponding author. Tel.: þ36 52 512900; fax: þ36 52 512915.
E-mail address: katho.agnes@science.unideb.hu (Á. Kathó).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.07.042

A. Udvardy et al. / Journal of Organometallic Chemistry 717 (2012) 116e122
117
Scheme 1. Water-soluble phosphanes used in this study.
Fig. 1. Changes in UVevis spectra measured in the solution of cis-[RuCl2(dmso)4] (1)
and 2 pta as a function of time. Conditions: c(1) ¼ 0.001 M; T ¼ 25 ꢁC; t ¼ 0, 15, 30, 45,
60, 90 and 120 min.
its derivatives with cis- or trans-[RuCl2(dmso)4] hitherto have not been
studied.
Herein we report the use of 1 for the synthesis and character-
ization of several new water-soluble Ru(II)-complexes containing
the ligands shown in Scheme 1, and an exploratory study of their
catalytic activity in the hydrogenation and isomerization of allylic
alcohols. Strikingly,1 itself was only scarcely used [31,32] as catalyst
in such reactions so its study was also accomplished.
Since both pta and 1 are soluble in water, their reaction was
studied in aqueous medium, as well. At room temperature, only the
characteristic singlet resonance of 2 (
d
¼ ꢀ57.9 ppm in D2O) was
observed in the 31P NMR spectra independent of the [pta]:[1] ratio
being 1 or 2. In contrast, at [pta]:[1] ¼ 3, albeit in the first 30 min of
the reaction exclusively 2 was detected, later a new singlet
2. Results and discussion
(
d
¼ ꢀ52.9 ppm) grew in gradually. Formation of this new species at
room temperature is slow even at higher ligand excess
([pta]:[1] ¼ 4). The singlet 31P NMR resonance of this new
compound is slightly different from that of trans-[RuCl2(pta)4]
2.1. Reactions of cis-[RuCl2(dmso)4] with water-soluble phosphanes
According to the literature [10], boiling of a toluene suspension
of 1 and three equivalents of the water-soluble phosphane,
mtppms, for 2 h resulted in formation of the mononuclear
[RuCl2(dmso)(mtppms)3]. However, we found this reaction rather
slow and incomplete and 31P NMR indicated the formation of more
than one product. No significant improvement/optimization could
be reached by varying the ligands (mtppms or mtppts), ligand to
metal ratio (1e3), solvents (toluene, methanol or water), reaction
time or reaction temperature.
(
d
¼ ꢀ51.6 ppm in D2O) [21,33], however, it shows a similar pres-
ence of magnetically equivalent phosphane ligands. We reasoned,
that during the reaction of 1 with pta in water, aquation could lead
to the formation of trans-[Ru(H2O)2(pta)4]2þ (6). This is corrobo-
rated by the finding that when [RuCl2(dmso)2(pta)2] (2) was reac-
ted first with AgNO3 followed by the addition of 2 equivalents
of pta, after a reaction time of 2 h at room temperature only the
singlet at
d
¼ ꢀ52.9 ppm was observed. The same signal was
observed when 1 was dehalogenated in reaction with AgNO3, fol-
lowed by addition of 4 equivalents of pta. Furthermore, addition of
KCl (5 Clꢀ/Ru) to these solutions resulted in the appearance of the
31P NMR signal of trans-[RuCl2(pta)4] (5) on the expense of the one
at ꢀ52.9 ppm.
In contrast to the aromatic phosphanes, pta reacted cleanly with
1 in chloroform. The reaction was followed by UVevis spectro-
photometry (Fig. 1). The isosbestic point at
formation of a single product (2). Formation of 2 became complete
l
¼ 346 nm refers to the
in 2 h and there were no further spectral changes.
Note, that in the reaction of pta and [Ru(H2O)6]2þ only cis-
[Ru(H2O)2(pta)4]2þ could be detected [7]. The cis-[Ru(H2O)2(pta)4]2þ
compound was also obtained by addition of AgOTf to the product
mixture of cis-[RuCl2(pta)4] and [RuCl(H2O)(pta)4]þ formed by
visible light irradiation of 5 in water [34].
Only one singlet at
d
¼ ꢀ60.7 ppm (in CDCl3) appeared in the 31
P
NMR spectrum. Based on integrated 1H signal intensities of free
and coordinated dmso as well as those of coordinated pta we
concluded that the product was [RuCl2(dmso)2(pta)2] (2). The
singlet 31P signal refers to the phosphanes being in trans position
each to the other (Scheme 2). This observation is in agreement with
that substitution of chloride in this solvent is not favored. The
molecular structure of 2 in solid state was confirmed by single
crystal x-ray diffraction (see later).
It is also worth mentioning, that in contrast to the reaction of
[Ru(H2O)6]2þ and pta, formation of mono- or tris-phosphane
complexes was not observed.
In acidic solutions both free and coordinated pta can be
protonated on one of the nitrogen atoms. Fig. 2 shows the shift of
the 31P NMR signal of [RuCl2(dmso)2(pta)2] as a function of the
acidity of its aqueous (D2O) solutions.
HendersoneHasselbach analysis of the data gave pKa ¼ 3.40
(applying the pH ¼ pD ꢀ0.44 scaling [35]) and the 31P NMR shifts
calculated with this value are also shown on Fig. 2. Literature values
of the pKa of pta vary in the range of 5.63e6.0 [7,36e38], so the
protonation of coordinated pta in 2 takes place under more acidic
conditions relative to the free ligand. Single crystals of 2a were
obtained from hydrochloric acid solutions of 2. X-ray diffraction
analysis of the molecular structure of 2a (see Supplementary
information: Fig. S1) showed that both phosphane ligands had one
protonated nitrogen each.
At room temperature, coordination of a further phosphane
ligand to 2 is slow and at a 4:1 [pta]:[1] ratio only [RuCl2(dm-
so)2(pta)2] (2) was formed in the first 90 min of the reaction. During
the same reaction time but at reflux temperature, an approximately
3:2 mixture of 2 and the known trans-[RuCl2(pta)4], 5 was obtained
(Scheme 2) [21,33]; upon further boiling the latter compound
precipitated from the solution.
Based on these observations [RuCl2(dmso)2(pta)2] could be
synthesized in pure form when [RuCl2(dmso)4] and pta were let to
react in a 1:2 ratio in chloroform for 2 h at room temperature (yield
82%). In aqueous solution 2 is characterized by a singlet resonance
at
d
¼ ꢀ57.9 ppm in the 31P NMR spectrum (Table 1).

118
A. Udvardy et al. / Journal of Organometallic Chemistry 717 (2012) 116e122
Scheme 2. Synthesis of Ru(II)-complexes containing triazaphosphaadamantanes.
The most intensive peak in the ESI mass spectrum of 2 at
2.2. Molecular structures of cis-cis-trans-[RuCl2(dmso)2(pta)2] (2),
m/z
¼
643.030 belongs to the monoprotonated molecule,
cis-cis-trans-[RuCl2(dmso)2(ptaH)2]Cl2 (2a) and cis-cis-trans-
[RuCl2(dmso)2(pta-Me)2](CF3SO3)2 (4) in solid state
conceivably [RuCl2(dmso)2(pta)(ptaH)]þ (Fig. S2), furthermore, loss
of dmso and chloride are also indicated by the signals at
m/z ¼ 565.070 ([RuCl2(dmso)(pta)(ptaH)]þ) and at m/z ¼ 607.048
([RuCl(dmso)2(pta)2]þ).
Results of X-ray structure determinations are summarized in
Table 2.
The reaction of 1 and (pta-Bn)Cl in aqueous solution at room
temperature at a [pta-Bn]:[1] ¼ 2 ratio yielded 3 with [RuCl2(dm-
so)2(pta-Bn)2]2þ as the sole product. The UVevisible spectrum of
the reaction mixture underwent changes similar to those shown
above for the case of 1 with two equivalents of pta, and the spectral
parameters of 3 are also similar to those of 2. The reaction was
complete in 1.5 h, and no sign of any other species was detected in
the NMR spectra even at higher temperature (up to T ¼ 70 ꢁC).
3 is stable to air and its best solvent is water. Due to its charge
solubility of 3 in water is approximately 1.5 times higher than that
of the neutral 2 (see Experimental). The most intensive ESI-MS
peak at m/z ¼ 576.100 belongs to [RuCl2(dmso)2(pta-Bn)]þ (Fig. S2).
Search of the Cambridge Structural Database (Ver. 5.33, Update
May, 2012) [39] revealed that all RuCl2P2S2 complexes in the data-
base contain exclusively bidentate ligands with PeS, PeP or SeS
donor pairs. In fact, 2, 2a and 4 are the first crystallographically
characterized complexes with RuCl2P2S2 coordination containing
monodentate ligands. The two phosphorus atoms are in trans-
position, however, the PeRueP angles significantly deviate from
180ꢁ being 161ꢁ in 2, 168ꢁ in 2a and 165ꢁ in 4. In the vast number of
RuP2 complexes (over 4500 hits in CSD) the PeRueP angles rarely
deviate from 180ꢁ or 90ꢁ: in the crystals obtained from [Ru(H2O)6]2þ
with pta or its derivatives [7] (trans-[Ru(H2O)4(pta)2]2þ, trans-
[Ru(H2O)4(pta-Me)2]4þ, trans-[Ru(H2O)4(pta-H)2]4þ) as well as in
trans-[RuI4(pta-Me)2] [40] and trans-[RuCl4(pta-H)2] [41] this angle
is 180ꢁ as ruthenium atom is in the inversion center of the lattice.
In addition, for [RuCl2(PPh3)2X ] (X ¼ further coordinating
ligand) complexes the only complex with non-linear PeRueP
bonds is RuCl2(PPh3)3 [42e44]. In contrast, Ru(II) complexes
containing neutral or protonated pta seem to be more prone for
displaying non-linear PeRueP angles. For example, earlier we
The
mono-dmso
complex
ion,
[RuCl2(dmso)(pta-Bn)]þ
(m/z ¼ 500.003) and chloride-associated ions such as {[RuCl2(dm-
so)2(pta-Bn)2]Cl}þ (m/z ¼ 860.100) and {[RuCl2(dmso)(pta-Bn)2]
Cl}þ (m/z ¼ 782.100), could also be identified.
[RuCl2(dmso)2(pta-Me)2](CF3SO3)2 (4) was prepared in the
reaction of 1 with (pta-Me)CF3SO3. This ligand and 1 ([pta-
Me]:[1] ¼ 2) were reacted in water (or methanol) at room
temperature for
2 h yielding exclusively [RuCl2(dmso)2(pta-
Me)2]2þ what was isolated as triflate salt.
58
56
54
52
50
48
46
4 is stable to air and its solubility is approximately the double of
that of the neutral 2, and is somewhat higher than that of 3. The
most intensive ESI-MS peak at m/z
¼
499.947 belongs to
[RuCl2(dmso)2(pta-Me)]þ (Fig. S2). The mono-dmso complex ion,
[RuCl2(dmso)(pta-Me)]þ (m/z ¼ 421.947) and triflate-associated
ions such as {[RuCl2(dmso)2(pta-Me)2](CF3SO3)}þ (m/z ¼ 821.013)
and {[RuCl2(dmso)(pta-Me)2](CF3SO3)}þ (m/z
¼
743.005), and
{[RuCl2(pta-Me)2](CF3SO3)}þ (m/z
identified.
¼
665.039) could also be
Table 1
31P NMR data of water soluble Ru(II)ephosphane complexes in D2O.
31P NMR (ppm)
[RuCl2(dmso)2(pta)2] (2)
ꢀ57.9a
ꢀ38.9
ꢀ36.4
ꢀ51.6
ꢀ52.9
[RuCl2(dmso)2(pta-Me)2](CF3SO3)2 (3)
[RuCl2(dmso)2(pta-Bn)2]Cl2 (4)
trans-[RuCl2(pta)4] (5)
1
2
3
4
5
pD
trans-[Ru(H2O)2(pta)4]2þ (6)
Fig. 2. Experimental (squares) and calculated (solid line) 31P NMR chemical shift of
[RuCl2(dmso)2(pta)2] vs pD.
a
In CDCl3:
d
¼ ꢀ60.7 ppm.

A. Udvardy et al. / Journal of Organometallic Chemistry 717 (2012) 116e122
119
Table 2
Summary of crystallographic data and structure refinement results for the complexes.
Compound no.
2$CHCl3
17H37Cl5N6O2P2S2Ru
761.91
2a$3H2O
4$H2O
Empirical formula
Formula weight/g molꢀ1
Crystal system, space group
a/b/c (Ǻ)
C
C17H44Cl4N6O5P2S2Ru
769.5
Monoclinic, P21/n (No. 14)
10.022(5), 13.533(2), 22.796(5)
90, 95.04(2), 90
3079.8(17)
4
1.66
C20H42Cl2F6N6O9P2S4Ru
986.79
Triclinic, Pꢀ1 (No. 2)
Triclinic, Pꢀ1 (No. 2)
9.074(5), 9.861(5), 17.200(5)
14.164(5), 17.108(5) 17.570(5)
ꢁ
a
/ꢁ,
b
/ꢁ,
g
/
95.12 (1), 92.48 (1), 106.90 (1)
1462.8 (12)
2
1.73
74.99 (1), 82. 32(1), 70.16 (1)
3863 (2)
4
1.697
0.92
V/Ǻ3
Z
Dcalc/mg mꢀ3
m
(Mo-Ka)/mmꢀ1
1.27
1.13
Crystal color/morphology
Crystal size
T/K
Yellow/prism
Yellow/prism
0.3 ꢂ 0.25 ꢂ 0.2
293
Orange/block
0.45 ꢂ 0.3 ꢂ 0.16
293
0.3 ꢂ 0.25 ꢂ 0.22
293
Rint/%
2.1
4.1
6.8
Reflections: collected
Reflections unique
Reflections observed, I > 2
No. of parameters
5884
5327
3578
358
0.051
0.123
0.99
5962
5469
4798
376
0.069
0.188
1.13
14 753
14 137
7873
927
0.083
s
(I)
R[F2 > 2
s
(F2)]/%
wR(F2)/%
0.23
1.01
GOF
have found [21] 165ꢁ in cis-[RuCl2(pta)4] and 163ꢁ for the
protonated analog, cis-[RuCl2(pta-H)4]4þ. Later it was shown [33],
that in trans-[RuCl2(pta)4], too, the PeRueP angle for the trans
phosphanes significantly differed from 180ꢁ. PMe3-containing
Ru(II) complexes behave similarly as pta complexes with bent
PeRueP coordination, e.g. 164e165ꢁ in [RuCl2(PMe3)4] [45,46].
For structures 2, 2a and 4 bond distances are in the expected
range (see captions of Figs. 3 and 4, and Fig. S1). CSD data for
comparison: in pta-containing Ru(II) complexes the average
RueCl and RueP distances are 2.44(13) Å and 2.32(16) Å,
respectively, and for all RuS2P2 complexes RueS bond distances
are 2.41(41) Å.
The structure of 4 contains two complexes in the asymmetric
unit with the appropriate 4 triflate counter ions. The water mole-
cule in 4 is in two positions with occupancy of 0.5 and various
orientation in the channel. The structures of 2 and 4 are stabilized
by CeH/O, CeH/N, CeH/F or CeH/Cl hydrogen bonds.
The solid state structure of 2a is also stabilized by both elec-
trostatic and secondary interactions. Extensive hydrogen bond
network is formed between water molecules or protonated pta
ligands as hydrogen donors and water oxygen atoms or chloride
ions as acceptors. However, all five water positions in the structure
have partial occupancy of 0.5 resulting in 2.5 equivalents of solvent
water per molecules of 2a complex. The layered structure contains
water filled solvent channels.
2.3. Isomerization of allylic alcohols catalyzed by Ru(II)edmso
complexes
Redox isomerization of allylic alcohols to the respective oxo
derivatives is a synthetically valuable procedure since it allows
a stepwise transformation (oxidation and reduction of conjugated
alcohol and C]C functions, respectively) in a single procedure
[29,47e49]. cis-[RuCl2(dmso)4] has already been applied as catalyst
for isomerization of 3-buten-2-ol to butan-2-one in homogeneous
water-diglyme solvent mixtures, however, as high temperatures as
130 ꢁC had to be used for meaningful reaction rates [31]. Gimeno
et al. studied the reduction of 1-octen-3-ol by hydrogen transfer
from 2-propanol with 1 as catalyst in homogeneous solution [32].
The reaction yielded octan-3-one as major product together with
16% octan-3-ol. Furthermore, at a substrate/catalyst ratio of 100 the
reaction required 9 h (T ¼ 82 ꢁC) to reach full conversion. These
literature reports prompted us to investigate the catalytic proper-
ties of 1 in more detail, especially since no investigations were done
with this catalyst in aqueouseorganic biphasic systems. We also
checked the catalytic activities of the pta-containing Ru(II)-
complexes 2e5. Under inert atmosphere (Ar or N2), isomerization
Fig. 3. ORTEP view of 2 at 50% probability level. Solvate chloroform molecule is
omitted for clarity. Selected bond length and bond angle data: Ru1eP11: 2.3866(18) Å;
Ru1eP21: 2.3623(18) Å; Ru1eS1: 2.2522(17) Å; Ru1eS2: 2.2644(19) Å; Ru1eCl1:
2.449(2) Å; Ru1eCl2: 2.4292(17) Å; P21eRu1eP11: 161.53(6)ꢁ; S1eRu1eS2: 89.31(6)ꢁ;
Cl1eRu1eCl2: 89.83(6)ꢁ.
Fig. 4. ORTEP view of 4 at 50% probability level. Water molecules and triflate counter
ions are omitted for clarity, only one molecule from the asymmetric unit is shown.
Selected average bond length and bond angle data: RueP: 2.365(9) Å; RueS:
2.265(6) Å; RueCl: 2.440(5) Å; PeRueP: 165(5)ꢁ; SeRueS: 90.3(9)ꢁ; CleRueCl: 86(2)ꢁ.

120
A. Udvardy et al. / Journal of Organometallic Chemistry 717 (2012) 116e122
of 1-octen-3-ol in a water-toluene biphasic mixture was slow or did
not proceed at all. According to the known mechanism of homo-
geneously catalyzed redox isomerizations the reactions proceed
through the transient formation of hydridometal complexes and in
many cases the hydrogen source is the substrate allylic alcohol
itself. Nevertheless, hydride donors such as H2, 2-propanol or
aqueous formate can facilitate the formation of the catalytically
active hydrido species [47].
Under hydrogen the reaction catalyzed by 1 led to a highly
selective conversion of 1-octen-3-ol (in 1 h, TOF ¼ 42 hꢀ1) to octan-
3-one (83%) with only 2% of the hydrogenated product, octan-3-ol
(Scheme 3). This result demonstrates for the first time, that in
a dihydrogen atmosphere 1 can be successfully used for redox
isomerization of 1-octen-3-ol under mild conditions with high
activity and selectivity to octan-3-one.
Scheme 4. Isomerization of allylic alcohols catalyzed by 1 in the presence of Na-
formate. Conditions: 0.01 mmol 1; 0.50 mmol HCOONa in 3 mL water; 0.08 mL 1-
octen-3-ol (0.50 mmol) in 1 mL toluene.
3. Conclusions
Hydrogen gas is flammable and explosive, however, in many
cases can be replaced by solutions of Na-formate in water as safe H-
donor. Furthermore, catalytic transfer hydrogenation of oxo-
compounds from aqueous Na-formate is well studied and the
conditions of C]O/C]C selectivity are known. Therefore isomeri-
zationactivities of 1e5 werealso studied in the presence of HCOONa.
An aqueous solution of 1 and HCOONa (1:50) was intensively
stirred at 80 ꢁC under argon with a toluene solution of 1-octen-3-ol
yielding exclusively octan-3-one in 1 h. In other words, despite the
presence of an H-donor, no hydrogenation of the resulting ketone
was observed. This is in contrast to the results of Gimeno et al. who
in the same reaction with the same catalyst observed considerable
formation of 1-octen-3-ol in homogeneous 2-propanol solution
[32]. In addition, with Na-formate as H-source in aqueouseorganic
biphasic system the reaction proceeded much faster (1 instead of
9 h for full conversion).
Other allylic alcohols reacted also with 100% selectivity with
respect to the formation of the corresponding ketones (Scheme 4).
Isomerization of 1-octen-3-ol was investigated in detail. Origi-
nally the reaction mixture was pale yellow what turned to deeper
yellow in the first few minutes of the reaction, routinely run for 1 h.
The temperature dependence of the conversion showed (Fig. 5)
that the reaction proceeded slowly below 60 ꢁC. Therefore further
measurements were done at 80 ꢁC.
The easily available cis-[RuCl2(dmso)4] is useful as a Ru(II)-
source not only in organic solvents, but in water, as well. 1,3,5-
Triaza-7-phosphaadamantane (pta) is soluble in both types of
media and its reactions with cis-[RuCl2(dmso)4] resulted in the
same product, cis-cis-trans-[RuCl2(dmso)2(pta)2] (2) in both CHCl3
and water. N-alkyl derivatives of pta (L ¼ {pta-Bn}Cl; {pta-Me}
CF3SO3) also easily replace two dmso ligands in trans positions of
cis-[RuCl2(dmso)4] in aqueous solution to form air-stable, cis-cis-
trans-[RuCl2(dmso)2(L)2] complexes (3, 4). Of the new compounds,
2, 2a and
4 are the first crystallographically characterized
complexes with RuCl2P2S2 coordination containing monodentate
ligands. The PeRueP angles in these trans-bisphosphane
complexes significantly deviate from 180ꢁ (161ꢁ in 2, 168ꢁ in 2a and
165ꢁ in 4).
It was shown here for the first time, that apart from its useful
role in the synthesis of water-soluble Ru(II)-complexes, cis-
[RuCl2(dmso)4] is an excellent catalyst for aqueouseorganic
biphasic isomerization of allylic alcohols. The reactions proceeded
with 100% to the respective ketones using Na-formate as an H-
source. Under the same conditions the activities of 2e4 are 45e65%
of that of cis-[RuCl2(dmso)4], and the reactions are also less selec-
tive leading to the formation of small amounts of octan-3-ol, too.
Recycling of the catalyst was attempted the following way. After
1 h reaction, stirring was stopped, the phases were separated, a new
batch of the toluene solution of 1-octen-3-ol was added to the
catalyst-containing aqueous phase and the stirring continued.
Although the selectivity to octan-3-one remained 100%, the
conversion dropped to 36% in the second, and to 4% in the third cycle.
Of the various pta-containing Ru(II)-complexes of this study
2e4 proved less active than 1, nevertheless they catalyzed the
formation of octan-3-one with considerable selectivity (Fig. 6).
However, in case of [RuCl2(pta)4] (5) only a slight activity was
determined (6% conversion in 1 h). This is in agreement with the
known low catalytic activity of this tetrakisphosphino-Ru(II)
complex in other catalytic reactions (hydrogenation, hydrogen
transfer from formate) [21].
Concerning the reaction mechanism, one of the possible path-
ways is the isomerization of allylic alcohols to saturated ketones
followed by hydrogenation of the latter to saturated alcohols.
However, in independent reactions no hydrogenations of the
respective ketones occurred (either with H2 or with formate),
therefore with the catalysts described above we consider isomeri-
zation and hydrogenation of allylic alcohols as parallel reactions.
4. Experimental section
4.1. General remarks
Allylic alcohols (Aldrich) and other reagents and solvents were
commercially available and used as received. The water-soluble
phosphane ligands, mtppms [50], mtppts (mtppts ¼ P(C6H4-3-
SO3Na)3) [51], pta, [52], (pta-Bn)Cl (1-benzyl-1-azonia-3,5-diaza-
7-phosphaadamantyl chloride) [36], and cis-[RuCl2(dmso)4] (1) [8],
100
80
60
40
20
0
40
50
60
T( C)
70
80
Fig. 5. Isomerization of 1-octen-3-ol catalyzed by 1 as a function of temperature.
Conditions: 0.01 mmol [RuCl2(dmso)4]; 0.50 mmol HCOONa in 3 mL water; 0.08 mL
(0.50 mmol) 1-octen-3-ol in 1 mL toluene, t ¼ 1 h.
Scheme 3. Hydrogenation and isomerization of 1-octen-3-ol.

A. Udvardy et al. / Journal of Organometallic Chemistry 717 (2012) 116e122
121
4.2.2. Preparation of cis-cis-trans-[RuCl2(dmso)2(pta-Bn)2]Cl2, (3)
100
80
60
40
20
0
1 (200 mg 0.41 mmol) dissolved in 3 mL of water was added to
an aqueous solution (2 mL) of (pta-Bn)Cl (234 mg, 0.82 mmol). The
mixture was stirred for 2 h at room temperature in the dark. Then
the solvent was removed under vacuum and the residue was
redissolved in a small amount of methanol. Diethyl ether was
added to the solution whereupon a yellow solid precipitated. This
was washed with acetone and with diethyl ether and dried under
Ar. Yield 246 mg, 66%. Anal. calc. for RuC30Cl4H50N6O2P2S2 (3$2H2O)
(M ¼ 895.71) C 38.67, H 5.84, N 9.02%; found C 38.25, H 6.17, N
8.79%. lmax(H2O)/nm 341 (ε/dm3 molꢀ1 cmꢀ1 691).
1H NMR: (360 MHz, D2O, 25 ꢁC)
d
¼ 3.29e4.27 (m, 8H, NCH2P),
3.64 (s, 12H, S-dmso, CH3), 4.19 (m, 4H, NþCH2Ph), 4.31 (m, 4H,
NþCH2P), 4.51e4.61 (m, 4H, NCH2N), 4.92e5.09 (m, 8H, NþCH2N),
7.57e7.46 (m, 10H, Ph) ppm; 13C NMR (90 MHz, D2O, 25 ꢁC),
1
2
3
4
5
Fig. 6. Reduction and/or isomerization of 1-octen-3-ol catalyzed by complexes 1e5
using Na-formate as an H-source. Conditions: 0.01 mmol Ru-complex; 0.50 mmol
HCOONa in 3 mL water; 0.50 mmol 1-octen-3-ol in 1 mL toluene; T ¼ 80 ꢁC, t ¼ 1 h
(A conversion, ketone, alcohol).
d
¼ 47.25 (t, JPC ¼ 8 Hz, NCH2P), 50.16 (s, S-dmso, CH3), 51.99 (d,
JPC ¼ 8 Hz, NþCH2P), 66.37 (s, NCH2N), 69.80 (s, NþCH2Ph), 78.71 (s,
NþCH2N), 124.22 (s, Ph), 129.46 (s, Ph), 131.18 (s, Ph), 132.83 (s, Ph)
ppm; P{1H} NMR (145 MHz, D2O, 25 ꢁC)
d
¼ ꢀ36.4 (s) ppm. MS
31
(ESIþ): m/z observed 860.100, calcd. 860.265 for {[RuCl2(dm-
so)2(pta-Bn)2]Cl}þ. S25 ¼ 50 mg/mL water.
were prepared according to the literature. (pta-Me)CF3SO3 [25] was
kindly supplied by Prof. A. Romerosa (U. Almería, Spain). 1 is a light
sensitive compound [9,53], therefore its reactions were studied
with the careful exclusion of light.
ꢁ
C
4.2.3. Preparation of cis-cis-trans-[RuCl2(dmso)2(pta-
Me)2](CF3SO3)2, (4)
All reactions and manipulations were carried out under argon
atmosphere. Reaction mixtures were analyzed by gas chromatog-
raphy (HP5890 Series II; Chrompack WCOT Fused Silica
30 mꢂ32 mm CP WAX52CB; FID; carrier gas: argon). The products
were identified by comparison to known compounds. 1H, 31P and
13C NMR spectra were recorded on a Bruker Avance 360 MHz
spectrometer and referenced to 3-(trimethylsilyl)propanesulfonic
acid Na-salt (DSS). ESI mass data were collected on a BRUKER
BioTOF II ESI-TOF spectrometer.
In the dark, 1 (100 mg 0.21 mmol) and (pta-Me)(CF3SO3)
(132.7 mg, 0.41 mmol) was dissolved in 5 mL of water. The solution
was stirred for 4 h at room temperature and then the solvent was
removed under vacuum. The residue was dissolved in a small
amount of methanol and 4 was precipitated with diethyl ether to
yield a pale yellow solid. This was washed with acetone and with
diethyl ether and dried under Ar. Yield 134 mg, 67%. X-ray quality
crystals were obtained by slow diffusion of methanol into aqueous
solution of 4. Anal. calc. for RuC20Cl2F6H42N6O8P2S2 (4$2H2O)
(M ¼ 906.62) C 23.86, H 4.60, N 8.34, S 12.74%; found C 23.99, H
4.53, N 8.18, S 13.00%. lmax(H2O)/nm 344 (ε/dm3 molꢀ1 cmꢀ1 480).
Solubilities were determined by incremental addition of the
compounds to water. Complete dissolution was checked by laser
light scattering.
1H NMR: (360 MHz, D2O, 25 ꢁC),
d
¼ 2.84 (s, 6H, NþeCH3), 3.38 (s,
12H, S-dmso, CH3), 4.32 (s, 8H, NCH2P), 4.44e4.38 (4H, m, NþCH2P),
4.52 (m, 4H, NCH2N), 4.91e5.10 (m, 8H, NþCH2N) ppm; 1H NMR:
4.2. Synthesis and characterization of Ru(II) complexes
(360 MHz, MeOD, 25 ꢁC),
d
¼ 4.31 (s, 6H, NþeCH3), 4.81 (s, 12H, S-
4.2.1. Preparation of cis-cis-trans-[RuCl2(dmso)2(pta)2], (2)
dmso, CH3), 5.83 (m, 8H, NCH2P), 5.90 (m, 4H, NþCH2P), 5.95 (m, 4H,
In the dark, a mixture of 1 (400 mg 0.82 mmol) and pta (259 mg,
1.64 mmol) in chloroform (5 mL) was stirred for 2 h at room
temperature. Then most of the solvent was removed under vacuum
and the residue was triturated with diethyl ether to provide a pale
yellow solid. This was washed with acetone and with diethyl ether
and dried under Ar to result in a strongly hygroscopic solid. Yield
527 mg (82%). X-ray quality crystals were grown by slow diffusion
of diethyl ether into a chloroform solution of 2 at ꢀ15 ꢁC. Anal. calc.
for RuC16Cl2H36N6O2P2S2 (2$0.5 CHCl3) (M ¼ 642.30) C 28.22, H
5.23, N 11.97, S 9.13%; found C 28.67, H 5.40, N 12.17, S 9.98%.
NCH2N), 6.61e6.69 (m, 8H, NþCH2N) ppm; 13C NMR (90 MHz, D2O,
25 ꢁC)
d
¼ 46.97 (t, JPC ¼ 7 Hz, NCH2P), 49.43 (s, NþeCH3), 50.14 (s, S-
dmso, CH3), 55.38 (t, NþCH2P), 68.79 (s, NCH2N), 79.99 (s, NþCH2N),
121.34 (m, CF3SO3ꢀ) ppm; 31P{1H} NMR (145 MHz, 25 ꢁC) in D2O
d
¼ ꢀ39.61 (s), in MeOD
d
¼ ꢀ37.67 (s) ppm; 19F{1H} NMR
(283 MHz, D2O, 25 ꢁC)
d
¼ ꢀ79.10 (s, CF3SOꢀ3 ) ppm. MS (ESIþ): m/z
observed 821.013, calcd. 821.022 for {[RuCl2(dmso)2(pta-
me)2](CF3SO3)}þ. S25 ¼ 63 mg/mL water.
ꢁ
C
4.3. 31P NMR pH titrations
S25
449).
¼ 34 mg/mL water. lmax(H2O)/nm 338 (ε/dm3 molꢀ1 cmꢀ1
ꢁC
A pH-dependent series of 31P NMR spectra were recorded on
a Bruker 360 MHz instrument at 25 ꢁC and 0.2 mol/dm3 KNO3 ionic
strength. D2O was used as a solvent. The pH measurements in the pH
range 1.1e7.0 for [RuCl2(dmso)2(pta)2], 2 were performed in 0.5 cm3
vessels at a complex concentration of 0.01 mol/dm3. Small amounts
ofcc. NaOD andDNO3 solutions were usedto adjust thepH measured
using a Radelkis OK117 pH meter and a combined electrode.
1H NMR: (360 MHz, CDCl3, 25 ꢁC)
4.43 (s, 12H, PCH2N), 4.52 (s, 12H, NCH2N) ppm; 1H NMR:
(360 MHz; D2O, 25 ꢁC)
¼ 3.31 (s, 12H, S-dmso, CH3), 4.26 (s, 12H,
PCH2N), 4.43 (s, 12H, NCH2N) ppm; 13C NMR (90 MHz, CDCl3, 25 ꢁC)
d
¼ 3.35 (s, 12H, S-dmso, CH3),
d
d
¼ 51.18 (s, S-dmso, CH3), 51.39 (t, JPC ¼ 7 Hz PCH2N), 73.07 (s,
NCH2N), ppm; 31P{1H} NMR (145 MHz, 25 ꢁC) in CDCl3 d ¼ ꢀ60.7 (s),
in D2O
d
¼ ꢀ57.9 (s) ppm. MS (ESIþ): m/z observed 643.030, calcd.
643.031 for [RuCl2(dmso)2(pta)(pta-H)]þ.
4.4. X-ray crystallographic studies
Crystals of cis-cis-trans-[RuCl2(dmso)2(ptaH)2]Cl2, (2a) were
obtained by dissolving 10 mg of 2 in 1 mL of 0.1 M HCl and then it
X-ray data collection was performed using a Bruker-Nonius
MACH3 diffractometer equipped with a point detector using
was layered with 1 mL of ethanol. Anal. calc. for RuC16Cl4H38
-
N6O2P2S2 (2a$3H2O) C 24.97, H 5.76, N 10.92, S 8.33%; found C 24.91,
H 5.53, N 10.82, S 8.33%.
graphite-monochromated Mo-K
structures were solved by the SIR-92 program [54] and refined by
a
radiation,
l
¼ 0.71073 Å. The

122
A. Udvardy et al. / Journal of Organometallic Chemistry 717 (2012) 116e122
full-matrix least-squares method on F2, with all non-hydrogen
atoms refined with anisotropic thermal parameters except in the
solvent region in 2 since chloroform in two orientations occupies
a channel in the lattice (Fig. S1.a). Refinement was performed using
the SHELXL-97 package [55]; publication material was prepared
with the WINGX suite [56]. Hydrogen atoms were located
geometrically and refined in the rigid mode or found at the
difference Fourier map. Solvent water molecules in 2a and 4
(Fig. S1.b and S1.c) have partial occupancy and can have various
orientations forming different hydrogen bond networks with
acceptors resulting shift and errors even in the last stage of the
refinement.
[8] I.P. Evans, A. Spencer, G.J. Wilkinson, J. Chem. Soc., Dalton Trans. (1973) 204e209.
[9] E. Alessio, G. Mestroni, G. Nardin, W.M. Attia, M. Calligaris, G. Sava, S. Zorzet,
Inorg. Chem. 27 (1988) 4099e4106.
[10] T. Suarez, B. Fontal, M. Reyes, F. Bellandi, R.R. Contreras, E. Millan, P. Cancines,
D. Paredes, Trans. Met. Chem. 28 (2003) 217e219.
[11] I.A. Abdallaoui, D. Sémeril, P.H. Dixneuf, J. Mol. Catal. A: Chem. 182e183
(2002) 577e583.
[12] E. Duliere, B. Tinant, A. Schanek, M. Devillers, J. Marchand-Brynaert, Inorg.
Chim. Acta 301 (2000) 147e151.
[13] L.F. Rhodes, C. Sorato, L.M. Venanzi, F. Bachechi, Inorg. Chem. 27 (1988)
604e610.
[14] I. Rojas, F. Lopez-Linares, N. Valencia, C. Bianchini, J. Mol. Catal. A: Chem. 144
(1999) 1e6.
[15] E. Alessio, Chem. Rev. 104 (2004) 4203e4242.
[16] J.M. Davey, K.L. Moerman, S.F. Ralph, R. Kanitz, M.M. Sheil, Inorg. Chim. Acta
281 (1998) 10e17.
[17] M. Brindell, S.K.C. Elmroth, G. Stochel, J. Inorg. Biochem. 98 (2004)
1367e1377.
[18] V. Mahalingam, N. Chitrapriya, F.R. Fronczek, K. Natarajan, Polyhedron 29
(2010) 3363e3371.
4.5. General procedure for catalytic isomerization of allylic alcohols
Under an inert atmosphere, the catalyst precursor (0.01 mmol)
and Na-formate (0.5 mmol) were dissolved in 3 mL of deoxygen-
ated water. The solution was then heated to the indicated
temperature and then allylic alcohol (0.5 mmol, in 1 mL of toluene)
was introduced. The system was rapidly stirred for 1 h and then was
cooled to room temperature. The separated organic phase was
filtered through a short silica gel column and was subjected to gas
chromatography.
[19] P. Mura, M. Canalli, A. Casini, C. Babbiani, L. Messori, J. Inorg. Biochem. 104
(2010) 111e117.
[20] M.J. Clarke, Coord. Chem. Rev. 232 (2002) 69e93.
[21] D.J. Darensbourg, F. Joó, M. Kannisto, Á. Kathó, J.H. Reibenspies, D.J. Daigle,
Inorg. Chem. 33 (1994) 200e208.
[22] A.D. Phillips, L. Gonsalvi, A. Romerosa, F. Vizza, M. Peruzzini, Coord. Chem.
Rev. 248 (2004) 955e993.
[23] L. Gonsalvi, M. Peruzzini, in: M. Peruzzini, L. Gonsalvi (Eds.), Phosphorus
Compounds: Advanced Tools in Catalysis and Material Sciences
(Catalysis by Metal Complexes), vol. 37, Springer, London, 2011, pp.
183e212. ch. 7.
[24] D.J. Daigle, A.B. Pepperman, S.L. Vail, J. Heterocycl. Chem. 11 (1974) 407e408.
[25] A. Romerosa, T. Campos-Malpartida, C. Lidrissi, M. Saoud, M. Serrano-Ruiz,
M. Peruzzini, J.A. Garrido-Cardenas, F. Garcia-Maroto, Inorg. Chem. 45 (2006)
1289e1298.
[26] F.-X. Legrand, F. Hapiot, S. Tilloy, A. Guerriero, M. Peruzzini, L. Gonsalvi,
E. Monflier, Appl. Catal. A: Gen. 362 (2009) 62e66.
Acknowledgments
The authors are indebted to Prof. Antonio Romerosa (U. Almería,
Spain) for the generous supply of (pta-Me)CF3SO3 and for the useful
advices on the synthesis of 4, as well as for support of the stay of A.
Udvardy in his laboratory. Helpful discussions with Prof. Ferenc Joó,
[27] N. Six, A. Guerriero, D. Landy, M. Peruzzini, L. Gonsalvi, F. Hapiot, E. Monflier,
Appl. Catal. Sci. Technol. 1 (2011) 1347e1353.
[28] V. Cadierno, J. Francos, J. Gimeno, Chem. Eur. J. 14 (2008) 6601e6605.
[29] B. Gonzalez, P. Lorenzo-Luis, M. Serrano-Ruiz, É. Papp, M. Fekete, K. Csépke,
}
Dr. Katalin Osz and Mr. Imre Szatmári are gratefully acknowledged.
}
K. Osz, Á. Kathó, F. Joó, A. Romerosa, J. Mol. Catal. A: Chem. 326 (2010) 15e20.
Thanks are due to Dr. Attila Kiss-Szikszay for the elementary
analyses and to Dr. Lajos Nagy for the ESI-MS measurements.
This research was supported by the EU and co-financed by the
European Social Fund through the Social Renewal Operational
Programme under the projects TÁMOP-4.2.1/B-09/1/KONV-2010-
0007 and TÁMOP-4.2.2-08/1-2008-0012 (CHEMIKUT). Financial
support of TEVA Hungary Ltd. and that of the National Research
Fund of Hungary (OTKA K 101372) is also appreciated. A. Udvardy is
grateful for the predoctoral employment grant TÁMOP-4.2.2/B-10/
1/KONV-2010-0024.
[30] W.H. Ang, A. Casini, G. Sava, P.J. Dyson, J. Organomet. Chem. 696 (2011) 989e998.
[31] R.C. Van der Drift, J.W. Sprengers, E. Bouwman, W.P. Mul, H. Kooijman,
A.L. Spek, E. Drent, Eur. J. Inorg. Chem. 8 (2002) 2147e2155.
[32] V. Cadierno, J. Francos, J. Gimeno, N. Nebra, Chem. Commun. (2007)
2536e2538.
[33] C.A. Mebi, B.J. Frost, Inorg. Chem. 46 (2007) 7115e7120.
[34] R. Girotti, A. Romerosa, S. Manas, M. Serrano-Ruiz, R.N. Perutz, Inorg. Chem. 48
(2009) 3692e3698.
}
[35] K. Osz, G. Lente, Cs. Kállay, J. Phys. Chem. B 109 (2005) 1039e1104.
[36] K.J. Fisher, E.C. Alyea, N. Shahnazarian, Phosphorus, Sulfur, Silicon 48 (1990)
37e40.
[37] D.J. Darensbourg, J.B. Robertson, D.L. Larkins, J.H. Reibenspies, Inorg. Chem. 38
(1999) 2473e2481.
[38] C. Scolaro, A. Bergamo, L. Brescacin, R. Delfino, M. Cocchietto, G. Laurenczy,
T.J. Geldbach, G. Sava, P.J. Dyson, J. Med. Chem. 48 (2005) 4161e4171.
[39] F.R. Allen, Acta Cryst. B. 58 (2002) 380e388.
Appendix A. Supplementary material
[40] P. Smolenski, F.P. Pruchnik, Z. Ciunik, T. Lis, Inorg. Chem. 42 (2003)
3318e3322.
[41] D.N. Akbayeva, S. Moneti, M. Peruzzini, L. Gonsalvi, A. Ienco, F. Vizza, C. R.
Chim. 8 (2005) 1491e1496.
[42] J. La Placa, J.A. Ibers, Inorg. Chem. 4 (1965) 778e783.
[43] R.D. Ernst, R. Basta, A.M. Arif, Z. Kristallogr. NCS 218 (2003) 49e51.
[44] A.R. Cowley, J.R. Dilworth, C.A. Maresca, W. von Beckh, Acta Crystallogr., Sect.
E: Struct. Rep. Online 61 (2005) 1237e1239.
[45] H.K. Gupta, P.E. Lock, N. Reginato, J.F. Britten, M.J. McGlinchey, Can. J. Chem. 84
(2006) 277e287.
CCDC 859702e859704 contain the supplementary crystallo-
graphic data for the ruthenium complexes 2, 2a and 4. These data
can be obtained free of charge from Cambridge Crystallographic
Data Centre via http://www.ccdc.cam.ac.uk/data-request/cif.
Appendix B. Supplementary material
Supplementary data related to this article can be found online at
http://dx.doi.org/10.1016/j.jorganchem.2012.07.042.
[46] C. Fu, T.B. Wen, Acta Crystallogr., Sect. E: Struct. Rep. Online 67 (2010) 14.
[47] N. Ahlsten, A. Bartoszewicz, B. Martin-Matute, Dalton Trans. 41 (2012)
1660e1670.
[48] P. Servin, R. Laurent, L. Gonsalvi, M. Tristany, M. Peruzzini, J.-P. Majoral,
A.-M. Caminade, Dalton Trans. (2009) 4432e4434.
[49] T. Campos-Malpartida, M. Fekete, F. Joó, Á. Kathó, A. Romerosa, M. Saoud,
W. Wojtków, J. Organomet. Chem. 693 (2008) 468e474.
[50] F. Joó, J. Kovács, Á. Kathó, A.C. Bényei, T. Decuir, D.J. Darensbourg, Inorg. Synth.
32 (1998) 1e8.
[51] W.A. Herrmann, C.W. Kohlpaintner, Inorg. Synth. 32 (1998) 8e25.
[52] D.J. Daigle, Inorg. Synth. 32 (1998) 40e45.
[53] M. Brindell, G. Stochel, V. Bertolasi, R. Boaretto, S. Sostero, Eur. J. Inorg. Chem.
16 (2007) 2353e2359.
[54] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl. Crystallogr. 26
(1993) 343e350.
[55] G.M. Sheldrick, Acta Crystallogr. A. 64 (2008) 112e122.
[56] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837e838.
References
[1] F. Joó, in: S. Kobayashi (Ed.), Water in Organic Synthesis, Science of Synthesis,
Georg Thieme Verlag KG, Stuttgart New York, 2012, pp. 95e119.
[2] F. Joó, Á. Kathó, in: Chao-Jun Li (Ed.), Handbook of Green Chemistry: Reactions
in Water, Wiley-VCH, Weinheim, 2010, pp. 389e408.
[3] F. Joó, Á. Kathó, in: J.G. de Vries, C.J. Elsevier (Eds.), Handbook of Homogeneous
Hydrogenation, vol. 3, Wiley-VCH, Weinheim,2007, pp. 1327e1359(Chapter38).
[4] F. Joó, Aqueous Organometallic Catalysis, Kluwer, Dordrecht, 2001.
[5] J. Bravo, S. Bolano, L. Gonsalvi, M. Peruzzini, Coord. Chem. Rev. 254 (2010)
555e607.
[6] P. Bernard, M. Biner, A. Ludi, Polyhedron 9 (1990) 1095e1097.
[7] J. Kovács, F. Joó, A.C. Bényei, G. Laurenczy, Dalton Trans. (2004) 2336e2340.