Redox isomerisation of allylic alcohols catalysed by water-soluble ruthenium complexes in aqueous systems

Article abstract of DOI:10.1016/j.jorganchem.2007.11.011

The process of catalytic isomerisation of various allylic alcohols (alk-1-en-3-ols) into saturated ketones under mild conditions is reported. The water-soluble Na₄[{RuCl₂(mtppms)₂}₂] complex, previously reported by us as a precursor to very active hydrogenation catalysts was also found an active catalyst of the redox isomerisation of allylic alcohols in aqueous media. The new Na[Ru(CO)Cp(mtppms)₂] as well as Na₄[{RuCl(μ-Cl)(C{double bond, long}C{double bond, long}CPh₂)(mtppms)₂}₂] and Na₂[RuClCp(mtppms)₂] also showed good to excellent catalytic activities for redox isomerisations in aqueous systems at 50-80 °C under inert atmosphere.

Full text of DOI:10.1016/j.jorganchem.2007.11.011

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 468–474
www.elsevier.com/locate/jorganchem
Redox isomerisation of allylic alcohols catalysed by
water-soluble ruthenium complexes in aqueous systems
a
b
b,c,
c
´
*
´
´
, Agnes Katho ,
Tatiana Campos-Malpartida , Marianna Fekete , Ferenc Joo
a,
a
c
*
´
Antonio Romerosa , Mustapha Saoud , Wojciech Wojtkow
a
´
Area de Quı´mica Inorga´nica, Facultad de Ciencias, Universidad de Almer´ıa, 04120 Almer´ıa, Spain
b Research Group of Homogeneous Catalysis, Hungarian Academy of Sciences, P.O. Box 7, H-4010 Debrecen, Hungary
c Institute of Physical Chemistry, University of Debrecen, P.O. Box 7, H-4010 Debrecen, Hungary
Received 3 August 2007; received in revised form 5 November 2007; accepted 7 November 2007
Available online 13 November 2007
Abstract
The process of catalytic isomerisation of various allylic alcohols (alk-1-en-3-ols) into saturated ketones under mild conditions is
reported. The water-soluble Na4[{RuCl2(mtppms)2}2] complex, previously reported by us as a precursor to very active hydrogenation
catalysts was also found an active catalyst of the redox isomerisation of allylic alcohols in aqueous media. The new Na[Ru
(CO)Cp(mtppms)2] as well as Na4[{RuCl(l-Cl)(C@C@CPh2)(mtppms)2}2] and Na2[RuClCp(mtppms)2] also showed good to excellent
catalytic activities for redox isomerisations in aqueous systems at 50–80 °C under inert atmosphere.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Allylic alcohols; Redox isomerisation; Catalysis; Water-soluble complexes; mtppms; Ruthenium
1. Introduction
In most previous investigation, isomerisation processes
have been studied in organic solvents, such as THF [7,8]
and alkanes [9]. Very efficient catalyst systems were devel-
oped based on ruthenium complexes [10–12]. For example,
the bis(allyl)-ruthenium(IV) dimer, [{Ru(g3:g3-C10H16)(l-
Catalytic isomerisation of allylic alcohols (e.g. Scheme
1) is an attractive strategy for the synthesis of saturated
carbonyl compounds [1–4]. Such internal redox reactions
(transpositions) show 100% atom economy and therefore
much effort has been spent on the study of these processes
following the seminal works of Blum [5] and Trost [6].
Redox isomerisation of an allylic alcohol can be regarded
as an internal oxidation followed by reduction (or the
reverse sequence). However, sensitive substrates may not
survive the conditions of oxidation and/or reduction there-
fore catalytic redox isomerisations are especially useful in
syntheses requiring mild reaction conditions.
Cl)Cl}2]
(C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl)
catalysed the isomerisation of oct-1-en-3-ol in THF at
75 °C with a turnover frequency (TOF) as high as
62500 hÀ1 [TOF = (mol converted substrate)(mol cata-
lyst)À1 hÀ1] [12]. A specific application is the reduction of
allylic alcohols in propan-2-ol when the isomerisation
and consequent transfer hydrogenation is catalyzed by
the same complex, [{RuCl(l-Cl)(g6-C6Me6)}2] [13]. Isom-
erisation of allylic alcohols was also studied with Rh(I)-cat-
alysts in phase-transfer assisted aqueous-organic biphasic
systems [14] in which, however, the catalytically active
Rh(I) complex resided in the organic phase.
*
Corresponding authors. Tel.: +36 52512900; fax: +36 52512915
Water as an environment-friendly solvent for organic
reactions attracts more and more interest both from indus-
trial and academic viewpoints [15–18]. The most common
´
(F. Joo); tel.: +34 638140119; fax: +34 950015008 (A. Romerosa).
´
E-mail addresses: fjoo@delfin.unideb.hu (F. Joo), romerosa@ual.es
(A. Romerosa).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.11.011

T. Campos-Malpartida et al. / Journal of Organometallic Chemistry 693 (2008) 468–474
469
In addition to tertiary phosphine-containing catalysts, a
few complexes with N-heterocyclic carbene ligands were
also used as catalysts of redox isomerisation of allylic alco-
hols in aqueous media showing a maximum turnover fre-
quency of 65 hÀ1 [36,37].
R
cat.
R
OH
O
Scheme 1. Isomerisation of 1-alkene-3-ols.
For long, we have been interested in the syntheses and
catalytic properties of water-soluble organometallic com-
plexes of ruthenium(II) [38] and in the effects of the
aqueous phase on reactions catalyzed by such complexes
[39–41]. Here, we describe the catalytic activity of Na4
[{RuCl2(mtppms)2}2] (1), Na4[{RuCl(l-Cl)(C@C@CPh2)
(mtppms)2}2] (2), [42] and Na2[RuClCp(mtppms)2] (3),
[43] in the isomerisation of allylic alcohols in water. In
addition, the synthesis and some catalytic properties of
the novel water-soluble complex Na[Ru(CO)Cp(mtppms)2]
(4), are also reported. (See Scheme 2.)
and efficient catalysts in aqueous media are transition
metal complexes containing water-soluble phosphines,
such as the monosulfonated and trisulfonated triphenyl-
phosphines, usually as their sodium salts (mtppms-Na
[19,20] and mtppts-Na3 [21,22], respectively). A wide range
of homogeneous catalysts containing rhodium, ruthenium,
palladium, iridium, and other metals coordinated by water
soluble phosphine ligands have been reported [15–18,23].
Water-soluble ruthenium(II) complexes of mtppms
(such as Na4[{RuCl2(mtppms)2}2] (1)) have been shown
to act as selective catalysts for the hydrogenation of a,b-
unsaturated aldehydes [24,25] as well as of the stereoselec-
tive hydrogenation of disubstituted alkynes [26]. The pH of
the aqueous phase decisively influenced the selectivity what
was attributed to the pH-dependent formation of the
mono- and dihydride species, Na3[RuHCl(mtppms)3] and
Na3[RuH2(mtppms)3], respectively [27,28]. These findings
call attention to a thorough investigation of the pH-effects
in aqueous organometallic catalytic processes.
The catalytic isomerisation of allylic alcohols in aqueous
systems has already been investigated. McGrath and Grub-
bs used [Ru(H2O)6](tos)2 (tos = p-toluenesulfonate) for
their mechanistic studies on allyl alcohol isomerisation in
water [29]. Other ruthenium-based catalysts for aqueous
processes included [{Ru(g3:g3-C10H16)(l-Cl)Cl}2] [12],
[RuCl2(g6-p-cymene){j-(P)-PPh3Àn(OCH2CH2NMe3)n}]
[SbF6]n (n = 1, 2 or 3) [30], [RuCl2(g6-p-cymene){j-(P)-
PPh3Àn(OCH2CH2NMe2)n}] (n = 1,2 or 3) [30],
[RuCl2(g6-arene){P(CH2OH)3}] [31] and [RuCl2(g6-
arene) (THPA)] (THPA = 2,4,10-trimethyl-1,2,4,5,7,10-
hexaaza-3-phosphatricyclo-[3.3.1.13,7]decane) [32].
Several water-soluble rhodium(I) complexes were also
applied as catalyst in such reactions [33–35]. The turnover
frequencies determined under optimum conditions were
generally less than 500 hÀ1, with the notable exception of
the catalyst prepared in situ from Rh2(SO4)3 and mtppts-
Na3 (TOF = 2520 hÀ1 in the reaction of oct-1-en-3-ol in
THF at 80 °C [34]). It should be noted that in the above
studies no attempts were made to control the pH of the
aqueous solutions (phases), e.g. by using appropriate
buffers.
2. Results and discussion
2.1. Catalytic isomerisation of oct-1-en-3-ol in water
The catalytic isomerisation by water soluble ruthenium
complexes 1–4 of terminal allylic alcohols has been studied.
Reactions were performed in 3 mL of water using 0.5 mol%
of ruthenium catalyst and 1 mmol of the corresponding
allylic alcohol. Progress of the reactions was monitored
by gas chromatography or 1H NMR spectroscopy. The
effects of various reaction parameters on the isomerisation
of oct-1-en-3-ol catalysed by the water-soluble ruthenium
complex Na4[{RuCl2(mtppms)2}2] (1) are shown in Figs.
1–4.
As shown in Fig. 1, water-soluble complex 1 was active
in catalysis of the isomerisation of oct-1-en-3-ol to give
selectively 3-octanone. No products other than 3-octanone
were detected. After a slight induction period the reaction
proceeds steadily with a turnover frequency (TOF) of 79
(mol substrate)(mol Ru)À1 hÀ1. (Turnover frequencies cal-
culated for the middle part of the S-curve and for the sake
of comparison of catalysts TOF-s are given for 1 mol of Ru
rather than for 1 mol of the complexes of which 1 and 2 are
dimeric in contrast to the monomeric 3 and 4.)
The yield of the transformation was observed to be
dependent of the pH of the aqueous phase (Fig. 2). After
1 h at 50 °C the highest isomerisation yield was obtained
at pH 5.0 (45%). In more acidic solutions the catalytic
activity of 1 dropped sharply. Therefore in further studies
the pH of the reaction was adjusted to the range of 5–7.
A study of the reaction rate as a function of temperature
was undertaken in the range from 20 to 60 °C. It is seen in
Fig. 3 that there was hardly any reaction below 40 °C, how-
ever, above this temperature the reaction rate increased
exponentially with increasing temperatures. It is important
to point out that at 60 °C a conversion of 97% is obtained
in a reaction time of 1 h, corresponding to a TOF of
Table 1
Isomerisation of oct-1-en-3-ol catalyzed by 2 as a function of the pH
pH
Conversion (%)
2.2
4.0
5.0
7.0
51
97
100
16
101 hÀ1
.
Catalysis of the isomerisation reaction by 1 was also
studied in the presence of free mtppms; the results are
Conditions: 15.5 mg 2 (0.013 mmol Ru), 0.15 mL oct-1-en-3-ol (1.0 mmol),
80 °C, 3 mL 0.1 M phosphate buffer, 1 h reaction time.

470
T. Campos-Malpartida et al. / Journal of Organometallic Chemistry 693 (2008) 468–474
Ph
4
4
P
P
P
Cl
P
C
Cl
Cl
Cl
C
Ph
C
C
P
P
Ru
Ru
Ru
P
Ru
P
Cl
C
Ph
Cl
Cl
Cl
C
Ph
1
2
2
Ph P
2
P =
Ru
Ru
Cl
P
P
CO
SO
3
P
P
3
4
Scheme 2. Structures of complexes 1–4.
100
80
60
40
20
0
100
80
60
40
20
0
0
20
40
Temperature (°C)
60
80
0
0.5
1
1.5
Time (h)
2
2.5
3
Fig. 1. Isomerisation of oct-1-en-3-ol catalysed by 1 as a function of time.
Conditions: 10.0 mg 1 (0.01 mmol Ru), 0.16 mL oct-1-en-3-ol (1.04 mmol),
50 °C, 3 mL 0.1 M phosphate buffer, pH 7.0.
Fig. 3. Isomerisation of oct-1-en-3-ol catalysed by 1 as a function of
temperature. Conditions: 10.0 mg 1 (0.01 mmol Ru), 0.16 mL oct-1-en-3-ol
(1.04 mmol), 3 mL 0.1 M phosphate buffer, pH 7.0, 1 h reaction time.
50
40
30
20
10
0
40
30
20
10
0
0
0.5
1
1.5
2
2.5
0
2
4
6
8
10
12
[
m
tppms]/[Ru] (mol/mol)
pH
Fig. 4. Effect of free mtppms on the isomerisation of oct-1-en-3-ol
catalysed by 1. Conditions: 10.0 mg 1 (0.01 mmol Ru), 0.16 mL oct-1-en-3-
ol (1.04 mmol), 50 °C, 3 mL 0.1 M phosphate buffer, pH 7.0, 1 h reaction
time.
Fig. 2. Isomerisation of oct-1-en-3-ol catalysed by 1 as a function of the
pH of the aqueous phase. Conditions: 10.0 mg 1 (0.01 mmol Ru), 0.16 mL
oct-1-en-3-ol (1.04 mmol), 50 °C, 3 mL 0.1 M phosphate buffer, 1 h
reaction time.
In summary, these experiments showed that oct-1-en-3-
ol could be rapidly and quantitatively isomerized to 3-octa-
none (97%) by 1 in water under very mild conditions
depicted in Fig. 4. The results show a strong inhibition of
the reaction by the ligand excess, therefore the best cata-
lytic activity was observed in the absence of excess mtppms.
(60 °C, pH 7) with a TOF as high as 101 hÀ1
.

T. Campos-Malpartida et al. / Journal of Organometallic Chemistry 693 (2008) 468–474
471
This promising result led us to investigate the catalytic
100
80
60
40
20
0
activity of other water-soluble ruthenium complexes con-
taining mtppms. The allenylidene ruthenium complex
Na4[{RuCl(l-Cl)(C@C@CPh2)(mtppms)2}2] (2) [42] was
studied in the isomerisation of oct-1-en-3-ol into 3-octa-
none under similar reaction conditions to those with 1 as
catalyst. Allenylidene and vinylidene ruthenium complexes
are among the most efficient catalysts in catalysed alkene
isomerisation [44,45] but of that kind of complexes 2 is
the only example known in literature which shows good
solubility in water.
Although complex 2 is an active catalyst of the isomeri-
sation process, its activity at 50 °C was lower than that
observed for 1. Nevertheless at 80 °C and pH 5.0 the com-
plex mediated the quantitative isomerisation of oct-1-en-3-
ol into the corresponding ketone (Table 1). It is important
to point out that this reaction is very sensitive to the pH of
the reaction mixture as the conversion yield dropped down
from 100% to 16% when the pH was modified from 5 to 7.
These results evidenced two important points: (a) coor-
dination of an allenylidene ligand to the central metal ion
may lead to a reduction of the isomerisation yield, and
(b) a precise control of the reaction pH is mandatory in
case of these kind of catalysts. Nevertheless, at the opti-
mum pH the activity of 2 (TOF = 77 hÀ1 at pH 5.0) was
comparable to that of 1.
0
2
4
6
8
pH
Fig. 5. Isomerisation of oct-1-en-3-ol catalyzed by 3 as a function of pH.
Conditions: 4.5 mg 3 (0.0045 mmol Ru), 0.75 mL oct-1-en-3-ol (5.0 mmol),
80 °C, 3 mL of 0.1 M phosphate buffer, 0.5 h reaction time.
100
80
60
40
20
0
Na2[RuClCp(mtppms)2] (3) [43] is a water-soluble half-
sandwich complex of ruthenium. This compound showed
excellent catalytic activity in the isomerisation of oct-1-
en-3-ol at 80 °C. With 1 mol% catalyst 100% conversions
were achieved in the pH range 2.2–7.0 and the effect of
the pH on the reaction rate could be observed only with
0
20
40
60
80
100
a
high substrate/catalyst loading, i.e. [S]/[C]=1100
(Fig. 5). Under the conditions of Fig. 5 the highest activity
(100% conversion) corresponds to TOF = 2226 hÀ1
Temperature (°C)
.
The rate of the isomerisation of oct-1-en-3-ol increased
sharply with the temperature (Fig. 6). It is noteworthy that
this catalyst remains active even at room temperature. This
compares favourably to the case of 1, where hardly any
activity could be observed below 40 °C (vide supra).
Na2[RuClCp(mtppms)2] (3) showed pronounced stabil-
ity in water. The 31P{1H} NMR spectrum of the complex
in aqueous solution did not change appreciably during
24 h at 40 °C, and only after 4 days was its decomposition
to unidentified products observed. The stability of 3 in
water suggests no extensive ligand dissociation from the
Fig. 6. Isomerisation of oct-1-en-3-ol catalyzed by 3 as a function of
temperature. Conditions: 9 mg 3 (0.009 mmol), 0.15 mL oct-1-en-3-ol
(1.0 mmol), 3 mL of 0.1 M phosphate buffer, pH 4.0, 0.5 h reaction time.
complex. This is in line with the finding that even at high
chloride excess the catalytic activity of 3 is decreased only
by 15% (Table 2). However, it cannot be excluded that
reaction of 3 with allylic alcohols generates a chloride-free
Ru(II)-hydride complex with loosely bound mtppms
ligands, which in turn is capable of fast catalysis of the
redox isomerisation.
In order to clarify the role of ligand elimination from 3
in the catalytic isomerisation of the oct-1-en-3-ol in water,
we
synthesized
the
carbonyl
complex
Na[Ru
Table 2
(CO)Cp(mtppms)2] (4) in which the ClÀ ligand in 3 was
substituted by CO. The reaction of CO with 3 did not pro-
ceed at 40 °C in 24 h, however, on the addition of AgOTf
Na[Ru(CO)Cp(mtppms)2] (4) was readily obtained. This
complex is water-soluble and stable in the temperature
range used for catalytic evaluations. At pH 7.0, 4 catalyzed
the redox isomerisation of oct-1-en-3-ol to octan-3-one
with a TOF as low as 10 hÀ1. This result shows that
Isomerisation of oct-1-en-3-ol catalyzed by 3 as a function of chloride
concentration of the aqueous phase
[ClÀ] (M)
[ClÀ]/[Ru]
Conversion (%)
TOF (hÀ1
)
0.1
0.2
0.4
67
133
267
100
92
85
222
204
189
Conditions: 4.5 mg 3 (0.0045 mmol Ru), 0.15 mL oct-1-en-3-ol (1.0 mmol),
80 °C, 3 mL of 0.1 M phosphate buffer, 0.5 h reaction time.

472
T. Campos-Malpartida et al. / Journal of Organometallic Chemistry 693 (2008) 468–474
replacement of chloride by a tightly bound CO blocks
catalysis to a large extent. The remaining activity may be
due to phosphine dissociation under catalysis conditions.
(C@C@CPh2)(mtppms)2}2] (2), Na2[RuClCp(mtppms)2]
(3), and to a lesser extent Na[Ru(CO)Cp(mtppms)2] (4)
are active catalysts of redox isomerisation of allylic alco-
hols in water and in aqueous-organic biphasic systems.
(In general, such transpositions are catalyzed by Ru-
hydride species, so complexes 1–4 are better described as
catalyst precursors.) Of the four complexes 3 turned out
to be the most active with turnover frequencies as high as
2226 hÀ1, nevertheless 1 and 2 also showed TOFs in the
range of 70–100 hÀ1 which corresponds to good catalytic
performance in comparison with the catalyst reported ear-
lier in the literature.
Although it is not possible to make detailed statements
on the mechanistic features of these reactions (furthermore
not all four catalysts may work according to the same
mechanism), a common feature of the isomerisation of
allylic alcohols in water with 1–3 is the strong influence
of pH. It is worth recalling, that the catalysis of allylic alco-
hol isomerisations in organic solvents is strongly acceler-
ated by bases, the most widely used base being KOtBu
[7–13]. In some cases it was explicitly shown that the base
is needed for the formation of the catalytically active
Ru(II)-hydride species [9] (however, we did not investigate
the formation of such hydrides in the reactions of 1–4 and
allylic alcohols). Furthermore, one of the accepted mecha-
nisms of the redox isomerisation of allylic alcohols includes
the formation of alkoxo-intermediates [29] or an g3-oxo-
allyl coordination of the substrate [5,12]. Such coordina-
tions may be also facilitated by the presence of appropriate
bases, therefore an increase of the basicity of the aqueous
phase may lead to the increase of the catalytic activity.
Conversely, the sharp decrease of the catalytic activities
of 1 and 3 above pH 5 suggests that in alkaline solutions
the strong coordination of hydroxide prevents the coordi-
nation of allylic alcohols and stops catalysis.
2.2. Isomerisation of allylic alcohols catalysed by complexes
1–4
The catalytic properties of complexes 1–4 were com-
pared in the redox isomerisation of several alk-1-en-3-ols.
Although there is a difference in the temperature in case
of 1 (50 °C) and 2 and 3 (80 °C), the data of Table 3 show
unambiguously that all the three complexes displayed high
catalytic activities in the redox isomerisation of this set of
substrates. With the exception of prop-2-en-1-ol (allyl alco-
hol) the yields of corresponding carbonyl compounds
obtained by using 2 and 3 are uniformly high. In contrast,
4 was again found less suitable for this type of catalysis,
and for meaningful conversions at 50 °C, pH 7.0 reaction
times as long as 2.5 h were needed (oct-1-en-3-ol: 25%;
hept-1-en-3-ol: 38%; hex-1-en-3-ol; 20%, pent-1-en-3-ol
20%). The case of allyl alcohol deserves special mention
since the conversions obtained with catalysts 1 and 2 were
strikingly low compared to the results with the other sub-
strates in Table 3. The isomerisation of this compound
gives rise to the formation of propanal, while with all the
other substrates the corresponding methyl ketones are
obtained. Aldehydes may undergo CO-abstraction leading
to the formation of less active catalysts. In order to check
this possibility, following the reaction of allyl alcohol with
1 as catalyst we have pumped the reaction mixture dry and
recorded the IR spectrum of the residue (in KBr) – a med-
ium strong absorption band was observed at 1923 cmÀ1
.
Although this frequency does not correspond to the
m(CO) values of the known cis-Na2[RuCl2(CO)2(mtppms)2]
(2000 and 2060 cmÀ1) [46], or to that of Na2[RuCl2-
(CO)(mtppms)2] (1971 cmÀ1) [47], it supports the assump-
tion of the formation of Ru-carbonyls. Nevertheless, the
exact nature of the transformations of 1 during the isomeri-
sation of allylic alcohol needs further elucidation.
3. Experimental
3.1. General remarks
2.3. General discussion
All reactions and manipulations were routinely per-
formed under an atmosphere of dry nitrogen or argon
using standard vacuum-line and Schlenk techniques. Sol-
vents were dried and deoxygenated under nitrogen/vacuum
before use. Reagents were obtained from Sigma–Aldrich-
Fluka and Lancaster and used without purification.
Doubly distilled water was used throughout. Gas chro-
matographic measurements were made on a Hewlett-Pack-
ard HP 5890 Series II equipment using a 2 m Carbowax
20 M on 80/100 Chromosorb 3.5% KOH column and
The results described in this communication show
that Na4[{RuCl2(mtppms)2}2] (1), Na4[{RuCl(l-Cl)-
Table 3
Isomerisation of allylic alcohols catalyzed by complexes 1–3
Substrate
Conversion (%)
1
2
3
Oct-1-en-3-ol
Hept-1-en-3-ol
Hex-1-en-3-ol
Pent-1-en-3-ol
But-1-en-3-ol
Prop-2-en-1-ol
39
36
96
90
100
10
100
99
99
93
88
55
100
97
99
98
98
1
FID. H NMR spectra were recorded in D2O or CDCl3
solutions on a Bruker AM300 or on a Bruker AVANCE
DRX300 spectrometer operating at ca. 300 MHz (1H)
and ca. 75.4 MHz (13C), respectively. Peak positions are
reported relative to tetramethylsilane calibrated against
the residual solvent resonance (1H) or the deuterated sol-
vent multiplet (13C). 31P{1H} NMR spectra were recorded
100
Conditions: 0.01 mmol catalyst, 1 h reaction time, 3 mL 0.1 M phosphate
buffer. (1) Substrate 1.04 mmol, 50 °C, pH 7.0; (2) substrate 1.00 mmol,
80 °C, pH 5.0; (3) substrate 1.00 mmol, 80 °C, pH 4.0.

T. Campos-Malpartida et al. / Journal of Organometallic Chemistry 693 (2008) 468–474
473
on the same instrument operating at ca. 121 MHz. Chemi-
cal shifts were measured relative to external 85% H3PO4
with downfield values taken as positive.
frequencies were calculated from the yields of isomerized
products obtained in the given reaction times (usually
0.5–1.0 h).
3.2. Synthesis of complexes
4. Conclusion
3.2.1. Known compounds
Na4[{RuCl2(mtppms)2}2] (1), Na4[{RuCl(l-Cl)(C@C@
CPh2)(mtppms)2}2] (2), Na2[RuClCp(mtppms)2] (3), and
Na[Ru(CO)Cp(mtppms)2] (4) showed good to excellent
catalytic activities (with turnover frequencies up to
2226 hÀ1) in the transpositions of simple allylic alcohols
in homogeneous aqueous solutions or in two-phase reac-
tions. Replacement of chloride in 3 by a strongly bound
CO led to a substantial drop in the catalytic activity which
shows the need for an easy-to-substitute ligand for good
catalytic activity. It is also essential to adjust the pH of
the aqueous phase to its optimum value which for the
above catalysts was found in the range of 4–7.
The water-soluble phosphine ligand, mtppms-Na
(mtppms-Na@Ph2P(C6H4-3-SO3Na)) and the complexes
Na4[{RuCl2(mtppms)2}2] (1) [20], Na4[{RuCl(l-Cl)
(C@C@CPh2) (mtppms)2}2] (2) [42], and Na2[RuClCp
(mtppms)2] (3) [43] were prepared according to the
literature.
3.2.2. Synthesis of Na[Ru(CO)Cp(mtppms)2] (4)
A Schlenk vessel containing Na2[RuClCp(mtppms)2] (3;
0.1 g, 0.107 mmol) dissolved in 10 mL of ethanol was
cooled at 0 °C and then CO was bubbled through the solu-
tion for 20 min. Into the resulting pale yellow solution
0.030 g (0.12 mmol) of AgOTf was added and the solution
was stirred for further 1 h at room temperature, then fil-
tered and the solvent evaporated. The resulting pale yellow
solid was dissolved in ethanol (5 mL) and precipitated by
diethyl ether (4 mL). The pale yellow precipitate was recov-
ered by filtration, washed with diethyl ether (2 Â 2 mL) and
Acknowledgements
The authors are grateful for the financial support pro-
´
vided by the Junta de Andalucıa (PAI), the Ministerio de
´
Tecnologıa of Spain (MCYT) (Project
Ciencia
y
CTQ2006-06552/BQU.MCRTN), the European Comission
Research Directorate General Human Resources and
Mobility (AQUACHEM Project; MRTN-CT-2003-
503864), the European Cooperation in the Field of Science
and Technology (COST) Actions D17 and D29, the Hun-
garian-Spanish Intergovernmental Collaboration in Science
air dried. Yield: 66.8%; S25;H O: 70 mg/cm3. Elemental anal-
2
ysis for C42H33O7P2S2NaRu Á H2O (918.019): Found: C,
54.72; H, 3.80; S, 6.69%; Calc. C, 54.90; H, 3.84; S, 6.97.
IR (KBr, cmÀ1): 1975 m(CO), 1189, 1224 m(SO3); 1H
NMR (300.13 MHz, CD3OD, T = amb.): d = ppm 2.32
(s, CH3Ph, 3H), 5.20 (s, Cp, 5H), 6.93–8.02 (m, aromatic,
28H); 13C{1H} NMR (75.494 MHz, CD3OD, T = amb.):
´
and Technology (TeT E-10/2005; HH2005-0001) and the
Hungarian National Research and Technology Office – Na-
tional Research Fund (NKTH-OTKA K 68482). T.C.-M.
thanks the Ministerio de Asuntos Exteriores y de Coopera-
2
d = ppm 203.02 (t, JCP = 17.80 Hz, RuCO), 126.35–
145.40 (m, aromatic), 90.86 (s, Cp); 31P{1H} NMR
(121.49 MHz, CD3OD, T = amb.): d = ppm 43.41 (s,
mtppms).
´
´
cion – Agencia Espanola de Cooperacion Internacional
˜
(MAE-AECI) for a predoctoral fellowship. W.W. is grate-
ful for an AQUACHEM ER fellowship. The travel grants
provided by COST Action D29 for M.F. and T.C.-M. are
gratefully acknowledged.
3.2.3. Stability study of 4 in water
Complex 4 (10 mg, 0.01 mmol) was dissolved in 0.5 mL
of water in a 5 mm NMR tube. The 31P{1H} NMR spec-
trum was recorded from 25 to 95 °C, in which temperature
range it was not appreciably modified.
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