Single and double metallic layer-containing ruthenium dendrimers. Synthesis and catalytic properties

Article abstract of DOI:10.1039/b406272h

The reaction of a series of phosphanyl-terminated carbosilane dendrimers displaying only one phosphorus ligand per arm with [RuCl₂(p-cymene)] ₂ resulted in the grafting of RuCl(p-cymene) moieties on the periphery of the dendrimer. In these species, the chloride ligand is easily displaced by the organic bases pyridine, 4-cyanopyridine and 4,4'-bipyridine to afford new cationic metallodendrimers. NMR studies have confirmed the chirality of the ruthenium centre. The species containing 4,4'-bipyridine reacts through the uncoordinated pyridyl nitrogen with a new equivalent of [RuCl ₂(p-cymene)]₂ or [RhCl(CO)₂]₃2 to lead to homo- or hetero-bimetallic layer-containing dendrimeric systems. The ruthenodendrimers were tested as catalysts in the transfer hydrogenation of cyclohexanone by propan-2-ol and their activity compared with that of some analogous mononuclear ruthenium(II) complexes.

Full text of DOI:10.1039/b406272h

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F U L L P A P E R
Single and double metallic layer-containing ruthenium
dendrimers. Synthesis and catalytic properties
Inma Angurell, Guillermo Muller, Mercè Rocamora, Oriol Rossell* and Miquel Seco
Departament de Química Inorgànica, Universitat de Barcelona, Martí i Franquès, 1-11,
E-08028 Barcelona, Spain. E-mail: oriol.rossell@qi.ub.es
Received 26th April 2004, Accepted 4th June 2004
First published as an Advance Article on the web 8th July 2004
The reaction of a series of phosphanyl-terminated carbosilane dendrimers displaying only one phosphorus ligand per
arm with [RuCl2(p-cymene)]2 resulted in the grafting of RuCl(p-cymene) moieties on the periphery of the dendrimer. In
these species, the chloride ligand is easily displaced by the organic bases pyridine, 4-cyanopyridine and 4,4′-bipyridine to
afford new cationic metallodendrimers. NMR studies have confirmed the chirality of the ruthenium centre. The species
containing 4,4′-bipyridine reacts through the uncoordinated pyridyl nitrogen with a new equivalent of [RuCl2(p-cymene)]2
or [RhCl(CO)2]2 to lead to homo- or hetero-bimetallic layer-containing dendrimeric systems. The ruthenodendrimers were
tested as catalysts in the transfer hydrogenation of cyclohexanone by propan-2-ol and their activity compared with that of
some analogous mononuclear ruthenium(II) complexes.
Introduction
The preparation of organometallic dendrimers constitutes one of the
most exciting frontiers of current chemical research because these
compounds may have the potential for a range of applications in
different areas of science and technology owing to their precisely
defined nanoscale, often globular, molecular structure.1
Althoughexamplescontainingmetalsasdendrimercores, branch-
ing centres, or building block connectors have been published, the
majority of the compounds include organometallic fragments as
terminal groups. In many cases, such species are synthesized by
2
3
reacting -PR2 or -NR2 functionalized dendrimers on the surface
with metal complexes containing labile ligands. Processes based
on direct complexation of alkyne-terminated dendrimers have also
been described.4 Following these synthetic procedures, metallo-
dendrimers of almost all the transition metals are known.5 In the last
five years we have reported the synthesis of carbosilane dendrimers
decorated on the surface by Au,6 Pd,7 Pt,7 Rh,8 and Ir8 fragments.
Some of these compounds have proved to be catalytically active in
processes such as the hydrovinylation of styrene6 or the hydrogen-
ation of 1-hexene.7 Furthermore, gold dendrimers were found to
be excellent precursors for the synthesis of mixed transition metal
clusters grafted on the periphery of the dendrimer.9 Here, we report
the formation of new neutral and cationic ruthenium carbosilane
dendrimers and their activity in the catalytic transfer hydrogenation
process. In addition, we discuss a new synthetic method for the
preparation of double metallic layer dendritic systems, which may
contribute to homogeneous catalysis in the near future.
Chart 1
The 29Si{1H}NMR spectrum showed two or four silicon
environments expected for 1[Ru]4 or 3[Ru]8, respectively. In
both cases external silicon is coupled with the phosphorus nucleus
Results and discussion
Neutral ruthenium dendrimers
1
The alkyldiphenylphosphino terminated carbosilane dendrimers
studied here are shown in Chart 1. Their synthesis and
characterization have been reported elsewhere.6 It should be noted
that the presence of –CH2–CH2–SiMe2– spacers in 3 reduces
the surface congestion and increases the solubility in common
organic solvents.
(2J (SiP) = 14.8 Hz for 1[Ru]4 and 15.1 Hz for 3[Ru]8). The H
spectrum showed the resonances for the methyl, methylene, and
ethylene protons, as well as the presence of the p-cymene ligand.
The molecular peaks in the ES mass spectrum at m/z 2361.4
([M − Cl]+) (calcd. 2359.1) and 1162.06 ([M − 2Cl]2+) (calcd.
1161.8) for 1[Ru]4 and 1761.6 ([M − 3Cl]3+) (calcd. 1761.4) and
1314.2 ([M − 4Cl]4+) (calcd. 1312.2) for 3[Ru]8 confirms the
identity of the ruthenodendrimers. The metallation of dendrimer
2 was not so straightforward. When 2 was allowed to react with
[RuCl2(p-cymene)]2 in a 2:1 P:Ru molar ratio, the 31P NMR
spectroscopy showed two broad signals at  20 and −24 which were
resolved in two others at low temperature. This is consistent with
a mixture of compounds resulting from the aleatory distribution of
the ruthenium fragments on the surface of the dendrimer. Note that,
statistically, species going from 2[Ru]0 to 2[Ru]8 can be formed.
The ruthenium-containing dendrimers 1[Ru]4 and 3[Ru]8 were
obtained by the reaction between 1 or 3 with [RuCl2(p-cymene)]2
in dichloromethane at room temperature [eqn. (1)]. The metallation
was complete within minutes as shown by 31P NMR spectroscopy.
Thus, the complete complexation of the PPh2 end groups was
confirmed by the absence of unreacted phosphine units along with
the emergence of a new signal showing the expected deshielding
effect. The identity of the dendrimers was further confirmed by
elemental analysis as well as H, 13C and 29Si NMR spectroscopy.
1
2 4 5 0
D a l t o n T r a n s . , 2 0 0 4 , 2 4 5 0 – 2 4 5 7
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4

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1
Moreover, some of these species may show positional isomers due
to different possibilities of grafting the ruthenium fragments onto
the phosphino-terminated branches. Interestingly, the remaining
free phosphine ligands of each component of the mixture reacted
with ClAu(tht) allowing the grafting of ClAu units on the periphery
of the dendrimer. Thus, we obtained a mixture of metallodendrimers
with a 1:1 P:metal (ruthenium + gold) ratio for all of them. It is
remarkable that in the MALDI-TOF experiments, all P–Ru bonds
were cleaved and only the gold-containing fragments peaks
[2 + m(AuCl) − Cl]+ were detected, those at 2566,93 (m = 3) and
2799,92 (m = 4) being the most intense. Obviously, the number of
ruthenium fragments in each of the species in the initial mixture
can be inferred from the number of AuCl units, given that the total
number of AuCl and [RuCl2(p-cymene)] moieties should be eight.
took 27 days. Interestingly, both the H and 13C NMR spectra
showed two groups of signals for the p-cymene group and the 31P
NMR spectrum showed two very close peaks of similar intensity at
 30.6 and 31.0. Both groups of signals appear to be attributable to
the presence of two isomers resulting from the high steric crowding
on the periphery of the dendrimer. When a DMSO solution of
2[Ru]4 was heated the two peaks in the 31P NMR spectrum did
4+
not collapse in the range of temperatures studied. Despite these
results, the slowness of the reaction made us discontinue the initial
strategy: we decided to perform our studies on the less congested
dendrimer 1[Ru]4, which has only one phosphorus ligand for each
branch and is more easily accessed. Thus, the reaction of 1[Ru]4
with pyridine in methanol gave, after the addition of (NH4)PF6, the
cationic dendrimer 1[Ru(py)]44+ in 24 h. The species containing the
organic bases 4,4′-bipyridine, 1[Ru(bipy)]44+, and 4-cyanopyridine,
1[Ru(CNpy)]44+, were obtained similarly [eqn. (4)]. The 1H and the
13C NMR spectra of all these cationic species feature interesting
points. For example, the methyl groups of the p-cymene in 1
[Ru(py)]44+ appear split at  1.09 and 0.96, and this fact confirms
that the substitution of the chloride ligand for the pyridine breaks
the symmetry plane passing through the ruthenium and makes
the metal centre chiral. In addition, the high congestion on the
ruthenium precludes the free rotation of both the p-cymene and
the pyridine ligands. Moreover, the lack of free rotation induces
the protons of the methylene group (–CH2P) to become diastereo-
(1)
4+
topic. For 1[Ru(py)]4 they have been assigned to the signals at
 2.23 and 1.78 by 2D-COSY and NOESY experiments and this
was corroborated by comparison with a HSQC 1H–13C experiment
carried out on the analogous 1[Ru(bipy)]44+. The latter species
displays one bipyridine ligand with two non-equivalent rings: the
protons belonging to the ring bonded to the ruthenium were named
H, and H and those of the second and non-coordinate ring, H′
and H′. Unexpectedly, the alpha protons of both rings resonated
simultaneously at  8.74 in CD2Cl2 while the 13C NMR spectrum
showed the expected two signals for the alpha carbon atoms at 
156.8 and 151.1 (and, obviously, two more for each one of the
It is worth noting that the addition of a new amount of the
dinuclear Ru compound to the solution of 2 to achieve the P:Ru
molar ratio 1:1 gave a complicated 31P NMR spectrum, in which
signals at 20.1, 21.3 and 7.4 ppm were the most intense. Despite
the different strategies employed, we were unable to obtain the
expected 2[Ru]8 dendrimer and this result suggests that because
of the steric congestion on the surface of 2, not all the branches are
able to coordinate the ruthenium fragment. This behavior is in clear
contrast with that found for the model compound Me2Si(CH2PPh2)2,
which reacted with [RuCl2(p-cymene)]2 in a 2:1 P:Ru molar ratio
to afford a mixture of three compounds, (the starting dimethyl-
silane, the mono- and the dimetallated ruthenium). However, the
addition of a new equivalent of the ruthenium complex gave pure
Me2Si(CH2PPh2RuCl2(p-cymene))2 according to the 31P NMR
spectrum ( 21.4) [eqn. (2)]. Obviously, in this case the small
volume of the methyl ligands helps the branches to span to avoid
steric impediments.
1
rest of the carbon atoms). 2D-COSY and HSQC H–13C experi-
ments revealed that the identical shift for the alpha protons of the
bipyridine rings was simply a coincidence. The proton integration
ratio confirmed the structure proposed in all cases. The (CN) band
in the IR spectrum may be used also as a useful diagnostic tool
for the chloride displacement by L. Thus, the bonding of L to the
ruthenium centre shifts the absorption to higher frequencies (about
15 cm−1).
In order to graft a bifunctional N, P ligand through the N
donor atom to the dendrimer and thus, consequently, to have a
new phosphorus atom for the coordination of other new metal
fragments, we reacted the ligand pyPPh2 with the dendrimer
1[Ru]4. After several hours of stirring, the 31P NMR spectrum of
the solution evidenced a mixture of two products, as a result of
the coordination of the N, P ligand through both functions. This
Cationic ruthenium dendrimers and synthesis of double
metallic layer dendritic systems
We anticipated that the abstraction of one chloride atom from the
ruthenium centre grafted to the dendrimer would give the possibility
of generating a vacant binding site which could be occupied by a
bifunctional ligand, such as 4,4′-bipyridine. Thus, for example,
in this case, the uncoordinated pyridyl nitrogen could serve as
the coordination site for a second metal fragment, consequently
generating double metal layer dendrimeric systems. To this end,
1
fact was further confirmed by H and 13C NMR spectroscopy. To
correct our strategy, we designed the reaction of the same dendrimer
1[Ru]4 with the gold complex (py)PPh2AuCl. Now, the strong
coordination of the gold to the phosphorus makes the nitrogen atom
the only coordination site facing the dendrimer. Indeed, although
the reaction proceeded slowly, 31P NMR spectroscopy revealed
that the gold complex displaces the chloride ligand in 1[Ru]4 and
is grafted into the surface of the dendrimer [eqn. (5)]. After twenty
days of stirring, (NH4)PF6 was added to the solution and a solid
was separated. The 31P NMR spectrum showed two products: the
4+
the 2[Ru]4 was thought to be an appropriate precursor. There-
fore, in order to establish the best reaction conditions for its
synthesis we first examined the formation of the model compound
[Me2Si(CH2PPh2)2{RuCl(p-cymene)}]PF6. This was success-
fully prepared by stirring Me2Si(CH2PPh2)2 with a solution of
[RuCl(NCMe)2(p-cymene)]PF6. The reaction was completed in
ten days and the product was unambiguously characterized by
spectroscopy. Using the same method, 2 let us isolate the cationic
4+
expected bimetallic dendrimer 1[RuAu]4 and unreacted starting
4+
dendrimer 2[Ru]4 [eqn. (3)]. The complete reaction, however,
dendrimer 1[Ru]4. The proton integration indicated that the mixture
(2)
D a l t o n T r a n s . , 2 0 0 4 , 2 4 5 0 – 2 4 5 7
2 4 5 1

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(3)
(4)
contained 70% of the gold-dendrimer. 1[RuAu]44+ was not isolated.
In the 1H NMR spectrum, the H of the pyridine ring appeared at 
8.77, very close to that found, for example, in 1[Ru(py)]44+( 8.65).
The carbosilane dendrimer exhibited the expected 13C and 29Si NMR
spectral features. On the other hand, note that the coordination of
the gold complex to the dendrimer induces only a slight upfield
shift of about 0.4 ppm of the phosphorus signal of the AuPPh2 unit,
as expected. These observations are clearly consistent with the
formation of the bimetallic Ru/Au dendrimer, but unfortunately,
neither the slowness nor the yield of the process made it
attractive. Thus, we sought to enter this area by paying attention
4+
The reaction of 1[Ru(bipy)]4 with [RhCl(CO)2]2 proceeded
similarly [eqn. (6)]. It was monitored by IR spectroscopy in
the (CO) region showing the IR bands of the RhCl(CO)2 unit
to shift to higher frequencies (about 2088 and 2010 cm−1) in
comparison with the starting [RhCl(CO)2]2. Besides, the (CN)
band for 1[Ru(bipy)]4 at 1595 cm−1 was shifted to 1609 cm−1,
overlapping with the frequency due to the other CN group bonded
to the ruthenium. The H NMR spectrum was also informative in
4+
1
that the two H′s appeared slightly shifted in relation to the starting
ruthenium dendrimer. The methyl, methylene, and ethylene protons
as well as the p-cymene resonances are also present with the correct
proton integration. Like dendrimer 1[Ru(bipy)Ru]44+, the stability
of 1[Ru(bipy)Rh]44+ in solution was rather reduced and the attempts
to register the 13C NMR spectrum resulted in the decomposition of
the product. Probably the very high steric congestion derived from
the volume of the metal fragments makes the stabilization of the
final product difficult.
4+
to the coordinative ability of the cationic dendrimer 1[Ru(bipy)]4
towards some metal fragments. We first studied the reaction of
1[Ru(bipy)]44+ with ClAu(tht) in CH2Cl2. The process was carried
out at room temperature but no reaction was observed after several
hours. This was not surprising due to the fact that gold has little
tendency to coordinate to nitrogen donor atoms. Then, we tested the
4+
reaction of 1[Ru(bipy)]4 with [RuCl2(p-cymene)]2 in acetone-d6
However, despite the instability of these species, the methodology
reported here opens up a route for the synthesis of multilayer metal
dendrimers.
in an attempt to attach a new RuCl2(p-cymene) unit to the second
pyridine ring of the 4,4′-bipyridine [eqn. (6)].After 2 h the 31P NMR
spectrum showed the phosphorus signal slightly shifted downfield
in relation to the starting ruthenium dendrimer. In addition, the
1H NMR spectrum showed the presence of two different cymene
groups with a 1:1 ratio. Moreover, the signal corresponding to the
H′ at  8.92 was displaced at  9.31 ppm after the reaction, confirm-
ing the incorporation of the ruthenium fragment into the molecule.
The IR spectrum of the new species revealed the shift of the (CN)
frequency of the reagent from 1595 cm−1 to 1609 cm−1. Workup
Catalytic transfer hydrogenation of cyclohexanone
In recent years, the attachment of molecular precursors of homo-
geneous catalysts to soluble dendrimer supports has received consi-
derable attention because of the potential advantages regarding the
fixation and recovery or recycling of catalyst.1d,1g,10 The dendrimers
have a well-defined structure with the possibility of attaching a
known large number of active sites on the periphery while basically,
retaining the properties of the simple molecular counterpart.
Therefore, dendrimers loaded mainly with Ni, Pd, Ru and
Rh complexes have been tested as supports for homogeneous
catalysts in a wide number of reactions. Generally, the results
show a slightly lower range of activities than those obtained with
of the solution allowed us to obtain a yellow powder in moderate
4+
yields. All these facts show that the dendrimer 1[Ru(bipy)Ru]4
,
displaying a double layer of ruthenium atoms, has been really
4+
obtained. Unfortunately, 1[Ru(bipy)Ru]4 is not very stable in
solution and it decomposes rapidly, so we were unable to take the
13C NMR spectrum.
2 4 5 2
D a l t o n T r a n s . , 2 0 0 4 , 2 4 5 0 – 2 4 5 7

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(5)
(6)
conventional homogeneous catalysts, probably due to their reduced
accessibility.
ruthenium(II) complexes have proved efficient homogeneous
catalysts for the reduction of ketones and imines. Noyori and
Hashiguchi have successfully developed the asymmetric version of
the reaction with chiral bidentate ligands,13 where different reaction
mechanisms are proposed to operate.14 Furthermore, bidentate
chiral ligands have been attached to Fréchet’s polyether dendritic
wedges giving excellent enantiomeric excesses but limited TOF
values (<100 h−1) in the model reaction with acetophenone.15 On
the other hand, Deng et al.16 reported the synthesis of a nitrogen
functionalized dendrimer and its application to the asymmetric
transfer hydrogenation.
The catalytic hydrogenation of organic substrates is one of the
most widely studied processes. An alternative method, which
avoids the use of gaseous hydrogen and allows the use of standard
reflux techniques, consists of hydrogen transfer reactions. The
hydrogen is supplied by a donor molecule (usually alcohols, formic
acid), which itself undergoes dehydrogenation during the course of
the reaction. These catalytic systems are relatively stable, easy to
handle and environmentally friendly.11
For example, ruthenium complexes of the type [RuCl2(PPh3)3]
have been used as homogeneous catalysts for reduction of both
aliphatic and aromatic ketones by propan-2-ol12 and (6-arene)–
A previous paper8 has described our test of a rhodium dendritic
system in the hydrogenation of olefins. Here, we compare the
D a l t o n T r a n s . , 2 0 0 4 , 2 4 5 0 – 2 4 5 7
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Table 1 Transfer hydrogenation of cyclohexanone using mononuclear
Ru(II) catalytic systemsa
Table 2 Transfer hydrogenation of cyclohexanone using Ru(II) catalytic
systemsa
Entry Catalystb T/°C Base/cat/substratec Time/min Conversion
Entry
Catalyst
Yield (%)b
TOF50/h−1c
(%)d
1
2
3
4
5
6
[RuCl2(p-cymene)(PPh3)]
[RuCl2(p-cymene)(PMePh2)]
[RuClpy(p-cymene)(PMePh2)]PF6
1[Ru]4
1[Ru(py)]4
3[Ru]8
61
81
56
34
26
19
1135
1250
1110
680
450
270
1
2
3
4
5
6
7
8
19
10
11
12
13
14
15
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
r.t.
r.t.
r.t.
82
82
82
82
82
82
82
82
r.t.
82
82
82
24/1/100
4/1/100
1440
1440
1440
30
60
30
60
30
60
30
60
1440
15
30
60
3.9
4.8
7
93
100
87
95
84
100
61.8
98
6.6
96
81
24e/1/100
24/1/100
24/1/100
12/1/100
12/1/100
6/1/100
a Conditions: reactions were carried out at 82 °C using t-BuOK/catalyst/
cyclohexanone ratio: 6/1/1000. bYield of cyclohexanol determined after
30 min reaction. GC determined. c Turnover frequencies ((mol product/mol
catalyst)/time) were calculated at 50% conversion.
6/1/100
6/1/1000
6/1/1000
6/1/100
6/1/100
6/1/1000
6/1/1000
(entries 4 and 5), following the same trend found for the
mononuclear species. Moreover, in standard conditions the
cationic species raises only 62% conversion, showing probable
decomposition of the catalyst. The third generation dendrimer
3[Ru]8 is less active than the first generation one (entries 4, 5 and
6). Nevertheless our ruthenodendrimers show higher activities than
those reported in the literature for other dendrimeric systems.16
Fig. 1 shows conversion of cyclohexanone versus time.
Variation of TOF values with time points to the existence of an
induction period necessary for the formation of an active species
as represented tentatively in Scheme 1. The cationic and the third
generation dendrimers showed deactivation or clear decomposition
giving limited conversions.
>99
a Results from duplicated experiments. b A: [RuCl2(p-cymene)(PPh3)];
B: [RuCl2(p-cymene)(PMePh2)]. c Ratio t-BuOK/cat/cyclohexanone.
d Conversions determined by GC. e Base: NaOH.
activity of the analogous (6-arene)–ruthenium(II) dendritic species
with ruthenium(II) mononuclear complexes in the reduction of
cyclohexanone by the hydrogen transfer reaction [eqn. (7)].
We performed preliminary catalytic studies on the transfer
hydrogenation of cyclohexanone by propan-2-ol for screening
optimal conditions using the mononuclear complexes [RuCl2(p-
cymene)(PPh3)] and [RuCl2(p-cymene)(PMePh2)] as catalysts. As
shown in Table 1 experiments at room temperature were carried
out with different substrate/catalyst/base ratios, using t-BuOK as
base. Very low activities were found for both catalysts (entries 1–3
and 12), and the use of NaOH instead of t-BuOK as base did not
improve significantly the activity of the system. When the reactions
were carried out in refluxing propan-2-ol, the activity increased and
total conversion was found after 30 min with a substrate/catalyst
ratio of 100/1 and no dependence on substrate/base ratio being
observed (entries 4, 6, 8 and 13). For better measurements of
activities the substrate/catalyst ratio was increased to 1000/1 and
total conversion was achieved after 1 h reaction (entries 11 and 15).
Therefore we established the standard conditions for the reaction,
82 °C temperature and a cyclohexanone/catalyst/t-BuOK ratio of
1000/1/6. For good reproducibility of the catalytic results the t-
BuOK solution must be freshly prepared.
Under the same conditions, the catalytic activity of 1[Ru]4,
Fig. 1 Mol% of hydrogenation of cyclohexanone vs. time using monomer
and metallodendrimer Ru(II) compounds as precursors.
4+
1[Ru(py)]4
and 3[Ru]8 metallodendrimers and related
mononuclear complexes [RuCl2(p-cymene)(PPh3)] [RuCl2(p-
cymene)(PMePh2)] and [RuCl(p-cymene)(PMePh2)(py)]PF6 in the
transfer hydrogenation of cyclohexanone by propan-2-ol has been
investigated and the results are displayed in Table 2.
Mononuclear species can be observed to show better activities
than analogous complexes reported in the literature containing
only PPh3 ligand12a or arene and phosphine ligand13c when
similar reaction conditions are used. The neutral complex containing
PMePh2 ligand is more active than that containing PPh3 (entries 1
and 2). Analogously the neutral complex is also more active than
the corresponding cationic complex with pyridine ligand [RuCl(p-
cymene)(PMePh2)(py)]PF6 (entries 2 and 3) but in the same order
of magnitude. The system seems to be slightly more active when the
electron density of the metal centre increases.
Scheme 1
Experimental
All reactions were carried out under an atmosphere of dry nitrogen
using standard Schlenk techniques. Solvents were distilled from
sodium/benzophenone ketyl (thf and Et2O), CaCl2 and storage over
molecular sieves (acetone) or dried with CaCl2 and distilled from
CaH2 (CH2Cl2) under N2 prior to use. Elemental analyses (C, H)
were performed at the Servicio de Microanálisis del Centro de
Investigación y Desarrollo del Consejo Superior de Investigaciones
Científicas (CSIC). 1H, 13C{1H}, 29Si{1H} and 31P{1H} NMR
On the other hand, dendrimeric systems show lower activities
than that found for related mononuclear complexes. Table 2
shows that among first generation dendrimers, the neutral species
1[Ru]4 is more active than the cationic analogue 1[Ru(py)]4
(7)
2 4 5 4
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spectra were recorded at 25 °C on Bruker 250, Bruker 500 and
Mercury 400 spectrometers. Chemical shifts are reported in ppm
CH2P), 0.74 (d, 12H, 3J(HH) = 6.9 Hz, CH(CH3)2), −1.04 (s,
6H, CH3Si); C(CDCl3): 134.8 (d, 1J(CP) = 43.3, ipso-C6H5),
132.9 (d, 2J(CP) = 8.9 Hz, o-C6H5), 130.6 (s, p-C6H5), 128.4
(d, 3J(CP) = 9.7 Hz, m-C6H5), 108.0 (s, C–CH(CH3)2), 92.9 (s,
1
relative to external standards (SiMe4 for H, 13C and 29Si, 85%
H3PO4 for 31P) and coupling constants are given in Hz. Infrared
spectra were recorded with FT-IR 520 Nicolet or Impact 400
Nicolet spectrometers in the 4000–400 cm−1 range as KBr pellets.
MS (ES) spectra were recorded on a Fisons VG Quatro spectro-
meter. MALDI-TOF spectra were recorded on a Voyager DE-RP
(Perspective Biosystems) time-of-flight (TOF) spectrometer using
as a matrix SA (salicylic acid). The GC analysis was performed on
a Hewlett-Packard 5890 Series II gas chromatograph (50 m, HP
Ultra-2 ((5% phenyl)-methylpolysiloxane) with a FID detector.
The starting materials [RuCl2(p-cymene)]2,17 4-pyridyl-
diphenylphosphine,18 ClAu(tht),19 [RhCl(CO)2]2,20 [RuCl2-
2
2
C–CH3), 90.7 (d, J(CP) = 4.3 Hz, C6H4), 85.2 (d, J(CP) = 6.2
Hz, C6H4), 30.1 (s, CH(CH3)2), 21.4 (s, CH(CH3)2), 17.3 (s, CH3),
11.8 (d, 1J(CP) = 22.4 Hz, CH2P), 0.19 (s, CH3Si); Si(CDCl3): 1.96
2
(t, J(SiP) = 13.5 Hz, Si); P(CDCl3): 21.4 (s, PPh2). MS (ES+):
m/z = 1035.7 [M − Cl]+, 499.2 [M − 2Cl]2+.
Si0(C1H2C2H2Si1{(CH3)(CH2PPh2RuCl2(p-cymene))2})4 (2-
[Ru]8). Experimental conditions and workup were identical to
those of the preparation of 1[Ru]4 using 190 mg (0.10 mmol) of
dendrimer 2 and 244 mg (0.40 mmol) of [RuCl2(p-cymene)]2.
P(CD2Cl2, 298K): 21.3 (s), 20.1 (sbr), 7.4 (s).
(p-cymene)(PPh3)],21
[RuCl2(p-cymene)(PMePh2)],22
and
phosphine-terminated dendrimers 1, 2 and 3 were prepared
following published procedures.7,9 Other reagents were purchased
from commercial suppliers.
Si0(C1H2C2H2Si1{(CH3)(CH2PPh2)(CH2PPh2RuCl2(p-
cymene))})4. Experimental conditions and workup were identical
to those of the preparation of 1[Ru]4 using 190 mg (0.10 mmol)
of dendrimer 2 and 122 mg (0.20 mmol) of [RuCl2(p-cymene)]2.
Si(CD2Cl2): 9.4 (s, Si0), 4.0 (m, Si1); P(CD2Cl2, 298K): 21.3
(m, PPh2Ru), −23.3 (m, PPh2); P(CD2Cl2, 220K): 21.7, 21.3
(s, PPh2Ru), −24.6, −24.9 (s, PPh2).
Syntheses
Si0(C1H2C2H2Si1(CH3)2CH2PPh2RuCl2(p-cymene))4 (1[Ru]4).
To a solution of dendrimer 1 (180 mg, 0.15 mmol) in 20 ml of
CH2Cl2 was added [RuCl2(p-cymene)]2 (188 mg, 0.30 mmol) and
the mixture was stirred at room temperature for 1 h. The solvent was
evaporated to dryness, the residue was washed with diethyl ether
and dried under vacuum. The complex was obtained as a red solid
(360 mg, 98%). (Found: C, 54.32; H, 6.12. C108H144Cl8P4Ru4Si5
requires C, 54.17; H, 6.06%; M 2394.6); H(CDCl3): 7.95 (m, 16H,
Si0(C1H2C2H2Si1{(CH3)(CH2PPh2AuCl)(CH2PPh2RuCl2(p-
cymene))})4. Experimental conditions and workup were identical
to those of the preparation of 1[Ru]4 using 190 mg (0.10 mmol)
of dendrimer 2, 122 mg (0.20 mmol) of [RuCl2(p-cymene)]2 and
128 mg (0.40 mmol) of ClAu(tht). MS (MALDI-TOF): 2335.1
[M − 6RuCl2(p-cymene)-Cl]+, 2566.9 [M − 5RuCl2(p-cymene)-
Cl]+, 2799.9 [M − 4RuCl2(p-cymene)-Cl]+, 3032.4 [M − 3RuCl2(p-
cymene)-Cl]+, 3264.2 [M − 2RuCl2(p-cymene)-Cl]+; Si(CD2Cl2):
8.8 (s, Si0), 2.0 (m, Si1); P(CD2Cl2): 21.8–20.1 (m, PPh2Ru,
PPh2Au).
3
C6H5), 7.47 (m, 24H, C6H5), 5.19 (d, 8H, J(HH) = 6 Hz, C6H4),
4.99 (d, 8H, 3J(HH) = 6 Hz, C6H4), 2.50 (sep, 4H, 3J(HH) = 7.0 Hz,
2
CH(CH3)2), 1.93 (d, 8H, J(HP) = 14.5 Hz, CH2P), 1.81 (s, 12H,
3
CH3), 0.74 (d, 24H, J(HH) = 7.0 Hz, CH(CH3)2), −0.3–(−0.55)
(m, 40H, CH2Si, CH3Si); C(CDCl3): 134.8 (d, 1J(CP) = 43.3,
ipso-C6H5), 132.7 (d, 2J(CP) = 8.7 Hz, o-C6H5), 130.8 (s, p-C6H5),
3
128.4 (d, J(CP) = 9.6 Hz, m-C6H5), 107.8 (s, C–CH(CH3)2), 92.5
[Si0(C1H2C2H2Si1(CH3)(CH2PPh2)2RuCl(p-cymene))4][PF6]4
(2[Ru]44+). To a solution of [RuCl2(p-cymene)]2 (74 mg, 0.12 mmol)
in 20 ml of acetonitrile was added (NH4)PF6 (42 mg, 0.24 mmol).
The mixture was stirred overnight and the NH4Cl formed was
removed by filtration through Celite. To this solution was added
another of 2 (115 mg, 0.06 mmol) in 10 ml of thf and the mixture
was stirred for 27 days. The solvent was evaporated to dryness and
the product was recrystallised with CH3CN/diethyl ether. A yellow
solid was obtained (132 mg, 73%). (Found: C, 53.01; H, 4.98.
C156H180Cl4F24P12Ru4Si5 requires C, 52.50; H, 5.08%; M 3569.3);
H(acetone-d6): 7.7–7.1 (m, 80H, C6H5), 6.02 (m, 8H, C6H4), 5.41
(dbr, 4H, C6H4), 5.32 (dbr, 4H, C6H4), 2.61 (m, 2H, CH(CH3)2), 2.34
(m, 10H, CH(CH3)2, CH2P), 1.56–1.42 (m, 8H, CH2P), 1.19 (m,
(s, C–CH3), 91.0 (d, 2J(CP) = 4 Hz, C6H4), 85.3 (d, 2J(CP) = 6 Hz,
C6H4), 30.1 (s, CH(CH3)2), 21.3 (s, CH(CH3)2), 17.4 (s, CH3), 10.7
(m, CH2P), 8.6 (s, C2H2Si1), 2.2 (s, C1H2Si0), −2.2 (s, CH3Si1);
Si(CDCl3): 8.9 (s, Si0), 3.6 (d, 2J(SiP) = 14.8 Hz, Si1); P(CDCl3):
22.7 (s, PPh2). MS (ES+): m/z = 2361.4 [M − Cl]+, 1162.1
[M − 2Cl]2+, 762.6 [M − 3Cl]3+.
Si0(C1H2C2H2Si1(C1H3)2C3H2C4H2Si2(C2H3)(C5H2C6H2Si3-
(C3H3)2CH2PPh2RuCl2(p-cymene))2)4 (3[Ru]8).
Experimental
conditions and workup were identical to those of the prepara-
tion of 1[Ru]4. (183 mg, 88%). (Found: C, 54.10; H, 6.48.
C244H356Cl16P8Ru8Si17 requires C, 54.37; H, 6.66%; M 5390.6);
H(CDCl3): 7.99 (m, 32H, C6H5), 7.47 (m, 48H, C6H5), 5.20 (m,
16H, C6H4), 5.00 (m, 16H, C6H4), 2.50 (sep, 8H, 3J(HH) = 7.0 Hz,
3
12H, CH3), 1.01 (d, 12H, J(HH) = 6.8 Hz, CH(CH3)2), 0.83 (d,
12H, 3J(HH) = 6.8 Hz, CH(CH3)2), 0.26–(−0.39) (m, 28H, CH2Si,
CH3Si); C(acetone-d6): 133.5–128.8 (m, C6H5), 96.4 (sbr, C6H4),
91.8 (sbr, C6H4), 30.9 (s, CH(CH3)2), 20.9, 20.8 (s, CH(CH3)2), 15.0
(s, CH3), 10.5 (m, CH2P), 8.4 (s, C2H2Si1), 2.8 (s, C1H2Si0), 1.9 (s,
CH3Si), −1.2 (s, CH3Si); Si(acetone-d6): 2.0 (sbr, Si1); P(acetone-
d6): 31.0, 30.6 (s, PPh2), −144.2 (sep, PF6−). MS (ES+): m/z = 1639.6
[M − 2PF6]2+, 1045.8 [M − 3PF6]3+, 747.4 [M − 4PF6]4+.
2
CH(CH3)2), 1.95 (d, 16H, J(HP) = 14.0 Hz, CH2P), 1.82 (s, 24H,
3
CH3), 0.73 (d, 48H, J(HH) = 7.0 Hz, CH(CH3)2), 0.28–(−0.53)
(m, 148H, CH2Si, CH3Si); C(CDCl3): 134.9 (d, 1J(CP) = 43.0,
ipso-C6H5), 132.8 (d, 2J(CP) = 8.5 Hz, o-C6H5), 130.8 (s, p-C6H5),
128.4 (d, 3J(CP) = 9.1 Hz, m-C6H5), 107.8 (s, C–CH(CH3)2),
2
92.5 (s, C–CH3), 91.1 (s, C6H4), 85.3 (d, J(CP) = 5.5 Hz, C6H4),
30.1 (s, CH(CH3)2), 21.3 (s, CH(CH3)2), 17.4 (s, CH3), 14.3 (d,
1J(CP) = 14.3 Hz, CH2P), 8.9 (s, C6H2Si3), 7.0, 6.6, 4.7, 4.2, 2.7
(s, CH2Si), −2.1 (s, CH3Si3), −4.2 (s, CH3Si1), −6.6 (s, CH3Si2);
Si(CDCl3): 7.9 (s, Si2), 5.7 (s, Si1), 3.7 (d, 2J(SiP) = 15.1 Hz, Si3);
P(CDCl3): 22.7 (s, PPh2). MS (ES+): m/z = 1761.6 [M − 3Cl]3+,
1314.2 [M − 4Cl]4+, 1162.4 [M − 4Cl–2RuCl2(p-cymene)]4+,
1008.3 [M − 4Cl-4RuCl2(p-cymene)]4+.
[(CH3)2Si(CH2PPh2)2RuCl(p-cymene)][PF6].
Experimental
conditions and workup were identical to those for the prepara-
tion of 2[Ru]44+. (445 mg, 89%). (Found: C, 52.81; H, 5.31.
C38H44ClF6P3RuSirequiresC,52.32;H,5.08%;M872.3);H(CDCl3):
7.66–7.34 (m, 20H, C6H5), 5.66 (d, 2H, 3J(HH) = 6 Hz, C6H4), 5.25
(d, 2H, 3J(HH) = 6 Hz, C6H4), 2.34 (m, 3H, CH(CH3)2, CH2P), 1.43
3
(m, 2H, CH2P), 1.31 (s, 3H, CH3), 0.98 (d, 6H, J(HH) = 7.0 Hz,
(CH3)2Si(CH2PPh2RuCl2(p-cymene))2.Experimentalconditions
and workup were identical to those of the preparation of 1[Ru]4.
(444 mg, 93%). (Found: C, 53.80; H, 5.49. C48H58Cl4P2Ru2Si
requires C, 53.93; H, 5.47%; M 1069.0); H(CDCl3): 7.83(m, 8H,
C6H5), 7.42 (m, 12H, C6H5), 5.11 (d, 4H, 3J(HH) = 6.2 Hz, C6H4),
4.93(d, 4H, 3J(HH) = 6.2Hz, C6H4), 2.43(sep, 2H, 3J(HH) = 6.9 Hz,
CH(CH3)2), 0.01 (s, 3H, CH3Si), −0.37 (s, 3H, CH3Si); C(CDCl3):
138.7 (d, 1J(CP) = 24.4, ipso-C6H5), 133.3 (pt, 2J(CP) = 5 Hz,
2
o-C6H5), 132.2 (s, p-C6H5), 131.3 (pt, J(CP) = 4.4 Hz, o′-C6H5),
3
131.0 (s, p′-C6H5), 129.3 (pt, J(CP) = 5 Hz, m-C6H5), 128.9 (pt,
3J(CP) = 5 Hz, m′-C6H5), 126.6 (s, C–CH(CH3)2), 101.4 (s, C–CH3),
94.9, 92.9 (s, C6H4), 30.7 (s, CH(CH3)2), 21.6 (s, CH(CH3)2), 16.5 (s,
2
CH(CH3)2), 1.74 (s, 6H, CH3), 1.71 (d, 4H, J(HP) = 13.7 Hz,
D a l t o n T r a n s . , 2 0 0 4 , 2 4 5 0 – 2 4 5 7
2 4 5 5

View Article Online
CH3), 10.8 (pt, 1J(CP) = 11.6 Hz, CH2P), 1.42 (sbr, CH3Si), 1.11 (sbr,
−
2J(SiP) = 14 Hz, Si1); P(CD2Cl2): 25.3 (s, PPh2), −144.2 (sep, PF6 ).
−
CH3Si); P(CDCl3): 29.3 (s, PPh2), −144.3 (sep, PF6 ). MS (ES+):
MS (ES+): 937 [M − 3PF6]3+, 667.0 [M − 4PF6]4+. IR: max/cm−1
m/z = 727.6 [M − PF6]2+.
(CN) 1647, 1616 (KBr).
[Si0(C1H2C2H2Si1(CH3)2CH2PPh2RuCl(4,4′-bipy)(p-cymene))4]-
[PF6]4 (1[Ru(bipy)]44+). Asolution of 1[Ru]4 (215 mg, 0.09 mmol)
in 10 ml of methanol was added to a solution of 4,4′-bipyridine
(280 mg, 1.76 mmol) in 10 ml of methanol, dropwise and with
vigorous stirring. The mixture was stirred for 24 h. Then, a solution
of NH4PF6 (63 mg, 0.36 mmol) in 5 ml of methanol was added
and stirred for 2 h. The orange solid was filtered off, washed
several times with diethyl ether and dried under vacuum. (195 mg,
63%). H(CD2Cl2): 8.74 (m, 16H, bipy(H, H′)), 7.91 (m, 8H,
o-C6H5), 7.71 (m, 8H, m-C6H5), 7.66 (m, 4H, p-C6H5), 7.51 (m,
8H, bipy(H′)), 7.46 (d, 8H, 3J(HH) = 6.8 Hz, bipy(H)), 7.39 (m,
8H, o′-C6H5), 7.20 (m, 4H, p′-C6H5), 7.08 (m, 8H, m′-C6H5), 5.36
[Si0(C1H2C2H2Si1(CH3)2CH2PPh2RuCl(p-cymene)(pyPPh2-
AuCl))4][PF6]4 (1[RuAu]44+). Experimental conditions and workup
4+
were identical to those for the preparation of 1[Ru(bipy)]4
.
(46 mg, 53%). H(CD2Cl2): 8.77 (sbr, 8H, py(H)), 7.98–7.05 (m,
88H, C6H5, py(H)), 5.47–4.99 (m, 16H, C6H4), 2.44 (m, 8H,
CH(CH3)2, CH2P), 1.91 (m, 4H, CH2P), 1.75 (s, 12H, CH3), 1.16
(m, 12H, CH(CH3)2), 1.03 (m, 12H, CH(CH3)2), 0.1–(−0.58) (m,
40H, CH2Si, CH3Si); C(CD2Cl2): 156.3 (s, py(C)), 134.7–128.1
(m, C6H5), 125.0 (s, py(C)), 90.9, 89.3, 86.2, 85.2 (m, C6H4), 30.6
(s, CH(CH3)2), 21.8, 20.9 (s, CH(CH3)2), 17.4 (s, CH3), 15.0 (m,
CH2P), 8.6 (C2H2Si1), 2.2 (C1H2Si0), −2.6 (CH3Si1); Si(CD2Cl2):
2
9.2 (s, Si0), 4.6 (d, J(SiP) = 14.7 Hz, Si1); P(CD2Cl2): 32.1 (s,
3
3
−
PPh2Au), 25.5 (s, PPh2Ru), −144.4 (sep, PF6 ). IR: max/cm−1 (CN)
(d, 4H, J(HH) = 6 Hz, C6H4(A′)), 5.28 (d, 4H, J(HH) = 6 Hz,
3
C6H4(A)), 5.25 (d, 4H, J(HH) = 6 Hz, C6H4(B′)), 5.18 (d, 4H,
1628, 1603 (KBr).
3J(HH) = 6 Hz, C6H4 (B)), 2.34 (d, 4H, 2J(HP) = 15 Hz, CHaHbP),
2.30 (sep, 4H, 3J(HH) = 7 Hz, CH(CH3)2), 1.76 (s, 12H, CH3), 1.73
[RuCl(p-cymene)(PMePh2)(py)][PF6]. Experimental condi-
tions and workup were identical to those for the preparation of
1[Ru(bipy)]44+. (97 mg, 94%). H(CDCl3): 8.76 (m, 2H, py(H)),
7.48–7.20 (m, 13H, C6H5, py(H), py(H)), 5.76 (dd, 1H,
3J(HH) = 6 Hz, J = 1.2 Hz, C6H4(A′)), 5.65 (d, 1H, 3J(HH) = 6 Hz,
3
(m, 4H, CHaHbP), 1.10 (d, 12H, J(HH) = 7 Hz, CH(CH3)2), 0.99
(d, 12H, 3J(HH) = 7 Hz, CH(CH3)2), −0.17 (m, CH2Si), −0.24 (m,
CH2Si), −0.40 (s, CH3Si), −0.60 (s, CH3Si) (40H); C(CD2Cl2):
156.8 (s, bipy(C)), 151.1 (s, bipy(C′)), 148.2 (s, bipy(C)),
143.1 (s, bipy(C′)), 132.7–132.5 (m, o-, o′-C6H5), 132.0, 130.9
(s, p-, p′-C6H5), 129.6 (m, m-C6H5), 128.6 (m, m′-C6H5), 123.3
(s, bipy(C)), 121.4 (s, bipy(C′)), 110.4 (s, C–CH(CH3)2),
100.4 (s, C–CH3), 91.7 (s, C6H4 (B)), 90.4 (s, C6H4 (A′)), 89.1
(s, C6H4 (B′)), 88.0 (C6H4 (A)), 30.7 (s, CH(CH3)2), 22.1, 21.8 (s,
CH(CH3)2), 17.6 (s, CH3), 12.45 (d, 1J(CP) = 25.4 Hz, CH2P), 8.8
(s, C2H2Si1), 2.3 (s, C1H2Si0), −2.1, −2.5 (s, CH3Si1); Si(CD2Cl2):
9.2 (s, Si0), 4.5 (m, Si1); P(CD2Cl2): 25.2 (s, PPh2), −144.2 (sep,
3
C6H4(A)), 5.61 (d, 1H, J(HH) = 6 Hz, C6H4(B′)), 5.44 (d, 1H,
3J(HH) = 6 Hz, C6H4(B)), 2.30 (sep, 1H, 3J(HH) = 6.9 Hz,
2
CH(CH3)2), 2.17 (d, 3H, J(HP) = 9.9 Hz, CH3P), 1.72 (s, 3H,
CH3), 1.11 (d, 3H, 3J(HH) = 6.9 Hz, CH(CH3)2), 1.00 (d, 3H,
3J(HH) = 6.9 Hz, CH(CH3)2); C(CDCl3): 155.8 (s, py(C)),
138.7 (s, py(C)), 132.1 (pt, 2J(CP) = 9.3 Hz, o-C6H5), 131.4,
131.0 (s, p-, p′-C6H5), 129.2 (d, 3J(CP) = 10.1 Hz, m-C6H5),
3
128.8 (d, J(CP) = 10.8 Hz, m′-C6H5), 126.1 (s, py(C)), 112.2
−
PF6 ). MS (ES+): m/z = 1583.2 [M − 2PF6]2+, 1505.8 [M − 2PF6-
2
(d, J(CP) = 4.7 Hz, C–CH(CH3)2), 103.6 (s, C–CH3), 91.4, 90.1,
bipy]2+, 1426.8 [M − 2PF6-2bipy]2+, 1008.6 [M − 3PF6]2+, 956.6
[M − 3PF6-bipy]3+, 904.1 [M − 3PF6-2bipy]3+. IR: max/cm−1 (CN)
1613, 1595 (KBr).
88.5, 85.9 (s, C6H4), 30.9 (s, CH(CH3)2), 22.3, 22.2 (s, CH(CH3)2),
1
18.0 (s, CH3), 14.0 (d, J(CP) = 34.7 Hz, CH3P); P(CDCl3): 16.8
−
(s, PPh2), −144.2 (sep, PF6 ). MS (ES+): 550.8 [M − PF6]+. IR:

max/cm−1 (CN) 1602 (KBr).
[Si0(C1H2C2H2Si1(CH3)2CH2PPh2RuCl(p-cymene)(py))4]-
[PF6]4 (1[Ru(py)]44+). Experimental conditions and workup were
4+
Syntheses of 1[Ru(bipy)Rh]4 and 1[Ru(bipy)Ru]44+. The
4+
identical to those for the preparation of 1[Ru(bipy)]4 (55 mg,
4+
dendrimer 1[Ru(bipy)]4 (12 mg, 3.5 mol) was solved in 2 ml
of acetone-d6 and 2 mg (7 mol) of [RhCl(CO)2]2 or 4 mg (7 mol)
of [RuCl2(p-cymene)]2 was added. The reactions were monitored
by NMR.
76%). H(CD2Cl2): 8.65 (m, 8H, py(H)), 7.90–7.11 (m, 52H, C6H5,
py(H), py(H)), 5.33–5.19 (m, 16H, C6H4), 2.23 (m, 8H, CH(CH3)2,
CHaHbP), 1.78 (m, 4H, CHaHbP), 1.72 (s, 12H, CH3), 1.09 (d, 12H,
3J(HH) = 6.8 Hz, CH(CH3)2), 0.96 (d, 12H, 3J(HH) = 6.8 Hz,
CH(CH3)2), −0.1–(−0.58) (m, 40H, CH2Si, CH3Si); C(CD2Cl2):
156.2 (s, py(C)), 139.0 (s, py(C)), 132.8–132.4 (m, o-, o′-C6H5),
1[Ru(bipy)]44+. H(acetone-d6): 8.92 (d, 8H, 3J(HH) = 5.9 Hz,
bipy(H)), 8.76 (m, 8H, bipy(H′)), 8.15–7.13 (m, 56H,
C6H5, bipy(H), bipy(H′)), 5.75 (d, 3J(HH) = 6 Hz), 5.61 (d,
3
131.9, 131.1 (s, p-, p′-C6H5), 129.5 (d, J(CP) = 9.6 Hz, m-C6H5),
3
128.6 (d, J(CP) = 9.6 Hz, m′-C6H5), 125.9 (s, py (C)), 110.7 (s,
3
3
3J(HH) = 6 Hz), 5.47 (d, J(HH) = 6 Hz), 5.34 (d, J(HH) = 6 Hz)
C–CH(CH3)2), 100.1 (s, C–CH3), 92.0, 90.2, 88.5, 87.8 (m, C6H4),
30.7 (s, CH(CH3)2), 22.0, 21.8 (s, CH(CH3)2), 17.5 (s, CH3), 12.1
(m, CH2P), 8.8 (s, C2H2Si1), 2.3 (s, C1H2Si0), −2.2, −2.5 (s, CH3Si1);
Si(CD2Cl2): 9.2 (s, Si0), 4.4 (d, 2J(SiP) = 14.2 Hz, Si1); P(CD2Cl2):
25.2 (s, PPh2), −144.2 (sep, PF6−). MS (ES+): 1429.7 [M − 2PF6]2+,
906.0 [M − 3PF6]3+. IR: max/cm−1 (CN) 1603 (KBr).
(16H, C6H4), 2.41 (m, 8H, CH(CH3)2, CHaHbP), 1.83 (s, 12H,
3
3
CH3), 1.14 (d, J(HH) = 6.8 Hz), 1.02 (d, J(HH) = 6.8 Hz) (24H,
CH(CH3)2), 0.1–(−0.52) (m, 40H, CH2Si, CH3Si); P(acetone-d6):
25.2 (s, PPh2Ru), −144.1 (sep, PF6). IR: max/cm−1 (CN) 1613,
1595 (KBr).
3
1[Ru(bipy)Rh]44+. H(acetone-d6): 8.97 (d, 8H, J(HH) = 5 Hz,
[Si0(C1H2C2H2Si1(CH3)2CH2PPh2RuCl(4-CNpy)(p-cymene))4]-
bipy(H)), 8.85 (m, 8H, bipy(H′)), 8.14–7.13 (m, 56H,
[PF6]4 (1[Ru(CNpy)]44+). Experimental conditions and workup
4+
C6H5, bipy(H), bipy(H′)), 5.75 (d, 3J(HH) = 6 Hz), 5.61 (d,
were identical to those for the preparation of 1[Ru(bipy)]4
.
3
3
3J(HH) = 6 Hz), 5.47 (d, J(HH) = 6 Hz), 5.34 (d, J(HH) = 6 Hz)
(76 mg, 71%). H(CD2Cl2): 8.76 (m, 8H, CNpy(H)), 7.70–7.14
(m, 48H, C6H5, CNpy(H)), 5.39–5.24 (m, 16H, C6H4), 2.22
(m, 8H, CH(CH3)2, CHaHbP), 1.82 (m, 4H, CHaHbP), 1.75 (s,
(16H, C6H4), 2.41 (m, 8H, CH(CH3)2, CHaHbP), 1.83 (s, 12H,
3
3
CH3), 1.14 (d, J(HH) = 6.8 Hz), 1.02 (d, J(HH) = 6.8 Hz) (24H,
CH(CH3)2), 0.1–(−0.52) (m, 40H, CH2Si, CH3Si); P(acetone-d6):
25.4 (s, PPh2Ru), −144.1 (sept, PF6). IR: max/cm−1 (CO) 2088,
2010, (CN) 1609 (KBr).
3
12H, CH3), 1.08 (d, 12H, J(HH) = 6.8 Hz, CH(CH3)2), 0.98 (d,
12H, 3J(HH) = 6.8 Hz, CH(CH3)2), −0.16 (m, CH2Si), −0.38 (s,
CH3Si), −0.57 (s, CH3Si) (40H); C(CD2Cl2): 157.0 (s, CNpy(C)),
132.8 (m, o-, o′-C6H5), 132.2, 131.4 (s, p-, p′-C6H5), 129.8 (m,
m-C6H5), 129.0 (m, m′-C6H5), 123.3 (s, CNpy(C)), 121.1 (s,
CNpy(C)), 110.8 (s, C–CH(CH3)2), 100.6 (s, C–CH3), 92.2,
90.5, 89.0, 88.5 (m, C6H4), 30.9 (s, CH(CH3)2), 22.3, 21.9 (s,
CH(CH3)2), 17.8 (s, CH3), 12.4 (m, CH2P), 9.0 (m, C2H2Si1),
2.5 (m, C1H2Si0), −1.9, −2.3 (s, CH3Si1); Si(CD2Cl2): 3.4 (d,
1[Ru(bipy)Ru]44+. H(acetone-d6): 8.84 (m, 8H, bipy(H)), 9.31
(m, 8H, bipy(H′)), 8.15–7.13 (m, 56H, C6H5, bipy(H), bipy(H′)),
5.7–5.4 (m, 32H, C6H4), 3.05 (m, 4H, CH(CH3)2), 2.41 (m, 8H,
CH(CH3)2, CHaHbP), 2.13 (s, 12H, CH3), 1.80 (s, 12H, CH3),
1.37 (m, 24H, CH(CH3)2), 1.14 (m), 1.02 (m) (24H, CH(CH3)2),
2 4 5 6
D a l t o n T r a n s . , 2 0 0 4 , 2 4 5 0 – 2 4 5 7

View Article Online
(f) S. Arévalo, E. de Jesús, F. J. de la Mata, J. C. Flores and R. Gómez,
Organometallics, 2001, 20, 2583 and references therein.
6 (a) M. Benito, O. Rossell, M. Seco and G. Segalés, Inorg. Chim. Acta,
1999, 291, 247; (b) O. Rossell, M. Seco, A. M. Caminade and J. P.
Majoral, Gold Bull., 2001, 34, 88.
0.1–(−0.52) (m, 40H, CH2Si, CH3Si); P(acetone-d6): 25.5, 25.4
(s, PPh2Ru), −144.1 (sep, PF6). IR: max/cm−1 (CN) 1609 (KBr).
General procedure for catalysed hydrogen transfer
The precursor complex (6 × 10−3 mmol) was dissolved in 3 ml of
a freshly prepared solution 0.012M of t-BuOK in propan-2-ol at
room temperature. The resulting solution was stirred for 30 min.
Then 10 ml of a 0.6M solution of cyclohexanone in propan-2-ol
was added. The solution was stirred at room temperature or at 82 °C
for the required time. Before evaluation by GC of the cyclohexanol
amount, the mixture was diluted with ethyl acetate and the solution
passed through a short column (silica gel).
7 M. Benito, O. Rossell, M. Seco, G. Muller, J. I. Ordinas, M. Font-
Bardia and X. Solans, Eur. J. Inorg. Chem., 2002, 2477.
8 I. Angurell, G. Muller, M. Rocamora, O. Rossell and M. Seco, Dalton
Trans., 2003, 1194.
9 (a) M. Benito, O. Rossell, M. Seco and G. Segalés, Organometallics,
1999, 18, 5191; (b) M. Benito, O. Rossell, M. Seco, G. Segalés,
V. Maraval, R. Laurent, A. M. Caminade and J. P. Majoral, J.
Organomet. Chem., 2001, 622, 33; (c) M. Benito, O. Rossell, M. Seco
and G. Segalés, J. Organomet. Chem., 2001, 619, 245.
10 (a) G. E. Oosterom, J. N. H. Reek, P. C. J. Kamer and P. W. N. M. van
Leeuwen, Angew. Chem., Int. Ed. Engl., 2001, 40, 1828; (b) D. Astruc
and F. Chardac, Chem. Rev., 2001, 101, 2991.
Acknowledgements
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Financial support for this work was generously given by the
DGICYT (Projects BQU2000-0644 and BQU2001-3358 and the
CIRIT (Project 2001SGR 00054). I. A. is indebted to the Ministerio
de Ciencia y Tecnología for a scholarship.
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D a l t o n T r a n s . , 2 0 0 4 , 2 4 5 0 – 2 4 5 7
2 4 5 7