Influence of arene dissociation and phosphine coordination on the catalytic activity of [RuCl(κ2-triphos)(p-cymene)]PF6

Article abstract of DOI:10.1016/j.jorganchem.2011.02.022

The catalytic activity of a ruthenium(II)-p-cymene complex containing a partially coordinated triphosphine ligand, [RuCl(κ²-triphos)(p- cymene)]PF₆ 1, has been investigated in the hydrogenation of styrene to ethylbenzene. The influen

Full text of DOI:10.1016/j.jorganchem.2011.02.022

Journal of Organometallic Chemistry 696 (2011) 2485e2490
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Influence of arene dissociation and phosphine coordination on the catalytic
activity of [RuCl(
k
2-triphos)(p-cymene)]PF6
*
Adrian B. Chaplin, Paul J. Dyson
Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 January 2011
Accepted 18 February 2011
The catalytic activity of a ruthenium(II)-p-cymene complex containing a partially coordinated triphos-
phine ligand, [RuCl(k
2-triphos)(p-cymene)]PF6 1, has been investigated in the hydrogenation of styrene
to ethylbenzene. The influence of arene dissociation and coordination of the free phosphine donor group
on the catalytic activity have been probed directly and indirectly by comparison to structural analogues.
k
2-dppp)(p-cymene)]PF6 2, or a labile arene
Keywords:
Ruthenium
Homogeneous catalysis
Hydrogenation
Tripodal ligands
Phosphine ligands
Analogues of 1 containing in a diphosphine ligand, [RuCl(
ligand, [RuCl(
k
2-triphos)( 6-PhCO2Et)]PF6 3, show significantly enhanced catalytic activity e demon-
h
strating the importance of ligand coordination/dissociation dynamics in ruthenium(II)-arene compounds
during catalysis. These observations are supported by thermolysis reactions of 1 in DMSO. In addition,
improved syntheses of 1 and 2 are reported together with the solid-state structures of syn-1, syn-3 and
[Ru(h k
3-C8H13)( 3-triphos)]PF6.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
ruthenium(II)-arene pre-catalysts include alkyne oxidation [9],
CeC bond formation [10], olefin metathesis [11], DielseAlder
reactions [12], and free-radical polymerization [13]. As part of our
on-going investigations on the catalytic activity of ruthenium(II)-
arene complexes [14,15], we report here further on a complex
Tripodal triphosphine ligands continue to find widespread
application in coordination chemistry and catalysis [1,2]. Among
these ligands, the C3 symmetric phosphine 1,1,1-tris(diphenyl-
phosphinomethyl)-ethane (triphos) and it’s derivatives are the
most extensively investigated, forming a large variety of transition
metal complexes, many of which have been evaluated as catalysts
containing a k k
2-coordinated triphos ligand, [RuCl( 2-triphos)(p-
cymene)]PF6 1. Isolation and characterisation of two isomers of
this complex together with a study of their catalytic activity is
described. The role of arene and phosphine coordination on the
catalytic activity has been probed by comparison to structural
analogues and thermolysis reactions.
[1e3]. While predominately forming complexes adopting a k3
coordinaton mode [2], triphos is also known to partially bind to
metal centres in a
2-manner [4]. The interconversion between
-
k
these two coordination modes, by ‘arm-off, arm-on’ dissociation/
association of one of the phosphine centres, has significant
consequences for the reactivity of the complex [5]. Examples of
dynamic coordination include reversible arm-off triphos dissocia-
2. Results and discussion
The
readily prepared by reaction of triphos with the activated ruthe-
nium arene precursor, [Ru2( -Cl)3(p-cymene)2]PF6 and [NH4]PF6 in
k k
2-triphos complex [RuCl( 2-triphos)(p-cymene)]PF6 1 is
tion and concomitant addition of CO to [Rh(CO)H(
under hydroformylation conditions [6], and equilibration between
3 and k2 1- coordination modes in [Rh(COD)( 3-triphos)]PF6 on
addition of [RuCl2(p-cymene)]2 [7].
k
3-triphos)],
m
k
m:
,
k
k
refluxing methanol [16]. Two isomers of 1, differing by the orien-
tation of the pendant arm of the triphos ligand with respect to the
metallocyclic ring, are formed in a 1:1 ratio. Separation was ach-
ieved by selective precipitation of the less soluble anti-1 from
methanol and subsequent recrystallisation, allowing the definitive
characterisation of both isomers e absent in the initial communi-
Ruthenium(II)-arene complexes have been used extensively as
catalyst precursors in many different reactions. Complexes of
this type bearing chiral amino-amido ligands are especially
notable as catalysts for the asymmetric transfer hydrogenation
of carbonyl compounds [8]. Other transformations mediated by
cation [16]. The k
2-coordination of the triphos ligand is readily
apparent from the 1H and 31P{1H} NMR spectra of 1, the later
showing two 31P environments (integral 2:1 ratio) for each of the
isomers. The resonances of the two phosphorous centres are
observed at 26.9 and 25.2 ppm for the syn- and anti-isomers,
* Corresponding author. Fax: þ41 (0) 21 693 97 80.
E-mail address: paul.dyson@epfl.ch (P.J. Dyson).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.02.022

2486
A.B. Chaplin, P.J. Dyson / Journal of Organometallic Chemistry 696 (2011) 2485e2490
Fig. 1. 1H NMR spectra of syn-1 (top) and anti-1 (bottom) (CDCl3, 293 K).
Fig. 2. Ball and stick representations of syn-1 (left) and syn-3 (right). Counter anions, solvent molecules and hydrogen atoms are omitted for clarity. Selected bond lengths (Å): syn-
1: Ru1-P1, 2.3278(14); Ru1-P2, 2.3295(14); Ru1-Cl1, 2.4038(12), Ru1-C, 2.223(5) e 2.324(5). syn-3: Ru1-P1, 2.328(2); Ru1-P2, 2.330(2); Ru1-Cl1, 2.401(2); Ru1-C, 2.216(6) e 2.276(6).
respectively. Both are similar to that observed for [RuCl(
k
2-dppp)(p-
TlPF6 in CH2Cl2 at room temperature (Chart 1) [19]. The solid-state
cymene)]PF6 2 (25.5 ppm) [17]. The chemical shifts of the uncoor-
dinated phosphorus centres (syn-1, ꢀ29.1; anti-1, ꢀ27.6 ppm) are
similar to that of free triphos (ꢀ25.8 ppm). Inequivalent hydrogen
environments on C9 and large differences in the chemical shift
values of H10 and H11 between the isomers (Dd ¼ 0.65 and
0.93 ppm, respectively) are observed by 1H NMR spectroscopy
(Fig. 1). Both structural assignments are supported by solid-state
structures determined by X-ray diffraction; that of syn-1 is
depicted Fig. 2 and that of anti-1 was reported earlier [16]. Both
structures exhibit comparable structural metrics to related
ruthenium(II)-arene phosphine complexes [15,17,18]. The triphos
configuration assignments are consistent with those observed in
structure of syn-3 is depicted in Fig. 2. The structure demonstrates
the
h
6-coordination of the arene ligand [Ru1-C ¼ 2.216(6)e
2.276(6) Å] and the adoption of a “piano-stool” geometry about the
ruthenium centre. In solution the structure observed in the solid-
state is retained; notably the 1H NMR spectrum of syn-3 exhibits
chemical shifts for H9, H10 and H11 that are similar to those in syn-1.
The 31P resonances for the triphos ligand are observed at 25.5
and ꢀ30.7 in a 2:1 ratio, comparable to 1.
To establish the relative binding strength of the arene ligands,
thermolysis reactions were carried by heating solutions of 1e3 in
DMSO (Scheme 1). These reactions were monitored in situ using 31P
fac-[ReX(CO)3(
k
2-triphos)] (X ¼ Cl, Br) [4c]. No interconversion
6
between the isomers was observed on prolonged heating in MeOH.
O
5
4
1
7
PF6
Structural analogues of 1 containing a diphosphine ligand,
[RuCl(
triphos)(
k -
2-dppp)(p-cymene)]PF6 2, or a labile arene ligand, [RuCl(k2
h
O
6-PhCO2Et)]PF6 3, where chosen to investigate the role of
Ru
PPh2
Cl
the free phosphine donor and arene dissociation in the catalytic
Ph2P
9
PPh2
8
activity of 1, respectively. Complex 2 was prepared via a new
10
9
procedure from [RuCl(PPh3)(k
1-dppp)(p-cymene)]PF6 by intra-
11
molecular substitution of PPh3 in almost quantitative yield [18b].
Complex 3 is new and was isolated as the syn-isomer in modest
syn-3
yield from the reaction between [RuCl2(h
6-PhCO2Et)]2, triphos and
Chart 1.

A.B. Chaplin, P.J. Dyson / Journal of Organometallic Chemistry 696 (2011) 2485e2490
2487
k1
PPh2
PPh2
PF6
1
[RuCl(DMSO)2(κ3-triphos)]PF6
Ph2P
Ph2P
O
O
6
4
k2
Ru
H
Ru
Cl
k1'
Ph2P
Ph2P
[RuCl(DMSO)3(κ2-triphos)]PF6
syn-3
7
5
Ph2
P
Ph2
P
Scheme 1. Thermally induced arene displacement from 1 and syn-3 in DMSO.
Cl
Cl
Cl
P
P
Ru
Ru
{1H} NMR spectroscopy. At elevated temperatures,1 and syn-3 react
Ph2
P
Ph2
Cl
with DMSO ultimately resulting in the formation of [RuCl(DM-
P
Ph2
Ph2
k k
3-triphos)]PF6 4, by arene displacement and 3-coordination
8
SO)2(
of the triphos ligand [20]. The identity of this new complex was
confirmed by independent synthesis, as the BF4- salt, from [RuCl(k3
Chart 2.
-
triphos)]2(BF4)2. The formation of 4 from 1 at 90 and 100 ꢁC
proceeds without the observation of any intermediates and the rate
is approximately two times faster for syn-1 than anti-1 (Table 1).
Substitution of ethyl benzoate by DMSO in syn-3 occurs at much
lower temperatures (ꢂ50 ꢁC) and proceeds via an intermediate
species, identified by the presence of an additional pair of reso-
nances at 29.1 and ꢀ27.3 ppm, in 2:1 ratio, in the 31P{1H} NMR
spectrum. This intermediate species is tentatively assigned as
enables the pendant phosphine to access the metal centre more
readily. The positive
Sz value for the formation of 4 from 5
D
suggests a mechanism with significant dissociative character.
The catalytic activity of 1 and the structural analogues 2 and syn-
3 were evaluated for the hydrogenation of styrene to ethyl benzene
in THF (S:C ¼ 2000:1, 50 bar H2, 90 ꢁC, 2 h). A range of
k
3-triphos
complexes; [RuCl(OAc)(k h k
3-triphos)] 6 [24], [Ru( 3-C8H13)( 3-tri-
[Ru(DMSO)3Cl(k
2-triphos)]PF6 5 on the basis of the aforementioned
phos)]PF6 7 (see Supporting information for solid-state structure)
[25], and [Ru2( -Cl)3(
3-triphos)2]Cl 8 [26], were also evaluated
31P{1H} NMR data and because the appearance of uncoordinated
ethyl benzoate, shown by 1H NMR spectroscopy, parallels its
formation by 31P{1H} NMR spectroscopy [21]. The relative ease in
which ethyl benzoate is substituted, in comparison to p-cymene, is
in line with the more electron deficient nature of the arene,
a feature that previous synthetic strategies have exploited [22]. In
comparison to 1 and syn-3, no arene displacement was observed for
2 on heating at 90 ꢁC in DMSO for 12 h.
m
k
under the same conditions for comparison purposes (Chart 2,
Table 2).
The catalytic activity of each isomer of 1 was similar and low
(<5% conversion), even under these relatively forcing conditions.
Addition of mercury, as a selective poison for heterogeneous cata-
lysts [27], did not inhibit catalytic activity suggesting that, while
low, the observed activity is the result of homogenous catalysis. In
contrast to 1, good conversion was observed with the related
diphosphine complex (2, 79% conversion). The active species in
The activation parameters for arene displacement in syn-3 have
been determined by 31P{1H} NMR spectroscopy; values for 1 were
estimated from the measured rates at 90 and 100 ꢁC (Table 1). The
[RuCl(k h
2-diphosphine)( 6-arene)]þ systems are believed to be
D
Sz for the arene displacement steps
formed following chloride dissociation (rate limiting) and coordi-
nation of dihydrogen [15b]. With this in mind, and in view of the
slow rate of arene loss observed under similar conditions, the most
reasonable explanation for the low activity for 1 is that the triphos
significantly negative values of
are indicative of a large degree of associative character. To account
for these observations, mechanisms involving h6 4 ring slippage
/
h
of the arene ligand and coordination of the pendant phosphine arm
in 1, and DMSO in syn-3, seem probable. Similar mechanisms have
been proposed for arene exchange in chromium(0)-arene
ligand suppresses activity by undergoing k2 k3 coordination
e
following chloride dissociation, preventing subsequent coordina-
tion of dihydrogen. Complex syn-3 was found to be a highly active
catalyst precursor under the conditions; the activity in this case is
may be attributed to facile arene loss as demonstrated during the
compounds [Cr(CO)2L(
bidentate ligand that facilitates this process by
[23]. The lower magnitude of
Sz for the reaction of syn-3 implies
a somewhat more concerted process in comparison to 1, which are
characterised by
Sz values of much higher magnitude. This
h
6-arene)], where L is a
k
1-coordinated
2-coordination
k
D
thermolysis reactions described above. The k
3-triphos complexes
6e8 also showed good catalytic activity. Moreover, the acetate
complex 5 was found to be an exceptional catalyst, even when
D
difference could be reflective of the more labile nature of the ethyl
benzoate ligand in syn-3 in comparison to the p-cymene ligand in 1,
which appears to require the associated coordination of the
pendant triphos arm to effect ring slippage (cf. reactivity of 2). The
enhanced rate of p-cymene substitution in syn-1, in comparison to
anti-1, is in agreement with the mechanistic proposal for these
complexes, as the conformation of the triphos ligand in syn-1
Table 2
Hydrogenation of styrene to ethylbenzene catalysed by 1e3 and 6e8
(0.05 mol% Ru).a
Precatalyst
Temp/ꢁC
Conversion
syn-1
syn-1b
anti-1
anti-1b
2
syn-3
syn-3
6
90
90
90
90
90
90
50
90
50
90
90
3%
4%
4%
Table 1
5%
Kinetic data for arene displacement from 1 and syn-3 in DMSO.a
79%
100%
<1%
100%
100%
53%
93%
rxn
Rate (t1/2
)
Activation parameters
Hz kJ molꢀ1 Sz Jmolꢀ1Kꢀ1
90 ꢁC
100 ꢁC
D
D
syn-1
anti-1
syn-3
1
1
10
2
9 ꢃ 2 h
20 ꢃ 7 h
<3 minc
<3 minc
4.4 ꢃ 0.3 h
9.7 ꢃ 1.1 h
<3 minc
w80b
w ꢀ120b
w ꢀ140b
ꢀ38 ꢃ 9
þ29 ꢃ 11
6
w70b
7
91 ꢃ 3
8c
<3 minc
112 ꢃ 4
a
Conditions: 5.0 ꢄ 10ꢀ6 mol pre-catalyst, S:C ¼ 2000:1, 2 ml THF, 100 mg octane
(internal standard), 50 bar H2, 2 h. Conversion determined by GC; Ethyl benzene was
the only product observed. Values averaged over duplicate runs.
a
Determined by 31P{1H} NMR spectroscopy, [Ru] ¼ 10 mM. 1, 10 or 2 refers to the
corresponding process indicated in Scheme 1.
b
b
Approximate values e estimated from rate at two different temperatures.
0.1 ml Hg added.
c
c
Extrapolated from lower temperature data.
5.0 ꢄ 10ꢀ6 mol/ruthenium.

2488
A.B. Chaplin, P.J. Dyson / Journal of Organometallic Chemistry 696 (2011) 2485e2490
catalytic runs were preformed at 50 ꢁC (for comparison syn-4 was
inactive) [24]. The high activity of the
3-triphos complexes,
3.1. Preparation of [RuCl(
k
2-triphos)(p-cymene)]PF6 1
k
particularly those containing chloride ligands, and the trends
established from thermolysis reactions together suggest that the
active species for 1 and syn-3 are mostly likely based on the
A
suspension of [Ru2(m
-Cl)3(p-cymene)2]PF6, (0.58 g,
0.80 mmol), [NH4]PF6 (0.13, 0.80 mmol) and (PPh2CH2)3CMe
(1.00 g, 1.60 mmol) in MeOH (200 ml) was heated at reflux for 3 h.
After cooling, the solution was slowly concentrated in vacuo at RT.
Following the onset of precipitation, the composition of the solu-
tion phase was monitored by 31P{1H} NMR spectroscopy until
precipitation of anti-isomer was nearly complete (ca. 143 ml). The
solid was filtered, washed with diethyl ether (ca. 25 ml) and dried
in vacuo to yield 0.67 g (40% by ruthenium) of the anti-isomer as
a yellow powder. The filtrate was reduced to dryness and the
residue extracted with CH2Cl2 through celite. The resulting crude
product was recrystallised from hot MeOH to yield 0.49 g (29% by
ruthenium) of the syn-isomer as a yellow crystalline solid. Yellow
crystals of the syn-isomer suitable for X-ray diffraction were
obtained by recrystallisation from CH2Cl2-pentane at RT. Isolated
yields of the anti-isomer (30e40% by ruthenium) and syn-isomer
(10e40% ruthenium) varied between different preparations. NMR
data are in agreement with the literature data [16], with data for
each isomer presented here.
[RuCl(k
3-triphos)]þ moiety.
Hydrogenation of the aromatic ring was not observed during
the hydrogenation of styrene with all complexes studied. Complex
1 (mixture of isomers) has been previously reported to be a cata-
lyst precursor for the homogeneous hydrogenation of arenes [16].
Related ruthenium(II)-arene diphosphine complexes have also
been suggested to be catalyst precursors for both heterogeneous
and homogenous catalysed hydrogenation of benzene, depending
on the diphosphine, anion and reaction conditions [28]. However,
under similar conditions to those reported previously (except
using a glass-lined autoclave and Teflon coated magnetic stirrer
bar in place of an autoclave with stainless steel fittings) no benzene
or toluene hydrogenation was observed with syn-1 or anti-1. This
lack of activity is consistent with the strong arene coordination in
these complexes, demonstrated by the thermolysis reactions. It
seems plausible that the reported activity for the hydrogenation of
arenes with 1 may be due to the formation (or presence) of cata-
lytic active nanoparticles [27a,29]. Notably, closely related homo-
geneous complexes immobilized on surfaces containing metal
particles have been shown to hydrogenate arenes under pseudo-
homogeneous conditions [30]. It is also noteworthy that nano-
particle catalysts tend to give significantly higher reaction rates in
hydrogenation reactions and are also capable of hydrogenating
aromatic systems [31].
syn-1: 1H NMR (CDCl3, 400 MHz):
d 7.08e7.66 (m, 26H),
6.77e6.88 (m, 4H), 5.79 (d, JHH ¼ 6.2, 2H, H2), 5.64 (d, JHH ¼ 6.3,
3
3
2H, H3), 3.18 (dt, 2JHH ¼ 14.6, JPH ¼ 4.3, 2H, H9), 2.41 (dt, 2JHH ¼ 14.6,
0
JPH ¼ 6.4, 2H, H9 ), 1.93 (sept, 3JHH ¼ 6.9, 1H, H6), 1.58e1.62 (m, 2H,
H
10), 1.41 (s, 3H, H5), 1.02 (s, 3H, H11), 0.79 (d, 3JHH ¼ 6.9, 6H, H7). 13
C
{1H} NMR (CDCl3,100 MHz):
d
128e139 (m),123.7 (br, C4),105.2 (br,
C1), 95.5 (t, JPC ¼ 3, C3), 92.5 (br, C2), 45.0e45.4 (m, C10), 38.2 (d,
2
2JPC ¼ 16, C8), 33.0e34.0 (m, C11 þ C9), 30.0 (s, C6), 21.4 (s, C7),16.7 (s,
In summary, under controlled conditions complex 1 shows low
activity as a pre-catalyst for the hydrogenation of styrene to ethyl-
C5). 31P{1H} NMR (CDCl3, 162 MHz):
d
26.9 (s, 2P, RuePPh2), ꢀ29.1
(s, 1P, pend-PPh2), ꢀ144.1 (sept, 1JPF ¼ 714, 1P, PF6,). ESI-MS (CH2Cl2,
60 ꢁC, 5.0 kV) positive ion: m/z, 895 [M]þ; negative ion: m/z, 145
[PF6]ꢀ. Anal. Calcd for C51H53ClF6P4Ru (1040.30 gmolꢀ1): C, 58.88;
H, 5.13. Found: C, 58.84; H, 5.11. anti-1: 1H NMR (CDCl3, 400 MHz):
benzene. This low activity may be attributed to k2
ek
3 coordination of
the triphos ligandand tothestabilityof the Ru-p-cymene bond. These
assertions are supported by the high catalytic activity of structural
analogues, containing instead a diphosphine ligand (2) or a labile
arene ligand (syn-3), and thermolysis reactions in DMSO. The iden-
tification of these factors are relevant to the future development of
catalytically active ruthenium(II)-arene compounds and complexes
containing the triphos ligand.
d
7.26e7.64 (m, 30H), 5.80 (d, 3JHH ¼ 6.4, 2H, H3), 5.76 (d, 3JHH ¼ 6.4,
2H, H2), 3.40 (dt, JHH ¼ 14.2, JPH ¼ 4.1, 2H, H9), 2.21e2.27 (m, 2H,
2
2
H
10), 2.16 (dt, JHH ¼ 14.1, JPH ¼ 7.4, 2H, H9’), 1.85 (s, 3H, H5), 1.49
(sept, JHH ¼ 6.8, 1H, H6), 0.77 (d, JHH ¼ 6.9, 6H, H7), 0.09 (s, 3H,
3
3
H
11). 13C{1H} NMR (CDCl3, 100 MHz): 128e139 (m), 118.9 (br, C4),
d
110.4 (br, C1), 97.7 (br, C3), 90.0 (br, C2), 50.0e50.5 (m, C10), 39.0 (d,
2JPC ¼ 14, C8), 34.2e34.8 (m, C9), 30.7 (br d, 3JPC ¼ 9, C11), 29.6 (s, C6),
3. Experimental section
22.0 (s, C7), 18.4 (s, C5). 31P{1H} NMR (CDCl3, 162 MHz):
d 25.2 (s, 2P,
All manipulations were carried out under a nitrogen atmo-
sphere using standard Schlenk techniques. CH2Cl2, diethyl ether,
benzene, toluene and pentane, were dried under nitrogen using
a solvent purification system (Innovative Technology Inc). Octane
and CH2ClCH2Cl were distilled from CaH2 and P2O5, respectively,
and stored over molecular sieves under nitrogen. All other solvents
were p.a. quality and saturated with nitrogen prior to use, with the
exception of DMSO which was purchased extra dry (<50 ppm H2O)
over molecular sieves under N2 from ACROS. Styrene was saturated
RuePPh2), ꢀ27.6 (s, 1P, pend-PPh2), ꢀ144.1 (sept, 1JPF ¼ 714, 1P, PF6).
ESI-MS (CH2Cl2, 60 ꢁC, 5.0 kV) positive ion: m/z, 895 [M]þ; negative
ion: m/z, 145 [PF6]ꢀ. Anal. Calcd for C51H53ClF6P4Ru
(1040.30 gmolꢀ1): C, 58.88; H, 5.13. Found: C, 58.86; H, 5.35.
3.2. Preparation of [RuCl(
k
2-dppp)(p-cymene)]PF6
2
A
solution of [RuCl(PPh3)(
k
1-dppp)(p-cymene)]PF6 (0.15 g,
0.14 mmol) in CH2ClCH2Cl (20 ml) was heated at reflux for 60 min.
The solution was concentrated to ca. 2 ml and the product
precipitated, as a yellow powder, by addition of diethyl ether
(30 ml). The precipitate was filtered, washed with diethyl ether
(3 ꢄ 10 ml) and pentane (2 ꢄ 10 mL) and dried in vacuo. Yield: 0.11 g
(96%). NMR data are in agreement with the literature data [17].
with nitrogen and stored over molecular sieves. [Ru2(
cymene)2]PF6 [32], [RuCl(PPh3)(
1-dppp)(p-cymene)]PF6 [18b],
[RuCl2(
6-PhCO2Et)]2 [22d], [RuCl(OAc)( 3-triphos)] [24], [RuCl(k3
triphos)]2(BF4)2 [24], [Ru(
3-C8H13)( 3-triphos)]PF6 [25], and
[Ru2( -Cl)3(
3-triphos)2]Cl [26] were prepared as described else-
m-Cl)3(p-
k
h
k
-
h
k
m
k
where. All other chemicals are commercial products and were
used as received. NMR spectra were recorded on a Bruker Avance
400 MHz spectrometer at room temperature unless otherwise
stated. Chemical shirts are given in ppm and coupling constants (J)
in Hz. NMR labelling schemes for 1 and syn-3 are detailed in Fig. 1
and Chart 1, respectively. ESI-MS were recorded on a Thermo
Finnigan LCQ DecaXP Plus quadrupole ion trap instrument using
a literature protocol [33]. Microanalyses were performed at the
EPFL.
3.3. Preparation of [RuCl(
k
2-triphos)(
h 3
6-PhCO2Et)]PF6
A suspension of [RuCl2(
h
6-PhCO2Et)]2 (0.20 g, 0.31 mmol),
(PPh2CH2)3CMe (0.39 g, 0.62 mmol) and TlPF6 (0.22 g, 0.63 mmol,
highly toxic!) in CH2Cl2 (25 ml) was stirred at RT for 14 h. The
suspension was then filtered through celite and the solvent
removed in vacuo. Recrystallisation of the resulting residue by slow
evaporation of a CH2Cl2epentane solution gave syn-3 as a yellow

A.B. Chaplin, P.J. Dyson / Journal of Organometallic Chemistry 696 (2011) 2485e2490
2489
powder. Yield: 0.069 g (11%/ruthenium). Yellow crystals of syn-3
Acknowledgement
suitable for X-ray diffraction were obtained from a CH2Cl2 solution
layered with toluene and pentane at RT. anti-3 could not be
obtained in pure form.
This work was supported by the EPFL and the Swiss National
Science Foundation. We thank the New Zealand Foundation for
Research, Science and Technology for a Top Achiever Doctoral
Fellowship (A. B. C.) and Dr R. Scopelliti and Dr E. Solari for technical
support.
syn-3: 1H NMR (CD2Cl2, 400 MHz): 7.40e7.65 (m, 20H, PPh2C9),
d
3
6.79e7.31 (m, 10H, PPh2C10), 6.51 (d, JHH ¼ 6.1, 2H, H3), 6.05 (t,
3
3JHH ¼ 5.6, 1H, H1), 5.55e5.70 (m, 2H, H2), 4.05 (q, JHH ¼ 7.0, 2H,
2
2
2
H6), 3.22 (dt, JHH ¼ 14.5, JPH ¼ 5, 2H, H9), 2.51 (dt, JHH ¼ 14.5,
0
2JPH ¼ 7, 2H, H9 ), 1.52e1.57 (m, 2H, H10), 1.24 (t, 3JHH ¼ 7.0, 3H, H7),
Appendix. Supplementary information
0.99 (s, 3H, H11). 13C{1H} NMR (CD2Cl2, 100 MHz):
d
161.4 (s, C5),
128e139 (m), 102.8 (t, 2JPC ¼ 3, C3), 96.3 (br, C4), 91.5 (br, C1), 90.4 (t,
Supplementary data related to this article can be found online at
doi:10.1016/j.jorganchem.2011.02.022.
2JPC ¼ 2, C2), 63.0 (s, C6), 43.3e43.7 (m, C10), 38.6 (d, 2JPC ¼ 17, C8),
33.9 (q, 3JPC ¼ 11, C11), 33.2 (td, 1JPC ¼ 19, 3JPC ¼ 7, C9), 13.9 (s, C7). 31
P
{1H} NMR (CDCl3, 162 MHz):
d
25.5 (s, 2P, RuePPh2), ꢀ30.7 (s, 1P,
References
pend-PPh2), ꢀ144.3 (sept, JPF ¼ 711, 1P, PF6). 31P{1H} NMR (d6-
1
DMSO, 162 MHz):
d
26.5 (s, 2P, RuePPh2), ꢀ30.8 (s, 1P, pend-
1
[1] Recent examples include: (a) F.M.A. Geilen, B. Engendahl, A. Harwardt,
W. Marquardt, J. Klankermayer, W. Leitner, Angew. Chem. Int. Ed. 49 (2010)
5510;
PPh2), ꢀ144.1 (sept, JPF ¼ 713, 1P, PF6). ESI-MS (CH2Cl2, 60 ꢁC,
5.0 kV) positive ion: m/z, 911 [M]þ; negative ion: m/z, 145 [PF6]ꢀ.
Anal. Calcd for C50H49ClF6O2P4Ru (1056.35 gmolꢀ1): C, 56.85; H,
4.68. Found: C, 56.93; H, 4.72. anti-3: 31P{1H} NMR (CDCl3,162 MHz,
(b) M.F. Cain, R.P. Hughes, D.S. Glueck, J.A. Golen, C.E. Moore, A.L. Rheingold,
Inorg. Chem. 49 (2010) 7650;
(c) J.M. Walker, A.M. Cox, R. Wang, G.J. Spivak, Organometallics 29 (2010)
6121.
complex only):
d
24.6 (s, 2P, RuePPh2), ꢀ28.1 (s, 1P, pend-PPh2).
3.4. Preparation of [RuCl(DMSO)2(
3-triphos)]BF4 (4.BF4)
This complex is prepared quantitatively by dissolving [RuCl(k3
[2] (a) J.-C. Hierso, R. Amardeil, E. Bentabet, R. Boussier, B. Gautheron, P. Meunier,
P. Kalck, Coord. Chem. Rev. 236 (2004) 143;
(b) H.A. Mayer, W.C. Kaska, Chem. Rev. 94 (1994) 1239;
(c) F.A. Cotton, B. Hong, Prog. Inorg. Chem. 40 (1992) 179.
[3] (a) A.A.N. Magro, G.R. Eastham, D.J. Cole-Hamilton, Chem. Commun. (2007)
3154;
k
-
triphos)]2(BF4)2 in d6-DMSO and was characterised in situ by NMR
(b) P. Barbaro, C. Bianchini, A. Meli, M. Moreno, F. Vizza, Organometallics 21
(2002) 1430;
(c) J.-X. Chen, J.F. Daeuble, D.M. Brestensky, J.M. Stryker, Tetrahedron 56
(2000) 2153;
(d) H.T. Teunissen, C.J. Elsevier, Chem. Commun. (1998) 1367;
(e) C. Bianchini, A. Meli, Acc. Chem. Res. 31 (1998) 109;
(f) V. Sernau, G. Huttner, M. Friz, L. Zsolnai, O. Walter, J. Organomet. Chem. 453
(1993) C23;
(g) P. Barbaro, C. Bianchini, P. Frediani, A. Meli, F. Vizza, Inorg. Chem. 31 (1992)
1523;
spectroscopy. 4.BF4 is unstable in the absence of DMSO.
1H NMR (d6-DMSO, 400 MHz, N2, 293 K):
d 7.53e6.99 (m, 30H),
2.33 (br, 6H, CH2), 1.48 (br, 3H, CH3). OSMe2 were not unambigu-
ously located. 31P{1H} NMR (d6-DMSO, 162 MHz, N2, 293 K):
d 35.1
(br (fwhm w 23 Hz), 3P).
For low temperature characterisation: A screw cap NMR tube was
charged with [RuCl(
k
3-triphos)]2(BF4)2 (7 mg) and placed under
(h) C. Bianchini, A. Meli, M. Peruzzini, F. Vizza, P. Frediani, P. Frediani,
J.A. Ramirez, Organometallics 9 (1990) 226.
a nitrogen atmosphere. Dry DMSO (0.05 ml) followed by CD2Cl2
(0.45 ml) were then added and the tube sealed. Yield: 93% of 4.BF4
by 31P{1H} NMR spectroscopy. Consistent with the structural
assignment, cooling to 183 K resolves the broad 31P resonance
observed at RT into resonances at 40.4 and 20.0 ppm in a 2:1 ratio
(see Supporting information).
[4] For example: (a) M. Kandiah, G.S. McGrady, A. Decken, P. Sirsch, Inorg. Chem.
44 (2005) 8650;
(b) P.K. Baker, M. Al-Jahdali, M.M. Meehan, J. Organomet. Chem. 648 (2002)
99;
(c) D.H. Gibson, H. He, M.S. Mashuta, Organometallics 20 (2001) 1456;
(d) M.A. Rida, C. Copéret, A.K. Smith, J. Organomet. Chem. 628 (2001) 1;
(e) A.M. Bond, R. Colton, A. van der Bergen, J.N. Walter, Inorg. Chem. 39 (2000)
4696 (and references therein);
(f) G. Reinhard, R. Soltek, G. Huttner, A. Barth, O. Walter, L. Zsolnai, Chem. Ber.
129 (1996) 97;
(g) S.G. Davis, S.J. Simpson, H. Felkin, F. Tadj, O. Watts, J. Chem. Soc. Dalton
Trans. (1983) 981.
1H NMR (CD2Cl2 þ 10% v/v DMSO, 400 MHz, N2, 293 K):
d
7.03e7.45 (m, 30H), 2.30e2.36 (m, 6H, CH2), 1.49e1.55 (m, 3H,
CH3). OSMe2 were not unambiguously located. 13C{1H} NMR
127e136 (m),
(CD2Cl2 þ 10% v/v DMSO, 100 MHz, N2, 293 K):
d
3
37.7e37.9 (m, C(CH2)), 37.1 (q, JPC ¼ 11, CH3), 33.2e33.8 (m, CH2).
[5] (a) C. Landgrafe, W.S. Sheldrick, M. Südfed, Eur. J. Inorg. Chem. (1998) 407;
(b) D.J. Rauscher, E.G. Thaler, J.C. Huffman, K.G. Caulton, Organometallics 10
(1991) 2209;
OSMe2 were not unambiguously located. 31P{1H} NMR
(CD2Cl2 þ 10% v/v DMSO, 162 MHz, 293 K, N2):
d
37.5 (br, 3P). 31P
{1H} NMR (CD2Cl2 þ 10% v/v DMSO, 162 MHz, 183 K, N2):
d 40.4 (d,
(c) J. Ott, L.M. Venanzi, C.A. Ghilardi, S. Midollini, A. Orlandini, J. Organomet.
Chem. 291 (1985) 89;
2
2JPP ¼ 46, 2P, RuePPh2), 20.0 (t, JPP ¼ 46, 1P, RuePPh2).
(d) W.O. Siegl, S. Lapporte, J.P. Collman, Inorg. Chem. 12 (1973) 674;
(e) W.O. Siegl, S. Lapporte, J.P. Collman, Inorg. Chem. 10 (1971) 2158.
[6] G. Kiss, I. Hováth, Organometallics 10 (1991) 3798.
[7] A.B. Chaplin, P.J. Dyson, Eur. J. Inorg. Chem. 47 (2008) 381.
[8] (a) J. Hannedouche, G.J. Clarkson, M. Wills, J. Am. Chem. Soc. 126 (2004) 986;
(b) R. Noyori, M. Yamakawa, S. Hashiguchi, J. Org. Chem. 66 (2001) 7931;
(c) K.-J. Haack, S. Hashiguchi, A. Fujii, T. Ikariya, R. Noyori, Angew. Chem. Int.
Ed. 36 (1997) 285;
(d) R. Noyori, S. Hashiguchi, Acc. Chem. Res. 30 (1997) 97.
[9] W. Ren, J. Liu, L. Chen, X. Wan, Adv. Synth. Catal. 352 (2010) 1424.
[10] R. Martinez, M.-O. Simon, R. Chevalier, C. Pautigny, J.-P. Genet, S. Darses, J. Am.
Chem. Soc. 131 (2009) 7887.
3.5. Catalytic studies
All catalytic experiments were conducted using a home-built
multi-cell autoclave containing an internal temperature probe.
Each glass reaction vessel was charged with the pre-catalyst,
substrate, internal standard (100 mg octane) and solvent and
then placed inside the autoclave and sealed. This procedure was
carried out in air. Following flushing with H2 (3 ꢄ 10 bar), the
autoclave was heated to the desired temperature under H2 (10 bar)
and then maintained at the desired pressure for the duration of the
catalytic run. The autoclave was then cooled to ambient tempera-
ture (typically ꢅ5 min when run at 50 ꢁC, ꢅ10 min when run at
90 ꢁC) using an external water-cooling jacket and the pressure
released. Conversions were determined by GC analysis of the
samples using a Varian chrompack CP-3380 gas chromatograph,
with species verified by comparison to authentic samples.
[11] (a) L.R. Jimenez, B.J. Gallon, Y. Schrodi, Organometallics 29 (2010) 3471;
(b) R. Castarlenas, P.H. Dixneuf, Angew. Chem. Int. Ed. 42 (2003) 4524;
(c) M. Bassetti, F. Centola, D. Sémeril, C. Bruneau, P.H. Dixneuf, Organome-
tallics 22 (2003) 4459;
(d) A. Fürstner, M. Liebl, C.W. Lehmann, M. Picquet, R. Kunz, C. Bruneau,
D. Touchard, P.H. Dixneuf, Chem. Eur. J. 6 (2000) 1847;
(e) M. Picquet, C. Bruneau, P.H. Dixneuf, Chem. Commun. (1998) 2249;
(f) A. Fürstner, M. Picquet, C. Bruneau, P.H. Dixneuf, Chem. Commun. (1998)
1315.
[12] D. Carmona, M.P. Lamata, F. Viguri, R. Rodríguez, F.J. Lahoz, I.T. Dobrinovitch,
L.A. Oro, Dalton Trans. (2008) 3328.

2490
A.B. Chaplin, P.J. Dyson / Journal of Organometallic Chemistry 696 (2011) 2485e2490
[13] F. Simal, A. Demonceau, A.F. Noels, Angew. Chem. Int. Ed. 38 (1999) 538.
[14] (a) A.B. Chaplin, Chimia 62 (2008) 217;
(d) B. Therrien, T.R. Ward, M. Pilkington, C. Hoffmann, F. Gilardoni, J. Weber,
Organometallics 17 (1998) 330.
(b) A.B. Chaplin, P.J. Dyson, Organometallics 26 (2007) 4357;
(c) A.D. Phillips, G. Laurenczy, R. Scopelliti, P.J. Dyson, Organometallics 26
(2007) 1120;
[23] (a) M.F. Semmelhack, A. Chlenov, D.M. Ho, J. Am. Chem. Soc. 127 (2005) 7759;
(b) E.P. Kündig, M. Kondratenko, P. Romanens, Angew. Chem. Int. Ed. 37
(1998) 3146.
(d) C. Daguenet, P.J. Dyson, Organometallics 25 (2006) 5811;
(e) T.J. Geldbach, G. Laurenczy, R. Scopelliti, P.J. Dyson, Organometallics 25
(2006) 733;
[24] A.B. Chaplin, P.J. Dyson, Inorg. Chem. 47 (2008) 381.
[25] T.V. Ashworth, A.A. Chalmers, E. Meintjies, H.E. Oosthuizen, E. Singleton,
Organometallics 3 (1984) 1485.
(f) T.J. Geldbach, P.J. Dyson, J. Am. Chem. Soc. 126 (2004) 8114.
[15] (a) A.B. Chaplin, P.J. Dyson, Organometallics 26 (2007) 2447;
(b) C. Daguenet, R. Scopelliti, P.J. Dyson, Organometallics 23 (2004) 4849.
[16] C. Boxwell, P.J. Dyson, D.J. Ellis, T. Welton, J. Am. Chem. Soc. 124 (2002) 9334.
[17] S.B. Jensen, S.J. Rodger, M.D. Spicer, J. Organomet. Chem. 556 (1998) 151.
[18] (a) A.B. Chaplin, Z. Béni, C.G. Hartinger, H.B. Hamidane, A.D. Phillips, R. Scopelliti,
P.J. Dyson, J. Cluster Sci. 19 (2008) 295;
[26] B.D. Yeomans, D.G. Humphrey, G.A. Heath, J. Chem. Soc. Dalton Trans. (1997)
4153.
[27] (a) J.A. Widegren, R.F. Finke, J. Mol. Catal. A: Chem. 198 (2003) 317;
(b) D.R. Anton, R.H. Crabtree, Organometallics 2 (1983) 855.
[28] (a) L. Zhang, L. Wang, X.-Y. Ma, R.-X. Li, X.-J. Li, Catal. Commun. 8 (2007)
2238;
(b) L. Zhang, Y. Zhang, X.-G. Zhou, R.-X. Li, X.-J. Li, K.-C. Tin, N.-B. Wong,
J. Mol. Catal. A. Chem. 256 (2006) 171.
[29] (a) M.H.G. Prechtl, M. Scariot, J.D. Scholten, G. Machado, S.R. Teixeira,
J. Dupont, Inorg. Chem. 47 (2008) 8995;
(b) A.B. Chaplin, C. Fellay, G. Laurenczy, P.J. Dyson, Organometallics26(2007) 586.
[19] Although low yielding (ca. 66% by 31P{1H} NMR spectroscopy), the syn-isomer
was formed selectively using this procedure (syn:anti w 3:1) allowing pure
syn-3 to be isolated readily by recrystallisation (11% yield/Ru). The synthetic
procedures available for the synthesis of 3 were limited by the low thermal
stability of this complex.
(b) R.R. Deshmukh, J.W. Lee, U.S. Shin, J.Y. Lee, C.E. Song, Angew. Chem. Int. Ed.
47 (2008) 8615;
(c) C.M. Hagen, L. Vieille-Petit, G. Laurenczy, G. Süss-Fink, R.G. Finke, Organ-
ometallics 24 (2005) 1819.
[20] Small quantities of [Ru2(m-Cl)3(k
3-triphos)2]þ can also be detected during the
thermolysis of both 1 and syn-3 in DMSO.
[30] (a) P. Barbaro, C. Bianchini, V. Dal Santo, A. Meli, S. Moneti, C. Pirovano,
R. Psaro, L. Sordelli, F. Vizza, Organometallics 27 (2008) 2809;
(b) P. Barbaro, C. Bianchini, V. Dal Santo, A. Meli, S. Moneti, R. Psaro, A. Scaffidi,
L. Sordelli, F. Vizza, J. Am. Chem. Soc. 128 (2006) 7065;
(c) C. Bianchini, V. Dal Santo, A. Meli, S. Moneti, M. Moreno, W. Oberhauser,
R. Psaro, L. Sordelli, F. Vizza, Angew. Chem. Int. Ed. 42 (2003) 2636.
[31] (a) A. Gual, C. Godard, S. Castillón, C. Claver, Dalton Trans. 39 (2010) 11499;
(b) P.J. Dyson, Dalton Trans. (2003) 2964;
[21] A solutionof syn-3 in d6-DMSO was heatedat 50ꢁC for20 min and then cooled to
RT [data for 5: 31P{1H} NMR (d6-DMSO, 162 MHz, 293 K):
d 29.1 (br, 2P,
RuePPh2), ꢀ27.3 (s, 1P, pend-PPh2), ꢀ144.1 (sept, 1JPF ¼ 713, 1P, PF6)]. The syn-
3:5 ratio was 1:0.18 (only trace quantity of 4) by integration of 31P{1H} NMRdata.
The ratio of coordinated {
d
3.93 (q, 3JHH ¼ 7 Hz, CH2)} to uncoordinated {
d 4.32 (q,
3JHH ¼ 7 Hz, CH2)} ethyl benzoate was 1:0.20 by integration of 1H NMR data.
[22] (a) T.J. Geldbach, M.R.H. Brown, R. Scopelliti, P.J. Dyson, J. Organomet. Chem.
690 (2005) 5055;
(c) J.A. Widegren, R.G. Finke, J. Mol. Catal. A: Chem. 191 (2003) 187.
[32] M.A. Bennett, A.K. Smith, J. Chem. Soc. Dalton Trans. (1974) 233.
[33] P.J. Dyson, J.S. McIndoe, Inorg. Chim. Acta 354 (2003) 69.
(b) B. Therrien, A. König, T.R. Ward, Organometallics 18 (1999) 1565;
(c) B. Therrien, T.R. Ward, Angew. Chem. Int. Ed. 38 (1999) 405;