Catalytic activity of bis-phosphine ruthenium(ii)-arene compounds: Structure - Activity correlations

Article abstract of DOI:10.1021/om070050d

The phosphine dissociation characteristics of a range of bis-phosphine ruthenium(II)-arene complexes, [Ru(PPh₃)(PR₃) (η⁶-arene)]PF₆ (arene = p-cymene: PR₃ = PPhMe₂, PPh₃, P(p-tol)₃, PPh₂ ⁱPr; arene = PhMe: PR₃ = PPhMe₂, PPh ₃), [Ru(PPh₃)(η²-PPh₂(C ₆H₄O))(η⁶-p-cymene)]PF₆, and [RuCl(PPh₃)(η⁷PPh₂(CH₂) ₃Ph)]PF₆, have been investigated by a combination of ligand exchange kinetics (with P(p-tol)₃ in THF) and tandem electrospray ionization mass spectrometry (ESI-MS/MS). Trends in reactivity established from these studies were rationalized in terms of steric bulk, on the arene or phosphine, and conformational freedom of the phosphine ligands. A good correlation is found between these trends, especially from the ESI-MS/MS data, and activity of the complexes as catalyst precursors for the hydrogenation of styrene to ethyl benzene (in THF). The most active catalyst precursors show good activity under comparatively mild conditions (e.g., TOF ≥ 2000 h ^-1 for styrene hydrogenation in THF at 50 °C under 50 bar of H₂). The X-ray structures of [RuCl(PPh₃)(PPhMe ₂)(η⁶-p-cymene)]PF₆, [RuCl(PPh ₃)(PPh₂ⁱPr)(η⁶-p-cymene)]PF ₆, [RuCl(PPh₃)(P(p-tol)₃)(η⁶-p- cymene)]PF₆, and [RuCl(η²-PPh₂(C ₆H₄O))(η₆-p-cymene)] are also reported.

Full text of DOI:10.1021/om070050d

Organometallics 2007, 26, 2447-2455
2447
Catalytic Activity of Bis-phosphine Ruthenium(II)-Arene
Compounds: Structure-Activity Correlations
Adrian B. Chaplin and Paul J. Dyson*
Institut des Sciences et Inge´nierie Chimiques, Ecole Polytechnique Fe´de´rale de Lausanne (EPFL),
CH-1015 Lausanne, Switzerland
ReceiVed January 18, 2007
The phosphine dissociation characteristics of a range of bis-phosphine ruthenium(II)-arene complexes,
i
[Ru(PPh3)(PR3)(η6-arene)]PF6 (arene ) p-cymene: PR3 ) PPhMe2, PPh3, P(p-tol)3, PPh2 Pr; arene )
PhMe: PR3 ) PPhMe2, PPh3), [Ru(PPh3)(η2-PPh2(C6H4O))(η6-p-cymene)]PF6, and [RuCl(PPh3)(η7-
PPh2(CH2)3Ph)]PF6, have been investigated by a combination of ligand exchange kinetics (with P(p-tol)3
in THF) and tandem electrospray ionization mass spectrometry (ESI-MS/MS). Trends in reactivity
established from these studies were rationalized in terms of steric bulk, on the arene or phosphine, and
conformational freedom of the phosphine ligands. A good correlation is found between these trends,
especially from the ESI-MS/MS data, and activity of the complexes as catalyst precursors for the
hydrogenation of styrene to ethyl benzene (in THF). The most active catalyst precursors show good
activity under comparatively mild conditions (e.g., TOF g 2000 h-1 for styrene hydrogenation in THF
at 50 °C under 50 bar of H2). The X-ray structures of [RuCl(PPh3)(PPhMe2)(η6-p-cymene)]PF6, [RuCl-
(PPh3)(PPh2iPr)(η6-p-cymene)]PF6, [RuCl(PPh3)(P(p-tol)3)(η6-p-cymene)]PF6, and [RuCl(η2-PPh2(C6H4O))-
(η6-p-cymene)] are also reported.
Chart 1a
Introduction
Half-sandwich ruthenium(II)-arene complexes are an im-
portant and widely used class of organometallic compound,
which exhibit a diverse range of coordination chemistry and
show considerable potential as precursors for catalytic organic
transformations.1,2 Among these complexes, those bearing one
η1-phosphine ligand have been established as useful catalyst
precursors for a wide range of reactions. Examples include
hydrogenation,3 free-radical polymerization of vinyl monomers,4
dienylalkyne cyclization,5 olefin cyclopropanation,6 the anti-
Markovnikov hydration of terminal alkynes,7 and the propar-
a Arene ) p-cymene: PR3 ) PPhMe2 (1a), PPh3 (1b), P(p-tol)3 (1c),
i
PPh2 Pr (1d). Arene ) PhMe: PR3 ) PPhMe2 (1e), PPh3 (1f).
Scheme 1
* E-mail: paul.dyson@epfl.ch.
(1) For examples see: (a) Rigby, J. H.; Kondratenko, M. A. Top.
Organomet. Chem. 2004, 7, 181. (b) Geldbach, T. J.; Dyson, P. J. J. Am.
Chem. Soc. 2004, 126, 8114. (c) Naota, T.; Takaya, H.; Murahashi, S.-I.
Chem. ReV. 1998, 98, 2599. (d) Noyori, R.; Hashiguchi, S. Acc. Chem.
Res. 1997, 30, 97. (e) Bennett, M. A. Coord. Chem. ReV. 1997, 166, 225.
(f) Bennett, M. A In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Elsevier: Oxford, 1995; Vol.
7, p 549. (g) Le Bozec, H.; Touchard, D.; Dixneuf, P. H. AdV. Organomet.
Chem. 1989, 29, 163.
(2) For examples see: (a) Qiu, L.; Kwong, Y.; Wu, J.; Lam, W. H.;
Chan, S.; Yu, W.-Y.; Li, Y.-M.; Guo, R.; Zhou, Z.; Chan, A. S. C. J. Am.
Chem. Soc. 2006, 128, 5955. (b) Daguenet, C.; Dyson, P. J. Organometallics
2006, 25, 5811. (c) Daguenet, C.; Scopelliti, R.; Dyson, P. J. Organome-
tallics 2004, 23, 4849. (d) Daguenet, C.; Dyson, P. J. Organomatallics 2004,
23, 6080. (e) Ghebreyessus, K. Y.; Nelson, J. H. J. Organomet. Chem. 2003,
669, 48. (f) Mashima, K.; Kusano, K.-H.; Sato, N.; Matsumura, Y.-I.;
Nozaki, K.; Kumobayashi, H.; Sayo, N.; Hori, Y.; Ishizaki, T.; Akutagawa,
S.; Takaya, H. J. Org. Chem. 1994, 59, 3064.
gylation of heterocycles with propargyl alcohols.8 Furthermore,
cationic allenylidene complexes bearing phosphine co-ligands,
e.g., [Ru(dCdCdCPh2)Cl(PR3)(η6-p-cymene)]+, have found
applications as catalysts for olefin metathesis.9
Given that a large number of molecular catalysts require a
ligand dissociation step (typically dissociation of phosphine)
in order for the catalysts to enter the catalytic cycle,10 we decided
to investigate the reactivity of a variety of bis-phosphine
ruthenium(II)-arene complexes, comprising triphenylphosphine
(3) (a) Geldbach, T. J.; Laurenczy, G.; Scopelliti, R.; Dyson, P. J.
Organometallics 2006, 25, 733. (b) Bennett, M. A.; Huang, T. -N.; Smith,
A. K.; Turney, T. W. J. Chem. Soc., Chem. Commun. 1978, 583.
(4) Simal, F.; Demonceau, A.; Noels, A. F. Angew. Chem., Int. Ed. 1999,
38, 538.
(5) Merlic, C. A.; Pauly, M. E. J. Am. Chem. Soc. 1996, 118, 11319.
(6) (a) Leadbeater, N. E.; Scott, K. A.; Scott, L. J. J. Org. Chem. 2000,
65, 3231. (b) Simal, F.; Jan, D.; Demonceau, A.; Noels, A. F. Tetrahedron
Lett. 1999, 40, 1653.
(8) Bustelo, E.; Dixneuf, P. H. AdV. Synth. Catal. 2005, 347, 393.
(9) (a) Castarlenas, R.; Dixneuf, P. H. Angew. Chem., Int. Ed. 2003, 42,
4524. (b) Bassetti, M.; Centola, F.; Se´meril, D.; Bruneau, C.; Dixneuf, P.
H. Organometallics 2003, 22, 4459. (c) Akiyama, R.; Kobayashi, S. Angew.
Chem., Int. Ed. 2002, 41, 2602. (d) Fu¨rstner, A.; Liebl, M.; Lehmann, C.
W.; Picquet, M.; Kunz, R.; Bruneau, C.; Touchard, D.; Dixneuf, P. H.
Chem.-Eur. J. 2000, 6, 1847. (e) Picquet, M.; Bruneau, C.; Dixneuf, P. H.
Chem. Commun. 1998, 2249. (f) Fu¨rstner, A.; Picquet, M.; Bruneau, C.;
Dixneuf, P. H. Chem. Commun. 1998, 1315.
(7) (a) Hansen, H. D.; Nelson, J. H. Organometallics 2000, 19, 4740.
(b) Tokunaga, M.; Wakatsuki, Y. Angew. Chem., Int. Ed. 1998, 37, 2867.
(10) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochman, M. AdVanced
Inorganic Chemistry, 6th ed.; John Wiley & Sons: New York, 1999.
10.1021/om070050d CCC: $37.00 © 2007 American Chemical Society
Publication on Web 03/23/2007

2448 Organometallics, Vol. 26, No. 9, 2007
Chaplin and Dyson
Scheme 2
Table 1. Selected 31P{1H} and 13C{1H} NMR Data for [RuCl(PPh3)(PR3)(η6-arene)]PF6 (CDCl3, 293 K)a
1a
1b
1c
1d
1e
1f
2
3b
arene
PR3
PPh3
PR3
2JPP
C1
p-cymene
PhMe
p-cymene
PPh2(C6H4O)
26.0
54.3
48
PPh2(CH2)3Ph
i
PPhMe2
27.0
3.5
54
99.0
128.0
PPh3
20.8
P(p-tol)3
20.3
19.8
52
100
134
PPh2 Pr
23.5
18.8
50
98.8
132
PPhMe2
31.9
3.7
56
84.0
118.0
PPh3
22.4
22.9
17.5
51
96.3
101.0
100.7
131.8
83.5
122.6
99.0
123.1
C4
b
a Labels as in Schemes 1 and 2. Chemical shifts in ppm and coupling constants (J) in Hz. From ref 12, in (CD3)2CO; assignment of 31P{1H} NMR data
has been corrected. C1 ) i-C6H4(CH2)3PPh2 and C4 ) p-C6H4(CH2)3PPh2.
and other η1-phosphines of varying electronic strength and steric
bulk, of general formula [RuCl(PPh3)(PR3)(η6-arene)]PF6 (1),
an anionic bidentate ortho-oxy-substituted phosphine (2), and
an arene-tethered phosphine (3), Chart 1. Although a number
of complexes of this type have previously been reported,1f,g there
is a paucity of investigations into their catalytic activity and
dissociation characteristics. This is somewhat surprising given
the utility of the monophosphine complexes and the related
diphosphine complexes.2 Seeking to explore the catalytic value
of this class of complex, we report here an investigation of their
phosphine dissociation characteristics and activity as catalyst
precursors for the hydrogenation of styrene. A combination of
tandem electrospray ionization mass spectrometry (ESI-MS/MS)
and ligand exchange kinetics has been used to assess their
dissociation properties, and correlations with their catalytic
activity are highlighted.
bis-phosphine complexes exhibit two doublets of equal intensity
with large 2JPP couplings of ca. 52 Hz, whereas the coordinated
phosphine resonances of the bis-triphenylphosphine compelxes
1b and 1f are observed as singlets; see Table 1. Chemical shifts
of the coordinated PPh3 ligand ranged from 20.3 to 31.9 ppm,
with the signals at higher frequency corresponding to complexes
containing PPhMe2. The structures of these complexes are
1
further corroborated by both H and 13C NMR spectroscopy.
Of note, the signals of the C4 atoms (see Schemes 1 and 2 for
labeling) are generally found at higher frequency than the other
arene atoms. This is indicative of reduced coordination of the
arene and is in line with the large degree of steric bulk from
the phosphine co-ligands (the effect is most pronounced in
1b-d).
The solid-state structures of 1a, 1c, and 1d have been
determined by X-ray diffraction, depicted in Figure 1, and
exhibit comparable structural parameters to the structures of 1b‚
BF4,13 1f,14 and 3;12 all contain large P-Ru-P angles of ca.
98° (see Table S1). As a consequence of the steric bulk in the
coordination sphere, there is a significant elongation of the Ru-
C4 bond lengths in comparison to the other Ru-C bonds for
1a-d and 1f (av Ru1-C4, 2.33 Å; av Ru1-Cav, 2.28 Å), in
keeping with the 13C NMR spectroscopic data (see above). The
Ru1-C1 bond in 1d is also significantly elongated [2.334(11)
Å]. In comparison, there is no significant Ru-C bond lengthen-
ing observed in 3, presumably due to the tethering of the arene.
The coordination mode of ortho-oxy-substituted triphenylphos-
phine in 5 is further verified by X-ray crystallography
(Figure 2).
Results and Discussion
1. Synthesis. The preparation of the bis-phosphine complexes
[Ru(PPh3)(PR3)(η6-arene)]PF6, 1, was achieved using the general
route involving substitution of the labile acetonitrile ligand in
the complex [RuCl(NCMe)(PPh3)(η6-arene)]PF6 (arene ) p-
cymene, 4a; PhMe, 4b), with the appropriate phosphine in CH2-
Cl2 at room temperature (Scheme 1).11 Additionally, 1b and 1f
were also prepared in high yield from reaction of triphenylphos-
phine with [RuCl2(PPh3)(η6-arene)] and [NH4]PF6 in MeOH or
CH2Cl2-MeOH, at slightly elevated temperatures. The synthesis
of the bis-phosphine complex containing an anionic bidentate
ortho-oxy-substituted triphenylphosphine, [Ru(PPh3)(η2-PPh2-
(C6H4O))(η6-p-cymene)]PF6, 2, was accomplished in two steps,
starting from the dinuclear ruthenium complex [RuCl2(η6-p-
cymene)]2. Reaction of the dimer with the hydoxy-substituted
phosphine and Cs2CO3 gave the chelate complex [RuCl(η2-PPh2-
(C6H4O))(η6-p-cymene)], 5, which then afforded 2 upon reaction
with PPh3 in EtOH under reflux followed by metathesis using
[NH4]PF6 (Scheme 2). Complex 3 was prepared according to a
literature protocol.12
2. Tandem Mass Spectrometry and Ligand Exchange
Kinetics. ESI-MS of 1-3 in each case gave strong parent ion
peaks with the expected isotope patterns. Collision-induced
(13) Lalrempuia, R.; Carroll, R. J.; Kollipara, M. R. J. Coord. Chem.
2003, 56, 1499.
(14) Polam, J. R.; Porter, L. C. Inorg. Chim. Acta 1993, 205, 119.
(15) In general, only qualitative trends can be made, as the collision
energy is not well defined in CID MS/MS when using quadrupole ion trap
instruments (ref 22a). Although it is possible to obtain quantitative gas phase
dissociation energies using mass spectrometry (e.g., Hammad, L. A.; Gerdes,
G.; Chen, P. Organometallics 2005, 24, 1907; Westmore, J. B.; Rosenberg,
L.; Hooper, T. S.; Willett, G. D.; Fisher, K. J. Organometallics 2002, 21,
5688), the instruments required tend to be more elaborate and experiments
are time intensive. This investigation demonstrates that useful trends can
be extracted rapidly (e.g., ESI-MS/MS measurements in this work were
completed in less than one day and under identical conditions) using a simple
mass spectrometry method on common instrumentation.
The structures of these compounds are readily confirmed by
31P{1H} NMR spectroscopy. The spectra of the asymmetrical
(11) Chaplin, A. B.; Fellay, C.; Laurenczy, G.; Dyson, P. J. Organo-
metallics 2007, 26, 586.
(12) Smith, P. D.; Gelbrich, T.; Hursthouse, M. B. J. Organomet. Chem.
2002, 659, 1.

Catalytic ActiVity of Bis-phosphine Ru(II)-Arene Compounds
Organometallics, Vol. 26, No. 9, 2007 2449
Table 2. Key Bond Lengths (Å) and Angles (deg) for 1a, 1c,
and 1d
1a
1c
1d
Ru1-Cl1
2.414(2)
2.350(2)
2.372(2)
2.263(6)
2.326(6)
2.28(3)
2.383(2)
2.369(2)
2.397(2)
2.308(6)
2.328(6)
2.28(4)
2.397(3)
2.377(4)
2.395(3)
2.334(11)
2.325(12)
2.28(5)
Ru1-P1
Ru1-P2
Ru1-C1
Ru1-C4
Ru1-Cav
Cl1-Ru1-P1
Cl1-Ru1-P2
P1-Ru1-P2
83.68(6)
88.45(6)
97.10(6)
88.80(5)
86.43(6)
99.53(6)
89.77(11)
83.04(11)
98.15(11)
Figure 2. ORTEP representation of 5 (selected molecule from the
asymmetric cell). Thermal ellipsoids are drawn at the 50%
probability level. A disordered component of the p-cymene ring
(C8, C90, C100) is shown with dashed bonds. Solvent molecule is
omitted for clarity.
Figure 1. ORTEP representation of 1a (top), 1c (middle), and 1d
(bottom). Thermal ellipsoids are drawn at the 50% probability level.
Solvent molecules and counter anions are omitted for clarity.
Relevant bond parameters are given in Table 2.
dissociation (CID) of the PPh3 ligand was found to be the
primary pathway for the parent ions by ESI-MS/MS (Figure
3). To obtain a qualitative scale of PPh3 dissociation energy,
changes in the relative intensities of parent ion fragments were
monitored as the normalized collision energy (E) was in-
creased.15,16 Changes in the fragmentation for 1b with E are
illustrated in Figure 4 , and data for this and the other complexes
are compiled in Table 3. From inspection of these data, all
recorded under identical conditions, several key trends can be
Figure 3. ESI-MS/MS of 1a, 1b, 1e, and 1f at 20% normalized
collision energy [CH2Cl2, 80 °C, 5.0 kV].
established. First, as the steric bulk in the coordination sphere
is increased, either by substitution on the arene ring (p-cymene
> PhMe) or due to the steric bulk of the co-phosphine (PPh3 ≈
i
P(p-tol)3 ≈ PPh2 Pr . PPhMe2), the Ru-PPh3 bond is more
(16) The normalized collision energy (E) is a standardized collision
energy scale based on the amplitude of the applied resonance excitation rf
voltage (used for inducing fragmentation) and the mass of the parent ion.
The amplitude of the rf voltage is given by (E/0.3)(mb + a), where m (u)
is the parent mass and a (V) and b (V/u) are instrument-dependent
parameters (tick amp intercept and slope). This is a useful quantity, as it
normalizes out the differences between instruments and the parent mass
effect. More details can be found in: Lopez, L. L.; Tiller, P. R.; Senko, M.
W.; Schwartz, J. C. Rapid Commun. Mass Spectrom. 1999, 13, 663.
readily fragmented. Second, fragmentation is reduced when
rotation of the Ru-PR3 bonds is restricted, such as in 2 and 3.
In addition to loss of PPh3, additional fragmentation paths can
i
be observed for 1d-f. In the case of 1d, PPh2 Pr loss is
observed, while for both 1e and 1f arene loss can also be
observed. Owing to the relatively high collision energy required

2450 Organometallics, Vol. 26, No. 9, 2007
Chaplin and Dyson
Figure 5. Exchange reaction of 1b with P(p-tol)3 in THF at 26 °C
with kinetic fit: 1b (9), 1c ([), [RuCl(P(p-tol)3)2(η6-p-cymene)]+,
6 (2).18
Figure 4. ESI-MS/MS of 1b at different normalized collision
energy [CH2Cl2, 80 °C, 5.0 kV].
Scheme 3. Exchange Kinetics of 1-3
to achieve dissociation of the PPh3 ligand in 1e, loss of PPhMe2
also becomes significant.
The ease of PPh3 loss, as shown by ESI-MS/MS, follows
the order 1b ≈ 1d ≈ 1c > 1f > 1a > 2 > 3 > 1e. The lability
of the PPh3 ligand is further confirmed by supplementary
experiments involving ligand exchange with P(p-tol)3 under
pseudo-first-order conditions (Scheme 3). Substitution of PPh3
is observed for all of the bis-phosphine complexes at 60 °C,
with the exception of 1e, although the rate of exchange varies
Figure 6. Eyring plots for the exchange reactions of 1b (squares)
and 1d (circles). Filled and open points correspond to exchange 1
and 2, respectively.
i
significantly; see Table 3. Substitution of PPh2 Pr is also
exchange of both PPh3 and P(p-tol)3 results in a statistical
mixture of the bis-phosphine complexes 1c, 1b, and [RuCl(P(p-
tol)3)2(η6-p-cymene)]PF6 (6)18 (K ) 0.25, Scheme 4). This
process occurs at an appreciable rate at room temperature, with
the equilibrium composition reached in ca. 1 day (Figure 7).
By following the rate of approach to equilibrium at different
temperatures by 31P{1H} NMR spectroscopy the activation
parameters for the forward and reverse reactions can be
estimated (Table 5) and are similar to those determined for the
exchange reactions described above. These parameters, together
with the absence of free phosphine signals in the 31P{1H} NMR
spectra during the equilibration, further suggest a dissociative
mechanism and highlight the lability of the phosphine ligands
in the complexes with sterically crowded coordination spheres.
observed for complex 1d, although at much reduced rate
compared to PPh3 substitution (t1/2(1) ) 37 s vs t1/2(2) ) 33
min), consistent with the observed fragmentation pattern of this
complex. No substitution of PPhMe2 is observed for 1a or 1e.
These data correlate well with those of the ESI-MS/MS, with
1b-d showing the most rapid exchange, with an appreciable
rate at room temperature (an example is given in Figure 5).
The temperature dependence of the exchange reactions of 1b
and 1d was determined and shows good Eyring behavior (Figure
6). The resulting activation parameters (∆Hq ca. 112 kJ mol-1
,
∆Sq ca. +50 J mol-1 K-1, Table 4) are consistent with a
dissociative mechanism.11,17
Complex 1c is also observed to undergo a related ligand
exchange process in THF without added phosphine, in which
Table 3. ESI-MS/MS, Kinetic, and Catalytic Data for 1-3
ESI-MS/MSa
exchange (THF, 60 °C)b
catalysis
arene
PR3
[M - PPh3]+/[M]+ (E ) 20%)
E1/2c/%
t1/2(1)
t1/2(2)
T100%d/°C
1a
1b
1c
1d
1e
1f
2
p-cymene
p-cymene
p-cymene
p-cymene
PhMe
PPhMe2
PPh3
0.17
14.3
5.6
21.3
16.0
16.6
16.2i
23.9j
19.4m
22.0
22.3
1.2 days
43 se,f
80
50
50
50
80
60
90
90
P(p-tol)3
80 sf,g
37 se,f
i
PPh2 Pr
20.0h
0.01
0.81l
0.08
0.07
33 min
k
PPhMe2
PPh3
PPh2(C6H4O)
-
PhMe
p-cymene
57 mine
3.4 days
>3 days
86 mine
3
Ph(CH2)3PPh2
b
c
a ESI-MS/MS conditions: CH2Cl2, 80 °C, spray voltage 5.0 kV. Exchange with P(p-tol)3 (20 equiv). E required to obtain a relative intensity for [M -
PPh3] of 50%. Error ( 0.2%. Temperature required for 100% conversion of styrene to ethyl benzene under the catalytic conditions: 5.0 × 10-6 mol of
d
precatalyst, S:C ) 2000:1, 60 min, 2 mL of THF, 50 bar of H2, 100 mg of octane added as internal standard. Conversions determined by GC (values reported
e
f
g
h
as average of at least three experiments). 30 equiv of P(p-tol)3. Extrapolated from lower temperature data. From second exchange with PPh3 in 1b. [M
i
i
i
j
k
- PPh2 Pr] (35%) observed. [M - PPh2 Pr] (17%) observed. [M - PhMe] (35%) and [M - PPhMe2] (7%) observed. No exchange detected after ca. 60
l
h. [M - PhMe] (35%) observed. m[M - PhMe] (24%) observed.

Catalytic ActiVity of Bis-phosphine Ru(II)-Arene Compounds
Organometallics, Vol. 26, No. 9, 2007 2451
Table 4. Activation Parameters for the Exchange Reactions
of 1b and 1da
rxn
∆Hq/kJ mol-1
∆Sq/J mol-1 K-1
R2
fit
1b
1d
1
112 ( 3
112 ( 5
111 ( 4
110 ( 14
+56 ( 10
+50 ( 20
+54 ( 14
+20 ( 40
0.998
0.996
0.999
0.985
2b
1
2
a THF, 30 equiv of P(p-tol)3. Errors originate from the standard errors
from linear fits of ln(kobs/T) versus 1/T, i.e., σ(∆Hq) ) Rσ(slope), σ(∆Sq)
b
) Rσ(intercept). Corresponds to single ligand exchange of 1c.
Figure 8. Correlation of catalytic activity (see Table 3, footnote
d) with relative fragmentation energy determined by ESI-MS/MS
(see Table 3, footnote c).
Table 3. The activity follows the order 1b ≈ 1c ≈ 1d > 1f >
1a > 1e > 2 ≈ 3. A good correlation is found between the
ESI-MS/MS data and the catalytic activity (Figure 8). Notably,
1b-d show the highest activity (active at T e 50 °C). The
catalytic activity increases with more bulky arene (1a > 1e; 1b
> 1f) and phosphine (1b > 1c ≈ 1d . 1a; 1f > 1e) ligands.
In agreement with the ESI-MS/MS data, 2 and 3 require higher
temperatures to observe catalytic activity, showing a similar
temperature dependence to the related complex [RuCl(η2-dppm)-
(η6-p-cymene)]PF6 (7) (active at T g 80 °C).19 For comparison
the neutral complex [RuCl2(PPh3)(η6-p-cymene)] (8)20 remains
essentially inactive up to 90 °C.
2
Figure 7. Equilibration of 1c ([; 20.7, 20.0 ppm, JPP ) 52 Hz)
in THF at 22 °C, 1b (20.9 ppm; 9), and 6 (19.6 ppm; 2).
Scheme 4. Equilibration of 1c
Table 5. Activation Parameters for the Equilibration of 1c
in THFa
rxn
∆Hq/kJ mol-1
∆Sq/J mol-1 K-1
R2
fit
3. Concluding Remarks. The phosphine dissociation char-
acteristics of a range of bis-phosphine ruthenium(II)-arene
complexes have been investigated in both the gas and solution
phase using tandem electrospray ionization mass spectrometry
(ESI-MS/MS) and ligand exchange kinetics, respectively. Using
this combination of techniques a number of trends in reactivity
are firmly established, which are generally steric in origin,
apparent to some degree from NMR and solid-state character-
ization, and show good correlation with the observed catalytic
activity. Furthermore, the good agreement between these two
properties suggests that phosphine dissociation is the rate-
determining step for the generation of the active catalytic
species. The most active catalyst precursors show good activity
under comparably mild conditions (TOF g 2000 h-1 for styrene
hydrogenation in THF at 50 °C under 50 bar of H2).
3
-3
116 ( 8
116 ( 8
+40 ( 30
+50 ( 30
0.995
0.995
a Errors originate from the standard errors from linear fits of ln(kobs/T)
versus 1/T [i.e., σ(∆Hq) ) Rσ(slope), σ(∆Sq) ) Rσ(intercept).
Table 6. Catalytic Activity of 1-3, 7, and 8a
conversion/%
complex 30 °C 40 °C 50 °C 60 °C 70 °C 80 °C 90 °C
1a
1b
1c
1d
1e
1f
2
0(3)
22(4) 100
74(8)
10(5) 60(7)
5(3) 54(11)
100
100
100
1(3)
100
3(3) 100
1(3)
5(4)
0(3) 32(17) 100
0(3) 57(30) 100
3
In particular, ESI-MS/MS proved to be an effective tool in
assessing the catalytic activity by establishing reliable qualitative
trends in phosphine dissociation energy. The correlation is
especially satisfying owing to the simplicity of the mass
spectrometry method, avoiding the necessity for quantitative
phosphine dissociation measurements. Therefore this technique
may be suitable, more generally, for rapid catalyst screening of
other transition metal systems, naturally charged or with
“electrospray friendly” ligands,21 involving ligand dissociation
as a rate-determining step. ESI-MS as a tool for catalyst
7
8
2(3) 70(3)
2(3) 3(3)
100
5(3)
a Conditions: 5.0 × 10-6 mol of catalyst, S:C ) 2000:1, 60 min, 2 mL
of THF, 50 bar of H2, 100 mg of octane added as internal standard.
Conversions determined by GC. Values reported as average of at least three
experiments; estimated error given in parentheses.
The catalytic activity of the bis-phosphine complexes 1-3
was investigated as a function of temperature, in 10 °C
increments, for the hydrogenation of styrene in THF (50 bar of
H2, 60 min). These data are listed in Table 6, with the
temperature corresponding to 100% conversation also listed in
(19) Jensen, S. B.; Rodger, S. J.; Spicer, M. D. J. Organomet. Chem.
1998, 556, 151.
(17) (a) Bunten, K. A.; Farrar, D. H.; Poe¨, A. J.; Lough, A. J.
Organometallics 2000, 19, 3674. (b) Serron, S. A.; Nolan, S. P. Organo-
metallics 1995, 14, 4611. (c) Dias, P. B.; Minas de Piedade, M. E.; Simo˜es,
J. A. M. Coord. Chem. ReV. 1994, 135-136, 737.
(18) Complex 6 has been prepared for reference. A method similar to
that of 1b was used (see Experimental Section for full details).
(20) Bennett, M. A.; Smith, A. K. J. Chem. Soc., Dalton Trans. 1974,
233.
(21) (a) Farrer, N. J.; McDonald, R.; McIndoe, J. S. Dalton Trans. 2006,
4570. (b) Evans, C.; Nicholson, B. K. J. Organomet. Chem. 2003, 665, 95.
(c) Decker, C.; Henderson, W.; Nicholson, B. K. J. Chem. Soc., Dalton
Trans. 1999, 3507.

2452 Organometallics, Vol. 26, No. 9, 2007
Chaplin and Dyson
2
2
2
Scheme 5
97.7 (d, JPC ) 4, C6), 96.4 (d, JPC ) 3, C2), 90.7 (d, JPC ) 9,
C3), 89.1 (d, JPC ) 10, C5), 30.9 (s, C8), 21.7 (s, C9/10), 21.1 (s,
2
C10/9), 16.5 (s, C7), 15.1 (d, JPC ) 36, PMe′), 15.1 (d, JPC ) 33,
1
1
PMe). 31P{1H} NMR (CDCl3): δ 27.0 (d, 2JPP ) 54, 1P, RuPPh3),
2
1
3.5 (d, JPP ) 54, 1P, RuPPhMe2), -144.1 (sept, JPF ) 713, 1P,
PF6). ESI-MS (CH2Cl2) positive ion: m/z 671 [M]+; negative ion:
m/z 145 [PF6]-. Anal. Calcd for C36H40ClF6P3Ru (816.15 g mol-1):
C, 52.98; H, 4.94. Found: C, 52.97; H, 4.75.
Preparation of [RuCl(PPh3)2(η6-p-cymene)]PF6 (1b). Method
A: A suspension of [RuCl2(PPh3)(η6-p-cymene)] (0.300 g, 0.53
mmol), PPh3 (0.277 g, 1.06 mmol), and [NH4]PF6 (0.061 g, 0.58
mmol) in MeOH (20 mL) was stirred at 35 °C for 2 h. The solvent
was removed in vacuo and the residue extracted through Celite
with CH2Cl2 (ca. 20 mL). The product was then isolated, as a yellow
powder, by precipitation with pentane and washed with EtOH (10
mL) and pentane (2 × 10 mL). Yield: 0.39 g (78%).
screening is an area of current interest,22 although this particular
application appears to be novel.
Experimental Section
Method B: A solution of [RuCl(NCMe)(PPh3)(η6-p-cymene)]-
PF6 (1.00 g, 1.39 mmol) and PPh3 (1.09 g, 4.16 mmol) in CH2Cl2
(40 mL) was stirred at RT for 3 h. The product was precipitated
by the addition of excess diethyl ether (ca. 200 mL) and washed
with diethyl ether (2 × 40 mL). Purification by precipitation from
CH2Cl2 by addition of pentane gave the pure product as a yellow
powder. Yield: 1.07 g (82%). NMR data are in agreement with
the literature,13 although a more thorough characterization is
All organometallic manipulations were carried out under a
nitrogen atmosphere using standard Schlenk techniques. CH2Cl2
and THF were dried catalytically under dinitrogen using a
solvent purification system, manufactured by Innovative Techno-
logy Inc. All other solvents were p.a. quality and saturated with
nitrogen prior to use. [RuCl(NCMe)(PPh3)(η6-p-cymene)]PF6,11
[RuCl2(PPh3)(η6-p-cymene)],20 [RuCl2(η6-PhMe)]2,20 [RuCl2(η6-p-
cymene)]2,20 ortho-PPh2(C6H4OH),23 and [Ru(PPh3)(η7-PPh2(CH2)3-
Ph)]PF612 were prepared as described elsewhere. [RuCl(η2-dppm)-
(η6-p-cymene)]PF6 was prepared by metathesis of [RuCl(η2-
dppm)(η6-p-cymene)]Cl in a similar manner as previously described
for [RuCl(η2-dppm)(η6-p-cymene)]BF4 (ref 2c); NMR data were
in agreement with the literature.19 All other chemicals are com-
mercial products and were used as received. Spectra were recorded
with a Bruker Avance 400 spectrometer at room temperature, unless
otherwise stated. Chemical shirts are given in ppm and coupling
constants (J) in Hz. The NMR labeling for complex 2 is given in
Scheme 2; all other complexes are labeled similarly (see Scheme
5 for some examples). ESI-MS were recorded on a Thermo Finnigan
LCQ DecaXP Plus quadrupole ion trap instrument. CH2Cl2 was
used as the solvent for all experiments with a capillary temperature
of 80 °C and spray voltage of 5.0 kV. The instrument parameters
a and b for the ESI-MS/MS experiments16 were 0.001080 V and
0.460908 V/u, respectively. Microanalyses were performed at the
EPFL.
1
included here. H NMR (CDCl3): δ 7.13-7.54 (m, 30H, PPh),
3
5.55-5.67 (m, 2H, H2), 5.07 (d, JHH ) 6.1, 1H, H3), 2.72 (sept,
3JHH ) 6.9, 1H, H6), 1.25 (d, 3JHH ) 7.0, 6H, H7), 1.10 (s, 3H, H5).
13C{1H} NMR (CDCl3): δ 127-135 (m, PPh), 131.8 (C4), 100.7
2
2
(s, C1), 97.4 (t, JPC ) 2, C2), 89.1 (t, JPC ) 5, C3), 31.5 (s, C6),
21.4 (s, C7), 15.3 (s, C5). 31P{1H} NMR (CDCl3): δ 20.8 (s, 2P),
1
-144.4 (sept, JPF ) 713, 1P, PF6). ESI-MS (CH2Cl2) positive
ion: m/z 795 [M]+; negative ion: m/z 145 [PF6]-.
Preparation of [RuCl(P(p-C6H4Me)3)(PPh3)(η6-p-cymene)]PF6
(1c). A solution of [RuCl(NCMe)(PPh3)(η6-p-cymene)]PF6 (0.50
g, 0.70 mmol) and P(p-C6H4Me)3 (2.50 g, 8.21 mmol) in CH2Cl2
(50 mL) was stirred at RT for 30 min. The product was precipitated
by the addition of excess diethyl ether (ca. 150 mL) and the
precipitate washed with diethyl ether (2 × 50 mL). Purification by
precipitation twice from CH2Cl2-pentane gave the pure product
as a yellow powder. Yield: 0.46 g (67%). Orange crystals suitable
for X-ray diffraction were obtained by recrystallization from a
mixture of CH2Cl2, toluene, and pentane at -20 °C. 1H NMR
(CDCl3): δ 6.93-7.53 (m, 27H, PPh + H12 + H13), 5.57-5.64
(m, 1H, H2), 5.48-5.57 (m, 1H, H6), 5.13 (d, 3JHH ) 6.1, 1H, H3),
5.00 (d, 3JHH ) 6.1, 1H, H5), 2.71 (sept, 3JHH ) 6.8, 1H, H8), 2.37
(s, 9H, H15), 1.26 (d, 3JHH ) 6.8, 3H, H9), 1.22 (d, 3JHH ) 6.8, 3H,
H10), 1.07 (s, 3H, H7). 13C{1H} NMR (CDCl3, selected peaks
only): δ 134 (C4), 100 (C1), 97 (C2), 96 (C6), 89 (C3), 89 (C5).
Preparation of [RuCl(PPhMe2)(PPh3)(η6-p-cymene)]PF6 (1a).
To a solution of [RuCl(NCMe)(PPh3)(η6-p-cymene)]PF6 (0.50 g,
0.70 mmol) in CH2Cl2 (30 mL) was added PPhMe2 (0.4 mL, 2.81
mmol), and the solution was stirred at RT for 30 min. The product
was precipitated by the addition of excess diethyl ether (ca. 150
mL) and the precipitate washed with diethyl ether (2 × 50 mL).
Yield: 0.54 g (96%) as a yellow powder. Orange crystals suitable
for X-ray diffraction were obtained from a solution of CHCl3
2
31P{1H} NMR (CDCl3): δ 20.3 (d, JPP ) 52, 1P, RuPPh3), 19.8
(d, 2JPP ) 52, 1P, RuP(p-tol)3), -144.3 (sept, 1JPF ) 713, 1P, PF6).
ESI-MS (CH2Cl2) positive ion: m/z 837 [M]+; negative ion: m/z
145 [PF6]-. Anal. Calcd for C49H50ClF6P3Ru (982.37 g mol-1)‚2/
3(Et2O): C, 60.15; H, 5.54. Found: C, 60.43; H, 5.28.
1
layered with toluene and pentane at 4 °C. H NMR (CDCl3): δ
3
3
7.40-7.75 (m, 20H, PPh), 5.90 (dd, JHH ) 6.0, JPH ) 3, 1H,
H6), 5.46 (d, JHH ) 5.6, 1H, H3), 5.02 (dd, JHH ) 6.0, JPH ) 5,
3
3
3
1H, H2), 4.94 (d, 3JHH ) 6.4, 1H, H5), 2.58 (sept, 3JHH ) 7.0, 1H,
i
Preparation of [RuCl(PPh2 Pr)(PPh3)(η6-p-cymene)]PF6 (1d).
H8), 1.60 (d, JPH ) 10, 3H, PMe), 1.29 (s, 3H, H7), 1.22 (d, JPH
2
2
3
3
A solution of [RuCl(NCMe)(PPh3)(η6-p-cymene)]PF6 (0.50 g, 0.70
) 11, 3H, PMe′), 1.10 (d, JHH ) 7.0, 3H, H9), 1.10 (d, JHH
)
i
1
mmol) and PPh2 Pr (0.48 g, 2.09 mmol) in CH2Cl2 (20 mL) was
7.0, 3H, H10). 13C{1H} NMR (CDCl3): δ 139.0 (d, JPC ) 48,
2/3
1
stirred at RT for 2.5 h. The product was precipitated by the addition
of excess diethyl ether (ca. 100 mL) and the precipitate washed
with diethyl ether (2 × 50 mL). Recrystallization from CH2Cl2-
pentane gave the product as orange crystals. Yield: 0.36 g (58%).
Orange crystals suitable for X-ray diffraction were obtained by
recrystallization from CH2Cl2-pentane at -20 °C. 1H NMR
PPhMe2), 134.5 (d,
J
) 9, PPh3), 133.5 (d, JPC ) 47, PPh3),
PC
4
4
131.3 (d, JPC ) 2, PPh3), 130.8 (d, JPC ) 3, PPhMe2), 129.4 (d,
2/3
3/2
3/2
J
J
) 8, PPhMe2), 129.2 (d,
J
) 10, PPhMe2), 128.7 (d,
PC
PC
2
2
) 10, PPh3), 128.0 (dd, JPC ) JPC ) 3, C4), 99.0 (s, C1),
PC
(22) (a) Henderson, W.; McIndoe, J. S. Mass Spectrometry of Inorganic,
3
3
Coordination and Organometallic Compounds: Tools-Techniques-Tricks;
John Wiley & Sons: Chichester, 2005. (b) Markert, C.; Pfalz, A. Angew.
Chem., Int. Ed. 2004, 43, 2498. (c) Chen, P. Angew. Chem., Int. Ed. 2003,
42, 2832.
(23) Ainscough, E. W.; Brodie, A. M.; Chaplin, A. B.; O’Connor, J.
M.; Otter, C. Dalton Trans. 2006, 1264.
(CDCl3): δ 7.00-7.85 (m, 25H, PPh), 6.13 (dd, JHH ) 6.2, JPH
) 5, 1H, H6), 5.81 (d, JHH ) 6.1, 1H, H5), 5.31 (dd, JHH ) 6.2,
3JPH ) 5, 1H, H2), 4.44 (d, 3JHH ) 5.6, 1H, H3), 2.68 (br, 1H, H11),
2.60 (sept, 3JHH ) 7.0, 1H, H8), 1.29 (d, 3JHH ) 7.0, 3H, H9), 0.96-
3
3
1.12 (obscured, 3H, H12), 1.07 (d, JHH ) 7.0, 3H, H10), 1.02 (s,
3

Catalytic ActiVity of Bis-phosphine Ru(II)-Arene Compounds
Organometallics, Vol. 26, No. 9, 2007 2453
3
3
3H, H7), (d, JPH ) 15, JHH ) 6.6, 3H, H13). 13C{1H} NMR
(0.28 g, 1.07 mmol), and [NH4]PF6 (0.19 g, 1.14 mmol) in 1:1
MeOH-CH2Cl2 (50 mL) was stirred at 35 °C for 2 h, then at
50 °C for 2 h. The solution was concentrated, giving a yellow solid,
which was filtered and washed with EtOH (2 × 30 mL) and then
diethyl ether (3 × 20 mL). Yield: 0.59 g (69%) as a yellow powder.
(CDCl3): δ 126-136 (m, PPh), 132 (C4), 99.6 (br, C6), 98.8 (s,
C1), 95.7 (d, 2JPC ) 3, C2), 87.5 (d, 2JPC ) 10, C3), 85.5 (d, 2JPC
)
10, C5), 31.4 (s, C8), 31.0 (d, 1JPH ) 25, H11), 21.7 (s, C9), 21.0 (s,
2
C10), 19.4 (d, JPC ) 4, C13), 18.6 (s, C12), 15.5 (s, C7). 31P{1H}
NMR (CDCl3): δ 23.5 (d, 2JPP ) 50, 1P, RuPPh3), 18.8 (d, 2JPP
)
Method B: A solution of [RuCl(NCMe)(PPh3)(η6-PhMe)]PF6
(0.10 g, 0.15 mmol) and PPh3 (0.12 g, 0.46 mmol) in CH2Cl2 (5
mL) was stirred at RT for 3 h. The product was precipitated by the
addition of excess diethyl ether (ca. 50 mL) and the precipitate
washed with diethyl ether (2 × 10 mL) and pentane (2 × 10 mL).
i
1
50, 1P, RuPPh2 Pr), -144.2 (sept, JPF ) 713, 1P, PF6). ESI-MS
(CH2Cl2) positive ion: m/z 761 [M]+; negative ion: m/z 145 [PF6]-.
Anal. Calcd for C43H46ClF6P3Ru(906.27 g mol-1)‚3/4(CH2Cl2): C,
54.17; H, 4.94. Found: C, 54.45; H, 4.70.
Preparation of [RuCl2(PPh3)(η6-PhMe)]. A solution of [RuCl2-
(η6-PhMe)]2 (0.50 g, 0.95 mmol) and PPh3 (0.62 g, 2.36 mmol) in
CH2Cl2 (20 mL) was stirred at RT for 90 min. The product was
then precipitated by the addition of hexane and washed with diethyl
ether (2 × 10 mL) and then pentane (2 × 10 mL). Yield: 0.86 g
1
Yield: 0.10 g (75%). H NMR (CDCl3): δ 7.20-7.35 (m, 18H,
PPh3), 7.35-7.50 (m, 12H, PPh3), 5.73-5.82 (m, 2H, H2), 5.05 (t,
3JHH ) 5.4, 1H, H1), 4.69 (d, 3JHH ) 6.0, 2H, H3), 2.11 (s, 3H, H5).
2/3
13C{1H} NMR (CDCl3): δ 133.9 (t,
J
) 5, PPh3), 131.0 (br,
PC
PPh3), 128.5 (t, 3/2JPC ) 5, PPh3), 122.6 (t, 2JPC ) 3, C4), 98.3 (br,
(86%) as an orange powder. 1H NMR (CDCl3): δ 7.76 (t, 3JHH
)
C2), 94.6 (t, 2JPC ) 5, C3), 83.5 (s, C1), 19.2 (s, C5). 31P{1H} NMR
8.8, 6H, PPh), 7.34-7.50 (m, 9H, PPh), 5.18-5.28 (m, 4H, H2 +
H3), 4.58 (t, 3JHH ) 5.0, 1H, H1), 2.28 (s, 3H, H5). 13C{1H} NMR
(CDCl3): δ 134.2 (d, 2/3JPC ) 9, PPh3), 130.4 (d, 4JPC ) 2, PPh3),
128.1 (d, 3/2 JPC ) 10, PPh3), 108.7 (d, 2JPC ) 6, C4), 89.0 (br, C2),
1
(CDCl3): δ 22.4 (s, 1P, RuPPh3), -144.3 (sept, JPF ) 713, 1P,
PF6). ESI-MS (CH2Cl2) positive ion: m/z 753 [M]+; negative ion:
m/z 145 [PF6]-. Anal. Calcd for C43H38ClF6P3Ru(898.21 g mol-1)‚1/
2(CH2Cl2): C, 55.54; H, 4.18. Found: C, 55.27; H, 4.12.
88.8 (d, JPC ) 6, C3), 81.3 (s, C1), 18.7 (s, C5). 31P{1H} NMR
2
Preparation of [RuCl(η2-PPh2(o-C6H4O))(η6-p-cymene)] (5).
A suspension of [RuCl2(η6-p-cymene)]2 (1.50 g, 2.45 mmol), PPh2-
(o-C6H4OH) (1.44 g, 5.17 mmol), and Cs2CO3 (0.80 g, 2.45 mmol)
in MeOH (100 mL) was heated at reflux for 1 h. The solution was
cooled to RT and the solvent removed in vacuo. The residue was
extracted with CH2Cl2 (60 mL) through Celite and hexane (ca. 60
mL) added. Concentration, followed by cooling to -20 °C, gave
the product as an orange-red crystalline solid. Yield: 2.13 g (79%).
Orange crystals suitable for X-ray diffraction were obtained from
a solution of CH2Cl2 layered with toluene and pentane at 4 °C. 1H
NMR (CDCl3): δ 7.94-5.05 (m, 2H, PPh), 7.31-7.52 (m, 8H,
PPh), 7.15-7.24 (m, 1H, H12), 7.07-7.15 (m, 1H, H14), 6.95-
(CDCl3): δ 28.2 (s, 1P). Anal. Calcd for C25H23Cl2PRu (526.41 g
mol-1): C, 57.04; H, 4.40. Found: C, 56.65; H, 4.14.
Preparation of [RuCl(NCMe)(PPh3)(η6-PhMe)]PF6 (4b). A
suspension of [RuCl2(PPh3)(η6-PhMe)] (0.8 g, 1.52 mmol) and
[NH4]PF6 (0.32 g, 1.96 mmol) in CH3CN (40 mL) was heated at
reflux for 2 h. The solution was cooled to RT and the solvent
removed in vacuo. The residue was then extracted with CH2Cl2
(50 mL) through Celite. Recrystallization from CH2Cl2-diethyl
ether removed a small amount of red-purple impurity. Yield: 0.89
1
g (85%) as a yellow powder of ∼95% purity. H NMR (CDCl3):
δ 7.45-7.63 (m, 15H, PPh3), 6.01 (d, 3JHH ) 5.9, 1H, H3), 5.86-
5.94 (m, 1H, H2), 5.42 (d, 3JHH ) 5.7, 1H, H5), 5.30-5.37 (m, 1H,
3
7.05 (m, 1H, H15), 6.45-6.55 (m, 1H, H13), 5.66 (d, JHH ) 6.1,
3
H6), 4.85 (t, JHH ) 5.2, 1H, H3), 2.37 (s, 3H, H7), 1.97 (s, 3H,
3
3
1H, H3), 5.42 (d, JHH ) 4.7, 1H, H6), 5.10 (d, JHH ) 6.1, 1H,
H2), 4.74 (d, 3JHH ) 5.0, 1H, H5), 2.60 (sept, 3JHH ) 6.8, 1H, H8),
2.10 (s, 3H, H7), 1.21 (d, 3JHH ) 6.8, 3H, H9), 1.10 (d, 3JHH ) 6.8,
NCMe). 13C{1H} NMR (CDCl3): δ 134.1 (d,
J
) 10, PPh3),
2/3
PC
4
1
131.5 (d, JPC ) 3, PPh3), 130.4 (d, JPC ) 51, PPh3), 128.9 (d,
) 11, PPh3), 127.2 (s, NCMe), 114.5 (d, 2JPC ) 6, C4), 93.0
3/2
3H, H10). 13C{1H} NMR (CDCl3): δ 177.7 (d, JPC ) 20, C16),
2
J
PC
(br, C2), 91.4 (d, 2JPC ) 8, C3), 89.6 (s, C6), 86.6 (d, 2JPC ) 2, C5),
84.7 (s, C1), 19.0 (s, C7), 3.3 (s, NCMe). 31P{1H} NMR (CDCl3):
δ 35.6 (s, 1P), -144.2 (sept, 1JPF ) 713, 1P, PF6). ESI-MS (CH2-
Cl2) positive ion: m/z 491 (29%) [M - MeCN]+, 532 [M]+;
negative ion: m/z 145 [PF6]-.
138.6 (d, 1JPC ) 48, PPh2), 134.9 (d, 2/3JPC ) 10, PPh2), 132.5 (d,
4JPC ) 2, C14), 131.9 (br, C12), 131.4 (d, 2/3JPC ) 10, PPh2), 130.7
(d, 4JPC ) 3, PPh2), 129.9 (d, 4JPC ) 3, PPh2), 129.3 (d, 1JPC ) 57,
3/2
3/2
PPh2), 128.5 (d,
J
) 10, PPh2), 128.1 (d,
J
) 11, PPh2),
PC
PC
119.6 (d, 3JPC ) 9, C15), 115.1 (d, 3JPC ) 7, C13), 113.9 (d, 1JPC
)
56, C11), 104.9 (s, C4), 95.7 (s, C1), 92.5 (d, 2JPC ) 6, C2), 86.5 (d,
Preparation of [RuCl(PPhMe2)(PPh3)(η6-PhMe)]PF6 (1e). To
a solution of [RuCl(NCMe)(PPh3)(η6-PhMe)]PF6 (0.30 g, 0.44
mmol) in CH2Cl2 (5 mL) was added PPhMe2 (0.25 mL, 1.76 mmol),
and the solution was stirred at RT for 5 min. The product was
precipitated by the addition of excess diethyl ether (ca. 50 mL)
and the precipitate washed with diethyl ether (2 × 10 mL) and
pentane (2 × 10 mL). Yield: 0.23 g (67%) as a yellow powder.
1H NMR (CDCl3): δ 7.45-7.82 (m, 20H, PPh), 5.83-5.90 (m,
2JPC ) 6, C5), 86.3 (d, JPC ) 3, C3), 85.4 (d, JPC ) 4, C6), 30.7
(s, C8), 22.3 (s, C9 + C10), 18.0 (s, C7). 31P{1H} NMR (CDCl3): δ
50.5 (s, 1P). Anal. Calcd for C28H28ClOPRu (548.03 g mol-1): C,
61.37; H, 5.15. Found: C, 61.20; H, 5.10.
2
2
Preparation of [Ru(PPh3)(η2-PPh2(o-C6H4O))(η6-p-cymene)]-
PF6 (2). A suspension of [RuCl(η2-PPh2(o-C6H4O))(η6-p-cymene)]
(1.00 g, 1.82 mmol) and PPh3 (1.30 g, 5.00 mmol) in EtOH (100
mL) was heated at reflux for 2 h. The solution was cooled to RT
and a solution of [NH4]PF6 (0.81 g, 5.00 mmol) in water (100 mL)
added. The solid was then isolated by decantation and washed with
water (3 × 50 mL). The solid was then dissolved in CH2Cl2 and
dried with Na2SO4 and the product precipitated by addition of excess
1H, H2), 5.47 (d, JHH ) 6.4, 1H, H5), 5.26-5.34 (m, 1H, H6),
3
4.68 (t, 3JHH ) 5.6, 1H, H1), 4.28 (d, 3JHH ) 5.6, 1H, H3), 2.04 (d,
2JPH ) 10, 3H, PMe), 2.00 (s, 3H, H7), 0.76 (d, JPH ) 11, 3H,
2
PMe′). 13C{1H} NMR (CDCl3): δ 142.4 (d, JPC ) 50, PPhMe2),
1
134.4 (d, 2/3JPC ) 10, PPh3), 132.9 (d, 1JPC ) 48, PPh3), 131.6 (d,
4JPC ) 2, PPh3), 130.6 (d, JPC ) 3, PPhMe2), 129.2 (d,
J
)
4
2/3
1
PC
diethyl ether. Yield: 0.89 g (53%) as a yellow powder. H NMR
3/2
3/2
2
(CDCl3): δ 6.4-8.0 (m, 25H, PPh), 7.06-7.12 (m, 1H, H14), 7.00-
7.06 (m, 1H, H12), 6.82 (dd, 3JPH ) 8, 3JHH ) 5.3, 1H, H15), 6.48-
10, PPhMe2), 128.9 (d,
J
) 10, PPh3), 128.7 (d,
J
) 8,
PC
PC
PPhMe2), 118.0 (dd, JPC ) 4, JPC ) 2, C4), 97.2 (d, JPC ) 9,
2
2
2
2
2
C3), 96.9 (d, JPC ) 4, C6), 95.1 (d, JPC ) 2, C2), 94.5 (d, JPC
)
3
6.57 (m, 1H, H13), 5.51 (d, JHH ) 5.9, 1H, H3), 5.25-5.30 (m,
10, C5), 84.0 (s, C1), 18.8 (s, C7), 17.0 (d, JPC ) 34, PMe), 12.2
1
3
1H, H2), 5.09-5.17 (m, 1H, H6), 4.98 (d, JHH ) 5.9, 1H, H5),
(d, JPC ) 36, PMe′). 31P{1H} NMR (CDCl3): δ 31.9 (d, JPP
)
1
2
3
3
2.62 (sept, JHH ) 6.9, 1H, H8), 1.90 (s, 3H, H7), 1.25 (d, JHH
)
56, 1P, RuPPh3), 3.7 (d, 2JPP ) 56, 1P, RuPPhMe2), -144.1 (sept,
1JPF ) 713, 1P, PF6). ESI-MS (CH2Cl2) positive ion: m/z 629 [M]+;
negative ion: m/z 145 [PF6]-. Anal. Calcd for C33H34ClF6P3Ru
(774.07 g mol-1): C, 51.21; H, 4.43. Found: C, 51.53; H, 4.38.
6.9, 3H, H9), 1.16 (d, JHH ) 6.8, 3H, H10). 13C{1H} NMR
3
(CDCl3): δ 178.1 (d, 2JPC ) 20, C16), 137.7 (d, 1JPC ) 51, PPh2),
133.8 (br, PPh3), 133.3 (br, C12), 132.8 (d, JPC ) 1, C14), 132.5
4
2/3
2/3
4
(d,
J
) 10, PPh2), 131.5 (d,
J
) 10, PPh2), 131.0 (d, JPC
PC
PC
4
Preparation of [RuCl(PPh3)2(η6-PhMe)]PF6 (1f). Method A:
) 2, PPh2), 130.9 (d, JPC ) 2, PPh2), 130.8 (br, PPh3), 129.2 (d,
A solution of [RuCl2(PPh3)(η6-PhMe)] (0.50 g, 0.95 mmol), PPh3
J
) 11, PPh2), 128.8 (d,
J
) 11, PPh2), 128.3 (br, PPh3),
3/2
3/2
PC
PC

2454 Organometallics, Vol. 26, No. 9, 2007
Table 7. Crystal Data and Details of the Structure Determinations
Chaplin and Dyson
1a
1c
1d
5
formula
C36H40ClF6P3Ru
C49H50ClF6P3Ru‚
2CH2Cl2
C43H46ClF6P3Ru‚
2CH2Cl2
2(C28H28ClOPRu)‚
CHCl3
M
816.11
1152.17
1076.08
1215.36
T [K]
100(2)
140(2)
140(2)
140(2)
cryst syst
space group
a [Å]
b [Å]
c [Å]
monoclinic
P2(1)/c
16.448(3)
10.956(2)
19.134(4)
orthorhombic
Pbca
16.4780(13)
18.9480(14)
32.554(3)
orthorhombic
Pna2(1)
24.0009(15)
11.5170(7)
16.6737(11)
monoclinic
P2(1)/c
17.4380(12)
22.1460(15)
14.6340(10)
R [deg]
â [deg]
δ [deg]
V [Å3]
Z
93.26(3)
103.876(6)
3442.4(12)
4
1.575
0.732
3.10 < θ < 25.03
35 341
6012 [Rint ) 0.0859]
6012/36/429
R1 ) 0.0641,
wR2 ) 0.1258
1.254
10164.2(14)
8
1.506
0.723
2.99 < θ < 25.03
59 683
8868 [Rint ) 0.1077]
8868/66/638
R1 ) 0.0672,
wR2 ) 0.1497
1.079
4608.9(5)
4
1.551
0.791
3.10 < θ < 25.03
27 346
7478 [Rint ) 0.0950]
7478/361/548
R1 ) 0.0625,
wR2 ) 0.1282
0.863
5486.5(6)
4
1.471
0.893
3.01 < θ < 25.03
32 203
9584 [Rint ) 0.0997]
9584/578/695
R1 ) 0.0467,
wR2 ) 0.0565
0.754c
density µ [g cm-3
]
µ [mm-1
θ range [deg]
no. of measd reflns
no. of unique reflns
no. data/restr/params
R1, wR2 [I > 2σ(I)]a
]
GoFb
2
2
b
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) {∑[w(Fo2 - Fc )2]/∑[w(Fo )2]}1/2. GoF ) {∑[w(Fo2 - Fc )2]/(n - p)}1/2 where n is the number of data and p is the
c
number of parameters refined. The GoF is lower than normal owing to weak reflections, although the low angle data are good. If reflections with θ < 23°
are taken, the structure converges with a GoF ) 0.939 and a completeness of 0.997.
123.1 (t, 2JPC ) 2, C4), 120.5 (d, 3JPC ) 10, H15), 115.9 (d, 3JPC
)
1JPF ) 713, 1P, PF6). Anal. Calcd for C52H56ClF6P3Ru (1024.45 g
mol-1): C, 60.97; H, 5.51. Found: C, 61.00; H, 5.24.
2
2
7, C13), 115.3 (d, JPC ) 56, C11), 99.0 (s, C1), 97.9 (d, JPC ) 3,
2
2
2
C6), 96.3 (d, JPC ) 3, C2), 92.8 (d, JPC ) 8, C3), 86.6 (d, JPC
)
Kinetics Experiments. Exchange kinetics of 1-3 with P(p-tol)3
were monitored using 31P{1H} NMR spectroscopy, integrating
relative to an internal standard of PO(OEt)3 in toluene (in sealed
capillary tubes). Ru concentrations were ∼5 mM. Equilibration of
1c was monitored using 31P{1H} NMR spectroscopy in THF. Ru
concentrations were ∼20 mM. All samples were prepared under
nitrogen and then transferred into screw-cap NMR tubes under
nitrogen. The temperature was determined before and after each
measurement using an external temperature probe and showed good
agreement ((0.2 K). Integrations were preformed using NM-
RICMA, an iterative fitting application for MatLab.24
All exchange reactions of 1-3 showed excellent first-order
behavior under the conditions (full data are listed in Table S2).
Data for the reactions involving only one ligand exchange (20 equiv
of P(p-tol)3/Ru) were fitted to single-exponential functions (Origin
7.0). Treatment of data for complexes with sequential exchange
reactions (30 equiv of P(p-tol)3/Ru) was carried out by least-squares
fitting of eqs 1-3 with Scientist 2.0 (example fit is given in Figure
5 and corresponds to entries 2 and 6 in Table S2).25 The multistep
treatment for complex 1d is only necessary at one temperature
owing to large difference in rates of exchange; single-exponential
functions are used for all other temperatures.
9, C5), 31.4 (s, C8), 22.8 (s, C9), 20.8 (s, C10), 18.1 (s, C7). 31P{1H}
NMR (CDCl3): δ 54.3 (d, 2JPP ) 48, 1P, RuPPh2), 26.0 (d, 2JPP
)
48, 1P, RuPPh3), -144.2 (sept, 1JPF ) 713, 1P, PF6). ESI-MS (CH2-
Cl2) positive ion: m/z 775 [M]+; negative ion: m/z 145 [PF6]-.
Anal. Calcd for C46H43F6OP3Ru (919.83 g mol-1): C, 60.07; H,
4.71. Found: C, 60.41; H, 4.80.
Preparation of [RuCl2(P(p-tol)3)(η6-p-cymene)]. A solution of
[RuCl2(η6-p-cymene)]2 (1.00 g, 1.63 mmol) and P(p-tol)3 (1.49 g,
4.85 mmol) in CH2Cl2 (50 mL) was stirred at RT for 3 h. The
product was precipitated by addition of hexane (120 mL) and
concentration of the solution. Recrystallization from CH2Cl2-
hexane gave the product as an orange powder. Yield: 1.75 g (88%).
1H NMR (CDCl3): δ 7.10-7.78 (m, 12H, PC6H4Me), 5.21 (d, 3JHH
3
3
) 5.9, 2H, H3), 4.97 (d, JHH ) 5.6, 2H, H2), 2.90 (sept, JHH
)
6.9, 1H, H6), 2.36 (s, 9H, PC6H4Me), 1.88 (s, 3H, H5), 1.13 (d,
3JHH ) 6.9, 6H, H7). 13C{1H} NMR (CDCl3): δ 140.3 (d, JPC
)
)
)
4
2
1
3, PC6H4Me), 134.3 (d, JPC ) 10, PC6H4Me), 130.7 (d, JPC
3
2
48, PC6H4Me), 128.7 (d, JPC ) 10, PC6H4Me), 111.1 (d, JPC
4, C4), 95.7 (s, C1), 88.8 (d, JPC ) 3, C2), 87.2 (d, JPC ) 6, C3),
30.3 (s, C6), 21.9 (s, PC6H4Me), 21.4 (s, C7), 17.8 (s, C5). 31P{1H}
NMR (CDCl3): δ 23.0 (s, 1P). Anal. Calcd for C31H35Cl2PRu-
(610.57 g mol-1)‚0.2(CH2Cl2): C, 59.71; H, 5.69. Found: C, 60.01;
H, 5.50.
2
2
[A] ) e-k (t-t )[A]0
(1)
(2)
1
1
Preparation of [RuCl(P(p-tol)3)2(η6-p-cymene)]PF6 (6). A
suspension of [RuCl2(P(p-tol)3)(η6-p-cymene)] (0.50 g, 0.82 mmol),
PPh3 (0.274 g, 0.90 mmol), and [NH4]PF6 (0.174 g, 1.07 mmol) in
MeOH (30 mL) was stirred at 35 °C for 2 h. The solvent was
removed in vacuo and the residue extracted through Celite with
CH2Cl2 (ca. 40 mL). The product was then isolated by precipitation
with hexane (ca. 150 mL) and washed with EtOH (2 × 20 mL)
and pentane (1 × 10 mL). Yield: 0.67 g (79%) as a yellow powder.
1H NMR (CDCl3): δ 6.94-7.38 (m, 24H, PC6H4Me), 5.45-5.56
k1[A]0(e-k (t-t ) - e-k (t-t )
)
2
1
1
1
[B] )
k2 - k1
k1e-k (t-t ) - k2e-k (t-t )
2
1
1
1
[C] ) [A]0 1 +
(3)
(
)
k2 - k1
The rate constants for the forward (k3) and reverse reactions (k-3
)
3
3
(m, 2H, H2), 5.06 (d, JHH ) 6.2, 1H, H3), 2.71 (sept, JHH ) 6.9,
were calculated from the rate of approach to equilibrium (eq 4)
and the equilibrium constant (k-3 ) k3K-1).26 The activation
parameters for the forward and reverse reactions were determined
1H, H6), 2.38 (s, 18H, PC6H4Me), 1.24 (d, JHH ) 7.0, 6H, H7),
3
1.07 (s, 3H, H5). 13C{1H} NMR (CDCl3): δ 140.6 (s, PC6H4Me),
129-134 (m, PC6H4Me), 131 (C4), 100.0 (s, C1), 97.3 (br, C2),
88.9 (t, 2JPC ) 5, C3), 31.3 (s, C6), 21.4 (s, C7), 21.3 (s, PC6H4Me),
15.3 (s, C5). 31P{1H} NMR (CDCl3): δ 19.2 (s, 2P), -144.4 (sept,
(24) Helm, L.; Borel, A.; Yerly, F. NMRICMA 3.0 for Matlab; Institut
des Sciences et Inge´nierie Chimiques: EPFL Lausanne, 2004.

Catalytic ActiVity of Bis-phosphine Ru(II)-Arene Compounds
Organometallics, Vol. 26, No. 9, 2007 2455
from the temperature dependence of the rate constants using the
Eyring equation. Full data are found in Table S3.
least-squares on F2) using SHELXTL.28,31 Absorption corrections
were applied to the data sets of 1a (multiscan, SADABS),28 1c
(empirical, DELABS),32 and 1d (empirical multiscan).33 The
structure of 1d was refined using the twinned refinement method,
with a BASF parameter of 0.09056. All non-hydrogen atoms were
refined anisotropically, with hydrogen atoms placed in calculated
positions using the riding model with the exception of those on C8
in 5, which were located on the Fourier difference map and then
constrained. Disorder in the counterion in 1c was modeled by
splitting it over two sites. Disorder in the p-cymene ring of one of
conformations in the asymmetric cell of 5 was modeled by splitting
the isopropyl moiety over two sites. Disorder in the phenyl rings
of the other conformation of 5 was modeled by splitting them over
two sites, restraining the geometry of the rings and restraining the
displacement parameters. Restraints were also applied to the
displacement parameters of other atoms in these two conformations
of 5, the coordinated atoms of the p-cymene ring in 1a, selected
atoms of the counterion and solvent in 1c, and to all atoms in the
structure of 1d. Graphical representations of the structures were
made with ORTEP3.34
[1c]0(1 + e-8k t
)
3
[1c] )
(4)
2
Catalytic Evaluations. All catalytic experiments were conducted
using a home-built multicell autoclave containing an internal
temperature probe. Each glass reaction vessel was charged with
the precatalyst (5.0 × 10-6 mol), styrene (0.01 mol, S:C ) 2000:
1, ACROS, dried over molecular sieves), internal standard (100
mg octane, distilled from CaH2 under nitrogen and stored under
nitrogen over molecular sieves), and solvent (2 mL of THF, dried
catalytically under nitrogen and stored under nitrogen over molec-
ular sieves) and then placed inside the autoclave, which was then
flushed with H2 (3 × 10 bar). The autoclave was then heated to
the desired temperature under H2 (5 bar) and then maintained at
50 bar for the duration of the catalytic run (60 min). The autoclave
was then cooled to ambient temperature 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. Ethyl benzene was the
only product observed.
Crystallography. Relevant details about the structure refinements
are given in Table 7, and selected geometrical parameters for 1a,
1c and 1d are found in Table 2. Data were collected on a KUMA
CCD diffractometer system (1c, 1d, 5) and Bruker APEX II CCD
diffractometer system (1a) using graphite-monochromated Mo KR
radiation (0.71073 Å) and a low-tempetature device. Data reduction
was performed using CrysAlis RED27 (1c, 1d, 5) and EvalCCD28,29
(1a). Structures were solved using SIR9730 and refined (full-matrix
Acknowledgment. This work was supported by the EPFL
and the Swiss National Science Foundation. We are grateful to
Dr. R. Scopelliti and Dr. E. Solari for assistance with crystal-
lography and Dr. G. Laurenczy for helpful discussions. We also
thank the New Zealand Foundation for Research, Science and
Technology for a Top Achiever Doctoral Fellowship (A.B.C.).
Supporting Information Available: Crystallographic informa-
tion for 1a, 1c, 1d, and 5 in CIF format and Tables S1-S3.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM070050D
(25) The system is under pseudo-first-order conditions, and the reactions
are considered irreversible owing to the large excess of P(p-tol)3 (Scheme
3). The concentrations of the initial complex A, intermediate B, and final
complex C were the dependent variables and t the independent. The
parameters t1, k1, k2, and [A]0 ([A], [B], [C] were in arbitrary units) were
refined during the fitting.
(29) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M.
M. J. Appl. Crystallogr. 2003, 36, 220.
(30) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G.; Polidori, G. G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(26) Moore, J. W.; Pearson, R. G. Kinetics and Mechanism, 3rd ed.;
John Wiley & Sons: New York, 1981; p 304.
(27) CrysAlis RED; Oxford Diffraction Ltd.: Abingdon, Oxfordshire,
U.K., 2003.
(31) Sheldrick, G. M. SHELXTL; University of Go¨ttingen: Germany,
1997.
(32) Walker, N.; Stuart, D. Acta Crystallogr. Sect. A 1983, 39, 158.
(33) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(34) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
(28) EValCCD; Bruker AXS, Inc.: Madison, WI, 1997.