Reactivity and catalytic activity of a robust ruthenium(II)-triphos complex

Article abstract of DOI:10.1021/ic701773a

The ruthenium(II)-triphos acetato complex [RuCl(OAc)(κ³- triphos)] (triphos = (PPh₂CH₂)₃CMe) has been found to be an active catalyst precursor for the hydrogenation of 1-alkenes under relatively mild conditions (5-50 bar H₂, 50°C). In contrast to related triphenylphosphine complexes, [RuCl(OAc)(κ³- triphos)] is much less air sensitive and high catalytic activities were achieved when catalyst samples were prepared without exclusion of air or moisture. Substitution of the acetato ligand can be effected by treatment of acid, affording [Ru₂(μ-Cl)₃(κ;³-triphos) ₂]Cl and [RuCl(κ³-triphos)]₂(BF ₄)₂ with aqueous HCl and [Et₂OH]BF₄, respectively, or by heating with dmpm in the presence of [NH ₄]PF₆, resulting in formation of [RuCl(κ ²-dmpm)(κ³-triphos)]PF₆ (dmpm = PMe ₂CH₂PMe₂). A hydride complex, [RuHCl(κ³-triphos)], formed by acetato-mediated heterolytic cleavage of dihydrogen is proposed as the active catalytic species. An inner-sphere, monohydride mechanism is suggested for the catalytic cycle, with chloro and triphos ligands playing a spectator role. These mechanistic proposals are consistent with reactivity studies carried out on [RuCl(OAc) (κ³-triphos)] and [RuH(OAc)(κ³-triphos)] and supported by a computational analysis. The solid-state structures of [RuCl(OAc)(κ³-triphos)], [RuCl(κ³-triphos)] ₂(BF₄)₂, and [RuCl(κ²-dmpm) (κ³-triphos)]PF₆ have been established by X-ray diffraction.

Full text of DOI:10.1021/ic701773a

Inorg. Chem. 2008, 47, 381−390
Reactivity and Catalytic Activity of a Robust Ruthenium(II)
Complex
−Triphos
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 September 10, 2007
The ruthenium(II)
be an active catalyst precursor for the hydrogenation of 1-alkenes under relatively mild conditions (5
50 C). In contrast to related triphenylphosphine complexes, [RuCl(OAc)(
3-triphos)] is much less air sensitive and
high catalytic activities were achieved when catalyst samples were prepared without exclusion of air or moisture.
Substitution of the acetato ligand can be effected by treatment of acid, affording [Ru2(
-Cl)3(κ3-triphos)2]Cl and
[RuCl(
3-triphos)]2(BF4)2 with aqueous HCl and [Et2OH]BF4, respectively, or by heating with dmpm in the presence
of [NH4]PF6, resulting in formation of [RuCl( PMe2CH2PMe2). A hydride complex,
2-dmpm)( 3-triphos)]PF6 (dmpm
[RuHCl(
3-triphos)], formed by acetato-mediated heterolytic cleavage of dihydrogen is proposed as the active catalytic
−triphos acetato complex [RuCl(OAc)(
κ
3-triphos)] (triphos
)
(PPh2CH2)3CMe) has been found to
−50 bar H2,
°
κ
µ
κ
κ
κ
)
κ
species. An inner-sphere, monohydride mechanism is suggested for the catalytic cycle, with chloro and triphos
ligands playing a spectator role. These mechanistic proposals are consistent with reactivity studies carried out on
[RuCl(OAc)(
structures of [RuCl(OAc)(
established by X-ray diffraction.
κ
3-triphos)] and [RuH(OAc)(
κ
3-triphos)] and supported by a computational analysis. The solid-state
3-triphos)]2(BF4)2, and [RuCl( 2-dmpm)( 3-triphos)]PF6 have been
κ
3-triphos)], [RuCl(
κ
κ
κ
Introduction
Bianchini and co-workers, in particular, pioneered the use
of this ligand in transition-metal catalysis using platinum
group metals for a number of processes, including hydro-
genation and hydroformylation of alkenes,3 hydrogenation
of N-heterocycles,4 oxidation of catechols,5 coupling reactions
of alkynes,6 and hydrogenation, hydrogenolysis, and hy-
drodesulfurization of thiophenes.7 Functionalization of the
triphos ligand by derivation of the bridgehead atom with
Tripodal triphosphine ligands have found widespread
applications in coordination chemistry.1 Among these ligands,
the C3-symmetric 1,1,1-tris(diphenylphosphinomethyl)ethane
(triphos) and its derivatives are the most extensively inves-
tigated, forming a large variety of transition-metal complexes,
many of which have found applications in catalysis.1,2
* To whom correspondence should be addressed. E-mail: paul.
dyson@epfl.ch.
(1) (a) Hierso, J.-C.; Amardeil, R.; Bentabet, E.; Boussier, R.; Gautheron,
B.; Meunier, P.; Kalck, P. Coord. Chem. ReV. 2004, 236, 143. (b)
Mayer, H. A.; Kaska, W. C. Chem. ReV. 1994, 94, 1239. (c) Cotton,
F. A.; Hong, B. Prog. Inorg. Chem. 1992, 40, 179.
(3) (a) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Frediani, P.;
Frediani, P.; Ramirez, J. A. Organometallics 1990, 9, 226. (b)
Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Fujiwara, Y.; Jintoku,
T.; Taniguchi, H. J. Chem. Soc., Chem. Commun. 1988, 299. (c)
Bianchini, C.; Meli, A.; Laschi, F.; Ramirez, J. A.; Zanello, P. Inorg.
Chem. 1988, 27, 4429.
(4) (a) Barbaro, P.; Bianchini, C.; Meli, A.; Moreno, M.; Vizza, F.
Organometallics 2002, 21, 1430. (b) Bianchini, C.; Barbaro, P.;
Macchi, M.; Meli, A.; Vizza, F. HelV. Chim. Acta 2001, 84, 2895.
(5) (a) Barbaro, P.; Bianchini, C.; Frediani, P.; Meli, A.; Vizza, F. Inorg.
Chem. 1992, 31, 1523. (b) Barbaro, P.; Bianchini, C.; Mealli, C.; Meli,
A. J. Am. Chem. Soc. 1991, 113, 3181. (c) Bianchini, C.; Frediani,
P.; Laschi, F.; Meli, A.; Vizza, F.; Zanello, P. Inorg. Chem. 1990, 29,
3402.
(2) (a) Chaplin, A. B.; Dyson, P. J. Eur. J. Inorg. Chem. 2007, 4973. (b)
Magro, A. A. N.; Eastham, G. R.; Cole-Hamilton, D. J. Chem.
Commun. 2007, 3154. (c) Rosales, M.; Vallejo, R.; Soto, J. J.; Chaco´n,
G.; Gonza´lez, AÄ .; Gonza´lez, B. Catal. Lett. 2006, 106, 101. (d) Rosales,
M.; Gonza´lez, A.; Gonza´lez, B.; Moratinos, C.; Pe´rez, H.; Urdaneta,
J.; Sa´nchez-Delgado, R. A. J. Organomet. Chem. 2005, 690, 3095.
(e) Chen, J.-X.; Daeuble, J. F.; Brestensky, D. M.; Stryker, J. M.
Tetrahedron 2000, 56, 2153. (f) Sung, K.-M.; Huh, S.; Jun, M.-J.
Polyhedron 1999, 18, 469. (g) Teunissen, H. T.; Elsevier, C. J. Chem.
Commun. 1998, 1367. (h) Sernau, V.; Huttner, G.; Friz, M.; Zsolnai,
L.; Walter, O. J. Organomet. Chem. 1993, 453, C23. (i) Bianchini,
C.; Meli, A.; Peruzzini, M.; Vizza, F.; Zanobni, F. Coord. Chem. ReV.
1992, 120, 193. (j) Ott, J.; Tombo, G. M. R.; Schmid, B.; Venanzi, L.
M.; Wang, G.; Ward, T. R. Tetrahedron Lett. 1989, 30, 6151. (k)
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(6) Bianchini, C.; Meli, A.; Peruzzini, M.; Vacca, A.; Vizza, F. Organo-
metallics 1991, 10, 645.
(7) (a) Bianchini, C.; Meli, A.; Vizza, F. J. Organomet. Chem. 2004, 689,
4277. (b) Bianchini, C.; Meli, A. J. Chem. Soc., Dalton Trans. 1996,
801. (c) Bianchini, C.; Meli, A. Acc. Chem. Res. 1998, 31, 109.
10.1021/ic701773a CCC: $40.75
Published on Web 11/29/2007
© 2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 1, 2008 381

Chaplin and Dyson
Scheme 1
Scheme 2. Preparation of 2 and 4
Figure 1. Variable-temperature 31P{1H} NMR (CD2Cl2) spectra of 2.
appropriate moieties has allowed formation of metalloden-
drimers8 or immobilization of metal complexes into/onto
silica,9 polymers,10 or biphases,11 facilitating catalyst reuse
or modifying reactivity. Such immobilization is comple-
mented by the tridentate nature of the ligand, stabilizing the
metal center during catalysis and reducing leaching.
Despite extensive use of ruthenium(II)-phosphine com-
plexes in hydrogenation,12 there are few examples of well-
defined ruthenium(II)-triphos complexes that catalyze this
process. This paucity is somewhat surprising owing to the
successful application of [RuCl2(PPh3)3] (1, Scheme 1) and
related complexes containing trisphosphine ligands in hy-
drogenation.12,13 The air sensitivity of 1, as a result of facile
triphenylphosphine dissociation in solution, significantly
limits its application, and the increased stability provided
by the tripodal nature of the triphos ligand makes it an
attractive ligand for enhancing the stability of the ruthenium-
(II)-phosphine complexes. Well-defined ruthenium(II)-
triphos complexes employed for hydrogenation include
[RuH(κ2-BH4)(κ3-triphos)],14 [Ru(NCMe)3(κ3-triphos)]+,4a,14
and [RuHCl(CO)(κ3-triphos)].2f Complexes containing the
functionalizedtriphosligandsulfos,(PPh2CH2)3CCH2(C6H4)SO3-,
have also been employed together with ruthenium(II) in
hydrogenation.9c,d,11a
Building upon the highly successful application of ruthe-
nium(II)-diphosphine acetato complexes as hydrogenation
catalysts, developed by Noyori and co-workers,15 and as part
of our investigations of ruthenium(II)-phosphine com-
plexes,16 we report here on the reactivity and hydrogenation
activity of the ruthenium(II)-triphos acetato complex (2,
Scheme 1). Determination of the catalytic activity of 2 is
supplemented by relevant mechanistic studies, a computa-
tional analysis, and comparisons to the activity of 1 and the
related tris-triphenylphosphine complex [RuCl(OAc)(PPh3)3],
3.17
Figure 2. ORTEP representation of 2, thermal ellipsoids drawn at 50%
probability. Key bond lengths (Å) and angles (deg): Ru1-Cl1, 2.448(2);
Ru1-P1, 2.277(3); Ru1-P2, 2.282(2); Ru1-P3, 2.275(2); Ru1-O1, 2.249-
(5); Ru1-O2, 2.198(6); Ru1-C6, 2.580(9); Ru1-C6-C7, 173.0(6); Cl1-
Ru1-P1, 95.29(8); Cl1-Ru1-P2, 99.67(8); Cl1-Ru1-P3, 171.05(7);
Cl1-Ru1-C6, 78.4(2); P1-Ru1-P2, 86.28(8); P1-Ru1-P3, 89.11(9);
P2-Ru1-P3, 88.37(8); P1-Ru1-C6, 138.6(2); P2-Ru1-C6, 135.1(2);
P3-Ru1-C6, 93.1(2); O1-Ru1-O2, 59.7(2).
2
and 37.0 ppm), respectively, with a JPP coupling constant
of 40 Hz (Figure 1). This broadening suggests a certain
degree of stereochemical nonrigidity, although coalescence
was not reached within the boiling point limit of the solvent.18
Similar behavior has been observed for a series of κ3-triphos
complexes [Ru(L-L′)(NCMe)(κ3-triphos)]OTf (L-L′ ) κ2-
S-diorganyldithiocarbamate/κ2-N,S-thioamide) prepared by
Landgrafe and co-workers, although derivates formed by
(8) Findeis, R. A.; Gade, L. H. Eur. J. Inorg. Chem. 2003, 99.
(9) Metal-impregnated silica: (a) Barbaro, P.; Bianchini, C.; Santo, V.
D.; Meli, A.; Moneti, S.; Psaro, R.; Scaffidi, A.; Sordelli, L.; Vizza,
F. J. Am. Chem. Soc. 2006, 128, 7065. (b) Bianchini, C.; Santo, V.
D.; Meli, A.; Moneti, S.; Moreno, M.; Oberhauser, W.; Psaro, R.;
Sordelli. L.; Vizza, F. Angew. Chem., Int. Ed. 2003, 42, 2536. Silica
alone: (c) Bianchini, C.; Santo, V. D.; Meli, A.; Moneti, S.; Moreno,
M.; Oberhauser, W.; Psaro, R.; Sordelli, L.; Vizza, F. J. Catal. 2003,
213, 47. (d) Bianchini, C.; Santo, V. D.; Meli, A.; Oberhauser, W.;
Psaro, R.; Vizza, F. Organometallics 2000, 19, 2433. (e) Bianchini,
C.; Burnaby, D. G.; Evans, J.; Frediani, P.; Meli, A.; Oberhauser, W.;
Psaro, R.; Sordelli, L.; Vizza, F. J. Am. Chem. Soc. 1999, 121, 5961.
(10) Bianchini, C.; Frediani, M.; Vizza, F. Chem. Commun. 2001, 479.
(11) (a) Rojas, I.; Linares, F. L.; Valencia, N.; Bianchini, C. J. Mol. Cat.
A 1999, 144, 1. (b) Bianchini, C.; Frediani, P.; Sernau, V. Organo-
metallics 1995, 14, 5458.
(12) (a) Morris, R. H. Handbook of Homogenous Hydrogenation; de Vries,
J. G., Elsevier, C. J., Eds.; Wiley-VCH: Weinheim, 2007; Vol. 1, p
45. (b) Kitamura, M.; Noyori, R. Ruthenium in Organic Synthesis;
Murahashi, S.-I., Ed.; Wiley-VCH: Weinheim, 2004; p 3.
(13) Evans, D.; Osborn, J. A.; Jardine, F. H.; Wilkinson, G. Nature 1965,
208, 1203.
(14) Bianchini, C.; Meli, A.; Moneti, S.; Vizza, F. Organometallics 1998,
17, 2636.
(15) Noyori, R. Angew. Chem., Ind. Ed. 2002, 41, 2008.
Results and Discussion
1. Synthesis and Characterization. Substitution of PPh3
in 3 by triphos in toluene under reflux affords 2 in high yield
(93%) as an analytically pure, air-stable solid (Scheme 2).
The 31P{1H} NMR spectrum of 2 at room temperature
contains two broad resonances at 40.5 and 36.7 ppm (CD2-
Cl2, 2:1 ratio), which upon progressive cooling to -10 °C
sharpen into well-defined doublet and triplet resonances (40.4
382 Inorganic Chemistry, Vol. 47, No. 1, 2008

ActiWity of a Robust Ruthenium(II)-Triphos Complex
Figure 3. 31P{1H} NMR (CD2Cl2, 293 K) spectrum of 7 together with assignments and simulated regions.
Scheme 3
substitution of the acetonitrile ligand were found to be
stereochemically rigid at ambient temperature.19 The related
hydride complex, [RuH(OAc)(κ3-triphos)], 4, prepared in an
analogous fashion to 2 (used for mechanistic investigations
described below), in contrast, exhibits sharp and well-defined
resonances at room temperature in the 31P{1H} NMR
spectrum. The doublet and triplet resonances are located at
61.0 and 6.2 ppm, respectively (2:1 ratio, CD2Cl2), and the
2JPP coupling constant of 4 is reduced in comparison to 2
(40 vs 20 Hz). A characteristic doublet of triplets is observed
at -2.78 ppm in the H NMR spectrum of 4, with JPH
coupling constants of 122 and 20 Hz.
The solid-state structure of 2 has been determined by X-ray
diffraction and is depicted in Figure 2. The ruthenium center
has a distorted octahedral geometry, the triphos ligand
adopting the expected fac-geometry. The distortion from ideal
octahedral geometry predominantly results from the small
chelate angle of the acetato ligand [59.7(2)°] and the
significant bending of the chloro ligand away from the axial
axis [P3-Ru1-Cl1 ) 171.05(7)°]. The bending of the chloro
ligand appears to be steric in origin; three protons from the
neighboring phenyl groups lie within the corresponding
combined van der Waals radii (2.95 Å; H9, H15, and H39).
These features are also observed in the related complex fac-
[RuCl(OAc)(κ3-(PCy2CH2)2PPh)] [O-Ru-O, 58.9(1)°; Pax-
Ru-Cl, 170.6(1)°].20
2. Substitution Reactions of 2. The ability of the acetato
ligand in 2 to undergo substitution on treatment of acid was
demonstrated by reaction with aqueous HCl under biphasic
conditions, resulting in formation of the trichloro-bridged
ruthenium dimer 5, Scheme 3. Alternatively, reaction of 2
at low temperature with [Et2OH]BF4, containing the weakly
coordinating tetrafluoroborate anion, affords a 16 VE dichloro-
bridged ruthenium dimer [RuCl(κ3-triphos)]2(BF4)2, 6. The
31P{1H} NMR spectrum of 6 exhibits a single resonance at
55.8 ppm (CD2Cl2), which is also detected in low intensity
initially on reaction of 2 with HCl. The structure of 6 was
confirmed by ESI-MS, the presence of a molecular ion peak
1
2
(16) (a) Chaplin, A. B.; Dyson, P. J. Organometallics 2007, 26, 4357. (b)
Chaplin, A. B.; Dyson, P. J. Organometallics 2007, 26, 2447. (c)
Chaplin, A. B.; Fellay, C.; Laurenczy, G.; Dyson, P. J. Organometallics
2007, 26, 586. (d) Chaplin, A. B.; Scopelliti, R.; Dyson, P. J. Eur. J.
Inorg. Chem. 2005, 4762. (e) Geldbach, T. J.; Chaplin, A. B.; Ha¨nni,
K. D.; Scopelliti, R.; Dyson, P. J. Organometallics 2005, 24, 4974.
(f) Daguenet, C.; Scopelliti, R.; Dyson, P. J. Organometallics 2004,
23, 4849.
(17) Mainz, V. V.; Andersen, R. A. Organometallics 1984, 3, 675.
(18) Estimated coalescence temperature in CD2Cl2 is 80 °C (from high-
pressure experiments).
(19) Landgrafe, C.; Sheldrick, W. S.; Su¨dfeld, M. Eur. J. Inorg. Chem.
1998, 407.
(20) Jian, G.; Rheingold, A. L.; Haggerty, B. S.; Meek, D. W. Inorg. Chem.
1992, 31, 900.
Inorganic Chemistry, Vol. 47, No. 1, 2008 383

Chaplin and Dyson
Table 1. 31P NMR Chemical Shifts and Coupling Constants for 7
Obtained by Simulation Analysis (excluding Anion Resonance)
not inhibit the catalytic activity of 2 significantly.23 Under
higher pressure (50 bar H2) complete hydrogenation of
styrene could be achieved with 1-3 in 1 h (TOFs g 10 000
h-1). Interestingly, only 2 was detected by 31P NMR
spectroscopy following catalysis under these conditions,
suggesting that formation of the active catalyst is reversible.
If the samples were prepared in air, large reductions in
activity were observed for 1 and 3 (TOFs of 200 and 900
h-1, respectively), while the activity for 2 remained high
(TOF of 7400 h-1).
δ/ppm
J/Hz
A
M
X
41.4
3.2
-37.6
JAM ) 35, JAX ) 28
JMM ) 42, JMX ) 263 (trans), JMX ) 23 (cis)
JXX ) -62
at m/z + 761 corresponding to the dication, and single-crystal
X-ray diffraction (see below). Substitution of the acetato
ligand in 2 can also be effected using the basic diphosphine
dmpm in the presence of [NH4]PF6, affording [RuCl(κ2-
dmpm)(κ3-triphos)]PF6 (7, dmpm ) PMe2CH2PMe2). The
reaction proceeds via the presence of an intermediate species,
tentatively assigned as [Ru(κ1-OAc)(κ2-dmpm)(κ3-triphos)]+
on the basis of 31P{1H} NMR data. The coordination
geometry of the phosphine ligands in 7 is confirmed by the
presence of a distinct and non-first-order AMM′XX′ coupling
system in the 31P{1H} NMR spectrum (Figure 3). The
spectral parameters were extracted by simulation analysis
and are listed in Table 1. Of note, the value of the larger
JMX coupling constant (263 Hz) is typical for trans-
coordinated phosphines.21 The coordination of the chloro
ligand is confirmed by ESI-MS (7 exhibits a strong molecular
ion peak at m/z + 897), 1H NMR spectroscopy, and single-
crystal X-ray diffraction.
The solid-state structures of 6 and 7 are depicted in Figure
4. The structure of 6 contains two ruthenium centers, with
distorted square pyramidal geometries, bridged by two chloro
ligands. The Ru‚‚‚Ru separation of 3.8732(7) Å in 6 is
significantly larger than that in [Ru2(µ-Cl)3(κ3-triphos)2]BPh4
(8) [3.455(1) Å] owing to enlarged Ru-Cl-Ru angles [6,
102.49(4)°; 8, 88.00(9)°, 87.64(11)°].22 Both the Ru-Cl [6,
avg. 2.49 Å; 8 avg. 2.48 Å] and the Ru-P [6, 2.26 Å; 8,
avg. 2.30 Å] bonds in 6 are similar to those in 8. A similar
distorted octahedral geometry to that of 2 is found for the
structure of 7; however, the Ru-Cl [2, 2.448(2) Å; 7, 2.5012-
(11), 2.4884(11) Å] and Ru-P(triphos) [2, avg. 2.28 Å; 7
avg. 2.37 Å] bonds are significantly elongated in comparison.
The larger bite angle [69.00(4)°, 69.99(4)°] and increased
steric bulk around the donor atoms of dmpm, in comparison
to that of the acetato ligand [59.7(2)°], could be partially
responsible for the elongation, although electronic differences
between these two ligand also may play a role.
Complexes 1 and 3 both catalyzed the hydrogenation of
1-hexene under 5 bar of H2, achieving higher conversions
than those observed for styrene under the same conditions.
In contrast, 2 is significantly less active, requiring 50 bar of
H2 to achieve significant conversion (TOF of 6800 h-1). Both
1 and 2 showed low activity (TOFs < 300 h-1) for
hydrogenation of cyclohexene under 50 bar of H2, although
3 proved to be an effective catalyst, achieving a TOF of 6200
h-1.
The observed activity of 1 is in line with previous reports,
which indicate that it is an extremely active catalyst precursor
for terminal alkenes but poorly active for internal alkenes.12
Conversion of 1 into the active hydride species, [RuHCl-
(PPh3)3], probably involves THF-mediated intermolecular
heterolytic cleavage under the conditions employed. The
enhanced catalytic activity of 3, in comparison to 1, could
be due to more facile intramolecular heterolytic cleavage,
of dihydrogen assisted by the acetato ligand (in a similar
manner to that described below), although the high activity
for cyclohexene hydrogenation may also imply that the
acetato ligand plays a more intimate role during catalysis.
The mechanism of 2 for alkene hydrogenation is discussed
below.
4. Mechanistic Investigations. To further establish aspects
of the catalytic chemistry of 2, reactions with dihydrogen
were carried out in the absence of alkene substrates. Although
no products were formed from 2 under 50 bar of H2 at 50 °C,
addition of a large excess of NEt3 (20 equiv) resulted in an
equilibrium reaction involving formation of 4, as indicated
1
by H and 31P{1H} NMR spectroscopy (Scheme 4). Under
50 bar of H2 the equilibrium ratio of 2:4 was 12:1, which
was reduced to 10:1 on further pressurization to 80 bar of
H2. Following cooling the sample to room temperature,
depressurization, and degassing, 4 reverted back to 2. The
reverse reaction, formation of 2 from 4, could also be effected
at ambient temperature in the absence of dihydrogen by
reaction of 4 with NEt3‚HCl (3 equiv), affording 2 rapidly
and quantitatively. The proposed mechanism for this process,
depicted in Scheme 5, involves the stepwise κ2-κ1 dissocia-
tion of the acetato ligand and coordination of dihydrogen.
Heterolytic cleavage of dihydrogen, mediated through either
the acetato ligand or NEt3, and substitution of the chloro
ligand by κ1-κ2 coordination of acetato ligand then affords
4. Although the κ3-κ2 dissociation of triphos is also
conceivable, the proposed mechanism has a literature pre-
3. Hydrogenation of Alkenes. The catalytic evaluation
of 1-4 was performed in THF at 50 °C with a substrate to
catalyst ratio of 10 000:1 using 5 or 50 bar H2. As both 1
and 3 are air sensitive, samples were prepared under an inert
atmosphere in a glove box. The results from these investiga-
tions are listed in Table 2. Although 2 was less active than
the triphenylphosphine complexes (TOFs of 6400 and 8000
h-1 for 1 and 3, respectively), a TOF of 3000 h-1 could be
achieved for hydrogenation of styrene under 5 bar of H2.
Under these conditions, the hydride analogue 4 was found
to be inactive and addition of mercury to catalyst solutions
of 2, as a selective poison for heterogeneous catalysts, did
(21) Manson, J. Multinuclear NMR; Plenum Press: New York, 1987; p
369.
(22) Rhodes, L. F.; Sorato, C.; Venanzi, L. M.; Bachechi, F. Inorg. Chem.
1988, 27, 604.
(23) (a) Widegren, J. A.; Finke, R. F. J. Mol. Catal. A: Chem. 2003, 198,
317. (b) Anton, D. R.; Crabtree, R. H. Organometallics 1983, 2, 855.
384 Inorganic Chemistry, Vol. 47, No. 1, 2008

ActiWity of a Robust Ruthenium(II)-Triphos Complex
Figure 4. ORTEP representations of 6 and 7 (one of the two molecular units in the asymmetric cell); thermal ellipsoids drawn at 50% probability. Counteranion
omitted for clarity. Symmetry equivalent atoms in the structure of 6 labeled with an asterisk (*) were obtained by the symmetry operation 1 - x, 1 - y, 1
- z.
Table 2. Hydrogenation of Alkenes with 1-4a
preparation
alkene
styrene
styrene
styrene
styrene
styrene
styrene
styrene
styrene
styrene
styrene
styrene
1-hexene
1-hexene
1-hexene
1-hexene
cyclohexene
cyclohexene
cyclohexene
H2/bar
TOFavg/h-1
1
2
2b
3
4
1
2
3
1
2
3
1
2
2
3
1
2
3
N2
N2
N2
N2
N2
N2
N2
N2
Air
Air
Air
N2
N2
N2
N2
N2
N2
N2
5
5
5
5
5
50
50
50
50
50
50
5
5
50
5
6400
3000
2600
8000
<100
10 000
10 000
10 000
200
Figure 5. Optimized structure of the model species I.
7400
900
9800c
200c
6800c
10 000c
200
50
50
50
<100
6200
a Conditions: 1.0 × 10-6 mol precatalyst, S:C ) 10 000:1, 2 mL of
THF, 100 mg of octane (internal standard), 50 °C, 60 min. Conversion
determined by GC. Values averaged over duplicate runs. b 0.1 mL of Hg
added. c Isomerization <5% total product (as indicated by the presence of
trans-2-hexene).
Figure 6. Relaxed potential-energy surfaces for the elongation of metal-
ligand bonds in the model species I. Labels as defined in Figure 5.
Scheme 4. Reaction of 2 with H2 in the Presence of NEt3
10 bar of D2 at 50 °C, rapid deuteration (t1/2 < 5 min) of the
hydride ligand occurs, affording the deuterated complex 9
(Scheme 6). The structure of 9 is further supported by the
observation of 2JPD couplings in the 31P{1H} NMR spectrum
2
(2JPD(cis) ) 3 Hz, JPD(trans) ≈ 19 Hz). Complex 4 was
cedent involving reaction of [Ru(κ1-O2CCF3)(κ2-O2CCF3)-
(κ3-triphos)] with H2O.24
also found to react with styrene (20 equiv) at room
temperature, establishing an equilibrium reaction with the
alkyl complex [Ru(CH2CH2Ph)(OAc)(κ3-triphos)] (10), pre-
sumably via κ2 coordination of the alkene and hydride
insertion (4:10 ) 4:1, Scheme 6). Complex 10 was identified
by the presence of a doublet at 50.7 ppm and triplet at 1.9
ppm in a 2:1 ratio with a 2JPP coupling constant of 20 Hz by
The lack of catalytic activity observed for the hydride
analogue 4 suggests that the chloro ligand plays an important,
spectator role during catalysis with 2. Complex 4 is also a
valuable model system to gain further insights into the
reactivity of 2. For example, the possibility of dynamic κ2-
κ1 dissociation of the acetato ligand and dihydrogen coor-
dination in these complexes was investigated by reaction of
4 with deuterium by high-pressure NMR spectroscopy. Under
31P{1H} NMR spectroscopy (CD2Cl2, 293 K). H and 13C
1
NMR spectroscopy also corroborate the structure well,
although complete NMR characterization is limited by the
presence of an excess of styrene and 4. The related complex,
[RuH(O2CCF3)(PPh3)3], is known to undergo a similar
(24) Herold, S.; Mezzetti, A.; Venanzi, L. M.; Albinati, A.; Lianza, F.;
Gerfin, T.; Gramlich, V. Inorg. Chim. Acta 1995, 235, 215.
Inorganic Chemistry, Vol. 47, No. 1, 2008 385

Chaplin and Dyson
Scheme 5. Proposed Mechanism of the Equilibrium between 2 and 4 ([Ru] ) [Ru(κ3-triphos)])
Scheme 6. Reaction of 4 with Deuterium (CD2Cl2, 50 °C, 10 bar D2) and Styrene (CD2Cl2, rt, 20 equiv of styrene)
Scheme 7. Proposed Mechanism for the Hydrogenation of Alkenes with 2 (Ru ) [RuCl(κ3-triphos)])
Table 3. Geometry Comparison between the Model Species I and 2
reversible reaction forming [Ru(Et)(O2CCF3)(PPh3)3] upon
pressurization with ethylene.25
bond lengths (Å) and angles (deg)
calcd
expt
On the basis of the established mechanism for [RuHCl-
(PPh3)3]12a,26 and the above experimental observations, the
mechanism depicted in Scheme 7 is proposed for hydrogena-
tion of alkenes with 2. Chloro and triphos ligands are
spectator ligands throughout, while the acetato ligand is
proposed to play an important role in the formation of the
active hydride species V by undergoing κ2-κ1 dissociation
and assisting the heterolytic cleavage of dihydrogen (IIfIII).27
The heterolytic cleavage of dihydrogen with carboxylato
ligands has literature precedent in the proposed mechanism
of catalysis with [Ru(BINAP)(O2CR)2].28 The proposed
catalytic cycle comprises a classical inner-sphere, hydride
route mechanism involving coordination of the alkene (VI),
hydride insertion (VIfVII), coordination of dihydrogen
(VIII), and σ-bond metathesis (VIIIfV).
Ru1-Cl1
2.46
2.27
2.27
2.28
2.19
2.19
2.54
171.4
178.6
86.7
89.7
90.0
60.2
2.448(2)
2.277(3)
2.282(2)
2.275(2)
2.249(5)
2.198(6)
2.580(9)
173.0 (6)
171.05 (7)
86.28(8)
89.11(9)
88.37(8)
59.7(2)
Ru1-P1
Ru1-P2
Ru1-P3
Ru1-O1
Ru1-O2
Ru1-C6
Ru1-C6-C7
Cl1-Ru1-P3
P1-Ru1-P2
P1-Ru1-P3
P2-Ru1-P3
O1-Ru1-O2
diffraction (Figure 2, comparison of structural parameters
in Table 3), verifying the computational procedure (see
Experimental Section). One notable difference between these
two structures is the lack of significant bending of the chloro
ligand out of the axial axis in the calculated structure [P3-
Ru1-Cl1 ) 178.6 (calcd), 171.06(7)° (expt)]. The absence
of this deviation in the model structure, containing a much
less sterically demanding triphosphine, strengthens the sug-
gestion that this bending in 2 is the result of steric
interactions. Calculated relaxed potential-energy surfaces for
elongation of metal-ligand bonds in the model species I
indicates that the κ2-κ1 dissociation of the acetato ligand is
the most facile dissociation pathway, in agreement with the
proposed mechanism for generation of the active catalytic
species (Figure 6).
The proposed mechanism is supported by a computational
analysis using a model system in which the phenyl rings
have been replaced by hydrogen atoms ([Ru] ) [RuCl(κ3-
(PH2CH2)3CMe)] and R ) H in Scheme 7). The optimized
geometry of the model species I (Figure 5) shows good
agreement with the structure of 2 determined by X-ray
(25) Rose, D.; Gilbert, J. D.; Richardson, R. P.; Wilkinson, G. J. Chem.
Soc. A 1969, 2610.
(26) Crabtree, R. H. The Organometallic Chemistry of the Transition Metals,
4th Ed.; John Wiley & Sons: Hoboken, 2005.
(27) The heterolytic activation of dihydrogen with the acetato ligand is
speculative, although it is consistent with the observed reactivity of 2
with acids and the computational analysis.
Calculated Gibbs free energies and geometries of the
species involved in the proposed mechanism are depicted in
(28) Ashby, M. T.; Halpern, J. J. Am. Chem. Soc. 1991, 113, 589.
386 Inorganic Chemistry, Vol. 47, No. 1, 2008

ActiWity of a Robust Ruthenium(II)-Triphos Complex
Figure 7. Calculated Gibbs free energies (above) and geometries (below, with key distances in Å) for species involved in the proposed mechanism of
alkene hydrogenation with 2.
Table 4. Crystallographic Data for 2, 6, and 7
2
6
7
formula
MW
C43H42ClO2P3Ru
820.20
C82H78B2Cl2F8P6Ru 2
1695.92
2C46H53ClF6P6Ru·3CH2Cl 2
2339.23
T [K]
100(2)
100(2)
100(2)
cryst syst
space group
a [Å]
b [Å]
c [Å]
R [deg]
â [deg]
δ [deg]
V [Å3]
monoclinic
P21/c
10.082(6)
15.654(8)
27.322(18)
triclinic
P1
triclinic
P1
12.4280(12)
12.5183(15)
14.0167(18)
114.580(9)
97.356(10)
102.402(9)
1877.9(4)
1
1.500
0.666
3.33 e θ e 25.03
33 227
12.473(3)
20.205(4)
22.009(3)
77.643(11)
80.115(15)
73.574(14)
5160.5(16)
2
1.505
0.752
3.32 e θ e 25.03
10 3188
96.45(5)
4285(4)
4
1.271
0.573
3.30 e θ e 25.03
31 611
7426 [Rint ) 0.0936]
7426/6/453
0.0871, 0.2159
1.061
Z
density [gcm-3
]
µ (mm-1
)
θ range [deg]
measd reflns
unique reflns
6593 [Rint ) 0.0806]
6593/0/495
0.0424, 0.0830
1.088
18 099 [Rint ) 0.0384]
18 099/0/1194
0.0435, 0.0938
1.196
no. of data/restr/param
R1, wR2 [I > 2s(I)]a
GoFb
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) {∑[w(Fo2 - Fc )2]/∑[w(Fo )2]}1/2
.
b GoF ) {∑[w(Fo2 - Fc )2]/(n - p)}1/2, where n is the number of data and p is the
number of parameters refined.
Figure 7. On the basis of these data, the κ2-κ1 dissociation
of the acetato ligand and coordination of dihydrogen (IfII)
is suggested to be the limiting step for generation of the
active hydride species (V), in agreement with the observed
pressure dependence on the hydrogenation of 1-alkenes and
reactions of dihydrogen with 2. The heterolytic cleavage of
dihydrogen with the κ1-acetato ligand (IIfIII) is calculated
to proceed with a low-energy barrier [1.7 kcal mol-1]. In
comparison, the estimated energy barrier for HCl loss is at
least 10 times higher on the basis of attempted, although
unsuccessful, optimizations of the corresponding transition
state. A large energy barrier for complete dissociation of
acetic acid is implied from the relative energies of V and
IV,29 suggesting that acetic acid could compete with coor-
dination of the substrate. Experimentally, this suggestion is
supported by the detection of only 2 following hydrogenation
of styrene (sample prepared under N2) and the reversible
nature of the reactions of 2 with hydrogen. Competition
(29) This aspect is probably overestimated in the gas phase.
Inorganic Chemistry, Vol. 47, No. 1, 2008 387

Chaplin and Dyson
chemicals are commercial products and used as received (including
[RuCl2(PPh3)3], Fluka). NMR spectra were recorded on a Bruker
Avance 400 MHz spectrometer at room temperature unless
otherwise stated. Chemical shifts are given in ppm and coupling
constants (J) in Hz. High-pressure in situ NMR measurements were
performed in sapphire NMR tubes.31 Simulation analysis of the 31P-
{1H} NMR spectrum of 7 was carried out using g-NMR.32 The
NMR labeling schemes for 2 and 4 (Scheme 2), 6 and 7 (Scheme
3), and 10 (Scheme 6) have been previously detailed. 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.
should be more pronounced for larger substrates, owing to
the steric bulk of the triphos ligand, and thus, acetic acid
coordination could be the reason for the low activity observed
for cyclohexene with 2. The rate-determining step for the
catalytic cycle is suggested to be the σ-bond metathesis,
consistent with that suggested for [RuHCl(PPh3)3],12a as this
step has the highest calculated energy barrier in the cycle.
Concluding Remarks
Aspects of the reactivity and catalytic activity of the
ruthenium(II)-triphos acetato complex [RuCl(OAc)(κ3-
triphos)] have been established. Substitution of the acetato
ligand in [RuCl(OAc)(κ3-triphos)] is readily effected by
treatment with acid, affording [Ru2(µ-Cl)3(κ3-triphos)2]Cl and
the 16 VE dimer [RuCl(κ3-triphos)]2(BF4)2 with aqueous HCl
and [Et2OH]BF4, respectively. Substitution of the acetato
ligand can also be effected by heating with a basic diphos-
phine, dmpm, in the presence of [NH4]PF6, resulting in
formation of [RuCl(κ2-dmpm)(κ3-triphos)]PF6. Although no
new products are apparent on pressurization of [RuCl(OAc)-
(κ3-triphos)] with dihydrogen and heating to 50 °C, supple-
mentary experiments with added base and deuteration
experiments of the related hydride complex [RuH(OAc)(κ3-
triphos)] indicate the presence of reversible and rapid
processes involving κ2-κ1 dissociation of the acetato ligand
and coordination of dihydrogen.
Catalytic experiments with [RuCl(OAc)(κ3-triphos)] dem-
onstrated the high activity of this complex for hydrogenation
of 1-alkenes. While less active than the related compounds
[RuCl(OAc)(PPh3)3] and [RuCl2(PPh3)3], the triphos complex
showed much greater tolerance to air. For experiments carried
out at 50 °C with 50 bar of H2 in THF (samples prepared
under N2), TOFs of g10 000 (7400 h-1 for samples prepared
in air) and 6800 h-1 could be obtained for hydrogenation of
styrene and 1-hexene, respectively. The hydride complex,
[RuHCl(κ3-triphos)], formed by acetato-mediated heterolytic
cleavage of dihydrogen is proposed as the active catalytic
species. An inner-sphere, hydride route mechanism is sug-
gested for the catalytic cycle, with chloro and triphos ligands
playing a spectator role. These mechanistic proposals are
consistent with reactivity studies carried out on [RuCl(OAc)-
(κ3-triphos)] and [RuH(OAc)(κ3-triphos)] and supported by
a computational analysis.
Preparation of [RuCl(OAc)(κ3-triphos)] (2). A suspension of
[RuCl(OAc)(PPh3)3] (2.50 g, 2.54 mmol) and (PPh2CH2)3CMe (1.59
g, 2.54 mmol) in toluene (100 mL) was heated under reflux for 30
min. The solution was then cooled to RT, and the product, as a
yellow powder, was isolated by filtration and washed with toluene
(3 × 50 mL) and diethyl ether (3 × 50 mL). Yield: 1.94 g (93%).
Yellow crystals suitable for X-ray diffraction were obtained from
a CH2Cl2 solution layered with cyclohexane at RT. 1H NMR (CD2-
Cl2, 400 MHz, 263 K): δ 6.80-7.84 (m, 30H), 2.18-2.36 (m,
6H, H2 + H3), 1.97 (s, 3H, H6), 1.53 (br, 3H, H4). 13C{1H} NMR
(CD2Cl2, 100 MHz, 263 K): δ 186.5 (br, C5), 127-138 (m), 37.8
2
3
1
(q, JPC ) 3, C1), 37.5 (q, JPC ) 10, C4), 33.0 (br d, JPC ) 32,
C3), 32.1 (br t, JPC ) 20, C2), 25.7 (s, C6). 31P{1H} NMR (CD2-
3
Cl2, 162 MHz, 263 K): δ 40.4 (d, JPP ) 40, 2P, Ru-PPh2C2),
2
37.0 (t, 2JPP ) 40, 1P, Ru-PPh2C3). Anal. Calcd for C43H42ClO2P3-
Ru (820.25 g mol-1): C, 62.97; H, 5.16. Found: C, 62.98; H, 5.26.
Preparation of [RuH(OAc)(κ3-triphos)] (4). A suspension of
[RuH(OAc)(PPh3)3] (0.30 g, 0.38 mmol) and (PPh2CH2)3CMe (0.24
g, 0.38 mmol) in toluene (30 mL) was heated under reflux for 30
min. The solution was then cooled to RT, and the product was
isolated, as yellow powder, by filtration and washed with toluene
(2 × 10 mL) and diethyl ether (2 × 10 mL). Yield: 0.15 g (50%).
1H NMR (CD2Cl2, 400 MHz): δ 6.87-7.82 (m, 30H), 2.23-2.34
(m, 2H, H3), 2.23 (br d, 2JHH ) 16, 2H, H2), 2.14 (br d, 2JHH ) 16,
2H, H2′), 2.03 (s, 3H, H6), 1.53 (s, 3H, H4), -2.78 (dt, 2JPH ) 122,
2JPH ) 20, 1H, Ru-H). 13C{1H} NMR (CD2Cl2, 100 MHz): δ
3
182 (C5), 126-140 (m), 39 (br, C1), 37.9 (q, JPC ) 10, C4), 35.3
1
3
3
1
(dt, JPC ) 22, JPC ) 3, C3), 33.5 (td, JPC ) 18, JPC ) 5, C2),
24.1 (s, C6). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 61.0 (d, 2JPP
)
20, 2P, Ru-PPh2C2), 6.4 (t, JPP ) 20, 1P, Ru-PPh2C3). Anal.
Calcd for C43H43O2P3Ru (785.80 g mol-1): C, 65.73; H, 5.52.
Found: C, 65.45; H, 5.54.
2
Preparation of [Ru2(µ-Cl)3(κ3-triphos)]Cl (5) from [RuCl-
(OAc)(κ3-triphos)] (2). A biphasic mixture of [RuCl(OAc)(κ3-
triphos)] (0.10 g, 0.12 mmol) in CH2Cl2 (20 mL) and aqueous HCl
(100 mM, 20 mL) was stirred vigorously at RT for 1 h. The organic
phase was separated, washed with H2O (3 × 50 mL), and then
dried with Na2SO4. The product was obtained as a microcrystalline
yellow solid by recrystallization from CH2Cl2-hexane. Yield:
0.078 g (81%). NMR data are in agreement with the literature data.34
Preparation of [RuCl(κ3-triphos)]2(BF4)2 (6). To a solution of
[RuCl(OAc)(κ3-triphos)] (0.20 g, 0.24 mmol) in CH2Cl2 (20 mL),
cooled to -78 °C, HBF4‚OEt2 (0.035 mL, 0.26 mmol) was added,
and the solution was stirred for 5 min before slowly warming to
RT and stirring for a further 30 min. The product was then
Experimental Section
All organometallic manipulations were carried out under a
nitrogen atmosphere using standard Schlenk techniques. CH2Cl2,
toluene, diethyl ether, and THF were dried under nitrogen using a
solvent purification system, manufactured by Innovative Technology
Inc. Octane was distilled from CaH2 and stored over molecular
sieves under nitrogen. CD2Cl2 (for NMR experiments under N2)
was distilled from CaH2 and stored under nitrogen. All other
solvents were p.a. quality and saturated with nitrogen prior to use.
Styrene, 1-hexene, and cyclohexene were saturated with nitrogen
and stored over molecular sieves. [RuCl(OAc)(PPh3)3]17 and [RuH-
(OAc)(PPh3)3]30 were prepared as described elsewhere. All other
(31) Cusanelli, A.; Frey, U.; Richens, D. T.; Merbach, A. E. J. Am. Chem.
Soc. 1996, 118, 5265.
(32) Budzelaar, P. H. M. g-NMR, v4.0; IvorySoft, 1997.
(33) Dyson, P. J.; McIndoe, J. S. Inorg. Chim. Acta 2003, 354, 69.
(34) Rhodes, L. F.; Sorato, C.; Venanzi, L. M.; Bachechi, F. Inorg. Chem.
1988, 27, 604.
(30) Mitchell, R. W.; Spencer, A.; Wilkinson, G. J. Chem. Soc., Dalton
Trans. 1973, 846.
388 Inorganic Chemistry, Vol. 47, No. 1, 2008

ActiWity of a Robust Ruthenium(II)-Triphos Complex
precipitated by addition of toluene (20 mL). The microcrystalline
orange solid was then washed with toluene (2 × 10 mL) and diethyl
ether (10 mL) and dried in vacuo. Yield: 0.14 g (68%). Red crystals
suitable for X-ray diffraction were obtained from a CH2Cl2 solution
of the hydride resonance is observed (t1/2 < 5 min). 31P{1H}
NMR (CD2Cl2, 162 MHz, D2): δ 61.1 (dt, JPP ) 20, JPD
) 3, 2P, Ru-PPh2C2), 6.2 (virtual pentet, J ) 19, 1P,
Ru-PPh2C3)
2
2
1
layered with diethyl ether at RT. H NMR (CD2Cl2, 400 MHz,
(c) Reaction with PhCHCH2: A solution of 4 (8 mg) and
PhCHCH2 (0.02 mL, 20 equiv) in CD2Cl2 (0.7 mL) was analyzed
by NMR spectroscopy. Formation of a small amount of new species
was observed and assigned to [Ru(CH2CH2Ph)(OAc)(κ3-triphos)]
(10) by NMR spectroscopy (see below).35 The ratio of 4:10 was
N2): δ 6.90-7.37 (m, 30H), 2.62-2.70 (m, 6H, H2), 1.86-1.92
(m, 3H, H3). 13C{1H} NMR (CD2Cl2, 100 MHz, N2): δ 128-133
(m), 41.4 (br, C1), 36.0-36.4 (m, C3), 33.9-34.5 (m, C2). 31P{1H}
NMR (CD2Cl2, 162 MHz, N2): δ 55.8 (s, 6P). 11B{1H} NMR (CD2-
Cl2, 128 MHz, N2): δ -1.1 (s, BF4). ESI-MS (CH2Cl2, 60 °C, 5.0
kV) positive ion, m/z, 761 [M]2+; negative ion, m/z, 87 [BF4]-.
Anal. Calcd for C82H78B2Cl2F8P6Ru2 (1696.02 g mol-1)·1/2(CH2-
Cl2): C, 56.48; H, 4.55. Found: C, 56.50; H, 4.71
1
constant at 4:1, despite the large excess of PhCHCH2, by both H
1
and 31P{1H} NMR spectroscopy. H NMR (CD2Cl2, 400 MHz,
N2): δ 6.87-7.82 (m, obscured, Ph), 2.66-2.76 (m, 2H, H8), 2.44-
2.54 (m, 2H, H2), 2.3-2.37 (m, obscured, H2′ + H3), 2.15 (s, 3H,
H6), 1.62 (br, 3H, H4), 1.44-1.52 (m, 2H, H7). 13C{1H} NMR (CD2-
Cl2, 100 MHz, N2, selected peaks only): δ 183 (C5), 39 (C4), 38
(C8), 35 (C7, tentative), 35 (C2), 25 (C6). 31P{1H} NMR (CD2Cl2,
162 MHz, N2): δ 50.7 (d, 2JPP ) 20, 2P, Ru-PPh2C2), 1.9 (t, 2JPP
) 20, 1P, Ru-PPh2C3).
Preparation of [RuCl(κ2-dmpm)(κ3-triphos)]PF6 (7). To a
suspension of [RuCl(OAc)(κ3-triphos)] (0.10 g, 0.12 mmol) and
[NH4]PF6 (0.03 g, 0.18 mmol) in CH2ClCH2Cl (10 mL), Me2PCH2-
PMe2 (0.022 mL, 0.14 mmol) was added. The suspension was
heated at 50 °C for 3 h and then filtered. The filtrate was
concentrated to ca. 1 mL, and the product was precipitated by
addition of excess diethyl ether (50 mL). The precipitate was then
washed with diethyl ether (3 × 20 mL) and dried in vacuo. Yield:
0.11 g (90%) as a pale yellow powder. Yellow crystals suitable
for X-ray diffraction were obtained from a CH2Cl2 solution layered
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, substrate, internal standard (100 mg octane), and
solvent and then placed inside the autoclave and sealed. This
procedure was either carried out in air or a glove box (general
procedure). Following flushing with H2 (desired pressure 5 bar, 4
× 5 bar; otherwise, 3 × 10 bar), the autoclave was heated to 50 °C
under H2 (desired pressure 5 bar, 5 bar; desired pressure 50 bar,
10 bar) and then maintained at the desired pressure for the duration
of the catalytic run. The autoclave was then cooled to ambient
temperature (typically e5 min) 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.
Computational Methods. All geometry optimizations and
frequency calculations were carried out using the Gaussian03 suite
of programs.36 Density functional theory using the hybrid B3LYP
functional and pruned grid consisting of 75 radial shells and 302
angular points was used for all geometry optimizations and
frequency calculations. The 6-31G(d,p) basis set used for all atoms
except Ru, for which the LanL2DZ basis set and pseudo potentials
were used. The nature of each of the stationary points was
determined by vibrational analysis. Energies for the small molecules
used in this study and the optimized geometries and energies of
model complexes (together with relaxed potential energy surface
data) are collected in Tables S1-S3.
1
with hexane at RT. H NMR (CD2Cl2, 400 MHz): δ 6.73-7.77
(m, 30H), 4.11-4.30 (m, 1H, H5), 2.70-2.86 (m, 1H, H5′), 2.48
2
(br d, JPH ) 8, 2H, H3), 2.40-2.50 (m, 2H, H2), 2.25-2.40 (m,
2H, H2′), 1.77-1.86 (m, 6H, PMe2), 1.46 (br, 3H, H4), 0.85-0.94
(m, 6H, PMe′2). 13C{1H} NMR (CD2Cl2, 100 MHz): δ 127-140
1
1
3
(m), 45.4 (t, JPC ) 29, C5), 41.1 (dt, JPC ) 27, JPC ) 6, C3),
38.0 (q, JPC ) 10, C4), 36.4-36.5 (m, C1), 31.3-31.8 (m, C2),
3
16.5-17.0 (m, PMe′2), 14.5-14.9 (m, PMe2). 31P{1H} NMR (CD2-
Cl2, 162 MHz): δ 40.9-41.9 (m, 1P, Ru-PPh2C3), 1.6-4.8 (m,
2P, Ru-PPh2C2), -39.2 to -36.1 (m, 2P, Ru-PMe2), -145.2
1
(sept, JPF ) 711, 1P, PF6). ESI-MS (CH2Cl2, 60 °C, 5.0 kV)
positive ion, m/z, 897 [M]+; negative ion, m/z, 145 [PF6]-. Anal.
Calcd for C46H53ClF6P6Ru (1042.28 g mol-1): C, 53.01; H, 5.13.
Found: C, 52.75; H, 5.13.
Reactions of [RuCl(OAc)(κ3-triphos)] (2) with H2. Reactions
of 2 were carried out in sapphire NMR tubes and analyzed by NMR
spectroscopy. All manipulations were carried out under a nitrogen
atmosphere.
(a) Attempted reaction with H2: 0.45 mL of a CD2Cl2 (0.7 mL)
solution of 2 (10 mg) was pressurized under H2 (50 bar) and heated
at 50 °C for 30 min. No reaction was observed.
(b) Reaction with H2 and NEt3: 0.45 mL of a CD2Cl2 (0.7 mL)
solution of 2 (12.5 mg) and NEt3 (0.04 mL, 20 equiv) was
pressurized under H2 (50 bar) and heated at 50 °C for 30 min,
resulting in formation of a small quantity of 4 (2:4 ) 12:1). The
solution was cooled to RT and pressurized with further H2 (to 80
bar) and heated again at 50 °C for 30 min (2:4 ) 10:1). The solution
was cooled to RT and after releasing the pressure degassed by
bubbling with N2, which resulted in the removal of peaks attributed
to 4 in the NMR spectra.
(35) Assignment notes: (a) a 3JHH coupling was detected between H7 and
H8 by COSY; (b) a 3JPC coupling was detected between H8 and a Ph
peak at 128 ppm by C,H long-range correlation spectroscopy.
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Reactions of [RuH(OAc)(κ3-triphos)] (4). All manipulations
were carried out under a nitrogen atmosphere.
(a) Reaction with NEt3‚HCl: To a solution of 4 (3 mg) in CD2-
1
Cl2 (0.5 mL), NEt3‚HCl (∼3 equiv) was added. 31P{1H} and H
NMR spectroscopy indicated that 2 was formed quantitatively. A
trace quantity of H2 was detected by the presence of weak singlet
1
at 4.64 ppm by H NMR spectroscopy.
(b) Reaction with D2: 0.45 mL of a CD2Cl2 (0.7 mL) solution
of 4 (8 mg) was added to a sapphire NMR which was sealed and
pressurized with D2 (10 bar) then heated at 50 °C. Rapid deuteration
Inorganic Chemistry, Vol. 47, No. 1, 2008 389

Chaplin and Dyson
Crystallography. Relevant details about the structure refinements
are given in Table 4. Data collection for the X-ray structure
determinations was performed on a BRUKER APEX II CCD
diffractometer system using graphite-monochromated Mo KR
radiation (0.71073 Å) and a low-temperature device. Data reduction
was performed using EvalCCD.37 Structures were solved using
SIR9738 and refined (full-matrix least-squares on F2) using SHELX-
TL.39 An absorption correction (multiscan, SADABS) was applied
to the data sets of 6 and 7.40 All non-hydrogen atoms were refined
anisotropically with hydrogen atoms placed in calculated positions
using the riding model. Problematic solvent disorder in the solution
of 2 was treated using the SQUEEZE algorithm.41 The [BF4]-
counterion in 6 was split over two sites as was one solvent molecule
in 7. Restrains were made to the displacement parameters of some
of the atoms of these disordered molecules and one atom in a phenyl
ring of 2. Graphical representations of the structures were made
with ORTEP3.42
Acknowledgment. This work was supported by the EPFL
and the Swiss National Science Foundation. We are grateful
to Dr. Rosario Scopelliti and Dr. E. Solari for assistance with
crystallography. 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 2, 6, and 7 (CIF format) and Tables S1-S3. This material
is available free of charge via the Internet at http://pubs.acs.org.
(37) Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.; Schreurs, A. M.
M. J. Appl. Crystallogr. 2003, 36, 220; Bruker AXS, Inc.: Madison,
WI, 1997.
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vazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(39) Sheldrick, G. M. SHELXTL; University of Go¨ttingen: Go¨ttingen,
Germany, 1997; Bruker AXS, Inc.: Madison, WI, 1997.
(40) Bruker AXS, Inc.: Madison, WI, 1997.
IC701773A
(41) (a) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool;
Utrecht University: The Netherlands, 2007. (b) Spek, A. L. J. Appl.
Crystallogr. 2003, 36, 7.
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390 Inorganic Chemistry, Vol. 47, No. 1, 2008