446 Organometallics, Vol. 28, No. 2, 2009
Beach et al.
Synthesis of RuHCl(H2)(IMes)(PCy3) (2b). Solid IMes (46 mg,
0.15 mmol) was added to orange RuHCl(H2)(PCy3)2 2a (100 mg,
0.142 mmol) in 5 mL of benzene. No color change is apparent,
but 31P{1H} NMR monitoring indicated complete reaction at 1.5 h
at 23 °C: only signals for free phosphine and 2b (integration 1:1)
were observed in an aliquot removed at this time. The solvent was
stripped off, and hexanes (2 mL) added. An orange powder was
obtained on cooling to -35 °C overnight. This was filtered off,
washed with cold hexanes (3 × 3 mL), and dried under vacuum.
Yield: 73 mg (71%; limited by partial solubility in hexanes).
replacing the H2 ligand by CO improves hydrogenation
efficiency, particularly at elevated temperatures. Independent
thermolysis experiments suggest that this reflects a positive
influence on catalyst lifetime associated with the low lability
of the CO ligand, as complexes 3a/b are much more stable
than their dihydrogen analogues 2a/b. The π-acidity of the
carbonyl group may also play a part: while this will have
detrimental effects on catalyst initiation via ligand loss, as
well as oxidative addition of H2, it offers the advantage of
decreasing the susceptibility of the complex to nucleophilic
attack. The significantly greater robustness of the CO com-
plexes appears to compensate for their lower activity, by
maintaining higher concentrations of active catalyst over the
time scale of hydrogenation.
1
31P{1H} NMR (C6D6, Ar): 56.3 (s, PCy3). H NMR: 6.82 (s, 4H,
Mes m-CH), 6.16 (s, 2H, NCHdCHN), 2.37 (s, 12H, o-CH3), 2.14
(s, 6H, p-CH3), 1.88-1.10 (m, 33H, PCy3), -16.44 (s, 3H,
RuH(H2)). Hydride T1(min): 36.6 ms (C7D8, 253 K, 300 MHz;
corresponds to a H-H distance of 1.03 Å). 13C{1H} NMR: 196.0
2
(d, JPC ) 100 Hz, NCN), 138.1 (s, Mes p-C), 137.1 (s, Mes Ci),
136.5 (s, Mes o-C), 129.1 (s, Mes m-CH), 121.4 (s, NCdCN), 35.3
Experimental Section
2
2
2
(d, JPC ) 17 Hz, Cy), 30.6 (d, JPC ) 2 Hz, Cy), 28.0 (d, JPC
)
General Procedures. Reactions were carried out at room
temperature (23 °C) under argon, using standard Schlenk or
glovebox techniques, unless otherwise stated. Dry, oxygen-free
solvents were obtained using a Glass Contour solvent purification
system and stored over Linde 4 Å molecular sieves. CDCl3 and
C6D6 were degassed by consecutive freeze/pump/thaw cycles and
dried over activated sieves (Linde 4 Å). [RuCl2(COD)]n,56
RuHCl(PPh3)3,57 RuHCl(CO)(PCy3) 3a,33 RuHCl(CO)(IMes)(P-
Cy3) 3b,33 IMes,58 and substrates S3,59 S4,9 and S59 were
prepared according to literature methods. H2 (UHP grade) was
obtained from BOC Gases and used as received. Styrene and
allylbenzene (Aldrich) were distilled from CaH2 under vacuum
and stored at -35 °C under Ar in the dark. Tetrahydronaphtha-
lene was distilled from Na metal, freeze-pump-thaw degassed,
and stored over Linde 4 Å molecular sieves under Ar. Ethyl-
benzene (Aldrich) and PCy3 (Strem) were used as received. NMR
spectra were recorded on a Bruker Avance 300 or Avance-500
10 Hz, Cy), 26.9 (s, Cy), 21.1 (s, p-CH3), 19.0 (s, o-CH3). IR
(Nujol): ν(Ru-H) 2047 cm-1. Anal. Calcd for C39H60ClN2PRu: C,
64.66; H, 8.35; N, 3.87. Found: C, 64.63; H, 7.98; N, 3.70. NMR
spectra under N2 (24 h) show ca. 70% RuHCl(N2)(IMes)(PCy3)
2
6b: δP 45.0 (s, PCy3); δH -27.63 ppm (d, RuH, JHP ) 21.4 Hz).
Attempted Synthesis of RuHCl(H2)(PCy3)2 2a from RuH-
Cl(PPh3)3 4: Partial Formation of RuHCl(PCy3)(PPh3)2 5. Solid
PCy3 (31 mg, 0.11 mmol) was added to purple 4 (50 mg, 0.054
mmol) in 10 mL of C6H6, and H2 was bubbled through the
suspension. No color change was observed after 3 h, but integration
1
of the H NMR signals against the quartet for 4 at -17.5 ppm
indicates 70% unreacted 4 in the soluble portion. Complete
conversion was hampered by competing decomposition of the
product over a further 20 h reaction. 31P{1H} NMR for 5 (C6D6):
2
2
73.3 (d, JPP ) 118 Hz, 2P, PPh3), 29.1 (t, JPP ) 118 Hz, 1P,
1
2
PCy3). Key H NMR for 5 (C6D6): -18.1 (td, JHP ) 29 and 18
Hz). 1H-31P HMBC correlations between the 31P{1H} NMR doublet
1
spectrometer at 298 K, unless otherwise specified. H and 13C
1
and the aromatic H NMR signals support identification of 5 as a
NMR spectra were referenced to the residual proton and carbon
signals of the deuterated solvent. Peaks are reported in ppm,
relative to TMS (1H, 13C) or 85% H3PO4 (31P) at 0 ppm. IR
spectra were measured on a Bomem MB100 IR spectrometer.
Microanalysis was carried out by Guelph Chemical Laboratories
Ltd., Guelph, Ontario.
bis(PPh3) complex.
Hydrogenation Reactions. (a) Representative procedure for
hydrogenation of molecular substrates. Solid RuHCl(H2)(PCy3)2 2a
(14 mg, 0.0198 mmol) was added to a glass-lined Parr autoclave
containing a solution of styrene (2.083 g, 0.020 mol, 1.0 M) with
tetrahydronaphthalene as internal standard (1.322 g, 0.010 mol) in
20 mL of C6H6 in the glovebox. The autoclave was sealed, removed
from the drybox, purged with H2, and pressurized to 1000 psi H2
at 23 °C. Samples were analyzed by GC-FID. Kinetic runs on S1
were monitored by removing 1 mL samples at set time intervals
using the sampler tube. The first 0.5 mL was discarded; from the
second half, a 5 µL aliquot was removed, diluted to 1.00 mL with
CH2Cl2, and analyzed (GC). Reactions of other substrates were
carried out at a bath temperature of 55 °C. Reactions of S3 were
Synthesis of RuHCl(H2)(PCy3)2 (2a). In a modification of a
literature method,34 a suspension consisting of [RuCl2(COD)]n (400
mg, 1.43 mmol), PCy3 (850 mg, 3.0 mmol), NEt3 (199 µL, 1.43
mmol), and 2-propanol (20 mL) was stirred at 200 psi H2 and 80
°C for 40 h. The resulting orange precipitate was filtered off, washed
with EtOH (3 × 3 mL) and then cold hexanes (5 × 4 mL), and
dissolved in 15 mL of CH2Cl2 under H2. A bright orange solid was
obtained by filtering through Celite to remove a dark, insoluble
impurity, concentrating to 0.2 mL, and adding 5 mL of cold hexanes
under 1 atm of H2. The precipitate was filtered off, washed with
hexanes (3 × 3 mL), and reprecipitated from a minimum volume
of toluene by adding hexanes under H2 and chilling at -35 °C for
1 h, and then dried under vacuum. Yield: 0.511 g (73%). 31P{1H}
1
analyzed by GC-FID; of S2, by H NMR.
(b) Representative procedure for hydrogenation of polymer
substrates. A solution of S4 (183 mg, 0.722 mmol, 1.0 M in CH2Cl2)
with 1,3,5-trimethoxybenzene (51 mg, 0.30 mmol, 0.2 M in CH2Cl2)
as internal standard was subjected to hydrogenation as above (1000
psi H2, 55 °C). Following reaction, volatiles were removed under
reduced pressure and the residues were dissolved in CDCl3 for 1H
NMR analysis. Conversions were determined through comparison
of integrals between olefinic signals (S4: br m, 5.58 ppm) and the
methoxy singlet of trimethoxybenzene (3.77 ppm). For S5, conver-
sions were quantified by comparing the olefinic/galactopyranose
CH signal at 5.60-5.30 ppm with the galactopyranose C5 CH
multiplet at 4.59 ppm.
1
NMR (C6D6, Ar): 54.2 (s). H NMR (C6D6, Ar): 2.3-0.9 (m, 66
H, Cy), -16.3 (br s, 3H, RuH(H2). Under N2, ca. 10% RuHCl(N2)-
(PCy3)2 is observed: δP 43.7 (s);52 δH -27.26 (t, 1 H, RuH, 2JPH
18.3 Hz).
)
(56) Genet, J. P.; Pinel, C.; Ratovelomanana-Vidal, V.; Mallart, S.;
Pfister, X.; Cano De Andrade, M. C.; Laffitte, J. A. Tetrahedron: Asymmetry
1994, 5, 665–674.
(57) Schunn, R. A.; Wonchoba, E. R.; Wilkinson, G. Inorg. Synth. 1971,
13, 131–134.
(58) Arduengo, A. J.; Krafczyk, R.; Schmutzler, R.; Craig, H. A.;
Goerlich, J. R.; Marshall, W. J.; Unverzagt, M. Tetrahedron 1999, 55,
14523–14534.
Thermolysis of 2 and 3. In a representative procedure, a solution
of 2a (8 mg, 0.011 mmol) and OdPPh3 (4 mg, 0.014 mmol) was
dissolved in CH2Cl2 (0.75 mL, with a 50 µL spike of C6D6 as
deuterium lock for shimming) in a J. Young NMR tube. An initial
(59) Fu¨rstner, A.; Langemann, K. Synthesis 1997, 792–803.