Synthesis and reactivity of hybrid phosphido- and thiolato-bridged diruthenium complexes

Article abstract of DOI:10.1021/om800749e

Reactions of the monophosphido-bridged diruthenium(III) complexes [Cp*RuCl(μu-PR₂)(μ-Cl)RuClCp*] with a variety of (alkylthio)trimethylsilanes afford the hybrid phosphido- and thiolato-bridged diruthenium complexes [Cp*RuCl(μ-PR₂)(μ-SR′) RuClCp*]. Although some newly prepared hybrid diruthenium complexes are found to work as catalysts toward propargylic substitution reactions of propargylic alcohols with nucleophiles, their catalytic activity is lower than that of the methanethiolato-bridged diruthenium complex.

Full text of DOI:10.1021/om800749e

Organometallics 2008, 27, 6039–6042
6039
Synthesis and Reactivity of Hybrid Phosphido- and
Thiolato-Bridged Diruthenium Complexes
Yoshihiro Miyake, Satoshi Endo, Masahiro Yuki, Yoshiaki Tanabe, and
Yoshiaki Nishibayashi*
Institute of Engineering InnoVation, School of Engineering, The UniVersity of Tokyo, Yayoi, Bunkyo-ku,
Tokyo 113-8656, Japan
ReceiVed August 1, 2008
Scheme 1
Summary: Reactions of the monophosphido-bridged diruthe-
nium(III) complexes [Cp*RuCl(µ-PR2)(µ-Cl)RuClCp*] with a
Variety of (alkylthio)trimethylsilanes afford the hybrid phos-
phido- and thiolato-bridged diruthenium complexes [Cp*RuCl(µ-
PR2)(µ-SR′)RuClCp*]. Although some newly prepared hybrid
diruthenium complexes are found to work as catalysts toward
propargylic substitution reactions of propargylic alcohols with
nucleophiles, their catalytic actiVity is lower than that of the
methanethiolato-bridged diruthenium complex.
Multimetallic complexes bridged by heteroatom ligands have
attracted considerable attention as potentially useful catalysts
for a variety of organic transformations, because the nature of
the bridging ligands is expected to play an important role in
the reactivity of multimetallic complexes.1 We have already
found a unique catalytic activity of the alkanethiolato-bridged
diruthenium complexes [Cp*RuCl(µ-SR)]2 (1) toward propar-
gylic substitution reactions of propargylic alcohols with a variety
of nucleophiles.2,3 More recently, we have prepared the mono-
phosphido-bridged diruthenium complexes [Cp*RuCl(µ-PR2)(µ-
Cl)RuClCp*] (2) and found a unique catalytic activity of the
dimethylphosphido-bridged complex 2a toward the redox
isomerization of propargylic alcohols 3 followed by sequential
Friedel-Crafts reaction with heteroaromatic compounds to give
the ꢀ-arylated ketones 5 without any formation of the propar-
gylated substituted product 4. The result was in sharp contrast
to the formation of 4 in the reaction of 3 with heteroaromatic
compounds in the presence of a catalytic amount of 1 (Scheme
1).4
starting from 2, because complexes 2 have a bridging chloride
ligand which may be easily substituted with a variety of
heteroatom ligands. Herein, we report a useful preparative
method for the hybrid phosphido- and thiolato-bridged diru-
thenium complexes5 from reactions of 2 with (alkylthio)- and
(arylthio)trimethylsilanes and their catalytic activity toward
propargylic substitution reactions of propargylic alcohols with
nucleophiles.
Results and Discussion
Heating of 2a with 1-3 equiv of (alkylthio)- and (arylth-
io)trimethylsilanes (R′S-SiMe3) in tetrahydrofuran (THF) at
40 °C for 16 h gave the corresponding hybrid phosphido- and
thiolato-bridged diruthenium complexes [Cp*RuCl(µ-PMe2)(µ-
i
SR’)RuClCp*] (6: R′ ) Pr (6a), Bn (6b), Ph (6c)) in 70%,
68% and 55% yields, respectively (Scheme 2). Only the
formation of syn isomers (syn-6a and syn-6b) was observed in
the reactions with iPrS-SiMe3 and BnS-SiMe3, while only the
anti isomer (anti-6c) was isolated in the reactions with
PhS-SiMe3. When the diethylphosphido-bridged complex 2b
was used as a precursor, the corresponding complex syn-6d was
obtained in 42% yield. Next, the reaction of syn-6a with 1 equiv
of silver trifluoromethanesulfonate (AgOTf; OTf ) SO3CF3)
in THF at room temperature for 16 h proceeded smoothly to
give the corresponding monocationic diruthenium complex
[Cp*Ru(µ-Cl)(µ-PR2)(µ-SiPr)RuCp*]OTf ([7][OTf]) in 55%
yield (Scheme 2).
As an extension of our study on the preparation and reactivity
of diruthenium complexes, we have now envisaged the prepara-
tion of diruthenium complexes bridged by other heteroatoms
(1) (a) Catalysis by Di- and Polynuclear Metal Cluster Complexes;
Adams, R. D., Cotton, F. A., Eds.; Wiley-VCH: New York, 1998. (b) Metal-
Metal Bonds and Clusters in Chemistry and Catalysis; Fackler, J. P., Ed.;
Plenum: New York, 1990.
(2) For recent examples, see: (a) Nishibayashi, Y.; Uemura, S. Curr.
Org. Chem. 2006, 10, 135. (b) Yamauchi, Y.; Onodera, G.; Sakata, K.;
Yuki, M.; Miyake, Y.; Uemura, S.; Nishibayashi, Y. J. Am. Chem. Soc.
2007, 129, 5175. (c) Inada, Y.; Yoshikawa, M.; Milton, M. D.; Nishibayashi,
Y.; Uemura, S. Eur. J. Org. Chem. 2006, 881. (d) Nishibayashi, Y.; Shinoda,
A.; Miyake, Y.; Matsuzawa, H.; Sato, M. Angew. Chem., Int. Ed. 2006,
45, 4835. (e) Nishibayashi, Y.; Milton, M. D.; Inada, Y.; Yoshikawa, M.;
Wakiji, I.; Hidai, M.; Uemura, S. Chem. Eur. J. 2005, 11, 1433. (f) Inada,
Y.; Nishibayashi, Y.; Uemura, S. Angew. Chem., Int. Ed. 2005, 44, 7715.
(g) Ammal, S. C.; Yoshikai, N.; Inada, Y.; Nishibayashi, Y.; Nakamura, E.
J. Am. Chem. Soc. 2005, 127, 9428.
(3) (a) Nishibayashi, Y.; Imajima, H.; Onodera, G.; Hidai, M.; Uemura,
S. Organometallics 2004, 23, 26. (b) Nishibayashi, Y.; Imajima, H.;
Onodera, G.; Inada, Y.; Hidai, M.; Uemura, S. Organometallics 2004, 23,
5100.
(4) Miyake, Y.; Endo, S.; Nomaguchi, Y.; Yuki, M.; Nishibayashi, Y.
Organometallics 2008, 27, 4017.
These phosphido- and thiolato-bridged diruthenium com-
1
plexes 6 and [7][OTf] were characterized by H and 31P{1H}
NMR spectroscopy, and the molecular structures of syn-6a and
anti-6c were confirmed by X-ray analysis. ORTEP drawings
of syn-6a and anti-6c are shown in Figures 1 and 2, respectively.
(5) For examples of phosphido- and thiolato-bridged diruthenium
complexes, see: (a) Tschan, M. J.-L.; Che´rioux, F.; Therrien, B.; Karmazin-
Brelot, L.; Su¨ss-Fink, G. Acta Crystallogr. 2006, E62, m2916. (b) Cabeza,
J. A.; Mulla, F.; Riera, V. J. Organomet. Chem. 1994, 470, 173.
10.1021/om800749e CCC: $40.75
2008 American Chemical Society
Publication on Web 10/24/2008

6040 Organometallics, Vol. 27, No. 22, 2008
Notes
Scheme 2
Table 1. Bond Distances and Redox Properties of 1a and syn-6a
syn-6a 1a
The bond distances between the two ruthenium atoms in both
6a and 6c (2.8839(5) and 2.86682(15) Å) are slightly longer
than that of the methanethiolate-bridged diruthenium complex
[Cp*RuCl(µ-SMe)]2 (1a) (2.8354(7) Å),3a but they are in accord
with the generally known Ru-Ru single bond (2.71-3.02 Å).6
On the other hand, the redox property of syn-6a was found to
be quite different from that of 1.7 The cyclic voltammogram of
syn-6a showed one reversible oxidation wave at E1/2 ) -0.08
V and one irreversible oxidation wave at Epa ) +0.92 V, while
Ru-Ru (Å)
2.8839(5)
2.8354(7)
oxidn potential (V) -0.08 (E1/2), +0.92 (Ep,a) -0.04 (E1/2), +0.89 (E1/2
)
Table 2. Propargylic Substitution Reactions of Propargylic Alcohols
with Nucleophilesa
that of 1a exhibited two reversible oxidation waves at E1/2
)
-0.04 and +0.89 V.4 Bond distances and redox properties of
syn-6a and 1a are summarized in Table 1.
Next, we investigated the catalytic activities of 6 and [7][OTf]
toward propargylic substitution reactions of propargylic alcohols
with nucleophiles for comparison with that of 1a. Typical results
are shown in Table 2. Propargylation of 2-methylfuran with
1-phenyl-2-propyn-1-ol (3) in the presence of a catalytic amount
a All reactions of 3 or 8a (0.60 mmol) with nucleophiles were carried
out in the presence of a catalyst (5 mol %) and NH4BF4 (10 mol %).
b Isolated yield. c ClCH2CH2Cl was used as a solvent. d 2-Methylfuran
(10 equiv) was used as a nucleophile. e Ethanol was used as a solvent.
f For 36 h.
of syn-6a, syn-6b, and [7][OTf] gave the corresponding prop-
argylated product (4a) in lower yields (Table 2, runs 2, 3, and
5). Unfortunately, anti-6c did not work as a catalyst for this
reaction (Table 2, run 4). On the other hand, the reaction of
1,1-bis(4-methylphenyl)-2-propyn-1-ol (8a) with ethanol under
the same reaction conditions proceeded slowly to give the
corresponding propargylic ether (9a) (Table 2, run 6). A longer
reaction time increased the yield of 9a (Table 2, run 7). These
results indicate that the newly prepared hybrid-bridged diru-
thenium complexes have a catalytic activity toward the prop-
argylic substitution reactions, although their catalytic activity
is lower than that of 1a.
Figure 1. ORTEP drawing of syn-6a. Hydrogen atoms are omitted
for clarity. Thermal ellipsoids are drawn at the 50% probability
level. Selected bond lengths (Å): Ru1-Ru2, 2.8839(5); Ru1-P1,
2.2939(10); Ru2-P1, 2.2947(10); Ru1-S1, 2.3180(10); Ru2-S1,
2.3079(9); Ru1-Cl1, 2.4317(9); Ru2-Cl2, 2.4188(9).
To obtain more information on the reaction pathway of the
propargylic substitution reactions catalyzed by 6, we have tried
the isolation of the corresponding allenylidene complex and its
stoichiometric reaction with alcohol. The reaction of syn-6a with
1 equiv of 8a in the presence of 10 equiv of MgSO4 and 1.5
(6) (a) Gao, Y.; Jennings, M. C.; Puddephatt, R. J.; Jenkins, H. A.
Organometallics 2001, 20, 3500. (b) Engel, D. W.; Moodley, K. G.;
Subramony, L.; Haines, R. J. J. Organomet. Chem. 1988, 349, 393, and
references therein.
(7) A Pt stick as a working electrode and a Pt wire as a counter electrode
were used in CH2Cl2 containing 0.1 M nBu4NClO4 at room temperature.
All potentials were measured against an Ag/Ag+ reference electrode and
converted to the values vs Fc/Fc+.
Figure 2. ORTEP drawing of anti-6c · THF. Hydrogen atoms and
THF are omitted for clarity. Thermal ellipsoids are drawn at the
50% probability level. Selected bond lengths (Å): Ru1-Ru2,
2.86682(15): Ru1-P1, 2.2894(4); Ru2-P1, 2.2857(4); Ru1-S1,
2.3410(4); Ru2-S1, 2.3258(4); Ru1-Cl1, 2.4614(5); Ru2-Cl2,
2.4462(5).

Notes
Organometallics, Vol. 27, No. 22, 2008 6041
Scheme 3
revealed that the nature of bridging ligands has a remarkable
effect on their catalytic activity. We believe that the result
described in this paper may provide a new concept to design
polynuclear transition-metal complexes useful for organic
transformations. Further work is currently in progress to prepare
other hybrid heteroatom-bridged diruthenium complexes.
Experimental Section
equiv of NH4BF4 in THF at room temperature for 1 h gave the
corresponding allenylidene complex [10][BF4] in 99% isolated
yield (Scheme 3). The molecular structure of [10][BF4] is
supported by comparison of the spectral data with those of the
allenylidene complex [11][BF4] derived from 1a and 8a.
Treatment of [10][BF4] with EtOH in the presence of 3 equiv
of 1,1-diphenyl-2-propyn-1-ol (8b) at 60 °C for 6 h afforded
9a in only 2% yield together with 9b in 13% yield (Scheme 4).
This result was in sharp contrast to the stoichiometric reaction
of the allenylidene complex [11][BF4], where both 9a and 9b
were obtained in much higher yield.2e,3
Previously, we proposed the reaction pathway for the prop-
argylic substitution reaction catalyzed by 1, as shown in Scheme
5.3 Results in Scheme 4 may indicate that, in the case of syn-
6a, either the step of a nucleophilic attack to A (step a in Scheme
5) does not proceed smoothly or the ligand exchange with
another propargylic alcohol (step c in Scheme 5) does not occur
readily. The difficulty of the charge transfer between two
ruthenium atoms in the hybrid complex syn-6a may correspond
to its lower catalytic activity.8
1
General Considerations. H NMR (270 MHz) and 31P NMR
(109 MHz) spectra were recorded on a JEOL Excalibur 270
spectrometer in a suitable solvent. Elemental analyses were
performed at the Microanalytical Center of The University of
Tokyo. Mass spectra were measured on a JEOL JMS-700 mass
spectrometer. All reactions were carried out under a dry nitrogen
atmosphere. Solvents were dried by the usual methods and
distilled before use. Monophosphido-bridged diruthenium com-
plexes[Cp*RuCl(µ-PR2)(µ-Cl)RuClCp*] (2) were prepared ac-
cording to the literature procedures.4 The propargylic substituted
products 4a, 9a, and 9b and the allenylidene complex [11][BF4]
are known compounds.2e
Preparation of Phosphido- and Thiolato-Bridged Diruthe-
nium(III) Complexes 6. A typical experimental procedure for 6a
is described below. To a solution of diisopropyl disulfide (112.7
mg, 0.75 mmol) in THF (3.0 mL) was added sodium metal (34.5
mg, 1.5 mmol), and the mixture was stirred at room temperature.
After 16 h, a solution of chlorotrimethylsilane (179.3 mg, 1.7 mmol)
in THF (1.0 mL) was added, and the mixture was stirred for an
additional 1 h. To the resulting solution were added [Cp*RuCl(µ2-
Cl)(µ2-PMe2)RuClCp*] (2a; 327.3 mg, 0.51 mmol) and THF (5.0
mL), and the mixture was stirred at 40 °C for 16 h. The solvent
was removed under reduced pressure and the residue was extracted
with CH2Cl2 (50 mL). The extract was filtered through Celite under
a nitrogen atmosphere, and the filtrate was concentrated under
reduced pressure. The residue was recrystallized from CH2Cl2-n-
hexane to give dark red needles of 6a (244.2 mg, 0.36 mmol, 70%).
1H NMR (CD2Cl2): δ 1.32 (d, 6H, J ) 6.8 Hz), 1.62-1.68 (m,
33H), 2.16 (d, 3H, J ) 10.5 Hz), 4.12 (sep, 1H, J ) 6.8 Hz).
Scheme 4
31P{1H} NMR (CD2Cl2):
δ 211.4 (s). Anal. Calcd for
Scheme 5
C25H43Cl2PRu2S: C, 44.18; H, 6.38. Found: C, 43.90; H, 6.32.
Dimethylphosphido- and Phenylmethanethiolato-Bridged
Diruthenium(III) Complex 6b. Yield: 68%. Dark red blocks. 1H
NMR (CD2Cl2): δ 1.55 (d, 30H, J ) 0.81 Hz), 1.72 (d, 3H, J )
11.6 Hz), 2.12 (d, 3H, J ) 10.5 Hz), 3.97 (s, 2H), 7.18-7.57 (m,
5H). 31P{1H} NMR (CD2Cl2): δ 214.0 (s). Anal. Calcd for
C29H43Cl2PRu2S: C, 47.86; H, 5.96. Found: C, 48.08; H, 5.96.
Dimethylphosphido- and Benzenethiolato-Bridged Diruthe-
1
nium(III) Complex 6c. Yield: 55%. Dark red blocks. H NMR
(CD2Cl2): δ 1.59 (d, 30H, J ) 0.81 Hz), 2.36 (d, 3H, J ) 12.2
Hz), 2.62 (d, 3H, J ) 11.1 Hz), 7.20-7.34 (m, 5H). 31P{1H} NMR
(CD2Cl2): δ 264.3 (s). HRMS: m/z calcd for C28H41ClPRu2S [M -
Cl] 679.0452, found 679.0460.
Diethylphosphido- and 2-Propanethiolato-Bridged Diruthe-
1
nium(III) Complex 6d. Yield: 42%. Dark red blocks. H NMR
In summary, a variety of hybrid phosphido- and thiolato-
bridged diruthenium complexes were newly prepared from the
monophosphido-bridged diruthenium complexes, which are
useful precursors for the diruthenium complexes bridged by
different heteroatoms. Although the produced phosphido- and
thiolato-bridged diruthenium complexes were found to work as
catalysts for the propargylic substitution reactions of propargylic
alcohols with nucleophiles, their catalytic activity was lower
than that of the dithiolato-bridged complexes. These results
(CD2Cl2): δ 1.09-1.21 (m, 3H), 1.31-1.38 (m, 9H), 1.62 (d, 30H,
J ) 0.81 Hz), 2.20-2.49 (m, 4H), 4.10 (sep, 1H, J ) 6.95 Hz).
31P{1H} NMR (CD2Cl2):
δ 241.8 (s). Anal. Calcd for
C27H47Cl2PRu2S: C, 45.82; H, 6.69. Found: C, 45.76; H, 6.61.
Preparation of Cationic Dimethylphosphido- and 2-Pro-
panethiolato-Bridged Diruthenium(III) Complex [7][OTf]. To
a solution of 6a (135.7 mg, 0.20 mmol) in THF (3 mL) was
added AgOTf (51.5 mg, 0.20 mmol), and the mixture was stirred
at room temperature for 16 h. The solvent was removed under
reduced pressure, and the residue was extracted with CH2Cl2
(20 mL). The extract was filtered through Celite under a nitrogen
atmosphere, and the filtrate was concentrated under reduced
pressure. The residue was recrystallized from acetone-Et2O to
(8) We have previously reported that the bond distances between two
ruthenium atoms in a variety of chalcogenolato-bridged diruthenium
complexes have an effect on the charge transfer, which seems to be a key
step in promoting propargylic substitution reactions.3

6042 Organometallics, Vol. 27, No. 22, 2008
Notes
Table 3. Summary of Crystallographic Data.
give dark red blocks of [7][OTf] (88.9 mg, 0.11 mmol, 55%).
1
Major isomer: H NMR (CD2Cl2) δ 1.04 (d, 6H, J ) 7.0 Hz),
syn-6a
anti-6c · THF
C32H49OPSCl2Ru2
785.82
1.80 (d, 30H, J ) 1.4 Hz), 2.34 (d, 3H, J ) 12.4 Hz), 2.39 (d,
formula
fw
C25H43PSCl2Ru2
679.69
3H, J ) 10.8 Hz), 2.65 (sep, 1H, J ) 7.0 Hz); 31P{1H} NMR
1
(CD2Cl2) δ 270.3 (s). Minor isomer: H NMR (CD2Cl2) δ 1.54
cryst size/mm
0.50 × 0.25 × 0.20 0.35 × 0.30 × 0.25
(d, 6H, J ) 7.0 Hz), 1.74 (d, 30H, J ) 1.4 Hz), 2.06 (d, 3H, J
) 11.3 Hz), 2.52 (d, 3H, J ) 11.1 Hz), 3.73 (sep, 1H, J ) 7.0
Hz); 31P{1H} NMR (CD2Cl2) δ 270.3 (s). Anal. Calcd for
C26H43ClF3O3PRu2S2: C, 39.36; H, 5.46. Found: C, 39.33; H,
5.33.
color, habit
cryst syst
space group
a/Å
b/Å
c/Å
brown, block
monoclinic
P21/c (No. 14)
17.0596(7)
8.9122(3)
dark brown, block
triclinic
j
P1 (No. 2)
10.5851(4)
12.3136(7)
13.1597(7)
78.4177(17)
81.6515(15)
89.9665(16)
1661.78(14)
2
18.6207(7)
Preparation of [Cp*RuCl(µ-PMe2)(µ-SiPr)Ru(Cp*)(CdCdC-
(p-tol)2)]BF4 ([10][BF4]). The phosphido- and thiolato-bridged
complex syn-6a (102 mg, 0.15 mmol), NH4BF4 (20.2 mg, 0.19
mmol), and MgSO4 (185.5 mg) were placed in a 50 mL flask under
N2. Anhydrous THF (20 mL) was added, and then the mixture was
magnetically stirred at room temperature. After the addition of 1,1-
bis(4-methylphenyl)-2-propyn-1-ol (8a; 73.1 mg, 0.31 mmol), the
reaction flask was kept at room temperature for 1 h. Then, the
solvent was removed under reduced pressure, and the residue was
extracted with CH2Cl2 (20 mL). The extract was filtered through
Celite under a nitrogen atmosphere, and the filtrate was concentrated
under reduced pressure. The residue was recrystallized from toluene/
pentane to give a dark purple solid of [10][BF4] (142.4 mg, 0.15
mmol, 99%). 1H NMR (CD2Cl2): δ 1.25 (d, 3H, J ) 7.0 Hz), 1.32
(d, 3H, J ) 6.8 Hz), 1.71 (s, 15H), 1.72 (d, 3H, J ) 11.1 Hz), 1.85
(s 15H), 2.20 (d, 3H, J ) 10.8 Hz), 2.35 (s, 6H), 4.07 (sep, 1H, J
) 7.8 Hz), 7.21 (d, 4H, J ) 7.8 Hz), 7.57 (d, 4H, J ) 8.1 Hz).
R/deg
ꢀ/deg
93.9558(14)
γ/deg
V/Å3
2824.32(18)
4
Z
dc/g cm-3
1.598
14.011
23 756
1.570
12.047
16 605
µ(Mo KR)/cm-1
no. of data collected
no. of unique data
R1a (I > 2σ(Ι))
wR2b
6352 (Rint ) 0.040) 7556 (Rint ) 0.016)
0.0322
0.0761
1.050
0.0220
0.0494
1.000
0.000
goodness of fit indicatorc
largest shift/esd, final cycle
0.000
residual electron density/e Å-3 +1.96/-1.25
+0.72/-0.66
2
2 2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo - Fc ) /∑w(Fo2)2]1/2
,
2
2
where
w
)
1/[pFo
+
qσ(Fo2)]/(4Fo
)
(p
)
0.0003 (syn-6a),
0
(anti-6c · THF); q ) 1.0000 (syn-6a), 2.7450 (anti-6c · THF)). c [∑w(Fo
2
- Fc ) /(Nobservns - Nparams)]1/2
2 2
.
31P{1H} NMR (CD2Cl2):
δ 225.8 (s). Anal. Calcd for
J ) 7.0 Hz), 2.30 (s, 6H), 2.82 (s, 1H), 3.52 (q, 2H, J ) 7.0
Hz), 7.10 (d, 4H, J ) 8.4 Hz), 7.43 (d, 4H, J ) 8.4 Hz).
X-ray Crystallography. Crystallographic data for syn-6a and
anti-6c are summarized in Table 3. The crystals were immersed
in immersion oil (Sigma-Aldrich, Cat. Code I0890) on a nylon
loop and mounted on a Rigaku RAXIS RAPID imaging plate.
Data were collected at -100 °C under a cold nitrogen stream
using graphite-monochromated Mo KR radiation (λ ) 0.710 69
Å). Empirical absorption corrections were applied. Structures
were solved by direct methods9 and refined on F2 by full-matrix
least squares using the Crystal Structure software package.10
Anisotropic thermal parameters were introduced for all non-
hydrogen atoms. All hydrogen atoms were generated at calcu-
lated positions (dC-H ) 0.97 Å) and treated as riding atoms with
isotropic thermal factors. Crystallographic data are also given
in a CIF file in the Supporting Information.
C42H57BClF4PRu2S: C, 53.14; H, 6.05. Found: C, 52.96; H, 6.30.
Ruthenium-Catalyzed Propargylation of 2-Methylfuran
with Propargylic Alcohol. A typical experimental procedure for
the reaction of 2-methylfuran with 1-phenyl-2-propyn-1-ol (3)
in the presence of 6a is described below. In a 20 mL flask were
placed syn-6a (20.5 mg, 0.03 mmol) and NH4BF4 (6.0 mg, 0.06
mmol) under N2. Anhydrous and degassed 1,2-dichloroethane
(15.0 mL) was added, and then the mixture was magnetically
stirred at room temperature. After the addition of 1-phenyl-2-
propyn-1-ol (3; 78.8 mg, 0.60 mmol) and 2-methylfuran (493
mg, 6.0 mmol), the reaction flask was kept at 60 °C for 1 h.
The resulting mixture was filtered through Florisil and Celite,
and the filtrate was concentrated under reduced pressure. The
residue was purified by column chromatography (SiO2, eluent
n-hexane/ethyl acetate 20/1) to give 4a (30.8 mg, 0.157 mmol,
26% yield) as a yellow oil.2e 1H NMR (CDCl3): δ 2.23 (s, 3H),
2.41 (d, 1H, J ) 2.7 Hz), 4.99 (s, 1H), 5.88 (s, 1H), 6.06 (d,
1H, J ) 3.0 Hz), 7.24-7.43 (m, 5H).
Ruthenium-Catalyzed Reaction of Propargylic Substitu-
tion Reactions of Propargyl Alcohol with EtOH. A typical
experimental procedure for the reaction of 1-bis(4-methylphe-
nyl)-2-propyn-1-ol (8a) with EtOH catalyzed by syn-6a is
described below. In a 20 mL flask were placed syn-6a (20.6
mg, 0.03 mmol) and NH4BF4 (6.4 mg, 0.06 mmol) under N2.
Anhydrous and degassed EtOH (15.0 mL) was added, and then
the mixture was magnetically stirred at room temperature. After
the addition of 1,1-bis(4-methylphenyl)-2-propyn-1-ol (8a; 141.6
mg, 0.60 mmol), the reaction flask was kept at 60 °C for 20 h.
The resulting mixture was filtered through Florisil and Celite,
and the filtrate was concentrated under reduced pressure. The
residue was purified by column chromatography (SiO2, eluent
n-hexane/ethyl acetate 20/1) to give 9a (56.5 mg, 0.214 mmol,
36% yield) as a yellow oil.2e 1H NMR (CDCl3): δ 1.25 (t, 3H,
Acknowledgment. This work was supported by Grants-
in-Aid for Scientific Research on Priority Area (No. 18066003,
”Molecular Theory for Real Systems”) and for Young
Scientists (S) (No. 19675002) from the Ministry of Educa-
tion, Culture, Sports, Science and Technology of Japan.
Supporting Information Available: CIF files giving X-ray
crystallographic data for syn-6a and anti-6c. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM800749E
(9) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(10) Crystal Structure Analysis Package; Rigaku and Rigaku/MSC,
Tokyo, Japan, 2000-2005.