Facile oxygenation reactions of ruthenium acetylide complex containing substituted olefinic group

Article abstract of DOI:10.1039/c0dt01551b

Reaction of the ruthenium acetylide complex Cp(dppe)RuC≡CCH(OMe) CPh₂-CH₂CH=CMe₂ (5a) with oxygen readily gives acetone and the acyl complex 6 in almost quantitative yield. Protonation of 5a is followed by an elimination o

Full text of DOI:10.1039/c0dt01551b

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PAPER
Facile oxygenation reactions of ruthenium acetylide complex containing
substituted olefinic group†
Hsuan Yang, Chia-Pei Chung, Ying-Chih Lin* and Yi-Hong Liu
Received 8th November 2010, Accepted 31st January 2011
DOI: 10.1039/c0dt01551b
Reaction of the ruthenium acetylide complex Cp(dppe)RuC CCH(OMe)CPh2–CH2CH CMe2 (5a)
with oxygen readily gives acetone and the acyl complex 6 in almost quantitative yield. Protonation of 5a
is followed by an elimination of MeOH and a hydroxyl addition at Ca in the presence of water to give
the hydroxycarbene complex 7a. The structures of the acyl complex 6 and the hydroxycarbene complex
7c are fully characterized by single crystal X-ray diffraction analysis.
rearrangements because “non-classical” cations may participate
as reaction intermediates.12 Additionally, the cycloisomerization,13
Introduction
metathesis,14 skeletal rearrangements,15 and ene reactions16 of
transition metal-catalyzed carbocyclization of enynes17 reveal
a practical strategy for synthesizing five-membered and six-
membered alkenes and dienes. With all of these developments,
reaction of oxygen with enyne is still rare. Previously, we described
the development of ruthenium-mediated isomerizations of 1,5-
enynes18 involving a formal metathesis process of the terminal
vinyl group with the C C of the vinylidene group via an unusual
mechanism. We continued our study to the skeletal rearrangement
of 1,6-propargylic enynes in the Cp(PPh3)2Ru system19 and to
the analogous dppe system, in which a new facile oxidation was
observed. Compared to PPh3, dppe ligand is apt to expose the
Ca atom of the ruthenium vinylidene or allenylidene complex that
leads to much easier attack at Ca by other nucleophiles. As a result,
the dppe ligand plays a crucial role in reactions involving Ca.
Gimeno and co-workers have reported the steric properties of this
very similar metal fragment.20 These phenomena show that small
steric differences of the ancillary ligands in the metal auxiliary are
able to completely change the reaction pathway. Herein we report
our results on the study of the reaction of a propargyl alcohol with
a substituted olefinic group.
Oxidation of an organic molecule is a fundamental and practical
challenge in chemistry and biology.1 As an ideal oxidant, O2 offers
appealing prospects.2 However, because of its mechanistically
complicated ground state,3 O2 is also a kinetically slow oxidant.
Two-electron oxidations of stable organic substrates are impeded
by the triplet electronic structure of the ground-state. One-electron
oxidations suffer from the disfavored thermodynamics of the ini-
tial step.4 Commonly, O2 reacts with hydrocarbons by a free radical
auotoxidation mechanism. The initial hydroperoxide normally
displays unpredictable reactivity under the reaction conditions,
and frequently nondiscriminating product formation is observed.5
Recently a number of papers reported interesting reactions of
C
C triple bond by the participation of O2. The cleavage of triple
bonds in enynols involving gold-catalyzed cascade reactions of
enynols with O2, in which gold was utilized to catalyze independent
reactions.6 The use of O2 as the sole oxidant7 for the oxidation
of alkynes catalyzed by PdBr2 and CuBr2 provided an access to
1,2-diketones. A report on the Cu-catalyzed oxidative amidation-
diketonization reaction of terminal alkynes using O2 as the oxidant
via dioxygen activation was also reported.8 Palladium-catalyzed
oxidative alkynylation of alkenes using tert-propargylic alcohols
via a C–C bond cleavage under an oxygen atmosphere afforded
the corresponding ene-yne compounds.9
In the past decades, enynes have been extensively used in
organic synthesis through transition metal-catalyzed reactions
because a variety of products can be obtained from fairly
simple substrates under mild conditions.10 Metal-catalyzed cy-
cloisomerizations of enynes have recently been expanded signif-
icantly in the synthesis of natural products.11 Metal-catalyzed
cycloisomerization of enynes often leads to various skeletal
Results and discussion
Facile oxygenation
As shown in Scheme 1, the vinylidene complex 2a, tethering a
dimethyl allyl moiety at C4, was prepared as the major product
from the reaction of 4,4-diphenylsubstituted propargylic alcohol
1a with Cp(dppe)RuCl in high yield. We previously reported
that the reaction10 of Cp(PPh3)2RuCl with 1a, in the presence
of NH4PF6 in methanol at room temperature for 6 h afforded
the analogous cationic g-methoxyvinylidene complex 2a¢ and the
carbene complex 3a¢ in a ratio of 4 : 1, Scheme 1. However, in
the Cp(dppe)RuCl system, complex 2a and the methoxycarbene
Department of Chemistry, National Taiwan University, Taipei, Taiwan,
106, Republic of China. E-mail: yclin@ntu.edu.tw; Fax: 886-2-23636359;
Tel: 886-2-33661657
† CCDC reference numbers 798980 and 798981. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/c0dt01551b
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shows an IR v(C O) stretching band at 1601 cm-1, within the
range for an acyl complex.21
Single crystals of complex 6 were obtained from a mixture of
CH2Cl2–MeOH at room temperature. An ORTEP type view of
complex 6 is shown in Fig. 1, with selected bond distances and
angles. The complex possesses distorted three-legged piano-stool
coordination geometry around the ruthenium center which bound
to Cp, dppe and acyl groups. Obviously a C–C bond formation
occurred between Cb and the unsaturated internal carbon of the
allylic group, forming a five-membered ring, and formation of a
C
O double bond is also observed. The terminal three-carbon-
unit of 5a is no longer on the ligand. The Ru(1)–C(1) bond length
Scheme 1
˚
in 6 of 2.030(2) A shows a typical Ru–C single bond for a metal
acyl group.22 The C(2)–C(6) bond length of 1.329(2) A indicates a
˚
C
C bond and the C(1)–C(2)–C(3) bond angle of 120.4(1)◦ also
complex 4a were obtained in a ratio of 15 : 1 and no cyclization
product was observed. To separate 2a and 4a, the mixture was
treated with excess NEt3 in CH2Cl2 under nitrogen. Only the
vinylidene complex 2a was converted to the corresponding neutral
acetylide complex 5a by deprotonation reaction, and separation
of 4a and 5a was achieved by chromatography. However, complex
4a was not obtained in pure form due to the low yield.
confirms the sp2 geometry for C(2).
Complexes 2a and 5a are characterized by NMR spectroscopy.
In the 1H NMR spectrum of 2a in CDCl3, two multiplet peaks at d
2.16 and 1.82 are assigned to the methylene protons and two singlet
peaks at d 1.37 and 1.19 are assigned to two methyl groups. The
31P NMR spectrum of 2a exhibits two doublet resonances with an
AB pattern at d 80.21 and 79.87 with 2Jpp = 19.6 Hz indicating the
presence of a stereogenic carbon center in the vinylidene ligand.
The 13C NMR spectrum of 2a shows the resonance of Ca at d
337.59 as a triplet peak. In addition, four singlet signals at d
119.01, 109.84, 77.60 and 36.47 are assigned to CH, CbH, Cg
and CH2, respectively.
Fig. 1 ORTEP drawing of the ruthenium complex 6. For clarity,
aryl groups of the 1,2-bis(diphenylphosphino)ethane ligand on Ru
except the ipso carbons are omitted (thermal ellipsoid is set at the
1
The H NMR spectrum of 5a shows three singlet peaks at d
2.63, 1.57 and 1.29 assigned to the protons of the methoxy group
and the two methyl groups, respectively. The 31P NMR spectrum
of 5a exhibits two doublet resonances at d 86.89 and 85.80 with
2Jpp = 21.1 Hz. However, our attempts to obtain the 13C spectrum
of complex 5a in the presence of trace oxygen at room temperature
failed. As shown in Scheme 1, complex 5a was converted to the
neutral acyl complex 6 and acetone. This transformation can
be accelerated by bubbling air through the solution in almost
quantitative yield in 10 mins. The terminal three-carbon-unit of
5a was converted to acetone. For the analogous PPh3 complex 2a¢,
a similar deprotonation yielded 5a¢. Subsequent oxygenation of
5a¢ also proceeded to form 6¢ in the presence of oxygen, but only
in about 29% yield in 4 days and the reaction was accompanied
with formation of phosphine oxide OPPh3 in significant amount.
Complex 6 is characterized by NMR spectroscopy as well as
single crystal X-ray diffraction analysis. In the 13C NMR spectrum
of 6, the resonance assigned to Ca appears at d 260.66 as a triplet
˚
50% probability level). Selected bond distances (A) and angles (deg):
Ru(1)–C(1), 2.030(2); C(1)–O(1), 1.244(2); C(1)–C(2), 1.510(2); C(3)–O(2),
1.434(2); C(7)–O(2), 1.419(2); C(2)–C(6), 1.329(2); C(2)–C(3), 1.514(2);
C(5)–C(6), 1.509(2); Ru(1)–C(1)–O(1), 126.5(1); Ru(1)–C(1)–C(2),
121.1(1); O(1)–C(1)–C(2), 112.4(1); C(1)–C(2)–C(3), 120.4(1);
C(2)–C(3)–C(4), 103.0(1); C(3)–C(4)–C(5), 101.2(1); C(4)–C(5)–C(6),
102.4(1); C(6)–C(2)–C(3), 109.6(1).
To study the effect of methyl groups on the olefinic unit, we
synthesized the analogous complex 5b, having only one methyl
group on the terminal carbon of the tethering allyl group from
a trans and cis mixture of 4,4-diphenyloct-6-en-1-yn-3-ol (1b).
Complex 5b consists of a mixture of trans and cis isomers of
the terminal methyl group. The similar oxygenation reaction of
5b was also completed in 1 h, and the same acyl complex 6 and
acetaldehyde were observed spectroscopically. No reaction was
observed when complex 5a was treated with ethyl vinyl ether
or another activated olefin containing an electron-withdrawing
group, under nitrogen or even under reflux.
2
with JCP = 12.9 Hz. The resonances of CH, the CH with a
neighboring OMe and the methylene groups of the five-membered
1
ring appear at d 132.65, 88.35 and 43.93, respectively. In the H
Hydroxycarbene complex
NMR spectrum, resonances of the methylene group appear at d
3.32 and 2.07 with 2JHH = 16.0 Hz as two broad doublets. The 31
P
Using the same procedure as that used for the preparation of
5a, two other acetylide complexes 5c and 5d containing 4,4-
disubstituted acetylide ligand each tethering a non-substituted
terminal vinyl group were obtained from 1c and 1d, respectively,
NMR spectrum of 6 exhibits two doublet resonances at d 97.45
2
and 90.22 with Jpp = 21.9 Hz again indicating the presence of a
stereogenic carbon center in the five-membered ring. Complex 6
3704 | Dalton Trans., 2011, 40, 3703–3710
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Scheme 2. Facile oxygenation, observed in 5a and 5b, was not
found for 5c and 5d. However, in the presence of water, treatment
of the acetylide complexes 5a, 5c and 5d with HBF4 in ether
at 0 ◦C generated the corresponding light orange ruthenium
hydroxycarbene complexes 7a, 7c and 7d, respectively, all as
solid precipitates in high yield. Complexes 7a, 7c and 7d were
characterized by NMR data and additionally complex 7c was
characterized by a single crystal X-ray diffraction analysis.
Fig. 2 ORTEP drawing of the ruthenium complex 7c. For clarity, aryl
groups of the 1,2-bis(diphenylphosphino)ethane ligand on Ru except the
ipso carbons are omitted (thermal ellipsoid is set at the 50% proba-
˚
bility level). Selected bond distances (A) and angles (deg): Ru(1)–C(1),
1.950(3); C(1)–C(2), 1.472(4); C(2)–C(3), 1.320(5); C(5)–C(6), 1.496(5);
C(6)–C(7), 1.291(6); C(1)–O(1), 1.345(4); Ru(1)–C(1)–O(1), 125.2(2);
Ru(1)–C(1)–C(2), 127.3(2); C(1)–C(2)–C(3), 126.1(3); C(2)–C(3)–C(4),
127.5(3); C(4)–C(5)–C(6), 115.1(3); C(5)–C(6)–C(7), 124.3(4).
Scheme 2
The 31P NMR spectrum of 7c exhibits a singlet peak at d 95.32.
No methoxy resonance is found in the H NMR spectrum of
complex 7c. The H NMR spectrum of 7c displays two doublet
1
1
7c in the NMR spectrum were observed and the resonance of
2c gradually disappeared. This implies that the reaction of 5c
to give 7c could proceed via the vinylidene complex 2c. Indeed,
direct treatment of 2c with HBF4, in the presence of water,
afforded complex 7c. The elimination of MeOH, which gives
the allenylidene intermediate in the presence of acid, is proposed
because of the basicity of the characteristic methoxy group on
the vinylidene complex 2c. A similar MeOH elimination process
has been reported by Werner and co-workers.29 The dehydration
of hydroxyvinylidene derivatives have been promoted by catalytic
quantities of acid.29 After elimination of MeOH, the electrophilic
character of Ca in the allenylidene intermediate favors the
addition of water at Ca to give the hydroxycarbene complex 7c,
Scheme 2.30,31
peaks at d 6.11 and 5.68 with 3JHH = 15.5 Hz assigned to Cg–H and
Cb–H, respectively, indicating a trans configuration of the double
bond. The doublet peak at d 2.74 is assigned to the methylene
protons. The 13C NMR spectrum of 7c shows a triplet resonance
at d 285.44 assigned to Ru Ca.
Recrystallization of 7c from CH2Cl2–hexane at room temper-
ature for 2 days afforded light orange single crystals suitable for
X-ray diffraction analysis. The solid-state molecular structure of7c
has been determined. An ORTEP diagram is shown in Fig. 2. The
˚
short Ru(1)–C(1) metal–carbon distance of 1.952(4) A is a metal
carbon double bond. Similar bond lengths have been reported in
other related ruthenium carbene complexes.23 The bond length
˚
of C(1)–O(1) of 1.343(4) A is considered as a C–O single-bond.
Gladfelter and co-workers have found that the C–O distance
Nevertheless, the protonation of the acetylide complex 5c¢
containing PPh3 ligand with HBF4 in the presence of water
only yielded the vinylidene product 2c¢ like many other acetylide
complexes in the literature.32 When excess HBF4 was added to the
ether solution, the allenylidene complex was observed. However,
no hydroxycarbene complex could be obtained. The steric effect
of the PPh3 ligand could be significant in blocking the Ca atom.
in Ru2(dmpm)2(CO)4[m-C(OH)C2(CO2Me)2] complex, a dimer
containing conjugate system, is 1.39(3) A. The bond lengths
24
˚
2
of Csp –O in organic compounds are commonly in the range of
˚
˚
1.29(3)–1.40(7) A; the shortened single bond is 1.29(3) A in C C–
˚
C( O)–OH and the elongated bond is 1.40(7) A in C–C( O)–O–
2
C
C. However, the bond lengths of Csp O are around 1.18(7)–
25
˚
1.25(4) A indicating a carbonyl compound. Complex 7c is
thus a hydroxycarbene complex. Transition metal hydroxycarbene
complexes are known to be synthesized by direct protonation of
a metal acyl complex.26 Other hydroxycarbene complexes, such as
[(dppp)(CO)3Mn C(OH)-CH3]27 and OsCl2[ C(OH)C3H3(Ph-
Possible mechanism
A rational and simplified mechanism for the formation of 6 is
proposed in Scheme 3. Molecular oxygen readily reacts possibly
via a [2+2+2] cyclization with the 1,6-enyne ligand of complex 5a.
A C–C bond formation between Cb and the unsaturated internal
carbon of the allylic group gives the intermediate A.
28
2)2](CO)(PPh3)2 have been reported.
When the protonation reaction of 5c was carried out with a
dilute solution of HBF4/ether/H2O at 0 ◦C to slow down the
1
reaction rate in an NMR tube, both H resonances of 2c and
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Conclusions
The novel oxygenation reaction of the ruthenium 1,2-
bis(diphenylphosphino)ethane acetylide complexes containing
4,4-disubstituted-1,6-enynes is reported. With the presence of one
or two methyl groups at the terminal carbon of the tethering vinyl
group, the acetylide complexes 5a, 5b and 5a¢ display unexpected
facile reaction with oxygen. The reaction results in a C–C bond
formation between Cb and the central olefinic carbon of the allylic
group followed by the elimination of acetone to give the acyl
complex 6 and 6¢. Protonation of the acetylide complexes 5a, 5c
and 5d is followed by a MeOH elimination. Then addition of a
hydroxyl group, in the presence of H2O, at Ca yields the hydroxy-
carbene complexes 7a, 7c and 7d, respectively. Protonation of
the analogous triphenylphosphine acetylide complex with HBF4
yields the vinylidene product only, most likely owing to the steric
effect of the phosphine ligand blocking Ca for the addition of a
hydroxyl group.
Scheme 3
This process presumably requires photo-activation of oxygen
to a singlet state. A number of ruthenium complexes have
been used as sensitizers in photo reactions involving oxygen.33
Therefore, we carried out the reaction in the dark and found
no effect on the formation of 6. Thus the ruthenium metal
center may serve to assist this [2+2+2] cyclization possibly by
providing a coordination site leading to B as shown in Scheme 4.
Then the intermediate B transforms, via C and A, to the acyl
product 6 and acetone. In the Cp(PPh3)2Ru system, low yield
of 6¢ was accompanied with substantial formation of OPPh3.
This indicates that phosphine dissociation, which was caused
by the steric effect between phosphine ligands and the two
phenyl groups in the enyne chain, may indeed occur in this
oxygenation reaction. The studies of Juge´ demonstrated that
the oxidation of olefin with molecular oxygen, promoted by a
transition metal catalyst and thiophenol, resulted in a C C bond
cleavage giving the corresponding carbonyl derivatives.34 Jones
and co-workers reported that 1,4-diphenyl-2-benzopyran-3-one
endo-peroxides was easily accessible through singlet oxygenation
of a-pyrone.35 In addition, the studies of Schuster demonstrated
that thermal decomposition of 1,4-diphenyl-2-benzopyran-3-one
endo-peroxide led to o-xylylene peroxide, which subsequently
rearranged to give o-dibenzoylbenzene.36 The decarboxylation
preserved the peroxide linkage in the form of the 1,2-dioxin
moiety in the o-xylylene peroxide. The 1,4-cycloaddition between
molecular oxygen and conjugated dienes was proposed in the
photooxygenation of a-pyrone. These reactions had been known
for years, and oxygen in a singlet excited state is considered as the
active species in these reactions.37 This concerted Diels–Alder-like
mechanism i.e. a two-step mechanism involving an intermediate,
which rearranges to give the endo-peroxide, have been proposed,
but the required reaction time is usually long. In our enyne case,
oxygen addition to 5a very likely proceeds via coordination to the
metal giving the endo-peroxide intermediate A via B and C, then
eliminates acetone to yield the acyl product 6.
Experimental
General procedures
The manipulations were performed under an atmosphere of dry
nitrogen using vacuum-line and standard Schlenk techniques.
Solvents were dried by standard methods and distilled under
nitrogen before use. The ruthenium complex Cp(dppe)RuCl38 and
compounds 1a–1d39 were prepared by following the method re-
ported in the literature. The C and H analyses were carried out with
a Perkin-Elmer 2400 microanalyzer. Mass spectra were recorded
using a LCQ Advantage (ESI) and JEOL SX-102A (FAB). X-
ray diffraction studies were carried out at the Regional Center
of Analytical Instrument at the National Taiwan University.
NMR spectra were recorded on Bruker Avance-400 and DMX-
500 FT-NMR spectrometers at room temperature (unless stated
otherwise) and are reported in units of d with residual protons in
the solvents as a standard.
Reaction of 1a and 1b with [Ru]Cl. A typical experimental
procedure for the reaction of [Ru]Cl with enyne is described
below. To a Schlenk flask containing Cp(dppe)RuCl (0.10 g,
0.24 mmol), NH4PF6 (0.10 g, 0.61 mmol) and 1,6-enyne 1a
(0.104 g, 0.36 mmol), 20 mL of MeOH was added at room tem-
perature. The resulting solution was stirred at room temperature
for four days and MeOH was then removed under vacuum. The
product was dissolved in CH2Cl2 and the mixture was filtered
through Celite to remove the insoluble precipitates. The volatiles
of the filtrate were removed under vacuum and the solid residue
was extracted with a small volume of dichloromethane followed by
re-precipitation by addition of 60 mL of diethyl ether. Precipitates
thus formed were collected in a glass frit, washed with diethyl
ether and dried under vacuum to give a mixture of the vinylidene
complex 2a and the methoxycarbene complex 4a (0.11 g, total yield
73%). The ratio of complexes 2a to 4a is about 15 : 1. Complex 2a
in the mixture is used for the next step without further purification.
Spectroscopic data for 2a: 1H NMR (CDCl3): d 7.45–6.53 (m, 30H,
3
Ph); 5.36 (s, 5H, Cp); 4.67 (t, JHH = 7.3 Hz, 1H, CH CMe2);
4.04 (d, 3JHH = 9.0 Hz, 1H, Cg–H); 3.25–2.94 (m, 5H, Cb–H and
dppe); 2.92 (s, 3H, OMe); 2.58, 2.16 (m, 2H, CH2); 1.37, 1.19 (s,
6H, CH3). 13C NMR (CDCl3, 15 ◦C): d 337.59 (t, 2JPC = 16.6 Hz,
Scheme 4
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Ca); 148.41–125.83 (Ph); 119.01 (CH CMe2); 109.84 (Cb); 92.39
(Cp); 77.60 (Cg); 55.98 (OMe); 55.83 (CPh2); 36.47 (CH2); 28.10–
23.3 Hz, Ca), 84.45 (Cp), 78.57 (Cg), 56.87 (CPh2), 56.15 (OMe),
26.01 (CH2), 25.80, 17.76 (two singlet, CH CMe2). MS ESI m/z:
995.3 (M+1)+. Anal. Calcd. For C63H58OP2Ru: C, 76.11; H, 5.88.
Found: C, 75.97; H, 6.01.
27.59 (m, dppe). 31P NMR (CDCl3): d 80.21, 79.87 (two d, 2Jpp
=
19.6 Hz, dppe). Pure complex 2a was not obtained. Spectroscopic
data for 4a: 31P NMR (CDCl3): d 91.47 (s, dppe). The synthesis
of a mixture of 2b and 4b (also in a ratio of 15 : 1 with total
yield of 71%) followed the same procedure. Spectroscopic data
Synthesis of 6. Oxygen gas was gently bubbled through a
solution of the acetylide complex 5a (0.06 g, 0.07 mmol) in CDCl3
at room temperature for 10 min. The acetylide complex 5a was
transformed into the acyl complex 6 in almost quantitative yield.
The solvent was removed in vacuo and the neutral ruthenium acyl
complex 6 (0.059 g, 100% yield) was obtained. Treatment of the
acetylide complex 5b with oxygen gas in CDCl3 also generated
1
for 2b: H NMR (CDCl3): d 7.99–6.65 (m, 30H, Ph); 5.36 (s,
5H, Cp); 5.11 (m, 1H, CH CHMe); 4.84 (m, 1H, CH CHMe);
4.01 (d, 3JHH = 9.0 Hz, 1H, Cg–H); 3.08–2.73 (m, 5H, Cb–H and
dppe); 2.92 (s, 3H, OMe); 2.62, 2.23 (m, 2H, CH2); 1.47 (d, 3JHH
=
=
◦
2
6.1 Hz, 3H, CH3). 13C NMR (CDCl3, 15 C): d 337.49 (t, JPC
1
complex 6. Spectroscopic data for 6: H NMR (CDCl3): d 7.91–
15.8 Hz, Ca); 148.20–125.90 (Ph); 129.45 (CH CHMe); 109.78
(Cb); 92.40 (Cp); 80.32 (Cg); 55.96 (OMe); 55.73 (CPh2); 39.56
(CH2); 28.17–27.64 (m, dppe), 18.09 (CH3). 31P NMR (CDCl3): d
80.23, 79.98 (two d, 2Jpp = 19.8 Hz, dppe). No attempt was made to
purify complex 2b. Spectroscopic data for 4b: 31P NMR (CDCl3):
d 91.38 (s, dppe).
6.66 (m, 30H, Ph); 4.90 (s, 1H, CH); 4.82 (s, 5H, Cp); 4.41 (t,
3
2JHH = 2.4 Hz, 1H, C CH); 3.32, 2.07 (two d, JHH = 16.0 Hz,
2H, CH2); 3.19 (s, 3H, OMe); 3.07–2.88, 2.43–2.26 (m, 4H, dppe).
13C NMR (C6D6): d 260.66 (t, 2JPC = 12.9 Hz, Ca); 160.03–125.16
(Ph); 132.65 (C CH); 88.35 (CH); 85.94 (Cp); 59.65 (CPh2); 58.71
(OMe); 43.93 (CH2); 27.01, 24.23 (two m, CH2 of dppe). 31P NMR
2
Synthesis of 5a and 5b. To a solution of the mixture of 2a
and 4a (0.11 g, ca. 0.12 mmol) obtained directly from 1a in
dichloromethane (20 mL) in a 150 mL round-bottom flask, excess
triethylamine (2 mL) was added at room temperature and the
mixture was stirred overnight. Then, volatiles were removed in
vacuo and ether (5 mL ¥ 3) was added to extract the residue,
which was filtered through Celite and the solvent of the filtrate
was removed under vacuum to give the light yellow acetylide
(CDCl3): d 97.45, 90.22 (two d, Jpp = 21.9 Hz, dppe). MS ESI
m/z: 843.2 (M+1)+. Anal. Calcd for C50H46O2P2Ru: C, 71.33; H,
5.51. Found: C, 71.27; H: 5.46.
Synthesis of 6¢. The solution of complex 5a¢ (70 mg,
0.07 mmol) in CDCl3 was exposed to air at room temperature
for 2 days. The reaction was monitored by 31P NMR spectroscopy.
At the end of the reaction complex 6¢ and OPPh3 in a ratio of 1 : 2.1
were observed. Then the solvent was removed under vacuum and
the residue dissolved in ether. The solution was passed through
a column packed with neutral aluminium oxide using ether as
the eluent. A yellow band was collected to yield the neutral acyl
complex 6¢ (0.02 g, 29% yield). Spectroscopic data for 6¢: 1H NMR
(CDCl3): d 7.42–7.06 (m, 40H, Ph); 5.22 (br, s, 1H, C CH); 5.18
1
complex 5a (0.06 g, 54% yield). Spectroscopic data for 5a: H
3
NMR (CDCl3): d 7.82–6.56 (m, 30H, Ph); 4.76 (t, 1H, JHH
=
6.6 Hz, CHCMe2); 4.20 (s, 1H, HCOMe); 4.70 (s, 5H, Cp); 2.72
(m, 2H, CH2); 2.63 (s, 3H, OMe); 1.56, 1.26 (two s, 6H, CH3). 31
P
2
NMR (CDCl3): d 86.89, 85.80 (two d, Jpp = 21.1 Hz, dppe).
Anal. Calcd. For C53H52OP2Ru: C, 73.34; H, 6.04. Found: C,
73.07; H, 6.01. The synthesis of 5b in 68% yield followed the
same procedure. Spectroscopic data for 5b: 1H NMR (CDCl3): d
7.87–7.09 (m, 30H, Ph); 5.18–5.04 (m, 2H, CH); 4.76 (s, 5H,
Cp); 4.32 (s, 1H, HCOMe); 2.69 (s, 3H, OMe); 2.64 (m, 2H, CH2);
3
(s, 1H, CH); 4.39 (s, 5H, Cp); 3.49, 2.43 (two d, JHH = 16.4 Hz,
2H, CH2); 3.07 (s, 3H, OMe). 31P NMR (CDCl3): d 52.44, 51.33
(two d, 2Jpp = 35.4 Hz, PPh3).
Reactions of 1c–1d with [Ru]Cl. To a Schlenk flask containing
Cp(dppe)RuCl (0.10 g, 0.24 mmol), NH4PF6 (0.10 g, 0.61 mmol)
and 1,6-enyne 1c (0.095 g, 0.36 mmol), 20 mL of MeOH was added
at room temperature. The mixture was stirred under nitrogen at
room temperature for 4 days and MeOH was then removed under
vacuum. The product was dissolved in CH2Cl2 and the mixture
was filtered through Celite. The solvent was then removed under
vacuum, and the solid residue was extracted with a small volume
of dichloromethane followed by re-precipitation by a 60 mL of
stirred diethyl ether. Precipitates thus formed were collected in
a glass frit, washed with diethyl ether and dried under vacuum.
The final product can be obtained as a red powder 2c (0.12 g,
2
1.57 (d, Jpp = 5.9 Hz, 3H, CH3). 31P NMR (CDCl3): d 86.95,
85.55 (two d, 2Jpp = 21.7 Hz, dppe). 13C NMR (CDCl3): d 139.14–
125.31 (Ph), 135.03 (CH CHMe), 125.43 (CH CHMe), 105.69
(Cb), 105.83 (t, 2JPC = 25.0 Hz, Ca), 82.64 (Cp), 78.29 (Cg), 56.01
(CPh2), 54.97 (OMe), 30.12 (CH2), 18.26 (CH3). MS ESI m/z:
855.0 (M+1)+.
Synthesis of 5a¢. To a Schlenk flask containing the mixture
of 2a¢ and 4a¢ (in a ratio of 4 : 1, 0.10 g, 0.09 mmol), excess
NaOMe (0.10 g, 2.27 mmol) in 30 mL MeOH was added at
room temperature. The resulting solution was stirred at room
temperature for 15 mins and the solvent was then removed under
vacuum. The product was dissolved in CH2Cl2 and the mixture
was filtered through Celite to remove the insoluble precipitates.
Then the solvent of the filtrate was removed under vacuum and
the solid residue was extracted with diethyl ether to yield the light
yellow acetylide complex 5a¢ (0.06 g, 89% yield). Spectroscopic
data for 5a¢: 1H NMR (CDCl3): d 7.41–7.06 (m, 40H, Ph); 5.06 (t,
1H, 3JHH = 5.8 Hz, CHCMe2); 4.69 (s, 1H, HCOMe); 4.14 (s, 5H,
Cp); 3.16 and 2.99 (two m, 2H, CH2); 2.96 (s, 3H, OMe); 1.58, 1.26
1
85.6%). Spectroscopic data for 2c: H NMR (CDCl3): d 7.65–
6.68 (m, 30H, Ph); 5.37 (s, 5H, Cp); 5.13 (m, 1H, CH CH2);
3
3
4.78 (d, JHH = 9.8 Hz, 1H, cis CH2); 4.76 (d, JHH = 16.9 Hz,
3
1H, trans CH2); 4.04 (d, JHH = 9.0 Hz, 1H, Cb–H); 3.09, 2.94
(m, 4H, dppe); 3.0◦7 (s, 3H, OMe); 2.68, 2.34 (m, 2H, CH2). 13C
2
NMR (CDCl3, 15 C): d 337.54 (t, JPC = 15.9 Hz, Ca); 145.24–
126.07 (Ph); 134.01 (CH CH2); 117.68 (CH CH2); 109.64 (Cb);
92.45 (Cp); 80.33 (Cg); 55.93 (OMe); 42.39 (CH2); 28.15–27.77 (m,
(two s, 6H, CH3). 31P NMR (CDCl3): d54.83, 54.57 (two d, 2Jpp
=
dppe). 31P NMR (CDCl3): d 80.12, 79.79 (two d, Jpp = 19.6 Hz,
2
◦
37.3 Hz).13C NMR (CDCl3, 5 C): d 160.59–127.04 (Ph), 133.13
dppe); Pure complex 2c was not obtained. The synthesis of 2d
followed the same procedure. Spectroscopic data for 2d: (ratio of
(CH CMe2), 121.05 (CH CMe2), 108.50 (Cb), 104.56 (t, 2JPC
=
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Dalton Trans., 2011, 40, 3703–3710 | 3707
©

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isomers about 1 : 1) 1H NMR (CD3COCD3): d 8.52–6.63 (m, 25H,
Ph); 5.93 and 5.24 (two m, 1H, CH CH2); 5.73 and 5.60 (two s,
0.15 mmol), diluted by ether (2 mL), was added drop wise to the
solution at 0 ◦C. Light yellow precipitate formed immediately, but
addition of HBF4 was continued until no further solid formed.
The precipitate was filtered and washed with ether (5 mL ¥ 2)
and dried under vacuum to give the final product 7a (0.090 g, in
83% yield) as light yellow powder. The syntheses of 7c and 7d
followed the same procedure. Spectroscopic data for 7a: 1H NMR
(CDCl3): d 11.45 (br, 1H, OH); 7.60–6.73 (m, 25H, Ph); 6.27 (d,
5H, Cp); 4.84 (d, 3JHH = 17.4 Hz, 1H, trans CH2); 4.77 (d, 3JHH
=
10.2 Hz, 1H, cis CH2); 3.17 and 2.92 (two s, 3H, OMe); 3.00–2.79
(m, 4H, dppe); 2.32–2.11 (m, 2H, CH2); 0.86 and 0.81 (two s, 3H,
CH3). 13C NMR (CD3COCD3, 15 ◦C): d 338.72 (t, 2JPC = 16.2 Hz),
2
338.19 (t, JPC = 16.0 Hz, Ca); 144.29–126.76 (Ph); 134.29 and
134.21 (CH CH2); 117.81, 117.52 (CH CH2); 109.66, 109.61
(Cb); 93.32 (Cp); 81.08, 80.95 (Cg); 56.56, 56.55 (OMe); 42.39
(CH2); 28.36–27.24 (m, dppe). 31P NMR (CD3COCD3): d 79.83,
3
3JHH = 15.5 Hz, 1H, Cg–H); 5.63 (d, JHH = 15.5 Hz, 1H, Cb–
H); 5.37 (m, 1H, CH CH2); 4.76 (s, 5H, Cp); 1.41, 1.26 (s, 6H,
CH3). 31P NMR (CDCl3): d 95.22 (s, dppe). Spectroscopic data for
7c: 1H NMR (CDCl3): d 11.36 (br, 1H, OH); 7.68–6.80 (m, 30H,
Ph); 6.11, (d, 3JHH = 15.5 Hz, 1H, CgH); 5.68 (d, 3JHH = 15.5 Hz,
1H, CbH); 5.27 (m, 1H, CH CH2); 4.94 (d, 3JHH = 19.5 Hz, 1H,
2
2
79.20 (two d, Jpp = 20.6 Hz, dppe); 79.29, 78.98 (two d, Jpp
20.5 Hz, dppe). Pure complex 2d was not obtained.
=
Syntheses of 5c, 5d and 5a¢. Complex 2c (0.12 g, 0.14 mmol)
was treated with excess K2CO3 (0.19 g, ca. 10 equiv.) in methanol
(20 mL). The mixture was stirred in air at room temperature for
10 min and MeOH was removed under vacuum. The residue was
dissolved in ether, then filtered through Celite and the solvent was
removed under vacuum to give the yellow acetylide complex 5c
(0.11 g, 90% yield). Spectroscopic data for 5c: 1H NMR (C6D6): d
3
trans CH2); 4.93 (d, JHH = 11.2 Hz, 1H, cis CH2); 4.76 (s,
3
5H, Cp); 2.96, 2.60 (two m, 4H, dppe); 2.74 (d, JHH = 7.1 Hz,
2
2H, CH2). 13C NMR (CDCl3): d 285.37 (t, JPC = 11.4 Hz, Ca);
144.61 (Cb); 138.84 (Cg); 134.00 (CH CH2); 133.92–126.47 (Ph);
118.81 (CH CH2); 90.55 (Cp); 52.82 (CPh2); 42.82 (CH2); 28.95
2
(m, JPC = 22.7 Hz, dppe). 31P NMR (CDCl3): d 95.27 (s, dppe).
7.78–6.97 (m, 30H, Ph), 5.36 (m, 1H, CH CH2), 4.77 (d, 3JHH
=
MS ESI m/z: 827.2 (M+). Anal. Calcd. For C50H47OP2Ru: C,
72.62; H, 5.73. Found: C, 72.70; H, 5.78. Spectroscopic data for
7d: 1H NMR (CDCl3): d 11.26 (br, 1H, OH); 7.75–6.82 (m, 25H,
9.9 Hz, 1H, cis CH2), 4.74 (d, 3JHH = 18.6 Hz, 1H, trans CH2),
4.70 (s, 5H, Cp), 4.25 (s, 1H, CH), 2.68 (d, 3JHH = 7.0 Hz, 2H, CH2),
2.63 (s, 3H, OMe), 2.37–2.06 (m, 4H, dppe). 13C NMR (C6D6):
d 147.19–125.39 (Ph), 136.89 (CH CH2), 116.68 (CH CH2),
3
3
Ph); 6.10 (d, JHH = 16.0 Hz, 1H, CgH); 5.59 (d, JHH = 16.0 Hz,
1H, CbH); 5.37 (m, 1H, CH CH2); 4.99 (d, 3JHH = 15.6 Hz, 1H,
trans CH2); 4.96 (d, 3JHH = 9.0 Hz, 1H, cis CH2); 4.85 (s, 5H,
Cp); 3.12, 2.60 (two m, 4H, dppe); 2.44 and 2.30 (two m, 2H,
CH2); 1.22 (s, 3H, CH3). 31P NMR (CDCl3): d 94.81, 94.60 (two
d, 2Jpp = 19.4 Hz, dppe). MS ESI m/z: 765.2 (M+). Anal. Calcd.
For C45H45OP2Ru: C, 70.66; H, 5.93. Found: C, 70.58; H, 5.82.
2
105.49 (Cb), 106.14 (t, JPC = 25.1 Hz, Ca), 82.63 (Cp), 55.67
(OMe), 54.95 (CPh2), 51.54 (Cg), 43.57 (CH2), 28.75–28.37, 27.72–
27.36 (two m, dppe). 31P NMR (C6D6): d 86.87, 85.55 (two d,
2Jpp = 22.0 Hz, dppe). MS ESI m/z: 841.2 (M+1)+. Anal. Calcd.
For C51H48OP2Ru: C, 72.93; H, 5.76. Found: C, 72.96; H, 5.78.
The synthesis of 5d followed the same procedure. Spectroscopic
1
data for 5d: (ratio of isomers about 1 : 1) H NMR (C6D6): d
X-ray structure determination of 6 and 7c. A single crystal of 6
suitable for an X-ray diffraction study was glued to a glass fiber and
mounted on a Nonius Kappa CCD diffractometer. The diffraction
data were collected using 3 kW sealed-tube molybdenum Ka
radiation (T = 295 K). The exposure time was 5 s per frame.
Multiscan absorption correction was applied, and decay was
negligible. Data were processed, and the structures were solved
and refined by the SHELXTL program.40 The structure was solved
7.87–6.78 (m, 25H, Ph), 5.70 (m, 1H, CH CH2), 5.09 (d, 3JHH
=
3
15.0 Hz, 1H, trans CH2), 4.98 (d, JHH = 10.0 Hz, 1H, cis
3
CH2), 4.83, 4.77 (two s, 5H, Cp), 3.99 (d, JHH = 10.6 Hz,
1H, CH), 3.25, 3.03 (two s, 3H, OMe), 2.75–2.55 (m, 2H, CH2),
2.54–2.52, 2.30–2.06 (two m, 4H, dppe), 1.42, 1.40 (two d, 3H,
CH3). 13C NMR (C6D6): d 147.19–125.39 (Ph), 136.87, 136.80
(CH CH2), 116.36, 116.26 (CH CH2), 106.62, 106.52 (Cb),
2
105.02, 104.52 (two t, JPC = 25.8 Hz, Ca), 82.67, 82.56 (Cp),
55.68, 55.61 (OMe), 46.56, 46.55 (Cg), 43.89, 43.88 (CH2), 28.57–
27.75 (m, dppe). 31P NMR (CDCl3): d 87.28, 86.91 (two d, 2Jpp
=
Table 1 Crystal Data and Refinement Parameters for Complexes 6 and
21.2 Hz, dppe), 87.01, 86.78 (two d, 2Jpp = 21.7 Hz, dppe). MS ESI
m/z: 779.2 (M+1)+. Anal. Calcd. For C46H46OP2Ru: C, 71.03; H,
5.96. Found: C, 70.95; H, 5.88. The synthesis of 5a¢ followed the
same procedure. Spectroscopic data for 5a¢:1H NMR (C6D6): d
7c
6
7c
Formula
C50H46O2P2Ru
841.88
C101H94O2P4Ru2B2F8·CH2Cl2
7.81–6.89 (m, 40H, Ph), 5.94 (m, 1H, CH CH2), 5.17 (d, 3JHH
=
=
Formula weight
Crystal system
Space group
998.62
3
Triclinic
Monoclinic
P21/n
17.2 Hz, 1H, trans CH2), 5.06 (s, 1H, CH), 5.02 (d, JHH
¯
10.2 Hz, 1H, cis CH2), 4.36 (s, 5H, Cp), 3.52 (d, 3JHH = 6.9 Hz,
2H, CH2), 3.24 (s, 3H, OMe). 13C NMR (C6D6): d 147.17–125.80
(Ph), 136.79 (CH CH2), 117.20 (CH CH2), 109.37 (Cb), 104.58
(t, 2JPC = 23.75 Hz, Ca), 85.73 (Cp), 78.85 (CPh2), 56.36 (OMe),
56.27 (Cg), 44.41 (CH2). 31P NMR (C6D6): d 51.29, 50.92 (two
P1
˚
a/A
9.7453(2)
9.8887(2)
21.9565(3)
102.050(1)
96.640(1)
101.361(2)
2001.44(6)
2
10.0082(3)
20.6549(5)
21.9508(6)
90
95.564(2)
90
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
2
d, Jpp = 37.40 Hz, PPh3). MS ESI m/z: 967.3 (M+1)+. Anal.
3
˚
V/A
4516.3(2)
2
Calcd. For C61H54OP2Ru: C, 75.84; H, 5.63. Found: C, 75.92;
H, 5.86.
Z
Reflns collected
46602
9189(0.0285)
20880
10056 (0.0358)
0.817
Indep reflns (Rint)
Goodness-of-fit on F2 0.944
Syntheses of 7a, 7c and 7d. A Schlenk flask was charged with
the acetylide complex 5a (0.11 g, 0.13 mmol) in ether (20 mL)
after atmosphere was replaced with nitrogen. HBF4 (54% in ether,
R1, wR2 [I > 2s(I)]
R1, wR2 (all data)
0.0228/0.0567
0.0282/0.0585
0.0427/0.1034
0.0843/0.1132
3708 | Dalton Trans., 2011, 40, 3703–3710
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The Royal Society of Chemistry 2011
©

View Article Online
using direct methods and confirmed by Patterson methods refined
on intensities of data to give R1 and wR2 for unique observed
reflections (I > 2s(I)). Hydrogen atoms were placed geometrically
using the riding model with thermal parameters set to 1.2 times
those for the atoms to which the hydrogens are attached and
1.5 times those for the methyl hydrogen atoms. Solid-state structure
determinations were similarly carried out for 7c. Table 1 gives
parameters of the crystal data and refinement for complexes 6
(CCDC 798981) and 7c. (CCDC 798980). For 7c, a model with a
CH2Cl2 hemisolvate with a half-occupied solvent site (disordered
over a centre of inversion) was used to the exceptionally large
thermal ellipsoids of the CH2Cl2 moiety.
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Acknowledgements
This research is supported by the National Science Council and
National Center of High-Performance Computing of Taiwan, the
Republic of China.
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