Reactions of ruthenium Cp phosphine complex with 4,4-disubstituted-1,6- enynes: Effect of methyl substituents in the olefinic fraction

Article abstract of DOI:10.1021/ja906745j

We studied chemical reactions of Cp(PPh₃)₂RuCl with nine 1,6-enyne compounds (1-4, 8, 12, 19, 21, and 22) in which the triple bond is associated with propargylic alcohol and the olefinic group has various substituted methyl groups. F

Full text of DOI:10.1021/ja906745j

Published on Web 12/02/2009
Reactions of Ruthenium Cp Phosphine Complex with
4,4-Disubstituted-1,6-Enynes: Effect of Methyl Substituents in
the Olefinic Fraction
Chia-Pei Chung, Chien-Chih Chen, Ying-Chih Lin,* Yi-Hong Liu, and Yu Wang
Department of Chemistry, National Taiwan UniVersity, Taipei, Taiwan 106, Republic of China
Received August 10, 2009; E-mail: yclin@ntu.edu.tw
Abstract: We studied chemical reactions of Cp(PPh3)2RuCl with nine 1,6-enyne compounds (1-4, 8, 12,
19, 21, and 22) in which the triple bond is associated with propargylic alcohol and the olefinic group has
various substituted methyl groups. For the enyne compounds 1-3 with no substituted methyl group, the
reaction takes place at the propargylic alcohol first giving the allenylidene complex 6 which could undergo
a skeletal rearrangement to yield the disubstituted vinylidene complex 7. By changing the propargylic alcohol
to propargylic ether, the reaction gives the carbene complex 10 as the major product and the butadiene
complex 9 by a cyclization reaction as the minor product. For enyne 12 with two methyl groups at the
terminal carbon of the olefinic part, formation of either of the carbene complexes 15 and 16 with a substituted
cyclopentenyl ring at CR or the vinylidene complex 17 is controlled by the use of solvent. For the formation
of 15 and 16, a C-C bond-forming cyclization reaction is proposed to occur at Cꢀ in an intermediate where
the triple bond is π-coordinated. However, for the vinylidene intermediate, the reaction may proceed by the
formation of the allenylidene, which undergoes a retro-ene reaction to bring about cleavage of the dimethyl
substituted allyl group giving 17. For two enynes 21 and 22 where each olefinic portion is internally substituted
with one methyl group, two vinylidene complexes 23 and 24 each with a five-membered ring bonded at Cꢀ
are isolated. The reaction proceeds via formation of an allenylidene intermediate followed by a cyclization
at Cγ. Stabilization of the cationic charge by the presence of methyl subsituents clearly controls the reaction
pathway to give different products. These chemical reactions and their mechanisms are corroborated by
structure determinations of five ruthenium complexes using single crystal X-ray diffraction analysis.
Introduction
lyzed cycloisomerization of 1,6-enynes represents an efficient
strategy for a variety of five-membered and six-membered
Reactions of enynes catalyzed by electrophilic late-transition
metal complexes have attracted much attention because a variety
of products can be obtained from fairly simple substrates under
mild conditions.1 Various metal vinylidene and allenylidene
complexes have been proven to be key intermediates for many
alkyne transformations.2 These have contributed to the rational
design of new catalytic reactions. As a result of the compatibility
and the utilization of very diverse precursors, the metal-catalyzed
cycloisomerization of enyne systems has recently expanded on
synthetically versatile developments, including notably applica-
tions in the total synthesis of natural products.3 Metal-catalyzed
cycloisomerization of enynes often leads to various skeletal
rearrangements because “nonclassical” cations may participate
as reaction intermediates.4 For example, transition-metal cata-
alkenes and dienes.5 Recently, the ruthenium-catalyzed carbon-
carbon forming reactions between propargylic alcohol and
alkenes, which were explained reasonably by proposing a
concerted ruthenium-allenylidene-ene reaction process, were
reported. However, only phenyl propargylic alcohol derivatives
could be employed as starting materials.6 We have recently
described the development of ruthenium-mediated isomeriza-
tions of 1,5-enynes to furnish another type of 1,5-enynes and
cycloisomerizations to produce alkoxycyclohexenes in the
presence of alcohol. This process was supported by the
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9
18366 J. AM. CHEM. SOC. 2009, 131, 18366–18375
10.1021/ja906745j  2009 American Chemical Society

Effect of Methyl Substituents in the Olefinic Fraction
A R T I C L E S
Scheme 1
ruthenium-mediated skeletal rearrangement via an unusual
mechanism involving a formal metathesis process of the terminal
vinyl group with the CdC of the vinylidene group.7
As an extension of our previous study, we have now
envisaged to develop the ruthenium-mediated reactions of 1,6-
propargyl enynes affording the corresponding skeletal rear-
rangement and cycloisomerization complexes with an excellent
yield. Here, following our previous observation, the reactions
are expected to occur between CR-Cꢀ or Cꢀ-Cγ and the
terminal allyl group. The present paper describes successful
results of these novel reactions via rearrangement from alle-
nylidene intermediates and π-coordinated species by controlling
the methyl-substituted-olefinic group of substrates and reaction
conditions.
Results and Discussion
Reactions of Enynes with No Methyl Group on the Olefinic
Part. Modification of the original preparative procedure of
ruthenium vinylidene complexes tethering terminal vinyl group
at Cγ7 has allowed the synthesis of a number of cationic
γ-hydroxyvinylidene8-10 ruthenium complexes from [Ru]Cl
([Ru] ) Cp(PPh3)2Ru). For example, treatment of [Ru]Cl with
1,6-enyne 1, a 4,4-diphenylsubstituted propargylic alcohol
tethering a terminal allyl moiety also at C4, in the presence of
NH4PF6 in CH2Cl2 at room temperature in 6 h afforded the
cationic γ-hydroxyvinylidene complex 5a in good yield (Scheme
1). Other γ-hydroxyvinylidene ruthenium complexes 5b-d were
similarly prepared form 2-4, respectively.
complexes 6a-c were obtained with moderate yields and could
be characterized by 31P and 1H NMR spectroscopy. Typical 1H
resonance of Cγ-H of the allenylidene ligand is more downfield
than that of Cꢀ-H of the corresponding vinylidene precursor.
For example, the 1H NMR spectrum of 5a consist of two doublet
resonances at δ 4.45 and δ 5.44 with 3JHH ) 8.15 Hz assigned
to Cꢀ-H and Cγ-H respectively, and two doublet resonances
2
at δ 42.42 and δ 44.35 with JPP ) 26.13 Hz in the 31P NMR
spectrum. The 1H NMR spectrum of 6a displays a singlet
resonance at δ 9.08 assigned to Cγ-H and a singlet signal
appears at δ 45.69 in the 31P NMR spectrum.
When left for 1 day in CHCl3 solution at room temperature,
the vinylidene complexes 5a-c underwent a slow but spontane-
ous dehydration to give the allenylidene complexes 6a-c all
with the distinctive dark green color. These allenylidene
The dehydration reactions of 5 at room temperature are slow.
These reactions are speeded up when heated. However, the
conditions to induce dehydration of 5 stimulate a new interesting
skeletal rearrangement between the allenylidene ligand and the
pending allylic group, see Scheme 1. The rearrangement takes
place when a solution of 6a in chloroform was heated at 60 °C
for 3 h, leading to the disubstituted vinylidene complex 7a as
the only product. Heating complex 5a in CHCl3 at 60 °C for
6 h also generated 6a and subsequently led to the allyl migration
product 7a in good yield (Scheme 1). Complexes 5b and 5c
also show the same reactivity to yield the corresponding products
7b and 7c.
Transformation of 5a to 7a is a result of migration of terminal
allylic group to the allenylidene Cꢀ which could proceed via
either a direct 1,3-allyl shift11 or Cope rearrangement.12 To
ascertain the mechanism, a deuterium labeling experiment was
explored (Scheme 2). Treatment of 1-d2 with [Ru]Cl afforded
complex 5a-d2. Interestingly, the mixture of 7a′-d2 and 7a′′-d2
were obtained with a ratio of 2:1 from 99% deuterated 5a-d2 at
60 °C in CHCl3 (Figure 1). Obviously, a direct 1,3-allyl shift
from Cδ to Cꢀ gave complex 7a′-d2. The Cope rearrangement
which involves the interaction between the terminal carbon of
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J. AM. CHEM. SOC. VOL. 131, NO. 51, 2009 18367

A R T I C L E S
Chung et al.
Scheme 2
Figure 2. ORTEP drawing of the cationic complex 7a. For clarity, aryl
groups of the triphenylphosphine ligands on Ru except the ipso carbons
and PF6- are omitted (thermal ellipsoid is set at the 50% probability level).
Selected bond distances (Å) and angles (deg): Ru(1)-C(1), 1.860(3);
C(1)-C(2), 1.310(4); C(2)-C(3), 1.521(4); C(3)-C(4), 1.497(8); C(4)-C(5),
1.305(11); C(2)-C(6), 1.479(4); C(6)-C(7), 1.344(4); Ru(1)-C(1)-C(2),
173.9(2);C(1)-C(2)-C(3),122.1(3);C(1)-C(2)-C(6),120.0(3);C(2)-C(6)-C(7),
131.2(3); C(6)-C(7)-C(8), 125.5(3); C(6)-C(7)-C(14), 117.5(3); C(3)-
C(4)-C(5), 123.2(12).
the allylic double bond and Cꢀ forming a transition state with
a six-membered ring yields the product 7a′′-d2. At 40 °C, the
reaction gave a mixture of 7a′-d2 and 7a′′-d2 in a ratio of 40:9.
The 1,3-allyl shift plays the major role for this transformation.
However, as the temperature decreases, the product from the
Cope rearrangement decreases.
The bulkier the R1 and R2 group, particularly in 6a and 6b,
the easier the approach of the terminal double bond of the allylic
group to Cꢀ and the reaction would occur more readily. The
conjugation in the vinyl-vinylidene ligand may be the driving
force for the formation of 7a and 7b. Thus, for 1,6-enyne 3,
with one phenyl group replaced by a methyl group, transforma-
tion of 5c with a less bulky vinylidene ligand to 6c required
heating to 60 °C with much longer reaction time (12 h).
Subsequently, the allyl migration product 7c with a cis:trans
ratio ) 1:10 was obtained.
Structures of air stable complexes 7a-c and the ratio of
isomers of 7c have been determined by NMR and NOESY
spectroscopy. The solid state structure of 7a was further
determined by a single crystal X-ray diffraction analysis. Single
crystals of complex 7a were obtained from acetone/diethyl ether
at 5 °C. An ORTEP type view of the cationic complex 7a is
shown in Figure 2, with selected bond distances and angles.
The complex possesses distorted three-legged piano-stool
coordination geometry around the ruthenium center which bound
to the Cp group and two PPh3 ligands and the disubstituted
vinylidene group. The bond length of Ru(1)-C(1) in 7a of
1.860(3) Å and the C(1)-C(2) bond length of 1.310(4) Å show
a typical RudCdC bonding skeletal. The Ru(1)-C(1)-C(2)
bond angle of 173.9(2)o also shows almost linear geometry. The
bond distances of C(2)-C(3), C(3)-C(4) and C(4)-C(5) are
1.521(4), 1.497(8) and 1.305(11), respectively, confirming that
the allylic group is tethering at Cꢀ of the vinylidene ligand.
No rearrangement was observed for complex 5d with two
methyl groups at Cδ even under forced reaction condition at
60 °C for 48 h. Under NMR monitoring, 50% of complex 5d
would undergo dehydration reaction to yield the allenylidene
complex 6d after thermal treatment for 1 h at 60 °C. However,
Cγ of the allenylidene complex 6d was easily reacted with trace
of water molecule possibly because of the steric effect and
slowly went back to 5d at room temperature. Therefore, no
skeletal rearrangement product was observed. Although transi-
tion metal promoted sigmatropic rearrangement3,13 and Claisen-
rearrangement of enynes14 are reported in the literature, the
[1,3]-sigmatropic C- to C-rearrangement are still rare, and the
allenylidene-ene reaction we described here is the first example
of an intramolecular C-C bond formation in a metal complex
via the rearrangement. It is known that most of cationic
vinylidene complexes react with alcohol to give alkoxycarbene
complexes.15 However, the vinylidene complexes 7a-c contain-
ing two PPh3 ligands are inert to various alcohols even under
refluxing condition perhaps due to the electron-rich character
and the bulkier fragment of the disubstituted vinylidene ligand.
Interestingly, when 1,6-enyne 8, with a propargylallylether
group, was reacted with [Ru]Cl in the presence of NH4PF6 in
CH2Cl2, typical reaction to form vinylidene complex did not
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Figure 1. Part of the 1H NMR spectrum of the mixture containing 7a′-d2
and 7a′′-d2 obtained from 99% deuterated 5a-d2 at 60 °C.
9
18368 J. AM. CHEM. SOC. VOL. 131, NO. 51, 2009

Effect of Methyl Substituents in the Olefinic Fraction
A R T I C L E S
Scheme 3
Figure 3. ORTEP drawing of the cationic ruthenium complex 9. For clarity,
aryl groups of the triphenylphosphine ligands on Ru except the ipso carbons
and PF6- are omitted (thermal ellipsoid is set at the 50% probability level).
Selected bond distances (Å) and angles (deg): Ru(1)-C(1), 2.210(4);
Ru(1)-C(2), 2.196(4); Ru(1)-C(6), 2.193(4); Ru(1)-C(7), 2.207(4);
C(1)-C(2), 1.408(5); C(2)-C(6), 1.416(5); C(6)-C(7), 1.395(5); C(1)-
C(2)-C(6), 121.7(3); C(2)-C(6)-C(7), 122.1(3).
occur; instead, the η4-butadiene complex 9 and the carbene
complex 10 (Scheme 3) were obtained in a ratio of 1:5. To
separate two products, the mixture containing 9 and 10 was
treated with excess NaOMe in methanol. Addition of a methoxy
group to Cγ of the carbene ligand of 10 generated the vinyl
complex 11. Then this mixture was passed through a neutral
Al2O3 column eluted with ether/CH2Cl2. Collecting the first and
the second bands separately resulted in the yellow vinyl product
11 and the light-yellow butadiene product 9. The reaction
through path A was inhibited by performing the reaction in the
presence of additional PPh3 and produced 10 as the only product.
Demethoxylation of complex 11 could proceed spontaneously
in the presence of NH4PF6 salt at 60 °C and reversed back to
complex 10. However, when the reaction of 8 with [Ru]Cl was
carried out in methanol, the expected vinylidene complex
tethering an allyloxy group at Cγ was not observed; instead,
the reaction produced the methoxyvinylidene complex 5e as the
only product with no 9 or 10 detected. Formation of 5e proceeds
via an allenylidene intermediate by elimination of allyl alcohol
followed by addition of methanol. Then under thermal condition
in CHCl3, methanol elimination of 5e giving 6a was followed
by the rearrangement mentioned above to yield 7a.
Figure 4. ORTEP drawing of the ruthenium complex 11. For clarity, aryl
groups of the triphenylphosphine ligands on Ru except the ipso carbons
are omitted (thermal ellipsoid is set at the 50% probability level). Selected
bond distances (Å) and angles (deg): Ru(1)-C(1), 2.087(3); C(1)-C(2),
1.316(4); C(2)-C(3), 1.509(4); Ru(1)-C(2)-C(3), 126.9(2); C(1)-C(2)-
C(3), 126.6(3).
The structures of 9, 10, and 11 were determined by NMR
spectroscopy and both complexes 9 and 11 were characterized
by single crystal X-ray diffraction analysis. Complex 9 shows
16
1
several unusual resonances in its H NMR spectrum. Two
doublet resonances at δ 0.16 and 0.05 coupled with the
phosphine ligand with 3JPH ) 17.03 and 18.50 Hz, respectively,
are assigned to two separate terminal methylene protons of the
butadiene ligand. Resonances of other two hydrogen atoms of
the same terminal methylene groups appear as two singlet peaks
at δ 4.10 and 3.94. The two terminal carbons of the butadiene
ligand show two doublet resonances at δ 43.41 and 42.24 both
with 2JCP ) 4.65 Hz in its 13C NMR spectrum. In the 1H NMR
spectrum of 10, a characteristic doublet of triplet resonance at
3
3
δ 15.24 with JHH ) 12.95 Hz and JPH ) 9.10 Hz is assigned
3
to CR-H and a triplet resonance at δ 7.84 with JHH ) 12.95
Hz is assigned to Cꢀ-H. For 11, because of the stereogenic
center at Cγ, the 31P NMR spectrum shows two doublet
2
resonances at δ 49.06 and 47.29 with JPP ) 37.51 Hz.
Resonance of CR-H appears as multiplet resonance at δ 7.82
1
in the H NMR spectrum.
Single crystals of complexes 9 and 11 are obtained from
acetone/methanol/diethylether and acetone, respectively. ORTEP-
type views of the cationic complex 9 and the neutral complex
11 are shown in Figures 3 and 4, respectively, and their selected
bond distances and angles are collected. For 9, the butadiene
ligand bonds to the Ru atom via C(1), C(2), C(6), and C(7)
adopting an exo configuration. A bond formation between C(2)
and C(6) with a distance of 1.416(5) Å had occurred between
the two alkyne and alkene internal carbon atoms of the 1,6-
enyne ligand, forming a coordinated butadiene system with the
four Ru-C distances being approximately equal. For 11, the
addition of a methoxy group at Cγ forming the neutral vinyl
complex is clearly seen. The bond length of Ru-C(1) of 11 is
significantly longer than the Ru-C(1) double bond of the
(15) (a) Adams, R. D.; Davison, A.; Selegue, J. P. J. Am. Chem. Soc. 1979,
101, 7232–7238. (b) Miller, D. C.; Angelici, R. J. Organometallics
1991, 10, 79–89. (c) Cadierno, V.; Gamasa, M. P.; Gimeno, J.;
Gonza´lez-Cueva, M.; Lastra, E.; Borge, J.; Garc´ıa-Granda, S.; Pe´rez-
Carren˜o, E. Organometallics 1996, 15, 2137–2147. (d) Cadierno, V.;
Garc´ıa-Garrido, S. E.; Gimeno, J. AdV. Synth. Catal. 2006, 348, 101–
110. (e) Bustelo, E.; Jime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
Organometallics 2007, 26, 4300–4309. (f) Pino-Chamorro, J. A.;
Bustelo, E.; Puerta, M. C.; Valerga, P. Organometallics 2009, 28,
1546–1557.
(16) (a) Nagashima, H.; Michino, Y.; Ara, K. I.; Fukahori, T.; Itoh, K. J.
Organomet. Chem. 1991, 406, 189–196. (b) Mu¨ller, J.; Qiao, K.;
Siewing, M.; Westphal, B. J. Organomet. Chem. 1993, 458, 219–
224.
9
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A R T I C L E S
Chung et al.
Scheme 4
Scheme 5
out the reactions of 1 and 12 with [Ru]Cl in the presence of
NH4PF6 in EtOH (Scheme 5). As expected, no cycloisomer-
ization to form the η4-butadiene complex was observed. The
reaction of 1 with [Ru]Cl in EtOH indeed forms the same
alkenylcarbene complex 10 as that from the reaction of 8 with
[Ru]Cl. Interestingly, the reaction of [Ru]Cl with 1,6-enyne 12,
having two methyl groups on the terminal carbon of the tethering
allyl group, gave the carbene complex 13, tethering with an
unsaturated linear chain, and the other carbene complex 14 with
a substituted cyclopentenyl ring in a ratio of 3.5:1. Because
complex 13 is insoluble in EtOH, two complexes 13 and 14
are easily separated. Both complexes 13 and 14 are characterized
by NMR data and additionally complex 13 is characterized by
a single crystal X-ray diffraction analysis.
vinylidene complex 7a, and the C(1)-C(2) distance of 1.316(4)
Å reveals a double bond.
A rational mechanism for the formation of 9 and 10 is
proposed in Scheme 4. From the initially formed π-coordinated
species A, there are two pathways to form two different
products. Pathway A proceeds by coordination of the triple bond
followed by dissociation of a PPh3 ligand accompanied with
filling in the vacant site by the allylic group to form B. A C-C
bond formation via an oxidative coupling then gave a ruthena-
cyclopentene intermediate C. Subsequent ꢀ-hydrogen elimina-
tion giving D is followed by successive migration of hydride
to afford 9.17 Alternatively, a cyclization with a C-C bond
formation accompanied with a direct 1,3-hydrogen shift also
forms 9. Pathway B to yield the alkenylcarbene18 complex 10
may involve a pericyclic retro-ene cleavage19 of the vinylidene
species E formed from the initially π-coordinated species
The spectroscopic data of 13, similar to its analog 10, consist
of a characteristic doublet of a triplet resonance at δ 15.27 with
3JHH ) 12.76 Hz and 3JPH ) 9.04 Hz assigned to CR-H and a
3
triplet resonance at δ 7.77 with JHH ) 12.76 Hz assigned to
1
1
Cꢀ-H in the H NMR spectrum. In the H NMR spectrum of
14, the relatively downfield triplet resonance at δ 16.58 with
3JPH ) 9.04 Hz is assigned to CR-H, two singlet resonances at
δ 1.03 and 0.92 are assigned to the two methyl groups. Single
crystals of complex 13 were obtained from acetone/ethanol. An
ORTEP type view of the cationic complex is shown in Figure
5 and selected bond distances and angles are collected. The
C(1)-C(2) distance of 1.442(6) Å reveals a shorter single bond
suggesting a contribution of the zwitterionic resonance form.22
The torsional angle of 172.95° for the skeletal C(1)-C(2)-C(3)-
C(4) suggested the trans configuration of C(2)-C(3) double
bond.
1
generating 10 and acrolein. In the H NMR spectra of the
reaction mixture, three multiplets at δ 9.50, 6.23, and 6.09
attributed to acrolein were observed. It has been shown that
thermolysis of propargylic ethers at 350-450 °C leads to allenes
and carbonyl compounds by a retro-ene transformation.20 In our
case we believe that mediation of a transition metal reduces
the activation energy for the metalloretro-ene reaction21 thus
allows the reaction to occur at lower temperature.
Reactions of Enynes with Methyl Substituents. To prove that
the vinylcarbene complex is generated by a retro-ene reaction
which is independent of the enyne substrate used, we carried
The above-mentioned reactions of [Ru]Cl with propargylic
ether 8, propargylic alcohol 1 and 12 in EtOH via vinylidene
intermediate species provide a simple and direct method for
preparing ruthenium alkenylcarbene complexes involving a
metal-assisted retro-ene reaction. Besides, in the reactions of
1,6-enyne 1-4 and 8, with no methyl group on the olefinic part,
formation of analogous complex of 14 was not observed. This
inspires us to attempt more experiments and investigate the
controlling factor in the substrates used in these reactions.
As shown in Scheme 6, the reaction of 12 with [Ru]Cl in the
presence of NH4PF6 in CH2Cl2 yielded the hydroxylvinylidene
complex 5f and the carbene complex 15 with a cyclopentenyl
ring in a ratio of 10:1. Besides, when the reaction was carried
out in methanol for 1 day, the methoxylvinylidene complex 5g
and 16 in a ratio of 4:1 were obtained. Complex 16 was isolated
as the only product if the reaction time was prolonged for 4
(17) (a) Mitsudo, T. A.; Zhang, S. W.; Nagao, M.; Watanabe, Y. J. Chem.
Soc., Chem. Commun. 1991, 598–599. (b) Trost, B. M.; Indolese, A.
J. Am. Chem. Soc. 1993, 115, 4361–4362. (c) Trost, B. M.; Tanoury,
G. J.; Lautens, M.; Chan, C.; MacPherson, D. T. J. Am. Chem. Soc.
1994, 116, 4255–4267. (d) Krafft, M. E.; Wilson, A. M.; Dasse, O. A.;
Bonaga, L. V. R.; Cheung, Y. Y.; Fu, Z.; Shao, B.; Scott, I. L.
Tetrahedron Lett. 1998, 39, 5911–5914.
(18) Castarlenas, R.; Eckert, M.; Dixneuf, P. H. Angew. Chem., Int. Ed.
2005, 44, 2576–2579.
(19) (a) Oppolzer, W.; Snieckus, V. Angew. Chem., Int. Ed. Engl. 1978,
17, 476–486. (b) Dubac, J.; Laporterie, A. Chem. ReV. 1987, 87, 319–
334.
(20) (a) Viola, A.; Collins, J. J.; Filipp, N. Tetrahedron 1981, 37, 3765–
3811. (b) Va´rnai, P.; Keseru¨, G. M. J. Org. Chem. 1996, 61, 5831–
5836.
(22) Esteruelas, M. A.; Liu, F.; On˜ate, E.; Sola, E.; Zeier, B. Organome-
tallics 1997, 16, 2919–2928.
(21) Oppolzer, W. Angew. Chem., Int. Ed. Engl. 1989, 28, 38–52.
9
18370 J. AM. CHEM. SOC. VOL. 131, NO. 51, 2009

Effect of Methyl Substituents in the Olefinic Fraction
A R T I C L E S
Scheme 7
Figure 5. ORTEP drawing of the cationic complex 13. For clarity, aryl
groups of the triphenylphosphine ligands on Ru except the ipso carbons
and PF6- are omitted (thermal ellipsoid is set at the 50% probability level).
Selected bond distances (Å) and angles (deg): Ru(1)-C(1), 1.922(5);
C(1)-C(2), 1.442(6); C(2)-C(3), 1.315(7); Ru(1)-C(1)-C(2), 124.7(4);
C(1)-C(2)-C(3), 123.5(5).
methanol,1c,d,5a,24 respectively. To clarify that the formation of
15 and 16 was not via the allenylidene intermediate, the reaction
of d-labeled enyne 12, monodeuterted at the terminal alkyne,
was explored. The product 15-d, with the deuterium appeared
exclusively at CR, as indicated by the absence of the 1H
resonance at δ 15.56, suggests that the CR-H of 15 is not
originated from the terminal methyl group via the allenylidene
intermediate. This labeling result confirms that the formation
of 15 and 16 is via the π-coordinated species F. And the fact
that no cyclization was observed for 1-4 and 8 strongly suggests
the participation of the tertiary carbocationic intermediate G in
the reaction of 12 with two terminal methyl groups. The
formation of the carbene complex 14 described above also
conformed with the mechanism in Scheme 7.
Furthermore, dehydration of 5f and methanol elimination of
5g in CHCl3 at 60 °C both generated 6e and subsequently
liberated the allyl group leading to the vinylidene complex 17
in good yield. Comparing with the 1,3-allyl shift and the Cope
rearrangement of 5a-c and 5e via allenylidene-ene reaction,
further transformation of 5f and 5g each with two methyl groups
should proceed by a different pathway. On the basis of literature
reports on cyclization reactions of similar enynes,5c,6b,d the
mechanism for the transformation is also proposed as shown in
Scheme 7. The vinylidene complexes 5f and 5g first form the
allenylidene complex 6e. Then a retro-ene reaction involving
the terminal double bond of the allenylidene ligand and the
terminal methyl group of the allyl unit results in the conjugated
vinylidene complex 17 with elimination of 2-methylbutadiene.
Possible reason for 6e to take a different pathway from that of
6a might be the steric effect. In 6e, with two methyl groups,
the olefin is away from Cꢀ thus fails to undergo a Cope
rearrangement. An additional point is that the retro-ene reaction
cannot take place for 6a, with no methyl substituent at the olefin
portion.
Scheme 6
days in methanol. A series of 2D NMR studies and mass
spectroscopy establish the structures of 15 and 16. In the H
1
NMR spectra, the relatively downfield triplet resonances at δ
15.57 for 15 and δ 16.57 for 16 are assigned to CR-H. The
two singlet resonances at δ 4.71 and 4.43 for 15 are assigned
to two protons of the terminal olefin and two singlet resonances
at δ 1.09 and 0.86 for 16 to two methyl groups.
The lack of carbene products in the reactions of 1-4 and 8
leads us to believe that this cycloisomerization of 12 to form
carbene complexes 15 and 16 proceeds through an unusual
pathway.5d-f As shown in Scheme 7, the vinylidene complexes
5f and 5g could come from F with the triple bond π-coordinated
to the metal center. In the other competitive electrophilic
pathway, the activation of the triple bond of enynes by a metal
center generates species with high electrophilicity and triggers
the nucleophilic attack of a double bond to the activated triple
bond by an exo-dig pathway.3e,f,4b,d,23 The formation of 15 and
16 may then involve a 5-exo-dig cyclization of F to give the
tertiary carbocation G stabilized by the presence of two methyl
groups, ultimately leading to 15 in CH2Cl2 and 16 in
(23) (a) Echavarren, A. M.; Nevado, C. Chem. Soc. ReV. 2004, 33, 431–
436. (b) An˜orbe, L.; Dom´ınguez, G.; Pe´rez-Castelles, J. Chem.sEur.
J. 2004, 10, 4938–4943. (c) Fairlamb, I. J. S. Angew. Chem., Int. Ed.
2004, 43, 1048–1052. (d) Toullec, P. Y.; Genin, E.; Leseurre, L.;
Geneˆt, J.-P.; Michelet, V. Angew. Chem., Int. Ed. 2006, 45, 7427–
7430. (e) Lee, S. I.; Chatani, N. Chem. Commun. 2009, 371–384.
(24) (a) Galland, J.-C.; Savignac, M.; Geneˆt, J.-P. Tetrahedron Lett. 1997,
38, 8695–8697. (b) Me´ndez, M.; Mun˜oz, M. P.; Echavarren, A. M.
J. Am. Chem. Soc. 2000, 122, 11549–11550. (c) Nevado, C.;
Charruault, L.; Michelet, V.; Nieto-Oberhuber, C.; Mun˜oz, M. P.;
Me´ndez, M.; Rager, M.-N.; Geneˆt, J.-P.; Echavarren, A. M. Eur. J.
Org. Chem. 2003, 706–713.
9
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A R T I C L E S
Chung et al.
Scheme 8
Scheme 9
Figure 6. ORTEP drawing of the ruthenium acetylide complex 25i. For
clarity, aryl groups of the triphenylphosphine ligands on Ru except the ipso
carbons are omitted (thermal ellipsoid is set at the 50% probability level).
Selected bond distances (Å) and angles (deg): Ru(1)-C(1), 2.025(2);
C(1)-C(2), 1.207(3); C(2)-C(3), 1.521(4); C(3)-C(7), 1.490(5); C(5)-C(6),
1.338(4);C(6)-C(8),1.451(4);Ru(1)-C(1)-C(2),175.0(2);C(1)-C(2)-C(3),
169.1(3); C(7)-C(3)-C(4), 104.1(3); C(5)-C(6)-C(7), 109.8(2); C(3)-
C(7)-C(6), 106.1(2); C(8)-C(6)-C(7), 123.6(3).
tonation of 25i at 0 °C yielded the vinylidene complex 23i. No
attempt was made to purify complex 24i from the mixture.
Complex 5j also shows the same reactivity to yield the
corresponding products 23j-26j.
The structures of complexes 23-26 are determined by 2D-
NMR, and complex 25i is fully characterized by a single crystal
X-ray diffraction analysis. The 31P NMR data exhibit two
doublet resonances at δ 51.85 and 51.40 with 2JPP ) 37.58 Hz
for 25i and at δ 51.66 and 51.30 with 2JPP ) 37.98 Hz for 26i.
Single crystals of complex 25i were obtained from CH2Cl2/
diethyl ether at 5 °C. An ORTEP type view of complex 25i is
shown in Figure 6, and selected bond distances and angles are
listed. The complex exhibits the usual acetylide structure in a
three-legged piano-stool geometry. Obviously a C-C bond
formation had occurred between Cγ and the terminal carbon of
the allylic group, forming a five-membered ring. The alkynyl
ligand is nearly linear (Ru(1)-C(1)-C(2) angle of 175.0(2)°).
The bond lengths of Ru(1)-C(1) of 2.025(2) Å, C(1)-C(2) of
1.207(3) Å and C(2)-C(3) of 1.521(4) Å show a typical
acetylide bond skeletal. The bond length of C(3)-C(7) of
1.490(5) Å attests the C-C bond formation and the separations
C(5)-C(6) of 1.338(4) Å and C(6)-C(8) of 1.451(4) Å
correspond, respectively, to a double and a single bond.
A pathway for the cyclization reaction is proposed as shown
in Scheme 9.6a,c The allenylidene complex acts as an enophile
to afford the vinylidene complexes 23 and 24 via the
allenylidene-ene reaction. The dehydration of 5 occurs spon-
taneously to form the allenylidene complex H. A C-C bond
formation between the alkene moiety of the methyl allyl group
and Cγ of the allenylidene ligand results in the alkynyl complex
I bearing a cationic charge at the methyl-substituted tertiary
carbon of the five-membered ring. Subsequent 1,5-proton shift
gives the final products 23i and 24i. The driving force for this
process seems to be the stability of the tertiary carbocationic
species I, since for the other types of ruthenium vinylidene
complexes 5a-e with no methyl group on the allylic group no
cyclization reaction was observed. The fact that the enynes 21
and 22 did not form the cyclic carbene via cyclization through
Deprotonation of 17 gave the ruthenium acetylide complex
18 as a light yellow powder. Further allylation at Cγ with allyl
iodide yielded the vinylidene complex 7a which is the same
product as that obtained from the skeletal rearrangement of 6a
(Scheme 8). We also treated the fluorene enyne 19 with [Ru]Cl
in the presence of NH4PF6 salt resulting in formation of the
vinylidene complex 5h, analogous to 17 obtained from 6e. By
the same principle, deprotonation of complex 5h yielded the
acetylide complex 20 and then alkylation at Cγ with allyl iodide
yielded the vinylidene complex 7b which is the same product
from the rearrangement of 6b under thermolytic condition.
Furthermore, the reactions of [Ru]Cl with enynes 21 and 22,
with one methyl group added to the internal carbon of the allyl
group, afforded the hydroxyvinylidene complexes 5i and 5j,
respectively. These complexes undergo an intramolecular cy-
clization via allenylidene intermediate to form different vi-
nylidene complexes each containing a five-membered ring, see
Scheme 9. For example, heating a chloroform solution of 5i to
60 °C afforded the vinylidene complex 23i together with its
isomer 24i in a ratio of 5:1, as determined by NMR. Both
complexes each with a stereogenic center at Cγ display two
doublet resonances at δ 43.92 and 43.72 with 2JPP ) 25.75 Hz
2
for 23i and at δ 43.48 and 42.84 with JPP ) 26.58 Hz for 24i
in their 31P NMR spectra. The mixture of vinylidene complexes
23i and 24i, contaminated with a few unidentifiable side
products, was converted to the corresponding acetylide com-
plexes 25i and 26i by deprotonation for removal of the side
products. Column chromatography yielded a mixture of yellow
powder 25i and 26i. The pure product 25i could be obtained
by recrystallization of the mixture in acetone at 0 °C. Repro-
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Effect of Methyl Substituents in the Olefinic Fraction
A R T I C L E S
Cp(PPh3)2RuCl26 and compounds 1-4, 8, 12, 19, 21, and 2227 were
prepared by following the method reported 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 tem-
perature (unless stated otherwise) and are reported in units of δ
with residual protons in the solvents as a standard.
Reactions of 1-4 with [Ru]Cl: Syntheses of 5a-d. A typical
experimental procedure for the reaction of [Ru]Cl with enyne is
described below. To a Schlenk flask charged with [Ru]Cl (0.20 g,
0.27 mmol) and NH4PF6 (0.09 g, 0.55 mmol) was added 1,6-enyne
1 (0.84 g, 0.32 mmol) and 30 mL of dichloromethane under
nitrogen. The resulting solution was stirred at room temperature
overnight. After that, the solution was filtered through Celite to
remove the insoluble precipitates, then the volatiles were removed
under vacuum and the solid residue was extracted with a small
volume of dichloromethane followed by reprecipitation 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 light-orange powder 5a (0.27
mg, 89%). The syntheses of 5b-j followed the same procedure.
Spectroscopic data of 5a: 1H NMR (δ, CDCl3): 6.89-7.42 (m, 40H,
Ph); 5.45 (m, 1H, CHdCH2); 5.44 (t, 3JHH ) 8.15 Hz, 1H, Cγ-H);
a π-coordinated species might be due to the lack of a tertiary
carbocation intermediate such as G described in Scheme 7. On
the other hand, the reason that 12 would not proceed the
cyclization reaction described in Scheme 9 might be a result of
disfavoring the formation of a vinylidene with a four-member
ring.
Esteruelas and his co-workers have reported the stoichiometric
Diels-Alder-type addition of dienes to the Cꢀ-Cγ double bond
of allenylidene complexes to give the corresponding substituted
vinylidene complexes.25 Uemura and co-workers described the
first example of the use of the Cꢀ-Cγ double bond of
allenylidene complexes as an enophile in the catalytic process
with a diruthenium complex.6a The allenylidene-ene reaction
described here is the first example of intramolecular C-C bond
forming system by controlling the substituted methyl group of
substrates and reaction conditions to lead to allyl migration or
cyclization products.
Conclusions
In summary, we report reactions of 1,6-enynes with [Ru]Cl
to yield different products by controlling the substituted methyl
group of substrates and reaction conditions. The mechanisms
via various reaction pathways including skeletal rearrangement,
retro-ene cleavage, and cyclization reactions are also proposed.
These results can be interpreted by different modes of the
coordination of the triple bond of the propargylic alcohol/ether
in a π-coordination mode or in the form of vinylidene complex
with the oxygen functionality in proximity. For the reactions
of enynes 1-3, the interaction between the allylic group and
Cꢀ of the resulting allenylidene ligand causes 1,3-allyl shift and
Cope rearrangement simultaneously to yield 7. This alle-
nylidene-ene reaction described here is the first example of
intramolecular C-C bond formation via Cope rearrangement
in organometallic system. With a propargylic ether group, the
reaction of compound 8 gives 10 as the major product via a
pericyclic retro-ene cleavage and the butadiene complex 9 by a
cyclization reaction as the minor product. The reaction of enyne
1 in ethanol gives 10 as the only product. For enyne 12, a C-C
bond forming cyclization reaction is observed in the intermediate
with π-coordinated triple bond giving the carbene complexes
15 and 16 with a substituted cyclopentenyl ring at CR via a
tertiary carbocationic species. However, the allenylidene com-
plex 6e derived from the vinylidene intermediate undergoes a
retro-ene reaction to bring about cleavage of the dimethyl
substituted allyl group giving complex 17. Deprotonation of 17
and further alkylation at Cγ with allyl iodide yields 7a. In the
reactions of enynes 21 and 22, unobserved allenylidene com-
plexes act as an enophile to afford the vinylidene complexes
23 and 24 each with a five-membered ring bonded at Cꢀ via
the allenylidene-ene reaction.
3
3
5.06 (d, JHH ) 17.15 Hz, 1H, CHdCHH); 4.98 (d, JHH ) 4.77
3
Hz, 1H, CHdCHH); 4.97 (s, 5H, Cp); 4.45 (d, JHH ) 8.15 Hz,
1H, Cꢀ-H); 3.13 (dd, 2JHH ) 14.32 Hz, 3JHH ) 7.35 Hz, 1H, CHH);
2
3
2.94 (dd, JHH ) 14.32 Hz, JHH ) 6.34 Hz, 1H, CHH); 1.92 (d,
3JHH ) 8.15 Hz, 1H, OH). 13C NMR (δ, CDCl3, 5 °C): 345.24 (t,
2JCP ) 13.70 Hz, CR); 143.80-127.98 (Ph); 133.94 (CHdCH2);
118.20 (CHdCH2); 115.70 (Cꢀ); 94.80 (Cp); 70.07 (Cγ); 55.92
(C); 42.19 (CH2). 31P NMR (δ, CDCl3): 42.42, 44.35 (2 d, Jpp
)
2
26.13 Hz). MS (FAB+) m/z: 953.3. Anal. Calcd for C60H53F6OP3Ru:
C, 65.63; H, 4.87. Found: C, 65.31; H, 4.56.
Syntheses of 6. A dilute solution of hydroxyvinylidene complex
5a (0.10 g, 0.09 mmol) in dichloromethane (0.5 mL) was transferred
to an Al2O3 (Acidic, activity grade I, height of column ca. 5 cm)
chromatography column. Elution with dichloromethane collected
a green band. The solution was removed under vacuum, and the
solid residue was extracted with a small volume of dichloromethane
followed by reprecipitation with 60 mL of stirred hexane. Precipi-
tates thus formed were collected in a glass frit, washed with hexane,
and dried under vacuum. The final product was obtained as a deep-
green powder 6a (0.04 g, 41%). Complexes 6a-c are too active to
be purified for mass spectrum, 13C NMR and elemental analysis.
Spectroscopic data of 6a: 1H NMR (δ, CDCl3): 9.08 (s, 1H, Cγ-H);
6.95-7.40 (m, 40H, Ph); 5.68 (m, 1H, CHdCH2); 5.02-5.07 (m,
2H, CHdCH2); 4.90 (s, 5H, Cp); 3.28 (d,3JHH ) 6.86 Hz, 2H, CH2).
31P NMR (δ, CDCl3): 45.69 (s).
Syntheses of 7. A solution of allenylidene complex 6a (0.11 g,
0.09 mmol) in chloroform (3 mL) was stirred at 60 °C for 6 h
under nitrogen. Then the solution was cooled to room temperature
and filtered through Celite to remove the insoluble precipitates. Then
the volatiles were removed under vacuum and the solid residue
was extracted with a small volume of dichloromethane followed
by being reprecipitated with 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 was
obtained as a pink powder 7a (0.10 g, 89%). An alternative and
more straightforward method to prepare compounds 5a involves
the treatment of the ruthenium vinylidene complexes 5a in
Experimental Section
Typical experimental procedures and spectroscopic data of the
representative products are described. Further experimental details
and spectroscopic data of other products are summarized in the
Supporting Information.
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
(26) Bruce, M. I.; Wallis, R. C. Aust. J. Chem. 1979, 32, 1471–1485.
(27) (a) Marco-Contelles, J.; Ruiz-Caro, J.; Mainetti, E.; Devin, P.;
Fensterbank, L.; Malacria, M. Tetrahedron 2002, 58, 1147–1158. (b)
Lemie´re, G.; Gandon, V.; Cariou, K.; Hours, A.; Fukuyama, T.;
Dhimane, A. L.; Fensterbank, L.; Malacria, M. J. Am. Chem. Soc.
2009, 131, 2993–3006.
(25) Baya, M.; Buil, M. L.; Esteruelas, M. A.; Lopez, A. M.; On˜ate, E.;
Rodr´ıguez, J. R. Organometallics 2002, 21, 1841–1848.
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A R T I C L E S
Chung et al.
chloroform and was followed by further reaction at 60 °C for 6 h
to generate the dehydration allenylidene complex 6a and subse-
quently the allyl migration product 7a. The purification was the
same with the description above. Spectroscopic data of 7a: 1H NMR
(δ, CDCl3): 6.86-7.70 (m, 40H, Ph); 5.97 (s, 1H, CHdC(Ph)2);
5.64 (m, 1H, CHdCH2); 5.07 (d, 3JHH ) 10.06 Hz, 1H, CHdCHH);
4.85 (d, 3JHH ) 15.53 Hz, 1H, CHdCHH); 4.80 (s, 5H, Cp); 2.70
(d,3JHH ) 6.57 Hz, 2H, CH2). 13C NMR (δ, CDCl3): 354.23 (t,
2JCP ) 14.59 Hz, CR); 144.41 (CPh2); 142.83-128.85 (Ph); 134.76
(CHdCH2); 125.21 (Cꢀ); 117.43 (CHd)CH2); 114.17 (CH); 94.07
(Cp); 29.35 (CH2). 31P NMR (δ, CDCl3): 41.83 (s). MS (FAB+)
m/z: 935.2. Anal. Calcd for C60.5H53F6O0.5P3Ru (crystal containing
0.5 equiv of methanol was used for analysis): C, 66.30; H, 4.87.
Found: C, 66.12; H, 5.10.
H, 5.83. Found: 75.42; H, 5.93. The same procedure was used for
the reaction of 19 with [Ru]Cl to synthesize 20.
Reactions of 12 with [Ru[Cl: Syntheses of 13 and 14. The
syntheses of the mixture 13 and 14 followed the standard procedure
of synthesis of 5a in EtOH for 3 days. Extraction of the mixture
with EtOH and collected the precipitate to obtain 13. The filtrates
were passed through a neutral Al2O3 column eluted CH2Cl2.
Collecting the green band followed by drying under vacuum resulted
in the product 14. Spectroscopic data of 13 and 14 are given in
Supporting Information.
Syntheses of 5f and 15. The syntheses of the mixture 5f and 15
followed the same procedure of synthesis of 5a in CH2Cl2.
Extraction of the mixture with benzene and collected the precipitate
to obtain 5f. The filtrates were passed through a neutral Al2O3
column eluted CH2Cl2. Collecting the green band followed by
drying under vacuum resulted in the product 15. Spectroscopic data
Reactions of 8 with [Ru[Cl: Syntheses of 9, 10, and 11. The
experimental procedure of syntheses complexes 9 and 10 was the
same with the synthesis of 5a described above. The mixture 9 and
10 (0.32 g) was treated with excess NaOMe (0.02 g, 0.36 mmol)
in methanol (10 mL), and the light-yellow precipitate formed
immediately. Stirring was continued until no further solid was
formed. The solvent was removed under vacuum, and the residue
was passed through a neutral Al2O3 column eluted with ether/
CH2Cl2. Collecting the yellow band and the second light-yellow
band solution separately followed by drying under vacuum resulted
in the yellow vinyl product 11 (0.22 g, 76%) and light-yellow diene
product 9 (0.04 g, 13%). A solution of complex 11 (0.20 g, 0.21
mmol) with NH4PF6 (0.09 g, 0.55 mmol) in CHCl3 was stirred for
3 h at 60 °C under nitrogen atmosphere. After being cooled to room
temperature, the solution was filtered through Celite to remove the
insoluble precipitates and volume of the filtrate is reduced to 5 mL.
The resulting solution was added into a solution of 60 mL
vigorously stirred hexane. Brown precipitates thus formed were
collected, washed with hexane, and dried under vacuum to afford
1
3
of 15: Yield: 0.03 g (8%). H NMR (δ, CDCl3): 15.57 (t, JHP
)
11.20 Hz, 1H, CR-H); 6.83-7.72 (m, 41H, Ph and C ) CH);
4.83 (s, 5H, Cp); 4.71 (s, 1H, CdCHH); 4.43 (s, 1H, C ) CHH);
3.97 (t, 3JHH ) 7.90 Hz, 1H, CH); 3.21 (dd, 3JHH ) 14.10 Hz,3JHH
) 7.90 Hz, 1H, CHH); 2.42 (dd, 3JHH ) 14.10 Hz,3JHH ) 7.90 Hz,
1H, CHH); 1.30 (s, 3H, CH3). 13C NMR (δ, CDCl3): 308.53 (t,
2JCP ) 15.97 Hz, CR); 163.29 (Cꢀ); 149.54 (CdCH); 147.57-126.81
(Ph); 144.63 (CdCH2); 115.12 (CdCH2); 94.92 (Cp); 62.77 (C);
55.74 (CH); 45.11 (CH2); 18.30 (CH3). 31P NMR (δ, CDCl3): 45.61,
2
45.28 (2 d, JPP ) 25.24 Hz). MS ESI m/z: 964.2 (M+1)+. Anal.
Calcd for C62H55F6P3Ru: C, 67.20; H, 5.00. Found: C, 67.44; H,
5.21.
Syntheses of 5g and 16. Preparation of the mixture 5g and 16
was carried out in MeOH and followed the same procedure as the
syntheses of 5f and 15. Spectroscopic data of 16: Yield: 0.06 g
(18%). 1H NMR (δ, CDCl3): 16.57 (t, 3JHP ) 9.90 Hz, 1H, CR-H);
6.84-7.41 (m, 41H, Ph and CdCH); 4.68 (s, 5H, Cp); 3.62 (t,
3JHH ) 8.40 Hz, 1H, CH); 3.20 (dd, 3JHH ) 14.15 Hz,3JHH ) 8.40
Hz, 1H, CHH); 2.05 (dd, 3JHH ) 14.15 Hz,3JHH ) 8.40, 1H, CHH);
1.09 (s, 3H, CH3); 0.86 (s, 3H, CH3). 13C NMR (δ, CDCl3): 318.28
1
10 (0.22 g, 97%). Spectroscopic data of 9: H NMR (δ, CDCl3):
6.98-7.62 (m, 25H, Ph); 5.67 (m, 1H, CHdCH2); 5.61 (s, 1H,
CHOCH2); 4.97 (m, 2H, CHdCH2); 4.69 (s, 5H, Cp); 4.46 (dd,
2JHH ) 12.39 Hz, 3JHH ) 5.48 Hz, 1H,); 4.17 (d, 2JHH ) 17.75 Hz,
1H, CHH); 4.11 (m, 1H, OCHH); 4.10 (s, 1H, OCHCdCHH); 3.94
2
(t, JCP ) 14.28 Hz, CR); 165.20 (Cꢀ); 150.96 (CdCH);
148.23-126.74 (Ph); 93.61 (Cp); 78.41 (COMe); 61.50 (C); 56.95
2
(s, 1H, CdCHH); 3.64 (d, JHH ) 17.75 Hz, 1H, CHH); 0.16 (d,
(CH); 48.74 (OMe); 43.67 (CH2); 23.36 (CH3); 19.15 (CH3). 31P
3
2
3JHP ) 17.03 Hz, 1H, CdCHH); 0.05 (d, JHP ) 18.50 Hz, 1H,
NMR (δ, CDCl3): 47.75, 47.48 (2 d, JPP ) 28.20 Hz). MS ESI
OCHCdCHH). 13C NMR (δ, CDCl3): 146.00-126.28 (Ph); 134.03
(CHdCH2); 116.51 (CHd)CH2); 111.42 (OCHCdCH2); 110.08
(CdCH2); 90.70 (CHOCH2); 72.36 (OCH2); 61.38 (CPh2); 50.96
m/z: 996.2 (M+1)+. Anal. Calcd for C63H59F6OP3Ru: C, 66.37; H,
5.22. Found: C, 66.55; H, 5.31.
Syntheses of 6e, 17 and 18. The syntheses of 6e, 17, and 18
followed the same procedure as the syntheses of 6a, 7a, and 11.
Complex 6e is too active to be purified for mass spectrum, 13C
2
2
(CH2); 43.41 (d, JCP ) 4.65 Hz, OCHCdCH2); 42.24 (d, JCP
)
4.65 Hz, CdCH2). 31P NMR (δ, CDCl3): 57.20 (s). MS ESI m/z:
732.2 (M+1)+. Anal. Calcd For C47H47F6O1.50P2Ru (crystal contain-
ing 0.5 equiv of diethyl ether was used for analysis): C, 61.84; H,
5.19. Found: C, 61.98; H, 4.99. Spectroscopic data of 10: 1H NMR
NMR and elemental. Spectroscopic data of 17: Yield: 0.18 g (82%).
3
1H NMR (δ, CDCl3): 7.02-7.42 (m, 40H, Ph); 6.45 (d, JHH
)
10.52 Hz, 1H, Cγ-H); 5.54 (dt, 3JHH ) 10.52 Hz, 4JHP ) 2.38 Hz,
Cꢀ-H); 5.19 (s, 5H, Cp). 13C NMR (δ, CDCl3, 5 °C): 361.99 (t,
2JCP ) 15.85 Hz, CR); 141.35, (Cδ); 138.86-127.30 (Ph); 117.23
(Cꢀ); 109.49 (Cγ); 95.04 (Cp). 31P NMR (δ, CDCl3): 42.78 (s).
MS ESI m/z: 896.2 (M+1)+. Anal. Calcd for C57H47F6P3Ru: C,
65.83; H, 4.56. Found: C, 65.92; H, 4.79. Spectroscopic data of
18: Yield: 0.16 g (84%). 1H NMR (δ, C6D6): 6.90-8.18 (m, 40H,
Ph); 6.81 (s, 1H, Cγ-H); 4.43 (s, 5H, Cp). 13C NMR (δ, C6D6):
144.59 (Cγ); 142.41-126.34 (Ph); 125.97 (t, 2JCP ) 24.78 Hz, CR);
116.38 (Cγ); 115.44 (Cꢀ) 85.94 (Cp). 31P NMR (δ, C6D6): 50.95
(s). MS ESI m/z: 895.1 (M+1)+. Anal. Calcd for C57H46P2Ru: C,
76.58; H, 5.19. Found: C, 76.74; H, 5.32.
3
3
(δ, CDCl3): 15.24 (dt, JHH ) 12.95 Hz, JHP ) 9.10 Hz, 1H,
3
CR-H); 7.84 (t, JHH ) 12.95 Hz, 1H, Cꢀ-H); 7.16-7.81 (m,
3
41H, Ph and Cγ-H); 5.52 (m, 1H, CH ) CH2); 5.21 (d, JHH
)
3
17.05 Hz, 1H, CHdCHH); 5.09 (d, JHH ) 10.30 Hz, 1H,
CHdCHH); 4.90 (s, 5H, Cp); 3.29 (d, 3JHH ) 6.85 Hz, 2H, CH2).
13C NMR (δ, CDCl3): 309.29 (t, 2JCP ) 9.18 Hz, CR); 156.65 (Cγ);
153.09 (Cꢀ); 143.76-127.12 (Ph); 133.93 (CHdCH2); 118.83
(CHdCH2); 95.00 (Cp); 54.69 (C); 42.73 (CH2). 31P NMR (δ,
CDCl3): 46.97 (s). MS ESI m/z: 938.2 (M+1)+. Anal. Calcd for
C60H53F6P3Ru: C, 66.60; H, 4.94. Found: 66.39; H, 5.10. Spectro-
1
scopic data of 11: H NMR (δ, d-toluene): 7.82 (m, 1H, CR-H);
3
6.88-7.76 (m, 40H, Ph); 5.73 (m, 1H, CHdCH2); 5.45 (dd, JHH
Reactions of 21-22 with [Ru[Cl: Syntheses of 23-26. The
syntheses of the crude products 23 and 24 followed the same
procedure as the synthesis of 7a, and the reaction was carried out
in CHCl3 at 60 °C for 30 min. The deprotonation of 23i and 24i
followed the same procedure as the synthesis of 11 giving 25i and
26i, respectively. The pure product 25i as crystals could be obtained
by recrystallization of the mixture in acetone at 0 °C (0.07 g, 80%).
No attempt was made to purify complex 26i from the mixture. A
diluted solution of HBF4 ·Et2O (48%, 0.02 mL, 0.11 mmol) in
diethyl ether was added dropwise at 0 °C to a stirred solution of
3
3
) 16.50 Hz, JHH ) 8.18 Hz, 1H, Cꢀ-H); 4.81 (d, JHH ) 10.26
3
Hz, 1H, CHdCHH); 4.69 (d, JHH ) 17.15 Hz, 1H, CHdCHH);
3
4.29 (s, 5H, Cp); 4.24 (d, JHH ) 8.18 Hz, 1H, Cγ-H). 3.08 (s,
3H, OMe); 3.05 (m, 1H, CHH), 2.89 (m, 1H, CHH). 13C NMR (δ,
d-toluene, 5 °C): 151.55 (t, 2JCP ) 18.36 Hz, CR); 147.60-124.64
(Ph); 136.34 (Cꢀ); 136.24 (CHdCH2); 117.10 (CHdCH2); 91.46
(Cγ); 86.68 (Cp); 56.37 (C); 55.46 (OMe); 44.48 (CH2). 31P NMR
2
(δ, d-toluene): 49.06, 47.29 (2 d, Jpp ) 37.51 Hz). MS ESI m/z:
939.2 (M+1 - OMe)+. Anal. Calcd for C61H56OP2Ru: C, 75.68;
9
18374 J. AM. CHEM. SOC. VOL. 131, NO. 51, 2009

Effect of Methyl Substituents in the Olefinic Fraction
A R T I C L E S
25i (0.10 g, 0.10 mmol) in 20 mL of diethyl ether. Immediately,
an insoluble solid precipitated, but the addition was continued until
no further solid was formed. The solution was then decanted, and
the brown solid was washed with diethyl ether (3 × 5 mL) and
dried in vacuum to yield 23i (0.10 g, 92%). Complex 24i could
only be obtained in the mixture by the protonation procedure
mentioned above. Spectroscopic data of 23i: 1H NMR (δ, CDCl3):
6.87-7.43 (m, 40H, Ph); 5.79 (s, 1H, CH ) CMe); 4.87 (s, 5H,
2.52 (m, 1H, CHH); 2.18 (m, 1H, CHH). 13C NMR (δ, CDCl3):
The signal of triplet CR is too weak to be detected. 147.46-126.47
(Ph); 131.79 (CdCH2); 116.35 (Cꢀ); 107.24 (CdCH2); 94.43 (Cp);
57.94 (CPh2); 46.46 (C(Ph)2CH2) 41.00 (CH2); 39.73 (Cγ). 31P
NMR (δ, CDCl3): 43.48, 42.84 (2 d, 2Jpp ) 26.58 Hz). Anal. Calcd
for C61H53BF4P2Ru: C, 70.73; H, 5.16. No attempt was made to
purify complex 24i from the mixture.
3
Cp); 4.18 (d, JHH ) 8.62 Hz, 1H, Cꢀ-H); 4.05 (m, 1H, Cγ-H);
Acknowledgment. This research is supported by the National
Science Council and National Center of High-Performance Com-
puting of Taiwan, the Republic of China. We thank the reviewers
for suggesting more deuteration experiments leading to better
understanding of the mechanism.
2
3
2.48 (dd, JHH ) 15.99 Hz, JHH ) 6.89 Hz, 1H, CHH); 2.09
(dd,2JHH ) 15.99 Hz,3JHH ) 5.00 Hz, 1H, CHH); 1.81 (s, 3H, CH3).
2
13C NMR (δ, CDCl3): 346.29 (t, JCP ) 15.72 Hz, CR);
147.46-126.47 (Ph); 139.11 (CMe); 131.01 (CHdCMe); 117.41
(Cꢀ); 94.48 (Cp); 65.20 (CPh2); 44.87 (CH2); 43.14 (Cγ); 16.90
2
(CH3). 31P NMR (δ, CDCl3): 43.92, 43.72 (2 d, Jpp ) 25.75 Hz).
Supporting Information Available: More characterization data
of ruthenium complexes and complete crystallographic data for
7a, 9, 11, 13, and 25i. This material is available free of charge
via the Internet at http://pubs.acs.org.
MS ESI m/z: 950.2 (M+1)+. Anal. Calcd for C61H53BF4P2Ru: C,
70.73; H, 5.16. Found: C, 70.97; H, 5.42. Spectroscopic data of
1
24i: H NMR (δ, CDCl3); 6.87 -7.43 (m, 40H, Ph); 5.05 (s, 1H,
CdCHH); 4.93 (s, 1H, C ) CHH); 5.01 (s, 5H, Cp); 4.11 (d, 3JHH
) 7.13 Hz, 1H, Cꢀ-H); 3.84 (m, 1H, Cγ-H); 3.36 (d, 2JHH ) 17.04
Hz, 1H, C(Ph)2CHH); 2.85 (d, 2JHH ) 17.04 Hz, 1H, C(Ph)2CHH);
JA906745J
9
J. AM. CHEM. SOC. VOL. 131, NO. 51, 2009 18375