Synthesis, characterization, and reactivity of ruthenium bis-allyl complexes with chiral phosphine-phosphite ligands

Article abstract of DOI:10.1021/om300018s

A series of ruthenium bis-allyl complexes of formula Ru(η³- 2-MeC₃H₄)₂(P-OP) (1) which incorporate chiral phosphine-phosphite ligands (P-OP) have been prepared and characterized. Compounds 1 exist in solution as a mixture of two diastereomers (maj and min) differing in the configuration at the metal. Both isomers are in equilibrium in solution, and their ratio varies with the nature of the P-OP ligand. Along the series, higher values of the maj/min ratio were observed with complexes bearing less sterically encumbered phosphite groups. In reactions of compounds 1 with protic reagents removal of one or two allyl ligands has been observed. Thus, reaction of 1h with pentachlorophenol produces the mixed allyl-phenoxide 3h, whereas reaction of 1a or 1h with tiglic acid produces the corresponding tiglates 4a,h, respectively. In addition, compounds 1 generate active catalysts for the hydrogenation of tiglic and 2-methyl-2-pentenoic acids. By appropriate optimization of the structure of the P-OP ligand, enantioselectivities up to 89% ee were obtained in these reactions. In addition, complexes 1 also catalyze the ROMP reaction of norbornene, although low initiation rates have been observed for this process.

Full text of DOI:10.1021/om300018s

Article
pubs.acs.org/Organometallics
Synthesis, Characterization, and Reactivity of Ruthenium Bis-Allyl
Complexes with Chiral Phosphine-Phosphite Ligands
†
†
†
‡
†
́
́
Monica Vaquero, Sergio Vargas, Andres Suarez, Sergio E. Garcıa-Garrido, Eleuterio Alvarez,
́
́
́
Manuel Mancera,§ and Antonio Pizzano*,†
†
́
Instituto de Investigaciones Quımicas (IIQ), Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Avda
Amer
́
ico Vespucio No. 49, Isla de la Cartuja, 41092 Sevilla, Spain
‡
́
́
Departamento de Quımica Organ
́
ica e Inorgan
́
ica, Instituto de Quımica Organometal
́
ica “Enrique Moles” (Unidad Asociada al
CSIC), Universidad de Oviedo, 33006 Oviedo, Spain
§
́
Departamento de Quımica Organ
́
ica y Farmaceu
́
tica, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
S
* Supporting Information
ABSTRACT: A series of ruthenium bis-allyl complexes of
formula Ru(η3-2-MeC3H4)2(P-OP) (1) which incorporate
chiral phosphine-phosphite ligands (P-OP) have been
prepared and characterized. Compounds 1 exist in solution
as a mixture of two diastereomers (maj and min) differing in
the configuration at the metal. Both isomers are in equilibrium
in solution, and their ratio varies with the nature of the P-OP
ligand. Along the series, higher values of the maj/min ratio
were observed with complexes bearing less sterically
encumbered phosphite groups. In reactions of compounds 1
with protic reagents removal of one or two allyl ligands has been observed. Thus, reaction of 1h with pentachlorophenol
produces the mixed allyl-phenoxide 3h, whereas reaction of 1a or 1h with tiglic acid produces the corresponding tiglates 4a,h,
respectively. In addition, compounds 1 generate active catalysts for the hydrogenation of tiglic and 2-methyl-2-pentenoic acids.
By appropriate optimization of the structure of the P-OP ligand, enantioselectivities up to 89% ee were obtained in these
reactions. In addition, complexes 1 also catalyze the ROMP reaction of norbornene, although low initiation rates have been
observed for this process.
on C2-symmetric diphosphines. Moreover, the range of ligands
based on phosphorus fragments grows continuously and ligands
incorporating a range of functionalities such as phosphite,
phosphinite, phosphoramidite, and aminophosphine have
gained prominence.9 Notably, these phosphorus fragments
possess electronic properties different from those of phos-
phines;10 therefore, the synthesis of Ru allyl complexes based
on the latter ligands and a comparison of their reactivity and
catalytic performance with those of pertinent diphosphine
examples constitute a topic of interest.
Chiral phosphine-phosphite ligands are becoming an
important class of ligands for asymmetric catalysis. A wide
range of transformations such as hydroformylation, hydro-
genation, and conjugate addition, among others, have been
achieved very efficiently with catalysts based on these ligands.11
In this respect, we have studied the synthesis and application in
enantioselective hydrogenation of a family of highly modular
phosphine-phosphites based on simple ethane or benzene
backbones (P-OP). Thus, following an extensive catalyst
screening, highly enantioselective rhodium catalysts for several
INTRODUCTION
■
Ruthenium allyl complexes bearing phosphine ligands con-
stitute an important class of compounds in homogeneous
catalysis. They have shown a rich reactivity and have been
applied in diverse catalytic processes such as enantioselective
hydrogenations,1 ROMP reactions,2 and carboxylic acid
additions to alkynes,3 among other transformations.4 Moreover,
regarding activation of these complexes for the attainment of
reactive species, stoichiometric reactions involving removal of
allyl ligands have also been a subject of considerable interest.
For instance, several studies about the hydrogenation of some
allyl complexes to give interesting polyhydrides have been
described.5 In addition, protonation reactions have also been
studied thoroughly, and a diverse range of reagents such as
hydracids, phenols, and 1,3-dicarbonyl compounds have shown
allyl elimination from the complex.6 In this regard, protonation
of bis-allyl diphosphine complexes provides a very convenient
procedure for the nontrivial preparation of ruthenium dihalide
derivatives, which are excellent catalyst precursors for the
hydrogenation of several types of olefins and ketones.7
Concerning the application of ruthenium allyl complexes in
asymmetric catalysis, it should be noted that, with few
exceptions,8 the examples reported in the literature are based
Received: January 10, 2012
Published: April 19, 2012
© 2012 American Chemical Society
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Scheme 1. Preparation of Allyl Complexes 1
types of olefins have been obtained.12 In this contribution we
present the preparation of a series of ruthenium allyl complexes
based on P-OP ligands which, to the best of our knowledge, are
the first Ru examples incorporating chiral phosphine-phosphite
ligands. These complexes have been structurally studied in
detail, and several aspects of their reactivity involving allyl
elimination have been examined. Finally, their behavior in the
enantioselective hydrogenation of α,β-unsaturated acids as well
as in the ROMP reaction of norbornene has also been
investigated.
RESULTS AND DISCUSSION
■
Preparation of Phosphine-Phosphite Ruthenium Allyl
Complexes. A series of complexes of formulation [Ru(η3-2-
MeC3H4)2(P-OP)] (1a−j) have been prepared by reactions
between [Ru(η3-2-MeC3H4)2(COD)]13 and a stoichiometric
amount of the desired phosphine-phosphite (P-OP = 2a−j) in
hexanes (Scheme 1). The reaction is quite general and allows
the synthesis of a wide variety of complexes 1. Only the
reaction with ligand 2b led to a complex reaction mixture, and
we were unable to isolate the desired compound 1b.
Figure 1. Quadrant diagrams for Λ and Δ diastereomeric bis-allyl
complexes.
Solid-State Structure of Compounds 1. One of the most
interesting features of compounds 1 is the presence of a
stereogenic center on the metal with either Λ or Δ
configuration. Therefore, for complexes with P-OP ligands
possessing a stereogenic element (all but 2h, due to rapid
atropisomerization of the phosphite biphenyl moiety) two
diastereomers are possible. The two diastereomeric structures
can be distinguished readily with a typical quadrant diagram
(Figure 1). Then, the diastereomer with configuration Λ places
allyl ligands in quadrants II and IV, while the diastereomer with
Δ configuration at the metal distributes the allyl ligands in
quadrants I and III.
complexes 1a,g have been studied by X-ray diffraction. ORTEP
views, along with selected bond distances and angles, are
depicted in Figures 2 and 3, respectively. Both complexes show
a distorted-octahedral structure, with the phosphorus atoms
and two of the terminal allyl carbon atoms in the equatorial
plane, while the other two terminal carbons occupy the axial
positions. The phosphine-phosphite bite angle (89°) is similar
to values previously found in Rh, Ir, and Pd complexes,12,14
whereas P−Ru−C angles range between 86 and 96°. As
observed before in complexes with P-OP ligands, the Ru−P
bond of the phosphite is shorter than that of the phosphine (ca.
0.1 Å). Moreover, no significant differences in the structure of
the Ru(η3-2-Me-C3H4)2 fragment of 1a,g are observed, despite
the different sizes of the phosphite groups. Also remarkably,
Upon these considerations, we were interested in determin-
ing the metal configuration in some selected examples. Thus,
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Figure 2. ORTEP view of complex 1a. Selected bond lengths (Å) and angles (deg): Ru(1)−C(47) = 2.179(3), Ru(1)−C(48) = 2.261(3), Ru(1)−
C(49) = 2.213(4), Ru(1)−P(1) = 2.2227(11), Ru(1)−P(2) = 2.3095(10); P(1)−Ru(1)−P(2) = 89.45(4), C(49)−Ru(1)−P(1) = 90.67(10),
C(45)−Ru(1)−P(1) = 93.50(9), P(1)−Ru(1)−C(44) = 87.13(10), C(45)−Ru(1)−P(2) = 89.79(10), C(48)−Ru(1)−P(2) = 88.55(10).
Figure 3. ORTEP view of complex 1g. Selected bond lengths (Å) and angles (deg): Ru(1)−C(33) = 2.220(2), Ru(1)−C(34) = 2.1891(18),
Ru(1)−C(35) = 2.2712(19), Ru(1)−P(1) = 2.1999(5), Ru(1)−P(2) = 2.3337(5); P(1)−Ru(1)−P(2) = 89.071(17), P(1)−Ru(1)−C(29) =
86.05(6), P(1)−Ru(1)−C(31) = 87.67(5), C(33)−Ru(1)−P(2) = 90.48(5), C(35)−Ru(1)−P(2) = 93.29(5).
both compounds show a Λ configuration at the metal
irrespective of their phosphite biaryl configuration.
determined by 31P{1H} NMR and range between 1.3 in the
case of 1c and higher than 20 in the case of 1g (Table 1). Thus,
larger values are observed in the case of smaller phosphite
Solution Behavior of Complexes 1. Most studies
considering ruthenium configurations in bis-allyl diphosphine
complexes are restricted to the structure in the solid state,
whereas the behavior in solution has not been investigated in
great detail. It is therefore of interest to investigate the existence
of isomers of compounds 1 in solution and the Ru
configuration of the preferred isomer in each case. This goal
is facilitated by the existence of two different phosphorus
functionalities, which allow us to analyze in detail the structures
of the isomers by NMR techniques.
1
fragments. Both sets of signals show resonances in the H,
13C{1H}, and 31P{1H} NMR spectra corresponding to P-OP
and two η3-2-Me-C3H4 ligands. In contrast, compound 1h
provides more simple spectra which contain only one set of
signals. Atropisomerization of the biphenyl fragment rapidly
exchanges isomers with R and S phosphite biaryl configurations
at room temperature; therefore, the spectra for 1h correspond
to a mixture of two enantiomers differing in Ru configuration.
In order to analyze the structural features of the two isomers
of complexes 1, the resonances of the allyl ligands have been
studied in detail. Both ligands are nonequivalent, as a result of
the C1 symmetry of the P-OP ligand, and give two
As expected, most of complexes 1 showed the presence of
two isomers (which will be denoted from now on as maj and
min) in solution. The ratio between the two species has been
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a
(Ca and Cc) and the doublets of doublets attributed to terminal
allyl carbons in equatorial positions (Cb and Cd).
Table 1. 31P{1H} NMR Data of Isomers of Complexes 1
complex
maj/min
6.0
isomer
δPO
δPC
2JPP
Further analysis requires the assignment of equatorial
terminal carbons trans to each phosphorus atom. For that
purpose, compound 1e, characterized by a P-stereogenic
phosphine fragment, has been studied. This compound shows
a maj/min ratio around 9, which facilitates the study of the
preferred isomer. An analysis by a 2D-NOESY experiment
allows us to assign the allyl protons in positions syn (Ha−Hd)
and anti (Ha′−H′) to the 2-Me groups. In addition, meaningful
NOE contacts between anti protons of an allyl group and the
ortho protons of the P-Ph fragment (Figure 5), indicate the
1a
maj-1a
min-1a
maj-1c
min-1c
maj-1d
min-1d
maj-1e
min-1e
maj-1f
min-1f
168.4
154.3
161.7
158.8
168.5
154.3
162.1
152.7
177.8
173.4
175.0
157.5
157.2
156.1
180.2
42.3
40.2
2.5
40
47
50
52
40
47
46
51
44
58
47
46
35
40
47
1c
1d
1e
1f
1.3
4.0
1.4
41.3
39.4
21.6
15.7
45.6
44.6
36.5
42.4
40.1
32.3
37.7
42.9
9.0
14.0
>20
2.0
bc
,
1g
1h
1i
maj-1g
1h
maj-1i
min-1i
maj-1j
1j
13.1
d
min-1j
a
2
Chemical shifts in ppm and JPP values in Hz. Spectra were obtained
b
in CD2Cl2 unless stated otherwise. min isomer not observed.
c
d
Obtained in CDCl3. Phosphite signal overlapped with that of the
maj isomer. 2JPP could not be determined, due to the broad phosphine
Figure 5. Selected NOE contacts observed in compound maj-1e.
signal.
differentiated groups of resonances. Thus, in the 13C{1H} NMR
one signal is observed for each terminal carbon (Ca−Cd, Figure
4), between 35 and 49 ppm, while each central carbon atom
gives a resonance around 100 ppm. Most interestingly,
resonances of the terminal carbons show a different coupling
pattern with 31P nuclei, which is repeated along the series.
Then, two of them appear as singlets, whereas the other two
appear as doublets of doublets. Typically, one of the latter is
characterized by JCP constants around 45 and 5 Hz, whereas the
coupling constants in the other doublet of doublets have values
around 20 and 5 Hz. From these observations, the singlets can
reasonably be assigned to terminal carbons in axial positions
existence of an allyl group in quadrant III and hence a Δ
configuration for the maj isomer. Other contacts between allyl
protons and phosphite tBu groups are in good accord with this
structure. From these observations and with the help of a
13C−1H HMQC experiment it is possible to assign the doublet
of doublets with the higher JCP value, that corresponding to Cb,
to the terminal allyl carbon in a position trans to the
phosphorus of the phosphite. Consequently, Cd can finally be
assigned to the equatorial carbon trans to the phosphine. From
this analysis the resonances for terminal allyl carbons in the
13C{1H} NMR spectra have been assigned to the rest of
complexes 1.
Figure 4. Notation of terminal allyl nuclei and corresponding region in the 13C{1H} NMR spectrum of 1f in CD2Cl2.
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Figure 6. Intramolecular interconversion between maj and min isomers of 1.
As a further step we were committed to assign the
configuration of the maj and min isomers in other complexes.
As mentioned above, compound 1g has shown a Λ
configuration in the solid state. In addition, only the maj
isomer is observed in solution. An analysis of the 2D-NOESY
experiment is in good accord with a Λ configuration for the maj
isomer. Moreover, compound 1f, which contains the same
phosphite fragment as 1g, displays analogous behavior. The maj
isomer is very predominantly observed (maj/min = 14), and
the NMR data are in good accord with a Λ configuration for
the maj isomer.
To determine the configuration of the maj isomer of 1a, a
crystalline sample of this compound was dissolved at −80 °C in
CD2Cl2, and a 31P{1H} NMR spectrum was registered at this
temperature. This spectrum showed only one isomer. When the
temperature was raised, a second species appeared. At room
temperature a 6/1 ratio was observed favoring the isomer
exclusively observed at −80 °C. The maj/min ratio did not
change significantly when the temperature was lowered again.
These observations, in connection with the Λ configuration
observed for 1a in solid state (see above), allow us to conclude
that the maj isomer in solution also corresponds to a Λ
configuration.
Regarding the preferred configuration, it should be
mentioned that for both 1f and 1g a Λ configuration is highly
favored. However, in the case of compound 1a, which has the
opposite configuration in the biaryl phosphite, the config-
uration is also Λ. Moreover, 1e also has an S phosphite
fragment, while the configuration of maj-1e is Δ. Then, the
preferred metal configuration does not correlate with the
phosphite biaryl configuration. It should be noted, however,
that a common feature of solid-state structures of 1a,g is the
existence of an axial phosphine substituent in quadrant IV
which finds an adjacent allyl group with the 2-Me group
oriented anti with respect to this phosphine substituent. This
structural feature looks more general and is also present in
other bis-allyl complexes with chiral diphosphines,7b,15 although
we cannot find a clear explanation for this arrangement.
The results mentioned above also indicate the existence of an
equilibrium between the maj and min isomers of 1a. Moreover,
the ratio between diastereomers depends on the solvent. As
stated, the value of the maj/min ratio is 6 in CD2Cl2 at room
temperature, while it increases to 8 in hexanes and to 16 in
C6D6. In order to investigate the exchange mechanism between
maj and min isomers, we have examined in more detail the
behavior in solution of 1c. This compound gives a 1/1.3 ratio of
the two isomers; therefore, the NMR signals of both species
have enough intensity to be studied. Initially, the exchange
between the two isomers of 1c has been evidenced in a 31P−31P
EXSY experiment by the appearance of cross-peaks between
the two isomers in the phosphine and the phosphite regions.
1
On the other hand, an analysis of the H−1H EXSY spectrum
does not show exchanges between the syn and anti protons of
allyl methylene groups. This observation excludes the existence
of η3−η1-rotation−η3 mechanisms.16 Moreover, no intra-
molecular exchanges have been observed. All the exchanges
detected involve signals of the maj and min isomers. This
feature rules out the existence of mechanisms produced by
phosphorus decoordination, rotation, and coordination.14a
Upon these observations it can be concluded that the
mechanism should be nondissociative, which is a dynamic
process frequently found in octahedral compounds.17 In
particular, exchanges between Ha, Hb, Hc, and Hc′ protons of
the maj isomer with Hd, Hc, Hb, and Hb′ protons of the min
isomer, respectively, can be assigned. This pattern allows us to
explain the interconversion between diastereomers of 1c by
simple allyl migration through axial positions (path ii, Figure
6).18 Conversely, allyl migration through the more hindered
equatorial plane (path i) does not match the results, as this
mechanism would exchange Ha and Hb protons with Hd and
Hc, respectively.
Stoichiometric Reactions of Compounds 1. Due to the
interesting reactivity reported for bis-allyl ruthenium diphos-
phine complexes, we were interested in examining the behavior
of compounds 1 in several representative reactions. Initially,
some allyl protonation reactions were examined. Then, reaction
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Scheme 2. Protonation Reactions of Allyls 1
Figure 7. ORTEP view of complex 3h. Selected bond lengths (Å) and angles (deg): Ru(1)−C(53) = 2.134(2), Ru(1)−C(54) = 2.254(2), Ru(1)−
C(55) = 2.302(2), Ru(1)−O(4) = 2.1731(15), Ru(1)−Cl(1) = 2.4924(6), Ru(1)−P(1) = 2.1607(5), Ru(1)−P(2) = 2.3061(6); C(53)−Ru(1)−
P(1) = 98.75(7), C(53)−Ru(1)−O(4) = 90.53(8), P(1)−Ru(1)−O(4) = 168.69(5), P(1)−Ru(1)−C(55) = 109.95(7), C(53)−Ru(1)−P(2) =
99.28(7), P(1)−Ru(1)−P(2) = 89.91(2).
between 1h and 2 equiv of pentachlorophenol at room
temperature yielded the monoallyl monophenoxide compound
3h (Scheme 2). Interestingly, no bis-phenoxide complex was
observed, despite heating the reaction mixture to 50 °C for 16
h. This behavior contrasts with the easy displacement of two
allyl ligands in diphosphine analogues described by Werner.6a,b
Compound 3h is characterized by one group of resonances in
the 31P{1H} NMR spectrum, composed by doublets at 16.9 and
133.6 ppm with JPP = 71 Hz. This coupling constant is higher
than values observed for complexes 1, which range between 35
and 58 Hz. In addition, the presence of an allyl ligand is
evidenced by resonances for the terminal CH2 groups. Thus, in
the 1H NMR spectrum signals at 2.00, 2.30, 2.70, and 3.98 ppm
are observed, while the corresponding carbons appear in the
13C{1H} NMR experiment as a broad singlet at 42.1 ppm and a
broad doublet centered at 74.1 ppm (JCP = 22 Hz). The
assignment of these resonances has been further confirmed by a
13C−1H HMQC experiment. Considering the 2JCP value for the
doublet, this signal can tentatively be assigned to a terminal
carbon in a position trans to a phosphine group. Confirmation
of this structural proposal has been provided by a X-ray
diffraction study (Figure 7). Complex 3h displays a distorted-
octahedral structure with the two phosphorus atoms, the
oxygen of the phenoxide, and an allyl terminal carbon in the
equatorial plane. Accordingly, the remaining terminal carbon of
the allyl group and the coordinated Cl atom are placed in axial
positions. As observed before, the Ru−P bond distance of the
phosphite is shorter than that of the phosphine (2.161 and
2.306 Å, respectively). Moreover, the value of the Ru−Cl bond
distance (2.492 Å) is in the typical range for Ru complexes with
this halo-phenoxy ligand. A notable feature of this structure is
the asymmetric bonding of the allyl ligand, evidenced by a
substantial difference in distances between the Ru and the
terminal allyl carbon atoms. Thus, a bond length of 2.134 Å is
observed for Ru(1)−C(53), while the Ru(1)−C(55) bond
distance is 2.302 Å. As reference values, it can be mentioned
that the differences between the Ru−CH2 bond distances in 1a
are much smaller (0.03−0.05 Å). In addition, the C(54)−
C(55) bond is shorter than C(53)−C(54) (1.397 and 1.445 Å,
respectively). These bonds are shorter and longer, respectively,
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than C(terminal)−C(central) bonds in 1a. Overall, these data
can be interpreted in terms of a more pronounced σ
component for the Ru(1)−C(53) bond, while the ruthenium
interaction with C(54) and C(55) atoms resembles an olefin−
metal interaction. Moreover, these considerations are in good
agreement with the low-field shift of the resonance of the
terminal carbon trans to the phosphine from the typical range
observed in compounds 1 (ca. 35−45 ppm).
conditions. Attempts at room temperature under hydrogen
pressures between 4 and 20 atm, in MeOH or PrOH (entries
1−3, Table 2), did not show conversion. Alternatively, when
i
In addition, protonation reactions with tiglic acid (5a) have
also been examined, as the removal of allyl ligands is expected
in the hydrogenation of unsaturated acids (see below). For
instance, complex 1h reacted slowly with 5a at room
temperature, while at 50 °C the reaction proceeded at a
appreciable rate. After a 12 h heating period complete
conversion into the corresponding bis-tiglate 4h was observed
(Scheme 2).19 The complex is characterized by two doublets in
the 31P{1H} NMR spectrum centered at ca. 144 and 51 ppm
(JPP = 79 Hz). On the other hand, one singlet for each tBu and
a
Table 2. Hydrogenation of 5a using Complex 1h
P(H2)
conversn
(%)
entry
1
S/C
temp (°C)
(atm)
solvent
MeOH
100 room
4
20
20
0
0
0
temp
room
temp
room
temp
2
3
MeOH
iPrOH
MeOH
1
one group of signals for each tiglate were observed in the H
4
5
40
40
4
4
100
100
NMR spectrum. Moreover, 4h displays fluxional behavior in
MeOH/CH2Cl2
(1/1)
1
solution. Then, cross-peaks in the H−1H EXSY experiment
t
6
7
8
500 40
1000 40
100 50
4
4
4
MeOH/CH2Cl2
(1/1)
100
100
0
between the olefin proton signals of the tiglates, between Bu
group singlets at positions 3 and 3′, as well as between those at
positions 5 and 5′, were detected. These observations can be
explained by the existence of an atropisomerization of the
phosphite group, already mentioned for 1h, although tiglate
migration with a concomitant switch in metal configuration, as
discussed for 1c, may also take place. On the other hand, the
protonation of allyl 1a with 5a at 50 °C has been monitored by
31P{1H} NMR. These spectra show the disappearance of both
isomers of 1a while two new species appeared. The
predominant one is characterized by two doublets centered at
141.6 and 48.4 ppm (JPP = 81 Hz). The minor species shows a
MeOH/CH2Cl2
(1/1)
CH2Cl2
a
All hydrogenations were completed under the conditions specified.
Reactions were carried out at room temperature with an initial
hydrogen pressure of 4 bar. Reaction time 24 h. The conversion was
1
determined by H NMR.
the reaction was performed at 40 °C, complete conversion was
observed in MeOH (entry 4). As the solubility of 1h in MeOH
is low, a MeOH/CH2Cl2 (1/1) mixture was also tested at 40
°C. Complete conversion was observed again (entry 5). This
solvent mixture provides a rather active catalyst able to
complete reactions at S/C values of 500 and 1000 in 24 h
(entries 6 and 7). In contrast, no conversion was observed in
pure CH2Cl2 at 50 °C (entry 8). The performance of 1a in the
hydrogenation of 5a was next examined. The data obtained
showed a dramatic influence of the solvent on enantioselectivity
similar pattern with two doublets at 144.2 and 50.0 ppm (JPP
=
80 Hz). At the final stage of the reaction the minor species
disappeared and only the major compound was observed. This
compound (4a) has been fully characterized, and the data
obtained are in accord with a bis-tiglate formulation. Upon
comparison with the formation of 4h, a reasonable proposal for
the less thermodynamically stable, minor species observed
during the generation of 4a is a diastereomer differing in metal
configuration.
i
(Table 3). Thus, complete conversions in MeOH and PrOH
a
In relation with the application of allyl complexes 1 in
catalytic hydrogenation, we have also explored their reactivity
under hydrogen pressure. Thus, when a solution of 1h in C6D12
is heated at 60 °C under 2 atm of hydrogen, no reaction was
observed after 12 h. In contrast, addition of 5a starts the allyl
activation and the hydrogenation reaction (see below).
Moreover, when compound 1a was dissolved in CD2Cl2 and
heated at 60 °C under hydrogen, reaction of the allyl complex
was observed, leading to a mixture in which several hydride
species were observed. No further characterization of these
species has been achieved, due to the complexity of this system.
We do note, however, the presence of a quintet at 3.0 ppm with
Table 3. Hydrogenation of 5a using Complex 1a
entry temp (°C)
solvent
MeOH
conversn (%) ee (%) (confign)
1
2
3
4
5
6
40
40
40
40
60
60
100
100
100
53
20 (R)
23 (R)
39 (R)
77 (R)
77 (R)
82 (R)
THF/MeOH (1/3)
iPrOH
n-hexane
n-hexane
100
75
b
n-hexane
a
Reactions were carried with an initial hydrogen pressure of 4 bar at S/
C = 100, unless otherwise stated. Reaction time 24 h. The conversion
1
was determined by H NMR and enantiomeric excess (ee) by chiral
1
GC. The configuration was determined by comparison of optical
a coupling constant of 1.7 Hz in the H NMR spectra. This
b
rotations with literature values.21a Reaction at S/C = 1000.
signal is attributable to CD2HCl and points to the participation
of ruthenium chlorides in this reaction.20
Asymmetric Hydrogenation of Unsaturated Acids. We
next studied the performance of bis-allyl complexes 1 in the
catalytic hydrogenation of 5a and (E)-2-methyl-2-pentenoic
acid (5b) as representative examples of prochiral α,β-
unsaturated acids (eq 1).21 Initially, a set of hydrogenations
of 5a with 1h was prepared to find appropriate reaction
were observed, although the enantioselectivities were low (20
and 39% ee, respectively, entries 1 and 3). Complete
conversion and low ee values were likewise observed in a
THF/MeOH mixture (entry 2). On the other hand,
enantioselectivity increased up to 77% ee in n-hexane (entry
4). However, the reaction in this solvent is slower under these
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i
conditions and conversion was only moderate. An increase in
temperature to 60 °C produced a complete conversion without
erosion of enantioselectivity (entry 5). The use of a lower
catalyst loading (S/C = 1000) also produced a good value of
conversion and a small increase in enantioselectivity (entry 6).
Interestingly, 1a showed poor performance in alcoholic
solvents, which are usually the solvents of choice for the Ru-
catalyzed hydrogenation of unsaturated acids.21 This observa-
tion can be attributed to the detrimental role of an alcohol in
the catalytic cycle, as well as to a reduced stability of the chiral
phosphite group under the reaction conditions.
selectivity values were observed in MeOH and PrOH (entries
1 and 3), while almost no reaction was observed in CH2Cl2
(entry 2). Moreover, an important increase in enantioselectivity
up to 77% ee was observed in n-hexane (entry 6). The results
with 4a reproduce well the solvent effect observed with 1a in
terms of both conversion and enantioselectivity. Therefore, as
expected, both precatalysts should lead to the same catalyst.
However, despite allyl activation not being needed in the case
of 4a, any differences in reaction rate do not lead to enhanced
conversion after 24 h when comparing 1a and 4a (entry 4,
Table 3, and entry 6, Table 5).
The influence of the P-OP ligand in the hydrogenation of 5a
was next investigated by comparing the performance of
complexes 1 (Table 4). The results obtained indicate that all
In a complementary experiment, the hydrogenation of 5a (4
equiv) with 1h under 2 atm of hydrogen in C6D12 at 60 °C was
monitored. After 14 h, the reaction mixture displayed signals of
tiglate 4h and unreacted 1h in a 1/1 approximate ratio. As the
reaction proceeded, disappearance of the signals of 5a was
a
Table 4. Hydrogenation of Acids 5 using Complexes 1
1
observed in the H NMR spectra. Moreover, no signals were
entry
substrate
cat. precursor
conversn (%)
ee (%) (confign)
detected in the hydride region. In addition, the 31P{1H} NMR
spectra showed several overlapped signals around 148.0 and
58.5 ppm. These chemical shift values are similar to those of the
bis-tiglate 4h and can be assigned to carboxylate species of
formula Ru(O2CCCH-Me)n(O2CCHCH2Me)2−n (2h; n = 0,
1).22
1
2
3
4
5
6
7
8
5a
5a
5a
5a
5a
5a
5a
5b
1a
1c
1d
1f
100
37
77 (R)
55 (R)
65 (R)
41 (S)
87 (S)
67 (R)
77 (R)
89 (S)
100
20
1g
1i
100
100
66
The broadly accepted mechanism for the hydrogenation of
acrylic acids with Ru diphosphine catalysts proposes that the
hydrogen atom delivered at position 2 comes from the gas
phase (through a Ru hydride), whereas the atom at position 3
results from a protonation step produced by the solvent or the
carboxylic acid at low hydrogen pressures. Moreover, at higher
pressures competitive hydrogenolysis also takes place.23 In
addition, exchange between hydrogen gas and acid protons has
been observed.22,23a The present system also shows this
exchange. Then, in a deuteration experiment of 5a catalyzed
by 1a (4 atm D2, S/C = 100, 60 °C, C6D12), extensive labeling
of the carboxylic position (MeCHC(Me)COOH/MeCH
C(Me)COOD ratio 0.1/1.0) was observed after 6 h. After this
reaction time no reduced product was detected. In a parallel
reaction run, a 60% conversion was observed after 24 h, the
product obtained being fully deuterated at positions 2 and 3, as
well as at the carboxylic group. Deuteration at position 3 can
reasonably be ascribed to protonation by MeCHC(Me)-
COOD, as proposed before in the hydrogenation of 5a in
supercritical CO2.24
1j
1g
100
a
Reactions were carried with an initial hydrogen pressure of 4 bar at S/
C = 100 in n-hexane at 60 °C. Reaction time 24 h. The conversion was
1
determined by H NMR and enantiomeric excess (ee) by chiral GC.
The configuration was determined by comparison of optical rotations
with literature values.21a
catalyst precursors based on diarylphosphino groups, except 1f,
gave full conversion. On the other hand, for dialkylphosphino
derivatives, only 1g gave full conversion. In addition, this
catalyst precursor gave the best enantioselectivity of the series
(87% ee, entry 5). Likewise, this catalyst precursor hydro-
genates 5b with a good value of enantioselectivity (89% ee,
entry 8). From a practical point of view we were interested to
examine catalyst precursor 1j, which due to a straightforward
preparation of the BINOL phosphine-phosphite 2j is easier to
obtain than 1g. Unfortunately, 1j was less active and
enantioselective than 1g (entries 7 and 5).
Considering the slow release of allyl ligands in the reaction
between complexes 1 and 5a, we were interested in comparing
the performance of 1a and 4a in 5a hydrogenation. A series of
reactions in different solvents were prepared (Table 5). As
observed before with 1a, complete conversion but low
ROMP Reaction of Norbornene. Another interesting
application of Ru bis-allyl complexes is with regard to their use
as catalyst precursors for the ROMP reaction (eq 2).2 More
a
Table 5. Hydrogenation of 5a using Tiglate 4a
entry
temp (°C)
solvent
conversn (%)
ee (%) (confign)
specifically, the Leitner group described the behavior of bis-allyl
complexes bearing highly basic chelating trialkylphosphine in
the ROMP reaction of norbornene.2a Interestingly, this reaction
proceeds without an additional activator and the formation of
the requisite metallacyclobutane species from the Ru(η3-2-
MeC3H4)2 moiety is proposed. Inspired by this study, we were
interested on examining the performance of allyl complexes 1
in the ROMP reaction of norbornene.
A series of ROMP reactions of norbornene indicated that
compounds 1 led to active catalysts in this reaction (Table 6).
However, conversions were generally low and only 1g gave a
good value (74%, entry 4). Polymeric materials obtained from
1
2
3
4
5
6
40
MeOH
CH2Cl2
iPrOH
100
3
19 (R)
nd
40
40
100
3
30 (R)
nd
40
benzene
n-hexane
n-hexane
room temp
40
0
nd
69
77 (R)
a
Reactions were carried with an initial hydrogen pressure of 4 bar at S/
C = 100 in n-hexane at 60 °C. Reaction time 24 h. The conversion was
determined by H NMR and enantiomeric excess (ee) by chiral GC.
1
The configuration was determined by comparison of optical rotations
with literature values.21a
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a
slow and only a small part of the Ru allyl precursor acts as a
catalyst.
Table 6. ROMP Reaction of Norbornene with Complexes 1
entry
precursor
yield (%)
trans (%)
Mn
PDI
1
2
3
1a
1c
1f
6
24
18
74
4
79
70
67
78
79
70
36 900
8 300
2.3
3.3
3.6
2.8
1.4
4.2
EXPERIMENTAL SECTION
■
General Procedures. All reactions and manipulations were
performed under nitrogen or argon, either in a Braun Labmaster
100 glovebox or using standard Schlenk-type techniques. All solvents
were distilled under nitrogen with the following desiccants: sodium
benzophenone ketyl for diethyl ether and tetrahydrofuran (THF),
sodium for hexanes and toluene, CaH2 for dichloromethane, and
NaOMe for methanol. Phosphine-phosphite ligands 2 were prepared
as described previously.12 [Ru(η3-2-MeC3H4)2(COD)] was synthe-
sized according to a literature procedure.13 All other reagents were
purchased from commercial suppliers and used as received. NMR
spectra were obtained on Bruker DPX-300, DRX-400, and DRX-500
spectrometers. 31P{1H} NMR shifts were referenced to external 85%
16 200
4 800
bc
,
4
5
6
1g
1h
1i
41 600
6 400
10
a
Reactions were carried out at 40 °C in CH2Cl2 ([norbornene] = 0.35
M), at S/C = 100. The reaction time was 24 h, unless otherwise stated.
% trans: percentage of trans olefinic bonds as determined by 1H NMR.
PDI: polydispersity index (Mw/Mn). Mn and PDI values were
determined by GPC (CHCl3). The obtained polymers are completely
soluble in CHCl3, unless otherwise noted. The reaction time was 7 h.
The product was not fully soluble in CHCl3; % trans, Mn, and PDI
b
c
1
H3PO4, while 13C{1H} and H shifts were referenced to the residual
values refer to the soluble part in CHCl3.
signals of deuterated solvents. All data are reported in ppm downfield
from Me4Si. All NMR measurements were carried out at 25 °C, unless
otherwise stated. maj and min denote major and minor diastereomers,
respectively. GC analyses were performed by using a Hewlett-Packard
Model HP 6890 chromatograph. HRMS data were obtained on a
JEOL JMS-SX 102A mass spectrometer, and ESI-MS experiments
were carried out in a Bruker 6000 apparatus by the Mass Spectrometry
Services of the Universidad de Sevilla (CITIUS) and Instituto de
these reactions were characterized by IR and NMR spectros-
copy as polynorbornene.25 Depending on the P-OP ligand the
cis/trans ratio ranges from 67% produced by 1f (entry 3) to
79% obtained in the reactions performed with 1a and 1h
(entries 1 and 5). Moreover, molecular weights of the obtained
polymers also depend on the P-OP ligand, although they are
significantly lower than those obtained by Leitner (Mn = 210
000−381 000). In addition, broad molecular weight distribu-
tions, indicated by the high polidispersity index (PDI) values,26
were obtained. Along the series, higher molecular weight and
lower PDI were obtained with precatalysts 1a,h. An interesting
aspect is the ratio of ruthenium complex acting as polymer
initiator. Considering the yield and the molecular weight of the
polymers obtained, it is apparent that only small parts of the Ru
species act as polymerization initiators.27 This amount is as low
́
Investigaciones Quimicas (IIQ), respectively. Elemental analyses were
run by the Analytical Service of the IIQ in a Leco CHNS-932
elemental analyzer. Optical rotations were measured on a Perkin-
Elmer Model 341 polarimeter. IR spectra were acquired on a Bruker
Vector 22 instrument. Gel permeation chromatography (GPC)
analyses were performed using a Waters apparatus equipped with a
Waters 2414 refractive index detector and two Styragel HR columns
(7.8 × 300 mm) linked in series, thermostated at 60 °C, and using
CHCl3 as the mobile phase at a flow rate of 0.5 mL/min. Molecular
weights were estimated against polystyrene standards.
[Ru(η3-2-MeC3H4)2(2a)] (1a). A solution of [Ru(η3-2-
MeC3H4)2(COD)] (0.096 g, 0.30 mmol) and 2a (0.200 g, 0.30
mmol) in n-hexane (5 mL) was refluxed for 9 h, and the solvent was
removed under vacuum. The resulting residue was washed with
MeOH (3 × 5 mL), yielding the desired product as a 6/1 mixture of
1
as 1% in the case of 1a,h. Moreover, H NMR monitoring of a
reaction performed at S/C = 10 with 1g only showed signals for
starting allyl, unreacted norbornene, and polymer. Therefore,
only a small part of the starting allyl should be responsible for
the catalysis and the rate of chain propagation is therefore
higher than that of initiation.
1
two diastereomers (CD2Cl2): white solid (0.175 g, 66%). H NMR
(CD2Cl2, 500 MHz): δ 0.86 (br s, 1H, MeC(CHH)2 (maj)), 0.89 (m,
1H, MeC(CHH)2 (min)), 0.98 (s, 9H, CMe3 (maj)), 1.10 (m, 2H,
MeC(CHH)2 (maj) + MeC(CHH)2 (min)), 1.15 (s, 9H, CMe3
(min)), 1.17 (s, 9H, CMe3 (min)), 1.24 (m, 1H, MeC(CHH)2
(maj)), 1.26 (s, 9H, CMe3 (maj)), 1.34 (m, 2H, MeC(CHH)2
(maj) + MeC(CHH)2 (min)), 1.43 (br s, 1H, MeC(CHH)2 (maj)),
1.44 (m, 1H, MeC(CHH)2 (min)), 1.55 (s, 3H, Ar-Me (maj)), 1.58 (s,
3H, Ar-Me (min)), 1.61 (s, 3H, Ar-Me (min)), 1.62 (d, 3JHP = 15.5 Hz,
1H, MeC(CHH)2 (maj)), 1.67 (m, 1H, MeC(CHH)2 (min)), 1.76 (s,
3H, MeC(CH2)2 (min)), 1.81 (s, 3H, Ar-Me (maj)), 1.86 (s, 3H,
MeC(CH2)2 (maj)), 1.98 (m, 1H, MeC(CHH)2 (min)), 2.03 (s, 3H,
MeC(CH2)2 (min)), 2.04 (s, 3H, MeC(CH2)2 (maj)), 2.21 (s, 3H, Ar-
Me (maj)), 2.23 (s, 3H, Ar-Me (min)), 2.25 (s, 3H, Ar-Me (min)),
2.27 (s, 3H, Ar-Me (maj)), 2.37 (br s, 1H, MeC(CHH)2 (min)), 2.45
(br s, 1H, MeC(CHH)2 (maj)), 2.79 (br s, 1H, MeC(CHH)2 (min)),
2.88 (br, 1H, MeC(CHH)2 (maj)), 6.67 (dd, 3JHP = 8.0 Hz, 3JHH = 8.0
Hz, 1H, H arom (min)), 6.74 (dd, 3JHP = 8.0 Hz, 3JHH = 8.0 Hz, 2H, 2
CONCLUSIONS
■
A series of Ru allyl complexes of formulation [Ru(η3-2-
MeC3H5)2(P-OP)] has been prepared and characterized. These
compounds exist as mixtures of two diastereomers which differ
in the configuration at the metal, the preferred configuration
and the ratio between maj and min isomers being dependent
on the P-OP ligand. Allyl ligand protonation with 5a and
pentachlorophenol has been studied, and these reactions lead
to the corresponding bis-tiglate and monoallyl phenoxy
derivatives.
Complexes 1 are effective catalysts for the hydrogenation of
α,β-unsaturated acids. This reaction has shown the important
influence of the solvent, and the best results are obtained in n-
hexane. Optimization of the catalytic system by tuning the
reaction conditions and selecting the appropriate P-OP ligand
has allowed the reduction of these substrates with enantiose-
lectivities up to 89% ee. Moreover, deuteration studies and
hydrogenation monitoring by NMR indicate a behavior similar
to that exhibited by diphosphine derivatives.
3
3
H arom (maj)), 6.79 (dd, JHP = 8.0 Hz, JHH = 8.0 Hz, 1H, H arom
(maj)), 6.90 (m, 1H, H arom (maj)), 6.95 (s, 1H, H arom (maj)), 7.02
3
(t, JHH = 7.5 Hz, 1H, H arom (maj)), 7.06 (s, 1H, H arom (min)),
7.10 (s, 1H, H arom (min)), 7.17−7.30 (m, 5H, 5 H arom (maj)),
7.43 (m, 3H, 3 H arom (maj)), 7.54 (dd, 3JHP = 8.0 Hz, 3JHH = 8.0 Hz,
2H, 2 H arom (min)), 7.58 (dd, 3JHP = 8.0 Hz, 3JHH = 8.0 Hz, 2H, 2 H
arom (maj)). 31P{1H} NMR (CD2Cl2, 202 MHz): major δ 42.3 (d, P−
C), 168.4 (d, P−O, JPP = 40 Hz); minor δ 40.2 (d, P−C), 154.3 (d, P−
O, JPP = 47 Hz). 13C{1H} NMR (CD2Cl2, 126 MHz): major δ 16.0
(Ar-Me), 16.4 (Ar-Me), 19.8 (Ar-Me), 20.5 (Ar-Me), 25.4 (MeC-
(CH2)2), 26.6 (MeC(CH2)2), 31.7 (CMe3), 32.1 (CMe3), 35.0
Finally, compounds 1 are also active in the ROMP reaction
of norbornene, although they are less active than their bis-allyl
diphosphine counterparts. In this reaction, the initiation step is
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Organometallics
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(CMe3), 35.9 (CMe3), 36.7 (MeC(CH2)2), 39.2 (dd, JCP = 21 Hz, JCP
= 5 Hz, MeC(CH2)2), 44.2 (MeC(CH2)2), 45.8 (dd, JCP = 46 Hz, JCP
= 4 Hz, MeC(CH2)2), 98.6 (MeC(CH2)2), 100.9 (MeC(CH2)2), 124.5
(d, JCP = 5 Hz, CH arom), 124.5 (CH arom), 128.0 (d, JCP = 9 Hz, CH
arom), 128.1 (CH arom), 128.2 (CH arom), 128.2 (CH arom), 128.3
(CH arom), 130.1 (CH arom), 130.1 (d, JCP = 5 Hz, CH arom), 130.2
(CH arom), 130.8 (CH arom), 131.0 (Cq arom), 132.0 (Cq arom),
128.3 (CH arom), 128.6 (CH arom), 129.5 (2 CH arom), 129.6 (m, 3
Cq arom), 130.6 (CH arom), 130.8 (CH arom), 131.2 (2 Cq arom),
131.5 (Cq arom), 131.6 (Cq arom), 134.5 (Cq arom), 134.9 (Cq arom),
135.4 (2 Cq arom), 135.5 (2 Cq arom), 136.4 (2 Cq arom), 136.7 (Cq
arom), 137.3 (Cq arom), 146.8 (d, JCP = 6 Hz, Cq arom (maj)), 147.0
(d, JCP = 10 Hz, Cq arom (min)), 147.6 (d, JCP = 16 Hz, Cq arom
(maj)), 149.1 (d, JCP = 15 Hz, Cq arom (min)), 156.0 (m, Cq arom
(maj) + Cq arom (min)). MS (ESI, THF): m/z 748.2 ([M]+, 100).
Fragmentation of ion m/z 748.2: 638.1 ([M − 2C4H7]+, 100). Anal.
Calcd for C40H56O3P2Ru: C, 64.2; H, 7.6. Found: C, 64.2; H, 8.0.
[Ru(η3-2-MeC3H4)2(2d)] (1d). A solution of [Ru(η3-2-
MeC3H4)2(COD)] (0.046 g, 0.13 mmol) and 2d (0.094 g, 0.13
mmol) in n-hexane (3 mL) was refluxed for 5 h, and the solvent was
removed under vacuum. The resulting mixture was cooled to 0 °C, and
the precipitated solid was filtered off and washed with cold n-hexane (2
× 2 mL). Compound 1d was isolated as a 4/1 mixture of two
diastereomers (CD2Cl2): white solid (0.069 g, 57%). Due to the low
proportion of the minor diastereomer, only signals assignable to the
132.5 (CH arom), 132.5 (d, JCP = 8 Hz, 2 CH arom), 133.8 (dd, JCP
=
44 Hz, JCP = 3 Hz, Cq arom), 134.3 (Cq arom), 135.0 (Cq arom), 135.1
(Cq arom), 135.2 (Cq arom), 135.5 (Cq arom), 137.5 (Cq arom), 137.9
(d, JCP = 13 Hz, 2 CH arom), 147.2 (d, JCP = 9 Hz, Cq arom), 147.3
(d, JCP = 9 Hz, Cq arom), 155.2 (d, JCP = 10 Hz, Cq arom). Due to
spectrum complexity and low signal intensities, 2 Cq atoms could not
be assigned. MS (ESI, 2-propanol): m/z 872 ([M]+, 100), 817 ([M −
C4H7]+, 16). Fragmentation of ion m/z 872: 762 ([M − 2C4H7]+,
100). Anal. Calcd for C50H60O3P2Ru: C, 68.9; H, 6.9. Found: C, 68.8;
H, 7.2.
[Ru(η3-2-MeC3H4)2(2c)] (1c). A solution of [Ru(η3-2-
MeC3H4)2(COD)] (0.063 g, 0.20 mmol) and 2c (0.100 g, 0.20
mmol) in n-hexane (5 mL) was refluxed for 9 h. The resulting mixture
was cooled to −10 °C, and the precipitated solid was filtered off and
washed with cold n-hexane (2 × 2 mL). Compound 1c was isolated as
a 1.3/1 mixture of two diastereomers (CD2Cl2): white solid (0.070 g,
50%). 1H NMR (CD2Cl2, 500 MHz): δ 0.78 (dd, 3JHP = 18.0 Hz, 3JHP
= 9.0 Hz, 1H, MeC(CHH)2 (maj)), 0.80 (s, 1H, MeC(CHH)2 (min)),
1
major isomer are reported. H NMR (C6D6, 500 MHz): δ 1.26 (m,
2H, 2 MeC(CHH)2), 1.27 (s, 9H, CMe3), 1.55 (s, 3H, Ar-Me), 1.59 (s,
9H, CMe3), 1.63 (s, 3H, Ar-Me), 1.74 (m, 2H, 2 MeC(CHH)2), 1.89
(m, 4H, MeC(CHH)2 + MeC(CH2)2), 1.93 (s, 6H, 2 PAr-Me), 2.05
(s, 3H, Ar-Me), 2.09 (s, 3H, Ar-Me), 2.11 (s, 6H, 2 PAr-Me), 2.14 (m,
1H, MeC(CHH)2), 2.22 (s, 3H, MeC(CH2)2), 2.91 (br s, 1H,
MeC(CHH)2), 3.44 (br s, 1H, MeC(CHH)2), 6.67 (s, 1H, H arom),
6.75 (m, 3H, 3 H arom), 6.81 (s, 1H, H arom), 6.88 (m, 1H, H arom),
6.97 (m, 1H, H arom), 7.11 (s, 1H, H arom), 7.17 (m, 1H, H arom),
7.37 (s, 1H, H arom), 7.60 (d, 3JHP = 9.3 Hz, 2H, 2 H arom). 31P{1H}
NMR (CD2Cl2, 121 MHz): major δ 41.3 (d, P−C), 168.5 (d, P−O, JPP
= 40 Hz); minor δ 39.4 (d, P−C), 154.3 (d, P−O, JPP = 47 Hz).
13C{1H} NMR (C6D6, 202 MHz): δ 15.9 (Ar-Me), 16.3 (Ar-Me), 19.5
(Ar-Me), 20.2 (Ar-Me), 21.0 (2 PAr-Me), 21.2 (2 PAr-Me), 25.3
(MeC(CH2)2), 26.2 (MeC(CH2)2), 31.6 (CMe3), 32.3 (CMe3), 34.9
(CMe3), 35.9 (CMe3), 36.9 (MeC(CH2)2), 38.9 (dd, JCP = 21 Hz, JCP
= 6 Hz, MeC(CH2)2), 44.5 (MeC(CH2)2), 46.0 (dd, JCP = 46 Hz, JCP
= 4 Hz, MeC(CH2)2), 98.0 (MeC(CH2)2), 101.0 (MeC(CH2)2), 124.1
(d, JCP = 5 Hz, CH arom), 124.6 (d, JCP = 3 Hz, CH arom), 128.3 (CH
arom), 128.4 (CH arom), 128.9 (Cq arom), 129.8 (CH arom), 130.0
(CH arom), 130.1 (2 CH arom), 130.2 (CH arom), 130.3 (CH
arom), 130.7 (Cq arom), 131.3 (dd, JCP = 43 Hz, JCP = 9 Hz, Cq arom),
131.7 (Cq arom), 131.8 (d, JCP = 46 Hz, Cq arom), 133.6 (d, JCP = 41
Hz, Cq arom), 134.4 (Cq arom), 134.6 (Cq arom), 134.8 (m, 2 Cq
arom), 135.7 (CH arom), 135.8 (CH arom), 136.9 (Cq arom), 137.0
(Cq arom), 137.0 (Cq arom), 137.1 (Cq arom), 137.7 (Cq arom), 147.3
(d, JCP = 8 Hz, Cq arom), 147.4 (d, JCP = 15 Hz, Cq arom), 155.4 (d,
JCP = 12 Hz, Cq arom). MS (ESI, THF): m/z 928 ([M]+, 100).
Fragmentation of ion m/z 928: 818 ([M − 2C4H7]+, 100). Anal. Calcd
for C54H68O3P2Ru: C, 69.9; H, 7.4. Found: C 69.7; H, 7.7.
3
0.84 (s, 1H, MeC(CHH)2 (maj)), 0.91 (d, JH3P = 15.5 Hz, 1H,
3
MeC(CHH)2 (min)), 0.95 (dd, JHP = 18.0 Hz, JHP = 9.0 Hz, 1H,
2
MeC(CHH)2 (maj)), 1.00 (s, 9H, CMe3 (maj)), 1.02 (d, JHP = 7.0
3
3
Hz, 3H, PMe (maj)), 1.12 (dd, JHP = 21.0 Hz, JHP = 4.0 Hz, 1H,
MeC(CHH)2 (maj)), 1.14 (d, 2JHP = 7.0 Hz, 3H, PMe (min)), 1.18 (s,
9H, CMe3 (min)), 1.30 (br s, 1H, MeC(CHH)2 (maj)), 1.37 (m, 1H,
3
MeC(CHH)2 (min)), 1.37 (s, 9H, CMe3 (min)), 1.47 (d, JHP = 14.0
3
Hz, 1H, MeC(CHH)2 (min)), 1.48 (d, JHP = 14.0 Hz, 1H,
MeC(CHH)2 (maj)), 1.54 (s, 3H, Ar-Me (maj)), 1.59 (s, 9H, CMe3
(maj)), 1.69 (s, 3H, Ar-Me (min)), 1.72 (s, 3H, Ar-Me (min)), 1.75 (s,
3H, MeC(CH2)2 (min)), 1.80 (s, 3H, MeC(CH2)2 (maj)), 1.83 (s,
2
3H, Ar-Me (maj)), 1.84 (d, JHP = 7.0 Hz, 6H, PMe (maj) + PMe
(min)), 1.88 (s, 3H, MeC(CH2)2 (min)), 1.90 (s, 3H, MeC(CH2)2
(maj)), 1.90 (m, 1H, MeC(CHH)2 (min)), 2.03 (br s, 1H,
3
MeC(CHH)2 (maj)), 2.05 (d, JHP = 12.0 Hz, 1H, MeC(CHH)2
(min)), 2.20 (s, 3H, Ar-Me (maj)), 2.21 (s, 3H, Ar-Me (min)), 2.26 (s,
3H, Ar-Me (maj)), 2.29 (s, 3H, Ar-Me (min)), 2.39 (br s, 1H,
MeC(CHH)2 (min)), 2.75 (br s, 1H, MeC(CHH)2 (min)), 3.00 (br s,
1H, MeC(CHH)2 (maj)), 6.30 (dd, 3JHH = 7.5 Hz, 4JHP = 4.0 Hz, 1H,
3
4
H arom (min)), 6.71 (dd, JHH = 7.5 Hz, JHP = 4.5 Hz, 1H, H arom
(maj)), 6.94 (s, 1H, H arom (maj)), 7.03 (s, 1H, H arom (min)), 7.10
(dd, 3JHH = 7.5 Hz, 3JHH = 7.5 Hz, 1H, H arom (min)), 7.11 (s, 1H, H
arom (min)), 7.17 (m, 2H, H arom (maj) + H arom (min)), 7.22 (s,
1H, H arom (maj)), 7.27 (m, 2H, H arom (maj) + H arom (min)),
[Ru(η3-2-MeC3H4)2(2e)] (1e). This compound was prepared from
phosphine-phosphite 2e by the procedure described for 1a: white solid
(0.038 g, 28%). Complex 1e exists in solution (CD2Cl2) as a mixture
3
3
7.50 (dd, JHP = 7.5 Hz, JHH = 7.5 Hz, 1H, H arom (maj)). 31P{1H}
NMR (CD2Cl2, 202 MHz): major δ 2.5 (d, P−C), 161.7 (d, P−O, JPP
= 50 Hz); minor δ 1.4 (d, P−C), 158.8 (d, P−O, JPP = 52 Hz).
13C{1H} NMR (CD2Cl2, 75 MHz): δ 13.6 (d, JCP = 27 Hz, PMe
(min)), 13.9 (d, JCP = 21 Hz, PMe (maj)), 16.2 (Ar-Me (maj)), 16.5 (2
Ar-Me (min) + Ar-Me (maj)), 19.9 (Ar-Me (maj)), 20.0 (Ar-Me
(min)), 20.3 (Ar-Me (min)), 20.6 (Ar-Me (maj)), 20.7 (d, JCP = 31 Hz,
PMe (maj)), 22.9 (d, JCP = 32 Hz, PMe (min)), 24.8 (MeC(CH2)2
(min)), 26.0 (MeC(CH2)2 (maj)), 26.4 (MeC(CH2)2 (maj)), 27.0
(MeC(CH2)2 (min)), 30.8 (CMe3 (min)), 31.4 (CMe3 (maj)), 32.1
(CMe3 (maj)), 32.2 (CMe3 (min)), 34.7 (CMe3 (min)), 35.0
(MeC(CH2)2 (maj)), 35.1 (CMe3 (maj)), 35.6 (MeC(CH2)2
(min)), 35.9 (CMe3 (maj)), 36.0 (CMe3 (min)), 36.9 (MeC(CH2)2
(min)), 39.8 (MeC(CH2)2 (maj)), 39.9 (dd, JCP = 19 Hz, JCP = 5 Hz,
MeC(CH2)2 (maj)), 42.8 (dd, JCP = 21 Hz, JCP = 4 Hz, MeC(CH2)2
(min)), 45.2 (dd, JCP = 46 Hz, JCP = 4 Hz, MeC(CH2)2 (maj)), 48.2
(dd, JCP = 45 Hz, JCP = 4 Hz, MeC(CH2)2 (min)), 97.9 (MeC(CH2)2
(maj)), 98.9 (MeC(CH2)2 (min)), 100.9 (MeC(CH2)2 (maj)), 101.5
(MeC(CH2)2 (min)), 123.4 (d, JCP = 47 Hz, CH arom (min)), 123.8
(d, JCP = 49 Hz, CH arom (maj)), 127.3 (dd, JCP = 37 Hz, JCP = 8 Hz,
Cq arom), 128.0 (CH arom), 128.2 (CH arom), 128.3 (2 CH arom),
1
of two isomers in a 9/1 ratio. H NMR (CD2Cl2, 500 MHz): δ 0.51
(dd, 3JHP = 19.0 Hz, 3JHP = 8.5 Hz, 1H, MeC(CHH)2), 0.72 (d, 3JHP
=
14.5 Hz, 1H, MeC(CHH)2), 0.94 (s, 9H, CMe3), 1.15 (br s, 1H,
MeC(CHH)2), 1.44 (br s, 1H, MeC(CHH)2), 1.52 (s, 9H, CMe3),
1.55 (s, 3H, Ar-Me), 1.57 (m, 1H, MeC(CHH)2), 1.82 (s, 3H,
MeC(CH2)2), 1.92 (s, 3H, Ar-Me), 1.96 (s, 3H, MeC(CH2)2), 2.17 (d,
2JHP = 7.5 Hz, 3H, PMe), 2.19 (m, 1H, MeC(CHH)2), 2.21 (s, 3H, Ar-
Me), 2.34 (s, 3H, Ar-Me), 2.50 (br s, 1H, MeC(CHH)2), 2.78 (br s,
3
4
1H, MeC(CHH)2), 6.30 (dd, JHH = 7.5 Hz, JHP = 5.0 Hz, 1H, H
3
arom), 6.88 (s, 1H, H arom), 6.92 (m, 1H, H arom), 6.96 (dd, JHP
=
=
7.0 Hz, 3JHH = 7.0 Hz, 2H, 2 H arom), 7.04 (dd, 3JHH = 7.5 Hz, 3JHH
7.5 Hz, 1H, H arom), 7.10−7.28 (m, 5H, 5 H arom). 31P{1H} NMR
(CD2Cl2, 202 MHz): major δ 15.7 (d, P−C), 152.7 (d, P−O, JPP = 51
Hz); minor δ 21.6 (d, P−C), 162.1 (d, P−O, JPP = 46 Hz). 13C{1H}
NMR (CD2Cl2, 101 MHz): δ 16.5 (2 Ar-Me), 19.8 (Ar-Me), 20.2 (Ar-
Me), 22.5 (d, JCP = 32 Hz, PMe), 23.8 (MeC(CH2)2), 26.1
(MeC(CH2)2), 30.2 (CMe3), 31.6 (CMe3), 34.4 (CMe3), 35.2
(CMe3), 38.7 (MeC(CH2)2), 39.8 (MeC(CH2)2), 40.9 (dd, JCP = 19
Hz, JCP = 5 Hz, MeC(CH2)2), 48.6 (dd, JCP = 42 Hz, JCP = 4 Hz,
3560
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Organometallics
Article
MeC(CH2)2), 101.1 (MeC(CH2)2), 102.1 (MeC(CH2)2), 123.2 (CH
arom), 123.8 (CH arom), 127.7 (CH arom), 127.8 (CH arom), 127.9
(CH arom), 128.0 (CH arom), 128.2 (CH arom), 130.9 (2 CH
arom), 132.0 (d, JCP = 7 Hz, 2 CH arom), 133.2 (Cq arom), 134.6 (Cq
arom), 135.2 (Cq arom), 135.7 (Cq arom), 136.3 (2 Cq arom), 137.1
(Cq arom), 137.4 (Cq arom), 141.9 (m, 2 Cq arom), 157.6 (d, JCP = 15
Hz, Cq arom). Because of spectrum complexity and low signal
intensities, three quaternary aromatic carbons of the minor
diastereomer could not be assigned. MS (ESI, THF): m/z 810.3
([M]+, 100). Fragmentation of ion m/z 810.3: 700.1 ([M − 2C4H7]+,
100). Satisfactory elemental analysis could not be obtained for this
compound, due to its high solubility and tendency to retain solvent.
[Ru(η3-2-MeC3H4)2(2f)] (1f). This compound was obtained by
following the procedure described for 1e, as a mixture of two
diastereomers in a 14/1 ratio (CD2Cl2): white solid (0.030 g, 43%).
Due to the low proportion of the minor diastereomer, only signals
arom), 123.0 (CH arom), 123.9 (CH arom), 129.2 (2 CH arom),
129.3 (Cq arom), 129.5 (Cq arom), 129.5 (m, Cq arom), 130.2 (CH
arom), 130.3 (CH arom), 133.3 (Cq arom), 133.5 (Cq arom), 137.1
(Cq arom), 137.5 (Cq arom), 148.0 (d, JCP = 5 Hz, Cq arom), 149.1 (d,
JCP = 14 Hz, Cq arom), 157.1 (d, JCP = 10 Hz, Cq arom). MS (ESI,
THF): m/z 692. 2 ([M]+ , 100). Anal. Calcd for
C36H48O3P2Ru·1/2C6H14: C, 63.7; H, 7.5. Found: C, 63.6; H, 7.4.
[Ru(η3-2-MeC3H4)2(2h)] (1h). This complex was synthesized by
following the procedure described for 1a: white solid (0.118 g, 82%).
3
1H NMR (CDCl3, 300 MHz): δ 0.82 (d, JHP = 13.2 Hz, 1H,
3
3
MeC(CHH)2), 0.98 (s, 9H, CMe3), 1.08 (dd, JHP = 15.7 Hz, JHP
=
9.2 Hz, 1H, MeC(CHH)2), 1.19 (br s, 1H, MeC(CHH)2), 1.33 (s, 9H,
CMe3), 1.34 (s, 9H, CMe33), 1.39 (s, 9H, CMe3), 1.50 (br s, 3H,
3
MeC(CHH)2), 1.66 (dd, JHP = 17.1 Hz, JHP = 4.2 Hz, 1H,
MeC(CHH)2), 1.78 (s, 3H, MeC(CH2)2), 1.81 (m, 1H, MeC-
(CHH)2), 2.05 (s, 3H, MeC(CH2)2), 2.32 (br s, 1H, MeC(CHH)2),
2.73 (br s, 1H, MeC(CHH)2), 6.10 (dd, 3JHH = 7.8 Hz, 4JHP = 4.8 Hz,
1
assignable to the major one are reported. H NMR (CD2Cl2, 500
3
1H, H arom), 6.81 (m, 5H, 5 H arom), 7.02 (td, 3JHH = 6.9 Hz, 4JHH
=
MHz): δ 0.79 (d, JHP = 14.0 Hz, 1H, MeC(CHH)2), 0.90 (br s, 1H,
3
3
1.5 Hz, 1H, H arom), 7.13 (m, 3H, 3 H arom), 7.20 (d, 4JHH = 2.4 Hz,
1H, H arom), 7.30 (d, 4JHH = 2.4 Hz, 1H, H arom), 7.35 (d, 4JHH = 2.4
Hz, 1H, H arom), 7.40 (m, 3H, 3 H arom), 7.62 (m, 2H, 2 H arom).
31P{1H} NMR (CDCl3, 162 MHz): δ 42.4 (d, P−C), 157.5 (d, P−O,
MeC(CHH)2), 1.14 (dd, JHP = 15.5 Hz, JHP = 4.5 Hz, 1H,
3
3
MeC(CHH)2), 1.19 (dd, JHP = 14.5 Hz, JHP = 9.0 Hz, 1H,
MeC(CHH)2), 1.34 (d, 3JHP = 12.3 Hz, 1H, MeC(CHH)2), 1.49 (br s,
1H, MeC(CHH)2), 1.94 (s, 3H, MeC(CH2)2), 1.96 (s, 3H, Ar-Me),
2.04 (s, 3H, Ar-Me), 2.08 (s, 3H, MeC(CH2)2), 2.30 (s, 3H, Ar-Me),
2.36 (s, 3H, Ar-Me), 2.57 (br s, 1H, MeC(CHH)2), 2.84 (br s, 1H,
MeC(CHH)2), 6.63 (d, 3JHH = 8.0 Hz, 1H, H arom), 6.86 (m, 3H, 3 H
arom), 7.02−7.30 (m, 8H, 8 H arom), 7.47 (m, 4H, 4 H arom), 7.69
J
PP = 46 Hz). 13C{1H} NMR (CDCl3, 75 MHz): δ 25.5 (MeC(CH2)2),
25.7 (MeC(CH2)2), 30.8 (CMe3), 30.9 (CMe3), 31.8 (CMe3), 31.8
(CMe3), 34.7 (CMe3), 34.8 (CMe3), 35.5 (CMe3), 36.0 (CMe3), 39.4
2
2
(MeC(CH2)2), 42.1 (MeC(CH2)2), 42.8 (dd, JCP = 27 Hz, JCP = 7
3
3
(dd, JHP = 8.7 Hz, JHH = 8.7 Hz, 2H, 2 H arom). 31P{1H} NMR
(CD2Cl2, 202 MHz): major δ 45.6 (d, P−C), 177.8 (d, P−O, JPP = 44
Hz); minor δ 44.6 (d, P−C), 173.4 (d, P−O, JPP = 58 Hz). 13C{1H}
NMR (CD2Cl2, 126 MHz): δ 17.5 (Ar-Me), 17.6 (Ar-Me), 20.3 (Ar-
Me), 20.4 (Ar-Me), 26.0 (MeC(CH2)2), 26.2 (MeC(CH2)2), 37.2
(MeC(CH2)2), 43.5 (MeC(CH2)2), 44.3 (dd, JCP = 21 Hz, JCP = 5 Hz,
MeC(CH2)2), 48.5 (dd, JCP = 44 Hz, JCP = 4 Hz, MeC(CH2)2), 99.2
(MeC(CH2)2), 101.7 (MeC(CH2)2), 119.7 (CH arom), 119.9 (d, JCP
= 3 Hz, CH arom), 124.3 (d, JCP = 5 Hz, CH arom), 124.5 (CH
arom), 128.0 (CH arom), 128.1 (2 CH arom), 128.3 (CH arom),
128.5 (CH arom), 129.2 (Cq arom), 129.3 (CH arom), 129.4 (CH
arom), 129.5 (Cq arom), 130.5 (CH arom), 130.6 (CH arom), 131.0
(CH arom), 131.8 (CH arom), 131.9 (CH arom), 132.4 (dd, JCP = 40
Hz, JCP = 4 Hz, Cq arom), 133.7 (Cq arom), 134.0 (Cq arom), 135.3
(Cq arom), 135.6 (Cq arom), 137.4 (Cq arom), 137.6 (Cq arom), 138.1
(CH arom), 138.2 (CH arom), 147.4 (d, JCP = 5 Hz, Cq arom), 148.7
(d, JCP = 13 Hz, Cq arom), 155.5 (d, JCP = 11 Hz, Cq arom). MS (ESI,
THF): m/z 760.2 ([M]+, 100). Anal. Calcd for C42H44O3P2Ru: C,
66.4; H, 5.8. Found: C, 66.1; H, 5.8.
Hz, MeC(CH2)2), 48.7 (dd, JCP = 44 Hz, 2JCP = 2 Hz, MeC(CH2)2),
2
99.9 (MeC(CH2)2), 102.3 (MeC(CH2)2), 123.5 (CH arom), 123.8 (d,
JCP = 8 Hz, CH arom), 124.2 (CH arom), 124.5 (CH arom), 127.3
(CH arom), 127.7 (CH arom), 127.8 (CH arom), 127.9 (CH arom),
128.0 (CH arom), 128.2 (CH arom), 128.7 (CH arom), 129.9 (CH
arom), 130.0 (d, JCP = 4 Hz, Cq arom), 130.7 (CH arom), 131.4 (CH
arom), 131.8 (Cq arom), 132.1 (CH arom), 132.2 (CH arom), 134.4
(dd, JCP = 41 Hz, JCP = 1 Hz, Cq arom), 135.1 (Cq arom), 135.5 (Cq
arom), 137.1 (CH arom), 137.2 (CH arom), 138.6 (d, JCP = 1 Hz, Cq
arom), 139.3 (d, JCP = 6 Hz, Cq arom), 145.1 (Cq arom), 145.4 (Cq
arom), 148.3 (d, JCP = 14 Hz, Cq arom), 149.2 (d, JCP = 15 Hz, Cq
arom), 155.9 (d, JCP = 12 Hz, Cq arom). MS (ESI, THF): m/z 928.3
([M]+, 100). Fragmentation of ion m/z 928.3: 818.2 ([M − 2C4H7]+,
100). Anal. Calcd for C54H68O3P2Ru: C, 69.9; H, 7.4. Found: C, 69.9;
H, 7.6.
Ru(η3-2-MeC3H4)2(2i)] (1i). This complex was obtained by
following the procedure described for 1a as a mixture of two
diastereomers in a 2/1 ratio (CD2Cl2): white solid (0.057 g, 43%). 1H
3
NMR (CD2Cl2, 500 MHz): δ 0.21 (d, JHP = 14.0 Hz, 1H,
[Ru(η3-2-MeC3H4)2(2g)] (1g). This compound was obtained by
following the procedure described for 1a, as a single isomer: white
MeC(CHH)2 (maj)), 0.55 (dd, JHP = 16.5 Hz, JHP = 9.0 Hz, 1H,
3
3
3
3
MeC(CHH)2 (min)), 0.73 (dd, JHP = 16.0 Hz, JHP = 8.5 Hz, 1H,
1
3
3
solid (0.040 g, 70%). H NMR (C6D6, 500 MHz): δ 0.78 (dd, JHP
=
=
MeC(CHH)2 (maj)), 0.76 (d, JHP = 14.0 Hz, 1H, MeC(CHH)2
11.0 Hz, 3JHH = 6.5 Hz, 3H, CHMe2), 1.03 (dd, 3JHP = 13.5 Hz, 3JHH
(min)), 0.87 (br s, 1H, MeC(CHH)2 (min)), 0.89 (br s, 1H,
MeC(CHH)2 (maj)), 1.19 (m, 1H, MeC(CHH)2 (min)), 1.22 (s, 9H,
CMe3 (min)), 1.26 (br s, 2H, MeC(CHH)2 (maj) + MeC(CHH)2
(min)), 1.32 (s, 9H, CMe3 (maj)), 1.46 (s, 3H, Ar-Me (maj)), 1.47 (s,
3H, MeC(CH2)2 (maj)), 1.48 (s, 9H, CMe3 (maj)), 1.51 (s, 3H, Ar-Me
(min)), 1.58 (s, 9H, CMe3 (min)), 1.76 (dd, 3JHP = 15.0 Hz, 3JHP = 5.5
Hz, 1H, MeC(CHH)2 (maj)), 1.77 (s, 3H, Ar-Me (min)), 1.81 (s, 3H,
MeC(CH2)2 (min)), 1.85 (s, 3H, Ar-Me (maj)), 1.97 (s, 3H,
MeC(CH2)2 (min)), 1.98 (br s, 1H, MeC(CHH)2 (min)), 2.06 (s,
3H, MeC(CH2)2 (maj)), 2.07 (br s, 1H, MeC(CHH)2 (maj)), 2.15 (d,
3JHP = 13.0 Hz, 1H, MeC(CHH)2 (maj)), 2.19 (s, 3H, Ar-Me (maj)),
2.20 (s, 3H, Ar-Me (min)), 2.22 (s, 6H, Ar-Me (maj) + Ar-Me (min)),
2.24 (m, 1H, MeC(CHH)2 (min)), 2.83 (m, 5H, CH2P (maj) +
CHHP (min) + MeC(CHH)2 (maj) + MeC(CHH)2 (min)), 3.03 (m,
1H, CHHP (min)), 4.50−4.80 (m, 4H, OCH2 (maj) + OCH2 (min)),
6.88 (ddd, 3JHP = 7.5 Hz, 3JHH = 7.5 Hz, 4JHH = 2.0 Hz, 2H, 2 H arom
3
3
7.0 Hz, 3H, CHMe2), 1.13 (dd, JHP = 13.5 Hz, JHH = 7.0 Hz, 3H,
CHMe2), 1.15 (br s, 1H, MeC(CHH)2), 1.21 (dd, 3JHP = 14.5 Hz, 3JHH
= 6.5 Hz, 3H, CHMe2), 1.38 (br s, 1H, MeC(CHH)2), 1.43 (br d, 3JHP
= 12.5 Hz, 1H, MeC(CHH)2), 1.55 (dd, 3JHP = 15.5 Hz, 3JHP = 4.0 Hz,
1H, MeC(CHH)2), 1.70 (dd, JHP = 13.0 Hz, JHP = 9.5 Hz, 1H,
MeC(CHH)2), 1.78 (s, 3H, Ar-Me), 1.79 (m, 4H, Ar-Me + CHMe2),
1.85 (d, 3JHP = 11.5 Hz, 1H, MeC(CHH)2), 1.98 (s, 3H, MeC(CH2)2),
2.00 (s, 3H, Ar-Me), 2.03 (s, 3H, Ar-Me), 2.21 (s, 3H, MeC(CH2)2),
2.71 (m, 1H, CHMe2), 2.92 (br s, 1H, MeC(CHH)2), 3.10 (br s, 1H,
3
3
3
3
MeC(CHH)2), 6.83 (d, JHH = 8.0 Hz, 1H, H arom), 6.90 (t, JHH
=
7.5 Hz, 1H, H arom), 6.96 (d, 3JHH = 8.0 Hz, 1H, H arom), 7.00−7.08
(m, 4H, 4 H arom), 7.34 (d, JHH = 8.5 Hz, 1H, H arom). 31P{1H}
3
NMR (CD2Cl2, 121 MHz): δ 36.5 (d, P−C), 175.0 (d, P−O, JPP = 47
Hz). 13C{1H} NMR (CD2Cl2, 126 MHz, 308 K): δ 17.0 (d, JCP = 5
Hz, CHMe2), 17.4 (2 Ar-Me), 19.1 (CHMe2), 20.1 (d, JCP = 4 Hz,
CHMe2), 20.2 (Ar-Me), 20.4 (Ar-Me), 20.8 (d, JCP = 4 Hz, CHMe2),
22.2 (d, JCP = 15 Hz, CHMe2), 25.5 (MeC(CH2)2), 26.2 (MeC-
(CH2)2), 27.8 (d, JCP = 19 Hz, CHMe2), 35.4 (MeC(CH2)2), 38.2 (d,
JCP = 4 Hz, MeC(CH2)2), 42.5 (dd, JCP = 45 Hz, JCP = 5 Hz,
MeC(CH2)2), 43.7 (dd, JCP = 20 Hz, JCP = 5 Hz, MeC(CH2)2), 98.5
(MeC(CH2)2), 98.6 (MeC(CH2)2), 119.6 (CH arom), 120.0 (CH
3
3
(maj)), 6.96 (s, 1H, H arom (min)), 7.01 (dd, JHP = 7.0 Hz, JHH
=
7.0 Hz, 2H, 2 H arom (min)), 7.07 (s, 1H, H arom (maj)), 7.12 (s,
1H, H arom (maj)), 7.18 (s, 1H, H arom (min)), 7.20 (m, 6H, 3 H
arom (maj) + 3 H arom (min)), 7.43 (m, 6H, 3 H arom (maj) + 3 H
3
4
arom (min)), 7.67 (ddd, JHP = 7.0 Hz, 3JHH = 7.0 Hz, JHH = 2.5 Hz,
2H, 2 H arom (maj)), 7.75 (dd, 3JHP = 7.5 Hz, 3JHH = 7.5 Hz, 2H, 2 H
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Organometallics
Article
arom (min)). 31P{1H} NMR (CD2Cl2, 202 MHz): major: δ 40.1 (d,
P−C), 157.2 (d, P−O, JPP = 35 Hz); min: δ 32.3 (d, P−C), 156.1 (d,
P−O, JPP = 40 Hz). 13C{1H} NMR (CD2Cl2, 101 MHz): δ 15.9 (Ar-
Me (min)), 16.0 (Ar-Me (maj)), 16.2 (Ar-Me (maj)), 16.3 (Ar-Me
(min)), 19.6 (Ar-Me (maj)), 19.9 (Ar-Me (min)), 20.4 (Ar-Me (min)),
20.4 (Ar-Me (maj)), 25.9 (MeC(CH2)2 (min)), 26.3 (MeC(CH2)2
(maj)), 26.4 (MeC(CH2)2 (maj)), 26.5 (MeC(CH2)2 (min)), 30.3
(dd, JCP = 26 Hz, JCP = 11 Hz, CH2P (min)), 31.2 (CMe3 (maj)), 31.3
(CMe3 (min)), 31.8 (dd, JCP = 26 Hz, JCP = 4 Hz, CH2P (maj)), 32.6
(CMe3 (min)), 32.8 (CMe3 (maj)), 34.2 (CMe3 (maj)), 34.8 (CMe3
(min)), 36.1 (CMe3 (min)), 36.3 (MeC(CH2)2 (maj)), 36.7 (CMe3
(maj)), 38.2 (MeC(CH2)2 (min)), 38.9 (MeC(CH2)2 (maj)), 40.2
(MeC(CH2)2 (min)), 40.5 (dd, JCP = 21 Hz, JCP = 5 Hz, MeC(CH2)2
(min)), 46.8 (dd, JCP = 42 Hz, JCP = 4 Hz, MeC(CH2)2 (maj)), 47.3
(d, JCP = 49 Hz, MeC(CH2)2 (min)), 47.8 (d, JCP = 22 Hz,
MeC(CH2)2 (maj)), 63.6 (m, OCH2 (min) + OCH2 (maj)), 99.2
(MeC(CH2)2 (maj)), 99.3 (MeC(CH2)2 (min)), 99.7 (MeC(CH2)2
(maj)), 99.9 (MeC(CH2)2 (min)), 127.7 (CH arom (min) + CH
arom (maj)), 127.8 (CH arom (min) + CH arom (maj)), 127.9 (CH
arom (min) + CH arom (maj)), 128.0 (CH arom (min)), 128.1 (2
CH arom (min) + 2 CH arom (maj)), 128.2 (CH arom (maj)), 128.4
(CH arom (maj)), 129.5 (CH arom (min)), 129.6 (CH arom (min)),
129.6 (CH arom (maj)), 130.7 (d, JCP = 10 Hz, Cq arom (maj)), 131.1
(Cq arom (maj) + Cq arom (min)), 131.3 (Cq arom (maj) + Cq arom
(min)), 131.7 (Cq arom (min)), 132.1 (CH arom (min) + CH arom
(maj)), 132.2 (CH arom (min) + CH arom (maj)), 132.7 (Cq arom
(min)), 133.8 (CH arom (min)), 133.9 (CH arom (min)), 134.2 (CH
arom (maj)), 134.3 (CH arom (maj)), 134.5 (Cq arom (maj)), 135.0
(d, JCP = 6 Hz, Cq arom (maj)), 135.3 (Cq arom (maj)), 136.7 (Cq
arom (maj) + 2 Cq arom (min)), 137.3 (Cq arom (maj)), 137.4 (Cq
arom (min)), 137.5 (Cq arom (maj)), 137.6 (Cq arom (min)), 138.0
(Cq arom (maj)), 138.1 (Cq arom (min)), 146.6 (m, Cq arom (min) +
(d, JCP = 14 Hz, Cq arom), 157.0 (d, JCP = 10 Hz, Cq arom). MS (ESI,
2-propanol): m/z 692.2 ([M]+, 100). Anal. Calcd for C40H44O3P2Ru:
C, 65.3; H, 6.0. Found: C, 65.2; H, 6.0.
[Ru(η2-OC6Cl5)(η3-2-MeC3H4)2(2h)] (3h). A solution of 1h (0.078
g, 0.08 mmol) and pentachlorophenol (0.044 g, 0.17 mmol) in
CH2Cl2 (2 mL) was stirred at room temperature for 5 h. The resulting
mixture was evaporated and recrystallized at −20 °C in n-hexane. The
solid obtained was filtered and washed with n-hexane, giving 3h as a
yellow solid (0.039 g, 41%). 1H NMR (CD2Cl2, 500 MHz): δ 0.92 (s,
9H, CMe3), 1.36 (s, 9H, CMe3), 1.38 (s, 9H, CMe3), 1.56 (s, 9H,
CMe3), 2.00 (br s, 1H, MeC(CHH)2), 2.11 (br s, 3H, MeC(CH2)2),
2.30 (s, 1H, MeC(CHH)2), 2.70 (br s, 1H, MeC(CHH)2), 3.98 (s,
1H, MeC(CHH)2), 5.93 (br s, 1H, H arom), 6.90 (s, 3H, 3H arom),
7.01 (s, 3H, 3H arom), 7.15 (m, 4H, 4H arom), 7.28 (d, JHH = 2.2 Hz,
1H, 1H arom), 7.48 (d, JHH = 2.2 Hz, 1H, 1H arom), 7.52 (s, 3H, 3H
arom), 8.15 (br s, 1H, H arom). 31P{1H} NMR (CD2Cl2, 202.5 MHz):
δ 16.9 (d, P−C), 133.6 (d, P−O, JPP = 71 Hz). 13C{1H} NMR
(CD2Cl2, 202.5 MHz): δ 25.4 (CH3CH), 31.3 (CMe3), 31.6 (br s,
CMe3), 31.7 (CMe3), 31.8 (CMe3), 35.0 (2 CMe3), 35.6 (CMe3), 36.1
(CMe3), 42.5 (br, MeC(CHH)2), 74.0 (d, JCP = 22 Hz, MeC(CHH)2),
114.1 MeC(CHH)2), 120.1 (Cq arom), 121.8 (CH arom), 122.6 (d,
JCP = 4 Hz, Cq arom), 124.1 (CH arom), 124.7 (Cq arom), 125.1 (CH
arom), 125.2 (CH arom), 127.3 (d, JCP = 9 Hz, 2 CH arom), 127.9
(CH arom), 128.1 (d, JCP = 9 Hz, 2 CH arom), 128.3 (Cq arom),
128.6 (CH arom), 129.4 (br, Cq arom), 129.5 (CH arom), 130.3 (CH
arom), 131.0 (Cq arom), 131.9 (Cq arom), 132.2 (Cq arom), 132.6 (d,
JCP = 9 Hz, 2 CH arom), 133.0 (CH arom), 134.3 (Cq arom), 134.6
(Cq arom), 134.8 (d, JCP = 10 Hz, 2 CH arom), 136.1 (CH arom),
138.8 (Cq arom), 139.4 (d, JCP = 5 Hz, Cq arom), 146.3 (Cq arom),
147.1 (Cq arom), 147.5 (d, JCP = 18 Hz, Cq arom), 148.1 (d, JCP = 16
Hz, Cq arom), 157.9 (br, Cq arom), 159.9 (br, Cq arom). Anal. Calcd
for C56H61P2O4Cl5Ru: C, 59.1, H, 5.40. Found: C, 59.0; H, 5.7.
[Ru(η2-O2CC(Me)CHMe)2(2a)] (4a). A solution of 1a (0.056 g,
0.067 mmol) and 5a (0.013 g, 0.13 mmol) in CH2Cl2 (3 mL) was
stirred at 50 °C for 70 h. The resulting mixture was evaporated and
recrystallized in n-hexane. The precipitated solid was filtered and
Cq arom (may)), 147.4 (d, JCP = 6 Hz, Cq arom (min)), 148.5 (d, JCP
=
16 Hz, Cq arom (maj)). One signal corresponding to a quaternary
aromatic carbon of the minor isomer could not be assigned. MS (ESI,
2-propanol): m/z 824.3 ([M]+, 100), 769.2 ([M − C4H7]+, 33).
Fragmentation of ion m/z 824.3: 714.1 ([M − 2C4H7]+, 100).
Satisfactory elemental analysis could not be obtained for this
compound due to its high solubility and tendency to retain solvent.
[Ru(η3-2-MeC3H4)2(2j)] (1j). A solution of [Ru(COD)(η3-2-
MeC3H4)2] (0.065 g, 0.18 mmol) and 2j (0.101 g, 0.18 mmol) in
hexane (3 mL) was refluxed for 5 h. The resulting mixture was cooled
to 0 °C, and the precipitated solid was filtered off and washed with
cold hexane (2 × 2 mL). Compound 1j was isolated as a 16/1 mixture
of two diastereomers (CD2Cl2): white solid (0.070 g, 50%). Due to
the low proportion of the minor diastereomer, only signals assignable
to the major derivative are reported. 1H NMR (CD2Cl2, 500 MHz): δ
0.75 (br s, 1H, MeC(CHH)2), 0.98 (m, 4H, CHMe2 + MeC(CHH)2),
1
washed with n-hexane to give 4a as a yellow solid (0.054 g, 84%). H
NMR (300 MHz, CD2Cl2): δ 0.81 (s, 9 H, CMe3), 1.28 (s, 9 H,
CMe3), 1.39 (s, 3 H, Ar-Me), 1.49 (s, 3 H, CH3C(CO2H)), 1.61 (s,
6H, CH3CH), 1.69 (s, 3H, CH3C(CO2H)), 1.79 (s, 3H, Ar-Me),
2.24 (s, 6H, Ar-Me), 6.34 (bm, 2H, CH3CH), 6.91 (m, 1H, 1H
arom), 7.04 (m, 3H, 3H arom), 7.16 (m, 3H, 3H arom), 7.28 (m, 3H,
3H arom), 7.43 (m, 4H, 4H arom), 7.59 (m, 2H, 2H arom). 31P NMR
(CD2Cl2, 121 MHz): 49.9 (P−C, JPP = 79 Hz), 143.0 (P−O). 13C{1H}
NMR (CD2Cl2, 125.7 MHz): δ 10.7 (CH3C(CO2H)), 10.9
(CH3C(CO2H)), 14.1 (CH3CH), 14.2 (CH3CH), 16.6 (Ar-
Me), 16.8 (Ar-Me), 20.4 (Ar-Me), 20.6 (Ar-Me), 30.8 (br, CMe3), 32.5
(br, CMe3), 34.6 (br, CMe3), 36.2 (br, CMe3), 122.4 (br, CH arom),
123.7 (br, CH arom), 128.1 (CH arom), 128.3 (d, JCP = 9 Hz, 2 CH
arom), 128.7 (d, JCP = 10 Hz, 2 CH arom), 129.9 (br, CH arom),
130.4 (br, CH arom), 130.9 (br, CH arom), 132.0 (Cq), 132.4 (2 Cq),
132.7 (2 Cq), 133.5 (CH3CH), 133.7 (br, 3 CH arom), 134.4
(CH3CH), 135.0 (m, 3 CH arom), 135.2 (Cq), 137.9 (Cq), 138.9
(br Cq), 139.7 (br, Cq), 145.3 (Cq), 147.7 (d, JCP = 16 Hz, Cq), 157.3
(br, Cq), 185.7 (br, CO2), 186.1 (br, CO2). Two signals for Cq atoms
could not be located due to spectrum crowding. HRMS (FAB): m/z
960.2858, [M]+ (exact mass calculated for C52H60O7P2Ru 960.2395).
[Ru(η2-O2CC(Me)CHMe)2(2h)] (4h). A solution of 1h (0.085 g,
0.09 mmol) and 5a (0.018 g, 0.18 mmol) in CH2Cl2 (2 mL) was
stirred at 50 °C for 24 h. The resulting mixture was evaporated and
recrystallized in n-hexane. The solid obtained was filtered and washed
1.12 (dd, 3JHP = 13.8 Hz, 3JHH = 7.1 Hz, 3H, CHMe2), 1.17 (dd, 3JHP
=
3
13.8 Hz, JHH = 7.0 Hz, 3H, CHMe2), 1.19 (m, 1H, MeC(CHH)2),
3
1.34 (m, 5H, CHMe2 + 2 MeC(CHH)2), 1.61 (dd, JHP = 13.5 Hz,
3JHP = 9.7 Hz, 1H, MeC(CHH)2), 1.85 (s, 3H, MeC(CH2)2), 2.04 (s,
3H, MeC(CH2)2), 2.05 (m, 1H, CHMe2), 2.72 (s, 1H, MeC(CHH)2),
2.89 (s, 1H, MeC(CHH)2), 2.98 (m, 1H, CHMe2), 6.85 (m, 1H, H
arom), 7.14 (d, 3JHH = 9.0 Hz, 1H, H arom), 7.26 (m, 5H, 5 H arom),
3
7.43 (m, 4H, 4 H arom), 7.65 (d, JHH = 8.7 Hz, 1H, H arom), 7.98
(m, 4H, 4 H arom). 31P{1H} NMR (CD2Cl2, 202 MHz): major δ 37.7
(br s, P−C), 180.2 (br d, P−O, JPP = 47 Hz); minor 42.9 (br s, P−C),
180.2 (overlapped signal, P−O). 13C{1H} NMR (CD2Cl2, 101 MHz):
δ 17.2 (d, JCP = 4 Hz, CHMe2), 19.1 (CHMe2), 20.2 (d, JCP = 3 Hz,
CHMe2), 20.7 (d, JCP = 3 Hz, CHMe2), 22.3 (d, JCP = 15 Hz, CHMe2),
25.7 (MeC(CH2)2), 26.1 (MeC(CH2)2), 28.3 (d, JCP = 22 Hz,
CHMe2), 35.6 (MeC(CH2)2), 38.5 (d, JCP = 3 Hz, MeC(CH2)2), 43.2
(m, 2 MeC(CH2)2), 98.9 (MeC(CH2)2), 99.1 (MeC(CH2)2), 122.6
(br s, Cq arom), 122.9 (CH arom), 123.3 (2 CH arom), 123.7 (CH
arom), 125.1 (CH arom), 125.2 (CH arom), 126.2 (CH arom), 126.4
(CH arom), 127.1 (CH arom), 127.2 (CH arom), 128.5 (CH arom),
128.6 (CH arom), 129.6 (CH arom), 129.7 (CH arom), 130.4 (CH
arom), 130.6 (CH arom), 131.4 (Cq arom), 131.5 (2 Cq arom), 133.0
(2 Cq arom), 133.2 (Cq arom), 149.0 (d, JCP = 5 Hz, Cq arom), 150.1
1
with n-hexane, giving 4h as a yellow solid (0.046 g, 49%). H NMR
(500 MHz, CD2Cl2): δ 0.85 (s, 9 H, CMe3), 1.30 (s, 9 H, CMe3), 1.36
(s, 9 H, CMe3), 1.43 (s, 9 H, CMe3), 1.52 (br s, 3H, CH3C-
(CO2H)), 1.68 (s, 3H, CH3C(CO2H)), 1.69 (s, 6H, 2
CH3CH), 6.11 (dd, 1H, JHP = 4.9, 7.9 Hz, 1H arom), 6.56 (brm,
1H, CH3CH), 6.73 (br m, 1H, CH3CH), 6.99 (m, 4H, 4H arom),
7.15 (m, 3H, 3H arom), 7.27 (m, 3H, 3H arom), 7.45 (m, 4H, 4H
arom), 7.52 (m, 1H, 1H arom), 7.65 (m, 2H, 2H arom). 31P NMR
(202.5 MHz, CD2Cl2): δ 51.1 (P−C, JPP = 79 Hz), 143.9 (P−O).
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Organometallics
Article
13C{1H} NMR (CD2Cl2, 125.7 MHz): δ 11.1 (s, CH3CH), 11.3 (s,
CH3CH), 14.1 (s, CH3C(CO2H)), 14.2 (s, CH3C(CO2H)),
30.3 (CMe3), 30.9 (CMe3), 31.8 (2 CMe3), 35.0 (CMe3), 35.2 (CMe3),
35.5 (CMe3), 36.4 (CMe3), 120.8 (CH arom), 121.4 (CH arom),
122.4 (CH arom), 124.5 (d, JCP = 7 Hz, CH arom), 124.8 (CH arom),
125.5 (CH arom), 127.0 (CH arom), 128.4 (d, JCP = 11 Hz, CH
arom), 128.8 (d, JCP = 11 Hz, CH arom), 128.9 (CH arom), 129.7 (d,
JCP = 5 Hz, Cq), 130.0 (2 Cq), 130.4 (Cq), 130.9 (Cq), 131.2 (CH
arom), 132.0 (Cq), 132.6 (CH arom), 133.0 (Cq), 133.1 (CH arom),
133.4 (d, JCP = 10 Hz, CH arom), 135.1 (d, JCP = 12 Hz, CH arom),
135.2 (CH3CH), 135.2 (Cq), 136.1 (CH3CH), 140.3 (Cq), 140.8
(Cq), 146.5 (Cq), 147.6 (Cq), 148.3 (Cq), 156.4 (Cq), 186.0 (CO2),
186.7 (CO2). Anal. Calcd for C56H70O7P2Ru·1/2C6H14: C, 66.8; H, 7.3.
Found: C, 67.0; H, 7.2.
ACKNOWLEDGMENTS
■
We gratefully acknowledge Dr. P. M. Nieto (IIQ) for assistance
in 31P−31P EXSY experiments. the MICINN (CTQ2009-
11867, CTQ2009-08746 and the CONSOLIDER-INGENIO,
CSD2007-00006, FEDER support), the EU (PITN 2008-
́
215193), and the Junta de Andalucia (2008/FQM-3830). We
also thank Dr. Reddy’s group for a generous gift of enantiomers
of 3,3′-di-tert-butyl-5,5′,6,6′-tetramethyl-2,2′-bisphenol. M.V.
and S.E.G.-G. thank the MICINN for a FPI fellowship and a
́
Ramon y Cajal contract, respectively.
REFERENCES
■
General Procedure for ROMP Reactions of Norbornene. A
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* Supporting Information
Figures showing the superposition of Ru(P)2(η3-2-MeC3H4)2
fragments of Λ-1a and Λ-1d, M+ isotope patterns, selected
NMR spectra, and crystallographic data. This material is
available free of charge via the Internet at http://pubs.acs.org.
(9) For some recent reviews see: (a) Fernan
P.; Panossian, A.; Vidal-Ferran, A. Chem. Rev. 2011, 111, 2119. (b) van
Leeuwen, P. W. N. M.; Kamer, P. C. J.; Claver, C.; Pamies, O.;
́ ́
dez-Perez, H. C.; Etayo,
̀
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Dieguez, M. Chem. Rev. 2010, 111, 2077. (c) Tang, W.; Zhang, X.
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Chem., Int. Ed. 2010, 49, 2486. (e) Phosphorus Ligands in Asymmetric
AUTHOR INFORMATION
■
Catalysis: Synthesis and Applications; Borner, A., Ed.; Wiley: Weinheim,
̈
Corresponding Author
Germany, 2008.
*E-mail: pizzano@iiq.csic.es.
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Notes
The authors declare no competing financial interest.
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(27) Initiation efficiency can be estimated from: initiation efficiency
(%) = 100 × Mn(theoretical)/Mn(observed), where Mn(theoretical)
corresponds to the expected value of Mn assuming 100% initiation
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dx.doi.org/10.1021/om300018s | Organometallics 2012, 31, 3551−3564