Influence of electron-deficient ruthenium(I) carbonyl carboxylates on the vinylogous reactivity of metal carbenoids

Article abstract of DOI:10.1021/om700888f

Highly electrophilic ruthenium(I) mixed carbonyl carboxylate complexes exhibit catalytic activity in the cyclopropanation of styrene with methyl phenyldiazoacetate. A particular advantage of these catalysts is their propensity to enhance vinylogous reactivity in the reactions of vinyldiazoacetates. The catalytic study was conducted on four known ruthenium(I) mixed carbonyl carboxylate complexes and four new complexes, namely, [Ru ₂(O₂C(2,3,4-F)₃C₆H₂) ₂(CO)₅], [Ru₂(O₂C(2,4,6-F) ₃C₆H₂)₂(CO)₅], [Ru ₂(O₂CC₆F₅)₂(CO) ₅], and [Ru₂(O₂C(3,5-CF₃) ₂C₆H₃)₂(CO)₄]. All complexes have been prepared by a combination of solvent-free techniques: melt reactions of ruthenium carbonyl with a benzoic acid followed by gas-phase sublimation-deposition of the products under reduced pressure. X-ray crystallographic characterization revealed a tetranuclear dimer of dimers type of structure for the [Ru₂(O₂CR) ₂(CO)₅] complexes and a polymeric chain for [Ru ₂(O₂C(3,5-CF₃)₂C₆H ₃)₂(CO)₄]. Both motifs are built on diruthenium(I,I) units linked in the solid state by axial Ru ... O interactions. The solution behavior of the polynuclear ruthenium(I) complexes in solvents of varying coordination ability has been investigated to show a breakage of weak Ru ... O contacts, resulting in the formation of one- and two-end open dimetal units.

Full text of DOI:10.1021/om700888f

1750
Organometallics 2008, 27, 1750–1757
Influence of Electron-Deficient Ruthenium(I) Carbonyl Carboxylates
on the Vinylogous Reactivity of Metal Carbenoids
Yulia Sevryugina,† Beth Weaver,† Jørn Hansen,‡ Janelle Thompson,‡
Huw M. L. Davies,*,‡ and Marina A. Petrukhina*,†
Department of Chemistry, UniVersity at Albany, State UniVersity of New York, Albany, New York 12222,
and Department of Chemistry, UniVersity at Buffalo, State UniVersity of New York,
Buffalo, New York 14260-3000
ReceiVed September 4, 2007
Highly electrophilic ruthenium(I) mixed carbonyl carboxylate complexes exhibit catalytic activity in
the cyclopropanation of styrene with methyl phenyldiazoacetate. A particular advantage of these catalysts
is their propensity to enhance vinylogous reactivity in the reactions of vinyldiazoacetates. The catalytic
study was conducted on four known ruthenium(I) mixed carbonyl carboxylate complexes and four new
complexes, namely, [Ru2(O2C(2,3,4-F)3C6H2)2(CO)5], [Ru2(O2C(2,4,6-F)3C6H2)2(CO)5], [Ru2(O2CC6F5)2-
(CO)5], and [Ru2(O2C(3,5-CF3)2C6H3)2(CO)4]. All complexes have been prepared by a combination of
solvent-free techniques: melt reactions of ruthenium carbonyl with a benzoic acid followed by gas-phase
sublimation-deposition of the products under reduced pressure. X-ray crystallographic characterization
revealed a tetranuclear “dimer of dimers” type of structure for the [Ru2(O2CR)2(CO)5] complexes and a
polymeric chain for [Ru2(O2C(3,5-CF3)2C6H3)2(CO)4]. Both motifs are built on diruthenium(I,I) units
linked in the solid state by axial Ru · · · O interactions. The solution behavior of the polynuclear ruthenium(I)
complexes in solvents of varying coordination ability has been investigated to show a breakage of weak
Ru · · · O contacts, resulting in the formation of one- and two-end open dimetal units.
Scheme 1. Resonance Picture of Vinylogous Reactivity
Introduction
The rhodium-catalyzed reactions of vinyldiazoacetates have
been shown to have broad synthetic potential. A number of very
powerful synthetic methods have been developed, which exploit
the highly selective transformations of the rhodium-stabilized
vinylcarbenoid intermediates generated under these conditions.
These include a number of C-C bond formation reactions
including cyclopropanations,1,2 the tandem cyclopropanation/
Cope rearrangement,3–7 [3+2] cycloadditions,8,9 C-H inser-
tions,10,11 and the combined C-H activation/Cope rearrange-
ment.11–13 All of these reactions involve initial attack of the
vinylcarbenoids at the carbenoid center. An interesting phe-
nomenon, however, associated with these vinylcarbenoids is that
in certain systems it is possible to have competing electrophilic
reactivity at the terminal site (Scheme 1).14,15 This type of
behavior is common in Fischer vinylcarbenes16 but has not been
extensively developed with the transient metal carbenoids
derived from vinyldiazoacetates, primarily because convenient
methods for controlling vinylogous reactivity have not been
developed.
* To whom correspondence should be addressed. E-mail: marina@
albany.edu, hdavies@buffalo.edu
† University at Albany.
‡ University at Buffalo.
(1) Doyle, M. P.; McKervey, M. A.; Ye, T. Modern Catalytic Methods
for Organic Synthesis with Diazo Compounds: From Cyclopropanes to
Ylides; 1998.
One of the challenges associated with the use of vinyldiaz-
oacetates in synthesis is the requirement of a very active catalyst
to induce rapid nitrogen extrusion since many of the vinyldia-
zoacetates are prone to 6π-electrocyclization to form pyrazoles.4
The dirhodium(II,II) tetracarboxylates were discovered to be
the optimal catalysts for this chemistry, and they have been
predominantly used in all the new vinylcarbenoid synthetic
(2) Lebel, H.; Marcoux, J.-F.; Molinaro, C.; Charette, A. B. Chem. ReV.
2003, 103, 977–1050.
(3) Davies, H. M. L. Tetrahedron 1993, 49, 5203–5223.
(4) Davies, H. M. L.; Bruzinski, P.; Hutcheson, D. K.; Kong, N.; Fall,
M. J. J. Am. Chem. Soc. 1996, 118, 6897–6907.
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56, 3817–3824.
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(7) Davies, H. M. L.; Stafford, D. G.; Doan, B. D.; Houser, J. H. J. Am.
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3348.
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(9) Davies, H. M. L.; Xiang, B.; Kong, N.; Stafford, D. G. J. Am. Chem.
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(11) Davies, H. M. L.; Beckwith, R. E. J. Chem. ReV. 2003, 103, 2861–
2903.
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Lett. 1990, 31, 6299–6302.
(12) Davies, H. M. L.; Dai, X.; Long, M. S. J. Am. Chem. Soc. 2006,
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6727.
10.1021/om700888f CCC: $40.75
2008 American Chemical Society
Publication on Web 03/25/2008

Ruthenium(I) Carbonyl Carboxylate Catalysts
Organometallics, Vol. 27, No. 8, 2008 1751
Scheme 2. Carbenoid vs Vinylogous Reactivity15
diruthenium(I,I) carbonyl dicarboxylates that are effective
catalysts for the decomposition of diazoacetates and that they
strongly enhance vinylogous reactivity over the traditional
chemistry at the carbenoid site.
Diruthenium(I,I) carbonyl carboxylates of the general formula
[Ru2(µ2-O2CR)2(CO)4L2] and polymeric compounds of the
composition [Ru2(µ2-O2CR)2(CO)4] have been utilized in inter-
and intramolecular reactions of diazoacetates and diazoaceta-
mides by Maas and co-workers.20–27 The complexes are air
stable, and since Ru(I) is isoelectronic to Rh(II), one can expect
roughly a similar reactivity profile between the two classes of
complexes. The diruthenium(I,I) carbonyl carboxylate com-
plexes have not been explored as catalysts for the reactions of
vinyldiazoacetates. As our goal was to enhance vinylogous
reactivity, we tested a family of electrophilic diruthenium(I,I)
mixed carbonyl carboxylate complexes of the general formula
[Ru2(O2CR)2(CO)n]: n ) 5, R ) CF3 (I), (2,4-CF3)2C6H3 (II),
(3,5-CF3)2C6H3 (III), (2,3,4-F)3C6H2 (IV), (2,4,6-F)3C6H2 (V),
C6F5 (VI); n ) 4, R ) CF3 (VII), (3,5-CF3)2C6H3 (VIII). The
synthesis of and structural information on I-III and VII have
been reported previously, while compounds IV-VI and VIII
are reported here for the first time (Scheme 4). In this paper we
first describe the syntheses, characterization, and solution
behavior of these complexes, followed by their catalytic activity.
Scheme 3. O-H Insertion18
Results and Discussion
methods developed to date.10,11,17 During these studies, it was
discovered that vinylcarbenoids unsubstituted at the vinyl
terminus could display electrophilic character at the vinylogous
position. This is illustrated in the reaction of vinyldiazoacetate
1 with N-carbomethoxypyrrole, which resulted in the formation
of a mixture of tropane 2, derived from a tandem cyclopropa-
nation/Cope rearrangement, and the alkylation product 3, derived
from reaction at the vinylogous site (Scheme 2).15 The product
distribution is dependent on the solvent and catalyst, where a
more polar solvent and electron-deficient catalyst favor reaction
at the vinylogous site. The only way to form exclusively the
alkylation product was to use a very bulky ester to block
reactivity at the carbenoid site.15 This is not an ideal solution,
however, because the ester is too bulky to be hydrolyzed, and
due to its size, it triples the molecular weight of the vinyldia-
zoacetate.
A possible approach to enhance the vinylogous reactivity
would be to use dimetal complexes that have different electronic
properties from the dirhodium complexes previously used as
catalysts (Scheme 2). Preliminary studies have been conducted
with in situ generated dimolybdenum complexes, which dem-
onstrate in O-H insertion reactions that vinylogous reactivity
can be achieved even with vinylcarbenoids unsubstituted at the
vinyl terminus (Scheme 3).18 This system, however, was very
limited, because it could only be applied to O-H insertions.
Furthermore, the in situ generated complex was unstable and
its actual structure remains uncertain. An alternative approach
has been recently described for enhancing vinylogous reactivity
in X-H insertions by using mononuclear metal complexes.19
These transformations have been proposed to be Lewis acid
catalyzed reactions and to not involve carbenoid intermediates.
To further develop the use of dimetal complexes to enhance
vinylogous reactivity, it would be highly desirable to have air-
stable, structurally well-defined catalysts. This paper describes
Synthesis. The synthetic methods to isolate complexes
I-VIII in pure crystalline form have been developed in our
group.28 The first diruthenium(I,I) carbonyl carboxylate [Ru2-
(O2CCF3)2(CO)5] (I) was prepared by refluxing Ru3(CO)12 with
trifluoroacetic acid in a mixture of noncoordinating solvents,
while [Ru2(O2CCF3)2(CO)4] (VII) was synthesized in a ligand
exchange reaction from commercially available [Ru2-
(O2CCH3)2(CO)4].29 Recently, we have prepared a series of the
mixed carbonyl fluorinated benzoates of ruthenium(I) by adapt-
ing the procedures reported by Strähle based on melt reactions
of Ru3(CO)12 with a corresponding benzoic acid.30,31 As a result,
products of the composition [Ru2(O2CR)2(CO)n] [n ) 5, R )
(2,4-CF3)2C6H3 (II), (3,5-CF3)2C6H3 (III),28 (2,3,4-F)3C6H2 (IV),
(2,4,6-F)3C6H2 (V), and C6F5 (VI); n ) 4, R ) (3,5-CF3)2C6H3
(VIII)] were isolated as air-stable crystalline solids. While I-VI
are soluble in most organic solvents, VIII shows a very limited
solubility in noncoordinating solvents. The synthetic route for
each compound combined a melt reaction at the temperature
slightly above the melting point of an acid with consequent
removal of unreacted acid by several resublimations under
reduced pressure. This was followed by crystal growth using a
gas-phase sublimation-deposition technique that was proven
(20) Buck, S.; Maas, G. J. Organomet. Chem. 2006, 691, 2774–2784.
(21) Grohmann, M.; Buck, S.; Schaeffler, L.; Maas, G. AdV. Synth. Catal.
2006, 348, 2203–2211.
(22) Leger, C.-D.; Maas, G. Z. Naturforsch. (B) 2004, 59, 573–578.
(23) Maas, G. Chem. Soc. ReV. 2004, 33, 183–190.
(24) Maas, G.; Seitz, J. Tetrahedron Lett. 2001, 42, 6137–6140.
(25) Maas, G.; Werle, T.; Alt, M.; Mayer, D. Tetrahedron 1993, 49,
881–888.
(26) Werle, T.; Maas, G. AdV. Synth. Catal. 2001, 343, 37–40.
(27) Werle, T.; Schaeffler, L.; Maas, G. J. Organomet. Chem. 2005,
690, 5562–5569.
(28) Sevryugina, Y.; Olenev, A. V.; Petrukhina, M. A. J. Cluster Sci.
2005, 16, 217–229.
(29) Petrukhina, M. A.; Sevryugina, Y.; Andreini, K. W. J. Cluster Sci.
2004, 15, 451–467.
(17) Davies, H. M. L. Eur. J. Org. Chem. 1999, 2459–2469.
(18) Davies, H. M. L.; Yokota, Y. Tetrahedron Lett. 2000, 41, 4851–
(30) Spohn, M.; Straehle, J.; Hiller, W. Z. Naturforsch. (B) 1986, 41B,
541–547.
4854.
(19) Yue, Y.; Wang, Y.; Hu, W. Tetrahedron Lett. 2007, 48, 3975–
(31) Spohn, M.; Vogt, T.; Straehle, J. Z. Naturforsch. (B) 1986, 41B,
1373–1380.
3977.

1752 Organometallics, Vol. 27, No. 8, 2008
Scheme 4. Schematic Representation of Structures of I-VIII
SeVryugina et al.
to be very effective for crystallization of volatile electrophilic
metal complexes in the absence of exogenous ligands.32
Additionally, all diruthenium(I,I) carbonyl carboxylates pre-
sented in this study were structurally characterized to allow
direct structure–reactivity correlations. It is important to em-
phasize the advantage of the gas-phase deposition technique that
affords new metal catalysts in high yields as pure single-phase
crystalline materials. Their use in catalytic transformations may
allow a direct estimate of the structural and electronic differences
in the catalytic properties of diruthenium(I,I) complexes.
Structural Characterization. The X-ray structural analysis
of the newly prepared diruthenium(I,I) pentacarbonyl fluoroben-
zoates IV-VI displayed a centrosymmetric tetranuclear core
that may be viewed as a “dimer of dimers” structure [Ru2(O2-
CR)2(CO)5]2 (Figure 1), similar to that in previously reported
compounds of this series, I29 and II.28 Two ruthenium centers
within the dimer are cis-bridged by two carboxylate ligands at
a Ru-Ru distance ranging from 2.6579(2) Å in IV to 2.6710(2)
Å in V. Interestingly, the intermetallic separation is noticeably
different for the two compounds IV and V, having the same
molecular formula, [Ru2(O2CF3C6H2)2(CO)5]2, but different
disposition of the fluorine substituents (2,3,4- vs 2,4,6-).
Additionally, each dinuclear core accommodates five carbonyl
groups: one at an axial position and the remaining four at
equatorial sites. The Ru-C distances to equatorial carbonyl
groups are considerably shorter (1.855(5)-1.859(2) Å) than
those to axial carbonyl groups (1.993(5)-2.009(2) Å). The
diruthenium units are linked together by two weak Ru · · · O axial
contacts ranging from 2.302(3) in VI to 2.3234(14) Å in V.
The geometric parameters of IV-VI, together with those for
previously reported I-III, are summarized in Table 1. No
significant discrepancies in bond lengths and angles are noticed
in this series of compounds.
interactions between neighboring dimetal blocks (Figure 2). The
Ru-Ru distance within the dimetal unit is 2.6343(7) Å, which
is longer than that in VII of 2.6271(9) Å, while the axial Ru · · · O
contacts of 2.294(4) Å are shorter in VIII vs VII (2.325(6) Å).
Each Ru atom also has two equatorial carbonyl groups with an
average Ru-C distance of 1.849(7) Å.
On the basis of structural characteristics of I-VIII, we expect
that carbenoid formation occurs through axial coordination of
the diruthenium(I,I) unit to a diazoacetate. A necessary pre-
liminary step would involve cleavage of weak Ru · · · O inter-
dimer contacts to produce open Lewis acidic metal centers,
which will become sites of catalytic activity (Scheme 5). This
is illustrated here by solution crystallization of a toluene adduct
of complex III, [Ru2(O2C(3,5-CF3)2C6H3)2(CO)5 · (C6H5CH3)]
(IX), and a water adduct of complex I, [Ru2(O2CCF3)2-
(CO)4 · (H2O)2] (X) (Figure 3). In our previous work28 we
established similar dissociation processes in the gas phase
through isolation of adducts with aromatic donor substrates,
which additionally illustrated high electrophilicity of the
prepared diruthenium(I,I) complexes. In contrast to the gas-phase
reactions resulting in a breakage of intermolecular contacts
between the dimetal units in both classes of ruthenium com-
plexes, in solution strong coordinating solvents (like water,
tetrahydrofuran, or alcohols) are required to break the chain
polymeric structures of VII and VIII.
Determination of Catalytic Activity of Ru(I) Complexes.
The activities of ruthenium complexes I-VIII as catalysts for
carbenoid transformations were initially evaluated in the cy-
clopropanation reaction between methyl phenyldiazoacetate (7)
and styrene (Scheme 6). This transformation is effective with
various dirhodium catalysts and was thus considered an ap-
propriate test reaction for catalytic activity. The reactions were
conducted in dichloromethane by syringe pump addition of
phenyldiazoacetate 7 to a solution of excess styrene and the
ruthenium catalyst (1 mol%). Reactions at room temperature
gave fairly low yields for all complexes I-VIII (0-26%). The
highest yields were obtained with complexes I and IV-VI
(13-26%). Reactions in refluxing dichloromethane, however,
produced the cyclopropane in moderate to good yields for all
the catalysts (42-69% yield). The main side-reaction was the
formation of carbene dimers. The significant improvement in
yields and reactivity with temperature may be attributed to
thermally enhanced dissociation of dimeric and polymeric
complexes of these species to open up the axial active sites for
catalysis. The lowest yields were obtained with complexes VII
and VIII in reactions conducted both at room temperature and
at reflux. These two catalysts lack axial CO ligands and have
chain polymeric structures in the solid state and are therefore
expected to have lower solubility in dichloromethane compared
to complexes I-VI. The latter complexes, containing axial CO
ligands, which form “dimer of dimer” type structures, dissociate
in solutions more easily than VII and VIII.
The newly prepared complex VIII exhibits a polymeric
structure similar to that of VII formed by axial ruthenium-oxygen
Figure 1. Molecular view of complex IV. Ru purple, O red, C
gray, F green, H light gray. Complexes V and VI have similar
structures.

Ruthenium(I) Carbonyl Carboxylate Catalysts
Organometallics, Vol. 27, No. 8, 2008 1753
Table 1. Selected Bond Distances (Å) and Angles (deg) in a Series of Ruthenium(I) Carbonyl Carboxylates of the General Formula
[Ru2(O2CR)2(CO)5]2
28
(CF3)2C6H3
F3C6H2
29
CF3
2,4-
3,5-
2,3,4-
2,4,6-
C6F5
R
I
II
III
IV
V
VI
Ru(1)-Ru(2)
Ru-Ocarboxylate
2.6728(2)
2.1394(12)
2.3437(12)
2.6654(7)
2.130(3)
2.301(2)
2.6859(8)
2.098(3)
2.6579(2)
2.1275(14)
2.3162(13)
2.6710(2)
2.1307(14)
2.3234(14)
2.6671(5)
2.125(3)
2.302(3)
a
Ru(1) · · · O(1A)
Ru(1) · · · Ru(1A)
2.9065(9)
1.866(5)
1.969(5)
1.134(5)
1.116(6)
a
Ru-COeq
1.864(2)
1.991(2)
1.139(2)
1.126(2)
1.863(4)
2.002(4)
1.134(5)
1.114(5)
1.859(2)
2.009(2)
1.139(3)
1.114(3)
1.858(2)
2.007(2)
1.140(3)
1.115(3)
1.855(5)
1.993(5)
1.144(6)
1.118(6)
Ru(2)-COax
a
C-Oeq
C-Oax
Ru-Ru · · · Ru
Ru-Ru · · · Oax
Ru-Ru-Cax
173.961(19)
157.56(3)
170.43(5)
157.66(6)
166.56(13)
154.31(3)
168.61(6)
157.93(3)
168.27(6)
156.11(7)
166.99(13)
169.28(13)
a Averaged.
more toward vinylogous reactivity (entry 4).18 Reactions with
Ru(I) catalysts I-III show an even more pronounced shift
toward vinylogous reactivity. For these complexes, the products
derived from vinylogous reactivity always constitute >80% of
the products. The E/Z distribution of 6 varies somewhat as well
and may reflect the preference of the carbenoid to exist in an
s-trans conformation. The product yields are relatively low,
possibly due to reduced reactivity of the catalysts at room
temperature, but the trend toward vinylogous reactivity is very
pronounced. The ruthenium-catalyzed reactions gave a 4:1 ratio
of products favoring terminus reactivity in a system, which under
the standard rhodium-catalyzed reaction gave exclusive reaction
at the carbenoid site.
Figure 2. Fragment of a polymeric chain in complex VIII. Ru
Enhancing Vinylogous Reactivity in C-C Bond Form-
ing Reactions. The scope of the ruthenium-catalyzed reactions
would be greatly enhanced if selective vinylogous reactivity
could be achieved in C-C bond forming reactions. Rhodium-
catalyzed vinyldiazoacetates unsubstituted at the vinyl terminus
can give rise to vinylogous reactivity, but the selectivity is poor
unless a very bulky ester group is used.14 In order to test this
possibility, the reaction of vinyldiazoacetate 9 with cyclopen-
tadiene was examined. Previously, this transformation has been
conducted with dirhodium(II,II) systems, which gave a mixture
of compounds 10 and 11 (Scheme 8), where 10 arises from
initial nucleophilic attack at the terminal position of the
intermediate vinylcarbenoid and 11 is the product of a tandem
cyclopropanation/Cope rearrangement (carbenoid reactivity).14
The reactions were conducted at room temperature, due to the
intrinsic thermal instability of the vinyldiazoacetate, with a large
excess of trapping agent (20 equiv). Reaction between methyl
vinyldiazoacetate 9 and cyclopentadiene in the presence of
diruthenium(I,I) complexes I, II, and VI led cleanly to the
bicyclic products cis/trans-10 in moderate yields (37-54%) with
an isomer ratio of about 2:1 in all cases. Compared to previously
reported dirhodium(II,II)-catalyzed reactions, there is remarkable
control of site selectivity, and only the product(s) 10 arising
from vinylogous reactivity can be observed. Only partial control
is achieved, even with the highly electron-deficient Rh2(TFA)4,
for dirhodium(II,II) complexes.14
purple, O red, C gray. F and H atoms are omitted for clarity.
The diastereoselectivity of the reaction of 7 with styrene is
generally very high with dirhodium(II,II) complexes as catalysts
(>94% de).33 With the diruthenium(I,I) catalysts the diastereo-
selectivities are not as high (50-83% de). The attenuated
diastereoselectivity observed for the ruthenium-catalyzed reac-
tions is presumably due to the higher electrophilic character of
these complexes compared to previously used dirhodium
catalysts, which lowers the discriminating abilities of the
resulting carbenoid intermediates.
Vinylogous Reactivity in O-H Insertions. The crucial
question regarding the diruthenium(I,I)-catalyzed reactions of
vinyldiazoacetates was whether these electrophilic catalysts
would enhance reactivity at the terminal position of the
vinylcarbenoid intermediate. As discussed in the introduction,
a test reaction for vinylogous Vs carbenoid reactivity is the metal-
catalyzed decomposition of a vinyldiazoacetate in methanol
(Scheme 7).18 The resulting distribution of products, arising from
nucleophilic attack of methanol at the terminal position (products
E-6 and Z-6) or the carbenoid carbon (products 5a,b), reflects
vinylogous vs carbenoid reactivity. Results from O-H insertion
reactions of methyl phenylvinyldiazoacetate (4) and methanol
catalyzed by diruthenium(I,I) complexes I-III in comparison
with previously reported Mo species and dirhodium complexes
Rh2(S-TBSP)4 and Rh2(OAc)4 are shown in Scheme 7. Dirhod-
ium complexes typically give only products arising from
nucleophilic attack at the carbenoid carbon (entries 5 and 6),
while Mo complexes have been shown to shift the reactivity
The proposed reaction mechanism14,15 (Scheme 9) is con-
sidered to proceed by initial nucleophilic attack at the vinylogous
site to form zwitterionic intermediate 13. This intermediate then
cyclizes to form a second metal carbenoid intermediate 14,
which then undergoes a [1,2]-hydride shift and elimination to
form 10. The dependence of the isomer ratio of 10 on catalyst
structure supports the existence of the second carbene interme-
diate 14.
(32) Dikarev, E. V.; Filatov, A. S.; Clerac, R.; Petrukhina, M. A. Inorg.
Chem. 2006, 45, 744–751.
(33) Davies, H. M. L.; Rusiniak, L. Tetrahedron Lett. 1998, 39, 8811–
8812.

1754 Organometallics, Vol. 27, No. 8, 2008
Scheme 5. Dissociation of Tetra- and Polynuclear Complexes to Form Diruthenium(I,I) Units
SeVryugina et al.
Scheme 6. Cyclopropanation of Styrene
Scheme 7. O-H Insertion
Enhancement of vinylogous reactivity appears to be a general
phenomenon, as illustrated for the reaction using N-Boc pyrrole
as the trapping agent (Scheme 10). This reaction afforded cis/
trans isomers of the alkylation product 15, presumably arising
from initial nucleophilic attack at the terminal position of the
vinylcarbenoid. The yields of 15 were somewhat higher but
comparable to those obtained with cyclopentadiene (45-57%).
Again, only the products derived from vinylogous reactivity
were observed, and the formation of Z-15 was strongly preferred
over E-15.
18
a
Values from the literature.
In conclusion, the diruthenium(I,I) complexes investigated
here can be active catalysts in carbenoid transformations at
low catalyst loadings (1 mol %). The activity can be
modulated by the association propensity of the active
complexes in solution. The diruthenium catalysts require more
vigorous reaction temperatures than dirhodium(II,II) catalysts,
but they have promising synthetic potential because they
cause significant enhancement of vinylogous vs carbenoid
reactivity of vinylcarbenoids. The study demonstrates that
the catalyst is an essential control element for enhancing
reactivity at the terminal position of vinylcarbenoids. Future
studies will be directed toward further optimization of the
diruthenium catalysts with the ultimate goal of broadening
the scope of the vinylogous reactivity and achieving enan-
tioselective variants of this chemistry.
Experimental Section
General Procedures. All synthetic reactions and manipulations
with diruthenium(I,I) complexes were carried out under a dry
dinitrogen atmosphere using standard Schlenk techniques. Sublima-
tion-deposition procedures were performed in small evacuated (ca.
10-2 Torr) glass ampules (ca. 7 cm long with an o.d. of 1.1 cm),
which were placed in electric furnaces having a small temperature
gradient along the length of the tube. Ru3(CO)12 was obtained from
Strem. 2,3,4-Trifluorobenzoic, (2,3,4-F)3C6H2COOH, 2,4,6-trifluo-
robenzoic, (2,4,6-F)3C6H2COOH, and pentafluorobenzoic, C6F5-
COOH, acids were purchased from SynQuest Fluorochemicals and
used as received. All other materials were purchased from Aldrich
or Acros and used without further purification unless stated.
All catalytic reactions were conducted in flame-dried glassware
under an inert Ar atmosphere. Reagents were used as received from
commercial suppliers. Dichloromethane was purified by passage
Figure 3. Molecular view of compounds IX and X.

Ruthenium(I) Carbonyl Carboxylate Catalysts
Organometallics, Vol. 27, No. 8, 2008 1755
Scheme 8. Vinylogous Reactivity in Reaction with Cyclo-
pentadiene
in an ampule, which was then placed in a sand bath at 150 °C. A
brown melt was formed instantly, but reaction was allowed to
proceed for a total of 30 min. After that, the ampule was sealed
and excess of unreacted acid was removed by sublimation at 90
°C for 3 days. The resulting yellow crude powder was collected in
an ampule and placed in a furnace at 125 °C. First pale yellow
crystals of IV appeared in the cold zone after 4 days, but only in
a month their yield achieved 50%. Anal. Calcd for C38H8F12O18Ru4:
C, 32.93; O, 20.80; H, 0.58. Found: C, 32.96; O, 21.21; H, 0.77.
IR (KBr, cm-1): 3094(sh), 2105(s), 2050(s), 2017(s), 1998(s),
1960(s), 1948(s), 1634(m), 1615(w), 1569(s), 1550(m), 1514(m),
1487(w), 1475(m), 1412(s), 1321(sh), 1284(m), 1240(w), 11445(sh),
1047(m), 955(m), 829(sh), 814(m), 778(m), 726(w), 713(w),
693(w), 644(m), 568(w), 524(w), 506(w). 1H NMR (CDCl3, 22 °C):
δ 7.67, 7.05 (C-Harom) with an integrated ratio of 1:1, respectively.
19F NMR (CDCl3, 22 °C): δ -129.75, -132.34, -160.92.
Preparation of [Ru2(O2C(2,4,6-F)3C6H2)2(CO)5] (V). The title
compound was obtained in a melt reaction between Ru3(CO)12
(0.120 g, 0.19 mmol) and (2,4,6-F)3C6H2COOH (0.165 g, 0.94
mmol). Starting materials were loaded in an ampule, which was
then placed in a sand bath at 154 °C. A red melt was formed
instantly, but reaction was allowed to proceed for a total of 20 min.
After that, the ampule was sealed and excess unreacted acid was
removed by sublimation at 120 °C for 5 days. The resulting orange
crude powder was collected in an ampule and placed in a furnace
at 163 °C. First yellow crystals of V appeared in the cold zone
after 1 day. After 4 days the yield is 30%. Anal. Calcd for
C38H8F12O18Ru4: C, 32.93; O, 20.80; H, 0.58. Found: C, 32.51; O,
21.10; H, 0.69. IR (KBr, cm-1): 3113(sh), 3091(sh), 2108(s),
2048(s), 2025(s), 2007(s), 1987(sh), 1948(s), 1695(w), 1660(w),
1643(s), 1617(sh), 1603(s), 1585(s), 1553(m), 1535(w), 1500(w),
1484(w), 1442(w), 1419(s), 1409(s), 1350(m), 1172(w), 1144(m),
1121(s), 1041(m), 998(m), 854(sh), 844(m), 783(w), 751(w),
733(w), 663(w), 626(m), 573(w), 522(w), 512(w). 1H NMR (CDCl3,
22 °C): δ 6.68 (C-Harom). 19F NMR (CDCl3, 22 °C): δ -103.47,
-107.45.
Preparation of [Ru2(O2CC6F5)2(CO)5] (VI). The title compound
was obtained in a melt reaction between Ru3(CO)12 (0.020 g, 0.03
mmol) and C6F5COOH (0.036 g, 0.17 mmol). Starting materials
were loaded in an ampule, which was then placed in a sand bath at
120 °C. A bright orange melt was formed instantly, but reaction
was allowed to proceed for a total of 35 min. After that, the ampule
was sealed and excess unreacted acid was removed by sublimation
at 90 °C for 5 days. The resulting orange crude powder was
collected in an ampule and placed in a furnace at 145 °C for a
week (yield 70%). Anal. Calcd for C38F20O18Ru4: C, 29.83; O,
18.84. Found: C, 30.03; O, 18.46. IR (KBr, cm-1): 2107(s), 2043(s),
2022(s), 2016(s), 1956(s), 1646(m), 1598(s), 1575(sh), 1525(m),
1501(m), 1489(m), 1471(w), 1435(m), 1409(s), 1302(w), 1124(w),
1112(w), 1008(m), 993(m), 950(w), 889(m), 782(m), 771(m). 19F
NMR (CDCl3, 22 °C): δ -139.52, -161.06.
15
a
Values from the literature.
Scheme 9. Proposed Reaction Mechanism
Scheme 10. Vinylogous Reactivity in Reaction with N-Boc
pyrrole
through a bed of activated A2 alumina (Grubbs type solvent purifier)
and then degassed by bubbling Ar through the solvent for 15-20
min prior to use. N-Boc pyrrole was distilled before use. Styrene
was filtered through a plug of silica before use. Methyl phenyl-
diazoacetate (7) and methyl phenylvinyldiazoacetate (4) were
synthesized according to literature procedures.34 Thin-layer chro-
matography (TLC) was performed on aluminum-backed plates
precoated with silica (0.25 mm, 60F-254), which were developed
using UV fluorescence (254 nm) and phosphomolybdenic acid.
Column chromatography was carried out on Merck silica gel 60
(230-400 mesh).
Instruments. For characterization of metal catalysts the NMR
spectra were recorded on a Varian Gemini spectrometer at 300 MHz
1
for H and 282 MHz for 19F at 22 °C using SiMe4 and CFCl3 as
internal standards. The infrared spectra were obtained using KBr
pellets on a Nicolet Magna 550 FTIR spectrometer. Elemental
analyses were performed by Canadian Microanalytical Service,
Delta, BC, Canada.
For characterization of products of catalytic reactions the 1H
NMR spectra were recorded on either a 400 or 500 MHz Varian
Inova, and 13C NMR at 75 MHz with the sample solvent being
CDCl3 unless otherwise noted. Tetramethylsilane was used as an
internal reference standard. All coupling constants were rounded
to the nearest half-integer. Mass spectral determinations were carried
out by GC-MS (EI) and LC-MS (ESI) in the Instrument Center,
Department of Chemistry, University at Buffalo.
Preparation of [Ru2(O2C(3,5-CF3)2C6H3)2(CO)4] (VIII). The
title compound can be synthesized following the same procedure
as for [Ru2(O2C(3,5-CF3)2C6H3)2(CO)5]28 but using higher tem-
peratures and longer reaction times. Thus, conducting a melt
reaction at 170-180 °C for 40 min and subliming the crude powder
at 180 °C would quantitatively produce the title product in 70%
yield. A tiny amount of dichroic red crystals of [Ru2(O2C(3,5-
CF3)2C6H3)2(CO)5] and yellow crystals of [Ru2(O2C(3,5-
CF3)2C6H3)2(CO)6] are separated in the gas-phase sublimation
procedure. Single crystals of VIII suitable for X-ray data collection
were obtained in a transport reaction when [Ru2(O2C(3,5-
CF3)2C6H3)2(CO)5] (III) (0.019 g, 0.01 mmol) was cosublimed with
dibenzocorannulene, C28H14 (0.002 g, 0.006 mmol), at 180 °C. The
crystal growth took 3 weeks and the title product appeared with
ca. 20% yield. IR (KBr, cm-1): 3099(w), 2060(s), 2014(s), 1979(s),
1957(m), 1627(m), 1539(s), 1469(w), 1456(m), 1429(m), 1342(s),
Preparation of Metal Catalysts. Preparation of [Ru2(O2C-
(2,3,4-F)3C6H2)2(CO)5] (IV). The title compound was obtained in
a melt reaction between Ru3(CO)12 (0.020 g, 0.03 mmol) and (2,3,4-
F)3C6H2COOH (0.038 g, 0.22 mmol). Starting materials were loaded
(34) Davies, H. M. L.; Panaro, S. A. Tetrahedron 2000, 56, 4871–4880.

1756 Organometallics, Vol. 27, No. 8, 2008
SeVryugina et al.
1325(sh), 1279(s), 1188(m), 1155(sh), 1137(s), 1130(m), 915(m),
> 2σ(I) (R1 ) 0.0475, wR2 ) 0.1169 for 3796 unique reflections)
and a goodness of fit of 1.061. Final difference map is between
+1.870 and -1.474 e/Å3. For VIII full-matrix least-squares
refinement on F2 converged at R1 ) 0.0461 and wR2 ) 0.1003 for
433 parameters and 3548 reflections with I > 2σ(I) (R1 ) 0.0673,
wR2 ) 0.1095 for 4623 unique reflections) and a goodness of fit of
1.023. Final difference map is between +1.102 and -0.626 e/Å3.
For IX full-matrix least-squares refinement on F2 converged at R1
) 0.0441 and wR2 ) 0.1035 for 550 parameters and 5533 reflections
with I > 2σ(I) (R1 ) 0.0654, wR2 ) 0.1155 for 7438 unique
reflections) and a goodness of fit of 1.007. Final difference map is
between +1.024 and -0.711 e/Å3. For X full-matrix least-squares
refinement on F2 converged at R1 ) 0.0177 and wR2 ) 0.0444 for
261 parameters and 3376 reflections with I > 2σ(I) (R1 ) 0.0183,
wR2 ) 0.0449 for 3475 unique reflections) and a goodness of fit of
1.075. Final difference map is between +0.527 and -0.622 e/Å3.
Catalytic Reactions. Cyclopropanations. Reactions at 23 °C:
To a rigorously dried round flask was added the diruthenium(I,I)
catalyst (1 mol %) dissolved in CH2Cl2(1 mL). Styrene (0.25-0.3
mL, 2.1-2.6 mmol, 10 equiv) was added and the solution stirred
at room temperature for a few minutes under Ar to ensure complete
catalyst dissolution. Diazoacetate 7 (0.035 g, 0.2 mmol, 1 equiv)
was dissolved in CH2Cl2 (3 mL) and added to the reaction over
3 h via syringe pump, and the solution was then allowed to stir
overnight at room temperature. The mixture was then concentrated
in Vacuo. Reactions at 40 °C: To a rigorously dried round flask
was added the diruthenium(I,I) catalyst (1 mol %) dissolved in
CH2Cl2 (2 mL) under Ar atmosphere. Styrene (0.3 mL, 2.6 mmol,
13 equiv) was added, and the solution was heated to reflux. Methyl
phenyldiazoacetate 7 (0.035 g, 0.2 mmol, 1 equiv) was dissolved
in dry CH2Cl2 (3 mL) and added to the reaction mixture with a
syringe pump at the top of the reflux condenser over 3 h. The
solution was then allowed to stir for 2-5 h at reflux until all diazo
compound was decomposed (monitored by TLC). The mixture was
cooled to room temperature, concentrated in Vacuo, analyzed
by crude 1H NMR spectroscopy, and purified by flash column
chromatography (SiO2, 10% Et2O/pentane) to afford a white solid.
Data for Z-8: 1H NMR (400 MHz, CDCl3): δ 7.11-7.09 (m, 3H),
7.03-7.00 (m, 5H), 6.76-6.74 (m, 2H), 3.63 (s, 3H), 3.11 (dd,
1H, J ) 7.0, 9.5 Hz), 2.13 (dd, 1H, J ) 5.0, 9.5 Hz), 1.86 (dd, 1H,
J ) 5.0, 7.0 Hz). The spectroscopic data are consistent with the
previously reported results.35
1
847(m), 789(m), 768(m), 710(m), 682(m). H NMR ((CD3)2CO,
22 °C): δ 8.47, 8.22 (C-Harom) with an integrated ratio of 2:1. 19F
NMR (CDCl3, 22 °C): δ -62.41.
Preparation of [Ru2(O2C(3,5-CF3)2C6H3)2(CO)5 · (C6H5CH3)]
(IX). [Ru2(O2CCF3)2(CO)5] (I) (0.035 g, 0.06 mmol) was dissolved
in 10 mL of toluene. The yellow solution was filtered to a round-
bottom flask, which was then connected to a tube with a pre-
evacuated mineral oil. Orange crystals of IX appeared in 1 day in
80-90% yield.
Preparation of [Ru2(O2CCF3)2(CO)4 · (H2O)2] (X). [Ru2(O2-
CCF3)2(CO)4] (VII) (0.050 g, 0.09 mmol) was dissolved in 2 mL
of toluene, followed by the addition of several drops of water. The
red-colored solution was filtered to a clean round-bottom flask,
which was then connected to a tube with a pre-evacuated mineral
oil. Orange crystals of X appeared after 1 month in 80-90% yield.
X-ray Crystallographic Study. X-ray crystal data and refine-
ment details for IV: C38H8F12O18Ru4, fw ) 1384.72, yellow block,
0.23 × 0.06 × 0.05 mm, monoclinic P21/n, a ) 10.3336(5) Å, b
) 11.8386(6) Å, c ) 18.0531(10) Å, ꢀ ) 106.042(1)°, V )
2122.53(19) Å3, Z ) 2, Dc ) 2.167 g · cm-3, µ ) 1.527 mm-1, T
) 173(2) K, θmax ) 28.27°. For V: C38H8F12O18Ru4, fw ) 1384.72,
yellow block, 0.07 × 0.06 × 0.05 mm, monoclinic P21/n, a )
10.2883(5) Å, b ) 15.4363(8) Å, c ) 14.0317(7) Å, ꢀ )
110.340(1)°, V ) 2089.47(18) Å3, Z ) 2, Dc ) 2.201 g · cm-3, µ
) 1.551 mm-1, T ) 173(2) K, θmax ) 28.26°. For VI:
C38F20O18Ru4, fw ) 1528.66, yellow block, 0.10 × 0.09 × 0.08
mm, triclinic P1, a ) 9.6158(10) Å, b ) 10.5643(11) Å, c )
11.7591(12) Å, R ) 112.876(1)°, ꢀ ) 95.196(2)°, γ ) 91.192(2)°,
V ) 1094.0(2) Å3, Z ) 1, Dc ) 2.320 g · cm-3, µ ) 1.518 mm-1
,
T ) 173(2) K, θmax ) 25.00°. For VIII: C22H6F12O8Ru2, fw )
828.41, orange needle, 0.13 × 0.05 × 0.02 mm, triclinic P1, a )
9.6393(7) Å, b ) 11.3055(8) Å, c ) 14.1228(10) Å, R )
72.102(1)°, ꢀ ) 73.861(1)°, γ ) 67.004(1)°, V ) 1326.11(16) Å3,
Z ) 2, Dc ) 2.075 g · cm-3, µ ) 1.269 mm-1, T ) 173(2) K, θmax
) 24.99°. For IX: C30H14F12O9Ru2, fw ) 948.55, orange plate,
0.11 × 0.08 × 0.04 mm, triclinic P1, a ) 11.5905(7) Å, b )
11.9241(7) Å, c ) 13.0024(8) Å, R ) 76.263(1)°, ꢀ ) 73.727(1)°,
γ ) 77.817(1)°, V ) 1655.44(17) Å3, Z ) 2, Dc ) 1.903 g · cm-3
,
µ ) 1.032 mm-1, T ) 173(2) K, θmax ) 28.15°. For X:
C8H4F6O10Ru2, fw ) 576.25, orange block, 0.25 × 0.10 × 0.07
mm, monoclinic P21/c, a ) 12.6491(5) Å, b ) 8.7326(3) Å, c )
13.6260(5) Å, ꢀ ) 99.274(1)°, V ) 1485.45(9) Å3, Z ) 4, Dc )
2.577 g · cm-3, µ ) 2.157 mm-1, T ) 173(2) K, θmax ) 28.28°.
Bruker SMART APEX CCD-based X-ray diffractometer system,
Mo KR radiation (λ ) 0.71073 Å). Data were corrected for
absorption effects using the empirical methods SADABS (minimum/
maximum apparent transmissions are 0.7203/0.9276, 0.8992/0.9265,
0.8630/0.8882, 0.8524/0.9751, 0.8949/0.9599, and 0.6147/0.8637
for IV, V, VI, VIII, IX, and X, respectively). All non-hydrogen
atoms were refined anisotropically, except for disordered carbon
and fluorine atoms of four CF3 groups in VIII, three CF3 groups
in IX, and one CF3 group in X, for which disorder was modeled
over three rotational orientations. Hydrogen atoms in IV-VI and
X were found in the difference Fourier map and refined indepen-
dently, while their refinement in VIII and IX was mixed. For IV
full-matrix least-squares refinement on F2 converged at R1 ) 0.0207
and wR2 ) 0.0502 for 341 parameters and 4770 reflections with I
> 2σ(I) (R1 ) 0.0221, wR2 ) 0.0507 for 4997 unique reflections)
and a goodness of fit of 1.111. Final difference map is between
+0.430 and -0.542 e/Å3. For V full-matrix least-squares refinement
on F2 converged at R1 ) 0.0219 and wR2 ) 0.0532 for 341
parameters and 4455 reflections with I > 2σ(I) (R1 ) 0.0254, wR2
) 0.0546 for 4920 unique reflections) and a goodness of fit of 1.048.
Final difference map is between +0.489 and -0.349 e/Å3. For VI
full-matrix least-squares refinement on F2 converged at R1 ) 0.0438
and wR2 ) 0.1130 for 361 parameters and 3410 reflections with I
O-H Insertions. The diruthenium catalyst (0.007 g, 0.004
mmol, 1 mol %) was added to a rigorously dried round-bottom
flask purged with Ar. Anhydrous methanol (1 mL) was added to
dissolve the catalyst. Methyl phenylvinyldiazoacetate 4 (0.4 mmol,
1 equiv) was dissolved in anhydrous methanol (3 mL) and added
to the reaction mixture over 3 h via syringe pump. The reaction
mixture was allowed to stir at room temperature under argon for
24 h, concentrated in Vacuo, and then analyzed by crude 1H NMR
spectroscopy. Purification by flash column chromatography (SiO2,
10% Et2O/petroleum ether to 50% diethylether/petroleum ether
gradient) resulted in a colorless oil. Reaction with I with 0.2 mmol
of 4: Z-6:E-6:5a:5b ) 75:11:14:0 (0.022 g, 0.109 mmol, 45% yield);
reaction with II: Z-6:E-6:5a:5b ) 67:15:18:0 (0.022 g, 0.107 mmol,
26% yield); reaction with III: Z-6:E-6:5a:5b ) 62:18:20:0 (0.027
g, 0.132 mmol, 28% yield). Data for Z-6: 1H NMR (500 MHz,
CDCl3): δ 7.47-7.28 (m, 5H), 6.32 (dd, J ) 11.5, 9 Hz, 1H), 5.97
(d, J ) 9 Hz, 1H), 5.87 (d, J ) 11.5 Hz, 1H), 3.75 (s, 3H), 3.34 (s,
1
3H). Data for E-6: HNMR (500 MHz, CDCl3): δ 7.44-7.29 (m,
5H), 6.97 (dd, J ) 6, 15.5 Hz, 1H), 6.10 (d, J ) 15.5 Hz, 1H),
4.78 (d, J ) 6 Hz, 1H), 3.72 (s, 3H), 3.33 (s, 3H). Data for 5a,b:
1H NMR (500 MHz, CDCl3): δ 7.41-7.28 (m, 5H), 6.77 (d, J )
15.5, 1H), 6.20 (dd, J ) 7, 15.5, 1H), 4.43 (d, J ) 7, 1H), 3.79 (s,
(35) Thompson, J. L.; Davies, H. M. L. J. Am. Chem. Soc. 2007, 129,
6090–6091.

Ruthenium(I) Carbonyl Carboxylate Catalysts
Organometallics, Vol. 27, No. 8, 2008 1757
3H), 3.46 (s, 3H). The spectroscopic data are consistent with the
previously reported results.18
Et2O/pentane) resulted in 15 as a colorless oil. Catalyst I (37.6 mg,
0.14 mmol, 57%): 11:1 cis/trans-ratio; catalyst II (30 mg, 0.11
mmol, 45%): 13:1 cis/trans ratio; catalyst VI (35.6 mg, 0.13 mmol,
54%): 25:1 cis/trans ratio. Data for cis-15: TLC (10% Et2O/
pentane): Rf ) 0.39. 1H NMR (500 MHz, CDCl3): δ 7.21 (m, 1H),
6.43 (dt, 1H, JL ) 11.5 Hz, JS)7.0 Hz), 6.08 (t, 1H, J ) 3.0 Hz),
6.01 (m, 1H), 5.87 (m, 1H), 5.85 (m, 1H), 4.24 (d, 2H, J ) 11.0
Hz), 3.73 (s, 3H), 1.59 (s, 9H). 13C NMR (75 MHz, CDCl3): δ
166.6, 149.4, 147.0, 132.6, 121.2, 119.5, 112.0, 110.1, 83.7, 51.1,
28.7, 28.0. IR (film, cm-1): 2981(m), 1741(s), 1724(s), 1644(m),
1493(m), 1438(m), 1397(m), 1371(m), 1338(s), 1318(s), 1236(m),
1172(s), 1124(s), 1064(m). MS (ESI): m/z (rel. int.) 288 (31), 266
(100), 210 (17), 166 (46). HRMS (ESI): m/z calcd for [C14H19O4N
+ Na] 288.1206; found [M + Na] 288.1208.
Reaction with Cyclopentadiene. The diruthenium catalyst
(0.002 mmol, 1 mol %) was added to a rigorously dried round-
bottom flask, and cyclopentadiene (0.33 g, 5.0 mmol, 20 equiv)
and CH2Cl2 (2 mL) were added under an Ar atmosphere. Vinyl-
diazoacetate 9 (0.032 g, 0.25 mmol, 1 equiv) was dissolved in
CH2Cl2 (3 mL) and added to the reaction mixture over 2 h with a
syringe pump. The mixture was then stirred for a further 9-12 h
at room temperature until complete consumption of the diazo
compound. The solvent was removed in Vacuo and the crude residue
analyzed by 1H NMR. Purification by flash column chromatography
(SiO2, 10% Et2O/pentane) resulted in cis/trans-10 as a colorless
oil. With catalyst I (22 mg, 0.13 mmol, 54%): 2:1 isomer ratio;
catalyst II (15.0 mg, 0.09 mmol, 37%): 2:1 isomer ratio; catalyst
VI (16.4 mg, 0.10 mmol, 40%): 2.4:1 isomer ratio. Data for 10:
1H NMR (400 MHz, CDCl3): δ 6.28 (dd, J ) 3.0, 5.5 Hz, 1H),
6.00 (dd, J ) 3.0, 5.5 Hz, 1H), 5.92 (s, 1H), 3.67 (s, 3H), 3.32 (m,
1H), 3.08 (m, 1H), 2.57 (dm, 1H), 2.34 (dm, 1H), 1.70-1.67 (m,
1H), 1.47 (d, J ) 8.0 Hz, 1H). The spectroscopic data are consistent
with the previously reported results.15
Reaction with N-Boc Pyrrole. The diruthenium catalyst (0.002
mmol, 1 mol %) was dissolved in dry CH2Cl2 (2 mL) under Ar
atmosphere, and N-Boc pyrrole (20 equiv) was added. Vinyldiaz-
oacetate 9 (0.25 mmol, 1 equiv) was dissolved in dry CH2Cl2 (3
mL) and added to the reaction mixture over 2 h with a syringe
pump. After the addition was complete the reaction was stirred at
rt for a further 9–12 h, concentrated in Vacuo, and analyzed by
crude 1H NMR. Purification by flash column chromatography (10%
Acknowledgment. M.P. thanks the Donors of the Ameri-
can Chemical Society Petroleum Research Fund (PRF
#42910-AC3) and the National Science Foundation Career
Award (NSF-0546945) for partial support of this work, and
the National Science Foundation funding of the NMR
spectrometer (CHE-0342660) at the University at Albany.
H.M.L.D. thanks the National Science Foundation (CHE-
0350536 and CHE-0750273) for support of this work.
Supporting Information Available: Four CIF files providing
crystallographic data for compounds IV-VI, and VIII. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM700888F