Metallacyclopentatriene-butadienyl carbene rearrangement in the oxidative coupling of alkynes mediated by [RuCp(SbR3)(CH3CN)2]+ (R = Ph, n-Bu)

Article abstract of DOI:10.1021/om030039n

The oxidative coupling of alkynes is investigated as promoted by the half-sandwich compound [RuCp(SbR₃)(CH₃CN)₂]PF₆ (R = Ph, n-Bu). There are various ways by which the initially formed electrophilic metallacyclopentatriene complex rearranges to a stable product. In the case where the alkyne disposes of an α-alkyl substituent, intramolecular 1,2 hydrogen migration leads to a butadienyl carbene complex as obtained by using 2,8-decadiyne or HC≡CCH₂R′ (R′ = n-Pr, Ph, OH). A conceivable mechanism for this reaction sequence is established by means of DFT/B3LYP calculations. In line with experiment, the existence of two isomeric butadienyl carbene complexes is proposed. In the case of R′ = Ph and OH the butadienyl carbene is not the final product but rearranges to give η³-allyl-vinyl and η³-allyl-acyl complexes. In the absence of an α-alkyl substituent as for HC≡CC₆H₉, HC≡CC₆H₁₀-OH, and HC≡CCMe₂OH, η³-butadienyl-vinyl complexes are formed. Finally, from the alkynes HC≡CPh, HC≡CBu^t, and HC≡CSiMe₃ no tractable materials are obtained.

Full text of DOI:10.1021/om030039n

2124
Organometallics 2003, 22, 2124-2133
Meta lla cyclop en ta tr ien e-Bu ta d ien yl Ca r ben e
Rea r r a n gem en t in th e Oxid a tive Cou p lin g of Alk yn es
Med ia ted by [Ru Cp (SbR3)(CH3CN)2]+ (R ) P h , n -Bu )†
Eva Becker,‡ Kurt Mereiter,§ Michael Puchberger, Roland Schmid,‡ and
Karl Kirchner*,‡
Institute of Applied Synthetic Chemistry, Institute of Chemical Technologies and Analytics,
and Institute of Material Chemistry, Vienna University of Technology, Getreidemarkt 9,
A-1060 Vienna, Austria
Received J anuary 17, 2003
The oxidative coupling of alkynes is investigated as promoted by the half-sandwich
compound [RuCp(SbR3)(CH3CN)2]PF6 (R ) Ph, n-Bu). There are various ways by which the
initially formed electrophilic metallacyclopentatriene complex rearranges to a stable product.
In the case where the alkyne disposes of an R-alkyl substituent, intramolecular 1,2 hydrogen
migration leads to a butadienyl carbene complex as obtained by using 2,8-decadiyne or HCt
CCH2R′ (R′ ) n-Pr, Ph, OH). A conceivable mechanism for this reaction sequence is
established by means of DFT/B3LYP calculations. In line with experiment, the existence of
two isomeric butadienyl carbene complexes is proposed. In the case of R′ ) Ph and OH the
butadienyl carbene is not the final product but rearranges to give η3-allyl-vinyl and η3-allyl-
acyl complexes. In the absence of an R-alkyl substituent as for HCtCC6H9, HCtCC6H10-
OH, and HCtCCMe2OH, η3-butadienyl-vinyl complexes are formed. Finally, from the alkynes
HCtCPh, HCtCBut, and HCtCSiMe3 no tractable materials are obtained.
In tr od u ction
butadienyl carbenes. Pathway (i) is favored if the ER3
co-ligand is not too bulky and appreciably nucleophilic
toward carbon. The alternative pathway (ii) is preferred
if at least two conditions are met, namely, a weakly
nucleophilic co-ligand as is the case for E ) As and Sb
and an alkyne with an R-alkyl substituent.
The present work is intended to investigate in some
more detail the metallacyclopentatriene-butadienyl
carbene conversion at [RuCp(SbR3)(CH3CN)2]PF6 (R )
Ph (1a ), n-Bu (1b)). In the preceding paper we used 2,8-
decadiyne as the alkyne.2 Here now we perform a
labeling study by applying 2,8-decadiyne-d6 to help
elucidate the intimate mechanism of the 1,2 hydrogen
shift. Furthermore we will use a range of terminal
alkynes HCtCCH2R′, with and without R-alkyl sub-
stituents, to get some hints as to the reactivity of
butadienyl carbene complexes, including their behavior
toward bases. Finally the mechanistic considerations
will be supported by DFT/B3LYP calculations.
Recent studies of the interactions between the [RuCp-
(ER3)]+ moiety, derived from labile [RuCp(ER3)(CH3-
CN)2]PF6, and alkynes have revealed a subtle and
diverse coordination chemistry.1,2 Thus, depending on
the ER3 co-ligand, where E is a group 15 element, and
the structure of the alkyne, a large variety of oxidative
coupling products has been encountered such as allyl,
butadienyl, allenyl, and vinylidene complexes. It would
appear that there is a common initial step featured by
the formation of a highly electrophilic cationic metal-
lacyclopentatriene species3 which is stabilized by sub-
sequent rearrangement(s). The two main reaction
schemes are (i) ligand migration, which gives initially
allyl carbenes, and (ii) a 1,2 hydrogen shift resulting in
† Dedicated to Prof. J ohn P. Hunt, a very respected friend and
colleague, on the occasion of his 80th birthday.
* Corresponding author. E-mail: kkirch@mail.zserv.tuwien.ac.at.
‡ Institute of Applied Synthetic Chemistry.
§ Institute of Chemical Technologies and Analytics.
Resu lts a n d Discu ssion
Institute of Material Chemistry.
(1) (a) Ru¨ba, E.; Mereiter, K.; Schmid, R.; Kirchner, K. Chem.
Commun. 2001, 1996. (b) Ru¨ba, E.; Mereiter, K.; Schmid, R.; Sapunov,
V. N.; Kirchner, K.; Schottenberger, H.; Calhorda, M. J .; Veiros, L. F.
Chem. Eur. J . 2002, 8, 3948.
(2) Becker, E.; Ru¨ba, E.; Mereiter, K.; Schmid, R.; Kirchner, K.
Organometallics 2001, 20, 3851.
(3) For metallacyclopentatriene complexes see: (a) Albers, M. O.;
deWaal, D. J . A.; Liles, D. C.; Robinson, D. J .; Singleton, E.; Wiege,
M. B. J . Chem. Soc., Chem. Commun. 1986, 1680. (b) Gemel, C.;
LaPense´e, A.; Mauthner, K.; Mereiter, K.; Schmid, R.; Kirchner, K.
Monatsh. Chem. 1997, 128, 1189. (c) Pu, L.; Hasegawa, T.; Parkin, S.;
Taube, H. J . Am. Chem. Soc. 1992, 114, 2712. (d) Hirpo, W.; Curtis,
M. D. J . Am. Chem. Soc. 1988, 110, 5218. (e) Kerschner, J . L.; Fanwick,
P. E.; Rothwell, I. P. J . Am. Chem. Soc. 1988, 110, 8235. (f) Hessen,
B.; Meetsma, A.; van Bolhuis, F.; Teuben, J . H.; Helgesson, G.; J agner,
S. Organometallics 1990, 9, 1925. (g) Ernst, C.; Walter, O.; Dinjus, E.;
Arzberger, S.; Go¨rls, H. J . Prakt. Chem. 1999, 341, 801.
Syn th etic Asp ects. As already described,1,2 com-
plexes 1a and 1b react with 2,8-decadiyne to give via a
metallacyclopentatriene intermediate (2) the butadienyl
carbenes 3a and 3b (Scheme 1). The involvement of a
metallacylopentatriene intermediate on the pathway to
butadienyl carbenes is evident from 1H and 13C{1H}
NMR spectroscopic studies. Thus, the resonances in the
13C{1H} NMR spectrum of [RuCp(dC2(CH3)2C2(CH2)4)-
(SbPh3)]+ (2) at 330.3 and 171.3 ppm can be associated
with the CR and Câ ring carbons, respectively.2 The
unusual downfield shifted resonances of the CR carbon
atoms is in agreement with an unsaturated bis-carbene
10.1021/om030039n CCC: $25.00 © 2003 American Chemical Society
Publication on Web 04/17/2003

Oxidative Coupling of Alkynes
Organometallics, Vol. 22, No. 10, 2003 2125
Sch em e 1
ligand. The analogous phosphine-based metallacyclo-
pentatriene [RuCp(dC2(CH3)2C2(CH2)4)(PCy3)]+ also ex-
hibits the characteristic resonances of the CR and Câ ring
carbons at 325.6 and 170.6 ppm, respectively1a (cf. the
neutral metallacyclopentatriene RuCp(dC2(Ph)2C2H2)-
Br, for which the respective resonances of the CR and
Câ atoms are found at 271.1 and 156.0 ppm3a). This
conversion involves a net 1,2 hydrogen shift. To estab-
lish whether an intramolecular or intermolecular mi-
gration process is operative, we treat here 1a with 2,8-
decadiyne-d6 in acetone, whereupon 3a -d6 was obtained
butadienyl carbene in the presence of tert-butylamine,
a process clearly related to our findings.5
The reactivity of 3a has been tested by treating it with
bases. As a result, NEt3 or n-BuLi leads to deprotona-
tion of one methyl substituent to yield the neutral
complex RuCp(-CdCH2)C(CH2)4C-η2-CHdCH2)(SbPh3)
(4). This reaction is particularly clean if a solution of
3a in CH2Cl2 is chromatographed over basic Al2O3,
affording 4 in 68% isolated yield (Scheme 1). With 3b,
on the other hand, no reaction took place. Product 4 was
characterized by a combination of elemental analysis
1
1
and H and 13C{1H} NMR spectroscopies. Characteristic
quantitatively. The comparison of its H NMR spectrum
solution 1H NMR spectroscopic data include two dou-
blets at 5.46 (Hb) and 4.68 (Ha) ppm with a coupling
with that of 3a obtained from 2,8-1a and 2,8-decadiyne
acetone-d6 shows that the resonances of the methyl
substituent and the resonances of the -CHdCH2 unit
are absent. There is no indication that scrambling with
hydrogen from the solvent occurred. Complementarily,
the 2H spectrum of 3a -d6 exhibits exclusively four
resonances at 4.89-4.31 (Da), 3.22-2.37 (Dc), 2.15 (CD3),
and 1.47-1.03 (Db) ppm. In addition, a crossover study
was conducted in which an equimolar mixture of 2,8-
decadiyne and 2,8-decadiyne-d6 was reacted with 1a in
acetone-d6 at room temperature, revealing that only 3a
and 3a -d6 were formed. Accordingly, no scrambling of
D was observed, and it is therefore reasonable to assume
that hydrogen migration has taken place in an intra-
molecular fashion. On the basis of this competition
experiment a large primary kinetic isotope effect of kH/
kD(25 °C) ) 10.0 ( 0.5 was observed, clearly showing
that C-H (or C-D) bond cleavage is involved in the
rate-determining step. The magnitude of this isotope
effect would be consistent with a direct 1,2 hydrogen
(or 1,2 deuterium) migration.
2
constant J HH ) 2.4 Hz assignable to the hydrogen
atoms of the vinyl -CdCH2 unit and two doublets and
one triplet a 4.79 (Hd), 2.73 (He), and 4.62 (Hc) ppm with
3
a cis and trans coupling constant J HH ) 8.9 Hz
assignable to the hydrogen atoms of the butadienyl
moiety. The 13C{1H} NMR signals appearing at 161.0,
62.6, and 31.5 ppm are assignable to the vinyl carbon
atom C1 and the coordinated olefinic carbon atoms C5
and C6, respectively. All other resonances are unre-
markable.
It is worth noting that the formation of 4 is reversible.
In fact, addition of H2SO4 leads to a clean back-
transformation to 3a . If D2SO4 is used instead, the
isotopomer 3a -d6 is obtained. That is, quantitative
scrambling of D into the methyl substituent has taken
place. This behavior can be interpreted in terms of an
equilibrium reaction occurring between 3a and 4.
The structural identity of 4 was established by X-ray
crystallography. The result depicted in Figure 1 shows
It may be noted that a 1,2 hydrogen shift is hitherto
known only for electrophilic, typically cationic, alkyl
carbenes such as [FeCp(CO)2(dC(CH3)2)]+ and related
species.4 Taube and co-workers reported for the first
time the conversion of the dicationic osmacyclopenta-
triene complex [Os(en)2(dC2(CH3)2C2(CH3)2)]2+ to a
(4) For carbene to olefin conversions see: (a) Casey, C. P.; Miles,
W. H.; Tukada, H. J . Am. Chem. Soc. 1985, 107, 2924. (b) Bodnar, T.;
Cutler, A. R. J . Organomet. Chem. 1981, 213, C13. (c) Fischer, E. O.;
Held, W. J . Organomet. Chem. 1976, 112, C59.
(5) Pu, L.; Hasegawa, T.; Parkin, S.; Taube, H. J . Am. Chem. Soc.
1992, 114, 7609.

2126 Organometallics, Vol. 22, No. 10, 2003
Becker et al.
F igu r e 1. Structural view of [RuCp(-CdCH2)C(CH2)4C-
η2-CHdCH2)(SbPh3)] (4) showing 20% thermal ellipsoids
(H atoms outside the triene system C6-7-8-13-14-15
omitted for clarity). Selected bond lengths (Å) and angles
(deg): Ru-C(1-5)av 2.209(5), Ru-C(7) 2.092(4), Ru-C(14)
2.169(5), Ru-C(15) 2.188(5), Ru-Sb 2.529(1), C(6)-C(7)
1.346(6), C(7)-C(8) 1.459(6), C(8)-C(13) 1.328(6), C(13)-
C(14) 1.482 (6), C(14)-C(15) 1.393(7), C(7)-Ru-C(14)
78.4(1), C(7)-C(8)-C(13)-C(14) 2.7(6).
F igu r e 2. Structural view of [RuCp(dCHC(n-Bu)CH-η2-
CHdCH-n-Pr)(SbPh3)]PF6 (3c) showing 20% thermal el-
lipsoids (H atoms outside the butadienyl carbene system
and PF6- omitted for clarity). Selected bond lengths (Å) and
angles (deg): Ru-C(1-5)av 2.239(8), Ru-C(6) 1.908(6),
Ru-C(13) 2.260(5), Ru-C(14) 2.188(6), Ru-Sb 2.567(1),
C(6)-C(7) 1.439(8), C(7)-C(12) 1.346(8), C(12)-C(13)
1.462(8), C(13)-C(14) 1.422(8), C(6)-Ru-C(13) 76.7(2),
C(6)-C(7)-C(12)-C(13) 2.2(8).
a three-legged piano stool conformation with SbPh3,
with the two CdC bonds butadienyl moiety, and the
vinyl carbon atom as the legs. The Ru-C(7) bond
distance of 2.092(4) Å is in line with a metal carbon
single bond. The Ru-C(14) and Ru-C(15) bond dis-
tances are 2.169(5) and 2.188(5) Å, respectively. The
butadienyl C-C bonds C(8)-C(13), C(13)-C(14), and
C(14)-C(15) show the expected short-long-short pat-
tern (1.328(6), 1.482(6), and 1.393(7) Å, in the same
order). The Ru-Sb bond length of 2.529(1) Å may be
compared with the 2.575(1) Å in 3a .
We now turn to the reaction of 1 with various
terminal alkynes HCtCCH2R′ noting a dramatic sub-
stituent effect of R′ on the outcome. With R′ ) n-Pr, Ph,
the same result was obtained as with 2,8-decadiyne,
giving the butadienyl carbenes 3c-e. Interestingly, the
structure of 3c contains the butadienyl moiety in a
distorted s-trans conformation rather than distorted
s-cis as found in 3a . The solid-state structure of 3c is
depicted in Figure 2 with important bond distances
reported in the caption. Overall, the structure is similar
to that of 3a , i.e., a typical three-legged piano stool
conformation with SbPh3, with the two CdC bonds of
the butadienyl moiety and the carbene carbon atom as
the legs. The most notable feature is the short Ru-C(6)
bond distance of 1.908(6) Å, reflecting a metal carbon
double bond. The Ru-C(13) and Ru-C(14) bond dis-
tances are 2.260(5) and 2.188(8) Å, respectively. Fur-
thermore, the butadienyl C-C bonds C(7)-C(12), C(12)-
C(13), and C(13)-C(14) again show the expected short-
long-short pattern of 1.346(8), 1.462(8), and 1.422(8)
Å, respectively. Compound 3c crystallizes also as as the
acetone solvate 3c‚(CH3)2CO, which agrees in the inner
part of the Ru complex very well with its unsolvated
counterpart but differs in the conformations of both
alkyl side chains (C(8)-C(11) and C(15)-C17)). Struc-
tural data of this compound have been deposited under
CCDC-201214.
and η3-allyl-acyl complexes of the types [RuCp(η3-
CH2C(CH2Ph)CH-η1-CdCH-Ph)(SbR3)]PF6 (5a ,b)2 and
[RuCp(η3-CH2CCH2-CHdCH-η1-CO)(SbR3)]PF6 (6a ,b),
respectively (Scheme 2). The only exception is when
HCtCCH2Ph is reacted with 1a , where [RuCp(dCHC-
(CH2Ph)CH-η2-CHdCH-Ph)(SbPh3)]PF6 (3d ) was iso-
lated and characterized. Crystals grown from 5a in
acetone showed two different types, which, from single-
crystal X-ray crystallographic analysis, turned out to
be the acetone solvate 5a ‚(CH3)2CO and the ansolvate
5a ′. Both kinds of crystals were obtained by diffusion
of Et2O into acetone solutions at room temperature,
giving at first the unstable solvate and on prolonged
standing the stable ansolvate. The ORTEP plots are
depicted in Figures 3 and 4 along with some selected
bond distances and angles. Accordingly, while both
possess a type of “three-legged piano stool” molecular
structure, with SbPh3, the three carbon atoms of the
η3-allyl moiety, and the vinyl carbon atom as the legs,
they differ stereochemically. In 5a ‚(CH3)2CO, the phenyl
substituent of the vinyl unit is cis to the allyl moiety,
in contrast to trans in 5a ′.
In the allyl vinyl system of 5a ′ all four carbon atoms
of the C1-4 chain are bonded to the RuCp fragment. The
C1-4 chain is nearly planar, with a torsion angle of
9.6(6)°. The Ru-C(9) distance is 2.123(4) Å, typical of a
Ru-C vinyl single bond. The allyl moiety is bonded
asymmetrically to the metal center with the Ru-C
bonds to the terminal allyl carbon atoms C(6) and C(8)
(2.223(4) and 2.191(4) Å, respectively) being longer than
the Ru-C bond to the central allyl carbon atom C(7)
(2.187(4) Å). The C-C distances within the allyl vinyl
moiety are relatively uniform. The C(6)-C(7), C(7)-
C(8), and C(8)-C(9) bond distances are 1.412(6), 1.409(6),
and 1.416(6) Å, respectively, while the C(9)-C(10)
When R′ ) Ph and OH, the butadienyl carbene
complexes initially formed are not the final products but
undergo further rearrangements giving η3-allyl-vinyl

Oxidative Coupling of Alkynes
Organometallics, Vol. 22, No. 10, 2003 2127
Sch em e 2
F igu r e 4. Structural view of trans-[RuCp(η3-CH2C(CH2-
Ph)CH-η1-CdCH-Ph)(SbPh3)]PF6 (5a ′) showing 20% ther-
F igu r e 3. Structural view of cis-[RuCp(η3-CH2C(CH2Ph)-
-
mal ellipsoids (aromatic H atoms and PF6 omitted for
CH-η1-CdCH-Ph)(SbPh3)]PF6‚(CH3)2CO (5a ‚(CH3)2CO)
clarity). Selected bond lengths (Å) and angles (deg): Ru-
C(1-5)av 2.183(8), Ru-C(6) 2.223(4), Ru-C(7) 2.187(4),
Ru-C(8) 2.191(4), Ru-C(9) 2.123(4), Ru-Sb 2.599(1),
C(6)-C(7) 1.412(6), C(7)-C(8) 1.409(6), C(8)-C(9) 1.416 (6),
C(9)-C(10) 1.329(6), C(8)-C(9)-C(10)-C(11) -162.1(5).
-
showing 20% thermal ellipsoids (aromatic H atoms, PF6
,
and (CH3)2CO omitted for clarity). Selected bond lengths
(Å) and angles (deg): Ru-C(1-5)av 2.200(10), Ru-C(6)
2.232(8), Ru-C(7) 2.184(8), Ru-C(8) 2.164(8), Ru-C(9)
2.086(8), Ru-Sb 2.575(1), C(6)-C(7) 1.398(11), C(7)-C(8)
1.436(11), C(8)-C(9) 1.407 (11), C(9)-C(10) 1.301(10),
C(8)-C(9)-C(10)-C(11) 10.1(17).
at 7.36 (H3) and 7.36 (H2) ppm with the coupling
3
constant J HH ) 6.8 Hz. In the 13C{1H} NMR spectrum
the acyl carbon atom is revealed by a characteristic
singlet at 234.9 ppm, while the carbon atoms of the
olefin unit are observed at 150.0 and 147.8 ppm,
assignable to C3 and C2, respectively. The three allyl
carbons appear as signals at 119.4, 68.0, and 44.5 ppm,
assignable to C4, C5, and C6, respectively. The Cp ligand
shows a singlet at 93.5 ppm. The NMR spectra of 6b
are analogous. In the absence of crystals of 6a and 6b
suitable for a single-crystal X-ray diffraction study, the
structural assignment has been achieved by means of
1H and 13C NMR GIAO calculations based on the
optimum DFT/B3LYP model of [RuCp(η3-CH2CCH2-
distance is 1.329(6) Å, typical of a C-C double bond.
The bond distances in 5a ‚(CH3)2CO are very similar.
Complexes 6a and 6b are air-stable compounds.
Support for the formulations comes from elemental
analysis as well as from 1H, 13C{1H} NMR and IR
spectroscopy. The carbonyl stretching frequency of the
1
acyl moiety in 6a is observed at 1688 cm-1. In the H
NMR spectrum of 6a the Cp ring is found as a singlet
at 5.81 ppm. The allyl moiety exhibits signals in the
range 4.22-4.27 (2H, H5a, H6a), 4.21 (1H, H6s), and 4.02
(1H, H5s). The hydrogen atoms of the noncoordinated
double bond display two characteristic doublets centered

2128 Organometallics, Vol. 22, No. 10, 2003
Becker et al.
Sch em e 3
F igu r e 5. Experimental and calculated (DFT/B3LPY-
GIAO) 13C chemical shifts δ (in ppm relative to TMS) for
[RuCp(η3-CH2CCH2-CHdCH-η1-CO)(SbBun3)]PF6 (6b )
(spectrum A, solvent ) acetone-d6) and the DFT optimized
model [RuCp(η3-CH2CCH2-CHdCH-η1-CO)(SbMe3)]+ (spec-
trum B), respectively (signals of SbBun3 and SbMe3 carbon
atoms have been omitted for clarity).
CHdCH-η1-CO)(SbMe3)]+. The calculated NMR spectra
are in excellent agreement with the experimental values
(see Experimental Section). In Figure 5 is compared the
13C NMR spectrum of 6a with that of the model complex
[RuCp(η3-CH2CCH2CHdCH-η1-CO)(SbMe3)]+.
The actual mechanism for the formation of 6 remains
unclear, since H NMR monitoring of the reaction of 1
spectroscopy and elemental analysis. Since the overall
spectroscopic features are very similar, we describe only
those of 7a . Characteristic signals of the 1H NMR
spectrum include two doublets centered at 8.10 and 6.84
ppm (4J HH ) 3.5 Hz) assignable to H4 and H6, respec-
tively. In the 13C{1H} NMR spectrum the η3-butadienyl
unit is recognized by resonances at 197.4, 133.9, 94.1,
and 66.4 ppm, assignable to C3, C4, C2, and C1, respec-
tively.8 Furthermore, the η1-vinyl unit exhibits two
signals at 165.5 and 119.6 ppm, assignable to C5 and
C6, respectively.
Finally, the interaction of the alkynes HCtCPh, HCt
CBut, and HCtCSiMe3 with 1 did not result in any
tractable materials. In these particular cases, as it
would appear, no suitable reaction path is accessible to
stabilize the initial metallacyclopentatriene intermedi-
ate.
Mech a n istic Asp ects. A conceivable pathway for the
reaction of the model bisacetonitrile complex [RuCp-
(SbH3)(NCH)2]+ (A) with the alkynes HCtCH and HCt
CCH3 used as model substrates is shown in Figure 6
based on DFT/B3LYP calculations using Gaussian98
(energy in kcal/mol).
The reliability of the computational method (details
in Experimental Section) is supported by the good
agreement between the calculated geometries of the two
isomeric butadienyl carbene complexes E and G with
the X-ray structures for the related complexes 3a and
3c despite the absence of substituents in the model. The
1
with propargylic alcohol at low temperatures did not
reveal any intermediates. That is, only the disappear-
ance of 1 and the quantitative formation 6 is observed.
Notwithstanding this, a conceivable intermediate might
be a hydroxycarbene complex6 as result of an olefin-to-
carbene rearrangement involving a 1,2 hydrogen shift
from a butadienyl carbene (Scheme 2). It is well known
indeed that the conversion of an activated olefin into a
heteroatom-stabilized carbene is a thermodynamically
favorable process.7 During the reaction water is liber-
1
ated, as detected by H NMR spectroscopy.
The alkynes utilized so far contain an R-alkyl sub-
stituent capable of facile 1,2 hydrogen shift. In the
following we also take other ones lacking R-C-H bonds,
namely, HCtCC6H9 and the propargylic alcohols HCt
CC6H10OH and HCtCCMe2OH. In these three cases η3-
butadienyl-vinyl complexes are formed, as presented in
Scheme 3. Thus with 1b the compounds [RuCp(η1-CHC-
(C6H9)CHd(η3-CC(CH2)4CH)(SbBun3)]PF6 (7b), [RuCp-
(η1-CHC(C6H10OH)CHd(η3-CC(CH2)4CH)(SbBun3)]PF6
(8), and [RuCp(η1-CHC(Me)2OHCHd(η3-CC(Me)CH2)-
(SbR3)]PF6 (9) are obtained. HCtCC6H9 was also re-
acted with 1a , resulting in [RuCp(η1-CHC(C6H9)CHd
(η3-CC(CH2)4CH)(SbPh3)]PF6 (7a ).
All of these are air-stable compounds and were
1
identified by a combination of H and 13C{1H} NMR
(6) Casey, C. P.; Czerwinski, C. J .; Fusie, K. A.; Hayashi, R. K. J .
Am. Chem. Soc. 1997, 119, 3971, and references therein.
(8) For η3-butadienyl complexes see: (a) Slugovc, C.; Mereiter, K.;
Schmid, R.; Kirchner, K. Eur. J . Inorg. Chem. 1999, 1141, 1. (b) Yi, C.
S.; Liu, N.; Rheingold, A. L.; Liable-Sands, L. M. Organometallics 1997,
16, 3910. (c) Werner, H.; Wiedmann, R.; Steinert, P.; Wolf, J . Chem.
Eur. J . 1997, 3, 127. (d) Bruce, M. I.; Duffy, D. N.; Liddell, M. J .;
Tiekink, E. R. T.; Nicholson, B. K. Organometallics 1992, 11, 1527. (e)
Bruce, M. I.; Hambly, T. W.; Liddell, M. J .; Snow, M. R.; Swincer, A.
G.; Tiekink, E. R. T. Organometallics 1990, 9, 96.
(7) (a) Coalter, J . N.; Spivak, G. J .; Gerard, H.; Clot, E.; Davidson,
E. R.; Eisenstein, O.; Caulton, K. G. J . Am. Chem. Soc. 1998, 120, 9388.
(b) Coalter, J . N.; Bollinger, J . C.; Huffman, J . C.; Zwanziger, U. W.;
Caulton, K. G.; Davidson, E. R.; Gerard, H.; Clot, E.; Eisenstein, O.
New J . Chem. 2000, 24, 9. (c) Slugovc, C.; Mereiter, K.; Schmid, R.;
Kirchner, K. Organometallics 1998, 17, 827. (d) Heinekey, D. M.;
Radzewich, C. E. Organometallics 1998, 17, 51.

Oxidative Coupling of Alkynes
Organometallics, Vol. 22, No. 10, 2003 2129
F igu r e 6. Profile of the B3LYP potential energy surfaces (in kcal/mol) for the conversion of A to the two isomeric butadienyl
carbenes E and G.
F igu r e 7. Optimized B3LYP geometries of the equilibrium structures and transition states B, C, D, TSBC, and TSCD
(distances in Å) and calculated (DFT-GIAO) 13C chemical shifts δ (in ppm relative to TMS) for C (italic)
detailed structures of the entities B-G and the corre-
sponding transition states TSBC-TSF G are displayed in
Figures 7 and 8.
tion state TSBC revealed a moderate activation barrier
of 8.8 kcal/mol. The formation of C is strongly exother-
mic, releasing 34.1 kcal/mol. In this reaction step a new
carbon-carbon bond starts to form, noting a C‚‚‚C
distance decrease from 2.73 in B to 2.11 in TSBC, to
reach 1.37 Å in species C, characteristic of a CdC bond.
Simultaneously the two acetylene ligands have to reori-
ent themselves, so that two of the Ru-C bonds become
stronger (distances decrease from 2.326, 2.25 (B), via
2.15, 2.13 (TSBC) to 1.92, 1.97 Å (C), and the other two
weaker. These changes occur smoothly, with the transi-
tion state occupying an intermediate position somewhat
closer to the bisacetylene complex than to the metalla-
cycle. Note that the CR-Câ distances are still rather
short, exhibiting a triple-bond character (1.27 and 1.27
compared to 1.25 Å in the starting structure B), while
Câ-Câ′ is still away from a bonding distance (2.11 Å).
The calculated structure of C compares well with the
The overall reaction from A to E and G is exothermic
by -30.2 and -29.4 kcal/mol, respectively. In the initial
step the ligated acetonitrile molecules are replaced by
the acetylenes to give the bis-acetylene complex B. Such
processes, as is known from experiment, proceed by a
dissociative mechanism,9 whereas the associative alter-
native needing concomitant η5 f η3 ring slippage to
preserve the 18-electron count can be ruled out. Note
that the overall substitution reaction A + 2 HCtCH f
B + 2HCN is endothermic by 14.4 kcal/mol. Oxidative
coupling of the acetylene ligands in B brings us in a
symmetry-allowed process to the coordinatively satu-
rated metallacyclopentatriene C. Location of the transi-
(9) Luginbu¨hl, W.; Zbinden, P.; Pittet, P. A.; Armbruster, T.; Bu¨rgi,
H.-B.; Merbach, A. E.; Ludi, A. Inorg. Chem. 1991, 30, 2350.

2130 Organometallics, Vol. 22, No. 10, 2003
Becker et al.
F igu r e 8. Optimized B3LYP geometries of the equilibrium structures and transition states E, F , G, TSDE, TSDF , and
TSF G (distances in Å).
X-ray structures of the related species containing the
CpRuBr and RuCp* fragments.3a,g GIAO calculations
based on the optimum DFT model of C give 13C NMR
chemical shifts of CR, Câ, and CH3 in good agreement
with the experimental values of a similar compound
(Figure 7). For comparison, the resonances of CR, Câ,
and CH3 carbon atoms in the 13C{1H} NMR spectrum
of [RuCp(dC2(CH3)2C2(CH2)4)(SbPh3)]+ (2) give rise to
signals at 330.3, 171.3, and 53.5 ppm, respectively. The
unusually downfield shifted proton signals of the CH3
substituent can be interpreted to mean that the C-H
bonds are prone to cleavage, in other words, that the
hydrogens are rather acidic.
estimate of the kinetic isotope effect for the conversion
of C to D is provided by the difference in zero-point
energies at transition state TSCD when hydrogen is
replaced by deuterium. This estimate gives a value of
kH/kD ) 10.8, in excellent agreement with the experi-
mental value.
Also seen in Figure 6, facile rotation about the agostic
C-H bond in a clockwise fashion affords eventually via
TSDE the butadienyl carbene E, in which the butadienyl
moiety adopts a distorted s-cis conformation. Alterna-
tively, counterclockwise rotation affords via intermedi-
ate F the isomeric butadienyl carbene G. The rotation
barriers are very small, being 2.1, 0.1, and 4.4 kcal/mol
for the reaction of D to E, D to F , and F to G,
respectively. Since the energy difference between the
isomers E and G is extremely small (only 0.8 kcal/mol),
the preference of either E or G will be guided by the
substituents of the alkynes. This is in keeping with
experiment (cf. the structures of 3a and 3c).
Therefore, C may be capable of undergoing a direct
1,2 hydrogen shift to give via TSCD the intermediate
D, featuring an agostic C-H bond and still one metal
carbon double bond (path a in Figure 6). This reaction
is endothermic (6.5 kcal/mol) with a comparatively high
activation barrier of 35.9 kcal/mol. (Both solvation and
tunneling effects10 may be important in hydrogen shift
reactions, which could lower the high activation barrier.
Such effects, however, are not taken into account by
DFT calculations.) Note further that TSCD lies closer
to D than to C, since the CH3-C bond is already short
toward a double-bond character. As the reaction pro-
ceeds, the CH3-C bond decreases from 1.50 Å in C to
1.40 Å in TSCD and finally reaches 1.35 Å in D, being a
typical CdC bond. This is accompanied by migration of
a hydrogen atom (essentially a proton) along the π-cloud
of the C-C double bond. Thus, the rate-determining
step for the formation of butadienyl carbenes is the
conversion of C to D, which is expected to exhibit a large
primary kinetic isotope effect. In accordance with the
high activation barrier, intermediate C could be de-
As suggested by a reviewer, an alternative mechanism
for the conversion of C to butadienyl carbenes may
proceed via a C-H activation (â-elimination) route (path
b in Figure 6) involving species such as H and I. While
from a thermodynamic point of view H might be indeed
accessible despite the endothermic nature of this reac-
tion (18.1 kcal/mol), kinetically such a process may be
rather prohibitive for geometric reasons; that is, the
methyl C-H bonds due to the rigid five-membered
metallacycle (the Ru-CR-CH3 angle in C is 126.3°) may
be unable to approach the metal center. It has to be
noted also that all attempts to locate a transition state
for this process failed. It is interesting to note, however,
that species H is able to undergo facile C-H bond
cleavage (â-elimination), requiring only 2.6 kcal/mol to
give the hydride η2-penta-1,3,4-trien-1-yl complex I.
Unclear is the onward reaction from I to eventually yield
E and/or G. In fact, the reductive elimination process
to follow might not be easily achieved, requiring severe
1
tected by H and 13C NMR spectroscopy even at room
temperature and, moreover, a large primary kinetic
isotope effect of kH/kD ) 10.0 has been determined. An
(10) For tunneling in hydrogen shift reactions see: Hess, B. A., J r.
J . Org. Chem. 2001, 66, 5897, and references therein.

Oxidative Coupling of Alkynes
Organometallics, Vol. 22, No. 10, 2003 2131
band was collected. After removal of the solvent, the yellow
solid was washed with pentane and dried under vacuum.
Yield: 59 mg (68%). Anal. Calcd for C33H33RuSb: C, 60.75; H,
5.10. Found: C, 60.69; H, 5.14. 1H NMR (δ, CD2Cl2, 20 °C):
7.53-7.25 (m, 15H, Ph), 5.46 (d, J HH ) 2.4 Hz, 1H, Hb), 4.82
(s, 5H, Cp), 4.79 (d, J HH ) 8.9 Hz, 1H, Hd), 4.68 (d, J HH ) 2.4
Hz, 1H, Ha), 4.62 (t, J HH ) 8.9 Hz, 1H, Hc), 2.73 (d, J HH ) 8.9
Hz, 1H, He), 2.37-1.05 (m, 8H, CH2). 13C{1H} NMR (δ, CD2-
Cl2, 20 °C): 161.0 (1C, C2), 146.4; 146.2 (2C, C3,4), 135.6 (2C,
Ph2,6), 134.9 (1C, Ph1), 129.3 (1C, Ph1), 128.5 (2C, Ph3,5), 115.4
(1C, C1), 82.0 (5C, Cp), 62.6 (1C, C5), 31.5 (1C, C6), 25.8; 25.6;
23.8; 22.9 (4C, CH2).
rehybridization and rearrangement steps particularly
if it is to proceed in an intramolecular fashion.
Con clu sion
In this paper we hope to have clarified the ways by
which oxidative coupling of alkynes occurs at labile
[RuCp(SbR3)(CH3CN)2]PF6. By applying 2,8-decadiyne-
d6 and crossover experiments we could show that the
1,2 hydrogen migration as part of the metallacyclopen-
tatriene-butadienyl carbene transformation takes place
in an intramolecular fashion. The large primary kinetic
isotope effect points to a direct hydrogen shift (proton
migration) without the involvement of hydride species.
Furthermore, the various reaction products formed
depending on the substituent R′ of the alkyne HCt
CCH2R′ may be useful for further studies.
Exp er im en ta l Section
Gen er a l In for m a tion . All manipulations were performed
under an inert atmosphere of argon by using Schlenk tech-
niques. All chemicals were standard reagent grade and used
without further purification. The solvents were purified ac-
cording to standard procedures.11 The deuterated solvents were
purchased from Aldrich and dried over 4 Å molecular sieves.
[RuCp(SbPh3)(CH3CN)2]PF6 (1a ) and [RuCp(SbBun3)(CH3CN)2]-
PF6 (1b) have been prepared according to the literature.12 The
synthesis and characterization of complexes 2, 3a -e, 5a , and
5b have been already reported previously.2 1H, 2H, and 13C-
{1H} NMR spectra were recorded on a Bruker AVANCE-250
spectrometer and were referenced to SiMe4 and benzene-d6 (set
to 7.36 ppm), respectively. 1H and 13C{1H} NMR signal
assignments were confirmed by 1H-COSY, DEPT-135, 1H-13C-
HSQC, and 1H-13C-HMBCexperiments.
Rea ction of 4 w ith D2SO4. A 5 mm NMR tube was charged
with 4 (30 mg, 0.046 mmol) in CDCl3 (0.5 mL). Upon addition
of D2SO4 98% (6.1 µL, 0.115 mmol) the color of the solution
changed from yellow to dark red. The reaction was monitored
1
by H and 13C NMR spectroscopy, and quantitative formation
1
of 3a -d3 was observed. H NMR (δ, CDCl3, 20 °C): 7.65-7.03
3
(m, 15H, Ph), 5.34 (s, 5H, Cp), 5.29 (t, J HH ) 10.5 Hz, Ha),
3
3.63 (d, J HH ) 10.1 Hz, Hb), 2.69-1.18 (m, 8H, CH2), 1.71 (d,
3J HH ) 10.7 Hz, Hc). 13C{1H} NMR (δ, CDCl3, 20 °C): 334.4
(1C, C2), 191.4 (1C, C3), 160.2 (1C, C4), 135.3 (3C, Ph1,2,6), 131.4
(1C, Ph4), 130.3 (2C, Ph3,5), 88.2 (5C, Cp), 75.5 (1C, C5), 50.5-
49.0 (m, 1C, C1), 43.9 (1C, C6), 36.4; 26.1; 22.2; 22.0; (4C, CH2).
[CpRu (dC2(CD3)C(CH2)4C-η2-CDdCD2)(SbP h 3)]P F6 (3a -
d 6). A solution of 1a (100 mg, 0.134 mmol) in CH2Cl2 (5 mL)
was treated with 2,8-decadiyne-d6 (21.9 µL, 0.147 mmol), and
the reaction mixture was stirred for 24 h, whereupon the color
of the solution turned red. After that the volume of the solution
was reduced to about 1 mL, Et2O was slowly added, and a red
microcrystalline precipitate was formed. The supernatant was
decanted, and the solid was washed twice with Et2O and dried
under vacuum. Yield: 87 mg (82%). 1H NMR (δ, acetone-d6,
20 °C): 7.77-7.29 (m, 15H, Ph), 5.56 (s, 5H, Cp), 2.57-1.40
2
(m, 8H, CH2). H NMR (δ, acetone, 20 °C): 4.89-4.31 (m, 1D,
Da), 3.22-2.73 (m, 1D, Db), 2.15 (s, 3D, CD3), 1.47-1.03 (m,
[Ru Cp (η3-CH2CCH2-CHdCH-η1-CO)(SbP h 3)]P F 6 (6a ).
A solution of 1a (140 mg, 0.188 mmol) in 5 mL of CH2Cl2 (5
mL) was treated with 2.5 equiv of propargylic alcohol (27.3
µL, 0.469 mmol) and stirred at room temperature for 24 h.
After removal of the solvent under reduced pressure, a red-
brown solid was obtained, which was purified by column
chromatography (neutral Al2O3/CH3NO2). The red-brown band
was collected. Yield: 125 mg (92.0%). Anal. Calcd for C26H26F6-
OPRuSb: C, 43.24; H, 3.63. Found: C, 43.30; H, 3.57. 1H NMR
1D, Db).
(δ, acetone-d6, 20 °C): 7.82-7.09 (m, 15H, Ph), 7.36 (d, J HH
)
6.8 Hz, 1H, H2), 5.81 (s, 5H, Cp), 5.33 (d, J HH ) 6.8 Hz, 1H,
H3), 4.27-4.22 (m, 2H H5,6a), 4,21 (d, J HH ) 2.5 Hz, 1H, H6s),
4.02 (d, J HH ) 2.5 Hz, 1H, H5s). 13C{1H} NMR (δ, acetone-d6,
20 °C): 234.6 (1C, CO), 150.0 (1C, C3), 147.8 (1C, C2), 135.7
(2C, Ph2,6), 135.4 (1C, Ph1), 131.7 (1C, Ph4), 130.2 (1C, Ph3,5),
119.4 (1C, C4), 93.5 (5C, Cp), 68.0 (1C, C5), 44.5 (1C, C6). IR
(KBr, cm-1): 1688 (νCdO).
Cp Ru (-CdCH2)C(CH2)4C-η2-CHdCH2)(SbP h 3) (4). To a
solution of 1a (100 mg, 0.134 mmol) in CH2Cl2 (5 mL) was
added 1.2 equiv of 2,8-decadiyne (21.9 µL, 0.147 mmol),
whereupon the solution turned immediately dark red. After
stirring for 24 h, the volume of the solution was reduced to
about 1 mL and chromatographed over basic Al2O3. The yellow
[Ru Cp (η3-CH2CCH2-CHdCH-η1-CO)(SbBu n 3)]P F 6 (6b).
This complex has been prepared analogously to 6a with 1b
(300 mg, 0.437 mmol) and propargylic alcohol (55.9 µL, 0.961
mmol) as the starting materials. Yield: 291 mg (96%). Anal.
Calcd for C23H38F6OPRuSb: C, 39.56; H, 5.48. Found: C, 39.64;
H, 5.54. 1H NMR (δ, acetone-d6, 20 °C): 7.85 (d, J HH ) 6.8 Hz,
1H, H2), 5.76 (d, J HH ) 6.8 Hz, 1H, H3), 5.73 (s, 5H, Cp), 4.01
(11) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon: New York, 1988.
(12) Becker, E.; Slugovc, C.; Ru¨ba, E.; Standfest-Hauser, C.; Mere-
iter, K.; Schmid, R.; Kirchner, K. J . Organomet. Chem. 2002, 649, 55.

2132 Organometallics, Vol. 22, No. 10, 2003
Becker et al.
Hz, 1H, H6), 5.60 (s, 5H, Cp), 3.71 (d, J HH ) 6.8 Hz, 1H, H1),
1
2
3.51 (s, 1H, OH), 3.31 (td, J HH ) 17.7 Hz, J HH ) 6.8 Hz, 1H,
CH2), 2.98-1.16 (m, 35H, CH2), 0.90 (t, J HH ) 7.2 Hz, 9H, CH3).
13C{1H} NMR (δ, acetone-d6, 20 °C): 197.8 (1C, C3), 171.7 (1C,
C5), 134.0 (1C, C4), 119.0 (1C, C6), 91.9 (5C, Cp), 90.6 (1C, C2),
73.2 (1C, C7), 37.8; 37.8; 29.6; 27.4; 25.5; 22.0; 21.9; 21.7; 21.1
(9C, CH2), 28.3; 25.6; 13.0 (9C, CH2), 12.8 (3C, CH3).
(d, J HH ) 3.0 Hz, 1H, H6s), 4.00 (s, 1H, H6a), 3.90 (d, J HH ) 3.0
Hz, 1H, H5s), 3.73 (s, 1H, H5a), 2.14-1.94 (m, 6H, Bu), 1.69-
1.52 (m, 6H, Bu), 1.49-1.31 (m, 6H, Bu), 0.92 (t, J HH ) 7.3
Hz, 9H, CH3). 13C{1H} NMR (δ, acetone-d6, 20 °C): 235.2 (1C,
C1), 151.1 (1C, C3), 148.3 (1C, C2), 117.9 (1C, C4), 92.2 (5C,
Cp), 66.2 (1C, C5), 42.0 (1C, C6), 27.6 (3C, CH2), 25.4 (3C, CH2),
15.5 (3C, CH2), 12.7 (3C, CH3). IR (KBr, cm-1): 1678 (νCdO).
Ca lcu la ted 1H a n d 13C NMR Sp ectr a for [Ru Cp (η3-
CH2CCH2-CHdCH-η1-CO)(SbMe3)]+. 1H NMR: 7.73 (1H,
H2), 5.78 (1H, H3), 5.38 (5H, Cp), 3.76 (1H, H5s), 3.26 (1H, H5a),
3.24 (1H, H6a), 3.21 (1H, H6s), 0.54 (9H, CH3). 13C NMR: 234.0
(C1), 148.0 (C3), 140.2 (C2), 118.5 (C4), 91.3 (Cp, C7), 71.6 (C5),
48.2 (C6), 7.7 (Me).
[R u Cp (η1-CH C(Me)2OH CH d(η3-CC(Me)CH 2)(Sb R 3)]-
P F 6 (9). This complex has been prepared analogously to 7a
with 1b (300 mg, 0.437 mmol) and 2-methylbut-3-yn-2-ol (93.2
µL, 2.885 mmol) as the starting materials. The crude product
was purified by column chromatography (neutral Al2O3/CH2-
Cl2/acetone). Yield: 245 mg (76%). Anal. Calcd for C27H46F6-
OPRuSb: C, 42.99; H, 6.15. Found: C, 42.89; H, 6.25. 1H NMR
(δ, acetone-d6, 20 °C): 8.22 (d, J HH ) 3.4 Hz, 1H, H4), 7.00 (d,
J HH ) 3.4 Hz, 1H, H6), 5.66 (s, 5H, Cp), 3.79 (s, 1H, OH), 3.41
(d, J HH ) 1.1 Hz, 1H, H1), 2.42 (s, 3H, CH3), 2.34 (d, J HH ) 1.1
Hz, 1H, H1), 1.43 (s, 3H, CH3), 1.42 (s, 3H, CH3), 1.90-1.78
(m, 6H, CH2), 1.64-1.48 (m, 6H, CH2), 1.43-1.32 (m, 6H, CH2),
0.90 (t, J HH ) 7.3 Hz, 9H, CH3). 13C{1H} NMR (δ, acetone-d6,
20 °C): 199.5 (1C, C3), 171.9 (1C, C5), 133.5 (1C, C4), 117.9
(1C, C6), 90.7 (5C, Cp), 83.8 (1C, C2), 68.9 (1C, C7), 32.9 (1C,
C1), 30.2; 30.1 (2C, CH3), 28.1; 25.6 (6C, CH2), 22.7 (1C, CH3),-
13.2 (3C, CH2),12.8 (3C, CH3).
[Cp R u (η1-CH C(C6H 9)CH d(η3-CC(CH 2)4CH )(Sb P h 3)]-
P F 6 (7a ). To a solution of 1b (100 mg, 0.134 mmol) in CH2Cl2
(5 mL) was added 1-ethynylcyclohexene (31.4 µL, 0.295 mmol),
and the reaction mixture was stirred for 2 h at room temper-
ature. After removal of the solvent, the product was collected
on a glass frit, washed with Et2O, and dried under vacuum.
Yield: 110 mg (94%). Anal. Calcd for C39H40F6PRuSb: C, 53.44;
1
H, 4.60. Found: C, 53.41; H, 4.64. H NMR (δ, acetone-d6, 20
4
°C): 8.10 (d, J HH ) 3.5 Hz, 1H, H4), 7.57-6.90 (m, 15H, Ph),
4
6.84 (d, J HH ) 3.5 Hz, 1H, H6), 5.90-5.76 (m, 1H, H8), 5.83
(s, 5H, Cp), 4.10-3.95 (m, 1H, H1), 3.02-1.19 (m, 16H, CH2).
13C{1H} NMR (δ, acetone-d6, 20 °C): 197.4 (1C, C3), 165.5 (1C,
C5), 135.9 (6C, Ph2,6), 135.5 (3C, Ph1), 133.9 (1C, C4), 133.6
(3C, Ph4), 130.0 (6C, Ph3,5), 124.4 (1C, C7), 123.9 (1C, C8), 119.6
(1C, C6), 94.1 (1C, C2), 93.0 (5C, Cp), 66.4 (1C, C1), 29.8-21.3
(8C, CH2).
[Cp R u (η1-CH C(C6H 9)CH d(η3-CC(CH 2)4CH )(Sb Bu n 3)]-
P F 6 (7b). This complex has been prepared analogously to 7a
with 1b (100 mg, 0.146 mmol) and 1-ethynyl cyclohexene (37.6
µL, 0.321 mmol) as the starting materials. Yield: 108 mg
(91%). Anal. Calcd for C33H52F6PRuSb: C, 48.54; H, 6.42.
Found: C, 48.49; H, 6.37. 1H NMR (δ, acetone-d6, 20 °C): 8.13
Com p u ta tion a l Deta ils. All calculations were performed
using the Gaussian98 software package on the Silicon Graph-
ics Origin 2000 of the Vienna University of Technology.13 The
geometry and energy of the model complexes and the transition
states were optimized at the B3LYP level14 with the Stuttgart/
4
4
(d, J HH ) 3.4 Hz, 1H, H4), 7.11 (d, J HH ) 3.4 Hz, 1H, H6),
3
6.02-5.94 (m, 1H, H8), 5.65 (s, 5H, Cp), 3.72 (d, J HH ) 6.9
(13) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J . R.; Zakrzewski, V. G.; Montgomery, J . A.,
J r.; Stratmann, R. E.; Burant, J . C.; Dapprich, S.; Millam, J . M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J .;
Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo,
C.; Clifford, S.; Ochterski, J .; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J . B.; Cioslowski, J .; Ortiz, J . V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.;
Fox, D. J .; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; J ohnson, B. G.; Chen,
W.; Wong, M. W.; Andres, J . L.; Head-Gordon, M.; Replogle, E. S.;
Pople, J . A. Gaussian 98, revision A.7; Gaussian, Inc.: Pittsburgh, PA,
1998.
3
Hz, 1H, H1), 3.40-1.47 (m, 28H, CH2), 1.36 (q, J HH ) 7.3 Hz,
3
6H, CH2), 0.89 (t, J HH ) 7.3 Hz, 9H, CH3). 13C{1H} NMR (δ,
acetone-d6, 20 °C): 197.5 (1C, C3), 162.3 (1C, C5), 136.4 (1C,
C4), 135.3 (1C, C7), 123.6 (1C, C8), 118.3 (1C, C6), 92.8 (5C,
Cp), 91.4 (1C, C2), 61.8 (1C, C1), 29.0-14.1 (17C, CH2), 13.6
(3C, CH3).
[(R u C p (η1 -C H C (C 6 H 1 0 O H )C H d(η3 -C C (C H 2 )4 C H )-
(SbBu n 3)]P F 6 (8). This complex has been prepared analo-
gously to 7a with 1b (100 mg, 0.146 mmol) and 1-ethynylcy-
clohexanol (40 mg, 0.161 mmol) as the starting materials.
Yield: 85 mg (71%). Anal. Calcd for C33H54F6OPRuSb: C,
47.49; H, 6.52. Found: C, 49.47; H, 6.59. 1H NMR (δ, acetone-
d6, 20 °C): 8.14 (d, J HH ) 3.4 Hz, 1H, H4), 6.95 (d, J HH ) 3.4
(14) (a) Becke, A. D. J . Chem. Phys. 1993, 98, 5648. Miehlich, B.;
Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200. (b)
Lee, C.; Yang, W.; Parr, G. Phys. Rev. B 1988, 37, 785.

Oxidative Coupling of Alkynes
Organometallics, Vol. 22, No. 10, 2003 2133
Ta ble 1. Deta ils for th e Cr ysta l Str u ctu r e Deter m in a tion s of Com p lexes 4, 3c, 5a ‚(CH3)2CO, a n d 5a ′
4
3c
5a ‚(CH3)2CO
5a ′
formula
fw
cryst size, mm
space group
a, Å
C
33H33RuSb
C35H40F6PRuSb
828.46
C44H42F6OPRuSb
954.57
C41H36F6PRuSb
896.49
652.41
0.14 × 0.12 × 0.10
P21/c (No. 14)
9.796(3)
15.368(5)
18.601(6)
101.82(1)
2741(2)
4
0.80 × 0.40 × 0.08
P21/n (No. 14)
11.459(3)
20.681(5)
14.668(4)
90.86(2)
3476(2)
4
1.583
223(2)
1.313
1656
0.60 × 0.40 × 0.02
P21/n (No. 14)
14.081(6)
12.488(5)
24.055(9)
99.52(1)
4172(3)
4
1.520
297(2)
1.107
1912
0.72 × 0.18 × 0.11
P21/n (No. 14)
13.382(4)
18.470(6)
14.760(5)
98.01(2)
3613(2)
4
1.648
223(2)
1.270
1784
b, Å
c, Å
â, deg
V, Å3
Z
F
calc, g cm-3
T, K
1.581
297 (2)
1.556
µ, mm-1 (Mo KR)
F(000)
1304
abs corr
multiscan
27
24 251
5973
3931
331
multiscan
25
35 096
6042
9168
397
0.049
0.065
multiscan
30
10 425
6801
3560
487
0.056
0.124
multiscan
27
41 666
7863
6224
454
0.038
0.055
θmax, deg
no. of reflns measd
no. of unique reflns
no. of rflns I > 2σ(I)
no. of params
R1 (I > 2σ(I))a
R1 (all data)
0.035
0.074
wR2 (all data)
0.075
-0.56/1.15
0.119
-0.93/1.46
0.150
-0.82/0.79
0.110
-0.83/1.53
diff Four. peaks min/max, e Å-3
R1 ) ∑||Fo| - ||Fc||/∑|Fo|, wR2 ) [∑(w(Fo - Fc2)2)/∑(w(Fo2)2)]1/2
.
a
2
Dresden ECP (SDD) basis set15 to describe the electrons of the
Ru and Sb atoms. For the H and C atoms the 6-31g** basis
set was employed.16 A vibrational analysis was performed to
confirm that the structures of the model compounds have no
imaginary frequency. The transition state structure was
relaxed after applying a small perturbation to ensure that it
is connected to the corresponding reactant and product. A
vibrational analysis was also performed to confirm that it has
only one imaginary frequency. The geometries were optimized
and 5a ′ were obtained by diffusion of Et2O into acetone or CH2-
Cl2 solutions. Crystal data and experimental details are given
in Table 1. X-ray data were collected on a Bruker Smart CCD
area detector diffractometer (graphite-monochromated Mo KR
radiation, λ ) 0.71073 Å, 0.3° ω-scan frames). Corrections for
Lorentz and polarization effects, for crystal decay, and for
absorption were applied.17 The structures were solved by direct
methods using the program SHELXS97.18 Structure refine-
ment on F2 was carried out with program SHELXL97.18 All
non-hydrogen atoms were refined anisotropically. Most hy-
drogen atoms were inserted in idealized positions and were
refined riding with the atoms to which they were bonded. Some
crucial hydrogen atoms were refined in x, y, and z using only
C-H distance restraints.
1
without constraints (C1 symmetry). H and 13C chemical sifts
were calculated at the B3LYP level of theory for the optimized
structure of [RuCp(η3-CH2CCH2-CHdCH-η1-CO)(SbMe3)]+
using the gauge-independent atomic orbital (GIAO) method
in Gaussian 98 with the above basis sets. Chemical shifts are
given with respect to Si(Me3)4 (TMS) at the same computa-
tional level.
X-r a y Str u ctu r e Deter m in a tion for 4, 3c, 5a ‚(CH3)2CO,
a n d 5a ′. Crystals of 4 were obtained by diffusion of pentane
into a CH2Cl2 solution, whereas crystals of 3c, 5a ‚(CH3)2CO,
Ack n ow led gm en t. Financial support by the “Fonds
zur Fo¨rderung der Wissenschaftlichen Forschung”
(Project No. P14681-CHE) is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Listings of atomic
coordinates, anisotropic temperature factors, and bond lengths
and angles for 4, 3c, 5a ‚(CH3)2CO, and 5a ′. This material is
available free of charge via the Internet at http://pubs.acs.org.
(15) (a) Haeusermann, U.; Dolg, M.; Stoll, H.; Preuss, H. Mol. Phys.
1993, 78, 1211. (b) Kuechle, W.; Dolg, M.; Stoll, H.; Preuss, H. J . Chem.
Phys. 1994, 100, 7535. (c) Leininger, T.; Nicklass, A.; Stoll, H.; Dolg,
M.; Schwerdtfeger, P. J . Chem. Phys. 1996, 105, 1052.
(16) (a) McClean, A. D.; Chandler, G. S. J . Chem. Phys. 1980, 72,
5639. (b) Krishnan, R.; Binkley, J . S.; Seeger, R.; Pople, J . A. J . Chem.
Phys. 1980, 72, 650. (c) Wachters, A. J . H. J . Chem. Phys. 1970, 52,
1033. (d) Hay, P. J . J . Chem. Phys. 1977, 66, 4377. (e) Raghavachari,
K.; Trucks, G. W. J . Chem. Phys. 1989, 91, 1062. (f) Binning, R. C.;
Curtiss, L. A. J . Comput. Chem. 1995, 103, 6104. (g) McGrath, M. P.;
Radom, L. J . Chem. Phys. 1991, 94, 511.
OM030039N
(17) Bruker, Programs SMART, version 5.054; SAINT, version 6.2.9;
SADABS, version 2.03; XPREP, version 5.1; SHELXTL, version 5.1;
Bruker AXS Inc.: Madison, WI, 2001.
(18) Sheldrick, G. M. SHELX97, Program System for Crystal
Structure Determination; University of Go¨ttingen: Germany, 1997.