Reactions of Cp*RuCl(COD) with alkynes: Isolation of dinuclear metallacyclopentatriene complexes

Article abstract of DOI:10.1021/om8002202

The reactions of Cp*RuCl(COD) with alkynes in different solvents were investigated. Treatment of Cp*RuCl(COD) with phenylacetylene in benzene or dichloromethane gives the ruthenacyclopentatriene complex Cp*RuCl(2,5-Ph₂C₄H₂) and free COD. In methanol, a formal [2+2+2] cycloaddition of the COD ligand with PhC≡CH occurred and the reaction produces a tricyclo[4.2.2.0^2.5]dec-7-ene (C₆H₅-C₁₀H₁₃) and its complex [Cp*Ru(η⁶-C₆H₅-C₁₀H ₁₃)]Cl along with the dinuclear ruthenacyclopentatriene complex [Cp*RuCl(η²,η⁴,μ-2,5-Ph₂C ₄H₂)RuCp*]Cl. 3-Hexyne was found to be unreactive toward Cp*RuCl(COD) in benzene or dichloromethane at room temperature. In methanol, it reacts with Cp*RuCl(COD) to give a tricyclo[4.2.2.0 ^2.5]dec-7-ene (Et₂-C₁₀H₁₂) and the dinuclear ruthenacyclopentatriene complex [Cp*RuCl(η², η⁴,μ-C₄Et₄)RuCp*]Cl. 1-Hexyne was found to react with Cp*RuCl(COD) in C₆D₆, CD ₂Cl₂, and diethyl ether to give the neutral dinuclear ruthenacyclopentadiene complex Cp*RuCl₂(η², η⁴,μ-C₄H₂Bu₂)RuCp* along with free COD, while in methanol it gives a tricyclo[4.2.2.0 ^2.5]dec7-ene (Bu-C₁₀H₁₃) and Cp*RuCl ₂(η²,η⁴,μ-C₄H ₂Bu₂)RuCp*.

Full text of DOI:10.1021/om8002202

5122
Organometallics 2008, 27, 5122–5129
Reactions of Cp*RuCl(COD) with Alkynes: Isolation of Dinuclear
Metallacyclopentatriene Complexes
Li Zhang, Herman Ho-Yung Sung, Ian Duncan Williams, Zhenyang Lin,* and Guochen Jia*
Department of Chemistry, The Hong Kong UniVersity of Science and Technology, Clear Water Bay,
Kowloon, Hong Kong, People’s Republic of China
ReceiVed March 9, 2008
The reactions of Cp*RuCl(COD) with alkynes in different solvents were investigated. Treatment of
Cp*RuCl(COD) with phenylacetylene in benzene or dichloromethane gives the ruthenacyclopentatriene
complex Cp*RuCl(2,5-Ph2C4H2) and free COD. In methanol, a formal [2+2+2] cycloaddition of the
COD ligand with PhCt CH occurred and the reaction produces a tricyclo[4.2.2.02,5]dec-7-ene (C6H5-
C10H13) and its complex [Cp*Ru(η6-C6H5-C10H13)]Cl along with the dinuclear ruthenacyclopentatriene
complex [Cp*RuCl(η2,η4,µ-2,5-Ph2C4H2)RuCp*]Cl. 3-Hexyne was found to be unreactive toward
Cp*RuCl(COD) in benzene or dichloromethane at room temperature. In methanol, it reacts with
Cp*RuCl(COD) to give a tricyclo[4.2.2.02,5]dec-7-ene (Et2-C10H12) and the dinuclear ruthenacyclopen-
tatriene complex [Cp*RuCl(η2,η4,µ-C4Et4)RuCp*]Cl. 1-Hexyne was found to react with Cp*RuCl(COD)
in C6D6, CD2Cl2, and diethyl ether to give the neutral dinuclear ruthenacyclopentadiene complex
Cp*RuCl2(η2,η4,µ-C4H2Bu2)RuCp* along with free COD, while in methanol it gives a tricyclo[4.2.2.02,5]dec-
7-ene (Bu-C10H13) and Cp*RuCl2(η2,η4,µ-C4H2Bu2)RuCp*.
with unsaturated substrates to give reactive metallacycles. In
agreement with the proposed mechanisms, complexes relevant
to the proposed intermediates in some of the catalytic reactions
have been successfully isolated from the reactions of alkynes
with Cp*RuCl(COD), for example, ruthenacyclopentatrienes,4,10,11
η4-cyclobutadiene,5,10d and η6-benzene complexes.10a,e
An interesting question is how COD is initially removed from
Cp*RuCl(COD) to generate the catalytically active species.
Since COD is a weakly coordinating ligand, it is reasonable to
assume that COD is displaced by substrates under catalytic
conditions. However, it may also be possible that the COD
ligand may first react with an unsaturated substrate to give a
less coordinating species, which then subsequently dissociates
from the ruthenium center. In connection with our study on
catalytic cycloaddition reactions of alkynes with azides mediated
by Cp*RuCl(COD),9 we have carefully studied the reactions
of Cp*RuCl(COD) with alkynes in benzene, dichloromethane,
and methanol. Our results show that the COD ligand is removed
by simple dissociation when the reactions were carried out in
Introduction
Cp*RuCl(COD) has been widely used as a catalytic precursor
for reactions involving alkynes,1 for example, cyclotrimerization
of alkynes to give benzene derivatives,2 coupling of enynes with
diazoalkanes to give alkenylbicyclo[3.1.0]hexanes,3 dimerization
of alkynes in the presence of carboxylic acids to give 1,3-dienes4
or alkylidenecyclobutadienes,5 [2+2+2] cocyclization of diene-
yne to give cyclohexenes,6 [2+2] cycloaddition reactions of
alkynes with olefins to give cyclobutenes,7 [2+2+2] cycload-
ditions of diynes with electron-deficient carbon-heteroatom
multiple bonds to give heterocycles,8 and cycloaddition of
alkynes with azides to give triazoles,9 to name a few. It is
generally believed that the active species contains a Cp*RuCl
or Cp*Ru+ fragment, which can undergo oxidative coupling
* Corresponding authors. E-mail: chjiag@ust.hk.
(1) De´rien, S.; Dixneuf, P. H. J. Organomet. Chem. 2004, 689, 1382.
(2) See for example: (a) Yamamoto, Y.; Hashimoto, T.; Hattori, K.;
Kikuchi, M.; Nishiyama, H. Org. Lett. 2006, 8, 3565. (b) Yamamoto, Y.;
Hattori, K.; Nishiyama, H. J. Am. Chem. Soc. 2006, 128, 8336. (c)
Yamamoto, Y.; Ishii, J.; Nishiyama, H.; Itoh, K. J. Am. Chem. Soc. 2005,
127, 9625. (d) Yamamoto, Y.; Ishii, J.; Nishiyama, H.; Itoh, K. J. Am. Chem.
Soc. 2004, 126, 3712. (e) Yamamoto, Y.; Hata, K.; Arakawa, T.; Itoh, K.
Chem. Commun. 2003, 1290. (f) Yamamoto, Y.; Arakawa, T.; Ogawa, R.;
Itoh, K. J. Am. Chem. Soc. 2003, 125, 12143. (g) Kirchner, K.; Calhorda,
M. J.; Schmid, R.; Veiros, L. F. J. Am. Chem. Soc. 2003, 125, 11721.
(3) Monnier, F.; Vovard-LeBray, C.; Castillo, D.; Aubert, V.; De´rien,
S.; Dixneuf, P. H.; Toupet, L.; Ienco, A.; Mealli, C. J. Am. Chem. Soc.
2007, 129, 6037.
(4) Le Paih, J.; Monnier, F.; De´rien, S.; Dixneuf, P. H.; Clot, E.;
Eisenstein, O. J. Am. Chem. Soc. 2003, 125, 11964.
(5) (a) Le Paih, J.; De´rien, S.; Demerseman, B.; Bruneau, C.; Dixneuf,
P. H.; Toupet, L.; Dazinger, G.; Kirchner, K. Chem.-Eur. J. 2005, 11,
1312. (b) Le Paih, J.; De´rien, S.; Bruneau, C.; Demerseman, B.; Toupet,
L.; Dixneuf, P. H. Angew. Chem., Int. Ed. 2001, 40, 2912.
(8) (a) Yamamoto, Y.; Kinpara, K.; Ogawa, R.; Nishiyama, H.; Itoh,
K. Chem.-Eur. J. 2006, 12, 5618. (b) Yamamoto, Y.; Kinpara, K.; Saigoku,
T.; Takagishi, H.; Okuda, S.; Nishiyama, H.; Itoh, K. J. Am. Chem. Soc.
2005, 127, 605. (c) Yamamoto, Y.; Takagishi, H.; Itoh, K. J. Am. Chem.
Soc. 2002, 124, 28. (d) Yamamoto, Y.; Takagishi, H.; Itoh, K. Org. Lett.
2001, 3, 2117.
(9) Zhang, L.; Chen, X.; Xue, P.; Sun, H. H. Y.; Williams, I. D.;
Sharpless, K. B.; Fokin, V. V.; Jia, G. J. Am. Chem. Soc. 2005, 127, 15998.
(10) (a) Ernst, C.; Walter, O.; Dinjus, E.; Arzberger, S.; Gorls, H. J.
Prakt. Chem. 1999, 341, 801. (b) Ernst, C.; Walter, O.; Dinjus, E. J.
Organomet. Chem. 2001, 627, 249. (c) Yamamoto, Y.; Kataoka, H.; Kinpara,
K.; Nishiyama, H.; Itoh, K. Lett. Org. Chem. 2005, 2, 219. (d) Yamamoto,
Y.; Arakawa, T.; Itoh, K. Organometallics 2004, 23, 3610. (e) Yamamoto,
Y.; Arakawa, T.; Itoh, K. J. Am. Chem. Soc. 2003, 125, 12143.
(11) Ruthenacyclopentatrienes have also been obtained from the reactions
of alkynes with other starting materials, for example, from CpRuBr(COD).
(a) Yamada, Y.; Mizutani, J.; Kurihara, M.; Nishihar, H. J. Organomet.
Chem. 2001, 637-639, 80. (b) Albers, M. O.; de Waal, D. J. A.; Liles,
D. C.; Robinson, D. J.; Singleton, E.; Wiege, M. B. J. Chem. Soc., Chem.
Commun. 1986, 1682. From RuCp*(tmeda)C1: (c) Gemel, C.; La Pensee,
A.; Mauthner, K.; Mereiter, K.; Schmid, R.; Kirchner, K. Monatsh. Chem.
1997, 128, 1189.
(6) Tanaka, D.; Sato, Y.; Mori, M. J. Am. Chem. Soc. 2007, 129, 7730.
(7) See for example: (a) Burton, R. R.; Tam, W. J. Org. Chem. 2007,
72, 7333. (b) Burton, R. R.; Tam, W. Org. Lett. 2007, 9, 3287. (c) Jordan,
R. W.; Villeneuve, K.; Tam, W. J. Org. Chem. 2006, 71, 5830. (d) Liu, P.;
Jordan, R. W.; Kibbee, S. P.; Goddard, J. D.; Tam, W. J. Org. Chem. 2006,
71, 3793. (e) Riddell, N.; Tam, W. J. Org. Chem. 2006, 71, 1934. (f)
Villeneuve, K.; Tam, W. Organometallics 2006, 25, 843.
10.1021/om8002202 CCC: $40.75
2008 American Chemical Society
Publication on Web 09/04/2008

Reactions of Cp*RuCl(COD) with Alkynes
Organometallics, Vol. 27, No. 19, 2008 5123
Scheme 1
benzene and dichloromethane, but is reactive toward alkynes
when the reactions were carried out in methanol. During this
study, we have isolated interesting dinuclear metallacyclopen-
tatriene complexes. The details of the findings are reported in
this paper.
THF or dichloromethane)4,10 and the η6-arene complex [Cp*Ru-
(η6-1,2,4-Ph3C6H3)]Cl (in dichloromethane)10a,e have been
previously reported. However, the fate of COD in the reactions
was not mentioned.
In this work, we have reinvestigated the reaction of
Cp*RuCl(COD) with PhCt CH in benzene, dichloromethane,
and methanol. As indicated by an in situ NMR experiment, the
reaction of Cp*RuCl(COD) with PhCt CH (in 1:5 molar ratio)
in C6D6 produced cleanly the ruthenacyclopentatriene complex
Cp*RuCl(2,5-Ph2C4H2) (1) and free COD (Scheme 1). The
reaction is essentially completed in ca. 5.5 h at room temper-
ature. A similar result was obtained when the reaction was
carried out in dichloromethane. In the literature, reaction of
Cp*RuCl(COD) with PhCt CH in a molar ratio of ca. 1:50 in
dichloromethane was reported to give the η6-arene complex
[Cp*Ru(η6-1,2,4-Ph3C6H3)]Cl.10a In our reaction conditions, the
η6-arene complex was not detectable by NMR. The formation
Results and Discussion
In order to answer the question raised in the Introduction,
we have carried out reactions of Cp*RuCl(COD) with pheny-
lacetylene, 3-hexyne, and 1-hexyne in various solvents. Scheme
1 summarizes the reactions carried out and the results obtained.
It is clear that the course of the reactions is affected by the
solvents.
Reaction of Cp*RuCl(COD) with Phenylacetylene. The
reactions of Cp*RuCl(COD) with phenylacetylene to give the
ruthenacyclopentatriene complex Cp*RuCl(2,5-Ph2C4H2) (1) (in

5124 Organometallics, Vol. 27, No. 19, 2008
Zhang et al.
of 1 in the reaction is clearly indicated by the observations of
the characteristic 1H NMR (C6D6) signals at 1.18 (C5Me5) and
7.14 (RudC(Ph)CH) ppm and 13C{1H} NMR (C6D6) signals
at 262.6 (RudC), 154.8 (RudC(Ph)CH), 105.9 (C5Me5), and
9.7 (C5Me5) ppm. The presence of free COD is indicated by
the 1H NMR spectrum (C6D6), which shows signals at 2.29 (s,
CH2) and 5.66 (s, CH) ppm, and by the 13C{1H} NMR spectrum
(C6D6), which shows signals at 28.1(CH2) and 77.6 (CH) ppm.
Different products were obtained when the reaction was
carried out in methanol. When a mixture of Cp*RuCl(COD)
and phenylacetylene (in 1:5 molar ratio) in methanol was stirred
at room temperature for 0.5 h, a green solution was produced.
1
The in situ H NMR experiment (in CD3OD) shows that the
reaction produced the cationic complexes [Cp*Ru(η6-C6H5-
C10H13)]Cl (2Cl) and [Cp*RuCl(η2,η4,µ-2,5-Ph2C4H2)RuCp*]Cl
(3Cl) (in ca. 1:1.6 molar ratio) along with the organic compound
C6H5-C10H13 (4) (Scheme 1). The ruthenacyclopentatriene
complex Cp*RuCl(2,5-Ph2C4H2) (1), the η6-arene complex
[Cp*Ru(η6-1,2,4-Ph3C6H3)]Cl,10a and free COD were not de-
tectable by NMR. We also carried out the reaction with a molar
ratio of 1:2 between Cp*RuCl(COD) and phenylacetylene in
deuterated methanol. The in situ 1H NMR shows that
Cp*RuCl(COD) similarly reacted with phenylacetylene to give
a mixture of 2, 3, and 4, although the reaction is slower and
some unreacted Cp*RuCl(COD) (ca. 16%) was detectable by
NMR after 40 min. Again, no ruthenacyclopentatriene complex
Cp*RuCl(2,5-Ph2C4H2) (1) and free COD were detected.
A pure sample of compound 4 can be obtained from the
reaction mixture by chromatography. However, complexes 2Cl
and 3Cl can be isolated only as a mixture and attempts to
separate complexes 2Cl and 3Cl by recrystallization and/or
column chromatography failed. With a hope to separate
complexes 2Cl and 3Cl, a mixture of 2Cl and 3Cl in methanol
was treated with NaBPh4; thereby complexes 2Cl and 3Cl were
converted to [Cp*Ru(η6-C6H5-C10H13)]BPh4 (2BPh4) and
[Cp*RuCl(η2,η4,µ-2,5-Ph2C4H2)RuCp*]BPh4 (3BPh4), respec-
tively, which were precipitated out from methanol. However,
it was still difficult to separate 2BPh4 from 3BPh4 by either
recrystallization or chromatography. Fortunately, we were able
to obtain single crystals of both 2BPh4 and 3BPh4, which allow
us to determine their solid state structures (see below) and assign
Figure 1. Crystal structure of cation 2. The hydrogen atoms are
omitted and the probability level used for the ellipsoids is 30%.
Selected bond lengths (Å): Ru(1)-C(3), 2.154(3); Ru(1)-C(4),
2.157(3); Ru(1)-C(2), 2.178(3); Ru(1)-C(5), 2.189(3); Ru(1)-C(13),
2.209(3); Ru(1)-C(15), 2.209(3); Ru(1)-C(14), 2.212(3); Ru(1)-
C(1), 2.214(4); Ru(1)-C(16), 2.215(3); Ru(1)-C(12), 2.218(3);
Ru(1)-C(11), 2.267(3); C(11)-C(17), 1.470(5).
1
the corresponding H NMR signals.
Figure 2. Crystal structure of cation 3. The hydrogen atoms are
omitted, and the probability level used for the ellipsoids is 30%.
Selected bond lengths (Å): Ru(1)-Ru(2), 2.6691(2); Ru(2)-C(1),
2.102(2); Ru(2)-C(4), 2.090(2); Ru(2)-Cl(1), 2.3432(5); Ru(1)-
C(1), 2.105(2); Ru(1)-C(2), 2.171(2); Ru(1)-C(3), 2.171(2);
Ru(1)-C(4), 2.086(2); C(1)-C(2), 1.425(3); C(2)-C(3), 1.417(3);
C(3)-C(4), 1.425(3).
Compound 4 is a known compound and was previously
obtained from the coupling reaction of phenylacetylene with
COD mediated by (η5-C9H7)RuCl(COD) (in neat COD).12 The
identity of 4 produced in our reaction can be readily assigned
1
by comparing its H and 13C{1H} NMR data with those of
reported ones.
to another ruthenium. The Ru(1)-Ru(2) distance (2.6691(2) Å)
is expected for a Ru-Ru single bond. The distances between
Ru(1) and carbons (C(1), C(4)) that are directly bonded to Ru(2)
(2.105(2) and 2.086(2) Å) are shorter than those between Ru(1)
and carbons (C(2), C(3)) that are not directly bonded to Ru(2)
(2.171(2), 2.171(2) Å). The four C atoms (C(1), C(2), C(3),
and C(4)) are almost coplanar, while the Ru(2)-C(1)-C(2)
-C(3)-C(4) ring is puckered and the folding angle along the
C(1) · · · C(4) line is 18.6°. The solid state structure is supported
by the solution NMR data. For example, the 1H NMR spectrum
The structure of complex 2BPh4 has been determined by an
X-ray diffraction study, and a view of cation 2 is shown in
Figure 1. The X-ray diffraction study confirms that the complex
contains a ligand derived from a formal [2+2+2] cycloaddition
reaction between COD and phenylacetylene. The solid state
structure is supported by the solution NMR data. For example,
1
the H NMR (in CDCl3) spectrum of 2BPh4 shows a charac-
1
teristic vinyl H NMR signal at 6.58 ppm and those of the
coordinated aryl group in the region 4.9-5.3 ppm.
The structure of complex 3BPh4 has also been determined
by an X-ray diffraction study. As shown in Figure 2, the
complex contains a five-membered metallacycle in which the
two phenyl groups are on the two CR atoms and the hydrogen
atoms on the two Cꢀ atoms. The metallacycle is η5-coordinated
1
of 3BPh4 (in CDCl3) shows a H NMR signal at 6.40 ppm for
the two CH’s of the metallacycle. In the 13C{1H} NMR
spectrum of 3Cl (in CD3OD), the signals of RuCR and CH of
the metallacycle were observed at 198.1 and 97.1 ppm,
respectively.
The structure of cation 3 can be described as a ruthenacy-
clopentatriene being complexed through its five-membered
(12) Alvarez, P.; Gimeno, J.; Lastra, E.; Garcia-Granda, S.; Van der
Maelen, J. F.; Bassetti, M. Organometallics 2001, 20, 3762.

Reactions of Cp*RuCl(COD) with Alkynes
Organometallics, Vol. 27, No. 19, 2008 5125
Chart 1
Scheme 2
3BPh4 has two less valence electrons when compared with
complexes 7 and 9-16. The metallacyclic ring of 3BPh4
formally donates six electrons to the other ruthenium. Thus it
can be best described as a dinuclear metallacyclopentatriene
complex. To the best of our knowledge, it is the first example
of this type of complexes having such an electron count. It
should be noted that the distinction between metallacyclopen-
tadiene and metallacyclopentatriene is based on their different
electron counts.
Despite the difference in electron count, the overall structural
features associated with Ru(η2,η4,µ-C4R4) of 3BPh4 are very
similar to those of dinuclear ruthenacyclopentadiene complexes
such as 7b and 10. The only notable difference is the Ru-Ru
distance: the Ru-Ru distance in 3BPh4 (2.6691(5) Å) is slightly
shorter than those of 7b (2.745(2) Å), 11a (2.831(1) Å), and
11b (2.867(1) Å).16 Clearly, 3BPh4 shows a slightly more
contracted Ru2 moiety. Another reported complex closely related
to 3BPh4 is the paramagnetic dinuclear complex [Cp*Ru(MeCN)-
(η2,η4,µ-2,5-Ph2C4H2)RuCp*](CF3SO3) (17).20 The C-C dis-
tances (1.30(1)-1.37(1) Å) of the metallacycles as well as the
Ru-Ru distance (2.6609(8) Å) in 17 are shorter than those of
3BPh4.
metallacycle with a Cp*Ru+ cation in an η5-coordination mode.
The X-ray structures of related uncomplexed ruthenacyclopen-
tatrienes including Cp*RuCl(2,5-Ph2C4H2),10a,e CpRuBr(2,5-
Ph2C4H2),11b and Cp*RuCl(2,5-Br2C4H2)10b have been reported.
In comparison with those in these compounds, the Ru(2)-C(1)
(2.102(2) Å) and Ru(2)-C(4) (2.090(2) Å) bonds of complex
3BPh4 are significantly lengthened (for example, being 1.969(4)
Å for Cp*RuCl(2,5-Ph2C4H2)). The C-C bond distances
(C(1)-C(2), 1.425(3) Å; C(2)-C(3), 1.417(3) Å; C(3)-C(4),
1.425(3) Å) are also slightly longer than the corresponding ones
in uncomplexed ruthenacyclopentatrienes. For example, the
corresponding C-C bond distances are 1.40(2), 1.37(1), and
1.40(2) Å in Cp*RuCl(2,5-Ph2C4H2).10a It is interesting to note
that the C-C bond distances of the metallacycle in 3BPh4 are
almost identical, whereas significant bond distance alternations
were observed for uncomplexed ruthenacyclopentatrienes.
Complex 3BPh4 is structurally related to well-known di-
nuclear metallacyclopentadiene complexes.13 A large number
of such complexes are known. Complexes 7 and 9-1614-19 are
the reported examples of such dinuclear ruthenium complexes
(Chart 1). In complexes 7 and 9-14, the ruthenacyclopentadiene
ring formally donates five electrons to the other ruthenium based
on a covalent bonding model. In complexes 15 and 16, the
ruthenacyclopentadiene ring formally donates four electrons to
the other ruthenium. A simple electron-counting suggests that
Scheme 2 shows a plausible mechanism for the formation of
2-4. The chloride ligand in Cp*RuCl(COD) could initially be
displaced by PhCt CH to give the cationic alkyne complex A,
which could undergo oxidative coupling to give intermediate
B. An insertion reaction in B would give C, which could
undergo reductive elimination to generate complex D containing
4 as a ligand. Complex D can rearrange to give the more stable
η6-arene complex 2Cl, or dissociate 4 from the metal center to
generate a reactive Cp*RuCl fragment. Further reaction of the
Cp*RuCl fragment with PhCt CH, presumably through inter-
mediate E and 1, could give complex 3Cl. E could be formed
from D via an intermediate, in which phenylacetylene and ligand
4 are both coordinated to the metal center. Although 1 was not
detected in the reaction in methanol, its involvement in the
formation of 3Cl is consistent with the following observation.
When a 1:1 mixture of Cp*RuCl(COD) and 1 in methanol was
treated with phenylacetylene, 1 was completely consumed to
give a 1:3 mixture of [Cp*Ru(η6-C6H5-C10H13)]Cl (2Cl) and
[Cp*RuCl(η2,η4,µ-2,5-Ph2C4H2)RuCp*]Cl (3Cl).
(13) Dolgushin, F. M.; Yanovsky, A. I.; Antipin, M. Y. Russ. Chem.
ReV. 2004, 73, 517.
(14) Campion, B. K.; Heyn, R. H.; Tilley, T. D. Organometallics 1990,
9, 1106.
(15) Nishio, M.; Matsuzaka, H.; Mizobe, Y.; Tanase, T.; Hidai, M.
Organometallics 1994, 13, 4214.
(16) (a) Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Fukushima,
M.; Tanaka, M.; Moro.oka, Y. Organometallics 1994, 13, 1129. (b) Omori,
H.; Suzuki, H.; Morooka, Y. Organometallics 1989, 8, 1576.
(17) Cabeza, J. A.; del Rio, I.; Grepioni, F.; Moreno, M.; Riera, V.;
Suarez, M. Organometallics 2001, 20, 4190.
(18) Yamamoto, Y.; Miyabe, Y.; Itoh, K. Eur. J. Inorg. Chem. 2004,
3651, and references therein.
(19) Brady, L. A.; Dyke, A. F.; Garner, S. E.; Knox, S. A. R.; Irving,
A.; Nicholis, S. M.; Orpen, A. G. J. Chem. Soc., Dalton Trans. 1993, 487.
(20) He, X. D.; Chaudret, B.; Dahan, F.; Huang, Y. S. Organometallics
1991, 10, 970.

5126 Organometallics, Vol. 27, No. 19, 2008
Zhang et al.
A sequence similar to the transformation of A to D has been
proposed and studied computationally for the catalytic coupling
reactions of COD with alkynes to give tricyco[4.2.2.02,5]dec-
7-enes catalyzed by CpRuCl(COD) in methanol.21 Formation
of η6-arene complex 2Cl is not surprising, as arene complexes
have also been isolated from the formal [2+2+2] coupling
reactions of [Cp*Ru(H2O)(NBD)]+ with arylalkynes or aryla-
llenes.22 Stable mononuclear cyclopentatriene complexes have
been isolated from the reactions of alkynes with complexes
containing a (cyclopentadienyl)RuCl fragment, for example,
CpRuBr(COD), Cp*RuCl(COD), and Cp*RuCl(Me2NCH2CH2-
NMe2).4,10,11 Reactive mononuclear ruthenacyclopentatrienes are
formed in the reactions of alkynes with cationic complexes such
23
as [CpRu(PR3)(CH3CN)2]PF6 and [CpRuL(CH3CN)2]PF6 (L
) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene).24 The di-
nuclear complexes 7b,c were obtained from the reactions of
[Cp*RuCl]4 with HCt CR (R ) H, SiMe3) in toluene,14 and
7a,d from the reactions of Cp*RuCl(Me2NCH2CH2NMe2) with
HCt CR (R ) n-Bu, CO2Et) in ether.11c Interestingly, the
paramagnetic complex 17 was obtained from the reaction of
PhCt CH with [Cp*Ru(CH3CN)3](SO3CF3) in THF.20
Reaction of Cp*RuCl(COD) with 3-Hexyne. To further
investigate the effect of solvent on the course of the reaction,
we have also investigated the reaction of Cp*RuCl(COD) with
3-hexyne in benzene, dichloromethane, and methanol. As
indicated by in situ NMR experiments, no appreciable reactions
between Cp*RuCl(COD) and EtCt CEt (in 1:5 molar ratio) in
C6D6 or CD2Cl2 were observed after a mixture of Cp*RuCl(COD)
and EtCt CEt (in 1:5 molar ratio) was stood at room temperature
for 4 h, suggesting that EtCt CEt is much less reactive than
PhCt CH.
Figure 3. Structure of cation 5. The hydrogen atoms are omitted
and the probability level used for the ellipsoids is 30%. Selected
bond lengths (Å): Ru(1)-Ru(2), 2.6650(3); Ru(2)-C(1), 2.073(2);
Ru(1)-C(4), 2.087(3); Ru(2)-Cl(1), 2.3394(7); Ru(1)-C(1), 2.086
(2); Ru(1)-C(2), 2.186(3); Ru(1)-C(3), 2.197(3); Ru(1)-C(4),
2.091(3); C(1)-C(2), 1.416(4); C(2)-C(3), 1.435(4); C(3)-C(4),
1.424(4).
is shown in Figure 3. The X-ray diffraction study confirms that
the complex is also a dinuclear ruthanacyclopentatriene complex,
in which the 1,2,3,4-tetraethyl-1,3-butadiene fragment (C(1)-
C(2)-C(3)-C(4)) is linked to Ru(2) to give rise to a five-
memebered metallacycle, which is η5-coordinated to Ru(1).
Overall, the structural features associated with the metallacycle
of 5BPh4 are very similar to those of 3BPh4. The Ru(1)-Ru(2)
distance is 2.6650(3) Å. The distances between Ru(1) and
carbons (C(1), C(4)) that are directly bonded to Ru(2) (2.086(2)
and 2.091(3) Å) are also shorter than those between Ru(1) and
carbons (C(2), C(3)) that are not directly bonded to Ru(2)
(2.186(2), 2.197(3) Å). The four C atoms (C(1), C(2), C(3),
and C(4)) are almost coplanar, while the Ru(2)-C(1)-C(2)-
C(3)-C(4) ring is puckered and the folding angle along the
C(1) · · · C(4) line is 18.5°. Consistent with the solid state
When a mixture of Cp*RuCl(COD) and EtCt CEt (in 1:5
molar ratio) in methanol was stirred at room temperature for
1
0.5 h, a green solution was produced. The in situ H NMR
experiment showed that the reaction produced the cationic
dinuclear complex [Cp*RuCl(η2,η4,µ-C4Et4)RuCp*]Cl (5Cl) and
the organic compound 6. On treatment with NaBPh4, 5Cl is
converted to [Cp*RuCl(η2,η4,µ-C4Et4)RuCp*]BPh4 (5BPh4),
which was isolated as a green solid in 78% yield (Scheme 1).
Again no ruthenacyclopentatriene complex and free COD were
detected by NMR.
A pure sample of the organic compound 6 can be obtained
by chromatography. The compound has been characterized by
NMR and MS spectroscopies. In particular, the MS spectrum
shows the expected molecular ion peak at m/z 190. The 13C{1H}
NMR (in CDCl3) spectrum shows an olefinic signal at 138.3
ppm.
1
structure, the H NMR spectrum (in CD2Cl2) shows two sets
of Cp* and ethyl signals. The 13C{1H} NMR (CD2Cl2) spectrum
shows two 13C{1H} signals of the metallacycle at 215.2 (CR)
and 87.4 (Cꢀ) ppm.
Reaction of Cp*RuCl(COD) with 1-Hexyne. In terms of
chemical composition, complexes 3Cl and 5Cl are the same as
7 in that they all contain two Cp*Ru fragments, two chlorides,
and one C4R4 chain. However, complexes 7 are neutral
complexes with both chlorides coordinated to ruthenium,
whereas complexes 3Cl and 5Cl are cationic complexes with
only one chloride coordinated to ruthenium. Complexes 7 were
previously obtained from the reactions of alkynes with
[Cp*RuCl]4, Cp*RuCl(P-iPr3), and Cp*RuCl(Me2NCH2CH2-
NMe2) in toluene or ether.11c,14 In the present study, 3Cl and
5Cl were obtained from the reactions of Cp*RuCl(COD) in
methanol. The difference could be caused by either solvent effect
or the reaction conditions or substrates.
If the difference is caused by solvent effects, one would
expect that 5Cl could be converted to the neutral complex
Cp*RuCl2(η2,η4,µ-C4Et4)RuCp* (5′) in nonpolar solvents such
as benzene and dichloromethane, and the complex Cp*RuCl2-
(η2,η4,µ-2,4-n-Bu2C4H2)RuCp* (7a) could be converted to the
cationic complex [Cp*RuCl(η2,η4,µ-2,4-n-Bu2C4H2)RuCp*]Cl
(7a′) in polar solvents. Experimentally, it is found that 5Cl is
almost insoluble in benzene and that no new NMR signals could
be found in this solvent. In addition, there is no appreciable
Complex 5BPh4 has been characterized by NMR, X-ray
diffraction, and elemental analysis. A view of the complex cation
(21) (a) Trost, B. M.; Imi, K.; Indolese, A. F. J. Am. Chem. Soc. 1993,
115, 8831. (b) Huang, X.; Lin, Z. Organometallics 2003, 22, 5478.
(22) (a) Xue, P.; Zhu, J.; Liu, S. H.; Huang, X.; Ng, W. S.; Sung,
H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G. Organometallics 2006, 25, 2344.
(b) Liu, S. H.; Huang, X.; Ng, W. S.; Wen, T. B.; Lo, M. F.; Zhou, Z. Y.;
Williams, I. D.; Lin, Z.; Jia, G. Organometallics 2003, 22, 904.
(23) See for example: (a) Pavlik, S.; Jantscher, F.; Mereiter, K.; Kirchner,
K. Organometallics 2005, 24, 4899. (b) Becker, E.; Mereiter, K.; Puchberger,
M.; Schmid, R.; Kirchner, K.; Doppiu, A.; Salzer, A. Organometallics 2003,
22, 3164. (c) Ruba, E.; Mereiter, K.; Schmid, R.; Kirchner, K.; Bustelo,
E.; Puerta, M. C.; Valerga, P. Organometallics 2002, 21, 2912. (d) Mauthner,
K.; Soldouzi, K. M.; Mereiter, K.; Schmid, R.; Kirchner, K. Organometallics
1999, 18, 4681.
(24) See for example: (a) Becker, E.; Stingl, V.; Dazinger, G.; Mereiter,
K.; Kirchner, K. Organometallics 2007, 26, 1531. (b) Becker, E.; Stingl,
V.; Mereiter, K.; Kirchner, K. Organometallics 2006, 25, 4166. (c) Becker,
E.; Stingl, V.; Dazinger, G.; Puchberger, M.; Mereiter, K.; Kirchner, K.
J. Am. Chem. Soc. 2006, 128, 6572.

Reactions of Cp*RuCl(COD) with Alkynes
Organometallics, Vol. 27, No. 19, 2008 5127
Table 1. Crystallographic Details for 2BPh4 (2BPh4 · 0.5CH2Cl2), 3BPh4 (3BPh4 · 0.5CH2Cl2 · 0.5hexane), and 5BPh4
(5BPh4 · 0.5CH2Cl2 · 0.25hexane)
2BPh4 · 0.5CH2Cl2 3BPh4 · 0.5CH2Cl2 · 0.5hexane
50.5H54BClRu 63.5H70BCl2Ru2
5BPh4 · 0.5CH2Cl2 · 0.25hexane
formula
mol wt
symmetry
space group
a, Å
C
C
C58H74.5Cl2BRu2
1055.53
monoclinic
P2(1)/n
11.5277(8)
12.1013(9)
35.559(3)
90
95.1990(10)
90
4940.1(6)
4
1.419
0.758
3.62-52.00
27 528
9499
0.0331
808.27
1117.05
monoclinic
P2(1)/c
18.51220(10)
11.58180(10)
27.5397(2)
90
106.6259(6)
90
5657.78(7)
4
triclinic
j
P1
11.9964(3)
17.8392(4)
19.5444(5)
96.154(2)
101.260(2)
94.707(2)
4055.66(17)
4
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
Dcald, g cm-3
1.325
1.313
µ, mm-1
3.980
5.463
2θ range, deg
no. of data collected
no. of unique data
R(int)
9.30-135.00
29 879
8.34-142.96
24 977
14 006
10 402
0.0269
0.0235
no. of params/restraints
goodness-of-fit on F2
R1 [I > 2σ(I)]
wR2 (all data)
peak and hole, e Å-3
945/6
1.011
0.0429
0.1246
637/10
1.034
0.0294
0.0754
587/0
1.037
0.0331
0.0760
0.800/-0.932
0.482/-0.594
0.770/-0.555
difference in the NMR data of 5Cl in CD2Cl2 and CD3OD. The
observations suggest that 5Cl was not converted to 5′ in benzene
or dichloromethane.
Experimental Section
All manipulations were carried out at room temperature under a
nitrogen atmosphere using standard Schlenck techniques unless
otherwise stated. Solvents were distilled under nitrogen from sodium
benzophenone (hexane, ether, THF), sodium (benzene), or calcium
hydride (CH2Cl2). The starting materials [Cp*RuCl2]2 and
Cp*RuCl(COD)25 were prepared following the procedures described
in the literature. All other reagents were used as purchased from
Aldrich Chemical Co. USA. Microanalyses were performed by
M-H-W Laboratories (Phoenix, AZ). 1H and 13C{1H} spectra were
collected on a Bruker ARX 300 MHz spectrometer or a Bruker
AV 400 MHz spectrometer.
The neutral complex Cp*RuCl2(η2,η4,µ-2,4-n-Bu2C4H2)Ru-
Cp* (7a) was previously prepared from the reaction of
Cp*RuCl(Me2NCH2CH2NMe2) with HCt C-n-Bu.11c In the
present work, we prepared complex 7a (Cp*RuCl2(η2,η4,µ-2,4-
n-Bu2C4H2)RuCp*) from the reaction of [Cp*RuCl]4 with
HCt C-n-Bu in benzene. Again, no appreciable difference in
the NMR data of 7a in benzene and methanol was observed.
Thus it appears that solvent effects may not be the major cause
for the adoption of the neutral or cationic forms.
Reactions of Cp*RuCl(COD) with PhCt CH in Benzene
and Dichloromethane. To an NMR tube were added CD2Cl2 or
C6D6 (0.5 mL), Cp*RuCl(COD) (10 mg, 0.026 mmol), and
phenylacetylene (0.015 mL, 0.13 mmol). The mixture was stood
at room temperature for 5.5 h. A 1H NMR experiment showed that
all Cp*RuCl(COD) was consumed to give free COD and Cp*RuCl-
(2,5-Ph2C4H2) (1). Characteristic NMR data for 1 are as follows.
1H NMR (CD2Cl2, 300 MHz): δ 1.33 (s, 15 H, C5Me5), 7.46 (s, 2
H, RuC(Ph)CH). 13C{1H} NMR (CD2Cl2, 75.5 MHz): δ 262.2 (s,
RuC), 154.7 (s, RuC(Ph)CH), 106.3 (C5Me5), 9.7 (C5Me5). 1H NMR
(C6D6, 300 MHz): δ 1.18 (s, 15 H, C5Me5), 7.14 (s, 2 H,
RuC(Ph)CH). 13C{1H} NMR (C6D6, 75.5 MHz): δ 262.6 (RudC),
154.8 (RuC(Ph)CH), 105.9 (C5Me5), 9.7 (C5Me5). Characteristic
Further experiment shows that complex 7a was produced
along with organic compound 8 from the reaction of Cp*RuCl-
(COD) with HCt C-n-Bu (1:3 molar ratio) in methanol (Scheme
1). We also noted that 7a was also produced (along with free
COD) from the reactions of Cp*RuCl(COD) with HCt C-n-
Bu in C6D6, CD2Cl2, and diethyl ether. We therefore believe
that the substrates play a major role in determining the relative
stability of the neutral and cationic forms.
A possible explanation for the relative stability of the cationic
and neutral forms of 7, 3Cl, and 5Cl is as follows. In complexes
3Cl and 5Cl, both CR carbon atoms are attached with a
substitutent, while only one CR carbon atom of 7 has a
substituent. Apparently the additional substituent in 3Cl or 5Cl
pushes one of the chloride ligands out of the coordination sphere
due to steric effects.
1
NMR data for COD: H NMR (C6D6, 300 MHz): δ 2.29 (s, 8 H,
CH2), 5.66 (s, 4 H, CH). 13C{1H} NMR (C6D6, 75.5 MHz): δ 28.1
1
(CH2) and 77.6 (CH). H NMR (CD2Cl2, 300 MHz): δ 2.49 (s, 8
H, CH2), 5.69 (s, 4 H, CH). 13C{1H} NMR (CD2Cl2, 75.5 MHz):
δ 28.1 (CH2) and 77.1 (CH).
In summary, we have carefully studied the reactions of
Cp*RuCl(COD) with alkynes in different solvents. In nonpolar
solvents, EtCt CEt was found to be unreactive toward
Cp*RuCl(COD), but PhCt CH reacts with Cp*RuCl(COD) to
give the ruthenacyclopentatriene complex Cp*RuCl(2,5-
Ph2C4H2)andfreeCOD.HCt C-n-BureactswithCp*RuCl(COD)
to give the neutral dinuclear ruthenacyclopentadiene complex
Cp*RuCl2(η2,η4,µ-C4H2Bu2)RuCp* along with free COD. In
methanol, a formal [2+2+2] cycloaddition of the COD ligand
with alkynes followed by oxidative coupling of the alkyne
occurred to give either cationic dinuclear ruthenacyclopen-
tatriene complexes or neutral dinuclear ruthenacyclopentadiene
complexes, depending on the alkynes.
Reactions of Cp*RuCl(COD) with PhCt CH in Methanol.
PreparationofComplexes2Cland3Cl.AmixtureofCp*RuCl(COD)
(0.300 g, 0.789 mmol) and phenylacetylene (0.435 mL, 3.95 mmol)
in methanol (10 mL) was stirred at room temperature for 0.5 h to
give a green solution. An in situ 1H NMR showed that all
Cp*RuCl(COD) was consumed to give a mixture of 4, [Cp*Ru(η6-
C6H5-C10H13)]Cl (2Cl), and [Cp*RuCl(2,5-Ph2C4H2)RuCp*]Cl
(3Cl). The mixture was concentrated to dryness and the residue
was washed with diethyl ether (10 mL × 5) and benzene (5 mL)
to give 270 mg of a green powder, which was identified to be a
(25) Oshima, N.; Suzuki, H.; Moro-oka, Y. Chem. Lett. 1984, 1161.

5128 Organometallics, Vol. 27, No. 19, 2008
Zhang et al.
mixture of 2Cl and 3Cl (4:3 molar ratio). The washings were
concentrated to dryness to give a brown oil, from which a pure
sample of compound 4 was obtained via chromatography using
hexane as the eluting solvent and silica gel as the adsorbent.
Characterization data of complex 2Cl: 1H NMR (CD3OD, 400
MHz): δ 1.23 -1.30 (m, 2 H), 1.96 (s, 15 H, C5Me5), 2.10-2.15
(m, 4 H), 2.28-2.35 (m, 4 H), 2.73 (br, 1 H), 2.95 (br, 1 H),
5.85-5.92 (m, 3 H, η5-Ph), 6.13-6.14 (m, 2 H, η5-Ph), 6.95 (d, 1
H, J(HH) ) 6.8 Hz, CHdC). 13C{1H} NMR (CD3OD, 100.6 MHz):
δ 10.9 (C5Me5), 18.7 (CH2), 18.8 (CH2), 21.1 (CH2), 21.4 (CH2),
35.9 (CH), 36.20 (CH), 36.26 (CH), 36.5 (CH), 84.7 (η5-Ph), 84.8
(η5-Ph), 88.5 (η5-Ph), 88.7 (η5-Ph), 97.5 (C5Me5), 103.5 (η5-Ph),
139.5 (CHdC), 140.0 (CHdC). MS: m/z 446 (M + 1 - Cl-).
Characterization data of complex 3Cl: 1H NMR (CD3OD, 400
MHz): δ 0.97 (s, 15 H, C5Me5), 1.27 (s, 15 H, C5Me5), 6.62 (d, 2
H, J(HH) ) 8.0 Hz, Ph), 6.99 (s, 2 H, C(Ph)dCH), 7.24-7.27 (m,
2 H, Ph), 7.36-7.39 (m, 2 H, Ph), 7.45-7.49 (m, 2 H, Ph), 7.90
(d, 2 H, J(HH) ) 7.6 Hz, Ph). 13C{1H} NMR (CD3OD, 100.6
MHz): δ 9.1 (C5Me5), 10.7 (C5Me5), 97.1 (RuC(Ph)CH), 101.1
(C5Me5), 108.9 (C5Me5), 123.6 (Ph), 129.5 (Ph), 130.6 (Ph), 131.6
(Ph), 137.6 (Ph), 148.6 (Ph), 198.1 (RuC(Ph)). MS: m/z 713 (M -
J(HH) ) 7.6 Hz, 6 H, CH2CH3), 1.97-2.06 (m, 2 H, CH2CH3),
2.21-2.34 (m, 4 H, CH2CH3), 2.82-2.89 (m, 2 H, CH2CH3).
13C{1H} NMR (CD3OD, 75.5 MHz): δ 8.3 (C5Me5), 9.4 (C5Me5),
14.3 (CH2CH3), 21.8 (CH2CH3), 33.8 (CH2CH3), 99.7 (RuCC),
106.6 (C5Me5), 114.8 (C5Me5), 214.5 (RuCC). FAB-MS: m/z 637
1
(M + 1 - 2Cl-). Characterization data of 6: H NMR (CDCl3,
300 MHz): δ 0.96 (t, J(HH) ) 7.5 Hz, 6 H, CH2CH3), 1.10 (m, 2
H), 1.82-1.98 (m, 4 H), 2.03-2.18 (m, 8 H), 2.21-2.25 (m, 2 H).
13C{1H} NMR (CDCl3, 75.5 MHz): δ 14.0 (CH2CH3), 18.4, 21.3,
23.6, 36.0 (CH), 37.5 (CH), 138.3 (CdC). MS: m/z 190.
Formation of Complexes 5BPh4 and 6. A mixture of
Cp*RuCl(COD) (0.426 g, 1.12 mmol) and 3-hexyne (0.637 mL,
5.61 mmol) in methanol (10 mL) was stirred at room temperature
for 0.5 h to give a green solution. The solution was concentrated
to dryness to give a brown oil. To the residue was added a methanol
(2 mL) solution of NaBPh4 (0.384 g, 1.12 mmol). The mixture was
stirred at room temperature for several minutes to give a green
precipitate, which was collected by filtration, washed with methanol
(3 mL × 3) and diethyl ether (10 mL × 3), and then dried under
vacuum. Yield: 0.417 g (78%). The filtrate was concentrated to
dryness to give a brown oil. Pure samples of compound 6 could be
obtained from the brown oil via chromatography using hexane as
the eluting solvent and silica gel as the adsorbent. Characterization
data of complex 5BPh4: Anal. Calcd for C56H70BClRu2: C, 67.83;
1
Cl-). Characterization data of 4: H NMR (CDCl3, 300 MHz): δ
1.21-1.27 (m, 3 H), 1.94-2.03 (m, 4 H), 2.19-2.27 (m, 3 H),
2.57-2.60 (m, 1 H), 3.00 (br, 1 H), 6.59 (dd, J(HH) ) 6.8, 1.4
Hz, 1 H, CHdC), 7.18-7.21 (m, 1 H, Ph), 7.23-7.34 (m, 2 H,
Ph), 7.40-7.43 (m, 2 H, Ph). 13C{1H} NMR (CDCl3, 75.5 MHz):
δ 17.9, 18.2, 20.5, 20.5, 33.9, 35.2, 35.8, 124.9, 126.7, 128.6, 129.6,
139.7, 145.2. MS: m/z 210.
1
H, 7.12. Found: C, 68.00; H, 7.12. H NMR (CD2Cl2, 400 MHz):
δ 0.33 (t, J(HH) ) 7.2 Hz, 6 H, CH2CH3), 1.12 (s, 15 H, C5Me5),
1.51 (s, 15 H, C5Me5), 1.66 (t, J(HH) ) 7.8 Hz, 6 H, CH2CH3),
1.75-1.79 (m, 2 H, CH2CH3), 1.94-2.04 (m, 4 H, CH2CH3),
2.57-2.62 (m, 2H, CH2CH3), 6.85 (t, J(HH) ) 7.0 Hz 4 H, BPh4),
6.99 (t, J(HH) ) 7.4 Hz, 8 H, BPh4), 7.30 (br, 8 H, BPh4). 13C{1H}
NMR (CD2Cl2, 100.6 MHz): δ 10.0 (C5Me5), 11.1 (C5Me5), 15.4
(CH2CH3), 15.8 (CH2CH3), 22.8 (CH2CH3), 34.8 (CH2CH3), 87.4
(RuCC), 99.9 (C5Me5), 106.9 (C5Me5), 115.4 (BPh4), 122.4 (BPh4),
126.3 (BPh4), 136.6 (BPh4), 215.2 (RuCC). FAB-MS: 638 (M -
BPh4 - Cl-).
Preparation of Complexes 2BPh4 and 3BPh4. A mixture of
Cp*RuCl(COD) (0.500 g, 1.32 mmol) and phenylacetylene (0.726
mL, 6.58 mmol) in methanol (10 mL) was stirred at room
temperature for 0.5 h to give a green solution. The reaction mixture
was concentrated to dryness, and then was added a methanol (2
mL) solution of NaBPh4 (0.384 g, 1.12 mmol). The mixture was
stirred at room temperature for several minutes to give a green
precipitate, which was collected by filtration, washed with methanol
(3 mL × 3) and diethyl ether (10 mL × 3), and then dried under
vacuum to give a green solid composed of [Cp*Ru(η6-C6H5-
C10H13)]BPh4 (2BPh4) and [Cp*RuCl(η2,η4,µ-2,5-Ph2C4H2)-
RuCp*]BPh4 (3BPh4) (in 1:1.6 molar ratio). The filtrate was
concentrated to dryness, to give a brown oil. A pure sample of
compound 4 was obtained from the brown oil via chromatography
using hexane as the eluting solvent and silica gel as the adsorbent.
Preparation of Complex 7a. Complex 7a has been reported by
K. Kirchner et al.11c We synthesized 7a by the reaction of
[Cp*RuCl]4 and 1-hexyne in benzene at 0 °C. The detailed
procedure is as follows. A mixture of [Cp*RuCl2]2 (0.500 g, 1.63
mmol) and zinc dust (1.06 g, 16.3 mmol) in ethanol (30 mL) was
stirred at room temperature overnight to give a yellow precipitate
of [Cp*RuCl]4. The ethanol was removed by filtration. The reaction
flask containing the residue, including [Cp*RuCl]4, ZnCl2, and
unreacted Zn dust, was immersed in an ice-water bath. After that,
benzene (10 mL) and 1-hexyne (0.375 mL, 3.26 mmol) were added,
and the reaction mixture was stirred for 3 h around 0 °C to give a
brownish-red solution. After removal of ZnCl2 and the unreacted
Zn dust by filtration, the filtrate was concentrated to dryness to
give a dark red powder, which was then washed with Et2O and
dried under vacuum. Yield: 100 mg (16%). Characteristic data for
1
Characterization data of 2BPh4: H NMR (CDCl3. 400 MHz): δ
0.95 (br, 2 H), 1.74 (s, 15 H, C5Me5), 1.97-2.03 (m, 2 H),
2.11-2.25 (m, 6 H), 2.64 (br, 1 H), 2.70 (br, 1 H), 4.89-4.94 (m,
3 H, η5-Ph), 5.30-5.32 (m, 2 H, η5-Ph), 6.58 (d, 1 H, J(HH) )
6.8 Hz, CHdC), 6.92-6.95 (m, BPh4), 7.06-7.09 (m, BPh4), 7.49
(br, BPh4). MS: m/z 446 (M + 1 - BPh4-). Characterization data
1
of 3BPh4: H NMR (CDCl3, 400 MHz): δ 0.77 (s, 15 H, C5Me5),
1
1.19 (s, 15 H, C5Me5), 6.40 (s, 2 H, C(Ph)dCH), 6.45 (m, 2 H,
Ph), 6.92-6.95 (m, BPh4), 7.06-7.09 (m, BPh4), 7.15-7.18 (m, 4
H, Ph), 7.27-7.31 (m, 4 H, Ph), 7.38-7.42 (m, 2 H, Ph), 7.49 (br,
7a are as follows. H NMR (C6D6, 400 MHz): δ 1.18 (s, C5Me5),
1.93 (s, C5Me5), 5.23 (d, J(HH) ) 1.50 Hz, RuC(Bu)dCH), 8.77
(d, J(HH) ) 1.65 Hz, RuCHdC(Bu)). 1H NMR (CD3OD, 400
MHz): δ 1.44 (s, C5Me5), 1.81 (s, C5Me5), 5.51 (d, J(HH) ) 1.38
Hz, RuC(Bu)dCH) and 8.71 (d, J(HH) ) 1.68 Hz, RuCHdC(Bu)).
13C{1H} NMR (C6D6, 100.6 MHz): δ 8.7 (C5Me5), 10.4 (C5Me5),
13.8 (Bu), 14.2 (Bu), 23.17 (Bu), 23.23 (Bu), 31.3 (Bu), 32.2 (Bu),
33.4 (Bu), 42.0 (Bu), 91.9. 93.0, 102.5, 108.2, 164.9
(RuCHdC(Bu), 183.7 (RuC(Bu))CH).
-
BPh4), 7.52 (m, 2 H, Ph). MS: m/z 678 (M - BPh4 - Cl-).
Reactions of Cp*RuCl(COD) with EtCt CEt in Methanol.
Formation of Complexes 5Cl and 6. A mixture of Cp*RuCl(COD)
(0.300 g, 0.790 mmol) and 3-hexyne (0.449 mL, 3.95 mmol) in
methanol (10 mL) was stirred at room temperature for 0.5 h. The
solution turned green and was concentrated to dryness to give a
brown oil. The residue was washed with hexane (10 mL × 5) and
dried under vacuum to give a green powder. Yield: 0.157 g (56%).
The washings were concentrated to dryness to give a brown oil.
Pure samples of compound 6 could be obtained from the brown
oil via chromatography using hexane as the eluting solvent and
silica gel as the adsorbent. Characterization data of complex 5Cl:
1H NMR (CD3OD, 300 MHz): δ 0.52 (t, J(HH) ) 7.4 Hz, 6 H,
CH2CH3), 1.39 (s, 15 H, C5Me5), 1.69 (s, 15 H, C5Me5), 1.84 (t,
Reactions of Cp*RuCl(COD) with 1-Hexyne in Methanol.
Observation of 7a and 8. To an NMR tube was added
Cp*RuCl(COD) (16.5 mg, 0.0435 mmol) and CD3OD (0.5 mL).
The reaction mixture changed to dark red immediately upon the
addition of 1-hexyne (0.015 mL, 0.130 mmol). An in situ 1H NMR
(CD3OD) spectrum showed that Cp*RuCl(COD) was completely
consumed and mainly converted to 7a and 8. Characteristic proton
signals of 7a in 1H NMR (CD3OD, 300 MHz): δ 8.71 (d, J(HH) )

Reactions of Cp*RuCl(COD) with Alkynes
Organometallics, Vol. 27, No. 19, 2008 5129
1.68 Hz, RuCHdC(Bu)), 5.51 (d, J ) 1.38 Hz, RuC(Bu)dCH),
1.81 (s, C5Me5), and 1.44 (s, C5Me5). After the reaction mixture
was concentrate to dryness under vacuum, 8 could be obtained by
extraction of the residue with hexane. 1H NMR (CDCl3, 300 MHz)
of 8: δ 0.89 (t, J(HH) ) 7.1 Hz, 3 H), 1.07-1.09 (m, 2 H),
1.33-1.38 (m, 4 H), 1.86-2.11 (m, 10 H), 2.25 (br, 1 H), 2.32
(br, 1 H), 5.84 (dd, J(HH) ) 6.6, 1.3 Hz, 1 H, CHdC(Bu)).
13C{1H} NMR (CDCl3, 100 MHz) of 8: δ 13.8, 17.5, 17.9, 20.0,
20.7, 22.2, 29.7, 32.8, 34.5, 34.7, 35.4, 36.7, 125.6 (CHdC(Bu)),
146.8 (C(Bu)dCH).
Crystal Structure Analyses. Crystals of 2BPh4, 3BPh4, and
5BPh4 were grown from their CH2Cl2 solutions layered with hexane.
2BPh4 is cocrystallized with CH2Cl2 to give 2BPh4 · 0.5CH2Cl2, and
3BPh4 and 5BPh4 are cocrystallized with CH2Cl2 and hexane to
give 3BPh4 · 0.5CH2Cl2 · 0.5hexane and 5BPh4 · 0.5CH2Cl2 · 0.25-
hexane, respectively. The intensity data of 5BPh4 were collected
with a Bruker Smart APEX CCD diffractometer with graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å) at 100 K. Lattice
determination and data collection were carried out using SMART
v.5.625 software.26 Data reduction and absorption correction by
empirical methods were performed using SAINT v 6.2627 and
SADABS v 2.03,28 respectively. Structure solution and refinement
were performed using the SHELXTL v.6.10 software package.29
The data of 2BPh4 and 3BPh4 were collected on an Oxford
Diffraction XcaliburS Ultra with CCD area detector and Enhance
Ultra Cu KR radiation (λ ) 1.54178Å) at 173 K. Lattice
determination, data collection, and reduction were carried out using
CrysAlisPro 171.32.5. Absorption corrections were performed using
the built-in SADABS program of the CrysAlisPro program suite.
Structure solutions and refinements were performed using the
SHELXTL v.6.10 software package. All the structures were solved
by direct methods, expanded by difference Fourier syntheses, and
refined by full matrix least-squares on F2. All non-hydrogen atoms
were refined anisotropically with a riding model for the hydrogen
atoms. Further details on crystal data, data collection, and refine-
ments are summarized in Table 1.
Acknowledgment. This work was supported by the Hong
Kong Research Grant Council (Project Nos. HKUST 601306
and HKUST 602304).
Supporting Information Available: X-ray crystallographic files
(CIF). This material is available free of charge via the Internet at
http://pubs.acs.org.
(26) SMART V 5.625, Software for the CCD Detector System; Bruker
AXS: Madison, WI, 2001.
OM8002202
(27) SAINT V 6.26, Software for the CCD Detector System; Bruker
AXS: Madison, WI, 2001.
(28) SADABS V 2.03, Software for the CCD Detector System; Bruker
AXS: Madison, WI, 2003.
(29) Sheldrick, G. M. SHELXTL, v. 6.10, Structure Determination
Software Suite; Bruker AXS: Madison, WI, 2000.