Ruthenium catalyzed homocoupling of terminal alkynes

Article abstract of DOI:10.1007/PL00010158

Several complexes of the type RuTp(L)(L′)Cl (L, L′ = P, N, O donors) were tested with respect to their ability of promoting catalytic C-C-coupling reactions of terminal acetylenes. When L = tertiary phosphine, predominantly dimerization occurs, RuTp(PPh

Full text of DOI:10.1007/PL00010158

Monatshefte fuÈr Chemie 129, 221±233 (1998)
Ruthenium Catalyzed Homocoupling
of Terminal Alkynes
Christian Slugovc1, Daniel Doberer1, Christian Gemel1, Roland Schmid1,
Karl Kirchner1;Ã, Berthold Winkler2, and Franz Stelzer2;Ã
1
Institute of Inorganic Chemistry, Technical University of Vienna, A-1060 Vienna, Austria
2
Institute of Chemical Technology of Organic Materials, Technical University of Graz, A-8010
Graz, Austria
Summary. Several complexes of the type RuTp(L)(L0)Cl (L, L0 ˆ P, N, O donors) were tested with
respect to their ability of promoting catalytic C±C-coupling reactions of terminal acetylenes. When
L ˆ tertiary phosphine, predominantly dimerization occurs, RuTp(PPh3)2H being the most ef®cient
pre-catalyst. In the absence of a phosphine ligand, polymerization takes place with RuTp(COD)Cl as
the most effective pre-catalyst. Both product distribution and conversion depend strongly on the
substituent of the alkyne and to a lesser extent on the co-ligands of the ruthenium complex. The
catalytically active species is the 16eꢀ alkynyl complex RuTp(L)(±C:C±R) which in case of
L ˆ PCy3 and R ˆ Bun could be trapped as RuTp(PCy3)(±C:CBun)(CO).
Keywords. Ruthenium; Poly(acetylene); Conjugated polymers; Dimerization; Trispyrazolylborate.
Rutheniumkatalysierte Homokupplung von terminalen Alkinen
0
È
Zusammenfassung. Die Fahigkeit einiger Komplexe des Typs RuTp(L)(L )Cl, C±C-Kupplungsreak-
tion terminaler Alkine zu katalysieren, wurde getestet. Ist L ein Phosphin und L0 ein labiler Ligand,
È
so dimerisieren die Alkine, wahrend sie in Abwesenheit von Phosphinen polymerisieren.
RuTp(PPh3)2H ist der beste Katalysator fuÈr die Dimerisierung, RuTp(COD)Cl fuÈr die Polymerisa-
È
tion. Produktverteilung und Ausbeute sind in erster Linie vom Substituenten am Alkin abhangig, aber
auch von den Liganden am Ruthenium. Die katalytisch aktive Spezies ist der 16eꢀ-Alkinyl-Komplex
RuTp(L)(±C:C±R), der im Falle von L ˆ PCy3 und R ˆ Bun als RuTp(PCy3)(±C:C±Bun)(CO)
abgefangen werden konnte.
Introduction
The transition metal catalyzed dimerization of terminal alkynes is an effective
method for the formation of enynes. Its synthetic application in organic synthesis
has been limited, however, due to the low selectivity on dimeric products [1].
Recent advances in transition metal mediated selective dimerization reactions
fueled a resurgence of interest in this type of reaction [2]. We have recently shown
that RuTp(PPh3)2Cl (1 Tp ˆ hydridotris(pyrazolyl)borate) is an ef®cient pre-
* Corresponding author

222
C. Slugovc et al.
catalyst for the selective coupling of HC:CR (R ˆ Ph, SiMe3, n-Bu, and t-Bu) to
give 1,4- and 2,4-disubstituted butenynes [3]. If two pyridine moieties are
substituted for the PPh3 units, no dimeric but instead polymeric products are
obtained. Interestingly, in the presence of an excess of allyl alcohol this pathway
becomes of minor importance, and predominantly allyl vinyl ethers are obtained
[4].
In order to establish the factors that control the reactivity of the catalyst and
consequently the selectivity of the C±C coupling process, we report here on the
coupling of HC:CPh with complexes 1, RuTp(PPh3)(=C=CHPh)Cl (2),
RuTp(PPh3)(py)Cl (3), RuTp(PPh3)(PMe3)Cl (4), RuTp(PPh3)(CO)Cl (5), RuTp
(PBun3)2Cl (6), RuTp(PCy3)(OMe)Cl (7, Cy ˆ cyclohexyl), RuTp(dppe)Cl
(8, dppe ˆ Ph2PCH2CH2PPh2), RuTp(pn)Cl (9, pn ˆ Ph2PCH2CH2NMe2),
RuCp*(pn)Cl (10, Cp* ˆ pentamethylcyclopentadienyl), Ru(pn)2Cl2 (11), and
RuTp(PPh3)2H (12) acting as catalyst precursors. Mechanistic details will be
presented and, in addition, we describe the polymerization of some terminal
alkynes [5] mediated by RuTp(COD)Cl (13, COD ˆ 1,5-cyclooctadiene) and
RuTp(py)2Cl (14).
Results and Discussion
Dimerization
As has been shown previously [3], complex 1 catalyzes the coupling of terminal
alkynes to give butenynes. The catalytic cycle is initiated by loss of a PPh3 ligand
and formation of the coordinatively unsaturated species RuTp(PPh3)Cl as
1
monitored by 31Pf Hg NMR spectroscopy in benzene-d6 at 80ꢁC. Upon adding
HC:CPh (10 equiv), the neutral vinylidene complex RuTp(PPh3)(Cl)(=C=CHPh)
(2) is formed as an intermediate; no other intermediate could be detected by NMR
spectroscopy in addition to the reaction products 1a and 1b in the further course of
the reaction (Table 1). The use of isolated compound 2 in an independent reaction
catalyzes the coupling of HC:CPh in a fashion nearly identical to 1 (Table 1). A
possible reaction scheme could involve the coordinatively unsaturated alkyne
complex RuTp(PPh3)(±C:CPh) formed by the liberation of HCl (Scheme 1), a
proposal in accordance with other investigations [6, 9a, 9b]. In order to establish the
mechanism of this process, complexes 3±12 have been tested as possible catalyst
precursors for the dimerization of HC:CPh.
Scheme 1

Homocoupling of Terminal Alkynes
223
Complex 3 is slightly less reactive than 1 affording about 80% conversion. The
selectivity, however, remains unchanged (Table 1). In the course of the reaction,
1
release of py rather than of PPh3 is observed by H NMR spectroscopy. The
catalytically active species should thus be the same alkynyl complex as that
originating from 1. Complexes 4, 6, and 7, on the other hand, are both less reactive
and selective, the conversion rate dropping to 10, 14, and 50%, respectively.
Complex 5 is catalytically inactive. Likewise, complex 8, containing the chelating
ligand dppe, does not show any catalytic activity. Complex 9, featuring the
hemilabile phosphino-amine ligand Ph2PCH2CH2NMe2 which is able to provide
temporarily a coordination site due to reversible Ru-N bond cleavage, exhibits
some although modest reactivity. The conversion is merely 13% (Table 1), the
main outcome being the unusual coupling product RuTp(Cl)(ꢀ3(P, C, C)-
Ph2PCH=CHC(Ph)=CH2) reported previously [7]. The isoelectronic RuCp*
complex 10 turned out to be more reactive than 9 but shows no selectivity,
yielding a 1:1 mixture of the E and Z isomers 1a and 1b. In the case of 11, the
selectivity of the reaction is reversed giving predominantly the head-to-head dimer
(Z)-1,4-diphenyl-1-buten-3-yne (Ib) with about 70% conversion.
The poor reactivity of most of these complexes can be attributed to the lack of
substitutive reactivity. Whereas ligands forming weak metal±ligand bonds (weak
bases such as PPh3, py) and/or sterically demanding ligands (e.g. PPh3, PCy3)
facilitate the formation of a 16eꢀ intermediate, ꢁ acceptor ligands such as CO
suppress ligand dissociation. Furthermore, the presence of bulky and/or hemilabile
ligands promotes the subsequent formation of vinylidene complexes.
The most ef®cient catalyst precursor both in terms of reactivity and selectivity
is complex 12. As the primary step, a release of PPh3 can be observed by means of
1
31Pf Hg NMR spectroscopy. The conversion is essentially quantitative, and the
head-to-head dimer (E)-1,4-diphenyl-1-buten-3-yne (Ia) is formed selectively
(Table 1). The catalytically active species is expected to be the same alkynyl
complex RuTp(PPh3)(±C:CHPh) as that arising from 1, but presumably
originating from insertion of the alkyne into the Ru±H bond [1, 2] giving ®rst a
vinyl intermediate which then undergoes ꢂ-bond metathesis with another alkyne
molecule releasing an ole®ne and the catalytically active 16eꢀ alkynyl species
(Scheme 2). This process appears to be more facile than that described in Scheme
1, as becomes apparent in the case of aliphatic alkynes which are generally less
reactive than the aromatic ones. Thus, the dimerization of HC:CBut catalyzed by 1
yields exclusively the respective Z-enyne. The conversion, however, is low (10%)
even after 68 h at re¯ux in toluene. Complex 12 exhibits the same selectivity as 1,
but the conversion is increased to 16% already after 20 h under the same reaction
condition.
Scheme 2

224
C. Slugovc et al.
In order to provide further evidence for a 16eꢀ akynyl complex as a reactive
intermediate in the catalytic cycle, RuTp(PCy3)(=C=CHBun)Cl (15) has been
treated with the strong base LiNPr2i (1 equiv) at ꢀ80ꢁC under a CO atmosphere.
Under this condition, the coordinatively unsaturated intermediate RuTp(PCy3)-
(±C:C±Bun) is initially formed and subsequently trapped as RuTp(PCy3)(±C:C±
Bun)(CO) (16). Which has been isolated in 69% yield (Scheme 3) and was
1
characterized by elemental analysis as well as H, 13C{1H}, and 31P{1H} NMR
spectroscopy.
Scheme 3
In the 1H NMR spectrum of 16, the characteristic peak of the vinylidene proton
at 4.06 ppm [8] is missing now, and in the 13C{1H} NMR spectrum of 16,
characteristic resonances for the Cꢃ and Cꢄ atoms of the alkyne moiety are found at
95.9 (JCP ˆ 15.2 Hz) and 105.9 ppm, respectively. The CO ligand gives rise to a
doublet centered at 207.3 ppm (JCP ˆ 15.3 Hz). The resonances of the Tp and PCy3
ligands are in the expected ranges.
After liberation of HCl in the absence of a potential ligand such as CO, a
second alkyne molecule is readily added to the alkynyl intermediate followed by a
selectivity determining C±C coupling step as depicted in Scheme 4. Accordingly,
the C4 unsaturated product is eventually liberated from an intermediate ꢂ-organyl
metal species by ꢂ-bond metathesis with an additional alkyne molecule.
Scheme 4

Homocoupling of Terminal Alkynes
225
The majority of all hitherto known catalytic dimerizations of terminal alkynes
to C4 units are migratory insertions of acetylenes into ꢂ metal±carbon bonds
proceeding, for instance, via alkynyl±vinylidene or alkynyl±vinyl coupling
(Bianchini mechanism) [9]. In the case of late transition metals, enynyl inter-
mediates could be isolated occasionally giving predominantly (Z) head-to-head
coupling products [10]. A somewhat other mechanism appears to operate in the
case of early transition metals, lanthanides, and actinides, where preferentially (E)
head-to-head and head-to-tail dimers together with trimeric and even oligomeric
coupling products are obtained. The catalytically active species in all these cases is
a metal alkynyl complex generated by the intervention of strongly basic ligands
such as hydride and alkyl groups.
Thus, the stereo- and regioselectivity of the dimerization should vary with the
substituent on the alkyne. This indeed has been shown by us and others [1, 2, 3].
Similar results have been found in this work while studying the catalytic
dimerization of HC:CR (R ˆ SiMe3 (II), Bun (III), But (IV), CH2Ph (V), C6H11
(VI), COOEt (VII)) with 12 as precatalyst. As can be seen from Table 2, terminal
alkynes which are able to form a conjugated system with the intermediate
vinylidene or vinyl complexes appear to yield exclusively 1,4-enynes (E and/or Z),
suggesting the operation of the Bianchini mechanism. Whether an E or Z isomer is
formed depends on the ligand environment of the ruthenium complex (cf. Table 1,
complexes 11 and 12) as well as on the size of the substituent of the alkyne. For
smaller alkynes, the insertion of another alkyne is often faster than the elimination
of enynes; thus, also trimeric [11] or even oligomeric products are generated.
Indeed, with VII and 12 as the catalyst, the main product is an oligomeric species
Table 1. Conversion and product distribution of the catalytic dimerization of HC:CPh
Catalyst
Conversion (%)a
Ia (%)
Ib (%)
Ic (%)
RuTp(PPh3)2Cl (1)
98b
98b
80b
10
±
91
91
92
59
±
6
5
±
±
±
±
±
±
±
±
±
±
±
±
±
RuTp(PPh3)(=C=CHPh)Cl (2)
RuTp(PPh3)(py)Cl (3)
RuTp(PPh3)(PMe3)Cl (4)
RuTp(PPh3)(CO)Cl (5)
RuTp(PBun3)2Cl (6)
RuTp(PCy3)(OMe)Cl (7)
RuTp(pn)Cl (8)
6
41
±
14
50
13b
±
75
65
75
±
25
35
21
±
RuTp(dppe)Cl (9)
RuCp*(PPh3)H3 [2a]
RuCp*(pn)Cl (10)
Ru(pn)2Cl2 (11)
85
63
70
99
33
50
10
92
67
50
90
8
RuTp(PPh3)2H (12)
a
b
Conversions are for isolated products; oligo- or polymeric byproduct

226
C. Slugovc et al.
Table 2. Conversion and product distribution of the catalytic dimerization of acetylenes with
RuTp(PPh3)2H (2) as pre-catalyst
H-C:C-R
Conversion (%)a
a (%)
b (%)
c (%)
R ˆ Ph (I)
99
67
34
16
65
86
17b
92
±
8
69
21
100
26
15
±
±
R ˆ SiMe3 (II)
R ˆ n-Bu (III)
R ˆ t-Bu (IV)
R ˆ CH2Ph (V)
R ˆ C6H11 (VI)
R ˆ COOEt (VII)
29
47
32
30
85
44
±
100
±
a
b
Conversions are for isolated products; yield of dimeric species
obtained in 83% yield (cf. Table 3). On the other hand, acetylene to vinylidene
isomerizations are known to be sluggish for aliphatic alkynes [2, 12]. Therefore,
the direct insertion of ꢅ2-alkynes into the Ru-alkynyl ꢂ-bond produces
preferentially 1,3-enynes in a fashion similar to early transition metal catalyzed
dimerizations of alkynes.
Oligo- and Polymerization
In order to study the oligo- or polymeric by-products formed in the catalytic
dimerizations of terminal alkynes, we focused on those complexes affording high
yields of polymeric products. Prerequisite for such a catalyst is the availability of
two vacant coordination sites. Here we report on the ability of RuTp(COD)Cl (13)
and RuTp(py)2Cl (14) to promote oligo -and polymerizations of some terminal
alkynes. As is known from our recent studies [4], in boiling DMF the COD ligand
in 13 is labile and can be readily replaced by a variety of ligands. An intermediate
in this reaction, although neither isolated nor spectroscopically detected, might be
RuTp(DMF)2Cl. Likewise, the py ligands in 14 are labile and are readily replaced
by other potential ligands in DMF as the solvent. In a typical procedure, HC:CR
(0.3 M, R ˆ Ph, Bun, COOEt) was added to a suspension of the catalyst (13-14,
2 mol%) in DMF (5 ml). The sealed Schlenk tube was heated in an oil bath at
150ꢁC. Some experimental results are listed in Table 3. Noteworthy, in toluene or
benzene 13 did not react at all, whereas 14 reacted only with great reluctance. In
fact, 13 is stable in re¯uxing toluene even in the presence of potential ligands [4].
ꢀ
In the presence of 13, HC:CPh gave after 30 min a polymer with Mn ˆ
7056 g/mol and PDI ˆ 1.48. This process is a non-living polymerization, since
prolongation of the reaction time to 20 h led to polymer degradation, resulting in a
ꢀ
polymer of half the size of that in entry 1 (Mn ˆ 3972 g/mol, PDI ˆ 1.39). This
thermally induced degradation can generally be rationalized in terms of three
processes: intrachain backbiting, intramolecular cyclization, and interchain
reactions [13]. For a mechanism to be suggested in the present case, the
1
conformation of the poly(phenylacetylene) should be known. The H NMR
spectrum of entry 1 has a broad peak in the aromatic region (7.6±6.0 ppm) together
with some small peaks at 7.84, 7.77, and 7.74 ppm assignable to 1,2,4- and 1,3,5-
triphenylbenzene (7.74 ppm) [13, 14]. No resonances of cis-backbones could be

Homocoupling of Terminal Alkynes
227
Table 3. Catalytic polymerization of some terminal acetylenes
PDIb
ꢀnc
a
ꢀ
Mn
Entry
HC:CR
Catalyst
Time (h)
Yield (%)
1
2
3
4
5
Ph
13
13
14
13
13
0.5
20
20
20
5
98
99
98
77
60
7056
3972
4139
1109
1062
1.48
1.39
1.42
1.31
1.30
69
39
41
15
10
Ph
Ph
Bun
COOEt
a
b
c
ꢀ
Mn ˆ number average molecular weight; PDI ˆ polymerization distribution index; ꢀn ˆ number
average degree of polymerization
observed in the range of 6.3±6.1 ppm [13]. A very small and broad peak was
detected within 4.1±3.4 ppm, pointing to the occurrence of some intramolecular
cyclization products [15]. In the IR spectrum absorptions of cis-backbones are
typically observed at 740 cmꢀ1, whereas the less signi®cant peak of trans-
backbones at 1265 cmꢀ1 is not observed [16]. These results point to a trans-cisoidal
structure with some cis-transoidal substructures in line with literature reports on
thermally induced double bond isomerization from cis-transoidal to trans-cisoidal
structures above 80ꢁC with concomitant degradation of the polymer chain [14].
This degradation, mostly intrachain backbiting and intramolecular cyclization, is
possible only for cis-subsequences [13] which may explain the missing resonance
at 740 cmꢀ1 in entry 2. All cis-substructures disappeared and molecular weights
decreased upon prolonged heating. In the SEC (size exclusion chromatography)
ꢀ
ꢀ
analysis, a second peak with Mp ˆ 535 g/mol (Mp ˆ molecular weight at peak
maximum) could be detected which may assigned to 1, 2, 4- and 1, 3, 5-
triphenylbenzene. It has to be noted that for the calibration of the SEC analysis,
poly(styrene) is used with a macroscopic structure quite different to that of the
poly(acetylene)s or triphenylbenzene analyzed. Moreover, SEC is sensitive to the
hydrodynamic volume of the compounds, and this may explain the deviation of the
ꢀ
experimental Mp value from the actual molecular weight of triphenylbenzene
1
(306.42 g/mol). Nevertheless, in the H NMR spectrum signals of the substituted
benzenes are present. Similar results were obtained with catalyst 14 (cf. entries 2
and 3).
n
ꢀ
In the presence of 13, HC:CBu formed an oligomer with Mn ˆ 1109 g/mol
1
and PDI ˆ 1.31 with only 77% yield after 20 h. The H NMR spectrum shows
peaks at 7.28 and 6.81 ppm (in a 1:7 ratio) assignable to the vinylic protons of a cis
and trans backbone. From the integration of the aliphatic region some cyclizations
can be concluded. In the 13C{1H} NMR spectrum, resonances for the vinylic
carbons are observed at 143.3, 142.6, 139.0, and 126.9 ppm, suggesting again a
mixture of (at least) cis and trans substructures. No evidence of cyclotrimerization
products was found. The IR spectrum, surprisingly, showed peaks at 2017 cmꢀ1

228
C. Slugovc et al.
and 1957 cmꢀ1, which can be assigned to a ꢆ(C:C) and a ꢆ(C=C=C) vibration, but
no corresponding resonances were found by NMR spectroscopy. We assume that
these groups act as terminating structures in the oligomer produced via a
metathesis mechanism.
ꢀ
In the presence of 13, HC:C-COOEt formed an oligomer with Mn ˆ 1062 g/
mol and PDI ˆ 1.30 in 60% yield after 5 h. The remaining 40% were found to be
cyclotrimerization products, with the 1, 2, 4- and 1, 3, 5-derivatives in a 1:3 ratio.
The cyclotrimers might also stem from a direct cyclotrimerization reaction in
parallel fashion. The oligomer seems to be non ordered in view of the broad
resonance of the vinylic protons (6.4±6.1 ppm) and the broadened 13C{1H} NMR
resonances. Presumably, cycloaddition reactions may have occurred to some extent
based on the signals of the allylic protons at 3.1±2.8 ppm.
In summary, the present catalysis presumably proceeds via a metathesis
mechanism. The stereochemistry of the transition state of the coupling reaction
determines the primary structure of the polymer [13, 17]. If bulky substituents (Ph)
are involved, a trans dominated polymer backbone is generated which is more
dif®cult to degradate. In this case, longer polymer chains are obtained. Small sub-
stituents (Bun, COOEt), on the other hand, give rise to polymers of a cis dominated
structure which can be readily degradated. Therefore, and also because of the high
temperature needed for pre-catalyst activation, short oligomers are afforded.
Experimental
General
All manipulations were performed under an inert atmosphere of argon using Schlenk techniques. All
chemicals were standard reagent grade and used without further puri®cation. The solvents were
puri®ed according to standard procedures [18]. The deuterated solvents were purchased from Aldrich
Ê
and dried over 4 A molecular sieves. RuTp(PPh3)2Cl (1) [19], RuTp(PPh3)(=C=CHPh)Cl (2) [3],
RuTp(PPh3)(py)Cl (3) [3], RuTp(PPh3)(PMe3)Cl (4) [20], RuTp(PPh3)(CO)Cl (5) [3], RuTp(PCy3)
(OMe)Cl (7) [8], RuTp(pn)Cl (8) [4], RuTp(dppe)Cl (9) [4], RuCp*(pn)Cl (10) [11], Ru(pn)2Cl2 (11)
[21], RuTp(PPh3)2H (12) [22], RuTp(COD)Cl (13) [4], RuTp(py)2Cl (14) [4], and RuTp(PCy3)
(=C=CHBun)Cl (15) [8] were prepared according to the literature. 1H, 13C{1H}, and 31P{1H} NMR
spectra were recorded on a Bruker AC-250 spectrometer operating at 250.13, 62.86 and 101.26 MHz,
respectively, and were referenced to SiMe4 and H3PO4 (85%). Microanalysis were done by the
Microanalytical Laboratories of the University of Vienna. FT-IR spectra were taken on a Bomem
FT-IR M 100; samples were cast from dichloromethane solutions on NaCl plates. For molecular
weight determination by size exclusion chromatographie (SEC) at T ˆ 25ꢁC the following
arrangement was used: THF as solvent, a Merck-Hitachi L6200 intelligent pump combined with a
6
5
3
Ê
degasser and pulse dampener, Polymer Standard Service seperation columns (10 , 10 , and 10 A)
and a Viscotek model 200 differential refractometer-viscometer. Poly(styrene) standards
(Mp ˆ 685ꢀ1.8  106, PDI < 1.1) by Polymer Standard Service were used for calibration.
RuTp(PBun3)2Cl (6)
13 (315 mg, 0.688 mmol) and PBun3 (348 mg, 1.49 mmol) were combined in DMF (4 ml) and re¯uxed
for 2 h. The volume of the solution was reduced to about 0.5 ml, and the product was precipitated by
addition of 4 ml of n-hexane. The residue was collected on a glass frit, washed with n-hexane, and
dried in vacuo.

Homocoupling of Terminal Alkynes
229
Yield: 234 mg (44%); C33H64BCIN6P2Ru (754.20 g/mol); calcd.: C 52.55, H 8.55, N 11.14;
found: C 52.57, H 8.54, N 11.20; 1H NMR (ꢇ, CDCl3, 20ꢁC): 7.92 (2H, Tp), 7.68 (1H, Tp), 7.57 (2H,
Tp), 7.33 (1H, Tp), 6.09±6.06 (m, 3H, Tp), 1.77 (m, 6H), 1.20±0.73 (m, 21H) ppm; 13C{1H} NMR (ꢇ,
CDCl3, 20ꢁC): 148.0 (1C, Tp), 144.6 (2C, Tp), 136.6 (1C, Tp), 135.3 (2C, Tp), 105.8 (1C, Tp), 105.7
(2C, Tp), 26.8 (t, JPC ˆ 17.6 Hz, 3C), 26.2 (bs, 3C), 25.3 (t, JPC ˆ 8.8 Hz, 3C), 14.4 (s, 3C) ppm;
31P{1H} NMR (ꢇ, CDCl3, 20ꢁC): 22.4 ppm.
RuTp(PCy3)(-C:C-Bun)(CO) (16)
RuTp(PCy3)(=C=CHBun)Cl (15) (100 mg, 0.141 mmol) and LDA (15.1 mg, 0.141 mmol) were
combined at ꢀ80ꢁC in 4 ml of THF under a CO atmosphere and allowed to warm to room
temperature. The solvent was removed in vacuo, the resulting solid was redissolved in CH2Cl2, the
remaining solid was ®ltered off, the volume of the solution was reduced to about 0.5 ml and the
product was precipitated by addition of 4 ml n-hexane. The residue was collected on a glass frit,
washed with n-hexane, and dried in vacuo.
Yield: 68 mg (69%); C34H49BN6OPRu (700.66 g/mol); C 58.29, H 7.05, N 11.99; found: C 58.50,
H 7.25, N 11.76; 1H NMR (ꢇ, Acetone-d6, 20ꢁC): 8.04 (1H, Tp), 7.86 (2H, Tp), 7.80 (1H, Tp), 7.64
(1H, Tp), 7.53 (1H, Tp), 6.29 (1H, Tp), 6.27 (1H, Tp), 6.15 (1H, Tp), 2.27ꢀ1.23 (m, 32H), 0.90ꢀ0.82
(m, 8H) 13C{1H} NMR (ꢇ, Acetone-d6, 20ꢁC): 207.3 (d, JPC ˆ 15.3 Hz, CO), 146.5 (Tp), 145.7 (Tp),
144.3 (Tp), 137.6 (Tp), 136.7 (Tp), 135.6 (Tp), 107.3 (Tp), 106.5 (Tp), 106.4 (Tp), 105.9 (Ru-C:C-
Bu), 95.9 (d, JPC ˆ 15.2 Hz, Ru-C:C-Bu), 36.2, 35.9, 34.9, 31.4±28.9, 27.6, 23.3, 14.8 ppm; 31P{1H}
NMR (ꢇ, Acetone-d6, 20ꢁC): 50.0 ppm.
Catalytic dimerization of terminal alkynes
In a typical procedure, alkynes H-C:C-R (0.3 M, R ˆ Ph, SiMe3, Bun, But, CH2Ph, C6H11, COOEt)
were added to a suspension of the catalyst (1±12, 2 mol%) in toluene (5 ml), and the sealed Schlenk
tube was heated in an oil bath for 20 h at 111ꢁC. After that time the reaction mixture was evaporated
to dryness under vacuum, and the coupling products were extracted with n-hexane. The solvent was
again removed under vacuum affording isomeric mixtures of coupling products. The product
distribution was determined by 1H NMR spectroscopy. Where necessary for identi®cation,
separation of isomers was performed by column chromatography (silica gel, Merck, grade 60,
Ê
70±230 mesh, 60 A).
(E)-1,4-Diphenylbut-3-en-1-yne (Ia)
1H NMR (ꢇ, CDCl3, 20ꢁC): 7.57ꢀ7.37 (m, 10 H, Ph), 7.12 (d, 1H, J ˆ 16.3 Hz, H3), 6.45 (d, 1H,
J ˆ 16.3 Hz, H4) ppm; 13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 141.7 (1C, C4), 136.7 (1C, Ph), 132.0 (2C,
Ph), 129.1 (2C, Ph), 129.0 (1C, Ph), 128.8 (2C, Ph), 128.6 (1C, Ph), 126.7 (2C, Ph), 123.8 (1C, Ph),
108.6 (1C, C3), 92.2 (1C, C1), 89.4 (1C, C2) ppm.
(Z)-1,4-Diphenylbut-3-en-1-yne (Ib)
1H NMR (ꢇ, CDCl3, 20ꢁC): 8.07ꢀ7.97 (m, 2 H, Ph), 7.63ꢀ7.38 (m, 8H,Ph), 6.77 (d, 1H, J ˆ 11.8 Hz,
H4), 6.02 (d, 1H, J ˆ 11.8 Hz, H3) ppm; 13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 138.7 (1C, C4), 136.6 (1C,
Ph), 131.5 (1C, Ph), 128.9ꢀ123.4 (10C, Ph), 107.0 (1C, C3), 95.9 (1C, C1), 88.3 (1C, C2) ppm.
(Z)-1,4-Di(trimethylsilyl)but-3-en-1-yne (IIb)
1H NMR (ꢇ, CDCl3, 20ꢁC): 6.26 (d, 1 H, J ˆ 15.2 Hz), 6.16 (d, 1H, J ˆ 15.2 Hz), 0.19 (s, 18H,
SiMe3) ppm; 13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 146.8 (1C, C3), 125.4 (1C, C4), 105.8 (1C, C1), 99.2
(1C, C2), 0.3 (3C), ꢀ0.5 (3C) ppm.

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1,3-Di(trimethylsilyl)but-3-en-1-yne (IIc)
1H NMR (ꢇ, CDCl3, 20ꢁC): 6.12 (d, 1 H, J ˆ 3.5 Hz), 5.70 (d, 1H, J ˆ 3.5 Hz), 0.16 (s, 18H) ppm;
13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 135.6 (1C, C3), 135.4 (1C, C4), 125.4 (1C, C4), 107.2 (1C, C1),
99.1 (1C, C2), 0.7 (3C), ꢀ1.6 (3C) ppm.
(E)-Dodec-7-en-5-yne (IIIa)
1H NMR (ꢇ, CDCl3, 20ꢁC): 6.04 (dt, 1 H, J ˆ 16.1 Hz, J ˆ 7.0 Hz, H8), 5.45 (dt, 1H, J ˆ 16.1 Hz,
J ˆ 2.3 Hz, H7), 2.35ꢀ2.05 (m, 4H), 1.70ꢀ1.24 (m, 8H), 0.91 (t, 6H) ppm; 13C{1H} NMR (ꢇ, CDCl3,
20ꢁC): 132.9 (C8), 110.9 (C7), 90.1 (C6), 81.7 (C5), 31.3, 31.0, 30.1, 22.3, 19.2, 17.7, 14.0, 13.6 ppm.
(Z)-Dodec-7-en-5-yne (IIIb)
1H NMR (ꢇ, CDCl3, 20ꢁC): 5.82 (dt, 1 H, J ˆ 11.0 Hz, J ˆ 7.0 Hz, H8), 5.48 (dt, 1H, J ˆ 11.0 Hz,
J ˆ 2.2 Hz, H7), 2.34ꢀ2.07 (m, 4H), 1.72ꢀ1.24 (m, 8H), 0.93 (t, 6H) ppm; 13C{1H} NMR (ꢇ, CDCl3,
20ꢁC): 142.1 (C8), 110.3 (C7), 88.7 (C6), 80.0 (C5), 31.3, 31.0, 30.1, 22.6, 19.5, 17.8, 14.1, 13.6 ppm.
2-Butyloct-1-en-3-yne (IIIc)
1H NMR (ꢇ, CDCl3, 20ꢁC): 5.20 (d, 1 H, J ˆ 2.4 Hz, H1), 5.12 (d, 1H, J ˆ 2.4 Hz, H1), 2.44ꢀ2.37 (m,
4H), 1.77ꢀ1.26 (m, 8H), 0.94 (t, 6H) ppm; 13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 142.9 (C2), 119.5 (C1),
91.6 (C4), 84.3 (C3), 31.2, 30.8, 26.4, 22.0, 18.3, 17.9, 14.1, 13.6 ppm.
(Z)-2,2,7,7-(Tetramethyl)oct-5-en-3-yne (IVb)
1H NMR (ꢇ, CDCl3, 20ꢁC): 5.72 (d, 1 H, J ˆ 12.0 Hz, H6), 5.38 (d, 1H, J ˆ 12.0 Hz, H5), 1.28 (s,
9H), 1.22 (s, 9H) ppm; C{1H} NMR (ꢇ, CDCl3, 20 ꢁC): 152.9 (C6), 118.5 (C5), 106.4 (C4), 67.3
13
(C3), 29.8, 29.7, 27.5 (Me), 27.3 (Me) ppm.
(E)-1,6-Diphenylhex-4-en-2-yne (Va)
1H NMR (ꢇ, C6D6, 20ꢁC): 7.80ꢀ6.90 (m, 10 H, Ph), 6.20 (dt, 1H, J ˆ 16.2, 6.6 Hz, H5), 5.51 (d, 1H,
J ˆ 16.2 Hz, H4), 3.46 (s, 2H, H1), 3.04 (2H, d, J ˆ 6.6 Hz, H6) ppm; 13C{1H} NMR (ꢇ, C6D6, 20ꢁC):
139.0 (C4), 128.9 (Ph), 128.7 (Ph), 128.6 (Ph), 128.1 (Ph), 126.5 (Ph), 111.6 (C5), 88.5 (C3), 83.6
(C2), 39.3 (C6), 25.6 (C1) ppm.
(Z)-1,6-Diphenylhex-4-en-2-yne (Vb)
1H NMR (ꢇ, C6D6, 20ꢁC): 7.84ꢀ6.85 (m, 10 H, Ph), 6.65 (d, 1H, J ˆ 11.8, 5.5 Hz, H4), 5.80 (d, 1H,
J ˆ 11.8 Hz, H4), 3.76 (s, 2H, H1), 3.14 (2H, d, J ˆ 5.5 Hz, H6) ppm; 13C{1H} NMR (ꢇ, C6D6, 20ꢁC):
139.8 (C4), 128.9 (Ph), 128.7 (Ph), 128.6 (Ph), 128.1 (Ph), 126.5 (Ph), 112.6 (C5), 88.6 (C3), 83.6
(C2), 39.2 (C6), 25.6 (C1) ppm.
5-Phenyl-2-(phenylmethyl)-pent-1-en-3-yne (Vc)
1H NMR (ꢇ, C6D6, 20ꢁC): 7.82ꢀ6.90 (m, 10 H, Ph), 5.41 (d, 1H, J ˆ 1.5 Hz, H1), 5.05 (d, 1H,
J ˆ 1.5 Hz, H1), 3.36 (s, 2H, CH2), 3.33 (s, 2H, CH2), ppm; C{1H} NMR (ꢇ, C6D6, 20ꢁC): 142.2
13
(C2), 129.4 (Ph), 128.7 (Ph), 128.6 (Ph), 128.2 (Ph), 126.6 (Ph), 121.3 (C1), 91.6 (C3), 87.2 (C4), 44.1
(CH2Ph), 25.8 (C5) ppm.

Homocoupling of Terminal Alkynes
231
(E)-1,4-Di(1-cyclohexenyl)but-3-en-1-yne (VIa)
1H NMR (ꢇ, CDCl3, 20ꢁC): 6.57 (d, 1H, J ˆ 15.9 Hz, H4), 6.01 (m, 1H, cHex), 5.84 (m, 1H, cHex),
5.61 (d, J ˆ 15.9 Hz, H3), 2.16ꢀ2.13 (6H), 1.69ꢀ1.60 (6H) ppm; C{1H} NMR (ꢇ, CDCl3, 20ꢁC):
13
144.6 (1C, C4), 134.7 (cHex2), 133.2 (cHex1), 132.6 (cHex1), 133.2 (cHex2), 104.9 (1C, C3), 93.1
(1C, C1), 87.5 (1C, C2), 29.9, 24.5, 23.3, 23.1, 22.94, 22.90, 22.88, 22.2 ppm.
(Z)-1,4-Di(1-cyclohexenyl)but-3-en-1-yne (VIb)
1H NMR (ꢇ, CDCl3, 20ꢁC): 6.10 (m, 1H, cHex), 6.05 (d, 1H, J ˆ 11.8 Hz, H4), 5.97 (m, 1H, cHex),
5.42 (d, J ˆ 11.8 Hz, H3), 2.17ꢀ2.13 (6H), 1.69ꢀ1.60 (6H) ppm; C{1H} NMR (ꢇ, CDCl3, 20ꢁC):
13
142.1 (1C, C4), 136.2 (cHex2), 135.3 (cHex1), 132.7 (cHex2), 133.2 (cHex1), 104.5 (1C, C3), 96.7
(1C, C1), 85.4 (1C, C2), 29.5, 26.7, 23.3, 23.1, 22.94, 22.90, 22.88, 22.2 ppm.
(E)-But-3-en-1-yne-1,4-dicarboxylic acid, diethylester (VIIa)
1H NMR (ꢇ, CDCl3, 20ꢁC): 6.77 (d, 1H, J ˆ 16.0 Hz, H4), 6.45 (d, 1H, J ˆ 16.0 Hz, H3), 4.28 (m, 2H,
CH2), 4.25 (q, 2H, CH2), 1.32 (t, 3H, CH3), 1.30 (t, 3H, CH3) ppm; 13C{1H} NMR (ꢇ, CDCl3, 20ꢁC):
165.0 (COOEt), 160.0 (COOEt), 136.0 (C4), 122.1 (C3), 87.6 (C2), 82.0 (C1), 63.0 (OCH2CH3), 61.9
(OCH2CH3), 14.7 (2C, OCH2CH3) ppm.
1,3,5-Benzenetricarboxylic acid, triethylester (VIId)
1H NMR (ꢇ, CDCl3, 20ꢁC): 8.81 (s, 3H, Ph2;4;6), 4.40 (q, 6H, CH2CH3), 1.42 (t, 9H, CH2CH3) ppm;
13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 165.5 (3C, COOCH2CH3), 134.9 (3C, Ph2;4;6), 132.0 (3C, Ph1;3;5),
62.2 (3C, COOCH2CH3), 14.9 (3C, COOCH2CH3) ppm.
1,2,4-Benzenetricarboxylic acid, triethylester (VIIe)
1H NMR (ꢇ, CDCl3, 20ꢁC): 8.37 (d, J ˆ 1.9 Hz, 1H, Ph3), 8.17 (dd, J ˆ 1.9 Hz, J ˆ 7.8 Hz, 1H, Ph5),
7.75 (d, J ˆ 7.8 Hz, 1H, Ph6), 4.38 (m, 6H, CH2CH3), 1.38 (m, 9H, CH2CH3) ppm; 13C{1H} NMR (ꢇ,
CDCl3, 20ꢁC): 167.9 (1C, COOCH2CH3), 167.1 (1C, COOCH2CH3), 165.6 (1C, COOCH2CH3),
136.8 (1C, Ph1), 133.2 (1C, Ph), 132.6 (1C, Ph), 132.5 (1C, Ph), 130.6 (1C, Ph3), 129.4 (1C, Ph6),
62.5 (1C, COOCH2CH3), 62.4 (2C, COOCH2CH3), 14.6 (s, 3C, COOCH2CH3) ppm.
Catalytic oligo- and polymerization of terminal alkynes
In a typical procedure, alkynes (0.3 M, R ˆ Ph, COOEt, Bun) were added to a suspension of the
catalyst (13, 14; 2 mol%) in DMF (5 ml), and the sealed Schlenk tube was heated in an oil bath at
150ꢁC. After the time given below, the reaction mixture was evaporated to dryness, volatiles were
removed under vacuum, and the product was analyzed.
Poly(phenylacetylene)
ꢀ
ꢀ
ꢀ
(a) Reaction time: 30 min; catalyst: 13; yield: 98%; SEC: Mn ˆ 7056, Mw ˆ 10440, Mp ˆ 9180,
1
PDI ˆ 1.48; H NMR (ꢇ, CDCl3, 20ꢁ): 7.84 (s) 7.77 (s), 7.74 (s), 7.6ꢀ6.0 (bm), 4.1ꢀ3.4 (bs) ppm;
13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 128.0ꢀ123.2 ppm; IR: 3075 (w), 3053 (w), 3022 (w), 2919 (w),
1964 (w), 1598 (m), 1492 (m), 1448 (m), 1314 (w), 1217 (w), 1031 (w), 740 (m), 757 (s), 698 (s)
cmꢀ1
.

232
C. Slugovc et al.
ꢀ
ꢀ
ꢀ
(b) Reaction time: 20 h; catalyst: 13; yield: 99 %; SEC: Mn ˆ 3972, Mw ˆ 5503; Mp ˆ 4986,
1
ꢁ
ꢀ
PDI ˆ 1.39; additional byproduct: Mp ˆ 535; H NMR (ꢇ, CDCl3, 20 C): 7.84, 7.77 (s), 7.74 (s),
7.6ꢀ6.0 (bm), 4.1ꢀ3.4 (bs) ppm; 13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 142.3ꢀ130.6, 128.0ꢀ123.2 ppm;
IR: 3075 (w), 3053 (w), 3022 (w), 2919 (w), 1964 (w), 1598 (m), 1492 (m), 1448 (m), 1314 (w),
1217 (w), 1031 (w), 757 (s), 698 (s) cmꢀ1
.
ꢀ
ꢀ
ꢀ
(c) Reaction time: 20 h; catalyst: 14; yield: 98%; SEC: Mn ˆ 4138; Mw ˆ 5854; Mp ˆ 4778,
ꢀ
PDI ˆ 1.42; additional byproduct: Mp ˆ 607; NMR and IR spectra as above.
Oligo(n-hexyne)
ꢀ
ꢀ
ꢀ
Reaction time: 20 h; catalyst: 13; yield: 77%; SEC: Mn ˆ 1109; Mw ˆ 1461; Mp ˆ 1014,
1
PDI ˆ 1.31; H NMR (ꢇ, CDCl3, 20ꢁC): 7.28 (s, 0.15H), 6.81 (s, 1H), 2.58ꢀ2.52 (m),
2.23ꢀ1.89 (bm), 1.61ꢀ2.36 (bm), 0.95ꢀ0.88 (m) ppm; 13C{1H} NMR (ꢇ, CDCl3, 20ꢁC): 143.3,
142.6, 139.0, 126.9, 126.5, 36.3, 24.2, 32.8ꢀ31.0, 23.8ꢀ23.5, 23.2, 14.6 ppm; IR: 2981 (s), 2925 (2),
2856 (s), 2027 (m), 1957 (m), 1726 (m), 1605 (m), 1463 (s), 1381 (s), 1314 (m), 1221 (m), 1117 (m),
1050 (m), 900 (w), 863 (w), 758 (w), 721 (w) cmꢀ1
.
Oligo(ethylpropionate)
ꢀ
ꢀ
ꢀ
Reaction time: 5 h; catalyst: 13; yield: 60%; SEC: Mn ˆ 1062, Mw ˆ 1384; Mp ˆ 921, PDI ˆ 1.30;
1
oligomers were seperated by precipitation on addition of methanol; H NMR (ꢇ, CDCl3, 20ꢁC):
6.41ꢀ6.07 (bm) 4.30ꢀ4.21 (bm), 3.1ꢀ2.8 (bm), 1.42ꢀ1.21 (bm) ppm; 13C{1H} NMR (ꢇ, CDCl3,
20ꢁC): 165.8ꢀ165.5, 135.0ꢀ132.1, 61.7ꢀ61.2, 14.9±14.7 ppm; IR: 2983 (m), 2936 (w), 2090 (w),
2081 (w), 2069 (w), 2003 (w), 1963 (w), 1725 (s), 1472 (w), 1450 (w), 1391 (w), 1370 (m), 1304
(m), 1249 (s), 1187 (m), 1114 (m), 1029 (m), 935 (w), 863 (w), 767 (w) cmꢀ1
.
Acknowledgements
È
Financial support by the Fonds zur Forderung der Wissenschaftlichen Forschung is gratefully
acknowledged (Project No. 11896).
References
[1] For an overview of literature concerning catalytic dimerization of terminal alkynes see: Trost
BM, Sorum MT, Chan C, Harms AE, RuÈhter G (1997) J Am Chem Soc 119: 698
[2] (a) Yi CS, Liu N (1996) Organometallics 15: 3968; (b) Straub T, Haskel A, Eisen MS (1995) JAm
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[3] Slugovc C, Mereiter K, Zobetz E, Schmid R, Kirchner K (1996) Organometallics 15: 5275
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[5] For leading references see: (a) Wegner G (1981) Angew Chem 93: 352; (b) Chien JCW (1984)
Polyacetylene. In: Chemistry, Physics and Material Sciences. Academic Press, New York; (c)
Gibson HW, Skotheim TJ (ed) (1986) Handbook of Conducting Polymers. Marcel Dekker, New
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p 353
[6] Bruce MI, Hall BC, Zaitseva NN, Skelton BW, White AH (1996) J Organomet Chem 552: 307

Homocoupling of Terminal Alkynes
233
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[8] Gemel C, Kickelpick G, Schmid R, Kirchner K (1997) J Chem Soc Dalton Trans 2119
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113: 5433; (c) Barbaro P, Bianchini C, Peruzzini M, Polo A, Zanobini F, Frediani P (1994) Inorg
Chim Acta 220: 5
[10] For crystal structures of coordinated enynes see: (a) Alcock NW, Hill AF, Melling RP (1991)
Organometallics 10: 3898; (b) Liles DC, Verhoeven PFM (1996) J Organomet Chem 522: 33; (c)
Yang SM, Chan MCW, Cheung KK, Che CM, Peng SM (1997) Organometallics 16: 2819 and
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[11] Mauthner K, Slugovc C, Mereiter K, Schmid R, Kirchner K (1997) Organometallics 16: 1956
[12] Bruce MI (1991) Chem Rev 91: 197
[13] Kunzler J, Percec V (1990) J Polym Sci Polym Chem Ed 28: 1221 and references therein
[14] Simionescu CI, Percec V, Dumitrescu S (1977) J Polym Sci Polym Chem Ed 15: 2497
[15] (a) Mayo FR (1968) J Am Chem Soc 90: 1289; (b) Kirchner K, Riederle K (1983) Angew
Makromol Chem 111: 1; (c) Chong YK, Rizzardo E, Solomon DH (1983) J Am Chem Soc 105:
7761
[16] Tsonis CP, Farona MF (1979) J Polym Sci Polym Chem Ed 17: 1779
[17] Percec V (1983) Polym Bull 10: 1
[18] Perrin DD, Armarego WLF (1988) Puri®cation of Laboratory Chemicals, 3rd edn. Pergamon,
New York
[19] Alcock NW, Burns ID, Claire KS, Hill AF (1992) Inorg Chem 31: 2906
[20] Slugovc C, Sapunov VN, Wiede P, Merieter K, Schmid R, Kirchner K (1997) J Chem Soc Dalton
Trans 4209
[21] Shen JY, Slugovc C, Wiede P, Mereiter K, Schmid R, Kirchner K (1998) Inorg Chim Acta
268: 69
[22] Tenorio MJ, Tenorio MAJ, Puerta MC, Valerga P (1997) Inorg Chim Acta 259: 77
Received July 10, 1997. Accepted September 26, 1997