A simple synthesis of tetraethynylethenes and representative molecular structures of some dicobalt derivatives

Article abstract of DOI:10.1016/S0022-328X(02)02191-5

Palladium-copper catalysed cross-coupling reactions of tetracholoroethene with terminal acetylenes RC≡CH (R = SiMe₃, C₆H₅, C₆H₄CN-4) in refluxing triethylamine afford the corresponding tetraethynylethenes in 30-60% isolated yields. The reaction of 1,6- bis(trimethylsilyl)-3,4-bis (trimethylsilylethynyl)-hex-3-ene-1,5-diyne with [Co₂(CO)₆(L₂)] [L₂ = (CO)₂ or μ-dppm] affords complexes in which one or two (trans) acetylene moieties are coordinated by a dicobalt fragment.

Full text of DOI:10.1016/S0022-328X(02)02191-5

Journal of Organometallic Chemistry 670 (2003) 178ꢀ187
/
www.elsevier.com/locate/jorganchem
A simple synthesis of tetraethynylethenes and representative
molecular structures of some dicobalt derivatives
Olivia F. Koentjoro, Philipp Zuber, Horst Puschmann, Andres E. Goeta,
Judith A.K. Howard, Paul J. Low *
Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK
Received 22 October 2002; received in revised form 16 December 2002; accepted 16 December 2002
Abstract
Palladiumꢀ
C6H4CN-4) in refluxing triethylamine afford the corresponding tetraethynylethenes in 30ꢀ
bis(trimethylsilyl)-3,4-bis(trimethylsilylethynyl)-hex-3-ene-1,5-diyne with [Co2(CO)6(L2)] [L2ꢁ
/
copper catalysed cross-coupling reactions of tetracholoroethene with terminal acetylenes RCÅ
60% isolated yields. The reaction of 1,6-
(CO)2 or m-dppm] affords complexes
/
CH (RꢁSiMe3, C6H5,
/
/
/
in which one or two (trans) acetylene moieties are coordinated by a dicobalt fragment.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Alkyne; Tetraethynylethene; Cobalt carbonyl complexes
1. Introduction
many of the isomers of substituted TEE’s using palla-
dium catalysed coupling reactions of terminal alkynes
with 3-(dibromomethylidene)penta-1,4-diynes, and also
through a multi-step sequence beginning with the cross-
coupling alkynes with dimethyl 2,3-dibromofumarate,
and subsequent elaboration (Schemes 1 and 2) [4,26,27].
To date, our own work with highly ethynylated
compounds has focussed on the synthesis, structure
and properties of organometallic species derived from
Substituted derivatives of 3,4-bis(ethynyl)-hex-3-ene-
1,5-diyne (tetraethynylethene, TEE, 1) have been the
subject of a great deal of recent attention on the basis of
the large non-linear optical response which they have
been shown to offer [1ꢀ
building blocks in the preparation of more extended
conjugated systems [10ꢀ14], and as p-electron donors
[15,16]. The reversible photoisomerism of the TEE
framework also lends itself to the construction of
molecular scale switching components, which have
proved to be remarkably resistant to photo fatigue
/
9], their potential for use as
/
linear conjugated polyynes [28ꢀ31]. In seeking to extend
/
these studies to cross-conjugated polycarbon ligands we
were drawn to the TEE framework. Given the demon-
strated utility of dichloroethenes in the preparation of
ene-ynes via palladiumꢀcopper catalysed cross-coupling
/
[17ꢀ19].
/
reactions [32,33], we decided to investigate tetrachlor-
oethene as a reagent in the synthesis of tetraethyny-
lethenes. Here we report the initial results of these
investigations.
Early synthetic methods to substituted TEE’s in-
cluded dimerisation of bis(ethynyl)methylene carbenes
[20,21] and the reductive dimerisation of 3-bromopenta-
1,4-diynes [22,23]. More recently, Jones and co-workers
have devised routes to tetraethynylethenes via a carbe-
noid coupling protocol [24,25], while the Diederich
group have devised elegant, multi-step synthetic meth-
odologies which allow the regio-specific synthesis of
2. Results and discussion
2.1. Cross-coupling reactions with tetrachloroethene
* Corresponding author. Tel.: ꢂ
3844737.
E-mail address: p.j.low@durham.ac.uk (P. Low).
/
44-191-3743114; fax: ꢂ44-191-
/
The Pd(PPh3)4 (2.5%)ꢀ
coupling reaction of Me3SiCÅ
/
CuI (2.5%) catalysed cross-
CH with tetrachlor-
/
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(02)02191-5

O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ
/187
179
Scheme 1. Synthesis of cis tetraethynylethenes. (a) (i) BuLi (ii) HCO2Et (iii) Hꢂ. (b) BaMnO4 (c) CBr4, PPh3 (d) R2CÅ
(e) K2CO3, MeOH.
/CH, Pd(PPh3)4, CuI, BuNH2
oethene in refluxing NHiPr2 afforded a mixture of
products, the major components of which were identi-
fied by GC-MS as the desired 1,6-bis(trimethylsilyl)-3-4-
bis[(trimethylsilyl)ethynyl]hex-3-ene-1,5-diyne (2) (ca.
40%), dichloro-bis(trimethylsilyl)-hexenediyne (three
isomers, ca. 23%), chloro-bis(trimethylsilyl)-hexene-
diyne (one isomer, ca. 6%), 1,6-bis(trimethylsilyl)-3-
(trimethylsilylethynyl)-hex-3-ene-1,5-diyne (5, ca. 11%)
catalyst [Pd(PPh3)4, PdCl2(PPh3)2, Pd2(dba)3ꢀ
Pd2(dba)3ꢀ
PtBu3] were varied. Analysis of the reaction
mixture obtained from the NEt3ꢀPd(PPh3)4 reaction by
/
dppf,
/
/
GC-MS indicated the relatively clean formation of 1,6-
bis(trimethylsilyl)-3-4-bis[(trimethylsilyl)ethynyl]hex-3-
ene-1,5-diyne. When these conditions were employed on
preparative scale, we were pleased to find that isolation
of the product (30%) could be achieved simply by
filtration of the reaction mixture, to remove the
precipitated trialkylammonium salts, followed by pre-
cipitation of the product in acidified MeOH and
recrystallisation (Scheme 3). The isolation of gram scale
quantities of 2 in this manner is competitive with the
four-step method detailed by Diederich which affords 2
in 25% overall yield.
and the diyne Me3SiCÅ
/
CCÅ/CSiMe3 (ca. 14%), with
yields estimated from the integrated area of each peak in
the GC trace (Scheme 3).
Extensive extraction and chromatography procedures
failed to adequately separate the partially coupled and
hydrodehalogenated compounds from 2 and so in an
attempt to identify conditions which would minimise the
production of these by-products, we re-examined the
reaction using a combinatorial array in which solvent
(NEt3, NHEt2, NHiPr2) and source of the palladium
CAUTIONARY NOTE: In the presence of trace
amount of the amine reaction solvent sufficient methox-
ide is generated during the precipitation step to desily-
Scheme 2. Synthesis of trans tetraethynylethenes. (a) R1CÅ
/
CSnBu3, PdCl2(PPh3)2 (b) DIBAL-H (c) PCC (d) CBr4, Zn, PPh3 (e) (i) LDA (ii) R2Ã
halide.
/X.
DIBAL-Hꢁdiisobutylaluminium hydride; PCCꢁpyridinium chlorochromate; Xꢁ
/
/
/

180
O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ187
/
Scheme 3. Synthesis of symmetrical tetraethynylethenes from tetrachloroethene. (a) Pd(PPh3)4, CuI, NEt3 (b) Pd(PPh3)4, CuI, NHi Pr2 (Xꢁ
isomers; XꢁH, one isomer).
/
Cl, three
/
late the highly ethynylated reaction products, which
upon concentration may spontaneously detonate. It is
therefore essential that the precipitation be carried out
in MeOH acidified by addition of several drops of HCl.
Any alkylammonium salt so produced is removed by
recrystallisation.
stark contrast to the failed Eglington-type coupling of
tetraiodoethene with copper phenylacetylide [20]. How-
ever, attempts to cross-couple more electron-rich al-
kynes, including ferrocenylacetylene, with tetrachlor-
ethylene have not yet been successful.
The palladiumꢀcopper catalysed cross-coupling of
tetrachloroethene to other terminal alkynes proceeded
smoothly under similar conditions (Scheme 3). For
/
2.2. Reactions of 2 with Co2(CO)6(L2) (Lꢁ
m-dppm)
/
CO, L2ꢁ
/
example, the Pd(0)ꢀCu(I) (5%) catalysed reaction of
/
Dicobalt carbonyls [Co2(CO)6(L2)] react readily with
alkynes to afford complexes of general type [Co2(mꢀ
h2-
alkyne)(CO)4(L2)] [34]. These compounds often crystal-
lise readily, and as such are appealing derivatives for
establishing the nature of otherwise difficult to char-
acterise acetylenes [35].
In an effort to obtain further evidence for the
products formed in diisopropylamine, we allowed the
crude product mixture to react with [Co2(CO)6(m-
dppm)] in refluxing benzene. The reaction was followed
by TLC and, when adjudged complete, the solvent was
removed and the residue purified by preparative TLC.
tetrachloroethene with excess phenylacetylene in reflux-
ing triethylamine afforded 1,6-bis(phenyl)-3,4-bis(phe-
nylethynyl)-hex-3-ene-1,5-diyne (3) in 60% yield after
chromatographic work-up. This compound has been
prepared previously by carbenoid coupling routes, albeit
in only 11% yield [20], and also by the procedure
illustrated in Scheme 1 [15]. Compound 3 was identified
by comparison of the spectroscopic data with that
previously reported. The substituted arylalkyne 4-ethy-
nylbenzonitrile also coupled smoothly under analogous
conditions to afford 4 (42%).
/
The dicobalt complexes [Co2(m,h2-Me3SiC2CÅ
(CO)4(m-dppm)] (29%), [{Co2(CO)4(m-dppm)}2-
{m,h2:m,h2-(Me3SiC2C(H)Ä
C(C2SiMe3)CÅCSiMe3}] (6,
9%) and [Co2{m,h2-Me3SiC2C(CÅ
CSiMe3)ÄC(CÅCSi-
/
CSiMe3)-
Compound 4 was exceptionally insoluble in all
common solvents. However, sufficient material could
be dissolved in hot d6-DMSO to permit a 1H-NMR
spectrum to be obtained. The expected pattern in the
/
/
/
/
/
aromatic region was observed (d 7.77, 7.93; 2ꢃ
JHH 10 Hz). The IR spectrum contained absorption
bands at 2224 [n(CN)] and 1600 [n(CÄ
C)] cmꢄ1. The
parent ion was observed in the EI mass spectrum (m/zꢁ
528).
The successful preparation of 3 and 4 by Pdꢀ
catalysed coupling reactions of tetrachloroethene is in
/
d,
Me3)2}(CO)4(m-dppm)] (7, 44%) were obtained. The
complexes were identified by the usual spectroscopic
methods and, in the case of 6 and 7, single crystal X-ray
analysis (see Section 2.3).
ꢁ
/
/
/
Identification of [Co2(m,h2-Me3SiC2CÅ
/
CSiMe3)-
/Cu
(CO)4(m-dppm)] was not difficult, and the spectroscopic
data collected was in good agreement with that pre-

O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ
/187
181
viously reported [36,37]. The IR spectrum of 6 contained
three strong n(CO) bands (2021s, 1997vs, 1970vs cmꢄ1),
as expected for a compound of the type [Co2(alkyne)-
(CO)4(m-dppm)] bearing an electron withdrawing group
the SiMe3 groups and suggested coordination of two
alkyne moieties. This supposition was confirmed by the
FAB-MS of the product which contained an isotopic
envelope at m/z 872 arising from the [Mꢄ
4CO]ꢂ ion,
/
[38]. Three resonances of equal integrated area at ꢄ
/
0.17,
and further fragment ions corresponding to the loss of a
further eight CO ligands. The compound was therefore
confirmed as a bis(dicobalt) complex. Regiochemical
information was contained in the 13C-NMR spectrum,
with the observation of five quaternary carbon reso-
nances (d 83.69, 105.10, 107.10, 113.34 and 127.83)
indicating the formation of the trans disubstituted
material [26].
0.13, 0.40 ppm in the 1H-NMR spectrum were found for
the three SiMe3 groups. The methylene groups of the
dppm ligands gave rise to a partially resolved doublet of
triplet resonance, and an unresolved multiplet from the
overlap of two protons from one CH2 moiety and the
vinyl proton. The 13C-NMR spectrum gave further
support for the proposed structure with three trimethyl-
silyl resonances at d ꢄ
/
0.18, 0.98 and 1.27 ppm. Only
The minor product (10) was obtained as a redꢀbrown
/
two acetylenic resonances could be detected at d 106.04
and 106.40 ppm, while the aromatic, methylene and
carbonyl resonances were all found in the expected
regions of the spectrum. The FAB-MS contained the
molecular ion at m/z 1545, confirming the coordination
of two alkynyl groups by Co2(CO)4(m-dppm) fragments.
The IR spectrum of the tetraethynyl derivative 7
contained three strong n(CO) bands (2023s, 1999vs,
1973s cmꢄ1) and four SiMe3 resonances in both the 1H-
and 13C-NMR spectra. Only seven of the quarternary
carbon resonances were observed, falling in the range d
crystalline material. Again, three n(CO) bands were
1
found in the IR spectrum, but the H resonances from
the SiMe3 groups were not fully resolved giving rise to
two resonances at 0.23 and 0.39 ppm in a 1:3 ratio. The
13C-NMR spectrum was better resolved and clearly
indicated the presence of four distinct SiMe3 groups,
together with resonances from all 10 quaternary carbons
(d 84.01, 97.47, 100.73, 102.97, 104.39, 104.54, 105.55,
111.67, 112.22, 134.72 ppm) . These observations,
together with the mass spectrum which contained ions
corresponding to [Mꢄ
product as the mono-substituted derivative [{Co2-
(CO)6}(m,h2-Me3SiC2C(CÅ
CSiMe3)ÄC(CÅCSiMe3)2)].
/
nCO]ꢂ (nꢁ
/
1ꢀ/6), confirmed the
98.23ꢀ
informative, with isotopic envelopes centred at m/z
999 attributed to [MꢄCOꢂ
H]ꢂ, and at m/z 970, 942,
914 from [Mꢄ 2, 3, 4).
nCO]ꢂ (nꢁ
/111.14 ppm. The FAB-MS was particularly
/
/
/
/
/
In no case did we detect complexes in which three or
four of the alkynyl moieties had been coordinated by
dicobalt moieties.
/
/
Compound 7 was also obtained as the only product
(69%) from the reaction of [Co2(CO)6(m-dppm)] with
one equivalent of a pure sample of 2. Reaction of 7 with
a further equivalent of [Co2(CO)6(m-dppm)] afforded
2.3. Molecular structures
small amounts of [{Co2(CO)4(m-dppm)}2{mꢀ
/
h2:h2-
The crystal and molecular structures of many TEE
Me3SiC2C(CÅCSiMe3)C(CÅCSiMe3)C2SiMe3}] (8), in
/
/
derivatives have been solved [8,9,19,20,26] [39ꢀ42]. The
/
which coordination of a second Co2(CO)4(m-dppm)
moiety to the least sterically hindered triple bond in 7
has occurred. Spectroscopic data from 8 were consistent
with the proposed structure, with the expected n(CO)
band pattern, and NMR resonances at d 0.22 and 0.55
assigned to the two distinguishable SiMe3 moieties. The
FAB-MS contained the molecular ion (m/z 1640), and
fragment ions derived from carbonyl losses. The struc-
ture was confirmed crystallographically (see below).
The reactions of 2 with an excess of the less sterically
demanding reagent [Co2(CO)8] were also investigated.
Two complexes were obtained in good to modest yield
and separated by preparative TLC. The major product
formed was the dark green double adduct
conjugated carbon skeleton is essentially planar as a
result of the extensive p-conjugation, and bond lengths
˚
of 1.34ꢀ
1.17ꢀ
angles around the CÄ
and in the case of 2 vary between 118.2 and 125.38 for
C(8)ÃC(3)ÃC(2,4) and as little as 116.5 for C(2)ÃC(3)Ã
/
1.37 A for the central CÄ
/
C double bond and
˚
/
1.22 A for the CÅ
/
C triple bonds are typical. The
/C carbons are rather more flexible,
/
/
/
/
C(4) [26]. The molecular structures of 6, 7 and 8 were
determined. Crystallographic details are summarised in
Table 1, with selected bond lengths and angles contained
in Tables 2 and 3, respectively.
The molecular structures of 6 (Fig. 1), 7 (Fig. 2) and 8
(Fig. 3) display a range of systematic variations which are
readily attributed to the steric properties of the coordi-
nated dicobalt fragments. The disorder in the molecular
structure of 8 was modelled in terms of a 1808 rotation of
[{Co2(CO)6}2{m,h2-Me3SiC2C(CÅ
/
CSiMe3)Ä
/
C(CÅ
/
CSi-
Me3)C2SiMe3}] (9, 67%). While the IR spectrum con-
tained three strong carbonyl bands (2088 s, 2056 vs,
2030 vs cmꢄ1) confirming coordination of at least one
alkyne moiety, more information was contained in the
1H- and 13C-NMR spectra. Two resonances of equal
the uncoordinated eneꢀ
occupancies of 75:25. The Co2(mꢀ
dppm) portion(s) of each molecule (6ꢀ
able. The CoÃCo bond lengths fall between 2.4664(4)
/
yne fragment about C2Ã
h2-alkyne)(CO)4(m-
8) are unremark-
/
C3, with
/
/
/
1
˚
intensity at d 0.25 and 0.40 in the H-NMR spectrum
were matched by 13C resonances (ꢄ
and 2.5168(14) A, with the longer bonds associated with
6 and 8. The coordinated CÃC bonds in 6 [1.363(10),
/0.39 and 1.48) for
/

182
O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ187
/
Table 1
Crystallographic details for 6, 7, 8
6
7
8
Empirical formula
Formula weight
Crystal system
Co4P4O8Si3C75H72
1731.07
Triclinic
×
/
2(CH2Cl2)×/0.5(CH3OH)
Co2P2O4Si4C51H58
1027.13
Triclinic
Co4P4O8Si4C80H80
1641.40
Monoclinic
P21/n
¯
P1/
¯
P1/
Space group
˚
/
/
a (A)
˚
16.187(1)
16.160(1)
16.986(2)
72.923(3)
89.949(4)
83.932(4)
4221.3(6)
2
12.846(1)
14.881(2)
17.221(1)
109.391(4)
95.169(3)
115.508(4)
2695.5(4)
2
11.529(2)
18.967(2)
19.026(3)
90
b (A)
˚
c (A)
a (8)
b (8)
104.118(7)
90
g (8)
3
V (A )
˚
4034.8(10)
2
0.999
Z
m (mmꢄ1
)
1.068
0.804
Crystal size
0.20ꢃ
/
0.15ꢃ
/
0.05
0.40ꢃ/0.19ꢃ/0.17
0.44ꢃ
/
0.20ꢃ0.14
/
Reflections measured
Unique reflections (Rint
Parameters refined
46 934
19 221 (0.1399)
912
22 544
13 117 (0.0190)
568
45 514
10 018 (0.0485)
478
)
R, wR (F2ꢀ
/
2s)
R, wR (all data)
0.0874, 0.2239
0.2027, 0.2902
0.0382, 0.0975
0.0502, 0.1054
0.0569,0.1195
0.0893, 0.1388
Table 2
Selected bond lengths (A) for 6, 7, 8
Table 3
Selected bond angles for 6, 7, 8
˚
6
7
8
6
7
8
Co(1)Ã
Co(3)Ã
Co(1)Ã
Co(2)Ã
Co(3)Ã
Co(4)Ã
C(1)Ã
C(2)Ã
C(3)Ã
C(4)Ã
C(3)Ã
C(6)Ã
C(7)Ã
C(8)Ã
C(9)Ã
C(1)Ã
C(5)Ã
C(6)Ã
C(10)Ã
/
Co(2)
Co(4)
P(1)
2.4845(14)
2.5168(14)
2.220(2)
2.4664(4) 2.4904(9)
2.4904(9) (C1?Ã
2.2205(6) 2.2052(10)
2.2154(6) 2.2254(11)
2.2052(10) (Co1?Ã
2.2254(11) (Co2?Ã
Si(1)Ã
C(1)ÃC(2)Ã
C(2)ÃC(3)Ã
C(3)ÃC(4)Ã
C(2)ÃC(3)Ã
C(4)ÃC(3)Ã
C(3)ÃC(8)Ã
C(3)ÃC(8)Ã
C(8)ÃC(9)Ã
/
C(1)Ã
/
C(2)
144.5(6) 146.7(2) 130.2(4)
135.9(7) 141.0(2) 139.8(5)
113.5(6) 118.9(2) 112.7(5)
173.0(8) 174.5(2) 175.6(8)
/
/
C2?)
/
/
C(3)
C(4)
C(5)
C(8)
C(8)
C(7)
C(9)
C(10)
/
/
/
/P(2)
2.217(2)
/
/
/P(3)
2.241(2)
2.207(2)
/
P1?)
P2?)
/
/
121.6(7) 124.8(2) 125.1(5) (C2Ã
124.9(6) 116.2(2) 122.2(5) (C4Ã
124.1(2) 125.1(5) (C3Ã
127.6(7) 120.2(2) 122.2(5) (C3Ã
139.4(7) 174.7(2) 139.8(5) (C3?Ã
/
C3Ã
C3Ã
C3?Ã
C3?Ã
C2?Ã
/
C3?)
C3?)
/P(4)
/
/
/
/
/
/
C(2)
C(3)
C(4)
C(5)
C(8)
C(7)
C(8)
C(9)
C(10)
Si(1)
Si(2)
Si(3)
1.363(10)
1.487(9)
1.349(3)
1.471(3)
1.448(3)
1.214(3)
1.365(3)
1.196(3)
1.447(3)
1.427(3)
1.196(3)
1.854(2)
1.844(2)
1.838(2)
1.845(2)
1.354(7)
1.475(6)
1.441(9)
1.222(11)
/
/
/
/
C2?)
C4?)
/
/
/
/
/
/
1.444(10)
1.201(11)
1.355(10)
/
/
/
/
C1?)
/
/
1.357(9) (C3Ã
1.354(7) (C1?Ã
1.475(6) (C2?Ã
1.441(9) (C3?Ã
1.222(11) (C4?Ã
1.873(6)
/
C3?)
/
/C2?)
/
/C3?)
/
1.455(9)
1.369(10)
1.846(8)
1.846(9)
/C4?)
˚
1.369(10) A] display the usual elongation relative to
/
/C5?)
/
the uncoordinated CÅ
/
C alkynyl moieties [1.20(1)ꢀ
/
/
1.837(8)
˚
1.22(1) A].
The C(3)Ã
/
1.873(6) (C1?Ã
1.837(8) (C5?Ã
/Si1?)
/
C(8) CÄ
A] are similar to those normally encountered in TEE
derivatives. The formal CÃC single bonds C(2)ÃC(3) (6,
7, 8) and C(8)ÃC(9) (6) linking the cluster coordinated
alkyne moieties to the central C(3)ÃC(8) core display a
trend towards elongation relative the C(4)ÃC(3) and
C(8)ÃC(7), which is attributed to the difference in
/
C bond lengths [1.355(10)ꢀ
/
1.365(3)
/Si(4)
1.846(7)
/Si2?)
˚
Co(1)Ã
Co(1)Ã
Co(2)Ã
Co(2)Ã
Co(3)Ã
Co(3)Ã
Co(4)Ã
Co(4)Ã
/
C(1)
C(2)
C(1)
C(2)
C(9)
C(10)
C(9)
C(10)
1.972(7)
1.972(7)
1.992(8)
1.949(7)
1.932(7)
1.991(8)
2.020(7)
1.996(7)
1.973(2)
1.993(2)
1.980(2)
1.960(2)
1.909(7)
1.914(6)
2.034(6)
2.021(6)
/
/
/
/
/
/
/
/
1.914(6) (Co1?Ã
1.909(7) (Co1?Ã
2.021(6) (Co2?Ã
2.034(6) (Co2?Ã
/
C2?)
C1?)
C2?)
C1?)
/
/
/
/
/
/
/
/
hybridisation at the cluster carbon C(2), and also C(9)
in the case of 6.
The cobalt clusters and pendant ethynyl groups are
found positioned around the olefinic core in a manner
which reduces the steric interactions between them. In
˚
1.369(10) A], 7 [1.349(3) A] and 8 [1.354(5) A] are equal
˚
˚
within the limits of precision. The CoÃC(alkyne) bonds
/
the case of the triethynyl derivative 6, the CoÃ
vectors are approximately perpendicular, with the
Si(3)Me3 group occupying a portion of the void space
/
Co
˚
˚
span the range 1.909(7)ꢀ
/
2.034(6) A, averaging 1.975 A,
C bond lengths [1.349(3)ꢀ
while the coordinated CÃ
/
/

O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ
/187
183
Fig. 1. An ORTEP plot of a molecule of 6, showing the atom labelling scheme. Hydrogen atoms have been omitted for clarity.
around C(8). The Co(3)Ã
appear to have some influence on the C(4)Ã
group, which bends away from the cluster giving slightly
abnormal C(8)ÃC(3)ÃC(4) [124.9(6)8] and C(2)ÃC(3)Ã
C(4) [113.58] bond angles.
/
Co(4) cluster moiety would
3. Conclusion
The Pd(0)ꢀ
terminal alkynes with tetrachloroethene in NEt3 affords
/
C(5) alkynyl
/
Cu(I) catalysed coupling reaction of
/
/
/
/
the corresponding tetraethynylethenes relatively cleanly
Fig. 2. A diagram showing the molecular structure of 7 and the atom labelling scheme. Hydrogen atoms have been omitted for clarity.

184
O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ187
/
Fig. 3. The molecular structure of 8, with hydrogen atoms omitted for clarity.
and in good yield. The alkyne moieties are available for
coordination by up to two dicobalt fragments, giving the
trans isomers as expected on steric grounds.
4.3. 1,6-Bis(trimethylsilyl)-3-4-
bis[(trimethylsilyl)ethynyl]hex-3-ene-1,5-diyne (2)
Dry NEt3 (100 ml) was introduced to an oven-dried
Schlenk flask and rigorously deoxygenated by three
freeze-pump-thaw sequences. Tetrachloroethylene (1.00
ml, 9.77 mmol) was added followed by trimethylsilyl-
acetylene (7.00 ml, 49.53 mmol), Pd(PPh3)4 (0.26 g, 0.23
mmol) and CuI (0.05 g, 0.26 mmol). The solution was
heated at reflux overnight forming a dark red solution
and white precipitate of the alkyl ammonium salts. The
precipitate was removed by filtration, and the filtrate
concentrated to afford a brown semi-crystalline mass
which was washed with acidified MeOH and filtered to
afford a light brown solid which was recrystallised from
hot EtOH to afford the title compound (1.16 g, 30 %).
4. Experimental
4.1. General conditions
All reactions were carried out under dry high-purity
nitrogen using standard Schlenk techniques. Solvents
were dried and distilled from conventional agents prior
to use. Preparative TLC was performed on 20ꢃ20 cm
/
glass plates coated with silica gel (Merck GF254, 0.5 mm
thick). Literature methods were used to prepare tri-
methylsilylacetylene [43], 4-ethynylbenzonitrile [44],
Pd(PPh3)4 [45], [Co2(CO)6(m-dppm)] [46]. All other
reagents were purchased and used as received.
IR (Nujol): n(CÅ
/
C) 2166 m, 2147 m; n(CÄ
cmꢄ1. H-NMR (499 MHz, CDCl3): d 0.23 (SiMe3, s).
13C-NMR (125 MHz, CDCl3): d ꢄ
0.20 (SiMe3), 100.93
(CÅC), 105.30 (CÅC), 118.78 (CÄ
C). EIꢂ-MS (m/z):
412 [M]ꢂ.
/
C) 1612 w
1
/
/
/
/
4.2. Instrumental measurements
4.4. 1,6-Bis(phenyl)-3,4-bis(phenylethynyl)-hex-3-ene-
1,5-diyne (3)
Infrared spectra were recorded using calcium fluoride
cells of 0.5 mm path length, or NaCl plates using a
Niolet Avatar FT-IR spectrometer. NMR spectra were
recorded in CDCl3 and referenced against the solvent
resonances using Varian Mercury 200 and 400, and
Varian Inova 500 spectrometers. EI-MS were obtained
on an Autospec instrument. FAB-MS were recorded at
the EPSRC National Mass Spectrometry Facility,
Swansea. Microanalyses were performed in house.
Dry NEt3 (100 ml) was introduced to an oven-dried
Schlenk flask and rigorously deoxygenated by three
freeze-pump-thaw sequences. Tetrachloroethylene (1.0
ml, 9.8 mmol) was added followed by phenylacetylene
(4.3 ml, 39 mmol), Pd(PPh3)4 (0.60 g, 0.49 mmol) and
CuI (0.09 g, 0.47 mmol). The yellow mixture was heated
at reflux turning red overnight. The mixture was filtered

O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ
/187
185
and the filtrate concentrated. The concentrated filtrate
was diluted with CH2Cl2 and purified by column
MHz, CDCl3): d ꢄ
35.82, 38.44 (2ꢃbr, 2ꢃ
2ꢃCÅC), 125.41ꢀ139.47 (m, Ph), 203.04, 204.38,
207.06, 207.61 (4ꢃs, 4ꢃCO). FAB-MS (m/z): 1545
[M]ꢂ, 1517 [MꢄCO]ꢂ, 1489 [Mꢄ2CO]ꢂ. Anal. Calc.
/
0.18, 0.98, 1.27 (3ꢃ
/
s, 3ꢃ
/
SiMe3),
/
/
CH2P2), 106.04, 106.40 (2ꢃs,
/
chromatography (silica, 1:1 CH2Cl2ꢀ
duct was contained in the bright yellow band and
recrystallised from CHCl3ꢀEtOH (60 %). IR (Nujol):
/
C6H14). The pro-
/
/
/
/
/
/
/
/
n(CÅ
/
C) 2192m cmꢄ1. 1H-NMR (200 MHz): 7.3ꢀ
7.6 (m,
/
Co4P4O8Si3C75H72 requires: C, 58.25; H, 4.66. Found:
C, 57.79; H, 4.70%.
Ph). 13C-NMR (62.9 MHz): 87.4; 98.9; 117.2; 122.6;
128.4; 129.0; 131.7. MS (EI): m/z 428 [Mꢂ]; 350 (Mꢂ
ꢄ
/
Phꢄ
/
H); 226 [Mꢂꢄ
/
2PhCÅ/C).
4.7. [Co2(CO)4(m-dppm){m,h2-Me3SiC2C(CÅ
CSiMe3)ÄC(CÅCSiMe3)2}] (7)
/
4.5. 1,6-Bis(4?-cyanophenyl)-3-4-bis[(4?-
cyanophenyl)ethynyl]hex-3-ene-1,5-diyne (4)
/
/
A round bottomed flask was charged with 2 (0.10 g,
0.24 mmol) and [Co2(CO)6(m-dppm)] (0.05 g, 0.08
mmol) which were dissolved in dry C6H6 (20 ml) and
the reaction mixture heated at reflux. Three further
portions of [Co2(CO)6(m-dppm)] were added at 15 min
intervals. After the final addition, the reaction was
allowed to react for a further 20 min before chromato-
Dry NEt3 (100 ml) was introduced to an oven-dried
Schlenk flask and rigorously deoxygenated by three
freeze-pump-thaw sequences. Tetrachloroethylene (0.25
ml, 2.44 mmol) was added followed by 4-ethynylbenzo-
nitrile (1.25 g, 9.84 mmol), Pd(PPh3)4 (0.14 g, 0.12
mmol) and CuI (0.02 g, 0.10 mmol). The solution was
heated at reflux overnight forming a dark red solution
with brown precipitate. The precipitate was collected by
filtration, and the filtrate concentrated. The precipitate
was purified by column chromatography (silica gel,
C3H6O). The product was recrystallised from hot
MeCN containing a small amount of Me2SO (0.54 g,
graphic workup by preparative TLC (20:80 CH2Cl2ꢀ
C6H14). The major band (brown) was crystallised
(CH2Cl2ꢀMeOH) to afford the title compound 7 (0.16
/
/
g, 62 %). IR (cyclohexane): n (CO) 2023 s, 1999 vs, 1973
1
s cmꢄ1. H-NMR (499 MHz, CDCl3): d 0.02 (s, 9H,
SiMe3), 0.09 (s, 9H, SiMe3), 0.26 (s, 9H, SiMe3), 0.32 (s,
42 %). IR (Nujol), n (cmꢄ1): 2224 w (CN), 1600 w (CÄ
/
9H, SiMe3), 3.53, 3.73 (2ꢃ
(m, 20H, Ph). 13C-NMR (125 MHz, CDCl3): d 0.12,
0.41, 0.78, 2.42 (4ꢃs, 4ꢃSiMe3), 36.52 (br, CH2P2),
98.23, 104.54, 105.47, 106.85, 107.16, 110.13, 111.14
(7ꢃs, 7 CÅC), 128.62ꢀ141.23 (m, Ph), 204.75, 207.09
(2ꢃs, CO). FAB-MS (m/z): 999ꢀ915 [Mꢄ
nCO]ꢂ (nꢁ
1ꢀ4). Anal. Calc. Co2P2O4Si4C51H58 requires: C, 57.83;
H, 5.52. Found: C, 57.08; H, 5.93%.
/
m, 2ꢃ
/
1H, CH2); 7.09ꢀ7.20
/
1
C). H-NMR (d6-DMSO): d 7.77, 7.93 (2ꢃ
Hz, 2ꢃ
8 H, C6H4). EIꢂ-MS (m/z): 528 [M]ꢂ. Anal.
Calc. C38H16N4×0.5Me2SO requires: C, 80.41; H, 3.26;
N, 9.62. Found: C, 80.87; H: 2.89; N, 9.96%.
/
d, JHH
ꢁ10
/
/
/
/
/
/
/
/
/
/
/
/
4.6. [{Co2(CO)4(m-dppm)}2{m,h2-(Me3SiC2C(H)Ä
C(CÅCSiMe3)2}] (6)
/
/
/
The crude product from the NHiPr2 preparation of 2
(0.10 g) and [Co2(CO)6(m-dppm)] (0.14 g, 0.23 mmol)
were dissolved in dry C6H6 (20 ml) and the mixture
stirred at reflux for 15 min after which additional
[Co2(CO)6(m-dppm)] (0.12 g, 0.19 mmol) was added
and the reaction allowed to reflux for a further 20 min.
The reaction was then cooled and the solvent removed
in vacuo. Purification of the residue by preparative TLC
4.8. [{Co2(CO)4(m-dppm)}2{mꢀ
/
h2:h2-Me3SiC2C(CÅ
/
CSiMe3)C(CÅCSiMe3)C2SiMe3}] (8)
/
A C6H6 solution (20 ml) of complex 7 (0.18 g, 0.17
mmol) and [Co2(CO)6(m-dppm)] (0.40 g, 0.6 mmol) was
heated at reflux for 3 h. The reaction mixture was
allowed to cool, and the solvent removed in vacuo to
give a residue which was purified by preparative TLC
(20:80 CH2Cl2ꢀ
green bands. These were identified as [Co2(CO)4(m-
dppm)(m,h2-Me3SiC2CÅ
CSiMe3)] (red, 29%), [Co2-
(CO)4(m-dppm)(m,h2-{Me3SiC2C(CÅ
CSiMe3)ÄC(CÅC-
SiMe3)2}] (7) (brown, 44%), and [{Co2(CO)4(m-
dppm)}2{m,h2-(Me3SiC2C(H)Ä
C(CÅCSiMe3)}] (6)
(green, 9%), respectively. All the products were crystal-
lised from CH2Cl2ꢀMeOH.
Compound 6 IR (cyclohexane): n (CO) 2021 s, 1997
vs, 1970 vs cmꢄ1 1H-NMR (499 MHz, CDCl3): d
0.17 (s, 9H, SiMe3), 0.13 (s, 9H, SiMe3), 0.40 (s, 9H,
SiMe3), 3.26 (m, 2H, CH2), 3.42 (ÄCH, br, 1H), 3.50 (m,
2H, CH2), 6.94ꢀ
7.54 (m, 20H, Ph). 13C-NMR (399
/
C6H14) afforded red, yellowꢀ/brown and
(1:1 CH2Cl2ꢀ
were crystallised (CH2Cl2ꢀ
/
C6H14). The two principal bands (brown)
MeOH) to afford 7 (upper
/
/
/
/
/
band, 10%) and the title compound 8 (lower band, 0.032
g, 11%). Compound 8 IR (cyclohexane), n (cmꢄ1): 2127
/
/
w (CÅ
1H-NMR (499 MHz, CDCl3), (d): 0.22 (SiMe3, s, 9H),
0.55 (SiMe3, s, 9H), 3.51 (CH2, m, 2H), 7.17ꢀ7.72
(aromatic, m, 20H). FAB-MS (m/z): 1640 [M]ꢂ, 1612ꢀ
1416 [Mꢄ 1ꢀ8). Anal. Calc. Co4P4O8-
nCO]ꢂ (nꢁ
/C), 2024 m (CO), 2001 s (CO), 1976 m (CO).
/
/
/
.
/
/
/
ꢄ
/
Si4C80H80 requires: C, 58.53; H, 4.88. Found: C, 58.79;
/
/
H, 5.13%.

186
O. Koentjoro et al. / Journal of Organometallic Chemistry 670 (2003) 178ꢀ187
/
4.9. Reaction of 1,6-bis(trimethylsilyl)-3-4-
bis[(trimethylsilyl)ethynyl]hex-3-ene-1,5-diyne with
[Co2(CO)8]
carbon atoms belonging to the minor component
(0.25(1) occupancy) of a modelled disorder. For the
three structures, all hydrogen atoms were geometrically
placed and allowed to ride on their parent C atom with
A sample of 2 (0.05 g, 0.12 mmol) and Co2(CO)8 (0.11
g, 0.32 mmol) were dissolved in dry C6H6 (10 ml). The
reaction was stirred for 2 h then the solvent removed in
vacuo. The product was purified by preparative TLC
Uiso (H)ꢁ
molecules and with Uiso (H)ꢁ
cases. Idealized CÃH distances were fixed at 0.95 A for
aromatic groups, 0.98 for CH3 groups, 0.99 for CH2
groups and 0.84 for the OH of a methanol. Crystal data
and further experimental and refinement details are
listed in Table 1.
/
1.5 Ueq(C) for methyl groups and solvent
/1.2 Ueq(C) for all other
˚
/
(30:70 CH2Cl2ꢀ
crystallised (CH2Cl2ꢀ
{m,h2-Me3SiC2C(CÅ
CSiMe3)Ä
(9) (0.082 g, 67%), while the minor brown band afforded
[{Co2(CO)6}(m,h2-Me3SiC2C(CÅ
CSiMe3)ÄC(CÅ
/
C6H14). The major green band was
C6H14) to afford [{Co2(CO)6}2-
C(CÅCSiMe3)C2SiMe3}]
/
/
/
/
/
/
/
CSiMe3)2)] (10) (0.011 g, 17%). Despite repeated
attempts, consistent microanalytical results were not
obtained.
6. Supplementary material
Crystallographic data (excluding structure factors) for
the structural analysis have been deposited with the
Cambridge Crystallographic Data Centre, CCDC nos.
Compound 9 IR (cyclohexane): n (CO) 2088 s, 2056
1
vs, 2030 vs cmꢄ1. H-NMR (499 MHz): d 0.25 (SiMe3,
s, 18H), 0.40 (SiMe3, s, 18H). 13C-NMR (125 MHz): d
195010ꢀ195012 for structures of 7, 6 and 8, respectively.
/
ꢄ
/
0.39, 1.48 (2ꢃ
113.34, 127.83 (5ꢃ
FAB-MS (m/z): 872 [Mꢄ
10 IR (cyclohexane): n (CO) 2089 s, 2056 vs, 2030 vs
cmꢄ1 1H-NMR (499 MHz, CDCl3): d 0.23 (s, 9H,
SiMe3), 0.39 (s, 27H, 3ꢃ
SiMe3). 13C-NMR (125 MHz,
CDCl3): d ꢄ0.62, ꢄ0.36, ꢄ0.18, 1.12 (4ꢃSiMe3),
84.01, 97.47, 100.73, 102.97, 104.39, 104.54, 105.55,
111.67, 112.22, 134.72 (10ꢃs, 10ꢃCÅC, CÄC), 200.24
(CO). FAB-MS (m/z): 670ꢀ530, [Mꢄ 1ꢀ6).
nCO]ꢂ (nꢁ
/
s, 2ꢃ
s, 5ꢃ
4CO]ꢂ.
/
SiMe3), 83.69, 105.10, 107.10,
Copies of this information may be obtained free of
charge The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1E2, UK (Fax: ꢂ44-1223-336033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
/
/
CÅC, CÄC), 200.50 (CO).
/
/
/
/
.
/
/
/
/
/
Acknowledgements
/
/
/
/
/
/
/
/
We thank the EPSRC and the University of Durham
for funding this work. OFK holds a University of
Durham Isobelle Fleck Scholarship and an Overseas
Research Award. JAKH holds an EPSRC Senior
Research Fellowship. We thank the EPSRC National
Mass Spectrometry Service (University of Cardiff) for
FAB-MS data.
5. Crystallographic details
Single crystal diffraction data for 6, 7 and 8 were
collected at 120 K, using graphite-monochromated Moꢀ
Ka radiation (lꢁ0.71073), on a Bruker SMART CCD
/
/
diffractometer equipped with a Cryostream N2 flow
cooling device [47]. Cell parameters were determined
and refined using the SMART software [48] and raw
frame data were integrated using the SAINT program
[49]. The structures were all solved by direct methods
and refined by full-matrix least-squares agains F2 of all
data, using the SHELXTL suite of programs [50]. The
reflection intensities were corrected for absorption
effects by numerical integration based on measurements
and indexing of the crystal faces using SHELXTL soft-
ware for 7 [50], and by the multi-scan method based on
multiple scans of identical and Laue equivalent reflec-
tions using SADABS for 6 and 8 [51]. All non-hydrogen
atoms for 6 were refined with anisotropic atomic
displacement parameters (adps), except those of the
disordered and/or partially occupied dichloromethane
and methanol solvent molecules which were refined with
isotropic adps. All non-hydrogen atoms for 7 were
refined with anisotropic adps. For 8, all non-hydrogen
atoms were refined with anisotropic adps, except five
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