Dimerization of titanacyclocumulenes to titanium substituted radialenes: Synthesis, stability and reactions of five-membered titanacyclocumulenes with a coupling of two 1,4-diphenyl-1,3-butadiyne between two titanocene molecules to radialene-like fused titanacyclopentadiene compounds

Article abstract of DOI:10.1016/S0022-328X(98)01114-0

The reactions of the excellent titanocene source Cp₂Ti(η²-Me₃SiC₂SiMe ₃) with different 1,4-substituted 1,3-butadiynes RC≡C-C≡CR give, by substitution of the acetylene in a one to one complexation of titanocene and the diyne, different five-membered titanacyclocumulenes Cp₂Ti[η⁴-(1-2-3-4)-RC₄R]. While these complexes are very stable for R = ^tBu, the metallacyclocumulene with R = Ph is unstable in solution and stabilizes by dimerization to dinuclear isomers: a fused titanacyclopentadiene-titanacyclopentene complex 1 and a compound 2 consisting of two fused titanacyclopentadiene ring systems and thus possessing a titanium substituted radialene structure. With the monomethyl-cyclopentadienyl complex (H₄MeC₅)₂Ti(η²-Me ₃SiC₂SiMe₃) in the reaction with PhC≡C-C≡CPh the titanium substituted radialene 7 was isolated in a low yield among some other as yet unidentified complexes. Complexes 2 and 7 were investigated by an X-ray crystal structure analysis.

Full text of DOI:10.1016/S0022-328X(98)01114-0

Journal of Organometallic Chemistry 578 (1999) 125–132
Dimerization of titanacyclocumulenes to titanium substituted
radialenes: synthesis, stability and reactions of five-membered
titanacyclocumulenes with a coupling of two
1,4-diphenyl-1,3-butadiyne between two titanocene molecules to
radialene-like fused titanacyclopentadiene compounds
Paul-Michael Pellny a, Vladimir V. Burlakov 1, Normen Peulecke a, Wolfgang Baumann a,
Anke Spannenberg a, Rhett Kempe a, Volkhard Francke b, Uwe Rosenthal a,*
a Abteilung ‘Komplexkatalyse’, Institut fu¨r Organische Katalyseforschung an der Uni6ersita¨t Rostock, Buchbinderstrasse 5-6,
D-18055 Rostock, Germany
b Uni6ersita¨t-GH Siegen, FB 8, OC II, D-57068 Siegen, Germany
Received 24 July 1998
Abstract
The reactions of the excellent titanocene source Cp2Ti(h2-Me3SiC2SiMe3) with different 1,4-substituted 1,3-butadiynes RCꢀC–
CꢀCR give, by substitution of the acetylene in a one to one complexation of titanocene and the diyne, different five-membered
titanacyclocumulenes Cp2Ti[h4-(1-2-3-4)–RC4R]. While these complexes are very stable for R=tBu, the metallacyclocumulene
with R=Ph is unstable in solution and stabilizes by dimerization to dinuclear isomers: a fused titanacyclopentadiene–titana-
cyclopentene complex 1 and a compound 2 consisting of two fused titanacyclopentadiene ring systems and thus possessing a
titanium substituted radialene structure. With the monomethyl–cyclopentadienyl complex (H4MeC5)2Ti(h2-Me3SiC2SiMe3) in the
reaction with PhCꢀC–CꢀCPh the titanium substituted radialene 7 was isolated in a low yield among some other as yet
unidentified complexes. Complexes 2 and 7 were investigated by an X-ray crystal structure analysis. © 1999 Elsevier Science S.A.
All rights reserved.
Keywords: Titanocene; Alkyne; Butadiyne; Cyclocumulene; Radialene; C–C-coupling
the coupling of polyynes R(CꢀC)nR. Since these
polyalkyne compounds are difficult to investigate, bu-
tadiynes R(CꢀC)2R as the smaller homologues were
first used as model compounds in reactions with ti-
tanocene and zirconocene [5]. In this series of investiga-
tions we could often illustrate unexpected results of
different complexations, C–C-single bond cleavage and
different types of coupling reactions (Scheme 1) [6].
The resulting products strongly depend on the sub-
stituents R, the metals and the employed stoichiometry
[6]. The bis(trimethylsilyl)acetylene titanocene and zir-
conocene complexes generate the unstable metallocenes,
‘Cp2M’ (M=Ti, Zr) [6] under mild conditions, which
1. Introduction
In modern acetylene chemistry [1] synthesis of carbon
rich compounds is an intensively researched area, which
is also directed toward organometallic polymers with
conjugated p systems [2]. Such compounds form the
basis for high-grade materials in the field of material
science [3]. For the synthesis of various carbon net-
works [4] it is interesting to understand the principles of
* Corresponding author.
1 On leave from the Institute of Organoelement Compounds of the
Russian Academy of Sciences, Moscow, Russia.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01114-0

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P.-M. Pellny et al. / Journal of Organometallic Chemistry 578 (1999) 125–132
Scheme 1.
react with tBuCꢀC–CꢀCtBu to give five-membered
metallacyclocumulenes [7,8]. The X-ray diffraction
studies of these complexes have shown the ring system
to be planar and containing three CꢁC double bonds
from which the central bond is internally coordinated
to the metal center. Later on, an alternative bonding
description, a diyne–metallocene complex without a
central double bond, was preferred [9]. In the reaction
of Ni(0) complexed 1,4-diphenyl-1,3-butadiyne with ti-
tanocene and zirconocene sources, we observed an ex-
ternal complexation of the central bond of the
five-membered cyclocumulenes resulting in hetero-
bimetallic systems [10]. We could show by detailed
investigations that the metallacyclocumulenes are the
key intermediates in the complexation leading to dinu-
clear complexes, in the C–C-single bond cleavage reac-
tion as well as in the four different types of coupling
reactions (Scheme 1) [8,10,11]. Therefore it is valuable
to study the factors which influence the stability and
reactivity of metallacyclocumulenes.
2. Results and discussion
Recently published results concerning the reaction of
Cp2Ti(h2-Me3SiC2SiMe3) [6b] with an equimolar
amount of PhCꢀC–CꢀCPh in n-hexane at room tem-
perature (r.t.) describe an air and moisture sensitive
orange–brown material of the phenylsubstituted titana-
cyclocumulene soiled with small amounts of green and
red–brown crystals (Scheme 2) [11].
After standing 3 days in toluene solution green crys-
tals of the dinuclear complex 1 (46%) together with a
small amount of a red–brown by-product 2 (18%),
both with an identical elemental composition, were
observed (Scheme 2). Complex 1 was characterized by
NMR and X-ray structural analysis [11], while the
structure of complex 2 has not been solved satisfacto-
rily and was a subject of investigation described in this
work.
The dimerization of 1,2,3-trienes to 4-radialenes is
not unusual [13]. The thermal [13] as well as the Ni(0)
catalyzed dimerization of cyclohepta-1,2,3-triene to a
tricyclic [4]radialene, whose structure was confirmed by
X-ray diffraction, was described [14]. Due to the low
temperature and the presence of titanocene we suggest
a titanium catalyzed dimerization for the formation of
2. The molecular structure of 2 [12] was also character-
ized by X-ray crystal structure analysis. The results
Herein we report about the reaction of the phenyl-
substituted five-membered titanacyclocumulene to com-
pound 2 which consists of two fused titanacyclopenta-
diene ring systems, having an unprecedented [5e,f,g]
radialene-like structure, and about attempts to prepare
analogous methylsubstituted compounds.

P.-M. Pellny et al. / Journal of Organometallic Chemistry 578 (1999) 125–132
127
Scheme 2.
ucts of protolysis are evident from the coupling con-
provide strong evidence for a dinuclear complex which
contains two fused titanacyclopentadiene ring systems.
The titanacyclopentadienes are phenylsubstituted in the
a and a% position and anellated at the b and b% carbon
atoms. However, the poor quality of the determination
made it impossible to discuss bond lengths and angles
in detail. Nevertheless, connectivity has been
established.
Due to complex 2 being completely insoluble in all
solvents which do not degrade the complex solid-state
NMR spectra were recorded. The findings are consis-
tent with the radialene description. The resonances of
the cyclopentadienyl ligands and the titanium-bound
olefinic carbon atoms appear doubled. Hence, the envi-
ronment of the metal atoms must modestly deviate
from ideal C26 symmetry. This is also found in the
analogous complex 7 (see below) with slightly different
titanium–carbon distances within the metallacyclic
subunits.
Acidolysis of complex 2 by hydrogen chloride in
dioxane does not lead to the metal-free radialene. The
organic product is the cis-3,4-dibenzylidene-1,6-
diphenyl-1-hexene-5-yne 3a, exclusively, probably
formed by a typical acidolytic reaction of the titana-
cyclopentadiene 2 to the unstable radialene and a sub-
sequent H shift with a ring opening reaction (Scheme
3). Compound 3a was characterized by GC, MS, NMR
and elemental analysis.
In the analogous reaction of complex 1 with hydro-
gen chloride in dioxane only the trans-3,4-dibenzyli-
dene-1,6-diphenyl-1-hexene-5-yne 3b was formed, also
characterized by GC, MS, NMR and elemental analysis
(Scheme 4). The different configurations of the prod-
3
stant J(H,H) across the double bonds (3a, cis: 12 Hz;
1
3b, trans: 16 Hz), as confirmed by H-NOE measure-
ments. The formation of the cis-product 3a starting
from 2 on the one hand and of the trans-compound 3b
as resulting from 1 on the other hand supports the
different structures of 2 and 1.
To study the influence of different substituents R of
the butadiynes RCꢀC–CꢀCR and of substituted Cp-lig-
ands on the possibility of obtaining stable metallacy-
clocumulenes, we conducted the experiments described
hereafter. In this series we also tried to obtain better
crystals for crystal structure analysis of a titanium
substituted radialene.
In the reaction of Cp2Ti(h2-Me3SiC2SiMe3) with
MeCꢀC–CꢀCMe we were not able to isolate or to
detect a methylsubstituted titanacyclocumulene. Only a
mixture of the dinuclear complex [Cp2Ti]2[m-h2-(1-3)-
h2-(2-4)-trans,trans-(MeC4Me)] 4 and the fused titana-
cyclopentadiene–titanacyclopentene complex 5, being
analogous to 1, were isolated. The mononuclear titana-
cyclopentadiene complex 6 was obtained as a by-
product (Scheme 5). No radialene-like compound,
analogous to 2, was found.
Employing a different stoichiometry pure complex 4
was obtained as the sole product (Scheme 6).
When using the corresponding monomethyl–cy-
clopentadienyl complex (H4MeC5)2Ti(h2-Me3SiC2Si-
Me3) [15] instead of Cp2Ti(h2-Me3SiC2SiMe3) in the
reaction with PhCꢀC–CꢀCPh the radialene 7 could be
isolated in a very low yield among some other yet
unidentified complexes (Scheme 7).
The molecular structure of 7 [16] was also character-
ized by X-ray crystal structure analysis. The results

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P.-M. Pellny et al. / Journal of Organometallic Chemistry 578 (1999) 125–132
Scheme 3.
confirm, as found for 2, a dinuclear complex which
contains two fused titanacyclopentadiene ring systems.
The titanacyclopentadienes are phenylsubstituted in the
a and a% position and anellated at the b and b% carbon
atoms (Fig. 1).
was indicated after 4 days at r.t. In the reaction of
(Me5C5)2Zr(h2-Me3SiC2SiMe3) with MeCꢀC–CꢀCMe
four yet unidentified complexes were indicated after 24
h at 60°C, next to 80% of the starting material. An
explanation for this behaviour is suggested by the sub-
stitution of silylacetylene in Cp2Zr(THF)(h2-
Me3SiC2SiMe3) for ethylene in an associative
mechanism [18] (commencing addition of ethylene and
subsequent elimination of silylacetylene). It is assumed
that the steric restrictions resulting from the bulky
permethylcyclopentadienyl ligands prevent similar reac-
tions with the diynes. Nevertheless, using a different
reaction path and starting with (Me5C5)2ZrCl2 and
magnesium in the presence of PhCꢀC–CꢀCPh the five-
membered zirconacyclocumulene (Me5C5)2Zr[h4-(1-2-3-
4)-PhC4Ph] [19] was prepared. In contrast to the
titanocene complex Cp2Ti[h4-(1-2-3-4)-PhC4Ph], which
is unstable in solution and dimerizes to complexes 1
and 2, the permethylzirconocene complex is very stable
both as a solid and in solution.
The obtained data for the central radialene unit of
complex 7 [C15–C16 1.528(4), C15–C16a 1.525(4),
˚
C1–C16 1.344(4), C8–C15 1.336(4) A, C15–C16–C15a
89.8(2), C16–C15–C16a 90.2(2), C15a–C16–C1
142.6(3), C15–C16–C1 127.6(3), C8–C15–C16
127.5(3), C8–C15–C16a 142.3(3)°] are comparable to
those in the cyclobutane ring of the [4]radialene men-
tioned above [14] (e.g. single bonds of 1.484(2) (little
˚
ring) and 1.492(2) A (large ring); double bonds
˚
1.326(2), 1.326(1) A; angles in the ring 90.01(7),
89.99(7)°, angles at the double bonds in the fused rings
132.93(9), 133.07(8)°, the others 136.90(8), 136.91(8)°).
The four-membered cyclobutane ring C15, C15a, C16,
C16a is planar and coplanar with the two fused titana-
cyclopentadiene ring systems (deviations Ti −0.0201,
C1 0.0205, C8 0.0202, C15 −0.0049, C16 −0.0056;
Tia +0.0201, C1a −0.0205, C8a −0.0202, C15a
3. Conclusion
˚
+0.0049, C16a +0.0056 A). The planes of the phenyl
groups bonded to one titanacyclopentadiene ring are
twisted to each other (19.6°) and show angles of 47.6
and 60.9° to the plane of the central four-membered
ring.
In the reactions of titanocene fragments with 1,4-di-
substituted 1,3-butadiynes RCꢀC–CꢀCR the stability
and reactivity of the obtained five-membered titanacy-
clocumulenes strongly depend on the substituents em-
ployed. With R=SiMe3 the cyclocumulene is unstable
and a C–C-bond cleavage is favored. With R=tBu the
cyclocumulene is very stable and unreactive toward e.g.
carbon dioxide, water, acetone etc. For R=Ph the
titanacyclocumulene is stable as a solid, but not in
solution. In solution it can react like a cyclocumulene,
like an alkyne complex or simultaneously as a cyclocu-
mulene and an alkyne complex [11].
The permethyltitanocene analogue (Me5C5)2Ti(h2-
Me3SiC2SiMe3) [6b] did not react with PhCꢀC–CꢀCPh
and Me3SiCꢀC–CꢀCSiMe3 in a reaction time of 5 days
at room temperature. Similarily in the reaction of the
corresponding
permethylzirconocene
complex
(Me5C5)2Zr(h2-Me3SiC2SiMe3) [17] with PhCꢀC–
CꢀCPh no substitution of the acetylene for the diyne
Three reaction pathways (i–iii) seem possible leading
to the titanium substituted radialene 2: the titanacy-
clocumulene can react like organic cyclocumulenes do,
e.g. coupling with another cyclocumulene (i) (Scheme
8).
This pathway includes the formation of a substituted
metallacyclopentane by an oxidative coupling of two
central double bonds of two different cyclocumulenes
with a metal complex as assumed also in the metal
catalyzed dimerization of cyclohepta-1,2,3-triene to the
Scheme 4.

P.-M. Pellny et al. / Journal of Organometallic Chemistry 578 (1999) 125–132
129
Scheme 5.
tricyclic [4]radialene [14]. According to this idea the
bond description for the starting metallacyclocumulenes
as a diyne-metallocene complex without a central dou-
ble bond [9] does not appear realistic.
The dimerization processes lead to carbon rich metal
complexes from which the examples of radialene-like
molecules such as 2 and 7 were unknown so far.
Alternatively, the dimerization to the radialene could
also start from two alkyne complexes (ii) (Scheme 8). A
hint of the possibility of such an intermediate is given
by the existence of a similar nickel(0) complex with two
bridging butadiynes (LNi)2(m-h2,h2-Me3SiCꢀC–CꢀCSi-
Me3)2, L=2,6-dimethylpyridine, which was isolated
and characterized by X-ray crystal structure analysis [20].
A third possibility is to start with a substituted
titanacyclopentadiene which can react with a further
titanocene moiety to yield the titanium substituted radi-
alene 2 (iii) (Scheme 8). A similar reaction path was
proposed for the reaction of Me3SiCꢀC–CH2–
CꢀCSiMe3 with zirconocene [5g]. The pathway (i) leads
to a product with the former butadiyne entity being
bonded to one titanium atom, while (ii) and (iii) result
in a bonding to two titanium atoms.
4. Experimental
4.1. General
All operations were carried out in an inert atmo-
sphere (argon) with standard Schlenk techniques. Sol-
vents
were
freshly
distilled
from
sodium
tetraethylaluminate under argon prior to use. Deuter-
ated solvents were treated with sodium or sodium te-
traethylaluminate, distilled and stored under argon. The
following spectrometers were used: NMR, Bruker ARX
400 (liquids) and Bruker MSL 300 (solids); IR, Nicolet
Magna 550 (Nujol mulls using KBr plates); MS, AMD
402. Melting points were measured in sealed capillaries
on a Bu¨chi 535 apparatus.
Further experiments using two differently substituted
butadiynes can provide an answer to the question of the
actual reaction pathway.
4.2. Synthesis of compounds
4.2.1. Preparation of 2
A sample of 0.442 g (2.18 mmol) of PhCꢀC–CꢀCPh
was dissolved in 10 ml of THF. The solution was added
to 0.746 g (2.14 mmol) of Cp2Ti(Me3SiC2SiMe3). After
5 h the solution was filtered from a green precipitate
and placed at r.t. After 14 days red–brown crystals
formed in the green solution. They were separated,
washed with THF and dried in vacuum to give 0.220 g
(27%) of complex 2, m.p. 259–261°C. Calc. for
Scheme 6.

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P.-M. Pellny et al. / Journal of Organometallic Chemistry 578 (1999) 125–132
Scheme 7.
C52H40Ti2 (760.65) C: 82.11, H: 5.30; Found C: 81.52,
H: 5.38.
1H-NMR (THF-d8): l/ppm 6.85 (d, J=12.3 Hz, 1H,
1-H), 6.48 (dd, J=12.3 and 1.8 Hz, 1H; 2-H), 7.48 (br
s, 1H; 3-CH), 7.17 (1H; 4-CH), 7.42, 7.17, 7.09 (o, m, p
1-Ph), 7.61, 7.26, 7.17 (o, m, p 3-Ph), 7.81, 7.30, 7.21 (o,
m, p 4-Ph), 7.59 (o 6-Ph), 7.39 (m, p 6-Ph). 13C-NMR
(THF-d8): l/ppm 135.0 (C1), 127.2 (C2), 138.3 (C3),
131.9 (3-CH), 122.0 (C4), 136.5 (4-CH), 88.2 (C5), 98.3
(C6), 137.7, 129.2, 128.8, 128.2 (i, o, m, p 1-Ph), 138.2,
130.2, 128.7, 127.9 (i, o, m, p 3-Ph), 137.7, 130.0, 128.7,
128.8 (i, o, m, p 4-Ph), 124.2, 132.2, 129.2, 129.2 (i, o,
m, p 6-Ph).
13C-NMR (solid state, CP/MAS technique, chemical
shifts referenced against external adamantane, l 38.4):
l/ppm 181.3 and 179.7 (C–Ti), 147.6, 144.6 (quart. C,
ipso-Ph or four-membered ring), 128.0, 126.4, 123.8
(CH Ph), 113.0 and 111.9 (Cp).
4.2.2. Acidolysis of 2
To 0.382 g (0.50 mmol) of complex 2 under argon,
7–8 ml of THF and 1 ml of a 4 M solution of HCl in
1,4-dioxane were added. The resulting suspension (com-
plex 2 is totally insoluble in THF, benzene, di-
ethylether, n-hexane) was stirred, and after 5 min the
dark precipitate of 2 dissolved and fine red crystals of
Cp2TiCl2 formed. After 30 min the solvent was evapo-
rated and the residue was extracted with 15 ml (3×5
ml) diethylether. The red precipitate was washed with
n-hexane and dried in vacuum to give 0.242 g (97%) of
Cp2TiCl2. The filtrate was evaporated to dryness in
vacuum to give 0.201 g (93%) of a light-yellow oil,
which during 1 day, transformed into a yellow solid of
cis-3a. M.p. 98–100°C (after recrystallization from n-
hexane). Calc. for C32H24 (408.54) C: 94.08, H: 5.92;
Found C: 93.84, H: 5.84.
MS (70 eV): 408 [M]+.
4.2.3. Acidolysis of 1
A total of 0.369 g (0.49 mmol) of complex 1 was
dissolved in 20 ml of THF under argon and the green
solution was filtered. To this solution 1 ml of a 4 M
solution of HCl in 1,4-dioxane was added and the
resulting mixture was stirred. The color of the solution
rapidly changed to red. After 10 min the solvent was
evaporated in vacuum and the residue was extracted
with 15 ml (3×5 ml) of diethylether. The red precipi-
tate was washed with n-hexane and dried in vacuum to
give 0.225 g (93%) of Cp2TiCl2. The filtrate was evapo-
rated by an argon stream and the resulting yellow
crystals were dried in vacuum to give 0.192 g (97%) of
light-yellow needles of trans-3b, m.p. 142–147°C (after
recrystallization from n-hexane). Calc. for C32H24
(408.54) C: 94.08, H: 5.92; Found C: 93.74, H: 5.64.
1H-NMR (THF-d8): l/ppm 7.01 (d, J=16.4 Hz, 1H,
1-H), 7.26 (d, J=16.4 Hz, 1H, 2-H), 7.02 (s, 1H,
3-CH), 7.12 (s, 1H, 4-CH), 7.46, 7.29, 7.20 (o, m, p
1-Ph), 7.46, 7.37, 7.26 (o, m, p 3-Ph), 8.06, 7.41, 7.31 (o,
m, p 4-Ph), 7.45, 7.32, 7.31 (o, m, p 6-Ph). 13C-NMR
(THF-d8): l/ppm 135.4 (C1), 125.5 (C2), 141.2 (C3),
131.5 (3-CH), 123.6 (C4), 138.4 (4-CH), 89.7 (C5), 97.8
(C6), 138.4, 127.3, 129.3, 128.4 (i, o, m, p 1-Ph),
137.6c, 130.6, 128.9, 128.0 (i, o, m, p 3-Ph), 138.3c,
129.9, 128.9, 129.1 (i, o, mc, p 4-Ph), 124.3, 132.0, 129.2,
129.1 (i, o, m, p 6-Ph);
assignment may be inter-
changed. MS (70 eV): 408 [M]+.
4.2.4. Preparation of 4
A
total
of
0.784
g
(2.25
mmol)
of
Cp2Ti(Me3SiC2SiMe3) was dissolved in 10 ml of THF
under argon, and a solution of 0.090 g (1.15 mmol) of
MeCꢀC–CꢀCMe in 5 ml of THF was added. The color
Fig. 1.

P.-M. Pellny et al. / Journal of Organometallic Chemistry 578 (1999) 125–132
131
Scheme 8.
of the mixture quickly changed from yellow to green.
After 1 day the solution was filtered, evaporated in
vacuum to 10 ml, treated with 10 ml of n-hexane and
cooled to −30°C. After 1 day green crystals formed,
the solution was decanted, the crystals were washed
with n-hexane and dried in vacuum to give 0.251 g
(56%) of complex 4; m.p. 253–254°C (dec. under ar-
gon). Calc. for C26H26Ti2 (434.25) C: 71.91, H: 6.03;
Found C: 71.44, H: 6.24.
1H-NMR (THF-d8): l/ppm 0.54 (s, 3H, 5-Me), 1.06
(s, 3H, 1-Me), 1.72 (s, 3H, 22-Me), 1.77 (s, 3H, 2-Me),
5.93, 6.28 (2 s, 10H each, Cp). 13C-NMR (THF-d8):
l/ppm 4.1 (2-Me), 20.7 (5-Me), 21.5 (1-Me), 22.5 (22-
Me), 82.0, 85.4 (CꢀC), 111.7, 115.3 (Cp), 121.4 (C2),
126.8 (C3), 172.2 (C4), 188.5 (C22), 196.0 (C5), 215.1
(C1); see Ref. [11] for the numbering scheme. MS (70
eV): 512 [M]+; IR (Nujol mull): 2188 cm−1 (wCꢀC).
1H-NMR (C6D6): l/ppm 2.43 (s, 6H, Me), 5.26 (s,
10H, Cp). 13C-NMR (C6D6): l/ppm 25.5 (Me), 105.6
(Cp), 126.9 (CꢁCMe), 218.2 (CꢁCMe). MS (70 eV): 434
[M]+, 217 [M/2]+, 178 [Cp2Ti]+.
4.2.6. Preparation of 7
A total of 0.221 g (1.09 mmol) of PhCꢀC–CꢀCPh
was dissolved in 10 ml of THF. The solution was added
to 0.376
g
(1.00 mmol) of (H4MeC5)2Ti(h2-
Me3SiC2SiMe3) [15]. After 5 h the solution was filtered
and allowed to stand at r.t. After 30 days dark–brown
crystals formed which were separated, washed with
THF and dried in vacuum to give 0.040 g (10%) of
complex 7, m.p. 230–234°C. Calc. for C56H48Ti2
(816.76) C: 82.35, H: 5.92; Found C: 81.70, H: 5.40.
1H-NMR (THF-d8): l/ppm 1.83 (s, 12H, Me), 5.61
(‘t’, 8H, H4MeC5), 6.05 (‘t’, 8H, H4MeC5), 6.60 (m, 8H,
o Ph), 6.72 (m, 12H, m, p Ph).
4.2.5. Preparation of 5
A total of 0.235 g (3.01 mmol) of MeCꢀC–CꢀCMe in
10 ml of n-hexane was added to a solution of 0.986 g
(2.83 mmol) of Cp2Ti(Me3SiC2SiMe3) in 5 ml of n-hex-
ane. The color of the mixture changed from yellow to
green and a precipitate formed. After 30 min the solu-
tion was filtered from a green solid which contained
60% of complex 4 (determined by NMR). The solution
was allowed to stand under argon at r.t. After 1 day
green crystals deposited which were washed with n-hex-
ane and dried in vacuum to give 0.217 g (30%) of
complex 5 (dec.=140°C). Calc. for C32H32Ti2 (512.37)
C: 75.02, H:6.30; Found C: 75.23, H: 6.15.
Acknowledgements
This research was supported by the Max-Planck-
Gesellschaft, the Fonds der Chemischen Industrie and

132
P.-M. Pellny et al. / Journal of Organometallic Chemistry 578 (1999) 125–132
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3
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