Studies of the nature of the catalytic species in the α-olefin polymerisation processes generated by the reaction of diamido(cyclopentadienyl) titanium complexes with aluminium reagents as cocatalysts

Article abstract of DOI:10.1002/ejic.200400661

The reaction of the diamido(chloro)cyclopentadienyltitanium compounds TiCp^Rx[1,2-C₆H₄(NR′)₂]Cl [Cp_Rx = η⁵-C₅H₅, η⁵-C₅(CH₃)₅, η⁵-C₅;H₄(SiMe₃); R′ = CH₂tBu, Pr] with the Grignard reagent MgClR (R = Me, CH ₂Ph) affords the monomethyl and monobenzyl derivatives TiCp ^Rx[1,2-C₆H₄(NR′)₂]R. Upon addition of methylaluminoxane (MAO), the chloro- and alkyltitanium complexes show low activity towards the polymerisation of ethylene and styrene. However, no methylation was observed during the treatment of trimethylaluminium with the chloro compounds TiCp^Rx[1,2-C₆H₄(NR′) ₂]Cl. Instead, these reactions give the dinuclear aluminium complexes Al₂[1,2-C₆H₄(NR′)₂]Me ₄ (R′ = CH₂tBu, Pr) through transmetallation of the diamido ligand, suggesting a deactivation process of the catalysts in the olefin polymerisation reactions. In an additional effort to model the catalytic species, stoichiometric reactions between the methyl derivatives TiCp ^Rx[1,2-C₆H₄(NR′)₂]Me and solid methylaluminoxane (MAO) were studied by NMR spectroscopy. Monitoring of these reactions revealed the formation of zwitterionic species depending on the nature of the solvent. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Full text of DOI:10.1002/ejic.200400661

FULL PAPER
Studies of the Nature of the Catalytic Species in the α-Olefin Polymerisation
Processes Generated by the Reaction of Diamido(cyclopentadienyl)titanium
Complexes with Aluminium Reagents as Cocatalysts
[a]
[a]
´
VanessaTabernero and Tomas Cuenca*
Keywords: Titanium / Diamido ligands / Olefin polymerisation / Trimethylaluminium / Methylaluminoxane
The reaction of the diamido(chloro)cyclopentadienyltitanium
compounds TiCpRx[1,2-C6H4(NRЈ)2]Cl [CpRx = η5-C5H5, η5-
C5(CH3)5, η5-C5H4(SiMe3); RЈ = CH2tBu, Pr] with the Grig-
plexes Al2[1,2-C6H4(NRЈ)2]Me4 (RЈ = CH2tBu, Pr) through
transmetallation of the diamido ligand, suggesting a deac-
tivation process of the catalysts in the olefin polymerisation
nard reagent MgClR (R = Me, CH2Ph) affords the monome- reactions. In an additional effort to model the catalytic spe-
thyl and monobenzyl derivatives TiCpRx[1,2-C6H4(NRЈ)2]R. cies, stoichiometric reactions between the methyl derivatives
Upon addition of methylaluminoxane (MAO), the chloro- and
alkyltitanium complexes show low activity towards the poly-
merisation of ethylene and styrene. However, no methylation
was observed during the treatment of trimethylaluminium
with the chloro compounds TiCpRx[1,2-C6H4(NRЈ)2]Cl. In-
TiCpRx[1,2-C6H4(NRЈ)2]Me and solid methylaluminoxane
(MAO) were studied by NMR spectroscopy. Monitoring of
these reactions revealed the formation of zwitterionic species
depending on the nature of the solvent.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
stead, these reactions give the dinuclear aluminium com- Germany, 2005)
Introduction
pounds bearing a chelate ligand such as diimino(pyrid-
ino)[16,17] (Fe and Co), imino(phenoxo)[13,18] (Ni), di-
amido[19,20] (Ti) and iminobis(phenoxo)[21Ϫ23] ligands(Zr)
are examples which have provided excellent activity for
α-olefin polymerisation and in some cases for promoting
copolymerisation of an α-olefin with polar monomers[24] as
well as living polymerisation.[25Ϫ27]
In recent years, one of the achievements in transition me-
tal organometallic chemistry has been the development of
ZieglerϪNatta catalysis for the polymerisation of ethylene
and α-olefins and the research in this field has resulted in a
good understanding of the mechanism of the olefin polym-
erisation process.[1Ϫ6] According to this, the minimum re-
quirement for a catalyst precursor has been established as
the existence of an unreactive ancillary ligand system (gen-
erally the cyclopentadienyl ligand) with at least two coordi-
nation sites which can be activated to provide a metal alkyl
bond cis to a vacant coordination site for monomer bind-
ing. Descriptions of group 4 metal complexes with these
features used as catalysts for olefin polymerisation have
been extensive.[4,7Ϫ12] However, examples of precatalysts
containing only one such group which can be active for ole-
fin polymerisation are scarce.[13Ϫ15]
As part of our investigations directed at obtaining a new
class of organometallic compounds combining cyclopen-
tadienyl and diamido ligands, we recently published the
synthesis of diamido(chloro)cyclopentadienyltitanium com-
pounds TiCpRx[1,2-C6H4(NRЈ)2]Cl [CpRx ϭ η5-C5H5, η5-
C5(CH3)5, η5-C5H4(SiMe3); RЈ ϭ CH2tBu, Pr] and as as-
sessment of their behaviour as precatalysts for α-olefin pol-
ymerisation. As a continuation of this field, we report her-
ein the synthesis of alkyl derivatives TiCpRx[1,2-
C6H4(NRЈ)2]R and their activation with solid MAO to give
active species in ethylene and styrene polymerisation reac-
tions. To identify the nature of the catalytic species in the
olefin polymerisation processes arising from the interaction
of this class of precursor of organometallic complexes (with
only one alkyl group bonded to the metal centre) with alu-
minium compounds as cocatalysts, the reactions of the
chloro compounds TiCpRx[1,2-C6H4(NRЈ)2]Cl with tri-
methylaluminium (TMA) and the methyl compounds
TiCpRx[1,2-C6H4(NRЈ)2]Me with solid methylaluminoxane
(MAO) were tested. The objective of the present work was
to gain a direct insight into the role of these species in poly-
merisation activity.
Over the past few years a growing interest in developing
organometallic compound alternatives to classical group 4
cyclopentadienyl complexes has emerged. Some of the more
significant recent developments have occurred with early
and late transition metal systems. High-performance com-
[a]
´
´
´
Departamento de Quımica Inorganica, Universidad de Alcala,
Campus Universitario,
´
28871 Alcala de Henares Spain
Fax: (internat.) ϩ 34-91-8854683
E-mail: tomas.cuenca@uah.es
338
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200400661
Eur. J. Inorg. Chem. 2005, 338Ϫ346

Studies of the Nature of the Catalytic Species in the α-Olefin Polymerisation Processes
FULL PAPER
chlorinated solvents could not be obtained since the corre-
sponding chloro compounds are formed in these solvents.
In contrast, the TiCpRx[1,2-C6H4(NCH2tBu)2]R derivatives
can be dissolved in chlorinated solutions for long periods
without transformation into the corresponding chloro com-
pounds since the neopentyl substituent affords greater steric
protection for the metal centre than the propyl substituent.
The NMR spectra of these compounds show patterns for
the proton and carbon resonances similar to those de-
scribed for the analogous chloro compounds.[28] The 1H res-
onances (C6D6, room temperature) of the cyclopentadienyl
protons appear at δ ϭ 6.01Ϫ6.15 for the Cp and δ ϭ
1.45Ϫ1.71 for the C5Me5 ligands. The C5H4(SiMe3) ring
protons give AAЈBBЈ spin systems at δ ϭ 6.13Ϫ6.53. The
methyl protons of the SiMe3 group exhibit one singlet lo-
cated at δ ϭ 0.17Ϫ0.31. The spectra for the propyl com-
pounds show sets of multiplets and triplet resonances for
the N-CH2ϪCH2ϪCH3 fragment protons, while the ex-
pected signals for the neopentyl ligand protons can be ob-
served in the spectra of the corresponding derivatives. The
phenyl protons of the diamido ligands appear as two mul-
Results and Discussion
Synthesis of Dialkyl Derivatives
The reaction of 1 equiv. of MgClR (R ϭ Me, 3 m solution
in THF; R ϭ CH2Ph, 2 m solution in THF) with a solution
of TiCpRx[1,2-C6H4(NRЈ)2]Cl [CpRx
ϭ
η5-C5H5, η5-
C5(CH3)5, η5-C5H4(SiMe3); RЈ ϭ CH2tBu, Pr] in hexane at
Ϫ78 °C proceeds with substitution of the chloro ligand by
the alkyl group affording the methyl and benzyl derivatives
TiCpRx[1,2-C6H4(NRЈ)2]R (1Ϫ12) (Scheme 1, Table 1). The
methyl (1 and 2) and the benzyl (7 and 8) compounds were
isolated, after purification, as red and dark solids respec-
tively, while the complexes 3Ϫ6 and 9Ϫ12 exist as red or
dark oils which are difficult to handle and recrystallise due
to their very high solubility in all common solvents. For
compound 8, the alkylation of the TiϪCl bond in hexane
is not totally effective due to steric hindrance at the ti-
tanium centre and a mixture of the chloro and the benzyl
compounds is obtained. However, the reaction between
Ti(η5-C5Me5)[1,2-C6H4(NCH2tBu)2]Cl and MgClBz in a
polar solvent proceeds with the formation of the pure
benzyl complex 8.
1
tiplets in the usual range. Furthermore, the H NMR spec-
tra show the expected signals assignable to the methyl and
the benzyl ligands attached to titanium. Similar structural
features to those described from 1H NMR spectroscopy can
be deduced from the 13C{1H} NMR spectra (C6D6, room
temperature). These spectroscopic data are in agreement
with Cs symmetry and are consistent with the presence of
a mirror plane containing the Ti and Cα atoms of the alkyl
groups bisecting the NϪTiϪN angle of the chelate diam-
ido ligand.
Scheme 1
In this type of complex, the diamido ligand can adopt
different coordination modes and has two possible confor-
mation modes (supine or prone) relative to the cyclopen-
tadienyl ring. A Nuclear Overhauser Enhancement (NOE)
study of the benzyl complex 7 containing the Cp ligand
enabled us to distinguish between these two possible dispo-
sitions. Irradiation of the Cp resonance resulted in a signifi-
cant NOE enhancement in the methylene signals of the neo-
pentyl group, while no NOE enhancements in the phenyl
signals were observed. These observations suggest that the
neopentyl group is located close to the Cp ring with the
diamido ligand adopting a supine conformation, in accord-
ance with the chemical shifts observed for the cyclopen-
Table 1. Amido- and titanium-alkyl groups in compounds 1Ϫ12
CpRx
RЈ
R
η5-C5H5
CH2tBu
Pr
Me
CH2Bz
Me
CH2Bz
Me
CH2Bz
Me
CH2Bz
Me
CH2Bz
Me
(1)
(7)
(4)
(10)
(2)
(8)
(5)
(11)
(3)
(9)
(6)
(12)
η5-C5Me5
CH2tBu
Pr
1
η5-C5H4(SiMe3)
CH2tBu
Pr
tadienyl ring protons in the H NMR spectrum which are
not influenced by phenylene magnetic anisotropy.[29] Simi-
lar results were obtained for the corresponding chloro de-
rivatives which is consistent with the disposition found in
the solid state using X-ray crystallography.[28]
CH2Bz
Polymerisation Reactions
Complexes 1Ϫ12 are soluble in aromatic hydrocarbons,
dichloromethane, chloroform, diethyl ether and alkanes
Given our interest in the polymerisation chemistry of
(hexane and pentane). They are air- and moisture-sensitive group 4 diamido(cyclopentadienyl)-[15,30,31] or dialkoxome-
in solution as well as in the solid state, although they can tal complexes,[32] we undertook a study of α-olefin poly-
be stored unchanged for weeks under an inert gas. The merisation processes of the alkyldiamido(cyclopentadienyl)
complexes were characterised by the usual analytical and compounds TiCpRx[1,2-C6H4(NRЈ)2]R with methylalumin-
spectroscopic methods. In some cases, the 1H NMR spectra oxane (MAO) as a cocatalyst. The reaction conditions and
of the TiCpRx[1,2-C6H4(NPr)2]R compounds in deuterated the results are summarised in Table 2 and 3. The results
Eur. J. Inorg. Chem. 2005, 338Ϫ346
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339

V. Tabernero, T. Cuenca
FULL PAPER
show the averages of two or more polymerisation runs pentadienyltitanium precatalysts,[41Ϫ46] with low molecular
which showed good reproducibility between them.
weights (as deduced from their Tm analyses).
B(C6F5)3 was also used as a cocatalyst in our polymeri-
sation experiments but, unfortunately, no catalytic activity
was observed even after using TIBA as scavenger in the
reaction mixture. In the catalyst systems obtained by com-
bining 1 or 2 with B(C6F5)3, the colour of the solutions
were different from those obtained in the reaction with solid
MAO as a cocatalyst, suggesting that different species are
formed. While 1 and solid MAO mixtures result in a green
solution, a red colour was observed using B(C6F5)3 as a
cocatalyst. These results can be attributed to the ability of
aluminium derivatives to abstract the diamido ligand pro-
viding the alkyl group requirement for polymerisation in a
ZieglerϪNatta manner, whereas this possibility is unavail-
able in the perfluoroborane compound.
Table 2. Polymerisation studies of ethylene with TiCpRx[1,2-
C6H4(NRЈ)2]R in the presence of MAO as cocatalyst
Entry
Catalyst[a]
Activity[b]
∆Hm (J gϪ1 [c]
)
Tm °C)[c]
1
2
3
4
5
6
7
1
2
3
4
7
8
10
8.0
4.3
1.6
47
3.0
7.5
51
59
45
52
55
24
45
28
130
126
122
130
133
129
135
[a] Reaction conditions: temperature ϭ 25 °C, 10 mg of precatalyst,
molar ratio Al/Ti ϭ 400, 50 mL of toluene, 5 atm of ethylene press-
[b]
[c]
ure, 15 min. g PE/mmol Ti h atm. Determined by DSC.
The low activity trend observed for the TiCpRx[1,2-
C6H4(NRЈ)2]R precatalysts in the α-olefin polymerisation
reactions might be due to a catalyst decomposition process
through ligand abstraction by MAO which may cause par-
tial or complete loss of the ligand thus resulting in one or
more inactive species for α-olefin polymerisation.[47] In an
effort to model the nature of the catalytic species generated
in these catalyst systems, the reactions of the cyclopen-
tadienyldiamido, monochloro and monoalkyltitanium de-
rivatives with trimethylaluminium (TMA) and solid methyl-
aluminoxane MAO were examined.
Table 2. Polymerisation studies of styrene with TiCpRx[1,2-
C6H4(NRЈ)2]R in the presence of MAO as a cocatalyst
Entry
Catalyst[a]
Activity[b]
Tm(°C)
1
2
3
4
5
6
7
1
2
25
35
15
18
15
10
13
252
250
260
248
256
246
257
3
4
7
8
Reactions of TiCpRx[1,2-C6H4(NRЈ)2]Cl with TMA
10
Attempts to obtain methyltitanium derivatives under the
conditions described above from the Ti(η5-C5H5)[1,2-
C6H4(NR)2]Cl starting compound using alkylating alu-
minium reagents such as TMA were unsuccessful. The
methylated products was not observed but evolution of the
starting material by ligand transfer from titanium to alu-
minium occurred.
Treatment of a red-brown solution of the monochloro
compound Ti(η5-C5H5)[1,2-C6H4(NCH2tBu)2]Cl in hexane
at Ϫ78 °C with one equivalent of TMA resulted in the im-
[a] Reaction conditions: temperature ϭ 50 °C, 10 mg of precatalyst,
molar ratio Al/Ti ϭ 400, 50 mL of toluene, 5 mL styrene, 15 min.
g PS/mmol Ti h. Determined by DSC.
[b]
[c]
When activated with MAO, low activities for ethylene
homopolymerisation were obtained with the neopentyl
compounds 1Ϫ3 and 7Ϫ8 (Entries 1Ϫ3 and 5Ϫ6), while
moderate activities with the propyl complexes 4 and 10 (En-
tries 4 and 7) were observed (Table 2). These activity values
show a pronounced dependence on the steric requirements
of the diamido ligand with the higher activity observed for
the smaller substituent on the nitrogen atom of the amido
ligand. Similar control of steric crowding at the metal centre
has been observed in bulky amidinato complexes.[33,34] The
activities exhibited for these complexes are of the same or-
der of magnitude as those described for similar diamido(cy-
clopentadienyl)titanium compounds,[35Ϫ37] although they
are smaller than those reported for noncyclopentadienyl di-
amido complexes.[17,38,39] Polymer samples show melting
point values (Tm measured by DSC) typical of high-den-
sity polyethylene.
The TiCpRx[1,2-C6H4(NRЈ)2]R precatalysts were tested
for styrene polymerisation upon activation with MAO but
poor catalytic activities were found (Table 3). The observed
activity values are markedly lower than those obtained with
the well-known CpTiCl3 used as a reference point.[40] The
PS samples obtained are in the range typical for syndiotac-
tic polymers (NMR spectroscopy), as expected for cyclo- Scheme 2
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Eur. J. Inorg. Chem. 2005, 338Ϫ346

Studies of the Nature of the Catalytic Species in the α-Olefin Polymerisation Processes
FULL PAPER
mediate formation of a yellow solution but the expected group 4[53] and more recently for group 6[54] complexes
monomethyl titanium complex 1 was not observed (moni- bearing diamido ligands. We believe that the resistance of
toring by NMR spectroscopy). Concentration of the solu- the monocyclopentadienyl diamido chloro titanium com-
tion enabled isolation of the amidoalane compound Al2[1,2- plexes to form the alkylated product in the reaction with
C6H4(NCH2tBu)2]Me4 (13) and a mixture of unidentified aluminium reagents and the ligand transfer processes are
and intractable titanium species. Similarly, when the reac- associated with the low activity of the chloro complexes
tion was carried out in a Ti:Al molar ratio of 1:100, forma- TiCpRx[1,2-C6H4(NRЈ)2]Cl for ethylene and styrene poly-
tion of the amidoalane was observed along with a more merisations. These results provide an insight into the nature
complicated final mixture of products. In an analogous re- of the catalytic species generated during the olefin poly-
action, treatment of Ti(η5-C5H5)[1,2-C6H4(NPr)2]Cl with merisation processes through interaction of the precatalyst
TMA (in a Ti:Al molar ratio 1:1 and 1:100) afforded the based on titanium complexes with the aluminium reagents
amidoalane compound Al2[1,2-C6H4(NnPr)2]Me4 (14) as cocatalysts.
(Scheme 2).
Reaction between Ti(η5-C5H5)[1,2-C6H4(NCH2tBu)2]Me
(1) and Solid MAO
These aluminium compounds can be synthesised as pure
substances through
a direct route by treating 1,2-
C6H4(NHRЈ)2 (RЈ ϭ CH2tBu, Pr) with 2 equiv. of TMA in
In order to obtain a better understanding of the nature
toluene with partial precipitation of the aluminium com- of the active species and the chemical behaviour of the
pounds occurring in 1 h (Scheme 2). Reactions between TiCpRx[1,2-C6H4(NRЈ)2]R precatalyst systems in the ethyl-
amines and aluminium compounds are well known[48Ϫ50] ene and styrene polymerisation processes, the reaction of 1
and in the first step, an adduct of the type NϪAl is prob- with solid MAO was carried out using a stoichiometric 1:1
ably formed which then eliminates methane generating the Ti/Al ratio and studied by 1H NMR spectroscopy. Solid
amidoaluminium compound.
MAO was selected to avoid the inexorable presence of free
Compound 13 was characterised by elemental analysis, TMA in commercial MAO[55] since this compound causes
while the elemental analysis values found for 14 were inac- transmetallation which could be a crucial factor in the evol-
curate due to the presence of small amounts of impurities ution of the reaction.
1
which could not be removed although both aluminium
The H NMR spectrum recorded immediately after mix-
compounds were also characterised by spectroscopic meth- ing the reagents in CD2Cl2 at room temperature shows a
ods. The 1H NMR spectra (C6D6, room temperature) show broadening of Ti-Me resonance accompanied by a down-
1
two different types of methyl groups with each signal corre- field shift with respect to the initial situation.[56] In the H
sponding to six protons (see Exp. Sect.). The proposed NMR spectrum of 1, the methyl group protons appear at
structural dispositions (Figure 1) are similar to those de- δ ϭ Ϫ1.5. After the reaction with MAO, this resonance
scribed for analogous compounds[18,51,52] in which two ‘‘Al- overlaps with the corresponding MAO signals. These fea-
Me2’’ moieties are symmetrically chelated by a diamido li- tures are in accordance with the interaction of the methyl
gand. They exhibit two aluminium centres with tetrahedral group of compound 1 with the aluminium atoms present in
geometry and two nitrogen atoms forming a four membered the MAO which act as Lewis acidic sites[57Ϫ61] (Structure A
butterfly shaped metallacycle. Methyl groups are positioned in Scheme 3) or, alternatively, with abstraction of this
in two different chemical environments with two being lo- methyl group to generate an anionic aluminium centre
cated towards the phenyl group and the other being orien- which interacts with the cationic titanium atom through
tated in the opposite direction.
methyl group bridging (Structure B in Scheme 3). The
broadness could be due to the closer position of the methyl
group, initially bound to titanium, to the ‘‘diversification’’
centres provided by different Lewis acidic sites present in
MAO.[62,63] The broadening of Ti-Me resonances of an ad-
duct with MAO has also been reported by Talsi et al.[59,64]
When the polarity of the solvent is high, as in this case,
methyl group abstraction by MAO is favoured and solvent-
separated ion pairs are preferentially formed.[65Ϫ67] After
allowing the sample to stand for one day in solution, the 1H
NMR spectrum shows clear formation of the chlorinated
compound Ti(η5-C5H5)[1,2-C6H4(NCH2tBu)2]Cl which
indicates chloro abstraction from the solvent.
Figure 1. Proposed structural disposition for compounds 13 and 14
When the same reaction is carried out in a less polar
solvent such as C6D6, the process proceeds in a different
Such reactions starting from monocyclopentadienyl di- way. Initially, after mixing the reagents at room temperature
1
amido titanium compounds forming aluminium derivatives for 5 min, the H NMR spectrum features are consistent
therefore indicate that transmetallation reactions offer a with the formation of the zwitterionic species in which the
facile reaction pathway in early transition metal complexes. methyl ligand acts as a bridging group between the titanium
Similar transmetallation reactions have been proposed for and aluminium centres (Structure A in Scheme 3 favoured).
Eur. J. Inorg. Chem. 2005, 338Ϫ346
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341

V. Tabernero, T. Cuenca
FULL PAPER
C6H4(NRЈ)2]R compounds from the reaction of the corre-
sponding chloro derivatives with Grignard reagents has
been described. After activation with methylaluminoxane,
the diamido complexes exhibit low activity towards α-olefin
polymerisation. While the chloro derivatives TiCpRx[1,2-
C6H4(NRЈ)2]Cl can be easily methylated by reaction with
MgClMe, reaction with trimethylaluminium results in the
transmetallation of the diamido ligand to produce dinuclear
aluminium compounds. This behaviour must be associated
with the low activity of the chloro and alkyl derivatives in
the ethylene and styrene polymerisations. The reactivity of
the alkyl complexes TiCpRx[1,2-C6H4(NRЈ)2]R with MAO
has also been studied by NMR spectroscopy. This indicated
the formation of intermediate species which can be con-
sidered to exert an important effect on the catalytic activity
of these precatalysts in the α-olefin polymerisation process.
Experimental Section
General Considerations: All manipulations of air- and moisture-
sensitive materials were performed under argon using Schlenk and
high-vacuum line techniques or in a glove box model MO40-2. Sol-
˚
vents were predried with activated molecular sieves (4 A) and were
then purified by distillation under argon before use by employing
the appropriate drying/deoxygenating agent. Deuterated solvents
were degassed by several freeze-thaw cycles and stored in ampoules
equipped with Young’s Teflon valves over activated molecular si-
Scheme 3
˚
eves (4 A). C, H and N microanalyses were performed with a
PerkinϪElmer 2400 microanalyser. NMR spectra, measured at 25
°C, were recorded with a Varian Unity FT-300 (1H NMR at
300 MHz, 13C NMR at 75 MHz) spectrometer and chemical shifts
were referenced to SiMe4 via the 13C resonances and the residual
protons (1H) of the deuterated solvent. MAO was purchased from
Witco as a toluene solution (10% wt). Reagent grade styrene (Ald-
rich) was distilled under reduced pressure from calcium hydride
and stored in a refrigerator under argon. The polymerisation sol-
vent was dried by heating to reflux in the presence of sodium/
benzophenone under argon. MgClMe (3 m solution in THF) and
MgClBz (2 m solution in THF) were purchased from Aldrich and
used as received. The chlorinated compounds TiCpRx[1,2-
C6H4(NRЈ)2]Cl [CpRx ϭ η5-C5H5, η5-C5(CH3)5, η5-C5H4(SiMe3);
RЈ ϭ CH2tBu, Pr] and the N,NЈ-dialkyl-1,2-phenylenediamines 1,2-
C6H4(NHRЈ)2 (RЈ ϭ CH2tBu, Pr) were prepared as described in
previous work.[28]
It is believed that the formation of separated ions, in this
case, is not favoured because there is no stabilisation con-
ferred by solvent coordination. After 1 d in solution, no
significant changes in the 1H NMR spectrum were ob-
served.
When the solution in C6D6 was saturated[68Ϫ70] with eth-
ylene, polyethylene was not formed. However, the addition
of a polar monomer such as methyl methacrylate (MMA)
to the C6D6 solution caused the displacement of the MAO
initially attached to the titanium centre. The 1H NMR spec-
trum shows signals indicating the presence of the methyl-
ated compound 1 (Scheme 3) and a complicated set of res-
onances assignable to products exhibiting interactions be-
tween MMA and MAO.
Treatment of compound 1 with an excess of solid MAO
was rather difficult to study by NMR spectroscopy because
the signals of the products overlap with the MAO reson-
ances. We suggest the excess aluminium centres provided
by such a large amount of solid MAO, used generally for
polymerisation runs, could cause the deactivation of the
TiCpRx[1,2-C6H4(NRЈ)2]R catalysts by transmetallation re-
actions of the diamido groups in a similar way to obser-
vations made in the reaction of TiCpRx[1,2-C6H4(NRЈ)2]Cl
with TMA.
Preparation of MAO Samples: To obtain MAO with a reduced
amount of TMA, a sample of commercial MAO was distilled under
vacuum at 20 °C. The white powder obtained (polymeric MAO
with residual TMA ca. 3 wt-%) was stored in dry box before use in
the preparation of the samples. Calculated quantities of the desired
compound and solid MAO were taken into the dry box to prepare
the samples with the desired Ti/Al ratio. Solids were mixed and the
selected solvent was added directly to the NMR tube equipped with
a Young’s Teflon valve. All operations were carried out at room
temperature.
Polymerisation Procedure: For ethylene polymerisation, the typical
procedure was as follows. Toluene (50 mL), solid MAO (Al/Ti ϭ
400) and the desired precatalyst (10 mg) in a sealed glass vial were
placed in a high-pressure glass reaction vessel (Büchi). Sub-
Conclusion
The synthesis and characterisation of new monocyclo-
pentadienyl
diamido
alkyl
titanium
TiCpRx[1,2- sequently, the polymerisation temperature was adjusted and the
342
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 338Ϫ346

Studies of the Nature of the Catalytic Species in the α-Olefin Polymerisation Processes
FULL PAPER
mixture was pressurized to 5 atm for 1 h before cracking the vial.
After 15 min of venting of the ethylene gas and quenching with
HCl/CH3OH (10 mL), the reaction was stopped. The solution was
then poured into a large excess of this solvent mixture and the
resultant polyethylene was separated by filtration, washed several
times (HCl/CH3OH) and dried under vacuum overnight. Polym-
erisation of styrene was performed under argon in toluene at 50
°C using solid MAO as the cocatalyst according to the following
procedure. Toluene (30 mL), styrene (5 mL) and MAO were in-
jected into the Schlenk flasks with magnetic stirring at the desired
temperature. The titanium compound was dissolved in toluene (5
mL) and added to the mixture. In a manner similar to the poly-
ethylenes, the polystyrenes were coagulated with a large excess of
acidified methanol and isolated by filtration.
Ti[η5-C5H4(SiMe3)][1,2-C6H4(NCH2tBu)2](CH3) (3): Compound 3
was prepared by treating Ti[η5-C5H4(SiMe3)][1,2-C6H4(NCH2-
tBu)2]Cl (0.22 g, 0.47 mmol) with a 3 m solution of MeMgCl in
THF (0.16 mL) according to the procedure described for 1 and was
obtained as a red-brown oil (0.11 g, 2.46 mmol, 52%). The isolated
oil consisted mainly of 3 and some LiCl as an impurity which could
not be removed. The correct elemental analytical data could not be
obtained, although satisfactory spectroscopic data were obtained.
1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 7.31 (s, 4 H, Ph), 6.53,
6.28 (AAЈBBЈ spin system, 2 H, 2 H, C5H4), 4.00 (d, J ϭ 12.0 Hz,
2 H, CH2), 3.95 (d, J ϭ 12.0 Hz, 2 H, CH2), 0.75 (s, 18 H, tBu),
0.28 (s, 9 H, SiMe3), Ϫ0.91 (s, 3 H, CH3) ppm. 1H NMR (300 MH,
CDCl3, 25 °C): δ ϭ 7.33 (m, 4 H, Ph), 6.46, 6.31 (AAЈBBЈ spin
system, 2 H, 2 H, C5H4), 4.00 (s, 4 H, CH2), 0.73 (s, 18 H, tBu),
0.19 (s, 9 H, SiMe3), Ϫ1.49 (s, 3 H, CH3) ppm. 13C{1H} NMR
(75 MHz, C6D6, 25 °C): δ ϭ 125.5 (ipso-Ph), 126.2, 119.1 (Ph),
115.2 (ipso-C5H4), 120.1, 114.9 (C5H4), 66.1 (CH2), 35.8 (ipso-tBu),
33.2 (TiϪCH3), 28.9 (tBu), 0.29 (SiMe3) ppm.
Characterisation of Polymers: The thermal properties of the
samples were studied using a PerkinϪElmer DSC 6 instrument
calibrated by measuring the melting point of indium. Thus,
5Ϫ10 mg each of the dried polymers were fused into standard alu-
minium pans and measured using the following temperature pro-
gramme for polyethylene samples: first a heating phase (10 °C/min)
from 50 to 200 °C, followed by a cooling phase (Ϫ10 °C/min) to
50 °C. The peak maximum of the second heating curve was indi-
cated as the melting point (Tm). ∆Hm derived from the data of the
second heating course of the DSC was selected. Polystyrene
samples were subjected to the following steps: heating at 10 °C/min
from 30 to 270 °C and then cooling at 10 °C/min from this tem-
perature to 30 °C and finally heating at 10 °C/min from 30 to 270
°C to obtain the melting peak temperature (Tm). The NMR-PS
samples were prepared by dissolving the polymer in tetrachloro-
1,2-dideuterioethane. The spectra were recorded at 25 °C.
Ti(η5-C5H5)[1,2-C6H4(NCH2CH2CH3)2](CH3) (4): A 3 m solution
of MeMgCl in THF (0.53 mL) was added to a stirred solution of
Ti(η5-C5H5)[1,2-C6H4(NCH2CH2CH3)2]Cl (0.54 g, 1.59 mmol) in
hexane (50 mL) at Ϫ78 °C. The cooling bath was removed and the
reaction mixture was slowly warmed to room temperature and
stirred for 12 h. The residue was filtered and the solution concen-
trated and cooled. Compound 4 was obtained as a dark oil (0.37 g,
1.16 mmol, 73%). C18H26N2Ti (318.30): calcd. C 67.92, H 8.23, N
8.80; found C 68.30; H 8.15; N 9.01. 1H NMR (300 MHz, C6D6,
25 °C): δ ϭ 7.33 (m, 2 H, Ph), 7.00 (m, 2 H, Ph), 6.11 (s, 5 H,
C5H5), 3.67 (m, 4 H, CH2), 1.35 (m, 4 H, CH2), 0.65 (t, J ϭ 7.5 Hz,
6 H, CH3), Ϫ0.25 (s, 3 H, CH3) ppm. 13C{1H} NMR (75 MHz,
C6D6, 25 °C): δ ϭ 125.0, 115.1 (Ph), 129.7 (ipso-Ph), 113.1 (C5H5),
57.5 (NϪCH2), 35.9 (TiϪCH3), 24.9 (CH2), 12.1 (CH3) ppm.
Ti(η5-C5H5)[1,2-C6H4(NCH2tBu)2](CH3) (1): A 3 m solution of
MeMgCl in THF (0.42 mL, 0.93 mmol) was added to a solution
of Ti(η5-C5H5)[1,2-C6H4(NCH2tBu)2]Cl (0.50 g, 1.27 mmol) in
hexane (50 mL) at Ϫ78 °C. The cooling bath was removed and the
reaction mixture was warmed to room temperature after stirring
for 12 h. The resultant residue was filtered and the solution cooled
to Ϫ40 °C to afford 1 as a red solid (0.35 g, 74%). C22H34N2Ti
(374.40): calcd. C 70.58, H 9.15, N 7.48; found C 70.50, H 9.29, N
7.51. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 7.33 (s, 4 H, Ph),
6.15 (s, 5 H, C5H5), 3.89 (d, J ϭ 12.6 Hz, 2 H, CH2), 3.83 (d, J ϭ
12.6 Hz, 2 H, CH2), 0.71 (s, 18 H, tBu), Ϫ0.90 (s, 3 H, CH3) ppm.
1H NMR (300 MHz, CDCl3, 25 °C): δ ϭ 7.36 (m, 4 H, Ph), 6.28
(s, 5 H, C5H5), 4.01(s, 4 H, CH2), 0.73 (s, 18 H, tBu), Ϫ1.46 (s, 3
H, CH3) ppm. 13C{1H} NMR (75 MHz, C6D6, 25 °C): δ ϭ 126.1,
118.9 (Ph), 124.8 (ipso-Ph), 113.1 (C5H5), 65.6 (CH2), 33.3 (Ti-
CH3), 35.7 (ipso-tBu), 28.6 (tBu) ppm.
Ti(η5-C5Me5)[1,2-C6H4(NCH2CH2CH3)2](CH3) (5): A 3 m solution
of MeMgCl in THF (0.17 mL) was added to a solution of Ti(η5-
C5Me5)[1,2-C6H4(NCH2CH2CH3)2]Cl (0.21 g, 0.51 mmol) in hex-
ane (50 mL) at Ϫ78 °C. The cooling bath was removed and the
reaction mixture was slowly warmed to room temperature and
stirred for 12 h. After filtration, the resultant solution was concen-
trated and cooled to Ϫ20 °C. Complex 5 was obtained as a black
oil (0.12 g, 0.31 mmol, 60%). C23H36N2Ti (388.43): calcd. C 71.12,
H 9.34, N 7.21; found C 70.83, H 9.15, N 7.01. 1H NMR
(300 MHz, C6D6, 25 °C): δ ϭ 7.28 (m, 2 H, Ph), 6.89 (m, 2 H, Ph),
3.64 (m, 2 H, NϪCH2), 3.47 (m, 2 H, NϪCH2), 1.68 (s, 15 H,
C5Me5), 1.60 (m, 4 H, CH2), 0.80 (t, J ϭ 7.5 Hz, 6 H, CH3), 0.82
(s, 3 H, CH3) ppm. 13C{1H} NMR (75 MHz, C6D6, 25 °C): δ ϭ
130.0 (ipso-Ph), 123.0, 113.4 (Ph), 119.5 (ipso-C5Me5), 53.3
(NϪCH2), 48.1 (TiϪCH3), 23.4 (CH2), 12.4 (CH3), 10.7 (C5Me5)
ppm.
Ti(η5-C5Me5)[1,2-C6H4(NCH2tBu)2](CH3) (2): Compound 2 was
prepared by treating Ti(η5-C5Me5)[1,2-C6H4(NCH2tBu)2]Cl Ti[η5-C5H4(SiMe3)][1,2-C6H4(NCH2CH2CH3)2](CH3) (6): Com-
(1.86 g, 4.00 mmol) in hexane with a 3 m solution of MeMgCl in
THF (1.33 mL) according to the procedure described for 1 and
was obtained as a dark solid (1.40 g, 3.15 mmol, 78%). C27H44N2Ti
(444.54): calcd. C 72.95, H 9.98, N 6.30; found C 72.98, H 9.87, N
pound 6
was prepared by treating Ti[η5-C5H4(SiMe3)][1,2-
C6H4(NCH2CH2CH3)2]Cl (0.17 g, 0.41 mmol) with a 3 m solution
of MeMgCl in THF (0.14 mL, 0.41 mmol) according to the pro-
cedure described for 4 and was obtained as a dark oil (0.11 g,
6.15. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 7.22 (m, 4 H, Ph), 0.28 mmol, 68%). C21H34N2SiTi (390.48): calcd. C 64.60, H 8.78,
3.86 (d, J ϭ 13.2 Hz, 2 H, CH2), 3.67 (d, J ϭ 13.2 Hz, 2 H, CH2), N 7.17; found C 65.06, H 8.92, N 7.12. 1H NMR (300 MHz, C6D6,
1.56 (s, 15 H, C5Me5), 0.96 (s, 3 H, CH3), 0.91 (s, 18 H, tBu) ppm.
25 °C): δ ϭ 7.32 (m, 2 H, Ph), 6.99 (m, 2 H, Ph), 6.40, 6.29
1H NMR (300 MHz, CDCl3, 25 °C): δ ϭ 7.24 (m, 2 H, Ph), 7.18 (AAЈBBЈ spin system, 2 H, 2 H, C5H4), 3.78 (m, 4 H, CH2), 1.36
(m, 2 H, Ph), 3.87 (d, J ϭ 13.2 Hz, 2 H, CH2), 3.59 (d, J ϭ 13.2 Hz, (m, 4 H, CH2), 0.67 (t, J ϭ 7.5 Hz, 6 H, CH3), 0.22 (s, 9 H, SiMe3),
2 H, CH2), 1.58 (s, 15 H, C5Me5), 0.78 (s, 18 H, tBu), 0.57 (s, 3 H,
Ϫ0.23 (s, 3 H, CH3) ppm. 1H NMR (300 MHz, CDCl3, 25 °C):
δ ϭ 7.22 (m, 2 H, Ph), 6.94 (m, 2 H, Ph), 6.47, 6.45 (AAЈBBЈ spin
CH3) ppm. 13C{1H} NMR (75 MHz, C6D6, 25 °C): δ ϭ 124.6 (ipso-
Ph), 123.3, 116.6 (Ph), 117.9 (ipso-C5Me5), 61.2 (CH2), 50.5 system, 2 H, 2 H, C5H4), 3.86 (m, 4 H, CH2), 1.46 (m, 4 H, CH2),
(TiϪCH3), 36.9 (ipso-tBu), 29.5 (tBu), 10.5 (C5Me5) ppm. 0.79 (t, J ϭ 7.5 Hz, 6 H, CH3), 0.19 (s, 9 H, SiMe3), Ϫ0.69 (s, 3
Eur. J. Inorg. Chem. 2005, 338Ϫ346
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
343

V. Tabernero, T. Cuenca
FULL PAPER
H, CH3) ppm. 13C{1H} NMR (75 MHz, C6D6, 25 °C): δ ϭ 125.8 Ti(η5-C5H5)[1,2-C6H4(NCH2CH2CH3)2](CH2Ph) (10): A 2 m solu-
(ipso-C5H4), 125.0, 115.2 (Ph), 120.3, 115.5 (C5H4), 58.4 (NϪCH2), tion of BzMgCl in THF (1.27 mL) was added dropwise to a stirred
35.0 (Ti-CH3), 23.7 (CH2), 12.0 (CH3), 0.60 (SiMe3) ppm, the sig-
nal for ipso-Ph is not observed.
solution of Ti(η5-C5H5)[1,2-C6H4(NCH2CH2CH3)2]Cl (0.85 g,
2.51 mmol) in hexane (50 mL) at Ϫ78 °C. After the addition was
complete, the reaction mixture was warmed to room temperature
and stirred for 12 h. The white precipitate formed was filtered and
the resultant solution cooled to Ϫ40 °C. A dark oil was collected
after filtration and was characterised as 10 (0.69 g, 1.75 mmol,
70%). Due to its high solubility in all common solvents 10 could
Ti(η5-C5H5)[1,2-C6H4(NCH2tBu)2](CH2Ph) (7): A 2 m solution of
BzMgCl in THF (0.63 mL, 1.27 mmol) was added dropwise to a
stirred solution of Ti(η5-C5H5)[1,2-C6H4(NCH2tBu)2]Cl (0.50 g,
1.27 mmol) in hexane (50 mL) at Ϫ78 °C. After the addition was
complete, the reaction mixture was warmed to room temperature
and stirred for 12 h. The white precipitate formed was filtered and
the resultant solution cooled to Ϫ40 °C. A red-brown solid was
collected after filtration which was characterised as 7 (0.30 g,
0.66 mmol, 53%). C28H38N2Ti (450.50): calcd. C 74.65, H 8.50, N
6.22; found C 74.30, H 8.40, N 6.10. 1H NMR (300 MHz, C6D6,
25 °C): δ ϭ 7.35 (s, 4 H, Ph), 7.17, 6.86, 6.57 (t, t, d, 5 H, CH2Ph),
6.01 (s, 5 H, C5H5), 3.89 (d, J ϭ 13.8 Hz, 2 H, CH2), 3.81 (d, J ϭ
13.5 Hz, 2 H, CH2), 0.89 (s, 2 H, CH2Ph), 0.68 (s, 18 H, tBu) ppm.
1
not be recrystallised and an accurate analysis was not possible. H
NMR (300 MHz, C6D6, 25 °C): δ ϭ 7.36 (m, 2 H, Ph), 6.97 (m, 2
H, Ph), 7.12, 6.84, 6.63 (t, t, d, 5 H, CH2Ph), 6.01 (s, 5 H, C5H5),
3.57 (m, 4 H, CH2), 1.63 (s, 2 H, CH2Ph), 1.27 (m, 4 H, CH2), 0.59
(t, J ϭ 7.3 Hz, 6 H, CH3) ppm. 13C{1H} NMR (75 MHz, C6D6,
25 °C): δ ϭ 149.2 (ipso-CH2Ph), 126.2 (ipso-Ph), 125.4, 114.5 (Ph),
125Ϫ128 (CH2Ph), 115.5 (C5H5), 62.9 (CH2Ph), 57.2 (NϪCH2),
23.9 (CH2), 11.8 (CH3).
1H NMR (300 MHz, CDCl3, 25 °C): δ ϭ 7.50 (m, 2 H, Ph), 7.40 Ti(η5-C5Me5)[1,2-C6H4(NCH2CH2CH3)2](CH2Ph) (11): Com-
(m, 2 H, Ph), 6.97, 6.60, 6.32 (t, t, d, 5 H, CH2Ph), 6.07 (s, 5 H, pound 11 was prepared by treating Ti(η5-C5Me5)[1,2-
C5H5), 4.05 (d, J ϭ 13.8 Hz, 2 H, CH2), 3.97 (d, J ϭ 13.5 Hz, 2 C6H4(NCH2CH2CH3)2]Cl (0.80 g, 1.96 mmol) with a 2 m solution
H, CH2), 0.74 (s, 18 H, tBu), 0.44 (s, 2 H, CH2Ph) ppm. 13C{1H}
NMR (75 MH, C6D6, 25 °C): δ ϭ 150.0 (ipso-CH2Ph), 126.4, 118.9
of BzMgCl in THF (0.98 mL) according to the procedure described
for 10 and was obtained as a black oil (0.70 g, 1.51 mmol, 77%).
(Ph), 128.1, 127.8, 120.8 (CH2Ph), 124.9 (ipso-Ph), 114.8 (C5H5), C29H40N2Ti (464.53): calcd. C 74.98, H 8.68, N 6.03; found C
65.8 (CH2), 61.52 (CH2Ph). 35.8 (ipso-tBu), 29.1 (tBu) ppm.
74.02, H 8.32, N 5.98. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 7.18
(m, 2 H, Ph), 6.69 (m, 2 H, Ph), 6.80Ϫ7.11 (m, 5 H, CH2Ph), 3.50
(t, J ϭ 8.4 Hz, 4 H, CH2), 2.25 (s, 2 H, CH2Ph), 1.71 (s, 15 H,
C5Me5), 1.49 (broad, 4 H, CH2), 0.75 (t, J ϭ 7.5 Hz, 6 H, CH3)
ppm. 13C{1H} NMR (75 MHz, C6D6, 25 °C): δ ϭ 150.9 (ipso-
CH2Ph), 126Ϫ128 (CH2Ph), 123.0, 113.3 (Ph), 121.0 (ipso-Ph),
120.6 (ipso-C5Me5), 73.1 (CH2Ph), 53.8 (N-CH2), 22.5 (CH2), 12.0
(CH3), 11.0 (C5Me5) ppm.
Ti(η5-C5Me5)[1,2-C6H4(NCH2tBu)2](CH2Ph) (8): Compound
8
was prepared by treating Ti(η5-C5Me5)[1,2-C6H4(NCH2tBu)2]Cl
(0.50 g, 1.07 mmol) in toluene (50 mL) at Ϫ78 °C with a 2 m solu-
tion of BzMgCl in THF (0.54 mL) according to the procedure de-
scribed for 7. Recrystallisation of the final product with pentane
afforded
C33H48N2Ti (520.64): calcd. C 76.13, H 9.29, N 5.38; found C
76.43, H 9.37, N 5.61. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 7.23 Ti[η5-C5H4(SiMe3)][1,2-C6H4(NCH2CH2CH3)2](CH2Ph)
8 as a dark-red solid (0.40 g, 0.77 mmol, 72%).
(12):
Compound 12 was prepared by treating Ti[η5-C5H4(SiMe3)][1,2-
C6H4(NCH2CH2CH3)2]Cl (0.34 g, 0.83 mmol) with a 2 m solution
(s, 4 H, Ph), 7.22, 7.12, 6.95 (t, t, d, 5 H, CH2Ph), 4.05 (d, J ϭ
13.5 Hz, 2 H, CH2), 3.97 (d, J ϭ 13.5 Hz, 2 H, CH2), 2.67 (s, 2 H,
1
CH2Ph), 1.45 (s, 15 H, C5Me5), 0.95 (s, 18 H, tBu) ppm. H NMR of BzMgCl in THF (0.41 mL) according to the procedure described
(300 MHz, CDCl3, 25 °C): δ ϭ 7.33 (m, 2 H, Ph), 7.21 (m, 2 H,
Ph), 7.18, 6.95, 6.89 (t, t, d, 5 H, CH2Ph), 3.92 (d, J ϭ 13.5 Hz, 2
for 10 and was obtained as a black oil (0.25 g, 0.53 mmol, 64%).
C27H38N2SiTi (466.58): calcd. C 69.51, H 8.21, N 6.00; found C
H, CH2), 4.14 (d, J ϭ 13.5 Hz, 2 H, CH2), 2.39 (s, 2 H, CH2Ph), 68.92, H 8.02, N 5.94. 1H NMR (300 MHz, C6D6, 25 °C): δ ϭ 7.34
1.42 (s, 15 H, C5Me5), 0.86 (s, 18 H, tBu) ppm. 13C{1H} NMR
(m, 2 H, Ph), 6.92 (m, 2 H, Ph), 6.99, 6.84, 6.66 (t, t, d, 5 H,
(75 MHz, C6D6, 25 °C): δ ϭ 151.3 (ipso-CH2Ph), 127Ϫ128 CH2Ph), 6.40, 6.13 (AAЈBBЈ spin system, 2 H, 2 H, C5H4), 3.68 (t,
(CH2Ph), 123.7, 117.6 (Ph), 124.7 (ipso-Ph), 119.0 (ipso-C5Me5), J ϭ 7.5 Hz, 4 H, CH2), 1.68 (s, 2 H, CH2Ph), 1.33 (m, 4 H, CH2),
74.5 (CH2Ph), 60.9 (CH2), 37.4 (ipso-tBu), 30.1 (tBu), 10.6
(C5Me5) ppm.
0.64 (t, J ϭ 7.5 Hz, 6 H, CH3), 0.19 (s, 9 H, SiMe3) ppm. 1H NMR
(300 MHz, CDCl3, 25 °C): δ ϭ 7.26 (m, 2 H, Ph), 6.99 (m, 2 H,
Ph), 6.94, 6.64, 6.36 (t, t, d, 5 H, CH2Ph), 6.45, 6.22 (AAЈBBЈ spin
system, 2 H, 2 H, C5H4), 3.74 (t, J ϭ 7.5 Hz, 4 H, CH2), 1.46 (m,
4 H, CH2), 1.39 (s, 2 H, CH2Ph), 0.78 (t, J ϭ 7.5 Hz, 6 H, CH3),
0.22 (s, 9 H, SiMe3) ppm. 13C{1H} NMR (75 MHz, C6D6, 25 °C):
δ ϭ 149.8 (ipso-CH2Ph), 125Ϫ128 (CH2Ph), 125.4, 115.6 (Ph),
120.8, 118.1 (C5H4), 63.4 (CH2Bz), 57.9 (NϪCH2), 24.0 (CH2),
12.1 (CH3), 0.78 (SiMe3) ppm, the signal for ipso-C5H4 is not ob-
served.
Ti[η5-C5H4(SiMe3)][1,2-C6H4(NCH2tBu)2](CH2Ph) (9): Com-
pound
9
was prepared by treating Ti[η5-C5H4(SiMe3)][1,2-
C6H4(NCH2tBu)2]Cl (0.22 g, 0.47 mmol) with a 2 m solution of
BzMgCl in THF (0.23 mL) according to the same procedure de-
scribed for 8 and was obtained as a red-brown oil (0.15 g,
0.28 mmol, 61%). C31H46N2SiTi (522.68): calcd. C 71.24, H 8.87,
N 5.36; found C 70.80, H 8.72, N 5.20. 1H NMR (300 MHz, C6D6,
25 °C): δ ϭ 7.33 (s, 4 H, Ph), 7.17, 6.86, 6.64 (t, t, d, 5 H, CH2Ph),
6.51, 6.18 (AAЈBBЈ spin system, 2 H, 2 H, C5H4), 3.99 (d, J ϭ Al2[1,2-C6H4(NCH2tBu)2]Me4 (13): A 2 m solution of TMA (1.21
13.5 Hz, 2 H, CH2), 3.93 (d, J ϭ 13.8 Hz, 2 H, CH2), 0.85 (s, 2 H,
CH2Ph), 0.71 (s, 18 H, tBu), 0.31 (s, 9 H, SiMe3) ppm. H NMR
mL, 2.42 mmol) in toluene was added to a solution of 1,2-
C6H4(NHCH2tBu)2 (0.3 g, 1.21 mmol) in toluene (30 mL) at Ϫ78
1
(300 MHz, CDCl3, 25 °C): δ ϭ 7.45 (m, 2 H, Ph), 7.38 (m, 2 H, °C. After stirring for 12 h, the solvent was completely removed and
Ph), 6.96, 6.66, 6.32 (t, t, d, 5 H, CH2Ph), 6.34, 6.15 (AAЈBBЈ spin the resultant solid extracted successively with hexane/toluene mix-
system, 2 H, 2 H, C5H4), 3.96 (s, 4 H, CH2), 0.73 (s, 18 H, tBu),
tures. The resultant solution was concentrated and cooled to Ϫ20
0.45 (s, 2 H, CH2Ph), 0.28 (s, 9 H, SiMe3) ppm. 13C{1H} NMR °C to give a purple solid which was identified as 13 (0.32 g,
(75 MHz, C6D6, 25 °C): δ ϭ 150.8 (ipso-CH2Ph), 126.5, 119.6 (Ph), 0.88 mmol, 73%). C20H38Al2N2 (360.50): calcd. C 66.64, H 10.62,
126Ϫ128 (CH2Ph), 124.9 (ipso-Ph), 122.5, 115.9 (C5H4), 66.1
(CH2), 60.2 (CH2Ph), 35.9 (ipso-tBu), 29.2 (tBu), 1.6 (SiMe3) ppm,
the signal for ipso-C5H4 is not observed.
N 7.77; found C 65.98, H 10.26, N 7.39. 1H NMR (300 MHz,
C6D6, 25 °C): δ ϭ 6.81 (m, 2 H, Ph), 6.97 (m, 2 H, Ph), 2.93 (s, 4
H, CH2), 0.89 (s, 18 H, tBu), Ϫ0.07 (s, 6 H, AlϪCH3), Ϫ0.90 (s, 6
344
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 338Ϫ346

Studies of the Nature of the Catalytic Species in the α-Olefin Polymerisation Processes
FULL PAPER
[20]
[21]
[22]
1
J. D. Scollard, D. H. McConville, N. C. Payne, J. J. Vittal,
Macromolecules 1996, 29, 5241Ϫ5243.
Y. Yoshida, S. Matsui, Y. Takagi, M. Mitani, M. Nitabaru, T.
Nakano, H. Tanaka, T. Fujita, Chem. Lett. 2000, 1270Ϫ1271.
Y. Yoshida, S. Matsui, Y. Takagi, M. Mitani, T. Nakano, H.
Tanaka, N. Kashiwa, T. Fujita, Organometallics 2001, 20,
4793Ϫ4799.
Y. Yoshida, J. Saito, M. Mitani, Y. Takagi, S. Matsui, S. Ishii,
T. Nakano, N. Kashiwa, T. Fujita, Chem. Commun. 2002,
1298Ϫ1299.
S. Mecking, L. K. Johnson, L. Wang, M. Brookhart, J. Am.
Chem. Soc. 1998, 120, 888Ϫ899.
B. J. Burger, M. E. Thompson, W. D. Cotter, J. E. Bercaw, J.
Am. Chem. Soc. 1990, 112, 1566Ϫ1577.
C. M. Killian, D. J. Tempel, L. K. Johnson, M. Brookhart, J.
H, AlϪCH3) ppm. H NMR (300 MHz, CDCl3, 25 °C): δ ϭ 6.88
(s, 4 H, Ph), 3.02 (s, 4 H, CH2), 1.03 (s, 18 H, tBu), Ϫ0.45 (s, 6 H,
Al-CH3), Ϫ1.33 (s, 6 H, AlϪCH3) 13C{1H} NMR (75 MHz, C6D6,
25 °C): δ ϭ 142.8 (ipso-Ph), 121.9, 114.0 (Ph), 56.7 (CH2), 33.7
(ipso-tBu), 29.4 (tBu), Ϫ5.4, Ϫ11.1 (broad, AlϪCH3) ppm.
Al2[1,2-C6H4(NCH2CH2CH3)2]Me4 (14): The same procedure de-
scribed for 13 using the TMA solution in toluene (2.44 mL,
4.89 mmol) and 1,2-C6H4(NCH2CH2CH3)2 (0.47 g, 2.44 mmol)
gave 14 as a dark purple oil (0.40, 1.31 mmol, 54%). An elemental
analysis could not be obtained due to the presence of small
amounts of impurities which could not be removed. 1H NMR
(300 MHz, C6D6, 25 °C): δ ϭ 6.85 (m, 2 H, Ph), 6.51 (m, 2 H, Ph),
2.72 (m, 4 H, CH2), 1.58 (m, 4 H, CH2), 0.68 (t, J ϭ 7.2 Hz, 6 H,
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
1
CH3), Ϫ0.13 (s, 6 H, AlϪCH3), Ϫ1.04 (s, 6 H, AlϪCH3) ppm. H
Am. Chem. Soc. 1996, 118, 11664Ϫ11665.
M. Brookhart, J. M. Desimone, B. E. Grant, M. J. Tanner,
Macromolecules 1995, 28, 5378Ϫ5380.
V. Tabernero, T. Cuenca, E. Herdtweck, Eur. J. Inorg. Chem.
2004, 3154Ϫ3162.
M. L. H. Green, J. Sassmannshausen, Chem. Commun. 1999,
115Ϫ116.
NMR (300 MHz, CDCl3, 25 °C): δ ϭ 6.90 (m, 2 H, Ph), 6.70 (m,
2 H, Ph), 2.99 (m, 4 H, CH2), 1.71 (m, 4 H, CH2), 1.01 (t, J ϭ
7.2 Hz, 6 H, CH3), Ϫ0.47 (s, 6 H, AlϪCH3), Ϫ1.46 (s, 6 H,
AlϪCH3) ppm. 13C{1H} NMR (75 MHz, C6D6, 25 °C): δ ϭ 141.6
(ipso-Ph), 112.6, 122.4 (Ph), 46.5 (CH2), 23.3 (CH2), 12.0 (CH3),
Ϫ6.4, Ϫ13.0 (broad, AlϪCH3) ppm.
J. C. Flores, J. C. W. Chien, M. D. Rausch, Organometallics
1995, 14, 1827Ϫ1833.
´
R. Gomez, R. Duchateau, A. N. Chernega, J. H. Teuben, F. T.
Edelmann, M. L. H. Green, J. Organomet. Chem. 1995, 491,
Acknowledgments
Generous financial assistance from the DGICYT (Project
MAT2001-1309) is gratefully acknowledged.
153Ϫ158.
[32]
[33]
[34]
[35]
M. Gonzalez-Maupoey, T. Cuenca, L. M. Frutos, O. Castano,
E. Herdtweck, Organometallics 2003, 22, 2694Ϫ2704.
M. P. Coles, D. C. Swenson, R. F. Jordan, V. G. Young, Or-
ganometallics 1997, 16, 5183Ϫ5194.
S. J. Kim, I. N. Jung, B. R. Yoo, S. H. Kim, J. J. Ko, D. J.
Byun, S. O. Kang, Organometallics 2001, 20, 2136Ϫ2144.
[1]
´
A. T. Rappe, W. M. Skiff, C. J. Casewit, Chem. Rev. 2000,
`
S. Daniele, C. Drost, B. Gehrhus, S. M. Hawkins, P. B. Hitch-
100, 1435Ϫ1456.
[2]
[3]
[4]
cock, M. F. Lappert, P. G. Merle, S. G. Bott, J. Chem. Soc.,
Dalton Trans. 2001, 3179Ϫ3188.
T. I. Gountchev, T. D. Tilley, Inorg. Chim. Acta 2003, 345,
81Ϫ88.
G. G. Hlatky, Coord. Chem. Rev. 2000, 199, 235Ϫ329.
H. G. Alt, A. Koppl, Chem. Rev. 2000, 100, 1205Ϫ1221.
P. C. Möhring, N. J. Coville, J. Organomet. Chem. 1994, 479,
1Ϫ29.
[36]
[37]
[38]
[39]
[40]
[41]
[42]
[43]
[44]
[45]
[46]
[5]
H. H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger, R. M.
Waymouth, Angew. Chem. Int. Ed. Engl. 1995, 34, 1143Ϫ1170.
M. Bochmann, J. Chem. Soc., Dalton Trans. 1996, 255Ϫ270.
S. W. Ewart, M. J. Sarsfield, D. Jeremic, T. L. Tremblay, E. F.
Williams, M. C. Baird, Organometallics 1998, 17, 1502Ϫ1510.
W. Kaminsky, M. Arndt, in Polymer Synthesis/Polymer Cataly-
sis, vol. 127 (‘‘Advances in Polymer Science’’), Springer-Verlag,
Berlin, 1997, pp. 143Ϫ187.
G. Guerra, P. Longo, L. Cavallo, P. Corradini, L. Resconi, J.
Am. Chem. Soc. 1997, 119, 4394Ϫ4403.
A. M. Thayer, Chem. Eng. News 1995, 73, 15Ϫ20.
K. B. Sinclair, R. B. Wilson, Chem. Ind. 1994, 857Ϫ862.
V. K. Gupta, S. Satish, I. S. Bhardwaj, J. Macromol. Sci. Rev.
Macromol. Chem. Phys. 1994, C34, 439Ϫ514.
`
S. Daniele, P. B. Hitchcock, M. F. Lappert, Chem. Commun.
1999, 1909Ϫ1910.
N. A. H. Male, M. ThorntonPett, M. Bochmann, J. Chem.
Soc., Dalton Trans. 1997, 2487Ϫ2494.
Y. M. Jeon, S. J. Park, J. Heo, K. Kim, Organometallics 1998,
17, 3161Ϫ3163.
S. Saccheo, G. Gioia, A. Grassi, D. E. Bowen, R. F. Jordan, J.
Mol. Catal. A: Chem. 1998, 128, 111Ϫ118.
A. Zambelli, L. Oliva, C. Pellecchia, Macromolecules 1989,
22, 2129Ϫ2130.
N. Ishihara, M. Kuramoto, M. Uoi, Macromolecules 1988,
21, 3356Ϫ3360.
N. Ishihara, T. Seimiya, M. Kuramoto, M. Uoi, Macromol-
ecules 1986, 19, 2464Ϫ2465.
A. Kucht, H. Kucht, S. Barry, J. C. W. Chien, M. D. Rausch,
Organometallics 1993, 12, 3075Ϫ3078.
P. Longo, A. Proto, A. Zambelli, Macromol. Chem. Phys. 1995,
196, 3015Ϫ3029.
A. Grassi, M. Caprio, A. Zambelli, D. E. Bowen, Macromol-
ecules 2000, 33, 8130Ϫ8135.
I. Kim, R. F. Jordan, Macromolecules 1996, 29, 489Ϫ491.
J. J. Eisch, K. Mackenzie, H. Windisch, C. Krüger, Eur. J. Inorg.
Chem. 1999, 153Ϫ162.
M. M. Lynam, L. V. Interrante, C. H. Patterson, R. P.
Messmer, Inorg. Chem. 1991, 30, 1918Ϫ1922.
Z. Jiang, L. V. Interrante, D. Kwon, F. S. Tham, R. Kullnig,
Inorg. Chem. 1991, 30, 995Ϫ1000.
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
T. R. Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich,
R. H. Grubbs, D. A. Bansleben, Science 2000, 288, 1750Ϫ1751.
´
M. Gonzalez-Maupoey, T. Cuenca, L. M. Frutos, O. Castan˜o,
E. Herdtweck, Organometallics 2003, 22, 2694Ϫ2704.
J. Cano, P. Royo, M. Lanfranchi, M. A. Pellinghelli, A. Tiripic-
chio, Angew. Chem. Int. Ed. 2001, 40, 2495Ϫ2496.
G. J. P. Britovsek, M. Bruce, V. C. Gibson, B. S. Kimberley, P.
J. Maddox, S. Mastroianni, S. J. McTavish, C. Redshaw, G. A.
Solan, S. Stromberg, A. J. P. White, D. J. Williams, J. Am.
Chem. Soc. 1999, 121, 8728Ϫ8740.
G. J. P. Britovsek, V. C. Gibson, B. S. Kimberley, P. J. Maddox,
S. J. McTavish, G. A. Solan, A. J. P. White, D. J. Williams,
Chem. Commun. 1998, 849Ϫ850.
C. M. Wang, S. Friedrich, T. R. Younkin, R. T. Li, R. H.
Grubbs, D. A. Bansleben, M. W. Day, Organometallics 1998,
17, 3149Ϫ3151.
J. D. Scollard, D. H. McConville, J. Am. Chem. Soc. 1996,
118, 10008Ϫ10009.
[47]
[48]
[49]
[50]
[51]
[52]
[17]
[18]
[19]
J. J. Byers, B. S. Lee, W. T. Pennington, G. H. Robinson, Poly-
hedron 1992, 11, 967Ϫ972.
J. L. Atwood, S. M. Lawrence, C. L. Raston, J. Chem. Soc.,
Chem. Commun. 1994, 73Ϫ74.
Eur. J. Inorg. Chem. 2005, 338Ϫ346
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
345

V. Tabernero, T. Cuenca
FULL PAPER
[53]
[63]
[64]
X. H. Bei, D. C. Swenson, R. F. Jordan, Organometallics 1997,
C. J. Harlan, S. G. Bott, A. R. Barron, J. Am. Chem. Soc. 1995,
117, 6465Ϫ6474.
K. P. Bryliakov, N. V. Semikolenova, D. V. Yudaev, M. Ystenes,
E. Rytter, V. A. Zakharov, E. P. Talsi, Macromol. Chem. Phys.
2003, 204, 1110Ϫ1117.
V. Volkis, M. Shmulinson, C. Averbuj, A. Lisovskii, F. T. Edel-
mann, M. S. Eisen, Organometallics 1998, 17, 3155Ϫ3157.
J. Sassmannshausen, M. E. Bochmann, J. Rosch, D. Lilge, J.
Organomet. Chem. 1997, 548, 23Ϫ28.
E. Giannetti, G. M. Nicoletti, R. Mazzocchi, J. Polym. Sci.
Pol. Chem. 1985, 23, 2117Ϫ2134.
R. F. Jordan, C. S. Bajgur, R. Willett, B. Scott, J. Am. Chem.
Soc. 1986, 108, 7410Ϫ7411.
R. F. Jordan, R. E. Lapointe, P. K. Bradley, N. Baenziger, Or-
ganometallics 1989, 8, 2892Ϫ2903.
H. Yasuda, K. Tatsumi, T. Okamoto, K. Mashima, K. Lee, A.
Nakamura, Y. Kai, N. Kanehisa, N. Kasai, J. Am. Chem. Soc.
1985, 107, 2410Ϫ2422.
16, 3282Ϫ3302.
E. A. Ison, K. A. Abboud, I. Ghiviriga, J. M. Boncella, Or-
[54]
ganometallics 2004, 23, 929Ϫ931.
L. Resconi, S. Bossi, L. Abis, Macromolecules 1990, 23,
4489Ϫ4491.
C. Sishta, R. M. Hathorn, T. J. Marks, J. Am. Chem. Soc. 1992,
114, 1112Ϫ1114.
I. Tritto, S. X. Li, M. C. Sacchi, G. Zannoni, Macromolecules
[55]
[65]
[66]
[67]
[68]
[69]
[70]
[56]
[57]
1993, 26, 7111Ϫ7115.
I. Tritto, R. Donetti, M. C. Sacchi, P. Locatelli, G. Zannoni,
[58]
Macromolecules 1999, 32, 264Ϫ269.
K. P. Bryliakov, N. V. Semikolenova, D. V. Yudaev, V. A. Zakh-
[59]
arov, H. H. Brintzinger, M. Ystenes, E. Rytter, E. P. Talsi, J.
Organomet. Chem. 2003, 683, 92Ϫ102.
K. P. Bryliakov, N. V. Semikolenova, V. A. Zakharov, E. P.
[60]
Talsi, J. Organomet. Chem. 2003, 683, 23Ϫ28.
D. E. Babushkin, N. V. Semikolenova, V. A. Zakharov, E. P.
[61]
Received July 29, 2004
Early View Article
Published Online November 24, 2004
Talsi, Macromol. Chem. Phys. 2000, 201, 558Ϫ567.
S. Pasynkiewicz, Polyhedron 1990, 9, 429Ϫ453.
[62]
346
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