Group 4 metallocene complexes with non-bridged and tetramethyldisiloxane- bridged methyl-phenyl-cyclopentadienyl ligands: Synthesis, characterization and olefin polymerization studies

Article abstract of DOI:10.1016/j.jorganchem.2004.06.059

meso- and rac-Diastereomers of the Me-Ph-cyclopentadienyl-disubstituted zirconocene and tetramethyldisiloxane-bridged ansa-metallocene dichlorides (M = Zr, Hf) have been isolated by transmetallation of their lithium salts to MCl₄ and characterized by NMR spectroscopy and X-ray diffraction methods. The zirconocene dichlorides activated with MAO are active catalysts for ethene and propene polymerization. The non-vicinal methyl-phenyl-substituted zirconocene dichlorides meso-and rac-[Zr{η⁵-(1-Ph-3-Me-C ₅H₃)}₂Cl₂] and [Zr(η ⁵-C₅H₅){η⁵-(1-Ph-3-Me-C ₅H₃)}Cl₂] have been isolated by transmetallation of the lithium salt Li(1-Ph-3-Me-C₅H₃) to ZrCl₄(THF)₂ and [Zr(η⁵-C₅H ₅)Cl₃ ? DME] (DME = dimethoxyethane), respectively. Similar transmetallation of the lithium salt Li₂[(Me-Ph-C ₅H₂SiMe₂)₂O] to MCl₄ gave the ansa-metallocenes [M{η⁵-(Me-Ph-C₅H ₂SiMe₂)₂O}Cl₂] (M = Zr, Hf) for which the meso- and rac-diastereomers were separated. The dimethyl and dibenzyl derivatives of these metallocenes were also prepared and the structure of all of these compounds determined by NMR spectroscopy. The molecular structure of rac-[Zr{η⁵-(2-Me-4-Ph-C₅H₂SiMe ₂)₂O}Cl₂] was determined by single crystal X-ray diffraction methods. The activity of the dichlorometallocenes/MAO catalysts for ethene and propene polymerization was evaluated.

Full text of DOI:10.1016/j.jorganchem.2004.06.059

Journal of Organometallic Chemistry 689 (2004) 4395–4406
www.elsevier.com/locate/jorganchem
Group 4 metallocene complexes with non-bridged and
tetramethyldisiloxane-bridged methyl-phenyl-cyclopentadienyl
ligands: synthesis, characterization and olefin polymerization studies
*
´
Gema Martınez, Pascual Royo , Marta E.G. Mosquera
´ ´ ´ ´
Departamento de Quımica Inorganica. Universidad de Alcala. Campus Universitario, E-28871 Alcala de Henares, Spain
Received 30 April 2004; accepted 30 June 2004
Available online 3 August 2004
Abstract
The non-vicinal methyl-phenyl-substituted zirconocene dichlorides meso-and rac-[Zr{g5-(1-Ph-3-Me-C5H3)}2Cl2] and [Zr(g5-
C5H5){g5-(1-Ph-3-Me-C5H3)}Cl2] have been isolated by transmetallation of the lithium salt Li(1-Ph-3-Me-C5H3) to ZrCl4(THF)2
and [Zr(g5-C5H5)Cl3 ÆDME] (DME=dimethoxyethane), respectively. Similar transmetallation of the lithium salt Li2[(Me-Ph-
C5H2SiMe2)2O] to MCl4 gave the ansa-metallocenes [M{g5-(Me-Ph-C5H2SiMe2)2O}Cl2] (M=Zr, Hf) for which the meso- and
rac-diastereomers were separated. The dimethyl and dibenzyl derivatives of these metallocenes were also prepared and the structure
of all of these compounds determined by NMR spectroscopy. The molecular structure of rac-[Zr{g5-(2-Me-4-Ph-C5H2Si-
Me2)2O}Cl2] was determined by single crystal X-ray diffraction methods. The activity of the dichlorometallocenes/MAO catalysts
for ethene and propene polymerization was evaluated.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Cyclopentadienyl; Zirconium; Hafnium; Disiloxane; ansa-Metallocenes; Olefin-Polymerization
1. Introduction
Me2Cl)2Cl2] and similar hydrolytic cleavage of Si–
NMe2 bonds gave the tetramethylcyclopentadienyl tita-
nium derivative [5]. These group 4 metal [6] and similar
praseodymium and ytterbium [7] compounds with un-
substituted and t-butyl-substituted [6,8] cyclopentadie-
nyl rings were isolated following the method reported
for the first titanium derivative [9], by reaction of the
metal halides with the sodium or potassium salts of
the dicyclopentadienyl ligand. The related bis(indenyl)
titanium and zirconium complexes were also reported
[10,11] and used as catalyst precursors for ethene and
propene polymerization [10]. Related doubly-disilox-
ane-bridged [12,13] and di- and polynuclear monocyclo-
pentadienyl-type titanium complexes [14] have also been
isolated and their catalytic activity for styrene polymer-
ization studied [15]. Except for [Ti{(g5-C5Me4Si-
Me2)2O}Cl2] [5] all of the X-ray molecular structures
studied for this type of ansa-metallocene compounds
Studies related to olefin polymerization processes [1]
have oriented most efforts made to design new types of
group 4 metallocene compounds using variously substi-
tuted cyclopentadienyl, indenyl and fluorenyl ligands
and different bridging systems. Tetramethyldisiloxane-
bridged ansa-metallocenes are an interesting group of
complexes. Some lanthanide and group 4 tetramethyldi-
siloxane-bridged ansa-metallocenes related to the ferro-
cenophane derivative reported previously [2] have been
isolated. We reported [3,4] the preparation of the group
4 metal complexes [M{(g5-C5H4SiMe2)2O}Cl2] by hy-
drolysis of the chlorosilyl derivatives [M(g5-C5H4Si
*
Corresponding author. Tel.: +34-91-8854765; fax: +34-91-
8854683.
E-mail address: pascual.royo@uah.es (P. Royo).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.06.059

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4396
Me
Ph
Me
Me
Me
Si
Ph
SiMe2
Me
Me
Si
M
O
M
Zr
Cl
Cl
Si
Cl
R
R
N
Cl
tBu
Ph
Me
Me
Me
(c)
(b)
Scheme 1.
(a)
show the lateral location of the disiloxane bridge with
respect to the MCl2 moiety (Scheme 1(a)) with both cy-
clopentadienyl rings twisted to bring closer two carbon
atoms located in a position with respect to the bridge.
Tetramethylethylene- and dimethylsilyl-bridged ansa-
metallocenes with the disubstituted methyl-phenyl-cy-
clopentadienyl ligand have been reported previously
[16] and we have recently prepared [17] one new dimeth-
ylsilyl-bridged ansa-zirconocene (Scheme 1(b)) and one
Cp-silyl-g1-amido zirconium complex (Scheme 1(c)) in
which the Me and Ph groups are always located in
2,4-positions with respect to the bridgehead carbon
atom. We were interested in studying the effect of these
disubstituted rings on the behaviour of ansa-metalloce-
nes bridged by the tetramethyldisiloxane group compared
with the corresponding unbridged metallocenes. In this
work we describe the synthesis and structural character-
ization of [Zr{g5-(1-Ph-3-Me-C5H3)}2X2] and [Zr(g5-
C5H5){g5-(1-Ph-3-Me-C5H3)}X2] (X=Cl, Me, CH2Ph)
zirconocene complexes with non-bridged cylopentadie-
nyl rings and tetramethyldisiloxane-bridged ansa-metal-
locene derivatives [M{g5-(Me-Ph-C5H2SiMe2)2O}X2]
(M=Zr, Hf; X=Cl, Me, CH2Ph) containing the Me-
Ph-disubstituted cyclopentadienyl ligand. The catalytic
activity of the dichlorozirconocenes combined with
MAO for ethene and propene polymerization has been
evaluated.
by fractional crystallization and they cannot be distin-
guished by NMR spectroscopy because both show sim-
1
ilar patterns of signals in their H and 13C spectra. The
plane of symmetry of the meso-2 and the C2-axis of the
rac-2 isomers make the two cyclopentadienyl rings
equivalent exhibiting one singlet for the ring-methyl pro-
tons, three multiplets due to the ABC spin system of the
ring protons and the expected three multiplets for two
equivalent phenyl rings. Consistently both isomers also
show almost identical sets of signals in their 13C NMR
spectra (see Section 4). Alkylation of this mixture
(meso-2+rac-2) with
2 equivalents of LiMe and
MgCl(CH2Ph) gave meso–rac mixtures of the corre-
sponding dimethyl and dibenzyl zirconium complexes
[Zr{g5-(1-Ph-3-Me-C5H3)}2R2] (R=Me meso-3+rac-3,
CH2Ph meso-4+rac-4) which were isolated as white (3)
and yellow (4) microcrystalline solids and identified by
elemental analysis and NMR spectroscopy. A definitive
structural assignment of the meso-3 isomer was easily
made because its NMR spectra show two singlets (1H)
and two signals (13C) due to two non-equivalent zirconi-
um-methyl groups whereas the rac-3 isomer shows one
signal (1H and 13C) for both equivalent zirconium-me-
thyl groups. The isomers occur in a molar ratio 1/0.9.
Similarly, the methylene protons of the two non-equiva-
lent benzyl-zirconium groups of the meso-4 isomer ap-
pear in the 1H NMR spectrum as two multiplets
whereas only one multiplet is observed for the equiva-
lent benzyl-zirconium substituents of rac-4 (see Section
4). The isomers occur in a ca. 2/1 molar ratio.
2. Results and discussion
The analogous dichloro zirconocene [Zr(g5-C5H5)-
{g5-(1-Ph-3-Me-C5H3)}Cl2] 5 with mixed cyclopentadie-
nyl rings can be prepared by reaction of the lithium salt 1
with 1 equivalent of [Zr(g5-C5H5)Cl3 ÆDME] in toluene
at room temperature and isolated in 79% yield as a
yellow solid. Alkylation of complex 5 with LiMe and
MgCl(CH2Ph) in diethyl ether gave the dialkyl complexes
[Zr(g5-C5H5){g5-(1-Ph-3-Me-C5H3)}R2] (R=Me 6,
CH2Ph 7) which were isolated as a colourless oil and a
yellow microcrystalline solid, respectively. Compounds
6–7 are soluble in all the usual organic solvents whereas
5 is partially soluble in alkanes and all three are very air
sensitive compounds, although they can be stored for
2.1. Dicyclopentadienyl zirconium complexes
As shown in Scheme 2, reaction of the lithium salt Li
[1-Ph-3-Me-C5H3] 1 [16] with 0.5 equivalents of ZrCl4 in
hexane gave the dicyclopentadienyl zirconium complex
[Zr{g5-(1-Ph-3-Me-C5H3)}2Cl2] 2 which was isolated
as a yellow microcrystalline solid in 74% yield and char-
acterized by elemental analysis and NMR spectroscopy.
The enantiotopic faces of the disubstituted cyclopen-
tadienyl rings afford a mixture of two diastereomers
meso-2 and rac-2 in an almost equimolar ratio (1/0.8).
Pure samples of meso-2 and rac-2 could not be isolated

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4397
Ph
Ph
Me
Me
Me
Me
Cl
Cl
LiMe
R
Zr
Zr
R
MgCl(CH2Ph)
Ph
Ph
meso-2 + rac-2
ZrCpCl3.DME
ZrCl4
Me
R = Me meso-3 + rac-3
CH2Ph meso-4 + rac-4
Ph
Me
Me
Li+
1
Ph
Ph
R
Cl
Cl
LiMe
Zr
R
Zr
MgCl(CH2Ph)
5
R = Me 6, CH2Ph 7
Scheme 2.
long periods under an inert atmosphere. They were iden-
tified by elemental analysis and NMR spectroscopy. The
enantiotopic face of the 1-3-disubstituted cyclopentadie-
nyl ring makes the complexes 5–7 to be asymmetric mol-
ecules. Their 1H and 13C NMR spectra show three
multiplets (1H) and five signals (13C) for the disubstitut-
ed-rings, three multiplets (1H) and four signals (13C) for
the phenyl groups and two singlets (1H) and two signals
(13C) due to the ring-methyl and the unsubstituted cyclo-
pentadienyl groups. The non-equivalent methyl-zirconi-
um groups appear as two singlets in the 1H NMR
spectrum of complex 6 whereas the expected four dou-
blets were observed for the methylenic protons of the dib-
enzyl zirconium complex 7 (see Section 4).
may also contain the corresponding mixture of isomers
represented in Scheme 3. When this reaction was carried
out in diethyl ether for 4 h at room temperature the in-
soluble dilithium salt was obtained by filtration in 32%
1
yield as a white solid. The H NMR spectrum of this
compound in C6D6/C5D5N showed one single set of sig-
nals corresponding to one unique isomer. It consists of
one singlet for four equivalent Si-methyl groups, one
singlet for two equivalent ring-methyl groups and the
three signals expected for equivalent ring-phenyl groups,
along with two doublets for the ring protons of two
equivalent cyclopentadienyl rings (see Section 4). These
spectral features are consistent with the structures pro-
posed for 9a or 9c isomers which cannot be distin-
guished because each would have a similar set of
signals. When the same reaction was carried out remov-
ing the solvent under vacuum without previous filtra-
tion, a yellowish solid was isolated in 60% yield. The
1H NMR spectrum of this solid shows the same set of
2.2. Disiloxane-bridged ansa-dicyclopentadienyl compl-
exes
Reaction of 2 equivalents of the dilithium salt 1 with
the dichlorodisiloxane [(SiMe2Cl)2O] in THF afforded
the dicyclopentadienylsiloxane [(Me-Ph-C5H3SiMe2)2O]
8, which was isolated as a yellow-orange viscous liquid
in 77% yield. Assuming that silicon is always bound to
the sp3 ring-carbon atom, that the methyl and phenyl
substituents are located at 2–4 positions with respect
to the bridgehead carbon atom and that the silyl group
is never located in a position with respect to both methyl
and phenyl groups [17], three possible isomers of 8 could
Me
Ph
Me
Me
E
E
Me
Ph
Ph
Ph
Li+
Li+
Li+
Li+
9b
9a
Ph
Ph
1
be formed. However the H NMR spectrum of com-
E
pound 8, probably containing a mixture of isomers
showed very broad signals that prevented a reasonable
structural assignment.
Me
Me
E = Me2Si-O-SiMe2
Li+
Li+
9c
Deprotonation of 8 with 2 equivalents of nBuLi gave
the dilithium salt Li2[(Me-Ph-C5H2SiMe2)2O] 9 which
Scheme 3.

´
G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4398
signals observed for 9a or 9c and a new set consistent
with that expected for the 9b isomer in a molar ratio
3:1, respectively. It shows two singlets each correspond-
ing to two methyl protons of two non-equivalent SiMe2
groups and two singlets due to two non-equivalent ring
methyl groups.
As shown in Scheme 4, reaction of ZrCl4 Æ2THF with
1 equivalent of the dilithium salt containing one single
isomer (9a or 9c) in toluene gave the dichlorozircono-
cene [Zr{g5-(Me-Ph-C5H2SiMe2)2O}Cl2] 10 in 53%
yield as a yellow crystalline solid which was character-
ized by elemental analysis and NMR spectroscopy.
The 1H NMR spectrum of 10 confirmed that it is a mix-
ture of two diastereomers in a 6:1 molar ratio, each ex-
hibiting a similar set of signals.
Crystals of this minor isomer of good quality suita-
ble for X-ray diffraction were isolated and its molecular
structure determined to confirm that it corresponds to
the [Zr{g5-(2-Me-4-Ph-C5H2SiMe2)2O}Cl2] rac-10a
1
diastereomer which is also consistent with the H and
13C NMR spectra. Therefore it is possible to conclude
that the unique isomer detected in the starting dilithi-
um salt is 9a, which reacts with ZrCl4 Æ2THF to give
a mixture of the two possible meso-10a and rac-10a
diastereomers.
When the same reaction with ZrCl4 Æ2THF was carried
out using the dilithium salt containing a mixture of 9a
and 9b, the yellow solid isolated contained the same mix-
ture of meso-10a and rac-10a coming from 9a together
with
a
new isomer [Zr{g5-(2-Me-4-Ph-C5H2)[(Si-
Recrystallization from toluene gave pure small
crystals of the less soluble major component of this mix-
ture. Although the crystals were too small for full anal-
ysis by X-ray diffraction methods and precise values for
bond lengths and angles could not be determined, it was
possible to obtain a sketch of its molecular structure
which corresponds to the [Zr{g5-(2-Me-4-Ph-C5H2Si-
Me2)2O}Cl2] meso-10a diastereomer. The 1H and 13C
NMR spectra are consistent with this structure. From
the mother liquor it was possible to isolate samples con-
taining the more soluble minor component although
always contaminated by small variable amounts of
meso-10a.
Me2)2O](g5-(2-Ph-4-Me-C5H2))}Cl2] 10b, which could
not be separated by repeated crystallization and was
identified by NMR spectroscopy as one of the two possi-
ble diastereomers formed from 9b, the molar ratio of the
three isomers meso-10a:rac-10a:10b was 1:0.6:0.7.
Similar reaction with HfCl4 gave a yellow solid con-
taining a mixture in a 3:1 molar ratio of the meso-:
rac-diastereomers of the dichlorohafnocene [Hf{g5-(2-
Me-4-Ph-C5H2SiMe2)2O}Cl2] 11a containing insignifi-
cant amounts of the 11b isomer. This mixture could be
enriched in the meso-11a diastereomer after repeated re-
crystallization from toluene to give a 15:1 molar ratio of
the meso–rac diastereomers.
Ph
Ph
Ph
Me
Me
Me
Ph
Me
Zr
Me
Me
Me
Si
Me
Me
Si
Si
Si
Si
ZrCl4.2THF
9
O
O
O
M
M
+
+
Cl
Cl
Me
Cl
Cl
Me
Cl
Cl
Me
Si
Me
Me
Me
Me
Me
Ph
Me
Ph
M = Zr rac-10a
Hf rac-11a
10b
M = Zr meso-10a
Hf meso-11a
LiMe
MgCl(CH2Ph)
Ph
Me
Me
Me
Si
Si
O
M
R
R
Me
Me
Me
Ph
M = Zr, R = Me meso-12a
CH2Ph meso-13a
Hf, R = Me meso-14a
CH2Ph meso-15a
Scheme 4.

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4399
The 1H and 13C NMR spectra of 10b in CDCl3
showed four signals (1H, 13C) for methyl-silicon and
two signals for methyl-ring groups consistent with its
formulation as an asymmetric molecule. One of the ring
methyl singlets is significantly shifted highfield (d 1.51)
probably due to the anisotropic effect on the methyl
group located in a-position, as it was also observed for
the related dimethylsilylene-bridged compound identi-
fied as the meso-isomer by its X-ray molecular structure
[17]. For this reason we tentatively assign the meso-con-
figuration for 10b.
According to the static structure determined by X-
1
ray diffraction studies the H NMR spectra of the rac-
10a and rac-11a isomers should show four singlets for
silicon-methyl and two singlets for ring-methyl groups
whereas only two silicon-methyl and one ring-methyl
singlets should be observed for the meso-10a and
meso-11a isomers. However, it has been reported [6,9]
that a dynamic exchange due to the twist of the siloxane
group slipping between the two opposite sides of the
ring takes place at room temperature with interconver-
sion of these molecules into their mirror images. This
fluxional behaviour also occurs for these metallocenes
with two methyl-phenyl disubstituted rings exchanging
the position of the silicon-methyl groups between the
ring-methy- and phenyl substituents to give the aver-
aged spectrum observed. This behaviour justifies the
view that in solution at 25 ꢁC the rac-isomers give the
same pattern of signals observed for the meso-isomers.
The assignment of the two similar sets of signals ob-
served in the NMR spectra of mixtures containing
meso- and rac-10a was based on the spectra of isolated
samples of each isomer and confirmed by their X-ray
molecular structures. However, the structural assign-
ment of meso- and rac-11a isomers suggested preparing
the dialkyl derivatives for which the meso-isomer shows
two easily identifiable non-equivalent alkyl groups,
whereas the rac-isomer should present equivalent alkyl
groups.
Alkylation of the zirconium meso-10a isomer with
LiMe and MgCl(CH2Ph) in diethyl ether gave the
meso-dialkyl complexes [Zr{g5-(2-Me-4-Ph-C5H2Si-
Me2)2O}R2] (R=Me meso-12a, CH2Ph meso-13a) as a
colourless solid and a yellow oil, respectively. Similar al-
kylation of the hafnium dichloride 11 containing a mix-
ture previously enriched to a molar ratio 15:1 of the
meso- and rac-isomers, respectively allowed isolation
of pure meso-isomers [Hf{g5-(2-Me-4-Ph-C5H2Si-
Me2)2O}R2] (R=Me meso-14a, CH2Ph meso-15a), as a
colourless solid and a yellow-orange oil, respectively,
which were characterized by elemental analysis and
NMR spectroscopy (see Section 4).
Fig. 1. ORTEP representation of the molecular structure of com-
pound rac-10a (1S, 10S) enantiomer. Thermal ellipsoids are drawn at
the 30% probability level. The H atoms were omitted for clarity.
(a) View from the axis bisecting the Cl–Ti–Cl angle. (b) Top view
perpendicular to the ZrCl2 plane.
The coordination geometry of the zirconium atom in
rac-10a is similar to that observed in meso-10a both cor-
responding to the typical distorted tetrahedron formed
by the ring centroids and the chlorine atoms as found
for related titanocene [9] and zirconocene [3] derivatives
with non-bridged or bridged cyclopentadienyl ligands.
The Zr–Cl bond lengths for rac-10a are slightly different
˚
[Zr–Cl(1) 2.4274(11); Zr–Cl(2) 2.4363(10) A], with the
The X-ray molecular structure of rac-10a (1S, 10S)
enantiomer is shown in Fig. 1 with the atomic labelling
scheme and selected bond lengths and angles are listed in
Table 1.
longer corresponding to the bond trans to the siloxy
moiety. The Cl–Zr–Cl angle of 96.72(5)ꢁ is within the
range found for dichlorozirconocenes such as
[ZrCl2{l-[(g5-C5H4)SiMe2OSiMe2(g5-C5H4)]}] [3] and

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4400
Table 1
Selected interatomic distances (bonding and non-bonding, A) and
bond angles (ꢁ) for rac-10a (1S, 10S) enantiomer
rable to those reported for metallocenes containing non-
bridged cyclopentadienyl ligands. This tilting brings the
˚
two a-carbons [C(2).....C(7)] nearer (3.126 A) whereas
˚
the distances between the distant carbons [C(4).....C(10)
and C(5).....C(9)] are 5.026 and 4.824 A, respectively,
˚
and those between the middle carbon atoms
[C(3).....C(6)] and the bridgehead atoms [C(1).....C(8)]
˚
are 3.942 and 3.563 A, respectively. This seems to be
the most favourable disposition for the large bite of
the disiloxane bridge in which the two g5-coordinated
cyclopentadienyl rings are almost identical, although
the C(Cp)–Zr bond distances are significantly spread
out in a rather broad range between 2.482(3) and
Interatomic distances
Zr(1)–Cl(1)
Zr(1)–Cl(2)
Zr(1)–C(1)
Zr(1)–C(2)
Zr(1)–C(3)
Zr(1)–C(4)
Zr(1)–C(5)
Zr(1)–C(6)
Zr(1)–C(7)
Zr(1)–C(8)
Zr(1)–C(9)
Zr(1)–C(10)
Si(1)–C(1)
Si(2)–C(8)
Si(1)–C(11)
Si(1)–C(12)
Si(2)–C(13)
Si(2)–C(14)
O(1)–Si(1)
O(1)–Si(2)
2.4274(11)
2.4363(10)
2.494(3)
2.561(4)
2.545(3)
2.573(3)
2.507(3)
2.555(3)
2.482(3)
2.500(3)
2.596(3)
2.579(3)
1.866(4)
1.873(3)
1.839(5)
1.849(5)
1.840(4)
1.846(4)
1.640(3)
1.633(3)
Zr–Cp(1)a
Zr–Cp(2)a
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(1)–C(5)
C(2)–C(21)
C(4)–C(41)
C(6)–C(7)
C(7)–C(8)
C(8)–C(9)
C(9)–C(10)
C(6)–C(10)
C(6)–C(61)
C(9)–C(91)
C(2)..... C(7)
C(4)..... C(10)
C(5)..... C(9)
C(3)..... C(6)
C(1)..... C(8)
2.2319
2.2378
1.436(5)
1.397(5)
1.420(5)
1.402(4)
1.425(5)
1.514(5)
1.477(5)
1.407(5)
1.441(4)
1.425(5)
1.407(5)
1.420(5)
1.483(5)
1.503(5)
3.126
˚
2.596(3) A, as a consequence of the asymmetric disposi-
tion of the bridge. However significant differences are
observed for the ring C–C distances, the shortest being
one of the internal distances [C(2)Me–C(3) 1.397(5)
˚
and C(6)Ph–C(7) 1.407(5) A] whereas the others, also in-
ternal with the bridgehead carbons are the longest
5.026
4.824
˚
[C(1)–C(2)Me 1.436(5) and C(7)–C(8) 1.441(4) A]; the
middle distances are exactly the same for both rings
[C(3)–C(4)Ph and C(6)Ph–C(10) 1.420(5), C(1)–C(5)
3.942
3.563
˚
and C(8)–C(9)Me 1.425(5) A], whereas the distal dis-
tances show intermediate values [C(4)Ph–C(5) 1.402(4)
˚
and C(9)Me–C(10) 1.407(5) A]. These C–C distances
seem to be unaffected by the presence of the methyl
and phenyl substituents.
Bond angles
Cl(1)–Zr(1)–Cl(2)
Si(2)–O(1)–Si(1)
Cp(1)–Zr–Cp(2)a
96.72(5)
139.94(18)
132.74
O(1)–Si(1)–C(1)
O(1)–Si(2)–C(8)
Cp–Cpb
107.71(14)
108.22(14)
50.86
a
Cp(1) is the centroid of C(1), C(2), C(3), C(4), C(5) and Cp(2) is
the centroid of C(6), C(7), C(8), C(9), C(10).
b
Dihedral angle between the least-squares cyclopentadienyl planes.
2.3. Olefin polymerization results
The
C5H3)}2Cl2] 2 (meso+rac), [Zr(g5-C5H5){g5-(1-Ph-3-
Me-C5H3)}Cl2]
and [Zr{g5-(2-Me-4-Ph-C5H2Si-
dichlorozirconocenes
[Zr{g5-(1-Ph-3-Me-
[ZrCl2{l-[(g5-C5H4-tBu)SiMe2OSiMe2(g5-C5H4-tBu)]}]
˚
[5]. The Zr–Cp(centroid) distances [2.2319 and 2.2378 A]
5
are not significantly different from those observed in re-
lated compounds.
˚
The Si–C(Cp) bond lengths [average 1.870 A] are
slightly longer than the Si–C(Me) distances [average
˚
1.846 A], as previously observed in similar compounds
˚
[3,5,9,16]. The average Si–O distances of 1.636 A are
Me2)2O}Cl2] meso-10a were used as catalyst precursors
for the polymerization of ethene being activated with a
large excess methylalumoxane (MAO:Zr=1500:1) as a
10% toluene solution. All experiments were carried out
in toluene under 1.0 bar of ethene in a glass reactor, us-
ing a 4.4·10ꢀ3 M toluene solution of the precursor zir-
conocene. Compounds 2 and 5 show activities between
1100 and 1300 kg molꢀ1 hꢀ1 barꢀ1 at 70 ꢁC, slightly lower
similar to those found in siloxanes. However, the Si–O–
Si angle [139.94(18)ꢁ] resembles that of [ZrCl2{l-[(g5-
C5H4-tBu)SiMe2OSiMe2(g5-C5H4-tBu)]}] [5] [138.1(3)ꢁ],
which is significantly smaller than in [ZrCl2{l-[(g5-
C5H5)SiMe2OSiMe2(g5-C5H5)]}] [3] [143.5(1)ꢁ] or in
common open chain siloxanes (142–145ꢁ) [18]. This
structural difference could be due to the steric conges-
tion owing to the presence of the substituents in the
ring.
The most remarkable features observed for rac-10a
are the eclipsed configuration of the two cyclopentadie-
nyl rings (Fig. 1(b)) and the asymmetrical disposition of
the bridge with respect to the bisector of the Cl–Zr–Cl
angle as also found for related compounds with disilox-
ane bridges [3,5,9,11]. Both rings of rac-10a are tilted
with an angle between the Cp planes of 50.86ꢁ and a
Cp(centroid)–Zr–Cp(centroid) angle of 132.74ꢁ, compa-
than that found for Cp2ZrCl2 (1500 kg molꢀ1 hꢀ1 barꢀ1
)
used as reference under comparable conditions. The cat-
alytic activity decreases slightly to values between 800
and 1000 kg molꢀ1 hꢀ1 barꢀ1 at 20 ꢁC and both catalysts
display almost the same activities after 30 min accounting
for their stability, although they decrease slowly for long-
er periods. The ansa-metallocene meso-10a shows a sig-
nificantly lower activity (600 kg molꢀ1 hꢀ1 barꢀ1
)
which is almost independent of the temperature, decreas-
ing slightly after 30 min under the same conditions. The
molecular weight of the polyethylene resulting from cat-
alyst 2 (3.9·105 g molꢀ1) is much higher than those com-
ing from catalysts 5 (1.6·104 g molꢀ1) and meso-10a
(4.5·104 g molꢀ1). However compound 2 which is a mix-
ture of meso- and rac-isomers gives a polyethylene of high

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4401
polydispersity (7.6) accounting for the presence of more
than one active centre, whereas the distribution of
molecular weights is narrower for 5 (3.4) and meso-10a
(3.6).
Compound meso-10a was also studied as catalyst
precursor for polymerization of propene under 5.0 bar
at 70 ꢁC. The catalytic activity was 200 kg molꢀ1 hꢀ1
barꢀ1 to give the expected atactic polymer.
a M. Braun dry box. Solvents used were previously dried
and freshly distilled under argon. Deuterated solvents
from Scharlau were degassed, dried and stored over mo-
lecular sieves. MgBrPh, MgCl(CH2Ph), MgSO4, nBuLi,
MeLi, ZrCl4, HfCl4, (Me2SiCl)2O and Me2SiCl2 were
obtained from commercial sources and used as received.
[1-Ph-3-Me-C5H3]Li 1 [16], [Zr(g5-C5H5)Cl3 ÆDME] [19]
and ZrCl4 Æ2THF [20] were isolated by reported
methods.
1H and 13C NMR spectra were recorded on a Varian
Unity VXR-300 or Varian Unity 500 Plus instruments.
Chemical shifts, in ppm, are measured relative to resid-
3. Conclusions
1
The dichloro zirconocene complex [Zr{g5-(1-Ph-3-
Me-C5H3)}2Cl2] containing non-bridged cyclopentadie-
nyl ligands is easily synthesized by transmetallation of
the corresponding lithium salt to ZrCl4 resulting in for-
mation of an approximately equimolar mixture of meso-
and rac-diastereomers, which could not be separated by
repeated recrystallization. However the corresponding
dialkyl derivatives are easily distinguished by NMR
spectroscopy, allowing a definitive assignment of their
meso- and rac-configuration. Similar transmetallation
to CpZrCl3 leads to the mixed-ring zirconocene complex
[Zr(g5-C5H5){g5-(1-Ph-3-Me-C5H3)}Cl2] for which the
methyl and benzyl derivatives were also obtained.
Related dichloro ansa-zirconocene and hafnocene
complexes [M{g5-(Me-Ph-C5H2SiMe2)2O}Cl2] with te-
tramethyldisiloxane bridges are isolated by similar
transmetallation reactions resulting in the formation of
two types of isomers, namely those with 2,20-Me2-4,40-
Ph2-(C5H2)2 enantiofaces, leading to the corresponding
meso- and rac-diastereomers and those with 2,40-Me2-
4,20-Ph2-(C5H2)2 enantiofaces for which formation of
one unique diastereomer was observed. Most of these
mixtures of diastereomers could be resolved by repeated
recrystallization and single components were identified
by NMR spectroscopy and X-ray diffraction methods.
The structure and behaviour of these tetramethyldisi-
loxane-bridged ansa-metallocenes is similar to those
reported for compounds of this type.
ual H and 13C resonances for C6H6-d6 and CHCl3-d1
used as solvents and coupling constants are in Hz. C,
H analyses were carried out with a Perkin–Elmer 240-
C analyzer.
4.2. Synthesis of [Zr{g5-(1-Ph-3-Me-C5H3)}2Cl2]
(meso-2+rac-2)
Hexane (150 ml ) was added to a mixture of the lith-
ium salt 1 (4.00 g, 24.60 mmol) and ZrCl4 (2.84 g, 12.30
mmol) at ꢀ78 ꢁC. The mixture was allowed to warm to
room temperature and stirred for 12 h. After filtration of
the LiCl, the solvent was removed under vacuum and
the residue washed with hexane (2 · 20 ml) and dried
under vacuum to give a yellow microcrystalline solid
characterized as a mixture of meso-2 and rac-2 in a mo-
1
lar ratio 1:0.8 (4.32 g, 9.14 mmol, 74%). H NMR (300
MHZ, CDCl3, 25 ꢁC): 2.05a/2.01b (s, 6H, CH3), 5.77a,b
(m, 2H, C5H3), 6.36a/6.39b (m, 2H, C5H3), 6.45a/6.42b
(m, 2H, C5H3), 7.01a/7.06b (m, 2H, HpC6H5), 7.12a/
7.17b (m, 4H, HmC6H5), 7.31a/7.34b (m, 4H, HoC6H5).
13C NMR (75 MHz, CDCl3, 25 ꢁC): 15.5a/15.4b (CH3),
113.7a/114.3b (C5H3), 116.1a/116.7b (C5H3), 117.1a/
117.2b (C5H3), 125.5a/125.5b (CmC6H5), 125.7a,b (Cipso
MeC5H3), 127.7a/128.7b (CpC6H5), 129.0a,b (CoC6H5),
-
129.7a/130.0b (Cipso-PhC5H3), 133.1a/132.1b (Cipso
-
C6H5). Data for the majora and minorb isomers. Anal.
Calc. for C24 H22Cl2Zr: C, 61.00; H, 4.69. Found: C,
61.38; H, 4.85%.
The three dichloro zirconocenes with non-bridged
[Zr{g5-(1-Ph-3-Me-C5H3)}2Cl2] (meso+rac), [Zr(g5-
C5H5){g5-(1-Ph-3-Me-C5H3)}Cl2] and bridged cyclo-
pentadienyl rings meso-[Zr{g5-(2-Me-4-Ph-C5H2Si-
Me2)2O}Cl2] activated with MAO show high catalytic
activity for ethene polymerization comparable to
Cp2ZrCl2 and the ansa meso-zirconocene is also an ac-
tive catalyst for atactic polypropylene.
4.3. Synthesis of [Zr{g5-(1-Ph-3-Me-C5H3)}2Me2]
(meso-3+rac-3)
A 1.6 M Et2O solution of methyllithium (0.90 ml,
1.60 mmol) was added at ꢀ78 ꢁC to a solution of
meso-2+rac-2 (0.25 g, 0.53 mmol) in diethyl ether (30
ml). The reaction mixture was stirred for 12 h while it
was warmed slowly to room temperature. The solvent
was removed under vacuum and the residue was ex-
tracted into hexane (25 ml). After filtration, the solvent
was removed at reduced pressure and the residue was
dried under vacuum to give a white microcrystalline sol-
id characterized as a mixture of meso-3 and rac-3 in a
4. Experimental
4.1. General methods
All manipulations were performed under an inert at-
mosphere of argon using standard Schlenk techniques or
1
molar ratio 1:0.9 (0.19 g, 0.44 mmol, 84%). meso-3: H

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4402
NMR (300 MHz, C6D6, 25 ꢁC): ꢀ0.21 (s, 3H, Zr–CH3),
ꢀ0.03 (s, 3H, Zr–CH3), 1.82 (s, 6H, CH3), 5.57 (m, 2H,
C5H3), 5.86 (m, 2H, C5H3), 5.89 (m, 2H, C5H3), 6.99 (m,
2H, HpC6H5), 7.09 (m, 4H, HmC6H5), 7.16 (m, 4H,
HoC6H5). 13C NMR (75 MHz, C6D6, 25 ꢁC): 16.0
(CH3), 33.7 (Zr–CH3), 34.9 (Zr–CH3), 108.3 (C5H3),
110.8 (C5H3), 113.9 (C5H3), 124.4 (Cipso-MeC5H3),
125.8 (CmC6H5), 127.4 (CpC6H5), 129.1 (Cipso-PhC5H3),
129.6 (CoC6H5), 135.9 (Cipso-C6H5). rac-3: 1H NMR
(300 MHz, C6D6, 25 ꢁC): ꢀ0.11 (s, 6H, Zr–CH3), 1.87
(s, 6H, CH3), 5.49 (m, 2H, C5H3), 5.80 (m, 2H, C5H3),
5.93 (m, 2H, C5H3), 6.99 (m, 2H, HpC6H5), 7.09 (m,
4H, HmC6H5), 7.16 (m, 4H, HoC6H5). 13C NMR (75
MHz, C6D6, 25 ꢁC): 16.1 (CH3), 34.1 (Zr–CH3), 107.6
4.5. Synthesis of [Zr(g5-C5H5){g5-(1-Ph-3-Me-C5H3)}Cl2] (5)
Toluene (100 ml) was added to a mixture of the lith-
ium salt 1 (3.00 g, 18.40 mmol) and [Zr(g5-C5H5)Cl3 Æ
DME] (6.52 g, 18.40 mmol) at ꢀ78 ꢁC. The mixture
was allowed to warm to room temperature and stirred
for 12 h. The yellow solution was filtered and after re-
moval of the solvent under vacuum, the residue was
washed with hexane (60 ml) and dried under vacuum
to give complex 5 as a yellow solid (5.62 g, 14.70 mmol,
1
79%). H NMR (300 MHz, CDCl3, 25 ꢁC): 2.32 (s, 3H,
CH3), 6.18 (s, 5H, C5H5), 6.18 (m, 1H, C5H3), 6.65 (m,
1H, C5H3), 6.73 (m, 1H, C5H3), 7.30 (m, 1H, HpC6H5),
7.42 (m, 2H, HmC6H5), 7.53 (m, 2H, HoC6H5). 13C
NMR (75 MHz, CDCl3, 25 ꢁC): 15.6 (CH3), 110.9
(C5H3), 116.5 (C5H5), 117.2 (C5H3), 117.8 (C5H3),
125.8 (CmC6H5), 125.9 (Cipso-MeC5H3), 127.8 (CpC6H5),
(C5H3), 110.2 (C5H3), 113.8 (C5H3), 124.5 (Cipso
-
Me,C5H3), 125.3 (CmC6H5), 127.2 (CpC6H5), 129.5
(Cipso-PhC5H3), 129.6 (CoC6H5), 136.2 (Cipso-C6H5).
Anal. Calc. for C26H28Zr: C, 72.33; H, 6.54. Found:
C, 71.90; H, 5.93%.
129.2 (CoC6H5), 129.3 (Cipso-PhC5H3), 133.8 (Cipso
C6H5). Anal. Calc. for C17H16Cl2Zr: C, 53.39; H, 4.22
-
Found: C, 52,91; H, 4.18%.
4.4. Synthesis of [Zr{g5-(1-Ph-3-Me-C5H3)}2(CH2Ph)2]-
(meso-4+rac-4)
4.6. Synthesis of [Zr(g5-C5H5){g5-(1-Ph-3-Me-C5H3)}
Me2] (6)
A 2 M THF solution of MgClBz (0.70 ml, 1.40 mmol)
was added at ꢀ78 ꢁC to a solution of 2 (rac and meso)
(0.25 g, 0.53 mmol) in diethyl ether (50 ml). The reaction
mixture was stirred for 12 h while it was warmed slowly
to room temperature. The solvent was removed under
vacuum and the residue was extracted into hexane (50
ml). The yellow solution was filtered and concentrated
to 10 ml under vacuum and cooled to ꢀ30 ꢁC to give
a mixture of meso-4 and rac-4 in a molar ratio 1:0.5 as
a yellow crystalline solid which was collected by filtra-
tion and dried under vacuum (0.21 g, 0.40 mmol,
A 1.6 M Et2O solution of methyllithium (1.00 ml,
1.60 mmol) was added at ꢀ78 ꢁC to a solution of 5
(0.41 g, 1.17 mmol) in diethyl ether (20 ml). The reaction
mixture was stirred for 12 h while it was warmed slowly
to room temperature. The solvent was removed under
vacuum and the residue was extracted into hexane (40
ml). The colourless solution was filtered and after re-
moval of the solvent under vacuum, complex 6 was col-
lected as a colourless oil and dried under vacuum (0.23
g, 0.70 mmol, 64%). 1H NMR (300 MHz, C6D6, 25
ꢁC): ꢀ0.14 (s, 3H, Zr-CH3), ꢀ0.12 (s, 3H, Zr-CH3),
1.97 (s, 3H, CH3), 5.62 (s, 5H, C5H5), 5.70 (m, 1H,
C5H3), 5.90 (m, 1H, C5H3), 5.97 (m, 1H, C5H3), 6.95
(t, 1H, J=7.2, HpC6H5), 7.08 (t, 2H, J=7.3, HmC6H5),
7.16 (d, 2H, J=7.2, HoC6H5). 13C NMR (75 MHz,
C6D6, 25 ꢁC): 15.2 (CH3), 31.0 (Zr-CH3), 31.4 (Zr-
CH3), 105.0 (C5H3), 109.2 (C5H3), 111.2 (C5H5), 112.9
(C5H3), 124.4 (CmC6H5), 125.0 (Cipso-MeC5H3), 126.7
(CpC6H5), 128.8 (CoC6H5), 128.9 (Cipso-PhC5H3), 135.3
(Cipso-C6H5). Anal. Calc. for C19H22Zr: C, 66.81; H,
6.49. Found: C, 66.94; H, 6.72%.
1
71%). meso-4: H NMR (300 MHz, C6D6, 25 ꢁC): 1.67
(m, 2H, CH2-Ph), 1.75 (m, 2H, CH2-Ph), 1.98 (s, 6H,
CH3), 5.54 (m, 2H, C5H3), 5.71 (m, 2H, C5H3), 5.91
(m, 2H, C5H3), 6.98 (m, 4H, C6H5), 7.05 (m, 8H,
C6H5), 7.25 (m, 8H, C6H5). 13C NMR (75 MHz,
C6D6, 25 ꢁC): 14.6 (CH3), 65.8 (Zr-CH2-Ph), 66.6 (Zr-
CH2-Ph), 110.7 (C5H3), 113.4 (C5H3), 114.7 (C5H3),
121.5 (Cipso-MeC5H3), 125.5 (C6H5), 126.2 (C6H5),
126.7 (C6H5), 127.6 (C6H5), 128.3 (C6H5), 128.4
(C6H5), 128.6 (Cipso-PhC5H3), 135.1 (Cipso-C6H5),
152.9 (Cipso-CH2-Ph). rac-4: 1H NMR (300 MHz,
C6D6, 25 ꢁC): 1.75 (m, 4H, CH2-Ph), 1.98 (s, 6H,
CH3), 5.54 (m, 2H, C5H3), 5.76 (m, 2H, C5H3), 5.91
(m, 2H, C5H3), 7.04 (m, 4H, C6H5), 7.07 (m, 8H,
C6H5), 7.22 (m, 8H, C6H5). 13C NMR (75 MHz,
C6D6, 25 ꢁC): 14.8 (CH3), 64.1 (Zr-CH2-Ph), 111.1
4.7. Synthesis of [Zr(g5-C5H5){g5-(1-Ph-3-Me-
C5H3)}(CH2Ph)2] (7)
A 2 M THF solution of MgCl(CH2Ph) (1.90 ml, 1.90
mmol) was added at ꢀ78 ꢁC to a solution of 5 (0.41 g,
1.17 mmol) in diethyl ether (20 ml). The reaction mix-
ture was stirred for 12 h while it was warmed slowly
to room temperature. The solvent was removed under
vacuum and the residue was extracted into hexane (50
ml). The yellow solution was filtered, concentrated to
(C5H3), 112.9 (C5H3), 115.1 (C5H3), 124.3 (Cipso
-
MeC5H3), 125.2 (C6H5), 126.4 (C6H5), 127.1 (C6H5),
128.5 (C6H5), 128.8 (C6H5), 128.9 (Cipso-PhC5H3),
135.0 (Cipso-C6H5), 153.1 (Cipso-CH2-Ph). Anal. Calc.
for C38H36Zr: C, 78.16; H, 6.21. Found: C, 78.35; H,
5.93%.

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4403
10 ml under vacuum and cooled to ꢀ30 ꢁC to give com-
plex 7 as a yellow crystalline solid which was dried under
vacuum (0.71 g, 1.30 mmol, 73%). 1H NMR (300 MHz,
C6C6, 25 ꢁC): 1.81 (d, 1H, J=10.7, CH2-Ph), 1.87 (2d,
2H, J=10.7, CH2-Ph), 1.87 (s, 3H, CH3), 1.95 (d, 1H,
J=10.7, CH2-Ph), 5.46 (s, 5H, C5H5), 5.71 (m, 1H,
C5H3), 5.79 (m, 1H, C5H3), 5.93 (m, 1H, C5H3), 6.91
(m, 4H, C6H5), 7.00 (m, 4H, C6H5), 7.08 (m, 3H,
C6H5), 7.21 (m, 4H, C6H5). 13C NMR (75 MHz, C6C6,
25 ꢁC): 14.9 (CH3), 61.4 (Zr-CH2-Ph), 62.2 (Zr-CH2-
Ph), 106.8 (C5H3), 111.7 (C5H3), 113.6 (C5H5), 115.6
(C5H3), 121.3 (C6H5), 123.5 (Cipso-MeC5H3), 124.5
(C6H5), 124.8 (C6H5), 126.3 (C6H5), 126.1 (C6H5),
127.1 (C6H5), 128.5 (C6H5), 128.9 (Cipso-PhC5H3),
ꢁC): 0.62 (s, 6H, SiCH3), 0.68 (s, 6H, SiCH3), 2.17 (s,
3H, CH3), 2.39 (s, 3H, CH3), 6.15 (d, 1H, J=2.0,
C5H2), 6.29 (d, 1H, J=2.3, C5H2), 6.32 (d, 1H, J=2.0,
C5H2), 6.55 (d, 1H, J=2.3, C5H2), 6.94 (m, 2H, C6H5),
7.27 (m, 4H, C6H5), 7.56 (m, 4H, C6H5). Anal. Calc.
for C28H32Li2Si2O: C, 73.98; H, 7.09. Found: C, 73.23;
H, 6.44%.
4.10. Synthesis of [Zr{g5-(2-Me-4-Ph-C5H2SiMe2)2O}-
Cl2] (meso-10a+rac-10a) and [Zr{g5-(2-Me-4-Ph-
C5H2)[(SiMe2)2O](g5-(2-Ph-4-Me-C5H2)}Cl2] (10b)
4.10.1. Method a
Toluene (20 ml) was added to a mixture of the dilith-
ium salt 9a (1.48 g, 3.25 mmol) and ZrCl4 Æ2THF (1.22 g,
3.25 mmol) cooled at ꢀ78 ꢁC. The light yellow suspen-
sion was allowed to warm to room temperature and stir-
red for 12 h. After filtration of the LiCl, the solution was
concentrated to 15 ml and cooled to ꢀ30 ꢁC to give a
yellow crystalline solid (1.03 g, 1.72 mmol, 53%) identi-
fied as a mixture of two diastereomers (meso-10a, rac-
10a) in a molar ratio 6:1. Repeated recrystallization into
toluene allowed pure samples of meso-10a to be isolated,
whereas rac-10a was always contaminated by small
134.7 (Cipso-C6H5), 152.6 (Cipso-CH2-Ph), 153.6 (Cipso
CH2-Ph). Anal. Calc. for C31H30Zr: C, 75.40; H, 6.12.
-
Found: C, 74.93; H, 5.91%.
4.8. Synthesis of [(Me-Ph-C5H3SiMe2)2O] (8)
A solution of (Me2SiCl)2O (2.41 ml, 12.30 mmol) in
dry diethyl ether (50 ml) was added dropwise to a solu-
tion of 2 equivalents of the lithium salt 1 (4.00 g, 24.60
mmol) in THF (20.0 ml) at 0 ꢁC. After the addition was
complete, the mixture was allowed to warm gradually to
room temperature and then stirred for 12 h. The sol-
vents were removed under vacuum and the residue ex-
tracted into hexane and filtered to give a yellow
solution. The hexane was then removed under vacuum
to give a yellow oil characterized as compound 8 (4.32
1
amounts of meso-10a. meso-10a: H NMR (300 MHz,
CDCl3, 25 ꢁC): 0.39 (s, 6H, SiCH3), 0.51 (s, 6H, SiCH3),
2.40 (s, 6H, CH3), 6.74 (d, 2H, J=2.4, C5H2), 6.86 (d,
2H, J=2.4, C5H2), 7.11 (m, 10H, C6H5). 13C NMR
(75 MHz, CDCl3, 25 ꢁC): 1.6 (SiCH3), 2.7 (SiCH3),
18.3 (CH3), 113.2 (C5H2), 117.2 (Cipso-SiC5H2), 121.9
(C5H2), 125.7 (CoC6H5), 127.6 (CpC6H5), 128.4
(CmC6H5), 132.1 (Cipso-MeC5H2), 133.2 (Cipso-PhC5H2),
142.0 (Cipso-C6H5). rac-10a: 1H NMR (300 MHz,
CDCl3, 25 ꢁC): 0.29 (s, 6H, SiCH3), 0.38 (s, 6H, SiCH3),
2.40 (s, 6H, CH3), 6.46 (d, 2H, J=2.2, C5H2), 6.84 (d,
2H, J=2.4, C5H2), 7.24 (m, 2H, HpC6H5), 7.33 (m,
4H, HmC6H5), 7.59 (m, 4H, HoC6H5). 13C NMR (75
MHz, CDCl3, 25 ꢁC): 1.6 (SiCH3), 2.2 (SiCH3), 17.8
(CH3), 113.2 (C5H2), 116.1 (Cipso-SiC5H2), 121.5
(C5H2), 126.8 (CoC6H5), 127.7 (CpC6H5), 128.2
(CmC6H5), 132.5 (Cipso-MeC5H2), 132.7 (Cipso-PhC5H2),
136.5 (Cipso-C6H5). Anal. Calc. for C28H32Si2OCl2Zr: C,
55.79; H, 5.35. Found: C, 55.48; H, 5.40.f
1
g, 9.50 mmol, 77%). H NMR (300 MHz, CDCl3, 25
ꢁC): ꢀ0.25/ꢀ0.15 (SiCH3), 1.96/2.10 (CH3), 3.18/3.39
(H Csp3) 5.93/6.67 (H Csp2) 7.17/7.45 (H Ph).
4.9. Synthesis of Li2[(Me-Ph-C5H2SiMe2)2O] (9)
A 1.6 M hexane solution of n BuLi (24.26 ml, 39.30
mmol) was added at ꢀ78 ꢁC to a stirred solution of 8
(8.70 g, 19.60 mmol) in diethyl ether (400 ml). The mix-
ture was allowed to warm to room temperature and stir-
red for 4 h. The resulting insoluble lithium salt was
filtered, washed with hexane (150 ml) and dried under
vacuum to give a white solid characterized as the isomer
9a (2.80 g, 6.26 mmol, 32%). Following an alternative
method the solvent was removed under vacuum from
the suspension obtained after stirring for 4h without
previous separation of 9a. The resulting solid residue
was washed with hexane (2·100 ml) and dried under
vacuum to give a yellowish solid characterized as a mix-
ture of the 9a and 9b isomers in a molar ratio 3:1 (5.36 g,
4.10.2. Method b
The same procedure described in method a) was fol-
lowed using the mixture of the lithium salts 9a and 9b to
give a mixture containing meso-10a, rac-10a and 10b in a
molar ratio 1:0.6:0.7. Pure samples of 10b could not be
1
isolated by repeated recrystallization into toluene. H
1
1.78 mmol, 60%). H NMR for 9a (300 MHz, pyridine-
NMR for 10b (300 MHz, CDCl3, 25 ꢁC): ꢀ0.05 (s,
3H, SiCH3), 0.33 (s, 3H, SiCH3), 0.40 (s, 3H, SiCH3),
0.60 (s, 3H, SiCH3), 1.51 (s, 3H, CH3), 2.27 (s, 3H,
CH3), 6.27 (d, 1H, J=2.3, C5H2), 6.50 (d, 1H, J=2.3,
C5H2), 6.78 (d, 1H, J=2.3, C5H2), 7.14 (d, 1H, J=2.3,
C5H2), 7.24 (m, 2H, HpC6H5), 7.33 (m, 4H, HmC6H5),
d5/benzene-d6, 25 ꢁC): 0.64 (s, 12H, SiCH3), 2.56 (s, 6H,
CH3), 6.11 (d, 2H, J=1.8, C5H2), 6.71 (d, 2H, J=2.3,
C5H2), 6.79 (t, 2H, J=8.0, HpC6H5), 7.08 (t, 4H,
J=9.8, HmC6H5), 7.52 (d, 4H, J=8.2, HoC6H5). 1H
NMR for 9b (300 MHz, pyridine-d5/benzene-d6, 25

´
G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4404
7.61 (m, 4H, HoC6H5). 13C NMR for 10b (75 MHz,
CDCl3, 25 ꢁC): 0.8 (SiCH3), 1.4 (SiCH3), 3.2 (SiCH3),
3.3 (SiCH3), 15.2 (CH3), 18.1 (CH3), 115.5 (C5H2),
117.7 (Cipso-SiC5H2), 119.8 (Cipso-SiC5H2), 122.0
(C5H2), 122.9 (C5H2), 123.7 (C5H2), 126.0 127.4, 127.8,
128.0, 128.6, 143.1 (C6H5), 130.1 (Cipso-MeC5H2),
135.0 (Cipso-MeC5H2), 160.4 (Cipso-PhC5H2), 166.8
(Cipso-PhC5H2).
C6H5). 13C NMR (75 MHz, C6D6, 25 ꢁC): 1.9 (SiCH3),
2.7 (SiCH3), 17.2 (CH3), 39.3 (Zr-CH3), 41.2 (Zr-CH3),
107.9 (C5H2), 117.6 (Cipso-SiC5H2), 125.4 (C5H2),
126.8 (CoC6H5), 128.6 (CpC6H5), 129.6 (CmC6H5),
132.6 (Cipso-MeC5H2), 134.5 (Cipso-PhC5H2), 147.9
(Cipso-C6H5). Anal. Calc. for C30H38Si2OZr: C, 64.11;
H, 6.81. Found: C, 64.08; H, 6.78.
4.13.
Me2)2O}(CH2Ph)2] (meso-13)
Synthesis
of
[Zr{g5-(2-Me-4-Ph-C5H2Si-
4.11.
Me2)2O}Cl2] (meso-11a+rac-11a)
Synthesis
of
[Hf{g5-(2-Me-4-Ph-C5H2Si-
A 2 M THF solution of MgClBz (1.60 ml, 3.20
mmol) was added to a solution of meso-10 (1.00 g,
1.65 mmol) in ethyl ether (20 ml). The reaction mixture
was stirred for 12 h, the solvent was removed under
vacuum and the residue was extracted into hexane
(30 ml). After filtration, the solvent was removed at re-
duced pressure and the residue was dried under vacu-
um to give a yellow oil characterized as meso-13
(0.55 g, 0.77 mmol, 47%). 1H NMR (300 MHz,
C6D6, 25 ꢁC): 0.31 (s, 6H, SiCH3), 0.34 (s, 6H, SiCH3),
1.32 (m, 2H, CH2-Ph), 1.79 (m, 2H, CH2-Ph), 2.00 (s,
6H, CH3), 6.31 (d, 2H, J=2.4, C5H2), 6.52 (d, 2H,
J=2.4, C5H2), 6.84 (m, 2H, C6H5 and CH2-Ph), 7.00
(m, 4H, C6H5 and CH2-Ph), 7.07 (m, 6H, C6H5 and
CH2-Ph), 7.25(m, 8H, C6H5 and CH2-Ph). 13C NMR
(75 MHz, C6D6, 25 ꢁC): 1.6 (SiCH3), 2.2 (SiCH3),
16.8 (CH3), 70.2 (Zr-CH2Ph), 71.6 (Zr-CH2Ph), 109.4
(CH2-Ph), 114.2 (C5H2), 117.4 (Cipso-SiC5H2), 121.9
(C5H2), 122.6 (CH2-Ph), 126.4 (CoC6H5), 126.9
(CH2-Ph), 127.2 (CH2-Ph), 127.5 (CpC6H5), 127.6
(CH2-Ph), 127.8 (CH2-Ph), 128.1 (CH2-Ph), 128.5
(CH2-Ph), 128.7 (CmC6H5), 132.1 (Cipso-MeC5H2),
134.1 (Cipso-PhC5H2), 135.9 (Cipso-CH2-Ph), 151.7
(Cipso-C6H5), 152.8 (Cipso-CH2-Ph). Anal. Calc. for
C42H46Si2OZr: C, 70.63; H, 6.49. Found: C, 70.56;
H, 6.43.
The same procedure described to prepare 10 from a
mixture of the lithium salts 9a and 9b was followed using
HfCl4 (1.04 g, 3.25 mmol) to obtain the ansa-metallo-
cene 11a as a yellow crystalline solid (0.90 g, 1.30 mmol,
58%) containing a mixture of two diastereomers (meso-
11a and rac-11a) in a molar ratio 3:1, which was in-
creased to 15:1 after repeated recrystallization into tolu-
ene. meso-11a: 1H NMR (300 MHz, CDCl3, 25 ꢁC): 0.37
(s, 6H, SiCH3), 0.48 (s, 6H, SiCH3), 2.38 (s, 6H, CH3),
6.73 (d, 2H, J=2.4, C5H2), 6.84 (d, 2H, J=2.4, C5H2),
7.01 (m, 10H, C6H5). 13C NMR (75 MHz, CDCl3, 25
ꢁC): 1.5 (SiCH3), 2.8 (SiCH3), 18.1 (CH3), 113.3
(C5H2), 117.7 (Cipso-SiC5H2), 122.1 (C5H2), 125.7
(CoC6H5), 127.6 (CpC6H5), 128.4 (CmC6H5), 132.1
(Cipso-MeC5H2), 142.1 (Cipso-PhC5H2), 170.0 (Cipso-C6H5).
1
rac-11a: H NMR (300 MHz, CDCl3, 25 ꢁC): 0.35 (s,
6H, SiCH3), 0.44 (s, 6H, SiCH3), 2.37 (s, 6H, CH3),
6.46 (d, 2H, J=2.2, C5H2), 6.85 (d, 2H, J=2.3, C5H2),
7.24 (m, 2H, HpC6H5), 7.33 (m, 4H, HmC6H5), 7.61
(m, 4H, HoC6H5). 13C NMR (75 MHz, CDCl3, 25 ꢁC):
1.7 (SiCH3), 2.1 (SiCH3), 17.7 (CH3), 113.3 (C5H2),
117.2 (Cipso-SiC5H2), 121.6 (C5H2), 126.8 (CoC6H5),
127.8 (CpC6H5), 128.8 (CmC6H5), 133.3 (Cipso-MeC5H2),
147.3 (Cipso-PhC5H2), 157.2 (Cipso-C6H5). Anal. Calc.
for C28H32Si2OCl2Hf: C, 48.73; H, 4.67. Found: C,
48.32; H, 4.67.
4.14.
Me2)2O}Me2] (meso-14)
Synthesis
of
[Hf{g5-(2-Me-4-Ph-C5H2Si-
4.12.
Me2)2O}Me2] (meso-12)
Synthesis
of
[Zr{g5-(2-Me-4-Ph-C5H2Si-
The same procedure described to prepare meso-12
was followed using a 1.6 M Et2O solution of methyllith-
ium (1.80 ml, 2.89 mmol) and meso-11 containing small
amounts of rac-11 (molar ratio 15:1) (1.00 g, 1.44 mmol)
in 20 ml of ethyl ether, to give pure meso-14 after recrys-
tallization, as a white solid (0.53 g, 0.81 mmol, 57%). 1H
NMR (300 MHz, C6D6, 25 ꢁC): ꢀ0.45 (s, 3H, Hf-CH3),
ꢀ0.12 (s, 3H, Hf-CH3), 0.32 (s, 6H, SiCH3), 0.37 (s, 6H,
SiCH3), 2.11 (s, 6H, CH3), 6.10 (d, 2H, J=2.4, C5H2),
6.65 (d, 2H, J=2.4, C5H2), 7.00 (m, 2H, HpC6H5),
7.02 (m, 4H, HmC6H5), 7.52 (m, 4H, HoC6H5). 13C
NMR (75 MHz, C6D6, 25 ꢁC): 1.8 (SiCH3), 2.6 (SiCH3),
17.1 (CH3), 39.2 (Zr-CH3), 41.1 (Zr-CH3), 107.7 (C5H2),
17.4 (Cipso-SiC5H2), 125.2 (C5H2), 126.6 (CoC6H5), 128.1
(CpC6H5), 128.4 (CmC6H5), 132.5 (Cipso-MeC5H2), 134.3
A 1.6 M Et2O solution of methyllithium (2.10 ml,
3.36 mmol) was added at ꢀ78 ꢁC to a solution of
meso-10 (1.00 g, 1.65 mmol) in 20 ml of ethyl ether.
The reaction mixture was stirred for 12 h while it was
warmed slowly to room temperature. The solvent was
removed under vacuum and the residue was extracted
into hexane (30 ml). After filtration of the LiCl, the so-
lution was concentrated to 10 ml under vacuum and
cooled to ꢀ30 ꢁC to give meso-12 as a white crystalline
solid (0.57g, 1.02 mmol, 62%). 1H NMR (300 MHz,
C6D6, 25 ꢁC): ꢀ0.46 (s, 3H, Zr-CH3), ꢀ0.13 (s, 3H,
Zr-CH3), 0.29 (s, 6H, SiCH3), 0.36 (s, 6H, SiCH3),
2.21 (s, 6H, CH3), 6.05 (d, 2H, J=2.4, C5H2), 6.61 (d,
2H, J=2.4, C5H2), 6.97 (m, 4H, C6H5), 7.08 (m, 6H,

´
G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4405
Table 2
Summary of crystal data and structure refinement parameters for rac-
10a
(Cipso-PhC5H2), 147.0 (Cipso-C6H5). Anal. Calc. for
C30H38Si2OHf: C, 55.50; H, 5.90. Found: C, 55.48; H,
5.89%.
Empirical formula
C28H32Cl2OSi2Zr
4.15.
Me2)2O}(CH2Ph)2] (meso-15)
Synthesis
of
[Hf{g5-(2-Me-4-Ph-C5H2Si-
Formula weight
Temperature (K)
602.84
293(2)
Monoclinic/P21/n
Crystal system/space group
Unit cell dimensions
The same procedure described to prepare meso-14
was followed using a 2 M THF solution of MgClBz
(1.45 ml, 2.90 mmol) and meso-11 (1.00 g, 1.44 mmol)
in diethyl ether (20 ml) to give meso-15 as a yellow-or-
ange oil (0.63 g, 0.79 mmol; 55%). 1H NMR (300
MHz, C6D6, 25 ꢁC): 0.37 (s, 6H, SiCH3), 0.39 (s, 6H,
SiCH3), 1.89 (m, 2H, CH2-Ph), 2.10 (m, 2H, CH2-
Ph), 2.30 (s, 6H, CH3), 6.41 (m, 4H, C5H2), 6.99 (m,
8H, C6H5), 7.05 (m, 4H, C6H5), 7.12 (m, 8H, C6H5).
13C NMR (75 MHz, C6D6, 25 ꢁC): 1.8 (SiCH3), 2.9
(SiCH3), 18.1 (CH3), 66.0 (Zr-CH2Ph), 67.1 (Zr-
˚
a (A)
12.2763(19)
18.377(3)
12.7789(8)
˚
b (A)
˚
c (A)
b (ꢁ)
Volume (A )
Z, calculated density (g/cm3)
,100.072(7)
2838.5(7)
3
˚
4, 1.411
0.71073
Radiation Mo Ka
Absorption coefficient (mmꢀ1
F(000)
)
0.679
1240
3.07–27.50
H Range for data collection (ꢁ)
Limiting indices
ꢀ15 6 h 6 15,ꢀ23 6 k 6 23,
ꢀ16 6 l 6 16
53475/6445 [0.1456]
98.9%
Reflections collected/unique [Rint
Completeness to theta=27.50
Absorption correction
]
CH2Ph), 108.2 (CH2-Ph), 111.3 (C5H2), 118.9 (Cipso
-
SiC5H2), 120.1 (C5H2), 121.9 (CH2-Ph), 125.5
(CoC6H5), 126.0 (CH2-Ph), 127.5 (CH2-Ph), 127.8
(CpC6H5), 128.1 (CH2-Ph), 128.4 (CH2-Ph), 128.6
(CH2-Ph), 129.6 (CH2-Ph), 130.1 (CmC6H5), 133.1
Analytical
Max. and min. transmission
Data/restrains/parameters
Goodness-of-fit
0.792 and 0.724
6445/0/307
1.066
Final R indices [I > 2r(I)]
R indices (all data)
Largest diff. peak and hole (e A )
R1 =0.0460, wR2 =0.0918
R1 =0.0891, wR2 =0.1113
0.534 and ꢀ0.551
(Cipso-MeC5H2), 138.6 (Cipso-PhC5H2), 139.8 (Cipso
-
3
CH2-Ph), 141.8 (Cipso-C6H5), 150.8 (Cipso-CH2-Ph).
Anal. Calc. for C42H46Si2OHf: C, 62.94; H, 5.78.
Found: C, 63.10; H, 5.60%.
˚
4.16. X-ray crystallographic study of rac-10a
the zirconocene catalyst. The reaction was stopped by
addition of 5 ml of acidified methanol (1:1 HCl/metha-
nol). Polymers were recovered by filtration, washed with
methanol and dried under vacuum at 80 ꢁC for 1 d. The
molecular weight of the resulting polyethylene was eval-
uated by GPC.
A similar procedure was followed for propene polym-
erization using a glass autoclave equipped with a heating
bath, mechanical stirrer and connection to argon-
vacuum lines. The reactor was charged at 25 ꢁC with
600 ml of freshly distilled heptane and 10.0 ml of a
10% toluene solution of MAO (MAO/Zr=1500) and
then saturated with propene at 5.0 bar and thermostat-
ted at variable temperatures. Polymerization was started
by injection of 0.01 mmol of the zirconocene catalyst
from a previously prepared toluene solution. The poly-
mer was recovered and treated as described above.
Suitable single crystals for the X-ray diffraction study
were grown by standard techniques from a saturated
solution of rac-10a in toluene. Crystal colour, shape
and size were yellow, prism, and 0.96 · 0.41 · 0.34 mm,
respectively. X-ray data were collected on a Kappa-
CCD area detecting diffraction system using a Mo Ka
radiation (See Table 2). The unit cell was determined from
172 reflections. Crystal structure was solved by direct
methods (SIR 92 [21]) and refined using full-matrix least
squares on F2 (SHELXL 97 [22]). All non-hydrogen atoms
were anisotropically refined. Hydrogen atoms were geo-
metrically placed and left riding on their parent atoms.
The racemic mixture of both enantiomers was observed.
4.17. Polymerization procedures
Polymerizations were carried out in a glass reactor
equipped with a heating bath, magnetic stirrer and
connection to argon-vacuum lines. The reactor was
evacuated, flushed several times with argon and then
charged at 25 ꢁC with 40 ml of freshly distilled toluene
and 4.0 ml of a 10% toluene solution of MAO (MAO/
Zr=1500). The solution was saturated with ethene at
1.0 bar and thermostatted at variable temperatures.
Polymerization was started by injection of 1.0 ml of a
previously prepared 4.4·10ꢀ3 M toluene solution of
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 237160 for rac-10a. Copies
of this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44-1223-366-033; e-mail: depos-
it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).

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G. Martınez et al. / Journal of Organometallic Chemistry 689 (2004) 4395–4406
4406
[7] J. Gra¨per, R.D. Fischer, G. Paolucci, J. Organomet. Chem. 471
(1994) 87.
Acknowledgement
[8] S.-S. Xu, T. Wu, H.-L. Cui, X.-L. Dai, B.-Q. Wang, X.-Z. Zou,
Y. Li, Chem. J. Chin. Univ. 23 (2002) 1891.
We gratefully acknowledge Ministerio de Ciencia y
´
Tecnologıa (project MAT2001-1309) for financial sup-
port. G.M. acknowledges Repsol-YPF and MECD for
[9] M.D. Curtis, J.J. DꢀErrico, D.N. Duffy, P.S. Epstein, L.G. Bell,
Organometallics 2 (1983) 1808.
[10] W. Song, K. Shackett, J.C.W. Chien, M.D. Rausch, J. Organo-
met. Chem. 501 (1995) 375.
´
Fellowships. We thank T. Exposito (CSIC) for determi-
nation of molecular weights of polyethylene.
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(1996) 181.
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