Hydrazonide titanium derivatives synthesis, characterization and catalytic activity in olefin polymerization molecular structure of (Ti(η5-C5H4SiMe3)Cl(μ- N2CPh2)]2

Article abstract of DOI:10.1016/S0022-328X(02)01733-3

Reaction of the mixed dicyclopentadienyl titanium compound in toluene at -78 °C, gives the hydrazonide(1-) derivatives ('metalloazine') Ti(h⁵-C₅Me ₅) (C₅H₅)Cl[N(H)NCPh₂] and Ti(η⁵

Full text of DOI:10.1016/S0022-328X(02)01733-3

Journal of Organometallic Chemistry 663 (2002) 173ꢃ182
/
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Hydrazonide titanium derivatives
Synthesis, characterization and catalytic activity in olefin
polymerization. Molecular structure of [Ti(h5-C5H4SiMe3)Cl(m-
N2CPh2)]2
Vanessa Tabernero a, Toma´s Cuenca a,ꢀ, Eberhardt Herdtweck b
a
´
´
´
´
Departamento de Quımica Inorganica, Edificio de Farmacia, Universidad de Alcala, Campus Universitario, 28871 Alcala de Henares, Spain
b Anorganisch-chemisches Institut, Technische Universitat Munchen, Lichtenbergstrasse 4, D-85747 Garching bei Munchen, Germany
¨
¨
¨
Received 3 June 2002; accepted 18 July 2002
Dedicated to Professor Pascual Royo on the occasion of his 65th birthday
Abstract
Reaction of the mixed dicyclopentadienyl titanium compound Ti(h5-C5Me5)(C5H5)Cl2 with LiN(H)NCPh2, in toluene at ꢁ
78 8C, gives the hydrazonide(1ꢁ
derivatives (‘metalloazine’) Ti(h5-C5Me5)(C5H5)Cl[N(H)NCPh2] and Ti(h5-
C5Me5)(C5H5)[N(H)NCPh2]2 in high yield. The titanium trichloro compound Ti[h5-C5H4(SiMe2Cl)]Cl3 reacts with hydrazone
[H2NꢀNꢁCPh2] in the presence of one equivalent of NEt3 to afford the hydrazonide(1ꢁ
) compound Ti[h5-C5H4(Si-
Me2Cl)]Cl2[N(H)NCPh2)], while in the presence of two equivalents of NEt3 the cyclopentadienyl-amido derivative Ti[h5-
/
/
)
/
/
/
C5H4(SiMe2ꢀ
/
h1-NNCPh2)]Cl2 is obtained. Mono-hydrazonide(1ꢁ
/
) compounds Ti(CpR)Cl2[N(H)NCPh2)] [CpRꢂ
h5-C5Me5,
/
h5-C5H4(SiMe3)] were synthesized by treatment of the corresponding monocyclopentadienyl trichloro derivatives Ti(CpR)Cl3 with
hydrazone in the presence of one equivalent of NEt3. The dinuclear complex [Ti(h5-C5H4SiMe3)Cl(m-N2CPh2)]2 has been prepared
by reaction of Ti(h5-C5H4SiMe3)Cl2[N(H)NCPh2)] with NEt3 in toluene and alternatively by reaction of Ti(h5-C5H4SiMe3)Cl3 with
hydrazone and two equivalents of NEt3. The molecular structure of [Ti(h5-C5H4SiMe3)Cl(m-N2CPh2)]2 was determined by single-
crystal X-ray diffraction methods and contains two [Ti(h5-C5H4SiMe3)Cl] units bridged by two hydrazonide(2ꢁ
/
) ligands which
form a symmetrical ‘Ti2(NN)2’ core. These hydrazonide compounds have been activated with MAO and are suited to olefin
polymerization.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Hydrazonide; Cyclopentadienyl-amido; Titanium; Olefin polymerization
1. Introduction
which the formally 14-electron cationic active species
[MCp2?R]ꢄ is generated in the presence of a cocatalyst
[1,2]. Monocyclopentadienyl compounds MCp?X3 have
also been used with success in the polymerization of
different types of olefins [3]. The electronically less
saturated and sterically less hindered 10-electron catio-
nic species [MCp?R2]ꢄ might exhibit even higher
activities than the dicyclopentadienyl species. Another
family of compounds are the cyclopentadienyl-amido
complexes which, in recent years, have gained wide-
spread importance as catalysts for the polymerization
and copolymerization of olefins [4]. The search for a
new a-olefin polymerization catalyst based on non-
Cyclopentadienyl titanium and zirconium derivatives
represent the most versatile class of organometallic
compounds as homogeneous ZieglerꢃNatta olefin poly-
merization catalysts. The most successful precursor
catalysts are the dicyclopentadienyl derivatives
/
MCp2?X2 (Mꢂ
/
Ti, Zr; Cp?ꢂ
/
substituted or unsubsti-
halo, alkyl), from
tuted h5-cyclopentadienyl ligand; Xꢂ
/
ꢀ Corresponding author. Tel.:
8854683
E-mail address: tomas.cuenca@uah.es (T. Cuenca).
ꢄ
/
34-91-8854655; fax:
ꢄ/34-91-
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 7 3 3 - 3

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V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ182
/
cyclopentadienyl Group 4 metal complexes is a field of
recent and increased interest involving academic and
industrial research groups [5]. Octahedral zirconium
complexes in particular were found to promote olefin
polimerization, inducing tacticity in the resulting poly-
mers [6].
We have recently reported an efficient and versatile
alternative strategy to prepare cyclopentadienyl-amido
derivatives via the reaction of primary amines [7] with
the chlorosilyl-substituted cyclopentadienyl compound
[Ti(h5-C5H4SiMe2Cl)Cl3] [8] in the presence of a base
(NEt3). Similar reactions with diamines afforded a new
type of cyclopentadienyl-amido complex bearing a
pendant NHR functionality [9]. Part of our current
interest is to extend this synthetic methodology to
produce new types of amido and linked cyclopentadie-
nyl-amido Group 4 metal compounds.
Scheme 1.
isolated as a pale orange solid in 61% yield (Scheme 2).
Here we report the synthesis of titanium hydrazonide
derivatives (‘metalloazines’) by reaction of Ti(CpR)Cl3
These results allow us to suggest that the Tiꢀ
/Cl bond
(CpRꢂ
with hydrazone H2Nꢀ
Alternatively, hydrazonide compounds can be synthe-
sized by ligand metathesis between
Ti(h5-
/
h5-C5H4SiMe2Cl, h5-C5(CH3)5, h5-C5H4SiMe3)
/ /
undergoes a selective aminolysis reaction with hydra-
zone to give the amido titanium derivative 3.
Nꢁ
CPh2 in the presence of NEt3.
Selective reactivity of the Mꢀ
polar lithium amide has also been described, while
similar reactivity of both SiꢀCl and TiꢀCl bonds with
/
Cl bond toward highly
/
/
C5Me5)(C5H5)Cl2 and LiN(H)NCPh2. The activation
of such complexes with methylaluminoxane (MAO)
should produce catalytic properties in the olefin poly-
merization process. Results on olefin polymerization
using these derivatives as precursor catalysts and the
characterization of the polyolefins obtained are also
reported.
water and amine reagents was previously observed for
other titanium and zirconium derivatives [8]. From
compound
compound 6 is formed by subsequent elimination of
HCl after aminolysis of the SiꢀCl bond, mediated by
the presence of NEt3 in the reaction mixture
[7a]. Analogous mono-hydrazonide(1ꢁ) compounds
Ti(CpR)Cl2[N(H)NCPh2)] [CpRꢂ
h5-C5Me5 (4), h5-
3,
the
cyclopentadienyl-silyl-amido
/
/
/
C5H4(SiMe3) (5)] can be synthesized by reaction of the
corresponding monocyclopentadienyl trichloro deriva-
tives Ti(CpR)Cl3 with hydrazone in the presence of one
equivalent of NEt3 (Scheme 2). Treatment of 5 with
NEt3 in toluene gives the dinuclear complex [Ti(h5-
C5H4SiMe3)Cl(m-N2CPh2)]2 (7) as an analytically pure
red compound, in which two titanium atoms are doubly
2. Results and discussion
2.1. Preparation and characterization of the complexes
The reaction of LiN(H)NCPh2, obtained by addition
of a solution of LinBu in hexane to benzophenonehy-
drazone in dry THF at ꢁ
the mixed dicyclopentadienyl titanium compound Ti(h5-
C5Me5)(C5H5)Cl2, in toluene at ꢁ78 8C, gives the
chloro hydrazonide(1ꢁ) derivative (‘metalloazine’) [10]
Ti(h5-C5Me5)(h5-C5H5)Cl[N(H)NCPh2] (1). The bis-
hydrazonide(1ꢁ complex
Ti(h5-C5Me5)(h5-
/
78 8C under argon [10], with
bridged by a hydrazonide(2ꢁ) ligand. Compound 7 is
/
also synthesized by reaction of Ti(h5-C5H4SiMe3)Cl3
with hydrazone and two equivalents of NEt3 in toluene
(Scheme 3). Unlike 5, a toluene solution of compound 4
remains unaltered in the presence of an excess of NEt3
and the formation of a dinuclear analogue to 7 is not
observed, probably due to the high steric demand of the
substituted cyclopentadienyl ring.
/
/
/
)
C5H5)[N(H)NCPh2]2 (2) is easily formed by treatment
of Ti(h5-C5Me5)(h5-C5H5)Cl2 with two equivalents of
the lithium salt (Scheme 1).
The titanium trichloro compound Ti[h5-C5H4(Si-
Me2Cl)]Cl3 [8] reacts in toluene, at room temperature,
Complexes 1ꢃ7 are air and moisture-sensitive, both in
/
solution and in the solid state. They can, however, be
stored unaltered for weeks if strictly anaerobic condi-
tions are maintained. They are soluble in chlorinated
solvents (chloroform and dichloromethane) as well as in
aromatic hydrocarbons (benzene, toluene) and slightly
soluble in hexane and pentane.
with hydrazone (H2Nꢀ
equivalents of NEt3, with aminolysis of the Siꢀ
one of the TiꢀCl bonds, to afford the cyclopentadienyl-
amido derivative Ti[h5-C5H4(SiMe2ꢀh1-NNCPh2)]Cl2
(6) in high yield (80%), whereas the same reaction with
1 equivalent of NEt3 gives the mono-hydrazonide(1ꢁ
compound Ti[h5-C5H4(SiMe2Cl)]Cl2[N(H)NCPh2)] (3),
/
Nꢁ
/
CPh2) in the presence of two
/Cl and
/
/
/)
The IR spectra of all of these complexes show
characteristic absorptions for n(Tiꢀ/N) around 700

V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ
/182
175
Scheme 2.
cmꢁ1 and n(Nꢀ
cmꢁ1. These spectra do not show any n(Nꢁ
tions above 1600 cmꢁ1, possibly due to an electronic
delocalization over the CꢀNꢀNꢀ
unit [11,12b]. 1H-
/
H) vibrations between 3200 and 3400
C) vibra-
tives have been synthesized by migratory insertion of a
ligand into a zirconium coordinate diazoalkane mole-
/
cule [11] and some h2-N,N?-hydrazonide(2ꢁ
/
) titanium
/
/
/
complexes are also known [12]. Alternatively, h1-N,N?
coordination has been suggested for the intermediate
titanium species Ti(h5-C5H5)Cl(NNCPh2) [12a,12c] and
the compound Ti(h5-C5H5)2(PMe3)(NNCPh2) [13].
Although a similar h1-N,N? coordination mode could
not be ruled out for the hydrazonide ligands in the
dicyclopentadienyl compounds 1 and 2 due to the
smaller ionic radii of titanium compared with zirconium
and the greater space requirement of the C5Me5 ligand,
an h2-N,N? bonding of the hydrazonide ligand to the
titanium atom is proposed for these compounds
(Scheme 1). The spectroscopic data for the monocyclo-
NMR spectra (C6D6 or CDCl3, room temperature) for
complexes 1 and 2 show singlets for the pentamethyl-
and cyclopentadienyl ring protons, while for complexes
3, 5, and 6 one AA?BB? spin system (two resonances) for
the C5H4 ring protons and one singlet for the SiMe2 or
SiMe3 groups are observed, as would be expected from
the symmetry of the proposed structures for these
compounds. The same spectroscopic features are also
observed in the 13C-NMR spectra. A feature associated
1
with the H-NMR spectra of these compounds is the
resonance for the amido proton. They exhibit one signal
pentadienyl derivatives 3ꢃ
structure with a mirror plane containing the Tiꢀ
CꢀCipso(Ph2) unit (the coplanar TiꢀN(ꢀSi)ꢀNꢀ
so(Ph2) fragment for compound 6) bisecting the Clꢀ
Cl angle and the cyclopentadienyl ring (Scheme 2)
[11b,14,15] making both phenyl groups non-equivalent
in the corresponding NMR spectra. Compound 6
symbolizes a structural variation of the classical cyclo-
pentadienyl-amido titanium derivatives [16] in which the
hydrazonide moiety has been employed as a donor
ligand in place of the amido ligand.
/
6 are support the proposed
NꢀNꢀ
CꢀCip-
Tiꢀ
(d 8.5ꢃ
/
10.5) shifted downfield with respect to the
CPh2 resonance (d 4.53), indicating that
/
/
/
(H2)NꢀNꢁ
/
/
/
/
/
/
/
/
the hydrazonide(1ꢁ) ligand adopts an amido coordina-
/
tion mode [11]. The 1H- and 13C-NMR spectra also
show the presence of two non-equivalent phenyl groups
/
/
indicating a coplanar Tiꢀ
pointing to sp2 hybridization for the nitrogen and
carbon atoms and suggesting a TiꢀN p-bond interaction
with hindered rotation around the CꢁN bond.
h2-N,N?-Hydrazonide(1ꢁ h2-N,N?-alkyl
and
hydrazonide(1ꢁ) dicyclopentadienyl zirconium deriva-
/
Nꢀ
/
Nꢀ
/
Cꢀ
/
Cipso(Ph2) fragment
/
/
/
)
/
Scheme 3.

176
V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ182
/
The reactions of 1, 3 and 4 with alkylating reagents
Table 1
Selected interatomic distances (A) and angles (8) for complex 7
˚
have been studied. However, all attempts made to
alkylate these complexes under varying conditions al-
ways gave unresolvable mixtures of unidentified com-
pounds.
a
a
A
B
Bond distances
Ti1ꢀCl1
Ti1ꢀN1
2.3480(11)
2.148(3)
2.021(3)
2.392(4)
2.343(4)
2.337(4)
2.353(4)
2.363(4)
1.870(3)
1.324(4)
1.323(4)
2.3393(11)
2.153(3)
1.996(3)
2.402(3)
2.355(4)
2.345(4)
2.339(3)
2.350(3)
1.898(3)
1.339(4)
1.315(4)
2.2. Molecular structure of [Ti(h5-C5H4SiMe3)Cl(m-
N2CPh2)]2 (7)
Ti1ꢀN2
Ti1ꢀC11
Ti1ꢀC12
Ti1ꢀC13
Ti1ꢀC14
Ti1ꢀC15
Ti1ꢀN2_a
N1ꢀN2
The structure of complex 7 was confirmed by a single-
crystal X-ray diffraction study. Fig. 1 shows an ORTEP
view of the structure along with the atom-labelling
scheme. Selected bond distances and angles with their
standard deviations are listed in Table 1.
N1ꢀC1
Bond angles
The structure shows 7 as a dimeric complex where two
‘Ti(h5-C5H4SiMe3)Cl’ units are bridged by two diphenyl
Cl1ꢀTi1ꢀN1
Cl1ꢀTi1ꢀN2
Cl1ꢀTi1ꢀN2_a
N1ꢀTi1ꢀN2
N1ꢀTi1ꢀN2_a
N2ꢀTi1ꢀN2_a
Ti1ꢀN1ꢀN2
Ti1ꢀN1ꢀC1
N2ꢀN1ꢀC1
92.00(8)
112.45(9)
95.74(9)
92.42(7)
116.35(8)
96.48(9)
hydrazonide(2ꢁ) ligands. In the asymmetric unit cell
/
two independent crystallographic molecules A and B
were found around a centre of inversion. Both are
equivalent within estimated S.D.’s. We focus the discus-
36.89(11)
119.71(11)
86.44(12)
66.35(17)
169.1(2)
37.41(10)
117.48(11)
85.38(12)
64.93(16)
171.3(2)
sion therefore on molecule A. Each hydrazonide(2ꢁ)
/
ligand is bonded side-on to one titanium atom and end-
on to the other titanium centre. If the centroid of the
cyclopentadienyl ring and the midpoint of the
124.0(3)
123.8(3)
Ti1ꢀN2ꢀN1
Ti1_aꢀN2ꢀN1
Ti1ꢀN2ꢀTi1_a
76.76(17)
154.0(2)
93.56(13)
77.66(17)
149.6(2)
94.62(13)
hydrazonide(2ꢁ
coordination site, the coordination geometry around the
titanium centre can be best described as tetrahedral. In
/
) Nꢀ
/
N bond is considered as a single
The translation of symmetry code to equivalent positions is:
_aꢂꢁx, 1ꢁy, 1ꢁz.
The labels are given for A. For further details see text and Section
a
the side-on disposition, the Tiꢀ
bridge nitrogen is slightly shorter [Ti1ꢀ
than that for the nitrogen carrying the CPh2 substituent
/
N bond length for the
˚
4.
/
N2 2.021(3) A]
˚
distances are, respectively, slightly longer and shorter
than those of the known titanium compounds Ti[(h5-
[Ti1ꢀ
/
N1 2.148(3) A]. The Ti1ꢀ
/
N2 and Ti1ꢀ
/
N1 bond
C5Me4)SiMe2(h2-NNMe2)]X2 (Xꢁ
/
Cl, Me) [15b] and
comparable to those of the Ti(h5-C5H5)(h2-
NHNMe2)Cl2 and Ti(h5-C5H5)(h2-NPhNH2)Cl2 [14].
The Ti1ꢀ
and the titanium, nitrogen and C1 atoms lie in a plane.
The angles in the triangle are Ti1ꢀN1ꢀN2 66.35(17)8,
Ti1ꢀN2ꢀN1 76.76(17)8 and very acute at the metal
centre N1ꢀTi1ꢀN2 36.89(11)8. Comparable structures
/
N1ꢀ/N2 system is an almost isosceles triangle
/
/
/
/
/
/
for analogous titanium and other transition metal
derivatives have been found [17]. The ‘Ti1N2N1’ and
‘Ti1_aN2_aN1_a’ fragments are connected through two
Tiꢀ
1.870(3) A] forming an almost planar ‘Ti1N2Ti1_-
aN2_a’ ring. The short Ti1ꢀN2_a bond distance in the
1.90 A suggests a ppꢃdp-interaction be-
tween the titanium and nitrogen atoms [18]. The Nꢀ
/
N bonds, which show equal distances [Ti1ꢀ
/N2_a
˚
/
˚
range 1.80ꢃ
/
/
/N
˚
˚
[N1ꢀ
distances are shorter than the single bonds, indicating
significant multiple NꢀN and NꢀC bond character.
/
N2 1.324(4) A] and Nꢀ
/
C [N1ꢀ
/
C1 1.323(4) A] bond
/
/
These structural features indicate an electronic deloca-
Fig. 1. ORTEP drawing view of the molecular structure of molecule A
in compound 7 along with the atomic labelling scheme. The thermal
ellipsoids are drawn at the 50% probability level. The hydrogen atoms
are omitted for clarity.
lization over the Ti1_aN2N1C1 unit.
Analogous structures have been reported by Floriani
and Leigh for similar titanium derivatives. The com-

V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ
/182
177
ligands. The Ti1ꢀ
/
N1 bond distance is of the order of
that found for donor N0
/
Ti bonds [18]. The Ti1_aꢀ
/
N2ꢀN1 angle at 154.0(2)8 is closer than the correspond-
/
ing angle in the compound [Ti(h5-C5H5)Cl(NNPh2)]2
[19] for which an almost linear disposition (171.4(2)8)
has been proposed.
The Cp rings are planar. The Tiꢀ
/
Cring distances range
˚
from 2.392(4) to 2.337(4) A and the TiꢀCl distance is
/
˚
Fig. 2. Comparison of the ‘TiN2TiN2’ structure core defined in the
[Ti(h5-C5H5)Cl]2(m-N2CPh2)
2.3480(11) A. These distances are very similar to those
found in typical titanium chloro-cyclopentadienyl deri-
vatives.
compounds
[12c]
(A),
[Ti(h5-
C5H5)Cl(NNPh2)]2 [19] (B) and [Ti(h5-C5H4SiMe3)Cl(m-N2CPh2)]2
(7) (C).
2.3. Olefin polymerization
pound [Ti(h5-C5H5)Cl]2(m-N2CPh2)2 [12c] contains two
hydrazonide ligands h2-N,N? bonded to the same
titanium atom, while the second titanium centre is
bonded at very short distances to the terminal nitrogens
only (Fig. 2A). The complex [Ti(h5-C5H5)Cl(NNPh2)]2
[19] shows one hydrazonide ligand symmetrically end-on
bridging while the other hydrazonide ligand is both
bridging and bonded side-on to one of the titanium
atoms (Fig. 2B). Compound 7 exhibits a different
‘TiN2TiN2’ structure core with the disposition for the
two h2-N,N? hydrazonide ligands as shown in Fig. 2C.
The side-on structure has been previously observed, but
the presence of two symmetric titanium environments in
the same dinuclear compound is unique. The steric
hindrance caused by the ring must influence the final
structural disposition. For unsubstituted cyclopentadie-
nyl derivatives the existence of metastable forms in
solution has been proposed [19] which under crystal-
lization yield a determined disposition in the solid state.
For substituted cyclopentadienyl rings, the symmetrical
disposition must be favoured as the thermodynamically
more stable form in solution (for 7 we only observed by
NMR spectroscopy the formation of a symmetrical
disposition) and in the solid state. When the steric
demands of the cyclopentadienyl ring increase the
formation of the dinuclear compound is not observed.
When a similar reaction to prepare 7 is carried out with
the pentamethyl-cyclopentadienyl derivative, even in the
presence of an excess of hydrazone and NEt3, only the
mononuclear compound 4 is formed.
Treatment of the titanium hydrazonide compounds
with MAO affords catalytic species which polymerize
ethylene, propylene and styrene. The reaction conditions
and results are summarized in Tables 2ꢃ4. We carried
/
out ethylene polymerizations at 25 and 50 8C and at 1
and 5 atm of ethylene pressure. The complexes exhibit
activities comparable to those observed for Ti(h5-
C5H5)Cl3/MAO and higher than those observed for
Ti(h5-C5Me5)Cl3/MAO [20]. The polymerization data in
Table 1 reveal that the chloro dicyclopentadienyl
compound 1/MAO (entry 5) shows the highest activity
at 25 8C and 1 atm of monomer pressure. Among the
monocyclopentadienyl compounds 3, 5 and 6, the
catalytic efficiency in terms of activity decreases in the
order Ti[h5-C5H4(SiMe2Cl)]Cl2[N(H)NCPh2)]/MAOꢀ
Ti[h5-C5H4(SiMe3)]Cl2[N(H)NCPh2)]/MAOꢀTi[h5-
C5H4(SiMe2ꢀ
h1-NNCPh2)]Cl2/MAO with the cyclopen-
/
/
/
tadienyl-amido system showing the same activity at 25
and 50 8C. The polyethylenes (PE’s) produced by these
catalysts exhibit single DSC endotherms consistent with
a single active species for each catalyst. The melting
point Tm of a PE depends upon its molecular weight and
linearity [21]. The Tm of the obtained polymers (about
115 8C consistently made at all polymerization experi-
ments) with the mono- and dicyclopentadienyl titanium
hydrazonide derivatives are lower than those reported
for linear high molecular weight polyethylene (HLPE,
about 1348). This finding suggests a low molecular
weight of the polymer products obtained or a branched
polyethylene. The cyclopentadienyl-amido compound
showed a similar Tm value with increasing Tp.
The synthesized complexes were activated with MAO
and also tested for homogeneous propylene polymeriza-
tion at 50 8C and 5 atm of monomer pressure. Table 3
summarized the results obtained. The activities in the
polymerization of propylene are lower than for the
production of polyethylene and polystyrene. The poly-
propylenes produced by these compounds are all atactic
in nature, as indicated by the absence of melting
transitions.
The formation of 7 could be explained by the
dimerization of two transient h1-hydrazonide com-
pounds ‘Ti(h5-C5H4SiMe3)Cl(NNCPh2)’ [12a,12c]. The
titanium(III) complex Ti(h5-C5H5)2(PMe3)(NNCPh2)
[13] in which the diazoalkane moiety adopts an h1-
coordination has been described. The structural para-
meters concerning the ‘TiNNC’ fragment in the titaniu-
m(III) complex are very comparable with those found
for the ‘Ti1_aꢀ
range observed for [Ti(h5-C5H5)Cl(NNPh2)]2 [19]. The
N2_a
/
N2ꢀ
/
N1ꢀ/C1’ unit in 7 and fall in the
difference in length between the Ti1ꢀ
/
N2 and Ti1ꢀ
/
˚
(0.151 A) in 7 suggests an asymmetric bridging imido
character for the terminal nitrogen of the hydrazide
Polymerizations of styrene with the dicyclopentadie-
nyl (1/MAO and 2/MAO) and mono-cyclopentadienyl

178
V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ182
/
Table 2
Polymerization results of ethylene with the hydrazonide titanium derivatives and MAO
a
a
b
Entries
Catalysts
Al/Ti
T
(8C)
P (atm)
Activity
Tm (8C) c, DHm (J gꢁ1
)
1
2
3
4
5
6
6
6
3
5
1
2
100
100
100
100
100
100
25
50
25
25
25
25
1
5
1
1
1
1
14
14
55
44
66
28
115.45, 83.75
115.77, 163.4
117.35, 150.70
116.76, 199.0
116.41, 212.10
116.44, 190.80
a
Molar ratio of AlꢃTi.
/
b
c
gPE (mmol Ti atm h)ꢁ1
Determined by DSC.
.
compounds (3/MAO, 5/MAO and 6/MAO) were per-
formed in toluene at 50 8C and the observed results are
summarized in Table 4. The 1/MAO and 2/MAO
systems were inactive in the styrene polymerization
process and the activity for the 3/MAO, 5/MAO and
6/MAO catalytic systems decreases in the order Ti[h5-
Table 4
Polymerization results of styrene with the hydrazonide titanium
derivatives and MAO
a
b
Entries
Catalysts
Activity
Tm (8C) c, DHm (J gꢁ1
)
1
2
3
4
5
6
3
5
1
2
17
11
6
243.99, 29.23
241.62, 24.86
242.03, 33.04
C5H4(SiMe2 ꢀ
/
h1-NNCPh2)]Cl2/MAOꢀ
/
Ti[h5-C5H4(Si-
Me2Cl)]Cl2[N(H)NCPh2)]/MAO ꢀ
/
Ti[h5-C5H4(Si-
ꢃ/
ꢃ/
ꢃ/
ꢃ/
Me3)]Cl2[N(H)NCPh2)]/MAO, with the activities in the
production of polystyrene of the same order as poly-
ethylene. The polystyrene polymers obtained are syn-
diotactic as indicated by the DSC analysis.
a
Reaction conditions: 4ꢅ10ꢁ5 mol of titanium compound pre-
cursor; solventꢂtoluene (35 ml); monomerꢂstyrene (5 ml);
temperatureꢂ50 8C.
b
gPE (mmol Ti atm h)ꢁ1
Determined by DSC.
.
c
3. Conclusions
N2CPh2)]2 or the cyclopentadienyl-amido derivative
Ti[h5-C5H4(SiMe2ꢀh1-NNCPh2)]Cl2 were obtained, de-
pending on the nature of the cyclopentadienyl substi-
tuent. The crystal structure of the [Ti(h5-
C5H4SiMe3)Cl(m-N2CPh2)]2 compound has been deter-
mined by X-ray diffraction methods. The structure
shows a dimeric compound containing two titanium
We describe here the preparation of dicyclopentadie-
nyl hydrazonide titanium derivatives by reaction of
Ti(h5-C5Me5)(C5H5)Cl2 with LiN(H)NCPh2. Monocy-
clopentadienyl hydrazonide titanium complexes have
/
also been synthesized by Tiꢀ
tions of Ti(CpR)Cl3 with hydrazone [H2Nꢀ
the presence of amine to bind the eliminated HCl. When
one equivalent of NEt3 is used, the hydrazonide(1ꢁ
/Cl bond aminolysis reac-
/
NꢁCPh2] in
/
atoms doubly bridged by a hydrazonide(2ꢁ) ligand in a
/
/)
symmetrical disposition. The catalytic activity for olefin
polymerization of these compounds activated with
MAO has been tested and studied.
compounds Ti(CpR)Cl2[N(H)NCPh2)] [CpRꢂ
h5-
/
C5H4(SiMe2Cl), h5-C5Me5, h5-C5H4(SiMe3)] are ob-
tained, while in the presence of two equivalents of
NEt3 the dinuclear complex [Ti(h5-C5H4SiMe3)Cl(m-
Table 3
Polymerization results of propylene with the hydrazonide titanium derivatives and MAO
a
a
b
Entries
Catalysts
Al/Ti
T
(8C)
P (atm)
Activity
1
2
3
4
5
6
3
5
1
2
100
100
100
100
100
50
50
50
50
50
5
5
5
5
5
4
ꢃ
0.5
/
1
0.6
a
Molar ratio of Alꢃ
/
Ti.
gPE (mmol Ti atm h)ꢁ1
b
.

V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ
/182
179
4. Experimental
Anal. Calc. for C41H42N4Ti: C, 77.14; H, 6.89; N, 8.77.
Found: C, 75.21; H, 6.67; N, 8.69%. 1H-NMR (C6D6): d
All manipulations were performed under Ar using
Schlenk and high-vacuum line techniques or a glovebox
model HE-63. The solvents were purified by distillation
under Ar before use by employing the appropriate
drying/deoxygenated agent. Deuterated solvents were
8.75 (s, 2H, NH), 7.89, 7.22 (ortho-Ph), 7.20ꢃ
6.33 (s, 5H, C5H5), 1.40 (s, 15H, C5Me5). 1H-NMR
(CDCl3): d 8.47 (s, 2H, NH), 7.60ꢃ7.07 (Ph), 6.23 (s,
5H, C5H5), 1.52 (s, 15H, C5Me5). 13C{1H}-NMR
(C6D6): d 140.8 (CꢁN), 136.4, 136.2 (Cipso, Ph),
131.1ꢃ126.1 (Ph), 120.0 (C5Me5), 115.5 (C5H5), 11.8
(C5Me5). IR (Nujol mulls, cmꢁ1): 699.5 n(Tiꢀ
N), 3420
n(NꢀH).
/
7.00 (Ph),
/
/
˚
stored over activated 4 A molecular sieves and degassed
/
by several freeze-thaw cycles. H2Nꢀ
/
Nꢁ/CPh2 and NEt3
/
were purchased from commercial sources and used after
purification and distillation. LiN(H)NCPh2 [10], Ti(h5-
C5Me5)(C5H5)Cl2 [22], Ti[h5-C5H4(SiMe2Cl)]Cl3 [8],
Ti[h5-C5(CH3)5]Cl3 [23] and Ti[h5-C5H4(SiMe3)]Cl3
[24] were prepared by known procedures. C, H and N
/
4.3. Ti[h5-C5H4(SiMe2Cl)]Cl2[N(H)NCPh2)] (3)
A solution of H2NꢀNꢁCPh2 (1.88 g, 9.6 mmol) in
/
/
microanalyses were performed on a Perkinꢃ
/
Elmer 240B
C6H5CH3 (30 ml) was quickly added to a C6H5CH3
solution (30 ml) of Ti[h5-C5H4(SiMe2Cl)]Cl3 (3.0 g, 9.6
mmol) and NEt3 (1.35 ml, 9.6 mmol) at r.t. The reaction
and/or Heraeus CHNꢀO-Rapid microanalyzer. The
/
analytical data found for compound 2 deviated from
expected values since LiCl could not be completely
eliminated from the mixture. IR spectra were recorded
mixture was stirred for 12 h resulting in an orangeꢃ
yellow solution and a white residue. After filtration,
the solvent was completely removed to give an orangeꢃ
yellow solid. Repeated recrystallization from
C6H5CH3ꢃC6H14 at ꢁ40 8C gave 3 as an analytically
/
(Nujol mulls) on a Perkinꢃ/Elmer Spectrum 2000
/
spectrophotometer; only selected IR data are reported.
NMR spectra, measured at 25 8C, were recorded on a
Varian Unity 300 (1H at 300 MHz and 13C at 75 MHz)
and 500 Plus (1H at 300 MHz and 13C at 125 MHz)
spectrometers and chemical shifts are referenced to
residual protons and carbon signals of the solvent.
/
/
pure sample (2.78 g, 5.88 mmol, 61% yield). Anal. Calc.
for C20H21Cl3N2SiTi: C, 50.84; H, 5.94; N, 4.45. Found:
C, 50.44; H, 5.77; N, 4.63%. 1H-NMR (C6D6): d 9.66 (s,
1H, NH), 8.29, 7.75 (ortho-Ph), 7.15ꢃ6.80 (Ph), 6.50,
/
6.09 (2H, 2H, AA?BB? spin system, C5H4), 0.57 (s, 6H,
SiMe2). H-NMR (CDCl3): d 10.15 (s, 1H, NH), 8.00,
1
4.1. Ti(h5-C5Me5)(h5-C5H5)Cl[N(H)NCPh2] (1)
7.98 (ortho-Ph), 7.60ꢃ
AA?BB? spin system, C5H4), 0.67 (s, 6H, SiMe2).
13C{1H}-NMR (C6D6): d 144.1 (Cꢁ
N), 135.7, 134.3
(Cipso, Ph), 131ꢃ128 (Ph), 125.7, 120.3 (C5H4), Cipso
C5H4 not observed, 2.8 (SiMe2). IR (Nujol mulls,
cmꢁ1): 692 n(Tiꢀ
N), 3200 n(NꢀH).
/
7.20 (Ph), 6.98, 6.75 (2H, 2H,
LiN(H)NCPh2 (1.00 g, 4.94 mmol) in 20 ml of THF
was added to a solution of Ti(h5-C5Me5)(C5H5)Cl2 (1.58
/
g, 4.94 mmol) in 50 ml of C6H5CH3 at ꢁ
/
78 8C. The
/
ꢀ
/
reaction mixture was warmed to room temperature (r.t.)
and then stirred for 12 h, resulting in a dark violet
solution along with a white residue. The mixture was
filtered and the solvent was removed under reduced
pressure to give a dark violet crystalline solid. Recrys-
/
/
4.4. Ti[h5-C5(CH3)5]Cl2[N(H)NCPh2)] (4)
tallization from C6H5CH3ꢃ
/
C6H14 at ꢁ
/
40 8C gave 1 as
Following the same procedure described for the
an analytically pure sample (1.32 g, 2.76 mmol, 56%
yield). Anal. Calc. for C28H31ClN2Ti: C, 70.23; H, 6.47;
preparation of 3, using 0.34 g (1.73 mmol) of H2Nꢀ
/
Nꢁ
/
CPh2, 0.5 g (1.73 mmol) of Ti[h5-C5(CH3)5]Cl3 and
1
N, 5.85. Found: C, 69.74; H, 6.45; N, 5.88%. H-NMR
0.24 ml (1.73 mmol) of NEt3 compound 4 was obtained
as an analytically pure sample (0.30 g, 6.68 mmol, 42%
yield). Anal. Calc. for C23H26Cl2N2Ti: C, 61.52; H, 6.24;
(C6D6): d 10.53 (s, 1H, NH), 7.87 (ortho-Ph), 7.30ꢃ
(Ph), 6.21 (s, 5H, C5H5), 1.55 (s, 15H, C5Me5). 1H-NMR
(CDCl3): d 10.48 (s, 1H, NH), 7.57ꢃ7.10 (Ph), 6.20 (s,
5H, C5H5), 1.71 (s, 15H, C5Me5). 13C{1H}-NMR
(C6D6): d 140.2 (C ꢁN), 134.8 (Cipso, Ph), 130.5 (Cipso
Ph), 129.4ꢃ127.2 (Ph), 122.4 (C5Me5), 116.2 (C5H5),
12.3 (C5Me5). IR (Nujol mulls, cmꢁ1): 690 n(Tiꢀ
N),
3200 n(NꢀH).
/
7.00
1
/
N, 6.24. Found: C, 62.26; H, 6.51; N, 6.04%. H-NMR
(C6D6): d 9.21 (s, 1H, NH), 8.27 (ortho-Ph), 7.30ꢃ
(Ph), 1.87 (s, 15H, C5Me5). 1H-NMR (CDCl3): d 9.26 (s,
1H, NH), 7.85 (ortho-Ph), 7.55ꢃ7.15 (Ph), 2.07 (s, 15H,
C5Me5). 13C{1H}-NMR (C6D6): d 142.7 (C ꢁ
N), 137.8,
137.3 (Cipso, Ph), 136ꢃ126 (Ph), 125.6 (C5Me5), 12.6
(C5Me5). IR (Nujol mulls, cmꢁ1): 695 n(Tiꢀ
N), 3280
n(NꢀH).
/6.80
/
,
/
/
/
/
/
/
/
4.2. Ti(h5-C5Me5)(h5-C5H5)[N(H)NCPh2]2 (2)
/
The procedure described for the preparation of
compound 1, using LiN(H)NCPh2 (1.43 g, 7.00 mmol)
and Ti(h5-C5Me5)(C5H5)Cl2 (1.12 g, 3.50 mmol) gave 2
as a dark violet solid (1.26 g, 1.97 mmol, 56% yield).
4.5. Ti[h5-C5H4(SiMe3)]Cl2[N(H)NCPh2)] (5)
Following the same procedure described for the
preparation of 3, using 0.58 g (2.95 mmol) of H2Nꢀ
/

180
V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ182
/
Nꢁ
/
CPh2, 0.86 g (2.95 mmol) of Ti[h5-C5H4(SiMe3)]Cl3
4.8. X-ray single crystal structure determination of 7
General remarks: Suitable single crystals for the X-ray
and 0.41 ml (2.95 mmol) of NEt3 compound 5 was
obtained as an analytically pure sample (0.77 g, 1.70
mmol, 58% yield). Anal. Calc. for C21H24Cl2N2SiTi: C,
55.90; H, 5.32; N, 6.21. Found: C, 55.24; H, 6.09; N,
5.57%. 1H-NMR (C6D6): d 9.48 (s, 1H, NH), 8.32, 7.05
diffraction study were grown ꢁ
/
40 8C from a saturated
solution in C6H5CH3ꢃC6H14 1:1. A clear red crystal
/
fragment was selected, coated with perfluorinated ether,
fixed in a capillary and transferred to the diffractometer
and the cold nitrogen stream (Oxford Cryosystem). The
intensity data were collected at 173 K. Preliminary
examination and data collection were carried out on a
kappa-CCD device (NONIUS MACH3) at the window
of a rotating anode (NONIUS FR591) with graphite
(ortho-Ph), 7.20ꢃ6.80 (Ph), 6.50, 6.11 (2H, 2H, AA?BB?
/
spin system, C5H4), 0.24 (s, 9H, SiMe3). 1H-NMR
(CDCl3): d 9.85 (s, 1H, NH), 8.00, 7.95 (ortho-Ph),
7.50ꢃ
C5H4), 0.25 (s, 9H, SiMe3). 13C{1H}-NMR (C6D6): d
143.5 (CꢁN), 135.8, 134.5 (Cipso, Ph), 131ꢃ127.9 (Ph),
126.4, 119.8 (C5H4), Cipso C5H4 not observed, ꢁ0.3
N), 3250
/
7.20 (Ph), 6.93, 6.70 (2H, 2H, AA?BB? spin system,
/
/
ꢀ
/
/
monochromated MoꢃKa radiation. Data were corrected
/
(SiMe3). IR (Nujol mulls, cmꢁ1): 694 n(Tiꢀ
/
for Lp effects. Potential absorption and uncertain decay
effects of the crystal were corrected during the scaling
procedure. Data collection: Data collection were per-
n(Nꢀ
/H).
4.6. Ti[h5-C5H4(SiMe2ꢀ
/
h1-NNCPh2)]Cl2 (6)
formed within the U-range of 1.88B
exposure time of 120 s per image (four sets, 324 images,
dxꢂ40 mm, D8/DVꢂ2.08). A total number of 29 790
/
U B25.388 with an
/
A solution of H2Nꢀ
/
Nꢁ/CPh2 (0.63 g, 3.20 mmol) in
/
/
C6H5CH3 (30 ml) was quickly added to a C6H5CH3
solution (30 ml) of Ti[h5-C5H4(SiMe2Cl)]Cl3 (1.0 g, 3.20
mmol) and NEt3 (0.89 ml, 6.40 mmol) at r.t. The
reaction mixture was stirred for 12 h resulting in an
reflections were integrated. After merging a sum of 7585
independent reflections remained and was used for all
calculations [25a]. The unit cell parameters were ob-
tained after the scaling procedure from 6990 indepen-
dent reflections. Solution and refinement: The structure
was solved by a combination of direct methods and
difference-Fourier syntheses. Full-matrix least-square
refinements were carried out by minimizing S w(Fo2 ꢁ
Fc2)2 with SHELXL-97 weighting scheme and stopped at
orangeꢃ
tion, the solvent was completely removed to give a red
solid. Repeated recrystallization from C6H5CH3ꢃC6H14
at ꢁ40 8C gave 6 as an analytically pure sample (1.10 g,
2.53 mmol, 80% yield). Anal. Calc. for
/red solution and a white residue. After filtra-
/
/
C20H20Cl2N2SiTi: C, 55.21; H, 4.60; N, 6.44. Found:
1
C, 55.61; H, 5.04; N, 6.02%. H-NMR (C6D6): d 8.17,
shift/errB0.001. All non-hydrogen atoms of the Ti
/
complex where refined anisotropically. All hydrogen
atoms were found in the difference-Fourier map and
refined with individual isotropic thermal displacement
parameters. Neutral atom scattering factors for all
atoms and anomalous dispersion corrections for the
non-hydrogen atoms were taken from International
Tables for X-Ray Crystallograpy [25b]. All calculations
were performed on a DEC 3000 AXP workstation and
an Intel Pentium II PC with the STRUX-V [25c] system
including the programs PLATON [25d], SIR-92 [25e], and
SHELXL-97 [25f]. Crystal data, intensity collection data
and refinement parameters are given in Table 5. The
asymmetric unit contains two crystallographic indepen-
dent molecules (A and B); each located around a centre
of inversion.
7.41 (ortho-Ph), 7.26ꢃ
AA?BB? spin system, C5H4), 0.80 (s, 6H, SiMe2). H-
NMR (CDCl3): d 8.06, 8.04 (ortho-Ph), 7.60ꢃ7.45 (Ph),
5.59, 5.54 (2H, 2H, AA?BB? spin system, C5H4), 0.61 (s,
6H, SiMe2). 13C{1H}-NMR (C6D6): d 152.0 (Cꢁ
N),
135.8, 135.3 (Cipso, Ph), 132ꢃ127 (Ph), 118.1, 117.0
(C5H4), 2.65 (SiMe2) Cipso C5H4 not observed. IR
(Nujol mulls, cmꢁ1): 694 n(Tiꢀ
N).
/
6.95 (Ph), 5.65, 5.56 (2H, 2H,
1
/
/
/
ꢀ
/
/
4.7. [Ti(h5-C5H4SiMe3)Cl(m-N2CPh2)]2 (7)
Following the same procedure described for the
preparation of 3, using 0.67 g (3.43 mmol) of H2Nꢀ
/
Nꢁ
/
CPh2, 1.0 g (3.43 mmol) of Ti[h5-C5H4(SiMe3)]Cl3
and 0.95 ml (6.86 mmol) of NEt3 compound 7 was
obtained as an analytically red pure sample (0.86 g, 1.04
mmol, 30% yield). Anal. Calc. for C21H23ClN2SiTi: C,
60.80; H, 5.59; N, 6.75. Found: C, 60.82; H, 5.80; N,
4.9. Polymerization procedures
Toluene for polymerization was distilled in the pre-
sence of Na and benzophenone under a nitrogen atmo-
sphere. Ethylene and propylene of polymerization grade
were used as received. Styrene was purified by distilla-
tion at reduced pressure from calcium hydride. MAO
was prepared from commercially available MAO (Witco
10%) by removing C6H5CH3 and the excess amount of
AlMe3 under vacuum. Polymerization runs were per-
formed in a thermostated reactor (Buchiglauster) fitted
6.50%. 1H-NMR (C6D6): d 8.29, 7.56 (ortho-Ph), 7.40ꢃ
/
7.00 (Ph), 5.72, 5.59 (2H, 2H, AA?BB? spin system,
C5H4), 0.36 (s, 9H, SiMe3). H-NMR (CDCl3): d 8.08,
1
7.63 (ortho-Ph), 7.58ꢃ
0.12 (s, 9H, SiMe3). 13C{1H}-NMR (C6D6): d 150.9 (Cꢁ
N), 136.0, 135.8 (Cipso, Ph), 131ꢃ128.8 (Ph), 119.8
(Cipso C5H4), 118.1, 116.8 (C5H4), 0.12 (SiMe3). IR
(Nujol mulls, cmꢁ1): 696 n(Tiꢀ
N).
/7.48 (Ph), 5.49 (br, 4H, C5H4),
/
/
ꢀ
/
/

V. Tabernero et al. / Journal of Organometallic Chemistry 663 (2002) 173ꢃ
/182
181
Table 5
Crystallographic data for complex 7
5. Supplementary material
Crystallographic data (excluding structure factors) for
the structure reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre,
CCDC no. 186721 for compound 7. Copies of this
data may be obtained free of charge on application to
The Director, CCDC, 12 Union Road, Cambridge CB2
7
Chemical formula
Formula weight
T (K)
C42H46Cl2N4Si2Ti2
829.65
173
Red/fragment
Triclinic
Colour/shape
Crystal system
Space group
¯
P1 (No. 2)
1EZ, UK (Fax:
ꢄ44-1223-336033; e-mail: depos-
/
/
˚
a (A)
9.6780(2)
12.3549(2)
18.2507(5)
79.4657(8)
80.6063(7)
82.1580(15)
2103.88(8)
2
it@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
Acknowledgements
3
˚
V (A )
Z
Financial support by DGICYT (Project MAT2001-
1309) is gratefully acknowledged. V.T.M. acknowledges
Comunidad de Madrid (CAM) for the award of Fellow-
ship. We are grateful to Professor A.G. (University of
Salerno, Italy) for facilities to carry out the polymeriza-
tion experiments.
rcalc (g cmꢁ3
)
1.310
0.598
m (mmꢁ1
F(000)
)
864
0.25ꢅ0.13ꢅ0.05
1.88ꢃ25.38
ꢁ115h 511, ꢁ145k 514,
ꢁ215l 521
29 790
Crystal size (mm)
U Range (8)
Data collected
/
Reflections integrated
Independent reflections
Observed reflections
[Iꢀ 2s(I)]
7584 (all) [Rintꢂ0.040]
5943 (observed)
References
Parameters refined
R1 (observed/all)
653
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Sandwich Complexes as Metallocene Analogues in Metallocenes,
0.0519/0.0731
0.1045/0.1145
Goodness-of-fit (observed/ 1.038/1.038
wR2 (observed/all)
vol. 1 (Chapter 6), Wiley-VCH, New York, 1998, pp. 339ꢃ340;
/
(b) A.L. McKnight, R.M. Waymouth, Chem. Rev. 98 (1998)
2587.
all)
ꢁ3
˚
Max/min Ds (e A
)
ꢄ1.29/ꢁ0.69
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with a 500 ml glass vessel, using C6H5CH3 as the
solvent. The conditions were adjusted as required for
each experiment. The ethylene and propylene pressures
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charged with MAO and C6H5CH3, followed by an
injection of a C6H5CH3 solution of the complex and
MAO. After the solution was saturated with monomer,
the polymerization process was started. Polymerization
was stopped by pouring the reaction mixture into
acidified EtOH. The polymer was filtered, washed with
EtOH and dried under vacuum at 60 8C overnight.
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¨
Waymouth, Angew. Chem. Int. Ed. Engl. 34 (1995) 1143;
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