Synthesis, structures, and catalytic properties of dimeric constrained geometry diphenylcyclopentadienyl-phenoxyoxochlorotitanium(IV) complexes

Article abstract of DOI:10.1016/j.poly.2004.09.035

High-yield synthesis (>90%) of two dimeric diphenyl cyclopentadienyl- phenoxyoxochlorotitanium(IV) complexes 3, and 4 has been achieved by hydrolysis of the monomeric 2-(3,4-diphenyl-cyclopentadienyl)-4,6-di-tert-butyl phenoxytitanium dichloride (1) and 2

Full text of DOI:10.1016/j.poly.2004.09.035

Polyhedron 24 (2005) 1793–1797
www.elsevier.com/locate/poly
Synthesis, structures, and catalytic properties
of dimeric constrained geometry
diphenylcyclopentadienyl–phenoxyoxochlorotitanium(IV) complexes
a
a,c,
b
a
a
Zhang Yuetao , Mu Ying *, Li Guanghua , Lu Chunsheng , Xiao Tingting ,
¨
a
a
a
b
Xu Jiansheng , Zhang Yanrong , Zhu Dongsheng , Feng Shouhua
a
School of Chemistry, Jilin University, 10 Qianwei Road, Changchun 130013, PeopleÕs Republic of China
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, School of Chemistry, Jilin University, 10 Qianwei Road,
b
Changchun 130013, PeopleÕs Republic of China
Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, Jilin University, Changchun 130013, PeopleÕs Republic of China
c
Received 13 February 2004; accepted 20 September 2004
Available online 3 August 2005
Abstract
High-yield synthesis (>90%) of two dimeric diphenyl cyclopentadienyl–phenoxyoxochlorotitanium(IV) complexes 3, and 4 has
been achieved by hydrolysis of the monomeric 2-(3,4-diphenyl-cyclopentadienyl)-4,6-di-tert-butyl phenoxytitanium dichloride (1)
and 2-(3,4-diphenyl-cyclopentadienyl)-6-tert-butyl phenoxytitanium dichloride (2). The molecular structure of 3 has been deter-
mined by single-crystal X-ray analysis. Both complexes have been characterized by 1H and 13C NMR spectroscopy. When activated
with Bu3Al and Ph3CþBðC6F5Þ ꢀ, complexes 3 and 4 exhibit reasonable catalytic activity for ethene polymerization, producing
i
4
polyethylenes with moderate molecular weights and melting temperatures.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: Constrained geometry catalysts; Ethylene polymerization; Metallocenes; Titanium
1. Introduction
pentadienyl ligand received less attention although a
number of catalysts of this type have also been
reported [19–27]. Recently, we have reported a series
of new constrained geometry cyclopentadienyl–pheno-
xytitanium dichloride complexes [28] by modifying
the ligand of Marks catalyst [29]. During the course
of study on the stability of these new complexes, it
was found these complexes can be easily hydrolysized
to produce dimeric oxo-bridged complexes in solution.
While they are stable to air and moisture in solid state
and can be left in air for several days without obvious
decomposition. Here, we report the synthesis and
characterization of the dimeric oxo-bridged complexes,
as well as their catalytic performance in ethene
polymerization.
Group 4 constrained geometry metallocene catalysts
which have an appended chelating heteroatom donor
group on the cyclopentadienyl ligand have received
extensive attention in recent years [1,2]. Especially the
constrained geometry catalysts with a pendant nitrogen
donor on the cyclopentadienyl ligand have been widely
studied in industry [3–8] as well as academic institu-
tions [9–18]. In comparison, the constrained geometry
catalysts with a pendant oxygen donor on the cyclo-
*
Corresponding author. Tel.: +86 431 8499983/+86 431 8949334;
fax: +86 431 5193421.
E-mail address: ymu@mail.jlu.edu.cn (M. Ying).
0277-5387/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.09.035

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Z. Yuetao et al. / Polyhedron 24 (2005) 1793–1797
2. Experimental
2.1. General comments
2.3. Preparation of {[g5;g1-2-(3,4-Ph2Cp)-6-tBu-
C6H3O]TiCl}2O (4)
Complex 4 (100 mg, 0.207 mmol) was prepared in the
same way as described above for the synthesis of 3
(Scheme 1). Pure 4 (86 mg, 91.2% was obtained as
yellow solid); Anal. Calc. for C54H48Cl2O3Ti2 (911.60):
C, 71.15; H, 5.31. Found: C, 71.09; H, 5.27%. ESI-
MS, m/z: 814.4 [M ꢀ 2Cl ꢀ 2CH2 + 1H]+, 701.4
[M ꢀ 2CO ꢀ 4CH2 ꢀ 2Cl ꢀ 2Me + 2H]+; MALDI-MS,
m/z: 730.8 [M ꢀ 2CO ꢀ 4CH2 ꢀ 2Cl + 2H]+, 366.7 [li-
gand]+. 1H NMR (CDCl3, 300 MHz; 298 K) d 6.77–
All non-hydrolytic procedures were carried out under
a nitrogen atmosphere (ultra-high purity) using stan-
dard schlenk techniques [30]. Solvents were dried and
distilled prior to use [31]. Polymerization grade ethene
was further purified by passage through columns of
n
10 A molecular sieves and MnO. Al(iBu)3, BuLi and
TiCl4 were purchased from Aldrich. 2-(3, 4-diphenyl
cyclopentadienyl)-4, 6-di-tert-butyl phenoxytitanium
dichloride (1), 2-(3, 4-diphenyl cyclopentadienyl)-6-
tert-butyl phenoxytitanium dichloride (2) [28], and
Ph3C+B(C6F5)ꢀ [32–34] were prepared according to lit-
erature procedures. NMR spectra were measured using
a Varian Unity-400 or Varian Mercury-300 NMR spec-
trometer. Hydrolysis reactions were carried out in air
using commercial solvents without purification.
4
7.59 (m, 26H, Ph and 2H, Cp), 4.60 (d, JH–H = 3 Hz,
2H, Cp), 1.29 (s, 18H, Ph–tBu). 13C NMR (CDCl3,
75 MHz; 298 K) d 174.0, 143.7, 136.1, 134.4, 132.3,
131.5, 130.4, 130.1, 129.9, 129.8, 129.6, 128.7, 128.4,
128.3, 128.0, 127.0, 126.5, 125.9, 122.3, 35.0, 29.7 ppm.
2.4. X-ray structure determinations of 3
Single crystals of 3 suitable for X-ray structural anal-
ysis were obtained from solution of CH2Cl2:hexane (V/
V = 1/3). Diffraction data were collected at 293 K on a
Bruker SMART-CCD diffractometer (graphite-mono-
2.2. Preparation of {[g5;g1-2-(3,4-Ph2Cp)-4,6-di-tBu-
C6H2O]TiCl}2O (3)
Complex 1 (100 mg, 0.185 mmol) was dissolved in
CH2Cl2 (20 mL), the color of the solution changed
slowly from red to yellow (Scheme 1). After 24 h, the
solvent was removed to leave a yellow solid. Recrystal-
lization from CH2Cl2:hexane (1:3) gave pure 3 as
orange yellow crystals (88.3 mg, 93.0%). Anal. Calc.
for C62H64Cl2O3Ti2 (1023.81): C, 72.73; H, 6.30.
˚
chromated Mo Ka-radiation: k = 0.71073 A). Details
of the crystal data, data collections, and structure refine-
ments are summarized in Table 1. The structure was
solved by direct method [35] and refined by full-matrix
least-squares on F2. All non-hydrogen atoms were re-
fined anisotropically and the hydrogen atoms were in-
cluded in idealized position. All calculations were
performed using the SHELXTL [36] crystallographic soft-
ware packages.
Found: C, 72.67; H, 6.25%. ESI-MS, m/z: 927.6
t
[M ꢀ Bu ꢀ 3CH2 + 2H]+,
814.4
[M ꢀ 2tBu ꢀ 2Cl
ꢀ 2CH2 + 3H]+, 701.4 [M ꢀ 2tBu ꢀ 2CO ꢀ 6CH2 ꢀ
2Cl + 2H]+; MALDI-MS, m/z: 842.7 [M ꢀ 2CO ꢀ
4CH2 ꢀ 2Cl + 2H], 422.7 [ligand]+. H NMR (CDCl3,
1
2.5. Polymerization reactions
300 MHz; 298 K) d 6.73–7.58 (m, 24H, Ph), 6.81 (d,
4JH–H = 3 Hz, 2H, Cp), 4.49 (d, JH–H = 3 Hz, 2H,
4
A dry 250 mL steel autoclave was charged with
70 mL of toluene, thermostated at desired temperature
and saturated with ethene (1.0 bar). The polymerization
reaction was started by injection of a mixture of catalyst
and Al(iBu)3 iꢀn toluene (5 mL) and a solution of
Cp), 1.40 (s, 18H, Ph–tBu), 1.30 (s, 18H, Ph–tBu).
13C NMR (CDCl3, 75 MHz; 298 K) d 171.8, 145.7,
143.8, 134.9, 133.4, 132.8, 131.3, 130.4, 130.3, 129.8,
129.6, 129.5, 128.5, 128.3, 128.2, 128.0, 126.6, 124.0,
122.8, 35.3, 35.1, 32.1, 29.9 ppm.
Ph3CþBðC6F5Þ in toluene (5 mL) at the same time.
4
Ph
Ph
Ph
R3
Cl
Ph
O
R4
O
H2O
Cl
Ti
Ti
Ti
O
Cl
O
R4
R1
Cl
Ph
Ph
R3
R
R3 = tBu (3), tBu (4)
R4= tBu (3), H (4)
t
R= Bu (1), tBu (2)
R1= tBu (1), H( 2)
Scheme 1. Synthetic procedure of complexes 3–4.

Z. Yuetao et al. / Polyhedron 24 (2005) 1793–1797
1795
1H and 13C NMR spectra of 3 and 4 are obviously
complicated than those of 1 and 2, which could be
attributed to that the dimeric oxo-bridged complexes
3 and 4 both adopt a chiral environment about Ti
atom. For this reason, the two phenyl groups on the
Cp ring and the two protons of the Cp group of 3
and 4 are inequivalent. As a result, the number of
inequivalent C in 13C NMR spectra of 3 and 4 is six
more than that of complexes 1 and 2, respectively.
Due to steric repulsion between two units of the mole-
Table 1
Crystal data and structural refinements details for 3
Empirical formula
Formula weight
Crystal system
Temperature (K)
Wavelength (A)
C31H32ClO1.50Ti
511.92
monoclinic
293(2)
0.71073
C2/c
24.863(5)
9.902(2)
˚
Space group
˚
a (A)
˚
b (A)
˚
c (A)
23.726(6)
106.540(5)
5599(2)
b (ꢁ)
Volume (A )
1
3
˚
cule, the H NMR signal for one of the two protons
shifts to high-field (d = 4.49 ppm for 3, d = 4.60 ppm
for 4), while the signal for the other proton does not
change very much compared to the Cp protons of com-
plexes 1 and 2 [28] (6.81 ppm for 3, the signal for 6 is
mixed with the signals of the Ph protons). The cou-
pling constant (4JH–H) of the two protons for 3 and 4
are both about 3 Hz.
Z
8
Dc (g cmꢀ3
F(0 0 0)
)
1.215
2152
0.423
Absorption coefficient (mmꢀ1
Scan type
2h Range (ꢁ)
Reflections collected
Reflections unique (Rint
)
x ꢀ 2h
3.42 6 2h 6 46.56
6354
)
3983 (0.0381)
full-matrix least-squares on F2
3983/7/312
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
3.2. Crystal structure of 3
0.917
R1 = 0.0522, wR2 = 0.1155
R1 = 0.1047, wR2 = 0.1327
0.355 and ꢀ0.281
The molecular structure of complex 3 was deter-
mined by single crystal diffraction analysis. The ORTEP
drawing of the molecular structure is shown in Fig. 1.
The selected bond lengths and angles are summarized
in Table 2. The molecular structure consists of two
{[g5;g1-2-(3,4-Ph2Cp)-4,6-di-tBu-butyl-C6H2O]TiCl}
units linked by Ti–O–Ti linkage. Selected bond lengths
and angles for one unit will be used in subsequent dis-
cussions. The whole molecule adopts a C2-symmetric
structure. The geometry around titanium can be
described as pseudo-tetrahedral, which is defined by a
substituted cyclopentadienyl ring, a chloride atom,
and two oxygen atoms (one is from the oxo-bridge,
the other is from the phenoxy). The Cp(cent)–Ti1–O2
angle of 105.9ꢁ is slightly smaller than the one in 2
Largest difference peak
ꢀ3
˚
and hole (e A
)
The vessel was repressurized to needed pressure with
ethene immediately and the pressure was kept by contin-
uously feeding monomer. After 30 min, the polymeriza-
tion was quenched by injecting acidified methanol [HCl
(3 M):methanol = 1:1]. The mixture was stirred over-
night and the polymer was collected by filtration,
washed with water, methanol, and dried in vacuo.
3. Results and discussions
3.1. Synthesis and analysis of complexes 3 and 4
It has been found that complexes 1 and 2 are stable to
air and moisture in solid state and can be left in air for
several days without obvious change [28]. They also ex-
hibit good thermostability and could be heated to about
200 ꢁC without decomposition. However, complexes 1
and 2 can be easily hydrolyzed in solution to produce
corresponding dimeric oxo-bridged complexes 3 and 4,
which can be obtained in high yields by dissolving 1
and 2 in wet solvent, such as CH2Cl2, toluene, and hex-
anes. Similar hydrolysis reaction for titanocene type
complexes has been reported previously [37–39]. In some
instances, stable polynuclear oxo-bridged species con-
taining dimer, trimer and tetramer had been produced
by aerobic oxidation [40] or hydrolysis processes [41–
45]. In our case, only the dimeric hydrolytic product 3
or 4 has been obtained and no polynuclear oxo-bridged
complex has been observed.
Fig. 1. Structure of complex 3. (Thermal ellipsoids are drawn at the
30% probability level.)

1796
Z. Yuetao et al. / Polyhedron 24 (2005) 1793–1797
Table 2
3.3. Ethene polymerization studies
Selected bond lengths and angles for complex 3
Ti(1)–O(1)
Ti(1)–C(1)
Ti(1)–C(3)
Ti(1)–C(5)
O(2)–C(7)
C(1)–C(6)
C(4)–C(26)
Ti(1)–H(5)
O(1)–Ti(1)–O(2)
Cp1(cent)–Ti(1)–O(1)
Ti(1)–Cp1(cent)–C(1)
C(1)–C(6)–C(7)
C(7)–O(2)–Ti(1)
Ti(1)–O(2)
Ti(1)–C(2)
Ti(1)–C(4)
Ti(1)–Cl(1)
Cp(cent)–Ti(1)
C(3)–C(20)
1.8125(9)
2.332 (4)
2.470(4)
2.309(4)
1.377(4)
1.473(5)
1.483(5)
2.861
104.16(10)
119.1
87.1
113.7(4)
128.9(3)
1.842(3)
2.385(4)
2.396(4)
2.2607(15)
2.051
Complexes 3 and 4 were studied as ethene polymeriza-
tion catalysts and the results were summarized in Tableꢀ3.
Upon activation with Al(iBu)3 and Ph3CþBðC6F5Þ
,
4
complexes 3 and 4 both show good catalytic activity for
ethene polymerization, producing polyethylenes with
moderate molecular weights and melting temperatures.
The order of the catalytic activity for ethene polymeriza-
tion under similar conditions (see run 2, 5 on Table 3) is
3 > 4, which could be attributed to the nature of the sub-
stituents on the phenolate. As seen from the structures of
complexes 3 and 4, the electron-donating effect of the tBu
group at the para position of the phenolate would in-
crease the catalytic activity of complex 3. For both 3
and 4, the catalytic activity increases with the increase
in Al/Ti ratio and reaches the highest catalytic activities
with the Al/Ti ratio about 40. Further increasing in the
Al/Ti ratio results in decrease in the catalytic activity.
Under the same conditions the catalytic activities for
ethene polymerization of complexes 3 (1.8–3.1 · 106 g
polymer/mol Ti) and 4 (1.3–2.3 · 106 g polymer/mol Ti)
are roughly equal to those of their corresponding dichlo-
ride complexes 1 (1.9–3.2 · 106 g polymer/mol Ti) and 2
(1.3–2.0 · 106 g polymer/mol Ti) [28], which could be
explained by that the catalytic active species produced
during the polymerization from 1 and 2 should be the
same as that produced from 3 and 4.
1.477(6)
2.957
106.58(10)
102.48(11)
105.9
Ti(1)–H(2)
O(2)–Ti(1)–Cl(1)
O(1)–Ti(1)–Cl(1)
Cp1(cent)–Ti(1)–O(2)
C(6)–C(1)–Cp(cent)
C(6)–C(7)–O(2)
169.3
114.5(4)
(106.7ꢁ) [28], indicating similar sterically open features
for 3 to complexes 1 and 2 as catalyst precursors. The
Ti1–Cring (av.) distance of 2.378 A is slightly longer than
˚
˚
the one in 2 2.362 A. The distances of Ti1–C2
˚
˚
2.384(5) A and Ti1–C3 (2.470(4) A) are longer than
the one of Ti1–C5 (2.309(4)) and Ti1–C4 (2.396(4)),
respectively, which could be obviously attributed to
the sterical repulsion between the bulky ligands on the
two Ti atoms. The phenolate plane – Cp plane dihedral
angle is 86.0ꢁ and the (phenolate)C–C(ring) vector is
bent 10.3ꢁ from the Cp ring plane. The corresponding
data for 2 are 86.5ꢁ and 9.4ꢁ, reflecting more steric
strain in 3 than in 2. The Ti–O2 bond lengths of
1.842(3) A is shorter than that in 2 (1.818(4) A) and
the Ti–O–C7 angles of 128.9(3)ꢁ is larger than the one
in 2 (129.8(4)ꢁ), indicating less Ti–O double-bond char-
acter in complex 3 [17,46–48].
4. Conclusions
Two new dimeric oxo-bridged cyclopentadienyloxo-
chlorotitanium(IV) complexes 3 and 4 have been syn-
thesized by hydrolysis of the corresponding dichlorides
1 and 2. Structures of 3 and 4 have been confirmed by
1H and 13C NMR spectra and X-ray crystallographꢀy.
When activated with iBu3Al and Ph3CþBðC6F5Þ
,
4
˚
˚
complexes 3 and 4 exhibit reasonable catalytic activity
for ethylene polymerization, producing polyethylenes
with moderate molecular weights and melting
temperatures.
Table 3
Summary of ethene polymerization catalyzed by complexes 3 and 4 (activated by Ph3C+[B(C6F5)4]ꢀ)a
Run
Catalyst
Al:Ti
T (ꢁC)
Amount of polymer (g)
Activityb
Mgc· 10ꢀ4
Tm (ꢁC)d
1
2
3
4
5
6
a
3
3
3
4
4
4
20
40
60
20
40
60
80
80
80
80
80
80
2.11
3.07
1.78
1.44
2.29
1.31
2160
3143
1822
1313
2088
1194
4.5
3.9
4.7
5.0
4.3
4.8
122.7
123.2
124.1
124.3
125.4
126.4
Polymerization conditions: solvent 80 mL of toluene, catalyst 1 mg, B/Ti ratio 1.5, time 30 min, ethene pressure 5 bar.
kg PE (mol Ti)ꢀ1 hꢀ1
b
c
.
Measured in decahydro-naphthalene at 135 ꢁC.
d
Determined by DSC at a heating rate of 10 ꢁC minꢀ1
.

Z. Yuetao et al. / Polyhedron 24 (2005) 1793–1797
1797
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