Novel titanium(IV) complexes stabilized by 2-hydroxybenzyl alcohol derivatives as catalysts for UHMWPE production

Article abstract of DOI:10.1016/j.jorganchem.2017.12.027

A series of titanium (IV) complexes (2, 5-7) stabilized by a substituted 2-hydroxybenzyl alcohols (1, 4) – were synthesized. Structures of complexes 6-7 were determined by X-ray diffraction. Titanium atom in the tetrameric complex 6 has an octahedral envi

Full text of DOI:10.1016/j.jorganchem.2017.12.027

Accepted Manuscript
Novel titanium(IV) complexes stabilized by 2-hydroxybenzyl alcohol derivatives as
catalysts for UHMWPE production
Vladislav A. Tuskaev, Svetlana C. Gagieva, Dmitry A. Kurmaev, Sergey V. Zubkevich,
Nikolay A. Kolosov, Evgenii K. Golubev, Galina G. Nikiforova, Victor N. Khrustalev,
Boris M. Bulychev
PII:
S0022-328X(17)30721-0
10.1016/j.jorganchem.2017.12.027
JOM 20222
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 27 October 2017
Revised Date: 22 December 2017
Accepted Date: 23 December 2017
Please cite this article as: V.A. Tuskaev, S.C. Gagieva, D.A. Kurmaev, S.V. Zubkevich, N.A. Kolosov,
E.K. Golubev, G.G. Nikiforova, V.N. Khrustalev, B.M. Bulychev, Novel titanium(IV) complexes stabilized
by 2-hydroxybenzyl alcohol derivatives as catalysts for UHMWPE production, Journal of Organometallic
Chemistry (2018), doi: 10.1016/j.jorganchem.2017.12.027.
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ACCEPTED MANUSCRIPT
To: Journal of Organometallic Chemistry, Special Issue "Organometallic Chemistry in Russia"
is dedicated to Prof. I.P. Beletskaya.
Research Paper
Novel titanium(IV) complexes stabilized by 2-hydroxybenzyl
alcohol derivatives as catalysts for UHMWPE production
a b
a
a
Vladislav A. Tuskaev , Svetlana C. Gagieva , Dmitry A. Kurmaev , Sergey V.
a
a
b,c
b
Zubkevich , Nikolay A. Kolosov , Evgenii K. Golubev , Galina G. Nikiforova ,
b,d
a
Victor N. Khrustalev , Boris M. Bulychev
a
Department of Chemistry, M. V. Lomonosov Moscow State University,1 Leninskie Gory, 119991
Moscow, Russian Federation.Fax: +7 (495) 932 8846. E-mail: b.bulychev@highp.chem.msu.ru
b
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, 119991 Moscow, Russian Federation
с
Enikolopov Institute of Synthetic Polymer Materials, Russian Academy of Sciences,
Profsoyuznaya Str., 70, 117393 Moscow, Russian Federation
d
Inorganic Chemistry Department, Peoples' Friendship University of Russia, 6 Miklukho-
Maklaya St., 117198 Moscow, Russian Federation
Keywords: Ziegler-Natta Polymerization, titanium, ethylene, Ultra-High Molecular Weight
Polyethylene
ABSTRACT A series of titanium (IV) complexes (2, 5-7) stabilized by a substituted 2-
hydroxybenzyl alcohols (1, 4) – were synthesized. Structures of complexes 6-7 were determined
by X-ray diffraction. Titanium atom in the tetrameric complex 6 has an octahedral environment
created by chlorine atom and five oxygen atoms. The main structural feature of 7 is a
centrosymmetric Ti O cage which is built of two seco-norcubanes Ti O sharing a common
4
6
4
3
Ti O -face. A coordination polyhedron around the titanium atoms is the distorted octahedron,
2
2
with the long Ti─
µ-O and short Ti─O bonds. All resulting complexes are moderately or highly
active in ethylene polymerization in the presence of {3Et AlCl + Bu Mg} binary co-catalyst.
2
2
6
Resulting polymers are linear ultrahigh molecular weight polyethylenes (up to 7.9 10 g/mole).
Polymers are suitable for the modern processing methods – the solvent-free solid state formation
of super high-strength (tensile strength over 2.0 – 2.4 GPa) and high-modulus (elastic modulus
up to 130 GPa) oriented film tapes.

ACCEPTED MANUSCRIPT
1
. Introduction
Ultrahigh molecular weight polyethylene (UHMWPE) is a unique polymer with
outstanding physical and mechanical properties (i.e., high strength and stiffness, good wear
characteristics, chemical resistance, low coefficient of friction), and the ability to maintain these
properties over a wide temperature range. Therefore, it is one of the most promising construction
materials and can be used in a wide range of applications such as bearings, pulleys, and joint
replacement prostheses in the human body [1].
UHMWPE cannot be processed by conventional methods due to the extremely high
viscosity of the polymer melt, resulting from the large number of entanglements between chains
[
2]. Lately some novel synthetic methods for synthesis of a UHMWPE with a reduced number of
entanglements have been developed by using traditional Ziegler-Natta catalysts [3-4] and
homogeneous single-site catalysts [5-7]. The basic principle of these methods is to create
conditions for fast crystallization of polymeric chains and to reduce the entanglement density.
Thus, by careful selection of a catalyst, an activator and the conditions of the polymerization
process, in some cases, it is possible to obtain a nascent reactor powder with a morphology close
to that of PE single-crystal mats, which, in turn, can allow to use the solventless methods for its
processing. We have previously shown that a disentangled UHMWPE can also be obtained on
titanium complexes with OO-type ligands [8-9]. Examples of such structures are shown in
Figure 1.
A
B
C
D
Fig. 1. Examples of titanium(IV) complexes with 2-hydroxybenzyl alcohol derivatives,
catalyzing the synthesis of UHMWPE.
In contrast to bis(phenoxyimine) titanium complexes, which require large amounts of
methylalumoxane activator, complexes with OO-type ligands “work” in the presence of
“conventional” organoaluminum compounds. Unlike the MAO, these substances are
stoichiometric compounds and are substantially cheaper. Taking into account the fact that high

ACCEPTED MANUSCRIPT
quality reactor powder is obtained during the first 15-30 minutes of the polymerization process,
the possibility of activator cost reduction seems very attractive at the stage of large-scale
production of UHMWPE
It was shown in [8-13] that the ability to produce UHMWPE using titanium (IV)
complexes with OO-type ligands is determined not only by the structure of the pre-catalyst, but
also by the nature of the activator. Thus, the activation of such pre-catalysts with “pure”
organoaluminium compounds (MAO, AlAlk or Et AlCl) at best leads to the production of low
3
2
5
6
molecular weight (< 5·10 D) polyethylene. The formation of polyethylene with MW > 1·10 D
was observed only when a binary activator containing magnesium and aluminum alkyl halides
was used or when mixtures of Ti complex and magnesium chloride, obtained in situ, were
activated with “conventional” organoaluminum compounds [10-13]. The best and reproducible
results were obtained by activating the complexes with a mixture of {3Et AlCl + Bu Mg},
2
2
proposed in [14]. The use of this activator leads to a sharp increase in the rate of the
polymerization reaction and to significant changes in the morphology of the resulting
polyethylene. This effect was explained by the formation of heterometallic titanium-magnesium
complexes forming the active centers of these catalytic systems [10, 15-16].
2
-
The aim of this work is to synthesize of titanium (IV) complexes with modified OO -
type saligenin ligands, whose structures were expected to be more convenient for the formation
of heterometallic titanium-magnesium complexes and to study their catalytic properties in the
ethylene polymerization reaction.
Experimental
All manipulations with air-sensitive materials were performed with rigorous exclusion of
oxygen and moisture in oven-dried Schlenk glassware on a dual manifold Schlenk line,
interfaced to a high-vacuum line. Argon and ethylene of special-purity grade (Linde gas) were
dried by purging through a Super Clean™ Gas Filters.
Toluene was distilled over Na/benzophenone ketyl and the water content was periodically
controlled by Karl-Fischer coulometry by using a Methrom 756 KF apparatus. Ligand 2, 2-
Hydroxy-3-methoxy-5-bromo-benzaldehyde was obtained in accordance to [17], its reduction
with sodium borohydride in methanol yielded a ligand 2 [18]. Ligand 1, 2,4-di-tert-bytyl-6-
hydroxymethylphenol, was synthesized as described [19]. Coordination compound 2 was
1
13
synthesized according to [20]. The H and C NMR spectra of these compounds were found to
match the published data. Dichloro-bis(isopropoxy)titanium was prepared following literature
procedures [21]. Diethylaluminum chloride and di-n-butylmagnesium (Aldrich) were used as 1.0
M solution in heptane.

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NMR spectra were recorded on Bruker AMX-400 instrument. Deuterated solvents
(
CDCl THF-d8) were degassed by freeze-pump-thaw vacuum cycles and stored over 3 Å
3
,
molecular sieves. Chemical shifts are reported in ppm vs. SiMe and were determined by
4
reference to the residual solvent peaks. All coupling constants are given in Hertz.
4
-Bromo-2-(hydroxymethyl)-6-methoxyphenol (4)
The yield was 0.50 g (70%). Found (%): C, 41.17; H, 3.85; Br, 34.26. C H BrO .
8
9
3
1
Calculated (%): C, 41.23; H, 3.89; Br, 34.28. H NMR (400 MHz, CDCl ), δ: 3.88 (s, 3H); 4.12
3
(s, 1H); 4.70 (s, 2H); 6.03 (s. 1 H); 6.93 (s. 1 H); 7.03 (s. 1 H).
(2-methanolato-3-methoxy-5-bromo-phenolato)dichlorodi(propan-2-ol)titanium
(IV),
LTiCl (iPrOH) (5). Compound 4 (0.23 g, 1 mmol) and toluene (5 mL) were placed into a
2
2
Schlenk tube equipped with a magnetic stirrer under argon, followed by the addition of
i
о
TiCl (O Pr) (0.24 g, 1 mmol) in toluene (5 mL) (0 С). The resulting red precipitate was filtered
2
2
off and recrystallized from toluene. The yield was 0.32 g (68%). Found (%): C, 35.66; H, 4.89;
Cl, 14.95; Ti, 10.07. C H BrCl O Ti. Calculated (%): C, 35.78; H, 4.93; Cl, 15.09; Br, 17.00;
14
23
2
5
1
Ti, 10.18. H NMR (400 MHz, THF-d8), δ: 1.08 (d, 12H); 3.82 (s, 3H); 3.88 (m, 2H); 4.59 (s, 2
H); 5.52 (s, 2H); 6.93 (s, 1H, Ar-H); 7.14 (s, 1 H, Ar-H).
Tetrakis-{(2-methoxy-4-bromo-6-cloromethylphenolato)-(isopropoxy)-chloro-di(µ-oxy)}
tetra-titanium (IV), L Ti Cl (iPrO) (µ-O) (6)
4
4
4
4
4
Compound 4 (0.23 g, 1 mmol) and toluene (5 mL) were placed into a Schlenk tube equipped
i
with a magnetic stirrer under argon, followed by the addition of TiCl (O Pr) (0.24 g, 1 mmol) in
2
2
о
toluene (5 mL). The reaction mixture was stirred at 50 С. The resulting dark red precipitate was
filtered off and recrystallized from toluene. The yield was 0.35 g (86%). Found (%): C, 32.26; H,
3
1
.39; Cl, 17.31; Ti, 11.67. C H Br Cl O Ti . Calculated (%): C, 32.31; H, 3.45; Cl, 17.34; Br,
44 56 4 8 16 4
1
9.54; Ti, 11.71. H NMR (400 MHz, thf-d8), δ: 1.06 (s, 12H); 1.09 (s. 12H); 3.45 (s, 4 H); 3.90
(
s, 12H); 4.07 (s, 4H); 4.68 (s, 8 H); 7.27- 7.41 (m, 8 H).
Hexakis-{(2-methanolato-3-methoxy-5-bromo-phenolato)(tetra-isopropoxy} tetra-titanium
IV), L Ti (iPrO) (µ-O) (7)
(
6
4
4
4
Compound 4 (0.23 g, 1 mmol) and toluene (5 mL) were placed into a Schlenk tube equipped
i
with a magnetic stirrer under argon, followed by the addition of Ti(OPr ) (0.28 g, 1 mmol) in
4
toluene (5 mL). The resulting yellow precipitate was filtered off and recrystallized from toluene.
The yield was 0.24 g (80%). Found (%): C, 39.58; H, 3.87; Ti, 10.42. C H Br O Ti .
60
71
6
22
4
1
Calculated (%): C, 39.70; H, 3.94; Br, 26.41; Ti, 10.55. H NMR (400 MHz, thf-d8), δ: 1.07 (s,
2H), 1.09 (s, 12H), 3.80 (s, 4 H); 3.93 (s, 18H); 4.77 (s, 2H); 4.89 (s, 12 H); 7.13-7.35 (m, 12
H).
1

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The single-crystal X-ray diffraction data for 6 and 7 were collected on a three-circle Bruker
APEX-II CCD diffractometer ( (MoK )-radiation, graphite monochromator, and scan
λ
ϕ
ω
α
mode) and corrected for absorption using the SADABS program [22]. The data were indexed
and integrated using the SAINT program [23]. For details, see Table S1. The structures were
2
determined by direct methods and refined by full-matrix least square technique on F in
anisotropic approximation for non-hydrogen atoms. The independent parts of the unit cells
contained one (in the case of 6) and half (in the case of 7) toluene solvate molecules. The
hydrogen atom of the OH-group in 1 was objectively localized in the difference-Fourier map and
refined isotropically with fixed displacement parameters [U (H) = 1.5U (O)]. The other
iso
eq
hydrogen atoms in 6 and 7 were placed in calculated positions and refined within the riding
model with fixed isotropic displacement parameters [U (H) = 1.5U (C) for the methyl groups
iso
eq
and 1.2U (C) for the other groups]. All calculations were carried out using the SHELXTL
eq
program suite [24]. Crystallographic data for 6 · 4CH C H and 7 · CH C H have been
3
6
5
3
6
5
deposited with the Cambridge Crystallographic Data Center, CCDC 1570592 and CCDC
570593, respectively. The supplementary crystallographic data can be obtained free of charge
1
from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Polymerization of ethylene
The ethylene polymerization was performed in a 100-ml reactor (Parr Instrument Co.)
equipped with a magnetic stirrer and inlets for loading components of catalytic systems and
ethylene at a total pressure of ethylene and toluene vapours of 0.7 atm. Toluene (100 ml) and the
necessary amount of a co-catalyst - 3Et AlCl/Bu Mg or 3Et Al Cl /Bu Mg were loaded in the
2
2
3
2
3
2
reactor. The reactor was heated to a specified temperature, and the reaction mixture was
saturated with ethylene. Polymerization was started by the addition of pre-catalyst to the reaction
mixture. The pressure of ethylene was maintained constant during polymerization.
Polymerization was stopped through the addition of 10% HCl solution in ethanol to the reactor.
The polymer was filtered off, washed several times with water-ethanol mixture, and dried under
vacuum at 50-60 ºC until a constant weight was achieved.
Polymer evaluation methods
DSC was performed by the differential scanning calorimeter DSC-822e (Mettler-Toledo,
Switzerland) at the heating rate 10 ºC/min in air. Viscosity-average molecular weight of
synthesized UHMWPE samples was calculated with the Mark-Houwink equation:
4
1.37
MW = 5.37·10 [η] [25], where: MW = viscosity-average molecular weight (g/mol); [η] =
1
/2
intrinsic viscosity in decalin at 135°C (dl/g); [η]= (2η -2lnη ) /0.056 (η
sp
- specific
sp
r
viscosity decalin at 135°C; η - relative viscosity in decalin at 135°C; η = η +1.
r
r
sp

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The mechanical characteristics of the oriented materials prepared with the synthesized
polymers were evaluated on the oriented tapes obtained by a solid state processing of UHMWPE
nascent reactor powders according to the procedure outlined in [7]. Monolithic tapes uniform
over the entire length (100 mm in thickness and 10 mm in width) were formed at a pressure and
shear deformation below the polymer melting point (124-126 ºC). The tapes were subjected to
uniaxial drawing while using a Spinline Daca equipment. The drawing temperature was set 4 ºC
below the polymer melting point. The mechanical characteristics of the tapes were measured
with a Hounsfield H1KS machine at the gauge length of the tested samples 120 mm with 2
mm/min initial deformation rate. The reported values were the average of at least 8 samples.
2
. Results and discussion
2
-
In the present work, the OO type ligands - derivatives of 2-(hydroxymethyl)-phenols
were used for the synthesis of titanium (IV) complexes. This type of ligand contains two
hydroxyl groups, which differ significantly in acidity and, in addition, can be easily modified by
introducing electron-donating or electron-withdrawing substituents that substantially change the
electronic properties of chelating ligands. Thus, by the interaction of ligand 1, containing two
bulky tert-butyl groups, with dichloro-bis(isopropoxy)titanium (IV) (Scheme 1), complex 2 was
obtained, (its structure was established by X-ray diffraction [20]). Complex 2 in the presence of
Et AlCl oligomerizes higher α-olefins [20], but when a binary activator is used, as shown in
2
present paper, it catalyzes the formation of UHMWPE.

ACCEPTED MANUSCRIPT
t-Bu
t-Bu
O
O
t-Bu
t-Bu
t-Bu
O
O
O
t-Bu
t-Bu
Cl
Ti Cl
O
Ti
t-Bu
a
O
OH
O
OH
2
1
t-Bu
i-Pr
t-Bu
O
O
O
O
Cl
O
OH
OH
OH
Ti
b
a
Cl
O
O
O
Br
Br
O
Br
i-Pr
4
5
3
d
c
i-Pr
O
Br
Br
Cl
O
Br
O
i-Pr
O
O
Cl
O
Br
O
O
O
Ti
Ti
Ti
Cl
O
O
O
O
O
Ti
O
Cl
i-Pr
Br
O
O
O
Cl
i-Pr
O
O
i-Pr
Ti
O
O
O
Cl
O
O
i-Pr
O
O
O
Ti
O
Ti
Br
Ti
O
Br
O
Cl
O
Br
O
O
O
i-Pr
O
O
i-Pr
Br
Br
Cl
6
7
a TiCl (OiPr) , toluene, r.t.; b NaBH , MeOH; c TiCl (OiPr) , toluene, ∆; d Ti(OiPr)
2
2
2
4
2
2
Scheme 1. Synthesis of Ti(IV) complexes 2, 5-7.
It was assumed that the introduction of electron-withdrawing substitution, eg bromine in
th
5
position of ligand 4, would lead to a decrease in the electron density at the titanium atom, and
introduction of the methoxy group into the ortho-position to the phenolic hydroxyl would
promote the formation of heterometallic titanium-magnesium complexes, considered in the
works [10-13, 15-16]) To verify this assumption, ligand 4 was obtained by the reduction of 3-
methoxy-5-bromosalicylic aldehyde 3 with sodium borohydride, and further interaction with
i
TiCl (O Pr) in toluene at room temperature led to the formation of a complex 5. The fact of the
2
2
formation of this compound was confirmed only by elemental analysis, NMR spectroscopy and
mass spectrometry.
The interaction of ligand 4 with TiCl (OiPr) at an elevated temperature (50 °C) is
2
2
accompanied by the replacement of oxygen from hydroxymethyl group with chlorine atom,
resulting in the formation of a tetrameric guaiacol complex 6. The Ti-O-Ti bridging oxygen

ACCEPTED MANUSCRIPT
atoms in 6 result most likely from hydrolysis by adventitious water in the solvent. At the same
time, the interaction of ligand 4 with titanium (IV) isopropoxide leads to the formation of a
tetranuclear complex 7.
A
B
Fig. 2. A. Molecular structure of complex 6 (50% ellipsoids). Hydrogen atoms are omitted for
clarity. B. Molecular structure of complex 7 (50% ellipsoids). The alternative position of the
disordered propoxy substituent is depicted by dashed lines. The disordered toluene solvate
molecule is not shown.
The structures of the products 6 and 7 were unambiguously established by X-ray
diffraction study and are shown in Figures 2A and 2B respectively, along with the atomic
numbering schemes. The pertinent bond lengths and angles are given in Table S2-S3.
The titanium complex 6 crystallizes in the tetragonal space group I4 /a and represents a
1
i
tetramer [(HOPr )(L)(Cl)Ti─O─] (L = organic ligand) comprising the central eight-membered
4
Ti O -ring. The observed tetra-nuclear complex has the intrinsic S ( 4) symmetry and, in the
4
4
4
crystal, occupies a special position on the 4-fold rotoinversion axis. The Ti O -ring is roughly
4
4
planar (rms deviation is 0.159 Å). Each titanium atom has the distorted octahedral environment
by the two bridged-O atoms, two O atoms of organic ligand, O atom of coordinated isopropanol,
and Cl atom of terminal chloride ligand. The organic ligands are bidentate and form the chelate
five-membered rings to titanium atoms, with the oxygen atoms arranged coplanar to the bridged-
O atoms (rms deviation is 0.064 Å). Consequently, the isopropanolic and chloride ligands are
disposed above and below the main plane of complex 6 alternating along the perimeter of the
Ti O -ring. This structure is stabilized by the four intramolecular O─H⋅⋅⋅Cl hydrogen bonds
4
4
[
(
O4─H4O⋅⋅⋅Cl1 (¾+y, 1¼–x, ¼–z), O⋅⋅⋅Cl 3.140(3), H⋅⋅⋅Cl 2.33(6) Å, ∠ O─H⋅⋅⋅Cl 175(5)°]
Figure 3A). The bridged oxygen atoms are not equidistant relative to the two titanium atoms,
apparently, due to the trans-effect. The endo-cyclic O─Ti─O bond angles in the Ti O -ring are
4
4

ACCEPTED MANUSCRIPT
larger than 90°, and the intra-chelate O─Ti─O bond angles in the organic ligands are smaller
than 90°.
The main structural feature of 7 is centrosymmetric Ti O cage which is built of two seco-
4
6
norcubanes Ti O sharing a common Ti O -face. The two ─CH O-groups of the central four-
4
3
2
2
2
3
2
membered Ti O -ring are µ , and the other ─CH O-groups are µ -bridges. All six organic
2
2
2
ligands are bidentate and form the six-membered chelate rings to titanium atoms making each of
them penta-coordinated. The terminal isopropoxy groups occupy sixth coordination positions at
the titanium atoms. Hence, a coordination polyhedron around the titanium atoms is the distorted
3
octahedron, with the long Ti─µ-O and short Ti─O bonds (Table S3). As expected, the Ti─µ -O
2
bonds are longer than the Ti─µ -O bonds, and the Ti─Oterminal bonds are shorter than the
Ti─Ochelate bonds. Moreover, the endo-cyclic O─Ti─O bond angles (<90°) are significantly
smaller than the exo-cyclic (>90°) ones. It should be noted that the methoxy substituents of the
organic ligands lie practically within their aromatic planes (planes of benzene ring and adjacent
atoms).
It should be noted that the titanium complexes with unsubstituted guaiacol [Ti (µ-
2
2
2
O)Cl (η -guaiacolato) ] and [Ti (η -guaiacolato) ] are described in the work [20].
2
4
4
8
According to X-ray data, each complex contains alkoxo-groups and/or chlorine atoms, that
easily exchange on alkyl-groups during treatment with magnesium- or organoaluminum
compounds, that is a necessary condition for the formation of catalytic systems of the Ziegler
type.
Catalytic properties of compounds 2, 5–7 in ethylene polymerization are summarized in
Table 1
a
Table 1. Ethylene Polymerization by 2, 5 -7 /(Et AlCl:Bu Mg) catalytic systems.)
2
2
[
Al]/ Weight
Bulk
Deg. of
crystal.,
%
b
d
A
M ,
d
c
w
Run Complex
[Ti]
of PE,
g
density,
Tm
6
1
0
3
g/cm
1
2
3
.
.
.
2
300
500
2.5
4.1
3.8
0.092
0.072
0.05
1430
2340
2190
65
68
73
142
143
144
1.87
2.04
3.20
2
5
3
00
00
f
4
.
5
3
2.1
4.8
4.5
1.5
0.075
0.047
0.044
0.089
1200
2740
2570
860
76
81
71
63
145
145
145
142
6.00
3.14
2.90
7.90
5
6
7
.
.
.
6
7
300
300
300
f
7
a
-6
Polymerizations carried out in 100 mL of toluene with 5 10 mol of catalyst at a constant 0.7 atm
ethylene pressure for 30 min, temperature 30 °C, [Et AlCl]/[Bu Mg] = 3:1.
kg of PE (mol of Ti atm) h .
2
2
b
-1 -1

ACCEPTED MANUSCRIPT
c
d
e
f
Melting temperatures determined by DSC at second heating of PE samples.
Degree of crystallinity were determined by DSC by use of value ∆H 100% = 288 J/g [26].
M was measured by viscosimetry;
Et Al Cl instead of Et AlCl
m
w
3
2
3
2
The maximum catalytic activity in this series - 2740 kg PE / mole Ti h atm was
demonstrated by complex 6, activated by the binary cocatalyst {3Et AlCl + MgBu }. Probably
2
2
this fact can be related to the presence of the µ2-oxygen bridge in the complex 6. It is known that
the chiral Lewis acid possessing the key Ti-O-Ti unit showed higher reactivity and selectivity in
asymmetric synthesis [27]. Similar dimeric structures with oxygen bridges are much less
commonly used as catalysts for ethylene polymerization. For example, catalytic systems based
on heterometallic titanium-aluminum complexes LAlCH (µ-O)M(CH ) Cp, when M=Ti, Zr; Cp
3
3 2
=
C H or C Me and L = CH(N(2,6-i-Pr C H )(CMe)) , are significantly superior in terms of
5 5 5 5 2 6 3 2
thermal stability and activity to monometallic half-sandwich titanium trialkyl compounds [28].
The tetrameric complex Ti (µ-O)(η -guaiacolato) exceeds the activity (per gram of metal) of the
2
2
4
2
monomeric complex TiCl (η -guaiacolato) by more than 25 times. It should also be noted that
2
2
in this case the activation was carried out by the mixture of AlEt /AlEt Cl and the high
3
2
productivity of the systems was achieved with the use of complexes immobilized on MgCl [29].
2
The catalytic activities of complexes 5 and 7 also are rather high – 2200 - 2570 kg PE /
mole Ti atm h. Replacement Et AlCl on Et Al Cl in a binary activator leads to a significant
2
3
2
3
decrease in the activity of both complex 5 and 7. At the same time, this replacement is
6
accompanied by a significant increase in the molecular weight of the polymer - from 3.2 to 6 10
6
D for complex 5 and from 2.9 to 7.9 10 D for pre-catalyst 7.
The activity of complex 2, which does not contain a methoxy-group capable to bind a
metal atom in the ortho position to the phenolic hydroxyl, is significantly inferior to complexes
stabilized with ligand 4. The degree of crystallinity and molecular weight of PE obtained on
complex 2, as well as the mechanical properties of oriented film tapes, also have the worst
performance in this series. This fact indirectly confirms the advisability of introducing additional
donor atoms into this series of ligands.
All obtained polymers lack branching at the main chain which is evident from the
-1
absence of IR absorption band at 1378 cm characteristic of the symmetric deformational
vibrations of CH groups. The bulk density of UHMPE nascent reactor powders has anomalously
3
3
low values - from 0.04 to 0.09 g/cm (Table 1), which indirectly indicates an irregular highly
porous surface of the particles. The melting point and degree of crystallinity are typical for
UHMWPE [25, 30] and are in the range of 142-145 ºС and 65-81% respectively (Table 1). At

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the same time, explicit differences in the values of the bulk density, melting points, and degree of
crystallinity of reactor powders were not found.
The processing of UHMWPE reactor powders obtained on pre-catalysts 2, 5-7 into high-
modulus oriented film tapes was carried out by preparing monolithic samples under pressure and
shear deformation at an elevated temperature below polymer melting point with subsequent
uniaxial stretching by the method described in [7]. Criteria for the quality of the resulting
oriented film tapes were: homogeneity of the resulting filament along the width and homogeneity
of the samples masses within one multiplicity at one length.
Table 2 shows the mechanical characteristics of film tapes prepared from reactor powders
6
obtained in runs 2-3 and 5-6 (table 1) with MW = 2.0 - 3.2·10 D.
Table2. Mechanical properties of monolithic UHMWPE film tapes
a
Run
Complex
Drawing
ratio
Breaking
strength,
GPа
Elongation,
%
Elastic
modulus,
GPa
90
2
2
3
3
5
5
6
6
2
2
5
5
6
6
7
7
20
24
24
28
24
28
20
24
1.90
1.95
2.14
1.94
2.21
2.35
2.14
1.94
1.88
2.18
2.50
2.74
2.07
2.39
2.98
2.83
100
130
113
133
112
90
110
a
Numbering corresponds to Table 1.
Stress-strain curves of UHMWPE orientated film tapes are shown in Figure 3. In a number of
cases (curve b in Fig. 3), a single-stage character of film rupture is observed, indicating
uniformity of the samples, and close values of elongations and elastic modulus for a series of
samples with the same drawing ratio confirm the high quality of UHMWPE reactor powder.

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b
c
2000
a
1000
0
0
1
2
3
Elongation, %
Fig. 3. Stress-elongation curves for UHMWPE orientated tapes from UHMWPE powder
obtained in runs 5 (a); 3(b) and 6(c).
The maximum value of tensile strength (2.4 GPa), with an average tensile modulus (112-
1
33 GPa), was observed for UHMWPE powder, obtained on pre-catalyst 6. This may be due to
high degree of crystallinity, since other known properties of the obtained UHMWPE samples
differ little from each other.
Conclusion
2
-
In summary, three novel mono- and tetranuclear titanium(IV) complexes (5-7) bearing [OO]
ligand were synthesized in high yields. Structures of complexes 6-7 were established by X-ray
diffraction. Titanium atom in the tetrameric complex 6 has an octahedral environment created by
chlorine atoms and five oxygen atoms. A coordination polyhedron around the titanium atoms in
complex 7 is the distorted octahedron. The main structural feature of 7 is a centrosymmetric
Ti O cage which is built of two seco-norcubanes Ti O sharing a common Ti O -face. these
4
6
4
3
2
2
complexes contains alkoxo-groups and chlorine atoms, which are easily removed by treatment
with organometallic compounds. All complexes discussed in present work were activated only in
the presence of a binary co-catalyst {3Et AlCl + Bu Mg} and exhibited moderate to high
2
2
-1
-1
activities towards ethylene polymerization (860-2700 kg of PE (mol of Ti atm) h ), giving
UHMWPE with high T . It was shown that the replacement of Et AlCl for Et Al Cl is
m
2
3
2
3
accompanied by a decrease in activity; with a simultaneous significant increase in the molecular
weight of the polymer. Proposed catalysts in suitable reaction conditions (room temperature, low
monomer pressure, low catalyst concentration) produce nascent UHMWPE powders with a low
3
bulk density (0.05-0.09 g/cm ), which can be processed to super high-strength (tensile strength
up to 2.4 GPa) and high-modulus (elastic modulus up to 130 GPa) oriented film tapes by solvent-
free solid state method.

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Acknowledgments
This work was financially supported by the Russian Science Foundation (Project No 16-13-
0502).
1
References
[
1]
M. S. Kurtz, Ultra-high molecular weight polyethylene in total joint replacement, in:
The Uhmwpe Handbook, Elsevier Inc., 2004
[
[
[
2]
3]
4]
R. W. Rendell, K. L. Ngai, G. B. McKenna, Macromolecules 20 (1987) 2250.
Y. L. Joo, O. H. Han, H. K. Lee, J. K. Song, Polymer 41 (2000) 1355.
Y. K. Joo, H. Zhou, S.G. Lee, H. K. Lee, J. K. Song, J. Appl. Polym. Sci. 98 (2005)
7
18.
S. Rastogi, D. Lippits, G. R. Peters, R. W .M. Graf, Y. Yao, H. Spiess, Nat. Mater. 4
2005) 635.
[
5]
(
[
[
6]
7]
G. Ronca, H. Forte, Y. Tjaden, S. Rastogi, Polymer 53 (2012) 2897.
A. N. Ozerin, S. S. Ivanchev, S. N. Chvalun, V. A. Aulov, N. I. Ivancheva, N. F.
Bakeev, Polym. Sci. Ser. A 54 (2012) 950.
[
[
8]
9]
S. Ch. Gagieva, V. A. Tuskaev, I. V. Fedyanin, A. I. Sizov, E. S. Mikhaylik, E. K.
Golubev,
B
M.
Bulychev,
Polyhedron
122
(2017)
179,
http://dx.doi.org/10.1016/j.poly.2016.11.007
S. Ch Gagieva, V. A. Tuskaev, I. V. Fedyanin, M. I. Buzin, V. G. Vasil'ev, G. G.
Nikiforova, E. S. Afanas'ev, S. V. Zubkevich, D. A. Kurmaev, N. A. Kolosov, E. S.
Mikhaylik, E. K. Golubev, A. I. Sizov, B. M. Bulychev, J. Organomet. Chem. 828
(2017) 89, http://dx.doi.org/10.1016/j.jorganchem.2016.11.026.
[
[
10] M. V. Solov’ev, S. Ch. Gagieva, V. A. Tuskaev, N. M. Bravaya, O. E. Gadalova, V.
N. Khrustalev, A. O. Borissova, and B. M. Bulychev, Russ. Chem. Bull.,
International Edition, 60 (2011) 2227-2235, DOI: 10.1007/s11172-011-0342-1
11] V. A. Tuskaev, S. Ch Gagieva, M. V. Solov'ev, D. A. Kurmaev, N. A. Kolosov, I. V.
Fedyanin, B. M. Bulychev, J. Organomet. Chem. 797 (2015) 159-164,
DOI:10.1016/j.jorganchem.2015.08.017.
[
[
[
12] S. Ch. Gagieva, I. V. Fedyanin, V. A. Tuskaev, T. M. Zvukova, B. M. Bulychev, J.
Organomet. Chem., 802 (2016) 9-14, DOI:10.1016/j.jorganchem.2015.11.007.
13] V. A. Tuskaev, S. C. Gagieva, V. I. Maleev, A. O. Borissova, M. V. Solov’ev, Z. A.
Starikova, B. M. Bulychev, Polymer 54 (2013) 4455-4462.
14] Y.V. Kissin, R.I. Mink, A. J. Brandolini, T. E. Nowlin, J. Polym. Sci. Part A Polym.
Chem. 47 (2009) 3271.
[
[
[
15] L. Y. Ustynyuk, B. M. Bulychev, Mendeleev Commun. 26 (2016) 45-48.
16] L. Y. Ustynyuk, B. M. Bulychev, J. Organomet. Chem. 793 (2015) 160-170.
17] E.-K. Jung, L. I. Pilkington, D. Barker, Synthesis 49 (2017) 1190, DOI: 10.1055/s-
0
036-1588939.
18] P. M. Deya, M. Dopico, A. G. Raso, J. Morey, J. M. Saa, Tetrahedron 43 (1987)
523, DOI:10.1016/S0040-4020(01)81645-8.???
[
3
[
[
19] I. Cepanec, H. Mikuldas, V. Vinkovic, Synth. Commun. 31 (2001) 2913.
20] S.Ch. Gagieva, N.A. Kolosov, D.A. Kurmaev, I.V. Fedyanin, V.A. Tuskaev, B.M.
Bulychev, Russ Chem Bull, International Edition, 63 (2014) 2748.
[
21] K. Mikami, M. Terada, T. Nakai, J. Am. Chem. Soc. 112 (1990) 3949.

ACCEPTED MANUSCRIPT
[
22] G. M. Sheldrick, SADABS, v. 2.03, Bruker/Siemens Area Detector Absorption
Correction Program; Bruker AXS Inc., Madison, WI, 2003.
23] Bruker, SAINT, v. 8.27A, Bruker AXS Inc., Madison, WI, 2012.
24] G. M. Sheldrick, Acta Cryst., 2015, C71, 3/
25] S. M. Kurtz, The UHMWPE Handbook: Ultra-high Molecular Weight Polyethylene
in Total Joint Replacement, Elsevier Academic Press, 2004.
[
[
[
[
[
[
[
[
26] B. Wunderlich, C.M. Cormier, J. Polym. Sci. Part A 2 Polym. Phys. 5 (1967) 987-
9
88.
27] H. Hanawa, T. Hashimoto, and K. Maruoka, J. Am. Chem. Soc. 125 (2003) 1708-
709.
1
28] P. M. Gurubasavaraj, H. W. Roesky, B. Nekoueishahraki, A. Pal, and R. Herbst-
Irmer, Inorg. Chem. 2008, 47, 5324-5331.
29] P. K. Sobota, J. Przybylak, L. B. Utko, A. J. L. Jerzykiewicz, M. F. C. Pombeiro, G.
da Silva, and K. Szczegot Chem. A Eur. J. 7 (2001) 951-958.
30] S. K. Garkhail, (2005). Easily processable ultra high molecular weight polyethylene
with narrow molecular weight distribution Eindhoven: Technische Universiteit
Eindhoven DOI: 10.6100/IR583519.

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Highlights
2
-
Novel titanium complexes bearing [OO] ligands were synthesized and fully characterized.
Complexes in the presence of {Et AlCl+Bu Mg } produced high molecular weight polyethylene
2
2
6
(
up to 7.9 10 g/mole).
Polymers are suitable for the solvent-free formation of high-strength (up 2.4 GPa) and high-
modulus (up to 130 GPa) oriented film tapes.