Preparation of linear low-density polyethylene from ethylene by tandem catalysis of titanium(IV) and nickel(II) non-metallocene catalysts

Article abstract of DOI:10.1016/j.poly.2015.06.024

Non-metallocene titanium(IV) complexes of 2-hydroxymethylphenol derivatives [O^O]TiCl₂ 2ⁱPrOH (2-3), which can form a tandem catalytic system with a phenoxy-imine nickel complex (1), were firstly used as an in situ copolymerization catalyst to prepare linear low-density polyethylene (LLDPE) with ethylene as the sole monomer stock and Et₂AlCl/Bu₂Mg as the cocatalyst. During the reaction, 1/Et₂AlCl oligomerized ethylene to linear α-olefins with high activity and selectivity, while 2-3/Et₂AlCl+Bu₂Mg copolymerized ethylene with the in situ generated α-olefins to LLDPE with high activity (up to 7.4 × 10⁵ g/mol Ti h atm). The influence of the reaction conditions upon the catalytic activity and polymer structures and properties have been researched. The polymers were characterized by differential scanning calorimetry (DSC), high temperature gel permeation chromatography (GPC) and high temperature ¹³C NMR spectroscopy and they were proven to be LLDPE with ethyl and butyl branches. The compositions of comonomers were tuned efficiently from 2% to 6% by different reaction conditions such as reaction temperature, Ni/Ti molar ratio and Al/(Ni+Ti) molar ratio. The melting points, degree of crystallinity and molecular weights (2.7 × 10⁵-1.5 × 10⁶) also changed correspondingly with the reaction conditions.

Full text of DOI:10.1016/j.poly.2015.06.024

Accepted Manuscript
Preparation of linear low-density polyethylene from ethylene by tandem catal-
ysis of titanium(IV) and nickel(II) non-metallocene catalysts
S.Ch. Gagieva, D.A. Kurmaev, V.A. Tuskaev, S.V. Zubkevich, A.O. Borissova,
I.V. Fedyanin, B.M. Bulychev
PII:
S0277-5387(15)00340-X
http://dx.doi.org/10.1016/j.poly.2015.06.024
POLY 11371
DOI:
Reference:
Polyhedron
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Received Date:
Accepted Date:
25 April 2015
7 June 2015
Please cite this article as: S.Ch. Gagieva, D.A. Kurmaev, V.A. Tuskaev, S.V. Zubkevich, A.O. Borissova, I.V.
Fedyanin, B.M. Bulychev, Preparation of linear low-density polyethylene from ethylene by tandem catalysis of
titanium(IV) and nickel(II) non-metallocene catalysts, Polyhedron (2015), doi: http://dx.doi.org/10.1016/j.poly.
2015.06.024
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Preparation of linear low-density polyethylene from ethylene by
tandem catalysis of titanium(IV) and nickel(II) non-metallocene
catalysts
Gagieva S.Ch.1*, Kurmaev D.A.1,2, Tuskaev V.A.1,2, Zubkevich S.V.1, Borissova A.O
2
,
Fedyanin I. V. 2, Bulychev B.M.1
1 Moscow State University, Chemical Department, Leninskie Gory 11, Moscow
119991, Russia
2 Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow 119991, Russia
Abstract
Non-metallocene titanium(IV) complexes of 2-hydroxymethylphenol derivatives
[O^O]TiCl2 2iPrOH (2-3), which can form a tandem catalytic system with a phenoxy-
imine nickel complex (1), were firstly used as an in situ copolymerization catalyst to
prepare linear low-density polyethylene (LLDPE) with ethylene as the sole monomer
stock and Et2AlCl/Bu2Mg as the cocatalyst. During the reaction, 1/Et2AlCl
oligomerized ethylene to linear α-olefins with high activity and selectivity, while 2-
3/Et2AlCl+Bu2Mg copolymerized ethylene with the in situ generated α-olefins to
LLDPE with high activity (up to 7.4 x 105 g/mol Ti h atm). The influence of the
reaction conditions upon the catalytic activity and polymer structures and properties
have been researched. The polymers were characterized by differential scanning
calorimetry (DSC), high temperature gel permeation chromatography (GPC) and high
temperature 13C NMR spectroscopy and they were proven to be LLDPE with ethyl and
butyl branches. The compositions of comonomers were tuned efficiently from 2-6%
by different reaction conditions such as reaction temperature, Ni/Ti molar ratio and
Al/(Ni + Ti) molar ratio. The melting points, degree of crystallinity and molecular
weights (2.7 x 105-1.5 x 106) also changed correspondingly with the reaction
conditions.
Keywords: oligomerization, nickel(II), copolymerization, titanium(IV), tandem
catalysis, branched polyethylene
1

* Corresponding author.
Fax: +7 (495) 932 8846. E-mail: sgagieva@yandex.ru (S.C. Gagieva)
Introduction
Linear low-density polyethylene (LLDPE) is an important member of the
family of polyethylenes which has better mechanical strength and processability than
high-density polyethylene (HDPE) due to the presence of short-chain branches.
Typically, LLDPE is obtained by ethylene copolymerization with α-olefin
comonomers with Ziegler–Natta catalysts or single-site catalysts. In the 1980s, Kissin
and Beech1,2 reported a one-step method for producing branched polyethylene from
only ethylene using a dual function catalytic system, which is well known as a tandem
reaction or in situ copolymerization.
In this procedure, a tandem reaction is carried out by two catalysts: 1-alkenes
are produced by one catalyst from ethylene and then copolymerized by the other in
situ with ethylene to produce LLDPE. The most interesting advantage over common
approaches is that only ethylene is used as a raw material. Products with different
properties can be obtained just by adjusting the reaction conditions and the molar ratio
of the two catalysts. Various combinations of homogeneous oligomerization and
polymerization catalysts have been employed in tandem catalysis (For reviews, see
references3-5).
We recently reported that a titanium(IV) complex supported by a 2-
hydroxymethylphenol derivative, ([O^O]2-TiCl2) (2) developed in our group,6,7 is
capable of copolymerizing ethylene with higher α-olefins (1-hexene > 1-octene > 1-
decene) in the presence of a binary cocatalyst - {3Et2AlCl+Bu2Mg}.8 With the desire
to obtain LLDPE, we sought a tandem catalyst system that comprises a selective
oligomerization catalyst with 2. We needed an oligomerization catalyst that produces a
narrow distribution of α-olefins, exhibits a low propensity for polymer production and
operates compatibly with the Et2AlCl/Bu2Mg-activated system. To this end, we chose
the nickel complex [FI]2Ni (1)9 (Figure 1).
2

3
2
1
Figure 1. The non-metallocene catalyst used in the present paper
Here we report a new tandem catalytic system, comprising of [O^O]TiCl2
2iPrOH (2-3) as copolymerization catalysts and [FI]2Ni (1) (Figure 1) as an
oligomerization catalyst, to synthesize branched polyethylenes, which exhibit good
processability and mechanical properties. The polymerization results and properties of
the branched polyethylenes are discussed in detail.
Results and discussion
2.1 Synthesis and characterization.
In this work, we synthesized a new catalyst 3 with a structure similar to 2 but
bearing the bulkier adamantyl group. The stoichiometric reaction of 2-adamantyl-4-
tert-butylphenol10 with hexafluoroacetone afforded 2-(1-adamantyl)-4-tert-butyl-6-
[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl] phenol in a good isolated yield
11
(Scheme 1). Further reaction with an equivalent of (i-PrO)2TiCl2 in toluene afforded
the titanium complex 3.
3

c
a
b
3
a
b
с
Ad-Br, C7H18; (CF3)2CO, CCl4; (i-Pr)2TiCl2, C6H5-CH3
Scheme 1. Synthesis of complex 3.
1
All the ligands and complexes were characterized by FT-IR, H and 13C NMR
measurements as well as by elemental analysis. FT-IR spectrum of complex 3, in
contrary to the spectrum of the free ligand, contained Ti–O and Ti–Cl bands at 592
and 405 cm-1, respectively.12 In the IR spectrum, the isopropanol OH stretching
frequencies shifted to lower values (3406 cm-1) with a weaker intensity compared with
those of the corresponding free alcohol. The complex is stable below 110 °C (DSC
data).
The structure of complex 3 as a 2:1 toluene solvate was established by a single-
crystal X-ray diffraction experiment. In the crystal structure the Ti atom is in a
distorted octahedral environment formed by two chlorine and four oxygen atoms (Fig.
2). The distribution of bond lengths in the coordination polyhedron is very similar to
those previously observed in complex 2:6 both Ti-O bonds with the coordinated i-
PrOH molecules are considerably longer than those with the saligenin ligand (Ti1-O1
1.7822(14), Ti1-O2 1.8185(14), Ti1-O3 2.1396(15), Ti1-O4 2.1273(16), Ti1-Cl1
2.3738(6), Ti1-Cl2 2.3503(6) Å). The bond lengths and angles in the ligands are close
to the average values for the corresponding molecular fragments from the Cambridge
Structural Database. The hydrogen atoms of the i-PrOH groups participate in
intermolecular O-H...Cl hydrogen bonds (O3...Cl2A 3.186(2), O4...Cl1A 3.128(2) Å),
linking the molecules into infinite chains along the crystallographic a axis.
4

Figure 2. General view of the crystal structure of complex 3 with thermal ellipsoids at
the 50% probability level. Hydrogen atoms, except for those of the coordinated i-
PrOH moieties, are omitted for clarity.
Reactivity profile of individual catalysts. The reactivities of compounds 1 and 2
toward ethylene have been reported in the literature.6,7,9 In this section, however, we
report on the performances obtained under our experimental conditions. These
measurements will provide a baseline for comparing the performances of the dual
catalyst systems.
The nickel bisphenoxyiminato complex 1 can be used as an ethylene oligomerization
catalyst to obtain linear α-olefins with high activity.9 The influence of the reaction
temperature and Al/Ni molar ratio upon catalytic activities and oligomer distributions
have been researched. However, since titanium complexes 2 and 3 show activity only
in the presence of a binary cocatalyst {3Et2AlCl + Bu2Mg}, we investigated the
oligomerization of ethylene with not only the organoaluminum activator, but with the
aforementioned binary system. The results of this study are presented in Table 1.
Activated by Et2AlCl, catalyst 1 exhibits high catalytic activities, as shown in
Table 1. As the temperature was increased from 30 to 80°C, the activity decreased
from 6.3 to 0.7 kg mol−1 Ni h−1bar-1 (runs 3 and 5, Table 1). In the presence of MAO
or Et3Al, complex 1 did not show any noticeable catalytic activity (runs 6 and 7).
5

Table 1. Ethylene oligomerization with 1/OAC a
Run
[Al]/[Ni]
[Ni],
mol
TOF
Cocatalyst
Oligomer (%)
b)
С4
С6
С8 and higher
1 c)
2 d)
3
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
МАО
60/1
60/1
4 10-5
4 10-5
5 10-6
5 10-6
5 10-6
5 10-6
5 10-6
85
68
70
25
5
39
59
55
17
90
56
38
39
78
5
3
4
5
150/1
300/1
150/1
150/1
150/1
120
105
4
5 e)
12
-
6
7
Et3Al
-
8
Et2AlCl/
Et3Al
Et2AlCl
150/150/1 4 10-5
22
3
95 f)
2
9 g)
10 h)
60 /1
4 10-5
18
29
58
60
34
36
8
4
Et2AlCl
200/1
1,5 10-5
а) Oligomerization carried out in 50 mL of toluene at a constant ethylene pressure for
30 min, temperature 30 oC, b) Turn over frequency, [mol(C2H4)/mol(cat.) h] c) ethylene
pressure 2 atm, d) temperature 50 oC, e) temperature 80 oC, f) С6 - share [mol%] of all
hexene isomers, g) [Bu2Mg]/[Ni]= 20/1, h) reaction time 60 min.
The Al/Ni ratio has a great effect on the catalytic activity and the distribution
of α-olefins. The activity increased to a maximum at an Al/Ni molar ratio of 150/1,
then decreased as the ratio rose further to 300/1 (Runs 3 and 4). The main products at
an Al/Ni molar ratio of 60/1 were the isomers of butene (70%), hexene (25%) and
octene (5%). Increasing this ratio up to 200/1 was accompanied by some changes in
the distribution of the reaction products (60, 36 and 4%, respectively). The
distributions of α-olefins were not significantly changed when Bu2Mg was added to
the reaction mixture (58, 34 and 8%, correspondingly).
Ethylene polymerization with 2/Et2AlCl+Bu2Mg has been reported in the
literature.6 The catalyst is efficient in incorporating α-olefins in the PE chain with high
activity and stability.7 The ethylene polymerization results of complex 3 under
different reaction conditions are presented in Table 2 (runs 9 and 10).
The polymerization behavior of the 1/2 and 1/3 catalytic systems were
investigated in two ways: the Ni catalyst was added first, followed by addition of the
Ti catalyst (method I); the Ni and Ti catalysts were added simultaneously (method II).
The effects of the reaction temperature, Ni/Ti and Al/(Ni + Ti) molar ratios on the
6

copolymerization activities and properties of the copolymers were researched. The
branching degrees, molecular weights and melting temperatures were measured by 13C
NMR (Fig. 3), GPC and DSC, respectively. The results are summarized in Table 2.
Table 2. Preparation of LLDPE by tandem catalysis of Ni (1) and Ti (2-3) catalysts a
А b
M.p.,
oC с
χ, %
Mw, Mn
Mw/Mn
copol
Run Catalysts
[Al]/[
Ti]
P,
atm.
CM
,
mol. %
1
2
300/1
1
1315 142.7 61.8 1.21 x 106,
2.11 x 105
5.7
2
3
500/1
300/1
1
1
2140 144.8
n.d.
2
740
380
571
553
142.2
1.40 x 106,
3.77 x 105
7.34 x 105,
1.82 x 104
3.7
40.3
6.5
2
6
6
2
0
2/1
4
5
300/1
300/1
300/1
5
3
3
134.9
2/1
2/1
2/1
137.0 51.7 3.17 x 105,
4.84 x 104
138
6 d
41.2 5.10 x 105,
8.0
6.37 x 104
7e
8 f
9
300/1
300/1
300/1
3
3
1
710
142.4 60.7
n.d.
n.d.
2/1
2/1
3
traces
1886 139.3 57.8 1.17 x 106,
5.3
6.22 x 105
10
11
12
300/1
300/1
960/1
3
3
3
1080
89
587
143
139
62.5 ins. in TCB
n.d.
3
3/1
3/1
136.7 51.9 2.70 x 105,
1.33 x 104
20.3
7.1
3
3
4
13
640/1
300/1
3
3
653
212
137.5
2.99 x 105,
3.80 x 104
2.85 x 105,
8.61 x 103
3/1
3/1
14d
135.4
33.1
a Copolymerization/polymerization carried out in 50 mL of toluene with 5 µmol of
catalyst at a constant ethylene pressure for 30 min, temperature 30 oC,
{[Et2AlCl]/[Bu2Mg] =3:1} as cocatalyst, both catalysts were added simultaneously,
[Al]/[Ni]= 60:1, [Ti]/[Ni]=1:10 mol/mol;
b kg PE (mol of Ti-1 h-1atm-1) Melting temperatures determined by DSC at a second
c
heating of the PE samples.d catalysts were introduced sequentially; e [Ti]/[Ni]=1:1
mol/mol; f [Ti]/[Ni]= 1:50 mol/mol.
As can be seen from Table 2, the optimal ratio is [Ti]/[Ni] = 1/10 (compare
runs 6, 7 and 8). The optimal molar [Ti]/[Ni] ratio for producing branched
polyethylene is 1/10 (run 6). When the molar ratio was increased to 1:1, unbranched
polyethylene and small amount of oligomers were detected (Run 7, Table 2). By
7

increasing the ratio of [Ti]/[Ni] to 1/50, only oligomers were obtained (Run 8, Table
2).
Compared to the procedure using catalyst 2 alone, the activity of tandem
catalytic system decreased noticeably from 1315 to 740 kg/mol Ti-1 h-1 atm-1, probably
because of the competition of ethylene between the Ni and Ti active centers. The
content of branches (predominantly, ethyl) in the copolymers was calculated from the
IR and 13C NMR data (according to the literature,13-14 the presence of ethyl branches
could be confirmed by resonances at δ = 11.19, 26.67 and 39.64 ppm and butyl
branches by that at δ = 23.40 ppm). The polymers produced by Ti complexes 2-3 alone
exhibit only a single peak, typical of the main chain of HDPE.
The tandem catalytic system 3/1 produced copolymers with lower molecular
weight but with a slightly higher (3-4%) percentage of butyl branches and a broad
molecular weight distribution. Samples of the polymers produced in runs 3-6 contain
2-6% of butyl branches.
Increasing the ethylene pressure from 1 to 3 atm (Table 2, entry 3 vs entry 5)
resulted in a decrease in both the molecular weight (from 1.40 x 106 to 3.17 x 105) and
melting point (from 142.2 to 135.1°С) of the polymers with a simultaneous increase
the value of the molecular mass distribution, which indicates the formation of
heterogeneous active sites.
The sequential introduction of the catalysts (a 30 minute pre-exposure with
pre-catalyst 1, then pre-catalyst 2 was introduced) leads to a slight decrease in the
molecular weight (from 1.2 x 106 to 5.1 x 105 and increased values of the molecular
weight distribution (5.7 to 8.0) of the polymers formed (Table 2, entry 3 vs entry 6).
Incorporation of butene is minimal, but the polymers are characterized by a slightly
lower value of their melting points.
A similar pattern is observed for the catalyst system 3/1. Sequential
introduction of the catalysts leads to a decrease of the molecular weight, a slight
increase of the comonomer incorporation (3-4%) and a noticeable increase of the
polydispersity index.
The obtained polymer samples, containing up to 6% of butyl branches, are
characterized by relatively high molecular weights (from 3.17 x 105 to 1.40 x 106) and
melting points (from 142.2 to 135.1 °C).
8

Figure 3. 13C NMR of polyethylene prepared by tandem catalysts (1 - run 4, 2
- run 5 and 3 - run 14 in Table 2).
Conclusion
Branched polyethylene has been produced by using nickel bisphenoxyiminato
complex
1
and dichlorotitanium complexes
2
or 3, stabilized by 2-
hydroxymethylphenole derivatives. The polymerization conditions largely affect the
magnitude of the catalytic activity, along with the composition and structure of the
resulting polymer.
The results showed that polyolefins with low melting points, low crystallinity
and more branches were obtained by the simultaneous adding of the catalysts. The
melting point and crystallinity of the polyethylene decreased with an increase of the
Ni/Ti molar ratio as well as with a decrease of the polymerization temperature.
Compared to the titanium catalyst in the tandem system, the bulkier o-
adamantyl complex 3 had a higher activity for ethylene polymerization, while the o-
tert-butyl catalyst 2 gave stronger copolymerization ability behavior.
9

Materials and methods.
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 Super Clean™ Gas Filters. Toluene,
n-hexane, diethyl ether and tetrahydrofuran were distilled over Na/benzophenone
ketyl. Dichloromethane was distilled over calcium hydride. The water contents in
these solvents were periodically controlled by Karl-Fischer coulometry using a
Methrom 756 KF apparatus. Benzene-d6 and toluene-d8 were stored over Na/K alloy
and degassed by freeze-pump-thaw cycles before being vacuum transferred directly.
CDCl3 and CD2Cl2 were degassed and stored over 4 Å sieves. Unless otherwise noted,
all reagents were purchased from Sigma-Aldrich. Polymethylaluminoxane (Witco)
was used as a 10% solution in toluene. 2-Adamanthyl-4-tert-buthylphenol and
dichlorodiisopropoxytitanium were prepared by following literature procedures.10,11
Physical and analytical measurements.
NMR spectra were recorded on Bruker AMX-400. Chemical shifts are reported
in ppm vs. SiMe4 and were determined by reference to the residual solvent peaks. All
coupling constants are given in Hertz. IR spectra were recorded on a Magna-IR 750
spectrophotometer. Elemental analysis was performed by the microanalytical
laboratory at the A. N. Nesmeyanov Institute of Organoelement Compounds.
Gel permeation chromatography (GPC) of polymer samples was carried out in
1,2,4-trichlorobenzene at 135 °C on a Waters GPCV-2000 chromatograph with the use
of a PLgel 5 µm MIXED-C column. Molecular masses were estimated using the
universal calibration curve plotted relative to polystyrene standards.
Thermogravimetric analysis of the samples was performed on a NETZSCH
STA-Jupiter449 C. Measurements were carried out in a flow of argon (100 ml/min) in
the temperature range 40-300 ºC. The heating rate was 5 °C/min.
X-ray diffraction data for complex 3 were collected on a Bruker Apex Duo
diffractometer (λ(MoKα) = 0.71072Å, ω-scans with 0.6° step and 15 s per frame
exposure, 2θ < 56°). Dark red crystals of C29H42Cl2F6O4Ti·0.5(C7H8) at 120 K are
triclinic, space group P-1, a = 10.9664(6), b = 11.6063(6), c = 15.0987(8) Å, α =
97.7690(10), β = 99.4200(10), γ = 106.5390(10) °, V = 1783.51(16) Å3, Z = 2, dcalc = 1.366
g cm-3. Intensities of 8609 independent reflections (Rint = 0.0520) out of 20488
10

collected were used in the structure solution and refinement. The structure was solved
by direct methods and refined by the full-matrix least-squares technique against F2 in
the anisotropic-isotropic approximation. Hydrogen atoms connected to oxygen atoms
of the coordinated i-PrOH moieties were located from the difference Fourier synthesis,
the positions of all other hydrogen atoms were calculated. Hydrogen atoms except
those of OH groups were refined in a riding model with Uiso = 1.5Ueq and Uiso = 1.2Ueq
of the connected methyl and all other carbon atoms. The refinement converged to R1 =
0.0433 (calculated for 6033 observed reflections with I>2σ(I)) wR2 = 0.0941 and GOF =
1.034. All calculations were performed with the SHELX software package.15 Structural
parameters and reflection data have been deposited at the Cambridge Crystallographic
Data Center (CCDC), reference number 1023306.
Bis(N-salicylidene-2,6-di-isopropylaniline)nickel(II) (1) was synthesized as
described in the literature9 as a green crystalline powder, yield: 67%, IR (KBr, cm-1):
ν(C=N) 1607. MS (m/z): 618 (M, 42.17), 338 (34.00). Anal. Calcd. for C38H44N2NiO2:
C, 73.68; H, 7.16; N, 4.52. Found: C, 73.53; H, 7.02; N, 4.37.
2-[2,2,2-Trifluo-1-hydroxy-1-(trifluoromethyl)ethyl]-4,6-di-tert-buthyl]phenol
was synthesized as described in the literature16 as white crystals, yield: 92%. Anal.
Calcd. for C17H22F6O2: C, 54.84; H, 5.96; O, 8.59; F, 30.61. Found: C, 54.79; H, 5.82;
F, 30.50. 1H NMR (400 MHz, CDCl3) δ: 7.77 (s, 1H, Ar-H), 7.42 (s, 1H, Ar-H), 5.34
(br.s, 1H, OH), 1.43 (s, 9H, tBu), 1.29 (s, 9H, tBu). 13C NMR (400 MHz, CDCl3) δ:
19
153.58, 141.94, 134.74, 126.42, 122.44, 115.75, 36.33, 34.51, 31.49, 30.02. F NMR
(400 MHz, CDCl3) δ: 2.52 (s).
2-[2,2,2-Trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]-4-tert-butyl-6-(1-
adamantyl)-phenol. To a pre-dried ampule, 6.32 g (0.02 mol) of 1-adamantyl-4-tert-
butyl-phenol10 and 25 ml of CCl4 were introduced under argon flow. After the solution
was degassed it was cooled down to -35 °C and 5.0 g (∼0.03 М) of 1,1,1,3,3,3-
hexafluoroacetone was added over a period of 20 min. The ampule was sealed and
incubated for 24 h at r.t. Upon completion, the ampule was frozen, unsealed and the
remaining gas was removed by argon and trapped in a washing bottle. The organic
phase was concentrated under reduced pressure. The crude product was purified by
recrystallization from n-hexane to give the title compound as colorless crystals. Yield:
11

1
5.12 g (57%). H NMR (400 MHz, CDCl3) δ: 7.85 (s, 1H, Ar-H), 7.36 (s, 1H, Ar-H),
5.47 (s,1H, OH), 2.14-2.11 (m, 9H, Ad-H), 1.79 (s, 6H, Ad-H), 1.28 (s, 9H, t-Bu). 13C
NMR (400 MHz, CDCl3) δ: 153.58, 141.67, 137.44, 126.18, 121.93, 111.45, 77.16,
77.16, 76.84, 76.53, 40.51, 37.35, 36.84, 34.25, 31.20, 28.89. 19F NMR (400 MHz,
CDCl3) δ: 1.39 (s). Anal. Calcd. for C23H28F6O2: C, 61.33; H, 6.27; F, 25.30. Found:
C, 61.23; H, 6.44; F, 24.91.
{2-[α,α-Bis(trifluoromethyl)methanolato]-4,6-di-tert-butyl-phenolato}dichlorodi
(propan-2-ol)titanium, (2) was synthesized as described in the literature.6 The yield
of brownish black crystals was 59%. Ti, 7.89. 1H NMR (400 MHz, CD2Cl2) δ: 7.59 (s,
1 H, Ar-H), 7.47 (s, 1H, Ar-H), 4.83-4.79 (m, 2H), 4.02-3.83 (m, 2H), 1.45 (s, 9H, t-
Bu), 1.44 (s, 6H, (CH3)2), 1.42 (s, 6H, (CH3)2), 1.32 (s, 9 H, t-Bu). 13C NMR (400
MHz, CDCl3) δ: 137.72, 134.90, 126.37, 125.56, 123.18, 122.39, 77.16, 35.83, 35.36,
34.99, 34.53, 31.50, 31.46, 30.37, 29.98, 24.69.19F NMR (400 MHz, CDCl3) δ: 4.15
(s). Anal. Calcd. for C23H36Cl2F6O4Ti: C, 45.49; H, 5.64; Cl, 11.68; F, 18.77. Found
(%): C, 45.33; H, 5.62.
({2-[α,α-Bis(trifluoromethyl)methanolato]-4-tert-butyl-6-(1-adamantyl)-
phenolato}- dichlorodi(propan-2-ol)titanium), (3). A Schlenk tube fitted with a
magnetic stirring bar was charged under argon with compound 1 (0.45 g, 1.0 mmol)
and toluene (10 mL). Then (i-PrO)2TiCl2 (0.28 g, 1 mmol) in toluene (10 mL) was
added. After the formation of a red precipitate, the mixture was heated to
homogenization. On cooling, the red crystals that formed were filtered off and washed
1
with toluene. Yield: 0.41 g (62 %). H NMR (400 MHz, CDCl3) δ: 7.12 (s, 1Н), 6.92
(s, 1Н), 4.80 (m, 12Н), 3.80 (br.s., 2H), 3.54 (m, 4Н), 1.47 (s, 12H), 1.43 (s, 9Н). 13C
NMR (400 MHz, C6D6) δ: 137.58, 129.28, 128.97, 128.65, 125.55, 125.23, 124.91,
31.46, 30.58, 24.55, 21.29, 21.03, 20.78, 20.52, 20.27, 20.01, 19.76. 19F NMR (400
MHz, CDCl3) δ: 1.39 (br. s). Anal. Calcd. for C29H42Cl2F6O4Ti: C, 50.67; H, 6.16.
Found (%): C, 49.93; H, 6.02.
Oligomerization of ethylene was performed in a 100 ml reactor (Parr
Instrument Co.) equipped with a magnetic stirrer and inlets for loading components of
the catalytic systems and ethylene at a total ethylene and toluene vapor pressure of 1.7
atm. Toluene (50 ml) and the necessary amount of the cocatalyst (a mixture of
Et2AlCl/Bu2Mg (3:1), Me3Al or (MeAlO)n (MAO)) were loaded in the reactor. The
12

reactor was heated to a specified temperature and the reaction mixture was saturated
with ethylene. Oligomerization was initiated by addition of the pre-catalyst to the
reaction mixture. The pressure of ethylene was maintained as constant during the
oligomerization. After the desired time, the reaction solution was quickly cooled down
and then quenched with 5 ml 5% dilute hydrochloric acid. After being washed with
water and dried with Na2SO4, the organic compounds were characterized by gas
chromatography and GC–MS to determine the composition and molar mass
distribution
Polymerization/ in situ copolymerization of ethylene
A procedure similar to the oligomerization was used. For the ethylene
polymerization, only a solution of the polymerization catalyst was added to the
reactor. For the in situ copolymerization, solutions of the oligomerization and
copolymerization catalysts were added at the same time. After the desired time, the
polymerization was quenched with acidified ethanol (100 mL, 10 vol.% HCl in
ethanol). The precipitated polymer was filtered off, washed with ethanol and then
dried under vacuum overnight at 50 °C to constant weight.
Acknowledgment This work was financially supported by the Russian
Foundation for Basic Research (Project Nos. 14-03-00603a, 13-03-12181, 12-03-
00511, 14-03-31260).
References
1. D.L. Beach, Y.V. Kissin, J. Polym. Sci., Part A: Polym. Chem. 22 (1984)
3027-3042, DOI: 10.1002/pol.1984.170221125.
2. Y.V. Kissin, D.L. Beach, J. Polym. Sci., Part A: Polym. Chem. 24 (1986)
1069-1084, DOI: 10.1002/pola.1986.080240601.
3. Z.J.A. Komon, G. C. Bazan, Macromol. Rapid Commun. 22 (2001) 467-478,
DOI: 10.1002/1521-3927(20010401)22:7<467::AID-MARC467>3.0.CO;2-O.
4. J.-C. Wasilke, S.J. Obrey, R. T. Baker, G.C. Bazan, Chem. Rev. 105 (2005)
1001-1020, DOI:10.1021/cr020018n.
5. C. Robert, C. M. Thomas, Chem. Soc. Rev. 42 (2013) 9392-9490, DOI:
10.1039/c3cs60287g.
13

6. M. V. Solov’ev, S. Ch. Gagieva, V. A. Tuskaev, N. M. Bravaya, O. E.
Gadalova, V. N. Khrustalev, A. O. Borissova, B. M. Bulychev, Russ. Chem.
Bull. 60 (2011) 2227-2235.
7. L.A. Rishina, S. S. Lalayan, S. Ch. Gagieva, V.A. Tuskaev, A. N.
Shchegolikhin, D. P. Shashkin, Y. V. Kissin, Journal of Research Updates in
Polymer Science 3 (2014) 216-226, DOI: http://dx.doi.org/10.6000/1929-
5995.2014.03.04.3.
8. Y. V. Kissin, R. I. Mink, A. J. Brandolini, T. E. Nowlin, J. Polym. Sci. A:
Polym. Chem. 47 (2009) 3271-3285, DOI: 10.1002/pola.23391.
9. I. Kim, C. H. Kwak, J. S. Kim, C.-S. Ha, Appl. Catal. A: General 287 (2005)
98-107, doi:10.1016/j.apcata.2005.03.026.
10. B. I. No, Yu. L. Zotov, E. V. Shishkin, V. N. Karev, J. Gen. Chem. USSR
(Engl. Transl.) 59 (1989) 81.
11. K. Mikami, M. Terada, T. Nakai, J. Am. Chem. Soc. 112 (1990) 3949-3954,
DOI: 10.1021/ja00166a035.
12. K. Nakamoto (Ed.), Infrared and Raman Spectra of Inorganic and Coordination
Compounds: Applications in Coordination Organometallic and Bioinorganic
Chemistry, Wiley, New York, 1997. p. 400.
13. J.C. Randall, J. Macromol Sci. Rev. Macromol. Chem. Phys. C 29 (1989) 201-
317, DOI:10.1080/07366578908055172.
14. G.B. Galland, R. Quijada, R. Rojas, G.C. Bazan, Z.J.A. Komon,
Macromolecules 35 (2002) 339-345, DOI:10.1021/ma010744c.
15. G. M. Sheldrick, Acta Cryst. Sect.
doi:10.1107/S0108767307043930.
A
64 (2008) 112-122,
16. V. I. Dyachenko, M. V. Galakhov, A. F. Kolomiets, A. V. Fokin, Izv. Akad.
Nauk SSSR, Ser. Khim., 1989, 923 [Bull. Acad. Sci. USSR, Div. Chem. Sci.
(Engl. Transl.), 1989, 38, 831].
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Graphical abstract synopsis
Novel titanium complexes bearing 2-hydroxymethylphenol derivatives were
synthesized. In combination with a phenoxyimine nickel complex, Et2AlCl and Bu2Mg
this catalyst system is able to produce linear low-density polyethylene (LLDPE) with
ethylene as the sole monomer stock with high activity (up to 7.4 x 105 g/mol Ti h atm).
15

Graphical abstract
Alk = Et, Bu, ...
C2H4
LLDPE
2 R = tBu
3 R = Ad
1
Et2AlCl
Et2AlCl/Bu2Mg
16