Q. Zhang et al. / Journal of Organometallic Chemistry 804 (2016) 18e25
23
these complexes possess a relatively crowded hepta-coordinating
4.3. Synthesis of 2,6-Et2C6H3(2-Py)NH (HL2)
environment around their central titanium atoms. Upon activa-
tion with AliBu3 and Ph3CB(C6F5)4, complexes 1e4 all exhibit
excellent catalytic activity for ethylene and propylene polymeri-
zation, producing high molecular weight linear polyethylene and
high molecular weight atactic polypropylene. Among these com-
plexes, the bulkiest complex 1 shows the highest catalytic activity
for ethylene polymerization while the least bulky complex 4 shows
the highest catalytic activity for propylene polymerization under
similar conditions.
Compound HL2 was synthesized in the same manner as
described for HL1 with 2-bromopyridine (1.58 g, 10.0 mmol) and
2,6-diethylaniline (1.49 g, 10.0 mmol) as the starting materials. Pure
product (2.04 g, 9.01 mmol, 90.1%) was obtained as a white crys-
talline material. 1H NMR (CDCl3, 300 MHz, 298 K):
d
8.13 (d, J ¼ 5 Hz,
1H, PyH), 7.35 (t, J ¼ 8 Hz, 1H, PyH), 7.25 (d, J ¼ 7 Hz, 1H, PhH), 7.19
(d, J ¼ 7 Hz, 2H, PhH), 6.62 (t, J ¼ 6 Hz, 1H, PyH), 6.35 (br, 1H, NH),
6.00 (d, J ¼ 8 Hz, 1H, PyH), 2.61 (q, J ¼ 7 Hz, 4H, CH2CH3), 1.15 (t,
J ¼ 7 Hz, 6H, CH2CH3) ppm.
4. Experimental section
4.4. Synthesis of 2,6-Me2C6H3(2-Py)NH (HL3)
4.1. General methods
Compound HL3 was synthesized in the same manner as
described for HL1 with 2-bromopyridine (1.58 g, 10.0 mmol) and
2,6-dimethylaniline (1.21 g, 10.0 mmol) as the starting materials.
Pure product (1.83 g, 9.23 mmol, 92.3%) was obtained as a white
All manipulations involving air- and/or moisture-sensitive
compounds were carried out under nitrogen atmosphere (ultra-
high purity) using either standard Schlenk or glove box techniques.
Toluene, diethyl ether, THF, n-pentane and n-hexane were distilled
under nitrogen in the presence of sodium and benzophenone.
CH2Cl2 was dried by distilling over calcium hydride before use.
Cp*TiCl3 [31] and Ph3CB(C6F5)4 [32] were prepared according to
literature procedures. Polymerization grade ethylene and propyl-
ene was further purified by passage through columns of 5 Å mo-
lecular sieves and MnO. AliBu3, n-BuLi, TiCl4, 2-bromopyridine,
crystalline material. 1H NMR (CDCl3, 300 MHz, 298 K)
d 8.14 (d,
J ¼ 5.1 Hz, 1H, PyH), 7.44e7.32 (m, 1H, PyH), 7.14 (s, 3H, PhH),
6.69e6.60 (m, 1H, PyH), 6.18 (br, 1H, NH), 6.02 (d, J ¼ 8.4 Hz, 1H,
PyH), 2.23 (s, 6H, ArCH3) ppm.
4.5. Synthesis of 4-MeC6H3(2-Py)NH (HL4)
Pd(OAc)2,
NaOtBu,
DPEphos,
2,6-dimethylaniline,
2,6-
Compound HL4 was synthesized in the same manner as
described for HL1 with 2-bromopyridine (1.58 g, 10.0 mmol) and 4-
methylaniline (1.07 g, 10.0 mmol) as the starting materials. Pure
product (1.67 g, 9.09 mmol, 90.9%) was obtained as a white crys-
diethylaniline, 2,6-diisopropylaniline and 4-methylaniline were
purchased from Aldrich or Acros. 1H and 13C NMR spectra were
recorded using a Varian Mercury-300 or a Bruker Avance III-400
NMR spectrometer. 13C NMR spectra of the polymers were recor-
ded on a Bruker Avance III-400 NMR spectrometer at 135 ꢁC with o-
C6D4Cl2 as the solvent. The viscosity-averaged molecular weight
talline material. 1H NMR (CDCl3, 400 MHz, 298 K)
d 8.17 (ddd,
J ¼ 5.0, 1.9, 0.9 Hz, 1H, PyH), 7.46 (ddd, J ¼ 8.5, 7.2, 1.9 Hz, 1H, PyH),
7.23e7.12 (m, 4H, PhH), 6.81 (dt, J ¼ 8.4, 0.9 Hz, 1H, PyH), 6.69 (ddd,
J ¼ 7.2, 5.0, 0.9 Hz, 1H PyH), 2.33 (s, 3H, PhCH3) ppm.
(Mh) of the polyethylene samples was measured in decahy-
dronaphthalene at 135 ꢁC by a Ubbelohde viscometer according to
the following equation: [
h
] ¼ 6.77 ꢀ 10ꢂ4
M
h
0.67. The molecular
4.6. Synthesis of complex 1
weights and molecular weight distributions of the atactic poly-
propylene samples were determined at 40 ꢁC by gel permeation
chromatography equipped with a Waters 515 HPLC pump, four
columns (HMW 7 THF, HMW 6E THF ꢀ 2, HMW 2 THF) and a
Waters 2414 refractive index detector. THF was used as the eluent
at a flow rate of 1.00 mL/min against polystyrene standards with
Mark-Houwink corrections. The melting points of the poly-
ethylenes were measured by differential scanning calorimetry
(DSC) on a NETZSCH DSC 204 at a heating/cooling rate of 10 ꢁC/min
from 35 to 160 ꢁC and the data from the second heating scan were
used.
A solution of nBuLi (1.60 M in n-hexane, 3.9 mL, 6.25 mmol) was
slowly added to a solution of 2,6-iPr2C6H3(2-Py)NH (1.59 g,
6.25 mmol) in n-hexane (20 mL) at ꢂ20 ꢁC, during which period a
large amount of white precipitate formed. The reaction mixture
was allowed to warm to room temperature and stirred for 5 h. The
resultant precipitate was collected on a frit, washed with cold n-
hexane (2 ꢀ 10 mL) and dried under vacuum to give 2,6-iPr2C6H3(2-
Py)NLi as a white solid. Then Cp*TiCl3 (1.45 g, 5.00 mmol) and
2,6-iPr2C6H3(2-Py)NLi (1.30 g, 5.00 mmol) were mixed in toluene
(15 mL) at ꢂ78 ꢁC. The reaction mixture was allowed to warm to
room temperature first and then stirred at 50 ꢁC overnight. The
precipitate was filtered off and the filtrate was concentrated to
leave a dark brown residue. Recrystallization from CH2Cl2/n-hexane
gave pure product 1 (1.69 g, 3.33 mmol, 66.7%) as reddish brown
crystals. Anal. Calcd. for C27H36Cl2N2Ti (507.36): C, 63.92; H, 7.15; N,
5.52. Found: C, 63.66; H, 7.09; N, 5.67. 1H NMR (CDCl3, 300 MHz,
4.2. Synthesis of 2,6-iPr2C6H3(2-Py)NH (HL1)
Pd(OAc)2 (22.4 mg, 0.10 mmol), NaOtBu (1.15 g, 12.0 mmol) and
DPEphos (80.8 mg, 1.15 mmol) were mixed with a solution of 2-
bromopyridine (1.58 g, 10.0 mmol) and 2,6-diisopropylaniline
(1.77 g, 10.0 mmol) in toluene (20 mL) under nitrogen atmo-
sphere. This suspension was stirred at 95 ꢁC overnight. The reaction
mixture was cooled to room temperature and quenched with water
(40 mL). The mixture was extracted with ethyl acetate (3 ꢀ 20 mL).
The combined organic phases were dried with anhydrous MgSO4,
filtered and concentrated by distillation under reduced pressure to
give an solid crude product and the solid product was recrystallized
from absolute ethanol to yield the pure product HL1 (2.33 g,
9.16 mmol, 91.6%) as a white powder. 1H NMR (CDCl3, 300 MHz,
298 K):
d 8.09 (m, 1H, PyH), 7.32e7.24 (m, 1H, PyH), 7.17e7.10 (m,
3H, PhH), 6.54 (m, 1H, PyH), 5.55e5.50 (m, 1H, PyH), 3.25e3.15 (m,
2H, CH(CH3)2), 2.29 (s, 15H, CpCH3), 1.28 (d, J ¼ 6.8 Hz, 6H,
CH(CH3)2), 0.93 (d, J ¼ 6.8 Hz, 6H CH(CH3)2) ppm. 13C NMR (CDCl3,
75 MHz, 298 K): d 167.1, 147.3, 144.0, 143.2, 140.9, 134.1, 126.5, 123.9,
112.6, 105.0(ArC, PyC), 28.0 (CH(CH3)2), 25.6 (CH(CH3)2), 23.8
(CH(CH3)2), 14.2 (CpCH3) ppm.
4.7. Synthesis of complex 2
298 K)
d
8.13 (dd, J ¼ 5.1, 1.9 Hz, 1H, PyH), 7.39e7.20 (m, 4H, PyH,
PhH), 6.62 (m, 1H, PyH), 6.15 (br, 1H, NH), 5.99 (d, J ¼ 8.4 Hz, 1H,
PyH), 3.20 (m, J ¼ 6.9 Hz, 2H, CH(CH3)2), 1.14 (d, J ¼ 6.9 Hz, 12H,
CH(CH3)2) ppm.
A solution of nBuLi (1.60 M in n-hexane, 7.9 mL, 12.5 mmol) was
slowly added to a solution of 2,6-Et2C6H3(2-Py)NH (2.83 g,
12.5 mmol) in n-hexane (20 mL) at ꢂ20 ꢁC, during which period a