844 Organometallics, Vol. 23, No. 4, 2004
Mahanthappa et al.
3
Cp-H), 4.49 (q, 1H, J H-H ) 6.5 Hz, -NCHPhCH3), 1.70 (3H,
rapid stirring for at least 30 min with a continuous ethylene
feed. In a drybox, a stock solution of titanium organometallic
compound (∼0.5-1 mg/mL 1-hexene) and a stock solution of
iprAFPB (1-3 mg/mL toluene) were prepared. The desired
amount of stock solution containing the titanium complex was
diluted with 1-hexene to a total volume of 2 mL and loaded
into a 25 mL double-ended injection tube, while the desired
amount of iprAFPB stock solution was diluted with 1-hexene
to a total volume of 3 mL and loaded into a 50 mL double-
ended injection tube. The polymerization was initiated as
follows: autoclave stirring was halted, the ethylene feed was
disconnected, the reactor was vented by 10 psi, and the
solution of organotitanium complex was injected under eth-
ylene pressure. Once the pressure reached a maximum (15 s),
the reactor was vented by 10 psi for a second time, and the
iprAFPB solution was introduced under ethylene pressure;
stirring of the reactor was recommenced upon the second
injection. The polymerizations were maintained at a constant
temperature ((1 °C) using an ethylene glycol/water cooling
loop. After a set reaction time, polymerizations were quenched
by injection of 10 mL of methanol under argon pressure (250
psi) while slowly venting the reactor. The contents of the
reactor were subsequently poured into a solution of methanolic
HCl and stirred for 12 h. Tacky polymers were allowed to settle
overnight to ensure complete product isolation. The acidic
methanol was decanted and the resulting polymer was rinsed
twice with 50 mL of methanol, followed by drying in a vacuum
oven at 60 °C for at least 8 h.
d, 3J H-H ) 6.5 Hz, NCHPhCH3), 1.27 (9H, s, (CH3)3CN-), 0.417
(s, 3H, Ti-CH3), 0.388 (s, 3H, Ti-CH3). 13C NMR (100 MHz,
C6D6, 19 °C): δ (ppm) 145.01, 128.73, 127.05, 113.47, 61.82,
60.825, 48.09 (1J C-H ) 121.03 Hz), 47.78 (1J C-H ) 121.03 Hz),
27.54, 17.43. 13C NMR (100 MHz, CDCl3, 19 °C): δ (ppm)
144.65, 128.43, 127.83, 126.76, 113.08, 61.96, 60.65, 47.67,
47.19, 27.54, 17.33. Anal. Calcd for C19H29NOTi: C 68.05, H
8.72, N 4.18. Found: C 67.68, H 8.94, N 3.98.
Cp *TiMe2(ON(tBu )(CHP h Me)) (5). Synthesis is analogous
to that of 4 except that Cp*TiCl3 (0.921 g, 3.18 mmol) and
tBu-R-phenylnitrone (0.564 g, 3.18 mmol) were used. Yield: not
1
taken. H NMR (500 MHz, C6D6, 20 °C): δ (ppm) 7.55 (d, 2H,
3J H-H ) 8.0 Hz, o-C6H5), 7.2 (app t, 2H, J H-H ) 9.5 Hz,
3
m-C6H5), 7.09 (app t, 1H, 3J H-H ) 9.5 Hz, p-C6H5), 4.38 (q, 1H,
3J H-H ) 8.5 Hz, -NCHPhCH3), 1.78 (s, 15H, (C(CH3))5), 1.67
3
(3H, d, J H-H ) 8.5 Hz, NCHPhCH3), 1.15 (9H, s, (CH3)3CN-
), 0.49 (s, 3H, Ti-CH3), 0.46 (s, 3H, Ti-CH3). 13C{1H} NMR
(125 MHz, C6D6, 20 °C): δ (ppm) 145.56, 128.16, 127.82,
127.49, 120.73, 62.84, 62.14, 49.53, 49.20, 27.64, 19.51, 11.38.
This sample could not be obtained in analytically pure form
due to its high degree of pentane solubility.
2,6-Diisop r op yl-N,N-d im eth yla n ilin iu m Tetr a k is(p en -
ta flu or op h en yl)bor a te (ip r AP F B). Excess anhydrous gas-
eous HCl (generated by the dehydration of concentrated
HCl(aq) and with concentrated H2SO4) was bubbled through
a solution of 2,6-diisopropyl-N,N-dimethylaniline (2.0 g, 9.74
mmol) in 25 mL of Et2O at room temperature to generate a
white precipitate. The resulting anilinium hydrochloride was
filtered on a medium frit in air, and the solid was washed with
Et2O (3 × 10 mL) to remove any excess aniline and dried under
vacuum for 12 h at room temperature. Yield: 1.3 g (55% based
on the aniline).
MAO Activa tion . All polymerizations were carried out in
a 300 mL stainless steel autoclave equipped with a mechanical
stirrer. MAO (100 mg) was suspended in 35 mL of 1-hexene
and was loaded into a 150 mL double-ended injection tube
equipped with quick-connect fittings. The autoclave was
evacuated on a vacuum line and flushed four times with 100
psi of ethylene. The reactor was vented to 10 psig, and the
MAO/1-hexene suspension was injected into the reactor under
the desired ethylene pressure. This solution was allowed to
equilibrate under continuous ethylene feed with rapid stirring
for at least 30 min. In a drybox, a stock solution of titanium
organometallic compound (∼0.5-1 mg/mL 1-hexene) was
prepared. The desired amount of stock solution containing the
titanium complex was diluted with 1-hexene to a total volume
of 2 mL and loaded into a 25 mL double-ended injection tube.
The polymerization was initiated by disconnecting the ethylene
feed, venting the reactor by 10 psi, and injecting the solution
of organotitanium complex under ethylene pressure. The
polymerizations were maintained at a constant temperature
((1 °C) using an ethylene glycol/water cooling loop. After a
set reaction time, the polymerizations were quenched by
injection of 10 mL of methanol under argon pressure (250 psi)
while slowly venting the reactor. The reactor contents were
poured into a solution of methanolic HCl and stirred for 12 h.
Tacky polymers were allowed to settle overnight to ensure
complete product isolation. The acidic methanol was decanted,
and the resulting polymer was rinsed twice with 50 mL of
methanol, followed by drying in a vacuum oven at 60 °C for
at least 8 h.
A 100 mL Schlenk tube was charged with 2,6-diisopropyl-
N,N-dimethylanilinium chloride (0.588 g, 2.43 mmol) and
(Et2O)2.5LiB(C6F5)4 (80% purity) (2.503 g, 2.59 mmol) as solids,
and 60 mL of dry CH2Cl2 was added at room temperature
under nitrogen. After stirring for 72 h at room temperature,
the reaction was Schlenk filtered through Celite and the filter
cake was washed with 120 mL of CH2Cl2. The solvent was
removed under vacuum from the combined filtrates to yield a
bubbly, white solid. This solid was treated with 10 mL of
CH2Cl2 and 100 mL of pentane to precipitate the solid white
product, which was collected by filtration and washed with
pentane (3 × 50 mL). 1H NMR (500 MHz, CDCl3, 19 °C): δ
3
(ppm) 7.65 (br s, 1H, N-H), 7.54 (dd, 1H, J H-H ) 7.75 Hz,
3J H-H ) 8.0 Hz, p-C6H3), 7.44 (dd, 1H, J H-H ) 8.0 Hz, J H-H
3
4
3
4
) 1.5 Hz, m-C6H3) 7.32 (dd, 1H, J H-H ) 7.75 Hz, J H-H ) 1.5
Hz, m-C6H3), 3.46 (s, 3H, N-CH3), 3.45 (s, 3H, N-CH3), 3.13
3
3
(qq, 1H, J H-H ) 7.0 Hz, J H-H ) 6.5 Hz, -CH(CH3)2), 2.85
(qq, 1H, 3J H-H ) 7.0 Hz, 3J H-H ) 6.5 Hz, -CH(CH3)2), 1.39 (d,
3
3
3H, J H-H ) 6.5 Hz, -CH(CH3)(CH3)), 1.34 (d, 3H, J H-H
)
7.0 Hz, -CH(CH3)(CH3)). 13C{1H} NMR (125 MHz, CDCl3, 19
°C): δ (ppm) 149.07, 147.16, 141.16, 139.16, 138.67, 137.23,
135.34, 132.20, 129.16, 125.86, 47.66, 29.66, 29.22, 24.01,
23.62. Anal. Calcd for C38H24NBF20: C 51.55, H 2.73, N 1.58.
Found: C 51.74, H 2.98, N 1.70.
E t h ylen e-H exen e Cop olym er iza t ion
P r oced u r e:
ip r AF P B Activa tion . All polymerizations were carried out in
a 300 mL stainless steel autoclave equipped with a mechanical
stirrer. Polymerizations employing iprAFPB activation were
carried out as follows: 60 mg of triisobutylaluminum (TIBA)
dissolved in 35 mL of 1-hexene was loaded into a 150 mL
double-ended injection tube equipped with quick-connect fit-
tings. The autoclave was evacuated on a vacuum line and
flushed four times with 100 psi of gaseous ethylene. The
reactor was vented to 10 psig, and the TIBA/hexene solution
was injected into the reactor under the desired ethylene
pressure. Then this solution was allowed to equilibrate with
P olym er Ch a r a cter iza tion . 13C{1H} NMR spectra (75.4
MHz) were obtained on a Varian Unity Inova 300 spectrometer
using a 10 mm broad-band probe operating at 100 °C. Samples
were prepared as solutions of 80 mg of polymer in 2.5 mL of
90:10 (v/ v) 1,2-dichlorobenzene/benzene-d6 containing ∼2 mg
of chromium(III) acetylacetonate as a spin lattice relaxation
agent. An inverse-gated decoupled pulse sequence with a pulse
repetition delay of 5 s was used to acquire a minimum of 3000
transients per sample. Weight and number average molecular
weights (Mw and Mn) were obtained by gel permeation chro-
Mahanthappa, Mahesh K.
