Acrylonitrile Polymerization
A R T I C L E S
Elemental analyses were performed by Midwest Microlab. GPC
measurements were performed on a Waters 150C high-temperature
GPC. Samples were dissolved in DMF at 40 °C. Molecular weights
were determined versus polystyrene standards and corrected by use of
experimentally determined Mark-Houwink parameters. Details are
given in the Supporting Information.
NMR (290 K, CD2Cl2): δ 2.03 (m, 6H), 1.80-1.90 (m, 24H), 1.75-
1.80 (m, 6H), 1.30-1.45 (m, 24H), 1.24 (m, 6H). 13C{1H} NMR (290
K, CD2Cl2): δ 31.8 (t, J ) 11 Hz, C1), 31.8 (s, C3), 27.3 (t, J ) 5 Hz,
C2), 26.2 (s, C4). 31P{1H} NMR (290 K, CD2Cl2) δ: 24.9 (s, PCy3),
-144.2 (septet, J ) 710 Hz, PF6-). 19F NMR (290 K, CD2Cl2): δ
1
73.7 (d, J ) 710 Hz). H NMR (190 K, CD2Cl2): δ 1.93 (m, 6H),
1.78 (m, 24H), 1.67 (m, 6H), 1.27 (m, 24H), 1.12 (m, 6H). 13C{1H}
NMR (190 K, CD2Cl2): δ 30.6 (s, C3), 29.8 (t, J ) 11 Hz, C1), 26.3
(t, J ) 6 Hz, C2), 25.2 (s, C4). 31P{1H} NMR (190 K, CD2Cl2): δ
25.1 (s, PCy3), -144.5 (septet, J ) 710 Hz, PF6-). Anal. Calcd for
C36H66CuF6P3: C, 56.20; H, 8.65. Found: C, 56.07; H, 8.54.
NMR spectra were recorded on Bruker DMX-500 or DRX-400
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spectrometers. H and 13C chemical shifts are referenced to residual
solvent signals: CD2Cl2, δ1H ) 5.32 and δ13C ) 53.8; toluene-d8, δ1H
) 2.09 and δ13C ) 20.4; THF-d8, δ1H ) 3.58 and δ13C ) 67.4; DMSO,
δ1H ) 2.49 and δ13C ) 39.5. These values were used at all temperatures.
31P and 19F chemical shifts are reported relative to external H3PO4 (85%)
and external neat CFCl3, respectively, at room temperature. Coupling
constants smaller than 5 Hz in 13C spectra were determined by
apodization with a Gaussian function. Polymer 13C NMR spectra were
recorded for 10 wt % DMSO solutions in sealed NMR tubes at 60 °C
with an acquisition time of 2 s and without a relaxation delay. Using
a relaxation delay of 6 s yielded the same values for tacticity and
branching. An internal Ph3PO standard was used to quantify signal
intensities in 31P NMR spectra. Temperatures in VT NMR experiments
were calibrated by use of MeOH as a chemical thermometer.53
Electrospray mass spectra (ESI-MS) were recorded on freshly
prepared samples (ca. 1 mg/mL in CH2Cl2) by use of an Agilent 1100
LC-MSD spectrometer incorporating a quadrupole mass filter with a
m/z range of 0-3000. A 5 µL sample was injected by flow injection
by use of an autosampler. Purified nitrogen was used as both the
nebulizing and drying gas. Typical instrumental parameters were:
drying gas temperature 350 °C, nebulizer pressure 35 psi, drying gas
flow 12.0 L/min, and fragmentor voltage 0 or 70 V. In all cases where
assignments are given, observed isotope patterns closely matched
calculated isotope patterns. The listed m/z value corresponds to the most
intense peak in the isotope pattern.
Me2CuLi‚LiI.17c A suspension of CuI (500 mg, 2.63 mmol) in Et2O
(10 mL) was cooled to -60 °C. A solution of MeLi in Et2O (2.9 mL,
1.7 M, 4.9 mmol) was added by syringe. The suspension was stirred
for 4 h, while it warmed to -30 °C, yielding a slurry of yellow CuMe
in a colorless supernatant (ATTENTION: CuMe is explosiWe when
dry. See ref 16 for information concerning safe handling and disposal
of this compound.) The slurry was filtered cold and hexane (10 mL)
was added to the filtrate. The solvents were removed from the filtrate
under vacuum and the remaining solid was dried for 3 h under vacuum
to yield 512 mg of a yellow powder, which was stored at -40 °C and
used without further purification. This material was contaminated with
0.25 equiv of CuMe. 1H NMR spectra in THF-d8 contained signals for
Me2CuLi and Me3Cu2Li, formed by the reaction of CuMe with Me2-
CuLi.27b
Acrylonitrile Polymerizations with 1. Details are provided in Table
4. Method A: The desired amounts of initiator and toluene (typically
5.00 g) were placed in a 100 mL Schlenk flask equipped with a stirring
bar and a rubber septum. The solution was stirred for 5-15 min at the
desired temperature, and acrylonitrile (typically 2.0 mL) was added
by syringe with exclusion of light. The mixture was stirred for the
desired time (typically 40 min) to yield in most cases highly viscous
polymer suspensions. The polymerization was quenched by adding HCl/
EtOH (10 mL of a 1 M solution), followed by EtOH (80 mL). The
polymer was separated by filtration, washed repeatedly with acetone,
1 M HCl/H2O, boiling water, and acetone, and then dried for at least
12 h under vacuum. Method B: The desired amounts of initiator and
toluene were placed in a 50 mL reaction tube equipped with a Teflon
stopcock. The solution was cooled to -196 °C and the desired amount
of acrylonitrile was added by vacuum transfer. The reaction tube was
sealed and placed into a bath at the desired temperature. The mixture
was stirred for the desired amount of time, and the polymer was isolated
by the procedure described in method A.
Cy3PCuMe (1).9a A flask was charged with CuI (0.95 g, 5.0 mmol)
and PCy3 (1.5 g, 5.5 mmol), and Et2O (20 mL) was added by cannula.
The suspension was cooled to -35 °C and stirred for 15 min. A solution
of MeLi in Et2O (5.2 mL, 1.0 M, 5.2 mmol) was added by syringe and
the suspension was stirred for 45 min at -35 °C. The solvent was
evaporated while the temperature was kept below -10 °C to yield an
off-white solid. The solid was dried for 1 h at room temperature under
vacuum. The solid was extracted with toluene/pentane (1/1, 3 × 10
mL). The extracts were cooled to -40 °C for 1 week to yield colorless
crystals (820 mg, 46%). In solution, 1 is in equilibrium with 3 below
1
260 K. H NMR (190 K, CD2Cl2): δ 1.65-1.85 (m, 1 + 3), 1.55-
1.65 (m, 1), 1.35-1.45 (m, 3), 1.1-1.35 (m, 1 + 3), -0.73 (s, 3H, 3,
Me), -1.11 (s, 3H, 1, Me). 13C{1H} NMR (190 K, CD2Cl2): δ 31.2 (t,
J ) 7 Hz, 3, C1), 30.2 (d, J ) 3 Hz, 1, C3), 30.0 (d, J ) 19 Hz, 1,
C1), 29.6 (s, 3, C3), 27.1 (t, J ) 5 Hz, 3, C2), 26.6 (d, J ) 11 Hz, 1,
C2), 25.5 (s, 3, C4), 25.5 (s, 1, C4), -5.9 (br s, 3, Me), -8.6 (br s, 1,
Me). 31P{1H} NMR (190 K, CD2Cl2): δ 17.4 (s, 1), 11.8 (s, 3). NMR
data for other solvents and temperatures are given in the Supporting
Information.
[Cy3PCH2CH2CN]Cl.54 A flask was charged with PCy3 (100 mg,
0.356 mmol), [Me3NH]Cl (35.5 mg, 0.356 mmol), and MeCN (1 mL).
AN (0.7 mmol) was added by vacuum transfer at -196 °C. The
resulting slurry was heated to reflux for 10 min to give a clear solution.
The solution was cooled to room temperature and layered with ethyl
acetate (2 mL). After 12 h a crystalline precipitate was obtained. The
precipitate was isolated by filtration, washed with ethyl acetate, and
dried for 1 h under vacuum to yield a colorless powder (36 mg, 27%).
1H NMR (330 K, DMSO-d6): δ 3.00-3.05 (m, JPH ) 9 Hz, -CH2CN,
2H), 2.77-2.81 (m, JPH ) 13 Hz, -CH2P+Cy3 2H), 2.59-2.63 (q, 2JPH
{Cy3PCu(µ-I)}2 (4).25 A suspension of CuI (20 mg, 0.11 mmol)
and PCy3 (29 mg, 0.10 mmol) in CD2Cl2 was heated in a sealed NMR
1
3
) JHH ) 11 Hz, P+CH(CH2-)2, 3H), 1.90-1.92 (m, 6H), 1.80-1.83
tube to reflux for 10 min to yield a clear solution. H NMR (290 K,
CD2Cl2): δ 1.95 (m, 9H), 1.79 (m, 6H), 1.71 (m, 3H), 1.49 (m, 6H),
1.26 (m, 9H). 13C{1H} NMR (290 K, CD2Cl2): δ 32.4 (d, J ) 16 Hz,
C1), 30.5 (s, C3), 27.8 (d, J ) 11 Hz, C2), 26.6 (s, C4).
[Cu(PCy3)2][PF6] (5). PCy3 (250 mg, 0.89 mmol) and [Cu(NCMe)4]-
[PF6] (150 mg, 0.38 mmol) were dissolved in CH2Cl2 (5 mL) and the
clear solution was stirred for 2 h at room temperature. The solvent
was removed under vacuum, Et2O (10 mL) was added, and the resulting
slurry was stirred for 30 min at room temperature. The precipitate was
collected by filtration, washed with Et2O (2 × 10 mL), and dried under
vacuum to yield 250 mg (0.32 mmol, 81%) of a colorless powder. 1H
(m, 6H), 1.55-1.71 (m, 3H), 1.48-1.58 (m, 6H), 1.29-1.43 (m, 9H).
13C{1H} NMR (330 K, DMSO-d6): δ 118.5 (CN), 28.8 (d, J ) 40 Hz,
C1), 25.7 (d, J ) 4 Hz, C3), 25.6 (d, J ) 12 Hz, C2), 24.4 (d, J ) 2
Hz, C4), 10.8 (d, J ) 44 Hz, PCH2CH2CN), 10.4 (d, J ) 3 Hz,
PCH2CH2CN). 31P{1H} NMR (330 K, DMSO-d6): δ 34.6. Assignments
and coupling constants are derived from selective 1H and 31P decoupling
experiments. ESI-MS (MeOH) [Cy3PCH2CH2CN]+: Calcd m/z 334.3,
found 334.2. Anal. Calcd for C21H37PNCl‚(H2O)0.5: C, 66.56; H, 10.11;
N, 3.70. Found: C, 66.53; H, 10.09; N, 3.77. (1H NMR analysis of the
(54) Adapted from
a synthesis of [Ph3PCH2CH2CN]Cl: Teichmann, H.;
(53) Van Geet, A. L. Anal. Chem. 1970, 42, 679.
Thierfelder, W.; Kochmann, W. DD 100960, 1972.
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J. AM. CHEM. SOC. VOL. 126, NO. 7, 2004 2123