Palladium-catalyzed synthesis of pure, regiodefined polymeric triarylamines

Article abstract of DOI:10.1021/ja990632p

Triarylamine polymers were prepared by palladium-catalyzed amination of aryl halides, and the electrochemical and magnetic properties of these materials were studied. Through a careful evaluation of the catalytic and polymer chemistry involved in this pro

Full text of DOI:10.1021/ja990632p

J. Am. Chem. Soc. 1999, 121, 7527-7539
7527
Palladium-Catalyzed Synthesis of Pure, Regiodefined Polymeric
Triarylamines
Felix E. Goodson, Sheila I. Hauck, and John F. Hartwig*
Contribution from the Department of Chemistry, Yale UniVersity, P.O. Box 208107,
New HaVen, Connecticut 06520-8107
ReceiVed March 1, 1999
Abstract: Triarylamine polymers were prepared by palladium-catalyzed amination of aryl halides, and the
electrochemical and magnetic properties of these materials were studied. Through a careful evaluation of the
catalytic and polymer chemistry involved in this process, triarylamine polymers that are exclusively linear and
free of phosphorus impurity in the polymer chain have been prepared. To suppress molecular weight-limiting
side reactions from palladium-catalyzed poly(N-arylaniline) polymerizations, a number of phosphines were
screened in reactions of small molecules to form triarylamines. Of these phosphines, tris(o-methoxymeth-
ylphenyl)phosphine (7) and tri(tert-butyl)phosphine (8) led to quantitative amination without ligand arylation,
aryl bromide hydrodehalogenation, or exchange of phosphine aryl groups with the aryl bromide. When these
phosphines were used in polymerizations, significant improvements in molecular weights were observed, but
an additional molecular weight limiting side reaction, the formation of cyclic oligomers, was not affected.
Strategies to minimize cyclizations that compete with chain growth were explored, including the use of
oligomeric monomers that greatly reduced the formation of cyclic oligomers. A chromatographic method
completely removed low molecular weight cyclic oligomers. A number of poly(N-arylaniline) derivatives with
Mw values as high as 105 g/mol were synthesized by using the optimized palladium-catalyzed method, and the
electronic and magnetic properties of these materials were investigated by cyclic voltammetry, magnetic
susceptibility, and EPR spectroscopy.
Introduction
these substituents create further structural ambiguity during the
electrophilic polymerization because their directing properties
may counteract the para-directing property of the amino group.
Poly(m-aniline)15-19 and oligomeric aniline derivatives with
alternating meta and para regiochemistry20 have been presented
recently as possible candidates for organic ferromagnetic
applications. Derivatives of poly(m-aniline) have been synthe-
sized by the copper-mediated Ullmann coupling.15,19 However,
these polymerizations are accompanied by the formation of
insoluble fractions, which may have resulted from cross-
linking.16
Since the discovery in 1985 that doped polyaniline is capable
of conducting electricity in the metallic regime,1 research has
focused on using this material in applications such as electrodes
in lightweight batteries2,3 and as flexible, hole-transport layers
in electroluminescent devices.4,5 Particularly appealing aspects
of this material are the simple and inexpensive synthesis by
chemical6 or electrochemical7-9 oxidation of aniline and the
moisture and air stability of its conductive form.1 Although
dominated by para regiochemistry, it is likely that ortho and
meta defects as well as biphenyl defects formed by C-C
coupling occur uncontrollably during the synthesis of this
material.10 Furthermore, the derivatives of this material that can
be formed by the aniline oxidation are limited. Derivatives with
substituents on the aromatic rings have been prepared,11-14 but
A general method to prepare a variety of aniline derivatives
would allow one to optimize and tune the properties of
arylamine polymers. Recent research by our group21,22 and
Buchwald’s23-25 has led to a highly efficient synthesis of tertiary
(1) MacDiarmid, A. G.; Chiang, J.-C.; Halpern, M.; Huang, W.-S.; Mu,
S.-L.; Somasiri, N. L. D.; Wu, W.; Yaniger, S. I. Mol. Cryst. Liq. Cryst.
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A. G. J. Polym. Sci., Polym. Chem. Ed. 1994, 32, 2147.
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10.1021/ja990632p CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/06/1999

7528 J. Am. Chem. Soc., Vol. 121, No. 33, 1999
Goodson et al.
aromatic amines from primary or secondary amines and aryl
bromides. In addition, studies by workers at Tosoh in Japan
have revealed a system for formation of tertiary amines that
provides yields and turnover numbers that are appropriate for
commercial applications.26,27
N-aryl substituent. Finally, a preparation of triarylamine poly-
mers by C-N bond formation would eliminate the possibility
of forming cross-linked polymer and may, therefore, generate
unambiguously linear material.
In communication form,41 we have reported that palladium-
mediated aminations could generate donor-acceptor triaryl-
amine copolymers in high yields and moderate molecular
weight, and poly(N-arylaniline) materials with molecular weights
near 5000. These polymerizations underwent three molecular
weight limiting events. First, CH activation of the tolyl groups
on the tri(o-tolyl)phosphine ligands42 used in the amination
reaction resulted in incorporation of phosphorus atoms into the
polymer chains, and most likely led to end-capping of the chains
by phosphines and by hydrogen atoms. Second, hydrodehalo-
genation of the aryl halide led polymer end-capping and limited
the scope of polymer that could be prepared with high molecular
weight to those produced from electron-poor aryl bromide
monomers. Third, cyclization of intermediate oligomers com-
peted with chain growth. This cyclization reduced the molecular
weights of the polymer samples and broadened the molecular
weight distributions.
During the past two years, several research groups have
published the preparation of polymeric aryl- and diarylamines.
However, these reports contain little information on the purity
of the polymers produced from this chemistry or information
on why one catalyst system provides different results from
another. For example, small-molecule model studies were not
reported that would reveal minor side products, and evaluation
of whether linear, ligand-free polymer was formed was not
presented. Kanbara used the palladium-mediated amination
chemistry to develop a synthesis of poly(aryleneamines) with
alkyl spacers in the polymer backbone28,29 and has reported
polymeric triarylamines with attached chromophores.30,31 Kan-
bara32 and Meyer33 have independently reported the synthesis
of parent poly(m-aniline), and Meyer has shown that these
polymers contain some cross-linking and BINAP ligand. Buch-
wald prepared and studied the electrochemistry of pure, discrete,
oligomeric models for poly(p-aniline).34,35
Our group has studied triarylamine materials and we have
reported discrete oligomers36 and dendrimers37 that show
interesting magnetic and electronic properties. As small mol-
ecules, triarylamines have particularly interesting electronic and
magnetic properties. They generate some of the most stable
radical cations, and they are readily oxidized to this aminium
state. Because of these properties, triarylamines have been
valuable for hole transport layers in LED applications and have
been used to observe high-spin polyradicals. Polymeric triaryl-
amines should combine the chemical properties of the small
molecules with the physical properties of macromolecules, while
providing a number of advantages over polyanilines that have
secondary arylamine linkages. For example, triarylamine mac-
romolecules should form more stable radicals than analogous
diarylamines or carbon-based radicals, considering their higher
stability as small molecules.38,39 Further, a few studies suggest
that triarylamines may have conductive properties that are
similar to those of poly(p-aniline),40 and in these cases one could
tune the electronic properties of the nitrogen and perhaps control
solid-state structures by using appropriate functionality on the
In this paper, we present studies that overcome these
limitations on the palladium-catalyzed synthesis of triarylamine
polymers and our success in generating polymers that are free
of cyclic oligomers and of phosphorus in the polymer chain,
even when electron-rich aryl bromides are involved. Amination
reactions on small molecules were used to find ligands that
would minimize phosphine incorporation and aryl halide hy-
drodehalogenation. In addition, strategies were followed to
reduce the impact of competing cyclization by using oligomeric
monomers. Alternatively, we found that Sephadex chromatog-
raphy would remove cyclic oligomers. These studies led to the
isolation of polymer that is free of phosphorus and cyclic
oligomer. With pure polymer in hand, we obtained preliminary
electronic and magnetic characterization of selected examples
of the polymeric triarylamines.
Results and Discussion
Effect of Ligand on Amination of Electron-Poor Aryl
Bromides. It is well-known that quantitative condensation
reactions are required to produce high molecular weight
polymers by a step growth mechanism. Thus, improvements
on the preparation of triarylamine polymers has relied upon our
ability to prevent phosphine arylation (eq 1)41-44 and aryl halide
hydrodehalogenation processes45 that occur in the palladium-
catalyzed amination to form triarylamines. Initially, we sought
(25) Marcoux, J.-F.; Wagaw, S.; Buchwald, S. L. J. Org. Chem. 1997,
62, 1568.
(26) Nishiyama, M.; Yamamoto, T.; Koie, Y. Tetrahedron Lett. 1998,
39, 617.
(27) Yamamoto, T.; Nishiyama, M.; Koie, Y. Tetrahedron Lett. 1998,
39, 2367.
(28) Kanbara, T.; Honma, A.; Hasegawa, K. Chem. Lett. 1996, 1135.
(29) Kanbara, T.; Izumi, K.; Narise, T.; Hasegawa, K. Polym. J. 1998,
30, 66.
(30) Kanbara, T.; Imayasu, T.; Hasegawa, K. Chem. Lett. 1998, 709.
(31) Kanbara, T.; Oshima, M.; Imayasu, T.; Hasegawa, K. Macromol-
ecules 1998, 31, 8725.
(32) Kanbara, T.; Izumi, K.; Nakadani, Y.; Narise, T.; Hasegawa, K.
Chem. Lett. 1997, 1185.
(33) Spetseris, N.; Ward, R. E.; Meyer, T. Y. Macromolecules 1998,
31, 3158.
(34) Singer, R. A.; Sadighi, J. P.; Buchwald, S. L. J. Am. Chem. Soc.
1998, 120, 213.
a phosphine with similar activity to tri(o-tolyl)phosphine (1)
that lacked the o-methyl C-H bonds that undergo phosphine
arylation. In rough initial studies, we found that reactions
involving tris(o-methoxyphenyl)phosphine as ligand were slug-
(35) Sadighi, J. P.; Singer, R. A.; Buchwald, S. L. J. Am. Chem. Soc.
1998, 120, 4960.
(36) Louie, J.; Hartwig, J. F. Macromolecules 1998, 31, 6737.
(37) Louie, J.; Hartwig, J. F.; Fry, A. J. J. Am. Chem. Soc. 1997, 119,
11695.
(41) Goodson, F. E.; Hartwig, J. F. Macromolecules 1998, 31, 1700.
(42) Louie, J.; Hartwig, J. F. Angew. Chem., Int. Ed. Engl. 1996, 35,
2359.
(43) Beller, M.; Fischer, H.; Herrmann, W. A.; O¨ fele, K.; Brossmer, C.
Angew. Chem., Int. Ed. Engl. 1995, 34, 1848.
(38) Tris(4-bromophenyl)aminium hexachloroantimonate is stable enough
to be sold commercially (Aldrich).
(39) Chow, Y. L. In ReactiVe Intermediates; Abramovitch, R. A., Ed.;
Plenum Press: New York, 1980; Vol. 1, pp 151-262.
(40) Ishikawa, M.; Kawai, M.; Ohsawa, Y. Synth. Met. 1991, 40, 231.
(44) Herrmann, W. A.; Brossmer, C.; O¨ fele, K.; Reisinger, C.-P.;
Priermeier, T.; Beller, M.; Fischer, H. Angew. Chem., Int. Ed. Engl. 1995,
34, 1844.
(45) Hartwig, J. F.; Richards, S.; Baran˜ano, D.; Paul, F. J. Am. Chem.
Soc. 1996, 118, 3626.

Synthesis of Pure, Regiodefined Polymeric Triarylamines
J. Am. Chem. Soc., Vol. 121, No. 33, 1999 7529
Table 1. Screening of Phosphines for Amination of Electron-Poor
Aryl Halides
Table 2. Polymerization Results with Electron-Poor Aryl Bromide
Monomersa
d
e
f
entry phosphine concn,b M % yieldc Mn
Mw
Mp
1
2
3
4
5
6
1
3
7
8
1
8
1
1
1
1
0.25
0.25
87
60
60
88
82
83
8400 28800 24300
12600 61100 49400
11500 71500 56100
14900 88000 88100
8400 41400 43600
11500 123500 116200
a Polymerizations were run for 3 days at 90 °C in benzene with a
catalyst loading of 2% (Pd/Br) and 3 equiv of phosphine per palladium.
Listed values are the average of at least two trials. Molecular weights
were measured by GPC and reported values are relative to polystyrene
standards. b Approximate concentration determined by mmol of each
monomer per mL of solvent. c Nonquantitative yields were due to gel
formation. d Number-averaged molecular weight. e Weight-averaged
molecular weight. f Molecular weight at peak maximum.
reactions containing the phosphines 3, 7, and 8 gave essentially
quantitative yield. Pure product 9 was isolated in about 95%
yield in these cases. These results suggested that 3, 7, and 8
are good candidates for polymerizations that form polymeric
triarylamines.
Polymerizations with Electron-Poor Aryl Bromides. Po-
lymerizations were carried out between 4,4′-dibromobenzophe-
none 10 and diaminobiphenyl monomer 11 to form polymer
12 (eq 3) with various phosphines and at varied concentrations.
a Determined by 1H NMR integrations relative to a 1,3,5-trimethoxy-
benzene internal standard. Values in parentheses reflect isolated yields.
Reported values are the average of at least two trials.
gish, while reactions containing tris[o-(trifluormethyl)phenyl]-
phosphine as ligand did not run to completion when using 5
mol % catalyst. We conjectured that the methoxyphenyl phos-
phine bound too strongly to the metal and that the trifluoro-
methylphenyl phosphine bound too weakly. Therefore, we
prepared mixed phosphines 2 and 3 shown in Table 1 in the
hopes of obtaining a ligand with intermediate binding ability
that would give better results.
During the course of this work, a number of groups published
results with different ligands that improved the yields of various
palladium-catalyzed amination reactions. In particular, Buchwald
showed that the amination with acyclic secondary alkylamines
was improved when Kumada’s ligand 4 was used.25 We were
intrigued with this result, but the expense of 4 limited its
practicality. Thus we prepared the more readily available 5,46
6,47 and 748 (Table 1). Very recently, Nishiyama, Yamamoto,
and Koie showed that the use of tri(tert-butyl)phosphine (8)
gave high yields and turnover numbers in the formation of
N-arylpiperazines26 and triarylamines.27
To test if these phosphines would be suitable for formation
of triarylamine polymers in the absence of concomitant phos-
phine arylation, we attempted the amination of 4-bromoben-
zophenone with ditolylamine using accurate 1:1 ratios of the
reagents and a combination of the various phosphines and
palladium acetate to form triarylamine 9 (eq 2). Reactions were
The results are presented in Table 2. Although the data indicate
only a marginal increase in number-averaged molecular weight
with use of the new phosphines, weight-averaged molecular
weights, as well as molecular weight at the maximum intensity
of the GPC trace (peak molecular weight), were improved
dramatically. Phosphine 8 provided the highest molecular weight
data. As mentioned in the Introduction, we have shown
previously for polymerizations using P(o-tolyl)3 as ligand that
coupling to form macrocyclic products can compete with linear
chain growth. The macrocyclic products were identified by both
MALDI MS of crude polymer samples and isolation of a
macrocyclic product from a reaction under high dilution
conditions.41 The increase in Mw but small change in Mn in the
polymerizations using phosphine 8 is consistent with increased
yields of the amination reaction with little effect on the
competing cyclization. As a result, peak molecular weight
increases, but low molecular weight spikes due to cyclic
oligomers are unchanged, creating a broader molecular weight
distribution. This effect can be seen in Figure 1, which shows
the chromatograms for polymers formed with phosphines 1 and
8 (Table 2, entries 1 and 4). Previously, the polymerization of
10 with a m-diaminobenzene monomer showed a marked effect
of concentration on molecular weight caused by competing
cyclization and chain growth; lower concentrations resulted in
lower molecular weights.41 During the synthesis of 12, the effect
of concentration on molecular weight was less straightforward
and appeared to result from two factors. Under dilute conditions
(Table 2, entries 5 and 6), the cyclization was more favored
conducted in benzene-d6, and the yields of 9 were evaluated
with respect to a trimethoxybenzene internal standard. For the
phosphines that gave the most promising results, isolated yields
were also obtained. The results of these experiments are
presented in Table 1. These data show that 1 does promote the
reaction in good yield, but the reactions are not quantitative.
One of the mixed phosphines 2, Kumada’s ligand 4, and two
of the analogues of 4, ligands 5 and 6, gave good yields, but
they were lower than those for reactions involving 1. In contrast,
(46) Cookson, E. A.; Crofts, P. C. J. Chem. Soc. C 1966, 2003.
(47) Terfort, A.; Brunner, H. J. Chem. Soc., Perkin Trans. 1 1996, 1467.
(48) Letsinger, R. L. J. Org. Chem. 1958, 23, 1806.

7530 J. Am. Chem. Soc., Vol. 121, No. 33, 1999
Goodson et al.
Table 3. Screening of Phosphines for Amination of Electron-Rich
Aryl Halides
phosphine % yielda % arenea
phosphine % yielda % arenea
1
2
3
4
85
68
85
77
12
b
trace
trace
5
6
7
8
60
59
94 (88)
97 (88)
15
17
6
a Determined by 1H NMR integrations relative to a 1,3,5-trimethoxy-
benzene internal standard. Values in parentheses reflect isolated yields.
Reported values are the average of at least two trials. b A number of
products were formed with overlapping resonances.
the new phosphines would reduce side reactions during ami-
nation of more electron rich aryl halides. In particular, aryl halide
dehydrohalogenation occurs to a greater extent during reactions
with more electron rich aryl halides,24,45,49 and polymerizations
to form some of our target poly(N-arylaniline)s would involve
coupling of electron-rich oligomers containing aryl halide
termini. To evaluate the ligands for such polymerizations, we
again conducted reactions with model substrates. In this case,
the reaction of (N,N-dimethylamino)-4-bromobenzene with
diphenylamine to form triarylamine 13 (eq 4) was used as a
model. Reactions were again run in deuterated solvent, and
Figure 1. GPC chromatograms for polymer 12 synthesized with
phosphines 1 (dotted line) and 8 (solid line).
yields were determined by NMR spectrometry. Isolated yields
were obtained for the most promising candidates, and the results
are listed in Table 3.
Two of the phosphines showed improved results relative to
tri-o-tolylphosphine 1. Reactions containing either phosphine
7 or 8 gave triarylamine 13 in significantly higher yields than
those employing 1, and these yields were close enough to
quantitative to warrant investigation in polymerization studies.
No hydrodehalogenation was detectable when 8 was used as
the ligand. The crude NMR spectra for reactions of 7 and 8
were spectacularly clean; the 88% isolated yields reflect only
mechanical losses in isolation. Thus, ligands 7 and 8 were
carried forward for the synthesis of polymers discussed in the
next section.
The other phosphines showed lower yields, but the reasons
for the reduced yields were not always straightforward. For
example, Kumada’s ligand 4 significantly reduced the amount
of arene formed, but the reaction yield was still lower than when
1 was used as ligand. Reactions containing phosphine 2
produced several unidentified byproducts in addition to forming
triarylamine 13. Reactions employing mixed phosphine 3 gave
higher yields than did those employing 1, but the yield was not
high enough to generate high molecular weight triarylamine
polymer.
An additional problem with Kumada’s ligand 4 and the
diphenylphosphino benzyl ether ligands 5 and 6 was detected
in these studies. Reactions involving 4, 5, and 6 produced
triphenylamine as a side product observed by GC-MS. This
byproduct most likely resulted from exchange of phosphine and
palladium-bound aryl groups known to occur in ArPdL2X
complexes.50,51 This aryl group exchange leads to incorporation
of phosphorus into the polymer backbone as well as end-capping
of the polymer with an aryl group.52 Thus, the formation of
Figure 2. 31P NMR spectra for samples of polymer 12 synthesized
with phosphines 1 (A), 3 (B), 7 (C) and 8 (D).
than at high concentrations and the number-averaged molecular
weight was slightly lower. However, the reaction appeared to
proceed further to completion as evidenced by the higher weight
average and peak molecular weights.
To determine if phosphines 3, 7, and 8 were reducing the
phosphorus incorporation as designed by eliminating tolyl group
arylation, polymer samples that were generated from reactions
containing the different ligands were analyzed by 31P NMR after
Soxhlet extraction of the samples for 12 h with hexane solvent.
As shown in Figure 2, the sample formed using tri-o-tolylphos-
phine as ligand showed a strong signal in the triarylphosphine
region, with other weaker signals in the phosphine oxide region
of the spectrum. However, we were pleased to find that the
polymer generated using ligands 3, 7, and 8 showed no
detectable 31P signals after data collection for 12 h.
(49) Driver, M. S.; Hartwig, J. F. J. Am. Chem. Soc. 1996, 118, 7217.
(50) Kong, K.-C.; Cheng, C.-H. J. Am. Chem. Soc. 1991, 113, 6313.
(51) Goodson, F. E.; Wallow, T. I.; Novak, B. M. J. Am. Chem. Soc.
1997, 119, 12441.
Catalytic Chemistry of Polymerizations Involving Electron-
Rich Aryl Halides. Although the above results led to improved
polymerizations using dibromobenzophenone, it was unclear if

Synthesis of Pure, Regiodefined Polymeric Triarylamines
J. Am. Chem. Soc., Vol. 121, No. 33, 1999 7531
Table 5. General Polymerization Resultsa
Table 4. Results for the Polymerization of 11 with 14a
%
concn,d
M
%
e
f
g
phosphine cat.b P/Pdc
yield Mn
Mw
Mp
1
7
8
1
1
8
8
8
8
8
2
2
2
2
2
2
2
0.5
0.05
2
3
3
3
3
3
3
3
3
3
6
1
1
1
79
8900 32100 18400
85 16100 45200 42500
95 13600 102100 103600
94
84
90 19300 107200 140000
95 11800 69300 104200
85 11800 65500 89200
78 11700 70300 96900
93 12600 85200 128600
0.25
0.125
0.25
0.125
0.125
0.125
0.125
6800 15500 13600
6700 13800 13200
a Polymerizations were run for 3 days at 90 °C in benzene. Listed
values are the average of at least two trials. Molecular weights were
measured by GPC and reported values are relative to polystyrene
standards. b Percent catalyst (Pd/Br). c Phosphine-to-palladium ratio.
d Approximate concentration determined by mmol of each monomer
per mL of solvent. e Number-averaged molecular weight. f Weight-
averaged molecular weight. g Molecular weight at peak maximum.
triarylamine, even in the trace amounts that were observed in
these reactions, must be prevented if pure polymer is to be
obtained.
Polymerizations Involving Electron-Rich Aryl Bromides.
To test the viability of phosphines 7 and 8 in actual polycon-
densations, and to optimize the conditions of the polymeriza-
tions, a series of reactions between 1,4-dibromobenzene (14)
and diaminobiphenylene monomer 11 to form polymer 15 (eq
5) were conducted. In these polymerizations, reaction parameters
a Polymerizations were run for 3 days at 90 °C in benzene at 1 M
concentration with 0.5% Pd/Br catalyst load and 3 phosphines per
palladium. Listed values are the average of at least two trials. Molecular
weights were measured by GPC and reported values are relative to
polystyrene standards. b Number-averaged molecular weight. c Weight-
averaged molecular weight. d Molecular weight at peak maximum.
electron-rich and electron-poor polymers in good yields and with
high molecular weights. To test the generality of this system
and to obtain a route into a series of poly(N-arylanilines),
polymerizations were performed using a variety of monomers,
and the results are presented in Table 5. The donor/acceptor
copolymer 19 was formed in good yield with a number-averaged
molecular weight of almost 20000. Samples of meta, and
alternating meta-para poly(N-arylaniline) 20 and 21 were
prepared with very high weight-averaged and peak molecular
weights, although the number-averaged values were reduced by
formation of cyclic oligomer.
Formation of cyclic oligomers was confirmed by mass
spectrometry and the amount of this cyclic material depended
on the regiochemistry of the arylene moieties. As noted in our
previous report,41 the p-poly(N-arylaniline) material 22 is less
susceptible to cyclization than are the isomeric versions contain-
ing meta linkages. This assertion is supported by the higher
molecular weight data and the absence of GPC peaks due to
oligomeric material. The identity of the peaks due to oligomers
in the GPC traces of polymerizations involving m-phenylene
units was corroborated by MALDI mass spectrometry. In the
case of an A2B2 polymerization reaction, such as that between
a m-dibromobenzene and N-aryl phenylene diamines, linear
oligomers can contain an unequal number of the two monomers,
but cyclic oligomers would have only an equal number of the
two monomers. In the case of an AB polymerization odd or
even numbers of monomers would be present in the cyclic or
oligomeric linear material. MALDI MS analysis of the crude
samples from the reaction of 14 with 16 or the reaction of 17
with 16 in Table 5 showed only oligomers containing an equal
number of the two monomer units. For example, peaks due to
the proton adducts of tetramer, hexamer, octamer, decamer, etc.
were observed in both cases, but peaks due to trimer, pentamer,
etc. were not observed. To confirm the appropriateness of the
MALDI MS analysis, the polymer formed by condensation of
N-aryl-3-bromoaniline to form polymer 20 in Table 6 was
subjected to MALDI MS and showed the presence of oligomers
containing both odd and even numbers of monomers.
such as phosphine, substrate concentration, catalyst load, and
phosphine-to-palladium ratio were all varied, and the results
are listed in Table 4. At 1 M concentration, polymers generated
by using either ligand 7 or 8 showed significantly higher
molecular weights than those produced by using ligand 1.
Number averaged molecular weights for samples formed with
7 appeared to be slightly higher than those for samples from 8,
although weight-averaged and peak values were higher for the
latter. The similarity of reactions involving these two ligands,
combined with the commercial availability of 8, led us to use
8 for the majority of the subsequent polymerization studies.29
The effect of concentration on the molecular weight of
polymer 15 appeared to result from the same competing factors
as it did in the synthesis of polymer 12 (vide supra). When 8
was used as the phosphine, optimal molecular weights for this
polymer were obtained at 0.25 M concentration (entry 6). The
other variables mentioned above appeared to have little effect
on polymer molecular weight. Catalyst loadings as low as 0.05%
gave polymers with high molecular weights and facilitated
catalyst removal from the crude polymer upon workup. The
molecular weight was insensitive to the phosphine-to-palladium
ratio (entry 10) and to the use of either arene or dioxane solvent.
Given these results, it appeared that a combination of Pd-
(OAc)2 and 8 as catalyst was ideal for the synthesis of both
(52) Goodson, F. E.; Wallow, T. I.; Novak, B. M. Macromolecules 1998,
31, 2047.

7532 J. Am. Chem. Soc., Vol. 121, No. 33, 1999
Goodson et al.
Table 6. Removal of Cyclic Oligomers by Sephadex Filtration
Figure 4. 13C NMR spectrum for polymer 28.
Scheme 1. “Oligomeric Monomer” Strategy for the
Synthesis of m-poly(N-arylaniline) 28
Figure 3. GPC chromatograms for polymer 20 (dotted line), formed
with monomeric monomers, and polymer 28 (solid line), formed from
pentameric monomers.
Overall, we have demonstrated that P(t-Bu)3 and the P,O
ligand 7 eliminates the problem of phosphorus incorporation
into the polymer, and P(t-Bu)3 greatly reduces aryl bromide
hydrodehalogenation, thereby producing triarylamine polymers
with number-averaged molecular weights greater than 25000.
This value corresponds to chains that are, on average, over 100
arylamine units in length.
Strategies To Eliminate Competing Cyclization. The
dashed line in Figure 3 presents the GPC chromatogram for
polymer 20. This trace contains a sharp spike that corresponds
to a cyclic tetramer (as determined by MALDI mass spectrom-
etry). We reasoned that polymerizations initiated with “mono-
mers” that were already five arylamine units in length could
not form the cyclic tetramer and might significantly reduce the
formation of the cyclic oligomers. Therefore, we developed the
route in Scheme 1 to bromo- and amino-terminated pentameric
monomers. Diaminomonomer 23 was simply reacted in 1,3-
dibromobenzene solvent using a combination of palladium
acetate and DPPF (bis(diphenylphosphino)ferrocene)49 as cata-
lyst to form dibromotrimer 24 in 78% yield after distillation of
the excess dibromobenzene and column chromotography of the
residue. This material was transformed into the diaminotrimer
25 via amination with an excess of the appropriate aniline
derivative. Treatment with acid to extract excess aniline and
column chromotography of the material remaining in the organic
layer gave 25 in 89% yield. These simple procedures were
repeated to yield the dibromopentamer 26 and diaminopentamer
27 in 80% and 89% isolated yields.
amount of cyclic oligomer formed in this polymerization relative
to that formed between the two true monomers. A small amount
of cyclic oligomer of higher molecular weight was still present,
revealing the high propensity of triarylamine oligomers to adopt
a conformation that undergoes cyclization. In contrast to the
1H and 13C NMR spectra of polymers prepared from true
monomers, the NMR spectra presented in Figure 4 for the
polymer 28 prepared from oligomeric monomers are clearly
resolved. Thus, the amount of cyclic material is low,53 and the
polymer contains regular, meta regiochemistry.
Reaction of 26 and 27 in the presence of NaO-t-Bu as base
and a combination of 0.5% Pd(OAc)2 and phosphine 8 as
catalyst precursor produced meta poly(N-arylaniline) derivative
28 in 79% isolated yield with molecular weight data Mn )
12100, Mw ) 74800, and Mp ) 87100 (average of two
experiments). As can be seen from the GPC chromatograms
depicted in Figure 3, this strategy did dramatically reduce the
As discussed above, large amounts of cyclic oligomer were
obtained when using simple monomers for the formation of
(53) High molecular weight cyclic material may display the same NMR
spectra as linear polymeric mateiral. Thus, we can conclude that the amount
of cyclic oligomer is low, but we cannot comment on the presence or
absence of high molecular weight cyclic material.

Synthesis of Pure, Regiodefined Polymeric Triarylamines
J. Am. Chem. Soc., Vol. 121, No. 33, 1999 7533
Scheme 2. “Oligomeric Monomer” Strategy for the
Synthesis of Alternating m- and p-Poly(N-arylaniline) 33
poly(N-arylaniline) with alternating meta and para regiochem-
istry. Thus, the “oligomeric monomer” strategy was also applied
to the synthesis of these materials as shown in Scheme 2.
Diaminotrimer 31 and dibromopentamer 32 were polymerized
under the identical conditions to those described above for 26
and 27 to yield polymer 33 in 71% yield with molecular weight
values of Mn ) 14600, Mw ) 74100, and Mp ) 84200 (average
of two trials). Monomers with butoxy rather than methoxy
substituents were used in this case because the polymer
containing methoxy substituents was insoluble. GPC showed
that polymer 33 contained much less cyclic oligomer than those
produced from true monomers.
Although the “oligomeric monomer” strategy did not com-
pletely eliminate formation of cyclic material, it did greatly
reduce the quantities of cyclic impurities in the polymer samples
and involved the use of discrete oligomers of poly(N-arylaniline)
derivatives that were prepared without using protecting groups.
To obtain material that was completely void of cyclic oligomers,
we sought a method to separate linear polymer from cyclic
oligomer upon workup. Filtration of the polymer samples
through a 12 in. × 1.5 in. column of Sephadex LH-60 SEC
resin using THF as eluent removed the low molecular weight
cyclic materials. Table 6 gives molecular weight data for specific
polymer samples before and after this treatment. The molecular
weight distributions for these materials are greater than the 2.0
value of an ideal step-growth polymerization. It is not clear if
our molecular weight distribution results from aspects of the
palladium chemistry, selective loss of certain molecular weight
fractions upon workup, or the presence of high molecular weight
cyclic material. Nevertheless, NMR spectra of samples obtained
from filtration contained the appropriate number of well-resolved
resonances and GPC traces showed the absence of low molec-
ular weight cyclic materials.
Figure 5. Cyclic voltammograms for (A) polymer 33, (B) polymer
21, and (C) polymer 15.
were observed for polymer 33 (Figure 5a) at 0.161, 0.411, and
0.794 V vs Ag/AgCl (calibrated with Fc/Fc+ ) 0.178 V). The
peak-to-peak separations for the first two waves were 67 and
65 mV, which are very close to the theoretical value of 59 mV
and which suggest one electron redox phenomena. The third
wave displayed a considerably larger amplitude and peak-to-
peak separation (122 mV), suggesting a multielectron process.
The two-electron wave of polymer 33 was resolved into two
single electron waves in the CV of polymer 21 (Figure 5b),
giving a total of four single-electron redox processes at 0.227,
0.475, 0.867, and 1.027 V. Janssen and co-workers have studied
small molecule versions of these polymers, and they found a
similar four-wave voltammogram for a meta,para N-phenyl-
aniline tetramer.20 They suggested that the first two waves arose
from removal of a single electron from neighboring p-phe-
nylenediamine units of the molecule, while the second set of
waves resulted from oxidation of the second nitrogen in the
para unit. It is probable that an analogous redox behavior is
occurring in our polymeric samples (Scheme 3). The cyclic
voltammogram for the alternating aminobiphenylene aniline
polymer 15 with para regiochemistry (Figure 5c) was similar
to those of 21 and 33, but the individual waves within the two
primary regimes were less well resolved.
Oxidation waves for the all meta polymer 28 (Figure 6a) were
visible at 0.381 and 0.588 V before a destructive oxidation
occurred at about 0.9 V; the corresponding reduction waves were
less visible. The voltammogram was unchanged after repeated
scans, indicating that the low intensity of the reduction peaks
Cyclic Voltammetry Studies. Alternating meta and para
poly(N-arylaniline)s 21 and 33 exhibited resolved and reversible
cyclic voltammograms (Figure 5). Three distinct redox waves

7534 J. Am. Chem. Soc., Vol. 121, No. 33, 1999
Goodson et al.
Table 7. UV-Vis and Thermal Characterization of Selected
Polymers
Figure 6. Cyclic voltammograms for (A) polymer 28 and (B) polymer
22.
Scheme 3. Possible Oxidation States for
Poly(N-arylaniline)s with Alternating Meta and Para
Regiochemistry
a Wavelength of maximum absorbance. b Temperature at which
polymer decomposition begins (°C).
Cyclic voltammograms for the donor-acceptor polymers 12
and 19 are presented in Figure 7, parts a and b. Aminobiphen-
ylene/benzophenone polymer 12 exhibited two well-resolved
redox processes at 0.556 and 0.748 V. The narrow peak-to-
peak distances (71 and 67 mV, respectively) for the two waves
again suggested that these correspond to single-electron pro-
cesses, which are most likely the first and second oxidation of
the benzidene moieties. The m-phenylenediamine/benzophenone
polymer 19 showed only a single oxidation wave at 0.681 V.
As was the case with the m-poly(N-arylaniline) derivatives, the
corresponding reduction wave was less pronounced. The absence
of a second oxidation of 19 before the destructive oxidation
of the polymer at 1.3 V suggests that the second nitrogen
unit of the oxidized phenylenediamine ring is not readily
oxidized.
UV-Visible Spectroscopy of Oxidized Polymers. The
oxidation of polymers 15, 28, and 33 with bis(trifluoroacetoxy)-
iodobenzene was monitored by UV-vis spectroscopy. A
solution of polymer in dichloromethane that was 0.1 mM in
repeat unit was treated repeatedly under nitrogen with ca. 0.1
equiv of a 0.01 M solution of bis(trifluoroacetoxy)iodobenzene
in dichloromethane. The neutral polymers were colorless
solutions that exhibited a single band in dichloromethane (Table
7). With the addition of oxidant, there was an incremental
decrease in intensity of the absorption of the neutral polymer
that was accompanied by the appearance and increase in
intensity of two new bands attributed to the oxidized polymer.
In addition, the color of the solutions turned a yellow-green
color. As shown in Figure 8a, the para linked polymer 15
showed a decrease in the band at 367 nm and formation of bands
is not due to oxidative decomposition of the sample. The shape
of the cyclic voltammogram for polymer 20 with tert-butyl
substituents on the N-aryl groups is similar to that of 28, but
the waves are shifted to 0.462 and 0.682 V. These data
demonstrate the ability to tune the redox potential with the
N-aryl substituent; replacement of the electron-rich methoxy side
groups with the electron-neutral tert-butyl groups makes the
polymer more difficult to oxidize.
The all-para polymer 22 (Figure 6b) exhibits a well-defined
and chemically reversible redox wave at 0.030 V, with
subsequent processes that are poorly defined. The large peak-
to-peak width for the primary process suggests that multiple
electrons may be involved and that the discrete oxidation states
associated with the parent poly(p-aniline)1 may not be present
with this polymer. However, it should be noted that this material
was considerably less soluble than the other polymers. Thus,
we conducted voltametric analysis with low molecular weight
samples (Mn ) 6500, Mw ) 14000, synthesized with a 40%
excess of dibromobenzene monomer) to maintain homogeneous
solutions. As a result, the broad peaks may be due to end-group
effects that might result from the shorter chain lengths.

Synthesis of Pure, Regiodefined Polymeric Triarylamines
J. Am. Chem. Soc., Vol. 121, No. 33, 1999 7535
However, when the oxidation was conducted at 0.9 mM a
shoulder at 450 nm was observed.
These data indicate that the polymers formed from palladium-
catalyzed amination reactions are clean enough to give straight-
forward oxidation behavior that is typical of triarylamine small
molecules. Further, the observation of a band near 900 nm is
similar to that of oxidized and protonated “leucoemeraldine”
polyaniline, for which polymer 15 is an organic-soluble N-aryl
analogue. Further, the observation of clean UV-vis spectra for
the oxidation process with clear isosbestic points indicates that
the radical cation form of the polymer is relatively stable at
room temperature.
Magnetic Susceptibility Measurements and EPR. One
might expect that oxidation of every nitrogen in the all-meta-
linked polymer 28 and every other nitrogen in 33 would generate
a system with ferromagnetic coupling of the spins as a result
of their meta disposition at the phenyl ring. With clear evidence
that bis(trifluoroacetoxy)iodobenzene does oxidize the triaryl-
amine polymer containing alternating meta and para linkages,
samples of 33 in CH2Cl2 were oxidized with 0.45 and 2.70
equiv/nitrogen atom of bis(trifluoroacetoxy)iodobenzene, and
the magnetic susceptibility of the resulting samples was
measured by the method of Evans.54 Reaction of 33 with 0.9
and 5.4 equiv of oxidant per repeat unit led to NMR shifts that
corresponded to gram susceptibilites of 2.1 × 10-6 and 2.3 ×
10-6 cm3/g, respectively. Janssen reported that this oxidant was
only strong enough to remove electrons from the first set of
oxidation waves (vide supra) in meta-para triarylamine oligo-
mers,20 and our UV-vis studies on 33 showed that additional
oxidation with bis(trifluoroacetoxy)iodobenzene did not occur
after adding 1 equiv of oxidant per monomer. Thus, the gram
susceptibilities for the two samples of 33 generated with
different quantities of oxidant were essentially identical. A
substantial amount of the material remained oxidized at room
temperature over the course of 24 h, but the magnetic
susceptibility for oxidized 33 did decay to 1.2 × 10-6 after 2.5
h at room temperature and to 0.8 × 10-6 after 24 h. Janssen
reported that the oxidized form of discrete oligomeric materials
was stable for several weeks.55 As one might expect from the
UV-vis data above, oxidation of all meta-linked polymer 28
gave no detectable paramagnetic shift for an oxidized polymer
when treated with bis(trifluoroacetoxy)iodobenzene.
Figure 7. Cyclic voltammograms for (A) polymer 12 and (B) polymer
19.
Oxidized 33 also exhibited a very strong EPR signal at 70 K
in CH2Cl2. The spectrum consisted of a single, featureless line
centered at about 3300 G corresponding to a ∆Ms ) (1
transition typical for spin ) 1/2 organic radicals. We were
unable to observe a ∆Ms ) (2 transition in the g ) 4 region
that would have indicated higher spin states resulting from
ferromagnetic coupling. However, other research in our group
has found the observation of this transition in N-arylaniline
oligomers to be solvent dependent; transitions in the g ) 4
region that were not observed in CH2Cl2 were detected in
butyronitrile solvent.56 Unfortunately, polymer 33 was not
soluble in butyronitrile. Further experiments to characterize the
magnetic properties of these materials are currently in progress.
Thermal Characterization of Polymers. One goal for
preparing these triarylamine polymers was to create an organic-
soluble material that had the electrochemical properties of
triarylamine small molecules and the thermal and physical
properties of high molecular weight polymers. Samples of
polymers were subjected to thermal gravimetric analysis (TGA).
Figure 8. UV-vis spectra for oxidation of (A) polymer 15 and (B)
polymer 33.
at 450 and 900 nm along with isosbestic points at 298 and 400
nm. As shown in Figure 8b, the meta-para linked polymer 33
showed a decrease in the band at 315 nm and formation of bands
at 430 and 900 nm, along with isosbestic points at 280 and 361
nm. Little additional oxidation was observed upon treatment of
polymers 15 and 33 with increasing quantities of bis(trifluoro-
acetoxy)iodobenzene. In contrast to the clean oxidation of 33,
the all-meta linked polymer 28 showed no change in the UV-
vis spectrum when oxidant was added to a 0.1 mM solution.
(54) Evans, D. F. J. Chem. Soc. 1959, 2003.
(55) Wienk, M. M.; Janssen, R. A. J. J. Chem. Soc., Chem. Commun.
1996, 267.
(56) Louie, J. Ph.D. Dissertation Thesis, Yale University, 1998.

7536 J. Am. Chem. Soc., Vol. 121, No. 33, 1999
Goodson et al.
of Bu4NPF6. X-Band EPR measurements were conducted on 1 mM
solutions on a Varian E9 spectrometer interfaced with a MacIntosh
Computer. The UV-vis oxidations utilized a Perkin-Elmer Lambda 6
spectrophotometer. GPC chromatograms were recorded in THF solvent
with a Waters HPLC system consisting of a 515 HPLC pump, 410
differential refractometer, Styrogel columns, and Millenium soft-
ware. The listed values are relative to known standards of polysty-
rene. Mass spectrometry analyses were performed by the Mass
Spectrometry Facility at the University of Illinois at Urbana-Cham-
paign. Analytical data were obtained by Robertson Microlit Labora-
tories, Inc. All polymeric materials were subjected to elemental analy-
sis. However, incomplete combustion of the materials led to large
deviations in repeated analyses of the same sample and significant
quantities of ash were produced in the combustion analyses. Thus,
analyses are reported, along with the percentage of ash residue that
was obtained.
Bis[2-(trifluoromethyl)phenyl]mono(2-methoxyphenyl)-
phosphine (2). A solution of 0.667 g (1.67 mmol) of bis[2-(trifluo-
romethyl)phenyl]monochlorophosphine in dry THF was chilled to -78
°C under nitrogen in a 50 mL Schlenk flask. A Grignard solution
prepared from 0.411 g (2.20 mmol) of 2-bromoanisole and 58.8 mg
(2.40 mmol) of Mg was added dropwise via cannula. The flask was
allowed to warm to room temperature, and then fitted with a reflux
condenser. The reaction was then refluxed overnight, resulting in a
deep reddish-brown solution. The solvent was removed in vacuo, and
the residue was extracted with ether and rinsed with brine. After the
organic phase was dried (MgSO4), the solvent was removed with a
rotary evaporator. The residue was then chromatographed on silica with
5% EtOAc in hexanes. The material from chromatography was then
recrystallized in the drybox from THF/pentane, resulting in the isolation
of 0.255 g (0.596 mmol, 35.7%) of 2 as a white solid: 1H NMR (C6D6)
δ 3.05 (s, 3H), 6.40 (m, 1H), 6.68 (m, 2H), 6.86 (m, 4H), 7.05 (br,
1H), 7.15 (br, 2H), 7.47 (m, 2H); 13C NMR (C6D6) δ 55.3, 110.7, 121.5,
125.0 (q, J ) 275 Hz), 125.1 (br), 126.8 (q, J ) 5.4 Hz), 129.0, 130.9,
131.4, 134.3, 135.1 (br), 136.1, 136.6 (d, J ) 31.6 Hz), 161.3 (d, J )
16.8 Hz); 31P NMR (C6D6) δ -28.2 (complex heptet). Anal. Calcd for
C21H15F6OP: C, 58.89; H, 3.53. Found: C, 58.78; H, 3.54.
Bis(2-methoxyphenyl)mono[2-(trifluoromethyl)phenyl]-
phosphine (3). A 100 mL Schlenk flask charged with 2.02 g (14.7
mmol) of PCl3, 30 mL of dry THF, and a stirbar was chilled to -78
°C under nitrogen. A Grignard solution made from 3.30 g (14.7 mmol)
of 2-bromobenzotrifluoride and 0.388 g of Mg (1.1 equiv) was added
dropwise from an addition funnel. The reaction was warmed to room
temperature and allowed to stir for 5 h. The solvent was removed in
vacuo and 50 mL of fresh THF was added. The solution was then
chilled to -78 °C, and a second Grignard reagent synthesized from
5.50 g (29.4 mmol) 2-bromoanisole and 0.846 g (35.3 mmol) of Mg
was added dropwise via cannula. The reaction was allowed to warm
to room temperature, and the flask was fitted with a reflux condenser.
After the solution was heated at reflux overnight, the reaction was
quenched with 2 mL of methanol, and the solvent was removed in
vacuo. The residue was dissolved in ethyl acetate, rinsed with brine,
and dried over MgSO4. After removal of the solvent, the crude product
was suspended in cold ether and filtered. It was then recrystallized from
degassed ethanol/ethyl acetate until colorless to yield 2.25 g (5.76 mmol,
39.2%) of 3 as a white solid: 1H NMR (C6D6) δ 3.14 (s, 6H), 6.46
(dd, J ) 7.8 Hz, 6.0 Hz, 2H), 6.74 (t, J ) 7.2 Hz, 2H), 6.86 (m, 2H),
6.94 (br, 2H), 7.09 (t, J ) 7.5 Hz, 2H), 7.34 (m, 1H), 7.54 (m, 1H);
13C NMR (C6D6) δ 55.2, 110.6, 121.2, 125.4 (q, J ) 273 Hz), 125.7
(d, J ) 17.5 Hz), 126.3 (m), 128.7, 130.4, 131.4, 134.0, 135.4 (m),
136.7, 138.1 (d, J ) 31.1 Hz), 161.6 (d, J ) 16.5 Hz); 31P NMR (C6D6)
δ -29.1 (q, J ) 95.3 Hz). Anal. Calcd for C21H18F3OP: C, 64.62; H,
4.65. Found: C, 64.52; H, 4.60.
The polymers were found to be thermally stable with decom-
position occurring at temperatures greater than 400 °C as shown
in Table 7. Thus, the palladium-catalyzed amination chemistry
does produce materials with reversible oxidation chemistry and
high thermal stability. With the appropriate tuning of N-aryl
side chains, amorphous polymers with high glass transition
temperatures should be accessible.
Conclusions
We have shown that the use of phosphines such as 7 and 8
reduces side reactions which had previously limited the mo-
lecular weight and purity of triarylamine polymers produced
from palladium-catalyzed chemistry. The strategies for eliminat-
ing these reactions are likely to be useful for other palladium-
catalyzed polymerization processes, including the preparation
of pure samples of diarylamine polymers. The use of an alkyl
or simple methoxymethylarylphosphine eliminated aryl group
exchanges and eliminated phosphine arylation that occurred with
tri-o-tolylphosphine. Tri-o-tolylphosphine had been used previ-
ously in polymer chemistry because it does not undergo aryl
group exchange. The use of ligands 7 and 8 substantially
improved molecular weight and produced phosphine-free poly-
mer samples, but additional strategies were necessary to
overcome cyclization processes that competed with chain
growth. Cyclization was minimized through the polymerization
of “pentameric monomers”. In addition, cyclic impurities were
removed by filtration of the sample through a Sephadex column.
The materials were studied by cyclic voltammetry and showed
a number of interesting features, including a demonstration that
the redox potential can be tuned by varying the N-aryl side chain.
The oxidized form of polymer 33 with alternating meta and
para regiochemistry that was observed by UV-vis spectroscopy
after oxidation with bis(trifluoroacetoxy)iodobenzene was shown
to be paramagnetic by the Evans method and to exhibit a strong
ESR signal. Overall, these polymers constitute thermally stable,
organic soluble polymers with reversible oxidation chemistry
involving radical cations that display good stability at room
temperature in solution.
Experimental Section
General Methods. Schlenk-line or drybox techniques were used for
all air-sensitive manipulations. 1H NMR spectra were acquired at 500
MHz using a Bruker AM-series spectrometer. Proton-decoupled 13C
NMR spectra were similarly obtained at 125 MHz, while proton-
decoupled 31P NMR spectra were obtained at 202 MHz using a GE
Omega 300 spectrometer. 1H and 13C chemical shifts are referenced to
residual proton signals in the deuterated solvent; 31P chemical shifts
are reported relative to an external standard of 85% phosphoric acid.
Toluene, THF, ether, benzene, and pentane solvents were distilled from
sodium/benzophenone prior to use. Dichloromethane was distilled from
calcium hydride prior to use. Bis[2-(trifluoromethyl)phenyl]monochlo-
rophosphine,57 o-(diphenylphosphino)methoxymethylbenzene (5),46 1-[2′-
(diphenylphosphino)phenyl]methoxyethane (6),47 and tris(o-methoxy-
methylphenyl)phosphine (7)48 were prepared by literature procedures.
4,4′-Dibromobenzophenone (10), 1,4-dibromobenzene (14), 4,4′-dibrom-
biphenyl, diphenylamine, and ditolylamine were purchased from
commercial suppliers and were sublimed under reduced pressure prior
to use; 1,3-dibromobenzene (17) was similarly purchased and vacuum
distilled from calcium hydride. Other chemicals were used as received
from commercial suppliers. Cyclic voltammetry was carried out on a
BAS CV-27 Voltammograph. A platinum and a Ag/AgCl electrode
were used as working and reference electrodes, and the reported
potentials were calibrated with an external sample of ferrocene. All
runs were performed in 1 mM solutions in dry CH2Cl2 in the presence
Model Amination Reactions on Small Molecules. A reactant stock
solution that was 0.1 M in aryl halide, 0.1 M in diarylamine, and 0.09
M in 1,3,5-trimethoxybenzene was prepared in a drybox in dry C6D6.
A catalyst stock solution which was 2.0 mM in Pd(OAc)2 was prepared
similarly. In the drybox, 6.0 µmol samples of the various phosphines
were weighed into separate vials, along with 14.4 mg (0.150 mmol) of
sodium tert-butoxide. Each vial was then charged with 1.0 mL of the
reactant stock (0.10 mmol of reactants), 1.0 mL of the catalyst stock
(57) Sihler, R.; Werz, U.; Brune, H.-A. J. Organomet. Chem. 1989, 368,
213.

Synthesis of Pure, Regiodefined Polymeric Triarylamines
J. Am. Chem. Soc., Vol. 121, No. 33, 1999 7537
(2.0 µmol of Pd), and a stirbar. The vials were then sealed with a Teflon-
lined screw-cap, removed from the drybox, and heated in a 90 °C oil
bath. Reactions between di(p-tolyl)amine and 4-bromobenzophenone
were heated for 24 h, while the reactions between diphenylamine and
4-bromo-N,N-dimethylaminobenzene were allowed to proceed for 48
h. Aliquots were then removed from the vials and placed into 5 mm
NMR tubes. The yields were determined by integrating the resonances
for the methyl protons vs the 1,3,5-trimethoxybenzene internal standard.
The results for these experiments are presented in Tables 1 and 3.
4-(N,N-Di(p-tolyl)amino)benzophenone (9). In a drybox, a 5 mL
screw-capped test tube was charged with 117.5 mg (0.450 mmol) of
4-bromobenzophenone, 88.9 mg (0.450 mmol) of di(p-tolyl)amine, 64.8
mg (0.675 mmol) of sodium tert-butoxide, 2.0 mg (9.0 µmol) of Pd-
(OAc)2, 5.5 mg (27 µmol) of tri(tert-butyl)phosphine, 3 mL of benzene,
and a stirbar. The tube was sealed with a Teflon-lined screw cap,
removed from the drybox, and heated in a 90 °C oil bath for 18 h. The
reaction was then rinsed with saturated NH4Cl (2 mL), and the resulting
aqueous phase was washed twice with 1 mL of ether. The organic layers
were combined and dried over MgSO4. Removal of the solvent with a
rotary evaporator followed by chromatography on silica (10% EtOAc
in hexanes) resulted in a bright yellow oil. This oil was heated in a
Kugelrohr oven at 60 °C under a dynamic 5 mTorr vacuum for 2 h to
yield 163.4 mg (0.433 mmol, 96.3%) of 9 as a yellow, glassy resin
which fluoresced strongly in the green under ambient light: 1H NMR
(CDCl3) δ 2.34 (s, 6H), 6.79 (dt, J ) 8.9 Hz, 2.5 Hz, 2H), 7.08 (d, J
) 8.4 Hz, 4H), 7.14 (d, J ) 8.4 Hz, 4H), 7.45 (t, J ) 7.7 Hz, 2H),
7.53 (tt, J ) 7.4 Hz, 1.3 Hz, 1H), 7.68 (dt, Jd ) 8.9 Hz, Jt ) 2.5 Hz,
2H), 7.76 (d, J ) 6.9 Hz, 2H); 13C NMR (CDCl3) δ 20.9, 118.3, 126.1,
128.1, 128.6, 129.6, 130.2, 131.5, 132.0, 134.5, 138.7, 143.9, 152.3,
195.1. Anal. Calcd for C27H23NO: C, 85.91; H, 6.14; N, 3.71. Found:
C, 86.03; H, 6.06; N, 3.71.
[4-(N′,N′-Dimethylamino)phenyl]diphenylamine (13). A procedure
identical with that for the isolation of 9 was followed utilizing 90.0
mg (0.450 mmol) of 4-bromo-N,N-dimethylaminobenzene and 76.1 mg
(0.450 mmol) of diphenylamine. Chromatography with 5% EtOAc in
hexanes resulted in the isolation of 114.1 mg (0.396 mmol, 88.0%) of
13 as a white crystalline solid: 1H NMR (C6D6) δ 2.47 (s, 6H), 6.49
(dt, J ) 9.0 Hz, 2.0 Hz, 2H), 6.81 (t, J ) 7.5 Hz, 2H), 7.07 (t, J ) 7.4
Hz, 4H), 7.10 (d, J ) 9.0 Hz, 2H), 7.18 (d, J ) 7.5 Hz, 4H); 13C NMR
(C6D6) δ 40.5, 114.1, 121.7, 123.0, 128.2, 129.3, 137.7, 148.1, 149.0.
Anal. Calcd for C20H20N2: C, 83.30; H, 6.99; N, 9.71. Found: C, 83.09;
H, 6.84; N, 9.64.
Bisamine Monomer Synthesis, General Procedure. In a drybox,
15.0 mmol of dibromide, 45.0 mmol of substituted aniline, 169 mg
(0.750 mmol, 2.5%) of palladium acetate, 0.830 g (1.50 mmol) of bis-
(diphenylphosphino)ferrocene, and 4.30 g (45.0 mmol) of sodium tert-
butoxide were weighed directly into a 50 mL screw-capped test tube.
A stirbar was added along with 40 mL of toluene. The tube was then
sealed with a cap, removed from the drybox, and heated in a 90 °C oil
bath for 12 h. The reaction product was isolated as described below
for each compound.
dibromobenzene and 6.70 g (45.0 mmol) of 4-tert-butylaniline. The
crude reaction was treated with 20 mL of 2% HCl and extracted 3
times into 30 mL of diethyl ether. The organic phases were then
combined and dried over MgSO4. The solvent was removed under
reduced pressure, and the resulting material was chromatographed on
silica gel eluting with 5% ethyl acetate in hexanes. The resulting solid
was recrystallized from hexanes/ethyl acetate to yield 4.30 g (11.5
mmol, 76.7% yield) of 16 as colorless needles: 1H NMR (500 MHz,
C6D6) δ 1.25 (s, 18H), 5.00 (s, 2H), 6.52 (dd, J ) 8.0, 2.0 Hz, 2H),
6.59 (m, 1H), 6.94 (dd, J ) 6.6, 2.0 Hz, 4H), 7.06 (t, J ) 8.0 Hz, 1H),
7.21 (dd, J ) 6.6, 2.0 Hz, 4H); 13C NMR (125 MHz, C6D6) δ 31.6,
34.2, 105.5, 109.5, 119.3, 126.3, 130.3, 140.9, 144.1, 145.6. Anal. Calcd
for C26H32N2: C, 83.82; H, 8.66; N, 7.52. Found: C, 83.92; H, 8.66;
N, 7.52.
N,N′-Di(4-sec-butylphenyl)-1,4-phenylenediamine (18). The above
general procedure was followed using 0.707 g (3.00 mmol) of 1,4-
dibromobenzene and 1.34 g (9.00 mmol) of 4-sec-butylaniline. The
crude reaction was treated with 20 mL of 2% HCl and extracted three
times into 30 mL of diethyl ether. The organic phases were then
combined and dried over MgSO4. The solvent was removed under
reduced pressure and the resulting material was chromatographed on
silica gel eluting with 10% ethyl acetate in hexanes. The resulting solid
was taken into a drybox and recrystallized from air-free ether and
pentane to give 0.635 g (1.70 mmol, 56.7% yield) of 18 as white, flaky
crystals: 1H NMR (500 MHz, C6D6) δ 0.84 (t, J ) 7.5 Hz, 6H), 1.20
(d, J ) 6.5 Hz, 6H), 1.53 (m, 4H), 2.44 (m, 2H), 4.90 (s, 2H), 6.85 (s,
4H), 6.86 (d, J ) 7.5 Hz, 4H), 7.05 (d, J ) 7.5 Hz, 4H); 13C NMR
(125 MHz, C6D6) δ 12.5, 22.4, 31.6, 41.3, 117.3, 120.6, 128.5, 137.9,
139.3, 142.9. Anal. Calcd for C26H32N2: C, 83.82; H, 8.66; N, 7.52.
Found: C, 83.63; H, 8.73; N, 7.43.
N,N′-Di(4-methoxyphenyl)-1,3-phenylenediamine (23). The above
general procedure was followed using 14.2 g (60.0 mmol) of 1,3-
dibromobenzene, 22.2 g (180 mmol) of p-anisidine, and 100 mL of
toluene in a 200 mL Schlenk flask. The crude reaction was treated
with 100 mL of 0.5 M citric acid and extracted three times with 100
mL of chloroform. The organic phases were then combined and dried
over MgSO4. The solvent was evaporated under reduced pressure. The
resulting solid was washed with 30% ethyl acetate in hexanes and
recrystallized from hexanes/ethyl acetate to yield 14.0 g (43.8 mmol,
73.0% yield) of 23 as pale purplish needles: 1H NMR (500 MHz, C6D6)
δ 3.32 (s, 6H), 4.83 (s, 2H), 6.39 (m, 3H), 6.74 (m, 4H), 6.91 (m, 4H),
7.06 (t, J ) 8.1 Hz, 1H); 13C NMR (125 MHz, C6D6) δ 55.0, 103.2,
107.6, 114.8, 122.8, 130.3, 136.3, 146.8, 155.8. Anal. Calcd for
C20H20N2O2: C, 74.98; H, 6.29; N, 8.74. Found: C, 74.77; H, 6.37; N,
8.96.
N,N′-Di(4-n-butoxyphenyl)-1,3-phenylenediamine (29). The above
general procedure was followed using 0.707 g (3.00 mmol) of 1,3-
dibromobenzene and 1.98 g (9.00 mmol) of 4-n-butoxyaniline. The
crude reaction was treated with 20 mL of 0.5 M citric acid and extracted
three times with 30 mL of diethyl ether. The organic phases were then
combined and dried over MgSO4. The solvent was removed under
reduced pressure and the resulting material was chromatographed on
silica gel eluting with 10% ethyl acetate in hexanes. The resulting solid
was recrystallized from hexanes/ethyl acetate to yield 0.942 g (2.33
mmol, 77.6% yield) of 29 as colorless needles: 1H NMR (500 MHz,
C6D6) δ 0.83 (t, J ) 7.5 Hz, 6H), 1.34 (m, 4H), 1.57 (m, 4H), 3.64 (t,
J ) 6.5 Hz, 4H), 4.86 (s, 2H), 6.41 (m, 3H), 6.80 (d, J ) 9.0 Hz, 4H),
6.93 (d, J ) 8.8 Hz, 4H), 7.07 (t, J ) 7.9 Hz, 1H); 13C NMR (125
MHz, C6D6) δ 13.9, 19.5, 31.7, 67.9, 103.2, 107.6, 115.5, 122.9, 130.3,
136.2, 146.9, 155.4. Anal. Calcd for C26H32N2O2: C, 77.19; H, 7.97;
N, 6.92. Found: C, 77.18; H, 8.01; N, 6.81.
N,N′-Di(4-sec-butylphenyl)-4,4′-diaminobiphenyl (11). The above
general procedure was followed using 4.68 g (15.0 mmol) of 1,4-
dibromobiphenyl and 6.71 g (15.0 mmol) of 4-sec-butylaniline in 40
mL of toluene. The crude reaction was treated with 100 mL of 0.5 M
citric acid and extracted 3 times into 100 mL of chloroform. The organic
phases were then combined and dried over MgSO4. The solvent was
evaporated under reduced pressure. Silica gel chromatography of the
resulting material, eluting with 10% ethyl acetate in hexanes, gave a
yellow solid. This solid was washed with cold 10% ethyl acetate in
hexanes to remove colored impurities, and the resulting material was
recrystallized from degassed hexanes/ethyl acetate to yield 5.33 g (11.9
mmol, 79.3% yield) of 11 as white crystals: 1H NMR (500 MHz, C6D6)
δ 0.84 (t, J ) 7.3 Hz, 6H), 1.20 (d, J ) 7.0 Hz, 6H), 1.53 (m, 4H),
2.45 (m, 2H), 5.09 (s, 2H), 6.93 (dd, J ) 8.4 Hz, 1.6 Hz, 8H), 7.02 (d,
J ) 8.4 Hz, 4H), 7.45 (d, J ) 8.5 Hz, 4H); 13C NMR (125 MHz, C6D6)
δ 12.5, 22.3, 31.6, 41.4, 118.0, 118.9, 127.6, 128.1, 133.7, 140.5, 141.4,
142.9. Anal. Calcd for C32H36N2: C, 85.67; H, 8.09; N, 6.24. Found:
C, 85.59; H, 7.95; N, 6.15.
General Polymerization Procedure. In a drybox, 0.250 mmol of
bisamine and dihalide were weighed into a 1 dram screw-capped vial
along with 72 mg (0.75 mmol) of sodium tert-butoxide, a stirbar, and
0.250 mL (0.5 mol %) of a stock solution that is 0.01 mM in Pd-
(OAc)2 and 0.03 mM in tri(tert-butyl)phosphine (8). The vial was sealed
with a Teflon-lined serum cap, removed from the drybox, and placed
in a 90 °C oil bath. The mixture became fluid within a few minutes,
and then formed a gel soon afterward. The reaction was heated for an
additional 3 days to ensure complete reaction. After treatment with 2
mL of 0.5 M citric acid, the crude polymer was extracted three times
N,N′-Di(4-tert-butylphenyl)-1,3-phenylenediamine (16). The above
general procedure was followed using 3.54 g (15.00 mmol) of 1,3-

7538 J. Am. Chem. Soc., Vol. 121, No. 33, 1999
Goodson et al.
into 2 mL of the workup solvent (see below for specific procedures).
Stirring and application of heat and sonication was often necessary at
this stage to completely dissolve the polymer. The organic layers were
combined and the resulting polymer solution was then extracted with
5% KCN to remove residual catalyst. After drying over MgSO4,
removal of the solvent resulted in a film, which was dissolved in a
minimum amount of workup solvent. The polymer product was then
precipitated by transferring the solution into 50 mL of methanol by
pipet. The solid was isolated via filtration or centrifugation, rinsed with
water, methanol, and hexanes, and then dried in vacuo. For yields and
variations on the conditions, see Tables 2 and 4-6.
Polymerization of 10 with 11. Using the general procedure, polymer
12 was extracted with chloroform and isolated via filtration to yield
12 as a yellow-orange filmy solid: 1H NMR (500 MHz, CDCl3) δ
0.86 (t, J ) 7.2 Hz, 6H), 1.25 (d, J ) 6.7 Hz, 6H), 1.60 (m, 4H), 2.60
(m, 2H), 7.05 (d, J ) 8.3 Hz, 4H), 7.11 (d, J ) 8.3 Hz, 4H), 7.14 (d,
J ) 8.2 Hz, 4H), 7.20 (d, J ) 8.0 Hz, 4H), 7.50 (d, J ) 8.1 Hz, 4H),
7.70 (d, J ) 8.2 Hz, 4H); 13C NMR (125 MHz, CDCl3) δ 12.3, 21.7,
31.2, 41.1, 119.7, 125.4, 126.0, 127.6, 128.2, 130.4, 131.6, 135.9, 144.0,
145.8, 151.4, 193.8. Anal. Calcd for C42H42N4O: C, 86.22; H, 6.75;
N, 4.46. Found: C, 83.90; H, 6.68; N, 4.08; Ash, 0.50.
Polymerization of 11 with 14. Using the general procedure, the
polymer was extracted with toluene and isolated via filtration to yield
15 as an off-white filmy solid: 1H NMR (500 MHz, CDCl3) δ 0.86 (t,
J ) 7.1 Hz, 6H), 1.24 (d, J ) 6.5 Hz, 6H), 1.58 (m, 4H), 2.56 (m,
2H), 7.02 (s, 4H), 7.08 (s, 8H), 7.12 (d, J ) 7.9 Hz, 4H), 7.43 (d, J )
7.5 Hz, 4H); 13C NMR (125 MHz, CDCl3) δ 12.3, 21.7, 31.2, 41.0,
123.0, 124.3, 125.1, 127.0, 127.7, 134.0, 142.3, 142.7, 145.3, 146.8.
Anal. Calcd for C38H38N2: C, 87.31; H, 7.33; N, 5.36. Found: C, 85.24;
H, 7.30; N, 4.91; Ash, 1.08.
Polymerization of 14 with 18. Using the general procedure, the
polymer was extracted with toluene and isolated via filtration to yield
22 as an off-white filmy solid. Very little cyclic oligomer was formed
during this polymerization: 1H NMR (500 MHz, CDCl3) δ 0.835 (t, J
) 7.3 Hz, 3H), 1.22 (d, J ) 6.8 Hz, 3H), 1.57 (br m, 2H), 2.54 (br m,
1H), 6.95 (br s, 4H), 7.04 (br s, 4H); 13C NMR (125 MHz, CDCl3) δ
12.3, 21.7, 31.2, 40.9, 122.9 (br), 124.6, 127.6, 141.6 (br), 142.6 (br),
145.6 (br). Anal. Calcd for C16H17N: C, 86.06; H, 7.67; N, 6.27.
Found: C, 84.28; H, 7.54; N, 5.59; Ash, 2.08.
Dibromotrimer (24). In a drybox, 1.28 g (4.00 mmol) of 23, 1.16
g (12.1 mmol) of sodium tert-butoxide, 177.2 mg (0.320 mmol) of
bis(diphenylphosphino)ferrocene, 36.0 mg (0.160 mmol) of Pd(OAc)2,
and 50 mL of 1,3-dibromobenzene were combined in a 100 mL Schlenk
flask along with a stirbar. The flask was removed from the drybox,
placed under nitrogen, and heated in a 100 °C oil bath for 24 h to form
a red-brown suspension. The resulting solution was then treated with
water, and the layers were separated. The aqueous phase was rinsed
twice with 20 mL of chloroform. The organic layers were combined
and dried over MgSO4. Evaporation of the chloroform was followed
by removal of the excess dibromobenzene by distillation in a Kugelrohr
apparatus (50 °C, 5 mTorr vacuum). The residue was then chromato-
graphed on silica eluting with 5% ethyl acetate in hexanes. A slightly
brownish resin was obtained, which was heated in a Kugelrohr oven
overnight at 50 °C under a 5 mTorr vacuum to remove residual solvent
and provide 1.95 g (3.10 mmol, 77.5%) of 24 as a brownish resin: 1H
NMR (500 MHz, C6D6) δ 3.25 (s, 6H), 6.62-6.63 (multiple resonances,
6H), 6.70 (t, J ) 8.0 Hz, 2H), 6.84-6.90 (multiple resonances, 9H),
6.99 (s, 1H), 7.34 (s, 2H); 13C NMR (125 MHz, C6D6) δ 54.9, 115.4,
118.0, 118.6, 120.7, 123.3, 124.6, 124.9, 128.1, 130.5, 130.6, 139.8,
148.7, 149.8, 157.3. Anal. Calcd for C32H26Br2N2O2: C, 60.97; H, 4.16;
N, 4.44. Found: C, 61.05; H, 4.29; N, 4.21.
Polymerization of 10 with 16. Using the general procedure, the
polymer was extracted with chloroform and isolated via filtration to
yield 19 as a bright yellow filmy solid. Removal of the majority of
cyclic impurities was achieved by filtration of 150 mg through a 12
in. × 1.5 in. column of Sephadex LH-60 SEC resin using THF as eluent.
The resulting polymer was isolated as before (70.9% recovery) and
extracted with hexanes using a Soxhlet apparatus for 3 h to remove
BHT and other impurities from the product: 1H NMR (500 MHz,
CDCl3) δ 1.29 (s, 18H), 6.84 (d, J ) 7.6 Hz, 2H), 6.99 (d, J ) 8.3 Hz,
4H), 7.06 (d, J ) 8.3 Hz, 4H), 7.19 (br, 2H), 7.29 (d, J ) 8.3 Hz, 4H),
7.643 (d, J ) 8.3 Hz, 4H); 13C NMR (125 MHz, CDCl3) δ 31.4, 34.4,
119.7, 120.8, 122.1, 125.4, 126.4, 128.6, 130.4, 131.4, 143.5, 147.6,
147.7, 151.0, 193.6. Anal. Calcd for C39H38N2O: C, 85.05; H, 6.95;
N, 5.08. Found: C, 82.74; H, 6.72; N, 4.68; Br, <0.05; Ash, 1.18.
Polymerization of 16 with 17. Using the general procedure, the
polymer was extracted with toluene and isolated via filtration to yield
20 as an off-white filmy solid. Removal of the majority of cyclic
impurities was achieved by filtration of 70 mg through a 12 in. × 1.5
in. column of Sephadex LH-60 SEC resin using THF as eluent. The
resulting polymer was isolated as before (73.2% recovery) and extracted
with hexanes with a Soxhlet apparatus for 3 h to remove BHT and
other impurities from the product: 1H NMR (500 MHz, CDCl3) δ 1.21
(s, 9H), 6.59 (dd, Jd ) 8.0 Hz, Jd ) 1.8 Hz, 2H), 6.78 (s, 1H), 6.85 (d,
J ) 8.6 Hz, 2H), 6.98 (t, J ) 8.0 Hz, 1H), 7.09 (d, J ) 9.0 Hz, 2H);
13C NMR (125 MHz, CDCl3) δ 31.4, 34.1, 118.3, 119.8, 123.0, 125.7,
144.5, 145.0, 148.3. Anal. Calcd for C16H17N2: C, 86.05; H, 7.67; N,
6.27. Found: C, 85.43; H, 7.64; N, 6.10; Ash, 0.51.
Polymerization of 14 with 16. Using the general procedure, the
polymer was extracted with toluene and isolated via filtration to yield
21 as an off-white filmy solid. Removal of the majority of cyclic
impurities could be achieved by filtration of 70 mg through a 12 in. ×
1.5 in. column of Sephadex LH-60 SEC resin (with THF as eluent).
The resulting polymer was isolated as before (66.3% recovery) and
extracted with hexanes using a Soxhlet apparatus for 3 h to remove
BHT and other impurities from the product: 1H NMR (500 MHz,
CDCl3) δ 1.25 (s, 18H), 6.56 (dd, J ) 8.0 Hz, 2.0 Hz, 2H), 6.87 (s,
1H), 6.90 (s, 4H), 6.95 (d, J ) 9.0 Hz, 4H), 6.99 (t, J ) 8.0 Hz, 1H),
7.17 (d, J ) 9.0 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 31.5, 34.2,
117.2, 118.2, 123.3, 125.1, 125.8, 129.5, 142.5, 144.8, 145.1, 148.5.
Anal. Calcd for C32H34N4: C, 86.05; H, 7.67; N, 6.27. Found: C, 85.21;
H, 7.37; N, 6.35.
Diaminotrimer (25). In a drybox, 1.79 g (2.83 mmol) of 24, 1.26
g (10.2 mmol) of p-anisidine, 1.02 g (10.6 mmol) of sodium tert-
butoxide, 152.5 mg (0.275 mmol) of bis(diphenylphosphino)ferrocene,
30.5 mg (0.135 mmol) of Pd(OAc)2, and 10 mL of toluene were
combined in a 50 mL sealable reaction tube along with a stirbar. The
tube was removed from the drybox and heated in a 100 °C oil bath for
24 h to form a red-brown suspension. The suspension was then extracted
with 2% HCl (2 × 10 mL) followed by saturated NaHCO3 (2 × 10
mL). The aqueous phases were then rinsed twice with 10 mL of ether.
The organic layers were combined and dried over MgSO4. Evaporation
of the solvent was followed by chromatography on silica with 20%
ethyl acetate in hexanes to yield a slightly brownish resin. The resin
was heated in a Kugelrohr oven overnight at 50 °C under a 5 mTorr
vacuum to remove residual solvent, resulting in the isolation of 1.80 g
(2.52 mmol, 89.1%) of 25 as a brownish resin: 1H NMR (500 MHz,
C6D6) δ 3.26 (s, 6H), 3.31 (s, 6H), 4.81 (s, 2H), 6.53 (dd, J ) 8.0 Hz,
2.1 Hz, 2H), 6.66-6.71 (multiple resonances, 12H), 6.82 (dd, J ) 8.0
Hz, 2.1 Hz, 2H), 6.87 (d, J ) 8.5 Hz, 4H), 6.96-7.02 (multiple
resonances, 3H), 7.12 (d, J ) 8.9 Hz, 4H), 7.29 (t, J ) 2.1 Hz, 1H);
13C NMR (125 MHz, C6D6) δ 54.9, 55.0, 109.2, 111.2, 114.7, 114.8,
115.1, 117.1, 118.4, 122.3, 128.3, 130.0, 130.1, 136.0, 141.1, 146.4,
149.5, 149.6, 155.7, 156.7. Anal. Calcd for C46H42N4O4: C, 77.29; H,
5.92; N, 7.84. Found: C, 77.20; H, 6.04; N, 7.54.
Dibromopentamer (26). A procedure analogous to that for the
preparation of 24 was employed using 1.76 g (2.46 mmol) of 25, 0.713
g (7.43 mmol) of sodium tert-butoxide, 109 mg (0.196 mmol) of bis-
(diphenylphosphino)ferrocene, 22.1 mg (0.0984 mmol) of Pd(OAc)2,
and 30 mL of 1,3-dibromobenzene in a 50 mL sealable reaction tube.
The crude product was chromatographed on silica with a gradient of
10-15% EtOAc in hexanes to yield an orange solid. This solid was
recrystallized in cold ether to yield 2.01 g (1.96 mmol, 79.7% yield)
of 26 as a beige powder: 1H NMR (500 MHz, C6D6) δ 3.23 (s, 6H),
3.26 (s, 6H), 6.57-6.66 (multiple resonances, 10H), 6.77 (dm, Jd )
6.0 Hz, 4H), 6.83 (dm, Jd ) 8.5 Hz, 2H), 6.87-6.92 (multiple
resonances, 8H), 6.97 (d, J ) 9.0 Hz, 4H), 7.01 (t, J ) 8.2 Hz, 2H),
7.05 (t, J ) 2.1 Hz, 2H), 7.09 (t, J ) 2.0 Hz, 1H), 7.12 (t, J ) 7.6 Hz,
1H), 7.34 (t, J ) 2.0 Hz, 2H); 13C NMR (125 MHz, C6D6) δ 54.9,
115.1, 115.2, 117.4, 118.3, 118.6, 120.4, 123.2, 124.3, 124.6, 125.6,
127.5, 128.5, 129.3, 130.1, 130.2, 130.5, 140.0, 140.5, 148.5, 149.1,

Synthesis of Pure, Regiodefined Polymeric Triarylamines
J. Am. Chem. Soc., Vol. 121, No. 33, 1999 7539
149.3, 150.0, 156.7, 157.1. Anal. Calcd for C58H48Br2N4O4: C, 67.97;
H, 4.72; N, 5.47. Found: C, 68.18; H, 5.06; N, 5.21.
was heated in a Kugelrohr oven overnight at 50 °C under a 5 mTorr
vacuum, yielding 0.878 g (0.984 mmol, 64.7%) of 31 as a brownish
resin: 1H NMR (500 MHz, C6D6) δ 0.81-0.86 (multiple resonances,
12H), 1.31-1.39 (multiple resonances, 8H), 1.54-1.61 (multiple
resonances, 8H), 3.58 (t, J ) 6.3 Hz, 4H), 3.66 (t, J ) 6.5 Hz, 4H),
4.77 (s, 2H), 6.69 (d, J ) 8.5 Hz, 4H), 6.74 (d, J ) 9.0 Hz, 4H), 6.78
(dd, Jd ) 8.0 Hz, 2.0 Hz, 2H), 6.82 (d, J ) 9.1 Hz, 4H), 6.85 (d, J )
9.0 Hz, 4H), 7.04 (t, J ) 8.1 Hz, 1H), 7.12 (d, J ) 8.8 Hz, 4H), 7.16-
7.20 (multiple resonances, 5H); 13C NMR (125 MHz, C6D6) δ 13.9
(two overlapping resonances), 19.5, 19.6, 31.6, 31.7, 67.7, 67.9, 114.3,
114.8, 115.5, 115.6, 117.7, 121.3, 126.5, 126.7, 129.9, 136.8, 140.9,
141.0, 141.4, 150.1, 154.9, 155.7. Anal. Calcd for C58H66N4O4: C,
78.88; H, 7.53; N, 6.34. Found: C, 78.66; H,7.44; N, 6.14.
Dibromopentamer (32). A procedure analogous to that for the
preparation of 24 was employed using 0.574 g (0.643 mmol) of 31,
0.184 g (2.00 mmol) of sodium tert-butoxide, 28.3 mg (0.0.0511 mmol)
of bis(diphenylphosphino)ferrocene, 5.9 mg (0.018 mmol) of Pd(OAc)2,
and 6 mL of 1,3-dibromobenzene in a 50 mL screw-capped test tube.
The crude product was chromatographed on silica with 2% EtOAc in
hexanes to yield a yellowish resin, which was heated in a Kugelrohr
oven overnight at 50 °C under a 5 mTorr vacuum to remove residual
solvent, yielding 0.570 g (0.478 mmol, 74.3%) of 32 as a yellowish
resin: 1H NMR (500 MHz, C6D6) δ 0.81-0.84 (multiple resonances,
12H), 1.31-1.36 (multiple resonances, 8H), 1.52-1.58 (multiple
resonances, 8H), 3.56-3.59 (multiple resonances, 8H), 6.70-6.73
(multiple resonances, 8H), 6.75 (s, 1H), 6.77 (dd, Jd ) 8.1 Hz, Jd )
2.0 Hz, 4H), 6.90 (dm, Jd ) 7.5 Hz, 2H), 6.93-6.99 (multiple
resonances, 9H), 7.04 (d, J ) 8.9 Hz, 4H), 7.09-7.12 (multiple
resonances, 6H), 7.40 (t, J ) 2.0 Hz, 2H); 13C NMR (125 MHz, C6D6)
δ 13.9, 14.0, 19.5 (two overlapping resonances), 31.6, 31.7, 67.7 (two
overlapping resonances), 115.7, 115.9, 116.0, 116.8, 119.5, 123.4, 123.7,
123.8, 124.5, 125.7, 127.7, 127.8, 130.1, 130.6, 140.1, 140.6, 141.9,
144.1, 149.5, 150.6, 156.4, 156.7. Anal. Calcd for C70H72Br2N4O4: C,
70.47; H, 6.08; N, 4.49. Found: C, 70.21; H, 5.93; N, 4.49.
Diaminopentamer (27). A procedure analogous to that for the
preparation of 25 was employed using 0.800 g (0.780 mmol) of 26,
0.288 g (2.34 mmol) of p-anisidine, 0.334 g (3.50 mmol) of sodium
tert-butoxide, 50.0 mg (0.0903 mmol) of bis(diphenylphosphino)-
ferrocene, 10.0 mg (0.044 mmol) of Pd(OAc)2, and 3.5 mL of toluene.
Chromatography of the crude product on silica with 25% EtOAc in
hexanes resulted in a slightly brownish resin, which was heated in a
Kugelrohr oven overnight at 50 °C under a 5 mTorr vacuum to remove
residual solvent, yielding 0.769 g (0.692 mmol, 88.8%) of 27 as a
brownish resin: 1H NMR (500 MHz, C6D6) δ 3.23 (s, 6H), 3.25 (s,
6H), 3.31 (s, 6H), 4.78 (s, 2H), 6.53 (dd, J ) 8.0 Hz, 1.6 Hz, 2H),
6.59-6.71 (multiple resonances, 16H), 6.76-6.79 (multiple resonances,
6H), 6.86 (d, J ) 8.9 Hz, 4H), 6.93-6.99 (multiple resonances, 6H),
7.01 (d, J ) 8.9 Hz, 4H), 7.08 (d, J ) 8.9 Hz, 4H), 7.18 (t, J ) 2.1
Hz, 2H); 13C NMR (125 MHz, C6D6) δ 54.8, 54.9, 55.0, 109.2, 111.2,
114.8, 114.9, 115.0, 115.1, 116.9, 117.0, 117.1, 118.1, 118.3, 122.2,
127.4, 127.7, 129.9, 130.0, 130.1, 136.0, 140.8, 141.1, 146.3, 149.2,
149.3, 149.5, 149.6, 155.6, 156.5, 156.6. Anal. Calcd for C72H64N6O6:
C, 77.96; H, 5.89; N, 7.58. Found: C, 77.71; H,5.67; N, 7.45.
Polymerization of 26 with 27. In a drybox, a 1 dram vial was
charged with 51.2 mg (0.0500 mmol) of 26, 55.5 mg (0.0500 mmol)
of 27, 14.4 mg (0.150 mmol) of sodium tert-butoxide, 50 µL of a
benzene stock solution 0.01 mM in Pd(OAc)2 and 0.03 mM in 8, an
additional 50 µL of benzene, and a stirbar. The vial was sealed with a
Teflon-lined serum cap, removed from the drybox, and placed in a 90
°C oil bath for 3 days. Using the general procedure, the polymer was
extracted into toluene. 63.0 mg (0.0400 mmol, 80.0% yield) of polymer
28 was isolated as a white filmy solid: 1H NMR (500 MHz, CDCl3)
δ 3.67 (s, 3H), 6.49 (d, J ) 7.5 Hz, 2H), 6.67-6.70 (multiple
resonances, 3H), 6.89-6.94 (multiple resonances, 3H); 13C NMR (125
MHz, CDCl3) δ 55.3, 114.5, 116.6, 117.6, 126.7, 129.3, 140.4, 148.5,
155.8. Anal. Calcd for C13H11NO: C, 79.17; H, 5.62; N, 7.10. Found:
C, 77.84; H, 5.56; N, 6.82; Ash, 1.69.
Polymerization of 31 with 32. In a drybox, a 1 dram vial was
charged with 0.1715 g (0.1940 mmol) of 31, 0.2317 g (0.1940 mmol)
of 32, 59.9 mg (0.582 mmol) of sodium tert-butoxide, 194 µL of a
benzene stock solution that was 0.01 mM in Pd(OAc)2 and 0.03 mM
in 8, an additional 200 µL of benzene, and a stirbar. The vial was sealed
with a Teflon-lined serum cap, removed from the drybox, and placed
in a 90 °C oil bath for 3 days. Using the general procedure, the poly-
mer was extracted with toluene resulting in the isolation of 266.0 mg
(0.139 mmol, 71.9% yield) of polymer 33 as a white filmy solid.
Removal of the majority of cyclic impurities was achieved by filtration
through a 12 in. × 1.5 in. column of Sephadex LH-60 SEC resin (with
THF as eluent). The resulting polymer was isolated as before (53.6%
recovery) and extracted with hexanes using a Soxhlet apparatus for 3
h to remove BHT and other impurities from the product: 1H NMR
(500 MHz, CDCl3) δ 0.95 (t, J ) 7.5 Hz, 6H), 1.45 (m, 4H), 1.70 (m,
4H), 3.87 (t, J ) 6.4 Hz, 4H), 6.46 (dd, Jd ) 8.0 Hz, 1.5 Hz, 2H), 6.67
(s, 1H), 6.75 (d, J ) 9.0 Hz, 4H), 6.85 (s, 4H), 6.95-6.98 (multiple
resonances, 5H); 13C NMR (125 MHz, CDCl3) δ 13.9, 19.2, 31.4, 67.8,
114.8, 115.1, 115.6, 124.4, 126.5, 129.3, 140.4, 142.4, 148.9, 155.3.
Anal. Calcd for C32H34N2O2: C, 80.30; H, 7.16; N, 5.85. Found: C,
76.12; H, 6.57; N, 5.71; Ash, 1.77.
Oxidation of Polymers with Bis(trifluoroacetoxy)iodobenzene,
General Procedure. In a drybox, 0.010 mmol of polymer was weighed
into a 1.0 mL volumetric flask. The flask was filled with dichlo-
romethane to provide a 0.010 M solution. This solution was diluted
1:100 and 2 mL of this solution was placed into a UV-vis cuvette.
Increments of between 2.0 and 4.0 µL (0.020-0.040 µmol, 0.10-0.20
equiv) of a 0.010 M solution of bis(trifluoroacetoxy)iodobenzene in
dichloromethane were added to the polymer solution in the drybox.
The cuvette was removed from the drybox after each addition and the
oxidation was monitored by UV-vis spectroscopy.
Dibromotrimer (30). In a drybox, 0.809 g (2.00 mmol) of 29, 0.580
g (6.05 mmol) of sodium tert-butoxide, 88.6 mg (0.160 mmol) of bis-
(diphenylphosphino)ferrocene, 18.0 mg (0.080 mmol) of Pd(OAc)2, 50
g of 1,4-dibromobenzene, and 5 mL of toluene were combined in a 50
mL sealable reaction tube. The reaction was removed from the drybox
and heated in a 100 °C oil bath for 24 h to form a red-brown suspension.
This suspension was then poured while hot into 150 mL of toluene
and extracted with saturated NH4Cl. The aqueous phase was rinsed
twice with 20 mL of ether. The organic layers were combined and
dried over MgSO4. Evaporation of the solvent was followed by removal
of the excess dibromobenzene by distillation in a Kugelrohr apparatus
(50 °C, 5 mTorr). The residue was then chromatographed on silica
with 1% ethyl acetate in hexanes to yield an off-white solid, which
was rinsed with cold 1% ethyl acetate in hexanes and then dried in
vacuo to yield 1.20 g (1.68 mmol, 84.0%) of 30 as a white powder:
1H NMR (500 MHz, C6D6) δ 0.84 (t, J ) 7.4 Hz, 6H), 1.35 (m, 4H),
1.56 (m, 4H), 3.59 (t, J ) 6.5 Hz, 4H), 6.66-6.70 (multiple resonances,
6H), 6.77 (d, J ) 8.9 Hz, 4H), 6.92-6.94 (multiple resonances, 6H),
7.11 (d, J ) 9.0 Hz, 4H); 13C NMR (125 MHz, C6D6) δ 14.0, 19.5,
31.6, 67.8, 114.4, 115.8, 117.0, 118.0, 124.3, 127.7, 130.3, 132.3, 140.0,
147.3, 149.1, 156.7. Anal. Calcd for C38H38Br2N2O2: C, 63.88; H, 5.36;
N, 3.92. Found: C, 63.71; H, 5.20; N, 3.80.
Diaminotrimer (31). A procedure analogous to that for the
preparation of 25 was employed using 1.09 g (1.52 mmol) of 26, 0.750
g (4.55 mmol) of 4-butoxyaniline, 0.539 g (5.61 mmol) of sodium tert-
butoxide, 82.3 mg (0.148 mmol) of bis(diphenylphosphino)ferrocene,
16.4 mg (0.073 mmol) of Pd(OAc)2, and 10 mL of toluene. Chroma-
tography of the crude product on silica with a gradient of 5-10%
EtOAc in hexanes resulted in a slightly brownish resin that rapidly
darkened in air. This resin was then taken into a drybox, dissolved in
1 mL of ether, and filtered through a plug of silica to remove the
oxidized material. The solvent was removed in vacuo, and the residue
JA990632P