Poly (p-phenylenephosphaalkene): A π-conjugated macromolecule containing P=C bonds in the main chain

Article abstract of DOI:10.1002/1521-3773(20020703)41:13<2389::AID-ANIE2389>3.0.CO;2-6

An unprecedented yellow polymer with low-coordinate phosphorus atoms in the backbone has been prepared. The material is soluble in polar organic solvents, and moderate molecular weights (M_n = 2900-10500 g mol^-1) were estimated from <

Full text of DOI:10.1002/1521-3773(20020703)41:13<2389::AID-ANIE2389>3.0.CO;2-6

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[4] A. Caneschi, A. Cornia, A. C. Fabretti, S. Foner, D. Gatteschi, R.
Grandi, L. Schenetti, Chem. Eur. J. 1996, 2, 1379.
[5] R. W. Saalfrank, I. Bernt, E. Uller, F. Hampel, Angew. Chem. 1997,
109, 2596; Angew. Chem. Int. Ed. Engl. 1997, 36, 2482.
[6] G. L. Abbati, A. Cornia, A. F. Fabretti, A. Caneschi, D. Gatteschi,
Inorg. Chem. 1998, 37, 1430.
Poly(p-phenylenephosphaalkene):
A p-Conjugated Macromolecule Containing
ˆ
P C Bonds in the Main Chain**
Vincent A. Wright and Derek P. Gates*
[7] For example, R. W. Wagner, Das Rheingold, Schott, Mainz, 1873.
[8] A. L. Dearden, S. Parsons, R. E. P. Winpenny, Angew. Chem. 2001,
113, 155; Angew. Chem. Int. Ed. 2001, 40, 152.
[9] A. M¸ller, C. Serain, Acc. Chem. Res. 2000, 33, 2.
[10] A. J. Blake, C. M. Grant, S. Parsons, J. M. Rawson, R. E. P. Winpenny,
J. Chem. Soc. Chem. Commun. 1994, 2363.
[11] Representative references are: a) I. M. Atkinson, C. Benelli, M.
Murrie, S. Parsons, R. E. P. Winpenny, Chem. Commun. 1999, 285;
b) N. V. Gerbeleu, Yu. T. Struchkov, G. A. Timco, A. S. Batsanov,
K. M. Indrichan, G. A. Popovich, Dokl. Akad. Nauk. SSSR 1990, 313,
1459; c) E. J. L. McInnes, C. Anson, A. K. Powell, A. J. Thomson, S.
Poussereau, R. Sessoli, Chem. Commun. 2001, 89.
[12] S.-X. Liu, S. Lin, B.-Z. Lin, C.-C. Lin, J.-Q. Huang, Angew. Chem.
2001, 113, 1118; Angew. Chem. Int. Ed. 2001, 40, 1084.
[13] For example, D. Fenske, A. Fischer, Angew. Chem. 1995, 107, 340;
Angew. Chem. Int. Ed. Engl. 1995, 34, 307.
[14] a) K. L. Taft, C. D. Delfs, G. C. Papaefthymiou, S. Foner, D. Gatteschi,
S. J. Lippard, J. Am. Chem. Soc. 1994, 114, 823; b) C. Benelli, S.
Parsons, G. A. Solan, R. E. P. Winpenny, Angew. Chem. 1996, 108,
1967; Angew. Chem. Int. Ed. Engl. 1996, 35, 1825; c) M. Frey, S. G.
Harris, J. M. Holmes, D. A. Nation, S. Parsons, P. A. Tasker, R. E. P.
Winpenny, Chem. Eur. J. 2000, 6, 1407; d) A. Caneschi, A. Cornia,
A. C. Fabretti, D. Gatteschi, Angew. Chem. 1999, 111, 1372; Angew.
Chem. Int. Ed. 1999, 38, 1295; e) S. P. Watton, R. Fuhrmann, L. E.
Pence, A. Caneschi, A. Cornia, G. L. Abbati, S. J. Lippard, Angew.
Chem. 1997, 109, 2917; Angew. Chem. Int. Ed. Engl. 1997, 36, 2774.
[15] P. L. Jones, K. J. Byrom, J. C. Jeffery, J. A. McCleverty, M. D. Ward,
Chem.Commun. 1997, 1361.
[16] a) G. A. Ardizzoia, M. A. Angaroni, G. L. Monica, F. Cariati, S.
Cenini, M. Moret, N. Masciocchi, Inorg. Chem. 1991, 30, 4347; b) C.-
H. Chang, K. C. Hwang, C.-S. Liu, Y. Chi, A. J. Carty, L. Scoles, S.-M.
Peng, G.-H. Lee, J. Reedijk, Angew. Chem. 2001, 113, 4787; Angew.
Chem. Int. Ed. 2001, 40, 4651.
Approximatelytwentyyears ago, several examples of stable
neutral compounds possessing acyclic (p p) p bonds involv-
ing the heavier p-block elements were prepared.[1] Subse-
quently, the synthesis, structures, and reactivity of numerous
low-coordinate molecules has received extensive studyand
continues to attract considerable attention.[2] Despite current
interest in the preparation of organic macromolecules pos-
sessing p-conjugated backbones,[3] to our knowledge, the
incorporation of heavy-element multiple bonds into a p-
conjugated polymer is unprecedented.[4, 5] Furthermore, the
incorporation of inorganic elements into the polymer back-
bone is synthetically challenging and often results in materials
with unique properties.[6] Therefore, the development of
methods to prepare p-conjugated polymers containing heav-
ier main-group (p p) p bonds is of fundamental interest, and
mayultimatelylead to materials with novel properties. [7] The
poly(p-phenylenevinylene)s (PPVs) are an exciting class of
ˆ
luminescent organic macromolecules containing C C bonds
which pose manysnythetic challen-
ges.[3a,c, 8] However, the possible incor-
poration of other stable multiple
bonds, such as the well-established
[9]
ˆ
P C moiety, into the PPV structure
has not been explored.[10] Herein, we
report the synthesis and characteriza-
tion of a poly(p-phenylenephosphaalkene), a p-conjugated
macromolecule containing phosphorus(iii) carbon double
bonds in the polymer backbone.
[17] Crystal data for 1: crystal dimensions 0.15 Â 0.30 Â 0.60 mm, mono-
clinic, space group P21/c, a ˆ 21.14(1), b ˆ 27.16(1), c ˆ 19.274(9) ä,
b ˆ 104.99(1)8, Vˆ 10689(1) ä3, Z ˆ 2, 1calcd ˆ 1.321 gcmÀ3, 2qmax
ˆ
An elegant and general route to phosphorus(iii) carbon
double bonds involves the rapid and thermodynamically
favorable [1,3]-silatropic rearrangement of an acylphosphane
to a phosphaalkene (Scheme 1).[1a] From a preparative stand-
point, this method is probablythe most convenient and
versatile route to phosphaalkenes with minimal steric pro-
tection.[11] We initiated our investigations bypreparing model
compounds 1 and 2 for the polymer 3, under conditions
chosen to mimic a typical condensation polymerization.
Therefore, phosphaalkene 1 was prepared in the absence of
solvent bystirring mesitylene-2-carboxylic acid chloride and
PhP(SiMe3)2 at 508C for several days. Analysis of the reaction
mixture by 31P NMR spectroscopyshowed onlytwo signals
43.88, MoKa (l ˆ 0.710730 ä), q-2q scan, Tˆ 298 K, 13445 measured
reflections, 12909 independent reflections (Rint ˆ 0.0268), 12391
reflections included in the refinement. Lorentz, polarization correc-
tions were applied, m ˆ 0.867 mmÀ1, (D/s) ˆ 0.095, 1262 parameters
refined, R1 ˆ 0.0624 (for 8482 reflections with I > 2s(I)), wR2 ˆ 0.1453
(on F 2). Max./min. residual peaks in the final difference map 0.619/ À
0.414 eäÀ3. A crystal of 1 was mounted in a glass capillarywith drops
of mother liquor because of its sensitivityto air exposure. The
structure was solved bydirect methods using SHELXS-86 and refined
byfull-matrix least-squares techniques on F 2 using SHELXL-93. All
non-hydrogen atoms were refined anisotropically, except for the
solvent molecules, which were refined isotropically. All hydrogen
atoms were introduced at calculated positions as riding on bonded
atoms. CCDC-180394 (1) contains the supplementarycrystallographic
data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ,
UK; fax: (‡44)1223-336-033; or deposit@ccdc.cam.ac.uk).
[*] Prof. D. P. Gates, V. A. Wright
Department of Chemistry
[18] a) K. L. Taft, G. C. Papaefthymiou, S. J. Lippard, Science 1993, 259,
1302; b) A. Caneschi, A. Cornia, S. J. Lippard, G. C.Papaefthymiou,
R. Sessoli, Inorg. Chim. Acta 1996, 243, 295.
[19] B. P. Murch, F. C. Bradley, P. D. Boyle, V. Papaefthymiou, L. Que, Jr.,
J. Am. Chem. Soc. 1987, 109, 7993.
Universityof British Columbia
2036 Main Mall, Vancouver, BC, V6T 1Z1 (Canada)
Fax : (‡1)604-822-2847
E-mail: dgates@chem.ubc.ca
[20] T. Smith, S. A. Friedberg, Phys. Rev. 1968, 176, 660.
[**] We thank the Natural Sciences and Engineering Research Council
(NSERC) of Canada and the Universityof British Columbia for
support of this work, and Prof. M. Wolf for the use of UV/Vis and IR
equipment.
[21] R. Hoffmann, Sci. Am. 1993, 268, 66.
Supporting information for this article is available on the WWW under
http://www.angewandte.org or from the author.
Angew. Chem. Int. Ed. 2002, 41, No. 13
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[15]
highlyviscous and eyllow.
Poly(p-phenylenephosphaal-
kene) (3) was purified byprecipitation of the polymer from
a concentrated THF solution with cold hexanes (ca. À308C)
and subsequent drying in vacuo. The brittle yellow solid
(yield, 35%) was dissolved in C6D6 and analyzed by 31P NMR
spectroscopy, which showed broad overlapping signals for the
E and Z isomers in 3 and for the polymer end groups (see
Figure 1).[16] The 29Si NMR (DEPT) spectrum exhibited three
signals (d ˆ 21 and 18, 3 (OSiMe3); 1.4 ppm (d), 3 P(SiMe3)2
end groups) with the signals arising from OSiMe3 groups in 3
showing similar chemical shifts to those in 1 (d ˆ 21.3,
18.2 ppm).
Figure 1. 31P NMR spectrum (C6D6) of 3 (trial 2) after precipitation with
hexanes.
Scheme 1. The [1,3]-silatropic rearrangement of an acylphosphane to a
phosphaalkene.
An estimate of the molecular weight (Mn) of several
samples was obtained from relative integration of the
31
[17]
ˆ
P NMR signals for P(SiMe3)2 end groups and P C units.
The results are shown in Table 1; samples of 3 had moderate
degrees of polymerization (Xn, n in 3) between 5 and 21, not
(d ˆ 149.2, 54% and 134.0, 46%), assigned to the E and
Z isomers of 1, respectively. After distillation (1108C;
0.1 mmHg), analytically pure 1 was isolated as a pale yellow
liquid (yield, 75%).
≈
Table 1. Selected characterization data for 1, 2, and 3.
Examples of molecules possessing two or more phosphaal-
kene moieties bridged byarylene spacers are uncommon;
≈
*
*
Compound
tpolym
[h]
Xn
Mn
UV/Vis
lmax [nm]
Z/E
[12]
[gmolÀ1
]
furthermore, there are onlytwo previous reports of bis(phos-
phaalkene)s prepared through [1,3]-silatropic rearrange-
ment.[11b, 12b] Thus, we set out to prepare 2 from a concentrated
solution of PhP(SiMe3)2 (2 equiv) and 4 in THF and hexanes.
After several days of heating and monitoring by 31P NMR
spectroscopy, the PhP(SiMe3)2 was completelyconsumed, and
pure 2 (yield, 42%) was isolated as a colorless powder from a
concentrated hexanes solution (À358C). Unexpectedly, the
31P NMR spectrum of 2 in CDCl3 shows eight resonances
distributed over the regions expected for E- (44%) and Z-
phosphaalkene (56%) isomers. In addition, there were six
resolved signals for OSiMe3 groups in the 1H NMR spectrum.
Four signals are expected for the three possible isomers (E,E;
E,Z; Z,Z), thus, we postulate that the additional NMR signals
arise from restricted rotation of the P ˆ C groups about the
central aryl plane in 2.
1
2
328
550
2900
10500
6300
6300
310
314
328
338
334
334
0.85
1.27
1.12
1.14
1.06
1.05
3 (trial 1)
3 (trial 2)
3 (trial 3)
3 (trial 4)
21
27
28
34
5
21
12
12
≈
* Mn and Xn were estimated using end-group analysis (see ref. [17]).
unusual for a step-growth reaction. Moreover, the elemental
analyses, including chlorine analysis for two samples, were
consistent with the molecular weights estimated from end-
group analysis. The 13C NMR spectrum exhibited resonances
consistent with the assigned structure and, importantly, broad
ˆ
signals for the C P moietywere detected at d ˆ 212 and
198 ppm. The infrared spectra of films of 3 were remarkably
similar to those for 1, 2, and other analogous phosphaal-
kenes.[11a] The thermal stabilityof 3 was assessed bythermo-
gravimetric analysis (TGA) under dry helium. The polymer 3
was stable to weight loss up to 1908C, whereupon approx-
imately40% was lost, followed byan additional 20% at
4008C. After heating to 8008C, 40% of the mass remained as
a black solid.
In order to prepare the target poly(p-phenylenephospha-
alkene), two bifunctional starting reagents (4 and 5) were
required. The silylated phosphane 5 was prepared bytreating
1,4-diphosphanobenzene[13] with MeLi (4 equiv) in diethyl
ether followed byaddition of Me SiCl (4 equiv).[14] Analyti-
3
callypure 5 was obtained as a colorless solid after vacuum
sublimation at 1008C. The thermolysis of 4 and 5 was
conducted just above their melting temperature (858C) in a
vacuum-sealed Pyrex tube. In a typical experiment, after
about 24 h the initiallycolorless, free-flowing liquid was
The electronic structure of the new phosphaalkenes pre-
pared was probed in THF solution (ca. 10À5 m) byusing UV/
Vis spectroscopy. Few detailed UV/Vis studies have been
conducted on phosphaalkenes,[12e, 18] although there are two
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CH3), 2.32 (s, 3H; p-CH3), À0.05 ppm (s, 9H; OSi(CH3)3); 13C NMR
possible chromophores; (n p*) and (p p*). Typical spectra
for the polymer (3) and model compounds (1 and 2) are
shown in Figure 2. Broad absorbances were observed for 1
(lmax ˆ 310 nm) and 2 (lmax ˆ 314 nm). Analysis of poly(p-
phenylenephosphaalkene) (3) revealed a broad absorbance
(lmax ˆ 328 338 nm) and a tail stretching into the visible
1
1
ˆ
(CDCl3, 100.6 MHz): E-1: d ˆ 197.3 (d, J (C,P) ˆ 49 Hz; C P), 138.5 (d, J
(C,P) ˆ 39 Hz; i-Ph), 138.0 (d, 2J (C,P) ˆ 9 Hz; i-Mes), 137.4 (s; p-Mes),
134.2 (d, 3J (C,P) ˆ 5 Hz; o-Mes), 133.0 (d, 2J (C,P) ˆ 13 Hz; o-Ph), 128.0 (s;
3
m-Mes), 127.7 (d, J (C,P) ˆ 6 Hz; m-Ph), 127.5 (s; p-Ph), 21.0 (s; p-CH3),
19.9 (s; o-CH3), 0.3 0.1 ppm (m; OSi(CH3)3), Z-1: d ˆ 210.2 (d, 1J (C,P) ˆ
1
2
ˆ
41 Hz; C P), 139.5 (d, J (C,P) ˆ 44 Hz; i-Ph), 138.1 (s; p-Mes), 136.8 (d, J
(C,P) ˆ 28 Hz; i-Mes), 136.5 (d, 3J (C,P) ˆ 8 Hz; o-Mes), 133.3 (d, 2J
(C,P) ˆ 13 Hz; o-Ph), 128.4 (s; m-Mes), 128.1 (s; m-Ph), 127.5 (s; p-Ph), 21.1
(s; p-CH3), 20.7 (s; o-CH3), 0.3 0.1 ppm (m; OSi(CH3)3); 29Si NMR (C6D6,
79.5 MHz): d ˆ 21.3 (s), 18.2 ppm (s); UV/Vis (THF): lmax (e) ˆ 310 nm
(6000); IR (neat): nÄ ˆ 2921 (m), 2853 (m), 1601 (w), 1456 (s), 1377 (m), 1252
(vs), 1187 (vs), 847 cmÀ1 (s); MS (EI, 70 eV): m/z (%): 330 (3), 329 (10), 328
‡
‡
(44) [M ], 253 (1), 252 (4), 251 (23) [M À C6H5], 148 (9), 147 (100)
[C10H11O], 74 (5), 73 (72) [C3H9Si]; elemental analysis: C19H25OPSi: calcd
C 69.48, H 7.67, found C 69.54, H 7.60.
2: To a mixture of bis(trimethylsilyl)phenylphosphane (0.93 g, 3.7 mmol)
and 4 (0.47 g, 1.8 mmol) was added hexanes:tetrahydrofuran (5 mL:2 mL)
until dissolved. The solution was stirred at 858C in a closed vessel for a
several days and 31P NMR spectroscopyshowed quantitative formation of
2. The solvent was removed in vacuo giving a pale yellow oil, from which 2
was isolated (0.42 g, 42%) as a colorless powder from hexanes at À358C. 2:
31P NMR (CDCl3, 121.5 MHz): d ˆ 155.2 (s, 20%), 154.9 (s, 4%), 150.7 (s,
2%), 149.5 (s, 18%), 134.0 (s, 23%), 131.8 (s, 4%), 129.9 (s, 12%),
1
129.6 ppm (s, 17%); H NMR (CDCl3, 300.1 MHz): d ˆ 7.8 6.9 (m, 10H;
Figure 2. UV/Vis spectra of: 1 –– ; 2 - - - -; 3 (trial 3) –– ; 3 (trial 4)
.
Ph-H), 2.39, 2.38, 2.23, 2.19, 2.11, 2.05, 2.02 (s, 12H; Ar-CH3), 0.38, 0.31,
0.30 (s; OSi(CH3)3, E isomers (44%)), À0.09, À0.10, À0.15 ppm (s;
OSi(CH3)3, Z isomers (56%)); 13C NMR (CDCl3, 75.5 MHz,): d ˆ 211.8 (d,
1
1J (C,P) ˆ 44 Hz; C ˆ P, Z-2), 198.6 (d, J (C,P) ˆ 49 Hz; C P, E-2), 140
ˆ
region. We speculate that the bathochromic shift observed for
poly(p-phenylenephosphaalkene) compared with 1 and 2
suggests some degree of p-conjugation through the phenylene
137 (m; i-Ph and i-Ar), 134 132 (m; o-Ph), 131 130 (m; o-Ar), 128 127
(m; m-Ph and p-Ph), 19 17 (m; Ar-CH3), 0.8 0.1 ppm (m; OSi(CH3)3);
UV/Vis (THF): lmax (e) ˆ 314 nm (28000); IR (neat): nÄ ˆ 3052 (s), 2956
(vs), 2922 (sh), 1451 (sh), 1432 (s), 1251 (vs), 1192 (vs), 981 (s), 900 (sh),
854 cmÀ1 (vs); MS (EI, 70 eV): m/z (%): 553 (3), 552 (12), 551 (35), 550 (82)
ˆ
and P C units. However, the red shift for 3 is less than that for
trans-PPV compared with trans-stilbene (ca. 426 nm vs. 294/
‡
‡
[M ], 475 (4), 474 (6), 473 (26) [M À Ph], 443 (2), 442 (3), 441 (7)
307 nm), which we attribute to conformational nonplanarity
‡
‡
[M À PHPh], 371 (4), 370 (12), 369 (51) [M À P(Ph)SiMe3], 74 (9), 73
in the main chain, caused bythe bulkyC Me4 groups in 3.[19, 20]
(100) [SiMe3]; elemental analysis: calcd C 65.42, H 7.32, found C 65.32, H
7.47.
6
In addition, the breadth of the absorbance for 3 maybe
caused, in part, bythe mixture of isomers present ( Z/E ꢀ 1.1;
compare cis-stilbene (276 nm) and trans-stilbene (294/
307 nm)),[20] and/or the polydispersity of the material. Further
studies are necessaryto confirm the extent of p-conjugation
in 3.
3: The same procedure was followed for each trial (1 4). All glassware was
rinsed with Me3SiCl and flame dried prior to use. Compounds 4 (0.601 g,
2.32 mmol) and 5 (1.00 g, 2.32 mmol) were mixed as finelyground powders,
and flame sealed in vacuo in a thick-walled Pyrex tube. The sample was
placed in a preheated (858C) oven, whereupon the solids melted forming a
colorless, free-flowing liquid. After 6 8 h, the mixture showed an increase
in viscosityand was yellow. The reaction was monitored until the liquid was
almost immobile (ca. 24 h), and the yellow/orange material was removed
from the oven. The tube was broken, Me3SiCl was removed in vacuo, and
the residue dissolved in a minimum amount of THF (ca. 3 mL). The viscous
solution was evenlydistributed over the walls of the flask, and cold hexanes
(ca. À308 C) were added rapidly to precipitate the polymer as a yellow
solid. The hexanes-soluble fraction was removed and the polymer 3
remained (0.384 g, 35%) as a bright yellow glassy solid after drying
in vacuo. 3: 31P NMR (CDCl3; 121.5 MHz): d ˆ 157 149 (br m; E-3), 138
124 (br m; Z-3), À137 ppm (br; P(SiMe3)2 end groups; see Table 1 for Z/E
ratio, and degree of polymerization for each trial). All integrations for end-
group analyses are reported with a relaxation delay of 2.0 s; however,
spectra were obtained byusing 20 s and 30 s delays, and integrals were
identical. 29Si NMR (CDCl3, 79.5 MHz): d ˆ 21.7 20.5 (br m), 18.4 17.0
(br m), 1.4 ppm (d; 1J(Si, P) ˆ 26 Hz, end groups); 1H NMR (CDCl3,
400.1 MHz): d ˆ 7.8 6.6 (br m; C6H4), 2.5 2.1 (br m; C6(CH3)4), 0.5
À 0.5ppm (br m; Si(CH3)3); 13C NMR (CDCl3, 100.6 MHz): d ˆ 211.9 (br;
In summary, we have prepared and characterized the first
ˆ
p-conjugated polymer containing P C bonds in the main
chain. Future studies will explore the scope of this synthetic
methodologyand attempt to develop routes to air- and
moisture-stable poly(p-phenylenephosphaalkene)s.
Experimental Section
All manipulations were performed under a nitrogen atmosphere in a glove
box or using standard Schlenk techniques. Assignment of NMR spectra
were made with the aid of COSY, APT, HMQC, and HMBC experiments.
The E and Z isomers of 1, 2, and 3 were assigned bycomparison with
analogous systems; the signals arising from the E isomer are observed
downfield from those of the Z isomer in the 31P NMR spectrum.[11, 21]
ˆ
ˆ
Z-C P), 197.9 (br; E-C P), 142.0 (br; i-C6Me4), 139.1 (br; i-C6H4), 132.4,
130.2 (br; o-C6H4, o-C6Me4), 18.6, 17.5 (br s; C6(CH3)4), 0.7, 0.2 ppm (br s;
OSi(CH3)3); UV/Vis (see Table 1); IR (film): nÄ ˆ 2955 (m), 2921 (m), 2849
(m), 1252 (vs), 1187 (s), 846 cmÀ1 (vs); elemental analysis: [C24H34O2P2-
Si2]n ‡ [C26H43O2P2Si3Cl]: trial 1 calcd (n ˆ 5) C 59.80, H 7.32, found C
59.89, H 7.26, trial 3 calcd (n ˆ 12) C 60.43, H 7.28, Cl 0.57, found C 60.27, H
7.39, Cl 0.62, trial 4 calcd (n ˆ 12) C 60.43, H 7.28, Cl 0.57, found C 59.64, H
7.39, Cl 1.10.
1: Bis(trimethylsilyl)phenylphosphane (5.6 g, 22.0 mmol) and mesitylene-
2-carboxylic acid chloride (4.0 g, 21.9 mmol) were stirred at 508C, and over
several days quantitative conversion to 1 was observed by 31P NMR
spectroscopy. Pure 1 (5.4 g, 75%) was isolated as a pale yellow liquid after
vacuum distillation (b.p. 1108C, 0.1 mmHg). 1: 31P NMR (121.5 MHz,
C6D6): d ˆ 149.2 (s, 54%, E-1), 134.0 ppm (s, 46%, Z-1); 1H NMR
(400.1 MHz, CDCl3): E-1: d ˆ 7.13 7.01 (m, 5H; o, m, p-Ph), 6.73 (s, 2H;
m-Mes), 2.20 (s, 9H; o, p-CH3), 0.42 ppm (s, 9H; OSi(CH3)3), Z-1: d ˆ 7.79
(m, 2H; o-Ph), 7.35 (m, 3H; m, p-Ph), 6.91 (s, 2H; m-Mes), 2.48 (s, 6H; o-
Received: March 7, 2002 [Z18848]
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[1] Selected earlybreakthroughs in the synthesis of stable compounds
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H. Wenzel, Z. Krystallogr. 1995, 210, 224; c) A. Jouaiti, M. Geoffroy,
G. Terron, G. Bernardinelli, J. Am. Chem. Soc. 1995, 117, 2251; d) H.
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ˆ
ˆ
ˆ
ˆ
ꢁ
containing P C, P P, Si C, Si Si, P C bonds: a) G. Becker, Z. Anorg.
Allg. Chem. 1976, 423, 242; b) T. C. Klebach, R. Lourens, F.
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[3] For reviews, see: a) Handbook of Conducting Polymers, 2 ed. (Eds.:
T. A. Skotheim, R. L. Elsenbaumer, J. R. Reynolds), Dekker, New
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[13] E. M. Evleth, L. D. Freeman, R. I. Wagner, J. Org. Chem. 1962, 27,
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[14] The phosphane (5) was mentioned previously, however, detailed
synthetic procedures were not described. R. Appel, P. Fˆlling, B.
Josten, W. Schuhn, H. V. Wenzel, F. Knoch, Z. Anorg. Allg. Chem.
1988, 556, 7. Our synthetic procedure and spectroscopic data are
provided in the Supporting Information.
[15] Heating the polymerization mixture for 48 h at 858C resulted in an
insoluble yellow gel which swelled reversibly in THF. Analysis of the
swollen gel by 31P NMR spectroscopyshowed broad resonances
similar to those for the soluble polymer 3. Presumably, this material is
partiallycross-linked or high molecular weight 3.
[16] Samples of 3 exhibit no change in their NMR spectra after several
months of storage in THF solution under an inert atmosphere. Upon
exposure to moisture, solutions of 3 rapidly undergo partial hydrolysis,
and signals arising from -PH2 and -PHSiMe3 end groups were
observed byusing 31P NMR spectroscopy. Excess water results in
partial hydrolysis of the O-SiMe3 side groups giving an enol, which
ꢁ
[4] The spontaneous polymerization of PhC P has been reported. NMR
spectroscopic analysis suggests that the polymer is mainly composed
1
ˆ
of saturated trivalent phosphane moieties with P C units being a
tautomerizes to acylphosphane (d ˆ À16 ppm; JPH ˆ 232 Hz).
minor component. D. A. Loy, G. M. Jamison, M. D. McClain, T. M.
Alam, J. Polym. Sci. Part A 1999, 37, 129.
[17] The molecular weights of 3 were estimated byintegration of the
P(SiMe3)2 and P C signals in the 31P NMR spectrum (relaxation
ˆ
[5] The intriguing polymeric metal, (SN)x, is a superconductor at 0.26 K,
however the electronic structure of this solid-state inorganic material
is still under investigation. For a recent review, see: A. J. Banister, I. B.
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[7] For recent examples of conjugated polymers containing inorganic
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delays of between 2 and 30 s resulted in identical ratios). A statistical
(50:50) mixture of C(O)Cl and P(SiMe3)2 end groups was assumed;
consistent with elemental analysis and the trace of C(O)Cl (d ˆ
170 ppm) detected in the baseline of the 13C NMR spectrum. We
speculate that the small resonance at 50 ppm in the 31P NMR spectrum
of 3 is caused byminor cross-linking of the polymer chains. To date,
the sensitivityof 3 towards oxygen and moisture has precluded GPC
analysis. Thus far, MALDI-TOF MS has not been successful, perhaps
because of the reactivityof 3 with hydroxy-containing matrices.
[18] H. Kawanami, K. Toyota, M. Yoshifuji, J. Organomet. Chem. 1997,
535, 1.
[19] Incorporation of 2,3,5,6-tetramethyl-1,4-phenylene units into PPV
leads to a blue shift of 20 30 nm in the absorbance spectrum.
See S. Chung, D. W. Lee, D. Oh, C. E. Lee, J. Jin, Acta Polym. 1999, 50,
298.
[20] W. W. Simmons, The Sadtler Handbook of Ultraviolet Spectra, Sadtler
Research Laboratories, Philadelphia, 1979.
[21] For a discussion of the NMR spectra of phosphaalkenes see E. Fluck
in Topics in Phosphorus Chemistry, Vol. 10, Wiley, New York, 1980,
p. 193, and references therein.
[8] J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K.
Mackay, R. H. Friend, P. L. Burns, A. B. Holmes, Nature 1990, 347,
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Carbon Copy, Wiley, New York,1998; R. Appel in Multiple Bonds and
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Scherer), Thieme, Stuttgart, 1990; J. F. Nixon, Chem. Rev. 1988, 88,
1327; F. Mathey, Acc. Chem. Res. 1992, 25, 90; L. Weber, Eur. J. Inorg.
Chem. 2000, 2425.
ˆ
[10] The poly(azomethines), C N analogues of PPV, have been known
since the 1920s (R. Adams, R. E. Bullock, W. C. Wilson, J. Am. Chem.
Soc. 1923, 45, 521) and soluble derivatives exhibiting photolumines-
cence, liquid crystallinity, high thermal stability, and high tensile
strength are known. See for example: P. W. Morgan, S. L. Kwolek,
T. C. Pletcher, Macromolecules 1987, 20, 729; T. Matsumoto, F.
Yamada, T. Kurosaki, Macromolecules 1997, 30, 3547; O. Thomas, O.
Ingan‰s, M. R. Andersson, Macromolecules 1998, 31, 2676.
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b) G. Becker, O. Mundt, Z. Anorg. Allg. Chem. 1978, 443, 53; c) G.
Becker, W. Becker, G. Uhl, Z. Anorg. Allg. Chem. 1984. 518, 21; d) R.
Pietschnig, E. Niecke, M. Nieger, K. Airola, J. Organomet. Chem.
1997, 529, 127; e) A. Gr¸nhagen, U. Pieper, T. Kottke, H. W. Roesky,
2392
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