Synthesis of cymantrene-containing organometallic polymers using the Suzuki coupling

Article abstract of DOI:10.1021/om960737q

The synthesis of a novel rigid-rod phenylene - cymantrenylene copolymer using the Suzuki coupling as the polymer forming reaction is reported.

Full text of DOI:10.1021/om960737q

5470
Organometallics 1996, 15, 5470-5472
Syn th esis of Cym a n tr en e-Con ta in in g Or ga n om eta llic
P olym er s Usin g th e Su zu k i Cou p lin g
Sepas Setayesh and Uwe H. F. Bunz*
Max-Planck-Institut fu¨r Polymerforschung, Ackermannweg 10, 55021 Mainz, FRG
Received August 26, 1996X
Summary: The synthesis of a novel rigid-rod phenylene-
cymantrenylene copolymer using the Suzuki coupling as
the polymer forming reaction is reported.
cymantrenes are obtained only with great effort. In this
paper we describe a general route for the synthesis of
1,2,3-trifunctionalized cymantrene monomers and their
use in the synthesis of the corresponding polymers.
Monometalation of cymantrene with sec-BuLi is a
facile process.11 The ring metalation can be ortho-
directed by substituents such as acetal or alkyne
groups.12 At first direct double metalation of the
cymantrene nucleus (-78 °C, 2 h, THF) with 4.5 equiv
of sec-BuLi and subsequent workup with chlorotri-
methylsilane was attempted (in contrast to Gladysz’s
CpRe(NO)PPh3Cl complex); no defined product could be
isolated, however.13 We anticipated that in the synthe-
sis of a rigid-rod organometallic polymer with structure
A, the monomer(s) would require solubilizing group(s).
Acetals derived from formylcymantrene are easily pre-
pared and should allow by virtue of their ortho-directing
power the synthesis of 2,5-disubstituted cymantrenes.
Reaction of the acetal 1 (prepared from formylcyman-
trene and 2,2-dimethylpropanediol under the influence
of catalytic amounts of TsOH)14 with 4.5 equiv of sec-
BuLi for 1 h at -78 °C in THF and subsequent workup
with chlorotrimethylsilane permitted the isolation of a
yellow crystalline material in 71% yield (mp 92 °C, after
The Suzuki coupling is the reaction of an arylboronic
acid with an aromatic halide (preferably a bromide)
catalyzed by Pd(0) to give the corresponding biaryl1 in
excellent yields. While it was developed for the con-
struction of natural products containing biaryl units,2
this coupling reaction turned out to be efficient for the
synthesis of rigid-rod polyarylenes, particularly of the
poly-p-phenylene type.3 The difunctional coupling reac-
tions result in degrees of polymerization up to Pn
≈
100.4a,5 Organic rigid-rod polymers are valuable in
materials science for different reasons, including the
design of novel liquid crystalline phases4b and stable and
transferable mono- and multilayers,4c as well as for NLO
and similar applications.4d
The direct Suzuki coupling of arenes ligated by
organometallic fragments, in contrast, is rare and
includes only a couple of examples.5-7 None of these
have been used for the synthesis of rigid-rod organo-
metallic polymers, which are emerging as attractive
candidates for many applications in materials science.8-10
The synthesis of rigid-rod type polymers with 1,3-
disubstituted cyclopentadienyl complexes introduced as
links in the main chain was hampered by the difficult
synthesis of the corresponding monomers, so that
polymers of the structure A are virtually unknown. For
1
chromatography over flash silica gel).15 The H NMR
spectrum of this compound displayed only one signal
in the Cp region at δ 4.76 (2 H) and one signal in the
region expected for TMS groups (δ 0.25, 18 H). The
corresponding 13C NMR spectrum showed 10 signals,
of which three were attributed to the cyclopentadienyl
ring, viz. the ones at δ 89.3 (s, 2 C) and 92.2 (d, 2C) and
the singlet at 118.0 (1 C). Diagnostic is the band at δ
225.3, attributed to the CO groups. The magnetic
(8) (a) Altmann, M.; Bunz, U. H. F. Angew. Chem., Int. Ed. Engl.
1995, 34, 569. Altmann, M.; Enkelmann, V.; Lieser, G.; Bunz, U. H.
F. Adv. Mater. 1995, 7, 726. (b) Nishihara, H.; Shimura, T.; Ohkubo,
A.; Matsuda, N.; Aramaki, K. Adv. Mater. 1993, 5, 752.
(9) Long, N. J . Angew. Chem., Int. Ed. Engl. 1995, 34, 21.
(10) Manners, I. Angew. Chem. 1996, 108, 1712. Manners, I. Adv.
Organomet. Chem. 1995, 37, 131 and references cited therein.
(11) Lo Sterzo, C.; Stille, J . Organometallics 1989, 8, 2331.
(12) (a) Bunz, U. H. F.; Enkelmann, V.; Beer, F. Organometallics
1995, 14, 2490. (b) Loim, N. M.; Kondratenko, M. A.; Sokolov, V. I. J .
Org. Chem. 1994, 59, 7485 and references cited therein.
the synthesis of a cymantrenylene-phenylene copoly-
mer, for example, the corresponding 1,3-dihalogenated
X Abstract published in Advance ACS Abstracts, November 15, 1996.
(1) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
(2) Suzuki, A. Pure Appl. Chem. 1994, 66, 213. Yamamoto, T.;
Hayashi, Y.; Yamamoto, A. Bull. Chem. Soc. J pn. 1978, 51, 2091.
(3) Schlu¨ter, A.-D.; Wegner, G. Acta Polym. 1993, 44, 59. Scherf,
U.; Mu¨llen, K. Synthesis 1992, 23. Rehahn, M.; Schlu¨ter, A.-D.;
Wegner, G.; Feast, W. J . Polymer 1989, 30, 1060.
(4) (a) Scherf, U.; Mu¨llen, K. Makromol. Chem., Rapid Commun.
1991, 12, 489. (b) Witteler, H.; Lieser, G.; Wegner, G.; Schulze, G.
Makromol. Chem., Rapid Commun. 1993, 14, 471. (c) Rulkens, R.;
Wegner, G.; Enkelmann, V.; Schulze, M. Ber. Bunsen-Ges. Phys. Chem.
1996, 100, 707 and references cited therein.
(5) Knapp, R.; Rehahn, M. J . Organomet. Chem. 1993, 452, 235.
Knapp, R.; Rehahn, M. Makromol. Chem., Rapid Commun. 1993, 14,
451.
(6) Harre, K.; Enkelmann, V.; Schulze, M.; Bunz, U. H. F. Chem.
Ber. 1996, 129, 1323.
(13) Crocco, G. L.; Gladysz, J . A. Chem. Ber. 1988, 121, 375 and
references cited therein.
(14) Synthesis of 1: formylcymantrene (24.6 g, 106 mmol), 2,2-
dimethylpropan-1,3-diol (54.0 g, 519 mmol), and p-toluenesulfonic acid
(2.00 g, 8.40 mmol) are dissolved in 600 mL of toluene. This solution
is heated to reflux for 4 h using a Dean-Stark trap. The solvent is
evaporated and the crude product dissolved in 1 L of pentane. Washing
the organic phase with 300 mL of the methanol/water (1:1), drying
over MgSO4, and evaporating the solution give rise to the isolation of
32.2 g (95%) of 1 after chromatography over silica gel (pentane/
dichloromethane; 1:1); mp 71-72 °C. IR (KBr): ν 3114, 2966, 2858,
2842, 2018, 1925, 1394, 1108 cm-1
. δ
1H NMR (200 MHz, CDCl3):
0.75 (s, 3 H), 1.24 (s, 3 H), 3.52 (d, J ) 11 Hz, 2 H), 3.68 (d, J ) 11 Hz,
2 H), 4.63 (s, 2 H), 4.97 (s, 2 H), 5.09 (s, 1 H). 13C NMR (50 MHz,
CDCl3): δ 21.7, 22.9, 30.1, 77.4, 81.0, 82.6, 96.6, 102.0, 224.7. MS (EI,
70 eV): m/z (%) 318 (11, M+) 262 (2, M - 2CO), 234 (10, M - 3CO),
204 (100). Anal. Calcd for C14H15O5Mn (318.25): C, 52.8; H, 4.8.
Found: C, 52.8; H, 4.8.
(7) Uemura, M.; Nishimura, H. Tetrahedron Lett. 1993, 34, 107.
Uemura, M.; Nishimura, H.; Kamikawa, K.; Nakayama, K.; Hayashi,
Y. Tetrahedron Lett. 1994, 35, 1909.
S0276-7333(96)00737-6 CCC: $12.00 © 1996 American Chemical Society

Communications
Organometallics, Vol. 15, No. 26, 1996 5471
Ta ble 1. Yield a n d Su bstitu en t Key for 2 a n d 3
Sch em e 1
yield of
yield of
∑ of
2, 3
substituent
2 (%)
3 (%)
yield (%)
a
b
c
d
Li
SiMe3
SMe
I
71
53
77
5
32
3
76
85
80
resonance data exclude the structure 3b, which would
have a lower symmetry, and clearly indicated the
formation of the bis-silylated 2b (R ) TMS). The
proposed structure for this product was corroborated by
the mass spectroscopic analysis displaying the molec-
ular ion at m/z 462 followed by a signal at m/z 378
assigned to the fragment M - 3CO.
Using column chromatography, we were also able to
isolate the mono(trimethylsilyl)-substituted cymantrene
3b in a yield of 5%.15 The reaction of 2a with methyl
disulfide gave rise to the isolation of a 53% yield of 2c
and 32% of the mono(methyl thioether) 3c. Treating
2a with diiodoethane led to the isolation of the desired
diiodide 2d in 77% yield, while the corresponding
monofunctionalized 3d had formed in 3% yield. The
direct precursor to the trisubstituted cymantrenes 2b-d
must have been the corresponding dilithio compound
2a . Multiply lithiated cymantrenes have been previ-
ously reported by Winter, obtained during studies of
metal-metal exchange reactions.16 In another study
performed by Su¨nkel,17 the formation of di- or multi-
lithiated species during a halogen-metal exchange
involving pentabromocymantrene was discounted and
a stepwise halogen metal-exchange-functionalization
process was invoked instead. The results of our meta-
lation experiment are the first to clearly demonstrate
that the cymantrene nucleus can be lithiated doubly in
a 1,3-selective fashion, leading now to the facile syn-
thesis of 1,2,3-trisubstituted cymantrenes.
(15) Double metalation of 1, synthesis of 2d : acetal 1 (5.00 g, 15.7
mmol) was dissolved in 100 mL of water and oxygen-free THF and
the solution cooled to -78 °C. To this solution was added sec-BuLi
(54.0 mL, 1.3 mol L-1 in cyclohexane, 70.7 mmol, 4.50 equiv). The
solution, which darkened considerably, was stirred for 1 h at this
temperature and then reacted with a solution of 1,2-diiodoethane (27.0
g, 94.2 mmol) in 50 mL of THF. Considerable evolution of gas
accompanied this process. After 15 min the reaction mixture was
warmed to 21 °C; aqueous workup and washing of the organic phase
with sodium thiosulfate solution resulted in the isolation of 6.91 g (77%)
of 2d after chromatography over silica gel (pentane/dichloromethane;
4:1) and, as a second fraction, 207 mg (3.0%) of the monoiodide 3d .
2d : mp 121-122 °C; IR (KBr) ν 2963, 2850, 2017, 1956, 1932, 1391,
The synthesis of iodides 2d and 3d allowed us to
explore the Suzuki coupling reaction of 3d with the
(16) Bretschneider-Hurley, A.; Winter, C. H. J . Am. Chem. Soc.
1994, 116, 6468.
(17) Su¨nkel, K.; Kempinger, W. J . Organomet. Chem. 1994, 478, 201.
Su¨nkel, K.; Motz, D. Angew. Chem., Int. Ed. Engl. 1988, 27, 939.
(18) Suzuki couplings, synthesis of 4: 3d (200 mg, 0.450 mmol),
biphenylboronic acid (118 mg, 0.596 mmol), and Pd(dppfe)Cl2 (19 mg,
23 mmol) are dissolved in 20 mL of degassed THF. Na2CO3 (2 M
solution in water, 5 mL) is added and the solution is heated under
argon to reflux for 3 days. Aqueous workup gives rise to the isolation
of 164 mg (77%) of 4 after chromatography over silica gel (pentane/
dichloromethane; 7:3). 4: mp 139-140 °C; IR (KBr) ν 2956, 2929, 2850,
2019, 1927, 1102 cm-1; 1H NMR (200 MHz, acetone-d6) δ 0.79 (s, 3 H),
1.29 (s, 3 H), 3.69 (m, 4 H), 4.94 (s, 1 H), 5.33 (s, 3 H), 7.55 (m 9 H);
13C NMR (75 MHz, CD2Cl2) δ 21.8, 23.2, 30.3, 77.9, 79.3, 83.8, 84.4,
97.0, 100.5, 105.0, 127.3, 127.3, 128.0, 129.3, 130.0, 132.0, 140.7, 141.2,
224.9; MS (EI, 70 eV) m/z (%) 470 (3, M+), 386 (15, M - 3CO), 355
(73). Anal. Calcd for C26H23O5Mn (470.40): C, 66.4; H, 4.9. Found:
C, 66.2; H, 4.9. Synthesis of 5: 2d (400 mg, 0.702 mmol), biphenyl-
boronic acid (354 mg, 1.80 mmol), and Pd(PPh3)4 (41 mg, 43 µmol) were
dissolved in 30 mL of degassed DMF. Na2CO3 (2 M, 5 mL) was added,
and the solution was heated under argon to 80 °C for 3 days. Aqueous
1115 cm-1 1H NMR (200 MHz, CDCl3) δ 0.81 (s, 3 H), 1.43 (s, 3H),
;
3.61 (d, J ) 11 Hz, 2 H), 3.84 (d, J ) 11 Hz, 2 H), 4.96 (s, 2 H), 5.11
(s, 1 H); 13C NMR (75 MHz, CDCl3) δ 21.8, 23.7, 30.0, 43.9, 78.0, 91.1,
99.5, 101.7, 223.6; MS (EI, 70 eV) m/z (%) 570 (10, M+), 514 (1, M -
2CO), 486 (34, M - 3CO), 456 (28). Anal. Calcd for C14H13O5MnI2
(570.04): C, 29.5; H, 2.3. Found: C, 29.6; H, 2.3. 3d : mp 95-96 °C;
IR (KBr) ν 2959, 2851, 2024, 1934, 1393, 1109 cm-1 1H NMR (200
;
MHz, CDCl3) δ 0.77 (s, 3 H), 1.24 (s, 3 H), 3.62 (m, 4 H), 4.67 (s, 1 H),
4.91 (s, 1 H), 4.96 (s, 1 H), 5.11 (s, 1 H); 13C NMR (50 MHz, CDCl3) δ
21.7, 23.0, 30.1, 46.2, 77.8, 81.7, 82.2, 89.1, 97.8, 103.6, 224.1; MS (EI,
70 eV) m/z (%) 444 (8, M+), 388 (2, M+ - 2CO), 360 (23, M+ - 3CO),
330 (73). Anal. Calcd for C14H14O5MnI (444.10): C, 37.9; H, 3.2.
Found: C, 37.7; H, 3.0. In a similar way, starting from 1 (1.00 g, 3.15
mmol), sec-BuLi (11.0 mL, 14.2 mmol), and chlorotrimethylsilane (1.70
g, 15.8 mmol), the two silylated cymantrenes 2b (1.00 g, 71%, mp 92
°C) and 3b (61 mg, 5.0%) were obtained as crystalline yellow materials.
workup gives rise to the isolation of 371 mg (80%) of
chromatography over silica gel (pentane/dichloromethane, 7:3). 5: mp
152 °C; IR (KBr) ν 2959, 2932, 2855, 2024, 1923, 1112 cm-1 1H NMR
5 after
;
(200 MHz, acetone-d6) δ 0.73 (s, 3 H), 1.14 (s, 3 H), 3.58 (d, J ) 13 Hz,
3 H), 3.66 (d, J ) 13 Hz, 2 H), 5.29 (s, 2 H), 5.32 (s, 1 H), 7.55 (m, 10
H), 7.77 (d, J ) 12 Hz, 4 H), 7.84 (d, J ) 11 Hz, 4 H); 13C NMR (75
MHz, CD2Cl2) δ 22.5, 24.3, 30.5, 79.1, 83.1, 98.2, 99.7, 107.3, 127.4,
127.8, 128.3, 129.6, 131.6, 132.9, 141.2, 141.7, 225.5; MS (FD) m/z (%)
622 M+. Anal. Calcd for C38H31O5Mn (622.60): C, 73.3; H, 5.0.
Found: C, 73.3; H, 5.0. Polymerization reactions were carried out as
follows. Synthesis of 7a : 2d (300 mg, 0.526 mmol), Na2CO3 (2 M, 5
mL), and Pd(PPh3)4 (30 mg, 26 µmol) were dissolved in 10 mL of
oxygen-free DMF. The solution was heated to 40 °C for 7 days. 1,4-
Phenylenediboronic acid (89.5 mg, 0.540 mmol) was dissolved in 10
mL of degassed DMF and was added to this solution over 5 days. After
aqueous workup the polymer was precipitated into methanol and
pentane: yield 166 mg (80%); IR (KBr) ν 2958, 2932, 2869, 2019, 1937,
2b: IR (KBr) ν 2954, 2902, 2847, 2007, 1937, 1918, 1245, 1133 cm-1
;
1H NMR (200 MHz, CDCl3) δ 0.25 (s, 18 H), 0.78 (s, 3 H), 1.26 (s, 3 H),
3.51 (d, J ) 11 Hz, 2 H), 3.69 (d, J ) 11 Hz, 2 H), 4.76 (s, 2 H), 5.12
(s, 1 H); 13C NMR (50 MHz, CDCl3) δ 0.7, 22.1, 23.7, 30.1, 77.2, 89.3,
92.2, 99.0, 118.0, 225.3; MS (EI, 70 eV) m/z (%) 462 (10, M+), 378 (18,
M - 3CO), 348 (100). Anal. Calcd for C20H31O5MnSi2 (462.57): C,
51.9; H, 6.8. Found: C, 51.9; H, 6.6 3b: IR (KBr) ν 2959, 2850, 2020,
1928, 1474, 1396, 1123 cm-1 1H NMR (200 MHz, CDCl3) δ 0.26 (s, 9
;
H), 0.77 (s, 3 H), 1.24 (s, 3 H), 3.61 (m, 4 H), 4.72 (s br, 2 H), 5.09 (s
br, 2 H); 13C NMR (50 MHz, CDCl3) δ 0.1, 21.8, 23.1, 30.1, 77.4, 82.3,
83.4, 86.2, 91.3, 97.6, 110.4, 224.9; MS (FD) m/z (%) 390 (100, M+).
Anal. Calcd for C17H23O5MnSi (390.43): C 52.3; H, 5.9. Found: C,
52.5; H, 5.9. In a similar way 2c (684 mg, 53%; mp 106 °C) and 3c
(367 mg, 32%; mp 63-65 °C) are obtained after chromatography
(aluminum oxide, pentane/dichloromethane 9:1). 2c: IR (KBr) ν 2958,
1174 cm-1 1H NMR (300 MHz, CD2Cl2) δ 0.71 (s, 3 H), 1.10 (s, 3 H),
;
3.52 (d, J ) 11 Hz, 2 H), 3.71 (d, J ) 11 Hz, 2 H), 5.02 (s, 2 H), 5.23
(s, 1 H), 7.69 (s, 4 H), 13C NMR (75 MHz, CD2Cl2) δ 22.1, 24.0, 30.1,
78.7, 83.1, 98.3, 99.1, 106.2, 130.4, 133.3, 225.1. Anal. Calcd for
2925, 2849, 2019, 1935, 1122, 1020 cm-1 1H NMR (200 MHz, CDCl3)
;
δ 0.79 (s, 3 H), 1.27 (s, 3 H), 2.27 (s, 6 H), 3.62 (d, J ) 11 Hz, 2 H),
3.78 (d, J ) 11 Hz, 2 H), 4.68 (s, 2 H), 5.41 (s, 1 H); 13C NMR (50 MHz,
CDCl3) δ 17.8, 21.6, 22.9, 29.9, 77.7, 79.0, 97.5, 98.5, 103.6, 223.7; MS
(EI, 70 eV) m/e (%) 410 (11, M+), 326 (38, M - 3CO), 311 (28). Anal.
Calcd for C16H19O5MnS2 (410.39): C, 46.8; H, 4.7; S, 15.6. Found: C,
46.7; H, 4.6; S, 15.7. 3c: IR (KBr) ν 2959, 2928, 2852, 2021, 1933,
1111, 1021 cm-1; 1H NMR (200 MHz, CDCl3) δ 0.77 (s, 3 H), 1.25 (s, 3
H), 2.27 (s, 3 H), 3.67 (m, 4 H), 4.61 (s, 1 H), 4.73 (s, 1 H), 5.08 (s, 1 H),
5.25 (s, 1 H); 13C NMR (50 MHz, CDCl3) δ 18.6, 21.6, 22.9, 30.0, 77.6,
79.4, 82.1, 82.6, 96.6, 101.7, 102.2, 224.2; MS (EI, 7 eV) m/z (%) 364
(12, M+), 280 (22, M+ - 3CO), 250 (80). Anal. Calcd for C15H17O5-
MnS (364.30): C, 49.5; H, 4.7; S, 8.8. Found: C, 49.9; H, 4.8; S, 8.6.
C
20H17O5Mn (392.29): C 61.2; H, 4.4. Found: C, 58.6; H, 4.6.
Synthesis of 7b: same procedure as described for 7a , using 2,5-dihexyl-
1,4-phenylenediboronic acid (180 mg, 0.54 mmol). The polymer formed
was precipitated into methanol: yield of 7b 208 mg (77%); IR (KBr) ν
2955, 2928, 2856, 2018, 1935, 1106 cm-1 1H NMR (200 MHz, CDCl3)
;
δ 0.70 (s, 3 H), 0.90 (s b, 6 H), 1.14 (s, 3 H), 1.27 (m, 12 H), 1.60 (m, 4
H), 2.64 (s b, 4 H), 3.15 (s b, 2 H), 3.31 (s b, 2 H), 4.86 (s b, 3 H), 7.36
(s, 2 H); 13C NMR (75 MHz, CD2Cl2) δ 14.1, 15.1, 21.6, 22.7, 29.2, 30.3,
31.9, 32.8, 78.0, 83.9, 96.7, 102.6, 107.9, 130.4, 135.6, 139.3, 225.1. Anal.
Calcd for C32H41O5Mn (560.61): C, 68.6; H, 7.32. Found: C, 67.1; H,
7.82.

5472 Organometallics, Vol. 15, No. 26, 1996
Communications
Sch em e 2
commercially available biphenylboronic acid and Pd-
(dppfe)Cl2 in a THF/water/Na2CO3 mixture for 3 days
at 80 °C. This protocol gave rise to the isolation of the
desired coupling product 4 in 72% yield; reaction of the
diiodide 3d with biphenylboronic acid acidsas a model
reaction for the synthesis of the desired polymerssyielded
the corresponding bis(biphenylated)cymantrene 5 in
80% yield.
1,4-Phenylenediboronic acid can also be coupled with
2d under the influence of 2.5 mol % Pd(dppfe)Cl2 to form
polymer 7a in 80% yield after precipitation from metha-
nol and pentane. The polydispersity Mw/Mn of the
material was determined by gel permeation chroma-
tography to Dn ) 6.0 with Mn ) 1.2 × 104 (corresponds
to a degree of polymerization Dp of ∼30 with regard to
the phenylene cymantrenylene unit, suggesting that 60
bonds have been found during the polymerization). The
observed polydispersity is relatively high but is not
without precedence4b for a polycondensation reaction,
probably due to partial catalyst decomposition or alter-
ation, and the material (7a ) has the expected constitu-
tion, as can be seen by its 13C NMR spectrum. Eleven
signals are observed; at δ 22.1 and 24.0 the two quartets
for the two methyl groups can be found and the
connecting quarternary carbon emerges at δ 30.1, while
the CH2-O and the CH-O2 groups appear at δ 78.7 and
106.2, respectively. The group of lines appearing at δ
83.1, 98.3, and 99.1 are assigned to the cyclopentadienyl
ligand, while the aromatic carbons were recorded at
130.4 and 133.3 ppm. The signal assigned to the three
CO groups at δ 225.1 shows that the cymantrene units
did not degrade in the course of the reaction. Only one
set of signals, even though considerably broadened, was
observed, despite the fact that the polymer perhaps is
formed as a mixture of diastereomers, caused by the
presence of the symmetry-breaking Mn(CO)3 group. The
benzene-1,4-diyl unit resembles the bridging butadiyne-
1,4-diyls, which were also found to efficiently isolate the
stereoactive cymantrene units of our recently prepared
linear fullerenyne segments.12a
The polymerization reaction of 2d can be carried out
as well with 2,5-dihexyldiboronic acid, giving rise to the
isolation of the copolymer 7b with hexyl side chains.
The Mn and polydispersity Dp values are similar (11 ×
103, 6.4) to those of the polymer 7a , indicating that the
presence of the hexyl groups does not decrease the
efficiency of the polymer formation.
In conclusion, we have been able to show that,
starting from the acetal 1, 2,5-disubstituted cyman-
trenes can be obtained by a double-metalation/electro-
philic functionalization strategy. Inter alia, the corre-
sponding 2,5-diiodide 2d was synthesized via this route
and used to build benzene-cymantrenylene copolymers
by the Suzuki coupling. Thereby, we obtained the first
rigid-rod organometallic polymers containing cyman-
trene units in the backbone. The outlined approach
should be transferable to the synthesis of other conju-
gated all-carbon-backbone polymers carrying Cp com-
plexes in the main chain. Further investigation into the
scope of the coupling reaction with different Cp com-
plexes as well as the material properties of these
unusual polymers will be reported in the future.
Ack n ow led gm en t. We gratefully thank the DFG,
Stiftung Volkswagen, and Fonds der Chemischen In-
dustrie for financial aid. U.H.F.B. thanks the DFG for
a Habilitanden-scholarship and Prof. K. Mu¨llen for
generous support.
OM960737Q