Synthesis and properties of new stacked metallocene polymers

Article abstract of DOI:10.1021/om9902939

The substituted cyclopentadienes 5a,b are readily prepared in two steps from benzyloxybenzaldehyde and 4-dimethylaminobenzaldehyde by condensation with cyclopentadiene followed by lithium aluminum hydride reduction of the fulvenes 4a,b. Coupling of the zinc salts of 5a,b with 1,8-diiodonaphthalene in the presence of a catalytic amount of CuI gives the cyclopentadienylated iodonaphthalenes 6a,b. This new protocol represents a significant improvement over earlier procedures for the preparation of such compounds. Conversion of 6a,b to the ferrocenes 7a,b, followed by a second cyclopentadienylation step, affords 8a,b or 9a. These serve as monomers for the synthesis of polymers 1d,e and copolymers 1f-h. These materials show increased molecular weights and improved solubility compared with 1b,c and analogues, in which the cyclopentadienyl-ring substituents are alkyl chains.

Full text of DOI:10.1021/om9902939

4098
Organometallics 1999, 18, 4098-4106
Syn th esis a n d P r op er ties of New Sta ck ed Meta llocen e
P olym er s
Richard D. A. Hudson, Bruce M. Foxman,* and Myron Rosenblum*
Department of Chemistry, Brandeis University, 415 South Street,
Waltham, Massachusetts 02453-2728
Received April 22, 1999
The substituted cyclopentadienes 5a ,b are readily prepared in two steps from benzyloxy-
benzaldehyde and 4-dimethylaminobenzaldehyde by condensation with cyclopentadiene
followed by lithium aluminum hydride reduction of the fulvenes 4a ,b. Coupling of the zinc
salts of 5a ,b with 1,8-diiodonaphthalene in the presence of a catalytic amount of CuI gives
the cyclopentadienylated iodonaphthalenes 6a ,b. This new protocol represents a significant
improvement over earlier procedures for the preparation of such compounds. Conversion of
6a ,b to the ferrocenes 7a ,b, followed by a second cyclopentadienylation step, affords 8a ,b or
9a . These serve as monomers for the synthesis of polymers 1d ,e and copolymers 1f-h . These
materials show increased molecular weights and improved solubility compared with 1b,c
and analogues, in which the cyclopentadienyl-ring substituents are alkyl chains.
In tr od u ction
common organic solvents is poor. In our earlier paper,
we examined the effect of long chain alkyl substituents
in the monomer on the properties of the resulting
polymer and observed a measure of improvement in
both polymer size and solubility. In the present paper
we report the preparation and polymerization of several
aryl-substituted monomers and a further improvement
in the general methodology for monomer synthesis.
The design and synthesis of macromolecules that
incorporate transition metals or transition metal com-
plexes as essential structural elements constitutes an
area of growing research interest, promoted largely by
the prospect that such materials may possess novel
optical, redox, magnetic, or electrical properties.1 Sev-
eral members of this class have thus far been shown to
exhibit liquid crystal behavior2 and significant nonlinear
optical3 properties.
We recently reported the preparation of the first
members of a structurally unique class of organometallic
polymer 1 in which the component metallocene units
are constrained to a face-to-face, stacked arrangement,
through their peri-substitution on a naphthalene spacer.4
Owing to the restricted degrees of freedom within these
columnar metallocene polymers, they behave as rigid
rod type polymers,5 and consequently their solubility in
* To whom correspondence should be sent. E-mail: Rosenblum@
Brandeis.edu.
(1) Chisholm, M. H. Angew. Chem., Int. Ed. Engl. 1991, 30, 673-
674, and references therein. Pittman, C. U.; Carraher, C. E.; Zeldin,
M.; Sheats, J . E.; Culbertson, B. M. Metal-Containing Polymeric
Materials; Plenum: New York, 1996. Manners, I. Angew. Chem., Int.
Ed. Engl. 1996, 35, 1602-1621, and references therein. Buretea, M.
A.; Tilley, T. D. Organometallics 1997, 16, 1507-1510. Nguyen, P.;
Lough, A. J .; Manners, I. Macromol. Rapid Commun. 1997, 18, 953-
959. Gomez-Elipe, P.; Macdonald, P. M.; Manners, I. Angew. Chem.,
Int. Ed. Engl. 1997, 16, 762-764. Yamamoto, T.; Morikita, T.;
Maruyama, T.; Kubota, K.; Katada, M. Macromolecules 1997, 30,
5390-5396. Cardona, C. M.; Kaifer, A. E. J . Am. Chem. Soc. 1998,
120, 4023-4024, and references therein. Rehahn, M. Acta Polym. 1998,
49, 201-224, and references therein.
Exp er im en ta l Section
Gen er a l P r oced u r es a n d Ch em ica ls. Reactions were
carried out using standard Schlenk techniques under an argon
atmosphere. Tetrahydrofuran was freshly distilled from so-
dium benzophenone ketyl, and pyridine was stored over 4 Å
molecular sieves before being distilled from CaH under an
argon atmosphere. Anhydrous dimethoxyethane6 was used as
received.
Elemental analyses were performed by QTI Co, Salem, NJ ,
and by Desert Analytics, Tucson, AZ. HPLC analyses were
carried out using a system incorporating a Waters model 410
automated gradient controller, a model 510 pump, a model
U6-K injector, a model 401 refractive index detector, a Waters
746 data module, and Waters Ultrasytragel columns (104 and
500 Å). HPLC grade pyridine was used as received and run
at 0.8 mL/min. A calibration curve for gel permeation analysis
(2) Takahasi, S.; Takai, Y.; Morimoto, H.; Sonogashira, K.; Hagihara,
K. Mol. Cryst. Liq. Cryst. 1982, 82, 139. Abe, A.; Kimura, N.; Tabata,
S. Macromolecules 1991, 24, 6238.
(3) Frazier, C. C.; Guha, S.; Chen, W. P.; Cockerham, P. L.; Porter,
P. L.; Chauchard, E. A.; Lee, C. H. Polymer 1987, 28, 553. Kanis, D.
R.; Ratner, M. A.; Marks, T. J . J . Am. Chem. Soc. 1990, 112, 8203-
8204, and references therein. Kanis, D. R.; Ratner, M. A.; Marks, T.
J . Chem. Rev. 1994, 94, 195-242. Long, N. J . Angew. Chem., Int. Ed.
Engl. 1995, 34, 21-38.
(4) Rosenblum, M.; Nugent, H. M.; J ang, K.-S.; Labes, M. M.;
Cahalane, W.; Klemarczyk, P.; Reiff, W. M. Macromolecules 1995, 28,
6330-6342, and references therein.
(5) Ballauff, M. Angew. Chem., Int. Ed. Engl. 1989, 28, 253-267.
(6) Aldrich Chemical Co., Milwaukee, MI.
10.1021/om9902939 CCC: $15.00 © 1999 American Chemical Society
Publication on Web 09/10/1999

New Stacked Metallocene Polymers
Organometallics, Vol. 18, No. 20, 1999 4099
of polymers 1d -h in pyridine solution was established using
polystyrene standards in the same solvent. Polymers reported
in Tables 2 and 3 were found to be partially soluble in pyridine,
but insoluble in THF. The use of polystyrene standards in
these determinations finds support in the correlation of GPC-
derived Mn values, using these standards, with those derived
from end group analysis for the closely related alkyl-substi-
tuted polymers.4
4-Ben zyloxyben zyl-1- a n d 2-cyclop en ta d ien e (5a ). Fol-
lowing the procedure of Hafner14 a flame-dried flask was
charged with LAH (0.304 g, 8.0 mmol), and dry diethyl ether
(15 mL) was added. A solution of 4a (0.988 g, 3.8 mmol) in
dry diethyl ether (15 mL) was added dropwise, and this was
accompanied by vigorous effervescence. The solution was
stirred for a further 1 h, after which time the characteristic
yellow fulvene color had been discharged. The gray suspension
was transferred to a large conical flask cooled in an ice/water
bath, and cold methanol (10 mL) was added dropwise (CAU-
TION!) followed by 2 N HCl (30 mL), causing the solution to
separate into two clearly defined phases. The mixture was
extracted with diethyl ether (2 × 50 mL), and the combined
organic portions were washed with water (2 × 100 mL) and
brine (50 mL). The solvent was removed in vacuo, and the
residue was purified by flash chromatography on silica gel (30:
70 diethyl ether/hexanes) to afford 5a as a pale yellow oil and
as an inseparable mixture of isomers in the ratio 1:1. 1H NMR
(400 MHz, CDCl3): δ 2.84 (m, 2 H, CHCH2CH, isomer A or
B), 2.96 (m, 2 H, CHCH2CH, isomer A or B), 3.63 (br s, 2 H,
CHCH2CH isomer A or B), 3.67 (br s, 2 H, CpCH2, isomer A
or B), 5.03 (s, 4H, CH2Ph, isomer A and B), 5.98 (m, 1 H, CH,
isomer A or B), 6.12 (m, 1 H, CH, isomer A or B), 6.24 (m, 1
H, CH, isomer A or B), 6.39 (m, 3 H, CH, isomer A and B),
6.89 (m, 4 H, Ar-H, isomer A and B), 7.10 (m, 4 H, Ar-H,
isomer A and B), 7.44-7.30 (m, 10 H, Ar-H, isomer A and
B). Anal. Calcd for C19H18O: C, 87.0; H, 6.9. Observed: C, 86.9;
H, 6.8.
Zinc chloride6 (98%) was dried with TMSCl according to the
method of So and Boudjouk7 and heated to just below the
melting point under vacuum prior to use. FePy4(SCN)2,8
Ni(NH3)6Br2,9 NiBr2‚2DME,10 and NiCl2‚2THF11 were prepared
according to the literature. FeCl2 (anhydrous beads, ∼10 mesh,
99.9%)6 was used as received. 1,8-Diiodonaphthalene was
prepared according to the procedure of House12 from com-
mercially available 1,8-diaminonaphthalene.6 The crude prod-
uct was obtained as light brown crystals and was further
purified by sublimation and recrystalization to afford yellow
crystals, mp 109-110 °C. All other chemicals and reagents
were used as received without further purification.
6-(4-Ben zyloxyp h en yl)fu lven e (4a ). Following the pro-
cedure of Stone and Little,13 pyrrolidine (2.13 g, 30.0 mmol)
was added to a solution of 4-benzyloxybenzaldehyde (5.00 g,
23.6 mmol) and freshly cracked cyclopentadiene (3.17 g, 48
mmol) in MeOH (24 mL). A thick orange precipitate formed
after a few minutes, and stirring was continued overnight. An
aqueous solution of acetic acid (2 mL in approximately 50 mL
of water) was added, and the mixture was extracted with
diethyl ether (3 × 100 mL). The extracts were combined and
washed with water (2 × 100 mL) and brine (50 mL) before
being dried over MgSO4. The solvent was removed in vacuo,
and the residue was purified by flash chromatography on silica
gel (30:70 diethyl ether/hexanes) to afford 4a as a red solid
(5.78 g, 95%). IR (KBr): 2908, 1600, 1509, 1466, 1348, 1258,
4-Dim eth yla m in oben zyl-1-a n d 2-cyclop en ta d ien e (5b).
The procedure above was followed using LAH (0.76 g, 20 mmol)
and 3b (2.01 g, 10.2 mmol) in diethyl ether (100 mL). Workup
and purification as before (silica gel, 30:70 diethyl ether:
hexanes) afforded 5b as a pale yellow oil (1.54 g, 76%), and as
an inseparable mixture of isomers in the ratio of 1:1 (by nmr).
IR (thin film) 2885, 1613, 1519, 1475, 1443, 1340, 1161, 804
1
1175, 1003, 820, 759, 745, 696, 618 cm-1. H NMR (300 MHz,
1
cm-1; H NMR (300 MHz, CDCl3) δ 2.84 (m, 2 H, CHCH2CH,
CDCl3): δ 5.11 (s, 2 H, OCH2Ph), 6.32 (m, 1 H, Cp-H), 6.49
(m, 1 H, Cp-H), 6.67 (m, 1 H, Cp-H), 6.73 (m, 1 H, Cp-H),
7.01 (d, J ) 9.2 Hz, 2 H, Ar-H), 7.17 (s, 1 H, CpdCH), 7.40
(m, 4 H, Ar-H), 7.58 (d, J ) 8.6 Hz, 2 H, Ar-H). 13C NMR
(100.5 MHz, CDCl3) δ 70.2, 115.3, 120.1, 127.6, 127.7, 128.3,
128.8, 129.95, 130.0, 132.7, 135.2, 136.7, 138.4, 143.6, 160.0.
Anal. Calcd for C19H16O: C, 87.7; H, 6.2. Observed: C, 87.5;
H, 6.2.
isomer A or B), δ 2.89 (s, 3 H, N(CH3)2, isomer A or B), 2.89
(s, 3 H, N(CH3)2, isomer A or B), 2.95 (m, 2 H, CHCH2CH
isomer A or B), 3.60 (s, 2 H, Ph-CH2, isomer A or B), 3.63 (s,
2 H, Ph-CH2 isomer A or B), 5.98 (m, 1 H, CH, isomer A or B),
6.23 (m, 1 H, CH, isomer A or B), 6.39 (m, 1 H, CH, isomer A
or B), 6.40 (m, 3 H, CH, isomer A and B), 6.68 (d, J ) 8.6 Hz,
2 H, CHC(NMe2)CH, isomer A or B), 6.69 (d, J ) 8.6 Hz, 2 H,
CHC(NMe2)CH, isomer A or B) 7.04 (d, J ) 7.0 Hz, 2 H,
CHC(CHdCp)CH, isomer A or B), 7.07 (d, J ) 7.0 Hz, 2 H,
CHC(CHdCp)CH, isomer A or B). 13C NMR (100.5 MHz,
CDCl3): δ 35.3 (C-6, isomer A or B), 36.3 (C-6 isomer A or B),
40.8 (N(CH3)2 isomer A and B), 41.2 (C-5, isomer A or B), 43.0
(C-5, isomer A or B), 112.90 (C-9, isomer A or B), 112.92 (C-9,
isomer A or B), 126.9 (C-4, isomer A or B), 127.4 (C-4, isomer
A or B), 128.3 (C-1, isomer A or B), 129.2 (C-2, isomer A or B),
129.2 (C-8, isomer A or B), 129.3 (C-8, isomer A or B), 131.1
(C-1, isomer A or B), 132.3 (C-3, isomer A or B), 133.7 (C-2,
isomer A or B), 134.7 (C-3, isomer A or B), 146.6 (C-10, isomer
A and B), 149.1 (C-7, isomer A and B). Anal. Calcd for
6-(4-Dim eth yla m in op h en yl)fu lven e (4b). The same pro-
cedure as above was followed with 4-dimethylaminobenz-
aldehyde (4.00 g, 26.8 mmol), pyrrolidine (2.92 g, 41.1 mmol),
and freshly cracked cyclopentadiene (4.51 g, 68.5 mmol) in
MeOH (27 mL). The mixture was stirred overnight and worked
up as above to afford 4b as an orange solid after chromatog-
raphy (silica gel, 30:70 diethyl ether/hexanes) (4.87 g, 92%).
IR (KBr): 2896, 1597, 1525, 1370, 1346, 1233, 1197, 909, 815,
756, 622 cm-1 1Η ΝΜR (300 MHz, CDCl3): δ 3.00 (s, 6 H,
.
N(CH3)2), 6.33 (m, 1 H, Cp-H), 6.43 (m, 1 H, Cp-H), 6.62 (m,
1 H, Cp-H), 6.67 (d, J ) 7.0 Hz, 2 H, CHC(NMe2)CH), 6.79
(m, 1 H, Cp-H), 7.12 (s, 1 H, CpdCH), 7.56 (d, J ) 7.0 Hz, 2
H, CHC(CHdCp)CH). 13C (100.5 MHz, CDCl3): δ 40.0 (N(CH3)2),
111.8 (C9), 119.4 (C1), 124.6 (C7), 127.5 (C4), 128.0 (C3), 132.7
(C8), 133.6 (C2), 139.8 (C6), 140.7 (C5), 151.0 (C10). Anal.
Calcd for C14H15N: C, 85.3; H, 7.6; N, 7.1. Observed: C, 85.2;
H, 7.6; N, 6.9.
C
14H17N: C, 84.4; H, 8.5; N, 7.0. Observed: C, 84.7; H, 8.8; N,
6.9.
1-Iod o-8-(4-b en zyloxyb en zylcyclop en t a d ien yl)n a p h -
th a len e (6a ). To a solution of 5a (1.31 g, 5.0 mmol) in THF
(15 mL) at 0 °C was added n-butyllithium (2.0 mL, 5.0 mmol,
2.5 M solution in hexanes), and the mixture was stirred for 1
h. Zinc chloride (0.82 g, 6.0 mmol) was added as a solution in
THF (12 mL), and the mixture was stirred for a further 1 h.
1,8-Diiodonaphthalene (1.14 g, 3.0 mmol) in THF (5.0 mL) was
introduced by syringe, and copper iodide (10 mg) was added
in one portion. The reaction was stirred for 1 h and then
poured into a separating funnel containing a saturated aque-
ous NH4Cl solution (30 mL). The mixture was extracted into
diethyl ether (3 × 50 mL), and the organic portions were
(7) So, J .-H.; Boudjouk, P. Inorg. Chem. 1990, 29, 1592.
(8) Kauffman, G. B.; Albers, R. A.; Harlan, F. L. In Inorganic
Syntheses; Parry, R., Ed.; McGraw-Hill Co.: New York, 1970; Vol. 12,
pp 251-256.
(9) Watt, G. W. In Inorganic Syntheses; Audrieth, L. F., Ed.;
McGraw-Hill: New York, 1950; Vol. 3, pp 194-196.
(10) Organometallic Syntheses, King, R. B., Ed.; Academic Press:
New York, 1965; Vol. 1, p 72.
(11) Kohler, R. H.; Doll, K. H.; Fladerer, E.; Geike, W. A. Transition
Metal Chem. 1981, 6, 126.
(12) House, H. O.; Koepsel, D. G.; Campbell, W. J . Org. Chem. 1972,
37, 1003.
(13) Stone, K. J .; Little, R. D. J . Org. Chem. 1984, 49, 1849-1853.
(14) Hafner, K. Liebigs Ann. Chem. 1957, 606, 79-89.

4100 Organometallics, Vol. 18, No. 20, 1999
Hudson et al.
combined and dried over MgSO4. The solvent was removed in
vacuo, and the residue was purified by flash chromatography
on silica gel (5:95 diethyl ether/hexanes) to afforded 6a as a
very pale yellow oil (0.831 g, 54%) and as two inseparable
isomers (3- and 4-benzyloxybenzyl-substituted Cp) in the ratio
3:4 (by NMR). IR (solution in CH2Cl2): 2931, 1603, 1500, 1452,
8.3 Hz, 2 H, Ar-H), 6.92 (d, J ) 8.3 Hz, 2 H, Ar-H), 6.96 (d,
J ) 8.3 Hz, 2 H, Ar-H), 7.14 (m, 3 H, H5′, Ar-H), 7.30-7.45
(m, 10 H, H3′,4′,6′, Ar-H), 7.60 (dd, J ) 1.7, 7.5 Hz, 1 H, H2′,
Ar-H), 7.67 (d, J ) 7.5 Hz, 1 H, H7′, Ar-H).
1-Iod o-8-(4-d im et h yla m in ob en zylcyclop en t a d ien yl)-
n a p h th a len e (6b). The same procedure as for the preparation
of 6a was followed. Cyclopentadiene 5b (1.55 g, 7.8 mmol) in
dry THF (15 mL) was treated with n-butyllithium (3.75 mL,
6.0 mmol, 2.5 M solution in hexanes) at 0 °C followed by zinc
chloride (1.63 g, 12.0 mmol). The mixture was stirred for 1 h,
and 1,8-diiodonaphthalene (1.895 g, 5.0 mmol) in THF (1.0 mL)
was added along with copper iodide (2 mg). The mixture was
stirred for a further 1 h and worked up and purified as above
to afford 6b as a pale yellow oil (0.95 g, 42%) as two
inseparable isomers (3- and 4-dimethylaminobenzyl-substi-
tuted Cp) in the ratio 3:4 (by NMR). IR (solution in CH2Cl2):
2926, 2853, 1613, 1558, 1520, 456, 1358, 819 cm-1. Major
Isomer 1H NMR (300 MHz, CDCl3): δ 2.88 (s, 6 H, N(CH3)2,
major isomer), 2.89 (s, 6 H, N(CH3)2), 2.89 (m, 4 H, CH2 (Cp)
major and minor isomers), 3.64 (s, 2 H, CpCH2Ph, major
isomer), 3.71 (s, 2 H, CpCH2Ph, minor isomer), 6.15 (m, 2 H,
Cp-H, major and minor isomers), 6.26 (m, 2 H, Cp-H, major
and minor isomers), 6.66 (d, J ) 8.9 Hz, 2 H, Ar-H, major
isomer), 6.68 (d, J ) 8.9 Hz, 2 H, Ar-H, minor isomer), 7.02
(dd, J ) 7.4, 7.6 Hz, 1 H, H6, major isomer), 7.04 (dd, J ) 7.4,
7.6 Hz, 1 H, H6, minor isomer), 7.12 (d, J ) 8.9 Hz, 4 H, Ar-
H, major and minor isomers), 7.37 (m, 4 H, H2,4, major and
minor isomers), 7.70 (dd, J ) 3.4, 6.8 Hz, 1 H, H3, major
isomer), 7.74 (dd, J ) 3.4, 6.8 Hz, 1 H, H3, minor isomer), 7.78
(bd, J ) 7.9 Hz, H5, minor isomer), 7.80 (bd, J ) 7.9 Hz, H5,
major isomer), 8.14 (dd, J ) 1.3, 7.3 Hz, H7, minor isomer),
8.16 (dd, J ) 1.3, 7.3 Hz, H7, major isomer). Anal. Calcd for
196, 1176, 1023, 819 cm-1 1H NMR (400 MHz, CDCl3): δ
.
3.05-3.20 (m, 2 H, CHCH2CH, minor isomer), 3.30-3.50 (m,
2 H, CHCH2CH major isomer), 3.70 (s, 2H, CpCH2 major
isomer), 3.79 (s, 2H, CpCH2 minor isomer), 5.05 (s, 2H,
OCH2Ph, major isomer), 5.05 (s, 2H, OCH2Ph, minor isomer),
6.19 (m, 2 H, CH, major and minor isomers), 6.24 (m, 2 H, CH
major and minor isomers), 6.86 (m, 4H, Ar-H, major and
minor isomers), 7.06 (m, 2H, H6, major and minor isomers),
7.20 (d, J ) 8.0 Hz, 4H, Ar-H, major and minor isomers),
7.30-7.46 (m, 14 H, Ar-H, H2,6 major and minor isomers),
7.74 (m, 2 H, H3, major and minor isomers), 7.83 (m, 2 H, H5,
major and minor isomers), 8.19 (m, 2 H, H7, major and minor
isomers. A second compound 12a , the product resulting from
double cyclopentadienylation of diiodonaphthalene followed by
intramolecular Diels Alder cyclization, was recovered from this
reaction. This was obtained as a white crystaline solid (10%).
IR (KBr): 3033, 2926, 1610, 1509, 1454, 1382, 1299, 1240,
-1
1175, 1026, 819, 780, 736, 696 cm
.
1H NMR (400 MHz,
CDCl3): δ 2.12 (bd, J ) 18.7 Hz, 1 H, dicyclopentadiene-H1,exo),
2.79 (m, 1H, dicyclopentadiene-H7), 2.81 (m, 1 H, dicyclopen-
tadiene-H3a), 3.06(d, J ) 15.5 Hz, CH2Ph), 3.08 (bs, 1H,
dicyclopentadiene-H4), 3.10 (bd, J ) 18.7 Hz, 1H, dicyclopen-
tadiene-H1,endo), 3.32 (bs, 1H, dicyclopentadiene-H8), 3.34 (d,
J ) 15.5 Hz, 1H, CH2Ph), 3.42 (d, J ) 16.0 Hz 1 H, CH2Ph),
3.56(d, J ) 16.0 Hz, 1 H, CH2Ph), 5.08 (s, 2 H, OCH2Ph), 5.17
(bs, 1 H, dicyclopentadiene-H2), 5.77 (bs, 1 H, dicyclopenta-
diene-H6), 6.83 (d, J ) 8.3 Hz, 2 H, Ar-H), 6.97 (d, J ) 8.3
Hz, 2 H, Ar-H), 7.02 (d, J ) 8.3 Hz, 2 H, Ar-H), 7.18 (m, 3
H, Ar-H), 7.3-7.42 (m, 10 H, Ar-H), 7.47 (m, 2 H, Ar-H),
7.60 (dd, J ) 1.7, 7.5 Hz, 1 H, Ar-H), 7.67 (d, J ) 7.5 Hz, 1 H,
Ar-H). 13C NMR (100.5 MHz, CDCl3): δ 34.5, 36.9, 37.8, 54.7,
54.9, 56.3, 65.0, 67.8, 70.2, 70.3, 114.8, 115.0, 117.8, 124.3,
125.1, 125.5, 125.8, 126.7, 127.1, 127.7, 127.74, 128.1, 128.14,
128.8, 128.7, 128.8, 130.1, 130.4, 130.8, 131.8, 132.0, 133.9,
137.3, 137.4, 138.8, 142.1, 146.1, 153.0, 157.3, 157.5. Anal.
Calcd for C48H40O2: C, 88.9; H, 6.2. Observed: C, 88.7; H, 6.2.
C
24H22NI: C, 63.9; H, 4.9. Observed: C, 63.9; H, 4.8.
As before, a second product is formed in this reaction
through double cyclopentadienylation of diiodonaphthalene.
The resulting dicyclopentadiene product was recovered from
the reaction mixture in 16% yield as a white crystaline solid
(0.418 g, 0.8 mmol). Mp: 208-210 °C. IR (KBr): 2900, 1616,
-1
1521, 1443, 1350, 1225, 1159, 948, 816, 804, 881, 774 cm
.
1H NMR (400 MHz, CDCl3): δ 2.11 (bd, J ) 18.7 Hz, 1 H,
dicyclopentadiene-H1exo), 2.78 (bs, 1 H, dicyclopentadiene-
H7), 2.82 (bs, 1 H, dicyclopentadiene-H3a), 2.87 (s, 6 H, NMe2),
2.96 (s, 6 H, NMe2), 2.98 (d, J ) 15.9 Hz, 1 H, CH2Ph), 3.05
(bd, J ) 18.7 Hz, 1H, dicyclopentadiene-H1,endo), 3.06 (bs, 1
H, dicyclopentadiene-H4), 3.31 (d, J ) 15.9 Hz, 2 H, CH2Ph),
3.32 (bs, 1 H, dicyclopentadiene-H8), 3.39 (d, J ) 14.7 Hz, 2
H, CH2Ph), 3.56 (d, J ) 16.5 Hz, 2 H, CH2Ph) 5.16 (s, 1 H,
dicyclopentadiene-H2) 5.78 (s, 1 H, dicyclopentadiene-H6),
6.62 (d, J ) 8.6 Hz, 2 H, Ar-H), 6.76 (d, J ) 8.6 Hz, 2 H,
Ar-H), 6.99 (d, J ) 8.6 Hz, 2 H, Ar-H), 7.16 (m, 3 H, C-5,
Ar-H), 7.35 (m, 3 H, Ar-H), 7.59 (dd, J ) 1.8, 6.7 Hz, 1 H,
Ar-H), 7.65 (d, J ) 7.9 Hz, 1 H, Ar-H). 13C NMR (100.5 MHz,
CDCl3): δ 34.6, 36.7, 37.7, 41.1, 41.2, 54.89, 54.94, 56.4, 65.1,
67.9, 113.1, 113.2, 117.9, 124.3, 125.1, 125.5, 125.8, 126.7,
126.8, 127.8, 127.9, 128.2, 129.8, 130.1, 131.0, 134.0, 139.1,
142.6, 146.4, 149.3, 149.4, 153.2. Anal. Calcd for C38H38N2: C,
87.4; H, 7.3; N, 5.4. Found: C, 87.1; H, 7.3; N, 5.2. The
structure of this compound (12b) has been established by X-ray
analysis.
This Diels-Alder product (12a ), together with an isomer
13a , was also obtained from diiodonaphthalene by treatment
with excess 5a anion as follows. Compound 5a (0.79 g. 3.0
mmol) was dissolved in THF (10 mL) and cooled to 0 °C. BuLi
(01.2 mL, 3.0 mmol, 2.5 M solution in hexanes) was added
dropwise, and the reaction was stirred for 1 h, before zinc
chloride (0.68 g, 5.0 mmol) in THF (5 mL) was added. After a
further 1 h, 1,8-diiodonaphthalene (0.30 g, 0.79 mmol) and CuI
(0.03 g, 0.15 mmol) were added in THF (15 mL). The mixture
was stirred at room temperature for 2 h, after which it had
become black. The solution was poured into a separating
funnel charged with concentrated aqueous NH4Cl solution (30
mL) and was extracted with diethyl ether (2 × 30 mL). The
combined organic extracts were washed with water (2 × 50
mL) and dried over MgSO4. The Diels-Alder products were
obtained as an inseparable mixture of isomers in the ratio 1:2
(by NMR analysis of the crude material) and in 72% yield after
purifcation by column chromatography on silica gel with 30:
70 ether/hexanes as the eluant. A portion of the mixture was
dissolved in a minimum of hot hexane and allowed to stand
overnight. Colorless crystals were obtained, which were shown
to be the major isomer 12a by comparison with the NMR
spectrum of the product obtained above. After evaporation, the
mother liquor was found to be greatly enriched in the minor
The Diels-Alder products 12b and 13b were obtained
separately by treatment of 5b (0.40 g, 2.0 mmol), dissolved in
THF (10 mL) at 0 °C with BuLi (0.80 mL, 2.0 mmol, 2.5 M
solution in hexanes). The solution was stirred for 1 h, before
zinc chloride (0.41 g, 3.0 mmol) in 5 mL of THF was added.
After a further 1 h 1,8-diiodonaphthalene (0.15 g, 0.4 mmol)
and CuI (0.02 g, 0.1 mmol) were added in 10 mL of THF. The
reaction was worked up as in the preparation of 12,13a , and
12b was isolated from the mixture by crystallization. After
evaporation, the mother liquor was found to be greatly
enriched in the minor isomer 13b. 1H NMR (400 MHz,
CDCl3): δ 2.10 (bd, J ) 20.0 Hz, 1 H, C-1-HR), 2.72 (bs, 1 H,
1
isomer 13a . H NMR (400 MHz, CDCl3) δ 2.11 (bd, J ) 18.7
Hz, 1H, H1R), 2.79 (bs, 1 H, H3a) 2.80 (bs, 1 H, H7), 2.95 (m, 2
H, H4, H8), 3.08 (m, 2 H, H1â, CH2Ph), 3.31 (bs, 1 H, CH2Ph)
3.44 (m, 2 H, CH2Ph), 5.05 (s, 2 H, OCH2Ph), 5.08 (s, 2 H,
OCH2Ph), 5.06 (bs, 1 H, H2), 5.68 (bs, 1 H, H5), 6.82 (d, J )

New Stacked Metallocene Polymers
Organometallics, Vol. 18, No. 20, 1999 4101
Ta ble 1. Da ta for th e X-r a y Diffr a ction Stu d y of
12b
multiplets, 6 H, R and â Fc-H, dl and meso), 4.99 (s, 4 H,
OCH2Ph, dl and meso), 6.83 (d, J ) 8.25 Hz, 4H, Ar-H, dl
and meso), 6.98 (dd, J ) 7.33, 7.33 Hz, 0.5 H, H6 dl or meso),
6.99 (dd, J ) 7.33, 7.33 Hz, 1 H, H6 dl or meso), 6.99 (dd, J )
7.6, 7.6 Hz, 1 H, H3 dl or meso), 7.06 (dd, J ) 7.6, 7.6 Hz, 1 H,
H3 dl or meso), 7.11 (d, J ) 8.9 Hz, 2H, Ar-H, dl or meso),
7.14 (d, J ) 8.9 Hz, 2H, Ar-H, dl or meso), 7.24 (m, 1 H, Ar-
H, dl or meso), 7.22-7.42 (m, 11 H, Ar-H), 7.55 (dd, J ) 9.2,
0.9 Hz, H4, dl or meso), 7.57 (dd, J ) 9.2, 0.9 Hz, H4, dl or
meso), 7.77 (dd, J ) 8.3, 1.5 Hz, H5, dl or meso), 7.78 (dd, J )
8.3, 1.5 Hz, H5, dl or meso), 8.05 (dd, J ) 7.0, 1.22 Hz, H2, dl
or meso), 8.06 (dd, J ) 7.3, 1.2 Hz, H7, dl or meso), 8.12 (dd, J
) 7.3, 1.2 Hz, H7 dl or meso). Anal. Calcd for C58H44FeO2I2:
C, 64.3; H, 4.1. Observed: C, 64.0; H, 3.7.
chemical formula
12b, C38H38N2
a, Å
10.1514(13)
b, Å
12.533(2)
c, Å
23.520(2)
â, deg
V, Å3
Z
101.15(1)
2935.9
4
fw
522.74
P21/n [C52h; No. 14]
space group
T, °C
λ, Å
21(1)
1.54178, graphite monochromator
1.183
0.484
F
calc, g cm-3
µ, mm-1
absorp corr
data collection
no. of reflns measd
Ra
empirical transm factors 0.939-1.00
(h, -k, -l (to 2θ ) 156°)
6314; 6165 in unique set; Rint ) 0.012
0.0403
3,3′-Bis(4-dim eth ylam in oben zyl)-1,1′-bis(8-iodo-1-n aph -
th yl)fer r ocen e (7b). Following the same procedure as above,
the anion of 6b (0.70 g, 1.55 mmol) was formed in THF (10
mL) at -78 °C with KOtBu (0.20 g, 1.8 mmol). Freshly washed
(3 × 10 mL) FePy4(SCN)2 (0.98 g, 2.0 mmol) was added, and
the reaction was allowed to warm to room temperature
followed by stirring for 1 h. Workup and purification as above
afforded 7b (0.45 g, 61%) as a red solid and as a 1:1 mixture
of dl and meso forms. A small amount of 6b (0.118 g, 17%)
was also recovered after chromatography. IR (KBr): 2882,
1612, 1520, 1350, 1192, 1162, 947, 81, 763 cm-1. 1H NMR (400
MHz, CDCl3): δ 2.87 (s, 6 H, dl or meso), 2. 88 (s, 6 H, dl or
meso), 3.59 (s, 4 H, dl or meso), 3.67 (s, 4 H, dl or meso), 4.07,
4.17, 4.19, 4.21, 4.22, 4.40 (2 pairs of 3 multiplets, 12 H, R
and â Fc-H, dl and meso), 6.62 (d, J ) 6.1 Hz, 4 H, Ar-H, dl
or meso), 6.64 (d, J ) 6.1 Hz, 4 H, Ar-H, dl or meso), 6.9 (m,
6 H, H3 dl and meso, H5, dl or meso), 7.03 (dd, J ) 7.6, 7.64
Hz, 2 H, H5, dl or meso), 7.11 (m, 4 H, Ar-H, dl and meso),
7.54 (d, J ) 7.9 Hz, 2 H, H4, dl or meso), 7.56 (d, J ) 7.9 Hz,
2 H, H4, dl or meso), 7.78 (d, J ) 8.3 Hz, 4 H, H5, dl and meso),
8.04 (dd, J ) 0.9, 7.3 Hz, 2 H, H5, dl or meso), 8.06 (dd, J )
0.9, 7.0 Hz, 4 H, H7, dl and meso), 8.09 (dd, J ) 0.9, 7.3 Hz, 2
H, H5, dl or meso). Anal. Calcd for C48H42FeN2I2: C, 60.2; H,
4.4; N, 2.9. Observed: C, 59.7; H, 4.6; N, 2.8.
b
Rw
0.0524
a
2
R ) ∑||Fo| - |Fc||/∑|Fo|. bRw ) {∑w[|Fo| - |Fc|]2/∑w|Fo| }1/2
.
C-7), 2.73 (bs, 1 H, C-3a), 2.87 (bs, 1 H, C8), 2.88 (bs, 1 H,
CH2Ph), 2.90 (d, J ) 8.0 Hz, C-4), 3.00 (bd, J ) 20.0 Hz, 1H,
C-1-Hâ), 3.26 (d, J ) 17.6 Hz, 1 H, CH2Ph), 3.32 (bs, 1 H,
CH2Ph), 3.49 (d, J ) 17.6 Hz, 1 H, CH2Ph), 5.06 (s, 1 H, C-2),
5.68 (s, 1 H, C-5), 6.60 (d, J ) 8.6 Hz, 2 H, Ar-H), 6.92 (d, J
) 8.6 Hz, 2 H, Ar-H), 7.08 (d, J ) 8.6 Hz, 2 H, Ar-H), 7.16
(m, 1 H, C-5′), 7.35 (m, 3 H, C-3′, C-4′, C-6′), 7.59 (dd, J ) 1.8,
6.7 Hz, 1 H, C-2′), 7.65 (d, J ) 7.9 Hz, 1 H, C-7′).
X-r a y St r u ct u r e Det er m in a t ion of C38H 38N2 (12b ).
Crystallographic data for compound 12b are summarized in
Table 1. Data were collected on a Nonius CAD-4U diffrac-
tometer (Cu KR radiation, λ ) 1.54178 Å).15 Data were
processed using the Nonius MolEN package;16 the structure
was solved by direct methods (SIR-92).17 Full-matrix least-
squares refinement was carried out using the Oxford Univer-
sity CRYSTALS-PC system.18 All nonhydrogen atoms were
refined using anisotropic displacement parameters; H atoms
were refined using isotropic displacement parameters. Draw-
ings were produced using the Oxford University program
CAMERON.19 Bond lengths and angles lie within expected
ranges for strained molecules. A full report on the structure
is available as a CIF file.
3,3′-Bis(4-ben zyloxyben zyl)-1,1′-bis(8-iod o-1-n a p h th yl)-
fer r ocen e (7a ). To a solution of 5a (0.50 g, 0.97 mmol) in dry
THF (10 mL) at -78 °C was added KOtBu (0.11 g, 1.0 mmol)
also in THF (2 mL), and the dark red mixture was stirred for
15 min. FePy4(SCN)2 (0.98 g, 2.0 mmol) (previously washed
with dry THF (3 × 10 mL)) was added as a slurry in one
portion before the flask was allowed to warm slowly to room
temperature. After stirring for a further 1 h the reaction was
quenched with water and extracted with diethyl ether (3 ×
50 mL). The combined organic phases were washed with
saturated aqueous CuSO4 (4 × 50 mL) and water (50 mL).
Purification by flash chromatography on silica gel (30:65:5
toluene/hexanes/ether) afforded 7a as a red solid (0.329 g, 63%)
and as a 1:1 mixture of dl and meso forms. IR (KBr): 3031,
2910, 1610, 1509, 1452, 1239, 1174, 1026, 816, 763, 735, 696
cm-1. 1H NMR (400 MHz, CDCl3): δ 3.58 (s, 2 H, FcCH2), 3.67
(s, 2 H, FcCH2), 4.05, 4.15, 4.19, 4.20, 4.27, 4.43 (2 pairs of 3
3,3′-Bis(4-ben zyloxyben zyl])-1,1′-bis(8-cyclopen tadien yl-
1-n a p h th yl)fer r ocen e (8a ). Cyclopentadienylzinc chloride
was prepared from freshly cracked cyclopentadiene (132 mg,
2.0 mmol) in dry THF (30 mL) at 0 °C by the addition of
n-butyllithium (0.8 mL, 2.0 mmol of a 2.5 M solution in
hexanes) followed by zinc chloride (54 mg, 4.0 mmol) in THF
(10 mL). The mixture was stirred for 1 h, and 7a (328 mg, 0.3
mmol) in THF (5 mL) was introduced by syringe. Copper iodide
(3 mg, 1.5 × 105 mol, 5 mol %) was added, and the reaction
mixture was allowed to warm to room temperature. After
stirring for 30 min the solution had become very dark brown.
The mixture was poured into a separating funnel charged with
a saturated aqueous solution of NH4Cl (25 mL) and extracted
with diethyl ether (3 × 50 mL). The organic portions were
combined and washed with water (2 × 50 mL) and brine (50
mL) before being dried over MgSO4. The solvent was removed
in vacuo, and purification by flash chromatography on silica
gel (30:65:5 toluene/hexanes/ether) afforded 8a (0.303 g, 98%),
a complex mixture of diastereoisomers, as a red solid. 1H NMR
(400 MHz, CDCl3): δ 2.1-2.5 (m, 2 H, CH2 (Cp)), 2.60-2.90
(m, 2 H, CH2 (Cp)), 3.30-3.95 (m, 10 H, Fc-CH2, R and â Fc-
H), 5.1 (bs, 4 H, OCH2Ph), 5.74-6.05 (m, 6 H, CH (Cp), 6.67-
7.04 (m, 10 H, Ar-H), 7.10-7.78 (m, 20 H, Ar-H). Anal. Calcd
for C68H54FeO2: C, 85.2; H, 5.6. Observed: C, 85.2; H, 5.7.
3,3′-Bis(4-d im eth yla m in oben zyl])-1,1′-bis(8-cyclop en -
ta d ien yl-1-n a p h th yl)fer r ocen e (8b). Following the proce-
dure as above, 7b (0.520 g, 0.544 mmol) and copper iodide (10
mg) were added to a solution of cyclopentadienylzinc chloride
(15.0 mmol in THF (20 mL)) at 0 °C. After warming to room
temperature and stirring for 30 min the mixture was worked
up and purified as above to afford 8b (0.392 mg, 86%) as a
(15) Straver, L. H. CAD4-EXPRESS; Enraf-Nonius: Delft, The
Netherlands, 1992.
(16) Fair, C. K. MolEN, An Interactive Structure Solution Procedure;
Enraf-Nonius: Delft, The Netherlands, 1990.
(17) Altomare, A.; Cascarano, G.; Giacovazzo G.; Guagliardi A.;
Burla M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435.
(18) Watkin, D. J .; Prout, C. K.; Carruthers, J . R.; Betteridge, P.
W. CRYSTALS Issue 10; Chemical Crystallography Laboratory: Uni-
versity of Oxford, Oxford, 1996.
1
complex mixture of diastereoisomers, as a red solid. H NMR
(19) Watkin, D. J .; Prout, C. K.; Pearce, L. J . CAMERON; Chemical
Crystallography Laboratory: University of Oxford, Oxford, 1996.
(400 MHz, CDCl3): δ 2.30-2.54 (m, 2 H, CH2 (Cp)), 2.60-2.80

4102 Organometallics, Vol. 18, No. 20, 1999
Hudson et al.
Ta ble 3. F er r ocen e-Nick elocen e Cop olym er s
Ta ble 2. F er r ocen e P olym er s
experi- monomer
reaction
conditions
polymer
(mg)e
experi- monomer
reaction
polymer
(mg)e
ment
(mg)
Mw (DPw)d
Mn
ment
(mg)
conditions Mw (DPw)d
Mn
1
2
3
8a (65)
8a (80)
8b (50)
a
b
c
188 500 (186) 18 800 1d (60)
49 300 (49) 13 500 1d (61)
1
2
3
8a (65)
8b (100)
9a (350)
a
b
c
7900 (8)
1700 1f (30)
43 700 (49) 4100 1g (95)
14 100 (16)
2700 1e (49)
26 300 (19) 8400 1h (56)f
a
8
b
a
9
b
THF, (Me3Si)2NK, FePy4(SCN)2,
55 °C, 10 days. 1,2-
Pyridine, (Me3Si)2NK, Ni(NH3)6Br2, 100 °C, 7 days. Pyri-
dine, (Me3Si)2NNa, NiBr2 1,2-dimethoxyethane, 100 °C, 7 days.
Dimethoxyethane, (Me3Si)2Na, FeCl2, 100 °C, 2 days. c THF/
toluene (1:1), n-C4H9Li, FePy4(SCN)2,8 reflux, 2 days. Weight
c THF, (Me3Si)2NNa, NiPy4(SCN)2,8 25 °C, 3 days. Weight aver-
d
d
average degree of polymerization. e After processing to remove
monomer and metal salts (see Experimental Section).
age degree of polymerization. e After processing to remove mono-
mer and metal salts. See Experimental Section. f Unreacted
starting material (250 mg) was recovered.
(m, 2 H, CH2 (Cp)), 2.88, 2.89, 2.92 (bs 12 H, N(CH3)2) 3.12-
3.96 (m, 12 H, Fc-CH2, R and â Fc-H), 5.76-6.12 (m, 6 H,
heated to 100 °C and stirred for the time given. After 2 or 3
days extra equivalents of base and metal salt were added.
The reaction was deemed complete when there was a
considerable amount of precipitation and the supernatant was
fairly colorless. The mixture was cooled and solvent was
removed under reduced pressure. The solid was washed with
ether (2 × 10 mL) by stirring for 15 min followed by filtration.
The residue was further washed with methanol or ethanol (10
mL) in an analogous manner, and this was followed by rinsing
with ether and drying under vacuum. The solids were ex-
tracted with pyridine in a Soxhlet apparatus until the solution
over the sample was clear. The solutions were evaporated to
dryness, and the extracts were subjected to GPC analysis.
CH, (Cp)), 6.59-7.76 (m, 20 H, Ar-H). Anal. Calcd for C58H52
-
FeN2: C, 83.7; H, 6.3; N, 3.4. Observed: C, 83.5; H, 6.6; N,
3.1.
3,3′-Bis(4-ben zyloxyben zyl)-1,1′-bis(8-[4-ben zyloxyben -
zylcyclop en ta d ien yl]-1-n a p h th yl)fer r ocen e (9a ). Follow-
ing the procedure above, 7a (0.30 g, 0.28 mmol) was added in
THF (1 mL) to a solution of 4-benzyloxybenzylcyclopentadi-
enylzinc chloride prepared from 4a (0.42 g, 1.6 mmol), n-
butyllithium (0.6 mL, 1.5 mmol, 2.5 M solution in hexanes),
and zinc chloride (0.41 g, 3.0 mmol) as before, in THF (10 mL).
Copper iodide (10 mg) was added, and the solution was stirred
at room temperature for 1 h, after which it had become very
dark in color. Workup and purification (silica gel, 50:40:10
toluene/hexanes/ether) afforded 9a (complex mixture of iso-
mers) as a red solid (0.370 g, 99%). IR (KBr): 3031, 2900, 1610,
1510, 1454, 1376, 1298, 1239, 1174, 1025, 824, 771, 735, 696
Resu lts a n d Discu ssion
The general synthetic sequence for the preparation
of monomers 3 and their conversion to polymers 1 is
summarized in Scheme 1. This sequence employs readily
available, inexpensive starting materials, is convergent,
and is relatively short. Moreover, it is readily adapted
to the preparation of wide variety of cyclopentadienyl-
ring-substituted analogues of the parent monomer 3 (R
) R′ ) H), employing a flexible and operationally simple
route. Finally, copolymers can be prepared in which
ferrocene nuclei alternate with other metallocene cen-
ters along the polymer chain.
A significant improvement in the cyclopentadienyl
coupling steps has now been achieved by replacement
of RCpCu‚SMe2 reagents with RCpZnCl salts. Use of
the copper reagent required that the coupling reactions
be carried out for extended periods of time at -23 °C,
since the copper salts decompose rapidly above this
temperature. With the more robust zinc salts, the
reaction can be carried out conveniently at 0 °C with
considerably improved yield and ease of workup. For
example, intermediates 2 (R ) H) and (R ) 2-octyl) were
obtained in 95% and 94% yields, respectively, using
cyclopentadienylzinc salts, compared with 49% and 79%
yields for these products obtained with the earlier
protocol. Moreover, we found that the coupling reactions
employing zinc salts are catalyzed by CuI and, under
these conditions, are complete within an hour or less
at 0 °C. Indeed, the coupling reaction becomes so facile
under these reaction conditions that small amounts of
the Diels-Alder cycloadducts, derived from the double
cyclopentadienylation of diiodonaphthalene, are formed
along with 2.
1
cm-1. H NMR (400 MHz, CDCl3): δ 2.60-2.80 (m, 4 H, CH2
(Cp)), 3.20-4.00 (m, 16 H, CpCH2, Fc-CH2, R and â Fc-H),
4.99 (bs, 8 H, OCH2Ph), 5.50-6.90 (m, 4 H, CH, (Cp)), 6.74-
7.02 (m, 16 H, Ar-H), 7.16-7.44 (m, 28 H, Ar-H), 7.59 (m, 2
H, H2 or H7), 7.70 (m, 2 H, H2 or H7). Anal. Calcd for C96H78
-
FeO4: C, 85.3; H, 5.8. Observed: C, 85.1; H, 5.8.
Gen er a l P r oced u r e for P r ep a r a t ion of F er r ocen e
P olym er s. The monomer (1 equiv) was dissolved in the solvent
of choice (5 mL approximately) under argon, and 1.2 equiv of
base was added at room temperature. The mixture generally
became much darker in color, and after stirring for 30 min
the appropriate metal salt was introduced (1 equiv) either as
a slurry (FePy4(SCN)2) in the solvent used or as a solid (FeCl2)
in one portion. The mixture was heated to the temperature
specified and stirred for the time given (see Tables 1 and 2).
After 2 or 3 days additional equivalents of base and metal salt
were generally added.
The reaction was stopped when it was judged that the
polymerization was complete, as evidenced by the amount of
precipitation and color of the supernatant (usually clear and
fairly colorless). The mixture was cooled and the solvent was
removed under reduced pressure. The solid was washed with
ether (2 × 10 mL) by stirring for 15 min followed by filtration.
The residue was further washed with methanol or ethanol (10
mL), water (10 mL), and HCL (1 N, 10 mL) in an analogous
manner. This was followed by rinsing with ethanol and ether
to dry the sample before storing under vacuum for several
hours. The remaining solid was continuously extracted over-
night in a Soxhlet apparatus with pyridine as the solvent. After
removal of solvent the solid was further washed with cold then
hot toluene, to remove lower mass components, before deter-
mination of molecular weights.
Gen er a l P r oced u r e for P r ep a r a tion of F er r ocen e-
Nick elocen e Cop olym er s. The scale of each polymerization
reaction and the yield of polymer obtained are given in Tables
2 and 3. The monomer (1 equiv) was dissolved in pyridine
(freshly distilled from CaH2) (5 mL) under argon, and sodium
bis(trimethylsilyl)amide (1.2 equiv) was added at room tem-
perature. The mixture generally became much darker, and
after stirring for 30 min the appropriate metal salt was
introduced (1 equiv) as a solid in one portion. The mixture was
Following the first preparation of polymeric, stacked
ferrocenes, and ferrocene copolymers, a principal focus
of our research has been the preparation of more soluble
analogues of the parent polymers. We had earlier
reported4 that a modest improvement in the solubility
of the parent polymer 1a could be achieved by introduc-

New Stacked Metallocene Polymers
Organometallics, Vol. 18, No. 20, 1999 4103
Sch em e 1
ing long chain aliphatic substituents on one or both of
the cyclopentadienyl rings of the precursor monomer 3.
Such a general strategy has been employed in improving
the solubility of poly(p-phenylene), polythiophenes, poly-
(p-arylenevinylene), poly(p-phenyleneethynylene), and
polypyrroles20 Thus, the benzene-soluble fraction of the
parent unsubstituted polymer 1a , obtained as a dark
red solid, had only a modest Mw and Mn of 3000 (DP )
5) and 2300, respectively. By contrast, polymerization
of monomer 3b, in the presence of sodium hexamethyl-
disilazide and ferrous chloride, gave a polymer 1b, from
which a benzene-soluble, dark purple fraction, with
Mw) 18 400 (DP ) 25) and Mn ) 14 400 was obtained.
Nevertheless, much of the product polymer remained
insoluble in common solvents. In an attempt to further
improve polymer solubility, a doubly substituted mono-
mer 3c was prepared and subjected to polymerization.
The product polymer was found to be insoluble in
benzene, but slightly soluble in THF. GPC analysis of
this solution showed a bimodal peak distribution with
a major peak at 4700 and a minor component at
136 000.
polymers. Such bulky substituents have been shown to
improve the solubility of a number of polyimides, with
little reduction in their thermal stability.22 Accordingly,
the fulvenes 4a and 4b, prepared in high yield from the
readily available aldehydes,13 were reduced, following
the method of Hafner14 to give 5a and 5b as a mixture
of 3- and 4-substituted 1-arylcyclopentadienes. These
were, in turn, coupled with 1,8-diiodonaphthalene to
give a 3:4 mixture of the isomeric 1-iodo-8-(3 and
4-arylmethylcyclopentadienyl)naphthalenes 6a and 6b
(Scheme 2).
It is of interest to note in passing that these products
were each accompanied by small amounts of a mixture
of two isomeric Diels-Alder products, derived through
biscyclopentadienylation of the diiodide. These cyclo-
addition products are formed in approximately a 2:1
ratio either directly by biscyclopentadienylation of di-
iodonaphthalene or by cyclopentadienylation of 6a or
6b. An X-ray crystal structure analysis of the major
isomer derived from 6b (Figure 1) shows this material
to have structure 12b.
TOCSY NMR analysis23 of the well-separated vinyl
proton resonances in the bicycloheptene and cyclopen-
tene rings in both the crystalline material 12b and in
These results prompted us to examine the use of cardo
groups21 to improve the solubility of these metallocene
(20) Rehahn, M.; Schuter, A. D.; Lenz, R. W. Eur. Polym. J . 1983,
19, 1043. J en, K. Y.; Oboodi, R.; Elsembaumer, R. L. Polym. Mater.
Sci. Eng. 1985, 53, 79. Osterholm, J .-E.; Laakao, M. J .; Nyholm, P.
Synth. Met. 1989, 28, C435. Askari, S. H.; Rughooputh, S. D.; Wudl,
F. Synth. Met. 1989, 29, E129. Han, C.-C.; Elsembaumer, R. L. Mol.
Cryst. Liq. Cryst. 1990, 189, 183. Giesa, R.; Schulz, R. C. Makromol.
Chem. 1990, 191, 857. Ruhe, J .; Ezquerra, T. A.; Wegner, G. Synth.
Met. 1989, 28, C177.
(22) Yang, C.-P.; Lin, J .-H. J . Polm. Sci., Part A: Polym. Chem.
1993, 31, 2153-2163. Hsiao, S.-H.; Li, C.-T. Macromolecules 1998, 31,
7213-7127.
(23) TOCSY (total correlation spectroscopy). Levitt, M.; Freeman,
R.; Frenkiel, T. J . Magn. Reson. 1982, 47, 328. Bax, A.; Davis, D. J .
Magn. Reson. 1985, 65, 355. Experiments were carried out with an
arrayed mix time from 0 to 0.20 s, with the best results being obtained
with a mix of 0.15 s for examination of protons in the bicycloheptene
ring and a mix of 0.2 s for protons adjacent to cyclopentene vinyl
protons.
(21) Korshak, V. V.; Vinogradova, S. V.; Vygodskii, Y. S. Rev.
Macromol. Chem. 1974, 12, 45-142.

4104 Organometallics, Vol. 18, No. 20, 1999
Hudson et al.
Sch em e 2a
a
Reaction conditions: (i) CpH, pyrrolidine, MeOH, 25 °C, 18 h. (ii) LAH, Et2O, 25 °C, 2 h. (iii) BuLi, THF, 0 °C, 30 min; ZnCl2,
t
0 °C, 30 min; 1,8-diiodonaphthalene, CuI (1 mol %), 0 °C, 30 min. (iv) BuOK, THF, 0 °C, 30 min; FePy4(SCN)2, 25 °C, 2 h. (v)
CpZnCl, THF, CuI (5 mol %), 25 °C, 30 min. (vi) RCpZnCl, THF, CuI (17 mol %), 25 °C, 1 h.
solutions enriched in the minor isomer shows that the
two substances are isomeric with respect to substitution
at C-5 and C-6 in the bicycloheptene ring. The minor
Diels-Alder adduct must therefore have structure 13.
Thus, of the four possible Diels-Alder products, 12-
15, only the two derived from intermediate 10 are
formed. The same results are obtained in the prepara-
tion of 6a from diiodonaphthalene or by independent
cyclopentadienlyation of 6a itself. These relationships
are shown in Scheme 3.
We found that the transformation of 6a and 6b to the
corresponding diastereomeric mixture of ferrocenes 7a
and 7b was best achieved using the FePy4(SCN)2 salt8
as a source of Fe(II).24 Cyclopentadienylation of 7a and
7b yielded the effective monomers 8a and 8b, which
were then subjected to polymerization by treatment
with base and either an Fe(II) or Ni(II) salt. These
transformations are summarized in Scheme 2.
Exploratory polymerizations of monomers 8a , 8b, and
9a were carried out in several solvents and in the
presence of several different bases and salts, to examine
the effect of these variables on the ferrocene polymers
and ferrocene-nickelocene copolymers formed in these
reactions. The results of these experiments are sum-
marized in Tables 1 and 2. In general, yields of crude
polymer obtained in the polymerization reactions were
high. However, since chain growth proceeds by step
condensations, involving complexation of cyclopentadi-
enide by a partially soluble metal salt, polymerizations
were relatively slow. These reactions were therefore
generally carried out over a period of several days, at
(24) This complex salt was found to be superior to FeCl2 in the
reaction, possibly owing to its greater solubility over the latter salt.
Care must be taken in handling this material, as it is readily oxidized
to the purple Fe(III) salt on standing. The oxidized salt can, however,
be easily removed by washing the complex salt several times with THF
before using it.

New Stacked Metallocene Polymers
Organometallics, Vol. 18, No. 20, 1999 4105
F igu r e 1. Molecular structure of compound 12b.
Sch em e 3
elevated temperatures. Thus, copolymerization of mono-
mer 9a , in which metal complexation is retarded by
cyclopentadienyl-ring substitution, was far from com-
plete after 3 days of reaction at room temperature. The
dark brown to black polymeric products are generally
insoluble in toluene, but a significant portion of these
was found to be soluble in pyridine. These pyridine-
soluble fractions were subjected to GPC analysis and
exhibited a significantly higher molecular weight dis-
tribution and polydispersity than had been observed for
the corresponding alkyl-chain-substituted polymers.4
For example, high molecular weight ferrocene polymers
1b (R ) 2-octyl, R′ ) H) typically had Mw and Mn values
of 18 000 (DPw ) 21) and 14 000, respectively, after
fractionation, while those derived from the polymeri-
zation of 8a were obtained as pyridine-soluble fractions
with considerably larger molecular weights and poly-
dispersity (Table 2 ). In contrast to alkyl-substituted
polymers, which gave amorphous solids on removal of
solvent, evaporation of solvent from pyridine solutions
of these higher molecular materials left a pale amber
film of the polymer. The limited number of experiments

4106 Organometallics, Vol. 18, No. 20, 1999
Hudson et al.
involving polymerization of the 4-dimethylaminobenzyl-
substituted monomer 8b suggests that this substituent
is not as effective as the 4-benzyloxybenzyl group in
solubilizing ferrocene-derived polymers (Table 2). How-
ever this substituent appears to be more effective in
solubilizing ferrocene-nickelocene copolymers. Thus the
2-octyl-substituted copolymer 1b, reported earlier (M )
Fe, M′ ) Ni),4 exhibited Mw and Mn of 5700 (DPw )7)
and 1500 in THF or toluene solutions and was poorly
soluble in pyridine. By contrast, iron-nickel copolymers
derived from monomer 8b showed a moderate solubility
in pyridine and had a significantly higher distribution
of molecular weights (Table 3 ).
compared to their alkyl-chain-substituted analogues.
Other members of this class of cyclic substituent may
prove to be more effective.
Ack n ow led gm en t. This research was supported by
grants from the Petroleum Research Fund (30907-AC1)
and by the E. I. du Pont Company, which are gratefully
acknowledged. B.M.F. wishes to thank the National
Science Foundation (Grant CHE-9305789) and Polaroid
Corporation for grants in support of X-ray equipment.
Su p p or tin g In for m a tion Ava ila ble: CIF file containing
data for the structure of 12b. This material is available free
of charge via the Internet at http://pubs.acs.org.
In conclusion, we have shown that cardo-substituted
monomers 8a ,b give polymeric metallocenes which show
increased solubility, especially in pyridine solutions,
OM9902939