Poly{ferrocene(phenylene)bis(silylenevinylene)}s via platinum- and rhodium-catalyzed hydrosilylation of diethynylbenzenes with 1,1′- bis(dimethylsilyl)ferrocene

Article abstract of DOI:10.1021/om049166p

Ferrocene-containing polymers with one and two ferrocenes per repeat unit have been prepared via hydrosilylation polymerization of dialkynes and ferrocene-containing bis-enynes with 1,1′-bis(dimethylsilyl)ferrocene (1) using Karstedt's catalyst (platinum-divinyltetra-methyldisiloxane) and Rh(PPh₃)₃I. Addition of equivalent amounts of 1 and various dialkynes {RC≡C-X-C≡CR (R = H, SiMe₃, X = C ₆H₄ (1,4- and 1,3-); R = H, X = SiMe₂; R = Ph, X = nothing)} gave polymers 2a-f with varying regiochemical distributions. All polymers were characterized using ¹H, ¹³C, and ²⁹Si NMR spectroscopy, MALDI-TOF mass spectrometry, and elemental analyses. Novel ferrocene-containing bis-enynes (4a,b) were prepared by hydrosilylation addition of 1 to 2 equiv of 1,4-bis(trimethylsilyl)butadiyne and 1,4-bis-(trimethylsilylethynyl)benzene, respectively. Desilylation of 4a,b gave ferrocene-containing bis(enyne)s (5a,b) that were used as monomers for the synthesis of polymers with two ferrocenes per repeat unit (6a,b). The X-ray crystal structure of the bis(enyne) 4a has also been described, and the redox behavior of polymers 2a-e (Pt), 2a (Rh), and 2c (Rh) were studied using cyclic voltammetry. In all cases a single reversible redox wave was observed, attributed to the Fe(II)-Fe(III) redox couple of the ferrocene center.

Full text of DOI:10.1021/om049166p

1458
Organometallics 2005, 24, 1458-1467
Poly{ferrocene(phenylene)bis(silylenevinylene)}s via
Platinum- and Rhodium-Catalyzed Hydrosilylation of
Diethynylbenzenes with 1,1′-Bis(dimethylsilyl)ferrocene
Rajsapan Jain, Roger A. Lalancette, and John B. Sheridan*
Department of Chemistry, Rutgers, The State University of New Jersey,
University Heights, Newark, New Jersey 07102
Received October 26, 2004
Ferrocene-containing polymers with one and two ferrocenes per repeat unit have been
prepared via hydrosilylation polymerization of dialkynes and ferrocene-containing bis-enynes
with 1,1′-bis(dimethylsilyl)ferrocene (1) using Karstedt’s catalyst (platinum-divinyltetra-
methyldisiloxane) and Rh(PPh3)3I. Addition of equivalent amounts of 1 and various dialkynes
{RCtC-X-CtCR (R ) H, SiMe3, X ) C6H4 (1,4- and 1,3-); R ) H, X ) SiMe2; R ) Ph, X
) nothing)} gave polymers 2a-f with varying regiochemical distributions. All polymers were
1
characterized using H, 13C, and 29Si NMR spectroscopy, MALDI-TOF mass spectrometry,
and elemental analyses. Novel ferrocene-containing bis-enynes (4a,b) were prepared by
hydrosilylation addition of 1 to 2 equiv of 1,4-bis(trimethylsilyl)butadiyne and 1,4-bis-
(trimethylsilylethynyl)benzene, respectively. Desilylation of 4a,b gave ferrocene-containing
bis(enyne)s (5a,b) that were used as monomers for the synthesis of polymers with two
ferrocenes per repeat unit (6a,b). The X-ray crystal structure of the bis(enyne) 4a has also
been described, and the redox behavior of polymers 2a-e (Pt), 2a (Rh), and 2c (Rh) were
studied using cyclic voltammetry. In all cases a single reversible redox wave was observed,
attributed to the Fe(II)-Fe(III) redox couple of the ferrocene center.
Introduction
Manytypesofpolymercontainsiliconinthebackbone,1a,6,7
and hydrosilylation is one of many useful synthetic
approaches to such species.6 For example, electrolumi-
nescent silicon-containing poly(phenylenevinylene)s (Si-
PPV)s have been prepared via Wittig and Heck reac-
tions as well as via hydrosilylation.7 Recently, Mori and
co-workers showed Rh(PPh3)3I to be a highly effective
catalyst in hydrosilylation polyadditions to form (E) or
(Z) type phenylenevinylene organosilicon polymers with
good regiocontrol.8
In recent years there has been an enormous interest
in the design and synthesis of metal-containing poly-
mers linked via π-conjugated organic/inorganic bridges.1
Many transition metals such as Cr, Mo, W, Mn, Fe, Ru,
Co, Rh, Ni, Pd, Pt, and Au have been successfully
incorporated into the backbone of polymers,1d with
metallocenes and, in particular, ferrocene-containing
polymers,1c,2,3 as well as rigid-rod organometallic frame-
works, being common.1c,2 Most noteworthy are the well-
defined high molecular weight poly(ferrocenylsilane)s
prepared via the ring-opening polymerization (ROP) of
silicon-bridged [1]ferrocenophanes,4 in which electro-
chemical studies showed two reversible oxidation waves
indicative of electronic interactions between adjacent Fe
centers.1c,2a,b,4,5
(5) (a) Zechel, D. L.; Foucher, D. A.; Pudelski, J. K.; Yap, G. P. A.;
Rheingold, A. L.; Manners, I. J. Chem. Soc., Daltons Trans. 1995, 1893.
(b) Manners, I. J. Inorg. Organomet. Polym. 1993, 3, 185. (c) Barlow,
S.; O’Hare, D. Chem. Rev. 1997, 97, 637.
(6) See for example: (a) Pang Y.; Ijadi-Maghsoodi, S.; Barton, T. J.
Macromolecules 1993, 26, 5671. (b) Chen, R.-M.; Chien, K.-M.; Wong,
K.-T.; Jin, B.-Y.; Luh, T.-Y.; Hsu, J.-H.; Fann, W. J. Am. Chem. Soc.
1997, 119, 11321. (c) Yamashita, H.; Uchimaru, Y. J. Chem. Soc.,
Chem. Commun. 1999, 1763. (d) Tsumura, M.; Iwahara, T.; Hirose, T.
Polym. J. 1995, 27, 1048. (e) Silicon-Based Polymer Science; Zeigler,
J. M., Fearon, F. W. G., Eds.; Advances in Chemistry Series 224;
American Chemical Society, Washington, D.C., 1990. (f) Organosilicon
Chemistry-From Molecules to Materials; Auner, N., Weis, J., Eds.;
VCH: Germany, 1994. (g) Organosilicon Chemistry II-From Molecules
to Materials, edited by Auner, N.; Weis J. VCH: Germany, 1996. (h)
Organosilicon Chemistry III-From Molecules to Materials; Auner, N.,
Weis, J., Eds.; Wiley-VCH: Germany, 1998. (i) Hengge, E. In Orga-
nosilicon Chemistry-From Molecules to Materials; Auner, N., Weis,
J., Eds.; VCH: Germany, 1994; pp 275-283. (j) Miller, R. D.; Michl,
J. Chem. Rev. 1989, 89, 1359. (k) Birot, M.; Pillot, J.-P.; Dunogue`s.
Chem. Rev. 1995, 95, 1443.
(7) (a) Kim, H. Y.; Ryu, M.-K.; Lee, S.-M. Macromolecules 1997, 30,
1236. (b) Jung, S.-H.; Kim, H. K.; Kim, S.-H.; Kim, Y. H.; Jeoung, S.
C.; Kim, D. Macromolecules 2000, 33, 9277. (c) Kim, H. K.; Ryu, M.-
K.; Kim, K.-D.; Lee, S.-M.; Cho, S.-W.; Park, J.-W. Macromolecules
1998, 31, 1114. (d) Son, D. Y.; Bucca, D.; Keller, T. M. Tetrahedron
Lett. 1996, 37, 1579. (e) Kim, D. S.; Shim, S. C. J. Polym. Sci., Part A
1999, 37, 2933. (f) Kim, D. S.; Shim, S. C. J. Polym. Sci., Part A 1999,
37, 2263.
* To whom correspondence should be addressed. E-mail: jsheridn@
newark.rutgers.edu.
(1) See for example: (a) Inorganic and Organometallic Polymers II-
Advanced Materials and Intermediates; Wisian-Neilson, P., Allcock,
H. R., Wynne, K. J., Eds.; ACS Symp. Ser. 572; Washington, DC, 1994.
(b) Manners I. Angew. Chem., Int. Ed. Engl. 1996, 35, 1602, and
references therein. (c) Nguyen, P.; Go´mez-Elipe, P.; Manners, I. Chem.
Rev. 1999, 99, 1515, and references therein. (d) Sheats, J. E.; Carraher,
C. E.; Pittman, C. U. Metal Containing Polymer Systems; Plenum: New
York, 1985.
(2) (a) Manners I. Adv. Organomet. Chem. 1995, 37, 131, and
references therein. (b) Manners I. Angew. Chem., Int. Ed. Engl. 1996,
35, 1602, and references therein. (c) Kingsborough, R. P.; Swager T.
M. In Progress in Inorganic Chemistry; Karlin K. D., Ed.; 1999; Vol.
48, pp 123-233, and references therein.
(3) Gonsalves, K. E.; Chen, X. In Ferrocenes; Togni, A., Hayashi,
T., Eds.; VCH: Germany, 1995; Chapter 10, pp 497-527, and refer-
ences therein.
(4) Foucher, D. A.; Tang, B.-Z.; Manners, I. J. Am. Chem. Soc. 1992,
114, 6246.
10.1021/om049166p CCC: $30.25 © 2005 American Chemical Society
Publication on Web 02/19/2005

Poly{ferrocene(phenylene)bis(silylenevinylene)}s
Organometallics, Vol. 24, No. 7, 2005 1459
Scheme 1
Hydrosilylation has also been used for the formation
of oligosilicon species that serve as templates for orga-
nometallic polymers bearing transition metals such as
Cr, Mo, and Co,9 ferrocene-containing dendrimers,10 and
three-dimensional organometallic polymers such as
poly(ferrocenyloctasilsesquioxane)s.11 The grafting of
vinylferrocene to a methylhydrosiloxane-dimethylsi-
loxane copolymer12 and the modification of Si-H side
groups of poly(ferrocenylsilane)s to form thermotropic
liquid crystalline polymers are other examples.13 Fi-
nally, hydrosilylation of diphenyl- and diethyldiethyn-
ylsilane with 1,1′-bis(methylphenylsilyl)ferrocene was
reported to give poorly defined oligomeric species.14
We now report the incorporation of silyl, phenylene-
vinylene, and ferrocene groups into a polymer backbone
via hydrosilylation polymerization using a Pt catalyst
(Karstedt’s catalyst) and RhI(PPh3)3. The products are
poly{ferrocene(phenylene)bis(silylenevinylene)}s and are
compared to model compounds, reported in the subse-
quent article.15
Results and Discussion
Platinum-Catalyzed Polymerizations. Treatment
of equimolar amounts of 1 and various dialkynes
resulted in polymers 2a-f (Pt) as orange powders or
gums (Scheme 1).
Poly{ferrocene(phenylene)bis(silylenevin-
ylene)}s 2a,c (Pt). Poly{ferrocene(1,4-phenylene)bis-
(silylenevinylene)} (2a (Pt)) was isolated as an orange
powder in 87% yield and was soluble in common organic
solvents such as CH2Cl2, THF, benzene, and n-hexane.
It was characterized by 1H (Figure 1), 13C, and 29Si NMR
spectroscopy (Table 1), MALDI-TOF mass spectrometry
(Table 2), and elemental analysis and contained two
randomly arranged R- and â-(E) vinylene groups as
previously reported for other Pt-catalyzed hydro-
silylations.6a,7e,f,11,16 The overall R-/â-(E) ratio was de-
termined as 0.56(1 - x)/0.44(x) (1H NMR) and is in close
agreement with model compound 3a (Pt) (Figure 2) (R-/
â-(E) ratio ) 0.52/0.48).15 Distinct olefinic peaks at δ
5.63, 5.88-5.90 for the R-geminal protons and δ 6.63-
6.71 and 7.01-7.07 for the two â-(E) vicinal protons
concurred with assignments in model compounds 3a
(Pt) and 3d (Pt).15 Other spectral data were also in
excellent agreement with these model compounds. Small
aliphatic proton peaks at δ 1.29 and 2.13 arising from
the hydrosilylation of the divinyltetramethyldisiloxane
ligand of the catalyst were also observed. Lewis has
documented that during an induction period the catalyst
reacts with the silane in the presence of O2 to form the
hydrosilylated ligand and yellow colloidal Pt particles.17
(8) (a) Mori, A.; Takahisa, E.; Kajiro, H.; Nishihara, Y.; Hiyama, T.
Macromolecules 2000, 33, 1115. (b) Mori, A.; Takahisa, E.; Kajiro, H.;
Nishihara, Y.; Hiyama, T. Polyhedron 2000, 19, 567. (c) Mori, A.;
Takahisa, E.; Yamamura, Y.; Kato, T.; Mudalige, A. P.; Kajiro, H.;
Hirabayashi, K.; Nishihara, Y.; Hiyama, T. Organometallics 2004, 23,
1755.
(9) (a) Kuhnen, T.; Ruffolo, R.; Stradiotto, M.; Ulbrich, D.; McGlinchey,
M. J.; Brook, M. A. Organometallics 1997, 16, 5042. (b) Kuhnen, T.;
Stradiotto, M.; Ruffolo, R.; Ulbrich, D.; McGlinchey, M. J.; Brook, M.
A. Organometallics 1997, 16, 5048.
(10) (a) Cuadrado, I.; Carmen, M. C.; Alonso, B.; Mora`n, M.; Losada,
J.; Belsky, V. J. Am. Chem. Soc. 1997, 119, 7613. (b) Garc´ıa, B.; Casado,
C. M.; Cuadrado, I.; Alonso, B.; Mora´n, M.; Losada, J. Organometallics
1999, 18, 2349.
1
The H NMR spectrum of 2a (Pt) showed both Si-
(Me)2X and CtCH end group peaks at δ 0.21 and 2.76,
(11) Mora´n, M.; Casado, C. M.; Cuadrado, I. Organometallics 1993,
12, 4327.
(12) Inagaki, T.; Lee, H. S.; Skotheim, T. A.; Okamoto, Y. J. Chem.
Soc., Chem. Commun. 1989, 1181.
(16) (a) Hiyami, T.; Kusumoto, T. In Comprehensive Organic Syn-
thesis; Trost B. M., Flemings, I., Eds.; Pergamon: Oxford, England,
1991; Vol. 8, pp 763-792, and references therein. (b) Chauhan, M.;
Hauck, B. J.; Keller, L. P.; Boudjouk, P. J. Organomet. Chem. 2002,
645, 1.
(17) (a) Lewis, L. N. J. Am. Chem. Soc. 1990, 112, 5998. (b) Stein,
J.; Lewis, L. N.; Gao, Y.; Scott, R. A. J. Am. Chem. Soc. 1999, 121,
3693.
(13) (a) Liu, X.-H.; Bruce, D.; Manners, I. J. Organomet. Chem. 1997,
548, 49. (b) Liu, X.-H.; Bruce, D.; Manners, I. J. Chem. Soc., Chem.
Commun. 1997, 289.
(14) Asatiani, L. P.; El-Agamey, A. A.; Diab, M. A. J. Polym. Sci.,
Part A 1983, 21, 2529.
(15) Jain, R.; Choi, H.-J.; Sheridan, J. B.; Lalancette, R. A., following
article in this issue.

1460 Organometallics, Vol. 24, No. 7, 2005
Jain et al.
Figure 1. 1H NMR spectrum of polymer 2a (Pt).
recorded {Mn ) 11 700 (PDI ) 2.4)}. Prolonged reflux
of the reaction did not increase the molecular weight
despite the fact that the alkynyl end group could still
1
be detected in the H NMR spectrum, possibly due to
decomposition of the silane end groups or their reaction
with the catalyst ligand. Several reports describe hy-
drosilylation polymerizations that give cyclic struc-
tures;6d,18 however the presence of end group signals
appears to rule out such species in this case.
Similarly, polymer 2c (Pt) derived from 1,3-diethyn-
ylbenzene and 1 was isolated as an orange sticky solid
in 68% yield (Scheme 1). The sticky nature of related
polymers with 1,3-substituted aryl groups has been
reported previously as opposed to the powdery nature
of the 1,4-polymers.18c,19,20 Polymer 2c (Pt) was fully
characterized (Table 1) and has an R-/â-(E) ratio of 0.53/
0.47, consistent with that of 3a (Pt) and 3f (Pt).15 End
Figure 2. Model compounds for poly{ferrocene(phenylene)-
bis(silylenevinylene)}s.
1
group peaks in the H NMR spectrum at δ 2.76 and δ
0.24 confirmed a linear AB type structure, and MALDI-
TOF MS data showed the formula weight of the repeat
unit to be 428, an (AB)n structure, and a degree of
polymerization of 12 (M ) 5139.69) (Table 2).
respectively, confirming a linear AB type polymeric
structure. The nature of X was not determined since no
residual silane protons could be seen in the spectrum.
The MALDI-TOF mass spectrum also confirmed an AB
type polymer with a repeat unit of 428 mass units (the
sum of the formula masses of the two monomers is 428).
The heaviest species detected by this method had n )
17 (M ) 7295.3) (Table 2), whereas GPC gave Mn as
9630, PDI ) 3.2. Light scattering values were also
(18) (a) Li, Y.; Kawakami, Y. Macromolecules 1998, 31, 5592. (b)
Kim, C.; Choi, S. K.; Park, E.; Jung, I. J. Kor. Chem. Soc. 1997, 41,
88. (c) Tsumura, M.; Iwahara, T.; Hirose, T. J. Polym. Sci., Part A 1996,
34, 3155.
(19) Zhang, R.; Mark, J. E.; Pinhas, A. R. Macromolecules 2000, 33,
3508.
(20) Yoon, K.; Son, D. Y. Macromolecules 1999, 32, 5210.

Poly{ferrocene(phenylene)bis(silylenevinylene)}s
Organometallics, Vol. 24, No. 7, 2005 1461

1462 Organometallics, Vol. 24, No. 7, 2005
Jain et al.
Poly[ferrocene(phenylene)bis{silylene(trimeth-
ylsilyl)vinylene}s, 2b,d (Pt). Oligomers 2b (Pt) and
2d (Pt) were respectively prepared from 1,4-bis(tri-
methylsilylethynyl)benzene and 1,3-bis(trimethylsilyl-
ethynyl)benzene and 1 in 75% and 70% yields (Scheme
1). In these reactions, attack of the silane on the internal
carbon of the alkyne (syn addition) (due to the bulky
TMS group) led to mostly R-geometry (1 - x > 0.96) in
the oligomers, in close agreement with model com-
pounds 3b (Pt), 3e (Pt), and 3g (Pt).15
Using end group analysis the average number of
repeat units was determined to be quite low (n ) 4),
but Kim and co-workers have recorded similar trends
in the hydrosilylation of bulky dialkynes such as 4,4′-
diethynylbiphenyl with Ph2SiH2, where only four repeat
units were present in the oligomer.7e The 1H NMR
spectrum of 2b shows olefinic peaks at δ 6.55, 6.58-
6.64 {cf. 3b (Pt), 3e (Pt)}15 assigned to major R-isomers,
and a peak corresponding to the end group, CtCSiMe3,
was clearly detected in the 29Si DEPT NMR spectrum
at δ -18.0.
Polymer 2d (Pt) was similarly characterized and
showed end group SiMe3 protons {attached to alkene
(δ 0.22)} {attached to alkyne (δ -0.13 to -0.12)} as well
as a signal for the end group SiMe2H protons at δ 0.30.
In this case, end group silyl proton SiMe2H was seen
as a very small peak at δ 4.5. GPC analysis gave a Mn
value of 1710 (PDI ) 1.73), and the MALDI-TOF MS
data were similar to that of 2b (Pt) with (AB)n (n )
2-4) and (AB)n - A (n ) 2-8) patterns (A ) dialkyne)
(Table 2).
Polymers from Nonaryl Alkynes. Poly{ferrocene-
tris(dimethylsilylene)bis(vinylene)}, 2e (Pt), was pre-
pared from diethynyl(dimethyl)silane and 1 as a sticky
orange solid in 85% yield (Scheme 1) and had a regio-
chemical distribution that was exclusively â(E-); that
is, Si adds only to terminal alkynyl carbons.9a End group
analysis of the alkynyl protons gave an average value
for n of 11 (Mn ≈ 4500), whereas GPC gave Mn ) 3520
(PDI ) 3.84) and MALDI-TOF MS (Figure 3) showed a
maximum value of n ) 12 and an (AB)n type structure
with both alkynyl and silane end groups (Table 2).
Hydrosilylation polymerization of 1,4-diphenylbuta-
diyne with 1 gave 2f (Pt) as an orange powder in 52%
yield (Scheme 1). Whereas the model compound 3i
results from exclusive attack of the silane at the phenyl-
substituted carbons of the diyne, in the case of the
polymer another isomeric form resulting from syn
addition was also observed (Table 1). MALDI-TOF MS
confirmed an exclusive (AB)n-A type structure (A )
dialkyne) with the highest molecular weight species
having n ) 10 (M ) 5249.03) (Table 2); in contrast GPC
analysis gave Mn ) 1860 (PDI ) 1.74).
Hydrosilylation Polymerizations Using Iodotris-
(triphenylphosphine)rhodium(I). Treatment of
equimolar amounts of 1 and 1,4-diethynylbenzene in
THF at room temperature with Rh(I) as the catalyst
afforded 2a (Rh) as an orange powder in 62% yield
(Scheme 1). The polymerization was extremely slow (13
days), and at the end of the reaction the thick THF
slurry of crude 2a (Rh) was precipitated into methanol.
Three different regioisomers were present in 2a (Rh)
{â-(Z), â-(E), and R-} in a 0.93(1 - x):0.07(x):trace ratio.
The hydrosilylation of 1,4-diethynylbenzene with 1,4-,

Poly{ferrocene(phenylene)bis(silylenevinylene)}s
Organometallics, Vol. 24, No. 7, 2005 1463
Figure 3. MALDI-TOF MS of polymer 2e (Pt).
Table 2. MALDI-TOF MS Data of Polymers {[(AB)n-H]+} and/or {[(AB)n-A-H]+} Where A Is the Dialkyne and
B Is 1
polymer (repeat unit Da)
MS (Da) data
2a (Pt) (428.5)
858.0, 1287.2, 1715.0, 2145.5, 2575.2, 3004.3, 3434.2, 3863.5, 4292.4, 4723.1,
5152.1, ..., 7296.3 ((AB)17-H)+
2c (Pt) (428.5)
2b (Pt) (572.9)
2d (Pt) (572.9)
2e (Pt) (410.6)
2f (Pt) (504.6)
858.0, 1286.5, 1715.0, 2143.3, 2571.8, 3000.0, 3428.0, 3856.7, 4284.6, 4713.1,
5140.7 ((AB)12-H)+
844.5, 1146.7, 1417.2, 1719.6, 1990.0, 2292.4, 2562.6, 2865.3, 3135.5, 3363.5
((AB)6-H)+
844.2, 1146.7, 1417.3, 1719.8, 1990.4, 2292.4, 2563.0, 3136.11, 3709.8, 4282.8,
4855.9 ((AB)8-A-H)+
822.2, 1232.5, 1643.3, 2054.2, 2465.3, 2876.4, 3287.8, 3699.4, 4110.9, 4523.0,
4931.3, 5343.6 ((AB)13-H)+
708.4, 1213.0, 1717.6, 2222.0, 2726.7, 3231.3, 3736.1, 4240.6, 4745.5, 5250.0
((AB)10-A-H)+
6a (849.2)
6b (1001.4)
2a (Rh) (428.5)
850.2, 1699.2, 2548.6, 3398.6, 4248.9, 5099.4, 5950.6, 6801.4, 7652.3 ((AB)9-H)+
1002.9, 2004.3, 3007.4, 4007.6, 5009.5, 6011.8 ((AB)6-H)+
857.2, 1285.4, 1713.4, 2141.5, 2569.6, 3000.6, 3429.1, 3858.3, 4287.1, 4715.2,
5143.9 ((AB)12-H)+
2c (Rh) (428.5)
857.8, 1286.6, 1715.0, 2143.9, 2572.3, 3429.1, 5142.1, ..., 7284.4 ((AB)17-H)+
1,3-bis(dimethylsilyl)benzene using Rh(PPh3)3I also re-
sults in a similar â-(Z):â-(E) distribution of 0.96:0.04 and
0.91:0.09, respectively.8a
MALDI-TOF MS confirmed an (AB)n type structure with
the largest detectable n ) 12 (M ) 5142.9 Da, Table 2).
Polymer 2c (Rh) was obtained similarly as a sticky
orange solid, in 76% yield from 1 with 1,3-diethynyl-
benzene (Scheme 1), and has a similar isomeric ratio to
2a (Rh). The NMR data for 2c (Rh) showed â-(Z)-
olefinic protons that matched those of model compound
3f (Rh)15 and â-(E)-olefin signals like those of polymer
2c (Pt). MALDI-TOF MS gave the highest detectable
value for n in a (AB)n type structure of 17 (7283.4 Da,
Table 2) (GPC; n ) 5, Mn ) 3650; PDI ) 2.69).
Unfortunately, reaction of 1 with 1,4-bis(trimethyl-
silylethynyl)benzene using [Rh(PPh3)3I] gave 2b in 49%
yield (Mn ) 2450; PDI ) 1.89, GPC) that was indistin-
guishable from 2b (Pt). Thus, under reflux conditions
the Rh catalyst does not display any different specificity.8a
1
The H NMR spectrum of 2a (Rh) shows the â-(Z)
olefinic protons as two broad doublets at δ 6.12, 7.42
with methyl protons of this isomer as a broad singlet
at δ 0.39 {cf. 3a (Rh), 3d (Rh)}.15 Two types of end
group protons at δ 4.69 (Si-H) and 3.32 (CtCH) are
indicative of a noncyclic (AB)n type polymer. Other
assignments for 2a (Rh) were in good agreement with
model compounds 3a (Rh), 3d (Rh), and polymer 2a
(Pt). For example, the 29Si DEPT NMR clearly shows
the â-(Z) Si at δ -13.2, â-(E) at δ -9.2, and R- at δ -7.3
ppm with the end group Si-H at δ -18.2. End group
analysis gave the average value of n as 16, GPC data
had Mn ) 4660 with an unusually high PDI of 14.8, and

1464 Organometallics, Vol. 24, No. 7, 2005
Jain et al.
Scheme 2
Table 3. Cyclic Voltammetric Dataa
NMR spectroscopy, elemental analysis, and X-ray crys-
tallography from crystals grown from n-hexane at -78
°C (Figure 4).
polymer
Epa (V)
Epc (V)
E° (V)
2a (Pt)
2b (Pt)
2c (Pt)
2d (Pt)
2e (Pt)
2a (Rh)
2c (Rh)
ferrocene
0.20
0.25
0.20
0.31
0.23
0.20
0.23
0.21
0.13
0.15
0.13
0.13
0.12
0.13
0.15
0.06
0.17
0.20
0.17
0.22
0.18
0.17
0.19
0.14
a Measured in a THF solution containing ca. 1 mM of the
monomer unit and 0.1 M of [(n-Bu)4N]PF6. Sweep rate ) 50 mV
s-1
.
Syntheses of Ferrocene-Containing Bis(enyne)s
and Polymers with Two Ferrocenes per Repeat
Unit. Attempted hydrosilylation polymerization of 1,4-
bis(trimethylsilyl)butadiyne with 1 failed to proceed
beyond the formation of the single adduct HSi(Me)2Fc-
Si(Me)2(C(TMS)dCH-CtC-TMS) {Fc ) (η-C5H4)Fe-
(η-C5H4)}. This single hydrosilylated product was char-
Figure 4. Molecular structure of 4a, showing the atom-
numbering scheme and using 30% probability thermal
ellipsoids. Bond lengths (Å): C6-C7 1.356(9), C6-C8
1.451(9), C8-C9 1.202(9), Si1-C10 1.852(7), Si1-C6
1.881(7), Si3-C7 1.880(7), C9-Si2 1.826(8). Bond angles
(deg): C6-C8-C9 171.6(7), Si2-C9-C8 177.9(7), C7-C6-
C8 121.5(6), C7-C6-Si1 126.0(5), C8-C6-Si1 112.4(5).
1
acterized only by GC-MS ([M]+ ) 496) and H NMR
spectroscopy and has a characteristic septet centered
at δ 4.66 for Si(Me)2H. A similar sluggish reaction was
observed in the synthesis of polymer 2f (Pt), although
prolonged reaction time did eventually lead to polym-
erization in that case.
The addition of one further equivalent of diyne to the
single adduct HSi(Me)2-Fc-Si(Me)2(C(TMS)dCH-Ct
C-TMS) did however give further hydrosilylated prod-
uct 4a as an orange solid in 45% yield (Scheme 2). The
attack of the silane was syn at the internal carbon
bearing no trimethylsilyl group (i.e., bis-R product), as
previously documented in the Pt- and Rh-catalyzed
hydrosilylation of 1,4-bis(trimethylsilyl)butadiyne with
HSiCl2Me and HSiR3 (R ) Me, Et, Ph).21 Product 4a
was fully characterized by GC-MS, 1H, 13C, and 29Si
Complex 4a is a good candidate for further hydrosi-
lylation polymerization if the trimethylsilyl groups are
removed. Thus, desilylation of 4a with KOH/water in
methanol gave 5a as an orange solid in 87% yield
(Scheme 2). Noteworthy features are a [M]+ of 546 in
the GC-MS, the alkynyl protons at δ 3.18 in the 1H NMR
spectrum, and the alkynyl carbons (δ 86.1, 87.6) in the
13C NMR spectrum (Table 1). The trimethylsilyl group
attached to the double bond was not removed and is
seen as a signal in the 29Si NMR spectrum at δ -8.5.
With complex 5a in hand, an oligomer with two
ferrocenes per repeat unit can be accessed from equi-
molar amounts of 1 and 5a. The product, 6a, was
isolated as an orange sticky solid in 86% yield (Scheme
(21) (a) Bock, H.; Seidl, H. J. Am. Chem. Soc. 1968, 90, 5694. (b)
Marciniec, B., Eds. Comprehensive Handbook on Hydrosilylation;
Pergamon: Oxford, 1992, and references therein. (c) Kusumoto, T.;
Hiyama, T. Chem Lett. 1985, 1405.

Poly{ferrocene(phenylene)bis(silylenevinylene)}s
Organometallics, Vol. 24, No. 7, 2005 1465
Scheme 3
3). The regiochemistry was exclusively â-(E) due to the
bulky alkenyl substituent on the internal carbon of 5a.
Hydrosilylation of the double bonds was not observed,
consistent with the fact that enynes show greater
susceptibility of the triple bond toward hydrosilyla-
tion.6f,9a,22 Full characterization of 6a was completed
(Epc), and average potential (E°) are listed in Table 3.
The presence of a single wave suggests no interaction
between the metal centers and may be due to ineffective
redox-matching between the spacer groups and the
ferrocene units, as suggested by Swager and co-work-
ers.23 Moreover, the organosilicon spacer may be too
long, permitting only very weak and unresolvable
electronic interactions between iron centers.24
1
using H, 13C, and 29Si NMR spectroscopy, as well as
MALDI-TOF MS (Tables 1 and 2).
Having established a method to incorporate two
ferrocene units in the backbone per repeat unit, this
method was applied to another system. First, 2 equiv
of 1,4-bis(trimethylsilylethynyl)benzene was reacted
with 1 to give 4b as an orange solid in 41% yield
(Scheme 2). Two inseparable isomers, bis-R (4b, major)
and R-,â-(E) (4b, minor) in a 0.83/0.17 ratio, were
Conclusions
Hydrosilylation polymerization of 1,1′-bis(dimethyl-
silyl)ferrocene (1) and dialkynes leads to characterizable
low molecular weight polymers and oligomers in which
ferrocene and silylenevinylenephenylene groups form
the backbone. The new polymers were fully character-
ized and compared to model complexes. Electrochemical
studies indicate little electronic interaction between
adjacent metal centers in the polymer backbone.
1
formed. Mixture 4b was fully characterized using H,
13C, and 29Si NMR spectroscopy (Table 1). Removal of
the terminal trimethylsilyl groups from 4b gave 5b in
96% yield (Scheme 2), again as two isomeric forms in
the same 0.8/0.2 ratio.
The aryl-based ferrocenyl bis(enyne) (5b) was then
reacted with 1 and Karstedt’s catalyst in THF for 3 days
to afford oligomer 6b. In contrast to the exclusive
formation of the â-(E) regiochemistry in oligomer 6a, a
ratio of 0.48(1 - x) {â-(E)} and 0.52(x) (R-) was obtained,
very similar to that of polymers 2a (Pt) and 2c (Pt) as
well as model compound 3a (Pt).15
Experimental Section
Materials. Karstedt’s catalyst (platinum-divinyltetrameth-
yldisiloxane complex; 3-3.5% Pt concentration in vinyl-
terminated poly(dimethylsiloxane)) was purchased from Gelest,
Inc. (Tullytown, PA). All alkynes used were purchased from
GFS Chemicals, Inc. (Columbus, OH) and were used as
received. 1,1′-Bis(dimethylsilyl)ferrocene (1),25 1,4-diethynyl-
benzene,26 Rh(PPh3)3I,27 and diethynyl(dimethyl)silane28 were
prepared using previously described literature methods.
Equipment. The preparation, purification, and reactions
of all complexes described were performed under an inert
atmosphere of dry nitrogen using standard Schlenk techniques
Electrochemical Studies
Cyclic voltammetry was used to investigate electronic
interactions between iron centers in the poly{ferrocene-
(phenylene)bis(silylenevinylene)}s {2a-e (Pt), 2a,c
(Rh)}, and the results were compared to the model
compounds 1,1′-bis{dimethyl(phenylvinylene)silyl}ferro-
cenes (3a-c) and bis{ferrocenylsilylenevinylene}phen-
ylenes (3d-i). For all polymer samples, a single revers-
ible redox wave was observed (Fe(II)-Fe(III) redox
couple) and the anodic potential (Epa), cathodic potential
(23) Zhu, S. S.; Carroll, P. J.; Swager, T. M. J. Am. Chem. Soc. 1996,
118, 8713.
(24) Long, N. J.; Martin, A. J.; Vilar, R.; White, A. J. P.; Williams,
D. J.; Younus M. Organometallics 1999, 18, 4261.
(25) Corriu, R. J. P.; Devylder, N.; Gue´rin, C.; Henner, B.; Jean, A.
Organometallics 1994, 13, 3194.
(26) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.
Synth. 1980, 627.
(27) Osborn, J. A.; Jardine, F. H.; Young, J. F.; Wilkinson, G. J.
Chem. Soc. (A) 1966, 1711.
(22) Marciniec, B. Appl. Organomet. Chem. 2000, 14, 527, and
references therein.
(28) Kraihanzel, C. S.; Losee, M. L. J. Organomet. Chem. 1967, 10,
427.

1466 Organometallics, Vol. 24, No. 7, 2005
Jain et al.
unless otherwise stated. Hydrosilylation experiments were
carried out with a trace amount of air to promote catalysis.
Solvents were dried over Na/benzophenone (THF) and CaH2
(n-hexane, CH2Cl2) and were freshly distilled prior to use.
NMR spectra were recorded on Varian VXR-400S (400 MHz)
and Varian Unity Inova (500 MHz) NMR Fourier transform
spectrometers. The solvent used for NMR studies was C6D6
as purchased from Cambridge Isotope Laboratories, Inc.
(Andover, MA). Gas chromatography-mass spectrometry (GC-
MS) was performed on a Hewlett-Packard HP 6890 series gas
chromatograph connected to a HP 5973 mass selective detec-
tor. Elemental analyses were performed by Robertson Microlit
Laboratories, Inc. (Madison, NJ). Chromatography was per-
formed on silica gel (100-200 mesh, purchased from Fisher
Scientific Co., or Sorbent Technologies, Atlanta, GA). Filtra-
tions used Celite purchased from Fisher that was preheated
and dried before use. MALDI-TOF mass spectrometry was
performed on a Perspective (PE) Biosystems Voyager System
6078 MALDI linear/reflectron time-of-flight mass spectrom-
eter, equipped with a pulsed nitrogen laser (337 nm). The
instrument was operated in the linear, positive-ion, high-
voltage (20 kV) mode. Molecular weight distributions were
analyzed by gel permeation chromatography using a Waters
Associates 2690 separations unit, with Ultrastyragel columns
with a pore size between 500, 103, and 105 Å, and a Waters
410 differential refractometer. Polystyrene standards pur-
chased from Aldrich were used for calibration purposes. Cyclic
voltammetry studies were performed using a platinum wire
counter electrode, a gold wire working electrode, and a Ag/
AgCl reference electrode connected to a EG&G Princeton
Applied Research potentiostat Model 273. Measurements were
conducted at ambient temperature under nitrogen in THF
using 0.1 M [(n-Bu)4N]PF6 as supporting electrolyte. Sample
concentrations were 1.0 mM, and cyclic voltammograms were
recorded at sweep rates of 50-200 mV s-1. Under these
conditions ferrocene has the following potentials: Epc 0.06 V;
Epa 0.21 V; E° 0.14 V.
under vacuum overnight gave polymer 2a (Rh) as an orange
solid (yield 0.058 g, 62%). Mn ) 4660; Mw/Mn ) 14.8. Anal.
Calcd for (C24H28Si2Fe)n: C, 67.27; H, 6.59. Found: C, 65.38;
H, 6.18.
Polymer 2c (Rh) was similarly prepared from 1,3-diethyn-
ylbenzene at room temperature over 4 days as a sticky orange
solid in 76% yield. Mn ) 3,650; Mw/Mn ) 2.69. Anal. Calcd for
(C24H28Si2Fe)n: C, 67.27; H, 6.59. Found: C, 66.14; H, 6.91.
Preparation of 4a. Karstedt’s catalyst (1 drop) was added
to a solution of 1,4-bis(trimethylsilyl)butadiyne (0.060 g, 0.31
mmol) and 1 (0.047 g, 0.155 mmol) in THF (7 mL) with a trace
of air and stirred at room temperature for 2 days. Drying in
vacuo, chromatography on silica gel (70-100 µm, 21 × 2 cm)
loading with 0.5 mL of hexane and eluting with hexane,
followed by evaporation in vacuo gave 4a as an orange solid
(yield 0.048 g, 45%). m/z ) 690 (M+). Anal. Calcd for C34H58-
Si6Fe: C, 59.08; H, 8.46. Found: C, 59.00; H, 8.39.
Preparation of 4b. Karstedt’s catalyst (1 drop) was added
to a solution of 1,4-bis(trimethylsilylethynyl)benzene (0.277 g,
1.02 mmol) and 1 (0.155 g, 0.513 mmol) in THF (10 mL) with
a trace of air and refluxed for 2 days. Drying in vacuo gave an
orange oil, which was chromatographed on silica gel (70-100
µm, 30 × 3 cm) loading with 1.5 mL of hexane and eluting
with hexane. Evaporation of solvent in vacuo gave 4b as an
orange oil (yield 0.176 g, 41%).
Preparation of 5a. A solution of KOH (0.008 g, 0.142
mmol) in water (0.5 mL) was added to a solution of 4a (0.048
g, 0.069 mmol) in methanol (15 mL) and stirred for 1 day at
room temperature. Evaporation to dryness, extraction with
hexane (3 × 10 mL), filtration through Celite, and removal of
hexane in vacuo followed by chromatography on silica gel (70-
100 µm, 15 × 2 cm) loading with 0.5 mL of hexane and eluting
with hexane gave 5a as an orange solid (yield 0.033 g, 87%).
m/z ) 546 (M+). Anal. Calcd for C28H42Si4Fe: C, 61.50; H, 7.74.
Found: C, 62.01; H, 7.04.
Compound 5b was prepared similarly from 4b over 2 days
in 96% yield.
General Synthesis of 2a-f (Pt). The general syntheses
of 2a-f (Pt) are illustrated by the synthesis of 2a (Pt) below.
Preparation of 2a (Pt). Karstedt’s catalyst (1 drop) was
added to a solution of 1,4-diethynylbenzene (0.188 g, 1.49
mmol) and 1,1′-bis(dimethylsilyl)ferrocene (1) (0.451 g, 1.49
mmol) in THF (7 mL) along with a trace of air and refluxed
for 2 days. Drying in vacuo, dissolution in a minimum amount
of THF (3.5 mL), and precipitation into methanol gave 2a (Pt)
as a bright orange precipitate, which was washed with
methanol (3 × 20 mL) and dried under vacuum overnight, yield
0.556 g, 87%. Mn ) 9630; Mw/Mn ) 3.2 (RI detector) and Mn )
11 700; Mw/Mn ) 2.4 (light scattering). Anal. Calcd for (C24H28-
Si2Fe)n: C, 67.27; H, 6.59. Found: C, 65.86; H, 6.94.
Preparation of Polymer 6a. Karstedt’s catalyst (1 drop)
was added to a solution of 5a (0.028 g, 0.051 mmol) and 1
(0.016 g, 0.052 mmol) in THF (2 mL) with a trace of air and
stirred at room temperature for 2 days. Drying in vacuo gave
a sticky orange solid, which was dissolved in a minimum of
THF (0.4 mL) and precipitated into methanol to give a sticky
orange precipitate. Washing with methanol (3 × 10 mL) and
drying under vacuum overnight gave polymer 6a as a sticky
orange solid (yield 0.038 g, 86%).
Polymer 6b was prepared similarly from 5b at room
temperature over 3 days in 59% yield.
X-ray Crystal Structure Determination. Crystals of 4a
were mounted on a glass fiber using cyanoacrylate cement.
Intensity data were collected on a Siemens P4 diffractometer
at 296 K, using a graphite-monochromated Mo KR radiation
(λ ) 0.71073 Å). The θ-2θ scan technique was applied with
variable scan speeds. The intensities of three standard reflec-
tions were measured every 97 reflections, and corrections were
applied. The data were corrected for Lorentz and polarization
effects, and empirical absorption corrections were applied to
the data set. The structure was solved by direct methods. Non-
hydrogen atoms were refined anisotropically by full-matrix
least-squares methods to minimize ∑w(Fo - Fc)2, where w-1
) σ2(F) + g(F)2. Hydrogen atoms were included in calculated
positions (C-H from 0.93 to 0.98 Å depending on type of
bonding). Crystal data, data collection, and least-squares
parameters are listed in Table 2. All calculations were
performed and graphics created using SHELXTL-97.
MALDI-TOF MS of Polymers. Approximately 1-2 mg of
polymer was dissolved in 1 µL THF and added to 1 µL of the
matrix in THF (mix). The matrix solution was prepared by
dissolving 23 mg of 1,8,9-anthracenetriol (dithranol) (MW )
226.23 g/mol) in 1 mL of THF (0.1 mol/L) + 1 µL of 5 g/L THF
solution of silver trifluoroacetate (MW ) 220.88 g/mol) + 10
2b (Pt): reflux, 2 days; orange powder; yield 75% Mn
1920; Mw/Mn ) 1.73. Anal. Calcd for (C30H44Si4Fe)n: C, 62.90;
H, 7.74. Found: C, 60.32; H, 7.83.
)
2c (Pt): room temperature, 4 days; orange sticky solid; yield
68% Mn ) 9120; Mw/Mn ) 21.7. Anal. Calcd for (C24H28Si2-
Fe)n: C, 67.27; H, 6.59. Found: C, 67.05; H, 6.52.
2d (Pt): reflux, 2 days; orange powder; yield 70% Mn
1710; Mw/Mn ) 1.73. Anal. Calcd for (C30H44Si4Fe)n: C, 62.90;
H, 7.74. Found: C, 62.67; H, 7.55.
)
2e (Pt): room temperature, 4 days; orange sticky solid; yield
85% Mn ) 3520; Mw/Mn ) 3.84. Anal. Calcd for (C20H30Si3-
Fe)n: C, 58.51; H, 7.37. Found: C, 55.75; H, 7.20.
2f (Pt): room temperature, 4 days; orange powder; yield
52% Mn ) 1860; Mw/Mn ) 1.74.
Preparation of 2a (Rh). Iodotris(triphenylphosphine)-
rhodium(I) (2 mg) was added to a solution of 1,4-diethynyl-
benzene (0.028 g, 0.218 mmol) and 1 (0.066 g, 0.222 mmol) in
THF (5 mL) and stirred at room temperature for 13 days.
Drying in vacuo, dissolution in a minimum of THF (0.5 mL),
and precipitation into methanol (40 mL) gave a bright orange
precipitate. Washing with methanol (3 × 10 mL) and drying

Poly{ferrocene(phenylene)bis(silylenevinylene)}s
Organometallics, Vol. 24, No. 7, 2005 1467
µL of trifluoroacetic acid (1%). Finally, 1 µL of the mix was
spotted on a stainless steel target plate and air-dried prior to
acquisition.
also grateful to Dr. Hong Li of the mass spectrometry
facility in the Department of Biochemistry at the
University of Medicine and Dentistry of New Jersey in
Newark, NJ, for assistance with MALDI-TOF spectrom-
etry.
Acknowledgment. We are grateful to Prof. Ian
Manners and Dr. Kevin Kulbaba at the University of
Toronto for the collection of GPC data on some of the
polymer samples and Prof. James Schlegel of this
department for electrochemical measurements. We thank
the National Science Foundation for GPC and electro-
chemical instrumentation at Rutgers-Newark provided
through the NSF-MRI program (MRI 0116066). We are
Supporting Information Available: Tables of crystal-
lographic data for 4a (Pt) and selected 1H, 13C, and 29Si NMR
spectra and MALDI-TOF mass spectra of the polymers re-
ported are available free of charge via the Internet at
http://pubs.acs.org.
OM049166P