Synthesis, characterization, and photocontrolled ring-opening polymerization of sila[1]ferrocenophanes with multiple alkyne substituents

Article abstract of DOI:10.1021/om060767l

Sila[1]ferrocenophanes with multiple alkyne substituents [Fe(η-C ₅H₄)2Si(C≡C^tBu)₂] (2) and [Fe(η-C₅H₄)₂Si(Me)C≡CC≡CPh] (5) have been synthesized and structurally characterized. These compounds are prepared by reacting [LiC≡C^tBu] or [LiC≡CC≡CPh] with sila[1]ferrocenophanes containing silicon-chlorine bonds. Ring-opening polymerizations (ROP) of 2 and 5 have been studied using transition metalcatalyzed, thermal, anionic, and photocontrolled routes. Thermal and anionic ROP both failed to give significant amounts of polymer (<30%). And unlike most other ferrocenophanes, 2 cannot be polymerized by Karstedt's catalyst, possibly due to chelation of the catalyst by the acetylide ligands. Platinum-catalyzed ROP of 5 was also relatively ineffective, giving polymers with bimodal molecular weight distributions in moderate yields. Nevertheless, living polymerization of 2 and 5 was possible using photocontrolled ROP with NaCp as initiator. The key to photocontrolled ROP was the reduced basicity of NaCp compared to BuLi, as the latter reacted with the carbon-carbon triple bonds in the ferrocenophanes. Metal complexation of the triple bonds in 5 was also examined; this species reacted with [Co₂(CO)₈] to give [Fe(η-C₅H₄)₂Si(Me){Co₂(CO) ₆C₂Co₂(CO)₆C₂Ph}] (7), a bimetallic ferrocenophane with five metal atoms.

Full text of DOI:10.1021/om060767l

Organometallics 2007, 26, 1217-1225
1217
Synthesis, Characterization, and Photocontrolled Ring-Opening
Polymerization of Sila[1]ferrocenophanes with
Multiple Alkyne Substituents
Wing Yan Chan,† Alan J. Lough,† and Ian Manners*,†,‡
Department of Chemistry, UniVersity of Toronto, 80 St. George Street, Toronto, Ontario, Canada,
M5S 3H6, and the School of Chemistry, UniVersity of Bristol, Bristol, England, B58 1TS
ReceiVed August 23, 2006
Sila[1]ferrocenophanes with multiple alkyne substituents [Fe(η-C5H4)2Si(CtCtBu)2] (2) and [Fe(η-
C5H4)2Si(Me)CtCCtCPh] (5) have been synthesized and structurally characterized. These compounds
are prepared by reacting [LiCtCtBu] or [LiCtCCtCPh] with sila[1]ferrocenophanes containing silicon-
chlorine bonds. Ring-opening polymerizations (ROP) of 2 and 5 have been studied using transition metal-
catalyzed, thermal, anionic, and photocontrolled routes. Thermal and anionic ROP both failed to give
significant amounts of polymer (<30%). And unlike most other ferrocenophanes, 2 cannot be polymerized
by Karstedt’s catalyst, possibly due to chelation of the catalyst by the acetylide ligands. Platinum-catalyzed
ROP of 5 was also relatively ineffective, giving polymers with bimodal molecular weight distributions
in moderate yields. Nevertheless, living polymerization of 2 and 5 was possible using photocontrolled
ROP with NaCp as initiator. The key to photocontrolled ROP was the reduced basicity of NaCp compared
to BuLi, as the latter reacted with the carbon-carbon triple bonds in the ferrocenophanes. Metal
complexation of the triple bonds in 5 was also examined; this species reacted with [Co2(CO)8] to give
[Fe(η-C5H4)2Si(Me){Co2(CO)6C2Co2(CO)6C2Ph}] (7), a bimetallic ferrocenophane with five metal atoms.
Scheme 1. Synthesis of Ferrocenophane 2 with Two
Acetylide Substituents
Introduction
Metal-containing polymers have received increasing attention
in recent years due to their unique properties and potential uses
as functional materials.1,2 For example, polymetallaynes have
shown interesting behavior such as lyotropic liquid crystallinity,
optical nonlinearity, photoconductivity, and luminescence.3-5
Conjugated metallopolymers have been investigated for uses
in electroluminescent and photosensitizing devices,6 as well as
chemical and biological sensors.7 In addition to linear polymers,
metallodendrimers8 are also of interest since incorporation of
organometallic species into the core or the periphery of
dendrimers imparts electroactivity, optical response, and catalytic
properties,9,10 allowing the fabrication of sensors for gases and
biomolecules.11 Furthermore, metal-containing polymers have
found applications as precursors to ceramics embedded with
magnetic or catalytically active nanoparticles,12-14 lithographic
resists,15,16 and supramolecular materials.17,18
Polyferrocenylsilanes (PFS) represent a subset of polymet-
allocenes that have been extensively studied over the last decade.
These materials are readily synthesized through ring-opening
polymerization (ROP) of strained [1]ferrocenophanes using
* Corresponding author. E-mail: Ian.Manners@Bristol.ac.uk.
† University of Toronto.
‡ University of Bristol.
(1) (a) Archer, R. D. Inorganic and Organometallic Polymers; John
Wiley & Sons Inc: New York, 2001. (b) Abd-El-Aziz, A. S., Harvey, P.
D., Eds. Macromol. Symp. 2004, 209, 1-251.
(2) (a) Manners, I. Science 2001, 294, 1664-1666. (b) Manners, I.
Synthetic Metal-Containing Polymers; Wiley-VCH: Weinheim, 2004.
(3) Long, N. J.; Williams, C. K. Angew. Chem., Int. Ed. 2003, 42, 2586-
2617.
(11) Chase, P. A.; Klein Gebbink, R. J. M.; van Koten, G. J. Organomet.
Chem. 2004, 689, 4026-4054.
(12) MacLachlan, M. J.; Ginzburg, M.; Coombs, N.; Coyle, T. W.; Raju,
N. P.; Greedan, J. E.; Ozin, G. A.; Manners, I. Science 2000, 287, 1460-
1463.
(13) Berenbaum, A.; Ginzburg-Margau, M.; Coombs, N.; Lough, A. J.;
Safa-Sefat, A.; Greedan, J. E.; Ozin, G. A.; Manners, I. AdV. Mater. 2003,
15, 51-55.
(14) Lastella, S.; Jung, Y. J.; Yang, H.; Vajtai, R.; Ajayan, P. M.; Ryu,
C. Y.; Rider, D. A.; Manners, I. J. Mater. Chem. 2004, 14, 1791-1794.
(15) Johnson, B. F. G.; Sanderson, K. M.; Shephard, D. S.; Ozkaya, D.;
Zhou, W.; Ahmed, H.; Thomas, M. D. R.; Gladden, L.; Mantle, M. Chem.
Commun. 2000, 1317-1318.
(16) Chan, W. Y.; Clendenning, S. B.; Berenbaum, A.; Lough, A. J.;
Aouba, S.; Ruda, H. E.; Manners, I. J. Am. Chem. Soc. 2005, 127, 1765-
1772.
(17) Lohmeijer, B. G. G.; Schubert, U. S. Angew. Chem., Int. Ed. 2002,
41, 3825-3829.
(18) Beck, J. B.; Rowan, S. J. J. Am. Chem. Soc. 2003, 125, 13922-
13923.
(4) Nguyen, P.; Go´mez-Elipe, P.; Manners, I. Chem. ReV. 1999, 99,
1515-1548.
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2002, 35, 3506-3513.
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Metal-Coordination Polymers, Macromolecules Containing Metal and
Metal-Like Elements; John Wiley & Sons: New York, 2005; Vol. 5.
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Polyhedron 2006, 25, 585-590.
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10.1021/om060767l CCC: $37.00 © 2007 American Chemical Society
Publication on Web 01/26/2007

1218 Organometallics, Vol. 26, No. 5, 2007
Chan et al.
Scheme 2. Ring-Opening Polymerization of Ferrocenophane
2 to Give PFS 3
Co, Mo, and Ni have been successfully introduced.16,27 The
resulting highly metalized PFS have applications as precursors
to magnetic nanoparticles28,29 and lithographic resists,16,30,31 and
potentially for the fabrication of spintronic devices.32
Figure 1. Molecular structure of 2 (thermal ellipsoids at 30%
probability). Hydrogen atoms have been removed for clarity, and
the disordered tert-butyl group (C19* to C22*) is not shown.
The presence of a second metal in the polymer (in addition
to iron) imparts interesting properties to the material, allowing
the patterning of silicon substrates on the micronscale using
electron-beam lithography and photolithography.16 Although the
metallopolymers used in that study contained at least 25% metal
by weight, it is still desirable for several applications to further
increase the metal loading per repeat unit. This will allow access
to a wider range of ratios between the two metals in the polymer,
which is of interest in the systematic synthesis of Fe-containing
bimetallic alloys. In addition, ceramics containing higher
densities of metal nanoparticles should be accessible, which is
potentially important for spintronic device applications.
One strategy to increase metal density is to add another
carbon-carbon triple bond to the ferrocenophane for metal
complexation. In principle, this might be achieved in two
ways: (1) by using two acetylide substituents at silicon or (2)
by the introduction of a conjugated diyne substituent at silicon.
In this paper, we sequentially discuss each of these approaches.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 2
Si(1)-C(1)
1.881(4)
1.872(4)
1.815(4)
1.816(4)
1.215(5)
1.466(5)
1.190(6)
1.509(7)
2.6667(14)
C(1)-Si(1)-C(6)
C(11)-Si(1)-C(17)
Si(1)-C(11)-C(12)
C(11)-C(12)-C(13)
Si(1)-C(17)-C(18)
C(17)-C(18)-C(19)
R
97.74(17)
114.31(19)
173.4(4)
179.2(4)
173.2(4)
Si(1)-C(6)
Si(1)-C(11)
Si(1)-C(17)
C(11)-C(12)
C(12)-C(13)
C(17)-C(18)
C(18)-C(19)
Fe(1)-Si(1)
166.3(5)
19.26(24)
thermal,19 transition metal-catalyzed, and anionic routes.20,21
Recently, our group reported the photocontrolled living anionic
ROP of sila[1]ferrocenophanes.22,23 In this method, UV excita-
tion of the ferrocenophane monomer selectively weakens the
iron-Cp bond, allowing the use of a mildly basic anion such
as NaCp to initiate living polymerization. After the polymeri-
zation is quenched, PFS materials with narrow molecular weight
distributions (PDI < 1.1) are obtained.24
A current direction in our group is the development of
synthetic strategies to increase the metal density in PFS to yield
highly metalized polymers.25 This can be achieved by introduc-
ing acetylide groups at the silicon atom of PFS to allow further
reaction with transition metal complexes.26 So far, clusters of
Results and Discussion
Synthesis and Characterization of a Sila[1]ferrocenophane
with Two Acetylenic Substituents (2). Sila[1]ferrocenophane
2 containing two acetylide substituents at silicon was synthesized
by reacting ferrocenophane 1, containing a SiCl2 bridge, with
lithium tert-butyl acetylide (Scheme 1).26,33
After multiple recrystallizations from a mixture of toluene
and hexanes, sila[1]ferrocenophane 2 was isolated in 21% yield34
as an red-orange powder. Its 1H NMR spectrum contained only
one Cp resonance at δ 4.41 ppm, as the R- and â-protons are
coincidental, and the methyl resonance was found at δ 1.11 ppm.
(19) Foucher, D. A.; Tang, B. Z.; Manners, I. J. Am. Chem. Soc. 1992,
114, 6246-6248.
(20) Ni, Y.; Rulkens, R.; Manners, I. J. Am. Chem. Soc. 1996, 118, 4102-
4114.
(21) Manners, I. Chem. Commun. 1999, 857-865.
(22) Tanabe, M.; Manners, I. J. Am. Chem. Soc. 2004, 126, 11434-
11435.
(23) Tanabe, M.; Vandermeulen, G. W. M.; Chan, W. Y.; Cyr, P. W.;
Vanderark, L.; Rider, D. A.; Manners, I. Nat. Mater. 2006, 5, 467-470.
(24) Prior work by Miyoshi and co-workers has shown that photolytic
polymerization of phosphorus-bridged [1]ferrocenophanes in THF without
an anionic initiator is also possible; however, the molecular weight
distribution is considerably more broad (PDI > 1.6) and the system is not
living. See: Mizuta, T.; Onishi, M.; Miyoshi, K. Organometallics 2000,
19, 5005-5009. Mizuta, T.; Imamura, Y.; Miyoshi, K. J. Am. Chem. Soc.
2003, 125, 2068-2069.
(27) Chan, W. Y.; Berenbaum, A.; Clendenning, S. B.; Lough, A. J.;
Manners, I. Organometallics 2003, 22, 3796-3808.
(28) Clendenning, S. B.; Han, S.; Coombs, N.; Paquet, C.; Rayat, M.
S.; Grozea, D.; Brodersen, P. M.; Sodhi, R. N. S.; Yip, C. M.; Lu, Z.-H.;
Manners, I. AdV. Mater. 2004, 16, 291-296.
(29) Liu, K.; Clendenning, S. B.; Friebe, L.; Chan, W. Y.; Zhu, X. B.;
Freeman, M. R.; Yang, G. C.; Yip, C. M.; Grozea, D.; Lu, Z.-H.; Manners,
I. Chem. Mater. 2006, 18, 2591-2601.
(30) Cheng, A. Y.; Clendenning, S. B.; Yang, G.; Lu, Z.-H.; Yip, C.
M.; Manners, I. Chem. Commun. 2004, 780-781.
(31) Clendenning, S. B.; Aouba, S.; Rayat, M. S.; Grozea, D.; Sorge, J.
B.; Brodersen, P. M.; Sodhi, R. N. S.; Lu, Z.-H.; Yip, C. M.; Freeman, M.
R.; Ruda, H. E.; Manners, I. AdV. Mater. 2004, 16, 215-219.
(32) Theoretical calculations by M. B. A. Jalil indicated that a nan-
ogranular-in-gap structure can be used as a magnetic field-controlled
nanoswitch: Jalil, M. B. A. IEEE Trans. Magn. 2002, 38, 2613-2615.
(33) The phenyl analogue of 2 was previously reported (see ref 26). We
have changed the pendent substituent to tert-butyl to promote solubility of
the resulting polyferrocenylsilane.
(25) Selected examples of highly metallized polymers and dendrimers:
(a) Johnson, B. F. G.; Sanderson, K. M.; Shephard, D. S.; Ozkaya, D.;
Zhou, W.; Ahmed, H.; Thomas, M. D. R.; Gladden, L.; Mantle, M. Chem.
Commun. 2000, 1317-1318. (b) Humphrey, M. G. Macromol. Symp. 2004,
209, 1-21. (c) Mˆıinea, L. A.; Sessions, L. B.; Ericson, K. D.; Glueck, D.
S.; Grubbs, R. B. Macromolecules 2004, 37, 8967-8972. (d) Sicard, S.;
Be´rube´, J.-F.; Samar, D.; Messaoudi, A.; Fortin, D.; Lebrun, F.; Fortin,
J.-F.; Decken, A.; Harvey, P. D. Inorg. Chem. 2004, 43, 5321-5334. (e)
Li, Z.; Dong, Y.; Qin, A.; Lam, J. W. Y.; Dong, Y.; Yuan, W.; Sun, J.;
Hua, J.; Wong, K. S.; Tang, B. Z. Macromolecules 2006, 39, 467-469. (f)
Scholz, S.; Leech, P. J.; Englert, B. C.; Sommer, W.; Weck, M.; Bunz, U.
H. F. AdV. Mater. 2005, 17, 1052-1056.
(34) As 2 is extremely soluble in toluene and hexanes, repeated
recrystallizations (to remove traces of unidentified impurities) resulted in
its reduced yield.
(26) Berenbaum, A.; Lough, A. J.; Manners, I. Organometallics 2002,
21, 4415-4424.

Sila[1]ferrocenophanes with Multiple Alkyne Substituents
Organometallics, Vol. 26, No. 5, 2007 1219
Table 2. Attempts at ROP of Monomer 2 to Give PFS 3
a
ROP method
TM-cat.
TM-cat.
TM-cat.
catalyst/initiator
reaction conditions
conversion to polymer/isolated yield
Mn
Karstedt’s
PtCl2
21.5 h, 50 °C
2.5 h, 25 °C
5 h, 25 °C
0% conversion
100% conversion
40% yield
gel
b
PtCl2
bimodalc
thermal (solution)
none
none
24 h, 160 °C
in xylenes
20% conversion
thermal (solution)
24 h, 175 °C
in mesitylene
1 h, 185 °C
-78 °C to 25 °C
1.5 h, 5 °C
30% conversion
thermal (bulk)
anionic
photocontrolled
none
15% yield
multiple uncharacterized products
80% yield
trimodalc
nBuLi
NaCp
9.6 × 103 (1.15)
b
c
a The polydispersity index is given in parentheses. Et3SiH (ranging from 0.05 to 0.5 equiv) was added. See Experimental Section for detailed molecular
weight distributions.
Scheme 3. Photocontrolled Living Ring-Opening Polymerization of Ferrocenophane 2 to Give PFS 3
The 13C NMR spectrum of 2 showed two Cp resonances at δ
78.2 and 75.6 ppm, and the ipso-Cp resonance at δ 29.9 ppm.
A dramatic upfield shift of the ipso-Cp resonance from that of
ferrocene (ca. δ 70 ppm) is typical for ferrocenophanes, as the
Cp ligands are tilted toward each other to form a strained
structure. The 29Si NMR spectrum of 2 showed a single
resonance at δ -55.3 ppm.
The molecular structure of 2 was confirmed using single-
crystal X-ray crystallography. Figure 1 is the ORTEP diagram
of 2, and Table 1 lists pertinent bond lengths and angles for
this compound.
after 24 h) in both cases. Thermal ROP of 2 in bulk at 185 °C
was also unproductive, as it gave a gel and only a small amount
of soluble polymer. When we attempted to ring-open 2 using a
n
stoichiometric amount of BuLi in order to test the feasibility
of anionic ROP, we observed multiple Cp and methyl resonances
in the 1H NMR spectrum of the product, suggesting the acetylide
groups do not tolerate such a strong base. The synthesis of well-
defined PFS 3 was finally achieved using photocontrolled ROP.
In this method, NaCp was used as an anionic initiator to
polymerize a photoactivated ferrocenophane at 5 °C.22,23 In
contrast to the situation with nBuLi, the less basic NaCp initiator
is compatible with the acetylide substituents in 2, allowing the
preparation of soluble bis(acetylide)-substituted PFS 3 with a
narrow, monomodal molecular weight distribution in 80%
isolated yield (Scheme 3).
The molecular structure of 2 confirmed the expected atom
connectivity. The tilt angle (R) of 19.26(24)° between the two
Cp rings is typical for sila[1]ferrocenophanes. The carbon-
carbon triple bond lengths in 2 are 1.215(5) Å (C(11)-C(12))
and 1.190(6) Å (C(17)-C(18)), respectively. These distances
are comparable to that of the triple bond in free acetylene (1.20
Å).35 The Fe-Si distance of 2.6667(14) Å in 2 also falls within
the normal range of sila[1]ferrocenophanes (cf. d(Fe-Si) )
2.55-2.75 Å).36,37 The two alkynes in 2 are almost linear,
with bond angles around the acetylenic carbons ranging from
166.3(5)° to 179.2(4)°. The geometric parameters of 2 are similar
to those of its phenyl analogue.26
Ring-Opening Polymerization of Sila[1]ferrocenophane 2
to Give Polyferrocenylsilane 3. We attempted the ROP of 2
under various conditions (Scheme 2 and Table 2). We began
by using Karstedt’s catalyst to induce ROP; however, this route
failed to give polymer at either 25 or 50 °C. This may be a
consequence of the coordination of Pt by both acetylide groups
in 2, thereby deactivating the catalyst.38 When PtCl2 was used
as an alternate catalyst in toluene, an orange gel was formed
after 2.5 h at 25 °C, suggesting the formation of very high
molecular weight and/or cross-linked polymer. We have previ-
ously demonstrated the use of Et3SiH for polymer molecular
weight control in the Pt-catalyzed ROP of ferrocenophanes.39
When Et3SiH was added to the polymerization of 2 with PtCl2,
PFS 3 with a bimodal molecular weight distribution was
consistently obtained in less than 50% yield.40 Next, we tried
refluxing a xylenes or mesitylene solution of 2 to induce thermal
ROP, but the reaction was sluggish (maximum 30% conversion
PFS 3 was fully characterized by NMR spectroscopy.
1
Compared to that of 2, the H NMR spectrum of 3 showed
downfield shifts of both Cp resonances (to δ 4.91 and 4.67 ppm)
and the methyl resonance (to δ 1.23 ppm). As the Cp ligands
are no longer tilted in PFS 3, the ipso-Cp carbon resonance
was found at δ 68.0 ppm, much closer to the 13C resonance of
ferrocene (ca. δ 70 ppm). As expected, the 29Si NMR signal of
3 at δ -46.0 is shifted downfield from that of 2 (δ -55.3 ppm).
GPC analysis of 3 gave Mn ) 9600 and PDI ) 1.15, indicating
(35) Elschenbroich, C.; Salzer, A. Organometallics: A Concise Introduc-
tion; VCH Publishers Inc.: New York, 1992.
(36) Pudelski, J. K.; Foucher, D. A.; Honeyman, C. H.; Lough, A. J.;
Manners, I.; Barlow, S.; O’Hare, D. Organometallics 1995, 14, 2470-
2479.
(37) Zechel, D. L.; Hultzsch, K. C.; Rulkens, R.; Balaishis, D.; Ni, Y.;
Pudelski, J. K.; Lough, A. J.; Manners, I.; Foucher, D. A. Organometallics
1996, 15, 1972-1978.
(38) When we reacted monomer 2 with Karstedt’s catalyst in a
stoichiometric reaction, we observed the complete conversion of monomer
1
2 to various unidentified products (by H NMR) after 3 h at 25 °C.
(39) (a) Go´mez-Elipe, P.; Resendes, R.; Macdonald, P. M.; Manners,
I. J. Am. Chem. Soc. 1998, 120, 8348-8356. (b) Temple, K.; Ja¨kle, F.;
Sheridan, J. B.; Manners, I. J. Am. Chem. Soc. 2001, 123, 1355-1364.
(40) A typical bimodal GPC trace contains a peak at Mn ≈ 5000-30 000
(ca. 90% of all polymer) and a higher molecular weight peak at Mn ≈ 106-
107 (ca. 10% of all polymer). Molecular weights of the polymer formed
varied depending on the amount of PtCl2 and Et3SiH used, but all molecular
weight distributions were bimodal.

1220 Organometallics, Vol. 26, No. 5, 2007
Chan et al.
Table 3. Photocontrolled ROP of 2 to Give PFS 3a
isolated yield
of 3 (%)
[M]:[I] time (h)
Mn expected Mn foundb PDI
25:1
50:1
75:1
2
2
4
83
89
88
9400
18 700
28 100
9400
24 100
43 100
1.11
1.11
1.15
b
a Irradiations were performed at 5 °C with THF as solvent. Molecular
weights relative to polystyrene standards.
Figure 2. Molecular structure of 5 (thermal ellipsoids at 30%
probability). Hydrogen atoms have been removed for clarity, and
only one of the two independent molecules of 5 in an asymmetric
unit is shown.
Scheme 4. Synthesis of Ferrocenophane 5 with a Diyne
Substituent
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 5
Si(1A)-C(1A)
Si(1A)-C(6A)
1.885(4)
1.879(4)
C(1A)-Si(1A)-C(6A)
96.42(16)
C(11A)-Si(1A)-C(12A) 110.03(19)
Si(1A)-C(12A)-C(13A) 176.7(3)
C(12A)-C(13A)-C(14A) 178.6(4)
C(13A)-C(14A)-C(15A) 176.7(5)
C(14A)-C(15A)-C(16A) 175.8(4)
Si(1A)-C(12A) 1.827(4)
C(12A)-C(13A) 1.203(5)
C(13A)-C(14A) 1.384(5)
C(14A)-C(15A) 1.201(5)
C(15A)-C(16A) 1.437(5)
the polymer was essentially monodisperse and possessed a well-
defined microstructure.
R
21.04(24)
We briefly explored the possibility of molecular weight
control in the photocontrolled ROP of 2. Three monomer to
initiator ratios were studied, and the results are summarized in
Table 3. In all three experiments, monomodal PFS 3 with narrow
molecular weight distributions was obtained in good yields. The
low PDI values indicate this is a living polymerization.
Synthesis and Characterization of a Sila[1]ferrocenophane
with a Diyne Substituent (5). Next, we investigated the second
strategy to increase metal loading, i.e., introduction of a diyne
substituent at silicon. Sila[1]ferrocenophane 5, containing a
conjugated diyne, was synthesized by substitution of chloro-
substituted sila[1]ferrocenophane 4 with the appropriate lithium
salt (Scheme 4). After recrystallization from a mixture of toluene
and hexanes, monomer 5 was isolated in 40% yield41 as a red
Fe(1A)-Si(1A)
2.6961(12)
Scheme 5. Ring-Opening Polymerization of Ferrocenophane
5 to Form PFS 6
1
solid. The H NMR spectrum of 5 showed four multiplets in
the Cp region (δ 4.41 to 3.81 ppm), typical for a ferrocenophane
with asymmetric substitution at silicon. The ipso-Cp carbon
resonance of 5 was found at δ 29.1 ppm, comparable to that of
monomer 2 (cf. δ 29.9 ppm). The 29Si NMR spectrum of 5
contained a single resonance at δ -26.9 ppm.
A single-crystal X-ray diffraction study was performed to
confirm the molecular structure of 5. Figure 2 shows the ORTEP
diagram of 5, and Table 4 contains a summary of geometric
parameters.
The molecular structure of 5 was as expected.42 The tilt angle
(21.04(24)°) and Fe-Si distance (2.6961(12) Å) of 5 are
comparable to those of 2 (cf. R ) 19.26(24)°, d(Fe-Si) )
2.6667(14) Å). Also, carbon-carbon bond lengths in the diyne
substituent alternate between that of a single bond (1.384(5) to
1.437(5) Å) and a triple bond (1.201(5) to 1.203(5) Å). As in
2, the carbon-carbon triple bonds in 5 are approximately linear,
and bond angles around the acetylenic carbons range from
175.8(4)° to 178.6(4)°.
Ring-Opening Polymerization of Sila[1]ferrocenophane 5
to Give Polyferrocenylsilane 6. Although some conjugated
diynes have been known to polymerize in a topochemical 1,4-
addition in the solid state upon exposure to heat, UV-visible
light, or γ-rays,43 monomer 5 is stable when stored at 25 °C in
an inert atmosphere glovebox. An inspection of the unit cell of
5 reveals that the diyne substituents of adjacent monomers are
probably not packed closely enough for polymerization to take
place in the solid state.44 We then attempted to deliberately
polymerize 5 using various methods. Beginning with transition
metal-catalyzed ROP, we used Karstedt’s catalyst and Et3SiH
for molecular weight control. We were successful in forming
PFS 6Karstedt’s in 50% yield (Scheme 5). In contrast to monomer
5, no polymer was formed when Karstedt’s catalyst was used
to polymerize monomer 2. This difference in reactivity is likely
due to the varying geometry of the two carbon-carbon triple
bonds in the ferrocenophanes. In monomer 2, the two alkynes
are positioned such that they can chelate a metal ion; however,
the two triple bonds in monomer 5 are conjugated in a linear
fashion and chelate formation is not possible. As a result, the
behavior of monomer 5 in Karstedt’s-catalyzed ROP mirrors
that of ferrocenophanes with one acetylide substituent at the
silicon (they readily polymerize),26 but monomer 2 does not.
The highly asymmetrical substitution at the silicon atom of
monomer 5 offers the possibility of forming a stereoregular
polymer, as the steric demands of the methyl and diyne
substituents are significantly different. We therefore investigated
the effects of ROP protocols on the microstructure of PFS 6.
1
The H NMR spectrum of PFS 6Karstedt’s synthesized using
(41) The rather low yield of 5 is a consequence of the reduced purity of
PhCtCCtCLi, as not all of 4 is consumed in the reaction depicted in
Scheme 3.
(42) There are two independent molecules of 5 in an asymmetric unit of
the crystal lattice, but their bond lengths and bond angles are identical within
experimental error. Geometric parameters quoted in the article are that of
one independent molecule.
Karstedt’s catalyst shows a broad methyl resonance at δ 0.75
ppm, clearly indicating that the polymer was not stereoregular.
GPC analysis of PFS 6Karstedt’s also showed that the molecular
(44) Diyne monomers need to be spaced at 4.9 Å with a 45° declination
(43) Enkelmann, V. Chem. Mater. 1994, 6, 1337-1340.
angle; see ref 43 for details.

Sila[1]ferrocenophanes with Multiple Alkyne Substituents
Organometallics, Vol. 26, No. 5, 2007 1221
Figure 3. (a) 100 MHz 13C{1H} NMR spectrum of PFS 6PtCl2 (expansion of Cp region). (b) 79.4 MHz 29Si{1H} NMR spectrum of PFS
6PROP
.
Scheme 6. Clusterization of Ferrocenophane 5 with [Co2(CO)8] to Give Ferrocenophane 7
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
weight distribution was bimodal. When PtCl2 was used as an
7‚0.5C7H8
alternate catalyst for transition metal-catalyzed ROP, PFS 6PtCl2
1
Si(1)-C(1)
1.887(5)
1.888(5)
1.350(6)
1.435(6)
1.362(5)
2.4489(9)
2.4693(9)
2.6848(15)
C(1)-Si(1)-C(6)
Si(1)-C(12)-C(13)
C(12)-C(13)-C(21)
C(13)-C(21)-C(20)
C(21)-C(20)-C(28)
R
96.8(2)
149.9(4)
141.8(4)
143.1(4)
140.8(4)
19.54(28)
was formed in 78% yield and the H NMR spectrum of this
Si(1)-C(6)
sample also contained a methyl resonance at δ 0.75 ppm. The
Cp resonances of PFS 6PtCl2 occur in pairs in the 13C NMR
spectrum, showing dyad resolution for an atactic polymer
(Figure 3a). However, the molecular weight distribution of PFS
6PtCl2 was broad and bimodal (fraction 1: Mn ) 3.8 × 106,
PDI ) 1.81, 15%; fraction 2: Mn ) 4.0 × 104, PDI ) 3.05,
85%). Thermal ROP of 5 was also attempted: when performed
in either refluxing xylenes or mesitylene, a gel was obtained
after 1 h of heating, suggesting the formation of very high
molecular weight and/or cross-linked polymer. In the case of
xylenes, a small amount of soluble PFS 6xylenes was isolated
C(12)-C(13)
C(13)-C(21)
C(20)-C(21)
Co(1)-Co(2)
Co(3)-Co(4)
Fe(1)-Si(1)
(13% yield), and its 1H and 13C NMR spectra were very similar
to those of PFS 6PtCl2, again suggesting the formation of an
atactic polymer. Next, we tried photocontrolled ROP of 5 with
NaCp as initiator. After 2 h of photolysis, PFS 6PROP was
isolated in 87% yield following precipitation into hexanes. In
contrast to the polymers from thermal and metal-catalyzed ROP,
1
the H NMR spectrum of this sample contained sharp signals
and a single methyl resonance at δ ) 0.74 ppm. Furthermore,
its 29Si NMR spectrum showed a well-resolved 3 line pattern
due to triad resolution in an approximate 1:2:1 ratio centered
at δ ) -22.1 ppm, suggesting the polymer is atactic (Figure
3b).37 GPC analysis also confirmed that PFS 6PROP is well-
defined with a narrow molecular weight distribution (Mn )
8400, PDI ) 1.10). Comparing all the polymerization methods,
photocontrolled ROP of 5 gave PFS 6 with the most narrow
molecular weight distribution; however, none of the routes gave
a stereoregular polymer.
Clusterization of the Triple Bond in Sila[1]ferrocenophane
5 Using [Co2(CO)8]. As one of the goals of this research is to
further increase the metal content of highly metallized PFS, we
want to confirm that the clusterization reactions we have
previously developed27 will apply to the diyne-substituted sila-
Figure 4. Molecular structure of 7‚0.5C7H8 (thermal ellipsoids at
30% probability). Hydrogen atoms have been omitted for clarity.

1222 Organometallics, Vol. 26, No. 5, 2007
Chan et al.
Table 6. Selected Crystal, Data Collection, and Refinement Parameters for 2, 5, and 7‚0.5C7H8
2
5
7·0.5C7H8
formula
Mr
C22H26FeSi
374.37
C21H16FeSi
352.28
C33H16Co4FeO12Si·0.5C7H8
970.19
cryst syst
space group
color
a, Å
b, Å
monoclinic
P2(1)/c
orthorhombic
Pca21
red
19.0405(5)
7.5017(1)
23.3594(6)
90
triclinic
P1h
orange-red
14.4265(3)
12.7510(5)
11.5855(5)
90
106.64(3)
90
2041.92(13)
150(1)
dark brown
8.8609(4)
9.3119(4)
22.3450(8)
83.815(3)
83.552(3)
85.989(2)
1818.27(13)
150(1)
c, Å
R, deg
â, deg
γ, deg
V, Å3
temperature, K
Z
90
90
3336.57(13)
150(1)
8
1.403
0.971
4
2
F
calc, g cm-3
1.218
0.797
792
0.10 × 0.10 × 0.10
2.56-27.52
17 865
1.772
2.273
966
0.22 × 0.16 × 0.05
2.58-27.57
21 552
µ(Mo KR), mm-1
F(000)
1456
cryst size, mm3
θ range, deg
0.34 × 0.12 × 0.04
2.72-27.48
19 318
no. of reflns collected
no. of indep reflns
4668
6599
8201
(Rint ) 0.0974)
(Rint ) 0.0565)
(Rint ) 0.0973)
abs corr
semiempirical from equivalents
max. and min. transmn coeff
no. of params refined
GoF on F2
0.927 and 0.863
254
1.034
0.0557
0.1589
0.967 and 0.755
419
1.017
0.0384
0.0895
0.893 and 0.694
514
0.991
0.0521
0.1402
R1a (I > 2σ(I))
wR2b (all data)
Peak and hole, e Å-3
0.576 and -0.454
0.448 and -0.497
0.592 and -0.820
[1]ferrocenophane.45 We chose to test the reactivity of monomer
5 with [Co2(CO)8], as the complexation reaction should proceed
at room temperature. When monomer 5 and [Co2(CO)8] were
reacted in toluene for 2 h, both carbon-carbon triple bonds
were transformed into Co2C2 clusters. After recrystallization
from a mixture of toluene and hexanes, cobalt-clusterized
ferrocenophane 7 was isolated in 62% yield as a dark brown
solid (Scheme 6).
Summary
We have synthesized two ferrocenophanes containing multiple
carbon-carbon triple bonds in different geometric arrangements.
Ferrocenophane 2 contains two acetylide substituents at silicon,
while ferrocenophane 5 has a diyne substituent at silicon. The
geometry of the triple bonds affects the polymerization behavior
of these ferrocenophanes. For example, the two carbon-carbon
triple bonds in ferrocenophane 2 could form a chelate with an
incoming metal catalyst, apparently deactivating the Karstedt’s
catalyst in transition metal-catalyzed ROP. Hence, monomer 2
could only be polymerized to give well-defined PFS 3 using
photocontrolled ROP. In contrast to monomer 2, monomer 5
contains two conjugated carbon-carbon triple bonds. Since
chelate formation is not possible with ferrocenophane 5, it can
be polymerized using Karstedt’s catalyst to give PFS 6.
Preparation of PFS 6 with a narrow molecular weight distribu-
tion was possible through photocontrolled ROP; the polymer
formed was atactic and not stereoregular. It is significant that
photocontrolled ROP allowed the living polymerizations of
monomers 2 and 5 to give materials with narrow molecular
weight distributions when living anionic ROP using BuLi failed.
Both PFS 3 and 6 are important precursors to highly metalized
PFS, as they allow the incorporation of up to five metal atoms
per polymer repeat unit.
1
Upon clusterization of the diyne substituent, all H NMR
signals of 7 were found downfield from those of 5. A similar
shift was observed in the 13C NMR spectrum of 7, as the ipso-
Cp carbon resonance moved from δ 29.1 ppm in 5 to δ 33.2
ppm in 7. The 29Si NMR spectrum of 7 contained a singlet at
δ -11.5 ppm, downfield from that of 5 (cf. δ -26.9 ppm). To
confirm the molecular structure of 7, a single-crystal X-ray
diffraction study was performed. Figure 4 shows the ORTEP
diagram of 7‚0.5C7H8, and Table 5 lists selected geometric
parameters for this compound.
The molecular structure of 7‚0.5C7H8 confirmed the expected
atomic arrangement. Introduction of the cobalt clusters did not
affect the tilt angle of the ferrocenophane, but bond distances
in the diyne substituent have increased significantly. Upon
clusterization, the carbon-carbon triple bonds lengthened from
1.201(5) Å to 1.362(5) Å, and the single bond lengthened from
1.384(5) Å to 1.435(6) Å. The conjugated diyne also changed
from an almost linear to a bent geometry, with more acute bond
angles around the carbon atoms in 7‚0.5C7H8 (140.8(4)° to
149.9(4)°). These changes in bond length and angles in the
diyne substituent upon clusterization are expected as the carbon
atoms rehybridize from sp to approaching sp3. For the Co2C2
clusters, the cobalt-cobalt axes lie perpendicular to the carbon-
carbon axes. The cobalt-cobalt bond distances in 7‚0.5C7H8
are similar to those in other ferrocenophanes containing cobalt
clusters.27
We have also explored metal complexation of the diyne
substituent in ferrocenophane 5. Reaction of 5 with [Co2(CO)8]
resulted in clusterization of both carbon-carbon triple bonds
and the formation of bimetallic ferrocenophane 7 in 62%
yield. We are currently studying the metal complexation of PFSs
3 and 6 and pyrolysis of the resulting materials to form
ceramics.46
Experimental Section
nBuLi (1.6 M in hexanes), tBuCtCH, (CH3)3SiCl, Et3SiH, NaCp
(2 M in THF), and PhCtCH were purchased from Aldrich. tBuCt
(45) Previous clusterization experiments of bis(acetylide)-substituted
ferrocenophanes using [Co2(CO)8] revealed that the products have a
tendency to spontaneously ring-open to give a silanol. See ref 27 for details.
(46) For preliminary results of the metal complexation experiments, see
ref 23.

Sila[1]ferrocenophanes with Multiple Alkyne Substituents
Organometallics, Vol. 26, No. 5, 2007 1223
CH was dried over 4 Å molecular sieves, and Et3SiH, (CH3)3SiCl,
and PhCtCH were distilled before use. [Co2(CO)8] was purchased
from STREM and sublimed immediately before use. Reactions
involving [Co2(CO)8] required ambient light to proceed. Karstedt’s
catalyst (platinum-divinyltetramethyldisiloxane complex, 2.1-2.4
wt % Pt in xylenes) was purchased from Gelest and used as
received. PtCl2 was purchased from Pressure Chemicals and used
as received. Compounds 1,37 4,37 and HCtCCtCPh47 were
synthesized according to literature procedures. Deprotonation of
-55.3; MS (EI, 70 eV) m/z (%) 374 (64); HRMS (EI, 70 eV) calcd
for C22H2456FeSi 374.115319, found 374.116033, fit 1.9 ppm; UV-
vis (25 °C, THF) λmax ) 482 nm, ꢀ ) 340 L‚mol-1‚cm-1
.
Attempted ROP of 2 Using Karstedt’s Catalyst. 2 (50 mg,
0.13 mmol) was dissolved in C6D6 (1 mL) in an NMR tube, and
Karstedt’s catalyst (5 µL) was added. The reaction was monitored
1
by H NMR spectroscopy and showed no changes after 3 h. The
1
solution was then heated at 50 °C for 21.5 h, and a H NMR
spectrum taken at this point confirmed there was no reaction.
When this reaction was repeated in the presence of Et3SiH (0.1
equiv), analysis of the mixture by 1H NMR spectroscopy after 5 h
at 25 °C showed 4% conversion to polymer.
Attempted ROP of 2 Using PtCl2. 2 (50 mg, 0.13 mmol) was
dissolved in toluene (1 mL) and a trace of PtCl2 was added. An
orange gel was obtained after 2.5 h of stirring. Addition of more
toluene failed to completely dissolve the gel.
n
HCtCCtCPh with BuLi in Et2O gave LiCtCCtCPh.
Most reactions and manipulations were performed under an
atmosphere of prepurified N2 using Schlenk techniques or in an
inert atmosphere glovebox. Unless specified as ACS grade, solvents
were dried using the Grubbs method48 or standard methods followed
by distillation. The air- and moisture-stable polymers 3 and 6 were
1
handled in air with ACS grade solvents after workup. H (400
MHz), 13C (100.5 MHz), and 29Si (79.4 MHz) NMR spectra were
recorded on a Varian Unity 400 spectrometer. 1H resonances were
referenced internally to the residual protonated solvent resonances.
13C resonances were referenced internally to the deuterated solvent
resonances, and 29Si resonances were referenced externally to TMS.
Molecular weights were determined by gel permeation chroma-
tography (GPC) using a Viscotek GPC MAX liquid chromatograph
equipped with a Viscotek triple detector array. The triple detector
array consists of a deflection refractometer, a four-capillary
differential viscometer, and a right angle laser light scattering
detector (λ0 ) 670 nm). Conventional calibration was used and
molecular weights were determined relative to polystyrene standards
purchased from American Polymer Standards. A flow rate of 1.0
mL/min was used with ACS grade THF as the eluent. Electron
impact (EI) mass spectra were recorded with a Micromass 70S-
250 mass spectrometer in electron impact mode. The calculated
isotopic distribution for each ion was in agreement with experi-
mental values. Elemental analyses were performed using a Perkin-
Elmer 2400 C/H/N analyzer. Ultraviolet-visible spectra were
recorded using a Perkin-Elmer Lambda 900 UV/vis/NIR spectrom-
eter. Photocontrolled polymerizations were carried out with a Philips
HPK 125 high-pressure mercury-arc lamp. A Pyrex filter was placed
inside the quartz immersion well to filter out wavelengths below
310 nm, and a thermostated water bath was used to maintain the
reaction temperature at 5 °C.
Synthesis of 2. nBuLi (1.6 M, 28.0 mL, 44.8 mmol) was added
dropwise to an Et2O solution (50 mL) of tBuCtCH (5.9 mL, 47.9
mmol) at 0 °C. The solution was kept at 0 °C for 60 min, and it
was added dropwise to a solution of 1 (6.02 g, 21.3 mmol) in Et2O
(200 mL) at -30 °C. The reaction mixture was allowed to warm
to 25 °C and was stirred for a further 2 h. (CH3)3SiCl (10 drops)
was added, and the orange suspension was stirred for 15 min. All
volatile materials were removed in vacuo, and the orange residue
was dried under vacuum overnight. Hexanes (5 × 75 mL) was then
added, and the red solution was filtered through a glass frit to
remove LiCl. The filtrate was concentrated in vacuo to give a red-
orange solid. Recrystallization in toluene/hexanes (4:1) gave 3.85
g of 2 as a red-orange powder. Repeated recrystallizations using
the same solvents gave highly purified 2, yield 1.65 g (21%). This
stringent purification protocol is necessary to obtain highly pure
monomer for photocontrolled ROP reactions. Crystals suitable for
X-ray crystallography were obtained from a toluene/hexanes (2:5)
solution at -35 °C.
Transition Metal-Catalyzed ROP of 2 Using PtCl2 in the
Presence of Et3SiH. 2 (201 mg, 0.54 mmol) was dissolved in
toluene (4 mL), and Et3SiH (4.3 µL, 0.027 mmol) was added. PtCl2
(7 mg, 0.024 mmol) was added, and the suspension was stirred for
5 h. The suspension became orange and slightly viscous. Precipita-
tion into rapidly stirred ACS grade MeOH (25 mL) gave a yellow
gummy solid. It was washed three times with ACS grade MeOH
and dried overnight under high vacuum, yield 85 mg (42%). GPC
analysis revealed a bimodal molecular weight distribution: peak
1, Mn > 106, 8%; peak 2, Mn ) 7.3 × 103, Mw ) 2.3 × 104,
PDI ) 3.11, 92%. The exact molecular weights of the two peaks
depend on the amount of PtCl2 and Et3SiH used. Et3SiH amounts
ranging from 0.05 to 0.5 molar equiv (with respect to 2) were tested,
but the molecular weight distribution remains bimodal.
Attempted Thermal ROP of 2 in Solution. 2 (203 mg, 0.54
mmol) was dissolved in xylenes (4 mL), and the solution was heated
1
at 160 °C. An aliquot was taken after 24 h, and analysis by H
NMR spectroscopy showed 20% conversion to polymer. When an
analogous reaction was performed using mesitylene as solvent and
heating at 175 °C, conversion of 30% was achieved after 24 h.
Attempted Thermal ROP of 2 in Bulk. 2 (196 mg, 0.52 mmol)
was sealed inside an evacuated Pyrex tube and heated at 185 °C
for 60 min until the molten solid was no longer free flowing. ACS
grade THF (2 mL) was used to extract soluble materials from the
solid, but a gel was formed. The soluble fraction was precipitated
into ACS grade MeOH (75 mL) to give a fine yellow powder.
Centrifugation of the suspension followed by drying under high
1
vacuum gave a light brown solid, yield 30 mg (15%). H NMR
analysis of the brown solid showed the presence of polymer. GPC
analysis of the brown solid revealed a trimodal distribution: peak
1, Mn > 106, 13%; peak 2, Mn ) 3.0 × 105, Mw ) 1.8 × 106,
PDI ) 5.91, 82%; peak 3, Mn ) 2.9 × 103, Mw ) 6.0 × 103,
PDI ) 2.04, 5%.
Attempted Ring-Opening of 2 Using a Stoichiometric Amount
n
of BuLi. 2 (100 mg, 0.27 mmol) was dissolved in THF (1 mL),
and the red solution was cooled to -78 °C for 10 min. nBuLi (0.17
mL of 1.6 M solution, 0.27 mmol) was added dropwise, and the
solution was allowed to warm to 25 °C. (CH3)3SiCl (0.1 mL) was
added to the brown solution, and the solution was concentrated to
dryness to give an oil. The 1H NMR spectrum of the residue showed
multiple broad resonances at δ 4.9-4.1, 1.8-0.8, and 0.4-0.1 ppm.
Photocontrolled ROP of 2 to Give PFS 3. In the absence of
light, 2 (100 mg, 0.27 mmol) was dissolved in THF (2 mL) in a
Schlenk tube, and NaCp (2 M, 6.7 µL, 0.014 mmol) was added
using a microsyringe. The solution was photolyzed at 5 °C for 1.5
h, and the color changed from dark red to orange. Five drops of
degassed, ACS grade MeOH was added, and the solution was stirred
for 5 min. The orange solution was precipitated into rapidly stirred
ACS grade MeOH (50 mL) to give a yellow, fluffy solid. Filtration
through a fritted glass funnel followed by drying under high vacuum
gave PFS 3 as a pale yellow solid, yield 80 mg (80%).
For 2: 1H NMR (400 MHz, C6D6, 25 °C) δ 4.41 (br m, 8 H,
Cp), 1.11 (s, 18 H, CH3); 13C{1H} NMR (100.5 MHz, C6D6, 25
°C) δ 118.7 (2 C, SiCtCtBu), 78.2 (4 C, Cp), 76.0 (2 C, SiCt
CtBu), 75.6 (4 C, Cp), 30.6 (6 C, C(CH3)3), 29.9 (2 C, ipso-Cp),
28.5 (2 C, C(CH3)3); 29Si{1H} NMR (79.4 MHz, C6D6, 25 °C) δ
(47) Kende, A. S.; Smith, C. A. J. Org. Chem. 1988, 53, 2655-2657.
(48) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518-1520.

1224 Organometallics, Vol. 26, No. 5, 2007
Chan et al.
For 3: 1H NMR (400 MHz, C6D6, 25 °C) δ 4.91 (br m, 4 H,
Cp), 4.67 (br m, 4 H, Cp), 1.23 (s, 18 H, CH3); 13C{1H} NMR
(100.5 MHz, C6D6, 25 °C) δ 116.6 (2 C, SiCtCtBu), 79.3 (2 C,
SiCtCtBu), 74.8 (4 C, Cp), 74.1 (4 C, Cp), 68.0 (ipso-Cp), 31.0
(6 C, C(CH3)3), 28.5 (2 C, C(CH3)3); 29Si{1H} NMR (79.4 MHz,
C6D6, 25 °C) δ -46.0; GPC Mn ) 9.6 × 103, Mw ) 1.1 × 104,
PDI ) 1.15; UV-vis (25 °C, THF) λmax ) 439 nm, ꢀ ) 185
Transition Metal-Catalyzed ROP of 5 Using PtCl2 to Give
PFS 6PtCl2. 5 (50 mg, 0.14 mmol) was dissolved in toluene (1 mL),
and Et3SiH (11 µL, 0.069 mmol) was added to the solution with a
microsyringe. A trace amount of PtCl2 was then added, and the
mixture was stirred for 2 h. The orange suspension was passed
through a 0.45 µm syringe filter to remove Pt, and the solution
was precipitated into dry hexanes (20 mL). An orange solid was
isolated and washed with a small amount of hexanes and then dried
overnight, yield 39 mg (78%).
L‚mol-1‚cm-1
.
The above procedure was also used in molecular weight control
experiments of PFS 3, with irradiation times specified in Table 3.
Synthesis of 5. LiCtCCtCPh (399 mg, 3.02 mmol) was
dissolved in Et2O (50 mL), and the solution was cooled to -35
°C. This was added dropwise to an Et2O solution (50 mL) of 4
(798 mg, 3.04 mmol) at -50 °C. The reaction mixture was allowed
to warm to 25 °C, and (CH3)3SiCl (5 drops) was added. The red
suspension was stirred for 20 min, and all volatile materials were
removed in vacuo. After drying under high vacuum for 2 h, the
orange residue was extracted with hexanes (4 × 30 mL) and filtered
through a glass frit to remove LiCl. The filtrate was concentrated
to dryness to give an orange solid, which was recrystallized twice
from toluene/hexanes (1:1) at -35 °C to give a red solid, yield
423 mg (40%). Crystals suitable for X-ray crystallography were
grown by slow evaporation of a hexanes solution at 25 °C.
For 5: 1H NMR (400 MHz, C6D6, 25 °C) δ 7.33-7.29 (m, 2 H,
ortho-Ph), 6.89-6.82 (m, 3 H, meta- and para-Ph), 4.41-4.37 (m,
4 H, Cp), 4.36-4.32 (m, 2 H, Cp), 3.84-3.81 (m, 2 H, Cp), 0.49
(s, 3 H, CH3); 13C{1H} NMR (100.5 MHz, C6D6, 25 °C) δ 133.0
(Ph), 129.7 (para-Ph), 128.6 (Ph), 121.3 (ipso-Ph), 90.5, 85.9, 78.5,
75.1 (CtCCtCPh), 78.34, 78.26, 76.6, 74.4 (Cp), 29.1 (ipso-Cp),
-3.4 (CH3); 29Si{1H} NMR (79.4 MHz, C6D6, 25 °C) δ -26.9;
MS (EI, 70 eV) m/z (%) 352 (100); HRMS (EI, 70 eV) calcd for
C21H1656FeSi 352.037068, found 352.038185, fit 3.2 ppm. Anal.
Calcd for C21H16FeSi: C, 71.65; H, 4.58. Found: C, 71.38; H, 4.82;
For 6PtCl2: )
1H NMR (400 MHz, C6D6, 25 °C) δ 7.33 (d, 3JHH
7.2 Hz, 2 H, ortho-Ph), 6.90-6.83 (m, 3 H, meta- and para-Ph),
4.50, 4.40, 4.29, 4.25 (br s, 8 H, Cp), 1.14-1.04 (m, CH3CH2 of
end group), 0.90-0.82 (m, CH3CH2 of end group), 0.75 (br s, 3 H,
Me); 13C{1H} NMR (100.5 MHz, C6D6, 25 °C) δ 133.0, 129.4
(para-Ph), 128.6 (Ph), 121.7 (ipso-Ph), 89.9, 89.7, 78.4, 75.5 (Ct
CCtCPh), 74.7, 74.6, 74.4, 74.3, 73.2, 73.1 (Cp), 68.3, 68.2 (ipso-
Cp), 8.1, 7.8 (CH3CH2 of end group), 5.0, 3.4 (CH3CH2 of end
group), -1.1 (Me); 29Si{1H} NMR (79.4 MHz, C6D6, 25 °C): δ
-22.1; GPC peak 1, Mn ) 3.8 × 106, Mw ) 6.9 × 106, PDI )
1.81, 15%; peak 2, Mn ) 4.0 × 104, Mw ) 1.2 × 105, PDI ) 3.05,
85%.
Attempted Thermal ROP of 5 in Solution. 5 (165 mg, 0.47
mmol) was dissolved in mesitylene (1 mL), and the solution was
heated at 180 °C. A solvent-swellable gel was obtained after 1 h.
This experiment was repeated with xylenes as solvent and heating
at 160 °C. After 1 h 10 min, an orange solution and an orange gel
were formed. Precipitation of the solution into ACS grade MeOH
gave orange fibers. An orange solid was obtained after drying under
high vacuum, yield 25 mg (15%). Its 1H NMR spectrum contained
peaks corresponding to PFS 6 only: 1H NMR (400 MHz, C6D6,
25 °C) δ 7.34 (br s, 2 H, ortho-Ph), 6.86 (br s, 3 H, meta- and
para-Ph), 4.50, 4.41, 4.30, 4.26 (br m, 8 H, Cp), 0.75 (s, 3 H, Me);
13C{1H} NMR (100.5 MHz, C6D6, 25 °C) δ 133.0 (Ph), 129.5
(para-Ph), 128.6 (Ph) 121.7 (ipso-Ph), 89.9, 89.7, 78.5, 75.5 (Ct
CCtCPh), 74.71, 74.67, 74.4, 74.3, 73.2, 73.1 (Cp), 69.32, 68.26
(ipso-Cp), -1.1 (CH3).
UV-vis (25 °C, THF): λmax ) 482 nm, ꢀ ) 300 L‚mol-1‚cm-1
.
Transition Metal-Catalyzed ROP of 5 Using Karstedt’s
Catalyst. 5 (50 mg, 0.14 mmol) was dissolved in toluene (1 mL),
and Et3SiH (11 µL, 0.069 mmol) and Karstedt’s catalyst (5 µL)
were sequentially added. The solution was stirred for 1 h 5 min,
and it became slightly viscous and dark orange. Precipitation into
dry hexanes gave a yellow powder, which were collected by
filtration. Drying under high vacuum gave PFS 6Karstedt’s as an
orange solid, yield 25 mg (50%).
Photocontrolled ROP of 5 to Give PFS 6PROP. In the absence
of light, 5 (99 mg, 0.28 mmol) was dissolved in THF (ca. 2 mL)
in a Schlenk tube. NaCp (2 M, 5.7 µL, 0.0114 mmol) was added,
and the red solution was photolyzed at 5 °C for 2 h. The solution
became orange and slightly viscous. Five drops of (CH3)3SiCl was
added to quench the polymerization, and precipitation into dry
hexanes (20 mL) gave PFS 6PROP as an orange, gummy solid, yield
86 mg (87%).
When this reaction was performed in the absence of Et3SiH, a
dark red solution was formed after 5.5 h with no increase in
1
viscosity. Analysis of the reaction mixture by H NMR and MS
For 6PROP: )
1H NMR (400 MHz, C6D6, 25 °C) δ 7.33 (d, 3JHH
showed the presence of PFS 6 and the possible formation of the
cyclic dimer of 5.49 Because the cyclic dimer of 5 could not be
separated from PFS 6, we were unable to obtain definitive
characterization data.
For cyclic dimer of 5: MS (EI, 70 eV) m/z (%) 704 (23), 84
(100).
For 6Karstedt’s:
1H NMR (400 MHz, C6D6, 25 °C) δ 7.34 (d, 3JHH
7.6 Hz, 2 H, ortho-Ph), 6.90-6.83 (m, 3 H, meta- and para-Ph),
4.50, 4.41, 4.30, 4.26 (br s, 8 H, Cp), 4.18 (br s, 5 H, Cp end group),
0.74 (s, 3 H, CH3), -0.01 (s, 9 H, Si(CH3)3 end group); 13C{1H}
NMR (100.5 MHz, C6D6, 25 °C) δ 133.0 (Ph), 129.4 (para-Ph),
128.6 (Ph) 121.7 (ipso-Ph), 89.9, 89.6, 78.4, 75.5 (CtCCtCPh),
74.8, 74.7, 74.4, 74.3, 73.2, 73.1 (Cp), 68.33, 68.27 (ipso-Cp), -0.9
(Si(CH3)3 end group), -1.1 (CH3); 29Si{1H} NMR (79.4 MHz,
C6D6, 25 °C) δ -22.1; GPC Mn ) 8.4 × 103, Mw ) 9.2 × 103,
PDI ) 1.10; UV-vis (25 °C, THF) λmax ) 445 nm, ꢀ ) 220
L‚mol-1‚cm-1
) 6.8 Hz, 2 H, ortho-Ph), 6.98-6.90 (m, 3 H, meta- and para-
Ph), 4.51, 4.41, 4.30, 4.26 (m, 8 H, Cp), 1.14-1.10 (CH3CH2 of
3
end group), 0.88 (t, JHH ) 6.8 Hz, CH3CH2 of end group), 0.75
(s, 3 H, CH3); 13C{1H} NMR (100.5 MHz, C6D6, 25 °C) δ 133.0
(Ph), 129.5 (para-Ph), 128.6 (Ph), 121.7 (ipso-Ph), 89.9, 89.7, 78.4,
75.5 (CtCCtCPh), 74.6, 74.4, 74.3, 73.2, 73.1 (Cp), 68.3, 68.2
(ipso-Cp), 8.2, 7.8 (CH3CH2 of end group), 5.0, 3.4 (CH3CH2 of
end group), -1.1 (CH3); 29Si{1H} NMR (79.4 MHz, C6D6, 25 °C)
δ -22.1 (poorly resolved pseudotriplet); GPC analysis showed a
bimodal distribution: peak 1, Mn ) 4.3 × 106, Mw ) 8.9 × 106,
PDI ) 2.05, 9%; peak 2, Mn ) 3.1 × 104, Mw ) 7.3 × 104, PDI
) 2.35, 91%.
Synthesis of 7. 5 (100 mg, 0.28 mmol) and [Co2(CO)8] (200
mg, 0.58 mmol) were dissolved in toluene (2 mL) to give a dark
brown solution. The solution was stirred at 25 °C for 2 h while
vented to an oil bubbler to release evolved CO. All volatile materials
were removed in vacuo to give a dark brown solid, which was
recrystallized from toluene/hexanes (1:2) to give dark brown
crystals, yield 160 mg (62%). Crystals suitable for X-ray crystal-
lography were obtained from the same recrystallization.
For 7: 1H NMR (400 MHz, C6D6, 25 °C) δ 7.72 (d, 3JHH ) 7.2
3
Hz, 2 H, ortho-Ph), 7.09 (t, JHH ) 7.2 Hz, 2 H, meta-Ph), 7.03-
(49) The formation of a cyclic dimer has been previously observed in
Karstedt’s-catalyzed ROP without Et3SiH, when a ferrocenophane with a
phenylacetylide substituent was polymerized in THF. See ref 26 for details.
6.96 (m, 1 H, para-Ph), 4.47, 4.40, 4.35, 3.91 (br m, 8 H, Cp),
0.72 (s, 3 H, CH3); 13C{1H} NMR (100.5 MHz, C6D6, 25 °C) δ

Sila[1]ferrocenophanes with Multiple Alkyne Substituents
Organometallics, Vol. 26, No. 5, 2007 1225
199.7, 199.1 (CO), 138.7, 129.4, 129.3, 129.2 (Ph), 125.6, 99.8,
93.5, 79.7 (C(Co2(CO)6)C-C(Co2(CO)6)CPh), 78.5, 78.2, 76.2, 76.0
(Cp), 33.2 (ipso-Cp), -0.2 (CH3); 29Si{1H} NMR (79.4 MHz, C6D6,
25 °C) δ -11.5; MS analysis was not possible, as the sample
decomposed in the spectrometer. Anal. Calcd for C36.5H20Co4FeO12-
Si‚0.5C7H8: C, 45.19; H, 2.08. Found: C, 45.05; H, 2.14.
X-ray Crystallography. Selected crystal, data collection, and
refinement parameters for 2, 5, and 7‚0.5C7H8 are given in Table
6. Single X-ray diffraction data were collected at 150(1) K using
a Nonius Kappa-CCD diffractometer and monochromated Mo KR
radiation (λ ) 0.71073 Å). The data were integrated and scaled
using the Denzo-SMN package.50 The SHELXTL/PC package was
used to solve and refine the structures.51 Refinement was by full-
matrix least-squares on F2 using all data (negative intensities
included). Hydrogen atoms were placed in calculated positions and
included in the refinement in riding motion approximations.
One of the tert-Bu groups in 2 was found to be positionally
disordered over two sites. Initial refinement showed that the two
components have equal occupancies, and the occupancies were fixed
at 50% in the final refinement cycles. For 7‚0.5C7H8, one molecule
of toluene was found to crystallize with two molecules of 7 in the
lattice.
CCDC-626572 (2), CCDC-626573 (5), and CCDC-626574 (7‚
0.5C7H8) contain the supplementary crystallographic data for this
paper. They can be obtained free of charge via the Internet at
www.ccdc.cam.ac.uk/conts/retrieving.html.
Acknowledgment. W.Y.C. thanks the Natural Sciences and
Engineering Research Council of Canada for a Canada Graduate
Scholarship and the Walter C. Sumner Foundation for a
fellowship. I.M. thanks the European Union for a Marie Curie
Chair and the Royal Society for a Wolfson Research Merit
Award.
Supporting Information Available: Supplementary crystal-
lographic data for 2, 5, and 7 in CIF format. This material is
available free of charge via the Internet at http://pubs.acs.org.
(50) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307-
326.
(51) Sheldrick, G. M. SHELXTL/PC V 5.1; Bruker Analytical X-ray
Systems: Madison, WI, 1997.
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