Synthesis, characterization, and the platinum-catalyzed ring-opening polymerization and stereoselective dimerization of silicon-bridged [1]ferrocenophanes with acetylenic substituents

Article abstract of DOI:10.1021/om0204078

Reaction of the lithium acetylides LiC≡CR (R = Ph, nBu) with the silicon-bridged [1]ferrocenophane Fe(η-C₅H₄)₂Si(Me)Cl (2a) at -78 °C was found to result in selective substitution of Cl, forming sila[1]ferrocenophanes with acetylenic substituents Fe(η-C₅H₄)₂-Si(Me)C≡CR (4, R = Ph; 5, R = nBu). A similar reaction of sila[1]ferrocenophane Fe(η-C₅H₄)₂SiCl₂ (2b) with 2 equiv of LiC≡CPh resulted in the substitution of both Cl atoms, forming Fe(η-C₅H₄)₂Si(C≡CPh)₂ (6). Transition metal-catalyzed ring-opening polymerization of monomers 4, 5, and 6 resulted in the formation of high molecular weight (M_n > 10⁴-10⁵) polyferrocenylsilanes with acetylenic substituents, [Fe(η-C₅H₄)₂Si(Me)C≡CR]_n (7, R = Ph; 8, R = nBu) and [Fe(η-C₅H₄)₂Si(C≡CPh)₂] _n (9), respectively. The cyclic dimer [Fe(η-C₅H₄)₂-Si(Me)C≡CPh]₂ (10) was isolated from the polymerization mixture derived from 4. The dimer was shown to exist in the cis configuration by single-crystal X-ray diffraction. Detailed studies on the polymerization of 4 have shown that the ratio of high polymer 7 to cyclic dimer 10 formed in the reaction is highly solvent and concentration dependent. Pyrolysis of polymers 7 and 8 during thermogravimetric analysis (TGA) studies have resulted in the formation of black magnetic ceramics in the highest yields found to date for uncrosslinked polyferrocenylsilane homopolymers (2 h, 900 °C; 7, 81%; 8, 61%).

Full text of DOI:10.1021/om0204078

Organometallics 2002, 21, 4415-4424
4415
Syn th esis, Ch a r a cter iza tion , a n d th e P la tin u m -Ca ta lyzed
Rin g-Op en in g P olym er iza tion a n d Ster eoselective
Dim er iza tion of Silicon -Br id ged [1]F er r ocen op h a n es
w ith Acetylen ic Su bstitu en ts
Andrea Berenbaum, Alan J . Lough, and Ian Manners*
Department of Chemistry, University of Toronto, 80 St. George Street,
Toronto, Ontario, Canada M5S 3H6
Received May 22, 2002
Reaction of the lithium acetylides LiCtCR (R ) Ph, nBu) with the silicon-bridged
[1]ferrocenophane Fe(η-C5H4)2Si(Me)Cl (2a ) at -78 °C was found to result in selective
substitution of Cl, forming sila[1]ferrocenophanes with acetylenic substituents Fe(η-C5H4)2-
Si(Me)CtCR (4, R ) Ph; 5, R ) nBu). A similar reaction of sila[1]ferrocenophane Fe(η-
C5H4)2SiCl2 (2b) with 2 equiv of LiCtCPh resulted in the substitution of both Cl atoms,
forming Fe(η-C5H4)2Si(CtCPh)2 (6). Transition metal-catalyzed ring-opening polymerization
of monomers 4, 5, and 6 resulted in the formation of high molecular weight (Mn > 104-105)
polyferrocenylsilanes with acetylenic substituents, [Fe(η-C5H4)2Si(Me)CtCR]n (7, R ) Ph;
8, R ) nBu) and [Fe(η-C5H4)2Si(CtCPh)2]n (9), respectively. The cyclic dimer [Fe(η-C5H4)2-
Si(Me)CtCPh]2 (10) was isolated from the polymerization mixture derived from 4. The dimer
was shown to exist in the cis configuration by single-crystal X-ray diffraction. Detailed studies
on the polymerization of 4 have shown that the ratio of high polymer 7 to cyclic dimer 10
formed in the reaction is highly solvent and concentration dependent. Pyrolysis of polymers
7 and 8 during thermogravimetric analysis (TGA) studies have resulted in the formation of
black magnetic ceramics in the highest yields found to date for uncrosslinked polyferroce-
nylsilane homopolymers (2 h, 900 °C; 7, 81%; 8, 61%).
In tr od u ction
Metal-containing polymers are of considerable inter-
est, as such materials offer potential access to useful
redox, magnetic, optical, preceramic, or catalytic proper-
ties1 and functional supramolecular structures.2 One
class of metallopolymers, the polyferrocenylsilanes (PFSs)
(1), have been synthesized via the ring-opening polym-
erization (ROP) of strained silicon-bridged [1]ferro-
cenophane monomers (2)3 using thermal,4 anionic,5 and
transition metal-catalyzed6 methodologies.7,8
(1) See, for example: (a) Archer, R. D. Inorganic and Organometallic
Polymers; Wiley-VCH: New York, 2001. (b) Nguyen, P.; Go´mez-Elipe,
P.; Manners, I. Chem. Rev. 1999, 99, 1515. (c) Kingsborough, R. P.;
Swager, T. M. Prog. Inorg. Chem. 1999, 48, 123. (d) Manners, I. Science
2001, 294, 1664.
(2) See: (a) Massey, J . A.; Winnik, M. A.; Manners, I.; Chan, V. Z.-
H.; Ostermann, J . M.; Enchelmaier, R.; Spatz, J . P.; Mo¨ller, M. J . Am.
Chem. Soc. 2001, 123, 3147. (b) Steffen, W.; Kohler, B.; Altmann, M.;
Scherf, U.; Stitzer, K.; zur Loye, H. C.; Bunz, U. H. F. Chem. Eur. J .
2001, 7, 117. (c) Park, C. M.; McAlvin, J . E.; Fraser, C. L.; Thomas, E.
L. Chem. Mater. 2002, 14, 1225. (d) Gohy, J .-F.; Lohmeijer, B. G. G.;
Platinum-catalyzed ROP of sila[1]ferrocenophanes
remains the most convenient route to polyferrocenylsi-
lanes found to date.6,9 The high temperatures utilized
in thermal ROP make it undesirable for thermally
sensitive substituents. Furthermore, a method of mo-
lecular weight control has yet to be found for the
Schubert, U. S. Macromolecules 2002, 35, 4560.
(3) The first sila[1]ferrocenophane 2 (R ) R′ ) Ph) was synthesized
by Osborne and co-workers, see: (a) Osborne, A. G.; Whiteley, R. H.
J . Organomet. Chem. 1975, 101, C27, (b) Stoeckli-Evans, H.; Osborne,
A. G.; Whiteley, R. H. Helv. Chim. Acta 1976, 59, 2402.
(4) Foucher, D. A.; Tang, B.-Z.; Manners, I. J . Am. Chem. Soc. 1992,
114, 6246.
(5) (a) Ni, Y.; Rulkens, R.; Manners, I. J . Am. Chem. Soc. 1996, 118,
4102. (b) Rulkens, R.; Lough, A. J .; Manners, I. J . Am. Chem. Soc.
1994, 116, 797.
(7) (a) Manners, I. Chem. Commun. 1999, 857. (b) A range of other
[1]ferrocenophanes with different bridging elements have been pre-
pared that also undergo ROP. See: Manners, I. Can. J . Chem. 1998,
76, 371.
(6) (a) Ni, Y.; Rulkens, R.; Pudelski, J . K.; Manners, I. Macromol.
Rapid Commun. 1995, 16, 637. (b) Reddy, N. P.; Yamashita, H.;
Tanaka, M. Chem. Commun. 1995, 22, 2263.
10.1021/om0204078 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 09/19/2002

4416 Organometallics, Vol. 21, No. 21, 2002
Berenbaum et al.
Sch em e 1. Rea ction of 2a or 2b w ith Li[CtCR]; Syn th esis of 4 (R ) P h , R′ ) Me), 5 (R ) n Bu , R′ ) Me),
a n d 6 (R ) P h , R′ ) CtCP h )
thermal ROP of sila[1]ferrocenophanes. Although ex-
tremely narrow polydispersities, molecular weight con-
trol, and access to interesting architectures such as
block copolymers are all benefits of utilizing anionic-
initiated ROP of sila[1]ferrocenophanes, the stringent
monomer and solvent purity requirements make this
method challenging to use.5 On the other hand, transi-
tion metal-catalyzed ROP of sila[1]ferrocenophanes can
be performed on a large scale using only reasonably pure
monomer to give high yields of high molecular weight
(Mn > 105) polymer with reasonable polydispersity
indices (commonly 1.5-1.9).6,9,10 Additionally, the mo-
lecular weight of the polyferrocenylsilane can be con-
trolled by the addition of a species containing an Si-H
functionality which can then “compete” with molecules
of 2 for addition to the growing polymer chain, resulting
in “capped” polyferrocenylsilanes, 3.10 Addition of si-
lanes of differing reactivity has been found to lead to
molecular weight control plots of differing slope.11 Using
silanes of differing architecture, block,12 star,10 and
heteroatom-containing13 polymers have also been pre-
pared.
sila[1]ferrocenophanes with acetylenic substituents.
Such species are of interest as precursors to polyferro-
cenylsilane homopolymers with high ceramic yields as
a result of potentially efficient, thermally induced cross-
linking chemistry. In addition, complexation of the
acetylenic groups offers opportunities for further metal-
lization of the ring-opened polymers.16
Resu lts a n d Discu ssion
Recent developments on the substitution chemistry
of sila[1]ferrocenophanes with Si-Cl bonds (e.g., 2a )
with organic nucleophiles14 have allowed for the selec-
tive synthesis of sila[1]ferrocenophanes with a wide
range of functionality not available by other methods.17
We therefore decided to undertake the synthesis of sila-
[1]ferrocenophanes with acetylenic substituents through
the reaction of Si-Cl bonds with lithium acetylides.
Syn th esis a n d Ch a r a cter iza tion of Acetylid e-
Su bstitu ted Sila [1]fer r ocen op h a n es 4-6. The ad-
dition of an ether solution of Li[CtCPh] to a solution
of 2a in the same solvent at low temperature (-78 °C)
was found to result in selective substitution of the Cl
atom for a phenylacetylene group with formation of LiCl
(Scheme 1) upon warming to 25 °C. After workup, the
desired product 4 was obtained as a red crystalline solid
in good (65%) yield after recrystallization from hexanes/
toluene (ca. 50:50) at -30 °C.
The 1H NMR spectrum was consistent with the
assigned structure. Four separate resonances were
observed in the Cp region (δ ) 4.51, 4.44, 4.40, and 3.91
ppm), which is characteristic of unsymmetrically sub-
stituted [1]ferrocenophanes. The resonance for the
methyl group was observed at a chemical shift of δ )
0.61 ppm (cf. 2a δ ) 0.52 ppm).18 A single resonance
was observed in the 29Si NMR spectrum at a chemical
We have recently been studying the preparation of
functional polyferrocenylsilanes.14,15 We now report
details of the synthesis and polymerization behavior of
(8) For the recent work of other groups on [1]ferrocenophanes and
the synthesis of ring-opened polyferrocenes, see, for example: (a)
Brandt, P. F.; Rauchfuss, T. B. J . Am. Chem. Soc. 1992, 114, 1926. (b)
Stanton, C. E.; Lee, T. R.; Grubbs, R. H.; Lewis, N. S.; Pudelski, J . K.;
Callstrom, M. R.; Erickson, M. S.; McLaughlin, M. L. Macromolecules
1995, 28, 8713. (c) Mizuta, T.; Onishi, M.; Miyoshi, K. Organometallics
2000, 19, 5005. (d) Compton, D. L.; Brandt, P. F.; Rauchfuss, T. B.;
Rosenbaum, D. F.; Zukoski, C. F. Chem. Mater. 1995, 7, 2342. (e) Heo,
R. W.; Somoza, F. B.; Lee, T. R. J . Am. Chem. Soc. 1998, 120, 1621. (f)
Brunner, H.; Klankermayer, J .; Zabel, M. J . Organomet. Chem. 2000,
601, 211. (g) Herberhold, M.; Hertel, F.; Milius, W.; Wrackmeyer, B.
J . Organomet. Chem. 1999, 582, 352. (h) Antipin, M. Y.; Vorontsov, I.
I.; Dubovik, I. I.; Papkov, V.; Cervantes-Lee, F.; Pannell, K. H. Can.
J . Chem. 2000, 78, 1511. (i) Calleja, G.; Carre´, F.; Cerveau, G.; Labbe´,
P.; Coche-Gue´rente, L. Organometallics 2001, 20, 4211. (j) Papkov, V.
S.; Gerasimov, M. V.; Dubovik, I. I.; Sharma, S.; Dementiev, V. V.;
Pannell, K. H. Macromolecules 2000, 33, 7107. (k) Espada, L.;
Shadaram, M.; Robillard, J .; Pannell, K. H. J . Inorg. Organomet.
Polym. 2000, 10, 169. (l) Barlow, S.; Rohl, A. L.; Shi, S.; Freeman, C.
M.; O’Hare, D. J . Am. Chem. Soc. 1996, 118, 7578. (m) Sun, Q.; Lam,
J . W. Y.; Xu, K.; Xu, H.; Cha, J . A. K.; Wong, P. C. L.; Wen, G.; Zhang,
X.; J ing, X.; Wang, F.; Tang, B.-Z. Chem. Mater. 2000, 12, 2617.
(9) Temple, K.; J a¨kle, F.; Sheridan, J . B.; Manners, I. J . Am.Chem.
Soc. 2001, 123, 1355.
(14) (a) J a¨kle, F.; Vejzovic, E.; Power-Billard, K. N.; MacLachlan,
M. J .; Lough, A. J .; Manners, I. Organometallics 2000, 19, 2826. (b)
Ginzburg, M.; Galloro, J .; J a¨kle, F.; Power-Billard, K. N.; Yang, S. M.;
Sokolov, I.; Lam, C. N. C.; Neumann, A. W.; Manners, I.; Ozin, G. A.
Langmuir 2000, 16, 9609.
(15) (a) Power-Billard, K. N.; Manners, I. Macromolecules 2000, 33,
26. (b) J a¨kle, F.; Wang, Z.; Manners, I. Macromol. Rapid Commun.
2000, 21, 1291.
(10) Go´mez-Elipe, P.; Resendes, R.; Macdonald, P. M.; Manners, I.
J . Am. Chem. Soc. 1998, 120, 8348.
(11) Bartole, A.; Resendes, R.; Manners, I. Manuscript in prepara-
tion.
(12) (a) Resendes, R.; Massey, J . A.; Dorn, H.; Power, K. N.; Winnik,
M. A.; Manners, I. Angew. Chem., Int. Ed. 1999, 38, 2570. (b) Resendes,
R.; Massey, J . A.; Dorn, H.; Winnik, M. A.; Manners, I. Macromolecules
2000, 33, 8.
(13) J a¨kle, F.; Berenbaum, A.; Lough, A. J .; Manners, I. Chem. Eur.
J . 2000, 6, 2762.
(16) Berenbaum, A.; Ginzburg, M.; Coombs, N.; Lough, A. J .; Safa-
Sefat, A.; Greedan, J . E.; Ozin, G. A.; Manners, I. Unpublished results.
(17) The variety of sila[1]ferrocenophane functionality was previ-
ously restricted to that accessible via alkoxy, aryloxy, or amino
substitution of Si-Cl bonds, see: Nguyen, P.; Stojcevic, G.; Kulbaba,
K.; MacLachlan, M. J .; Liu, X. H.; Lough, A. J .; Manners, I. Macro-
molecules 1998, 31, 5977.
(18) Zechel, D. L.; Hultzsch, K. C.; Rulkens, R.; Balaishis, D.; Ni,
Y.; Pudelski, J . K.; Lough, A. J .; Manners, I.; Foucher, D. A. Organo-
metallics 1996, 15, 1972.

Silicon-Bridged [1]Ferrocenophanes
Organometallics, Vol. 21, No. 21, 2002 4417
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 4
Si(1)-C(1)
Si(1)-C(6)
Si(1)-C(12)
C(12)-C(13)
1.880(3)
1.878(3)
1.834(3)
1.197(4)
C(13)-C(14)
1.440(4)
Si(1)-C(12)-C(13)
C(12)-C(13)-C(14)
R
172.4(3)
177.7(3)
20.53(14)
Fe(1)-Si(1)
2.6917(9)
96.50(13)
112.35(14)
C(1)-Si(1)-C(6)
C(11)-Si(1)-C(12)
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 6
Si(1)-C(1)
Si(1)-C(6)
Si(1)-C(11)
Si(1)-C(19)
C(11)-C(19)
1.869(2)
1.870(2)
1.827(2)
1.822(2)
3.03a
C(12)-C(20)
5.11a
Si(1)-C(19)-C(20)
C(11)-C(12)-C(13)
C(19)-C(20)-C(21)
R
174.92(18)
178.8(2)
178.0(2)
Fe(1)-Si(1)
2.6408(6)
99.00(6)
112.36(9)
172.98(18)
C(1)-Si(1)-C(6)
C(11)-Si(1)-C(19)
Si(1)-C(11)-C(12)
19.23(12)
a
Nonbonding distance.
F igu r e 1. Molecular structure of 4 (thermal ellipsoids at
30% probability, hydrogen atoms have been removed for
clarity).
F igu r e 2. Molecular structure of 6 (thermal ellipsoids at
30% probability, hydrogen atoms have been removed for
clarity).
shift of -27.8 ppm (cf. 2a δ ) 5.75 ppm).18 To further
explore the structure of 4, a single-crystal X-ray dif-
fraction study was performed. The molecular structure
of 4 is shown in Figure 1, and selected bond lengths and
angles are given in Table 1.
The tilt-angle between the Cp rings of 4 (R) was found
to be 20.53(14)°, which is within the normal range found
for sila[1]ferrocenophanes (16-21°).19 The Fe-Si dis-
tance of 2.6917(9) Å was also within the range of values
obtained previously (ca. 2.55-2.75 Å). The acetylene
moiety was observed to possess a slightly nonlinear
geometry. The Si(1)-C(12)-C(13) angle was found to
be 172.4(3)°, and the C(12)-C(13)-C(14) angle was
177.7(3)°.
The hexynyl-substituted sila[1]ferrocenophane 5 was
isolated as a red crystalline solid in moderate (48%)
yield from the analogous low-temperature reaction of
Li[CtC(CH2)3CH3] with 2a . The yield could be in-
creased by further concentration of the supernatant and
subsequent crystallization at -55 °C and was only a
reflection of the dramatically increased solubility of 5
over 4. Multinuclear NMR, MS, and EA were used to
confirm the assigned structure.
6, which is consistent with a symmetrical structure. A
single resonance was observed in the 29Si NMR spec-
trum at a chemical shift of -54.2 ppm. To further
characterize the structure of 6, a single-crystal X-ray
diffraction study was performed. The molecular struc-
ture of 6 is shown in Figure 2, and selected bond lengths
and angles are given in Table 2.
The tilt-angle, R, in 6 was found to be 19.23(12)°,
which is slightly smaller than that found for 4 (20.53-
(14)°). Additionally, the Fe-Si distance was determined
to be slightly shorter (for 4, 2.6917(9) Å; for 6, 2.6408-
(6) Å). The C(11)-Si(1)-C(19) angle was found to be
112.36(9)°. The nonbonding distance between the cen-
troids of the acetylene substituents was found to be
4.07 Å.
Tr a n sition Meta l-Ca ta lyzed Rin g-Op en in g P o-
lym er iza tion of 4 a n d 5; Syn th esis of P olyfer r oce-
n ylsila n es 7 a n d 8 w ith Acetylen ic Sid e Gr ou p s.
The presence of acetylenic functionalities might be
expected to hinder the metal-catalyzed ROP of [1]-
ferrocenophanes due to strong coordination to catalyti-
cally active species, or side reactions.20 However, we
found that acetylide-substituted sila[1]ferrocenophane
4 was readily polymerized in toluene solution via the
addition of a solution of platinum-divinyltetramethyl-
disiloxane complex in xylene, hereafter referred to as
the “Pt0 catalyst” (ca. 0.3 mol % Pt). The reaction
mixture was observed to gradually change color from
red to deep orange and was allowed to stir for ca. 16 h.
The polymerization mixture was precipitated into rap-
idly stirred methanol and was washed multiple times
with hexanes (to remove low molecular weight species).
After workup, the air- and moisture-stable 7 was
obtained in high yield (93%) (Scheme 2). Analysis by
gel permeation chromatography (GPC) of the light
The addition of 2 equiv of the lithium salt of phenyl-
acetylene to a solution of 2b in ether at low temperature
was also performed (Scheme 1). This was found to result
in the substitution of each of the Cl atoms for a
phenylacetylene moiety, the first example of successful
nucleophilic disubstitution of 2b. After workup, the
desired product, 6, was isolated as a red crystalline solid
in moderate (47%) yield from a dichloromethane/hex-
1
anes (25:75) solution at -30 °C. The H NMR spectrum
was in agreement with the assigned structure. In
contrast to the cases of 4 and 5, only two resonances
were observed in the Cp region (δ ) 4.49, 4.43 ppm) of
(19) (a) Pudelski, J . K.; Foucher, D. A.; Honeyman, C. H.; Lough,
A. J .; Manners, I.; Barlow, S.; O’Hare, D. Organometallics 1995, 14,
2470. (b) Barlow, S.; Drewitt, M. J .; Dijkstra, T.; Green, J . C.; O’Hare,
D.; Whittingham, C.; Wynn, H. H.; Gates, D. P.; Manners, I.; Nelson,
J . M.; Pudelski, J . K. Organometallics 1998, 17, 2113.
(20) Pt-catalyzed insertion of alkynes into the strained Si-Cp bond
of sila[1]ferrocenophanes has been reported. See: Sheridan, J . B.;
Temple, K.; Lough, A. J .; Manners, I. J . Chem. Soc., Dalton Trans.
1997, 711.

4418 Organometallics, Vol. 21, No. 21, 2002
Berenbaum et al.
Sch em e 2. P olym er iza tion of 4-6 w ith a P t0
Ca ta lyst; Syn th esis of P olyfer r ocen ylsila n es 7-9
fully resolved into individual signals. The 29Si NMR
spectrum was also consistent with the formation of an
atactic polymer. Three poorly resolved signals in a 1:2:1
intensity ratio characteristic of triad resolution were
observed at a chemical shift centered at δ ) -25.2 ppm.
This polymer has previously been prepared from the
reaction of Li[CtC(CH2)3CH3] with the Si-Cl function-
alities on the backbone of polymer 1 (R ) Me, R′ ) Cl)
synthesized via the thermal ROP of 2a .18 NMR spectral
data for the polymers were very similar for the two
methods of preparation. However, the major difference
between the two methods was in the molecular weight
(8: Mn ) 1.2 × 106; substitution onto 2a , Mn ) 5.0 ×
104) and PDI (8: 1.6; substitution onto 1 (R ) Me, R′ )
Cl), 2.6). The higher molecular weight and lower PDI
achieved in this study clearly show the advantages of
this new route over the previously reported synthesis
of 8 from substitution onto PFS 1 (R ) Me, R′ ) Cl).
Tr a n sition Meta l-Ca ta lyzed P olym er iza tion of 6;
Syn th esis of P olyfer r ocen ylsila n e 9 w ith Tw o
Acetylen ic F u n ction a lities a t Silicon . The polym-
erization of bis(phenylacetylenyl)sila[1]ferrocenophane
6 was also explored. Analogous to the previous polym-
erization studies, a solution of Pt0 catalyst in xylene (ca.
0.3 mol % Pt) was added to a stirred C6D6 solution of 6,
that was then stirred for a further ca. 20 h. Ring-opened
polymer 9 was isolated after workup as a light orange
fibrous material in good yield (86%) (Scheme 2).
orange polymer 7 gave a value for the Mn of 1.64 × 105
Da and a PDI of 1.6.21
The multinuclear NMR data were consistent with the
formation of 9. Only two signals were observed in the
Cp region (δ ) 4.93, 4.79 ppm), as is typical for
symmetrically substituted polyferrocenylsilanes. The
29Si NMR spectrum showed a single resonance at a
chemical shift of δ ) -44.3 ppm (cf. monomer 6, δ )
-54.2 ppm). In addition, GPC measurements showed
that 9 was of high molecular weight (Mn ) 7.68 × 104,
PDI ) 1.5) but significantly lower than that of polymers
7 and 8.
The multinuclear NMR data were consistent with the
formation of an atactic polymer. Five separate reso-
nances were observed in the Cp region of the H NMR
1
spectrum (δ ) 4.56-4.34 ppm). The 13C NMR spectrum
showed a complicated pattern of resonances in the Cp
region (δ ) 74.8-73.0 ppm) as well as a set of signals
in a 1:2:1 intensity pattern due to triad resolution for
the Si-Me resonance at ca. δ ) -0.6 ppm. The 29Si NMR
spectrum was also consistent with the formation of an
atactic polymer.22 A poorly resolved (even after 25 840
repetitions of a DEPT pulse sequence) but recognizable
three signals in a 1:2:1 ratio due to triad resolution were
detected centered at δ ) -23.8 ppm.
Isolation of Cyclic Dim er 10 For m ed as a Bypr od-
u ct fr om th e ROP of 4. Interestingly, when the
polymerization of 4 was conducted in THF instead of
toluene, a red crystalline material, 10, was isolated from
the supernatant after precipitation of the polymer into
hexanes. The 1H NMR spectrum showed four multiplets
in the Cp region (10, δ ) 4.90, 4.47, 4.33, 4.24 ppm; cf.
4, δ ) 4.51, 4.44, 4.40, 3.91 ppm). The resonance
corresponding to the Si-Me group was observed at a
chemical shift of δ ) 0.75 ppm, which is downfield
shifted from that of the monomer 4 (δ ) 0.61 ppm) and
only slightly upfield from that of the high polymer 7
(δ ) 0.81 ppm). The 29Si NMR spectrum showed a single
resonance at a chemical shift of δ ) -24.3 ppm, which
is again downfield shifted from that of the monomer 4
(δ ) -27.8 ppm) and only slightly upfield from the
chemical shift of the silicon atoms in the backbone of
the polymer 7 (δ ) -23.8 ppm). The EI mass spectrum
of the material showed a peak at 656 amu, which
corresponds to a M+ ion for a cyclic dimer structure.
Analogous to the synthesis of 7, a solution of the Pt0
catalyst in xylene (ca. 0.3 mol % Pt) was added to a
stirred toluene solution of 5. The solution was again
observed to gradually change color from red to deep
orange, and the light orange fibrous material isolated
was dried under high vacuum to give the air-stable
polyferrocene 8 in good yield (67%) (Scheme 2). Analysis
by GPC gave a value for the Mn of 1.21 × 106 and a
PDI of 1.6.
The multinuclear NMR data were again consistent
with the formation of an atactic polymer. Five separate
resonances were observed in the Cp region of the 1H
NMR spectrum (δ ) 4.56-4.32 ppm). The 13C NMR
spectrum showed multiple resonances in the Cp region
(δ ) 74.5-72.8 ppm) as well as the expected resonances
corresponding to the hexynyl substituent. A resonance
at δ ) -0.2 ppm for the methyl group on silicon was
observed. Due to the atactic nature of the polymer, this
signal did not appear as a singlet; however it was not
To confirm the nature of the product, a single-crystal
X-ray diffraction study was performed on crystals
isolated from slow evaporation of a saturated hexanes
solution of 10. See Figure 3a for the molecular structure
of 10 and Table 3 for selected bond lengths and angles.
(21) See the Experimental Section for details on the GPC procedure.
(22) Temple, K.; Massey, J . A.; Chen, Z. H.; Vaidya, N.; Berenbaum,
A.; Foster, M. D.; Manners, I. J . Inorg. Organomet. Polym. 1999, 9,
189.

Silicon-Bridged [1]Ferrocenophanes
Organometallics, Vol. 21, No. 21, 2002 4419
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 10
Si(1)-C(1)
Si(2)-C(6)
Si(1)-C(11)
Si(2)-C(16)
C(22)-C(23)
C(31)-C(32)
1.845(3)
1.848(3)
1.848(3)
1.851(3)
1.203(4)
1.203(4)
C(1)-Si(1)-C(11)
C(6)-Si(2)-C(16)
C(21)-Si(1)-C(22)
C(30)-Si(2)-C(31)
Si(1)-C(22)-C(23)
Si(2)-C(31)-C(32)
116.18(13)
112.32(13)
107.96(15)
107.07(14)
173.1(3)
C(22)-C(23)-C(24)
176.7(3)
177.8(3)
-10.3(3)
1.7(2)
C(31)-C(32)-C(33)
R1
R2
176.4(3)
Ta ble 4. Su m m a r y of th e Resu lts Obta in ed for th e
P olym er iza tion of 4 in Tolu en e, CH2Cl2, a n d THF
solvent
Mn
Mw
(volume)a
polymer:dimerb (Da × 105)c (Da × 105)c PDIc
toluene (1 mL)
toluene (2 mL)
CH2Cl2 (1 mL)
THF (1 mL)
THF (4.5 mL)
THF (20 mL)
11.3:1
9.9:1
9.9:1
5.9:1
1.9:1
0.7:1
3.40
4.00
3.27
2.74
1.79
1.43
6.04
6.58
5.41
4.68
3.08
2.32
1.8
1.7
1.7
1.7
1.8
1.6
a
b
Volume/50 mg of 4. Obtained from an average of the values
obtained from integration of both the Me and Ph 1H NMR signals
arising from 7 and 10 in reaction mixtures of the polymerization
of 4. c Obtained from GPC analysis of isolated 7.
the molecule in the anti-conformation (i.e., that in which
the ring resembles the chair conformation of cyclohex-
ane). A similar dimer (11) has been reported in the
reaction mixture when 2 (R ) R′ ) Me) has been
polymerized via metal-catalyzed ROP.6a The X-ray
structure of 11 was obtained after synthesis by a
separate route.23 The Si-Cipso distances in 10 (av ) 1.85
Å) are slightly but significantly shorter than the corre-
sponding distances in 4 (av ) 1.88 Å). The Cipso-Si-
Cipso angles in 10 of 116.18(13)° and 112.32(13)° are
substantially more obtuse than the corresponding angle
in 4 (96.50(13)°), indicating a loss of ring strain in the
transition from monomer to cyclic dimer. Of particular
interest is the fact that there is significant tilting of the
Cp rings of 10 in the solid state structure. One of the
ferrocene units (containing Fe2) possesses virtually
planar rings (ring tilt ) 1.7(2)°), and the other (contain-
ing Fe1) has a ring tilt of 10.3(3)° in the manner opposite
that found in [1]ferrocenophanes (see Figure 3b). The
dimethyl analogue 11 shows a symmetric ring tilt of 4.9-
(3)° in the manner opposite that found in [1]ferro-
cenophanes.23 The unsymmetrical tilting found in the
solid state structure of 10 is then most likely due to a
factor other than the conformational requirements of
the ring. Also of note are the torsional angles indicating
the twisting of the Cp rings within each ferrocene unit.
For the ferrocene moiety with an R angle of 1.7° the Cp
rings were measured to be rotated 76.2° with respect
to each other. The Cp rings of the other ferrocene unit
were rotated by 34.5° with respect to each other. This
is also in contrast to dimer 11, which displays torsional
angles of only 13.2(5)°.23 The most likely cause of this
structural distortion in 10 lies in the preference of the
phenylacetylene moieties to pack efficiently in the solid
state, so that they are aligned down the a axis (see
Figure 3c).
F igu r e 3. (a) Molecular structure of 10 (thermal ellipsoids
at 30% probability, hydrogen atoms have been removed for
clarity). (b) The ferrocene unit (left) showing a ring tilt of
-10.3(3)° (thermal ellipsoids at 30% probability, substit-
uents on silicon and hydrogen atoms removed for clarity).
(c) Cell-packing diagram for 10 down the a axis (thermal
ellipsoids at 10% probability, hydrogen atoms have been
removed for clarity).
As the initial results for the polymerization of 4 were
intriguing, especially with respect to the fact that only
(23) (a) Zechel, D. L.; Foucher, D. A.; Pudelski, J . K.; Yap, G. P. A.;
Rheingold, A. L.; Manners, I. J . Chem. Soc., Dalton Trans. 1995, 1893.
(b) The structure of 11 was reported independently by an alternate
route, see: Park, J .; Seo, Y.; Cho, S.; Whang, D.; Kim, K.; Chang, T. J .
Organomet. Chem. 1995, 489, 23. The analogue with bridging SiCl2
groups has also been structurally characterized and shown to possess
a small symmetric ring tilt of 3.5°. See ref 8i.
The X-ray data confirmed the molecular structure of
10 to be a cyclic dimer existing in the conformation
where the substituents on Si are in a cis orientation and

4420 Organometallics, Vol. 21, No. 21, 2002
Berenbaum et al.
component of the reaction mixture was the cis form of
cyclic dimer 10 (ca. 44% yield). Importantly, no other
1
species were detectable in either the H or 29Si NMR
spectrum.24 Since no signals within the NMR detection
limit assignable to the trans form of cyclic dimer 10 were
observed under any experimental conditions studied, we
conclude that the dimerization is highly stereoselective,
strongly favoring the cis form.
Deta iled Stu d ies of th e ROP of 6; In flu en ce of
th e P r esen ce of Tw o P h en yl Acetylen e Su bstitu -
en ts. As high polymer 7 was shown to be atactic, the
only step that appears to proceed with stereoselectivity
in the polymerization of 4 is the formation of the cyclic
dimer, 10. It is likely that the geometry of an intermedi-
ate or transition state highly favors addition of a
molecule of 4 in one particular orientation due to the
steric asymmetry of its substituents: the long rigid
phenyl acetylene group and the small, approximately
spherical methyl group. If the second addition of a
molecule of 4 to the site for the initiated polymer chain
(presumably at the surface of a Pt colloid)9 is less
favorable in the trans configuration for steric reasons,
then the polymerization of 6 should proceed much less
efficiently than the polymerization of 4, as two long rigid
phenyl acetylene substituents are present. We therefore
examined the ROP of 6 in further detail to evaluate any
evidence for such behavior.
the cis form of cyclic dimer 10 was isolated, we decided
to investigate this reaction further. Emphasis was
placed on determining if the dimer was formed stereo-
selectively (or if the isolation of the cis form was due to
differential crystallization) and if there was indeed a
solvent and concentration effect on the ratio of dimer
10 to polymer 7.
(i) P olym er iza tion of 6 in Tolu en e a n d THF . To
allow a quantitative comparison of the ROP behavior
of 6 with that of 4, a polymerization study was per-
formed under conditions identical to that previously
used for the latter in toluene (Table 4, entry 2). After
Deta iled Stu d ies of th e ROP of 4: In flu en ce of
Solven t a n d Con cen tr a tion on th e Ra tio of High
P olym er 7 to Cyclic Dim er 10. We first decided to
explore the influence of the nature of solvent on the ratio
of high polymer 7 to cyclic dimer 10 and the molecular
weight of the isolated polymer 7. A series of polymeriza-
tions (2-3 per solvent) were set up using a constant
ratio of monomer 4, solvent volume, and catalyst. The
solvents selected were toluene, CH2Cl2, and THF. The
results of this study are summarized in Table 4.
The results of this study clearly show that the product
distribution arising from 7 is highly solvent dependent.
The levels of cyclic dimer 10 are highest when the
polymerization is conducted in THF, which is presum-
ably why this red crystalline material was not observed
to form from the supernatants of the precipitation steps
of the initial studies of the polymerization carried out
in toluene. The molecular weight of the isolated polymer
7 was not significantly different (within GPC error, ca.
10%) for polymerizations conducted in toluene and
CH2Cl2; however, in the case of THF, significantly lower
molecular weight material was isolated.
The transition metal-catalyzed ROP of 4 was also
conducted at two concentrations in toluene and three
in THF. The results of this study (summarized in Table
4) indicate that there is a significant concentration
dependence for the product distribution. This effect was
observed for both THF and toluene. Interestingly, even
when the polymerization was carried out at extreme
dilution in THF (50 mg/20 mL), a small amount of high
polymer 7 was formed (ca. 31% yield by 1H NMR),
although at this concentration unreacted monomer 4 is
present (ca. 25% yield) even after 22 h. The major
1
18.5 h, analysis by H NMR spectroscopy showed the
presence of three sets of signals in the Cp region (the
resonances in the Ph region were overlapping and,
therefore, not resolvable into the individual components
of the product mixture). The most intense set (δ ) 4.93,
4.79 ppm) was assigned to the high polymer 9, and
signals corresponding to unreacted monomer 6 (δ )
4.49, 4.43 ppm) were also observed. A new set of signals
observed at chemical shifts of δ ) 5.10 and 4.33 were
also detected and were assigned to a cyclic dimer 12 (cf.
10 δ ) 4.90, 4.47, 4.33, 4.24 ppm). Integration of the
resonances gave a ratio of 9.8:0.95:1 for the reaction
mixture components 9:6:12. The ratio of polymer to
dimer was similar to the value obtained for the polym-
erization of 4 in toluene at the same dilution after 16 h
(ratio of polymer 7 to dimer 10 was 9.9:1); however, two
important differences were noted. First, the presence
of residual monomer after a period of ca. 20 h was
observed only in the case of the polymerization of 4 at
high dilution in THF. Second, the molecular weight of
the polymer 9 isolated from the ROP of 6 was substan-
tially lower than that of 7 formed under identical
conditions, and the distribution was found to be bimodal
in nature (9: fraction 1: Mn ) 5.9 × 104, PDI ) 2.1,
DPn ) 1.4 × 102; smaller fraction 2: Mn ) 1.8 × 103,
PDI ) 1.5, DPn ) 4; 7: Mn ) 4.0 × 105, PDI ) 1.7,
DPn ) 1.2 × 103).
In the case of the polymerization of 4, changing the
solvent to THF and diluting the reaction mixture was
(24) We have previously found that the cis and trans forms of the
cyclic dimers formed in the metal-catalyzed ROP of 2a have signifi-
cantly different 1H and 29Si NMR spectra. See: ref 18.

Silicon-Bridged [1]Ferrocenophanes
Organometallics, Vol. 21, No. 21, 2002 4421
observed to increase the amount of cyclic dimer 10. We
therefore performed a ROP experiment for a dilute
solution of 6 in THF. Upon stirring for 18.5 h, no color
1
change was noted. Analysis by H NMR spectroscopy
of the product mixture showed that the major compo-
nent was unreacted 6 with smaller resonances assigned
to polymer 9. Integration of the signals showed that the
ratio of monomer 6 to polymer 9 was 8.2:1; that is, the
conversion to polymer was only ca. 11%. Upon dropwise
addition of the reaction mixture into stirred hexanes,
very little precipitate was observed to form, and only
trace amounts of high polymer 9 were isolated. The
molecular weight of this isolated polymer was shown
to be low compared to that of 7 formed under similar
conditions and the distribution was bimodal (fraction
1: Mn ) 2.7 × 104, PDI ) 1.6, DPn ) 65; smaller fraction
2: low molecular weight oligomers, Mn < 1000).
F igu r e 4. TGA traces of polymers 7 and 8.
active catalytic center as the metallamacrocyclic poly-
ferrocenylsilane chains grow larger.9 In the case of 6,
there is no preferred mode of addition, as two acetylenic
substituents are present. The result is a more sluggish
ROP process.
(ii) P olym er iza t ion of 6 in C6D6 Mon it or ed by
NMR. The results of the aforementioned polymerization
studies of 6 suggested that the ROP proceeded with less
efficiency than that of 4. To provide convincing ad-
ditional support for this assertion, we undertook a
comparative investigation of the polymerization of 6 and
Th er m ogr a vim etr ic An a lysis (TGA) Stu d ies of
Com p ou n d s 7 a n d 8. Polyferrocenylsilanes have been
shown to be of utility in the formation of shaped and
patterned ceramics which display tunable magnetic
properties via pyrolysis.8m,25-27 However, to date, the
pyrolysis of soluble polyferrocenylsilane homopolymers
has produced ceramic materials only in relatively low
yield.27 The high ceramic yields needed for shape
retention in the pyrolysis process have been achieved
only through the use of thermally polymerizable cross-
linkable monomers (e.g., 2, R, R′ ) µ-(CH2)3).25 Unfor-
tunately, the cross-linked polymer network formed
initially is insoluble, which does not lend well to solution
or melt-processing techniques.
1
4 using H NMR to monitor the course of the reaction.
A solution of Pt0 catalyst in xylenes (ca. 0.3 mol %)
was added to a solution of 4 in C6D6 in an NMR tube.
1
After a 40 min period, an H NMR spectrum was taken,
and integration of the Ph resonances showed a 6.2:1.0:
1.2 ratio for the components 7:4:10 present in the
product mixture. This corresponds to a ca. 88% conver-
sion of monomer 4 into dimer 10 and high polymer 7 at
this time. An additional NMR spectrum taken after 3 h
40 min showed that no residual 4 was present, and the
ratio of 7 to 10 was 5.0:1.
When an analogous experiment was performed with
6, after 40 min, 1H NMR analysis involving integration
of the Cp resonances showed a 1:2.7:0.1 ratio between
the components 9:6:12 present in the product mixture.
This corresponds to a ca. 29% conversion of monomer 6
into dimer 12 and high polymer 9 at this time. After 2
h 40 min NMR showed a ratio for 9:6:12 of 1.0:1.4:0.1,
corresponding to a ca. 44% conversion of 6 into products.
An additional NMR spectrum after a 24 h period showed
the ratio of 9:6:12 to be 8.5:1.3:1.1, corresponding to a
ca. 88% conversion to products. The same conversion
for 4 was achieved after 40 min.
As acetylenic groups have been shown to provide an
effective site for thermal cross-linking of organometallic
oligomers and polymers28 while leaving the precursor
polymer soluble at ambient temperature, we decided to
investigate the pyrolysis of PFSs 7 and 8 by TGA under
an N2 flow.
As shown in Figure 4, relatively high ceramic yields
are formed in each case (for 7, 81%; for 8, 61%). In both
cases, the temperature at which significant weight loss
begins is ca. 350 °C, and the temperature at which loss
of volatile material ceases is ca. 600 °C. As expected,
the ceramic yield of the polymer containing phenyl
substituents was higher than that containing the ali-
phatic butyl group. Encouragingly, both ceramics took
the shape of the polymer initially placed in the TGA pan,
These results confirmed that the polymerization of 6
proceeds much slower than the polymerization of 4
under identical conditions. The results for the ROP of
6 in toluene also show that, in comparison to the ROP
of 4, the molecular weight of the resultant polyferroce-
nylsilane is significantly lower. Very low conversion of
6 into oligomers/polymer was observed in dilute THF
solution, which is again different from the polymeriza-
tion of 4 under analogous conditions which proceeds
with ca. 75% conversion. We tentatively explain the
stereoselective formation of the cis dimer 10 from 4 in
terms of the existence of a sterically preferred mode of
addition of the second molecule of monomer 4 to the site
for the growing polymer chain. Clearly, this effect is
more pronounced at the initial stage of chain growth
than at the later stages in the polymerization, as high
polymer 7 is atactic. We propose that this might be a
consequence of the reduction of steric hindrance at the
(25) 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.
(26) Ginzburg, M.; MacLachlan, M. J .; Yang, S. M.; Coombs, N.;
Coyle, T. W.; Raju, N. P.; Greedan, J . E.; Herber, R. H.; Ozin, G. A.;
Manners, I. J . Am. Chem. Soc. 2002, 124, 2625.
(27) (a) Ceramic yields of 45% (1000 °C, 4 h) have been detected for
poly(ferrocenylmethylvinylsilane). See: Petersen, R.; Foucher, D. A.;
Tang, B.-Z.; Lough, A.; Raju, N. P.; Greedan, J . E.; Manners, I. Chem.
Mater. 1995, 7, 2045. (b) The insoluble PFS poly(ferrocenyldihydrosi-
lane) has a ceramic yield of 63% at 1000 °C. See: Pudelski, J . K.;
Rulkens, R.; Foucher, D. A.; Lough, A. J .; Macdonald, P. M.; Manners,
I. Macromolecules 1995, 28, 7301.
(28) See: (a) Corriu, R. J . P.; Devylder, N.; Guerin, C.; Henner, B.;
J ean, A. J . Organomet. Chem. 1996, 509, 249. (b) Houser, E. J .; Keller,
T. M. Macromolecules 1998, 31, 4038.

4422 Organometallics, Vol. 21, No. 21, 2002
Berenbaum et al.
cooled to ca. -78 °C, and the LiCtCPh suspension was added
dropwise. The reaction mixture was allowed to warm to room
temperature, stirred for a further 1 h period, and filtered to
remove the white (LiCl) precipitate, and all volatile material
was removed under high vacuum. The red solid was recrystal-
lized from hexanes/toluene (ca. 50:50) at -30 °C to give 4,
yield: 0.75 g (65%).
For 4: 1H NMR (400 MHz, C6D6, 20 °C) δ 7.50-7.47 (m, 2
H, Ph), 6.95-6.92 (m, 3 H, Ph), 4.51 (m, 2 H, Cp), 4.44 (m, 2
H, Cp), 4.40 (m, 2 H, Cp), 3.91 (m, 2 H, Cp), 0.61 (s, 3 H, Me);
13C{1H} NMR (100.4 MHz, C6D6, 20 °C) δ 132.5, 129.2, 128.6
(Ph), 123.0 (ipso-Ph), 107.7 (PhCCSi), 89.7 (PhCCSi), 78.21,
78.17, 76.7, 74.6 (Cp), 30.4 (ipso-Cp), -3.0 (Me); 29Si NMR (79.3
MHz, C6D6, 20 °C) δ -27.8; MS (70 eV, EI) m/z (%) 328 (100)
[M+], 313 (13) [M+ - CH3]. Anal. Calcd for C19H16FeSi: C
69.51, H 4.92. Found: C 69.13, H 4.39.
Syn th esis of 5. In a typical reaction, nBuLi (11.3 mL, 1.6
M in hexanes, 18.1 mmol) was added dropwise to a stirred 0
°C solution of 1-hexyne (1.56 g, 2.18 mL, 19.0 mmol) in 30 mL
of Et2O and allowed to stir for a further 15 min. In a separate
flask 2a (5.0 g, 19.0 mmol) was dissolved in Et2O (200 mL)
and cooled to ca. -78 °C, and the LiCtCBu suspension was
added dropwise. The reaction mixture was allowed to warm
to room temperature and stirred for an additional 1 h, followed
by removal of all volatile material under high vacuum. The
residue was dissolved in a minimal amount of hexanes, filtered
through a fritted glass disk to remove the LiCl, and crystallized
at -55 °C to give 5, yield: 2.67 g (48 %). The yield could be
increased by concentration of the supernatant and subsequent
crystallization at -55 °C.
and both were attracted to a bar magnet, which is highly
interesting for potential materials applications.25
Su m m a r y
Sila[1]ferrocenophanes with acetylenic substituents
(4-6) have been prepared in good yields from silicon-
bridged [1]ferrocenophanes with Si-Cl moieties. These
monomers have been shown to undergo facile transition
metal-catalyzed ROP in the presence of a platinum
catalyst to give high molecular weight polyferrocenyl-
silanes (7-9) with acetylenic substituents. Significantly,
the presence of CtC bonds in the monomers led to no
detrimental effects on the ROP process. Cyclic dimer
10 was isolated from the polymerization mixture derived
from 4 and was shown to possess an interesting solid
state structure whereby one of the ferrocene moieties
possessed a ring tilt of -10.3(3)°. The ratio of cyclic
dimer 10 to high polymer 7 was shown to be highly
solvent dependent, with the most dimer formed in THF
solution at dilute concentrations. Work is currently
underway in our laboratory which aims to explore the
reactivity of monomers 4-6 and polymers 7-9 toward
transition metal complexes with the goal of producing
highly metallized monomers and polymers as well as
ceramics derived therefrom.
Exp er im en ta l Section
For 5: 1H NMR (400 MHz, C6D6, 20 °C) δ 4.51 (m, 2 H, Cp),
4.45 (m, 2 H, Cp), 4.38 (m, 2 H, Cp), 3.90 (m, 2 H, Cp), 2.07
(tr, J (HCH2, HCH2) ) 6.8 Hz, 2 H, CH2CH2CH2CH3), 1.33 (m, 4
H, CH2CH2CH2CH3), 0.76 (tr, J (HCH3, HCH2) ) 7.2 Hz, 3 H,
CH2CH2CH2CH3), 0.58 (s, 3 H, Me); 13C{1H} NMR (100.4 MHz,
C6D6, 20 °C) δ 110.2 (CCSi), 80.2 (CCSi), 78.1, 78.0, 76.6, 74.7
(Cp), 31.2 (ipso-Cp), 30.7 (CH2CH2CH2CH3), 22.1 (CH2CH2CH2-
CH3), 19.8 (CH2CH2CH2CH3), 13.6 (CH2CH2CH2CH3), -2.8
(Me); 29Si NMR (79.3 MHz, C6D6, 20 °C) δ -29.1; MS (70 eV,
EI) m/z (%) 308 (100) [M+]. Anal. Calcd for C17H20FeSi: C
66.22, H 6.55. Found: C 66.07, H 6.47.
The Pt0 catalyst used in these studies, platinum-divinyltet-
ramethyldisiloxane complex (2.1-2.4 wt % in xylene), was
obtained from Gelest and used as purchased. Phenylacetylene
and 1-hexyne were obtained from Aldrich, distilled under
partial vacuum, and stored under an atmosphere of N2. 2a and
2b were synthesized according to literature procedures.18
Most reactions and manipulations were carried out under
an atmosphere of prepurified nitrogen using either Schlenk
techniques or an inert-atmosphere glovebox. Solvents were
distilled from Na and stored under N2. The air- and moisture-
stable polymers 7-9 and cyclic dimer 10 were handled under
air with ACS grade solvents after workup. 1H NMR spectra
(400 MHz), 13C NMR spectra (100.4 MHz), and 29Si NMR
spectra (79.3 MHz) were recorded on a Varian Unity 400
spectrometer. All solution 1H and 13C NMR spectra were
referenced internally to protonated solvent shifts. 29Si NMR
spectra were referenced externally to SiMe4. Mass spectra were
obtained with the use of a VG 70-250S mass spectrometer
operating in electron impact (EI) mode. The calculated isotopic
distribution for each ion was in agreement with experimental
values. Molecular weight estimates were obtained via gel-
permeation chromatography (GPC) using a Waters Associates
2690 Separations Module equipped with a column heater,
Ultrastyragel columns with pore sizes of 103-105 Å, an in-
line degasser, and a differential refractometer. The GPC
possesses a triple detection system (refractive index, light
scattering, viscosity) such that absolute molecular weights are
reported. A flow rate of 1.0 mL/min was used, and the eluent
was THF. Polystyrene standards purchased from American
Polymer Standards were used for calibrating the instrument
response. Thermogravimetric analyses (TGA) were performed
using a Perkin-Elmer TGA-7 analyzer under nitrogen at a
heating rate of 10 °C/min. Elemental analysis was performed
by Quantitative Technologies Inc., Whitehouse, NJ .
Syn th esis of 6. nBuLi (6.6 mL, 1.6 M in hexanes, 10.6
mmol) was added dropwise to a stirred 0 °C solution of
phenylacetylene (1.2 mL, 10.9 mmol) in ca. 25 mL of Et2O and
allowed to stir for an additional 15 min. In a separate flask
2b (1.53 g, 5.4 mmol) was dissolved in Et2O (ca. 50 mL) and
cooled to ca. -78 °C, and the LiCtCPh suspension was added
dropwise. The reaction mixture was allowed to warm to room
temperature, stirred for a further 1 h period, and filtered to
remove the white precipitate, and all volatile material was
removed under high vacuum. The red solid was recrystallized
from CH2Cl2/hexanes (25:75) at -30 °C to give 6, yield: 1.05
g (47%).
1
For 6: H NMR (400 MHz, C6D6, 20 °C) δ 7.42-7.40 (m, 4
H, Ph), 6.95-6.86 (m, 6 H, Ph), 4.49 (m, 4 H, Cp), 4.43 (m, 4
H, Cp); 13C{1H} NMR (100.4 MHz, C6D6, 20 °C) δ 132.7, 129.5,
128.5 (Ph), 122.5 (ipso-Ph), 108.1, (PhCCSi), 86.9 (PhCCSi),
78.7, 75.6 (Cp), 28.2 (ipso-Cp); 29Si NMR (79.3 MHz, C6D6, 20
°C) δ -54.2; MS (70 eV, EI) m/z (%) 414 (100) [M+].
P olym er iza tion of 4. In a typical reaction, a solution of
Pt0 catalyst in xylenes (ca. 0.3 mol % Pt) was added to a stirred
solution of 4 (1.5 g, 4.6 mmol) in toluene (ca. 25 mL). After 1
h time a color change from red to orange was noted. The
reaction mixture was allowed to stir for ca. 20 h, after which
time the solution was precipitated into stirred methanol. The
light orange precipitate was washed three times with hexanes
and was dried under high vacuum to give the light orange
powder 7, yield: 1.4 g (93%).
Syn th esis of 4. In a typical reaction, nBuLi (2.2 mL, 1.6
M in hexanes, 3.5 mmol) was added dropwise to a stirred 0 °C
solution of phenylacetylene (0.39 g, 3.8 mmol) in 25 mL of
Et2O, and the reaction mixture was allowed to stir for an
additional 15 min. In a separate flask 2a (1.0 g, 3.8 mmol)
was dissolved in Et2O (50 mL), and the resulting solution was
For 7: 1H NMR (400 MHz, C6D6, 20 °C) δ 7.58-7.57 (m, 2
H, Ph), 6.96-6.95 (m, 3 H, Ph), 4.56 (br s, 4 H, Cp), 4.51 (br
s, 1 H, Cp), 4.50 (br s, 1 H, Cp), 4.37 (br s, 1 H, Cp), 4.34 (br

Silicon-Bridged [1]Ferrocenophanes
Organometallics, Vol. 21, No. 21, 2002 4423
s, 1 H, Cp), 0.81 (s, 3 H, Me); 13C{1H} NMR (100.4 MHz, C6D6,
20 °C) δ 132.3, 128.9, 128.7 (Ph), 123.7 (ipso-Ph), 106.8,
(PhCCSi), 93.5 (PhCCSi), 74.8-73.0 (m, Cp), 69.1 (ipso-Cp),
-0.6 (Me); 29Si NMR (79.3 MHz, C6D6, 20 °C) δ -23.8 (3 poorly
resolved signals in a 1:2:1 intensity pattern due to atacticity
74.2, 71.9, 71.4 (Cp), 69.3 (ipso-Cp), 2.8 (Me); 29Si NMR (79.3
MHz, C6D6, 20 °C) δ -24.3; UV-vis (25 °C, THF) λ 467 nm, ꢀ
3.6 × 102 L mol-1 cm-1; MS (70 eV, EI) m/z (%) 656 (41) [M+].
Anal. Calcd for C38H32Fe2Si2: C 69.51, H 4.92. Found: C 69.66,
H 4.83.
of polymer); UV-vis (25 °C, THF) λ 447 nm, ꢀ 1.7 × 102
L
P olym er iza tion of 4 in Tolu en e, CH2Cl2, or THF . A
solution of Pt0 catalyst in xylenes (ca. 0.3 mol %) was added
to a stirred solution of 4 (50 mg, 0.15 mmol) in the appropriate
solvent (toluene, 1 or 2 mL; CH2Cl2, 1 mL; THF, 1 or 4.5 mL).
The polymerizations were allowed to stir for a further 16 h at
room temperature. A sample was taken at this time for
analysis by 1H NMR spectroscopy. The remaining reaction
mixture was precipitated into stirred methanol, the superna-
tant discarded, and the fibrous orange polymer washed twice
with fresh methanol and dried under high vacuum. The
polymerization was performed twice at each concentration.
Yields: 7tol-1m L ) 27 mg (72%); 7tol-2m L ) 30 mg (80%);
7CH 2Cl2-1m L ) 21 mg (56%); 7TH F -1m L ) 17 mg (45%);
7THF -4.5m L ) 15 mg (40%).29
mol-1 cm-1; GPC Mn ) 1.64 × 105; Mw ) 2.61 × 105; PDI )
1.6. Anal. Calcd for (C19H16FeSi)n: C 69.51, H 4.92. Found: C
69.80, H 4.53.
P olym er iza tion of 5. In a typical reaction, Pt0 catalyst in
xylenes (ca. 0.3 mol % Pt) was added to a stirred solution of 5
(0.30 g, 0.97 mmol) in toluene (ca. 2 mL). After 1 h time a
color change from red to orange was noted. The reaction
mixture was allowed to stir a further 18 h, after which time
the solution was precipitated into stirred methanol. The light
orange precipitate was washed three times with hexanes and
was dried under high vacuum to give the orange gummy
polymer 8, isolated yield: 0.20 g (67%).
For 8: 1H NMR (400 MHz, C6D6, 20 °C) δ 4.56, 4.54, 4.48,
4.35, 4.32 (br s, Cp), 2.17, (br tr, 2 H, CH2CH2CH2CH3), 1.52-
1.36 (m, 4 H, CH2CH2CH2CH3), 0.84 (br m, 3 H, CH2CH2-
CH2CH3), 0.79 (br s, 3 H, Me); 13C{1H} NMR (100.4 MHz, C6D6,
20 °C) δ 108.8 (BuCCSi), 83.4 (BuCCSi), 74.5, 74.2, 72.8 (Cp),
69.8 (ipso-Cp), 31.1 (CH2CH2CH2CH3), 22.3 (CH2CH2CH2CH3),
20.0 (CH2CH2CH2CH3), 13.8 (CH2CH2CH2CH3), -0.2 (m, Me);
29Si{1H} NMR (79.3 MHz, C6D6, 20 °C) δ -25.2 (3 poorly
resolved signals in a 1:2:1 intensity pattern due to atacticity
of polymer); GPC Mn ) 1.21 × 106; Mw ) 1.80 × 106; PDI )
1.6. The GPC trace and the molecular weight value did not
change significantly upon dilution of the sample, which rules
out artifacts caused by aggregation.
P olym er iza tion of 6. In a typical reaction, a solution of
Pt0 catalyst in xylenes (ca. 0.3 mol % Pt) was added to a stirred
solution of 6 (0.050 g, 0.12 mmol) in C6D6 (ca. 1 mL). After 1
h time a color change from red to orange was noted. The
reaction mixture was allowed to stir for ca. 20 h, after which
time the solution was precipitated into stirred methanol. The
light orange precipitate was washed three times with hexanes
and was dried under high vacuum to give the light orange
powder 9, yield: 43 mg (86%).
P olym er iza tion of 4 in Dilu te THF Solu tion . A solution
of Pt0 catalyst in xylenes (ca. 0.3 mol %) was added to a stirred
solution of 4 (50 mg, 0.15 mmol) in THF (20 mL). The
polymerization was allowed to stir for a further 22 h at room
temperature before all volatile material was removed under
high vacuum. The residue was taken up in C6D6 and analyzed
by NMR (1H, 29Si). Spectroscopic yields (1H NMR): 720m L
31%; 1020m L ) 44%; unreacted 4 ) 25%.
)
P olym er iza tion of 6 in Tolu en e. A solution of Pt0 catalyst
in xylenes (ca. 0.3 mol %) was added to a stirred solution of 6
(25 mg, 0.06 mmol) in toluene (1 mL). The polymerization was
allowed to stir for a further 18.5 h at room temperature,
whereupon the color was observed to change from red to
orange. A sample was taken at this time for analysis by 1H
NMR spectroscopy. The remaining reaction mixture was
precipitated into stirred hexanes, the supernatant discarded,
and the fibrous orange polymer washed twice with fresh
hexanes and dried under high vacuum. Isolated yield: 91m L
)
10 mg (53%).29 Mn1 ) 5.9 × 104, Mw1 ) 1.3 × 105, PDI ) 2.1;
Mn2 ) 1.8 × 103, Mw2 ) 2.7 × 103, PDI ) 1.5.
P olym er iza tion of 6 in THF . A solution of Pt0 catalyst in
xylenes (ca. 0.3 mol %) was added to a stirred solution of 6
(50 mg, 0.12 mmol) in THF (5 mL). The polymerization was
allowed to stir for a further 18.5 h at room temperature,
whereupon the color was observed to remain red during this
period of time. A sample was taken at this time for analysis
by 1H NMR spectroscopy. The remaining reaction mixture was
precipitated into stirred hexanes, the supernatant discarded,
and a very small amount of orange polymer was isolated on a
fritted glass disk. This material was washed with fresh
hexanes and dried under high vacuum. Yield: 95m L ) trace.
Mn1 ) 2.7 × 104, Mw1 ) 4.4 × 104, PDI ) 1.6; Mn2 ) 8.1 × 102,
Mw2 ) 1.9 × 103, PDI ) 2.3.
For 9: 1H NMR (400 MHz, C6D6, 20 °C) δ 7.56-7.50 (m, 4
H, Ph), 6.94-6.88 (m, 6 H, Ph), 4.93 (br s, 4 H, Cp), 4.79 (br
s, 4 H, Cp); 13C{1H} NMR (100.4 MHz, C6D6, 20 °C) δ 132.5,
129.1, 128.6 (Ph), 123.2 (ipso-Ph), 107.2, (PhCCSi), 90.6
(PhCCSi), 75.4, 74.3 (Cp), 66.9 (ipso-Cp); 29Si NMR (79.3 MHz,
C6D6, 20 °C) δ -44.3; GPC (polystyrene calibration) Mn
)
7.68 × 104; Mw ) 1.13 × 105; PDI ) 1.5.
Cyclic Dim er 10 Isola ted a s a Byp r od u ct of th e P o-
lym er iza tion of 4. In one case, a significant amount of red
crystalline material was obtained from condensation of the
hexanes washes from the precipitation of the polymerization
reaction mixture. The yield of high molecular weight polymer
isolated was correspondingly lower. For this experiment, 0.46
g (1.4 mmol) of 4 was dissolved in THF (ca. 5 mL). Pt0 catalyst
(ca. 0.3 mol % Pt) was added to the stirred solution, and the
reaction mixture was allowed to stir for a further 16 h.
Precipitation into stirred hexanes followed by three hexanes
washes resulted in the isolation of a light orange precipitate,
which was dried under high vacuum to give 0.26 g (57% yield)
of the high polymer 7. Condensation of the supernatant from
the initial precipitation along with the collected hexanes
washes resulted in the isolation of a red crystalline material,
10: yield ) 0.10 g (22%). Crystals of suitable quality for single-
crystal X-ray diffraction were grown from slow evaporation of
a saturated hexanes solution of 10 at 25 °C.
P olym er iza tion of 4 in C6D6 Mon itor ed by NMR. A
solution of Pt0 catalyst in xylenes (ca. 0.3 mol %) was added
to a solution of 4 (25 mg, 0.08 mmol) in C6D6 (0.5 mL) in an
NMR tube. The contents of the tube were mixed well and the
tube placed in a sonication bath to ensure adequate mixing of
the components. After a 40 min period, a 1H NMR spectrum
was taken, and integration of the Ph resonances showed a 6.2:
1.0:1.2 ratio between the 7:4:10 present in the product mixture.
This corresponds to a ca. 88% conversion of monomer 4 into
dimer 10 and high polymer 7 at this time. An additional NMR
spectrum taken after 3 h 40 min showed that no residual 4
was present, and the ratio of 7 to 10 was 5.04:1.
P olym er iza tion of 6 in C6D6 Mon itor ed by NMR. A
solution of Pt0 catalyst in xylenes (ca. 0.3 mol %) was added
to a solution of 6 (8 mg, 0.02 mmol) in C6D6 (0.5 mL) in an
NMR tube. The contents of the tube were mixed well and the
For 7: Mn ) 1.69 × 105; Mw ) 2.75 × 105; PDI ) 1.6.
For 10: 1H NMR (400 MHz, C6D6, 20 °C) δ 7.41-7.39 (m, 4
H, Ph), 6.95-6.84 (m, 6 H, Ph), 4.90 (m, 4 H, Cp), 4.47 (m, 4
H, Cp), 4.33 (m, 4 H, Cp), 4.24 (m, 4 H, Cp), 0.75 (s, 6 H, Me);
13C{1H} NMR (100.4 MHz, C6D6, 20 °C) δ 132.2, 128.6, 128.5
(Ph), 123.8 (ipso-Ph), 106.4, (PhCCSi), 94.2 (PhCCSi), 75.6,
(29) These yields are calculated on the basis of the fact that 25% of
the solution was removed for analysis by 1H NMR spectroscopy.

4424 Organometallics, Vol. 21, No. 21, 2002
Ta ble 5. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
Berenbaum et al.
4
6
10
formula
Mr
C
19H16FeSi
C26H18FeSi
414.34
C38H32Fe2Si2
656.52
328.26
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
orthorhombic
Pbca
10.5076(3)
12.2932(5)
23.8440(9)
90
monoclinic
P21/c
14.5767(3)
10.45430(10)
13.1120(3)
90
92.2280(10)
90
1996.62(6)
4
monoclinic
P21/c
12.2437(3)
9.5283(3)
26.9516(6)
90
91.824(2)
90
3142.63(14)
4
90
90
3079.98(19)
8
1.416
1.046
1360
Z
F
calc, g cm-3
1.378
0.823
856
1.388
1.026
1360
µ(Mo KR), mm-1
F(000)
cryst size, mm
θ-range, deg
no. of reflns collected
no. of ind reflns
abs corr
0.30 × 0.24 × 0.13
3.07-27.48
14 891
3521
multiscan
0.8760
0.7443
192
1.020
0.0445
0.30 × 0.20 × 0.18
2.80-27.53
20 743
4568
multiscan
0.8659
0.7903
254
1.032
0.0346
0.23 × 0.20 × 0.02
2.62-25.01
17 513
5513
semiempirical
0.9798
0.7983
382
1.037
0.0401
max. and min.
transmn coeff
no. of params refined
GoF on F2
R1a (I>2σ(I))
wR2b (all data)
0.1179
0.420/-0.397
0.0926
0.285/-0.394
0.0910
0.267/-0.399
peak/hole (e Å-3
)
R1 ) ∑||Fo| - |Fo||/∑|Fo|. wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo2)2]}1/2
.
a
b
2
tube placed in a sonication bath to ensure adequate mixing of
the components. After a 40 min period, a 1H NMR spectrum
was taken, and integration of the Cp resonances showed a
1:2.7:0.11 ratio between the 9:6:12 present in the product
mixture. This corresponds to a ca. 29% conversion of monomer
6 into dimer 12 and high polymer 9 at this time. An NMR
spectrum taken after 2 h 40 min showed a ratio for 9:6:12 of
1.0:1.4:0.10, corresponding to a ca. 44% conversion of 6 into
products. An additional NMR spectrum after a 24 h period
showed the composition to consist of a ratio of 8.5:1.3:1.1 for
9:6:12, corresponding to a ca. 88% conversion to products.
X-r a y Str u ctu r a l Ch a r a cter iza tion . A summary of se-
lected crystallographic data are given in Table 5. Data were
collected on a Nonius KappaCCD diffractometer using graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å). A combina-
tion of 1° phi and omega (with kappa offsets) scans was used
to collect sufficient data. The data frames were integrated and
scaled using the Denzo-SMN package.30
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary
publication nos. CCDC-190582 (4), CCDC-190583 (6), and
CCDC-190584 (10). Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK (fax: (+44) 1223 336-033; e-mail: deposit@
ccdc.cam.ac.uk).
Ackn owledgm en t. We wish to acknowledge a Natu-
ral Science and Engineering Research Council of Canada
(NSERC) postgraduate scholarship for A.B., and I.M.
is grateful to the University of Toronto for a McLean
Fellowship (1997-2003), the Ontario Government for
a PREA Award (1999-2003), and the Canadian Gov-
ernment for a Canada Research Chair (2001-). We also
wish to thank Se´bastien Fournier for obtaining the TGA
traces, as well as Kevin Kulbaba, Alex Bartole, and Dr.
Scott Clendenning for obtaining the GPC data.
The structures were solved and refined using the
SHELXTL\ PC V5.131 package. Refinement was by full-matrix
least squares on F2 using all data (negative intensities
included). Hydrogen atoms were included in calculated posi-
tions.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data for compounds 4, 6, and 10 including tables of crystal
data, atomic coordinates, bond lengths and angles, and aniso-
tropic thermal parameters. This material is available free of
charge via the Internet at http://pubs.acs.org.
(30) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
(31) Sheldrick, G. M. SHELXTL\ PC V5.1; Bruker Analytical X-ray
Systems: Madison, WI, 1997.
OM0204078