Synthesis and reactivity of [2]ferrocenophanes containing C-Pb and C-Zr bridges

Article abstract of DOI:10.1016/j.poly.2005.07.019

The synthesis, characterization and reactivity of novel carbometalla[2]ferrocenophanes (η-C₅Me₄)Fe(η- C₅H₄)CH₂ER₂ (14) and (15) (E = Pb, R = Ph or E = Zr, R = (η-C₅H₅)) are reported. Compounds 14 and 15 were prepared by the reaction of the dilithiated species (η-C₅Me₄)Fe(η-C₅H₄Li)CH ₂Li · xTMEDA with the appropriate dichlorodiorganoplumbane or dichlorozirconocene in low yields (ca. 20%). The Pb species 14 was characterized by ¹H and ¹³C NMR, and MS, however it could not be cleanly separated from pentamethylferrocene. Moreover, it was found that the C-Pb bonds of 14 underwent facile cleavage, and under ambient light or at room temperature, 14 decomposed to Pb₂Ph₆ and pentamethylferrocene. Compound 15, on the other hand, was stable and readily purified; this species was characterized by ¹H and ¹³C NMR, UV-Vis, MS, and elemental analysis. Single crystal X-ray diffraction studies of this compound revealed the presence of a moderate degree of ring-tilt with a value of α = -5.5(2)°(a negative value is used to denote tilting away from the bridging elements), and a potentially moderate degree of strain due to a large β(Zr) of 31.6(1)°(angle between Cp′(Fe) plane and ipso-Cp′-Zr bond). Attempted thermal ring-opening polymerization (ROP) of 15 resulted only in decomposition and attempted transition metal-catalyzed and photolytic ROP were also unsuccessful. The reaction of 15 with HCl · Et₂O resulted in cleavage of the C-Zr bonds, and led to the formation of pentamethylferrocene.

Full text of DOI:10.1016/j.poly.2005.07.019

Polyhedron 25 (2006) 429–436
www.elsevier.com/locate/poly
Synthesis and reactivity of [2]ferrocenophanes containing C–Pb
and C–Zr bridges
*
Alexandra Bartole-Scott, Alan J. Lough, Ian Manners
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ont., Canada, M5S 3H6
Received 4 May 2005; accepted 8 July 2005
Available online 1 September 2005
Dedicated to Professor Malcolm Chisholm for his outstanding and scholarly contributions to chemistry.
Abstract
The synthesis, characterization and reactivity of novel carbometalla[2]ferrocenophanes (g-C5Me4)Fe(g-C5H4)CH2ER2 (14) and
(15) (E = Pb, R = Ph or E = Zr, R = (g-C5H5)) are reported. Compounds 14 and 15 were prepared by the reaction of the dilithiated
species (g-C5Me4)Fe(g-C5H4Li)CH2Li Æ xTMEDA with the appropriate dichlorodiorganoplumbane or dichlorozirconocene in low
yields (ca. 20%). The Pb species 14 was characterized by 1H and 13C NMR, and MS, however it could not be cleanly separated from
pentamethylferrocene. Moreover, it was found that the C–Pb bonds of 14 underwent facile cleavage, and under ambient light or at
room temperature, 14 decomposed to Pb2Ph6 and pentamethylferrocene. Compound 15, on the other hand, was stable and readily
1
purified; this species was characterized by H and 13C NMR, UV–Vis, MS, and elemental analysis. Single crystal X-ray diffraction
studies of this compound revealed the presence of a moderate degree of ring-tilt with a value of a = ꢀ5.5(2)ꢀ (a negative value is used
to denote tilting away from the bridging elements), and a potentially moderate degree of strain due to a large b(Zr) of 31.6(1)ꢀ (angle
between Cp0(Fe) plane and ipso-Cp0–Zr bond). Attempted thermal ring-opening polymerization (ROP) of 15 resulted only in
decomposition and attempted transition metal-catalyzed and photolytic ROP were also unsuccessful. The reaction of 15 with
HCl Æ Et2O resulted in cleavage of the C–Zr bonds, and led to the formation of pentamethylferrocene.
ꢁ 2005 Elsevier Ltd. All rights reserved.
Keywords: Ring-strain; Ferrocenophane; Plumbane; Zirconocene; Ring-opening polymerization
1. Introduction
of silicon-bridged [1]ferrocenophanes such as 1 ((ERx)y
= SiMe2) to yield high molecular weight polymer 2 [3],
the polymerization methods have been successfully ex-
panded to include transition metal-catalyzed ROP
[9,10], living anionic ROP [11], and photolytic ROP
[12]. In addition, the ROP protocol has been extended
to include other atoms in the bridge (E = B, P, Ge,
Sn, S) [5–7], different metals (e.g., Ru, Cr and Ti) and
also alternative p hydrocarbon ligands [6,7]. The result-
ing ring-opened polymers are attracting considerable
attention due to their interesting physical and prece-
ramic properties [13–20], and copolymers incorporating
a ferrocene-containing block have intriguing applica-
tions in supramolecular chemistry [21,22]. In addition,
[1]Ferrocenophanes have been the focus of much re-
cent research due to the ring-strain imposed upon these
organometallic species by the bridging of the cyclopen-
tadienyl (Cp) rings by one atom [1–7]. This ring-strain
leads to interesting reactivity for these compounds,
and has led to their use in surface derivatization meth-
ods [8] and ring-opening polymerization (ROP) reac-
tions [3,4]. Since the initial report of the thermal ROP
*
Corresponding author. Tel./fax: +4169786157.
E-mail addresses: abartole@chem.utoronto.ca (A. Bartole-Scott),
imanners@chem.utoronto.ca (I. Manners).
0277-5387/$ - see front matter ꢁ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.07.019

430
A. Bartole-Scott et al. / Polyhedron 25 (2006) 429–436
polyferrocenylsilanes have recently been used in the area
of redox-responsive photonic crystals [23], as etch resists
for the nanopatterning of substrates [24] and as precur-
sors to patterned metal catalysts for the growth of car-
bon nanotubes [25].
received comparatively less attention. Previous work
has shown that highly strained hydrocarbon-bridged
monomers 7 (M = Fe, R = H, Me, E2 = CH2CH2) and
the analogous [2]ruthenocenophane (7) (M = Ru,
R = H, E2 = CH2CH2), undergo thermal ROP [29,30],
whereas ring-opening metathesis polymerization of
[2]ferrocenophane (7) (M = Fe, R = H, E2 = CH@CH)
has also been described [31]. In contrast, [2]metalloceno-
phanes with Si–Si bridges such as 7 (M = Fe or Ru,
E2 = SiMe2SiMe2), are relatively unstrained and resist
ROP [32], whereas an analogue with a Ge–Ge bridge
(7: M = Fe, E2 = GeMe2GeMe2) has been successfully
polymerized [33].
(ERx)y
ROP
Fe
Fe
(ERx)y
n
2
1
Examples of [1]ferrocenophanes with transition met-
als in the bridge have also been explored. Broussier
et al. [26] reported the synthesis and reactivity of [1]fer-
rocenophanes (3) containing group 4 bridges. Analogues
containing titanium, zirconium and hafnium bridges
were prepared and single crystal X-ray diffraction of
3b (L = t-BuCp) determined the tilting of the cyclopen-
tadienyl rings to be moderate (a = 6.0ꢀ). These [1]ferro-
cenophanes were shown to be reactive towards water
and oxygen, in addition to heavier chalcogens leading
to insertion of the chalcogen into the ipso-Cp–Zr bond
[26]. In addition, we recently reported the synthesis of
a zirconium-bridged [1]ruthenocenophane (4) with a lar-
ger tilt angle of the metallocene fragment (a = 10.4ꢀ)
[27].
R
R
E
E
E
∆
M
M
E
or metal catalyst
R
n
R
8: M = Fe or Ru,
R = H or Me,
7: M = Fe or Ru,
R = H or Me,
E2 = CH2CH2 or CH=CH
E2 = SiMe2SiMe2 or GeMe2GeMe2
E2 = CH2CH2 or CH=CH
E2 = GeMe2GeMe2
Recently, our group has studied the synthesis and
ROP behaviour of [2]ferrocenophanes with unsymmetri-
cal C–E bridges 9–13 [34,35]. It was shown for com-
pounds 9–11 (E = Si, P, S) as the covalent radius of E
was varied, the ring-strain was varied accordingly [34].
The least strained of these species (9, a = 11.8(1)ꢀ) was
found to be completely resistant to polymerization un-
der all conditions studied, whereas the more strained
species 10 (aavg = 16.5ꢀ) and 11 (a = 18.5(1)ꢀ) were
found to undergo successful ROP. This work recently
prompted us to explore the synthesis and ROP behav-
iour of the [2]ferrocenophanes 12 and 13. The presence
of weak C–Ge and C–Sn bonds were expected to in-
crease reactivity of group 14 carbo[2]ferrocenophanes,
despite the decrease in tilt angle between the cyclopenta-
dienyl rings. It was found however that the C–E bonds
of 12 and 13 were insufficiently weak to permit ring-
opening polymerization [35].
Fe
ML2
Ru
Zr(t BuCp)2
3a: M= Ti, L =Cp, t-BuCp
3b: M= Zr, L = Cp, t-BuCp
3c: M = Hf, L = Cp, t-BuCp
4
Attempts have also been made to introduce heavy
atoms into ferrocenophane structures. Ferrocene was
reacted with n-BuLi in hexanes to yield a mixture
of (g-C5H5)Fe(g-C5H4Li) and (g-C5H4Li)2Fe to
which Ph3PbCl and Ph2PbCl2 were added in situ
[28]. The products isolated were a mixture of the
plumbylferrocene (5), and the [1,10]diplumbylferroce-
nophane (6). These products were characterized by
NMR, MS and elemental analysis; however single
crystals were not obtained, and no evidence for the
formation of a [1]plumbaferrocenophane was reported
[28].
Me
Me
Me
Me
Me
Me
Me
Me
CH2
ERx
CH2
ER2
Fe
Fe
9
: ERx = SiMe2
12 : E = Ge, R = Me, Ph
13 : E = Sn, R = Me, t-Bu, Mes
Ph2
Pb
10 : E = P, R = Ph, Mes
11 : ERx = S
PbPh3
Fe
Fe
Fe
In this paper, we report on our attempts to further ex-
plore the area of carbon-heteroatom bridged [2]ferroce-
nophanes via the introduction of heavy main group
elements and transition metals into the bridge. We report
the synthesis and reactivity of the novel carbo-
plumba[2]ferrocenophane (14) and carbozircona[2]ferro-
cenophane (15).
Pb
Ph2
5
6
The preparation and reactivity of [1]ferrocenophanes
have been well explored over the past few decades, how-
ever until recently the area of [2]ferrocenophanes has

A. Bartole-Scott et al. / Polyhedron 25 (2006) 429–436
431
2. Results and discussion
apparent overlapping with the Cp0 and Cp* resonances.
In the solid state CP-MAS 13C NMR, a peak was ob-
served for the ipso-Cp0 at 156 ppm which is consistent
with the ipso-Cp0 resonances of 3b observed at
159 ppm [26]. The ipso-Cp* resonance was observed as
a shoulder at 80 ppm of the broad peak at 86 ppm cor-
responding to Cp* carbon resonances. In moderately
strained [1]ferrocenophanes [5–7] and C–E bridged
[2]ferrocenophanes [34,35], the resonances for the ipso-
Cp0 and/or ipso-Cp* carbons are shifted upfield which
is consistent with a deviation from planar sp2 hybridiza-
tion imposed by the bridging of the rings. By compari-
son with NMR characterization of 3b [26], 9 [34], 12
[35], it appears that 15 is relatively unstrained.
2.1. Attempted synthesis of lead-bridged
[2]ferrocenophanes
We attempted to prepare the C–Pb bridged [2]ferro-
cenophane (14) from the reaction of (g-C5Me4)Fe-
(g-C5H4Li)CH2Li Æ xTMEDA with Ph2PbCl2. This
regenerated the precursor pentamethylferrocene as the
major isolated product in addition to the desired C–Pb
bridged [2]ferrocenophane (14). The mixture was isolated
as an orange gummy material in 17% total yield. 1H NMR
characterization demonstrated the fraction of 14 in the
reaction solution to be approximately 25%. One feature
of the 1H NMR spectrum of 14 is the methylene resonance
observed at 3.23 ppm which is significantly more down-
field than in compounds 9–13, and the 1H–207Pb coupling
observed for these protons (J(207Pb/1H) = 54 Hz). The
structure of 14 was also confirmed by 13C NMR analysis
and mass spectrometry. The impetus for preparing
compound 14 was to further weaken the C–E bond of
group 14-containing carbo[2]ferrocenophanes (E = Si,
Ge, Sn) which do not undergo ring-opening polymeriza-
tion under thermal, transition metal-catalyzed, anionic
or photolytic conditions [34,35]. Indeed, compound 14
possesses weak C–Pb bonds such that this species is both
sensitive to light and temperature; attempts to recrystal-
lize 14 from a concentrated hexanes solution under an in-
ert atmosphere at room temperature led to the deposition
of a black precipitate, the formation of Ph3PbPbPh3
and an increase in the amount of (g-C5Me5)Fe(g-C5H5)
Me
Me
Me
Me
Me
Me
CH2Li
CH2
THF/toluene
RT, 3h
Me
Me
.
Fe
Fe
+
Cp2ZrCl2
TMEDA
Cp
Zr
Li
Cp
15
2.3. X-ray structural analysis of [2]ferrocenophane (15)
Suitable single crystals of 15 were obtained through
low temperature (ꢀ30 ꢀC) recrystallization from a con-
centrated toluene solution. Only one type of species
was found in the unit cell. The molecular structure of
15 is shown in Fig. 1, and selected bond angles are given
in Table 1. Of note in the molecular structure of 15 is the
‘‘bowtie’’ configuration of the Cp0Cp*Fe and Cp2Zr
rings and the relatively small a angle (ꢀ5.5(2)ꢀ) found
between the planes of the Cp0 and Cp* rings. (Note.
The negative a angle denotes tilting of the cyclopenta-
dienyl rings away from the C–Zr bridge.) The tilt angle
is expected to be moderate due to the large size of the
1
as detected by H NMR and X-ray diffraction. At low
temperature (ꢀ30 ꢀC), decomposition did not occur as
readily, however 14 could still not be successfully isolated
in pure form from mixtures containing (g-C5Me5)Fe(g-
C5H5).
˚
zirconium atom (rcov = 1.55 A) [36] in comparison with
Me
Me
other heteroatom-bridged [2]ferrocenophanes (cf. 12b,
Me
˚
a = 7.1(1)ꢀ, Sn: rcov = 1.40 A) [35]. Due to the presence
CH2
Me
Fe
of two bridging atoms, it was expected that 15 would
exhibit a smaller a angle relative to the corresponding
[1]ferrocenophane (3b) (a = 6.0ꢀ) [26], however the tilt-
ing of the cyclopentadienyl rings away from the bridge
was unanticipated. This structure represents a rare case
of [n]ferrocenophanes that contain ‘‘negative’’ tilt angles
[37], and the first example for a [2]ferrocenophane that
we are aware of. Since the tilt angle of the pentamethyl-
ferrocene fragment is small, other structural parameters
may be of importance when discussing the strain of this
compound. For example, the zirconium atom is found in
an approximate tetrahedral environment (i.e., C(6)–Zr–
C(15) = 109.0(1)ꢀ, Cp-centroid–Zr–Cp-centroid = 126.6(2)ꢀ)
which may indicate moderate strain at the bridging
atom, the staggering angle is relatively small (r =
1.3(5)ꢀ) (r = angle with which the Cp(Fe) rings deviate
from an eclipsed conformation) and the torsional
PbPh2
14
2.2. Synthesis and characterization of C–Zr bridged
[2]ferrocenophane (15)
We attempted to prepare the C–Zr bridged [2]ferro-
cenophane (15) by the reaction of (g-C5Me4)Fe(g-
C5H4Li)CH2Li Æ xTMEDA with (g-C5H5)2ZrCl2.
yellow product precipitated from THF/toluene, and
1H and 13C NMR analysis confirmed the structure of
the product was 15, which was isolated in 19% yield. In
the 13C NMR spectrum (in C6D6), however, it was diffi-
cult to assign the ipso-Cp0 and ipso-Cp* (Cp* = C5Me4)
resonances due to low solubility of 16 in C6D6 and
A

432
A. Bartole-Scott et al. / Polyhedron 25 (2006) 429–436
Fig. 1. Molecular structure of 15 showing 30% thermal ellipsoids. Hydrogen atoms are omitted for clarity. (a) View depicting ZrCp2 environment.
(b) Side view displaying tilt of Cp*FeCp0 fragment.
Table 1
Comparison of structural data for 9, 11–13, and 15a
b1 (ꢀ)
b2 (ꢀ)
r (ꢀ)
0.1(2)
10.0(2)
11.5(8)
2.8(3)
s (ꢀ)
0.5(2)
17.9(3)
16.5(3)
3.9(2)
kmax (nm) (e, Mꢀ1 cmꢀ1
)
d
Bridging moiety
a (ꢀ)
9b
CH2–SiMe2
CH2–S
CH2–GePh2
CH2–SnMes2
CH2–ZrCp2
11.8(1)
18.5(1)
11.81(5)
7.1(1)
7.3(3)
9.3(2)
7.2(3)
3.8(2)
1.9(3)
17.9(3)
10.6(2)
17.6(2)
17.3(1)
31.6(1)
458 (120)
475 (243)
462 (173)
454 (131)
366 (299)e
11b
12ac
13bc
15
ꢀ5.5(2)
1.3(5)
1.5(2)
a
b1 = b(CH2), b2 = b(E), where E = Si, S, Ge, Sn, Zr.
b
c
See Ref. [34].
See Ref. [35].
In hexanes.
In THF.
d
e
angle (s) is 1.5(2)ꢀ (s = angle between the CH2–ZrCp2
bond and the plane containing the Cp*/Cp0(Fe) cent-
roids and iron atom) which would suggest that 15 may
possess a small degree of strain. In addition, the struc-
ture revealed a b(CH2) of 1.9(3)ꢀ (angle between Cp*
plane and ipso-Cp*–CH2 bond) and a b(Zr) of 31.6(1)ꢀ
(angle between Cp0(Fe) plane and the ipso-Cp0–Zr
bond). These results suggest that 15 possesses some
degree of strain, since in non-bridged ferrocenes these
angles would be expected to approach zero [38]. In addi-
tion, in comparison with other carbon-heteroatom
bridged [2]ferrocenophanes 9–13 [34,35], compound 15

A. Bartole-Scott et al. / Polyhedron 25 (2006) 429–436
433
contains the largest b(E) (where E = Si, P, S, Ge, Sn,
Zr).
through the reaction of (g-C5Me4)Fe(g-C5H4Li)-
CH2Li Æ xTMEDA and dichlorodiphenylplumbane or
dichlorozirconocene. Species 14 could not be isolated
in pure form from pentamethylferrocene (g-C5Me5)-
Fe(g-C5H5), however it was found that this compound
possessed weaker C–E bonds (E = Si, Ge, Sn, Pb) than
the analogous group 14-containing carbo[2]ferroceno-
phanes 9, 12 and 13 since it decomposed under ambient
light and room temperature conditions. By contrast,
compound 15 which is the first example of a carbo[2]-
ferrocenophane containing a transition metal as the
bridging heteroatom, was isolated as yellow crystals
with a moderate ring-tilt (a = ꢀ5.5(2)ꢀ). Attempts to in-
duce ring-opening polymerization under thermal, transi-
tion metal-catalyzed or photolytic conditions were
unsuccessful; however the C–M bonds underwent cleav-
age in the presence of a strong protic acid.
2.4. Attempted ROP of [2]ferrocenophane (15)
The thermal polymerization behaviour of 15 was ini-
tially investigated by heating a sample in an evacuated
tube at temperatures up to 300 ꢀC for up to 48 h. Alter-
natively, a sample was heated in solution (C6D6) in an
1
NMR tube at 50 ꢀC for up to 96 h. In each case, H
NMR analysis displayed peaks corresponding to unre-
acted 15 as well as amounts of (g-C5Me5)Fe(g-C5H5).
Transition metal-catalyzed ROP, which is a very
useful method for preparing high molecular weight
polyferrocenylsilanes and for achieving molecular weight
control of these polymers [39], was also explored as a
means to polymerize 15. Karstedtꢀs catalyst was added
to a sample of 15 in solution in an NMR tube at 25 ꢀC.
1
However, after 48 h H NMR characterization of this
solution revealed the presence only of unreacted 15. This
sample was then heated to 40 ꢀC for 96 h. The conversion
of 15 to (g-C5Me5)Fe(g-C5H5) in 40% yield after 96 h,
was most probably a result of the heating of the sample.
Photolytic ROP is a novel polymerization method for
ferrocenophanes, and is expected to become an impor-
tant technique for the preparation of polyferrocenylsil-
anes [12]. Photolytic treatment in the presence of
phosphines has also been recently shown to induce
ring-opening reactions of [2]ferrocenophanes 7 (M =
Fe or Ru, E2 = CH2CH2) [12d]. In order to probe the
reactivity of 15, photolytic ring-opening reactions were
attempted. Samples of 15 in the presence of catalytic
and equimolar amounts of Na[g-C5H5], equimolar
amounts of the stronger donor Li[C5H4Me], and equi-
molar amounts of bis(diphenylphosphino)ethane were
irradiated for several hours. In each case, only unreacted
4. Experimental
4.1. Materials
All reagents, unless otherwise specified, were pur-
chased from Aldrich Chemical Co. and were used as re-
ceived. Solvents were dried by standard procedures and
distilled immediately prior to use. Cp2ZrCl2 was recrys-
tallized from a concentrated CHCl3 solution prior to
use. Karstedtꢀs catalyst (2.1–2.4% Pt in xylenes) was
purchased from Gelest and used as received. Ph2PbCl2
was purchased from Strem Chemical Co. and was used
as received. (g-C5Me4)Fe(g-C5H4Li)CH2Li Æ xTMEDA
was prepared according to the literature procedures
[35].
4.2. Equipment
1
15 was detected by H NMR characterization.
All reactions and manipulations were performed un-
der an inert atmosphere (prepurified N2) using either
standard Schlenk techniques or an inert atmosphere
2.5. Reaction of 15 in the presence of a strong protic acid
1
A sample of 15 was treated with an equimolar
amount of HCl (2.0 M in Et2O) at room temperature.
The solution immediately changed colour to a deep
glovebox (Mbraun). H NMR (400 or 300 MHz) and
13C NMR (100.5 MHz) spectra were recorded on
Varian Unity 400 or Varian Mercury 300 spectrome-
1
1
red. After solvent was removed, H NMR showed the
ters. All solution H and 13C NMR spectra were refer-
presence of two products. One of the products was iden-
tified as pentamethylferrocene, however the fate of the
{ZrCp2} fragment could not be conclusively identified.
Reaction with HCl seems to successfully ring-open 15,
however the reaction is not limited to breaking only
one C–Zr bond.
enced internally to residual protonated solvent shifts.
Solid state CP-MAS 13C spectra were obtained on a
Bruker DSX200 instrument with a spin rate of
8 KHz. UV–Vis spectra were obtained using a Per-
kin–Elmer Lambda 900 UV–Vis–near-IR spectropho-
tometer in THF at concentrations of 3.6 mmol Lꢀ1
.
Mass spectra were obtained with the use of a VG
70-250S mass spectrometer operating in electron im-
pact (EI) mode. The calculated isotopic distribution
for each ion was in agreement with experimental val-
ues. The photoirradiation experiments were performed
by placing the reaction flask next to a 125-W high
3. Summary
The synthesis of carboplumba[2]ferrocenophane (14)
and carbozircona[2]ferrocenophane (15) was achieved

434
A. Bartole-Scott et al. / Polyhedron 25 (2006) 429–436
pressure Hg arc lamp (Philips). The emission was
filtered by Pyrex glass (k > ca. 300 nm). Elemental
analyses were obtained using a Perkin–Elmer Series II
2400 CHNS analyzer maintained by the Analest facility
at the University of Toronto.
was complete, the deep purple solution was allowed to
stir at room temperature for 2 additional hours. The
resulting solution was filtered under N2 resulting in the
collection of a light yellow precipitate. This powder
was washed with cold toluene (5–10 mL) and residual
solvent was removed under vacuum overnight. The
product is stable in air for several hours in the solid
state. Recrystallization of this material at ꢀ30 ꢀC from
a concentrated solution in hot toluene afforded 15 as yel-
low crystals. Yield: 1.31 g (19%). 1H NMR (C6D6,
400 MHz, 25 ꢀC): d = 5.61 (s, 10H, Zr(g-C5H5)2), 3.81
(ps t, 2H, C5H4), 3.21 (ps t, 2H, C5H4), 1.82 (s, 6H,
C5Me4), 1.08 (s, 2H, CH2-Zr), 1.01 (s, 6H, C5Me4)
ppm. 13C NMR (C6D6, 100 MHz, 25 ꢀC): d = 105.6
(Zr(g-C5H5)2), 85.6 (C5Me4), 84.6 (C5Me4), 76.9
(C5H4), 76.5 (C5H4), 12.7 (C5Me4), 12.3 (C5Me4), -2.7
(CH2-Zr) ppm. Cp-MAS 13C NMR (100.6 MHz,
k = 8 KHz, 25 ꢀC) d = 156 (ipso-Cp0), 106 (Zr(g-
C5H5)2), 86 (C5Me4), 80 (ipso-Cp*), 77 (C5H4), 76
(C5H4), 15 (C5Me4), 14 (C5Me4), ꢀ3 (CH2-Zr) ppm.
UV–Vis (THF): kmax = 366 nm (e = 299 Mꢀ1 cmꢀ1).
MS (70 eV, EI): m/z (%) 474 (100) [M+], 338 (49)
[M+] ꢀ C5Me4CH2, 254 (35) [M+] ꢀ ZrCp2. Anal. Calc.
for C25H28ZrFe (475): C, 63.16; H, 5.93. Found: C,
63.32; H, 6.25%.
4.3. Synthesis of (g-C5Me4)Fe(g-C5H4)CH2PbPh2 (14)
To
a
suspension of (g-C5Me4)Fe(g-C5H4Li)-
CH2Li Æ xTMEDA (x = 0.66) (2.0 g, 5.8 mmol) in Et2O
(150 mL) kept at ꢀ78 ꢀC was added slowly with stirring
a solution of Cl2PbPh2 (3.0 g, 6.9 mmol) in 150 mL
Et2O also kept at ꢀ78 ꢀC. The resulting solution was al-
lowed to stir for 2.5 h at ꢀ78 ꢀC in the absence of light.
The orange solution was then allowed to warm to room
temperature and was filtered cold to remove LiCl. Sol-
vent was removed under vacuum for approximately 5 h
after which time the product was extracted from hexanes,
filtered cold once more and solvent was removed com-
pletely to yield a light orange gummy material. The prod-
uct contained quantities of (g-C5Me5)Fe(g-C5H5) and
attempts to isolate 14 were unsuccessful. The product is
light and temperature sensitive as attempts to recrystal-
lize at room temperature under inert atmosphere led to
a black precipitate on the side of the vial, formation of
crystals of Ph3PbPbPh3 confirmed by single crystal
X-ray diffraction; (see [40]) and an increase in the amount
of (g-C5Me5)Fe(g-C5H5) as observed by 1H NMR anal-
ysis. Purification of 14 from a concentrated hexanes solu-
tion at ꢀ30 ꢀC proved unsuccessful. Crude yield: 0.61 g
(17%). 1H NMR (400 MHz, C6D6, 25 ꢀC): d = 7.77–
7.75 (m/m, J(207Pb/H) = 72 Hz, 4H, o-C6H5), 7.31–7.27
(m/m, J(207Pb/H) = 38.4 Hz, 4H, m-C6H5), 7.15 (m,
2H, p-C6H5), 4.46 (ps t/m, J(207Pb/H) = 12.4 Hz, 2H,
C5H4), 3.80 (ps t/m, J(207Pb/H) = 12.4 Hz, 2H, C5H4),
3.23 (s/d, J(207Pb/H) = 54 Hz, 2H, CH2-Pb), 2.24 (s,
6H, C5Me4), 1.77 (s, 6H, C5Me4) ppm. 13C NMR
(100 MHz, C6D6, 25 ꢀC): d = 155.5 (J(207Pb/13C) =
30 Hz, ipso-C6H5), 137.1 (J(207Pb/13C) = 15 Hz,
o-C6H5), 131.1 (p-C6H5), 128.2 (J(207Pb/13C) = 11 Hz,
m-C6H5), 107.2 (J(207Pb/13C) = 35 Hz, ipso-C5Me4), 92.4
(J(207Pb/13C) = 10 Hz, C5Me4), 82.6 (J(207Pb/13C) =
9 Hz, C5Me4), 80.1 (C5H4), 79.5 (C5H4), 71.8
(J(207Pb/13C) = 16 Hz, ipso-C5H4), 29.3 (J(207Pb/13C) =
430 Hz, CH2-Pb), 11.9 (C5Me4), 11.7 (C5Me4) ppm. MS
(70 eV, EI): m/z (%) 616 (27) [M+], 439 (43)
[M+] ꢀ Fe ꢀ C5Me4, 254 (100) [M+] ꢀ PbPh2.
4.5. Attempted thermal polymerization of 15
A sample of 15 (0.5 g) was sealed in an evacuated
Pyrex tube and heated up to 300 ꢀC for 48 h, however
there was no observable increase in viscosity. The
1
resulting material was characterized by H NMR and
contained unreacted 15 as well as (g-C5Me5)Fe(g-
C5H5).
Alternatively, a solution of 15 (25 mg) in C6D6
(1.5 mL) was heated in an NMR tube under inert atmo-
sphere at 50 ꢀC for a period up to 96 h. After approxi-
mately 12 h, 1H NMR characterization revealed 15%
conversion to (g-C5Me5)Fe(g-C5H5). After 96 h, 1H
NMR characterization displayed very broad peaks and
70% conversion to (g-C5Me5)Fe(g-C5H5). No other
products could be isolated.
4.6. Attempted platinum-catalyzed ring-opening reactions
of 15
To a solution of 15 (25 mg) in C6D6 (1.5 mL) was
added Karstedtꢀs catalyst (0.5% wt, 6.46 lL) in an
NMR tube. The mixture was allowed to react under in-
ert atmosphere for 48 h, after which time 1H NMR char-
acterization displayed only the presence of 15. This
solution was then heated to 40 ꢀC for a period up to
96 h. After approximately 48 h, no change was observed
in the 1H NMR spectrum. At 96 h, 1H NMR character-
ization revealed approximately 40% conversion to (g-
C5Me5)Fe(g-C5H5).
4.4. Synthesis of (g-C5Me4)Fe(g-C5H4)CH2ZrCp2 (15)
To a solution of (g-C5Me4)Fe(g-C5H4Li)CH2Li Æ
xTMEDA (x = 0.66) (5.0 g, 14.5 mmol) in a THF/tolu-
ene mixture (50/50 v/v, 15 mL/15 mL) was added very
slowly with stirring a solution of Cp2ZrCl2 (4.23 g,
14.5 mmol) in a THF/toluene mixture (50/50 v/v,
15 mL/15 mL) at room temperature. After the addition

A. Bartole-Scott et al. / Polyhedron 25 (2006) 429–436
435
4.7. Attempted photolytic ring-opening reactions of 15
5. Supplementary material
A solution of 15 (50 mg, 105 lmol) in THF (1 mL) in
a Schlenk flask was treated with: (i) 10% Na(C5H5)
(2.0 M in THF, 5.25 lL), (ii) 1 equivalent of Na(C5H5)
CCDC 270933 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
(2.0 M in THF), 52.5 lL), (iii)
1 equivalent of
Li(C5H4CH3) (9.0 mg), and (iv) 1 equivalent of bis(diph-
enylphosphino)ethane (41.9 mg). Solutions were placed
in a 5 ꢀC bath and irradiated for approximately 3–5 h.
In each case, only unreacted 15 could be detected by
1H NMR.
Acknowledgements
We thank the Natural Science and Engineering
Research Council of Canada (NSERC) for funding this
research. In addition, A. Bartole-Scott would like to
thank the Ontario Government for an O.G.S. scholar-
ship (2004–2005) and I. Manners is grateful to the
Government of Canada for a CRC award (2001–
2008). We also thank Dr. Andrew Baer from the Solid
State NMR facility at the University of Toronto for help
performing CP-MAS experiments.
4.8. Reaction of 15 in the presence of a strong protic acid
One equivalent of HCl Æ Et2O (2 M in Et2O,
31.5 lL) was added dropwise to a yellow solution of
15 (30 mg, 63.1 lmol) in Et2O (2 mL) at room temper-
ature. Upon addition of HCl Æ Et2O, the solution
immediately changed colour to deep red. The mixture
was allowed to stir for an additional hour and
remained a deep red colour, after which time solvent
was removed under vacuum. Initial 1H NMR
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