1,1′-(1-Propene-1,3-diyl)-ferrocene: Modified synthesis, crystal structure, and polymerisation behaviour

Article abstract of DOI:10.1016/j.jorganchem.2003.12.001

The dehydro[3](1,1′)ferrocenophanes, 1,1′-(1-propene-1,3-diyl)-ferrocene (3a), and 1,1′-(3-phenyl-1-propene-1,3-diyl)-ferrocene (3b) were synthesised under Shapiro conditions from the tosylhydrazones of the corresponding α-oxo-[3](1,1′)ferrocenophanes. Electrochemistry shows 3a is oxidised at smilar potential to ferrocene; according 3a can be chemically oxidised using silver trifluoromethanesulfonate. The structure of 3a shows a ring tilt of 11.3°. Attempts to polymerise 3a using the ROMP initiator Mo(CHCMe₂Ph)[N(2,6-ⁱPr₂ C₆H₃)][OCMe(CF₃)₂] ₂ led to a mixture of insoluble material and a soluble mixture of apparently cyclic oligomers ([3a]_n).

Full text of DOI:10.1016/j.jorganchem.2003.12.001

Journal of Organometallic Chemistry 689 (2004) 775–780
www.elsevier.com/locate/jorganchem
1,10-(1-Propene-1,3-diyl)-ferrocene: modified synthesis,
crystal structure, and polymerisation behaviour
a
Christofer Arisandy , Andrew R. Cowley , Stephen Barlow
a
a,b,
*
a
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
b
School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State Street, Atlanta, GA 30332-0400, USA
Received 3 November 2003; accepted 9 December 2003
Abstract
The dehydro[3](1,10 )ferrocenophanes, 1,10 -(1-propene-1,3-diyl)-ferrocene (3a), and 1,10 -(3-phenyl-1-propene-1,3-diyl)-ferrocene
(3b) were synthesised under Shapiro conditions from the tosylhydrazones of the corresponding a-oxo-[3](1,10 )ferrocenophanes.
Electrochemistry shows 3a is oxidised at smilar potential to ferrocene; according 3a can be chemically oxidised using silver triflu-
oromethanesulfonate. The structure of 3a shows a ring tilt of 11.3°. Attempts to polymerise 3a using the ROMP initiator
Mo(CHCMe2Ph)[N(2,6-iPr2C6H3)][OCMe(CF3)2]2 led to a mixture of insoluble material and a soluble mixture of apparently cyclic
oligomers ([3a]n).
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Ferrocenophane; Ferrocene polymer; ROMP
1. Introduction
functionalities into polymers [15–19]. The use of ROMP
to polymerise [3]ferrocenophanes with unsaturated
bridges has not been reported; although the resulting
polymers would not be conjugated, there are precedents
suggesting that hydride could be abstracted from
CH@CH–CH2 bridges [20] to afford cationic polymers
with the (CH)þ3 bridges facilitating interesting interme-
tallic interactions [20,21]. Here we report: an improved
synthesis of 1,10 -(1-propene-1,3-diyl)-ferrocenes, i.e. de-
hydro[3](1,10 )ferrocenophanes (3); the crystal structure
of 1,10 -(1-propene-1,3-diyl)-ferrocene (3a); and pre-
liminary studies of the behavior of 3a when treated with
ROMP initiators.
Recently there has been considerable interest in
polymers incorporating ferrocene (and to a lesser extent
other metallocenes) into their main chain [1–3]. Many of
the best methods for making high molecular weight well-
defined species involve the ring-opening of strained
ferrocenophanes: [2]ferrocenophanes with C2H4 bridges
have been polymerised thermally [4]; [1]ferrocenophanes
with various heteroatom bridges have been polymerised
thermally [5,6], anionically [7], or using transition-metal
catalysts [8,9]; [3]ferrocenophanes with S3 bridges have
been converted to polymers through sulfur abstraction
by phosphines [10]; and [2]ferrocenophanes [11] and
[4]ferrocenophanes [12,13] with unsaturated hydrocar-
bon bridges have been polymerised using ROMP [14].
ROMP offers, under certain circumstances, possibilities
to synthesize conjugated polymers, to obtain narrow
molecular weight distributions, to control the nature of
the end groups, to obtain well-defined block copoly-
mers, and to incorporate a wide range of chemical
2. Experimental
2.1. General
Cyclic voltammograms were recorded using a glassy-
carbon working electrode, a platinum wire auxillary
electrode and a silver wire pseudo-reference electrode.
Measurements were made on deoxygenated THF
solutions ca. 0.1 M in [nBu4N]þ[PF6]ꢀ. Potentials were
* Corresponding author. Tel.: +404-385-6053; fax: +404-385-6057.
E-mail address: stephen.barlow@chemistry.gatech.edu (S. Barlow).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.12.001

776
C. Arisandy et al. / Journal of Organometallic Chemistry 689 (2004) 775–780
referenced to the ferrocene/ferrocenium couple at 0 V by
comparison to ferrocene under the same conditions.
Gel-permeation chromatography (GPC) was carried
out using PLgel Mixed-A columns calibrated with
it is uncertain whether the atomic coordinates are cor-
rect. Geometric parameters derived from the coordi-
nates of these atoms should be regarded as unreliable.
No attempt was made to model the disorder of the cy-
clopentadienyl fragments or of the iron atom. Deter-
mination of the absolute structure shows the crystal to
be twinned by inversion (the refined value of the Flack
Parameter is 0.52(3)). Hydrogen atoms were positioned
geometrically after each cycle of refinement. A four-term
Chebychev polynomial weighting scheme was applied.
Refinement converged satisfactorily to give R ¼ 0:0275,
polystyrene narrow standards (Mp ¼ 580 ꢀ 11:6ꢁ10ꢀ6
)
in THF, with toluene as a flow marker. The THF
was degassed with helium and pumped at a rate of
1 ml minꢀ1 at 30 °C. The ROMP initiators, [Ru] and
[Mo] were obtained from Strem, whilst other chemicals
were obtained from Aldrich.
2.2. X-ray crystallography
Rw ¼ 0:0288, and S ¼ 1:0574, with residual electron
ꢀꢀ3
density minimum and maxima of )0.50 and 0.51 e A
,
An orange–yellow platy single crystal of 3a
(C13H12Fe, RMM ¼ 224.09) of approximate dimen-
sions 0.06 ꢁ 0.18 ꢁ 0.23 mm, grown by slow evaporation
of a hexane solution, was mounted on a glass fibre using
perfluoropolyether oil and cooled rapidly to 150 K in a
stream of cold N2 using an Oxford Cryosystems
CRYOSTREAM unit. Diffraction data (6520 reflec-
tions, 5:0° 6 h 6 27:5°) were measured using an Enraf-
Nonius Kappa CCD diffractometer (graphite-mono-
respectively. Full crystallographic data for the structural
analysis of 3a has been deposited with the Cambridge
Crystallographic Data Centre, CCDC 222272.
2.3. 1,10 -(1-Propene-1,3-diyl)-ferrocene (3a)
A solution of 2a [24] (1.2 g, 3 mmol) in dry THF (50
ml) was heated to 60 °C. To this solution was added
dropwise a solution of lithium di-iso-propylamide (1 g, 9
mmol) in dry THF (20 ml). Emission of a gas was ob-
served and the solution gradually turned to brown. The
reaction was stirred at reflux temperature for 4 hours
and then cooled to room temperature. Volatiles were
removed under reduced pressure and the remaining solid
was extracted with diethyl ether (3 ꢁ 100 ml). The
combined ether extracts were washed with water
(2 ꢁ 150 ml) and then with saturated NaCl(aq) (1 ꢁ 100
ml, dried over MgSO4, and then evaporated under re-
duced pressure. Finally, the product was purified by
column chromatography on silica gel, eluting with
hexane, to yield a yellow crystalline solid in variable
yield (20–40%). 1H NMR (benzene-d6, 300 MHz) d 6.10
(dt, J ¼ 10:5, 2.8 Hz, 1H, CH@), 5.81 (dt, J ¼ 10:5, 3.9
Hz, 1H, CH@), 4.05 (t, J ¼ 1:8 Hz, 2H, C5H4CH), 4.03
(t, J ¼ 1:8 Hz, 2H, C5H4CH), 3.97 (t, J ¼ 1:8 Hz, 2H,
C5H4CH), 3.84 (t, J ¼ 1:8 Hz, 2H, C5H4CH), 2.54 (dd,
J ¼ 3:9, 2.8 Hz, 2H, CH2). 13C NMR (CDCl3, 75 MHz)
d 139.5 (CH@), 120.9 (CH@), 85.7 (C5H4 quat.), 84.4
(C5H4 quat.), 71.2 (C5H4CH), 70.2 (C5H4CH), 69.1
(C5H4CH), 69.0 (C5H4CH), 24.8 (CH2). UV–Vis
(CH2Cl2): kmaxðꢀmax) 448 nm (245 Mꢀ1 cmꢀ1). EI-MS
m/z 224 (Mþ). Analysis (%): Found (Calculated); C,
69.61 (69.68); H, 5.42 (5.40).
ꢀ
chromated Mo Ka radiation, k ¼ 0:71073 A). Intensity
data were processed using the DENZO-SMN package
[22]. The crystal was found to be orthorhombic, with
ꢀ
ꢀ
a ¼ 7:5774ð3Þ A, b ¼ 9:9886ð4Þ A, c ¼ 12:5472ð5Þ,
V ¼ 949:7 A , Z ¼ 4, qcalc ¼ 1:567 g cmꢀ3, and l ¼
3
ꢀ
1:536 mmꢀ1. Examination of the systematic absences of
the intensity data showed the space group to be either
Pbnm or Pbn21. All attempts to solve the structure in the
former space group were unsuccessful. The structure
was solved in the space group Pbn21 using the direct-
methods program SIR92 [22], which located all non-
hydrogen atoms. Examination of the resulting model
clearly showed no crystallographic mirror plane to be
present, confirming the assignment of symmetry. A
semi-empirical absorption correction was employed
(minimum and maximum transmission coefficients of
0.70 and 0.91, respectively) based on equivalent reflec-
tions. Subsequent full-matrix least-squares refinement
on F was carried out using the CRYSTALS Program
Suite [23] (2167 unique reflections, Rint ¼ 0:035, 1749
with I > 3rðIÞ). Coordinates and anisotropic thermal
parameters of all non-hydrogen atoms were refined. The
resulting structure showed abnormal geometry of the
alkene bridge, with the molecule appearing to have a
highly symmetric structure with approximate point
group 2mm (C2v). In addition, the thermal parameters of
the bridge C atoms seemed to be excessively large. The
molecule was therefore modelled as disordered over two
orientions related by a non-crystallographic mirror
plane. The coordinates, isotropic thermal parameters
and site occupancies of the bridging atoms were refined,
with chemically equivalent bond lengths and angles re-
strained to their common means. The two positions for
the disordered bridge closely overlap and consequently
2.4. 1,10 -(1-Propene-1,3-diyl)-ferrocenium trifluorome-
thanesulfonate ([3a]þ[CF3SO3]ꢀ)
A solution of AgCF3SO3 (47 mg, 0.17 mmol) in dry
THF (5 ml) was added dropwise to a solution of 3a (41
mg, 0.18 mmol) in dry THF (5 ml). The solution rapidly
turned deep green, and a fine silver precipitate was ob-
served. The mixture was stirred for an hour and
the volatiles were removed under reduced pressure. The

C. Arisandy et al. / Journal of Organometallic Chemistry 689 (2004) 775–780
777
remaining solid was washed with diethyl ether (3 ꢁ 10
ml) and then extracted into dry CH2Cl2 (20 ml). After
filtration through a bed of Celite, the solution was then
layered with dry pentane (100 ml), resulting in the slow
precipitation of a green solid (27 mg, 0.12 mmol, 70%).
aqueous saturated NaCl (1 ꢁ 20 ml), dried over MgSO4,
and evaporated under reduced pressure. The product
was purified by crystallization from hexane to give a
yellow solid in 15–25% yield. 1H NMR (CDCl3, 300
MHz) d 7.75 (d, J ¼ 8:0 Hz, 2H, Ph o-HCH), 7.00–7.30
(m, overlapping peaks, 3H, Ph m- and p-H), 6.50 (m,
2H, 2 ꢁ CH@), 4.50 (t, J ¼ 1:8 Hz, 1H, C5H4CH), 4.46
(t, J ¼ 1:8 Hz, 1H, C5H4CH), 4.42 (t, J ¼ 1:8 Hz, 1H,
C5H4CH), 4.35 (t, J ¼ 1:8 Hz, 2H, C5H4 CH), 4.20 (t,
J ¼ 1:8 Hz, 2H, C5H4CH), 4.02 (t, J ¼ 1:8 Hz, 1H,
C5H4 CH), 2.64 (d, J ¼ 3:8 Hz, 1H, CHPh). 13C NMR
(CDCl3, 75 MHz) d 129.6 (Ph or CH@), 129.0 (Ph or
CH@), 128.5 (Ph or CH@), 127.0 (Ph or CH@), 126.8
(Ph or CH@), 126.0 (Ph or CH@), 71.2 (C5H4), 70.5
(C5H4), 70.3 (C5H4), 70.1 (C5H4), 69.8 (C5H4), 69.2
(C5H4), 68.0 (C5H4), 26.0 (CHPh) (some overlap of Cp
ES-MS: m/z 224 ([3a]þ). UV–Vis (CH2Cl2): kmax (ꢀmax
)
613 nm (833 Mꢀ1 cmꢀ1). Analysis (%): Found (Calcu-
lated); C, 33.91 (33.96); H, 2.57 (2.64); Fe, 12.61 (12.15).
2.5. 1,10 -[1-(p-Toluenesulfonyl)hydrazono-3-phenyl-pro-
pane-1,3-diyl]-ferrocene (2b)
To a solution of the corresponding ketone, 1b [25] (80
mg, 0.25 mmol) in ethanol (10 ml) was added dropwise
p-toluene sulphonyl hydrazide (46 mg, 0.25 mmol) in
acetic acid (0.5 ml). This mixture was heated to reflux
for 2 h and then cooled to room temperature. Volatiles
were removed under reduced pressure and the product
was dissolved in CH2Cl2 (10 ml). This solution was
washed with saturated aqueous NaHCO3 (3 ꢁ 15 ml)
and then dried over MgSO4. Finally the volatiles were
removed under reduced pressure to afford a yellow–or-
ange crystalline material (96.9 mg, 0.20 mmol, 80%). 1H
NMR (CDCl3, 300 MHz) d 7.75 (t, J ¼ 8:0 Hz, 2H, Ph
m-CH ), 7.06–7.24 (m, 7H, overlapping peaks, Ph o- and
p-CH and tolyl CH), 4.42 (t, J ¼ 1:8Hz, 1H, C5H4CH),
4.40 (t, J ¼ 1:8 Hz, 1H, C5H4CH), 4.38 (t, J ¼ 1:8 Hz,
2H, C5H4CH), 4.05 (t, J ¼ 1:8 Hz, 2H, C5H4 CH), 4.25
(t, J ¼ 1:8 Hz, 1H, C5H4CH), 3.95 (t, J ¼ 1:8 Hz, 1H,
C5H4CH), 3.63 (dd, J ¼ 2:3Hz, 12.9 Hz, 1H, CHPh),
3.28 (apparent t, J ¼ 12:9 Hz, 1H, CH2 [H cis to
CHPh]), 2.95 (dd, J ¼ 2:3 Hz, 12.9 Hz, 1H, CH2 [H
trans to CHPh]), 2.45 (s, 3H, CH3). 13C NMR (CDCl3,
75 MHz) d 155.9 (C@N), 143.7 (Ar quat.), 143.1 (Ar
quat.), 135.0 (Ar quat.), 129.3 (ArCH), 128.2 (ArCH),
127.7 (ArCH), 126.7 (ArCH), 126.3 (ArCH), 89.9 (C5H4
quat.), 72.5 (C5H4CH), 71.7 (C5H4 quat.), 71.2 (C5H4
2 ꢁ overlapping CH), 71.0 (C5H4CH), 70.9 (C5H4CH),
68.5 (C5H4CH), 68.3 (C5H4CH), 67.6 (C5H4CH), 49.6
(CHPh), 45.5 (CH2), 21.8 (C H3). UV–Vis (EtOH) kmax
(ꢀmax) 442 nm (515 Mꢀ1 cmꢀ1). ES-MS: m/z 484 (Mþ,
20%), 300 (100%, Mþ–NNHTs). Analysis (%): Found
(Calculated); C, 64.14 (64.47); H, 5.04 (4.99); N, 5.74
(5.78); Fe,11.53 (11.45).
13C resonances is assumed). UV–Vis (EtOH) kmax (ꢀmax
)
444 nm (255 Mꢀ1 cmꢀ1). Analysis (%): Found (Calcu-
lated); C, 75.39 (76.02); H, 5.37 (5.62).
2.7. Polymerization experiments
In a nitrogen-filled Vacuum Atmospheres glove-box,
3a (25 mg, 0.11 mmol) was loaded into an NMR tube
and dissolved in dry benzene-d6 (0.5 ml). A solution of
ROMP initiator [Ru] or [Mo] (1/10, 1/20 or 1/50 equiv-
alent) in dry benzene-d6 (0.5 ml) was added rapidly to
the solution and shaken. The yellow solution was then
heated (up to 60 °C for [Ru]; up to 40 °C for [Mo]) and
the progress of the reaction was monitored by 1H NMR
spectroscopy.
In the case of a [Mo]-initiated reaction heated for 40
°C, the reaction was quenched after 3 days by addition
of excess benzaldehyde. Volatiles were removed under
reduced pressure to give a yellow solid. Soluble material
4a was extracted into THF (3 ꢁ 1 ml) and evaporated
under reduced pressure to give an orange solid in ca.
60% yield. ES-MS m/z 896 (1%, [3a]þ4 ), 672 (5%, [3a]3þ),
594 (1%), 532 (1%), 448 (90%, [3a]þ2 ), 429 (1%), 370
(1%), 266 (100%), 224 (45%, [3a]þ), 178 (20%). EI-MS
1120 (3%, [3a]þ5 ), 896 (100%, [3a]þ4 ), 887 (10%), 672
(64%, [3a]þ3 ), 448 (36%, [3a]þ2 ), 342 (48%), 224 (93%,
[3a]þ), 121 (36%). Analysis (%): Found (Calculated for
[3a]n); C, 68.98 (69.68); H, 5.38 (5.40).
2.6. 1,10 -(3-Phenyl-1-propene-1,3-diyl)-ferrocene (3b)
3. Results and discussion
A solution of 2b (0.15 g, 0.5 mmol) in dry THF (10
ml) was heated to 60 °C. To this solution was added
dropwise a solution of lithium di-iso-propylamide (0.2 g,
1.8 mmol) in dry THF (5 ml). The reaction was stirred at
reflux temperature for 4 h and then cooled to room
temperature. Volatiles were removed under reduced
pressure and the remaining solid was extracted with
diethyl ether (3 ꢁ 20 ml). The combined ether extracts
were washed with water (2 ꢁ 25 ml) and then with
1,10 -(1-Propene-1,3-diyl)-ferrocene, 3a, has previously
been synthesized by several methods. Subjecting the tosyl
hydrazone of b-oxo-[3](1,10 )ferrocenophane to Bamford–
Stevens conditions affords 3a in 70% yield [26]. The
corresponding reaction with the tosyl hydrazone of
a-oxo-[3](1,10 )ferrocenophane, 2a, is considerably less
efficient, with a reported yield of 22% [24]. However, a-
oxo-[3](1,10 )ferrocenophane, 1a, can be obtained readily

778
C. Arisandy et al. / Journal of Organometallic Chemistry 689 (2004) 775–780
from ferrocene in one step by a low-temperature Friedel–
Crafts reaction with acryloyl chloride [27], whereas its b
isomer is only accessible via amulti-step synthesis [26]. We
have found that this conversion of the tosyl hydrazone of
a-oxo-[3](1,10 )ferrocenophane to 3a may be accomplished
in generally somewhat higher, although variable, yield
under Shapiro conditions (i.e. a soluble base in a polar
solvent at moderate temperature; Scheme 1) [28,29], than
reported under Bamford–Stevens conditions (insoluble
base, non-polar solvent, high temperature) [30]. We were
also able to extend this reaction to 1,10 -(3-phenyl-1-pro-
pene-1,3-diyl)-ferrocene (3b) – a phenyl-substituted de-
rivative of 3a.
3a is oxidised at essentially the same potential as
ferrocene. 3a can be chemically oxidized to green
[3a]þ[CF3SO3]ꢀ using AgCF3SO3; the visible absorption
spectrum of the salt shows an absorption at 613 nm
(ꢀmax 830 Mꢀ1 cmꢀ1) in dichloromethane, similar to that
of unsubstituted ferrocenium [31].
Fig. 1. View of the molecular structure of 3a with 50% thermal ellip-
soids; for clarity, hydrogen atoms are omitted and only one of the two
orientations of the disordered bridge is shown. C11–C13 is the
CH@CH double bond.
strain to be polymerisable using ROMP. As in the
structures of many other ring-tilted ferrocenophanes,
We obtained single crystals of 3a suitable for X-ray
structure determination from hexane. The molecular
structure is shown in Fig. 1; details of the structure de-
termination are given in the experimental details (see
above) and in information deposited at the Cambridge
Crystallographic Data Centre, CCDC 222272. The
structure is somewhat disordered (see Section 2); this
principally affects the reliability of parameters concern-
ing the three-carbon bridge. The most prominent feature
of the structure, which should be relatively unaffected by
the disorder is the ring tilt of 11.3°. This angle is
somewhat larger than those observed for other
[3](1,10 )ferrocenophanes with saturated bridges (8.8–
10.9°) [32–36]; comparable dehydro[3](1,10 )ferroceno-
phanes, 1,10 -(1-ferrocenyl-1-propene-1,3-diyl)-ferrocene
and 1,10 -(1,3-diferrocenyl-3-methyl-1-propene-1,3-diyl)-
ferrocene, have ring tilts of 12.3° and 12.6°, respectively
[39,37,38]. Ring tilts of 7.2° and 11.1° have been
reported for two independent molecules of the unsatu-
rated [4]ferrocenophane, 1,10 -(1-methoxybutadiene-1,4-
diyl)-ferrocene [40]; values of 21.6° and 23° have been
reported for CH2CH2 and CH@CH bridged [2]ferroce-
nophanes, respectively [4,11]. The observed ring tilt for
3a suggests that this species may possess sufficient ring
ꢀ
the Fe–Cipso bonds (2.009(3) and 2.010(3) A) are sig-
nificantly shorter than the bonds between iron and the
ꢀ
more distant carbon atoms (2.032(3)–2.037(3) A for
ꢀ
carbons adjacent to bridge; 2.059(3) – 2.064(5) A for the
carbons non-adjacent to the bridge).
We have made preliminary investigations of the re-
action of 3a with two commercial ROMP initiators,
Ru(CHPh)(PCy3)2Cl2 {Cy ¼ cyclohexyl} ([Ru]) and Mo-
(CHCMe2Ph)[N(2, 6-iPr2C6H3)][OCMe(CF3)2]2 ([Mo]).
Reaction of 3a with [Ru] was monitored by following the
disappearance of the initiator carbene peak (20.6 ppm)
in the 1H NMR spectrum; after seven days heating at 60
°C in benzene-d6, this peak was still present, although
diminished in intensity, and, although some new peaks
had appeared, peaks attributable to the monomer still
remained and indicated that ca. 30% of the 3a was still
present. When [Mo] was used in benzene-d6, the carbene
peak was observed to completely disappear after three
days heating at 40 °C, and the monomer was essentially
totally consumed. Solid material had also appeared in
this time. After quenching with benzaldehyde and re-
moval of volatiles, ca. 60% of the residues were found to
be soluble in THF. GPC analysis of this soluble material
–
CF SO
3
Fe
3
AgCF SO
3
3
THF
O
R
NNHTs
LDA, THF
reflux
TsNHNH ,
2
AcOH, EtOH
+
–
[3a] [CF SO ]
3
3
Fe
Fe
Fe
reflux
[Mo], C H
6
6
40 ˚C
R
R
Fe
1a, R = H
1b, R = Ph
2a, R = H
2b, R = Ph
3a, R = H
3b, R = Ph
n
4a (+ insoluble solids)
Scheme 1. Preparation and reactions of dehydro[3](1,10 )ferrocenophanes.

C. Arisandy et al. / Journal of Organometallic Chemistry 689 (2004) 775–780
779
(THF vs. polystyrene standards) showed low molecular-
weight material (Mn ¼ 350; Mw ¼ 535; Mzþ1 ¼ 1484;
PDI ¼ 1.53; it should be noted that the lowest molecular
weight standards employed were characterised by
Mp ¼ 580 and and so these values indicated for the
molecular weights of the oligomers are only very crude
estimates). Interestingly, the main identifiable peaks in
both electrospray and electron-impact mass spectra of
the soluble fraction correspond to 3a and its low mo-
lecular weight oligomers; although both experiments
may be complicated by fragmentations, it is notable that
no evidence is found for species of the type shown in
Scheme 2(a) and (b), where oligomers have terminal
PhCMe2CH@ and PhCH@ groups from the initiator
and benzaldeyde respectively. Moreover, elemental
analysis is consistent with a formulation as [3a]n. Cyclic
structures for the oligomers would be consistent with the
mass spectra and the analytical data (Scheme 2(c)).
Presumably the THF-insoluble fraction consists of
higher molecular weight species, either linear or cyclic.
Cyclic voltammetry of 4a shows a single quasi-reversible
wave at essentially the same potential as ferrocene; no
metal–metal interactions would be expected to be de-
tected given the length of the non-conjugated bridge
[41], and similar environments for each ferrocene would
be anticipated even though a variety of species are likely
to be present.
In summary, we have presented an improved synthesis
of dehydro[3](1,10 )ferrocenophanes and reported the first
crystal structure of a member of this class without bulky
substituents. The slow initiation observed in the reactions
of 3a with [Ru] and [Mo] suggests that future attempts to
polymerise dehydro[3](1,10 )ferrocenophanes should be
carried out with a more active catalyst, such as the tung-
sten species used for the the polymerisation of dehy-
dro[4](1,10 )ferrocenophanes [12,13]. The formation of
insoluble orange material in the present study suggests
that poly{dehydro[3] (1,10 )ferrocenophane} is not highly
soluble and therefore suggests that future work should
employ derivatives bearing solubilising groups. The
extension of the preparation of 3a to its phenyl derivative
3b suggest that such solubilisation could readily be
achieved by synthesis of an aryl derivative where the aryl
group bears a long alkyl chain. It should also be noted that
soluble polymers can potentially be obtained through
copolymerisation with other monomers; for example, a
block copolymer of norbornene and dehydro(1,10 )[2]fer-
rocenophane was soluble, whereas the homopolymer was
insoluble [11].
Acknowledgements
We thank the Royal Society for partial funding of
this project, Dr. Graham Webster for help with GPC
measurements, and Dr. Tim Brunker for help producing
Fig. 1.
References
ꢁ
[1] P. Nguyen, P. Gomez-Elipe, I. Manners, Chem. Rev. 99 (1999)
1515.
[2] R.D.A. Hudson, J. Organomet. Chem. 637–639 (2001) 47.
[3] I. Manners, Science 294 (2001) 1664.
[4] J.M. Nelson, P. Nguyen, R. Petersen, H. Rengel, P.M. Macdon-
ald, A.J. Lough, I. Manners, N.P. Raju, J.E. Greedan, S. Barlow,
D. OÕHare, Chem. Eur. J. 3 (1997) 573.
[5] D.A. Foucher, B.-Z. Tang, I. Manners, J. Am. Chem. Soc. 114
(1992) 6246.
[6] M.T. Nguyen, A.F. Diaz, V.V. DementÕev, K.H. Pannell, Chem.
Mater. 5 (1993) 1389.
[7] R. Rulkens, Y.Z. Ni, I. Manners, J. Am. Chem. Soc. 116 (1994)
12121.
[8] Y. Ni, R. Rulkens, J.K. Pudelski, I. Manners, Makromol. Chem.
Rapid Commun. 14 (1995) 637.
[9] N.P. Reddy, H. Yamashita, M. Tanaka, J. Chem. Soc., Chem.
Commun. (1995) 2263.
[10] P.F. Brandt, T.B. Rauchfuss, J. Am. Chem. Soc. 114 (1992)
1926.
[11] M.A. Buretea, T.D. Tilley, Organometallics 16 (1997) 1507.
[12] C.E. Stanton, T.R. Lee, R.H. Grubbs, N.S. Lewis, J.K. Pudelski,
M.R. Callstrom, M.S. Erickson, M.L. McLaughlin, Macromole-
cules 28 (1995) 8713.
[13] R.W. Heo, F.B. Somoza, T.R. Lee, J. Am. Chem. Soc. 120 (1998)
1621.
[14] (a) ROMP has also be used to synthesize polymers with pendant
ferrocenyl groups D. Albagli, G. Bazan, M.S. Wrighton, R.R.
Schrock, J. Am. Chem. Soc. 114 (1992) 4150;
(b) K.J. Watson, S.T. Nguyen, C.A. Mirkin, J. Organomet. Chem.
606 (2000) 79, and ring-closing olefin metathesis has been used to
synthesize 1,10 -(2-butene-1,3-diyl)-ferrocenes;
(c) A.J. Locke, C. Jones, C.J. Richards, J. Organomet. Chem. 637–
639 (2001) 669;
Ph
Fe
Ph
n
Fe
(a)
Fe
Ph
(d) M. Ogasawara, T. Nagano, T. Hayashi, J. Am. Chem. Soc. 124
(2002) 9068.
[15] W.J. Feast, Makromol. Chem., Macromol. Symp. 53 (1992)
317.
Fe
n-1
Ph
(c)
[16] R.H. Grubbs, S.J. Miller, G.C. Fu, Acc. Chem. Res. 28 (1995)
446.
n
(b)
[17] R.R. Schrock, Top. Organomet. Chem. 1 (1998) 1.
[18] R.H. Grubbs, E. Khosravi, Mater. Sci. Technol. 20 (1999) 65.
[19] M.R. Buchmeiser, Chem. Rev. 100 (2000) 1565.
Scheme 2. Possible linear (a and b) and cyclic (c) structures for oligo-
and poly-3a.

780
C. Arisandy et al. / Journal of Organometallic Chemistry 689 (2004) 775–780
€
[34] O. Kadkin, C. Nather, W. Friedrichsen, J. Organomet. Chem. 649
(2002) 161.
[20] L.M. Tolbert, X. Zhao, Y. Ding, L.A. Bottomley, J. Am. Chem.
Soc. 117 (1995) 12891.
[21] S. Barlow, L.M. Henling, M.W. Day, W.P. Schaefer, J.C. Green,
T. Hascall, S.R. Marder, J. Am. Chem. Soc. 124 (2002) 6285.
[22] Z. Otwinowski, W. Minor, in: C.W. Carter, R.M. Sweet (Eds.),
Processing of X-ray Difraction Data Collected in Oscillation
Mode, Methods Enzymol., 276, Academic Press, New York, 1997.
[23] D.J. Watkin, C.K. Prout, J.R. Carruthers, P.W. Betteridge,
CRYSTALS – Issue 10, Chemical Crystallography Laboratory,
Oxford, UK, 1996.
[35] T.J. Brunker, C. Arisandy, A.R. Cowley, L.H. Rees, S. Barlow, D.
OÕHare, J. Organomet. Chem. 689 (2004) 252.
[36] An FeIII species – the TCNQ salt of [3](1,10 )ferrocenophane – has
a greater ring tilt than 3a to enable it to accommodate the longer
Fe–C bonds found in ferrocenium systems C. Willi, A.H. Reis, E.
Gebert, J.S. Miller, Inorg. Chem. 20 (1981) 313.
[37] T.M. Trnka, R.C. Kerber, Acta Crystallogr. C 51 (1995) 871.
[38] C.-F. Chiu, C.-L. Hwang, D.-S. Pan, Y.J. Chen, K.S. Kwan, J.
Organomet. Chem. 563 (1998) 95–99.
[24] M. Applebaum, R.W. Fish, M. Rosenblum, J. Org. Chem. 29
(1964) 2452.
[39] (a) Structures have also been determined for [3]metallocenophanes
in which there are are three sp2 carbon atoms in the bridge – i.e. a
double bond within the bridge, and an exo double bond from the
remaining carbon. For example, ring tilts of 12.6°–12.8° have been
found for 1,10 -[1-(dialkylamino)butadiene-1,3-diyl]ferrocenes
[25] A.J. Locke, C.J. Richards, Organometallics 18 (1999).
[26] A. Sonoda, I. Moritani, J. Organomet. Chem. 26 (1971) 133.
[27] T.D. Turbitt, W.E. Watts, J. Organomet. Chem. 46 (1972) 109–
117.
€
€
S. Knuppel, R. Frohlich, G. Erker, J. Organomet. Chem. 586
[28] R.H. Shapiro, M.J. Heath, J. Am. Chem. Soc. 89 (1967) 5734–
5735.
(1999) 218;
€
€
[29] R.H. Shapiro, M.F. Lipton, K.J. Kolonko, R.L. Buswell, L.A.
Capuano, Tetrahedron Lett. (1975) 1811–1814.
(b) P. Liptau, S. Knuppel, G. Kehr, O. Kataeva, R. Frohlich, G.
Erker, J. Organomet. Chem. 637–639 (2001) 621, and a ring tilt of
9.7° in the 1,10 -[3-(2,4-dihydroxyphenyl)butadiene-1,3-diyl]cobalt-
ocenium cation;
[30] W.R. Bamford, T.S. Stevens, J. Chem. Soc. (1952) 4735–4740.
[31] M. Fontani, F. Peters, W. Scherer, W. Wachter, M. Wagner, P.
Zanello, Eur. J. Inorg. Chem. (1998) 1453.
(c) P.D. Beer, M.G.B. Drew, D. Hesek, S.M. Lacy, J. Organomet.
Chem. 511 (1996) 207.
[32] S.-J. Jong, J.-M. Fang, Org. Lett. 2 (2000) 1947.
€
€
[33] P. Liptau, S. Knuppel, G. Kehr, O. Kataeva, R. Frohlich, G.
[40] J.K. Pudelski, M.R. Callstrom, Organometallics 13 (1994) 3095.
[41] S. Barlow, D. OÕHare, Chem. Rev. 97 (1997) 637.
Erker, J. Organomet. Chem. 637–639 (2001) 621.