Synthesis, structure, and redox chemistry of ethenyl and ethynyl ferrocene polyaromatic dyads

Article abstract of DOI:10.1021/om0492653

A series of ferrocenyl-arene dyads, Fc-C=C-Ar, trans-Fc-CH=CH-Ar, and Fc-CH=CH-CH=CH-Ar (Ar = phenyl, 1-naphthyl, 2-naphthyl, 9-phenanthryl, 9-anthryl, 1-pyrenyl, 3-perylenyl) have been synthesized. Their structures and spectroelectrochemical properties are discussed. The molecular structures of several have been determined by X-ray diffraction and the observed structures compared with global free-energy minimized calculated structures. In the solid state all ethynyl dyads have the aromatic ring orthogonal to the ferrocenyl cyclopentadienyl rings, whereas calculations predict a coplanar orientation. Calculated and observed structures agree for the ethenyl dyads with the rings orthogonal and coplanar for the anthryl and pyrenyl dyads, respectively. In most cases the solid-state structures are stabilized by offset π-stacking interactions between the polycyclic hydrocarbon rings. The two bands in the electronic spectra of the neutral dyads are due to the individual aryl and ferrocenyl end-groups. Upon oxidation at the [Fc]^+/0 couple, the ferrocenyl transition is replaced by LMCT bands at lower energy and a new weak band in the NIR assigned to a Fc⁺ ←aryl transition; these assignments are supported by resonance Raman spectra, and the energy of the Fc⁺← aryl transition correlates with the ionization energy of the aryl group. These are therefore electrochromic dyads.

Full text of DOI:10.1021/om0492653

Organometallics 2005, 24, 2051-2060
2051
Synthesis, Structure, and Redox Chemistry of Ethenyl
and Ethynyl Ferrocene Polyaromatic Dyads
Laurence Cuffe,† Richard D. A. Hudson,† John F. Gallagher,† Sarah Jennings,†
C. John McAdam,‡ Rosamond B. T. Connelly,‡ Anthony R. Manning,,†
Brian. H. Robinson,*,‡ and Jim Simpson‡
Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland, and
Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
Received September 21, 2004
A series of ferrocenyl-arene dyads, Fc-CtC-Ar, trans-Fc-CHdCH-Ar, and Fc-CHd
CH-CHdCH-Ar (Ar ) phenyl, 1-naphthyl, 2-naphthyl, 9-phenanthryl, 9-anthryl, 1-pyrenyl,
3-perylenyl) have been synthesized. Their structures and spectroelectrochemical properties
are discussed. The molecular structures of several have been determined by X-ray diffraction
and the observed structures compared with global free-energy minimized calculated
structures. In the solid state all ethynyl dyads have the aromatic ring orthogonal to the
ferrocenyl cyclopentadienyl rings, whereas calculations predict a coplanar orientation.
Calculated and observed structures agree for the ethenyl dyads with the rings orthogonal
and coplanar for the anthryl and pyrenyl dyads, respectively. In most cases the solid-state
structures are stabilized by offset π-stacking interactions between the polycyclic hydrocarbon
rings. The two bands in the electronic spectra of the neutral dyads are due to the individual
aryl and ferrocenyl end-groups. Upon oxidation at the [Fc]+/0 couple, the ferrocenyl transition
is replaced by LMCT bands at lower energy and a new weak band in the NIR assigned to a
Fc+ r aryl transition; these assignments are supported by resonance Raman spectra, and
the energy of the Fc+ r aryl transition correlates with the ionization energy of the aryl
group. These are therefore electrochromic dyads.
Introduction
surface materials.7 Structure-property relationships for
derivatives of electron-rich ferrocenyl and alkylferroce-
nyl groups linked to electron acceptors (including metal-
centered acceptors) are well established.2,3 In these
compounds charge separation may become important
as the acceptor strength increases, but in most cases
the LUMO is centered on the acceptor with some
delocalization onto the unsaturated link. Many ex-
amples are based on ferrocenyl-substituted arylethenes
or arylethenyl oligomers (aryl ) phenyl, thiophenyl), yet
surprisingly few reports describe the chemistry of larger
aromatic analogues.8,9
Ferrocenyl derivatives fulfill many of the broad
criteria for the development of molecular materials for
specific technological application.1 In particular, donor-
acceptor assemblages incorporating the ferrocenyl group
as a donor have been the subjects of considerable recent
research, as their attractive electronic and physical
properties make them suitable candidates for NLO
materials,2-5 electrode surface modifiers,6 and magnetic
* To whom correspondence should be addressed. E-mail:
anthony.manning@ucd.ie; brobinson@alkali.otago.ac.nz.
† University College Dublin.
The ferrocenyl-ferrocenium redox couple adds a
further dimension to an investigation of these donor-
acceptor compounds. Ferrocenyl [Fe(II)]-ferrocenium
[Fe(III)] mixed-valence species, formed when diferroce-
nyl systems are partially oxidized, have been extensively
studied,10 and many display classical Class II donor-
acceptor behavior. In contrast, donor-acceptor chem-
istry where the ferrocenium cation is potentially the
acceptor to a non-ferrocenyl donor has been reported4,11
‡ University of Otago.
(1) Marder, S. R. Inorganic Materials, 2nd ed.; Bruce, D. W., O’Hare,
D., Eds.; Wiley: Chichester, 1996. (b) Long N. J. Angew. Chem., Int.
Ed. Engl. 1995, 34, 21. (c) Hudson, R. D. A. J. Organomet. Chem. 2001,
637-639, 47.
(2) (a) Barlow, S.; Bunting, H. E.; Ringham, C.; Green, J. C.; Bublitz,
G. U.; Boxer, S. G.; Perry, J. W.; Marder, S. R. J Am Chem Soc. 1999,
121, 3715. (b) Barlow S. Inorg. Chem. 2001, 40, 7047.
(3) Barlow, S.; Marder, S. R. Chem. Commun. 2000, 1555.
(4) Malaun, M.; Kowallick, R.; McDonagh, A. M.; Marcaccio, M.;
Paul, R. L.; Asselberghs, I.; Clays, K.; Persoons, A.; Bildstein, B.;
Fiorini, C.; Nunzi, J.-M.; Ward, M. D.; McCleverty, J. A. J. Chem. Soc.,
Dalton Trans. 2001, 3025.
(5) (a) Asiri, A. M. Appl. Organomet. Chem. 2001, 15, 907. (b)
Stankovic, E.; Toma, S.; Boxel, R. V.; Asselberghs, I.; Persoons, A. J.
Organomet. Chem. 2001, 637-639, 426, and references therein. (c) Li,
G.; Song, Y.; Hou, H.; Li, L.; Fan, Y.; Zhu, Y.; Meng, X.; Mi, L. Inorg.
Chem. 2003, 42, 913. (d) Shin, D. M.; Lee, I. S.; Chung, Y. K. Eur. J.
Inorg. Chem. 2003, 2311. (e) Mata, J. A.; Peris, E.; Uriel, S.; Llusar,
R.; Asselberghs, I.; Persoons, A. Polyhedron 2001, 20, 2083.
(6) Armstrong, N. R.; Carter, C.; Donley, C.; Simmonds, A.; Lee, P.;
Brumbach, M.; Kippelen, B.; Domercq, B.; Yoo, S. Thin Solid Films
2003, 445, 342. (b) Zou, C.; Wrighton, M. S. J. Am. Chem. Soc. 1990,
1I2, 7578.
(7) Miller, J. S.; Epstein, A. J. Angew. Chem., Int. Ed. Engl. 1994,
33, 385.
(8) McKinney, J. D.; Anderson, P. A.; Hamor, T. A.; Jones, C. J.;
Paxton, K.; Porch, A. J. Organomet. Chem. 1998, 558, 147.
(9) (a) Liu, S. G.; Perez, I.; Martin, N.; Echegoyen, L. E. J. Org.
Chem. 2000, 65, 9092. (b) Butler, I. R.; Callabero, A. G.; Kelly, G. A.;
Amey, J. R.; Kraemer, T.; Thomas, D. A.; Light, M. E.; Gelbrich, T.;
Coles, S. J. Tetrahedron Lett. 2004, 45, 467.
(10) Ribou, A.-C.; Launay, J.-P.; Sachtleben, M. L.; Li, H.; Spangler,
C. W. Inorg. Chem. 1996, 35, 3735.
(11) Mendiratta, A.; Barlow S.; Day, M. W.; Marder S. R. Organo-
metallics 1999, 18, 454.
10.1021/om0492653 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 03/19/2005

2052 Organometallics, Vol. 24, No. 9, 2005
Cuffe et al.
Scheme 1. Preparation of Ethynyl and Ethenyl
Compounds
but not explored to any extent. Of interest to us is the
possibility of modulating the emission characteristics
of fluorophores using the different quenching charac-
teristics of the ferrocenyl group and the ferrocenium
cation. Both energy and electron transfer may be
involved in quenching processes, depending on the
nature of the excited species.12 Recent work from this
laboratory has provided examples of both enhanced and
reduced emission upon oxidation of the ferrocenyl
moiety.13-15 If reversible, this feature provides an on-
off fluorescent switch capability. To date, we have
concentrated on fluorophores that were good electron
acceptors in the ground state (naphthalimides, acri-
dones, acridines). The work reported in this paper was
carried out in order to extend ferrocenyl dyad chemistry
to those where the non-ferrocenyl component was a
donor. Donor end-groups were required that would have
orbitals of suitable configurations and energies to allow
them to communicate via a conjugated π-linkage to both
the ferrocenyl (Fc) and ferrocenium (Fc+) moieties. It
was also recognized that intermolecular as well as
intramolecular interactions can perturb ground and
excited states where the donor has aromatic functional-
ity; for example, π-stacking was a feature of the
structural and spectroelectrochemistry of Fc-π-linked-
naphthalimide dyads.15 A set of donors that fulfilled
these criteria were the polycyclic aromatic hydrocar-
bons. Those selected (1- and 2-naphthyl, phenanthryl,
anthryl, pyrenyl, and perylenyl) have a range of oxida-
tion potentials more positive than ferrocene and the
ability to π-stack. Herein, we describe the synthesis and
structural and spectroelectrochemical features of the
neutral precursors, Fc-CtC-Ar, Fc-CHdCH-Ar, and
Fc-CHdCH-CHdCH-Ar, and the spectroscopic prop-
erties of the ferrocenium dyads derived from them. The
calculated orbital configurations, a detailed analysis of
the low-energy electronic spectra for ferrocenyl-arene
and related dyads, and emission behavior are reported
elsewhere.16
Scheme 2. Mechanism for Isomerization
Scheme 3. Preparation of Dienes
aldehyde (Scheme 1). Both diastereomers were obtained
from the reactions, but no attempt was made to separate
them. They were converted to the E form by refluxing
with molecular iodine in CH2Cl2 solution. The accepted
mechanism for cis-trans isomerization in organic sub-
strates is shown in Scheme 2a, but for ferrocenyl
alkenes a mechanism via a fulvene intermediate of a
ferrocenium species could be considered (Scheme 2b). 8
and 10 have been prepared previously19 by the SmI2-
promoted reaction of FcCHO with ArCH2Br and by the
cross-metathesis of ArCHdCH2 with Fc-CHdCH2.20 8,
13, and 15 have been prepared previously from FcCHO
with the Wittig reagent derived from the appropriate
ferrocenyl or aryl triphenylphosphonium salt.8,21
The dienes 15-18 were prepared from Fc-CHdCH-
CHO22 and the appropriate arylmethylphosphonium
salt (Scheme 3). This reaction generated a mixture of
various isomers that were converted to the E,E-isomer
by refluxing with a crystal of iodine.
1-18 were orange to red-orange crystalline solids,
with the exception of 4, which was obtained as a red-
orange oil. They were soluble in a range of common
organic solvents, polar and nonpolar, but particularly
dichloromethane. The degree of solubility decreased
with the size of the polyaromatic. All compounds were
characterized by microanalysis, mass spectra, and NMR
and IR spectroscopy. The IR spectra are generally
unremarkable, but when Ar ) phenyl, 1- and 2-naph-
thyl, and pyrenyl (1-3, 6), the νCtC band is split in both
solution and solid-state (KBr) spectra, an effect perhaps
attributable to Fermi coupling.23 This splitting has also
Results and Discussion
The ferrocenyl arylethynes (Fc-CtC-Ar) were pre-
pared by Sonogashira coupling of ethynylferrocene with
the respective arylbromide [R ) 1-naphthyl (2),17 2-naph-
thyl (3), 9-phenanthryl (4), 9-anthryl (5)] or aryliodide
i
[R ) 1-pyrenyl (6), 3-perylenyl (7)] in boiling Pr2NH
(Scheme 1). Fc-CtC-phenyl (1)18 was prepared using
similar conditions by the coupling of FcI with ethynyl-
benzene. Interestingly, similar attempts to prepare 6
from 1-ethynylpyrene and FcI were unsuccessful.
The ferrocenyl arylethenes 8-12, 13,8 and 14 were
prepared by Wittig reaction of ferrocenylmethyl tri-
phenylphosphonium iodide with the respective aryl
(12) Fery-Forgues, S.; Delavaux-Nicot, B. J. Photochem. Photobiol.
A 2000, 132, 137, and references therein.
(13) McGale, E. M.; Robinson. B. H.; Simpson, J. Organometallics
2003, 22, 931.
(14) McAdam, C. J.; Robinson, B. H.; Simpson, J. Organometallics
2000, 19, 3644.
(19) Jong, S.-J.; Fang, J.-M. J. Org. Chem. 2001, 66, 3533.
(20) (a) Yasuda, T.; Abe, J.; Iyoda, T.; Kawai, T. Chem. Lett. 2001,
812. (b) Yasuda, T.; Abe, J.; Yoshida, H.; Iyoda, T.; Kawai, T. Adv.
Synth. Catal. 2002, 344, 705.
(21) (a) Pauson, P. L.; Watts, W. E. J. Chem. Soc. 1963, 2990. (b)
Drefahl, G.; Plotner, G.; Winnefeld, I. Ber. 1962, 95, 2788.
(22) Spangler, C. W.; McCoy, R. K. Synth. Commun. 1988, 18, 51.
(23) Paul, F.; Mevellec, J.-Y.; Lapinte, C. J. Chem. Soc., Dalton
Trans. 2002, 1783.
(15) McAdam, C. J.; Morgan, J. L.; Robinson, B. H.; Simpson, J.
Organometallics 2003, 22, 5126.
(16) Flood, A.; Gordon, K.; Kjaergaard, H.; Manning, A. M.; McAd-
am, C. J.; Robinson, B. H.; Simpson, J. Dalton, submitted for publica-
tion.
(17) Rausch, M. D.; Siegel, A. J. Org. Chem. 1969, 34, 1974.
(18) Rausch, M. D.; Siegel, A.; Klemann, L. P. J. Org. Chem. 1966,
31, 2703.

Ethenyl and Ethynyl Ferrocene Polyaromatic Dyads
Organometallics, Vol. 24, No. 9, 2005 2053
Table 1. Selected 13C NMR, Electrochemical, and Spectral Data
H
phenyl
1-naphth.
2-naphth.
phenan.
anthryl
pyrenyl
peryl.
13C NMRa
Fc-CtC
CtC-R
Fc-CdC
CdC-R
82.7
88.4
93.5
88.8
93.2
100.1
82.6
135.6
121.9
94.4
94.8
73.6
85.8
83.9
86.2
84.1
85.0
84.4
134.7
111.1
127.0
126.1
130.0
123.0
127.5
126.2
130.5
123.5
130.4
123.0
130.1
122.8
E[Fc]+/0
b
Fc-CtC
Fc-CdC
λmax
0.72
0.56
0.67
0.55
0.68
0.55
0.67
0.54
0.67
0.56
0.67
0.59
0.67
0.55
0.67
0.55
B(Fc-CtC)c
B (Fc-CdC)c
B′(Fc-CtC)e
B′′
443
446
446
446
456
403-524
583
384-500
590
873
956
446
458
400-464
580
420-492
446
457
410-484
587
382-500
590
898
955
d
d
446
457
458-570 625
d
d
456
420
412-476
711
380-472
700
1120
1050
505e
810
530e
800
1210
1310
575
B′(Fc-CdC)e
B′′
401-475
585
471-570 650
C(Fc-CtC)f
C(Fc-CdC)f
797
900
850
959
1020
1110
a In CDCl3. b In CH2Cl2, Pt, 0.1 M TBAPF6 at 20 °C. c In CH2Cl2; λ nm range for structured band B′. d Obscured by aryl transition.
e Electrochemically generated ferrocenium species, CH2Cl2, λ nm. f ꢀ for C increases from Ph 0.7 to pyrenyl 1.6 (mol-1 cm-1 L × 10-3).
drogen (Figure 1a) is calculated to be 6.02 kJ/mol. All
the ethenyl aryls are able to adopt this sterically less
hindered conformation that allows ethenyl and aryl
coplanarity. The exception is the ethenylanthryl dyad
12, where an unusually low Fc-CHd shift of 6.71 (Table
1) suggests that coplanarity is not maintained (as in the
solid state, vide infra). Anomalous behavior associated
with this particular dyad will be noted consistently
throughout this paper.
A JHH coupling constant of 16 Hz confirmed the trans-
(E)-conformation of the ethene compounds. Chemical
Figure 1. Steric interaction in ethenyl PAH derivatives.
shifts for the ferrocenyl and aryl components in the
been observed for other ferrocenyl alkynes24a and in
butadienyl compounds 15-18 closely resembled their
ethenyl counterparts. The alkenyl protons showed the
appropriate coupling (doublet 15 Hz, H1 and -4; dd 15,
11 Hz, H2 and -3) for an E,E-configuration, and this
order of connectivity was confirmed by TOCSY mea-
surements.
1,1′′-bis(arylethynyl)biferrocenes,24b where νCtC is split
when Ar ) phenyl, 1-naphthyl, and pyrenyl compounds,
but not anthryl.
Complete assignments of 1H and 13C NMR resonances
were made using homonuclear (COSY, NOESY, and
TOCSY) and heteronuclear (DEPT, HSQC, and CIGAR)
methods. Selected 13C data are given in Table 1; full 1H
and 13C NMR assignments are given in the Supporting
Information. The three ferrocene resonances (HR, Hâ,
13C NMR spectra of the Fc-CtC-Ar, 1-7, and Fc-
CHdCH-Ar, 8-14, compounds resembled their respec-
tive ferrocenyl precursors, Fc-CtC-H and Fc-CHd
CH2; the Ar component of 8-14, that of the respective
vinyl arene.26 13C chemical shifts of the four ferrocenyl
carbon signals (ipso, R, â, and Cp) were more dependent
on the π-linker than the Ar group (Table S1). HSQC,
1
and C5H5) in the H NMR showed a small progression
to lower field with increasing size of the aryl group in
both the ethene and ethyne series. The assignment of
ferrocenyl HR to low field of Hâ for Fc-CtC-Ar follows
a study of 2,5-dideutero derivatives of ethynylferrocene
and Fc-CtC-phenyl.25 An assignment of HR protons
to low field of Hâ for Fc-CHdCH-Ar was confirmed
by NOE and CIGAR correlations and agrees with that
for vinylferrocene.25 Our assignment of the alkene
protons (Fc-CHd and dCH-Ar) from NOE is consis-
tent with those of ethenylarenes26 and backed up by
CIGAR correlations. The NOEs reflect a conformational
preference (seen also in the solid-state structures) that
where possible avoids “fjord” type interactions27 between
proximal hydrogens. For 13, the calculated difference
in energy between the configuration with minimium
proximal interactions (Figure 1b) and that in which the
ferrocenyl-CHd is closest to the proximal pyrene hy-
4
supported by JCH CIGAR correlations, showed the
ferrocenyl CR resonance is low field of Câ for the ethyne
series but reversed in the ethene series. There is some
confusion in the literature24,28 on this point. Assignment
of the alkyne carbon resonances was based on a con-
sistent 3JCH correlation (CIGAR) of an ortho-aryl proton
to one of the ethyne 13C resonances, and assignment of
the ethene 13C resonances was unambiguous from
HSQC. Subtle variations occur with Ar so that for δ(Fc-
CtC) and δ(Fc-CHdCH), the lowest chemical shifts
were observed for Ar ) Ph (1 and 8) or 2-naphthyl, and
the highest for 9-anthryl (5 and 12), whereas for δ(Ct
C-Ar) and δ(CHdCH-Ar) the trend is reversed and
shifts decreased in the series from 1 f 7 and 8 f 14.
Structural Analysis. Structures and atom-number-
ing schemes for the alkyne complexes 5, 6, and 7 are
(24) (a) Stepnicka, P.; Trojan, L.; Kubista, J.; Ludvik, J. J. Orga-
nomet. Chem. 2001, 637-639, 291. (b) McAdam, C. J. Unpublished
work.
(28) (a) Koridze, A. A.; Petrovskii, P. V.; Mokhov, A. I.; Lutsenko,
A. I. J. Organomet. Chem. 1977, 136, 57. (b) Pickett, T. E.; Richards,
C. J. Tetrahedron Lett. 1999, 40, 5251. (c) Yuan, Z.; Stringer, G.; Jobe,
I. R.; Kreller, D.; Scott, K.; Koch, L.; Taylor, N. J.; Marder, T. B. J.
Organomet. Chem. 1993, 452, 115.
(25) Rausch, M. D.; Siegel, A. J. Organomet. Chem. 1969, 17, 117.
(26) Katritzky, A. R.; Hitchings, G. J.; King, R. W.; Zhu, D. W. Magn,
Reson, Chem. 1991, 29, 2.
(27) Bartle, K. D.; Jones, D. W. Adv. Org. Chem. 1972, 8, 317.

2054 Organometallics, Vol. 24, No. 9, 2005
Cuffe et al.
Figure 3. Perspective views of the ethenyl dyads (a) 12
and (b) 13 showing the atom-numbering schemes. For
clarity only the first two C atoms of the consecutively
numbered cyclopentadienyl rings have been labeled.
tween the two alkene moieties. The C(11)dC(12) bond
in 13 is longer (1.339(4) Å) and the C(12)-C(13)
distance, 1.466(4) Å, shorter than the corresponding
vectors for 12, 1.323(3) and 1.484(3) Å respectively.
However, it is not possible to determine whether these
differences result from steric or electronic effects. The
cyclopentadienyl rings in both ferrocene moieties are
again eclipsed, with interplanar angles of 1.8(6)° for 12
and 1.9(3)° for 13. The structures of 8 and 10 have also
been reported,20 but unfortunately no metrical details
are currently available to allow comparison with the
structures reported here. However the molecular struc-
ture figures suggest that for both their C5H4, CHdCH,
and aromatic groups lie close to the same plane as found
for 13, rather than the situation found in 12, where the
aromatic group lies approximately perpendicular to that
plane.
Figure 2. Perspective views of the ethynyl dyads, (a) 5,
(b) 6, and (c) 7, showing the atom-numbering schemes. For
clarity only the first two C atoms of the consecutively
numbered cyclopentadienyl rings have been labeled.
shown in Figure 2a-c, and those of the alkene systems
12 and 13 in Figure 3a,b. Selected bond length and
angle data for all compounds are given in Table 2, with
packing information in Table 3.
An important question in this series of dyads is the
relative orientation of the ferrocenyl and polyaromatic
rings. Knowledge of this detail is important in the
interpretation of the spectroscopic and redox data.
Therefore the X-ray structures of 5-7, 12, and 13 were
compared with those predicted from B3LYP calculations
of the energy-minimized structures. In all of the alkyne
derivatives 5-7, the cyclopentadienyl and polyaromatic
rings are essentially orthogonal in the solid state,
whereas the calculated minimized structures predict
them to be coplanar. In contrast, there is good agree-
ment between the calculated minimized structure and
the solid-state structure for the ethenylanthracene
derivative 12. Here the free global minimum was found
to occupy a geometry in which the substituted cyclo-
pentadienyl ring is almost perpendicular to the plane
The structures of 5, 6, and 7 comprise an alkyne unit
C(11)tC(12) substituted with a ferrocenyl group at
C(11) and the polyaromatic hydrocarbon at C(12). 5 has
an anthracene residue substituted in the 9-position, 6
a 1-substituted pyrene, and 7 a 3-substituted perylene
moiety. The C(11)tC(12) distances are unremarkable
and do not vary significantly with the nature of the
hydrocarbon substituent. The cyclopentadienyl rings of
each of the ferrocene residues are approximately eclipsed,
with interplanar angles of 0.83(12)° for 5, 0.61(19)° for
6, and 1.4(5)° for 7.
Structures of the alkene complexes 12 and 13 confirm
E-configurations of the ferrocenyl and hydrocarbon
substituents on the C(11) and C(12) atoms of the alkene
units. There are small but significant differences be-

Ethenyl and Ethynyl Ferrocene Polyaromatic Dyads
Organometallics, Vol. 24, No. 9, 2005 2055
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 5-7, 12, and 13
5
6
7
12
13
C(10)-C(11)
C(11)-C(12)
C(12)-C(13)
C(13)-C(14)
C(13)-C(26)
C(13)-C(30)
C(14)-C(15)
C(14)-C(19)
C(15)-C(16)
C(16)-C(17)
C(16)-C(27)
C(16)-C(31)
C(17)-C(18)
C(17)-C(32)
C(18)-C(19)
C(19)-C(20)
C(19)-C(28)
C(20)-C(21)
C(21)-C(22)
C(21)-C(26)
C(21)-C(32)
C(22)-C(23)
C(23)-C(24)
C(23)-C(28)
C(24)-C(25)
C(25)-C(26)
C(25)-C(32)
C(26)-C(27)
C(26)-C(31)
C(27)-C(28)
C(28)-C(29)
C(29)-C(30)
C(30)-C(31)
1.434(4)
1.192(4)
1.439(4)
1.411(5)
1.421(5)
1.440(3)
1.195(3)
1.444(3)
1.404(3)
1.427(3)
1.437(8)
1.221(8)
1.425(8)
1.376(7)
1.456(3)
1.323(3)
1.484(3)
1.411(2)
1.411(3)
1.447(4)
1.339(4)
1.466(4)
1.407(4)
1.413(3)
1.434(7)
1.377(7)
1.425(5)
1.433(4)
1.354(5)
1.417(5)
1.379(3)
1.429(3)
1.433(3)
1.357(3)
1.408(3)
1.378(4)
1.409(3)
1.443(3)
1.427(3)
1.400(7)
1.477(7)
1.391(4)
1.430(4)
1.429(4)
1.417(6)
1.381(7)
1.424(7)
1.389(9)
1.351(9)
1.363(5)
1.346(3)
1.351(3)
1.345(4)
1.427(5)
1.395(5)
1.443(3)
1.398(3)
1.425(3)
1.399(4)
1.376(4)
1.427(3)
1.392(3)
1.442(4)
1.399(4)
1.416(4)
1.390(4)
1.376(4)
1.395(5)
1.429(5)
1.439(4)
1.426(8)
1.412(8)
1.388(3)
1.430(3)
1.436(3)
1.427(7)
1.357(8)
1.404(8)
1.345(5)
1.413(5)
1.416(3)
1.437(3)
1.424(3)
1.359(3)
1.443(3)
1.345(3)
1.411(4)
1.398(4)
1.421(4)
1.431(4)
1.354(4)
1.442(4)
1.354(5)
1.418(5)
1.391(7)
1.468(6)
1.431(6)
1.382(7)
1.427(6)
1.395(8)
1.380(8)
1.419(7)
1.422(7)
1.363(3)
1.426(3)
1.427(3)
1.438(3)
1.418(4)
1.429(4)
C(1)‚‚‚C(5) ring:
av C-C
1.412(6)
1.420(4)
1.40(2)
1.40(7)
1.408(6)
C(6)‚‚‚C(10) ring:
av C-C
1.426(6)
2.039(7)
2.043(8)
1.430(9)
2.055(2)
2.056(6)
1.406(16)
2.023(13)
2.026(11)
1.418(9)
2.01(4)
2.041(7)
1.422(13)
2.034(5)
2.041(3)
Fe-C(1‚‚‚5) av
Fe-C(6‚‚‚10) av
C(10)-C(11)-C(12)
C(11)-C(12)-C(13)
178.2(4)
179.1(4)
178.7(3)
175.3(3)
178.7(7)
177.1(7)
126.42(18)
123.28(18)
126.4(3)
126.5(3)
Table 3. Orientation of the Rings Data
of 83.89(5)° to one another, with an angle of 62.58(14)°
between the anthracene and alkene [C(10)‚‚‚C(13)]
planes. A second minimization with the substituted
cyclopentadienyl ring constrained to lie in the an-
thracene plane afforded a structure 25.98 kJ/mol higher
in energy. The solid-state and calculated structures for
the ethenylpyrene derivative 13 are also reasonably
congruent but with a markedly different orientation of
the cyclopentadienyl and polyaromatic rings compared
to 12. Here the free global minimum was found with
the substituted cyclopentadienyl ring almost coplanar
with the pyrene ring. This compares with the solid-state
structure, where the corresponding angle is 33.93(13)°
with an angle of 35.6(3)° between the pyrene and alkene
[C(10)‚‚‚C(13)] planes.
Given the small energy differences between the
calculated orthogonal and coplanar orientations of the
cyclopentadienyl and polyaromatic rings in most mol-
ecules, it is likely that these orientations and molecular
packing are determined by optimization of offset π-stack-
ing interactions29 in the solid state. This appears to be
the case with the probable exception of 13. Representa-
tive views of typical π-stacking motifs are shown in
Figure 4a-c, with details of the parallel displacement
interactions shown in Table 3; all packing motifs are
given in the Supporting Information.
displacement parameters for π-stacked aromatic ringsa
R/degb â/degc d/Åd Cg-Cg/Åe Nf
2.34 27.17 3.585
1.89-3.26 27.08-29.48 3.393-3.447 3.897-3.898
compd
5
4.029
2
8
6
7
0.00-2.25 19.54-24.67 3.385-3.425 3.615-3.771 10
12
13
3.85
28.70
3.634
4.143
2
4
1.43-2.68 54.85-59.19 3.020-3.151 5.474-5.902
a Data from PLATON.30 b Dihedral angle between stacked ring
planes. c Angle(s) between the ring centroid vector and the ring
normal to the plane(s) of one of the aromatic PAH rings. This
defines the degree of displacement between the stacked rings.
d Perpendicular distance between the planes of the stacked rings.
e Centroid-centroid vector length between stacked aromatic rings.
f Number of aromatic rings in the PAH moiety involved in
significant off-set π-stacking interactions.
of the anthracene residue. In the solid-state structure
the best fit planes of the anthracene and substituted
cyclopentadienyl rings are found to subtend an angle
(29) Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885.

2056 Organometallics, Vol. 24, No. 9, 2005
Cuffe et al.
Figure 5. Electronic spectra in CH2Cl2, Fc-CtC-(2)-
naphthyl, 3 (s), Fc-CHdCH-(2)-naphthyl, 10 (- - -). Band
B# is the second ferrocenyl d-d transition and is only
discernible for compounds 1-4 and 8.
for 5-7 may be largely determined by such packing
effects. The exception to this argument is 12. Simple
steric considerations as well as the calculations de-
scribed above point to the presence of strong nonbonding
interactions between the alkene H on C2 and the 1- and
8-H atoms of the anthryl group, which destabilize the
all-planar situation by ca. 25.98 kJ/mol. It is also
interesting to note however that, in the previously
reported structure8 of a TCNQ complex of 13, strong
offset π-stacking occurs between the pyrene rings and
TCNQ molecules in interleaving stacks, with the incli-
nation between the pyrene and substituted cyclopenta-
dienyl rings reduced to 16.9°.
Spectroscopy of Neutral Dyads. The electronic
spectra of the neutral dyads 1-18 between 300 and
1300 nm show two groups of absorption bands (Figure
5). A are the more intense (ꢀ > 9000), lie between 300
and 450 nm, and have wavelengths which increase with
increasing annelation of the Ar group. B are weaker (ꢀ
< 4000), lie between 440 and 460 nm, and have
wavelengths that do not vary greatly with Ar (Table 1).
Absorption bands in the electronic spectra of the
parent arenes are divided into the shorter â bands (ꢀ )
ca. 104-106) and the longer wavelength, substituent-
sensitive p bands (ꢀ ) ca. 104), which become red-shifted
with increasing annelation.31 Bands A are assigned to
the p bands of the Ar end-groups. The large red shifts
of A compared with their ArH or Ar-CtC-H counter-
parts are due to the Fc-CtC group acting as a donor;
this raises the energy of the Ar HOMO (confirmed by
B3LYP calculations) and lowers the energy of its π-π*
transition. Vibrational fine structure similar to that
found in the parent arene is visible in band A of the
alkyne dyads. It has been observed recently32 that
ethynyl substitution of a PAH causes an average
bathochromic shift of 18 nm in the wavelength of its p
band with retention (but broadening) of its vibrational
fine structure. As it is known that this vibrational fine
structure is reduced when the aromatic residue is
engaged in more extensive conjugation, this suggests
Figure 4. π-Stacking motifs for (a) 5, symmetry relation
between the two molecules 1+x, y, z; (b) 7, 2-x, -y, -z;
and (c) 13, x, y-1, z.
These data reveal considerable similarities between
the π-interactions between the anthracene rings in 5
and 12 and between the pyrene and perylene moieties
of 6 and 7. In both cases this is limited to interactions
between pairs of molecules rather than extending
throughout the structure. In the alkyne dyads 6 ad 7
(see for example Figure 4b), the orthogonal placement
of the ferrocene moieties with respect to the polyaro-
matic rings facilitates stacking between pairs of mol-
ecules related by a pseudo C2 axis; this effectively
optimizes interactions between all of the aromatic rings
of the pyrene and perylene systems (Table 3). In
contrast, the degree of offset π-stacking between the
pyrene rings of 13, while again limited to pairs of
molecules, is significantly less than is observed for the
related alkyne derivative, with large displacement
angles and inter-centroid distances (Figure 4c, Table 3).
This suggests that offset π-stacking plays little part in
stabilizing the solid-state structure in this case and
strengthens the view that the trend toward orthogonal
disposition of the cyclopentadienyl and polycyclic rings
(30) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.
(31) (a) Clar, E. Polycyclic Hydrocarbons, Vol. 1; Academic Press:
London, 1964. (b) Jones, R. N. Chem. Rev. 1947, 41, 353.
(32) Marsh, N. D.; Mikolajczak, C. J.; Wornat, M. J. Spectrochim.
Acta Part A 2000, 56, 1499.

Ethenyl and Ethynyl Ferrocene Polyaromatic Dyads
Organometallics, Vol. 24, No. 9, 2005 2057
that conjugation of the Ar and FcCtC π-systems is not
important in our dyads. With the ethenyl dyads, how-
ever, the absorption bands A are, in most cases, broad
and featureless and at lower energies than their ethynyl
counterparts. This suggests that the ferrocenyl group
perturbs the arene π-orbitals where there is ethenyl,
but not ethynyl, connectivity between the ferrocenyl and
arene components. The poorer conjugation through an
alkyne connection has been noted in other ferrocenyl
systems.3 Yet again, 12 is anomalous in that band A
for 12 is higher in energy than for the equivalent band
in 5 and displays vibrational fine structure. This implies
the absence of ferrocenyl-anthryl electronic interactions
and is consistent with the inability of 12 to form a
planar molecule as a consequence of intramolecular
steric interactions (see above).
Figure 6. UV-vis OTTLE spectra of 2 (0-0.7 V, CH2Cl2).
The energy of Bs446 nm for the ethyne series and
457 nm for the ethene seriessis invariant with Ar and
solvent and tracks closely those for Fc-CtC-Fc (452
nm, ꢀ ) 820) and Fc-CHdCH-Fc (458 nm, ꢀ ) 1450)33
and Fc-(CHdCH)2-Fc at 466 nm (ꢀ ) 2800).10 Two
weak metal-centered d-d bands at 325 and 440 nm
characterize ferrocene and ferrocenyl compounds where
the substituents are not strong acceptors or involved in
conjugation.3,34 B is therefore assigned to the low-energy
ferrocenyl transition; it is obscured by the π-π* transi-
tion in the perylenyl dyads. This conclusion is reinforced
by the resonance Raman spectra. For example, the
resonance Raman spectrum of 5 (λexc ) 457.9 nm)
mirrors that of Fc-CtCH, with enhancement of the νCt
C band at 2202 cm-1 and of the ferrocenyl bands at 1100
and 298 cm-1, but no enhancement of the anthracene
vibrational modes. This assignment is supported by
B3LYP calculations, and a detailed analysis will be
given in a subsequent paper.16 If there was significant
conjugation, the aryl orbitals would mix with the
ferrocenylmetal d orbitals so the lowest energy band in
the dyads would be a metal to ligand charge transition.
The above data therefore show that the ferrocenyl group
is the donor and that there is little communication
between the two end-groups of the dyads.
Spectroelectrochemical Properties. Compounds
1-18 display the expected one-electron chemically
reversible Fc+/Fc0 couple in cyclic voltammetric scans.
The potential is dependent on the type of unsaturated
link (Table 1) and is almost independent of Ar. For the
ethynyl dyads E[Fc]+/0 is 0.67-0.68 V in CH2Cl2 (all
potentials vs [FeCp*2]+/0) and for most ethenyl dyads
0.55 ( 0.01 V. These potentials are similar to those for
Fc-CtC-H (0.72 V) or Fc-CHdCH2 (0.56 V) and other
ethenyl/ethynyl ferrocenyl systems with donor sub-
stituents.2a,4,13,25,35 Ethenylferrocenes with electron-
withdrawing groups have higher potentials; for example,
E[Fc]+/0 ) ∼0.58 and 0.60 V for Fc-CHdCH-p-NO2-
phenyl2a and Fc-CHdCH-naphthalimide,15 respec-
tively. Again, 12 is anomalous, being more difficult to
oxidize than other ethenyl dyads. Attempts to isolate
the chemically generated cations were unsuccessful.
Cyclic voltammetry also shows complex reduction pro-
cesses on the cathodic scans of all dyads associated with
the formation of radical anions; these correspond to
those found in the electrochemistry of the parent arene.
Parameters from the ESR spectra of the radical anions
generated electrochemically at 213 K (see Experimental
Section) are identical to those of the respective arene
radical anion, which locates the LUMO for the dyads
on the aromatic component. The electrochemical data
support the view that the ferrocenyl and arene compo-
nents function as independent entities in these dyads.
OTTLE vibrational and electronic spectra show con-
sistent isosbestic points and complete reversibility when
the potential is cycled (0.0-0.7 V), attesting to the
stability of the monocations 1+-18+. Representation of
these cations as {Fc+}-CtC-{aryl} in the ground state
is indicated by the vibrational data. Although the aryl
vibrational modes are unaffected by oxidation, the Fc-
based vibrational bands shift in the same way as those
of ferrocene upon oxidation. For example, the resonance
Raman spectrum of 5+ shows a shift of the Fc ring-
breathing mode of +7 cm-1, and there is a typical Fc+
band at 1113 cm-1 in the infrared spectrum.
Significant changes occur in the electronic spectra
upon oxidation (Figure 6). Band A undergoes a small
blue shift, as the Fc-(π-link) is a much weaker donor
in the oxidized species. If we follow the dictum enunci-
ated above that the vibrational structure on the ππ*
transition reflects the relative ring orientations, then
the orthogonal structure is retained in all of the ethyne
ferrocenium derivatives. Likewise, there appears to be
no change in the ring orientation for the ethenyl
analogues upon oxidation; the anthryl derivative is still
anomalous. Band B in the neutral dyad is replaced by
a complex structured feature, B′, covering a wide energy
range, and B′′ at lower energy and very weak intensity.
Unlike B however, the structure and energy of these
two bands are dependent on the aryl group and solvent,
but still essentially independent of the type of π-link
(Table 1). An important observation is that the reso-
nance Raman spectra resonant with band B′ (λexc
)
457.9 nm) show an enhancement of modes associated
with both the arene and Fc+ units. Furthermore, Fc/
Fc+ ring-breathing modes show an increased resonance
enhancement on going to the monocations, whereas
there is a 3-fold decrease in enhancement in the
equivalent modes for FcH to FcH+. These data imply
that the Fc-based modes are deriving enhancement from
an additional electronic transition that is not isolated
on the metallocene. This substantiates a charge transfer
(33) Rosenblum, M.; Brawn, N.; Papenmeier, J.; Applebaum, M. J.
Organomet. Chem. 1966, 6, 173.
(34) Sohn, Y. S.; Hendrickson, D. N.; Gray, H. B. J. Am. Chem. Soc.
1971, 93, 3603.

2058 Organometallics, Vol. 24, No. 9, 2005
Cuffe et al.
groups. Subtle packing effects and π-stacking determine
the orientation of the Cp(Fc) ring relative to the arene
ring plane in the solid state; the rings are essentially
coplanar in the ethenyl and orthogonal in the ethynyl
dyads. Given the importance of intermolecular interac-
tions, it should be possible to freeze specific ring plane
orientations with the appropriate choice of ring substit-
uents. With the exception of the ethenylanthryl dyad,
there are only small variations in physical properties
with the aryl end-group for a particular π-linkage. Why
the spectroscopic and redox properties of 12 and 12+ in
solution, as well the solid-state structure of 12, are so
different is a puzzle, unless the strong nonbonding
interactions that are a feature of this dyad cause a
significant perturbation of the electronic structure.
Calculations do not support this premise however.
Oxidation of the dyads at the ferrocenyl end-group
creates a situation where the relative energies and
overlap of ferrocenium and aryl orbitals stimulate a
classical donor-acceptor interaction that does not occur
in the neutral precursors. The energy of the resulting
weak LMCT transition in the NIR can be predicted for
the ionization energy of the aryl end-group. Further-
more, the absorption of NIR radiation can be switched
on or off via the ferrocenyl couple, an electrochromic
system.37 The challenge is to increase, by an order of
magnitude, the extinction coefficient of the NIR absorp-
tion so that the materials have technological signifi-
cance.
Figure 7. Correlation of band C energy against aryl
oxidation potential; CH2Cl2; potential in volts.
assignment for B′ with the excited state having both
ferrocenyl and arene character. The most striking new
features are the low intensity, charge transfer bands C
(Figure 5b, Table 1). Bands C are assigned to the LMCT
transitions, Fc+ r {CtC-Ar}. This LMCT assignment
is supported by the following observations: first, de-
pendence of the energy of C on the aryl end-group (Table
1); second, a large negative solvatochromic shift of
1000-1500 cm-1 on going from CH2Cl2 to MeCN,
supportive of a larger dipole in the ground state than
the excited state; third, the trend in the energies of C
should correlate with the difference in energy between
the donor and acceptor orbitals. Given that the energy
of the acceptor orbital, approximated by the [Fc]+/0
reduction potential, is constant for a specific π-link,
these energies should correlate with energy of the donor
aryl orbital. Plots of the electrochemical oxidation
potentials or ionization energies of the respective aryl
versus the energy of band C are indeed linear (Figure
7); the ethene energies are red-shifted relative to their
ethyne counterparts except for the anthryl dyads.
Finally, there is an enhancement of both arene and Fc+
vibrational modes in the resonance Raman spectrum of
the monocations. Bands similar to C have been ob-
served4,11,36 for many arrays where donor end-groups
have been connected to a ferrocenium moiety via an
unsaturated link, and a detailed spectroscopic analysis
and theoretical calculations of these LMCT transitions
will be given in another paper.16
Experimental Section
Solvents were dried and distilled by standard procedures,
and all reactions unless stated were performed under nitrogen.
Microanalyses were carried out by the Campbell Microana-
lytical Laboratory, University of Otago. Melting points were
recorded on an Electrothermal digital melting point apparatus
and are uncorrected. Mass spectra were recorded on a Kratos
MS80RFA instrument with an Iontech ZN11NF atom gun. IR
spectra were recorded on a Perkin-Elmer Spectrum BX FT-
IR spectrometer, 1H and 13C NMR spectra on Varian Unity
Inova 300 and 500 MHz spectrometers in CDCl3 (7.26 ppm)
at 25 °C, and electronic spectra on a Varian Cary 500 UV-vis
spectrophotometer. Cyclic and square-wave voltammetry in
CH2Cl2 were performed using a three-electrode cell with a
polished Pt 1 mm disk working electrode; solutions were ∼10-3
M in electroactive material and 0.10 M in supporting electro-
lyte (recrystallized TBAPF6). Data were recorded on an EG &
G PAR 273A or Powerlab/4sp computer-controlled potentiostat.
Scan rates of 0.05-1 V s-1 were typically employed for cyclic
voltammetry and for square-wave voltammetry, square-wave
step heights of 5 mV and a square amplitude of 25 mV with a
frequency of 15 Hz. All potentials are referenced to deca-
methylferrocene; E1/2 for sublimed ferrocene was 0.55 V.
Infrared and UV-vis OTTLE data were obtained from stan-
dard cells with platinum grid electrodes. ESR spectra were
obtained using a Bruker EMX X-band spectrometer equipped
with a Bruker variable-temperature accessory, a Systron-
Donner microwave frequency counter, and a Bruker gauss-
meter; ca. 5 mM THF/TBAPF6 solutions of the compound were
reduced electrochemically in situ. The B3LYP method was
used for all calculations with a 6-31G(D) basis set; the program
was the G98 revision A7i, and where geometries were con-
strained, this was done using the ADDREDUNDANT key word
after which the appropriate dihedral angles were set. Molec-
Conclusion
This sequence of ferrocenyl-aryl dyads with ethenyl
and ethynyl π-linkages has given an additional insight
into the structural and spectral parameters that would
impact on their incorporation in NLO and fluorophore
materials. The Fc-CdC- or Fc-CtC- component acts
as the donor in the ground state, and there is no
communication between the ferrocenyl and aryl end-
(35) (a) Fink, H.; Long, N. J.; Martin, A. J.; Opromolla, G.; White,
A. J. P.; Williams, D. J.; Zanello, P. Organometallics 1997, 16, 2646.
(b) Jones, N. D.; Wolf, M. O.; Giaquinta, D. M. Organometallics 1997,
16, 1352. (c) Sato, M.; Shintate, H.; Kawata, Y.; Sekino, M.; Katada,
M.; Kawata, S. Organometallics 1994, 13, 1956. (d) Osella, D.;
Gambino, O.; Nervi, C.; Ravera, M.; Vittoria Russo, M.; Infante, G.
Inorg Chim. Acta 1994, 225, 35. (e) Wong, W.-Y.; Lu, G.-L.; Ng, K.-F.;
Wong, C.-K.; Choi, K.-H. J. Organomet. Chem. 2001, 637-639, 159.
(f) Siemeling, U.; Vorfield, U.; Neumann, B.; Stammler, H.-G.; Zanello,
P.; Fabrizi de Biani, F. Eur. J. Inorg. Chem. 1999, 1. (g) Hsung, R. P.;
Chidsey, C. E. D.; Sita, L. R. Organometallics 1995, 14, 4808.
(36) Toma, S.; Gaplovsky, A.; Hudecek, M.; Langfelderova, Z.
Monatsh. Chem. 1985, 116, 357.
(37) Ward, M. D.; McCleverty, J. A. J. Chem. Soc., Dalton Trans.
2002, 275.

Ethenyl and Ethynyl Ferrocene Polyaromatic Dyads
Organometallics, Vol. 24, No. 9, 2005 2059
ular orbital contour plots were prepared by importing the
Gaussian 98 output files into MOLDEN. Formylvinylfer-
rocene,22 ferrocenylmethyl(triphenyl)phosphonium iodide,38
and 3-iodoperylene39 were prepared according to literature
procedures. Other compounds were commercial reagents, used
as received. Although syntheses of 10, 13, and 15 have been
previously described,8,19-21 1H NMR and IR data were not
included and are thus included here for completeness.
thiosulfate solution (10 mL) and water followed by extraction,
drying, and removal of the solvent as before. The solid residue
was purified by column chromatography on silica gel with
hexane/CH2Cl2 (4:1) eluant, and the product was crystallized
from CH2Cl2/hexane to give orange crystals (0.155 g, 23%), mp
125-128 °C. Anal. Calcd for C22H18Fe: C, 78.11; H, 5.33.
1
Found: C, 78.09; H, 5.44. MS: m/e 339 (MH+). H NMR (δ):
4.19 (s, 5H, C5H5), 4.33 (t, 2H, Fc-Hâ), 4.56 (t, 2H, Fc-HR), 6.93
[d (J ) 16 Hz), Fc-CHd], 7.48 [d (J ) 16 Hz), dCH-naphth],
7.49 (m, naphth-H3), 7.5 (m, 2H, naphth-H6, H7), 7.70 (m,
naphth-H2), 7.78 (m, naphth-H4) 7.87 (m, naphth-H5), 8.19
Synthesis of Ethynyl Dyads. (9-Anthryl)ethynylfer-
rocene (5). A typical preparation, that of 5, follows. Ethynyl-
ferrocene (0.252 g, 1.2 mmol), 9-bromoanthracene (0.206 g, 0.8
mmol), and catalytic amounts (0.2 mol %) of PdCl2(PPh3)2 and
CuI were refluxed in 10 mL of iPr2NH for 30 min. Solvent was
removed under vacuum and the reaction mixture separated
using chromatography on SiO2 with a hexane/CH2Cl2 (3:1)
eluant to give orange crystals of 5 (0.141 g, 46%), mp 218-
220 °C. Anal. Calcd for C26H18Fe: C, 80.85; H, 4.70. Found:
C, 80.84; H, 4.68. MS: m/e 386 (M+). 1H NMR (δ): 4.34 (s,
5H, C5H5), 4.36 (t, 2H, Fc-Hâ), 4.72 (t, 2H, Fc-HR), 7.52 (m,
2H, anthr-H3/6), 7.61 (m, 2H, anthr-H2/7), 8.02 (m, 2H, anthr-
H4/5), 8.42 (s, anthr-H10), 8.61 (m, 2H, anthr-H1/8). IR (CH2-
(m, naphth-H8). IR (CH2Cl2): 950 (E-CHdCH wag) cm-1
.
(E)-(2-Naphthyl)ethenylferrocene (10). From FcCH2-
PPh3+I-/2-naphthaldehyde; orange crystals (46%), mp 165-
167 °C. Anal. Calcd for C22H18Fe: C, 78.11; H, 5.33. Found:
1
C, 78.05; H, 5.32. MS: m/e 339 (MH+). H NMR (δ): 4.16 (s,
5H, C5H5), 4.31 (t, 2H, Fc-Hâ), 4.52 (t, 2H, Fc-HR), 6.87 [d (J )
16 Hz), dCH-naphth], 7.01 [d (J ) 16 Hz), Fc-CHd], 7.45 (m,
2H, naphth-H6, H7), 7.68 [dd (J ) 9, 2 Hz), naphth-H3], 7.76
(m, naphth-H1), 7.8 (m, 3H, naphth-H4, H5, H8). IR (CH2-
Cl2): 959 (E-CHdCH wag) cm-1
.
Cl2): νCtC 2203 cm-1
.
(E)-(9-Phenanthryl)ethenylferrocene (11). From FcCH2-
PPh3+I-/9-phenanthrenecarboxaldehyde; orange red crystals
(51%), mp 133-135 °C. Anal. Calcd for C26H20Fe: C, 80.41;
H, 5.15. Found: C, 80.13; H, 5.23. MS: m/e 389 (MH+). 1H
NMR (δ): 4.22 (s, 5H, C5H5), 4.35 (t, 2H, Fc-Hâ), 4.59 (t, 2H,
Fc-HR), 7.01 [d (J ) 16 Hz), Fc-CHd], 7.47 [d (J ) 16 Hz),
dCH-phen], 7.6 (m, 4H, phen-H2, H3, H6, H7), 7.91 (s, phen-
H10), 7.92 (m, phen-H1), 8.24 (m, phen-H8), 8.67 (m, phen-
H4), 8.75 (m, phen-H5). IR (CH2Cl2): 958 (E-CHdCH wag)
(2-Naphthyl)ethynylferrocene (3). From ethynylferrocene/
2-bromonaphthalene; orange crystals (59%), mp 135 °C. Anal.
Calcd for C22H16Fe: C, 78.59; H, 4.80. Found: C, 78.34; H,
4.88. MS: m/e 337 (MH+). 1H NMR (δ): 4.28 (s, 5H, C5H5),
4.27 (t, 2H, Fc-Hâ), 4.55 (t, 2H, Fc-HR), 7.49 (m, 2H, naphth-
H6, H7), 7.55 [dd (J ) 8, 2 Hz), naphth-H3], 7.79 (m, naphth-
H4), 7.82 (m, 2H, naphth-H5, H8), 8.01 (m, naphth-H1). IR
(CH2Cl2): νCtC 2221, 2210 cm-1
.
cm-1
.
(9-Phenanthryl)ethynylferrocene (4). From ethynylfer-
rocene/9-bromophenanthrene; red-orange oil (30%). MS: m/e
(E)-(9-Anthryl)ethenylferrocene (12). From FcCH2-
PPh3+I-/9-anthraldehyde; orange crystals (36%), mp 177-178
°C. Anal. Calcd for C26H20Fe: C, 80.41; H, 5.15. Found: C,
80.23; H, 5.45. MS: m/e 389 (MH+). 1H NMR (δ): 4.29 (s, 5H,
C5H5), 4.38 (t, 2H, Fc-Hâ), 4.63 (t, 2H, Fc-HR), 6.71 [d (J ) 16
Hz), Fc-CHd], 7.48 (m, 4H, anthr-H2/7, H3/6), 7.51 [d (J ) 16
Hz), dCH-anthr], 8.02 (m, 2H, anthr-H4/5), 8.39 (s, anthr-
H10), 8.40 (m, 2H, anthr-H1/8). IR (CH2Cl2): 958 (E-CHdCH
1
387 (MH+). H NMR (δ): 4.32 (s, 5H, C5H5), 4.32 (t, 2H, Fc-
Hâ), 4.65 (t, 2H, Fc-HR), 7.60 (m, phen-H2), 7.66 (m, phen-H3),
7.72 (m, 2H, phen-H6, H7), 7.87 (m, phen-H1), 8.04 (s, phen-
H10), 8.52 (m, phen-H8), 8.67 (m, phen-H4), 8.71 (m, phen-
H5). IR (CH2Cl2): νC≡C 2209 cm-1
.
(1-Pyrenyl)ethynylferrocene (6). From ethynylferrocene/
1-iodopyrene; red-orange crystals (37%), mp 212-214 °C. Anal.
Calcd for C28H18Fe: C, 81.97; H, 4.42. Found: C, 82.00; H,
4.41. MS: m/e 411 (MH+). 1H NMR (δ): 4.34 (s, 5H, C5H5),
4.34 (t, 2H, Fc-Hâ), 4.68 (t, 2H, Fc-HR), 8.03 [t (J ) 8 Hz), pyr-
H7], 8.05, 8.09 {2 × [d (J ) 9 Hz)] pyr-H4, H5}, 8.12, 8.17 {2
× [d (J ) 8 Hz)], pyr-H3, H2}, 8.20 (m, 2H, pyr-H6, H9), 8.23
[d (J ) 8 Hz), pyr-H8], 8.63 [d (J ) 9 Hz), pyr-H10]. IR (CH2-
wag) cm-1
.
(E)-(1-Pyrenyl)ethenylferrocene (13). From FcCH2-
PPh3+I-/1-pyrenecarboxaldehyde; red crystals (46%), mp 190-
191 °C. Anal. Calcd for C28H20Fe: C, 81.55; H, 4.85. Found:
1
C, 81.43; H, 5.00. MS: m/e 413 (MH+). H NMR (δ): 4.22 (s,
5H, C5H5), 4.34 (t, 2H, Fc-Hâ), 4.64 (t, 2H, Fc-HR), 7.14 [d (J )
16 Hz), Fc-CHd], 7.78 [d (J ) 16 Hz), dCH-pyr], 8.00 [t (J )
8 Hz), pyr-H7], 8.05 (s, 2H, pyr-H4, H5), 8.13 [d (J ) 9 Hz),
pyr-H9], 8.16 [d (J ) 8 Hz), pyr-H3], 8.18 [d (J ) 8 Hz), 2H,
pyr-H6, H8], 8.27 [d (J ) 8 Hz), pyr-H2], 8.45 [d (J ) 9 Hz),
Cl2): νCtC 2221, 2202 cm-1
.
(3-Perylenyl)ethynylferrocene (7). From ethynylferrocene/
3-iodoperylene; red-orange crystals (19%), mp >220 °C (with
dec). Anal. Calcd for C32H20Fe: C, 83.49; H, 4.38. Found: C,
pyr-H10]. IR (CH2Cl2): 956 (E-CHdCH wag) cm-1
.
1
83.24; H, 4.63. MS: m/e 460 (M+). H NMR (δ): 4.31 (s, 5H,
(E)-(3-perylenyl)ethenylferrocene (14). From FcCH2-
PPh3+I-/3-perylenecarboxaldehyde; red crystals (74%), mp 170
°C. Anal. Calcd for C32H22Fe: C, 83.13; H, 4.80. Found: C,
C5H5), 4.32 (t, 2H, Fc-Hâ), 4.63 (t, 2H, Fc-HR), 7.50 (m, 2H,
per-H8, H11), 7.61 (m, per-H5), 7.70 (m, 3H, per-H2, H9, H10),
8.15 (m, per-H1), 8.20, 8.23 [2 × (m), per-H7, H12], 8.26 (m,
1
83.32; H, 4.68. MS: m/e 462 (M+). H NMR (δ): 4.20 (s, 5H,
per-H6), 8.27 (m, per-H4). IR (CH2Cl2): νCtC 2207 cm-1
.
C5H5), 4.35 (t, 2H, Fc-Hâ), 4.58 (t, 2H, Fc-HR), 6.98 [d (J ) 16
Hz), Fc-CHd], 7.41 [d (J ) 16 Hz), dCH-per], 7.49 (m, 2H,
per-H8, H11), 7.55 (m, per-H5), 7.68, 7.69 [2 × (m), per-H9,
H10], 7.72 [d (J ) 8 Hz), per-H2], 8.04 (m, per-H4), 8.19 [d (J
) 8 Hz), per-H1], 8.19, 8.21 [2 × (m), per-H7, H12], 8.24 (m,
Synthesis of Ethenyl Dyads. (E)-(1-Naphthyl)ethenyl-
ferrocene (9). 1-Naphthaldehyde (0.630 g, 4.0 mmol) was
dissolved in THF (50 mL), and ferrocenylmethyl triphenylphos-
phonium iodide (0.966 g, 2.0 mmol) was added. Solid KOtBu
(0.224 g, 2.0 mmol) was introduced in one portion, and the
mixture was stirred at room temperature for 2 h. The reaction
was quenched with water (100 mL), extracted with diethyl
ether (100 mL), washed with water, and dried over MgSO4.
Concentration in vacuo afforded an orange solid. This was
redissolved in dichloromethane (10 mL) and heated at reflux
with a crystal of iodine until TLC indicated the presence of
only one isomer. The solution was washed with aqueous
per-H6). IR (CH2Cl2): 956 (E-CHdCH wag) cm-1
.
Synthesis of Butadienyl Dyads. (E,E)-(Phenyl)buta-
dienylferrocene (15). tBuOK (0.033 g, 0.2 mmol) was added
to a solution of [PhCH2PPh3]Br (0.106 g, 0.2 mmol) in dry ether
(25 mL). After 30 min, FcCHdCHCHO (0.048 g, 0.19 mmol)
was added to the solution and the mixture stirred overnight.
It was quenched with water (25 mL) and the organic layer
washed with more water, dried over magnesium sulfate, and
evaporated to dryness to give an orange solid. This was
redissolved in dichloromethane (10 mL) and heated at reflux
with a crystal of iodine until TLC indicated the presence of
only one isomer. The solution was washed with aqueous
(38) Baumgarten, H. E., Ed. Organic Syntheses; Wiley: New York,
1973; Collect. Vol. V, p 434.
(39) Inouye, M.; Hyodo, Y.; Nakazumi, H. J. Org. Chem. 1999, 64,
2704.

2060 Organometallics, Vol. 24, No. 9, 2005
Cuffe et al.
Table 4. Crystal Data
5
6
7
12
13
chem formula
fw
C
26H18Fe
C28H18Fe
410.27
C32H20Fe
460.33
monoclinic
P21/c
0.735
R1 ) 0.0754
wR2 ) 0.2192
R1 ) 0.0891
wR2 ) 0.2279
C26H20Fe
C28H20Fe
386.25
388.27
412.29
cryst syst
monoclinic
P21/c
0.849
R1 ) 0.0423
wR2 ) 0.1010
R1 ) 0.0608
wR2 ) 0.1075
triclinic
triclinic
monoclinic
P21/c
0.778
R1 ) 0.0363
wR2 ) 0.0594
R1 ) 0.1020
wR2 ) 0.0696
space group
P1h
0.826
R1 ) 0.0374
wR2 ) 0.0894
R1 ) 0.0515
wR2 ) 0.0930
P1h
absorp coeff/mm-1
final R indices [I>2σ(I)]
0.812
R1 ) 0.0345
wR2 ) 0.1033
R1 ) 0.0436
wR2 ) 0.0905
R indices (all data)
unit cell dimens
a/Å
7.265(3)
11.059(4)
22.303(8)
90
91.824(5)
90
7.810(5)
9.956(6)
13.205(8)
107.540(6)
101.733(7)
100.521(6)
925.4(10)
2
11.4212(10)
10.8680(10)
17.2066(16)
90
99.6090(10)
90
7.7278(4)
10.5188(9)
12.0885(8)
101.449(5)
100.901(4)
95.453(5)
936.69(11)
2
19.12(3)
7.379(9)
14.89(3)
90
110.62(3)
90
1966(5)
4
168(2)
23 370
4001
b/Å
c/Å
R/deg
â/deg
γ/deg
volume/Å3
Z
1791.2(10)
4
2105.8(3)
4
temp/K
no. of reflns collected
no. of indep reflns
168(2)
163(2)
158(2)
294(2)
3710
11 682
14 350
5507
2421
3719
4127
4528
[R(int) ) 0.0275]
[R(int) ) 0.0463]
[R(int) ) 0.0233]
[R(int) ) 0.00142]
[R(int) ) 0.0841]
sodium thiosulfate solution (10 mL) and water followed by
extraction, drying, and removal of the solvent as before. The
solid residue was purified by column chromatography on silica
gel with hexane/CH2Cl2 (1:3) to give orange crystals (0.037 gm,
63%), mp 198-201°C. Anal. Calcd for C20H18Fe: C, 76.45; H,
5.77. Found: C, 76.33; H, 5.64. MS: m/e 315 (MH+). 1H NMR
(δ): 4.13 (s, 5H, C5H5), 4.28 (t, 2H, Fc-Hâ), 4.41 (t, 2H, Fc-HR),
6.44 [d (J ) 15 Hz), Fc-CHd], 6.54 [d (J ) 15 Hz), dCH-
naphth], 6.56 [dd (J ) 10, 15 Hz), Fc-CHdCH], 6.85 [dd (J )
10, 15 Hz), CHdCH-naphth], 7.22 (m, phenyl-H4), 7.32 (m,
2H, phenyl-H3/5), 7.42 (m, 2H, phenyl-H2/6).
(E,E)-(2-Naphthyl)butadienylferrocene (16). From
FcCHdCH-CHO/(2-naphthyl)-CH2PPh3+I-; orange crystals
(36%), mp 203-204 °C. Anal. Calcd for C24H20Fe: C, 79.14;
H, 5.53. Found: C, 79.34; H, 6.21. MS: m/e 365 (MH+). 1H
NMR (δ): 4.15 (s, 5H, C5H5), 4.30 (t, 2H, Fc-Hâ), 4.44 (t, 2H,
Fc-HR), 6.48 [d (J ) 15 Hz), dCH-naphth], 6.62 [dd (J ) 10,
15 Hz), CHdCH-naphth], 6.69 [d (J ) 15 Hz), Fc-CHd], 6.98
[dd (J ) 10, 15 Hz), Fc-CHdCH], 7.44 (m, 2H, naphth-H6, H7),
7.64 [dd (J ) 9, 2 Hz), naphth-H3], 7.8 (m, 4H, naphth-
H1,4,5,8).
sorption corrections applied using SADABS.40 For 12, data
were obtained at 294(2) K on a Siemens P4 diffractometer.
The absorption corrections were undertaken using ψ-scans and
the program XEMP in XSCANS.41
All structures were solved by direct methods using SHELXS42
and refined by full-matrix least-squares on F2 using TI-
TAN200043 and SHELXL-97.42 Non-hydrogen atoms were
assigned anisotropic temperature factors, with hydrogen atoms
included in calculated positions. High and increasing temper-
ature factors for the C1-C5 atoms of the unsubstituted
cyclopentadienyl ring in 12 indicated that the ring was
disordered over two sites. The disorder was resolved by
refining two unique positions for these atoms with their
occupancy factors f and f ′ refined such that f ′ ) 1 - f. The
final value of f refined to 0.568(16). The final difference Fourier
synthesis for 13 revealed a high peak (∼2 e Å-3) close to the
C20 atom of the perylene ring. This clearly contributes to the
relatively high residuals observed in the refinement. However,
no sensible chemical assignment of the peak could be made
and there was no indication of it resulting from disorder.
(E,E)-(9-Anthryl)butadienylferrocene (17). From FcCHd
CH-CHO/(9-anthryl)-CH2PPh3+I-; orange crystals (10%). Anal.
Calcd for C28H22Fe: C, 81.17; H, 5.35. Found: C, 80.78; H,
5.56. MS: m/e 415 (MH+). 1H NMR (δ): 4.19 (s, 5H, C5H5),
4.38 (t, 2H, Fc-Hâ), 4.63 (t, 2H, Fc-HR), 6.48 [d (J ) 15 Hz),
Fc-CHd], 6.69 [dd (J ) 10, 15 Hz), CHdCH-anthr], 6.85 [dd
(J ) 10, 15 Hz), Fc-CHdCH], 7.38 [d (J ) 15 Hz), dCH-anthr],
7.48 (m, 4H, anthr-H2/7, H3/6), 8.01 (m, 2H, anthr-H4/5), 8.35
(m, 2H, anthr-H1/8), 8.38 (s, anthr-H10).
(E,E)-(1-Pyrenyl)butadienylferrocene (18). From FcCHd
CH-CHO/(1-pyrenyl)-CH2PPh3+I-; orange crystals (20%). Anal.
Calcd for C30H22Fe: C, 82.20; H, 5.06. Found: C, 82.12; H,
5.07. MS: m/e 439 (MH+). 1H NMR (δ): 4.19 (s, 5H, C5H5),
4.35 (t, 2H, Fc-Hâ), 4.50 (t, 2H, Fc-HR), 6.57 [d (J ) 15 Hz),
Fc-CHd], 6.80 [dd (J ) 10, 15 Hz), Fc-CHdCH], 7.14 [dd (J )
10, 15 Hz), CHdCH-pyr], 7.62 [d (J ) 15 Hz), dCH-pyr], 8.00
[t (J ) 8 Hz), pyr-H7], 8.1 (m, 6H, pyr-H3-6,8,9), 8.28 [d (J )
8 Hz), pyr-H2], 8.46 [d, (J ) 9 Hz), pyr-H10].
Acknowledgment. We thank Prof. Ward T. Robin-
son and Dr. Jan Wikaira (University of Canterbury) for
X-ray data collection, Dr. Amar Flood for the resonance
Raman data, and Drs. Keith Gordon and Henrik Kjaer-
gaard for helpful discussions.
Supporting Information Available: Final positional and
equivalent thermal parameters are given in the deposited
tables, all bond lengths and angles, anisotropic thermal
parameters, and hydrogen positional and isotropic displace-
ment parameters for all compounds. Calculated global mini-
mized structures and packing motifs are given in Figures S1-
1
S4. H and 13C NMR are given in Tables S1-S5 and Figures
S5-S11. This material is available free of charge via the
Internet at http://pubs.acs.org
OM0492653
X-ray Data Collection, Reduction, and Structure So-
lution for 5-7, 12, and 13. Crystal data for compounds 5-7,
12, and 13 are given in Table 4. Data for 5-7 and 13 were
collected at low temperatures on a Bruker SMART CCD
diffractometer, processed using SAINT40 with empirical ab-
(41) XEMP absorption correction routine in XSCANS, Siemens,
1996.
(42) Sheldrick, G. M. SHELXS: a program for the solution of crystal
structures from diffraction data, 1990; SHELXL-97: a program for the
refinement of crystal structures, 1997; University of Go¨ttingen,
Germany.
(40) SMART (control) and SAINT (integration) software; Bruker
AXS: Madison WI, 1994. SADABS (correction for area detector data);
Bruker, 1997.
(43) Hunter K. A.; Simpson J. TITAN2000: A molecular graphics
program to aid structure solution and refinement with the SHELX
suite of programs; University of Otago, New Zealand, 1999.