New soluble bis[nona-, octa-, and pentamethylferrocenes] as molecular wires with a metal-to-metal distance of up to 40 ? #

Article abstract of DOI:10.1021/om960676w

Methylated ferrocenes are useful building blocks for novel materials in molecular electronics with advantageous properties in comparison to normal ferrocene derivatives. The presence of nine, eight, or five methyl substituents leads to (i) a decrease in oxidation potential, (ii) amplified donor capacity with correspondingly increased stability of the ferrocenium salts, and, most significantly, (iii) increased solubility. A modular synthetic approach based on standard Wittig chemistry affords π-conjugated soluble nona-, octa-, and pentamethylated biferrocenes, bridged by up to five vinylene-phenylene subunits. These biferrocenes with spacers are molecular wires with a metal-to-metal distance of up to 40 A? and an effective conjugation pathway of up to 50 A?.

Full text of DOI:10.1021/om960676w

392
Organometallics 1997, 16, 392-402
New Solu ble Bis[n on a -, octa -, a n d
p en ta m eth ylfer r ocen es] a s “Molecu la r Wir es” w ith a
Meta l-to-Meta l Dista n ce of u p to 40 Å#
Andreas Hradsky,† Benno Bildstein,*,†,‡ Norbert Schuler,†
Herwig Schottenberger,*,†,§ Peter J aitner,† Karl-Hans Ongania,|
Klaus Wurst,† and J ean-Pierre Launay*,
Institut fu¨r Allgemeine, Anorganische, und Theoretische Chemie, Universita¨t Innsbruck,
Innrain 52a, A-6020 Innsbruck, Austria, Institut fu¨r Organische Chemie,
Universita¨t Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria, and Molecular Electronics
Group, Centre d’Elaboration de Mate´riaux et d’Etudes Structurales, CNRS,
29 Rue J eanne Marvig, 31055 Toulouse Cedex, France
Received August 9, 1996X
Methylated ferrocenes are useful building blocks for novel materials in molecular
electronics with advantageous properties in comparison to normal ferrocene derivatives. The
presence of nine, eight, or five methyl substituents leads to (i) a decrease in oxidation
potential, (ii) amplified donor capacity with correspondingly increased stability of the
ferrocenium salts, and, most significantly, (iii) increased solubility. A modular synthetic
approach based on standard Wittig chemistry affords π-conjugated soluble nona-, octa-, and
pentamethylated biferrocenes, bridged by up to five vinylene-phenylene subunits. These
biferrocenes with spacers are “molecular wires” with a metal-to-metal distance of up to 40
Å and an effective conjugation pathway of up to 50 Å.
Sch em e 1. P r in cip a l Com p on en ts of Molecu la r
Wir es
In tr od u ction
In comparison to the well-developed chemistry of
ferrocene with its numerous applications1 in organic
synthesis, homogeneous catalysis, and materials sci-
ence, the analogous chemistry of methylated ferrocene
derivatives is limited.2 Ferrocenes made up of one
pentamethylcyclopentadienide (Cp*) and one substi-
tuted cyclopentadienide [(H3C)nCp-R; n ) 0-4; R )
functional group or bridging ligand] should display
favorable properties in terms of increased solubility,3
lowered oxidation potential, amplified donor capacity,
and hence increased stability3 of the corresponding
ferrocenium cations, which could be exploited for im-
proved materials in molecular electronics.4 Molecular
wires5 are mixed-valence bimetallic compounds with a
conjugating bridging ligand that allows electronic com-
munication between the two redox termini (Scheme 1).
For example, such systems are known with oligoene
bridging ligands between ruthenium pentamine com-
plexes6 or between simple ferrocenes,7 where the elec-
tronic coupling can be experimentally verified for up to
18 Å separated electrophores.
† Institut fu¨r Allgemeine, Anorganische, und Theoretische Chemie.
‡ Correspondence regarding pentamethylferrocenes to this author.
Telefax: Int. code + 512-507-2934. E-mail: benno.bildstein@uibk.ac.at.
§ Correspondence regarding octa- and nonamethylferrocenes to
this author. Telefax: Int. code + 512-507-2934. E-mail: herwig.
schottenberger@uibk.ac.at.
| Institut fu¨r Organische Chemie.
(3) (a) Rybinskaya, M. I.; Kreindlin, A. Z.; Petrovskii, P. V.; Minyaev,
R. M.; Hoffmann, R. Organometallics 1994, 13, 3903. (b) Turpeinen,
U.; Kreindlin, A. Z.; Petrovskii, P. V.; Rybinskaya, M. I. J . Organomet.
Chem. 1992, 441, 109. (c) Kreindlin, A. Z.; Fedin, E. I.; Petrovskii, P.
V.; Rybinskaya, M. I.; Minyaev, R. M.; Hoffmann, R. Organometallics
1991, 10, 1206. (d) Yanovsky, Y.; Struchkov, Y. T.; Kreindlin, A. Z.;
Rybinskaya, M. I. J . Organomet. Chem. 1989, 369, 125. (e) Bashkin,
J . K.; Kinlen, P. J . Inorg. Chem. 1990, 29, 4507.
(4) (a) Tour, J . M. Chem. Rev. 1996, 96, 537. (b) J ones, L., II;
Pearson, D. L.; Schumm, J . S.; Tour, J . M. Pure Appl. Chem. 1996,
68, 145. (c) Manriquez, J . M.; Ward, M. D.; Reiff, W. M.; Calabrese, J .
C.; J ones, N. L.; Caroll, P. J .; Bunel, E. E.; Miller, J . S. J . Am. Chem.
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T. E.; Rheingold, A. L. J . Am. Chem. Soc. 1987, 109, 5680. (e) Voegeli,
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1986, 108, 7010. (f) Hendrickson, D. N.; Kramer, J . A. Inorg. Chem.
1980, 19, 3330. (g) Le Vanda, C.; Bechgaard, K.; Cowan, D. O.; Rausch,
M. D. J . Am. Chem. Soc. 1977, 99, 2964. (h) Brown, G. M.; Meyer, T.
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Paris, 1991; New J . Chem. 1991, 15, 97 (special issue). (b) J oachim,
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Tarutani, S.; Spangler, C. W. Inorg. Chem. 1994, 33, 1325. (b)
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CNRS.
#
Dedicated to Professor K.-E. Schwarzhans on the occasion of his
60th birthday.
X Abstract published in Advance ACS Abstracts, J anuary 1, 1997.
(1) Ferrocenes; Togni, A., Hayashi, T., Eds.; VCH Verlagsgesellschaft
mbH: Weinheim, Germany, 1995; and references cited therein.
(2) (I) Pentamethylferrocenes: (a) Nelsen, S. F.; Chen, L.-J .; Ramm,
M. T.; Voy, G. T.; Powell, D. R.; Accola, M. A.; Seehafer, T. R.; Sabelko,
J . J .; Pladziewicz, J . R. J . Org. Chem. 1996, 61, 1405. (b) Abbenhuis,
H. C. L.; Burckhardt, U.; Gramlich, V.; Togni, A.; Albinati, A.; Mu¨ller,
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P. Organometallics 1995, 14, 5000. (II) Nona- and octamethylfer-
rocenes: (g) Schmitt, G.; O¨ zman, S. Chem. Z. 1976, 100, 143. (h) Zou,
C.; Wrighton, M. S. J . Am. Chem. Soc. 1990, 112, 7578. (i) Kreindlin,
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metallics 1996, 15, 3885.
S0276-7333(96)00676-0 CCC: $14.00 © 1997 American Chemical Society

Soluble “Molecular Wires”
Organometallics, Vol. 16, No. 3, 1997 393
In this contribution we report on the synthesis of
soluble methylated biferrocenes with increased (up to
40Å) metal-to metal distances, using standard Wittig
and/or Wittig-Horner olefination procedures.8 The
bridging ligands were selected to be phenylene-vi-
nylene oligomers, which combine chemical stability with
good charge conducting properties in comparison to
oligoene,7 oligoyne,9 and oligophenyleneyne compounds.10
The number of solubilizing and cation-stabilizing methyl
substituents on the metallocenyl termini were system-
atically varied from 9 to 5 with the anticipation of (i)
increasing the solubility with the number of methyl
groups attached to the ferrocenyl electrophores and (ii)
progressively stabilizing the oxidized ferrocenium spe-
cies according to the number of electron-donating meth-
yl substituents.
F igu r e 1. Molecular structure of 4, showing the atom-
numbering scheme. Hydrogen atoms are omitted for clarity.
The cyclopentadienyl carbons of ferrocene 1 are C(1)-C(10),
and the methyl carbons of ferrocene 1 are C(01)-C(09).
Torsion angles: C(12)-C(11)-C(10)-C(9) ) -6.0(3.2)°;
C(11)-C(12)-C(13)-C(18) ) 10.8(3.4)°. Angle of Cp plane
[C(6)-C(10)] to phenyl plane [C(13)-C(18)] ) 10.5(1.1)°.
Resu lts a n d Discu ssion
(a ) Gen er a l Syn th etic Ap p r oa ch . Biferrocenes
with olefinic conjugating bridging ligands are most
easily prepared by Wittig and/or Wittig-Horner reac-
tions,8 similar to published results11 on related oligo-
(phenylene-vinylenes). The necessary synthons for the
stepwise construction of such biferrocenes are thus
methylated ferrocene aldehydes, terephthaldialdehyde,
and the hydroxymethyl derivatives as the phosphonium
progenitors, respectively. Fortunately, in contrast to the
normal product distribution of Wittig protocols,8 the
desired (E)-vinylferrocenes are favored for the first
homologation step, although in general always E/Z-
mixtures are formed.12 The isomer distribution of the
Wittig products of ferrocene aldehydes13 is strongly
influenced by the base used in the preparation of the
ylide, and potassium tert-butoxide14 seems to be the base
of choice for maximized yields of (E)-olefins. The
resulting isomer mixtures are usually difficult to sepa-
rate by chromatography, but sometimes the (E)-olefins
can be obtained by selective crystallization (see Experi-
mental Section). In addition, according to our own
experience, acidic isomerizations12 to the thermody-
namically favored (E)-olefins are not applicable for
highly methylated ferrocenes. To circumvent these
restrictions, Wittig-Horner olefinations utilizing p-
phenylene bis(phosphonate)15 as a convenient “bis-
(ylide)” progenitor are preferable, especially for the
construction of the central phenylene-vinylene bridging
units in the higher oligomers. (Ferrocenylmethyl)-
triphenylphosphonium and 1,1′-ferrocenediylbis(meth-
yltriphenylphosphonium) salts16 are usually synthesized
by multistep procedures via the methyl iodides of the
corresponding ((dimethylamino)methyl)metallocenes.
Since the availability of numerous metallocenyl alde-
hydes and the alcohols derived thereof has been signifi-
cantly improved during the recent years,17 it seemed
encouraging to apply a one-pot elimination-substitution
sequence according to Hamanaka and Kosuge,18 which
proved to be the most simple and efficient route to the
desired ylide progenitors.
(b ) Non a - a n d Oct a m et h yla t ed F er r ocen es
(Sch em e 2). In this manner, ((octa- and nonamethyl-
ferrocenyl)methyl)triphenylphosphonium salts 1a ,b and
2 can be obtained in high yield. In addition to their
characterization by the usual spectroscopic methods (see
Experimental Section), X-ray structure analyses of 1b
and 2 confirm their identity. These two solid-state
structures are very similar to the published structure
of (ferrocenylmethyl)triphenylphosphonium iodide16 and
present no unexpected features; therefore the details of
these crystal structures are included in the Supporting
Information only.
Besides these normal (monocationic) phosphonium
salts, the stabilizing effect of the methyl substituents
allows also the isolation of the green air-stable ((octa-
methylferroceniumyl)methyl)triphenylphosphonium di-
cation (1c), whose single-crystal structure is included
in the Supporting Information. Starting from phospho-
nium salts 1a ,b and 2 the corresponding ylides afford
the “spacered” aldehydes 3 and 4 by reaction with excess
terephthaldialdehyde. In accord with NMR analysis the
solid-state structures of 3 (Supporting Information) and
4 (Figure 1, Table 1) clearly show an E-configuration.
Only twinned crystals could be obtained in the case of
4; however the structure could be solved with cor-
respondingly rather high residuals in the final structure
refinement, but the connectivity of the molecule is
nevertheless unequivocally determined.
(7) Ribou, A.-C.; Launay, J .-P.; Sachtleben, M. L.; Li, H.; Spangler,
C. W. Inorg. Chem. 1996, 35, 3735; and references cited therein.
(8) Maryanoff, B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863.
(9) Reference 4a and references cited therein.
(10) (a) Nock, H.; Buchmeiser, M.; Polin, J .; Lukasser, J .; J aitner,
P.; Schottenberger, H. Mol. Crystallogr. Liq. Crystallogr. Sci. Technol.,
Sect. A 1993, 235, 237. (b) Launay, J .-P. Unpublished results. (c) Polin,
J .; Buchmeiser, M.; Nock, H.; Schottenberger, H. Mol. Crystallogr. Liq.
Crystallogr. Sci. Technol., Sect. A 1996, in press.
(11) (a) Ghosal, S.; Samoc, M; Prasad, P. N.; Tufariello, J . J . J . Phys.
Chem. 1990, 94, 2847. (b) Drefahl, G.; Plo¨tner, G. Chem. Ber. 1958,
91, 1274. (c) Katz, H. E.; Bent, S. F.; Wilson, W. L.; Schilling, M. L.;
Ungashe, S. B. J . Am. Chem. Soc. 1994, 116, 6631. (d) Gill, R. E.;
Meetsma, A.; Hadziioannou, G. Adv. Mater. 1996, 8, 212. (e) Schenk,
R.; Gregorius, H.; Meerholz, K.; Heinze, J .; Mu¨llen, K. J . Am. Chem.
Soc. 1991, 113, 2634.
(16) Glidewell, C.; Zakaria, C. M. Acta Crystallogr. 1994, C50, 233
and references cited therein.
(12) Pauson, P. L.; Watts, W. E. J . Chem. Soc. 1963, 2990.
(13) (a) Wurst, K.; Elsner, O.; Schottenberger, H. Synlett 1995, 833.
(b) Rodriguez, J .-G.; Onate, A.; Martin-Villamil, R. M.; Fonseca, I. J .
Organomet. Chem. 1996, 513, 71.
(14) Fitjer, L.; Quabeck, U. Synth. Commun. 1985, 15, 855.
(15) Lee, J .-K.; Schrock, R. R.; Baigent, D. R.; Friend, R. H.
Macromolecules 1995, 28, 1966.
(17) (a) Dong, T.-Y.; Lai, L.-L. J . Organomet. Chem. 1996, 509, 131.
(b) Iftime, G.; Moreau-Bossuet, C.; Manoury, E.; Balavoine, G. G. A.
Chem. Commun. 1996, 527. (c) Mueller-Westerhoff, U. T.; Yang, Z.;
Ingram, G. J . Organomet. Chem. 1993, 463, 163. (d) Balavoine, C. G.
A.; Doisneau, G.; Fellebeen-Khan, T. J . Organomet. Chem. 1991, 412,
381. (e) Wright, M. E. Organometallics 1990, 9, 853.
(18) Hamanaka, N.; Kosuge, S.; Iguchi, S. Synlett 1990, 139.

394 Organometallics, Vol. 16, No. 3, 1997
Sch em e 2. Syn th esis of Com p ou n d s 1-7
Hradsky et al.
As will also be seen in other following structures, the
vinylene-phenylene subunit(s) is (are) usually out of
plane to the ferrocenyl group and with respect to each
other, resulting in a twisted conformation in the solid
state with the consequence of crystallographically im-
posed chirality for these molecules. Therefore the con-
tents of the unit cell correspond to a racemic mixture
in these cases. For compound 4 the respective torsion
angles are -6.0(3.2) and 10.8(3.4)° (Figure 1). Similar
values for successive twisting of vinylene and phenylene
segments have recently been published for a purely
organic all-E oligo(phenylene-vinylene).11d
Reaction of the ylide derived from phosphonium salt
1a with octamethylferrocenyl aldehyde yields an E/Z-
mixture of the symmetrical olefin 5a ,b, whereas the
E-isomer 5a can be also obtained more conveniently by
a McMurry19 reaction from the aldehyde, in analogy to
other carbonyl ferrocenes.20
only the torsion angle between the cyclopentadienyl
plane and the double bond is higher in value (23.28°
for 5a and 15.1° for (E)-diferrocenylethylene), most
likely due to the steric requirements of the methyl
substituents.
Bis-olefination of terephthaldialdehyde with 2 equiv
of octamethylferrocenyl ylide yields the vinylene-phen-
ylene-vinylene bridged biferrocene 6 in the all-E con-
formation as is evidenced by the observation of the
1
typical E-coupling constants of 16 Hz in the H NMR
spectrum. The solid-state structure (Figure 3, Table 1)
confirms this stereochemistry with regard to the double
bonds and shows that the vinylene phenylene cyclopen-
tadienyl subunits are twisted in relation to each other
with torsion angles of 20.68 and 12.60°, respectively.
(19) (a) McMurry, J . E. Chem. Rev. 1989, 89, 1513. (b) McMurry, J .
E. Acc. Chem. Res. 1983, 16, 405. (c) Betschart, D.; Seebach, D. Chimia
1989, 43, 39.
Figure 2 (see also Table 1) shows the result of an
X-ray structure analysis of 5a which can be compared
to the structure of (E)-diferrocenylethylene.21 The
overall structural parameters are of course very similar;
(20) Bildstein, B.; Denifl, P.; Wurst, K.; Andre´, M.; Baumgarten, M.;
Friedrich, J .; Ellmerer-Mu¨ller, E. Organometallics 1995, 14, 4334 and
references cited therein.
(21) Denifl, P.; Hradsky, A.; Bildstein, B.; Wurst, K. J . Organomet.
Chem. 1996, 523, 79.

Soluble “Molecular Wires”
Organometallics, Vol. 16, No. 3, 1997 395
properties of 16 or 18 methyl groups, the disappointing
low solubility of 7 precludes the synthesis of longer
systems.
(c) P en ta m eth ylfer r ocen es (Sch em e 3). By es-
sentially analogous chemistry as described above the
corresponding pentamethylated compounds are acces-
sible: Reduction of pentamethylferrocenyl aldehyde2c
with lithium triethylborohydride affords (hydroxymeth-
yl)pentamethylferrocene (8), which is a progenitor of
(pentamethylferrocenyl)methylphosphonium salt and
the ylide derived thereof, prepared by the method of
Hamanaka and Kosuge.18 Biferrocenes 9a ,b are ob-
tained as an E/Z-mixture, from which the E-isomer (9a )
can be separated by selective crystallization.
The X-ray structure of compound 9a is interesting
from a crystallographer’s point of view: Only merohe-
drically twinned crystals were available, but the struc-
ture could be solved without problems with good final
R values (Table 1); there are two independent half-
molecules (with an inversion center located in the center
of the olefinic bond) in the asymmetric unit. One of the
molecules (Figure 5) is regularly ordered, whereas the
second molecule (Figure 6) is disordered in a 50:50%
ratio with regard to the orientations of the trans-olefinic
moiety. Interestingly, the very same type of disordering
has been published recently for the homologous (E)-1,2-
bis(pentamethylruthenocenyl)ethylene.22 The confor-
mation of 9a in the solid state [angle C(11a)-C(11)-
C(10)-C(9) ) -7.51°] can be compared to the analogous
5a , which shows increased torsion due to steric hin-
drance by the methyl groups of the substituted cyclo-
pentadienyl rings (see above).
F igu r e 2. Molecular structure of 5a , showing the atom-
numbering scheme. Hydrogen atoms are omitted for clarity.
Numbering of the ferrocenyl carbons is analogous to 4.
Distances: Fe(1) to Cp plane [C(6)-C(10)] ) 1.656(1) Å;
Fe(1) to Cp plane [C(1)-C(5)] ) 1.662(1) Å. Angles: Cp
plane [C(6)-C(10)] to Cp plane [C(1)-C(5)] ) 0.51(0.17)°;
C(6)-C(10)-C(11)-C(11a) ) -24.90(0.48)°.
Reaction of 2 equiv of pentamethylferrocenyl aldehyde
with the bis(ylide) derived from p-xylylenebis(triphen-
ylphosphonium bromide) yields the (vinylene)2(phenyl-
ene)1 “spacered” biferrocene 10, which is the system
analogous to compound 6. The gross features of the
crystal structures of 10 (Figure 7, Table 1) and 6 (see
above) are quite similar, but in the case of 10 smaller
torsion angles corresponding to less twisting of the
vinylene phenylene cyclopentadienyl subunits [angle
C(11)-C(12)-C(13)-C(14) ) -1.79°; angle C(12)-
C(11)-C(10)-C(9) ) -11.37°] are observed, due to less
interaction in the solid state by neighboring molecules.
In accord with these smaller distortions, the metal-to-
metal distance of 10 is slightly shortened to 13.291(2)
Å in comparison to 13.332(3) Å in 6.
Further elongation by similar methods as described
for the octa- and nonamethylated compounds gives
access to the (vinylene)2(phenylene)2-spacered aldehydes
11a ,b, which are a chiral molecules due to successive
twisting of the cyclopentadienyl, vinylene, and phen-
ylene subunits with respect to each other. In the
crystalline state (Figure 8, Table 1) a racemic mixture
of both enantiomers make up the contents of the unit
cell, analogous to the structure of the one vinylene-
phenylene unit shorter nonamethylated aldehyde 4. The
helical twisting in 11a is reflected in torsion angles of
-5.75, -2.67, 13.53, and 12.07°, respectively, similar
in value to that for compound 4 and to that for a recently
published all-E oligo(phenylene-vinylene).11d
F igu r e 3. Molecular structure of 6, showing the atom-
numbering scheme. Hydrogen atoms are omitted for clarity.
Numbering of the ferrocenyl carbons is analogous to 4.
Distances: Fe(1)-Fe(1a) ) 13.332(3) Å; Fe(1) to Cp plane
[C(6)-C(10)] ) 1.653(1) Å; Fe(1) to Cp plane [C(1)-C(5)]
) 1.659(1) Å. Angles: Cp plane [C(6)-C(10)] to Cp plane
[C(1)-C(5)] ) 1.94(23)°; C(12)-C(11)-C(10)-C(6) ) 20.68-
(49)°; C(11)-C(12)-C(13)-C(14) ) 12.6(47)°; Cp plane
[C(6)-C(10)] to phenyl plane [C(13)-C(13a)] ) 32.18(35)°.
The metal-to-metal distance (through space) equals
13.332(3) Å, and the sum of bond lengths (corresponding
to the conjugation pathway from Fe(1) to Fe(1a)) is
16.845 Å. As can be seen from a packing plot (Figure
4), the relatively large angle (32.18°) of the plane of the
phenylene ring [C(13)-C(15) and C(13a)-C(15a)] to the
plane of the cyclopentadienyl ring [C(6)-C(10)] might
be due to steric repulsion by neighboring molecules.
Further elongation of 3 (see Scheme 2) with the bis-
(ylide) prepared from p-xylylene-bis(triphenylphospho-
nium bromide) gives access to the (vinylene)4-(phen-
ylene)3-bridged biferrocene 7 which precipitates during
its formation from the reaction mixture and is insoluble
in all common solvents (with the exception of hot
toluene). Due to this poor solubility, characterization
of 7 is limited to IR and FAB-mass spectroscopy and no
NMR-spectroscopic determination of the E/Z stereo-
chemistry is possible, but the low solubility indicates
the existence of 7 as a rigid rod with an all-E configu-
ration. Thus within this series of octa- or nonameth-
ylated biferrocenes, despite the anticipated solubilizing
Coupling of the mono(ylide) derived from p-xylylene-
bis(diethylphosphonate) with pentamethylferrocenyl al-
(22) Sato, M.; Kudo, A.; Kawata, Y.; Saitoh, H. Chem. Commun.
1996, 25.

396 Organometallics, Vol. 16, No. 3, 1997
Hradsky et al.
F igu r e 4. Packing of molecules of 6.
point of 275-80 and 180-185 °C, respectively. Also,
in the UV-vis spectra different λmax absorptions (354
and 388 nm) are observed, indicating different stereo-
chemistry of the newly formed double bonds. The
Wittig-Horner methodology is known to favor E-con-
figurated products,8 suggesting an all-E configuration
to the latter product. Similarly to 12, NMR analysis
did not give any conclusive result due to unresolved
couplings and X-ray crystallography was not possible
until now because the obtained crystals were to small
for a single-crystal analysis. Nevertheless, compound
13 is still soluble with good solubility in dichlo-
romethane and THF and constitutes to our knowledge
the longest soluble π-conjugated biferrocene prepared
so far. Under the same assumptions as stated for 12
(see above), the metal-to-metal distance in 13 can be
estimated to approximately 40 Å with a conjugation
pathway of 51 Å (Figure 9).
Con clu sion s a n d P er sp ectives. Nona-, octa-, and
pentamethylated ferrocenyl aldehydes or methylphos-
phonium salts are the key synthons for the preparation
of soluble, conjugated biferrocenes by standard Wittig
and/or Wittig-Horner olefinations with vinylene-phen-
ylene oligomers as bridging ligands between the two
redox-active metallocenyl termini. The methyl substit-
uents of the metallocenyl groups are necesssary to
ensure increased solubility and enhanced stability of the
oxidized species in comparison to nonmethylated spac-
ered biferrocenes. Interestingly, the pentamethylated
systems show superior solubility in direct comparison
to their higher methylated analogues. These com-
pounds serve as model systems for molecular wires,
allowing the examination of the intervalence transfer
(up to 40 Å) between the terminal electrophores of the
mixed-valence biferrocenes. Such investigations are in
progress and will be published elsewhere.
F igu r e 5. Molecular structure of 9a (nondisordered
molecule A), showing the atom-numbering scheme (hydro-
gen atoms omitted for clarity). Distances: Fe(1) to Cp plane
[C(6)-C(10)] ) 1.660(4) Å; Fe(1) to Cp* plane [C(1)-C(5)]
) 1.644(4) Å. Angles: Cp plane [C(6)-C(10)] to Cp* plane
[C(1)-C(5)] ) 0.00(65)°; C(11a)-C(11)-C(10)-C(9) ) -7.51-
(206)°.
dehyde in situ and subsequent coupling with 11a yields
(vinylene)4(phenylene)3-spacered biferrocene 12, which
shows good solubility in contrast to the essentially
insoluble nonamethylated analogue 7. The exact ster-
eochemistry with regard to E or Z configurations of the
newly formed double bonds cannot be determined due
to the observation of only broad signals with unresolved
coupling in the 1H NMR spectrum. Although X-ray-
quality crystals have not yet been obtained, 12 repre-
sents a soluble biferrocene with a conjugation pathway
of 33.6 Å and an estimated metal-to-metal distance of
26.5 Å, assuming (i) an all E-configuration with respect
to the double bonds, (ii) a trans conformation with
respect to the terminal metallocenyl units, and (iii) twist
angles of similar values as in the structurally character-
ized shorter compounds described above.
Exp er im en ta l Section
Gen er a l Com m en ts. Standard techniques and instru-
mentation for spectroscopic and physical measurements have
been described previously.23 Tetramethylcyclopentadiene as
a starting compound for the synthesis of octamethylferrocene
and octamethylferrocene aldehyde was obtained from Raylo
Chemicals, Edmonton, Alberta, Canada.
Reaction of 2 equiv of spacered aldehyde 11a with the
bis(ylide) of p-xylylenebis(triphenylphosphonium bro-
mide) [Wittig reaction] or p-xylylenebis(diethylphospho-
nate) [Wittig-Horner reaction] affords R,ω-bis(penta-
methylferrocenyl)(vinylene)6(phenylene)5 (13) in 59% or
42% yield, respectively, as a red powder with a melting
(23) Lukasser, J .; Angleitner, H.; Schottenberger, H.; Kopacka, H.;
Schweiger, M.; Bildstein, B.; Ongania, K.-H.; Wurst, K. Organometal-
lics 1995, 14, 5566.

Soluble “Molecular Wires”
Organometallics, Vol. 16, No. 3, 1997 397
Sch em e 3. Syn th esis of Com p ou n d s 8-13
a
Legend: (i) LiB(C2H5)3H; (ii) P(C6H5)3‚HBr/-H2O; (iii) (H5C6)3PdCHC6H4CHdP(C6H5)3; (iv) (H5C6)3PdCHC6H4CHdO/t-BuOK/
OdCHC6H4CHdO; (v) (EtO)2P(O)dCHC6H4CH2P(O)(OEt)2/t-BuOK; (vi) (EtO)2P(O)dCHC6H4CHdP(O)(OEt)2.
X-r a y Str u ctu r e Deter m in a tion s of 1b,c, 2-4, 5a , 6, 9a ,
10a , a n d 11a . A Siemens P4 diffractometer with graphite-
monochromatized Mo KR radiation (λ ) 71.073 pm) was used
for data collection. Crystal data, data collection, and refine-
ment parameters of 4, 5a , 6, 9a , 10, and 11a are summarized
in Table 1 (for 1b,c, 2, and 3, see Supporting Information).
The unit cells were determined by the automatic indexing of
25 centered reflections and confirmed by examination of the
axial photographs. Data were measured via ω-scan and
corrected for Lorentz and polarization effects. Scattering
factors for neutral atoms and anomalous dispersion corrections
were taken from the ref 24, and an empirical absorption
correction25 was made. The structures were solved by direct
methods, SHELXS-86,26 and refined by a full-matrix least-
squares procedure using SHELXL-93.27 All non-hydrogen
atoms were refined with anisotropic displacement parameters.
Hydrogen atoms were placed in calculated positions. For
tables of complete crystallographic data, bond lengths, bond
angles, anisotropic thermal parameters, calculated hydrogen
atomic coordinates, and final atomic coordinates, see the
Supporting Information.
(1′,2,2′,3,3′,4,4′,5-Octam eth ylfer r ocen yl)m eth yl)tr iph en -
ylp h osp h on iu m Br om id e (1a ) (P r otocol Accor d in g to
Ref 18). A mixture of 1-(hydroxymethyl)-1′,2,2′,3,3′,4,4′,5-
octamethylferrocene2i (1.300 g, 3.96 mmol) [CAS Reg. No.
128925-13-3], triphenylphosphine hydrobromide (1.360 g, 3.96
mmol, 1 mequiv), and 120 mL of toluene was refluxed for 30
min until separation from the eutectic condensate was com-
(24) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, 1974; Vol. IV, pp 72-98.
(25) (a) North, A. C. T.; Phillips, D.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351. (b) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39,
158.
(26) Sheldrick, G. M. SHELXS-86: Program for Crystal Structure
Solutions; University of Go¨ttingen: Go¨ttingen, Germany, 1986.
(27) Sheldrick, G. M. SHELXL-93: Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Go¨ttingen, Germany,
1993.

398 Organometallics, Vol. 16, No. 3, 1997
Hradsky et al.
F igu r e 9. Estimated distances for 13.
Cl2. The CH2Cl2 layers were combined, and the solvent was
evaporated. Yield: 2.264 g (88%) of yellow air-stable micro-
crystalline solid.
Da ta for 1a . Mp: 212-214 °C. Anal. Calcd for C37H42
-
BrFeP: C, 68.01; H, 6.48. Found: C, 67.81; H, 6.45. MS
(FAB): m/z 573.4 (M+ of cation, 100%). UV-vis (CH2Cl2 [λmax
(nm)/log ꢀ]): 266/4.03; 273/3.98; 397.0/2.87. IR data (KBr):
3054 w, 2961 m, 2940 m, 2900 m, 2853 m, 1586 m, 1481 m,
1437 s, 1381 m, 1107 s, 1032 m, 997 m, 864 m, 754 vs, 740 vs,
719 m, 713 m, 692 vs, 511 s, 499 s, 472 m, 449 m cm-1
.
1H
NMR (CD3CN): δ 0.61, 1.29 , 2.25 (26H, 3s, CH3 and CH2);
3.71 (1H, bs, C-H of Cp); 7.64, 7.68, 7.84, 7.88 (15H, m, C6H5).
13C NMR (CD3CN): δ 8.70, 9.48, 10.65 (CH3 and CH2); 130.37,
135.15, 135.57 (C6H5).
F igu r e 6. Molecular structure of 9a (disordered molecule
B), showing the two orientations (1:1) of the E-olefinic
moiety C(30)-C(31a)-C(31c)-C(30a) and C(30)-C(31b)-
C(31d)-C(30a), respectively.
((1′,2,2′,3,3′,4,4′,5-Octam eth ylfer r ocen yl)m eth yl)tr iph en -
ylp h osp h on iu m Tetr a flu or obor a te (1b). To a solution of
tetrafluoroboric acid (54% in ether) (0.050 g, 0.027 g, 0.30
mmol) in 40 mL of toluene was added a solution of triphen-
ylphosphine (0.080 g, 0.30 mmol) in 40 mL of toluene and a
solution of 1-(hydroxymethyl)-1′,2,2′,3,3′,4,4′,5-octamethylfer-
rocene28 (0.100 g, 0.30 mmol) [128925-13-3] in 30 mL of
toluene. The mixture was refluxed for 10 min, until the
separation from a eutectic condensate was complete in a
Dean-Stark trap. TLC (silica/ether) showed no remaining
starting material. By cooling, a yellow solid precipitated,
which was filtered off and dried. Yield: 0.184 g (91.5%) of
yellow air-stable microcrystalline solid.
Da ta for 1b. Mp: 248-249 °C. Anal. Calcd for C37H42
-
F igu r e 7. Molecular structure of 10, showing the atom-
numbering scheme (hydrogen atoms are omitted for clar-
ity). Distances: Fe(1)-Fe(1a) ) 13.291(2) Å; Fe(1) to Cp
plane [C(6)-C(10)] ) 1.660(2) Å; Fe(1) to Cp* plane [C(1)-
C(5)] ) 1.645(2) Å. Angles: Cp plane [C(6)-C(10)] to Cp*
plane [C(1)-C(5)] ) 2.71(0.33)°; C(12)-C(11)-C(10)-C(9)
) -11.37(0.66)°; C(11)-C(12)-C(13)-C(14) ) -1.79(0.66)°;
Cp plane [C(6)-C(10)] to phenyl plane [C(13)-C(13a)] )
13.73°.
BF4FeP: C, 67.30; H, 6.41. Found: C, 67.23; H, 6.39. MS
(FAB): m/z 573.2 (M+ of cation, 100%). HR-MS (FAB): m/z
573.23266 (M+ of cation; exact mass calcd for C37H42FeP,
573.2327). IR data (KBr): 3064 w, 2965 m, 2944 m, 2902 m,
1588 m, 1485 s, 1441 vs, 1381 s, 1111 vs (b), 997 s, 752 s, 739
s, 719 s, 692 vs, 519 s, 509 s, 497 s, 470 m, 451 m cm-1. Single
crystals were obtained from dichloromethane/acetone (v:v )
1:1) (Supporting Information, Figure 10).
((1′,2,2′,3,3′,4,4′,5-Oct a m et h ylfer r ocen iu m yl)m et h yl)-
tr ip h en ylp h osp h on iu m Bis(tetr a flu or obor a te) (1c). A 5
mg (0.0075 mmol) amount of 1b was dissolved in 5 mL of a
mixture (v:v ) 1:1) of dichloromethane and acetone; under
stirring, 3 drops of a 54% solution of tetrafluoroboric acid in
ether and 5 drops of a 30% solution of H2O2 in water were
added, and the mixture changed color to green. Upon standing
the product crystallized and was isolated by filtration (2 mg,
35.4% yield) as dark green air-stable crystals.
Da ta for 1c. Mp: 285-290 °C. Anal. Calcd for C37H42
-
B2F8FeP: C, 59.48; H, 5.67. Found: due to only 2 mg of
material available, no analysis was possible. MS (FAB): not
observed, 286.6 (M+/2 of bis(cation)). UV-vis (CH2Cl2 [λmax
(nm)/log ꢀ]): 276.0/4.24; 317.0/4.05. IR data (KBr): 3424 m
(b), 2963 w, 2923 w, 2853 w, 1655 w, 1638 w, 1470 w, 1459 w,
1437 m, 1391 m, 1109 s, 1090 s, 1038 s, 758 m, 744 m, 721 m,
694 m, 515 w, 493 w cm-1. Single crystals were obtained from
dichloromethane/acetone (v:v ) 1:1) (Supporting Information,
Figure 11).
((Non a m et h ylfer r ocen yl)m et h yl)t r ip h en ylp h osp h o-
n iu m Br om id e (2) (P r oced u r e Accor d in g to th e Meth od
of R efs 18 a n d 28). To a cold solution (-50 °C) of
formylnonamethylferrocene2h,i (0.634 g, 1.86 mmol) [90310-18-
2] in 25 mL of anhydrous THF was added by syringe 2.05 mL
of a 1 M solution of lithium triethylborohydride in THF (0.217
g, 2.05 mmol). The color of the solution immediately changed
F igu r e 8. Molecular structure of 11a , showing the atom-
numbering scheme (hydrogen atoms are omitted for clar-
ity). Distances: Fe(1) to Cp plane [C(6)-C(10)] ) 1.649(5)
Å; Fe(1) to Cp* plane [C(1)-C(5)] ) 1.655(5) Å. Angles: Cp
plane [C(6)-C(10)] to Cp* plane [C(1)-C(5)] ) 1.70(0.96)°;
Cp plane [C(6)-C(10)] to phenyl plane [C(13)-C(16)] )
7.28(0.78)°; phenyl plane [C(13)-C(16)] to phenyl plane
[C(21)-C(26)] ) 26.92(0.50)°; C(12)-C(11)-C(10)-C(6) )
-5.75(1.9)°; C(11)-C(12)-C(13)-C(18) ) -2.67(1.99)°;
C(17)-C(16)-C(19)-C(20) ) 13.53(2.11)°; C(19)-C(20)-
C(21)-C(22) ) 12.07(1.62)°.
plete in a Dean-Stark trap. By cooling, a yellow solid
precipitated, which was filtered off and washed with 20 mL
of ether and dried. The organic yellow filtrate, which contains
some additional product, was reduced in volume (to about 20
mL) and extracted with 70 mL of water. The aqueous layer
was washed with 30 mL of ether and re-extracted with CH2-
(28) Elsner, O. Diploma Thesis, Innsbruck, 1995; p 114.

Soluble “Molecular Wires”
Organometallics, Vol. 16, No. 3, 1997 399
from deep red to dark yellow. The mixture was allowed to
warm to ambient temperature and was stirred further for 90
min at room temperature. TLC (silica/n-hexane/ether ) 1:1)
showed no remaining starting material. After the THF was
removed in vacuo the residue was extracted with 30 mL of
water and 50 mL of ether, the combined etheral layers were
washed with 80 mL of water, the ether was evaporated, the
remaining crude solid product was dissolved in 100 mL of
toluene, and triphenylphosphine hydrobromide (0.639 g, 1.86
mmol, 1 mequiv) was added in one portion. The mixture was
refluxed for 15 min until the separation from eutectic conden-
sate was complete in a Dean-Stark trap. By cooling, a yellow
solid precipitated, which was filtered off, washed with 20 mL
ether, and dried, affording 0.829 g (66.7%) of 2 as a yellow
air-stable microcrystalline solid.
NMR (CDCl3): δ 1.67 (15H, s, 5 × CH3 of unsubst. Cp); 1.78
(6H, s, 2 × CH3 of subst. Cp); 1.95 (6H, s, 2 × CH3 of subst.
3
Cp); 6.70 (1H, d, J trans(1H-1H) ) 16 Hz, CHdCH); 7.03 (1H,
3
d, J trans(1H-1H) ) 16 Hz, CHdCH); 7.56, 7.82 (4H, m, C6H4);
9.96 (1H, s, CHdO). 13C NMR (CDCl3): δ 9.30, 10.60 (9 ×
CH3); 79.46, 79.73, 82.37 (Cp); 124.29, 125.34, 130.39, 132.15,
134.05, 145.09 (C6H4 and CHdCH); 191.46 (CHdO). Single
crystals were obtained from CH2Cl2 (Table 1, Figure 1,
Supporting Information).
1,2-Bis(1′,2,2′,3,3′,4,4′,5-oct a m et h ylfer r ocen yl)et h en e
(5a ,b). Meth od A (Wittig Rea ction ). A suspension of
((1′,2,2′,3,3′,4,4′,5-octamethylferrocenyl)methyl)triphenylphos-
phonium bromide (1a ) (0.350 g, 0.54 mmol) in 15 mL of
anhydrous THF in a Schlenk vessel was cooled to -40 °C and
converted to the corresponding ylide in the usual manner (see
above) with 0.066 g (0.59 mmol, 1.1 mequiv) of potassium tert-
butoxide. The red mixture was stirred for 5 min with the
cooling bath removed, and 0.192 g (0.59 mmol, 1.1 mequiv) of
formyl-1′,2,2′,3,3′,4, 4′,5-octamethylferrocene [CAS No. 128925-
12-2] was added. The mixture was stirred at room tempera-
ture for 30 min and refluxed for a further 150 min. The THF
was removed in vacuo, and the crude product was purified by
column chromatography (silica, CH2Cl2/n-hexane ) 2:1), yield-
ing 0.067 g of 5a ,b (20.2% or 37.5% based on recovered starting
material) as a red air-stable solid, consisting of a 1:3 mixture
of trans (5a ) and cis (5b) according to NMR analysis.
Da ta for 2. Mp: 228-233 °C, dec. Anal. Calcd for C38
-
H
44BrFeP: C, 68.38; H, 6.64. Found: C, 68.15; H, 6.62. MS
(FAB): m/z 588 (M+ of cation, 11%), 325.3 (M+ - P(C6H5)3,
100%). UV-vis (CH2Cl2 [λmax (nm)/log ꢀ]): 266.5/4.07; 273.5/
4.04. IR data (KBr): 3052 w, 2967 m, 2940 m, 2900 m, 2861
m, 1481 m, 1437 vs, 1379 m, 1107 vs, 1032 m, 995 m, 754 s,
735 vs, 719 m, 690 s, 511 m, 501 s, 493 m cm-1. Single crystals
were obtained from CH3CN (Supporting Information, Figure
12).
4-[2-(1′,2,2′,3,3′,4,4′,5-Oct a m et h ylfer r ocen yl)et h en yl]-
ben za ld eh yd e (3). A Schlenk vessel was charged with
((1′,2,2′,3,3′,4,4′,5-octamethylferrocenyl)methyl)triphenylphos-
phonium bromide (1a ) (1.00 g, 1.53 mmol) and 15 mL of
anhydrous THF, the resulting suspension was cooled to -40
°C, potassium tert-butoxide (0.189 g, 1.68 mmol, 1.1 mequiv)
was added in one portion, and the red suspension was stirred
for 10 min in an ice/water bath. Subsequently, terephthal-
aldehyde (0.821 g, 6.12 mmol, 4 mequiv) was added, and the
deep purple solution was allowed to warm to room temperature
during 1 h. At this point TLC (silica/CH2Cl2/n-hexane ) 2:1)
showed no further reaction. The solvent was removed in
vacuo, the residue was washed with 35 mL of saturated
ammonium chloride solution and extracted with 50 mL ether,
the combined organic layers were dried with Na2SO4, solvents
were evaporated, and the crude product was purified by
column chromatography (silica/CH2Cl2/n-hexane ) 2:1), yield-
ing 0.336 g (51.3%) of 3 as a purple air-stable solid.
Meth od B (McMu r r y Rea ction ). A suspension of 5.254
g (14.2 mmol) of TiCl3‚3THF in 40 mL of DME (dimethoxy-
ethane) was reduced with 325 mg (46.9 mmol) of lithium
powder by immersing the reaction vessel in an ultrasonic
cleaning bath at room temperature for 30 min. To the
resulting black suspension of low-valent titanium was added
300 mg (0.920 mmol) of formyl-1′,2,2′,3,3′,4, 4′,5-octamethyl-
ferrocene [CAS No. 128925-12-2], and sonication was continued
for an additional 1/2 h. Workup: DME was removed in vacuo,
the mixture was poured into water, the organic material was
extracted with three portions of ether, and the combined
organic layers were washed with water and dried with Na2-
SO4. After removal of solvents, the crude product mixture was
purified by chromatography as described above, yielding 0.164
g (28.7%) of a mixture of trans (5a ) and cis (5b) according to
NMR analysis. Fractional crystallization from n-hexane af-
forded 69 mg (12.1% yield) of large single crystals of trans-
(5a ).
Da ta for 3. Mp: 93-95 °C. Anal. Calcd for C27H33FeO:
C, 75.52; H, 7.75. Found: C, 75.55; H, 7.75. MS (EI, 70 eV):
m/z 428.5 (M+, 100%). HR-MS (FAB): m/z 429.18804 (M+;
exact mass calcd for C27H33FeO, 429.18808). UV-vis (CH2-
Cl2 [λmax (nm)/log ꢀ]): 360.5/4.36; 530.0/3.64. IR data (KBr):
3040 w, 2961 w, 2900 w, 1697 vs, 1593 m, 1564 m, 1308 m,
1213 m, 1165 s, 1030 m, 962 s, 860 s, 843 m, 821 vs, 798 m,
Da ta for 5a ,b. MS (EI, 70 eV): m/z 620.5 (M+, 100%); 312
(CH3)8FcCH2, 97%). IR data (KBr): 3056 w, 2905 w, 2716 w,
1628 w, 1449 m, 1427 m, 1375 m, 1261 m, 1084 m, 1028 m,
955 m, 858 m, 820 s, 802 s, 694 m, 507 m, 464 s cm-1
.
1H
787 s, 501 s, 468 s, 459 s, 451 s cm-1 1H NMR (CD3CN): δ
.
1.62, 1.66, 1.81, 1.97 (12H, each signal: 3H, s, CH3 of Cp);
NMR (CDCl3): δ 1.43, 1.56, 1.60, 1.63, 1.67, 1.69, 1.72, 1.74,
1.81, 1.86, 1.98 (CH3); 3.30 (s, CH of Cp); 6.68, 6.85, 7.33, 7.42
(CHdCH). 13C NMR (CDCl3): δ 9.06, 9.28, 9.66, 9.75, 9.83,
10.93, 11.02, 11.08, 11.15 (8 × CH3); 71.28, 79.20, 79.48, 80.60,
80.75, 81.74 (Cp); 125.63, 126.38, 126.47, 128.47, 128.62,
133.48, 133.87 (CH of the E and Z double bonds).
2.21 (12H, s, 4 × CH3 of Cp); 3.31 (1H, s, CH of Cp); 6.77 (1H,
3
3
d, J trans(1H-1H) ) 16 Hz, CHdCH); 7.14 (1H, d, J trans(1H-
1H) ) 16 Hz, CHdCH); 7.66, 7.82 (4H, m, C6H4); 9.92 (1H, s,
CHdO). 13C NMR (CD3CN): δ 9.52, 10.09, 11.39 (8 × CH3);
72.39 (CH of Cp); 77.72, 80.75, 81.66, 83.57 (Cp); 125.1, 126.5,
131.1, 133.3 (C6H4 and CHdCH); 192.8 (CHdO). Single
crystals were obtained from CH2Cl2 (Supporting Information,
Figure 13).
Da ta for 5a . Mp: 219-220 °C. Anal. Calcd for C38H52
-
Fe2: C, 73.55; H, 8.45. Found: C, 73.54; H, 8.43. MS (EI, 70
eV): m/z 620.5 (M+, 100%). UV-vis (CH2Cl2 [λmax (nm)/log
ꢀ]): 318.0/4.23; 461.5/3.26. IR data (KBr): 3060 w, 2965 s,
2944 m, 2859 s, 2714 m, 1630 w, 1476 w, 1458 m, 1439 m,
1374 s, 1261 w, 1111 m, 1080 w, 1028 s, 966 m, 818 m, 515 w,
4-[2-(Non am eth ylfer r ocen yl)eth en yl]ben zaldeh yde (4).
In analogy to the synthesis of 3, compound 4 was prepared by
starting from ((nonamethylferrocenyl)methyl)triphenylphos-
phonium bromide (2) (0.300 g, 0.45 mmol), resulting in 0.118
g (59.3% yield) of 4-[2-(nonamethylferrocenyl)ethenyl]benzal-
dehyde (4) as air-stable purple flakes.
482 w, 449 s cm-1 1H NMR (CD2Cl2): δ 1.60, 1.63, 1.69, 1.79
.
(CH3); 3.30 (s, CH of Cp); 6.24 (2H, s(br), CHdCH). 13C NMR
(CD2Cl2): δ 9.36, 9.91, 11.25 (CH3); 71.76, 78.48, 80.85, 81.02,
81.51, 81.72 (Cp); 125.42 (CHdCH). Single crystals were
obtained from n-hexane (Table 1, Figure 2; Supporting Infor-
mation).
Da ta for 4. Mp: 174-175 °C. Anal. Calcd for C28H35
-
FeO: C, 75.84; H, 7.96. Found: C, 75.87; H, 7.98. MS (EI,
70 eV): m/z 442 (M+, 100%). HR-MS (FAB): m/z 443.203749
(M+; exact mass calcd for C28H35FeO, 443.203727). UV-vis
(CH2Cl2 [λmax (nm)/log ꢀ]): 365.5/4.35; 539.0/3.64. IR data
(KBr): 2965 w, 2948 w, 2903 w, 2857 w, 1694 m, 1626 w, 1598
1,4-Bis[2-(1′,2,2′,3,3′,4,4′,5-octa m eth ylfer r ocen yl)eth en -
yl]ben zen e (6). Similarly to the synthesis of compounds 5a ,b,
((1′,2,2′,3,3′,4,4′,5-octamethylferrocenyl)methyl)triphenylphos-
phonium bromide (1a ) (0.250 g, 0.383 mmol) was converted
1
vs, 1562 w, 1377 w, 1215 w, 1165 m, 1028 w, 820 w cm-1. H

400 Organometallics, Vol. 16, No. 3, 1997
Hradsky et al.
Ta ble 1. Cr ysta l a n d Str u ctu r e Refin em en t for Da ta for 4, 5a , 6, 9a , 10, a n d 11a
5a
4
6
mol formula
fw
cryst system
space group
a (pm)
C28H34FeO
442.40
C40H50Fe2
642.50
C46H58Fe2
722.62
monoclinic
P21/c (No. 14)
995.4(2)
1176.2(2)
1659.7(4)
90
102.90(2)
90
1.8941(7)
2
monoclinic
P21/c (No. 14)
1425.0(5)
1114.9(5)
1497.4(12)
90
104.58(4)
90
2.302(2)
4
monoclinic
P21/c (No. 14)
956.5(3)
1241.5(3)
1414.3(3)
90
106.11(2)
90
1.6135(7)
2
b (pm)
c (pm)
R (deg)
â (deg)
γ (deg)
V (nm3)
Z
temp (K)
213(2)
1.276
0.672
944
213(2)
1.322
0.926
684
223(2)
1.267
0.797
772
d(calcd) (Mg/m3)
abs coeff (mm-1
F(000)
)
color, habit
red platelet
red column
red prism
cryst size (mm)
θ range for data collcn (deg)
index ranges
0.38 × 0.32 × 0.19
3.35-20.50
0 e h e 14
-1 e k e 11
-14 e l e 15
2286
0.85 × 0.3 × 0.2
3.20-24.99
0 e h e 11
-1 e k e 14
-16 e l e 16
3295
0.6 × 0.3 × 0.11
3.06-24.00
-1 e h e 10
-1 e k e 12
-18 e l e 18
3803
no. of rflns collcd
no. of indep rflns
no. of rflns with I > 2σ(I)
abs cor
max and min transm
refinement method
data/restraints/parms
goodness-of-fit on F2
final R indices [I > 2σ(I)
2015 (Rint ) 0.0426)
2824 (Rint ) 0.0217)
2880 (Rint ) 0.0251)
1587
2412
2315
none
ψ-scan
0.643 and 0.589
ψ-scan
0.925 and 0.808
full-matrix least-squares on F2 full-matrix least-squares on F2 full-matrix least-squares on F2
1962/0/270
1.115
R1 ) 0.1106
wR2 ) 0.2940
R1 ) 0.1445
wR2 ) 0.4003
1590 and -657
2818/0/189
1.042
2880/0/333
1.038
R1 ) 0.0334
wR2 ) 0.0782
R1 ) 0.0444
wR2 ) 0.0883
294 and -403
R1 ) 0.0354
wR2 ) 0.0815
R1 ) 0.0519
wR2 ) 0.0897
244 and -234
R indices (all data)
largest diff peak and hole (e‚nm-3
)
9a
10
11a
mol formula
fw
C32H40Fe2
536.34
C40H46Fe2
638.47
C32H32FeO
488.43
cryst system
space group
a (pm)
b (pm)
c (pm)
monoclinic
P21/n (No. 14)
1759.0(6)
1085.6(3)
1673.0(3)
90
118.32(2)
90
2.8123(13)
4
triclinic
P1h (No. 2)
831.6(2)
937.7(2)
1239.9(2)
98.86(1)
108.86(1)
107.41(1)
0.8387(3)
1
monoclinic
P21 (No. 4)
838.9(4)
883.3(6)
1795.9(9)
90
101.24(3)
90
1.3052(13)
2
R (deg)
â (deg)
γ (deg)
V (nm3)
Z
temp (K)
208(2)
1.267
1.049
1136
213(2)
1.264
0.891
338
213(2)
1.243
0.599
516
d(calcd) (Mg/m3)
abs coeff (mm-1
F(000)
)
color, habit
cryst size (nm)
θ range for data collcn (deg)
index ranges
red platelet
0.55 × 0.55 × 0.12
3.07-21.00
-17 e h e 6
-10 e k e 1
-12 e k e 14
3113
red platelet
red platelet
0.3 × 0.3 × 0.05
2.31-18.50
-1 e h e 7
-16 e l e 15
-16 e l e 15
2100
0.5 × 0.25 × 0.09
3.19-23.00
-1 e h e 8
-9 e k e 9
-13 e l e 13
2843
no. of rflns collcd
no. of indep rflns
no. of rflns with I > 2σ(I)
abs cor
max and min transm
refinement method
data/restraints/parms
goodness-of-fit on F2
final R indices [I > 2σ(I)]
2635 (Rint ) 0.0194)
2284 (Rint ) 0.0243)
1767 (Rint ) 0.0287)
2198
1838
1430
none
ψ-scan
0.861 and 0.750
ψ-scan
0.926 and 0.862
full-matrix least-squares on F2 full-matrix least-squares on F2 full-matrix least-squares on F2
2635/0/321
1.069
R1 ) 0.0511
wR2 ) 0.1131
R1 ) 0.0679
wR2 ) 0.1222
373 and -428
2284/0/195
1.044
1767/1/312
1.090
R1 ) 0.0434
wR2 ) 0.968
R1 ) 0.0613
wR2 ) 0.1061
352 and -261
R1 ) 0.0466
wR2 ) 0.0933
R1 ) 0.0702
wR2 ) 0.1035
246 and -203
R indices (all data)
largest diff peak and hole (e‚nm-3
)
with 0.047 g (0.420 mmol, 1.1 mequiv) of potassium tert-
butoxide to the corresponding ylide and olefinated with 0.026
g (0.191 mmol, 0.5 mequiv) of terephthalaldehyde. After the
usual workup (see above) and chromatography (silica, CH2-
Cl2/n-hexane ) 2:1) 0.075 g (54.4%) of 6 was obtained as an
air-stable, orange-red microcrystalline solid.
Da ta for (6). Mp: 158-161 °C. Anal. Calcd for C46H58
-
Fe2: C, 76.45; H, 8.09. Found: C, 76.53; H, 8.06. MS (EI, 70

Soluble “Molecular Wires”
Organometallics, Vol. 16, No. 3, 1997 401
eV): m/z 722.5 (M+, 100%). HR-MS (FAB): m/z 722.32348
(M+; exact mass calcd for C46H58Fe2, 722.32372). UV-vis (CH2-
Cl2 [λmax (nm)/log ꢀ]): 362/4.29; 490/3.60. IR data (KBr): 3056
w, 2963 w, 2902 w, 1626 w, 1468 w, 1447 w, 1427 w, 1373 m,
1261 m, 1095 m, 1028 s, 955 m, 858 m, 820 vs, 800 vs, 505 m,
Mp: 85-90 °C. MS (FAB): m/z 531.29 (M+ of cation, 100%).
IR (KBr): 3058 m, 2964 m, 2906 m, 1629 w, 1588 w, 1482 m,
1385 m, 1111 s, 1061 s, 1040 s, 998 s, 920 m, 745 s cm-1. No
NMR spectra could be obtained, probably due to paramagnetic
impurities, but the phosphonium salt is sufficiently pure for
the following step:
460 vs, 445 s cm-1
.
1H NMR (CDCl3): δ 1.52, 1.65, 1.70, 1.80,
1.96 (48H, 5 × s, 16 × CH3); 3.29 (2H, s, CH of Cp); 6.65 (2H,
((Pentamethylferrocenyl)methyl)phosphonium tetrafluoro-
borate (108 mg, 0.17 mmol) was converted to the correspondig
ylide with 19 mg (0.17 mmol) of potassium tert-butoxide in
THF. Addition of 48 mg (0.17 mmol) of 1,2,3,4,5-pentamethyl-
1′-formylferrocene and aqueous workup and chromatography
(silica, n-hexane) yielded a red oil, consisting of trans-1,2-bis-
(1,2,3,4,5-pentamethylferrocen-1′-yl)ethylene (9a ) and cis-1,2-
bis-(1,2,3,4,5-pentamethylferrocen-1′-yl)ethylene (9b), respec-
tively. From this mixture, crystallization afforded red crystals
(35 mg, 0.065 mmol, 38.4% yield) of the trans-isomer (9a ): Mp
210 °C.
d, J trans(1H-1H) ) 16 Hz, CHdCH); 6.85 (2H, d, J trans(1H-
1H) ) 16 Hz, CHdCH); 7.40 (4H, s, C6H4). 13C NMR (CDCl3):
δ 8.44, 8.83, 9.31, 9.44, 9.88, 10.65, 11.13, 11.18 (16 × CH3);
71.47, 79.37, 80.82, 80.96, 81.94 (Cp); 125.68, 126.47, 126.51
(C6H4 and CHdCH). Single crystals were obtained from
acetone (Table 1, Figures 3 and 4; Supporting Information).
1,4-Bis{2-[4-(2-(1′,2,2′,3,3′,4,4′,5-octa m eth ylfer r ocen yl)-
eth en yl)p h en yl]eth en yl}ben zen e (7). p-Xylylenebis(tri-
phenylphosphonium bromide) (0.167 g, 0.21 mmol) [CAS Reg.
No. 40817-03-6] was converted to the corresponding bis(ylide)
with potassium tert-butoxide (0.050 g, 0.45 mmol, 2.1 mequiv)
in THF and was allowed to react with 2 equiv of 4-[2-(1′,2,2′,-
3,3′,4,4′,5-octamethylferrocenyl)ethenyl]benzaldehyde (3) (0.200
g, 0.47 mmol, 2.2 mequiv) for 2 h at room temperature and
for additional 15 min at reflux temperature. During the course
of the reaction the product precipitated as a red solid. After
cooling to ambient temperature 30 mL of ether was added and
the precipitate was filtered off, washed with one portion of
ether, water, and acetone, and dried in vacuo, yielding 0.040
g (20.4%) of 7 as an air-stable red solid.
3
3
Da ta for th e Mixtu r e of 9a a n d 9b. Anal. Calcd for C32
-
H
40Fe2: C, 71.66; H, 7.52. Found: C, 71.59; H, 7.54. MS (EI,
70 eV): m/z 536.5 (M+, 59%); 404.5 (M+ - Cp*, 44%). HR-MS
(FAB): m/z 536.18280 (M+; exact mass calcd for C32H40Fe2,
536.18288). UV-vis (THF [λmax (nm)/log ꢀ]): 453.0/2.99; 460.0/
2.99. IR data (KBr): 3081 m, 2964 s, 2946 s, 2904 s, 2858 s,
1623 w, 1476 s, 1453 s, 1428 m, 1380 s, 1262 m, 1071 s, 1032
s, 951 m, 851 m cm-1 1H NMR (CD2Cl2): δ 1.82-1.87 (30H,
.
3s, CH3); 3.46-3.80 (8H, 6m, subst. Cp); 6.02, 6.12 (2H, 2s,
CHdCH). 13C NMR (CDCl3): δ 11.0-11.1 (CH3); 69.1-80.1
(Cp and Cp*); 123.3, 124.3 (CHdCH). Single crystals of 9a
were obtained from n-hexane (Table 1, Figures 5 and 6;
Supporting Information).
Da ta for 7. Mp: 200-205 °C, dec. Anal. Calcd for C62H70
-
Fe2: C, 80.34; H, 7.61. Found: C, 80.40; H, 7.58. MS (FAB):
m/z 926.5 (M+, 3%); 307 (CH3)8Fc, 100%). UV-vis (CH2Cl2
[λmax (nm)/log ꢀ]): 400.5/4.87; 503.0/4.12. IR data (KBr): 3023
m, 2965 m, 2944 m, 2902 m, 2859 m, 1626 s, 1595 s, 1516 s,
1425 m, 1377 m, 1109 m, 1080 m, 1030 s, 960 vs, 854 m, 825
s, 547 s, 466 s cm-1. Due to insolubility in all common solvents,
no NMR analysis was possible.
1,2,3,4,5-P en tam eth yl-1′-(h ydr oxym eth yl)fer r ocen e (8).
A solution of 820 mg (2.9 mmol) of 1,2,3,4,5-pentamethyl-1′-
formylferrocene in 30 mL of THF was cooled to 0 °C, and 4.4
mL of a 1.0 M THF solution of lithium triethylborohydride (4.4
mmol) was added. After the solution was stirred for 5 min
the cooling bath was removed, and stirring was continued for
a further 60 min. Aqueous workup and chromatography
(aluminum oxide, n-hexane/ether (v/v ) 1/1) as eluent) afforded
700 mg (2.5 mmol, 86.2% yield) of 1,2,3,4,5-pentamethyl-1′-
(hydroxymethyl)ferrocene (8) as yellow crystals.
1,4-Bis(1,2,3,4,5-p en t a m et h ylfer r ocen -1′-yl-et h en yl)-
ben zen e (“(r,ω-Bis(p en ta m eth ylfer r ocen yl)[(vin ylen e)2-
(p h en ylen e)]”) (10). A 126 mg (0.33 mmol) amount of
p-xylylenebis(diethylphosphonate) [CAS Reg. No. 4546-04-7],15
dissolved in 30 mL THF, was converted to the corresponding
bis(ylide) by addition of 79 mg (0.7 mmol) of potassium tert-
butoxide at a temperature of -80 °C and subsequent warming
to room temperature under efficient stirring. The resulting
orange solution was cooled to -80 °C, and 200 mg (0.7 mmol)
of 1,2,3,4,5-pentamethy-1′-formylferrocene was added. The
cooling bath was removed, and the mixture was stirred for 6
h. Aqueous workup and chromatography (silica, ether/n-
hexane (v/v ) 1/1) as eluent) afforded 155 mg (0.24 mmol,
72.7% yield) of trans,trans-1,4-bis((1,2,3,4,5-pentamethylfer-
rocen-1′-yl)ethenyl)benzene (10) as red crystals.
Da ta for 8. Mp: 90-92 °C. Anal. Calcd for C16H22FeO:
C, 67.15; H, 7.75. Found: C, 66.88; H, 7.72. MS (EI, 70 eV):
m/z 286 (M+, 98%); 270 (M+ - OH, 23%); 256 (M+ - CH2OH,
38%). IR data (KBr): 3664-3269 m, br; 2900 m, 1478 m, 1382
Da ta for 10. Mp: 199-203 °C. Anal. Calcd for C40H46
-
Fe2: C, 75.25; H, 7.26. Found: C, 75.18; H, 7.29. MS (EI, 70
eV): m/z 638.5 (M+, 100%); 448.5 (M+ - FeCp*, 19%). HR-
MS (FAB): m/z 638.23864 (M+; exact mass calcd for C40H46
-
s, 1038 s, 814 s cm-1
.
1H NMR (CD2Cl2): δ 1.65 (15H, s, CH3);
Fe2, 638.22982). UV-vis (THF [λmax (nm)/log ꢀ]): 358/4.57;
481/3.97. IR data (KBr): 2964 s, 2906 s, 2856 s, 1630 m, 1513
m, 1474 m, 1459 m, 1380 m, 1262 m, 1096 m, 1071 m, 1032 s,
3.72 (5H, br m, subst. Cp and OH); 4.20 (2H, s, CH2). 13C NMR
(CD2Cl2): δ 10.4 (CH3); 59.9 (CH2); 71.0, 73.0 (Cp); 79.9 (C1′ of
subst. Cp); 80.4 (Cp*).
953 s, 861 m cm-1 1H NMR (CD2Cl2): δ 1.83 (30H, s, CH3);
.
3.88 (4H, m, subst. Cp); 3.94 (4H, subst. Cp); 6.56, 6.72 (each
1,2-Bis(1,2,3,4,5-p en t a m et h ylfer r ocen -1′-yl)et h ylen e
(“(r,ω-bis(p en ta m eth ylfer r ocen yl)[vin ylen e]”) (9a ,b). In
a Schlenk vessel 200 mg (0.7 mmol) of 1,2,3,4,5-pentamethyl-
1′-(hydroxymethyl)ferrocene (8) was dissolved in 20 mL of dry
dichloromethane, and the contents were cooled to -80 °C. To
the stirred solution was added 0.22 mL (1.6 mmol) of a 54%
etheral solution of tetrafluoroboric acid, causing immediate
change in color from orange to intense red, indicative of
formation of the corresponding (pentamethylferrocenyl)meth-
ylium tetrafluoroborate. The mixture was stirred for a further
10 min at a temperature of -80 °C, and 184 mg (0.7 mmol) of
triphenylphosphine was added; the cooling bath was removed,
and stirring was continued for 1 h, during which time the color
changed from red to brownish yellow. Solvents and volatile
materials were removed in vacuo, the residue was triturated
four times with 20 mL portions of diethyl ether, and the
resulting green ((1,2,3,4,5-pentamethylferrocen-1′-yl)methyl)-
triphenylphosphonium tetrafluoroborate was dried in vacuo,
yielding 340 mg (0.56 mmol, 78.6%) of green, solid material.
3
signal: 2H, d, J trans(1H-1H) ) 15.9 Hz, CHdCH); 7.42 (4H,
s, C6H4). 13C NMR (CD2Cl2): δ 11.1 (CH3); 69.8, 73.8 (Cp);
81.3 (Cp*); 83.8 (C1 of subst. Cp); 125.2, 126.1, 126.7, 137.0
(CHdCH and (C6H4). Single crystals were obtained from CH2-
Cl2/EtOH (Table 1, Figure 7; Supporting Information).
4-(2-(1,2,3,4,5-P en t a m et h ylfer r ocen -1′-yl)et h en yl)-4′-
for m ylst ilb en e (“P en t a m et h ylfer r ocen yl[(vin ylen e)2-
(p h en ylen e)2] Ald eh yd e”) (11a ,b). To a suspension of 3 g
(3.8 mmol) of p-xylylenebis(triphenylphosphonium bromide)
[CAS Reg. No. 40817-03-6] in 50 mL of THF at a temperature
of -30 °C was added 430 mg (3.8 mmol) of potassium tert-
butoxide, and the mixture was stirred for 0.5 h at -30 °C. The
cooling bath was removed, and stirring was continued for 45
min, during which time the color of the solution gradually
changed to orange, indicative of formation of the mono(ylide).
The mixture was coooled to -30 °C, 700 mg (2.5 mmol) of
1,2,3,4,5-pentamethyl-1′-formylferrocene was added, and fur-
ther stirring for 2 h afforded the mono-olefination product in

402 Organometallics, Vol. 16, No. 3, 1997
Hradsky et al.
solution. The mixture was once again cooled to -30 °C, and
with 430 mg (3.8 mmol) of potassium tert-butoxide the second
phosphonium group was converted to the ylide, which was
olefinated with 510 mg (3.8 mmol) of terephthalaldehyde in a
similar manner as described above. After the mixture was
stirred overnight, aqueous workup and chromatography (silica,
ether/hexane (v/v ) 1/2) as eluent) produced three products.
The first orange fraction yielded 250 mg of a mixture of 10
and 4-(2-(1,2,3,4,5-pentamethylferrocen-1′-yl)ethenyl)-4′-meth-
ylstilbene methylferrocene, and the second and third red
fractions were different isomers (700 mg, 1.43 mmol, 57.3%
yield of trans/trans-isomer (11a ) and 240 mg, 0.49 mmol,
19.6% yield of cis/trans-isomer (11b)) of the desired aldehyde:
Da ta for 11a . Red crystals formed. Mp: 220 °C, dec. Anal.
Calcd for C32H32FeO: C, 78.69; H, 6.60. Found: C, 78.65; H,
6.56. MS (EI, 70 eV): m/z 488.5 (M+, 100%); 353.5 (M+ - Cp*,
63%). HR-MS (FAB): m/z 488.17828 (M+; exact mass calcd
for C32H32Fe2, 488.18026). IR data (KBr): 2966 w, 2906 m,
2856 w, 2746 w, 1698 s, 1690 s, 1659 s, 1598 s, 1383 m, 1034
mmol) amount of p-xylylenebis(triphenylphosphonium bro-
mide) was converted to the corresponding bis(ylide) by depro-
tonation with 31 mg (0.25 mmol) of potassium tert-butoxide
in a similar manner as described above. Addition of 120 mg
(0.25 mmol) of 4-(2-(1,2,3,4,5-pentamethylferrocen-1′-yl)eth-
enyl)-4′-formylstilbene (“pentamethylferrocenyl[(ene)2(phenyl-
ene)2]aldehyde”) (11a ) at a temperature of -80 °C and stirring
overnight gave a red solution. Aqueous workup and chroma-
tography (silica, dichloromethane/hexane (v/v ) 1/2)) yielded
46 mg (0.05 mmol, 59%) R,ω-bis(pentamethylferrocenyl)[(ene)6-
(phenylene)5] (13) as the first fraction, and 40 mg of unreacted
pentamethylferrocenyl[(ene)2(phenylene)2] aldehyde (11a ) as
the second fraction.
Meth od B (Wittig-Hor n er Rea ction ). A 57 mg (0.15
mmol) amount of p-xylylenebis(diethylphosphonate)15 was
converted to the corresponding bis(ylide) by deprotonation with
35 mg (0.31 mmol) of potassium tert-butoxide in a similar
manner as described above. Addition of 150 mg (0.31 mmol)
of 4-(2-(1,2,3,4,5-pentamethylferrocen-1′-yl)ethenyl)-4′-formyl-
stilbene (“pentamethylferrocenyl[(ene)2(phenylene)2] alde-
hyde”) (11a ) at a temperature of -80 °C and subsequent
refluxing for 5 days gave a red solution. Aqueous workup and
chromatography (silica, dichloromethane/hexane (v/v ) 1/2))
yielded 50 mg (0.05 mmol, 42%) of R,ω-bis(pentamethylferro-
cenyl)[(ene)6(phenylene)5] (13) as the first fraction and 35 mg
of unreacted pentamethylferrocenyl[(ene)2(phenylene)2] alde-
hyde (11a ) as the second fraction.
m, 824 s cm-1
.
1H NMR (acetone-d6): δ 1.82 (15H, s, CH3);
3.87-4.28 (4H, m, subst. Cp); 6.64-7.93 (12H, m, olefinic and
aromatic H); 9.71, 10.01 (1H, 2s, CHO). 13C NMR (acetone-
d6): δ 11.0 (CH3); 70.3-77.9 (Cp and Cp*); 125.1-132.7
(olefinic and aromatic C); 192.1 (CHO). Single crystals were
obtained from n-hexane (Table 1, Figure 8; Supporting Infor-
mation).
Da ta for 11b. A red oil formed. Mp: not available. MS
(FAB): m/z 489 (M+, 23%); 461.6 (M+ - CHO, 15%); 281.2 (M+
- CHdCHC6H4CHO, 97%). IR data (KBr): 2962 w, 2927 w,
2860 w, 1729 s, 1702 s, 1602 s, 1382 m, 1119 s, 1040 s, 807 s
Da ta for 13. A red powder formed. Mp: 275-280 °C
(product of method A); mp 180-185 °C (product of method B).
Anal. Calcd for C72H70Fe2: C, 82.59; H, 6.74. Found: C, 82.67;
H, 6.81. MS (FAB): m/z 1046.7 (M+, 12%); 842.5 (M+ - FeCp*
cm-1 1H NMR (CDCl3): δ 1.81 (15H, s, CH3); 3.84-4.32 (4H,
.
m, subst. Cp); 6.54-7.72 (12H, m, olefinic and aromatic H);
9.93, 9.95 (1H, 2s, CHO). 13C NMR (CDCl3): δ 11.0 (CH3);
68.2-76.2 (Cp and Cp*); 126.1-131.9 (olefinic and aromatic
C); not observed, CHO.
- Me, 77%); 780.5 (M+ - CHCpFeCp*, 15%); 576.2 (M+
-
C6H4-CHdCHCpFeCp*, 100%). HR-MS (FAB): m/z 1046.43908
(M+; exact mass calcd for C72H70Fe2, 1046.41815). UV-vis for
product of method B (THF [λmax (nm)/log ꢀ]): 387.5/4.82; 500/
shoulder. IR data (KBr): 3020 w, 2964 s, 2923 s, 2854 s, 1630
r,ω-Bis(p en t a m et h ylfer r ocen yl)[(vin ylen e)4(p h en yl-
en e)3] (12). A 57 mg (0.15 mmol) amount of p-xylylenebis-
(diethylphosphonate) [CAS Reg. No. 4546-04-7],15 dissolved in
20 mL of THF, was converted to the corresponding mono(ylide)
by addition of 17 mg (0.15 mmol) of potassium tert-butoxide
at a temperature of -80 °C and subsequent warming to room
temperature under efficient stirring. The resulting orange
solution was cooled to -80 °C, 56 mg (0.15 mmol) of 1,2,3,4,5-
pentamethyl-1′-formylferrocene was added, and the mixture
was refluxed for 3 h to complete the mono-olefination. After
cooling of the mixture to -80 °C a second portion of 17 mg
(0.15 mmol) of potassium tert-butoxide was added and the
mixture was allowed to warm to room temperature. The so
formed dark solution of the ylide was olefinated by addition
of 73 mg (0.15 mmol) of 4-(2-(1,2,3,4,5-pentamethylferrocen-
1′-yl)ethenyl)-4′-formylstilbene (11a ) at a temperature of -80
°C and subsequent refluxing for 12 h. Aqueous workup and
chromatography (silica, ether/n-hexane (v/v ) 1/1)) afforded
50 mg (0.06 mmol, 40% yield) of 12 as red crystals.
m, 1515 m, 1459 m, 1380 m, 1262 s, 1098 s, 1030 s, 807 s cm-1
.
1H NMR (CD2Cl2): δ 1.84 (30H, s, CH3); 3.86 (4H, m, subst.
Cp); 3.92 (4H, subst. Cp); 6.53-6.76 (8H, m, CHdCH); 7.41
(12H, s, C6H4). 13C NMR (CD2Cl2): δ 11.1 (CH3); 69.8, 73.7
(Cp); 81.3 (Cp*); 83.8 (C1 of subst. Cp); 125.2-126.7 (CHdCH
and C6H4).
Ack n ow led gm en t. This work was supported by the
European HCM-project “Electron and Energy Transfer
in Model Systems and their Implications for Molecular
Electronics” (Grant No. CHRX-CT94-0538) and by the
Austrian Science Foundation, Vienna, Austria (Grants
P10182 and P09791TEC).
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement details, anisotropic thermal
parameters, fractional atomic coordinates and isotropic ther-
mal parameters for the non-hydrogen atoms, all bond lengths
and angles, and fractional atomic coordinates for the hydrogen
atoms for 1a ,b, 2-4, 5a , 6, 9a , 10, and 11a and ORTEP
diagrams for 1b,c, 2, and 3 (Figures 10-13) (76 pages).
Ordering information is given on any current masthead page.
The authors have deposited atomic coordinates for structures
1b,c, 2-4, 5a , 6, 9a , 10, and 11a with the Cambridge
Crystallographic Data Centre. The coordinates can be ob-
tained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, Lensfield Road, Cambridge, CB2 1EW,
U.K.
Da ta for 12. Mp: 185-190 °C. Anal. Calcd for C56H58
-
Fe2: C, 79.81; H, 6.94. Found: C, 80.06; H, 6.97. MS (FAB):
m/z 843.1 (M+, 16%); 652.3 (M+ - FeCp*, 10%). HR-MS
(FAB): m/z 842.32238 (M+; exact mass calcd for C56H58Fe2,
842.32373). UV-vis (THF [λmax (nm)/log ꢀ]): 359/4.38; 481/
3.73. IR data (KBr): 2964 m, 2925 m, 1630 w, 1262 s, 1100 s,
1028 s, 861 m, 803 s cm-1 1H NMR (CD2Cl2): δ 1.84 (30H, s,
.
CH3); 3.86 (4H, m, subst. Cp); 3.92 (4H, subst. Cp); 6.53-
6.76 (8H, m, CHdCH); 7.41 (12H, s, C6H4). 13C NMR (CD2-
Cl2): δ 11.1 (CH3); 69.8, 73.7 (Cp); 81.3 (Cp*); 83.8 (C1 of subst.
Cp); 125.2-126.7 (CHdCH and C6H4).
r,ω-Bis(p en t a m et h ylfer r ocen yl)[(vin ylen e)6(p h en yl-
en e)5] (13). Meth od A (Wittig Rea ction ). A 100 mg (0.125
OM960676W