Decomplexation of cyclopentadienylmanganese tricarbonyls under very mild conditions: A novel route to substituted cyclopentadienes and their application in organometallic synthesis

Article abstract of DOI:10.1021/om010274a

Photolysis of cyclopentadienylmanganese tricarbonyl derivatives in the presence of a proton source leads to decomplexation and formation of the free cyclopentadiene in excellent yield. In contrast, attempted decomplexation using Ce(IV) or Fe(III) leads merely to decomposition products. It is proposed that, upon photolytic loss of a CO ligand, coordination of methanol or water facilitates an intramolecular proton transfer to the cyclopentadienyl ring. This method is applicable to polyfunctional molecules such as ethynylestradiol. In this new synthetic approach, these cymantrenes have also been used as precursors to the corresponding iron, tungsten, titanium, and rhenium complexes via the generation of the intermediate cyclopentadienes.

Full text of DOI:10.1021/om010274a

4554
Organometallics 2001, 20, 4554-4561
Decom p lexa tion of Cyclop en ta d ien ylm a n ga n ese
Tr ica r bon yls u n d er Ver y Mild Con d ition s: A Novel
Rou te to Su bstitu ted Cyclop en ta d ien es a n d Th eir
Ap p lica tion in Or ga n om eta llic Syn th esis
Siden Top,*,† El Bachir Kaloun,† Ste´phanie Toppi,† Audrey Herrbach,†
Michael J . McGlinchey,‡ and Ge´rard J aouen*,†
Laboratoire de Chimie Organome´tallique, Ecole Nationale Supe´rieure de Chimie de Paris,
UMR CNRS 7576, 11, rue Pierre et Marie Curie, 75231 Paris Cedex 05, France,
and Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada
Received April 3, 2001
Photolysis of cyclopentadienylmanganese tricarbonyl derivatives in the presence of a proton
source leads to decomplexation and formation of the free cyclopentadiene in excellent yield.
In contrast, attempted decomplexation using Ce(IV) or Fe(III) leads merely to decomposition
products. It is proposed that, upon photolytic loss of a CO ligand, coordination of methanol
or water facilitates an intramolecular proton transfer to the cyclopentadienyl ring. This
method is applicable to polyfunctional molecules such as ethynylestradiol. In this new
synthetic approach, these cymantrenes have also been used as precursors to the correspond-
ing iron, tungsten, titanium, and rhenium complexes via the generation of the intermediate
cyclopentadienes.
In tr od u ction
enyls are now available with a wide variety of simple
functional groups: alkyls,6 silyls,7 aryls,8 formyls,8
acids,8 esters,8 alcohols,9 amines,9 vinyls,10 halogens,11
sulfides,12 phosphines,13 and boryls.14 Among the prin-
cipal strategies employed are as follows: (i) the Friedel-
Crafts reaction, whenever the organometallic substrate
permits, which unfortunately is frequently not the
case,8c (ii) an extension of Thiele’s reaction,15 which
involves electrophilic attack on the nucleophilic cyclo-
Some years ago, we proposed a mild decomplexation
method in the (arene)Cr(CO)3 series, useful for synthetic
purposes in organic chemistry.1 The reaction, based on
a photochemical oxidation in air and sunlight, at room
temperature, produced quantitative amounts of substi-
tuted aromatics; since then this approach has been
extensively developed.2 Curiously, this idea has not been
extrapolated to the metal cyclopentadienyl series, where
the breaking of π-bonds, either chemically (e.g. with
lithium on ferrocene)3 or electrochemically,4 leads to the
formation of unstable cyclopentadienyls that are dif-
ficult to manipulate. It would be quite different if,
during the liberation of the cyclopentadienide anion, the
intermediate could be kept in a stable form: for ex-
ample, as a neutral cyclopentadiene.
Inorg. Chem. 1994, 16, 185. (f) Coville, N. J .; du Plooy, K. E.; Pickl, W.
Coord. Chem. Rev. 1992, 116, 1. (g) J utzi, P.; Dahlhaus, J . Coord.
Chem. Rev. 1994, 137, 179. (h) Herberhold, M. In Ferrocenes; Togni,
A., Hayashi, T., Eds; VCH: Weinheim, Germany, 1995.
(6) (a) Kauffmann, T.; Ennen, J .; Lhotak, H.; Rensing, A.; Steinsei-
fer, F.; Woltermann, A. Angew. Chem., Int. Ed. Engl. 1980, 19, 328.
(b) J utzi, P.; Siemeling, U. J . Organomet. Chem. 1995, 500, 175. (c)
J utzi, P.; Dahlhaus, J . Synthesis 1993, 684. (d) Kohl, F. X.; J utzi, P.
J . Organomet. Chem. 1983, 243, 119. (e) Charrier, C.; Mathey, F. J .
Organomet. Chem. 1979, 170, C41. (f) Erker, G.; Mollenkopf, C. J .
Organomet. Chem. 1994, 483, 173.
The cyclopentadienyl ligand, because of its size,
robustness and electron count, is one of the most useful
coordinating ligands in organometallic chemistry. Its
almost ubiquitous nature has led to a plethora of articles
on its functionalization,5 such that metal cyclopentadi-
(7) Ciruelos, S.; Cuenca, T.; Gomez-Sal, P.; Monzanero, A.; Royo, P.
Organometallics 1995, 14, 177.
(8) (a) Hart, W. P.; Macomber, D. W.; Rausch, M. D. J . Am. Chem.
Soc. 1980, 102, 1196. (b) J ones, S. S.; Rausch, M. D.; Bitterwolf, T. E.
J . Organomet. Chem. 1990, 396, 279. (c) Mabrouk, S. T.; Hart, W. P.;
Rausch, M. D. J . Organomet. Chem. 1997, 527, 43. (d) Gronbeck, D.
A.; Matchett, S. A.; Rosenblum, M. Tetrahedron Lett. 1990, 31, 4977.
(9) (a) Plenio, H.; Warnecke, A. Organometallics 1996, 15, 5066. (b)
Plenio, H.; Burth, D. Organometallics 1996, 15, 1151. (c) Plenio, H.;
Burth, D. Organometallics 1996, 15, 4054. (d) Plenio, H.; Burth, D. Z.
Anorg. Allg. Chem. 1996, 622, 225.
* To whom correspondence should be addressed. G.J .: Tel, 33-1 43
26 95 55; fax, 33-1 43 26 00 61; e-mail, J aouen@ext.jussieu.fr.
† Ecole Nationale Supe´rieure de Chimie de Paris.
‡ McMaster University.
(1) J aouen, G.; Dabard, R. Tetrahedron Lett. 1971, 1015.
(2) (a) J aouen, G. In Transition Metal Organometallics in Organic
Synthesis; Alper, H., Ed.; Academic Press: New York, 1978; Vol. 2, p
65. (b) J aouen, G.; Meyer, A. Tetrahedron Lett. 1976, 3547. (c) J aouen,
G.; Meyer, A. J . Am. Chem. Soc. 1975, 97, 4667. (d) Top, S.; J aouen,
G. J . Org. Chem. 1981, 46, 18. (e) Top, S.; Meyer, A.; J aouen, G.
Tetrahedron Lett. 1979, 3537.
(3) Osgerby, J . M.; Pauson, P. L. J . Chem. Soc. 1961, 4605.
(4) Chaloyard, A.; El Murr, N. Inorg. Chem. 1980, 19, 3217.
(5) (a) Macomber, D. W.; Hart, W. P.; Rausch, M. D. Adv. Organomet.
Chem. 1982, 21, 1. (b) J utzi, P. Adv. Organomet. Chem. 1986, 26, 217.
(c) J aniak, C.; Schumann, H. Adv. Organomet. Chem. 1991, 33, 291.
(d) Okuda, J . Top. Curr. Chem. 1991, 160, 97. (e) Okuda, J . Comments
(10) Macomber, D. W.; Hart, W. P.; Rausch, M. D.; Priester, R. D.;
Pittman, C. V., J r. J . Am. Chem. Soc. 1982, 104, 884.
(11) Conway, B. G.; Rausch, M. D. Organometallics 1985, 4, 688.
(12) Brossier, R.; Bourdon, C.; Blacque, O.; Vallat, A.; Kubicki, M.
M.; Gautheron, B. Bull. Soc. Chim. Fr. 1996, 133, 843.
(13) (a) Mathey, F.; Lamyin, J . P. Tetrahedron 1975, 31, 2685. (b)
Szymoniak, J .; Besanc¸on, J .; Dormond, A.; Mo¨ıse, C. J . Org. Chem.
1990, 55, 1429. (c) Rudie, A. W.; Lichtenberg, D. W.; Katcher, M. L.;
Davison, A. Inorg. Chem. 1978, 17, 2859. (d) Schore, N. E. J . Am. Chem.
Soc. 1979, 101, 7410.
(14) (a) Herberich, G. E.; Fischer, A. Organometallics 1996, 15, 58.
(b) Larkin, S. A.; Golden, J . T.; Shapiro, P. J .; Yap, G. P. A.; Foo, D.
M. J .; Rheingold, A. L. Organometallics 1996, 15, 2393.
10.1021/om010274a CCC: $20.00 © 2001 American Chemical Society
Publication on Web 09/25/2001

Novel Route to Substituted Cyclopentadienes
Organometallics, Vol. 20, No. 22, 2001 4555
Sch em e 1
and efficient decomplexation to generate the corre-
sponding free cyclopentadiene.26 In addition, the precur-
sors should not only be readily prepared but also be
sufficiently stable for easy handling and storage. In
terms of the initial choice of organometallic system, it
is clear that an easily oxidizable, carbonylated half-
sandwich complex, CpM(CO)x, is preferable to a sand-
wich molecule, CpMCp′, because of the ease of bond
breaking, as well as simplification of the reaction and
of the purification procedures. In view of the known
relative instability and handling difficulties associated
with Cp′Co(CO)2 systems, we chose to focus our efforts
on the Cp′Mn(CO)3 (cymantrene) series of half-sand-
wiches which are stable in air but which can be
conveniently oxidized when in solution.30
pentadienides of sodium, lithium, or thallium,8a,b (iii)
the action of bases on fulvenes10,16 (iv) the action of
nucleophiles on diazocyclopentadiene (C5H4N2),17 (v) the
transformation of cyclopentenone,9a,18 and (vi) the con-
struction of substituted rings by means of various
coupling methods.6c,19 The variety of preparation meth-
ods utilized demonstrates both the absence of a domi-
nant synthetic strategy suitable for all cases and the
necessity of seeking new approaches to deal with novel
problems.
We have recently published our preliminary findings
in this area31 and now present the results of a more
complete mechanistic and synthetic study, including the
attachment of a number of organometallic fragments to
molecular frameworks that exhibit estrogenic or anti-
estrogenic activity.
We here describe a new synthetic approach that
allows ready access to different families of cyclopenta-
dienylmetal complexes whose substituents possess a
degree of complexity compatible with the production of
fine chemicals. Due to the therapeutic, analytical, or
structural imperatives inherent in our bio-organome-
tallic studies,20 we chose to attempt to bind CpM
fragments within complex biomolecules. These included
the incorporation of CpRe(CO)3 into hormones21 or
antibodies,22 of CpFeCp′ or CpCp′TiCl2 onto antitumoral
agents,23 and of CpW(CO)3R onto proteins.24 In the
particular case of radiopharmaceuticals possessing rela-
tively short-lived isotopes, it is especially crucial that
the synthetic routes be as rapid as possible and use the
minimum number of steps.17e,25
Resu lts a n d Discu ssion
Syn th etic Asp ects. To test the viability of the
approach, initial experiments were carried out using the
propionylcymantrenes 1a -c as precursors to the dia-
rylalkenes 2a -c. This latter type of skeleton, with OH
instead of OMe groups, recognizes the estrogen receptor
and shows a strong estrogenic effect, while with an
-O(CH2)3NMe2 chain in place of an OMe group, it
becomes an antiestrogenic entity.23b A simple exchange
of metals would thus permit changes in the properties
(structure, cytotoxicity, radiopharmaceutical properties)
of this system.
As shown in Scheme 2, McMurry coupling reactions
between 1 and 4,4′-dimethoxybenzophenone yield the
corresponding alkenes 2. Molecule 1a is itself easily
obtained almost quantitatively by the Friedel-Crafts
reaction between cymantrene and propionyl chloride in
CS2 in the presence of AlCl3.32 The Friedel-Crafts
reaction with methylcymantrene gives two isomers,
1b,c, which were separated by chromatography and
identified by NMR. Heating an equimolar mixture of 1
and dimethoxybenzophenone in THF in the presence of
In this context, the hypothetical transformations
depicted in Scheme 1 require that several criteria be
satisfied. First of all, the precursors must undergo mild
(15) (a) Thiele, J . Chem. Ber. 1900, 33, 666; 1901, 34, 68. (b)
Okuyama, T.; Ikenovchi, Y.; Fueno, T. J . Am. Chem. Soc. 1978, 100,
6162.
(16) (a) Knox, E. R.; Pauson, P. L. J . Chem. Soc. 1961, 4610. (b)
Hine, J .; Knight, D. B. J . Org. Chem. 1970, 35, 3946. (c) Erker, G.;
Mollenkopf, C. J . Organomet. Chem. 1994, 483, 173.
(17) (a) Day, V. W.; Stults, B. R.; Reimer, K. J .; Shaver, A. J . Am.
Chem. Soc. 1974, 96, 1227. (b) Reimer, K. J .; Shaver, A. J . Organomet.
Chem. 1975, 93, 239. (c) Herrmann, W. A.; Reiter, B.; Huber, M. J .
Organomet. Chem. 1977, 140, 55. (d) Herrmann, W. A. Chem. Ber.
1978, 111, 2458. (e) Minutolo, F.; Katzenellenbogen, J . A. J . Am. Chem.
Soc. 1998, 120, 4514.
(18) (a) Gubitosa, G.; Boldt, M.; Brintzinger, H. H. J . Am. Chem.
Soc. 1977, 99, 5174. (b) de Azevedo, C. G.; Boese, R.; Newman, D. A.;
Vollhardt, K. P. C. Organometallics 1995, 14, 4980.
(19) Takahashi, T.; Sun, W.-H.; Xi, C.; Kotora, M. Chem. Commun.
1997, 2069.
(20) (a) J aouen, G.; Vessie`res, A.; Butler, I. S. Acc. Chem. Res. 1993,
26, 261. (b) J aouen, G.; Vessie`res, A. Pure Appl. Chem. 1989, 61, 565.
(21) Top, S.; El Hafa, H.; Vessie`res, A.; Quivy, J .; Vaissermann, J .;
Hughes, D. W.; McGlinchey, M. J .; Mornon, J .-P.; Thoreau, E.; J aouen,
G. J . Am. Chem. Soc. 1995, 117, 8372.
(22) Salmain, M.; Gunn, M.; Gorfti, A.; Top, S.; J aouen, G. Biocon-
jugate Chem. 1993, 4, 424.
(23) (a) Top, S.; Tang, J .; Vessie`res, A.; Carrez, D.; Provot, C.;
J aouen, G. J . Chem. Soc., Chem. Commun. 1996, 955. (b) J aouen, G.;
Top, S.; Vessie`res, A.; Leclercq, G.; J in, L.; Quivy, J .; Croisy, A. C.R.
Acad. Sci. Paris, Ser. IIc 2000, 3, 89.
(24) Salmain, M.; Gorfti, A.; J aouen, G. Eur. J . Biochem. 1998, 258,
192.
(25) (a) J aouen, G.; Top, S.; Vessie`res, A.; Alberto, R. J . Organomet.
Chem., 2000, 600, 23. (b) Alberto, R.; Schibli, R.; Egli, A.; Schubiger,
P. A.; Abram, U.; Kaden, T. A. J . Am. Chem. Soc. 1998, 120, 7987.
33
the McMurry reagent Zn/TiCl4 produced compounds
2a -c in yields ranging from 85 to 50%. These complexes
are yellow, stable in air in the solid state, and can be
stored in the dark for several months with no trace of
decomposition
Initial attempts to generate the free cyclopentadienes
derived from 2 focused on chemical oxidation methods.
(26) In special cases, nitroferrocenyl compounds,27 nickelocene,28 and
manganocene29 can also produce free, substituted cyclopentadienes.
(27) Salter, R.; Pickett, T. E.; Richards, C. J . Tetrahedron: Asym-
metry 1998, 9, 4239.
(28) Moberg, C. J . Organomet. Chem. 1976, 108, 125.
(29) Unseld, D.; Krivykh, V. V.; Heinze, K.; Wild, F.; Artus, G.;
Schmalle, U.; Berke, H. Organometallics 1999, 18, 1525.
(30) (a) Piper, T. S.; Cotton, F. A.; Wilkinson, G. J . Inorg. Nucl.
Chem. 1955, 1, 165. (b) King, R. B.; Stone, F. G. A. Inorg. Synth. 1963,
7, 99.
(31) Top, S.; Kaloun, E. B.; J aouen, G. J . Am. Chem. Soc. 2000, 122,
736.
(32) (a) Cais, M.; Feldkimel, M. Tetrahedron Lett. 1961, 13, 440. (b)
Fischer, E. O.; Fellmann, W. J . Organomet. Chem. 1963, 1, 191.
(33) (a) McMurry, J . E. J . Am. Chem. Soc. 1974, 96, 1708. (b)
McMurry, J . E. Acc. Chem. Res. 1983, 16, 405.

4556 Organometallics, Vol. 20, No. 22, 2001
Top et al.
Sch em e 2
Sch em e 4
P h otolytic Decom p lexa tion Meth od s. By analogy
to our earlier use of sunlight to bring about the decom-
plexation of (arene)Cr(CO)3 complexes, exposure of an
ethereal solution of 2a to daylight for 1 h led to the
complete disappearance of the starting material but
yielded, after chromatographic separation, only 14% of
the required cyclopentadiene 3a . Moreover, numerous
other orange products were observed whose NMR
spectra in the vinyl region bore a close resemblance to
that of the material resulting from the attempted
decomplexations using Ce(IV) or Fe(III) salts. When a
solution of 2a in 50/50 ether/methanol was exposed to
sunlight, the yield of 3a improved to 34%.
Sch em e 3
Encouraged by these observations, decomplexations
were then attempted with use of a high-pressure
mercury lamp that covered the range from 240 nm into
the visible region, with a dominant line at 366 nm; a
Pyrex filter was used to remove wavelengths below 300
nm. Under these conditions, irradiation of an anhydrous
ether solution of 2a for 45 min yielded 19% of 3a and
21% recovery of starting material; addition of a trace of
trifluoracetic acid to the previous solution boosted the
yield of 3a after photolysis to 50%. More impressively,
when the solvent was changed to 2:1 methanol/ether,
the isolated yield of 3a after chromatographic purifica-
tion was 80%. Application of these latter conditions to
the methyl derivatives 2b,c produced the corresponding
cyclopentadienes 3b,c in excellent yields, 82% and 91%,
respectively. The cyclopentadienes are relatively stable
against polymerization and can be kept for several days
with refrigeration.
It is evident that monosubstitution of a cyclopenta-
diene can lead to the three isomers shown in Scheme 4.
However, the NMR spectra of 3a reveal the presence of
only two isomers, each of which possesses a methylene
group, thus eliminating the 5-substituted isomer 3a ′′′
Ceric ammonium nitrate34 and iodine35 have each been
used to oxidize (arene)Cr(CO)3 complexes so as to
release the free arene; likewise, ferric nitrate brings
about the efficient decomplexation of (alkyne)Co2(CO)6
clusters.36 Addition of (NH4)2[Ce(NO3)6] to a solution of
2a in THF, or in a THF/methanol mixture, caused
considerable evolution of gas and complete disappear-
ance of the cymantrene complex. Thin-layer chroma-
tography yielded an orange material, more polar than
2a , whose NMR spectrum indicated the formation of a
complex mixture of organic products, none of which were
the desired cyclopentadiene 3a , shown in Scheme 3.
Likewise, treatment of 2a with ferric nitrate also
resulted in the destruction of the starting material
without detectable formation of 3a . In contrast, when
a THF solution of 2a and iodine was heated for 1 h at
60 °C, 98% of the manganese complex was recovered
unchanged.
1
as a possibility. Careful scrutiny of the H-1H COSY
1
and H-13C shift-correlated 2D spectra allowed the 1-
and 2-substituted isomers 3a ′ and 3a ′′, respectively, to
be distinguished. When initially produced, isomer 3a ′′
is favored over 3a ′ by a ratio of approximately 2:1 but,
after a period of 9 days in the NMR tube, the spectra of
the sample were reacquired and revealed that this
isomeric ratio had been essentially reversed. Appar-
ently, the linearly fully conjugated system 3a ′ is the
thermodynamically favored product. However, since
these cyclopentadienes are deprotonated as the first step
in their use as reagents for the preparation of cyclopen-
tadienyl derivatives of other metals, separation is not
necessary.
To identify the hydrogen source necessary for the
generation of the cyclopentadiene 3a , the photolyses
were repeated in the presence of a small quantity of D2O
(0.4 mL in 20 mL of ether). Irradiation for 20 min gave
a 32% yield of 3a ; incorporation of the deuterium label
into the cyclopentadiene ring was established not only
from the diminution of the intensity of the methylene
(34) (a) Trahanovsky, W. S.; Hall, R. A. J . Organomet. Chem. 1975,
96, 71. (b) Corriu, R. J . P.; Moreau, J . J . E.; Praet, H. Organometallics
1989, 8, 2779.
(35) Rodriguez, J . G.; Urrutia, A. J . Chem. Soc., Perkin Trans. 1
1995, 665.
(36) Nicholas, K. M.; Siegel, J . J . Am. Chem. Soc. 1985, 107, 4999.

Novel Route to Substituted Cyclopentadienes
Organometallics, Vol. 20, No. 22, 2001 4557
Sch em e 5
Sch em e 6
resonances in the NMR spectrum but also from the mass
spectrum that clearly exhibited a parent peak for the
monodeuterated cyclopentadienes. Similar results were
observed with CD3OD.
Syn th eses of Ti, F e, W, a n d Re Com p lexes. The
ready availability of the functionalized cyclopentadiene
3a permits the incorporation of a variety of other
organometallic fragments. Typically, as exemplified in
Scheme 5, treatment of 3a with butyllithium, to give
4a , followed by addition of CpTiCl3, BrRe(CO)5, or FeCl2
yields the corresponding cyclopentadienyl complexes
5-7, respectively, in yields ranging from 45 to 64%. The
tungsten complex 8 was prepared by deprotonation
using sodium hydride, reaction with W(CO)6, and finally
addition of methyl iodide. The rhenium complex 6 is also
preparable from the thallium salt of 3a . Although no
attempts have been made to optimize the yields of 5-8,
the viability of the method has been clearly established.
Decom p lexa t ion of a Mn Com p lex of E t h y-
n ylest r a d iol. Gratifyingly, photolysis of cymantrene
complexes in protic media is also applicable to the
hormonal system 9 and produces the free ligand 10 in
64% yield (73% based on starting material consumed;
Scheme 6). We are unaware of any previous syntheses
of uncomplexed hormonal cyclopentadienes, but we note
the very recent report by Cesati and Katzenellenbogen
that rhenium complexes of such molecules are, in
principle, preparable via their stannylation methodol-
ogy.37
acetylide.39 Nevertheless, the present approach provides
a convenient, inexpensive, and relatively high yield
route to a series of bio-organometallic molecules of
intense current interest.
In fr ar ed Stu dy. CpMn(CO)2(L) complexes are known
for many types of ligands L.40 In general, they are
obtained by photolysis of CpMn(CO)3 in the presence
of the ligand and give rise to two νCO stretches in the
infrared. The compound (C5H5)Mn(CO)2(THF) exhibits
IR bands at 1921 and 1850 cm-1 but decomposes
gradually over the course of time.40a When the manga-
nese tricarbonyl complex 2a was photolyzed in THF, and
the progress of the reaction was monitored by IR, the
corresponding Cp′Mn(CO)2(THF) was found to absorb
at 1850 cm-1, but the second band anticipated at ∼1920
cm-1 is obscured by unreacted starting material. After
irradiation for 45 min, when approximately 50% of 2a
had reacted, the photolysis was stopped. The reaction
mixture was left at ambient temperature overnight,
Other potential routes to 10 and related systems
could, for example, involve either a palladium coupling
procedure to incorporate an alkynyl substituent38 or
treatment of an appropriate cyclopentenone with an
(39) Bunel, E. E.; Valle, L.; J ones, N. L.; Carroll, P. J .; Gonzalez,
M.; Munoz, N.; Manriquez, J . M. Organometallics 1988, 7, 789.
(40) (a) Giordano, P. J .; Wrighton, M. S. Inorg. Chem. 1977, 16, 160.
(b) Caulton, K. G. Coord. Chem. Rev. 1981, 38, 1. (c) Strohmeier, W.;
Bardeau, C.; Hobe, D. V. Chem. Ber. 1963, 96, 3254.
(37) Cesati, R. R., III; Katzenellenbogen, J . A. J . Am. Chem. Soc.
2001, 123, 4093.
(38) Dyker, G.; Heiermann, J .; Miura, M.; Inoh, J .-I.; Pivsa-Art, S.;
Satoh, T.; Nomura, M. Chem. Eur. J . 2000, 6, 3426.

4558 Organometallics, Vol. 20, No. 22, 2001
Top et al.
Sch em e 7
absorption around 350 nm but nevertheless does absorb
light as far as 420 nm. In contrast, the hormonal
derivative has an absorption maximum at 336 nm, with
a molar extinction coefficient of 1100.
When 2a is irradiated, even with sunlight, formation
of the free cyclopentadiene 3a is observed, the yield
depending on the particular experimental conditions.
The initially formed 16-electron species Cp′Mn(CO)2 can
be stabilized, either strongly by good Lewis bases such
as phosphines or weakly by such ligands as THF.
However, in the latter case, decomposition does not lead
to diene formation, unless the coordinating ligand is also
a proton donor. The IR data presented already implicate
Cp′Mn(CO)2(MeOH) as a viable intermediate, and it is
reasonable to postulate that intramolecular proton
transfer to the five-membered ring generates the cor-
responding (η4-cyclopentadiene)Mn(CO)2OMe complex,
which decomposes with liberation of the diene, as
depicted in Scheme 7.
Alternatively, one could envisage an oxidative addi-
tion process to give (Cp′)Mn(CO)2(H)(OMe), by analogy
to the formation of (C5H5)Mn(CO)2(H)(SiEt3) when
cymantrene is irradiated in the presence of HSiEt3.41
However, in view of the well-established proclivity of
cymantrene derivatives, especially complexes of the type
Cp′Mn(CO)[PR3]2, to undergo protonation at the rela-
tively basic metal center,42 an oxidative addition process
is considered an unlikely eventuality in the present case.
F igu r e 1. UV-visible spectra: (1) (C5H5)Mn(CO)3 (6.25
× 10-4 M); (2) steroidal cymantrene complex 9 (10-4 M);
(3) cymantrene complex 2a (10-4 M); (4) methylcymantrene
complex 2c (10-4 M).
after which time all the Cp′Mn(CO)2(THF) had decom-
posed, but no cyclopentadiene 3a had formed. In con-
trast, a parallel experiment, in which 2a was photolyzed
in 50/50 ether/methanol for 50 min, yielded an IR
spectrum showing intense absorptions at 1921 and 1850
cm-1, implying the formation of Cp′Mn(CO)2(MeOH).
After 2 h irradiation, all νCO bands had disappeared,
and subsequent chromatography furnished 3a in 38%
isolated yield. The relatively low yield is attributable
to successive removal of samples for IR analysis.
Mech a n istic Im p lica tion s. The generation of a
cyclopentadiene derived by decomposition of a cyman-
trene requires a source of a proton, or a hydrogen atom,
presumably from the solvent. Indeed, the use of deu-
terated solvents, such as D2O or CD3OD, as described
above, supports this view. These studies have also
shown that classic oxidants, such as ceric or ferric salts,
do not lead to formation of the free cyclopentadiene. In
contrast, UV photolysis in a protic solvent (methanol,
water, or trifluoroacetic acid) provides a perfectly ac-
ceptable route to the required dienes.
It is evident that these two approaches do not follow
the same pathway; one can reasonably assume that
classic chemical oxidants generate cyclopentadienyl
radicals or radical cations. However, even in methanol,
which can function as either a proton donor or a source
of hydrogen radicals, the desired cyclopentadiene is not
formed; instead, the products appear to be a complex
mixture, perhaps derived from radical coupling reac-
tions. It is well-known that cymantrenes undergo pho-
tolysis; as illustrated in Figure 1, the parent molecule
(C5H5)Mn(CO)3 exhibits an absorption maximum at 330
nm.40a Figure 1 also shows data for the cymantrenes
2a ,c, as well as for the (ethynylestradiol)manganese
complex 9. The former possesses only a rather weak
Con clu sion s
This work has shown that it is possible to generate
cyclopentadienes by a simple photolytic decomplexation
of the corresponding cymantrene. It has been clearly
demonstrated that a proton source, such as an alcohol,
water, or a carboxylic acid, is necessary to obtain the
cyclopentadiene in synthetically useful yields. The
mechanism proposed involves photolytic elimination of
a carbonyl group, coordination of the ROH ligand,
intramolecular proton (or deuteron) transfer to form the
η4-cyclopentadiene, and finally, liberation of the desired
diene.
This method allows the synthesis of multifunctional-
ized cyclopentadienes not accessible by present proce-
(41) (a) J etz, W.; Graham, W. A. G. Inorg. Chem. 1971, 10, 4. (b)
Smith, R. A.; Bennett, M. J . Acta Crystallogr. 1977, B33, 113. (c) Young,
K. M.; Wrighton, M. S. Organometallics 1989, 8, 1063.
(42) (a) Lokshin, B. V.; Ginzburg, A. G.; Setkina, V. N.; Kursanov,
D. N.; Nemirovskaya, I. B. J . Organomet. Chem. 1972, 37, 347. (c)
Ginzburg, A. G.; Okulevich, P. O.; Setkina, V. N.; Panosyan, G. A.;
Kursanov, D. N. J . Organomet. Chem. 1974, 81, 201.

Novel Route to Substituted Cyclopentadienes
Organometallics, Vol. 20, No. 22, 2001 4559
was hydrolyzed with 100 mL of a 10% Na2CO3 solution. After
ether extraction and solvent removal, the crude product (2.12
g) was chromatographed on silica gel plates with 1:5 ethyl
ether/pentane as eluent to give 2a (1.25 g, 83% yield).
Recrystallization from ethyl ether/pentane furnished yellow
crystals, mp 91 °C. 1H NMR (200 MHz, CDCl3): δ 7.10 (d, 2H),
7.01 (d, 2H), 6.84 (d, 2H), 6.80 (d, 2H) (aromatic rings), 4.54
(t, 2H), 4.47 (t, 2H) (C5H4), 3.81 (s, 3H, OCH3), 3.80 (s, 3H,
OCH3), 2.31 (q, 2H, CH2CH3), 1.05 (t, 3H, CH2CH3). Anal.
Calcd for C26H23O5Mn: C, 66.38, H, 4.93. Found: C, 66.45, H,
5.00.
dures and has even been applied to a hormonal steroid.
Moreover, the ready availability of these cyclopenta-
dienes facilitates the syntheses of a wide range of other
metal complexes, as exemplified by the Ti, Fe, Re, and
W systems described herein. We believe that this new
approach will offer a variety of new perspectives in
organometallic chemistry.
Exp er im en ta l Section
Gen er a l Da ta . Starting materials were synthesized using
standard Schlenk techniques, under an argon atmosphere; the
17R-ethynylestradiol complex 9 was prepared as previously
described.21 Anhydrous THF and diethyl ether were distilled
from sodium/benzophenone. Methanol (Prolabo) was used
without any further purification. Thin-layer chromatography
was performed on silica gel 60 GF254. UV photolyses were
carried out with a Heraeus TQ150 150 W high-pressure Hg
lamp. FT-IR spectra were recorded on a BOMEM Michelson-
1,1′-Bis(p -a n isyl)-2-(2-m et h ylcym a n t r en yl)-1-b u t en e
(2b). Following the procedure used for 2a , 4,4′-dimethoxyben-
zophenone (0.726 g, 3 mmol), zinc (1.170 g, 18 mmol), TiCl4
(1.710 g, 9 mmol), and 1b (0.822 g, 3 mmol) yielded 2b (0.937
g, 64%) as a yellow oil. 1H NMR (CDCl3, 200 MHz): δ 7.10 (d,
2H), 6.89 (d, 2H), 6.85 (d, 2H), 6.65 (d, 2H) (aromatic rings),
4.86 (m, 1H), 4.46 (m, 1H), 4.36 (m, 1H) (C5H3), 3.83 (s, 3H,
OCH3), 3.75 (s, 3H, OCH3), 2.30 (m, 2H, CH2CH3), 1.40 (s, 3H,
Me), 1.12 (t, 3H, J ) 7.5 Hz, CH2CH3). MS (EI, 70 eV): m/z
484 [M+], 400 [(M - 3CO)+].
1
100 spectrometer. H and 13C NMR spectra were acquired on
Bruker 200, 250, and 400 MHz spectrometers. Mass spectrom-
etry was performed on a Nermag R 10-10C spectrometer.
Melting points were measured with a Kofler device. Elemental
analyses were performed by the Regional Microanalysis De-
partment of the Universite´ Pierre et Marie Curie.
1,1′-Bis(p-an isyl)-2-(3-m eth ylcym an tr en yl)-1-bu ten e (2c).
Analogously, 4,4′-dimethoxybenzophenone (2.270 g, 9.35 mmol),
zinc (2.860 g, 44 mmol), TiCl4 (6.900 g, 36.39 mmol), and 1c
(2.550 g, 9.30 mmol) yielded 2c (2.15 g, 48%) as a yellow solid,
mp 74 °C. 1H NMR (CDCl3, 200 MHz): δ 7.09 (d, 2H), 7.02 (d,
2H) (aromatic ring), 6.85 (d, 2H), 6.81 (d, 2H) (aromatic ring),
4.39 (s, 2H), 4.29 (s, 1H) (C5H3), 3.80 (s, 6H, OCH3's), 2.28 (m,
2H, CH2CH3), 1.83 (s, 3H, Me), 1.03 (t, 3H, J ) 7.3 Hz,
CH2CH3). IR (CH2Cl2): νCO 2012, 1926 cm-1. MS (EI, 70 eV):
m/z 484 [M+], 400 [(M - 3CO)+], 55 [Mn+]. Anal. Calcd for
(P r op ion ylcyclop en t a d ien yl)t r ica r b on ylm a n ga n ese
(1a ). In a Schlenk tube purged with argon, cymantrene (3.00
g, 14.70 mmol) and propionyl chloride (1.35 g, 14.70 mmol)
were dissolved in carbon disulfide (30 mL). AlCl3 (0.977 g, 7.35
mmol) was added in small portions to the solution of cyman-
trene, and the solution became red. After 1.5 h, the CS2 was
removed under vacuum and the oil obtained was hydrolyzed
with water at 0 °C. After extraction with diethyl ether (3 ×
20 mL) and drying over magnesium sulfate, the solution was
concentrated, whereupon addition of pentane yielded (propio-
nylcyclopentadienyl)tricarbonylmanganese (3.540 g, 92%) as
a yellow powder. Recrystallization from diethyl ether/pentane
furnished yellow crystals, mp 250 °C. 1H NMR (200 MHz,
CDCl3): δ 5.44 (t, 2H, J ) 2.1 Hz, η5-C5H4), 4.85 (t, 2H, J )
2.1 Hz, η5-C5H4), 2.64 (q, 2H, CH2), 1.17 (t, 3H, CH3). 13C NMR
(50 MHz, CDCl3): δ 197.9 (CO), 91.5 (C1 of η5-C5H4), 86.4 (2C,
C5H4), 83.4 (2C, C5H4), 32.2 (CH2), 7.9 (CH3). IR (CH2Cl2): νCO
at 2030 (s), 1948 (s), 1686 cm-1 (m). Anal. Calcd for C11H9O4-
Mn: C, 50.79, H, 3.46. Found: C, 50.83, H, 3.41.
C
27H25O5Mn: C, 66.94, H, 5.16. Found: C, 66.81, H, 5.30.
Ch em ica l Oxid a tion s of 2a . (a) When (NH4)2Ce(NO3)6
(0.274 g, 0.5 mmol) was added to 2a (0.056 g, 0.12 mmol) in
1:1 THF/methanol (2 mL), gas evolution was evident and the
solution became orange with complete dissolution of the cerium
salt. After it was stirred for 2 h, the solution was concentrated
and chromatographed on silica gel plates with 1:3 ethyl ether/
pentane as eluent. An orange fraction (20 mg) was isolated,
and 2a had completely disappeared. The NMR spectrum of
this mixture of organic compounds could not be assigned.
(b) When iodine (0.152 g, 0.6 mmol) was added to 2a (0.140
g, 0.3 mmol) in THF (15 mL), and the mixture was stirred at
room temperature for 3 h and then at 60 °C for 1 h, 98% of
starting material was recovered after workup.
(2-Meth yl-1-p r op ion ylcyclop en ta d ien yl)- a n d (3-Meth -
y l-1-P r o p i o n y lc y c lo p e n t a d i e n y l)t r i c a r b o n y lm a n -
ga n ese (1b,c). As for the synthesis of 1a , (η5-C5H4Me)Mn-
(CO)3 (4.150 g, 19 mmol), propionyl chloride (2.560 g, 27.6
mmol), and AlCl3 (2.530 g) gave, after workup, a crude product
that was chromatographed on a silica gel column with 1:10
ethyl ether/petroleum ether as eluent. The first to elute was
1b (1.240 g, 23.7%) as a yellow solid. 1H NMR (200 MHz,
CDCl3): δ 5.28 (s, 1H), 4.71 (m, 2H) (η5-C5H3), 2.65 (q, 2H,
CH2CH3), 2.28 (s, 3H, COCH3), 1.16 (t, 3H, CH2CH3). Anal.
Calcd for C12H11O4Mn: C, 52.57, H, 4.04. Found: C, 52.47, H,
4.06. Subsequently, 1c (2.140 g, 41.3%) was collected as a
(c) When powdered Fe(NO3)3 (0.500 g, 0.9 mmol) was added
to 2a (0.140 g, 0.3 mmol) in dichloromethane (15 mL), the
solution became orange and then brown after 4.5 h of stirring.
After separation by TLC, 2a (0.008 g, 6%) and an orange
fraction (0.028 g) were obtained. The NMR spectrum of the
orange fraction appeared to be identical with that isolated from
the reaction with ceric ion.
P h otolysis Rea ction s. (a ) In Su n ligh t. When 2a (0.110
g, 0.23 mmol) was dissolved in technical grade diethyl ether
(5 mL), and the solution was exposed to sunlight for 1 h, a
brown powder precipitated from the solution. The remaining
solution was subjected to TLC on silica gel using 1:6 ethyl
ether/pentane as eluent to give 3a (0.011 g, 14%) as a beige
oil, together with 0.039 g of an unidentified orange oil. In a
parallel experiment, using 1:2 diethyl ether/methanol as the
solvent, 3a (34%) was isolated and 2a (20.6%) was recovered.
(b) UV Ir r a d ia tion s. (i) When a long tube containing 2a
(0.402 g, 0.85 mmol) dissolved in a mixture of technical grade
ethyl ether (15 mL) and methanol (30 mL) was irradiated using
a UV lamp (TQ150), significant gas evolution was observed
and, after 1 h, a brown powder precipitated. The solution was
filtered through a filter funnel filled with silica gel of thickness
0.5 mm, and the solvent was subsequently removed by
evaporation. TLC on silica gel with 1:6 ethyl ether/pentane
as eluent gave 3a (0.228 g, 81%) as a beige oil, whose NMR
indicated the presence of two isomers. 1H NMR of major
1
yellow oil. H NMR (200 MHz, CDCl3): δ 5.35 (s, 1H), 5.27 (s,
1H), 4.70 (s, 1H) (η5-C5H3), 2.59 (q, 2H, CH2CH3), 2.03 (s, 3H,
COCH3), 1.16 (t, 3H, CH2CH3). Anal. Calcd for C12H11O4Mn:
C, 52.57, H, 4.04. Found: C, 52.71, H, 4.35.
1,1′-Bis(p-a n isyl)-2-cym a n tr en yl-1-bu ten e (2a ). TiCl4
(1.71 g, 9 mmol) was added dropwise to a suspension of zinc
powder (1.17 g, 12 mmol) in THF (30 mL) at 0 °C. The blue
mixture obtained was heated at reflux for 2 h, the solution
became black, and the oil bath was removed. A second solution
was prepared by dissolving 4,4′-dimethoxybenzophenone (0.882
g, 3 mmol) and propionylcymantrene (1a ; 0.780 g, 3 mmol) in
THF (15 mL). The latter solution was added dropwise to the
first solution, and the resulting mixture was then heated again
for 2 h. After it was cooled to room temperature, the mixture

4560 Organometallics, Vol. 20, No. 22, 2001
Top et al.
product, 3a ′′ (200 MHz, CDCl3): δ 7.10 (d, 2H), 6.86 (d, 2H)
(aromatic ring), 6.96 (d, 2H), 6.70 (d, 2H) (aromatic ring), 6.25
(pseudoquintet, J ≈ 1.5 Hz, 1H, H1), 6.19 (dd, J ≈ 5 Hz, J ≈
1.5 Hz, H3), 5.95 (doublet of pseudoquartets, J ) 5.1 Hz, J )
1.4 Hz, H4), 3.83 (s, 3H, OCH3), 3.77 (s, 3H, OCH3), 3.01 (m,
2H, CH2 of Cp ring), 2.42 (q, 2H, CH2CH3), 1.01 (t, CH2CH3).
A second isomer, 3a ′, about one-third of the mixture, was
distinguished from the first by the following NMR signals: δ
6.45 (d,t, J ≈ 5 Hz, J ≈ 1 Hz, H4), 6.41 (m, 1H) 6.20 (m, H3),
3.81 (s, 3H, OCH3), 3.78 (s, 3H, OCH3), 2.65 (m, 2H, CH2 of
Cp ring), 2.41 (q, 2H, CH2CH3), 1.02 (t, CH2CH3).
(ii) UV photolysis of 2a in anhydrous diethyl ether alone
gave 3a (19%) and 2a (21% recovered). Photolysis of 2a in
diethyl ether containing 2 drops of CF3COOH gave a 50% yield
of 3a .
(iii) When 2a (0.141 g, 0.3 mmol) was dissolved in anhydrous
ethyl ether (15 mL) and CD3OD (99.8% D) (2 mL), and the
solution was irradiated for 30 min, chromatographic separation
gave 3a -d (0.029 g, 32%), together with recovered starting
material 2a (0.055 g, 39%). MS (EI, 70 eV): m/z 333 [M]+, 304,
289, 273.
(iv) When 2a (0.141 g, 0.3 mmol) was dissolved in anhydrous
ethyl ether (15 mL) and D2O (99.9%-D) (0.4 mL) and the
solution was irradiated for 40 min, chromatographic separation
gave 3a -d (0.032 g, 32%) together with recovered starting
material 2a (0.020 g, 14%).
(v) Following the procedure above, 2b (0.301 g, 0.62 mmol)
was irradiated for 40 min. Chromatography on silica gel plates
with 1:10 ethyl ether/pentane as eluent gave 3b (0.176 g, 82%)
as a colorless oil. 1H NMR (CDCl3, 200 MHz): δ 7.15-6.60
(m, 8H) (aromatic rings), 6.50-6.20 (m, 2H, C5H3 ring), 3.83
(s, 3H, OCH3), 3.73 (s, 3H, OCH3), 3.04, 2.75 (CH2's of C5H4
ring isomers), 2.27, 2.26 (2 q, 2H, CH2CH3), 1.64 (s, 3H, Me),
0.94 (t, 3H, J ) 7.2 Hz, -CH2CH3).
0.95 mmol) was added dropwise. The solution of the lithium
salt 4a was stirred for 1.5 h while the temperature was allowed
to rise slowly to -20 °C, and the solution became orange. The
solution was recooled to -70 °C, then CpTiCl3 (0.262 g, 1.19
mmol) was added as a solid in one portion, and the solution
immediately turned dark red. After the mixture was stirred
for 3 h, the THF was removed under vacuum and the residue
was dissolved in dichloromethane; after filtration and removal
of solvent, 5 (0.260 g, 64%) was obtained as a red solid and
was recrystallized from CH2Cl2/pentane to give red-black
crystals, mp 216 °C. 1H NMR (200 MHz, CDCl3): δ 7.20 (d,
2H), 6.88 (d, 2H) (aromatic ring), 7.00 (d, 2H), 6.81 (d, 2H)
(aromatic ring), 6.49 (s, 5H, C5H5), 6.27 (t, 2H), 6.15 (t, 2H)
(C5H4), 3.82 (s, 3H, OCH3), 3.81 (s, 3H, OCH3), 2.44 (q, 2H,
CH2CH3), 1.00 (t, 3H, CH2CH3). MS (DCI): m/z 532 [(M +
NH4)+], 333. Anal. Calcd for C28H28Cl2O2Ti: C, 65.26, H, 5.48.
Found: C, 65.41, H, 5.52.
Syn th esis of Rh en iu m Com p lex 6. (a ) F r om a Lith iu m
Sa lt. The lithium salt 4a was prepared from 3a (0.075 g, 0.22
mmol) as described above, and a solution of BrRe(CO)5 (0.089
g, 0.22 mmol) in THF (2 mL) was added at 0 °C. The mixture
was heated at reflux for 2.5 h, and after hydrolysis with ice
water, ether extraction, and solvent removal, the residue was
chromatographed on silica gel plates using 1:9 ether/pentane
as eluent to give 6 (0.060 g, 45% yield), mp 110 °C, as a
colorless solid. IR (CH2Cl2): νCO at 2017 (s) and 1923 cm-1 (s).
1H NMR (200 MHz, CDCl3): δ 7.08 (d, 2H), 6.85 (d, 2H)
(aromatic ring), 7.03 (d, 2H), 6.80 (d, 2H) (aromatic ring), 5.11
(t, 2H), 5.07 (t, 2H) (C5H4), 3.80 (s, 3H, OCH3), 3.79 (s, 3H,
OCH3), 2.27 (q, 2H, CH2CH3), 1.07 (t, 3H, CH2CH3). MS (EI,
70 eV): m/z 602 [M+], 518 [(M - 3CO)+], 220, 205. Anal. Calcd
for C26H23O5Re: C, 51.90, H, 3.85. Found, C, 51.82, H, 3.83.
(b) F r om a Th a lliu m Sa lt. Freshly prepared 3a (0.075 g,
0.22 mmol) dissolved in diethyl ether (1 mL) was cooled to 0
°C and treated with TlOEt (0.110 g, 0.44 mmol), and the
solution was stirred for 15 min at 0 °C before the cooling bath
was removed and the stirring maintained for another 15 min.
After removal of the solvent, the yellow solid obtained was
washed with pentane (3 mL) and BrRe(CO)5 (0.089 g, 0.22
mmol) in THF (4 mL) was added. The mixture was heated at
reflux for 4 h, and a white solid precipitated from the solution.
After filtration and removal of most of the solvent, the crude
product was chromatographed on silica gel plates using 1:9
ether/pentane as eluent to give 6 (0.049 g, 37% yield).
(vi) As described above, 2c (0.144 g, 0.30 mmol) was
irradiated for 45 min. Chromatography on silica gel plates with
1:10 ethyl ether/pentane as eluent gave 3c (0.094 g, 91%) as
1
a colorless oil. H NMR (CDCl3, 400 MHz): δ 7.13-6.69 (m, 8
H) (aromatic rings), 2.36 (m, 2H, CH2CH3), 1.92 (s, 3H, Me),
1.09 (m, 3H, CH2CH3); first isomer, 6.25 (s, 1H), 6.01 (s, 1H),
(C5H3 ring), 3.83 (s, 3H, OCH3), 3.79 (s, 3H, OCH3), 2.88 (s,
2H, CH2 of C5H4 ring); second isomer, 6.01 (s, 1H), 5.56 (s,
1H) (C5H3 ring), 3.82 (s, 3H, OCH3), 3.80 (s, 3H, OCH3), 2.61
(s, 2H, CH2 of C5H3 ring).
(vii) When 9 (0.100 g, 0.2 mmol) dissolved in technical grade
ethyl ether (10 mL) and methanol (10 mL) was irradiated for
30 min, a brown powder precipitated. The solution was filtered
through a filter funnel filled with silica gel of thickness 0.5
mm, and the solvent was subsequently removed by evapora-
tion. TLC on silica gel with 2:3 ethyl ether/pentane as eluent
gave the decomplexed steroidal cyclopentadiene 10 (0.047 g,
64%) as a colorless oil, together with recovered 9 (0.013 g). 1H
NMR (200 MHz, CDCl3): δ 7.16 (d, 1H, H1), 6.77 (m, 1H of Cp
ring), 6.65 (dd, 1H, H2), 6.58 (d, 1H, H4) 6.51 (m, 1H of Cp
ring), 6.40 (m, 1H of Cp ring), 3.15 (m, 2H of Cp ring), 2.81
(m, 2H, H6) 0.93 (s, 3H, Me13).
In fr a r ed Mea su r em en ts. In a Schlenk tube, 2a (0.110 g,
0.23 mmol) was dissolved in anhydrous THF (10 mL) and
subjected to UV irradiation. Every 20 min, a small sample of
the solution was syringed into an argon-purged infrared cell
and the spectrum quickly recorded. Two bands at 1921 and
1850 cm-1 grew in while the IR bands of the starting complex
progressively decreased. After 55 min of irradiation, the
solution was left in the tube overnight, but the intermediate
Cp′Mn(CO)2(THF) had completely decomposed without form-
ing 3a . In an identical experiment using 1:1 diethyl ether/
methanol as a solvent, two bands appeared at 1921 and 1850
cm-1; subsequently, 3a was isolated in 38% yield.
Syn t h esis of Ir on Com p lex 7. As described above, the
lithium salt 4a was prepared from 3a (0.361 g, 1.08 mmol),
recooled to -50 °C, and treated with FeCl2 (0.068 g, 0.54 mmol)
in THF (10 mL), and the mixture was heated at reflux for 1 h.
After hydrolysis with ice water, ether extraction (3 × 30 mL),
and solvent removal, the residue was chromatographed on a
silica gel column using 1:1 ethyl ether/pentane as eluent to
1
give 7 (0.390 g, 54%) as a red solid, mp 196 °C. H NMR (200
MHz, CDCl3): δ 7.07 (d, 2H), 6.85 (d, 2H) (aromatic ring), 6.94
(d, 2H), 6.76 (d, 2H) (aromatic ring), 4.05 (m, 2H), 3.80 (m,
2H) (C5H4), 3.81 (s, 3H, OCH3), 3.80 (s, 3H, OCH3), 2.59 (q,
2H, CH2CH3), 1.02 (t, 3H, CH2CH3). 13C NMR (50 MHz,
CDCl3): δ 157.8, 137.5, 137.1, 136.5, 131.1, 130.5, 113.4, 113.3
(C6H4’s; CdC), 87.8, 70. 6, 69.1 (C5H4), 55.1 (OMe), 27.9 (CH2-
CH3), 15.4 (CH2CH3). MS (EI, 70 eV): m/z 718 [M+], 387, 330,
149. Anal. Calcd for C46H46O4Fe: C, 76.88, H, 6.45. Found, C,
76.79, H, 6.43.
Syn th esis of Tu n gsten Com p lex 8. NaH (0.059 g, 1.3
mmol) (dispersion in mineral oil) was placed in a Schlenk tube
and washed with hexane, and THF (12 mL) was added. After
the mixture was cooled to 0 °C, a solution of 3a (0.031 g, 0.93
mmol) in THF (2 mL) was added dropwise; the solution became
purple after stirring for 1 h, and W(CO)6 (0.515 g, 1.47 mmol)
was added in one portion. The mixture was heated at reflux
overnight, the solution was cooled again to -20 °C, MeI (1.240
g, 8.73 mmol) was added, and the stirring was maintained for
5 h. After hydrolysis with ice water, ether extraction, and
Syn th esis of Tita n iu m Com p lex 5. Freshly prepared 3a
(0.262 g, 0.79 mmol) dissolved in THF (4 mL) was cooled to
-70 °C, and n-BuLi (0.87 mL of a 1.6 M solution in hexane,

Novel Route to Substituted Cyclopentadienes
Organometallics, Vol. 20, No. 22, 2001 4561
solvent removal, the residue was chromatographed on silica
gel plates using 1:4 ether/pentane as eluent to give 8 (0.319 g,
56%) as a colorless solid, mp 93 °C. IR (cyclohexane): νCO at
2014 (s) and 1925 cm-1 (s). 1H NMR (200 MHz, CDCl3): δ 7.11
(d, 2H), 6.87 (d, 2H) (aromatic ring), 7.03 (d, 2H), 6.81 (d, 2H)
(aromatic ring), 5.14 (t, 2H), 4.96 (t, 2H) (C5H4), 3.81(s, 3H,
OCH3), 3.80 (s, 3H, OCH3), 2.32 (q, 2H, CH2CH3), 1.05 (t, 3H,
CH2CH3). 13C NMR (50 MHz, CDCl3): δ 236.3 (CO’s), 158.5,
158.3, 136.1, 135.7, 130.4, 130.1, 114.1, 113.7 (C6H4), 142.7,
130.7 (CdC), 91.5, 89.3 (C5H4), 55.1 (OMe), 28.0 (CH2CH3),
15.0 (CH2CH3), 9.7 (W-Me). MS (EI, 70 eV): m/z 614 [M+],
529, 515 [(M - 3CO - Me)+], 484. Anal. Calcd for C27H26O5W:
C, 52.78, H, 4.27. Found, C, 52.87, H, 4.28.
Ackn owledgm en t. Financial support from the “Cen-
tre National de la Recherche Scientifique” and from the
DeBiopharm Co. is gratefully acknowledged. We also
thank a reviewer for perceptive comments.
OM010274A