Synthesis, structures, and reactivity of mono- and bis(ferrocenyl)- substituted group 14 metallocenes

Article abstract of DOI:10.1021/om0400393

New mono- and bis(ferrocenyl)-substituted germanocenes and stannocenes have been synthesized in good yield by the reaction between group 14 dichlorides (Cl₂Ge-dioxane, Cl₂Sn) and the lithium salts of the corresponding mono- and bis(cyclopentadienyl)-substituted ferrocenes. The X-ray crystal structure analyses of germanocenes 3a and 4a reveal a bent sandwich structure with an angle between the cyclopentadienyl planes of 45.4° and 40.9° for 3a and 4a, respectively. Mass spectrometry and electrochemical studies show the stabilization of the generated transient cations by ferrocenyl groups, particularly in the germanium series. Their reactions with electrophilic reagents such as catechol and cycloaddition with o-quinone also are reported and show, in the latter case, an increase of the specific reactivity of the dimethylcyclopentadienyl moiety.

Full text of DOI:10.1021/om0400393

Organometallics 2004, 23, 3147-3152
3147
Syn th esis, Str u ctu r es, a n d Rea ctivity of Mon o- a n d
Bis(fer r ocen yl)-Su bstitu ted Gr ou p 14 Meta llocen es
Mounia J oudat,† Annie Castel,*,† Fabien Delpech,† Pierre Rivie`re,*,† Ali Mcheik,†
Heinz Gornitzka,† Ste´phane Massou,‡ and Alix Sournia-Saquet§
Laboratoire d’He´te´rochimie Fondamentale et Applique´e, UMR no. 5069,
Universite´ Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Ce´dex 4, France,
Service Ge´ne´ral de RMN, Universite´ Paul Sabatier, 118 Route de Narbonne,
31062 Toulouse Ce´dex 4, France, and Laboratoire de Chimie de Coordination,
UPR no. 8241, 205 Route de Narbonne, 31077 Toulouse Ce´dex 4, France
Received March 17, 2004
New mono- and bis(ferrocenyl)-substituted germanocenes and stannocenes have been
synthesized in good yield by the reaction between group 14 dichlorides (Cl2Ge‚dioxane, Cl2-
Sn) and the lithium salts of the corresponding mono- and bis(cyclopentadienyl)-substituted
ferrocenes. The X-ray crystal structure analyses of germanocenes 3a and 4a reveal a bent
sandwich structure with an angle between the cyclopentadienyl planes of 45.4° and 40.9°
for 3a and 4a , respectively. Mass spectrometry and electrochemical studies show the
stabilization of the generated transient cations by ferrocenyl groups, particularly in the
germanium series. Their reactions with electrophilic reagents such as catechol and
cycloaddition with o-quinone also are reported and show, in the latter case, an increase of
the specific reactivity of the dimethylcyclopentadienyl moiety.
In tr od u ction
and redox ability of transition metals. The first inves-
tigations of such interactions have been concentrated
on homobimetallic compounds and especially on linked
ferrocenes.1a,c The chemistry of heterobimetallic com-
plexes with a fused ring system has been developed
rather late because of the difficulty in synthesizing such
derivatives. Indeed, the introduction of two different
metals into connected cyclopentadienyl rings, for ex-
ample, implies two selective and successive metalations
of the ligands, which are possible only in a few cases
with appropriate substituents.
Surprisingly, despite the abundant literature on this
topic, there is, to the best of our knowledge, no report
of mixed main group metal/transition metal bridged
bimetallic complexes. Indeed, examples of heterobi-
metallic complexes in which the two metals are directly
linked are quite common, but the main group element
may be best considered as a ligand.3 Interestingly, main
group metallocenes present a formal analogy with their
transition metal counterparts. This offers a unique
opportunity to switch from ferrocene as end group to
its main group element analogue and to study the
influence of such a modification. Among main group
metallocenes, group 14 species have been widely stud-
ied4 since the synthesis of the first group 14 sandwich
compound [Cp2Pb]5 was described. In contrast to transi-
tion metal metallocenes of type (η5-C5H5)2M, which
involve parallel and symmetrically bound cyclopenta-
Bimetallic and polymetallic complexes featuring un-
saturated bridging ligands between the metal centers
have been extensively investigated over the past de-
cade.1 This interest arises from the possible existence
of interactions between the metal centers allowing
potential modification of the properties of one metal
center by the intrinsic properties of the second inorganic
moiety. Indeed, such a cooperative effect is expected to
induce at times dramatic changes in structural, spec-
troscopic, chemical, and physical properties compared
to their monometallic counterparts. For example, in
stoichiometric and catalytic processes, bimetallic com-
plexes may have higher reaction rates and could lead
to transformations that do not occur with mononuclear
species.2 Their potential use as models of molecular
electronic devices has also focused much attention.
Featuring a highly delocalized π system that links the
metal fragments, they can exhibit a variety of finely
tunable behavior according mainly to the size, nature,
* Corresponding authors. E-mail: castel@chimie.ups-tlse.fr and
riviere@chimie.ups-tlse.fr.
† Laboratoire d’He´te´rochimie Fondamentale et Applique´e, UMR no.
5069.
‡ Service Ge´ne´ral de RMN, Universite´ Paul Sabatier.
§ Laboratoire de Chimie de Coordination, UPR no. 8241.
(1) (a) Barlow, S.; O’Hare, D. Chem. Rev. 1997, 97, 637. (b) Manners,
I. Angew. Chem., Int. Ed. Engl. 1996, 35, 1602. (c) McCleverty, J . A.;
Ward, M. D. Acc. Chem. Res. 1998, 31, 842. (d) Heo, R. W.; Lee, T. R.
J . Organomet. Chem. 1999, 578, 31. (e) Nguyen, P.; Gomez-Elipe, P.;
Manners, I. Chem. Rev. 1999, 99, 1515. (f) Launey, J . P. Chem. Soc.
Rev. 2001, 30, 386.
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Organic Germanium, Tin and Lead Compounds; Rappoport, Z., Eds.;
Wiley: Chichester, UK, 2002; Vol. 2, p 1241.
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J . Organomet. Chem. 1990, 400, 1. (c) J utzi, P. In The Chemistry of
Organic Silicon Compounds; Patai, S., Rappoport, Z., Apeloig, Y., Eds.;
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Chem. Rev. 1999, 99, 969.
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A.; Lahoz, F. J .; Werner, H.; Oro, L. A. Organometallics 1998, 17, 683.
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Bisello, A.; Crociani, L.; Gambaro, A.; Ganis, P.; Manoli, F.; Sante, S.;
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10.1021/om0400393 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 05/18/2004

3148 Organometallics, Vol. 23, No. 13, 2004
J oudat et al.
dienyl ligands, the main group analogues show a
bewildering variety of bonding arrangements. Their
typical bent structure and the structural role of their
metal valence electrons are still subjects of controversy.6
Their chemical and electrochemical properties also have
been shown to be totally different, as evidenced by an
irreversible one-electron oxidation process for group 14
metallocenes. We have recently extended this analogy
between the two families of metallocenes with the
preparation of the p-phenylene- and p-biphenylene-
bridged germanocenes and stannocenes,7 which are the
group 14 analogues of dimetallocenes.
As a part of our continuing attempts to expand the
chemistry of group 14 polymetallic complexes, we have
initiated a study on a series of ferrocenyl-substituted
germanocenes and stannocenes, anticipating that such
association will result in unusual structural and chemi-
cal properties. Indeed, ferrocene, which is well-known
for its electron-donor character,8 possibly would provide
additional stabilization to the germanocenyl or stanno-
cenyl moiety for both the neutral form and the oxidized
state. Additionally, its presence might improve the
electronic interaction particularly since the bridging
ligand (fulvalene) was chosen taking into account that
it allows strong coupling between metal centers. This
work describes the preparation, the full characterization
including crystal structure determinations, and the
voltammetric study of the first mixed (group 14-transi-
tion group elements) heterodimetallocenes. Some reac-
tivity tests will be presented in order to provide insights
of the chemical behavior of these species.
F igu r e 1. Crystal structure of 3a at the 50% probability
level for the thermal ellipsoids. Selected bond lengths (Å)
and angles (deg): Ge(1)-C(1) 2.343(9), Ge(1)-C(2) 2.399-
(8), C(5)-C(8) 1.443(10), C(1)-C(5)-C(8) 126.2(8), C(5)-
C(8)-C(12) 124.9(8).
F igu r e 2. Crystal structure of 4a at the 50% probability
level for the thermal ellipsoids. Selected bond lengths (Å)
and angles (deg): Ge(1)-C(1) 2.458(2), Ge(1)-C(5) 2.382-
(2), Ge(1)-C(13) 2.420(2), Ge(1)-C(14) 2.355(2), C(1)-C(8)
1.464(3), C(2)-C(1)-C(8) 126.5(2), C(17)-C(13)-C(20) 126.1-
(2).
Resu lts a n d Discu ssion
Syn th eses a n d Str u ctu r es. Compounds 3 and 4
were formed as red or orange solids in good yield (68-
86%) by nucleophilic substitution reactions on Cl2Ge‚
dioxane or Cl2Sn by the corresponding lithiated ligands
in THF at low temperature (eq 1 and 2).
No trace of polymeric products was observed. The
ligand 2, as might be expected, acts as a chelate, leading
to the more stable form 4. Compounds 3 and 4 are stable
under an inert atmosphere at room temperature but
may be stored at low temperature (-30 °C). They are
soluble in common organic solvents such as THF,
toluene, diethyl ether, and dichloromethane. The ferro-
cenyl germanocenes 3a and especially 4a are the most
stable in solution, and crystals suitable for single-crystal
analysis were obtained from a toluene solution at -30
°C within several days. The structures, determined by
single-crystal X-ray diffraction, are shown in Figures 1
and 2 with selected bond lengths and angles. The two
germanocenes have the typical bent structure4a,d of
group 14 metallocenes with angles between the dim-
ethylcyclopentadienyl planes of 45.4° for 3a and 40.9°
for 4a . These values are comparable to those observed
in bridged digermanocenes7a (40°) and in germanocene9
itself (50.4°). Moreover, these deviations are similar
whatever the geometry of the complexes is, i.e., trans
conformation in 3a or chelated form in 4a . The germa-
nium atoms do not reside between the dimethylcyclo-
pentadienyl ring centers but are slightly displaced
toward the carbon atoms C(1) and C(2) (for 3a ) and C(1)
(6) (a) Beswick, M. A.; Palmer, J . S.; Wright, D. S. Chem. Soc. Rev.
1998, 27, 225. (b) Smith, J . D.; Hanusa, T. P. Organometallics 2001,
20, 3056. (c) Rayon, V. M.; Frenking, G. Chem. Eur. J . 2002, 8, 4693.
(d) Budzelaar, P. H. M.; Engelberts J . J .; van Lenthe, J . H. Organo-
metallics 2003, 22, 1562.
(7) (a) Rouzaud, J .; Castel, A.; Rivie`re, P.; Gornitzka, H.; Manriquez,
J . M. Organometallics 2000, 19, 4678. (b) Rouzaud, J .; J oudat, M.;
Castel, A.; Delpech, F.; Rivie`re, P.; Gornitzka, H.; Manriquez, J . M.;
Chavez, I. J . Organomet. Chem. 2002, 651, 44.
(8) Calabrese, J . C.; Cheng, L. T.; Green, J . C.; Marder, S. R.; Tam,
W. J . Am. Chem. Soc. 1991, 113, 7227.
(9) Grenz, M.; Hahn, E.; du Mont, W. W.; Pickardt, J . Angew. Chem.,
Int. Ed. Engl. 1984, 23, 61.

Ferrocenyl-Substituted Group 14 Metallocenes
Organometallics, Vol. 23, No. 13, 2004 3149
F igu r e 3. Cyclic voltammograms of compounds 3a and 1 (bold) (10-3 M) in THF under argon atmosphere measured at
platinum disk (r ) 0.5 mm) at room temperature. Scan rate 0.1 V/s, supporting electrolyte NBu4NBF4 (0.1 M). Potentials
referenced to ECS electrode.
and C(5) (for 4a ). Another interesting structural feature
is the torsion angle between adjacent cyclopentadienyl
and dimethylcyclopentadienyl rings. For 3a , which
exists in a transoid conformation, a quasi coplanar
system is observed for the fulvalenide moiety with
dihedral angles C(9)-C(8)-C(5)-C(1) of -1.1° and
C(12)-C(8)-C(5)-C(4) of -9.1°. In contrast, 4a exhibits
a clear deviation with dihedral angles C(2)-C(1)-C(8)-
C(12) of 21.9° and C(5)-C(1)-C(8)-C(9) of 21.7°. These
values are similar to those reported for the ligand 210
(23.5° and 26.1°) and for Fc(η5-C5Me4)2Fe11 (20°), show-
ing that this deviation probably results from the steric
hindrance of the methyl groups rather than from
structural deformation induced by the germanium atom.
The 1H and 13C NMR spectra of 3 and 4 are consistent
with a dimetallocene structure. The equivalence of CH3
and CH groups of the dimethylcyclopentadienyl groups
indicates π-linked structures. As expected, the two
proton pairs H(2′), H(5′) and H(3′), H(4′) of the ferrocenyl
moiety are nonequivalent, and a complete assignment
was obtained from homonuclear (COSY) and hetero-
nuclear experiments (HSQC and HMBC). In addition,
the 119Sn NMR spectra exhibit a high-field resonance
(δ ) -2071 ppm for 3b and δ ) 2017 ppm for 4b) in
the typical region for stannocenes,4a confirming their
π-linked structures. Interestingly, in contrast to group
14 metallocenes and dimetallocenes, molecular ions with
the expected isotopic pattern were observed for 3a , 4a ,
and 4b, respectively, at m/z 628, 442, and 488, respec-
tively, suggesting a stabilization of the cationic forms
by the ferrocenyl groups. The [FcC5H2Me2M]+ fragments
(M ) Ge, m/z 351; M ) Sn, m/z 397) characteristic of
the group 14 metallocenes4b also were observed.
that contain two equivalent redox centers, the ∆E
separation between the two redox events is indicative
of the degree of interaction. In the case of heterobi-
metallic complexes, the ∆E value that is of importance
to evaluate interaction is the difference between the
redox potential of one metal of the heterobimetallic
species and the redox potential of the corresponding
monometallic compound.12 Cyclic voltammetry (in THF
with [Bu4N]BF4 as supporting electrolyte) of 3a (Figure
3) reveals an irreversible oxidation peak at 406 mV (vs
SCE) similar to that obtained for decamethylger-
manocenes under the same experimental conditions.13
The second quasi reversible anodic process was at-
tributed to the concomitant oxidation of the two ferro-
cenyl groups. Linear voltammetry confirms this assign-
ment: the Fe(III)/Fe(II) wave is about twice as large as
the one-electron oxidation wave of the germanocene
group. The difference between this last oxidation peak
(740 mV) and that obtained for the ligand 1 (646 mV)
seems to indicate some degree of interaction between
the ferrocenyl groups and the germanocene moiety.
Comparable results were obtained for the stannocene
3b (425 and 724 mV for the oxidation peaks), but some
decomposition appeared after 20 min. Surprisingly, 4a
presents a completely different behavior. Although the
first oxidation peak of the germanocene group is ob-
served at 303 mV, we have an irreversible redox event
at 530 mV from the ferrocenyl group. Even if the origin
of this phenomenon still remains uncertain, such ir-
reversibility for a ferrocenyl moiety is not unprecedented
and has already been observed for a diferrocenyl-
titanium complex.14 Interestingly, the oxidation poten-
tial of germanocene occurs at lower potential than that
of 3a (∆E ) 103 mV). Such lowering of the first
Electr och em ica l Stu d y of Com p lexes 3a ,b a n d
4a . Cyclic voltammetry is a useful tool to investigate
metal-metal interactions. In homobimetallic systems
(12) Begley, M. G.; Mountford, P.; Stewart, P. J .; Swallow, D.; Wan,
S. J . Chem. Soc., Dalton Trans. 1996, 1323.
(13) J utzi, P.; Holtmann, U.; Kanne, D.; Kru¨ger, C.; Blom, R.;
Glester, R.; Hyla-Kryspin, I. Chem. Ber. 1989, 122, 1629.
(14) Kotz, J . C.; Vining, W.; Coco, W.; Rosen, R.; Diad, A. R.; Garcia,
M. H. Organometallics 1983, 2, 68.
(10) Plenio, H. Organometallics 1992, 11, 1856.
(11) Scott, P.; Rief, U.; Diebold, J .; Brintzinger, H. H. Organome-
tallics 1993, 12, 3094.

3150 Organometallics, Vol. 23, No. 13, 2004
J oudat et al.
oxidation potential is comparable to that observed in
the iron series with bis(fulvalene)diiron and biferro-
cene.1a,15 This indicates, in agreement with the mass
spectral results, a greater stabilization of the cation in
the di(fulvanide) structure and also provides evidence
for a significant interaction between the two metal
centers. Thus, although the redox event is irreversible
for the germanocene moiety, the presence of the ferro-
cenyl group induces significant changes in the redox
properties of the germanium fragment.
Rea ction s w ith 3,5-Di-ter t-bu tylca tech ol a n d 3,5-
Di-ter t-bu tyl-or th o-qu in on e. As shown in the electro-
chemical study, modifications of the typical reducing or
nucleophilic properties (for example, enhanced for 4a )
compared to those of the corresponding group 14 met-
allocenes may be expected. Therefore, we decided to
carry out some typical reactivity tests in order to obtain
some insight into the potential changes in the chemical
reactivity. We first tried a typical electrophilic attack16
by a protic reagent. Treatment of 3 and 4 with 3,5-di-
tert-butylcatechol effectively gave the ligand 1 or 2 and
the corresponding cyclic divalent species 517 and 67b (eq
3). However for 4a , the cleavage is more difficult, only
a 50% conversion was obtained after 12 h at room
temperature, while, under the same conditions, com-
plete reaction occurred with the other complexes. This
result probably is due to the chelating structure, which
hinders the cleavage of the germanium-(dimethylcyclo-
pentadienyl) π-bonds.
donating group such as ferrocene, favoring Diels-Alder
heterocyclization18 and consequently the formation of
7 and 8. Recently, we have performed the direct cyclo-
addition reaction of ligands 1 with the same ortho-
quinone, thus providing evidence for its feasibility.19
These reactions occur on the more substituted double
bond of the dimethylcyclopentadienyl group, leading to
the exclusive formation of one isomeric form, the endo-
product on the basis of an X-ray diffraction study.
Ligand 2 similarly reacted with ortho-quinone in THF
solution at room temperature, giving selectively cyclo-
adduct 8, which was identified as the endo-isomer on
1
the basis of the H and 13C spectra (eq 5).
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were carried out
under a dry nitrogen atmosphere using standard Schlenk
techniques and dry solvents. 1D NMR spectra were recorded
on Bruker AC 80 (80.13 MHz) and ARX 400 (400.13 MHz) (1H),
AC 200 (50.32 MHz) and ARX (100.62 MHz) (13C), and ARX
400 (111.93 MHz) (119Sn). All 2D NMR spectra (COSY, cor-
relation spectroscopy; HSQC, heteronuclear single quantum
correlation; HMBC, heteronuclear multiple bound correlation)
were acquired at 298 K on a Bruker ARX-400 spectrometer
equipped with an inverse 1H/broadband z gradient probe. To
perform these experiments, standard pulse sequences of the
Bruker library were used. Data were processed on a SGI O2
workstation using Bruker Xwinnmr 2.1 software. Mass spectra
were measured with a Hewlett-Packard HP 5989A in the
electron impact mode (70 eV) or a Rybermag R10-10 spec-
trometer operating in the electron impact mode or by chemical
desorption (DCI, CH4). Voltammetric measurements were
carried out with a homemade potentiostat20 using the interrupt
method to minimize the uncompensated resistance (iR) drop.
Experiments were performed at room temperature in an
airtight three-electrode cell connected to a vacuum/argon line.
The reference electrode consisted of a saturated calomel
electrode (SCE) separated from the solution by a bridge
compartment. The counter electrode was a platinum wire of
ca. 1 cm3 apparent surface. The working electrode was a Pt
electrode (diameter ) 1 mm). The supporting electrolyte
[n-Bu4N]BF4 (Fluka, electrochemical grade) was dried under
vacuum for 1 h. THF was distilled over sodium prior use. The
To verify the presence of divalent germanium sites
in these complexes, we performed an oxidative cyclo-
addition reaction with 3,5-di-tert-butyl-ortho-quinone17
(eq 4). Treatment of 3a or 4a with an excess of ortho-
quinone at room temperature in THF led to immediate
disappearance of the green color of ortho-quinone.
Instead of the expected germanium(IV) cycloadduct, we
observed the formation of 5, suggesting a cycloaddition
with elemental germanium. Concurrent competitive
heterocycloaddition with ligands 1 and 2 occurred,
giving, respectively, 7 and 8.
(15) (a) Morrison, W. H.; Krogsrud, S.; Hendrickson, D. N. Inorg.
Chem. 1973, 12, 1998. (b) Levanda, C.; Bechgaard, K.; Cowan, D. O.
J . Org. Chem. 1976, 41, 2700.
(16) J utzi, P.; Hampel, B. Organometallics 1986, 5, 730.
(17) Rivie`re, P.; Castel, A.; Satge´, J .; Guyot, D. J . Organomet. Chem.
1986, 315, 157.
(18) (a) Findel, K. T. In The Chemistry of the Quinonic Compounds;
Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1988; Vol. II, p 537.
(b) Desimoni, G.; Tacconi, G. Chem. Rev. 1975, 75, 651. (c) Nair, V.;
Kumar, S. J . Chem. Soc., Perkin Trans. 1996, 1, 443.
(19) J oudat, M.; Rouzaud, J .; Castel, A.; Delpech, F.; Rivie`re, P.;
Gornitzka, H.; Massou, S. Inorg. Chem. Acta 2004, 357, 259.
(20) Cassoux, P.; Dartiguepeyron, R.; de Montauzon, D.; Tommasino,
J . B.; Fabre, P. L. Actual. Chim. 1994, 1, 49.
This result may be interpreted as an increase of the
dienic reactivity of the C5H3Me2 system by an electron-

Ferrocenyl-Substituted Group 14 Metallocenes
Organometallics, Vol. 23, No. 13, 2004 3151
solutions used during the electrochemical studies were typi-
cally 10-3 M in the studied compound and 0.1 M in supporting
electrolyte. Cyclic voltammetry was performed in the potential
range of -2 to 2 versus SCE at 0.1 V/s. Before each measure-
ment, the working electrode was polished with Emery paper
(Norton A621). A quasi steady state behavior is obtained by
linear voltammetry at 5 mV/s. All reported potentials in the
present paper are referred to a SCE electrode. Melting points
(CDCl3,100.6 MHz) δ 12.48 (CH3-C(3) and CH3-C(4), J (C-
117/119Sn) ) 15.5 Hz), 66.07 (C(3′) and C(4′)), 67.79 (C(2′) and
C(5′)), 83.53 (C(1′), J (C-117/119Sn) ) 13.8 Hz), 108.55 (C(1),
J (C-117/119Sn) ) 41.2 Hz), 109.54 (C(2) and C(5)), 124.03 (C(3)
and C(4), J (C-117/119Sn) ) 40.2 Hz); 119Sn NMR (CDCl3, 111.9
MHz) -2017 ppm; MS/EI [M]•+ m/z 488 (100%). Anal. Calcd
for C24H24SnFe: C, 59.19; H, 4.97. Found: C, 58.57; H, 4.51.
Cr ysta l Da ta for 3a a n d 4a . 3a : C34H34Fe2Ge, M ) 626.90,
monoclinic, C2, a ) 21.280(4) Å, b ) 6.167(1) Å, c ) 12.005(3)
Å, â ) 120.017(4)°, V ) 1364.0(5) Å3, Z ) 2, T ) 193(2) K.
3219 reflections (2058 independent, Rint ) 0.0459) were
collected. Largest electron density residue: 0.758 e Å-3, R1 (for
were measured on
a Leitz microscope or Electrothermal
apparatus (capillary). Elemental analyses were performed by
the Centre de Microanalyse de l’Ecole Nationale Supe´rieure
des Inge´nieurs en Arts Chimiques Et Technologiques. The
starting materials, the mono- and bis(cyclopentadienyl)-
substituted ferrocenes, 1 and 2,10,11 and Cl2Ge‚dioxane21 were
prepared according to the previously reported procedure.
P r ep a r a tion of 3a . n-Butyllithium (1.19 mmol) (1.6 M
solution in hexane) was added to a stirred solution of 1 (0.30
g, 1.08 mmol) in THF (5 mL) at -78 °C. The mixture was
warmed to room temperature and stirred for 30 min. Then, a
solution of Cl2Ge‚dioxane (0.13 g, 0.54 mmol) in THF (3 mL)
was added at -78 °C. The temperature was slowly raised to
room temperature, and the mixture was stirred for 2 h. The
solvents were removed under reduced pressure, and the
residual solid was extracted with toluene. The extracts were
filtered and concentrated, giving an orange powder of 3a (0.26
g, 78%). Crystallization from toluene at -30 °C gave orange
I > 2σ(I)) ) 0.0539 and wR2 ) 0.1156 (all data) with R1
)
∑||Fo| - |Fc||/∑|Fo| and wR2 ) (∑w(Fo - Fc2)2/∑w(Fo2)2)0.5. 4a :
2
C
24H24FeGe, M ) 440.87, monoclinic, C2/c, a ) 20.119(1) Å, b
) 21.3232(1) Å, c ) 18.009(1) Å, â ) 90.338(1)°, V ) 7725.8(9)
Å3, Z ) 16, T ) 193(2) K. 23 319 reflections (8429 independent,
Rint ) 0.0251) were collected. Largest electron density resi-
due: 0.364 e Å-3, R1 (for I > 2σ(I)) ) 0.0286 and wR2 ) 0.0747
(all data). All data for both structures were collected at low
temperatures using an oil-coated shock-cooled crystal on a
Bruker-AXS CCD 1000 diffractometer with Mo KR radiation
(λ ) 0.71073 Å). The structure was resolved by direct methods
(SHELXS-97),22 and all non hydrogen atoms were refined
anisotropically using the least-squares method on F2.23 The
files CCDC 238502 (3a ) and CCDC 238503 (4a ) contain the
supplementary crystallographic data for this paper. These data
can be obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the CCDC, 12 Union Road, Cambridge
CB21EZ,UK;fax: +441223336033;e-mail: deposit@ccdc.cam.ac.uk).
Rea ction of 3 a n d 4 w ith 3,5-Di-ter t-bu tylca tech ol. A
solution of the catechol (0.06 g, 0.27 mmol) in 2 mL of THF
was added to 3a (0.17 g, 0.27 mmol) in 5 mL of THF. The
solution was stirred for 12 h at room temperature, and the
volatile solvents were removed in vacuo. Analysis of the
residue by 1H NMR spectroscopy showed the formation of 5
(28%) and 1 (72%), confirmed by mass spectrometry (5, m/z
294; 1, m/z 278). A similar procedure was used for the other
complexes, and the results are as follows: 3b: 6 (37%), 1
(63%); 4a : 4a residual (52%), 5 (24%), 2 (24%); 4b: 6 (53%),
2 (47%).
1
crystals suitable for X-ray analysis: mp 190 °C dec; H NMR
(CDCl3, 400 MHz) δ 1.98 (s, 12H, CH3-C(3) and CH3-C(4)), 4.05
(s, 10H, C5H5), 4.18 (m, 4H, C(3′)-H and C(4′)-H), 4.30 (m, 4H,
C(2′)-H and C(5′)-H), 5.76 (s, 4H, C(2)-H and C(5)-H); 13C{1}
NMR (CDCl3,100.6 MHz) δ 12.41 (CH3-C(3) and CH3-C(4)),
66.14 (C(3′) and C(4′)), 67.71 (C(2′) and C(5′)), 69.65 (C5H5),
82.23 C(1′), 108.35 (C(2) and C(5)), 122.20 C(1), 123.32 (C(3)
and C(4)); MS/EI [M]•+ m/z 628 (2%). Anal. Calcd for C34H34
-
GeFe2: C, 65.14; H, 5.47. Found: C, 64.72; H, 5.17.
P r ep a r a tion of 3b. A similar procedure was used. 1 (0.29
g, 1.05 mmol) and Cl2Sn (0.10 g, 0.53 mmol) gave an orange
1
powder: 0.23 g (68%), mp 150 °C dec; H NMR (CDCl3, 400
MHz) δ 2.02 (s, 12H, CH3-C(3) and CH3-C(4)), 4.03 (s, 10H,
C5H5), 4.16 (m, 4H, C(3′)-H and C(4′)-H), 4.29 (m, 4H, C(2′)-H
and C(5′)-H), 5.82 (s, 4H, C(2)-H and C(5)-H); 13C{1} NMR
(CDCl3, 100.6 MHz) δ 12.49 (CH3-C(3) and CH3-C(4)), 65.98
(C(3′) and C(4′)), 67.55 (C(2′) and C(5′)), 69.68 (C5H5), 82.80
C(1′), 106.87 (C(2) and C(5)), 120.62 C(1), 121.97 (C(3) and
C(4)); 119Sn NMR (CDCl3, 111.9 MHz) -2071 ppm; MS/EI
[FcC5H2Me2Sn]•+ m/z 397 (6%). Anal. Calcd for C34H34SnFe2:
C, 60.68; H, 5.09. Found: C, 60.04; H, 4.65.
Rea ction of 3a a n d 4a w ith 3,5-Di-ter t-bu tyl-or th o-
qu in on e. A solution of the ortho-quinone (0.05 g, 0.25 mmol)
in 2 mL of THF was added to 3a (0.06 g, 0.10 mmol) in 3 mL
of THF. The solution was stirred for 6 h at room temperature,
and the volatile solvents were removed in vacuo. Analysis of
1
the residue by H NMR spectroscopy showed the formation of
P r ep a r a tion of 4a . A solution of n-butyllithium (1.57
mmol) in hexane (1.6 M) was added to a solution of 2 (0.26 g,
0.70 mmol) in THF (5 mL) at -78 °C. The mixture was warmed
to room temperature and stirred for 12 h. Then, a solution of
Cl2Ge‚dioxane (0.16 g, 0.70 mmol) in THF (6 mL) was added
at -78 °C. A procedure similar to the synthesis of 3a was used,
giving a dark red powder, 4a (0.27 g, 86%). Crystallization
from toluene at -30 °C gave dark red crystals; mp 200 °C dec;
1H NMR (CDCl3, 400 MHz) δ 2.12 (s, 12H, CH3-C(3) and CH3-
C(4)), 4.08 (m, 4H, C(3′)-H and C(4′)-H), 4.22 (m, 4H, C(2′)-H
and C(5′)-H), 5.33 (s, 4H, C(2)-H and C(5)-H); 13C{1} NMR
(CDCl3, 100.6 MHz) δ 12.45 (CH3-C(3) and CH3-C(4)), 66.19
(C(3′) and C(4′)), 68.05 (C(2′) and C(5′)), 82.84 C(1′), 108.60
(C(2) and C(5)), 110.98 C(1), 125.30 (C(3) and C(4)); MS/EI
[M]•+ m/z 442 (100%). Anal. Calcd for C24H24GeFe: C, 65.38;
H, 5.49. Found: C, 65.01; H, 5.46.
5 (15%) and cycloadduct 7 (60%), confirmed by mass spec-
trometry (5, m/z 294). A similar procedure was used for 4a ,
and the result is as follows: 5 (52%), cycloadduct 8 (24%).
P r ep a r a tion of 8. To a solution of 2 (0.20 g, 0.54 mmol) in
4 mL of THF was added a solution of ortho-quinone (0.24 g,
1.08 mmol) in 5 mL of THF. The mixture was stirred at 20 °C
overnight. The solvent was evaporated and the residue washed
with pentane. After filtration and drying, 0.15 g (34%) of 8
was obtained as an orange powder: mp 233 °C; 1H NMR
(CDCl3, 200 MHz) δ 1.21 (s, 18H, t-Bu), 1.44 (s, 18H, t-Bu),
2
1.41 (s, 12H, CH3-C(3) and CH3-C(4)), 2.32 (dd, J ) 15.7 Hz,
2
4
4J ) 2.0 Hz, 2H, C(5)-H), 2.72 (dd, J ) 15.7 Hz, J ) 1.2 Hz,
2H, C(5)-H), 4.10 (m, 8H, C5H4), 5.66 (sl, 2H, C(2)-H), 6.72 (d,
4
4J ) 2.3 Hz, 2H, C(10)-H), 6.82 (d, J ) 2.3 Hz, 2H, C(8)-H);
13C {1} NMR (CDCl3,100.6 MHz) δ 20.34 (CH3-C(3)), 23.05
(CH3-C(4)), 30.02, ((CH3)3C-C(7)), 31.68 ((CH3)3C-C(9)), 34.40
((CH3)3C-C(9)), 35.04 ((CH3)3C-C(7)), 45.58 C(5), 66.87, 69.37
(C(3′) and C(4′), 69.88, 70.47 (C(2′) and C(5′)), 80.69 C(1′), 84.48
C(4), 86.51 C(3), 111.78 C(10), 114.76 C(8), 126.54 C(2), 137.55
C(7), 140.90 (C(1) and C(6)), 142.86 C(9), 144.40 C(11); MS/EI
P r ep a r a tion of 4b. Stannocene 4b was synthesized using
a similar procedure (0.39 g (1.05 mmol) of 2 and 0.20 g (1.05
mmol) of Cl2Sn), yielding an orange powder: 0.38 g (75%); mp
180 °C dec; 1H NMR (CDCl3) δ 2.09 (s, 12H, CH3-C(3) and CH3-
C(4)), 4.01 (m, 4H, C(3′)-H and C(4′)-H), 4.13 (m, 4H, C(2′)-H
and C(5′)-H), 5.47 (s, 4H, C(2)-H and C(5)-H); 13C{1} NMR
(22) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473.
(23) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; University of Go¨ttingen, 1997.
(21) Mironov, V. F.; Gar, T. K. Kh. Obshch. Khim. 1975, 45, 103.

3152 Organometallics, Vol. 23, No. 13, 2004
J oudat et al.
[M]•+ m/z 810 (6%). Anal. Calcd for C52H66FeO4: C, 77.02; H,
8.20. Found: C, 76.44; H, 8.03.
Su p p or tin g In for m a tion Ava ila ble: Tables and figures
giving details of the electrochemical study and of the X-ray
structure determination, atomic coordinates, and bond dis-
tances and angles for 3a and 4a . This material is available
free of charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. The authors thank the Comite´
mixte Interuniversitaire Marocain (Action Inte´gre´e
Franco-Marocaine no. 216/SM/00) for partial financial
support.
OM0400393