Ferrocenediyl-bridged triiron complexes

Article abstract of DOI:10.1021/om0008528

The reaction of 2 equiv of CpFe(CO)₂I and 1,1′-dilithioferrocene in the presence of 2 equiv of PPh₃ is an intermolecular version of the reaction of CpFe(CO)₂I and (η⁵-C₅H₄Li)Fe (C₅H₄PPh₂). In the three-component procedure, the PPh₃ substitution for iodide on CpFe(CO)₂I is much faster than the nucleophilic Fc-addition at the Fe-center or at a CO ligand of CpFe(CO)₂I. This one-pot reaction proceeds through [CpFe(CO)₂PPh₃⁺] and yields CpFe(CO)(PPh₃)- [μ,C:η⁵-C(O)C₅H₄ ]Fe[μ,η⁵:η⁴-5-exo- (1′-C₅H₄)C₅H₅]Fe (CO)₂(PPh₃) (4) in 50% yield, with the 1,1′-dilithioferrocene participating twice in the nucleophilic Fc-additions: at the Cp-ring and at a CO ligand of [CpFe(CO)₂PPh₃⁺]. Complex 4 is a ferrocenediyl-bridged tri-Fe complex with three different Fe-centers: a metallocene Fe(II), a square-pyramidal pentacoordinate Fe(O), and a half-sandwich acyl-Fe(II). It has been found that, in the second Fc-additions, the pathway from (η⁵-C₅H₄Li)Fe[μ,η⁵: C-C₅H₄C(O)]FeCp(CO)(PPh₃) (9) to 4 proceeds normally, but the pathway from 9 to Fe[(μ,η⁵: C-C₅H₄)C(O)FeCp(CO)(PPh₃)]₂ (5) has been turned off. The preference of Fc-addition of 9 onto the Cp-ring of [CpFe(CO)₂PPh₃⁺] could be reasoned by a localization of the Li⁺ cation in 9.

Full text of DOI:10.1021/om0008528

2198
Organometallics 2001, 20, 2198-2206
F er r ocen ed iyl-Br id ged Tr iir on Com p lexes†
Lung-Shiang Luh,‡ Yuh-Sheng Wen,‡,§ Gyorgy Vanko,| and Ling-Kang Liu*,‡,§
Institute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, Republic of China,
Department of Chemistry, National Taiwan University,
Taipei, Taiwan 10607, Republic of China, and Department of Nuclear Chemistry,
Eotvos Lorand University, H-1518 Budapest 112, Hungary
Received October 4, 2000
The reaction of 2 equiv of CpFe(CO)2I and 1,1′-dilithioferrocene in the presence of 2 equiv
of PPh3 is an intermolecular version of the reaction of CpFe(CO)2I and (η5-C5H4Li)Fe(C5H4-
PPh2). In the three-component procedure, the PPh3 substitution for iodide on CpFe(CO)2I is
much faster than the nucleophilic Fc-addition at the Fe-center or at a CO ligand of CpFe-
(CO)2I. This one-pot reaction proceeds through [CpFe(CO)2PPh3+] and yields CpFe(CO)(PPh3)-
[µ,C:η5-C(O)C5H4]Fe[µ,η5:η4-5-exo-(1′-C5H4)C5H5]Fe(CO)2(PPh3) (4) in 50% yield, with the 1,1′-
dilithioferrocene participating twice in the nucleophilic Fc-additions: at the Cp-ring and at
a CO ligand of [CpFe(CO)2PPh3+]. Complex 4 is a ferrocenediyl-bridged tri-Fe complex with
three different Fe-centers: a metallocene Fe(II), a square-pyramidal pentacoordinate Fe(0),
and a half-sandwich acyl-Fe(II). It has been found that, in the second Fc-additions, the
pathway from (η5-C5H4Li)Fe[µ,η5:C-C5H4C(O)]FeCp(CO)(PPh3) (9) to 4 proceeds normally,
but the pathway from 9 to Fe[(µ,η5:C-C5H4)C(O)FeCp(CO)(PPh3)]2 (5) has been turned off.
The preference of Fc-addition for 9 onto the Cp-ring of [CpFe(CO)2PPh3+] could be reasoned
by a localization of the Li+ cation in 9.
In tr od u ction
(η5-C5H4Li)Fe(C5H4PPh2), with a pendant PPh2 ligand
on the other Cp-ring.6 When followed by a reaction with
an electrophile, CpFe(CO)2I, the reaction produces Cp-
Fe(CO)2(µ,η1:η5-C5H4)Fe(η5-C5H4PPh2), CpFe(CO)[µ,C:
η5-C(O)C5H4]Fe(µ,η5:P-C5H4PPh2), and CpFe(CO)(µ,η1:
η5-C5H4)Fe(µ,η5:P-C5H4PPh2).7 This reaction involves
the nucleophilic Fc-addition at the Fe-center of CpFe-
(CO)2I, with migratory insertion and CO de-insertion
at later stages to yield products in series (Scheme 1).8
As a comparative study, it would be of interest to
examine the reaction of 2 equiv of CpFe(CO)2I and 1,1′-
dilithioferrocene in the presence of 2 equiv of PPh3 in
detail. This reaction is an intermolecular version of the
above reaction between CpFe(CO)2I and (η5-C5H4Li)Fe-
(C5H4PPh2). As we report here, we have found that
under three-component conditions, the substitution of
the iodide of CpFe(CO)2I by PPh3 is much faster than
nucleophilic Fc-addition at the Fe-center or at a CO
ligand of CpFe(CO)2I. The reaction proceeds through an
intermediate, [CpFe(CO)2PPh3+], and results in the
interesting ferrocenediyl-bridged tri-Fe complex CpFe-
(CO)(PPh3)[µ,C:η5-C(O)C5H4]Fe[µ,η5:η4-5-exo-(1′-C5H4)-
C5H5]Fe(CO)2(PPh3) in 50% yield, with the 1,1′-dilithio-
ferrocene participating twice in the nucleophilic Fc-
additions: at the Cp-ring and at a CO ligand of
[CpFe(CO)2PPh3+].
Since its discovery half a century ago,1 ferrocene, an
electron-rich molecule, has displayed a variety of in-
triguing physical and chemical properties. Complexes
with a ferrocenyl group (Fc) directly bonded to a metal
are known, among which lithioferrocenes provide key
intermediates for further elaboration.2 The reaction
between metal halides and FcLi,3 the ferrocenyl transfer
from Fc2Hg,4 and the thermal or photoinduced decar-
bonylation of ferrocenoyl complexes5 are inter alia useful
methods for the preparation of ferrocenyl derivatives.
The ring-opening reaction of PhP(η5-C5H4)2Fe with
PhLi provides a monoanionic ferrocenediyl nucleophile,
† Dedicated to the memory of Prof. Kalman Burger.
‡ Academia Sinica.
§ National Taiwan University.
| Eotvos Lorand University.
(1) Rosenblum, M. Chemistry of the Iron Group Metallocenes;
Wiley: New York, 1965.
(2) Wright, M. E. Organometallics 1990, 9, 853 and references
therein.
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1989, 28, 2347. (b) Nesmeyanov, A. N.; Perevalova, E. G.; Grandberg,
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(8) The pathway for the replacement of the dangling PPh2 for iodide
in (η5-C5H5)Fe(CO)2I followed by the anionic carbon addition onto one
of the CO ligands could not be ruled out. In this pathway, the secondary
reactions are the CO de-insertion to liberate phosphine or CO.
10.1021/om0008528 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 05/03/2001

Ferrocenediyl-Bridged Triiron Complexes
Organometallics, Vol. 20, No. 11, 2001 2199
Sch em e 1
2H; δ 3.87, 2H) and one Cp resonance (δ 4.01, 5H). The
two IR νCO absorption bands at 1967 and 1908 cm-1 of
equal intensity and one 31P NMR peak at δ 74.1 are
consistent with those of other similar η4-Fe complexes.9
Hence, the molecular skeleton of 1 is readily deduced
to be a Fc-group connected to the methine carbon of a
5-exo-substituted cyclopentadiene which is η4-bonded to
Fe(CO)2(PPh3). On the other hand, the IR νCO absorption
bands at 1915 (carbonyl CO) and 1583 (keto CO) cm-1
and one 31P NMR peak at δ 76.4 for complex 2 are
typical of an iron-acyl complex, CpFe(CO)C(O)R-
(PPh3).10 The Fe-atom is chiral. As apparent from the
1H and 13C NMR spectra, complex 2 has four proton
signals (δ 4.16, 4.20, 4.34, 4.55) and four carbons signals
(δ 68.3, 68.6, 68.8, 69.7) for the substituted cyclopen-
tadienyl ring protons and the C2-C5 carbon atoms,
1
indicative of their magnetic nonequivalence. In the H
spectrum, there are two Cp resonances (δ 3.97, 4.43, 5H
× 2) for 2.
In our earlier studies, the presence of PPh3 in the
reaction of CpFe(CO)2X (X ) Cl, Br, I) and RLi (R )
Me, n-Bu, s-Bu, Ph) at low temperature did indeed give
an overall three-component transformation to yield (η4-
RC5H5)Fe(CO)2PPh3, which effectively changes the (η5-
C5H5) to metal bonding mode in CpFe(CO)2X to a (η4-
RC5H5) to metal bonding in (η4-RC5H5)Fe(CO)2PPh3
with the Fe-center concurrently reduced from Fe(II) to
Fe(0).9 The array of collected products includes
the Cp-alkylation product (η4-RC5H5)Fe(CO)2PPh3,
the CO-alkylation product CpFe(CO)C(O)R(PPh3),
the reduction-dimerization product [CpFe(CO)2]2,
and
Sch em e 2
the product of PPh3 substitution for CO, CpFe(CO)-
(PPh3)X.
The last two products either are found in trace
amounts or are not observable at all, and the CO-
alkylated CpFe(CO)C(O)R(PPh3) is at most minor. This
similar pattern has been observed for all three half-
sandwich iron halides and a range of lithiated alkyl and
aryl nucleophiles. We also noted that the C-based
nucleophiles (alkyl and aryl) add onto the Cp-ring,10 and
the O- and N-based nucleophiles add at CO.11 As an
example, the reaction with PhLi yields a branch ratio
of 71:4, favoring the Cp-ring phenylation product.
Nonetheless, CpFe(η5-C5H4Li) is different from these
C-based nucleophiles and has exhibited a product ratio
of ca. 1:2, preferring the CO-alkylation product. Appar-
ently, the interaction of the Cp carbons and Fe-center
in ferrocene shifts the anion toward acting as a non-C-
based nucleophile. The nature of such an interaction is
not yet understood.
Resu lts a n d Discu ssion
Mon oa n ion ic Nu cleop h ilic F c-Ad d ition s. The re-
action with monoanionic CpFe(η5-C5H4Li) was studied
first. An equimolar mixture of CpFe(CO)2I and PPh3 in
THF at low temperature was treated dropwise with a
stoichiometric amount of CpFe(η5-C5H4Li). During the
addition, the color of the solution gradually changed
from black to orange, along with the formation of a
yellow precipitate that redissolved by the end of the
reaction. PPh3 was incorporated into the products. Two
isomeric compounds were isolated corresponding to
nucleophilic Fc-addition at the Cp-ring, CpFe[µ,η5:η4-
5-exo-(1′-C5H4)C5H5]Fe(CO)2(PPh3) (1; 24.8%), and to
nucleophilic Fc-addition at the CO ligand, CpFe[µ,η5:
C-C5H4C(O)]FeCp(CO)(PPh3) (2; 47.1%), as shown in
Scheme 2.
Scheme 2 also shows the two-stage nature of the
three-component preparation of compounds 1 and 2. The
initial drops of CpFe(η5-C5H4Li) act as a reducing agent
(9) (a) Liu, L.-K.; Luh, L.-S. Organometallics 1994, 13, 2816. (b) Luh,
L.-S.; Liu, L.-K. Bull. Inst. Chem., Acad. Sin. 1994, 41, 39. (c) Liu,
L.-K.; Luh, L.-S.; Chao, P.-C.; Fu, Y.-T. Bull. Inst. Chem., Acad. Sin.
1995, 42, 1. (d) Luh, L.-S.; Eke, U. B.; Liu, L.-K. Organometallics 1995,
14, 440. (e) Luh, L.-S.; Liu, L.-K. Organometallics 1995, 14, 1514.
(10) (a) Bibler, J . P.; Wojcikci, A. Inorg. Chem. 1966, 5, 889. (b)
Butler, I. S.; Basolo, F.; Pearson, R. G. Inorg. Chem. 1967, 6, 2074. (c)
Green, M.; Westlake, D. J . J . Chem. Soc. A 1970, 367. (d) Pannell, K.
H. J . Chem. Soc., Chem. Commun. 1969, 1346.
The 1H NMR data of 1 contain three peaks for the
five ring protons of a η4-5-exo-substituted cyclopenta-
diene skeleton, in an integrated ratio of 2:1:2 and
progressively toward upfield for inner-diene H-atoms,
the endo H-atom, and the outer-diene H-atoms (δ 2.49,
3.46, and 5.09). In the 1H NMR spectrum, the ferrocenyl
skeleton exhibits two peaks of equal intensity (δ 3.78,
(11) (a) Liu, L.-K.; Eke, U. B.; Mesubi, M. A. Organometallics 1995,
14, 3958. (b) Eke, U. B.; Liao, Y. S.; Wen, Y. S.; Liu, L.-K. J . Chin.
Chem. Soc. 2000, 47, 109. (c) Liu, L.-K.; Peng, C. Unpublished results.

2200 Organometallics, Vol. 20, No. 11, 2001
Luh et al.
F igu r e 2. Molecular plot of (η5-C5H5)Fe[µ,η5:C-C5H4C(O)]-
Fe(CO)(PPh3)(η5-C5H5) (2) with the atomic numbering
sequence. The thermal ellipsoids are drawn at the 50%
probability level with H atoms omitted for clarity. Selected
bond lengths (Å): Fe1-P 2.202(2), Fe1-C1 2.121(5), Fe1-
C2 2.111(5), Fe1-C3 2.126(6), Fe1-C4 2.132(5), Fe(1)-C5
2.114(5), Fe1-C6 1.722(5), Fe1-C7 1.963(5), C6-O6 1.160-
(7), C7-O7 1.223(6), C7-C11 1.509(7), P-C21 1.834(5),
P-C31 1.848(5), P-C41 1.846(5). Selected bond angles
(deg): P-Fe1-C6 91.1(2), P-Fe1-C7 93.4(2), C6-Fe1-
C7 92.0(2), Fe1-C6-O6 178.1(5), Fe1-C7-O7 Fe1-C7-
C11 119.5(4), C7-C11-Fe2 124.7(4).
F igu r e 1. Molecular plot of (η5-C5H5)Fe[µ,η5:η4-5-exo-(1′-
C5H4)C5H5]Fe(CO)2(PPh3) (1) with the atomic numbering
sequence. The thermal ellipsoids are drawn at the 50%
probability level with H atoms omitted for clarity. Selected
bond lengths (Å): Fe1-P 2.225(3), Fe1-C2 2.126(9), Fe1-
C3 2.043(9), Fe1-C4 2.044(9), Fe1-C5 2.095(9), Fe1-C6
1.744(11), Fe1-C7 1.751(11), C6-O6 1.145(13), C7-O7
1.163(14), C1-C11 1.515(13), P-C21 1.848(10), P-C31
1.827(10), P-C41 1.845(9). Selected bond angles (deg):
P-Fe1-C6 97.3(3), P-Fe1-C7 94.8(3), C6-Fe1-C7 102.2-
(5), Fe1-C6-O6 178.1(5), Fe1-C7-C11 119.5(4), C7-
C11-Fe2 124.7(4).
C6tO6 at the apical position, PPh3 in the basal plane
trans to one of the double bonds, and C7tO7 trans to
the second double bond. The bulky ferrocenyl group is
exo to the cyclopentadiene ring and located away from
PPh3. The C2-, C3-, C4-, and C5-atoms of cyclopenta-
diene are coplanar within 0.005 Å. The distance between
C1 and the diene plane of C2-C5 is 0.582(2) Å, and the
plane of C2-C1-C5 is tilted 35.3(8)° away from Fe
toward the other side of the diene plane. The planes of
C1 and C11-C15 [deviation within 0.025 Å] and C11,
C1, Fe1, C6, and O6 [deviation within 0.015 Å] are
perpendicular to the diene, the angles being 90.8(3)° and
90.0(4)°, respectively. The interplanar angle between
them is 31.6(4)°. A very similar geometry has been
observed in (η4-PhCH2C5H5)Fe(CO)2(PPh3),16 (η4-PhC5H5)-
Fe(CO)2(PPh3), (η4-BuC5H5)Fe(CO)2(PPh3), and (η4-
MeC5H5)Fe(CO)2(PMePh2). The Fe1-P bond length is
2.225(3) Å, which is comparable to the average Fe(0)-P
length [2.242(34) Å]. The ferrocenyl Cp-rings are virtu-
ally eclipsed by a small staggered angle of 2.9°.
to initiate an electron-transfer chain catalysis12 of the
replacement of iodide on CpFe(CO)2I by PPh3. The
cation [CpFe(CO)2(PPh3)+] is rapidly obtained in this
reaction (as a yellow precipitate that redissolves along
the reaction coordinate).13 The initiator function of
CpFe(η5-C5H4Li)14 is a perfect match with its properties
because the concerned electron-transfer chain catalysis
is reductive in nature: a carbanion is known to function
inter alia as a reductant.15 The stoichiometric CpFe(η5-
C5H4Li) then acts as a normal nucleophile to add onto
the Cp-ring or one of the CO ligands of the cation. As a
Lewis acid, the cation is much more electrophilic than
neutral CpFe(CO)2I toward CpFe(η5-C5H4Li). Therefore,
mixing three components is equivalent to performing
the reaction of [CpFe(CO)2(PPh3)+][I-] with CpFe(η5-
C5H4Li).
The molecular structure of 2 with an atom numbering
scheme is shown in Figure 2. There are very few
examples of ferrocenoyl derivatives directly bonded to
another transition metal via the keto C-atom.17 Thermal
and photochemical decarbonylation often leads to fer-
rocenyl derivatives. Complex 2 adopts a three-legged
piano-stool geometry, and the Fe atom exists in a
distorted octahedral environment with the Cp-ring
occupying the fac sites and three legs being orthogonal.18
PPh3 is located away from the ferrocenyl moiety, in
which the Cp-rings are essentially eclipsed with a
staggered angle of 6.5°. The Fe1-P bond length is 2.202-
(2) Å. The torsion angle of P-Fe1-C7-C11 is -154.6-
(3)°. The acyl CO-group points away from the carbonyl
CO-group to minimize the dipole-dipole repulsion
X-r a y Str u ctu r es of 1 a n d 2. The molecular struc-
ture of 1 with the atom numbering scheme is shown in
Figure 1. To our knowledge, this is the first 5-exo-
(ferrocenyl)cyclopentadiene skeleton characterized by
X-ray diffraction. Complex 1 has one solvated CH2Cl2
molecule in the crystal. The bonding geometry around
Fe1 can be described as a pseudo-square-pyramid with
(12) Astruc, D. Electron Transfer and Radical Process in Transition
Metal Chemistry; VCH: New York, 1995.
(13) (a) Gipson, S. L.; Liu, L.-K.; Soliz, R. U. J . Organomet. Chem.
1996, 526, 393. (b) Liu, Z.; Gipson, S. L. J . Organomet. Chem. 1998,
553, 269. (c) Liu, L.-K. Bull. Inst. Chem., Acad. Sin. 1999, 46, 31.
(14) Traces of n-BuLi might be the actual reductive initiator.
(15) (a) Fieser; L. F.; Fieser, M. Reagents for Organic Synthesis;
Wiley: New York, 1967; Vol. 1, p 686. (b) Wakefield, B. J . In
Comprehensive Organometallic Chemistry. The Synthesis, Reactions
and Structures of Organometallic Compounds; Wilkinson, G., Stone,
F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, U.K., 1982; Vol. 7,
Chapter 44. (c) Wakefield, B. J . Organolithium Methods; Academic
Press: London, 1988. (d) Elschenbroich, Ch.; Salzer, A. Organometal-
lics. A Concise Introduction; VCH: Weinheim, Germany, 1989; pp 28-
34. (e) Encyclopedia of Reagents for Organic Synthesis; Paquett, L. A.,
Ed.; Wiley: New York, 1995; Vol. 5, pp 3530-3532.
(16) Sim, G. A.; Woodhouse, D. I.; Knox, G. R. J . Chem. Soc., Dalton
Trans. 1979, 629.
(17) Arce, A. J .; Bates, P. A.; Best, S. P.; Clark, R. J . H.; Deeming,
A. J .; Hursthouse, M. B.; McQueen, R. C. S.; Powell, N. I. J . Chem.
Soc., Chem. Commun. 1988, 478.
(18) Seeman, J . I.; Davies, S. G. J . Am. Chem. Soc. 1985, 107, 6522.

Ferrocenediyl-Bridged Triiron Complexes
Organometallics, Vol. 20, No. 11, 2001 2201
Sch em e 3
where the torsion angle of C6-Fe1-C7-O7 is 124.7-
(4)°. The P-Fe1-C7-C11 value is among the largest
reported,8a apparently due to steric repulsion. Other
structural parameters compare well with the published
ones.
1909 (overlapped), and 1583 cm-1. Its 31P NMR spec-
trum exhibits two resonances at δ 74.7 and 77.4. The
1H NMR and 13C NMR spectra clearly indicate a
magnetic nonequivalence in the molecule [eight proton
signals and eight carbon signals (C2-C5)] of the 1,1′-
1
disubstituted ferrocenediyl moiety. Four H NMR chemi-
Rea ction of 2 equ iv of Cp F e(CO)2I a n d 1,1′-
Dilit h iofer r ocen e in t h e P r esen ce of 2 eq u iv of
P P h 3. As obtained from the reaction between CpFe-
(CO)2I and FcLi in the presence of PPh3, the product
ratio for 1:2 was 1:2. The reaction of 2 equiv of CpFe-
(CO)2I and 1 equiv of 1,1′-dilithioferrocene in the pres-
ence of 2 equiv of PPh3 would give 1,1′-ferrocenediyl-
disubstituted products in a statistical manner, provided
that the two Fc-additions react independently. That is,
a ratio of 1:4:4 could be predicted for the three possible
tri-Fe complexes Fe{[µ,η5:η4-5-exo-(1′-C5H4)C5H5]Fe-
(CO)2(PPh3)}2 (3), CpFe(CO)(PPh3)[µ,C:η5-C(O)C5H4]Fe-
[µ,η5:η4-5-exo-(1′-C5H4)C5H5]Fe(CO)2(P Ph3) (4), and Fe-
[(µ,η5:C-C5H4)C(O)Fe(CO)(PPh3)Cp]2 (5).
cal shifts (δ 2.42, 2.46; δ 5.02, 5.07) and four 13C NMR
chemical shifts (δ 56.0, 56.9; δ 82.3, 82.5) have been
assigned to the inner and the outer diene protons and
carbons of the cyclopentadiene ligand. The significant
distinction is due to the chiral Fe-center of the iron-
acyl end. In 1, the inner and the outer diene protons
and carbons of cyclopentadiene show only one peak
each. A similar remote chiral influence was noticed in
[CpFe(CO)C(O)Me](µ,η1:η1-dppe)[(η4-5-exo-MeC5H5)Fe-
(CO)2].19 The molecular connectivity of 4 is a ferrocene-
diyl-bridged tri-Fe complex, one end in the form of (η4-
5-exo-RC5H5)Fe(CO)2(PPh3) and the other end in the
form of CpFe(CO)(PPh3)C(O)R, R ) ferrocenediyl. Struc-
turewise, 4 is very interesting with three Fe-centers in
three different environments: the η4-Fe is a pentacoor-
dinate Fe(0), the ferrocenediyl-Fe is an Fe(II) metal-
locene, and the acyl-Fe is a hexacoordinate Fe(II).
Mo1ssba u er Stu d y. Table 1 lists the Mo¨ssbauer
parameters of the three Fe-centers, as obtained at 80
K, on a constant-acceleration apparatus. The ferrocenyl-
Fe in 1-4 and 7 is low-spin Fe(II) with isomer shifts δ
ranging from 0.45 to 0.48 mm/s and quadrupole splitting
∆EQ ranging from 2.48 to 2.56 mm/s, in agreement with
the literature values, e.g., δ 0.45 mm/s, ∆EQ 2.38 mm/s
in Cp2Fe, δ 0.45 mm/s, ∆EQ 2.39 mm/s in ferrocenyl-
fullerene, δ 0.42 mm/s, ∆EQ 2.56 mm/s in (η5-C5Me5)2-
Fe,20 and δ 0.468 mm/s, ∆EQ 2.37 mm/s in oxidized
ferrocenyl(phenyl)phosphine.21 In 4, the η4-Fe, a dis-
torted square-pyramidal Fe(0), has been assigned to the
However, with 2 equiv of CpFe(CO)2I and 2 equiv of
PPh3 in the mixture and (η5-C5H4Li)2Fe(TMEDA) re-
placing FcLi to participate in the above three-component
reaction, only 3 (13%) and 4 (50%) were obtained, as
shown in Scheme 3. Compound 5, which was expected
to be produced in a quantity similar to that of 4, was
not observed at all. We believe that there is a molecular
self-assembly process going on upon reaction of (η5-C5H4-
Li)2Fe(TMEDA) which did not occur with FcLi.
Complex 3 reveals spectroscopic features very similar
to those of 1 without the singlet Cp resonance [IR νCO
1
1967, 1908 cm-1; H δ 2.43 (4H), 3.36 (2H), 5.05 (4H)
for η4-5-exo-substituted cyclopentadiene, δ 3.61 (4H),
3.72 (4H) for the monosubstituted cyclopentadienyl ring;
31P δ 74.1]. The molecular skeleton of 3 is thus a
ferrocenediyl group linking two identical η4-Fe(CO)2-
(PPh3) fragments. Complex 4 mainly shows a combina-
tion of the spectroscopic features of 1 and 2, leaving out
the singlet Cp resonance of the ferrocene skeleton. Its
IR spectrum reveals three νCO absorption bands at 1967,
(19) Luh, L.-S.; Liu, L.-K. Organometallics 1995, 14, 1514.
(20) Vertes, A.; Klencsar, Z.; Gal, M.; Kuzmann, E. Fullerene Sci.
Technol. 1997, 5, 97.
(21) Durfey, D. A.; Kirss, R. U.; Frommen, C.; Feighery, W. Inorg.
Chem. 2000, 39, 3506.

2202 Organometallics, Vol. 20, No. 11, 2001
Luh et al.
Ta ble 1. Mo1ssba u er P a r a m eter s of th e F e-Cen ter s in 1-4 a n d 7
ferrocenyl-Fe(II) acyl-Fe(II)
(η4-exo-RC5H5) Fe(0)
δ
∆EQ
(mm/s)
δ
∆EQ
(mm/s)
δ
∆EQ
(mm/s)
compd
(mm/s)
(mm/s)
(mm/s)
1
2
3
4
7
0.48
0.45
0.45
0.46
0.45
2.48
2.51
2.56
2.56
2.51
45%
47%
34%
32%
48%
0.09
1.49
55%
0.19
1.51
53%
0.08
0.06
1.55
1.62
66%
34%
0.20
0.20
1.68
1.67
34%
52%
Compounds 6 and 7 were transmetalated to (η5-C5H4-
Li)Fe[µ,η5:η4-5-exo-(1′-C5H4)C5H5]Fe(CO)2(PPh3) (8) and
(η5-C5H4Li)Fe[µ,η5:C-C5H4C(O)]FeCp(CO)(PPh3) (9), re-
spectively, and each of them was transferred to the 1:1
mixture of CpFe(CO)2I and PPh3 using a cannula. The
reaction of 8 produced 3 (22%) and 4 (27%), whereas
that of 9 yielded only 4 (53%) and no 5. These results
are shown in Schemes 5 and 6, respectively.
Sch em e 4
It is clear that, in the second Fc-additions, the
pathway from 9 to 4 proceeds normally, but the pathway
from 9 to 5 has been turned off. The preference of Fc-
addition onto the Cp-ring could be rationalized in terms
of a localization of the Li+ cation in 9. The drawing of 9
in Scheme 6 is in accordance with the molecular
structure 2 (Figure 2), with the proton at C17 substi-
tuted by the Li+ cation. In the close proximity of this
Li-atom are the keto O-atom and carbonyl O-atom of
the iron-acyl attached to the other Cp-ring. These
supramolecular attractions create a resultant arrange-
parameters of δ 0.06 mm/s and ∆EQ 1.62 mm/s, whereas
the half-sandwich acyl-Fe has been assigned to the
parameters of δ 0.20 mm/s and ∆EQ 1.68 mm/s. The
whole set of Mo¨ssbauer parameters is self-explanatory
in the table. If the η4-Fe is indeed Fe(0), then it accounts
for the smaller isomer shift value of the corresponding
doublet, since the higher is the (s-type) electronic
density on the Fe-atom and the lower is the observed
isomer shift.
ment, which gives more than just a steric barrier for
+
the reaction. When the electrophile [CpFe(CO)2PPh3
]
approaches 9 from its carbonyl CO end, the negative
end of the CO dipole has a strong interaction with this
Li+ cation. The disturbance is so large that the orienta-
tion necessary between the nucleophilic carbanion of 9
and the antibonding orbital of the carbonyl of the
electrophile could not be reached. And hence the Fc-
addition at CO does not occur. On the other hand, when
the electrophile [CpFe(CO)2PPh3+] approaches 9 from
its Cp-ring, the Cp-ring plane could be in a parallel
position to the ferrocenyl Cp of 9. The carbon atom of
the Cp-ring in the electrophile is also preactivated to
react with 9 according to the SN1 mechanism. [CpFe-
(CO)2PPh3+] has been reported to react with the bulky
anion [C(SiMe3)2(SiMe2H)-] very effectively.23
In addition to the major products shown in Schemes
3-6, we found that there was an array of minor
products, e.g., in the reaction employing 1,1′-dilithio-
ferrocene:
Step w ise Rea ction s. To further understand how the
second-stage Fc-addition proceeds in the reaction of (η5-
C5H4Li)2Fe(TMEDA), the Cp-ring without substitution
in 1 and 2 must be lithiated. The transmetalation
reaction of a SnBu3-group by lithium, originally devel-
oped by Seyferth in organic synthesis, was employed.22
In a stepwise manner, (η5-C5H4SnBu3)2Fe permits an
unsymmetrical functionalization of the ferrocene skel-
eton. Thus, (η5-C5H4SnBu3)2Fe was treated with slightly
greater than 1 molar equiv of n-BuLi and then intro-
duced dropwise to the equimolar mixture of CpFe(CO)2I
and PPh3 in THF at -78 °C, using the same procedure
as that used in the FcLi reaction. The reaction is shown
in Scheme 4. It gave the Cp-ring addition isomer
(η5-C5H 4Sn Bu 3)F e[µ,η5:η4-5-exo-(1′-C5H 4)C5H 5]F e-
(CO)2(PPh3) (6; 19%) and the CO-addition isomer (η5-
C5H4SnBu3)Fe[µ,η5:C-C5H4C(O)]FeCp(PPh3)(CO) (7; 37%).
The product ratio is similar to that of the FcLi result.
The η4-Fe moieties of 1 and 6 are virtually spectroscopi-
cally identical [IR νCO 1967, 1908 cm-1; 1H NMR δ 2.50,
3.49, 5.08 (η4-exo-RC5H5); 31P NMR δ 74.0]. So are the
the reduction-dimerization product [CpFe(CO)2]2
(4.5%),
the single Fc-addition products 1 (14%) and 2 (15%),
and
the protonation product ferrocene (8.6%).
Similarly in the reaction of 8, the minor products were
[CpFe(CO)2]2 (11%) and 1 (37.3%), and in the reaction
of 9, [CpFe(CO)2]2 (13%) and 2 (13.3%). In reactions
employing 8 and 9, 1 and 2 were formed presumably
when H2O was added to 8 and 9. The presence of 8 and
9 at the end of the reaction is also consistent with a
large steric barrier for the second-stage Fc-addition. In
the reaction employing (η5-C5H4Li)Fe(η5-C5H4SnBu3),
the minor products [CpFe(CO)2]2 (2%), 1 (8.4%), 2
Fe-acyl moieties of 2 and 7 [IR νCO 1914, 1583 cm-1
;
1H NMR δ 4.42 Cp; 31P NMR δ 76.4]. The results
suggest that the SnBu3 substituent on 6 and 7 does not
have a significant electronic impact.
(22) (a) Helling, J . F.; Seyferth, D. Chem. Ind. (London) 1961, 1568.
(b) Seyferth, D.; Hofmann, H. P.; Burton, R.; Helling, J . F. Inorg. Chem.
1962, 1, 227. (c) Seyferth, D.; Weiner, M. A. J . Am. Chem. Soc. 1961,
83, 3583. (d) Seyferth, D.; Weiner, M. A. J . Am. Chem. Soc. 1962, 84,
361. (e) Seyferth, D.; Vaughn, L. G. J . Am. Chem. Soc. 1964, 86, 883.
(23) Liu, L.-K.; Luh, L.-S. Organometallics 2000, 19, 374.

Ferrocenediyl-Bridged Triiron Complexes
Organometallics, Vol. 20, No. 11, 2001 2203
Sch em e 5
Sch em e 6
(7.6%), 4 (3.6%), and ferrocene (6.4%) were observed.
The presence of 1, 2, and 4 was believed to be due to
the 20% excess of n-BuLi used in the transmetalation.
In all of the reactions, noticeable amounts of [CpFe-
(CO)2]2 were observed, suggesting that the reductive
process involved with [CpFe(CO)2PPh3+] and/or [CpFe-
(CO)2I] competes with the Fc-addition.
about a 1:1 ratio (total yield 16%). The 1′,2′-isomer was
not observed, attributed to crowdedness. The reaction
mechanism producing 11a ,b involves the addition of the
+
Cp anion, which adds to the Cp-ring of [CpFe(CO)2PPh3
]
to yield 10a ,b. These compounds are deprotonated on
the cyclopentadiene that is not attached to Fe by the
free Cp anion to form the conjugate base [η4-5-exo-
(C5H4-)C5H5]Fe(CO)2PPh3 (12). The acid-base equilib-
rium is very quickly established (Scheme 7). Thus, also
as a C-based nucleophile, 12 produces 11a ,b. At the
same time, the Cp anion produces 10a ,b during later
stages of the reaction. To compensate for this problem,
the quantity of C5H5M was increased to 3 equiv to
maximize the yield of 10a ,b.
Indeed, 12 could be generated by treatment of pure
10a ,b with n-BuLi. When 12 reacted with [CpFe(CO)2-
PPh3+][I-], the products were 11a ,b. When 12 reacted
with FeCl3 following a literature procedure,24 the prod-
uct was 3 (38.5%, not optimized, Scheme 8).
Alter n a tive Rou te to 3. We have found that 3 could
be prepared in an alternative way upon building the η4-
Fe arm first and then the ferrocene core. C5H5Li is
readily generated by deprotonation of C5H6 using n-
BuLi. C5H5Na is available from commercial sources. The
reactivities of these two nucleophiles in the three-
component reaction are similar. The Cp anion is aro-
matic during the three-component reaction. After the
addition, it becomes a cyclopentadiene and is no longer
aromatic, however. The C5H5M (M ) Na, Li) reaction
gave two unseparated, isomeric η4-Fe products (in about
a 1:1 ratio, total yield 60%). One is [η4-5-exo-(1′-C5H5)-
C5H5]Fe(CO)2PPh3 (10a ), and the other is [η4-5-exo-(2′-
C5H5)C5H5]Fe(CO)2PPh3 (10b). The difference is only at
the site of substitution on the cyclopentadiene that is
not attached to Fe. There was no spectroscopic evidence
for the third possible isomer [η4-5-exo-(5′-C5H5)C5H5]-
Fe(CO)2PPh3 (10c). Compound 10c is believed to be the
immediate product that rearranges to 10a ,b by proton
shifts on the cyclopentadiene. There was no observation
of the CO-alkylation product either. Thus, the Cp anion
is different from Fc anions and acts as a normal C-based
nucleophile, preferring the Cp-ring alkylation in the
three-component reaction.
Con clu sion
The reaction of 1,1′-dilithioferrocene with the mixture
of CpFe(CO)2I and PPh3 is a one-pot operation in which
overall two types of Fc-additions result in 4, a ferro-
cenediyl-bridged tri-Fe complex. Complex 4 has been
created with three different Fe-centers: a metallocene
Fe(II), a square-pyramidal pentacoordinate Fe(0), and
a half-sandwich acyl-Fe(II).
Exp er im en ta l Section
The reaction of C5H5M and CpFe(CO)2I in the pres-
ence of PPh3 yielded the interesting extra bis(η4-Fe)
products (1′,3′-C5H4)[(C5H5-5-exo-η4)Fe(CO)2PPh3]2 (11a )
and (1′,4′-C5H4)[(C5H5-5-exo-η4)Fe(CO)2PPh3] (11b) in
All manipulations were performed under an atmosphere of
prepurified nitrogen with standard Schlenk techniques, and
(24) Chung, T.-M.; Chung, Y. K. Organometallics 1992, 11, 2822.

2204 Organometallics, Vol. 20, No. 11, 2001
Luh et al.
Sch em e 7
Sch em e 8
all solvents were distilled from an appropriate drying agent.25
Infrared spectra were recorded in CH2Cl2 using CaF2 optics
on a Perkin-Elmer Paragon 1000 FT-IR spectrometer. The H
Rea ction of Cp F e(CO)2I a n d Cp F e(η5-C5H4Li) in th e
P r esen ce of P P h 3. A solution of CpFe(η5-C5H4SnBu3) (1.6 g,
3.4 mmol) in THF (30 mL) was treated with n-BuLi (1.6 M in
n-hexane, 2.2 mL, 3.5 mmol) at -78 °C. After being stirred
for 30 min, the resulting solution of CpFe(η5-C5H4Li) was
cannula-transferred dropwise into the mixture of CpFe(CO)2I
(0.912 g, 3.0 mmol) and PPh3 (0.786 g, 3.0 mmol) in THF (100
mL) at -78 °C. During addition, the color of the solution
gradually changed from black to orange, accompanied by the
formation of a yellow precipitate that redissolved by the end
of the addition. After it had been stirred overnight, the solution
was quenched with water (200 mL) and then extracted with
Et2O (100 mL × 2). The combined organic layer was dried over
MgSO4 before being evaporated to dryness under vacuum. The
oily residue was purified through a SiO2 chromatography
column with 1:10 EtOAc/hexane as eluent, followed by removal
of the solvents, to give, according to the order of appearance,
the colorless SnBu4, the yellow ferrocene (0.048 g), the yellow
1 (0.46 g, 25%), the purple [CpFe(CO)2]2 (0.032 g, 6.0%), and
the orange 2 (0.88 g, 47%).
1
and 13C NMR spectra were obtained on the Brucker AC-200/
AC-300 spectrometers, in which chemical shifts were reported
in δ values relative to the residual solvent resonance of CDCl3
(1H, δ 7.24; 13C, δ 77.0). The 31P NMR spectra were obtained
on the Brucker AC-200/AC-300 spectrometers using 85% H3-
PO4 as an external standard (31P, δ 0.00). Mass spectra were
obtained on
a VG system, model 70-250S, spectrometer.
Microanalytical data were obtained with the use of a Perkin-
Elmer 240C elemental analyzer independently operated by the
Institute of Chemistry, Academia Sinica. Mo¨ssbauer spectra
were obtained at T ) 80 K with a Wissel spectrometer in
constant-acceleration mode. Isomer shift values are given with
respect to R-iron. The typical estimated error of the Mo¨ssbauer
parameters is (0.02 mm/s. CpFe(CO)2I,26 CpFe(η5-C5H4-
SnBu3),27 (η5-C5H4Li)2Fe(TMEDA),28 and (η5-C5H4SnBu3)2Fe29
were prepared according to literature procedures. All reagents
were obtained from commercial sources and used without
further purification.
1
1: IR (CH2Cl2, cm-1) 1967 (s), 1908 (s); H NMR (CDCl3) δ
2.49 (br, 2H, -CHdCHCHC5H4-), 3.46 (br, 1H, -CHd
CHCHC5H4-), 3.78, 3.87 (br, 2H × 2, C5H4), 4.01 (s, 5H, C5H5),
5.09 (br, 2H, -CHdCHCHC5H4-), 7.31-7.45 (m, 15H, Ph);
13C NMR (CDCl3) δ 54.6 (s, -CHdCHCHC5H4-), 55.7 (s,
-CHdCHCHC5H4-), 66.1, 70.0 (s, C5H4), 68.0 (s, C5H5), 82.0
(s, -CHdCHCHC5H4-), 95.3 (s, C5H4,ipso), 128.1, 128.3, 129.7,
(25) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon Press: Oxford, U.K., 1981.
(26) (a) Dombek, B. D.; Angelici, R. J . Inorg. Chim. Acta 1973, 345.
(b) Meyer, T. J .; J ohnson, E. C.; Winterton, N. Inorg. Chem. 1971, 10,
1673. (c) Inorg. Synth. 1971, 12, 36. (d) Inorg. Synth. 1963, 7, 110.
(27) Wright, M. E. Organometallics 1990, 9, 853.
(28) Rausch, M. D.; Ciappenelli, D. J . J . Organomet. Chem. 1967,
10, 127.
2
132.9, 133.1, 136.0, 136.5 (m, Ph), 219.5 (d, J PC ) 12.4 Hz,
(29) Dodo, T.; Suzuki, H.; Takiguchi, T. Bull. Chem. Soc. J pn. 1970,
43, 288.
CO); 31P NMR (CDCl3) δ 74.1 (s); MS (m/z) M+ 624 (parent

Ferrocenediyl-Bridged Triiron Complexes
Organometallics, Vol. 20, No. 11, 2001 2205
ion). Anal. Calcd for C35H29Fe2O2P: C, 67.34; H, 4.68. Found:
C, 67.44; H, 4.87.
order of appearance, SnBu4, orange oil CpFe(η5-C5H4SnBu3),
yellow ferrocene (0,06 g, 6.4%), yellow 1 (0.26 g, 8.4%), orange
(η5-C5H4SnBu3)Fe[µ,η5:η4-(5-exo-C5H4)C5H5]Fe(CO)2(PPh3) (6;
0.88 g, 19%), orange (η5-C5H4SnBu3)Fe[µ,η5:C-C5H4C(O)]FeCp-
(CO)(PPh3) (7; 1.69 g, 37%), purple [CpFe(CO)2]2 (0.02 g, 1%),
orange 2 (0.24 g, 7.6%), and orange 4 (0.19 g, 3.6%).
2: IR (CH2Cl2, cm-1) 1915 (s), 1583 (m); 1H NMR (CDCl3) δ
3.97, 4.43 (s, 5H × 2, C5H5), 4.16, 4.20, 4.34, 4.55 (br, 1H × 4,
C5H4), 7.31-7.52 (m, 15H, Ph); 13C NMR (CDCl3) δ 68.3, 68.6,
68.8, 69.7 (s × 4, C5H4), 69.2, 85.3 (s, C5H5 × 2), 97.3 (s,
C5H4,ipso), 127.9, 128.0, 129.5, 133.6, 136.5, 137.1 (m, Ph), 221.3
1
6: IR (CH2Cl2, cm-1) 1967 (s), 1908 (s); H NMR (CDCl3) δ
2
2
(d, J PC ) 33 Hz, CO), 270.3 (d, J PC ) 22 Hz, C(O)C5H4); 31P
NMR (CDCl3) δ 76.4 (s); MS (m/z) M+ 624 (parent ion). Anal.
Calcd for C35H29Fe2O2P: C, 67.34; H, 4.68. Found: C, 67.43;
H, 4.86.
0.83-1.59 (m, 27H, Bu), 2.50 (br, 2H, -CHdCHCHC5H4-),
3.47 (br, 1H, -CHdCHCHC5H4-), 3.73, 3.76, 3.80, 4.16 (br,
2H × 4, C5H4 × 2), 5.08 (br, 2H, -CHdCHCHC5H4-), 7.30-
7.45 (m, 15H, Ph); 13C NMR (CDCl3) δ 10.2, 10.7, 27.4, 29.2
(s, Bu), 54.6 (s, -CHdCHCHC5H4-), 55.7 (s, -CHdCHCH-
C5H4-), 66.0, 67.1, 70.7, 74.4 (s, C5H4 × 2), 82.0 (s, -CHd
CHCHC5H4-), 95.1 (s, C5H4,ipso), 128.1, 128.2, 129.6, 132.9,
Rea ction of Cp F e(CO)2I a n d (η5-C5H4Li)2F e(TMEDA)
in th e P r esen ce of P P h 3. The mixture of CpFe(CO)2I (0.77
g, 2.5 mmol) and PPh3 (0.65 g, 2.5 mmol) was dissolved in THF
(100 mL) at -78 °C. (η5-C5H4Li)2Fe(TMEDA) (0.395 g, 1.26
mmol) in THF (50 mL) was then added dropwise via a dropping
funnel. During the addition, the color of the solution gradually
changed from black to orange, accompanied by the formation
of a yellow precipitate that redissolved by the end of the
reaction. After complete addition, the solution was warmed
to room temperature and stirred overnight before the mixture
was quenched with water (200 mL) and extracted with Et2O
(100 mL × 2). The combined organic layer was dried over
MgSO4 and then evaporated to dryness under vacuum. The
oil-like residue was purified by SiO2 column chromatography
with 1:10 to 1:3 EtOAc/hexane as eluent to give, after solvent
removal, according to the order of appearance, yellow ferrocene
(0.02 g, 8%), yellow 1 (0.11 g, 14%), yellow Fe{[µ,η5:η4-(5-exo-
C5H4)C5H5]Fe(CO)2(PPh3)}2 (3; 0.17 g, 13%), purple [CpFe-
(CO)2]2 (0.02 g, 4%), orange 2 (0.12 g, 15%), and orange
CpFe(CO)(PPh3)[µ,C:η5-C(O)C5H4]Fe[µ,η5:η4-(5-exo-C5H4)C5H5]-
Fe(CO)2(PPh3) (4; 0.67 g, 50%).
2
133.0, 136.0, 136.5 (m, Ph), 219.5 (d, J PC ) 14 Hz, CO); 31P
NMR (CDCl3) δ 74.0 (s); MS (m/z) M+ 913 (parent ion). Anal.
Calcd for C47H55Fe2O2PSn: C, 61.81; H, 6.07. Found: C, 61.63;
H, 6.03.
7: IR (CH2Cl2, cm-1) 1914 (s), 1583 (m); 1H NMR (CDCl3) δ
0.85-1.61 (m, 27H, Bu), 3.83, 3.96, 4.00, 4.01, 4.06, 4.29, 4.50
(br, 1H × 8, C5H4 × 2), 4.42 (s, 5H, C5H5), 7.31-7.52 (m, 15H,
Ph); 13C NMR (CDCl3) δ 10.2, 13.7, 27.4, 29.3 (s, Bu), 68.1,
68.7, 69.0, 69.5, 72.8, 73.1, 74.8, 75.0 (s, C5H4 × 2), 85.2 (s,
C5H5), 97.0, 97.1 (s, C5H4,ipso × 2), 127.8, 128.0, 129.5, 132.8,
2
133.1, 133.5, 133.7, 136.3, 137.2 (m, Ph), 221.2 (d, J PC ) 33
2
Hz, CO), 270.2 (d, J PC ) 21 Hz, C(O)C5H4); 31P NMR (CDCl3)
δ 76.4 (s); MS (m/z) M+ 913 (parent ion). Anal. Calcd for C47H55
-
Fe2O2PSn: C, 61.81; H, 6.07. Found: C, 62.40; H, 6.00.
Rea ction of Cp F e(CO)2I a n d 8 in th e P r esen ce of P P h 3.
At -78 °C, complex 6 (0.913 g, 1.0 mmol) in THF (30 mL) was
treated with n-BuLi (1.6 M in hexane, 0.75 mL, 1.2 mmol) and
the reaction mixture was stirred for 1 h. The resulting lithiated
solution of (η5-C5H4Li)Fe[µ,η5:η4-(5-exo-C5H4)C5H5]Fe(CO)2-
(PPh3) (8) was transferred under nitrogen via a cannula
dropwise to the mixture of CpFe(CO)2I (0.304 g, 1.0 mmol) and
PPh3 (0.262 g, 1.0 mmol) in THF (50 mL) at -78 °C. After
complete addition, the orange solution was warmed to room
temperature and then stirred overnight before the mixture was
quenched with water (100 mL) and extracted with Et2O (50
mL × 2). The combined organic layer was dried over MgSO4
and then evaporated to dryness under vacuum. The oil-like
residue was purified by SiO2 column chromatography with 1:9
EtOAc/hexane as eluent, followed by removal of the solvents
to give, according to the order of appearance, SnBu4, yellow 1
(0.23 g, 37%), purple [CpFe(CO)2]2 (0.02 g, 11%), yellow 3 (0.24
g, 22%), and orange 4 (0.28 g, 27%).
Rea ction of Cp F e(CO)2I a n d 9 in th e P r esen ce of P P h 3.
At -78 °C, complex 7 (1.60 g, 1.75 mmol) in THF (30 mL) was
treated with n-BuLi (1.6 M in hexane, 1.31 mL, 2.1 mmol) and
stirred for 1 h. The resulting lithiated solution of (η5-C5H4Li)-
Fe[µ,η5:C-C5H4C(O)]FeCp(CO)(PPh3) (9) was then transferred
under nitrogen via a cannula dropwise to the mixture of CpFe-
(CO)2I (0.532 g, 1.75 mmol) and PPh3 (0.459 g, 1.75 mmol) in
THF (50 mL) at -78 °C. After complete addition, the orange
solution was warmed to room temperature and then stirred
overnight before it was quenched with water (100 mL) and
extracted with ether (50 mL × 2). The combined organic layer
was dried over MgSO4 and then evaporated to dryness under
vacuum. The oil-like residue was purified by SiO2 column
chromatography with 1:8 EtOAc/hexane as eluent to give, after
solvent removal, according to the order of appearance, orange
oil SnBu4, purple [CpFe(CO)2]2 (0.04 g, 13%), orange 2 (0.15
g, 13%), and orange 4 (0.98 g, 53%).
1
3: IR (CH2Cl2, cm-1) 1967 (s), 1908 (s); H NMR (CDCl3) δ
2.43 (br, 2H, -CHdCHCHC5H4-), 3.36 (br, 1H, -CHd
CHCHC5H4-), 3.61, 3.72 (br, 2H × 2, C5H4), 5.05 (br, 2H,
-CHdCHCHC5H4-), 7.36-7.41 (m, 15H, Ph); 13C NMR
(CDCl3) δ 54.5 (s, -CHdCHCHC5H4-), 55.9 (s, -CHd
CHCHC5H4-), 66.3, 67.3 (s, C5H4), 82.0 (s, -CHdCHCHC5H4-
), 95.1 (s, C5H4,ipso), 128.1, 128.3, 129.6, 132.9, 133.1, 135.9,
2
136.6 (m, Ph), 219.5 (d, J PC ) 14 Hz, CO); 31P NMR (CDCl3)
δ 74.1 (s); MS (m/z) M+ 1062 (parent ion). Anal. Calcd for
C
60H48Fe3O4P2: C, 67.82; H, 4.55. Found: C, 67.57; H, 4.70.
1
4: IR (CH2Cl2, cm-1) 1967 (s), 1909 (s), 1583 (m); H NMR
(CDCl3) δ 2.42, 2.46 (br, 1H × 2, -CHdCHCHC5H4-), 3.36
(br, 1H, -CHdCHCHC5H4-), 3.57, 3.60, 3.62, 3.72, 4.00, 4.03,
4.21, 4.34 (b, 1H × 8, C5H4 × 2), 4.39 (s, 5H, C5H5), 5.02, 5.07
(b, 1H × 2, -CHdCHCHC5H4-), 7.31-7.50 (m, 30H, Ph); 13
C
NMR (CDCl3) δ 55.0 (s, -CHdCHCHC5H4-), 56.0, 56.9 (s ×
2, -CHdCHCHC5H4-), 67.5, 69.2, 69.4, 69.5, 70.0 (s, C5H4
×
2), 82.3, 82.5 (s × 2, -CHdCHCHC5H4-), 85.5 (s, C5H5), 96.1,
97.9 (s, C5H4,ipso × 2), 128.4, 128.5, 129.6, 129.8, 133.3, 133.4,
134.2, 136.7, 137.1, 137.5, 138.0 (m, Ph), 219.9 (d, 2J PC ) 14.5
Hz, CO), 220.3 (d, 2J PC ) 13.6 Hz, CO), 221.8 (d, 2J PC ) 33 Hz,
2
CO), 265.7 (d, J PC ) 20.6 Hz, C(O)C5H4); 31P NMR (CDCl3) δ
74.7 (s), 77.4 (s); MS (m/z) M+ 1062 (parent ion). Anal. Calcd
for C60H48Fe3O4P2: C, 67.82; H, 4.55. Found: C, 68.12; H, 4.69.
R ea ct ion of Cp F e(CO)2I a n d (η5-C5H 4Sn Bu 3)F e(η5-
C5H4Li) in th e P r esen ce of P P h 3. At -78 °C, (η5-C5H4-
SnBu3)2Fe (3.82 g, 5.0 mmol) in THF (50 mL) was treated with
n-BuLi (1.6 M in hexane, 3.75 mL, 6.0 mmol) and the reaction
mixture was stirred for 1 h. The resulting lithiated solution
of (η5-C5H4SnBu3)Fe(η5-C5H4Li) was then transferred under
nitrogen via a cannula dropwise to the mixture of CpFe(CO)2I
(1.52 g, 5.0 mmol) and PPh3 (1.31 g, 5.0 mmol) in THF (100
mL) at -78 °C. After complete addition, the orange solution
was warmed to room temperature and then stirred overnight
before it was quenched with water (100 mL) and extracted with
Et2O (100 mL × 2). The combined organic layer was dried over
MgSO4 and then evaporated to dryness under vacuum. Puri-
fication by SiO2 column chromatography with 1:9 EtOAc/
hexane as eluent gave, after solvent removal, according to the
Rea ction of Cp F e(CO)2I a n d C5H5Na in th e P r esen ce
of P P h 3. A 3 equiv sample of C5H5Na (15 mL, 2 M) was added
dropwise to a solution of CpFe(CO)2I (3.04 g, 10 mmol) and
PPh3 (2.62 g, 10 mmol) in 150 mL of THF at -78 °C. The color
of the solution changed from black to orange-red during the
addition. After being warmed to room temperature, the solu-
tion was quenched with water (200 mL) and extracted with
diethyl ether (100 mL × 2). The organic layer was combined

2206 Organometallics, Vol. 20, No. 11, 2001
Luh et al.
with the ether extracts, and this solution was dried over
MgSO4 and then evaporated to dryness under vacuum. The
oily residue was purified by chromatography using a SiO2
column with 1:7 EtOAc/hexane as the eluent. The following
three bands separated in the order of appearance: unreacted
PPh3, yellow [η4-5-exo-(1′-C5H5)C5H5]Fe(CO)2PPh3 and [η4-5-
exo-(2′-C5H5)C5H5]Fe(CO)2PPh3 (10a ,b; 2.95 g, 60%), and yel-
low (1′,3′-C5H4)[(C5H5-5-exo-η4)Fe(CO)2PPh3]2 and (1′,4′-C5H4)-
[(C5H5-5-exo-η4)Fe(CO)2PPh3] (11a ,b; 0.75 g, 16%).
diffraction measurements were performed on a Nonius CAD-4
automated diffractometer, using graphite-monochromated Mo
KR radiation (λ ) 0.710 69 Å). Twenty-five high-angle reflec-
tions were used in a least-squares fit to obtain accurate cell
constants. Diffraction intensities were collected up to 2θ < 50°
using the θ/2θ scan technique, with background counts made
for half the total scan time on each side of the peak. Three
standard reflections, measured every hour, showed no signifi-
cant decrease in intensity during data collection. The reflec-
tions with Io > 2.0σ(Io) were judged as observations and were
used for solution and structure refinement. Data were cor-
rected for Lorentz-polarization factors. An empirical absorption
correction based on series of Ψ scans was applied to the data.
The structure was solved by direct methods30 and refined by
a full-matrix least-squares routine31 with anisotropic thermal
parameters for all non-hydrogen atoms (weight ) 1/[σ(Fo)2 +
0.0001(Fo)2], σ(Fo) from counting statistics). All hydrogen atoms
were placed isotropically at idealized positions (C-H ) 1.00
Å) and fixed in the calculation. Atomic scattering factor curves
fo, ∆f′, and ∆f′′ of Fe, P, O, and C and fo of H were taken from
the International Tables for X-ray Crystallography.32
10a : IR (CH2Cl2, cm-1) 1969 (s), 1913 (s); 1H NMR (C6D6) δ
2.62 (br, 2H, -CHdCHCH(C5H5)-), 2.56 (br, 2H, C5H5), 3.87
(br, 1H, -CHdCHCH(C5H5)-), 4.92 (br, 2H, -CHdCHCH-
(C5H5)-), 5.81 (br, 1H, C5H5), 6.02 (d, 1H, J HH ) 1.3 Hz, C5H5),
6.27 (d, 1H, J HH ) 1.9 Hz, C5H5), 6.97-7.50 (m, 15H, Ph); 31
P
NMR (C6D6) δ 73.8 (s). 10b: 1H NMR (C6D6) δ 2.43 (br, 2H,
-CHdCHCH(C5H5)-), 2.56 (br, 2H, C5H5), 3.92 (br, 1H,
-CHdCHCH(C5H5)-), 5.00 (br, 2H, -CHdCHCH(C5H5)-),
5.57 (br, 1H, C5H5), 6.04 (d, 1H, J HH ) 1.2 Hz, C5H5), 6.29 (d,
1H, J HH ) 1.8 Hz, C5H5), 6.97-7.50 (m, 15H, Ph). Anal. Calcd
for
C30H25FeO2P (mixture of 10a ,b ): C, 71.44; H, 5.00.
Found: C, 71.76; H, 5.08.
11a : IR (CH2Cl2, cm-1) 1971 (s), 1911 (s); 1H NMR (C6D6) δ
2.29 (br, 2H, C5H4), 2.52 (br, 4H, -CHdCHCH(C5H5)-), 3.80
(br, 2H, -CHdCHCH(C5H5)-), 4.90 (br, 4H, -CHdCHCH-
(C5H5)-), 5.57 (br, 2H, C5H4), 6.95-7.52 (m, 15H, Ph); 31P NMR
(C6D6) δ 73.8 (s). 11b: 1H NMR (C6D6) δ 2.16 (br, 2H, C5H4),
2.58 (br, 4H, -CHdCHCH(C5H5)-), 3.76 (br, 2H, -CHd
CHCH(C5H5)-), 5.00 (br, 4H, -CHdCHCH(C5H5)-), 5.31 (br,
1H, C5H4), 5.60 (br, 1H, C5H4), 6.95-7.52 (m, 15H, Ph). Anal.
Calcd for C55H44Fe2O4P2 (mixture of 11a ,b): C, 70.08; H, 4.71.
Found: C, 70.65; H, 5.07.
Rea ction s of 12. (a) n-BuLi (1.6 M in hexane, 2.0 mL, 3.2
mmol) was added dropwise via syringe to a yellow solution of
a mixture of 10a ,b (1.52 g, 3.0 mmol) in 20 mL of THF at 0
°C. The color of the solution changed from yellow to orange-
red. After being stirred for 1 h, the in situ generated lithium
reagent was cannula-transferred to the suspension of [CpFe-
(CO)2PPh3+][I-] in 50 mL of THF at -78 °C. The solution was
then warmed to room temperature over 2 h. The resulting
brown solution was quenched with water (200 mL) and
extracted with diethyl ether (100 mL × 2). The organic layer,
combined with the ether extracts, was dried over MgSO4 and
then evaporated to dryness under vacuum. The oily residue
was purified by chromatography using a SiO2 column with
1:2.5 CH2Cl2/hexane as eluent. The following three bands
separated in the order of appearance: PPh3, unreacted 10a ,b,
and the yellow 11a ,b (1.25 g, 44%).
Crystal data for 1: yellow prism (0.38 × 0.19 × 0.13 mm),
C
36H31Cl2Fe2O2P, fw ) 709.21, monoclinic, space group P21/c,
a ) 10.205(1) Å, b ) 14.914(1) Å, c ) 20.841(2) Å, â ) 90.29-
(1)°, V ) 3171.8(4) Å3, Z ) 4, F(000) ) 1460.29, Dcalcd ) 1.485
g cm-3, µ ) 1.17 mm-1, hkl -10 e h e +10, 0 e k e +16, 0 e
l e +22, R ) 0.051, Rw ) 0.072 for 2546 out of 4128 reflections.
Crystal data for 2: orange prism (0.44 × 0.22 × 0.22 mm),
C
35H29Fe2O2P, fw ) 624.27, monoclinic, space group P21/c, a
) 7.852(2) Å, b ) 34.484(4) Å, c ) 10.548(1) Å, â ) 103.62(2)°,
V ) 2775.6(9) Å3, Z ) 4, F(000) ) 1287.80, Dcalcd ) 1.494 g
cm-3, µ ) 1.13 mm-1, hkl -9 e h e +9, 0 e k e +40, 0 e l e
+12, R ) 0.040, Rw ) 0.044 for 2757 out of 4875 reflections.
Ack n ow led gm en t. We thank Academia Sinica and
the National Science Council, ROC, for their kind
financial support. Thanks are due to Prof. Attila Vertes
for assistance with the Mo¨ssbauer measurements.
Su p p or tin g In for m a tion Ava ila ble: For the structures
of 1 and 2, listing of crystallographic data, positional and
thermal parameters, bond distances and angles, and torsion
angles. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM0008528
(b) A solution of 10a ,b (0.756 g, 1.5 mmol) in THF (20 mL)
was treated with n-BuLi (1.6M in n-hexane, 1.0 mL, 1.6 mmol)
at 0 °C. After the solution was stirred for 1 h, anhydrous FeCl3
(0.146 g, 0.90 mmol) was added in one portion via an angled
tube. The mixture was then refluxed for 15 h. The solvent was
removed under vacuum to give a black residue, which was
purified by SiO2 column chromatography with 1:2 CH2Cl2/
hexane as eluent to give yellow 3 (0.307 g, 38%) and some
unidentified compounds.
(30) Main, P. In Crystallographic Computing 3: Data Collection,
Structure Determination, Proteins and Databases; Sheldrick, G. M.,
Krueger, C., Goddard, R., Eds.; Clarendon Press: Oxford, U.K., 1985;
pp 206-215.
(31) (a) Gabe, E. J .; Le Page, Y.; White, P. S.; Lee, F. L. Acta
Crystallogr. 1987, 43A, S294. (b) Gabe, E. J .; Le Page, Y.; Lee, F. L.
In Crystallographic Computing 3: Data Collection, Structure Deter-
mination, Proteins and Databases; Sheldrick, G. M., Krueger, C.,
Goddard, R., Eds.; Clarendon Press: Oxford, U.K., 1985; pp 167-174.
(32) International Tables for X-ray Crystallography; Ibers, J . A.,
Hamilton, W. C., Eds.; Kynoch: Birmingham, U.K., 1974; Vol. 4, Tables
2.2A and 2.3.1D.
X-r a y Str u ctu r e An a lysis. Single crystals of 1 and 2 were
grown by slow evaporation from CH2Cl2/hexane. The X-ray