(η5-C5H5)-Ring alkylation reaction with the C5H5 anion: towards the construction of tri-Fe complex Fe{[μ,η5:η4-5-exo-(1'-C5H4)C5H5]Fe(CO)2(PPh3)}2

Article abstract of DOI:10.1016/S0022-328X(01)00957-3

The reaction of (η⁵-C5H5)Fe(CO)2I with C5H5M (M=Na, Li) in the presence of PPh3 gives the Cp-ring alkylation η⁴-Fe products 10a,b. The compounds 10a,b could be deprotonated with n-BuLi to generate 12. When 12 reacts with FeCl3, the r

Full text of DOI:10.1016/S0022-328X(01)00957-3

Journal of Organometallic Chemistry 637–639 (2001) 549–557
www.elsevier.com/locate/jorganchem
(h5-C5H5)-Ring alkylation reaction with the C5H5 anion: towards
the construction of tri-Fe complex
Fe{[m,h5:h4-5-exo-(1%-C5H4)C5H5]Fe(CO)2(PPh3)}2
Lung-Shiang Luh a, Ling-Kang Liu a,b,
*
a Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan
b Department of Chemistry, National Taiwan Uni6ersity, Taipei 10607, Taiwan
Received 5 February 2001; received in revised form 23 February 2001; accepted 13 March 2001
Abstract
The reaction of (h5-C5H5)Fe(CO)2I with C5H5M (M=Na, Li) in the presence of PPh3 gives the Cp-ring alkylation h4-Fe
products 10a,b. The compounds 10a,b could be deprotonated with n-BuLi to generate 12. When 12 reacts with FeCl3, the reaction
produces the tri-Fe complex 6, Fe{[m,h5:h4-5-exo-(1%-C5H4)C5H5]Fe(CO)2(PPh3)}2, whose hydride abstraction with Ph3CPF6
results in 13, [Fe{[m,h5:h5-1-(1%-C5H4)C5H4]Fe(CO)2(PPh3)}2][PF6]2. A similar strategy was applied in the preparation of penta-Fe
complex 15, Fe[m-h5-C5H3-1,3-{(C5H5-5%-exo-h4)Fe(CO)2(PPh3)}2]2, which has four h4-Fe arms attached to a ferrocene core. The
compound 12, upon treatment with the W(CO)3(EtCN)3 then MeI sequence, gives the dimetallic h4-Fe, h5-W complex 17. The
endo-hydride of 17 could be abstracted with Ph3CPF6 to result in 18 whose reaction with C5H5Na proceeds smoothly with the
Cp-ring alkylation and gives h4-Fe products 19a,b. Treatment of 19a,b with n-BuLi, followed by the W(CO)3(EtCN)3 then MeI
sequence yields the trimetallic h5-W, h4-Fe, h5-W complex 20. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Cp-ring alkylation; Three-component reaction; Ferrocenediyl-bridged tri-Fe complex; Electron-transfer chain catalysis; Carbon
nucleophile; Hydride abstraction
1. Introduction
(=dppe) results in products of both Cp-ring butylation
and CO butylation [3]. There are two PPh2 groups in
dppe to serve as the phosphine ingredient in three-com-
ponent reaction. The isolated dppe-bridging products
are as follows: (h4-exo-BuC5H5)Fe(CO)2(m,h1:h1-dppe)-
(h4-exo-BuC5H5)Fe(CO)2 (3, 55%), (h4-exo-BuC5-
H5)Fe(CO)2(m,h1:h1-dppe)(h5-C5H5)Fe(CO)C(O)Bu (4,
18%), and (h5-C5H5)Fe(CO)C(O)Bu(m,h1:h1-dppe)(h5-
C5H5)Fe(CO)C(O)Bu (5, 1%). The two PPh2 groups of
dppe seem to proceed independently with the Cp-ring
butylation and/or CO butylation, such that the three
dppe-bridging species are collected in a statistic ratio, as
shown in Scheme 2. Accordingly, the Cp-ring butyla-
tion is ca. seven to eight times more favorable than the
CO butylation, e.g. an anionic carbon nucleophile
prefers the Cp-ring to CO.
At −78 °C, the reaction of RLi (R=n-Bu, s-Bu,
Me, Ph) and half-sandwich halide complex (h5-
C5H5)Fe(CO)2X (X=Cl, Br, and I) in the presence of
phosphine PR% (R% =Ph3, Ph2Me, PhMe2, Me3) pro-
3
3
duces (h4-exo-RC5H5)Fe(CO)2PR% (1) (Scheme 1) [1,2].
3
The overall three-component reaction is the Cp-ring
alkylation that shifts the bonding mode of metal to ring
from (h5-C5H5) to (h4-exo-RC5H5), the metal center
being concurrently reduced from Fe(II) to Fe(0). The
Cp-ring addition reaction is usually accompanied by a
minor CO addition that gives the acyl complex (h5-
C5H5)Fe(CO)(PR%)C(O)R (2) as a by-product.
3
As one example, the reaction of (h5-C5H5)Fe(CO)2I
with BuLi in the presence of Ph2PCH2CH2PPh2
Since its discovery half a century ago [4], ferrocene,
an electron-rich molecule, has displayed a variety of
intriguing physical and chemical properties. Complexes
with a ferrocenyl group (Fc) directly bonded to a metal
* Corresponding author. Tel.: +886-2-2789-8532; fax: +886-2-
2783-1237.
E-mail address: liuu@chem.sinica.edu.tw (L.-K. Liu).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00957-3

550
L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
Scheme 1.
are known, among which lithioferrocenes provide key
intermediates for further elaboration [5]. The reaction
between metal halides and FcLi [6], the ferrocenyl
transfer from Fc2Hg [7], and the thermal or photo-in-
duced decarbonylation of ferrocenoyl complexes [8]
are inter alia useful methods for the preparation of
ferrocenyl derivatives.
The above three-component reaction has been ex-
tended to that of two equivalents of (h5-C5H5)-
Fe(CO)2I, 1,1%-dilithioferrocene, and two equivalents
of PPh3 (see Scheme 3) [9]. It has been found that
under this condition, the substitution of the iodide on
(h5-C5H5)Fe(CO)2I by PPh3 is much faster than nucle-
ophilic Fc-addition at the Fe-center or at a CO ligand
of (h5-C5H5)Fe(CO)2I. The reaction thus proceeds
through the intermediate [(h5-C5H5)Fe(CO)2PPh3+]
and results in the interesting ferrocenediyl-bridged tri-
Fe complex (h5-C5H5)Fe(CO)(PPh3)[m,C:h5-C(O)C5-
H4]Fe[m,h5:h4-5-exo-(1%-C5H4)C5H5]Fe(CO)2(PPh3) (7,
51%), with the 1,1%-dilithioferrocene participating
twice in the nucleophilic Fc-additions: at the Cp-ring
and at a CO ligand of [(h5-C5H5)Fe(CO)2PPh+3 ]. This
reaction, however, results in only a smaller amount of
double-end h4-Fe tri-Fe complex Fe{[m,h5:h4-5-exo-
(1%-C5H4)C5H5]Fe(CO)2(PPh3)}2 (6, 13%) and no dou-
ble-end CO-alkylation product Fe[(m,h5:C-C5H4)C(O)-
Fe(CO)(PPh3)(h5-C5H5)]2 (8). A rationale for the ab-
sence of the last product has been proposed [9].
Here we would like to report the alternative pre-
paration of the double-end h4-Fe tri-Fe complex 6
that, a minor by-product with the 1,1%-dilithiofer-
rocene reaction, could seemingly be prepared by con-
structing the h4-Fe arms first and the ferrocene core
second.
Scheme 2.

L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
551
Scheme 3.
2. Experimental
from black to orange–red during the addition. After
being warmed to room temperature (r.t.), the solution
was quenched with H2O (200 ml) and extracted with
Et2O (100 ml×2). The organic layer, combined with
the ethereal extracts, was dried over MgSO4 and then
evaporated to dryness under vacuum. The oily residue
was purified by chromatography using a SiO2 column
with EtOAc/hexane=1:7 as an eluent. The following
three bands separated in the order of appearance: unre-
acted PPh3, yellow [h4-5-exo-(1%-C5H5)C5H5]Fe(CO)2-
(PPh3), and [h4-5-exo-(2%-C5H5)C5H5]Fe(CO)2(PPh3)
(10a,b; 2.95 g, 60%), and yellow 1%,3%-C5H4[(C5H5-5-
exo-h4)Fe(CO)2PPh3]2 and 1%,4%-C5H4[(C5H5-5-exo-
h4)Fe(CO)2PPh3] (11a,b; 0.75 g, 16%). In the process of
2.1. General
All manipulations were performed under an atmo-
sphere of prepurified nitrogen with standard Schlenk
techniques. All solvents were distilled from an appro-
priate drying agent [10]. Infrared spectra were recorded
in CH2Cl2 using CaF2 optics on a Perkin–Elmer
Paragon 1000 FT-IR spectrometer. The H- and 13C-
1
NMR spectra were obtained on Bruker AC200/AC300/
AMX400 spectrometers, with chemical shifts reported
in l values, downfield positive, relative to the residual
solvent resonance of CDCl3 (1H l 7.24, 13C l 77.0). The
31P-NMR spectra were obtained on Bruker AC200/
AC300 spectrometers using 85% H3PO4 as an external
standard (l 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. (h5-
C5H5)Fe(CO)2I was prepared according to the literature
procedure [11]. Other reagents were obtained from
commercial sources, e.g. Aldrich, Merck, Strem, etc.
and used without further purification.
1
purification, two sets of H-NMR data were differenti-
ated when one component was more concentrated than
the second.
1
10a: IR (CH2Cl2, cm−1) 1969 (s), 1913 (s); H-NMR
(C6D6) l 2.62 (b, 2H, –CHꢀCHCH(C5H5)–), 2.56 (b,
2H, C5H5), 3.87 (b, 1H, –CHꢀCHCH(C5H5)–), 4.92
(b, 2H, –CHꢀCHCH(C5H5)–), 5.81 (b, 1H, C5H5), 6.02
(d, 1H, JHH=1.3 Hz, C5H5), 6.27 (d, 1H, JHH=1.9 Hz,
C5H5), 6.97–7.50 (m, 15H, Ph); 31P-NMR (C6D6) l
73.8 (s). 10b: 1H-NMR (C6D6)
l 2.43 (b, 2H,
–CHꢀCHCH(C5H5)–), 2.56 (b, 2H, C5H5), 3.92 (b, 1H,
–CHꢀCHCH(C5H5)–), 5.00 (b, 2H, –CHꢀCHCH-
(C5H5)–), 5.57 (b, 1H, C5H5), 6.04 (d, 1H, JHH=1.2
Hz, C5H5), 6.29 (d, 1H, JHH=1.8 Hz, C5H5), 6.97–7.50
(m, 15H, Ph). Anal. Calc. for C30H25FeO2P (mixture of
10a,b): C, 71.44; H, 5.00. Found: C, 71.76; H, 5.08%.
2.2. Reaction of C5H5Na with 1:1
(p5-C5H5)Fe(CO)2I/PPh3
Three equivalents of C5H5Na (2 M, 15 ml) were
added dropwise into a solution of (h5-C5H5)Fe(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 solution changed
1
11a: IR (CH2Cl2, cm−1) 1971 (s), 1911 (s); H-NMR
(C6D6)
l
2.29 (b, 2H, C5H4), 2.52 (b, 4H,
–CHꢀCHCH(C5H5)–), 3.80 (b, 2H, –CHꢀCHCH(C5-

552
L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
H5)–), 4.90 (b, 4H, –CHꢀCHCH(C5H5)–), 5.57 (b, 2H,
C5H4), 6.95–7.52 (m, 15H, Ph); 31P-NMR (C6D6) l
73.8 (s). 11b: H-NMR (C6D6) l 2.16 (b, 2H, C5H4),
2.58 (b, 4H, –CHꢀCHCH(C5H5)–), 3.76 (b, 2H,
–CHꢀCHCH(C5H5)–), 5.00 (b, 4H, –CHꢀCHCH-
(C5H5)–), 5.31 (b, 1H, C5H4), 5.60 (b, 1H, C5H4),
6.95–7.52 (m, 15H, Ph). Anal. Calc. for C55H44Fe2O4P2
(mixture of 11a,b): C, 70.08; H, 4.71. Found: C, 70.65;
H, 5.07%.
2.5. Reaction between 6 and Ph3CPF6
1
A mixture of 6 (0.136 g, 0.13 mmol) and Ph3CPF6
(0.12 g, 0.31 mmol) was dissolved in 10 ml of CH2Cl2.
The solution gradually became purple. After being
stirred for 30 min, the mixture was added with H2O.
The CH2Cl2 layer was collected. The H2O layer was
extracted with CH2Cl2 for several times. The organic
layers were combined and dried over MgSO4. The
by-product Ph3CH was removed during recrystaliza-
tion/filtration procedure from CH2Cl2 and n-hexane.
The precipitate was washed with Et2O (20 ml×2) and
dried under vacuum to result in a red complex
[Fe{[m,h5:h5-1-(1%-C5H4)C5H4]Fe(CO)2(PPh3)}2][PF6]2
(13, 0.15 g, 86%).
2.3. Preparation of 11a,b from 10a,b
n-BuLi (1.6 M in n-hexane, 2.0 ml, 3.2 mmol) was
added dropwise via a syringe into a yellow solution of
mixtures of 10a,b (1.52 g, 3.0 mmol) in 20 ml of THF
at 0 °C. The color of solution changed from yellow to
orange–red. After being stirred for 1 h, the in-situ
generated lithium reagent was cannula-transferred into
the suspension solution of [(h5-C5H5)Fe(CO)2PPh3+][I−]
in 50 ml of THF at −78 °C. The solution was then
warmed to r.t. over 2 h. The resulting brown solution
was quenched with H2O (200 ml) and extracted
with Et2O (100 ml×2). The organic layer, combined
with the ethereal extracts, was dried over MgSO4 and
then evaporated to dryness under vacuum. The oily
residue was purified by chromatography using a SiO2
column with CH2Cl2/hexane=1:2.5 as an eluent.
The following three bands separated in the order of
appearance: PPh3, unreacted 10a,b, and yellow 11a,b
(1.25 g, 44%).
13: IR (CH2Cl2, cm−1) 2047 (vs), 2008 (s), 1996(s);
1H-NMR (acetone-d6) l 4.58, 4.93 (b, 2H×2, C5H4Fe),
5.37, 5.74 (b, 2H×2, C5H4FePPh3), 7.26–7.61 (m, Ph);
31P-NMR (acetone-d6) l 67.3 (s), –144.1 (sept). Anal.
Calc. for C60H66F12Fe3O4P4: C, 52.55; H, 4.85. Found:
C, 52.14; H, 4.69%.
2.6. Preparation of Fe[v-p5-C5H3-1,3-
{(C5H5-5%-exo-p4)Fe(CO)2(PPh3)}2]2 (15) and
attempted reaction between 15 and Ph3CPF6
A solution of 11a,b (0.706 g, 0.75 mmol) in THF (15
ml) was treated with n-BuLi (1.6 M in n-hexane, 0.5
ml) at 0 °C and stirred for 1 h. Anhydrous FeCl3 (0.15
g, 0.9 mmol) was added in one portion via a curved
tube to this brown solution. After being refluxed for 16
h, the solvent was removed under vacuum to give a
black residue, which was purified by SiO2 column chro-
matography with CH2Cl2/n-hexane=3/2 as an eluent
to afford yellow 15 (0.12 g, 17%). Some unidentified
compounds were also obtained which were cationic in
nature as shown by the IR peaks at ca. 2050 and 2010
2.4. Preparation of 6 from 10a,b
A solution of 10a,b (0.756 g, 1.5 mmol) in THF (20
ml) was treated with n-BuLi (1.6 M 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 a curved 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 an eluent to give yellow 6 (0.31 g, 39%) and some
unidentified compounds.
cm−1
.
15: IR (CH2Cl2, cm−1) 1966 (s), 1906 (s); H-NMR
(C6D6) l 2.65 (m, 4H, –CHꢀCHCHC5H3), 3.21 (s, 1H,
C5H3Fe), 3.35 (s, 1H, C5H3Fe), 3.60 (b, 2H, –CHꢀ
CHCHC5H3), 5.04 (m, 4H, –CHꢀCHCHC5H3), 7.00–
7.06, 7.51–7.61 (m, 30H, Ph); 13C-NMR (C6D6) l 55.6
(s, –CHꢀCHCHC5H3), 56.2 (s, –CHꢀCHCHC5H4),
57.6, 66.0 (s, C5H3), 82.4 (s, –CHꢀCHCHC5H3), 94.6
(s, Cipso), 128.4, 128.5, 129.7, 133.3, 133.4, 136.8, 137.1
(Ph), 220.2 (d, JPC=11 Hz, CO), 220.3 (d, JPC=11 Hz,
CO); 31P-NMR (C6D6) l 73.1 (s). Anal. Calc. for
C110H86Fe5O8P4: C, 68.14; H, 4.47. Found: C, 68.47; H,
4.71%.
1
1
6: IR (CH2Cl2, cm−1) 1967 (s), 1908 (s); H-NMR
(CDCl3) l 2.43 (b, 2H, –CHꢀCHCHC5H4–), 3.36 (b,
1H, –CHꢀCHCHC5H4–), 3.61, 3.72 (b, 2H×2, C5H4),
5.05 (b, 2H, –CHꢀCHCHC5H4–), 7.36–7.41 (m, 15H,
Ph); 13C-NMR (CDCl3) l 54.5 (s, –CHꢀCHCHC5H4–),
55.9 (s, –CHꢀCHCHC5H4–), 66.3, 67.3 (s, C5H4),
82.0 (s, –CHꢀCHCHC5H4–), 95.1 (s, C5H4ipso), 128.1,
128.3, 129.6, 132.9, 133.1, 135.9, 136.6 (m, Ph), 219.5
The reaction of 15 and four equivalents of Ph3CPF6
gave a number of cationic species on the basis of IR
(2050 and 2010 cm−1) and 31P-NMR (l 62–68) spec-
tra. As the cationic species were not differentiating
enough, detailed assignment of spectroscopic property
for each cationic species was not yet possible.
2
(d, JPC=14 Hz, CO); 31P-NMR (CDCl3) l 74.1 (s);
MS (m/z) [M+] 1062 (parent ion). Anal. Calc. for
C60H48Fe3O4P2: C, 67.82; H, 4.55. Found: C, 67.57; H,
4.70%.

L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
553
2.7. Fe(CO)2(PPh3)[v-(p4-C5H5)-5-exo-(1%-C5H4-p5)]-
M(CO)3Me, M=W, Mo (17, 17%)
volume of solution was reduced to about half the
original volume in vacuo. Et2O (30 ml) was then added.
The precipitate was filtered and washed with Et2O until
the washings were colorless, resulting in a yellow–or-
ange powder 18 (1.01 g, 94%).
(a) M=W. A solution of 10a,b (0.756 g, 1.5 mmol)
in THF (20 ml) was treated with n-BuLi (1.6 M in
n-hexane, 1.0 ml) at 0 °C and stirred for 1 h.
W(CO)3(EtCN)3 (0.866 g, 2.0 mmol) was then added in
one portion via a curved tube to the brown solution.
The solution became clear after being warmed up to
room temperature and was further stirred for 30 min.
MeI (1.0 ml) was added dropwise via a syringe. After
the mixture was stirred overnight, the solvent was re-
moved under vacuum to give a brownish residue, which
was purified by SiO2 column chromatography with
CH2Cl2/n-hexane=1/3 as an eluent to afford unreacted
starting materials (0.1 g) and yellow 17 (0.9 g, 76%).
17: IR (CH2Cl2, cm−1) 2011 (s), 1974 (s), 1916 (vs);
1H-NMR (C6D6) l 0.46 (s, 3H, Me), 2.36 (b, 2H,
–CHꢀCHCHC5H4), 3.34 (b, 1H, –CHꢀCHCHC5H4),
4.27 (s, 4H, C5H4), 4.81 (b, 2H, –CHꢀCHCHC5H4),
7.00–7.05, 7.44–7.49 (m, 15H, Ph); 13C-NMR (C6D6) l
–33.5 (s, Me), 52.6 (s, –CHꢀCHCHC5H4), 54.8 (s,
–CHꢀCHCHC5H4), 82.1 (s, –CHꢀCHCHC5H4), 89.3,
89.8 (s, C5H4), 119.4 (d, JPC=5.0 Hz, Cipso), 128.5,
128.7, 130.0, 133.1, 133.3, 135.8, 136.6 (Ph), 217.7 (s,
18: IR (CH2Cl2, cm−1) 2055 (m), 2021 (s), 1932 (vs);
1H-NMR (acetone-d6) l 0.35 (s, 3H, Me), 5.55, 5.84
(vt, JHH=2 Hz, 2H×2, C5H4Fe), 6.11, 6.24 (vt, JHH
=
2 Hz, 2H×2, C5H4W), 7.53–7.68 (m, 15H, Ph); 13C-
NMR (acetone-d6) l –30.8 (s, Me), 84.1, 90.1 (s,
C5H4Fe), 96.2, 96.4 (s, C5H4W), 98.5, 104.3 (s, Cipso),
130.5, 130.7, 133.2, 133.8, 133.9, 136.1, 136.5 (Ph);
31P-NMR (acetone-d6) l 67.0 (s), –138.3 (sept); MS
(m/z) [M+] 698 (parent ion). Anal. Calc. for
C34H26F6FeO5P2W: C, 43.87; H, 2.82. Found: C, 44.10;
H, 2.85%.
2.9. Reaction of C5H5Na with 18
A suspension of 18 (1.01 g, 1.09 mmol) in 30 ml of
THF was treated with C5H5Na (2.0 M in THF, 0.6 ml)
at −78 °C. The mixture became clear after the addi-
tion was completed and was further stirred for 2 h.
After being warmed up to r.t., the solution was
quenched with MeOH and then pumped dry to give an
oily residue. Purification by SiO2 column chromatogra-
phy with CH2Cl2/n-hexane=1/1 as an eluent afforded
yellow Fe(CO)2(PPh3)[m-(h4-C5H4)-5-exo-(1%-C5H5)-2-
(C5H4-h5)]W(CO)3Me and Fe(CO)2(PPh3)[m-(h4-C5H4)-
5-exo-(2%-C5H5)-2-(C5H4-h5)]W(CO)3Me, 19a,b (0.636
g, 69%). A second yellow band showed similar IR
pattern and 31P-NMR spectroscopic data to that of the
first band (0.15 g), presumably the bis(h4-Fe) products
that were not analyzed. The first band exhibited two
J
WC=30 Hz, COtrans), 219.2 (d, JPC=14 Hz, CO),
230.7 (s, CO); 31P-NMR (C6D6) l 73.6 (s); MS (m/z)
[M+] 786 (parent ion). Anal. Calc. for C34H27FeO5PW:
C, 51.94; H, 3.46. Found: C, 51.79; H, 3.52%.
(b) M=Mo. A procedure similar to the preparation
of 17 was used, employing Mo(CO)3(MeCN)3 instead
of W(CO)3(EtCN)3. The final purification by SiO2
column chromatography with CH2Cl2/n-hexane=1/3
as an eluent afforded yellow 17% (0.5 g, 72%).
17%: IR (CH2Cl2, cm−1) 2015 (s), 1973 (s), 1918 (vs);
1H-NMR (C6D6) l 0.38 (s, 3H, Me), 2.40 (b, 2H,
–CHꢀCHCHC5H4), 3.34 (b, 1H, –CHꢀCHCHC5H4),
4.29 (s, 4H, C5H4), 4.83 (b, 2H, –CHꢀCHCHC5H4),
7.01–7.03, 7.44–7.49 (m, 15H, Ph); 13C-NMR (C6D6) l
–21.0 (s, Me), 52.8 (s, –CHꢀCHCHC5H4), 55.0 (s,
–CHꢀCHCHC5H4), 82.1 (s, –CHꢀCHCHC5H4), 90.6,
91.0 (s, C5H4), 121.3 (s, Cipso), 128.5, 128.6, 130.0,
133.2, 133.3, 136.1, 136.5 (Ph), 219.2 (s, JPC=15 Hz,
CO), 227.9 (s, COtrans), 241.1 (s, CO); 31P-NMR (C6D6)
l 73.7 (s); MS (m/z) [M+] 698 (parent ion). Anal. Calc.
for C34H27FeO5PMo: C, 58.48; H, 3.90. Found: C,
58.19; H, 3.82%.
unseparated isomers, each with very complicated H-
1
NMR spectrum, corresponding to 1%- or 2%-substitution
on the cyclopentadiene without metal.
19a,b: IR (CH2Cl2, cm−1) 2008 (s), 1971 (s), 1918
(vs); 31P-NMR (C6D6) l 73.6 (s). MS (m/z) [M+] 850
(parent ion). Anal. Calc. for C39H31FeO5PW: C, 55.09;
H, 3.67. Found: C, 55.40; H, 3.87%.
2.10. Fe(CO)2(PPh3)[v-(p4-C5H4)-2-{(p5-C5H4)W-
(CO)3Me}-5-exo-{(p5-C5H4)W(CO)3Me}] (20)
A solution of 19a,b (0.595 g, 0.7 mmol) in THF (20
ml) was treated with n-BuLi (1.6 M in n-hexane, 0.5
ml) at 0 °C and stirred for 30 min. W(CO)3(EtCN)3
(0.28 g, 0.65 mmol) was added in one portion via a
curved tube to this brown solution. It became clear
after being warmed up to r.t. and was further stirred for
30 min. MeI (1.0 ml) was then added dropwise via a
syringe. The solution was stirred for additional 30 min.
Then the solvent was removed under vacuum to give a
brownish residue, which was purified by SiO2 column
chromatography with CH2Cl2/n-hexane=1/3 as an elu-
2.8. {Fe(CO)2(PPh3)[v,p5:p5-1-(1%-C5H4)C5H4]W(CO)3-
Me}PF6 (18)
A mixture of 17 (0.91 g, 1.16 mmol) and Ph3CPF6
(0.49 g, 1.26 mmol) was dissolved in 20 ml of CH2Cl2.
The color of solution changed gradually from orange to
yellow, accompanied by the formation of a yellow
precipitate after 30 min. After being stirred for 1 h, the

554
L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
ent to afford unreacted starting materials (0.2 g) and
yellow 20 (0.3 g, 57%).
tri-Fe 6 using an alternative method is very challenging
to organometallic chemists. Retrochemically, if one
wants to build the h4-Fe arm on Cp-ring first and make
the ferrocene core second, one must employ the Cp
anion in the three-component reaction. While C5H5Na
is available from commercial sources, the reactivity of
C5H5Li in three-component reaction is the same as that
of C5H5Na and is readily generated by deprotonation
of C5H6 using n-BuLi.
20: IR (CH2Cl2, cm−1) 2010 (s), 1974 (m), 1918 (vs);
1H-NMR (C6D6) l 0.43, 0.45 (s, 3H×2, Me), 1.85 (m,
1H, Hb), 3.40 (m, 1H, Hendo), 4.27, 4.34, 4.37, 4.50,
4.55, 4.63, 4.78, 4.80 (m, 1H×8, C5H4W), 4.76 (m, 1H,
Ha), 5.10 (m, 1H, Hc), 7.04–7.08, 7.34–7.40 (m, 15H,
Ph); 31P-NMR (C6D6) l 73.6 (s). Anal. Calc. for
C43H33FeO8PW2: C, 45.61; H, 2.94. Found: C, 45.80;
H, 3.09%.
The reaction of (h5-C5H5)Fe(CO)2I with C5H5M
(M=Na, Li) in the presence of PPh3 gives two unsepa-
rated, isomeric h4-Fe products (in about 1:1 ratio, total
yield 60%, see Scheme 4). One is 10a and the other 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
[h4-5-exo-(5%-C5H5)C5H5]Fe(CO)2PPh3 (10c). Com-
pound 10c is believed to be the immediate product that
rearranges to 10a,b by proton shifts on the cyclopenta-
diene. There was no observation of the CO alkylation
product (h5-C5H5)Fe(CO)(PPh3)C(O)(C5H5). Thus the
Cp anion is different from Fc anions and acts as a
normal carbon nucleophile, preferring the Cp-ring alky-
lation in the three-component reaction.
The 5-membered Cp anion is an aromatic reagent
during the three-component reaction. After addition,
however, the cyclopentadiene skeleton in products is no
more aromatic in bonding. The C5H5M reaction yielded
the interesting extra bis(h4-Fe) products 11a and 11b in
about 1:1 ratio (total yield 16%). The 1%,2%-isomer was
not observed, attributed to over crowding. The reaction
mechanism producing 11a,b involves the addition of the
Cp anion which adds to the Cp-ring of [(h5-
C5H5)Fe(CO)2PPh+3 ] to yield 10a,b. These compounds
are deprotonated on the cyclopentadiene that is not
attached to Fe by free Cp anion to form the conjugate
base [h4-5-exo-(C5H4−)C5H5]Fe(CO)2PPh3 (12). The
acid–base equilibrium is very quickly established. Thus,
also as a carbon nucleophile, 12 produces 11a,b when
the Cp anion produces 10a,b during later stages of the
reaction. In order to compensate for this problem, the
quantity of C5H5M was increased to three equivalents
in order to maximize the yield of 10a,b.
3. Results and discussion
3.1. [(p5-C5H5)Fe(CO)2PPh+3 ][I−] as the intermediate
for Cp-ring and/or CO alkylation
The preparation of the h4-Fe compounds in three-
component reaction is actually a two-stage transforma-
tion (Schemes 1–3), in which the ionic [(h5-
C5H5)Fe(CO)2PPh+3 ][I−] is the intermediate product
that receives the carbon nucleophile at the Cp-site or
the CO-site. The mechanism for in-situ, facile produc-
tion of [(h5-C5H5)Fe(CO)2PPh+3 ][I−] from (h5-C5H5)-
Fe(CO)2I and PPh3 is an electron-transfer chain cata-
lytic replacement of iodide on (h5-C5H5)Fe(CO)2I by
PPh3, with chemical initiation by the first drops of
anionic carbon nucleophile [12,13]. As an initiator at
the beginning of the reaction and a normal nucleophile
later, the carbanion nucleophiles have dual functions.
The initiator function is a perfect match with their
properties because the concerned electron-transfer
chain catalysis is reductive in nature: a carbanion is
known to function as a reductant, a base, and a nucle-
ophile [14].
For a range of lithiated alkyl and aryl nucleophiles,
the CO alkylation product (h5-C5H5)Fe(CO)(PPh3)-
C(O)R is generally minor, i.e. the carbon nucleophiles
(alkyl and aryl) favor addition onto the Cp-ring [1,2].
Yet for the ferrocenyl anions, the pattern doesn%t con-
form to the general carbon nucleophiles, attributed to
an interaction between the cyclopentadienyl carbons
and Fe-center in ferrocene with the nature of such
interaction not yet fully understood. The absence of
double-end CO-alkylation product 8 has been demon-
strated experimentally that the pathway from (h5-
C5H5)Fe(CO)(PPh3)[m,C:h5-C(O)C5H4]Fe(C5H4Li) (9)
and [(h5-C5H5)Fe(CO)2PPh+3 ][I−] to 8 is not available
because of a localization of the Li cation [9].
3.3. Preparation of 6 from 12 and its hydride
abstraction reaction
Treatment of pure 10a,b with n-BuLi generated 12.
When 12 reacted with [(h5-C5H5)Fe(CO)2PPh3+][I−], the
products were 11a,b (44%). When 12 reacted with FeCl3
following a literature procedure [15] the product
was mainly 6 (39%, Scheme 5) plus some unidenti-
3.2. Cp anion as the carbon nucleophile in
three-component reaction
fied by-products. The 5-endo-H on
a
(h4-5-exo-
Since the 1,1%-dilithioferrocene route produces 51% 7,
leaving the isomeric 6 only a minor by-product, an
attempt to specifically prepare the double-end h4-Fe
RC5H5)Fe(CO)2PPh3 moiety has been shown to be a
hydride that could be abstracted with a strong Lewis
acid, e.g. [PPh3C+] [16]. Accordingly, treatment of 6

L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
555
with Ph3CPF6, produces the double-end, cationic tri-Fe
complex 13 (86%, Scheme 5). The characteristic IR wCO
stretching bands of the neutral 6 are at 1967, 1908
cm−1 whereas those of the cationic 13 are at 2047, 2008
cm−1, the shift being 80–100 cm−1 to higher wave
numbers that are consistent to the fact that the Fe-cen-
ring from (h4-5-exo-RC5H5) to (h5-RC5H4), the metal
center being oxidized from Fe(0) to Fe(II).
Similar strategy has been applied to the preparation
of penta-Fe complex 15 that has four h4-Fe arms
attached to a ferrocene core. As shown in Scheme 6,
treatment of 11a,b with n-BuLi produced in-situ the
anion (1,3-C5H3−)[(C5H5-5%-exo-h4)Fe(CO)2PPh3]2 (14)
that, when reacted with FeCl3, resulted in 15 (17%) and
some unidentified compounds which were cationic in
nature. The hydride abstraction on 15 with excess
Ph3CPF6 was attempted, giving seemingly 16 on the
basis of IR and 31P-NMR spectra. However, it was also
noticed that in the mixture an array of compounds
from 15 to 16 were likely present, ranging from a
complex with (4 h4-Fe, 0 h5-Fe) arms attached to
1
ter in 13 has a higher oxidation state. The H-NMR
spectrum of 6 reveals a 2H:1H:2H pattern assigned to
the 5 H-atoms of the cyclopentadiene ring attached to
Fe at l 2.43, 3.36, 5.05 (in CDCl3). The hydride ab-
straction removes the 2H:1H:2H pattern completely. In
13, the 1H-NMR spectrum shows only the 2H:2H
pattern at l 5.37, 5.74 (in acetone-d6), characteristic for
a Cp-ring attached to Fe. The electrophilic abstraction
of the endo-hydride shifts the bonding mode of metal to
Scheme 4.
Scheme 5.

556
L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
Scheme 6.
Scheme 7.
ferrocene core to a complex with (0 h4-Fe, 4 h5-Fe)
arms. The yield of 15 in its preparation was low,
attributed to the presence of Lewis acid FeCl3 (or
ferrocenium) which presumably abstracted the endo-hy-
drides to produce mono- to tetra-(h5-Fe) by-products.
treated with the W(CO)3(EtCN)3 followed by MeI se-
quence [15] to give a dimetallic h4-Fe, h5-W complex 17
(76%) which has two directly connected five-membered
rings in different bonding environments. The Mo
analog 17% could also be obtained in 72% isolated yields
without any difficulty. The endo-hydride of 17 could be
abstracted in the same manner with Ph3CPF6 to result
in 18 (94%). The change of spectroscopic property from
17 to 18 is similar to the change from 6 to 13. In both
cases, there is a shift of wCO stretching bands towards
3.4. Preparation of CpW(CO)3Me deri6ati6es from 12
and their hydride abstraction reaction
As shown in Scheme 7, the anionic 12 could be

L.-S. Luh, L.-K. Liu / Journal of Organometallic Chemistry 637–639 (2001) 549–557
557
higher frequencies by 80–100 cm−1 in IR. There is also
[2] L.-K. Liu, L.-S. Luh, Organometallics 13 (1994) 2816.
[3] L.-K. Liu, L.-S. Luh, U.B. Eke, Organometallics 14 (1995)
440.
[4] (a) T.J. Kealy, P.L. Pauson, Nature 168 (1951) 1039;
(b) G. Wilkinson, M. Rosenblum, M.C. Whiting, R.B. Wood-
ward, J. Am. Chem. Soc. 74 (1952) 2125;
(c) M. Rosenblum, Chemistry of the Iron Group Metallocenes,
Wiley, New York, 1965.
[5] and references cited therein M.E. Wright, Organometallics 9
(1990) 853.
[6] (a) H. Buerger, C. Kluess, J. Organomet. Chem. 56 (1973)
269;
a change from the 2H:1H:2H pattern to the 2H:2H
1
pattern in H-NMR corresponding, respectively, to the
bonding of metal to ring from (h4-5-exo-RC5H5)Fe to
(h5-RC5H4)Fe.
Complex 18 is a derivative of [(h5-C5H4R)Fe-
(CO)2PPh+3 ] with R= –(h5-C5H4)W(CO)3Me and is
thus a substrate for C5H5Na. The reaction between 18
and C5H5Na proceeded smoothly with the Cp-ring
alkylation to give unseparated, isomeric 19a,b, in about
1:1 ratio (total yield 69%). The difference between 19a
and 19b is the site of substitution on the cyclopentadi-
ene that is not attached to Fe. There was no spectro-
scopic evidence for the third possible isomer
Fe(CO)2(PPh3)[m-(h4-C5H4)-5-exo-(5%-C5H5)-2-(C5H4-
h5)]W(CO)3Me (19c), believed to be the immediate
product rearranging to 19a,b by proton shifts on the
cyclopentadiene. Similar to Scheme 4, there were also
the bis(h4-Fe) by-products (not shown in Scheme 7)
that were nonetheless not studied presently. Treatment
of pure 19a,b with n-BuLi, followed by the W(CO)3-
(EtCN)3 then MeI sequence yielded the trimetallic h5-
W, h4-Fe, h5-W complex 20 (57%). For 20, the –(h5-
C5H4)W(CO)3Me substituents on the cyclopentadiene
ring are at the two- and five-position. The 1,5-isomers
were not observed due to steric reasons.
(b) M. Wedler, H.W. Roesky, F.T. Edelmann, U.Z. Behrens,
Naturforsch. Teil B 43 (1988) 1461;
(c) G.A. Razuvaeu, G.A. Domrachev, V.V. Sharutin, O.N.
Suvorova, J. Organomet. Chem. 141 (1977) 313;
(d) M. Herberhold, H. Kniesel, L. Haumaier, U. Thewalt, J.
Organomet. Chem. 301 (1986) 355;
(e) M. Herberhold, H. Kniesel, J. Organomet. Chem. 371
(1989) 205;
(f) M. Herberhold, H. Kniesel, L. Haumaier, A. Gieren, C.Z.
Ruiz-Perez, Naturforsch. Teil B 41 (1989) 1431;
(g) M. Herberhold, H. Kniesel, J. Organomet. Chem. 334
(1987) 347;
(h) M. Herberhold, W. Feger, U. Koelle, J. Organomet.
Chem. 436 (1992) 333;
(i) K.-H. Thiele, C. Krueger, T. Bartik, M. Dargatz, J.
Organomet. Chem. 352 (1988) 115;
(j) A.G. Osborne, R.H. Whiteley, J. Organomet. Chem. 181
(1979) 425.
[7] (a) T.M. Miller, K.J. Ahmed, M.S. Wrighton, Inorg. Chem. 28
(1989) 2347;
The hydride abstraction on 20 with Ph3CPF6 was
difficult. When abstraction was carried out at room
temperature for hours, very little cationic species could
be observed, likely due to steric reasons: there are two
bulky groups of –(h5-C5H4)W(CO)3Me in 20 and
[Ph3C+] is a bulky reagent.
(b) A.N. Nesmeyanov, E.G. Perevalova, K.I. Grandberg, D.A.
Lemenovskii, T.V. Baukova, O.B. Afanassova, J. Organomet.
Chem. 65 (1974) 131.
[8] K.H. Pannell, J.B. Cassias, G.M. Crawford, A. Flores, Inorg.
Chem. 15 (1976) 2671.
[9] L.-S. Luh, Y.-S. Wen, L.-K. Liu, Organometallics 20 (2001)
2198.
[10] D.D. Perrin, W.L.F. Armarego, D.R. Perrin, Purification of
Laboratory Chemicals, Pergamon Press, Oxford, UK, 1981.
[11] (a) B.D. Dombek, R.J. Angelici, Inorg. Chim. Acta 7 (1973)
345;
4. Conclusion
The reaction of (h5-C5H5)Fe(CO)2I with Cp anion in
the presence of PPh3 gives 10a,b. Treatment of 10a,b
with n-BuLi generates 12 that can react with FeCl3 to
produce 6 whose hydride abstraction results in 13. The
transformation from 10a,b to 17 could be repeated
similarly from 19a,b to 20, the cycle to bring 17 to 19a,b
being realized with an electrophilic hydride abstraction
then a Cp anion addition on the Cp-ring.
(b) T.J. Meyer, E.C. Johnson, N. Winterton, Inorg. Chem. 10
(1971) 1673;
(c) T.J. Meyer, E.C. Johnson, N. Winterton, Inorg. Synth. 12
(1971) 36;
(d) T.J. Meyer, E.C. Johnson, N. Winterton, Inorg. Synth. 7
(1963) 110.
[12] S.L. Gipson, L.-K. Liu, R.U. Soliz, J. Organomet. Chem. 526
(1996) 393.
[13] L.-K. Liu, Bull. Inst. Chem. Acad. Sin. 46 (1999) 31.
[14] (a) L.F. Fieser, M. Fieser, Reagents for Organic Synthesis,
vol. 1, Wiley, New York, 1967, p. 686;
(b) B.J. Wakefield, in: G. Wilkinson, F.G.A. Stone, E.W. Abel
(Eds.), Comprehensive Organometallic Chemistry. The Synthe-
sis, Reactions and Structures of Organometallic Compounds,
Ch. 44, vol. 7, Pergamon, Oxford, UK, 1982;
(c) B.J. Wakefield, in: Organolithium Methods, Academic
Press, London, 1988;
Acknowledgements
The authors thank Academia Sinica and the National
Science Council, ROC, for the financial support.
(d) Ch. Elschenbroich, A. Salzer, in: Organometallics. A Con-
cise Introduction, VCH, Weinheim, 1989, pp. 28–34;
(e) L.A. Paquett (Ed.), Encyclopedia of Reagents for Organic
Synthesis, vol. 5, Wiley, New York, 1995, pp. 3530–3532.
[15] T.-M. Chung, Y.K. Chung, Organometallics 11 (1992) 2822.
[16] L.-K. Liu, L.-S. Luh, Organometallics 15 (1996) 5263.
References
[1] L.-S. Luh, L.-K. Liu, Bull. Inst. Chem. Acad. Sin. 41 (1994)
39.