Functionalization of Cp4Fe4(CO)4 with Alkyl, Aryl, and Ferrocenyl Groups and the Preparation of Double Clusters [Cp3Fe4(CO)4(C5H4)] 2 and [Cp3Fe4(CO)4(C5H4)] 2[(C5H4)2Fe]

Article abstract of DOI:10.1021/om9902333

Reaction of Cp₄Fe₄(CO)₄ (1) with RLi and HBF₄ in sequence affords Cp₃Fe₄(CO)₄(C₅H₄R) (R= Me, Buⁿ, and Ph) in moderate yields. Further sequential PhLi/HBF₄ treatment of Cp₃Fe₄(CO)₄(C₅H₄Ph) produces Cp₂Fe₄(CO)₄(C₅H₄Ph) ₂. On the other hand, 1 reacts with lithium diisopropylamide (LDA) and bromoferrocene sequentially to produce a ferrocenylated cluster [Cp₃Fe₄(CO)₄(C₅H ₄)][(C₅H₄)FeCp] (3) and a double cluster [Cp₃Fe₄(CO)₄(C₅H₄)] ₂ (2). A similar LDA/dibromoferrocene treatment with 1 leads to 2, [Cp₃Fe₄(CO)₄(C₅H ₄)][(C₅H₄)(C₅H₄Br)Fe] (4), and a ferrocenyl-bridged double cluster [Cp₃Fe₄(CO)₄(C₅H₄)] ₂[(C₅H₄)₂Fe] (5). The new compounds have been characterized by elemental analysis and IR, mass, and NMR spectroscopy.

Full text of DOI:10.1021/om9902333

Organometallics 1999, 18, 3547-3550
3547
Notes
F u n ction a liza tion of Cp F e (CO) w ith Alk yl, Ar yl, a n d
4
4
4
F er r ocen yl Gr ou p s a n d th e P r ep a r a tion of Dou ble
Clu ster s [Cp F e (CO) (C H )] a n d
3
4
4
5
4
2
[
Cp F e (CO) (C H )] [(C H ) F e]
3
4
4
5
4
2
5
4 2
Wen-Yann Yeh,* Ching-Yuan Wu, and Leu-Wen Chiou
Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan 804
Received April 5, 1999
6
Summary: Reaction of Cp4Fe4(CO)4 (1) with RLi and
HBF4 in sequence affords Cp3Fe4(CO)4(C5H4R) (R) Me,
multielectron catalysis. Since its discovery, compound
7
-13
1 has been the subject of numerous research papers.
Recently, Rauchfuss and co-workers reported
n
14,15
Bu , and Ph) in moderate yields. Further sequential
func-
PhLi/ HBF4 treatment of Cp3Fe4(CO)4(C5H4Ph) produces
Cp2Fe4(CO)4(C5H4Ph)2. On the other hand, 1 reacts with
lithium diisopropylamide (LDA) and bromoferrocene
sequentially to produce a ferrocenylated cluster [Cp3Fe4-
tionalization of 1 to give Cp Fe (CO) (C H R) (R ) Bu,
3
4
4
5
4
Ph, C(OH)HCH , CO H, CHO, SPh, and PPh , etc.). We
3
2
2
have been independently investigating the substitution
1
6
reactions of 1 for many years. Presented in this note
are new derivatives of 1 containing alkyl, aryl, and
ferrocenyl substituents on the cyclopentadienyl ligands
as well as two novel double-clusters [Cp3Fe4(CO)4-
(CO)4(C5H4)][(C5H4)FeCp] (3) and a double cluster [Cp3-
Fe4(CO)4(C5H4)]2 (2). A similar LDA/ dibromoferrocene
treatment with 1 leads to 2, [Cp3Fe4(CO)4(C5H4)][(C5H4)-
(
[
C5H4Br)Fe] (4), and a ferrocenyl-bridged double cluster
Cp3Fe4(CO)4(C5H4)]2[(C5H4)2Fe] (5). The new com-
(C5H4)]2 and [Cp3Fe4(CO)4(C5H4)]2[(C5H4)2Fe].
pounds have been characterized by elemental analysis
and IR, mass, and NMR spectroscopy.
Exp er im en ta l Section
All manipulations were carried out under an atmosphere
1
7
2
of purified dinitrogen with standard Schlenk techniques. Cp -
In tr od u ction
1
8
19
20
Fe
2 4
(CO) , bis(diphenylphosphino)ferrocene, bromoferrocene,
and 1,1′-dibromoferrocene were prepared by literature meth-
2
1
The study of transition metal clusters is currently a
very active area of chemical research. The interest in
cluster compounds transcends their synthesis and unique
structural features. In addition, discrete, soluble metal
clusters often display catalytic activity and are studied
1
(
6) Bruce, D. W., O’Hare, D., Eds. Inorganic Materials: Wiley:
Chichester, U.K., 1997. (b) Interrante, L V., Hampden-Smith, M. J .,
Eds. Chemistry of Advanced Materials; Wiley-VCH: New York, 1998.
(7) (a) Trinh-Toan; Fehlhammer, W. P.; Dahl, L. F. J . Am. Chem.
Soc. 1972, 94, 3389. (b) Newman, M. A.; Trinh-Toan; Dahl, L. F. J .
Am. Chem. Soc. 1972, 94, 3383.
2
3
as models for the surface of bulk metals. Cp4Fe4(CO)4
4
(
1), originally reported by King, is one of the first
(8) Geatrix, P.; Greenwood, N. N. Discuss. Faraday Soc. 1969, 47,
1
26.
(
substances containing a tetrahedral cluster of metal
atoms. A unique feature of this stable cluster is that it
is electroactive, reversibly undergoing both reduction
9) Bock, C. R.; Wrighton, M. S. Inorg. Chem. 1977, 16, 1309.
(10) Frankel, R. B.; Reiff, W. M.; Meyer, T. J .; Cramer, J . L. Inorg.
Chem. 1974, 13, 2515.
11) Pittman, C. U., J r.; Ryan, R. C.; McGee, J .; O’Connor, J . P. J .
(
5
and oxidation, which property is essential to perform
Organomet. Chem. 1979, 178, C43.
important functions such as solar energy conversion and
(12) Symon, D. A.; Waddington, T. C. J . Chem. Soc., Dalton Trans.
1
973, 1879.
13) Okazaki, M.; Ohtani, T.; Inomata, S.; Tagaki, N.; Ogino, H. J .
(
(
1) (a) Adams, R. D. In Comprehensive Organometallic Chemistry
Am. Chem. Soc. 1998, 120, 9135.
(14) Westmeyer, M. D.; Massa, M. A.; Rauchfuss, T. B.; Wilson, S.
R. J . Am. Chem. Soc. 1998, 120, 114.
(15) For the first paper on the functionalization of 1, which described
the Friedel-Crafts acylation of the cluster, see: Massa, M. A.;
Rauchfuss, T. B. Chem. Mater. 1991, 3, 788.
II; Pergamon: Oxford, U.K., 1995; Vol. 10, p 1. (b) Chi, Y.; Hwang,
D.-K. In Comprehensive Organometallic Chemistry II; Pergamon:
Oxford, U.K., 1995; Vol. 10, p 85. (c) Shriver, D. F.; Kaesz, H. D.;
Adams, R. D. The Chemistry of Metal Cluster Complexes; VCH: New
York, 1990. (d) Bottomley, F.; Sutin, L. Adv. Organomet. Chem. 1988,
2
8, 339. (e) J ohnson, B. F. G., Ed. Transition Metal Clusters; Wiley:
New York, 1980.
2) (a) Gates, C., Guczi, L., Kn o¨ zlinger, H., Eds. Metal Clusters in
(16) (a) Chen, S.-B. M.S. Thesis, National Sun Yat-Sen University,
1993. (b) Chiou, L.-W. M.S. Thesis, National Sun Yat-Sen University,
1995. (c) Wu, C.-Y. M.S. Thesis, National Sun Yat-Sen University,
1998.
(17) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-
Sensitive Compounds, 2nd ed.; Wiley: New York, 1986.
(18) King, R. B. Organometallic Synthesis; Academic Press: New
York, 1965; Vol. 1, p 114.
(19) Bishop, J . J .; Davison, A.; Katcher, M. L.; Lichtenberg, D. W.;
Merrill, R. E.; Smark, J . C. J . Organomet. Chem. 1971, 27, 241.
(20) Bublitz, D. E.; Rinehart, K. L., J r. Org. React. 1969, 17, 1.
(21) Kovar, R. F.; Rausch, M. D.; Rosenberg, H. Organomet. Chem.
Synth. 1971, 1, 173.
(
Catalysis; Elsevier: Amsterdam, 1986. (b) Parshall, G. W.; Ittel, S. D.
Homogeneous Catalysis; Wiley: New York, 1992. (c) S u¨ ss-Fink, G.
Nachr. Chem. Technol. Lab. 1988, 36, 1110.
(3) (a) Muetterties, E. L. Bull. Soc. Chim. Belg. 1975, 84, 959. (b)
Albert, M. R.; Yates, J . T., J r. The Surface Scientist’s Guide to
Organometallic Chemistry; American Chemical Society: Washington,
D.C., 1987.
(
4) King, R. B. Inorg. Chem. 1966, 5, 2227.
(5) (a) Ferguson, J . A.; Meyer, T. J . Chem. Commun. 1971, 623. (b)
Ferguson, J . A.; Meyer, T. J . J . Am. Chem. Soc. 1972, 94, 3409.
1
0.1021/om9902333 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 07/20/1999

3
548 Organometallics, Vol. 18, No. 17, 1999
Notes
ods. Lithium diisopropylamide (LDA, 1.5 M in cyclohexane),
n-butyllithium (15% in n-hexane), methyllithium (1.4 M in
ether), phenyllithium (1.8 M, in cyclohexane-ether), tetra-
fluoroboric acid (85%, ether complex), and triphenylphosphine
were purchased from Aldrich and used as received. Solvents
were dried over appropriate reagents under dinitrogen and
distilled immediately before use. Preparative thin-layer chro-
matographic (TLC) plates were prepared from silica gel
an airtight syringe. The flask was then removed from the ice
bath, and the mixture was stirred at room temperature for 10
h, forming a dark green precipitate. The supernatant was
discarded, and the precipitate was washed with diethyl ether
and dried under vacuum. A solution of bromoferrocene (132
mg, 0.5 mmol) in THF (10 mL) was introduced, and the flask
was placed in an oil bath at 45-50 °C for 22 h. The solvent
was then removed on a rotary evaporator, and the residue was
subjected to TLC, eluting with ethyl acetate-dichloromethane-
n-hexane (1:1:3, v/v). The first band was the unreacted
(
Merck). Infrared spectra were recorded with a 0.1 mm path
1
CaF
2
solution cell on a Hitachi I-2001 IR spectrometer. H and
1
3
C NMR spectra were obtained on a Varian VXR-300 spec-
bromoferrocene. The second band was Cp (CO)
2
Fe
2
4
(5%). The
trometer at 300 and 75.4 MHz, respectively. Fast-atom-
bombardment (FAB) mass spectra were recorded by using a
VG Blotch-5022 mass spectrometer. Elemental analyses were
performed at the National Science Council Regional Instru-
mentation Center at National Chen-Kung University, Tainan,
Taiwan.
third band afforded [Cp Fe (CO) (C )][(C H )FeCp] (3) (90
3
4
4
5
H
4
5 4
mg, 23%). The fourth band recovered the starting material 1
in 33% yield. The materials after the fourth band were
collected and separated again by TLC, with ethyl acetate-
dichloromethane (3:1, v/v) as eluant. The second band afforded
3 4 4 5 4 2
[Cp Fe (CO) (C H )] (2) (17 mg, 6%). The remaining several
Alter n a tive Syn th esis of 1. Cp
2
Fe
2
(CO)
4
(100 mg, 0.28
bands were not characterized.
mmol), bis(diphenylphosphino)ferrocene (dppf, 188 mg, 0,34
mmol), and toluene (10 mL) were placed in a 100 mL Schlenk
flask. The mixture was heated to reflux under N for 10 h and
2
cooled to ambient temperature. The solvent was removed
under vacuum and the residue subjected to TLC, eluting with
dichloromethane. The first yellow band recovered dppf in 90%
yield. Isolation of the material forming the second green band
Compounds 2 and 3 were recrystallized from dichlo-
romethane-hexane at -20 °C to give dark green, air-stable
microcrystalline solids.
. Mass spectrum (FAB): m/z 1190 (M , 56Fe). IR (CH
+
2
2
Cl
2
):
-1
1
ν(CO) 1640 cm . H NMR (acetone-d
6
, 25 °C): δ 4.83 (s, 30H,
Cp), 4.78 (t, J H-H ) 2 Hz, 4H, C
). Anal. Calcd for C48
C, 48.09; H, 3.10.
: Mass spectrum (FAB): m/z 780 (M , 56Fe). IR (CH
5
H
Fe
4
), 4.68 (t, J H-H ) 2 Hz, 4H,
C
5
H
4
H
38
O
8
8
: C, 48.41; H, 3.22. Found:
afforded Cp
3
Fe
4
(CO)
4
(C
5
H
4
Ph) (1P h , 15 mg, 0.022 mmol, 16%
Fe
based on the Fe atoms). The third green band gave Cp
4
4
-
+
3
2
Cl
, 25 °C): δ 4.80 (t, J H-H ) 2
), 4.73 (t, J H-H ) 2 Hz, 2H, C -Fe ), 4.59
), 4.48 (t, J H-H ) 2 Hz, 2H, C Fe), 4.10
t, J H-H ) 2 Hz, 2H, C Fe), 3.89 (s, 5H, CpFe). Anal. Calcd
2
):
(
CO)
4
(1, 60 mg, 0.1 mmol, 71%).
-1 1
ν(CO) 1637 cm . H NMR (C
Hz, 2H, C -Fe
Fe
6 6
D
+
56
1
P h . Mass spectrum (FAB): m/z 672 (M , Fe) 613, 596,
5
H
4
4
5
H
H
5 4
4
4
-
1
1
4
95, 460, 443, 419. IR (C
6
H
6
): ν(CO) 1644 cm
.
H NMR
5 4
H ), 4.84
(
(
s, 15H, Cp
3
4
(
(
CDCl
t, 2H, C
. Mass spectrum (FAB): m/z 596 (M , 56Fe), 419. IR (C
3
, 20 °C): δ 7.78-7.23 (m, Ph), 5.01 (t, 2H, C
5
5
H
4
H
4
), 4.54 (s, 15H, Cp).
for C34
H
28
O
4
Fe
5
: C, 52.37; H, 3.62. Found: C, 52.47; H, 3.61.
+
1
6
H
6
):
i
Sequ en tia l LiNP r
(CO)
2 5 4 2 4
/(C H Br ) F e Tr ea tm en t of 1. Cp -
-
1 1
ν(CO) 1644 cm . H NMR (CDCl
Sequ en tia l RLi/HBF Tr ea tm en t of 1. Typically, an oven-
dried, 100 mL Schlenk flask was charged with Cp Fe (CO)
1) (50 mg, 0.084 mmol) and THF (5 mL) under N . The flask
3
, 20 °C): δ 4.77 (s, Cp).
Fe
4
4
(1) (250 mg, 0.42 mmol) was sequentially treated with
4
LDA (1.1 mL, 0.92 mmol) and dibromoferrocene (200 mg, 0.58
mmol) in a fashion identical with that above. The reaction
mixture was subjected to TLC, eluting with ethyl acetate-
dichloromethane-n-hexane (1:1:3, v/v). The first band was the
unreacted dibromoferrocene. The second band was [CpFe-
4
4
4
(
2
was placed in an ice bath, and PhLi (0.42 mmol) was slowly
introduced by a microsyringe, forming a yellow-green solution.
A methanol (2 mL) solution of HBF
4
(100 µL) was then
(
[
CO)
(C
2
]
4
2
(2%). The third band afforded [Cp
)(C Br)Fe] (4) (63 mg, 18%). The fourth band recov-
Fe (CO)
Fe] (5) (23 mg, 8%). The materials remaining
3 4 4 5 4
Fe (CO) (C H )]-
introduced into the flask, and the mixture was stirred at 0 °C
for 1 h. The volatile materials were removed under vacuum
and the residue separated by TLC, eluting with n-hexane-
dichloromethane-ethyl acetate (3:1:1, v/v). The first and
second green bands gave 1P h and unreacted 1 in 55% and
5
H
5 4
H
ered 1 (109 mg, 44%). The fifth band yielded [Cp
)] [(C
3
4
4
-
(
C
5
H
4
2
5 4 2
H )
on the TLC plates were extracted with methanol and purified
again by TLC, with ethyl acetate-dichloromethane (3:1, v/v)
as eluant. The second band afforded compound 2 (12 mg, 5%).
1
4% yield, respectively. Further PhLi/HBF
in an identical fashion led to 1P h in 41% yield.
Likewise, sequential MeLi/HBF and BuLi/HBF
of 1 afforded Cp Fe (CO) (C Me) (1Me, 40%) and (Cp
4
treatment of 1P h
2
The several other bands were not characterized.
4
4
treatments
Fe
. Mass spectrum (FAB): m/z 858 (M , 56Fe, 79Br). IR (CH
+
4
2
2
-
3
4
4
5
H
4
3
4
-
-1
1
Cl
H-H ) 2 Hz, 2H, C
Fe ), 4.63 (t, J H-H) 2 Hz, 2H, C
t, J H-H ) 2 Hz, 2H, C -Fe), 4.06 (t, J H-H ) 2 Hz, 2H, C
4 6
Br), 3.62 (t, J H-H ) 2 Hz, 2H, C H Br). C{ H} NMR (C D
): ν(CO) 1638 cm
.
H NMR (C
-Fe ), 4.73 (t, J H-H ) 2 Hz, 2H, C
-Fe),4.58 (s, 15H, Cp), 4.08
6 6
D , 25 °C): δ 4.76 (t,
n
(
CO)
acted 1.
P h
71, 495. IR (CH
0 °C): δ 7.78-7.23 (m, Ph), 4.89 (t, 2H, C
), 4.32 (s, 10H, Cp). Anal. Calcd for C36
H, 3.74. Found: C, 57.32; H, 3.70.
4
(C
5
H
4
Bu ) (1Bu , 52%), respectively, together with unre-
J
5
H
4
4
5 4
H -
4
5 4
H
. Mass spectrum (FAB): m/z 748 (M , 56Fe), 718, 647,
+
1
2
(
5
H
4
5
H
4
-
,
-
1
1
5
2
C
2
Cl
2
): ν(CO) 1640 cm
.
H NMR (CDCl
), 4.67 (t, 2H,
Fe : C, 57.75;
3
,
13
1
5
6
5
H
4
2
6
5 °C): δ 290 (CO), 289 (CO), 105.9, 94.7, 99.5, 72.4, 72.1, 70.4,
9.0 (Cp). Anal. Calcd for C34 BrFe : C, 47.56; H, 3.17.
5
H
4
H
28
O
4
4
H
27
O
4
5
Found: C, 47.44; H, 3.16.
. Mass spectrum (FAB): m/z 1374 (M , 56Fe). IR (CH
Me. Mass spectrum (FAB): m/z 610 (M , 56Fe), 596, 433,
+
1
+
5
2
Cl
, 25 °C): δ 4.86 (dd, J H-H ) 2
), 4.79 (dd, J H-H ) 2 Hz, 4H, C -Fe ),
.74 (s, 30H, Cp), 4.50 (dd, J H-H ) 2 Hz, 4H, C -Fe), 4.22
9
-Fe). Anal. Calcd for C58 Fe :
2
):
-
1
1
4
19. IR (THF): ν(CO) 1644 cm
.
H
H NMR (CDCl
), 4.39 (t, 2H, C
3
, 20 °C):
), 2.05
-1 1
ν(CO) 1640 cm . H NMR (C
Hz, 4H, C -Fe
6 6
D
δ 4.72 (s, 15H, Cp), 4.65 (t, 2H, C
s, 3H, Me). Anal. Calcd for C25
Found: C, 49.48; H, 3.57.
5
4
5
H
4
5
H
4
4
5
H
4
4
(
H
22
O
4
Fe
4
: C, 49.18; H, 3.60.
4
5 4
H
(
dd, J H-H ) 2 Hz, 4H, C
5
H
4
H
46
O
8
Bu . Mass spectrum (FAB): m/z 652 (M , 56Fe), 624, 596,
+
1
C, 50.72; H, 3.38. Found: C, 50.74; H, 3.45.
-
1
1
4
2
2
75, 419. IR (THF): ν(CO) 1648 cm . H NMR (acetone-d
0 °C):δ 4.66 (s, 15H, Cp), 4.59 (t, 2H, C ), 4.40 (t, 2H, C
.54 (t, 2H, Bu). 1.55-1.20 (m, 4H, Bu), 0.85 (t, 3H, Bu).
6
,
H ),
5 4
5
H
4
Resu lts a n d Discu ssion
i
Sequ en tia l LiNP r
oven-dried, 100 mL Schlenk flask was charged with Cp
CO) (1) (300 mg, 0.50 mmol) and freshly distilled diethyl
2
/(C
5
H
4
Br )F eCp Tr ea tm en t of 1. An
Syn th esis. Cp4Fe4(CO)4 (1, 71%) and Cp3Fe4(CO)4-
C5H4Ph) (1P h , 16%) have been obtained from ther-
4
4
Fe -
(
(
4
molysis of [CpFe(CO)2]2 and bis(diphenylphosphino)-
ether (30 mL) and THF (10 mL) under a dinitrogen atmo-
sphere. The flask was placed in an ice bath, and lithium
diisopropylamide (LDA, 1.34 mL, 2.01 mmol) was added via
4
ferrocene in refluxing toluene for 10 h. King originally
prepared 1 in 14% yield by heating [CpFe(CO)2]2 in

Notes
Organometallics, Vol. 18, No. 17, 1999 3549
Sch em e 1
reluxing xylene for 14 days. A modified method de-
scribed by White22 was to heat [CpFe(CO)2]2 and PPh3
in refluxing xylene to give 1 in 56% yield, whereas
To figure out if deprotonation reaction occurs in the
above reactions, compound 1 was successively treated
n
with Bu Li and bromoferrocene. The reaction mixture
1
4
Rauchfuss carried out the same reaction to obtain 1
after separation by TLC leads to mainly unreacted 1
(20%) and 1Bu (24%) and a ferrocenylated product [Cp3-
Fe4(CO)4(C5H4)][(C5H4)FeCp] (3) in 9% yield. Appar-
ently, the alkyl- and aryllithium reagents are capable
of functioning as a nucleophile, reducing agent, and base
in their reactions with 1.
(
(
27%), 1P h (3%), and a triiron cluster Cp3Fe3(CO)3-
PPh2) (1%). Rheingold23 prepared 1 in nearly 80% yield
by carrying out the above reaction under UV irradiation.
The discovery of 1P h by Rauchfuss is novel because it
was totally unsuspected in the previous reports. The
origin of the phenyl substituent in 1P h is not certain,
presumably from fragmentation of the phosphine co-
reactant.
It becomes clear that a strong base of poor nucleo-
philicity, such as lithium diisopropylamide (LDA) or
2
4
lithium tetramethylpiperidide (LTMP), should facili-
tate the deprotonation reaction. Thus, sequential treat-
ment of Cp Fe (CO) (1) with LDA and bromoferrocene
Reaction of 1 and RLi in THF at 0 °C followed by
acidification with HBF4 affords Cp3Fe4(CO)4(C5H4R) in
4
4
4
n
4
0%, 52%, and 55% yields for R ) Me (1Me), Bu (1Bu ),
significantly increases the yield of 3 (23%) together with
-
+
and Ph (1P h ), respectively. Further Ph /H treatment
of 1P h affords 1P h 2 in 41% yield (eq 1). Rauchfuss and
a novel fulvalenyl-bridged double cluster [Cp Fe (CO) -
3
4
4
(C H )] (2, 6%) and several uncharacterized products.
5
4
2
A similar reaction, but replacing bromoferrocene by
dibromoferrocene, affords 2 (5%), [Cp3Fe4(CO)4(C5H4)]-
[(C5H4)(C5H4Br)Fe] (4, 18%), and a ferrocenyl-bridged
double cluster [Cp3Fe4(CO)4(C5H4)]2[(C5H4)2Fe] (5, 8%).
The results are summarized in Scheme 1. In both
reactions, 1 is recovered in 33-45% yield even though
the reactions monitored by IR show no presence of 1
after introduction of LDA. Presumably, reduction of 1
competes with deprotonation reaction here and limits
the utility of the LDA reagent.
The use of LDA as a nonnucleophilic base, previously
1
4
shown by Rauchfuss on the functionalization of 1, is
a unique method because LDA is not commonly em-
2
5
ployed to metalate Cp ligands. Moreover, nucleophilic
displacement of the bromide atom from ferrocene de-
-
rivatives by [Cp3Fe4(CO)4(C5H4)] anion to generate 3-5
-
is an unusual reaction. It is normally the [CpFe(C5H4)]
2
-
and [Fe(C5H4)2] anions prepared from bromoferrocene
and ferrocene that react with electrophiles, such as acyl
halides and aldehydes, on the functionalization of
co-workers recently showed the reactions of 1 with
n
Bu Li and PhLi at -40 °C, following by adding Ph2S2
26
ferrocene. Finally, the formation of 2 is noted. It is
1
4
and workup in air, to afford 1Bu (44%) and 1P h (5%).
In the latter reaction, the low yield of 1P h was at-
tributed to reduction which competes with nucleophilic
addition at low temperature.
(24) (a) Bennett, M. A.; Wenger, E. Chem. Ber. 1997, 130, 1029. (b)
Lu, Z.; Abboud, K. A.; J ones, W. M. Organometallics 1993, 12, 1471.
(
25) Sun, X.; Kenkre, S. L.; Remenar, J . F.; Gilchrist, J . H.; Collum,
D. B. J . Am. Chem. Soc. 1997, 119, 4765.
26) (a) Togni, A., Halterman, R. L., Eds. Metallocenes; Wiley-
(
(
22) White, A. J . J . Organomet. Chem. 1979, 168, 197.
VCH: Weinheim, 1998. (b) Togni, A., Hayashi, T., Eds. Ferrocenes;
VCH: Weinheim, 1994.
(23) Landon, S. J .; Rheingold, A. J . Inorg. Chim. Acta 1981, 47, 187.

3
550 Organometallics, Vol. 18, No. 17, 1999
Notes
1
F igu r e 1. 300 MHz H NMR spectrum of compound 3 obtained in C
6
D
6
at 25 °C.
-
likely that [Cp3Fe4(CO)4(C5H4)] attacks 1 to afford the
cluster display a singlet resonance and each substituted
C5H4 group shows two sets of multiplet resonances,
consistent with a molecule of idealized Cs symmetry in
-
intermediate [(Cp3Fe4(CO)4)2(C5H4-C5H5)] , followed by
dehydration, which leads to 2.
1
Sp ectr oscop ic Ch a r a cter iza tion of New Com -
p ou n d s. The spectroscopic data of 1P h and 1Bu closely
agree with those recently reported by Rauchfuss and
co-workers. The new compounds 1Me, 1P h 2, and 2-5
give satisfactory C, H elemental analyses and have been
characterized by mass, IR, and NMR spectroscopy.
Compounds 1P h 2 and 1Me form air-stable, green
crystalline solids. The FAB mass spectrum of 1Me
presents the molecular ion peak at m/z 610, and 1P h 2
solution. The H NMR spectrum of 3 is illustrated in
Figure 1. The sharp singlets at δ 4.59 and 3.89 in a 3:1
ratio are attributed to the Cp3Fe4 and CpFe groups,
respectively, while the triplet signals at δ 4.80 and 4.73
are assigned to the C5H4Fe4 protons and the triplet
signals at δ 4.48 and 4.10 to the C5H4Fe protons. The
pseudo-triplet pattern apparently rises from overlap of
a doublet of doublets, where each ortho proton is coupled
with two magnetically nonequivalent meta protons and
vice versa.
1
4
1
at m/z 748. The H NMR of 1Me shows two singlets at
δ 2.05 and 4.71 for the Me and Cp protons and two
pseudo-triplets in equal intensity at δ 4.39 and 4.65 for
the C5H4 group. The H NMR pattern of 1P h 2 is
Con clu sion s
1
Several novel iron clusters, with the metal nuclearity
of 4, 5, 8, and 9, have been prepared from 1 through
functionalization of the Cp rings with methyl, butyl,
phenyl, ferrocenyl, and Cp3Fe4(CO)4(C5H4) groups. Com-
pound 1 is susceptible to nucleophilic addition, depro-
tonation, and reduction, depending on the nucleophilicity/
basicity of the organolithium reagents and the reaction
conditions. Preliminary cyclic voltammetric study of
these compounds shows interesting, but complicated
results. Efforts to isolate the oxidized/reduced species
of 2-5 through chemical redox methods as well as
investigation of their electrochemical properties are
currently undertaken.
identical with that of 1P h , clearly indicating that the
two phenyl substituents are located on different cyclo-
pentadienyl groups.
The FAB mass spectra of 2-5 display their molecular
ion peaks at m/z 1190, 780, 858, and 1374, respectively,
5
6
79
for Fe and Br isotopes. The isotopic distribution of
the envelope surrounding the molecular ions matches
that expected for these compounds, and there is good
agreement between the calculated mass distribution and
the observed mass spectra. The IR spectra of these
compounds in the carbonyl region present one broad
-1
absorption at 1640 cm for the triply bridging carbonyl
ligands, suggesting that their tetrahedral iron cores
remain intact.
We are grateful for support of this work by the
National Science Council of Taiwan.
1
The H NMR spectra of 2-5 are closely related, where
the unsubstituted Cp groups coordinated to the Fe4
OM9902333