Reactions of Doubly Bridged Bis(cyclopentadienes) with Iron Pentacarbonyl

Article abstract of DOI:10.1021/om030364a

When the doubly bridged bis(cyclopentadiene) ligand (Me ₂C)(Me₂Si)(C₅H₄)₂ (1) reacted with Fe(CO)₅ in refluxing toluene, the unusual product [(C₅H₆)(Me₂C)(Me₂Si)(η ⁵-C₅H₃)Fe(CO)]₂-(μ-CO) ₂ (2) with a hydrogenated double bond in one of the cyclopentadiene ligands, the diiron complex (Me₂C)(Me₂Si)[(η ⁵-C₅H₃)Fe(CO)₂]₂ (3), and the desilylation product 4 were obtained. When the reaction was performed in refluxing xylene, the novel complex (Me₂C)(η ⁵-C₅H₃)-(η⁵:η ¹-C₅H₃)[(Me₂Si)Fe(CO) ₂][Fe(CO)₂] (5) with an Fe-Si bond, which should be accompanied by the cleavage of a C-Si bond in the ligand, was isolated in addition to the complexes 2~4. When bis(cyclopentadienyl) ligands bridged with R₂C (R₂C = Me₂C, (CH₂)₅C) and Me₂E (E = Si, Ge) groups were used instead of 1, the similar novel complexes (R₂C)(η⁵-C₅H ₃)(η⁵: η¹-C₅H ₃)[(Me₂E)Fe(CO)₂][Fe(CO)₂] (R ₂C = Me₂C, E = Ge (7); R₂C = (CH ₂)₅C, E = Si (17), Ge (21)) with an Fe-E bond were obtained in addition to the diiron complexes (R₂C)(Me ₂E)[(η⁵-C₅H₃)Fe(CO)] ₂(μ-CO)₂ (R₂C = Me₂C, E = Ge (8) ; R₂C = (CH₂)₅C, E = Si (18), Ge (22)) and the desilylation or degermylation products. When a tert-butyl group was introduced into the cyclopentadienyl rings, or two phenyl groups were introduced at the bridging silicon atom instead of two methyl groups in 1, only the diiron complexes (Me₂C)(Me₂E)[(η⁵-t-BuC ₅H₂)Fe(CO)₂]₂ (E = Si(10), Ge (13)) and (Me₂C)(Ph₂Si)[(η⁵-C₅H ₃)Fe(CO)₂]₂ (15) were obtained, in addition to the desilylation or degermylation products. When a methylene bridge was used instead of an isopropylene bridge in 1 and 6, the partially hydrogenated complexes (Me₂E)(η³-CHC₅H ₆)(η⁵-C₅H₃)Fe(CO) ₃Fe(CO)₂ (E = Si (24), Ge (28)), the diiron complexes (CH₂)(Me₂E)[(η⁵-C₅H ₃)Fe(CO)]₂(μ-CO)_2n (E = Si (25), Ge (29)), and the desilylation or degermylation products were obtained. The molecular structures of 2, 3, 5, 7, 8, 10, 11t, 15, 17, 18, 21, 24, 25, 28, and 29 were determined by X-ray diffraction.

Full text of DOI:10.1021/om030364a

Organometallics 2003, 22, 5543-5555
5543
Rea ction s of Dou bly Br id ged Bis(cyclop en ta d ien es) w ith
Ir on P en ta ca r bon yl
Baiquan Wang,* Bolin Zhu, J ianyong Zhang, Shansheng Xu, Xiuzhong Zhou, and
Linhong Weng†
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, People’s Republic of China
Received May 14, 2003
When the doubly bridged bis(cyclopentadiene) ligand (Me2C)(Me2Si)(C5H4)2 (1) reacted with
Fe(CO)5 in refluxing toluene, the unusual product [(C5H6)(Me2C)(Me2Si)(η5-C5H3)Fe(CO)]2-
(µ-CO)2 (2) with a hydrogenated double bond in one of the cyclopentadiene ligands, the diiron
complex (Me2C)(Me2Si)[(η5-C5H3)Fe(CO)2]2 (3), and the desilylation product 4 were obtained.
When the reaction was performed in refluxing xylene, the novel complex (Me2C)(η5-C5H3)-
(η5:η1-C5H3)[(Me2Si)Fe(CO)2][Fe(CO)2] (5) with an Fe-Si bond, which should be accompanied
by the cleavage of a C-Si bond in the ligand, was isolated in addition to the complexes 2∼4.
When bis(cyclopentadienyl) ligands bridged with R2C (R2C ) Me2C, (CH2)5C) and Me2E
(E ) Si, Ge) groups were used instead of 1, the similar novel complexes (R2C)(η5-C5H3)(η5:
η1-C5H3)[(Me2E)Fe(CO)2][Fe(CO)2] (R2C ) Me2C, E ) Ge (7); R2C ) (CH2)5C, E ) Si (17), Ge
(21)) with an Fe-E bond were obtained in addition to the diiron complexes (R2C)(Me2E)-
[(η5-C5H3)Fe(CO)]2(µ-CO)2 (R2C ) Me2C, E ) Ge (8); R2C ) (CH2)5C, E ) Si (18), Ge (22))
and the desilylation or degermylation products. When a tert-butyl group was introduced
into the cyclopentadienyl rings, or two phenyl groups were introduced at the bridging silicon
atom instead of two methyl groups in 1, only the diiron complexes (Me2C)(Me2E)[(η5-t-
BuC5H2)Fe(CO)2]2 (E ) Si(10), Ge (13)) and (Me2C)(Ph2Si)[(η5-C5H3)Fe(CO)2]2 (15) were
obtained, in addition to the desilylation or degermylation products. When a methylene bridge
was used instead of an isopropylene bridge in 1 and 6, the partially hydrogenated complexes
(Me2E)(η3-CHC5H6)(η5-C5H3)Fe(CO)3Fe(CO)2 (E ) Si (24), Ge (28)), the diiron complexes
(CH2)(Me2E)[(η5-C5H3)Fe(CO)]2(µ-CO)2 (E ) Si (25), Ge (29)), and the desilylation or
degermylation products were obtained. The molecular structures of 2, 3, 5, 7, 8, 10, 11t, 15,
17, 18, 21, 24, 25, 28, and 29 were determined by X-ray diffraction.
In tr od u ction
Bridged bis(cyclopentadienyl) transition-metal com-
plexes have been investigated widely in recent years.
Bridged bis(cyclopentadienyl) ligands may be used in
the synthesis of ansa-metallocenes, which are well-
known catalyst precursors for stereospecific R-olefin
polymerization.1 Bridged bis(cyclopentadienyl) dinuclear
metal complexes in which two reactive metal centers
are held in close proximity could potentially exhibit
cooperative electronic and chemical effects that would
be useful in catalysis.2 In comparison with singly
bridged bis(cyclopentadienyl)metal complexes, doubly
bridged bis(cyclopentadienyl) ligands are more rigid,
which could result in unique properties in structures
and catalysis. Doubly bridged ansa-metallocenes (type
A) may offer a more constrained environment, which
represent a new class of stereorigid metallocene cata-
lysts for stereospecific R-olefin polymerization.3 In di-
nuclear complexes (types C and D), the doubly bridged
ligands restrict the relative orientation of the two
metals, locking the metals on either the same (cis) or
opposite (trans) faces of the ligand. Doubly bridged
dinuclear group IV metallocene complexes have been
investigated extensively as olefin polymerization cata-
lysts.4 In doubly bridged dinuclear or polynuclear met-
allocenes (M ) Fe, Co, Ni, Cr, V) the intramolecular
magnetic and electrostatic interactions between the
metal centers have been probed by cyclic voltammetry.5
Intramolecular electron transfer has also been observed
in highly concentrated solutions.5c
* To whom correspondence should be addressed. Fax: 86-22-
23502458. E-mail: bqwang@nankai.edu.cn.
† Present address: Department of Chemistry, Fudan University,
Shanghai 200433, People’s Republic of China.
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1253.
10.1021/om030364a CCC: $25.00 © 2003 American Chemical Society
Publication on Web 11/22/2003

5544 Organometallics, Vol. 22, No. 26, 2003
Wang et al.
Doubly bridged bis(cyclopentadienyl) dinuclear metal
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cently, we synthesized some doubly bridged bis(cyclo-
pentadienyl) diiron complexes by the reaction of differ-
ent doubly bridged ligands with Fe(CO)5.8 Here, we
further report the reaction of carbon and silicon or
germanium doubly bridged bis(cyclopentadienes) with
Fe(CO)5.
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Exp er im en ta l Section
Gen er a l Con sid er a tion s. Schlenk and vacuum line tech-
niques were employed for all manipulations. All solvents were
distilled from appropriate drying agents under argon prior to
use. 1H NMR spectra were recorded on a Bruker AC-P200
instrument, while IR spectra were recorded as KBr disks on
a Nicolet560 ESP FTIR spectrometer. Elemental analyses were
performed on a Perkin-Elmer 240C analyzer. (Me2C)(C5H5)2,9
(Me2C)(Me2Si)(C5H4)2 (1),9 (Me2C)(Me2Ge)(C5H4)2 (6),9 (Me2C)-
(t-BuC5H4)2,10 [(CH2)5C](C5H4)2,11 and (CH2)(C5H5)2 were
prepared according to the literature methods.
12
Rea ction of (Me2C)(Me2Si)(C5H4)2 (1) w ith F e(CO)5 in
Tolu en e. A solution of 1.43 g (6.24 mmol) of (Me2C)(Me2Si)-
(C5H4)2 (1) and 1.8 mL (13.7 mmol) of Fe(CO)5 in 50 mL of
toluene was refluxed for 16 h. After removal of solvent the
residue was chromatographed on an alumina column using
petroleum ether/CH2Cl2 as eluent. The first band (red) afforded
0.38 g (9%) of 2 as deep red crystals. The second band (green)
gave 0.82 g (29%) of 3 as deep green crystals. The third band
(red) afforded 0.12 g (5%) of 4 as deep red crystals. Data for 2
are as follows. Mp: 160 °C dec. Anal. Calcd for C34H42Fe2-
1
Si2O4: C, 59.83; H, 6.20. Found: C, 59.78; H, 6.23. H NMR
(CDCl3): δ 5.00 (s, 2H, C5H3), 4.68 (s, 2H, C5H3), 3.50 (s, 2H,
C5H3), 2.44 (m, 8H, CdCCH2), 1.77-1.45 (m, 4H, CH2CH2CH2),
1.63 (s, 6H, CMe), 1.30 (s, 6H, CMe), 0.55 (s, 6H, SiMe), 0.22
(s, 6H, Si-Me). IR (νCO, cm-1): 1950 (s), 1938 (s), 1763( s).
Data for 3 are as follows. Mp: 281-282 °C. Anal. Calcd for
C
19H18Fe2SiO4: C, 50.70; H, 4.03. Found: C, 50.35; H, 4.13.
1H NMR (CDCl3): δ 4.99 (s, 2H, C5H3), 4.80 (s, 2H, C5H3), 4.57
(s, 2H, C5H3), 1.52 (s, 3H, CMe), 1.43 (s, 3H, CMe), 0.62 (s,
3H, Si-Me), 0.58 (s, 3H, Si-Me). IR (νCO, cm-1): 1993 (s), 1950
(s), 1929 (s). Data for 4 are as follows.13 1H NMR (CDCl3): δ
5.16 (s, 4H, C5H4), 5.07 (s, 4H, C5H4), 1.40 (s, 6H, Me). IR (νCO
,
cm-1): 1988 (s), 1942 (s), 1774 (s).
Rea ction of (Me2C)(Me2Si)(C5H4)2 (1) w ith F e(CO)5 in
Xylen e. A solution of 2.8 g (12.3 mmol) of 1 and 3.4 mL (26
mmol) of Fe(CO)5 in 80 mL of xylene was refluxed for 10 h.
After removal of solvent the residue was chromatographed on
an alumina column using petroleum ether/CH2Cl2 as eluent.
The first band (yellow) afforded 0.32 g (6%) of 5 as yellow
crystals. The second band afforded 0.55 g (13%) of 2. The third
band gave 1.1 g (29%) of 3. The fourth band afforded 0.22 g
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Reactions of Bis(cyclopentadienes) with Fe(CO)5
Organometallics, Vol. 22, No. 26, 2003 5545
(4%) of 4. Data for 5 are as follows. Mp: 178 °C dec. Anal.
δ 6.33 (m, 2H, C5H3), 5.81 (s, 2H, C5H3), 3.02 (s, 2H, C5H3),
1.43 (s, 6H, CMe), 1.18 (s, 18H, CMe3), -0.02 (s, 6H, GeMe).
Calcd for C19H18Fe2SiO4: C, 50.70; H, 4.03. Found: C, 50.80;
1
H, 4.29. H NMR (CDCl3): δ 5.69 (m, 1H, C5H3), 5.40 (m, 1H,
Rea ction of 12 w ith F e(CO)5. A solution of 0.8 g (2.0
mmol) of 12 and 0.9 mL (6.8 mmol) of Fe(CO)5 in 30 mL of
xylene was refluxed for 7 h. After removal of solvent the
residue was chromatographed on an alumina column using
petroleum ether/CH2Cl2 as eluent. The first band (green) gave
0.04 g (3%) of 13 as dark green crystals. The second band (red)
afforded 0.05 g (5%) of 11t. 13: mp 214 °C. Anal. Calcd for
C27H34Fe2GeO4: C, 53.44; H, 5.65. Found: C, 53.60; H, 5.61.
1H NMR (CDCl3): δ 4.86 (s, 2H, C5H2), 4.64 (s, 2H, C5H2), 1.46
(s, 3H, CMe), 1.39 (s, 3H, CMe), 1.21 (s, 18H, CMe3), 0.73 (s,
3H, GeMe), 0.67 (s, 3H, GeMe). IR (νCO, cm-1): 1993 (s), 1942
(s), 1932 (s), 1902 (m).
C5H3), 5.00 (m, 1H, C5H3), 4.86 (m, 1H, C5H3), 4.40 (m, 1H,
C5H3), 4.32 (m, 1H, C5H3), 1.52 (m, 3H, CMe), 1.42 (s, 3H,
CMe), 0.70 (s, 3H, SiMe), 0.62 (s, 3H, Si-Me). IR (νCO, cm-1):
2017 (s), 1979 (s), 1952 (s), 1920 (s).
Rea ction of (Me2C)(Me2Ge)(C5H4)2 (6) w ith F e(CO)5. A
solution of 0.6 g (2.2 mmol) of 6 and 0.9 mL (6.8 mmol) of
Fe(CO)5 in 30 mL of xylene was refluxed for 10 h. After
removal of solvent the residue was chromatographed on an
alumina column using petroleum ether/CH2Cl2 as eluent. The
first band (yellow) afforded 0.36 g (26%) of 7 as orange-red
crystals. The second band (green) gave 0.12 g (9%) of 8 as black
crystals. The third band (red) afforded 0.04 g (4%) of 4. Data
P r ep a r a tion of (Me2C)(P h 2Si)(C5H4)2 (14). To a suspen-
sion of dilithium salts of (Me2C)(C5H5)2, prepared from 5.0 g
(29.0 mmol) of (Me2C)(C5H5)2 and 58 mmol of an n-BuLi hexane
solution in 100 mL of THF, was added slowly 7.3 g (29.0 mmol)
of Ph2SiCl2. After the mixture was refluxed for 2 days, the
solvents were removed under reduced pressure. The residue
was extracted with pentane. Upon concentration and cooling,
4.2 g (41%) of 14 was obtained as a light yellow solid. Mp:
114-115 °C. Anal. Calcd for C25H24Si: C, 85.17; H, 6.86.
for 7 are as follows. Mp: 185 °C dec. Anal. Calcd for C19H18
-
Fe2GeO4: C, 46.14; H, 3.67. Found: C, 45.64; H, 3.59. 1H NMR
(CDCl3): δ 5.62 (m, 1H, C5H3), 5.43 (m, 1H, C5H3), 4.97 (m,
1H, C5H3), 4.75 (m, 1H, C5H3), 4.35 (m, 2H, C5H3), 1.53 (s, 3H,
CMe), 1.44 (s, 3H, CMe), 0.80 (s, 3H, GeMe), 0.71 (s, 3H,
GeMe). IR (νCO, cm-1): 2016 (s), 1982 (s), 1952 (s), 1924 (s).
Data for 8 are as follows. Mp: 160 °C dec. Anal. Calcd for
C
19H18Fe2GeO4: C, 46.14; H, 3.67. Found: C, 45.96; H, 4.23.
1H NMR (CDCl3): δ 5.00 (m, 2H, C5H3), 4.62 (m, 2H, C5H3),
4.60 (m, 2H, C5H3), 1.51 (s, 3H, CMe), 1.48 (s, 3H, CMe), 0.81
(s, 3H, GeMe), 0.71 (s, 3H, GeMe). IR (νCO, cm-1): 1975 (s),
1938 (s), 1770 (s).
1
Found: C, 85.18; H, 6.80. H NMR (CDCl3): δ 7.80-7.00 (m,
10H, Ph H), 6.78 (m), 6.61 (m), 6.30-6.20 (m), 3.20 (m), 3.08
(s) (total 8H, C5H4), 1.64, 1.48, 1.43 (s, s, s, 6H, CMe).
Rea ction of 14 w ith F e(CO)5. A solution of 0.8 g (2.3
mmol) of 14 and 0.9 mL (6.8 mmol) of Fe(CO)5 in 30 mL of
xylene was refluxed for 7 h. After removal of solvent the
residue was chromatographed on an alumina column using
petroleum ether/CH2Cl2 as eluent. The first band (green) gave
0.10 g (8%) of 15 as dark green crystals. The second band (red)
afforded 0.20 g (22%) of 4. Data for 15 are as follows. Mp: 220
°C dec. Anal. Calcd for C27H34Fe2O4Si: C, 60.65; H, 3.86.
Found: C, 61.24; H, 3.59. 1H NMR (CDCl3): δ 7.84 (m, 2H,
Ph H), 7.67 (m, 2H, Ph H), 7.45-7.30 (m, 6H, Ph H), 5.26 (m,
2H, C5H3), 4.90 (m, 2H, C5H3), 4.67 (m, 2H, C5H3), 1.43 (s, 3H,
CMe), 1.11 (s, 3H, CMe). IR (νCO, cm-1): 1993 (s), 1942 (s),
1932 (s), 1902 (s).
Similarly, 0.60 g (2.2 mmol) of 6 reacted with 0.9 mL (6.8
mmol) of Fe(CO)5 in refluxing toluene for 19 h to give 0.11 g
(11%) of 8 and small amounts of 7 and 4.
P r ep a r a tion of (Me2C)(Me2Si)(t-Bu C5H3)2 (9). A 9.5 mL
portion of an n-BuLi solution in hexane (2.54 M, 24.6 mmol)
was added to a solution of 3.5 g (12.3 mmol) of (Me2C)(t-
BuC5H4)2 in 100 mL of THF at 0 °C. The mixture was stirred
for 24 h at room temperature to give a white suspension of
dilithium salts. To the suspension was added slowly 1.6 g (12.3
mmol) of Me2SiCl2. After the mixture was stirred for 48 h at
room temperature, the solvents were removed under reduced
pressure. The residue was extracted with pentane, and the
solvent was concentrated; 4.0 g (95%) of 9 was obtained as
light yellow crystals. Mp: 128 °C. Anal. Calcd for C23H36Si:
C, 81.10; H, 10.65. Found: C, 80.75; H, 8.81. 1H NMR
(CDCl3): δ 6.20 (s, 2H, C5H3), 5.86 (s, 2H, C5H3), 3.46 (s, 2H,
C5H3), 1.57 (s, 3H, CMe), 1.46 (s, 3H, CMe), 1.17 (s, 9H, CMe3),
1.11 (s, 9H, CMe3), 0.43 (s, 3H, SiMe), 0.33 (s, 3H, Si-Me).
Rea ction of 9 w ith F e(CO)5. A solution of 0.6 g (1.8 mmol)
of 9 and 0.9 mL (6.8 mmol) of Fe(CO)5 in 30 mL of xylene was
refluxed for 10 h. After removal of solvent the residue was
chromatographed on an alumina column using petroleum
ether/CH2Cl2 as eluent. The first band (green) gave 0.18 g
(18%) of 10 as dark green crystals. The second band (red)
afforded 0.02 g (2%) of 11t as deep red crystals. The third band
(red) afforded a trace amount of 11c as deep red crystals. Data
P r ep a r a tion of [(CH2)5C](Me2Si)(C5H4)2 (16). To a sus-
pension of dilithium salts of [(CH2)5C](C5H5)2, prepared from
2.0 g (9.4 mmol) of [(CH2)5C](C5H5)2 and 18.8 mmol of n-BuLi
hexane solution in 50 mL of THF, was added slowly 1.2 g (9.4
mmol) of Me2SiCl2. After the mixture was refluxed for 2 days,
the solvents were removed under reduced pressure. The
residue was extracted with pentane. After removal of solvent,
1.1 g (43%) of 16 was obtained as a light yellow liquid. 1H NMR
(CDCl3): δ 6.50-6.20 (m, 6H, C5H3), 3.63 (m, 2H, C5H3), 2.20-
1.20 (m, 10H, CH2), 0.50, 0.46 (s, s, total 3H, SiMe), -1.17,
-1.20 (s, s, total 3H, SiMe).
Rea ction of 16 w ith F e(CO)5. A solution of 0.35 g (1.4
mmol) of 16 and 0.6 mL (4.6 mmol) of Fe(CO)5 in 20 mL of
xylene was refluxed for 6 h. After removal of solvent the
residue was chromatographed on an alumina column using
petroleum ether/CH2Cl2 as eluent. The first band (yellow)
afforded 0.10 g (16%) of 17 as orange-red crystals. The second
band (green) gave 0.15 g (24%) of 18 as black crystals. The
third band (red) afforded 0.05 g (9%) of 19 as deep red crystals.
Data for 17 are as follows. Mp: 232 °C dec. Anal. Calcd for
for 10 are as follows. Mp: 220 °C dec. Anal. Calcd for C27H34
-
Fe2O4Si: C, 57.67; H, 6.09. Found: C, 57.71; H, 6.13. 1H NMR
(CDCl3): δ 4.86 (s, 2H, C5H2), 4.67 (s, 2H, C5H2), 1.48 (s, 3H,
CMe), 1.34 (s, 3H, CMe), 1.22 (s, 18H, CMe3), 0.57 (s, 3H,
SiMe), 0.54 (s, 3H, SiMe). IR (νCO, cm-1): 1997 (s), 1946 (s),
1926 (s), 1902 (m). Data for 11t are as follows. Mp: 222 °C
dec. Anal. Calcd for C25H30Fe2O4: C, 59.32; H, 5.97. Found:
1
C, 58.88; H, 6.61. H NMR (CDCl3): δ 5.08 (s, 2H, C5H3), 4.92
C
22H22Fe2SiO4: C, 53.91; H, 4.52. Found: C, 53.50; H, 4.70.
1H NMR (CDCl3) δ: 5.74 (m, 1H, C5H3), 5.39 (m, 1H, C5H3),
5.10 (m, 1H, C5H3), 4.86 (m, 1H, C5H3), 4.42 (m, 1H, C5H3),
4.31 (m, 1H, C5H3), 2.10-1.40 (m, 10H, CH2), 0.70 (s, 3H,
SiMe), 0.61 (s, 3H, SiMe). IR (νCO, cm-1): 2026 (s), 1981 (s),
1962 (s), 1918 (s). Data for 18 are as follows. Mp: 230 °C dec.
Anal. Calcd for C22H22Fe2SiO4: C, 53.91; H, 4.52. Found: C,
53.25; H, 4.92. 1H NMR (CDCl3): δ 4.99 (m, 2H, C5H3), 4.87
(m, 2H, C5H3), 4.62 (m, 2H, C5H3), 1.90-1.40 (m, 10H, CH2),
0.61 (s, 3H, SiMe), 0.55 (s, 3H, SiMe). IR (νCO, cm-1): 2002
(s), 1954 (s), 1934 (s), 1902 (m). Data for 19 are as follows.14
(m, 4H, C5H3), 1.34 (s, 6H, CMe), 1.32 (s, 18H, CMe3). IR (νCO
,
cm-1): 1977 (s), 1938 (s), 1803 (m), 1763 (s). Data for 11c are
as follows. 1H NMR (CDCl3): δ 5.08 (m, 2H, C5H3), 4.92 (m,
2H, C5H3), 4.88 (m, 2H, C5H3), 1.36 (s, 6H, CMe), 1.32 (s, 18H,
CMe3).
P r ep a r a tion of (Me2C)(Me2Ge)(t-Bu C5H3)2 (12). Using
a method similar to that described for 9, 12 was synthesized
from (Me2C)(t-BuC5H4)2, n-BuLi, and Me2GeBr2 in 91% yield
as light yellow crystals. Mp 145 °C. Anal. Calcd for C23H36Ge:
1
C, 71.73; H, 9.42. Found: C, 71.50; H, 8.87. H NMR (CDCl3):

5546 Organometallics, Vol. 22, No. 26, 2003
Wang et al.
1H NMR (CDCl3): δ 5.21 (m, 4H, C5H4), 4.95 (m, 4H, C5H4),
1.90-1.20 (m, 10H, CH2). IR (νCO, cm-1): 1998 (s), 1983 (s),
1777 (s).
(C5H4)2, n-BuLi, and Me2GeBr2 in 80% yield as light yellow
crystals. Mp: 69-70 °C. Anal. Calcd for C23H36Ge: C, 63.76;
1
H, 6.59. Found: C, 63.52; H, 7.46. H NMR (CDCl3): δ 6.50-
6.10 (m, 6H, C5H4), 3.70 (d, J ) 11.7 Hz, 1H, CH2), 3.54 (m,
3H, CH2 and C5H4), 0.71 (s, 3H, GeMe), -1.01 (s, 3H, GeMe).
Rea ction of 27 w ith F e(CO)5. A solution of 0.6 g (2.5
mmol) of 27 and 1.0 mL (7.6 mmol) of Fe(CO)5 in 30 mL of
xylene was refluxed for 6 h. After removal of solvent, the
residue was chromatographed on an alumina column using
petroleum ether/CH2Cl2 as eluent. The first band (red) afforded
0.05 g (4%) of 28 as red crystals. The second band (black) gave
0.12 g (10%) of 29 as black crystals. The third band (red)
afforded 0.08 g (9%) of 26. Data for 28 are as follows. Mp: 150-
152 °C. Anal. Calcd for C18H16Fe2O5Ge: C, 43.52; H, 3.25.
Found: C, 43.46; H, 3.35. 1H NMR (CDCl3): δ 5.08 (m, 2H,
CH and C5H3), 4.70 (m, 1H, C5H3), 4.02 (m, 1H, C5H3), 3.10-
2.80 (m, 2H, CH2), 2.20-1.80 (m, 4H, CH2), 0.52 (s, 3H, GeMe),
0.16 (s, 3H, GeMe). IR (νCO, cm-1): 2010 (s), 1966 (s), 1946 (s),
1918 (s). Data for 29 are as follows. Mp: 200 °C dec. Anal.
Calcd for C17H14Fe2O4Ge: C, 43.76; H, 3.02. Found: C, 44.00;
P r ep a r a tion of [(CH 2)5C](Me2Ge)(C5H4)2 (20). To a sus-
pension of 14.1 mmol of dilithium salts of [(CH2)5C](C5H5)2,
prepared in a manner similar to that for 16, was added slowly
3.7 g (14.1 mmol) of Me2GeBr2. After the mixture was refluxed
for 2 days, the solvents were removed under reduced pressure.
The residue was extracted with pentane. After removal of the
solvent 1.3 g (29%) of 20 was obtained as a light yellow oil. 1H
NMR (CDCl3): δ 6.50-6.20 (m, 6H, C5H3), 3.75 (s, 2H, C5H3),
2.20-1.20 (m, 10H, CH2), 0.70 (s, 3H, GeMe), -1.07 (s, 3H,
GeMe).
Rea ction of 20 w ith F e(CO)5. A solution of 0.50 g (1.6
mmol) of 20 and 0.6 mL (4.6 mmol) of Fe(CO)5 in 20 mL of
xylene was refluxed for 6 h. After removal of solvent the
residue was chromatographed on an alumina column using
petroleum ether/CH2Cl2 as eluent. The first band (yellow)
afforded 0.20 g (23%) of 21 as orange-red crystals. The second
band (green) gave 0.04 g (5%) of 22 as black crystals. The third
band (red) afforded 0.06 g (9%) of 19 as deep red crystals. Data
1
H, 3.05. H NMR (CDCl3): δ 5.33 (m, 2H, C5H3), 5.20 (m, 2H,
C5H3), 5.15 (m, 2H, C5H3), 3.12 (d, J ) 17.8 Hz, 1H, CH2), 2.75
(d, J ) 17.8 Hz, 1H, CH2), 1.04 (s, 3H, GeMe), 0.40 (s, 3H,
GeMe). IR (νCO, cm-1): 1973 (s), 1930 (s), 1803 (s), 1771 (s).
Cr ysta llogr a p h ic Stu d ies. Crystals of complexes 2, 3, 5,
7, 8, 10, 11t, 15, 17, 18, 21, 24, 25, 28, and 29 suitable for
X-ray diffraction were obtained from hexane/CH2Cl2 solution.
Data collection was performed on a Bruker SMART 1000
except for 7, which was performed on an Enraf-Nonius CAD-4
diffractometer, using graphite-monochromated Mo KR radia-
tion (ω-2θ scans, λ ) 0.710 73 Å). Empirical absorption
corrections were applied for 3 and 5, and semiempirical
absorption corrections were applied for 11t, 15, 17, 18, 21, 24,
25, 28, and 29. The structures were solved by direct methods
and refined by full-matrix least squares. All calculations were
performed using the SHELXL-97 or Siemens SHELXTL-PC
program system. The crystal data and summary of X-ray data
collection are presented in Table 1.
for 21 are as follows. Mp: 240 °C dec. Anal. Calcd for C22H22
-
Fe2GeO4: C, 49.41; H, 4.15. Found: C, 48.96; H, 3.95. 1H NMR
(CDCl3): δ 5.67 (m, 1H, C5H3), 5.42 (m, 1H, C5H3), 5.07 (m,
1H, C5H3), 4.74 (m, 1H, C5H3), 4.35 (m, 2H, C5H3), 2.10-1.30
(m, 10H, CH2), 0.79 (s, 3H, GeMe), 0.68 (s, 3H, GeMe). IR (νCO
,
cm-1): 2022 (s), 1976 (s), 1956 (s), 1921 (s). Data for 22 are as
follows. Mp: 240 °C dec. Anal. Calcd for C22H22Fe2SiO4: C,
1
49.42; H, 4.15. Found: C, 49.37; H, 4.20. H NMR (CDCl3): δ
5.01 (m, 2H, C5H3), 4.91 (m, 2H, C5H3), 4.70 (m, 2H, C5H3),
2.00-1.20 (m, 10H, CH2), 0.82 (s, 3H, GeMe), 0.68 (s, 3H,
GeMe). IR (νCO, cm-1): 1973 (s), 1942 (s), 1785 (m), 1767 (s).
P r ep a r a tion of (CH2)(Me2Si)(C5H4)2 (23). Using a method
similar to that described for 9, 23 was synthesized from
(CH2)(C5H4)2, n-BuLi, and Me2SiCl2 in 85% yield as light yellow
crystals. Mp: 57-58 °C. Anal. Calcd for C23H36Si: C, 77.93;
H, 9.20. Found: C, 77.40; H, 8.05. 1H NMR (CDCl3): δ 6.33
(m, 4H, C5H4), 6.23 (m, 2H, C5H4), 3.69 (d, J ) 14.2 Hz, 1H,
CH2), 3.59 (d, J ) 14.2 Hz, 1H, CH2), 3.40 (s, 2H, C5H4), 0.50
(s, 3H, SiMe), -1.14 (s, 3H, SiMe).
Resu lts a n d Discu ssion
Rea ction of 23 w ith F e(CO)5. A solution of 0.4 g (2.0
mmol) of 23 and 1.0 mL (7.6 mmol) of Fe(CO)5 in 40 mL of
xylene was refluxed for 7 h. After removal of solvent the
residue was chromatographed on an alumina column using
petroleum ether/CH2Cl2 as eluent. The first band (red) afforded
0.12 g (13%) of 24 as red crystals. The second band (black)
gave 0.2 g (24%) of 25 as black crystals. The third band (red)
afforded 0.08 g (11%) of 26 as deep red crystals. Data for 24
are as follows. Mp: 160-162 °C. Anal. Calcd for C18H16Fe2O5-
Si: C, 47.82; H, 3.57. Found: C, 47.56; H, 3.60. 1H NMR
(CDCl3): δ 5.10 (m, 1H, C5H3), 5.03 (s, 1H, CH), 4.64 (m, 1H,
C5H3), 4.02 (m, 1H, C5H3), 3.10-2.80 (m, 2H, CH2), 2.20-2.00
(m, 1H, CH2), 2.00-1.80 (m, 3H, CH2), 0.35 (s, 3H, Si-Me),
0.02 (s, 3H, Si-Me). IR (νCO, cm-1): 2010 (s), 1973 (s), 1954
(s), 1934 (s), 1803 (m). Data for 25 are as follows. Mp: 180 °C
dec. Anal. Calcd for C17H14Fe2O4Si: C, 48.38; H, 3.34. Found:
C, 47.20; H, 3.25. 1H NMR (CDCl3): δ 5.25 (m, 2H, C5H3), 5.20
(m, 2H, C5H3), 5.11 (m, 2H, C5H3), 3.09 (d, J ) 15.2 Hz, 1H,
CH2), 2.86 (d, J ) 15.2 Hz, 1H, CH2), 0.83 (s, 3H, SiMe), 0.24
(s, 3H, SiMe). IR (νCO, cm-1): 1977 (s), 1926 (s), 1811 (s), 1771
(s). Data for 26 are as follows.15 Mp: 250 °C dec. Anal. Calcd
for C15H10Fe2O4: C, 49.23; H, 2.75. Found: C, 49.39; H, 2.71.
1H NMR (CDCl3): δ 5.19 (m, 4H, C5H4), 4.93 (m, 4H, C5H4),
2.61 (s, 2H, CH2). IR (νCO, cm-1): 1958 (s), 1926 (s), 1775 (s),
1740 (m).
Rea ction of (Me2C)(Me2Si)(C5H4)2 (1) w ith F e-
(CO)5. The solution of the doubly bridged bis(cyclopen-
tadiene) ligand 1 and Fe(CO)5 in toluene was heated
under reflux for 16 h; complexes 2-4 were obtained
(Scheme 1).
Complex 2 is an intermolecular diiron complex. Its
IR spectrum exhibited two strong (1950, 1938 cm-1
)
terminal carbonyl bands and one bridging carbonyl band
1
(1763 cm-1). Its H NMR spectrum displayed three Cp
H proton peaks at 5.00 (2H), 4.68 (2H), and 3.50 (2H)
and multiplet allyl and alkyl proton peaks at 2.44 (8H)
and 1.77-1.45 (4H), respectively. On the basis of the
1
IR and H NMR spectra, elemental analysis, and X-ray
diffraction analysis, 2 was assigned to be [(C5H6)(Me2-
C)(Me2Si)(η5-C5H3)Fe(CO)]2(µ-CO)2, an unusual struc-
ture with a hydrogenated double bond in the uncoordi-
nated cyclopentadiene ligands. Complex 3 is a normal
intramolecular diiron complex. Its 1H NMR spectrum
displayed three Cp H proton peaks at 4.99 (2H), 4.80
(2H), and 4.57 (2H) ppm. However, its IR spectrum
exhibited only three strong terminal carbonyl bands at
1993, 1950, and 1929 cm-1, indicating that there are
no bridging carbonyl groups in the molecule of 3. This
has been further confirmed by X-ray diffraction analysis.
4 was assigned as the desilylation product (Me2C)[(η5-
P r epar ation of (CH2)(Me2Ge)(C5H4)2 (27). Using a method
similar to that described for 9, 27 was synthesized from (CH2)-
(14) Xu, S.; Zhang, J .; Zhu, B.; Wang, B.; Zhou, X.; Weng, L.
Transition Met. Chem. 2002, 27, 58.
(15) Bitterwolf, J . E. J . Organomet. Chem. 1986, 312, 197.
1
C5H3)Fe(CO)]2(µ-CO)2, on the basis of its H NMR and
IR spectra.13

Reactions of Bis(cyclopentadienes) with Fe(CO)5
Organometallics, Vol. 22, No. 26, 2003 5547
Ta ble 1. Cr ysta l Da ta a n d Su m m a r y of X-r a y Da ta Collection
2
3
5
7
8
10
11t
15
formula
C
17H21Fe-
O2Si
C
19H18Fe2-
O4Si
C
19H18Fe2-
O4Si
C
19H18Fe2-
GeO4
C
19H18Fe2-
GeO4
C
27H34Fe2-
O4Si
C
25H30Fe2-
O4
C
29H22Fe2-
O4Si
fw
341.28
monoclinic
C2/c
19.999(4)
13.788(3)
14.508(3)
90
123.423(4)
90
3338.8(12)
8
450.12
monoclinic
P21/n
9.1644(10)
13.8521(15) 13.3165(14)
15.3075(17) 17.2512(18)
450.12
494.64
494.62
562.33
monoclinic
P21/n
9.429(3)
10.627(3)
28.228(8)
90
92.313(5)
90
2826.2(13)
4
506.19
monoclinic
P21/c
18.743(6)
13.562(5)
19.554(7)
90
106.116(6)
90
4775(3)
8
574.26
triclinic
P1h
cryst syst
space group
a (Å)
b (Å)
c (Å)
orthorhombic orthorhombic monoclinic
Pbca
16.3299(17)
Pbca
P21/n
16.365(3)
13.290(3)
17.228(3)
90
90
90
3747(2)
8
1.754
3.1225
1984
9.162(4)
15.227(6)
12.986(5)
90
91.098(8)
90
1811.4(12)
4
1.814
8.394(4)
10.097(4)
16.130(7)
72.204(7)
79.040(7)
88.160(7)
1277.4(9)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90
90
90
90
102.103(2)
90
1900.0(4)
4
1.574
1.610
920
3751.4(7)
8
1.594
1.631
1840
Dcalcd (g cm-3
)
1.358
0.976
1432
1.322
1.097
1176
1.408
1.242
2112
1.493
1.216
588
µ (mm-1
F(000)
)
3.250
992
cryst size (mm) 0.1 × 0.15 × 0.25 × 0.2 × 0.25 × 0.22 × 0.35 × 0.35 × 0.30 × 0.20 × 0.30 × 0.25 × 0.40 × 0.22 × 0.20 × 0.15 ×
0.4
48.84
5296
0.15
52.82
10 993
0.15
50.04
14 723
0.40
0.15
50.04
6628
0.20
50.06
11 522
0.20
52.86
26 953
0.05
50.04
2425
max 2θ (deg)
no. of rflns
collected
no. of indep
rflns/Rint
50
3688
2999
2585/0.0582 3901/0.0607 3308/0.0963
2925/0.0560
4991/0.0564
9764/0.0978
2333/0.0277
no. of params
190
235
235
235
244
307
576
325
goodness of fit 1.042
1.019
1.001
1.17 (on F)
1.083
0.952
0.944
1.052
on F2
R1, wR2
(I > 2σ(I))
R1, wR2
(all data)
0.0634,
0.1701
0.0976,
0.1925
0.0375,
0.0352,
0.042, 0.045
(I g 3σ(I))
0.0744,
0.1770
0.0983,
0.1904
0.0480,
0.0965
0.0921,
0.1082
0.0554,
0.0865
0.1450,
0.1084
0.0630,
0.1160
0.1224,
0.1349
0.0793
0.0587,
0.0858
0.0492
0.0735,
0.0542
17
22H22Fe2-
O4Si
18
21
24
25
28
29
formula
C
C
22H22Fe2-
O4Si
C
22H22Fe2-
GeO4
C
18H16Fe2-
O5Si
C
17H14Fe2-
O4Si
C
36H32Fe4-
Ge2O10
C
17H14Fe2-
GeO4
fw
490.19
orthorhombic
P212121
10.006(4)
12.069(5)
17.325(8)
90
490.19
monoclinic
P21/c
9.505(3)
17.433(6)
13.411(5)
90
109.990(6)
90
2092.9(12)
4
534.69
orthorhombic
P212121
9.937(3)
12.085(4)
17.485(5)
90
452.10
triclinic
P1h
422.07
monoclinic
P21/m
8.300(4)
11.905(5)
9.169(4)
90
113.149(7)
90
833.1(6)
2
993.20
monoclinic
P2/c
10.092(4)
12.968(5)
29.395(10)
90
106.506(12)
90
3688(2)
4
466.57
monoclinic
P21/n
10.147(4)
13.971(5)
12.300(5)
90
104.543(7)
90
1687.9(11)
4
cryst syst
space group
a (Å)
b (Å)
c (Å)
7.895(6)
8.874(6)
13.927(10)
104.962(12)
90.808(13)
105.267(13)
905.8(11)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90
90
90
90
2092.2(16)
4
1.556
1.470
1008
2099.8(11)
4
1.691
2.811
1080
Dcalcd (g cm-3
)
1.556
1.469
1008
1.658
1.693
460
1.683
1.830
428
1.789
3.197
1984
1.836
3.482
928
µ (mm-1
F(000)
)
cryst size (mm)
0.30 × 0.25 ×
0.30 × 0.25 ×
0.25 × 0.20 ×
0.25 × 0.20 ×
0.30 × 0.25 ×
0.30 × 0.25 ×
0.26 × 0.20 ×
0.20
0.20
0.18
0.20
0.20
0.04
0.16
max 2θ (deg)
no. of rflns
collected
50.04
8690
50.06
8513
52.86
12 101
50.06
3693
50.04
3451
50.06
12 004
52.76
7797
no. of indep
rflns/Rint
3709/0.0255
3701/0.0328
4317/0.0562
3116/0.0485
1551/0.0258
6353/0.0838
3432/0.0497
no. of params
goodness of fit
on F2
263
1.033
262
1.007
266
1.004
235
1.061
123
1.055
469
1.007
218
0.973
R1, wR2
(I > 2σ(I))
R1, wR2
0.0261,
0.0497
0.0338,
0.0520
0.0320,
0.0749
0.0559,
0.0843
0.0407,
0.0581
0.0694,
0.0641
0.0646,
0.1290
0.1285,
0.1519
0.0284,
0.0617
0.0435,
0.0668
0.0778,
0.1264
0.1639,
0.1535
0.0369,
0.0644
0.0720,
0.0731
(all data)
Sch em e 1
When the reaction was carried out in refluxing xylene,
similar phenomena and faster reaction were observed
in comparison with the case for toluene. To our surprise,
the unexpected yellow complex 5 was isolated in addi-
tion to 2-4 (Scheme 2), which indicated that the higher
temperature favors the formation of 5. The IR spectrum

5548 Organometallics, Vol. 22, No. 26, 2003
Wang et al.
Sch em e 2
Sch em e 4
Sch em e 3
Sch em e 5
of 5 exhibited only terminal carbonyl bands (2017, 1979,
1
1952, 1920 cm-1). The H NMR spectrum of 5 displayed
six Cp H proton peaks at 5.69, 5.40, 5.00, 4.86, 4.40,
and 4.31 ppm, indicating the unsymmetrical structure.
X-ray diffraction analysis indicates that the novel
complex contains an Fe-Si bond, and the other iron
atom is coordinated with two cyclopentadienyl ligands
in an η5 and η1 manner in the meantime, indicating that
the formation of 5 should be accompanied by the
cleavage of a C-Si bond in the ligand.
We considered whether 3 might be an intermediate
to 4 or 5. However, when a xylene solution of 3 was
heated under reflux for 48 h, no 4 , 5, or any other
complex was observed by TLC monitoring. This suggests
that complexes 4 and 5 are formed during the reaction
and not from complex 3.
differing from the silicon analogue 3. Complex 4 is the
degermylation product in this case.
Rea ction of (Me2C)(Me2E)(t-Bu C5H3)2 (E ) Si (9),
Ge (12)) w ith F e(CO)5. To study the steric effect of
this reaction, a tert-butyl group was introduced onto the
cyclopentadienyl ring and ligands 9 and 12 were syn-
thesized. When ligand 9 or 12 and Fe(CO)5 in xylene
were heated under reflux, only the corresponding diiron
complex 10 or 13 and the desilylation or degermylation
product 11 were obtained (Scheme 4).
When the reactions were done in decahydronaphtha-
lene, the same products were obtained, indicating that
the bulky tert-butyl groups may prevent the formation
of the novel complex with an Fe-Si or Fe-Ge bond.
Similar to the case for the unsubstituted analogue 3,
the isopropylene and dimethylsilylene doubly bridged
bis(cyclopentadienyl) diiron complex 10 has no bridging
carbonyl groups (1997, 1946, 1926, 1902 cm-1). How-
ever, the isopropylene and dimethylgermylene doubly
bridged bis(cyclopentadienyl) diiron complex 13 has also
no bridging carbonyl groups (1993, 1942, 1932, 1902
cm-1), which is different from the case for the unsub-
stituted analogue 8, indicating that the introduction of
the bulky tert-butyl groups may increase the steric
repulsion between the tert-butyl groups, the substitu-
ents at bridge atoms, and Fe(CO)2 groups. Complex 11
is a mixture of cis and trans isomers. When the
reactions were done in refluxing toluene, no reaction
was found.
Rea ction of (Me2C)(Me2Ge)(C5H4)2 (6) w ith F e-
(CO)5. The reaction of 1 with Fe(CO)5 gave some
unexpected complexes. We sought to establish whether
these compounds are the normal result of these reac-
tions or species unique to this ligand. To find the
answer, the isopropylene and germylene doubly bridged
ligand 6 was used instead of 1, and it is found that, in
both refluxing toluene and xylene, similar products 7,
8, and 4 were obtained (Scheme 3). Complex 7 showed
five Cp H proton peaks at 5.62, 5.43, 4.97, 4.75, and 4.35
ppm in the 1H NMR spectrum and only terminal
carbonyl bands in the IR spectrum (2016, 1982, 1952,
1924 cm-1). X-ray diffraction analysis indicates that,
similar to the structure of the silicon analogue 5, 7
contains an Fe-Ge bond, and the other iron atom is
coordinated with two cyclopentadienyl ligands in an η5
and η1 manner in the meantime. This suggested that,
unlike the case for complex 2, complexes with this kind
of novel structure are not occasional products. Complex
7 can be formed at lower temperature (refluxing tolu-
ene), and the yield (26%) of 7 is much higher than that
of the silicon analogue 5 (6%), indicating that the
weakness of the C-Ge bond may promote the formation
of this kind of novel complex. Complex 8 is a normal
intramolecular diiron complex with both terminal and
bridging carbonyl groups (1975, 1938, 1770 cm-1),
Rea ction of (Me2C)(P h 2Si)(C5H4)2 (14) w ith F e-
(CO)5. To further study the steric effect of this reaction,
two phenyl groups were introduced onto the bridging
silicon atom instead of two methyl groups. When ligand
14 and Fe(CO)5 in toluene or xylene were heated under
reflux, only the corresponding diiron complexes 15 and
the desilylation product 4 were obtained (Scheme 5).
No analogue of 5 was obtained, indicating that the
two phenyls at the bridging silicon atom may also
prevent the formation of this kind of complex. Similar

Reactions of Bis(cyclopentadienes) with Fe(CO)5
Organometallics, Vol. 22, No. 26, 2003 5549
Sch em e 6
Sch em e 7
and at 0.71, -1.01 ppm (∆δ ) 1.72 ppm) for 27. This
suggested that the bridging methylene protons and
SiMe protons were situated in different shielding re-
gions by the double bonds due to the decreased repulsion
between the substituents at two bridge atoms in com-
parison with the isopropylene and silylene or germylene
doubly bridged ligands.
When ligand 23 or 27 and Fe(CO)5 in xylene were
heated under reflux, similar products 24 (or 28), 25 (or
29), and 2615 (Scheme 7) were obtained. No similarly
novel complex with an Fe-Si or Fe-Ge bond (analogue
of 5) was obtained in these cases, indicating that the
decreased steric effect may also not favor forming this
kind of novel complex.
to the case for other carbon and silicon doubly bridged
bis(cyclopentadienyl) diiron complexes (3 and 10), 15
also has no bridging carbonyl groups (1993, 1942, 1932,
1902 cm-1).
The IR spectrum of 24 exhibited four terminal car-
bonyl bands at 2010, 1973, 1954, and 1934 cm-1 and a
half-bridging carbonyl band at 1803 cm-1. However, the
IR spectrum of 28 exhibited only terminal carbonyl
bands at 2010, 1966, 1946, and 1918 cm-1. The 1H NMR
spectrum of 24 displayed three Cp H proton peaks at
5.10, 5.03, and 4.64 ppm, one vinyl proton peak at 4.02
ppm, and allyl or alkyl protons at 3.01 (2H), 2.90 (2H),
and 2.12 (2H) ppm, indicating the unusual structure.
X-ray diffraction analysis shows that the complex
contains an Fe-Fe bond. One iron atom is coordinated
with cyclopentadienyl ligand in an η5 manner, and the
other iron atom is coordinated in an η3 manner with
the allyl group consisting of the methylene bridge and
two bridgehead carbons. The other cyclopentadienyl ring
was hydrogenated partially. Complex 28 has a structure
and 1H NMR spectrum similar to those of 24. Complexes
25 and 29 are the normal intramolecular diiron com-
plexes with both terminal and bridging carbonyl groups,
differing from the other carbon and silicon doubly
bridged analogues 3, 10, 15, and 18. After complexation
with iron carbonyl, the splitting of the bridging meth-
Rea ction of [(CH2)5C](Me2E)(C5H4)2 (E ) Si (16),
Ge (20)) w ith F e(CO)5. To further study the steric
effect of this reaction, a 1,1-cyclohexylene bridge was
introduced instead of an isopropylene bridge and ligands
16 and 20 were synthesized. When ligand 16 or 20 and
Fe(CO)5 were heated under reflux in both xylene and
toluene, the same products 17 (or 21), 18 (or 22), and
1914 (Scheme 6) were obtained. Complexes 17 and 21
have unsymmetrical structures similar to those of 5 and
1
7. The H NMR spectra of 17 and 21 displayed six Cp
H proton peaks at 5.74, 5.39, 5.10, 4.86, 4.42, and 4.31
ppm and five Cp H proton peaks at 5.67, 5.42, 5.07, 4.74,
and 4.35 ppm, respectively. Complex 17 can be formed
at lower temperature (refluxing toluene), and the yield
(16%) of 17 is much higher than that of 5 (6%),
indicating that the increasing steric effect at the bridg-
ing carbon atom may promote the formation of this kind
of novel complex.
Similar to other carbon and silicon doubly bridged bis-
(cyclopentadienyl) diiron complexes (3, 10, and 15), 18
has no bridging carbonyl groups (2002, 1954, 1934, 1902
cm-1), but the carbon and germanium doubly bridged
bis(cyclopentadienyl) diiron complex 22 has both ter-
minal and bridging carbonyl groups (1973, 1942, 1785,
1767 cm-1).
1
ylene protons in H NMR spectra was increased (∆δ )
0.23 ppm for 25, 0.37 ppm for 29), but the splitting of
the Si-Me protons was much decreased (∆δ ) 0.59 ppm
for 25, 0.64 ppm for 29). This suggests that the Si-Me
protons are not situated at the shielding region by the
cyclopentadienyl groups again. Complex 26 is the desi-
lylation or degermylation product.15
Rea ction of (CH2)(Me2E)(C5H4)2 (E ) Si (23), Ge
(27)) w ith F e(CO)5. To further study the steric effect
of a bridging carbon atom on the reaction, a methylene
bridge was introduced instead of an isopropylene bridge
in 1, and ligands 23 and 27 were synthesized. It is
Molecu la r Str u ctu r es. The molecular structures of
2, 3, 5, 7, 8, 10, 11t, 15, 17, 18, 21, 24, 25, 28, and 29
are shown in Figures 1-15, respectively.
The molecule of 2 has Ci symmetry, consisting of two
equivalent moieties linked to each other by an Fe-Fe
bond (2.5522(15) Å) (Figure 1). The two ligands take a
stable trans conformation, and the two coordinated
cyclopentadienyl ring planes are parallel. The C-C bond
lengths of the uncoordinated five-membered ring are
1
interesting that in the H NMR spectra of 23 and 27
the bridging methylene protons were split as two double
peaks at 3.69, 3.59 ppm (∆δ ) 0.10 ppm) and 3.70, 3.54
ppm (∆δ ) 0.16 ppm) with J ) 14.2 and 11.7 Hz,
respectively. The SiMe protons were also split as two
single peaks at 0.50, -1.14 ppm (∆δ ) 1.64 ppm) for 23

5550 Organometallics, Vol. 22, No. 26, 2003
Wang et al.
F igu r e 1. ORTEP diagram of 2. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(1a) ) 2.5522(15), C(3)-Si(1) )
1.784(6), C(15)-Si(1) ) 1.797(7), C(7)-C(8) ) 1.623(7),
C(8)-C(11) ) 1.623(7), C(11)-C(15) ) 1.334(8), C(11)-
C(12) ) 1.532(9), C(12)-C(13) ) 1.512(12), C(13)-C(14) )
1.499(14), C(14)-C(15) ) 1.520(8); C(3)-Si(1)-C(15) )
101.7(3), C(7)-C(8)-C(11) ) 106.4(3).
F igu r e 3. ORTEP diagram of 5. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Si(1) ) 2.3222(10), Fe(1)-C(11) )
2.097(3), Fe(1)-C(15) ) 2.162(3), Fe(2)-C(15) ) 1.974(3),
Fe(2)-C(21) ) 2.080(3), Fe(2)-C(25) ) 2.080(3), C(5)-
C(11) ) 1.510(4), C(5)-C(21) ) 1.532(4), Si(1)-C(25) )
1.891(3); C(25)-Si(1)-Fe(1) ) 104.69(10), C(11)-C(5)-
C(21) ) 102.9(2), C(15)-Fe(2)-C(25) ) 87.14(12), C(15)-
Fe(2)-C(21) ) 79.83(12), Fe(2)-C(15)-Fe(1) ) 126.29(14).
F igu r e 2. ORTEP diagram of 3. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(2) ) 2.7747(6), Fe(1)-C(11) )
2.113(3), Fe(1)-C(15) ) 2.099(3), Fe(2)-C(21) ) 2.094(3),
Fe(2)-C(25) ) 2.107(3), Si(1)-C(15) ) 1.853(3), Si(1)-
C(25) ) 1.861(3), C(5)-C(11) ) 1.525(4), C(5)-C(21) )
1.511(4); C(21)-C(5)-C(11) ) 106.5(2), C(15)-Si(1)-C(25)
) 95.73(12).
1.334 Å (C(11)-C(15)), 1.532 Å (C(11)-C(12)), 1.512 Å
(C(12)-C(13)), 1.499 Å (C(13)-C(14)), and 1.520 Å
(C(14)-C(15)). Among them, only C(11)-C(15) bond is
a double bond; the others are single bonds, suggesting
that one cyclopentadiene of the doubly bridged ligand
was partially hydrogenated to cyclopentene. Whitesides
and Shelly investigated the mechanism of the reaction
of Fe(CO)5 with cyclopentadiene in detail.16 Following
their suggestion, the doubly bridged ligand may react
with an iron hydride intermediate as a hydrogen ac-
ceptor to give a double bond hydrogenated ligand which
can further react with Fe(CO)5 to form complex 2.
Complexes 3, 8, 10, 15, 18, 25, and 29 are intramo-
lecular diiron complexes. It is worth noting that the
carbon and silicon doubly bridged bis(cyclopentadienyl)
diiron complexes 3, 10, 15, and 18 have no bridging
carbonyl group and have unusually long Fe-Fe bond
distances, because the bridging carbonyl groups tend
F igu r e 4. ORTEP diagram of 7. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Ge(1)-Fe(2) ) 2.382(1), Fe(1)-C(11) ) 2.078-
(5), Fe(1)-C(15) ) 2.085(5), Fe(1)-C(25) ) 1.969(5), Fe-
(2)-C(21) ) 2.100(5), Fe(2)-C(25) ) 2.161(5), Ge(1)-C(11)
) 1.977(6), C(26)-C(15) ) 1.523(8), C(26)-C(21) ) 1.512-
(8), C(11)-Ge(1)-Fe(2) ) 102.9(2), C(15)-C(26)-C(21) )
103.4(4), C(25)-Fe(1)-C(11) ) 88.4(2), C(25)-Fe(1)-C(15)
) 80.1(2), Fe(2)-C(25)-Fe(1) ) 126.8(3).
to shorten metal-metal distances.19 The Fe-Fe bond
distances in these complexes (3, 2.7747(6) Å; 10, 2.7825-
(9) Å; 15, 2.766(2) Å; 18, 2.7522(9) Å) are evidently
(17) Bryan, R. F.; Greene, P. T.; Newlands, M. J . J . Chem. Soc. A
1970, 3068.
(18) Weaver, J .; Woodward, P. J . Chem. Soc., Dalton Trans. 1973,
1439.
(19) (a) Dahl, L. F.; Blount, J . F. Inorg. Chem. 1965, 4, 1373. (b)
Wei, C. H.; Dahl, L. F. J . Am. Chem. Soc. 1966, 88, 1821. (c) Mills, O.
S. Acta Crystallogr. 1958, 11, 620.
(16) Whitesides, T. H.; Shelly, J . J . Organomet. Chem. 1975, 92,
215.

Reactions of Bis(cyclopentadienes) with Fe(CO)5
Organometallics, Vol. 22, No. 26, 2003 5551
F igu r e 6. ORTEP diagram of 10. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(2) ) 2.7825(9), Fe(1)-C(11) )
2.091(4), Fe(1)-C(10) ) 2.110(4), Fe(2)-C(19) ) 2.106(4),
Fe(2)-C(20) ) 2.110(4), Si(1)-C(10) ) 1.850(4), Si(1)-
C(19) ) 1.849(4), C(5)-C(11) ) 1.544(5), C(5)-C(20) )
1.520(5); C(11)-C(5)-C(20) ) 106.5(3), C(10)-Si(1)-C(19)
) 96.32(18).
F igu r e 5. ORTEP diagram of 8. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(2) ) 2.4816(18), Fe(1)-C(11) )
2.138(9), Fe(1)-C(15) ) 2.121(10), Fe(2)-C(21) ) 2.135-
(9), Fe(2)-C(25) ) 2.158(9), Ge(1)-C(11) 1.929(10), Ge(1)-
C(21) ) 1.903(9), C(7)-C(15) ) 1.614(11), C(7)-C(25) )
1.525(10); C(15)-C(7)-C(25) ) 102.1(5), C(11)-Ge(1)-
C(21) ) 92.3(4).
two longer bridges (for example, (Me2C)(Me2Ge)[(η5-
C5H3)Fe(CO)]2(µ-CO)2 (8) 117.03°, (Me2Ge)2[(η5-C5H3)-
Fe(CO)]2(µ-CO)2 110.3°,8 (Me2SiSiMe2)2[(η5-C5H3)Fe-
(CO)]2(µ-CO)2 100.26°8) or a single bridge (97-110°).
Second, at both the bridging carbon and silicon atoms,
there are at least two substituent methyl groups. The
repulsion between the substituents at the two bridge
atoms and that between the substituents with the Fe2-
(CO)4 group make the dihedral angle between two
cyclopentadienyl ring planes (125-127°) much larger
than for the unsubstituted analogues (for example,
(CH2)(Me2Si)[(η5-C5H3)Fe(CO)]2(µ-CO)2 (25), 117.5°) and
favors the formation of a long Fe-Fe bond. However,
the bulk substituents at two bridge atoms (for example,
Ph2Si or (CH2)5C) also increase the repulsions between
the substituents and two cyclopentadienyl rings, which
make the dihedral angle between two cyclopentadienyl
ring planes (126.4° for 15, 125.1° for 18) and the Fe-
Fe distances (2.766(2) Å for 15, 2.7522(9) Å for 18)
slightly decreasing.14 The Fe-Fe distance in 10 (2.7825-
(9) Å) is the longest among the bis(cyclopentadienyl)
diiron complexes up to now. Further studies of the
effects of the unusually long Fe-Fe bond on the reactiv-
ity of these complexes are being continued in our group.
Complex 11t is a normal singly bridged bis(cyclopen-
tadienyl) diiron complex. Figure 7 shows that it is a
trans isomer, and there are two independent molecules
in the ratio of 1/1 (A/B) in the unit cell. The Fe-Fe bond
lengths are 2.4876(10) and 2.4902(12) Å, similar to those
for other single carbon atom bridged bis(cyclopentadi-
enyl) diiron complexes (Table 2).
Ta ble 2. Str u ctu r a l P a r a m eter Com p a r ison for
Bis(cyclop en ta d ien yl) Diir on Com p lexes
PL-PL
complex
M-M (Å)
(deg)a
refb
cis-[CpFe(CO)]2(µ-CO)2
2.531
92.8
17
13
Me2C[C5H4Fe(CO)]2(µ-CO)2
2.4836(6) 109.6(1),
109.3(1)
97.2
108.4
Me2Si[C5H4Fe(CO)]2(µ-CO)2
(CH2)5C[C5H4Fe(CO)]2(µ-CO)2
trans-Me2C[t-BuC5H3Fe(CO)]2-
(µ-CO)2 (11t)
2.512(3)
2.466(1)
18
14
tw
2.4876(10) 109.7
2.4902(12) 109.1
(Me2C)(Me2Si)[C5H3Fe(CO)2]2 (3) 2.7747(6) 126.92(9)
tw
(Me2C)(Me2Ge)[C5H3Fe(CO)]2-
(µ-CO)2 (8)
(Me2C)(Me2Si)[t-BuC5H2Fe-
(CO)2]2 (10)
2.4816(18) 117.03(27) tw
2.7825(9) 127.17(18) tw
(Me2C)(Ph2Si)[C5H3Fe(CO)2]2 (15) 2.766(2)
126.4
tw
tw
[(CH2)5C](Me2Si)[C5H3Fe(CO)2]2
(18)
(CH2)(Me2Si)[C5H4Fe(CO)]2-
(µ-CO)2 (25)
(CH2)(Me2Ge)[C5H4Fe(CO)]2-
(µ-CO)2 (29)
(Me2Ge)2[C5H4Fe(CO)]2(µ-CO)2
(Me2SiSiMe2)2[C5H4Fe(CO)]2-
(µ-CO)2
2.7522(9) 125.1
2.4833(13) 117.5
2.4877(11) 117.03
tw
tw
2.494(2)
110.3
8
8
2.5440(8) 100.26
a
b
PL ) plane of the cyclopentadienyl ring. tw ) this work.
greater than those found in other doubly bridged or
singly bridged bis(cyclopentadienyl) diiron complexes
(Table 2) and are the longest so far reported in the
literature for the bis(cyclopentadienyl) diiron complexes.
This may be attributed to two factors. At first, all these
complexes contain one carbon and one silicon atom
double bridge, which is the shortest bridge for the
doubly bridged bis(cyclopentadienyl) diiron complexes
up to now. The shorter bridges increase the intramo-
lecular nonbonding interactions and make the dihedral
angle between two cyclopentadienyl ring planes (125-
127°) much larger than for the related analogues with
Complexes 5, 7, 17, and 21 have similar novel
structures: one iron atom is coordinated with a cyclo-
pentadienyl ligand in an η5 manner, and the other iron
atom is coordinated with two cyclopentadienyl ligands
in an η1 and η5 manner in the meantime. All these
complexes contain an Fe-Si or Fe-Ge bond, indicating
that the formation of these complexes should be ac-
companied by the cleavage of a C-Si or C-Ge bond in
the ligand. The similar ruthenium complexes [Ru-
5
1
5
20
(CO)2]2(µ-η :η -C5H4)[µ-Me2Si-(η -C5H4)], [Ru(CO)2]2
-
(µ-η5:η1-C5Me4)[µ-Me2Si-(η5-C5H4)],21 and [(µ-η1:η5-C5H4)-

5552 Organometallics, Vol. 22, No. 26, 2003
Wang et al.
F igu r e 7. ORTEP diagram of 11t. Thermal ellipsoids are shown at the 30% level. There are two independent molecules
in a ratio of 1/1 (A/B) in the crystal structure. Selected bond lengths (Å) and angles (deg): Fe(1)-C(5) ) 2.134(4), Fe(1)-
Fe(2) ) 2.4876(10), Fe(2)-C(17) ) 2.128(4), Fe(3)-C(30) ) 2.137(4), Fe(3)-Fe(4) ) 2.4902(12), Fe(4)-C(42) ) 2.130(4),
C(5)-C(10) ) 1.512(5), C(10)-C(17) ) 1.534(6), C(30)-C(35) ) 1.524(6), C(35)-C(42) ) 1.525(6); C(5)-C(10)-C(17) )
109.3(3), C(30)-C(35)-C(42) ) 110.0(3).
F igu r e 9. ORTEP diagram of 17. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(2)-Si(1) ) 2.3222(12), Fe(1)-C(8) ) 2.089-
(3), Fe(1)-C(9) ) 2.096(3), Fe(1)-C(20) ) 1.985(3), Fe(2)-
C(16) ) 2.109(3), Fe(2)-C(20) ) 2.159(3), Si(1)-C(9) )
1.898(3), C(10)-C(8) ) 1.545(4), C(10)-C(16) ) 1.517(4);
C(9)-Si(1)-Fe(2) ) 105.40(9), Si(1)-Fe(2)-C(16) ) 91.20-
(7), Si(1)-Fe(2)-C(20) ) 86.01(7), Fe(2)-C(20)-Fe(1) )
128.53(13), C(8)-C(10)-C(16) ) 102.7(2).
F igu r e 8. ORTEP diagram of 15. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(2) ) 2.766(2), Fe(1)-C(5) ) 2.136-
(9), Fe(1)-C(9) ) 2.097(7), Fe(2)-C(10) ) 2.127(9), Fe(2)-
C(14) ) 2.086(8), Si(3)-C(5) ) 1.826(11), Si(3)-C(10) )
1.869(11), C(15)-C(9) ) 1.569(14), C(15)-C(14) ) 1.493-
(14); C(9)-C(15)-C(14) ) 105.9(8), C(5)-Si(3)-C(10) )
96.0(5).
7, 17, and 21 (2.3222(10), 2.382(1), 2.3222(12), and
2.3749(10) Å) are very close to those in the rearrange-
ment product [Me2E(η5-C5H4)Fe(CO)2]2 (Fe-Si ) 2.315-
(2) Å, Fe-Ge ) 2.379 Å),23 and much shorter than those
in acyclic molecules of the same type.24 This is consistent
with the thermal stability of 5, 7, 17, and 21.
Complexes 24 and 28 have similar structures. One
iron atom is coordinated with a cyclopentadienyl ligand
in an η5 manner, and the other iron atom is coordinated
in an η3 manner, with the allyl group consisting of the
methylene bridge and two bridgehead carbons. Similar
to complex 2, one of the cyclopentadienyl rings of 24 and
28 was hydrogenated partially to cyclopentene. In the
molecule of 24 the Fe(2)-C(3)-O(3) angle (156.9(8)°) is
22
Ru(CO)2]2 have been reported from the photolysis of
the silyl-bridged complexes Me2Si[η5-C5H4Ru(CO)2]2 and
Me2Si[η5-C5Me4Ru(CO)2]2 and the fulvalene derivative
(µ-η5-η5-C5H4C5H4)Ru2(CO)4, respectively. The struc-
tures of 5, 7, 17, and 21 are also somewhat similar to
the rearrangement products [Me2E(η5-C5H4)Fe(CO)2]2
(E ) Si, Ge).23 The Fe-Si or Fe-Ge bond lengths in 5,
(20) (a) Bitterwolf, T. E.; Shade, J . E.; Hansen, J . A.; Rheingold, A.
L. J . Organomet. Chem. 1996, 514, 13. (b) Bitterwolf, T. E.; Leonard,
M. B.; Horine, P. A.; Shade, J . E.; Hansen, J . A.; Rheingold, A. L.;
Staley, D. J .; Yap, G. P. A. J . Organomet. Chem. 1996, 512, 11.
(21) Fox, T.; Burger, P. Eur. J . Inorg. Chem. 2001, 795
(22) (a) Vollhardt, K. P. C.; Weidman, T. W. J . Am. Chem. Soc. 1983,
105, 1676. (b) Boese, R.; Cammack, J . K.; Matzger, A. J .; Pflug, K.;
Tolman, W. B.; Vollhardt, K. P. C.; Weidman, T. W. J . Am. Chem. Soc.
1997, 119, 6757.
(23) (a) Sun, H.; Xu, S.; Zhou, X.; Wang, H.; Wang, R.; Yao, X. J .
Organomet. Chem. 1993, 444, C41. (b) Xie, W.; Wang, B.; Dai, X.; Xu,
S.; Zhou, X. Organometallics 1998, 17, 5406.
(24) Parkanyi, L.; Pannell, K. H.; Hernandez, C. J . Organomet.
Chem. 1983, 252, 127.

Reactions of Bis(cyclopentadienes) with Fe(CO)5
Organometallics, Vol. 22, No. 26, 2003 5553
F igu r e 12. ORTEP diagram of 24. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(2) ) 2.771(2), Fe(1)-C(3) ) 2.400-
(10), Fe(1)-C(6) ) 2.106(8), Fe(1)-C(10) ) 2.133(7), Fe-
(2)-C(3) ) 1.814(9), Fe(2)-C(11) ) 2.095(7), Fe(2)-C(12)
) 2.107(7), Fe(2)-C(16) ) 2.223(8), Si(1)-C(6) ) 1.854(8),
Si(1)-C(16) ) 1.853(8), C(10)-C(11) ) 1.448(10), C(11)-
C(12) ) 1.406(10), C(12)-C(13) ) 1.505(10), C(13)-C(14)
) 1.511(12), C(14)-C(15) ) 1.512(11), C(15)-C(16) )
1.517(10), C(12)-C(16) ) 1.387(10); C(12)-C(11)-C(10) )
120.7(7), C(16)-C(12)-C(11) ) 122.7(7), C(6)-Si(1)-C(16)
) 98.7(4), O(1)-C(1)-Fe(1) ) 176.4(10), O(2)-C(2)-Fe(1)
) 175.5(8), O(3)-C(3)-Fe(1) ) 122.2(7), O(3)-C(3)-Fe(2)
) 156.9(8), O(4)-C(4)-Fe(2) ) 175.9(9), O(5)-C(5)-Fe(2)
) 175.1(8).
F igu r e 10. ORTEP diagram of 18. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(2) ) 2.7522(9), Fe(1)-C(5) ) 2.117-
(3), Fe(1)-C(9) ) 2.103(3), Fe(2)-C(16) ) 2.131(3), Fe(2)-
C(20) ) 2.116(3), Si(1)-C(5) ) 1.866(3), Si(1)-C(20) )
1.863(3), C(10)-C(9) ) 1.519(4), C(10)-C(16) ) 1.524(4);
C(9)-C(10)-C(16) ) 106.5(2), C(5)-Si(1)-C(20) ) 95.42-
(12).
F igu r e 11. ORTEP diagram of 21. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Ge(1)-Fe(1) ) 2.3749(10), Fe(1)-C(6) )
2.116(4), Fe(1)-C(5) ) 2.159(4), Fe(2)-C(5) ) 1.977(5), Fe-
(2)-C(16) ) 2.077(4), Fe(2)-C(17) ) 2.096(4), Ge(1)-C(17)
) 1.968(4), C(6)-C(10) ) 1.508(6), C(10)-C(16) ) 1.536-
(6); C(17)-Ge(1)-Fe(1) ) 103.79(13), Fe(2)-C(5)-Fe(1) )
129.2(2), C(6)-C(10)-C(16) ) 103.3(3).
F igu r e 13. ORTEP diagram of 25. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
angles (deg): Fe(1)-Fe(1A) ) 2.4833(13), Fe(1)-C(5) )
2.126(3), Fe(1)-C(9) ) 2.145(3), Si(1)-C(9) ) 1.869(3),
C(4)-C(5) ) 1.506(3); C(5)-C(4)-C(5A) ) 109.7(3), C(9)-
Si(1)-C(9A) ) 96.12(16).
much more bent than the others (Fe(1)-C(1)-O(1) )
176.4(10)°, Fe(1)-C(2)-O(2) ) 175.5(8)°, Fe(2)-C(4)-
O(4) ) 175.9(9)°, Fe(2)-C(5)-O(5) ) 175.1(8)°). The Fe-
(1)-C(3) and Fe(2)-C(3) distances are 2.400(10) and
1.814(9) Å, respectively. This suggests that the carbonyl
C(3)-O(3) exists as a half-bridging carbonyl, which is
consistent with the middle absorption at 1803 cm-1 in
the IR spectrum. The IR spectrum of 28 shows no
bridging carbonyl group (2010, 1966, 1946, 1918 cm-1),
but there still is an Fe-C-O bond angle (Fe(2)-C(2)-
O(2) ) 166.5(9)° for A, Fe(4)-C(19)-O(6) ) 164.1(13)°
for B) much more bent than the others, existing as a
half-bridging carbonyl. The Fe-Fe bond length in 24 is
2.771(2) Å, which is close to the Fe-Fe bond length in
3 (2.7747(6) Å). There are two independent molecules
in the ratio of 1/1 (A/B) in the unit cell of 28. The Fe-
Fe bond lengths are 2.816(2) and 2.798(2) Å, slightly
longer than that in 24 due to the atom radius of
germanium being larger than that of silicon. The Fe-

5554 Organometallics, Vol. 22, No. 26, 2003
Wang et al.
F igu r e 14. ORTEP diagram of 28. Thermal ellipsoids are shown at the 30% level. There are two independent molecules
as a ratio of 1/1 (A/B) in the crystal structure. Selected bond lengths (Å) and angles (deg): (A) Fe(1)-Fe(2) ) 2.816(2),
Fe(1)-C(6) ) 2.110(9), Fe(1)-C(10) ) 2.111(9), Fe(2)-C(11) ) 2.106(8), Fe(2)-C(12) ) 2.104(8), Fe(2)-C(16) ) 2.208(9),
Ge(1)-C(6) ) 1.929(10), Ge(1)-C(16) ) 1.931(9), C(10)-C(11) ) 1.473(12), C(11)-C(12) ) 1.369(13), C(12)-C(13) ) 1.518-
(12), C(13)-C(14) ) 1.500(14), C(14)-C(15) ) 1.563(12), C(15)-C(16) ) 1.548(12), C(12)-C(16) ) 1.411(13), C(12)-C(11)-
C(10) ) 122.6(9), C(11)-C(12)-C(16) ) 122.2(8), C(6)-Ge(1)-C(16) ) 96.5(4), Fe(2)-C(2)-O(2) ) 164.1(13), Fe(2)-C(1)-
O(1) ) 174.9(10), Fe(2)-C(3)-O(3) ) 175.4(10), C(11)-Fe(2)-Fe(1) ) 78.9(2), C(12)-Fe(2)-Fe(1) ) 105.4(2), C(16)-Fe(2)-
Fe(1) ) 99.0(2), Fe(1)-C(4)-O(4) ) 173.6(10), Fe(1)-C(5)-O(5) ) 175.5(10); (B) Fe(3)-Fe(4) ) 2.798(2), Fe(3)-C(24) )
2.113(9), Fe(3)-C(28) ) 2.129(9), Fe(4)-C(29) ) 2.110(9), Fe(4)-C(30) ) 2.106(9), Fe(4)-C(34) ) 2.218(9), Ge(2)-C(24) )
1.924(9), Ge(2)-C(34) ) 1.932(10), C(28)-C(29) ) 1.432(13), C(29)-C(30) ) 1.433(13), C(30)-C(31) ) 1.508(13), C(31)-
C(32) ) 1.574(15), C(32)-C(33) ) 1.490(14), C(33)-C(34) ) 1.516(12), C(30)-C(34) ) 1.442(14), C(28)-C(29)-C(30) )
123.4(10), C(29)-C(30)-C(34) ) 121.2(9), C(24)-Ge(2)-C(34) ) 97.1(4), Fe(4)-C(19)-O(6) ) 164.1(13), Fe(4)-C(20)-
O(7) ) 178.7(11), Fe(4)-C(21)-O(8) ) 177.0(11), C(29)-Fe(4)-Fe(3) ) 78.0(3), C(30)-Fe(4)-Fe(3) ) 106.4(3), C(34)-Fe-
(4)-Fe(3) ) 100.1(2), Fe(3)-C(22)-O(9) ) 177.2(9), Fe(3)-C(23)-O(10) ) 176.8(10).
There have been some reports about the cleavage of
the C-Si or C-Ge bond and the migration of the silyl
or germyl group.27-29 When C5H5EMe3 (E ) Si, Ge, Sn)
reacted with (MeCN)3M(CO)3 (M ) Cr, Mo, W), it was
found that GeMe3 and SnMe3 can easily migrate to the
metal atom to give C5H5(CO)3M-EMe3 (M ) Cr, Mo,
W; E ) Ge, Sn) but SiMe3 was much more difficult to
transfer.27a,28,29 The silyl-bridged diruthenium com-
plexes Me2Si[η5-C5H4Ru(CO)2]2 and Me2Si[η5-C5Me4Ru-
(CO)2]2 can rearrange to the similar novel complexes
[Ru(CO)2]2(µ-η5:η1-C5H4)[µ-Me2Si-(η5-C5H4)] and [Ru-
(CO)2]2(µ-η5:η1-C5Me4)[µ-Me2Si-(η5-C5H4)] with a Ru-
Si bond through the silyl single migration under pho-
tolysis.20,21 This allows us to consider that the complexes
with an Fe-Si or Fe-Ge bond in this work may be the
silyl or germyl single migration products, especially for
the complexes with an Fe-Ge bond, due to the weak-
ness of the C-Ge bond. The silyl migration may also
F igu r e 15. ORTEP diagram of 29. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths (Å) and
occur with a greater intramolecular nonbonding inter-
action and higher reaction temperature. When bulky
angles (deg): Fe(1)-Fe(2) ) 2.4877(11), Fe(1)-C(5) )
substituents were introduced onto the bridging carbon
2.153(4), Fe(1)-C(9) ) 2.117(4), Fe(2)-C(11) ) 2.120(3),
atom (ligand 16 and 20), silyl or germyl single migration
Fe(2)-C(15) ) 2.146(4), Ge(1)-C(5) ) 1.952(4), Ge(1)-
could be promoted due to the increased repulsion with
C(15) ) 1.946(4), C(9)-C(10) ) 1.511(5), C(11)-C(10) )
1.518(5); C(9)-C(10)-C(11) ) 109.8(3), C(5)-Ge(1)-C(15)
) 93.50(15).
the bulky substituents and complexes with an Fe-Si
or Fe-Ge bond were formed in higher yield (17, 16%;
21, 23%). When a methylene bridge was introduced
instead of an isopropylene bridge in 1 or 6, no similar
Fe bond lengths in 24 and 28 are consistent with those
found in other molecules with both η5 and η3 coordina-
tion (for example, 2.782(4) Å for (azulene)Fe2(CO)525),
due to the fact that the very strong (η3-allyl)-Fe linkage
stretches the relatively weak Fe-Fe bond in order to
maintain its own optimal geometry.26
(26) Cotton, F. A.; DeBoer, B. G.; Marks, T. J . J . Am. Chem. Soc.
1971, 93, 5069.
(27) (a) Heck, J .; Kriebisch, K.-A.; Mellinghoff, H. Chem. Ber. 1988,
121, 1753. (b) Xu, S.; Xie, W.; Zhou, X.; Wang, J .; Chen, H.; Guo, H.;
Miao, F. Chem. J . Chin. Univ. 1996, 17, 1065.
(28) Keppie, S. A.; Lappert, M. F. J . Organomet. Chem. 1969, 19,
P5.
(25) Churchill, M. R. Inorg. Chem. 1967, 6, 190.
(29) Abel, E. W.; Moorhouse S. J . Organomet. Chem. 1971, 28, 211.

Reactions of Bis(cyclopentadienes) with Fe(CO)5
Organometallics, Vol. 22, No. 26, 2003 5555
complex with an Fe-Si or Fe-Ge bond (analogue of 5)
was obtained, indicating that the larger intramolecular
nonbonding interactions may be the driving force of silyl
or germyl single migration. The yields of the complexes
with an Fe-Ge bond (7, 26%; 21, 23%) are much higher
than those with an Fe-Si bond (5, 6%; 17, 16%), which
can be attributed to the weakness of the C-Ge bond as
compared to the C-Si bond. However, when bulky
substituents were introduced onto the cyclopentadienyl
rings or the bridging silicon atom (ligand 9, 12, and 14),
silyl or germyl single migration is hindered and a
complex with an Fe-Si or Fe-Ge bond could not be
formed. However, the detailed mechanism needs further
studies.
formation of doubly bridged bis(cyclopentadienyl) diiron
complexes, as well as novel complexes containing Fe-
Si or Fe-Ge bonds. The factors effecting the structures
of diiron complexes and the formation of novel com-
plexes were discussed.
Ack n ow led gm en t. This work was financially sup-
ported by the National Natural Science Foundation of
China (No 29972023 and 20202004), the Research Fund
for the Doctoral Program of Higher Education, and the
Scientific Research Foundation for the Returned Over-
seas Chinese Scholars, State Education Ministry.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data collection details, final positional and thermal
parameters of the non-hydrogen atoms, general temperature
factors, and bond distances and angles for 2, 3, 5, 7, 8, 10,
11t, 15, 17, 18, 21, 24, 25, 28, and 29. This material is
available free of charge via the Internet at http://pubs.acs.org.
Con clu sion s
The reactions of carbon and silicon or germanium
doubly bridged bis(cyclopentadiene) ligands (Me2C)-
(Me2E)(C5H4)2 (E ) Si, Ge) with Fe(CO)5 result in the
OM030364A