Reactions of di-μ-carbonyl-cis-μ-(1-5-η:1′-5′-η-dicyclopentadienyl- dimethylsilane)b is(carbonyliron) with aryllithium reagents. Crystal structures of [Fe2(μ-CO){μ-C(OC2H5)C6H 5}(CO)2{(η<su

Article abstract of DOI:10.1016/S0022-328X(00)00622-7

The reactions of di-μ-carbonyl-cis-μ-(1-5-η:1′-5′-η-dicyclopentadienyl- dimethyl silane)bis(carbonyliron), [Fe₂(μ-CO)₂(CO)₂{(η⁵-C ₅H₄)₂Si(CH₃)₂}] (1), with

Full text of DOI:10.1016/S0022-328X(00)00622-7

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 617–618 (2001) 292–300
Reactions of
di-m-carbonyl-cis-m-(1-5-h:1%-5%-h-dicyclopentadienyl-dimethylsilane)
bis(carbonyliron) with aryllithium reagents. Crystal structures of
[Fe2(m-CO){m-C(OC2H5)C6H5}(CO)2{(h5-C5H4)2Si(CH3)2}] and
[Fe2(m-CO){m-C(OC2H5)C6H4OCH3-p}(CO)2{(h5-C5H4)2Si(CH3)2}]
Ruitao Wang, Jie Sun, Jiabi Chen *
Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu,
Shanghai 200032, People’s Republic of China
Received 7 July 2000; accepted 1 September 2000
Abstract
The reactions of di-m-carbonyl-cis-m-(1-5-h:1%-5%-h-dicyclopentadienyl-dimethyl silane)bis(carbonyliron), [Fe2(m-CO)2(CO)2{(h5-
C5H4)2Si(CH3)2}] (1), with aryllithium reagents, ArLi (Ar=C6H5, o-, m-, p-CH3C6H4, p-CH3OC6H4, p-ClC6H4, p-CF3C6H4), in
ether at low temperature afforded acylmetalate intermediates, followed by alkylation with Et3OBF4 in aqueous solution at 0°C or
in CH2Cl2 at −30°C gave the (dicyclopentadienyldimethylsilane)diiron bridging alkoxycarbene complexes [Fe2(m-CO){m-
C(OC2H5)Ar}(CO)2{(h5-C5H4)2Si(CH3)2}] (2, Ar=C6H5; 3, Ar=o-CH3C6H4; 4, Ar=m-CH3C6H4; 5, Ar=p-CH3C6H4; 6,
Ar=p-CH3OC6H4; 7, Ar=p-ClC6H4; 8, Ar=p-CF3C6H4), among which the structures of 2 and 6 have been established by
X-ray diffraction studies. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Reactions; Diiron; Aryllithium reagents; Bridging carbene complexes; Crystal structures
ing carbene and carbyne complexes have been synthe-
sized by Stone and co-workers by reactions [4–6] of
carbene and carbyne complexes with low-valent metal
species or by reactions [7] of neutral and anionic car-
byne complexes with metal hydrides and cationic metal
compounds. In our laboratory, one of the methods for
preparation of the bridging carbene and carbyne com-
plexes is to conduct the reactions of the highly elec-
trophilic cationic carbyne complexes of manganese and
rhenium, [h5-C5H5-(CO)2MꢀCPh]BBr4 (M=Mn or
Re), with carbonylmetal anion compounds. We found
that both cationic carbyne complexes reacted not only
with carbonylmetal monoanionic compounds such as
[NMe4][FeH(CO)4], Li[Co(CO)4], Na[h5-C5H5ꢀM(CO)3]
(M=Mo, W), and Na[Co(CO)3PPh3] but also with
1. Introduction
The increasing interest in the synthesis, structure and
chemistry of a variety of metal–metal bonded cluster
complexes stems largely from the fact that many such
complexes are well-known to have important roles in
many catalytic reactions [1–3]. Since many metal com-
plexes that contain bridging carbene and carbyne lig-
ands are themselves metal clusters or are the precursors
of metal cluster complexes, the chemistry of transition
metal bridging carbene and carbyne complexes is an
area of current interest. In this regards, we are inter-
ested in developing the methodologies of the synthesis
of transition metal bridging carbene and carbyne com-
plexes. Metal complexes that contain bridging carbene
and carbyne ligands have been examined extensively by
Stone and co-workers. A wide variety of dimetal bridg-
carbonylmetal
dianionic
compounds
such
as
Na2[Fe(CO)4], [NEt4]2[Fe2(CO)8], Na2[Fe3(CO)11], and
Na2[W(CO)5], and mixed-dimetal carbonyl anion com-
pounds
such
as
[N(Ph3P)2][FeCo(CO)8]
and
* Corresponding author. Fax: +86-21-64166128.
E-mail address: chenjb@pub.sioc.ac.cn (J. Chen).
[N(Ph3P)2][WCo(CO)9] to form the heteronuclear
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00622-7

R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
293
dimetal bridging carbene and/or bridging carbyne com-
plexes [8–10]. Recently, we found another new method
for preparation of the dimetal bridging carbene and
carbyne complexes: the reactions of olefin-ligated
dimetal carbonyl compounds with nucleophilic aryl-
lithium reagents, followed by alkylation with alkylating
reagent. For instance, the reactions of pentacarbonyl-
(cyclooctatetraene)diiron and bis(h5-cyclo-pentadi-
enyl)diiron tetracarbonyl with aryllithium reagents fol-
lowed by alkylation with Et3OBF4 gave the
olefin-coordinated dimetal bridging alkoxycarbene
complexes [Fe2{m-C(OEt)Ar}(CO)4(C8H8)] [11] (Scheme
1) and [Fe2(m-CO){m-C(OEt)Ar}(CO)2(h5-C5H5)2] [12]
(Scheme 2), respectively. This offers a new and useful
method for preparation and structural modification of
the dimetal bridging carbene complexes.
lar sieves under N2 atmosphere. Diethyl ether (Et2O)
was distilled from sodium benzophenone ketyl, while
petroleum ether (30–60°C) and CH2Cl2 were distilled
from CaH2. The neutral alumina (Al2O3, 200–300
mesh) used for chromatography was deoxygenated at
room temperature under high vacuum for 16 h, deacti-
vated with 5% w/w N2-saturated water, and stored
under N2. Compound [Fe2(m-CO)2(CO)2{(h5-C5H4)2Si-
(CH3)2}] (1) [13], Et3BF4 [14], and aryllithium reagents
[15–20] were prepared by literature methods.
The IR spectra were measured on a Perkin–Elmer
983G spectrophotometer. All 1H-NMR spectra were
recorded at ambient temperature in acetone-d6 with
TMS as the internal reference using a Bruker AM-300
spectrometer. Electron ionization mass spectra (EIMS)
were run on a Hewlett Packard 5989A spectrometer.
Melting points obtained on samples in sealed nitrogen-
filled capillaries are uncorrected.
In order to examine the scope of this new synthetic
method for dimetal bridging of carbene complexes and
the structural modification of the dimetal bridging car-
bene complexes, and to explore the effect of different
olefin ligands on the reaction products, we synthesized
di-m-carbonyl-cis-m-(1-5-h:1%-5%-h-dicyclopentadienyl-
2.1. Preparation of
[Fe2(v-CO)2(CO)2{(p5-C5H4)2Si(CH3)2}] (1)
dimethylsilane)bis(carbonyliron),
[Fe2(m-CO)2(CO)2-
We provide full details of this preparation since
neither its synthesis nor experimental procedure were
referred to in the Ref. [13]. A Schlenk flask was charged
with dicyclopentadienyldimethylsilane (4.00 g, 21.50
mmol), n-octane (75 ml), and Fe(CO)5 (5.50 ml (7.85 g,
40.10 mmol)). The mixture was heated at 135°C to
reflux under a N2 atmosphere for 20 h, during which
time the orange solution turned dark brown-red. The
resulting mixture was cooled to room temperature and
then evaporated under vacuum to dryness. The residue
was chromatographed on Al2O3 with petroleum ether
as the eluant. The brown-red band was eluted and
collected. After vacuum removal of the solvent, the
crude product was recrystallized from petroleum ether
or petroleum ether–CH2Cl2 at −30°C to give purple-
red crystals of complex 1 (7.80 g (47%, based on
Fe(CO)5)), m.p. 150°C (dec.); IR (CH2Cl2) w(CO) 1995
{(h5-C5H4)2Si(CH3)2}] (1), as starting material for use
in reactions with aryllithium reagents. These reactions
produced a series of (dicyclopentadienyldimethylsi-
lane)diiron bridging alkoxycarbene complexes. In this
work we describe these unusual reactions and the struc-
tural characterizations of the resulting products.
Scheme 1.
(vs, br), 1955 (vs), 1767 (vs, br) cm−1 1H-NMR
.
(CD3COCD3): l 5.60 (t, 4H, C5H4), 5.20 (t, 4H, C5H4),
0.43 (s, 6H, Si(CH3)2). MS: m/e 410 (M+), 382 (M+−
CO), 354 (M+−2CO), 326 (M+−3CO), 298 (M+−
4CO), 242 [(C5H4)2Si(CH3)2Fe+]. Anal. Calc. for
C16H14Fe2SiO4: C, 46.86; H, 3.44. Found: C, 46.66; H,
3.70%.
2.2. Reaction of 1 with C6H5Li to gi6e
[Fe2(v-CO){v-C(OC2H5)C6H5}(CO)2-
{(p5-C5H4)2Si(CH3)2}] (2)
Scheme 2.
2. Experimental
2.2.1. Alkylation in H2O
All procedures were performed under a dry, oxygen-
free N2 atmosphere using standard Schlenk techniques.
Solvents were reagent grade and dried by refluxing over
C6H5Li (1.34 mmol) was added dropwise with stir-
ring within 15 min to a solution of complex 1 (0.410 g,
1.00 mmol) dissolved in ether (80 ml) at −20°C [15].
The reaction mixture was stirred at −20 to −10°C for
,
appropriate drying agents and stored over 4 A molecu-

294
R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
2 h, during which time the orange–red solution gradu-
ally turned blackish red. The resulting solution then
evaporated under high vacuum at −20°C to dryness.
To the blackish solid residue obtained was added
Et3OBF4 [14] (ca. 5 g). This solid mixture was dissolved
in N2-saturated water (50 ml) at 0°C with vigorous
stirring and the mixture covered with petroleum ether
(30–60°C). Immediately afterwards, Et3OBF4 (ca. 10 g)
was added portionwise to the aqueous solution, with
strong stirring, until it became acidic. The aqueous
solution was extracted with petroleum ether. After re-
moval of the solvent under vacuum, the dark brown
residue was chromatographed on an alumina (neutral)
column (1.6×15–20 cm) at −25°C with 15:1
petroleum ether–CH2Cl2 as the eluant. The solvent was
removed in vacuo and the residue was recrystallized
from 10:1 petroleum ether–CH2Cl2 at −80°C to give
purple-red crystals of complex 2 (0.43 g (83%, based on
1)); m.p. 130–132°C (dec.); IR (CH2Cl2) w(CO) 1995
treatment in a similar manner as described for the
reaction in Section 2.2.1 afforded complex 3 (0.48 g
(91%, based on 1)) as purple-red crystals; m.p. 150–
152°C (dec.); IR (CH2Cl2) w(CO) 1984 (m), 1961 (vs,
br), 1748 (vs, br) cm−1 1H-NMR (CD3COCD3):l
.
7.30–6.96 (m, 4H, C6H4CH3), 5.48 (m, 2H, C5H4), 5.06
(m, 4H, C5H4), 4.67 (m, 2H, C5H4), 3.42 (q, 2H,
OCH2CH3), 2.18 (s, 3H, C6H4CH3), 0.86 (t, 3H,
OCH2CH3), 0.33 (s, 6H, Si(CH3)2). MS: m/e 530 (M+),
502 (M+−CO), 474 (M+−2CO), 446 (M+−3CO),
389 (M+−3COꢀCOC2H5), 312 (M+−3COꢀCOC2H5ꢀ
C6H5), 242 [(C5H4)2Si(CH3)2Fe+]. Anal. Calc. for
C25H26Fe2SiO4: C, 56.63; H, 4.94. Found: C, 56.38; H,
5.06%.
2.4. Reaction of 1 with m-CH3C6H4Li to gi6e
[Fe2(v-CO){v-C(OC2H5)C6H4CH3-m}(CO)2-
{(p5-C5H4)2Si(CH3)2}] (4)
.
(w), 1972 (vs, br), 1750 (s, br) cm−1 1H-NMR
(CD3COCD3): l 7.66 (d, 2H, C6H5), 7.16 (t, 2H, C6H5),
7.04 (t, 1H, C6H5), 6.05 (m, 2H, C5H4), 5.41 (m, 2H,
C5H4), 5.15 (m, 2H, C5H4), 4.84 (m, 2H, C5H4), 3.53 (q,
2H, OCH2CH3), 1.25 (t, 3H, OCH2CH3), 0.50 (s, 3H,
Si(CH3)2), 0.43 (s, 3H, Si(CH3)2). MS: m/e 516 (M+),
488 (M+−CO), 460 (M+−2CO), 432 (M+−3CO),
375 (M+−3COꢀCOC2H5), 298 (M+−3COꢀCOC2H5ꢀ
C6H5), 242 [(C5H4)2Si(CH3)2Fe+]. Anal. Calc. for
C24H24Fe2SiO4: C, 55.84; H, 4.69. Found: C, 55.75; H,
4.54%.
2.4.1. Alkylation in H2O
The reaction of complex 1 (0.410 g, 1.00 mmol) with
m-CH3C6H4Li (1.34 mmol) [16] was prepared as de-
scribed above in Section 2.2.1 at −20 to −10°C for 2
h. After evaporation of the solvent in vacuo, subse-
quent alkylation and further treatment of the resulting
residue in a manner similar to that described in Section
2.2.1 deep purple-red crystals of complex 4 (0.436 g
(82%, based on 1)) were yielded, m.p. 134–135°C
(dec.). IR (CH2Cl2)w(CO) 1972 (vs, br), 1939 (w), 1748
2.2.2. Alkylation in CH2Cl2
1
(vs, br) cm−1. H-NMR (CD3COCD3): l 7.45 (t, 2H,
Complex 1 (0.410 g, 1.00 mmol) was treated with
C6H5Li (1.34 mmol), as described above in Section
2.2.1, in ether at −20 to −10°C for 2 h. After removal
of the solvent under vacuum at −20°C, the residue was
dissolved in CH2Cl2 (30 ml) at −60°C. To this solution
of Et3OBF4 (0.250 g, 1.31 mmol) dissolved in CH2Cl2
(10 ml) was added dropwise with stirring within 15 min.
The reaction mixture turned from dark brown to
brown-red. After being stirred at −40 to −30°C for 1
h, the solvent was removed in vacuo at −30°C. Fur-
ther treatment of the resulting mixture as described
above gave the purple-red crystalline complex 2 (0.44 g
(85%, based on 1)) which was identified by its melting
C6H4CH3), 7.05 (t, 1H, C6H4CH3), 6.85 (m, 1H,
C6H4CH3), 6.04 (m, 2H, C5H4), 5.61 (m, 1H, CH2Cl2),
5.41 (m, 2H, C5H4), 5.15 (m, 2H, C5H4), 4.83 (m, 2H,
C5H4), 3.54 (q, 2H, OCH2CH3), 2.28 (s, 3H, C6H4CH3),
1.26 (t, 3H, OCH2CH3), 0.49 (s, 3H, Si(CH3)2), 0.43 (s,
3H, Si(CH3)2). MS: m/e 530 (M+), 502 (M+−CO),
474 (M+−2CO), 446 (M+−3CO), 389 (M+−
3COꢀCOC2H5), 312 (M+−3COꢀCOC2H5ꢀC6H5), 242
[(C5H4)2Si(CH3)2Fe+], 84 [CH2Cl+2 ]. Anal. Calc. for
C25H26Fe2SiO.41/2CH2Cl2: C, 53.48; H, 4.75. Found: C,
53.45; H, 4.61%.
1
point, IR, H-NMR and mass spectra.
2.4.2. Alkylation in CH2Cl2
2.3. Reaction of 1 with o-CH3C6H4Li to gi6e
[Fe2(v-CO){v-C(OC2H5)C6H4CH3-o}-(CO)2-
{(p5-C5H4)2Si(CH3)2}] (3)
Complex 1 (0.410 g, 1.00 mmol) was treated as
described in Section 2.2.1 with m-CH3C6H4Li (1.34
mmol) in ether at −20 to −10°C for 2 h. Further
treatment of the resulting mixture in a manner similar
to that described in Section 2.2.2 yielded complex 4
(0.43 g (81%, based on 1)) as deep purple-red crystals
which was identified by its m.p., IR, 1H-NMR and
mass spectra.
Similar to the procedures described above for the
reaction in Section 2.2.1, complex 1 (0.410 g, 1.00
mmol) with o-CH3C6H4Li (1.34 mmol) [16] at −20 to
−10°C for 2 h. The subsequent alkylation and further

R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
295
2.5. Reaction of 1 with p-CH3C6H4Li to gi6e
[Fe2(v-CO){v-C(OC2H5)C6H4CH3-p}-(CO)2-
{(p5-C5H4)2Si(CH3)2}] (5)
2.7. Reaction of 1 with p-ClC6H4Li to gi6e
[Fe2(v-CO){v-C(OC2H5)C6H4Cl-p}-(CO)2-
{(p5-C5H4)2Si(CH3)2}] (7)
n-C4H9Li (1.87 mmol) was added to a solution of
p-ClC6H4Br (0.237 g, 1.25 mmol) in ether (20 ml) at
−20°C. After stirring at room temperature for 30 min,
the resulting solution of p-ClC6H4Li [19] was reacted,
in a manner similar to that for the reaction of complex
1 with C6H5Li, with complex 1 (0.410 g, 1.00 mmol) in
ether (60 ml) at −40 to −10°C for 4 h. Subsequent
alkylation and further treatment similar to that used in
Section 2.2.2 yielded the purple-red crystalline 7 (0.47 g
(85%, based on 1)), m.p. 137–138°C (dec.). IR
(CH2Cl2) w(CO) 1993 (v), 1973 (vs, br),1765 (s, br)
Similarly, complex 1 (0.410 g, 1.00 mmol) dissolved
in ether (60 ml) was treated with p-CH3C6H4Li (1.34
mmol) [16] at −20 to −10°C for 2 h, followed by
alkylation; further treatment as described above for the
reaction in Section 2.2.1 produced deep purple-red crys-
tals of complex 5 (0.46 g (87%, based on 1)), m.p.
119–121°C (dec.). IR (CH2Cl2) w(CO) 1972 (vs, br),
1
1748 (vs, br) cm−1. H-NMR (CD3COCD3): l 7.52 (d,
2H, C6H4CH3), 6.97 (d, 2H, C6H4CH3), 6.04 (m, 2H,
C5H4), 5.40 (m, 2H, C5H4), 5.15 (m, 2H, C5H4), 4.82
(m, 2H, C5H4), 3.52 (q, 2H, OCH2CH3), 2.24 (s, 3H,
C6H4CH3), 1.23 (t, 3H, OCH2CH3), 0.49 (s, 3H,
Si(CH3)2), 0.42 (s, 3H, Si(CH3)2). MS: m/e 530 (M+),
502 (M+−CO), 474 (M+−2CO), 446 (M+−3CO),
389 (M+−3COꢀCOC2H5), 312 (M+−3COꢀCOC2H5ꢀ
C6H5), 242 [(C5H4)2Si(CH3)2Fe+]. Anal. Calc. for
C25H26Fe2SiO4: C, 56.63; H, 4.94. Found: C, 56.16; H,
4.73%.
1
cm−1. H-NMR (CD3COCD3):l 7.67 (d, 2H, C6H4Cl),
7.17 (d, 2H, C6H4Cl), 6.05 (m, 2H, C5H4), 5.60 (m, 2H,
C5H4), 5.16 (m, 2H, C5H4), 4.85 (m, 2H, C5H4), 3.57 (q,
2H, OCH2CH3), 1.28 (t, 3H, OCH2CH3), 0.50 (s, 3H,
Si(CH3)2), 0.43 (s, 3H, Si(CH3)2). MS: m/e 550 (M+),
522 (M+−CO), 494 (M+−2CO), 466 (M+−3CO),
409 (M+−3COꢀCOC2H5), 242 [(C5H4)2Si(CH3)2Fe+].
Anal. Calc. for C24H23ClFe2SiO4: C, 52.35; H, 4.21.
Found: C, 51.95; H, 4.22%.
2.8. Reaction of 1 with p-CF3C6H4Li to gi6e
[Fe2(v-CO){v-C(OC2H5)C6H4CF3-p}-(CO)2-
{(p5-C5H4)2Si(CH3)2}] (8)
2.6. Reaction of 1 with p-CH3OC6H4Li to gi6e
[Fe2(v-CO){v-C(OC2H5)-C6H4OCH3-p}(CO)2-
{(p5-C5H4)2Si(CH3)2}] (6)
A solution of p-CF3C6H4Br (0.338 g, 1.50 mmol) in
ether (20 ml) was mixed with n-C4H9Li (1.50 mmol).
After 40 min stirring at room temperature, the resulting
ether solution of p-CF3C6H4Li [20] was reacted, as
described in Section 2.2.1, with 1 (0.410 g, 1.00 mmol)
at −20 to 0°C for 3 h, followed by alkylation; further
treatment as described in Section 2.2.2 gave bright
purple-red crystals of complex 8 (0.52 g (89%, based on
1)), m.p. 145–146°C (dec.). IR (CH2Cl2) w(CO) 1974
A solution of p-CH3OC6H4Br (0.283 g, 1.50 mmol)
in ether (20 ml) was mixed with n-C4H9Li (1.50 mmol)
[17]. After 30 min stirring at room temperature, the
resulting ether solution of p-CH3OC6H4Li [18] was
reacted, as described in Section 2.2.1, with complex 1
(0.410 g (1.00 mmol)) at −20 to −5°C for 2 h. After
vacuum removal of the solvent at −30°C, the residue
was dissolved in CH2Cl2 (30 ml) at −70°C. To this
solution was added dropwise Et3OBF4 (0.250 g, 1.32
mmol) dissolved in CH2Cl2 (10 ml) with stirring within
15 min. After being stirred at −40 to −30°C for 1 h,
the solvent was removed under vacuum. Further treat-
ment of the residue as described for the preparation of
2 gave the deep brown-red crystalline complex 6 (0.46 g
(84%, based on 1)), m.p. 118–119°C (dec.). IR
(CH2Cl2) w(CO) 1994 (w), 1971 (vs, br), 1748 (vs, br)
.
(vs, br), 1939 (w), 1763 (s, br) cm−1 1H-NMR
(CD3COCD3):l 7.86 (d, 2H,C6H4CF3), 7.50 (d, 2H,
C6H4CF3), 6.09 (m, 2H, C5H4), 5.48 (m, 2H, C5H4),
5.20 (m, 2H, C5H4), 4.88 (m, 2H, C5H4), 3.50 (q, 2H,
OCH2CH3), 1.29 (t, 3H, OCH2CH3), 0.51 (s, 3H,
Si(CH3)2), 0.45 (s, 3H, Si(CH3)2). MS: m/e 584 (M+),
556 (M+−CO), 528 (M+−2CO), 500 (M+−3CO),
443 (M+−3COꢀCOC2H5), 242 [(C5H4)2Siꢀ(CH3)2Fe+].
Anal. Calc. for C25H23Fe2F3SiO4: C, 52.84; H, 3.97.
Found: C, 52.55; H, 3.99%.
. l 7.56 (dd, 2H,
cm−1 1H-NMR (CD3COCD3)
C6H4OCH3), 6.71 (dd, 2H, C6H4OCH3), 6.05 (m, 2H,
C5H4), 5.40 (m, 2H, C5H4), 5.14 (m, 2H, C5H4), 4.82
(m, 2H, C5H4), 3.74 (s, 3H, C6H4OCH3), 3.53 (q, 2H,
OCH2CH3), 1.26 (t, 3H, OCH2CH3), 0.49 (s, 3H,
Si(CH3)2), 0.42 (s, 3H, Si(CH3)2). MS: m/e 546 (M+),
518 (M+−CO), 490 (M+−2CO), 462 (M+−3CO),
405 (M+−3COꢀCOC2H5), 328 (M+−3COꢀCOC2H5-
C6H5), 242 [(C5H4)2Si(CH3)2Fe+]. Anal. Calc. for
C25H26Fe2SiO5: C, 54.97; H, 4.80. Found: C, 54.78; H,
4.79%.
2.9. X-ray crystal structure determinations of
complexes 2 and 6
The single crystals of 2 and 6 suitable for X-ray
diffraction study were obtained by recrystallization
from petroleum ether–CH2Cl2 solution at −80°C. Sin-
gle crystals were mounted on a glass fibre and sealed
with epoxy glue. The X-ray diffraction intensity data

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R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
Table 1
The details of the crystallographic data and the pro-
cedures used for data collection and reduction informa-
tion for 2 and 6 are given in Table 1. The selected bond
lengths and angles are listed in Table 2. The atomic
coordinates and Biso/Beq, anisotropic displacement
parameters, complete bond lengths and angles, least-
squares planes for 2 and 6 are given in the Supporting
Information. The molecular structures of 2 and 6 are
given in Figs. 1 and 2, respectively.
Crystal data and experimental details for complexes 2 and 6
2
6
Formula
Formula weight
Space group
C24H24O4SiFe2
516.23
C
546.26
25H26O5SiFe2
P21/n (no.14)
10.160(1)
18.180(4)
12.563(2)
96.86(1)
2304.0(7)
4
1.488
1064.00
13.37
P21/c (no.14)
16.486(9)
9.021(6)
16.834(9)
98.86(4)
2473(2)
4
1.467
1128.00
12.53
,
a (A)
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
3. Results and discussion
Dcalc (g cm−3
F (000)
)
m (Mo–Ka) (cm−1
)
Similar to the reactions of (cyclooctatetraene)diiron
hexacarbonyl and bis(m-cyclopentadienyl)diiron te-
tracarbonyl with aryllithium reagents [11,12], di-m-car-
bonyl-cis-m-(1-5-h:1%-5%-h-dicyclopentadienyldimethylsi-
lane)bis(carbonyliron), [Fe2(m-CO)2(CO)2{(h5-C5H4)2Si-
(CH3)2}] (1), was treated with a 30–35% molar excess
of aryllithium reagents, ArLi (Ar=C6H5, o-, m-, p-
CH3C6H4, p-CH3OC6H4, p-ClC6H4, p-CF3C6H4), in
ether at low temperature afforded acylmetalate interme-
diates, followed by alkylation with Et3OBF4 in aqueous
solution at 0°C or in CH2Cl2 at −30°C. After removal
of the solvents under vacuum at low temperature, the
residues were chromatographed on an alumina column
at −20 to −25°C, and the crude products were recrys-
tallized from petroleum ether–CH2Cl2 solution at
−80°C to give purple-red crystalline complexes 2–8
with the compositions [Fe2(m-CO){m-C(OC2H5)Ar}-
(CO)2{(h5-C5H4)2Si(CH3)2}] (Scheme 3) in 81–91% iso-
lated yields.
Radiation (monochromated
in incident beam)
Diffractometer
Temperature (°C)
Orientation reflections: no.;
range (2q), (°)
Scan method
Data collection range, 2q (°) 5–50
No.of unique data, total
No.of unique data with
I\2.00|(I)
Mo–Ka
Mo–Ka
,
,
(l=0.71069 A) (l=0.71069 A)
Rigaku AFC7R Rigaku AFC7R
20
20
25; 18.6−24.7
16; 10.4−19.6
ꢀ–2q
ꢀ–2q
5–45
2684
974
3872
2280
No.of parameters refined
281
273
Correction factors, max./min. 0.8699–1.0000
0.8683–1.1290
0.074
0.065
1.91
0.00
a
R
0.042
0.043
1.14
b
Rw
Quality-of-fit indicator c
Largest shift /esd. final cycle 0.00
Largest peak, e−
Minimum peak, e−
A
0.28
−0.29
0.50
−0.47
−3
,
−3
,
A
a R=ꢀꢁꢁFoꢁꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ
b Rw=[ꢀw (ꢁFoꢁ−ꢁFcꢁ)2/ꢀwꢁFoꢁ2]1/2; w=1/|2(ꢁFoꢁ)
Complexes 2–8 are formulated as the (dicyclopenta-
c Quality-of-fit=[ꢀw (ꢁFoꢁ−ꢁFcꢁ)2/(Nobs−Nparameters)]1/2
dienyldimethylsilane)diiron
bridging
alkoxy(aryl)-
carbene complexes on the basis of their elemental
analyses, spectroscopic studies, and the single-crystal
X-ray diffraction studies of complexes 2 and 6. Com-
plexes 2–8 are the first examples of silyl-bridged dicy-
clopentadienyl dimetal complexes with a bridging
carbene ligand, in which the dicyclopentadienyl–
dimethylsilane ligand coordinates the two iron atoms
through its two cyclopenta-dienyl ring in h5-bonding.
There are two bridging CO ligands which have the
same chemical environment in the starting material 1.
Therefore it was expected that di-bridging alkox-
y(aryl)carbene diiron complexes should exist in the
resulting products when treating complex 1 with aryl-
lithium reagents. However, no expected di-bridging
alkoxy(aryl)carbene diiron complexes or their deriva-
tives were obtained from the reactions even though
more than two molar equivalents of aryllithium reagent
were used for the reactions.
for 3872 and 2684 independent reflections, of which
2280 and 974 with I\2.00s(I) for 2 and 6 were
observable, were collected with a Rigaku AFC7R dif-
fractometer at 20°C using Mo–Ka radiation with an
ꢀ–2q scan mode within the ranges 5°52q550° for 2,
and 5°52q545° for 6, respectively.
The structures of 2 and 6 were solved by direct
methods and expanded using Fourier techniques. For 2,
the non-hydrogen atoms were refined anisotropically.
For 6, some non-hydrogen atoms were refined an-
isotropically, while the rest were refined isotropically.
For both complexes, the hydrogen atoms were included
but not refined. The final cycle of full-matrix least-
squares refinement was respectively based on 2280 and
974 observed reflections and 281, and 273 variable
parameters and converged with unweighted and
weighted agreement factors of R=0.042 and RW=
0.043 for 2 and R=0.074 and RW=0.065 for 6, respec-
tively. All the calculations were performed using the
teXsan crystallographic software package of Molecular
Structure Corporation.
In addition, complex 1 has two forms of coordinated
carbonyl ligands, terminal and bridging CO. It was
expected that the aryllithium reagents could attack both
terminal CO and bridging CO to produce an alkoxy-

R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
297
Table 2
Selected bond lengths (A) and angles (°) a for complexes 2 and 6
a
,
2
6
2
6
Fe(1)ꢀFe(2)
Fe(1)ꢀC(1)
Fe(2)ꢀC(1)
Fe(1)ꢀC(10)
Fe(2)ꢀC(10)
C(10)ꢀO(2)
Fe(1)ꢀC(8)
C(8)ꢀO(1)
2.513(1)
2.023(5)
2.021(5)
1.897(6)
1.914(6)
1.178(6)
1.746(6)
1.156(6)
1.735(6)
1.152(6)
51.6(1)
76.9(2)
51.5(1)
48.4(2)
82.5(2)
49.0(2)
97.3(2)
96.8(2)
2.503(6)
2.04(2)
2.05(3)
1.75(3)
2.02(4)
1.23(4)
1.73(3)
1.14(2)
1.68(3)
1.22(3)
52.2(7)
75.4(9)
52.4(8)
43.9(9)
82(1)
C(1)ꢀC(2)
C(1)ꢀO(4)
O(4)ꢀC(26)
C(26)ꢀC(27)
SiꢀC(17)
SiꢀC(18)
SiꢀC(23)
SiꢀC(24)
Fe(1)ꢀC(Cp) (avg.)
Fe(2)ꢀC(Cp) (avg.)
Fe(2)ꢀC(1)ꢀC(2)
Fe(1)ꢀC(10)ꢀO(2)
Fe(2)ꢀC(10)ꢀO(2)
Fe(1)ꢀC(8)ꢀO(1)
Fe(2)ꢀC(9)ꢀO(3)
Fe(1)ꢀC(17)ꢀSi
Fe(2)ꢀC(18)ꢀSi
C(17)ꢀSiꢀC(18)
C(1)ꢀC(2)ꢀC(3)
C(1)ꢀC(2)ꢀC(7)
O(4)ꢀC(26)ꢀC(27)
1.522(7)
1.413(6)
1.410(7)
1.469(8)
1.863(6)
1.862(6)
1.824(7)
1.849(7)
2.118
1.49(3)
1.44(3)
1.44(3)
1.50(4)
1.85(3)
1.85(3)
1.84(3)
1.84(3)
2.112
Fe(2)ꢀC(9)
C(9)ꢀO(3)
2.128
2.118
Fe(1)ꢀFe(2)ꢀC(1)
Fe(1)ꢀC(1)ꢀFe(2)
Fe(2)ꢀFe(1)ꢀC(1)
Fe(1)ꢀFe(2)ꢀC(10)
Fe(1)ꢀC(10)ꢀFe(2)
Fe(2)ꢀFe(1)ꢀC(10)
C(1)ꢀFe(1)ꢀC(10)
C(1)ꢀFe(2)ꢀC(10)
Fe(1)ꢀC(1)ꢀO(4)
Fe(1)ꢀC(1)ꢀC(2)
Fe(2)ꢀC(1)ꢀO(4)
123.1(4)
139.2(5)
138.3(5)
174.7(5)
173.8(5)
120.4(3)
119.5(4)
106.8(2)
119.1(5)
124.1(5)
110.4(5)
114(1)
160(3)
116(2)
174(2)
173(2)
121(1)
119(1)
106(1)
120(2)
121(2)
108(2)
53(1)
101(1)
93(1)
111(1)
127(1)
110(1)
113.5(3)
117.6(3)
113.2(3)
a Estimated standard deviations in the least significant figure are given in parentheses.
(aryl)arbene and a bridging alkoxy(aryl)carbene com-
plexes when treating complex 1 with aryllithium
reagents. However, only diiron bridging alkoxycarbene
complexes were obtained, which could be produced via
an attack of nucleophilic aryllithium reagents on a
bridging CO of complex 1. In fact, it is uncertain
whether the nucleophilic attack in the initial step occurs
actually on the bridging CO or the terminal CO. Brown
et al. [21] and Koelle [22] have shown that the nucle-
ophilic attack on the coordinated carbonyls relates to
the electron density at CO. In general, the CO having a
lower electron density is easily attacked by nucle-
ophiles. Atwood et al. [23], based on the experimental
results of the reaction of bis(h-cyclopentadienyl)diiron
tetracarbonyl with LiAlH4 and according to the view-
point of Brown and Koelle et al., presumed that in the
initial step of the reaction process, the nucleophilic
hydride attack at coordinated carbonyl occurred on the
terminal CO having a lower electron density but not on
the bridging CO having a higher electron density [24].
Our results of the reactions of 1 with the aryllithium
reagents seem to be contrary to the experimental results
of Atwood et al. However, we consider that the reac-
tion of a carbonylmetal compound having two forms of
coordinating CO groups (terminal and bridging CO)
with a nucleophilic reagent is very complicated. The
reaction course and resulting product of the carbonyl-
metal compound with nucleophile depend not only on
the structure of the metal carbonyls themselves but also
on the nucleophilic ability of the nucleophile and the
stability of the acylmetalate intermediate formed by the
reaction of carbonylmetal compound with nucleophile,
as well as the experimental conditions and others. Un-
der a different experimental system, the reaction path-
way could be different. As for the reaction of complex
Fig. 1. Molecular structure of 2, showing the atomic numbering
scheme. Thermal ellipsoids are shown at 40% probability.

298
R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
converted to the products (2–8) upon the alkylation
with alkylating reagents.
Complexes 2–8 are soluble in polar organic solvents
but only slightly soluble in non-polar solvents. They are
sensitive to air and temperature in solution but stable
for short periods on exposure to air at room tempera-
ture in the solid state. The IR spectra and the solution
1H-NMR spectra, as well as the mass spectra, are
consistent with the proposed structure shown in Scheme
3. The IR spectra of complexes 2–8 showed one to two
strong, broad CO absorption bands at 1939–1994
cm−1 and one CO absorption band at 1748–1765
cm−1 in the w(CO) region, which signified a (CO)2Fe(m-
CO) moiety in complexes 2–8 and suggested that only
one m-CO ligand converted into a bridging carbene
ligand upon the reaction of complex 1 with nucleophilic
aryllithium and subsequent alkylation with Et3OBF4 in
the four-carbonyl complex 1. The data given in the
Section 2 showed that the different aryl substituents
exerted certain influence on the absorption bands and
the w(CO) frequency, specifically, on the (m-CO) fre-
quency in these complexes. For example, complexes 7
and 8 with a electron-withdrawing group (p-ClC6H4 or
p-CF3C6H4) showed the w(m-CO) stretching vibration
band at 1763–1765 cm−1, shifting to high vibration
frequency by 15–17 cm−1, as compared with that (1748
cm−1) in complexes 3–6 with a electron-pushing group
Fig. 2. Molecular structure of 6, the atomic numbering scheme with
40% thermal ellipsoids.
1
(CH3C6H4 or CH3OC6H4). In the H-NMR spectra of
2–8 given in the Section 2, a triplet (ca.1.29–0.86 ppm)
and a quartet (ca. 3.57–3.42 ppm) and a set of multi-
plet (ca. 7.86–6.71 ppm) bands were observed for each
of the complexes, which showed characteristically the
presence of the ethoxy and aryl groups. From the
1H-NMR spectra, it also noted that the proton signals
attributed to the dicyclopentadienyl protons showed
only two resonances at 5.60 and 5.20 ppm in starting
complex 1 but four or three resonances at about 6.09–
4.67 ppm in the resulting complexes 2–8. This might
arise from the conversion of a bridging CO ligand into
a m-carbene ligand, leading to a change in the chemical
environment of the cyclopentadienyl ring in 2–8. The
mass spectra of complexes 2–8, given in Section 2,
showed the expected molecular ion peaks and principal
fragments produced by successive loss of CO ligands
and the m-carbene ligand, as well as the featured ions
bearing useful structural information from the frag-
ments generated by further cleavage of these principal
fragments.
The molecular structures of complexes 2 and 6, es-
tablished by X-ray diffraction studies, are shown in
Figs. 1 and 2, respectively. Complexes 2 and 6 have
approximately the same steric configuration. The m-
C(OC2H5)C6H5 moiety in 2 and the m-C(OC2H5)-
C6H4OCH3 moiety in 6 are on opposite sides of dicy-
clopentadienyl-dimethylsilane ligand, as can be visual-
ized in the ORTEP diagrams of 2 and 6 respectively in
Figs. 1 and 2. Both complexes are of the diiron system
Scheme 3.
1 with aryllithium reagents under the present condi-
tions, the nucleophilic aryllithium attack in the initial
step occurred on the bridging CO that is possible. In
the reaction, however, either aryllithium first attacked
the bridging CO or the aryllithium first attacked the
terminal CO, though of the acylmetalate intermediate
which might have isomers (terminal and bridging) that
can be converted to each other in the solution, only the
more stable acylmetalate intermediate formed can be

R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
299
,
with FeꢀFe bond distances of 2.513(1) and 2.503(6) A,
ring plane comprised of C(2) through C(7) is 130.36°, and
the dihedral angle between the Fe(1)Fe(2)C(1) and
Fe(1)Fe(2)C(10) planes is 154.81°. The angle between the
two cyclopentadienyl ring planes is 83.48°. The benzene
ring C(2)C(3)C(4)C(5)C(6)C(7) plane is, respectively,
oriented at an angle of 130.36, 74.32, and 32.52° with
respect to the Fe(1)Fe(2)C(1) plane, the Fe(1)Fe(2)C(10)
plane, and the SiC(17)Fe(1)Fe(2)C(18) plane; while the
benzene ring plane is oriented respectively at angles of
100.27 and 113.21° with respect to the Cp ring
C(13)C(14)C(15)C(16)C(17) plane and C(18)C(19)
C(20)C(21)C(22) plane. Thus, complex 2 exists in a cis
structure to avoid steric repulsion between the six-mem-
bered aryl ring and the dicyclopentadienyldimethylsilane
ligand.
respectively; the ethoxy and aryl groups are attached to
the one with the bridged CO group. The perpendicular
distances from the Fe atom to the Cp ring plane are
,
respectively 1.744(7) and 1.758(4) A in 2 and 1.76(1) and
,
1.73(2) A in 6. The least-squares plane calculations show
that in both complexes the carbon atoms in the two Cp
rings are coplanar and the two CO ligands coordinated
on the same Fe atom are not coplanar arising from
bridging. In complexes 2 and 6, there exists two different
coordinated CO ligands and the bond distances of
FeꢀC(CO) are also different. For example, in complex 2
FeꢀCO (bridged, sp2) distances are 1.897(6) and 1.914(6)
,
A, while FeꢀCO (nonbridged, sp) are 1.746(6) and 1.735
,
(6) A, respectively.
The structure of 6 (Fig. 2) is very similar to that of 2,
except that the substituent on the m-carbene carbon is a
p-methoxyphenyl group instead of a phenyl group. Many
structural features of 6 are essentially the same as those
in 2: the FeꢀFe distance, the two m-CꢀFe distances, and
the angle between the ligand planes C(13) through C(17)
and C(18) through C(22).
Although a number of dimetal bridging carbene com-
plexes have been synthesized by Stone et al. and by us
as mentioned in the Section 1, complexes 2–8, as dimetal
complexes with a bridging carbene ligand, were synthe-
sized in high yield by the reactions of a bis(m-CO)metal
compound with nucleophilic aryllithium reagents in
one-pot reaction. Analogous reactions were observed
only in the case of pentacarbonyl(cyclooctate-
traene)diiron and bis(h5-cyclopentadienyl)diiron tetra-
carbonyl compounds (Schemes 1 and 2). The title reac-
tion further demonstrates that it is a most direct, simple,
and convenient method for the preparation of such
dimetal bridging carbene complexes.
In complex 2, the distance of the FeꢀFe bond bridged
by the m-carbene ligand is close in value to that found
in analogous bridging carbene complex [Fe2(m-CO){m-
,
C(OEt)ꢀC6H5}(CO)2(h-C5H5)2] (2.512(1) A) [12] but ob-
viously shorter than that found in diiron bridging
carbene complexes [Fe2(m-CO){m-C(SEt)C6H5}(CO)2(h-
,
C5H5)2] (2.527(2) A) [25], [Fe2(m-CO){m-C(SC6H5)-
,
C6H5}(CO)2(h-C5H5)2] (2.523(2) A) [25], and [Fe2(m-
,
CO){m-C(OEt)C6H4CF3-p}(CO)4(C8H8)] (2.686(1) A)
[11]. The m-carbene carbon almost symmetrically bridges
the FeꢀFe bond with C(1)ꢀFe(1) of 2.023(5) and
,
C(1)ꢀFe(2) of 2.0021(5) A. The m-CꢀFe distances are
somewhat longer than the m-FeꢀCO bond (C(10)ꢀFe(1)
,
1.897(6), C(10)ꢀFe(2) 1.914(6) A) but approximately
equal to those in complexes [Fe2(m-CO){m-
C(SEt)C6H5}(CO)2(h5-C5H5)2] (C(1)ꢀFe(1) 2.03(1) and
,
C(1)ꢀFe(2) 2.00(1) A) [12], [Fe2(m-CO){m-C(SC6H5)-
C6H5}(CO)2(h5-C5H5)2] (C(1)ꢀFe(1) 2.026(8) and
,
C(1)ꢀFe(2) 2.032(8) A) [12], [Fe2{m-C(OEt)C6H4CF3-
,
p}(CO)4(C8H8)] (CꢀFe(1) 2.063(3) A, CꢀFe(2) 2.010(3))
[11], and [Fe2(m-CO){m-C(CN)NHPh}(CO)2(h5-C5H5)2]
,
,
(C(4)ꢀFe(1) 2.004(2) A, C(4)ꢀFe(2) 2.028(2) A) [26].
In 2, the benzene ring lies in the trans position of the
dicyclopentadienyl–dimethylsilane ligand. The Si atom
is bridged to the two Cp rings with the identical SiꢀC
bond lengths (SiꢀC(17) 1.863(6) and SiꢀC(18) 1.862(6)
4. Supplementary material
Tables of atomic coordinates, thermal parameters, H
atom coordinates, anisotropic displacement parameters,
complete bond lengths and angles, and least-squares
planes for complexes 2 and 6 are available. Crystallo-
graphic data for the structural analysis in this paper have
been deposited at the Cambridge Crystallographic Data
Centre. Copies of this information may be obtained free
of charge from The Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Fax: +44-1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
,
A). The C(17)ꢀSiꢀC(18) bond angle is 106.8(2)°. The Si,
Fe(1), Fe(2), C(17) and C(18) atoms lie essentially in the
same plane to construct a siliceous dimetal five-mem-
bered ring. The dihedral angles between the plane defined
by Si, C(17), Fe(1), Fe(2), and C(18) and the plane
comprised of Fe(1), Fe(2), and C(10) and the
SiC(17)Fe(1)Fe(2)C(18) plane and the Fe(1)Fe(2)C(1)
plane are 105.17 and 100.02°, respectively, while the
dihedral angle between the Fe(1)Fe(2)C(1) and
Fe(1)Fe(2)C(10) planes is 154.81°. The angles between
the SiC(17)Fe(1)Fe(2)C(18) and Cp ring C(13)C-
(14)C(15)ꢀC(16)C(17) planes and the SiC(17)Fe-
(1)Fe(2)C(18) and Cp ring C(18)C(19)C(20)ꢀC(21)C(22)
planes, respectively, are 84.39 and 83.41°. The dihedral
angle between the Fe(1)Fe(2)C(1) plane and the benzene
Acknowledgements
Financial support from the National Natural Science
Foundation of China and the Science Foundation of the
Chinese Academy of Sciences is gratefully acknowledged.

300
R. Wang et al. / Journal of Organometallic Chemistry 617–618 (2001) 292–300
[9] (a) Y.-J. Tang, J. Sun, J.-B. Chen, Organometallics 18 (1999)
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