Preparations and characterizations of homodinuclear complexes containing flyover bridge or cyclopentadienone ligands; X-ray crystal structures of Co2(CO)3(PPh3){μ-C(SiMe 3)=CH-CH=C(SiMe3)-CH=C(SiMe3)}, Co2(CO)2(μ-CO)2(η 4-2,5-bistrimethylsilylcyclopentadienone)2

Article abstract of DOI:10.1016/S0022-328X(98)01086-9

The reaction of Co₂(CO)₅(PPh₃)(μ-HCC-SiMe₃) (1b) with 2.5 equivalent amount of trimethylsilylacetylene in refluxed THF yielded two homodinuclear complexes containing 'flyover bridge' ligands, Co₂(CO)₃(PPh₃){μ-C(SiMe ₃)=CH-CH=C(SiMe₃)-CH=C(SiMe₃)} (2a) and a small amount of Co₂(CO)₂(μ-CO)₂(η ⁴-2,5-bistrimethylsilylcyclopentadienone)₂ (4). The yield of (4) was improved, while using about five equivalent amount of trimethylsilylacetylene. The crystal structures of (2a) and (4) were determined. The structure of (2a) can be regarded as a dimetallic frame contains three linked HCCSiMe₃ groups that are arranged in a 'flyover-bridge' geometry. Trimethylsilyl groups are attached to carbon atoms of the flyover bridge ligand at positions 1, 3, and 6. The ligand might be seen as the composition of two allyl groups, C1-C2-C3 and C4-C5-C6, which are joined by a single bond between C3 and C4. Each allyl group is bonded to one cobalt atom. 1,2,4-Tris-trimethysilanylbenzene was obtained from the degradation of the compound (2a). The crystal structure of (4) shows that two cyclopentadienone ligands, two terminal and two bridged carbonyls were found to be coordinated to both metal centers. The formation of the two cyclopentadienones is believed to take place via the transition metal-mediated cyclization of two alkynes with one carbon monoxide. 2,5-Bis(trimethylsilanyl)cyclopenta-2,4-dien-1-one (5) was obtained from the degradation of (4) by exposing to air in solution. The formation of (5) is believed to take place via the Diels-Alder type cyclization of two released cyclopentadienone ligands from (4).

Full text of DOI:10.1016/S0022-328X(98)01086-9

Journal of Organometallic Chemistry 580 (1999) 98–107
Preparations and characterizations of homodinuclear complexes
containing flyover bridge or cyclopentadienone ligands; X-ray crystal
structures of
Co2(CO)3(PPh3){m-C(SiMe3)ꢀCH–CHꢀC(SiMe3)–CHꢀC(SiMe3)},
Co2(CO)2(m-CO)2(h4-2,5-bistrimethylsilylcyclopentadienone)2 and
2,5-bis(trimethylsilanyl)cyclopenta-2,4-dien-1-one
Fung-E Hong *, Jyh-Yi Wu, Yueh-Chuan Huang, Chang-Ku Hung, Han-Mou Gau,
Chu-Chieh Lin
Department of Chemistry, National Chung-Hsing Uni6ersity, Taichung 40227, Taiwan, ROC
Received 26 August 1998
Abstract
The reaction of Co2(CO)5(PPh3)(m-HCꢁC–SiMe3) (1b) with 2.5 equivalent amount of trimethylsilylacetylene in refluxed THF
yielded two homodinuclear complexes containing ‘flyover bridge’ ligands, Co2(CO)3(PPh3){m-C(SiMe3)ꢀCH–CHꢀC(SiMe3)–
CHꢀC(SiMe3)} (2a) and a small amount of Co2(CO)2(m-CO)2(h4-2,5-bistrimethylsilylcyclopentadienone)2 (4). The yield of (4) was
improved, while using about five equivalent amount of trimethylsilylacetylene. The crystal structures of (2a) and (4) were
determined. The structure of (2a) can be regarded as a dimetallic frame contains three linked HCꢁCSiMe3 groups that are
arranged in a ‘flyover-bridge’ geometry. Trimethylsilyl groups are attached to carbon atoms of the flyover bridge ligand at
positions 1, 3, and 6. The ligand might be seen as the composition of two allyl groups, C1–C2–C3 and C4–C5–C6, which are
joined by a single bond between C3 and C4. Each allyl group is bonded to one cobalt atom. 1,2,4-Tris-trimethysilanylbenzene was
obtained from the degradation of the compound (2a). The crystal structure of (4) shows that two cyclopentadienone ligands, two
terminal and two bridged carbonyls were found to be coordinated to both metal centers. The formation of the two
cyclopentadienones is believed to take place via the transition metal-mediated cyclization of two alkynes with one carbon
monoxide. 2,5-Bis(trimethylsilanyl)cyclopenta-2,4-dien-1-one (5) was obtained from the degradation of (4) by exposing to air in
solution. The formation of (5) is believed to take place via the Diels–Alder type cyclization of two released cyclopentadienone
ligands from (4). © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Flyover bridge; Di-cobalt complexes; Homodinuclear complexes; Cyclopentadienone; Benzene
1. Introduction
one or both sets of filled p orbitals of the alkynes is well
known [2]. Among them, the reactions of Co2(CO)8
with various alkynes have been widely studied [3]. The
alkyne bridged compounds, Co2(CO)6(m-alkyne), are
simply formed from the direct thermal reaction of
Co2(CO)8 with an alkyne. The formation of metallacy-
clopentadiene rings in reactions with excess alkynes is
also well documented. It was via the linkage of two
Alkynes are highly reactive building blocks in synthe-
sis. Their interactions with various metal complexes
were extensively studied because of its potential in
catalysis [1]. The bonding of alkynes with metals using
* Corresponding author. Fax: +886-4-2862-547.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01086-9

F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
99
from the reaction of Co2(CO)8 with HCꢁC–SiMe3 in
the presence of one equivalent of PPh3 (Scheme 1).
High yields of (1a) might be achieved without the
presence of PPh3 [8]. Compounds (1a) and (1b) were
characterized by spectroscopic means.
Further reaction of Co2(CO)5(PPh3)(m-HCꢁC–Si
Me3) (1b) with 2.5 equivalents of trimethylsilylacetylene
in refluxed THF yielded two homobinuclear complexes
containing flyover bridge ligands, Co2(CO)3(PPh3){m-
C(SiMe3)ꢀCH–CHꢀC(SiMe3)–CHꢀC(SiMe3)} (2a) and
Scheme 1.
a
small amount of Co2(CO)2(m-CO)2(h4-2,5-bistri-
alkynes with metal center [4]. In some cases, a dimetal-
lic frame containing three linked acetylenes that are
arranged in a ‘flyover bridge’ geometry can be found in
low yield [5]. Corresponding benzene derivatives might
be obtained from thermal or chemical degradation of
the compound [3c]. There are few structural reports of
these type of compounds [6]. Here, we report one more
example of the preparation and crystal structure of
methylsilylcyclopentadienone)2 (4). The yield of the lat-
ter might be improved while (1a) was allowed to react
with about five equivalents of trimethylsilylacetylene.
There was no sign of forming Co2(CO)3(PPh3){m-
C(SiMe3)ꢀCH–C(SiMe3)ꢀCH–C(SiMe3)ꢀCH}
(2b),
presumably an isomer of (2a) (Scheme 2). The fact that
the metallapentadiene type compound, such as (3), was
not observed is noteworthy. The metallapentadiene
type of structure is generally regarded as the possible
intermediate while forming flyover bridge compounds.
Compound (2a) was characterized by spectroscopic
means as well as structural determination. The principal
structure of (2a) can be regarded as a dimetallic frame
contains three linked HCꢁCSiMe3 groups that are ar-
ranged in a ‘flyover bridge’ geometry (Fig. 1). Three
trimethylsilyl groups are attached to the six-carbon
ligand chain at positions 1, 3, and 6, respectively. The
ligand can be seen as the composition of two allyl
groups C1–C2–C3 and C4–C5–C6 which are joined
by a single bond between C3 and C4. The bond length
a
‘flyover bridged’ homobimetallic compound,
Co2(CO)3(PPh3){m-C(SiMe3)ꢀCH–CHꢀC(SiMe3)–CHꢀ
C(SiMe3)} (2a).
Monomeric substituted cyclopentadienones are not
stable and tend to undergo the Diels–Alder reaction to
form the dimeric compounds [7]. Here, we report, to
our knowledge, the first crystal structure of a cyclopen-
tadienone coordinated dicobalt compound, Co2-
(CO)2(m - CO)2(h4 - 2,5 - bistrimethylsilylcyclopentadi-
enone)2 (4). An unexpected structure feature was re-
vealed. This compound can be seen as the metal com-
plex containing monomeric cyclopentadienone synthon.
˚
of C3–C4 is 1.506 A which is longer than other bonds
(Table 2). The dihedral angle between the two allylic
planes is 59°. Each of the allyl groups are bonded to
both cobalt atoms. This ligand can be seen as a 6-p
electron donor, three to each metal center. The only
triphenylphosphine ligand is attached to one of the
cobalt atoms. Each cobalt atom obeys the EAN rule.
2. Results and discussion
An alkyne bridged homobimetallic compound,
Co2(CO)5(PPh3)(m-HCꢁC–SiMe3) (1b) was obtained
with a small amount of Co2(CO)6(m-HCꢁC–SiMe3) (1a)
Scheme 2.

100
F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
Fig. 1. ORTEP drawing with the numbering scheme of (2a). Hydrogen atoms were omitted for clarity.
are present and the phosphine ligand is absent. Com-
Four atoms, Co(1), C(1), Co(2), C(6) are almost
pound (2a) also showed one broad 31P signal around
53.3 ppm. The broad peak is due to the coupling
between phosphine and its attached cobalt (I=7/2).
An organic compound, which was characterized as
1,2,4-tris-trimethysilanylbenzene was obtained from the
degradation of the compound (2a) [8a]. This is also
coplanar. The bond lengths from C(6) to both cobalts
are rather small (Table 2). This is also true for C(1) to
both metals (Fig. 2). The structure of (2a) can be
regarded as a flyover bridge ligand wrapping the
cobalt–cobalt bond from one side of the molecule. The
other side of the molecule is relatively open and further
reaction presumably could take place there. The pres-
ence of the triphenylphosphine ligand on one of the
cobalt atoms does not seem to alter the structure partic-
ularly. However, the presence of the PPh3 ligand might
play a role in the crystallization of this compound. We
observed that these type of compounds are frequently
oily and difficult to crystallize without the presence of
the PPh3 ligand.
1
evidence that confirms the observed H-NMR of (2a).
The formation of this benzene derivative may have
resulted from the breaking of two Co–C s-bonds from
both metal centers and which then rejoined both ends
together. Similar observations were reported [9].
The preparation of (4)-like compounds from the re-
action of Co2(CO)8 with corresponding acetylenes had
been reported [10]. However, the yields of the reactions
were quite low and the crystal structures were not
available. In our case, (4) (Table 3) was obtained as the
major product in high yields while about five equivalent
amounts of trimethylsilylacetylene was used in the reac-
tion as shown in Scheme 1. The compound was charac-
terized by spectroscopic means. Red crystals of (4) were
grown in CH2Cl2 at 10°C and were sampled and sub-
jected to X-ray crystal structural determination (Fig. 3).
It was identified as a cyclopentadienone ligand coordi-
nated dicobalt compound. Interestingly, two cyclopen-
tadienone ligands, as well as two bridged carbonyls
were found to coordinate to both metal centers. It is
believed that the cyclopentadienone was formed by
head-to-head coupling of two trimethylsilylacetylenes
with a carbonyl through the metal-mediated cycliza-
tion. There are two molecules in an asymmetry unit of
A complicated coupling pattern and relatively larger
coupling constants for the protons on the flyover bridge
1
ligand were observed in the H-NMR of (2a). This is
probably due to the coupling effect from both vincinal
HC–CH protons as well as the triphenylphosphine
ligand. It is also supported by the fact that a much
more simpler coupling pattern was observed for (2c) in
which the triphenylphosphine ligand of (2a) was re-
placed by a carbonyl ligand (Scheme 3). In the reaction,
the PPh3 ligand, presumably, was pulled out by the
Lewis acid, BH3 and the activated species picked up
one CO from some decomposed species thus resulting
in the formation of (2c). Two doublets at 6.16 and 5.88
ppm, with the coupling constants of 6.4 Hz as well as
1
one singlet at 3.20 ppm were observed in H-NMR of
(2c). This indicates that the vincinal HC–CH protons

F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
101
Table 1
Crystal data (2a), (4) and (5)
No. of independent reflections
Empirical formula
Formula weight
Crystal system
Space group
C
36H45Co2O3PSi
C26H40Co2O6Si
C26H40Co2O6Si4
678.8
Monoclinic
P21/c
C22H40O2Si4
C22H40O2Si4
448.9
Monoclinic
P21/n
C36H45Co2O3PSi3
758.8
Triclinic
P1
Unit cell dimensions
˚
a (A)
10.365(2)
11.209(2)
17.097(2)
80.34(2)
86.44(2)
87.71(2)
1953.5(6)
2
1.2908
0.71073
1.014
4.0–50.0
2q/q
26.833(2)
11.694(1)
25.343(3)
12.206(2)
11.053(2)
20.950(2)
˚
b (A)
˚
c (A)
h (°)
i (°)
117.82(1)
102.69
k (°)
3
˚
V (A )
7033.1(16)
8
2757.4(7)
4
Z
Dcalc. (Mg m−3
)
1.282
0.71073
1.112
4.0–48.0
2q/q
1.081
0.71073
0.230
4.0–48.0
2q/q
˚
u(Mo–Ka) (A)
v (mm−1
)
Range (°)
Scan type
No. of reflections collected
No. of independent reflections
No. of observed reflections
No. of refined parameters
aRf for significant reflections
bRw for significant reflections
cGoF
7228
11256
10968
6613
4527
4303
3329
253
0.0423
0.0590
1.36
6820(Rint=1.91%)
5260(F\4.0|(F))
406
0.0369
0.0497
680
0.0501
0.0569
1.12
1.12
a Rf=[S(Fo−Fc)/SFo].
b Rw=Sw1/2(Fo−Fc)/Sw1/2Fo.
c GoF=[Sw(Fo−Fc)2/(Nrflns−Nparams)]1/2. w−1=|2(F)+0.0010F2.
singlet peaks, 5.47 and 0.32 ppm, were observed for this
compound in the H-NMR.
the cell. The molecule of (4) exhibits a pseudo-C2
symmetry. The substituents, –SiMe3, on the cyclopen-
tadienone are pointing away from each other thus
preventing steric hindrance. The triphenylphosphine lig-
and is absent here. Each cyclopentadienone ligand is
p-bonded to cobalt and donates four electrons in elec-
tron counting. Each cobalt center; therefore, is six
coordinated and thus obeys the EAN rule. The bond
1
Substituted cyclopentadienones tend to be dimerized
through the Diels–Alder type reaction. Therefore, to
find a practical reaction route to generate and stabilize
cyclopentadienones through the transition metal-medi-
ated cyclization of two alkynes with one carbon
monoxide is of interest to many people [7,11]. Com-
pound (4) constitutes useful monomeric cyclopenta-
dienone synthon [12].
The crystal structure of (4) has revealed that two
cyclopentadienone ligands are on the same side of
metal–metal bond, in contrast to previous beliefs. As
we know, the shape of a molecule in the solid state does
not actually reflect what it has to be in solution. One
might expect that (4) exhibits fluxional behavior in
solution under elevated temperature as does the struc-
tural related compound [CpFe(CO)2]2. The fluxional
˚
length between two cobalts is 2.542 A, which is slightly
longer than that of (2a). The double bonds, with an
˚
average length of 1.40 A, of the cyclopentadienone
ligands are longer than normal one, which is a common
observation for a p-bonding olefin. Two bridging car-
bonyls are found to coordinate to both cobalts about
the same distance. 1H- and 13C-NMR of (4) exhibit
simple patterns due to its symmetrical nature. Only two
Fig. 2. The symmetrical arrangement of atoms within the Co(1), C(1),
C(2), C(6) segment of the molecule.
Scheme 3.

102
F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
Table 2
spectra. It indicates that there is no fluxional for (4)
under our investigated temperature range, which is
quite different from the case of [CpFe(CO)2]2 (Scheme
4).
˚
Selected bond lengths (A) and bond angles (°) for (2a)
Bond distances
Co(1)–Co(2)
Co(1)–C(35)
Co(1)–C(2)
Co(1)–C(6)
Co(2)–C(36)
Co(2)–C(4)
Co(2)–C(6)
P–C(22)
Si(1)–C(1)
Si(1)–C(8)
Si(2)–C(4)
Si(2)–C(11)
Si(3)–C(6)
Si(3)–C(14)
C(34)–O(34)
C(36)–O(36)
C(2)–C(3)
2.471(1)
1.766(3)
2.069(3)
2.010(3)
1.779(4)
2.116(3)
2.017(3)
1.838(3)
1.876(3)
1.871(4)
1.885(3)
1.842(4)
1.876(3)
1.862(4)
1.135(4)
1.136(5)
1.418(4)
1.406(4)
Co(1)–P
2.202(1)
1.975(3)
2.086(3)
1.766(3)
2.025(3)
2.044(3)
1.828(3)
1.842(3)
1.865(5)
1.868(3)
1.874(5)
1.866(4)
1.864(5)
1.869(5)
1.146(4)
1.409(4)
1.506(4)
1.416(4)
Co(1)–C(1)
Co(1)–C(3)
Co(2)–C(34)
Co(2)–C(1)
Co(2)–C(5)
P–C(16)
The preparation of 2,5-bis(trimethylsilanyl)cyclo-
penta-2,4-dien-1-one (5) (Table 4) had been reported.
The compound was the organic products following the
oxidation of (h4-cyclopentadienone)(h5-C5H5)Co which
is the result of the catalytic reaction of trimethylsily-
acetylene with (h5-C5H5)Co(CO)2 [14]. In our case, it
was obtained from the degradation of (4) by exposing it
to air in solution. The conversion is quantitatively. The
crystal structure of (5) was determined. Two –SiMe3
groups are adjacent in (5). Nevertheless, no strong
repulsion is observed. The formation of (5) is believed
to take place via the Diels–Alder type of cyclization of
the two released cyclopentadienone ligands from (4)
(Scheme 5, Fig. 4).
P–C(28)
Si(1)–C(7)
Si(1)–C(9)
Si(2)–C(10)
Si(2)–C(12)
Si(3)–C(13)
Si(3)–C(15)
C(35)–O(35)
C(1)–C(2)
C(3)–C(4)
C(5)–C(6)
C(4)–C(5)
With respect to the so called ‘flyover-bridged’ com-
plexes, crystal structures of several closely related com-
pounds had been reported [6]. The arrangement of the
substituents on the flyover bridge ligand are at 1,3,6
carbon atoms while HCꢁCCMe3 or HCꢁCCF3 were
used as alkyne sources. In contrast, it was a head-to-tail
trimerization of the alkyne while PhCꢁCC(O)CH3 was
used. Steric effect may play an important role here. It is
obvious that the former arrangement prevailed while
the bulky substituent was used. Since the –SiMe3
groups are rather bulky, (2a) can be proved. The prepa-
ration of a closely related heterobimetallic compound,
MoCo(CO)4{m-CPhꢀCH–CHꢀCPh–CHꢀCPh–}(h5-C5
H5) (6), was reported without crystal structure [5c].
Unobservable coupling among the three protons of the
flyover bridge ligand in the 1H-NMR indicates that
there are no vincinal HC–CH protons in (6). It indi-
cates that the phenyl ring is not regarded as a very
bulky group and each of the three –Ph groups are
attached to 1,3,6 carbon atoms. In this way, the steric
Bond angles
Co(2)–Co(1)–P
P–Co(1)–C(35)
P–Co(1)–C(1)
Co(2)–Co(1)–C(2)
C(35)–Co(1)–C(2)
Co(2)–Co(1)–C(3)
C(35)–Co(1)–C(3)
C(2)–Co(1)–C(3)
P–Co(1)–C(6)
152.8(1)
97.1(1)
143.3(1)
76.5(1)
122.0(1)
73.3(1)
161.8(1)
39.9(1)
105.5(1)
105.0(1)
86.2(1)
Co(2)–Co(1)–C(35) 104.2(1)
Co(2)–Co(1)–C(1)
C(35)–Co(1)–C(1)
P–Co(1)–C(2)
C(1)–Co(1)–C(2)
P–Co(1)–C(3)
C(1)–Co(1)–C(3)
Co(2)–Co(1)–C(6)
C(35)–Co(1)–C(6)
C(2)–Co(1)–C(6)
52.8(1)
93.0(1)
106.3(1)
40.7(1)
91.4(1)
71.0(1)
52.3(1)
106.7(1)
116.3(1)
C(1)–Co(1)–C(6)
C(3)–Co(1)–C(6)
Co(1)–Co(2)–C(36) 104.7(1)
Co(1)–Co(2)–C(34) 145.4(1)
C(34)–Co(2)–C(36)
C(34)–Co(2)–C(1)
Co(1)–Co(2)–C(4)
C(36)–Co(2)–C(4)
Co(1)–Co(2)–C(5)
C(36)–Co(2)–C(5)
C(4)–Co(2)–C(5)
C(34)–Co(2)–C(6)
C(1)–Co(2)–C(6)
C(5)–Co(2)–C(6)
Co(1)–P–C(22)
95.9(2)
96.7(1)
74.7(1)
160.8(1)
76.7(1)
121.4(1)
39.5(1)
154.7(1)
102.9(1)
40.8(1)
118.4(1)
121.3(1)
101.3(1)
73.3(2)
66.0(2)
113.1(3)
101.1(2)
96.8(2)
116.6(2)
68.6(2)
75.7(1)
70.6(2)
Co(1)–Co(2)–C(1)
C(36)–Co(2)–C(1)
C(34)–Co(2)–C(4)
C(1)–Co(2)–C(4)
C(34)–Co(2)–C(5)
C(1)–Co(2)–C(5)
Co(1)–Co(2)–C(6)
C(36)–Co(2)–C(6)
C(4)–Co(2)–C(6)
Co(1)–P–C(16)
50.9(1)
107.3(1)
94.5(1)
87.4(1)
115.6(1)
115.7(1)
52.0(1)
93.4(1)
70.9(1)
107.7(1)
102.2(1)
103.6(2)
76.3(1)
109.6(2)
70.7(2)
69.4(2)
120.1(3)
67.5(2)
73.0(2)
116.3(3)
109.6(2)
C(16)–P–C(22)
C(16)–P–C(28)
Co(1)–P–C(28)
C(22)–P–C(28)
Co(1)–C(1)–Co(2)
Co(2)–C(1)–C(2)
Co(1)–C(2)–C(3)
Co(1)–C(3)–C(2)
C(2)–C(3)–C(4)
Co(2)–C(4)–C(5)
Co(2)–C(5)–C(4)
C(4)–C(5)–C(6)
Co(1)–C(6)–C(5)
Co(1)–C(1)–C(2)
Co(1)–C(2)–C(1)
C(1)–C(2)–C(3)
Co(1)–C(3)–C(4)
Co(2)–C(4)–C(3)
C(3)–C(4)–C(5)
Co(2)–C(5)–C(6)
Co(1)–C(6)–Co(2)
Co(2)–C(6)–C(5)
manner of [CpFe(CO)2]2 in solution was frozen at
−31°C [13].
A variable-temperature 1H-NMR experiment was
carried out for (4) in THF-d8. The experiment was
conducted in the range of −100 to 40°C. Each mea-
surement was taken at increments of 10°C. There was
no significant change judged by the appearance of the
Fig. 3. ORTEP drawing with the numbering scheme of (4). Hydrogen
atoms were omitted for clarity.

F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
103
Scheme 4.
hindrance between phenyl rings can be reduced to a
minimum.
and the whole bonding strengthened while the strong
electron-withdrawing substituents are present in the
ligand. The –CF3 is a strong electron-withdrawing sub-
stituent and is regarded as an important factor in
stabilizing the flyover bridge structure of Co2(CO)4{m-
C(CF3)ꢀCH–CHꢀC(CF3)–CHꢀC(CF3)}. However, in
the case of (2a) the –SiMe3 is not an electron-with-
drawing substituent at all. However, the flyover bridged
structure of (2a) is stable. One might argue that the
presence of the triphenylphosphine ligand provides the
necessary electron density which flows to the metal
centers thus enhancing the backbonding as a result.
In summary, the preparation and crystal structure
determination of (2a), another example of a dimetallic
frame containing a ‘flyover bridge’ ligand, was re-
ported. In complex (4), substituted cyclopentadienone
was formed by the metal-mediated coupling of two
alkynes and one carbon monoxide, and it can be seen
as a monomeric cyclopentadienone synthon.
The reaction of [MoCo(CO)6(PPh3)(h5-C5H5)] (7)
[15] with an excess of trimethylsilylacetylene in THF at
60°C yielded two heterobinuclear complexes containing
flyover bridge ligands, CpMoCo(CO)3{m- C(SiMe3)ꢀ
CH–CHꢀC(SiMe3)–CHꢀC(SiMe3)} (8a), and (8b). The
compound (8b) was presumably an isomer of (8a)
(Scheme 6).
Interestingly, a small amount of (1b) was also ob-
served. It was believed that the Mo–Co bond of (6) was
broken down and two cobalt fragments were joined
together to pick up one acetylene and form the bridged
structure [16]. The isomers of (8a) and (8b) had very
close Rf values. It was rather difficult to thoroughly
separate them from CTLC. However, we were managed
to get a small amount of reasonably pure (8a) from the
3. Experimental
3.1. Apparatus and materials
All preparations were performed in a nitrogen-
flushed glove box or in a vacuum system. Freshly
distilled solvents were used. All processes of separation
of the products were performed by Centrifugal Thin-
Layer Chromatography (TLC, Chromatotron, Har-
rison model 8924). 1H-, 31P- and 13C-NMR spectra were
recorded (Varian-VXR-300S spectrometer) at 300.00,
121.44 and 75.46 MHz, respectively; chemical shifts are
reported in ppm relative to internal TMS. 1H-NMR
spectra of variable temperature experiments were
recorded by the same machine. IR spectra of solution
in CH2Cl2 were recorded on a Hitachi 270-30 spectrom-
eter. Mass spectra were recorded on JOEL JMS-SX/SX
102A GC/MS/MS spectrometer. Elementary analysis
was recorded on a Heraeus CHN-O-S-Rapid.
1
front part of mixed band. H-, 13C-NMR and mass of
1
(8a) had been recorded. The H-NMR pattern of the
flyover bridge ligand of (8a) is similar to that of (2a).
This indicates that the arrangement of the substituents
on the flyover bridge ligand are at 1,3,6 carbon atoms
as in the case of (2a). The only triphenylphosphine
ligand came off from the metal center during the reac-
1
tion. The corresponding peaks of PPh3 in the H-NMR
were absent. This was also confirmed by the 13C-NMR.
Unfortunately, the attempt to grow crystals from (8a)
resulted in failure. Further characterization of (8a) was
not carried out due to the instability and small quantity
obtained from this compound. 1,2,4-Tris-trimethysi-
lanylbenzene had been obtained again from the degra-
dation of compound (8a). This was also a confirmation
1
3.1.1. Preparation of (1a)
of the observed H-NMR of (8a).
Into a 100 cm3 flask was placed Co2(CO)8 (400 mg,
1.17 mmol) and trimethylsilylacetylene (0.25 ml, 1.75
mmol) with 30 cm3 of THF. The solution was stirred
under 30°C during the following 3 h.
To stabilize the flyover bridge structure, the impor-
tance of the electronegative substituent is emphasized
[9]. It was believed that the backbonding from the
metal centers to the bridged ligand would be enhanced

104
F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
Table 3
˚
Selected bond lengths (A) and bond angles (°) for (4)
Bond lengths
Co(1)–Co(2)
Co(1)–C(2)
Co(1)–C(4)
Co(1)–C(12)
Co(1)–C(33)
Co(2)–C(21)
Co(2)–C(23)
Co(2)–C(25)
Co(2)–C(33)
Si(1)–C(6)
2.542(1) Co(1)–C(1)
2.074(7) Co(1)–C(3)
2.390(5) Co(1)–C(5)
1.809(9) Co(1)–C(13)
1.932(6) Co(2)–C(13)
2.062(8) Co(2)–C(22)
2.181(7) Co(2)–C(24)
2.166(6) Co(2)–C(32)
1.927(6) Si(1)–C(3)
1.849(9) Si(1)–C(7)
1.835(12) Si(2)–C(5)
2.074(7)
2.165(5)
2.179(6)
1.902(6)
1.916(6)
2.060(8)
2.398(5)
1.792(9)
1.869(6)
1.842(7)
1.881(6)
Scheme 5.
Subsequently, the resulting dark red solution was
filtered through a silica gel column. A dark red band
was collected and was identified as (1a). The yield was
94% (424 mg, 1.10 mmol).
Si(1)–C(8)
Si(2)–C(9)
Si(2)–C(11)
Si(3)–C(26)
Si(3)–C(28)
1.845(7) Si(2)–C(10)
1.859(7) Si(3)–C(23)
1.849(9) Si(3)–C(27)
1.773(15) Si(4)–C(25)
1.837(11)
1.870(7)
1.852(10)
1.860(6)
3.1.2. Characterization of (1b)
1H-NMR (CDCl3, l/ppm): 0.29 (s, 9H, –SiMe3),
6.37 (s, 1H, CH); 13C-NMR (CDCl3, l/ppm): 0.80 (s,
3C, –SiMe3), 85.27 (s, 1C, ꢁCH), 77.44 (s, 1C, ꢁC–
SiMe3), 200.49 (Co–CO’s); IR (CH2Cl2): w(CO) 2063(s),
2005(b) cm−1; MS m/z 384 (P+).
Si(4)–C(29)
Si(4)–C(31)
O(2)–C(12)
1.822(7) Si(4)–C(30)
1.852(9) O(1)–C(4)
1.124(11) O(3)–C(13)
1.824(13)
1.223(7)
1.159(8)
O(4)–C(24)
O(6)–C(33)
C(1)–C(5)
C(3)–C(4)
C(21)–C(22)
1.220(7) O(5)–C(32)
1.152(8) C(1)–C(2)
1.395(9) C(2)–C(3)
1.491(8) C(4)–C(5)
1.396(11) C(21)–C(25)
1.132(12)
1.446(8)
1.400(10)
1.510(8)
1.426(10)
3.1.3. Preparation of (1b)
Into a 100 cm3 flask was placed Co2(CO)8 (200 mg,
0.58 mmol), triphenylphosphine (153 mg, 0.58 mmol)
and trimethylsilylacetylene (0.13 ml, 0.88 mmol) with
30 cm3 of THF. The solution was stirred at 55°C during
the following 5 h.
C(22)–C(23)
1.405(10) C(23)–C(24)
1.504(9)
1.500(9)
C(24)–C(25)
Subsequently, the resulting dark red solution was
filtered through a small amount of silica gel. The filtrate
was evaporated under reduced pressure to yield the
crude product. Purification with centrifugal thin-layer
chromatography (eluent:hexane/CH2Cl2), a dark red
band was collected and was identified as (1b). The yield
was 40% (138 mg, 0.22 mmol).
Bond angles
Co(2)–Co(1)–C(1) 106.8(1)
Co(2)–Co(1)–C(2) 107.0(2)
Co(2)–Co(1)–C(3) 135.8(2)
C(1)–Co(1)–C(2)
C(1)–Co(1)–C(3)
Co(2)–Co(1)–C(4) 168.1(2)
C(2)–Co(1)–C(4) 62.0(2)
Co(2)–Co(1)–C(5) 135.3(2)
C(2)–Co(1)–C(5)
C(4)–Co(1)–C(5)
C(1)–Co(1)–C(12)
C(3)–Co(1)–C(12)
C(5)–Co(1)–C(12)
C(1)–Co(1)–C(13)
C(3)–Co(1)–C(13)
C(5)–Co(1)–C(13)
40.8(2)
66.6(2)
C(2)–Co(1)–C(3)
C(1)–Co(1)–C(4)
C(3)–Co(1)–C(4)
C(1)–Co(1)–C(5)
C(3)–Co(1)–C(5)
38.5(3)
62.2(2)
37.8(2)
38.2(2)
66.9(2)
66.2(2)
38.2(2)
137.7(3)
99.4(3)
99.6(3)
124.2(3)
97.2(2)
159.1(3)
Co(2)–Co(1)–C(12) 109.7(2)
C(2)–Co(1)–C(12)
C(4)–Co(1)–C(12)
137.9(2)
82.1(3)
Co(2)–Co(1)–C(13) 48.5(2)
C(2)–Co(1)–C(13)
C(4)–Co(1)–C(13)
C(12)–Co(1)–C(13)
C(1)–Co(1)–C(33)
C(3)–Co(1)–C(33)
C(5)–Co(1)–C(33)
C(13)–Co(1)–C(33)
C(3)–Si(1)–C(7)
C(3)–Si(1)–C(8)
C(7)–Si(1)–C(8)
C(1)–C(2)–C(3)
92.9(3)
132.4(2)
96.2(3)
94.2(3)
160.7(3)
97.5(2)
Co(2)–Co(1)–C(33) 48.7(2)
C(2)–Co(1)–C(33)
C(4)–Co(1)–C(33)
C(12)–Co(1)–C(33)
C(3)–Si(1)–C(6)
C(6)–Si(1)–C(7)
C(6)–Si(1)–C(8)
C(2)–C(1)–C(5)
Co(1)–C(3)–Si(1)
O(1)–C(4)–C(5)
C(1)–C(5)–C(4)
126.0(3)
132.7(2)
94.1(3)
109.6(3)
110.0(4)
109.3(5)
109.9(5)
130.9(4)
126.2(5)
106.1(5)
94.9(3)
106.7(3)
110.9(4)
110.3(4)
109.8(5)
127.9(5)
105.8(5)
O(1)–C(4)–C(3)
C(3)–C(4)–C(5)
Co(1)–C(12)–O(2) 178.4(5)
Co(1)–C(13)–O(3) 138.6(4)
Co(2)–C(32)–O(5) 177.2(6)
Co(1)–C(33)–O(6) 138.8(4)
Co(1)–C(13)–Co(2) 83.5(3)
Co(2)–C(13)–O(3) 137.9(4)
Co(1)–C(33)–Co(2) 82.4(3)
C(13)–Co(2)–C(33)
94.6(2)
Fig. 4. ORTEP drawing with the numbering scheme of (5). Hydrogen
atoms were omitted for clarity.

F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
105
Scheme 6.
3.1.4. Characterization of (1b)
3.1.7. Preparation of (4)
1H-NMR (CDCl3, l/ppm): 0.06 (s, 9H, –SiMe3),
5.52 (d, 1H, JPH=6.6 Hz), 7.38ꢀ7.49 (m, 15H, PPh3);
13C-NMR (CDCl3, l/ppm): 1.52 (3C, Me3Si–), 134.96
(d, JPC=40 Hz), 132.84 (d, JPC=11 Hz), 129.85 (d,
Into a 100 cm3 flask was placed (1a) (491 mg, 1.28
mmol) and trimethylsilylacetylene (0.90 ml, 6.39 mmol)
with 30 cm3 of THF. The solution was stirred at 40°C
during the following 15 h.
J
PC=1 Hz), 128.16 (d, JPC=10 Hz), 86.00, 72.67 (2C),
Subsequently, the resulting orange solution was
filtered through a small amount of silica gel. The filtrate
was evaporated under reduced pressure to yield the
crude product. Purification with centrifugal thin-layer
chromatography (eluent:hexane/CH2Cl2), a dark red
and an orange–red band were collected. The first band
was characterized as unreacted (1a) and the second
band was identified as (4). The yield of (4) was 25%
(220 mg, 0.324 mmol).
201.38, 205.82 (3C, Co–CO’s); IR (CH2Cl2): w(CO)
2058(s), 2000(s), 1955(sh) cm−1; MS m/z 643 (P+).
3.1.5. Preparation of (2a)
Into a 100 cm3 flask was placed (1b) (138 mg, 0.22
mmol) and trimethylsilylacetylene (1.46 mmol) with 30
cm3 of THF. The solution was stirred at 65°C during
the following 17 h.
Subsequently, the resulting orange solution was
filtered through a small amount of silica gel. The filtrate
was evaporated under reduced pressure to yield the
crude product. Purification with centrifugal thin-layer
chromatography (eluent:hexane/CH2Cl2), a purple band
was collected and was identified as (2a). The yield was
35% (59 mg, 0.077 mmol).
3.1.8. Characterization of (4)
1H-NMR (CDCl3, l/ppm): 0.32 (s, 36H, SiMe3), 5.47
1
(s, 4H, CH); H-NMR (THF-d8, l/ppm): 0.31 (s, 36H,
SiMe3), 5.93 (s, 4H, CH); 13C-NMR (d-THF, l/ppm):
−0.77 (12C, SiMe3), 90.00 (4C, C(SiMe3)), 103.22 (4C,
CH), 185.06 (2C, CO), 200.70 (2C, CO), 239.18 (2C,
CO); IR (CH2Cl2): w(CO)2068, 1842, 1629 cm−1; MS
m/z 678.8 (P+); Anal. Calc. for (4): C, 45.96; H, 5.89.
Found: C, 49.52; H, 6.24.
3.1.6. Characterization of (2a)
1H-NMR (CDCl3, l/ppm): 0.07 (s, 9H, –SiMe3),
0.21 (s, 9H, –SiMe3), 0.32 (s, 9H, –SiMe3), 3.58 (dd,
1H, JHH=17, 3 Hz), 4.66 (b, 1H), 6.08 (b, 1H), 7.2ꢀ
7.4 (m, 15H, PPh3); 13C-NMR (CDCl3, l/ppm): −
1.64, 0.66, 1.79 (9C, –SiMe3), 83.82, 97.88, 122.33,
127.63, 127.95 (6C, PPh3, d, JPC=9.4 Hz), 129.81 (3C,
PPh3), 133.49 (6C, PPh3, d, JPC=10.0 Hz), 134.63 (3C,
PPh3, d, JPC=39.6 Hz), 204.24, 203.89, 214.43 (3C,
3CO); 31P-NMR (CDCl3, l/ppm): l 53.3 (b, 1P); IR
(CH2Cl2): w(CO) 2010.3, 1962.5 cm−1; MS m/z 758 (P+);
Anal. Calc. for (2a): C, 56.98; H, 5.98. Found: C, 57.00;
H, 6.03.
3.1.9. Characterization of (5)
1H-NMR (THF-d8, l/ppm): 0.07 (m, 9H, –SiMe3),
0.11 (m, 9H, SiMe3), 0.20 (m, 9H, SiMe3), 0.26 (m, 9H,
SiMe3), 3.31 (d, 1H, CH, JHH=2.4 Hz), 5.99 (d, 1H,
CH, JHH=6.4 Hz), 6.20 (d, 1H, CH, JHH=6.4 Hz),
7.40(d, 1H, CH, JHH=2.4 Hz); 13C-NMR (THF-d8,
l/ppm): −2.31 (3C, SiMe3), −1.29 (3C, SiMe3), −
0.83 (3C, SiMe3), 0.05 (3C, SiMe3), 51.00 (1C,
C(SiMe3)), 53.77 (1C, C(SiMe3)), 55.12 (1C, C(SiMe3)),
72.01 (1C, CH), 130.73 (1C, CH), 137.90 (1C, CH),
156.30 (1C, C(SiMe3)), 167.52 (1C, CH), 206.00 (1C,

106
F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
Table 4
filtered through a small amount of silica gel. The filtrate
was evaporated under reduced pressure to yield the
crude product. Purification with centrifugal thin-layer
chromatography (eluent:hexane), firstly an orange band
of mixed (8a) and (8b) was obtained which was then
followed by a reddish brown band of (1b). Further
purification of (8a) from mixture was again carried out
by CTLC, with thinner silica coating plates and slower
solvent flow speed. The front part of the band was
collected.
˚
Selected bond lengths (A) and bond angles (°) for (5)
Bond lengths
O(1)–C(1)
Si(1)–C(5)
Si(1)–C(12)
Si(2)–C(2)
Si(2)–C(15)
Si(3)–C(9)
Si(3)–C(18)
Si(4)–C(6)
Si(4)–C(21)
C(1)–C(2)
C(2)–C(3)
C(4)–C(5)
C(5)–C(6)
C(6)–C(10)
C(8)–C(9)
1.220(3) O(2)–C(10)
1.914(3) Si(1)–C(11)
1.850(3) Si(1)–C(13)
1.878(3) Si(2)–C(14)
1.861(4) Si(2)–C(16)
1.887(2) Si(3)–C(17)
1.856(4) Si(3)–C(19)
1.902(2) Si(4)–C(20)
1.860(3) Si(4)–C(22)
1.487(3) C(1)–C(5)
1.322(3) C(3)–C(4)
1.572(3) C(4)–C(9)
1.601(4) C(6)–C(7)
1.549(3) C(7)–C(8)
1.518(4) C(9)–C(10)
1.199(3)
1.867(4)
1.870(3)
1.862(3)
1.851(4)
1.863(4)
1.857(4)
1.862(3)
1.864(4)
1.535(3)
1.499(3)
1.582(4)
1.527(4)
1.321(3)
1.550(3)
3.1.11. Characterization of (8a)
1H-NMR(CDCl3, l/ppm): l 0.07, 0.29, 0.35 (s, 18H,
Me3Si–), 4.85 (s, 5H, Cp), 4.34 (d, 1H, JHH=3.3 Hz),
5.13 (d, 1H, JHH=0.6 Hz), 6.14 (dd, 1H, JHH=3.3, 0.6
Hz); 13C-NMR (CDCl3, l/ppm): 0.19, 1.73, 2.36 (9C,
Me3Si–), 86.60 (5C, Cp), 118.95, 106.12, 87.82, 80.18,
77.21, 61.74 (6C), 184.63 (2C, Co–CO’s), 224.64 (1C,
Mo–CO’s); MS m/z 600 (P+ =M+2).
Bond lengths
C(5)–Si(1)–C(11)
C(11)–Si(1)–C(12) 106.2(1)
C(11)–Si(1)–C(13) 108.7(2)
106.6(1)
C(5)–Si(1)–C(11)
C(5)–Si(1)–C(13)
113.2(1)
110.0(1)
C(12)–Si(1)–C(13) 111.8(1)
C(2)–Si(2)–C(14)
C(14)–Si(2)–C(15) 109.4(2)
C(14)–Si(2)–C(16) 111.2(1)
C(9)–Si(3)–C(17)
C(17)–Si(3)–C(18) 109.8(2)
C(17)–Si(3)–C(19) 107.4(2)
C(6)–Si(4)–C(20)
C(20)–Si(4)–C(21) 111.7(1)
C(20)–Si(4)–C(22) 108.3(2)
O(1)–C(1)–C(2)
C(2)–C(1)–C(5)
Si(2)–C(2)–C(3)
C(2)–C(3)–C(4)
C(3)–C(4)–C(9)
Si(1)–C(5)–C(1)
C(1)–C(5)–C(4)
C(1)–C(5)–C(6)
Si(4)–C(6)–C(5)
C(5)–C(6)–C(7)
C(5)–C(6)–C(10)
C(6)–C(7)–C(8)
Si(3)–C(9)–C(4)
C(4)–C(9)–C(8)
C(4)–C(9)–C(10)
O(2)–C(10)–C(6)
C(6)–C(10)–C(9)
108.0(1)
C(2)–Si(2)–C(15)
C(2)–Si(2)–C(16)
C(15)–Si(2)–C(16) 111.3(2)
C(9)–Si(3)–C(18)
C(9)–Si(3)–C(19)
C(18)–Si(3)–C(19) 111.4(2)
C(6)–Si(4)–C(21)
C(6)–Si(4)–C(22)
C(21)–Si(4)–C(22) 106.5(2)
O(1)–C(1)–C(5)
Si(2)–C(2)–C(1)
C(1)–C(2)–C(3)
C(3)–C(4)–C(5)
C(5)–C(4)–C(9)
Si(1)–C(5)–C(4)
Si(1)–C(5)–C(6)
C(4)–C(5)–C(6)
Si(4)–C(6)–C(7)
Si(4)–C(6)–C(10)
C(7)–C(6)–C(10)
C(7)–C(8)–C(9)
Si(3)–C(9)–C(8)
Si(3)–C(9)–C(10)
C(8)–C(9)–C(10)
O(2)–C(10)–C(9)
107.9(1)
108.8(1)
3.1.12. Characterization of 1,2,4-tris-trimethysilanylben-
zene
1H-NMR(CDCl3): l 0.06(s, 9H, Me3Si–), 0.26 (s,
9H, Me3Si–), 0.37 (s, 9H, Me3Si–), 7.84 (s, 1H), 7.66
(d, 1H, JHH=7.4 Hz), 7.49 (d, 1H, JHH=7.4 Hz).
109.1(1)
109.2(1)
110.0(1)
110.6(1)
114.2(1)
105.2(1)
4. X-ray crystallographic studies
125.6(2)
109.7(2)
127.6(2)
115.6(2)
115.3(2)
107.2(2)
102.6(2)
111.8(2)
127.0(2)
104.5(2)
98.1(2)
110.8(2)
116.2(2)
105.8(2)
96.9(2)
130.0(2)
100.3(2)
124.8(2)
124.6(2)
107.8(2)
103.8(2)
106.0(2)
109.7(2)
120.7(2)
103.4(2)
112.6(2)
114.6(2)
94.6(2)
Suitable crystals of (2a), (4) and (5) were sealed in
thin-walled glass capillaries under nitrogen atmosphere
and mounted on a Siemens P4 diffractometer. The
crystallographic data were collected using a q–2q scan
mode with Mo–Ka radiation. The space group determi-
nation was based on a check of the Laue symmetry and
systematic absences, and was confirmed by the struc-
ture solution. The structure was solved by direct meth-
ods using Siemens SHELXTL PLUS package [17]. All
non-H atoms were located from successive Fourier
maps. Anisotropic thermal parameters were used for all
non-H atoms and fixed isotropic for H atoms that were
refined using riding model [18]. Crystallographic data
of (2a), (4) and (5) are summarized in Table 1.
109.9(2)
119.8(2)
119.0(2)
95.1(2)
129.7(2)
5. Supplementary material available
CO), 212.22 (1C, CO); MS m/z 448.9 (P+); Anal. Calc.
for (5): C, 58.89; H, 8.95. Found: C, 58.72; H, 8.98.
Atomic coordinates of (2a), (4) and (5), tables of
thermal parameters, bond lengths and angles, an-
isotropic thermal parameters, and H atom coordinates
have been deposited as supplementary material.
3.1.10. Preparation of (8a)
The synthesis of [MoCo(CO)6(PPh3)(h5-C5H5)] (7)
was done according to a procedure in the literature [16].
Into a 50 cm3 flask was placed (7) (429 mg, 0.67
mmol) and trimethylsilylacetylene (1 ml, 7.08 mmol)
with 30 cm3 of THF. The solution was stirred at 60°C
during the following 15 h.
Acknowledgements
We thank the National Research Council of the
ROC (Grant NSC-88-2113-M-005-022) for support.
Subsequently, the resulting orange solution was

F.-E. Hong et al. / Journal of Organometallic Chemistry 580 (1999) 98–107
107
p. 44. (c) M.J. Chetcuti, P.E. Fanwick, J.C. Gordon, Inorg.
Chem. 30 (1991) 4710.
References
[6] (a) G. Gervasio, E. Sappa, L. Marko´, J. Organomet. Chem. 444
(1993) 203. (b) O.S. Mills, G. Robinson, Proc. Chem. Soc. (1964)
187. (c) F.S. Stephens, Acta Crystallogr. Sect. A: Cryst. Phys.
Diffr. Theor. Gen. Crystallogr. 154 (1966) 21A.
[7] (a) M.A. Ogliaruso, M.G. Romanelli, E.J. Becker, Chem. Rev.
65 (1965) 261. (b) W. Hu¨bel, in: I. Wender, P. Pino (Eds.),
Organic Syntheses via Metal Carbonyls, vol. 1, Wiley, New
York, 1968, p. 273; P. Pino, G. Braca, in vol. 2, 1977, p. 419.
[8] (a) W. Hu¨bel, C. Ho¨gzand, Chem. Ber. 93 (1960) 103. (b) U.
Kru¨erke, W. Hu¨bel, Chem. Ber. 94 (1961) 2829.
[9] R.S. Dickson, P.J. Fraser, B.M. Gatehouse, J. Chem. Soc.
Dalton Trans. (1972) 2278.
[10] (a) G. Winkhaus, G. Wilkinson, J. Chem. Soc. (1961) 602. (b) P.
McArdle, A.R. Manning, J. Chem. Soc. A (1970) 2123.
[11] E.R.F. Gesing, J.P. Tane, K.P.C. Vollhardt, Angew. Chem. Int.
Ed. Engl. 19 (1980) 1023.
[12] (a) J.H. Bieri, A.S. Dreiding, T.C.C. Gartenmann, E.R.F.
Gesing, R.W. Kunz, R. Prewo, J. Organomet. Chem. 306 (1986)
241. (b) H.-J. Knolker, J. Heber, C.H. Mahler, Synlett (1992)
1002. (c) R. Boese, D. Blaser, R.L. Halterman, K.P.C. Vollhardt,
Angew. Chem. Int. Ed. Engl. 27 (1988) 553.
[13] F.A. Cotton, L. Kruczynski, A.J. White, Inorg. Chem. 13 (1974)
1402.
[14] E.R.F. Gesing, J.P. Tane, K.P.C. Vollhardt, Angew. Chem. Int.
Ed. Engl. 19 (1980) 1023.
[1] (a) S.G. Davies, Organotransition Metal Chemistry Applications
to Organic Synthesis, vol. 2, Pergamon, Oxford, 1982, p. 32 and
references therein. (b) G.W. Parshall, S.D. Ittel, Homogeneous
Catalysis, 2nd ed., Wiley, New York, 1992, Ch. 8. (c) K.P.C.
Vollhardt, Acc. Chem. Res. 10 (1977) 1. (d) B. Cornils, W.A.
Herrmann (Eds.), Applied Homogeneous Catalysis with
Organometallic Compounds, vol. 1, 2, VCH, New York, 1996.
[2] (a) J.L. Templeton, in: F.G.A. Stone, R. West (Eds.), Advances
in Organometallic Chemistry, vol. 29, Academic Press, New
York, 1989, p. 1. (b) C.M. Lukehart, Fundamental Transition
Metal Organometallic Chemistry, Brools/Cole Publishing Com-
pany, Monterey, CA, 1985. (c) D.M. Hoffmann, R. Hoffmann,
C.R. Fisel, J. Am. Chem. Soc. 104 (1982) 3858. (d) S.D. Jensen,
B.H. Robinson, J. Simpson, Organometallics 5 (1986) 1690. (e)
M. Gruselle, M.A. Kondratenko, H. El Amouri, J. Vaissermann,
Organometallics 14 (1995) 5242. (f) T.M. Wido, G.H. Young, A.
Wojcicki, Organometallics 7 (1988) 452. (g) W. Beck, Polyhe-
dron 7 (1988) 2253. (h) W. Beck, H.-J. Mu¨ller, U. Nagel, Angew.
Chem. Int. Ed. Engl. 25 (1986) 734. (i) H.-J. Mu¨ller, K. Polborn,
M. Steimann, W. Beck, Chem. Ber. 122 (1989) 1901. (j) F.-E.
Hong, C.-K. Hung, C.-C. Lin, J. Chin. Chem. Soc. 44 (1977) 43.
[3] (a) R.S. Dickson, Adv. Organomet. Chem. 12 (1974) 323. (b)
R.S. Dickson, G.R. Tailby, Aust. J. Chem. 23 (1971) 229. (c) U.
Kru¨erke, W. Hu¨bel, Chem. Ber. 94 (1961) 2829.
[15] I.-R. Lue, S.-C. Lo, C.-C. Lin, F.-E. Hong, Polyhedron 14
(1995) 1419.
[16] F.-E. Hong, I.-R. Lue, C.-C. Lin, J. Chin. Chem. Soc. 43 (1996)
483.
[4] (a) S.D. Chappell, D.J. Cole-Hamilton, Polyhedron 1 (1982) 739.
(b) D.L. Thorn, R. Hoffmann, Nouv. J. Chim. 3 (1979) 39.
[5] (a) R.D.W. Kemmitt, D.R. Russell, in: G. Wilkinson, F.G.A.
Stone, E.W. Abel (Eds.), Comprehensive Organometallic Chem-
istry, vol. 5, Pergamon, Oxford, 1982. (b) M.J. Chetcuti, in:
E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.), Comprehensive
Organometallic Chemistry II, vol. 10, Elsevier, New York, 1995,
[17] G.M. Sheldrick, SHELXTL PLUS User’s Manual. Revision 4.1
Nicolet XRD Corporation, Madison, Wisconsin, USA, 1991.
[18] Hydrogen atoms were ride on carbons or oxygens in their
˚
idealized positions and held fixed with C–H distances of 0.96 A.
.
.