Cooperative effects in π-ligand bridged dinuclear complexes XXII. New dinuclear bis(cyclopentadienediyl)ketone complexes containing molybdenum, tungsten, cobalt and iron

Article abstract of DOI:10.1016/S0022-328X(99)00171-0

Hydrolysis of the siloxyfulvene compounds {M}[η⁵-C₅H₄C(OTMS)(C₅Me ₄)] ({M}=Mo(CO)₃Me: 1a; {M}=W(CO)₃Me: 1b) affords {M}[η⁵-C₅H₄C(O)(C₅

Full text of DOI:10.1016/S0022-328X(99)00171-0

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Journal of Organometallic Chemistry 584 (1999) 329–337
Cooperative effects in p-ligand bridged dinuclear complexes XXII.
New dinuclear bis(cyclopentadienediyl)ketone complexes containing
molybdenum, tungsten, cobalt and ironꢀ,ꢀꢀ
Jan Ko¨rnich, Stephan Haubold, Jin He, Oliver Reimelt, Ju¨rgen Heck *
Institut fu¨r Angewandte und Anorganische Chemie, Uni6ersita¨t Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany
Received 16 February 1999
Abstract
Hydrolysis of the siloxyfulvene compounds {M}[h5-C5H4C(OTMS)(C5Me4)] ({M}=Mo(CO)3Me: 1a; {M}=W(CO)3Me: 1b)
affords {M}[h5-C5H4C(O)(C5Me4H)] ({M}=Mo(CO)3Me: 3a; {M}=W(CO)3Me: 3b) which are suitable precursors for the
synthesis of dinuclear complexes. The reactivity of the molybdenum and the tungsten compounds shows remarkable differences:
heating of 3a with Co2(CO)8 in the presence of 3,3-dimethylbut-1-ene reveals the heterodinuclear complex Me(CO)3Mo[(h5(Mo)–
C5H4)C(O)(h5(Co)–C5Me4)]Co(CO)2 (4a) along with the homodinuclear complex (CO)2Co[(h5-C5H4)C(O)(h5-C5Me4)]Co(CO)2
(5), the comparable reaction of 3b with Co2(CO)8 results in the formation of the heterodinuclear complex Me(CO)3W[(h5(W)–
C5H4)C(O)(h5(Co)–C5Me4)]Co(CO)2 (4b) only. The metal–metal bound complexes [(h5(M)–C5H4)C(O)(h5(M%)–
C5Me4)]MM%(CO)6 (M–M%) (M=W, M%=Mo: 8; M=M%=W: 9; M=M%=Mo: 10) are synthesized from the reaction of 3a or
3b with M%(CO)3(EtCN)3 (M%=Mo, W). When Mo(CO)6 is used in place of Mo(CO)3(EtCN)3 10 can also be obtained in addition
to [(h5-C5H3Me)C(O)(h5-C5Me4)]Mo2(CO)6 (Mo–Mo) (12) as an unexpected by-product. In complex 12 the cyclopentadienyl
ligand is regioselectively methylated in the vicinal position to the bridge-head atom. The synthesis of [(h5(Mo)–
C5H4)C(O)(h5(Fe)–C5Me4)]MoFe(CO)5 (Mo–Fe) (14) is achieved by reaction of 3a with Fe(CO)3(C8H14). An X-ray diffraction
study of the mononuclear siloxyfulvene Me(CO)3W[h5-C5H4C(OSiMe2t-Bu)(C5Me4)] (2) proves the fulvene-like structure of the
uncoordinated tetramethylated cyclo-C5-moiety. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Homo- and heterodinuclear complexes; Bis(cyclopentadiendiyl) bridged complexes; Tungsten; Molybdenum; Cobalt; Iron
1. Introduction
steps which can trigger new reactivity patterns: (i)
homo- or heterolytic cleavage of the metal–metal
bonds; (ii) regioselective oxidative additions of x–y or
(iii) release of one ligand and stabilisation of the coor-
dinatively unsaturated intermediate by an intermetallic
dative bond (Scheme 1).
A prerequisite to exploitation of the co-operative
effect is the prevention of the dissociation of the dinu-
clear complexes into mononuclear species which is ful-
filled in bis(cyclopentadiendiyl) bridged dinuclear
complexes [4–6].
Recently we reported a new strategy for the synthesis
of homo- and heterodinuclear bis(cyclopentadienediyl)
bridged complexes starting with the mononuclear
siloxyfulvene complexes {M}[h5-C5H4C(OTMS)(C5-
Me4)] and {M}[h5-C5H4C(O)(C5Me4H)] with {M}=
W(CO)3Me, Mn(CO)3. In this paper, we expand this
Ligand-bridged dinuclear complexes, especially in
combination with two different metal centers [1], still
attract attention in synthetic chemistry because of their
potential in new reactivity patterns [2] or new catalytic
reactivity [3] due to co-operative effects of metal centers
kept in close proximity. In particular, metal–metal
bond containing congeners are prone to unique initial
ꢀ 21st communication: J. Heck, G. Lange, M. Malessa, R. Boese,
D. Bla¨ser, Chem. Eur. J. 5 (1999) 659.
ꢀꢀ Dedicated to Professor Christoph Elschenbroich on the occa-
sion of his 60th birthday.
* Corresponding author. Tel.: +49-40-42838-6375, fax: +49-40-
42838-6348.
E-mail address: heck@chemie.uni-hamburg.de (J. Heck)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00171-0

330
J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
Scheme 1.
concept to synthesize complexes with the Mo(CO)3-
Me moiety, which exhibit remarkable differences in
reactivity compared with the analogous tungsten com-
pounds.
The fulvene moiety of 2 displays a pronounced bond
length alternation quite typical for this type of hydro-
carbon [8] (Table 2). An interesting feature is the
torsion along the exo-cyclic CꢀC double bond of the
fulvene. Due to the large groups attached to this bond
there is a high amount of strain which is partly relieved
by twisting out of the planar shape by 26°. The h5-
(C5H4)W(CO)3Me moiety is quite regular and shows no
significant deviations to related compounds.
2. Results and discussion
The
Mo-containing
siloxyfulvene
complex
Me(CO)3Mo[h5-C5H4C(OTMS)(C5Me4)] (1a) was syn-
thesized in very good yield according to the procedure
described recently for the preparation of the complexes
{M}[h5-C5H4C(OTMS)(C5Me4)] ({M}=W(CO)3Me:
1b, {M}=Mn(CO)3: 1c. The complex 1a was formed
by the reaction of Me(CO)3Mo(h5-C5H4COOMe) with
two equivalents of tetramethylcyclopentadienyl lithium
and a subsequent addition of an excess of Me3SiCl
(Scheme 2). To minimize the formation of by-products
due to the sensitivity of the Mo(CO)3Me moiety to-
wards basic reaction conditions, the synthesis of 1a was
performed at −25°C, in contrast to the synthesis of the
tungsten containing complex 1b, which can be prepared
at room temperature in good yields.
Scheme 2. Synthesis of 1a.
To confirm the formation of the siloxyfulvene com-
plexes, in our recent publication [7] we reported the
preliminary result of a molecular structure analysis of
the corresponding manganese complex (CO)3Mn[h5-
C5H4C(OTMS)(C5Me4)] (1c). Unfortunately, the X-ray
structure analysis of 1c was hampered by the poor
quality of the crystals and attempts to achieve suitable
crystals of 1a and 1b were even less successful. There-
fore, the derivative Me(CO)3W[h5-C5H4C(OSiMe2t-
Bu)(C5Me4)] (2) has now been synthesized containing a
tert-butyldimethylsilyl group instead of the trimethylsi-
lyl group in 1a–c. Beautiful orange–red crystals were
obtained, and the molecular structure was resolved in
very good quality (Table 1, Fig. 1).
Fig. 1. Molecular structure of 2. The thermal ellipsoids are at the 50%
probability level. The hydrogen atoms are omitted for clarity.

J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
331
Table 1
which were isolated as a mixture of the two isomers A
and B. The compounds 3a and 3b contain a non-coor-
dinated tetramethylcyclopentadiene ring and are suit-
able precursors for dinuclear species.
A rich chemistry of 3b has been reported previously
[7]. In comparison, the corresponding reactions of the
molybdenum complex 3a exhibit some surprising
results.
X-ray crystal structure, data collection and refinement data for 2
Crystal parameters
Formula
C25 H34 O4 Si W
610.48
173
71.073 (Mo–Ka)
Triclinic
P1
Formula weight (g mol−1
T (K)
)
u (pm)
Crystal system
Space group
Heating the tungsten complex 3b with Co2(CO)8 in
the presence of 3,3-dimethylbut-1-ene in THF afforded
the dinuclear species Me(CO)3W[(h5(W)–C5H4)C-
(O)(h5(Co)–C5Me4)]Co(CO)2 (4b) in high yields. The
same reaction with 3a yielded the expected heterodinu-
clear complex Me(CO)3Mo[(h5(Mo)–C5H4)C(O)(h5-
,
a (A)
847.0(2)
1207.9(4)
1353.3(7)
85.02(3)
82.74(3)
72.11(2)
1.304
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (nm3)
Z
2
(Co)–C5Me4)]Co(CO)2
(4a)
along
with
the
zcalc (g cm−3
)
1.554
4.50
0.2×0.25×0.4
Orange–red
homodinuclear derivative (CO)2Co[(h5-C5H4)C(O)(h5-
C5Me4)]Co(CO)2 (5) as a by-product (Scheme 4(a)). The
yields of 4a and 5 are approximately 40% each.
v (Mo–Ka) (mm−1
Crystal size (mm3)
Crystal color
)
To prove whether the substitution of the
Mo(CO)3Me moiety by Co(CO)2 is associated with the
coordination of Co(CO)2 to the tetramethylcyclopenta-
Data collection
Diffractometer used
Radiation
Monochromator
qmin,max (°)
Hilger & Watts
Mo–Ka (u=0.71073 A)
Graphite
,
2.5–25.0
Index ranges
−25h510; −165k517;
−195I519
Table 2
Reflections collected
Unique reflections
Rint
6624
,
Selected bond lengths (A), bond angles (°) and angles between planes
for 2
4583 (4422 I\2|(I))
0.0139
,
Bond lengths (A)
Refinement
Parameters
GOF
W–C11
W–C12
W–C13
W–C14
W–C15
W–C1
W–C2
W–C3
W–C4
237.1(7)
231.2(7)
233.0(7)
234.0(7)
235.3(7)
196.6(10)
199.3(8)
199.6(8)
229.3(9)
116.1(12)
115.8(10)
114.3(9)
C–C11
C–O
O–Si
C–C21
C21–C22
C22–C23
C23–C24
C24–C25
C25–C21
C22–C221
C23–C231
C24–C241
C25–C251
146.8(9)
137.3(7)
168.8(5)
135.7(9)
148.1(9)
136.3(9)
147.6(10)
134.8(10)
148.4(9)
150.5(9)
149.1(10)
151.0(9)
150.1(10)
294
1.086
0.0451/0.1058
R1/wR2
w−1 [a]
|2(F2o)+(0.0458 P)2+12.91P
4110/−3060
max, min resd (10−6 e pm−3
)
C1–O1
C2–O2
C3–O3
The spectroscopic features of 2 very much resemble
those of 1a–c with the exception of the NMR signals of
the Cp ligand and of the methyl groups of the silyl
substituent: the 1H-NMR spectrum of 2 reveals two
singlets for the methyl groups of the silyl substituent,
and four signals for the protons of the coordinated
cyclopentadienyl ligand, while in the spectra of 1a–c
the corresponding protons display an AA%MM% pattern
with two pseudo-triplets. The number of the 13C-NMR
signals for 2 confirms the anisochrony of the two
methyl substituents and four Cp positions.
Apparently, the steric influence of the tert-
butyldimethylsilyl group hinders the free rotation of the
h5-cyclopentadienyl moiety around the C11–C single
bond.
The siloxyfulvene complexes 1a and 1b were readily
hydrolyzed to {M}[h5-C5H4C(O)(C5Me4H)] ({M}=
Mo(CO)3Me: 3a; {M}=W(CO)3Me: 3b) (Scheme 3)
Bond angles (°)
W–C1–O1
W–C2–O2
W–C3–O3
C12–C11–C
C15–C11–C
C11–C–O
177.31(85) C21–C22–C23
178.59(88) C22–C23–C24
178.53(61) C23–C24–C25
127.24(59) C24–C25–C21
126.07(58) C21–C22–C221 126.87(56)
113.16(52) C221–C22–C23 124.79(60)
124.36(38) C22–C23–C231 127.48(66)
125.10(57) C231–C23–C24 123.61(62)
121.50(56) C23–C24–C241 121.83(66)
127.49(57) C241–C24–C25 128.14(69)
125.75(59) C24–C25–C251 126.39(62)
C251–C25–C21 125.44(61)
107.14(57)
108.88(58)
109.95(57)
107.12(59
C–O–Si
C21–C–C11
C21–C–O
C–C21–C22
C–C21–C25
Angles between planes
[Cp]: C11–15
[CO]: C11–C–O–C21
[Cp¦]: C21–25
[Cp]/[CO]
[CO]/[Cp¦]
[Cp]/[Cp¦]
29.13(42)
25.86(38)
50.36(34)

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J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
Scheme 3. Synthesis of 3a and 3b.
Scheme 4. Products isolated from the reaction of 3a and Co2(CO)8.
Scheme 5. Synthesis of the metal–metal bound complexes 8 and 9.
dienyl ring in 4a, a sample of 4a was heated with
Co2(CO)8 and 3,3-dimethylbut-1-ene in THF and the
reaction was monitored by IR spectroscopy (Scheme
4(b)). However, neither substitution of the Mo(CO)3Me
moiety by Co(CO)2 nor decomposition of 4a was ob-
served. Apparently, 4a is not a precursor for the forma-
tion of 5, and 5 is formed in a quite different way
requiring the initial reaction between 3a and Co2(CO)8;
the fate of the eliminated molybdenum fragment is yet
uncertain.
A very interesting feature of the chemistry of the
tungsten compound 3b is the formation of metal–metal
bound species in reactions with suitable metal car-
bonyls. Previously we reported the synthesis of the
heterodinuclear pentacarbonyl complexes [(h5(W)–
C5H4)C(O)(h5(M)–C5Me4)]WM(CO)5 (W–M) (M=
Fe: 6; M=Ru: 7) by reaction of 3b with Fe(CO)5 and
Ru3(CO)12, respectively [7]. Similarily it is possible to
prepare the hexacarbonyl compounds [(h5(W)–
C5H4)C(O)(h5(M)–C5Me4)]WM(CO)6 (W–M) (M=
Mo: 8, M=W: 9) (Scheme 5). Treatment of 3b with
M(CO)3(C2H5CN)3 (M=Mo, W) in diglyme at room
temperature first led to the formation of the complexes
Me(CO)3W[(h5(W) – C5H4)C(O)(h5(M) – C5Me4)]M -
(CO)3H (M=Mo, W) without a metal–metal bond,
which have not been isolated, but identified in the
1
reaction mixture by means of IR and H-NMR spec-
troscopy demonstrating the typical features of
Cp(CO)3WMe and Cp*M(CO)3H (M=W, H) entities.
Upon heating the solutions of the intermediate hydrido
complexes in diglyme the metal–metal bound species 8
and 9 were formed (Scheme 5). The yields in these

J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
333
reactions (23–39%) are limited due to the special mech-
anism of the metal–metal bond formation which is
discussed by Bergman et al. [9] (vide infra).
proven by repeating the reaction with the deuterated
derivative
(CD3)(CO)3Mo[h5-C5H4C(O)(C5Me4H)]
(3a–CD3). The main product again is 10, whereas
[{h5-C5H3(CD3)}C(O)(h5-C5Me4)]Mo2(CO)6 (12–CD3)
has been formed in small amounts (Scheme 6).
A quite similar chemistry of the molybdenum com-
plex 3a was expected, but in fact, there are considerable
differences in reactivity and product formation com-
pared to the reactions of 3b. The reaction of 3a with
Mo(CO)3(C2H5CN)3 in THF at room temperature gen-
erates Me(CO)3Mo[(h5(W)-C5H4)C(O)(h5(M)-C5Me4)]-
Mo(CO)3H (11) which is identified in situ by IR and
1H-NMR spectroscopy. Subsequent heating of the reac-
tion mixture yielded [(h5-C5H4)C(O)(h5-C5Me4)]Mo2-
(CO)6 (Mo–Mo) (10) which has been isolated in a yield
of 28%. In this case, the reaction conditions are less
strict than in the synthesis of 8 and 9 due to the higher
reactivity of the Mo(CO)3Me and Mo(CO)3H moieties
compared to the tungsten analogues.
Complex 10 can also be prepared by heating 3a and
Mo(CO)6 in refluxing p-xylene (Scheme 6). From this
reaction the new complex [(h5-C5H3Me)C(O)(h5-
C5Me4)]Mo2(CO)6 (Mo–Mo) (12) was isolated as a
remarkable side product which contains a monomethy-
lated cyclopentadiendiyl ligand with the Me substituent
in 2-position exclusively. 12 was unequivocally iden-
tified by means of IR, NMR and mass spectrometry,
but unfortunately gave unsatisfactory elemental analy-
sis only, probably due to solvent residues which could
not be stripped off completely even when drying the
oily material several days under reduced pressure. How-
ever, no indication was found for an acylated Cp ligand
as observed in the complex [(h5-C5H3C(O)Me)CH2(h5-
C5H4)]W2(CO)6 (W–W) [10].
It is very likely that there are differences in the
mechanism of the formation of the metal–metal bonds
in the complexes 10 and 12. However, it seems reason-
able to assume complex 11 as the precursor in both
cases. Complex 10 is probably formed in a similar
manner as described for the formation of Cp2Mo2(CO)6
from CpMo(CO)3Me and CpMo(CO)3H [9]. This
mechanism includes CO insertion into the metal–
methyl bond; the metal–metal bond is then generated
under elimination of acetaldehyde from the metal–acyl
intermediate. The CO deficiency in this reaction leads
to the formation of Cp2Mo2(CO)4 as a by-product
having a metal–metal triple bond; corresponding com-
plexes with a one-atom bridging unit between the two
cyclopentadiendiyl moieties are not known, since for
steric reasons this type of ligand does not allow the
almost linear conformation of the Cp–Mo–Mo–Cp
array as it is observed in Cp2Mo2(CO)4 [5b,11].
In the mechanism described above, the cyclopentadi-
enyl ligands are spectator ligands, and apparently not
directly involved in the conversion of the mononuclear
compounds into the dinuclear molybdenum complexes.
In contrast, it is quite obvious that the bis(cyclopenta-
diendiyl)ketone ligand is engaged in the formation of 12
from 11. A possible pathway is depicted in Scheme 7.
C–H activation and H2 elimination would generate an
intermediate 13 with a sigma bonded cyclopentadi-
enediyl ligand. Analogous compounds to 13 have re-
cently been described by Bitterwolf: et al. [12]. The
The new methyl substituent in 12 was formerly
bound to the molybdenum center in 3a. This has been
Scheme 6. Products of the reaction of 3a and Mo(CO)6 in refluxing p-xylene.
Scheme 7. Possible pathway for the formation of 12 starting with 11.

334
J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
Scheme 8. Synthesis of the metal–metal bound heteronuclear compound 14.
[(h5(Mo)-C5H4)C(O)(h5(Fe)-C5Me4)]MoFe(CO)5 (Mo–
Fe) (14) was achieved by utilizing Fe(CO)3(C8H14)2 [14],
which is an excellent transfer reagent for a Fe(CO)3 unit
to dienes at low temperatures. As an intermediate
Me(CO)3Mo[(h5(Mo)-C5H4)C(O)(h5(Fe)-C5Me4H)]Fe-
(CO)3 (15) was formed which was identified by the
characteristic carbonyl stretching bands of a (h4-di-
ene)Fe(CO)3 entity when the course of the reaction was
monitored by means of IR spectrocopy. Heating the
intermediate 15 in refluxing toluene afforded the
metal–metal bound heterodinuclear complex 14 which
was isolated in a 30% yield (Scheme 8).
All attempts to synthesize the analogous molybde-
num–ruthenium complex by using Ru(CO)3(C2H4)2
[15] as a synthon for a Ru(CO)3 fragment failed. We
have found no evidence that a Ru(CO)3 fragment has
been co-ordinated to the free cyclopentadiene ring in
3a.
methyl migration from the Mo center to the 2-position
of the C5H4-ligand together with the formation of the
metal–metal bond should lead to the Cp methylated
product 12. Comparable anion-induced migration reac-
tions of a hydrocarbyl ligand from a metal center to the
deprotonated Cp ligand have already been investigated
recently [13]. This pathway would explain the regiose-
lectivity of methyl migration since only the 2-methylcy-
clopentadienediyl isomer has been formed.
Attempts to synthesize the heterodinuclear com-
pound [(h5(Mo)-C5H4)C(O)(h5(W)-C5Me4)]MoW(CO)6
(Mo–W) by the reaction of 3a with W(CO)3(C2H5CN)3
at room temperature failed. However, at higher reac-
tion temperature an inseparable mixture of the com-
plexes [(h5(M)-C5H4)C(O)(h5(M%)-C5Me4)]M%M(CO)6
(M%–M) (M, M%=Mo, W) was obtained. Apparently,
in this reaction the Mo(CO)3Me moiety can be dis-
placed by a tungsten carbonyl fragment similar to the
reaction of Co2(CO)8 with 3a. In addition, no evidence
was found for a compound comparable to 12.
3. Experimental
The thermal instability of the Mo(CO)3Me moiety is
also observed when 3a is heated in refluxing p-xylene.
This reaction condition mainly leads to the decomposi-
tion of the starting material and small amounts of
Mo(CO)6 and 10 could be isolated from the reaction
mixture. Under the same conditions the tungsten com-
pound 3b is quite stable and shows only a slight ten-
dency to decompose.
The instability of 3a at elevated temperatures does
not allow the synthesis of heterodinuclear complexes
containing molybdenum–iron and molybdenum–ruthe-
nium bonds by simply heating of 3a with Fe(CO)5 and
Ru3(CO)12, respectively. The formation of the complex
All reactions were conducted under nitrogen using
standard Schlenk techniques. Solvents were dried with
the appropriate drying agents under nitrogen. Litera-
ture procedures were used to synthesize 3b [7],
Me(CO)3Mo[h5-C5H4COOMe] [16] and M(CO)3-
1
(C2H5CN)3 (M=Mo, W) [17]. H- and 13C-NMR spec-
tra were measured on a Varian Gemini 200 BB and
referenced against tetramethylsilane. IR spectra were
recorded on a Perkin–Elmer FT-IR 1720X using KBr
cells. Elemental analysis (C, H) were carried out on a
Heraeus CHN–O-Rapid, in the Institut fu¨r Anorganis-
che und Angewandte Chemie, Universita¨t Hamburg.

J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
335
3.1. Synthesis of Me(CO)3Mo[p5-C5H4C(OTMS)-
(C5Me4)] (1a)
3.3. Synthesis of Me(CO)3Mo[p5-C5H4C(O)(C5Me4H)]
(3a)
Me(CO)3Mo(h5-C5H4COOMe) (4.05 g; 13 mmol)
was dissolved in 100 ml of THF and cooled to −
25°C. Tetramethylcyclopentadienyl lithium (3.7 g; 28.6
mmol) was added and the mixture was stirred at −
25°C for 5 h. Subsequently, Me3SiCl (4.5 ml, 35
mmol) was added. After stirring for an additional 30
min, the solvent was removed under reduced pressure.
The resulting red residue was extracted with n-hex-
ane. Evaporation of the solvent and drying in vacuo
yielded 1a (5.30 g; 85%) as a red oil.
Anal. Calc. for C22H28MoO4Si (480.49): C, 55.00;
H, 5.87. Found: C, 54.63; H, 5.76. IR (THF, cm−1):
2017 (s), 1931 (s), 1581 (m). 1H-NMR (C6D6, 200
MHz): l 0.15 (s, 9H, SiMe3), 0.54 (s, 3H, Mo–Me),
1.77 (s, 3H, C5Me4), 1.78 (s, 3H, C5Me4), 1.80 (s, 3H,
C5Me4), 2.17 (s, 3H, C5Me4), 4.51 (t, 2H, C5H4), 5.03
(t, 2H, C5H4) (t=pseudo-triplet). 13C-NMR (C6D6,
A solution of 1a in THF was treated with a 10-fold
excess of water. The solvent was evaporated and the
resulting yellow–orange crystals were dried in vacuo to
afford a quantitative yield of 3a. F.p.: 85–90°C. Anal.
Calc. for C19H20MoO4 (408.31): C, 55.89; H, 4.94.
Found: C, 55.92; H, 5.15. IR (THF, cm−1): 2020 (s),
1
1932 (s), 1618 (m). H-NMR (C6D6, 360 MHz), isomer
A: l 0.63 (s, 3H, Mo–Me); 1.06 (d, J=7.6 Hz, 3H,
C5Me4H), 1.51 (s, 3H, C5Me4H), 1.58 (s, 3H, C5Me4H),
1.88 (d, J=2.3 Hz, 3H, C5Me4H), 3.22 (m, 1H,
C5Me4H), 4.36 (m, 1H, C5H4), 4.52 (m, 1H, C5H4), 4.94
(m, 1H, C5H4), 5.50 (m, 1H, C5H4); isomer B: l 0.47 (s,
3H, Mo–Me), 1.58 (s, 6H, C5Me4H), 1.81 (s, 6H,
C5Me4H), 3.66 (m, 1H, C5Me4H), 4.31 (m, 2H, C5H4),
5.18 (m, 2H, C5H4). 13C-NMR (C6D6, 50 MHz), isomer
A: l −19.1 (Mo–Me), 10.5 (C5Me4H), 11.9 (C5Me4H),
13.8 (C5Me4H), 14.8 (C5Me4H), 50.4 (C5Me4H), 92.3
(C5H4), 94.0 (C5H4), 94.1(C5H4), 96.9 (C5H4), 109.7
(C5H4), 135.6 (C5Me4H), 142.4 (C5Me4H), 148.2
(C5Me4H), 152.8 (C5Me4H), 185.6 (C5H4–C(O)–
C5Me4H), 226.1 (Mo–CO), 226.2 (Mo–CO), 238.8
50 MHz):
l 19.9 (Mo–Me), 0.8 (SiMe3), 11.3
(C5Me4), 11.8 (C5Me4), 13.8 (C5Me4), 14.2 (C5Me4),
92.7 (C5H4), 95 (b, C5H4), 112.0 (C5H4), 122.0
(C5Me4), 123.9 (C5Me4), 137.2 (C5Me4), 137.4
(C5Me4), 139.0 (C5Me4), 147.2 (ꢀC–O), 227.1 (Mo–
CO), 240.1 (Mo–CO).
(Mo–CO); isomer B:
l
−19.6 (Mo–Me), 11.2
(C5Me4H), 12.7 (C5Me4H), 70.0 (C5Me4H), 92.8
(C5H4), 96.0 (C5H4), 132.5 (C5Me4H), 139.7 (C5Me4H).
3.4. Synthesis of Me(CO)3Mo[(p5(Mo)-C5H4)C(O)-
(p5(Co)-C5Me4)]Co(CO)2 (4a) and (CO)2Co[(p5-
C5H4)C(O)(p5-C5Me4)]Co(CO)2 (5)
3.2. Synthesis of Me(CO)3W[p5-C5H4C(OSiMe2t-Bu)-
(C5Me4)] (2)
3b (0.296 g; 0.6 mmol) was added to a suspension
of NaH (0.10 g; 4 mmol) in THF. The mixture was
stirred until the H2 evolution ceased, and then
filtered. Subsequently, t-BuMe2SiCl (0.90 g; 0.6
mmol) was added to the red solution and the reaction
mixture was stirred for 30 min. After evaporation of
the solvent, the residue was extracted with n-hexane.
Removal of the solvent yielded 2 (0.327 g; 89%) as
red crystals. F.p.: 163–164°C. Anal. Calc. for
C25H34O4SiW (610.48): C, 49.19; H, 5.61. Found: C,
49.25; H, 5.78. IR (THF, cm−1): 2014 (s), 1921 (s),
3a (0.110 g; 0.27 mmol) and Co2(CO)8 (0.24 g; 0.7
mmol) were dissolved in a mixture of 30 ml THF and 5
ml 3,3-dimethylbut-1-ene. The course of the reaction
was monitored by means of IR spectroscopy. The solu-
tion was refluxed until the stretching band of the or-
ganic CO bridging group in 3a at 1618 cm−1 was no
longer detected. After evaporation of the solvent, the
residue was chromatographed on silica. Elution with
toluene separated two dark red bands: the first fraction
contained 4a, the second 5. The solvent was removed
under reduced pressure. The resulting red solids were
dried in vacuo. 0.058 g (41%) of 4a and 0.044 g (37%)
of 5 were isolated.
4a: F.p.: \85°C (dec.). Anal. Calc. for
C21H19CoMoO6 (522.25): C, 48.30; H, 3.67. Found: C,
48.66; H, 3.96. IR (THF, cm−1): 2024 (s), 2014 (s),
1957 (s), 1933 (s), 1637 (m). 1H-NMR (C6D6, 360
MHz): l 0.73 (s, 3H, Mo–Me), 1.46 (s, 6H, C5Me4),
1.67 (s, 6H, C5Me4), 4.46 (t, 2H, C5H4), 5.72 (t, 2H,
C5H4). 13C-NMR (C6D6, 50 MHz): l −18.5 (Mo–Me),
10.0 (C5Me4), 11.5 (C5Me4), 94.1 (C5H4), 96.0 (C5H4),
97.2 (C5Me4), 98.3 (C5H4), 101.5 (C5Me4), 108.5
(C5Me4), 187.5 (C5H4–C(O)–C5Me4), 205.3 (Co–CO),
225.7 (Mo–CO), 238.1 (Mo–CO).
1
1574 (w). H-NMR (C6D6, 200 MHz): l 0.02 (bs, 3H,
Si–Me), 0.15 (bs, 3H, Si–Me), 0.59 (s, 3H, W–Me),
1.03 (s, 9H, tert-Butyl), 1.76 (s, 3H, C5Me4), 1.79 (s,
3H, C5Me4), 1.83 (s, 3H, C5Me4), 2.19 (s, 3H,
C5Me4), 4.39 (bs, 1 H, C5H4), 4.58 (bs, 1 H, C5H4),
4.95 (bs, 1 H, C5H4), 5.22 (bs, 1 H, C5H4). 13C-NMR
(C6D6, 50 MHz): l −31.5 (W–Me), −3.8 (Si–Me),
−3.5 (Si–Me), 11.3 (C5Me4), 11.9 (C5Me4), 13.8
(C5Me4), 14.3 (C5Me4), 18.7 (C(Me)3), 25.9 (C(Me)3),
87.5 (C5H4), 90.7 (C5H4), 103.2 (C5H4), 109.7 (C5H4),
121.4 (C5Me4), 124.7 (C5Me4), 137.7 (C5Me4), 138.3
(C5Me4), 140.0 (C5Me4), 147.9 (ꢀC–O), 229.4 (W–
CO).

336
J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
5: F.p.: 77–78°C. Anal. Calc. for C21H19Co2O5
3.7. Synthesis of [(p5-C5H4)C(O)(p5-C5Me4)]Mo2(CO)6-
(Mo–Mo) (10) and [(p5-C5H3Me)C(O)(p5-C5Me4)]-
Mo2(CO)6 (Mo–Mo) (12)
(442.20): C, 51.61; H, 3.65. Found: C, 51.07; H, 3.78.
IR (THF, cm−1): 2033 (s), 2012 (s), 1973 (s), 1953 (s),
1
1633 (m). H-NMR (C6D6, 360 MHz): l 1.49 (s, 6H,
C5Me4), 1.71 (s, 6H, C5Me4), 4.50 (t, 2H, C5H4), 5.59 (t,
2H, C5H4). 13C-NMR (C6D6, 50 MHz): l 10.1 (C5Me4),
11.5 (C5Me4), 86.2 (C5H4), 87.9 (C5H4), 97.0 (C5Me4),
99.3 (C5H4), 100.5 (C5Me4), 102.9 (C5H4), 186.9 (C5H4–
C(O)–C5H4), 200–210 (broad, Co–CO).
(a) 3a (0.265g, 0.64 mmol) and Mo(CO)3(C2H5CN)3
(0.30 g; 0.87 mmol) were dissolved in THF (20 ml) and
stirred at room temperature for 1 h. Subsequently, the
solution was refluxed for 1.5 h. After removal of the
solvent, the residue was chromatographed on silica with
toluene. The last, dark red band was collected and after
removal of the solvent, 10 was obtained as a dark red
solid (0.101 g, 28%).
3.5. Synthesis of [(p5(W)-C5H4)C(O)(p5(Mo)-C5Me4)]-
WMo(CO)6 (W–Mo) (8)
(b) 3a (0.524 g; 1.28 mmol) and Mo(CO)6 (0.340 g;
1.29 mmol) were dissolved in 10 ml p-xylene and
refluxed for 2 h. Subsequently, the reaction mixture was
separated by column chromatography as described
above. The last two dark red fractions were collected,
the first one contained 12 (0.080 g; 11%), followed by
the main product 10 (0.230 g; 31%).
10: F.p.: \160°C (dec.). Anal. Calc. for
C21H16Mo2O7 (572.24): C, 44.08; H, 2.82. Found: C,
44.40; H, 3.08. IR (THF, cm−1): 2015 (s), 1964 (s),
1922 (s), 1908 (sh), 1889 (m), 1654 (w). 1H-NMR
(C6D6, 200 MHz): l 1.44 (s, 6H, C5Me4), 1.65 (s, 6H,
C5Me4), 4.38 (broad s, 2H, C5H4), 5.17 (t, 2H, C5H4).
13C-NMR (C6D6, 50 MHz): l 10.6 (C5Me4), 12.4
(C5Me4), 90.0 (C5H4), 91.1 (C5H4), 102.6 (C5Me4), 103.4
(C5H4), 104.1 (C5Me4), 109.5 (C5Me4), 183.1 (C5H4–
C(O)–C5Me4), 223.9 (Mo–CO), 228.0 (Mo–CO), 232.1
(Mo–CO), 236.8 (Mo–CO).
3b (0.530 g; 1.07 mmol) and Mo(CO)3(C2H5CN)3
(0.454 g; 1.31 mmol) were dissolved in diglyme (10 ml).
The mixture was heated to 100°C for 20 min and then
refluxed for 1 h. After evaporation of the solvent, the
resulting residue was chromatographed on silica with
toluene. Complex 8 was eluted as the last, dark red
band. After removal of the solvent, 8 was obtained as
dark red solid (0.270 g, 38%). F.p.: \180°C (dec.).
Anal. Calc. for C21H16MoO7W (660.15): C, 38.21; H,
2.44. Found: C, 38.29, H, 2.51. IR (THF, cm−1): 2013
(s), 1962 (s), 1919 (s), 1908 (sh), 1895 (m), 1655 (m).
1H-NMR (C6D6, 200 MHz, 20°C): l 1.42 (s, 6H,
C5Me4), 1.68 (bs, 6H, C5Me4), 4.33 (t, 2H, C5H4), 5.20
(t, 2H, C5H4). 1H-NMR (toluene-d8, 360 MHz, −
40°C): l 1.27 (s, 3H, C5Me4), 1.29 (s, 3H, C5Me4), 1.34
(s, 3H, C5Me4), 1.92 (s, 3H, C5Me4), 4.00 (m, 1H,
C5H4), 4.24 (m, 1H, C5H4), 4.90 (m, 1H, C5H4), 5.19
(m, 1H, C5H4). 13C-NMR (C6D6, 50 MHz, 20°C): l
10.7 (C5Me4), 12.4 (C5Me4), 88.5 (broad, C5H4), 89.5
(C5H4), 102.2 (C5H4), 102.5 (C5Me4), 109.0 (C5Me4),
183.4 (C5H4–C(O)–C5Me4), 211.6 (W–CO), 218.8
(W–CO), 227.3 (Mo–CO), 236.8 (Mo–CO).
12: IR (THF, cm−1): 2013 (s), 1962 (s), 1920 (s),
1906 (sh), 1887 (m), 1656 (w). 1H-NMR (C6D6, 200
MHz): l 1.40 (s, 3H, C5Me4), 1.44 (s, 3H, C5Me4), 1.47
(s, 3H, C5Me4), 1.90 (s, 3H, C5Me4), 2.01 (d, J=0.3
Hz, 3H, C5H3Me,), 4.09 (dd, H, C5H3Me), 4.71 (m, H,
C5H3Me), 5.28 (dd, H, C5H3Me). 13C-NMR (C6D6, 50
MHz): l 10.4 (C5Me4), 11.0 (C5Me4), 11.5 (C5Me4),
13.1 (C5Me4), 14.7 (C5H3Me), 87.1 (C5H3Me), 93.2
(C5H3Me), 93.4 (C5H3Me), 101.2, (C5H3Me) 102.1,
(C5Me4), 102.3, (C5Me4), 104.7, (C5Me4), 106.4,
(C5Me4), 111.3, (C5Me4), 186.0 (C5H3Me–C(O)–
C5Me4), 224.2 (Mo–CO), 225.1 (Mo–CO), 227.0 (Mo–
CO), 229.6 (Mo–CO), 233.3 (Mo–CO), 236.8
(Mo–CO).
3.6. Synthesis of [(p5-C5H4)C(O)(p5-C5Me4)]W2(CO)6
(W–W) (9)
3b (0.460 g; 0.92 mmol) and W(CO)3(C2H5CN)3
(0.580 g; 1.34 mmol) were dissolved in diglyme (10 ml)
and refluxed for
2
h.
A
second crop of
W(CO)3(C2H5CN)3 (0.100 g; 0.23 mmol) was added.
After refluxing the solution for additional 2 h and
work-up of the reaction mixture as described above
gave 9 (0.165 g; 23%) as a red solid. F.p.: 195–196°C.
Anal. Calc. for C21H16O7W2 (748.06): C, 33.72; H, 2.16.
Found: C, 34.14; H, 2.32. IR (THF, cm−1): 2012 (s),
3.8. Synthesis of [(p5(Mo)-C5H4)C(O)(p5(Fe)-C5Me4)]-
MoFe(CO)5 (Mo–Fe) (14)
1
1960 (s), 1916 (s), 1900 (sh), 1880 (m), 1660 (w). H-
Tricarbonyl[bis(cyclooctene)]iron (0.410 g; 1.1 mmol)
was added to a solution of 3a (0.450 g; 1.1 mmol) in
THF (50 ml) at −78°C. The stirred solution was
allowed to warm up to room temperature within 3 h.
After removal of the solvent, the residue was dissolved
in p-xylene (20 ml) and heated to 120°C for 1.5 h.
Subsequently, the solvent was removed and the result-
ing residue chromatographed on silica with toluene.
NMR (C6D6, 200 MHz): l 1.53 (s, 6H, C5Me4), 1.75
(broad s, 6H, C5Me4), 4.31 (t, 2H, C5H4), 5.17 (broad s,
2H, C5H4). 13C-NMR (C6D6, 50 MHz): l 10.6 (C5Me4),
12.4 (C5Me4), 89.0 (b, C5H4), 90.1 (C5H4), 100.4
(C5Me4), 102 (b, C5Me4), 102.2 (C5H4), 105.2 (C5Me4),
183.7 (C5H4–C(O)–C5Me4), 219.1 (W–CO), 223.9
(W–CO).

J. Ko¨rnich et al. / Journal of Organometallic Chemistry 584 (1999) 329–337
337
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The desired complex 14 was eluted as the last, red–
brown band. The solvent was evaporated, and 14 (0.174
g; 30%) was isolated as black crystals.
14: F.p. 185°C. Anal. Calc. for C20H16FeMoO6
(504.13): C, 47.65; H, 3.20. Found: C, 47.16; H, 3.59.
IR (THF, cm−1): 2011 (s), 1954 (s), 1908 (w), 1888 (s),
1
1660 (m). H-NMR (C6D6, 200 MHz): l 1.26 (s, 6H,
C5Me4), 1.54 (s, 6H, C5Me4), 4.36 (t, 2H, C5H4), 5.14 (t,
2H, C5H4). 13C-NMR (C6D6, 50 MHz): l 9.7 (C5Me4),
10.9 (C5Me4), 87.9 (C5H4), 90.2 (C5H4), 91.4 (C5Me4),
95.3 (C5Me4), 97.1 (C5H4), 107.2 (C5Me4), 184.9
(C5H4–C(O)–C5Me4), 224.4 (JC–W=49 Hz, M–CO).
3.9. X-ray structure analysis of 2
Suitable crystals for X-ray structure analysis were
obtained by cooling down a n-hexane solution of 2 to
−20°C. The data were recorded on a Hilger & Watts
(Y290) at −120°C, applying monochromatic Mo–Ka
rays. The structure was solved by direct methods using
SHELXS-86 [18]. Refinement on F2 was carried out by
full matrix least square techniques (SHELXL-93) [19]. An
empirical absorption correction was applied using DI-
FABS [20] from PLATON [21]. All non-hydrogen atoms
were refined with anisotropic thermal parameters. The
hydrogen atoms were refined at calculated positions
with a fixed isotropic thermal parameter related by a
factor of 1.2 to the value of the equivalent isotropic
thermal parameter of their carrier atoms. Weights were
optimized in the final refinement cycles.
Crystallographic data for the structural analysis has
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 114932 for compound 2.
Copies of this information may be obtained free of
charge from: The Director CCDC 12 Union Road
Cambridge, CB2 1 EZ UK Fax. (int code= +44-1223-
336-033; e-mail: deposit@ccdc.cam.ac.uk or www:http:/
/www.ccdc.cam.ac.uk.
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