Reactions of early-late heterobimetallics with oxiranes: New examples for cooperative reactivity

Article abstract of DOI:10.1016/j.jorganchem.2006.10.009

In the reaction of oxiranes and cobalt-containing early-late heterobimetallic (ELHB) compounds isolated or prepared in situ, acyl-cobalt complexes, Y₃M^EOCHRCH₂C(O)Co(CO)₄ (1, M^E = Ti, Zr, Hf), were ob

Full text of DOI:10.1016/j.jorganchem.2006.10.009

Journal of Organometallic Chemistry 692 (2007) 1817–1824
www.elsevier.com/locate/jorganchem
Reactions of early–late heterobimetallics with oxiranes: New
examples for cooperative reactivity
*
´
Attila Sisak , Erzsebet Halmos
Research Group for Petrochemistry of the Hungarian Academy of Sciences, University of Veszprem, P.O. Box 151, H-8201 Veszpre´m, Hungary
Received 31 August 2006; received in revised form 5 October 2006; accepted 6 October 2006
Available online 13 October 2006
´
Dedicated to Professor Gyula Palyi on the occasion of his 70th birthday in recognition of his important contributions in organometallic chemistry.
Abstract
In the reaction of oxiranes and cobalt-containing early–late heterobimetallic (ELHB) compounds isolated or prepared in situ, acyl-
cobalt complexes, Y3MEOCHRCH2C(O)Co(CO)4 (1, ME = Ti, Zr, Hf), were obtained. Some of the complexes 1 were isolated in form of
their derivatives substituted on the cobalt atom with PPh3. We have demonstrated that the ELHB compounds containing Group 4 metals
and silyl-cobalttetracarbonyls are analogous concerning their reactivity against oxiranes. The studied heterobimetallic systems mediated
the rearrangement of terminal oxiranes to ketones.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Early–late heterobimetallics; Cooperative reactivity; Oxiranes; Acyl-tetracarbonylcobalts; Ketone formation
1. Introduction
activation of an oxirane, by the complex Zr(Cp)2(l-
NtBu)Ir(Cp*) (2); oxirane activation is accompanied by
a rapid oxygen atom transfer, as shown in the following
equation [1,7]:
The cooperative reactivity of early–late heterobimetal-
lic (ELHB) complexes having a polar metal–metal bond
[1–10] has been exhaustively studied in the last 15 years
[1–8,10]. In general, the electropositive early metal (ME)
centre reacts with the more Lewis basic part of the sub-
strate, while its more Lewis acidic part will be activated
by the late metal (ML) complex fragment [1–3]. A result
of these interactions is the cleavage of the ME–ML single
bond. Most of the substrates investigated have at least
one multiple bond (C@O, C„N, S@O, etc.) [1–3,5].
Insertion of the C@O bond – i.e. the formation of an
ME–O and an ML–C bonds simultaneously – takes place
in the cases of various carbonyl compounds [1], and the
consecutive steps are strongly substrate-dependent [1,6].
Only one example exists, however, for the cooperative
2 + PhCHCH2O
Zr(Cp)2(μ-NtBu)(μ-O)Ir(Cp*)
ð1Þ
+ PhCH=CH2
We showed earlier that terminal oxiranes react with
silyl-cobalttetracarbonyls in the presence of carbon monox-
ide to give an isomeric mixture of (b-silyloxyacyl)-cobalt-
tetracarbonyls (3) [11]:
R’3SiCo(CO)4 + RCHCH2O + CO
–15 - +25 ˚C
ð2Þ
R’3SiOCHRCH2C(O)Co(CO)4
3a (major product)
On the basis of kinetic investigations, a mechanism involv-
ing the rapid formation of a tight ion pair, followed by a
rate-determining internal SN2 type substitution, and then
a fast CO insertion was suggested (Scheme 1).
*
Corresponding author. Tel.: +36 88 624718; fax: +36 88 624469.
E-mail address: sis014@almos.vein.hu (A. Sisak).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.10.009

1818
A. Sisak, E. Halmos / Journal of Organometallic Chemistry 692 (2007) 1817–1824
Si
Co(CO)4
O
+
SiCo(CO)4
O
fast
R
R
fast
-
(CO)4Co
Si
Si
Si
+
+
+
O
O
O
-
-
(CO)4Co
(CO)4Co
R
R
R
slow
slow
R
R
O
Co(CO)4
Si
Si
Co(CO)4
O
CO, fast
CO, fast
R
R
O
O
Co(CO)4
Si
Si
Co(CO)4
O
O
3a
3b
Scheme 1.
Now we report on analogous reactions starting from
heterobimetallic precursors isolated or prepared in situ,
as well as the transformations exhibited by the resulted
acyl-cobalt complexes.
ꢁ Y3MECl/NaCo(CO)4, at ꢀ40 to +20 ꢁC in THF
(Method B, cf. Ref. [9]).
ꢁ Y3MECl/NaCo(CO)4, at ꢀ40 to +20 ꢁC in toluene
(Method C, cf. Refs. [8,9]).
ꢁ (Cp)2Zr(H)Cl/Co2(CO)8 (2:1), at 20 ꢁC in toluene or
dichloromethane (Method D).
2. Results
ꢁ Y3MECl/Co2(CO)8/Mg (2:1:10), at 0–20 ꢁC in diethyl
The isolated ELHB complex, (iPrO)3Ti–Co(CO)4 [8],
reacted with methyloxirane in toluene solution under very
mild conditions (ꢀ40 to +20 ꢁC, Method A). The reaction
was followed by IR spectroscopy, which showed an acyl-
cobalttetracarbonyl as the main product (Table 1) (cf. Refs.
[11–13]). Analogous complexes were formed from the fol-
lowing in situ prepared ELHB systems and an excess of
oxiranes:
ether or dichloromethane (Method E).
i
(Y = acac, Cl, Cp, PrO; ME = Ti, Zr, Hf, see Chart 1).
The in situ prepared ELHB systems all reacted with oxir-
anes to give acyl-cobalttetracarbonyls even in the absence of
CO; the formation of some – partly insoluble – decomposi-
tion products and CO evolution were observed in these
reactions (see later). In one case, however, the intermediate

A. Sisak, E. Halmos / Journal of Organometallic Chemistry 692 (2007) 1817–1824
1819
Table 1
Properties of the acyl-cobalt complexes 1 and 4
Complex
Synthesis
method
IR (toluene, m(CO)/cmꢀ1
)
NMR (CDCl3, d)
1a
1b
1c
1d
A, B, C
2103m, 2041s, 2021vs,
2002vs, 1717m
2103m, 2042s, 2020vs,
2001vs, 1715m
2104m, 2045m, 2122vs,
2002vs 1715m
2108m, 2147s, 2125vs,
2007vs, 1719ma
B, C
B, D
B, C, E
1H: 0.80 (3H, t, J = 6.7 Hz, CH3), 1.3 (1H, m, CH3CH2CH2), 1.60 (2H, m, CH2CH), 3.34 (1H,
dd, J = 7.3 Hz, 11,2 Hz, CHaHbCO), 3.51 (1H, dd, J = 3.8 Hz, 11,2 Hz CHaHbCO), 3.86 (1H,
m, CHOTi), 6.31 (10H, s, C5H5)b
13C: 14.2 (CH3), 23.1 (CH3CH2), 28.6 (CH3CH2CH2), 34.5 (CH2O), 67.6 (CH2CO), 72.0 (CH)
118.8 (Cp), 204.3 (C„O), 228.1 (C@O)b
1e
1f
B, C, D, E
B
2107m, 2145s, 2125vs,
2006vs, 1719ma
2106m, 2043s, 2023vs,
2003vs, 1716mc
2046w, 1978vs, 1959vs,
1680w
4a
B, Cd
1H: 1.24 (18H, d, J = 6.6 Hz, (CH3)2CH), 1.36 (3H, d, J = 7.1 Hz, CH3CHCH2), 3.41 (2H, m,
CH2CO), 4.18 (1H, m, CH3CHCH2), 4.35 (3H, m, (CH3)2CH), 6.90–7.70 (m, 15H, C6H5)
13C: 19.3 (CH3CH) 22.1 ((CH3)2CH), 64.5 ((CH3)2CH), 68.9 (CH2CO), 73.1 (CH3CH), 129,3
(Cm), 131.5 (Cp), 133.7 (Co), 135.8 (Cipso), 205.5 (C„O), 230.3 (C@O)
4b
4c
a
B, Cd
C, Dd
2042w, 1977vs, 1959vs,
1685we
2044w, 1978vs, 1961vs,
1685we
1H: 1.05 (3H, d, J = 7.3 Hz, CH3), 3.37 (2H, m, CH2CO), 4.09 (1H, m, CH), 6.25 (10H, s,
C5H5), 6.75–7.60 (15H, m, C6H5)
1H: 1.03 (3H, d, J = 7.2 Hz, CH3), 3.34 (2H, d, CH2CO), 4.07 (1H, m, CH), 6.22 (10H, s,
C5H5), 6.70–7.55 (15H, m, C6H5)
In Et2O.
b
c
Chemical shifts assigned to 1d found in the reaction mixture (Cp)2TiCl2/Co2(CO)8/Mg/butyloxirane in CD2Cl2 under CO (Method E, see Section 5).
In THF.
d
e
Synthesis methods of the precursor complex 1a–c (see Section 5).
In toluene:methylcyclohexane = 2:1.
alkyl-cobalttetracarbonyl could be detected as well: in the
IR spectra of the system (Cp)2Zr(H)Cl/Co2(CO)8/butyloxi-
rane (Method D), the bands of both the alkyl- and acyl-
cobalt carbonyls were found (Fig. 1). An acyl-cobalttetra-
Complexes Y3MEOCHRCH2C(O)Co(CO)4 (1) could
not be obtained in pure form, since most of them decom-
posed over the course of a few hours at 20 ꢁC (1f even at
0 ꢁC) in solution. The stability increased in the order
1f ꢂ 1b ꢃ 1c ꢃ 1d ꢃ 1e < 1a. Decomposition products
and byproducts detected by IR spectroscopy include
Co2(CO)8 (Methods A–C, under CO), Co4(CO)12 (Meth-
ods A–E, under Ar), and (Cp)Co(CO)2 (Methods A–E,
during the preparation of 1b–e). Except 1f, the obtained
acyl-cobalttetracarbonyls could be stabilized to some
extent by adding triphenylphosphine to yield the monosub-
stituted derivatives 4 (Table 1). However, the isolated com-
plexes 4a–c also decomposed slowly under storage in a
refrigerator. Till now no crystals suitable for an X-ray anal-
ysis could be obtained from these compounds.
1
carbonyl was detected also by H and 13C NMR spectra
of the reaction mixture (Cp)2TiCl2/Co2(CO)8/Mg/butyloxi-
rane/CO (Method E) (Table 1). In general, the above reac-
tions are described by the following equation (Chart 1):
O
Y3MECo(CO)4
+
+ CO
R
-40 - +20°C
R
ð3Þ
O
O
Y3ME
Co(CO)4
1 (major product)
In the presence of a large excess of oxirane, the intensity
of the terminal m(CO) bands of 1 slowly decreased and this
was accompanied by a significant broadening and an
increase in the ‘‘acyl’’ m(CO) band. GC–MS analyses showed
that the oxirane was converted to a ketone, namely, methy-
loxirane into acetone, and butyloxirane into 2-hexanone.
Turnovers up to 20 could be achieved within 24 h at 20 ꢁC.
ME
Ti
Y3
R
(iPrO)3
Cl(Cp)2
Cl(Cp)2
Cl(Cp)2
Cl(Cp)2
(acac)3
Me
Me
Me
Bu
Bu
Me
1a
1b
1c
1d
1e
1f
Ti
Zr
Ti
Zr
Hf
3. Discussion
One of the new compounds, 1a, was prepared starting
from the ELHB complex (iPrO)3Ti–Co(CO)4 (Method A).
Chart 1.

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A. Sisak, E. Halmos / Journal of Organometallic Chemistry 692 (2007) 1817–1824
Fig. 1. IR spectra of the reaction mixture (Cp)2Zr(H)Cl/Co2(CO)8/butyloxirane in the m(CO) region (molar ratio = 2:1:3; [Co2(CO)8] = 0.03 mol/l; 20 ꢁC;
Ar atmosphere; toluene solvent). Reaction time: 15 min (a), 150 min (b), and 240 min (c). Symbols: main product 1e is not marked, intermediate alkyl-
tetracarbonylcobalt j, Co2(CO)8 d, Co4(CO)12 h, (Cp)Co(CO)2 }.
We suppose that heterobimetallic species are the actual pre-
cursors when using Methods B–E as well. In the absence of
the oxirane substrate, the conditions listed for Methods B
and C are suitable to form a ME–Co bond through the
reaction of (iPrO)3TiCl with NaCo(CO)4 (see Refs. [8,9]).
Till now, only heterobimetallic clusters have been obtained
from the systems (Cp)2TiCl2/Co2(CO)8 [14], (acac)3ME
Cl/NaCo(CO)4 (ME = Zr, Hf) [5], and (Cp)2Zr(H)Cl/Co2-
(CO)8 [15]. On the other hand, a cluster containing also a
Ti–Co bond, [(CO)9Co3CO]2(Cp)Ti–Co(CO)4 has been
isolated from the reaction mixture of CpTiCl3 and
NaCo(CO)4 [16].
of Method E), however, the complexes (Cp)2MECl2
(ME = Ti, Zr) are known to transform easily into ME(III)
species when reduced by metals like zinc or magnesium.
Recently, the titanium(III) complexes, (Cp)2TiOtBu (5a)
and (Cp*)2TiOtBu (5b), have been shown to undergo reac-
tion with Co2(CO)8 [17]. The heterobimetallic product iso-
lated in the case of 5b, (Cp*)2Ti(OtBu)(l-OC)Co(CO)3 (6),
contains a titanium atom connected to cobalt by an isocar-
bonyl bridge. On the other hand, a metal–metal-bonded
species, (Cp)2(OtBu)Ti–Ru(CO)2(Cp) (7) has been obtained
from the photochemically induced ‘‘radical–radical’’ reac-
tion of 5a with [CpRu(CO)2]2 [18]. While the reversible dis-
sociation of Co2(CO)8 to two Co(CO)4 radicals takes place
even at ambient temperature (see, e.g. Ref. [19]), a 7 type
Co2(CO)8 did not react with magnesium to give Co(ꢀ1)
containing products in diethyl ether/oxirane (cf. conditions

A. Sisak, E. Halmos / Journal of Organometallic Chemistry 692 (2007) 1817–1824
1821
intermediate of the formation of 6 may be considered. Nev-
ertheless, on the basis of our present experimental data, it is
not possible to decide which type of precursors – 6 or 7 or
both – are formed when Method E was applied.
It follows from the foregoing discussion that reaction (3)
represents a new example for the cooperative reactivity of
ELHB complexes. A related activation of oxiranes was
described very recently using CpRu(l-dppm)Mn(CO)4, a
heterobimetallic complex with a less polar metal–metal
bond [20]. The proposed pathway – supported by DFT cal-
culations – contains the following steps: (i) the heterolytic
cleavage of the Ru–Mn bond; (ii) coordination of the oxi-
rane oxygen atom to the Lewis acidic ruthenium centre;
(iii) ring opening by the Lewis basic manganese centre.
Steps (ii) and (iii) are analogous to those we proposed for
reaction (2) (Scheme 1) and to those which were suggested
by Coates and co-workers [13a,13b] and Allmendinger
et al. [13c] for ring opening of oxiranes by [Lewis acid]+
[Co(CO)4]ꢀ salts. A similar mechanism may also be applied
to reaction (3). Scheme 2 shows two possible routes for the
formation of 1: the precursors of acyl-cobaltteracarbonyls
may be metal–metal-bonded as well as an isocarbonyl-
Y3MEOCCo(CO)3
Y3ME
Co(CO)4
O
O
toluene
Et2O
R
R
R
3 ME
Co(CO)4
Y
O
O
-
Y3ME +
Co(CO)4
R
Y3ME
3ME
Y
+
+
O
O
-
(CO)4Co
R
R
-
(CO)4Co
R
O
Y3ME
Co(CO)4
CO
O
R
O
Y3ME
Co(CO)4
1
Scheme 2.

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A. Sisak, E. Halmos / Journal of Organometallic Chemistry 692 (2007) 1817–1824
R
R
−CO
MEO
MEO
+CO
Co(CO)4
C(O)Co(CO)4
O
R
R
MEO
MECo(CO)4
CoH(CO)4
+
+
+B H , −B
+B,− BH
decomp.
products
R
.
O
+
.
-
ME
ME
+
Co(CO)4
= oxirane, ketone
+
[Co(CO)4]
B
Scheme 3.
bridged species, furthermore, both contact and isolated ion
pairs may be intermediates depending on the solvent (see,
e.g. Refs. [11,13,17,21,22]). A nucleophilic attack of tetra-
carbonyl cobaltate on the sterically more accessible carbon
of the oxirane ring results in the formation of 1 through
ring opening and CO insertion.
The related properties of the high oxidation state inor-
ganic [23] and organometallic [24] compounds of Group
4 metals and Group 14 metalloids have been described sev-
eral times. The consequence of reactions (2) and (3) as well
as Scheme 1 and 2 is that such a relationship exists between
the ME–Co-bonded complexes containing Group 4 metals
and silyl-cobalttetracarbonyls.
The rearrangement of oxiranes to carbonyl compounds
catalyzed by various Lewis acids is well known [13,25].
The starting materials used in Methods A–E, however,
did not catalyse such a rearrangement; moreover, a ketone
was detected only when complexes 1 were also present.
Consequently this rearrangement should involve ELHB
compounds. In the proposed catalytic cycle outlined in
Scheme 3, substituents on ME are omitted. b-Hydride elim-
ination from the alkyl complex formed by the decarbonyla-
tion of 1 produces HCo(CO)4 and the ME enolate. The
base-mediated (base = e.g. oxirane) reaction of these two
species results in ketone and the ions ME+ and [Co(CO)4]ꢀ.
Recombination of the latter ionic species regenerates the
starting heterobimetallic complex (cf. Ref. [13]). The low
turnovers achieved may be explained by the decomposition
of the catalytically active species. A single-electron transfer
takes place presumably from [Co(CO)4]ꢀ to ME+ leading to
radicals.
4. Conclusions
We have found that early and late metals in the ELHB
complexes of the type Y3MECo(CO)4 – which may exist
both in metal–metal-bonded and in isocarbonyl-bridged
forms – activate oxiranes cooperatively. We have demon-
strated that these ELHB compounds and silyl-tetracarbon-
ylcobalts behave analogously since both classes of
compounds react with oxiranes through a carbonylative
ring-opening to give the acyl-tetracarbonylcobalt com-
plexes, Y3MEOCHRCH2C(O)Co(CO)4 and R03SiOCHR
CH2CðOÞCoðCOÞ4, respectively. This is a new example
for the related reactivity of the high oxidation state Group
4 metals and Group 14 metalloids in the organometallic
chemistry. The investigated ELHB systems mediated the
rearrangement of oxiranes to ketones but they are less
effective than certain Lewis acids.
5. Experimental
5.1. General
All manipulations involving air-sensitive compounds
employed Schlenk techniques using deoxygenated, dry sol-
vents and gases as well as reaction vessels with magnetic
stirring. Infrared spectra were recorded by using a 0.04–
0.12 mm CaF2 cuvette on Specord IR 75 (Carl Zeiss,
Germany) or Avatar 330 FT-IR (Thermo Nicolet, USA)
spectrometers, the former was calibrated with benzene
(1959.6 cmꢀ1) or polystyrene (1601.4 cmꢀ1). The NMR
measurements were performed on a Varian UNITY 300

A. Sisak, E. Halmos / Journal of Organometallic Chemistry 692 (2007) 1817–1824
1823
spectrometer and a Bruker Avance 400 spectrometer. Gas
chromatograms were recorded on a Hewlett–Packard
model 5830 A chromatograph (with FID), while GC–MS
analyses on a Hewlett–Packard 5890 Series II GC–MSD
equipment using SPB1 (Supelco) capillary columns (30 m).
Materials were mainly commercial products. Oxiranes
(Fluka) were dried by standard methods, distilled and
stored under CO or Ar. (Cp)2TiCl2, (Cp)2ZrCl2, and
(Cp)2Zr(H)Cl were purchased from Aldrich and used with-
out purification. Co2(CO)8 [26], NaCo(CO)4 [27], (iPrO)3-
TiCl [28], (acac)3HfCl [29] and (iPrO)3TiCo(CO)4 [8] were
prepared by the literature methods.
transformation of the alkyl intermediate to 1e, in addition,
traces of Co4(CO)12 and (Cp)Co(CO)2 were found.
Method E. Co2(CO)8 (342 mg, 1.0 mmol), (Cp)2TiCl2
(503 mg, 2.0 mmol), and Mg-turnings (240 mg, 10 mmol)
were suspended in diethyl ether (10 ml) at 0 ꢁC under Ar.
After stirring vigorously for 10 min, butyloxirane
(0.36 ml, 3.0 mmol) was added. The mixture was allowed
to warm up to 20 ꢁC, and stirred at this temperature for
5 h. The red-brown colour of the solution turned to
green-brown and its IR spectrum showed the bands of 1d
and (Cp)Co(CO)2 (traces).
5.3. Preparation of 4
5.2. Preparation of 1
Reaction mixtures from the preparation of 1a–c using
the above methods were filtered and evaporated at ꢀ20 to
0 ꢁC in vacuum. The residues were dissolved in dichloro-
methane (5 ml) at 0 ꢁC under CO and triphenylphosphine
(1.1 mmol/mmol of Co) was added at once with stirring.
Gas evolution took place immediately. The reaction mix-
tures were allowed to warm up to 20 ꢁC and stirred for
1 h. IR spectra of the solutions showed the quantitative con-
version of 1a–c to 4a–c. Then the solutions were filtered,
hexane (0.5–1 ml) were added and the products were crys-
tallized at ꢀ40 ꢁC. The yellow-brown microcrystals were fil-
tered, washed with 3 · 2 ml of hexane and dried in vacuum.
Compound 4a: Yield: 34% (based on NaCo(CO)4). Anal.
Calc. for C34H42O8PTiCo: C, 56.99; H, 5.91; Co, 8.22.
Found: C, 57.21; H, 6.02; Co, 8.07%.
Method A. To (iPrO)3TiCo(CO)4 (400 mg, 1.0 mmol)
suspended in toluene (10 ml) at ꢀ40 ꢁC under a CO atmo-
sphere, methyloxirane (0.35 ml, 5.0 mmol) was added at
once. The mixture was stirred for 30 min at this tempera-
ture and then was allowed to warm up slowly to
(ꢄ60 min) 20 ꢁC. The yellow solution turned to yellow-
brown. After stirring for 3 h, a probe was taken with a syr-
inge for IR spectroscopic analysis which showed the nearly
complete transformation of (iPrO)3TiCo(CO)4 to an acyl-
cobalttetracarbonyl (1a).
Method B. To a vigorously stirred solution of NaCo-
(CO)4 (194 mg, 1.0 mmol) in THF (10 ml), (acac)3HfCl
(511 mg, 1.0 mmol) was added at once under Ar at
ꢀ40 ꢁC. After 10 min, methyloxirane (0.35 ml, 5.0 mmol)
and toluene (0.1 ml, inner standard) were injected. The reac-
tion mixture was kept for 30 min at this temperature then
was allowed to warm up slowly (ꢄ30 min) to 10 ꢁC. Mean-
while a greenish blue precipitate was separated form the
brown solution. The maximum concentration of 1f was
detected by IR spectroscopy after stirring for ꢄ40 min at
10 ꢁC (ꢄ30% conversion of NaCo(CO)4). Afterwards the
intensity of the m(CO) bands of 1f decreased slowly except
the ‘‘acyl’’ m(CO) band. After 5 h reaction time, GC and
GC–MS analyses of the solution showed that 46% of methy-
loxirane was converted to acetone.
Method C. NaCo(CO)4 (194 mg, 1.0 mmol) and
(Cp)2ZrCl2 (292 mg, 1.0 mmol) were suspended in toluene
(10 ml) and stirred vigorously for 10 min under CO at
ꢀ40 ꢁC. Methyloxirane (0.35 ml, 5.0 mmol) was then added.
The procedure was continued similarly as for Method A.
The colour of the solution deepened to dark red-brown. In
3.5 h, the IR spectroscopic analysis showed the presence
of 1c as well as traces of NaCo(CO)4 and (Cp)Co(CO)2.
Method D. To (Cp)2Zr(H)Cl (258 mg, 1.0 mmol) sus-
pended in the mixture of toluene (5 ml) and butyloxirane
(0.36 ml, 3 mmol) under Ar at 20 ꢁC, Co2(CO)8 (171 mg,
0.5 mmol) in a toluene solution (5 ml) was added at once
with vigorous stirring. (Cp)2Zr(H)Cl was dissolved within
30 min, while the light brown solution turned to deep
red-brown. In 2 h, 1e, the corresponding alkyl-cobalt com-
plex, and some Co2(CO)8 were detected by IR spectros-
copy. Further stirring for 2 h resulted in the complete
Compound 4b: Yield: 26% (based on NaCo(CO)4). Anal.
Calc. for C35H31O5ClPTiCo: C, 59.63; H, 4.43; Co, 8.36.
Found: C, 59.79; H, 4.51; 8.29%.
Compound 4c: Yield: 18% (based on Co2(CO)8). Anal.
Calc. for C35H31O5ClPCoZr: C, 56.18; H, 4.18; Co 7.88.
Found: C, 55.98; H, 4.07, Co, 8.02%.
5.4. Attempt for the catalytic rearrangement of
methyloxirane
To the vigorously stirred suspension of NaCo(CO)4
(194 mg, 1.0 mmol) in toluene (10 ml) (iPrO)3TiCl
(261 mg, 1.0 mmol) was added at once under Ar at
ꢀ40 ꢁC. After stirring for 10 min, methyloxirane (3.5 ml,
50 mmol) and m-xylene (0.5 ml, inner standard) were
injected. The procedure was continued similarly as for
Method A, but the mixture was stirred for 24 h at 20 ꢁC.
GC analysis showed that 39% of methyloxirane was con-
verted to acetone.
Acknowledgments
The authors thank for the helpful discussions with Prof.
´
´
F. Ungvary, Prof. G. Szalontai (University of Veszprem)
and Dr. A. Sorkau (Martin Luther University, Halle-Wit-
tenberg) as well as for financial support from the Hungar-
ian Academy of Sciences and from the Hungarian Scientific
Research Fund (Grants OTKA T 17350 and T 34335).

1824
A. Sisak, E. Halmos / Journal of Organometallic Chemistry 692 (2007) 1817–1824
(c) M. Allmendinger, M. Zintl, R. Eberhardt, G.A. Luinstra, F.
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