Octacarbonyl dicobalt-catalyzed selective transformation of ethyl diazoacetate into organic products containing the ethoxycarbonyl carbene building block

Article abstract of DOI:10.1016/S1381-1169(03)00377-7

In the presence of 1 mol% octacarbonyl dicobalt ethyl diazoacetate can be transformed at room temperature and carbon monoxide pressure selectively into diethyl 2-diazo-3-oxo-pentanedicarboxylate or in the presence of an alcohol (methanol, ethanol, tert-bu

Full text of DOI:10.1016/S1381-1169(03)00377-7

Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
Octacarbonyl dicobalt-catalyzed selective transformation of ethyl
diazoacetate into organic products containing the
ethoxycarbonyl carbene building block
Robert Tuba, Ferenc Ungváry∗
Institute of Organic Chemistry, University of Veszprém and Research Group for Petrochemistry of the
Hungarian Academy of Sciences, H-8201 Veszprém, Hungary
Received 5 January 2003; accepted 9 April 2003
Abstract
In the presence of 1 mol% octacarbonyl dicobalt ethyl diazoacetate can be transformed at room temperature and carbon
monoxide pressure selectively into diethyl 2-diazo-3-oxo-pentanedicarboxylate or in the presence of an alcohol (methanol,
ethanol, tert-butanol), phenol or diethylamine into the corresponding malonic acid derivatives in high yields. Ethoxycarbonyl-
carbene-bridged dicobalt carbonyl complexes [␮2-{ethoxycarbonyl(methylene)}-␮2-(carbonyl)-bis(tricarbonyl-cobalt)
(Co–Co)] and [di-␮2(ethoxycarbonyl(methylene)}-bis(tricarbony-cobalt)(Co–Co)] proved to be intermediates in the catalytic
reactions.
© 2003 Elsevier Science B.V. All rights reserved.
Keywords: Carbene transfer; Octacarbonyl dicobalt
1. Introduction
ethyl diazoacetate as the carbene precursor, which
can be applied for high yield catalytic syntheses of
2-diazo-3-oxoglutarate or malonic acid derivatives.
Transition metal compounds are effective catalysts
of carbene transfer reactions using diazoalkane pre-
cursors [1,2] leading to carbenes and metal carbene
complexes [3–5], which are useful reagents in vari-
ous reactions, such as olefin cyclopropanation, olefin
metathesis, carbon–carbon double-bond formation,
insertion and rearrangement reactions [6–8]. The role
of the transition metal compounds in influencing the
selectivity of these reactions is still not clear. We
found a selective octacarbonyl dicobalt-catalyzed
carbene carbon monoxide coupling reaction using
2. Results
Ethyl diazoacetate dissolved in saturated hydrocar-
bons under atmospheric pressure of carbon monoxide
looses dinitrogen at room temperature in the presence
of 1 mol% Co2(CO)8. Starting with a 1.3 molar solu-
tion of ethyl diazoacetate, a ca. 50% conversion was
obtained in 2 days according to the infrared spectrum
of the reaction mixture following the drop in inten-
sity of the characteristic band of ethyl diazoacetate at
2112 cm−1. At the same time, four new very strong
absorptions appeared in the carbonyl stretching region
∗
Corresponding author. Tel.: +36-88-422-022x4156;
fax: +36-88-427-492.
E-mail address: ungvary@almos.vein.hu (F. Ungva´ry).
1381-1169/03/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S1381-1169(03)00377-7

60
R. Tuba, F. Ungva´ry / Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
at 2137, 1749, 1724 and 1672 cm−1. Repeating the
experiment but under 50 bar carbon monoxide pres-
sure, a complete conversion of ethyl diazoacetate was
found in 1 day in accord with Eq. (1).
Table 1
The effect of concentrations of Co2(CO)8, ethanol, and CO on the
formation of diethyl malonate (DEM) in the Co2(CO)8-catalyzed
reaction of ethyl diazoacetate (EDA), ethanol and carbon monoxide
at 25 ◦C in n-octane solution using 3 h reaction time
[Co2(CO)8]
(mol/dm3)
[EDA]
[EtOH]
PCO
(bar)
DEMa
2N2CHCO2Et + CO
(mol/dm3)
(mol/dm3)
(mol/dm3)
1 mol% Co2(CO)8
→
N2 + EtO2CCH2C(O)C(N2)CO2Et
0.14
0.14
0.14
0.14
0.14
0.14
0.095
0.045
0.017
0.14
0.14
0.14
0.14
0.14
0.14
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
1.45
0.00
0.49
0.97
1.94
2.92
4.97
2.92
2.92
2.92
2.92
2.92
2.92
2.92
2.92
2.92
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
3.0
3.7
6.5
11.5
16.0
23.0
0.00
0.43
0.57
0.54
0.55
0.54
0.40
0.18
0.07
0.81
1.06
1.37
1.34
1.11
0.85
25 ◦C,50 bar,24 h
(1)
At the end of the reaction, the IR spectrum of the
reaction solution showed in addition to the four very
strong bands the presence of the characteristic bands of
Co2(CO)8 at 2069, 2044, 2024, 1866, and 1857 cm−1
.
GLC analysis of the gas phase showed that 52% of
the total nitrogen of the starting ethyl diazoacetate was
found to be in the form of dinitrogen. The work up
[10] of the solution gave the known compound diethyl
2-diazo-3-oxoglutarate [9] in 91% isolated yield as a
pale yellow oil, which was unequivocally identified by
elemental analysis and by H and 13C NMR spectra.
1
a The concentration of diethyl malonate [DEM] was deter-
mined by quantitative IR analysis using the molar absorbance of
diethyl malonate εM = 843 cm2 mmol−1 at 1747 cm−1, and dou-
ble checked by quantitative GLC analysis using n-nonane as the
internal standard.
Completely different results were obtained in the
above experiments, if they were performed in the pres-
ence of an equimolar amount of additional reagents
such as methanol, ethanol, tert-butanol, phenol or di-
ethyl amine. Using these reagents, the selective forma-
tion of the corresponding malonate derivatives were
achieved in accord with Eqs. (2)–(4). The ethyl mal-
onate derivatives were isolated from the reaction mix-
tures by flash chromatography on silica gel in up
to 95% yields. The identity of these products was
concentrations of the reactants (Table 1), it could be
deduced that the rate of diethyl malonate formation is
proportional with the concentration of the Co2(CO)8
precatalyst, does not depend on the concentration of
ethanol above a 2:1 molar ratio, and is in a complex
manner dependent on the applied carbon monoxide
pressure in the experiment. Although the reaction
proceeds nearly to completion using 0.49 mol/dm3
ethanol and 0.14 mol/dm3 Co2(CO)8 concentrations
and excess ethyl diazoacetate (Entry 2), for prepara-
tive purposes, however, an equimolar ethyl diazoac-
etate:alcohol ratio, higher than atmospheric pressure
of CO, and 1 mol% Co2(CO)8 catalyst provide the
best practical conditions for the isolation of the reac-
tion product (see the examples in the Section 4).
By mixing an equimolar amount of ethyl dia-
zoacetate with solutions of octacarbonyl dicobalt
in n-octane at room temperature under atmospheric
pressure of carbon monoxide results according to
Eq. (5) in evolution of 2 mol of a 1:1 mixture of
carbon monoxide and dinitrogen (checked by a gas
burette and gas-chromatography). At the end of the
gas evolution, an orange colored cobalt complex with
1
2
checked by H, H, and 13C NMR spectroscopy and
GC–MS spectroscopy.
N2CHCO2Et + CO + CD3OD
1 mol% Co2(CO)8
→
N2 + EtO2CCHDCO2CD3
(2)
25 ◦C, 50 bar, 24 h
N2CHCO2Et + CO + ROH
1 mol% Co2(CO)8
→
N2 + EtO2CCH2CO2R,
25 ◦C, 50 bar, 24 h
R = Me, Et, tBu, Ph
(3)
(4)
N2CHCO2Et + CO + Et2NH
1 mol% Co2(CO)8
→
N2 + EtO2CCH2C(O)NEt2
25 ◦C, 50 bar, 24 h
From a comparison of the yields of diethyl malonate
at a given reaction time in experiments with different

R. Tuba, F. Ungva´ry / Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
61
the composition of Co2(CO)7(CHCO2Et) (1) was
isolated by column chromatography at 1 ◦C under
an argon atmosphere in 82% yield as an oil. The in-
frared spectrum of this compound in hexane solution
showed characteristic bands in the carbonyl stretching
range at 2112w, 2074s, 2056m, 2047s, 2042s, 1873m,
quantitatively to Co2(CO)8 and diethyl malonate ac-
cording to Eqs (7) and (8). The composition of the
reaction mixture was checked by quantitative infrared
spectroscopy using the known molar absorbance of
Co2(CO)8 εM = 1735 cm2 mmol−1 at 1857 cm−1 [11]
and that of diethyl malonate εM = 843 cm2 mmol−1
measured at 1747 cm−1. The amount of diethyl mal-
onate was double checked by quantitative gas chro-
matographic analysis.
1866m, 1854m, 1704w, and 1693w cm−1
.
Co2(CO)8 + N2CHCO2Et
◦
◦
→
10 C or 25 CCo2(CO)7(CHCO2Et) + CO + N2 (5)
Co2(CO)7(CHCO2Et) + 2CO + EtOH
1 bar
1
1
◦
Using a 2:1 molar ratio of ethyl diazoacetate and
Co2(CO)8 in the above preparation the evolution of
4 mol of a 1:1 mixture of carbon monoxide and dini-
trogen and the formation of an orange–yellow colored
complex was observed according to Eq. (6). From the
reaction mixture, a yellow oil with a composition of
Co2(CO)6(CHCO2Et)2 (2) was isolated in 73% yield
by column chromatography at 0 ◦C under an argon at-
mosphere. The infrared spectrum of this compound
in hexane solution showed characteristic bands in the
carbonyl stretching range at 2112m, 2082s, 2063m,
→
25 C, 50 barCo2(CO)8 + EtO2CCH2CO2Et
(7)
60 min
Co2(CO)6(CHCO2Et)2 + 4CO + 2EtOH
2
◦
→
25 C, 50 barCo2(CO)8 + 2EtO2CCH2CO2Et
(8)
60 min
The carbon monoxide uptake of complexes 1 and 2
could be followed at atmospheric pressure as well by
using a gasometric apparatus. Complex 2 showed a
much higher reactivity toward carbon monoxide than
complex 1, and the carbon monoxide uptake in both
cases was faster in the presence of ethanol. Monitor-
ing the infrared spectra of the reaction mixture in the
reaction of complex 2 with CO and ethanol at 25 ◦C,
resulted first in the simultaneous fast formation of
complex 1 and diethyl malonate (Eq. (9)) and then in
the slower conversion of complex 1 into Co2(CO)8
and diethyl malonate (Eq. (10)) (see Table 2).
2049s, and 1702w cm−1
.
Co2(CO)8 + 2N2CHCO2Et
◦
◦
→
10 C or 25 CCo2(CO)6(CHCO2Et)2 + 2CO + 2N2
1 bar
2
(6)
Under 50 bar carbon monoxide pressure in the pres-
ence of ethanol both complexes 1 and 2 converted
Table 2
The change in concentrations in the reaction of Co2(CO)6(CHCO2Et)2 (2) with carbon monoxide and ethanol at 25 ◦C and atmospheric
pressure in n-octane and the formation of diethyl malonate (DEM)
Reaction time (h)
[2]a (×102 mol/dm3)
[1]b (×102 mol/dm3)
[Co2(CO)8]c (×102 mol/dm3)
[DEM]d (×102 mol/dm3)
0
1.23
0.63
0.27
0.00
0.00
0.00
0.00
0.60
0.93
1.13
1.03
0.60
0.00
0.00
0.00
0.10
0.20
0.63
0.00
0.60
1.10
1.30
1.40
1.80
0.5
1.0
1.5
3.0
20
[EtOH]0 = 0.57 mol/dm3.
a The concentration of 2 was determined by quantitative IR analysis using the molar absorbance εM = 8246 cm2/mmol at 2082 cm−1
b The concentration of 1 was determined by quantitative IR analysis using the molar absorbance εM = 5484 cm2/mmol at 2074 cm−1
.
.
c The concentration of Co2(CO)8 was determined by quantitative IR analysis using the molar absorbance εM = 1735 cm2/mmol at
1857 cm−1 [11].
d The concentration of diethyl malonate [DEM] was determined by quantitative IR analysis using the molar absorbance of diethyl
malonate εM = 843 cm2/mmol at 1747 cm−1, and double checked by quantitative GLC analysis using n-nonane as the internal standard.

62
R. Tuba, F. Ungva´ry / Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
◦
Carbene transfer from nitrogen to various tran-
sition metal complexes are well known [6,7]. With
octacarbonyl dicobalt, however, only the reaction with
bis(trifluoromethyl)diazomethane has been estab-
lished so far, leading at room temperature in 28 days to
the complex [␮2-{bis(trifluoromethyl)methylene}-␮2-
(carbonyl)-bis(tricarbonyl-cobalt)(Co–Co), which was
isolated in 54% yield [12]. We found that Co2(CO)8
react with ethyl diazoacetate at ambient conditions
in a much faster reaction to give mono- and di-
ethoxycarbonylcarbene-bridged dicobalt carbonyl
complexes 1 and 2 depending on the applied mo-
lar ratio and reaction conditions. Structurally similar
dicobalt carbonyl complexes with bridging carbene
ligands are known [13–19] which were prepared by
other methods. Diazoalkanes, however, were success-
fully applied in the preparation of dinuclear cobalt
carbene complexes containing ␩5-cyclopentadienyl
ligands [20–25], and in the case of Co2(CO)6(DPPM)
(DPPM = bis(diphenylphosphino)methane) as the
starting complex [26].
2 + 2CO + EtOH
→
25 C, 1 bar1 + EtO2CCH2CO2Et
(9)
1 + 2CO + EtOH
◦
→
25 C, 1 barCo2(CO)8 + EtO2CCH2CO2Et
Solutions of complex 2 react with equimolar amounts
of diethyl amine or ethyl diazoacetate under carbon
monoxide according to Eqs. (11) and (12), respec-
tively.
(10)
2 + 2CO + Et2NH
10 ◦C, 1 bar
=
→
1 + EtO2CCH2C( O)NEt2
(11)
2 + 2CO + N2CHCO2Et
◦
→
10 C, 1 bar1 + EtO2CCH2C(O)C(N2)CO2Et
(12)
Following the carbon monoxide uptake in a gasomet-
ric apparatus at 10 ◦C using 0.020 mol/dm3 solutions
of complex 2 and equimolar amounts of ethyl dia-
zoacetate, ethanol or diethyl amine in n-octane, the
initial rate of carbon monoxide uptake was found to
be 0.1×10−5, 0.5×10−5, and 2.8×10−5 mol/dm3 s,
respectively.
Examples and indirect evidences for the metal-
mediated coupling of a carbene with carbon monox-
ide to form the corresponding ketene are numerous.
However, only one of them reports a catalytic reac-
tion in which the formation of a ketene intermediate
can be assumed. Miyashita et al. [27] found that
the reaction of Co2(CO)8 and the carbene precursor
CH2Br2 in the presence of Zn results in a cobalt
3. Discussion
= =
ketene complex Co2(CH2 C O)(CO)7 which cat-
The formation of the organic products can be
rationalized by assuming the reaction of an ethoxy-
carbonylketene intermediate with ethyl diazoac-
etate, alcohols, phenol or diethylamine, respectively
(Eq. (13)).
alyzes the methoxycarbonylation or aminocarbony-
lation of a mixture of CH2Br2 and Zn under carbon
monoxide pressure yielding methyl acetate (385%)
or N,N-diethylacetamide (184%) using methanol or
diethylamine as the additional reagents in the re-
action, respectively. In our experiments, Co2(CO)8
showed a so far unprecedented carbene transfer re-
activity with ethyl diazoacetate as the carbene pre-
cursor. A few examples are known for the coupling
of a free carbene with carbon monoxide even in the
absence of a metal [28,29]. The infrared and NMR
spectra of the reaction mixture in our case did not
reveal the presence of either free [30] or coordinated
ethoxycarbonylketene [31]. However, it is reasonable
to assume that in the coordination sphere of cobalt
the coupling of ethoxycarbonylcarbene with carbon
monoxide does occur in an equilibrium reaction. This
equilibrium is probably far on the left side keeping
= =
O C CHCO2Et + BH → BC(O)CH2CO2Et
t
(B=N2CCO2Et, CH3O, EtO, BuO, PhO, Et2N)
(13)
The possible source of the ethoxycarbonylketene
might be the cobalt-mediated coupling reaction of car-
bon monoxide with ethoxycarbonylcarbene (Eq. (14))
which latter can be formed by the cobalt-mediated
dinitrogen-loss of ethyl diazoacetate (Eq. (15)).
CHCO2Et + COCo (CO)
→
(14)
(15)
2
8
= =
O C CHCO2Et
N2CHCO2EtCo (CO)
→
8N2 + CHCO2Et
2

R. Tuba, F. Ungva´ry / Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
63
Scheme 1.
the ketene concentration low but still sufficient to
be scavenged by a suitable nucleophile. The obser-
vation that the CO uptake of the carbene complexes
1 and 2 is faster in the presence of ethanol or other
potential ketene scavenger support this assumption.
Ketenes either free [30] or coordinated to a transition
metal [31] are prone to nucleophilic attack on the
␣-carbon atom and are effectively scavenged by an
O- or N-nucleophiles such as an alcohol, phenol, or
diethylamine. If such nucleophile is not present in
the reaction mixture, ethyl diazoacetate act obviously
as an efficient C-nucleophile. The highly reactive
ethoxycarbonylketene [32] and ethyl diazoacetate give
accordingly diethyl 2-diazo-3-oxoglutarate (Eq. (16)).
ethyl ester [33]. The nucleophilic addition of an acyl-
diazomethane to aldehydes or imines requires a base
to remove the inherent acidic hydrogen of the acyldia-
zomethane [34]. Based on the observed intermediates
1 and 2 and their reactions with nucleophiles, the for-
mation of the organic products in the cobalt-mediated
carbene transfer reactions of ethyl diazoacetate is de-
picted in Scheme 1.
In summary, the presented highly efficient octacar-
bonyl dicobalt-catalyzed selective transformation of
ethyl diazoacetate into ethyl-2-diazo-3-oxoglutarate or
into various unsymmetrical malonic acid derivatives
might be a useful method in synthetic chemistry.
4. Experimental
4.1. General comments
Handling of the complexes was carried out un-
der an atmosphere of dry (P4O10) and deoxygenated
(BTS contact) argon or carbon monoxide utilizing
standard Schlenk techniques [35]. Solvents were
dried and distilled under an atmosphere of argon or
carbon monoxide according to standard procedures
(16)
A similar nucleophilic addition of ethyl diazoacetate
to benzoylketene was reported to give the correspond-
ing product, 2-diazo-3,5-dioxo-5-phenylpentanoicacid

64
R. Tuba, F. Ungva´ry / Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
[36]. IR spectra were recorded on a Specord IR 75
Carl Zeiss Jena spectrometer using 0.0265, 0.0765, or
0.212 mm CaF2 solution cells, calibrated by the inter-
N, 12.27. Found: C, 47.32; H, 5.24; N, 12.03. IR
(n-hexane) 2137 (εM = 635 cm2/mmol), 1747 (εM
=
588 cm2/mmol), 1724 (εM = 867 cm2/mmol), 1672
ference method [37]. H, H, and 13C NMR spectra
were recorded on a Varian Unity 300 spectrometer
at 300, 46, and 75.42 MHz, respectively. Chemical
shifts were referenced to residual solvent signals and
reported in ppm relative to TMS (δ 0 ppm). Mass
spectra were obtained on a HP 5890II/5971 GC–MSD
at 70 eV using a 25 m HP5, 0.2 ␮m column. Gas chro-
matographic analyses were performed on a HP 5890
instrument with FID, using a SPB 1 30 m, 0.32 ␮m
column. TLC tests were performed on Whatman
MK6F silica gel 40 Å analytical plates. The Rf values
refer to TLC tests using Et2O:CH2Cl2 = 1:9. Oc-
tacarbonyl dicobalt was prepared by a literature pro-
cedure [38], and was double recrystallized under an
atmosphere of carbon monoxide first from methylene
chloride and then from n-heptane. All other reagents
and solvents were obtained from Sigma–Aldrich.
Column chromatography was carried out using silica
gel, 200–400 mesh, 60 Å. Microanalyses were per-
formed using a CHNS-O EA1108-Elemental Analyser
(Carlo Erba).
(εM = 475 cm2/mmol) cm−1
.
1H NMR (CDCl3) δ
1
2
1.25 (t, 3H), 1.30 (t, 3H), 3.83 (s, 2H), 4.17 (q,
2H), 4.27 (q, 2H) ppm. 13C NMR (CDCl3) δ 14.01
=
(CH3CH2), 14.20 (CH3CH2), 46.41 (CH2C O),
61.18 (C(N2)), 61.29 (CH3CH2), 61.68 (CH3CH2),
161.10 (CH2C(O)), 167.02 (C(N2)CO2Et), 185.21
(EtO2CCH2) ppm.
4.3. Preparation of malonic acid derivatives
The procedure described above for the prepara-
tion of EtO2CCH2C(O)C(N2)CO2Et was applied, but
60 mmol of the reagent BH (BH = MeOH, CD3OD
t
(99.8 at.% D), EtOH, BuOH, PhOH, Et2NH) was
added in addition to the solution of ethyl diazoacetate
(6.51 g, 57 mmol) in n-pentane (40 ml).
4.3.1. EtO2CCH2CO2Me
7.74 g, 53 mmol, 93%, Rf = 0.61. 1H NMR
(CDCl3) δ 1.26 (t, 3H), 3.36 (s, 2H), 3 73 (s, 3H), 4.19
(q, 2H) ppm. 13C NMR (CDCl3) δ 14.00 (CH3CH2),
41.36 (CH2), 52.45 (CH3O), 61.45 (CH3CH2), 166.47
(CO2CH2CH3), 167.03 (CO2CH3) ppm.
4.2. Preparation of EtO2CCH2C(O)C(N2)CO2Et,
diethyl 2-diazo-3-oxoglutarate
4.3.2. EtO2CCHDCO2CD3
Ethyl diazoacetate (6.51 g, 57 mmol) and n-pentane
(40 ml) were placed into a stainless-steel autoclave
(107 ml total capacity) containing an open glass-insert
loaded with Co2(CO)8 (171 mg, 0.5 mmol) and was
pressurized at room temperature with CO to 50 bar
pressure. Shaking at room temperature was started af-
ter the pressurized autoclave was first cooled to 0 ◦C
and then the precatalyst (Co2(CO)8) dissolved by turn-
ing the autoclave upside down. After 24 h the pressure
was slowly released through a cold trap (−79 ◦C) and
the gas was analyzed on a 25 m, 0.53 mm column
packed with 0.54 ␮m molecular sieve. The solvent
from the resulting reaction mixture was removed under
vacuum and the brown oily residue was subjected to
flash chromatography [10] on silica gel 60 Å, 200–400
mesh using 9:1 = methylene chloride:diethylether
as the eluent to give EtO2CCH2C(O)C(N2)CO2Et
as a pale yellow oil after concentration in vacuum
(5.93 g 26 mmol, 91% yield). Rf = 0.59. Analy-
sis: Calculated for C9H12O5N2: C, 47.37; H, 5.30;
7.95 g, 53 mmol, 93%, Rf = 0.61. 1H NMR
(CDCl3) δ 1.26 (t, 3H), 3.36 (s, 1H), 4.19 (q, 2H) ppm.
2H NMR (CHCl3) δ 3.36 (s, 1D), 3.73 (s, 3D) ppm.
13C NMR (CDCl3) δ 13.99 (CH3CH2), 41.34 (CHD),
52.00 (CD3O), 61.53 (CH3CH2), 166.45 and 167.03
(CO2) ppm.
4.3.3. EtO2CCH2CO2Et
8.2 g, 51 mmol, 90%, Rf = 0.63. IR (n-hexane)
ν(C O) 1762 (εM = 699 cm2/mmol), 1747 (εM
=
=
843 cm2/mmol) cm−1
.
1H NMR (CDCl3) δ 1.26 (t,
6H), 3.34 (s, 2H), 4.19 (q, 4H) ppm. 13C NMR
(CDCl3) δ 14.04(CH3CH2), 41.63 (CH2), 61.45
(CH3CH2), 166.58 (CO2) ppm.
t
4.3.4. EtO2CCH2CO2 Bu
9.2 g, 52 mmol, 92%, Rf = 0.67. 1H NMR (CDCl3)
δ 1.26 (t, 3H), 1.45 (s, 9H), 3.26 (s, 2H), 4.18 (q,
1
2H) ppm. [[39]; H NMR (CCl4) δ 1.28 (t, 3H), 1.45
(s, 9H), 3.13 (s, 2H), 4.15 (q, 2H) ppm.] 13C NMR

R. Tuba, F. Ungva´ry / Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
65
(CDCl3) δ 14.04 (CH3CH2), 27.87 (CCH3), 42.92
(CH2), 61.24 (CH3CH2), 81.94 (CCH3) 165.79 and
166.98 (CO2) ppm.
1707 (εM = 263 cm2/mmol), 1693 (εM = 213 cm2/
mmol) cm−1. Analysis: Calculated for C11H6O9Co2:
Co, 29.465. Found: Co, 29.04. 1H NMR (CDCl3)
δ 1.21 (t, 3H), 4.08 (q, 2H), 5.73 (s, 1H) ppm. 13C
NMR (CDCl3) δ 13.94 (CH3), 61.48 (CH2), 94.60
(CH), 178.34 (CO2), 201.85 (CO) ppm.
4.3.5. EtO2CCH2CO2Ph
10.7 g, 55 mmol, 96%, Rf = 0.69. 1H NMR
(CDCl3) δ 1.31 (t, 3H), 3.59 (5, 2H), 4.25 (q, 2H),
7.10–7.40 (m, 5H) ppm. 13C NMR (CDCl3) δ 14.06
(CH3CH2), 41.65 (CH2), 61.80 (CH3CH2), 121.3
(o-C6H5), 126.19 (p-C6H5), 129.48 (m-C6H5), 150.37
(ipso-C6H5), 165.13 and 166.16 (CO2) ppm.
4.5. Preparation of Co2(CO)6(CHCO2Et)2,
[di-µ2-(ethoxycarbonyl-(methylene)}-bis
(tricarbonyl-cobalt) (Co–Co)] (2)
To a solution of Co2(CO)8 (411 mg, 1.2 mmol)
in n-pentane (36 ml) ethyl diazoacetate (308 mg,
2.7 mmol) was added drop-wise at 5 ◦C under an at-
mosphere of CO and stirred for an additional 30 min
applying a continuous purging with argon. The sol-
vent was removed in vacuum and the residue was
dissolved in methylene chloride (3 ml) and purified
by column chromatography (silica gel 60 Å, 200–400
mesh, 450/10 mm) at 1 ◦C under argon using methy-
lene chloride as the eluent. The first fraction (30 ml)
gave after concentration 1 (46 mg, 8%). The sec-
ond fraction (260 ml) gave after concentration pure
2 as a yellow oil (403 mg, 73%). 2, IR (n-hexane)
4.3.6. EtO2CCH2C(O)NEt2
3.2 g, 17 mmol, 30%, Rf = 0.16. IR (n-hexane)
ν(C O) 1749 (εM = 336 cm2/mmol), 1666 (εM
=
=
854 cm2/mmol) cm−1. MS (70 eV, EI): m/z (%):
187 (78) [M+], 142 (52) [M+–OEt], 100 (57)
[M+–CH2CO2Et], 72 (100) [M+–EtO2C, Et, CH].
1H NMR (CDCl3) δ 1.11 (t, 3H), 1.16 (t, 3H), 1.25 (t,
3H), 3.27 (q, 2H), 3.35 (q, 2H), 3.39 (s, 2H), 4.18 (q,
2H) ppm. 13C NMR (CDCl3) δ 12.75 ((CH3CH2)2N),
14.07 (CH3CH2O), 41.23 ((CH3CH2)2N), 42.56
(CH2), 61.33 (CH3CH2O), 165.11 and 167.83
(CO2) ppm.
ν(C O) 2112 (εM = 1670 cm2/mmol), 2082 (εM
=
≡
4.4. Preparation of Co2(CO)7(CHCO2Et),
[µ2-{ethoxycarbonyl(methylene)}-µ2-(carbonyl)-
bis(tricarbonyl-cobalt) (Co–Co)] (1)
8246 cm2/mmol), 2063 (εM
=
3360 cm2/mmol),
2
≡
2049 (εM
(εM
=
6400 cm /mmol), ν(C O) 1702
=
647 cm2/mmol) cm−1. Analysis: Calcu-
lated for C14H12O10Co2:C, 36.706; H, 2.641; Co,
25.729. Found: C, 36.54; H, 2.81; Co, 25.49. 1H
NMR (CDCl3) δ 1.23 (t, 3H), 4.08 (q, 2H), 4.55
(s, 1H) ppm. 13C NMR (CDCl3) δ 14.30 (CH3),
61.70 (CH2), 113.41 (CH), 179.60 (CO2), 196.63
(CO) ppm.
A solution of Co2(CO)8 (342 mg, 1 mmol) and
ethyl diazoacetate (160 mg, 1.4 mmol) in n-pentane
(30 ml) was stirred under an atmosphere of carbon
monoxide at 0 ◦C for 3.5 h. The solvent was re-
moved in a vacuum and the residue was dissolved
in methylene chloride (3 ml) and purified by col-
umn chromatography (450/10 mm) at 1 ◦C under
argon using methylene chloride as the eluant. The
first fraction (40 ml) gave after concentration and
crystallization at −79 ◦C pure unreacted Co2(CO)8
(36 mg, 10.5%). The second fraction (90 ml) gave
after concentration pure 1 as an orange oil (340 mg,
82%). The third fraction (100 ml) gave after concen-
tration 2 as a yellow oil (2 mg, 4%). 1, IR (n-hexane)
4.6. Reaction of 1 with EtOH under CO pressure
A solution of complex 1 (20 mg, 0.05 mmol) and
ethanol (4.6 mg, 0.1 mmol) in n-hexane (5 ml) was
placed into a glass liner of a stainless-steel autoclave
(total capacity = 12.8 ml) and pressurized at room
temperature with CO to 50 bar and was shaken for
60 min. The resulting brown solution showed the
presence of Co2(CO)8 (0.05 mmol, 100%) and diethyl
malonate (0.049 mmol, 98%) by quantitative infrared
spectroscopy at 1857 (εM = 1735 cm2/mmol [11])
and at 1747 (εM = 843 cm2/mmol) cm−1, respec-
tively. Gas chromatographic analysis using n-nonane
ν(C O) 2112 (εM = 818 cm2/mmol), 2074 (εM
=
≡
5484 cm2/mmol), 2056 (εM = 3003 cm2/mmol), 2047
(εM = 5329 cm2/mmol), 2042 (εM = 5484 cm2/
mmol), ν(C–O) 1873 (εM = 876 cm2/mmol), 1866
(εM = 646 cm2/mmol), 1854 (εM = 1399 cm2/mmol),

66
R. Tuba, F. Ungva´ry / Journal of Molecular Catalysis A: Chemical 203 (2003) 59–67
internal standard gave 0.048 mmol, 96% diethyl mal-
4.10. Reaction of 2 with diethylamine under
onate (response factor = 0.347).
atmospheric pressure of CO
To a solution of diethylamine (14.6 mg, 0.2 mmol)
in n-octane (5.98 ml) in a thermostated glass reactor
connected to a gas burette at 10 ◦C under an atmo-
sphere of CO a 4.0 ml aliquot of a 0.05 mol/dm3 stock
solution of 2 in n-octane was injected. The initial
rate of CO uptake (2.8 × 10−5 mol/dm3 s) was calcu-
lated from the first nine readings (frequency: 20 s) of
the gas burette. In 3 h, 0.32 mmol CO was absorbed
and quantitative infrared spectroscopy revealed a
97% conversion of complex 2 into complex 1 with
a simultaneous formation of EtO2CCH2C(O)NEt2
(0.17 mmol). Flash chromatography on silica gel
60 Å (200–400 mesh) with Et2O/CH2Cl2 = 1:4 gave
28 mg, 74% isolated yield of EtO2CCH2C(O)NEt2.
4.7. Reaction of 2 with EtOH under CO pressure
A solution of complex 2 (23 mg, 0.05 mmol) and
ethanol (18.5 mg, 0.4 mmol) in n-hexane (5 ml) was
placed into a glass liner of a stainless-steel autoclave
(total capacity = 12.8 ml) and pressurized at room
temperature with CO to 50 bar and was shaken for
60 mm. The resulting brown solution showed the
presence of Co2(CO)8 (0.049 mmol, 98%) and di-
ethyl malonate (0.095 mmol, 95%) by quantitative
infrared spectroscopy. Diethyl malonate found by gas
chromatographic analysis was 0.093 mmol, 93%.
4.8. Reaction of 2 with EtO2CCHN2 under
atmospheric pressure of CO
Acknowledgements
To a solution of ethyl diazoacetate (23 mg,
0.2 mmol) in n-octane (5.98 ml) in a thermostated glass
reactor connected to a gas burette at 10 ◦C under an
atmosphere of CO a 4.0 ml aliquot of a 0.05 mol/dm3
stock solution of 2 in n-octane was injected. The ini-
tial rate of CO uptake (0.1×10−5 mol/dm3 s) was cal-
culated from the first 15 readings (frequency: 30 s) of
the gas burette. In 24 h, 0.28 mmol CO was absorbed
and quantitative infrared spectroscopy revealed a 94%
conversion of complex 2 into complex 1 with a simul-
taneous formation of EtO2CCH2C(O)C(N2)CO2Et
(0.18 mmol).
The authors thank the Hungarian Academy of
Sciences and the Hungarian Scientific Research Fund
for financial support under Grant No OTKA T037817.
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