Cobalt-mediated oligomerization reactions of amino-substituted acetylene derivatives

Article abstract of DOI:10.1016/j.jorganchem.2005.03.056

Reactions of the aminoacetylenes Et₂N-C≡C-R (R = SiMe ₃, SPh, PPh₂; 1a-c) with (η⁵- pentamethylcyclopentadienyl)bis(ethene)cobalt yield the corresponding (η⁵-pentamethylcyclopentadienyl)(η⁴- cyclobutadiene)cobalt complexes 2a-c. Treatment of 1-phenylthio-2- diethylaminoacetylene 1b with three equivalents of CpCo(CO)₂ leads to the 1,3-dicobalta-bicyclobutane derivative 3′b. The analogous compound 3′d and the trinuclear cobalt complex 4′d are obtained from the reaction of bis(diethylamino)acetylene (1d) with (η⁵- cyclopentadienyl)bis(ethene)cobalt. Treatment of 1d with excess Co ₂(CO)₈ yielded unexpectedly a mixture of di- and tetranuclear cobalt-carbene complexes 7 and 8, most likely formed through interaction of oxygen. A designed route to 7 and 8 is found by reacting the tetraethyloxamide 6 with Co₂(CO)₈ and Co ₄(CO)₁₂, respectively. The catalytic cyclotrimerization reaction of the aminothioacetylene derivative 1b with [CpCo(CO)₂] or [Co₂(CO)₈] leads to tris(phenylthio)-tris(diethylamino) benzene derivative 9. The new compounds have been characterized by NMR spectroscopy, mass spectrometry as well as by X-ray structure analyses for 3′d, 7 and 8. The molecular structure of 3′d in the crystal reveals the presence of a bicyclobutane framework with a Co-Co distance (2.36 A?) lying between a single and a double bond, whereas the former CC triple bond is completely ruptured (2.13 A?). The Co-C(carbene) distances in 7 and 8 are 1.93 and 1.95 A?, respectively.

Full text of DOI:10.1016/j.jorganchem.2005.03.056

Journal of Organometallic Chemistry 690 (2005) 3251–3259
www.elsevier.com/locate/jorganchem
Cobalt-mediated oligomerization reactions of
amino-substituted acetylene derivatives
*
Avijit Goswami, Claus-Jurgen Maier, Hans Pritzkow, Walter Siebert
¨
Anorganisch-Chemisches Institut der Universita¨t, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Received 23 November 2004; revised 2 March 2005; accepted 2 March 2005
Available online 26 May 2005
Dedicated to Professor Peter I. Paetzold on the occasion of his 70th birthday
Abstract
Reactions of the aminoacetylenes Et2N–C„C–R (R = SiMe3, SPh, PPh2; 1a–c) with (g5-pentamethylcyclopentadienyl)bis(eth-
ene)cobalt yield the corresponding (g5-pentamethylcyclopentadienyl)(g4-cyclobutadiene)cobalt complexes 2a–c. Treatment of 1-
phenylthio-2-diethylaminoacetylene 1b with three equivalents of CpCo(CO)2 leads to the 1,3-dicobalta-bicyclobutane derivative
30b. The analogous compound 30d and the trinuclear cobalt complex 40d are obtained from the reaction of bis(diethylamino)acet-
ylene (1d) with (g5-cyclopentadienyl)bis(ethene)cobalt. Treatment of 1d with excess Co2(CO)8 yielded unexpectedly a mixture of di-
and tetranuclear cobalt-carbene complexes 7 and 8, most likely formed through interaction of oxygen. A designed route to 7 and 8 is
found by reacting the tetraethyloxamide 6 with Co2(CO)8 and Co4(CO)12, respectively. The catalytic cyclotrimerization reaction of
the aminothioacetylene derivative 1b with [CpCo(CO)2] or [Co2(CO)8] leads to tris(phenylthio)-tris(diethylamino)benzene derivative
9. The new compounds have been characterized by NMR spectroscopy, mass spectrometry as well as by X-ray structure analyses for
30d, 7 and 8. The molecular structure of 30d in the crystal reveals the presence of a bicyclobutane framework with a Co–Co distance
˚
˚
(2.36 A) lying between a single and a double bond, whereas the former CC triple bond is completely ruptured (2.13 A). The Co–
˚
C(carbene) distances in 7 and 8 are 1.93 and 1.95 A, respectively.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Aminoacetylenes; Benzene derivatives; Cobalt-carbene complexes; (Cyclobutadiene)cobalt complexes; Dinuclear cobalt complexes
1. Introduction
atom of the amino group with the adjacent sp carbon
atom in aminoalkynes, one can expect a variety of inter-
esting products from the reactions of transition metal
complexes with these heteroatom-substituted acetylenes.
Very recently, we have reported cobalt-mediated cyclo-
addition reactions of borylacetylenes [5]. The reactions
of borylacetylenes with the cobalt complexes CpCo(CO)2
and Co2(CO)8 did not give any carbene, carbyne or mul-
tinuclear cobalt complexes [3,5]. On the other hand, King
et al. [6] studied thermal reactions of C5H5M(CO)2
(M = Co, Rh) with the mono- and diaminoacetylenes
1a and 1d (Et2N–C„C–R, R = SiMe3, NEt2), in which
trimetallic complexes (C5H5)3M3C2(NEt2)(SiMe3) and
(C5H5)3M3C2(NEt2) were obtained by complete rupture
Over the last few decades, transition metal-mediated
cyclooligomerization of alkynes is a general and power-
ful method for constructing a vast range of cyclization
products [1]. It is astounding that among the many re-
ported reactions in this context [2], very few works have
so far been done with boryl- [3] and aminoalkynes [4].
Due to the possibility of interaction of the empty orbital
at the boron atom with the p system of the triple bond in
borylacetylenes and the lone electron pair of the nitrogen
*
Corresponding author. Fax: +49 6221 54 5609.
E-mail address: walter.siebert@urz.uni-heidelberg.de (W. Siebert).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.03.056

3252
A. Goswami et al. / Journal of Organometallic Chemistry 690 (2005) 3251–3259
of the carbon–carbon triple bond of the diaminoacety-
lene to form trigonal-bipyramidal clusters with carbon
atoms at the apical and transition metals at the equato-
rial vertices. It has also been found that a carbon–carbon
double bond in bis(1,3-dimethylimidazolidin)-2-ylidene
is cleaved by CpCo(CO)2 to form the corresponding
mononuclear cobalt-carbene complex [7]. The insertion
of 1-dialkylaminoacetylenes into the metal–carbene
bond has been studied by Do¨tz et al. [8], who noticed that
nitrogen atoms flanking carbon–carbon multiple bonds
cause an increase of their susceptibility to cleavage by
the transition metal complexes. This unique nitrogen
atom effect in amino-substituted acetylenes encouraged
us to perform further studies. Here, we report reactions
of the diethylaminoacetylenes 1a–d with cobalt
complexes.
(d = 2.12 ppm) for C5Me5 are found. The 29Si NMR
spectrum of 2a features a signal at d = ꢀ16.2 ppm.
The NMR spectroscopic data of 2a as well as of 2b
and 2c (see below) do not allow to distinguish between
the two possible geometrical isomers (cis- and trans-),
formed by head-to-head and head-to-tail dimerization
of 1a–c, respectively. This problem was addressed by
analyzing the major peaks in terms of the degradation
of the cyclobutadiene ring in the mass spectra. In gen-
eral, three different acetylenes are released from the
cis-isomer, whereas only one acetylene is detected in
the case of the trans-isomer [12]. The mass spectrum of
2a shows that only one acetylene is released from the
molecular ion, which confirms the identity of the
1
trans-isomer. The H NMR spectrum of 2b exhibits a
triplet (d = 1.24 ppm), a quartet (d = 3.06 ppm) and a
multiplet for C6H5 in addition to a singlet (d = 2.11
ppm) for the pentamethylcyclopentadienyl ligand. In
the 13C NMR spectrum of 2b, two signals (d = 70.82
and 89.82 ppm) for the two quarternary carbon atoms
of the C4 ring and a signal (d = 84.82 ppm) for the
C5Me5 ligand are detected. In the mass spectrum, the
molecular ion peak appears with the correct isotopic
2. Results and discussion
2.1. (g4-Cyclobutadiene)cobalt complexes 2a–c
In 1965, Pettit and coworkers [9] reported the first
generation of the tricarbonyl(g4-cyclobutadiene)iron
complex. Among the various synthetic methods, the
reactions of alkynes with transition metal complexes in
particular have been studied extensively during the past
four decades. In an analogous manner, reactions of
diethylaminoacetylenes 1a–c with (g5-pentamethylcyclo-
pentadienyl)bis(ethene)cobalt in a 2:1 ratio gave the
corresponding (g5-pentamethylcyclopentadienyl)(g4-cy-
clobutadiene)cobalt complexes 2a–c in good yield
(Scheme 1) [10]. However, the analogous complex
CpCoC4(NEt2)4 (20d, prime indicates C5H5 ligand versa
C5Me5 in 2) (Scheme 3) was not obtained from the reac-
tion of CpCo(C2H4)2 with the electron-rich (Et2N)2C2
(1d) [11]. In addition to 2a–c, trace amounts of dicobalt
complexes 3a–c were detected in the mass spectra.
The liquid cobalt complexes 2a–c were purified by
1
pattern. The H NMR spectrum of 2c features a triplet
(d = 1.27 ppm), a quartet (d = 3.05 ppm) and two multi-
plets (d = 7.29 and 7.62 ppm) for PPh2 in addition to a
singlet (d = 1.97 ppm) for the pentamethylcyclopenta-
dienyl ligand. In the 13C NMR spectrum of 2c, two sig-
nals (d = 68.95 and 94.69 ppm) for the two quarternary
carbon atoms of the C4 ring and a signal (d = 87.65
ppm) for the C5Me5 ligand are detected. The 31P
NMR spectrum of the cobalt complex 2c shows a singlet
at d = ꢀ13.5 ppm. EI-MS data confirm the identity of
compound 2c through the appearance of the molecular
ion peak with the expected isotopic pattern. In both
cases, no evidence for the presence of the cis-isomers
was found by MS.
2.2. Synthesis of di- and trinuclear cobalt complexes 30b,
30d and 40d
1
column chromatography and characterized by H, 13C,
29Si, 31P NMR spectroscopy as well as by mass spec-
trometry. In the 1H NMR spectrum of 2a, a singlet
(d = 0.15 ppm) for SiMe3, a triplet and a quartet
(d = 1.21 and 2.93 ppm) for the ethyl group and a singlet
As mentioned in Section 1, King et al. [6] have noticed
that treatment of the aminoacetylene derivatives 1a and
1d with CpCo(CO)2 at high temperature (130–140 ꢁC)
led to the trimetallic clusters (CpCo)3C2(SiMe3)(NEt2)
(40a) and (CpCo)3C2(NEt2)2 (40d), respectively. How-
ever, the reaction of the diethylaminoacetylene derivative
1b with CpCo(CO)2 in a 1:3 ratio at 115 ꢁC did not give
the trimetallic cluster 40b, but the dinuclear species 30b
was obtained in 41% yield (Scheme 2) [10]. Compound
Cp*Co(C2H4)2
NEt2
R
hexane
∆
Co
+
1
30b, a brown oil, was characterized by H, 13C NMR
(Cp*Co)2C2R(NEt2)
(trace)
+
2 Et2N
C
C
R
1
spectroscopy as well as by mass spectrometry. The H
Et2N
R
NMR spectrum of 30b shows a triplet (d = 1.21 ppm)
and a quartet (d = 3.03 ppm) in addition to the Cp reso-
nance (d = 5.03 ppm). In the 13C NMR spectrum, two
signals are found at d = 12.19 and 47.32 ppm for ethyl
a
b
c
a
b
c
3
R
a
1
SiMe3 SPh PPh2
b
c
2
R
SiMe SPh PPh2
SiMe SPh PPh2
R
3
3
Scheme 1.

A. Goswami et al. / Journal of Organometallic Chemistry 690 (2005) 3251–3259
3253
group along with the signal for the Cp resonance
NEt2
C
(d = 86.42 ppm). The 13C resonances of the two different
quarternary carbon atoms of the C–NEt2 and C–SPh
groups could not be resolved, possibly owing to broaden-
ing through coupling with the quadrupolar cobalt atoms.
The formation of the dicobalt complex 30b was sup-
ported by EI-MS through the appearance of the molecu-
lar ion peaks with the expected isotopic pattern.
Although the spectroscopic data clearly indicate the
presence of a dinuclear cobalt complex, it was not possi-
ble to deduce the connectivity in 30b with respect to co-
balt–cobalt and carbon–carbon bonding (see Scheme 2).
As shown in Scheme 3, the reaction of bis(diethyl-
amino)acetylene 1d with CpCo(C2H4)2 in a 2:1 ratio
did not give rise to the (g4-cyclobutadiene)cobalt com-
plex (20d), but formation of the dinuclear cobalt com-
plex 30d in good yield occurred by the complete
breaking of the carbon–carbon triple bond in 1d [11].
The black crystals were characterized by 1H NMR spec-
troscopy, mass spectrometry and an X-ray structure
2 (Et2N)2C2
Cp
Cp
1d
Co
Co
i: n = 4
Co
+
4'd
i: n = 1
C
Cp
n CpCo(C2H4)2
NEt2
i
Cp
Cp
NEt2
Et2N
Et2N
Co
Co
Co
C
C
NEt2
NEt2
Et2N
2'd
3'd
Scheme 3.
Co1A
Co1
1
analysis. The H NMR spectrum of 30d shows a triplet
(d = 0.93 ppm) and a quartet (d = 3.52 ppm) in addition
to one singlet (d = 4.90 ppm) for C5H5 (ratio 6:4:5).
When the reagents were reacted in a 1:2 ratio at room
temperature, the known [6a] green cluster 40d was ob-
tained (17% yield, characterized by EI-MS). Obviously,
the formation of the trigonal-bipyramid cluster 40d oc-
curred by insertion of a CpCo complex fragment into
30d, which causes the 1,3-dicobalta-bicyclo[1,1,0]butane
to transform into the trimetallic closo-cluster 40d having
2n + 2 = 12 SE. EI-MS data confirm the identity of com-
plex 40d through the appearance of the molecular ion
peak with the expected isotopic pattern.
The structure of 30d has been determined by perform-
ing a single crystal X-ray diffraction analysis, which
reveals a bicyclobutane C2Co2-framework. Fig. 1 exhib-
its a Co–Co bond and two bridging carbon atoms; each
cobalt atom carries a g5-bonded Cp ligand and each car-
bon atom (C1, C1A) bears a diethylamino group. Com-
plex 30d possesses a C2 axis passing through the middle
of Co–Co bond and C1–C1A vector. The bonding
parameters of 30d show that the Co1–C1 and Co1–
C1
C1A
N1A
N1
Fig. 1. Molecular structure of 30d in the solid state. Selected bond
˚
lengths (A) and bond angles [ꢁ]: Co1–Co1A, 2.366(1); Co1–C1,
1.830(3); Co1–C1A, 1.821(3); C1–C1A, 2.131; C1–N1, 1.312(4) and
C1–Co1–Co1A, 49.5(1); C1A–Co1–Co1A, 49.8(1); C1–Co1–C1A,
71.4(2); Co1–C1–Co1A, 80.8(1); Co1–C1–N1, 139.0(2); Co1A–C1–
N1, 139.7(2).
tween cobalt atoms, C1 and C1A. The solid state struc-
ture implies that the cobalt–cobalt bond is shorter than
˚
the Co–Co single bond (2.48 A) [14] and longer than
˚
Co@Co bond (2.18 A) [15]. Formation of organometal-
˚
lic complexes by breaking of a carbon–carbon triple
bond is also known for alkynes without amino substitu-
ents, as Vollhardt and coworkers [15,16], Yamazaki
et al. [17], and Butenscho¨n and coworkers [18] have re-
ported examples of similar metallocarbyne complexes.
C1A are rather short (1.82–1.83 A) in comparison to
˚
other cobalt–carbenes (1.88–2.10 A) [13]. The almost
equal bond distances between cobalt (Co1 and Co1A)
and the Ccarbyne atoms (C1 and C1A) suggest partial
double bond character due to electron delocalization be-
NEt2
C
Cp
Cp
3 CpCo(CO)2
(CpCo)2C2(NEt2)(SPh)
Co
Co
Et2NC2SPh
Co
C
toluene
Cp
3'b
4'b
1b
SPh
Scheme 2.

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A. Goswami et al. / Journal of Organometallic Chemistry 690 (2005) 3251–3259
NEt2
Et2N
1d
NEt2
C
Co2(CO)8
C
Co2(CO)8
- [CO2]
(CO)7Co2
C
NEt2
NEt2
O
7
O
O
C
C
C
OC
CO
Et2N
O
Co
NEt2
Co4(CO)12
- [CO2]
Et2N
NEt2
6
(CO)11Co4
C
Co
NEt2
OC
CO
O
8
C
O
5
Scheme 4.
2.3. Di- and tetranuclear cobalt-carbene complexes 7 and
8
N1
C1
An attempt to prepare the (acetylene)hexacarbonyl-
dicobalt cluster 5 from the reaction of bis(diethyla-
mino)acetylene (1d) with excess Co2(CO)8was not
successful, but the di- and tetranuclear cobalt-carbene
complexes 7 and 8 were obtained in low yield after the
reaction mixture had been stored for a long time at
room temperature [11]. To clarify their formation, the
novel Fischer-carbene complexes were obtained by a de-
signed route: treatment of the oxamide 6 [19] with
Co2(CO)8 and Co4(CO)12, respectively, gave the ex-
pected carbene complexes in moderate yields (Scheme
4) [10].
This indicates that in the former attempt the diamino-
acetylene 1d most likely was first oxidized to [Et2N–
C(O)]2 (6) or to [Et2N–C(O)–C(NEt2)]2, which on fur-
ther reaction with an excess of dicobaltoctacarbonyl
led to the cobalt-carbene complexes, characterized by
1H, 13C NMR spectroscopy, IR spectroscopy and mass
spectrometry. From the integration of the 1H NMR
peaks of 7 and 8, it is clear, the signals for the three dif-
ferent ethyl groups in amide and amino are not overlap-
ping with each other. However, correlation
spectroscopic measurements (H,H-COSY, HMQC,
HMBC) were carried out as suggested by a referee,
which reconfirmed our interpretation. Due to fast ex-
change of carbonyl groups [20] and the quadrupole mo-
ment of cobalt atoms [6b,21], only one small broad
signal is detected in the 13C NMR spectrum of com-
Co1
O1
Co2
C2
N2
Fig. 2. Molecular structure of 7 in the solid state. Selected bond
˚
lengths (A) and bond angles (ꢁ): C1–Co1, 1.930(2); C1–N1, 1.303(2);
C1–C2, 1.514(2); C2–N2, 1.342(2); Co1–Co2, 2.715(1) and Co1–C1–
N1, 129.5(1); Co1–C1–C2, 114.4(1); N1–C1–C2, 116.1(1); C1–Co1–
Co2, 173.67(4).
N1
Co4
Co1
C1
Co3
C2
Co2
N2
pound 7. The IR-spectrum of 8 shows bands at
ꢀ1
~
m ¼ 1974; 1996; 2009; 2016 and 2065 cm for termi-
O1
nal CO ligands and a weak band is observed at
ꢀ1
~
m ¼ 1846 cm for bridging CO group. The band for
the CO group of the carbene ligand is found at
ꢀ1
~
m ¼ 1652 cm
.
The cobalt complexes 7 and 8 were characterized by
performing a single crystal X-ray structure analysis
(Figs. 2, 3). Dark red crystals of 7 were grown from a
solution in hexane. The molecular structure of 7 shows
the Co2(CO)7 framework; the Co1 and Co2 each atom
is surrounded by three terminal CO ligands with stag-
Fig. 3. Molecular structure of 8 in the solid state. Selected bond
˚
lengths (A) and bond angles (ꢁ): C1–Co1, 1.955(3); C1–N1, 1.305(4);
C1–C2, 1.509(4); C2–N2, 1.353(4); Co1–Co2, 2.495(1); Co1–Co3,
2.473(1); Co2–Co3, 2.436(1); Co1–Co4, 2.544(1); Co2–Co4, 2.522(1);
Co3–Co4, 2.506(1) and Co1–C1–N1, 130.0(2); Co1–C1–C2, 115.9(2);
N1–C1–C2, 113.1.6(3); C1–Co1–Co2, 114.7(1); C1–Co1–Co3,
110.9(1); C1–Co1–Co4, 170.7(1).

A. Goswami et al. / Journal of Organometallic Chemistry 690 (2005) 3251–3259
3255
gered conformation and Co2 atom bears an additional
3. Conclusion
terminal CO group, which lies in line with the metal–me-
tal bond axis. The solid state structure of 7 indicates an
almost linear C1–Co1–Co2 moiety with a considerably
Reactions of diethylamino-substituted acetylenes
with Cp*Co(C2H4)2, CpCo(C2H4)2 and Co2(CO)8 have
been studied. The reactions of aminoalkyne derivatives
1a–d with bis(ethene)cobalt complexes discovered dur-
ing this work indicate two different modes of interac-
tions: (1) cyclization reactions to form mononuclear
(g4-cyclobutadiene)cobalt complexes 2a–c which involve
the interactions of the (C5Me5)Co fragment with the
carbon–carbon triple bond of the aminoacetylenes; (2)
complete cleavage of the carbon–carbon triple bond to
give the di- and trinuclear (C5H5)Co complexes 30d
and 40d containing the diethylaminocarbyne units. The
di- and tetranuclear cobalt-carbene complexes 7 and 8
are obtained from the reactions of tetraethyloxamide 6
with dicobaltoctacarbonyl and tetracobaltdodecacar-
bonyl, respectively. The tris(phenylthio)-tris(diethyla-
mino)benzene derivative 9 is formed from the catalytic
[2 + 2 + 2]-cyclotrimerization reaction of the aminoacet-
ylene 1b with [CpCo(CO)2] or [Co2(CO)8].
˚
longer Co–Co bond distance (2.715 A) than that in
˚
Co2(CO)8 (2.58 A).
Black crystals of 8 were obtained from a solution in
hexane, which crystallized with a hexane molecule in a
special position (inversion center). The four cobalt
atoms form a tetrahedral cluster with Co–Co distances
˚
of 2.436 to 2.544 A. The arrangement of three l2-bridg-
ing CO and nine terminal ligands is identical with that in
Co4(CO)12, in which one CO is replaced by the carbene
ligand. The bonding in the carbene ligands in 7 and 8 is
˚
very similar [Co1–C1: 1.930 vs. 1.955 A, C1–N1: 1.303
0
˚
˚
vs. 1.305 A; 3 d: 1.312 A]. The planes C1–Co1–N1–C2
and C2–C1–O1–N2 are almost perpendicular (88.7ꢁ vs.
85.1ꢁ).
2.4. [2 + 2 + 2]-Catalytic cyclotrimerization reaction
In refluxing toluene, only the aminothioacetylene
derivative 1b formed the light yellow tris(phenylthio)-
tris(diethylamino)benzene derivative 9 (70% yield) in
the presence of a catalytic amount of [CpCo(CO)2] or
[Co2(CO)8] (Scheme 5) [10]. The oily 9, well soluble in
common organic solvents, was purified by column chro-
matography and characterized by 1H and 13C NMR
spectroscopy as well as by mass spectrometry.
The 1H NMR spectrum of 9 exhibits a triplet
(d = 1.34 ppm) and a quartet (d = 3.17 ppm) in addi-
tion to the multiplets in the region d = 7.14 ꢀ 7.51
ppm. In the 13C NMR spectrum, two signals
(d = 121.3 and 132.5 ppm) are assigned to the ipso-
carbon atoms of the symmetrical central benzene ring.
No 13C signals for unsymmetric central aromatic ring
were found. Compound 9 was identified by mass spec-
trum through the appearance of the molecular ion
peak with the expected isotopic pattern. Attempts to
obtain the corresponding benzene derivatives from
the reactions of aminoalkynes 1a, 1c and 1d [11] with
catalytic amounts of [CpCo(CO)2] or [Co2(CO)8] were
not successful, which may be explained on steric
grounds.
4. Experimental
General. All reactions were performed under nitrogen
atmosphere using standard Schlenk techniques. Solvents
were dried with the appropriate drying agents and dis-
tilled under nitrogen atmosphere. Glasswares were dried
with heat-gun under high vacuum. Column chromatog-
raphy: silica gel 60 (Machery-Nagel). H, 13C and 31P
1
NMR: Bruker AC 200 spectrometer; 1H and 13C spectra
were referenced to (CH3)4Si and 31P spectra to H3PO4.
IR: Bruker Vector 22 FT-IR. Mass spectra were ob-
tained on Finnigan MAT 8230 plus spectrometers using
the EI and FAB techniques. Tetraethyloxamide (6) [19],
1-trimethylsilyl-2-diethylaminoacetylene (1a) [22], 1-
phenylthio-2-diethylaminoacetylene (1b) [23], 1-diph-
enylphosphino-2-diethylaminoacetylene
(1c)
[24],
bis(diethylamino)acetylene (1d) [25], (cyclopentadidie-
nyl)-bis(ethene)cobalt [26] and (pentamethylcyclopenta-
dienyl)-bis(ethene)cobalt [27] were prepared according
to the literature procedures. Dicobaltoctacarbonyl and
tetracobaltdodecacarbonyl were purchased from Strem.
SPh
NEt2
SPh
Et2N
PhS
i
i
(Et2N)3R3C6
3 Et2N
R
C
C
R = SiMe3, PPh2, NEt2
a
b
c
d
1
NEt2
R
SPh PPh2 NEt2
SiMe3
i 5 mole % [CpCo(CO)2] or
9
[Co2(CO)8]
Scheme 5.

3256
A. Goswami et al. / Journal of Organometallic Chemistry 690 (2005) 3251–3259
[Et2N–C(O)–C(NEt2)]2 [11] not previously reported in
the literature was prepared by the air oxidation of two
equivalents of bis(diethylamino)acetylene. The com-
pound was characterized only by EI-MS (m/z = 368).
4.2. Dinuclear cobalt complex 30b
To a stirred solution of (cyclopentadienyl)dica-
rbonylcobalt (1.18 g, 6.6 mmole) in 40 ml of toluene,
1-phenylthio-2-diethylaminoacetylene (1b) (450 mg, 2.2
mmole) was added slowly at 0 ꢁC. The reaction mixture
was heated at 115 ꢁC for 3 d. After filtration, the solvent
was removed by HV and the black residue was subjected
to column chromatography (SiO2; hexane:toluene 1:2).
4.1. (g5-Pentamethylcyclopentadienyl)-[g4-bis(trimethyl-
silyl)–bis(diethylamino)cyclobutadiene]cobalt(I) (2a),
(g5-pentamethylcyclopentadienyl)-[g4-bis(phenylthio)–
bis(diethylamino)-cyclobutadiene]cobalt(I) (2b), (g5-
pentamethylcyclopentadienyl)-[g4-bis(diphenylphos-
phino)–bis(diethylamino)cyclobutadiene]cobalt(I) (2c)
1
30b: 0.41 g (41%) brown oil. H NMR (200.1 MHz,
3
CDCl3): d = 1.21 [t, J(H,H) = 7.2 Hz, 6H; CH2CH3],
3
3.03 [q, J(H,H) = 7.1 Hz, 4H; CH2CH3], 5.03 (s, 10H,
Cp-H), 7.08–7.41 (m, 5H, C6H5) ppm. 13C NMR (50.3
MHz, CDCl3): d = 12.19 (CH2CH3), 47.32 (CH2CH3),
86.42 (CpC), 124.5, 125.4, 129.0, 138.9 (phenylthio)
ppm. MS (70 eV, EI): m/z (%) = 454 (65) [M+ + 1].
The corresponding aminoacetylene (1a: 0.41 g, 1b:
0.50 g, 1c: 0.68 g; 2.43 mmole) and (pentamethylcyclo-
pentadienyl)bis(ethene)cobalt (0.30 g; 1.21 mmole) were
heated at 70 ꢁC in hexane for 2 d. After cooling, the dark
solution was filtered and solvent was removed by HV.
The crude product was purified by column chromatog-
raphy (SiO2; hexane:toluene 1:1).
MS (70 eV, HR-EI): m/z (%) = 454.0425 (30) [M+ + 1;
12
C
1H2659Co214N32S: 454.0449]; Dmmu = ꢀ2.4.
22
4.3. Dinuclear cobalt complex 30d
1
2a: 0.40 g (62%) yellow oil. H NMR (200.1 MHz,
CDCl3): d = 0.15 [s, 18H, SiMe3], 1.21 [t,
3J(H,H) = 7.2 Hz, 12H; CH2CH3], 2.12 [s, 15H, Cp*-
To a stirred solution of (cyclopentadienyl)-bis(eth-
ene)cobalt (400 mg, 2.2 mmole) in 10 ml of pentane,
the bis(diethylamino)acetylene (1d) (750 mg, 4.5 mmole)
was added slowly at ꢀ70 ꢁC. After stirring overnight at
room temperature, the green solution was filtered, leav-
ing black needles in the frit. The solvent of the filtrate
was removed and the black residue was washed several
times with toluene and THF. Solvents were evaporated
by HV leaving a black residue. The mass spectra of
the black needles and the black residue were identical.
3
CH3], 2.93 [q, J(H,H) = 7.1 Hz, 8H; CH2CH3] ppm.
13C NMR (50.3 MHz, CDCl3): d = 0.95 (SiMe3), 11.29
(Cp*-CH3), 12.69 (CH2CH3), 47.70 (CH2CH3), 64.23,
91.58 (Cring), 89.98 (Cp*C) ppm. 29Si NMR (39.7
MHz, CDCl3): d = ꢀ16.2 ppm. MS (70 eV, EI): m/z
(%) = 532 (65) [M+], 470 (70) [M+ ꢀ NEt2], 363
[M+ ꢀ Me3SiC2NEt2], 194 (35) [Cp*Co+]. MS (70 eV,
12
HR-EI): m/z (%) = 532.3099 (50.0) [M+;
C
28
1H53-
59Co14N228Si2: 532.3079]; Dmmu = 2.0.
2b: 0.51 g (69%) brown oil. H NMR (200.1 MHz,
CDCl3): d = 1.24 [t, J(H,H) = 7.2 Hz, 12H; CH2CH3],
1
30d: 300 mg (65%). H NMR (200.1 MHz, C6D6):
1
3
d = 0.93 [t, J(H,H) = 7.1 Hz, 12H; CH2CH3], 3.52 [q,
3
3J(H,H) = 7.1 Hz, 8H; CH2CH3], 4.90 (s, 10H, C5H5).
MS (70 eV, EI): m/z (%) = 416 (70) [M+], 387 (25)
[M+ ꢀ Et], 330 (36) [M+ ꢀ NEt2CH2], 292 (5)
[M+ ꢀ CpCo], 124 (20) [CpCo], 28 (46) [C2H4].
3
2.11 [s, 15H, Cp*-CH3], 3.06 [q, J(H,H) = 7.1 Hz, 8H;
CH2CH3], 7.15–7.41 (m, 10H, C6H5) ppm. 13C NMR
(50.3 MHz, CDCl3): d = 11.18 (Cp*-CH3), 13.18
(CH2CH3), 48.31 (CH2CH3), 70.82, 89.82 (C4ring), 84.82
(Cp*C), 124.7, 125.4, 128.8, 138.3 (phenylthio) ppm.
MS (70 eV, EI): m/z (%) = 604 (65) [M+], 496 (20)
[M+ ꢀ SPh], 399 (2) [M+ ꢀ PhSC2NEt2], 194 (35)
4.4. Di- and tetranuclear cobalt-carbene complexes 7 and
8
[Cp*Co+]. MS (70 eV, HR-EI): m/z (%) = 604.2371
4.4.1. Procedure A
12
(82.5) [M+;
1.5.
C
34
1H4559Co14N232S2: 604.2356]; D mmu=
To a solution of 1.03 g of dicobaltoctacarbonyl (3.01
mmole) in hexane, bis(diethylamino)acetylene 1d was
added slowly at ꢀ30 ꢁC. After warming up to room tem-
perature, the reaction mixture was stirred for 3 d and fil-
tered. The solvent was evaporated by HV and the
residue purified by column chromatography (Al2O3,
hexane). After long time storage in hexane at room tem-
perature, a mixture of deep-red (7) and black crystals (8)
was obtained (total yield 30 mg).
1
2c: 0.59 g (65%) yellow oil. H NMR (200.1 MHz,
3
CDCl3): d = 1.27 [t, J(H,H) = 7.2 Hz, 12H; CH2CH3],
1.97 [s, 15H, Cp*-CH3], 3.05 [q, J(H,H) = 7.2 Hz, 8H;
3
CH2CH3], 7.29, 7.62 (m, 20H, C6H5) ppm. 13C NMR
(50.3 MHz, CDCl3): d = 10.94 (Cp*-CH3), 13.16
(CH2CH3), 48.06 (CH2CH3), 68.95, 94.69 (C4ring),
87.65 (Cp*C), 128.3, 131.9, 132.3, 139.4 (diph-
enylphosphino) ppm. 31P NMR (80.9 MHz, CDCl3):
d = ꢀ13.5. MS (FAB+): 756 (10) [M+], 563 (80)
[M+ ꢀ Cp* + 1], 475 (5) [M+ ꢀ Ph2PC2NEt2]. MS (70
4.4.2. Procedure B
To a solution of tetraethyloxamide 6 (0.11 g, 0.55
mmole) in 20 ml of hexane, cobaltcarbonyl complex
(dicobaltoctacarbonyl: 0.19 g; tetracobaltdodecacar-
eV, HR-FAB): m/z (%) = 756.3195 (12.0) [M+;
12
C
1H5559Co14N231P2: 756.3172]; Dmmu = 2.3.
46

A. Goswami et al. / Journal of Organometallic Chemistry 690 (2005) 3251–3259
3257
bonyl: 0.31 g; 0.55 mmole) was added slowly at ꢀ30 ꢁC.
The reaction mixture was allowed to stir for 3 d at room
temperature. The dark solution was filtered and purified
by column chromatography on aluminiumoxide (5%
water) with hexane as elute. The purified hexane solu-
tion was concentrated and a solid residue was obtained.
C(O)NCH2CH3], 2.35 [q, 3J(H,H) = 7.1 Hz, 4H;
NCH2CH3], 3.09 [q, 3J(H,H) = 7.1 Hz, 2H; C(O)NCH2-
3
CH3], 3.25 [q, J(H,H) = 7.1 Hz, 2H; C(O)NCH2CH3]
ppm. 13C NMR (50.3 MHz, CDCl3): d = 11.03
(NCH2CH3), 12.04, 13.45 (C(O)NCH2CH3), 37.76,
41.77 (C(O)NCH2CH3), 45.73 (NCH2CH3), 164.2
(C(O)NEt2), 200.9 (CO). IR (hexane): ~m ½cmꢀ1ꢁ ¼
1652ðvsÞ; 1846ðwÞ; 1974ðsÞ; 1996ðmÞ; 2009ðsÞ; 2016ðsÞ;
2065ðsÞ. FAB-MS: m/z (%) = 729 (11) [M+ + 1], 672 (18)
[M+ ꢀ 2CO], 644 (100) [M+ ꢀ 3CO], 616 (51) [M+ ꢀ
4CO], 588 (80) [M+ ꢀ 5CO], 560 (52) [M+ ꢀ 6CO], 532
(11) [M+ ꢀ 7CO], 504 (29) [M+ ꢀ 8CO]. MS (70 eV,
HR-FAB): m/z (%) = 728.8454 (55.0) [M+ + 1;
1
7: 101 mg (37%) red solid, m.p. 92–93 ꢁC, H NMR
(200.1 MHz, CDCl3): d = 0.92 [t, 3J(H,H) = 7.1 Hz, 6H;
NCH2CH3], 1.06 [t, J(H,H) = 7.0 Hz, 3H; C(O)NCH2-
3
3
CH3], 1.14 [t, J(H,H) = 7.0 Hz, 3H; C(O)NCH2CH3],
2.41 [q, 3J(H,H) = 7.2 Hz, 4H; NCH2CH3], 3.03 [q,
3J(H,H) = 7.1 Hz, 2H; C(O)NCH2CH3], 3.15 [q,
3J(H,H) = 7.1 Hz, 2H; C(O)NCH2CH3] ppm. 13C NMR
(50.3 MHz, CDCl3): d = 11.43 (NCH2CH3), 12.44,
13.85 (C(O)NCH2CH3), 38.16, 42.17 (C(O)NCH2CH3),
46.13 (NCH2CH3), 16ꢀ41.6 (C(O)NEt2), 200.2 (CO). ).
12
16
C
1H2159Co414N2 O12: 728.8424]; Dmmu = 3.0.
21
4.5. Tris(phenylthio)-tris(diethylamino)benzene
derivative 9
~
IR (hexane): m ½cm ꢁ ¼ 1651ðsÞ; 1992ðwÞ; 2026ðsÞ;
2058ðvsÞ. MS (70 eV, EI): m/z (%) = 470 (5) [M+ ꢀ CO],
398 (8) [M+ ꢀ NEt2 ꢀ CO], 370 (85) [M+ ꢀ NEt2 ꢀ
2CO], 342 (20) [M+ ꢀ NEt2 ꢀ 3CO], 314 (10) [M+ ꢀ
NEt2 ꢀ 4CO], 286 (80) [M+ ꢀ NEt2 ꢀ 5CO], 258 (50)
A mixture of 1-phenylthio-2-diethylaminoacetylene
(1b) (0.70 g, 3.41 mmole) and 5 mole% of [CpCo(CO)2]
(0.03 g) or [Co2(CO)8] (0.06 g) in 20 ml of toluene was
refluxed for 2 d. After cooling, the solvent was removed
to dryness and the product was isolated by column chro-
matography (SiO2; hexane).
9: 0.49 g (70%) light yellow oil. 1H NMR (200.1
MHz, CDCl3): d = 1.34 [t, 3J(H,H) = 7.0 Hz, 18H;
CH2CH3], 3.17 [q, 3J(H,H) = 7.1 Hz, 8H; CH2CH3],
7.41–7.51 (m, 15H, C6H5) ppm. 13C NMR (50.3 MHz,
[M+ ꢀ NEt2 ꢀ 6CO]. MS (70 eV, HR-EI): m/z (%) =
469.9956 (6.0) [M+ ꢀ CO;
C
1H2059Co214N216O7:
12
16
469.9934]; Dmmu = 2.2.
1
8: 164 mg (41%) black solid, m.p. 111–113 ꢁC, H
3
NMR (200.1 MHz, CDCl3): d = 0.85 [t, J(H,H) = 7.2
Hz, 6H; NCH2CH3], 1.00 [t, 3J(H,H) = 7.1 Hz, 3H;
C(O)NCH2CH3], 1.03 [t, 3J(H,H) = 7.1 Hz, 3H;
Table 1
Crystal data and structure refinement for 30d, 7 and 8
30d
7
8
Empirical formula
Formula weight
Crystal system
C20H30Co2N2
416.32
C17H20Co2N2O8
498.21
C24H27Co4N2O12
771.20
Tetragonal
P41212
Monoclinic
P21/c
Monoclinic
P21/n
Space group
Unit cell dimensions
˚
a (A)
14.769(7)
14.769(7)
10.1981(5)
19.7845(10)
11.4151(6)
90
15.535(4)
10.920(3)
18.597(5)
90
˚
b (A)
˚
c (A)
9.169(5)
90
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
90
111.99(1)
90
99.63(2)
90
3
˚
Volume (A )
2000(2)
4
1.383
2135.6(2)
4
1.550
3110.4(13)
4
1.647
Z
Calculated density (g cmꢀ3
)
l (mmꢀ1
F(000)
Crystal size (mm)
)
1.662
872
1.597
1016
2.156
1556
0.60 · 0.20 · 0.20
27.49
0.45 · 0.28 · 0.22
28.32
0.23 · 0.22 · 0.06
26.39
Hmax (ꢁ)
Index ranges
ꢀ19/19, ꢀ13/13, ꢀ11/11
ꢀ13/12, 0/25, 0/15
14571
ꢀ19/19, 0/13, 0/23
34415
Reflections collected
Independent reflections
Parameters
Goodness-of-fit on F2
R1[I > 2rI]
wR2 (All reflections)
T (K)
Residual electron density (e/A3)
2734
2304(0.016)
115
0.965
5135(0.026)
342
0.982
6370(0.099)
487
0.947
0.0321
0.0700
0.0263
0.0670
0.0344
0.0783
203(2)
0.223/ꢀ0.301
153(2)
0.517/ꢀ0.217
153(2)
0.827/ꢀ0.663

3258
A. Goswami et al. / Journal of Organometallic Chemistry 690 (2005) 3251–3259
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CDCl3): d = 12.40 (CH2CH3), 47.51 (CH2CH3), 121.3,
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C
1H4514N332S3: 615.2776];
36
12
(d) D.B. Grotjahn, in: E.W. Abel, F.G.A. Stone, G. Wilkinson,
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5. Crystal structure determinations of 30d, 7 and 8
Crystal data and details of the structure determina-
tions are listed in Table 1. Reflections were collected
for 30d with a Siemens-Stoe AED2 diffractometer, for
7 and 8 with a Bruker-AXS SMART 1000 diffractome-
(g) J.M. OÕConnor, B.S. Fong, H.-L. Ji, K. Hiibner, A.L.
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ter (Mo Ka radiation, k = 0.71073 A, graphite mono-
chromator, x-scan). Empirical absorption corrections
were applied. The structures were solved by direct meth-
ods and refined by least square methods based on F2
with all measured reflections (SHELXTL 5.1) [28]. All
non-hydrogen atoms were refined anisotropically. Crys-
tallographic data (excluding structure factors) for the
structures reported in this paper have been deposited
to the Cambridge Crystallographic Data Centre as sup-
plementary publication nos. CCDC-256504 (30d),
CCDC-256505 (7), CCDC-256506 (8). Copies of the
data can be obtained free of charge on application to
the CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK [fax: (internat.) +44 1223/336033; e-mail: deposit@
ccdc.cam.ac.uk].
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Inorg. Chem. (2004) 4223.
This work was supported by the Deutsche Fors-
chungsgemeinschaft (SFB 623) and the Fonds der
Chemischen Industrie.
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