Cobalt-mediated cyclooligomerization reactions of borylacetylenes

Article abstract of DOI:10.1002/ejic.200400063

Reaction of bis(diethylamino) acetylene (1) with lithium and chlorobis(dimethylamino)borane yields 1-[bis(dimethylamino)boryl]-2- (diethylamino)acetylene (2). Treatment of 1-aryl-2-(trimethylstannyl)acetylenes 3 with chlorobis(diisopropylamino)borane results in the quantitative formation of 1-aryl-2-[bis(diisopropylamino)boryl]acetylene compounds 4. The 1-aryl-2-borylacetylene derivatives 5, 6, and 7 are obtained by the reaction of 3 with the appropriate haloborane, or by reacting 4 with two equivalents of HCl and one equivalent of catechol, dithiocatechol and 2-hydroxythiophenol. The catalytic cyclotrimerizations of 5a-d with [CpCo(CO)₂] or [Co ₂(CO)₈] lead to isomeric mixtures of the triborylbenzene derivatives 8a-d and 8a′-d′, whereas 6a-d and 7a-b undergo cyclotrimerization only with catalytic amount of [Co₂(CO) ₈], to give isomeric mixtures of the triborylbenzene derivatives 12a-d/12a′-d′ and 13a-b/13a′-b′, respectively. The reaction of 2 with a stoichiometric amount of (η⁵- cyclopentadienyl)bis(ethene)cobalt leads to (η⁵-cyclopentadienyl) (η⁴-cyclobutadiene)cobalt complexes 9. The analogous complexes 10 and 11 are obtained by the reactions of 6 and 7 with a stoichiometric amount of (η⁵-cyclopentadienyl)dicarbonylcobalt. Treatment of Co ₂(CO)₈ with 5a, 6a, and 7a yields the dicobaltatetrahedranes 14a, 15a and 16a. Compound 15a reacts with two equivalents of diphenylacetylene and 1-(1,3,2-benzodioxaborolyl)-2- phenylacetylene (5a), to furnish (1,3,2-benzodithiaborolyl)pentaphenylbenzene (17) and bis(1,3,2-benzodioxaborolyl)(1,3,2-benzodithiaborolyl)triphenylbenzene (18), respectively. The new compounds have been characterized by NMR spectroscopy and mass spectrometry, as well as by X-ray structural analyses for 4a, 5a, 6a, and 10a. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200400063

FULL PAPER
Cobalt-Mediated Cyclooligomerization Reactions of Borylacetylenes
Avijit Goswami,[a] Claus-Jürgen Maier,[a] Hans Pritzkow,[a] and Walter Siebert*[a]
Dedicated to Professor Helmut Werner on the occasion of his 70th birthday
Keywords: Boranes / Catalysts / (Cyclobutadiene)cobalt complexes / Mono(boryl)acetylenes / Triborylbenzenes
Reaction of bis(diethylamino)acetylene (1) with lithium and
chlorobis(dimethylamino)borane yields 1-[bis(dimethylami-
pentadienyl)bis(ethene)cobalt leads to (η5-cyclopenta-
dienyl)(η4-cyclobutadiene)cobalt complexes 9. The analogous
no)boryl]-2-(diethylamino)acetylene (2). Treatment of 1-aryl- complexes 10 and 11 are obtained by the reactions of 6 and
2-(trimethylstannyl)acetylenes 3 with chlorobis(diisopropyl-
7 with a stoichiometric amount of (η5-cyclopentadienyl)di-
amino)borane results in the quantitative formation of 1-aryl- carbonylcobalt. Treatment of Co2(CO)8 with 5a, 6a, and 7a
2-[bis(diisopropylamino)boryl]acetylene compounds 4. The
1-aryl-2-borylacetylene derivatives 5, 6, and 7 are obtained
by the reaction of 3 with the appropriate haloborane, or by
reacting 4 with two equivalents of HCl and one equivalent
of catechol, dithiocatechol and 2-hydroxythiophenol. The
catalytic cyclotrimerizations of 5a−d with [CpCo(CO)2] or
[Co2(CO)8] lead to isomeric mixtures of the triborylbenzene
derivatives 8a−d and 8aЈ−dЈ, whereas 6a−d and 7a−b un-
dergo cyclotrimerization only with catalytic amount of
[Co2(CO)8], to give isomeric mixtures of the triborylbenzene
derivatives 12a−d/12aЈ−dЈ and 13a−b/13aЈ−bЈ, respectively.
yields the dicobaltatetrahedranes 14a, 15a and 16a. Com-
pound 15a reacts with two equivalents of diphenylacetylene
and 1-(1,3,2-benzodioxaborolyl)-2-phenylacetylene (5a), to
furnish (1,3,2-benzodithiaborolyl)pentaphenylbenzene (17)
and bis(1,3,2-benzodioxaborolyl)(1,3,2-benzodithiaborolyl)-
triphenylbenzene (18), respectively. The new compounds
have been characterized by NMR spectroscopy and mass
spectrometry, as well as by X-ray structural analyses for 4a,
5a, 6a, and 10a.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
The reaction of 2 with a stoichiometric amount of (η5-cyclo- Germany, 2004)
Introduction
derivatives, we have synthesized new mono(boryl)acetylene
derivatives with terminal boryl and amino or aryl substitu-
ents. Compound 2, which has both amino and boryl sub-
Over the past decades, the cyclooligomerization reactions stituents (Scheme 1), can react similarly to the pushϪpull
of alkynes with transition metal complexes have received acetylene Me2NϪCϵCϪCOOMe,[9] and undergoes dimer-
considerable attention.[1] [CpCo(CO)2][2] is a convenient ization.
and
efficient
reagent
for
the
syntheses
of
CpCoϪcyclobutadiene complexes,[3] cyclopentadienones,[4]
and benzene derivatives,[5] whereas [Co2(CO)8] is used in
PausonϪKhand[6] and [2ϩ2ϩ2] cyclotrimerization reac-
tions.
Scheme 1
Recently, we reported the Co-catalyzed [2ϩ2ϩ2] cyclo-
trimerization of mono-[7] and bis(catecholboryl)acety-
lenes.[8] With both types of acetylenes, only benzene deriva-
tives were obtained — no CpCo-cyclobutadiene complexes
were observed — even when using stoichiometric amounts
of [CpCo(CO)2] and the corresponding acetylene.
To study the influence of the substituents with respect to
the formation of CpCoϪcyclobutadiene and/or benzene
The influence of the substituents at the boryl group is of
particular interest, as amino groups at the boron center may
reduce its Lewis acidity. A large part of this work concen-
trates on the reactivity of arylalkynyl boranes 5, 6, and 7,
in which two oxygen atoms (in 5), two sulfur atoms (in 6)
and one oxygen and one sulfur atom (in 7) are bound to
the boron atom. It is expected that the heteroatoms have
different electronic and steric effects on the reactivity of the
acetylenes 5Ϫ7. In this paper, we report the syntheses,
structures and reactivities of the monoborylacetylene de-
rivatives 2 and 4Ϫ7.
[a]
Anorganisch-Chemisches Institut der Universität,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Fax: (internat.) ϩ49-(0)6221-54-5609
E-mail: walter.siebert@urz.uni-heidelberg.de
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DOI: 10.1002/ejic.200400063
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A. Goswami, C.-J. Maier, H. Pritzkow, W. Siebert
FULL PAPER
THF, the corresponding alkynes 5, 6, and 7 were obtained
as crystalline solids (Scheme 3). These compounds are sol-
uble in benzene and toluene, but are less soluble in hexane
Results and Discussion
Synthesis and Properties of Mono(boryl)acetylene
Derivatives 2, 4, 5, 6 and 7
1
and pentane. The H NMR spectra of 5Ϫ7 show the ex-
pected multiplicities of the aromatic protons in the region
δ ϭ 6.9Ϫ7.9 ppm. In the 13C NMR spectra, the signals for
the boron-bound carbon atoms were not observed; the sig-
nals for the β carbon atoms (δ ϭ 84Ϫ109 ppm) are shifted
to lower fields relative to the alkylacetylenes (δ ϭ
70Ϫ80 ppm),[13] which may indicate an interaction of the
empty orbital at the boron atom with the π system of the
triple bond.
Bis(diethylamino)acetylene (1) is obtained by treating 2-
fluoro-1,1-dichloroethene or trichloroethene with N,N-di-
substituted lithium amides and secondary amines.[10] In 1,
the NϪCϵC bond is cleaved by lithium in THF to give two
lithium compounds (Et2NLi and Et2NϪCϵCLi), which re-
act with various electrophiles. The mixture was treated with
chlorobis(dimethylamino)borane to give Et2NϪB(NMe2)2
(70%) and 1-amino-2-borylacetylene (2) (43%), which were
separated by fractional distillation (Scheme 1). Their com-
positions were determined by mass spectrometric and
NMR spectroscopic data.
The reactions of chlorobis(diisopropylamino)borane with
1-trimethylstannyl-2-arylacetylenes 3 led to light-yellow
compounds 4 in quantitative yields (Scheme 2). Com-
1
pounds 4[11] were characterized by H, 13C, and 11B NMR
spectroscopy, as well as by mass spectrometry.
Scheme 3
The structures of 5a and 6a were determined by per-
forming single-crystal X-ray analyses (Figures 2 and 3).
Each compound has a linear BϪCϵCϪC moiety (5a: ex-
actly; 6a: approximately) and the CϵC bond lengths are
slightly longer than those of normal alkyne compounds.
The BϪC bonds are rather short. This finding is in agree-
ment with structural data for oxygen-substituted bis(cate-
cholboryl)acetylenes.[14]
Scheme 2
In the 11B NMR spectrum, the signal at δ ϭ 26 ppm of
4a indicates a trigonal-planar boryl group, which we con-
firmed by X-ray structural analysis. In the linear
BϪCϵCϪC moiety (Figure 1) the CϵC bond is slightly
widened relative to other RϪCϵCϪR compounds (1.18
[12]
˚
A).
Figure 2. Molecular structure of 5a in the solid state; hydrogen
˚
atoms are omitted for clarity; selected bond lengths [A] and bond
angles [°]: C1ϪC2 1.196(5), C1ϪC6 1.447(5), B1ϪC2 1.513(5),
B1ϪO1 1.383(15), C1ϪC2ϪC6 180.0, C1ϪC2ϪB1 180.0
Figure 1. Molecular structure of 4a in the solid state; hydrogen
˚
atoms are omitted for clarity; selected bond lengths [A] and bond
angles [°]: C1ϪC2 1.210(14), C2ϪC3 1.434(14), N1ϪB1 1.434(8),
B1ϪC1 1.559(15), C1ϪC2ϪC3 180.0, C2ϪC1ϪB1 180.0
The syntheses of compounds 5, 6, and 7 were achieved
by two reaction procedures. A solution of 1-aryl-2-(trimeth-
ylstannyl)acetylene (3) in toluene was reacted with the cor-
responding haloborane to give 5Ϫ7. When compound 4
was treated with two equivalents of HCl and one equivalent
Figure 3. Molecular structure of 6a in the solid state; hydrogen
˚
atoms are omitted for clarity; selected bond lengths [A] and bond
angles [°]: C1ϪC2 1.207 (8), C2ϪC3 1.423(7), B1ϪC1 1.521(8),
of catechol or dithiocatechol or 2-hydroxythiophenol in B1ϪS1 1.796(6), C1ϪC2ϪC3 178.5(5), C2ϪC1ϪB1 177.6(5)
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Cobalt-Mediated Cyclooligomerization Reactions of Borylacetylenes
FULL PAPER
Trimerization of 5 to Triboryl-triarylbenzene Derivatives 8
Likewise, photochemical activation of [CpCo(CO)2] and
5aϪd did not yield (cyclobutadiene)cobalt complexes: only
the starting materials were recovered.
Only a few triborylbenzene derivatives are known,[15] of
which some have been prepared in low yields by Grignard
reactions. Recently, we obtained triborylbenzene deriva-
tives[7] by cyclotrimerization of monoborylacetylenes in the
presence of catalytic amount of dicarbonyl(η5-cyclopenta-
Catalytic Cycles with [CpCo(CO)2] and [Co2(CO)8]
The postulated mechanism of [CpCo(CO)2]-catalyzed
dienyl)cobalt. Analogously, in refluxing toluene, the mono- cyclotrimerization[5a,16] of acetylene is suggested for 5a. Un-
borylalkyne derivatives 5aϪd formed isomeric mixtures of der thermal conditions, two alkyne ligands displace the CO
the 1,3,5- and 1,2,4-triborylbenzene derivatives 8aϪd and groups to form a bis(alkyne)cobalt complex, followed by
8aЈϪdЈ in the presence of a catalytic amount of reductive coupling of the alkyne units to give a coordin-
[CpCo(CO)2] or [Co2(CO)8] (Scheme 4). The isomers could atively unsaturated cobaltacyclopentadiene complex. Coor-
not be separated.
dination of a third molecule of 5a could then lead to an 18-
VE complex, which undergoes alkyne insertion to form the
corresponding cobaltacycloheptatriene compound. Sub-
sequent reductive elimination of the CpCo complex frag-
ment leads to the formation of the triborylbenzene deriva-
tives 8a/8aЈ. Recently, Vollhardt et al.[17] reported the syn-
thesis of a (η2-alkyne)cobaltacyclopentadiene complex,
which indirectly proves the proposed catalytic cycle, al-
though no direct evidence for the intermediacy of the pos-
tulated cobaltacycloheptatriene was obtained. According to
ab initio and density functional theory (DFT) investigations
of the mechanism,[16] a cobaltacycloheptatriene is in fact
very unlikely to form.
Analogously, the catalytic oligomerization of 5a with oc-
tacarbonyldicobalt led to the triborylbenzene derivatives
8a/8aЈ in 71% yield. One of our aims is to isolate intermedi-
ates to shed more light on the catalytic cycle proposed
Scheme 4
The air-stable solids 8aϪd and 8aЈϪ8dЈ are light-yellow
in color and are not soluble in most organic solvents; 8a/
8aЈ dissolve partially in chloroform, whereas 8bϪd and
8bЈϪdЈ are slightly soluble in dichloromethane and toluene.
in Scheme 5, which is
a
short version of the
KnoxϪPausonϪSpicer mechanism.[18] In the first step,
elimination of two CO ligands leads to the unsaturated
species [Co2(CO)6], which reacts with 5a to give the boryl-
substituted dicobaltatetrahedrane complex 14a (A). Sub-
sequent elimination of CO and insertion of one molecule of
5a should yield the intermediate B, of which many examples
are known.[19] However, under our conditions, B was not
detected. A DielsϪAlder-type reaction of B with 5a may
1
Compounds 8aϪd and 8aЈϪdЈ were characterized by H,
13C, and 11B NMR spectroscopy, elemental analysis, and
mass spectrometry. The 11B NMR spectra exhibit broad sig-
nals at δ ϭ 24 ppm for 8a/8aЈ, δ ϭ 22 ppm for 8b/8bЈ and
1
8d/8dЈ, and δ ϭ 23 ppm for 8c/8cЈ. In the H NMR spec-
trum of 8a/8aЈ, several peaks appear in the region δ ϭ
7.2Ϫ7.6 ppm that are due to aromatic protons of the cate-
chol and phenyl substituents. In the 13C NMR spectrum,
three signals at δ ϭ 112.7, 123.2, and 147.8 ppm are ob-
served for the carbon atoms of the catechol groups. The
signal at δ ϭ 139.9 ppm is assigned to the ipso-carbon
atoms of the central ring of the isomer 8a and three signals
at δ ϭ 134.6, 137.3, and 142.5 ppm to the ipso-carbon
atoms of the central ring of the isomer 8aЈ. The 13C NMR
spectroscopic signals of the carbon atoms of the phenyl
substituents appear at δ ϭ 121.2, 128.5, 130.0, and
1
132.8 ppm. Similarly, the H NMR spectra of 8bϪd and
8bЈϪdЈ show the expected multiplets (in the region δ ϭ
6.9Ϫ7.6 ppm for the aromatic protons) and singlets near
δ ϭ 2.3Ϫ2.4 ppm (methyl groups). The 13C NMR spectra
reveal chemical shifts of the ipso-carbon atoms of the cen-
tral ring of the isomers 8bϪd near δ ϭ 140Ϫ141 ppm and
the ipso carbon atoms of the isomers 8bЈϪdЈ in the region
δ ϭ 136Ϫ148 ppm.
Thermal reactions of 5aϪd with a stoichiometric amount
of [CpCo(CO)2] did not provide any (cyclobutadiene)cobalt
complex: only the cyclotrimerization products were found. Scheme 5
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A. Goswami, C.-J. Maier, H. Pritzkow, W. Siebert
FULL PAPER
lead to C, which eliminate 8a/8aЈ and the pentacarbonyl- δ ϭ 57 ppm for 10b/10c. The 1H NMR spectra of 10 exhibit
dicobalt fragment reacts with CO and 5a to give 14a. We multiplets in the region δ ϭ 7.0Ϫ7.9 ppm that are due to
did not observe the postulated intermediates C and the ‘‘fly- the aromatic protons, in addition to the Cp resonances (δ ϭ
over’’ dicobaltacyclooctadiene complex D; several examples 4.6Ϫ4.9 ppm). Four quaternary carbon atoms of diboryl-
have been reported of the latter species.[18,20] It has been substituted (η4-cyclobutadiene)cobalt complexes 10 were
demonstrated that drastic conditions[21] or chemical pro- detected in the 13C NMR spectrum in the region δ ϭ
moters[18] transform D into arenes and, therefore, D is not 79Ϫ89 ppm. From the NMR spectra, it is not possible to
on the main path of the catalytic reaction to arenes.[18]
make a distinction between the trans (10aϪd) and cis iso-
mers (10aЈϪdЈ) of the cyclobutadiene complexes. For steric
reason, the trans isomers 10aϪd seem to be more favored,
which is confirmed by the solid state structure of 10a. How-
ever, several complexes are known that have cis-bis(trime-
thylsilyl)cyclobutadiene ligands.[1c,24] The problem was re-
solved unequivocally by analyzing the major peaks in terms
of the degradation of the cyclobutadiene ring in the mass
spectra. In general, three different acetylenes are released
from the molecular ion of the cis isomer, but only a single
acetylene is released from the trans isomer.[25] Here, in all
cases, three kinds of acetylenes were released from the mo-
lecular ion. Therefore, mass spectra gave evidence for both
the cis isomer and the trans isomers, but the cis isomer
could not be identified by NMR spectroscopic measure-
ments.
The structure of 10a was characterized by performing a
single-crystal X-ray diffraction analysis. Two independent
molecules were found; the structure of one is shown in Fig-
ure 4. The solid state structure of 10a reveals that both phe-
nyl groups, as well as one of dithiacatecholboryl groups, do
not lie in the plane of the cyclobutadiene ring. From the
internal bond angles of the cyclobutadiene ring of 10a, it is
found that there is a little deviation from the exact square-
planar shape because the internal bond angles for both the
carbon atoms attached to the boron atom are smaller than
those attached to the phenyl groups.
Synthesis of CpCo؊Diborylcyclobutadiene Complexes 9, 10
and 11
In 1965, Pettit et al.[22] reported the first generation of
the tricarbonyl(η4-cyclobutadiene)iron complex. Among
the various synthetic methods, the reactions of alkynes with
transition metal carbonyl complexes in particular have been
studied extensively during the last three decades.[23] In an
analogous manner, compound 2 was treated with (η5-cyclo-
pentadienyl)bis(ethene)cobalt in hexane and compounds 6
and 7 with dicarbonyl(η5-cyclopentadienyl)cobalt in re-
fluxing toluene to give the corresponding (η4-cyclobuta-
diene)(η5-cyclopentadienyl)cobalt complexes 9, 10, and 11
in good yields (Scheme 6). Purification of compounds 9a/
9aЈ by column chromatography on aluminum oxide led to
decomposition. Because of a paramagnetic impurity in the
crude product, compounds 9a/9aЈ could not be charac-
terized by NMR spectroscopy. EI-MS data confirm the
identity of 9a/9aЈ through the appearance of the molecular
ion peaks with the expected isotopic patterns. Compounds
10 and 11 are partially soluble in toluene and chloroform;
in methanol, a fast reaction, leading to the formation of
B(OMe)3, takes place.
Figure 4. Molecular structure of 10a in the solid state; hydrogen
˚
atoms are omitted for clarity; selected bond lengths [A] and bond
angles [°]: C1ϪC2 1.460 (5), C2ϪC3 1.465(5), C3ϪC4 1.476(5),
C4ϪC1 1.462(5), C1ϪB1 1.528(6), C3ϪB2 1.527(6), C2ϪC1ϪC4
89.2(3), C1ϪC2ϪC3 91.4(3), C2ϪC3ϪC4 88.5(3), C1ϪC4ϪC3
90.9(3)
Scheme 6
Purification of 10 and 11 can be accomplished by wash-
ing repeatedly with hexane. Complexes 10 and 11 were
characterized by H, 13C, and 11B NMR spectroscopy, el-
Similarly, 11B NMR spectra show broad signals at δ ϭ
1
1
emental analysis, and mass spectrometry. The 11B NMR 45 ppm for 11a/11aЈ and δ ϭ 46 ppm for 11b/11bЈ. The H
spectra show broad signals at δ ϭ 58 ppm for 10a/10d, and NMR spectra exhibit multiplets in the region δ ϭ
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Cobalt-Mediated Cyclooligomerization Reactions of Borylacetylenes
FULL PAPER
7.1Ϫ7.9 ppm that are due to aromatic protons. In the 13C tra reveal the signals of the ipso-carbon atoms of the central
NMR spectra of 11a/11aЈ and 11b/11bЈ, the signals in the ring of 13a at δ ϭ 132.8 ppm and at δ ϭ 132.7 ppm for 13b.
region δ ϭ 84Ϫ86 ppm are assigned to the ipso-carbon
atoms of the central C4 ring and to the signals of the Cp
carbon atoms (δ ϭ 83Ϫ87 ppm). The EI mass spectra of
11aϪb and 11aЈϪbЈ show ion fragmentations similar to
those mentioned above, with the expected isotopic patterns.
It is important to mention that no benzene derivatives were
observed in the reactions of [CpCo(CO)2] with the alkynes
6 and 7 (Scheme 6).
Synthesis and Properties of Dicobaltatetrahedranes 14a,
15a, and 16a
(Alkyne)hexacarbonyldicobalt complexes are obtained by
treating alkynes with Co2(CO)8.[27] Analogously, the mono-
(boryl)acetylene derivatives 5a, 6a, and 7a reacted with
Co2(CO)8 in CH2Cl2; elimination of two CO units resulted
in the corresponding complexes 14a, 15a and 16a
(Scheme 8). These compounds were isolated by column
chromatography as brown-red oils,[28] which we charac-
[Co2(CO)8]-Catalyzed Cyclotrimerization of 6 and 7 to
Triborylbenzenes 12 and 13
1
terized by H, 13C, and 11B NMR spectroscopy, IR spec-
Arnett et al.[26] prepared the sterically encumbered hexa-
isopropylbenzene by [Co2(CO)8]-catalyzed trimerization of
bis(isopropyl)acetylene. Analogously, in refluxing toluene,
the mono(boryl)acetylene derivatives 6 and 7 formed the
triborylbenzene derivatives 12 and 13 in the presence of a
catalytic amount of [Co2(CO)8] (Scheme 7). The isomeric
mixture (1,3,5- and 1,2,4-substituted) could not be sepa-
rated. Purifications of 12 and 13 were achieved by washing
repeatedly with hexane, toluene and CH2Cl2.
troscopy, and mass spectrometry.
Scheme 8
The 11B NMR spectrum of 14a shows a broad signal at
δ ϭ 33 ppm. The 1H NMR spectrum exhibits the signals of
the aromatic protons in the region δ ϭ 7.2Ϫ7.7 ppm. In the
13C NMR spectrum, the arene carbon atoms give rise to
signals at δ ϭ 112.6, 123.2, and 147.8 ppm for the catechol
unit and at δ ϭ 121.2, 128.5, 130.0, and 130.2 ppm for the
phenyl group. The signal of the carbon atom bound to the
boron atom are not observed, while the carbon atom at-
tached directly to the phenyl group appears at δ ϭ
104.3 ppm. The carbonyl ligands exhibit a signal in the 13C
NMR spectrum at δ ϭ 200.2 ppm.
Scheme 7
Similarly, in their 11B NMR spectra, the signals of the
complexes 15a and 16a appear at δ ϭ 59 and 47 ppm,
The compounds 12 and 13 are air-stable solids and are
not soluble in most common organic solvents; slight solu-
bility in chloroform enables NMR spectra to be measured.
All compounds were characterized by 1H, 13C, and 11B
NMR spectroscopy, elemental analysis, and mass spec-
trometry. The 11B NMR spectra show broad signals at δ ϭ
62 ppm for 12a/12aЈ and δ ϭ 60 ppm for 12b/12bЈ, 12c/12cЈ,
and 12d/12dЈ. In the 1H NMR spectra, multiplets (δ ϭ
6.9Ϫ7.9 ppm) are observed for the aromatic protons of
12aϪd and 12aЈϪdЈ. In the 13C NMR spectra, the signals
in the region δ ϭ 126Ϫ128 ppm are assigned to the ipso-
carbon atoms of the central ring of the isomers 12aϪc and
those in the region δ ϭ 128Ϫ141 ppm to the ipso carbon
atoms of the isomers 12aЈϪcЈ. The quaternary carbon
atoms of 12d/12dЈ were not observed.
1
respectively. The H NMR spectra show multiplets in the
regions δ ϭ 7.1Ϫ7.8 ppm for 15a and δ ϭ 7.1Ϫ7.5 ppm for
16a. The characteristic carbonyl ligands in the 13C NMR
spectra appear at δ ϭ 199.5 ppm for 15a and δ ϭ 200.6 ppm
for 16a.
Complex 14a can also act as a catalyst for the cyclo-
trimerization of 5a. When a catalytic amount of 14a and 1-
(catecholboryl)-2-phenylacetylene (5a) were heated in tolu-
ene, the triborylbenzene derivatives 8a/8aЈ were obtained in
good yield (Scheme 9).
The 11B NMR spectra of 13a/13aЈ exhibit broad signals
at δ ϭ 53 ppm and of 13b/13bЈ at δ ϭ 52 ppm. The H
1
NMR spectra show multiplets in the aromatic region for
the aryl protons of 13a/b and 13aЈ/bЈ. The 13C NMR spec- Scheme 9
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FULL PAPER
(1,3,2-Benzodithiaborolyl)pentaphenylbenzene and Bis(1,3,2-
benzodioxaborolyl)(1,3,2-benzodithiaborolyl)triphenyl-
benzene (17 and 18)
atom(s) with the cobalt center, which might prevent the for-
mation of coordinatively unsaturated cobaltacyclopentadi-
ene complexes (the postulated precursor en route to cyclo-
trimerization products). Instead of cyclotrimerization prod-
ucts, (η4-cyclobutadiene)cobalt complexes 10 and 11 are ob-
tained. Reactions of 5a, 6a, and 7a with a stoichiometric
amount of [Co2(CO)8] lead to the Co2C2 clusters 14a, 15a,
and 16a, respectively.
Recently, we have shown the use of C2Co2 clusters for the
preparation of different substituted arenes.[8] Analogously,
we have heated diphenylacetylene and a stoichiometric
amount of 15a in toluene, which resulted in the formation
of (1,3,2-benzodithiaborolyl)pentaphenylbenzene (17) in
good yield (Scheme 10). Compound 17 is not soluble in
common organic solvents and, therefore, NMR spectro-
scopic measurements were not possible. Compound 17 was
characterized by mass spectrometry, which confirms the
identity of 17 through the appearance of the molecular ion
peak at m/z ϭ 608.
Experimental Section
General: All reactions were performed under nitrogen using stand-
ard Schlenk techniques. Solvents were dried with the appropriate
drying agents and distilled under nitrogen. Glassware was dried
1
with a heat gun under high vacuum. H, 13C, and 11B NMR spec-
troscopy: Bruker AC 200 spectrometer; 1H and 13C spectra were
referenced to (CH3)4Si and 11B spectra to F3B·OEt2. IR spectra
were recorded on a Bruker IFS 28 FT spectrometer. Mass spectra
were obtained on Finnigan MAT 8230 plus spectrometers using
the EI technique. Elemental analyses were carried out at the Micro-
analytical Laboratory, University of Heidelberg. Melting points
(uncorrected) were obtained on a Büchi apparatus, using capillaries
that were filled under nitrogen and sealed. Bis(diethylamino)ace-
tylene[10] (1), (iPr2N)2BCl,[29] 1-aryl-2-(trimethylstannyl)acetyl-
enes[30] 3, and chlorocatecholborane[31] were prepared according to
literature procedures. Bromo(dithiocatechol)borane and bromo-
(1,3,2-benzothiaoxaborol), which have not been reported previously
in the literature, were prepared by the reactions of dithiocatechol
and 2-hydroxythiophenol with excess BBr3. Catechol, 4-methylcate-
chol, dithiocatechol, 4-methyldithiocatechol, and 2-hydroxymer-
captanol were purchased from Aldrich.
Scheme 10
Similarly, compound 15a was treated with two equiva-
lents of 1-(catecholboryl)-2-phenylacetylene (5a) in toluene
under reflux, which led to the formation of an isomeric mix-
ture 18 in moderate yield. Because of the complete insolu-
bility of compound 18, NMR spectroscopic measurements
were not possible. Compound 18 was characterized by EI
mass spectrometry, which indicated the molecular ion peak 1-[Bis(dimethylamino)boryl]-2-(diethylamino)acetylene (2): Bis(di-
ethylamino)acetylene (1, 1.18 g, 7.0 mmol) was added slowly at
room temperature to a stirred suspension of lithium powder
(0.34 g, 49.7 mmol) in diethyl ether (20 mL). The reaction mixture
was heated under reflux for 3 h. After cooling, the mixture was
stirred at ambient temperature for 40 h. The ether was evaporated
by vacuum, THF (20 mL) was added, and the THF solution was
heated for 1 h. The solid that formed was separated by filtration
and washed with a small amount of THF. After drying under high
vacuum, a green solid (a mixture of Et2NC2Li and LiNEt2) was
obtained. Chlorobis(dimethylamino)borane (1.26 g, 9.4 mmol) was
added within 10 min at Ϫ60 °C to a solution of lithium compounds
(0.85 g, 4.7 mmol) in THF (10 mL). The reaction mixture was
stirred for 16 h. After filtration, the solvent was evaporated under
high vacuum. Compound 2 and Et2B(NMe)2 were obtained by
fractional distillation. Yield 0.39 g (43%), colorless liquid, b.p. 50
of 18 at m/z ϭ 692.
Conclusions
We have studied the reactions of boryl-substituted acety-
lenes with catalytic and stoichiometric amounts of
[CpCo(C2H4)2], [CpCo(CO)2], and [Co2(CO)8]. [2ϩ2ϩ2]
Cyclotrimerization products 8 are obtained from the reac-
tions of (catecholboryl)acetylenes 5 with a catalytic amount
of [CpCo(CO)2] or [Co2(CO)8]. (η4-Cyclobutadiene)cobalt
complexes are not formed from (thermal and photochem-
ical) reactions of
5 with stoichiometric amount of
[CpCo(CO)2]. Treatment of nitrogen- and sulfur-bound
borylacetylenes 2, 6, and 7 with a stoichiometric amount of
[CpCo(C2H4)2] or [CpCo(CO)2] opened a long-sought route
to the new class of boryl-substituted (η4-cyclobutadiene)co-
balt complexes. Possibly because of steric reasons, the nitro-
gen-substituted borylacetylene 2 does not undergo catalytic
cyclotrimerization with [CpCo(C2H4)2] or [CpCo(CO)2].
On the other hand, triborylbenzene derivatives 12 and 13
are obtained from the reactions of 6 and 7, respectively,
with a catalytic amount of [Co2(CO)8]. Surprisingly, we
found that changing the heteroatom(s) bound to the boron
atom causes a remarkable difference in the reactivities of 6
and 7 when compared to that of 5. Most likely, this be-
1
3
°C/0.2 Torr. H NMR (200.1 MHz, CDCl3): δ ϭ 1.18 (t, JH,H
7.2 Hz, 6 H, CH2CH3), 2.68 (s, 12H, NCH3), 2.90 (q, JH,H
ϭ
3
ϭ
7.2 Hz, 4 H, CH2CH3) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ
12.90 (CH2CH3), 40.60 (NCH3), 48.20 (CH2CH3) ppm. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 26 ppm. MS (70 eV, EI): m/z (%) ϭ 195
(100) [Mϩ], 180 (31) [Mϩ Ϫ CH3], 123 (93) [Mϩ Ϫ NEt2].
1-[Bis(diisopropylamino)boryl]-2-phenylacetylene (4a) and 1-[Bis(di-
isopropylamino)boryl]-2-tolylacetylene (4b): Chlorobis(diisopropyl-
amino)borane (2.59 g, 10.5 mmol) in toluene (10 mL) was added
slowly at Ϫ78 °C to a stirred solution of 1-trimethylstannyl-2-aryl-
acetylene (3a: 2.80 g; 3b: 2.94 g; 10.5 mmol) in toluene (40 mL).
The reaction mixture was stirred overnight to reach room tempera-
ture, the solvent was evaporated under high vacuum, and the resi-
havior of 6 and 7 arises from interactions of the sulfur due was distilled.
2640  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjic.org
Eur. J. Inorg. Chem. 2004, 2635Ϫ2645

Cobalt-Mediated Cyclooligomerization Reactions of Borylacetylenes
FULL PAPER
4a: Yield 3.1 g (94%), pale-yellow liquid, b.p. 102 °C/0.01 Torr. H
CDCl3): δ ϭ 24 ppm. MS (70 eV, EI): m/z (%) ϭ 234 (100) [Mϩ].
1
3
NMR (200.1 MHz, CDCl3): δ ϭ 1.38 [d, JH,H ϭ 6.9 Hz, 24 H,
MS (70 eV, HR-EI): m/z (%)
ϭ
234.0834 (100) [Mϩ;
CH(CH3)2], 3.55 [sept., JH,H ϭ 6.9 Hz, 4 H, CH(CH3)2], 7.4Ϫ7.5
1H1111B16O2: 234.0852]; ∆mmu ϭ 1.8.
3
12
C
15
(m, C6H5, 5H) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 24.23
[CH(CH3)2], 46.71 [CH(CH3)2], 104.6 (CspϪCi), 125.1, 127.8,
128.3, 130.9 (C6H5) ppm; CspϪB not found. 11B NMR (64.2 MHz,
CDCl3): δ ϭ 26 ppm. MS (70 eV, EI): m/z (%) ϭ 312 (13) [Mϩ],
1-(4-Methylcatecholboryl)-2-tolylacetylene (5d): Starting materials:
4b (4.44 g, 13.6 mmol), HCl·OEt2 (13.6 mL, 27.2 mmol), 4-methyl-
catechol (1.68 g, 13.6 mmol). Yield 2.1 g (62%), brown solid, m.p.
73 °C (dec.). 1H NMR (200.1 MHz, CDCl3): δ ϭ 2.35 (s, 3 H,
CH3), 2.37 (s, 3 H, CH3), 6.9Ϫ7.5 (m, 7 H, Haryl) ppm. 13C NMR
(50.3 MHz, CDCl3): δ ϭ 21.40 and 21.65 (CH3), 83.81 (CspϪCi),
111.9, 113.1, 123.1, 138.9, 145.4, 147.5 (catechol), 119.0, 129.2,
132.0, 132.8 (tolyl) ppm; CspϪB not observed. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 23 ppm. MS (70 eV, EI): m/z (%) ϭ 248
297 (100) [Mϩ Ϫ CH3], 269 (87) [Mϩ Ϫ iPr], 212 (31) [Mϩ
Ϫ
N(iPr)2]. MS (70 eV, HR-EI): m/z (%) ϭ 312.2759 (8) [Mϩ;
12
C
20
1H3311B14N2: 312.2736]; ∆mmu ϭ 2.3.
4b: Yield: 3.0 g (87%), yellow liquid, b.p. 112 °C/0.02 Torr. 1H
3
NMR (200.1 MHz, CDCl3): δ ϭ 1.35 [d, JH,H ϭ 7.0 Hz, 24H,
CH(CH3)2], 2.32 (s, CH3, 3 H), 3.53 [sept., JH,H ϭ 6.9 Hz, 4H, (100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 248.1008 (100) [Mϩ;
3
12
CH(CH3)2], 7.3Ϫ7.6 (m, 4H, C6H5) ppm. 13C NMR (50.3 MHz,
CDCl3): δ ϭ 21.32 (CH3), 24.25 [CH(CH3)2], 46.81 [CH(CH3)2],
104.5 (CspϪCi), 125.3, 127.5, 128.7, 131.2 (C6H4) ppm; CspϪB not
found. 11B NMR (64.2 MHz, CDCl3): δ ϭ 26 ppm. MS (70 eV, EI):
C
16
1H1311B16O2: 248.1015]; ∆mmu ϭ 0.7.
1-(Dithiocatecholboryl)-2-phenylacetylene (6a): Starting materials:
3a (4.1 g, 15.4 mmol), H4C6S2BBr (3.55 g, 15.4 mmol). Yield 2.8 g
(72%), brown-red solid, m.p. 82 °C. 1H NMR (200.1 MHz, CDCl3):
δ ϭ 7.4Ϫ7.8 (m, 9 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3):
δ ϭ 84.01 (CspϪCi), 125.7, 126.5, 140.9 (dithiocatechol), 128.4,
129.7, 131.1, 132.2 (C6H5) ppm; CspϪB not observed. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 47 ppm. CI-MS: m/z (%) ϭ 252.1 [Mϩ]
(70)
m/z (%) ϭ 326 (100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 326.2899
12
(100) [Mϩ;
C
21
1H3511B14N2: 326.2893]; ∆mmu ϭ 0.6.
Two General Procedures for 1-Aryl-2-borylacetylenes 5, 6, and 7.
Procedure A: The appropriate 1-aryl-2-(trimethylstannyl)acetylene
3 was dissolved in toluene (50 mL) and then the corresponding
haloborane in toluene (10 mL) was added slowly at Ϫ20 °C. The
reaction mixture was stirred overnight at ambient temperature.
After evaporation of the solvent under high vacuum, a crystalline
solid was obtained.
1-(Dithiocatecholboryl)-2-tolylacetylene (6b): Starting materials: 3b
(1.7 g, 6.09 mmol), H4C6S2BBr (1.4 g, 6.09 mmol). Yield 1.2 g
(74%), light-yellow solid, m.p. 86 °C. 1H NMR (200.1 MHz,
CDCl3): δ ϭ 2.38 (s, 3 H, CH3), 7.15Ϫ7.50 (m, 8 H, Haryl) ppm.
13C NMR (50.3 MHz, CDCl3): δ ϭ 21.07 (CH3), 92.43 (CspϪCi),
122.2, 126.0, 140.9 (dithiocatechol), 126.8, 127.1, 128.4, 132.2 (to-
lyl) ppm; CspϪB not observed. 11B NMR (64.2 MHz, CDCl3): δ ϭ
Procedure B: The appropriate 1-aryl-2-[bis(diisopropylamino)-
boryl]acetylene 4 was dissolved in THF (50 mL) and then 2 equiv.
of HCl·Et2O (2 ) was added slowly at Ϫ78 °C. Stirring was con-
tinued for 45 min and NH2iPr2Cl formed as a white solid. The cor-
responding aromatic diol in THF (15 mL) was then added dropwise
and the reaction mixture was stirred overnight at room tempera-
ture. After filtration of the solid, the solution was reduced to near
dryness, and a crystalline product was obtained.
48 ppm. MS (70 eV, EI): m/z (%) ϭ 266 (100) [Mϩ]. MS (70 eV,
12
HR-EI): m/z (%)
ϭ
266.0401 (100) [Mϩ;
C
15
1H1111B32S2:
266.0395]; ∆mmu ϭ 0.6.
1-(4-Methyldithiocatecholboryl)-2-phenylacetylene (6c): Starting
materials: 4a (3.5 g, 11.2 mmol), HCl·OEt2 (11.2 mL, 22.4 mmol),
1-(Catecholboryl)-2-phenylacetylene (5a): Starting materials: 3a
4-methyldithiocatechol (1.75 g, 11.2 mmol). Yield 2.3 g (77%), yel-
1
(4.8 g, 18 mmol), H4C6O2BCl (2.78 g, 18 mmol). Yield 2.8 g (71%), low solid, m.p. 88 °C. H NMR (200.1 MHz, CDCl3): δ ϭ 2.42 (s,
1
orange-red solid, m.p. 76 °C. H NMR (200.1 MHz, CDCl3): δ ϭ
3 H, CH3), 7.13, 7.41, 7.64 (m, 8 H, Haryl) ppm. 13C NMR
7.2Ϫ7.7 (m, 9 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ (50.3 MHz, CDCl3): δ ϭ 21.07 (CH3), 93.37 (CspϪCi), 126.1, 126.8,
105.1 (CspϪCi), 112.7, 123.3, 147.9 (catechol), 121.2, 128.6, 130.1,
132.8 (C6H5) ppm; CspϪB not observed. 11B NMR (64.2 MHz,
127.1, 135.9, 137.6, 140.9 (dithiocatechol), 122.2, 128.4, 129.7,
132.2 (C6H5) ppm; CspϪB not observed. 11B NMR (64.2 MHz,
CDCl3): δ ϭ 25 ppm. MS (70 eV, EI): m/z (%) ϭ 220 (100) [Mϩ]. CDCl3): δ ϭ 47 ppm. MS (70 eV, EI): m/z (%) ϭ 266 (100) [Mϩ].
MS (70 eV, HR-EI): m/z (%)
ϭ
220.0715 (100) [Mϩ; MS (70 eV, HR-EI): m/z (%)
ϭ
266.0399 (100) [Mϩ;
1H911B16O2: 220.0695]; ∆mmu ϭ 2.0.
C
15
1H1111B32S2: 266.0395]; ∆mmu ϭ 0.4.
12
12
C
14
1-(Catecholboryl)-2-tolylacetylene (5b): Starting materials: 3b 1-(4-Methyldithiocatecholboryl)-2-tolylacetylene (6d): Starting ma-
(2.4 g, 8.6 mmol), H4C6O2BCl (1.32 g, 8.6 mmol). Yield 1.4 g
(69%), yellow solid, m.p. 72 °C (dec.). 1H NMR (200.1 MHz,
CDCl3): δ ϭ 2.35 (s, 3 H, CH3), 7.0Ϫ7.5 (m, 8 H, Haryl) ppm. 13C
terials: 3b (3.05 g, 10.9 mmol), CH3C6H3S2BBr (2.66 g,
10.9 mmol). Yield 2.2 g (72%), brown solid, m.p. 93 °C. H NMR
1
(200.1 MHz, CDCl3): δ ϭ 2.28 (s, 3 H, CH3), 2.38 (s, 3 H, CH3),
NMR (50.3 MHz, CDCl3): δ ϭ 21.67 (CH3), 103.4 (CspϪCi), 112.6, 7.1Ϫ7.6 (m, 7 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ
123.1, and 147.8 (catechol), 115.5, 121.3, 129.2, 132.7 (tolyl) ppm;
21.07, 21.67 (CH3), 83.81 (CspϪCi), 126.0, 126.8, 127.0, 135.8,
137.6, 140.9 (thiocatechol), 119.1, 129.2, 132.1, 140.2 (tolyl) ppm;
CspϪB not observed. 11B NMR (64.2 MHz, CDCl3): δ ϭ 25 ppm.
MS (70 eV, EI): m/z (%) ϭ 234 (100) [Mϩ]. MS (70 eV, HR-EI): CspϪB not observed. 11B NMR (64.2 MHz, CDCl3): δ ϭ 48 ppm.
m/z (%) ϭ 234.0833 (100) [Mϩ;
∆mmu ϭ 1.9.
C
15
1H1111B16O2: 234.0852];
MS (70 eV, EI): m/z (%) ϭ 280 (100) [Mϩ]. MS (70 eV, HR-EI):
12
12
m/z (%) ϭ 280.0562 (100) [Mϩ;
∆mmu ϭ 1.1.
C
16
1H1311B16S2: 280.0551];
1-(4-Methylcatecholboryl)-2-phenylacetylene (5c): Starting materi-
als: 3a (4.1 g, 15.4 mmol), CH3C6H3O2BCl (2.59 g, 15.4 mmol). 1-(1,3,2-Benzothiaoxaborolyl)-2-phenylacetylene (7a): Starting ma-
1
Yield 2.4 g (66%), yellow solid, m.p. 75 °C. H NMR (200.1 MHz,
terials: 4a (3.1 g, 9.93 mmol), HCl·OEt2 (9.93 mL, 19.86 mmol), 2-
CDCl3): δ ϭ 2.39 (s, CH3, 3 H), 6.9Ϫ7.6 (m, 8 H, Haryl) ppm. 13C hydroxyphenol (1.25 g, 9.93 mmol). Yield 1.8 g (76%), brown-red
NMR (50.3 MHz, CDCl3): δ ϭ 21.38 (CH3), 93.37 (CspϪCi), 111.9, solid, m.p. 66 °C. 1H NMR (200.1 MHz, CDCl3): δ ϭ 7.2Ϫ7.6 (m,
113.2, 123.6, 130.0, 145.7, 147.8 (catechol), 121.2, 128.8, 132.7,
9 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 108.9
(CspϪCi), 114.2, 123.5, 125.4, 126.3, 126.9, 156.7 (2-hydroxythio-
133.2 (C6H5) ppm; CspϪB not observed. 11B NMR (64.2 MHz,
Eur. J. Inorg. Chem. 2004, 2635Ϫ2645
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2641

A. Goswami, C.-J. Maier, H. Pritzkow, W. Siebert
FULL PAPER
phenol), 119.7, 128.5, 129.9, 132.6 (C6H5) ppm; CspϪB not ob- NMR (64.2 MHz, CDCl3): δ ϭ 22 (br.) ppm. MS (70 eV, EI): m/z
served. 11B NMR (64.2 MHz, CDCl3): δ ϭ 38 ppm. MS (70 eV,
EI): m/z (%) ϭ 236 (100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ
(%) ϭ 744 (100) [Mϩ], 612 (49) [Mϩ Ϫ H3CC6H3O2B ϩ 1]. MS
1
(70 eV, HR-EI): m/z (%) ϭ 744.3028 (100) [Mϩ; 12C48 H3911B316O6:
236.0462 (100) [Mϩ; 12C141H911B16O132S1: 236.0467]; ∆mmu ϭ 0.5. 744.3025]; ∆mmu ϭ 0.3. C48H39B3O6 (744.2): calcd. C 77.46, H
5.28; found C 77.05, H 5.59.
1-(1,3,2-Benzothiaoxaborolyl)-2-tolylacetylene (7b): Starting materi-
Catalyst ؍ [Co2(CO)8]: Mono(boryl)acetylene (5a: 1.76 g; 5b:
1.87 g; 5c: 1.87 g; 5d: 1.98 g; 8 mmol) and octacarbonyldicobalt
(0.136 g, 0.4 mmol, 5 mol%) were heated at 90 °C in toluene
(20 mL) for 2 days. Workup was carried out as above.
als: 3b (2.75 g, 9.85 mmol), H4C6OSBr (2.0 g, 9.85 mmol). Yield:
2.1 g (86%), yellow solid, m.p. 71 °C. 1H NMR (200.1 MHz,
CDCl3): δ ϭ 2.39 (s, 3 H, CH3), 7.2Ϫ7.6 (m, 8 H, Haryl) ppm. 13C
NMR (50.3 MHz, CDCl3): δ ϭ 21.66 (CH3), 109.3 (CspϪCi), 114.8,
123.8, 125.4, 126.2, 126.9, 156.6 (2-hydroxythiophenol), 118.4,
129.3, 132.5, 140.4 (tolyl) ppm; CspϪB not observed. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 38 ppm. MS (70 eV, EI): m/z (%) ϭ 250
Yields: 1.25 g (71%) of 8a/8aЈ; 1.45 g (77%) of 8b/8bЈ; 1.32 g (70%)
of 8c/8cЈ; 1.49 g (75%) of 8d/8dЈ.
(100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 250.0622 (100) [Mϩ;
[η4-Bis(diethylamino)bis(dimethylaminoboryl)cyclobutadiene](η5-
cyclopentadienyl)cobalt(I) (9): A solution of 2 (0.39 g, 2 mmol) in
12
C
15
1H1111B16O132S1: 250.0627]; ∆mmu ϭ 0.5.
hexane (5 mL) was added within 15 min at room temparature to a
solution of CpCo(C2H4)2 (0.36 g, 2 mmol) in hexane (20 mL). The
reaction mixture was stirred for 3 h. After filtration, the solvent
was evaporated under high vacuum and a brown-green cobalt com-
plex 9 was obtained. MS (70 eV, EI): m/z (%) ϭ 515 (5) [Mϩ ϩ 1],
341 (4) [C15H24B2CoN4ϩ], 205 (7) [C9H19B2N4ϩ], 58 (37)
[C3H8Nϩ], 28 (100) [C2H4ϩ].
Isomers of Tris(catecholboryl)triphenylbenzene (8a/8aЈ), Tris(cate-
cholboryl)tritolylbenzene (8b/8bЈ), Tris(4-methylcatecholboryl)tri-
phenylbenzene (8c/8cЈ), and Tris(4-methylcatecholboryl)tritolylben-
zene (8d/8dЈ). Catalyst ؍ [CpCo(CO)2]: Borylacetylene (5a: 1.32 g;
5b: 1.42 g; 5c: 1.42 g; 5d: 1.50 g; 6 mmol) and dicarbonylcobalt(η5-
cyclopentadienyl) (0.055 g, 0.3 mmol, 5 mol%) were heated at 90
°C in toluene (20 mL) for 3 days. The solid that formed was sepa-
rated and washed several times with small amount of solvents (8a/
8aЈ: toluene and CH2Cl2; 8b/8bЈ: hexane and toluene; 8c/8cЈ and
8d/8dЈ: hexane) and dried in vacuo.
[η4-Bis(dithiocatecholboryl)diphenyl(cyclobutadiene](η5-cyclo-
pentadienyl)cobalt(1) (10a/10aЈ), [η4-Bis(dithiocatecholboryl)ditolyl-
cyclobutadiene](η5-cyclopentadienyl)cobalt(1) (10b/10bЈ), [η4-Bis(4-
methyldithiocatecholboryl)diphenylcyclobutadiene](η5-cyclopenta-
dienyl)cobalt(1) (10c/10cЈ), [η4-Bis(4-methyldithiocatecholboryl)di-
tolylcyclobutadiene](η5-cyclopentadienyl)cobalt(1) (10d/10dЈ), [η4-
bis(1,3,2-benzo-thiaoxaborolyl)diphenylcyclobutadiene](η5-cyclo-
pentadienyl)cobalt(1) (11a/11aЈ), and [η4-Bis(1,3,2-benzothiaoxa-
8a/8aЈ: Yield 1.02 g (77%), yellow solid, m.p. 230 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 7.2Ϫ7.6 (m, 27 H, Haryl) ppm. 13C NMR
(50.3 MHz, CDCl3): δ ϭ 112.7, 123.2, 147.8 (catechol), 121.2,
128.5, 130.0, 132.8 (C6H5), 139.9 (central benzene, symm.), 134.6,
137.3, 142.5 (central benzene, unsymm.) ppm. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 24 (br.) ppm. MS (70 eV, EI): m/z (%) ϭ
660 (100) [Mϩ], 542 (42) [Mϩ Ϫ catB ϩ 1], 424 (15) [Mϩ Ϫ 2catB
borolyl)ditolylcyclobutadiene](η5-cyclopentadienyl)cobalt(1)
(11b/
11bЈ): Borylalkyne (6a: 2.01 g; 6b: 2.12 g; 6c: 2.12 g; 6d: 2.24 g; 7a:
1.88 g; 7b: 2.00 g; 8 mmol) was added at room temperature to a
solution of dicarbonylcobalt(η5-cyclopentadienyl) (0.72 g, 4 mmol)
in toluene (30 mL). The reaction mixture was heated under reflux
for 3 d. After cooling, the precipitate was collected by filtration,
washed several times with hexane, and dried in vacuo.
ϩ 1]. MS (70 eV, HR-EI): m/z (%) ϭ 660.2087 (100) [Mϩ;
12
C
42
1H2711B316O6: 660.2086]; ∆mmu ϭ 0.1. C42H27B3O6 (660.1):
calcd. C 76.42, H 4.12; found C 76.15, H 4.75.
8b/8bЈ: Yield 1.10 g (78%), yellow solid, m.p. 241 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 2.35 (s, 9 H, CH3), 7.0Ϫ7.4 (m, 24 H,
1
10a/10aЈ: Yield 1.42 g (56%), orange solid, m.p. 241 °C. H NMR
H
aryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 21.67 (CH3), 112.6,
(200.1 MHz, CDCl3): δ ϭ 4.72 (s, 5 H, CpϪH), 7.4Ϫ7.9 (m, 18 H,
Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 81.05, 82.10
(C4ring), 86.25 (CpϪC), 125.7, 126.5, 140.9 (dithiocatechol), 128.4,
129.7, 131.1, 132.2 (C6H5) ppm. 11B NMR (64.2 MHz, CDCl3):
δ ϭ 58 (br.) ppm. MS (70 eV, EI): m/z (%) ϭ 628 (100) [Mϩ], 478
(50) [Mϩ Ϫ BS2C6H4 ϩ 1], 450 (2) [Mϩ Ϫ PhCϵCPh], 376 (70)
[Mϩ Ϫ C6H4S2BCϵCPh], 302 (4) [Mϩ Ϫ C6H4S2BCϵCBS2C6H4].
123.1, 147.8 (catechol), 118.1, 129.2, 132.0, 132.7 (tolyl), 140.6 (cen-
tral benzene, symm.), 135.9, 139.2, 147.5 (central benzene, un-
symm.) ppm. 11B NMR (64.2 MHz, CDCl3): δ ϭ 22 (br.) ppm. MS
(70 eV, EI): m/z (%) ϭ 702 (8) [Mϩ], 584 (65) [Mϩ Ϫ catB ϩ 1],
466 (100) [Mϩ Ϫ 2catB ϩ 1]. MS (70 eV, HR-EI): m/z (%) ϭ
702.2551 (5) [Mϩ;
C
45
1H3311B316O6: 702.2556]; ∆mmu ϭ 0.5.
12
628.0222 (100) [Mϩ;
1H2311B259Co32S4: 628.0200]; ∆mmu ϭ 2.2. C33H23B2CoS4
C45H33B3O6 (702.2): calcd. C 76.97, H 4.74; found C 77.95, H 4.98.
MS (70 eV, HR-EI): m/z (%)
ϭ
12
C
33
8c/8cЈ: Yield 0.95 g (67%), yellow solid, m.p. 245 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 2.42 (s, 9 H, CH3), 7.1Ϫ7.6 (m, 24 H,
Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 21.60 (CH3), 112.0,
113.3, 123.3, 129.4, 145.6, 147.7 (catechol), 123.7, 129.2, 132.2,
132.9 (C6H5), 140.7 (central benzene, symm.), 139.1, 146.0, 148.0
(central benzene, unsymm.) ppm. 11B NMR (64.2 MHz, CDCl3):
δ ϭ 23 (br.) ppm. MS (70 eV, EI): m/z (%) ϭ 702 (100) [Mϩ], 570
(628.0): calcd. C 63.06, H 3.39; found C 62.21, H 3.58.
10b/10bЈ: Yield 1.53 g (58%), orange-red solid, m.p. 245 °C. 1H
NMR (200.1 MHz, CDCl3): δ ϭ 2.35 (s, 6 H, CH3), 4.82 (s, 5
H, CpϪH), 6.9Ϫ7.3 (m, 16 H, Haryl) ppm. 13C NMR (50.3 MHz,
CDCl3): δ ϭ 21.69 (CH3), 84.86 (CpϪC), 82.84, 83.41 (CBD),
124.8, 125.6, 139.9 (dithiocatechol), 127.5, 128.8, 130.2, 131.2 (to-
lyl) ppm. 11B NMR (64.2 MHz, CDCl3): δ ϭ 57 (br.) ppm. MS
(70 eV, EI): m/z (%) ϭ 656 (100) [Mϩ], 506 (30) [Mϩ Ϫ BS2C6H4
(95) [Mϩ Ϫ H3CC6H3O2B ϩ 1]. MS (70 eV, HR-EI): m/z (%) ϭ
702.2596 (100) [Mϩ;
C
45
1H3311B316O6: 702.2556]; ∆mmu ϭ 4.0.
12
ϩ 1], 450 (3) [Mϩ Ϫ H3CC6H4CϵCC6H4CH3], 390 (70) [Mϩ
C6H4S2BCϵCC6H4CH3], 330 (5) [Mϩ Ϫ C6H4S2BCϵCBS2C6H4].
MS (70 eV, HR-EI): m/z (%)
656.0519 (100) [Mϩ;
1H2711B259Co32S4: 656.0513]; ∆mmu ϭ 0.6. C35H27B2CoS4
Ϫ
C45H33B3O6 (702.2): calcd. C 76.97, H 4.74; found C 76.45, H 5.08.
8d/8dЈ: Yield 1.12 g (75%), pale yellow solid, m.p. 261 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 2.35 (s, 9 H, CH3), 2.39 (s, 9 H, CH3),
6.9Ϫ7.5 (m, 21 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ
21.37 and 21.48 (CH3), 111.9, 113.2, 123.1, 133.1, 145.7, 147.8
(catechol), 118.1, 129.0, 132.0, 132.7 (tolyl), 140.5 (central benzene,
symm.), 138.9, 145.3, 147.5 (central benzene, unsymm.) ppm. 11B
ϭ
12
C
35
(656.0): calcd. C 64.02, H 4.15; found C 64.34, H 4.59.
1
10c/10cЈ: Yield 1.45 g (55%), yellow solid, m.p. 247 °C. H NMR
(200.1 MHz, CDCl3): δ ϭ 2.36 (s, 6 H, CH3), 4.86 (s, 5 H, CpϪH),
2642
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 2635Ϫ2645

Cobalt-Mediated Cyclooligomerization Reactions of Borylacetylenes
FULL PAPER
7.1Ϫ7.9 (m, 16 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ
12a/12aЈ: 1.74 g (77%), black solid, m.p. Ͼ 300 °C. 1H NMR
20.96 (CH3), 79.72 (CpϪC), 82.45, 83.23 (C4ring), 124.5, 126.8, (200.1 MHz, CDCl3): δ ϭ 7.4Ϫ7.9 (m, 36 H, Haryl) ppm. 13C NMR
127.0, 135.9, 137.7 (dithiocatechol), 122.2, 128.8, 129.3, 132.8
(50.3 MHz, CDCl3): δ ϭ 125.8, 126.6, 141.0 (dithiocatechol), 126.9
(C6H5) ppm. 11B NMR (64.2 MHz, CDCl3): δ ϭ 57 (br.) ppm. MS (central benzene, symm.), 128.4, 128.9, 138.0 (central benzene, un-
(70 eV, EI): m/z (%) ϭ 656 (100) [Mϩ], 492 (50) [Mϩ
Ϫ
symm.), 128.6, 129.9, 131.2, 132.3 (C6H5) ppm. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 62 (v. br.) ppm. MS (70 eV, EI): m/z (%) ϭ
BS2C6H3CH3 ϩ 1], 478 (5) [Mϩ Ϫ PhCϵCPh], 390 (70) [Mϩ
Ϫ
H3CC6H3S2BCϵCPh], 302 (10) [Mϩ
Ϫ
H3CC6H3S2BCϵCB- 756 (100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 756.0742 (100)
S2C6H3CH3]. MS (70 eV, HR-EI): m/z (%) ϭ 656.0533 (100) [Mϩ;
[Mϩ;
C
42
1H2711B332S6: 756.0716]; ∆mmu ϭ 2.6. C42H27B3S6
12
12
C
35
1H2711B259Co32S4: 656.0513]; ∆mmu ϭ 2.0. C35H27B2CoS4 (756.4): calcd. C 66.66, H 3.60; found C 65.21, H 3.84.
(656.0): calcd. C 64.02, H 4.15; found C 64.49, H 4.77.
12b/12bЈ: 1.83 g (76%), black solid, m.p. 295 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 2.39 (s, 9 H, CH3), 7.2Ϫ7.5 (m, 24 H,
Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 21.27 (CH3), 122.4,
127.3, 141.2 (dithiocatechol), 126.3 (central benzene, symm.),
136.0, 137.8, 140.6 (central benzene, unsymm.), 127.0, 128.6, 129.9,
132.4 (tolyl) ppm. 11B NMR (64.2 MHz, CDCl3): δ ϭ 60 (v. br.)
10d/10dЈ: Yield 1.56 g (57%), orange solid, m.p. Ͼ 300 °C. 1H
NMR (200.1 MHz, CDCl3): δ ϭ 2.38 (s, 6 H, CH3), 2.42 (s, 6 H,
CH3), 4.68 (s, 5 H, CpϪH), 7.0Ϫ7.8 (m, 14 H, Haryl) ppm. 13C
NMR (50.3 MHz, CDCl3): δ ϭ 21.07 and 21.56 (CH3), 83.90
(CpϪC), 79.72, 89.76 (C4ring), 125.7, 126.4, 126.5, 135.2, 137.2,
140.8 (dithiocatechol), 128.2, 129.0, 130.0, 132.7 (tolyl) ppm. 11B
NMR (64.2 MHz, CDCl3): δ ϭ 58 (br.) ppm. MS (70 eV, EI): m/z
(%) ϭ 684 (15) [Mϩ], 520 (18) [Mϩ Ϫ BS2C6H3CH3 ϩ 1], 478 (10)
[Mϩ Ϫ H3CC6H4CϵCC6H4CH3], 404 (100) [Mϩ Ϫ H3CC6H3S2-
BCϵCC6H4CH3], 330 (22) [Mϩ Ϫ H3CC6H3S2BCϵCBS2C6H3CH3].
ppm. MS (70 eV, EI): m/z (%) ϭ 798 (100) [Mϩ]. MS (70 eV, HR-
12
EI): m/z (%) ϭ 798.1197 (100) [Mϩ;
C
45
1H3311B332S6: 798.1185];
∆mmu ϭ 1.2. C45H33B3S6 (798.5): calcd. C 67.66, H 4.17; found C
67.74, H 4.59.
12c/12cЈ: 1.90 g (79%), black solid, m.p. 297 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 2.33 (s, 9 H, CH3), 6.9Ϫ7.6 (m, 24 H,
MS (70 eV, HR-EI): m/z (%)
ϭ
684.0851 (100) [Mϩ;
1H3111B259Co16S4: 684.0826]; ∆mmu ϭ 2.5. C37H31B2CoS4
12
H
aryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 21.77 (CH3), 122.9,
C
37
(684.4): calcd. C 64.90, H 4.57; found C 64.38, H 5.07.
126.8, 127.8, 136.6, 138.3, 141.7 (dithiocatechol), 128.5 (central
benzene, symm.), 136.2, 138.0, 141.1 (central benzene, unsymm.),
127.5, 129.1, 130.4, 132.9 (C6H5) ppm. 11B NMR (64.2 MHz,
CDCl3): δ ϭ 60 (v. br.) ppm. MS (70 eV, EI): m/z (%) ϭ 798 (100)
11a/11aЈ: 1.64 g (68%), red-brown solid, m.p. 210 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 5.35 (s, 5 H, CpϪH), 7.4Ϫ7.9 (m, 18 H,
Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 83.98, 85.26
(C4ring), 87.26 (CpϪC), 113.8, 122.8, 125.3, 125.9, 127.4, 155.6 (2-
hydroxythiophenol), 120.5, 124.4, 128.9, 131.5 (C6H5) ppm. 11B
NMR (64.2 MHz, CDCl3): δ ϭ 45 (br.) ppm. MS (70 eV, EI): m/z
[Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 798.1185 (100) [Mϩ;
12
C
45
1H3311B332S6: 798.1185]; ∆mmu ϭ 0.0. C45H33B3S6 (798.5):
calcd. C 67.66, H 4.17; found C 67.89, H 4.75.
(%) ϭ 596 (50) [Mϩ], 462 (50) [Mϩ Ϫ BSOC6H4 ϩ 1], 418 (3) [Mϩ 12d/12dЈ: 2.05 g (81%), black solid, m.p. Ͼ 310 °C. 1H NMR
Ϫ PhCϵCPh], 360 (65) [Mϩ Ϫ C6H4SOBCϵCPh], 302 (4) [Mϩ
Ϫ
(200.1 MHz, CDCl3): δ ϭ 2.38 (s, 9 H, CH3), 2.41 (s, 9 H, CH3),
7.2Ϫ7.7 (m, 21 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ
21.17 and 21.78 (CH3), 126.2, 126.9, 127.1, 135.9, 137.7, 141.0 (di-
C6H4SOBCϵCBOSC6H4]. MS (70 eV, HR-EI): m/z (%)
ϭ
596.0665 (82) [Mϩ;
C
33
1H2311B259Co16O232S2: 596.0657];
12
∆mmu ϭ 0.8. C33H23B2CoO2S2 (596.2): calcd. C 66.44, H 3.89; thiocatechol), 119.2, 129.3, 132.2, 140.3 (tolyl) ppm; because of the
found C 65.89, H 4.56.
low solubility, the ipso-carbon atoms were not observed. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 60 (v. br.) ppm. MS (70 eV, EI): m/z (%) ϭ
11b/11bЈ: 1.56 g (62%), red solid, m.p. 221 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 2.32 (s, 6 H, CH3), 5.37 (s, 5 H, CpϪH),
7.1Ϫ7.5 (m, 16 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ
21.39 (CH3), 83.86 (CpϪC), 84.49, 86.23 (C4ring), 114.5, 123.5,
125.1, 125.9, 126.7, 156.3 (2-hydroxythiophenol), 118.1, 128.9,
132.2, 140.1 (tolyl) ppm. 11B NMR (64.2 MHz, CDCl3): δ ϭ 46
(br.) ppm. MS (70 eV, EI): m/z (%) ϭ 624 (80) [Mϩ], 490 (50) [Mϩ
Ϫ BSOC6H4 ϩ 1], 418 (2) [Mϩ Ϫ H3CC6H4CϵCC6H4CH3],
840 (100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 840.1680 (100)
[Mϩ;
C
48
1H3911B316S6: 840.1655]; ∆mmu ϭ 2.5. C48H39B3S6
12
(840.6): calcd. C 68.56, H 4.68; found C 67.38, H 5.15.
13a/13aЈ: 1.50 g (70%), red solid, m.p. 282 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 7.2Ϫ7.6 (m, 27 H, Haryl) ppm. 13C NMR
(50.3 MHz, CDCl3): δ ϭ 113.8, 122.8, 124.4, 125.3, 125.9, 155.6 (2-
hydroxythiophenol), 132.8 (central benzene, symm.), 135.2, 138.4,
141.2 (central benzene, unsymm.), 120.5, 128.0, 128.9, 131.5 (C6H5)
ppm. 11B NMR (64.2 MHz, CDCl3): δ ϭ 53 (br.) ppm. MS (70 eV,
EI): m/z (%) ϭ 708 (100) [Mϩ], 574 (10) [Mϩ Ϫ OSBC6H4 ϩ 1].
374 (45) [Mϩ Ϫ C6H4SOBCϵCC6H4CH3], 330 (9) [Mϩ
Ϫ
C6H4SOBCϵCBOSC6H4]. MS (70 eV, HR-EI): m/z (%)
ϭ
624.0985 (100) [Mϩ;
C
35
1H2732S216O211B259Co: 624.0970];
12
MS (70 eV, HR-EI): m/z (%)
ϭ
708.1415 (100) [Mϩ;
1H2711B316O332S3: 708.1401]; ∆mmu ϭ 1.4. C42H27B3O3S3
∆mmu ϭ 1.5. C35H27B2CoO2S2 (624.2): calcd. C 67.30, H 4.36;
found C 66.95, H 4.72.
12
C
42
(708.2): calcd. C 71.17, H 3.84; found C 71.07, H 4.26.
Isomers of Tris(dithiocatecholboryl)triphenylbenzene (12a/12aЈ),
Tris(dithiocatecholboryl)tritolylbenzene (12b/12bЈ), Tris(4-methyldi-
thiocatecholboryl)triphenylbenzene (12c/12cЈ), Tris(4-methyldithio-
catecholboryl)tritolylbenzene (12d,12dЈ), Tris(1,3,2-benzothiaoxa-
borolyl)triphenylbenzene (13a/13aЈ), and Tris(1,3,2-benzothiaoxa-
borolyl)tritolylbenzene (13b/13bЈ). Catalyst ؍ [Co2(CO)8]: Borylal-
kyne (6a: 2.26 g; 6b: 2.39 g; 6c: 2.39 g; 6d: 2.52 g; 7a: 2.12 g; 7b:
2.25 g; 9 mmol) and octacarbonyldicobalt (0.155 g, 0.45 mmol, 5
mole-%) were heated under reflux in toluene (20 mL) for 48 h. The
solid was separated and washed several times with small amounts
of solvents (12a/12aЈ: toluene and CH2Cl2; 12b/12bЈ: hexane and
toluene; 12c/12cЈ and 12d/12dЈ: hexane; 13a/13aЈ: toluene and
CH2Cl2; 13b/13bЈ: hexane and toluene) and dried in vacuo.
13b/13bЈ: Yield: 1.85 g (82%), red solid, m.p. 293 °C. 1H NMR
(200.1 MHz, CDCl3): δ ϭ 2.38 (s, 9 H, CH3), 7.2Ϫ7.6 (m, 24 H,
Haryl) ppm. 13C NMR (50.3 MHz, CDCl3): δ ϭ 21.39 (CH3), 114.5,
123.5, 125.1, 125.9, 131.7, 156.3 (2-hydroxythiophenol), 132.7 (cen-
tral benzene, symm.), 118.1, 126.7, 128.9, 132.2 (tolyl) ppm; ipso
carbon atoms of unsymm. ring were not observed. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 52 (br.) ppm. MS (70 eV, EI): m/z (%) ϭ
750 (70) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 750.1872 (100) [Mϩ;
12
C
45
1H3311B316O332S3: 750.1871]; ∆mmu ϭ 0.1. C45H33B3O3S3
(750.3): calcd. C 71.98, H 4.43; found C 71.09, H 4.93.
3-(1,3,2-Benzodioxaborolyl)-4-phenyl-1,2-bis(tricarbonylcobalta)-
tetrahedrane (14a), 3-(1,3,2-Benzodithiaborolyl)-4-phenyl-1,2-bis-
Eur. J. Inorg. Chem. 2004, 2635Ϫ2645
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2643

A. Goswami, C.-J. Maier, H. Pritzkow, W. Siebert
FULL PAPER
(tricarbonylcobalta)tetrahedrane (15a), and 3-(1,3,2-Benzothiaoxa-
16a: 1.40 g (45%), brown-red oil. 1H NMR (200.1 MHz, CDCl3):
δ ϭ 7.1Ϫ7.5 (m, 9 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3):
δ ϭ 108.7 (Cipso), 114.8, 123.8, 125.4, 126.2, 126.9, 156.6 (2-
hydroxythiophenol), 121.5, 128.4, 129.9, 132.5 (C6H5), 200.6 (CO)
ppm; CB was not observed. 11B NMR (64.2 MHz, CDCl3): δ ϭ
47 ppm. IR (hexane): ν˜ ϭ 2007 (s), 2022 (vs), 2044 (vs), 2060 (vs),
2076 (s) cmϪ1. MS (70 eV, EI): m/z (%) ϭ 522 (3) [Mϩ], 494 (7)
borolyl)-4-phenyl-1,2-bis(tricarbonylcobalta)tetrahedrane (16a):
A
solution of an alkyne (5a: 1.29 g; 6a: 1.48 g; 7a: 1.39 g; 5.9 mmol)
in CH2Cl2 (10 mL) was added at Ϫ20 °C to a solution of Co2(CO)8
(2.03 g, 5.9 mmol) in CH2Cl2 (20 mL). The mixture was stirred for
48 h at room temperature and the solvent was evaporated to near
dryness. The residue was separated by column chromatography
(Florisil; hexane) to give two fractions. Using hexane as the elu- [Mϩ Ϫ CO], 466 (10) [Mϩ Ϫ 2 CO], 438 (12) [Mϩ Ϫ 3 CO], 410
ent, [Co2(CO)8] was obtained first. The second fraction (hexane/
toluene, 1:4) contained the corresponding dicobalt complex.
(31) [Mϩ Ϫ 4 CO], 382 (15) [Mϩ Ϫ 5 CO], 354 (13), [Mϩ Ϫ 6 CO],
295 (6) [Mϩ Ϫ 6 CO Ϫ Co], 236 (100) [Mϩ Ϫ 6 CO Ϫ 2 Co]. MS
(70 eV,
HR-EI):
m/z
(%)
ϭ
521.8856
(3)
[Mϩ;
14a: Yield 1.51 g (50%), red oil. 1H NMR (200.1 MHz, CDCl3):
δ ϭ 7.2Ϫ7.7 (m, 9 H, Haryl) ppm. 13C NMR (50.3 MHz, CDCl3):
δ ϭ 104.3 (Cipso), 112.7, 123.2, 147.8 (catechol), 121.2, 128.5, 130.0,
132.8 (C6H5), 200.1 (CO) ppm; CB was not observed. 11B NMR
(64.2 MHz, CDCl3): δ ϭ 33 ppm. IR (hexane): ν˜ ϭ 2021 (vs), 2039
(s), 2057 (vs), 2081 (w), 2098 (s) cmϪ1. MS (70 eV, EI): m/z (%) ϭ
506 (2) [Mϩ], 478 (16) [Mϩ Ϫ CO], 450 (6.5) [Mϩ Ϫ 2 CO], 422
(13) [Mϩ Ϫ 3 CO], 394 (30) [Mϩ Ϫ 4 CO], 366 (53) [Mϩ Ϫ 5 CO],
338 (27) [Mϩ Ϫ 6 CO], 279 (30) [Mϩ Ϫ 6 CO Ϫ Co], 220 (100)
12
C
20
1H911B59Co216O732S1: 521.8826]; ∆mmu ϭ 3.0.
(1,3,2-Benzodithiaborolyl)pentaphenylbenzene and Bis(1,3,2-benzo-
dioxaborolyl)(1,3,2-benzodithiaborolyl)triphenylbenzene (17 and 18):
Diphenylacetylene (0.75 g, 4.2 mmol) or 1-(catacholboryl)-2-phe-
nylacetylene (5a; 0.92 g, 4.2 mmol) was added at room temperature
to a solution of 15a (1.12 g, 2.1 mmol) in toluene (30 mL). The
resulting mixture was stirred for 48 h under reflux. After cooling,
the dark-black precipitate was collected by filtration and washed
several times with hexane and toluene, and then dried in vacuo.
[Mϩ Ϫ 6 CO Ϫ 2 Co]. MS (70 eV, HR-EI): m/z (%) ϭ 505.9105
(2) [Mϩ;
C
20
1H911B59Co216O8: 505.9054]; ∆mmu ϭ 5.1.
12
17: 0.90 g (70%), dark solid, m.p. Ͼ 300 °C. MS (70 eV, EI): m/z
(%) ϭ 608 (100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 608.1818
15a: Yield 1.52 g (48%), brown-red oil. 1H NMR (200.1 MHz,
CDCl3): δ ϭ 7.1Ϫ7.8 (m, 9 H, Haryl) ppm. 13C NMR (50.3 MHz,
CDCl3): δ ϭ 72.56 (br., CB), 122.5 (Cipso), 125.5, 126.9, 137.4 (di-
thiocatechol), 128.1, 128.3, 130.2, 131.2 (C6H5), 199.5 (CO) ppm.
11B NMR (64.2 MHz, CDCl3): δ ϭ 59 ppm. IR (hexane): ν˜ ϭ 2007
(s), 2025 (s), 2044 (vs), 2060 (vs), 2088 (w) cmϪ1. MS (70 eV, EI):
(100) [Mϩ;
C
42
1H2911B32S2: 608.1803]; ∆mmu ϭ 1.5.
12
18: 1.10 g (75%), black solid, m.p. Ͼ 300 °C. MS (70 eV, EI): m/z
(%) ϭ 692 (100) [Mϩ]. MS (70 eV, HR-EI): m/z (%) ϭ 692.1633
(100) [Mϩ;
C
42
1H2711B316O432S2: 692.1629]; ∆mmu ϭ 0.4.
12
m/z (%) ϭ 538 (2) [Mϩ], 510 (3) [Mϩ Ϫ CO], 482 (5) [Mϩ Ϫ 2 CO], Crystal Structure Determinations of 4a, 5a, 6a, and 10a: Crystal
454 (2) [Mϩ Ϫ 3 CO], 426 (7) [Mϩ Ϫ 4 CO], 398 (12) [Mϩ Ϫ 5 data and details of the structure determinations are listed in
CO], 370 (15) [Mϩ Ϫ 6 CO], 311 (4) [Mϩ Ϫ 6 CO Ϫ Co], 252 (100) Table 1. Unique sets of intensity data were collected using a
[Mϩ Ϫ 6 CO Ϫ 2 Co]. MS (70 eV, HR-EI): m/z (%) ϭ 537.8536
BrukerϪAXS SMART 1000 diffractometer (Mo-Kα radiation, λ ϭ
˚
0.71073 A, graphite monochromator, ω-scan). Empirical absorp-
(2) [Mϩ;
C
20
1H911B59Co216O632S2: 537.8597]; ∆mmu ϭ 6.1.
12
Table 1. Crystal data and structural refinement for 4a, 5a, 6a, and 10a
4a
5a
6a
10a
Empirical formula
Molecular mass
Crystal system
Space group
C20H33N2B
312.29
monoclinic
C2/c
C14H9O2B
220.02
orthorhombic
Fdd2
C14H9S2B
252.14
monoclinic
P21
C33H23B2CoS4
628.30
triclinic
¯
P1
Unit cell
˚
a [A]
13.9717(7)
14.9033(8)
11.0036(6)
90
118.881(1)
90
2006.25(18)
4
1.034
19.626(5)
7.1519(18)
15.422(4)
90
90
90
2164.8(9)
8
14.419(2)
5.4955(8)
15.466(2)
90
102.885(3)
90
1194.6(3)
4
1.402
12.7008(7)
15.9541(9)
17.364(1)
87.270(1)
69.319(1)
88.105(1)
3287.5(3)
4
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
Volume [A ]
Z
Calcd. density [g cmϪ3
]
1.350
0.088
912
1.269
0.796
1288
µ [mmϪ1
F(000)
]
0.059
688
0.414
520
Crystal size [mm]
θmax. [°]
0.50 ϫ 0.34 ϫ 0.26
32.01
Ϫ20/18, 0/22, 0/16
9223
3421(0.0216)
173
1.045
0.35 ϫ 0.23 ϫ 0.07
32.10
0/29, 0/10, Ϫ21/22
5076
1717(0.0673)
98
1.072
0.17 ϫ 0.10 ϫ 0.01
27.11
Ϫ18/17, Ϫ7/ 6, 0/19
7208
4370(0.0625)
308
0.993
0.18 ϫ 0.07 ϫ 0.05
25.03
Ϫ14/15, Ϫ18/18, 0/20
35994
11615(0.0763)
725
0.870
Index ranges
Reflections collected
independent
Parameters
Goodness-of-fit on F2
R1 [I Ͼ 2σI]
0.0438
0.0713
0.0532
0.0503
wR2 (all reflections)
T [K]
0.1230
103(2)
0.532/Ϫ0.125
0.1678
103(2)
0.926/Ϫ0.367
0.1195
103(2)
0.462/Ϫ0.581
0.1162
298(2)
0.281/Ϫ0.542
Residual electron density [e/A3]
2644
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 2635Ϫ2645

Cobalt-Mediated Cyclooligomerization Reactions of Borylacetylenes
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